**1. Introduction**

Solar chimney with passive cooling tower design (SCPC) is a system that uses solar energy that strikes the aluminum and glass in a chimney to generate a buoyancy force in the chimney. This force drives outside hot air to pass through the evaporative pad (expanded paper) and causes reduction of indoor temperature, high humidity and constant enthalpy [1]. The thermal

© 2016 The Author(s). Licensee InTech. 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. © 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.

performance of solar chimneys using different configurations has been experimentally investigated by different researchers. The concept of metallic solar wall (MSW) on a full-scale model was studied for a single-room house under tropical climatic conditions in Thailand. It was shown that a MSW with 2 m height and 0.145 m air gap (cavity between glass and aluminum) can produce a mass flow rate up to 0.02 kg/s for a house with a base area of 11.55 m2 and a height of 2.68 m and optimum natural ventilation. Such low-cost solar chimney construction can significantly reduce heat gain in the house by creating adequate flow rate to improve thermal comfort [2]. The thermal performance of a solar chimney was investigated on a full-scale model under Mediterranean daylight and night-time conditions for natural ventilation.  The absorber wall was covered by glass of 0.1 m thickness to reduce the convection heat. With this configuration, a maximum flow rate of 374 m3 /h was reported at a solar intensity of 604 W/ m2 occurring at around 13:00 h. Discharge coefficient was experimentally determined to carry out volumetric flow rate calculation. It was concluded that the airflow rate through a solar chimney system is greatly affected by the pressure difference between openings caused by thermal gradients and by wind velocity [3]. An experiment of solar-induced ventilation strategy was conducted. The experiment consisted of two parts, namely, a roof solar collector and a vertical stack. The purpose of the roof solar collector was to capture as much solar radiation as possible, thus maximizing the air temperature inside the channel of the roof solar collector. The heated air inside the channel rose and flowed into the vertical stack due to the pressure difference between the two zones. Meanwhile, the vertical stack was important in providing significant height for sufficient stack pressure. The walls of vertical stack were insulated to minimize the heat loss to the environment. The findings indicated that the proposed strategy was able to enhance the stack ventilation, both in semi-clear sky and overcast sky conditions. The highest air temperature difference between the air inside the stack and the ambient air was achieved in the semi-clear sky condition, which was about 9.9°C (45.8–35.9°C). Besides, in the overcast sky condition, the highest air temperature difference was 6.2°C (39.3–33.1°C) [4]. Also, an experimental study of a vertical channel simulating a solar chimney and a Trombe wall was conducted. The vertical channel had a transparent cover and an absorber plate, painted matte black. The vertical channel was open at both ends, and its dimensions were 1.025 m high, 0.925 m wide and 0.02 m–0.11 m variable depth. Heat input to the absorber plate was supplied by electrical means (200–1000 W) in steps of 200 W. Air temperature and velocity measurements inside the channel were obtained. The results showed that air temperature was increased continuously along the channel height, while the cover and the absorber plate temperatures were not. The cover temperature, as well as the absorber plate temperature, increased continuously to the middle height and then began to decrease. The authors concluded that the mass flow rate is a function of the heat input as well as on the channel depth, while the efficiency of the system is a function of the heat input only [5].

for mechanical cooling systems [10]. This traditional technique was based on natural environmental conditions such as wind, water and vegetation to achieve significant indoor thermal comfort [11]. It was concluded that if passive solar solutions are integrated in existing buildings, building energy demand can be reduced [12]. Many researches have been conducted to examine passive cooling strategies in the buildings. Maerefat and Haghighi studied solar chimney integrated with evaporative cooling cavity. This integrated system was capable of providing good indoor conditions during daytime in the living room [10]. Alemu et al. developed a model using passive cooling technique in earth air tunnel. This model investigated the integration of passive techniques [13]. Developing solar chimney with direct evaporative cooling tower using numerical simulation was done using COMIS-TRNSYS software to provide indoor thermal comfort under the climatic conditions of Assiut, Egypt. The results show

[7, 8]. Macias et al. developed a passive cooling system for a residential building. Natural ventilation was enhanced with the aid of a solar chimney, and fresh air was cooled down by circulation within the duct area of the building. It was found that the passive cooling system allowed for ensuring thermal comfort through low conventional energy consumption based

No experimental studies were found for the integration of solar chimney with cooling strategies in residential buildings in Egypt except for the ventilated Trombe wall as a solar heating and cooling for building retrofitting in semiarid climate (Saint Katherine, Egypt) [15]. The purpose of using solar chimney is to generate natural air movement and improve stack-

ings in Egypt. The main aim of this study is to investigate the performance of an (SCPC) integrated within a room as a passive cooling technique to provide sufficient fresh cooled air, indoor comfort, and reduce room cooling loads. This stage is the second phase of a project for developing an integration of solar chimneys with passive cooling technique (SCPC) to reduce

A single room was built in Assiut University (El-Gorib site) in Assiut, Egypt. Room dimensions are 3.8 x 3.8 x 2.8 m (L × W × H) based on the previous numerical model of solar chimneys integrated with passive cooling [7, 8]. It is located at a latitude of 27°3'N and a longitude of 31°15′ E. In terms of climatic characteristics, Assiut is located in southern Upper Egypt zone. It is characterized by hot dry summers with a maximum outdoor temperature that ranges from 41–46°C and a minimum temperature that ranges from 16–21°C in the summer

at 2-minute time interval to analyze 1-year data (2015). **Figure 1** shows the temperature and humidity patterns of 2015. Selecting 2 months for monitoring (August and September) was done to test indoor environment using passive air conditions. These periods were selected to

in the winter. Outdoor climate analysis was done based on field measurements

/h with indoor thermal comfort of 80% acceptable range

New Passive Cooling as a Technique for Hot Arid Climate

http://dx.doi.org/10.5772/intechopen.74081

85

concentration and indoor comfort for low-energy build-

in the summer and 650

that the system generates 130.5 m3

on a 2-year monitoring period [14] .

induced ventilation with low CO2

to 800 W/m2

energy used in buildings in Assiut, Egypt.

