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Vitamin D is thought to exert a protective effect on renal disease progression, but the underlying molecular mechanism remains unclear. We investigated whether paricalcitol ameliorates tubular dysfunction and fibrosis in gentamicin (GM)-induced renal injury. Two groups of rats were treated with GM (100 mg * [kg.sup.-1] * [day.sup.-1]), one of which was cotreated with paricalcitol (0.3 [micro]g * [kg.sup.-l] * [day.sup.-1]) for 14 days and the other was not. The control group was treated with vehicle only. HK-2 cells were cultured with GM in the absence or presence of paricalcitol. Paricalcitol restored impaired renal function and the downregulated renal sodium transporters and aquaporin-1 expression caused by GM. ED- 1-expressing monocyte/macrophage accumulation induced by GM was attenuated by paricalcitol treatment. Paricalcitol prevented upregulated inflammatory cytokines (TNF-[alpha], IL-1[beta], INF-[gamma]) and adhesion molecules (monocyte chemoattractant protein-1, ICAM-1, VCAM-1) induced by GM. In addition, paricalcitol effectively reversed TGF-[beta]1-induced epithelial-to-mesenchymal transition (EMT) process and extracellular matrix accumulation in GM-induced nephropathy. Increased collagen deposition and fibrosis in GM-treated kidney were ameliorated by paricalcitol. Paricalcitol also attenuated the upregulated NF-KB and phosphorylated ERK1/2 expression in HK-2 cells cultured with GM. In conclusion, paricalcitol prevents GM-induced renal injury by inhibiting renal inflammation and fibrosis, the mechanism of which is the interruption of NF-KB/ERK signaling pathway and preservation of tubular epithelial integrity via inhibiting EMT process. inflammation; fibrosis doi: 10.1152/ajprenal.00471.2009

In this paper, we propose an injection-based axis switching (IAS) sensorless control scheme using a pulsating high-frequency (HF) signal to minimize position detection error and velocity estimation ripple resulting from the zero-current-clamping (ZCC) effect for surface-mounted permanent-magnet motors. When a pulsating carrier-signal voltage is injected in an estimated synchronous frame, the envelope of the resulting HF current measured in the stationary reference frame follows an amplitade-modulated pattern. Using this information, the IAS technique allows one to avoid multiple zero crossings of HF currents by adjusting the current phase angle according to the load condition. At no-load condition, the pulsating voltage is injected only on the d-axis, while the d-axis current is controlled to a certain nonzero value. Under a load condition, the injection voltage is switched to the q-axis, while the d-axis current drops back to zero. Thus, the proposed sensorless control enforces a much better estimation performance in a region of ZCC without a predefined offline commissioning test than the standard pulsating injection scheme. Experiments illustrate the effectiveness of the proposed method in suppressing the estimation error caused by the ZCC disturbance and in extending the system bandwidth. Index Terms--Estimated position error and velocity ripple, injection-based axis switching (IAS) sensorless control, pulsating high-frequency (HF) signal injection, zero-current-clamping (ZCC) effect.

This paper proposes an online compensation strategy for the unwanted disturbance voltage resulting from the zero-current clamping effect for high-frequency-signal-injection-based sensorless control schemes. We derive an analytical model that reveals intrinsic characteristics of the zero clamping effect for high-frequency signal injection. The model in this form is subsequently incorporated into the development of a specialized offline commissioning test to find motor inductances and a voltage distortion factor. From the sensitivity analysis of the effect on magnetic saturation, we confirm that the compensation error due to saturation has little negative impact on the proposed compensation method. The compensation result leads to an accurate position estimate in the zero-current clamping region. The proposed scheme does not rely on a complicated lookup table. Experiments demonstrate the superiority of the proposed method in suppressing the voltage distortions caused by the zero-current clamping effect. Index Terms--Analytical model, offline commissioning test, online compensation strategy for the unwanted disturbance voltage, zero-current clamping effect for high-frequency-signal-injection-based sensorless control.

This paper proposes a compensation strategy for the unwanted disturbance voltage due to inverter nonlinearity. We employ an emerging learning technique called support vector regression (SVR). SVR constructs a motor dynamic voltage model by a linear combination of the current samples in real time. The model exhibits fast observer dynamics and robustness to observation noise. Then the disturbance voltage is estimated by subtracting the constructed voltage model from the current controller output. The proposed method compensates for all of the inverter nonlinearity factors at the same time. All the processes in estimating distortions are independent of the dead time and power device parameters. From the analysis of the effect on current measurement errors, we confirmed that the sampling error had little negative impact on the proposed estimation method. Experiments demonstrate the superiority of the proposed method in suppressing voltage distortions caused by inverter nonlinearity. Index Terms--Current :measurement errors, disturbance voltage resulting from inverter nonlinearity, power device parameters, support vector regression (SVR).