**1. Introduction**

Recently, with the rapid development of wearable sensor environments, a human activity recognition (HAR) with consistently collected daily data and various learning classifiers has become a popular issue: a vision-based recognition using a camera [1], recognition of five daily activities with acceleration data from a mobile phone and vital signs [2], and recognition with acceleration data from a chest-wearable device [3], and so on. However, despite mature studies and analyses on simple actions, like walking, standing, or sitting, complex activities that are composed of many low-level contexts and show various sensor patterns with respect to the background contexts have not been deeply studied yet [4].

In this paper, we propose a method which recognizes the eating activities in real life. Providing automatically information related with eating activities, such as the time and duration of eating activities, is crucial for healthcare management systems for people, in general, automatic monitoring for patients, such as diabetics, whose eating activities should be carefully managed, or the elderly who live alone, and so on. Although there are already plentiful studies recognizing simple eating and other daily activities, their approach did not catch the very large variety of activities in real life and are, therefore, difficult to extend to real situations. Eating activities could be a very complicated activity

to recognize using sensors, especially with limited low-power sensors, as it could have different sensor patterns with respect to different backgrounds and spatial/temporal contexts. In this paper, we propose a probabilistic method, especially the Bayesian network, which is based on the idea that those complexities might be handled better with a probabilistic approach.

The paper is organized as follows: In Section 2, we provide some analyses to show the complexity of eating activities based on the real-life logging, and specify requirements to deal with those issues. In Section 3, we explore HAR-related works using low-level sensor data, and related theories analyzing components of human activity. In Section 4, we explain how to construct Bayesian networks in further detail, and verify their realistic usefulness in a variety of angles in Section 5. Finally, Section 6 concludes the paper and discusses future works.


**5. WDM approach using Polymer Optical Fiber Bragg Gratings (POFBGs)**

As previously stated, one solution to increase the POF's bandwidth, and thus its capacity, is the transmission of information over more than just a single wavelength. This is what is known the WDM approach. This architecture not only has been proved to be suitable for transmission information purposes but also has been demonstrated to be fully compatible with the inter‐ rogation of multiple remotely located intensity-based optical fiber sensors, thus taking advantage of the power loss reduction as well as the high scalability provided by the use of WDM devices.

The basis of WDM systems is the spectral characteristics of the optical multiplexers and demultiplexers which are used in the fiber plant instead of optical power splitters. Moreover, within these approaches, FBGs are usually employed both for monitoring purposes or providing an effective and compact strategy to operate in reflective configuration [77, 78]. These devices are a wavelength-selective filter fabricated inside the core of an optical fiber for which the reflected wavelength changes under the influence of external perturbations [79]. First FBGs were traditionally manufactured on silica optical fiber. More recently, FBGs have been inscribed into SI-POF [80] and microstructured Polymer Optical Fiber (mPOF) [81] based on PMMA, leading to what is called polymer optical fiber Bragg gratings (POFBGs). The reason for this development is the exploitation of polymer benefits such as larger elastic limit, higher maximum strain limit, larger temperature and humidity responses and low cost compared to silica, while maintaining the benefits of FBGs. And this fact is also true when considering FBGs as optical sensing elements [82, 83]. In addition, polymer reveals to be intrinsically more biocompatible than silica for as it may be used for *in vivo* biomedical applications where the use of glass is inappropriate due to danger from breakages. Nevertheless, limited effort has been directed towards synergizing biocompatible POF-based photonic sensing with the WDM interrogation method that allows multiplexing by the use of FBGs, with just a few exceptions [84]. The main underlying reason behind this lack of development is the mismatch between the optimum operating wavelength regions of POFs and the optical devices exploited for telecommunications purposes as aforementioned at the beginning of this chapter.

In this section, we intend to bridge the gap between a WDM compatible topology and the use of novel POFBGs by analyzing the feasibility of a hybrid silica-POF WDM network for remotely addressing multiple intensity-based self-referenced fiber-optic sensors. The proposed topol‐ ogy is compatible with the target of developing a single optical broadband network architec‐ ture which is capable of carrying many types of services without mutual interference nor design compromises. It may include the access network domain (e.g. FTTx) as well as up to the indoor scenario with the aim of a full converged network solution. This solution will open up the path for the development of converged WDM POF communication networks in the near future. Moreover, potential medical environments and biomedical applications based on all-optical POF-based solutions are also targeted taking advantage of the intrinsic POF biocompatible characteristics.

The proposed self-referenced hybrid topology above described is illustrated in Fig. 17. The novelties of this configuration in comparison with previous works [78, 85] are: a) the combi‐ nation of silica- and polymer- FBGs (the latter may be used for *in vivo* scenarios or just simply at the patient's vicinity if the target is a biocompatible optical system for medical applications); b) the usage of a single reference FBG; and c) an improved centralized monitoring unit (that can be remotely located up to units of km) which includes virtual instrumentation techniques and data processing. A broadband light source (BLS) is, either internally or externally, modulated at a single frequency ( *f* ). This modulated signal is launched into the remote sensing points via a broadband circulator and a Coarse Wavelength-Division Multiplexer (CWDM). Each remote sensing point located consists of a sensing POFBG placed after the fiber-optic sensor (FOS). A single silica FBG is located before the CWDM acting as a reference channel for the topology. Let assume the central wavelengths of the reference and sensing FBGs to be λSi and λPOF, respectively. The broadband optical circulator receives the reflected multiplexing signals from the reference and the sensor channels, in which the sensor information is encoded. At the remote monitoring unit, the optical signal is demultiplexed by a CWDM device and distributed to an array of photodetectors (PD) by means of a data acquisition board (DAQ) together with a band-pass filter (BPF), used to eliminate noise from all signals at frequencies outside the system frequency. Then, a phase-shift is applied to the reference and sensor digital signals. Finally, a virtual lock-in amplifier is used to interrogate all available sensor channels. A measurement parameter can be defined, *φK* , corresponding to the output phase of the signal for different phase-shifts (virtual delays) at the reception stage, see Eq. 1.

rogation of multiple remotely located intensity-based optical fiber sensors, thus taking advantage of the power loss reduction as well as the high scalability provided by the use of

406 Advances in Optical Fiber Technology: Fundamental Optical Phenomena and Applications

The basis of WDM systems is the spectral characteristics of the optical multiplexers and demultiplexers which are used in the fiber plant instead of optical power splitters. Moreover, within these approaches, FBGs are usually employed both for monitoring purposes or providing an effective and compact strategy to operate in reflective configuration [77, 78]. These devices are a wavelength-selective filter fabricated inside the core of an optical fiber for which the reflected wavelength changes under the influence of external perturbations [79]. First FBGs were traditionally manufactured on silica optical fiber. More recently, FBGs have been inscribed into SI-POF [80] and microstructured Polymer Optical Fiber (mPOF) [81] based on PMMA, leading to what is called polymer optical fiber Bragg gratings (POFBGs). The reason for this development is the exploitation of polymer benefits such as larger elastic limit, higher maximum strain limit, larger temperature and humidity responses and low cost compared to silica, while maintaining the benefits of FBGs. And this fact is also true when considering FBGs as optical sensing elements [82, 83]. In addition, polymer reveals to be intrinsically more biocompatible than silica for as it may be used for *in vivo* biomedical applications where the use of glass is inappropriate due to danger from breakages. Nevertheless, limited effort has been directed towards synergizing biocompatible POF-based photonic sensing with the WDM interrogation method that allows multiplexing by the use of FBGs, with just a few exceptions [84]. The main underlying reason behind this lack of development is the mismatch between the optimum operating wavelength regions of POFs and the optical devices exploited for

telecommunications purposes as aforementioned at the beginning of this chapter.

In this section, we intend to bridge the gap between a WDM compatible topology and the use of novel POFBGs by analyzing the feasibility of a hybrid silica-POF WDM network for remotely addressing multiple intensity-based self-referenced fiber-optic sensors. The proposed topol‐ ogy is compatible with the target of developing a single optical broadband network architec‐ ture which is capable of carrying many types of services without mutual interference nor design compromises. It may include the access network domain (e.g. FTTx) as well as up to the indoor scenario with the aim of a full converged network solution. This solution will open up the path for the development of converged WDM POF communication networks in the near future. Moreover, potential medical environments and biomedical applications based on all-optical POF-based solutions are also targeted taking advantage of the intrinsic POF

The proposed self-referenced hybrid topology above described is illustrated in Fig. 17. The novelties of this configuration in comparison with previous works [78, 85] are: a) the combi‐ nation of silica- and polymer- FBGs (the latter may be used for *in vivo* scenarios or just simply at the patient's vicinity if the target is a biocompatible optical system for medical applications); b) the usage of a single reference FBG; and c) an improved centralized monitoring unit (that can be remotely located up to units of km) which includes virtual instrumentation techniques and data processing. A broadband light source (BLS) is, either internally or externally, modulated at a single frequency ( *f* ). This modulated signal is launched into the remote sensing

WDM devices.

biocompatible characteristics.

$$\varphi\_K = \tan^{-1} \left[ \frac{\cdot \left( \sin \, \theta\_{Si} \star \beta\_k \bullet \sin \, \theta\_{POF\_k} \right)}{\cos \, \theta\_{Si} + \beta\_k \bullet \cos \, \theta\_{POF\_k}} \right] \tag{1}$$

where *θSi* and *θPOF k* are, respectively, the phase shifts for the reference and each sensor signal *k*, and *βk* is relates to the optical power received at the remote central unit being a function of the modulation index, the reflectivity of the silica FBG and the photodetector responsivity (for both sensing and reference wavelengths), the sensor power loss modulation, the insertion loss of the CWDM device, and the insertion loss related to the reflectivity, intrinsic attenuation and connectorization of the POFBGs. Further details of the mathematical framework can be seen in the works reported in [78, 86]. Parameter *φK* is insensitive to power fluctuations except for the sensor modulation thus performing as a self-reference measurement parameter. Its performance, i.e. linear behavior, maximum sensitivity, etc., is directly related to the digital phase-shifts applied at reception.

To test the feasibility of the topology shown in Fig. 17, a 2-sensor network was analyzed by modulating the BLS at f=1kHz by an acousto-optic modulator. The optical power was launched into the configuration via a broadband circulator. One silica FBG was used for reference purpose, being placed before the CWDM mux/demux. Its central wavelength and reflectivity were λSi=1550nm and 49%, respectively. A POFBG in 150μm cladding diameter few-moded mPOF was used for each remote sensing point, with central wavelengths λPOF1 =1525.2nm for FOS1 and λPOF2 =1567.0nm for FOS2. Their reflectivities were 27 % and 36 %, respectively. A singlemode VOA was used to emulate the sensor response and for calibration purposes. The reflected signals were demultiplexed by a CWDM and detected by three amplified InGaAs detectors. The amplifier gain was fixed at 70 dB for all measurements. A 14-bit low-cost DAQ was used to convert the electrical signals from the photodetectors to digital signals. Virtual instrumentation techniques were developed to implement the bandpass filter, the phase-shifts and the lock-in amplifiers at the reception stage.

