2,878 research outputs found
Modelling survival and connectivity of Mnemiopsis leidyi in the south-western North Sea and Scheldt estuaries
Three different models were applied to study the reproduction, survival and dispersal of Mnemiopsis leidyi in the Scheldt estuaries and the southern North Sea: a high-resolution particle tracking model with passive particles, a low-resolution particle tracking model with a reproduction model coupled to a biogeochemical model, and a dynamic energy budget (DEB) model. The results of the models, each with its strengths and weaknesses, suggest the following conceptual situation: (i) the estuaries possess enough retention capability to keep an overwintering population, and enough exchange with coastal waters of the North Sea to seed offshore populations; (ii) M. leidyi can survive in the North Sea, and be transported over considerable distances, thus facilitating connectivity between coastal embayments; (iii) under current climatic conditions, M. leidyi may not be able to reproduce in large numbers in coastal and offshore waters of the North Sea, but this may change with global warming; however, this result is subject to substantial uncertainty. Further quantitative observational work is needed on the effects of temperature, salinity and food availability on reproduction and on mortality at different life stages to improve models such as used here
Estudio de las comunidades de hongos formadores de micorrizas arbusculares en soja : relación con la nutrición fosforada en agroecosistemas
Tesis presentada para optar al Grado de Doctor en Ciencias NaturalesFil: Faggioli, Valeria S.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentin
Microwave Surface-Impedance Measurements of the Magnetic Penetration Depth in Single Crystal Ba1-xKxFe2As2 Superconductors: Evidence for a Disorder-Dependent Superfluid Density
We report high-sensitivity microwave measurements of the in-plane penetration
depth and quasiparticle scattering rate in several
single crystals of hole-doped Fe-based superconductor
BaKFeAs (). While power-law temperature
dependence of with the power is found in crystals with
large , we observe exponential temperature dependence of superfluid
density consistent with the existence of fully opened two gaps in the cleanest
crystal we studied. The difference may be a consequence of different level of
disorder inherent in the crystals. We also find a linear relation between the
low-temperature scattering rate and the density of quasiparticles, which shows
a clear contrast to the case of d-wave cuprate superconductors with nodes in
the gap. These results demonstrate intrinsically nodeless order parameters in
the Fe-arsenides.Comment: 4 pages, 4 figures, 1 table. Accepted for publication in Phys. Rev.
Lett. Changed title as suggested by the PRL editor
Risk factors for COPD exacerbations in inhaled medication users: the COPDGene study biannual longitudinal follow-up prospective cohort.
BackgroundDespite inhaled medications that decrease exacerbation risk, some COPD patients experience frequent exacerbations. We determined prospective risk factors for exacerbations among subjects in the COPDGene Study taking inhaled medications.Methods2113 COPD subjects were categorized into four medication use patterns: triple therapy with tiotropium (TIO) plus long-acting beta-agonist/inhaled-corticosteroid (ICS ± LABA), tiotropium alone, ICS ± LABA, and short-acting bronchodilators. Self-reported exacerbations were recorded in telephone and web-based longitudinal follow-up surveys. Associations with exacerbations were determined within each medication group using four separate logistic regression models. A head-to-head analysis compared exacerbation risk among subjects using tiotropium vs. ICS ± LABA.ResultsIn separate logistic regression models, the presence of gastroesophageal reflux, female gender, and higher scores on the St. George's Respiratory Questionnaire were significant predictors of exacerbator status within multiple medication groups (reflux: OR 1.62-2.75; female gender: OR 1.53 - OR 1.90; SGRQ: OR 1.02-1.03). Subjects taking either ICS ± LABA or tiotropium had similar baseline characteristics, allowing comparison between these two groups. In the head-to-head comparison, tiotropium users showed a trend towards lower rates of exacerbations (OR = 0.69 [95 % CI 0.45, 1.06], p = 0.09) compared with ICS ± LABA users, especially in subjects without comorbid asthma (OR = 0.56 [95% CI 0.31, 1.00], p = 0.05).ConclusionsEach common COPD medication usage group showed unique risk factor patterns associated with increased risk of exacerbations, which may help clinicians identify subjects at risk. Compared to similar subjects using ICS ± LABA, those taking tiotropium showed a trend towards reduced exacerbation risk, especially in subjects without asthma.Trial registrationClinicalTrials.gov NCT00608764, first received 1/28/2008
