Ethanol-induced vasoconstriction is mediated via redox-sensitive cyclo-oxygenase-dependent mechanisms

The present study investigated the role of ROS (reactive oxygen species) and COX (cyclooxygenase) in ethanol-induced contraction and elevation of [Ca(2+)](i) (intracellular [Ca(2+)]). Vascular reactivity experiments, using standard muscle bath procedures, showed that ethanol (1-800 mmol/l) induced contraction in endothelium-intact (EC(50): 306 +/- 34 mmol/l) and endothelium-denuded (EC(50): 180 +/- 40 mmol/l) rat aortic rings. Endothelial removal enhanced ethanol-induced contraction. Preincubation of intact rings with L-NAME [N(G)-nitro-L-arginine methyl ester; non-selective NOS (NO synthase) inhibitor, 100 mu mol/l], 7-nitroindazole [selective nNOS (neuronal NOS) inhibitor, 100 mu mol/l], oxyhaemoglobin (NO scavenger, 10 mu mol/l) and ODQ (selective inhibitor of guanylate cyclase enzyme, 1 mu mol/l) increased ethanol-induced contraction. Tiron [O(2)(-) (superoxide anion) scavenger, 1 mmol/l] and catalase (H(2)O(2) scavenger, 300 units/ml) reduced ethanol-induced contraction to a similar extent in both endothelium-intact and denuded rings. Similarly, indomethacin (non-selective COX inhibitor, 10 mu mol/l), SC560 (selective COX- I inhibitor, 1 mu mol/l), AH6809 [PGF(2 alpha) (prostaglandin F(2 alpha))] receptor antagonist, 10 mu mol/l] or SQ29584 [PGH(2)(prostaglandin H(2))/TXA(2) (thromboxane A(2)) receptor antagonist, 3 mu mol/l] inhibited ethanol-induced contraction in aortic rings with and without intact endothelium. In cultured aortic VSMCs (vascular smooth muscle cells), ethanol stimulated generation of O(2)(-) and H(2)O(2). Ethanol induced a transient increase in [Ca(2+)](i), which was significantly inhibited in VSMCs pre-exposed to tiron or indomethacin. Our data suggest that ethanol induces vasoconstriction via redox-sensitive and COX-dependent pathways, probably through direct effects on ROS production and Ca(2+) signalling. These findings identify putative molecular mechanisms whereby ethanol, at high concentrations, influences vascular reactivity. Whether similar phenomena occur in vivo at lower concentrations of ethanol remains unclear.

Harmonic identification using parallel neural networks in single-phase systems

In this paper, artificial neural networks are employed in a novel approach to identify harmonic components of single-phase nonlinear load currents, whose amplitude and phase angle are subject to unpredictable changes, even in steady-state. The first six harmonic current components are identified through the variation analysis of waveform characteristics. The effectiveness of this method is tested by applying it to the model of a single-phase active power filter, dedicated to the selective compensation of harmonic current drained by an AC controller. Simulation and experimental results are presented to validate the proposed approach. (C) 2010 Elsevier B. V. All rights reserved.

Integrating structural and input design of a 2-DOF high-speed parallel manipulator: A flexible model-based approach

This paper discusses the integrated design of parallel manipulators, which exhibit varying dynamics. This characteristic affects the machine stability and performance. The design methodology consists of four main steps: (i) the system modeling using flexible multibody technique, (ii) the synthesis of reduced-order models suitable for control design, (iii) the systematic flexible model-based input signal design, and (iv) the evaluation of some possible machine designs. The novelty in this methodology is to take structural flexibilities into consideration during the input signal design; therefore, enhancing the standard design process which mainly considers rigid bodies dynamics. The potential of the proposed strategy is exploited for the design evaluation of a two degree-of-freedom high-speed parallel manipulator. The results are experimentally validated. (C) 2010 Elsevier Ltd. All rights reserved.

Tropical woods: influence of density in hardness parallel and normal to the grain for some Brazilian tropical tree species

The aim of this work is to verify the possibility to correlating specific gravity and wood hardness parallel and perpendicular to the grain. The purpose is to offer one more tool to help in the decision about wood species choice for use in floors and sleepers. To reach this intent, we considered the results of standard tests (NBR 7190:1997, Timber Structures Design, Annex B, Brazilian Association of Technical Standards) to determine hardness parallel and normal to the grain in fourteen tropical high density wood species (over 850 kg/m(3), at 12% moisture content). For each species twelve determinations were made, based on the material obtained at Sao Carlos and its regional wood market. Statistical analysis led to some expressions to describe the cited properties relationships, with a determination coefficient about 0.8.

