Emerging infectious disease issues in blood safety.

Improvements in donor screening and testing and viral inactivation of plasma derivatives together have resulted in substantial declines in transfusion-transmitted infections over the last two decades. Most recently, nucleic acid testing techniques have been developed to screen blood and plasma donations for evidence of very recent viral infections that could be missed by conventional serologic tests. Nonetheless, the blood supply remains vulnerable to new and reemerging infections. In recent years, numerous infectious agents found worldwide have been identified as potential threats to the blood supply. Several newly discovered hepatitis viruses and agents of transmissible spongiform encephalopathies present unique challenges in assessing possible risks they may pose to the safety of blood and plasma products

CrO2: a self-doped double exchange ferromagnet

Band structure calculations of CrO2 carried out in the LSDA+U approach reveal a clear picture of the physics behind the metallic ferromagnetic properties. Arguments are presented that the metallic ferromagnetic oxide CrO2 belongs to a class of materials in which magnetic ordering exists due to double exchange (in this respect CrO2 turns out to be similar to the CMR manganates). It is concluded that CrO2 has small or even negative charge transfer gap which can result in self-doping. Certain experiments to check the proposed picture are suggested.Comment: 4 pages, 4 Figure

Orbital character of O 2p unoccupied states near the Fermi level in CrO2

The orbital character, orientation, and magnetic polarization of the O 2$p$ unoccupied states near the Fermi level ($E_F$) in CrO$_2$ was determined using polarization-dependent X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) from high-quality, single-crystal films. A sharp peak observed just above $E_F$ is excited only by the electric field vector ($\bf E$) normal to the tetragonal $c$-axis, characteristic of a narrow band ($\approx$ 0.7 eV bandwidth) constituted from O 2$p$ orbitals perpendicular to $c$ (O 2$p_y$) hybridized with Cr 3$d_{xz-yz}$ $t_{2g}$ states. By comparison with band-structure and configuration-interaction (CI) cluster calculations our results support a model of CrO$_2$ as a half-metallic ferromagnet with large exchange-splitting energy ($\Delta_{exch-split}$ $\approx$ 3.0 eV) and substantial correlation effects.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. B Rapid Com

The Benefits and the Costs of Using Auditory Warning Messages in Dynamic Decision Making Settings

The failure to notice critical changes in both visual and auditory scenes may have important consequences for performance in complex dynamic environments, especially those related to security such as aviation, surveillance during major events, and command and control of emergency response. Previous work has shown that a significant number of situation changes remain undetected by operators in such environments. In the current study, we examined the impact of using auditory warning messages to support the detection of critical situation changes and to a broader extent the decision making required by the environment. Twenty-two participants performed a radar operator task involving multiple subtasks while detecting critical task-related events that were cued by a specific type of audio message. Results showed that about 22% of the critical changes remained undetected by participants, a percentage similar to that found in previous work using visual cues to support change detection. However, we found that audio messages tended to bias threat evaluation towards perceiving objects as more threatening than they were in reality. Such findings revealed both benefits and costs associated with using audio messages to support change detection in complex dynamic environments

Superconductivity at 1 K in Cd2Re2O7

We report the first pyrochlore oxide superconductor Cd2Re2O7. Resistivity,magnetic susceptibility,and specific heat measurements on single crystals evidence a bulk superconductivity at 1 K. Another phase transition found at 200 K suggests that a peculiar electronic structure lies behind the superconductivity.Comment: 4 pages, 4 figures, PRL, in pres

Synthesis, Characterization and Magnetic Susceptibility of the Heavy Fermion Transition Metal Oxide LiV_{2}O_{4}

The preparative method, characterization and magnetic susceptibility \chi measurements versus temperature T of the heavy fermion transition metal oxide LiV_{2}O_{4} are reported in detail. The intrinsic \chi(T) shows a nearly T-independent behavior below ~ 30 K with a shallow broad maximum at about 16 K, whereas Curie-Weiss-like behavior is observed above 50-100 K. Field-cooled and zero-field-cooled magnetization M measurements in applied magnetic fields H = 10 to 100 G from 1.8 to 50 K showed no evidence for spin-glass ordering. Crystalline electric field theory for an assumed cubic V point group symmetry is found insufficient to describe the observed temperature variation of the effective magnetic moment. The Kondo and Coqblin-Schrieffer models do not describe the magnitude and T dependence of \chi with realistic parameters. In the high T range, fits of \chi(T) by the predictions of high temperature series expansion calculations provide estimates of the V-V antiferromagnetic exchange coupling constant J/k_{B} ~ 20 K, g-factor g ~ 2 and the T-independent susceptibility. Other possible models to describe the \chi(T) are discussed. The paramagnetic impurities in the samples were characterized using isothermal M(H) measurements with 0 < H <= 5.5 Tesla at 2 to 6 K. These impurities are inferred to have spin S_{imp} ~ 3/2 to 4, g_{imp} ~ 2 and molar concentrations of 0.01 to 0.8 %, depending on the sample.Comment: 19 typeset RevTeX pages, 16 eps figures included, uses epsf; to be published in Phys. Rev.