A 14b 200MS/s DAC with SFDR>78dBc, IM3
A 14-bit 200MS/s current-steering DAC with a novel digital calibration technique called dynamic-mismatch mapping (DMM) is presented. Compared to traditional static-mismatch mapping and dynamic element matching, DMM reduces the nonlinearities caused by both amplitude and timing errors, without noise penalty. This 0.14µm CMOS DAC achieves a state-of-the-art performance of SFDR>78dBc, IM
Systematic coarse-graining of epoxy resins with machine learning-informed energy renormalization
A persistent challenge in predictive molecular modeling of thermoset polymers
is to capture the effects of chemical composition and degree of crosslinking
(DC) on dynamical and mechanical properties with high computational efficiency.
We established a new coarse-graining (CG) approach that combines the energy
renormalization method with Gaussian process surrogate models of the molecular
dynamics simulations. This allows a machine-learning informed functional
calibration of DC-dependent CG force field parameters. Taking versatile epoxy
resins consisting of Bisphenol A diglycidyl ether combined with curing agent of
either 4,4-Diaminodicyclohexylmethane or polyoxypropylene diamines, we
demonstrated excellent agreement between all-atom and CG predictions for
density, Debye-Waller factor, Young's modulus and yield stress at any DC. We
further introduce a surrogate model enabled simplification of the functional
forms of 14 non-bonded calibration parameters by quantifying the uncertainty of
a candidate set of high-dimensional and flexible calibration functions. The
framework established provides an efficient methodology for chemistry-specific,
large-scale investigations of the dynamics and mechanics of epoxy resins.Comment: new version: minor updates to the force field and general formatting
after peer revie
Cohort Profile:The Dutch Perined-Lifelines birth cohort
BACKGROUND: Maternal nutrition status (e.g. dietary/nutrient intake) during pregnancy has been associated with pregnancy outcomes including birth weight, infant survival and metabolic health of the offspring during later life. During the past few years, maternal dietary intake, at least three months before conception, has been shown to affect pregnancy outcomes also. However, literature investigating this link is still scarce. The studies that have looked at preconception dietary intake in relation to pregnancy outcome were either animal studies, had small sample sizes or focused on only selected macronutrient intake rather than complete (macro)nutrient composition or dietary intakes (e.g. food groups). Therefore, we aim to investigate the association between preconception diet and pregnancy outcomes in a linked birth cohort. The main objective of this manuscript is to describe the methodology of establishing this birth cohort and to describe both the characteristics of the study population included as well as the representativeness in terms of dietary intake. METHODS: We created the birth cohort by linking two existing databases; a large population-based cohort study in the Netherlands (The Lifelines Cohort study) and the Dutch national birth registry (Perined), through a 'trusted third party'. The birth cohort contains information on maternal dietary intake during preconception as well as pregnancy outcomes. RESULTS AND DISCUSSION: In the Lifelines Cohort study, 3,418 pregnancies were available for linking with Perined. In total, 2,368 pregnancies (86.9%) were linked with Perined, resulting in the birth cohort. With this linked cohort we are able to provide insights on the associations between dietary intake before conception and pregnancy outcomes. Such data could potentially improve nutritional care for women of childbearing age. Lifestyle changes in the period preceding pregnancy may be most effective in improving pregnancy outcomes. A focus on this window of opportunity may provide both sufficient time, as well as a period when women are potentially motivated to adopt health optimizing behaviours
- …