Variability in Basal Melting Beneath Pine Island Ice Shelf on Weekly to Monthly Timescales

Ocean-driven basal melting of Amundsen Sea ice shelves has triggered acceleration, thinning, and grounding line retreat on many West Antarctic outlet glaciers. Here we present the first year-long (2014) record of basal melt rate at sub-weekly resolution from a location on the outer Pine Island Ice Shelf. Adjustment of the upper thermocline to local wind forced variability in the vertical Ekman velocity is the dominant control on basal melting at weekly to monthly timescales. Atmosphere-ice-ocean surface heat fluxes or changes in advection of modified Circumpolar Deep Water play no discernible role at these timescales. We propose that during other years, a deepening of the thermocline in Pine Island Bay driven by longer timescale processes may have suppressed the impact of local wind forcing on high-frequency upper thermocline height variability and basal melting. This highlights the complex interplay between the different processes and their timescales that set the basal melt rate beneath Pine Island Ice Shelf

Quantitative analysis of left atrial function in asymptomatic patients with b-thalassemia major using real-time three-dimensional echocardiography

<p>Abstract</p> <p>Background</p> <p>There is strong evidence that left atrial (LA) size is a prognostic marker in a variety of heart diseases. Recently, real-time three-dimensional echocardiography (RT3DE) has been reported as a useful tool for studying the phasic changes of the left atrial volumes. The aim of this study was to investigate the performance of the left atrium in beta-thalassemic patients with preserved left ventricular ejection fraction (EF) and no iron overload, using RT3DE.</p> <p>Methods</p> <p>Twenty-eight asymptomatic b-thalassemic patients (32.2 ± 4.3 years old, 17 men) who were on iron chelating therapy, as well as 20 age- and sex-matched healthy controls underwent transthoracic RT3DE. The patient group had normal echocardiographic systolic and diastolic indices, while there was no myocardial iron disposition according to MRI. Apical full volume data sets were obtained and LA volumes were measured at 3 time points of the cardiac cycle: (1) maximum volume (LAmax) at end-systole, just before mitral valve opening; (2) minimum volume (LAmin) at end-diastole, just before mitral valve closure; and (3) volume before atrial active contraction (LApreA) obtained from the last frame before mitral valve reopening or at time of the P wave on the surface electrocardiogram. From the derived values, left atrial active and passive emptying volumes, as well as the respective emptying fractions were calculated.</p> <p>Results</p> <p>Left ventricular EF (59.2 ± 2.5% patients vs. 60.1 ± 2.1% controls), E/A, E/E' were similar between the two groups. Differences in the LAmax, LAmin and LApreA between b-thalassemic patients and controls were non-significant, LAmax:(35.5 ± 13.4 vs 31.8 ± 9.8)cm³, LAmin:(16.0 ± 6.0 vs. 13.5 ±4.2)cm³, and LApreA:(25.4 ± 9.8 vs. 24.3 ± 7.2)cm³. However, left atrial active emptying fraction was reduced in the patient group as compared to the healthy population (34.3 ± 16.4% vs. 43.2 ± 11.4%, p < 0.05).</p> <p>Conclusion</p> <p>RT3DE may be a novel technique for the evaluation of LA function in asymptomatic patients with b-Thalassemia Major. Among three-dimensional volumes and indices, left atrial active emptying fraction may be an early index of LA dysfunction in the specific patient population.</p

Phylogeography of Japanese encephalitis virus:genotype is associated with climate

The circulation of vector-borne zoonotic viruses is largely determined by the overlap in the geographical distributions of virus-competent vectors and reservoir hosts. What is less clear are the factors influencing the distribution of virus-specific lineages. Japanese encephalitis virus (JEV) is the most important etiologic agent of epidemic encephalitis worldwide, and is primarily maintained between vertebrate reservoir hosts (avian and swine) and culicine mosquitoes. There are five genotypes of JEV: GI-V. In recent years, GI has displaced GIII as the dominant JEV genotype and GV has re-emerged after almost 60 years of undetected virus circulation. JEV is found throughout most of Asia, extending from maritime Siberia in the north to Australia in the south, and as far as Pakistan to the west and Saipan to the east. Transmission of JEV in temperate zones is epidemic with the majority of cases occurring in summer months, while transmission in tropical zones is endemic and occurs year-round at lower rates. To test the hypothesis that viruses circulating in these two geographical zones are genetically distinct, we applied Bayesian phylogeographic, categorical data analysis and phylogeny-trait association test techniques to the largest JEV dataset compiled to date, representing the envelope (E) gene of 487 isolates collected from 12 countries over 75 years. We demonstrated that GIII and the recently emerged GI-b are temperate genotypes likely maintained year-round in northern latitudes, while GI-a and GII are tropical genotypes likely maintained primarily through mosquito-avian and mosquito-swine transmission cycles. This study represents a new paradigm directly linking viral molecular evolution and climate

The role of the right inferior frontal gyrus in the pathogenesis of post-stroke psychosis.

