Basic fibroblast growth factor augments podocyte injury and induces glomerulosclerosis in rats with experimental membranous nephropathy

Podocyte injury is believed to contribute to glomerulosclerosis in membranous nephropathy. To identify the factors involved, we investigated the effects of basic fibroblast growth factor (bFGF), a cytokine produced by podocytes, on rats with membranous nephropathy (passive Heymann nephritis [PHN]). All rats received a daily i.v. bolus of 10 microg bFGF or vehicle from days 3-8 after PHN induction. In proteinuric PHN rats on day 8, bFGF injections further increased proteinuria. Podocytes of bFGF-injected PHN rats showed dramatic increases in mitoses, pseudocyst formation, foot process retraction, focal detachment from the glomerular basement membrane, and desmin expression. bFGF injections in PHN rats did not alter antibody or complement deposition or glomerular leukocyte influx. bFGF-injected PHN rats developed increased glomerulosclerosis when compared with control PHN rats. Also, bFGF induced proteinuria and podocyte damage in rats injected with 10% of the regular PHN-serum dose. None of these changes occurred in bFGF-injected normal rats, complement-depleted PHN rats or rats injected with 5% of the regular PHN serum dose. These divergent bFGF effects were explained in part by upregulated glomerular bFGF receptor expression, induced by PHN serum. Thus, bFGF can augment podocyte damage, resulting in increased glomerular protein permeability and accelerated glomerulosclerosis. This bFGF action is confined to previously injured podocytes. Release of bFGF from glomerular sources (including podocytes themselves) during injury may represent an important mechanism by which podocyte damage is enhanced or becomes self sustained.     

Analysis of fluorescence effects in a position-sensitive gas detector using a time-stamp time-to-digital converter

A position-sensitive gas proportional detector with delay line readout was used with the prototype of a time-stamp time-to-digital converter (TS-TDC). The distribution of simultaneous events in the detector upon irradiation by a ⁵⁵Fe source and synchrotron radiation was analysed as well as the influence of fluorescence on the point-spread function. It is shown that the additional information obtained with the TS-TDC can be used to reduce the distortions caused by fluorescence.     

Star-coupler-based optical cross-connect switch experiments withtunable receivers

An optical cross-connect switch using the star-coupler-based frequency-division-multiplex technique are discussed. Two specific tunable receivers have been implanted. The first is a heterodyne receiver with a tunable laser as the local oscillator (LO) and the second is a tunable filter followed by a direct-detection receiver. In the heterodyne receiver, the tunable LO was a monolithic three-section multiple-quantum-well distributed Bragg laser capable of a 1000-GHz tuning range. Receiver sensitivity was measured to be -38 dBm at 1 Gb/s (BER=10^-10). The power margin in the system substantiated feasibility for a 400×400 switch. In the tunable-filter receiver, the tunable filter is a tunable two-stage optical fiber Fabry-Perot filter design consisting of a narrowband filter followed by a wideband filter. The tuning of the filters is computer controlled, and the combined filter has a tuning range of 15000 GHz with a finesse of ≈5170. Therefore, it is capable of covering over 1000 channels of 2.9 GHz each     

Microscopic gain theory for group III nitride semiconductor quantum wells

The gain/absorption properties of III–V nitride quantum well systems are computed microscopically using multi-band semiconductor Bloch equations. Lineshape and dephasing are treated at the level of quantum kinetic theory in second Born approximation in the Markovian limit. The compositional and structural properties of the quantum wells are modelled using k · p theory. Numerical results are presented for the example of several InGaN/AIGaN structures.     

Correlative High‐Resolution Mapping of Strain and Charge Density in a Strained Piezoelectric Multilayer

A key to strain engineering of piezoelectric semiconductor devices is the quantitative assessment of the strain‐charge relationship. This is particularly demanding in current InGaN/GaN‐based light‐emitting diode (LED) designs as piezoelectric effects are known to degrade the device performance. Using the state‐of‐the‐art inline electron holography, we have obtained fully quantitative maps of the two‐dimensional strain tensor and total charge density in conventional blue LEDs and correlated these with sub‐nanometer spatial resolution. We show that the In_0.15Ga_0.85N quantum wells are compressively strained and elongated along the polar growth direction, exerting compressive stress/strain on the GaN quantum barriers. Interface sheet charges arising from a polarization gradient are obtained directly from the strain data and compared with the total charge density map, quantitatively verifying only 60% of the polarization charges are screened by electrons, leaving a substantial piezoelectric field in each In_0.15Ga_0.85N quantum well. The demonstrated capability of inline electron holography provides a technical breakthrough for future strain engineering of piezoelectric optoelectronic devices.     

Experimental Investigation of the Strain Rate Dependent Behaviour of 2D Biaxially and Triaxially Reinforced Braided Composites

The performance of 2D biaxially and triaxially reinforced braided carbon fibre composites under dynamic loading is evaluated in the presented study. The accurate manufacturing of tensile specimen made of braided sleeves is explained particularly with regard to efficiency and reproducibility. In order to determine reliable strain rate dependent properties, the high-speed testing procedure is discussed. Using five materials, the parameter identification is described and relevant material data is provided. The measured stiffnesses and strengths are used to predict the non-linear stress-strain behaviour with an earlier proposed phenomenological damage model for textile composites. The gained orthotropic property-profile provides the input parameters for a numerical analysis of braided composite components using the calibrated model.