**2. Test room and SCPC system description**

months. This zone has a global radiation range of 1000 to 1125 W/m2

It was concluded that a serious problem of discomfort exists inside houses in projects of new Assiut city based on natural ventilation strategy only [6–9]. Traditional passive techniques were used in ancient architectures to achieve the desired summer comfort without the need for mechanical cooling systems [10]. This traditional technique was based on natural environmental conditions such as wind, water and vegetation to achieve significant indoor thermal comfort [11]. It was concluded that if passive solar solutions are integrated in existing buildings, building energy demand can be reduced [12]. Many researches have been conducted to examine passive cooling strategies in the buildings. Maerefat and Haghighi studied solar chimney integrated with evaporative cooling cavity. This integrated system was capable of providing good indoor conditions during daytime in the living room [10]. Alemu et al. developed a model using passive cooling technique in earth air tunnel. This model investigated the integration of passive techniques [13]. Developing solar chimney with direct evaporative cooling tower using numerical simulation was done using COMIS-TRNSYS software to provide indoor thermal comfort under the climatic conditions of Assiut, Egypt. The results show that the system generates 130.5 m3 /h with indoor thermal comfort of 80% acceptable range [7, 8]. Macias et al. developed a passive cooling system for a residential building. Natural ventilation was enhanced with the aid of a solar chimney, and fresh air was cooled down by circulation within the duct area of the building. It was found that the passive cooling system allowed for ensuring thermal comfort through low conventional energy consumption based on a 2-year monitoring period [14] .

No experimental studies were found for the integration of solar chimney with cooling strategies in residential buildings in Egypt except for the ventilated Trombe wall as a solar heating and cooling for building retrofitting in semiarid climate (Saint Katherine, Egypt) [15]. The purpose of using solar chimney is to generate natural air movement and improve stackinduced ventilation with low CO2 concentration and indoor comfort for low-energy buildings in Egypt. The main aim of this study is to investigate the performance of an (SCPC) integrated within a room as a passive cooling technique to provide sufficient fresh cooled air, indoor comfort, and reduce room cooling loads. This stage is the second phase of a project for developing an integration of solar chimneys with passive cooling technique (SCPC) to reduce energy used in buildings in Assiut, Egypt.


**5. References**

168 Power Quality Harmonics Analysis and Real Measurements Data

(a) Before UPQC run (b) Switched on series device

(c) Switched on passive part (d) Switched on active part

To eliminate harmonics in power system, series APF and shunt APF are adopted. Series APF mainly eliminate harmonic voltage and avoid voltage sag or swell so as to protect critical load. It also helps to eliminate harmonic current if power source voltage is distorted. Shunt APF is to eliminate harmonic current avoiding it flowing through transmission line. UPQC

Fig. 21. Spectrums of utility voltage

**4. Conclusions**

**7**

*Spain*

**Characterization of Harmonic**

Luis Sainz1, Eduardo Caro2 and Sara Riera1 *1Department of Electrical Engineering, ETSEIB-UPC, 2Department of Electrical Engineering, GSEE-UCLM,*

 **Resonances in the Presence of**

**the Steinmetz Circuit in Power Systems**

An electric power system is expected to operate under balanced three-phase conditions; however, single-phase loads such as traction systems can be connected, leading to unbalanced line currents. These systems are single-phase, non-linear, time-varying loads closely connected to the utility power supply system. Among problems associated with them, special consideration must be given to the presence of unbalanced and distorted currents (Barnes & Wong, 1991; Capasso, 1998; Hill, 1994; Howroyd, 1989; Marczewski, 1999; Qingzhu et al., 2010a, 2010b). These operating conditions damage power quality, producing undesirable effects on networks and affecting the correct electric system operation (Arendse & Atkinson-Hope, 2010; Chen, 1994; Chen & Kuo, 1995; Chindris et. al., 2002; Lee & Wu, 1993; Mayer & Kropik, 2005). The unbalanced currents cause unequal voltage drops in distribution lines, resulting in load bus voltage asymmetries and unbalances (Chen, 1994; Qingzhu et al., 2010a, 2010b). For this reason, several methods have been developed to reduce unbalance in traction systems and avoid voltage asymmetries, for example feeding railroad substations at different phases alternatively, and connecting special transformers (e.g. Scott connection), Static Var Compensators (SVCs) or external balancing equipment (ABB Power Transmission, n.d.; Chen, 1994; Chen & Kuo, 1995; Hill, 1994; Lee & Wu, 1993; Qingzhu et al., 2010a, 2010b). The last method, which is incidentally not the most common, consists of suitably connecting reactances (usually an inductor and a capacitor in delta configuration) with the single-phase load representing the railroad substation (Barnes & Wong, 1991; Qingzhu et al., 2010a, 2010b). This method is also used with industrial high-power single-phase loads and electrothermal appliances (Chicco