**Figure 17.** Hybrid silica-POF WDM self-referenced topology for remotely addresing generic remote sensing points lo‐ cated at the patient's vicinity. Fiber-optic sensor (FOS).

The self-reference property was tested inducing power fluctuations in the modulated optical source through a VOA. Fig. 18 showed no changes in *φK* values after inducing 10 dB of power attenuation. It is worth mentioning that the proposed topology performs no noticeable crosstalk between adjacent channels. This means that both (or more) sensors could be inter‐ rogated simultaneously without mutual interference because of the high channel isolation of the CWDM demultiplexer. Experiments were carried out for the following phase shifts at the reception stage: *θSi* =0.83*π*, *θPOF* 1 =0.33*π*.

The performance of the proposed topology was further investigated obtaining resolution values far below than that of provided by most of the POF intensity based sensing solution reported in literature, and particularly for biomedical applications. Another interesting point is computing the power budget, which provides information about the maximum remote interrogation reaching distance and/or the maximum insertion losses only for sensing pur‐ poses. At the most restrictive sensing wavelength (in terms of reaching distance), a maximum length of 11 km could be obtained. For this calculation, a FOS power variation of 6 dB was considered, high enough to cover any biomedical input magnitude span. However, this reach distance can be easily improved by launching more optical power into the system, using optical devices with better insertion loss performance or using a more efficient technique to connect POFBGs. The aforementioned reaching distance could provide a remote monitoring service unit fully compliant for both short-reach networks (typically less than 1 km), i.e. LANs and inbuilding/in-hospital networks as well as suitable for medium reach-distances (typically up to 10 km). Furthermore, the latter value ensures applications in inter-hospital networks or to provide a convergent all-optical and straightforward connection between patient's homes and

a general practice service for telemedicine purposes. It should be mentioned that the above reaching distances are unbeatable if an all-POF-based optical network is intended to be deployed and a hybrid approach should be considered. Following this analysis, it can be concluded that the proposed topology do not provide limitations thus serving as the bottleneck of a multiple remote sensing scheme. 14 and straightforward connection between patient's homes and a general practice service for 15 telemedicine purposes. It should be mentioned that the above reaching distances are 16 unbeatable if an all-POF-based optical network is intended to be deployed and a hybrid 17 approach should be considered. Following this analysis, it can be concluded that the 18 proposed topology do not provide limitations thus serving as the bottleneck of a multiple

13 value ensures applications in inter-hospital networks or to provide a convergent all-optical

22 Optical Fiber

1 reported in literature, and particularly for biomedical applications. Another interesting 2 point is computing the power budget, which provides information about the maximum 3 remote interrogation reaching distance and/or the maximum insertion losses only for 4 sensing purposes. At the most restrictive sensing wavelength (in terms of reaching distance), 5 a maximum length of 11 km could be obtained. For this calculation, a FOS power variation 6 of 6 dB was considered, high enough to cover any biomedical input magnitude span. 7 However, this reach distance can be easily improved by launching more optical power into 8 the system, using optical devices with better insertion loss performance or using a more 9 efficient technique to connect POFBGs. The aforementioned reaching distance could provide 10 a remote monitoring service unit fully compliant for both short-reach networks (typically

21 Fig. 18. Output phase � self-reference test versus power fluctuations for different values of 22 sensor losses at the remote sensing point addressed by λPOF 1. **Figure 18.** Output phase *φ*1 self-reference test versus power fluctuations for different values of sensor losses at the re‐ mote sensing point addressed by λPOF 1.

#### 23 6. WDM extension over PF GIPOF links **6. WDM extension over PF GIPOF links**

19 remote sensing scheme.

20

The self-reference property was tested inducing power fluctuations in the modulated optical source through a VOA. Fig. 18 showed no changes in *φK* values after inducing 10 dB of power attenuation. It is worth mentioning that the proposed topology performs no noticeable crosstalk between adjacent channels. This means that both (or more) sensors could be inter‐ rogated simultaneously without mutual interference because of the high channel isolation of the CWDM demultiplexer. Experiments were carried out for the following phase shifts at the

**Figure 17.** Hybrid silica-POF WDM self-referenced topology for remotely addresing generic remote sensing points lo‐

DPOF k

DSi

**+** LOCK-IN AMPLIFIER

λSi=1550 nm

Optical Electrical Virtual

CWDM

CWDM

PD λPOF k

ADQ

DIGITAL PROCESSING

λPOF 1 λSi

408 Advances in Optical Fiber Technology: Fundamental Optical Phenomena and Applications

PD

DPOF k DSi

VPOF 1 VPOF k VSi

PD

**FOS**k

**FOS**1

φPOF k

**REMOTE CENTRAL UNIT**

λPOF k=1567 nm

λPOF 1=1525 nm

**REMOTE SENSING POINTS**

The performance of the proposed topology was further investigated obtaining resolution values far below than that of provided by most of the POF intensity based sensing solution reported in literature, and particularly for biomedical applications. Another interesting point is computing the power budget, which provides information about the maximum remote interrogation reaching distance and/or the maximum insertion losses only for sensing pur‐ poses. At the most restrictive sensing wavelength (in terms of reaching distance), a maximum length of 11 km could be obtained. For this calculation, a FOS power variation of 6 dB was considered, high enough to cover any biomedical input magnitude span. However, this reach distance can be easily improved by launching more optical power into the system, using optical devices with better insertion loss performance or using a more efficient technique to connect POFBGs. The aforementioned reaching distance could provide a remote monitoring service unit fully compliant for both short-reach networks (typically less than 1 km), i.e. LANs and inbuilding/in-hospital networks as well as suitable for medium reach-distances (typically up to 10 km). Furthermore, the latter value ensures applications in inter-hospital networks or to provide a convergent all-optical and straightforward connection between patient's homes and

reception stage: *θSi* =0.83*π*, *θPOF* 1 =0.33*π*.

cated at the patient's vicinity. Fiber-optic sensor (FOS).

VRef

BLS AOM

VRef

Pin

24 In this section a comparison between the achievable capacity over a single fiber channel and 25 over a WDM PF-GIPOF-based approach will be presented. It has been previously stated that 26 a typical WDM optical communication link requires both a multiplexer and a demultiplexer. 27 However, the addition of POF-WDM multiplexer and demultiplexer devices, results in a 28 bit-rate penalty as the available optical power on the system decreases due to their insertion In this section a comparison between the achievable capacity over a single fiber channel and over a WDM PF-GIPOF-based approach will be presented. It has been previously stated that a typical WDM optical communication link requires both a multiplexer and a demultiplexer. However, the addition of POF-WDM multiplexer and demultiplexer devices, results in a bitrate penalty as the available optical power on the system decreases due to their insertion losses. To establish the channel capacity comparative, a bit loading algorithm for DMT modulation format over PF-GIPOF has been considered. New power margin resulting from the additional losses considered in the system due to the WDM over POF approach are analyzed demon‐ strating the feasibility of PF-GIPOF WDM systems.

> The resulting theoretical Shannon capacity of an optical fiber channel can be calculated if its *f*3dB is known [14], modeled as a Gaussian low-pass filter. Therefore, from measure‐ ments of frequency response of different PF-GIPOF lengths, 3dB bandwidths can be obtained, and so their theoretical capacity limits operating in a single channel. This type of

fiber has been demonstrated to enable robust 2GbE (GbE, Gigabit Ethernet) and 10GbE baseband transmission over short reach distances ranging from 25m up to 100m for different link scenarios [87], even at OverFilled Launching (OFL) condition. These values are considered as an underneath estimation of the transmission limit of PF-GIPOFs as com‐ plex modulation formats, restricted mode launching schemes, equalization techniques or simultaneous data transmission over high-order latent PF-GIPOF passbands can be applied to enhance its aggregated capacity [88-90]. 14 transmission over high-order latent PF-GIPOF passbands can be applied to enhance its 15 aggregated capacity [88-90]. 16 Previous works have studied, analyzed and modeled the PF-GIPOF frequency response 17 taking into account most of the parameters that affect the latter. Some noteworthy PF-GIPOF

Recent Advances in Wavelength-Division-Multiplexing Plastic Optical Fiber Technologies

1 losses. To establish the channel capacity comparative, a bit loading algorithm for discrete

2 multitone (DMT) modulation format over PF-GIPOF has been considered. New power

3 margin resulting from the additional losses considered in the system due to the WDM over

5 The resulting theoretical Shannon capacity of an optical fiber channel can be calculated if its

6 f3dB is known [14], modeled as a Gaussian low-pass filter. Therefore, from measurements of

7 frequency response of different PF-GIPOF lengths, 3dB bandwidths can be obtained, and so

8 their theoretical capacity limits operating in a single channel. This type of fiber has been

9 demonstrated to enable robust 2GbE (GbE, Gigabit Ethernet) and 10GbE baseband

10 transmission over short reach distances ranging from 25m up to 100m for different link

11 scenarios [87], even at OverFilled Launching (OFL) condition. These values are considered

13 formats, restricted mode launching schemes, equalization techniques or simultaneous data

4 POF approach are analyzed demonstrating the feasibility of PF-GIPOF WDM systems.

23

Previous works have studied, analyzed and modeled the PF-GIPOF frequency response taking into account most of the parameters that affect the latter. Some noteworthy PF-GIPOF frequency response measurements are shown in Fig. 19, in which a good agreement between experimental results and the theoretical curves predicted by the model is observed. This figure shows the measured and theoretical frequency responses for a 50m, 75m and 100m-long 62.5μm core diameter PF-GIPOF link with OFL condition and employing a Fabry-Perot laser source operating at 1300nm. Further details of the mathematical framework and experiments are reported on [91] for the benefit of the readers. 18 frequency response measurements are shown in Fig. 19, in which a good agreement 19 between experimental results and the theoretical curves predicted by the model is observed. 20 This figure shows the measured and theoretical frequency responses for a 50m, 75m and 21 100m-long 62.5µm core diameter PF-GIPOF link with OFL condition and employing a 22 Fabry-Perot laser source operating at 1300nm. Further details of the mathematical 23 framework and experiments are reported on [91] for the benefit of the readers.

25 Fig. 19. Measured (solid line) and theoretical (dashed line) electrical responses for different 26 62.5 µm core diameter PF-GIPOF lengths. **Figure 19.** Measured (solid line) and theoretical (dashed line) electrical responses for different 62.5 μm core diameter PF-GIPOF lengths.

