Showing papers by "University of Seville published in 2000"

Fluid flow induced by nonuniform ac electric fields in electrolytes on microelectrodes. I. Experimental measurements

Abstract: Under the influence of an ac electric field, electrolytes on planar microelectrodes exhibit fluid flow. The nonuniform electric field generated by the electrodes interacts with the suspending fluid through a number of mechanisms, giving rise to body forces and fluid flow. This paper presents the detailed experimental measurements of the velocity of fluid flow on microelectrodes at frequencies below the charge relaxation frequency of the electrolyte. The velocity of latex tracer particles was measured as a function of applied signal frequency and potential, electrolyte conductivity, and position on the electrode surface. The data are discussed in terms of a linear model of ac electroosmosis: the interaction of the nonuniform ac field and the induced electrical double layer.

Quantum Key Distribution in the Holevo Limit

Abstract: A theorem by Shannon and the Holevo theorem impose that the efficiency of any protocol for quantum key distribution, $E$, defined as the number of secret (i.e., allowing eavesdropping detection) bits per transmitted bit plus qubit, is $E\ensuremath{\le}1$. The problem addressed here is whether the limit $E\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ can be achieved. It is showed that it can be done by splitting the secret bits between several qubits and forcing Eve to have only a sequential access to the qubits, as proposed by Goldenberg and Vaidman. A protocol with $E\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ based on polarized photons and in which Bob's state discrimination can be implemented with linear optical elements is presented.

Host adapted serotypes of Salmonella enterica.

Abstract: Salmonella constitutes a genus of zoonotic bacteria of worldwide economic and health importance. The current view of salmonella taxonomy assigns the members of this genus to two species: S. enterica and S. bongori. S. enterica itself is divided into six subspecies, enterica , salamae , arizonae , diarizonae , indica , and houtenae , also known as subspecies I, II, IIIa, IIIb, IV, and VI, respectively. Members of Salmonella enterica subspecies enterica are mainly associated with warm-blooded vertebrates and are usually transmitted by ingestion of food or water contaminated by infected faeces. The pathogenicity of most of the distinct serotypes remains undefined, and even within the most common serotypes, many questions remain to be answered regarding the interactions between the organism and the infected host. Salmonellosis manifests itself in three major forms: enteritis, septicaemia, and abortion, each of which may be present singly or in combination, depending on both the serotype and the host involved. Although currently over 2300 serovars of Salmonella are recognized, only about 50 serotypes are isolated in any significant numbers as human or animal pathogens and they all belong to subspecies enterica . Of these, most cause acute gastroenteritis characterized by a short incubation period and a severe systemic disease in man or animals, characterized by septicaemia, fever and/or abortion, and such serotypes are often associated with one or few host species. It is the intention of this review to present a summary of current knowledge of these host-adapted serotypes of S. enterica . The taxonomic relationships between the serotypes will be discussed together with a comparison of the pathology and pathogenesis of the disease that they cause in their natural host(s). Since much of our knowledge on salmonellosis is based on the results of work on Typhimurium, this serotype will often be used as the baseline in discussion. It is hoped that an appreciation of the differences that exist in the way these serotypes interact with the host will lead to a greater understanding of the complex host–parasite relationship that characterizes salmonella infections.

Fluid flow induced by nonuniform ac electric fields in electrolytes on microelectrodes. II. A linear double-layer analysis

Abstract: Frequency-dependent fluid flow in electrolytes on microelectrodes subjected to ac voltages has recently been reported. The fluid flow is predominant at frequencies of the order of the relaxation frequency of the electrode-electrolyte system. The mechanism responsible for this motion has been termed ac electro-osmosis: a continuous flow driven by the interaction of the oscillating electric field and the charge at the diffuse double layer on the electrodes. This paper develops the basis of a theoretical approach to this problem using a linear double layer analysis. The theoretical results are compared with the experiments, and a good correlation is found.

