1,862 research outputs found
Physiological serum 25-hydroxyvitamin D concentrations are associated with improved thyroid function—observations from a community-based program
Purpose: Vitamin D deficiency has been associated with an increased risk of hypothyroidism and autoimmune thyroid disease. Our aim was to investigate the influence of vitamin D supplementation on thyroid function and anti-thyroid antibody levels. Methods: We constructed a database that included 11,017 participants in a health and wellness program that provided vitamin D supplementation to target physiological serum 25-hydroxyvitmain D [25(OH)D] concentrations (>100 nmol/L). Participant measures were compared between entry to the program (baseline) and follow-up (12 ± 3 months later) using an intent-to-treat analysis. Further, a nested case-control design was utilized to examine differences in thyroid function over 1 year in hypothyroid individuals and euthyroid controls. Results: More than 72% of participants achieved serum 25(OH)D concentrations >100 nmol/L at follow-up, with 20% above 125 nmol/L. Hypothyroidism was detected in 2% (23% including subclinical hypothyroidism) of participants at baseline and 0.4% (or 6% with subclinical) at follow-up. Serum 25(OH)D concentrations ≥125 nmol/L were associated with a 30% reduced risk of hypothyroidism and a 32% reduced risk of elevated anti-thyroid antibodies. Hypothyroid cases were found to have higher mean serum 25(OH)D concentrations at follow-up, which was a significant positive predictor of improved thyroid function. Conclusion: The results of the current study suggest that optimal thyroid function might require serum 25(OH)D concentrations above 125 nmol/L. Vitamin D supplementation may offer a safe and economical approach to improve thyroid function and may provide protection from developing thyroid disease
Fermionic field theory for directed percolation in (1+1) dimensions
We formulate directed percolation in (1+1) dimensions in the language of a
reaction-diffusion process with exclusion taking place in one space dimension.
We map the master equation that describes the dynamics of the system onto a
quantum spin chain problem. From there we build an interacting fermionic field
theory of a new type. We study the resulting theory using renormalization group
techniques. This yields numerical estimates for the critical exponents and
provides a new alternative analytic systematic procedure to study
low-dimensional directed percolation.Comment: 20 pages, 2 figure
Temporal decorrelation of collective oscillations in neural networks with local inhibition and long-range excitation
We consider two neuronal networks coupled by long-range excitatory
interactions. Oscillations in the gamma frequency band are generated within
each network by local inhibition. When long-range excitation is weak, these
oscillations phase-lock with a phase-shift dependent on the strength of local
inhibition. Increasing the strength of long-range excitation induces a
transition to chaos via period-doubling or quasi-periodic scenarios. In the
chaotic regime oscillatory activity undergoes fast temporal decorrelation. The
generality of these dynamical properties is assessed in firing-rate models as
well as in large networks of conductance-based neurons.Comment: 4 pages, 5 figures. accepted for publication in Physical Review
Letter
Hot electron cooling by acoustic phonons in graphene
We have investigated the energy loss of hot electrons in metallic graphene by
means of GHz noise thermometry at liquid helium temperature. We observe the
electronic temperature T / V at low bias in agreement with the heat diffusion
to the leads described by the Wiedemann-Franz law. We report on
behavior at high bias, which corresponds to a T4 dependence
of the cooling power. This is the signature of a 2D acoustic phonon cooling
mechanism. From a heat equation analysis of the two regimes we extract accurate
values of the electron-acoustic phonon coupling constant in monolayer
graphene. Our measurements point to an important effect of lattice disorder in
the reduction of , not yet considered by theory. Moreover, our study
provides a strong and firm support to the rising field of graphene bolometric
detectors.Comment: 5 figure
Statistical-Mechanical Measure of Stochastic Spiking Coherence in A Population of Inhibitory Subthreshold Neurons
By varying the noise intensity, we study stochastic spiking coherence (i.e.,
collective coherence between noise-induced neural spikings) in an inhibitory
population of subthreshold neurons (which cannot fire spontaneously without
noise). This stochastic spiking coherence may be well visualized in the raster
plot of neural spikes. For a coherent case, partially-occupied "stripes"
(composed of spikes and indicating collective coherence) are formed in the
raster plot. This partial occupation occurs due to "stochastic spike skipping"
which is well shown in the multi-peaked interspike interval histogram. The main
purpose of our work is to quantitatively measure the degree of stochastic
spiking coherence seen in the raster plot. We introduce a new spike-based
coherence measure by considering the occupation pattern and the pacing
pattern of spikes in the stripes. In particular, the pacing degree between
spikes is determined in a statistical-mechanical way by quantifying the average
contribution of (microscopic) individual spikes to the (macroscopic)
ensemble-averaged global potential. This "statistical-mechanical" measure
is in contrast to the conventional measures such as the "thermodynamic" order
parameter (which concerns the time-averaged fluctuations of the macroscopic
global potential), the "microscopic" correlation-based measure (based on the
cross-correlation between the microscopic individual potentials), and the
measures of precise spike timing (based on the peri-stimulus time histogram).
In terms of , we quantitatively characterize the stochastic spiking
coherence, and find that reflects the degree of collective spiking
coherence seen in the raster plot very well. Hence, the
"statistical-mechanical" spike-based measure may be used usefully to
quantify the degree of stochastic spiking coherence in a statistical-mechanical
way.Comment: 16 pages, 5 figures, to appear in the J. Comput. Neurosc
Un outil de simulation adapté à la gestion des ressources en eau du territoire dans le cadre d’une démarche participative
National audienceThis paper presents a simulation tool adapted to water resources management on a territorial scale, as part of a participatory process. This tool combines the PILOTE-TER crop model and the Olympe technico-economical simulator. PILOTE-TER links the crop model Pilote developed by Irstea with a database managed through a graphical interface. It makes possible to use the Pilote model to evaluate the water demand and the crop yield at the scale of the field, the farm and the territory. The parameters of the model come from the results of experiments performed by Irstea. PILOTE-TER is linked to the technico-economic simulator Olympe (from INRA) to produce economical indicators. These tools are used for a territorial representation of agriculture build with local stakeholders, allowing the comparison of several scenarios (based on economical, policy or climate changes).Cet article présente un outil de simulation adapté à la gestion de ressources en eau à l’échelle d’un territoire dans le cadre de démarches participatives. Cet outil associe un modèle de culture, Pilote Ter, et le simulateur technico-économique Olympe. Pilote Ter intègre le modèle de culture Pilote développé par Irstea et un système de base de données géré à partir d’une interface graphique. Il permet une utilisation territorialisée du modèle de culture Pilote pour évaluer la demande en eau agricole et les rendements des cultures à l’échelle de la parcelle, de l’exploitation agricole et du territoire. Le paramétrage du modèle s’appuie sur les résultats des expérimentations menées par Irstea. Pilote Ter est couplé au simulateur technico-économique Olympe (INRA) pour produire des indicateurs économiques. Ces deux logiciels sont le support d’une représentation de l’agriculture du territoire co-construite avec les acteurs locaux permettant l’étude de scénarios économiques, réglementaires ou climatiques
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Getting to know you: A novel approach in segmenting the ageing consumer market
This presentation was given as part of the Brunel Institute for Ageing Studies (BIAS) Annual Conference 2012 by Mona Shekarriz from the School of Engineering and Design at Brunel University. The 2nd annual conference was hosted at Brunel University on the 15th February 2012
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