Showing papers by "University of Alcalá published in 1999"

Evaluación de la actividad científica a través de indicadores bibliométricos

Abstract: Los estudios bibliometricos tienen por objeto el tratamiento y analisis cuantitativo de las publicaciones cientificas. Forman parte de los «estudios sociales de la ciencia» y entre sus principales aplicaciones se encuentra el area de la politica cientifica. Estos estudios complementan de manera eficaz las opiniones y los juicios emitidos por los expertos de cada area proporcionando herramientas utiles y objetivas en los procesos de evaluacion de los resultados de la actividad cientifica. Sin embargo, dadas las repercusiones que estas evaluaciones tienen sobre la asignacion de fondos para la investigacion e, incluso, la promocion profesional de los investigadores, es necesario conocer bien las caracteristicas de los indicadores bibliometricos y las limitaciones que su uso conlleva. Una de las bases de datos mas utilizada es la del Science Citation Index. En el caso de la investigacion biomedica es util para analizar la produccion cientifica mas visible internacionalmente ya que tiene una buena cobertura de revistas biomedicas pero la investigacion mas clinica y de interes local que se publica en revistas espanolas no esta recogida en la misma. Los indicadores bibliometricos mas utilizados para medir la actividad cientifica se basan en los recuentos de las publicaciones y de las citas recibidas por los trabajos publicados, asi como en el impacto de las revistas de publicacion. El factor de impacto de las revistas es un indicador presente en casi todos los estudios bibliometricos; aunque en ocasiones se equipara alto factor de impacto con mayor calidad, este indicador mide especificamente la visibilidad y la difusion de los trabajos publicados en estas revistas mas que la calidad cientifica de los mismos.

Different Theoretical Approaches for the Study of the Mixed Tetraethylene Glycol Mono-n-dodecyl Ether/Hexadecyltrimethylammonium Bromide Micelles

Abstract: The mixed micelles C12E4 (tetraethylene glycol mono-n-dodecyl ether)/CTAB (hexadecyltrimethylammonium bromide) were studied. The surface tension results were analyzed on the basis of a treatment that considers the relation between the activity coefficients according to the Gibbs−Duhem equation. The results are compared with Rubingh's treatment, which considers the activity coefficients given by the regular solution theory. The conductivity of the samples and the aggregation numbers at low mixture concentration are also given.

Regional Convergence in Productivity and Productive Structure: The Spanish Case:

Abstract: This article analyzes the evolution of regional differences in Spain and emphasizes the importance of a disaggregate analysis at a sectoral level. In particular, the authors observe convergence in productivity at the aggregate regional level but not at the sectoral level. Aggregate convergence seems to be due to the gradual homogenization of regional productive structures. This result may modify some of the conclusions drawn in the recent literature regarding the mechanisms that have generated convergence. In addition, we examine the so-called beta convergence hypothesis using a fixed-effects model. The results show the importance of regional specificity captured by the fixed effects and have implications that are very different from those of beta convergence analyses with cross-section data.

Environmental and genetic variation in the haematocrit of fledgling pied flycatchers Ficedula hypoleuca

Abstract: We report a field study of the haematocrit of pied flycatcher (Ficedula hypoleuca) nestlings when close to fledging. First a descriptive study was conducted of both fledgling and adult haematocrit over 2 years to analyse correlates of variation in this trait. Then a swapping experiment was performed to see whether variation among fledglings had a measurable genetic component. Average fledgling haematocrits were lower than those of their male and female parents. Intraclass correlations among sibships in fledgling haematocrit were high in both years, indicating that the estimates of resemblance were inflated, probably by common environmental effects. Fledgling haematocrits were unrelated to date and number of young in the nest. Fledglings with a high haematocrit were heavy and had thick breast muscles. There were no significant relationships between the average fledgling haematocrit and those of the adults caring for them. Nest mite ectoparasites negatively affected fledgling haematocrit. The haematocrits of adults did not differ between sexes or years and in both sexes were unrelated to breeding date, body mass, age, clutch size or number of young reared. Females, but not males, caring for fledglings in nests infested by mites had a lower haematocrit than those rearing young in mite-free nests. The cross-fostering experiment indicated that almost all measured variation in haematocrit was explained by the nest where the bird was reared (67.2% of the explained variance), not by their nest of origin (7.8%), meaning that there was a very small, non-significant resemblance in the haematocrit of genetically related sibs when reared in different environments while unrelated nestlings reared in the same nestbox had similar haematocrits. The low proportion of variance explained by the familial component may be due to the high connection of haematocrit to fitness.

