2,353 research outputs found
Constraints on dark and visible mass in galaxies from strong gravitational lensing
We give a non-exhaustive review of the use of strong gravitational lensing in
placing constraints on the quantity of dark and visible mass in galaxies. We
discuss development of the methodology and summarise some recent results.Comment: To appear in proceedings of IAU Symposium 244, 'Dark Galaxies and
Lost Baryons', 25th - 29th June 2007. Nine pages, five figures. Version 2
updates bibliograph
The Oral Bacterial Microbiome of Interdental Surfaces in Adolescents According to Carious Risk
Adolescence is closely associated with a high risk of caries. The identification of specific
bacteria in an oral microniche, the interdental space of the molars, according to carious risk can
facilitate the prediction of future caries and the anticipation of the progression or stabilization of caries
in adolescents. A cross-sectional clinical study according to the bacteriological criteria of interdental
healthy adolescents and carious risk factorsâlow and highâusing a real-time polymerase chain
reaction technique was conducted. The presence of 26 oral pathogens from the interdental microbiota
of 50 adolescents aged 15 to 17 years were qualitatively and quantitatively analyzed. Bacteria
known to be cariogenic (Bifidobacterium dentium, Lactobacillus spp., Rothia dentocariosa, Streptococcus
cristatus, Streptococcus mutans, Streptococcus salivarius, Streptococcus sobrinus, and Streptococcus wiggsiae)
did not present differences in abundance according to carious risk. Periodontal bacteria from the
red complex are positively correlated with carious risk. However, only 3 bacteriaâS. sobrinus,
E corrodens and T. forsythiaâpresented a significant increase in the highest group. Estimating the risk
of caries associated with bacterial factors in interdental sites of molars in adolescents contributes to
the better definition of carious risk status, periodicity and intensity of diagnostic, prevention and
restorative service
Quantitative extraction of Meiofauna: A comparison of two methods
Two methods for the quantitative extraction of meiofauna from natural sandy sediments were investigated and compared: Cobb's decanting and sieving technique and the Oostenbrink elutriator. Both techniques were more efficient with pre-fixed samples than with fresh samples. The results indicated that elutriation is the more reliable method due to its low variability, 7,5% for nematodes and 8,4% for harpacticoids and mystacocarids compared to 11,2% and 29,0% respectively in the case of decantation. However, with samples containing 3 000 to 5 000 animals per 200 cc, decantation yielded 25% more animals than elutriation
When Darwin Met Einstein: Gravitational Lens Inversion with Genetic Algorithms
Gravitational lensing can magnify a distant source, revealing structural
detail which is normally unresolvable. Recovering this detail through an
inversion of the influence of gravitational lensing, however, requires
optimisation of not only lens parameters, but also of the surface brightness
distribution of the source. This paper outlines a new approach to this
inversion, utilising genetic algorithms to reconstruct the source profile. In
this initial study, the effects of image degradation due to instrumental and
atmospheric effects are neglected and it is assumed that the lens model is
accurately known, but the genetic algorithm approach can be incorporated into
more general optimisation techniques, allowing the optimisation of both the
parameters for a lensing model and the surface brightness of the source.Comment: 9 pages, to appear in PAS
Neutrino Mixing Discriminates Geo-reactor Models
Geo-reactor models suggest the existence of natural nuclear reactors at
different deep-earth locations with loosely defined output power. Reactor
fission products undergo beta decay with the emission of electron
antineutrinos, which routinely escape the earth. Neutrino mixing distorts the
energy spectrum of the electron antineutrinos. Characteristics of the distorted
spectrum observed at the earth's surface could specify the location of a
geo-reactor, discriminating the models and facilitating more precise power
measurement. The existence of a geo-reactor with known position could enable a
precision measurement of the neutrino oscillation parameter delta-mass-squared.Comment: 6 pages, 6 figures, minor revisions, submitted to PR
Low castes have poor access to visceral leishmaniasis treatment in Bihar, India
