**1. Introduction**

Since the last two decades, socially responsible entrepreneurial universities have started playing a crucial role in economic and regional developments through the collaborations and partnerships they established with their internal and external stakeholders. Particularly, socially responsible entrepreneurial universities, which adopt a stakeholder approach within the scope of the university-industry collaboration (UIC) ecosystem, coordinate their internal structures, and try to increase their cooperation with their stakeholders.

In the digital era we live in, it is argued that there are ecosystems where different insights, models, and approaches in the administrative sense are adopted and applied very quickly, conventional and contemporary channels are used together, and thus change and transformation takes place in many areas.

In recent years, universities have started playing important economic roles through their collaborations with their stakeholders. In general, universities mainly benefit from the development of the societies that exist in social and cultural areas. While adopting the stakeholder approach within the scope of the University-Industry Collaboration (UIC), they coordinate their internal structures and increase their cooperation with their stakeholders [1]. It can be stated that the institutions, which are evaluated as research universities, have a leadership role in the fields of R&D, innovation, and scientific research in the national sense, and they are also represented in scientific activities with their international partners in the global sense. It is denoted that distinguished scientists working in research-oriented universities that have their autonomous structure have significant contributions in maintaining targeted achievements in a country's higher education system and affect the increase in institutional prestige and resources [2].

It can be asserted that beside universities, industry and business stakeholders have a significant impact on the processes of change and transformation. In recent years, the most controversial management innovations have been the emergence of organizations such as Start-up and Spin-off, which are characterized as "sprout enterprises" and derived from large-scale companies (through young entrepreneurs) or universities (through entrepreneur academics). At first glance, such innovative approaches have enabled areas that seem opposite, such as the public sector, university, industry, and the business stakeholders to take a more convergent position and pursue various ways of collaboration [3]. In addition, several borderline interactions, including joint research or consultancy projects, have interlinked an enterprise and a university [4]. In this framework, the academic entrepreneurship can be considered as a training area and pioneer of Spin-off activity. The academics, who have seen themselves separate from the business stakeholders before, have so far been perfectly aware of the fact that the managers at the head of research groups are also acknowledged as business entrepreneurs. They see themselves as having the necessary organizational and leadership skills that are adequate to arrange small and even medium-sized businesses [5].

An entrepreneurial university model has emerged to generate socio-economic value in synergy with institutions and industries that open the boundaries of the university to the community of external actors and stakeholders [6]. Entrepreneurial universities aim to increase the wealth and prosperity of their societies by promoting a culture of innovation and competitiveness [7]. There is a symbiotic/complementary relationship between entrepreneurial universities and their regions. Policymakers consider the regional economic effects of universities. Particular attention has been paid to the increasing students' "externships" through industrial participation by the faculty and students, Spin-off company establishment, and "non-traditional" university policy and outreach services [8]. Entrepreneurial universities can foster frugal innovation by providing the necessary skills, supporting entrepreneurship and innovation initiatives, and conducting applied research to meet societal necessities [9].

So far, social entrepreneurship has emerged and spread in many countries, abruptly. Social entrepreneurship is the process of applying business and entrepreneurship principles to social problems. Social initiatives are those that are dedicated to solving social matters. The reason for their existence is not to maximize the

#### *The Impact of the Strategic Interests and Communicative Actions between the Socially… DOI: http://dx.doi.org/10.5772/intechopen.94343*

direct returns to shareholders, rather create a positive social impact [10]. Likewise, social enterprises are private organizations that adopt business strategies to achieve socially focused goals [11]. Various interface units such as technology development zones, research centers, and technology transfer offices that are associated with the entrepreneurial universities have also been reconstructed in public universities which have less emphasis on research. Thus, these interface units started to expand the scope of their duties by promoting the first stages of the R&D process with commercial potential and focused on obtaining commercially available findings in the next stages [12]. Yet, both university administration and individuals have become a necessity for the UIC interactions, a top-down and bottom-up approach ought to be used together. In the case of a university has a desire to expand the UIC activities, it is recommended that the university administration should establish long-term strategies and follow a holistic strategy approach [13].

The public sector and universities can evaluate new scenarios of successful collaboration with companies in their research assignments. For instance, companies and organizations originating from the cooperation of the three parties actively participate in science and technology parks [14]. It is worth noting that public policies have the potential to increase innovation efficiency developed in science and technology parks by suggesting or encouraging companies to adopt corporate social responsibility (CSR) practices in their strategies [15]. In this context, the CSR is primarily concerned with achieving results from organizational decisions on specific topics and issues that have beneficial effects rather than negative impacts on relevant corporate stakeholders (according to some normative standards) [16]. The social responsibility of the enterprise covers the economic, legal, ethical, and philanthropic expectations that society has from institutions at a certain time [17].

The theoretical framework of this study has been associated with the use of multimedia opportunities used in communicative actions, the collaboration between stakeholders, and the effect of interfaces on interactions between university and industry. "Communication Theory of Action," "Stakeholder Approach and the CSR nexus" and "Triple Helix" approach have significant effects on the formation of collaborations and interactions. The originality of this study is that the Technology Development Zone (TDZ), which is one of the interface structures in the UIC ecosystem and collaboration process. In essence, it highlights the importance of socially responsible entrepreneur universities. The TDZs, which contribute more and more to the innovation and entrepreneurship ecosystem, lead a crucial role that enhances both economic and social life within the scope of national and international projects. Communication and actions of companies actively working in the TDZs were examined by using a case study related to the CSR. The relationships between stakeholders, companies, and the UIC interfaces were analyzed by taking into account the CSR actions and stakeholder theory.


**2. Materials and methods**

In this study, 40 volunteers were used to record brain signals and MRI images in healthy, mild, and severely ill groups. The number of subjects is 19 in the healthy group, 11 in the mild patient group, and 10 in the severely ill group. Forty volunteers with an age range of 60 to 88 years have been used to record brain signals. All participants in all groups were right-handed. Nineteen participants in the Mini-Mental State Exam (MMSE) test scored between 23 and 30 and were included in the group of

### *EEG and MRI Processing for Alzheimer's Diseases DOI: http://dx.doi.org/10.5772/intechopen.107162*

healthy people. Eleven participants with an MMSE score of 19 to 22 were classified as mild-Alzheimer's patients, and finally, 10 participants with an MMSE score between 3 and 18 were included in the group of severe Alzheimer's patients.

The Powerlab SP device with two amplifiers was used to record the brain signal. In this device, three channels for recording the brain signal and one channel for recording the EOG signal, and the other channel for the external audio signal for stimulation have been used so that the stimulation signal and ERP do not occur simultaneously. The signal was recorded in 4-channel mode according to the standard 10–20. The sampling rate of the device is 1 kHz and 16 bits for each sample. Recording the brain signal in the form of subject training, recording the closed eye for 1 minute, recording the open eye for 1 minute, and recording while performing the task assigned to the subject, which includes A. Remembering the displayed shapes; B. The counting of target and non-target sounds in an oddball auditory test. After proper labeling by the physician in segregation of healthy individuals, and mild and severe Alzheimer's patients by MMSE test in the first part, how to record the brain signal in four steps is explained to people and they are asked to relax during Keep records to prevent the formation of motion artifacts and other unwanted factors, and this method of registration does not cause harm to the person. After preparing the subject, we perform the second step. In the closed eye mode, we record the signal for 1 minute. Then in the third step, the subject will be asked to open the eyes and record the signal for 1 minute. At the end of the third stage, the displayed images have no color so that the color feature does not have a different effect on different subjects. These images are displayed for 1 minute and after this time, the subject will be asked to close the eyes and recall the images (review the images) in the mind. Meanwhile, brain signals will be recorded for 1 minute. Participants will then be asked to open their eyes and express the shapes one by one aloud. In the last part, a sound with a frequency of 1 kHz called non-target sound and 1.5 kHz sound called target sound will be given to the subject. Before playing these two categories of sound, this step has been taught to the subject. In the fourth part of section (b), these sounds are played, and the subject is asked to press the right key as soon as hearing the target sound and the left key as soon as hearing the non-target sound. The interval between stimuli (sound playback) is 2 seconds and the sounds will be played randomly. The only important point is that 75% of the number of stimuli is non-target sound and 25% of the number of stimuli is target sound. If we assume the total number of stimuli to be 120, we will have a total of 30 target stimuli and 90 non-target stimuli, which can be randomly distributed between the non-target stimuli at 2-second intervals. The playing time of each sound (target and non-target) will be 300 milliseconds. This recording section is 276 seconds with the assumption of 120 excitations and the total signal recording time for each subject is approximately 10 minutes. A sample image of recording brain signals is shown in **Figure 1**.