24

27 From frequency response measurements, as shown in the above figure, the 3dB 28 baseband bandwidth can be easily identified and, therefore, the channel capacity can be 29 calculated. The PF-GIPOFs used are commercially available from Chromis Fiber with an From frequency response measurements, as shown in the above figure, the 3dB baseband bandwidth can be easily identified and, therefore, the channel capacity can be calculated. The PF-GIPOFs used are commercially available from Chromis Fiber with an attenuation of 55dB/km at 1300nm. For the frequency response measurements, a FP laser diode used as transmitter was externally AM modulated with a RF sinusoidal signal (up to 20GHz of

30 attenuation of 55dB/km at 1300nm. For the frequency response measurements, a FP laser

31 diode used as transmitter was externally AM modulated with a RF sinusoidal signal (up to

32 20GHz of modulation bandwidth) by means of an electro-optic (E/O) Mach-Zehnder

33 modulator (16GHz bandwidth). An InGaAs-photodetector (22GHz bandwidth) is used as

14 transmission over high-order latent PF-GIPOF passbands can be applied to enhance its 16 Previous works have studied, analyzed and modeled the PF-GIPOF frequency response 17 taking into account most of the parameters that affect the latter. Some noteworthy PF-GIPOF 18 frequency response measurements are shown in Fig. 19, in which a good agreement modulation bandwidth) by means of an E/O Mach-Zehnder modulator (16GHz band‐ width). An InGaAs-photodetector (22GHz bandwidth) is used as receiver. Bandwidth limitation from both transmitter and receiver can be neglected for links >50m. The channel capacity for each length, is calculated based on the transmission characteristics listed below, and is displayed in Table 1. For some applications, e.g. home network Ethernet transceiv‐ ers, eye safety operation is required and a limited averaged transmitted optical power of 0dBm has been considered.

**Table 1.** Calculated theoretical capacity over 62.5μm core diameter PF-GIPOF, at 1300nm.

23

fiber has been demonstrated to enable robust 2GbE (GbE, Gigabit Ethernet) and 10GbE baseband transmission over short reach distances ranging from 25m up to 100m for different link scenarios [87], even at OverFilled Launching (OFL) condition. These values are considered as an underneath estimation of the transmission limit of PF-GIPOFs as com‐ plex modulation formats, restricted mode launching schemes, equalization techniques or simultaneous data transmission over high-order latent PF-GIPOF passbands can be applied

Recent Advances in Wavelength-Division-Multiplexing Plastic Optical Fiber Technologies

1 losses. To establish the channel capacity comparative, a bit loading algorithm for discrete

2 multitone (DMT) modulation format over PF-GIPOF has been considered. New power

3 margin resulting from the additional losses considered in the system due to the WDM over

5 The resulting theoretical Shannon capacity of an optical fiber channel can be calculated if its

6 f3dB is known [14], modeled as a Gaussian low-pass filter. Therefore, from measurements of

7 frequency response of different PF-GIPOF lengths, 3dB bandwidths can be obtained, and so

8 their theoretical capacity limits operating in a single channel. This type of fiber has been

9 demonstrated to enable robust 2GbE (GbE, Gigabit Ethernet) and 10GbE baseband

10 transmission over short reach distances ranging from 25m up to 100m for different link

11 scenarios [87], even at OverFilled Launching (OFL) condition. These values are considered

12 as an underneath estimation of the transmission limit of PF-GIPOFs as complex modulation

410 Advances in Optical Fiber Technology: Fundamental Optical Phenomena and Applications

13 formats, restricted mode launching schemes, equalization techniques or simultaneous data

30 attenuation of 55dB/km at 1300nm. For the frequency response measurements, a FP laser

0 2 4 6 8 10 12 14 16 18 20 -18

**Figure 19.** Measured (solid line) and theoretical (dashed line) electrical responses for different 62.5 μm core diameter

From frequency response measurements, as shown in the above figure, the 3dB baseband bandwidth can be easily identified and, therefore, the channel capacity can be calculated. The PF-GIPOFs used are commercially available from Chromis Fiber with an attenuation of 55dB/km at 1300nm. For the frequency response measurements, a FP laser diode used as transmitter was externally AM modulated with a RF sinusoidal signal (up to 20GHz of

Frequency (GHz)

L=75m L=100m

L=50m

31 diode used as transmitter was externally AM modulated with a RF sinusoidal signal (up to

32 20GHz of modulation bandwidth) by means of an electro-optic (E/O) Mach-Zehnder

33 modulator (16GHz bandwidth). An InGaAs-photodetector (22GHz bandwidth) is used as

4 POF approach are analyzed demonstrating the feasibility of PF-GIPOF WDM systems.

Previous works have studied, analyzed and modeled the PF-GIPOF frequency response taking into account most of the parameters that affect the latter. Some noteworthy PF-GIPOF frequency response measurements are shown in Fig. 19, in which a good agreement between experimental results and the theoretical curves predicted by the model is observed. This figure shows the measured and theoretical frequency responses for a 50m, 75m and 100m-long 62.5μm core diameter PF-GIPOF link with OFL condition and employing a Fabry-Perot laser source operating at 1300nm. Further details of the mathematical framework and experiments

to enhance its aggregated capacity [88-90].

15 aggregated capacity [88-90].

26 62.5 µm core diameter PF-GIPOF lengths.

24

Normalized

PF-GIPOF lengths.

frequency

response, dBe

Theoretical Experimental However, this capacity analysis from the frequency response may result in large discrepancies at frequencies beyond the 3dB point and the PF-GIPOF has some latent high-order passbands [88]. Consequently, the Gaussian low-pass approximation reveals itself as a pessimistic approximation of the PF-GIPOF channel capacity, and expected capacity values of PF-GIPOF can be larger than those calculated in Table 1, even more if Restricted Mode Launching (RML) schemes are applied to the injection of light into the fiber.

25 Fig. 19. Measured (solid line) and theoretical (dashed line) electrical responses for different 27 From frequency response measurements, as shown in the above figure, the 3dB 28 baseband bandwidth can be easily identified and, therefore, the channel capacity can be 29 calculated. The PF-GIPOFs used are commercially available from Chromis Fiber with an On the other hand, DMT allows the possibility to allocate the number of bits and energy per subcarrier according to its corresponding signal-to-noise ratio (SNR), typically known as bitloading. To compute rate-adaptive bit-loading for the DMT over PF-GIPOF consideration Chow's algorithm has been implemented [92]. Initially, all subchannels were loaded with 4 information bits each. Table 2 shows the theoretical results on capacity when applying DMT over a single channel, based on the measured frequency response values up to 150m-long PF-GIPOFs. Compared to the results given in Table 1, it can be seen that for the shortest length (25m), the numerically computed capacity value is lower than theoretical counterpart. This result from bandwidth limitation of the external modulator bandwidth, considered in the computation. From lengths > 50m, the computed capacity is larger because the PF-GIPOF frequency response dominates over other bandwidth limitation factors. Due to the bandwidth limitation of the PF-GIPOF link itself, the signal-to-noise-ratio decreases for higher frequencies. Bit allocation resulting from the bit loading is shown in Fig. 20 for a 100m- and 150m-long PF-GIPOF single channel link, respectively.

Recent Advances in Wavelength-Division-Multiplexing Plastic Op **Table 2.** Theoretical DMT capacity over 62.5μm core diameter PF-GIPOF, at 1300nm. tical Fiber Technologies

Table 2.- Theoretical DMT capacity over 62.5µm core diameter PF-GIPOF, at 1300nm.

> 25m 577.1 50m 380.0 75m 276.9 100m 164.1 150m 77.1

> > Note: targeted BER=10-3

Numerical DMT over PF-GIPOF Capacity (Gbps)

Length (m)

8 capacity.

24 approach.

Fig. 20. Bit allocation per subchannel, resulting from bit-**Figure 20.** Bit allocation per subchannel, resulting from bit-loading at 100m and 150m.

5 POF WDM multiplexers and demultiplexers limits the available optical power budget 6 within the fiber link thus resulting in a bit-rate penalty. This is due to the fact that the OSNR 7 (Optical Signal-to-Noise ratio) of the system is being reduced, and so the fiber transmission

9 To establish a comparison between the PF-GIPOF single channel operation and its WDM 10 extension a 4-λ WDM approach has been considered. Regarding the latter, the PF-GIPOF 11 transmission capacity must be recalculated from: a) the new bit loading resulting from the 12 DMT modulation scheme and, b) the restriction on power margin resulting from the new 13 losses considered in the system due to the addition of the mux/demux devices in the optical 14 link. An insertion loss for a future PF-GIPOF 4-λ multiplexer/demultiplexer device of 15 around 2dB per channel [93, 94] is considered. Such a performance is better in terms of 16 insertion loss with respect to PMMA-GIPOF based splitters which can provide insertion 17 losses greater than 6dB (in the symmetric-case) [95]. Consequently, the power budget of the 18 WDM system, consisting of one PF-GIPOF based multiplexer or demultiplexer device at 19 each side of the optical fiber link, results in a 5dB power reduction per channel, if an optical 20 crosstalk of 1dB is also considered. It is worth mentioning that some authors have evaluated 21 power penalties close to 2.4dB when combining a 62.5µm core diameter PF-GIPOF and 22 WDM devices based on 50µm core diameter MMF [90]. Set of Fig. 21 shows the theoretical 23 bit loading including the aforementioned restriction in power budget due to the 4- λ WDM

loading at 100m and 150m. 1 It has been previously stated that for flexible high capacity GIPOF optical networks, 2 applying the WDM approach seems to be necessary. Apart from the physical transmission 3 characteristics of the PF-GIPOF, it is equally important to consider the optical components 4 introduced to deploy advanced WDM-based optical architectures. The addition of these It has been previously stated that for flexible high capacity GIPOF optical networks, applying the WDM approach seems to be necessary. Apart from the physical transmission characteris‐ tics of the PF-GIPOF, it is equally important to consider the optical components introduced to deploy advanced WDM-based optical architectures. The addition of these POF WDM multi‐ plexers and demultiplexers limits the available optical power budget within the fiber link thus resulting in a bit-rate penalty. This is due to the fact that the OSNR (Optical Signal-to-Noise ratio) of the system is being reduced, and so the fiber transmission capacity.

To establish a comparison between the PF-GIPOF single channel operation and its WDM extension a 4-λ WDM approach has been considered. Regarding the latter, the PF-GIPOF transmission capacity must be recalculated from: a) the new bit loading resulting from the DMT modulation scheme and, b) the restriction on power margin resulting from the new losses considered in the system due to the addition of the mux/demux devices in the optical link. An insertion loss for a future PF-GIPOF 4-λ multiplexer/demultiplexer device of around 2dB per channel [93, 94] is considered. Such a performance is better in terms of insertion loss with respect to PMMA-GIPOF based splitters which can provide insertion losses greater than 6dB (in the symmetric-case) [95]. Consequently, the power budget of the WDM system, consisting of one PF-GIPOF based multiplexer or demultiplexer device at each side of the optical fiber link, results in a 5dB power reduction per channel, if an optical crosstalk of 1dB is also considered. It is worth mentioning that some authors have evaluated power penalties close to 2.4dB when combining a 62.5μm core diameter PF-GIPOF and WDM devices based on 50μm core diameter MMF [90]. Set of Fig. 21 shows the theoretical bit loading including the afore‐ mentioned restriction in power budget due to the 4- λ WDM approach. 26 Optical Fiber

**Length (m) Numerical DMT over PF-GIPOF Capacity (Gbps)**

Fig. 20. Bit allocation per subchannel, resulting from bitloading at 100m and 150m.

