Goddard Robotic Telescope - Optical Follow-up of GRBs and Coordinated Observations of AGNs -

Since it is not possible to predict when a Gamma-Ray Burst (GRB) will occur or when Active Galactic Nucleus (AGN) flaring activity starts, follow-up/monitoring ground telescopes must be located as uniformly as possible all over the world in order to collect data simultaneously with Fermi and Swift detections. However, there is a distinct gap in follow-up coverage of telescopes in the eastern U.S. region based on the operations of Swift. Motivated by this fact, we have constructed a 14" fully automated optical robotic telescope, Goddard Robotic Telescope (GRT), at the Goddard Geophysical and Astronomical Observatory. The aims of our robotic telescope are 1) to follow-up Swift/Fermi GRBs and 2) to perform the coordinated optical observations of Fermi Large Area Telescope (LAT) AGN. Our telescope system consists of off-the-shelf hardware. With the focal reducer, we are able to match the field of view of Swift narrow instruments (20' x 20'). We started scientific observations in mid-November 2008 and GRT has been fully remotely operated since August 2009. The 3 sigma upper limit in a 30-second exposure in the R filter is ~15.4 mag; however, we can reach to ~18 mag in a 600-second exposures. Due to the weather condition at the telescope site, our observing efficiency is 30-40% on average.Comment: 14 pages, 14 figures, accepted for publication in ASR special issue on Neutron Stars and Gamma Ray Burst

EFFECT OF TEMPERATURE AND CASSAVA GENOTYPE ON THE DEVELOPMENT, FECUNDITY AND REPRODUCTION OF Bemisia tabaci SSA1

The Bemisia tabaci complex is currently recognised as key agricultural pests that cause economic damage globally. Temperature is the most important driver of changes in behaviour, abundance and distribution of insect pests, including the whitefly (Bemisia tabaci). The objective of this study was to evaluate the development, fecundity and reproduction of B. tabaci SSA1 on cassava genotypes under a range of temperatures. A laboratory study was conducted using three cassava genotypes (Alado alado, NAROCASS 1 and NASE 14) at five constant temperatures (16, 20, 24, 28 and 32 \ub0C). The parameters assessed included development duration, survival, fecundity and population parameters for B. tabaci SSA1. Temperature had significant effects (P<0.001) on development time, survival and fecundity of B. tabaci; while cassava genotype had no effect (P>0.05). An inverse relationship was observed between development time and temperature for all stages across all cassava genotypes. The total life cycle was 63.8 days at 16 \ub0C and 17.9 days at 32 \ub0C on NAROCASS 1. Survival for each stage throughout the entire life cycle increased with temperature and was highest at 32 \ub0C, although this was not significantly different from that at 28 \ub0C. Fecundity increased with temperature and was highest at 32 \ub0C on all cassava genotypes. For all cassava genotypes, the intrinsic rate of increase (rm), finite rate of increase (\u3bb) and net reproductive rate (Ro) increased with temperature, while mean generation time (T) reduced following a similar pattern. At 32 \ub0C, rm, Ro, \u3bb and T were 0.2, 48.7, 1.2 and 22.6 days, respectively; compared to 0.01, 1.9, 1.0 and 71.2 days at 16 \ub0C on Alado alado. Therefore, the ideal development temperature for B. tabaci SSA1 is 32 \ub0C. Thus, there is a risk of accelerated future expansion of B. tabaci SSA1 populations globally, with global warming and climate variability.Le complexe Bemisia tabaci est actuellement reconnu comme un ravageur agricole cl\ue9 causant des dommages \ue9conomiques \ue0 l\u2019\ue9chelle mondiale. La temp\ue9rature est le facteur le plus important des changements de comportement, d\u2019abondance et de r\ue9partition des insectes ravageurs, y compris l\u2019aleurode (Bemisia tabaci). L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer le d\ue9veloppement, la f\ue9condit\ue9 et la reproduction de B. tabaci SSA1 sur des g\ue9notypes de manioc sous une gamme de temp\ue9ratures. Une \ue9tude en laboratoire a \ue9t\ue9 men\ue9e en utilisant trois g\ue9notypes de manioc (Alado alado, NAROCASS 1 et NASE 14) \ue0 cinq temp\ue9ratures constantes (16, 20, 24, 28 et 32 \ub0C). Les param\ue8tres \ue9valu\ue9s comprenaient la dur\ue9e du d\ue9veloppement, la survie, la f\ue9condit\ue9 et les param\ue8tres de population pour B. tabaci SSA1. La temp\ue9rature a eu des effets significatifs (P<0,001) sur le temps de d\ue9veloppement, la survie et la f\ue9condit\ue9 de B. tabaci, tandis que le g\ue9notype du manioc n\u2019a eu aucun effet (p>0,05). Une relation inverse a \ue9t\ue9 observ\ue9e entre le temps de d\ue9veloppement et la temp\ue9rature pour tous les stades dans tous les g\ue9notypes de manioc. Le cycle de vie total \ue9tait de 63,8 jours \ue0 16 \ub0C et de 17,9 jours \ue0 32 \ub0C sur NAROCASS 1. La survie pour chaque \ue9tape tout au long du cycle de vie entier augmentait avec la temp\ue9rature et \ue9tait maximale \ue0 32 \ub0C. Cependant, la survie \ue0 28 \ub0C n\u2019\ue9tait pas significativement diff\ue9rente de celle observ\ue9e \ue0 32 \ub0C. La f\ue9condit\ue9 augmentait avec la temp\ue9rature et \ue9tait maximale \ue0 32 \ub0C sur tous les g\ue9notypes de manioc. Pour tous les g\ue9notypes de manioc, le taux d\u2019accroissement intrins\ue8que (rm), le taux d\u2019accroissement fini (\u3bb) et le taux net de reproduction (Ro) ont augment\ue9 avec la temp\ue9rature, tandis que le temps de g\ue9n\ue9ration moyen (T) a diminu\ue9 selon un sch\ue9ma similaire. A 32 \ub0C, rm, Ro, \u3bb et T \ue9taient respectivement de 0,2, 48,7, 1,2 et 22,6 jours ; contre 0,01, 1,9, 1,0 et 71,2 jours \ue0 16 \ub0C sur Alado alado. Par cons\ue9quent, d\u2019apr\ue8s cette \ue9tude, la temp\ue9rature de d\ue9veloppement id\ue9ale pour B. tabaci SSA1 est de 32 \ub0C. Ainsi, il existe un risque d\u2019expansion future acc\ue9l\ue9r\ue9e des populations de B. tabaci SSA1 \ue0 l\u2019\ue9chelle mondiale, avec le r\ue9chauffement climatique et la variabilit\ue9 climatique

