520 research outputs found

    Large-Scale Structure at z~2.5

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    We have made a statistically complete, unbiased survey of C IV systems toward a region of high QSO density near the South Galactic Pole using 25 lines of sight spanning 1.5<z<2.81.5<z<2.8. Such a survey makes an excellent probe of large-scale structure at early epochs. We find evidence for structure on the 1535h115-35h^{-1} proper Mpc scale (H0100H_0 \equiv 100 km s1s^{-1} Mpc1{-1}) as determined by the two point C IV - C IV absorber correlation function, and reject the null hypothesis that C IV systems are distributed randomly on such scales at the 3.5σ\sim 3.5\sigma level. The structure likely reflects the distance between two groups of absorbers subtending  13×5×21h3\sim~ 13 \times 5 \times 21h^{-3} and 7×1×15h3\sim 7 \times 1 \times 15h^{-3} Mpc3^3 at z2.3z\sim 2.3 and z2.5z \sim 2.5 respectively. There is also a marginal trend for the association of high rest equivalent width C IV absorbers and QSOs at similar redshifts but along different lines of sight. The total number of C IV systems detected is consistent with that which would be expected based on a survey using many widely separated lines of sight. Using the same data, we also find 11 Mg II absorbers in a complete survey toward 24 lines of sight; there is no evidence for Mg II - Mg II or Mg II - QSO clustering, though the sample size is likely still small to detect such structure if it exists.Comment: 56 pages including 32 of figures, in gzip-ed uuencoded postscript format, 1 long table not included, aastex4 package. Accepted for publication in ApJ Supplement

    On metal and ‘spoiled’ wine: analysing psimythion (synthetic cerussite) pellets (5th-3rd centuries BCE) and hypothesising gas-metal reactions over a fermenting liquid within a Greek pot

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    A Pb-based synthetic mineral referred to as psimythion (pl. psimythia) was manufactured in the Greek world at least since the 6th c BCE and routinely by the 4th c BCE. Theophrastus (On Stones, 56) describes its preparation from metallic Pb suspended over a fermenting liquid. Psimythion is considered the precursor of one of western art’s most prominent white pigments, i.e. lead white (basic lead carbonate or synthetic hydrocerussite). However, so far, and for that early period, published analyses of psimythia suggest that they consisted primarily of synthetic cerussite. In this paper, we set out to investigate how it was possible to manufacture pure cerussite, to the near exclusion of other phases. We examined the chemical and mineralogical composition (pXRF/XRD) of a small number of psimythion pellets found within ceramic pots (pyxis) from Athens and Boeotia (5th–4th c BCE) in the collection of the National Archaeological Museum (NAM), Athens. Analyses showed that the NAM pellets consisted primarily of Pb/cerussite with small amounts of Ca (some samples) and a host of metallic trace elements. We highlight the reference in the Theophrastus text to ‘spoiled wine’ (oxos), rather than ‘vinegar’, as has been previously assumed, the former including a strong biotic component. We carried out DNA sequencing of the pellets in an attempt to establish presence of microorganisms (Acetic Acid Bacteria). None was found. Subsequently, and as a working hypothesis, we propose a series of (biotic/abiotic) reactions which were likely to have taken place in the liquid and vapour phases and on the metal surface. The hypothesis aims to demonstrate that CO2 would be microbially induced and would increase, as a function of time, resulting in cerussite forming over and above hydrocerussite/other Pb-rich phases. Psimythion has for long been valued as a white pigment. What has perhaps been not adequately appreciated is the depth of empirical understanding from the part of psimythion manufacturers of the reactions between abiotic and biotic components within ‘oxos’/pot, as key drivers of minerals synthesis. Ultimately, psimythion manufacture may rest in understanding the nature of ‘oxos’, antiquity’s relatively little researched strongest acid

    Coherent information analysis of quantum channels in simple quantum systems

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    The coherent information concept is used to analyze a variety of simple quantum systems. Coherent information was calculated for the information decay in a two-level atom in the presence of an external resonant field, for the information exchange between two coupled two-level atoms, and for the information transfer from a two-level atom to another atom and to a photon field. The coherent information is shown to be equal to zero for all full-measurement procedures, but it completely retains its original value for quantum duplication. Transmission of information from one open subsystem to another one in the entire closed system is analyzed to learn quantum information about the forbidden atomic transition via a dipole active transition of the same atom. It is argued that coherent information can be used effectively to quantify the information channels in physical systems where quantum coherence plays an important role.Comment: 24 pages, 7 figs; Final versiob after minor changes, title changed; to be published in Phys. Rev. A, September 200