The first step in processing brain signals is to eliminate high- and low-frequency noise and interference and to remove motion artifacts. It is clear that the removal of unwanted factors such as motion artifacts, signal deviation from the baseline, high- and low-frequency noise, and reduction of sampling rate is necessary for proper processing of brain signals and extraction of optimal features, and this increases the accuracy of brain signal processing [11]. The motion artifacts in the brain signal are caused by contractions of the muscles of the head and neck as well as the movement of the electrode. On the other hand, transpiration also causes frequency interference. To eliminate these artifacts and noise from the city, a pass filter with cutoff frequencies of 0.5 to 45 Hz was used [12].

**Figure 1.** *A sample research participant during brain signal recording.*

Neuroimaging techniques, physiological signs, and genetic analysis are methods used to diagnose Alzheimer's disease [13]. To detect Alzheimer's disease in its early stages, neuroimaging methods are used, which include SPECT, PET, and magnetic resonance imaging. The problem with SPECT and PET is the risks of radiation and its very high cost, time-consuming, and inconvenient. Therefore, apart from all these neuroimaging methods, MRI imaging is one of the standard methods used to diagnose Alzheimer's disease. The advantage of this method is the ease of registration and economic cost over the above methods. MRI images should be at least 3 Tesla and the slices should be 3 mm thick so that acceptable images can be seen to examine the lesions of aging coils and spiral plaques. The MRI image is displayed in three different directions in **Figure 2**. Then, the appropriate image segmentation, mask, and sharp filter are used for pre-processing.

Various diagnostic tools from the clinical and processing areas for early diagnosis of Alzheimer's disease have been reviewed. Methods of blood tests, speech therapy, physical function, and hearing status were first examined by a physician and then diagnosed with mild Alzheimer's disease by recording an electroencephalogram and combining it with medical images [14]. First, the EEG signal is recorded from three channels Fz, Cz, Pz as unipolar and then MRI images from the peritoneal area. Combining MRI images and EEG signals can be a way to diagnose mild Alzheimer's disease. Medial temporal lobe atrophy, cerebrospinal fluid, white and gray matter volume, and asymmetry between the two hemispheres are effective features in MRI images to diagnose Alzheimer's disease. Another approach to EEG signal analysis is nonlinear and dynamic signal methods. The parameters that express nonlinear behavior are dual. The first category is parameters that emphasize the dynamics of signal behaviors such as entropy and Lyapunov's exponent. These parameters describe how the system behaves over time. The second category emphasizes the geometric nature of motion paths in state space, such as the correlation dimension. In this view, the system is allowed to move in the adsorption bed at the appropriate time and then, the geometric dimension of the adsorption bed is obtained. One of the most important tools used to understand the behavior and dynamics of time series of vital signals, which are mainly extracted from nonlinear systems, is the phase diagram.

Using this tool, the behavioral characteristics and chaotic nature of the data can be demonstrated appropriately and qualitatively, as well as important parameters such as the path of the system in the state space [15]. In order to draw this diagram using the recorded time series, it is enough to draw each sample at any time in terms of another sample in the previous time. **Figure 3** shows the two-dimensional phase curve, and **Figure 4** shows the three-dimensional phase curve of the Fz, Cz, and Pz channels of the EEG signal from a healthy person with the eyes closed.

Lyapanov's exponent shows the average convergence or divergence of the trajectory path in the phase space. The correlation dimension shows the number of

**Figure 3.** *Two-dimensional phase curve of Fz, Cz, Pz channels EEG signal in closed eye.*

**Figure 4.** *Three-dimensional phase curve of Fz, Cz, Pz channels EEG signal in closed eye.*

independent variables needed to describe the dynamics of the system and is another way to examine the chaotic signal. If the correlation dimension of a path is zero, it represents a steady state of the system, and if the value is equal to one, it represents prodigal behavior. The value of this variable is incorrect when chaotic behavior occurs. The higher the value of this parameter, the more complex the nonlinear system. Therefore, it can be said that the correlation dimension is the degree of complexity of the distribution of points in the phase space. **Figure 5** compares the correlation dimension of Pz channels between 3 groups of healthy people, mild patients, and severe patients. The amount of this feature decreases with the severity of the disease, which is evident in the Pz channel.

In patients with a clinical diagnosis of Alzheimer's disease, atrophy of the inner part of the temporal lobe is evident [16]. In the autosomal dominant form of Alzheimer's disease, atrophy of the inner part of the temporal lobe in patients, compared with controls, can be detected up to 3 years before the onset of clinical signs of cognitive impairment. In patients with Alzheimer's disease, hippocampal atrophy was reduced (10–50%), the amygdala was reduced to 40%, and parahippocampus was reduced to 40% compared with the control group, which was standardized for age. There is compelling evidence that atrophy of the internal structures of the temporal lobe, especially the hippocampus and entorhinal cortex, occurs early in the course of the disease and even before the onset of clinical symptoms [17]. The severity of changes in imaging of healthy elderly people makes it difficult to use MRI

#### **Figure 5.**

*Dimensional comparison of Pz channel correlation for three groups of healthy subjects, mild patient and severe patient.*

as a definitive diagnostic method. By the time mild symptoms appear, the volume of the hippocampus may have decreased by more than 25%. Clinically, a reduction in hippocampal volume is associated with the severity of clinical signs and symptoms of memory loss, the patient's score on cognitive evaluation tests, and pathological findings. **Figure 6** shows the determination of spinal atrophy and asymmetry. However, another group believes that there is no clear association between lesions in the course of dementia, including lesions of hyperexcitability of white matter on MRI, and the severity of the symptoms of post-adjustment cognitive impairment for age. They believe that due to the high sensitivity of MRI in the diagnosis of hyperexcitability lesions in T2 view and on the other hand the low specificity of these lesions in the diagnosis of the disease, there is a weak relationship between MRI findings and clinical and neuropathological symptoms. Eq. (1) shows how to determine medial temporal lobe atrophy (MTA):

**Figure 6.** *How to determine atrophy in MTA images.*

C: Unilateral lateral ventricle.

$$\begin{aligned} \text{MTA} &= (\text{A} - \text{B}) \times 10 \,\text{/C} \\\\ \text{Cleftt:} \,\text{Area} &= 187.3 \,\text{mm} 2, \angle \text{Avg} = 691.1, \text{Dev} = 128.3. \\\\ \text{Crightt:} &\,\text{Area} = 173.1 \,\text{mm} 2, \angle \text{Avg} = 648.2, \text{Dev} = 146.2. \\\\ \text{Aleft:} &\,\text{Area} = 324.7 \,\text{mm} 2, \angle \text{Avg} = 323.9, \text{Dev} = 238.1. \\\\ \text{Aright:} &\,\text{Area} = 325.5 \,\text{mm} 2, \angle \text{Avg} = 245.3, \text{Dev} = 191.3. \\\\ \text{Bleftt:} &\,\text{Area} = 200.3 \,\text{mm} 2, \angle \text{Avg} = 190.8, \text{Dev} = 121.6. \\\\ \text{Rightt:} &\,\text{Area} = 220.1 \,\text{mm} 2, \angle \text{Avg} = 160.4, \angle \text{Dev} = 118.3. \end{aligned}$$

When MTAi is calculated, two values are determined that each corresponds to a hemisphere. According to MTAi, the asymmetry index is calculated as Eq. (2), and the mean values of MTAi and IA for the three groups are given in **Table 1 (Figure 7)**.

$$IA = \left( \text{IMTAi} - \text{dMTAi} \right) / \left( \text{IMTAi} + \text{dMTAi} \right) \times 100 \tag{2}$$

Measurement of cerebrospinal fluid, gray matter, and white matter volumes from MRI images has been used to diagnose mild Alzheimer's disease [18].

