Magnetic resonance imaging based kidney volume assessment for risk stratification in pediatric autosomal dominant polycystic kidney disease

IntroductionIn the pediatric context, most children with autosomal dominant polycystic kidney disease (ADPKD) maintain a normal glomerular filtration rate (GFR) despite underlying structural kidney damage, highlighting the critical need for early intervention and predictive markers. Due to the inverse relationship between kidney volume and kidney function, risk assessments have been presented on the basis of kidney volume. The aim of this study was to use magnetic resonance imaging (MRI)-based kidney volume assessment for risk stratification in pediatric ADPKD and to investigate clinical and genetic differences among risk groups.MethodsThis multicenter, cross-sectional, and case-control study included 75 genetically confirmed pediatric ADPKD patients (5–18 years) and 27 controls. Kidney function was assessed by eGFR calculated from serum creatinine and cystatin C using the CKiD-U25 equation. Blood pressure was assessed by both office and 24-hour ambulatory measurements. Kidney volume was calculated from MRI using the stereological method. Total kidney volume was adjusted for the height (htTKV). Patients were stratified from A to E classes according to the Leuven Imaging Classification (LIC) using MRI-derived htTKV.ResultsMedian (Q1-Q3) age of the patients was 6.0 (2.0–10.0) years, 56% were male. There were no differences in sex, age, height-SDS, or GFR between the patient and control groups. Of the patients, 89% had PKD1 and 11% had PKD2 mutations. Non-missense mutations were 73% in PKD1 and 75% in PKD2. Twenty patients (27%) had hypertension based on ABPM. Median htTKV of the patients was significantly higher than controls (141 vs. 117 ml/m, p = 0.0003). LIC stratification revealed Classes A (38.7%), B (28%), C (24%), and D + E (9.3%). All children in class D + E and 94% in class C had PKD1 variants. Class D + E patients had significantly higher blood pressure values and hypertension compared to other classes (p > 0.05 for all).DiscussionThis study distinguishes itself by using MRI-based measurements of kidney volume to stratify pediatric ADPKD patients into specific risk groups. It is important to note that PKD1 mutation and elevated blood pressure were higher in the high-risk groups stratified by age and kidney volume. Our results need to be confirmed in further studies

Parallel connected GaN E-HEMT VSI-based servo drives for PMSMs

The operation of parallel-connected servo drives has the advantages of increasing the torque (hence the power) capacity, reliability, redundancy and modularity. However, smaller discrepancies of the system clocks of the independent microcontrollers, asynchronous pulse width modulation (PWM) carrier signals and hardware differences can make the output voltages of the parallel modules non-identical, which results in circulating currents. These circulating currents limit the parallel operation, introduce additional power dissipation, cause unbalanced power distribution and degrade the control performance. To eliminate the circulating currents separated DC supplies, coupled inductors (CIs), PWM techniques, modified control techniques etc. are proposed in the literature. In this study, a fault-tolerant parallel-connected gallium nitride enhancement-mode high electron mobility transistor voltage source inverter-based servo drive scheme that eliminates the need for CIs and separate DC supplies and also enables the use of a standard proportional-integral current control and a standard space vector PWM approach is proposed and tested. To evaluate the performances of the proposed scheme, up to six servo drives (limit-6 x 7 Arms) are connected in parallel and tested under various conditions with a 24 V permanent magnet synchronous motor (nominal-61.9 Arms). The results show that the parallel operation not only increases the torque capacity of the system but also increases modularity, flexibility, reliability and also redundancy

Comparison of the Effects of Nonlinearities for Si MOSFET and GaN E-HEMT Based VSIs

Nonlinearities in voltage source inverters (VSIs) such as; dead time, switching time, delay time, voltage drops on the power switches, parasitic capacitance, etc., are considered to be the main sources of the output voltage distortions. These distortions result in low-order harmonics in the output current, which in turn increase core losses and create torque ripples. In particular, for low-speed applications with low-inductance motors, the control performance and the stability of the system degrades substantially, especially when the system operates in the low-torque region. In this work, the effects of these nonlinearities on the phase current and on the current control of the silicon (Si) metal oxide semiconductor field effect transistor (MOSFET) based VSI are investigated with an air cored low inductance permanent magnet synchronous motor. Furthermore, Gallium nitride (GaN) enhancement mode high electron mobility transistor (E-HEMT) based VSI is proposed to overcome this problem. Next, improvements in the current control process are demonstrated by comparing the experimental results obtained by using GaN E-HEMT and Si MOSFET based VSIs. Results show that GaN E-HEMT based VSI is a better choice for applications, which require a high bandwidth control

