Showing papers by "Rovira i Virgili University published in 2002"
TL;DR: A formalism is presented that is able to cope simultaneously with the problem of search and the congestion effects that arise when parallel searches are performed, and expressions for the average search cost are obtained both in the presence and the absence of congestion.
Abstract: The problem of searchability in decentralized complex networks is of great importance in computer science, economy, and sociology. We present a formalism that is able to cope simultaneously with the problem of search and the congestion effects that arise when parallel searches are performed, and we obtain expressions for the average search cost both in the presence and the absence of congestion. This formalism is used to obtain optimal network structures for a system using a local search algorithm. It is found that only two classes of networks can be optimal: starlike configurations, when the number of parallel searches is small, and homogeneous-isotropic configurations, when it is large.
538 citations
TL;DR: In patients with ventilator-associated pneumonia, type-III-secreting isolates were associated with worse clinical outcomes, suggesting that this secretion system plays an important role in human disease.
Abstract: Objective: Pseudomonas aeruginosa is a frequent cause of ventilator-associated pneumonia. Recent evidence suggests that production of type III secretion proteins is correlated with increased pathogenicity in both cellular and animal models of infection. The objective of this study was to determine whether this system contributes to disease severity in humans with ventilator-associated pneumonia. Design: Retrospective pilot cohort study. Setting: University hospital. Patients: Thirty-five mechanically ventilated patients with bronchoscopically confirmed ventilator-associated pneumonia caused by P. aeruginosa. Measurements and Main Results: Ventilator-associated pneumonia was categorized as severe (patients died or had a recurrence of their pneumonia despite appropriate antibiotic therapy) or mild (patients uneventfully recovered from their pneumonia). The type III secretion genotypes and phenotypes of isolates cultured from the patients with ventilator-associated pneumonia were determined. Whereas every examined isolate harbored type III secretion genes, only 27 (77%) were capable of secreting detectable amounts of type III proteins in vitro. Twenty-two (81%) of the patients infected with these 27 isolates had severe disease. Of the eight isolates that did not secrete type III proteins, only three (38%) were cultured from patients with severe disease. Thus, infection with a type-III-secreting isolate correlated with severe disease (p <.05). In vitro assays indicated that ExoU, the type III effector protein most closely linked to mortality in animal models, was secreted in detectable amounts in vitro by 10 (29%) of the 35 examined isolates. Nine (90%) of these 10 isolates were cultured from patients with severe disease (p <.05 when compared with the nonsecreting isolates). In contrast, ExoS was secreted by 16 (46%) of the 35 examined isolates. Twelve (75%) of these 16 isolates were cultured from patients with severe disease (p =.14 when compared with the nonsecreting isolates). Conclusions: In patients with ventilator-associated pneumonia, type-III-secreting isolates were associated with worse clinical outcomes, suggesting that this secretion system plays an important role in human disease. Our findings support the hypothesis that antibodies targeted against these proteins may be useful as adjunctive therapy in intubated patients with P. aeruginosa colonization or infection.
392 citations
30 Sep 2002
TL;DR: This work presents one such PH (none was known so far) which can be proven secure against known-cleartext attacks, as long as the ciphertext space is much larger than the cleartext space.
Abstract: Privacy homomorphisms (PHs) are encryption transformations mapping a set of operations on cleartext to another set of operations on ciphertext. If addition is one of the ciphertext operations, then it has been shown that a PH is insecure against a chosen-cleartext attack. Thus, a PH allowing full arithmetic on encrypted data can be at best secure against known-cleartext attacks. We present one such PH (none was known so far) which can be proven secure against known-cleartext attacks, as long as the ciphertext space is much larger than the cleartext space. Some applications to delegation of sensitive computing and data and to e-gambling are briefly outlined.
305 citations
TL;DR: Taking into account the recent interest of tungstate as a new potential oral antidiabetic agent, an exhaustive evaluation of its toxicity in mammals is clearly necessary.