Null and approximate controllability for weakly blowing up semilinear heat equations

Abstract: We consider the semilinear heat equation in a bounded domain of Rd , with control on a subdomain and homogeneous Dirichlet boundary conditions. We prove that the system is null-controllable at any time provided a globally defined and bounded trajectory exists and the nonlinear term f(y) is such that |f(s)| grows slower than |s|log3/2(1+|s|) as |s|→∞ . For instance, this condition is fulfilled by any function f growing at infinity like |s|logp(1+|s|) with 1 2 , null controllability does not hold. The problem remains open when f behaves at infinity like |s|logp(1+|s|) , with 3/2≤p≤2 . Results of the same kind are proved in the context of approximate controllability.

A protein complex containing Tho2, Hpr1, Mft1 and a novel protein, Thp2, connects transcription elongation with mitotic recombination in Saccharomyces cerevisiae

Abstract: Transcription‐induced recombination has been reported in all organisms from bacteria to mammals. We have shown previously that the yeast genes HPR1 and THO2 may be keys to the understanding of transcription‐associated recombination, as they both affect transcription elongation and hyper‐recombination in a concerted manner. Using a yeast strain that has the wild‐type THO2 gene replaced by one encoding a His 6 ‐HA‐tagged version, we have isolated an oligomeric complex containing four proteins: Tho2, Hpr1, Mft1 and a novel protein that we have named Thp2. We have reciprocally identified a complex containing Hpr1, Tho2 and Mft1 using anti‐Mft1 antibodies in immunoprecipitation experiments. The protein complex is mainly nuclear; therefore, Tho2 and Hpr1 are physically associated. Like hpr1Δ and tho2Δ cells, mft1Δ and thp2Δ cells show mitotic hyper‐ recombination and impaired transcription elongation, in particular, through the bacterial lacZ sequence. Hyper‐recombination conferred by mft1Δ and thp2Δ is only observed in DNA regions under transcription conditions. We propose that this protein complex acts as a functional unit connecting transcription elongation with the incidence of mitotic recombination.

Slant submanifolds in sasakian manifolds

Abstract: . In this paper, we show new results on slant submanifolds of analmost contact metric manifold. We study and characterize slant submanifolds of K-contact and Sasakian manifolds. We also study the special class of three-dimen-sional slant submanifolds. We give several examples of slant submanifolds.1991 Mathematics Subject Classification. 53C15, 53C40.0. Introduction. Slant immersions in complex geometry were defined by B.-Y.Chen as a natural generalization of both holomorphic immersions and totally realimmersions [2]. Examples of slant immersions into complex Euclidean spaces C 2 andC 4 were given by Chen and Tazawa [2, 4, 5], while slant immersions of Ka¨hler C-spaces into complex projective spaces were given by Maeda, Ohnita and Udagawa[9].In a recent paper [7], A. Lotta has introduced the notion of slant immersion of aRiemannian manifold into an almost contact metric manifold and he has provedsome properties of such immersions. A. Lotta and A. M. Pastore have obtainedexamples of slant submanifolds in the Sasakian-space-form R

Ac electrokinetics: a survey of sub-micrometre particle dynamics

Abstract: Particles suspended in fluid exhibit motion when subjected to ac electric fields. The applied field results in forces on both the particles and the fluid, the study of which is referred to as ac electrokinetics. The ac electrokinetic techniques can be used for the controlled manipulation and characterization of particles, and the separation of mixtures. For sub-micrometre particles, Brownian motion is important and strong electric fields are required to overcome these effects. Planar micro-electrode arrays, fabricated using semiconductor manufacturing processes, can generate electric fields of the required strength from low potentials over a wide range of frequencies. This paper reviews and discusses sub-micrometre particle dynamics under the influence of dielectrophoretic and electrohydrodynamic forces. New experimental observations of the movement of sub-micrometre particles are also presented.

Anatomical variations in the human paranasal sinus region studied by CT.

Abstract: A precise knowledge of the anatomy of the paranasal sinuses is essential for the clinician. Conventional radiology does not permit a detailed study of the nasal cavity and paranasal sinuses, and has now largely been replaced by computerised tomographic (CT) imaging. This gives an applied anatomical view of the region and the anatomical variants that are very often found. The detection of these variants to prevent potential hazards is essential for the use of current of endoscopic surgery on the sinuses. In the present work, we have studied the anatomical variants observed in the nasal fossae and paranasal sinuses in 110 Spanish subjects, using CT in the coronal plane, complemented by horizontal views. We have concentrated on the variants of the nasal septum, middle nasal concha, ethmoid unciform process and ethmoid bulla, together with others of lesser frequency. The population studied showed great anatomical variability, and a high percentage (67%) presented one or more anatomical variants. Discounting agger nasi air cells and asymmetry of both cavities of the sphenoidal sinus, which were present in all our cases, the variations most often observed were, in order, deviation of the nasal septum, the presence of a concha bullosa, bony spurs of the nasal septum and Onodi air cells.

