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F Martín

Publications and source records attributed to F Martín.

At least 19 recordsLinked to original sources
PubMed2006

Experimental evidence of dynamic trapping in the scattering of H2 from Pd(110).

We have performed H2(D2) diffraction experiments on a Pd(110) surface using two different high-sensitivity set-ups. We have found that, although the total reflectivity of Pd(110) is comparable to that observed in other reactive systems, the corresponding H2(D2) diffraction patterns are quite different: no diffraction peak, including the specular one, is observed on Pd(110). This unexpected result is the consequence of dynamic trapping. Such interpretation is supported by classical dynamics calculations based on accurate ab initio potential energy surfaces.

Journal Article↗
PubMed2006

Kinematically complete study of dissociative ionization of by ion impact.

We present a kinematically complete study of dissociative ionization of D(2) by 13.6 MeV/u S(15+) ions. The experiment allows us to unravel the competing mechanisms, namely, direct single ionization, autoionization of doubly excited states, ionization excitation, and double ionization, and to analyze the corresponding electron angular distribution from fixed-in-space molecules. The conclusions are supported by theoretical calculations in which the correlated motion of all electrons and nuclei and the interferences between them are described from first principles.

Journal Article↗
PubMed2006

Enhancement and control of H2 dissociative ionization by femtosecond VUV laser pulses.

We report ab initio calculations of H2 ionization by VUV/fs 10(12) W/cm2 laser pulses including correlation and all electronic and vibrational degrees of freedom (DOF). Inclusion of the nuclear DOF leads to a substantial increase of resonance enhanced multiphoton ionization. By varying pulse duration, it is possible to control the ratio of dissociative to nondissociative ionization as well as the final H+(2) vibrational distribution. For pulses longer than 10 fs and proportional to omega>0.46 a.u., dissociative ionization entirely dominates, which is a very unusual situation in photoionization studies.

Journal Article↗
PubMed2006

The role of molecular rotation in activated dissociative adsorption on metal surfaces.

The role of molecular rotation in dissociative adsorption of H2 on the activated NiAl(110) metal surface is systematically investigated by means of classical dynamics calculations performed on ab initio six-dimensional potential energy surfaces. The calculations show that molecules rotate abruptly when they are close to the surface and that this rotation allows the molecules to adopt the orientation that is more convenient for dissociation (i.e., nearly parallel to the surface). Also, in reactive sectors of the NiAl(110) unit cell, there is an "angular threshold" below which molecules cannot dissociate. This angular threshold goes down as the incidence energy increases, which explains the rise of the dissociation probability and the fact that it reaches a value close to 1 at incidence energies of the order of 2 eV. The fact that switching on molecular rotation favors dissociation establishes a competition between dissociation and rotational excitation of reflected molecules above the dissociation threshold. Measurements on rotational excitation might thus bring indirect evidence on the dissociation dynamics. Sample calculations for nonactivated Pd(111) and activated Cu(110) metal surfaces suggest that some of these conclusions may be of general validity.

Journal Article↗
PubMed2006

Human metapneumovirus infections in hospitalised infants in Spain.

BACKGROUND: Human metapneumovirus (hMPV) causes lower respiratory tract infections, particularly in young children and the elderly. METHODS: A prospective study was conducted on the clinical characteristics of infants <2 years of age admitted to hospital for respiratory infection and the characteristics of hMPV infections were compared with those of infections caused by respiratory syncytial virus (RSV). Influenza A, B and C viruses, RSV, parainfluenza viruses, and adenoviruses were simultaneously detected in clinical samples by multiple reverse transcription nested-PCR assay. The presence of hMPV was tested in all samples using two separate RT-PCR tests. RESULTS: A respiratory virus was detected in 65.9% of the 749 children included in the study. hMPV, found in 69 of the positive nasopharyngeal aspirates (14%), was the most common virus after RSV. Peak incidence was in March and over 80% of children were <12 months of age. The most common diagnoses were recurrent wheezing (49.3%) and bronchiolitis (46.4%). Oxygen therapy was required by 58% of patients, and assisted ventilation by one. Clinical characteristics in the 18 co-infections were indistinguishable from those of single infections. Fifty one hMPV single infections were compared with 88 hRSV single infections. Recurrent wheezing was diagnosed more frequently in hMPV patients. All other variables tested were similar in both groups. CONCLUSIONS: hMPV was the second most frequent virus after RSV in infants <2 years of age hospitalised for respiratory infection and was associated with lower respiratory tract infections. hMPV occurred predominantly in springtime. Co-infections were frequent and clinically similar to single infections and RSV infections.

Acute Disease↗
PubMed2006

[Hemodialysis prospective multicentric quality study].

