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Effects of Hyperbaric Hypoxia on Some Enzyme Systems in the Mammalian Liver

The metabolic effects of hypobaric hypoxic stress on the mammalian liver were studied. The lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activity of mouse liver homogenates were measured after exposure to an equivalent altitude of 36,000 feet and compared to controls kept at zero altitude. After six and twelve hour incubation periods, the altitude exposed samples demonstrated a significantly higher LDH activity than controls. SDH activity remained unchanged from controls after six hours but was significantly lower than controls after a 12 hour exposure to altitude. It is concluded that the changes in enzyme activity reflect a metabolic control mechanism attempting to maintain adequate energy production during periods of exposure to hypobaric hypoxic stress

Dynamics of Quantum Dot Nuclear Spin Polarization Controlled by a Single Electron

We present an experimental study of the dynamics underlying the buildup and decay of dynamical nuclear spin polarization in a single semiconductor quantum dot. Our experiment shows that the nuclei can be polarized on a time scale of a few milliseconds, while their decay dynamics depends drastically on external parameters. We show that a single electron can very efficiently depolarize the nuclear spins and discuss two processes that can cause this depolarization. Conversely, in the absence of a quantum dot electron, the lifetime of nuclear spin polarization is on the time scale of a second, most likely limited by the non-secular terms of the nuclear dipole-dipole interaction. We can further suppress this depolarization rate by 1-2 orders of magnitude by applying an external magnetic field exceeding 1 mT.Comment: 5 pages, 3 figure

Costly Inflation Misperceptions

One of the consequences of the euro changeover in 2002 was that for a period of several years people considerably overestimated actual inflation. The goal of this paper is to study whether misperceptions of this kind may have real effects, that is, whether they induce people to alter their behaviour. We also discuss the question how far the euro changeover and the ensuing discussion about price stability contributed to the recession that followed the changeover. Looking at the German restaurant sector, we find that people’s misperceptions can have significant negative effects. The contraction this sector experienced in the months after the changeover was too pronounced to be explained by normal business cycle movements. We provide a discussion about the causes of these misperceptions and how to avoid them in future changeovers.euro changeover, perceived inflation

Alternative antibody for the detection of CA125 antigen: a European multicenter study for the evaluation of the analytical and clinical performance of the Access (R) OV Monitor assay on the UniCel (R) Dxl 800 Immunoassay System

Background: Cancer antigen CA125 is known as a valuable marker for the management of ovarian cancer. Methods: The analytical and clinical performance of the Access OV Monitor Immunoassay System (Beckman Coulter) was evaluated at five different European sites and compared with a reference system, defined as CA125 on the Elecsys System (Roche Diagnostics). Results: Total imprecision (%CV) of the OV Monitor ranged between 3.1% and 8.8%, and inter-laboratory reproducibility between 4.7% and 5.0%. Linearity upon dilution showed a mean recovery of 100% (SD+8.1%). Endogenous interferents had no influence on OV Monitor levels (mean recoveries: hemoglobin 107%, bilirubin 103%, triglycericles 103%). There was no high-dose hook effect up to 27,193 kU/L. Clinical performance investigated in sera from 1811 individuals showed a good correlation between the Access OV Monitor and Elecsys CA125 (R = 0.982, slope = 0.921, intercept = + 1.951). OV Monitor serum levels were low in healthy individuals (n = 267, median = 9.7 kU/L, 95th percentile = 30.8 kU/L), higher in individuals with various benign diseases (n = 549, medians = 10.9-16.4 kU/L, 95th percentiles = 44.2-355 kU/L) and even higher in individuals suffering from various cancers (n = 995, medians= 12.4-445 kU/L; 95th percentiles = 53.4-4664 kU/L). Optimal diagnostic accuracy for cancer detection against the relevant benign control group by the OV Monitor was found for ovarian cancer {[}area under the curve (AUC) 0.898]. Results for the reference CA125 assay were comparable (AUC 0.899). Conclusions: The Access OV Monitor provides very good methodological characteristics and demonstrates an excellent analytical and clinical correlation with Elecsys CA125. The best diagnostic accuracy for the OV Monitor was found in ovarian cancer. Our results also suggest a clinical value of the OV Monitor in other cancers

Electric field gradients from first-principles and point-ion calculations

Point-ion models have been extensively used to determine "hole numbers" at copper and oxygen sites in high-temperature superconducting cuprate compounds from measured nuclear quadrupole frequencies. The present study assesses the reliability of point-ion models to predict electric field gradients accurately and also the implicit assumption that the values can be calculated from the "holes" and not the total electronic structure. First-principles cluster calculations using basis sets centred on the nuclei have enabled the determination of the charge and spin density distribution in the CuO2-plane. The contributions to the electric field gradients and the magnetic hyperfine couplings are analysed in detail. In particular they are partitioned into regions in an attempt to find a correlation with the most commonly used point-ion model, the Sternheimer equation which depends on the two parameters R and gamma. Our most optimistic objective was to find expressions for these parameters, which would improve our understanding of them, but although estimates of the R parameter were encouraging the method used to obtain the gamma parameter indicate that the two parameters may not be independent. The problem seems to stem from the covalently bonded nature of the CuO2-planes in these structures which severely questions using the Sternheimer equation for such crystals, since its derivation is heavily reliant on the application of perturbation theory to predominantly ionic structures. Furthermore it is shown that the complementary contributions of electrons and holes in an isolated ion cannot be applied to estimates of electric field gradients at copper and oxygen nuclei in cuprates.Comment: 19 pages, 4 figure

Signatures of dynamically polarized nuclear spins in all-electrical lateral spin transport devices

The effect of nuclear spins in Fe/GaAs all-electrical spin-injection devices is investigated. At temperatures below 50 K, strong modifications of the non-local spin signal are found that are characteristic for hyperfine coupling between conduction electrons and dynamically polarized nuclear spins. The perpendicular component of the nuclear Overhauser field depolarizes electron spins near zero in-plane external magnetic field, and can suppress such dephasing when antialigned with the external field, leading to satellite peaks in a Hanle measurement. The features observed agree well with a Monte Carlo simulation of the spin diffusion equation including hyperfine interaction, and are used to study the nuclear spin dynamics and relate it to the spin polarization of injected electrons.Comment: 6 pages, 4 figure