Showing papers by "University of Seville published in 1998"

Biology of moderately halophilic aerobic bacteria

Abstract: The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms.

Ac electrokinetics: a review of forces in microelectrode structures

Abstract: Ac electrokinetics is concerned with the study of the movement and behaviour of particles in suspension when they are subjected to ac electrical fields. The development of new microfabricated electrode structures has meant that particles down to the size of macromolecules have been manipulated, but on this scale forces other than electrokinetic affect particles behaviour. The high electrical fields, which are required to produce sufficient force to move a particle, result in heat dissipation in the medium. This in turn produces thermal gradients, which may give rise to fluid motion through buoyancy, and electrothermal forces. In this paper, the frequency dependency and magnitude of electrothermally induced fluid flow are discussed. A new type of fluid flow is identified for low frequencies (up to 500 kHz). Our preliminary observations indicate that it has its origin in the action of a tangential electrical field on the diffuse double layer of the microfabricated electrodes. The effects of Brownian motion, diffusion and the buoyancy force are discussed in the context of the controlled manipulation of sub-micrometre particles. The orders of magnitude of the various forces experienced by a sub-micrometre latex particle in a model electrode structure are calculated. The results are compared with experiment and the relative influence of each type of force on the overall behaviour of particles is described.

Generation of Steady Liquid Microthreads and Micron-Sized Monodisperse Sprays in Gas Streams

Abstract: A new class of microscopic jet flows is here reported: for a certain range of physical parameters and geometrical configurations, a perfectly steady microscopic liquid thread can be formed by a laminar accelerating gas stream, eventually giving rise to a nearly monodisperse fine spray. Some interesting characteristics for many applications of this robust and versatile flow and related atomization technique are highlighted. Concentric multicomponent liquid threads can also be produced. A theoretical model is presented that shows agreement with experiments.

Hydrodynamics for granular flow at low density

Abstract: The hydrodynamic equations for a gas of hard spheres with dissipative dynamics are derived from the Boltzmann equation. The heat and momentum fluxes are calculated to Navier-Stokes order and the transport coefficients are determined as explicit functions of the coefficient of restitution. The dispersion relations for the corresponding linearized equations are obtained and the stability of this linear description is discussed. This requires consideration of the linear Burnett contributions to the energy balance equation from the energy sink term. Finally, it is shown how these results can be imbedded in simpler kinetic model equations with the potential for analysis of more complex states.

The thiobarbituric acid (TBA) reaction in foods: a review.

Abstract: The wide diffusion of 2-thiobarbituric acid (TBA) in the scientific literature is due to the TBA assay, or TBA test, which has been employed in the determination of autoxidative alterations of fats and oils. Two processes occur in autoxidation, generally: the free radical and the photo-oxidation mechanisms. The better studied is the free radical mechanism. The hydroperoxiepidioxides and bicycloendoperoxides are malonaldehyde (MDA) precursors. The absorption spectrum obtained with oxidized fatty foods is like the spectrum obtained when TBA and MDA react. However, during the secondary phase of the autoxidation process other aldehydes (alkanals, 2-alkenals, dienals) are formed which react with TBA, and they are responsible for off-flavors. Three kinds of pigments (yellow, orange, red adducts) are involved. Also, aromatic aldehydes, which constitute the flavor profile of diverse fruits and essential oils, form with TBA the characteristic arylidene-2-TBA acids. Other substances, such as ketones, ketosteroids, acids, esters, sugars, imides and amides, amino acids, oxidized proteins, pyridines, pyrimidines, and vitamins can react with TBA; they are named TBARS (substances that react with TBA), and form principally in meats and meat derivatives. Several organic or bio-organic acids, as shikimic and sorbic acids, react photometrically with TBA if a Malaprade reaction takes place before. A structural study of the red adduct TBA-MDA has been carried out.

