Distinctive Picosecond Spin Polarization Dynamics in Bulk Half Metals.

Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce an exotic picosecond spin dynamics. In particular, conversely to what is observed in conventional metals and semiconductors, the thermalization process in HMs leads to a long living partially thermalized configuration characterized by three Fermi-Dirac distributions for the minority, majority conduction, and majority valence electrons, respectively. Remarkably, these distributions have the same temperature but different chemical potentials. This unusual thermodynamic state is causing a persistent nonequilibrium spin polarization only well above the Fermi energy. Femtosecond spin dynamics experiments performed on Fe_{3}O_{4} by time- and spin-resolved photoelectron spectroscopy support our model. Furthermore, the spin polarization response proves to be very robust and it can be adopted to selectively test the bulk HM character in a wide range of compounds.

Topological electronic structure and Rashba effect in Bi thin layers: theoretical predictions and experiments.

The goal of the present review is to cross-compare theoretical predictions with selected experimental results on bismuth thin films exhibiting topological properties and a strong Rashba effect. The theoretical prediction that a single free-standing Bi(1 1 1) bilayer is a topological insulator has triggered a large series of studies of ultrathin Bi(1 1 1) films grown on various substrates. Using selected examples we review theoretical predictions of atomic and electronic structure of Bi thin films exhibiting topological properties due to interaction with a substrate. We also survey experimental signatures of topological surface states and Rashba effect, as obtained mostly by angle- and spin-resolved photoelectron spectroscopy.

[Design of a force sensor to evaluate the grasping movement]. / Développement d'un capteur de force pour l'analyse du comportement de grasping.

Grasping phenomena are abnormal motor behaviours described after cerebral lesions. They are defined as a stereotyped response, consisting of a progressive forced closure of the patient's hand on the examiner's fingers, when they are slowly moved exerting a strong pressure across the palm in an upward direction. Several types are described. The aim of the study was to develop a force sensor to evaluate the force of grasping in accordance with the force of dragging. The characteristics of this force sensor are presented and the clinical application in two selected patients demonstrated.

[Reentry tachycardia with complete atrioventricular dissociation probably connected with the right Mahaïm bundle]. / Tachycardie par réentrée avec dissociation auriculo-ventriculaire complète liée probablement à un faisceau de Mahaïm droit.

A case of reentrant tachycardia with narrow and wide ventricular complexes without appearances of preexcitation is reported. Electrophysiological investigation showed complete retrograde atrioventricular block during tachycardia; left bundle branch block did not show the tachycardia rate. The reentry loop probably comprised: the His bundle, the right bundle branch, a right Mahaïm bundle and possibly a myocardial bridge. Possible intra-hisian reentry is discussed. The initiation of the tachycardia is analysed together with the possible consequences of permanent cardiac pacing.

[Can the quality of renal grafts be judged on basis of the organ donors?]. / Peut-on juger de la qualité du greffon rénal à partir du donneur d'organes?

The aim of this study is to find brain dead organ donor parameters able to predict the functional value of a kidney graft after transplantation. It is a retrospective, multicenter study, set in the east of France (Besançon, Nancy, Reims, Strasbourg). All donors harvested over an 18 month period (n = 169), and kidney grafts transplanted in a recipient in the same region (n = 298) are studied. Recipients from another region receiving a kidney graft as well as kidney grafts transplanted in other regions are not studied. Parameters studied in the donor are: age, sex, etiology of brain death, vascular disease, hemodynamic stability, use of epinephrine, diuresis, creatinine level, graft preservation solution. Parameters studied in the recipient are: age, sex, first transplantation or not, cold ischemia duration, warm ischemia duration, early post-transplantation diuresis and creatinine level evolution, dialysis requirement, immunosuppression, creatinine level at 1, 6 and 12 month. During the early post transplantation period, 264 recipients recovered diuresis, and the creatinine level felt in 246 cases. 31 patients required dialysis. 12 months after transplantation, 128 patients had a normal graft function (creatinine level < 15 mg/l). No parameter in the donor was found able to predict kidney graft function after transplantation. In fact, it is the amount of several risk factors due to donor data, organ retrieval and preservation, and kidney transplantation which is responsible for the early graft function. This points out the importance of being very careful when there is already a risk factor due to old age or vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)

[Systemic candidiasis]. / Candidoses systémiques.

