2,189 research outputs found
Some solutions to the multivariate Behrens-Fisher problem for dissimilarity-based analyses
The essence of the generalised multivariate BehrensâFisher problem (BFP) is how to test the null hypothesis of equality of mean vectors for two or more populations when their dispersion matrices differ. Solutions to the BFP usually assume variables are multivariate normal and do not handle highâdimensional data. In ecology, species' count data are often highâdimensional, nonânormal and heterogeneous. Also, interest lies in analysing compositional dissimilarities among whole communities in nonâEuclidean (semiâmetric or nonâmetric) multivariate space. Hence, dissimilarityâbased tests by permutation (e.g., PERMANOVA, ANOSIM) are used to detect differences among groups of multivariate samples. Such tests are not robust, however, to heterogeneity of dispersions in the space of the chosen dissimilarity measure, most conspicuously for unbalanced designs. Here, we propose a modification to the PERMANOVA test statistic, coupled with either permutation or bootstrap resampling methods, as a solution to the BFP for dissimilarityâbased tests. Empirical simulations demonstrate that the type I error remains close to nominal significance levels under classical scenarios known to cause problems for the unâmodified test. Furthermore, the permutation approach is found to be more powerful than the (more conservative) bootstrap for detecting changes in community structure for real ecological datasets. The utility of the approach is shown through analysis of 809 species of benthic softâsediment invertebrates from 101 sites in five areas spanning 1960 km along the Norwegian continental shelf, based on the Jaccard dissimilarity measure
Numerical Modeling of the Internal Temperature in the Mammary Gland
The microwave thermometry method for the diagnosis of breast cancer is based
on an analysis of the internal temperature distribution.This paper is devoted
to the construction of a mathematical model for increasing the accuracy of
measuring the internal temperature of mammary glands, which are regarded as a
complex combination of several components, such as fat tissue, muscle tissue,
milk lobules, skin, blood flows, tumor tissue. Each of these biocomponents is
determined by its own set of physical parameters. Our numerical model is
designed to calculate the spatial distributions of the electric microwave field
and the temperature inside the biological tissue. We compare the numerical
simulations results to the real medical measurements of the internal
temperature.Comment: 8 pages, 4 figure
How acceptable are antiretrovirals for the prevention of sexually transmitted HIV? A review of research on the acceptability of oral pre-exposure prophylaxis and treatment as prevention
Recent research has demonstrated how antiretrovirals (ARVs) could be effective in the prevention of sexually transmitted HIV. We review research on the acceptability of oral pre-exposure prophylaxis (PrEP) and treatment as prevention (TasP) for HIV prevention amongst potential users. We consider with whom, where and in what context this research has been conducted, how acceptability has been approached, and what research gaps remain. Findings from 33 studies show a lack of TasP research, PrEP studies which have focused largely on men who have sex with men (MSM) in a US context, and varied measures of acceptability. In order to identify when, where and for whom PrEP and TasP would be most appropriate and effective, research is needed in five areas: acceptability of TasP to people living with HIV; motivation for PrEP use and adherence; current perceptions and management of risk; the impact of broader social and structural factors; and consistent definition and operationalisation of acceptability which moves beyond adherence
Numerical study of circulation on the inner Amazon Shelf
Author Posting. © Springer, 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Ocean Dynamics 58 (2008): 187-198, doi:10.1007/s10236-008-0139-4.We studied the circulation on the coastal
domain of the Amazon Shelf by applying the hydrodynamic
module of the Estuarine and Coastal Ocean
Model and Sediment Transport - ECOMSED. The first
barotropic experiment aimed to explain the major bathymetric
effects on tides and those generated by anisotropy
in sediment distribution. We analyzed the continental
shelf response of barotropic tides under realistic bottom
stress parametrization (Cd), considering sediment granulometry
obtained from a faciologic map, where river