Maternal energy expenditure does not change with flight costs or food availability in the pied flycatcher (Ficedula hypoleuca) : costs and benefits for nestlings

Abstract: We manipulated parental work load without changing brood size in a population of pied flycatchers Ficedula hypoleuca by removing two primaries (7 and 9) from each wing of females, thus reducing wing area and increasing flight costs. At other nests, we offered supplementary food in the form of live mealworms (10–20 g daily from hatching) to reduce brood demand and thus parental foraging costs. Other nests were left as controls. The daily energy expenditure of females feeding 12-day-old nestlings was measured with doubly labelled water D218O. Females in both treatments expended the same amount of energy, fed at the same rate and had similar body masses to birds in the control group. No effect of treatment on male mass and feeding effort was detected. More nestlings, however, died in nests of handicapped females. Nestlings of handicapped females had significantly lower body mass and haematocrit values than nestlings in food-supplemented nests, with nestlings in control nests occupying an intermediate position. The effects of both treatments on nestling mass, haematocrit values and mortality rates were only noticeable in nests infested with mites. Maternal energy expenditure is apparently constrained and offspring pay the costs imposed by reduced provisioning rate or increased demand caused by ectoparasites, while receiving benefits when food supply improves. The presumption that avian reproductive costs derive from changes in a flexible energy output may not be met in many cases.

Differential effects of N-methyl-D-aspartate receptor blockade on nociceptive somatic and visceral reflexes.

Abstract: N-methyl-D-aspartate (NMDA) receptors appear to play little part in nociceptive responses evoked by acute stimulation of normal somatic tissues, but rather are involved in hyperalgesic responses after peripheral injury and inflammation. Previous studies from this laboratory have shown important differences in the neural organization of somatic and visceral nociceptive pathways. Here, we have explored the role of NMDA receptors in processing acute visceral noxious input, compared with somatic noxious input. The left ureter was cannulated close to the bladder in adult female Wistar rats anaesthetized with pentobarbitone (50 mg/kg i.p). Graded distentions of the ureter (30 s, 25-80 mmHg) evoked increases in blood pressure. These responses were dose-dependently inhibited by the NMDA receptor ion channel blockers ketamine and memantine (ID50 = 2.4+/-1.6 and 14.5+/-1.3 mg/kg, i.v.), and by the Merz glycine site antagonist Mrz 2/ 576 (ID50 = 0.2+/-0.2 mg/kg). Graded pinch stimuli (30 s, 2-4 N) of one hind-paw evoked similar pressor responses which were not affected by ketamine (up to 10 mg/kg). Similarly, Mrz 2/576 did not affect responses to noxious pinch, whereas memantine (ID50 = 17+/-12 mg/kg) did inhibit responses to pinch stimuli. However, in the dose range used neither ketamine nor Mrz 2/576 inhibited a pressor response of non-nociceptive origin (produced by bilateral carotid occlusion) whereas memantine did. Thus the effects of memantine are likely due to a non-specific cardiovascular effect. These results show that NMDA receptor antagonists inhibit nociceptive reflexes evoked from the normal ureter, and suggest that NMDA receptors are involved in the processing of acute nociceptive inputs from viscera. We conclude that acute stimulation of normal visceral tissue provokes intense responses that recruit neural mechanisms mediated by NMDA receptors. However, in somatic pathways, these mechanisms are recruited only by an enhanced peripheral input such as that produced after injury or inflammation.