High Bandwidth Current Control via Nonlinear Compensation and GaN-based VSI

Nonlinearities in the voltage source inverter (VSI) such as dead time, switching time, delay time, voltage drops on the power switches, parasitic capacitances etc. are considered to be the main sources of the output voltage distortions. These distortions result in low order harmonics in the output current, which in turn increase core losses and create torque ripples. In particular, in the low speed and low torque applications the control performance and the stability of the system degrades substantially. Although as the switching frequency increases the effects of the dead time, the switching time and the delay time become more notable, to achieve a high current control bandwidth higher switching frequency is required. High performance VSI-fed motor drive can be realized both by reducing the effects of the VSI nonlinearities and by having a high current control bandwidth. In this work, GaN transistor based VSI-fed permanent magnet synchronous motor (PMSM) drive is used to achieve a high current control bandwidth. Since the current loop is the inner most loop of the control loop, it enables the outer speed and position loops to be faster. This high performance servo motor drive can be used in applications such as control of pedestals, robot arms, optic stabilizers, CNC machines, active vibration cancellers etc. that require high control bandwidths

Synthesis, Characterization and Optoelectrochemical Properties of Poly(2,5-di(thiophen-2-yl)-1-(4-(thiophen-3-yl)phenyl)-1H-pyrrole-co-EDOT)

A new polythiophene derivative was synthesized by electrochemical oxidative polymerization of 2,5-di( thiophen-2-yl)-1-(4-(thiophen-3-yl) phenyl)-1H-pyrrole (TTPP). The structure of the monomer was evaluated by H-1-NMR and FT-IR. The polymer (P(TTPP)) and its co-polymer with 3,4-ethylenedioxythiophene (P(TTPP-co-EDOT)) were synthesized via potentiostatic electrochemical polymerization. The resulting polymers were characterized by cyclic voltammetry (CV), FT-IR, SEM and UV-Vis spectroscopy, and conductivity measurements. Also, the spectroelectrochemical and electrochromic properties of P(TTPP-co- EDOT) were investigated. While P(TTPP) reveals no electrochromic activity, its co-polymer with EDOT has two different colours (yellow and blue). Optical contrast, switching time, lambda(max) and band gap (E-g) of (P(TTPP-co-EDOT)) were determined. (C) Koninklijke Brill NV, Leiden, 201

Synthesis and Characterization of Conducting Copolymers of Bisphenol A-Diglycidyl Ether with Thiophene Side-Groups and Pyrrole

Copolymers of bisphenol A-diglycidyl ether with thiophene side-groups and pyrrole were synthesized by electrochemical polymerization. Bisphenol A-diglycidyl ether with thiophene side-groups (DGEBATh) was obtained from the reaction between bisphenol A-diglycidyl ether (DGEBA) and thiophene-3-acetic acid. The syntheses of copolymers of DGEBATh and pyrrole were achieved electrochemically using three different supporting electrolytes, p-toluene sulfonic acid (PTSA), sodium dodecyl sulfate (SDS) and tetrabutylammonium tetrafluoroborate (TBAFB). Characterizations of DGEBATh and copolymers were performed by combination of techniques including cyclic voltammetry, scanning electron microscopy, gel permeation chromatography, differential scanning calorimetry, 1H-NMR and FT-IR. The conductivities were measured by the four-probe technique

Synthesis and Characterization of Conducting Copolymers of Quinoxaline Derivatives

WOS: 000288142700060Electrochemical copolymerizations of 2,3-di(2-thienyl)quinoxaline (M1), 6-methyl-2,3-di(2-thienyl)quinoxaline (M2), and 2,3-di(2-thienyl)quinoxaline-6-yl)(phenyl)methanone (M3) with 3,4-ethylenedioxy thiophene (EDOT) were carried out in CH3CN/TBABF(4) (0.1M) solvent-electrolyte couple via potentiodynamic electrolysis. The obtained copolymers were characterized by cyclic voltammetry (CV), Fourier transform-infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry analyses (TGA). The conductivity measurements of copolymers and PEDOT were performed by the four-probe technique. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1713-1719, 2011Research Foundation of Nigde University (Nigde-Turkey), TUBAContract grant sponsors: Research Foundation of Nigde University (FEB 2007-11) (Nigde-Turkey), TUBA