Discovery of a 3.6-hr Eclipsing Luminous X-Ray Binary in the Galaxy NGC 4214

We report the discovery of an eclipsing X-ray binary with a 3.62-hr period within 24" of the center of the dwarf starburst galaxy NGC 4214. The orbital period places interesting constraints on the nature of the binary, and allows for a few very different interpretations. The most likely possibility is that the source lies within NGC 4214 and has an X-ray luminosity of up to 7 e38 ergs/s. In this case the binary may well be comprised of a naked He-burning donor star with a neutron-star accretor, though a stellar-mass black-hole accretor cannot be completely excluded. There is no obvious evidence for a strong stellar wind in the X-ray orbital light curve that would be expected from a massive He star; thus, the mass of the He star should be <3-4 solar masses. If correct, this would represent a new class of very luminous X-ray binary -- perhaps related to Cyg X-3. Other less likely possibilities include a conventional low-mass X-ray binary that somehow manages to produce such a high X-ray luminosity and is apparently persistent over an interval of years; or a foreground AM Her binary of much lower luminosity that fortuitously lies in the direction of NGC 4214. Any model for this system must accommodate the lack of an optical counterpart down to a limiting magnitude of 22.6 in the visible.Comment: 7 pages, ApJ accepted versio

Field assessment of sediment trap efficiency under varying flow conditions

Knowledge of the collection efficiency of sediment traps, particularly under conditions of varying current speed, is presently more a matter of hope than confidence. We report here on a field experiment designed to determine, for a particular trap geometry, the effect of current speed and particle fall velocity on the collection efficiency of a moored trap relative to the presumably unbiased efficiency of an identical drifting trap. The experiment was performed in a deep estuarine tidal passage where a smoothly varying unidirectional flow and a spatially homogenous particle population mimicked laboratory flume conditions. A multiple-sample sediment trap integrated to a current meter partitioned the mass flux collected by the moored trap into one of four chambers according to the following speed intervals: \u3c12, 12–\u3c30, 30–\u3c50, and ≥50cm/s. The magnitude and particle characteristics of the flux collected at \u3c12 cm/s were indistinguishable from those simultaneously collected by drifting traps. At higher speeds, the relative efficiency of the moored trap ranged between 1% and 24% and the mean size and density of the trapped particles increased. These results support predictions based on laboratory studies that collection efficiency decreases with an increase in the trap Reynolds number or a decrease in particle fall velocity. The study demonstrates that consideration must be given to scaling both trap diameter and aspect ratio according to the expected flow conditions, and that knowledge of flow conditions at the trap mouth is necessary to properly interpret the flux data

A Hybrid Sequencing Approach Completes the Genome Sequence of Thermoanaerobacter ethanolicus JW 200

Thermoanaerobacter ethanolicus JW 200 has been identified as a potential sustainable biofuel producer due to its ability to readily ferment carbohydrates to ethanol. A hybrid sequencing approach, combining Oxford Nanopore and Illumina DNA sequence reads, was applied to produce a single contiguous genome sequence of 2,911,280 bp

Utilizing Monte Carlo Simulations to Optimize Institutional Empiric Antipseudomonal Therapy

Pseudomonas aeruginosa is a common pathogen implicated in nosocomial infections with increasing resistance to a limited arsenal of antibiotics. Monte Carlo simulation provides antimicrobial stewardship teams with an additional tool to guide empiric therapy. We modeled empiric therapies with antipseudomonal β-lactam antibiotic regimens to determine which were most likely to achieve probability of target attainment (PTA) of ≥90%. Microbiological data for P. aeruginosa was reviewed for 2012. Antibiotics modeled for intermittent and prolonged infusion were aztreonam, cefepime, meropenem, and piperacillin/tazobactam. Using minimum inhibitory concentrations (MICs) from institution-specific isolates, and pharmacokinetic and pharmacodynamic parameters from previously published studies, a 10,000-subject Monte Carlo simulation was performed for each regimen to determine PTA. MICs from 272 isolates were included in this analysis. No intermittent infusion regimens achieved PTA ≥90%. Prolonged infusions of cefepime 2000 mg Q8 h, meropenem 1000 mg Q8 h, and meropenem 2000 mg Q8 h demonstrated PTA of 93%, 92%, and 100%, respectively. Prolonged infusions of piperacillin/tazobactam 4.5 g Q6 h and aztreonam 2 g Q8 h failed to achieved PTA ≥90% but demonstrated PTA of 81% and 73%, respectively. Standard doses of β-lactam antibiotics as intermittent infusion did not achieve 90% PTA against P. aeruginosa isolated at our institution; however, some prolonged infusions were able to achieve these targets

