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Impedance Analysis (impedance + analysis)
Kinds of Impedance Analysis Selected AbstractsEstimation of Acute Fluid Shifts Using Bioelectrical Impedance Analysis in HorsesJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2007C. Langdon Fielding Background: Multi-frequency bioelectrical impedance analysis (MF-BIA) has been used to evaluate extracellular fluid volume (ECFV), but not fluid fluxes associated with fluid or furosemide administration in horses. If able to detect acute changes in ECFV, MF-BIA would be useful in monitoring fluid therapy in horses. Hypothesis: The purpose of this study was to evaluate the ability of MF-BIA to detect acute fluid compartment changes in horses. We hypothesized that MF-BIA would detect clinically relevant (10,20%) changes in ECFV. Animals: Six healthy mares were used in the study. Methods: This is an original experimental study. Mares were studied in 3 experiments: (1) crystalloid expansion of normally hydrated subjects, (2) furosemide-induced dehydration followed by crystalloid administration, and (3) acute blood loss followed by readministration of lost blood. MF-BIA measurements were made before, during, and after each fluid shift and compared to known changes in volume calculated based on the intravenous fluids that were administered in addition to urinary fluid losses. Mean errors between MF-BIA estimated change and known volume change were compared using nonparametric analysis of variance. Estimated ECFV pre- and post-fluid administration similarly were compared. The level of statistical significance was set at P < .05. Results: Results of the study revealed a statistically significant change in ECFV and total body water during crystalloid expansion and dehydration. Statistically significant changes were not observed during blood loss and administration. Mean errors between MF-BIA results and measured net changes were small. Conclusions and Clinical Importance: MF-BIA represents a practical and accurate means of assessing acute fluid changes during dehydration and expansion of ECFV using isotonic crystalloids with potential clinical applications in equine critical care. [source] Barium Non-Stoichiometry Role on the Properties of Ba1+xCe0.65Zr0.20Y0.15O3,, Proton Conductors for IT-SOFCsFUEL CELLS, Issue 5 2008S. Barison Abstract Proton conducting perovskite oxides have been widely investigated because of their potential as electrolytes for intermediate temperature solid oxide fuel cells. Among them, BaCeO3 - based materials exhibit good proton conductivity under a humidified hydrogen-containing atmosphere, but rather poor chemical stability in CO2 atmosphere. The substitution with Zr for Ce improves the chemical stability but reduces proton conductivity due to difficulties in fabricating dense materials. In the present work, single phase nanostructured powders of Ba1+xCe0.65Zr0.20Y0.15O3,, (x,=,0, 0.05, 0.10) solid solutions have been prepared by a modified sol,gel Pechini method with the final aim of evaluating the role of barium on their chemical and electrical properties. A significant influence of barium excess on the preparation and on properties of these materials has been demonstrated. In fact, density measurements evidenced that a 5 or 10,mol% nominal barium excess sensibly favoured the sintering process. Impedance analyses of sintered pellets confirmed the necessity of barium excess in order to avoid the lowering of proton conductivity, which has been evidenced for samples having stoichiometric barium content. Moreover, an unforeseen increase in chemical stability in CO2 -containing atmosphere with the growth of the barium excess was detected by thermogravimetric analyses. [source] The effect of ionic peneration on semiconducting behaviour of temporarily protective oil coating on the surface of AISI 304 stainless steelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2005Q. Zhong Abstract In this paper, the semiconducting behaviour of temporarily protective oil coatings on the surface of naked and prepassivated AISI 304 stainless steel immersed in 3% aqueous NaCl solution was studied by utilizing potential-capacitance methode, Mott-Schottky analysis and impedance analysis. It was pointed out that the temporarily protective oil coating behaves as a semiconductor during its degradation. The ionic penetration and the substrate greatly affect the conduction behaviour of the oil coating. On the surface of naked AISI 304 stainless steel, the oil coating behaves as a n-type semiconductor. With increasing immersion time, the donor density of the space charge layer in the temporarily protective oil coating increases from 1019 to 1025 m,3. However, on the surface of the prepassivated substrate the space charge layer in the oil coating is significantly affected by the oxide on the steel electrode. In this case immersion time does not influence the density of charge carriers in the oil coating (1021 m,3). Impedance analysis also verify above results. [source] Failure Mechanism of a Low-Temperature-Cofired Ceramic Capacitor with an Inner Ag ElectrodeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Yi-Ting Shih Failure mechanism of a multilayer ceramic capacitor (MLCC) made of a low-fire BaNd2Ti4O12(BNT)+ZnO,B2O3 (ZB) dielectric with an inner pure silver electrode at elevated temperatures and voltages has been investigated. A nonlinear current,voltage leakage characteristic is found when the degradation of MLCC occurs, and the time to failure decreases with increasing either the temperature or the voltage. Results of microstructure, composition, and impedance analyses reveal that the failure is caused by silver diffusion in the ZB glass during sintering and highly accelerated life test. [source] The role of fat mass index in determining obesityAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2010Gerson Peltz Objectives: The objective of this study is to compare body mass index (BMI), percent body fat (PBF), and fat mass index (FMI) and to investigate the accuracy of FMI as a convenient tool for assessing obesity. Design: Anthropometric measurements and bioelectrical impedance analyses were performed on 538 Mexican Americans (373 women and 165 men). Correlations between BMI and PBF and between FMI and PBF were investigated. The percentage of persons misclassified as obese using different classifications was calculated. Multiple linear regression analysis was performed to generate predictive models of FMI for males and females separately. Results: BMI and PBF were correlated in men (, = 0.877; P < 0.0001) and women (, = 0.966; P < 0.0001); however, 20 and 67.2% of the men and 9.2 and 84.2% of women, classified as normal weight and overweight by BMI, respectively, were diagnosed as obese by PBF. FMI and PBF were also correlated in men (, = 0.975; P < 0.0001) and women (, = 0.992; P < 0.0001). Four percent of the men classified as normal weight and 65.5% classified as overweight by BMI were obese by FMI, while 71.3% of women classified as overweight by BMI were obese by FMI. Misclassification of obesity between FMI and PBF categories was observed in 5.4% of men and 7.8% of women. Conclusions: The discrepancy observed between BMI and PBF reflects a limitation of BMI. Conversely, FMI accurately assessed obesity in our study of Mexican Americans, but further studies are necessary to confirm our findings in different ethnic groups. Am. J. Hum. Biol. 22:639,947, 2010. © 2010 Wiley-Liss, Inc. [source] Hydration of exercised Standardbred racehorses assessed noninvasively using multi-frequency bioelectrical impedance analysisEQUINE VETERINARY JOURNAL, Issue S36 2006A. WALLER Summary Reasons for performing study: In human and animal clinical practice, multi-frequency bioelectrical impedance analysis (MF-BIA) is increasingly used as a diagnostic tool to assess hydration of intra-and extracellular fluid compartments. Accurate determination of changes in hydration status within individuals over time has remained problematic due to the requirement for complete impedance-frequency relationships at the time points of interest. Objectives: To use MF-BIA in 13 Standardbred racehorses and 7 ,endurance' research horses to determine if MF-BIA could be used to track changes in total body water (TBW), intracellular fluid volume (ICFV) and extracellular fluid volume (ECFV) resulting from exercise. Methods: Jugular venous blood was sampled at rest and for 2,13 h following exercise. TBW, ECFV and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). TBW, ECFV, ICFV and PV were correlated to impedance measures and predictive equations used to determine hydration status from MF-BIA measures. Results: TBW loss continued throughout the recovery period, and was primarily borne by the ECF compartment at 90 min of recovery. Conclusions: MF-BIA predictions of compartmental hydration status were significantly correlated to measured/calculated decreases in these compartments. Potential relevance: Practical applications for MF-BIA in horses include monitoring of hydration status during transport and competition, assessment of body compostion, clinical health assessment and critical care management. [source] Arterial stiffening and cardiac hypertrophy in a new rat model of type 2 diabetesEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2006K.-C. Chang Abstract Background, We determined the effects of NIDDM on haemodynamic parameters describing arterial wall elasticity and cardiac hypertrophy in rats administered streptozotocin (STZ) and nicotinamide (NA), using the aortic impedance analysis. Methods, Male Wistar rats at 2 months were administered intraperitoneally 180 mg kg,1 of NA, 30 min before an intravenous injection of 50 mg kg,1 STZ, to induce type 2 diabetes. The STZ-NA rats were divided into two groups, 4 weeks and 8 weeks after induction of diabetes, and compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured by a high-fidelity pressure sensor and electromagnetic flow probe, respectively, and were then subjected to Fourier transformation for the analysis of aortic input impedance. Results, In each diabetic group, the experimental syndrome was characterized by a moderate and stable hyperglycaemia and a relative deficiency of insulin secretion. However, the 8-week but not the 4-week STZ-NA diabetic rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance. The diabetic syndrome at 8 weeks also contributed to an increase in aortic characteristic impedance, from 1·49 ± 0·33 (mean ± SD) to 1·95 ± 0·28 mmHg s mL,1 (P < 0·05), suggesting a detriment to the aortic distensibility in NIDDM. Meanwhile, the STZ-NA diabetic animals after 8 weeks had an increased wave reflection factor (0·46 ± 0·09 vs. 0·61 ± 0·13, P < 0·05) and decreased wave transit time (25·8 ± 3·8 vs. 20·6 ± 2·8 ms, P < 0·05). Ratio of the left ventricular weight to body weight was also enhanced in the 8-week STZ-NA diabetic rats. Conclusion, The heavy intensity with early return of the pulse wave reflection may augment systolic load of the left ventricle coupled to the arterial system, leading to cardiac hypertrophy in the rats at 8 weeks after following STZ and NA administration. [source] Nutritional supplements combined with dietary counselling diminish whole body protein catabolism in HIV-infected patientsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2000Berneis Background Weight loss and protein malnutrition are frequent complications in HIV-infected patients. The effect of an oral nutritional supplement combined with nutritional counselling on whole body protein metabolism was assessed. Materials and methods HIV-infected individuals with a body mass index < 21 kg m,2 or CD4-T cells < 500 , L,1 in stable clinical condition were randomly allocated to [ 1] receive either oral nutritional supplements (containing 2510 kJ, complete macro- and micronutrients) and dietary counselling (n = 8), or [ 2] identical monitoring but no supplements or specific nutritional advice (controls, n = 7). Whole body leucine