Optical properties of individual CdS/CdSe/CdS nanocrystals: spherical quantum wells as single-photon sources.

We have synthesized CdS(1.3 nm)/CdSe(1.7 nm)/CdS(3.4 nm) spherical quantum wells (SQWs) with a diameter of 13 nm and demonstrated the first photon-antibunching from their emission, labelling them as single-photon sources. Antibunching survives even at high excitation intensities, ruling-out strong emission from the bi-exciton. For the largest intensities, antibunching coupled to spectral measurements reveal the signature of a blue-shifted emission, associated to an irreversible photo-aging effect. A statistical analysis over 26 SQWs demonstrates a moderate correlation between the energy of the main and the blue-shifted emission. Intensity-timetraces recorded on 28 single SQWs show weak blinking, with a median time spent in the bright state of 89%. Their emission decay reveals a complex dynamic with either three or four exponential components. We assigned three of them to the neutral and singly-charged excitons and the slowest to defect emission. While SQWs have been initially designed for laser-oriented applications, we demonstrate that they can serve as efficient single-photon sources.

Self-assembled quantum dots in a nanowire system for quantum photonics.

Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-in-nanowire system that reproducibly self-assembles in core-shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells.

Probing single-charge fluctuations at a GaAs/AlAs interface using laser spectroscopy on a nearby InGaAs quantum dot.

We probe local charge fluctuations in a semiconductor via laser spectroscopy on a nearby self-assembled quantum dot. We demonstrate that the quantum dot is sensitive to changes in the local environment at the single-charge level. By controlling the charge state of localized defects, we are able to infer the distance of the defects from the quantum dot with ±5 nm resolution. The results identify and quantify the main source of charge noise in the commonly used optical field-effect devices.

[A rare cause of continuous thoracic murmur. A fistula between the internal mammary artery and the pulmonary circulation]. / Une cause rare de souffle continu du thorax. Fistule entre l'artère mammaire interne et la circulation pulmonaire.

The authors present a case of a continuous right lateral sternal murmur which led to the discovery of a systemic-to-pulmonary fistula at the origin of the internal mammary artery. The fact that the patient had a right pulmonary abscess with pyopneumothorax drained several years previously has led them to discuss the possible etiology of this fistula. The murmur disappeared after surgical treatment.

[Results of cardiac surgery in patients over 70 years of age. Apropos of a retrospective study of 170 patients]. / Résultats de la chirurgie cardiaque chez les patients âgés de plus de 70 ans. A propos d'une étude rétrospective concernant 170 patients.

The ever increasing age of the general population and the frequency of coronary and aortic lesions in patients aged 70 or older make cardiac surgery in the elderly a topic of current interest. In a retrospective study of 170 cases the overall mortality rate was 14 p. 100 (4.7 p. 100 in 1986). During the past two years (1985 and 1986), the mortality rates in patients with coronary disease who underwent elective surgery were 10 p. 100 and 4 p. 100 respectively. Emergency surgery (left coronary trunk and unstable angina excluded) and associated operations on the heart made the prognosis worse with overall mortality rates of 13 p. 100 and 15 p. 100 respectively (9 p. 100 in 1985, 10 p. 100 in 1986). In aortic valve surgery, hospital mortality rates were 28 p. 100 in 1985 and 6 p. 100 in 1986. Post-operative morbidity was high (52 p. 100 of patients) and consisted mostly of respiratory and neurological complications (14.7 p. 100 and 9.4 p. 100 respectively of all patients). Only 4 p. 100 of the patients developed peri-operative myocardial infarction. Functional results were satisfactory in both coronary disease and heart valve disease patients. The survival rate at 4 years was 74.5 +/- 10 p. 100 globally and 87.3 +/- 9 p. 100 in coronary patients operated upon electively. Thus, the considerable advances in surgical techniques and post-operative intensive care achieved during the last few years have significantly improved the results obtained in this population.(ABSTRACT TRUNCATED AT 250 WORDS)

[Symptomatology of hydatid cyst of the heart. Study of a continuous series of 13 cases and value of x-ray computed tomography]. / Séméiologie du kyste hydatique du coeur. Etude d'une série continue de 13 cas et intérêt du scanner.

Thirteen consecutive cases of cardiac hydatic cyst were studied. The cysts were usually multiple, predominantly left ventricular. There were two cases of rupture of left ventricular cysts with systemic embolism, and three ruptures of right ventricular cysts causing pulmonary embolism. The average age of the patients was 31 years: 12 patients lived in regions where hydatid disease was endemic. Other localisations of hydatic disease were found in 7 cases. Two patients were completely asymptomatic. Three patients presented with a tumoral syndrome. The presentation was atypical simulating coronary artery disease in 2 cases, valvular heart disease in 2 cases, pericarditis in 2 cases and bronchopneumonia in 3 cases. The electrocardiogramme showed sinus rhythm in all cases and changes of subepicardial ischaemia in 8 cases and acute cor pulmonale in 3 cases. Chest X-ray showed a localised deformation of the cardiac silhouette in 5 cases and calcification in 4 cases. Direct angiocardiographic signs were present in 2 out of 8 cases; usually there was an indirect image of endocavitary filling defect. The tumour was demonstrated by 2D echocardiography in the three most recent cases. The value of CAT was assessed in the last 2 cases: it was absolutely diagnostic in 1 case of septal localisation. The results were poor in the second case due to the presence of mitral calcification. Twelve patients underwent surgery; there were 3 deaths due to rupture and 1 death before surgery. The clinical presentation of cardiac hydatid disease is very variable and the diagnosis is difficult.(ABSTRACT TRUNCATED AT 250 WORDS)

