Determination Of Phase Angle Research Articles

Why should we incorporate the determination of phase angle by bioelectrical impedance into our routine practice in clinical nutrition?

Why should we incorporate the determination of phase angle by bioelectrical impedance into our routine practice in clinical nutrition?

Evaluation of the Relative Phase Comparison Method at Its Limits Used for Absolute Phase Determination of an AC Cage Current Shunt Group.

AC current shunts are used for precise current measurements. The application of AC current shunts requires that their amplitude phase characteristics are known. A group of three geometrically identical current shunts and a reference shunt are observed in this paper. The phase characteristics of the reference shunt have been previously obtained. A relative phase comparison has been made between the three geometrically identical shunts, and phase displacement values for each have been obtained. After this, the results are verified with the reference shunt. The relative method is most suitable for shunts, where their respective RC and L/R values are small (compared with 1/ω) and of the same order. The ratios of the nominal resistance values of the shunts used in this paper are at the limit of the given statement. The conclusion is that the method applied at the mentioned limits, in terms of the metrology-grade phase angle determination of current shunts, is not to be considered reliable at frequencies higher than 1 kHz.

Determinants of phase angle in Japanese patients with diabetes.

Phase angle, obtained using bioelectrical impedance analysis, non-invasively reflects the whole-body cellular condition and nutritional status and may be helpful as a prognostic factor. Patients with diabetes had a smaller phase angle than healthy subjects. However, the clinical significance of phase angle has not yet been elucidated. Therefore, the purpose of this study was to clarify the relationship between phase angle and HbA1c in patients with diabetes and the clinical relevance of phase angle. A retrospective, multicenter, cross-sectional study was conducted with Japanese patients with diabetes. Body composition was determined with bioelectrical impedance analysis, and this was used to obtain phase angle. Phase angle was assessed in relation to clinical parameters, body composition parameters, and HbA1c levels. A total of 655 patients were enrolled (400 men and 255 women, aged 57.1 ± 14.8years, body mass index 25.6 ± 5.2kg/m2, HbA1c 8.1 ± 1.9%). Even in patients with diabetes, the phase angle was higher in men than in women and did not differ between the types of diabetes. Multiple regression analysis, performed with phase angle as the objective variable, and age, sex, diabetes type, HbA1c, albumin level, and body mass index as explanatory variables, revealed that phase angle was negatively affected by HbA1c (B = -0.043, 95% Confidence interval: -0.07 to -0.02, p < 0.001). HbA1c, age, sex, albumin level, and body mass index were independent determinants of phase angle in participants with diabetes.

Bioelectrical impedance analysis in the BaSAlt cohort-study: the phase angle as an additional parameter for sarcopenia quantification among German nursing home residents?

Key summary pointsAimCan phase angle represents an additional parameter for quantifying sarcopenia among German nursing home residents?FindingsThere is a limitation of the phase angle in differentiating between “confirmed/ severe sarcopenia” with “no sarcopenia” and “probable sarcopenia” groups among multimorbid nursing home residents in Germany.MessageBioelectrical impedance analysis and determination of phase angle represent chances in the diagnostic of sarcopenia, but there is a limitation for differentiation in preliminary stage of sarcopenia among multimorbid NH residents.

A Comparative Study on the Physical and Rheological Properties of 60/70 and 80/100 Penetration Grade Bitumen in Malaysia

The engineering properties of a bitumen plays vital role in determining the suitability of the bitumen usage for a pavement structure. Presently, bituminous pavements in Malaysia are constantly subjected to high-speed loading of vehicles as well as increased pavement temperature due to extreme solar heat which causes rutting and fatigue failure issues. In this research, the 60/70 and 80/100 penetration grade bitumen were subjected to both physical and rheological testing. Physical testing was used to determine the softening point, ductility, penetration and penetration index value whereas rheological testing chiefly determined the engineering properties of the bitumen such as complex modulus and phase angle which interprets the stiffness and viscoelastic behavior. Physical testing results indicate that the 60/70 penetration grade bitumen possesses lower penetration value, higher softening point, adequate ductility and higher penetration index value compared to the 80/100 penetration grade bitumen. Besides, rheological results show that the complex modulus and rutting factor of 60/70 bitumen indicates good stiffness towards temperature rise compared to the 80/100 penetration grade bitumen, thus, posing better resistance towards permanent deformation. Additionally, the 60/70 penetration grade bitumen generally possesses better elasticity compared to the 80/100 penetration grade bitumen which is observed through the phase angle determination.