Reactive Oxygen Intermediates, Molecular Damage, and Aging: Relation to Melatonin

Abstract: Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger and indirect antioxidant. In terms of its scavenging activity, melatonin has been shown to quench the hydroxyl radical, superoxide anion radical, singlet oxygen, peroxyl radical, and the peroxynitrite anion. Additionally, melatonin's antioxidant actions probably derive from its stimulatory effect on superoxide dismutase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase and its inhibitory action on nitric oxide synthase. Finally, melatonin acts to stabilize cell membranes, thereby making them more resistant to oxidative attack. Melatonin is devoid of prooxidant actions. In models of oxidative stress, melatonin has been shown to resist lipid peroxidation induced by paraquat, lipopolysaccharide, ischemia-reperfusion, L-cysteine, potassium cyanide, cadmium chloride, glutathione depletion, alloxan, and alcohol ingestion. Likewise, free radical damage to DNA induced by ionizing radiation, the chemical carcinogen safrole, lipopolysaccharide, and kainic acid are inhibited by melatonin. These findings illustrate that melatonin, due to its high lipid solubility and modest aqueous solubility, is able to protect macromolecules in all parts of the cell from oxidative damage. Melatonin also prevents the inhibitory action of ruthenium red at the level of the mitochondria, thereby promoting ATP production. In humans, the total antioxidative capacity of serum is related to melatonin levels. Thus, the reduction in melatonin with age may be a factor in increased oxidative damage in the elderly.

hpttg, a human homologue of rat pttg, is overexpressed in hematopoietic neoplasms. Evidence for a transcriptional activation function of hPTTG.

Abstract: We have isolated a human cDNA clone encoding a novel protein of 22 kDa that is a human counterpart of the rat oncoprotein PTTG. We show that the corresponding gene (hpttg) is overexpressed in Jurkat cells (a human T lymphoma cell line) and in samples from patients with different kinds of hematopoietic malignancies. Analysis of the sequence showed that hPTTG has an amino-terminal basic domain and a carboxyl-terminal acidic domain, and that it is a proline-rich protein with several putative SH3-binding sites. Subcellular fractionation studies show that, although hPTTG is mainly a cytosolic protein, it is partially localized in the nucleus. In addition we demonstrate that the acidic carboxyl-terminal region of hPTTG acts as a transactivation domain when fused to a heterologous DNA binding domain, both in yeast and in mammalian cells.

Conocimiento Profesional y Epistemología de los Profesores, II: Estudios Empíricos y Conclusiones.

Abstract: In a previous paper we discuss the theoretic and methodological framework which we have considered for studying the professional knowledge of the teachers. In this paper we present a review of some empirical studies with significance to the analysis of the scientific and didactic conceptions of the teachers. We also present a synthesis of the data obtained by the authors of these studies as well as of the most important conclusions.

Application of the Absolute Nodal Coordinate Formulation to Large Rotation and Large Deformation Problems

Abstract: There are three basic finite element formulations which are used in multibody dynamics. These are the floating frame of reference approach, the incremental method and the large rotation vector approach. In the floating frame of reference and incremental formulations, the slopes are assumed small in order to define infinitesimal rotations that can be treated and transformed as vectors. This description, however, limits the use of some important elements such as beams and plates in a wide range of large displacement applications. As demonstrated in some recent publications, if infinitesimal rotations are used as nodal coordinates, the use of the finite element incremental formulation in the large reference displacement analysis does not lead to exact modeling of the rigid body inertia when the structures rotate as rigid bodies. In this paper, a simple non-incremental finite element procedure that employs the mathematical definition of the slope and uses it to define the element coordinates instead of the infinitesimal and finite rotations is developed for large rotation and deformation problems. By using this description and by defining the element coordinates in the global system, not only the need for performing coordinate transformation is avoided, but also a simple expression for the inertia forces is obtained. The resulting mass matrix is constant and it is the same matrix that appears in linear structural dynamics. It is demonstrated in this paper that this coordinate description leads to exact modeling of the rigid body inertia when the structures rotate as rigid bodies. Nonetheless, the stiffness matrix becomes nonlinear function even in the case of small displacements. The method presented in this paper differs from previous large rotation vector formulations in the sense that the inertia forces, the kinetic energy, and the strain energy are not expressed in terms of any orientation coordinates, and therefore, the method does not require interpolation offinite rotations. While the use of the formulation is demonstrated using a simple planar beam element, the generalization of the method to other element types and to the three dimensional case is straightforward. Using the finite element procedure presented in this paper, beams and plates can be treated as isoparametric elements.

