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This paper explores the way in which some lesbians rely on culturally circulated narratives about identity to assess safer sex and their potential risk of sexually transmitted infection (STI) and HIV. A well-established narrative within the literature about lesbian safer sex is that STI risk is non-existent. The implications of this are important because they demonstrate the perception of lesbian identity and notions of safety. This study focuses on how gender and sexuality contextualise an assessment of risk and safety for lesbians. This is vital to understand because there is still a lack of language about lesbian safer sex practices and techniques. Lesbians narrate their assessments of STI and HIV risk through the lenses of gender and sexuality – locating 'risk' in gay men and bisexual women. Using narrative analysis, I find that lesbians assess their risk by constructing characters from culturally circulated narratives steeped in homophobia and biphobia of the sensible lesbian, the risky gay man and the uncertain bisexual. [ABSTRACT FROM AUTHOR]

Range expansions are complex evolutionary and ecological processes. From an evolutionary standpoint, a populations' adaptive capacity can determine the success or failure of expansion. Using individual-based simulations, we model range expansion over a two-dimensional, approximately continuous landscape. We investigate the ability of populations to adapt across patchy environmental gradients and examine how the effect sizes of mutations influence the ability to adapt to novel environments during range expansion. We find that genetic architecture and landscape patchiness both have the ability to change the outcome of adaptation and expansion over the landscape. Adaptation to new environments succeeds via many mutations of small effect or few of large effect, but not via the intermediate between these cases. Higher genetic variance contributes to increased ability to adapt, but an alternative route of successful adaptation can proceed from low genetic variance scenarios with alleles of sufficiently large effect. Steeper environmental gradients can prevent adaptation and range expansion on both linear and patchy landscapes. When the landscape is partitioned into local patches with sharp changes in phenotypic optimum, the local magnitude of change between subsequent patches in the environment determines the success of adaptation to new patches during expansion. [ABSTRACT FROM AUTHOR]

Overdominance, or a fitness advantage of a heterozygote over both homozygotes, can occur commonly with adaptation to a new optimum phenotype. We model how such overdominant polymorphisms can reduce the evolvability of diploid populations, uncovering a novel form of epistatic constraint on adaptation. The fitness load caused by overdominant polymorphisms can most readily be ameliorated by evolution at tightly linked loci; therefore, traits controlled by multiple loosely linked loci are predicted to be strongly constrained. The degree of constraint is also sensitive to the shape of the relationship between phenotype and fitness, and the constraint caused by overdominance can be strong enough to overcome the effects of clonal interference on the rate of adaptation for a trait. These results point to novel influences on evolvability that are specific to diploids and interact with genetic architecture, and they predict a source of stochastic variability in eukaryotic evolution experiments or cases of rapid evolution in nature. [ABSTRACT FROM AUTHOR]

We describe a new method of estimating the selfing rate (S) in a mixed mating population based on a population structure approach that accounts for possible intergenerational correlation in selfing rate, giving rise to an estimate of the upper limit for heritability of selfing rate (h2). A correlation between generations in selfing rate is shown to affect one- and two-locus probabilities of identity by descent. Conventional estimates of selfing rate based on a population structure approach are positively biased by intergenerational correlation in selfing. Multilocus genotypes of individuals are used to give maximum-likelihood estimates of S and h2 in the presence of scoring artifacts. Our multilocus estimation of selfing rate and its heritability (MESH) method was tested with simulated data for a range of conditions. Selfing rate estimates from MESH have low bias and root mean squared error, whereas estimates of the heritability of selfing rate have more uncertainty. Increasing the number of individuals in a sample helps to reduce bias and root mean squared error more than increasing the number of loci of sampled individuals. Improved estimates of selfing rate, as well as estimates of its heritability, can be obtained with this method, although a large number of loci and individuals are needed to achieve best results. [ABSTRACT FROM AUTHOR]

Stress is generally thought to increase the strength of selection, although empirical results are mixed and general conclusions are difficult because data are limited. Here we compare the fitness effects of nine independent recessive mutations in Drosophila melanogaster in a high- and low-dietary-stress environment, estimating the strength of selection on these mutations arising from both a competitive measure of male reproductive success and productivity (female fecundity and the subsequent survival to adulthood of her offspring). The effect of stress on male reproductive success has not been addressed previously for individual loci and is of particular interest with respect to the alignment of natural and sexual selection. Our results do not support the hypothesis that stress increases the efficacy of selection arising from either fitness component. Results concerning the alignment of natural and sexual selection were mixed, although data are limited. In the low-stress environment, selection on mating success and productivity were concordant for five of nine mutations (four out of four when restricted to those with significant or near-significant productivity effects), whereas in the high-stress environment, selection aligned for seven of nine mutations (two out of two when restricted to those having significant productivity effects). General conclusions as to the effects of stress on the strength of selection and the alignment of natural and sexual selection await data from additional mutations, fitness components and stressors. [ABSTRACT FROM AUTHOR]

