8,483 research outputs found
A radiative transfer scheme for cosmological reionization based on a local Eddington tensor
A radiative transfer scheme is presented, based on a moment description of
the equation of radiative transfer and the so-called ``M1 closure model'' for
the Eddington tensor. This model features a strictly hyperbolic transport step
for radiation: it has been implemented using standard Godunov--like techniques
in a new code called ATON. Coupled to simple models of ionization chemistry and
photo-heating, ATON is able to reproduce the results of other schemes on a
various set of standard tests such as the expansion of a HII region, the
shielding of the radiation by dense clumps and cosmological ionization by
multiple sources. Being simple yet robust, such a scheme is intended to be
naturally and easily included in grid--based cosmological fluid solvers.Comment: 14 pages, 13 figures, submitted to MNRA
Measurement-based Run-to-run Optimization of a Batch Reaction-distillation System
Measurement-based optimization schemes have been developed to deal with uncertainty and process variations. One of the methods therein, labeled NCO tracking, relies on appropriate parameterization of the input profiles and adjusts the corresponding input parameters using measurements so as to satisfy the necessary conditions of optimality (NCO). The applicability of NCO-tracking schemes has been demonstrated on several academic-size examples. The goal of this paper is to show that it can be applied with similar ease to more complex real-life systems. Run-to-run optimization of a batch reaction-separation system with propylene glycol is used for illustration
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Analysis of mortality in a pooled cohort of Canadian and German uranium processing workers with no mining experience.
PurposeLong-term health risks of occupational exposures to uranium processing were examined to better understand potential differences with uranium underground miners and nuclear reactor workers.MethodsA cohort study of mortality of workers from Port Hope, Canada (1950-1999) and Wismut, Germany (1946-2008) employed in uranium milling, refining, and processing was conducted. Poisson regression was used to evaluate the association between cumulative exposures to radon decay products (RDP) and gamma-rays and causes of death potentially related to uranium processing.ResultsThe pooled cohort included 7431 workers (270,201 person-years of follow-up). Mean RDP exposures were lower than in miners while gamma-ray doses were higher than in reactor workers. Both exposures were highly correlated (weighted rho = 0.81). Radiation risks of lung cancer and cardiovascular diseases (CVD) in males were increased but not statistically significant and compatible with risks estimated for miners and reactor workers, respectively. Higher RDP-associated CVD risks were observed for exposures 5-14 years prior to diagnosis compared to later exposures and among those employed <5 years. Radiation risks of solid cancers excluding lung cancer were increased, but not statistically significant, both for males and females, while all other causes of death were not associated with exposures.ConclusionsIn the largest study of uranium processing workers to systematically examine radiation risks of multiple outcomes from RDP exposures and gamma-rays, estimated radiation risks were compatible with risks reported for uranium miners and nuclear reactor workers. Continued follow-up and pooling with other cohorts of uranium processing workers are necessary for future comparisons with other workers of the nuclear fuel cycle
Little evidence for entropy and energy excess beyond - An end to ICM preheating?
Non-gravitational feedback affects the nature of the intra-cluster medium
(ICM). X-ray cooling of the ICM and in situ energy feedback from AGN's and SNe
as well as {\it preheating} of the gas at epochs preceding the formation of
clusters are proposed mechanisms for such feedback. While cooling and AGN
feedbacks are dominant in cluster cores, the signatures of a preheated ICM are
expected to be present even at large radii. To estimate the degree of
preheating, with minimum confusion from AGN feedback/cooling, we study the
excess entropy and non-gravitational energy profiles upto for a
sample of 17 galaxy clusters using joint data sets of {\it Planck} SZ pressure
and {\it ROSAT/PSPC} gas density profiles. The canonical value of preheating
entropy floor of keV cm, needed in order to match cluster
scalings, is ruled out at . We also show that the feedback
energy of 1 keV/particle is ruled out at 5.2 beyond . Our
analysis takes both non-thermal pressure and clumping into account which can be
important in outer regions. Our results based on the direct probe of the ICM in
the outermost regions do not support any significant preheating.Comment: 6 pages, 4 figures, 1 table, Accepted in MNRAS Letter
Excess entropy and energy feedback from within cluster cores up to r
We estimate the "non-gravitational" entropy-injection profiles, ,
and the resultant energy feedback profiles, , of the intracluster
medium for 17 clusters using their Planck SZ and ROSAT X-Ray observations,
spanning a large radial range from up to . The feedback
profiles are estimated by comparing the observed entropy, at fixed gas mass
shells, with theoretical entropy profiles predicted from non-radiative
hydrodynamic simulations. We include non-thermal pressure and gas clumping in
our analysis. The inclusion of non-thermal pressure and clumping results in
changing the estimates for and by 10\%-20\%. When
clumpiness is not considered it leads to an under-estimation of keV cm at and keV cm at
. On the other hand, neglecting non-thermal pressure results in an
over-estimation of keV cm at and
under-estimation of keV cm at . For the
estimated feedback energy, we find that ignoring clumping leads to an
under-estimation of energy per particle keV at and
keV at . Similarly, neglect of the non-thermal
pressure results in an over-estimation of keV at
and under-estimation of keV at . We find entropy
floor of keV cm is ruled out at
throughout the entire radial range and keV at more than
3 beyond , strongly constraining ICM pre-heating scenarios. We
also demonstrate robustness of results w.r.t sample selection, X-Ray analysis
procedures, entropy modeling etc.Comment: 17 pages, 15 figures, 5 tables, Accepted in MNRA
Novel methods to estimate antiretroviral adherence: protocol for a longitudinal study.