It has been previously stated that for flexible high capacity GIPOF optical networks, applying the WDM approach seems to be necessary. Apart from the physical transmission characteris‐ tics of the PF-GIPOF, it is equally important to consider the optical components introduced to deploy advanced WDM-based optical architectures. The addition of these POF WDM multi‐ plexers and demultiplexers limits the available optical power budget within the fiber link thus resulting in a bit-rate penalty. This is due to the fact that the OSNR (Optical Signal-to-Noise

0 2 4 6 8 10 12 14 16 4

Frequency (GHz)

0 2 4 6 8 10 12 14 16 4

Frequency (GHz)

0 50 100 150 200 250

0 50 100 150 200 250

Subcarrier number

25

**25m** 577.1 **50m** 380.0 **75m** 276.9 **100m** 164.1 **150m** 77.1

412 Advances in Optical Fiber Technology: Fundamental Optical Phenomena and Applications

Note: targeted BER=10-3

Table 2.- Theoretical DMT capacity over 62.5µm core diameter PF-GIPOF, at 1300nm.

> 25m 577.1 50m 380.0 75m 276.9 100m 164.1 150m 77.1

> > Note: targeted BER=10-3

Numerical DMT over PF-GIPOF Capacity (Gbps)

Length (m)

8 capacity.

24 approach.

Recent Advances in Wavelength-Division-Multiplexing Plastic Op **Table 2.** Theoretical DMT capacity over 62.5μm core diameter PF-GIPOF, at 1300nm. tical Fiber Technologies

5

6

L=100m

L=150m

**Figure 20.** Bit allocation per subchannel, resulting from bit-loading at 100m and 150m.

ratio) of the system is being reduced, and so the fiber transmission capacity.

Bit allocation

 (bits)

7

8

9

1 It has been previously stated that for flexible high capacity GIPOF optical networks, 2 applying the WDM approach seems to be necessary. Apart from the physical transmission 3 characteristics of the PF-GIPOF, it is equally important to consider the optical components 4 introduced to deploy advanced WDM-based optical architectures. The addition of these 5 POF WDM multiplexers and demultiplexers limits the available optical power budget 6 within the fiber link thus resulting in a bit-rate penalty. This is due to the fact that the OSNR 7 (Optical Signal-to-Noise ratio) of the system is being reduced, and so the fiber transmission

5 6

Bit allocation

7 8 9

 (bits)

9 To establish a comparison between the PF-GIPOF single channel operation and its WDM 10 extension a 4-λ WDM approach has been considered. Regarding the latter, the PF-GIPOF 11 transmission capacity must be recalculated from: a) the new bit loading resulting from the 12 DMT modulation scheme and, b) the restriction on power margin resulting from the new 13 losses considered in the system due to the addition of the mux/demux devices in the optical 14 link. An insertion loss for a future PF-GIPOF 4-λ multiplexer/demultiplexer device of 15 around 2dB per channel [93, 94] is considered. Such a performance is better in terms of 16 insertion loss with respect to PMMA-GIPOF based splitters which can provide insertion 17 losses greater than 6dB (in the symmetric-case) [95]. Consequently, the power budget of the 18 WDM system, consisting of one PF-GIPOF based multiplexer or demultiplexer device at 19 each side of the optical fiber link, results in a 5dB power reduction per channel, if an optical 20 crosstalk of 1dB is also considered. It is worth mentioning that some authors have evaluated 21 power penalties close to 2.4dB when combining a 62.5µm core diameter PF-GIPOF and 22 WDM devices based on 50µm core diameter MMF [90]. Set of Fig. 21 shows the theoretical 23 bit loading including the aforementioned restriction in power budget due to the 4- λ WDM

1 **Fig. 21**. Theoretical bit loading for the 4- λ WDM approach over PF-GIPOF. (a) 100m ; (b)

2 150m. **Figure 21.** Theoretical bit loading for the 4- λ WDM approach over PF-GIPOF. (a) 100m ; (b) 150m.

3

16

**BIT**

**RATE**

**(Gbps)**

4 The corresponding aggregated WDM capacity is summarized in **Fig. 22** and compared to 5 the single channel operation. The achievable capacity of a single-λ WDM system does not 6 reach the best single channel results. For a single channel operation more than twice the 7 capacity compared to the single-λ capacity in the WDM approach. Therefore, assuming a 4-λ 8 WDM system using the full available optical power and with similar bit rate transmission 9 performances in each channel the total achievable capacity would overcome the OSNR and 10 bit-rate limitation due to the optical losses introduced in the power budget of the system. It 11 is also noticed that for longer PF-GIPOF lengths the ratio between transmission capacities 12 for single channel and single- λ operation diminishes. This fact is attributed to differential 13 mode attenuation (DMA) together with mode coupling effects in PF-GIPOF that leads to a 14 sub-linear increase dependency of the fiber bandwidth regarding its length. This favours the 15 resulting transmission capacity. The corresponding aggregated WDM capacity is summarized in Fig. 22 and compared to the single channel operation. The achievable capacity of a single-λ WDM system does not reach the best single channel results. For a single channel operation more than twice the capacity compared to the single-λ capacity in the WDM approach. Therefore, assuming a 4-λ WDM system using the full available optical power and with similar bit rate transmission perform‐ ances in each channel the total achievable capacity would overcome the OSNR and bit-rate limitation due to the optical losses introduced in the power budget of the system. It is also noticed that for longer PF-GIPOF lengths the ratio between transmission capacities for single channel and single- λ operation diminishes. This fact is attributed to differential mode attenuation (DMA) together with mode coupling effects in PF-GIPOF that leads to a sub-linear increase dependency of the fiber bandwidth regarding its length. This favours the resulting transmission capacity.

12345

**25m 50m 75m 100m 150m**

**Single channel WDM extension** 0 2 4 6 8 10 12 14 16 4

Frequency (GHz)

0 50 100 150 200 250

Subcarrier number

2 150m.

L=100m

Bit allocation

 (bits)

15 resulting transmission capacity.

3

16

3

9

8 23.

26 Optical Fiber

(a) (b)

1 Fig. 21. Theoretical bit loading for the 4- λ WDM approach over PF-GIPOF. (a) 100m ; (b)

L=150m

Bit allocation

 (bits)

0 2 4 6 8 10 12 14 16

Frequency (GHz)

27

0 50 100 150 200 250

Subcarrier number

4 The corresponding aggregated WDM capacity is summarized in Fig. 22 and compared to 5 the single channel operation. The achievable capacity of a single-λ WDM system does not 6 reach the best single channel results. For a single channel operation more than twice the 7 capacity compared to the single-λ capacity in the WDM approach. Therefore, assuming a 4-λ 8 WDM system using the full available optical power and with similar bit rate transmission 9 performances in each channel the total achievable capacity would overcome the OSNR and 10 bit-rate limitation due to the optical losses introduced in the power budget of the system. It 11 is also noticed that for longer PF-GIPOF lengths the ratio between transmission capacities 12 for single channel and single- λ operation diminishes. This fact is attributed to differential

**Figure 22.** Comparison of single channel operation and WDM extension over 62.5μm core diameter PF-GIPOFs. 4 On the other hand, capacity values for a 50µm core diameter PF-GIPOF following the same

On the other hand, capacity values for a 50μm core diameter PF-GIPOF following the same procedure and under the same constraints are also shown (from its frequency response measurements). Greater capacities can be achieved as increasing the core diameter due to the presence of strong mode coupling effects and less modal noise effect, as shown in Fig. 23. 5 procedure and under the same constraints are also shown (from its frequency response 6 measurements). Greater capacities can be achieved as increasing the core diameter due to 7 the presence of strong mode coupling effects and less modal noise effect, as shown in Fig.

10 Fig. 23. Comparison of single channel operation and WDM extension over a 100m- and **Figure 23.** Comparison of single channel operation and WDM extension over a 100m- and 150m-long link, at 1300nm, for different core diameter PF-GIPOFs.

13 Applying WDM can further enhance the transmission capacity via plastic optical fiber (POF) 14 systems. This chapter is intented to bridge the gap of WDM POF-based networks for in-15 home deployments, where POFs have become a competitive and low-cost solution as a 16 physical medium infrastructure. In-home link lengths are relatively short thus leading to a 17 more relaxed requirements regarding bandwidth x length product and attenuation per unit 18 length, respectively. However, due to the continuous increase of bit-rate demands from end-19 users for multimedia services new techniques oriented to overcome the POF bandwidth 20 limitation are being required. Beyond complex modulation formats in which the main goal 21 is to provide a single channel communication link with a high spectral efficient (i.e. bit/Hz), 22 one potential solution to expand the usable bandwidth of POF systems is to perform 23 multiple channels over a single POF. This is known as the wavelength division multiplexing

25 Nowadays, WDM is well-established in the infrared transmission windows for silica optical 26 fibers, but this technique needs to be adapated to VIS for POFs due to their spectral 27 attenuation behavior. And novel WDM POF devices and network topologies are necessary 28 to a final success of POF in-home penetration. These devices include POF

11 150m-long link, at 1300nm, for different core diameter PF-GIPOFs.

12 7. Discussion and Conclusions

24 (WDM) approach.


**4. Recent applications of simulated boundary layer flows**

Some recent wind engineering applications of the ABL simulations are presented. In general, this type of applications was referred to wind action on civil structures, but new studies related with ambient evaluation, urban design, and wind energy are being developed. In this work, experimental studies related to

high-rise and low building, atmospheric pollutant dispersion, rain-wind action on structures, and the turbulent wake of wind turbines will be shown.

#### **4.1 Wind tunnel study of the local aerodynamic loads on a high-rise building**

A study of the wind loads on a high-rise building was realized in the Prof. Jacek Gorecki wind tunnel using a 1/400 scale model [13]. The building is 240 m high; it is named Infinity Tower and it is built in Camboriu, RS, Brazil. Local mean, maximum, minimum, and *rms* pressure coefficients were measured by means of a Scanivalve pressure system.

Atmospheric boundary layer simulations similar to the full-depth simulation described in Section 2.2 were used. Some characteristics of the incident wind were modified according to the terrain features upwind model. Thus, two different mean velocity profiles were used according to the incident wind direction. Aerodynamic details were reproduced in the building model (**Figure 14**), and fluctuating local pressures in 511 tower points for 24 wind directions were measured. The effects of urban vicinity and topographic surrounding were considered by means of a detailed modeling.