The hypothesis that adaptation to local environments can increase mating success was tested using ten replicate lines of Drosophila melanogaster adapted either to 16 °C or to 25 °C. Competitive mating trials at both temperatures were performed with males taken from a pair of lines, one adapted to each temperature. There was no average increase in mating success for males adapted to the local environment. Although one pair of lines showed the expected pattern, another pair showed the reverse pattern. More data are needed on this hypothesis, preferably with lines that have more strongly adapted to local environments. [ABSTRACT FROM AUTHOR]

Electrical power usage contributes significantly to the operational costs of large computer systems. At the Hypersonic Missile Technology Research and Operations Center (HMT-ROC) our system usage patterns provide a significant opportunity to reduce operating costs since there are a small number of dedicated users. The relatively predictable nature of our usage patterns allows for the scheduling of computational resource availability. We take advantage of this predictability to shut down systems during periods of low usage to reduce power consumption. With interconnected computer cluster systems, reducing the number of online nodes is more than a simple matter of throwing the power switch on a portion of the cluster. The paper discusses these issues and an approach for power reduction strategies for a computational system with a heterogeneous system mix that includes a large (1560-node) Apple Xserve PowerPC supercluster. In practice, the average load on computer systems may be much less than the peak load although the infrastructure supporting the operation of large computer systems in a computer or data center must still be designed with the peak loads in mind. Given that a significant portion of the time, systems loads can be less than full peak, an opportunity exists for cost savings if idle systems can be dynamically throttled back, slept, or shut off entirely. The paper describes two separate strategies that meet the requirements for both power conservation and system availability at HMT-ROC. The first approach, for legacy systems, is not much more than a brute force approach to power management which we call Time-Driven System Management (TDSM). The second approach, which we call Dynamic-Loading System Management (DLSM), is applicable to more current systems with ‘Wake-on-LAN’ capability and takes a more granular approach to the management of system resources. The paper details the rule sets that we have developed and implemented in the two approaches to system power management and discusses some results with these approaches. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The evolution of resource sharing requires that the fitness benefits to the recipients be much higher than the costs to the giver, which requires heterogeneity among individuals in the fitness value of acquiring additional resources. We develop four models of the evolution of resource sharing by either direct or indirect reciprocity, with equal or unequal partners. Evolution of resource sharing by reciprocity requires differences between interacting individuals in the fitness value of the resource, and these differences must reverse although previous acts of giving are remembered and both participants survive. Moreover, inequality in the expected reproductive value of the interacting individuals makes reciprocity more difficult to evolve, but may still allow evolution of sharing by kin selection. These constraints suggest that resource sharing should evolve much more frequently by kin selection than by reciprocity, a prediction that is well supported by observations in the natural world. [ABSTRACT FROM AUTHOR]

Adaptation to new environments is a well-documented phenomenon. Individuals from populations maintained in a particular environment for multiple generations tend to be better able to survive and/or reproduce in that environment than their ancestors or other individuals adapted to alternative environments. A third major component of fitness, mating success, has not been well studied in replicated populations under selection in divergent environments. In this study, we used mating trials to compare the mating success of male Drosophila melanogaster adapted for 10 years to two different temperatures, 18 and 25°C. In competition for female partners, males had significantly higher mating success at their adapted temperature compared with males adapted to a different temperature. These results are consistent with the notion that those mutations favoured by natural selection also tend to be favoured by sexual selection. [ABSTRACT FROM AUTHOR]

The most commonly used method in evolutionary biology for combining information across multiple tests of the same null hypothesis is Fisher's combined probability test. This note shows that an alternative method called the weighted Z-test has more power and more precision than does Fisher's test. Furthermore, in contrast to some statements in the literature, the weighted Z-method is superior to the unweighted Z-transform approach. The results in this note show that, when combining P-values from multiple tests of the same hypothesis, the weighted Z-method should be preferred. [ABSTRACT FROM AUTHOR]