This delta-connected set, more commonly known as Steinmetz circuit, (Barnes & Wong, 1991; Jordi et al., 2002; Mayer & Kropik, 2005), allows the network to be loaded with symmetrical currents. Several studies on Steinmetz circuit design under sinusoidal balanced or unbalanced conditions aim to determine the reactance values to symmetrize the currents consumed by the single-phase load. Some works propose analytical expressions and optimization techniques for Steinmetz circuit characterization, (Arendse & Atkinson-Hope, 2010; Jordi et. al, 2002; Mayer & Kropik, 2005; Qingzhu et al., 2010a, 2010b; Sainz & Riera,

et al., 2009; Chindris et. al., 2002; Mayer & Kropik, 2005).

**1. Introduction**

Zhou, L.H., Fu, Q., Liu, C.S.(2009). Modeling and Control Analysis of a Hybrid Unified Power Quality Conditioner, Proceeding of 2009. Asia-Pacific Power and Energy Engineering Conference, pp.1-5, ISBN: 978-1-4244-2486-3 , Wuhan, March 27-31, 2009


2.3.3. Fourier Transform Infrared (FTIR)

The chemical structure changes of pristine bagasse, CLCNF and LCNF were characterized using a Fourier transform infrared spectrometer (Tensor II, Bruker, Ettlingen, Germany). FTIR spectra was collected in the wavenumber range from 400 to 4000 cm−1 with a resolution of 2 cm−1.

#### 2.3.4. Elemental Analysis

The nitrogen content of CLCNF and LCNF was analyzed using an elemental analyser (Elemantar Vario EL cube, Elementar, Hanau, Germany). All samples were freeze-dried prior to analysis. Each of the introduced quaternary ammonium group contains one nitrogen, so the quaternary ammonium group of the nanofiber samples are directly related to the nitrogen content.

## 2.3.5. Surface Charge Density

The surface charge densities of CLCNF and LCNF were determined using the polyelectrolyte titration method through a particle charge detector (PCD-05, BTG Mütek, Heidenheim an der Brenz, Germany). 10 mL of nanofiber suspension (0.01 wt% in water) was titrated with 0.001 N anion standard solution (Polyanetholesulfonic acid sodium) and 0.001 N cation standard solution (Polydadmac), and the surface charge density was calculated based on the consumption of standard solution.


2.6.1. NDUFA10

‐ The gene for NDUFA10 is found on chromosome 2. The encoded protein has 355 amino acids and a mass of about 40.8 kDa, with 35 N-terminal amino acids cleaved upon entry to the mitochondrion. Structurally, NDUFA10 has been identified as a member of the deoxynucleoside kinase (dNK) family [8], with the dNK domain (also known as the PF01712 family in the Pfam database), although it is unlikely to be an active enzyme. The protein is compact with a four-stranded parallel beta-sheet surrounded by numerous alpha-helices (see Figure 13). The human structure (PDB id = 5xtd) [9] did not reveal any ligands, but adenosine nucleotides have been found at the C-terminal ends of the beta-sheet in a pocket surrounded by alpha-helices in the mouse (PDB id-6g2j) [37] and sheep [65] structures. NDUFA10 is found on the matrix side of the membrane and primarily interacts with core subunits ND2 and NDUFS2. These interactions with the extended N-terminus of NDUFS2, and the matrix-side peripheral helices of ND2 are all centered over the C-terminal sector of ND2, which contains the broken helix that

is part of the proton translocation pathway. NDUFA10 also makes limited contact with the N-terminal regions of NDUFC1, NDUFC2, and NDUFB11 on the matrix side.  Structural features of two subunits from the ND2-module. NDUFA10, colored red, and NDUFC2, colored gold, are portrayed in ribbons. The site of one mutation, His48Leu in NDUFC2, is shown in space-filling and colored blue. The sites of three mutations in NDUFA10—Gly99Glu, Gln142Arg, and Leu294Pro—are shown in space-filling and colored yellow. The site of phosphorylation by PINK1, Ser250, is shown in space-filling and colored cyan. NDUFA10 likely binds an adenosine nucleoside, not shown.

‐ In knockout human cell line BN gel electrophoresis, only faint bands of complexes containing primarily membrane subunits are seen [11]. Perhaps because of its contacts with a Q-module, core subunit NDUFS2, and a core membrane subunit ND2, along with subunits at the interfaces of ND2/ND4 (NDUFC1 and NDUFC2) and of ND4/ND5 (NDUFB11), it appears to be a key subunit in assembly. Residue Ser250, which is found on the matrix surface, was reported to be phosphorylated by the kinase PINK1 [66], a kinase that is known to be imported into the mitochondrial matrix space [66,67]. This is a conserved amino acid, and phosphorylation appears to be important for complex I activity.

Three reports of clinical mutations in NDUFA10 have been described. The first patient had compound heterozygous mutations including one allele in which the start codon was changed to GTG, and a second in which p.Gln142Arg occurred [68]. This individual showed developmental problems at 10 months and was eventually diagnosed with Leigh syndrome. It is likely that the first mutation would significantly impair the translation unless an alternative start codon were available. The second mutation is found in the interior of the protein, and so the Arg likely disrupts the packing of the protein, especially because of the positive charge.