Some considerations referred to the extreme values approximation were realized in this work. The graph in **Figure 14** illustrates a fluctuating pressure registered at a measurement point. Mean values associated with different duration times of wind gusts (1, 4, and 16 s full-scale) can be obtained by means of this technique, and statistical extreme value analysis can be applied to improve the calculation of local wind loads.

#### **4.2 Wind tunnel study of the aerodynamic loads on a low structure**

There exist structures that due to its size, complexity, or importance justify turning to wind tunnel tests in order to optimize the structural design. A wind tunnel study of the Ezeiza Airport located in that village of Buenos Aires was realized in 2010 [14]. The study comprised the determination of both local and global wind actions.

It was carried out at the Prof. Jacek Gorecki wind tunnel of the UNNE, using different 1/200 scale models (**Figure 15**) that were compatible with the scale factor of the wind simulated in the wind tunnel. The real neighbor conditions were taken into account as well as the turbulent features of the atmospheric wind in agreement with the type of terrain. In this case, an ABL flow similar to the part-depth simulation described in Section 2.3 was used.

In addition to the mean load coefficients, peak coefficients were obtained by extreme value analysis using the Cook and Mayne method [15]. It is shown how

#### **Figure 14.**

*High-rise building scale model in the test section of the UNNE wind tunnel and detail of the fluctuating local pressure.*

**137**

**Figure 15.**

*Physical Models of Atmospheric Boundary Layer Flows: Some Developments and Recent…*

the application of this kind of analysis is influenced in this particular case and, in general terms, how the design of structures could be optimized by means of this

The prediction of the aerodynamic performance of concrete cable-stayed bridges can be realized by means of wind tunnel testing. The analyses of the structural stability under the aerodynamic actions must be included into the design verifications. The structural characteristics of cable-stayed bridges and the dynamic aspects of the aerodynamic actions implicate the application of special analyses of aerodynamic stability including flutter and vortex shedding. The determination of

the critical velocity is very important in the design of cable-stayed bridges.

models of the bridge deck and towers. Aerodynamic coefficients varying with wind incidence for the deck may be easily measured with pressure systems or force

A sectional model is used for the dynamic modeling of the deck. The sectional model must be ideally rigid to avoid the influence of the own model vibration in the experimental results. Details of the bridge deck must be represented. **Figure 16**, left, shows a picture of a 1:60 dynamic sectional model mounted in the test section of the wind tunnel of Prof. Joaquim Blessmann of the UFRGS. The deck corresponds to the Octávio Frias de Oliveira cable-stayed bridge, and the obtained results permitted to observe the differences in the deck

The relevant parameters in aeroelastic modeling are length, specific mass (density), and acceleration. The design of a full-aeroelastic model must reproduce the aerodynamic and dynamic characteristics of the structure of interest. The flow and geometric similarities must be respected and the Reynolds number considered for aerodynamic similarity. The most relevant frequencies and mode shapes must be reproduced to obtain dynamic similarity. The design of full-aeroelastic model includes bridge deck, cables, masts, and end supports. The complexity of this type of model can be observed in **Figure 16**, right, showing the full-aeroelastic model, the Octávio Frias de Oliveira cable-stayed bridge tested at the wind tunnel Prof.

The incident wind used to test sectional models is normally a turbulent uniform flow similar to the flow obtained with empty tunnel out the wall boundary layer and described in Section 2.1. Meanwhile, the full-aeroelastic model of the Octávio Frias de Oliveira cable-stayed bridge was tested using a full-depth boundary layer simulated

*Ezeiza Airport 1/200 models (partial) in the test section of the UNNE wind tunnel.*

First, static forces are obtained through force balance measurements for simple

*DOI: http://dx.doi.org/10.5772/intechopen.86483*

vertical and torsional responses [16].

Joaquim Blessmann of the UFRGS [17].

**4.3 Aerodynamic analysis of cable-stayed bridges**

kind of studies.

balance.

the application of this kind of analysis is influenced in this particular case and, in general terms, how the design of structures could be optimized by means of this kind of studies.


Author details

Natália Moya Rodrigues Pereira1 and Marcos Eduardo Scheicher2 \*

1 Biosciences Institute, UNESP, Rio Claro, São Paulo, Brazil

2 Physiotherapy and Occupational Therapy Department, UNESP, Marília, São Paulo, Brazil

\*Address all correspondence to<EMAIL_ADDRESS>
© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


**Preface to "Analytical Methods for Toxics Determination"**

In recent decades, but especially in recent years, the rapid spread of toxic species has occurred in all matrices. Evidently, these contaminants, both of inorganic and organic origin, represent very dangerous pollutants for human health, owing to their bioaccumulation and toxicity. They result from almost all human activities, such as, for example, industries, agriculture, vehicular traffic, and urban heating.

Considering that often these species occur in the various real matrices at extremely low concentrations, the various analytical methodologies must evidently demonstrate their possible application by verifying their accuracy and integrity at all steps: sampling, sample preparation, instrumental measurement, and statistical data processing.

Another extremely important aspect concerns the fact that the development of new analytical methodologies and the contemporary lack or inadequacy of regulations regarding the determination of toxic species in the most varied matrices can obviously give, to the legislator, the possibility to update and improve the abovementioned regulations.

This volume aims to attract contributions on all aspects linked to the different analytical methods used for the determination of toxic species in the most varied matrices—food, environmental, forensic, biological, and so on—focusing particularly on the fundamental parameters of interest to set up an analytical procedure, such as precision and trueness (that together give accuracy), the limits of detection and quantification, selectivity, and especially sensitivity.

> **Clinio Locatelli , Marcello Locatelli, Dora Melucci** *Editors*

#### *Article*


3.4 Conflict between phase equilibria and critical line description in binary mixtures

Reliable models for thermodynamic and phase behavior description of binary mixtures are facing problems of adequate estimation of the binary interaction parameters from the restricted set of VLE data. In spite of availability of strict

Azeotrope-Breaking Potential of Binary Mixtures in Phase Equilibria Modeling DOI: http://dx.doi.org/10.5772/intechopen.83769

relationships to obtain from EoS model, the different derivatives of thermodynamic values, for instance, the prediction of critical lines from the EoS with parameters restored from VLE data, is questionable due to diverse sources of uncertainty in both the used models and experimental data.

For illustration, we consider thermodynamic and phase behavior of water-carbon dioxide system near the critical point of water. Experimental data on p-ρ-T-x properties have been taken from [18]; data on phase equilibria and critical curve have been extracted from [19, 20]. The critical lines have been calculated using algorithm developed in [21]. Phase equilibria calculations have been carried out with Michelsen and Mollerup method [22] for cubic EoS. We performed phase equilibria and critical line calculations for the RK EoS with binary interaction parameters k12 and l12 used in standard mixing rules

$$\begin{aligned} b &= b\_{11}\mathbf{x}^2 + l\_{12}\mathbf{x}(\mathbf{1}-\mathbf{x})\left(\frac{b\_{11}+b\_{22}}{2}\right) + b\_{22}(\mathbf{1}-\mathbf{x})^2\\ a &= a\_{11}\mathbf{x}^2 + k\_{12}\mathbf{x}(\mathbf{1}-\mathbf{x})\sqrt{a\_{11}a\_{22}} + a\_{22}(\mathbf{1}-\mathbf{x})^2 \end{aligned} \tag{14}$$

and restored from different crisp convolution schemes. For simplicity, the results of calculation for phase equilibria and critical line are presented in Figures 5 and 6 only for most selected compromise schemes. The challenge of conflict between parameters retrieved from different sections of thermodynamic surface remains important for practically all EoS including sophisticated multiparameter equation of

## Figure 5.

Critical line of Н2О▬СО2 system [21]. ● Experimental data ▬ Best fit of VLE data °°°° von Neumann's coalition scheme [16] ─ ─ Best fit of critical curve.

where wi are the weight coefficients, K0

Distillation - Modelling, Simulation and Optimization

KCð Þ¼ X min ∑

KCð Þ¼ X minYn

is extenuation of uncertainty driving from vagueness.

find the values Х and λ that maximize λ that is subject to

i¼1

�

n i¼1

scalar nonlinear programming problem:

Neumann coalition scheme [16].

3.3 Fuzzy convolution scheme

ing of phase equilibria.

mixtures

78

is acceptable for decision-maker remaining in the coalition, and KC is a global tradeoff criterion. If it will be possible to come to an agreement about preference (weight) for each criterion, then the final decision can be found as a solution of

wi Kið Þ� X K0

If no concordance among decision-makers is concerning the weight choice, then arbitration network is preferable. Classical arbitration scheme was derived mathematically rigorously by Nash but very often criticized from common sense [16]:

Kið Þ� X K0

All crisp convolution schemes under discussion try to reduce an uncertainty deriving from conflict among different criteria in the Pareto domain. The next step

Zadeh [14] put the theory of fuzzy sets forward with explicit reference to the vagueness of natural language, when describing quantitative or qualitative goals of the system. Here we assume that local criteria as well as different constraints in the ill-structured situation can be represented by fuzzy sets. A final decision is defined by the Bellman and Zadeh model [17] as the intersection of all fuzzy criteria and constraints and is represented by its membership function μ(Х) as follows:

This problem is reduced to the standard nonlinear programming problems: to

λ≤ μKið Þ X , i ¼ 1, 2, …, n;

λ≤μCjð Þ X , j ¼ 1, 2, …, m

Here, by way of illustration, the new approach was introduced to estimate the Redlich-Kwong EoS parameters for simultaneous description of the phase equilibria and critical line data in binary mixtures, thermodynamically consistent description of the inhomogeneous data, and other inconsistency problems arising in the model-

3.4 Conflict between phase equilibria and critical line description in binary

Reliable models for thermodynamic and phase behavior description of binary mixtures are facing problems of adequate estimation of the binary interaction parameters from the restricted set of VLE data. In spite of availability of strict

� �

i

μð Þ¼ Х μКð Þ Х μСð Þ Х , X ∈ XP: (12)

In terms of game-theoretical approach, such coalition is defined as the von

� � � � �

i

i is an infimum of the desired result that

�, X ∈ XP: (10)

�, X ∈ XP: (11)

(13)

for imidazolium (IL)-based ionic liquids and industrial refrigerant mixtures. IL doping leads to the breaking of azeotrope in binary refrigerant mixtures that open the way for the azeotrope refrigerant mixture separation technologies in order to

Azeotrope-Breaking Potential of Binary Mixtures in Phase Equilibria Modeling

Applying the cubic model of the equation of state, only the critical properties and acentric factor of the individual components in mixtures are sufficient to define

