Behavior of Ceriporiopsis subvermispora during Pinus taeda biotreatment in soybean-oil-amended cultures

Pinus taeda wood chips were treated with the biopulping fungus Ceriporiopsis subvermispora in soybean-oil-amended cultures The secretion of oxalic acid and the accumulation of thiobarbituric acid reactive substances were significantly increased in soybean-oil-amended cultures By contrast the secretion of hydrolytic and oxidative enzymes was not altered in the cultures Biotreated wood samples were characterized for weight and component losses as well as by in-situ thioacidolysis Residual lignins were also extracted from biotreated wood using a mild-non-razing extraction procedure The lignins were characterized by (31)P nuclear magnetic resonance ((31)P-NMR) spectroscopy Soybean oil amendment in the cultures was found to affect lignin degradation routes however it inhibited depolymerization reactions detectable in the residual lignin that was retained in the biotreated wood As a consequence chemithermomechanical pulping of the biotreated samples was not improved by soybean oil amendment in the cultures Crown Copyright (C) 2010 Published by Elsevier Ltd All rights reserved

A novel electrocatalyst support with proton conductive properties for polymer electrolyte membrane fuel cell applications

The objective of this study is to graft the Surface of carbon black, by chemically introducing polymeric chains (Nafion (R) like) with proton-conducting properties. This procedure aims for a better interaction of the proton-conducting phase with the metallic catalyst particles, as well as hinders posterior support particle agglomeration. Also loss of active surface call be prevented. The proton conduction between the active electrocatalyst site and the Nafion (R) ionomer membrane should be enhanced, thus diminishing the ohmic drop ill the polymer electrolyte membrane fuel cell (PEMFC). PtRu nanoparticles were supported on different carbon materials by the impregnation method and direct reduction with ethylene glycol and characterized using amongst others FTIR, XRD and TEM. The screen printing technique was used to produce membrane electrode assemblies (MEA) for single cell tests in H(2)/air(PEMFC) and methanol operation (DMFC). In the PEMFC experiments, PtRu supported on grafted carbon shows 550 mW cm(-2) gmetal(-1) power density, which represents at least 78% improvement in performance, compared to the power density of commercial PtRu/C ETEK. The DMFC results of the grafted electrocatalyst achieve around 100% improvement. The polarization Curves results clearly show that the main Cause of the observed effect is the reduction in ohmic drop, caused by the grafted polymer. (C) 2009 Elsevier B.V. All rights reserved.

PVA-Hydrogel Entrapped Candida Guilliermondii for Xylitol Production from Sugarcane Hemicellulose Hydrolysate

Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing-thawing method. Entrapment experiments were planned according to a 2(3) full factorial design, using the PVA concentration (80, 100, and 120 g L(-1)), the freezing temperature (-10, -15, and -20 degrees C), and the number of freezing-thawing cycles (one, three, and five) as the independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the same bioconversion in a stirred tank reactor operated at 400 rpm, 30 degrees C, and 1.04 vvm air flowrate. At the end of fermentation, a maximum xylitol concentration of 28.7 g L(-1), a xylitol yield on consumed xylose of 0.49 g g(-1) and a xylitol volumetric productivity of 0.24 g L(-1) h(-1) were obtained.

Corrosion behavior of Ti-xNb-13Zr alloys in Ringer`s solution

Ti-6Al-4V alloy has been widely used in restorative surgery due to its high corrosion resistance and biocompatibility. Nevertheless, some studies showed that V and Al release in the organism might induce cytotoxic effects and neurological disorders, which led to the development of V-free alloys and both V- and Al-free alloys containing Nb, Zr, Ta, or Mo. Among these alloys, Ti-13Nb-13Zr alloy is promising due to its better biomechanical compatibility than Ti-6Al-4V. In this work, the corrosion behavior of Ti, Ti-6Al-4V, and Ti-xNb-13Zr alloys (x=5, 13, and 20) was evaluated in Ringer`s solution (pH 7.5) at 37 degrees C through open-circuit potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. Spontaneous passivity was observed for all materials in this medium. Low corrosion current densities (in the order of 10(-7) A/cm(2)) and high impedance values (in the order of 10(5) Omega cm(2) at low frequencies) indicated their high corrosion resistance. EIS results showed that the passivating films were constituted of an outer porous layer (very low resistance) and an inner compact layer (high resistance), the latter providing the corrosion resistance of the materials. There was evidence that the Ti-xNb-13Zr alloys were more corrosion resistant than both Ti and Ti-6Al-4V in Ringer`s solution.

