Experimental and numerical investigation of dynamic heat transfer parameters in packed bed

Dynamic experiments in a nonadiabatic packed bed were carried out to evaluate the response to disturbances in wall temperature and inlet airflow rate and temperature. A two-dimensional, pseudo-homogeneous, axially dispersed plug-flow model was numerically solved and used to interpret the results. The model parameters were fitted in distinct stages: effective radial thermal conductivity (K (r)) and wall heat transfer coefficient (h (w)) were estimated from steady-state data and the characteristic packed bed time constant (tau) from transient data. A new correlation for the K (r) in packed beds of cylindrical particles was proposed. It was experimentally proved that temperature measurements using radially inserted thermocouples and a ring-shaped sensor were not distorted by heat conduction across the thermocouple or by the thermal inertia effect of the temperature sensors.

Treatment of Aqueous Effluents Containing Phenol by the O(3), O(3)-UV, and O(3)-H(2)O(2) Processes: Experimental Study and Neural Network Modeling

In this work, the oxidation of the model pollutant phenol has been studied by means of the O(3), O(3)-UV, and O(3)-H(2)O(2) processes. Experiments were carried out in a fed-batch system to investigate the effects of initial dissolved organic carbon concentration, initial, ozone concentration in the gas phase, the presence or absence of UVC radiation, and initial hydrogen peroxide concentration. Experimental results were used in the modeling of the degradation processes by neural networks in order to simulate DOC-time profiles and evaluate the relative importance of process variables.

Integrated analysis of cooling water systems: Modeling and experimental validation

Cooling towers are widely used in many industrial and utility plants as a cooling medium, whose thermal performance is of vital importance. Despite the wide interest in cooling tower design, rating and its importance in energy conservation, there are few investigations concerning the integrated analysis of cooling systems. This work presents an approach for the systemic performance analysis of a cooling water system. The approach combines experimental design with mathematical modeling. An experimental investigation was carried out to characterize the mass transfer in the packing of the cooling tower as a function of the liquid and gas flow rates, whose results were within the range of the measurement accuracy. Then, an integrated model was developed that relies on the mass and heat transfer of the cooling tower, as well as on the hydraulic and thermal interactions with a heat exchanger network. The integrated model for the cooling water system was simulated and the temperature results agree with the experimental data of the real operation of the pilot plant. A case study illustrates the interaction in the system and the need for a systemic analysis of cooling water system. The proposed mathematical and experimental analysis should be useful for performance analysis of real-world cooling water systems. (C) 2009 Elsevier Ltd. All rights reserved.

Thermodynamics of aqueous solutions of polyelectrolytes: Experimental results for the activity of water in aqueous solutions of (a single synthetic polyelectrolyte and sodium chloride)

Experimental results for the activity of water in aqueous solutions of 10 single, synthetic polyelectrolytes (polysodium acrylate, polysodium methacrylate, polyammonium acrylate, polysodium ethylene sulfonate, and polysodium styrene sulfonate) and sodium chloride at 298.2 K are presented. The experimental work was performed by applying the isopiestic method with sodium chloride as a reference substance. As expected, the activity of water decreases when the concentration of a polyelectrolyte and/or sodium chloride increases. At constant concentration of a polyelectrolyte and sodium chloride, the activity of water depends on the monomer unit and the molecular mass of the polyelectrolyte. The new data are to be used in future work to develop and test models for the Gibbs excess energy of aqueous solutions of polyelectrolytes.

Thermodynamics of aqueous solutions of polyelectrolytes: Experimental results for the activity of water in aqueous solutions of some single synthetic polyelectrolytes

Experimental results for the activity of water in aqueous solutions of 10 single polyelectrolytes (two polysodium acrylates, two polysodium methacrylates, three polyammonium acrylates, two polysodium ethylene sulfonates, and one polysodium styrene sulfonate) at (298.2 and 323.2) K are reported. The isopiestic method was employed in these experiments with aqueous solutions of sodium chloride as references. The polyelectrolytes were characterized by three averaged molecular masses determined by gel permeation chromatography. Furthermore, the density and the refractive index increments of the aqueous polyelectrolyte solutions are reported. Although a similar pattern for the activity of water was observed for all systems (i.e., the osmotic coefficient increases with rising polyelectrolyte concentration), the experimental results show that this property depends on the monomer type as well as on the size of the polymer chain. The temperature (varied from (298.2 to 323.2) K) has only a small influence on the activity of water.

