447 research outputs found
Comparing faceted and smoothed tool surface descriptions in sheet metal forming simulation
This study deals with different tool surface description
methods used in the finite element analysis of sheet metal
forming processes. The description of arbitrarily-shaped tool
surfaces using the traditional linear finite elements is compared
with two distinct smooth surface description approaches:
(i) BĂ©zier patches obtained from the ComputerAided
Design model and (ii) smoothing the finite element
mesh using Nagata patches. The contact search algorithm is
presented for each approach, exploiting its special features in
order to ensure an accurate and efficient contact detection. The
influence of the tool modelling accuracy on the numerical
results is analysed using two sheet forming examples, the
unconstrained cylindrical bending and the reverse deep drawing
of a cylindrical cup. Smoothing the contact surfaces with
Nagata patches allows creating more accurate tool models,
both in terms of shape and normal vectors, when compared
with the conventional linear finite element mesh. The computational
efficiency is evaluated in this study through the total
number of increments and the required CPU time. The mesh
refinement in the faceted description approach is not effective
in terms of computational efficiency due to large discontinuities
in the normal vector field across facets, even when
adopting fine meshes.The authors gratefully acknowledge the financial
support of the Portuguese Foundation for Science and Technology (FCT)
via the projects PTDC/EME-TME/118420/2010 and PEst-C/EME/
UI0285/2013 and by FEDER funds through the program COMPETE –
Programa Operacional Factores de Competitividade, under the project
CENTRO-07-0224-FEDER-002001 (MT4MOBI). The first author is
also grateful to the FCT for the PhD grant SFRH/BD/69140/2010.info:eu-repo/semantics/publishedVersio
Is Nitric Oxide Decrease Observed with Naphthoquinones in LPS Stimulated RAW 264.7 Macrophages a Beneficial Property?
The search of new anti-inflammatory drugs has been a current preoccupation, due to the need of effective drugs, with less adverse reactions than those used nowadays. Several naphthoquinones (plumbagin, naphthazarin, juglone, menadione, diosquinone and 1,4-naphthoquinone), plus p-hydroquinone and p-benzoquinone were evaluated for their ability to cause a reduction of nitric oxide (NO) production, when RAW 264.7 macrophages were stimulated with lipopolysaccharide (LPS). Dexamethasone was used as positive control. Among the tested compounds, diosquinone was the only one that caused a NO reduction with statistical importance and without cytotoxicity: an IC25 of 1.09±0.24 µM was found, with 38.25±6.50% (p<0.001) NO reduction at 1.5 µM. In order to elucidate if this NO decrease resulted from the interference of diosquinone with cellular defence mechanisms against LPS or to its conversion into peroxynitrite, by reaction with superoxide radical formed by naphthoquinones redox cycling, 3-nitrotyrosine and superoxide determination was also performed. None of these parameters showed significant changes relative to control. Furthermore, diosquinone caused a decrease in the pro-inflammatory cytokines: tumour necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6). Therefore, according to the results obtained, diosquinone, studied for its anti-inflammatory potential for the first time herein, has beneficial effects in inflammation control. This study enlightens the mechanisms of action of naphthoquinones in inflammatory models, by checking for the first time the contribution of oxidative stress generated by naphthoquinones to NO reduction
The immunopathology of canine vector-borne diseases
The canine vector-borne infectious diseases (CVBDs) are an emerging problem in veterinary medicine and the zoonotic potential of many of these agents is a significant consideration for human health. The successful diagnosis, treatment and prevention of these infections is dependent upon firm understanding of the underlying immunopathology of the diseases in which there are unique tripartite interactions between the microorganism, the vector and the host immune system. Although significant advances have been made in the areas of molecular speciation and the epidemiology of these infections and their vectors, basic knowledge of the pathology and immunology of the diseases has lagged behind. This review summarizes recent studies of the pathology and host immune response in the major CVBDs (leishmaniosis, babesiosis, ehrlichiosis, hepatozoonosis, anaplasmosis, bartonellosis and borreliosis). The ultimate application of such immunological investigation is the development of effective vaccines. The current commercially available vaccines for canine leishmaniosis, babesiosis and borreliosis are reviewed
Synthetic sex pheromone in a long-lasting lure attracts the visceral leishmaniasis vector, lutzomyia longipalpis, for up to 12 weeks in Brazil
Current control methodologies have not prevented the spread of visceral leishmaniasis (VL) across Brazil. Here, we describe the development of a new tool for controlling the sand fly vector of the disease: a long-lasting lure, which releases a synthetic male sex pheromone, attractive to both sexes of Lutzomyia longipalpis. This device could be used to improve the effectiveness of residual insecticide spraying as a means of sand fly control, attracting L. longipalpis to insecticide-treated animal houses, where they could be killed in potentially large numbers over a number of weeks. Different lure designs releasing the synthetic pheromone (±)-9-methylgermacrene-B (CAS 183158-38-5) were field-tested in Araçatuba, São Paulo (SP). Experiments compared numbers of sand flies caught overnight in experimental chicken sheds with pheromone lures, to numbers caught in control sheds without pheromone. Prototype lures, designed to last one night, were first used to confirm the attractiveness of the pheromone in SP, and shown to attract significantly more flies to test sheds than controls. Longer-lasting lures were tested when new, and at fortnightly intervals. Lures loaded with 1 mg of pheromone did not attract sand flies for more than two weeks. However, lures loaded with 10 mg of pheromone, with a releasing surface of 15 cm2 or 7.5 cm2, attracted female L. longipalpis for up to ten weeks, and males for up to twelve weeks. Approximately five times more sand flies were caught with 7.5 cm2 10 mg lures when first used than occurred naturally in non-experimental chicken resting sites. These results demonstrate that these lures are suitably long-lasting and attractive for use in sand fly control programmes in SP. To our knowledge, this is the first sex pheromone-based technology targeting an insect vector of a neglected human disease. Further studies should explore the general applicability of this approach for combating other insect-borne diseases
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