A novel yeast gene, THO2 , is involved in RNA pol II transcription and provides new evidence for transcriptional elongation‐associated recombination

Abstract: We have identified two novel yeast genes, THO1 and THO2 , that partially suppress the transcription defects of hpr1 Δ mutants by overexpression. We show by in vivo transcriptional and recombinational analysis of tho2 Δ cells that THO2 plays a role in RNA polymerase II (RNA pol II)‐dependent transcription and is required for the stability of DNA repeats, as previously shown for HPR1 . The tho2 Δ mutation reduces the transcriptional efficiency of yeast DNA sequences down to 25% of the wild‐type levels and abolishes transcription of the lacZ sequence. In addition, tho2 Δ causes a strong increase in the frequency of recombination between direct repeats (>2000‐fold above wild‐type levels). Some DNA repeats cannot even be maintained in the cell. This hyper‐recombination phenotype is dependent on transcription and is not observed in DNA repeats that are not transcribed. The higher the impairment of transcription caused by tho2 Δ, the higher the frequency of recombination of a particular DNA region. The tho2 Δ mutation also increases the frequency of plasmid loss. Our work not only identifies a novel yeast gene, THO2 , with similar function to HPR1 , but also provides new evidence for transcriptional blocks as a source of recombination. We propose that there is a set of proteins including Hpr1p and Tho2p, in the absence of which RNA pol II transcription is stalled or blocked, causing genetic instability.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide modulate endotoxin-induced IL-6 production by murine peritoneal macrophages.

Abstract: Vasoactive intestinal peptide (VIP) is a neuropeptide synthesized by immune cells that can modulate several immune aspects, including the function of cells involved in the inflammatory response, such as macrophages and monocytes. Production and release of cytokines by activated mononuclear phagocytes is an important event in the pathogenesis of ischemia-reperfusion injury. VIP has been shown to attenuate the deleterious consequences of this pathologic phenomenon. We have investigated the effects of VIP and PACAP38 on the production of interleukin-6 (IL-6), a proinflammatory cytokine, by endotoxin-activated murine macrophages. Both neuropeptides exhibit a dual effect on the IL-6 production by peritoneal macrophages. Whereas VIP and PACAP inhibit with similar dose-response curves the release of IL-6 from macrophages stimulated with a LPS dose range from 100 pg/mL to 10 microg/mL, both neuropeptides enhance IL-6 secretion in unstimulated macrophages and in macrophages stimulated with very low LPS concentrations (1-10 pg/mL). The inhibition on LPS-induced IL-6 production is specific, presumably mediated through a subtype of the PACAP-R. VIP and PACAP regulate the production of IL-6 at a transcriptional level. These results were correlated with an inhibition on both IL-6 expression and release in endotoxemic mice in vivo. These findings support the idea that in the absence of stimulation or in the presence of low doses of LPS, VIP and PACAP could play a role in immune system homeostasis. However, under toxicity conditions associated with high LPS doses, VIP and PACAP could act as protective mediators that regulate the excessive release of IL-6 in order to reduce inflammation or shock.

