522 research outputs found

    Op Ed -- Opinions and Editorials

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    Estimating Deployed Airlift and Equipment Requirements for F-16 Aircraft in Support of the Advanced Logistics Project

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    The Advanced Logistics Project (ALP) is a 5-year DARPA effort to investigate automated architectures to increase the efficiency of logistics support for deploying combat forces. The Mission-Resource Value Assessment Tool (M-R VAT) is a joint AFIT/AFRL adjunct processor to the ALP. The purpose of the M-R VAT is to select optimal force packages to meet the needs of theater commanders. This research supports the development of the M-R VAT\u27s capability through the development of an airlift estimation function and validating equipment requirement rule-sets. This airlift estimation function will allow the M-R VAT optimization algorithms to constrain the selection of the optimal force package based upon the airlift estimator\u27s output versus available airlift. The rule-sets are used in support of the M-R VAT Time Phased Force Deployment list generator. Justification of existing rule-sets for equipment determination will allow for their use in the M-R VAT existing software structure. This will give M-R VAT the capability to determine logistics needs for a given force package. Major findings include: (1) the determination of a useful \u27best fit\u27 function for aggregate lift requirements; and (2) validation and demonstration of the utility of a family of rule-sets fore equipment

    Technical Note: Comparison of storage strategies of sea surface microlayer samples

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    The sea surface microlayer (SML) is an important biogeochemical system whose physico-chemical analysis often necessitates some degree of sample storage. However, many SML components degrade with time so the development of optimal storage protocols is paramount. We here briefly review some commonly used treatment and storage protocols. Using freshwater and saline SML samples from a river estuary, we investigated temporal changes in surfactant activity (SA) and the absorbance and fluorescence of chromophoric dissolved organic matter (CDOM) over four weeks, following selected sample treatment and storage protocols. Some variability in the effectiveness of individual protocols most likely reflects sample provenance. None of the various protocols examined performed any better than dark storage at 4 °C without pre-treatment. We therefore recommend storing samples refrigerated in the dark

    Recurrent invasion and extinction of a selfish gene

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    Homing endonuclease genes show super-Mendelian inheritance, which allows them to spread in populations even when they are of no benefit to the host organism. To test the idea that regular horizontal transmission is necessary for the long-term persistence of these genes, we surveyed 20 species of yeasts for the ω-homing endonuclease gene and associated group I intron. The status of ω could be categorized into three states (functional, nonfunctional, or absent), and status was not clustered on the host phylogeny. Moreover, the phylogeny of ω differed significantly from that of the host, strong evidence of horizontal transmission. Further analyses indicate that horizontal transmission is more common than transposition, and that it occurs preferentially between closely related species. Parsimony analysis and coalescent theory suggest that there have been 15 horizontal transmission events in the ancestry of our yeast species, through simulations indicate that this value is probably an underestimate. Overall, the data support a cyclical model of invasion, degeneration, and loss, followed by reinvasion, and each of these transitions is estimated to occur about once every 2 million years. The data are thus consistent with the idea that frequent horizontal transmission is necessary for the long-term persistence of homing endonuclease genes, and further, that this requirement limits these genes to organisms with easily accessible germ lines. The data also show that mitochondrial DNA sequences are transferred intact between yeast species; if other genes do not show such high levels of horizontal transmission, it would be due to lack of selection, rather than lack of opportunity

    Quantifying separation and similarity in a Saccharomyces cerevisiae metapopulation

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    Eukaryotic microbes are key ecosystem drivers; however, we have little theory and few data elucidating the processes influencing their observed population patterns. Here we provide an in-depth quantitative analysis of population separation and similarity in the yeast Saccharomyces cerevisiae with the aim of providing a more detailed account of the population processes occurring in microbes. Over 10 000 individual isolates were collected from native plants, vineyards and spontaneous ferments of fruit from six major regions spanning 1000 km across New Zealand. From these, hundreds of S. cerevisiae genotypes were obtained, and using a suite of analytical methods we provide comprehensive quantitative estimates for both population structure and rates of gene flow or migration. No genetic differentiation was detected within geographic regions, even between populations inhabiting native forests and vineyards. We do, however, reveal a picture of national population structure at scales above ~100 km with distinctive populations in the more remote Nelson and Central Otago regions primarily contributing to this. In addition, differential degrees of connectivity between regional populations are observed and correlate with the movement of fruit by the New Zealand wine industry. This suggests some anthropogenic influence on these observed population patterns