In this study, nonlinear property that reflects the dynamic nature of the brain signal, including Lyapunov exponent and correlation dimension, is also determined. On the other hand, in order to determine the optimal characteristics in three classes of healthy people, mild patients, and severe patients, the method of analysis of variance has been used. Brain signals from the three channels Fz, Cz, and Pz are recorded in four modes: closed-eye, open-eye, reminder, and stimulus. Forty-five properties are specified in the excitation mode. **Table 2** shows the results of analysis of variance for three channels of Fz, Cz, and Pz between the group of healthy individuals, and mild and severe patients [19]. This analysis method is used in the classification of three or more classes to determine the optimal and effective characteristics.

**Table 1.**

*Mean values of MTAi and IA for the three groups are given.*

### **Figure 7.** *Cerebrospinal fluid, gray and white matter volume in the image in 18th slice of a participant with mild AD.*

#### **Table 2.**

*Compare the number and types of optimum features between Fz, Cz, Pz channels.*

In this study, the purpose of using the classifier, after extracting the optimal characteristics of brain signals, was to separate the three groups of healthy people, mild and severe patients, and two classifiers such as SVM and the Elman neural network been used, aiming at comparing static and dynamic classifiers [20]. One of the classification methods with the teacher is the backup vector machine method. This view is based on statistical learning theory, but its implementation is similar to the neural network. This method was designed to separate data into two categories. Of course, if you use several SVMs in parallel and with different methods, this method can be used to classify data into more than two categories. SVM claims: It solves the major problem of neural networks, namely overfitting [21]. The results of EEG signal accuracy of different channels in different modes are determined at two levels (mildsevere, mild-healthy, and healthy-severe). Due to the linear separator for three classes containing poor results accuracy, levels are divided into two levels. In this study, a 2-layer Elman neural network was used which has 8 neurons in the latent layer and 1 neuron in the output layer [22]. The number of neural network inputs is equal to the number of features, and the number of hidden layer neurons is equal to the number of optimal features, and to determine the best results, various experiments with

different numbers of neurons in the hidden layer have been performed. In the hidden layer and the output, the Sigmoid activation function is used due to its nonlinear property. There are many training functions for teaching the Elman network, wherein in this study the Levenberg-Marquardt error propagation algorithm was used due to higher convergence than other training functions, and the condition for stopping neural network training is an error coefficient of 0.001.


**Abstract**

Diabetes mellitus can induce substantial damage to the conduction system of the heart, especially the sinoatrial node. This is due to hyperglycemia leading to bradyarrhythmia. DM, via the elevation of HG, generates the production of a number of insulting agents in the myocardium known as reactive oxygen species and reactive carbonyl species, which elicit direct damage to neuro-filament-M and β2-adrenergic receptors in the conducting system as well as a number of cardiac contractile, cation transporting and channel proteins. One cation channel protein is the hyperpolarization-activated cyclic nucleotide-gated potassium channel. It encodes the protein responsible for the hyperpolarizing-activated current or the "funny current" that participates in spontaneous diastolic membrane depolarization in sinoatrial node cells. Gene expression of these proteins and their physiological functions are decreased in the diabetic heart, which affects the generation of electrical impulses or action potentials resulting in increases in RR and PR intervals and QRS complex duration of the electrocardiogram. The heart rate and force of contraction of the myocardium are decreased leading to bradyarrhythmia and sudden cardiac death. This review attempts to explain the cellular mechanism(s) involved in diabetes-induced bradyarrhythmia with emphasis on cation-transporting proteins, especially the hyperpolarization-activated cyclic nucleotide-gated channels pacemaker current channels.

**Keywords:** diabetes mellitus, sinoatrial node (SAN), heart, cardiac conduction system, arrhythmias

## **1. Introduction**

Diabetes mellitus (DM) is a serious global disease that currently affects more than 480 million people, and its number is growing rapidly. DM results from hyperglycemia (HG) and it is responsible for many long-term complications [1]. Cardiovascular

diseases (CVDs) account for more than half of the observed mortality in the diabetic population [2]. Nodal myocytes spontaneously generate APs in the absence of hormonal and neural stimulation [3]. Decreased heart rate (HR) is a common finding in patients with type 1 diabetes mellitus (T1DM) [4] indicating that many of these patients are likely to have impaired pacemaker function [5]. Cardiovascular defects are the major cause of morbidity and mortality in diabetic patients [6]. The cause of cardiac conduction disorders (CCDs) in DM patients is not fully understood. It remains unclear whether autonomic neuropathy or CVDs play a role [7]. This review addresses the effects of DM on the cardiac conduction system (CCS) which in turn can lead to arrhythmias and subsequently, sudden cardiac death (SCD). But first, it is important to understand the normal physiology of the conduction system before considering the mechanism(s) that might underlie the pathophysiology of DM-induced electrical conduction defects in the heart and its treatment.


*2.5. Microbiological Analysis*

The effect of HPP treatment was evaluated on natural contaminating flora (aerobic mesophilic microorganisms, molds, and yeasts) and on *Listeria monocytogenes* serovar 4b [26] (CECT 4032) as pathogen microorganism [27]. The growth media used for the spreading of samples was plate count agar (Scharlau Chemie S. A., Sentmenat, Spain) for mesophilic aerobic; potato dextrose agar (Scharlau Chemie S. A., Sentmenat, Spain) for molds and yeasts; and tryptic soy agar (Scharlau Chemie S. A., Sentmenat, Spain) for *L. monocytogenes*. The incubation conditions were 48 h at 30 ◦C, 120 h (5 days) at 24 ◦C, and 48 h at 37 ◦C, respectively.

*L. monocytogenes* was artificially inoculated in the sample. The stock vials containing *L. monocytogenes* at a concentration ca. 109 cfu/mL were generated following the methods described by Saucedo-Reyes et al. and Pina-Pérez et al. [20,28]. Before HPP treatment, vials were inoculated in the chokeberry-skimmed milk samples at a final concentration of 108 cfu/mL. The counts for evaluating microorganism inactivation were performed before and after each HPP treatment. Two aliquots (0.1 mL) were taken from each sample, diluted with buffered peptone water (Scharlau Chemie S. A, Sentmenat, Spain), and plated in the respective agar. Two replicas of each treatment were obtained, and three repetitions of each treatment condition was performed. The survival fraction S = N/N0 and the level of inactivation Log10 (N/N0) were evaluated for each repetition.


Thermoelectric Nanostructured Perovskite Materials

*Megha Unikoth, George Varghese, Karakat Shijina and Hind Neelamkodan*

### **Abstract**

The global need for energy production from renewable resources and the effect of greenhouse gas, especially carbon dioxide is increasing day by day. Statistical survey shows that about 60% of the energy lost in vain worldwide, in the form of waste heat. The conversion of this waste into useful energy form will certainly play a major role in alternative energy technologies. Thermoelectric materials (TE) can harvest waste heat and convert this into electrical energy and vice versa. The development of highefficiency TE materials for waste-heat-recovery systems is necessary to bring vast economic and environmental benefits. The methods of synthesis,that is, control over particle size play an important role in controlling the properties of thermoelectric materials. The nanostructuring of thermoelectric materials can enhance the efficiency by quantum confinement effect and phonon scattering. Perovskites have a long history of being a potential candidate for thermoelectric applications, due to their fascinating electrical, mechanical, and thermal properties. Compared with other thermoelectric materials perovskites have the advantage of eco-friendliness, less toxicity and are highly elemental abundant. Owing to the high thermal conductivity and low electrical conductivity overall performance of perovskites is relatively poor. The hybrid perovskites overcome this difficulty and started to draw the attention to thermoelectric applications.