[Indications and results of surgery in native valve infectious endocarditis. Apropos of 104 surgically-treated cases]. / Indications et résultats de la chirurgie dans l'endocardite infectieuse sur valve native. A propos de 104 cas opérés.

From 1972 to 1984, 104 cases of aortic valve infectious endocarditis were treated surgically. The average age of the patients was 40 years and the majority were men (69/104). Forty patients had no previous cardiac disease; 44 patients had documented valvular heart disease, which was unlikely in the remaining 20 patients. There were 16 mitral valve, 55 aortic valve, 1 tricuspid, 30 mitro-aortic, 1 mitro-tricuspid and 1 mitro-aorto-tricuspid valve infections. Aerococcus viridans was isolated in only 4 out of 71 positive cultures: the prevalence of the infecting organisms was otherwise normal (30 staphylococcus, 30 streptococcus, 7 rare organisms). Forty one patients were operated because of haemodynamic deterioration, 13 for resistant infection and 13 for an association of both indications; 37 patients were operated for embolism or threatening vegetations. Eight patients were in functional Class I, 26 in Class II, 52 in Class III and 17 in Class IV. The patients were divided into 4 groups according to the degree of surgical emergency (26 extremely urgent, 26 semi urgent, 32 controlled endocarditis and 20 chronic endocarditis). The actuarial survival rate was 70% at 5 years. Poor prognostic factors were the presence of previous valve disease, the isolation of a staphylococcus and an aortic valve localisation. The degree of emergency and the precise surgical indication did not seem to be important. Most patients at long term were in functional Classes I or II. There was no preferential indication for bioprosthetic or mechanical valve replacement in endocarditis.(ABSTRACT TRUNCATED AT 250 WORDS)

[Tricuspid endocarditis with right-left shunt in the atrium]. / Endocardite tricuspidienne avec shunt droite-gauche à l'étage auriculaire.

A case of tricuspid regurgitation due to endocarditis causing a right-to-left shunt through a patent foramen ovale is reported. Tricuspid valve endocarditis occurred after septic abortion and caused valvular regurgitation with dyspnea and cyanosis. The diagnosis was made by echocardiography and the finding of peripheral arterial desaturation, and it was confirmed at surgery. The physiopathology of these right-to-left shunts is the same as that already described during traumatic tricuspid regurgitation: reopening of the foramen ovale by the right atrial dilatation and ventricularisation of right atrial pressures. The presence of a shunt is an indication for surgery.

[False subaortic aneurysm after surgery of calcified aortic stenosis. Apropos of a case treated successfully]. / Faux anévrysme sous-aortique après chirurgie d'un rétrécissement aortique calcifié.

The authors report a case of false aneurysm of the posterior subaortic region of the left ventricle after a technically difficult surgical decalcification in a case of aortic stenosis. At reoperation, the surgeon used the femoral artery and both vena cavae for canulation. A direct approach of this "vascular" tumour, which was exterior to the great vessels, confirmed the diagnosis and enabled the localisation of the internal orifice inside the left ventricle. This was closed simply by suturing. No previous cases of this kind were found in the literature. This report underlines the necessity of taking the greatest care when decalcifying this region in order to avoid this type of serious complication.

[Electrophysiological effects of intravenous magnesium sulfate in man]. / Effets électrophysiologiques du sulfate de magnésium intraveineux chez l'homme.

Magnesium salts have been used for many years to correct a wide variety of arrhythmias. A few experimental studies have been devoted to their electrophysiological effects, but these remain poorly documented in man, hence this study. An electrophysiological investigation was conducted in 24 patients before, and immediately after a bolus intravenous injection of magnesium sulphate in doses of 1.5 g to 12 patients (group I) and 3 g to 12 other patients (group II), followed by a continuous infusion at the rate of 1 mg/min. The drug had no influence on heart rate, duration of QRS, QT and QTc intervals and ventricular refractory period. A small, but statistically significant prolongation of HV (from 57 to 59 ms, p less than 0.05) was observed in group II. Analysis of the results in group I revealed a moderate but significant prolongation of the PR and AH intervals. The electrophysiological effects were distinctly more pronounced in group II patients, with significant prolongation of: PR and AH intervals, effective refractory period of the right atrium and AV node, Wenckebach's point, corrected sinus node recovery time and sinoatrial conduction time. These results demonstrate that magnesium sulphate principally acts on the sinus node, the AV node and the atrium, suggesting a blocking effect on calcium channels.