Candida proliferate within the body of patients with deficient cellular immunity either by the haematogenous route or by adjacency. This condition is often found in hospital patients. It explains the increasing incidence of disseminated candidiasis. They are preferentially found in patients who have had complicated surgery, mostly of the gastrointestinal tract and the heart, or transplant surgery (except for kidney transplants), or who have had prolonged intensive care. Other patients concerned are neonates with a low birth weight, haemato-oncology patients, heroin addicts and AIDS patients. Clinical signs are usually unspecific. When there is widespread involvement, clinical signs can be defined by the secondary locations, especially within the kidneys, lung, endocardium and brain in surgical patients, and liver and spleen in haemato-oncology patients. Eye, skin, gastrointestinal tract, and indeed, muscle lesions which are easily accessible, should be looked for routinely. This helps to ascertain the diagnosis, by showing the presence of Candida in the tissues. Moreover, isolating Candida from places which are normally sterile confirms deep-seated candidiasis. However, the presence of Candida in urine, bronchi, or drainage fluids is only the witness of saprophytism. This underlines the usefulness of immunological tests, which should soon benefit from the availability of new kits for the detection of cytoplasmic antigens. Indeed, the search for antibodies or circulating metabolites do not provide, at present, significantly different results in patients who have only been colonised and in those who have a systemic candidiasis. Interesting results are only obtained by showing the presence of mannans, in research laboratories. For treatment, amphotericin B remains the standard antifungal agent, and the association of amphotericin B with flucytosine the recommended association. However, drugs such as the new triazoles, among which fluconazole is particularly well tolerated and efficient, may considerably alter the principles of treatment. Finally, combining a fungal decontamination of the gut should help reduce the very high death rate of systemic candidiasis.

[Abscess of the atrium: a complication of central venous catheters]. / L'abcès de l'oreillette: une complication des cathéters veineux centraux.

A 27-year-old female patient was admitted for parenteral feeding and treatment of an acute episode of her steroid dependent Crohn's disease. An intravenous catheter was inserted, the tip being located in the right atrium. This central line was accidentally removed ten days later and replaced with another one also ending in the right atrium. The patient's condition improved over a four-week period. Thereafter, she suddenly became confused and complained of abdominal pain with contracture. She displayed renal failure, coagulation disorders, and decreased blood cell counts. This was followed by a septic shock requiring mechanical ventilation and adrenaline. Laparotomy failed to reveal a cause for the patient's condition. She improved and was extubated four days later. From then on, she had fever (39 degrees C) again. Her catheter was replaced, the tip of this third one being inside the superior vena cava. Staphylococcus epidermidis was obtained from the catheter tip, as well as from four consecutive blood cultures. Despite administration of three different antibiotics, the high fever persisted (40 degrees C). Finally, the occurrence of a systolic murmur led to the discovery, with cardiac ultrasonography, of a mobile right atrial abscess, which engaged into the tricuspid valve at every contraction. Surgery to remove this mass was rapidly carried out. The bacterium was the same as that which had been isolated from the catheter. The patient improved and was able to return home a fortnight later. The diagnosis and prevention of this complication is discussed. The tip of central venous catheter should not be kept inside the atrium.

[Value of hormonal treatment with triiodothyronine and cortisone in brain dead patients]. / Intérêt de l'hormonothérapie associant triiodothyronine et cortisone chez le patient en état de mort cérébrale.