In medicine a considerable amount of resources are used in research, but very little attention is paid to ensuring that the findings of research are implemented in routine clinical practice. This prospective study has the aim to evaluate the efficiency of some clinical management strategies (feedback, benchmarking and improving plans) on haemodialysis treatment results in 4 different dialysis centres. We collected consensus data related to haemodialysis results every 6-8 months and informed each centre about its own results (feedback) and how these related to the others(benchmarking). We designed improving plans for any bad result detected. By the end of two years of follow up, 294 patients had been included in the study. The results obtained at the end of the study had improved in comparison with those obtained at the beginning (statistically significant) for the following indicators: % of patients with Hb< 11 g/dl, % patients with Kt/v < 1.2, mean Kt/v, mean albumin, % patients with albumin< 3.5 g/dl y % patients with C reactive protein (CRP) > 5 mg/dl. No statistical changes were found in: mean erythropoietin (EPO) doses, blood pressure (BP), phosphorus plasmatic,calcium-phosphorus product, parathormone (PTHi) and vascular access distribution. We explained the absence of any improvement because of adequate start indicators in some areas (BP and vascular access), therapy with limited efficiency (calcitriol, calcium carbonate and others), lack of support resources (dietetic unit) or inadequate design/implementation of improving plans.In conclusion, our intervention illustrates that combined clinical management strategies(feedback, benchmarking and improving plans) are efficiency in improving some areas of haemodialysis treatment (anaemia, dialysis dose, nutrition and inflammation), although it does not improve calcium phosphate metabolism related indicators.

Aged↗
PubMed2005

Adsorption and scattering of H2 and D2 by NiAl(110).

We present quasiclassical dynamics calculations of H2 and D2 scattering by the NiAl(110) surface using a recently proposed six-dimensional potential-energy surface (PES) obtained from density-functional theory calculations. The results for dissociative adsorption confirm several experimental predictions using (rotationally hot) D2 beams, namely, the existence of a dissociation barrier, the small isotopic effect, the importance of vibrational enhancement, and the existence of normal energy scaling. The latter conclusion shows that normal energy scaling is not necessarily associated with weak corrugated surfaces. The results for rotationally elastic and inelastic diffractions are also in reasonable agreement with experiment, but they show that many more diffractive transitions are responsible for the observed structures than previously assumed. This points to the validity of the PES recently proposed [P. Riviere, H. F. Busnengo, and F. Martin, J. Chem. Phys. 121, 751 (2004)] to describe dissociative adsorption as well as rotationally elastic and inelastic diffractions in the H2NiAl(110) system.

Journal Article↗
PubMed2005

Coulomb stability limit of highly charged Cq+60 fullerenes.

We perform density functional theory calculations of Cq+60 and Cq+58 fullerenes as well as of transition states related to dissociation of Cq+60 into Cq-s(+)58 and C(s+)2 for charges q=0-14. For q< or =8, the lowest fission barrier corresponds to C+2 emission, whereas, for higher q values, the lowest barrier corresponds to the emission of two atomic fragments [2C]s+ with s> or =2. We conclude that the Coulomb stability limit corresponds to q=14.

Journal Article↗
PubMed2005

[The Framingham function overestimates stroke risk for diabetes and metabolic syndrome among Spanish population].

OBJECTIVE: To estimate stroke risk for diabetes, isolated or associated to metabolic syndrome (MS) according WHO and National Cholesterol Education Program (NCEP) criteria. DESIGN: Multicentre and prospective cohort study. SETTING: Primary health care. PARTICIPANTS: Subjects between 55-85 years-old without any evidence of stroke, included from 1998 in a random population sample for MS follow-up during routine practice in Reus (Tarragona, Spain). MAIN MEASUREMENTS: Stroke risk was achieved using Framingham function by means of a computerized algorithm using a diagnostic factorial design (diabetes and/or MS). Theoretical stroke risk and cumulated incidence of stroke events (1998-2003) were compared. RESULTS: Among 728 subjects (412 women, mean age =66 years old, body mass index =29 kg/m2), 457 (62.8%) did not have diabetes, nor MS, 93 (12.8%) had MS without diabetes, 72 (9.9%) diabetes without MS, and 106 (14.5%) presented both conditions (WHO rules). According NCEP criteria were 60.7%, 14.8%, 7.8%, and 16.7%, respectively. Ten-year estimated stroke risk accounted for (WHO/NCEP) 8.4/9.1%, 10.8/10.5%, 18/17.3%, and 18.8/19.1%. Cumulated incidence for stroke events were: 2.8%, 1.4%, 5.4%, and 3.8% (WHO), and 2.5%, 2.8%, 3.5%, and 5.8%, respectively (NCEP). CONCLUSIONS: Stroke risk scores were extremely increased among diabetic subjects irrespective to MS diagnose. The Framingham function probably overestimates stroke risk among Spanish individuals.

Diabetes Mellitus, Type 2↗
PubMed2005

A classical dynamics method for H2 diffraction from metal surfaces.

