Designing dual-plate meteoroid shields: A new analysis

Physics governing ultrahigh velocity impacts onto dual-plate meteor armor is discussed. Meteoroid shield design methodologies are considered: failure mechanisms, qualitative features of effective meteoroid shield designs, evaluating/processing meteoroid threat models, and quantitative techniques for optimizing effective meteoroid shield designs. Related investigations are included: use of Kevlar cloth/epoxy panels in meteoroid shields for the Halley's Comet intercept vehicle, mirror exposure dynamics, and evaluation of ion fields produced around the Halley Intercept Mission vehicle by meteoroid impacts

Alien Registration- Bamford, Ruby H. (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/24070/thumbnail.jp

Disaster warning system: Satellite feasibility and comparison with terrestrial systems. Volume 1: Executive summary

The Disaster Warning System (DWS) is a conceptual system which will provide the National Weather Service (NWS) with communication services in the 1980s to help minimize losses caused by natural disasters. The object of this study is a comparative analysis between a terrestrial DWS and a satellite DWS. Baseline systems satisfying the NOAA requirements were synthesized in sufficient detail so that a comparison could be made in terms of performance and cost. The cost of both baseline systems is dominated by the disaster warning and spotter reporting functions. An effort was undertaken to reduce system cost through lower-capacity alternative systems generated by modifying the baseline systems. By reducing the number of required channels and modifying the spotter reporting techniques, alternative satellite systems were synthesized. A terrestrial alternative with the coverage reduced to an estimated 95 percent of the population was considered

Disaster warning system: Satellite feasibility and comparison with terrestrial systems. Volume 2: Final report

For abstract, see Vol. 1

Overcoming the false-minima problem in direct methods: Structure determination of the packaging enzyme P4 from bacteriophage φ13

The problems encountered during the phasing and structure determination of the packaging enzyme P4 from bacteriophage φ13 using the anomalous signal from selenium in a single-wavelength anomalous dispersion experiment (SAD) are described. The oligomeric state of P4 in the virus is a hexamer (with sixfold rotational symmetry) and it crystallizes in space group C2, with four hexamers in the crystallographic asymmetric unit. Current state-of-the-art ab initio phasing software yielded solutions consisting of 96 atoms arranged as sixfold symmetric clusters of Se atoms. However, although these solutions showed high correlation coefficients indicative that the substructure had been solved, the resulting phases produced uninterpretable electron-density maps. Only after further analysis were correct solutions found (also of 96 atoms), leading to the eventual identification of the positions of 120 Se atoms. Here, it is demonstrated how the difficulties in finding a correct phase solution arise from an intricate false-minima problem. © 2005 International Union of Crystallography - all rights reserved

Transbilayer distribution of phospholipids in bacteriophage membranes

AbstractWe have previously demonstrated that the membranes of several bacteriophages contain more phosphatidylglycerol (PG) and less phosphatidylethanolamine (PE) than the host membrane from where they are derived. Here, we determined the transbilayer distribution of PG and PE in the membranes of bacteriophages PM2, PRD1, Bam35 and phi6 using selective modification of PG and PE in the outer membrane leaflet with sodium periodate or trinitrobenzene sulfonic acid, respectively. In phi6, the transbilayer distributions of PG, PE and cardiolipin could also be analyzed by selective hydrolysis of the lipids in the outer leaflet by phospholipase A2. We used electrospray ionization mass-spectrometry to determine the transbilayer distribution of phospholipid classes and individual molecular species. In each bacteriophage, PG was enriched in the outer membrane leaflet and PE in the inner one (except for Bam35). Only modest differences in the transbilayer distribution between different molecular species were observed. The effective shape and charge of the phospholipid molecules and lipid–protein interactions are likely to be most important factors driving the asymmetric distribution of phospholipids in the phage membranes. The results of this first systematic study on the phospholipid distribution in bacteriophage membranes will be very helpful when interpreting the accumulating high-resolution data on these organisms