Stabilized capillary microjet and devices and methods for producing same

Abstract: The invention is directed to a stable capillary microjet and a monodisperse aerosol formed when the microjet dissociates. A variety of devices and methods are disclosed which allow for the formation of a stream of a first fluid (e.g. a liquid) characterized by forming a stable capillary microjet over a portion of the stream wherein the microjet portion of the stream is formed by a second fluid (e.g. a gas). The second fluid is preferably in a different state from the first fluid-liquid-gas or gas-liquid combinations. However, the first and second fluids may be two different fluids in miscible in each other. The stable capillary microjet comprises a diameter dj at a given point A in the stream characterized by formula (I): wherein dj is the diameter of the stable microjet, ≅ indicates approximately equally to where an acceptable margin of error is ± 10 %, ς1 is the density of the liquid and ΔPg is change in second fluid pressure from the second fluid pressure at a low velocity region (feeding region) upstream of point A to the second fluid pressure at point A.

Upper semicontinuity of attractors for small random perturbations of dynamical systems

Abstract: The relationship between random attractors and global attractors for dynamical systems is studied. If a partial differential equation is perturbed by an E-small random term and certain hypotheses are satisfied, the upper semicontinuity of the random attractors is obtalned as c goes to zero. The results are applied to the Navier-Stokes equations and a problem of reaction-diffusion type, both perturbed by an additive white noise.

Fuel injection nozzle and method of use

Abstract: Atomized particles within a desired size range (eg, 1 micron to about 5 microns) are produced from two immiscible fluids, the first a fuel source containing the formulation to be atomized, and a second fluid source which is contained in a pressure chamber surrounding at least the area where the first liquid is to be provided The invention provides a method for the formation of small, relatively uniform fuel particles for use in internal combustion engines and a nozzle-type apparatus for providing the particles to a combustion chamber

A tutorial on wavelets from an electrical engineering perspective. I. Discrete wavelet techniques

Abstract: The objective of this paper is to present the subject of wavelets from a filter-theory perspective, which is quite familiar to electrical engineers. Such a presentation provides both physical and mathematical insights into the problem. It is shown that taking the discrete wavelet transform of a function is equivalent to filtering it by a bank of constant-Q filters, the non-overlapping bandwidths of which differ by an octave. The discrete wavelets are presented, and a recipe is provided for generating such entities. One of the goals of this tutorial is to illustrate how the wavelet decomposition is carried out, starting from the fundamentals, and how the scaling functions and wavelets are generated from the filter-theory perspective. Examples (including image compression) are presented to illustrate the class of problems for which the discrete wavelet techniques are ideally suited. It is interesting to note that it is not necessary to generate the wavelets or the scaling functions in order to implement the discrete wavelet transform. Finally, it is shown how wavelet techniques can be used to solve operator/matrix equations. It is shown that the "orthogonal-transform property" of the discrete wavelet techniques does not hold in numerical computations.

The cubic-tetragonal phase transition in strontium titanate: excess specific heat measurements and evidence for a near-tricritical, mean field type transition mechanism

Abstract: The transition between the cubic and tetragonal phase in shows an excess specific heat of . Comparison between the temperature evolution of the excess entropy and the structural order parameter Q shows within experimental errors . The apparent order parameter exponent was confirmed and analysed using a Landau-type expression for the excess Gibbs free energy with A = 0.70 J , B = 31.22 J , C = 42.17 J , K and K. The closeness to the tricritical point is seen by B < C; all thermodynamic data between 85 K and could be described selfconsistently using this approach although small deviations cannot be excluded in a temperature interval of less than 1 K around and a small tail of excess entropy at .

Device and method for creating spherical particles of uniform size

Abstract: Spherical particles having a size on the order of 0.1 to 100 microns in size are created by systems and devices of several types. The device includes a source of a stream of gas which is forced through a liquid held under pressure in a pressure chamber with an exit opening therein. The stream of gas surrounded by the liquid in the pressure chamber flows out of an exit orifice of the chamber into a liquid thereby creating a monodispersion of bubbles with substantially uniform diameter. The bubbles are small in size and produced with a relatively small amount of energy relative to comparable systems. Small particles of liquid may also be produced. Applications of the technology range from oxygenating sewage with monodispersions of bubbles to inhalation therapy with monodisperse aerosol dispersions of pharmaceutically active drugs.