Open-circuit voltages: Theoretical and experimental optimizations of rear passivated silicon solar cells using Fz and Cz wafers

The theoretical and experimental open-circuit voltage optimizations of a simple fabrication process of silicon solar cells n(+)p with rear passivation are presented. The theoretical results were obtained by using an in-house developed program, including the light trapping effect and metal-grid optimization. On the other hand, the experimental steps were monitored by the photoconductive decay technique. The starting materials presented thickness of about 300 pm and resistivities: FZ (0.5 Omega cm), Cz-type 1 (2.5 Omega cm) and Cz-type 2 (3.3 Omega cm). The Gaussian profile emitters were optimized with sheet resistance between 55 Omega/sq and 100 Omega/sq, and approximately 2.0 mu m thickness in accordance to the theoretical results. Excellent implied open-circuit voltages of 670.8 mV, 652.5 mV and 662.6 mV, for FZ, Cz-type 1 and Cz-type 2 silicon wafers, respectively, could be associated to the measured lifetimes that represents solar cell efficiency up to 20% if a low cost anti-reflection coating system, composed by random pyramids and SiO(2) layer, is considered even for typical Cz silicon. (C) 2009 Elsevier Ltd. All rights reserved.

Experimental Measurement of Water Diffusion through Fine Aggregate Mixtures

The water diffusion attributable to concentration gradients is among the main mechanisms of water transport into the asphalt mixture. The transport of small molecules through polymeric materials is a very complex process, and no single model provides a complete explanation because of the small molecule`s complex internal structure. The objective of this study was to experimentally determine the diffusion of water in different fine aggregate mixtures (FAM) using simple gravimetric sorption measurements. For the purposes of measuring the diffusivity of water, FAMs were regarded as a representative homogenous volume of the hot-mix asphalt (HMA). Fick`s second law is generally used to model diffusion driven by concentration gradients in different materials. The concept of the dual mode diffusion was investigated for FAM cylindrical samples. Although FAM samples have three components (asphalt binder, aggregates, and air voids), the dual mode was an attempt to represent the diffusion process by only two stages that occur simultaneously: (1) the water molecules are completely mobile, and (2) the water molecules are partially mobile. The combination of three asphalt binders and two aggregates selected from the Strategic Highway Research Program`s (SHRP) Materials Reference Library (MRL) were evaluated at room temperature [23.9 degrees C (75 degrees F)] and at 37.8 degrees C (100 degrees F). The results show that moisture uptake and diffusivity of water through FAM is dependent on the type of aggregate and asphalt binder. At room temperature, the rank order of diffusivity and moisture uptake for the three binders was the same regardless of the type of aggregate. However, this rank order changed at higher temperatures, suggesting that at elevated temperatures different binders may be undergoing a different level of change in the free volume. DOI: 10.1061/(ASCE)MT.1943-5533.0000190. (C) 2011 American Society of Civil Engineers.

Dynamic positioning systems: An experimental analysis of sliding mode control

Vessel dynamic positioning (DP) systems are based on conventional PID-type controllers and an extended Kalman filter. However, they present a difficult tuning procedure, and the closed-loop performance varies with environmental or loading conditions since the dynamics of the vessel are eminently nonlinear. Gain scheduling is normally used to address the nonlinearity of the system. To overcome these problems, a sliding mode control was evaluated. This controller is robust to variations in environmental and loading conditions, it maintains performance and stability for a large range of conditions, and presents an easy tuning methodology. The performance of the controller was evaluated numerically and experimentally in order to address its effectiveness. The results are compared with those obtained from conventional PID controller. (c) 2010 Elsevier Ltd. All rights reserved.

Experimental and theoretical study of transport properties in uniaxially pressed (Bi, Pb)(2)Sr(2)Ca(2)Cu(3)O(10+delta) ceramic samples

Experimental and theoretical studies on the magnetic field dependence of the electrical resistance R(B(a)) and the transport noise (TN) in polycrystalline high-T(c) superconductors subjected to different uniaxial compacting pressures were conducted. X-ray diffraction rocking curves were performed in different surfaces of the samples in order to investigated the degree of texture The results indicated an improvement of the degree of texture with increasing the uniaxial compacting pressure In theoretical simulations of the data, the polycrystalline superconductors were described as a series-parallel array of Josephson devices The intergranular magnetic field is described within the framework of the intragranular flux-trapping model and the distribution of the grain-boundary angles is assumed to follow the Rayleigh statistical function The proposed model describes well the experimental magnetoresistance R(B(a)) data We have found that the behavior of the R(B(a)) curves changes appreciably when different uniaxially compacting pressures are applied to the sample and such a changes are reproduced by the model when different grain-boundary angles distributions are used In addition, changes in the R(B(a)) dependence have their counterparts in the experimental transport noise signals (C) 2009 Elsevier B.V. All rights reserved

Characterization and Experimental Host Range of a Brazilian Tomato Isolate of Tomato severe rugose virus

We report the complete molecular characterization of the DNA-A and DNA-B of a Brazilian tomato isolate of Tomato severe rugose virus (ToSRV) and the experimental host range of the virus determined using white-fly transmission tests. Genome analysis showed that ToSRV has a close evolutionary relationship with Tomato rugose mosaic virus. Of 33 plants species inoculated with viruliferous Bemisia tabaci biotype B, 13 species were susceptible to ToSRV, nine asymptomatically. Therefore, ToSRV disease management strategy should include the control of infected weeds close to tomato fields.