kinetics and leucine oxidation rate were determined by [1,13C]-leucine infusions and lean and fat mass were measured before and 12 weeks after intervention. Results Leucine oxidation (protein catabolism) decreased in the group receiving nutritional intervention from 0.33 ± 0.02 to 0.26 ± 0.02 ,mol kg,1 min,1 after 12 weeks (P < 0.05; P < 0.05 vs. control group) but remained unchanged in the control group. Whole body leucine flux showed a tendency to decrease in the intervention group from 1.92 ± 0.19 to 1.73 ± 0.14 ,mol kg,1 min,1 (P = 0.07) and remained unchanged in the control group (2.21 ± 0.16 and 2.27 ± 0.14 ,mol kg,1 min,1, respectively). Lean body mass determined by bioelectrical impedance analysis increased in the nutritional intervention group from 84 ± 2 to 86 ± 2 per cent (P < 0.05) and fat mass decreased from 17 ± 2 to 14 ± 2 per cent (P < 0.05) of total body weight whereas neither mass changed in the control group. Nutritional intervention had no significant effect on lymphocyte CD4 counts, on plasma TNFR 55, TNFR 75 and ILR 2 concentrations and on quality of life. Conclusions The data demonstrate an anticatabolic effect of nutritional supplements combined with dietary counselling in HIV-infected subjects. They suggest that diminished whole body protein catabolism resulted in a change of body composition (increased lean mass, decreased fat mass). [source] Solvent-Free Ionic Liquid Electrolytes for Mesoscopic Dye-Sensitized Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Shaik M. Zakeeruddin Abstract Ionic liquids have been identified as a new class of solvent that offers opportunities to move away from the traditional solvents. The physical-chemical properties of ionic liquids can be tuned and controlled by tailoring their structures. The typical properties of ionic liquids, such as non-volatility, electrochemical stability and high conductivity, render them attractive as electrolytes for dye-sensitized solar cells. However, the high viscosity of ionic liquids leads to mass transport limitations on the photocurrents in the solar cells at full sunlight intensity, but the contribution of a Grotthous-type exchange mechanism in these viscous electrolytes helps to alleviate these diffusion problems. This article discusses recent developments in the field of high-performance dye-sensitized solar cells with ionic liquid-based electrolytes and their characterization by electrochemical impedance analysis. [source] Increased bacterial permeation in long-lasting ileoanal pouchesINFLAMMATORY BOWEL DISEASES, Issue 8 2006Anton J. Kroesen MD Abstract Background and Aims: Bacterial overgrowth appears to play an important role in the pathogenesis of ileoanal pouches. Therefore, the capability of bacterial permeation and its determinants is of great interest. The aim of this study was to examine bacterial permeation in the ileoanal pouch and to correlate the results with the degree of inflammation, the epithelial resistance, the mucosal transport function, and the age of the ileoanal pouches. Materials and Methods: Biopsies were taken from 54 patients before colectomy (n = 13; preileal pouch-anal anastomosis [IPAA]), and closure of ileostomy (n = 7; deviation), <1 year after closure of ileostomy (n = 8; intact pouch I), >1 year after closure of ileostomy (n = 16; intact pouch II), in the case of pouchitis (n = 11), and in 11 controls. Tissues were mounted in a miniaturized Ussing chamber. Escherichia coli was added to the mucosal side of the Ussing chamber, and the permeation was proven by serosal presence of E. coli. Epithelial and subepithelial resistance was determined by transmural impedance analysis. Active Na+ -glucose cotransport and active Cl, secretion were measured. Specimens were analyzed by fluorescent in situ hybridization with oligonucleotide probes targeting the bacterial 16s ribosomal RNA. The bacteria in and on the tissue were enumerated. Results: Bacterial permeation occurred in 2 of 13 pre-IPAA, 2 of 7 deviations, 0 of 8 intact pouch I, 9 of 16 intact pouch II, 5 of 11 pouchitis specimens, and 0 of 11 ileum controls. The frequency of bacterial permeation in the intact pouch II group is higher than in the intact pouch I group (P < 0.001). Epithelial resistance, mannitol fluxes, electrogenic chloride secretion, sodium-glucose cotransport of the bacterially permeated specimens versus nonpermeated of the intact pouch II group, and the pouchitis group and subepithelial resistance remained unchanged. Intramural bacteria could be detected by fluorescence in situ hybridization mainly in long-lasting pouches, but there was no correlation with bacterial permeation. Conclusions: The long-lasting ileoanal pouch is associated with increased bacterial permeability. This is not correlated with a disturbed function of the pouch mucosa but could be a precursor of pouchitis. [source] Body size and composition and colon cancer risk in womenINTERNATIONAL JOURNAL OF CANCER, Issue 6 2006Robert J. MacInnis Abstract Studies of colon cancer risk in males have reported strong positive associations with obesity, particularly with central adiposity. The association has been weaker and less consistent for women. In a prospective cohort study of women, body measurements were taken directly; fat mass and fat-free mass being estimated by bioelectrical impedance analysis and central adiposity by waist circumference and waist-to-hip ratio (WHR). Among 24,072 women followed on average for 10.4 years, 212 colon cancers were ascertained via the population cancer registry. We reviewed medical records of all cases and classified them according to anatomic site and stage. The central adiposity measures of WHR (hazard ratio per 0.1 unit increase = 1.31, 95% confidence interval (CI) 1.08,1.58) and waist circumference (hazard ratio per 10 cm increase = 1.14, 95% CI 1.02,1.28) were positively associated with colon cancer risk. There was little or no association between other anthropometric measures and risk of colon cancer. There was some evidence that the