**Keywords:** thermoelectric, figure of merit, nanostructuring, power generation, hybrid perovskites

### **1. Introduction**

The imbalance between energy production and demand is increasing day by day. While the conventional resources are being depleted, the challenges of researchers are concentrated on the power generation from renewable energy sources and on the efficient use of available resources. On the other hand, waste heat generation as greenhouse gas especially carbon dioxide is increasing in the environment. In internal combustion engines, only 25% of energy is used for vehicle mobility and accessories, approximately 40% of the fuel energy is wasted as exhaust gas, 30% is dissipated in the engine coolant and 5% is lost as radiation and friction. Here comes the importance of thermoelectric materials! The materials which can harvest heat from combustion of fossil fuels, sunlight, chemical reactions, nuclear decay, vehicles, etc., and convert it

into electrical energy and vice versa are thermoelectric materials. Thermoelectric power generation technology and the fields are now growing steadily due to their ability to convert heat into electricity and to develop cost-effective and pollution-free forms of energy conversion. A wide variety of thermoelectric materials has been identified and their properties have been explored. Among the oxide-based thermoelectric materials, rare earth-based perovskites are considered to be a potential material due to their fascinating electrical, mechanical, and thermal properties and high value of figure of merit. The thermoelectric materials in nanostructured form can enhance the performance of material by phonon scattering and quantum confinement effects [1–4].

### **2. Thermoelectric materials**

Thermoelectric materials have drawn vast attention due to the direct conversion between thermal and electrical energy. These materials can convert the heat energy to electrical energy and vice versa, thus providing an alternative source for power generation and refrigeration. Statistical survey shows that more than 60% of world's energy loss is in the form of heat. The high-performance thermoelectric materials can easily convert this heat into usable electrical energy. The thermoelectric system is an eco-friendly energy conversion technology with the advantages of high reliability, small size, feasibility in a wide temperature range, and no pollutants. The efficiency of the thermoelectric devices is small compared to Carnot's efficiency. The efficiency of these materials is defined in terms of figure of merit, ZT, which determines the thermoelectric performance.

$$ZT = \frac{\mathbb{S}^2 \sigma}{\kappa} T \tag{1}$$

where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. In order to get good performance, the value of ZT should be high. This can be achieved by increasing both the Seebeck coefficient and electrical conductivity and reducing the thermal conductivity.

The physics behind the thermoelectric power generation and the refrigeration is mainly governed by the three fundamental thermodynamic effects-the Seebeck, Thomson, and Peltier effects. When a temperature gradient is applied, an electrical potential gradient is generated, which is the Seebeck effect and is mainly used in the power generation. The Peltier effect is the reverse of the Seebeck effect in which a temperature gradient is established when a current is passed through the material and is used for refrigeration. Thomson heat is absorbed or released internally in the material if the flow of the Peltier heat is balanced by the temperature-dependent Seebeck coefficient. All the three effects are related to the heat transported by the charge carriers in the material as electrons or holes. Seebeck effect illustrating the working of a thermoelectric generator is given in **Figure 1**.

The thermoelectric efficiency (*ηP*) in the power generation mode as a function of average ZT is given by,

$$\eta\_P = \frac{T\_H - T\_C}{T\_H} \left( \frac{\sqrt{\mathbf{1} + Z T\_M} - \mathbf{1}}{\sqrt{\mathbf{1} + Z T\_M} + \frac{T\_C}{T\_H}} \right) \tag{2}$$

*Thermoelectric Nanostructured Perovskite Materials DOI: http://dx.doi.org/10.5772/intechopen.106614*

#### **Figure 1.**

*Illustration of the Seebeck effect, when heat flows through the junction current is generated.*

where TC, TH, and TM are the cold side, hot side, and average temperature respectively.

$$ZT\_M = \frac{1}{T\_H - T\_C} \int\_{T\_C}^{T\_H} ZTdT\tag{3}$$

A larger temperature difference can produce higher conversion efficiency, if the value of *ZTM*= 3 and *ΔT* = 400 K, *ηP* can reach 25%, comparable to that of traditional heat engines. The Seebeck effect is the thermoelectric power generation model and has application in advanced scientific fields. The thermoelectric cooling efficiency (*ηC*) is given by,

$$\eta\_C = \frac{T\_H}{T\_H - T\_C} \left( \frac{\sqrt{\mathbf{1} + Z T\_M} - \frac{T\_H}{T\_C}}{\sqrt{\mathbf{1} + Z T\_M} + \mathbf{1}} \right) \tag{4}$$

Similar to thermoelectric power generation, higher *ZTM* will produce a large cooling efficiency (*ηC*). For *ZTM*= 3 and *ΔT* = 20 K, *ηC* could reach 6%. The Peltier effect is a thermoelectric refrigeration model and is used to cool computer components to keep temperature within the limit or to maintain suitable functioning. The high ZT value is obtained only by increasing the value of S and σ and minimizing the κ. The complex relationship of thermoelectric parameters can be obtained from the Wiedemann-Franz law and Pisarenko relation, which is given by,

$$\mathcal{S} = \frac{8\pi^2 K\_B^2}{3eh^2} m^\* T \left(\frac{\pi}{3n}\right)^{\frac{2}{5}} \tag{5}$$

$$
\sigma = \frac{ne^2\tau}{m^\*} = ne\mu\tag{6}
$$

$$
\kappa\_{\text{total}} = \kappa\_{\text{electronic}} + \kappa\_{\text{lattice}} = L\sigma T + \kappa\_{\text{lattice}} \tag{7}
$$

where *K*B is the Boltzmann constant, h is the Planck constant, n is the carrier concentration, T is the absolute temperature, e is the electron charge, m\* is the effective mass, τ is the relaxation time, μ is the carrier mobility, and L is the Lorenz number. The electronic part of thermal conductivity is proportional to the electrical conductivity. Therefore, simultaneous enlargement of S and σ and the minimization of κ for high ZT values are very difficult. Over the past few decades, there is a lot of progress in the field of thermoelectrics to make an ideal material with ZT value greater than 3. There are many strategies for decoupling the relation between these parameters which includes phonon scattering mechanism, mass fluctuation strategy, rattling strategy, band engineering, 2D superlattice, and Panasonic approach. Energy filtering effects were also used in which an energy barrier was introduced by grain boundaries or nanocomposites [5]. According to the optimal working temperature, TE materials are classified into three – Bi2Te3 based low temperature (<400 K) materials, PbTebased material in the temperature range between 600 K and 900 K, and SiGe-based high temperature(>900 K) materials.

The first generation thermoelectric materials have ZT = 1 and the power generation efficiency is about 4–5%. The second generation materials pushed the ZT value up to 1.7 by nanostructuring and the obtained efficiency is 11–15%. The third generation material is under development and the predicted efficiency will be in the range of 15– 20%. The main goal will be to attain ZT ≥3 in future. PbTe is one of the most attractive thermoelectric materials [6].

The Skutterudites, Half-Heuslers, clathrates, and chalcogenides are hightemperature thermoelectric materials. Skutterudites are compounds with general formula MX3 where M = Co, Rh or Ir and X = P, and As or Sb (e.g., is CoSb3). These materials can influence the phonon transport mechanism, thereby reducing the lattice conductivity to very low level. X. Shi et al. reported that, for Ba0.08 La0.05 Yb0.04 Co4 Sb12 skutterudites has ZT = 1.7 at 850 K [7]. Half-Heuslers are alloys of the form ABX where A-Ti, Zr and Hf, B- CoSb, NiSn, etc. It was reported that, for n-type Hf0.5Zr 0.5NiSn0.99Sb0.01,0.8 ≤ ZT ≤ 1 was obtained at 600–700° C and for p-type Hf0.5Zr0.5CoSn0.2Sb0.8,0.5 ≤ ZT ≤ 0.8 due to the remarkable reduction in the lattice thermal conductivity [8].

