Optical Properties and Local Structure Evolution during Crystallization of Ga16Sb84 Alloy.

Phase-change memory is one of the most promising candidates for future memory technologies. However, most of the phase-change memories are based on chalcogenides, while other families of materials for this purpose remain insufficiently studied. In this work, we investigate the optical properties and microstructure of Ga16Sb84 by an in-situ ellipsometer and X-ray diffraction. Our experimental results reveal that the Ga16Sb84 films exhibit a relatively high crystallization temperature of ~250 °C, excelling in long data retention. In addition, a large optical contrast exists between the amorphous and crystalline states, which may make it suitable for use in optical discs. Molecular dynamics simulations indicate that a unique local structure order in the amorphous and crystalline phases is responsible for the optical properties observed in the experiment. The similarity found in the short-range orders of the amorphous and crystalline phases is beneficial to better understanding the fast phase transition of phase-change memory.

Liver-kidney transplantation in primary hyperoxaluria type-1: case report and literature review.

Primary hyperoxaluria type-1 (PH1) is a rare inherited autosomal recessive disorder in which a deficiency of the hepatic enzyme alanine-glyoxylate aminotransferase leads to endogenous oxalate overproduction, renal failure, systemic oxalate deposition and death. As hemodialysis provides insufficient oxalate clearance, patients ultimately require both liver and kidney transplantation for correction of the metabolic abnormality and oxalate excretion. Herein, we describe a young adult male with end-stage renal disease and systemic oxalosis causing progressive disabling multi-organ dysfunction while awaiting transplantation. We review the literature regarding liver-kidney transplantation and suggest that for patients with PH1, a standardized assessment of organ dysfunction and functional impairment may improve identification of patients requiring urgent transplantation thereby reducing the morbidity and mortality that can occur with delayed transplantation.

Relative hypoparathyroidism and hypoalbuminemia are associated with hip fracture in hemodialysis patients.

AIMS: Patients with end-stage renal disease treated by hemodialysis are at an increased risk of hip fracture. In the general population, hip fractures are associated with increased morbidity and mortality. The objective of this study was to assess the predictors and outcomes of hip fracture in the hemodialysis population, including quality of life post hip fracture. METHODS: A case-control study from 1999 to 2005 included 29 adult hemodialysis patients with hip fracture and 55 controls, matched on age, gender and number of years on hemodialysis. A logistic regression model was used to derive predictors of hip fracture. The association between time to death post hip fracture and parathyroid hormone was analyzed using a Kaplan-Meier curve. The ability to live independently 1 year after hip fracture was used as a measure of quality of life. RESULTS: Variables associated with hip fracture were a reduction in serum parathyroid hormone by 100 pg/ml (OR = 1.65, 95% CI 1.10, 2.46) and a decrease in serum albumin by 1 g/l (OR = 1.18, 95% CI 1.00, 1.39). 40% of the cases died within the first year post hip fracture. Median survival time in patients with hip fracture and a serum PTH value < 100 pg/ml was 17 days (95% CI 0, 37 days) as compared with 280 days (95% CI 103, 471 days) for those with a PTH value > 100 pg/ml (p < 0.02). Among the patients who survived, 53% were subsequently discharged to a long-term care facility. CONCLUSIONS: Relative hypoparathyroidism and hypoalbuminemia are associated with an increased risk of hip fracture in hemodialysis patients. There is also a significant reduction in quality of life in patients sustaining a hip fracture.

Potential use of mangroves as constructed wetland for municipal sewage treatment in Futian, Shenzhen, China.

A pilot-scale mangrove wetland was constructed in Futian, Shenzhen for municipal sewage treatment. Three identical belts (length: 33m, width: 3m, depth: 0.5m) were filled with stone (bottom), gravel and mangrove sand (surface). Seedlings of two native mangrove species (Kandelia candel, Aegiceras corniculatum) and one exotic species (Sonneratia caseolaris) were transplanted to the belts with one species for each belt. The hydraulic loading was 5m(3)d(-1) and hydraulic retention time 3d. High levels of removal of COD, BOD(5), TN, TP and NH(3)-N were obtained. The treatment efficiency of S. caseolaris and A. corniculatum was higher than that of K. candel. Faster plant growth was obtained for S. caseolaris. The substrate in the S. caseolaris belt also showed higher enzyme activities including dehydrogenase, cellulase, phosphatase, urease and beta-glucosidase. The removal rates of organic matter and nutrients were positively correlated with plant growth. The results indicated that mangroves could be used in a constructed wetland for municipal sewage treatment, providing post-treatment to remove coliforms was also included.

