3,322 research outputs found

    Flying in the face of nutritional variability: modeling the origins and consequences of phenotypic plasticity using Drosophila melanogaster

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    This thesis employs the model Drosophila melanogaster and the Geometric Framework for nutrition (GF) to explore origins, consequences and molecular underpinnings of phenotypic plasticity. The first two studies investigate the influence genetic polymorphism of foraging gene can have on population level phenotypic plasticity in response to variable larval nutrition. Chapter 2 shows that allelic variants of foraging differ subtly in their larval life history and phenotypic plasticity, yet these differences correspond to one variant displaying ‘nutrient generalist’ and the other ‘nutrient specialist’ feeding strategies. Chapter 3 demonstrates foraging acts as a plasticity gene, meaning that each allelic variant is capable of expressing alternate patterns of phenotypic plasticity in common nutritional environments. This study indicates that natural populations of D. melanogaster are capable of expressing two discrete modes of phenotypic plasticity, potentially facilitating future evolution under nutritional environment change. Chapter 4 analyses the influence variable larval nutrition has on the expression of D melanogaster sex combs, a male secondary sexual trait. By comparing the quality of sex combs between flies raised across diverse food environments, the study demonstrates that nutrition is critical in determining trait variability, suggesting nutrition has direct influence on microevolution via sexual selection. The final data chapter characterises the gene expression changes that occur within individuals of a population that has become adapted to an recent shift to a high-protein diet. Data from Chapter 5 indicates that in order to evolve a carnivore-like tolerance to utilising high-protein food as a principle source of calories, major changes in the expression of proteolysis and immune and stress response genes are required – supporting the ‘multiplex stress response’ hypothesis of ageing

    Masculine gender roles and therapy: A conceptual workshop

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    Traditional gender stereotypes, no matter how inaccurate they may be, still greatly affect how we view ourselves as men and women in our society. While all these stereotypes are constricting male stereotypes present some of the most limiting expectations for individuals. Within the realm of counseling and psychotherapy, these stereotypes conflict with such ideals as self exploration and emotional awareness and expression. This paper reviews past and recent research and theories on the development and reiteration of male stereotypes as well as how these expectations play a role in therapeutic techniques. A conceptual workshop model is also presented as an introduction into the area of male stereotypes and their impact on traditional therapeutic techniques. Ideas and suggestions for working therapeutically with males are also provided

    Use of Craigslist.org to Hook Up: Age Differences in Sex Requests, HIV Disclosure and Negotiated Safety among Men-Seeking-Men

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    Data from 984 “men-seeking-men” Craigslist.org postings in five cities were analyzed to assess differences in sexual requests, HIV status disclosure, and negotiated safety between young (18-24 years) and older (25 years and older) men who have sex with men (MSM). Young MSM were less likely than older MSM to post their HIV status or the preferred status of a partner (p=0.04), disclose and/or request a partner who was disease and drug free (p=.01), and request use of a condom in their posting (p=0.01). Interventions aimed at changing the culture and content of postings on Craigslist.org by encouraging HIV status disclosure and condom use preference are warranted, particularly for young MSM

    A comparison of minimum distance and maximum likelihood techniques for proportion estimation

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    The estimation of mixing proportions P sub 1, P sub 2,...P sub m in the mixture density f(x) = the sum of the series P sub i F sub i(X) with i = 1 to M is often encountered in agricultural remote sensing problems in which case the p sub i's usually represent crop proportions. In these remote sensing applications, component densities f sub i(x) have typically been assumed to be normally distributed, and parameter estimation has been accomplished using maximum likelihood (ML) techniques. Minimum distance (MD) estimation is examined as an alternative to ML where, in this investigation, both procedures are based upon normal components. Results indicate that ML techniques are superior to MD when component distributions actually are normal, while MD estimation provides better estimates than ML under symmetric departures from normality. When component distributions are not symmetric, however, it is seen that neither of these normal based techniques provides satisfactory results

    Time-based vertex reconstruction in the Compact Muon Solenoid

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    The Phase-II upgrades to the Large Hadron Collider will introduce a variety of new measurement devices to the CMS, including the High-Granularity Calorimeter (HGCAL). The increase in luminosity from these upgrades will also have the undesired side effect of vastly increasing pileup to a level at which the current machine learning vertex reconstruction (vertexing) algorithms cease to be effective. This will necessitate the development of further vertexing algorithms. Using high precision timing measurements from simulated events in the HGCAL, we design a vertex reconstruction algorithm that requires only the spatiotemporal arrival coordinates to reconstruct the interaction vertex of a collision with sub-millimeter resolution. We also analyse how particle energy and simulated time smearing affect this resolution and we apply this algorithm to more realistic H->γγ sets. To do this, we implement a set of filters to remove poorly-reconstructed events and introduce a new algorithm capable of reconstructing interaction vertices given the pointing data and arrival data of a single cluster. Progress on this work was ultimately hindered by extensive errors in the clustering algorithms used the generation of the datasets; should these errors be resolved, further work would include integration with tracker information and the application of these algorithms to high-pileup scenarios and QCD jets

    A study of the freshwater dinoflagellates Ceratium hirundinella and Ceratium furcoides with special reference to their taxonomy and recent history in the Lake District

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    Motile cells and cysts of Ceratium were studied usinglight and scanning electron microscopy. Two species, C. hirundinella and C. furcoides, were distinguished on the basis of the cell length to breadth ratio, the shape of the epithecaand the arrangement of apical plates. Cysts differed in shape and in the length of the horns. Analytical scanning electronmicroscopy demonstrated the presence of silicon in the multi-layered granular wall of the cysts of both species.The vertical distribution of viable cysts of C. furcoides and C. hirundinella was studied in 8 cm cores taken over threeseasons from Esthwaite Water, Cumbria. The diatom Stephanodiscus parvus was used as a marker species, to attribute a time scale to the cores. Some agreement was demonstrated between cyst numbers and past populations of Ceratium spp., although the majority of cysts occurred in the upper 4 cm of the cores. A study of the proportion of C. hirundinella to C. furcoides cells from 1946-1986 showed that the ratio of each species changed markedly over this period. It was concluded that the relative numbers of each species were determined by the proportion of cysts germinating in the spring, with parasitism an important factor in controlling cyst viability.Germination of the cysts of both species was induced in the laboratory. The excystment of C. furcoides was achieved down to a depth of 5.5 cm, from cysts with an equivalent age of approximately 7 years. Cysts from sediment which had been leftto dry out failed to germinate.The Ceratium populations of several southern sites were also studied. The number of Ceratium cells was shown to decline when the water column was disturbed, either by the input of water through high velocity jets, or the failure to form a stable thermocline. C. hirundinella was observed to be the more numerous of the two species in the reservoirs studied, but in Virginia Water Lake C. furcoides occurred in greater numbers. <p
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