Failure Mechanisms in Sand over a Deep Active Trapdoor

An experimental testing program was undertaken to investigate failure mechanisms induced by the active movement of a deep rectangular trapdoor underlying a granular soil. Reduced-scale models were tested under normal gravity as well as under an increased gravitational field using a centrifuge facility. Some models were used to evaluate the performance of both flexible and rigid pipes undergoing a localized loss of support. Failure mechanisms in the longitudinal direction of the models were characterized by a single, well-defined failure surface that developed within the limits of the trapdoor. However, failure mechanisms in the transverse direction of the models were characterized by multiple failure surfaces extending outside the limits of the trapdoor. Significant dilation of the soil located immediately above the trapdoor was identified in the failure of the models. The pattern of the failure mechanisms was found to be affected by the stress level and backfill density. Higher stress levels were found to lead to well-developed failure zones. The influence of backfill density was found to be more relevant in models involving flexible pipes. Pipes embedded within loose backfill were severely damaged after loss of support, while pipes embedded in dense backfill experienced negligible deformations. These results indicate that damage to pipelines caused by ground loss of support can be significantly minimized by controlling the compaction of the fill.

A survey on key management mechanisms for distributed Wireless Sensor Networks

Wireless Sensor Networks (WSNs) have a vast field of applications, including deployment in hostile environments. Thus, the adoption of security mechanisms is fundamental. However, the extremely constrained nature of sensors and the potentially dynamic behavior of WSNs hinder the use of key management mechanisms commonly applied in modern networks. For this reason, many lightweight key management solutions have been proposed to overcome these constraints. In this paper, we review the state of the art of these solutions and evaluate them based on metrics adequate for WSNs. We focus on pre-distribution schemes well-adapted for homogeneous networks (since this is a more general network organization), thus identifying generic features that can improve some of these metrics. We also discuss some challenges in the area and future research directions. (C) 2010 Elsevier B.V. All rights reserved.

Parallel Dynamic Optimization of Steel Risers

This paper addresses the use of optimization techniques in the design of a steel riser. Two methods are used: the genetic algorithm, which imitates the process of natural selection, and the simulated annealing, which is based on the process of annealing of a metal. Both of them are capable of searching a given solution space for the best feasible riser configuration according to predefined criteria. Optimization issues are discussed, such as problem codification, parameter selection, definition of objective function, and restrictions. A comparison between the results obtained for economic and structural objective functions is made for a case study. Optimization method parallelization is also addressed. [DOI: 10.1115/1.4001955]

Wear mechanisms and microstructure of pulsed plasma nitrided AISI H13 tool steel

AISI H13 tool steel discs were pulsed plasma minded during different times at a constant temperature of 400 degrees C Wear tests were performed in order to study the acting wear mechanisms The samples were characterized by X-ray diffraction, scanning electron microscopy and hardness measurements The results showed that longer nitriding times reduce the wear volumes. The friction coefficient was 0.20 +/- 0 05 for all tested conditions and depends strongly on the presence of debris After wear tests, the wear tracks were characterized by optical and scanning electron microscopy and the wear mechanisms were observed to change from low cycle fatigue or plastic shakedown to long cycle fatigue These mechanisms were correlated to the microstructure and hardness of the nitrided layer (C) 2010 Elsevier B V All rights reserved

Electronic scraps - Recovering of valuable materials from parallel wire cables

Every year, the number of discarded electro-electronic products is increasing. For this reason recycling is needed, to avoid wasting non-renewable natural resources. The objective of this work is to study the recycling of materials from parallel wire cable through Unit operations of mineral processing. Parallel wire cables are basically composed of polymer and copper. The following unit operations were tested: grinding, size classification, dense medium separation, electrostatic separation, scrubbing, panning, and elutriation. It was observed that the operations used obtained copper and PVC concentrates with a low degree of cross contamination. It was Concluded that total liberation of the materials was accomplished after grinding to less than 3 mm, using a cage mill. Separation using panning and elutriation presented the best results in terms of recovery and cross contamination. (C) 2007 Elsevier Ltd. All rights reserved.

