Pack Density Limitations of Hybrid Parachutes

The development and testing of the Orion crew capsule parachute system has provided a unique opportunity to study dense parachute packing techniques and limits, in order to establish a new baseline for future programs. The density of parachute packs has a significant influence on vibration loads, retention system stresses, and parachute mortar performance. Material compositions and pack densities of existing designs for space capsule recovery were compared, using the pack density of the Apollo main parachutes as the current baseline. The composition of parachutes has changed since Apollo, incorporating new materials such as Kevlar , Vectran , Teflon and Spectra . These materials have different specific densities than Nylon, so the densities of hybrid parachute packs cannot be directly compared to Nylon parachutes for determination of feasibility or volume allocation. Six parachute packs were evaluated in terms of weighted average solid density in order to achieve a non-dimensional comparison of packing density. Means of mitigating damage due to packing pressure and mortar firing were examined in light of the Capsule Parachute Assembly System (CPAS) and Apollo experience. Parachute design improvements including incorporation of modern materials and manufacturing processes serves to make CPAS the new knowledge base on which future spacecraft parachute systems will be built

Labor Productivity in Sawmills of the Eastern and Southeastern United States

A survey of sawmills in the eastern and southeastern regions of the United States was conducted. Responding mills produced an average of 12,661 MBf in calendar year 1984 and 76 percent reported annual sales of less than $10 million. The majority of sawmills utilized circular saw headrigs and the most common type of computer controlled/assisted equipment was a log carriage. Softwood sawmills were found to have significantly higher labor productivity than hardwood sawmills. Regression analysis indicated that labor productivity economies of scale exist within the softwood segment of the industry. Labor productivity increased with mill size but at a decreasing rate. No strong evidence of labor productivity economies of scale in the hardwood industry segment was found

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

New Universality Classes for Two-Dimensional σ\sigma-Models

We argue that the two-dimensional $O(N)$-invariant lattice $\sigma$-model with mixed isovector/isotensor action has a one-parameter family of nontrivial continuum limits, only one of which is the continuum $\sigma$-model constructed by conventional perturbation theory. We test the proposed scenario with a high-precision Monte Carlo simulation for $N=3,4$ on lattices up to $512 \times 512$, using a Wolff-type embedding algorithm. [CPU time $\approx$ 7 years IBM RS-6000/320H] The finite-size-scaling data confirm the existence of the predicted new family of continuum limits. In particular, the $RP^{N-1}$ and $N$-vector models do not lie in the same universality class.Comment: 10 pages (includes 2 figures), 211176 bytes Postscript, NYU-TH-93/07/03, IFUP-TH 34/9

Interventions in measles outbreaks: the potential reduction in cases associated with school suspension and vaccination interventions

Background: Measles is resurgent in the US, with more cases in 2019 than any year since 1992. Many of the cases were concentrated in three outbreaks in New York and Washington states, where local governments enacted intervention strategies in an attempt to limit the spread of measles. Regulations differed by location, suggesting guidance on the optimal interventions may be beneficial. Methods: We simulate the daily interactions of the populations of six metropolitan areas of Texas, US, using an agent-based model. The real-life vaccination rates of each school in these metropolitan areas are applied to simulated equivalents. A single case of measles is introduced to the population and the resulting number of cases counted. A range of public health interventions, focused on suspending unvaccinated students and mandatory vaccinations, were simulated during measles outbreaks and the reduction in the number of measles cases, relative to no intervention, recorded. Interventions were simulated only in schools with measles cases and in all schools in each metropolitan area. Results: Suspending unvaccinated students from school was associated with the greatest reduction in measles cases. In a plausible worst-case outbreak scenario, the number of cases is forecast to reduce by 68-96%. Interventions targeting all schools in a metropolitan area is not found to be associated with fewer measles cases than only targeting schools with measles cases, at 2018 vaccination rates. Targeting all schools also increases the cumulative number of school days missed by suspended students by a factor of 10-100, depending on the metropolitan area, compared to targeting only schools with measles cases. If vaccination rates drop 5% in the schools which are under-vaccinated in 2018, metropolitan area-wide interventions are forecast to be associated with fewer cases than school-specific interventions. Conclusions: Interventions that are quickly implemented and widely followed may reduce the size of measles outbreaks by up 96%. If vaccination rates continue to fall in Texas, metropolitan area-wide interventions should be considered in the event of an outbreak

