Simple and efficient estimation of photovoltaic cells and modules parameters using approximation and correction technique.

The behavior of solar cells and modules under various operational conditions can be determined effectively when their intrinsic parameters are accurately estimated and used to simulate the current-voltage (I-V) characteristics. This work proposed a new computational approach based on approximation and correction technique (ACT) for simple and efficient extraction of solar cells and modules parameters from the single-diode model. In this technique, an approximated value of series resistance (Rs) was first derived and used to determine the initial value of parallel resistance (Rp). Later, the final corrected values of Rs and Rp were obtained by resubstituting their approximated values in a five-loop iteration using the manipulated equations. For rapid evaluation and validation of the proposed technique, a software application was also created using MATLAB program. The correctness and robustness of the proposed technique was validated on five types of solar cells and modules operated at varied temperatures and irradiances. The lowest RMSE value was achieved for RTC France (7.78937E-4) and PVM 752 GaAs (2.10497E-4) solar cell. The legitimacy of ACT extracted parameters was established using a simple yet competitive implementation approach wherein the performance of the developed technique was compared with several state-of-the-art methods recently reported in the literature.

Classification of Hydration in Clinical Conditions: Indirect and Direct Approaches Using Bioimpedance.

Although the need to assess hydration is well recognized, laboratory tests and clinical impressions are impractical and lack sensitivity, respectively, to be clinically meaningful. Different approaches use bioelectrical impedance measurements to overcome some of these limitations and aid in the classification of hydration status. One indirect approach utilizes single or multiple frequency bioimpedance in regression equations and theoretical models, respectively, with anthropometric measurements to predict fluid volumes (bioelectrical impedance spectroscopy-BIS) and estimate fluid overload based on the deviation of calculated to reference extracellular fluid volume. Alternatively, bioimpedance vector analysis (BIVA) uses direct phase-sensitive measurements of resistance and reactance, measured at 50 kHz, normalized for standing height, then plotted on a bivariate graph, resulting in a vector with length related to fluid content, and direction with phase angle that indexes hydration status. Comparison with healthy population norms enables BIVA to classify (normal, under-, and over-) and rank (change relative to pre-treatment) hydration independent of body weight. Each approach has wide-ranging uses in evaluation and management of clinical groups with over-hydration with an evolving emphasis on prognosis. This review discusses the advantages and limitations of BIS and BIVA for hydration assessment with comments on future applications.

Validation of the laryngopharyngeal reflux color and texture recognition compared to pH-probe monitoring.

OBJECTIVE/HYPOTHESIS: The objective of this study was to determine the validity of our laryngopharyngeal reflux (LPR) diagnostic system from our previous study (Witt et al.) against the results of a standard pH probe monitoring. We hypothesized that subjects with abnormal pH probe results demonstrate color and texture abnormalities that would be classified as LPR according to artificial neural network (ANN) analysis. STUDY DESIGN: Retrospective analysis. METHODS: Eighty-two subjects, including 18 pH-positive, 11 pH-negative, and 53 control subjects were tested for LPR through multichannel intraluminal impedance 24-hour pH (MII-24pH) monitoring. Laryngoscopic images of all subjects were obtained. The hue and texture values of seven areas of interest, including true vocal folds, false vocal folds, arytenoids, and interarytenoid, were quantified using a hue calculation and two-dimensional Gabor filtering. These served as inputs for the ANN. This was used to classify images through pattern recognition, and a receiver operating characteristic (ROC) analysis was performed to determine the effectiveness of the diagnosis. RESULTS: Classification accuracy for the combined hue and texture was 87.40%, with an area under the ROC curve of 0.910. CONCLUSION: Although a previous study conducted classification based on RFS, this study suggests that color and texture analysis may be used to classify images based on the results of pH probing, a more objective approach for diagnosis. Additional studies should include more subjects to produce an even more accurate reading, and will use the color/texture analysis tool to test and confirm this application in a clinical setting. LEVEL OF EVIDENCE: 3B. Laryngoscope, 127:665-670, 2017.