associations were stronger for proximal tumors, but no evidence that risk differed by stage for any of the anthropometric measures. Central adiposity appears to be associated with colon cancer risk in women. © 2005 Wiley-Liss, Inc. [source] Nutrition Risk Factors for Survival in the Elderly Living in Canadian Long-Term Care FacilitiesJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 1 2004Johane P. Allard MD Objectives: To determine the role of nutritional parameters in influencing the risk of mortality in institutionalized elderly. Design: A prospective cohort study in which subjects had several nutritional parameters measured at baseline and were followed for 19 months. Time to death and mortality were recorded starting immediately after enrollment. Setting: Fourteen long-term care facilities (LTCFs). Participants: Four hundred eight elderly long-term care residents aged 60 and older who resided in the facility for more than 6 weeks. Measurements: At baseline, knee height, weight, mid-arm circumference (MAC), skin-fold thickness, and fat-free mass using bioelectric impedance analysis were measured. Covariates included demographic factors, length of stay in the facility, functional status, and medical diagnoses. Cox proportional hazards regression analysis was used to identify independent predictors of mortality. Results are reported as mean±standard error of the mean (SEM). Results: Overall, mortality rate was 28.4%. Univariate predictors included male sex, body mass index, MAC, and triceps skin fold. In multivariate analysis, male sex (hazard ratio (HR)=1.7, 95% confidence interval (CI)=1.2,2.7, P=.0096) and MAC less than 26 cm were significantly associated with increased risk of mortality (HR=4.8, 95% CI: 2.8,8.3, P<.0001). Conclusion: Among this elderly population living in LTCFs, MAC is the best nutritional predictor of mortality. [source] Ionic conductivity of solid polymer electrolytes for dye-sensitized solar cellsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Joo Wan Kim Abstract We developed an ionic conductivity model of solid polymer electrolytes for dye-sensitized solar cells (DSSCs) based on the Nernst,Einstein equation in which the diffusion coefficient is derived from the molecular thermodynamic model. We introduced concentration-dependence of the diffusion coefficient into the model, and the diffusion coefficient was expressed by differentiating the chemical potential by concentration. The ionic conductivities of polymer electrolytes (PEO/LiI/I2 system) were investigated at various temperatures and compositions. We prepared a set of PEO in which an EO : LiI mole ratio of 10 : 1 was kept constant for PEO·LiI·(I2)n compositions with n = 0.02, 0.05, 0.1, 0.15, 0.2, and 0.3 (mole ratio of LiI : I2). The ionic conductivities of the electrolytes were measured using a stainless steel/polymer-electrolyte/stainless steel sandwich-type electrode structure using alternating current impedance analysis. The values calculated using the proposed model agree well with experimental data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Evaluation of Mass Transfer Mechanisms During Osmotic Treatment of Plant MaterialsJOURNAL OF FOOD SCIENCE, Issue 6 2000N.K. Rastogi ABSTRACT: The proportion of intact, damaged, and ruptured (non-intact) cells (Zp) due to osmotic stress during osmotic treatment of potato was monitored using electrophysical measurement based on electrical impedance analysis. Osmotic stress on potato cell culture made cell membranes shrink thereby damaging the cells. The proportion of the ruptured and shrunk cells within the samples increased with the increase in concentration of solute in the osmotic solution. The osmotic removal of water from thin potato slices started at a critical osmotic pressure. Once the critical osmotic pressure was exceeded, mass transfer was rapid and the cells lost substantial amounts of water due to rupture of cell membranes. [source] Malnutrition and hypermetabolism are not risk factors for the presence of hepatic encephalopathy: A cross-sectional studyJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 4 2008Peter Sörös Abstract Background and Aim:, Hepatic encephalopathy is a frequent complication of cirrhosis. The present retrospective investigation was conducted to characterize metabolic alterations in cirrhotic patients with and without hepatic encephalopathy. We tested the hypothesis that reduced nutritional status or the degree of tissue catabolism are associated with the presence of hepatic encephalopathy. Methods:, We investigated 223 patients with histologically confirmed nonalcoholic cirrhosis without hepatic encephalopathy and with hepatic encephalopathy (grades 1,3). To assess liver function, nutritional status, and energy metabolism, a variety of biochemical and clinical tests were performed including anthropometric measurements, bioelectrical impedance analysis, and indirect calorimetry. Results:, Nutritional status and tissue catabolism were not significantly different between patients with and without hepatic encephalopathy. Conclusions:, Our data do not support the hypothesis that malnutrition or tissue catabolism are independent risk factors for the presence of hepatic encephalopathy in patients with nonalcoholic cirrhosis. [source] Ring-opening graft copolymerization of epoxide with polyaniline: Chemical properties and lithium ionic conductivity of the copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2001Isao Yamaguchi The NaH-promoted deprotonation of leucoemeraldine base polyaniline (LEB) and its subsequent treatment with phenyl glycidyl ether (PGE) caused the ring-opening polymerization of PGE to give a graft copolymer (LEB- g -PGE). LEB- g -PGE was soluble in acetone and chloroform, which were poor solvents for LEB. An LEB- g -PGE/LiBF4 composite film was obtained through the evaporation of a dimethylformamide solution containing LEB- g -PGE and LiBF4; the film showed an electroconductivity of 1.0 × 10,6 S cm,1 at 295 K, as determined by complex