Abstract: Tungstate is an oxyanion that has biological similarities to vanadate. In recent years, a number of studies have shown the antidiabetic effects of oral tungstate in animal models of diabetes. However, because of the tissue accumulation and potential toxicity derived from chronic administration of vanadium and tungsten compounds, the pharmacological use of vanadate or tungstate in the treatment of diabetes is not necessarily exempt from concern. In the context of a potential use in the treatment of human diabetes mellitus, the most relevant toxic effects of vanadium derivatives are reviewed and compared with those reported for tungsten. Hematological and biochemical alterations, loss of body weight, nephrotoxicity, immunotoxicity, reproductive and developmental toxicity, and behavioral toxicity have been reported to occur following exposure to vanadium compounds. Moreover, vanadium also has a mitogenic activity affecting the distribution of chromosomes during mitosis and inducing aneuploidy-related end points. In contrast to vanadate, studies about the toxic effects of tungstate are very scant. Early investigations in cats, rabbits, dogs, mice, and rats showed that tungstate was less toxic than vanadate when given intravenously. Although in vitro investigations showed a direct effect of tungstate on the embryo and fetus of mice at concentrations similar to those causing effects in vivo, information on the potential cellular toxicity of tungstate is particularly scarce. Taking into account the recent interest of tungstate as a new potential oral antidiabetic agent, an exhaustive evaluation of its toxicity in mammals is clearly necessary.
228 citations
TL;DR: Yeast colonies isolated from vineyard and cellar substrates were analysed and Saccharomyces cerevisiae was not the major species isolated as Candida sorbosa represented 76% of the species isolated.
207 citations
TL;DR: In this article, the authors studied the production of furfural by acid hydrolysis of olive stones, which in Spain are an abundant lignocellulosic residue derived from the extraction of olive oil.
Abstract: We studied the production of furfural by acid hydrolysis of olive stones, which in Spain are an abundant lignocellulosic residue derived from the production of olive oil. We focused on the hydrolysis in dilute sulfuric acid (0.05 to 0.250 mol l −1 ), at high temperature (220–240°C), and short reaction times, of a few minutes at the most. The experimental study was performed in a tubing-bomb reactor system that approximately reproduces the temperature profiles obtained in a continuous tubular reactor. We obtained maximum furfural yields ranging from 50% to 65% of the potential depending on acid concentration and temperature.
181 citations
TL;DR: This work focuses on the properties of the order parameter, the susceptibility, and the time correlations when approaching the critical point in the dynamical properties of a collection of models for communication processes, characterized by a single parameter xi.
Abstract: We study the dynamical properties of a collection of models for communication processes, characterized by a single parameter xi representing the relation between information load of the nodes and its ability to deliver this information. The critical transition to congestion reported so far occurs only for xi=1. This case is well analyzed for different network topologies. We focus on the properties of the order parameter, the susceptibility, and the time correlations when approaching the critical point. For xi 1, the transition to congestion is discontinuous and congestion nuclei arise.
174 citations
TL;DR: The concentrations of aluminium (Al), arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), tin (Sn), thallium (Tl), vanadium (V), and zinc (Zn) were determined in soil samples collected in Alcala de Henares (Madrid, Spain) as discussed by the authors.
173 citations
TL;DR: This study refutes the previous explanations for the reduction in plasma tHcy known to occur in pregnancy, namely, folic acid supplementation, hemodilution, and a decrease in serum albumin and suggests that the changes may be endocrine-based.
137 citations
15 Aug 2002
TL;DR: In this article, a tissue P system is proposed, which processes symbols in a multiset rewriting sense, in a net of cells similar to a neural net, each cell has a finite state memory, processes multisets of symbol-impulses, and can send impulses ("excitations") to the neighboring cells.
Abstract: Starting from the way the inter-cellular communication takes place by means of protein channels and also from the standard knowledge about neuron functioning, we propose a computing model called a tissue P system, which processes symbols in a multiset rewriting sense, in a net of cells similar to a neural net. Each cell has a finite state memory, processes multisets of symbol-impulses, and can send impulses ("excitations") to the neighboring cells. Such cell nets are shown to be rather powerful: they can simulate a Turing machine even when using a small number of cells, each of them having a small number of states. Moreover, in the case when each cell works in the maximal manner and it can excite all the cells to which it can send impulses, then one can easily solve the Hamiltonian Path Problem in linear time. A new characterization of the Parikh images of ET0L languages are also obtained in this framework.
129 citations
TL;DR: The basic principles of method validation and the different ways to validate a methodology, by inter-laboratory comparison or performing an in-house validation, are described.
Abstract: In this paper we shall discuss the concept of method validation, describe the various elements and explain its close relationship with fitness for purpose. Method validation is based on the assumption that a series of requirements are fulfilled and we shall explain how these requirements are selected, the way in which evidence is supplied and what work has to be carried out in the laboratory. The basic principles of method validation and the different ways to validate a methodology, by inter-laboratory comparison or performing an in-house validation, are also described.
TL;DR: It turns out that systems with promoters/inhibitors achieve universal computations without using the standard “auxiliary” features of membrane systems, for instance, without using catalysts.