Use of sugarcane bagasse as biomaterial for cell immobilization for xylitol production

This study provides a preliminary contribution to the development of a bioprocess for the contintious production of xylitol from hemicellulosic hydrolyzate utilizing Candida guilliermondii cells immobilized onto natural sugarcane bagasse fibers. To this purpose, cells of this yeast were submitted to batch tests of ""in situ"" adsorption onto crushed and powdered sugarcane bagasse after treatment with 0.5 M NaOH. The results obtained on a xylose-based semi-synthetic medium were evaluated in terms of immobilization efficiency, cell retention and specific growth rates of suspended, immobilized and total cells. The first two parameters were shown to increase along the immobilization process, reached maximum values of 50.5% and 0.31 g immobilized cells/g bagasse after 21 h and then sharply decreased. The specific growth rate of suspended cells continuously increased during the immobilization tests, while that of the immobilized ones, after an initial growth, exhibited decreasing values. Under the conditions selected for cell immobilization, fermentation also took place with promising results. The yields of xylitol and biomass on consumed xylose were 0.65 and 0.18 g/g, respectively, xylitol and biomass productivities 0.66 and 0.13 g L-1 h(-1), and the efficiency of xylose-to-xylitol bioconversion was 70.8%. (C) 2007 Elsevier Ltd. All rights reserved.

Tick saliva inhibits the chemotactic function of MIP-1 alpha and selectively impairs chemotaxis of immature dendritic cells by down-regulating cell-surface CCR5

Ticks are blood-feeding arthropods that secrete immunomodulatory molecules through their saliva to antagonize host inflammatory and immune responses. As dendritic cells (DCs) play a major role in host immune responses, we studied the effects of Rhipicephalus sanguineus tick saliva on DC migration and function. Bone marrow-derived immature DCs pre-exposed to tick saliva showed reduced migration towards macrophage inflammatory protein (MIP)-1 alpha, MIP-1 beta and regulated upon activation, normal T cell expressed and secreted (RANTES) chemokines in a Boyden microchamber assay. This inhibition was mediated by saliva which significantly reduced the percentage and the average cell-surface expression of CC chemokine receptor CCR5. In contrast, saliva did not alter migration of DCs towards MIP-3 beta, not even if the cells were induced for maturation. Next, we evaluated the effect of tick saliva on the activity of chemokines related to DC migration and showed that tick saliva per se inhibits the chemotactic function of MIP-1 alpha, while it did not affect RANTES, MIP-1 beta and MIP-3 beta. These data suggest that saliva possibly reduces immature DC migration, while mature DC chemotaxis remains unaffected. In support of this, we have analyzed the percentage of DCs on mice 48 h after intradermal inoculation with saliva and found that the DC turnover in the skin was reduced compared with controls. Finally, to test the biological activity of the saliva-exposed DCs, we transferred DCs pre-cultured with saliva and loaded with the keyhole limpet haemocyanin (KLH) antigen to mice and measured their capacity to induce specific T cell cytokines. Data showed that saliva reduced the synthesis of both T helper (Th)1 and Th2 cytokines, suggesting the induction of a non-polarised T cell response. These findings propose that the inhibition of DCs migratory ability and function may be a relevant mechanism used by ticks to subvert the immune response of the host. (c) 2007 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Neospora caninum excreted/secreted antigens trigger CC-chemokine receptor 5-dependent cell migration