The second patient was a boy with Leigh syndrome who, in a screen, was determined to have compound heterozygous mutations: p.Leu294Pro and c.383\_384insTAA (p.Ser218delinslS) [27]. These were found to be inherited from the father and mother, respectively. The latter mutation would likely lead to a degraded mRNA or protein. The former mutation p.Leu294Pro resides on an alpha-helix

at an interior location. The substitution of Leu by Pro might be disruptive, as this alpha-helix contacts two distinct regions of ND2. The immunoblotting of fibroblasts showed reduced levels of NDUFA10.

The third patient was initially diagnosed as having a nonlethal infantile mitochondrial disorder, and the mutation was discovered in a screen [69]. This individual developed brain lesions and was considered to have Leigh syndrome. His parents were third cousins, and DNA sequencing revealed him to be homozygous for p.Gly99Glu, while both parents were heterozygous for the same mutation. A deltoid muscle biopsy showed significant reduction of complex I activity (about 40–70% of normal levels). This amino acid is packed against the N-terminal amino acids of NDUFC1, and so the introduction of the negatively-charged Glu could disrupt the assembly of the membrane arm.

#### 2.6.2. NDUFC2

The gene for NDUFC2 is located on chromosome 11. The NDUFC2 protein is 119 amino acids, with a mass of 14.2 kDa. It is a double-pass transmembrane protein that contacts core subunit ND2, with both termini on the IMS side of the membrane. From the N-terminus, the protein enters the membrane in a non-helical stretch from Ser 19 to Arg29, and then residues 29–47 are alpha-helical. The second crossing of the membrane is alpha-helical from residues 56–97, extending into the IMS. NDUFC2 also contacts NDUFC1, NDUFB5, and NDUFA8 (see Figure 11), and it is part of the ND2 assembly module. NDUFC1 has a special role in sealing NDUFC2 from the lipid bilayer, with its single transmembrane helix parallel to the long helix of NDUFC2 and very limited contact to any other subunits in the membrane. The extension of the long alpha-helix into the IMS, residues 84–97, is the region that contacts NDUFA8 and NDUFB5 (see Figure 11). On the matrix side it contacts NDUFA10 (see Figure 13).

Mutations of NDUFC2 in three patients from two families were reported in 2020 [70]. The patients presented with symptoms of Leigh syndrome and reduced complex I activity but had different outcomes. In both families, the parents were healthy consanguineous first cousins and were heterozygous for the mutations. In one family, the mutation was a deletion of 22 base pairs near the C-terminus at residue His116, p.His116\_Arg119delins21. This would cause a frame shift and elimination of the normal stop codon at position 120. It was not clear how long the new reading frame would be. The transcript of this gene was identified at low levels, but the immunoblotting of fibroblast samples was negative, suggesting the degradation of the protein or a lack of expression. Little or no complex I was seen in native gels. Complexome profiling found evidence of Q-module assembly and ND4-module assembly but little else of complex I subunits. The daughter had no seizures and survived until at least age six, while her brother passed away at three years of age.

In the second family, the mutation was p.His58Leu. This patient had normal transcript levels but only slightly more evidence of complex I assembly. His58 is found on the matrix side of the membrane and starts the long helix that crosses the membrane. It sits between Val44 of NDUFC1 and Trp353 of NDUFA10 and is very near the phosphate group of a bound lipid. In the mouse structure (PDB id = 6g2j), the corresponding His59 is even more tightly packed between NDUFC1 and NDUFA10 residues, suggesting that a Leu substitution could be deleterious. This child had impaired growth and seizures and passed away at eight months.

NDUFC2 has a unique position in complex I. It is embedded in the membrane near the ND2-ND4 junction but contacts two subunits that are embedded at distant sites, with long extension to NDUFC2: NDUFA8 is found at the "heel" of the complex I boot, in the IMS, while NDUFB5 is found at the junction of ND4-ND5. Interactions in this network of subunits appear to be essential for complex I assembly.


*Article* **New Isomalabaricane-Derived Metabolites from a** *Stelletta* **sp. Marine Sponge**

**Sophia A. Kolesnikova 1,\*, Ekaterina G. Lyakhova 1, Anastasia B. Kozhushnaya 2, Anatoly I. Kalinovsky 1, Dmitrii V. Berdyshev 1, Roman S. Popov 1 and Valentin A. Stonik 1,2**

**Abstract:** In continuation of our studies on a Vietnamese collection of a *Stelletta* sp., sponge we have isolated two new isomalabaricane triterpenoids, stellettins Q and R (**1** and **2**), and four new isomalabaricane-derived *nor*-terpenoids, stellettins S-V **3**–**6**, along with previously known globostelletin N. Among them, compound **3** contains an acetylenic fragment, unprecedented in the isomalabaricane family and extremely rare in other marine sponge terpenoids. The structures and absolute configurations of all new compounds were established by extensive NMR, MS, and ECD analyses together with quantum-chemical modeling. Additionally, according to obtained new data we report the correction in stereochemistry of two asymmetric centers in the structures of two known isomalabaricanes, 15*R*,23*S* for globostelletin M and 15*S*,23*R* for globostelletin N.

