452 research outputs found
The Generalized Graetz Problem in Finite Domains
We consider the generalized Graetz problem associated with stationary convection-diïŹusion inside a domain having any regular three-dimensional translationally invariant section and ïŹnite or semi-inïŹnite extent. Our framework encompasses any previous âextendedâ and âconjugatedâ Graetz generalizations and provides theoretical bases for computing the orthogonal set of generalized two-dimensional Graetz modes. The theoretical framework includes both heterogeneous and possibly anisotropic diïŹusion tensors. In the case of semi-inïŹnite domains, the existence of a bounded solution is shown from the analysis of two-dimensional operator eigenvectors which form a basis of L2 . In the case of ïŹnite domains a similar basis can be exhibited, and the modeâs amplitudes can be obtained from the inversion of newly deïŹned ïŹnite domain operator. Our analysis includes both the theoretical and practical issues associated with this ïŹnite domain operator inversion as well as its interpretation as a multireïŹection image method. Error estimates are provided when numerically truncating the spectrum to a ïŹnite number of modes. Numerical examples are validated for reference conïŹgurations and provided in nontrivial cases. Our methodology shows how to map the solution of stationary convection-diïŹusion problems in ïŹnite three-dimensional domains into a two-dimensional operator spectrum, which leads to a drastic reduction in computational cost
The effect of passive heating on heat shock protein 70 and interleukin-6: a possible treatment tool for metabolic diseases?
Exercise and physical activity remain the gold standard methods of enhancing and maintaining health and wellbeing. However, in populations that benefit most from exercise, adherence is often poor and alternatives to exercise are important to bring about health improvements. Recent work suggests a role for passive heating (PH) and heat shock proteins (HSP) in improving cardio-metabolic health. The aim of this study was to investigate the expression of HSP70 and IL-6 in response to either exercise (EX) or PH and the subsequent effect on glucose control. Fourteen males volunteered and were categorized lean (BMI 23.5 ± 2.2 Kgm-2) or overweight (29.2 ± 2.7 Kgm-2) and completed 60 minutes of either moderate cycling at a fixed rate of metabolic heat production (EX) or warm water immersion in 40 ÌC water (PH). Extracellular HSP70 increased from baseline in both conditions with no differences between PH (0.98 ± 1.1 ngmL-1) or EX (0.84 ± 1.0 ngmL-1, P=0.814). IL-6 increased following both conditions with a 2 fold increase after PH and 4 fold after EX. Energy expenditure increased by 61.0 ± 14.4 kcal (79%) after PH. Peak glucose concentration after a meal immediately following PH was reduced when compared with EX (6.3 ± 1.4mmolL-1 vs. 6.8 ± 1.2mmolL-1; P<0.05). There was no difference in 24-hour glucose area under the curve between conditions. These data indicate the potential for thermal therapy as a novel treatment and management strategy for type 2 diabetes where adherence, or ability to exercise may be compromised
The circumstellar environment of T Tau S at high spatial and spectral resolution
We have obtained the first high spatial (0.05'') and spectral (R~35000)
resolution 2 micron spectrum of the T Tau S tight binary system using adaptive
optics on the Keck II telescope. We have also obtained the first 3.8 and 4.7
micron images that resolve the three components of the T Tau multiple system,
as well as new 1.6 and 2.2 micron images. Together with its very red
near-infrared colors, the spectrum of T Tau Sb shows that this T Tauri star is
extincted by a roughly constant extinction of Av~15 mag, which is probably the
0.7''x0.5'' circumbinary structure recently observed in absorption in the
ultraviolet. T Tau Sa, which is also observed through this screen and is
actively accreting, further possesses a small edge-on disk that is evidenced by
warm (390 K), narrow overtone CO rovibrational absorption features in our
