6,042 research outputs found
J0316+4328: a Probable "Asymmetric Double" Lens
We report a probable gravitational lens J0316+4328, one of 19 candidate
asymmetric double lenses (2 images at a high flux density ratio) from CLASS.
Observations with the Very Large Array (VLA), MERLIN and the Very Long Baseline
Array (VLBA) imply that J0316+4328 is a lens with high confidence. It has 2
images separated by 0.40", with 6 GHz flux densities of 62 mJy and 3.2 mJy. The
flux density ratio of ~19 (constant over the frequency range 6-22 GHz) is the
largest for any 2 image gravitational lens. High resolution optical imaging and
deeper VLBI maps should confirm the lensing interpretation and provide inputs
to detailed lens models. The unique configuration will give strong constraints
on the lens galaxy's mass profile.Comment: Accepted to MNRAS Letters. 5 pages, 6 figures, 3 table
A multi-beam HI survey of the Virgo Cluster - two isolated HI clouds ?
We have carried out a fully sampled large area ()
21cm \HI line survey of part of the Virgo cluster using the Jodrell Bank
multi-beam instrument. The survey has a sensitivity some 3 times better than
the standard HIJASS and HIPASS surveys. We detect 31 galaxies, 27 of which are
well known cluster members. The four new detections have been confirmed in the
HIPASS data and by follow up Jodrell Bank pointed observations. One object lies
behind M86, but the other 3 have no obvious optical counter parts upon
inspection of the digital sky survey fields. These 3 objects were mapped at
Arecibo with a smaller \am{3}{6} HPBW and a 4 times better sensitivity than the
Jodrell Bank data, which allow an improved determination of the dimensions and
location of two of the objects, but surprisingly failed to detect the third.
The two objects are resolved by the Arecibo beam giving them a size far larger
than any optical images in the nearby field. To our mass limit of and column density limit of
atoms cm these new
detections represent only about 2% of the cluster atomic hydrogen mass. Our
observations indicate that the \HI mass function of the cluster turns down at
the low mass end making it very different to the field galaxy \HI mass
function. This is quite different to the Virgo cluster optical luminosity
function which is much steeper than that in the general field. Many of the
sample galaxies are relatively gas poor compared to \HI selected samples of
field galaxies, confirming the 'anaemic spirals' view of Virgo cluster late
type galaxies.Comment: Accepted for publication in MNRA
Demixing of aqueous polymer two-phase systems in low gravity
When polymers such as dextran and poly(ethylene glycol) are mixed in aqueous solution biphasic systems often form. On Earth the emulsion formed by mixing the phases rapidly demixes because of phase density differences. Biological materials can be purified by selective partitioning between the phases. In the case of cells and other particulates the efficiency of these separations appears to be somewhat compromised by the demixing process. To modify this process and to evaluate the potential of two-phase partitioning in space, experiments on the effects of gravity on phase emulsion demixing were undertaken. The behavior of phase systems with essentially identical phase densities was studied at one-g and during low-g parabolic aircraft maneuvers. The results indicate the demixing can occur rather rapidly in space, although more slowly than on Earth. The demixing process was examined from a theoretical standpoint by applying the theory of Ostwald ripening. This theory predicts demizing rates many orders of magnitude lower than observed. Other possible demixing mechanisms are considered
The geometry of thermodynamic control
A deeper understanding of nonequilibrium phenomena is needed to reveal the
principles governing natural and synthetic molecular machines. Recent work has
shown that when a thermodynamic system is driven from equilibrium then, in the
linear response regime, the space of controllable parameters has a Riemannian
geometry induced by a generalized friction tensor. We exploit this geometric
insight to construct closed-form expressions for minimal-dissipation protocols
for a particle diffusing in a one dimensional harmonic potential, where the
spring constant, inverse temperature, and trap location are adjusted
simultaneously. These optimal protocols are geodesics on the Riemannian
manifold, and reveal that this simple model has a surprisingly rich geometry.
