Theory of winds in late-type evolved and pre-main-sequence stars

Recent observational results confirm that many of the physical processes which are known to occur in the Sun also occur among late-type stars in general. One such process is the continuous loss of mass from a star in the form of a wind. There now exists an abundance of either direct or circumstantial evidence which suggests that most (if not all) stars in the cool portion of the HR diagram possess winds. An attempt is made to assess the current state of theoretical understanding of mass loss from two distinctly different classes of late-type stars: the post-main-sequence giant/supergiant stars and the pre-main-sequence T Tauri stars. Toward this end, the observationally inferred properties of the wind associated with each of the two stellar classes under consideration are summarized and compared against the predictions of existing theoretical models. Although considerable progress has been made in attempting to identify the mechanisms responsible for mass loss from cool stars, many fundamental problems remain to be solved

Shareholder engagement for corporate governance in the light of the harmonization and transposition

Purpose: This comparative study holistically assesses the EU harmonization and various transposition strategies embraced by EU member states to implement measures for corporate governance, namely for the sustainable corporate governance. Design/Methodology/Approach: The contribution and the relevant methodology is based on a duality of purposes. They are (i) on a review and analysis of EU harmonization endeavors designed to shape the exercise of shareholders rights and specifically encouraging a longterm shareholder engagement as the vehicle to increase corporate social responsibility (CSR) and (ii) on a pioneering critical comparative Meta-analysis of selected transposition strategies and their potential to testify about the genuiness of the underlying commitment. Findings: Based on the holistically implied arguments and yielded results, it is proposed that, despite rather clear EU harmonization measures, there are dramatic differences in transposition strategies testifying about deep differences in the approach to corporate governance and CSR across the EU. Practical implications: Based on addressing its dual purposes, this study sheds a new light on the perception and attitude to the corporate governance, shareholder long-term engagement, CSR and their framework in the EU. This leads to a set of recommendations to increase the effectiveness and efficiency of the current harmonization endeavors. Originality/Value: Although this study organically builds upon recent studies about corporate governance and CSR, it brings a pioneering comparative assessment of transposition strategies and an innovative idea to use it as a well founded instrument to understand and appreciate the harmonization potential in this field and to improve it.peer-reviewe

Computational study of the hydrodefluorination of fluoroarenes at [Ru(NHC)(PR₃)<sub style="vertical-align: sub;">2</sub>(CO)(H)<sub style="vertical-align: sub;">2</sub>]: predicted scope and regioselectivities

Density functional theory calculations have been employed to investigate the scope and selectivity of the hydrodefluorination (HDF) of fluoroarenes, C6F6-nHn (n = 0-5), at catalysts of the type [Ru(NHC)(PR3)(2)(CO)(H)(2)]. Based on our previous study (Angew. Chem., Int. Ed., 2011, 50, 2783) two mechanisms featuring the nucleophilic attack of a hydride ligand at a fluoroarene substrate were considered: (i) a concerted process with Ru-H/C-F exchange occurring in one step; and (ii) a stepwise pathway in which the rate-determining transition state involves formation of HF and a Ru-sigma-fluoroaryl complex. The nature of the metal coordination environment and, in particular, the NHC ligand was found to play an important role in both promoting the HDF reaction and determining the regioselectivity of this process. Thus for the reaction of C6F5H, the full experimental system (NHC = IMes, R = Ph) promotes HDF through (i) more facile initial PR3/fluoroarene substitution and (ii) the ability of the NHC N-aryl substituents to stabilise the key C-F bond breaking transition state through F center dot center dot center dot HC interactions. This latter effect is maximised along the lower energy stepwise pathway when an ortho-H substituent is present and this accounts for the ortho-selectivity seen in the reaction of C6F5H to give 1,2,3,4-C6F4H2. Computed C-F bond dissociation energies (BDEs) for C6F6-nHn substrates show a general increase with larger n and are most sensitive to the number of ortho-F substituents present. However, HDF is always computed to remain significantly exothermic when a silane such as Me3SiH is included as terminal reductant. Computed barriers to HDF also generally increase with greater n, and for the concerted pathway a good correlation between C-F BDE and barrier height is seen. The two mechanisms were found to have complementary regioselectivities. For the concerted pathway the reaction is directed to sites with two ortho-F substituents, as these have the weakest C-F bonds. In contrast, reaction along the stepwise pathway is directed to sites with only one ortho-F substituent, due to difficulties in accommodating ortho-F substituents in the C-F bond cleavage transition state. Calculations predict that 1,2,3,5-C6F4H2 and 1,2,3,4-C6F4H2 are viable candidates for HDF at [Ru(IMes)(PPh3)(2)(CO)(H)(2)] and that this would proceed selectively to give 1,2,4-C6F3H3 and 1,2,3-C6F3H3, respectively.</p

The necessity of Darwin

© 2009 Stanley K. Sessions and Herbert C. Macgregor. This document is licensed to the public under the Creative Commons Attribution 3.0 License (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.February 12th, 2009 was Charles Darwin’s 200th birthday, and November 2009 represents the 150th anniversary of the publication of his transformative book, The Origin of Species. It seems a good time to look back and assess Darwin’s legacy within the perspective of current knowledge of genetics, cytogenetics, and molecular biology in general. Although a comprehensive understanding of evolution would no doubt have emerged eventually, it is difficult to imagine how anyone could have matched Darwin’s prodigious and sustained efforts, as well as his talent for explaining things in simple terms

