3,640 research outputs found

    Hyperextended Scalar-Tensor Gravity

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    We study a general Scalar-Tensor Theory with an arbitrary coupling funtion ω(ϕ)\omega (\phi ) but also an arbitrary dependence of the ``gravitational constant'' G(ϕ)G(\phi ) in the cases in which either one of them, or both, do not admit an analytical inverse, as in the hyperextended inflationary scenario. We present the full set of field equations and study their cosmological behavior. We show that different scalar-tensor theories can be grouped in classes with the same solution for the scalar field.Comment: latex file, To appear in Physical Review

    Multidimensional Cosmology: Spatially Homogeneous models of dimension 4+1

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    In this paper we classify all 4+1 cosmological models where the spatial hypersurfaces are connected and simply connected homogeneous Riemannian manifolds. These models come in two categories, multiply transitive and simply transitive models. There are in all five different multiply transitive models which cannot be considered as a special case of a simply transitive model. The classification of simply transitive models, relies heavily upon the classification of the four dimensional (real) Lie algebras. For the orthogonal case, we derive all the equations of motion and give some examples of exact solutions. Also the problem of how these models can be compactified in context with the Kaluza-Klein mechanism, is addressed.Comment: 24 pages, no figures; Refs added, typos corrected. To appear in CQ

    Airborne observations of aerosol microphysical properties and particle ageing processes in the troposphere above Europe

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    In-situ measurements of aerosol microphysical properties were performed in May 2008 during the EUCAARI-LONGREX campaign. Two aircraft, the FAAM BAe-146 and DLR Falcon 20, operated from Oberpfaffenhofen, Germany. A comprehensive data set was obtained comprising the wider region of Europe north of the Alps throughout the whole tropospheric column. Prevailing stable synoptic conditions enabled measurements of accumulating emissions inside the continental boundary layer reaching a maximum total number concentration of 19 000 particles cm<sup>−3</sup> stp. Ultra-fine particles as indicators for nucleation events were observed within the boundary layer during high pressure conditions and after updraft of emissions induced by frontal passages above 8 km altitude in the upper free troposphere. Aerosol ageing processes during air mass transport are analysed using trajectory analysis. The ratio of particles containing a non-volatile core (250 °C) to the total aerosol number concentration was observed to increase within the first 12 to 48 h from the particle source from 50 to 85% due to coagulation. Aged aerosol also features an increased fraction of accumulation mode particles of approximately 40% of the total number concentration. The presented analysis provides an extensive data set of tropospheric aerosol microphysical properties on a continental scale which can be used for atmospheric aerosol models and comparisons of satellite retrievals

    Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC

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    This study investigates the evolution of ship-emitted aerosol particles using the stochastic particle-resolved model PartMC-MOSAIC (Particle Monte Carlo model-Model for Simulating Aerosol Interactions and Chemistry). Comparisons of our results with observations from the QUANTIFY (Quantifying the Climate Impact of Global and European Transport Systems) study in 2007 in the English Channel and the Gulf of Biscay showed that the model was able to reproduce the observed evolution of total number concentration and the vanishing of the nucleation mode consisting of sulfate particles. Further process analysis revealed that during the first hour after emission, dilution reduced the total number concentration by four orders of magnitude, while coagulation reduced it by an additional order of magnitude. Neglecting coagulation resulted in an overprediction of more than one order of magnitude in the number concentration of particles smaller than 40 nm at a plume age of 100 s. Coagulation also significantly altered the mixing state of the particles, leading to a continuum of internal mixtures of sulfate and black carbon. The impact on cloud condensation nuclei (CCN) concentrations depended on the supersaturation threshold <i>S</i> at which CCN activity was evaluated. For the base case conditions, characterized by a low formation rate of secondary aerosol species, neglecting coagulation, but simulating condensation, led to an underestimation of CCN concentrations of about 37% for <i>S</i> = 0.3% at the end of the 14-h simulation. In contrast, for supersaturations higher than 0.7%, neglecting coagulation resulted in an overestimation of CCN concentration, about 75% for <i>S</i> = 1%. For <i>S</i> lower than 0.2% the differences between simulations including coagulation and neglecting coagulation were negligible. Neglecting condensation, but simulating coagulation did not impact the CCN concentrations below 0.2% and resulted in an underestimation of CCN concentrations for larger supersaturations, e.g., 18% for <i>S</i> = 0.6%. We also explored the role of nucleation for the CCN concentrations in the ship plume. For the base case the impact of nucleation on CCN concentrations was limited, but for a sensitivity case with higher formation rates of secondary aerosol over several hours, the CCN concentrations increased by an order of magnitude for supersaturation thresholds above 0.3%

