5,315 research outputs found

    Thermal disequilibration of ions and electrons by collisionless plasma turbulence

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    Does overall thermal equilibrium exist between ions and electrons in a weakly collisional, magnetised, turbulent plasma---and, if not, how is thermal energy partitioned between ions and electrons? This is a fundamental question in plasma physics, the answer to which is also crucial for predicting the properties of far-distant astronomical objects such as accretion discs around black holes. In the context of discs, this question was posed nearly two decades ago and has since generated a sizeable literature. Here we provide the answer for the case in which energy is injected into the plasma via Alfv\'enic turbulence: collisionless turbulent heating typically acts to disequilibrate the ion and electron temperatures. Numerical simulations using a hybrid fluid-gyrokinetic model indicate that the ion-electron heating-rate ratio is an increasing function of the thermal-to-magnetic energy ratio, βi\beta_\mathrm{i}: it ranges from ∼0.05\sim0.05 at βi=0.1\beta_\mathrm{i}=0.1 to at least 3030 for βi≳10\beta_\mathrm{i} \gtrsim 10. This energy partition is approximately insensitive to the ion-to-electron temperature ratio Ti/TeT_\mathrm{i}/T_\mathrm{e}. Thus, in the absence of other equilibrating mechanisms, a collisionless plasma system heated via Alfv\'enic turbulence will tend towards a nonequilibrium state in which one of the species is significantly hotter than the other, viz., hotter ions at high βi\beta_\mathrm{i}, hotter electrons at low βi\beta_\mathrm{i}. Spectra of electromagnetic fields and the ion distribution function in 5D phase space exhibit an interesting new magnetically dominated regime at high βi\beta_i and a tendency for the ion heating to be mediated by nonlinear phase mixing ("entropy cascade") when βi≲1\beta_\mathrm{i}\lesssim1 and by linear phase mixing (Landau damping) when $\beta_\mathrm{i}\gg1

    The Organizational Evolution of Markets for Wood Products in the Southern United States

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    This paper represents the first case study attempt to develop a transaction cost conceptual model to describe industry evolution of the paper and lumber industries in the Southern United States around the late 1800s and early 1900s. We use transaction cost theory to explain the co-evolution of markets for wood products noting that variation in the level and type of investments made in physical and human capital assets needed to manage paper and lumber miller operations had a significant influence on the use of wood dealer systems compared to more vertically organized business arrangements. We identify some testable hypotheses and areas of future research.Industry Evolution, Contracting, Property Rights, Vertical Integration, Forest Products, Industrial Organization, Research Methods/ Statistical Methods, L14, L24, L73, J24,

    An Examination of Financial Literacy Levels Amongst Owner/Managers of Small and Medium-Sized Enterprises

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    To date there has been limited research focusing on the financial literacy of small and medium business sized business. This research looks specifically at the level of financial literacy among small business owners/mangers within an Australian context. The purposes of the hypotheses are to understand the relationship between the financial literacy of the owners/managers of small businesses against both their demographic and company characteristics. More specifically, the key research question investigated in this study is: what is the level of financial literacy among small business owners/managers, and what are the determinants of the level of literacy The research has significant implications for small business, as the reason given for many small business failures relates to the financial ability of owners/managers. Therefore, the research should provide consequential information to industry-groups, small businesses, financial institutions and policy makers. The literature review defines financial literacy and small business and looks at the literature to date with respect to the relevant hypotheses. The methodology for the dissertation will exploratory and quantitative in nature and will use a multiple choice questionnaire for a survey into business in Australia. The sampling frame will consist of professional members of the Australian Institute of Management. The findings show that overall financial literacy can improve for SME owner managers, and that education in particular can assist to increase overall financial literacy