Bibliographic guide to the foundations of quantum mechanics and quantum information

Abstract: This is a collection of references (papers, books, preprints, book reviews, Ph. D. thesis, patents, web sites, etc.), sorted alphabetically and (some of them) classified by subject, on foundations of quantum mechanics and quantum information. Specifically, it covers hidden variables (``no-go'' theorems, experiments), interpretations of quantum mechanics, entanglement, quantum effects (quantum Zeno effect, quantum erasure, ``interaction-free'' measurements, quantum ``non-demolition'' measurements), quantum information (cryptography, cloning, dense coding, teleportation), and quantum computation.

Immigration as a democratic challenge : citizenship and inclusion in Germany and the United States

Abstract: Immigration raises a number of important moral issues regarding access to the rights and privileges of citizenship. At present, immigrants to most Western democracies do not enjoy the same rights as citizens, and must satisfy a range of conditions before achieving citizenship. In this book, Ruth Rubio-Marin argues that this approach is unjust and undemocratic, and that more inclusive policies are required. In particular, she argues that liberal norms of justice and democracy require that there should be a time threshold after which immigrants (legal and illegal) should either be granted the full rights of citizenship, or should be awarded nationality automatically, without any conditions or tests. The author contrasts her position with the constitutional practice of two countries with rich immigration traditions: Germany and the United States. She concludes that judicial interpretations of both constitutions have recognised the claim for inclusion of resident aliens, but have also limited that claim.

Fair allocation of transmission power losses

Abstract: In this paper, the issue of how transmission power losses should be allocated is addressed. First, it is shown that existing methodologies allocate interaction components regardless of the size of the involved partners. Then, several alternatives to split those terms are suggested which somehow take into account the relative contribution of each transaction. Although the ideas are presented by resorting to unbundled branch power flows, the proposed schemes are applicable on a nodal basis. A real example is finally included showing that the total losses assigned to a transaction may differ significantly depending on the allocation methodology adopted.

An intelligent system for false alarm reduction in infrared forest-fire detection

Abstract: Forest fires cause many environmental disasters, creating economical and ecological damage as well as endangering people's lives. Heightened interest in automatic surveillance and early forest-fire detection has taken precedence over traditional human surveillance because the latter's subjectivity affects detection reliability, which is the main issue for forest-fire detection systems. In current systems, the process is tedious, and human operators must manually validate many false alarms. Our approach, the False Alarm Reduction system, proposes an alternative real-time infrared-visual system that overcomes this problem. The FAR system consists of applying new infrared-image processing techniques and artificial neural networks (ANNs), using additional information from meteorological sensors and from a geographical information database, taking advantage of the information redundancy from visual and infrared cameras through a matching process, and designing a fuzzy expert rule base to develop a decision function. Furthermore, the system provides the human operator with new software tools to verify alarms.

Lipids in pharmaceutical and cosmetic preparations

Abstract: In this paper, a review of the applications of lipids in the pharmaceutical field has been reported. In a first stage, different lipids used as excipients in cosmetics and medicines have been described. Many vegetable oils are used in this sense: almond oil, apricot oil, avocado oil, borage oil, coffee oil, safflower oil, etc.; from de animal source, fish oil and bird oil can be employed as excipients in cosmetical formulations. Fats and waxes may be also used for this purpose. A broad range of phospholipids are suitable for use in cosmetics, pharmaceuticals and diagnosis. These substances are used as vehicle for therapeutic substances, such as liposomes. Finally, a study of lipids, as a function of their biological activity, as active substances for the elaboration of pharmaceuticals, cosmetics or nutritional supplements, was carried out. Carotenoids, retinoids, tocopherols are used for their antioxidant properties, that are important to health and diagnostic medicine.

