Pseudo-binary phase diagram for Zr-based in situ ß phase composites

The pseudo-binary (quasi-equilibrium) phase diagram for Zr-based bulk metallic glasses with crystalline in situ precipitates (ß phase) has been constructed from high-temperature phase information and chemical composition analysis. The phase evolution was detected in situ by high-energy synchrotron x-ray diffraction followed by Rietveld analysis of the data for volume fraction estimation. The phase diagram delineates phase fields and allows the control of phase fractions. Combined with related previous work by the authors, this diagram offers a unique opportunity to control both the morphology and volume of the dendritic ß phase precipitates to enhance the properties of the composites

In situ stress analysis of multilayer environmental barrier coatings

The biaxial stress and thermal expansion of multilayer doped-aluminosilicate environmental barrier coatings were measured in situ during cooling using microfocused high-energy X-rays in transmission. Coating stresses during cooling from 1000 °C were measured for as-sprayed and thermally cycled samples. In the as-sprayed state, tensile stresses as high as 75 MPa were measured in the doped-aluminosilicate topcoat at 375 °C, after which a drop in the stress occurred accompanied by through-thickness cracking of the two outermost layers. After thermally cycling the samples, the stress in the topcoat was reduced to approximately 50 MPa, and there was no drop in stress upon cooling. This stress reduction was attributed to a crystallographic phase transformation of the topcoat and the accompanying change in thermal expansion coefficient. The addition of a doped aluminosilicate to the mullite layer did not lower the stress in the topcoat, but may offer increased durability due to an increased compressive stress

Hydride precipitation and stresses in zircaloy-4 observed by synchrotron X-ray diffraction

The grain stresses within hydrides precipitated in rolled zircaloy-4 plates were determined by synchrotron X-ray diffraction experiments using an 80 keV photon beam and a high-speed area detector placed in transmission geometry. Results showed large compressive stresses (360 ± 20 MPa) in the hydrides along the plate rolling direction. The origin of these stresses was investigated by performing hydride dissolution/precipitation in situ for thermal cycles between room temperature and 400 C. A large stress hysteresis was observed, with a steady decrease on heating and an abrupt change on cooling. The observed stresses are explained by the constraint imposed by grain boundaries on the growth of hydride platelets on the rolling–transverse plane of the rolled plates.Fil: Santisteban, Javier Roberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Vicente Alvarez, Miguel Angel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Vizcaino, Pablo. Comisión Nacional de Energía Atómica. Centro Atómico Ezeiza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Banchik, A. D.. Comisión Nacional de Energía Atómica. Centro Atómico Ezeiza; ArgentinaFil: Almer, J. D.. No especifíca

The impact of moderate endurance exercise on cardiac telomeres and cardiovascular remodeling in obese rats

Introduction: Hypercaloric nutrition and physical inactivity cause obesity, a potential driver of myocardial apoptosis and senescence that may accelerate cardiac aging. Although physical activity reduces mortality, its impact on myocardial aging is insufficiently understood. Here we investigated the effects of a hypercaloric high-fat diet (HFD) and regular exercise training on cardiac cells telomeres and histomorphometric indices of cardiac aging. Methods: Ninety-six 4-months old female Sprague-Dawley rats were fed for 10 months normal (ND) or a HFD diet. Half of the animals in each group performed 30 min treadmill-running sessions on 5 consecutive days per week. At study end, cardiomyocyte cross-sectional area (CSA), interstitial collagen content, vascular density, apoptotic and senescent cells, relative telomere length (RTL), and expression of telomerase-reverse transcriptase (Tert) as marker of telomere-related senescence and apoptosis were analyzed. Results: Compared to ND, the HFD group developed obesity, higher CSA, lower capillary density and tended to have more apoptotic cardiomyocytes and interstitials cells. Myocardial RTL and the expression of Terf-1 and Terf-2 were comparable in sedentary HFD and ND animals. In the HFD group, regular moderate endurance exercise improved myocardial vascularization, but had no effect on CSA or apoptosis. Notably, the combination of exercise and HFD increased senescence when compared to sedentary ND or HFD, and reduced RTL when compared to exercise ND animals. Exercising HFD animals also showed a trend toward higher Tert expression compared to all other groups. In addition, exercise reduced Terf-1 expression regardless of diet. Conclusion: HFD-induced obesity showed no effects on myocardial telomeres and induced only mild morphologic alterations. Summarized, long-term moderate endurance exercise partially reverses HFD-induced effects but may even trigger cardiac remodeling in the context of obesity

High-sensitivity free space optical communications using low size, weight and power hardware

Free space optical communication systems with extremely high detector sensitivities are attractive for various applications with low size, weight and power requirements. For these practical systems, integrated hardware elements with small form factor are needed. Here, we demonstrate a communication link using a CMOS integrated micro-LED and array of single-photon avalanche diodes. These integrated systems provide a data rate of 100 Mb/s at a sensitivity of -55.2 dBm, corresponding to 7.5 detected photons per bit

Non-destructive metallurgical analysis of astrolabes utilizing synchrotron radiation.

From the experiments performed it is possible to determine a wide range of information about the metallurgy of the astrolabes studied. It was found that different brass alloys were used for components that were cast and those that were mechanically deformed. Chemical composition, forming history, and thickness measurements are all determined non-destructively, illustrating that this technique could be useful for many applications with metal artifact analysis where non-intrusive methods are required

Design, fabrication and application of GaN-based micro-LED arrays with individual addressing by n-electrodes

We demonstrate the development, performance and application of a GaN-based micro-light emitting diode (μLED) array sharing a common p-electrode (anode), and with individually addressable nelectrodes (cathodes). Compared to conventional GaN-based LED arrays, this array design employs a reversed structure of common and individual electrodes, which makes it innovative and compatible with n-type metal-oxide-semiconductor (NMOS) transistor-based drivers for faster modulation. Excellent performance characteristics are illustrated by an example array emitting at 450 nm. At a current density of 17.7 kA/cm2 in direct-current operation, the optical power and small signal electrical-to-optical modulation bandwidth of a single LED element with 24 μm diameter are over 2.0 mW and 440 MHz, respectively. The optimized fabrication process also ensures a high yield of working μLED elements per array, and excellent element-to-element uniformity of electrical/optical characteristics. Results on visible light communication are presented as an application of an array integrated with an NMOS driver. Data transmission at several hundred Mbps without bit error is achieved for single and multiple-μLED-element operations, under an on-off-keying modulation scheme. Transmission of stepped sawtooth waveforms is also demonstrated to confirm that the μLED elements can transmit discrete multi-level signals