1,204 research outputs found
Modelling magnetic flux emergence in the solar convection zone
[Abridged] Bipolar magnetic regions are formed when loops of magnetic flux
emerge at the solar photosphere. Our aim is to investigate the flux emergence
process in a simulation of granular convection. In particular we aim to
determine the circumstances under which magnetic buoyancy enhances the flux
emergence rate (which is otherwise driven solely by the convective upflows). We
use three-dimensional numerical simulations, solving the equations of
compressible magnetohydrodynamics in a horizontally-periodic Cartesian domain.
A horizontal magnetic flux tube is inserted into fully developed hydrodynamic
convection. We systematically vary the initial field strength, the tube
thickness, the initial entropy distribution along the tube axis and the
magnetic Reynolds number. Focusing upon the low magnetic Prandtl number regime
(Pm<1) at moderate magnetic Reynolds number, we find that the flux tube is
always susceptible to convective disruption to some extent. However, stronger
flux tubes tend to maintain their structure more effectively than weaker ones.
Magnetic buoyancy does enhance the flux emergence rates in the strongest
initial field cases, and this enhancement becomes more pronounced when we
increase the width of the flux tube. This is also the case at higher magnetic
Reynolds numbers, although the flux emergence rates are generally lower in
these less dissipative simulations because the convective disruption of the
flux tube is much more effective in these cases. These simulations seem to be
relatively insensitive to the precise choice of initial conditions: for a given
flow, the evolution of the flux tube is determined primarily by the initial
magnetic field distribution and the magnetic Reynolds number.Comment: 12 pages, 15 figures, 2 tables. Accepted for publication in Astronomy
and Astrophysic
Pruritus is a common feature in sheep infected with the BSE agent.
BACKGROUND: The variability in the clinical or pathological presentation of transmissible spongiform encephalopathies (TSEs) in sheep, such as scrapie and bovine spongiform encephalopathy (BSE), has been attributed to prion protein genotype, strain, breed, clinical duration, dose, route and type of inoculum and the age at infection. The study aimed to describe the clinical signs in sheep infected with the BSE agent throughout its clinical course to determine whether the clinical signs were as variable as described for classical scrapie in sheep. The clinical signs were compared to BSE-negative sheep to assess if disease-specific clinical markers exist.
RESULTS: Forty-seven (34%) of 139 sheep, which comprised 123 challenged sheep and 16 undosed controls, were positive for BSE. Affected sheep belonged to five different breeds and three different genotypes (ARQ/ARQ, VRQ/VRQ and AHQ/AHQ). None of the controls or BSE exposed sheep with ARR alleles were positive. Pruritus was present in 41 (87%) BSE positive sheep; the remaining six were judged to be pre-clinically infected. Testing of the response to scratching along the dorsum of a sheep proved to be a good indicator of clinical disease with a test sensitivity of 85% and specificity of 98% and usually coincided with weight loss. Clinical signs that were displayed significantly earlier in BSE positive cases compared to negative cases were behavioural changes, pruritic behaviour, a positive scratch test, alopecia, skin lesions, teeth grinding, tremor, ataxia, loss of weight and loss of body condition. The frequency and severity of each specific clinical sign usually increased with the progression of disease over a period of 16-20 weeks.