**Keywords:** isomalabaricanes; *Stelletta* sp.; marine sponge; terpenoid; structure elucidation


**1. Introduction**

Telemetry technology allows remote measurement and recording of signals such as biopotentials. This technology offers the advantage of long-term EEG recordings without causing unnecessary distress, as happens in EEG systems where implanted leads connect to the recording device through a cable. The EEG recordings can be used to detect changes in the brain activity after a traumatic event. The use of telemetry for EEG acquisition is the most reliable option in experimental studies due to the reduction of animal stress. Besides its current disadvantages, such as a reduced number of channels when compared to tethered EEG, telemetry can allow us to distinguish oscillatory brain patterns that become pathological after a neurological injury. Normal brain oscillatory synchronization can be correlated with cognitive function and behavioral state. However, abnormal brain oscillations can be caused by pathologies characterized by dysfunction of the cholinergic system and trauma, leading to epilepsy. This phenomenon is the result of abnormal hypersynchronous firing in certain neuronal populations in the brain. Although not all kinds of brain injury can induce epilepsy, the spike/wave activity present during epileptic seizures is of special relevance, because severe brain injury can, in most cases, induce epilepsy.

The combination of EEG acquired through telemetry and video is widely used for assessment of epileptic focus, to distinguish epileptic seizures from psychogenic non-epileptic seizures, reassessment for potential surgery to treat epilepsy and to study animal models. Nevertheless, the assessment of the long-term EEG changes that occur after brain injury is a challenge, because a large amount of data is accumulated. Reducing the sampling rate and/or the recording schedule is not an option since each subject may respond differently to the injury and treatment. Furthermore, seizure-like events do not occur in pre-determined periods, therefore arbitrary sampling would compromise acquisition and analysis. In order to acquire reliable results, one requires a good estimation of duration and frequency of seizures and/or the duration of sleep stages. Several studies have addressed the need for analytical tools capable of optimally performing spectral analyses and, in this chapter, we evaluate the advantages and disadvantages of some available tools. The reduction and removal of artifacts in the acquired data, spectral decomposition of the signal using fast Fourier and wavelet transforms, and batch-processing will also be discussed. We will provide a view of the role of telemetric EEG technology in neuroscience, focusing on the study of brain injury induced by chemical means. Approaches to assess long-term EEG changes, choices of acquisition parameters, and tools to analyze the EEG data will be introduced.

Use of Telemetric EEG in Brain Injury 201

classification of seizures if monitored continuously. Meierkord (1992) used video-EEG telemetry to identify frontal lobe epilepsy and differentiate it from pseudo-seizures in patients. Overall, the seizure duration was short (up to 60 sec) and inter-ictal epileptiform EEG activity was identified as well as ictal abnormalities. In a similar effort, Raymond and colleagues (1999) were able to distinguish epileptic seizures from "non-epileptic" seizures. They described that even though it is unusual, some patients may display both epileptic seizures and "non-epileptic" seizures. They combined video-EEG telemetry and MRI (not simultaneous) to help in diagnosis and, interestingly, in 12 of 14 patients, the first seizure was "non-epileptic", suggesting that long-term monitoring is necessary to avoid pitfalls in the diagnosis. Moreover, there are situations when patients do not show structural anomalies in the MRI (Scott *et al*., 1999) but the EEG reveals epileptiform patterns. In these specific cases, although the telemetric EEG does not show a clear cut identification of the epileptogenic site (due to the spatial resolution limitation), it is still a valuable tool*.* In an attempt to increase the spatial resolution of the EEG, Gross and co-workers (2000) used closely spaced electrodes to study frontal lobe epilepsy (32-64 channels) and found abnormalities that were apparent with 10-20 electrodes. Nevertheless, independent of the number of channels, it is very important to precisely evaluate the video-EEG recordings and, if necessary, review it. In a re-assessment of data collected during 17 months from 121 patients (video-EEG telemetry), Alsaadi and colleagues (2004) changed the diagnosis of 24%

**2.2 The use of EEG telemetry to study behavior and detect seizures in animal models**  Telemetry has been shown to be extremely useful in animal models, allowing approaches that could be considered non-ethical in humans. Several studies were conducted specifically to verify the efficacy of new technologies that allow miniaturization of the telemetry system. Both the study of normal physiological events such as thermoregulation, sleep and circadian cycle (Herold *et al*., 1998) and the mechanisms of different neuropathologies can be explored through the use of telemetric EEG in animal models. Dimpfel and colleagues (1988) performed the implantation of bipolar electrodes in cortical and sub-cortical structures of rats to allow long-term recording of EEG after different drug treatments, such as amitriptyline, imipramine, amitriptylinoxide, amphetamine, diazepam, haloperidol and LSD. Cotugno and co-workers (1996) described a method to surgically implant telemetry transmitters in rats and record the EEG. The transmitter is implanted in a dorsal subcutaneous pocket and two stainless steel electrodes placed in the skull are connected to the transmitter through a subcutaneous tunnel. The EEG is then collected by an antenna

Fitzgerald and colleagues (2003) adapted a method to record EEG in rats through telemetry and perform real-time fast Fourier transform. They used a Data Sciences International system (DSI; St. Paul, Minn.) to send raw EEG of rats injected with atropine, caffeine, ketamine or pentobarbarbital to an oscilloscope (DataSys 7200, Gould Instrument Systems, Valley View, Ohio) with storage, fast Fourier transform (FFT) and averaging features. Then, they calculated the relative power peaks for atropine (< or =5 Hz), caffeine (7.5 Hz) and ketamine (induced a shift from 5 to 10 Hz to < 5 Hz). Bastlund and co-workers (2004) used telemetry to record cortical EEG, EMG, and temperature for long-term monitoring (5-8 weeks) of epileptiform activity in rats injected with either pentylenetetrazole or kainic acid. Weiergräber and colleagues (2005) while studying transgenic mouse models of epilepsy and sleep disorders, used EEG recorded through telemetry playing a crucial role in the

of the patients after re-analyzing the data.

located in a receiver positioned under the animal.