spectrum. We find that T Tau Sa is most likely an intermediate-mass star
surrounded by a semi-transparent 2-3 AU-radius disk whose asymmetries and short
Keplerian rotation explain the large photometric variability of the source on
relatively short timescales. We also show that molecular hydrogen emission
exclusively arises from the gas that surrounds T Tau S and that its spatial and
kinematic structure, while providing suggestive evidence for a jet-like
structure, is highly complex.Comment: accepted for publication in the Astrophysical Journal; 41 pages, 10
figure
Exogenous surfactant application in a rat lung ischemia reperfusion injury model: effects on edema formation and alveolar type II cells
<p>Abstract</p> <p>Background</p> <p>Prophylactic exogenous surfactant therapy is a promising way to attenuate the ischemia and reperfusion (I/R) injury associated with lung transplantation and thereby to decrease the clinical occurrence of acute lung injury and acute respiratory distress syndrome. However, there is little information on the mode by which exogenous surfactant attenuates I/R injury of the lung. We hypothesized that exogenous surfactant may act by limiting pulmonary edema formation and by enhancing alveolar type II cell and lamellar body preservation. Therefore, we investigated the effect of exogenous surfactant therapy on the formation of pulmonary edema in different lung compartments and on the ultrastructure of the surfactant producing alveolar epithelial type II cells.</p> <p>Methods</p> <p>Rats were randomly assigned to a control, Celsior (CE) or Celsior + surfactant (CE+S) group (n = 5 each). In both Celsior groups, the lungs were flush-perfused with Celsior and subsequently exposed to 4 h of extracorporeal ischemia at 4°C and 50 min of reperfusion at 37°C. The CE+S group received an intratracheal bolus of a modified natural bovine surfactant at a dosage of 50 mg/kg body weight before flush perfusion. After reperfusion (Celsior groups) or immediately after sacrifice (Control), the lungs were fixed by vascular perfusion and processed for light and electron microscopy. Stereology was used to quantify edematous changes as well as alterations of the alveolar epithelial type II cells.</p> <p>Results</p> <p>Surfactant treatment decreased the intraalveolar edema formation (mean (coefficient of variation): CE: 160 mm<sup>3 </sup>(0.61) vs. CE+S: 4 mm<sup>3 </sup>(0.75); p < 0.05) and the development of atelectases (CE: 342 mm<sup>3 </sup>(0.90) vs. CE+S: 0 mm<sup>3</sup>; p < 0.05) but led to a higher degree of peribronchovascular edema (CE: 89 mm<sup>3 </sup>(0.39) vs. CE+S: 268 mm<sup>3 </sup>(0.43); p < 0.05). Alveolar type II cells were similarly swollen in CE (423 Όm<sup>3</sup>(0.10)) and CE+S (481 Όm<sup>3</sup>(0.10)) compared with controls (323 Όm<sup>3</sup>(0.07); p < 0.05 vs. CE and CE+S). The number of lamellar bodies was increased and the mean lamellar body volume was decreased in both CE groups compared with the control group (p < 0.05).</p> <p>Conclusion</p> <p>Intratracheal surfactant application before I/R significantly reduces the intraalveolar edema formation and development of atelectases but leads to an increased development of peribronchovascular edema. Morphological changes of alveolar type II cells due to I/R are not affected by surfactant treatment. The beneficial effects of exogenous surfactant therapy are related to the intraalveolar activity of the exogenous surfactant.</p
A Medium-Resolution Near-Infrared Spectral Library of Late Type Stars: I
We present an empirical infrared spectral library of medium resolution
(R~2000-3000) H (1.6 micron) and K (2.2 micron) band spectra of 218 red stars,
spanning a range of [Fe/H] from ~-2.2 to ~+0.3. The sample includes Galactic
disk stars, bulge stars from Baade's window, and red giants from Galactic
globular clusters. We report the values of 19 indices covering 12 spectral
features measured from the spectra in the library. Finally, we derive
calibrations to estimate the effective temperature, and diagnostic
relationships to determine the luminosity classes of individual stars from
near-infrared spectra.
