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J M Bofill

Publications and source records attributed to J M Bofill.

14 recordsLinked to original sources
PubMed2005

Inelastic electronic excitation and electron transfer processes in collisions between Mg(31S0) atoms and K+(1S0) ions studied by crossed beams in the 0.10-3.80-keV energy range.

Inelastic and charge-transfer excitation processes in collisions between ground-state neutral Mg atoms and K+ ions have been studied by means of a crossed molecular-beam technique. Decay fluorescent emissions from Mg(3 1P1),Mg(4 3S1), and Mg(3s(1)3d(1), 3(3)D3,2,1) as well as the phosphorescent emission due to Mg(3 3P1) have been observed from excited Mg atoms and the charge-transfer emission decays from K(4 2P 3/2,1/2), K(5 2P 3/2, 1/2), K(6 2S 1/2), and K(4 2D 5/2, 3/2) for excited K atoms. The corresponding absolute cross-sections values versus collision energy functions were determined in the 0.10-3.80 keV laboratory energy range. In order to interpret the experimental results, accurate ab initio full configuration-interaction calculations using pseudopotentials have been performed for the (Mg-K)+ system, giving a manifold of adiabatic singlet and triplet potential-energy curves correlating with the different collision channels, which allow a qualitative interpretation of the emission excitation functions measured for the different processes studied. A comparative study with other Mg-alkali ion systems previously studied is also included.

Journal Article↗
PubMed2004

Electronic excitation and charge transfer processes in collisions between Mg(3(1)S0) atoms and Rb+(1S0) ions in the 0.07-4.00 keV energy range.

Inelastic collision processes between neutral Mg atoms and Rb(+) ions, both in their ground states, have been studied by means of a crossed molecular beam technique measuring the decay fluorescence of the excited species formed. Emissions corresponding to Mg(3 (1)P(1)), Mg(3 (3)D(3,2,1)), and Mg(4 (3)S(1)), formed by direct target excitation, Rb(5 (2)P(3/2,1/2)), Rb(6 (2)P(3/2,1/2)) produced by electron capture and also the phosphorescent emission due to decay of Mg(3 (3)P(1)), have been detected and the corresponding absolute cross-section values measured both as total values and resolved into their J states. No polarization measurements could be made. Ab initio calculations using pseudopotentials have been performed and from these a manifold of adiabatic energy curves correlating with the different entry and exit channels have been obtained, allowing to propose a qualitative interpretation of the results, such as the shape of the cross section vs energy for different transitions and the oscillating nature of the branching ratios due to interference effects.

Journal Article↗
PubMed2001

Ab initio calculations on the mechanism of the oxidation of the hydroxymethyl radical by molecular oxygen in the gas phase: a significant reaction for environmental science.

The mechanism of the gas-phase reaction of *CH2OH+O2 to form CH2O+HO2* was studied theoretically by means of high-level quantum-chemical electronic structure methods (CASSCF and CCSD(T)). The calculations indicate that the oxidation of *CH2OH by O2 is a two-step process that goes through the peroxy radical intermediate *OOCH2OH (1), formed by the barrier-free radical addition of *CH2OH to O2. The concerted elimination of HO2* from 1 is predicted to occur via a five-membered ringlike transition structure of Cs symmetry, TS1, which lies 19.6 kcalmol(-1) below the sum of the energies of the reactants at 0 K. A four-membered ringlike transition structure TS2 of Cs symmetry, which lies 13.9 kcalmol(-1) above the energy of the separated reactants at 0 K, was also found for the concerted HO2* elimination from 1. An analysis of the electronic structures of TS1 and TS2 indicates that both modes of concerted HO2* elimination from 1 are better described as internal proton transfers than as intramolecular free-radical H-atom abstractions. The intramolecular 1,4-H-atom transfer in 1, which yields the alkoxy radical intermediate HOOCH2O*, takes place via a puckered ringlike transition structure TS3 that lies 13.7 kcalmol(-1) above the energy of the reactants at 0 K. In contrast with earlier studies suggesting that a direct H-atom abstraction mechanism might occur at high temperatures, we could not find any transition structure for direct H-atom transfer from the OH group of *CH2OH to the O2. The observed non-Arrhenius behavior of the temperature dependence of the rate constant for the gas-phase oxidation of *CH2OH is ascribed to the combined effect of the initial barrier-free formation of the *OO-CH2OH adduct with a substantial energy release and the existence of a low-barrier and two high-barrier pathways for its decomposition into CH2O and HO2*.