Leptin and Amylin Act in an Additive Manner to Activate Overlapping Signaling Pathways in Peripheral Tissues: In vitro and ex vivo studies in humans

OBJECTIVE: Amylin interacts with leptin to alter metabolism. We evaluated, for the first time, amylin- and/or leptin-activated signaling pathways in human peripheral tissues (hPTs). RESEARCH DESIGN AND METHODS: Leptin and amylin signaling studies were performed in vitro in human primary adipocytes (hPAs) and human peripheral blood mononuclear cells (hPBMCs) and ex vivo in human adipose tissue (hAT) from male versus female subjects, obese versus lean subjects, and subjects with subcutaneous versus omental adipose tissue. RESULTS: The long form of leptin receptor was expressed in human tissues and cells studied in ex vivo and in vitro, respectively. Leptin and amylin alone and in combination activate signal transducer and activator of transcription 3 (STAT3), AMP-activated protein kinase, Akt, and extracellular signal-regulated kinase signaling pathways in hAT ex vivo and hPAs and hPBMCs in vitro; all phosphorylation events were saturable at leptin and amylin concentrations of ∼50 and ∼20 ng/ml, respectively. The effects of leptin and amylin on STAT3 phosphorylation in hPAs and hPBMCs in vitro were totally abolished under endoplasmic reticulum stress and/or in the presence of a STAT3 inhibitor. Results similar to those in the in vitro studies were observed in hAT studied ex vivo. CONCLUSIONS: Leptin and amylin activate overlapping intracellular signaling pathways in humans and have additive, but not synergistic, effects in signaling pathways studied in hPTs in vitro and ex vivo

Efficacy of Metreleptin in Obese Patients With Type 2 Diabetes: Cellular and Molecular Pathways Underlying Leptin Tolerance

Objective: Metreleptin has been efficacious in improving metabolic control in patients with lipodystrophy, but its efficacy has not been tested in obese patients with type 2 diabetes. Research Design and Methods: We studied the role of leptin in regulating the endocrine adaptation to long-term caloric deprivation and weight loss in obese diabetic subjects over 16 weeks in the context of a double-blinded, placebo–controlled, randomized trial. We then performed detailed interventional and mechanistic signaling studies in humans in vivo, ex vivo, and in vitro. Results: In obese patients with diabetes, metreleptin administration for 16 weeks did not alter body weight or circulating inflammatory markers but reduced HbA$_{1c}$ marginally (8.01 $\pm$ 0.93–7.96 $\pm$ 1.12, P = 0.03). Total leptin, leptin-binding protein, and antileptin antibody levels increased, limiting free leptin availability and resulting in circulating free leptin levels of $\sim$50 ng/mL. Consistent with clinical observations, all metreleptin signaling pathways studied in human adipose tissue and peripheral blood mononuclear cells were saturable at $\sim$50 ng/mL, with no major differences in timing or magnitude of leptin-activated STAT3 phosphorylation in tissues from male versus female or obese versus lean humans in vivo, ex vivo, or in vitro. We also observed for the first time that endoplasmic reticulum (ER) stress in human primary adipocytes inhibits leptin signaling. Conclusions: In obese patients with diabetes, metreleptin administration did not alter body weight or circulating inflammatory markers but reduced HbA$_{1c}$ marginally. ER stress and the saturable nature of leptin signaling pathways play a key role in the development of leptin tolerance in obese patients with diabetes

Orbital state and magnetic properties of LiV_2 O_4

LiV_2 O_4 is one of the most puzzling compounds among transition metal oxides because of its heavy fermion like behavior at low temperatures. In this paper we present results for the orbital state and magnetic properties of LiV_2 O_4 obtained from a combination of density functional theory within the local density approximation and dynamical mean-field theory (DMFT). The DMFT equations are solved by quantum Monte Carlo simulations. The trigonal crystal field splits the V 3d orbitals such that the a_{1g} and e_{g}^{pi} orbitals cross the Fermi level, with the former being slightly lower in energy and narrower in bandwidth. In this situation, the d-d Coulomb interaction leads to an almost localization of one electron per V ion in the a_{1g} orbital, while the e_{g}^{pi} orbitals form relatively broad bands with 1/8 filling. 2The theoretical high-temperature paramagnetic susceptibility chi(T) follows a Curie-Weiss law with an effective paramagnetic moment p_{eff}=1.65 in agreement with the experimental results.Comment: 11 pages, 10 figures, 2 table

Repeated Quantum Error Detection in a Surface Code

The realization of quantum error correction is an essential ingredient for reaching the full potential of fault-tolerant universal quantum computation. Using a range of different schemes, logical qubits can be redundantly encoded in a set of physical qubits. One such scalable approach is based on the surface code. Here we experimentally implement its smallest viable instance, capable of repeatedly detecting any single error using seven superconducting qubits, four data qubits and three ancilla qubits. Using high-fidelity ancilla-based stabilizer measurements we initialize the cardinal states of the encoded logical qubit with an average logical fidelity of 96.1%. We then repeatedly check for errors using the stabilizer readout and observe that the logical quantum state is preserved with a lifetime and coherence time longer than those of any of the constituent qubits when no errors are detected. Our demonstration of error detection with its resulting enhancement of the conditioned logical qubit coherence times in a 7-qubit surface code is an important step indicating a promising route towards the realization of quantum error correction in the surface code.Comment: 12 pages, 11 figure