An infrared singularity in the damping rate for longitudinal gluons in hot QCD

We calculate $\gamma_l(0)$, the damping rate for longitudinal on-shell gluons with zero momentum in hot QCD using the hard-thermal-loop (htl) scheme. We find it to be divergent in the infrared, which means that in this scheme $\gamma_l(0)$ is different from $\gamma_t(0)$, the corresponding damping rate for transverse gluons which is known to be finite. This result suggests that the htl scheme is infrared sensitive and thus may need to be improved upon in this sector. We discuss this issue after we present our calculation.Comment: 11 pages, RevTeX. Two signs corrected. Same result but substantially rewritten with more emphasis on the infrared problem. References adde

The formation of H_2 and HD with the master equation approach

The formation of H2 and HD molecules on interstellar dust grains is studied using rate equation and master equation models. Rate equations are used in the analysis of laboratory experiments which examine the formation of molecular hydrogen on astrophysically relevant surfaces. However, under interstellar conditions, rate equations are not suitable for the calculation of reaction rates on dust-grain surfaces. Due to the low flux and the sub-micron size of the grains, the populations of H and D atoms on a single grain are likely to be small. In this case the reaction rates are dominated by fluctuations and should be calculated using stochastic methods. The rate of molecular hydrogen formation in interstellar clouds is evaluated using the master equation, taking into account the distribution of grain sizes.Comment: 10 pages, 2 figures. IAU symposium 231 conference proceeding

The diminishing liquidity premium

Previous evidence suggests that less liquid stocks entail higher average returns. Using NYSE data, we present evidence that both the sensitivity of returns to liquidity and liquidity premia have significantly declined over the past four decades to levels that we cannot statistically distinguish from zero. Furthermore, the profitability of trading strategies based on buying illiquid stocks and selling illiquid stocks has declined over the past four decades, rendering such strategies virtually unprofitable. Our results are robust to several conventional liquidity measures related to volume. When using liquidity measure that is not related to volume, we find just weak evidence of a liquidity premium even in the early periods of our sample. The gradual introduction and proliferation of index funds and exchange traded funds is a possible explanation for these results

Specification of spatial relationships in directed graphs of cell signaling networks

Graph theory provides a useful and powerful tool for the analysis of cellular signaling networks. Intracellular components such as cytoplasmic signaling proteins, transcription factors and genes are connected by links, representing various types of chemical interactions that result in functional consequences. However, these graphs lack important information regarding the spatial distribution of cellular components. The ability of two cellular components to interact depends not only on their mutual chemical affinity but also on co-localization to the same subcellular region. Localization of components is often used as a regulatory mechanism to achieve specific effects in response to different receptor signals. Here we describe an approach for incorporating spatial distribution into graphs, and for the development of mixed graphs where links are specified by mutual chemical affinity as well as colocalization. We suggest that such mixed graphs will provide more accurate descriptions of functional cellular networks and their regulatory capabilities and aid in the development of large-scale predictive models of cellular behavior

Enhancing Job Satisfaction for Teachers: A Strategy for Achieving Transformation of Secondary Education in Nigeria

The neglect of teachers’ needs have impacted negatively on our educational system in Nigeria. Indeed, the teaching profession has suffered untold hardship for quite sometimes now. This paper uses a theoretical approach to x-ray the factors responsible for poor job satisfaction among secondary school teachers. The paper also examines teachers’ job satisfaction as a strategy for transformation of secondary school education in Nigeria. Nigerian secondary school teachers need job satisfaction in the form of better condition of service, proper administrative and organizational structure, teaching aids should be provided and instructional materials among others. The last part of the paper contains conclusion and recommendations on the ways of achieving transformation in Nigerian secondary school education and job satisfaction for teachers

To browse, or not to browse? Third person effect among Ultra-Orthodox Jewish women, in regards to the perceived danger of the internet

Abstract The study looks at Jewish ultra-Orthodox women who use modern technologies, for purposes that are illegitimate in their community. Subjects’ perceived impacts of the Internet on self and others are analyzed, demonstrating a "third-person effect" in regards to the perceived dangers originating from the Internet. The correlations and possible implications of the "third-person effect" are discussed

Do firms buy their stock at bargain prices? : Evidence from actual stock repurchase disclosure

We use new data from SEC filings to investigate how S&P 500 firms execute their open market repurchase programs. We find that smaller S&P 500 firms repurchase less frequently than larger firms, and at a price which is significantly lower than the average market price. Their repurchase activity is followed by a positive and significant abnormal return which lasts up to three months after the repurchase. These findings do not hold for large S&P 500 firms. Our interpretation is that small firms repurchase strategically, whereas the repurchase activity of large firms is more focused on the disbursement of free cash. JEL Classification: G14, G30, G35 Keywords: Stock Repurchases, Stock Buybacks, Payout Policy, Timing, Bid-Ask Spread, Liquidit