impedance analysis. [source] Estimation of Acute Fluid Shifts Using Bioelectrical Impedance Analysis in HorsesJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2007C. Langdon Fielding Background: Multi-frequency bioelectrical impedance analysis (MF-BIA) has been used to evaluate extracellular fluid volume (ECFV), but not fluid fluxes associated with fluid or furosemide administration in horses. If able to detect acute changes in ECFV, MF-BIA would be useful in monitoring fluid therapy in horses. Hypothesis: The purpose of this study was to evaluate the ability of MF-BIA to detect acute fluid compartment changes in horses. We hypothesized that MF-BIA would detect clinically relevant (10,20%) changes in ECFV. Animals: Six healthy mares were used in the study. Methods: This is an original experimental study. Mares were studied in 3 experiments: (1) crystalloid expansion of normally hydrated subjects, (2) furosemide-induced dehydration followed by crystalloid administration, and (3) acute blood loss followed by readministration of lost blood. MF-BIA measurements were made before, during, and after each fluid shift and compared to known changes in volume calculated based on the intravenous fluids that were administered in addition to urinary fluid losses. Mean errors between MF-BIA estimated change and known volume change were compared using nonparametric analysis of variance. Estimated ECFV pre- and post-fluid administration similarly were compared. The level of statistical significance was set at P < .05. Results: Results of the study revealed a statistically significant change in ECFV and total body water during crystalloid expansion and dehydration. Statistically significant changes were not observed during blood loss and administration. Mean errors between MF-BIA results and measured net changes were small. Conclusions and Clinical Importance: MF-BIA represents a practical and accurate means of assessing acute fluid changes during dehydration and expansion of ECFV using isotonic crystalloids with potential clinical applications in equine critical care. [source] The stable isotope ketoisocaproic acid breath test as a measure of hepatic decarboxylation capacity: a quantitative analysis in normal subjects after oral and intravenous administrationLIVER INTERNATIONAL, Issue 9 2009Heiner K. Berthold Abstract Background and aims: There is no generally accepted kinetic evaluation method for the stable isotope [13C]ketoisocaproic acid (KIC) breath test. Differences found in the results between women and men are contradictory. Methods: Oral and intravenous breath tests using 1 mg/kg stable isotope-labelled KIC were performed in healthy male and female volunteers. A power exponential function was fitted to the mass spectrometric data of breath 13CO2 enrichment, allowing mathematical analysis of time-to-peak-excretion, half-excretion time, percent label recovery and parameters describing the shape of the curve. Body composition was determined using bioelectrical impedance analysis. Results: After oral administration, total label recovery after 3 h was about 22% and was not different between men (n=7) and women (n=8). The time to maximal label excretion was 0.67 ± 0.12 h in men and 0.9 ± 0.32 h in women (P=0.028) and the excretion curve showed an initially slower rise in women compared with men. Adjusting for lean body mass or body water abrogated the sex differences. Total label recovery after intravenous administration was about 9%, suggesting that the substrate was rapidly catabolized in the muscle compartment after intravenous administration. Conclusions: The modified power exponential function described allows standardized estimates of the KIC breath test results. When corrected for body composition, there are no differences in breath test results between men and women. The comparison between oral and intravenous results provides robust evidence that the KIC breath test measures predominantly hepatic and not muscle decarboxylation and is thus a highly specific liver function test. [source] The effect of ionic peneration on semiconducting behaviour of temporarily protective oil coating on the surface of AISI 304 stainless steelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2005Q. Zhong Abstract In this paper, the semiconducting behaviour of temporarily protective oil coatings on the surface of naked and prepassivated AISI 304 stainless steel immersed in 3% aqueous NaCl solution was studied by utilizing potential-capacitance methode, Mott-Schottky analysis and impedance analysis. It was pointed out that the temporarily protective oil coating behaves as a semiconductor during its degradation. The ionic penetration and the substrate greatly affect the conduction behaviour of the oil coating. On the surface of naked AISI 304 stainless steel, the oil coating behaves as a n-type semiconductor. With increasing immersion time, the donor density of the space charge layer in the temporarily protective oil coating increases from 1019 to 1025 m,3. However, on the surface of the prepassivated substrate the space charge layer in the oil coating is significantly affected by the oxide on the steel electrode. In this case immersion time does not influence the density of charge carriers in the oil coating (1021 m,3). Impedance analysis also verify above results. [source] New method of predicting dry weight using bioelectrical impedance analysis in haemodialysis patientsNEPHROLOGY, Issue 8 2009SEOUNG WOO LEE SUMMARY: Aim: There were significant differences in the slopes of the ultrafiltration (UF) amount removed during haemodialysis (HD) sessions versus the percentage change in the extracellular fluid/total body water ratio for the right lower extremity (ECF/TBWright leg) plot in normohydrated (NH) and overhydrated states. The purpose of this study was to develop and validate a method for predicting dry weight (DW) using these results. Methods: It was hypothesized that for patients to become NH, the slope of the UF amount versus the percentage