    Sex enhances adaptation by unlinking beneficial from detrimental mutations in experimental yeast populations

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    <p>Abstract</p> <p>Background</p> <p>The maintenance of sexuality is a classic problem in evolutionary biology because it is a less efficient mode of reproduction compared with asexuality; however, many organisms are sexual. Theoretical work suggests sex facilitates natural selection, and experimental data support this. However, there are fewer experimental studies that have attempted to determine the mechanisms underlying the advantage of sex. Two main classes of hypotheses have been proposed to explain its advantage: detrimental mutation clearance and beneficial mutation accumulation. Here we attempt to experimentally differentiate between these two classes by evolving <it>Saccharomyces cerevisiae </it>populations that differ only in their ability to undergo sex, and also manipulate mutation rate. We cannot manipulate the types of mutation that occur, but instead propagate populations in both stressful and permissive environments and assume that the extent of detrimental mutation clearance and beneficial mutation incorporation differs between them.</p> <p>Results</p> <p>After 300 mitotic generations interspersed with 11 rounds of sex we found there was no change or difference in fitness between sexuals and asexuals propagated in the permissive environment, regardless of mutation rate. Sex conferred a greater extent of adaptation in the stressful environment, and wild-type and elevated mutation rate sexual populations adapted equivalently. However, the asexual populations with an elevated mutation rate appeared more retarded in their extent of adaptation compared to asexual wild-type populations.</p> <p>Conclusions</p> <p>Sex provided no advantage in the permissive environment where beneficial mutations were rare. We could not evaluate if sex functioned to clear detrimental mutations more effectively or not here as no additional fitness load was observed in the mutator populations. However, in the stressful environment, where detrimental mutations were likely of more consequence, and where beneficial mutations were apparent, sex provided an advantage. In the stressful environment asexuals were increasingly constrained in their extent of adaptation with increasing mutation rate. Sex appeared to facilitate adaptation not just by more rapidly combining beneficial mutations, but also by unlinking beneficial from detrimental mutations: sex allowed selection to operate on both types of mutations more effectively compared to asexual populations.</p

    Readability and suitability of implantable hearing device information published online in English.

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    The aim of this Master of Audiology thesis was to investigate online English-language information relating to implantable hearing devices, such as cochlear implants, and bone-anchored hearing aids. Specific goals included: (1) to assess the readability of materials (Flesch-Kincaid, SMOG, Gunning-Fog), and relate this to adult literacy levels; (2), to assess suitability of online information (DISCERN, PEMAT, Plain Language, SAM+CAM), and relate this to search engine queries people use in order to research such information; and (3), to test whether or not organisation type, geographic location, and HONcode certification act as moderating factors on webpage readability and suitability. Methods included: surveying key search terms related to “implantable hearing devices,” obtained using convenience sampling (n=25), followed by refinement of search terms using Google Trends. Results showed that webpages placed high literacy demands on readers, requiring on average a 10-12th reading grade level for basic comprehension, which far exceeds recommendations set by several organisations. Serious shortcomings were also found concerning incomplete discussion of treatment choices, transparency of information sources, confusing visual aids, and frequent use of technical terms without sufficient lay explanation. Multivariate and univariate statistical analyses revealed no significant effect of webpage location, organisation type, or HONcode certification on readability and suitability measures. Conclusions: several aspects of webpage content design act as barriers to effective information gathering. However, neither HONcode certification nor web domain location nor organisation type seem to be among them

    The Effect of Angiotensin Converting Enzyme Genotype on Aerobic Capacity Following High Intensity Interval Training