Neospora caninum, the causative agent of neosporosis, is an obligate intracellular parasite considered to be a major cause of abortion in cattle throughout the world. Most studies concerning N. caninum have focused on life cycle, seroepidemiology, pathology and vaccination, while data on host-parasite interaction, such as host cell migration, mechanisms of evasion and dissemination of this parasite during the early phase of infection are still poorly understood. Here we show the ability of excreted/secreted antigens from N. caninum (NcESAs) to attract monocytic cells to the site of primary infection in both in vitro and in vivo assays. Molecules from the family of cyclophilins present on the NcESAs were shown to work as chemokine-like proteins and NcESA-induced chemoattraction involved G(i) protein signaling and participation of CC-chemokine receptor 5 (CCR5). Additionally, we demonstrate the ability of NcESAs to enhance the expression of CCR5 on monocytic cells and this increase occurred in parallel with the chemotactic activity of NcESAs by increasing cell migration. These results suggest that during the first days of infection, N. caninum produces molecules capable of inducing monocytic cell migration to the sites of infection, which will consequently enhance initial parasite invasion and proliferation. Altogether, these results help to clarify some key features involved in the process of cell migration and may reveal virulence factors and therapeutic targets to control neosporosis. (C) 2010 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

A simulation-based evolutionary multiobjective approach to manufacturing cell formation

The purpose of this paper is to propose a multiobjective optimization approach for solving the manufacturing cell formation problem, explicitly considering the performance of this said manufacturing system. Cells are formed so as to simultaneously minimize three conflicting objectives, namely, the level of the work-in-process, the intercell moves and the total machinery investment. A genetic algorithm performs a search in the design space, in order to approximate to the Pareto optimal set. The values of the objectives for each candidate solution in a population are assigned by running a discrete-event simulation, in which the model is automatically generated according to the number of machines and their distribution among cells implied by a particular solution. The potential of this approach is evaluated via its application to an illustrative example, and a case from the relevant literature. The obtained results are analyzed and reviewed. Therefore, it is concluded that this approach is capable of generating a set of alternative manufacturing cell configurations considering the optimization of multiple performance measures, greatly improving the decision making process involved in planning and designing cellular systems. (C) 2010 Elsevier Ltd. All rights reserved.

Dynamic behavior analysis of drill-threading process when machining AISI Al-Si-Cu(4) alloy

Conventional threading operations involve two distinct machining processes: drilling and threading. Therefore, it is time consuming for the tools must be changed and the workpiece has to be moved to another machine. This paper presents an analysis of the combined process (drilling followed by threading) using a single tool for both operations: the tap-milling tool. Before presenting the methodology used to evaluate this hybrid tool, the ODS (operating deflection shapes) basics is shortly described. ODS and finite element modeling (FEM) were used during this research to optimize the process aiming to achieve higher stable machining conditions and increasing the tool life. Both methods allowed the determination of the natural frequencies and displacements of the machining center and optimize the workpiece fixture system. The results showed that there is an excellent correlation between the dynamic stability of the machining center-tool holder and the tool life, avoiding a tool premature catastrophic failure. Nevertheless, evidence showed that the tool is very sensitive to work conditions. Undoubtedly, the use of ODS and FEM eliminate empiric decisions concerning the optimization of machining conditions and increase drastically the tool life. After the ODS and FEM studies, it was possible to optimize the process and work material fixture system and machine more than 30,000 threaded holes without reaching the tool life limit and catastrophic fail.

Experimental Analysis of Structural Change and Rheological Behavior of Macromolecular Solutions with Guar and Xanthan Gums in Crossflow Microfiltration Processing

The present paper reports on the structural change and rheological behavior of mixtures of macromolecular suspensions (guar and xanthan gums) in crossflow microfiltration processing. Mixtures in suspension of guar and xanthan gums at low concentrations (1,000 ppm) and different proportions were processed by microfiltration with membrane of nominal pore size of 0.4 mu m. The rheological behavior of the mixtures was investigated in rotational viscometers at two different temperatures, 25 and 40 C, at the beginning and at the end of each experiment. The shear stress (t) in function of the shear rate (gamma) was fitted and analyzed with the power-law model. All the mixtures showed flow behavior index values (n) lower than 1, characterizing non-Newtonian fluids (pseudoplastic). The samples of both mixtures and permeates were also analyzed by absorbency spectroscopy in infrared radiation. The absorbency analysis showed that there is good synergism between xanthan and guar gums without structure modifications or gel formation in the concentration process by microfiltration.

