Salmonella Pathogenesis and Processing of Secreted Effectors by Caspase-3

The enteric pathogen Salmonella enterica serovar Typhimurium causes food poisoning resulting in gastroenteritis. The S. Typhimurium effector Salmonella invasion protein A (SipA) promotes gastroenteritis by functional motifs that trigger either mechanisms of inflammation or bacterial entry. During infection of intestinal epithelial cells, SipA was found to be responsible for the early activation of caspase-3, an enzyme that is required for SipA cleavage at a specific recognition motif that divided the protein into its two functional domains and activated SipA in a manner necessary for pathogenicity. Other caspase-3 cleavage sites identified in S. Typhimurium appeared to be restricted to secreted effector proteins, which indicates that this may be a general strategy used by this pathogen for processing of its secreted effectors

Development of integrated thermionic circuits for high-temperature applications

Integrated thermionic circuits (ITC) capable of extended operation in ambient temperatures up to 500 C are studied. A set of practical design and performance equations is demonstrated. Experimental results are discussed in which both devices and simple circuits were successfully operated in 5000 C environments for extended periods. It is suggested that ITC's may become an important technology for high temperature instrumentation and control systems in geothermal and other high temperature environments

Natural Cycles, Gases

The major gaseous components of the exhaust of stratospheric aircraft are expected to be the products of combustion (CO2 and H2O), odd nitrogen (NO, NO2 HNO3), and products indicating combustion inefficiencies (CO and total unburned hydrocarbons). The species distributions are produced by a balance of photochemical and transport processes. A necessary element in evaluating the impact of aircraft exhaust on the lower stratospheric composition is to place the aircraft emissions in perspective within the natural cycles of stratospheric species. Following are a description of mass transport in the lower stratosphere and a discussion of the natural behavior of the major gaseous components of the stratospheric aircraft exhaust

Utilization of the Multiple Access Communications Satellite (MACSAT) in Support of Tactical Communications

Two MACSATs were launched on May 9, 1990 on a Scout launch vehicle from Vandenberg Air Force Base, California. After a short on-orbit check-out, these research and development satellites were placed into service providing operational communications support to 2d Marine Aircraft Wing units deployed to the Persian Gulf in support of Operations Desert Shield and Desert Storm. This support was provided from August 1990 until Operation Desert Storm was completed in April 1991. During this time, many lessons were learned that are directly applicable to the design and fielding of future small tactical communications satellites. This paper will highlight some of the lessons learned from supporting Operation Desert Shield, as well as other communications support missions

Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag

We study the electrophoretic separation of polyelectrolytes of varying lengths by means of end-labeled free-solution electrophoresis (ELFSE). A coarse-grained molecular dynamics simulation model, using full electrostatic interactions and a mesoscopic Lattice Boltzmann fluid to account for hydrodynamic interactions, is used to characterize the drag coefficients of different label types: linear and branched polymeric labels, as well as transiently bound micelles. It is specifically shown that the label's drag coefficient is determined by its hydrodynamic size, and that the drag per label monomer is largest for linear labels. However, the addition of side chains to a linear label offers the possibility to increase the hydrodynamic size, and therefore the label efficiency, without having to increase the linear length of the label, thereby simplifying synthesis. The third class of labels investigated, transiently bound micelles, seems very promising for the usage in ELFSE, as they provide a significant higher hydrodynamic drag than the other label types. The results are compared to theoretical predictions, and we investigate how the efficiency of the ELFSE method can be improved by using smartly designed drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule

Silicon materials task of the low cost solar array project. Phase 3: Effect of impurities and processing on silicon solar cells

The 13th quarterly report of a study entitled an Investigation of the Effects of Impurities and Processing on Silicon Solar Cells is given. The objective of the program is to define the effects of impurities, various thermochemical processes and any impurity-process interactions on the performance of terrestrial silicon solar cells. The Phase 3 program effort falls in five areas: (1) cell processing studies; (2) completion of the data base and impurity-performance modeling for n-base cells; (3) extension of p-base studies to include contaminants likely to be introduced during silicon production, refining or crystal growth; (4) anisotropy effects; and (5) a preliminary study of the permanence of impurity effects in silicon solar cells. The quarterly activities for this report focus on tasks (1), (3) and (4)

Democracy Derived? New Trajectories in Pluripotent Stem Cell Research

How has the development of human induced pluripotent stem cells (hiPSCs) modified the trajectory of stem cell research? Here, coauthorship networks of stem cell research articles and analysis of cell lines used in stem cell research indicate that hiPSCs are not replacing human embryonic stem cells, but instead, the two cell types are complementary, interdependent research tools. Thus, we conclude that a ban on funding for embryonic stem cell research could have unexpected negative ramifications on the nascent field of hiPSCs

Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541–750)

The first historically documented pandemic caused by Yersinia pestis began as the Justinianic Plague in 541 within the Roman Empire and continued as the so-called First Pandemic until 750. Although paleogenomic studies have previously identified the causative agent as Y. pestis, little is known about the bacterium’s spread, diversity, and genetic history over the course of the pandemic. To elucidate the microevolution of the bacterium during this time period, we screened human remains from 21 sites in Austria, Britain, Germany, France, and Spain for Y. pestis DNA and reconstructed eight genomes. We present a methodological approach assessing single-nucleotide polymorphisms (SNPs) in ancient bacterial genomes, facilitating qualitative analyses of low coverage genomes from a metagenomic background. Phylogenetic analysis on the eight reconstructed genomes reveals the existence of previously undocumented Y. pestis diversity during the sixth to eighth centuries, and provides evidence for the presence of multiple distinct Y. pestis strains in Europe. We offer genetic evidence for the presence of the Justinianic Plague in the British Isles, previously only hypothesized from ambiguous documentary accounts, as well as the parallel occurrence of multiple derived strains in central and southern France, Spain, and southern Germany. Four of the reported strains form a polytomy similar to others seen across the Y. pestis phylogeny, associated with the Second and Third Pandemics. We identified a deletion of a 45-kb genomic region in the most recent First Pandemic strains affecting two virulence factors, intriguingly overlapping with a deletion found in 17th- to 18th-century genomes of the Second Pandemic. © 2019 National Academy of Sciences. All rights reserved