2,342 research outputs found
Inorganic carbon dominates total dissolved carbon concentrations and fluxes in British rivers: application of the THINCARB model â thermodynamic modelling of inorganic carbon in freshwaters
River water-quality studies rarely measure dissolved inorganic carbon (DIC) routinely, and there is a gap in our knowledge of the contributions of DIC to aquatic carbon fluxes and cycling processes. Here, we present the THINCARB model (THermodynamic modelling of INorganic CARBon), which uses widely-measured determinands (pH, alkalinity and temperature) to calculate DIC concentrations, speciation (bicarbonate, HCO3â; carbonate, CO32 â; and dissolved carbon dioxide, H2CO3â) and excess partial pressures of carbon dioxide (EpCO2) in freshwaters. If calcium concentration measurements are available, THINCARB also calculates calcite saturation. THINCARB was applied to the 39-year Harmonised Monitoring Scheme (HMS) dataset, encompassing all the major British rivers discharging to the coastal zone. Model outputs were combined with the HMS dissolved organic carbon (DOC) datasets, and with spatial land use, geology, digital elevation and hydrological datasets. We provide a first national-scale evaluation of: the spatial and temporal variability in DIC concentrations and fluxes in British rivers; the contributions of DIC and DOC to total dissolved carbon (TDC); and the contributions to DIC from HCO3â and CO32 â from weathering sources and H2CO3â from microbial respiration. DIC accounted for > 50% of TDC concentrations in 87% of the HMS samples. In the seven largest British rivers, DIC accounted for an average of 80% of the TDC flux (ranging from 57% in the upland River Tay, to 91% in the lowland River Thames). DIC fluxes exceeded DOC fluxes, even under high-flow conditions, including in the Rivers Tay and Tweed, draining upland peaty catchments. Given that particulate organic carbon fluxes from UK rivers are consistently lower than DOC fluxes, DIC fluxes are therefore also the major source of total carbon fluxes to the coastal zone. These results demonstrate the importance of accounting for DIC concentrations and fluxes for quantifying carbon transfers from land, via rivers, to the coastal zone
Gene Function Classification Using Bayesian Models with Hierarchy-Based Priors
We investigate the application of hierarchical classification schemes to the
annotation of gene function based on several characteristics of protein
sequences including phylogenic descriptors, sequence based attributes, and
predicted secondary structure. We discuss three Bayesian models and compare
their performance in terms of predictive accuracy. These models are the
ordinary multinomial logit (MNL) model, a hierarchical model based on a set of
nested MNL models, and a MNL model with a prior that introduces correlations
between the parameters for classes that are nearby in the hierarchy. We also
provide a new scheme for combining different sources of information. We use
these models to predict the functional class of Open Reading Frames (ORFs) from
the E. coli genome. The results from all three models show substantial
improvement over previous methods, which were based on the C5 algorithm. The
MNL model using a prior based on the hierarchy outperforms both the
non-hierarchical MNL model and the nested MNL model. In contrast to previous
attempts at combining these sources of information, our approach results in a
higher accuracy rate when compared to models that use each data source alone.
Together, these results show that gene function can be predicted with higher
accuracy than previously achieved, using Bayesian models that incorporate
suitable prior information
The Cognitive Ageing, Nutrition and Neurogenesis trial: Design and progress
Introduction: Cohort studies indicate that long-chain n-3 polyunsaturated fatty acids and flavonoids may improve cognition and reduce dementia risk. The neuroprotective effects of these dietary components indicate that they are likely to be additive and potentially synergistic. Methods: The Cognitive Ageing, Nutrition and Neurogenesis trial hypothesizes that an intervention comprising long-chain n-3 polyunsaturated fatty acids (docosahexaenoic acid and eicosapentaenoic acid) and cocoa flavan-3-ols (n-3 FLAV) will mitigate the cognitive decline anticipated to naturally occur over 1 year in older adults with mild cognitive impairment or subjective memory impairment. A double-blinded, placebo-controlled parallel design is used. Two hundred fifty-nine adults (aged â„55 years) with mild cognitive impairment or subjective memory impairment were recruited and randomized to a control or n-3 FLAV group (1.5 g docosahexaenoic acid + eicosapentaenoic acid and 500 mg n-3 FLAV daily) for 12 months. Cognitive performance was measured three times over the 1-year intervention, at 0 (baseline), 3, and 12 months. The primary end point is hippocampus-sensitive cognitive function (e.g., number of false-positives on the Picture Recognition Task of the Cognitive Drug Research test battery). Secondary outcomes include additional cognitive measures, brain atrophy and blood flow (assessed by magnetic resonance imaging), vascular function, circulating biomarkers of cardiovascular and cognitive health, gut microflora speciation and metabolism, red blood cell fatty acid status, and urine flavan-3-ol metabolites. The intervention arms were matched for sex and apolipoprotein E4 status to allow retrospective exploratory analysis of the impact of these variables on response to intervention. Results: Screening began in 2015, with all baseline visits completed in March 2017. The intervention was finished in March 2018. Discussion: Cognitive Ageing, Nutrition and Neurogenesis aims to identify an effective diet-based intervention to prevent or delay cognitive impairment in cognitively at-risk individuals, which could ultimately contribute to a reduced population burden of dementia
High penetrances of BRCA1 and BRCA2 mutations confirmed in a prospective series
Penetrances of BRCA1 and BRCA2 mutations have been derived from retrospective studies, implying the possibility of ascertainment biases to influence the results
Coupling models of cattle and farms with models of badgers for predicting the dynamics of bovine tuberculosis (TB)
Bovine TB is a major problem for the agricultural industry in several
countries. TB can be contracted and spread by species other than cattle and
this can cause a problem for disease control. In the UK and Ireland, badgers
are a recognised reservoir of infection and there has been substantial
discussion about potential control strategies. We present a coupling of
individual based models of bovine TB in badgers and cattle, which aims to
capture the key details of the natural history of the disease and of both
species at approximately county scale. The model is spatially explicit it
follows a very large number of cattle and badgers on a different grid size for
each species and includes also winter housing. We show that the model can
replicate the reported dynamics of both cattle and badger populations as well
as the increasing prevalence of the disease in cattle. Parameter space used as
input in simulations was swept out using Latin hypercube sampling and
sensitivity analysis to model outputs was conducted using mixed effect models.
