Spin susceptibility of two-dimensional electrons in narrow AlAs quantum wells

We report measurements of the spin susceptibility in dilute two-dimensional electrons confined to a 45$\AA$ wide AlAs quantum well. The electrons in this well occupy an out-of-plane conduction-band valley, rendering a system similar to two-dimensional electrons in Si-MOSFETs but with only one valley occupied. We observe an enhancement of the spin susceptibility over the band value that increases as the density is decreased, following closely the prediction of quantum Monte Carlo calculations and continuing at finite values through the metal-insulator transition.Comment: 4+ pages, 4 figures. Dotted line added to Fig. 4(a) to clarify the QMC calculatio

Anomalous spin-splitting of two-dimensional electrons in an AlAs Quantum Well

We measure the effective Lande g-factor of high-mobility two-dimensional electrons in a modulation-doped AlAs quantum well by tilting the sample in a magnetic field and monitoring the evolution of the magnetoresistance oscillations. The data reveal that |g| = 9.0, which is much enhanced with respect to the reported bulk value of 1.9. Surprisingly, in a large range of magnetic field and Landau level fillings, the value of the enhanced g-factor appears to be constant.Comment: 4 pages, 3 figure

Apparent Metallic Behavior at B = 0 of a two-dimensional electron system in AlAs

We report the observation of metallic-like behavior at low temperatures and zero magnetic field in two dimensional (2D) electrons in an AlAs quantum well. At high densities the resistance of the sample decreases with decreasing temperature, but as the density is reduced the behavior changes to insulating, with the resistance increasing as the temperature is decreased. The effect is similar to that observed in 2D electrons in Si-MOSFETs, and in 2D holes in SiGe and GaAs, and points to the generality of this phenomenon

Another Avenue for Anatomy of Income Comparisons : Evidence from Hypothetical Choice Experiments

September 2010, Revised December 2010, Secondly Revised November 2011, Thirdly Revised May 2012, Fourthly Revised March 2013

D-Penicillamine Metabolism in an In-Vivo Model of Inflamed Synovium

Oxidation to disulphides is the chief metabolic transformation of D-penicillamine (D-pen) in patients with rheumatoid arthritis. Oxidation also occurs in many biological fluids in-vitro. Reduction of oxygen species may accompany the oxidation of D-pen under appropriate conditions and may mediate the anti-rheumatic action of D-pen. The transformation of D-pen therefore was examined in an in-vivo model of inflamed synovium. Subcutaneous air-pouches of groups of rats were treated with saline, 10% serum or 10% zymosan activated serum (ZAS). The transformation of D-pen to low molecular weight (LMW) metabolites and protein conjugates within the pouch was then assessed. The concentrations of total protein were significantly higher in the serum and ZAS-treated groups than in the saline-treated group and the inflammatory cell counts were significantly higher in the ZAS-treated group than in either of the other groups, as expected. D-pen oxidised rapidly to LMW metabolites and smaller amounts of D-pen-protein conjugate (D-pen-protein) in the air pouches of all animals. The rates of oxidation to LMW metabolites were greater in the ZAS-treated animals than the saline-treated group (p less than 0.005). The concentrations of D-pen-protein conjugate were also greater for the serum-treated and ZAS-treated animals than for the saline controls (p less than 0.005 in each case) at all times. Oxidation of D-pen therefore occurs at this site of inflammation and is influenced by local conditions. This may be important to understanding the forms in which D-pen exists in inflamed synovial joints and the way it may exert its antirheumatic activity