#### **2. Uses of telemetry technology**

The advance of remote recording of physiological data, such as biopotentials, by radio (Holter and Generelli, 1949) was a great advancement in the field of physiology. Telemetry has been used to assess physiological measures through the recording of biopotentials of subjects in remote locations for decades (Fischler & Frei, 1963; Hambrecht *et al*, 1963; Lee *et al*, 1964; Vreeland *et al*., 1963). The aerospace industry, NASA and the former USSR used telemetry to record electrocardiogram (ECG), electroencephalogram (EEG) and electromyogram (EMG) during different missions (Akulinichev & Baevskii, 1964; Blanc, Gravier, & Geier, 1967; Caldwell & Lewis, 1995; Frostjr *et al*, 1975; Helvey *et al*, 1964) with the objective to monitor pilots/astronauts, collecting information regarding changes in physiological parameters.

The technologies for recording of biopotentials remotely have been improving in parallel with different technologies. For example, the development of the transistor made possible the design of small and relatively power-efficient circuits, allowing small devices to be implanted (Jacobson and Mackay, 1957). Kamp (1984) described the use of a miniaturized 8-channel EEG amplifier combined with a standard radio transmitter/receiver system to record long-term EEG at the patient's residence. Van der Weide and Kamp (1984) created a system to record long-term home EEG in epileptic patients using radio telemetry transmitted over a regular telephone line. Wroe and co-workers (1987) combined telemetry and recording using a standard cassette system, allowing monitoring of epileptic patients in the clinic. Peng and colleagues (2001) used a regular telephone network to send data from a 20-channel EEG system to a monitoring center where the data could be stored and analyzed. Frequency resolution is very important when acquiring EEG signals and the use of frequency modulation (FM) technology allowed a higher sampling rate. Neihart & Harrison (2004) created an FM transmitter (433 MHz) powered by an inductive link (transcutaneous) to send biopotential data to a monopole antenna. A wireless multichannel recording system was designed by Mohseni and colleagues (2005) and featured integrated circuit AC amplification, DC input stabilization, time-division-multiplexing (each signal has a "timeslot") and wireless FM transmission (0.05-6 kHz)*.* Rizk and co-workers (2007) designed and implemented a singlechip to function as a 96-channel, brain-machine interface. The interface uses bidirectional communication, sampling the signals at 31.25 kHz and digitally suiting it for transmission, fulfilling the requirements for an implantable system. However, the newest existing techniques to implement brain-computer interfaces still face problems such as gliosis surrounding the implant and biocompatibility. Visual and auditory replacements and hand and limb prosthetics could revolutionize medicine, but there is still a long way to go (Rothschild, 2010). Finally, optical technology can potentially be used to transmit local field potential data (LFP) more accurately. Wei & Ziaie (2009) accomplished it designing a system composed of a printed circuit board (2.2 x 2.2 cm) to accommodate 4 amplifiers, 16 lightemitting diodes (LED) and a CCD camera to record the signal coming from the LED at 30 frames per second allowing reconstruction of a simulated LFP.

#### **2.1 The use of EEG telemetry to detect clinical seizures in patients**

The choice of what telemetry system to use in the clinic must be made according to the physician's expectations and requirements for an EEG system. The physician will determine the level of sophistication required for their EEG system (Schomer, 2006). In any case, although controversial, the EEG can be a potential marker to help in the diagnosis and

The advance of remote recording of physiological data, such as biopotentials, by radio (Holter and Generelli, 1949) was a great advancement in the field of physiology. Telemetry has been used to assess physiological measures through the recording of biopotentials of subjects in remote locations for decades (Fischler & Frei, 1963; Hambrecht *et al*, 1963; Lee *et al*, 1964; Vreeland *et al*., 1963). The aerospace industry, NASA and the former USSR used telemetry to record electrocardiogram (ECG), electroencephalogram (EEG) and electromyogram (EMG) during different missions (Akulinichev & Baevskii, 1964; Blanc, Gravier, & Geier, 1967; Caldwell & Lewis, 1995; Frostjr *et al*, 1975; Helvey *et al*, 1964) with the objective to monitor pilots/astronauts, collecting information regarding changes in