Psychotic symptoms have previously been reported following right hemisphere brain injury. We sought to identify the specific neuroanatomical basis of delusions following stroke by studying a series of patients with post-stroke psychosis. Lesion overlap analysis was conducted on three individuals with delusions following right hemisphere stroke. These cases were compared with a control group of patients with similar anatomical damage. The main outcome measures were presence of delusions and presence of behavioural susceptibility. The right inferior frontal gyrus and underlying white matter, including the superior longitudinal fasciculus and anterior corona radiata, were involved in all three cases. All three had a preexisting untreated psychiatric disorder. In contrast, only one of nine control cases with equivalent lesions had evidence of previous psychiatric disorder (p = 0.0182, Fisher’s exact test), and this was being treated at the time of stroke. We provide clinical evidence from patients with structural brain lesions implicating damage to the right inferior frontal lobe in the generation of persistent psychosis following stroke. We suggest that preexisting psychiatric disease provided a behavioural susceptibility to develop delusions in these individuals. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00415-014-7242-x) contains supplementary material, which is available to authorized users

Velocity vector imaging to quantify left atrial function

The aim of our study was to assess the feasibility of a new image analysis, velocity vector imaging (VVI), in the assessment of left atrial volumes (LAV) and left atrial ejection fraction (LAEF). We retrospectively analysed 100 transthoracic echocardiographic findings in 71 men, and 29 women (mean age 57 ± 19.8 years). Two subgroups of patients were defined: (1) with left ventricular (LV) EF > 50%, and (2) LV EF < 50%. For the VVI method of indexed LAV assessment we used the apical four-chamber view. From the displacement of LA endocardial pixels time–volume curves were extracted which provided automatically data regarding indexed maximum LAV (LAVImax), indexed minimum LAV (LAVImin), and LAEF. LAVs and LAEF by 2-dimensional echocardiograhy (2DE) were measured by Simpson’s biplane disc summation method. Comparing LAVImax, LAVImin, and LAEF by VVI versus 2DE in the total study population, we found significant correlations: r = 0.94, P < 0.0001, r = 0.94, P < 0.0001, r = 0.79, P < 0.0001, respectively. In addition, LAVImax ≥ 40 ml/m2 was 94% sensitive and 72% specific, LAVImin ≥ 27 ml/m2 was 90% sensitive and 86% specific, and LAEF < 30% was 80% sensitive and 96% specific for the detection of LV systolic dysfunction. There were highly significant inverse associations of LAVImax and LAVImin to LVEF. LAEF was also significantly related to LV systolic function. When comparing the time required for VVI and 2DE measurements, VVI led to 62% reduction in the measurement time. In conclusion, VVI is a feasible method for the assessment of LAVs and LAEF. It provides close agreement with that measured by conventional 2DE Simpson’s biplane method with significant time saved

Observation of an Exotic S=+1S=+1 Baryon in Exclusive Photoproduction from the Deuteron

In an exclusive measurement of the reaction $\gamma d \to K^+ K^- p n$, a narrow peak that can be attributed to an exotic baryon with strangeness $S=+1$ is seen in the $K^+n$ invariant mass spectrum. The peak is at $1.542\pm 0.005$ GeV/c$^2$ with a measured width of 0.021 GeV/c$^2$ FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is $5.2 \pm 0.6 \sigma$. The mass and width of the observed peak are consistent with recent reports of a narrow $S=+1$ baryon by other experimental groups.Comment: 5 pages, 5 figure

Measurement of Beam-Spin Asymmetries for Deep Inelastic π+\pi^+ Electroproduction

We report the first evidence for a non-zero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic region. Data have been obtained using a polarized electron beam of 4.3 GeV with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). The amplitude of the $\sin\phi$ modulation increases with the momentum of the pion relative to the virtual photon, $z$, with an average amplitude of $0.038 \pm 0.005 \pm 0.003$ for $0.5 < z < 0.8$ range.Comment: 5 pages, RevTEX4, 3 figures, 2 table

Measurement of the Polarized Structure Function σLT′\sigma_{LT^\prime} for p(e⃗,e′p)πop(\vec{e},e'p)\pi^o in the Δ(1232)\Delta(1232) Resonance Region

The polarized longitudinal-transverse structure function $\sigma_{LT^\prime}$ has been measured in the $\Delta(1232)$ resonance region at $Q^2=0.40$ and 0.65 GeV$^2$. Data for the $p(\vec e,e'p)\pi^o$ reaction were taken at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at an energy of 1.515 GeV. For the first time a complete angular distribution was measured, permitting the separation of different non-resonant amplitudes using a partial wave analysis. Comparison with previous beam asymmetry measurements at MAMI indicate a deviation from the predicted $Q^2$ dependence of $\sigma_{LT^{\prime}}$ using recent phenomenological models.Comment: 5 pages, LaTex, 4 eps figures: to be published in PRC/Rapid Communications. Version 2 has revised Q^2 analysi

Two-Nucleon Momentum Distributions Measured in 3He(e,e'pp)n

We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for `fast' nucleons (p > 250 MeV/c) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast pp and pn pairs are back-to-back with little momentum along the three-momentum transfer, indicating that they are spectators. Experimental and theoretical evidence indicates that we have measured distorted two-nucleon momentum distributions by striking the third nucleon and detecting the spectator correlated pair.Comment: 6 pages, 5 figures, submitted to PR

Search for the Θ+\Theta^+ pentaquark in the reaction γd→pK−K+n\gamma d \to p K^- K^+ n

A search for the \thp in the reaction $\gamma d \to pK^-K^+n$ was completed using the CLAS detector at Jefferson Lab. A study of the same reaction, published earlier, reported the observation of a narrow \thp resonance. The present experiment, with more than 30 times the integrated luminosity of our earlier measurement, does not show any evidence for a narrow pentaquark resonance. The angle-integrated upper limit on \thp production in the mass range of 1.52 to 1.56 GeV/c$^2$ for the $\gamma d \to pK^-\Theta^+$ reaction is 0.3 nb (95% CL). This upper limit depends on assumptions made for the mass and angular distribution of \thp production. Using \lamstar production as an empirical measure of rescattering in the deuteron, the cross section upper limit for the elementary $\gamma n \to K^-\Theta^+$ reaction is estimated to be a factor of 10 higher, {\it i.e.}, $\sim 3$ nb (95% CL).Comment: 5 figures, submitted to PRL, revised for referee comment