489 research outputs found
Toolbox approaches using molecular markers and 16S rRNA gene amplicon data sets for identification of fecal pollution in surface water
In this study, host-associated molecular markers and bacterial 16S rRNA gene community analysis using high-throughput sequencing were used to identify the sources of fecal pollution in environmental waters in Brisbane, Australia. A total of 92 fecal and composite wastewater samples were collected from different host groups (cat, cattle, dog, horse, human, and kangaroo), and 18 water samples were collected from six sites (BR1 to BR6) along the Brisbane River in Queensland, Australia. Bacterial communities in the fecal, wastewater, and river water samples were sequenced. Water samples were also tested for the presence of bird-associated (GFD), cattle-associated (CowM3), horse-associated, and human-associated (HF183) molecular markers, to provide multiple lines of evidence regarding the possible presence of fecal pollution associated with specific hosts. Among the 18 water samples tested, 83%, 33%, 17%, and 17% were real-time PCR positive for the GFD, HF183, CowM3, and horse markers, respectively. Among the potential sources of fecal pollution in water samples from the river, DNA sequencing tended to show relatively small contributions from wastewater treatment plants (up to 13% of sequence reads). Contributions from other animal sources were rarely detected and were very small
Microscale measurements reveal contrasting effects of photosynthesis and epiphytes on frictional drag on the surfaces of filamentous algae
SUMMARY 1. Filamentous algae are widespread in freshwater ecosystems worldwide with a significant presence in streams, rivers and lakes with sufficient light and nutrients. Although typically not a preferred food source for grazers, dense filamentous mats provide surfaces for epiphytic microorganisms that are more palatable, thus adding to stream productivity. 2. We tested the hypothesis that epiphytes change velocity gradients, and consequently shear stress and skin friction drag, near the surface of algal filaments. Using both digital holography and particle image velocimetry to measure micrometre-scale velocity fields, we found that the surface shear stress on filamentous algae was much greater when the algae were actively photosynthesising. The presence of attached diatoms significantly reduced surface shear stress, while those filaments were photosynthesising, compared with bare filaments. 3. A nutrient flux model, based on boundary layer thickness and surface shear stress, predicts that nutrient flux to the surface of a photosynthesising filament under measured flow conditions will be 1.5 times greater than for a preserved (i.e. dead) filament. Modelled nutrient flux to filaments with epiphytic assemblages dominated by diatoms is 75% of the flux to bare filaments under similar flow conditions. 4. The proposed positive feedback between photosynthesis, surface shear stress and nutrient flux could be an important biophysical mechanism that overcomes diffusion limited nutrient supply within dense algal mats, enhancing algal survival through increased nutrient flux to actively photosynthesising filaments and decreased sloughing risk for filaments with lower rates of photosynthesis (due to epiphyte coverage or other light-limiting factors)
Systemic Risk and Default Clustering for Large Financial Systems
As it is known in the finance risk and macroeconomics literature,
risk-sharing in large portfolios may increase the probability of creation of
default clusters and of systemic risk. We review recent developments on
mathematical and computational tools for the quantification of such phenomena.
Limiting analysis such as law of large numbers and central limit theorems allow
to approximate the distribution in large systems and study quantities such as
the loss distribution in large portfolios. Large deviations analysis allow us
to study the tail of the loss distribution and to identify pathways to default
clustering. Sensitivity analysis allows to understand the most likely ways in
which different effects, such as contagion and systematic risks, combine to
lead to large default rates. Such results could give useful insights into how
to optimally safeguard against such events.Comment: in Large Deviations and Asymptotic Methods in Finance, (Editors: P.
Friz, J. Gatheral, A. Gulisashvili, A. Jacqier, J. Teichmann) , Springer
Proceedings in Mathematics and Statistics, Vol. 110 2015
Sound comparisons: a new online database and resource for research in phonetic diversity
Sound Comparisons hosts over 90,000 individual word recordings and 50,000 narrow phonetic transcriptions from 600 language varieties from eleven language families around the world. This resource is designed to serve researchers in phonetics, phonology and related fields. Transcriptions follow new initiatives for standardisation in usage of the IPA and Unicode. At soundcomparisons.com, users can explore the transcription datasets by phonetically-informed search and filtering, customise selections of languages and words, download any targeted data subset (sound files and transcriptions) and cite it through a custom URL. We present sample research applications based on our extensive overage of regional and sociolinguistic variation within major languages, and also of endangered languages, for which Sound Comparisons provides a rapid first documentation of their diversity in phonetics. The multilingual interface and user-friendly, ‘hover-tohear’ maps likewise constitute an outreach tool, where speakers can instantaneously hear and compare the phonetic diversity and relationships of their native languages
Sound comparisons: A new online database and resource for research in phonetic diversity
Sound Comparisons hosts over 90,000 individual word recordings and 50,000 narrow phonetic transcriptions from 600 language varieties from eleven language families around the world. This resource is designed to serve researchers in phonetics, phonology and related fields. Transcriptions follow new initiatives for standardisation in usage of the IPA and Unicode. At soundcomparisons.com, users can explore the transcription datasets by phonetically-informed search and filtering, customise selections of languages and words, download any targeted data subset (sound files and transcriptions) and cite it through a custom URL. We present sample research applications based on our extensive overage of regional and sociolinguistic variation within major languages, and also of endangered languages, for which Sound Comparisons provides a rapid first documentation of their diversity in phonetics. The multilingual interface and user-friendly, ‘hover-tohear’ maps likewise constitute an outreach tool, where speakers can instantaneously hear and compare the phonetic diversity and relationships of their native languages
