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Biomedical subjects

P Ohresser

Publications and source records attributed to P Ohresser.

At least 19 recordsLinked to original sources
PubMed2005

Surface diffusion of Cr adatoms on Au(111) by quantum tunneling.

The low-temperature surface diffusion of isolated Cr adatoms on Au(111) has been determined using nonperturbing x rays. Changes in the x-ray magnetic circular dichroism spectral line shape together with Monte Carlo calculations demonstrate that adatom nucleation proceeds via quantum tunneling diffusion rather than over-barrier hopping for temperatures <40K. The jump rates are shown to be as much as 35 orders of magnitude higher than that expected for thermal over-barrier hopping at 10 K.

Journal Article↗
PubMed2005

Uniform magnetic properties for an ultrahigh-density lattice of noninteracting co nanostructures.

We report on the magnetic properties of two-dimensional Co nanoparticles arranged in macroscopically phase-coherent superlattices created by self-assembly on Au(788). Our particles have a density of 26 Tera/in2 (1 Tera=10(12)), are monodomain, and have uniaxial out-of-plane anisotropy. The distribution of the magnetic anisotropy energies has a half width at half maximum of 17%, a factor of 2 more narrow than the best results reported for superlattices of three-dimensional nanoparticles. Our data show the absence of magnetic interactions between the particles. Co/Au(788) thus constitutes an ideal model system to explore the ultimate density limit of magnetic recording.

Journal Article↗
PubMed2004

Oscillatory magnetic anisotropy in one-dimensional atomic wires.

One-dimensional Co atomic wires grown on Pt(997) have been investigated by x-ray magnetic circular dichroism. Strong changes of the magnetic properties are observed as the system evolves from 1D- to 2D-like. The easy axis of magnetization, the magnetic anisotropy energy, and the coercive field oscillate as a function of the transverse width of the wires, in agreement with theoretical predictions for 1D metal systems.

Journal Article↗
PubMed2004

Unraveling orbital ordering in La0.5Sr1.5MnO4.

Orbital ordering (OO) in the layered perovskite La0.5Sr1.5MnO4 has been investigated using the enhanced sensitivity of soft x-ray resonant diffraction at the Mn L edges. The energy dependence of an OO diffraction peak over the L(2,3) edges is compared to ligand-field calculations allowing a distinction between the influences of Jahn-Teller distortions and spin correlations. The energy dependence of the diffraction peak at the Mn L1 edge is remarkably different from that observed at the Mn K edge.

Journal Article↗
PubMed2002

Localized magnetic states of Fe, Co, and Ni impurities on alkali metal films.

X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) have been used to study transition metal impurities on K and Na films. The multiplet structure of the XAS spectra indicates that Fe, Co, and Ni have localized atomic ground states with predominantly d7, d8, and d9 character, respectively. XMCD shows that the localized impurity states possess large, atomiclike, magnetic orbital moments that are progressively quenched as clusters are formed. Ni impurities on Na films are found to be nonmagnetic, with a strongly increased d10 character of the impurity state. The results show that the high magnetic moments of transition metals in alkali hosts originate from electron localization.

Journal Article↗
PubMed1989

[Personal experience in hyperbaric oxygenation in decompression accidents].

We are confronted with a considerable failure rate in the treatment of neurological decompression accidents. Facing the relatively poor knowledge about the physiopathological mechanisms involved, we present results obtained with our own treatment procedures. It consists mainly of a maximized oxygen therapy. Our conclusive results can be explained in retrospect by the works of Leitch and Hallenbeck.

Accidents↗
PubMed1988

[Medical history of severe respiratory insufficiency].

To evaluate retrospectively health care in severe chronic respiratory failure, we interviewed 38 patients, admitted for the first time to a pulmonary intensive care unit for an acute episode. A standardised questionnaire was devoted to establishing if the patients were aware of chronic respiratory disease prior to admission, if they had visited a general practitioner or a chest clinic, and had undergone a lung function evaluation. Six patients were unaware of any respiratory disease prior to the acute episode. Six others realised they had suffered from a respiratory disease, but had failed to visit a physician. Among the remaining 26 patients, two-thirds had visited a chest physician. Fourteen of them had undergone spirometry and arterial blood gas measurements. One third had visited a general practitioner but spirometry was performed in only 3 and arterial blood gas analysis in only 1. Thus, chronic respiratory failure is sometimes ignored, and most of the time diagnosed with delay and inadequately evaluated.

Adult↗
PubMed1983

[Perineal gangrene. Apropos of 12 cases].