The risk matrix : drug-related deaths in prisons in England and Wales, 2015-2020

Aims: This article explores the factors contributing to drug-related deaths in English and Welsh prisons between 2015-2020. Methods: Based on content analysis of all Prison and Probation Ombudsman ‘other non-natural’ fatal incident investigation reports, descriptive statistics were generated. Qualitative analysis explored the circumstances surrounding deaths and key risk factors. Results: Most deaths were of men, whose mean age was 39 years. Drug toxicity was a main factor in causing death, exacerbated by underlying physical health conditions and risk-taking behaviours. A variety of substances were involved. New psychoactive substances became more important over time. A high proportion had recorded histories of substance use and mental illness. During this period, the prison system was under considerable stress creating dangerous environments for drug-related harm. Conclusion: This study highlights the process of complex interaction between substances used, individual characteristics, situational features and the wider environment in explaining drug-related deaths in prisons. Implications for policy and practice are discussed

Mode identification in rapidly rotating stars

Context: Recent calculations of pulsation modes in rapidly rotating polytropic models and models based on the Self-Consistent Field method have shown that the frequency spectrum of low degree pulsation modes can be described by an empirical formula similar to Tassoul's asymptotic formula, provided that the underlying rotation profile is not too differential. Aims: Given the simplicity of this asymptotic formula, we investigate whether it can provide a means by which to identify pulsation modes in rapidly rotating stars. Methods: We develop a new mode identification scheme which consists in scanning a multidimensional parameter space for the formula coefficients which yield the best-fitting asymptotic spectra. This mode identification scheme is then tested on artificial spectra based on the asymptotic formula, on random frequencies and on spectra based on full numerical eigenmode calculations for which the mode identification is known beforehand. We also investigate the effects of adding random frequencies to mimic the effects of chaotic modes which are also expected to show up in such stars. Results: In the absence of chaotic modes, it is possible to accurately find a correct mode identification for most of the observed frequencies provided these frequencies are sufficiently close to their asymptotic values. The addition of random frequencies can very quickly become problematic and hinder correct mode identification. Modifying the mode identification scheme to reject the worst fitting modes can bring some improvement but the results still remain poorer than in the case without chaotic modes

Lethal effects of high intensity violet 405-nm light on saccharomyces cerevisiae, candida albicans and on dormant and germinating spores of aspergillus niger

This study assessed the effects of high-intensity violet light on selected yeast and mould fungi. Cell suspensions of Saccharomyces cerevisiae, Candida albicans, and dormant and germinating spores (conidia) of the mould Aspergillus niger were exposed to high-intensity narrow band violet light with peak output at 405 nm generated from a light-emitting diode (LED) array. All three fungal species were inactivated by the 405-nm light without a requirement for addition of exogenous photosensitiser chemicals. Of the fungal species tested, S. cerevisiae was most sensitive and dormant conidia of A. niger were most resistant to 405-nm light exposure. Five-log10 colony forming units per millilitre (CFU ml1) reductions of the tested species required exposure doses of 288 J cm2 for S. cerevisiae, 576 J cm2 for C. albicans, and a much higher value of 2.3 kJ cm2 for dormant conidia of A. niger. During germination, A. niger conidia became more sensitive to 405-nm light exposure and sensitivity increased as germination progressed over an 8 h test period. Light exposure under aerobic and anaerobic conditions, together with results obtained using ascorbic acid as a scavenger of reactive oxygen species, revealed that 405-nm light inactivation in fungi involved an oxygen-dependent mechanism, as previously described in bacteria. The inactivation results achieved with yeast cells and fungal spores together with operational advantages associated with the use of a visible (nonultraviolet (UV)) light source highlight the potential of 405-nm light for fungal decontamination applications

The potential for dietary factors to prevent or treat osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease for which there are no disease-modifying drugs. It is a leading cause of disability in the UK. Increasing age and obesity are both major risk factors for OA and the health and economic burden of this disease will increase in the future. Focusing on compounds from the habitual diet that may prevent the onset or slow the progression of OA is a strategy that has been under-investigated to date. An approach that relies on dietary modification is clearly attractive in terms of risk/benefit and more likely to be implementable at the population level. However, before undertaking a full clinical trial to examine potential efficacy, detailed molecular studies are required in order to optimise the design. This review focuses on potential dietary factors that may reduce the risk or progression of OA, including micronutrients, fatty acids, flavonoids and other phytochemicals. It therefore ignores data coming from classical inflammatory arthritides and nutraceuticals such as glucosamine and chondroitin. In conclusion, diet offers a route by which the health of the joint can be protected and OA incidence or progression decreased. In a chronic disease, with risk factors increasing in the population and with no pharmaceutical cure, an understanding of this will be crucial

Dynamics of the fast solar tachocline: I. Dipolar field

One possible scenario for the origin of the solar tachocline, known as the "fast tachocline", assumes that the turbulent diffusivity exceeds eta>10^9 cm^2/s. In this case the dynamics will be governed by the dynamo-generated oscillatory magnetic field on relatively short timescales. Here, for the first time, we present detailed numerical models for the fast solar tachocline with all components of the magnetic field calculated explicitly, assuming axial symmetry and a constant turbulent diffusivity eta and viscosity nu. We find that a sufficiently strong oscillatory poloidal field with dipolar latitude dependence at the tachocline-convective zone boundary is able to confine the tachocline. Exploring the three-dimensional parameter space defined by the viscosity in the range log(nu)=9-11, the magnetic Prandtl number in the range Prm=0.1-10, and the meridional flow amplitude (-3 to +3 cm/s), we also find that the confining field strength B_conf, necessary to reproduce the observed thickness of the tachocline, increases with viscosity nu, with magnetic Prandtl number nu/eta, and with equatorward meridional flow speed. Nevertheless, the resulting B_conf values remain quite reasonable, in the range 10^3-10^4 G, for all parameter combinations considered here. The thickness of the tachocline shows a marked dependence on both time and latitude. A comparison with seismic constraints suggests that best agreement with our models is achieved for the highest values of nu and Prm considered here.Comment: 11 page