The clathrates are low thermal conductivity compounds with Type I having X2Y6E46 formula and Type II having X 8Y 16E136 formula, where X and Y are guest atoms, E - Si, Ge, or Sn. Ba8Ga16Ge30 shows a Seebeck coefficient of 45 to -150mVK1 and electrical conductivity of 1500–600Scm1 at 300–900 K. The thermal conductivity of this compound is 1.8 WK1 m1 at 300 K and is reduced to 1.25 W K1 m1 at 900 K which makes ZT = 1.35 [9]. Chalcogenides are compounds with sulfides, selenides, and tellurides present in them (e.g., Bi2Te3, PbTe, SnSe, SiGe, etc). Among the oxide materials, NaCo2O4 has 0.7 ≤ ZT ≤ 0.8 at 1000 K [10]. The other new thermoelectric materials include In4Se3-δ (ZT =1.48) [33], In4Se3-xCl0.03 (ZT = 1.53) [34], β-Cu2-xSe (ZT = 1.5) [11] and β-Zn4Sb3 (ZT = 1.35) [12]. Low dimensional thermoelectric materials have higher performance than bulk materials because the density of states near the Fermi level is enhanced due to the quantum confinement effects, thereby increasing the thermopower (S2 σ) and boundary scattering at the interfaces reduces the thermal conductivity more than electrical conductivity. Therefore, by reducing the size of materials to 1D and 2 D, a significant enhancement in the value of ZT is obtained. Hicks and Dresselhaus first improved the value of ZT >1 of 2D Bi2Te3 quantum well [13]. He reported that the enhancement of ZT was achieved by the quantum confinement of electrons and holes, which increases the S2 σ and the reduction in the thermal conductivity was attributed to various effects, such as scattering of phonons at interfaces, defects, or phonon localization. Venkatasubramanian et al. reported, ZT = 2.4 for Bi2Te3-Sb2Te3 quantum well superlatttice of 6 nm periodicity [14]. The quantum dot superlattice of PbTe–PbSeTe system developed by Harman and co-workers has ZT = 1.6, which is higher than the bulk (ZT = 0.34) [15].

*Thermoelectric Nanostructured Perovskite Materials DOI: http://dx.doi.org/10.5772/intechopen.106614*

Hochbaum et.al reported that at room temperature, 50 nm diameter nanowires of Silicon have ZT = 0.6, which is very much higher than the bulk [16]. Boukai et al. noticed that reducing the nanowire's diameter, a significant reduction in thermal conductivity is attained and ZT of 1 at 200 K was reported for nanowires of 20 nm diameter. Nanostructured thermoelectric materials are designed in such a way to introduce nanometer-sized interfaces and polycrystalline into the bulk materials [17]. The lattice thermal conductivity can be reduced by increasing phonon scattering. Nanostructured composites of grain size �5 nm–10 μm can be fabricated by hot pressing or spark plasma sintering of fine powders [18]. In nanostructured material families (PbTe based nanomaterials, Bi2Te3–based and SiGe–based nanocomposites) an enhancement in ZT value is noticed. S. Fan et al. reported that in Bi2Te3–based nanocomposites, Bi0.4 Sb1.6Te3 has a ZT of 1.8 at 316 K [19]. Biswas et.al suggested that 2% SrTe – containing PbTe nanocomposites have a ZT of 1.7 at 800 K and X.W.Wang et al. studied Si80Ge20P2 nanocomposites and reported the ZT value of 1.3 at 1173 K [20, 21]. Perovskites, as well as their hybrids, started to draw attention as a potential candidate for thermoelectric applications.

### **3. Perovskites**

The first perovskite CaTiO3 was discovered by Gustav Rose in 1839 and named in the honor of an eminent mineralogist Count Lev Alexevich von Perovski. Perovskites are compounds having the structure formula ABC3, where A - rare earth, alkaline earth, alkali, or large ions, such as Pb+2, Bi+3, B - transition metal ion, and C - O, Fl, Cl, I, etc., commonly seen as in the form of ABO3. A cation may be monovalent like Li, Na, K, divalent like Ca, Ba, Sr., or trivalent like La, Nd, Pr, which is cubo-octahedrally coordinated with 12 oxygen atoms while B cation as Ti, Ni, Fe, Co, or Mn is octahedrally coordinated with 6 oxygen atoms. The substituted and mixed compounds of the form A1-xA'xB1-yB'yO3 also come under this class with distorted nonstoichiometric oxygen deficient configuration. The pseudo-perovskites are a special class of perovskites with empty A-site and BO3 configurations (e.g., ReO3 and WO3). The most abundant materials in the earth's crust are MgSiO3 and FeSiO3 perovskites [22].

The stability of perovskites is determined by a factor called Goldsmith tolerance factor given by, *t* ¼ *rA*þ*r*0 ffiffi 2 p ð Þ *rB*þ*r*0 , where *rA* – ionic radii of A-cation, *rB* – ionic radii of Bcation, and *r0*-ionic radii of oxygen. The value of t will be unity for an ideal perovskite. For different values of t, these materials have different structures. If t > 1, the crystal structure will be hexagonal in which A ions are too big and B ions are too small (e.g., BaNiO3). If t = 1 the structure will be cubic with A and B ions having ideal size (e.g., SrTiO3, BaTiO3). The materials with 0.71 < t < 1 have orthorhombic/rhombohedral crystal structure where A ions are too small to fit into B ion interstices (e.g., CaTiO3/ GdFeO3) and for t < 0.7 materials have different structures in which A ions and B ions have similar ionic radii (e.g., FeTiO3) [23].

The coexistence of spin, charge, lattice, and orbital interactions in perovskite materials make them applicable in optoelectronics, spintronics, photocatalysis, sensors, piezoelectric devices, electrode in solid oxide fuel cells, and thermoelectrics. They have a lot of fascinating properties, such as multiferroicity (BaTiO3, BiFeO3), colossal magnetoresistance (manganites), superconductivity (cuprates), ferromagnetism (SrRuO3), metal-insulator transition (LaMnO3), thermoelectricity (LaCoO3), etc.


**3. Digital hearing aid**

to devices that could amplify sound through an electric circuit. The history of the electronic hearing aid is thus very similar to that of the technological evolution of the microphone, amplifier, and battery cell. Between 1989 and 1900, the Akouphone Company produced the first electronic hearing aids called "*Akoulallion*" and "*Akouphone,*" introducing a carbon microphone technique. The carbon transmitter was able to use an electric current to amplify weak signals by 20–30 dB [9]. The *Akoulallion* was large and was used on a table, while the *Akouphone* was portable. Miler Reese Hutchison—one of the company's founding presidents—established the Hutchison Acoustic Company in 1903 and produced "*Acousticon,*" an improved electric hearing aid that was further miniaturized (**Figure 5a**). Users wore the microphone and main body, put the battery in a bag, and held the earphone in their hands. The Danish company *Oticon* and the German company *Siemens* are two current makers of hearing aids that begun operations

**Figure 5.** (a) Early electronic hearing aid with carbon components: *Acousticon* model A (Hutchison Acoustic Company, 1905). (b) Early vacuum tube hearing aid: *Vactuphone* (Globe Ear-phone Company, 1921). (c) Behind-the-ear hearing aid-

embedded transistor amplifier (Zenith Diplomat Company, 1956).

**Figure 4.** (a) and (b) Flower-vase-type hearing aid for gathering multiple speakers' voices (F. C. Rein Co.) in 1810.

during this period.

154 An Excursus into Hearing Loss

(c) Acoustic throne for European royalty in 1819.

After achieving this level of hearing aid output gain and miniaturization, scientists and engineers began looking for further ways to improve hearing-aid convenience. For example, analog hearing aids amplify sound from all frequency ranges, which means that both speech and unnecessary background noises are amplified equally. Another problem was that the small size of the devices caused the speaker and microphone to be too close, and acoustic feedback generated uncomfortable levels of amplified sound. In 1996, these problems began to be addressed when hearing aids entered the age of digital sound. The digital hearing aid converts sound into a binary digital signal, which can then be modified by computer software. This type of signal modification is called digital signal processing (DSP) and is the biggest advantage of the digital hearing aid.