changes in ECF/TBWright leg plot should be same as that of NH patients and a method for predicting DW was developed. To validate the accuracy of this method, the ECF/TBWright leg was measured by eight-point tactile-electrode bioelectrical impedance analysis before and after HD in 17 newly enrolled NH patients. Using the current DW (cDW) of subjects as a reference, we compared the accuracies of pDW1 (our devised method) and pDW2 (the normovolaemia/hypervolaemia slope method). Results: The mean cDW, pDW1 and pDW2 values were 56.8 ± 7.9, 56.4 ± 7.7 and 56.3 ± 8.0 kg, respectively. No significant differences existed between cDW, pDW1 and pDW2. pDW1 had a lower root mean square error than pDW2 (1.12 vs 1.69). On the Bland,Altman plot, differences between pDW1 and cDW were closer to zero than between pDW2 and cDW. Conclusion: A new method was developed of predicting the DW using the relationship between the UF amount and the percentage change in the ECF/TBW ratio of the lower extremities after HD. The devised method appears to be as accurate as the normovolaemia/hypervolaemia slope method. [source] Body composition in older orthopaedic rehabilitation inpatients: Are field methods valid?NUTRITION & DIETETICS, Issue 3 2010Alison YAXLEY Abstract Aim:, The assessment of body composition is an important aspect of the determination of nutritional health. This cross-sectional measurement study aimed to assess the relative validity of a range of field techniques for the measurement of body composition in a sample of older orthopaedic inpatients participating in rehabilitation. Methods:, Assessment of percent fat-free mass of 31 adults, aged 65 years and over, was conducted under fasting conditions by two types of bioelectrical impedance analysis (multi-frequency and single frequency,using manufacturer's pre-programmed prediction equation) and compared with percent fat-free mass estimated by dual energy X-ray absorptiometry, a reference technique. Data from multi-frequency bioelectrical impedance analysis were also used to calculate percent fat-free mass from the prediction equation of Dey et al. for comparison. Skeletal muscle mass was derived from assessment of corrected arm muscle area and compared with skeletal muscle mass from dual energy X-ray absorptiometry analysis. Bland-Altman analysis was performed to determine the level of agreement between each field technique and dual energy X-ray absorptiometry. Results:, Mean bias and limits of agreement between single frequency bioelectrical impedance analysis and dual energy X-ray absorptiometry were ,5.7% (,24.0, 12.6), between multi-frequency bioelectrical impedance analysis (manufacturer's pre-programmed prediction equation) and dual energy X-ray absorptiometry were 1.4% (,13.4, 16.1), between multi-frequency bioelectrical impedance analysis (Dey et al. prediction equation) and dual energy X-ray absorptiometry were ,5.0% (,16.6, 6.6) and between skeletal muscle mass as derived from assessment of corrected arm muscle area and skeletal muscle mass from dual energy X-ray absorptiometry analysis ,0.97 kg (,8.37, 6.43). Conclusion:, None of the methods assessed are clinically acceptable for assessment of body composition in older orthopaedic rehabilitation patients; however, estimation of skeletal muscle mass, as derived from corrected arm muscle area, is likely to be of more use in the clinical setting as there is no requirement for patients to be fasted. [source] Unfavorable lipid profiles in mild obesity with excess body fat percentagePEDIATRICS INTERNATIONAL, Issue 1 2000Akiho Tamura Abstract Background: The aim of the present study was to investigate the usefulness of subclassifications of overweight children using the body fat percentage (Fat%) to predict the serum lipid profile. Methods: School children (431, 236 boys and 195 girls) aged 9,12 years were divided into three obesity groups (non-, mild and advanced obesity) and were further divided into two subgroups according to the Fat% measured by bioelectrical impedance analysis. The mean fasting serum lipid levels were also evaluated. Results: In the non-obesity and the advanced obesity groups, the Fat%-based subclassification demonstrated no essential differences in lipid profiles or in the prevalence of hyperlipidemia between the two subgroups. However, in the mild obesity group, the levels of low-density lipoprotein cholesterol and triglyceride and the atherogenic index were significantly higher and the high-density lipoprotein cholesterol level was significantly lower in the adipositic subgroup (Fat%, age/sex-specific cut-off value) than in the non-adipositic subgroup. Multiple comparison of lipid levels among all six categories of children indicated that the adipositic subgroup of mild obesity had no advantage over the advanced obesity group with respect to the atherogenic potential and that the non-adipositic subgroup of mild obesity showed no additional risks compared to the non-obesity group. Moreover, the prevalence of hyperlipidemia in the adipositic subgroup of mild obesity (50.0%) was significantly different from that in its non-adipositic counterpart (13.3%) and was equivalent to that in the advanced obesity group. Conclusions: These results suggest that Fat% evaluation is useful to divide mildly obese children into two distinct subtypes based on serum lipid profiles and that the excess Fat% in mildly obese school children is a predictor of atherogenesis. [source] Relationships between plasma leptin levels and body composition parameters measured by different methods in postmenopausal womenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2003Toivo Jürimäe The aim of this study was to determine the effects of body composition measured by different methods with different measurement errors on fasting plasma leptin level in normal body mass and obese postmenopausal women. It was hypothesized that the relationship between plasma leptin concentration and body fat is higher using more sophisticated laboratory methods (dual energy