Métodos de evaluación de la composición corporal: una revisión actualizada de descripción, aplicación, ventajas y desventajas / Methods of assessment of body composition: an updated review of description, application, advantages and disadvantages

El estudio de la composición corporal es un tema de interés creciente que puede ser utilizado tanto para la investigación como para fines clínicos. Para los profesionales de las ciencias de la salud es importante conocer las características de los diferentes métodos de evaluación y análisis de la composición corporal, ya que cambios en esta guardan relación directa con la salud y el riesgo de enfermedades. Actualmente, los métodos de análisis de la composición corporal son divididos en tres grupos, donde están el directo, los indirectos y los doblemente indirectos. El método directo es la disección de cadáveres. Entre los indirectos encontramos la tomografía axial computarizada, la resonancia magnética nuclear (RMN), la absorciometría dual de rayos X y la plestimografía; y en lo referente a los métodos doblemente indirectos destacan la antropometría y la impedancia bioelectrica. Asi, este trabajo tiene como objetivo revisar los métodos mas utilizados para el análisis de la composición corporal, describiéndoles, analizando sus aplicaciones, ventajas y desventajas. Se llevo a cabo una búsqueda de artículos en las bases de datos PubMed, Web of Science, Scopus, SportDiscus y Google Academico. Las palabras usadas fueron, body composition, body mass, body fat, muscle mass, fat mass, measurement, assessment y evaluation, aisladas o combinadas, y sus respectivos sinónimos en castellano y portugués. Fueron encontrados 221 artículos, de los cuales fueron seleccionados 59 para esta revisión. Se concluye que los diferentes métodos para evaluar la composición corporal presentan ventajas y desventajas, que deben ser analizados cuando se elige el método a ser empleado, para intentar minimizar sus desventajas y potencializar sus ventajas (AU)

The study of body composition is a topic of growing interest that can be used both for research and for clinical purposes. For professionals of health sciences is important to know the characteristics of the different methods of evaluation and analysis of body composition because, it changes are directly related to health and disease risk. Currently, methods of analysis of body composition are divided into three groups, which are direct, indirect and double indirect. The direct method is the dissection of cadavers. Indirect find computed tomography, magnetic resonance imaging, dual X-ray absorptiometry and plethysmography and in terms of the doubly indirect methods include anthropometry and bioelectrical impedance. Thus, this paper is aimed to review the most used for analysis of body composition by describing, analyzing their applications, advantages and disadvantages methods. Was conducted a search of article in databases PubMed, Web of Science, Scopus, SportDiscus and Google Scholar. The words used were, body composition, body mass, body fat, muscle mass, fat mass, measurement, assessment and evaluation, isolated or combined and their alternatives in Castilian and Portuguese. Were selected articles that were in English, Castilian and portuguese. They were found 221 articles, of which 59 were selected for this review. It is concluded that the different methods for assessing body composition have advantages and disadvantages, which should be analyzed when choosing the method to be used to try to minimize the disadvantages and empower its advantages (AU)

A new bioimpedance research device (BIRD) for measuring the electrical impedance of acupuncture meridians.

