Evaluation of temperature influence on embedded kinematic system

Dissertação de mestrado integrado em Engenharia Mecânica

Production of whey protein-based aggregates under ohmic heating

Formation of whey protein isolate protein aggregates under the influence of moderate electric fields upon ohmic heating (OH) has been monitored through evaluation of molecular protein unfolding, loss of its solubility, and aggregation. To shed more light on the microstructure of the protein aggregates produced by OH, samples were assayed by transmission electron microscopy (TEM). Results show that during early steps of an OH thermal treatment, aggregation of whey proteins can be reduced with a concomitant reduction of the heating chargeby reducing the come-up time (CUT) needed to reach a target temperatureand increase of the electric field applied (from 6 to 12 V cm1). Exposure of reactive free thiol groups involved in molecular unfolding of -lactoglobulin (-lg) can be reduced from 10 to 20 %, when a CUT of 10 s is combined with an electric field of 12 V cm1. Kinetic and multivariate analysis evidenced that the presence of an electric field during heating contributes to a change in the amplitude of aggregation, as well as in the shape of the produced aggregates. TEM discloses the appearance of small fibrillar aggregates upon the influence of OH, which have recognized potential in the functionalization of food protein networks. This study demonstrated that OH technology can be used to tailor denaturation and aggregation behavior of whey proteins due to the presence of a constant electric field together with the ability to provide a very fast heating, thus overcoming heat transfer limitations that naturally occur during conventional thermal treatments.

Surface phenomena and hydrodynamic effects on the deposition of Pseudomonas fluorescens

Biofilm adhesion to metals (copper, aluminium and brass) was studied at two different velocities and pH values of 7 and 9. Both bacteria and metals showed negative surface charges at those values of pH, which tends to slow down adhesion. Film densities increased with the fluid velocity and were also affected by the pH and by the growth rate of the bacteria. Long duration tests based on heat transfer measurements were run at five different fluid velocities and at pH = 7, showing in general an asymptotic behaviour and a control of deposition by adhesion and growth phenomena.

Experimentelle und numerische Untersuchungen zum Wärmeübergang in Mikrokanälen

Heat transfer, micro channel, single phase flow, two phase flow, boiling, boiling regions

Neuer Strahlschichtreaktor für Wärme- und Stofftransportprozesse

Spouted bed, reactor, heat transfer, mass transfer, pressure drop, modeling

Untersuchung inverser Probleme zur Bestimmung von Wärmeübergangskoeffizienten bei der Sprühkühlung

Heat transfer, inverse problem, spray cooling

Sabbatical stay at CREVER, University Rovira i Virgili

A three-year research proposal of international impact and quality was developed between the author and CREVER researchers, taking into account the infrastructure and research lines already being carried out at CREVER. The project is related to the study of new mixtures in thermal activated systems, by the addition of a third component to help the heat transfer processes. The project proposes the use of water and lithium nitrate as absorbents in ternary ammonia mixtures, varying the concentration with the objective of optimising the mixture for solar air conditioning purposes. Also, the research proposal will promote an intensive collaboration in the following years between CREVER and The Centro de Investigación en Energía-UNAM, Mexico.

Experimental investigation of transient natural convection cooling of high prandtl number fluid with variable viscosity

Report for the scientific sojourn at the James Cook University, Australia, between June to December 2007. Free convection in enclosed spaces is found widely in natural and industrial systems. It is a topic of primary interest because in many systems it provides the largest resistance to the heat transfer in comparison with other heat transfer modes. In such systems the convection is driven by a density gradient within the fluid, which, usually, is produced by a temperature difference between the fluid and surrounding walls. In the oil industry, the oil, which has High Prandtl, usually is stored and transported in large tanks at temperatures high enough to keep its viscosity and, thus the pumping requirements, to a reasonable level. A temperature difference between the fluid and the walls of the container may give rise to the unsteady buoyancy force and hence the unsteady natural convection. In the initial period of cooling the natural convection regime dominates over the conduction contribution. As the oil cools down it typically becomes more viscous and this increase of viscosity inhibits the convection. At this point the oil viscosity becomes very large and unloading of the tank becomes very difficult. For this reason it is of primary interest to be able to predict the cooling rate of the oil. The general objective of this work is to develop and validate a simulation tool able to predict the cooling rates of high Prandtl fluid considering the variable viscosity effects.