Abstract: The computational model of membrane computing (formalized through membrane systems, also called P systems) is based on the way that biological membranes define compartments, each having its set of molecules and (enzymes enhancing) reactions, with compartments communicating through the transport of molecules through membranes. In this paper we augment the basic model of membrane systems with promoters and inhibitors, which formalize the reaction enhancing and reaction prohibiting roles of various substances (molecules) present in cells. We formalize such membrane systems with promoters/inhibitors and investigate their basic properties. In particular we establish universality results, i.e., we provide characterizations of recursively enumerable sets (of vectors of natural numbers) using these systems. It turns out that systems with promoters/inhibitors achieve universal computations without using the standard “auxiliary” features of membrane systems, for instance, without using catalysts.
TL;DR: A new class of P systems that use simple evolution rules (classical evolution rules without communication targets) and symport/antiport rules (for communication) are proposed.
Abstract: We propose a new class of P systems that use simple evolution rules (classical evolution rules without communication targets) and symport/antiport rules (for communication).
TL;DR: In this paper, the production of carboxymethylcellulose (CMC) from several bleached cellulose pulps obtained from non-wood species was explored, and the degree of substitution (DS) of CMC was found to be dependent upon the source of cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second.
Abstract: This paper explores the production of carboxymethylcellulose (CMC) fromseveral bleached cellulose pulps obtained from non-wood species. The chemicalcomposition (α-cellulose, hemicellulose and lignin content), the degreeofswelling, viscosity, solubility in concentrated NaOH and crystallinity ofsoda/AQ cellulose pulps from abaca, jute, sisal, linen and Miscanthussinensis were determined. The pulps were carboxymethylated by one andtwo successive reaction steps in aqueous medium under identical conditions. Thedegree of substitution (DS) of CMC was found to be dependent upon the source ofthe cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second. The molar mass of CMC was found to bedependent on the initial intrinsic viscosity of the cellulose pulp. The weightaverage molar mass of our CMCs ranged from 1.5 × 105 to2.8 × 105. Increasing the DS up to 2 improved the CMC solubility, butviscosity slightly decreased due to a slight degradation of the polymer.
TL;DR: The theoretical developments of DNA computing are demonstrated by discussing a number of selected topics and an introduction to the basic structure of DNA and the basic DNA processing tools is given.
TL;DR: In this paper, a new approach is developed for estimating the limit of detection in second-order bilinear calibration with the generalized rank annihilation method (GRAM), which is based on recently derived expressions for prediction variance and bias.
TL;DR: While no significant effects of Al exposure between groups could be detected on behavior, the total number of synapses decreased with age and Al exposure, and the percentage of perforated synapses significantly increased in old Al-loaded rats.
Abstract: Aluminum (Al) is potentially toxic for mammals. In contrast to well documented Al neurotoxicity, neurobehavioral studies of Al in rodents have generally not produced robust or consistent results. In the present study, 16 young male (21 days old) and 16 old male (18 months) rats were exposed to 0 (control group) and 100 mg/kg/day of Al administered as Al nitrate nonahydrate in drinking water concurrently with citric acid (356 mg/kg/day) for a period of 100 days. At the end of the exposure period, rats were evaluated for motor activity in an open-field apparatus and learning in a passive avoidance test. After behavioral testing, rats were sacrificed and brain samples were collected to determine Al concentrations and to study synapses in the left CA1 fields of hippocampal formation. While no significant effects of Al exposure between groups could be detected on behavior, the total number of synapses decreased with age and Al exposure. In turn, the percentage of perforated synapses significantly increased in old Al-loaded rats.
TL;DR: The lack of differences between the current levels of metals and organic substances and the respective baseline concentrations, together with the absence of differences depending on the workplace indicate that the potential exposure of HWI workers to the analyzed compounds was insignificant.
Abstract: Objectives. To determine blood and urine concentrations of a number of metals and organic substances in workers at a hazardous-waste incinerator (HWI) 1 year after regular operations in the facility, and to compare these concentrations with the baseline levels. Methods. The employees were divided into three groups according to their workplaces. Plasma analyses of hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs 28, 52, 101, 138, 153 and 180) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and urinary analyses of 2,4- and 2,5-dichlorophenol (DCP), 2,4,5- and 2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP) and 1-hydroxypyrene (1-HP) were carried out. The blood concentrations of beryllium, manganese, mercury and lead, and the urine levels of cadmium, chromium, nickel and vanadium were also determined. Results. The current plasma HCB, PCB and PCDD/F levels, and the urine levels of chlorophenols (CLPs) and 1-HP did not show significant differences between workplace groups or the baseline concentrations. Moreover, no significant differences between metal levels could be observed. Discussion and conclusion. The lack of differences between the current levels of metals and organic substances and the respective baseline concentrations, together with the absence of differences depending on the workplace indicate that the potential exposure of HWI workers to the analyzed compounds was insignificant. According to these results, 1 year of potential exposure to the above metals and organic substances would not mean any specific health problem for the workers at the HWI.