OBJECTIVES: The aim of this article is to introduce an electrical bioimpedance device that uses an old and little-known impedance measuring technique to study the impedance of the meridian and nonmeridian tissue segments. DESIGN: Three (3) pilot experimental studies involving both a tissue phantom (a cucumber) and 3 human subjects were performed using this BIRD-I (Bioimpedance Research Device) device. This device consists of a Fluke RCL meter, a multiplexer box, a laptop computer, and a medical-grade isolation transformer. Segment and surface sheath (or local) impedances were estimated using formulae first published in the 1930s, in an approach that differs from that of the standard four-electrode technique used in most meridian studies to date. RESULTS: Our study found that, when using a quasilinear four-electrode arrangement, the reference electrodes should be positioned at least 10 cm from the test electrodes to ensure that the segment (or core) impedance estimation is not affected by the proximity of the reference electrodes. A tissue phantom was used to determine the repeatability of segment (core) impedance measurement by the device. An applied frequency of 100 kHz was found to produce the best repeatability among the various frequencies tested. In another preliminary study, with a segment of the triple energizer meridian on the lower arm selected as reference segment, core resistance-based profiles around the lower arm showed three of the other five meridians to exist as local resistance minima relative to neighboring nonmeridian segments. The profiles of the 2 subjects tested were very similar, suggesting that the results are unlikely to be spurious. CONCLUSIONS: In electrical bioimpedance studies, it is recommended that the measuring technique and device be clearly defined and standardized to provide optimal working conditions. In our study using the BIRD I device, we defined our standard experimental conditions as a test frequency of 100 kHz and the position of the reference electrodes of at least 10 cm from the test electrodes. Our device has demonstrated potential for use in quantifying the degree of electrical interconnection between any two surface-defined test meridian or nonmeridian segments. Issues arising from use of this device and the measurement Horton and van Ravenswaay technique were also presented.

Corrosion behaviour of Ti-15Mo alloy for dental implant applications.

The corrosion behaviour of Ti-15Mo alloy in 0.15M NaCl solution containing varying concentrations of fluoride ions (190, 570, 1140 and 9500 ppm) is evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and chronoamperometric/current-time transient (CTT) studies to ascertain its suitability for dental implant applications. The study reveals that there is a strong dependence of the corrosion resistance of Ti-15Mo alloy on the concentration of fluoride ions in the electrolyte medium. Increase in fluoride ion concentration from 0 to 9500 ppm shifts the corrosion potential (E(corr)) from -275 to -457 mV vs. SCE, increases the corrosion current density (i(corr)) from 0.31 to 2.30 microA/cm(2), the passive current density (i(pass)) from 0.07 to 7.32 mA/cm(2) and the double-layer capacitance (C(dl)) from 9.63 x 10(-5) to 1.79 x 10(-4)F and reduces the charge transfer resistance (R(ct)) from 6.58 x 10(4) to 6.64 x 10(3)Omega cm(2). In spite of the active dissolution, the Ti-15Mo alloy exhibit passivity at anodic potentials at all concentrations of the fluoride ions studied. In dental implants since the exposure of the alloy will be limited only to its 'neck', the amount of Mo ions released from Ti-15Mo alloy is not likely to have an adverse and hence, in terms of biocompatibility this alloy seems to be acceptable for dental implant applications. The results of the study suggest that Ti-15Mo alloy can be a suitable alternative for dental implant applications.

Electrical skin impedance at acupuncture points.

OBJECTIVES: To test whether electrical skin impedance at each of three acupuncture points (APs) is significantly lower than at nearby sites on the meridian (MP) and off the meridian (NP). DESIGN: Two instruments - Prognos (MedPrevent GmbH, Waldershof, Germany), a constant-current (DC) device, and PT Probe (designed for this study), a 100-Hz sinusoidal-current (AC) device-were used to record electrical impedance at three APs (right Gallbladder 14, right Pericardium 8, and left Triple Energizer 1), and two control sites for each AP. Each AP, MP, and NP was measured four times in random order with each device. SETTING: The study was conducted over a period of 4 days at the Oregon College of Oriental Medicine (OCOM). SUBJECTS: Twenty (20) healthy adults (14 women and 6 men), all recruited from the OCOM student body and faculty, participated in the study. RESULTS: The Prognos measurements had an intraclass correlation (ICC) = 0.84 and coefficient of variation (CV) = 0.43. The PT Probe had ICC = 0.81 and CV = 0.31. Impedance values at APs were not significantly less than at MPs or NPs. Impedance values at MPs were also not significantly less than NPs, although their individual p values were <0.05 in 4 of 6 cases. There was a significant trend of increasing impedance with repeated measurements with both the Prognos (p =0.003) and the PT Probe (p= 0.003). CONCLUSIONS: Within the reliability limits of our study methods, none of the three APs tested has lower skin impedance than at either of the nearby control points. These results are not consistent with previous studies that detected lower skin impedance at APs than nearby sites. Further study is necessary to determine whether MPs have lower skin impedance than nearby NPs. Our study suggests caution is warranted when developing, using, and interpreting results from electrodermal screening devices. Further studies are needed to clarify the clinically important and controversial hypothesis that APs are sites of lower impedance.