We test these optimal protocols via a numerical implementation of the
Fokker-Planck equation and demonstrate that the friction tensor arises
naturally from a first order expansion in temporal derivatives of the control
parameters, without appealing directly to linear response theory
Faking and the Validity of Personality Tests: An Experimental Investigation Using Modern Forced Choice Measures
Despite the established validity of personality measures for personnel selection, their susceptibility to faking has been a persistent concern. However, the lack of studies that combine generalizability with experimental control makes it difficult to determine the effects of applicant faking. This study addressed this deficit in two ways. First, we compared a subtle incentive to fake with the explicit âfake-goodâ instructions used in most faking experiments. Second, we compared standard Likert scales to multidimensional forced choice (MFC) scales designed to resist deception, including more and less fakable versions of the same MFC inventory. MFC scales substantially reduced motivated score elevation but also appeared to elicit selective faking on work-relevant dimensions. Despite reducing the effectiveness of impression management attempts, MFC scales did not retain more validity than Likert scales when participants faked. However, results suggested that faking artificially bolstered the criterion-related validity of Likert scales while diminishing their construct validity
Children's biobehavioral reactivity to challenge predicts DNA methylation in adolescence and emerging adulthood.
A growing body of research has documented associations between adverse childhood environments and DNA methylation, highlighting epigenetic processes as potential mechanisms through which early external contexts influence health across the life course. The present study tested a complementary hypothesis: indicators of children's early internal, biological, and behavioral responses to stressful challenges may also be linked to stable patterns of DNA methylation later in life. Children's autonomic nervous system reactivity, temperament, and mental health symptoms were prospectively assessed from infancy through early childhood, and principal components analysis (PCA) was applied to derive composites of biological and behavioral reactivity. Buccal epithelial cells were collected from participants at 15 and 18Â years of age. Findings revealed an association between early life biobehavioral inhibition/disinhibition and DNA methylation across many genes. Notably, reactive, inhibited children were found to have decreased DNA methylation of the DLX5 and IGF2 genes at both time points, as compared to non-reactive, disinhibited children. Results of the present study are provisional but suggest that the gene's profile of DNA methylation may constitute a biomarker of normative or potentially pathological differences in reactivity. Overall, findings provide a foundation for future research to explore relations among epigenetic processes and differences in both individual-level biobehavioral risk and qualities of the early, external childhood environment
Pharmacological management of unipolar depression
Objective : To be used in conjunction with ‘Psychological management of unipolar depression’ [Lampe et al. Acta Psychiatr Scand 2013;127(Suppl. 443):24–37] and ‘Lifestyle management of unipolar depression’ [Berk et al. Acta Psychiatr Scand 2013;127(Suppl. 443):38–54]. To provide clinically relevant recommendations for the use of pharmacological treatments in depression derived from a literature review.Method : Using our previous Clinical Practice Guidelines [Malhi et al. Clinical practice recommendations for bipolar disorder. Acta Psychiatr Scand 2009;119(Suppl. 439):27–46] as a foundation, these clinician guidelines target key practical considerations when prescribing pharmacotherapy. A comprehensive review of the literature was conducted using electronic database searches (PubMed, MEDLINE), and the findings have been synthesized and integrated alongside clinical experience.Results : The pharmacotherapy of depression is an iterative process that often results in partial and non-response. Beyond the initiation of antidepressants, the options within widely used strategies, such as combining agents and switching between agents, are difficult to proscribe because of the paucity of pertinent research. However, there is some evidence for second-line strategies, and a non-prescriptive algorithm can be derived that is based broadly on principles rather than specific steps.Conclusion : Depression is by its very nature a heterogeneous illness that is consequently difficult to treat. Invariably, situation-specific factors often play a significant role and must be considered, especially in the case of partial and non-response. Consulting with colleagues and trialling alternate treatment paradigms are essential strategies in the management of depression
Transmission of High-Power Electron Beams Through Small Apertures
Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the
energy-recovery linac at the Jefferson Laboratory's FEL facility through a set
of small apertures in a 127 mm long aluminum block. Beam transmission losses of
3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour
continuous run.Comment: arXiv admin note: text overlap with arXiv:1305.019
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