CONCLUSION: Our results suggest that BSE in sheep presents with relatively uniform clinical signs, with pruritus of increased severity and abnormalities in behaviour or movement as the disease progressed. Based on the studied sheep, these clinical features appear to be independent of breed, affected genotype, dose, route of inoculation and whether BSE was passed into sheep from cattle or from other sheep, suggesting that the clinical phenotype of BSE is influenced by the TSE strain more than by other factors. The clinical phenotype of BSE in the genotypes and breed studied was indistinguishable from that described for classical scrapie cases
Are white storks addicted to junk food? Impacts of landfill use on the movement and behaviour of resident white storks (Ciconia ciconia) from a partially migratory population
Background: The migratory patterns of animals are changing in response to global environmental change with many species forming resident populations in areas where they were once migratory. The white stork (Ciconia ciconia) was wholly migratory in Europe but recently guaranteed, year-round food from landfill sites has facilitated the establishment of resident populations in Iberia. In this study 17 resident white storks were fitted with GPS/GSM data loggers (including accelerometer) and tracked for 9.1 ± 3.7 months to quantify the extent and consistency of landfill attendance by individuals during the non-breeding and breeding seasons and to assess the influence of landfill use on daily distances travelled, percentage of GPS fixes spent foraging and non-landfill foraging ranges. Results: Resident white storks used landfill more during non-breeding (20.1 % ± 2.3 of foraging GPS fixes) than during breeding (14.9 % ± 2.2). Landfill attendance declined with increasing distance between nest and landfill in both seasons. During non-breeding a large percentage of GPS fixes occurred on the nest throughout the day (27 % ± 3.0 of fixes) in the majority of tagged storks. This study provides first confirmation of year-round nest use by resident white storks. The percentage of GPS fixes on the nest was not influenced by the distance between nest and the landfill site. Storks travelled up to 48.2 km to visit landfills during non-breeding and a maximum of 28.1 km during breeding, notably further than previous estimates. Storks nesting close to landfill sites used landfill more and had smaller foraging ranges in non-landfill habitat indicating higher reliance on landfill. The majority of non-landfill foraging occurred around the nest and long distance trips were made specifically to visit landfill. Conclusions: The continuous availability of food resources on landfill has facilitated year-round nest use in white storks and is influencing their home ranges and movement behaviour. White storks rely on landfill sites for foraging especially during the non-breeding season when other food resources are scarcer and this artificial food supplementation probably facilitated the establishment of resident populations. The closure of landfills, as required by EU Landfill Directives, will likely cause dramatic impacts on white stork populations
Palynological study of the pollen grain of i>Vitis vinifera L. cultivars. Some aspects of sculpturing and pollination
Scanning electron microscope analysis of pollen grains of 21 clones from 8 cultivars of Vitis vinifera L. has revealed no marked differences between them, except for some cultivars with heteropolar grains, and cultivars Jaen from Toledo and Tinto Fino from Madrid, which were small. Some details of pollen grain ornamentation and pollination are discussed
Broadband X-ray spectral analysis of the Seyfert 1 galaxy GRS 1734-292
We discuss the broadband X-ray spectrum of GRS 1734-292 obtained from
non-simultaneous XMM-Newton and NuSTAR observations, performed in 2009 and
2014, respectively. GRS1734-292 is a Seyfert 1 galaxy, located near the
Galactic plane at . The NuSTAR spectrum ( keV) is dominated by
a primary power-law continuum with and a high-energy
cutoff keV, one of the lowest measured by NuSTAR in a
Seyfert galaxy. Comptonization models show a temperature of the coronal plasma
of keV and an optical depth, assuming a slab
geometry, or a similar temperature and
assuming a spherical geometry. The 2009 XMM-Newton
spectrum is well described by a flatter intrinsic continuum
() and one absorption line due to Fe\textsc{XXV}
K produced by a warm absorber. Both data sets show a modest iron
K emission line at keV and the associated Compton reflection, due
to reprocessing from neutral circumnuclear material
Sarcomas primarios de hueso: estudio por citometría estática mediante análisis digital de imagen
Se presenta un estudio morfométrico y densitométrico mediante análisis digital
de imagen de una serie de 50 tumores óseos malignos (32 osteosarcomas, 12 condrosarcomas
y 6 histiocitomas fibrosos malignos de hueso), con el fin de evaluar la utilidad
de la técnica para establecer el grado y el pronóstico de estas neoplasias. Las variables
morfométricas y la disposición de la cromatina guardan una estrecha relación con el grado
histológico (Spearman; p < 0,05) y muestran diferencias estadísticamente significativas
entre los tumores considerados de alto y bajo grado en base a su presentación y evolución
clínica. La ploidía estimada por densitometría óptica se comporta como un factor pronóstico
independiente en el análisis multivariante de la serie de tumores de alto grado (COX;