Respuestas de prolactina al estrés inducido por un esfuerzo competitivo en natación / Prolactin responses to stress induced by a competitive swimming effort

El objetivo de este estudio fue evaluar las respuestas deprolactina (PRL) al estrés, de origen tanto psíquico comofisiológico, inducido por un esfuerzo competitivo ennatación. Trece nadadores, todos ellos varones (edad:18,62:t 0,78 alíos; talla: 174,95 +/- 1,80 cm; masa corporal: 65,11+/- 2,14 Kg; IMC: 21,28 +/- 0,66 Kg/m2; % grasa corporal: 10,75 +/- 1,00), fueron evaluados en tressituaciones experimentales: condiciones basales, pre- y postcompetición (100 m libres), en las que, además de valorar los niveles de ansiedad (a través del cuestionario STAI), se determinaron los niveles plasmáticos de PRL y ácido láctico. Los resultados obtenidos, muestran una clara respuesta dePRL al estrés psíquico observado en situación de precompetición, produciéndose unos aumentos en suconcentración plasmática del 37% en relación con loshallados en la situación basal (5,52 +/- 0,53 vs 4,02 +/-0,53 ng/mL, respectivamente; p<=0,05). Esta respuesta fue mucho más notable justo después de finalizar la prueba competitiva, donde, tras corregir la hemoconcentración detectada, se alcanzaron valores de 10,07 +/- 1,59 ng/mL, observándose aumentos del 82% respecto a la situación de pre-competición (p<=0,01) y del 150% respecto a la situación basal (p<=0,01). Los niveles de ácido láctico aumentaron significativamente justo después de finalizar el esfuerzo competitivo, aunque no mostraron relación alguna con los niveles de PRL alcanzados en esa misma situación. Si se encontró, por otra parte, una correlación significativa entre la concentración de PRL y los niveles de ansiedad post-esfuerzo. Se puede concluir, por tanto, que, además del estrés psíquico (ansiedad precompetitiva), el estrés fisiológico inducido por un esfuerzo competitivo en natación así como la intensidad de la ansiedad experimentada al finalizar dicho esfuerzo originan una importante respuesta de PRL

The aim of the present study was to evaluate the prolactin (PRL) responses to psychological and physiological stress induced by competitive swinIming effort. Thirteen male swimmers (age: 18.62 +/- 0.78 years; height: 174.95 +/- 1.80 cm; body mass: 65.11 +/- 2.14 Kg; BMI: 21.28 +/- 0.66 Kg/m2; % body fat: 10.75 +/- 1.00), took part in this investigation. The subjects were evaluated in three experimental trials: basal conditions, pre- and post- swimming competition (100 m freestyle) , in which fue anxiety levels (STAI questionnaire) and plasma PRL and lactate concentrations were registered. The results showan important PRL response to psychological stress observed in fue pre-competition situation, since fue PRL plasma concentration Tose 37% compared to that measured in basal conditions (5.52 +/- 0.53 ng/mL in pre-competition situation vs 4.02 +/- 0.53 ng/mL in basal conditions; p<=0.05). This responsewas more pronounced at the end of fue competition effort (reaching a concentration of 10.07 +/- 1.59 ng/mL, in grite of corrected haemoconcentration) , where increases of 82% compared to fue pre-competition situation (p<=0.01) and 150% with regard to fue plasma levels in basal conditions (p<=0.001) were observed. A significant rose in plasma lactate levels just at the end of the effort was found, although it did not seem to be related to PRL levels in the same situation. However, a significant correlation between PRL plasma concentration and post -exercise anxiety levels was observed. In conclusion, psychological stress (pre-competition anxiety), somatic stress induced by competitive swimming effort and fue intensity of the anxiety experimented at the end of this exercise give rise to an Ímportant PRL response

Electrical impedance along connective tissue planes associated with acupuncture meridians.