Phase angle and cellular health: inflammation and oxidative damage.

Phase angle is a composite measure that combines two raw bioelectrical impedance analysis measures: resistance and reactance. Phase angle has been considered an indicator of cellular health, integrity, and hydration. As inflammation and oxidative stress can damage cellular structures, phase angle has potential utility in early detecting inflammatory and oxidative status. Herein, we aimed to critically review the current understanding on the determinants of phase angle and its relationship with markers of inflammation and oxidative stress. We also discussed the potential role of phase angle in detecting chronic inflammation and related adverse outcomes. Several factors have been identified as predictors of phase angle, including age, sex, extracellular to intracellular water ratio, and fat-free mass. In addition to these factors, body mass index (BMI) also seems to influence phase angle. Available data also show that lower phase angle values are correlated (negligible to high correlation coefficients) with higher c-reactive protein, tumour necrosis factor-α, interleukin-6, and interleukin-10 in studies involving the general and aging populations, as well as patients with chronic conditions. Although fewer studies have evaluated the relationship between phase angle and markers of oxidative stress, available data also suggest that phase angle has potential to be used as an indicator (for screening) of oxidative damage. Future studies including diverse populations and bioelectrical impedance devices are required to confirm the validity and accuracy of phase angle as a marker of inflammation and oxidative stress for clinical use.

Research on switching method of low inertia microgrid parallel transformer

The vigorous development of clean energy technology has gradually led to the formation of a new power system. The new power system takes clean energy as the main supply, and has the advantages of clean, low-carbon, flexible and efficient. However, it has low inertia and is easily affected by energy fluctuation, resulting in protection misoperation. Microgrid has small volume and poor anti-interference ability. The magnetizing inrush current generated by parallel transformer during switching is very easy to lead to misoperation of transformer protection, which threatens the stability and safety of the whole power grid. Therefore, are switching method of parallel transformer is proposed. First, close all secondary circuit breakers, and then select the primary circuit breaker of one transformer for initial closing. After the closing is completed, conduct the closing operation again after the delay and phase angle determination. The two switching operations are completed, and the no-load closing operation is completed. Finally, the PSCAD simulation model is established to simulate the AC microgrid to verify the feasibility of this method.

POS-555 CORRELATION BETWEEN PHASE ANGLE, FLUID OVERLOAD, AND UNCONTROLLED NIGHTTIME BLOOD PRESSURE IN PATIENTS WITH CHRONIC HEMODIALYSIS

Hypertension in patients with chronic kidney disease (CKD) have a prevalence of up to 85%. Fluid overload is a predictor of mortality and a significant relationship between volume status and blood pressure (BP) has been reported. The approach of the volume status with bioelectrical impedance spectroscopy (BIS) and determination of phase angle (PhA) gains strength in nephrology. So far, no reference cut-off point to determine the relationship of the PhA with hydric overload or with some pattern of arterial hypertension had been reported.

Control of Three-Phase Power Electronic Converter With Power Controllers in Stationary Frame

This article concentrates on a three-phase power converter control system that uses voltages and currents in a stationary reference frame. The advantages of such a control system include the lack of transformation between stationary and rotating reference frames and hence, there is no need for an extra algorithm such as a phase-locked loop for the grid voltage phase-angle determination, as the power components are the same in every coordinate system. The method proposed in this article uses proportional-resonant-integral controllers for tracking referenced Akagi's instantaneous power components, which contain intentional oscillations of double grid frequency. Thanks to that, the sinusoidal converter current is maintained despite the negative sequence component in grid voltage. Different targets for converter current asymmetry, from corresponding, through symmetrical, to opposite to voltage asymmetry may be achieved, depending on the operation mode and the demanded power. Moreover, the power limitation method allowing limitation of the phase-current amplitude even for unbalanced phase currents was applied.

Fault Current Negative Contribution Method for Inverter-Based Distributed Generators Under Grid Unbalanced Fault

With the rapid increase of embedded inverter-based distributed generators (IBDGs), the active distributed network (ADN) is facing security and protection challenges because IBDGs will contribute extra fault current. In contrary to the existing method that IBDGs provide varying degrees of positive contribution to system fault current, in this article, a fault current negative contribution (FCNC) method is proposed for IBDGs to reduce the system fault current lower than the situation where without IBDGs embedded. In the proposed method, a maximum current phase angle adjustment (MCPAA) strategy is conducted for IBDGs to maximize its negative contribution, thus to minimize the system fault current. In order to obtain a more precise current phase angle, a voltage phase angle determination (VPAD) strategy is also formulated by considering the voltage angle difference on the electrical distance between IBDGs and fault bus. Extensive tests and relevant results have validated the feasibility of FCNC method to achieve a negative contribution of IBDGs on system fault current.