mud deposits and reworked sediments areas are well distinguished,
among others classes of sediments. Very low
Cd values were set in the fluid mud regions off the Amapa
coast (1.0 10-4 ), in contrast to values around 3:5 10-3
for coarser sediment regions off the Para coast. Three-dimensional
experiments represented the Amazon River
discharge and trade winds, combined to barotropic tide
influences and induced vertical mixing. The quasi-resonant
response of the Amazon Shelf to the M2 tide act on
the local hydrodynamics by increasing tidal admittance,
along with tidal forcing at the shelf break and extensive
fluid mud regions. Harmonic analysis of modeled
currents agreed well with analysis of the AMASSEDS
observational data set. Tidal-induced vertical shear provided
strong homogenization of threshold waters, which
are subject to a kind of hydraulic control due to the topographic
steepness. Ahead of the hydraulic jump, the
low-salinity plume is disconnected from the bottom and
acquires negative vorticity, turning southeastward. Tides
act as a generator mechanism and topography, via hydraulic
control, as a maintainer mechanism for the low-salinity
frontal zone positioning. Tidally induced southeastward
plume fate is overwhelmed by northwestward
trade winds so that, along with background circulation,
probably play the most important role on the plume fate
and variability over the Amazon Shelf
Use of mixed methods designs in substance research: a methodological necessity in Nigeria
The utility of mixed methods (qualitative and quantitative) is becoming increasingly accepted in health sciences, but substance studies are yet to substantially benefit from such utilities. While there is a growing number of mixed methods alcohol articles concerning developed countries, developing nations are yet to embrace this method. In the Nigerian context, the importance of mixed methods research is yet to be acknowledged. This article therefore, draws on alcohol studies to argue that mixed methods designs will better equip scholars to understand, explore, describe and explain why alcohol consumption and its related problems are increasing in Nigeria. It argues that as motives for consuming alcohol in contemporary Nigeria are multiple, complex and evolving, mixed method approaches that provide multiple pathways for proffering solutions to problems should be embraced
Alcohol consumption and body composition in a population-based sample of elderly Australian men
Background: Alcohol is calorie dense, and impacts activity, appetite and lipid processing. The aim of this study was to therefore investigate the association between alcohol consumption and components of body composition including bone, fat and lean tissue.Methods: Participants were recruited from a randomly selected, population-based sample of 534 men aged 65 years and older enrolled in the Geelong Osteoporosis Study. Alcohol intake was ascertained using a food frequency questionnaire and the sample categorised as nondrinkers or alcohol users who consumed B2, 3–4 or C5 standard drinks on a usual drinking day. Bone mineral density (BMD), lean body mass and body fat mass were measured using dual energy X-ray absorptiometry; overall adiposity (%body fat), central adiposity (%truncal fat) and body mass index (BMI) were calculated. Bone quality was determined by quantitative heel ultrasound (QUS).Results: There were 90 current non-drinkers (16.9 %), 266 (49.8 %) consumed 1–2 drinks/day, 104 (19.5 %) 3–4 drinks/day and 74 (13.8 %) C5 drinks/day. Those consuming C5 drinks/day had greater BMI (?4.8 %), fat mass index (?20.1 %), waist circumference (?5.0 %), %body fat (?15.2 %) and proportion of trunk fat (?5.3 %) and lower lean mass (-5.0 %) than non-drinkers after adjustment for demographic and lifestyle factors. Furthermore, they were more likely to be obese than non-drinkers according to criteria based on BMI (OR = 2.83, 95 %CI 1.10–7.29) or waist circumference (OR = 3.36, 95 %CI 1.32–8.54). There was an inverse relationship between alcohol consumption and QUS parameters and BMD at the mid forearm site; no differences were detected for BMD at other skeletal sites.Conclusion: Higher alcohol intake was associated with greater total and central adiposity and reduced bone quality.<br /
Bioassay guided purification of the antimicrobial fraction of a Brazilian propolis from Bahia state
