14,454 research outputs found

    Noncommutative Field Theory: Nonrelativistic Fermionic Field Coupled to the Chern-Simons Field in 2+1 Dimensions

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    We study a noncommutative nonrelativistic fermionic field theory in 2+1 dimensions coupled to the Chern-Simons field. We perform a perturbative analysis of model and show that up to one loop the ultraviolet divergences are canceled and the infrared divergences are eliminated by the noncommutative Pauli term.Comment: Some references adde

    A simple method for enhanced vibration-based structural health monitoring

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    This study suggests a novel method for structural vibration-based health monitoring for beams which only utilises the first natural frequency of the beam in order to detect and localise a defect. The method is based on the application of a static force in different positions along the beam. It is shown that the application of a static force on a damaged beam induces stresses at the defect which in turn cause changes in the structural natural frequencies. A very simple procedure for damage detection is suggested which uses a static force applied in just one point, in the middle of the beam. Localisation is made using two additional application points of the static force. Damage is modelled as a small notch through the whole width of the beam. The method is demonstrated and validated numerically, using a finite element model of the beam, and experimentally for a simply supported beam. Our results show that the frequency variation with the change of the force application point can be used to detect and in the same time localize very precisely even a very small defect. The method can be extended for health monitoring of other more complicated structures

    The Noncommutative Supersymmetric Nonlinear Sigma Model

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    We show that the noncommutativity of space-time destroys the renormalizability of the 1/N expansion of the O(N) Gross-Neveu model. A similar statement holds for the noncommutative nonlinear sigma model. However, we show that, up to the subleading order in 1/N expansion, the noncommutative supersymmetric O(N) nonlinear sigma model becomes renormalizable in D=3. We also show that dynamical mass generation is restored and there is no catastrophic UV/IR mixing. Unlike the commutative case, we find that the Lagrange multiplier fields, which enforce the supersymmetric constraints, are also renormalized. For D=2 the divergence of the four point function of the basic scalar field, which in D=3 is absent, cannot be eliminated by means of a counterterm having the structure of a Moyal product.Comment: 15 pages, 7 figures, revtex, minor modifications in the text, references adde

    Clinical Dilemma in the Treatment of a Patient with Microangiopathic Haemolytic Anaemia, Thrombocytopaenia and Severe Hypertension

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    While haemolytic uraemic syndrome in children is predominantly associated with Shiga toxin -producing Escherichia coli (typically 0157:H7), some cases occur without associated diarrhoea, or as the manifestation of an underlying disorder other than infection. Haemolytic uraemic syndrome is characterised by microangiopathic anaemia, thrombocytopaenia and renal failure, on occasion accompanied by severe hypertension. Malignant hypertension is a syndrome that sometimes exhibits the same laboratory abnormalities as haemolytic uraemic syndrome as it may share the same pathological findings: thrombotic microangiopathy. As clinical features of both entities overlap, the distinction between them can be very difficult. However, differentiation is essential for the treatment decision, since early plasma exchange dramatically reduces mortality in haemolytic uraemic syndrome not associated with diarrhoea. An increasing number of genetic causes of this pathology have been described and may be very useful in differentiating it from thrombotic microangiopathy due to other aetiologies. Despite advances in the understanding of the pathophysiology of haemolytic uraemic syndrome not associated with diarrhoea, the management often remains empirical. We describe a patient with simultaneous microangiopathic haemolytic anaemia, thrombocytopaenia and severe hypertension managed in the acute period of illness with plasma exchange

    A simple method for enhanced vibration-based structural health monitoring

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    This study suggests a novel method for structural vibration-based health monitoring for beams which only utilises the first natural frequency of the beam in order to detect and localise a defect. The method is based on the application of a static force in different positions along the beam. It is shown that the application of a static force on a damaged beam induces stresses at the defect which in turn cause changes in the structural natural frequencies. A very simple procedure for damage detection is suggested which uses a static force applied in just one point, in the middle of the beam. Localisation is made using two additional application points of the static force. Damage is modelled as a small notch through the whole width of the beam. The method is demonstrated and validated numerically, using a finite element model of the beam, and experimentally for a simply supported beam. Our results show that the frequency variation with the change of the force application point can be used to detect and in the same time localize very precisely even a very small defect. The method can be extended for health monitoring of other more complicated structures

    Hanbury Brown Twiss effect for ultracold quantum gases

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    We have studied 2-body correlations of atoms in an expanding cloud above and below the Bose-Einstein condensation threshold. The observed correlation function for a thermal cloud shows a bunching behavior, while the correlation is flat for a coherent sample. These quantum correlations are the atomic analogue of the Hanbury Brown Twiss effect. We observe the effect in three dimensions and study its dependence on cloud size.Comment: Figure 1 availabl