    Protein aggregate formation permits millennium-old brain preservation

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    Human proteins have not been reported to survive in free nature, at ambient temperature, for long periods. Particularly, the human brain rapidly dissolves after death due to auto-proteolysis and putrefaction. The here presented discovery of 2600-year-old brain proteins from a radiocarbon dated human brain provides new evidence for extraordinary long-term stability of non-amyloid protein aggregates. Immunoelectron microscopy confirmed the preservation of neurocytoarchitecture in the ancient brain, which appeared shrunken and compact compared to a modern brain. Resolution of intermediate filaments (IFs) from protein aggregates took 2–12 months. Immunoassays on micro-dissected brain tissue homogenates revealed the preservation of the known protein topography for grey and white matter for type III (glial fibrillary acidic protein, GFAP) and IV (neurofilaments, Nfs) IFs. Mass spectrometry data could be matched to a number of peptide sequences, notably for GFAP and Nfs. Preserved immunogenicity of the prehistoric human brain proteins was demonstrated by antibody generation (GFAP, Nfs, myelin basic protein). Unlike brain proteins, DNA was of poor quality preventing reliable sequencing. These long-term data from a unique ancient human brain demonstrate that aggregate formation permits for the preservation of brain proteins for millennia

    Avaliação da estratégia de tratamento parcial do rebanho no controle da mosca-dos-chifres.