Direct observation of the Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point

Spontaneous symmetry-breaking quantum phase transitions play an essential role in condensed matter physics. The collective excitations in the broken-symmetry phase near the quantum critical point can be characterized by fluctuations of phase and amplitude of the order parameter. The phase oscillations correspond to the massless Nambu$-$Goldstone modes whereas the massive amplitude mode, analogous to the Higgs boson in particle physics, is prone to decay into a pair of low-energy Nambu$-$Goldstone modes in low dimensions. Especially, observation of a Higgs amplitude mode in two dimensions is an outstanding experimental challenge. Here, using the inelastic neutron scattering and applying the bond-operator theory, we directly and unambiguously identify the Higgs amplitude mode in a two-dimensional S=1/2 quantum antiferromagnet C$_9$H$_{18}$N$_2$CuBr$_4$ near a quantum critical point in two dimensions. Owing to an anisotropic energy gap, it kinematically prevents such decay and the Higgs amplitude mode acquires an infinite lifetime.Comment: 12 pages, 4 figures in the main text+3 figures in Supplementary Informatio

Prevalence, treatment and correlates of depression in multiple sclerosis

BackgroundThe prevalence of depression in Multiple Sclerosis (MS) is often assessed by administering patient reported outcome measures (PROMs) examining depressive symptomatology to population cohorts; a recent review summarised 12 such studies, eight of which used the Hospital Anxiety and Depression Scale-Depression (HADS-D). In clinical practice, depression is diagnosed by an individual structured clinical interview; diagnosis often leads to treatment options including antidepressant medication. It follows that an MS population will include those whose current depressive symptoms meet threshold for depression diagnosis, plus those who previously met diagnostic criteria for depression and have been treated such that depressive symptoms have improved below that threshold. We examined a large MS population to establish a multi-attribute estimate of depression, taking into account probable depression on HADS-D, as well as anti-depressant medication use and co-morbidity data reporting current treatment for depression. We then studied associations with demographic and health status measures and the trajectories of depressive symptoms over time.MethodsParticipants were recruited into the UK-wide Trajectories of Outcome in Neurological Conditions-MS (TONiC-MS) study, with demographic and disease data from clinical records, PROMs collected at intervals of at least 9 months, as well as co-morbidities and medication. Interval level conversions of PROM data followed Rasch analysis. Logistic regression examined associations of demographic characteristics and symptoms with depression. Finally, a group-based trajectory model was applied to those with depression.ResultsBaseline data in 5633 participants showed the prevalence of depression to be 25.3% (CI: 24.2-26.5). There were significant differences in prevalence by MS subtype: relapsing 23.2% (CI: 21.8- 24.5), primary progressive 25.8% (CI: 22.5-29.3), secondary progressive 31.5% (CI: 29.0-34.0); disability: EDSS 0-4 19.2% (CI: 17.8-20.6), EDSS ≥4.5 31.9% (CI: 30.2-33.6); and age: 42-57 years 27.7% (CI: 26.0-29.3), above or below this range 23.1% (CI: 21.6-24.7). Fatigue, disability, self-efficacy and self esteem correlated with depression with a large effect size (&gt;.8) whereas sleep, spasticity pain, vision and bladder had an effect size &gt;.5. The logistic regression model (N=4938) correctly classified 80% with 93% specificity: risk of depression was increased with disability, fatigue, anxiety, more comorbidities or current smoking. Higher self-efficacy or self esteem and marriage reduced depression. Trajectory analysis of depressive symptoms over 40 months in those with depression (N=1096) showed three groups: 19.1% with low symptoms, 49.2% with greater symptoms between the threshold of possible and probable depression, and 31.7% with high depressive symptoms. 29.9% (CI: 27.6-32.3) of depressed subjects were untreated, conversely of those treated, 26.1% still had a symptom level consistent with a probable case (CI: 23.5-28.9).ConclusionA multi-attribute estimate of depression in MS is essential because using only screening questionnaires, diagnoses or antidepressant medication all under-estimate the true prevalence. Depression affects 25.3% of those with MS, almost half of those with depression were either untreated or still had symptoms indicating probable depression despite treatment. Services for depression in MS must be pro-active and flexible, recognising the heterogeneity of outcomes and reaching out to those with ongoing symptoms