Integral Piezoactuator System with Optimum Placement of Functionally Graded Material - A Topology Optimization Paradigm

Piezoactuators consist of compliant mechanisms actuated by two or more piezoceramic devices. During the assembling process, such flexible structures are usually bonded to the piezoceramics. The thin bonding layer(s) between the compliant mechanism and the piezoceramic may induce undesirable behavior, including unusual interfacial nonlinearities. This constitutes a drawback of piezoelectric actuators and, in some applications, such as those associated to vibration control and structural health monitoring (e. g., aircraft industry), their use may become either unfeasible or at least limited. A possible solution to this standing problem can be achieved through the functionally graded material concept and consists of developing `integral piezoactuators`, that is those with no bonding layer(s) and whose performance can be improved by tailoring their structural topology and material gradation. Thus, a topology optimization formulation is developed, which allows simultaneous distribution of void and functionally graded piezoelectric materials (including both piezo and non-piezoelectric materials) in the design domain in order to achieve certain specified actuation movements. Two concurrent design problems are considered, that is the optimum design of the piezoceramic property gradation, and the design of the functionally graded structural topology. Two-dimensional piezoactuator designs are investigated because the applications of interest consist of planar devices. Moreover, material gradation is considered in only one direction in order to account for manufacturability issues. To broaden the range of such devices in the field of smart structures, the design of integral Moonie-type functionally graded piezoactuators is provided according to specified performance requirements.

Modelling grain boundary migration during geometric dynamic recrystallization

High-angle grain boundary migration is predicted during geometric dynamic recrystallization (GDRX) by two types of mathematical models. Both models consider the driving pressure due to curvature and a sinusoidal driving pressure owing to subgrain walls connected to the grain boundary. One model is based on the finite difference solution of a kinetic equation, and the other, on a numerical technique in which the boundary is subdivided into linear segments. The models show that an initially flat boundary becomes serrated, with the peak and valley migrating into both adjacent grains, as observed during GDRX. When the sinusoidal driving pressure amplitude is smaller than 2 pi, the boundary stops migrating, reaching an equilibrium shape. Otherwise, when the amplitude is larger than 2 pi, equilibrium is never reached and the boundary migrates indefinitely, which would cause the protrusions of two serrated parallel boundaries to impinge on each other, creating smaller equiaxed grains.

Investigation of the residence time distribution in a plate heat exchanger with series and parallel arrangements using a non-ideal tracer detection technique

The objective was to study the flow pattern in a plate heat exchanger (PHE) through residence time distribution (RTD) experiments. The tested PHE had flat plates and it was part of a laboratory scale pasteurization unit. Series flow and parallel flow configurations were tested with a variable number of passes and channels per pass. Owing to the small scale of the equipment and the short residence times, it was necessary to take into account the influence of the tracer detection unit on the RID data. Four theoretical RID models were adjusted: combined, series combined, generalized convection and axial dispersion. The combined model provided the best fit and it was useful to quantify the active and dead space volumes of the PHE and their dependence on its configuration. Results suggest that the axial dispersion model would present good results for a larger number of passes because of the turbulence associated with the changes of pass. This type of study can be useful to compare the hydraulic performance of different plates or to provide data for the evaluation of heat-induced changes that occur in the processing of heat-sensitive products. (C) 2011 Elsevier Ltd. All rights reserved.

FtsH2 and FtsH5: two homologous subunits use different integration mechanisms leading to the same thylakoid multimeric complex

P>The Arabidopsis thylakoid FtsH protease complex is composed of FtsH1/FtsH5 (type A) and FtsH2/FtsH8 (type B) subunits. Type A and type B subunits display a high degree of sequence identity throughout their mature domains, but no similarity in their amino-terminal targeting peptide regions. In chloroplast import assays, FtsH2 and FtsH5 were imported and subsequently integrated into thylakoids by a two-step processing mechanism that resulted in an amino-proximal lumenal domain, a single transmembrane anchor, and a carboxyl proximal stromal domain. FtsH2 integration into washed thylakoids was entirely dependent on the proton gradient, whereas FtsH5 integration was dependent on NTPs, suggesting their integration by Tat and Sec pathways, respectively. This finding was corroborated by in organello competition and by antibody inhibition experiments. A series of constructs were made in order to understand the molecular basis for different integration pathways. The amino proximal domains through the transmembrane anchors were sufficient for proper integration as demonstrated with carboxyl-truncated versions of FtsH2 and FtsH5. The mature FtsH2 protein was found to be incompatible with the Sec machinery as determined with targeting peptide-swapping experiments. Incompatibility does not appear to be determined by any specific element in the FtsH2 domain as no single domain was incompatible with Sec transport. This suggests an incompatible structure that requires the intact FtsH2. That the highly homologous type A and type B subunits of the same multimeric complex use different integration pathways is a striking example of the notion that membrane insertion pathways have evolved to accommodate structural features of their respective substrates.

