A comparative Raman study between YbVO

Abstract. An orbital ordering effect is observed in YbVO 3 around 170 K while the crystal structure is orthorhombic (space group pnma). A monoclinic transition has been reported below T N = 104 K, while according to recent specific heat measurements, it occurs at 170 K. The crystal structure of YVO 3 at 300 K is also orthorhombic. It becomes monoclinic at T c = 200 K and back orthorhombic at T = 77 K. Spins order into the C-type antiferromagnetic structure below T N1 = 116 K and the order changes into the G-type antiferromagnetic structure below T N2 = 77 K. Controversial interpretations of YVO 3 Raman active excitations have been reported. For instance the 489 and 679 cm -1 excitations have been assigned either to phonons or orbitons in two recent studies. In this communication we present a micro-Raman study of YbVO 3 and YVO 3 Raman active excitations as a function of temperature in order to trace the multiple phase transitions. Also by comparing the two single crystals spectra and previous studies in rare-earth manganites, high energy Raman active excitations are tentatively assigned

Alias calculus, change calculus and frame inference

Abstract Alias analysis, which determines whether two expressions in a program may reference to the same object, has many potential applications in program construction and verification. We have developed a theory for alias analysis, the "alias calculus", implemented its application to an object-oriented language, and integrated the result into a modern IDE. The calculus has a higher level of precision than many existing alias analysis techniques. One of the principal applications is to allow automatic change analysis, which leads to inferring "modifies clauses", providing a significant advance towards addressing the Frame Problem. Experiments were able to infer the "modifies" clauses of an existing formally specified library. Other applications, in particular to concurrent programming, also appear possible. The article presents the calculus, the application to frame inference including experimental results, and other projected applications. The ongoing work includes building more efficient model capturing aliasing properties and soundness proof for its essential elements

Evaluation of polyelectrolyte complex-based scaffolds for mesenchymal stem cell therapy in cardiac ischemia treatment

b s t r a c t Three-dimensional (3D) scaffolds hold great potential for stem cell-based therapies. Indeed, recent results have shown that biomimetic scaffolds may enhance cell survival and promote an increase in the concentration of therapeutic cells at the injury site. The aim of this work was to engineer an original polymeric scaffold based on the respective beneficial effects of alginate and chitosan. Formulations were made from various alginate/chitosan ratios to form opposite-charge polyelectrolyte complexes (PECs). After freeze-drying, the resultant matrices presented a highly interconnected porous microstructure and mechanical properties suitable for cell culture. In vitro evaluation demonstrated their compatibility with mesenchymal stell cell (MSC) proliferation and their ability to maintain paracrine activity. Finally, the in vivo performance of seeded 3D PEC scaffolds with a polymeric ratio of 40/60 was evaluated after an acute myocardial infarction provoked in a rat model. Evaluation of cardiac function showed a significant increase in the ejection fraction, improved neovascularization, attenuated fibrosis as well as less left ventricular dilatation as compared to an animal control group. These results provide evidence that 3D PEC scaffolds prepared from alginate and chitosan offer an efficient environment for 3D culturing of MSCs and represent an innovative solution for tissue engineering

Improving Asset Price Prediction when All Models are False

Abstract This study considers three alternative sources of information about volatility potentially useful in predicting daily asset returns: past daily returns, past intraday returns, and a volatility index based on observed option prices. For each source of information the study begins with several alternative models, and then works from the premise that all of these models are false to construct a single improved predictive distribution for daily S&P 500 index returns. The criterion for improvement is the log predictive score, equivalent to the average probability ascribed ex ante to observed returns. The first implication of the premise is that conventional models within each class can be improved. The paper accomplishes this by introducing flexibility in the conditional distribution of returns, in volatility dynamics, and in the relationship between observed and latent volatility. The second implication of the premise is that model pooling will provide prediction superior to the best of the improved models. The paper accomplishes this by constructing ex ante optimal pools, which place a premium on diversification in much the same way as optimal portfolios. All procedures are strictly out-of-sample, recapitulating one-step-ahead predictive distributions that could have been constructed for daily returns beginning January 2, 1992, and ending March 31, 2010. The prediction probabilities of the optimal pool exceed those of the conventional models by as much as 7.75%. The optimal pools place substantial weight on models using each of the three sources of information about volatility