Origin of the low-frequency plateau and the light-scattering slow mode in semidilute poly(ethylene glycol) solutions.

A low-frequency plateau is often found in the rheological spectra of various kinds of semidilute solutions of polymers and other colloids; also, many such solutions have been reported to show slow-modes in their dynamic light scattering autocorrelation functions. Both these observations may lead to the hypothesis of weak associative network structures built by the dissolved polymer chains or colloidal building blocks. To challenge this hypothesis, we conduct a series of comparative studies on semidilute solutions of poly(ethylene glycol) by using classical rheology as well as passive microrheology based on dynamic light scattering, along with structural studies using static light scattering. Although we indeed find a low-frequency plateau using classical shear rheology, even at elevated temperatures where potential polymer aggregates should be broken, no such plateau is observed in any of our microrheology experiments. Also, dynamic and static light scattering studies on the polymer solutions do not confirm the presence of larger structural entities: no slow mode can be detected in the autocorrelation function of the scattering intensity signal, and this signal is angle independent if the samples are purified by a thorough procedure of filtration. Based on these findings, we conclude that the low-frequency plateau in classical rheology results is an instrument effect caused by erroneous recording of the phase angle, although the magnitude of the torque lies well within the resolution of the rheometer. We also conclude that slow modes in dynamic light scattering on solutions of poly(ethylene glycol) are impurity-based artifacts rather than due to actual associated structures.

Performance of CT-based low skeletal muscle index, low mean muscle attenuation, and bioelectric impedance derived low phase angle in the detection of an increased risk of nutrition related mortality

The aim of this study was to evaluate in a head to head comparison the performance of bioimpedance derived low phase angle (PA), CT-based low skeletal muscle index (SMI) and low mean muscle attenuation (MA), and Pandora Score (PS) to detect an increased nutrition related mortality in hospitalized patients. A total of 7736 patients were hospitalized in Dessau community hospital (Nov 11, 2016-Feb 05, 2017). In 227/7736 patients an abdominal CT scan was obtained and low values (below threshold) of skeletal muscle index (SMI) and mean muscle attenuation (MA) were obtained at L3 level using Slice-O-Matic. In 180/227 patients, malnutrition screening (NRS-2002≥3), determination of low PA (<5th percentile) and calculation of 30-day mortality risk (PS≥5%) were done within 6 days after the CT scan. PA was low in 116 (64%), SMI was low in 95 (53%), and MA was below threshold in 137 (77%) patients. Using hospital mortality (8.3%) as a gold standard, low SMI, low MA, or low PA showed high sensitivity (SMI 93.3%; MA 86.7%; PA 86.7%) and high negative predictive (NPV) values (SMI 98.9%; MA 95.3%; PA 96.9%) and improved specificity (NRS+SMI 65.5%; NRS+MA 50.3%; NRS+PA 50.3%) when combined with the criterion NRS≥3. Using hospital mortality as a gold standard, a PS≥36 (predicted mortality≥5%) showed a sensitivity of 73.3%, a specificity of 62.2% and an NPV of 96.4%. PS predicted mortality was ≥5% in 70 (39%) patients and was higher (median 5.2%; IQR: 2.8; 11.8 vs 1.7%; IQR: 1.0; 2.8; p<0.001) in patients with a low PA and this was also observed for low vs normal SMI (median 5.7%; IQR: 2.6; 11.1 vs 2.7%; IQR:1.4;5.5; p<0.001) but not for low vs normal MA (median 3.9%; IQR: 2.1; 8.8 vs 3.4%; IQR: 2.0; 8.1; ns). Determination of phase angle<5th percentile is a convenient non-invasive and inexpensive bedside method with high sensitivity and a high negative predictive value to detect patients at risk of nutrition related mortality with a performance comparable to CT derived skeletal muscle index or mean muscle attenuation.