[Inidications for multivalve prostheses]. / Les indications des prothèses pluri-valvulaires

The authors consider that the indications for surgery should take into account three unknowns: the natural history of the valvulopathies, our incomplete state of knowledge about the outcome in operated cases, and surgical progress, which may transform the whole subject in a short time. They emphasize the seriousness of the disorders in which mitral incompetence is associated with aortic stenosis and/or incompetence; such cases justify earlier surgery. By contrast, some cases of aortic incompetence, when associated with a predominant mitral valve lesion, may not constitute an indication for valve replacement. Tricuspid annuloplasty is a noteworthy advance which provides a simple answer to some of the problems.

[Application of echocardiography to the diagnosis of tricuspid valve diseases. Apropos of 103 cases]. / Apport de l'échocardiographie au diagnostic des valvulopathies tricuspidiennes. A propos de 103 cas.

In a series of 103 consecutive surgical patients, the normal and pathological echocardiographic appearances of the tricuspid valve were analysed and compared with the anatomical findings. It was possible to define the nature of the lesions by echocardiography, which was superior to angiography in this field. The right ventricular index (right ventricular dimension body surface area) correlated well with the mean pulmonary artery pressure (r = 0.75; p less than 0.001). The index may be useful in the long term follow-up of post-operative patients.

[Resistant ventricular tachycardia caused by right ventricular dysplasia. A case of surgical recovery reported 6 years after intervention]. / Tachycardie ventriculaire rebelle par dysplasie ventriculaire droite. Un cas de guérison chirurgicale rapporté à 6 ans de l'intervention.

A 52 year old patient with no previous medical history had an attack of ventricular tachycardia, the configuration of which showed left sided delay. Electrical reduction was followed by multiple recurrences. There were ST-T wave changes over the right precordium on the basal ECG. The hydro-electrolytic equilibrium was normal. Coronary angiography and selective left ventricular cineangiography were also normal. Right angiocardiography showed an aneurysmal deformation of the pulmonary infundibulum. The recurrence of attacks over a two year period led to several hospital admissions, demonstrating the failure of antiarrhytmic therapy. The attacks became so frequent in the last three months that surgery was undertaken. Epicardial mapping showed delayed potentials over the pulmonary infundibulum and surgery consisted in resection of the abnormal infundibular zone. The macro- and microscopic pathological findings were of wall thinning and muscular degeneration with fibrosis and fatty infiltration. The authors discuss the relationship between right ventricular dysplasia and a localised form of Uhl's anomaly. Six years after surgery the patient has had no recurrence of the arrhythmia or shown signs of cardiac failure in the absence of any drug therapy.

[Cardiac hydatidosis. Review of recent literature and report of 15 cases]. / L'hydatidose cardiaque. Revue de la littérature récente à propos d'une expérience de quinze cas.

In the context of a personal series of fifteen cases of hydatid cyst of the heart, the authors present a computerized review of the last one hundred cases published in the literature. The modern features of the disease are discussed together with its severity (mortality of 23.47% in 98 recent cases). Despite the considerable contribution of ultrasonography, computed tomography and magnetic resonance imaging, a certain number of pejorative criteria appear to persist:delayed diagnosis, diagnostic error, acute pulmonary oedema and incomplete surgical cure.

[Disobstruction of the inferior vena cava under extracorporeal circulation]. / Désobstruction cave inférieure sous circulation extra-corporelle.

An original technique used to remove obstructions of the inferior vena cava under cardiopulmonary bypass is described. This technique is indicated in pulmonary embolectomy or to dispose of a vena cava clot prolapsed into the right cardiac cavities. Through a rigid and blunt thoracic drain introduced via the right atrium, a Fogarthy venous catheter is pushed into the inferior vena cava, thus avoiding the risks of accidental passage into the supra-hepatic or renal veins and blockage in a thebesian valve. The catheter is inflated, then removed together with the drain, thereby freeing the caval lumen. The technique is reliable and reproducible, and it has proved very effective.

[Suspension of the heart during aortocoronary bypass. A simplified technic]. / Suspension du coeur au cours des pontages aorto-coronariens. Une technique simplifiée.

A technique for suspending the heart, thereby facilitating exposure of the coronary arteries, is described. In this perfectly simple and safe technique, the heart is suspended by a gauze compress passed behind the inferior vena cava and forming a sling.

[Peculiar indications and results of the use of a blood cell saver apparatus in cardiac surgery]. / Indications particulières et résultats de l'apport d'un appareil récupérateur de sang (ARS) en chirurgie cardiaque.

Results are reported of the use of autotransfusion by means of the blood cell saver in a group of patients at high risk for hemorrhage in Heart Surgery Department. Methods employed are described, and results are discussed: these were encouraging both from the clinical and biological viewpoints. The cost benefits of this procedure are emphasized and technical perspectives outlined with respect to recovery of plasma and platelets.