Atmosphere↗
PubMed2001

Point-dipole approximation of the exciton coupling model versus type of bonding and of excitons in porphyrin supramolecular structures.

The application of the exciton coupling model to interacting porphyrin chromophores is discussed. Covalently bonded systems and ionic or electrostatically bonded homoassociates require different orientations of the transition dipole moments in order to explain the experimental results: according to the symmetry of the assembly for covalently bonded porphyrins, and assuming isolated chromophores for ionic bonded porphyrins. Further, for covalently bonded systems, an extended exciton coupling has been demonstrated, but the ionic systems are in agreement with non-extended couplings. The relation of these facts to a molecular description of solid-state Wannier-Mott or Frenkel excitons is briefly discussed.

Journal Article↗
PubMed2001

Tropospheric formation of hydroxymethyl hydroperoxide, formic acid, H2O2, and OH from carbonyl oxide in the presence of water vapor: a theoretical study of the reaction mechanism.

We have carried out a theoretical investigation of the gas-phase reaction mechanism of the H2COO+ H2O reaction, which is interesting for atmospheric purposes. The B3LYP method with the 6-31G(d,p) and 6-311 + G(2d,2p) basis sets was employed for the geometry optimization of the stationary points. Additionally, single-point CCSD(T)/6-311 + G(2d,2p) energy calculations have been done for the B3LYP/6-311 + G(2d,2p) optimized structures. The reaction begins with the formation of a hydrogen-bond complex that we have calculated to be 6 kcalmol(-1) more stable than the reactants. Then, the reaction follows two different channels. The first one leads to the formation of hydroxymethyl hydroperoxide (HMHP), for which we have calculated an activation barrier of deltaGa(298) = 11.3 kcalmol(-1), while the second one gives HCO + OH + H2O, with a calculated activation barrier of deltaGa(298) = 20.9 kcalmol(-1). This process corresponds to the water-catalyzed decomposition of H2COO, and its unimolecular decomposition has been previously reported in the literature. Additionally, we have also investigated the HMHP decomposition. We have found two reaction modes that yield HCOOH+H2O; one reaction mode leads to H2CO + H2O2 and a homolytic cleavage, which produces H2COOH + OH radicals. Furthermore, we have also investigated the water-assisted HMHP decomposition, which produces a catalytic effect of about 14 kcalmol(-1) in the process that leads to H2CO + H2O2.

Journal Article↗
PubMed1996

IgG subclass deficiencies associated with bronchiectasis.

Only a small number of patients with IgG subclass deficiencies (IgGSD) have been observed to have bronchiectasis. Moreover, in the series of patients with bronchiectasis, IgGSD have not been found at any frequency, and the etiology of bronchiectasis remains unclear in 29 to 49% of cases. Serum concentrations of total IgG, IgA, and IgG subclasses as well as pulmonary function were measured in 65 patients (aged: 10 to 74 yr) with bronchiectasis of unknown etiology. An ELISA test was performed to quantify subclasses 1 through 4 using subclass-specific antihuman monoclonal antibodies. IgG subclass estimation in a healthy population with age-stratified normal ranges was derived from 100 adults, 37 children aged between 10 and 12 yr, and 27 adolescents aged between 13 and 16 yr. Serum concentrations of specific IgG antibodies to Haemophilus influenzae type b capsular polysaccharide (Hib-PRP) were also assayed by an ELISA test in 19 of the patients (10 with IgGSD and nine with non-IgGSD) and in 58 healthy individuals before and 3 wk after immunization with Hib-PRP conjugated to meningococcal outer membrane protein complex (OMPC). Thirty-one patients (48%) had low serum concentrations of one or more IgG subclasses (19 IgG2 deficiencies, 2 IgG3 deficiencies, 3 IgG4 deficiencies, and 7 combined subclass deficiencies). All patients showed increased levels of total IgG, IgG1, and IgA, but this rise was significantly higher in patients without IgGSD. Patients with IgGSD showed impaired antibody response to Hib-PRP compared with patients with non-IgGSD and the control group. IgGSD, particularly IgG2 deficiency, are not an unusual cause of bronchiectasis. Therefore, serum levels of IgG subclasses must be assayed whenever other causes of bronchiectasis have been ruled out.

Adolescent↗
PubMed1996

Nasal continuous positive airway pressure with supplemental oxygen in coexistent sleep apnoea-hypopnoea syndrome and severe chronic obstructive pulmonary disease.