Built-in surface electric field, piezoelectricity and photoelastic effect in GaN nanorods for nanophotonic devices.

Novel behaviors arising from the coupling between the built-in surface electric field, piezoelectricity, electron-hole pairs and external light beam were observed in GaN nanorods. An increase in the optical excitation density resulted in a blueshift in the photoluminescence spectra and a redshift in the frequency of the GaN A(1)(LO) phonon. The underlying mechanism was attributed to the screening of the built-in surface electric field by photoexcited carriers and, through the converse piezoelectric effect, a reduction in the internal strain. The existence of the built-in surface electric field in GaN nanorods was confirmed by scanning Kelvin probe microscopy. Our results firmly establish the existence of the photoelastic effect in GaN nanorods. In addition to underpinning the principle for applications in nanophotonic devices, this discovery also draws attention to the novel effects arising from the inherent large surface-to-volume ratio of nanostructures, which is possibly applicable to many other nanomaterials.

A micropuncture study of HCO3 reabsorption by the hypertrophied proximal tubule.

In rats with renal failure produced by excision of one kidney and infarction of large portions of the other kidney, given a low calcium, high phosphorus diet for 2-3 weeks, GFR was reduced by 80 percent, the fractional excretion of sodium increased from 7 to 23 percent, that of bicarbonate from 16 to 23 percent and that of water from 4 to 13 percent. Single nephron GFR in the remaining nephrons was nearly doubled and end-proximal TF/P(In) was depressed from 2.3 to 1.8, and proximal TF/P(HCO3) from 0.52 to 0.35, the latter figure corresponding to an increase of absolute proximal HCO(3) reabsorption from 1.7 to 3.5 nEq/min or from 2.8 to 3.2 Eq/L of single nephron glomerular filtrate. Acute parathyroidectomy had no influence on the fall of GFR or the rise of SNGFR in the remaining nephrons and failed to cause any significant changes in proximal tubular bicarbonate reabsorption. Parathyroidectomy, on the other hand, practically prevented the rise of the fractional excretion of sodium and of water and inverted the rise of the fractional excretion of bicarbonate to a fall. The data are interpreted to indicate that secondary hyperparathyroidism in renal failure impairs distal nephron bicarbonate and sodium reabsorption and, thus, contributes to the maintenance of sodium balance, but could possibly aggravate acidosis.

A micropuncture study of renal phosphate transport in rats with chronic renal failure and secondary hyperparathyroidism.

Micropuncture studies were carried out in rats to determine changes in tubular transport of phosphate which occur in chronic renal failure and secondary hyperparathyroidism. Rats underwent subtotal nephrectomy (NX) and were fed a low calcium, high phosphorus diet for 3--4 wk. Other groups consisted of normal control animals, normal rats infused with sodium phosphate to raise filtered load of phosphate, subtotal NX rats parathyroidectomized (PTX) on the day of experiment, and normal PTX rats infused with sodium phosphate. It was found that filtered phosphate/nephron is markedly increased in subtotal NX rats due to high single nephron filtration rates, proximal tubular fluid plasma phosphate ratios are less than 1.0, and fractional reabsorption of phosphate is decreased in the proximal tubule. More phosphate was present in the final urine than in surface distal convoluted tubules. Acute PTX in subtotal NX rats resulted in a striking increase in proximal phosphate reabsorption, and urinary phosphate became approximately equal to that remaining in surface distal tubules. Phosphate loading in normal rats reduced fractional reabsorption in the proximal tubule, but urinary phosphate was not greater than that at the end of surface distal tubules. Acute PTX in normal phosphate-loaded animals had no significant effect on proximal tubular phosphate reabsorption. These observations suggest that phosphate homeostasis in chronic renal failure is acheived by inhibition of proximal phosphate reabsorption, counteracting a greatly enhanced intrinsic capacity for reabsorption. In addition, the large amount of urinary phosphate is consistent either with secretion by the collecting ducts or with a disproportionately high contribution by deep nephrons. The changes in phosphate transport are mediated by parathyroid hormone and are completely abolished by acute removal of the hormone.