    Stellar rotation, binarity, and lithium in the open cluster IC4756

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    An important aspect in the evolutionary scenario of cool stars is their rotation and the rotationally induced magnetic activity and interior mixing. Stars in open clusters are particularly useful tracers for these aspects because of their known ages. We aim to characterize the open cluster IC4756 and measure stellar rotation periods and surface differential rotation for a sample of its member stars. Thirty-seven cluster stars were observed continuously with the CoRoT satellite for 78 days in 2010. Follow-up high-resolution spectroscopy of the CoRoT targets and deep Str\"omgren uvbyβuvby\beta and Hα\alpha photometry of the entire cluster were obtained with our robotic STELLA facility and its echelle spectrograph and wide-field imager, respectively. We determined high-precision photometric periods for 27 of the 37 CoRoT targets and found values between 0.155 and 11.4 days. Twenty of these are rotation periods. Twelve targets are spectroscopic binaries of which 11 were previously unknown; orbits are given for six of them. Six targets were found that show evidence of differential rotation with ΔΩ/Ω\Delta\Omega/\Omega in the range 0.04-0.15. Five stars are non-radially pulsating stars with fundamental periods of below 1d, two stars are semi-contact binaries, and one target is a micro-flaring star that also shows rotational modulation. Nine stars in total were not considered members because of much redder color(s) and deviant radial velocities with respect to the cluster mean. Hα\alpha photometry indicates that the cluster ensemble does not contain magnetically over-active stars. The cluster average metallicity is -0.08±\pm0.06 (rms) and its logarithmic lithium abundance for 12 G-dwarf stars is 2.39±\pm0.17 (rms). [...]Comment: A&A, in pres

    Juvenile Rainbow Trout Responses to Diets Containing Distillers Dried Grain with Solubles, Phytase, and Amino Acid Supplements

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    Distillers dried grain with solubles (DDGS) was evaluated in juvenile Shasta-strain rainbow trout Oncorhynchus mykiss diets during a 36-day feeding trial. Two experimental diets containing either 10% or 20% DDGS with supplemented amino acids (lysine, methionine, isoleucine, and histidine) and phytase were compared to a fish meal-only control diet. Tanks of trout receiving diets containing either concentration of DDGS weighed significantly less at the end of the trial and had significantly poorer feed conversion ratios than tanks of fish being fed the fish mealonly control. There was no significant difference in individual fish length, weight, condition factor, or any fish health measurements among diet treatments. Both the hepatosomatic index and viscerosomatic index were significantly less in the fish fed 10% DDGS than those fed the control diet. Body fat was significantly greater in the fish receiving 20% DDGS compared to fish fed either of the other two diets. Fillet composition, as determined by crude protein, crude lipid, ash, and water, was not significantly different among fish reared on any of the diets. There was also no significant difference in estimated protein digestibility coefficients among fish receiving any of the diets. The results suggest that DDGS, even if supplemented with essential amino acids and phytase, will lead to decreased juvenile rainbow trout growth at dietary concentrations of at 10% or greater

    A Bayesian method to incorporate hundreds of functional characteristics with association evidence to improve variant prioritization

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    The increasing quantity and quality of functional genomic information motivate the assessment and integration of these data with association data, including data originating from genome-wide association studies (GWAS). We used previously described GWAS signals ("hits") to train a regularized logistic model in order to predict SNP causality on the basis of a large multivariate functional dataset. We show how this model can be used to derive Bayes factors for integrating functional and association data into a combined Bayesian analysis. Functional characteristics were obtained from the Encyclopedia of DNA Elements (ENCODE), from published expression quantitative trait loci (eQTL), and from other sources of genome-wide characteristics. We trained the model using all GWAS signals combined, and also using phenotype specific signals for autoimmune, brain-related, cancer, and cardiovascular disorders. The non-phenotype specific and the autoimmune GWAS signals gave the most reliable results. We found SNPs with higher probabilities of causality from functional characteristics showed an enrichment of more significant p-values compared to all GWAS SNPs in three large GWAS studies of complex traits. We investigated the ability of our Bayesian method to improve the identification of true causal signals in a psoriasis GWAS dataset and found that combining functional data with association data improves the ability to prioritise novel hits. We used the predictions from the penalized logistic regression model to calculate Bayes factors relating to functional characteristics and supply these online alongside resources to integrate these data with association data