    The Deformable Universe

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    The concept of smooth deformations of a Riemannian manifolds, recently evidenced by the solution of the Poincar\'e conjecture, is applied to Einstein's gravitational theory and in particular to the standard FLRW cosmology. We present a brief review of the deformation of Riemannian geometry, showing how such deformations can be derived from the Einstein-Hilbert dynamical principle. We show that such deformations of space-times of general relativity produce observable effects that can be measured by four-dimensional observers. In the case of the FLRW cosmology, one such observable effect is shown to be consistent with the accelerated expansion of the universe.Comment: 20 pages, LaTeX, 3 figure

    Improved Parton Showers at Large Transverse Momenta

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    Several methods to improve the parton-shower description of hard processes by an injection of matrix-element-based information have been presented over the years. In this article we study (re)weighting schemes for the first/hardest emission. One objective is to provide a consistent matching of the POWHEG next-to-leading order generator to the Pythia shower algorithms. Another is to correct the default behaviour of these showers at large transverse momenta, based on a comparison with real-emission matrix elements

    Long-Term Outcomes of the Benefit-Finding Group Intervention for Alzheimer Family Caregivers: A Cluster-Randomized Double-Blind Controlled Trial

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    Objectives To examine the effects of the group benefit-finding intervention (BFT) for Alzheimer family caregivers up to 10-month follow-up. Design Cluster-randomized double-blind controlled trial. Setting Social centers and clinics. Participants 129 caregivers. Inclusion criteria were (a) primary caregiver aged 18+ and without cognitive impairment, (b) providing ≥14 care hours per week to a relative with mild-to-moderate Alzheimer's disease, and (c) scoring ≥3 on the Hamilton Depression Rating Scale. Exclusion criterion was care-recipient having parkinsonism or other forms of dementia. Interventions BFT (using cognitive reappraisal to find positive meanings) was evaluated against two forms of psychoeducation as controls—standard (STD-PE) and simplified (lectures only; SIM-PE) psychoeducation. All interventions had eight weekly sessions of 2 hours each. Measurements Primary outcome was depressive symptom, whereas secondary outcomes were global burden, role overload, and psychological well-being. Measures were collected at baseline, post-intervention, and 4- and 10-month follow-up. Results Mixed-effects regression showed that BFT's effect on depressive symptoms conformed to a curvilinear pattern, in which the strong initial effect leveled out after post-intervention and was maintained up to 10-month follow-up; this was true when compared against either control group. The effect on global burden was less impressive but moderate effect sizes were found at the two follow-ups. For psychological well-being, there was an increase in the BFT group at 4-month follow-up and a return to baseline afterwards. No effect on role overload was found. Conclusions Benefit-finding reduces depressive symptoms as well as global burden in the long-term, and increases psychological well-being in the medium-term

    Solar Wind Turbulence and the Role of Ion Instabilities

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    Detecting non-binomial sex allocation when developmental mortality operates

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    Optimal sex allocation theory is one of the most intricately developed areas of evolutionary ecology. Under a range of conditions, particularly under population sub-division, selection favours sex being allocated to offspring non-randomly, generating non-binomial variances of offspring group sex ratios. Detecting non-binomial sex allocation is complicated by stochastic developmental mortality, as offspring sex can often only be identified on maturity with the sex of non-maturing offspring remaining unknown. We show that current approaches for detecting non-binomiality have limited ability to detect non-binomial sex allocation when developmental mortality has occurred. We present a new procedure using an explicit model of sex allocation and mortality and develop a Bayesian model selection approach (available as an R package). We use the double and multiplicative binomial distributions to model over- and under-dispersed sex allocation and show how to calculate Bayes factors for comparing these alternative models to the null hypothesis of binomial sex allocation. The ability to detect non-binomial sex allocation is greatly increased, particularly in cases where mortality is common. The use of Bayesian methods allows for the quantification of the evidence in favour of each hypothesis, and our modelling approach provides an improved descriptive capability over existing approaches. We use a simulation study to situations where current methods fail, and we illustrate the approach in real scenarios using empirically obtained datasets on the sexual composition of groups of gregarious parasitoid wasps demonstrate substantial improvements in power for detecting non-binomial sex allocation in situations where current methods fail, and we illustrate the approach in real scenarios using empirically obtained datasets on the sexual composition of groups of gregarious parasitoid wasps
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