Characterizing upward lightning with and without a terrestrial gamma-ray flash

We compare two observations of gamma-rays before, during, and after lightning flashes initiated by upward leaders from a tower during low-altitude winter thunderstorms on the western coast of Honshu, Japan. While the two leaders appear similar, one produced a terrestrial gamma-ray flash (TGF) so bright that it paralyzed the gamma-ray detectors while it was occurring, and could be observed only via the weaker flux of neutrons created in its wake, while the other produced no detectable TGF gamma-rays at all. The ratio between the indirectly derived gamma-ray fluence for the TGF and the 95% confidence gamma-ray upper limit for the gamma-ray quiet flash is a factor of $1\times10^7$. With the only two observations of this type providing such dramatically different results -- a TGF probably as bright as those seen from space and a powerful upper limit -- we recognize that weak, sub-luminous TGFs in this situation are probably not common, and we quantify this conclusion. While the gamma-ray quiet flash appeared to have a faster leader and more powerful initial continuous current pulse than the flash that produced a TGF, the TGF-producing flash occurred during a weak gamma-ray "glow", while the gamma-ray quiet flash did not, implying a higher electric field aloft when the TGF was produced. We suggest that the field in the high-field region approached by a leader may be more important for whether a TGF is produced than the characteristics of the leader itself.Comment: 21 pages, 6 figures, accepted for publication by the Journal of Geophysical Research - Atmosphere

Breakup of land-fast sea ice in Lutzow-Holm Bay, East Antarctica, and its teleconnection to tropical Pacific sea surface temperatures

A large land-fast sea ice breakup occurred in 2016 in Lutzow-Holm Bay, East Antarctica. The breakup caused calving from the Shirase Glacier Tongue. Although similar breakups and calving have been observed in the past, the timing and magnitudes are not well-constrained. The ice's breakup latitude during 1997-2016 was analyzed to investigate the variables controlling breakup and examine correlation with local calving for a longer period. The breakup latitude in April had a persistently high correlation with sea surface temperature (SST) in the tropical Pacific, which exceeds correlations with local atmospheric variables. The years of five out of six observed calving events from the mid-20th century can correspond to those of warm SST episodes and calving-front retreat in the 1980s to warmer SST shift. Our proposed teleconnection between tropical SST and Antarctic sea ice could lead to better predictions of breakup and might impact the glacier flux for a wider region. Plain Language Summary Land-fast sea ice forms along the Antarctic coast, and it occasionally breaks up significantly. The breakup event influences the flow of glaciers, which is otherwise held back by the fast ice. The breakup of land-fast sea ice and the discharge of glaciers have significant multidecadal variability as well as interannual variability. This study explores what controls the breakup phenomena of land-fast sea ice in Antarctica and finds the linkage with tropical sea surface temperatures. We find the environmental factors which are relevant to the ice breakup, and those variables are originally driven by the teleconnection from the tropical Pacific. We believe that our study makes a significant contribution in climate science by offering a causal mechanism that explains the previously observed multidecadal variability in ice extent in this region. Our model can explain five out of the last six calving events in a major glacier connected to this bay, offering hope for future predictions of ice behavior. This will also merit the logistics to Antarctic research stations

Photon generation by laser-Compton scattering at the KEK-ATF

We performed a photon generation experiment by laser-Compton scattering at the KEK-ATF, aiming to develop a Compton based polarized positron source for linear colliders. In the experiment, laser pulses with a 357 MHz repetition rate were accumulated and their power was enhanced by up to 250 times in the Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while maintaining the laser pulse accumulation in the cavity. As a result, we observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, which corresponds to a yield of 10^8 photons in a second.Comment: 3 pages, 5 figures, Preprint submitted to TIPP09 Proceedings in NIM

DNA metabarcoding unveils multiscale trophic variation in a widespread coastal opportunist

A thorough understanding of ecological networks relies on comprehensive information on trophic relationships among species. Since unpicking the diet of many organisms is unattainable using traditional morphology‐based approaches, the application of high‐throughput sequencing methods represents a rapid and powerful way forward. Here, we assessed the application of DNA metabarcoding with nearly universal primers for the mitochondrial marker cytochrome c oxidase I in defining the trophic ecology of adult brown shrimp, Crangon crangon, in six European estuaries. The exact trophic role of this abundant and widespread coastal benthic species is somewhat controversial, while information on geographical variation remains scant. Results revealed a highly opportunistic behaviour. Shrimp stomach contents contained hundreds of taxa (>1,000 molecular operational taxonomic units), of which 291 were identified as distinct species, belonging to 35 phyla. Only twenty ascertained species had a mean relative abundance of more than 0.5%. Predominant species included other abundant coastal and estuarine taxa, including the shore crab Carcinus maenas and the amphipod Corophium volutator. Jacobs’ selectivity index estimates based on DNA extracted from both shrimp stomachs and sediment samples were used to assess the shrimp's trophic niche indicating a generalist diet, dominated by crustaceans, polychaetes and fish. Spatial variation in diet composition, at regional and local scales, confirmed the highly flexible nature of this trophic opportunist. Furthermore, the detection of a prevalent, possibly endoparasitic fungus (Purpureocillium lilacinum) in the shrimp's stomach demonstrates the wide range of questions that can be addressed using metabarcoding, towards a more robust reconstruction of ecological networks

