Receptor-Induced Thiolate Couples Env Activation to Retrovirus Fusion and Infection

According to current models of retrovirus infection, receptor binding to the surface subunit (SU) of the envelope glycoprotein (Env) triggers a conformational change in the transmembrane subunit (TM) that mediates virus fusion to cell membranes. To understand how this occurs, we investigated the role of the receptor Tva in avian leukosis virus-A (ALV-A) infection. We find that Tva binding induced the formation of a reactive thiolate on Cys38 (Cys38-S−) in SU. Both chemical and genetic inactivation of Cys38-S− completely abrogated ALV fusion and infection. Remarkably, Cys38-S− does not mediate isomerization of the SU-TM disulfide bond and is not required for Tva-induced activation of TM, including pre-hairpin association with membranes and low pH assembly of helical bundles. These findings indicate that, contrary to current models, receptor activation of TM is not sufficient for ALV fusion and infection and that formation of a reactive thiolate is an additional receptor-dependent step

Tuning biexciton binding and anti-binding in core/shell quantum dots

We use a path integral quantum Monte Carlo method to simulate excitons and biexcitons in core shell nanocrystals with Type-I, II and quasi-Type II band alignments. Quantum Monte Carlo techniques allow for all quantum correlations to be included when determining the thermal ground state, thus producing accurate predictions of biexciton binding. These subtle quantum correlations are found to cause the biexciton to be binding with Type-I carrier localization and strongly anti-binding with Type-II carrier localization, in agreement with experiment for both core shell nanocrystals and dot in rod nanocrystal structures. Simple treatments based on perturbative approaches are shown to miss this important transition in the biexciton binding. Understanding these correlations offers prospects to engineer strong biexciton anti-binding which is crucial to the design of nanocrystals for single exciton lasing applications.Comment: 10 pages, 11 figure

Manufacturing responsiveness as a competitive advantage and implementation in a make-to-order environment

Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; in conjunction with the Leaders for Manufacturing Program at MIT, 2005.Includes bibliographical references (p. 65-66).Many companies have been successful differentiating themselves and creating growth opportunities by developing a competitive advantage through their manufacturing operations. During the last century, this operational advantage has generally included economies of scale and the persistent pursuit of lower direct costs. However, this thesis contends that a cost focused manufacturing organization encourages decisions that in the long run make the organization rigid, inflexible and unable to implement innovations the market desires. Not unexpectedly, those companies that fail to recognize and incorporate changing market demands are relegated to reading about their competitor's successes in newspapers and journals. This thesis further presents an argument to shift the manufacturing organization's operational focus away from cost and towards time. More specifically, this thesis posits that firms should persistently pursue a reduction in the time required to manufacture a customer's order from receipt to shipment.(cont.) The ideas here are based largely on literature research as well as insights gained during the author's 6.5 month internship at ABB CNTDS. ABB CNTDS is a joint venture manufacturer of power distribution transformers located in Shanghai, P.R. China. Distribution transformers are produced in a make-to-order environment and include significant engineering and customization for each customer's order. The concepts can, however, be extended to any manufacturing organization looking to gain a competitive advantage through speed, innovation, and customer focus - thereby avoiding the undesirable state of low margin, cost competition.by Jason M. Smith.S.M.M.B.A

Jane Jacobs' ‘Cities First’ Model and Archaeological Reality

In The Economy of Cities, Jane Jacobs conjectured that the world's first cities preceded the origins of agriculture, a proposition that was most recently revived by Peter Taylor in the pages of this journal. Jacobs' idea was out of line with extant archaeological findings when first advanced decades ago, and it remains firmly contradicted by a much fuller corpus of data today. After a review of how and why Jacobs formulated her ‘cities first’ model, we review current archaeological knowledge from the Near East, China and Mesoamerica to document the temporal precedence of agriculture before urbanism in each of these regions. Contrary to the opinions of Jacobs and Taylor, archaeological data are in fact sufficiently robust to reconstruct patterns of diet, settlement and social organization in the past, and to assign dates to the relevant sites. Our response illustrates how generations of archaeological discoveries have yielded solid empirical foundations for the evaluation of wider social scientific debates.Anthropolog

Acute alcohol administration dampens central extended amygdala reactivity.