Brain death leads to substantial falls in the plasma levels of cortisol and tri-iodothyronine (T3). These alterations may be responsible for physiological instability in these patients, and impairment in donor organ function. A double-blind study was therefore designed to assess the possible improvement in metabolism and haemodynamic stability in brain-dead organ donors treated with T3 and cortisone. Forty adult brain-dead patients were randomly assigned to two groups, the patients of the treated group were given every hour, or half hour, 2 or 4 micrograms T3 and 100 mg hydrocortisone intravenously, and those of the placebo group normal saline. Both groups of patients received conventional management for brain-dead donors. The main assessment criterion was the haemodynamic course, appreciated by the Pasys, the CVP and the needs in dobutamine; the secondary criterion was the start, or worsening, of a metabolic acidosis, as judged by the pH, the level of arterial bicarbonate, and the needs in sodium bicarbonate. The two groups were comparable for age, sex, aetiology of brain death, the delay between brain death and the start of the experimental protocol, and the duration of this protocol. There were differences between the two groups, which were not statistically significant: improvement in haemodynamic profile (hormone group 9/20 versus placebo group 10/20); worsening in haemodynamic profile (2/20 vs 4/20); increased requirements in dobutamine (2/20 vs 4/20); decreased requirements in inotropic support (15/20 vs 13/20); mean dose of dobutamine (3.1 +/- 4.2 micrograms.kg-1 vs 2.5 +/- 3.8 micrograms.kg-1); metabolic acidosis (5/20 vs 5/20); mean bicarbonate dose (30.0 +/- 67.7 mmol vs 45.0 +/- 74.2 mmol); donors harvested (20/20 vs 18/20).(ABSTRACT TRUNCATED AT 250 WORDS)

[Rhabdomyolysis after ORL surgery in prolonged lateral position]. / Rhabdomyolyse au décours d'une chirurgie ORL en décubitus latéral prolongé.

Two cases are reported of upper limb rhabdomyolysis occurring after prolonged ENT cancer surgery, the patient being part of the time in the right lateral position, with the left forearm outstretched. Surgery consisted of a vertical hemilaryngectomy with immediate parascapular free graft reconstruction in a 48-year-old man (10 h of surgery, with 6 h in a lateral position) and the surgical removal of a neoplasm involving the mouth floor and larynx in a 62-year-old man including parascapsular free graft reconstruction (10 h of surgery, with 7 h in a lateral position). In the early postoperative period, the patients complained of severe pain in the left forearm. There was a tense painful swelling of the forearm, combined with an increase in creatinine kinase plasma concentration, and myoglobinaemia. The mechanism involved was most likely a compression of the forearm muscles, together with prolonged surgery and the patient position. The part played by the state of the patients is discussed. Diagnosis must be made as soon as possible, as the only efficient treatment consists of an early fasciotomy together with the administration of alkali to avoid renal failure.

[Measurement of cardiac output by thoracic electrical bioimpedance or thermodilution]. / Mesure du débit cardiaque par bioimpédance électrique thoracique ou par thermodilution.

The present study was designed to assess a new non invasive method for measuring cardiac output. The thoracic electrical bioimpedance method was compared with the reference one, thermodilution. The measurements were made simultaneously with NCCOM3 (bioimpedance) using the freeze data mode, and with a Swan-Ganz catheter and a haemodynamic computer (thermodilution). The study involved 11 spontaneously breathing patients in a steady haemodynamic state. Ten measurements were carried out with both methods for each patient. Statistical analysis of the 110 paired values was carried out by computer. The various statistical tests applied confirmed that there was a highly significant correlation between values for cardiac output obtained by each of these two methods (r = 0.818; p less than 0.005); they also showed a significantly more important dispersion of the measures for each patient with thermodilution. The mean value of the thermodilution "standard deviation" (0.64 l.min-1) was significantly more important (p less than 0.005) than the one with NCCOM3 (0.24 l.min-1). Thoracic electrical bioimpedance appeared a safe method for measuring cardiac output, providing the limits of the method are kept. The objective is not to replace the Swan-Ganz catheter, but to propose an alternative method for measuring cardiac output. This method is very interesting in many circumstances, particularly for intensive care patients: it is a non invasive technique, continual measurement is not time-limited, and its use is very easy.

