Acoustic Tests of a Flexible Spacecraft Model

Acoustic tests of flexible spacecraft mode

Estimates of nonequilibrium ionization phenomena in the inviscid Apollo plasma sheath

Nonequilibrium ionization in asymmetric plasma sheath determined for Apollo spacecraft at superorbital velocity reentr

One-loop corrections to the instanton transition in the two-dimensional Abelian Higgs model

We present an evaluation of the fluctuation determinant which appears as a prefactor in the instanton transition rate for the two-dimensional Abelian Higgs model. The corrections are found to change the rate at most by a factor of 2 for 0.4 < M_W/M_H < 2.0.Comment: DO-TH-94/17, 20 pages, 4 figures appended as uucompressed .eps files, LaTeX, needs epsfig.st

Mitochondrial oxidative stress and nitrate tolerance – comparison of nitroglycerin and pentaerithrityl tetranitrate in Mn-SOD(+/- )mice

BACKGROUND: Chronic therapy with nitroglycerin (GTN) results in a rapid development of nitrate tolerance which is associated with an increased production of reactive oxygen species (ROS). According to recent studies, mitochondrial ROS formation and oxidative inactivation of the organic nitrate bioactivating enzyme mitochondrial aldehyde dehydrogenase (ALDH-2) play an important role for the development of nitrate and cross-tolerance. METHODS: Tolerance was induced by infusion of wild type (WT) and heterozygous manganese superoxide dismutase mice (Mn-SOD(+/-)) with ethanolic solution of GTN (12.5 μg/min/kg for 4 d). For comparison, the tolerance-free pentaerithrityl tetranitrate (PETN, 17.5 μg/min/kg for 4 d) was infused in DMSO. Vascular reactivity was measured by isometric tension studies of isolated aortic rings. ROS formation and aldehyde dehydrogenase (ALDH-2) activity was measured in isolated heart mitochondria. RESULTS: Chronic GTN infusion lead to impaired vascular responses to GTN and acetylcholine (ACh), increased the ROS formation in mitochondria and decreased ALDH-2 activity in Mn-SOD(+/- )mice. In contrast, PETN infusion did not increase mitochondrial ROS formation, did not decrease ALDH-2 activity and accordingly did not lead to tolerance and cross-tolerance in Mn-SOD(+/- )mice. PETN but not GTN increased heme oxygenase-1 mRNA in EA.hy 926 cells and bilirubin efficiently scavenged GTN-derived ROS. CONCLUSION: Chronic GTN infusion stimulates mitochondrial ROS production which is an important mechanism leading to tolerance and cross-tolerance. The tetranitrate PETN is devoid of mitochondrial oxidative stress induction and according to the present animal study as well as numerous previous clinical studies can be used without limitations due to tolerance and cross-tolerance

Paradoxical roles of antioxidant enzymes:Basic mechanisms and health implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate “paradoxical” outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of “antioxidant” nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that “paradoxical” roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways

Visual ecology of aphids – a critical review on the role of colours in host finding

We review the rich literature on behavioural responses of aphids (Hemiptera: Aphididae) to stimuli of different colours. Only in one species there are adequate physiological data on spectral sensitivity to explain behaviour crisply in mechanistic terms. Because of the great interest in aphid responses to coloured targets from an evolutionary, ecological and applied perspective, there is a substantial need to expand these studies to more species of aphids, and to quantify spectral properties of stimuli rigorously. We show that aphid responses to colours, at least for some species, are likely based on a specific colour opponency mechanism, with positive input from the green domain of the spectrum and negative input from the blue and/or UV region. We further demonstrate that the usual yellow preference of aphids encountered in field experiments is not a true colour preference but involves additional brightness effects. We discuss the implications for agriculture and sensory ecology, with special respect to the recent debate on autumn leaf colouration. We illustrate that recent evolutionary theories concerning aphid–tree interactions imply far-reaching assumptions on aphid responses to colours that are not likely to hold. Finally we also discuss the implications for developing and optimising strategies of aphid control and monitoring

Noise annoyance and risk of prevalent and incident atrial fibrillation–A sex-specific analysis