Alcohol use is common, imposes a staggering burden on public health, and often resists treatment. The central extended amygdala (EAc)-including the bed nucleus of the stria terminalis (BST) and the central nucleus of the amygdala (Ce)-plays a key role in prominent neuroscientific models of alcohol drinking, but the relevance of these regions to acute alcohol consumption in humans remains poorly understood. Using a single-blind, randomized-groups design, multiband fMRI data were acquired from 49 social drinkers while they performed a well-established emotional faces paradigm after consuming either alcohol or placebo. Relative to placebo, alcohol significantly dampened reactivity to emotional faces in the BST. To rigorously assess potential regional differences in activation, data were extracted from unbiased, anatomically predefined regions of interest. Analyses revealed similar levels of dampening in the BST and Ce. In short, alcohol transiently reduces reactivity to emotional faces and it does so similarly across the two major divisions of the human EAc. These observations reinforce the translational relevance of addiction models derived from preclinical work in rodents and provide new insights into the neural systems most relevant to the consumption of alcohol and to the initial development of alcohol abuse in humans

Ducted magnetoacoustic waves in the solar corona

This thesis investigates the ducting of magnetoacoustic waves in coronal structures. The propagation of waves in current sheets and coronal loops has been examined in order to understand wave ducting in structured plasmas, and to provide an explanation of the observed oscillatory behaviour in the solar corona. Firstly a comprehensive review of the observations of loops and oscillations in the corona is given. An investigation into how the curvature of the loop alters the ducting of magnetoacoustic waves is then presented by studying the effect of the length, width and the density enhancement of the loop and also the frequency of oscillation. The effect of the curvature is to generate wave leakage from the loop. The guiding of magnetoacoustic waves by a current sheet is also considered. An investigation into the type of modes which may propagate and the time scales of oscillation is performed. Impulsively generated waves exhibit similar temporal signatures to observations of X-ray and radio emission. Periods of oscillation for all the ducted wave models are in good agreement with reported observations. The effect of a random boundary motion on a magnetospheric cavity is examined through numerical simulations. A broadband driving spectrum excites the quasi-monochromatic fast modes whose frequencies lie within the driving spectrum. These fast modes couple to an Alfvén mode if the frequency lies within the Alfvén continuum. The position of the resonant field lines and the Alfvén mode eigenfunction may be accurately calculated by assuming a periodic boundary motion. To conclude the work in this thesis the three-dimensional magnetic topologies surrounding neutral points are studied. The local linear magnetic structure about the null is found to depend only on a 3 X 3 matrix containing four parameters. The type of topology is dependent upon the nature of the eigenvalues and eigenvectors of this matrix

Room-temperature exciton-polaritons with two-dimensional WS2

Two-dimensional transition metal dichalcogenides exhibit strong optical transitions with significant potential for optoelectronic devices. In particular they are suited for cavity quantum electrodynamics in which strong coupling leads to polariton formation as a root to realisation of inversionless lasing, polariton condensationand superfluidity. Demonstrations of such strongly correlated phenomena to date have often relied on cryogenic temperatures, high excitation densities and were frequently impaired by strong material disorder. At room-temperature, experiments approaching the strong coupling regime with transition metal dichalcogenides have been reported, but well resolved exciton-polaritons have yet to be achieved. Here we report a study of monolayer WS$_2$ coupled to an open Fabry-Perot cavity at room-temperature, in which polariton eigenstates are unambiguously displayed. In-situ tunability of the cavity length results in a maximal Rabi splitting of $\hbar \Omega_{\rm{Rabi}} = 70$ meV, exceeding the exciton linewidth. Our data are well described by a transfer matrix model appropriate for the large linewidth regime. This work provides a platform towards observing strongly correlated polariton phenomena in compact photonic devices for ambient temperature applications.Comment: 12 pages, 6 figure

AWIPS II Application Development, a SPoRT Perspective

The National Weather Service (NWS) is deploying its nextgeneration decision support system, called AWIPS II (Advanced Weather Interactive Processing System II). NASA's Shortterm Prediction Research and Transition (SPoRT) Center has developed several software 'plugins' to extend the capabilities of AWIPS II. SPoRT aims to continue its mission of improving shortterm forecasts by providing NASA and NOAA products on the decision support system used at NWS weather forecast offices (WFOs). These products are not included in the standard Satellite Broadcast Network feed provided to WFOs. SPoRT has had success in providing support to WFOs as they have transitioned to AWIPS II. Specific examples of transitioning SPoRT plugins to WFOs with newly deployed AWIPS II systems will be presented. Proving Ground activities (GOESR and JPSS) will dominate SPoRT's future AWIPS II activities, including tool development as well as enhancements to existing products. In early 2012 SPoRT initiated the Experimental Product Development Team, a group of AWIPS II developers from several institutions supporting NWS forecasters with innovative products. The results of the team's spring and fall 2013 meeting will be presented. Since AWIPS II developers now include employees at WFOs, as well as many other institutions related to weather forecasting, the NWS has dealt with a multitude of software governance issues related to the difficulties of multiple remotely collaborating software developers. This presentation will provide additional examples of ResearchtoOperations plugins, as well as an update on how governance issues are being handled in the AWIPS II developer community