Outer Membrane Profiles of Clonally Related Klebsiella pneumoniae Isolates from Clinical Samples and Activities of Cephalosporins and Carbapenems

Abstract: Fifteen isolates of Klebsiella pneumoniae producing extended-spectrum beta-lactamases (ESBLs) isolated during a nosocomial outbreak were studied. The strains belonged to the same clonal type, as shown by pulsed-field gel electrophoretic analysis of chromosomal DNA. All the isolates were resistant to extended-spectrum cephalosporins, aztreonam, gentamicin, and fluoroquinolones and were susceptible to carbapenems, tobramycin, netilmicin, and amikacin. None of the isolates expressed the OmpK36 porin. Eight isolates, for which the MICs of cefoxitin were > or = 64 micrograms/ml, showed a diminished level or no expression of a 35-kDa porin. The MICs of meropenem, cefotaxime, and cefpirome were three to eight times higher for porin-deficient isolates than for isolates expressing the 35-kDa porin, but the MICs of imipenem increased two times for porin-deficient isolates compared to those for isolates expressing the porin. This MIC increase reverted to a level similar to that for the parental strain when porin-deficient isolates were transformed with the gene coding for the K. pneumoniae porin OmpK36. It is concluded that the high level of resistance to cefoxitin and the increase in the MICs of meropenem, cefotaxime, and cefpirome for the ESBL-producing K. pneumoniae isolates studied are associated with porin deficiency.

Device and method for creating dry particles

Abstract: Atomized particles within a desired size range (e.g., 1 micron to about 5 microns) are produced from two immiscible fluids, a first fluid source containing the formulation to be atomized, and a second fluid source which is contained in a pressure chamber surrounding at least the area where the first liquid is to be provided. Upon presentation of the first fluid source to the second, the second fluid is forced out of an opening positioned in front of the flow path of the formulation. The first and second fluids interact dynamically to form a stable capillary microjet, which in turn results in the formation of a focusing funnel at the opening. Formulation passing through this a focusing funnel will atomize upon exiting the opening of the pressurized chamber without physically contacting the perimeter of the opening.

Anti-oxidant mechanisms involved in gastroprotective effects of quercetin

Abstract: The anti-ulcerogenic and anti-oxidant effects of various flavonoids have been frequently reported. We investigated the cytoprotective properties of quercetin, a natural flavone, in gastric mucosal injury induced by 50% ethanol, since in this experimental model the pathogenesis of the lesions has been related with production of reactive oxygen species. The involvement of neutrophil infiltration and the capacity of this flavonoid to restrain the oxidative process produced in the gastric tissue after ethanol administration were also investigated. Oral pretreatment with the highest dose of quercetin (200 mg/kg), 120 min before absolute ethanol was the most effective anti-ulcer treatment. Thiobarbituric acid reactive substances in the gastric mucosa, an index of lipid peroxidation, were increased by ethanol injury, but the increase was inhibited by the administration of 200 mg/kg of quercetin. This dose also induced a significant enhancement in the levels of mucosal non-protein SH compounds (important anti-oxidant agents) and in glutathione peroxidase activity. Exposure of the gastric mucosa to 50% ethanol induced a significant increase in myeloperoxidase activity, an index of neutrophil infiltration. However, quercetin was not able to modify the increase in enzymatic activity generated by the necrotizing agent. The activity of superoxide dismutase enzyme involved in several antioxidant processes was also not significantly modified after quercetin treatment. These results suggest that the anti-ulcer activity of quercetin in this experimental model could be partly explained by the inhibition of lipid peroxidation, through decrease of reactive oxygen metabolites. However, the inhibition of neutrophil infiltration or the increase of superoxide dismutase activity does not appear to be involved in gastroprotective effect of this flavonoid.