<p>Abstract</p> <p>Background</p> <p>Brazilian propolis type 6 (Atlantic forest, Bahia) is distinct from the other types of propolis especially due to absence of flavonoids and presence of other non-polar, long chain compounds, but presenting good <it>in vitro </it>and <it>in vivo </it>antimicrobial activity. Several authors have suggested that fatty acids found in this propolis might be responsible for its antimicrobial activity; however, so far no evidence concerning this finding has been reported in the literature. The goals of this study were to evaluate the antibacterial activity of the main pure fatty acids in the ethanolic extract and fractions and elucidate the chemical nature of the bioactive compounds isolated from Brazilian propolis type 6.</p> <p>Methods</p> <p>Brazilian propolis type 6 ethanolic extract (EEP), hexane fraction (H-Fr), major fatty acids, and isolated sub-fractions were analyzed using high performance liquid chromatography (HPLC), high resolution gas chromatography with flame ionization detection (HRGC-FID), and gas chromatography-mass spectrometry (GC-MS). Three sub-fractions of H-Fr were obtained through preparative HPLC. Antimicrobial activity of EEP, H-Fr, sub-fractions, and fatty acids were tested against <it>Staphyloccus aureus </it>ATCC 25923 and <it>Streptococcus mutans </it>Ingbritt 1600 using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC).</p> <p>Results</p> <p>EEP and H-Fr inhibited the growth of the microorganisms tested; nevertheless, no antimicrobial activity was found for the major fatty acids. The three sub-fractions (1, 2, and 3) were isolated from H-Fr by preparative HPLC and only sub-fraction 1 showed antimicrobial activity.</p> <p>Conclusion</p> <p>a) The major fatty acids tested were not responsible for the antimicrobial activity of propolis type 6; b) Sub-fraction 1, belonging to the benzophenone class, was responsible for the antimicrobial activity observed in the present study. The identification of the bioactive compound will improve the development of more efficient uses of this natural product.</p
Peripheral neural cell sensitivity to mTHPC-mediated photodynamic therapy in a 3D in vitro model
Background: The effect of photodynamic therapy (PDT) on neural cells is important when tumours are within or adjacent to the nervous system. The purpose of this study was to investigate PDT using the photosensitiser, meta tetrahydroxyphenyl chlorin (mTHPC), on rat neurons and satellite glia, compared with human adenocarcinoma cell (MCF-7).Methods: Fluorescence microscopy confirmed that mTHPC was incorporated into all three cell types. Sensitivity of cells exposed to mTHPC-PDT (0â10 ”g mlâ1) was determined in a novel 3-dimensional collagen gel culture system. Cell death was quantified using propidium iodide and cell types were distinguished using immunocytochemistry. In some cases, neuron survival was confirmed by measuring subsequent neurite growth in monolayer culture.Results: MCF-7s and satellite glia were significantly more sensitive to PDT than neurons. Importantly, 4 ”g mlâ1 mTHPC PDT caused no significant neuron death compared with untreated controls but was sufficient to elicit substantial cell death in the other cell types. Initially, treatment reduced neurite length; neurons then extended neurites equivalent to those of untreated controls. The protocol was validated using hypericin (0â3 ”g mlâ1), which caused neuron death equivalent to other cell types.Conclusion: Neurons in culture can survive mTHPC-PDT under conditions sufficient to kill tumour cells and other nervous system cells
How Psychological Stress Affects Emotional Prosody
We explored how experimentally induced psychological stress affects the production and recognition of vocal emotions. In Study 1a, we demonstrate that sentences spoken by stressed speakers are judged by naive listeners as sounding more stressed than sentences uttered by non-stressed speakers. In Study 1b, negative emotions produced by stressed speakers are generally less well recognized than the same emotions produced by non-stressed speakers. Multiple mediation analyses suggest this poorer recognition of negative stimuli was due to a mismatch between the variation of volume voiced by speakers and the range of volume expected by listeners. Together, this suggests that the stress level of the speaker affects judgments made by the receiver. In Study 2, we demonstrate that participants who were induced with a feeling of stress before carrying out an emotional prosody recognition task performed worse than non-stressed participants. Overall, findings suggest detrimental effects of induced stress on interpersonal sensitivity
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