[Metformin-associated lactic acidosis precipitated by acute renal failure]. / Acidose lactique toxique à la metformine provoquée par une insuffisance rénale aiguë.

In type II diabetes treated with metformin, lactic acidosis is a rare but severe complication. Commonly patients with lactic acidosis show signs of shock, tissue hypoxia, acute hepatic or renal failure and the link between metformin therapy and lactic acidosis may be coincidental, associated or causal. Excessive plasma metformin concentrations show that lactic acidosis is due to a toxicological mechanism. The case of a 65-year-old woman with type II diabetes, in whom severe type B2 lactic acidosis secondary to metformin was precipitated by acute renal failure, is presented. The association of diuretics with non-steroidal anti-inflammatory drugs and colchicine was responsible for a volume depletion and an acute renal failure. Initial serum creatinine was 643 micromol x l(-1) and arterial blood gas analysis revealed a pH of 7.01. Aggressive volume expansion and correction of the acidosis with intravenous bicarbonate therapy failed. At the intensive care unit, calculated anion gap was 35 mmol x l(-1) (normal range 10-18) and lactate concentration was 12.4 mmol x l(-1), liver profile was normal. Prolonged haemodialysis using bicarbonate dialysate resulted in a favourable outcome. Toxicology confirmed retrospectively the presence of a plasma concentration of metformine of 20 mg x l(-1) (normal <2). One month after this episode she has made a recovery of tubular necrosis, although no longer prescribed metformin. Metformin should be temporally stopped when acute renal failure occurs or is anticipated; patient with acute renal failure and high calculated anion gap should benefit from lactate measurements. Early bicarbonate haemodialysis is an adequate treatment of lactic acidosis caused by accumulation of metformin associated with acute renal failure

Ferromagnetic Mn-doped Si0.3Ge0.7 nanodots self-assembled on Si(100).

Densely packed epitaxial Mn-doped Si(0.3)Ge(0.7) nanodots self-assembled on Si(100) have been obtained. Their structural properties were studied using reflection high-energy electron diffraction, energy dispersive x-ray diffraction, atomic force microscopy, extended x-ray absorption fine structure measurements and high-resolution transmission electron microscopy. Mn(5)Ge(1)Si(2) crystallites embedded in Si(0.3)Ge(0.7) were found. They exhibit a ferromagnetic behaviour with a Curie temperature of about 225 K.

Improvements to Hoang et al.'s method for measuring passive length-tension properties of human gastrocnemius muscle in vivo.

While the passive mechanical properties of a musculo-articular complex can be determined using the relationship between the articular angle and the passive torque developed in resistance to motion, the properties of different structures of the musculo-articular complex cannot be easily assessed. Recently, an elegant method has been proposed to estimate the passive length-tension properties of gastrocnemius muscle-tendon unit (Hoang et al., 2005). In the present paper, two improvements of this method are proposed to decrease the number of parameters required to assess the passive length-tension relationship from 9 to 2. Furthermore, these two parameters have physical meaning as they represent a passive muscle-tendon stiffness index (alpha) and the muscle-tendon slack length (l(0)). alpha and l(0) are relevant clinical parameters to study the chronic effects of aging, training protocols or neuromuscular pathologies on the passive mechanical properties of the muscle-tendon unit. Eight healthy subjects performed passive loading/unloading cycles at 5 degrees /s with knee angle at 6 knee angles to assess the torque-angle relationships and to apply the modified method. Numerical optimization was used to minimize the squared error between the experimental and the modeled relationships. The experiment was performed twice to assess the reliability of alpha and l(0) across days. The results showed that the reliability of the two parameters was good (alpha: ICC=0.82, SEM=6.1m(-1), CV=6.3% and l(0): ICC=0.83, SEM=0.29 cm, CV=0.9%). Using a sensitivity analysis, it was shown that the numerical solution was unique. Overall, the findings may provide increased interest in the method proposed by Hoang et al. (2005).