p < 0,001). La citometría estática, aunque más lenta e imprecisa que la citometría de flujo
en la determinación de los picos de ploidía, permite analizar el modelo de cromatina y
contribuye objetivamente al establecimiento del grado biológico de los tumores óseos.A densitometry and morphometric assessment by static image cytometry of
50 malignant bone tumors (32 osteosarcomas, 12 chondrosarcomas, and 6 malignant fibrous
histiocytomas of bone) was performed in order to assess the validity of the technic
in the pathobiological and prognostic evaluation of these neoplasms. A strong correlation
between the morphometric features, cromatine distribution and histologic grade was
found (Spearman; p < 0.05). These parameters are also statistically different for hight and
low grade tumors in clinical staging. The stimation of DNA ploidy by optic densitometry
is a significant prognostic factor in the multivariant analysis for the high grade tumors
(COX; p < 0.001). Although Flow cytometry is a better procedure to evaluate DNA ploidy
peaks, our study reveals static image cytometry as a useful technic for determine the
cromatine model and objective assessment of the biological grade of bone neoplasms
Livestock trade network: potential for disease transmission and implications for risk-based surveillance on the island of Mayotte
The island of Mayotte is a department of France, an outermost region of the European Union located in the Indian Ocean between Madagascar and the coast of Eastern Africa. Due to its close connection to the African mainland and neighbouring islands, the island is under constant threat of introduction of infectious diseases of both human and animal origin. Here, using social network analysis and mathematical modelling, we assessed potential implications of livestock movements between communes in Mayotte for risk-based surveillance. Our analyses showed that communes in the central region of Mayotte acted as a hub in the livestock movement network. The majority of livestock movements occurred between communes in the central region and from communes in the central region to those in the outer region. Also, communes in the central region were more likely to be infected earlier than those in the outer region when the spread of an exotic infectious disease was simulated on the livestock movement network. The findings of this study, therefore, suggest that communes in the central region would play a major role in the spread of infectious diseases via livestock movements, which needs to be considered in the design of risk-based surveillance systems in Mayotte
Estudio descriptivo retrospectivo de la fractura de cadera en un área de salud de la Comunidad Valenciana
Se presenta un estudio descriptivo de la fractura de cadera osteoporótica en el área de Salud 20 de la Comunidad Valenciana durante el año 2007. Se incluyó una serie consecutiva de 239 pacientes que sufrieron fractura de fémur proximal. Se diseñó una base de datos recogiendo información clínica como la edad, sexo, tipo de fractura y lateralidad, antecedentes personales, datos referidos al accidente, al ingreso y estancia, así como al tratamiento.A descriptive study of osteoporotic hip fracture in the Health area 20 of the Valencian Community in 2007. We included a consecutive series of 239 patients undergoing proximal femoral fracture. We created a database collecting clinical information such as age, sex, type of fracture and handedness, personal history, referred to the accident data, entry and stay, and treatment
Utilisation de la très haute résolution spatiale pour la caractérisation des habitats de rongeurs, vecteurs de zoonoses à La Réunion
Connaître la distribution des espèces vectrices de zoonoses est fondamentale pour comprendre les dynamiques épidémiologiques et caractériser les zones à risque. Cette distribution peut être appréhendée à différentes échelles : régionalement, l'aire de répartition de ces espèces définit les limites d'occurrence de la transmission d'agents pathogènes et, localement, leurs niches déterminent l'aléa. Cette dernière échelle requiert une connaissance très précise des milieux qui peut être acquise par l'analyse d'images satellite à très haute résolution spatiale. Dans le cadre d'un projet de recherche sur la leptospirose à La Réunion (LeptOI), cette étude propose de mesurer le potentiel d'utilisation d'une image Pléiades (produit rééchantillonné à 50 cm) pour caractériser la distribution locale de différents petits mammifères terrestres autour de l'Etang de Saint-Paul. Trois campagnes de piégeage ont permis la capture de 134 animaux appartenant à quatre des cinq espèces présentes à La Réunion (Rattus rattus, R. norvegicus, Suncus murinus et Tenrec ecaudatus). Une analyse orientée-objet de l'image Pléiades a permis de discriminer dix classes d'occupation des sols avec une précision totale de 83,6%. Des indices paysagers ont été calculés à partir de cette classification autour de chacun des pièges (distances les plus courtes aux classes d’occupation, densité de contours et pourcentages de surface des classes au sein de zones tampon de 50 et de 100 mètres). Trois zones ("humide", "anthropisée" et "sèche") sont clairement discriminées par ces variables, qui pourront être utilisées comme déterminants écologiques de différents profils épidémiologiques : la zone humide étant propice à la leptospirose et la zone anthropisée étant un lieu de cooccurrence des quatre espèces et ainsi potentiellement une zone d'échanges de pathogènes
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