Cassava whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), in sub-Saharan African farming landscapes: a review of the factors determining abundance

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a pest species complex that causes widespread damage to cassava, a staple food crop for millions of smallholder households in Sub-Saharan Africa. Species in the complex cause direct feeding damage to cassava and are the vectors of multiple plant viruses. Whilst significant work has gone into developing virus-resistant cassava cultivars, there has been little research effort aimed at understanding the ecology of these insect vectors. In this review we critically assess the knowledge base relating to factors that may lead to high population densities of Sub-Saharan African (SSA) Bemisia tabaci species in cassava production landscapes of East Africa. We focus first on empirical studies that have examined biotic or abiotic factors that may lead to high populations. We then identify knowledge gaps that need to be filled to deliver long-term sustainable solutions to manage both the vectors and the viruses that they transmit. We found that whilst many hypotheses have been put forward to explain the increases in abundance witnessed since the early 1990s, there are little available published data and these tend to have been collected in a piecemeal manner. The most critical knowledge gaps identified were: (i) understanding how cassava cultivars and alternative host plants impact B. tabaci population dynamics and its natural enemies; (ii) the impact of natural enemies in terms of reducing the frequency of outbreaks and (iii) the use and management of insecticides to delay or avoid the development of resistance. In addition, there are several fundamental methodologies that need to be developed and deployed in East Africa to address some of the more challenging knowledge gaps