BackgroundThere is currently no gold standard for assessing antiretroviral (ARV) adherence, so researchers often resort to the most feasible and cost-effective methods possible (eg, self-report), which may be biased or inaccurate. The goal of our study was to evaluate the feasibility and acceptability of innovative and remote methods to estimate ARV adherence, which can potentially be conducted with less time and financial resources in a wide range of clinic and research settings. Here, we describe the research protocol for studying these novel methods and some lessons learned.MethodsThe 6-month pilot study aimed to examine the feasibility and acceptability of a remotely conducted study to evaluate the correlation between: 1) text-messaged photographs of pharmacy refill dates for refill-based adherence; 2) text-messaged photographs of pills for pill count-based adherence; and 3) home-collected hair sample measures of ARV concentration for pharmacologic-based adherence. Participants were sent monthly automated text messages to collect refill dates and pill counts that were taken and sent via mobile telephone photographs, and hair collection kits every 2 months by mail. At the study end, feasibility was calculated by specific metrics, such as the receipt of hair samples and responses to text messages. Participants completed a quantitative survey and qualitative exit interviews to examine the acceptability of these adherence evaluation methods. The relationship between the 3 novel metrics of adherence and self-reported adherence will be assessed.DiscussionInvestigators conducting adherence research are often limited to using either self-reported adherence, which is subjective, biased, and often overestimated, or other more complex methods. Here, we describe the protocol for evaluating the feasibility and acceptability of 3 novel and remote methods of estimating adherence, with the aim of evaluating the relationships between them. Additionally, we note the lessons learned from the protocol implementation to date. We expect that these novel measures will be feasible and acceptable. The implications of this research will be the identification and evaluation of innovative and accurate metrics of ARV adherence for future implementation
Effective interactions in the colloidal suspensions from HNC theory
The HNC Ornstein-Zernike integral equations are used to determine the
properties of simple models of colloidal solutions where the colloids and ions
are immersed in a solvent considered as a dielectric continuum and have a size
ratio equal to 80 and a charge ratio varying between 1 and 4000. At an infinite
dilution of colloids, the effective interactions between colloids and ions are
determined for ionic concentrations ranging from 0.001 to 0.1 mol/l and
compared to those derived from the Poisson-Boltzmann theory. At finite
concentrations, we discuss on the basis of the HNC results the possibility of
an unambiguous definition of the effective interactions between the colloidal
molecules.Comment: 26 pages, 15 figure
Molecules empowering animals to sense and respond to temperature in changing environments
Adapting behavior to thermal cues is essential for animal growth and survival. Indeed, each and every biological and biochemical process is profoundly affected by temperature and its extremes can cause irreversible damage. Hence, animals have developed thermotransduction mechanisms to detect and encode thermal information in the nervous system and acclimation mechanisms to finely tune their response over different timescales. While temperature-gated TRP channels are the best described class of temperature sensors, recent studies highlight many new candidates, including ionotropic and metabotropic receptors. Here, we review recent findings in vertebrate and invertebrate models, which highlight and substantiate the role of new candidate molecular thermometers and reveal intracellular signaling mechanisms implicated in thermal acclimation at the behavioral and cellular levels
Rapport de mission d'appui au projet "DĂ©veloppement des recherches menĂ©es en zone de forĂȘt dense humide en agroforesterie : Application Ă la CĂŽte d'Ivoire" et compte-rendu de visite Ă Korhogo
Ce rapport prĂ©sente un rĂ©sumĂ© des travaux rĂ©alisĂ©s en 1991 et fait des propositions d'essais complĂ©mentaires en station ou en milieu rural. Ce sont de simples propositions dans le cas oĂč des financements supplĂ©mentaires pourraient ĂȘtre trouvĂ©s par les partenaires, et oĂč IDEFOR les approuverai
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