BACKGROUND: Acupuncture points and meridians are commonly believed to possess unique electrical properties. The experimental support for this claim is limited given the technical and methodological shortcomings of prior studies. Recent studies indicate a correspondence between acupuncture meridians and connective tissue planes. We hypothesized that segments of acupuncture meridians that are associated with loose connective tissue planes (between muscles or between muscle and bone) visible by ultrasound have greater electrical conductance (less electrical impedance) than non-meridian, parallel control segments. METHODS: We used a four-electrode method to measure the electrical impedance along segments of the Pericardium and Spleen meridians and corresponding parallel control segments in 23 human subjects. Meridian segments were determined by palpation and proportional measurements. Connective tissue planes underlying those segments were imaged with an ultrasound scanner. Along each meridian segment, four gold-plated needles were inserted along a straight line and used as electrodes. A parallel series of four control needles were placed 0.8 cm medial to the meridian needles. For each set of four needles, a 3.3 kHz alternating (AC) constant amplitude current was introduced at three different amplitudes (20, 40, and 80 microAmps) to the outer two needles, while the voltage was measured between the inner two needles. Tissue impedance between the two inner needles was calculated based on Ohm's law (ratio of voltage to current intensity). RESULTS: At the Pericardium location, mean tissue impedance was significantly lower at meridian segments (70.4 +/- 5.7 Omega) compared with control segments (75.0 +/- 5.9 Omega) (p = 0.0003). At the Spleen location, mean impedance for meridian (67.8 +/- 6.8 Omega) and control segments (68.5 +/- 7.5 Omega) were not significantly different (p = 0.70). CONCLUSION: Tissue impedance was on average lower along the Pericardium meridian, but not along the Spleen meridian, compared with their respective controls. Ultrasound imaging of meridian and control segments suggested that contact of the needle with connective tissue may explain the decrease in electrical impedance noted at the Pericardium meridian. Further studies are needed to determine whether tissue impedance is lower in (1) connective tissue in general compared with muscle and (2) meridian-associated vs. non meridian-associated connective tissue.

[Assessment of body composition--methods and practical aspects]. / Methodische und praktische Aspekte der Bestimmung der Körperzusammensetzung.

The analysis of the body composition is a valuable tool in assessing nutritional status, and provides additional information about health risks and prognosis. Several methods can be used to assess the various body components. To obtain valid data, well standardized measurements are obligatory. As regards interpretation, the investigator has to take into account the assumptions used for the respective method and possible methodological errors.

Chest impedance: characteristics of local patients.

The Pre-hospital Defibrillation Program in Singapore has in some cases demonstrated a lower amplitude of Ventricular Fibrillation (VF) than considered the norm. The Electrode Skin Impedance (ESI) refers to the skin impedance determined between two electrodes placed at specific positions on the body surface. The objective of this prospective study was to measure the ESI of patients at 5 Hz and 2 kHz frequencies, and assess its change with time from the application of electrodes, the difference between the ESI at two different sets of electrode placement positions and correlation with patient factors. Patients who were 25 years or older and not critically ill had their ESI measured with a modified Heart-Save 911 defibrillator, using signal frequencies at 5 Hz and 2 kHz, at 10 seconds, 1 and 2 minutes after electrodes application. Two sets of positions were used; Position 1 where an electrode is placed in the right infra-clavicular region and another just lateral to the apex beat on the left and Position 2, which represents the mirror image of Position 1. 36 each of male and female patients were studied. The mean age and weight were 59.9 +/- 13.5 years and 56.8 +/- 24.1 kg respectively. There was no significant correlation between the ESI and patients' body weight or sex. However, there was a significant decrease in the ESI with time from application of electrodes at both Positions (p < 0.05) with the two different frequencies. The ESI was lower when measured at lower frequencies and higher when taken at higher frequencies, but there was no statistically significant difference between the two mirror-image positions used. Thus, with lower frequency, the ECG amplitude of VF recorded on the automated external defibrillator could be enhanced.

