Biotransformation of explosives by the old yellow enzyme family of flavoproteins

Several independent studies of bacterial degradation of nitrate ester explosives have demonstrated the involvement of flavin-dependent oxidoreductases related to the old yellow enzyme (OYE) of yeast. Some of these enzymes also transform the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). In this work, catalytic capabilities of five members of the OYE family were compared, with a view to correlating structure and function. The activity profiles of the five enzymes differed substantially; no one compound proved to be a good substrate for all five enzymes. TNT is reduced, albeit slowly, by all five enzymes. The nature of the transformation products differed, with three of the five enzymes yielding products indicative of reduction of the aromatic ring. Our findings suggest two distinct pathways of TNT transformation, with the initial reduction of TNT being the key point of difference between the enzymes. Characterization of an active site mutant of one of the enzymes suggests a structural basis for this difference

Dark cloud chemistry in initially H-rich regions

The chemistry in dark regions of dense cores is explored as a function of the initial abundance ratio of H to H 2, on the assumption that some cores form on a timescale and are younger than the time required for the H :H 2 ratio to attain its equilibrium value. Observational diagnostics of non-equilibrium values of the initial H :H 2 ratio are identified. In initially H-rich material, the abundances of OH, NH 3, CN, and HNC are for some time higher than they are in initially H-poor material. In initially H-poor regions, the abundances of CO, species containing multiple carbon atoms in each molecule, and CS are larger for an (observationally significant) period than in initially H-rich material

First evidence for molecular interfaces between outflows and ambient clouds in high-mass star-forming regions?

We present new observations of the Cep A East region of massive star formation and describe an extended and dynamically distinct feature not previously recognized. This feature is present in emission from H2CS, OCS, CH3OH, and HDO at −5.5 km s−1 but is not traced by the conventional tracers of star-forming regions, H2S, SO2, SO, and CS. The feature is extended up to at least 0.1 pc. We show that the feature is neither a hot core nor a shocked outflow. However, the chemistry of the feature is consistent with predictions from a model of an eroding interface between a fast wind and a dense core; mixing between the two media occurs in the interface on a timescale of 10–50 yr. If these observations are confirmed by detailed maps and by detections in species also predicted to be abundant (e.g., HCO+, H2CO, and NH3), this feature would be the first detection of such an interface in regions of massive star formation. An important implication of the model is that a significant reservoir of sulfur in grain mantles is required to be in the form of OCS

A Theoretically-Based Mixed Methods Approach to Examining Mental Health Disorders and Help-Seeking Behaviors among University-Enrolled African American Men

Recent studies show that African American men in college are disproportionately experiencing high levels of psychological distress, increasing their risk of developing mental health symptoms associated with depression and anxiety. Despite being at higher risk for developing mental health symptoms, university-enrolled, African American men are not seeking help even when experiencing high levels of stress and anxiety, impacting their academic performance. The evidence base describing mental health symptom prevalence and evidence-based prevention strategies among university-enrolled, African American men is limited. To that end, this dissertation work utilized a concurrent, mixed methods approach, theoretically-based in the Social Ecological Model (SEM), to examine the prevalence and correlates of anxiety and depressive symptoms among university-enrolled, African American men, and the contextual factors that impact their perceptions of mental health-related help-seeking. Overall, findings showed that: 1) African American men on this campus are reporting endorsement of anxiety and depressive symptoms at lower rates compared to their male and female counterparts; 2) African American men are utilizing campus health services at lower rates compared to their male and female counterparts; 3) stressful life events are a robust predictor of anxiety and depressive symptoms among this population; and 4) formal therapeutic services may not be preferred or suitable for these men. Researchers, campus-based practitioners, and policymakers who wish to develop effective mental health prevention programs that attenuate mental health risk and increase help-seeking behavior among African American men should aim to expand on these findings and considerations. Importantly, future programming efforts should aim to promote peer-to-peer support and informal, nontraditional methods as viable points for future scientific inquiry, as well as for the development, implementation and evaluation of effective mental health prevention programs. This dissertation study is one of the first to focus specifically on mental health risk and help-seeking behaviors among African American men on a college campus. Hence, further quantitative and qualitative research is needed to improve mental health among this severely marginalized and vulnerable population. Implications for future research are discussed in the following chapters