The degenerated critical azeotrope point is a boundary state separating azeotrope and non-azeotrope and produces the limit of the critical azeotrope at xi ! 0 or at xi ! 1. The solution of the thermodynamic equation system for a degenerated

> 1 � Z4 1 � Z3

c2=Pc2 � 2 1ð Þ � k12

T2

c2=Pc2 þ T2

where the upper signs + or � correspond to x2 = 0 and the lower signs - to x2 = 1,

To define the azeotropic states, the parameters Zi can be expressed via critical (pseudocritical) temperatures Tci and pressures Pci of pure components and empirical binary interaction parameters k12 and l12 (17). The unlike pair interaction parameters Z2 and Z4 (i.e., a12 and b12) can be estimated solving simultaneously the system of Eqs. (17) for the given Z1 and Z3 (or the set of pure component constants a11, b11, a22,

> Z3 ¼ Tc2=Pc2 � Tc1=Pc1 Tc2=Pc2 þ Tc1=Pc1

Z4 ¼ Tc1=Pc1 � ð Þ 1 � l12 ðTc1=Pc1 þ Tc2=Pc2Þ þ Tc2=Pc2 Tc2=Pc2 þ Tc1=Pc1

The boundary between azeotrope and zeotrope states in Z1–Z2 plane at fixed values of Z3 and Z4 is a straight line. The definition of azeotropic and zeotropic

Double azeotropic phenomena can be observed in the global phase diagram only in the vicinity of the crossing point of two straight azeotropic borders in (Z1, Z2)

2 þ Ψ þ þ Ψ � , where Ψ � ¼ 1 � Z4

1 ¼ Ψ þ þ Ψ �

� 1

� �Λ, (16)

Tc1Tc2 ffiffiffiffiffiffiffiffi pc1pc2 p þ T2

c1=Pc1

1 � Z3

� 1 � �Λ: (18)

c1=Pc1

, (17)

:

,

ð15Þ

remove the environmentally harmful substances.

DOI: http://dx.doi.org/10.5772/intechopen.83769

the phase behavior in the interested sector of the parameters.

gives the following relationship for dimensionless parameters Zi:

b22) that are determined from the critical parameters of the components:

, Z2 ¼ T2

Z2 ¼ ∓Z1 � ð Þ 1 � Z1

4.1 Azeotrope-breaking criteria

critical azeotrope [5–7, 9]

Z1 ¼ T2

plane (Figures 8 and 9):

Z2i ¼ Ψ þ � Ψ �

81

2 þ Ψ þ þ Ψ � , Zi

T2

c2=Pc2 � T2

c2=Pc2 þ T2

states for refrigerants is depicted in Figure 7.

4.2 Double azeotrope-breaking criterion

c1=Pc1

c1=Pc1

respectively.


**Abstract**

Electronic design engineers struggle continuously to obtain a satisfactory trade-off between item performance and cost. On one hand, they would like to employ the best material and components available on the market and opt for time-consuming manufacturing processes in order to obtain high-performance parts. On the other hand, such choice would lead to high recurring cost making the part less attractive in the market. In this scenario, industrial engineering team becomes a crucial industrial entity. It assists the Design Engineers by providing design rules or guidelines. This guidance is intended to provide recommendation to the development team in order to define what is technically feasible and achievable inside an industrial process contest. These rules should not be too strict in order to guarantee acceptable part performance and therefore market attractiveness. The rules contain guidelines on mechanical, process and material aspects. This chapter will focus on design for manufacturing of electro-mechanical parts for the aerospace industry typically being a high-end and high-performance part. Nevertheless, cost and time remain a key aspect to guarantee. The effects of such rules on mechanical and electrical performance will be highlighted and discusses, with a specific focus ion high frequency electrical assemblies (1–30 GHz). It will also contain a review on microelectronic production techniques that impact on the part's electrical performance.

**Keywords:** design guidelines, design for assembly, design rules, aerospace products, avionics, preferred part list, prototyping, additive manufacturing, continuous improvement, six sigma, product manufacturing figure


**3.4. Discussion**

of network access including wireless and VPN connections. As a proxy, the IAS forwards

To start with fair baselines both EAP-CRA and Edu-roaming were implemented in LAN but in different IP subnets. Moreover to magnify the delay of authentication for Edu-roaming another setup on Internet was also implemented. The first topology is the Edu-roaming model. Since this is a proprietary model it was implemented on five Microsoft IAS that was installed on the Java virtual box. Because the Edu-roaming has federation level RADIUS servers and one root RADIUS server, we implemented five RADIUS servers in all. Two of the RADIUS servers were for the home and the foreign networks, two as the federation level RADIUS servers and the last one as the Root authentication server. Figure 6 shows the topology for Edu-

The second scenario was an implementation of Edu-roaming and EAP-CRA servers on the Internet. Five servers were installed at various remote sites in Brisbane Australia. In all scenarios, the time difference between the first RADIUS request message and the last RADIUS accept message was used for comparing the time taken for authentication. Ta‐ bles 4 and 5 lists the average times obtained on the LAN and Internet implementations

authentication and accounting messages to other RADIUS servers.

116 Selected Topics in WiMAX

**Figure 6.** Experimental Edu-roam Setup on LAN

roaming that was implemented by us.

over forty different trials.

Figure 7 confirms the potential of the EAP-CRA approach compared to the other methods. The main advantage of the EAP-CRA authentication mechanism is the use of only two messages to authenticate a wireless device in a FOREIGN network. Although the time taken between the FOREIGN AAA server and the HOME AAA server may vary depending on the traffic and/ or capacity of the wired network, the use of only two messages in a FOREIGN network makes CRA authentication mechanism very much reliable compared to other available techniques. Further, even if the foreign network uses a less secure authentication mechanism, it still will not affect the EAP-CRA supplicants since their PMKs are supplied by the HOME AAA servers not-withstanding the limitations of the foreign network.

Another significant advantage of the EAP-CRA is its reliance on the HOME security credentials to secure its clients in the foreign network. Hence, it can be assured that the EAP-CRA clients will have the same security guarantee as in their home network in the foreign network. Further, in the case of EAP-TLS authentication with CA-signed PKI certificates, clients will need only a single set of certificates signed by the CA accepted by the HOME AAA server. There will be no need for clients to carry a number of different certificates to authenticate with different networks. Hence, in this context, the EAP-CRA facilitates EAP-TLS authentication and makes it more practical and viable.

Although there are many other techniques proposed for distributed authentication, the advantages of the EAP-CRA technique is its simplicity, robustness and versatility. Unlike many other systems that require additional components such as a token management system or federation of RADIUS servers, the EAP-CRA system depends only on the existing infra‐ structure, hence, assuring simplicity. The use of existing CA-signed PKI certificates without necessitating other authentication mechanisms such as tokens or smart cards enables the EAP-CRA system to be confined. Further, EAP-CRA system is not limited to WLAN or WiMAX, it can be effectively used with any wireless network, harnessing the unique security features of that particular wireless network. Furthermore, the authentication mechanism (EAP-TLS, EAP-TTLS, EAP-PEAP etc.) used by the wireless network does not influence the EAP-CRA system because it does use any form of mappings between these protocols and the EAP-CRA protocol.

server. The signature of a server by the private key authenticates the server to the other server and the public key encryption ensures privacy of the transmitted message. To implement the transmitting of the messages between two authentication servers EAP-CRA suggests using of RADIUS protocol by creating a new attribute field which encapsulates the EAP-CRA message. The EAP-CRA message is the double encrypted message which will be located in the value

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On the negative aspect, the effectiveness of EAP-ERP will depend on the mutual trust estab‐ lished between the participating AAA servers. If the AAA servers do not have any form of prior agreement, it will be up to the discretion of a FOREIGN AAA server whether to accept

The Enhanced CRA protocol provides authentication in two modes; Full Authentication and Re-Authentication. With regard to mutual authentication CRA uses RADIUS servers as suggested in IEEE 802.1x. CRA suggests direct communication between radius servers by prearranged agreement or the servers could find each other dynamically. In case the RADIUS servers do not have a pre-arranged agreement they can use their CA-signed PKI certificates to

All AAA servers that participate in the CRA must possess a CA-signed PKI certificate and be capable of obtaining the CA-signed PKI certificates of other participating AAA servers. Assuming that all AAA Servers that participate in the CRA are in possession of their CA-signed PKI certificates, the CRA protocol can communicate between the FOREIGN and the HOME

Initial assumption of the CRA protocol is that each mobile Node is primarily associated with a Network, which in this context is referred to as the Home network. The security of the Home network and the authentication mechanism used must be robust. It is assumed that an EAP method such as EAP-TLS, EAP-PEAP or EAP-TTLS is used in the Home network. Therefore the values for MSKName, MSK, EMSK and the Time To Live (TTL) for these keys are available for the Peer. Since some of the EAP methods utilize CA-signed PKI certificates to authenticate and secure the communication CRA extends it to add more flexibility to certificate based authentication. We have chosen WLAN as the medium to illustrate the components and messaging of EAP-CRA. Firstly, both the peer and the Foreign Access Point (FAP) discover their capabilities and decide on a suitable protocol to authenticate each other. If both parties are capable of EAP-CRA then the FAP will compose an EAP request message to solicit the identity of the Peer. It should be mentioned that the key for hashing function is generated from

In an unknown network, the peer will first check if the TTL of MSK is still valid. Expired MSK will lead to a failed authentication and will prompt a full authentication. The peer will be

filed of the RADIUS attribute.

or deny an EAP-CRA request.

ascertain trust between servers.

**4.1. Full EAP-CRA authentication**

AAA servers securely.

the EMSK.

**4. Enhancements to EAP-CRA**

**Figure 7.** Comparison of Authentication Times

The above discussions illustrate the significance of the CRA approach and emphasize the need for a fast authentication mechanism as opposed to a hierarchical mechanism like the Edu-roam. Although Microsoft IAS provides a similar infrastructure to that of EAP-CRA, it is restricted to Microsoft EAP-PEAP authentications. In contrast EAP-CRA does not rely on any particular authentication protocol. It is designed to reap the maximum leverage of the authentication mechanism that is best for the particular home environment. Hence, when a hand-held device roams in a foreign network it will have the same security guarantee as in the home network.

EAP-CRA is differentiated by other EAP methods in the aspects of communication scope by covering both the foreign and the home authentication servers. Other EAP methods such as EAP-TLS or EAP-TTLS do not consider server to server communication. EAP-CRA provides authentication and communication privacy between the foreign and the home authentication servers based on public key infrastructure. The home and foreign servers have got the public certificates of each other. EAP-CRA encrypts the authentication message twice and then sends it to the other foreign server ensuring privacy and authenticity of the message. Any message from home server will first be signed by the home server's private key and then by the foreign servers public key. Same process happens if the foreign server sends a message to the home server. The signature of a server by the private key authenticates the server to the other server and the public key encryption ensures privacy of the transmitted message. To implement the transmitting of the messages between two authentication servers EAP-CRA suggests using of RADIUS protocol by creating a new attribute field which encapsulates the EAP-CRA message. The EAP-CRA message is the double encrypted message which will be located in the value filed of the RADIUS attribute.