Twelve cases of necrotizing infections of the perineum were seen over a 18 months period. The etiology was various. This serious affection seems to be more frequent now. The diagnosis is often late, particularly in the rectal injuries with a foreign body. Cellulitis was constant. Severe myonecrosis was present in 6 cases. Anaerobic organisms were found in 50% of the cases. Treatment consisted of initial radical debridement and repeated surgery, antibiotics, and hyperbaric oxygen which was systematically used in our cases. The importance of a diverting colostomy that was done in 10 cases was emphasized. The aggressiveness and advancing nature of the infection with myonecrosis, delayed diagnosis and delayed treatment, were the primary factors responsible for death. 4 of the 12 patients died.

Adult↗
PubMed1983

[Digitalis poisoning and severe respiratory insufficiency].

After seeing 9 cases of digitalis intoxication in patients with acute respiratory decompensation of chronic respiratory failure in one year in an intensive care unit, the authors decided to review the literature on the subject. They set out to: --determine the clinical, laboratory and electrical features of digitalis intoxication in patients with chronic respiratory failure, accounting for the frequency of supraventricular arrhythmias; --evaluate the frequency of this intoxication (20% in this study), introducing a definite risk factor, given the poor haemodynamic effectiveness of digitaloids in this indication; --establish a therapeutic management based on the use of anti-arrhythmics and especially on the prevention of predisposing factors (hypoxaemia--functional renal failure and abuse of diuretics).

Adult↗
PubMed1979

[Left ventricular function in chronic obstructive pulmonary disease after decompensation (author's transl)].

13 patients with chronic obstructive pulmonary disease (COPD) were studied for left ventricular function immediately after acute decompensation. Parameters of right and left ventricular function were measured. Mean pulmonary wedge pressure (Paw) was elevated (11.9 mm Hg) but there was no correlation between Paw and left ventricular end-diastolic pressure (LVEDP). The indices of left ventricular contractility were in the normal range. In 4 patients, LVEDP was too high. A correlation was established between RVEDP and LVEDP. Left ventricular compliance, as studied by the index of Diamond and Forrester, was abnormal. Two conclusions are discussed: (1) in COPD, Paw cannot indicate left ventricular dysfunction; (2) alteration of left ventricular compliance is possibly related to an elevation of RVEDP.

Aged↗
PubMed1978

[Haemodynamic data, blood gas measurements and coagulation disorders in acute respiratory failure of patients with chronic lung disease (author's transl)].

24 subjects with chronic obstructive pulmonary disease were investigated in the course of acute respiratory failure defined by hypoxaemia, hypercapnia and respiratory acidosis. Haemodynamic data of right heart catheterization and coagulation tests were particularly studied. 12 of these subjects had right heart failure defined by a rise of right ventricular end-diastolic pressure above 10 Torr. Coagulation tests brought evidence of consumption coagulopathy in 8 patients, 7 of whom had right heart failure. Data suggest a significant correlation between right heart failure and coagulation disorders in patients with acute exacerbation of chronic obstructive pulmonary disease. These disturbances, accompanied by reduction of pulmonary vascular area, could be in part related to the presence of microthrombi in pulmonary arterial vessels.

Aged↗
PubMed1977

[Early mortality after ingestion of caustic substances].

The authors define the management of a patient following emergency admission for the ingestion of a caustic liquid: immediate assessment by fibroscope oesophagoscopy; avoidance of all corticosteroid therapy and of the insertion of a gastric tube; parenteral alimentation. The frequency of early deaths has considerably decreased since the applications of this method, either as a result of shock or of the inhalation of caustic liquid.

Caustics↗
PubMed1976

[Bronchomotor tonus: per-operative bronchospasm].

The comprehension of the occurrence of bronchospasm during surgery is based on the knowledge of the factors which control bronchomotility: parasympathetic or cholinergic system, essentially bronchoconstrictor; sympathetic adrenergic system, with beta-2 effect, bronchodilator, and with alpha-bronchoconstrictor effect. It is also worth bearing in mind the chemical midiators, in particular, histamine contained in the mast cells, "slow reacting substance of anaphylaxis" which is a bronchoconstrictor substance of slow and prolonged action, Serotonin whose role is more modest. The last mediators known, prostaglandins, play an important role in the regulation of bronchomotility, PGE' are bronchodilators, PGF 2 alpha are bronchoconstrictors. With reference to the development of bronchospasm during anesthesia, one must bear in mind the background, and in particular of the allergy, of a past history of asthma and of the pre-operative functional respiratory condition. One must also bear in mind the anaesthesia, and the pharmacodynamic action of the substances used which can interfere with the phenomena controlling bronchomotor tone.

Adrenergic Fibers↗
PubMed1975

[Respiratory signs of surgical complications after abdominal operations].

The authors present 29 cases of post-operative respiratory complications in abdominal surgery in subjects without any past history of respiratory disorders. They stress the diagnostic value of these cases of acute respiratory failure shown in a third of the cases of surgical complications.

Acute Kidney Injury↗