The molecular condensations ahead of Herbig-Haro objects. II: a theoretical investigation of the HH 2 condensation

Clumps of enhanced molecular emission are present close to a number of Herbig-Haro (HH) objects. These enhancements may be the consequence of an active photochemistry driven by the UV radiation originating from the shock front of the HH object. On the basis of this picture and as a follow up to a molecular line survey toward the quiescent molecular clump ahead of the HH object, HH 2 (Girart et al. 2002), we present a detailed time and depth dependent chemical model of the observed clump. Despite several difficulties in matching the observations, we constrain some of the physical and chemical parameters of the clump ahead of HH 2. In particular, we find that the clump is best described by more than one density component with a peak density of 3 × 105 cm-3 and a visual extinction of ≤3.5 mag; its lifetime can not be much higher than 100 years and the impinging radiation is enhanced with respect to the ambient one by probably no more than 3 orders of magnitude. Our models also indicate that carbon-bearing species should not completely hydrogenate as methane when freezing out on grains during the formation of the clump

Macroeconomic, international trade and sectoral policies in livestock development. An analysis with particular reference to low income countries

Following a general introduction Section 1 review regional trends in production, consumption and trade and highlights some related policy issues. Section 2 then considers in conceptual terms the importance of macroeconomic, trade and other economic policies to provide a basis for the remainder of the paper. Section 3 examines agricultural and livestock development in major developing regions in relation to macroeconomic and trade policies whereas Section 4 looks at livestock sector policies. Recent West African experiences in livestock production and trade against a background of changes in international and regional economic policies are the focus of Section 5. The concluding Section 6 focuses on appropriate economic policies for livestock development in low income countries

Bessel processes, the Brownian snake and super-Brownian motion

We prove that, both for the Brownian snake and for super-Brownian motion in dimension one, the historical path corresponding to the minimal spatial position is a Bessel process of dimension -5. We also discuss a spine decomposition for the Brownian snake conditioned on the minimizing path.Comment: Submitted to the special volume of S\'eminaire de Probabilit\'es in memory of Marc Yo

On the absence of appreciable half-life changes in alpha emitters cooled in metals to 1 Kelvin and below

The recent suggestion that dramatic changes may occur in the lifetime of alpha and beta decay when the activity, in a pure metal host, is cooled to a few Kelvin, is examined in the light of published low temperature nuclear orientation (LTNO) experiments, with emphasis here on alpha decay. In LTNO observations are made of the anisotropy of radioactive emissions with respect to an axis of orientation. Correction of data for decay of metallic samples held at temperatures at and below 1 Kelvin for periods of days and longer has been a routine element of LTNO experiments for many years. No evidence for any change of half life on cooling, with an upper level of less than 1%, has been found, in striking contrast to the predicted changes, for alpha decay, of several orders of magnitude. The proposal that such dramatic changes might alleviate problems of disposal of long-lived radioactive waste is shown to be unrealistic.Comment: 27 pages, 12 figures, accepted for publication in Nucl.Phys.A. Revised version, including quantitative analysis of the sensitivity of nuclear orientation experiments, discussed in this work, to changes of alpha-decay lifetimes in metals at low temperatures. Conclusions remain unchange

Entanglement Dynamics in 1D Quantum Cellular Automata

Several proposed schemes for the physical realization of a quantum computer consist of qubits arranged in a cellular array. In the quantum circuit model of quantum computation, an often complex series of two-qubit gate operations is required between arbitrarily distant pairs of lattice qubits. An alternative model of quantum computation based on quantum cellular automata (QCA) requires only homogeneous local interactions that can be implemented in parallel. This would be a huge simplification in an actual experiment. We find some minimal physical requirements for the construction of unitary QCA in a 1 dimensional Ising spin chain and demonstrate optimal pulse sequences for information transport and entanglement distribution. We also introduce the theory of non-unitary QCA and show by example that non-unitary rules can generate environment assisted entanglement.Comment: 12 pages, 8 figures, submitted to Physical Review

Proposed Global Stratotype Sections and Points for the bases of the Selandian and Thanetian stages (Paleocene Series)

Prepared for the International Subcommission on Paleogene Stratigraph