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    International Journal of Exercise Science 7(3) : 250-259, 2014. Obesity increases the risk of developing type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Physical activity can reduce T2DM and CVD risk, and increase aerobic capacity, a significant predictor of all-cause mortality and morbidity. High intensity interval training (HIIT) produces similar improvements in aerobic capacity to continuous moderate exercise (CME). Different genotypes of angiotensin converting enzyme (ACE) have been implicated in improving aerobic capacity and therefore predicted health. This study investigated the effects of different ACE genotypes on the impact of 6 weeks of HIIT on aerobic capacity, and thus health status. 20 young adults were recruited for this study; test subjects completed 6 weeks of HIIT 3 times a week. VO2max was tested to determine aerobic capacity pre- and post-HIIT and DNA collected from saliva for determination ACE genotype. After 6 weeks of HIIT there was no significant change in VO2max; when subjects were separated into responder categories, high responders significantly increased their aerobic capacity whilst there was a large but non-significant decrease in non-responders. Subjects carrying a D-allele showed a significant increase in VO2max following HIIT indicating specific ACE genotypes may be associated with differing VO2max responses. These preliminary results suggest that HIIT can significantly reduce the time required for exercise whilst still achieving notable improvements in aerobic capacity in high responders; they also indicate that ACE D-allele carriers who would not usually be expected to show large VO2max responses following CME may yield equivalent aerobic capacity improvements following HIIT, and thereby reduce their overall morbidity and mortality disease risk

    Invasion and persistence of a selfish gene in the Cnidaria

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    Background. Homing endonuclease genes (HEGs) are superfluous, but are capable of invading populations that mix alleles by biasing their inheritance patterns through gene conversion. One model suggests that their long-term persistence is achieved through recurrent invasion. This circumvents evolutionary degeneration, but requires reasonable rates of transfer between species to maintain purifying selection. Although HEGs are found in a variety of microbes, we found the previous discovery of this type of selfish genetic element in the mitochondria of a sea anemone surprising. Methods/Principal Findings. We surveyed 29 species of Cnidaria for the presence of the COXI HEG. Statistical analyses provided evidence for HEG invasion. We also found that 96 individuals of Metridium senile, from five different locations in the UK, had identical HEG sequences. This lack of sequence divergence illustrates the stable nature of Anthozoan mitochondria. Our data suggests this HEG conforms to the recurrent invasion model of evolution. Conclusions. Ordinarily such low rates of HEG transfer would likely be insufficient to enable major invasion. However, the slow rate of Anthozoan mitochondrial change lengthens greatly the time to HEG degeneration: this significantly extends the periodicity of the HEG life-cycle. We suggest that a combination of very low substitution rates and rare transfers facilitated metazoan HEG invasion. © 2006 Goddard et al

    SquidLab—A user-friendly program for background subtraction and fitting of magnetization data

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    We present an open-source program free to download for academic use with a full user-friendly graphical interface for performing flexible and robust background subtraction and dipole fitting on magnetization data. For magnetic samples with small moment sizes or sample environments with large or asymmetric magnetic backgrounds, it can become necessary to separate background and sample contributions to each measured raw voltage measurement before fitting the dipole signal to extract magnetic moments. Originally designed for use with pressure cells on a Quantum Design MPMS3 SQUID magnetometer, SquidLab is a modular object-oriented platform implemented in Matlab with a range of importers for different widely available magnetometer systems (including MPMS, MPMS-XL, MPMS-IQuantum, MPMS3, and S700X models) and has been tested with a broad variety of background and signal types. The software allows background subtraction of baseline signals, signal preprocessing, and performing fits to dipole data using Levenberg–Marquardt non-linear least squares or a singular value decomposition linear algebra algorithm that excels at picking out noisy or weak dipole signals. A plugin system allows users to easily extend the built-in functionality with their own importers, processes, or fitting algorithms. SquidLab can be downloaded, under Academic License, from the University of Warwick depository (wrap.warwick.ac.uk/129665)
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