X-ray absorptiometry, DXA) in comparison with field methods (bioelectrical impedance analysis, BIA, or skinfold thickness) for body fat measurement because of the greater precision of DXA measurements. Thirty-five postmenopausal (55,83 years of age) healthy Estonian women were divided into two groups: BMI < 27kg/m2 as non obese (n = 18) and BMI> 27kg/m2 as obese (n = 17). Body composition was determined using DXA (total body, arms, legs, and trunk fat percent, fat mass, and LBM) and BIA methods. Body fat percent was significantly higher using the DXA method. Subcutaneous adipose tissue distribution was determined by measuring nine skinfold thicknesses. Body fat distribution was defined as the ratio of waist-to-hip (WHR) and waist-to-thigh (WTR) circumferences. Leptin was determined by means of radioimmunoassays. Leptin concentration was not significantly different between groups (19.0 ± 13.3 and 21.5 ± 21.5ng/ml in non obese and obese groups, respectively). Body fat percent and fat weight measured by DXA or BIA methods and all measured skinfold thickness values, except biceps and abdominal, were higher in obese women. Body height did not correlate significantly with leptin concentrations. The relationships between leptin concentration were highest with body weight (r = 0.67) and BMI (r = 0.73) values in the obese group. All measured body fat parameters using DXA or BIA methods correlated significantly with plasma leptin concentration in the obese group. LBM did not influence the leptin concentration in postmenopausal women. Stepwise multiple regression analysis indicated that the body fat percent measured using the DXA method was highly related to plasma leptin concentration in the obese group (63.2%; R2 × 100). When absolute fat mass parameters were considered, leptin concentration was related to the mass of arms fat tissue in the obese group of women (62.3%). Body fat percent measured by BIA was highly related to plasma leptin concentration in the obese group (63.3%). Only biceps skinfold thickness was related to leptin concentration (22.5% and 58.9%, in the nonobese and obese groups, respectively) from the nine measured skinfold thicknesses. WHR and WTR did not reflect leptin concentration in different groups of postmenopausal women. It was concluded that different methods of body composition estimation generate different correlations with plasma leptin concentration. Body fat percent and especially fat mass measured by DXA are the main predictors relating to plasma leptin concentration in obese, but not in nonobese, postmenopausal women. In addition, fat mass in arms measured by DXA and biceps skinfold thickness were also highly related to leptin concentration. Am. J. Hum. Biol. 15:628,636, 2003. © 2003 Wiley-Liss, Inc. [source] AC impedance analysis and EMI shielding effectiveness of conductive SBR compositesPOLYMER ENGINEERING & SCIENCE, Issue 10 2006G.T. Mohanraj Flexible conductive polymer composites were prepared using styrene,butadiene rubber (SBR) as a matrix and conductive carbon black as filler. The filler loading was varied from 10 to 60 phr. The complex AC impedance and electromagnetic interference shielding effectiveness (EMI SE) of the composites were measured at the microwave frequencies of 7.8,12.4 GHz. The effect of variation in filler concentration and measurement frequency on the AC impedance and EMI SE of the composites were investigated. Equivalent circuits describing the conduction behavior of the composites were determined by means of Nyquist plots. The complex electric modulus of the composites was also determined. Increase in the filler loading increased the capacitive nature of the materials. The composites were better defined by a parallel resistor,capacitor circuit in series with a resistor. The EMI SE was found to pass through a maximum with increase in frequency. However, with the increase in filler loading and sample thickness of the material, the EMI SE was found to increase continuously. POLYM. ENG. SCI., 46:1342,1349, 2006. © 2006 Society of Plastics Engineers. [source] Electricity generation from the treatment of wastewater with a hybrid up-flow microbial fuel cellBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Krishna P. Katuri Abstract The performance of a prototype up-flow single-chambered microbial fuel cell (MFC) for electrical power generation using brewery wastewater as fuel is reported. The designed reactor consisted of three zones, namely a lower anaerobic digestion zone, a central MFC zone, and an upper effluent clarifier zone. Tests were conducted in batch mode using a beer wastewater as the fuel/electron donor (COD concentration: 430,mg/L) and mixed consortia (both sewage microflora and anaerobic sludge) as a source of electrogenic bacteria. A stable current density of ,2,270,mA/m2 was generated under continuous polarization with a constant external resistance (0.01,k,) and cell polarization gave a peak power density of 330,mW/m2 at a current density of 1,680,mA/m2. Electrochemical impedance analysis showed that the overall internal resistance of the reactor was quite low, that is, 8.0,,. Cyclic voltammetric analysis of the anodic biofilm at low scan rate revealed quite complex processes at the anode, with three redox peaks, at potentials of 116, 214, and 319,mV (vs. NHE). Biotechnol. Bioeng. 