Patellofemoral complications following total knee arthroplasty. Correlation with implant design and patient risk factors

Grooming behavior of which the primary function appears to be the removal of lice on other (Tanaka and Takefushi [1993] Anthropological Science 101:187-193) was studied in Japanese maceques at Jigokudani Monkey Park, Japan, June 1990-July 1993. Several louse egg-handling techniques used during grooming were identified (with differences in efficiency) in a free-ranging group. In the low-ranking maternal lineages, the distribution of these techniques is quite homogeneous, suggesting social transmission with goal emulation (one form of social learning) based on maternal kin. However, there is considerable variation in the high-ranking matriline. The social system of dominance--the tendency of subordinates to groom more often than to be groomed--may result in oblique transmission of more effective techniques from low-ranking monkeys to some offspring of high-ranking females.     

Terahertz Emission in Asymmetric Quantum Wells by Frequency Mixing of Midinfrared Waves

Generation of terahertz (THz), and sub-THz, coherent waves has been demonstrated at room temperature in GaAs-AlGaAs asymmetric quantum wells by mixing two CO₂ laser beams. Two overlapping regimes were studied: the double resonance regime where three states are involved and the optical rectification which relies on two states only. The measured conversion efficiency of ~10^-7 W^-1 is in reasonable agreement with theoretical predictions. In addition, this technique of THz generation provides a model system to study the emission profile from an ensemble of radiating dipoles. For instance, backward emission and strong diffraction effects have been observed     

Pixelless thermal imaging with integrated quantum-well infraredphotodetector and light-emitting diode

A large pixelless thermal imager based on the epitaxial integration of a GaAs-AlGaAs quantum-well infrared photodetector and a GaAs light-emitting diode is demonstrated. The device transforms a mid-infrared (9 μm) scene to a near-infrared (0.82 μm) emission image with a temperature resolution of ~1 K, limited by the integration capacity of the near-visible camera     

Negative capacitance effect in semiconductor devices

Nontrivial capacitance behavior, including a negative capacitance (NC) effect, observed in a variety of semiconductor devices, is discussed emphasizing the physical mechanism and the theoretical interpretation of experimental data. The correct interpretation of NC can be based on the analysis of the time-domain transient current in response to a small voltage step or impulse, involving a self-consistent treatment of all relevant physical effects (carrier transport, injection, recharging, etc.). NC appears in the case of the nonmonotonic or positive-valued behavior of the time-derivative of the transient current in response to a small voltage step. The time-domain transient current approach is illustrated by simulation results and experimental studies of quantum well infrared photodetectors (QWIPs). The NC effect in QWIPs has been predicted theoretically and confirmed experimentally. The huge NC phenomenon in QWIP's is due to the nonequilibrium transient injection from the emitter caused by the properties of the injection barrier and the inertia of the QW recharging     

Meningiomas of the lateral ventricles of the brain in children

Meningiomas of the lateral ventricles of the brain are rare tumours, accounting for approximately 0.5-5% of all intracranial meningiomas. Their natural history and symptomatology and the possibilities of early diagnosis are presented. The intraventricular location of the slow-growing benign mass provides a compensatory mechanism in the form of reserve space, which contributes to the delay in clinical demonstration of symptoms and signs. This makes the choice of diagnostic procedure an essential problem. CT and MRI are useful in detecting these masses, and magnetic resonance angiography (MRA) has also proved to be of great value in demonstrating the vascular supply of the tumour. This paper deals with two cases. In case 1 CT, MRI and MRA and in case 2 CT examination proved to be very useful. The tumours were removed by a transcortical approach in the posterior area.     

The Influence of Modification,using Strontium and Antimony,on the Properties of AlSi6Cu2Mg and AlSi8Cu4MgMn Aluminium Alloys used for Automobile Castings

Abstract

A presentation is made of the influence of modification, using strontium and antimony, in changing the properties of cast aluminium alloys used in the production of automobile components. Research has embraced shrinkage, fluidity, density, feeding capacity, leak tightness and machinability. Suitable measurement standards required for defining the properties of these alloys have been developed. From the present results, it has been concluded that modification with strontium can be disadvantageous with regard to some properties, such as leak tightness and density, compared with the effect of modification with antimony.