**Figure 6** shows a computer interface through which the DSP installed in a hearing aid can be controlled after connecting the hearing aid to the computer. The most beneficial aspect

require any cords or cables. However, in modern society, wireless function is increasingly useful for connecting hearing aids to other electronic devices. For example, because holding a smartphone near one's ear is difficult when wearing a hearing aid, the wireless hearing aid can receive speech signals directly from the smartphone using Bluetooth technology. In the near future, users will be able to control the DSP from a smartphone app. Wireless hearing aids can also help when watching television. By wirelessly connecting to the TV, users can hear clear sound from a TV program without the sound needing to travel through the air. Thus, environmental noise can be minimized and reverberations in

Hearing Aids

157

http://dx.doi.org/10.5772/intechopen.73527

Digital hearing aids will likely continue to evolve and add new features and functions. For example, a hearing aid with Global Positioning System will make it easier to be found if it gets lost or misplaced. Like other wearable electronics, if hearing aids incorporate functions for measuring heart rate, step counts, and burned calories, they will become a type of wearable

Against a background of various technological advances, the hearing aid has continued to respond to user expectations. Are users today satisfied with the current hearing aid? Countries in Europe and Japan have conducted large-scale market research surveys called *EuroTrak* and *JapanTrak* since 2009 [10]. According to JapanTrak 2015, 1306 people with hearing loss filled out their marketing surveys. Along with a corresponding survey in the US (*MarkeTrak IX* in 2014), we can discuss how satisfied hearing-aid users are in countries whose citizens have

**Figure 7** shows basic demographic information. The percentage of people with hearing loss is higher for countries with aging populations (i.e., Germany, Italy, and Japan). However, the percentage of people with hearing loss who own hearing aids is lower in these countries than

**Figure 7.** (a) Percentage of people with hearing loss in several high-tech countries. (b) Percentage of people using hearing

a room can be ignored.

device that supports lifelong health.

access to the latest technology.

**4. User subjective assessment of hearing aids**

aids to the number of people with hearing loss in each country.

**Figure 6.** Example of software used to adjust a hearing aid's digital signal processing.

of the DSP is the ability to adjust the output gain in each one or one-third octave frequency band. The computer program designs the shape of a digital filter and modifies the signal passing through the filter (multichannel analysis). Because sound energy in human voice is distributed in a frequency range of 200 Hz to 4 kHz, unwanted noise can be weakened by amplifying only the desired frequency range. Audiograms of people with hearing loss differ according to individual sensitivity to each frequency band (e.g., high tone deafness, horizontal deafness, convex deafness, or concave deafness). The multichannel output can thus limit compensation to the frequency bands for which a person has difficulty in hearing.

The multichannel output is also useful for suppressing acoustic feedback. Acoustic feedback occurs when the following happens simultaneously: (1) attenuation of the speaker's voice by the time it reaches the microphone is less than the amount of sound gain and (2) the phases of the original and feedback signals are mostly overlapped. ITC and CIC hearing aids have a vent to reduce the uncomfortable feeling that can occur in the occluded ear, and the output sound transmitted through the vent can cause acoustic feedback. The solution is a feedback canceller in the hearing aid that identifies the offending frequency-repeating amplification and reduces the sound gain in the corresponding band.

The other important role of DSP is to create a compression system for the output sound. If a hearing aid amplifies sound linearly, it makes already loud sounds excessively loud. Patients with sensorineural hearing loss hear sounds above a certain sound level louder than normal listeners (recruitment hearing). Thus, the sound of a closing door or a cry from a child can annoy hearing aid users. The compression system suppresses the amplification of sounds above a certain sound level and instead fits them within the restricted dynamic range of the user. This system can therefore avoid unpleasant sounds, normalizes the perceived loudness, and improves speech intelligibility.

Another advantage of digital hearing aids is their ability to work wirelessly. In their times, the BTE hearing aid only had a short cord, and the ITC and CIC hearing aids did not require any cords or cables. However, in modern society, wireless function is increasingly useful for connecting hearing aids to other electronic devices. For example, because holding a smartphone near one's ear is difficult when wearing a hearing aid, the wireless hearing aid can receive speech signals directly from the smartphone using Bluetooth technology. In the near future, users will be able to control the DSP from a smartphone app. Wireless hearing aids can also help when watching television. By wirelessly connecting to the TV, users can hear clear sound from a TV program without the sound needing to travel through the air. Thus, environmental noise can be minimized and reverberations in a room can be ignored.

Digital hearing aids will likely continue to evolve and add new features and functions. For example, a hearing aid with Global Positioning System will make it easier to be found if it gets lost or misplaced. Like other wearable electronics, if hearing aids incorporate functions for measuring heart rate, step counts, and burned calories, they will become a type of wearable device that supports lifelong health.


**Abstract**

Various persistent organic pollutants (POPs) are increasingly being detected in numerous environmental matrices, including water. Even though there are currently some technologies for the elimination of these pollutants, it is necessary to evaluate their advantages, disadvantages, process time, and cost to find the optimal treatment depending on the characteristics of the pollutants and the matrix to remediate. This work was carried out to compare phase change technologies, advanced oxidation processes, and biological treatments for the elimination of POPs. In this chapter, a recent literature review of the aforementioned methods was performed. Studies are still being carried out to find the best way to eliminate POPs, as this depends on the treatment conditions, the type of water and the policies of each country, but biological treatments seem to be the best option so far.

**Keywords:** persistent organic pollutants, wastewater, treatment processes, phase change technologies, advanced oxidation processes, biological processes

## **1. Introduction**

In recent decades, the world population has grown exponentially, generating many negative ecological impacts, derived from residues such as drugs, pesticides, dyes, hormones, and personal care products. These wastes have persistent organic pollutants (POPs) in their composition [1–3].

POPs are usually halogenated and mostly chlorinated compounds that normally have nitro, sulfo, halogen, and/or aromatic residues that are responsible for their recalcitrance [4]. Its carbon-chlorine bonds are very stable against hydrolysis and at a higher number of these bonds, the higher is the resistance to degradation by biological or photolytic action. These POPs usually have ring structures with a single or branched chain. Due to their low solubility in water and high in lipids, they can pass through biological membranes and accumulate in the fat deposits of organisms [5]. Therefore, they can negatively affect human health and several other living organisms, causing mutagenicity, carcinogenicity, reproductive instability, as well as acute and chronic toxicity [3, 6].

The amounts of POPs used around the world have been considered a major concern, which is why 127 countries signed, on May 22, 2001, in Sweden, the Stockholm Convention, as part of the United Nations Environment Program (UNEP). This agreement initially generated a list with 12 of the most used priority toxic substances to prohibit and minimize their use [5, 7]. The number of chemical groups found on

this list continues to grow as new compounds that are part of this classification are identified, such as pentachlorophenol, nonylphenol, octylphenol, and dicofol [8].

The toxic properties of these substances persist for a long time in the environment and can travel long distances before being stored in fatty tissues [5, 7]. POPs are distinguished by being semi-volatile, which allows them to appear in the form of vapor and be present in the atmosphere. These POPs are transported long distances by air, soil, and water, affecting particularly fish and marine mammals. Due to the bioaccumulation properties of such pollutants, they can be transmitted through trophic chains [5, 9].

POPs can be found in large numbers of water bodies in concentrations ranging from ngL−1 to μgL−1, even in drinking water, but mainly in industrial, domestic, agricultural, and hospital discharges. These POPs are difficult to degrade with conventional wastewater treatments due to its physicochemical characteristics [1, 9].

Although there are current technologies for advanced wastewater treatment, they have limitations such as their high cost, the formation of toxic by-products and damage to the environment. Therefore, it is important to find, which method is optimal depending on the water characteristics. This chapter reviews the literature of existing processes and emerging technologies for the elimination of persistent organic pollutants in wastewater, analyzing their advantages, disadvantages, comparing time, cost, and degradation conditions of the treatment.

### **2. Treatment processes**

Unconventional wastewater treatment technologies have changed over time, developing a wide range of approaches to pollutant removal. Treatment processes are broadly divided into phase change technologies, advanced oxidation processes, and biological treatments.

Persistent organic pollutants comprise a wide range of various compounds and transformation products, but only those found mostly in the literature will be mentioned. It should be noted that the removal efficiencies were taken directly from the bibliography without any additional modification.

### **2.1 Phase change technologies**

These are processes capable of moving pollutants from one phase to another. They are commonly used in POPs removal and are divided into adsorption processes and membrane technologies filtration.

