Modeling Studies of Gravity Wave Dynamics in Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, and Induced Flow Responses

A compressible numerical model is applied for three-dimensional (3-D) gravity wave (GW) packets undergoing momentum deposition, self-acceleration (SA), breaking, and secondary GW (SGW) generation in the presence of highly-structured environments enabling thermal and/or Doppler ducts, such as a mesospheric inversion layer (MIL), tidal wind (TW), or combination of MIL and TW. Simulations reveal that ducts can strongly modulate GW dynamics. Responses modeled here include reflection, trapping, suppressed transmission, strong local instabilities, reduced SGW generations, higher altitude SGW responses, and induced large-scale flows. Instabilities that arise in ducts experience strong dissipation after they emerge, while trapped smaller-amplitude and smaller-scale GWs can survive in ducts to much later times. Additionally, GW breaking and its associated dynamics enhance the local wind along the GW propagation direction in the ducts, and yield layering in the wind field. However, these dynamics do not yield significant heat transport in the ducts. The failure of GW breaking to induce stratified layers in the temperature field suggests that such heat transport might not be as strong as previously assumed or inferred from observations and theoretical assessments. The present numerical simulations confirm previous finding that MIL generation may not be caused by the breaking of a transient high-frequency GW packet alone

The Nuclear Network: Multiplex Network Analysis for Interconnected Systems

States facing the decision to develop a nuclear weapons program do so within a broader context of their relationships with other countries. How these diplomatic, economic, and strategic relationships impact proliferation decisions, however, remains under-specified. Adding to the existing empirical literature that attempts to model state proliferation decisions, this article introduces the first quantitative heterogeneous network analysis of how networks of conflict, alliances, trade, and nuclear cooperation interact to spur or deter nuclear proliferation. Using a multiplex network model, we conceptualize states as nodes linked by different modes of interaction represented on individual network layers. Node strength is used to quantify factors correlated with nuclear proliferation and these are combined in a weighted sum across layers to provide a metric characterizing the proliferation behavior of the state. This multiplex network modeling approach provides a means for identifying states with the highest relative likelihood of proliferation—based only on their relationships to other states. This work demonstrates that latent conflict and nuclear cooperation are positively correlated with proliferation, while an increased trade dependence suggests a decreased proliferation likelihood. A case study on Iran’s controversial nuclear program and past nuclear activity is also provided. These findings have clear, policy-relevant conclusions related to alliance posture, sanctions policy, and nuclear assistance. Abstract ©The Authors

Ly-alpha Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field South

We describe the results of an extremely deep, 0.28 deg^2 survey for z = 3.1 Ly-alpha emission-line galaxies in the Extended Chandra Deep Field South. By using a narrow-band 5000 Anstrom filter and complementary broadband photometry from the MUSYC survey, we identify a statistically complete sample of 162 galaxies with monochromatic fluxes brighter than 1.5 x 10^-17 ergs cm^-2 s^-1 and observers frame equivalent widths greater than 80 Angstroms. We show that the equivalent width distribution of these objects follows an exponential with a rest-frame scale length of w_0 = 76 +/- 10 Angstroms. In addition, we show that in the emission line, the luminosity function of Ly-alpha galaxies has a faint-end power-law slope of alpha = -1.49 +/- 0.4, a bright-end cutoff of log L^* = 42.64 +/- 0.2, and a space density above our detection thresholds of 1.46 +/- 0.12 x 10^-3 h70^3 galaxies Mpc^-3. Finally, by comparing the emission-line and continuum properties of the LAEs, we show that the star-formation rates derived from Ly-alpha are ~3 times lower than those inferred from the rest-frame UV continuum. We use this offset to deduce the existence of a small amount of internal extinction within the host galaxies. This extinction, coupled with the lack of extremely-high equivalent width emitters, argues that these galaxies are not primordial Pop III objects, though they are young and relatively chemically unevolved.Comment: 45 pages, 15 figures, accepted for publication in the Astrophysical Journa

Identification of new drug targets and resistance mechanisms in Mycobacterium tuberculosis

Identification of new drug targets is vital for the advancement of drug discovery against Mycobacterium tuberculosis , especially given the increase of resistance worldwide to first- and second-line drugs. Because traditional target-based screening has largely proven unsuccessful for antibiotic discovery, we have developed a scalable platform for target identification in M. tuberculosis that is based on whole-cell screening, coupled with whole-genome sequencing of resistant mutants and recombineering to confirm. The method yields targets paired with whole-cell active compounds, which can serve as novel scaffolds for drug development, molecular tools for validation, and/or as ligands for co-crystallization. It may also reveal other information about mechanisms of action, such as activation or efflux. Using this method, we identified resistance-linked genes for eight compounds with anti-tubercular activity. Four of the genes have previously been shown to be essential: AspS, aspartyl-tRNA synthetase, Pks13, a polyketide synthase involved in mycolic acid biosynthesis, MmpL3, a membrane transporter, and EccB3, a component of the ESX-3 type VII secretion system. AspS and Pks13 represent novel targets in protein translation and cell-wall biosynthesis. Both MmpL3 and EccB3 are involved in membrane transport. Pks13, AspS, and EccB3 represent novel candidates not targeted by existing TB drugs, and the availability of whole-cell active inhibitors greatly increases their potential for drug discovery

Bostonia

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Centerscope

Centerscope, formerly Scope, was published by the Boston University Medical Center "to communicate the concern of the Medical Center for the development and maintenance of improved health care in contemporary society.