Crucial Physical Dependencies of the Core-Collapse Supernova Mechanism

We explore with self-consistent 2D F{\sc{ornax}} simulations the dependence of the outcome of collapse on many-body corrections to neutrino-nucleon cross sections, the nucleon-nucleon bremsstrahlung rate, electron capture on heavy nuclei, pre-collapse seed perturbations, and inelastic neutrino-electron and neutrino-nucleon scattering. Importantly, proximity to criticality amplifies the role of even small changes in the neutrino-matter couplings, and such changes can together add to produce outsized effects. When close to the critical condition the cumulative result of a few small effects (including seeds) that individually have only modest consequence can convert an anemic into a robust explosion, or even a dud into a blast. Such sensitivity is not seen in one dimension and may explain the apparent heterogeneity in the outcomes of detailed simulations performed internationally. A natural conclusion is that the different groups collectively are closer to a realistic understanding of the mechanism of core-collapse supernovae than might have seemed apparent.Comment: 25 pages; 10 figure

Magnetic Reconnection in Extreme Astrophysical Environments

Magnetic reconnection is a basic plasma process of dramatic rearrangement of magnetic topology, often leading to a violent release of magnetic energy. It is important in magnetic fusion and in space and solar physics --- areas that have so far provided the context for most of reconnection research. Importantly, these environments consist just of electrons and ions and the dissipated energy always stays with the plasma. In contrast, in this paper I introduce a new direction of research, motivated by several important problems in high-energy astrophysics --- reconnection in high energy density (HED) radiative plasmas, where radiation pressure and radiative cooling become dominant factors in the pressure and energy balance. I identify the key processes distinguishing HED reconnection: special-relativistic effects; radiative effects (radiative cooling, radiation pressure, and Compton resistivity); and, at the most extreme end, QED effects, including pair creation. I then discuss the main astrophysical applications --- situations with magnetar-strength fields (exceeding the quantum critical field of about 4 x 10^13 G): giant SGR flares and magnetically-powered central engines and jets of GRBs. Here, magnetic energy density is so high that its dissipation heats the plasma to MeV temperatures. Electron-positron pairs are then copiously produced, making the reconnection layer highly collisional and dressing it in a thick pair coat that traps radiation. The pressure is dominated by radiation and pairs. Yet, radiation diffusion across the layer may be faster than the global Alfv\'en transit time; then, radiative cooling governs the thermodynamics and reconnection becomes a radiative transfer problem, greatly affected by the ultra-strong magnetic field. This overall picture is very different from our traditional picture of reconnection and thus represents a new frontier in reconnection research.Comment: Accepted to Space Science Reviews (special issue on magnetic reconnection). Article is based on an invited review talk at the Yosemite-2010 Workshop on Magnetic Reconnection (Yosemite NP, CA, USA; February 8-12, 2010). 30 pages, no figure

Turing Patterns in Deserts

Abstract. Self-organised patterns of vegetation are a characteristic feature of many semi-arid regions. In particular, banded vegetation is typical on hillsides. Mathematical modelling is widely used to study these banded patterns, because there are no laboratory replicates. I will describe the development of spatial patterns in an established model for banded vegetation via a Turing bifurcation. I will discuss numerical simulations of the phenomenon, and I will summarise nonlinear analysis on the existence and form of spatial patterns as a function of the model parameter that corresponds to mean annual rainfall.

Exercise reduces inflammatory cell production and cardiovascular inflammation via instruction of hematopoietic progenitor cells

A sedentary lifestyle, chronic inflammation and leukocytosis increase atherosclerosis; however, it remains unclear whether regular physical activity influences leukocyte production. Here we show that voluntary running decreases hematopoietic activity in mice. Exercise protects mice and humans with atherosclerosis from chronic leukocytosis but does not compromise emergency hematopoiesis in mice. Mechanistically, exercise diminishes leptin production in adipose tissue, augmenting quiescence-promoting hematopoietic niche factors in leptin-receptor-positive stromal bone marrow cells. Induced deletion of the leptin receptor in Prrx1-creERT2; Leprfl/fl mice reveals that leptin’s effect on bone marrow niche cells regulates hematopoietic stem and progenitor cell (HSPC) proliferation and leukocyte production, as well as cardiovascular inflammation and outcomes. Whereas running wheel withdrawal quickly reverses leptin levels, the impact of exercise on leukocyte production and on the HSPC epigenome and transcriptome persists for several weeks. Together, these data show that physical activity alters HSPCs via modulation of their niche, reducing hematopoietic output of inflammatory leukocytes