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C Cisneros

Publications and source records attributed to C Cisneros.

At least 19 recordsLinked to original sources
PubMed2002

Experimental link of photoionization of Sc2+ to photorecombination of Sc3+: an application of detailed balance in a unique atomic system.

The principle of microscopic time reversal of physical processes, detailed balance, is widely used and depended upon in the theoretical community as a connection between photorecombination (PR) and photoionization (PI). This paper reports on a novel use of detailed balance and the comparison of experimental results obtained by two very distinct techniques to determine both the metastable fraction of an ion beam and partial Sc3+ PR cross sections and partial Sc2+ PI cross sections for the ground state and for two metastable states. The Sc2+ to Sc3+ system presents a unique opportunity to obtain comprehensive state-selective information by combining results from PR and PI experiments.

Journal Article↗
PubMed2001

Photoionization of metastable O+ ions: experiment and theory.

High-resolution absolute experimental measurements and two independent theoretical calculations were performed for photoionization of O+ ions from the 2P(o) and 2D(o) metastable levels and from the 4S(o) ground state in the photon energy range 30-35.5 eV. This is believed to be the first comparison of experiment and theory to be reported for photoionization from metastable states of ions. While there is correspondence between the predicted and measured positions and relative strengths of the resonances, the cross-section magnitudes and fine structure are sensitive to the choice of basis states.

Journal Article↗
PubMed2000

N+ charge transfer and N+2 dissociation in N2 at swarm energies.

This paper reports a drift-tube-mass-spectrometer measurement of the relative abundances of N+ and N+2 in pure nitrogen, over a ratio of electric field to gas density, E/N, from 800 to 7200 Td [1 townsend (Td)=10(-17) V cm(2)]. A proposed charge transfer dissociation scheme between the above two ions and N2 allowed us to obtain spatial rate coefficients for charge transfer and dissociation over the E/N range 800-2800 Td. Using previously measured cross sections for the above processes, and assuming a Maxwellian distribution of ion velocities, we calculated the reaction coefficients, which were found to be in good agreement with our measured values. In particular, the present results support the trend toward fairly high charge transfer cross section values for N+ energies above 10 eV. In the overlap range between 2.4 and 7.2 kTd, our concentration ratio [N(+)/N(+)(2)] is about five times smaller than that measured previously from a diffuse Townsend discharge in which electron impact is involved in addition to N+2 collisional dissociation with N2, but has the same trend. Thus it seems that, besides N+2 dissociation by electron impact, collisional dissociation becomes important at elevated values of E/N. In connection with previous discharge work in nitrogen, the present study may help explain the enhanced cathode yields observed.

Journal Article↗
PubMed2000

[Individual treatment of smoking addiction. Results using 2 and 4 mg nicotine gum].

We present the results of an open follow-up study aimed at analyzing the efficacy of combining psychological counseling with prescription of 2 and 4 mg nicotine gum to treat smokers. Two groups of smokers wer studied. Group A contained 124 subjects (74 men, 50 women) with a mean age of 37.4 (15.3) yr who were smokers of 15.3 (8.7) cigarettes/day. In this group physical addiction to nicotine was low, assessed as 1.7 (1.3) on the Fagerström test. Group B consisted of 107 subjects (61 men, 46 women) with a mean age of 38.9 (14.6) who were smokers of 26.9 (9.3) cigarettes/day and whose level of physical addiction to nicotine was moderate-to-high, assessed as 6.1 (2.4) on the Fagerström test. Standard deviations are shown between parentheses. Both groups were given minimal psychological counseling; additionally, patients were prescribed one piece of nicotine gum very 90 to 120 minutes during waking hours (2 mg in group A and 4 mg in group B). The dose was gradually reduced after the sixth to the eight week. The subjects were seen eight times over the first year (first day of consultation and during the first, second, fourth, eight and twelfth weeks after quitting, and again after six and twelve months). After twelve weeks of follow-up, sixty-one subjects (49%) in group A and 50 (47%) in group B were still abstinent. These proportions fell to 56 (45%) and 46 (43%), respectively, after one year of follow-up. Eighty-one percent of group A patients who were successful after three months of follow-up, and 87% of the successful group B patients, had used the nicotine gum as prescribed. Oropharyngeal, dental, and temporo-mandibular joint symptoms, hiccoughins, flatulence and heartburn were the most frequent side effects (ranging from 3% to 18%). Side effects were always slight and were not detected after the eighth week of treatment. In conclusion, combined therapy (minimal psychological counseling plus use of 2 or 4 mg nicotine gum depending on the level of physical addiction) yields a success rate between 43% and 45% still abstaining after one year of follow-up. Side effects are few and mild.

Adult↗
PubMed1999

Ionization, electron attachment, and drift in CHF3.

Using a pulsed Townsend technique, we have measured the effective ionization coefficient and the electron drift velocities in CHF(3). The density-normalized electric field intensity E/N ranged from 4 to 250 townsends (Td) (1 Td=10(-17) V cm(2)). The E/N value at which the effective ionization coefficient becomes zero was estimated to be 66 Td. For E/N<20 Td, the electron attachment coefficients are practically constant, and are compatible to within about +/-70% with previously measured values at thermal energies and above.

Journal Article↗
PubMed1992

Major bacterial infections following liver transplantation: a prospective study.

The incidence and characteristics of major bacterial infections were studied prospectively in 50 consecutive adult patients who underwent liver transplantation (LT). All patients received the same protocol of immunosuppression, bowel decontamination, antibiotics prophylaxis, and follow-up. Thirty-two patients (64%) had at least one episode of major bacterial infection. One death was directly related to a bacterial infection, accounting for 13% of postoperative mortality. The most critical period for infection was the first 2 months after surgery, when 69% of the infections occurred. The most frequent clinical presentations were bacteremia, pneumonia and abdominal abscesses. Eighty percent of the bacteremias had an identifiable source, the most frequent being intravascular catheters. Gram-positive microorganisms (69%) predominated over gram-negative rods (26%) and anaerobes (5%). The use of selective bowel decontamination (SBD) with norfloxacin may explain this predominance. Major bacterial infections are an important source of morbidity and mortality after LT. Efforts to prevent these infections and to determine their source and specific treatment, will improve the management and the outcome of these patients in the future.

Adult↗
PubMed1986

Post-traumatic diffuse axonal brain injury. Analysis of 78 patients studied with computed tomography.

A group of 78 severe head injury patients showing computerized tomography (CT) findings of the so-called "diffuse axonal injury" is analyzed. These patients represent 20% of the authors' series of severe head injury. Twenty-three patients showed small intraparenchymal haemorrhages in the CT scan study, 15 intraventricular haemorrhage and 40 patients had both intraparenchymal and intraventricular haemorrhages. Signs of brainstem haemorrhagic contusion were seen in 29 (38%) patients. Generalized brain swelling superimposed on the above findings was present in 75% of the cases. Raised intracranial pressure, which was found in 50% of the patients, correlated with the presence of ventriculocisternal collapse in the CT scan and an unfavourable outcome. Only 4 patients in this series made a good recovery, 13 developed a moderate disability, 11 a severe disability, 12 became vegetative and 38 (49%) died. The prognosis with this post-traumatic lesion is the worst in the authors' severe head injury series after excluding cases with subdural haematoma.

Adolescent↗