Behavior of Socket Base Connections Emphasizing Pedestal Walls

To evaluate the main design models for socket base connections of precast concrete structures, an experimental investigation was carried out on specimens of this connection with smooth and rough interfaces in contact with cast-in-place concrete. The specimens consisted of pedestal walls and were submitted to loads with large eccentricities. Based on the experimental results, two rational design models are proposed for this connection. One of these models accounts for the friction and is applied to socket bases with smooth interfaces. The main behavior model was verified for sockets with this type of interface and the design of the longitudinal walls as corbels is also suggested in this case. Because the behavior of the rough interface specimens was very close to a monolithic connection, the other proposed model is an adaptation of the bending theory to calculate the vertical reinforcement of socket bases with rough interfaces.

Analysis of the behavior of transverse walls of socket base connections

This paper presents a theoretical and experimental analysis of socket base connections of precast concrete structures with regard to the behavior of transverse walls. The experimental program included seven specimens, for which the type of interface in contact with cast-in-place concrete, the load eccentricities and the embedded lengths were all varied, A design model was proposed to calculate the reinforcements of the transverse walls. Based on the obtained results, some conclusions can be drawn: (a) The top of the transverse wall on the compression side of the smooth connections and the top of the two transverse walls of the rough connections are submitted to a bending-tension and this tension prevails on the bending; (b) The design model proposed for the calculation of the reinforcement of the transverse wall on the compression side provides the best prediction of the experimental results for all specimens when compared to the current design models; (c) For rough interfaces, the top of the transverse wall on the tension side is more requested than the top of transverse wall on the compression side; (d) The results of the proposed design model for the reinforcement of the transverse wall on the tension side of rough connections were in close agreement with the experimental results. (C) 2008 Elsevier Ltd. All rights reserved.

Contribution of headed studs to the composite behavior of the partially encased beams

The use of mechanical shear connectors, mainly headed stud bolts, is the most common way to achieve steel-concrete composite action. The encasement of the steel beam in the depth slab results in increase of strength and stiffness, reducing the total height of the floor. In this investigation, three partially encased composite beams were tested under flexural conditions and the main objective was to investigate some alternative positions for the headed studs. To provide longitudinal shear resistance between the I-shaped beam and the concrete, two positions of the,studs were investigated: vertically welded on the bottom flange and horizontally welded on the faces of the web. The experimental results have shown that the headed studs are effective to provide the composite action and increase the bending strength. Furthermore, the headed studs welded vertically on the bottom flange proved to be the most reliable position.

Constitutive model for long term municipal solid waste mechanical behavior

This paper presents some improvements in the model proposed by Machado et al. [Machado SL, Carvalho MF, Vilar OM. Constitutive model for municipal solid waste. J Geotech Geoenviron Eng ASCE 2002; 128(11):940-51] now considering the influence of biodegradation of organic matter in the mechanical behavior of municipal solid waste. The original framework considers waste as composed of two component groups; fibers and organic paste. The particular laws of behavior are assessed for each component group and then coupled to represent waste behavior. The improvements introduced in this paper take into account the changes in the properties of fibers and mass loss due to organic matter depletion over time. Mass loss is indirectly calculated considering the MSW gas generation potential through a first order decay model. It is shown that as the biodegradation process occurs the proportion of fibers increases, however, they also undergo a degradation process which tends to reduce their ultimate tensile stress and Young modulus. The way these changes influence the behavior of MSW is incorporated in the final framework which captures the main features of the MSW stress-strain behavior under different loading conditions. (C) 2007 Elsevier Ltd. All rights reserved.

Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater

The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR - Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 degrees C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530 +/- 37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller. (C) 2010 Elsevier Ltd. All rights reserved.