The technologies for recording of biopotentials remotely have been improving in parallel with different technologies. For example, the development of the transistor made possible the design of small and relatively power-efficient circuits, allowing small devices to be implanted (Jacobson and Mackay, 1957). Kamp (1984) described the use of a miniaturized 8-channel EEG amplifier combined with a standard radio transmitter/receiver system to record long-term EEG at the patient's residence. Van der Weide and Kamp (1984) created a system to record long-term home EEG in epileptic patients using radio telemetry transmitted over a regular telephone line. Wroe and co-workers (1987) combined telemetry and recording using a standard cassette system, allowing monitoring of epileptic patients in the clinic. Peng and colleagues (2001) used a regular telephone network to send data from a 20-channel EEG system to a monitoring center where the data could be stored and analyzed. Frequency resolution is very important when acquiring EEG signals and the use of frequency modulation (FM) technology allowed a higher sampling rate. Neihart & Harrison (2004) created an FM transmitter (433 MHz) powered by an inductive link (transcutaneous) to send biopotential data to a monopole antenna. A wireless multichannel recording system was designed by Mohseni and colleagues (2005) and featured integrated circuit AC amplification, DC input stabilization, time-division-multiplexing (each signal has a "timeslot") and wireless FM transmission (0.05-6 kHz)*.* Rizk and co-workers (2007) designed and implemented a singlechip to function as a 96-channel, brain-machine interface. The interface uses bidirectional communication, sampling the signals at 31.25 kHz and digitally suiting it for transmission, fulfilling the requirements for an implantable system. However, the newest existing techniques to implement brain-computer interfaces still face problems such as gliosis surrounding the implant and biocompatibility. Visual and auditory replacements and hand and limb prosthetics could revolutionize medicine, but there is still a long way to go (Rothschild, 2010). Finally, optical technology can potentially be used to transmit local field potential data (LFP) more accurately. Wei & Ziaie (2009) accomplished it designing a system composed of a printed circuit board (2.2 x 2.2 cm) to accommodate 4 amplifiers, 16 lightemitting diodes (LED) and a CCD camera to record the signal coming from the LED at 30

frames per second allowing reconstruction of a simulated LFP.

**2.1 The use of EEG telemetry to detect clinical seizures in patients**

The choice of what telemetry system to use in the clinic must be made according to the physician's expectations and requirements for an EEG system. The physician will determine the level of sophistication required for their EEG system (Schomer, 2006). In any case, although controversial, the EEG can be a potential marker to help in the diagnosis and

**2. Uses of telemetry technology**

physiological parameters.

classification of seizures if monitored continuously. Meierkord (1992) used video-EEG telemetry to identify frontal lobe epilepsy and differentiate it from pseudo-seizures in patients. Overall, the seizure duration was short (up to 60 sec) and inter-ictal epileptiform EEG activity was identified as well as ictal abnormalities. In a similar effort, Raymond and colleagues (1999) were able to distinguish epileptic seizures from "non-epileptic" seizures. They described that even though it is unusual, some patients may display both epileptic seizures and "non-epileptic" seizures. They combined video-EEG telemetry and MRI (not simultaneous) to help in diagnosis and, interestingly, in 12 of 14 patients, the first seizure was "non-epileptic", suggesting that long-term monitoring is necessary to avoid pitfalls in the diagnosis. Moreover, there are situations when patients do not show structural anomalies in the MRI (Scott *et al*., 1999) but the EEG reveals epileptiform patterns. In these specific cases, although the telemetric EEG does not show a clear cut identification of the epileptogenic site (due to the spatial resolution limitation), it is still a valuable tool*.* In an attempt to increase the spatial resolution of the EEG, Gross and co-workers (2000) used closely spaced electrodes to study frontal lobe epilepsy (32-64 channels) and found abnormalities that were apparent with 10-20 electrodes. Nevertheless, independent of the number of channels, it is very important to precisely evaluate the video-EEG recordings and, if necessary, review it. In a re-assessment of data collected during 17 months from 121 patients (video-EEG telemetry), Alsaadi and colleagues (2004) changed the diagnosis of 24% of the patients after re-analyzing the data.

#### **2.2 The use of EEG telemetry to study behavior and detect seizures in animal models**

Telemetry has been shown to be extremely useful in animal models, allowing approaches that could be considered non-ethical in humans. Several studies were conducted specifically to verify the efficacy of new technologies that allow miniaturization of the telemetry system. Both the study of normal physiological events such as thermoregulation, sleep and circadian cycle (Herold *et al*., 1998) and the mechanisms of different neuropathologies can be explored through the use of telemetric EEG in animal models. Dimpfel and colleagues (1988) performed the implantation of bipolar electrodes in cortical and sub-cortical structures of rats to allow long-term recording of EEG after different drug treatments, such as amitriptyline, imipramine, amitriptylinoxide, amphetamine, diazepam, haloperidol and LSD. Cotugno and co-workers (1996) described a method to surgically implant telemetry transmitters in rats and record the EEG. The transmitter is implanted in a dorsal subcutaneous pocket and two stainless steel electrodes placed in the skull are connected to the transmitter through a subcutaneous tunnel. The EEG is then collected by an antenna located in a receiver positioned under the animal.

Fitzgerald and colleagues (2003) adapted a method to record EEG in rats through telemetry and perform real-time fast Fourier transform. They used a Data Sciences International system (DSI; St. Paul, Minn.) to send raw EEG of rats injected with atropine, caffeine, ketamine or pentobarbarbital to an oscilloscope (DataSys 7200, Gould Instrument Systems, Valley View, Ohio) with storage, fast Fourier transform (FFT) and averaging features. Then, they calculated the relative power peaks for atropine (< or =5 Hz), caffeine (7.5 Hz) and ketamine (induced a shift from 5 to 10 Hz to < 5 Hz). Bastlund and co-workers (2004) used telemetry to record cortical EEG, EMG, and temperature for long-term monitoring (5-8 weeks) of epileptiform activity in rats injected with either pentylenetetrazole or kainic acid. Weiergräber and colleagues (2005) while studying transgenic mouse models of epilepsy and sleep disorders, used EEG recorded through telemetry playing a crucial role in the

Use of Telemetric EEG in Brain Injury 203

frequently affected areas, including the hippocampus, amygdala, pyriform cortex, and cortex (Turski *et al*., 1983b; Carpentier *et al*., 1990; Petras, 1994; Scremin *et al*., 1998; Shih *et al*., 2003). The situation becomes critical if the seizure is sustained for a prolonged period without significant interruption or recovery. When such an event takes place, the subject is experiencing *status epilepticus* (SE) and can years later display SRS. Under these circumstances, appropriate treatment is anticonvulsant therapy and monitoring (*i.e*. continuous video-EEG) in order to try to interrupt the process of epileptogenesis.