By exploring a large and computationally intensive parameter space we show that
of the available control strategies it is the frequency of TB testing and
whether or not winter housing is practised that have the most significant
effects on the number of infected cattle, with the effect of winter housing
becoming stronger as farm size increases. Whether badgers were culled or not
explained about 5%, while the accuracy of the test employed to detect infected
cattle explained less than 3% of the variance in the number of infected cattle
A Search for Jet Handedness in Hadronic Decays
We have searched for signatures of polarization in hadronic jets from decays using the ``jet handedness'' method. The polar angle
asymmetry induced by the high SLC electron-beam polarization was used to
separate quark jets from antiquark jets, expected to be left- and
right-polarized, respectively. We find no evidence for jet handedness in our
global sample or in a sample of light quark jets and we set upper limits at the
95% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing
power of the method proposed by Efremov {\it et al.}Comment: Revtex, 8 pages, 2 figure
Probabilistic machine learning and artificial intelligence.
How can a machine learn from experience? Probabilistic modelling provides a framework for understanding what learning is, and has therefore emerged as one of the principal theoretical and practical approaches for designing machines that learn from data acquired through experience. The probabilistic framework, which describes how to represent and manipulate uncertainty about models and predictions, has a central role in scientific data analysis, machine learning, robotics, cognitive science and artificial intelligence. This Review provides an introduction to this framework, and discusses some of the state-of-the-art advances in the field, namely, probabilistic programming, Bayesian optimization, data compression and automatic model discovery.The author acknowledges an EPSRC grant EP/I036575/1, the DARPA PPAML programme, a Google Focused Research Award for the Automatic Statistician and support from Microsoft Research.This is the author accepted manuscript. The final version is available from NPG at http://www.nature.com/nature/journal/v521/n7553/full/nature14541.html#abstract
Measurement of Branching Fractions and Rate Asymmetries in the Rare Decays B -> K(*) l+ l-
In a sample of 471 million BB events collected with the BABAR detector at the
PEP-II e+e- collider we study the rare decays B -> K(*) l+ l-, where l+ l- is
either e+e- or mu+mu-. We report results on partial branching fractions and
isospin asymmetries in seven bins of di-lepton mass-squared. We further present
CP and lepton-flavor asymmetries for di-lepton masses below and above the J/psi
resonance. We find no evidence for CP or lepton-flavor violation. The partial
branching fractions and isospin asymmetries are consistent with the Standard
Model predictions and with results from other experiments.Comment: 16 pages, 14 figures, accepted by Phys. Rev.
Recommended from our members
Measurement of B(B-->X_s {\gamma}), the B-->X_s {\gamma} photon energy spectrum, and the direct CP asymmetry in B-->X_{s+d} {\gamma} decays
The photon spectrum in B --> X_s {\gamma} decay, where X_s is any strange
hadronic state, is studied using a data sample of (382.8\pm 4.2) \times 10^6
e^+ e^- --> \Upsilon(4S) --> BBbar events collected by the BABAR experiment at
the PEP-II collider. The spectrum is used to measure the branching fraction B(B
--> X_s \gamma) = (3.21 \pm 0.15 \pm 0.29 \pm 0.08)\times 10^{-4} and the
first, second, and third moments = 2.267 \pm 0.019 \pm 0.032 \pm
0.003 GeV,, )^2> = 0.0484 \pm 0.0053 \pm 0.0077 \pm
0.0005 GeV^2, and )^3> = -0.0048 \pm 0.0011 \pm 0.0011
\pm 0.0004 GeV^3, for the range E_\gamma > 1.8 GeV, where E_{\gamma} is the
photon energy in the B-meson rest frame. Results are also presented for
narrower E_{\gamma} ranges. In addition, the direct CP asymmetry A_{CP}(B -->
X_{s+d} \gamma) is measured to be 0.057 \pm 0.063. The spectrum itself is also
unfolded to the B-meson rest frame; that is the frame in which theoretical
predictions for its shape are made.Comment: 37 pages, 19 postscript figures, submitted to Phys. Rev. D. No
analysis or results have changed from previous version. Some changes to
improve clarity based on interactions with Phys. Rev. D referees, including
one new Figure (Fig. 13), and some minor wording/punctuation/spelling
mistakes fixe
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
- âŠ