On the negative aspect, the effectiveness of EAP-ERP will depend on the mutual trust estab‐ lished between the participating AAA servers. If the AAA servers do not have any form of prior agreement, it will be up to the discretion of a FOREIGN AAA server whether to accept or deny an EAP-CRA request.


**7. Effect of fish oil (Omega3) and olive oil on membrane fluidity, ATPase activity in relapsing‐remitting multiple sclerosis.**

The mechanism of action for omega‐3 PUFAs is suggested to be attributed to immunomodu‐ lation and antioxidant action [24]. For instance, omega‐3 PUFAs decrease the production of inflammatory mediators (eicosanoids, cytokines, and ROS) and the expression of adhesion molecules. They both act directly by replacing AA as an eicosanoid substrate and inhibiting AA metabolism and indirectly by altering the expression of inflammatory genes through effects on transcription factor activation. Omega‐3 PUFAs also give rise to anti‐inflammatory mediators (resolvins and protectins) [25]. Effects of resolvins and protectins include reducing neutrophil trafficking, cytokine, and ROS regulation and lowering the magnitude of the inflammatory response [26].

Previously, we developed a twelve‐month randomized double‐blind controlled clinical trial in 50 patients with relapsing‐remitting MS. Patients received an oral dose of 4 g/day of fish oil (containing a total of 800 mg of EPA and 1600 mg of DHA) or olive oil. Fasting blood samples were collected at baseline and after 6 and 12 months of the trial, in order to evaluate the effect of consumption of omega‐3 PUFAs on some markers of oxidative stress at the peripheral level. The initial findings of this work were the decrease in serum levels of TNFα, IL‐1β, IL‐6, and nitric oxide metabolites compared with the placebo group [27].

On the other hand, after 12 months of intervention, supplementation with omega‐3 PUFAs significantly enhanced the quantities of serum omega‐3 highly unsaturated fatty acids compared with baseline values. Additionally, the levels of medium‐chain monounsaturated fatty acids were significantly decreased. The olive oil supplementation induced minor decreases in EPA and DHA levels after 12 months of intervention. There were significant increases in both EPA and DHA in the group given fish oil supplementation compared to the control group receiving olive oil. These increases were associated with a concomitant decrease in AA. Consequently, the omega‐3 fatty acid index in the fish oil group increased significantly, and the ratios of n‐6/n‐3 and AA/EPA were decreased [28].

No differences in glutathione reductase activity and content of reduced glutathione, oxidized glutathione, and oxidized/reduced glutathione ratio were seen after 12 months of supplemen‐ tation with omega‐3 PUFAs. However, a trend in favor of omega‐3 PUFAs supplementation was observed in GSSG levels and glutathione reductase activity at 12 months of intervention between the study groups [28].

A steady decrease in mitochondrial ATPase activity in platelets was observed in the groups given omega‐3 fatty acid and the control group receiving olive oil. Membrane fluidity of platelets was significantly reduced in MS patients. Interestingly, a significant increase in platelet membrane fluidity was observed in the groups receiving omega‐3 fatty acid and the control group receiving olive oil. As well, the fluidity of erythrocyte membranes was un‐ changed for both treatments (Unpublished results).

Epidemiological and experimental studies suggest an increased incidence of MS in popula‐ tions with a high intake of saturated fats mainly from animal sources. Therefore, by consuming a diet high in fatty acids, without an appropriate number of unsaturates, a shift is produced in the integrity and functionality of the membrane [29]. An optimal balance in the consumption of fatty acids includes 35% polyunsaturated fatty acids and 65% saturated fatty acids, and the appropriate proportion of PUFA to maintain membrane balance is 50% omega‐3 with 50% omega‐6. The above ratio was a factor that inactivated the CD4 autoreactive cells in the CNS, a phenomenon that prevents the production of proinflammatory cytokines and free radicals [30].

Membrane fluidity depends on the temperature, the ratio of saturated/PUFA fatty acids, the presence of "lipid rafts," and the proportion of cholesterol present at the membrane [31]. Previous studies in patients with rheumatoid arthritis had increased cell membrane rigidity compared to membranes from those receiving immunomodulatory treatment. Our results showed diminished platelet membrane fluidity in MS patients and that proper membrane fluidity is restored with treatment of omega3 PUFAs. The increase in platelet membrane fluidity is directly related to the incorporation of PUFA's. Furthermore, the increase in membrane fluidity is accompanied with a significant decrease in mitochondrial ATPase activity. This ensures that the activity of ATP synthesis in mitochondria remains elevated.


**Author details**

Linda Bitsch1 , Silva Atoyan2 , Barbara Richter1 \*, Jon Hanf1 and Taras Gagalyuk3

1 Hochschule Geisenheim University, Geisenheim, Germany

2 Armenian National Agrarian University, Yerevan, Armenia

3 Leibniz Institute of Agricultural Development in Transition Economies (IAMO), Halle (Saale), Germany

\*Address all correspondence to<EMAIL_ADDRESS>
© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


**3.2 Distribution**

*Drug Repurposing - Hypothesis, Molecular Aspects and Therapeutic Applications*

hydrolase of human blood [18].

colorectal cancer [20].

process [21].

transit time.

inhibition compared to oral dosing [19].

aspirin rather than salicylic acid. A complete picture of absorption track of aspirin is represented in **Figure 4** [16]. Approximately 70% of aspirin reaches the peripheral circulation intact with maximum serum concentrations observed at 25 min after administration. After entering the bloodstream, aspirin undergoes enzymatic hydrolysis to yield acetate and salicylic acid. The major enzymes hydrolyzing aspirin in plasma are believed to be cholinesterases [17]. Acetylhydrolase-I, an intracellular erythrocyte platelet-activating factor, has been characterized as the major aspirin

Intravenous aspirin has a distribution half-life of about 3 min and inhibits prostaglandin biosynthesis within 5 min of administration, reflecting the rapid onset of

Recent studies by Lichtenberger et al. demonstrated that aspirin could enter the lymph fluid directly when administered intragastrically or intraduodenally, potentially increasing its pharmacologic activity as a chemopreventive agent for

Rectal absorption of salicylate is also possible and cutaneous absorption may occur from salicylate containing rubefacients. Following oral administration of an aqueous solution, the absorption kinetics of aspirin is found to follow a first-order

The factors affecting absorption of salicylate are Rate of gastric emptying volume of food, pH of stomach contents, nervous state, concurrent drugs, exercise, posture, formulation and Disease states associated with altered gastrointestinal

**26**

**Figure 4.**

*In vivo reaction of aspirin.*

Once absorbed, salicylates are distributed extensively through body fluids. Reported values for the apparent volume of distribution (Vd) of salicylate range from 9.6 to 12.7 L in adults with similar values (0.12–0.14 L/kg) in children [22].

Both aspirin and salicylic acid are partially bound to serum proteins. The distribution of aspirin is further enhanced by binding to human serum albumin [23, 24]. Human serum albumin is the most abundant protein found in blood and is often used as a plasma shuttle for steroids, hormones, and other small molecules. Binding studies suggest a conformational change in albumin upon acetylation that can influence transport and metabolism of other critical metabolites and drugs. For example, aspirin-induced acetylation of albumin can inhibit glucose binding [25], while increasing the binding of other molecules, as observed with the increased affinity of acetylated albumin for the marker anion acetrizoate [26]. Aspirin's pharmacodynamic is also influenced by the interaction of other metabolites and serum albumin [24]. However, aspirin acetylation of serum albumin likely inhibits the binding of other metabolites commonly transported by albumin. In vitro studies have shown serum albumin binding and acetylation is dependent upon fatty acid binding, pH and temperature [27].

**Figure 5.** *Reactivity of aspirin in different biological environments of proteins.*

Both salicylic acid and aspirin have been found to diffuse slowly into the cerebrospinal fluid (CSF) due to the high degree of ionization of salicylic acid at the pH (7.4) of plasma. Salicylic acid readily crosses the placenta, fetal plasma concentrations being higher at birth than concurrent maternal concentrations [28].

#### **3.3 Metabolism and excretion**

Aspirin is rapidly converted to salicylic acid with a half-life of only 15–20 minutes [19]. This hydrolysis is due to nonspecific esterases found in many body. The acetyl component of aspirin after oral and intravenous dosing is found in gastric mucosal cells or is excreted as carbon dioxide after passing through the Krebs cycle [29]. During absorption, aspirin esterase activity in the gastrointestinal mucosal membranes contributes 28–35% of the hydrolysis of aspirin; though the activity of esterase enzyme may vary in relation to age and gender. Aspirin esterase activity is reduced in patients with alcoholic liver disease [17].

The major route of elimination of aspirin is through its hydrolyzed product salicylic acid. Salicylic acid is cleared from circulation via the kidneys with a serum half-life of approximately 2 h. A summary of the most common reactions of aspirin in biological systems are summarized in **Figure 5**.

Salicylic acid is partly excreted unchanged and partly metabolized. Free salicylic acid diffuses readily across the glomerulus and is also actively secreted by the proximal tubule. The conjugates of salicylic acid are also excreted via kidney, being dependent on glomerular filtration and tubular secretion. The hydroxylated metabolite gentisic acid is excreted in the same way as free salicylic acid [30].

#### **4. Pharmacodynamics of aspirin**

The most recognized mechanism of action of aspirin is to inhibit the synthesis of prostaglandins but this by itself does not explain the repertoire of anti-inflammatory effects of aspirin. Later, another mechanism was described: the induction of the production of aspirin-triggered lipoxins (ATLs) from arachidonic acid by acetylation of the enzyme cyclooxygenase-2. The availability of a stable analog of ATL has stimulated investigations on the use of this analog and it has been found that, similar to endogenously produced lipoxins, ATL resolves inflammation and acts as antioxidant and immunomodulator. If we consider that in PE and in the obstetric APS, there is an underlying inflammatory process; aspirin might be used based on the induction of ATL [31].

The COX-inhibitory activity of aspirin is contingent on the administered dose. Low doses, those ranging from 75 to 300 mg, result in selective inhibition in platelet TXA2 production without suppressing prostacyclin (PGI2), a common platelet antagonist and vasodilator. PGI2 is expected to be derived mainly from vascular COX-2 suggesting that COX- 2 inhibition is minimal in the low-dose regime. Increased doses (>1200 mg) have analgesic and anti-inflammatory properties, properties associated with the pathophysiological inhibition of COX-1 and COX-2. It is important to note that COX- 2 can also utilize arachidonic acid for synthesis of lipoxins, particularly 15-hydroxyeicosatetraenoic acid [32, 33]. It is unlikely that the COX-2 is more than 5% acetylated while platelet-derived COX-1 is likely to be >70% acetylated. This suggests that regular low-dose aspirin will invariably maintain COX-1 inhibition in circulating platelets, with minimal effect in the inhibition of peripheral COX-2 [34].