Cholesterol starvation decreases P34cdc2 kinase activity and arrests the cell cycle at G2

Abstract: As a major component of mammalian cell plasma membranes, cholesterol is essential for cell growth. Accordingly, the restriction of cholesterol provision has been shown to result in cell proliferation inhibition. We explored the potential regulatory role of cholesterol on cell cycle progression. MOLT-4 and HL-60 cell lines were cultured in a cholesterol-deficient medium and simultaneously exposed to SKF 104976, which is a specific inhibitor of lanosterol 14-α demethylase. Through HPLC analyses with on-line radioactivity detection, we found that SKF 104976 efficiently blocked the [14C]-acetate incorporation into cholesterol, resulting in an accumulation of lanosterol and dihydrolanosterol, without affecting the synthesis of mevalonic acid. The inhibitor also produced a rapid and intense inhibition of cell proliferation (IC50 = 0.1 μM), as assessed by both [3H]-thymidine incorporation into DNA and cell counting. Flow cytometry and morphological examination showed that treatment with SKF 104976 for 48 h or lo...

Measuring interdisciplinary collaboration within a university: The effects of the multidisciplinary research programme

Abstract: A Multidisciplinary Research Programme (MRP) is being developed since 1989 in the Universidad Complutense de Madrid (UCM), Spain, to support cross-disciplinary research projects. This paper analyses the incidence of interdisciplinarity in the UCM scientific publications over the period 1990-96 and tries to determine the success of the Programme at fostering cross-disciplinary research. Interdisciplinary in the UCM is measured through the collaboration of authors from different institutional addresses within the UCM, both in scientific publications and in research projects. Publications jointly signed by the different teams that collaborate in the projects were identified as an indicator of the success of the Programme in integrating disciplines. Interdisciplinary collaboration within the UCM showed an upward trend over time. Publications of MRP groups showed a higher interdisciplinary collaboration rate than the rest of the UCM (17% vs.9%). Dramatic repercussions of the Programme were not expected due to its limited magnitude, but it worked as a catalyst, enhancing interdisciplinary relations within the UCM. The interest of such a programme is supported by its effects, both direct effects on granted teams and indirect on the whole UCM community.

Sustained response to interferon-α or to interferon-α plus ribavirin in hepatitis C virus-associated symptomatic mixed cryoglobulinaemia

Abstract: Background : Hepatitis C virus (HCV) infection has been associated with mixed cryoglobulinaemia. Aim : To investigate the efficacy of anti-viral therapy on the eradication of HCV and its clinical manifestations in patients with HCV-associated symptomatic mixed cryoglobulinaemia. Patients and methods : 18 out of 32 patients with symptomatic mixed cryoglobulinaemia (MC group) received a 12-month course of interferon (3 MU three times a week, subcutaneously). Nonresponders or relapsers to this therapy were treated with interferon plus ribavirin (1200 mg/day, orally) for 12-months. 226 patients with HCV infection and without cryoglobulins were studied in comparison (Hepatitis C group). Serial quantification of serum HCV-RNA and cryoglobulins were performed. Results : In the MC group, 10 out of 18 patients (55%) receiving interferon showed an end of treatment response, but at the end of follow-up, only five (28%) patients had a sustained response. In the hepatitis C group, 91 patients (47%) showed an end of treatment response but only 42 (20%) a sustained response. In the MC group alanine transaminase, cryocrit and rheumatoid factor decreased significantly in responders, with an improvement or dissapearance of the MC-associated clinical manifestations. Alanine transaminase, cryocrit and rheumatoid factor increased in the relapsers and the clinical manifestations reappeared. Nonresponders and relapsers to interferon in the MC group were retreated with interferon plus ribavirin. Five out of eight nonresponders showed a end of treatment response but it was sustained in three of them. In the relapsers, treatment with combined therapy achieved a sustained response in four out of the five patients (80%). Conclusions : Interferon as monotherapy or combined with ribavirin is a safe and effective treatment in patients with HCV-associated MC. The presence of cryoglobulins does not affect the response to anti-viral treatment in patients with HCV infection. The eradication of HCV is associated with an improvement or dissapearance of MC-associated clinical manifestations.