Prediction of phase angles from dynamic modulus data and implications for cracking performance evaluation

The need for a viscoelastic characterisation of hot mix asphalt is increasing as advanced testing and modelling is incorporated through mechanistic-empirical pavement design and performance-based specifications. Viscoelastic characterisation includes measurement of the mixture stiffness and relative proportion of elastic and viscous response. The most common method is to measure the complex modulus, where dynamic modulus represents the stiffness and the phase angle represents the relative extent of elastic and viscous response. Determination of phase angle from temperature and frequency sweep tests has been challenging, unreliable and prone to error due to a high degree of variability and sensitivity to signal noise. There are also large amounts of historical dynamic modulus data that are either missing phase angle measurements or have poorly measured phase angle data that inhibit their use in further evaluation. This paper evaluates the robustness of phase angle estimation from stiffness data for asphalt mixtures. The objectives of the study are to: (1) evaluate the procedure of estimating phase angle from the slope of log-log stiffness master curve fitted with a generalised logistic sigmoidal curve and compare it with lab measurements and the Hirsch model; (2) assess the effect of measured and predicted phase angles on a mixture Black Space diagram; (3) evaluate the effect of using predicted phase angles on SVECD fatigue analysis particularly regarding damage characteristics curves and fatigue coefficients and (4) evaluate the impact on layered viscoelastic pavement analysis for critical distresses (LVECD) pavement fatigue performance evaluation due to the use of predicted phase angles. Three sets of independent mixtures were evaluated in this study comprising a wide range of mixture conditions. The results indicate good agreement between measured and predicted phase angle values in terms of shape and peak master curve values. In terms of magnitude, the values from both matched very well for certain sets of mixtures and subsequently manifested in similar performance predictions. However, for other sets of mixtures, a considerable difference was observed between measured and predicted phase angle values as well as SVECD and LVECD results. The differences may be attributed to the use of different types of linear variable displacement transducers (loose core versus spring loaded). Another possible explanation for the difference could be the contribution of plastic strain, which may create a difference in phase angles of 1–2°.

Multi-wavelength anomalous diffraction de novo phasing using a two-colour X-ray free-electron laser with wide tunability

Serial femtosecond crystallography at X-ray free-electron lasers (XFELs) offers unprecedented possibilities for macromolecular structure determination of systems prone to radiation damage. However, de novo structure determination, i.e., without prior structural knowledge, is complicated by the inherent inaccuracy of serial femtosecond crystallography data. By its very nature, serial femtosecond crystallography data collection entails shot-to-shot fluctuations in X-ray wavelength and intensity as well as variations in crystal size and quality that must be averaged out. Hence, to obtain accurate diffraction intensities for de novo phasing, large numbers of diffraction patterns are required, and, concomitantly large volumes of sample and long X-ray free-electron laser beamtimes. Here we show that serial femtosecond crystallography data collected using simultaneous two-colour X-ray free-electron laser pulses can be used for multiple wavelength anomalous dispersion phasing. The phase angle determination is significantly more accurate than for single-colour phasing. We anticipate that two-colour multiple wavelength anomalous dispersion phasing will enhance structure determination of difficult-to-phase proteins at X-ray free-electron lasers.

Hematological complications in anorexia nervosa.

Background/objectives:Anemia, leukopenia and, although less frequently, thrombocytopenia are possible hematological complications of anorexia nervosa considered strictly secondary to chronic malnutrition. This is a retrospective study on the prevalence of these disorders in a large cohort of 318 female patients with AN (20.4±5.6 years, body mass index (BMI) 15.9±1.6 kg/m2), recruited in the Outpatient Unit for Malnutrition secondary to Eating Disorders at the Department of Clinical Medicine and Surgery, Federico II University Hospital, since February 1991 to December 2012.Subjects/methods:Patients were studied on an outpatient basis after obtaining medical history, clinical examination, routine hematobiochemical and endocrine tests, electrocardiography, psychiatric interview and bioelectrical impedance analysis and, in particular, phase angle determination. All patients with other comorbidities, in particular with mean corpuscular volume <80 fl, were excluded for suspected genetic alteration in the synthesis of hemoglobin.Results:Hematologic data showed that 16.7% of patients had anemia, 7.9% neutropenia and 8.9% thrombocytopenia. These abnormalities were strictly related to the duration of illness (P=0.028), and to protein energy malnutrition, in particular, BMI and phase angle (P<0.001).Conclusions:Our study offers description of the incidence of hematologic defects in a selected and large sample of AN female patients, suggesting that its incidence is related to the degree and duration of protein energy malnutrition.

Processing of Complex Modulated Ultrasonic Signals in Gas Flow Metering

In ultrasonic gas flow metering the ultrasonic wave is complex modulated by natural or artificial structures in the fluid. The determination of the shifted phase angle makes problems if the limited range of the arctan-function is exceeded. It results in phase jumps and ambiguities of the phase angle [1]. This paper presents a new method of phase angle determination which is called differential procedure [2]. The differential procedure has been proved good to determine undersampled ultrasonic data in a wider range of phase shift. The expanded range of phase angle is advantageous for vortex measurement as well as for correlation measurement. Phase and amplitude modulation are physically mutually connected. Phase modulation corresponds to frequency modulation and results in connection with the receiving response of the ultrasound sensor in an additional nonlinear amplitude modulation.