    Ionization rates in a Bose-Einstein condensate of metastable Helium

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    We have studied ionizing collisions in a BEC of He*. Measurements of the ion production rate combined with measurements of the density and number of atoms for the same sample allow us to estimate both the 2 and 3-body contributions to this rate. A comparison with the decay of the number of condensed atoms in our magnetic trap, in the presence of an rf-shield, indicates that ionizing collisions are largely or wholly responsible for the loss. Quantum depletion makes a substantial correction to the 3-body rate constant.Comment: 4 pages, 3 figure

    Endotracheal Intubation – A Dilemma in Pre-hospital Care.

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    A intubação endotraqueal (IET), no pré-hospitalar, é considerada o “gold standard” na manutenção da via aérea de modo a fornecer a ventilação e oxigenação à pessoa em situação crítica, no entanto, está associada a várias complicações e riscos. Com este trabalho de revisão sistemática da literatura pretendeu-se compreender a relação entre a IET em emergência pré-hospitalar e o prognóstico da pessoa em situação crítica, colocando a seguinte questão: “Qual o impacto da intubação endotraqueal, em emergência pré-hospitalar, no prognóstico clínico do doente?”. Este trabalho de investigação iniciou-se com uma pesquisa da literatura de língua inglesa e portuguesa, nas bases de dados científicas MEDLINE, CINAHL, MedicLatina e Nursing and Allied Health Collection num horizonte temporal entre 2010 e 2014. A evidência destaca que a realização da intubação endotraqueal, no pré-hospitalar, está associada a piores taxas de reanimação cardiorrespiratória, ao aumento das taxas de mortalidade e ao aumento das comorbilidades. Estas conclusões reforçam a discussão em torno da prática da IET no pré-hospitalar e sensibilizam os profissionais de saúde para a limitação desta prática a casos em que exista indicação clínica segura

    The clustering conditions for managing creative tourism destinations: the Alqueva region case, Portugal

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    This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordThe paper discusses conditions and format of a cluster model to support the management of a potential creative tourism destination in a setting where regional cross-sectoral collaboration is lacking. Creative tourism development requires a flexible framework and a healthy collaboration environment, more so when associated with resources shared by several stakeholders. This article focuses on the tourism potential of archaeological knowledge discovered during the environmental impact assessment of the Alqueva dam (Alentejo, Portugal). Interviews were conducted with 38 regional actors in the tourism and heritage sectors, as well as the dam developers and the companies responsible for archaeological interventions. Findings indicate that the lack of specific local policy addressing archaeological heritage hampers its potential use for tourism development, which is further aggravated by the absence of stakeholder communication and cooperation. A conceptual cluster model for the management of creative tourism destinations based on heritage resources and other local resources is proposed.Portuguese national funding agency for Science, Research and Technology (FCT

    Runoff and erosion at the micro-plot and slope scale in a small burnt catchment, central Portugal

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    Wildfires can have important impacts on hydrological processes and soil erosion in forest catchments, due to the destruction of vegetation cover and changes to soil properties. However, the processes involved are non-linear and not fully understood. This has severely limited the understanding on the impacts of wildfires, especially in the up-scaling from hillslopes to catchments; in consequence, current models are poorly adapted for burnt forest conditions. The objective of this presentation is to give an overview of the hydrological response and sediment yield from the micro-plot to slope scale, in the first year following a wildfire (2008/2009) that burnt an entire catchment nearby the Colmeal village, central Portugal. The overview will focus on three slopes inside the catchment, with samples including: • Runoff at micro-plot scale (12 bounded plots) and slope scale (12 open plots); • Sediments and Organic Matter loss at micro-plot scale (12 bounded plots) and slope scale (12 open plots plus 3 Sediment fences); • Rainfall and Soil moisture data; • Soil Water Repellency and Ground Cover data. The analysis of the first year following the wildfire clearly shows the complexity of runoff generation and the associated sediment transport in recently burnt areas, with pronounced differences between hillslopes and across spatial scales as well as with marked variations through time. This work was performed in the framework of the EROSFIRE-II project (PTDC/AGR-CFL/70968/2006) which has as overall aim to predict soil erosion risk in recently burnt forest areas, including common post-fire forest management practices; the project focuses on the simultaneous measurement of runoff and soil erosion at multiple spatial scales.The results to be presented in this session are expected to show how sediment is generated, transported and exported in the Colmeal watershed; and contribute to understand and simulate erosion processes in burnt catchments, including for model development and evaluation
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