Paclitaxel associated with cholesterol-rich nanoemulsions promotes atherosclerosis regression in the rabbit

A cholesterol-rich nanoemulsion (LDE) that resembles LDL binds to the LDL receptors and after injection into the blood stream may concentrate in cells with LDL receptor overexpression, as occurs in neoplasias and other proliferative processes. Thus, LDE can be used as vehicle to target drugs against those cells. The current study was designed to verify in rabbits whether LDE concentrates in the lesioned rabbit artery and whether a paclitaxel derivative, paclitaxel oleate, associated to LDE could reduce the atherosclerotic lesions. Sixteen male New Zealand rabbits were fed a 1% cholesterol diet for 60 days. Starting from day 30 under cholesterol feeding, eight animals were treated with four weekly intravenous injections of LDE-paclitaxel (4 mg/kg) and eight with four weekly intravenous saline solution injections for additional 30 days. On day 60, the animals were sacrificed for analysis. The uptake of LDE labeled with [C-14]-cholesteryl oleate by the aortic arch of cholesterol-fed rabbits was twice as much that observed in animals fed only regular chow. LDE-paclitaxel reduced the lesion areas of cholesterol-fed animals by 60% and intima-media ratio fourfold and inhibited the macrophage migration and the smooth muscle cell proliferation and invasion of the intima. LDE-paclitaxel treatment had no toxicity. In conclusion, LDE-paclitaxel produced pronounced atherosclerosis regression without toxicity and has shown remarkable potential in cardiovascular therapeutics. (c) 2008 Published by Elsevier Ireland Ltd.

Effect of Simvastatin on the Generation of Autoantibodies Against Oxidized LDL and Progression of Atherosclerosis in Rabbits

Oxidized Low-Density Lipoproteins (oxLDL) and autoantibodies against oxLDL are important in the development of atherosclerotic lesions. Statins are efficacious in the control of dyslipidemia and prevention of atherosclerosis; however, many questions concerning the mechanism of action of such drugs remain unknown. This work investigated the effect of simvastatin on generation of autoantibodies against oxLDL and development of atherosclerosis in rabbits. The animals were divided into three groups: control, hypercholesterolemic, and hypercholesterolemic simvastatin (3.0 mg simvastatin/ kg body weight). Concentrations of autoantibodies against oxLDL were determined on days 0,30 and 60 of the experiment and the atherosclerotic lesions were evaluated at the end of the study. Simvastatin reduced intimal proliferation in the thoracic region, prevented arterial calcification and inhibited the generation of autoantibodies against oxLDL. In conclusion, daily administration of simvastatin slows down atherosclerotic lesion development in rabbits with induced hypercholesterolemia and inhibition on generation of autoantibodies against oxLDL contributes to the cardioprotective effect observed.

Influence of a probiotic soy product on fecal microbiota and its association with cardiovascular risk factors in an animal model

Background: Previous work showed that daily ingestion of an aqueous soy extract fermented with Enterococcus faecium CRL 183 and Lactobacillus helveticus 416, supplemented or not with isoflavones, reduced the total cholesterol and non-HDL-cholesterol levels, increased the high-density lipoprotein (HDL) concentration and inhibited the raising of autoantibody against oxidized low-density lipoprotein (ox-LDL Ab) and the development of atherosclerotic lesions. Objective: The aim of this study was to characterize the fecal microbiota in order to investigate the possible correlation between fecal microbiota, serum lipid parameters and atherosclerotic lesion development in rabbits with induced hypercholesterolemia, that ingested the aqueous soy extract fermented with Enterococcus faecium CRL 183 and Lactobacillus helveticus 416. Methods: The rabbits were randomly allocated to five experimental groups (n = 6): control (C), hypercholesterolemic (H), hypercholesterolemic plus unfermented soy product (HUF), hypercholesterolemic plus fermented soy product (HF) and hypercholesterolemic plus isoflavone-supplemented fermented soy product (HIF). Lipid parameters and microbiota composition were analyzed on days 0 and 60 of the treatment and the atherosclerotic lesions were quantified at the end of the experiment. The fecal microbiota was characterized by enumerating the Lactobacillus spp., Bifidobacterium spp., Enterococcus spp., Enterobacteria and Clostridium spp. populations. Results: After 60 days of the experiment, intake of the probiotic soy product was correlated with significant increases (P < 0.05) on Lactobacillus spp., Bifidobacterium spp. and Enterococcus spp. and a decrease in the Enterobacteria population. A strong correlation was observed between microbiota composition and lipid profile. Populations of Enterococcus spp., Lactobacillus spp. and Bifidobacterium spp. were negatively correlated with total cholesterol, non-HDL-cholesterol, autoantibodies against oxidized LDL (ox-LDL Ab) and lesion size. HDL-C levels were positively correlated with Lactobacillus spp., Bifidobacterium spp., and Enterococcus spp. populations. Conclusion: In conclusion, daily ingestion of the probiotic soy product, supplemented or not with isoflavones, may contribute to a beneficial balance of the fecal microbiota and this modulation is associated with an improved cholesterol profile and inhibition of atherosclerotic lesion development.

