Advances in mapping ice-free surfaces within the Northern Antarctic peninsula region using polarimetric RADARSAT-2 data

Ice-free areas within the Northern Antarctic Peninsula region are of interest for studying changes occurring to surface covers, including those related to glacial coverage, raised beach deposits and periglacial processes and permafrost. The objective of this work is to map the main surface covers within ice-free areas of King George Island, the largest island of the South Shetlands archipelago, using fully polarimetric RADARSAT-2 SAR data. Surface covers such as rock outcrops and glacial till, stone fields, patterned ground, and sand and gravel deposits form the most representative classes and account for 84 km2 of the ice-free areas on the island. A distribution of complex geomorphological features and landforms was obtained, being some of them considered indicators of periglacial processes and presence of permafrost.Published versio

Dust continuum and Polarization from Envelope to Cores in Star Formation: A Case Study in the W51 North region

We present the first high-angular resolution (up to 0.7", ~5000 AU) polarization and thermal dust continuum images toward the massive star-forming region W51 North. The observations were carried out with the Submillimeter Array (SMA) in both the subcompact (SMA-SubC) and extended (SMA-Ext) configurations at a wavelength of 870 micron. W51 North is resolved into four cores (SMA1 to SMA4) in the 870 micron continuum image. The associated dust polarization exhibits more complex structures than seen at lower angular resolution. We analyze the inferred morphologies of the plane-of-sky magnetic field (B_bot) in the SMA1 to SMA4 cores and in the envelope using the SMA-Ext and SMA-SubC data. These results are compared with the B_bot archive images obtained from the CSO and JCMT. A correlation between dust intensity gradient position angles (phi_{nabla I}) and magnetic field position angles (phi_B) is found in the CSO, JCMT and both SMA data sets. This correlation is further analyzed quantitatively. A systematically tighter correlation between phi_{nabla I} and phi_B is found in the cores, whereas the correlation decreases in outside-core regions. Magnetic field-to-gravity force ratio (Sigma_B) maps are derived using the newly developed polarization - intensity gradient method by Koch, Tang & Ho 2012. We find that the force ratios tend to be small (Sigma_B <= 0.5) in the cores in all 4 data sets. In regions outside of the cores, the ratios increase or the field is even dominating gravity (Sigma_B > 1). This possibly provides a physical explanation of the tightening correlation between phi_{nabla I} and phi_B in the cores: the more the B field lines are dragged and aligned by gravity, the tighter the correlation is. Finally, we propose a schematic scenario for the magnetic field in W51 North to interpret the four polarization observations at different physical scales.Comment: Accepted for publication in ApJ. 10 pages. 7 figure

Forward-Backward Charge Fluctuations at RHIC Energies

We use the ultra-relativistic quantum molecular dynamic UrQMD version 2.2 to study forward backward fluctuations and compare our results with the published data by the PHOBOS.Comment: 4 pages, 6 figures, poster presented at Strong & Electroweak Matter (SEWM2006), BNL, United States, May 10-13 200

The Effect of Dynamical Parton Recombination on Event-by-Event Observables

Within a dynamical quark recombination model we explore various proposed event-by-event observables sensitive to the microscopic structure of the QCD-matter created at RHIC energies. Charge fluctuations, charge transfer fluctuations and baryon-strangeness correlations are computed from a sample of central Au+Au events at the highest RHIC energy available ($\sqrt{s_{NN}}$=200 GeV). We find that for all explored observables, the calculations yield the values predicted for a quark-gluon plasma only at early times of the evolution, whereas the final state approaches the values expected for a hadronic gas. We argue that the recombination-like hadronization process itself is responsible for the disappearance of the predicted deconfinement signatures. This might explain why no fluctuation signatures for the transition between quark and hadronic matter was ever observed in the experimental data up to now. However, it might also be interpreted as a clear indication for a recombination like hadronization process at RHIC.Comment: 5 page

