4,143 research outputs found
Accuracy and stability analysis of horizontal discretizations used in unstructured grid ocean models
One important tool at our disposal to evaluate the robustness of Global
Circulation Models (GCMs) is to understand the horizontal discretization of the
dynamical core under a shallow water approximation. Here, we evaluate the
accuracy and stability of different methods used in, or adequate for,
unstructured ocean models considering shallow water models. Our results show
that the schemes have different accuracy capabilities, with the A- (NICAM) and
B-grid (FeSOM 2.0) schemes providing at least 1st order accuracy in most
operators and time integrated variables, while the two C-grid (ICON and MPAS)
schemes display more difficulty in adequately approximating the horizontal
dynamics. Moreover, the theory of the inertia-gravity wave representation on
regular grids can be extended for our unstructured based schemes, where from
least to most accurate we have: A-, B, and C-grid, respectively. Considering
only C-grid schemes, the MPAS scheme has shown a more accurate representation
of inertia-gravity waves than ICON. In terms of stability, we see that both A-
and C-grid MPAS scheme display the best stability properties, but the A-grid
scheme relies on artificial diffusion, while the C-grid scheme doesn't.
Alongside, the B-grid and C-grid ICON schemes are within the least stable.
Finally, in an effort to understand the effects of potential instabilities in
ICON, we note that the full 3D model without a filtering term does not
destabilize as it is integrated in time. However, spurious oscillations are
responsible for decreasing the kinetic energy of the oceanic currents.
Furthermore, an additional decrease of the currents' turbulent kinetic energy
is also observed, creating a spurious mixing, which also plays a role in the
strength decrease of these oceanic currents
EFEITOS DO PROTOCOLO DE ESTRESSORES SOBRE A PREFERÊNCIA DE ÁGUA COM SACAROSE EM RATOS
The goal of the present study was to investigate the effect of Chronic Mild Stress (CMS) on the preference for sucrose solution in rats at a continuous regimen of water deprivation in order to keep their weights at 85% ad lib. Ten male Wistar rats were submitted to 13 tests of consumption of water with and without sucrose, one of these subjects being exclusively exposed to those tests. Of the remaining subjects, one was also submitted to CMS for six consecutive weeks and besides that eight rats were also submitted to operant sessions (Concurrent VIVI). The results showed that the submission to CMS was not followed by a decrease (p > 0.05) in the preference for water with sucrose neither in the consumption tests, nor in operant sessions independently of the experimental condition. However, it was detected a significant decrease (p 0,05), nem nos testes de consumo, nem nas sessões operantes, independentemente da condição experimental. Entretanto, observou-se uma diminuição significativa (p < 0,05) no consumo de ração na gaiola viveiro enquanto os animais estavam sendo submetidos ao PE. Sugere-se que a redução no consumo de ração na gaiola viveiro seja uma medida alternativa para avaliar a diminuição do valor reforçador de um estímulo decorrente da exposição ao PE.Palavras-chave: Estressores crônicos moderados, privação, modelo animal, esquema concorrente VIVI, anedonia
Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
Hydrogen-burning is the root cause of the star-to-star abundance variations
of light nuclei in Galactic globular clusters (GC). In the present work we
constrain the physical conditions that gave rise to the observed abundance
patterns of Li, C, N, O, Na, Mg, Al, as well as Mg isotopes in the typical case
of NGC6752. We perform nucleosynthesis calculations at constant temperature,
adopting realistic initial abundances for the proto-cluster gas. We use a
detailed nuclear reaction network and state-of-the-art nuclear reaction rates.
Although simplistic, our analysis provides original results and new constraints
on the self-enrichment scenario for GCs. Our parametrized calculations allow us
to determine a narrow range of temperature where the observed extreme
abundances of all light elements and isotopes in NGC6752 are nicely reproduced
simultaneously. This agreement is obtained after mixing of the H-processed
material with 30 % of unprocessed gas. The observed C-N, O-Na, Mg-Al, Li-Na and
F-Na anticorrelations, as well as the behaviour of the Mg isotopes can be
recovered by assuming mixing with even larger dilution factors. Li production
by the stars that build up the other abundance anomalies is not mandatory in
the case of NGC 6752. Observations of O, Na, Mg and Al constrain the
temperature range for H-burning; such temperatures are encountered in the two
main candidate ``polluters'' proposed for GCs, namely massive AGBs and the most
massive main-sequence stars. (Abridged).Comment: 15 pages, 8 figures, accepted in Astronomy and Astrophysic
Tests of model predictions for the responses of stellar spectra and absorption-line indices to element abundance variations. Tests of model predictions for the responses of stellar spectra and absorption-line indices to element abundance variations.