Production and biochemical characterization of an α-amylase from the moderate halophile Halomonas meridiana

Abstract: Extracellular amylase production by the moderate halophile Halomonas meridiana was optimized and the enzyme was characterized biochemically. The highest amylase production was achieved by growing H. meridiana cultures in media with 5% salts and starch, in the absence of glucose until the end of the exponential phase. The amylase exhibited maximal activity at pH 7.0, being relatively stable in alkaline conditions. Optimal temperature and salinity for activity were 37°C and 10% NaCl, respectively. Moreover, activity at salinity as high as 30% salts was detected. Maltose and maltotriose were the main end products of starch hydrolysis, indicating an α-amylase activity.

Correlation between nuclear melatonin receptor expression and enhanced cytokine production in human lymphocytic and monocytic cell lines.

Abstract: The report shows that melatonin enhances IL-2 and IL-6 production by two human lymphocytic (Jurkat) and monocytic (U937) cell lines via a nuclear receptor-mediated mechanism. Jurkat cells express nuclear (RZRalpha, RORalpha1 and RORalpha2) and membrane (mt1) melatonin receptors, and melatonin binds to Jurkat nuclei and membranes with the same affinity described for human peripheral blood mononuclear cells (PBMCs). Melatonin enhances IL-2 production by Jurkat cells activated by either phytohemagglutinin (PHA) or phorbol myristate acetate (PMA). PHA activation of Jurkat cells does not change the profile of melatonin receptor expression; on the contrary, PMA activation negatively regulates the mtl receptor. In the absence of the membrane receptor, melatonin still activates IL-2 production. U937 cells express only the mtl receptor. Although melatonin binds to both U937 nuclei and membranes, CGP 52608, a ligand of the nuclear receptor for melatonin, does not inhibit melatonin binding to U937 nuclei, suggesting that a protein other than the RZR/RORalpha receptor was involved in the process. In U937 cells, melatonin did not modify basal production of IL-6 or when activated by PMA plus LPS (lipopolysaccharide), a treatment that downregulates the expression of the mtl receptor. However, in U937 cells activated with IFN-gamma, which induces the expression of the RORgamma1 and RORalpha2 nuclear receptors and represses the expression of the mt1 receptor, melatonin can activate IL-6 production. These results show that the expression of nuclear melatonin receptor is sufficient for melatonin to activate cytokine production in human lymphocytic and monocytic cell lines.

HPLC determination of catechins and caffeine in tea.Differentiation of green, black and instant teas

Abstract: A simple and fast high performance liquid chromatographic method for five catechins and caffeine using an ODS column and a water-acetonitrile-formic acid mobile phase system was developed. The catechins (epicatechin, catechin, epigallocatechin, epigallocatechin gallate, epicatechin gallate) and caffeine were separated by an acetonitrile gradient within 20 min. The detection limit of the method was approximately 10 ng for all the compounds (by injecting 10 microL). Several green, black and instant teas were analysed using this method. By using the studied compounds as chemical descriptors, linear discriminant analysis was performed and complete differentiation of the green, black and instant teas was achieved.

Role of breakup processes in fusion enhancement of drip-line nuclei at energies below the Coulomb barrier

Abstract: We carry out realistic coupled-channel calculations for the ${}^{11}\mathrm{Be}{+}^{208}\mathrm{Pb}$ reaction in order to discuss the effects of breakup of the projectile nucleus on subbarrier fusion. We discretize in energy the particle continuum states, which are associated with the breakup process, and construct the coupling form factors to these states on a microscopic basis. The incoming boundary condition is employed in solving coupled-channel equations, which enables us to define the flux for complete fusion inside the Coulomb barrier. It is shown that complete fusion cross sections are significantly enhanced due to the couplings to the continuum states compared with the no-coupling case at energies below the Coulomb barrier, while they are hindered at above barrier energies.