COST-G: towards a new GRACE and GRACE-FO combination

The combination service for time-variable gravity fields (COST-G) provides the full time-series of monthly GRACE gravity fields: COST-G GRACE RL01, combined in reprocessing mode, and a steadily growing time-series of monthly GRACE-FO gravity fields: COST-G GRACE-FO RL01 OP, combined on an operational basis. Both time-series are currently considered for re-combination. In case of GRACE, new high-quality time-series from Chinese analysis centers are available for combination. In case of GRACE-FO, a revision of the weighting scheme, developed in the frame of the Horizon2020 project Global Gravity-based Groundwater Product (G3P), and the availability of reprocessed GRACE-FO time-series from AIUB, CSR, GFZ, and JPL, lead to a significant improvement of the combined gravity fields. We present the preliminary re-combined GRACE and GRACE-FO time-series and quantify the differences with respect to the COST-G RL01 series in terms of signal and noise content

Specific shifts in the endocannabinoid system in hibernating brown bears

In small hibernators, global downregulation of the endocannabinoid system (ECS), which is involved in modulating neuronal signaling, feeding behavior, energy metabolism, and circannual rhythms, has been reported to possibly drive physiological adaptation to the hibernating state. In hibernating brown bears (Ursus arctos), we hypothesized that beyond an overall suppression of the ECS, seasonal shift in endocannabinoids compounds could be linked to bear's peculiar features that include hibernation without arousal episodes and capacity to react to external disturbance. We explored circulating lipids in serum and the ECS in plasma and metabolically active tissues in free-ranging subadult Scandinavian brown bears when both active and hibernating. In winter bear serum, in addition to a 2-fold increase in total fatty acid concentration, we found significant changes in relative proportions of circulating fatty acids, such as a 2-fold increase in docosahexaenoic acid C22:6 n-3 and a decrease in arachidonic acid C20:4 n-6. In adipose and muscle tissues of hibernating bears, we found significant lower concentrations of 2-arachidonoylglycerol (2-AG), a major ligand of cannabinoid receptors 1 (CB1) and 2 (CB2). Lower mRNA level for genes encoding CB1 and CB2 were also found in winter muscle and adipose tissue, respectively. The observed reduction in ECS tone may promote fatty acid mobilization from body fat stores, and favor carbohydrate metabolism in skeletal muscle of hibernating bears. Additionally, high circulating level of the endocannabinoid-like compound N-oleoylethanolamide (OEA) in winter could favor lipolysis and fatty acid oxidation in peripheral tissues. We also speculated on a role of OEA in the conservation of an anorexigenic signal and in the maintenance of torpor during hibernation, while sustaining the capacity of bears to sense stimuli from the environment

Peripheral Arterial and Venous Response to Tilt Test after a 60-Day Bedrest with and without Countermeasures (ES-IBREP)

We quantified the impact of 60-day head-down bed rest (HDBR) with countermeasures on arterial and venous response to tilt. Methods: Twenty-one males: 7 control (Con), 7 resistive vibration exercise (RVE) and 7 Chinese herb (Herb) were assessed. Subjects were identified as finisher (F) or non-finishers (NF) at the post-HDBR 20-min tilt test. The cerebral (MCA), femoral (FEM) arterial flow velocity and leg vascular resistance (FRI), the portal vein section (PV), the flow redistribution ratios (MCA/FEM; MCA/PV), the tibial (Tib), gastrocnemius (Gast), and saphenous (Saph) vein sections were measured by echography and Doppler ultrasonography. Arterial and venous parameters were measured at 3-min pre-tilt in the supine position, and at 1 min before the end of the tilt. Results: At post-HDBR tilt, MCA decreased more compared with pre-HDBR tilt in the Con, RVE, and Herb groups, the MCA/FEM tended to decrease in the Con and Herb groups (not significant) but remained stable in the RVE gr. FRI dropped in the Con gr, but remained stable in the Herb gr and increased in the RVE gr. PV decreased less in the Con and Herb groups but remained unchanged in the RVE gr. MCA/PV decreased in the Con and Herb groups, but increased to a similar extent in the RVE gr. Gast section significantly increased more in the Con gr only, whereas Tib section increased more in the Con and Herb groups but not in the RVE gr. The percent change in Saph section was similar at pre- and post-HDBR tilt. Conclusion: In the Con gr, vasoconstriction was reduced in leg and splanchnic areas. RVE and Herb contributed to prevent the loss of vasoconstriction in both areas, but the effect of RVE was higher. RVE and Herb contributed to limit Gast distension whereas only RVE had a protective effect on the Tib