Comparison of Steroid Modulation of Spontaneous Inhibitory Postsynaptic Currents in Cultured Hippocampal Neurons and Steady-State Single-Channel Currents from Heterologously Expressed a1b2g2L GABA A Receptors

ABSTRACT Neuroactive steroids are efficacious modulators of g-aminobutyric acid type A receptor (GABA A ) receptor function. The effects of steroids on the GABA A receptor are typically determined by comparing steady-state single-channel open probability or macroscopic peak responses elicited by GABA in the absence and presence of a steroid. Due to differences in activation conditions (exposure duration, concentration of agonist), it is not obvious whether modulation measured using typical experimental protocols can be used to accurately predict the effect of a modulator on native receptors under physiologic conditions. In the present study, we examined the effects of 14 neuroactive steroids and analogs on the properties of spontaneous inhibitory postsynaptic currents (sIPSCs) in cultured rat hippocampal neurons. The goal was to determine whether the magnitude of modulation of the decay time course of sIPSCs correlates with the extent of modulation and kinetic properties of potentiation as determined in previous singlechannel studies. The steroids were selected to cover a wide range of efficacy on heterologously expressed rat a1b2g2L GABA A receptors, ranging from essentially inert to highly efficacious (strong potentiators of single-channel and macroscopic peak responses). The data indicate a strong correlation between prolongation of the decay time course of sIPSCs and potentiation of single-channel open probability. Furthermore, changes in intracluster closed time distributions were the single best predictor of prolongation of sIPSCs. We infer that the information obtained in steady-state single-channel recordings can be used to forecast modulation of synaptic currents

Tropical Cyclone Inner-Core Kinetic Energy Evolution

Abstract Tropical cyclone (TC) destructive potential is highly dependent on the distribution of the surface wind-field. To gain a better understanding of wind structure evolution, TC 0-200 km wind-fields from aircraft reconnaissance flight-level data are used to calculate the low-level area-integrated kinetic energy (KE). The integrated KE depends on both the maximum winds and wind structure. To isolate the structure evolution, the average relationship between KE and intensity is first determined. Then the deviations of the KE from the mean intensity relationship are calculated. These KE deviations reveal cases of significant structural change, and, for convenience, are referred to as measurements of storm size (storms with greater (less) KE for their given intensity are considered large (small)). It is established that TCs generally either intensify and do not grow, or weaken or maintain intensity and grow. Statistical testing is used to identify conditions that are significantly different for growing versus non-growing storms in each intensification regime. Results suggest two primary types of growth processes: (1) secondary eyewall formation and eyewall replacement cycles, an internally dominated process; and (2) external forcing from the synoptic environment. One of the most significant environmental forcing is the vertical shear. Under light shear, TCs intensify but do not grow. Under moderate shear, they intensify less but grow more, and under very high shear they do not intensify or grow. As a supplement to this study, a new TC classification system based on KE and intensity is presented as a complement to the Saffir-Simpson hurricane scale.

Social Networks and the Business Value of Social Media

Abstract. Social Media (SM) is a participatory people-to-people media that leverages Web 2.0. Internet technology to facilitate individuals to connect to one another. SM assists in an effective dialogue between users, thus, enabling them to dynamically participate, review and contribute their thoughts, feelings, ideas, photos, videos, among others. Businesses are using SM to see how the products are being reviewed and rated by consumers and what the blogs and discussion boards are telling about their company and its products. Others are building businesses around this technology. By observing several blogs, discussion forums, social networking sites and general websites, we critically evaluate the impact of SM in the development of business. We also argue that description of SM should not be restricted to just social networking sites but must also include sites that bring service providers and customers together. We finally conclude by distilling our interpretations and findings

Altered development of CD8+ T cell lineages in mice deficient for the Tec kinases Itk and Rlk. Immunity. 2006; 25:93–104. [PubMed: 16860760

Summary Mutations affecting the Tec kinases Itk and Rlk decrease T cell receptor-induced Ca 2+ mobilization and Erk kinase activation and impair both positive and negative thymic selection. Itk 2/2 and Rlk 2/