### *2.1.1 Adsorption processes*

Different adsorption processes have been studied for the removal of different pollutants, but the use of activated carbon (AC) is the most frequent due to its high porosity and specific surface [10, 11]. In general, good results of POPs removal have been obtained with AC, up to 99% depending on the contaminant and the application time [12, 13]. This type of treatment lasts approximately 90–150 minutes depending on the amount of the adsorbent and the pollutant [14, 15].

Carbon nanotube adsorption (CNT) is another technology, consisting of an allotrope of carbon that has different adsorption characteristics depending on the degree of waviness, diameter, internal geometry, physicochemical properties, and the treatment process used to its synthesis. CNTs are defined as single-walled nanotubes (SWNT), which have an internal diameter of approximately 1.0 nm, and multiwalled nanotubes (MWNT), which consist of several concentric tubes or layers of

### *Methods for Persistent Organic Pollutants Removal in Wastewater: A Review DOI: http://dx.doi.org/10.5772/intechopen.99973*

laminated graphene. Currently, there are only limited studies of this technology, but single-walled nanotubes are known to be more effective in removing POPs [16, 17].

There are countless studies of the use of clay minerals in adsorption processes, of which it has been observed that, depending on the type of clay, the amount of nitrogen, iron or other present minerals, different removal efficiencies can be produced. Although these approaches have shown very promising results, more research is required as the fate of the contaminants and the removal mechanisms involved remain largely unknown [18, 19].

Other adsorbent materials for POPs removal include zeolites, mesoporous, microporous materials, resins, and metal oxides. In which the nature of the pollutant significantly influences. One limitation of the use of these materials is the sustainability of their production since the use of soils, clays or other natural materials can be unsustainable in the long term. On the other hand, as in the adsorption methods mentioned above, there has been a limited application of these materials for the removal of POPs [20, 21].

**Table 1** shows a comparison of some of the adsorption processes, in terms of removal percentages, degradation conditions and an approximation of the application costs. There is a wide range between the removal percentages depending on the type of contaminant; this may be due to the carboxyl and hydroxyl groups they contain. On the other hand, these processes worked with acidic to neutral pH and with temperatures ranging between 22–30°C. Operating costs vary depending on the type of material used and can range from 0.01 to 7 USD per m3 .

### **Table 1.**

*POPs removal characteristics by adsorption processes.*

In general, for adsorption processes, the characteristics of the adsorbent material dictate the efficiency of the removal process, mainly because this determines other properties such as pore size, metallic or non-metallic nature, and the ability to couple with a second treatment [22]. It should be noted that a significant limitation is that most research studies discuss laboratory-scale tests and do not provide information for the expansion or large-scale viability of the processes [17].

### *2.1.2 Membrane technologies*

Membrane processes are another type of phase change technology with great POPs removal capacities; they are based on the use of hydrostatic pressure to eliminate suspended solids and high or low molecular weight solutes, allowing the water passage through. The duration of these processes is approximately 2–8 hours [15]. As in adsorption processes, membranes are produced from different materials with specific filtering characteristics such as pore size, surface charge, and hydrophobicity, which will determine the type of contaminant that can be retained [17, 23].

Ultrafiltration (UF) has been used for the removal of a significant variety of POPs since this process has a pore size in the range of 0.001–0.1 mm. The removal efficiency may vary according to the type of membrane and the contaminant. Generally, highly water-soluble polar pollutants are efficiently removed by ultrafiltration compared to non-polar compounds, poorly soluble in water [24–26].

Nanofiltration (NF) can be used for the removal of some POPs due to its small pore size (10 to 100 Å). This process could be considered more efficient than ultrafiltration for contaminants removal. Another advantage is the lower cost since it operates at low water pressure [24, 25]. However, the half-life of the membranes and their cost should be considered.

Microfiltration (MF) is a technique that has many advantages, but unfortunately, it is not useful for the removal of POPs as it cannot remove contaminants smaller than 1.0 mm [27, 28].

Reverse osmosis (RO) and forward osmosis (FO) use a semi-permeable membrane to separate water from dissolved solids, especially ions, by osmotic pressure. In comparison, reverse osmosis is more effective for the removal of persistent organic pollutants, since it can remove particles up to 10 Å, as well as colloidal particles [29, 30].

Depending on the type of process and the type of contaminants, removal efficiencies are highly variable with values between 11 and 99%. This is associated with the molecular weight of the contaminants, the lower the better removal and vice versa. On the other hand, these technologies are of average cost, ranging from 0.3 to 0.5 USD per m3 , as shown in **Table 2**.

According to the membrane technologies discussed in this section, as the size of the pores decreases, the efficiency of the POPs removal process improves significantly. However, membrane plugging can occur due to particles and colloids present in the feed streams. These processes are still being updated to achieve greater elimination in terms of quantity and quality of contaminants.

In summary, phase change processes can be effective in removing some persistent organic pollutants. However, the final disposal of the contaminants is challenging, because they pass into the solid phase after treatment, in the case of adsorption, or flow with the rejected effluent, in the case of membrane processes. Therefore, POPs will continue to be a problem for the environment [17].

### **2.2 Advanced oxidation processes**

In recent years there has been great interest in advanced oxidation processes (AOP), due to their great capacity to decompose pollutants, which is associated with

*Methods for Persistent Organic Pollutants Removal in Wastewater: A Review DOI: http://dx.doi.org/10.5772/intechopen.99973*

### **Table 2.**

*Removal properties of POPs by membrane technologies.*

the production of hydroxyl radicals in situ (oxidation potential, 2.8 V) that mineralizes pollutants [17].

AOPs are processes with different routes of free radical production, with specific working conditions and they can involve different materials. These processes have been applied for the elimination of different POPs and their effectiveness depends on the concentration of the oxidizing agent, the pH of the reaction mixture, the chemical structure, the initial concentration of the target contaminant, the wavelength, the intensity of the source, and presence of other organic matter. Therefore, there is no single AOP capable of eliminating all persistent organic pollutants [17].

Some of the most used and best-performing AOPs for POPs removal are UV/ H2O2 treatment, Fenton, wet air oxidation, and ozonation. The combined UV/H2O2 process is more effective in degrading POPs in water than UV irradiation or H2O2 oxidation alone, due to photolysis of hydroxyl radicals that generate H2O2 [32].

UV/H2O2 wastewater treatment complemented with microwave irradiation is very effective because of its short reaction time, reduction in activation energy, smaller equipment size, ease of operation and high product performance [15].

The Fenton process is capable of oxidizing aromatic contaminants. Iron (II) reacts with hydrogen peroxide to form iron (III) and hydroxyl radicals. Iron (III) is regenerated back to Fe (II) by hydrogen peroxide in an acidic environment. This technology can be used as a pretreatment method to reduce the toxicity of contaminants. In addition, the Fenton process has variants, such as the Fenton-like and photo-Fenton processes. The Fenton-like process uses iron (III) as a catalyst to convert the reaction from homogeneous to heterogeneous process and is more economical and efficient compared to the classical Fenton process, while having a similar mechanism. On the other hand, the photo-Fenton process is a more efficient and less pH-dependent treatment method, in which hydrogen peroxide can generate hydroxyl radicals under ultraviolet light and iron (III) can accept an ultraviolet photon to regenerate iron (II) [33, 34].

Wet Air Oxidation (WAO) can be used to treat toxic organic wastewater, with high temperature and pressure alone or with catalysts. In this process, the microorganisms mix with gaseous oxygen at temperatures ranging from 150 to 400°C and with pressures of 2 to 40 MPa [35].

Ozonization is a good alternative to degrade POPs at a very fast rate. The method involves a direct reaction between molecular ozone and dissolved compounds or by transformation to oxidants, hydroperoxyl radicals and other species that react with the target compounds [36].

As shown in **Table 3**, AOPs have a high degradation performance for all studies, for which pH is important, with values between 3.5 and 7. Another great advantage is the short time of operation that goes from 0.5 to 8 hours. The main difference between these processes is the source of energy provided, which raises the cost

### **Table 3.**

*Advanced oxidation processes for POPs removal.*

between 7.5 and 9 USD per m3 , subsequently, solar radiation is a potential alternative to reduce it [15, 17].


