On the comparison between compound louvered-vortex generator fins and X-shaped louvered fins

A recent evolution in heat exchanger design is the use of compound designs. One of the designs under study is a combination between a louvered fin and vortex generators. Several possible placements of the vortex generators are studied. These compound designs are compared with the X-shaped louvered fin, which maximizes the louvered area. It is shown that the X-shaped louvered fin exhibits the same heat transfer enhancement mechanism as the compound design, with respect to the rectangular louvered fin. The X-shaped louvered fin outperforms all of the compound designs

Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats

Several studies suggest that cyclooxygenase (COX)-2 plays a pivotal role in the progression of ischemic brain damage. In the present study, we investigated the effects of selective inhibition of COX-2 with nimesulide (12 mg/kg) and selective inhibition of COX-1 with valeryl salicylate (VAS, 12-120 mg/kg) on prostaglandin E2 (PGE2) levels, myeloperoxidase (MPO) activity, Evans Blue (EB) extravasation and infarct volume in a standardized model of transient focal cerebral ischemia in the rat. Postischemic treatment with nimesulide markedly reduced the increase in PGE2 levels in the ischemic cerebral cortex 24 h after stroke and diminished infarct size by 48 % with respect to vehicle-treated animals after 3 days of reperfusion. Furthermore, nimesulide significantly attenuated the blood-brain barrier (BBB) damage and leukocyte infiltration (as measured by EB leakage and MPO activity, respectively) seen at 48 h after the initial ischemic episode. These studies provide the first experimental evidence that COX-2 inhibition with nimesulide is able to limit BBB disruption and leukocyte infiltration following transient focal cerebral ischemia. Neuroprotection afforded by nimesulide is observed even when the treatment is delayed until 6 h after the onset of ischemia, confirming a wide therapeutic window of COX-2 inhibitors in experimental stroke. On the other hand, selective inhibition of COX-1 with VAS had no significant effect on the evaluated parameters. These data suggest that COX-2 activity, but not COX-1 activity, contributes to the progression of focal ischemic brain injury, and that the beneficial effects observed with non-selective COX inhibitors are probably associated to COX-2 rather than to COX-1 inhibition

Development of a laser shock adhesion test for the assessment of weak adhesive bonded CFRP structures

Adhesive bondin,g bas a great poœnlial far future ligbtweight bigb-loaded structures in the a.eronautic industiy. A preœquisite for sucb an application is dtat the bond quality of the adhesive joint can be assessed in a non-destructive way. However, the use of da.ssicaJ Non•DesiiUctive Techniques (NDT) does not aUow the evaluation of the adhesion stren,gt:h of an adhesive bond yet This paper pn!sents an investigation made on weak composite bonds in on!er to develop a laser shock wave adhesion test First, the procedure to produce controlled weak bonds is desaibed. CFRP bonded samples are pn!pared in a spedfic way and characterized by ultrasonic techniques to assess the absence of any detectable defect. 1ben, for sorne of the .samples, their bond streDgth is evaluated by mechanical destructive œsts and ether .samples are loaded by v.arious intensity lasers shocks. The obtained results help to understand the behavior of the composite bonds under Jaser shock loading:. thanks to two post-mortem techrùques. 1becorrelation between the laser parameterS and the induced damage is demon.strated, The potential of the laser shock. technique to dl.saiminate different bond quallties is shawn, and the need for the œst optinùzationlsdÛ(

Local heat flux measurement technique for internal combustion engines

The heat transfer from the combustion gases to the cylinder wall affects the efficiency, emissions and power output of an internal combustion engine. Measuring the heat transfer requires a heat flux sensor inside the combustion chamber that has a short response time and is able to withstand the harsh conditions during combustion. In this work, a suitable sensor is introduced and the measured wall temperature, heat flux and convection coefficient are compared to those measured with a commercial sensor. It was found that both sensors measure the same convection coefficient, but a different wall temperature and heat flux. This is because the presence of the sensor in the combustion chamber wall affects these quantities. A method is proposed to cancel this effect and calculate the actual heat flux through the cylinder wall

Wide therapeutic time window for nimesulide neuroprotection in a model of transient focal cerebral ischemia in the rat

Results from several studies indicate that cyclooxygenase-2 (COX-2) is involved ischemic brain injury. The purpose of this study was to evaluate the neuroprotective effects of the selective COX-2 inhibitor nimesulide on cerebral infarction and neurological deficits in a standardized model of transient focal cerebral ischemia in rats. Three doses of nimesulide (3, 6 and 12 mg/kg; i.p.) or vehicle were administered immediately after stroke and additional doses were given at 6, 12, 24, 36 and 48 h after ischemia. In other set of experiments, the effect of nimesulide was studied in a situation in which its first administration was delayed for 3 to 24 h after ischemia. Total, cortical and subcortical infarct volumes and functional outcome (assessed by neurological deficit score and rotarod performance) were determined 3 days after ischemia. The effect of nimesulide on prostaglandin E2 (PGE2) levels in the injured brain was also investigated. Nimesulide dose-dependently reduced infarct volume and improved functional recovery when compared to vehicle. Of interest is the finding that neuroprotection conferred by nimesulide (reduction of infarct size and neurological deficits and improvement of rotarod performance) was also observed when treatment was delayed until 24 h after ischemia. Further, administration of nimesulide in a delayed treatment paradigm completely abolished PGE2 accumulation in the postischemic brain, suggesting that COX-2 inhibition is a promising therapeutic strategy for cerebral ischemia to target the late-occurring inflammatory events which amplify initial damage

Combined conduction and natural convection cooling of offshore power cables in porous sea soil

The power that can be carried by offshore power cables is often restricted by the temperature limit of the materials inside the cable. It is therefore essential to predict the heat transfer behavior of the dissipated power from the cable to the environment. Offshore cables are buried in the seabed, which is a porous structure of sea soil saturated with water. Both conduction of heat through the soil, as well as natural convection due to the flow of water through the porous soil, are possible ways of heat transfer. Most cases are best described as a combination of these heat transfer effects. In this paper, a numerical model is made to predict the heat transfer from the cable to the environment by modeling the surrounding soil as a porous medium. The influence of soil parameters such as conductivity, heat capacity and permeability, as well as geometrical parameters, such as burial depth and cable diameter, are tested. An analytical expression, which can estimate the heat transfer rate for conduction dominated heat flows, is used. For convection dominated heat flows, a correlation in function of the Darcy-modified Rayleigh number is used. For heat flows which are a combination of conduction and convection effects, an algebraic summation of the thermal conductance due to convection and conduction is found not to give adequate agreement with the simulations. It is shown that an asymptotic expansion of the limiting equations for conductive and convective heat transfer rate can be used to determine the total heat flow effectively. Several soil samples in the North Sea are analyzed, and the thermal properties are used as inputs for the model. These calculations show that conduction is the main heat transfer effect and that convection has a limited effect on the heat transfer