Various types of brain oscillations can be identified during the circadian cycle. A simplification of these types is exemplified in Fig. 1. Among normal function during the circadian cycle, sleep is of great importance and, obviously, sleep scoring or staging is fundamental as a tool in understanding normal and pathological situations. Gottesmann, (1992) described seven sleep-waking stages in the rat: 1 - attentive walking with dorsal hippocampus theta; 2 - quiet waking without theta pattern; 3 - sleep with cortical slow waves of increasing amplitude; 4 - deeper sleep with cortical spindles that progressively increase in number and amplitude; 5 - pre-paradoxal sleep events with high amplitude spindles that occur in parallel with thalamic sensory transmission to cortex; 6 - paradoxical sleep (eye movements are absent); 7 - paradoxical sleep with the characteristic rapid eye movements (REM). Since manual sleep scoring is laborious and time-consuming, several attempts have been made to automate this process. Gross and co-workers (2009) designed a MATLAB toolbox to perform semi-automated sleep scoring. The system is able to distinguish the states of waking, non-REM (NREM), transition-to-REM, and REM sleep if EEG and EMG are recorded simultaneously. Methods describing details for optimal EEG acquisition calibration, electrode application, signal filtering and power spectral analysis for

The search for the substrates of normal brain oscillations and its correlation with cognitive function, neurochemistry and behavioral states has been studied for several decades. Graf & Kastin, (1984) pointed that peptides can play a role, for example, in sleep, EEG and circadian patterns. Neurons that secrete orexins (excitatory neuropeptide hormones) are likely to be very important in promoting wakefulness during the circadian cycle and in controlling the transition to REM sleep. Also, hormones, like estradiol, can decrease sleep and increase locomotion (Mong *et al*., 2003). Among the neuroanatomical areas that play a role on sleep, the locus coeruleus is very important, generating brain states such as alertness. Its activation changes the EEG activity from typical non-alert patterns to alert patterns. The locus coeruleus also has a role in attention processes by changing the sensory responses of neocortical neurons and participating in orienting responses occurring in the forebrain that are closely linked to event-related potentials (Foote *et al*., 1991). EEG studies indicated that the noradrenergic connections from the locus coeruleus excite the upper brain areas, while activation of serotonergic pathways inhibits the same areas. A population of cholinergic neurons can induce and maintain paradoxical sleep and also induce a rapid and transient elevation of alertness (Kayama and Koyama, 1998). In other words projections from the locus coeruleus work as the arousal system. The suprachiasmatic nucleus located in the hypothalamus can also modulate sleep (Dijk and Duffy, 1999). The hypothalamic ventrolateral preoptic area and pons/basal forebrain can play a role on both arousing and sleep-inducing neuronal networks. The mentioned structures could play a role as an ON/OFF switch or transition from sleep to awake state and vice-versa. During sleep, one

**3.1 Normal brain oscillatory synchronization**

sleep research were described by Campbell (2009).

neurological characterization of various transgenic mouse models and giving valuable information about epilepsies and sleep disorders in humans. They emphasized that without restraint from tethered EEG systems, the subjects can be observed without interference in their physiology.

Williams and co-workers (2006) used a three EEG channel system (DSI; St. Paul, Minn.) to record interictal spikes and epileptiform activity in the cortex and hippocampus of rats. They studied the model of kainic acid-induced seizures and long-term telemetric EEG recording to investigate epileptogenesis. According to them, although the chance to perform prolonged recordings is a great advantage, the cost, surgical complexity and frequency resolution of the system are listed as disadvantages. Obviously, collecting the data is just the first step, and throughout the use of the same system, White and colleagues (2006) tested different algorithms to process very large EEG data files acquired over 13 days. They concluded that the quality of the EEG and the type of analysis method employed can affect the positive predictive value (PPV, or true positives divided by the sum of true positives and false positives) and sensitivity (true positives divided by the sum of true positives and false negatives). In that sense, both implantation surgery accuracy and telemetry device integrity may be very important factors.

Lapray and colleagues (2008) presented a cost-effective and reusable telemetry system to record EEG in rats. The system allows a sampling rate of 500 Hz (bi-directional) and a range of up to 3 meters. The data transmission rate is roughly 115 kbps and the receiver connected to a computer through the USB port. The software developed by the group allows the recording of simultaneous video, opening the possibility to efficiently correlate behavior and EEG patterns. Finally, the study not only of EEG, but also action potentials during normal behavior, can be benefited by telemetry. It is known that the activity of place cells is highly correlated with the animal's spatial position (O'Keefe and Speakman, 1987; O'Keefe *et al*., 1998). A very innovative system was created by Chen and co-workers (2008) that used telemetry to record brain potentials in 3D mazes to investigate the role of hippocampal place cells in rats. The wireless technology used was Bluetooth which allowed a range of 5 meters and sampling at up to 10 kHZ, drastically increasing the frequency resolution and satisfying the conditions to have single unit recordings.