Emory University

About: Emory University is a education organization based out in Atlanta, Georgia, United States. It is known for research contribution in the topics: Population & Medicine. The organization has 51959 authors who have published 122469 publications receiving 6010698 citations.

Liquidity and Market Efficiency

Abstract: Market efficiency, the timely incorporation of information into prices, remains a central and controversial issue in finance. The short-horizon predictability of returns from past order flows is an inverse indicator of efficiency. We analyze this predictability for NYSE stocks that traded every day from 1993 through 2002. Mid-quote return predictability is diminished when bid-ask spreads are narrower. Such predictability has declined over time with the minimum tick size. Variance ratios of five-minute and daily returns suggest that prices were closer to random walk benchmarks during decimal regimes than during regimes with higher tick sizes (and wider spreads). These findings support the notion that liquidity stimulates arbitrage activity, which, in turn, enhances market efficiency. Further, as the tick size decreased, open-close/close-open return variance ratios increased, while return autocorrelations decreased. This suggests an increased incorporation of private information into prices during more liquid regimes.

Enhancing SIV-specific immunity in vivo by PD-1 blockade

Abstract: Chronic immunodeficiency virus infections are characterized by dysfunctional cellular and humoral antiviral immune responses. As such, immune modulatory therapies that enhance and/or restore the function of virus-specific immunity may protect from disease progression. Here we investigate the safety and immune restoration potential of blockade of the co-inhibitory receptor programmed death 1 (PD-1) during chronic simian immunodeficiency virus (SIV) infection in macaques. We demonstrate that PD-1 blockade using an antibody to PD-1 is well tolerated and results in rapid expansion of virus-specific CD8 T cells with improved functional quality. This enhanced T-cell immunity was seen in the blood and also in the gut, a major reservoir of SIV infection. PD-1 blockade also resulted in proliferation of memory B cells and increases in SIV envelope-specific antibody. These improved immune responses were associated with significant reductions in plasma viral load and also prolonged the survival of SIV-infected macaques. Blockade was effective during the early (week 10) as well as late ( approximately week 90) phases of chronic infection even under conditions of severe lymphopenia. These results demonstrate enhancement of both cellular and humoral immune responses during a pathogenic immunodeficiency virus infection by blocking a single inhibitory pathway and identify a novel therapeutic approach for control of human immunodeficiency virus infections.

Molecular cloning and characterization of the constitutive bovine aortic endothelial cell nitric oxide synthase.

Abstract: The constitutive endothelial cell nitric oxide synthase (NOS) importantly regulates vascular homeostasis. To gain understanding of this enzyme, a pEF BOS cDNA library of 5 x 10(5) clones was prepared from bovine aortic endothelial cells (BAEC) and screened with a 2.8-kb cDNA BamHI fragment of rat brain NOS. Clone pBOS13 was found to express NO synthase activity when transfected into COS-7 cells. Sequence analysis revealed sequences compatible with binding domains for calcium/calmodulin, flavin mononucleotide, flavin adenine nucleotide and NADPH. The deduced amino acid sequence revealed a protein with a relative mol mass of 133,286, which is 58% homologous to the rat cerebellar NOS and 51% homologous to the mouse macrophage NOS. The amino-terminal portion of the protein exhibits several characteristics peculiar to the endothelial cell NOS. These include a proline-rich region and several potential sites for proline-directed phosphorylation as well as a potential substrate site for acyl transferase. Northern hybridization to mRNA from cultured BAEC revealed an abundant 4.8-kb message, which was not increased by coincubation with tumor necrosis factor alpha, but was markedly increased by exposure to shear stress for 24 h. The unique features of the endothelial cell NO synthase, particularly in the amino terminal portion of the molecule, may provide for novel regulatory influences of enzyme activity and localization.

Flexible piezotronic strain sensor

Abstract: Strain sensors based on individual ZnO piezoelectric fine-wires (PFWs; nanowires, microwires) have been fabricated by a simple, reliable, and cost-effective technique. The electromechanical sensor device consists of a single electrically connected PFW that is placed on the outer surface of a flexible polystyrene (PS) substrate and bonded at its two ends. The entire device is fully packaged by a polydimethylsiloxane (PDMS) thin layer. The PFW has Schottky contacts at its two ends but with distinctly different barrier heights. The I-V characteristic is highly sensitive to strain mainly due to the change in Schottky barrier height (SBH), which scales linear with strain. The change in SBH is suggested owing to the strain induced band structure change and piezoelectric effect. The experimental data can be well-described by the thermionic emission-diffusion model. A gauge factor of as high as 1250 has been demonstrated, which is 25% higher than the best gauge factor demonstrated for carbon nanotubes. The strain sensor developed here has applications in strain and stress measurements in cell biology, biomedical sciences, MEMS devices, structure monitoring, and more.