Very high two-dimensional hole gas mobilities in strained silicon germanium

We report on the growth by solid source MBE and characterization of remote doped Si/SiGe/Si two-dimensional hole gas structures. It has been found that by reducing the Ge composition to <=13% and limiting the thickness of the alloy layer, growth temperatures can be increased up to 950 °C for these structures while maintaining good structural integrity and planar interfaces. Record mobilities of 19 820 cm2 V−1 s−1 at 7 K were obtained in normal structures. Our calculations suggest that alloy scattering is not important in these structures and that interface roughness and interface charge scattering limit the low temperature mobilities

Determination of inorganic arsenic in water by a quartz crystal microbalance

A quartz crystal microbalance sensor has been developed for the determination of inorganic arsenic species in water. The gold electrode surface was modified by a self-assembled layer of dithiothreitol, and the frequency change of the modified crystal was proportional to the arsenic concentration from 0 to around 50 µg L-1, a range which spans the current US EPA maximum contaminent level of 10 µg L-1 in drinking water. As dithiothreitol is capable of reducing arsenate to arsenite, the sensor detects both species. The method was applied to the determination of arsenic in spiked rain, tap, pond and bottled water; recoveries not significantly different from 100% were obtained for a number of spike additions of less than 10 µg L -1. Arsenic was only detected in the bottled water sample, at a concentration of 8 µg L-1. This method is simple, fast, and inexpensive compared with other conventional arsenic detection methods, and has the potential to be used in the field. © 2013 The Royal Society of Chemistry

EFFECTS OF ORTHODONTIC ADHESIVE MATERIALS ON S. MUTANS AND LACTOBACILLI LEVELS IN HUMAN SALIVA

ABSTRAC

Effective mass and band nonparabolicity in remote doped Si/Si0.8Ge0.2 quantum wells

The effective masses in remote doped Si/Si0.8Ge0.2/Si quantum wells having sheet densities, Ns in the range 2 × 1011–1.1 × 1012 cm – 2 have been determined from the temperature dependencies of the Shubnikov–de Haas oscillations. The values obtained increase with magnetic field and Ns. This behavior is taken as evidence for the nonparabolicity of the valence band and accounts for the discrepancies in previously reported masses. Self-consistent band structure calculations for a triangular confinement of the carriers have also been carried out and provide confirmation of the increase in mass with Ns. Theory and experiment give extrapolated Gamma point effective masses of 0.21 and 0.20 of the free-electron mass, respectively

Compressive Response of Polycrystalline NiCoMnGa High-Temperature Meta-magnetic Shape Memory Alloys

The effects of the addition of quaternary element, Co, to polycrystalline NiMnGa alloys on their magnetic and shape memory properties have been investigated. NiCoMnGa polycrystalline alloys have been found to demonstrate good shape memory and superelasticity behavior under compression at temperatures greater than 100 °C with about 3% transformation strain and low-temperature hysteresis. It is also possible to train the material to demonstrate a large two-way shape memory effect

Metal Dicyanamides as Efficient and Robust Water-Oxidation Catalysts

Non-oxide cobalt-based water-oxidation electrocatalysts have received attention recently for their relative ease of preparation, they are stable both in acidic and basic media, and they have higher turnover frequencies than cobalt oxides. Recent studies show that one of the main bottlenecks in the implementation of non-oxide systems to water splitting is the low number of active metal sites, which is in the order of nmol cm−2. Herein, a new series of non-oxide water-oxidation catalysts has been introduced to the field. Cobalt dicyanamides are observed to have around four times higher surface active sites and better catalytic performances than cyanide-based systems. Long-term catalytic studies (70 h) at an applied potential of 1.2 V and electrochemical studies performed in solutions in pH values of 3.0–12.0 indicate that the compounds are robust and retain their structures even under harsh conditions. Moreover, the addition of Ni impurities to cobalt dicyanamides is a feasible method to improve their catalytic activities. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Exchange-bias phenomenon: The role of the ferromagnetic spin strucutre

The exchange bias of antiferromagnetic-ferromagnetic (AFM-FM) bilayers is found to be strongly dependent on the ferromagnetic spin configuration. The widely accepted inverse proportionality of the exchange bias field with the ferromagnetic thickness is broken in FM layers thinner than the FM correlation length. Moreover, an anomalous thermal dependence of both exchange bias field and coercivity is also found. A model based on springlike domain walls parallel to the AFM-FM interface quantitatively accounts for the experimental results and, in particular, for the deviation from the inverse proportionality law. These results reveal the active role the ferromagnetic spin structure plays in AFM-FM hybrids which leads to a new paradigm of the exchange bias phenomenon

Metal Insulator transition at B=0 in p-SiGe

Observations are reported of a metal-insulator transition in a 2D hole gas in asymmetrically doped strained SiGe quantum wells. The metallic phase, which appears at low temperatures in these high mobility samples, is characterised by a resistivity that decreases exponentially with decreasing temperature. This behaviour, and the duality between resistivity and conductivity on the two sides of the transition, are very similar to that recently reported for high mobility Si-MOSFETs.Comment: 4 pages, REVTEX with 3 ps figure

A novel approach for preventing esophageal stricture formation: olmesartan prevented apoptosis

Accidentally ingested corrosive substances can cause functional and structural damage to the esophageal tissue resulting in stricture formation. It has been reported that the administration of olmesartan (OLM) can have anti-inflammatory, antifibrotic and antiapoptotic effects on injured tissue. The aim of our study was to check if OLM could prevent formation of scars in the corrosive esophageal burn model. Fifty-one Wistar Albino rats were divided into six groups: Control, Sham, OLM, Sham + OLM, Burn, and Burn + OLM. Olmesartan (5 mg/kg) was given by gavage once per day for 21 consecutive days after injury. The morphology of the esophagus was assessed after Masson trichrome staining, and apoptosis was evaluated using the terminal deoxynucleotidyl transferased UTP nick end labeling (TUNEL) method. The serum nucleosomes (as an indicator of apoptosis), serum p53 protein, and esophageal tissue p53 protein levels of each group were measured by immunoassays. Muscularis mucosa damage, submucosal collagen deposition, and tunica muscularis injury in the Burn + OLM group decreased significantly compared with the Burn group (p &lt; 0.05). Similarly, the number of apoptotic cells in the Burn + OLM group decreased compared with the Burn group (p &lt; 0.05). Serum levels of nucleosomes and p53 and tissue of p53 protein did not differ between the groups. Exogenously administered OLM can effectively prevent the occurrence of esophageal strictures caused by corrosive esophageal burns. (Folia Histochemica et Cytobiologica 2014, Vol. 52, No. 1, 29–35