Effects of isoflavone-supplemented soy yogurt on lipid parameters and atherosclerosis development in hypercholesterolemic rabbits: a randomized double-blind study

Background: There is increasing interest in natural treatments to control dyslipidemia and reduce the risk of cardiovascular disease. Previous studies have demonstrated the beneficial effects of soy yogurt fermented with Enterococcus faecium CRL 183 and of dietary isoflavones on the lipid profile. The purpose of the present study was to investigate the effects of isoflavone-supplemented soy yogurt, fermented with E. faecium CRL183, on lipid parameters and atherosclerosis development in rabbits with induced hypercholesterolemia. Methods: Forty-eight rabbits were randomly assigned to eight groups fed on the following diets for 60 days: C - control; IY - isoflavone-supplemented soy yogurt; H - hypercholesterolemic (1.0% cholesterol wt/wt diet); HY - hypercholesterolemic plus soy yogurt; HIY - hypercholesterolemic plus isoflavone-supplemented soy yogurt; HP - hypercholesterolemic plus placebo; HI hypercholesterolemic plus isoflavone and HE - hypercholesterolemic plus pure culture of E. faecium CRL 183. Serum lipids and autoantibodies against oxLDL (oxLDL Ab) were analyzed on days 0, 30 and 60 of the treatment and the atherosclerotic lesions were quantified at the end of the experiment. Results: Soy yogurt, soy yogurt supplemented with isoflavones and placebo promoted significant reductions in total cholesterol level (38.1%, 27.0% and 26.6%, respectively). Significant increases in serum HDL-C concentration relative to group H were detected in animals that ingested soy yogurt, with or without the isoflavone supplement (55.2%), E. faecium culture (43.3%) or placebo (35.8%). Intake of soy yogurt and soy yogurt supplemented with isoflavones prevented the rise of oxLDL Ab during the study period. The extent of atherosclerosis in the thoracic and abdominal aortas was reduced in the HIY, HY and HP groups. However, when the whole aorta was analyzed, animals treated with soy yogurt supplemented with isoflavones exhibited the greatest reduction (51.4%, P < 0.05) in atherosclerotic lesion area, compared to group H. Conclusion: Soy yogurt could be consumed as an alternative means of reducing the risk of cardiovascular disease by improving the lipid profile and inhibiting oxLDL Ab formation. Our findings also suggest that isoflavone supplementation may enhance the antiatherosclerotic effect of soy yogurt.

Optimization of Pothomorphe umbellata (L.) Miquel topical formulations using experimental design

Pothomorphe umbellata is a native plant widely employed in the Brazilian popular medicine. This plant has been shown to exert a potent antioxidant activity on the skin and to delay the onset and reduce the incidence of UVB-induced skin damage and photoaging. The aim of this work was to optimize the appearance, the centrifuge stability and the permeation of emulsions containing R umbellata (0. 1% 4-nerolidylchatecol). Experimental design was used to study ternary mixtures models with constraints and graphical representation by phase diagrams. The constraints reduce the possible experimental domain, and for this reason, this methodology offers the maximum information while requiring the minimum investment. The results showed that the appearance follows a linear model, and that the aqueous phase was the principal factor affecting the appearance; the centrifuge stability parameter followed a mathernatic quadratic model and the interactions between factors produced the most stable emulsions; skin permeation was improved by the oil phase, following a linear model generated by data analysis. We propose as optimized P. umbellata formulation: 68.4% aqueous phase, 26.6% oil phase and 5.0% of self-emulsifying phase. This formulation displayed an acceptable compromise between factors and responses investigated. (c) 2007 Elsevier B.V. All rights reserved.