TL;DR: In this article, a life cycle inventory analysis was conducted to assess the environmental load, specifically CO2 (fossil) emissions and global warming potential (GWP), associated to the production of hydrogen by the steam reforming of hydrocarbon feedstocks (methane and naphtha) and vegetable oils (rapeseed oil, soybean oil and palm oil).
TL;DR: The current results show that the cement plant has a low impact on the metal and PCDD/F levels in the environment under direct influence of the facility.
TL;DR: Unique features of LHS method are utilized to create hybrid data sets and evaluate their performance relative to rank swapping and multivariate microaggregation using generalized information loss and disclosure risk measures.
Abstract: In previous work by Domingo-Ferrer et al., rank swapping and multivariate microaggregation has been identified as well-performing masking methods for microdata protection. Recently, Dandekar et al. proposed using synthetic microdata, as an option, in place of original data by using Latin hypercube sampling (LHS) technique. The LHS method focuses on mimicking univariate as well as multivariate statistical characteristics of original data. The LHS-based synthetic data does not allow one to one comparison with original data. This prevents estimating the overall information loss by using current measures. In this paper we utilize unique features of LHS method to create hybrid data sets and evaluate their performance relative to rank swapping and multivariate microaggregation using generalized information loss and disclosure risk measures.
TL;DR: The present results corroborate that for MSW incinerators with modern technologies, human PCDD/F exposure is mainly due to background contamination.
Abstract: Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) by municipal solid waste (MSW) incinerators cause concern to the populations living in the vicinity of these facilities. In this study, the health risks of PCDD/F exposure were assessed for adults and children living 500 and 1,000 m from the MSW incinerator. A comparative analysis was performed before (1998) and after (2000) pronounced decreases in PCDD/F air emissions from the stack were noted as a consequence of technical improvements in the facility. At 500 m, total environmental exposure to PCDD/Fs diminished from 5.102 × 10−5 to 1.271 × 10−5 ng I-TEQ/kg/day for adults, and from 8.131 × 10−5 to 2.656 × 10−5 ng I-TEQ/kg/day for children, which means a reduction of 75.1% for adults and 67.3% for children between 1998 and 2000. At 1,000 m, total environmental PCDD/F exposure diminished from 4.087 × 10−5 ng I-TEQ/kg/day in 1998 to 0.995 × 10−5 ng I-TEQ/kg/day in 2000 and from 6.294 × 10−5 ng I-TEQ/kg/day in 1998 to 1.983 × 10−5 ng I-TEQ/kg/day in 2000 for adults and children, respectively. However, these reductions are almost imperceptible compared with the contribution of dietary intake of PCDD/F to total exposure to these contaminants. The present results corroborate that for MSW incinerators with modern technologies, human PCDD/F exposure is mainly due to background contamination.
Journal Article•
TL;DR: This research is done mainly on the binary alphabet, and identifies a family of binary words, refered to as ``palindromic amiable'', such that two such words are palindromed if and only if they have the same image by the Parikh matrix mapping.
Abstract: In this paper we investigate the injectivity of the Parikh matrix mapping This research is done mainly on the binary alphabet We identify a family of binary words, refered to as ``palindromic amiable'', such that two such words are palindromic amiable if and only if they have the same image by the Parikh matrix mapping Some other related problems are discussed, too
TL;DR: Although after introduction of the technical improvements in the MSWI a notable reduction in the levels of PCDD/Fs in soil and vegetation has been noted, the median decreases have not been as great as it could be expected according to the very pronounced reductions in PC DD/F emissions from the stack.
TL;DR: In this paper, a large-eddy simulation (LES) technique was used for the simulations at two high Rayleigh numbers (Ra =10 6 and 10 8 ) and results were seen to be in agreement with direct numerical simulations (DNS) reported in the literature.
TL;DR: In this paper, the development of anxiety, from the pre-conception stage to the postpartum stage, in 96 women who wanted to have children, was evaluated with the State-Anxiety Inventory Questionnaire for Adults (STAI).
TL;DR: In this article, the rheological behavior of carboxymethylcelulloses (CMC) derived after one and two successive steps from different non-woodbleached cellulose pulps was investigated.