The immune-dependence of chemotherapy in experimental schistosomiasis

Experimental evidence indicates that immune effector mechanisms can enhance the activity of schistosomicidal drugs. Praziquantel, oxamniquine, hycanthone and antimony were less effective against Schistosoma mansoni infections in mice immunosuppressed by T cell-deprivation, than against comparable infection in normal mice. The schistosomicidal activities of praziquantel, oxamniquine and antimony have been experimentally enhanced by the synergistic action of immune sera. In passive serum transfer experiments a s. mansoni antigen of Mr 27 kD with non-specific esterase activity was identified as a potentially sensitive target for the antibodies that interact with praziquantel. Indirect immunofluorescence indicated that this antigen was exposed on the worm surface as a result of praziquantel treatment.

International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes

Challenging environmental conditions, including heat and humidity, cold, and altitude, pose particular risks to the health of Olympic and other high-level athletes. As a further commitment to athlete safety, the International Olympic Committee (IOC) Medical Commission convened a panel of experts to review the scientific evidence base, reach consensus, and underscore practical safety guidelines and new research priorities regarding the unique environmental challenges Olympic and other international-level athletes face. For non-aquatic events, external thermal load is dependent on ambient temperature, humidity, wind speed and solar radiation, while clothing and protective gear can measurably increase thermal strain and prompt premature fatigue. In swimmers, body heat loss is the direct result of convection at a rate that is proportional to the effective water velocity around the swimmer and the temperature difference between the skin and the water. Other cold exposure and conditions, such as during Alpine skiing, biathlon and other sliding sports, facilitate body heat transfer to the environment, potentially leading to hypothermia and/or frostbite; although metabolic heat production during these activities usually increases well above the rate of body heat loss, and protective clothing and limited exposure time in certain events reduces these clinical risks as well. Most athletic events are held at altitudes that pose little to no health risks; and training exposures are typically brief and well-tolerated. While these and other environment-related threats to performance and safety can be lessened or averted by implementing a variety of individual and event preventative measures, more research and evidence-based guidelines and recommendations are needed. In the mean time, the IOC Medical Commission and International Sport Federations have implemented new guidelines and taken additional steps to mitigate risk even further.

CD4+, CD8+ and CD4- CD8- T cell-subsets can confer protection against Leishmania m. mexicana infection

We studied the role of CD4+, CD8+, CD4- CD8- T cells and IgG anti-Leishmania after infection or vaccination in the CBA/ca mouse. Mice were either infected with L. m. mexicana promastigotes or vaccinated with parasite-membrane antigens incorporated into liposomes. Successfully vaccinated mice were used as cell-donors in adoptive transfer experiments. Naive, syngeneic recipients received highly-enriched CD4+, CD8+ or CD4- CD8- T cells from those two set of donors and challenged with live parasites. Our results showed that, both CD4+ and CD8+ T cells from infected or vaccinated donors conferred significant disease-resistance to naive recipients. In addition, adoptive transfer of CD4- CD8- T cells from vaccinated donors significantly delayed lesion growth in recipient mice. We concluded that vaccination of CBA mice correlates with the induction of protective CD4+, CD8+ and CD4- CD8- T cells and the synthesis of IgG anti-Leishmania.

Simulació numèrica de fenòmens de transferència de calor i dinàmics de fluids transitoris

The work carried out during the 4 year research activity can be barely classified in two main lines. On the one hand, a considerable effort is taken to address issues related with the verification of multi-dimensional and transient solutions that are obtained by numerical simulations. Within the studied cases, we can consider cases of piston-cylinder ows within geometries similar to those of hermetic reciprocating compressors.This issue is mentioned in Part I. On the other hand, numerical simulations of different phenomena have been performed. More emphasis has been given to the natural convection ow within enclosures. This is explained in Part II. The case extensively studied has been the natural convection ow. The natural convection ow within enclosures has attracted the attention of many researchers due to its potential to model numerous applications of engineering interest, such as cooling of electronic devices, air ow in buildings, heat transfer in solar collectors, among others. The natural convection studies corresponding to the parallelepipedic enclosures can be classified into two elementary classes: i) heating from a horizontal wall (heating from below); ii) heating from a vertical wall. The characteristic example of the former case is the Rayleigh-B_enard ow, however this research is on the cavities heated from the side. This configuration is referred commonly as the differentially heated cavity.