2010;107: 52,58. © 2010 Wiley Periodicals, Inc. [source] Telomere length and obesityACTA PAEDIATRICA, Issue 7 2008Raffaella Zannolli Abstract Aim: To assess the telomere length in apparently healthy obese and normal-weight subjects. Methods: Seventy-six Caucasian subjects were chosen including 53 children (age 8.2 ± 3.5 years) and 23 adults (age 40.5 ± 8.4 years). Among these, 22 (12 children and 10 adults) were obese with a body mass index (BMI, kg/m2) > 2 SD above the norm. Bioelectrical impedance analysis (BIA), measured with a multiple frequency analyzer, was used to estimate body composition. DNA extraction from white blood cells was used to estimate the telomere length by detection of terminal restriction fragments (TRF). Results: No difference was found between the TRF lengths of obese and normal children. Obese adults had shorter TRF lengths than adults who were not obese (mean TRF length difference, ,884.5; 95% confidence intervals ,1727 to ,41.8; t= 2.183; df = 17; p < 0.041). Conclusions: Obese adults have shorter telomeres than their normal-weight counterparts, while this phenomenon is not present in childhood. [source] Decreased hepatic RBP4 secretion is correlated with reduced hepatic glucose production but is not associated with insulin resistance in patients with liver cirrhosisCLINICAL ENDOCRINOLOGY, Issue 1 2009Matthias J. Bahr Summary Objective, Patients with liver cirrhosis have a high incidence of insulin resistance and diabetes. This study was designed to determine circulating levels and hepatic production of retinol-binding protein 4 (RBP4) in relation to parameters of hepatic and systemic metabolism in patients with liver cirrhosis. Design and method, Circulating RBP4 levels were measured in 19 patients with liver cirrhosis at different clinical stages of the disease and in 20 age-, sex- and body mass index (BMI)-matched controls. Hepatic production rates of RBP4 and glucose were assessed by measuring the arterial hepatic venous concentration difference together with hepatic blood flow. Insulin resistance was determined by the Quantitative Insulin Sensitivity Check Index (QUICKI) and the homeostasis model assessment of insulin resistance (HOMA-IR), energy expenditure by indirect calorimetry and body composition by bioelectrical impedance analysis (BIA). Results, Compared with controls, RBP4 levels in cirrhosis were decreased (8·1 ± 1·8 vs. 22·6 ± 2·4 mg/l, P < 0·001) due to decreased hepatic production (P < 0·05). RBP4 correlated with hepatic protein synthesis capacity (P < 0·01), but not with insulin resistance, energy expenditure, BMI or body fat mass. Plasma RBP4 correlated with hepatic glucose production (P < 0·05). Conclusions, These data demonstrate that RBP4 in cirrhosis (i) is decreased due to reduced hepatic production, (ii) is not associated with insulin resistance, and (iii) might have a beneficial role by decreasing hepatic glucose production and could thus also be regarded as a hepatokine. [source] Maximal explosive muscle power in obese and non-obese prepubertal childrenCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 3 2009Stefano Lazzer Summary Objective:, The objectives of the present study was to compare the maximal explosive muscle power developed by the lower limbs in obese and non-obese prepubertal children. Design:, Twenty-five obese [mean body mass index (BMI) z -score: 2·4] and 30 non-obese (mean BMI z -score: 0) children aged 8,12 years, participated in this study. Body composition was measured by bioelectrical impedance analysis and the maximal explosive power of the lower limbs was assessed by the Exercise-Ergometer (a sledge dynamometer). Results:, Absolute peak force (Fpeak) was higher in obese than in non-obese children by 18·2% (P<0·001). Peak speed (vpeak) was not significantly different between groups (P = 0·504). Consequently, absolute peak power (W,peak) was higher in obese than in non-obese children (+19·3%, P = 0·021). Considering gender differences, absolute Fpeak and vpeak were higher in boys than in girls by +12·3 and +17·4% (P<0·05), respectively, thus yielding higher absolute W,peak values in boys as compared to girls (+26·1%, P<0·001). Finally, W,peak normalized for fat-free mass (FFM) was not different between obese and non-obese children but higher in boys than in girls (+24·5%, P<0·001). Conclusions:, Power generation capability per unit of FFM was similar between obese and non-obese children but was significantly higher in boys than girls. On the clinical practice it seems important to devote supplementary care to sustain and improve the motor function of obese and non-obese girls. [source] Early supplementation of parenteral nutrition is capable of improving quality of life, chemotherapy-related toxicity and body composition in patients with advanced colorectal carcinoma undergoing palliative treatment: results from a prospective, randomized clinical trialCOLORECTAL DISEASE, Issue 10Online 2010T. Hasenberg Abstract Aim, Patients suffering from advanced colorectal cancer can experience unintended weight loss and/or treatment-induced gastrointestinal toxicity. Based on current evidence, the routine use of parenteral nutrition (PN) for patients with colorectal cancer is not recommended. This study evaluates the effect of PN supplementation on body composition, quality of life (QoL), chemotherapy-associated side effects and survival in patients with advanced colorectal cancer. Method, Eighty-two patients with advanced colorectal cancer receiving a palliative chemotherapy were prospectively randomized to either oral enteral nutrition supplement (PN-) or oral enteral nutrition supplement plus supplemental PN (PN+). Every 6 weeks body weight, body mass index (BMI), chemotherapy-associated side effects and caloric intake were assessed, haemoglobin and serum albumin were measured. Body composition was assessed by body impedance analysis, and QoL was evaluated by European Organization for Research and Treatment of Cancer (EORTC) QLQC30 questionnaire. Results, No differences were evident at baseline between the groups for age, sex, diagnosis, weight, BMI or QoL. A difference in BMI was observed by week 36, whereas differences of the mean body cell mass could be observed from week 6, albumin dropped significantly in the PN- group in week 36 and QoL showed significant differences from week 18. Chemotherapy-associated side effects were higher in PN-. The survival rate was significantly greater in the PN+ group. Conclusion, A supplementation with PN slows weight loss, stabilizes body-composition and improves QoL in patients with advanced colorectal cancer. Furthermore, it can reduce chemotherapy-related side effects. [source] | |||||||||||||||||||