Lower limits of Spartina densiflora and S. maritima in a Mediterranean salt marsh determined by different ecophysiological tolerances

Abstract: Summary 1 Salt marshes in south-west Spain are being invaded by Spartina densiflora, a South American introduction, although the native S. maritima still dominates many lower marshes. A transplant experiment was used to investigate the means by which physical and chemical factors may determine lower vegetation limits in the tidal frame. Both species were transplanted from a mid-level marsh to lower, unvegetated tidal flats. 2 The survival and growth of transplanted clumps and their constituent tillers were monitored on an elevational gradient. The photosynthetic competence of transplants was assessed by measurements of leaf gas exchange and the fast kinetics of chlorophyll fluorescence. Submergence period, salinity, redox potential and sulphide concentration in the sediment were also examined at the transplant sites. 3 Neither species survived for a year at the lowest transplant point (+ 1.04 m relative to Spanish Hydrographic Zero). At + 1.41 m elevation, S. maritima survived well but all clumps of S. densiflora died. At higher elevations (+ 1.46–1.67 m), clumps of both species had high survival rates. Tiller growth rates in surviving clumps of both species increased with elevation, but that of S. densiflora was more sensitive to low elevation. 4 S. maritima showed no impairment of photosynthetic performance, even at the lowest elevation; its rates of gas exchange were independent of elevation, as were its chlorophyll fluorescence parameters. In contrast, in S. densiflora the rate of CO2 uptake declined and stress to photosystem II (Fv/Fp) increased at lower elevations; both of these photosynthetic measurements were linearly related to sediment redox potential. Stomatal conductance did not vary with elevation. 5 S. maritima has a potentially wide elevational tolerance and an absolute lower limit substantially below that of S. densiflora. The progressively reduced growth and survival of S. densiflora at lower levels appear to result primarily from impairment of photosynthesis when root conditions are hypoxic. This effect is mediated through effects on the photochemical apparatus rather than on stomatal resistance to CO2 uptake. 6 These studies define lower limits to the fundamental niches of the two species in a Mediterranean-type salt marsh and thus provide a basis for future investigations of interactions between them. The correlation between chlorophyll fluorescence and long-term survival of S. densiflora suggests that this short-term measure may be a valuable tool.

Use of Real-Time PCR and Fluorimetry for Rapid Detection of Rifampin and Isoniazid Resistance-Associated Mutations in Mycobacterium tuberculosis

Abstract: Very fast amplification of DNA in small volumes can be continuously monitored with a rapid cycler that incorporates fluorimetric detection. Primers were designed to amplify a 157-bp fragment of the rpoB gene spanning codons 526 and 531 and a 209-bp fragment of the katG gene spanning codon 315 of Mycobacterium tuberculosis. Most mutations associated with resistance to rifampin (RMP) and isoniazid (INH) in clinical isolates occur in these codons. Two pairs of hybridization probes were synthesized; one in each pair was 3' labeled with fluorescein and hybridized upstream of the codon with the mutation; the other two probes were 5' labeled with LightCycler-Red 640. Each pair of probes recognized adjacent sequences in the amplicon. After DNA amplification was finished by using a LightCycler, the temperature at which the Red 640 probe melted from the product was determined in a 3-min melt program. Twenty M. tuberculosis clinical isolates susceptible to streptomycin, INH, RMP, and ethambutol and 36 antibiotic-resistant clinical M. tuberculosis isolates (16 resistant to RMP, 16 to INH, and 4 to both antimicrobial agents) were amplified, and the presence of mutations was determined using single-strand conformation polymorphism analysis, the LiQor automated sequencer, and the LightCycler system. Concordant results were obtained in all cases. Within 30 min, the LightCycler method correctly genotyped all the strains without the need of any post-PCR sample manipulation. Overall, this pilot study demonstrated that real-time PCR coupled to fluorescence detection is the fastest available method for the detection of RMP and INH resistance-associated mutations in M. tuberculosis clinical isolates.

Effect of Cigarette Smoking on Periodontal Status of Healthy Young Adults

Abstract: Background: It has been shown that tobacco is a significant risk factor for periodontal disease; however, there have been few studies on young populations where problems of general health can be discounted. The purpose of this study was to examine the influence of tobacco consumption on the periodontal condition of a young, healthy population. Methods: The study population consisted of 304 young Caucasian males (average age 19.38 ± 0.72 years) entering the Armed Forces. All the subjects completed a self-administered questionnaire on age, oral hygiene habits, previous dental examinations, and quantity and length of tobacco use. The periodontal examination consisted of the plaque index (PI); periodontal bleeding index (PBl); probing depth (PD); and clinical attachment level (CAL). One- and 2-way ANOVA was used to compare data recorded between smokers and nonsmokers. Results: Forty-six percent of subjects reported that they brushed their teeth at least once a day, but only 13% visited a dentist at least once...