The proton spin sum rule chiral bag prediction, an update

We reevaluate a quark model prediction using the new QCD evolution function calculated to the 3 loop order and conclude that this model compares favorably with the new experimental results.Comment: 10 pages, 2 figures available by request, give fax numbe

Mouse models for preeclampsia: disruption of redox-regulated signaling

The concept that oxidative stress contributes to the development of human preeclampsia has never been tested in genetically-defined animal models. Homozygous deletion of catechol-Omethyl transferase (Comt-/-) in pregnant mice leads to human preeclampsia-like symptoms (high blood pressure, albuminurea and preterm birth) resulting from extensive vasculo-endothelial pathology, primarily at the utero-fetal interface where maternal cardiac output is dramatically increased during pregnancy. Comt converts estradiol to 2-methoxyestradiol 2 (2ME2) which counters angiogenesis by depleting hypoxia inducible factor-1 alpha (HIF-1 alpha) at late pregnancy. We propose that in wild type (Comt++) pregnant mice, 2ME2 destabilizes HIF-1 alpha by inhibiting mitochondrial superoxide dismutase (MnSOD). Thus, 2ME2 acts as a pro-oxidant, disrupting redox-regulated signaling which blocks angiogenesis in wild type (WT) animals in physiological pregnancy. Further, we suggest that a lack of this inhibition under normoxic conditions in mutant animals (Comt-/-) stabilises HIF-1 alpha by inactivating prolyl hydroxlases (PHD). We predict that a lack of inhibition of MnSOD, leading to persistent accumulation of HIF-1 alpha, would trigger inflammatory infiltration and endothelial damage in mutant animals. Critical tests of this hypothesis would be to recreate preeclampsia symptoms by inducing oxidative stress in WT animals or to ameliorate by treating mutant mice with Mn-SOD-catalase mimetics or activators of PHD

Restricted feedback control of one-dimensional maps

Dynamical control of biological systems is often restricted by the practical constraint of unidirectional parameter perturbations. We show that such a restriction introduces surprising complexity to the stability of one-dimensional map systems and can actually improve controllability. We present experimental cardiac control results that support these analyses. Finally, we develop new control algorithms that exploit the structure of the restricted-control stability zones to automatically adapt the control feedback parameter and thereby achieve improved robustness to noise and drifting system parameters.Comment: 29 pages, 9 embedded figure

Direct Sensing of Endothelial Oxidants by Vascular Endothelial Growth Factor Receptor-2 and c-Src

BACKGROUND: ADPH oxidase-derived reactive oxygen species (ROS) play important roles in redox homeostasis and signal transduction in endothelial cells (ECs). We previously demonstrated that c-Src plays a key role in VEGF-induced, ROS-dependent selective activation of PI3K-Akt but not PLCγ-1-ERK1/2 signaling pathways. The aim of the present study was to understand how VEGFR-2-c-Src signaling axis 'senses' NADPH oxidase-derived ROS levels and couples VEGF activation of c-Src to the redox state of ECs. METHODOLOGY/PRINCIPAL FINDINGS: Using biotinylated probe that detects oxidation of cysteine thiol (cys-OH) in intracellular proteins, we demonstrate that VEGF induced oxidative modification in c-Src and VEGFR-2, and that reduction in ROS levels using siRNA against p47(phox) subunit of Rac1-dependent NADPH oxidase inhibited this phenomenon. Co-immunoprecipitation studies using human coronary artery ECs (HCAEC) showed that VEGF-induced ROS-dependent interaction between VEGFR-2 and c-Src correlated with their thiol oxidation status. Immunofluorescence studies using antibodies against internalized VEGFR-2 and c-Src demonstrated that VEGF-induced subcellular co-localization of these tyrosine kinases were also dependent on NADPH oxidsase-derived ROS. CONCLUSION/SIGNIFICANCE: These results demonstrate that VEGF induces cysteine oxidation in VEGFR-2 and c-Src in an NADPH oxidase-derived ROS-dependent manner, suggesting that VEGFR-2 and c-Src can 'sense' redox levels in ECs. The data also suggest that thiol oxidation status of VEGFR-2 and c-Src correlates with their ability to physically interact with each other and c-Src activation. Taken together, these findings suggest that prior to activating downstream c-Src-PI3K-Akt signaling pathway, VEGFR-2-c-Src axis requires an NADPH oxidase-derived ROS threshold in ECs

Magnetic Moments of the Octet Baryons in the Colour-Dielectric Model

Baryon magnetic moments are calculated in the colour-dielectric model with pion and kaon loops. The only free parameter of the model is determined from the nucleon isoscalar radius, and all SU(3) symmetry breaking, including that in the quark sector, is determined by mesonic masses and decay constants. Good agreement with experiment is obtained for the ratios of the magnetic moments, but the inclusion of kaons does not improve the results. The results obtained in this approach are significantly better than any that have been obtained in hedgehog-based models.Comment: LaTeX file, 19 pages, 4 postscript figure