Music Tune Restoration Based on a Mother Wavelet Construction
It is offered to use the mother wavelet function obtained from the local part of an analyzed music signal. Requirements for the constructed function are proposed and the implementation technique and its properties are described. The suggested approach allows construction of mother wavelet families with specified identifying properties. Consequently, this makes possible to identify the basic signal variations of complex music signals including local time-frequency characteristics of the basic one
Beach sand and the potential for infectious disease transmission: observations and recommendations
Recent studies suggest that sand can serve as a vehicle for exposure of humans to pathogens at beach sites, resulting in increased health risks. Sampling for microorganisms in sand should therefore be considered for inclusion in regulatory programmes aimed at protecting recreational beach users from infectious disease. Here, we review the literature on pathogen levels in beach sand, and their potential for affecting human health. In an effort to provide specific recommendations for sand sampling programmes, we outline published guidelines for beach monitoring programmes, which are currently focused exclusively on measuring microbial levels in water. We also provide background on spatial distribution and temporal characteristics of microbes in sand, as these factors influence sampling programmes. First steps toward establishing a sand sampling programme include identifying appropriate beach sites and use of initial sanitary assessments to refine site selection. A tiered approach is recommended for monitoring. This approach would include the analysis of samples from many sites for faecal indicator organisms and other conventional analytes, while testing for specific pathogens and unconventional indicators is reserved for high-risk sites. Given the diversity of microbes found in sand, studies are urgently needed to identify the most significant aetiological agent of disease and to relate microbial measurements in sand to human health risk
Study of Leading Hadrons in Gluon and Quark Fragmentation
The study of quark jets in e+e- reactions at LEP has demonstrated that the
hadronisation process is reproduced well by the Lund string model. However, our
understanding of gluon fragmentation is less complete. In this study enriched
quark and gluon jet samples of different purities are selected in three-jet
events from hadronic decays of the Z collected by the DELPHI experiment in the
LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are
defined by requiring a rapidity gap and their sum of charges is studied. An
excess of leading systems with total charge zero is found for gluon jets in all
cases, when compared to Monte Carlo Simulations with JETSET (with and without
Bose-Einstein correlations included) and ARIADNE. The corresponding leading
systems of quark jets do not exhibit such an excess. The influence of the gap
size and of the gluon purity on the effect is studied and a concentration of
the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is
observed, indicating that gluon jets might have an additional hitherto
undetected fragmentation mode via a two-gluon system. This could be an
indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.
Performance of [(18)F]flutemetamol amyloid imaging against the neuritic plaque component of CERAD and the current (2012) NIA-AA recommendations for the neuropathologic diagnosis of Alzheimer's disease
INTRODUCTION: Performance of the amyloid tracer [(18)F]flutemetamol was evaluated against three pathology standard of truth (SoT) measures including neuritic plaques (CERAD "original" and "modified" and the amyloid component of the 2012 NIA-AA guidelines). METHODS: After [(18)F]flutemetamol imaging, 106 end-of-life patients who died underwent postmortem brain examination for amyloid plaque load. Blinded positron emission tomography scan interpretations by five independent electronically trained readers were compared with pathology measures. RESULTS: By SoT, sensitivity and specificity of majority image interpretations were, respectively, 91.9% and 87.5% with "original CERAD," 90.8% and 90.0% with "modified CERAD," and 85.7% and 100% with the 2012 NIA-AA criteria. DISCUSSION: The high accuracy of either CERAD criteria suggests that [(18)F]flutemetamol predominantly reflects neuritic amyloid plaque density. However, the use of CERAD criteria as the SoT can result in some false-positive results because of the presence of diffuse plaques, which are accounted for when the positron emission tomography read is compared with the 2012 NIA-AA criteria
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Florbetapir F 18 amyloid PET and 36-month cognitive decline:a prospective multicenter study
This study was designed to evaluate whether subjects with amyloid beta (Aβ) pathology, detected using florbetapir positron emission tomorgraphy (PET), demonstrated greater cognitive decline than subjects without Aβ pathology. Sixty-nine cognitively normal (CN) controls, 52 with recently diagnosed mild cognitive impairment (MCI) and 31 with probable Alzheimer's disease (AD) dementia were included in the study. PET images obtained in these subjects were visually rated as positive (Aβ+) or negative (Aβ−), blind to diagnosis. Fourteen percent (10/69) of CN, 37% (19/52) of MCI and 68% (21/31) of AD were Aβ+. The primary outcome was change in ADAS-Cog score in MCI subjects after 36 months; however, additional outcomes included change on measures of cognition, function and diagnostic status. Aβ+ MCI subjects demonstrated greater worsening compared with Aβ− subjects on the ADAS-Cog over 36 months (5.66±1.47 vs −0.71±1.09, P=0.0014) as well as on the mini-mental state exam (MMSE), digit symbol substitution (DSS) test, and a verbal fluency test (P<0.05). Similar to MCI subjects, Aβ+ CN subjects showed greater decline on the ADAS-Cog, digit-symbol-substitution test and verbal fluency (P<0.05), whereas Aβ+ AD patients showed greater declines in verbal fluency and the MMSE (P<0.05). Aβ+ subjects in all diagnostic groups also showed greater decline on the CDR-SB (P<0.04), a global clinical assessment. Aβ+ subjects did not show significantly greater declines on the ADCS-ADL or Wechsler Memory Scale. Overall, these findings suggest that in CN, MCI and AD subjects, florbetapir PET Aβ+ subjects show greater cognitive and global deterioration over a 3-year follow-up than Aβ− subjects do
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