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    A mosca-dos-chifres (MDC) destaca-se dentre os principais ectoparasitos que acometem a pecuĂĄria de corte nacional. Seu controle Ă© realizado quase exclusivamente com produtos inseticidas, o que tem levado a sĂ©rios problemas de resĂ­duos e resistĂȘncia. Alternativas nĂŁo quĂ­micas e redução do uso de inseticidas tornam-se essenciais ao controle sustentĂĄvel deste parasito. O presente estudo avaliou a eficiĂȘncia do tratamento parcial do rebanho como estratĂ©gia de controle da MDC. Quatro experimentos foram conduzidos, utilizando produtos de diferentes classes inseticidas: lactona macrocĂ­clica (ivermectina), fenilpirazol (fipronil), piretrĂłide cipermetrina) e organofosforado+piretrĂłide (clorpirifĂłs+cipermetrina), em formulaçÔes pour-on. Em cada experimento, 200 vacas Nelore foram distribuĂ­das em quatro grupos, para avaliação do tratamento de 20%, 50% e 100% do rebanho, alĂ©m de um grupo nĂŁo tratado. Contagens periĂłdicas da MDC foram realizadas nos dias 0, 3, 7, 14, 21 e 28 em todos os animais. A eficĂĄcia dos produtos nos grupos tratados integralmente foi superior a 90% (exceto pela cipermetrina) ao final da 1ÂȘ semana pĂłs-tratamento, sendo de modo geral superior a dos tratados parcialmente nas duas semanas iniciais. Nos grupos tratados parcialmente, a eficĂĄcia foi geralmente maior nos grupos com maior frequĂȘncia de animais tratados. Independente da classe inseticida aplicada e do percentual de animais tratados (20% ou 50%), o tratamento parcial do rebanho apresentou trĂȘs caracterĂ­sticas principais: a) rĂĄpida e acentuada redução das infestaçÔes em todo o rebanho, b) menores nĂ­veis de redução das infestaçÔes e c) menor perĂ­odo de proteção, em relação ao tratamento de todo o rebanho. Apesar da redução no uso de inseticidas e do menor custo, a viabilidade do tratamento parcial do rebanho, como estratĂ©gia de controle da MDC, se limita a situaçÔes onde um menor nĂ­vel e perĂ­odo de eficĂĄcia sejam aceitĂĄveis, caso contrĂĄrio, tratamentos adicionais podem ser necessĂĄrios, comprometendo as vantagens da estratĂ©gia. As implicaçÔes do tratamento parcial do rebanho no desenvolvimento e manejo da resistĂȘncia a inseticidas devem ser avaliadas. The horn fly stands out among the main ectoparasites that affect national beef cattle. This livestock pest is controlled almost exclusively by insecticide products, which has led to serious residue and resistance issues. Non-chemical alternatives and reduction of insecticide use are essential for a sustainable control of this parasite. This study evaluated the efficiency of partial herd treatment as a strategy for controlling horn flies. Four experiments were conducted using products from different insecticide classes: macrocyclic lactone (ivermectin) phenylpyrazole (fipronil), pyrethroid (cypermethrin), and an organophosphate-pyrethroid mixture (chlorpyrifos + cypermethrin), in pour-on formulations. In each experiment, 200 Nelore cows were distributed in four groups for evaluation of the treatment of 20, 50, and 100% of the herd, besides an untreated group. Periodic fly counts were performed on days 0, 3, 7, 14, 21, and 28 in all animals. Product efficacy in the full-treated herd exceeded 90% (except for cypermethrin) at the end of the 1st week after treatment, being mostly higher than in partially treated groups in the first two weeks. In the groups partially treated, efficacy was generally higher in the groups with the largest frequency of treated animals. Regardless of the insecticide class and the percentage of treated animals (20% or 50%), the partial treatment of the herd showed three main features: a) fast and marked reduction in infestations throughout the herd, b) lower reduction of horn fly infestations, and c) shorter period of protection, when compared to the full herd treatment. Despite reduction in insecticide use and lower costs, viability of partial herd treatment as a strategy for controlling the horn fly is limited to situations where a lower level and protection period are acceptable; otherwise, the need for additional treatments tends to compromise the advantages of the strategy. The implications of partial herd treatment in the development and management of insecticide resistance should be evaluated.bitstream/item/129471/1/BP125.pd

    Marathon related death due to brainstem herniation in rehydration-related hyponatraemia: a case report

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    Introduction: Identifying marathon runners at risk of neurological deterioration at the end of the race (within a large cohort complaining of exhaustion, dehydration, nausea, headache, dizziness, etc.) is challenging. Here we report a case of rehydration-related hyponatraemia with ensuing brain herniation. Case presentation: We report the death of runner in his 30's who collapsed in the recovery area following a marathon. Following rehydration he developed a respiratory arrest in the emergency room. He was found to be hyponatraemic (130 mM). A CT brain scan showed severe hydrocephalus and brain stem herniation. Despite emergency insertion of an extraventricular drain, he was tested for brainstem death the following morning. Funduscopy demonstrated an acute-on-chronic papilledema; CSF spectrophotometry did not reveal any trace of oxyhemoglobin or bilirubin, but ferritin levels were considerably raised (530 ng/mL, upper reference value 12 ng/mL), consistent with a previous bleed. Retrospectively it emerged that the patient had suffered from a thunderclap headache some months earlier. Subsequently he developed morning headaches and nausea. This suggests that he may have suffered from a subarachnoid haemorrhage complicated by secondary hydrocephalus. This would explain why in this case the relatively mild rehydration-related hyponatremia may have caused brain swelling sufficient for herniation. Conclusion: Given the frequency of hyponatraemia in marathon runners (serum Na <135 mM in about 13%), and the non-specific symptoms, we discuss how a simple screening test such as funduscopy may help to identify those who require urgent neuroimaging
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