A summary of the pharmacodynamic action of aspirin is summarized in **Figure 6** [35, 36].

**29**

*Risk-Benefit Events Associated with the Use of Aspirin for Primary Prevention…*

*DOI: http://dx.doi.org/10.5772/intechopen.93286*

**5. Pharmacological action of aspirin**

Beneficial clinical impaction of aspirin is mainly anti-inflammatory and anti-pyretic action. Evidence suggests that aspirin is a better analgesic than salicylic acid [37, 38]. The analgesia produced by aspirin is dose-dependent, although

The generally accepted therapeutic plasma concentration range of salicylate for the treatment of chronic inflammatory disease is 15–30 mg/100 ml (150–300 mg/L

Other indications for aspirin use are angina pectoris, angina pectoris prophylaxis, ankylosing spondylitis, cardiovascular risk reduction, colorectal cancer, ischemic stroke, ischemic stroke (prophylaxis), myocardial infarction, myocardial infarction (prophylaxis), osteoarthritis, revascularization procedures (prophy-

The most common side effect of aspirin is gastrointestinal upset ranging from

the response does not parallel serum aspirin concentrations [39]. The dose of aspirin required for its antipyretic action is less than that required for

or 1–2 mmol/L), requiring daily doses in excess of 3 g [41].

laxis), rheumatoid arthritis and systemic lupus erythematosus [42].

gastritis to gastrointestinal bleed. Other adverse effects are as followed:

**5.1 Therapeutic effects**

*Pharmacodynamics of aspirin.*

analgesia [40].

**Figure 6.**

**5.2 Adverse effects**

*Risk-Benefit Events Associated with the Use of Aspirin for Primary Prevention… DOI: http://dx.doi.org/10.5772/intechopen.93286*

**Figure 6.**

*Drug Repurposing - Hypothesis, Molecular Aspects and Therapeutic Applications*

being higher at birth than concurrent maternal concentrations [28].

**3.3 Metabolism and excretion**

patients with alcoholic liver disease [17].

**4. Pharmacodynamics of aspirin**

based on the induction of ATL [31].

of peripheral COX-2 [34].

**Figure 6** [35, 36].

in biological systems are summarized in **Figure 5**.

Both salicylic acid and aspirin have been found to diffuse slowly into the cerebrospinal fluid (CSF) due to the high degree of ionization of salicylic acid at the pH (7.4) of plasma. Salicylic acid readily crosses the placenta, fetal plasma concentrations

Aspirin is rapidly converted to salicylic acid with a half-life of only 15–20 minutes [19]. This hydrolysis is due to nonspecific esterases found in many body. The acetyl component of aspirin after oral and intravenous dosing is found in gastric mucosal cells or is excreted as carbon dioxide after passing through the Krebs cycle [29]. During absorption, aspirin esterase activity in the gastrointestinal mucosal membranes contributes 28–35% of the hydrolysis of aspirin; though the activity of esterase enzyme may vary in relation to age and gender. Aspirin esterase activity is reduced in

The major route of elimination of aspirin is through its hydrolyzed product salicylic acid. Salicylic acid is cleared from circulation via the kidneys with a serum half-life of approximately 2 h. A summary of the most common reactions of aspirin

Salicylic acid is partly excreted unchanged and partly metabolized. Free salicylic acid diffuses readily across the glomerulus and is also actively secreted by the proximal tubule. The conjugates of salicylic acid are also excreted via kidney, being dependent on glomerular filtration and tubular secretion. The hydroxylated metabolite gentisic acid is excreted in the same way as free salicylic acid [30].

The most recognized mechanism of action of aspirin is to inhibit the synthesis of prostaglandins but this by itself does not explain the repertoire of anti-inflammatory effects of aspirin. Later, another mechanism was described: the induction of the production of aspirin-triggered lipoxins (ATLs) from arachidonic acid by acetylation of the enzyme cyclooxygenase-2. The availability of a stable analog of ATL has stimulated investigations on the use of this analog and it has been found that, similar to endogenously produced lipoxins, ATL resolves inflammation and acts as antioxidant and immunomodulator. If we consider that in PE and in the obstetric APS, there is an underlying inflammatory process; aspirin might be used

The COX-inhibitory activity of aspirin is contingent on the administered dose. Low doses, those ranging from 75 to 300 mg, result in selective inhibition in platelet TXA2 production without suppressing prostacyclin (PGI2), a common platelet antagonist and vasodilator. PGI2 is expected to be derived mainly from vascular COX-2 suggesting that COX- 2 inhibition is minimal in the low-dose regime. Increased doses (>1200 mg) have analgesic and anti-inflammatory properties, properties associated with the pathophysiological inhibition of COX-1 and COX-2. It is important to note that COX- 2 can also utilize arachidonic acid for synthesis of lipoxins, particularly 15-hydroxyeicosatetraenoic acid [32, 33]. It is unlikely that the COX-2 is more than 5% acetylated while platelet-derived COX-1 is likely to be >70% acetylated. This suggests that regular low-dose aspirin will invariably maintain COX-1 inhibition in circulating platelets, with minimal effect in the inhibition

A summary of the pharmacodynamic action of aspirin is summarized in

**28**

*Pharmacodynamics of aspirin.*


**2.3. Dry propagule fungi**

Several species in the Fungi Kingdom reproduce asexually by producing dry conidia, with no gelatinous matrix, and may or may not be affected by irrigation management.

Powdery mildew, for example, caused by a number of species on the *Erysiphaceae* (Ascomycota), can infect several hosts, and is characterized by the presence of a whitish growth (mycelium, conidiophores and conidia), mainly in the adaxial leaf surface. Still fairly dependent on humidity as several other pathogens, its development may increase until a maximum of 80% RH as reported for *Uncinula necator* in grapevine [32]. Nonetheless, different from other fungal diseases, sprinkler irrigation is harmful for powdery mildews disease progress. The mechanical impact of water droplets harms the fungal structures, hindering disease progress. This phenomenon was previously found by Ruppel et al. [33] who observed lower disease incidence on sprinkler-irrigated sugar beet fields when compared to furrow irrigated ones. The effect of free water in powdery mildew conidia was analyzed by Shomari and Kennedy [34] in conidia of *Oidium anacardii*, a pathogen of cashew, by immersion of infected leaves in water, exhibiting a significant reduction on spore germination after an immersion period of 4 h. This interaction with conidia is only seen before germination: after that phase, leaf wetness does not influence any further on the host tissue colonization.

As for the diseases caused by oomycetes and true fungi, bacterial diseases in plants may occur in the aerial plant parts, including leaves and fruits, causing several symptoms such as cankers, pustules, blights, spots and specks. The symptomatology may vary with plant variety,

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129

Bacterial diseases are strongly affected by irrigation. Water, because it is necessary for the epidemiological processes of dispersal, infection and colonization, is considered one of the most, if not the most, important inputs that move bacterial disease expression on most crops. Leaf wetness is essential for bacterial infection and colonization of aerial parts of the plants. Bacteria penetrate through wounds or natural openings such as stomata and hydathodes. From diseased plants, bacterial cells are dispersed within and among fields through aerosols, insects, windblown soil and sand particles, movement of plant propagules and water flow.

For instance, bacterial spot (*Xanthomonas euvesicatoria*) is a recurrent disease that can devastate pepper fields whenever warm, wet weather is present. The pathogen is seed borne and is responsible for the formation of leaf spots that harbors large number of bacterial cells. Upon impacting on lesions, droplets from rain or overhead irrigation disperse bacterial cells through many micro-droplets from infected plants to neighboring healthy plants, especially under windy conditions. In addition, when foliage is wet, farm operations allow bacterial cells from infected plants to be carried to healthy plants within or between field areas [39].

In this example, which applies to many other bacterial spot diseases, switching from overhead to drip irrigation will warrant necessary moisture accessible to the roots while keeping the foliage dry. It is necessary to keep in mind that, as discussed elsewhere in this chapter, other diseases and pests might be favored by one particular kind of irrigation. An overall analysis of the crop management is necessary for the decision-making process, in a way to

Viruses are intracellular pathogens not capable of reproducing outside a living cell but possessing the genetic means for the manipulation of the host replication machinery for such

Vectors of plant viruses have a major role on the epidemics of plant virus because they are needed for the transportation and introduction of the virus particles into the host plant cell [40]. Most plant viruses can be transmitted by one of several groups of insects. A minority may also be vectored by other organisms such as mites, nematodes and pseudofungi (as those from kingdom Protozoa) [41, 42]. Nematodes that disseminate plant viruses will be addressed below. In some cases, diseases of complex etiology combine damages from the nematode with

Irrigation water does not affect the several viral pre-infection stages that are found within the fungi and bacteria life cycles. When lacking or in excess, water and irrigation may cause physiological host changes, which may accentuate or attenuate symptoms or alter the relationship of the vector with the virus and the host plant [43]. In some cases, the virus may protect its host from severe drought by avoiding irreversible wilt, as reported by Xu et al. [44]. Another

cope with different diseases and obtain desirable yields.

**2.5. Viruses**

the virus, compounding losses.

action.

host age and climatic conditions [38].

Other examples of the irrigation effects over powdery mildew may be seen with *Leveillula taurica* in tomato, which displays a critical increase of incidence when the crop is drip-irrigated, due to the absence of free water on leaves [27]. On pumpkin, powdery mildew is progressively reduced with increasing water volumes applied by the conventional overhead sprinkler irrigation system [10].

Conversely, *Alternaria solani,* the causal agent of tomato and potato early blight, does not suffer any negative effects of sprinkler irrigation. In fact, *A. solani*, as the great majority of plant pathogens that form dry propagules, benefits from the increased leaf wetness duration delivered by irrigation systems that wet aerial plant parts. Processes such as spore production and germination rates are favored. Reduced amounts of water may not markedly affect the development of *Alternaria* diseases, since its dark, thick-walled, multicellular spores are resilient to desiccation. In addition, germination of *A. solani* can take place with the only source of moisture deriving from nighttime dew, without need for irrigations [6].

Fusarium head blights (*Fusarium graminearum, F. culmorum, F. avenaceum*) of maize, wheat and other Poaceae, are economically devastating diseases not only for the direct losses of reduced grain yield but also for the accumulation of mycotoxins in the produce. Timing of irrigation is determinant for avoiding the occurrence of these diseases, and water should be avoided before anthesis and early grain fill periods [35]. Irrigation or rain water stimulates spore production, dispersion and germination of the *Fusarium* and of its sexual form (*Gibberella zeae*). High humidity levels (>94%) are also a requirement for most of the disease cycle phases [36, 37].