Quantum key distribution without alternative measurements

Abstract: Entanglement swapping between Einstein-Podolsky-Rosen ~EPR! pairs can be used to generate the same sequence of random bits in two remote places. A quantum key distribution protocol based on this idea is described. The scheme exhibits the following features. ~a! It does not require that Alice and Bob choose between alternative measurements, therefore improving the rate of generated bits by transmitted qubit. ~b! It allows Alice and Bob to generate a key of arbitrary length using a single quantum system ~three EPR pairs!, instead of a long sequence of them. ~c! Detecting Eve requires the comparison of fewer bits. ~d! Entanglement is an essential ingredient. The scheme assumes reliable measurements of the Bell operator. PACS number~s!: 03.67.Dd, 03.67.Hk, 03.65.Bz The two main goals of cryptography are for two distant parties, Alice and Bob, to be able to communicate in a form that is unintelligible to a third party, Eve, and to prove that the message was not altered in transit. Both of these goals can be accomplished securely if both Alice and Bob are in possession of the same secret random sequence of bits, a ‘‘key’’ @1#. Therefore, one of the main problems of cryptography is the key distribution problem, that is, how do Alice and Bob, who initially share no secret information, come into the possession of a secret key, while being sure that Eve cannot acquire even partial information about it. This problem cannot be solved by classical means, but it can be solved using quantum mechanics @2#. The security of protocols for quantum key distribution ~QKD! such as the BennettBrassard 1984 ~BB84 !@ 2#, E91 @3#, B92 @4#, and other protocols @5,6#, is assured by the fact that while information stored in classical form can be examined and copied without altering it in any detectable way, it is impossible to do that when information is stored in unknown quantum states, because an unknown quantum state cannot be reliably cloned ~‘‘no-cloning’’ theorem @7#!. In these protocols security is assured by the fact that both Alice and Bob must choose randomly between two possible measurements. In this paper I introduce a QKD scheme which does not require that Alice and Bob choose between alternative measurements. This scheme is based on ‘‘entanglement swapping’’ @8‐10# between two pairs of ‘‘qubits’’ ~quantum two-level systems!, induced by a Bell operator measurement @11#. The Bell operator is a nondegenerate operator which acts on a pair of qubits i and j, and projects their combined state onto one of the four Bell states

Secretory responses of intact glomus cells in thin slices of rat carotid body to hypoxia and tetraethylammonium

Abstract: We have developed a thin-slice preparation of whole rat carotid body that allows us to perform patch-clamp recording of membrane ionic currents and to monitor catecholamine secretion by amperometry in single glomus cells under direct visual control. In normoxic conditions (PO2 ≈ 140 mmHg; 1 mmHg = 133 Pa), most glomus cells did not have measurable secretory activity, but exposure to hypoxia (PO2 ≈ 20 mmHg) elicited the appearance of a large number of spike-like exocytotic events. This neurosecretory response to hypoxia was fully reversible and required extracellular Ca2+ influx. The average charge of single quantal events was 46 ± 25 fC (n = 218), which yields an estimate of ≈140,000 catecholamine molecules per vesicle. Addition of tetraethylammonium (TEA; 2–5 mM) to the extracellular solution induced in most (>95%) cells tested (n = 32) a secretory response similar to that elicited by low PO2. Cells nonresponsive to hypoxia but activated by exposure to high external K+ were also stimulated by TEA. A secretory response similar to the responses to hypoxia and TEA was also observed after treatment of the cells with iberiotoxin to block selectively Ca2+- and voltage-activated maxi-K+ channels. Our data further show that membrane ion channels are critically involved in sensory transduction in the carotid body. We also show that in intact glomus cells inhibition of voltage-dependent K+ channels can contribute to initiation of the secretory response to low PO2.