Accumulation of deleterious mutations has important consequences for the evolution of mating systems and the persistence of small populations. It is well established that consanguineous mating can purge a part of the mutation load and that lethal mutations can also be purged in small populations. However, the efficiency of purging in natural populations, due to either consanguineous mating or to reduced population size, has been questioned. Consequences of consanguineous mating systems and small population size are often equated under "inbreeding" because both increase homozygosity, and selection is though to be more efficient against homozygous deleterious alleles. I show that two processes of purging that I call "purging by drift" and "purging by nonrandom mating" have to be distinguished. Conditions under which the two ways of purging are effective are derived. Nonrandom mating can purge deleterious mutations regardless of their dominance level, whereas only highly recessive mutations can be purged by drift. Both types of purging are limited by population size, and sharp thresholds separate domains where purging is either effective or not. The limitations derived here on the efficiency of purging are compatible with some experimental studies. Implications of these results for conservation and evolution of mating systems are discussed. [ABSTRACT FROM AUTHOR]

Theory predicts a significant relationship between the size of a population and the magnitude and composition of its genetic load, but few natural populations have been investigated. We examined the magnitude of genetic load due to recessive deleterious alleles (GL) both segregating and fixed within Gentianella germanica populations of varying size by selfing and reciprocally crossing plants within and between natural populations according to a partial diallel design and by comparing the performance of the experimental progeny in a common-garden experiment. The results show that GL for total fitness in small populations (fewer than 200 plants) was mainly due to fixed recessive deleterious alleles, whereas GL for total fitness in larger populations (more than 200 plants) appeared to be mainly due to segregating deleterious recessive alleles. The total fitness of selfed plants increased with decreasing population size, indicating some purging of deleterious alleles associated with declining population sizes. The magnitudes of GL due to fixed deleterious alleles in small populations and segregating deleterious alleles in large populations, however, were overall similar, suggesting that purging selection was an insignificant force when compared to genetic drift in determining the magnitude of GL in small natural populations in this species. The results of this study highlight the importance of population size in determining the dynamics of genetic loads of natural populations and are overall in line with a large body of theoretical work indicating that small populations may face higher extinction risks due to the fixation and accumulation of deleterious alleles of small effect. [ABSTRACT FROM AUTHOR]

Heritable variation in fitness is the fuel of adaptive evolution, and sex can generate new adaptive combinations of alleles. If the generation of beneficial combinations drives the evolution of recombination, then the level of recombination should result in changes in the response to selection. Three types of lines of Drosophila melanogaster varying in their level of genetic recombination were selected over 38 generations for geotaxis. The within-chromosome recombination level of these lines was controlled for 60% of the genome: chromosome X and chromosome II. The full recombination lines had normal, unmanipulated levels of recombination on these two chromosomes. Conversely, nonrecombination lines had recombination effectively eliminated within the X and second chromosomes. Finally, partial recombination lines had the effective rate of within-chromosome recombination lowered to 10% of natural levels for these two chromosomes. The rate of response to selection was measured for continuous negative geotaxis and for a fluctuating environment (alternating selection for negative and positive geotaxis). All selected Drosophila lines responded to selection and approximately 36% of the response to selection was because of the X and second chromosomes. However, recombination did not accelerate adaptation during either directional or fluctuating selection for geotaxis. [ABSTRACT FROM AUTHOR]

Presents a study which examined the effects of metapopulation processes on several different aspects of population genetics. Methods; Results and discussion; Implications for empirical studies.

Presents information on a study which considered the forces that may play a role in the adaptive evolution of premating isolation, direct selection on preferences and indirect selection against postmating, prezygotic incompatibilities. Mechanisms that may cause direct selection on preferences during speciation; Mechanisms that cause premating isolation evolution above and beyond traditional reinforcement.

Describes the stochastic hybrid accumulation of Dobzhansky-Muller incompatibilities as a function of time. Cases of compatibility speciation; Effects of genomic compartmentalization; Evolution of postzygotic isolation.

Discusses a study which contrasted two ways of representing the data in a phylogenetic tree. Comparison of the Poisson process approach and the survival analysis approach; Birth-death process models; Factors that affect apparent trends in diversification.