Secretory phospholipases A(2) isolated from Bothrops asper and from Crotalus durissus terrificus snake venoms induce distinct mechanisms for biosynthesis of prostaglandins E-2 and D-2 and expression of cyclooxygenases

The effects of myotoxin III (MT-III), a phospholipase A(2) (sPLA(2)) from Bothrops asper snake venom, and crotoxin B (CB), a neurotoxic and myotoxic sPLA2 from the venom of Crotalus durissus terrificus, on cyclooxygenases (COXs) expression and biosynthesis of prostaglandins (PGs) were evaluated, together with the mechanisms involved in these effects. Upon intraperitoneal injection in mice, both sPLA(2)s promoted the synthesis of PGD(2) and PGE(2), with a different time-course. MT-III, but not CB, induced COX-2 expression by peritoneal leukocytes without modification on COX-1 constitutive expression, whereas CB increased the constitutive activity of COX-1. MT-III increased the enzymatic activity of COX-1 and COX-2. Similar effects were observed when these sPLA(2)s were incubated with isolated macrophages, evidencing a direct effect on these inflammatory cells. Moreover, both toxins elicited the release of arachidonic acid from macrophages in vitro. inhibition of cPLA(2) by AACOCF(3), but not of iPLA(2) by PACOCF(3) or BEL, significantly reduced PGD2, PGE2 and arachidonic acid (AA) release promoted by MT-III. These inhibitors did not affect MT-III-induced COX-2 expression. In contrast, cPLA2 inhibition did not modify the effects of CB, whereas iPLA2 inhibition reduced PGD2 and AA production induced by CB. These findings imply that distinct regulatory mechanisms leading to PGs` synthesis are triggered by these snake venom sPLA(2)s. Such differences are likely to explain the dissimilar patterns of inflammatory reaction elicited by these sPLA(2)s in vivo. (C) 2008 Elsevier Ltd. All rights reserved.

The antipyretic effect of dipyrone is unrelated to inhibition of PGE(2) synthesis in the hypothalamus

BACKGROUND AND PURPOSE Bacterial lipopolysaccharide (LPS) induces fever through two parallel pathways; one, prostaglandin (PG)-dependent and the other, PG-independent and involving endothelin-1 (ET-1). For a better understanding of the mechanisms by which dipyrone exerts antipyresis, we have investigated its effects on fever and changes in PGE(2) content in plasma, CSF and hypothalamus induced by either LPS or ET-1. EXPERIMENTAL APPROACH Rats were given (i.p.) dipyrone (120 mg center dot kg-1) or indomethacin (2 mg center dot kg-1) 30 min before injection of LPS (5 mu g center dot kg-1, i.v.) or ET-1 (1 pmol, i.c.v.). Rectal temperature was measured by tele-thermometry. PGE(2) levels were determined in the plasma, CSF and hypothalamus by elisa. KEY RESULTS LPS or ET-1 induced fever and increased CSF and hypothalamic PGE(2) levels. Two hours after LPS, indomethacin reduced CSF and hypothalamic PGE(2) but did not inhibit fever, while at 3 h it reduced all three parameters. Three hours after ET-1, indomethacin inhibited the increase in CSF and hypothalamic PGE(2) levels but did not affect fever. Dipyrone abolished both the fever and the increased CSF PGE(2) levels induced by LPS or ET-1 but did not affect the increased hypothalamic PGE(2) levels. Dipyrone also reduced the increase in the venous plasma PGE(2) concentration induced by LPS. CONCLUSIONS AND IMPLICATIONS These findings confirm that PGE(2) does not play a relevant role in ET-1-induced fever. They also demonstrate for the first time that the antipyretic effect of dipyrone was not mechanistically linked to the inhibition of hypothalamic PGE(2) synthesis.