University of Houston

About: University of Houston is a education organization based out in Houston, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 23074 authors who have published 53903 publications receiving 1641968 citations.

A Resolution of the Distress Risk and Leverage Puzzles in the Cross Section of Stock Returns

Abstract: We revisit findings that returns are negatively related to financial distress intensity and leverage. These are puzzles under frictionless capital markets assumptions, but consistent with optimizing firms that differ in their exposure to financial distress costs. Firms with high costs choose low leverage to avoid distress, but retain exposure to the systematic risk of bearing such costs in low states. Empirical results are consistent with this explanation. The return premiums to low leverage and low distress are significant in raw returns, and even stronger in risk-adjusted returns. When in distress, low leverage firms suffer more than high leverage firms as measured by a deterioration in accounting operating performance and heightened exposure to systematic risk. The connection between return premiums and distress costs is apparent in subperiod evidence—both are small or insignificant prior to 1980 and larger and significant thereafter.

Electromechanical coupling in nonpiezoelectric materials due to nanoscale nonlocal size effects: Green’s function solutions and embedded inclusions

Abstract: In a piezoelectric material, an applied uniform strain can induce an electric polarization (or vice versa). Crystallographic considerations restrict this technologically important property to noncentrosymmetric systems. It has been shown both mathematically and physically that a nonuniform strain can potentially break the inversion symmetry and induce polarization in nonpiezoelectric materials. The coupling between strain gradients and polarization, and conversely between strain and polarization gradients, is investigated in this work. While the conventional piezoelectric property is nonzero only for certain select materials, the nonlocal coupling of strain and electric field gradients is (in principle) nonzero for all dielectrics, albeit manifesting noticeably only at the nanoscale, around interfaces or in general in the vicinity of high field gradients. Based on a field theoretic framework accounting for this phenomena, we (i) develop the fundamental solutions (Green's functions) for the governing equations, and (ii) motivated by eventual applications for quantum dots, solve the general embedded mismatched inclusion problem with explicit results for the spherical and cylindrical shape. Expectedly, our results for the aforementioned problems are size dependent and indicate generation of high electric fields reaching values of approximately hundreds of kV/m in selected sizes and locations---even in isotropic centrosymmetric nonpiezoelectric materials.

Nanoparticle orientation to control RNA loading and ligand display on extracellular vesicles for cancer regression

Abstract: Nanotechnology offers many benefits, and here we report an advantage of applying RNA nanotechnology for directional control. The orientation of arrow-shaped RNA was altered to control ligand display on extracellular vesicle membranes for specific cell targeting, or to regulate intracellular trafficking of small interfering RNA (siRNA) or microRNA (miRNA). Placing membrane-anchoring cholesterol at the tail of the arrow results in display of RNA aptamer or folate on the outer surface of the extracellular vesicle. In contrast, placing the cholesterol at the arrowhead results in partial loading of RNA nanoparticles into the extracellular vesicles. Taking advantage of the RNA ligand for specific targeting and extracellular vesicles for efficient membrane fusion, the resulting ligand-displaying extracellular vesicles were capable of specific delivery of siRNA to cells, and efficiently blocked tumour growth in three cancer models. Extracellular vesicles displaying an aptamer that binds to prostate-specific membrane antigen, and loaded with survivin siRNA, inhibited prostate cancer xenograft. The same extracellular vesicle instead displaying epidermal growth-factor receptor aptamer inhibited orthotopic breast cancer models. Likewise, survivin siRNA-loaded and folate-displaying extracellular vesicles inhibited patient-derived colorectal cancer xenograft.

Home Bias and International Risk Sharing: Twin Puzzles Separated at Birth

Abstract: We show that international home bias in bond and equity holdings declined during the late 1990s at the same time as international risk sharing increased. Also, countries with less home bias, on average, tended to obtain more risk sharing in international markets. Using panel data estimations, we demonstrate that less home bias is associated with more international risk sharing when both cross-sectional and time-series dimensions are taken into account. This indicates that lack of risk sharing and international home bias are closely related empirical phenomena.