Biological determinants of phase angle among Brazilian elite athletes

Biological determinants of phase angle among Brazilian elite athletes

Improving the scattering-factor formalism in protein refinement: application of the University at Buffalo Aspherical-Atom Databank to polypeptide structures

The University at Buffalo theoretical databank of aspherical pseudoatoms has been tested in the refinement of high-resolution (HR; d(max) < or = 0.44 A) and truncated ;low-resolution' (LR; d(max) = 0.83 A) X-ray diffraction data sets from the tripeptide Tyr-Gly-Gly monohydrate [Pichon-Pesme et al. (2000), Acta Cryst. B56, 728-737] and hexapeptide cyclo-(D,L-Pro)(2)-(L-Ala)4 monohydrate [Dittrich et al. (2002), Acta Cryst. B58, 721-727]. Application of the databank to LR data significantly lowers the conventional R factor, improves the determination of bonds and angles to within 0.002-0.003 A and 0.09-0.17 degrees of the values obtained from a complete multipolar refinement of HR data sets, improves the determination of phase angles by 2-6 degrees compared with the standard independent atom refinement (IAM), removes the majority of the bonding features from the residual Fourier difference maps and improves the atomic displacement parameters (ADPs) and the results of the Hirshfeld rigid-bond test. In the description of the aspherical density from experimental X-ray data, theoretical pseudoatoms were found to perform on the same level as the previously reported experimental databank [Pichon-Pesme et al. (1995), J. Phys. Chem. 99, 6242-6250; Jelsch et al. (1998), Acta Cryst. D54, 1306-1318], although no direct comparison of the two methods has been performed. The theoretical databank of aspherical pseudoatoms is shown to be a significant aid in the refinement of accurate experimental X-ray data from large molecular systems, in addition to its use in the reconstruction of molecular densities and the determination of electrostatic interaction energies.

Phase Angle From Bioelectrical Impedance Analysis: Population Reference Values by Age, Sex, and Body Mass Index

The use of bioelectrical impedance phase angle has been recommended as a prognostic tool in the clinical setting, but published reference data bases are discrepant and incomplete (eg, they do not consider body mass index [BMI], and data are lacking for children). Phase angle reference values stratified by age, sex, and BMI were generated in a large German data base of 15,605 children and adolescents and 214,732 adults, and the determinants of phase angle values were assessed. The reference values were applied to 3 groups of patients and compared with previously published reference values from the United States and Switzerland. Gender and age were the main determinants of phase angle in adults, with men and younger subjects having higher phase angles. In children and adolescents, age and BMI were the main determinants of phase angle. In normal and overweight adults, phase angle increased with increasing BMI, but there was an inverse association at a BMI >40 kg/m2. In cirrhosis, the prevalence of a low phase angle increased with the state of disease, whereas it was not different between patients with the metabolic syndrome and controls. There are considerable differences between phase angle reference values from different populations. These differences are not explained by age or BMI and may be due to differences between impedance analyzers. The determinants of phase angle differ between adults and children. In adults, the influence of BMI on phase angle depended on the BMI range. The prognostic value of phase angle may differ in different clinical settings. The use of population-specific and probably impedance-analyzer-specific reference values for phase angle is recommended.

Determination of phase angle and amplitude error of voltage and current transformers up to some 100 Hz for loss measurements on power transformers

For the load loss measurement of power transformers, current and voltage transformers with usually extremely low errors of phase angle and amplitude are used. However, even small errors of the measuring transformers may result in an error in the measured load loss. Therefore, national and international standards allow the correction of the measured value by the amount caused by phase angle and amplitude error of the measuring equipment [2–4]. The determination of the errors of phase angle and amplitude of measuring transformers is carried out on the basis of calibrated standard measuring transformers which are traceable to national standard equipment at rated frequency, e.g. at 50 and 60 Hz. For some applications – e.g. the load loss measurement of HVDC power transformers according to the draft of IEC standard 61378-2 [1] – a load loss measurement at frequencies other than rated frequency is required. For that, the errors of phase angle and amplitude of the measuring transformers must be known. This paper describes a method how to determine the phase angle and amplitude errors of the measuring transformers at arbitrary frequencies on the basis of the calibrated error values at rated frequency.