This paper is part of a larger effort aimed at building a near-IR spectral
library to be incorporated in population synthesis models, as well as, at
testing synthetic stellar spectra.Comment: 34 pages, 12 figures; accepted for publication at ApJS; the spectra
are available from the authors upon reques
Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure
Extracellular heat-shock protein 72 (eHsp72) concentration increases during exercise-heat stress when conditions elicit physiological strain. Differences in severity of environmental and exercise stimuli have elicited varied response to stress. The present study aimed to quantify the extent of increased eHsp72 with increased exogenous heat stress, and determine related endogenous markers of strain in an exercise-heat model. Ten males cycled for 90 min at 50% O2peak in three conditions (TEMP, 20°C/63% RH; HOT, 30.2°C/51%RH; VHOT, 40.0°C/37%RH). Plasma was analysed for eHsp72 pre, immediately post and 24-h post each trial utilising a commercially available ELISA. Increased eHsp72 concentration was observed post VHOT trial (+172.4%) (P<0.05), but not TEMP (-1.9%) or HOT (+25.7%) conditions. eHsp72 returned to baseline values within 24hrs in all conditions. Changes were observed in rectal temperature (Trec), rate of Trec increase, area under the curve for Trec of 38.5°C and 39.0°C, duration Trec ℠38.5°C and ℠39.0°C, and change in muscle temperature, between VHOT, and TEMP and HOT, but not between TEMP and HOT. Each condition also elicited significantly increasing physiological strain, described by sweat rate, heart rate, physiological strain index, rating of perceived exertion and thermal sensation. Stepwise multiple regression reported rate of Trec increase and change in Trec to be predictors of increased eHsp72 concentration. Data suggests eHsp72 concentration increases once systemic temperature and sympathetic activity exceeds a minimum endogenous criteria elicited during VHOT conditions and is likely to be modulated by large, rapid changes in core temperature
Prenatal Vitamin D Supplementation and Child Respiratory Health: A Randomised Controlled Trial
PMCID: PMC3691177This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Shape optimization for the generalized Graetz problem
We apply shape optimization tools to the generalized Graetz problem which is a convection-diffusion equation. The problem boils down to the optimization of generalized eigen values on a two phases domain. Shape sensitivity analysis is performed with respect to the evolution of the interface between the fluid and solid phase. In particular physical settings, counterexamples where there is no optimal domains are exhibited. Numerical examples of optimal domains with different physical parameters and constraints are presented. Two different numerical methods (level-set and mesh-morphing) are show-cased and compared
GYES, a multifibre spectrograph for the CFHT
We have chosen the name of GYES, one of the mythological giants with one
hundred arms, offspring of Gaia and Uranus, for our instrument study of a
multifibre spectrograph for the prime focus of the Canada-France-Hawaii
Telescope. Such an instrument could provide an excellent ground-based
complement for the Gaia mission and a northern complement to the HERMES project
on the AAT. The CFHT is well known for providing a stable prime focus
environment, with a large field of view, which has hosted several imaging
instruments, but has never hosted a multifibre spectrograph. Building upon the
experience gained at GEPI with FLAMES-Giraffe and X-Shooter, we are
investigating the feasibility of a high multiplex spectrograph (about 500
fibres) over a field of view 1 degree in diameter. We are investigating an
instrument with resolution in the range 15000 to 30000, which should provide
accurate chemical abundances for stars down to 16th magnitude and radial
velocities, accurate to 1 km/s for fainter stars. The study is led by
GEPI-Observatoire de Paris with a contribution from Oxford for the study of the
positioner. The financing for the study comes from INSU CSAA and Observatoire
de Paris. The conceptual study will be delivered to CFHT for review by October
1st 2010.Comment: Contributed talk at the Gaia ELSA conference 2010, S\`evres 7-11 June
2010, to be published on the EAS Series, Editors: C. Turon, F. Arenou & F.
Meynadie
Traffic Instabilities in Self-Organized Pedestrian Crowds
In human crowds as well as in many animal societies, local interactions among
individuals often give rise to self-organized collective organizations that
offer functional benefits to the group. For instance, flows of pedestrians
moving in opposite directions spontaneously segregate into lanes of uniform
walking directions. This phenomenon is often referred to as a smart collective
pattern, as it increases the traffic efficiency with no need of external
control. However, the functional benefits of this emergent organization have
never been experimentally measured, and the underlying behavioral mechanisms
are poorly understood. In this work, we have studied this phenomenon under
controlled laboratory conditions. We found that the traffic segregation
exhibits structural instabilities characterized by the alternation of organized
and disorganized states, where the lifetime of well-organized clusters of
pedestrians follow a stretched exponential relaxation process. Further analysis
show that the inter-pedestrian variability of comfortable walking speeds is a
key variable at the origin of the observed traffic perturbations. We show that
the collective benefit of the emerging pattern is maximized when all
pedestrians walk at the average speed of the group. In practice, however, local
interactions between slow- and fast-walking pedestrians trigger global
breakdowns of organization, which reduce the collective and the individual
payoff provided by the traffic segregation. This work is a step ahead toward
the understanding of traffic self-organization in crowds, which turns out to be
modulated by complex behavioral mechanisms that do not always maximize the
group's benefits. The quantitative understanding of crowd behaviors opens the
way for designing bottom-up management strategies bound to promote the
emergence of efficient collective behaviors in crowds.Comment: Article published in PLoS Computational biology. Freely available
here:
http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.100244
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