Education of Murine NK Cells Requires Both cis and trans Recognition of MHC Class I Molecules.

Although NK cells use invariant receptors to identify diseased cells, they nevertheless adapt to their environment, including the presence of certain MHC class I (MHC-I) molecules. This NK cell education, which is mediated by inhibitory receptors specific for MHC-I molecules, changes the responsiveness of activating NK cell receptors (licensing) and modifies the repertoire of MHC-I receptors used by NK cells. The fact that certain MHC-I receptors have the unusual capacity to recognize MHC-I molecules expressed by other cells (trans) and by the NK cell itself (cis) has raised the question regarding possible contributions of the two types of interactions to NK cell education. Although the analysis of an MHC-I receptor variant suggested a role for cis interaction for NK cell licensing, adoptive NK cell transfer experiments supported a key role for trans recognition. To reconcile some of these findings, we have analyzed the impact of cell type-specific deletion of an MHC-I molecule and of a novel MHC-I receptor variant on the education of murine NK cells when these mature under steady-state conditions in vivo. We find that MHC-I expression by NK cells (cis) and by T cells (trans), and MHC-I recognition in cis and in trans, are both needed for NK cell licensing. Unexpectedly, modifications of the MHC-I receptor repertoire are chiefly dependent on cis binding, which provides additional support for an essential role for this unconventional type of interaction for NK cell education. These data suggest that two separate functions of MHC-I receptors are needed to adapt NK cells to self-MHC-I.

Cooperative binding of estrogen receptor to imperfect estrogen-responsive DNA elements correlates with their synergistic hormone-dependent enhancer activity.

The Xenopus vitellogenin (vit) gene B1 estrogen-inducible enhancer is formed by two closely adjacent 13 bp imperfect palindromic estrogen-responsive elements (EREs), i.e. ERE-2 and ERE-1, having one and two base substitutions respectively, when compared to the perfect palindromic consensus ERE (GGTCANNNTGACC). Gene transfer experiments indicate that these degenerated elements, on their own, have a low or no regulatory capacity at all, but in vivo act together synergistically to confer high receptor- and hormone-dependent transcription activation to the heterologous HSV thymidine kinase promoter. Thus, the DNA region upstream of the vitB1 gene comprising these two imperfect EREs separated by 7 bp, was called the vitB1 estrogen-responsive unit (vitB1 ERU). Using in vitro protein-DNA interaction techniques, we demonstrate that estrogen receptor dimers bind cooperatively to the imperfect EREs of the vitB1 ERU. Binding of a first receptor dimer to the more conserved ERE-2 increases approximately 4- to 8-fold the binding affinity of the receptor to the adjacent less conserved ERE-1. Thus, we suggest that the observed synergistic estrogen-dependent transcription activation conferred by the pair of hormone-responsive DNA elements of the vit B1 ERU is the result of cooperative binding of two estrogen receptor dimers to these two adjacent imperfect EREs.

The β-sliding clamp directs the localization of HdaA to the replisome in Caulobacter crescentus.

The initiation of chromosome replication is tightly regulated in bacteria to ensure that it takes place only once per cell cycle. In many proteobacteria, this process requires the ATP-bound form of the DnaA protein. The regulatory inactivation of DnaA (RIDA) facilitates the conversion of DnaA-ATP into replication-inactive DnaA-ADP, thereby preventing overinitiation. Homologues of the HdaA protein, together with the β-clamp of the DNA polymerase (DnaN), are required for this process. Here, we used fluorescence resonance energy transfer experiments to demonstrate that HdaA interacts with DnaN in live Caulobacter crescentus cells. We show that a QFKLPL motif in the N-terminal region of HdaA is required for this interaction and that this motif is also needed to recruit HdaA to the subcellular location occupied by the replisome during DNA replication. An HdaA mutant protein that cannot colocalize or interact with DnaN can also not support the essential function of HdaA. These results suggest that the recruitment of HdaA to the replisome is needed during RIDA in C. crescentus, probably as a means to sense whether chromosome replication has initiated before DnaA becomes inactivated. In addition, we show that a conserved R145 residue located in the AAA+ domain of HdaA is also needed for the function of HdaA, although it does not affect the interaction of HdaA with DnaN in vivo. The AAA+ domain of HdaA may therefore be required during RIDA after the initial recruitment of HdaA to the replisome by DnaN.