The objective of our study was to assess the application of nasal continuous positive airway pressure (nCPAP) with supplemental oxygen for correction of upper airway obstructive episodes and hypoxaemia during sleep in stable patients with sleep apnoea-hypopnoea syndrome (SAHS) and severe chronic obstructive pulmonary disease (COPD). Ten male patients with symptomatic SAHS and severe COPD (forced expiratory volume in one second < 50% of predicted) were studied for three consecutive nights. Diagnostic polysomnography was performed the first night and repeated with increasing nCPAP levels, with and without supplemental oxygen on the second and third nights, respectively. Diagnostic polysomnography showed: mean (SD) apnoea-hypopnoea index 41 (22) events.h-1; mean arterial oxygen saturation (Sa,O2) was 86 (2)% and mean desaturation nadir was 81 (4)% during non-rapid eye movement (nREM) sleep and 80 (7)% and 73 (9)%, respectively during REM sleep. The application of nCPAP during the second night corrected apnoeas and hypopnoeas, but mean Sa,O2 remained < 90% in all patients. With the addition of oxygen at a flow of 1.5 L.min-1 at suboptimal nCPAP levels, we observed an increase in apnoea frequency, persistence of apnoeas at nCPAP levels which eliminated them when no supplemental oxygen was administered, and longer duration of apnoeas and hypopnoeas. However, when the effective nCPAP level of the second night was reached with supplemental oxygen during the third night, its efficacy in eliminating apnoeas and hypopnoeas was maintained and, furthermore, all patients presented Sa,O2 > 90%, with no greater hypercapnia cardiac arrhythmias. We conclude that nasal continuous positive airway pressure with supplemental oxygen constitutes a practical therapeutic alternative for hypoxic patients with sleep apnoea-hypopnoea syndrome and chronic obstructive pulmonary disease.

Aged↗
PubMed1995

Adult onset of nemaline myopathy presenting as respiratory insufficiency.

A 49-year-old woman was admitted to the hospital for hypercapnia. Pulmonary function testing showed small lung volumes without parenchymal lung disease. Muscle enzyme levels were normal and the EMG was nonspecific. Finally, muscle biopsy revealed abundant nemaline bodies characteristic of nemaline myopathy. Nasal intermittent pressure ventilation was started with a preset pressure ventilator during sleeping hours with a good response.

Female↗
PubMed1994

[Evaluation of replacement therapy in emphysema caused by alpha 1-antitrypsin deficiency].

Assessment of alpha 1-antitrypsin replacement therapy (AAT) for emphysema. Patient characteristics were analyzed along with the possible side effects of the treatment and its efficacy in maintaining appropriate AAT blood levels. Lung function changes were also studied. The treatment protocol began with 4 weekly intravenous doses of 60 mg/kg AAT (Prolastin) and continued with monthly doses of 240 mg/kg. AAT serum levels were measured before each dose. Every 6 months pulmonary function tests (spirometry, plethysmography and CO transfer) were performed. Thirteen patients (mean age 46 yr) have been studied since 1988. Mean initial FEV1 was 0.79 l. Over 250 doses have been infused with no significant side effects reported. AAT levels before treatment in 3 patients were lower than that considered protective (50 mg/dl). Function tests results indicated stabilization of spirometric values in most cases. Diagnosis of AAT deficiency is delayed considerably, meaning that significant functional deterioration takes place before replacement therapy begins. No side effects of treatment have been observed. Until an appropriate interval between doses has been established, each patient's AAT levels must be monitored.

Adult↗
PubMed1989

Time of exposure as a prognostic factor in avian hypersensitivity pneumonitis.

Spirometric values were subsequently evaluated in 22 patients suffering from hypersensitivity pneumonitis caused by avian problems. First spirometric values were abnormal in 18/22 (82%) of patients. A restrictive pattern was observed in 16/22 (72%) of patients and an obstructive pattern in 6/22 (27%). The TLCO was reduced in all cases (12/12). Improvement or normalization of the respiratory function occurred 3.4 +/- 2.4 months after the avian contact had ceased. At the end of the follow-up, parameters were normal in 13/22 (59%) of patients. The restrictive pattern remained unchanged in 7/22 (32%), and the obstructive pattern persisted in 4/22 (18%) of the patients. The TLCO was normal in 6/12 (50%) of patients. Neither age nor treatment with corticosteroids (13 patients) had a significant influence upon the evolution of the lung function. However, total recovery or significant improvement was observed in 12/12 (100%) of patients who had been in contact with birds less than 2 years, in contrast to 6/10 (60%) of patients with more than 2 years of contact (P = 0.002).

Adolescent↗