Abstract: This paper concerns the rheological behavior of carboxymethylcelulloses(CMC) derived after one and two successive steps from different non-woodbleached cellulose pulps. CMC rheological characterization was achieved in0.1M NaCl solution, as a function of polymer concentration. Theevidence of a critical concentration (C* < 1 g/L) is discussedfromsteady shear and dynamic experiments. Rheological properties of the CMC werefound to depend on the cellulose source reactivity and on their degree ofsubstitution (DS). Higher molecular weight of initial cellulose was accompaniedby higher apparent intrinsic viscosity of the CMC produced. Depending on theCMCconcentration and on the degree of etherification, the system behaves as asolution or as a gel. In the case of abaca CMC sample, it is shown that afteronly one step of chemical modification and above a polymer concentration of20 g/L, the system behaves as a gel. The gel behavior was studied asafunction of temperature. In the temperature range from 25 to 45°C, the rheological behavior was found to remain almostconstant due to the existence of dispersed swollen aggregates. This unusualcharacteristic represents an advantage for applications such as oil recovery inthe petroleum industry, where viscosity of the recovered fluid should not diminishwith temperature.
01 Jan 2002
TL;DR: Brockbank and McGill as mentioned in this paper present a set of instrumentos practicos for aquellos profesores de educacion superior que busquen una nueva experience of aprendizaje, tanto for sus estudiantes como for ellosmismos.
Abstract: El libro ofrece instrumentos practicos para aquellos profesores de educacion superior que busquen una nueva experiencia de aprendizaje, tanto para sus estudiantes como para ellosmismos El libro trata un tipo de aprendizaje real, genuino, relevante para el que aprende, ahora y en el futuro Este tipo de aprendizaje se extiende a las relaciones, trabajo y carrera, comunidad, sociedad y, en general, al mundo del que aprende Anne Brockbank e Ian McGill proporcionan un apoyo directo a los profesores que desean moverse de la ensenanza tradicional a la facilitacion del aprendizaje, transformando, de esta forma, las relaciones entre profesor y alumnos o entre los propios alumnos Las tecnologias de la informacion, aunque utiles, no son un sustituto del metodo de aprendizaje propuesto en el libro; la facilitacion permite a los que aprenden usar la tecnologia de forma complementaria, como parte del proceso de aprendizaje El libro permite a los profesores adquirir conocimiento sobre el proceso de facilitacion e incrementar sus habilidades como facilitadores Los autores enfatizan la importancia del dialogo reflexivo entre colegas y alumnos y exploran la importancia de la emocion, la accion y la cognicion en el aprendizaje Al mismo tiempo, examinan como pueden los profesores crear las mejores condiciones para el aprendizaje reflexivo
TL;DR: An accepting device based on the communication between finite automata working in parallel is introduced andHomomorphical characterizations of recursively enumerable languages are obtained starting from languages recognized by all variants of parallel communicating finite Automata systems having at most three components.
Abstract: An accepting device based on the communication between finite automata working in parallel is introduced. It consists of several finite automata working independently but communicating states to each other by request. Several variants of parallel communicating finite automata systems are investigated from their computational power point of view. We prove that all of them are at most as powerful as multi-head finite automata. Homomorphical characterizations of recursively enumerable languages are obtained starting from languages recognized by all variants of parallel communicating finite automata systems having at most three components. We present a brief comparison with the parallel communicating grammar systems. Some remarks suggesting that these devices might be mildly context-sensitive ones as well as a few open problems and directions for further research are also discussed.
TL;DR: In this article, the authors examined predicting factors and depressive antecedents of depression in early adulthood and determined differences by sex, finding that depressive symptoms were more significant in girls than in boys.
Abstract: This study prospectively examined predicting factors and depressive antecedents of depression in early adulthood and determined differences by sex. 199 adolescents aged 11–12 from the general community were followed up annually for 4 years and reassessed at 18 years of age. Sociodemographic data, depressive symptomatology, anxiety level, personality dimensions, self-esteem, academic aptitude and pubertal development were reported throughout this period and tested as possible risk variables of depression. At 18, depression was diagnosed using ICD-10 criteria. Of the cases of major depression (MDD) at eighteen, 30 % had been diagnosed as MDD between 12 and 14 years of age. Of the cases of MDD at eighteen, 80 % had had depressive symptomatology between the ages of 11 and 14. Subclinical scores in the Children's Depression Inventory (CDI) were early indicators of long-term risk. Gender differences were found in the risk pattern; depressive symptoms were more significant in girls than in boys. In boys, early anxious symptomatology was a significant predictor. This study reports cross-cultural data that support a continuity of depression from adolescence to young adulthood.