Desenvolvimento e validacao de equacoes para estimativa da massa corporal magra atraves da impedancia bioeletrica em mulheres / Development and validadtion of equations for the Estimation of lean body mass of woman by bioeletrical impedance

O principal objetivo dessa investigacao foi desenvolver e validar equacoes para estimativa da massa corporal magra atraves da impedancia bioeletrica em universitarias com idades de 18 a 21 anos.Para tanto, foram avaliados 58 mulheres que foram submetidas a protocolos de avaliacao por impedancia bioeletrica e pesagem hidrostatica,dobras cutaneas e perimetros.A tecnica de regressao multipla Stepwise foi utilizada para o desenvolvimento das equacoes preditivas e a analise de validacao das equacoes propostas foram determinadas atraves da correlacao de Pearson,teste t dependente e erro padrao de estimativa (EPE).As correlacoes multiplas e os erros padrao de estimativa das cinco equacoes propostas e validadas nesse estudo variaram de R=0,924 a 0,927 e EPE=1,60Kg a 1,70Kg,respectivamente.Nenhuma diferenca estatistica significativa(p maior 0,05)foi encontrada entre os valores medios mensurados e preditos da MCM.Os resultados desse estudo permitem as seguimntes conclusoes:a)as equacoes desenvolvidas sao validas para a estimativa da MCM para universitarias que estejam dentro dos limites dos valores das variaveis analisadas e,b)a equacao 03,que possui as variaveis massa corporal,estatura e resistencia,pode ser apontada como a preferencial,pois a mesma apresenta excelentes valores de correlacao multipla e erro padra de estimativa,alem da praticidade e simplicidade na avaliacao de grandes grupos

Estimation of total body and extracellular water using single- and multiple-frequency bioimpedance.

OBJECTIVE: To determine the precision and bias of single- and multiple-frequency bioimpedance estimates of total body water (TBW) and extracellular water (ECW) volumes in comparison with the true values for these volumes established by gold standard dilution techniques. DESIGN: Controlled, prospective, open-label investigation. SETTING: Private, not-for-profit university-affiliated, acute care hospital. PARTICIPANTS: Normal, healthy men (n = 8) and women (n = 6) volunteers, 25-46 years of age. INTERVENTIONS: A single oral dose of a mixture of deuterium oxide 10 g and bromine 30 mmol; bioimpedance analysis pre- and three hours postmixture administration. MAIN OUTCOME PARAMETERS: TBW and ECW volumes established by deuterium oxide and bromine dilutional spaces (gold standards), respectively, and single- and multiple-frequency bioimpedance estimates of those same volumes. RESULTS: The mean multiple-frequency bioimpedance (MFB) and single frequency bioimpedance (SFB) estimates of TBW, 41.2 and 42.1 L, respectively, were not statistically different (NS) from the 41.2 L deuterium oxide value. Although the two methods had similar precision (NS), MFB was less biased. For ECW, the mean MFB and SFB values of 19.5 and 24.8 L, respectively, were significantly different from the bromine value of 18.8 L (p = 0.013 and p = 0.001, respectively). MFB was the more precise and less biased predictor of ECW. CONCLUSIONS: Compared with SFB, the MFB approach is a more precise and less biased predictor of TBW and ECW volumes in young, healthy adults, and may offer more accurate assessment in subjects with aberrant physiology.