Conservation of major and minor jelly-roll capsid proteins in Polinton (Maverick) transposons suggests that they are bona fide viruses

Peer reviewe

Speech audiometry test with picture-related sentence lists in Modern Greek for partially hearing children

Objective: The aim of this study was to develop Greek Sentence Based Speech Audiometry Test in quiet test for Hearing Impaired (HI) children (G-SEBSAT). Methods: Seventy-six children were recruited following approval by the local ethics committee and after obtaining informed consent from their parents. The collection of vocabulary was based on showing pictures selected from popular reading materials in Greek to hearing impaired HI children. A grammatical content analysis was carried out to determine the average syntactic and morphological structures of the sentences used by the HI children. Ten picture related sentence lists were developed based on the vocabulary and the grammatical analysis, and recorded by a male native speaker of standard Modern Greek. These were presented to both normal hearing (NH) and HI children, and the average speech response threshold (SRT) as well as the slope of the SRT curve at the SRT level of 50% correct responses (S50) were recorded in both groups. Sentence lists were validated with respect to the variability of their difficulty within each group, as well the test-retest variability of the respective SRT scores. Results: The average speech response threshold (SRT) across all lists for HI children was 65.27 dB and the slope of the SRT curve at the SRT level of 50% correct responses was 3.11%/dB. The corresponding results across all lists for NH children were 17.66 dB and 9.7%/dB, respectively. The SRT of HI children were strongly positively correlated, in a statistically significant manner with the PTA in both the test and the retest sessions (test: r=0.750, P < 0.0005; retest: r=0.753, P < 0.0005). The Spearman correlation of the rankings of SRT values and the slope values was 0.998 and 0.997 respectively for the HI and 0.939 and 0.88, for the NH group, indicating very low variability across the test and retest sessions. In addition, the analysis of variance (ANOVA) of the average SRT in NH children and the SRT residuals in the HI group indicated that the different sentences were of the same difficulty within each group. ((F(9,81)=0.401, p=0.930 and (F(9,93)=2.241, p=0.025 respectively). Conclusions: A validated sentence based speech audiometry test was created in Greek for the first time. SRT and S50 values for both NH and HI children are comparable to similar tests developed in other languages

Nucleic and Amino Acid Sequences Support Structure-Based Viral Classification

Viral capsids ensure viral genome integrity by protecting the enclosed nucleic acids. Interactions between the genome and capsid and between individual capsid proteins (i.e., capsid architecture) are intimate and are expected to be characterized by strong evolutionary conservation. For this reason, a capsid structure-based viral classification has been proposed as a way to bring order to the viral universe. The seeming lack of sufficient sequence similarity to reproduce this classification has made it difficult to reject structural convergence as the basis for the classification. We reinvestigate whether the structure-based classification for viral coat proteins making icosahedral virus capsids is in fact supported by previously undetected sequence similarity. Since codon choices can influence nascent protein folding cotranslationally, we searched for both amino acid and nucleotide sequence similarity. To demonstrate the sensitivity of the approach, we identify a candidate gene for the pandoravirus capsid protein. We show that the structure-based classification is strongly supported by amino acid and also nucleotide sequence similarities, suggesting that the similarities are due to common descent. The correspondence between structure-based and sequence-based analyses of the same proteins shown here allow them to be used in future analyses of the relationship between linear sequence information and macromolecular function, as well as between linear sequence and protein folds. IMPORTANCE Viral capsids protect nucleic acid genomes, which in turn encode capsid proteins. This tight coupling of protein shell and nucleic acids, together with strong functional constraints on capsid protein folding and architecture, leads to the hypothesis that capsid protein-coding nucleotide sequences may retain signatures of ancient viral evolution. We have been able to show that this is indeed the case, using the major capsid proteins of viruses forming icosahedral capsids. Importantly, we detected similarity at the nucleotide level between capsid protein-coding regions from viruses infecting cells belonging to all three domains of life, reproducing a previously established structure-based classification of icosahedral viral capsids.Peer reviewe