    4-Chloroacetophenone [1-(4-Methoxyphenyl)ethylidene]Hydrazone

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    The crystal structure of the title mixed azine, C17H17CIN2O, contains four independent molecules, A-D, and molecule B is disordered. All four molecules have an N-N gauche conformation, with C-N-N-C torsion angles of 136.5 (4), 137.0 (4), -134.7 (4) and -134.7 (4)°, respectively. The phenyl rings are also somewhat twisted with respect to the plane defined by Cipso and the imine bond. On average, the combined effect of these twists results in an angle of 64.7° between the best planes of the two phenyl rings. Arene-arene double T-contacts are the dominant intermolecular interaction. The methoxy-substituted phenyl ring of one azine molecule interacts to form a T-contact with the methoxy-substituted phenyl ring of an adjacent molecule and, similarly, two chloro-substituted phenyl rings of neighboring molecules interact to form another T-contact. The only exception is for molecule B, for which the disorder leads to the formation of T-contacts between methoxy- and chloro-substituted phenyl rings. The prevailing structural motif of T-contact formation between like-substituted arene rings results in a highly dipole-parallel-aligned crystal structure

    BB Intermeson Potentials in the Quark Model

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    In this paper we derive quark model results for scattering amplitudes and equivalent low energy potentials for heavy meson pairs, in which each meson contains a heavy quark. This "BB" system is an attractive theoretical laboratory for the study of the nuclear force between color singlets; the hadronic system is relatively simple, and there are lattice gauge theory (LGT) results for V_BB(r) which may be compared to phenomenological models. We find that the quark model potential (after lattice smearing) has qualitative similarities to the LGT potential in the two B*B* channels in which direct comparison is possible, although there is evidence of a difference in length scales. The quark model prediction of equal magnitude but opposite sign for I=0 and I=1 potentials also appears similar to LGT results at intermediate r. There may however be a discrepancy between the LGT and quark model I=1 BB potentials. A numerical study of the two-meson Schrodinger equations in the (bqbar)(bqbar) and (cqbar)(cqbar) sectors with the quark model potentials finds a single "molecule", in the I=0 BB* sector. Binding in other channels might occur if the quark model forces are augmented by pion exchange.Comment: 30 pages, 5 figures, revtex and epsfig. Submitted to Phys. Rev.

    The Selberg trace formula for Dirac operators

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    We examine spectra of Dirac operators on compact hyperbolic surfaces. Particular attention is devoted to symmetry considerations, leading to non-trivial multiplicities of eigenvalues. The relation to spectra of Maass-Laplace operators is also exploited. Our main result is a Selberg trace formula for Dirac operators on hyperbolic surfaces

    4-Methoxybenzaldehyde Pentafluorophenyl-Methylidenehydrazone

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    The crystal structure of the mixed azine C15H9F5N2O is described. The molecule has a high degree of planarity. The two phenyl rings deviate from perfect planarity by less than 2° and the dihedral angles between the ipso-C atoms and the azine bridge also show a minute deviation from planarity of less than 2°. The only dihedral angle that indicates any significant twisting is the dihedral angle about the azine bridge [C1-N1-N2-C8 174.8 (6)°], and even this one is relatively small. Face-to-face arene-arene contacts are the dominant intermolecular interactions. There are double face-to-face contacts in which the two phenyl rings of one mixed azine interact with the two phenyl rings of another mixed azine. There are also single face-to-face contacts where one phenyl ring of one mixed azine interacts with a phenyl ring of another mixed azine. In the double face-to-face arene-arene contacts, the pentafluorinated phenyl ring of one mixed azine always interacts with the methoxy-substituted phenyl ring of another mixed azine. In the single face-to-face arene-arene contacts, the interactions are always between two pentafluorinated phenyl rings or two methoxy-substituted phenyl rings
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