A method that is widely used to analyse stellar populations in galaxies is to apply the theoretically derived responses of stellar spectra and line indices to element abundance variations, which are hereafter referred to as response functions. These are applied in a differential way, to base models, in order to generate spectra or indices with different abundance patterns. In this paper, sets of such response functions for three different stellar evolutionary stages are tested with new empirical [Mg/Fe] abundance data for the medium-resolution Isaac Newton Telescope library of empirical spectra (MILES). Recent theoretical models and observations are used to investigate the effects of [Fe/H], [Mg/H] and overall [Z/H] on spectra, via ratios of spectra for similar stars. The global effects of changes in abundance patterns are investigated empirically through direct comparisons of similar stars from MILES, highlighting the impact of abundance effects in the blue part of the spectrum, particularly for lower temperature stars. It is found that the relative behaviour of iron-sensitive line indices are generally well predicted by response functions, whereas Balmer line indices are not. Other indices tend to show large scatter about the predicted mean relations. Implications for element abundance and age studies in stellar populations are discussed and ways forward are suggested to improve the match with the behaviour of spectra and line-strength indices observed in real stars
The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge
We present the first results of the EMBLA survey (Extremely Metal-poor BuLge
stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge,
where the oldest stars should now preferentially reside. EMBLA utilises
SkyMapper photometry to pre-select metal-poor candidates, which are
subsequently confirmed using AAOmega spectroscopy. We describe the discovery
and analysis of four bulge giants with -2.72<=[Fe/H]<=-2.48, the lowest
metallicity bulge stars studied with high-resolution spectroscopy to date.
Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived
abundances of twelve elements. Given the uncertainties, we find a chemical
similarity between these bulge stars and halo stars of the same metallicity,
although the abundance scatter may be larger, with some of the stars showing
unusual [{\alpha}/Fe] ratios.Comment: 7 pages, 5 figures. Accepted for publication by MNRA
Cholesterol and the risk of grade-specific prostate cancer incidence: evidence from two large prospective cohort studies with up to 37 years' follow up
<b>Background</b>
High cholesterol may be a modifiable risk factor for prostate cancer but results have been inconsistent and subject to potential "reverse causality" where undetected disease modifies cholesterol prior to diagnosis.<p></p>
<b>Methods</b>
We conducted a prospective cohort study of 12,926 men who were enrolled in the Midspan studies between 1970 and 1976 and followed up to 31st December 2007. We used Cox-Proportional Hazards Models to evaluate the association between baseline plasma cholesterol and Gleason grade-specific prostate cancer incidence. We excluded cancers detected within at least 5 years of cholesterol assay.<p></p>
<b>Results</b>
650 men developed prostate cancer in up to 37 years' follow-up. Baseline plasma cholesterol was positively associated with hazard of high grade (Gleason score[greater than or equal to]8) prostate cancer incidence (n=119). The association was greatest among men in the 4th highest quintile for cholesterol, 6.1 to <6.69 mmol/l, Hazard Ratio 2.28, 95% CI 1.27 to 4.10, compared with the baseline of <5.05 mmol/l. This association remained significant after adjustment for body mass index, smoking and socioeconomic status.<p></p>
<b>Conclusions</b>
Men with higher cholesterol are at greater risk of developing high-grade prostate cancer but not overall risk of prostate cancer. Interventions to minimise metabolic risk factors may have a role in reducing incidence of aggressive prostate cancer
Patient characteristics and clinical management of patients with shoulder pain in U.S. primary care settings: Secondary data analysis of the National Ambulatory Medical Care Survey
BACKGROUND: Although shoulder pain is a commonly encountered problem in primary care, there are few studies examining its presenting characteristics and clinical management in this setting. METHODS: We performed secondary data analysis of 692 office visits for shoulder pain collected through the National Ambulatory Medical Care Survey (Survey years 1993–2000). Information on demographic characteristics, history and place of injury, and clinical management (physician order of imaging, physiotherapy, and steroid intraarticular injection) were examined. RESULTS: Shoulder pain was associated with an injury in one third (33.2% (230/692)) of office visits in this population of US primary care physicians. Males, and younger adults (age ≤ 52) more often associated their shoulder pain with previous injury, but there were no racial differences in injury status. Injury-related shoulder pain was related to work