Objectivesâ Bihar, the poorest state in India, concentrates most of the visceral leishmaniasis (VL) cases in the country. A large proportion of the poor rural communities where VL is endemic are marginalized by their socio-economic status, intrinsically related to the caste system. In this study, we evaluated whether people from low socio-economic strata had difficulties accessing VL treatment in Bihar. As a secondary outcome, we evaluated whether people delaying their VL treatment had poorer clinical indicators at admission. Methodsâ Data on 2187 patients with VL treated by MĂ©decins Sans FrontiĂšres (MSF) in Vaishali district from July 2007 to December 2008 were analysed. Patients who reported having onset of symptoms â„8âweeks before admission were defined as 'late presenters'. Logistic regression models were used to evaluate whether low castes had higher risk to be 'late presenters' compared to the rest of castes and whether 'late presenters' had poorer indicators at admission (i.e. haemoglobin level, spleen size). Resultsâ After adjusting for age, gender and distance to VL treatment facility, Mushars (the lowest caste in Bihar) had twice the odds to be 'late presenters' compared to the rest of castes (OR 2.05, 95% CI: 1.24-2.38). Subjects that had VL symptoms for â„8âweeks had a larger spleen and lower haemoglobin level than those that were treated earlier. Conclusionâ Low castes have poor access to VL treatment in Bihar, and late presenters have poorer clinical indicators at admission. These findings have implications at individual and community levels and should stimulate targeted VL control programmes to ensure that marginalized communities in Bihar are properly treated
Internets Influence On The Marketing Activities Of South African Companies
Although research studies regarding the Internets impact on marketing conducted in the past in different countries and at different times produced quite similar trends in responses, advances in Internet technologies and the increased Internet usage necessitated reinvestigating marketers perceptions as to the changes in marketing practices brought about by the Internet. This study sought to determine the South African marketing practitioners perceptions of the Internets influence on the practice of marketing in 2011 and compare these perceptions with those of marketers in Australia 2001 and Iran 2005.A cross-industry survey of the marketing practitioners at the top 100 companies listed on the Johannesburg Stock Exchange in South Africa was conducted by means of a self-administered questionnaire. Questionnaires were sent via e-mail to those marketing practitioners from whom telephonic permission had been obtained.The findings indicate that South African marketers perceive the Internet to have changed the way companies conceptualise their marketing activities, define their markets, and create value. This study contributes to the practice of marketing by outlining the potential uses of the Internet in marketing and indicating trends across three countries and time periods
Methodological Challenges in Studies Examining the Effects of Breakfast on Cognitive Performance and Appetite in Children and Adolescents
Breakfast is purported to confer a number of benefits on diet quality, health, appetite regulation, and cognitive performance. However, new evidence has challenged the long-held belief that breakfast is the most important meal of the day. This review aims to provide a comprehensive discussion of the key methodological challenges and considerations in studies assessing the effect of breakfast on cognitive performance and appetite control, along with recommendations for future research. This review focuses on the myriad challenges involved in studying children and adolescents specifically. Key methodological challenges and considerations include study design and location, sampling and sample section, choice of objective cognitive tests, choice of objective and subjective appetite measures, merits of providing a fixed breakfast compared with ad libitum, assessment and definition of habitual breakfast consumption, transparency of treatment condition, difficulty of isolating the direct effects of breakfast consumption, untangling acute and chronic effects, and influence of confounding variables. These methodological challenges have hampered a clear substantiation of the potential positive effects of breakfast on cognition and appetite control and contributed to the debate questioning the notion that breakfast is the most important meal of the day
Development of reverse-transcription PCR techniques to analyse the density and sex ratio of gametocytes in genetically diverse Plasmodium chabaudi infections
We have developed cross-genotype and genotype-specific quantitative reverse-transcription PCR (qRT-PCR) assays to detect and quantify the number of parasites, transmission stages (gametocytes) and male gametocytes in blood stage Plasmodium chabaudi infections. Our cross-genotype assays are reliable, repeatable and generate counts that correlate strongly (R(2)s > 90%) with counts expected from blood smears. Our genotype-specific assays can distinguish and quantify different stages of genetically distinct parasite clones (genotypes) in mixed infections and are as sensitive as our cross-genotype assays. Using these assays we show that gametocyte density and gametocyte sex ratios vary during infections for two genetically distinct parasite lines (genotypes) and present the first data to reveal how sex ratio is affected when each genotype experiences competition in mixed-genotype infections. Successful infection of mosquito vectors depends on both gametocyte density and their sex ratio and we discuss the implications of competition in genetically diverse infections for transmission success
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