The Water Vapor Abundance in Circumstellar Envelopes

Abstract: The maser emission of the para-H2O 313 → 220 line at 183 GHz in O-rich evolved stars has been modeled to account for the empirical characteristics of this line reported by Gonzalez-Alfonso et al. Likewise, efforts have been made to derive water vapor abundance in these sources. The Sobolev or large velocity gradient (LVG) method has been employed to study the intensity of this line as a function of source properties and physical conditions (i.e., mass-loss rate, p-H2O abundance, velocity field, kinetic temperature profile, stellar luminosity, and the set of collisional rates adopted in the calculations). It has been found that the intensity of the 313 → 220 line is sensitive to the mass-loss rate, the p-H2O abundance, and the terminal velocity of the envelope, but it is rather insensitive to the rest of the parameters in stars with high mass-loss rates ( > 10-6 M☉ yr-1). The models reproduce the main spectral characteristics of the emission at 183 GHz in the latter sources. A global fit to the data proves that the observational luminosities can be explained by assuming an H2O abundance relative to H2 [x(H2O)] of 1-2 × 10-4. Detailed fitting to the line profile in five selected objects yields a similar value for x(H2O). The validity of the LVG approach has been verified by modeling the maser emission at 183 GHz through a nonlocal radiative transfer code. The model calculations with both methods lead to similar results. The pumping of the first bending mode of water vapor through absorption of photons emitted by the dust and the star has been also simulated. This effect is found to be important in the pumping of the H2O rotational levels. Hence, in order to recover LVG results, the water abundance must be increased by a factor of ≈2 for stars with high mass-loss rates. Consequently, x(H2O) has been estimated to be 3 × 10-4 within a factor 2. With this value for x(H2O), the expected near- and far-infrared spectra of the circumstellar envelopes of O-rich stars for several mass-loss rates have also been computed. Hence, it is possible to predict that, in some stars, the ro-vibrational lines of the 6 μm water vapor band with wavelengths longer that 6.3 μm—the P-branch—can be observed in emission, rather than in absorption.

Short-term fire risk: foliage moisture content estimation from satellite data

Abstract: A description of methods used to determine short-term changes in fire danger is reviewed, mainly those based on the estimation of foliage moisture content (FMC). Applications of low-resolution data, acquired by the Advanced Very High Resolution Radiometer (AVHRR) on board the NOAA satellites, as well those based on high-resolution data, are examined. Examples of FMC estimation on Mediterranean areas are also presented, both for AVHRR and Landsat-TM data. In both cases, satellite data provide a higher confidence to estimate FMC in grasslands than in shrublands, although in both cases, some variables provide significant correlation, especially when the spring season is taken into account. The most sensitive variables for FMC estimation are based on short-wave infrared bands, and the combination of vegetation indices and surface temperature.

Maternal effects and the pervasive impact of nestling history on egg size in a passerine bird.

Abstract: Environmental conditions experienced during ontogeny may have important and permanent consequences for life-history traits of individuals. The aim of this work was to determine whether conditions experienced during early life, as expressed by prefledgling condition, have any bearing on the volume of eggs subsequently laid by females in a small passerine bird species, the pied flycatcher (Ficedula hypoleuca). I first show a genetic influence on egg volume by dam-offspring regression. The existence of maternal effects is shown by comparing resemblances between average egg volumes of offspring to those of their paternal and maternal grandmothers. Path analysis shows that when controlling for the influence of maternal egg volume, the average volume of eggs produced in a lifetime is positively related to the body condition of a female measured while she is still at the nest. Thus, body condition at fledgling affects egg volume beyond the ability of maternal egg volume to predict offspring egg volume. Although there may be a persistent maternal effect of egg volume on itself or linked to a property correlated with egg volume, the maternal performance trait involved remains unknown, except for maternal egg volume itself. Given the effects that egg volume may have on reproductive success, which are partly determined prior to leaving the nest, maternal effects may have important consequences for lifetime fitness of offspring.

Serum levels of beta-carotene, alpha-carotene and vitamin A in patients with Alzheimer's disease.

Abstract: To elucidate the possible role of carotenoids and vitamin A as risk factors for Alzheimer's disease (AD), we compared serum levels of beta-carotene and alpha-carotene, and vitamin A, measured by isocratic high performance liquid chromatography, of 38 AD patients and 42 controls. The serum levels of alpha-carotene did not differ significantly between AD patients and control groups. However, the serum levels of beta-carotene and vitamin A were significantly lower in the AD-patient group. These values did not correlate to age, age at onset or score on the MiniMental State Examination. Weight and body mass index were significantly lower in AD patients than in controls. These results suggest that low serum beta-carotene concentrations in AD patients could be related to a deficiency in dietary intake of this provitamin, although its possible relationship with risk for AD could not be excluded.