in over one-fifth (21.3% (43/202)) of visits. An x-ray was performed in 29.0% (164/566) of office visits, a finding that did not differ by gender, race, or by age status. Other imaging (CT scan, MRI, or ultrasound) was infrequently performed (6.5%, 37/566). Physiotherapy was ordered in 23.9% (135/566) of visits for shoulder pain. Younger adults and patients with a history of injury more often had physiotherapy ordered, but there was no significant difference in the ordering of physiotherapy by gender or race. Examination of the use of intraarticular injection was not possible with this data set. CONCLUSION: These data from the largest sample of patients with shoulder pain presenting to primary care settings offer insights into the presenting characteristics and clinical management of shoulder pain at the primary care level. The National Ambulatory Medical Care Survey is a useful resource for examining the clinical management of specific symptoms in U.S. primary care offices
Susceptibility to tuberculosis is associated with variants in the ASAP1 gene encoding a regulator of dendritic cell migration
Human genetic factors predispose to tuberculosis (TB). We studied 7.6 million genetic variants in 5,530 people with pulmonary TB and in 5,607 healthy controls. In the combined analysis of these subjects and the follow-up cohort (15,087 TB patients and controls altogether), we found an association between TB and variants located in introns of the ASAP1 gene on chromosome 8q24 (P = 2.6 × 10−11 for rs4733781; P = 1.0 × 10−10 for rs10956514). Dendritic cells (DCs) showed high ASAP1 expression that was reduced after Mycobacterium tuberculosis infection, and rs10956514 was associated with the level of reduction of ASAP1 expression. The ASAP1 protein is involved in actin and membrane remodeling and has been associated with podosomes. The ASAP1-depleted DCs showed impaired matrix degradation and migration. Therefore, genetically determined excessive reduction of ASAP1 expression in M. tuberculosis–infected DCs may lead to their impaired migration, suggesting a potential mechanism of predisposition to TB
Transcription of toll-like receptors 2, 3, 4 and 9, FoxP3 and Th17 cytokines in a susceptible experimental model of canine Leishmania infantum infection
Canine leishmaniosis (CanL) due to Leishmania infantum is a chronic zoonotic systemic disease resulting from complex interactions between protozoa and the canine immune system. Toll-like receptors (TLRs) are essential components of the innate immune system and facilitate the early detection of many infections. However, the role of TLRs in CanL remains unknown and information describing TLR transcription during infection is extremely scarce. The aim of this research project was to investigate the impact of L. infantum infection on canine TLR transcription using a susceptible model. The objectives of this study were to evaluate transcription of TLRs 2, 3, 4 and 9 by means of quantitative reverse transcription polymerase chain reaction (qRT-PCR) in skin, spleen, lymph node and liver in the presence or absence of experimental L. infantum infection in Beagle dogs. These findings were compared with clinical and serological data, parasite densities in infected tissues and transcription of IL-17, IL-22 and FoxP3 in different tissues in non-infected dogs (n = 10), and at six months (n = 24) and 15 months (n = 7) post infection. Results revealed significant down regulation of transcription with disease progression in lymph node samples for TLR3, TLR4, TLR9, IL-17, IL-22 and FoxP3. In spleen samples, significant down regulation of transcription was seen in TLR4 and IL-22 when both infected groups were compared with controls. In liver samples, down regulation of transcription was evident with disease progression for IL-22. In the skin, upregulation was seen only for TLR9 and FoxP3 in the early stages of infection. Subtle changes or down regulation in TLR transcription, Th17 cytokines and FoxP3 are indicative of the silent establishment of infection that Leishmania is renowned for. These observations provide new insights about TLR transcription, Th17 cytokines and Foxp3 in the liver, spleen, lymph node and skin in CanL and highlight possible markers of disease susceptibility in this model
Chemical compositions of Four B-type Supergiants in the SMC Wing
High-resolution UCLES/AAT spectra of four B-type supergiants in the SMC South
East Wing have been analysed using non-LTE model atmosphere techniques to
determine their atmospheric parameters and chemical compositions. The principle
aim of this analysis was to determine whether the very low metal abundances
(1.1 dex compared with Galactic value) previously found in the Magellanic
Inter Cloud region (ICR) were also present in SMC Wing. The chemical
compositions of the four targets are similar to those found in other SMC
objects and appear to be incompatible with those deduced previously for the
ICR. Given the close proximity of the Wing to the ICR, this is difficult to
understand and some possible explanations are briefly discussed.Comment: 11 pages, 2 figues, A&A accepte
- …