**Abstract**

The bracing indication for adults with spinal deformities is two-fold: (1) pain and (2) deformity. Although pain is more frequent in the adult population with scoliosis, there is no correlation between the angle of curvature and pain intensity. Pain is reportedly more frequent in patients who were operated. Non-specific pain can successfully be treated with stabilisation exercises; however, some patients may need brace treatment to improve their pain. Today, with the help of a simple clinical test, we can distinguish between different types of lower back pain allowing a differential approach to the symptom. There is some evidence that pain can successfully be reduced by these approaches mainly influencing the sagittal profile. In patients with bigger deformities and in patients aiming at reducing their deformity, pattern-specific scoliosis braces are a successful choice according to published research cases. The different specific brace types/designs along with the differential indication for these brace types will be described in this chapter.

**Keywords:** adult scoliosis, deformity, pain, brace treatment

## **1. Introduction**

General remarks regarding chronic back pain have been reviewed in a previous study focussing on brace treatment for patients with spinal deformities [1]: within the adult population, certain complaints and diagnoses are increasing such as low back pain, degenerative scoliosis and spinal stenosis. The number of symptomatic patients with spinal stenosis complaints is not known but the main aims of interventions are to improve pain management, functional and lifestyle choices [2]. Spinal stenosis surgery is increasing, and in the 1980s and early 1990s, it is suggested by Ciol et al. [3] that the numbers increased eight-fold. It is controversial to assume that sedentary lifestyles contribute to back pain, but few discussions continue in this topic of research. It is hypothesised that there are negative consequences to this type of lifestyle, initially within muscles, which ultimately lead to compensation in the structure and function of connective tissue [4].

A sedentary choice in lifestyle may initially lead to a negative change in posture, such as a loss of lumbar lordosis. This postural position correlates significantly with a prevalence of lower back pain (LBP) and spinal claudication. In the adult population, lower back pain and spinal claudication can progress to degenerative, de novo scoliosis [5].

Research focusing on younger adolescent female patients [6] demonstrated that non-specific LBP is reported even in this younger age group, especially those reporting a family member with lower back pain.

In 60% of secondary school pupils and 32% of students, lower back pain was a reported symptom. A correlation between lower back pain and displaying a sedentary position (p < 0.001 for pupils, and p < 0.02 for other students), and smoking (p < 0.001 for students and p < 0.02 for pupils) has shown to be statistical significant in analysis [7].

Furthermore, a beneficial consequence of an increase in physical activity and leisure time has shown to reduce musculoskeletal morbidity in patients of working age, specifically in those who have sedentary jobs [8].

Some studies argue the contrary and do not support the hypothesis that sedentary lifestyle contributes to lower back pain [9–11]. In one study, the lordotic angle seemed to have no influence on the prevalence of low back pain [9]. The presence of lordosis and the angle of lordosis alone may not be the only influential cause, but more specifically, it is the location of lordosis and shape of the posture, specifically the lordosis in the upper lumbar section of the spine that has the most effect upon reported pain levels [12, 13].

'Chronic low back pain' is an umbrella term and relates to patients reporting pain in the lumbar or sacral region or even in the sacroiliac pelvic joints. As the pelvis may be involved, the iliolumbar ligaments and even some radicular symptoms may also add to the complexity of the source of pain. With the presence of radicular symptoms, the nerve root affected would determine the origin of the lower back pain [14].

Without the presence of radicular symptoms, chronic lower back pain cannot be caused by a specific nerve root and may have a more complex cause involving L5/S1 or L4/5, and or the pelvis joints or ligaments [14].

Chronic low back pain without radicular symptoms and without any other specific clinical finding (for example, spondylolisthesis) is not classified and attributed in international research as being 'unspecific' or 'non-specific'. For bracing of this group of patients with chronic non-specific low back pain, simple physical tests have been published to predict the brace type the patient might benefit from. Based on the results of physical tests, a simple functional classification of 'non-specific' lower back pain has been developed [1].

In patients with scoliosis, besides the common cosmetics issues, pain is also a reported common issue [15]. Although back pain in patients with scoliosis is not related to the size of the curvature (Cobb angle) [16, 17], there is evidence that scoliosis patients experience statistically more back pain in later adulthood than agematched controls [18–21]. This back pain is not always disabling [19–21] and can be treated conservatively with reasonable success [16, 17, 22, 23]. While low back pain increases after surgery [24], pain in patients with scoliosis without surgery can be reduced with exercises, be it core stabilisation exercises [22, 23] or pattern-specific exercises (for example, Schroth) [16, 17].

In rare cases, the pain cannot be reduced using the functional exercise approach. For these cases, bracing can be successful [1, 12, 13, 25–27].

As outlined above in patients with scoliosis, we distinguish between different kinds of chronic back pain [28]. Most complaints come from the lower back region. Specific chronic low back pain stems from the lumbosacral region and can usually be referred to an injured or inflamed nerve root. This type of pain mainly is caused by a disc prolapse with compression of a nerve root. Specific low back pain needs a

### *Brace Treatment for Adults with Spinal Deformities DOI: http://dx.doi.org/10.5772/intechopen.92321*

specific treatment in order to reduce the nerve compression and, commonly, surgical decompression in case of significant impairment of the nerve [28].

But as already outlined, non-specific chronic low back pain cannot be referred to a single nerve root. In patients with chronic non-specific low back pain, there may be functional impairments of the sacroiliac joints, lumbar facet joints, overuse of the iliolumbar ligament and spinal stenosis, relative or absolute. Psychological issues also play a role in the development of chronic non-specific low back pain [14, 28]. This also applies to patients with spinal deformities.

Functionally, we may distinguish between postural low back pain (PLBP) and instability low back pain (ILBP) [1] (**Figure 1**). While PLBP mainly is related to loss of lumbar lordosis in later adulthood, ILBP is related to joint laxity or a definite instability like in patients with spondylolisthesis. Combinations of both entities are also possible [1].

In a study from 2009 [26], 130 patients presenting with spinal deformities (ranging from middle aged to older adults of 69 years old) and chronic unspecific low back pain were tested, using brace treatment for their chronic lower back pain. 16 of these patients presented with symptoms of spinal claudication. The sagittal re-alignment test (SRT) was applied (a lumbar hyperextension test) and a 'sagittal de-lordosation test' (SDT) to each participant. In addition, three female patients with spondylolisthesis were tested, including one female with symptoms of spinal claudication. 117 of the 130 patients reported a significant pain reduction when the SRT was applied. 13 patients, when applying the SDT also had significant reductions in pain. Three out of 130 patients had no significant change in their pain levels in either test. Pain intensity for all participants was high prior to the physical tests (VRS scale 0–5) and low while performing the physical test. These differences in pain scores were highly significant in analysis. There was an exception in three patients (2.3%): a clear distribution to one of the two classes was possible.

### **Figure 1.**

*The sagittal realignment test (SRT) seen on the left and the de-lordosation test (DT) with patient in the standing position. The sagittal realignment test (SRT)—a positive result in this test will present with an immediate reduction in chronic postural LBP (PLBP). The de-lordosation test (DT) pictured on the right—a positive result on this test will present with an immediate reduction in chronic LBP if this is due to instability low back pain (ILBP). Taken from [1] (Creative Commons Attribution Licence).*

117 patients were supplied successfully with a sagittal realignment brace and 13 with a sagittal de-lordosing brace. A clear distribution of the patients from this sample to either chronic postural or chronic instability back pain was possible. In 2.3%, a combined chronic low back pain was found. The authors concluded that chronic non-specific low back pain may be classified physically. The functional classification described is necessary to decide which specific conservative approach (lordosation/de-lordosation of the lumbar spine) should be used [1]. However, the topic spinal deformities in conjunction with brace treatment is not well established in the international literature and research. Therefore, a systematic PubMed review has been undertaken in order to find more studies with the aim to establish a scientific basis for treatment suggestions for this group of patients [15].