1,305 research outputs found

    Models of OH Maser Variations in U Her

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    Arecibo spectra of the mainline OH maser emission from U Her over more than a decade show variations of the OH emission over these time scales. These observations are combined with high spatial resolution VLBA maps to investigate the causes of the variations in the velocities of the maser components. Global properties of the dust shell, such as accelerations, variations in the pump and shell-wide magnetic field changes are examined as possibilities, and eliminated. A possible solution to the problem involving plasma turbulence and the local magnetic field is introduced, and the relevant time scales of the turbulence are calculated. The turbulent velocity field yields time scales of the turbulence are calculated. The turbulent velocity field yields time scales that are too long (of order centuries), while the turbulent magnetic field produces variations on appropriate time scales of a few years. A line-of-sight model of the turbulence is developed and investigated. The complete exploration of this solution requires extensive theoretical and observational work. Possible avenues of investigation of the plasma turbulence model are presented.Comment: 23 pages, 17 figures, ApJ: accepted Sept, 199

    The mineral nutrients in blue-grass

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    Tunable dipolar magnetism in high-spin molecular clusters

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    We report on the Fe17 high-spin molecular cluster and show that this system is an exemplification of nanostructured dipolar magnetism. Each Fe17 molecule, with spin S=35/2 and axial anisotropy as small as D=-0.02K, is the magnetic unit that can be chemically arranged in different packing crystals whilst preserving both spin ground-state and anisotropy. For every configuration, molecular spins are correlated only by dipolar interactions. The ensuing interplay between dipolar energy and anisotropy gives rise to macroscopic behaviors ranging from superparamagnetism to long-range magnetic order at temperatures below 1K.Comment: Replaced with version accepted for publication in Physical Review Letter

    Evaluating the Pennebaker Paradigm with Bereaved Emerging Adults: Applications of Text Analysis

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    Bereavement is an important research area as it can result in grief reactions that lead to serious psychological and health consequences, particularly for the at-risk group of emerging adults (Arnett, 2000; Balk, Walker, & Baker, 2010; Fisher, Murray, & Frazer, 1985; Stroebe, Schut, & Stroebe, 2007). Expressive writing is a well-researched intervention for trauma and adjustment, yet research repeatedly has revealed null results with the classic Pennebaker paradigm as a bereavement intervention (Stroebe et al., 2002; Stroebe, Schut, & Stroebe, 2006). It may be premature, however, to conclude expressive writing is ineffective for the bereaved due to limitations in extant research. For example, Pennebaker’s paradigm is based on the premise that participants freely choose the stressful topic to write about, whereas expressive writing bereavement studies have required participants to write about their loss (Collison & Gramling, manuscript in preparation). The present study reports on data from a larger study (Konig, Eonta, Dyal, & Vrana, 2014; N=246) that assessed psychological and physiological outcomes in college students who wrote about a traumatic stressor using Pennebaker’s paradigm. This provided the opportunity to rigorously test it with bereavement and compare death loss to other forms of trauma. Analyses examined the impact of expressive writing with the bereaved who freely identified death loss as the traumatic stressor (n=69) and were randomly assigned to either emotional disclosure or control writing on outcome measures of physical symptoms (PILL), event-related distress (DTS), and depression (CES-D). Linguistic Inquiry and Word Count (LIWC; Pennebaker, Mayne, & Francis, 1997) and Latent Semantic Analysis (LSA; Campbell & Pennebaker, 2003) results were also used to compare these groups. Exploratory analyses investigated potential differences between the bereaved and those who endorsed a non-bereavement trauma (“other trauma”; n=71) using outcome measures and text analytic techniques (i.e., PILL, DTS, CES-D; LIWC, LSA). Results were consistent with findings from previous expressive writing studies with the bereaved, in that the intervention resulted in no detectable benefits when compared with control writing. No remarkable differences between the bereaved and “other trauma” participants emerged. Researchers’ time may be better spent examining more clinically relevant writing exercises for bereavement interventions

    Legal determinants of external finance revisited : the inverse relationship between investor protection and societal well-being

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    This paper investigates relationships between corporate governance traditions and quality of life as measured by a number of widely reported indicators. It provides an empirical analysis of indicators of societal health in developed economies using a classification based on legal traditions. Arguably the most widely cited work in the corporate governance literature has been the collection of papers by La Porta et al. which has shown, inter alia, statistically significant relationships between legal traditions and various proxies for investor protection. We show statistically significant relationships between legal traditions and various proxies for societal health. Our comparative evidence suggests that the interests of investors may not be congruent with the interests of wider society, and that the criteria for judging the effectiveness of approaches to corporate governance should not be restricted to financial metrics

    Associations of body mass index, physical activity and sedentary time with blood pressure in primary school children from south-west England: a prospective study

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    Elevated blood pressure in children is a significant risk factor for the development of cardiovascular disease in adulthood. We examined how children's body mass index (BMI), physical activity and sedentary time at ages 9 and 11 are associated with blood pressure at age 11. Data were from 1283 children from Bristol, UK, who participated in the study aged 11 years, 797 of whom also participated in the study aged 9 years. Child height, weight and blood pressure were measured, and children wore accelerometers for five days, from which moderate-to-vigorous-intensity physical activity and sedentary minutes per day were derived. Multiple imputation of missing data and adjusted linear and logistic regression models were used to examine associations. Child BMI at 11 years was cross-sectionally associated with higher systolic and diastolic blood pressure (mean difference [95% confidence interval]: 0.91 [0.32 to 1.50] mm Hg and 1.08 [0.54 to 1.62] mm Hg, respectively, per standard deviation (SD) of BMI). BMI at age 9 was also positively associated with diastolic blood pressure at age 11 (1.16 mmHg per two years [0.49 to 1.84], per SD of BMI). For girls, sedentary time at age 9 years was associated with increased odds of having high systolic blood pressure at age 11 (odds ratio: 1.08 [1.01 to 1.16], per 10 minutes per day). There was no evidence of associations between sedentary time and blood pressure among boys. Similarly, there was little evidence that physical activity was associated with blood pressure in either cross-sectional or prospective analyses. Effective strategies are needed to prevent excess bodyweight among children in order to reduce cardiovascular disease risk

    Modelling Conformational Flexibility in a Spectrally Addressable Molecular Multi-Qubit Model System

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    Dipolar coupled multi-spin systems have the potential to be used as molecular qubits. Herein we report the synthesis of a molecular multi-qubit model system with three individually addressable, weakly interacting, spin (Formula presented.) centres of differing g-values. We use pulsed Electron Paramagnetic Resonance (EPR) techniques to characterise and separately address the individual electron spin qubits; CuII, Cr7Ni ring and a nitroxide, to determine the strength of the inter-qubit dipolar interaction. Orientation selective Relaxation-Induced Dipolar Modulation Enhancement (os-RIDME) detecting across the CuII spectrum revealed a strongly correlated CuII-Cr7Ni ring relationship; detecting on the nitroxide resonance measured both the nitroxide and CuII or nitroxide and Cr7Ni ring correlations, with switchability of the interaction based on differing relaxation dynamics, indicating a handle for implementing EPR-based quantum information processing (QIP) algorithms
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