BackgroundWhile chronic exposure to high levels of noise was demonstrated to increase the risk of various cardiovascular diseases, the association between noise annoyance and risk of cardiovascular disease remains still inconsistent. Recently, we showed that noise annoyance is associated with prevalent atrial fibrillation in the general population. However, the association between noise annoyance and risk of incident atrial fibrillation as well as potential sex-differences remain still elusive.Methods and results15,010 subjects from a German population-based cohort were examined at baseline (2007 to 2012) and follow-up five years later (2012 to 2017) to investigative the association between noise annoyance due to multiple sources and prevalent and incident atrial fibrillation. After multivariable adjustment, the results from logistic regression analyses revealed overall consistent and positive associations between noise annoyance and prevalent and incident atrial fibrillation in men, whereas this association was weaker in women, in particular with respect to incident atrial fibrillation. For instance, industrial noise annoyance was associated with 21% (95% confidence interval (CI) 9–34%) and 18% (8–29%) higher odds of prevalent atrial fibrillation in men and women, respectively. In prospective analysis, this association remained stable in men (odds ratio (OR) 1.25, 1.07–1.44), while in women no association was observed (OR 1.03, 0.89–1.18).ConclusionsThe findings suggest that noise annoyance can increase the risk of incident atrial fibrillation in a large population-based cohort and that men may be more sensitive to the adverse effects of noise annoyance with regard to the risk of atrial fibrillation

The humanistic roots of Islamic administration and leadership for education : philosophical foundations for cross-cultural and transcultural teaching

For a number of decades, a humanistic approach has been a minor but persistent one in the Western field of administrative and leadership studies, and only recently has been broadening to include other humanist traditions (Dierksmeier et al., 2011) and has yet to be fully explored in educational administration and its pedagogy and curriculum although some foundational work has been done (e.g., Samier, 2005). The focus in this chapter is on the Islamic humanist tradition as it relates to the teaching of educational administration and leadership in a Muslim context, with implications for cross-cultural and transcultural use. The second purpose of the chapter is to show the correspondences that exist between the Islamic and Western humanist traditions in terms of human values, knowledge and educational ideal, which in this chapter are argued to be close to the Western Idealist tradition and the German Bildung conception of education as well as the strong interpretive and hermeneutic foundations that originated in the Islamic tradition and which influenced the foundations of many relevant European schools of thought, particularly in the Enlightenment.The initial section of the chapter is a comparative examination of the central principles of the Islamic humanist tradition from the classical through to contemporary times with the Western humanist tradition as they relate to conceptions of the good, ethics, the construction of meaning and a set of higher order values predicated upon human dignity, integrity, empathy, well-being, and the public good (Goodman, 2003) covering a number of important scholars like Al Farabi, al Isfanhani, and Edward Said (e.g., Kraemer, 1986). In both, professions are viewed as meaningful work that allow for large measures of decision making, and are grounded in human qualities and needs including autonomy, freedom and emancipation balanced with responsibilities, obligations and duties to society. These are compared with the corresponding principles of knowledge in Western humanism which includes a strong constructivist view of reality (Makdisi, 1990). Secondly, the chapter examines the principles of good or ideal leadership and administration that humanism aims at in its preparation of officials, including those in the educational sector in both the classical Islamic tradition (Hassi, 2012) and Western approaches to humanistic administration and leadership (Czarniawska-Joerges & Guillet de Monthoux, 1994; Gagliardi & Czarniawska, 2006; Leoussi, 2000). The third section focusses on close correspondences that exist between the Islamic (Afsaruddin, 2016; al-Attas, 1980; Yasin & Jani, 2013) and Western (Aloni, 2007; Veugelers, 2011) humanist education traditions in terms of educational ideal as well as the kind of teaching practices that distinguish these traditions (Daiber, 2013; Dossett, 2014) as they apply to educational administration and leadership (Greenfield & Ribbins, 1993). The chapter concludes with a discussion of how the Islamic humanist tradition can contribute to cross-cultural and transcultural graduate teaching in international educational administration (Khan & Amann, 2013)