The embodied becoming of autism and childhood: a storytelling methodology

In this article I explore a methodology of storytelling as a means of bringing together research around autism and childhood in a new way, as a site of the embodied becoming of autism and childhood. Through reflection on an ethnographic story of embodiment, the body is explored as a site of knowledge production that contests its dominantly storied subjectivation as a ‘disordered’ child. Storytelling is used to experiment with a line of flight from the autistic-child-research assemblage into new spaces of potential and possibility where the becomings of bodies within the collision of autism and childhood can be celebrated

Zonal surface wind jets across the Red Sea due to mountain gap forcing along both sides of the Red Sea

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 36 (2009): L19605, doi:10.1029/2009GL040008.Mesoscale atmospheric modeling over the Red Sea, validated by in-situ meteorological buoy data, identifies two types of coastal mountain gap wind jets that frequently blow across the longitudinal axis of the Red Sea: (1) an eastward-blowing summer daily wind jet originating from the Tokar Gap on the Sudanese Red Sea coast, and (2) wintertime westward-blowing wind-jet bands along the northwestern Saudi Arabian coast, which occur every 10–20 days and can last for several days when occurring. Both wind jets can attain wind speeds over 15 m s−1 and contribute significantly to monthly mean surface wind stress, especially in the cross-axis components, which could be of importance to ocean eddy formation in the Red Sea. The wintertime wind jets can cause significant evaporation and ocean heat loss along the northeastern Red Sea coast and may potentially drive deep convection in that region. An initial characterization of these wind jets is presented.Supported by Award Numbers USA 00001, USA 00002, and KSA 00011 made by KAUST

Nontypeable haemophilus influenzae induces sustained lung oxidative stress and protease expression

© 2015 King et al. Nontypeable Haemophilus influenzae (NTHi) is a prevalent bacterium found in a variety of chronic respiratory diseases. The role of this bacterium in the pathogenesis of lung inflammation is not well defined. In this study we examined the effect of NTHi on two important lung inflammatory processes 1), oxidative stress and 2), protease expression. Bronchoalveolar macrophages were obtained from 121 human subjects, blood neutrophils from 15 subjects, and human-lung fibroblast and epithelial cell lines from 16 subjects. Cells were stimulated with NTHi to measure the effect on reactive oxygen species (ROS) production and extracellular trap formation. We also measured the production of the oxidant, 3-nitrotyrosine (3-NT) in the lungs of mice infected with this bacterium. NTHi induced widespread production of 3-NT in mouse lungs. This bacterium induced significantly increased ROS production in human fibroblasts, epithelial cells, macrophages and neutrophils; with the highest levels in the phagocytic cells. In human macrophages NTHi caused a sustained, extracellular production of ROS that increased over time. The production of ROS was associated with the formation of macrophage extracellular trap-like structures which co-expressed the protease metalloproteinase-12. The formation of the macrophage extracellular trap-like structures was markedly inhibited by the addition of DNase. In this study we have demonstrated that NTHi induces lung oxidative stress with macrophage extracellular trap formation and associated protease expression. DNase inhibited the formation of extracellular traps

Optoactivation of locus ceruleus neurons evokes bidirectional changes in thermal nociception in rats

International audiencePontospinal noradrenergic neurons are thought to form part of a descending endogenous analgesic system that exerts inhibitory influences on spinal nociception. Using optogenetic targeting, we tested the hypothesis that excitation of the locus ceruleus (LC) is antinociceptive. We transduced rat LC neurons by direct injection of a lentiviral vector expressing channelrhodopsin2 under the control of the PRS promoter. Subsequent optoactivation of the LC evoked repeatable, robust, antinociceptive (-4.7 degrees C +/- 1.0, p < 0.0001) or pronociceptive (-4.4 degrees C +/- 0.7, p < 0.0001) changes in hindpaw thermal withdrawal thresholds. Post hoc anatomical characterization of the distribution of transduced somata referenced against the position of the optical fiber and subsequent further functional analysis showed that antinociceptive actions were evoked from a distinct, ventral subpopulation of LC neurons. Therefore, the LC is capable of exerting potent, discrete, bidirectional influences on thermal nociception that are produced by specific subpopulations of noradrenergic neurons. This reflects an underlying functional heterogeneity of the influence of the LC on the processing of nociceptive information