Metabolic reprogramming involving glycolysis in the hibernating brown bear skeletal muscle

Background: In mammals, the hibernating state is characterized by biochemical adjustments, which include metabolic rate depression and a shift in the primary fuel oxidized from carbohydrates to lipids. A number of studies of hibernating species report an upregulation of the levels and/or activity of lipid oxidizing enzymes in muscles during torpor, with a concomitant downregulation for glycolytic enzymes. However, other studies provide contrasting data about the regulation of fuel utilization in skeletal muscles during hibernation. Bears hibernate with only moderate hypothermia but with a drop in metabolic rate down to ~ 25% of basal metabolism. To gain insights into how fuel metabolism is regulated in hibernating bear skeletal muscles, we examined the vastus lateralis proteome and other changes elicited in brown bears during hibernation. Results: We show that bear muscle metabolic reorganization is in line with a suppression of ATP turnover. Regulation of muscle enzyme expression and activity, as well as of circulating metabolite profiles, highlighted a preference for lipid substrates during hibernation, although the data suggested that muscular lipid oxidation levels decreased due to metabolic rate depression. Our data also supported maintenance of muscle glycolysis that could be fuelled from liver gluconeogenesis and mobilization of muscle glycogen stores. During hibernation, our data also suggest that carbohydrate metabolism in bear muscle, as well as protein sparing, could be controlled, in part, by actions of n-3 polyunsaturated fatty acids like docosahexaenoic acid. Conclusions: Our work shows that molecular mechanisms in hibernating bear skeletal muscle, which appear consistent with a hypometabolic state, likely contribute to energy and protein savings. Maintenance of glycolysis could help to sustain muscle functionality for situations such as an unexpected exit from hibernation that would require a rapid increase in ATP production for muscle contraction. The molecular data we report here for skeletal muscles of bears hibernating at near normal body temperature represent a signature of muscle preservation despite atrophying conditions

A Temporal Role Of Type I Interferon Signaling in CD8+ T Cell Maturation during Acute West Nile Virus Infection

A genetic absence of the common IFN- α/β signaling receptor (IFNAR) in mice is associated with enhanced viral replication and altered adaptive immune responses. However, analysis of IFNAR-/- mice is limited for studying the functions of type I IFN at discrete stages of viral infection. To define the temporal functions of type I IFN signaling in the context of infection by West Nile virus (WNV), we treated mice with MAR1-5A3, a neutralizing, non cell-depleting anti-IFNAR antibody. Inhibition of type I IFN signaling at or before day 2 after infection was associated with markedly enhanced viral burden, whereas treatment at day 4 had substantially less effect on WNV dissemination. While antibody treatment prior to infection resulted in massive expansion of virus-specific CD8+ T cells, blockade of type I IFN signaling starting at day 4 induced dysfunctional CD8+ T cells with depressed cytokine responses and expression of phenotypic markers suggesting exhaustion. Thus, only the later maturation phase of anti-WNV CD8+ T cell development requires type I IFN signaling. WNV infection experiments in BATF3-/- mice, which lack CD8-α dendritic cells and have impaired priming due to inefficient antigen cross-presentation, revealed a similar effect of blocking IFN signaling on CD8+ T cell maturation. Collectively, our results suggest that cell non-autonomous type I IFN signaling shapes maturation of antiviral CD8+ T cell response at a stage distinct from the initial priming event

Thrombospondins in the heart: potential functions in cardiac remodeling

Cardiac remodeling after myocardial injury involves inflammation, angiogenesis, left ventricular hypertrophy and matrix remodeling. Thrombospondins (TSPs) belong to the group of matricellular proteins, which are non-structural extracellular matrix proteins that modulate cell–matrix interactions and cell function in injured tissues or tumors. They interact with different matrix and membrane-bound proteins due to their diverse functional domains. That the expression of TSPs strongly increases during cardiac stress or injury indicates an important role for them during cardiac remodeling. Recently, the protective properties of TSP expression against heart failure have been acknowledged. The current review will focus on the biological role of TSPs in the ischemic and hypertensive heart, and will describe the functional consequences of TSP polymorphisms in cardiac disease