Electron Volt Spectroscopy On The SNS: Initial Facilities and Functional Design

A brief description is presented of the instrument which it is anticipated will be available at the beginning of SNS operations for the development and scientific use of electron volt inelastic neutron spectroscopy

The causes of career termination from sport and their relationship to post-retirement adjustment among elite-amateur athletes in Australia

Former athletes (N = 48) from a variety of sports provided information about the primary reason for their athletic retirement and the degree of adjustment required. Content analysis of reasons for retirement indicated that this sample of athletes retired from competitive sport for numerous reasons, including age, injury, deselection, and voluntary career termination. Subsequent comparisons between athletes who retired for voluntary and involuntary reasons indicated that involuntary retirement was associated with significantly greater emotional and social adjustment on career termination. In addition, the former athletes who experienced the greatest adjustment difficulty perceived the least personal control over the reasons for retirement. Implications for professional and applied work in the area are discussed, and suggestions are made regarding future research on career transitions from sport

A Systematic Review of How Multiple Stressors from an Extreme Event Drove Ecosystem-Wide Loss of Resilience in an Iconic Seagrass Community

A central question in contemporary ecology is how climate change will alter ecosystem structure and function across scales of space and time. Climate change has been shown to alter ecological patterns from individuals to ecosystems, often with negative implications for ecosystem functions and services. Furthermore, as climate change fuels more frequent and severe extreme climate events (ECEs) like marine heatwaves (MHWs), such acute events become increasingly important drivers of rapid ecosystem change. However, our understanding of ECE impacts is hampered by limited collection of broad scale in situ data where such events occur. In 2011, a MHW known as the Ningaloo Niño bathed the west coast of Australia in waters up to 4°C warmer than normal summer temperatures for almost 2 months over 1000s of kilometres of coastline. We revisit published and unpublished data on the effects of the Ningaloo Niño in the seagrass ecosystem of Shark Bay, Western Australia (24.6 – 26.6o S), at the transition zone between temperate and tropical seagrasses. Therein we focus on resilience, including resistance to and recovery from disturbance across local, regional and ecosystem-wide spatial scales and over the past 8 yearsThermal effects on temperate seagrass health were severe and exacerbated by simultaneous reduced light conditions associated with sediment inputs from record floods in the south-eastern embayment and from increased detrital loads and sediment destabilisation. Initial extensive defoliation of Amphibolis antarctica, the dominant seagrass, was followed by rhizome death that occurred in 60-80% of the bay’s meadows, equating to decline of over 1000 km2 of meadows. This loss, driven by direct abiotic forcing, has persisted, while indirect biotic effects (e.g. dominant seagrass loss) have allowed colonisation of some areas by small fast-growing tropical species (e.g. Halodule uninervis). Those biotic effects also impacted multiple consumer populations including turtles and dugongs, with implications for species dynamics, food web structure, and ecosystem recovery. We show multiple stressors can combine to evoke extreme ecological responses by pushing ecosystems beyond their tolerance. Finally, both direct abiotic and indirect biotic effects need to be explicitly considered when attempting to understand and predict how ECEs will alter marine ecosystem dynamics

Res Medica, Spring 1962, Volume III, Number 2

TABLE OF CONTENTSABDOMINAL CRISES II: I. S. R. Sinclair. F.R.C.S.NERVE CELLS AND NEUROGLIA: Professor D. Whitteridge, F.R.S. RESPIRATORY INADEQUACY:Charles E. Hope RES MEDICATHE TREATMENT OF RENAL DISEASES: J. A. Calvert. B.Sc. THE EDINBURGH INFLUENCE ON EARLY AMERICAN MEDICINE: Professor Sir Walter MercerSIR CHARLES BELL: Robert A. ButlerOFFICE-BEARERS 1961-1962RETROSPECT—225th SESSIONBOOK REVIE