Induction of the nicotinamide riboside kinase NAD⁺ salvage pathway in a model of sarcoplasmic reticulum dysfunction

Background Hexose-6-Phosphate Dehydrogenase (H6PD) is a generator of NADPH in the Endoplasmic/Sarcoplasmic Reticulum (ER/SR). Interaction of H6PD with 11 beta-hydroxysteroid dehydrogenase type 1 provides NADPH to support oxo-reduction of inactive to active glucocorticoids, but the wider understanding of H6PD in ER/SR NAD(P)(H) homeostasis is incomplete. Lack of H6PD results in a deteriorating skeletal myopathy, altered glucose homeostasis, ER stress and activation of the unfolded protein response. Here we further assess muscle responses to H6PD deficiency to delineate pathways that may underpin myopathy and link SR redox status to muscle wide metabolic adaptation. Methods We analysed skeletal muscle from H6PD knockout (H6PDKO), H6PD and NRK2 double knockout (DKO) and wild-type (WT) mice. H6PDKO mice were supplemented with the NAD(+) precursor nicotinamide riboside. Skeletal muscle samples were subjected to biochemical analysis including NAD(H) measurement, LC-MS based metabolomics, Western blotting, and high resolution mitochondrial respirometry. Genetic and supplement models were assessed for degree of myopathy compared to H6PDKO. Results H6PDKO skeletal muscle showed adaptations in the routes regulating nicotinamide and NAD(+) biosynthesis, with significant activation of the Nicotinamide Riboside Kinase 2 (NRK2) pathway. Associated with changes in NAD(+) biosynthesis, H6PDKO muscle had impaired mitochondrial respiratory capacity with altered mitochondrial acylcarnitine and acetyl-CoA metabolism. Boosting NAD(+) levels through the NRK2 pathway using the precursor nicotinamide riboside elevated NAD(+)/NADH but had no effect to mitigate ER stress and dysfunctional mitochondrial respiratory capacity or acetyl-CoA metabolism. Similarly, H6PDKO/NRK2 double KO mice did not display an exaggerated timing or severity of myopathy or overt change in mitochondrial metabolism despite depression of NAD(+) availability. Conclusions These findings suggest a complex metabolic response to changes in muscle SR NADP(H) redox status that result in impaired mitochondrial energy metabolism and activation of cellular NAD(+) salvage pathways. It is possible that SR can sense and signal perturbation in NAD(P)(H) that cannot be rectified in the absence of H6PD. Whether NRK2 pathway activation is a direct response to changes in SR NAD(P)(H) availability or adaptation to deficits in metabolic energy availability remains to be resolved

The Identification of the X-ray Counterpart to PSR J2021+4026

We report the probable identification of the X-ray counterpart to the gamma-ray pulsar PSR J2021+4026 using imaging with the Chandra X-ray Observatory ACIS and timing analysis with the Fermi satellite. Given the statistical and systematic errors, the positions determined by both satellites are coincident. The X-ray source position is R.A. 20h21m30.733s, Decl. +40 deg 26 min 46.04sec (J2000) with an estimated uncertainty of 1.3 arsec combined statistical and systematic error. Moreover, both the X-ray to gamma-ray and the X-ray to optical flux ratios are sensible assuming a neutron star origin for the X-ray flux. The X-ray source has no cataloged infrared-to-visible counterpart and, through new observations, we set upper limits to its optical emission of i' >23.0 mag and r' > 25.2mag. The source exhibits an X-ray spectrum with most likely both a powerlaw and a thermal component. We also report on the X-ray and visible light properties of the 43 other sources detected in our Chandra observation.Comment: Accepted for publication in the Astrophysical Journa