We present a discretization method that allows one to interpret measurements on diffraction of diatomic molecules from solid surfaces using six-dimensional (6D) classical trajectory calculations. It has been applied to the D2NiAl(110) and H2Pd(111) systems (which are models for activated and nonactivated dissociative chemisorption, respectively) using realistic potential energy surfaces obtained from first principles. Comparisons with experimental results and 6D quantum dynamical calculations show that, in general, the method is able to predict the relative intensity of the most important diffraction peaks. We therefore conclude that classical mechanics can be an efficient guide for experimentalists in the search for the most significant diffraction channels.

Journal Article↗
PubMed2005

[The RECORD project. continuous blood glucose monitoring among high risk subjects for developing diabetes in Spanish primary health care].

OBJECTIVE: To evaluate the accuracy of continuous blood glucose monitoring (CBGM) in order to asses diagnostic procedures and predict glycaemic status in type 2 prediabetes. DESIGN: Observational, multicenter, cross-sectional (phase 1) plus longitudinal, cohort follow-up study (phase 2). SETTING: Five primary health-care centers. INTERVENTIONS: A total of 84 high-risk subjects will be included after a non-diabetic oral glucose tolerance test (OGTT). A first CBGM using a subcutaneous microdialysis glucose sensor technique in order to obtain a continuous profile will be carried out. Two different cohorts, subjects with normal OGTT (n = 42) and individuals with prediabetic hyperglycemia (n = 42) will be established. Diagnoses will be revised at 12 and 24 month follow-up by means of an OGTT together with a new monitoring. MAIN MEASUREMENT: Demographical, clinical (including metabolic syndrome items), basic, and advanced analyses (inflammation emergent markers, insulinemia, C-peptide). CBGM computerized analysis comparing fasting, preprandial, postprandial, nocturnal period, and area under the curve of continuous profile with regular diagnoses, taking into account temporary concordance. Relationship of CBGM parameters with normal glucose tolerance or diabetes incidence. Evaluation of day-to-day quality of life of CBGM users by means of an standardized Likert questionnaire. DISCUSSION: This study seeks to demonstrate the effectiveness and feasibility of CBGM, more physiological than OGTT and based on an underestimated random blood glucose diagnostic criterion. This innovative system may provide interesting scientific data in the field of type 2 prediabetes.

Blood Glucose↗
PubMed2005

Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings.

To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed.

Environmental Pollution↗
PubMed2005

Lentiviral vectors transcriptionally targeted to hematopoietic cells by WASP gene proximal promoter sequences.

The development of vectors that express a therapeutic transgene efficiently and specifically in hematopoietic cells (HCs) is an important goal for gene therapy of hematological disorders. In order to achieve this, we used a 500 bp fragment from the proximal WASP gene promoter to drive the expression of the WASP cDNA in the context of a self-inactivating lentiviral vector. Single-round transduction of WASp-deficient herpesvirus saimiri (HVS)-immortalized cells as well as primary allospecific T cells from Wiskott-Aldrich syndrome (WAS) patients with this vector (WW) resulted in expression levels similar to those of control cells. Non-HCs were transduced with similar efficiency, but the levels of WASp were 135-350 times lower than those achieved in HCs. Additionally, transduction of WASp-deficient cells with WW conferred a selective growth advantage in vitro. Therefore, lentiviral vectors incorporating proximal promoter sequences from the WASP gene confer hematopoietic-specific, and physiological protein expression.

Animals↗
PubMed2005

[Comparison of three methods of inducing chronic elevation of intraocular pressure in the pig (experimental glaucoma)].

PURPOSE: To compare three methods of inducing experimental glaucoma in the adult pig, based on achieving chronic elevation of the intraocular pressure (IOP). METHODS: A total of 16 adult pigs were used in the present study. In all instances, the right eye was used as control and the left eye as the experimental eye. The animals were divided into three groups: 1) 3 pigs in which 3 episcleral veins were cauterized (experimental period = 21 weeks); 2) 6 animals in which the anterior chamber of the eye was injected with a solution containing latex fluorospheres (experimental period = 11 weeks); and 3) 4 pigs in which the anterior chamber of the eye was injected with a solution containing latex fluorospheres plus methylcellulose (experimental period = 11 weeks). RESULTS: The episcleral vein cauterization was the only method which produced a sustained elevation of the IOP throughout most of the experimental period. Moreover, the elevation of the IOP achieved by this method resulted in selective retinal ganglion cell (RGC) loss that affected mainly the mid-peripheral and peripheral retina and caused an increase in the mean soma area of the remaining RGCs. CONCLUSIONS: Cauterization of the episcleral veins resulted in a significant and sustained elevation of the IOP and RGC loss when compared with the other two approaches tested in the present study, which barely modified the pig's RGC distribution. Thus, we conclude that the episcleral vein cauterization is the best of the methods tested to induce experimental glaucoma in the pig.

Animals↗