La capacité d'imitation à la naissance: Elle existe, mais que signifie-t-elle?

Much of the research on early imitations is restricted to the problem of their existence, without trying to describe them. The aim of this research is to analyze the principal characteristics of neonatal imitations in order to differentiate them from the later imitations. The behaviours of 16 neonates were filmed. A facial and a manual model were used. A detailed analysis of newborn behaviour revealed several features of early imitations: They were selective, quite exact, integrated, and occurred with short-time latencies. These results are interpreted within a cognitive framework. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resonant tunneling diodes as sources for millimeter andsubmillimeter wavelengths

High quality resonant tunneling diodes have been fabricated and tested as sources for millimeter and submillimeter wavelengths. The devices have shown excellent I-V characteristics with peak-to-valley current ratios as high as 6:1 and current densities in the range of 50-150 kA/cm² at 300 K. Used as local oscillators, the diodes are capable of state of the art output power delivered by AlGaAs-based tunneling devices. As harmonic multipliers, a frequency of 320 GHz has been achieved by quintupling the fundamental oscillation of a klystron source     

(Zn, Mg)O/ZnO-based heterostructures grown by molecular beam epitaxy on sapphire: Polar vs. non-polar

Zinc oxide (ZnO) has recently attracted considerable attention because of its unique physical properties and its potential applications in the blue and UV spectral range. Up to now, ZnO-based heterostructures have mostly been grown in a c-orientation. The growth of non-polar layers along the a-direction [1 1 2¯ 0] has been proposed to avoid any built-in electric fields in the c-direction. Polar and non-polar quantum wells (QWs) embedded in (Zn, Mg)O barriers were grown on an optimized buffer. We compare the photoluminescence (PL) emission of a- and c-oriented QWs. From this comparison, we demonstrate that the QWs exhibit confinement but no indication of quantum confined Stark effect, contrary to what is observed in c-oriented structures. In the non-polar orientation, it is shown that the thermal quenching is not related to the thermal escape of excitons from the ZnO area, since the calculated activation energies are much lower.     

Optimization of large band-gap barriers for reducing leakage in bipolar cascade lasers

In order to study the characteristics of bipolar cascade lasers, we have developed a fully consistent transport model compatible with Esaki tunnel junctions (TJs). First, we compare the calculated electrical characteristics of TJs made of different InGaAsP lattice-matched to InP materials with different doping concentrations. Then, a complex (p-n)-(n/sup ++/p/sup ++/)-(p-n)-(n/sup ++/p/sup ++/)-p-n) structure is implemented. The Esaki junctions are cladded by doped InP current confining layers, the width of which is optimized to prevent electron leakage. We find that a 25-nm-wide InP barrier confines more than 98% of the electron current for a total injection current of 10 kA.cm/sup -2/ at room temperature. The predicted differential quantum efficiency is then 230%.     

Sporicidal effect of Presept and Chloramine B on Bacillus cereus spores

Recently the number of plastic operations of the cardiac valves is increasing. The authors present an account on 10 patients with stenosis of the aortic valve where they performed a reconstruction without the necessity of a prosthesis. Commissurotomy and rasping can be performed in patients when the basic anatomical shape and dimensions of the valve are preserved. None of the patients died, one was successfully reoperated on account of aortic insufficiency. The authors describe and discuss the tactics and technique of the operation. They discuss the possibility of reconstruction of the aortic valve in patients indicated for aortocoronary reconstruction where the aortic defect appears to be of minor impact.     

Emission and capture of electrons in multiquantum-well structures

The mechanisms of unipolar emission and capture of electrons are studied in multiquantum-well structures in relation with the quantum-well infrared photoconductors (QWIP's). We clarify the roles played by the physical parameters which appear in the different QWIP photoresponse models, i.e., the photoconductive and the photoemissive ones. We then describe the experimental procedures which allow us to independently determine these different parameters: deep level optical spectroscopy for the electron emission probability, impedance spectroscopy for the quantum-well capture velocity and thermal emission time, as well as the infrared photoconductive gain for the unipolar electron capture time. The measured dependence of these parameters on photon energy and electric field sheds light on the microscopic physical phenomena which are involved in quantum-well infrared photodetection. Theoretical results on optical phonon mediated transitions in an applied electric field from barrier to well states show good agreement with experiment at low fields but less dependence on the field. Finally, this theoretical approach allows us to connect the different parameters and solve the apparent discrepancy between the QWIP photoresponse models     

Development of the cribriform plate and of the lamina mediana

From September 1992 to November 1996, 28 patients underwent laparoscopic adrenalectomy at Osaka University Medical Hospital. They were compared with 25 instances of conventional open surgery performed between May 1990 and April 1996 at the same institution. Laparoscopic adrenalectomy was performed via either a transperitoneal or a retroperitoneal approach. The mean operative time of 375 minutes for laparoscopic adrenalectomy was significantly longer than that of 133 minutes for open surgery. The average hospital stay for laparoscopic surgery was significantly shorter than that of conventional open adrenalectomy. The convalescent period was also significantly shorter in the patients who had laparoscopic adrenalectomy. There was no statistical difference in blood loss during the operation or the number of doses of analgesics administered after operation in the two groups. We conclude that laparoscopic adrenalectomy is one of the options to be selected in surgically managing adrenal tumors. Laparoscopic adrenalectomy could become a standard operative procedure as instruments and techniques of laparoscopy improve significantly.