Shape memory alloy (SMA) composites are a class of smart materials in which embedded nitinol wires are used as actuators. Previous research in SMA composites has been limited to wires using one-way shape memory behavior. The objective of this paper is to assess the feasibility of using two-way shape memory (TWSM) training of nitinol, a nickel-titanium SMA, wires for their use as embedded actuators in SMA composites and to investigate the effects of processing conditions on SMA composite quality and actuation ability. Training of the TWSM behavior in nitinol was investigated for a range of initial strains and training cycles. In each case, over 50% of the initial strain can be recovered after training and trained response is generally stable after about 30 training cycles. SMA composite specimens were manufactured using either hot press or autoclave methods and several different types of cure cycles. Voids were found to congregate near the embedded wire surface and can typically be as high as 10% in these regions. Using a staged-cure cycle, the average void content was reduced to 1.3-1.5%. The effect of the composite cure cycle was found to have no significant effect on trained nitinol wire behavior. Finally, the structural behavior of an SMA composite beam was investigated by actuating wires through electrical resistance heating. The tip deflection of a cantilevered beam was found to be primarily composed of SMA transformational effects, however, some localized heating was evident. [ABSTRACT FROM PUBLISHER]

A model of the characteristics of outstanding teachers of the gifted was developed and validated using a technique developed in industry that is based on intensive interviewing of current job holders who have been nominated by peers as possessing exemplary characteristics. Ten outstanding and 10 average teachers of the gifted were interviewed. Outstanding teachers of the gifted differed from average teachers of the gifted on several critical competencies: enthusiasm, self-confidence, being a facilitator, being able to apply knowledge, having a strong achievement orientation, commitment to the role of gifted educator, and building program support for the gifted education program. [ABSTRACT FROM PUBLISHER]

Objectives: To describe the demographics and nature of injuries occurring on or around horses, to examine the nature of protective clothing in relation to these injuries, and to compare our data with previously published work in this area.Methods: Patients were identified using the term "sports injury-horse riding" from the departmental database for one calendar year from February 2000. Data were collected regarding demographics, injuries, protective clothing, and outcome. The data were then analysed and compared with the previously published literature.Results: 260 patients' records were analysed. The patients were mostly young (median age 26) and female (84.6%). The majority of patients had a single injury (88.8%). Seventeen per cent had an isolated head injury, all of which proved to be minor. Multiple injuries including the head accounted for 8.5% of all injuries. These again proved minor, bar one fatality where the helmet came off before impact. Upper limb injuries accounted for 29.2% of all injuries of which 61.8% sustained a fracture of which 36.2% were to the wrist. When compared with previous work the incidence and severity of head injury continues to decline while the relative number and severity of upper limb injuries increases.Conclusions: The majority of head injured riders are wearing approved helmets and sustaining only minor injury. There is currently no protective gear recommended for the upper limb and more specifically the wrist. This paper identifies the potential need for research and development of such protection. [ABSTRACT FROM AUTHOR]

Objectives: To determine the distribution of injuries in the eventing discipline of equestrian sports and the effectiveness of the protective equipment worn.Methods: Data on all injuries sustained in the cross country phase over fixed obstacles were collected from 54 days of competition from 1992 to 1997. This involved 16,940 rides.Results: Data on a total of 193 injuries were collected, which included two deaths. This represents an injury rate of 1.1%. Head and facial injuries represented the largest group (31%), with one third of these requiring treatment in hospital. All riders were wearing protective helmets and body protectors.Conclusions: Eventing is one of the most dangerous equestrian sports. Improved protective equipment, which is mandatory for 1999, should reduce the severity of these injuries. [ABSTRACT FROM AUTHOR]

A retrospective study of horse riding injuries in Berkshire was undertaken over a one year period from November 1983. The information was obtained from the Ambulance Service, the Jockey Club and the St. John Ambulance Brigade. There was a total of 103 injured persons with no deaths. Information from the Jockey Club was compared with the other two groups, the former sustaining more limb injuries and the latter more head injuries. A questionnaire was sent to all 42 ambulance patients. Thirty-eight had radiographs taken, 16 of which showed a fracture. Forty-one were wearing some form of hard hat, but if a safety strap was available it was attached in 24 cases. The dangers of riding are highlighted and the importance of adequate protective clothing emphasised. [ABSTRACT FROM PUBLISHER]

The article reports on the results of medical imaging examinations on a ten-year-old girl who presented with chest pain and who was later diagnosed with intrathoracic lipoma.

Older people do not lose their individuality when they become patients, argue Jonathan Webster and Moira Whitlock. [ABSTRACT FROM AUTHOR]