Diagnosis and treatment of aortic valve stenosis

The present review has attempted to summarize the classic symptoms and signs of aortic valve stenosis, especially in an adult. It is emphasized that all the classic signs rarely are present and their absence may mislead an unwary clinician. The diagnostic help provided by noninvasive tests, including echocardiography and phonocardiography, has been emphasized. A need for cardiac catheterization and angiography in most patients prior to corrective surgery is stressed. The natural history of the disease without operative intervention is dim and a significant risk of sudden death exists. The current surgical approach with immediate and long-term results is summarized. Finally, attention has been drawn to the special clinical circumstances when the aortic valve stenosis provides a strinkingly different clinical picture. We cannot find a better way to end this review than by quoting a warning note given by Thomas Lewis in 1920: "It is the faint cry of an anguished and fast failing muscle, which, when it comes, all should strain to hear, for it is not long repeated. A few months, a few years at most, and the end comes."     

The effect of light on the vitamin B2 and the vitamin A content of cheese

Edam type cheese was exposed to sunlight at ambient temperature and to fluorescent light at 5 °C. The loss of vitamin B₂ (riboflavin) and vitamin A was monitored in both the surface and inner layers of the cheese and the results compared with control samples kept in the dark. The loss of riboflavin when exposed to sunlight was shown to be primarily a surface effect but losses of vitamin A were similar throughout the cheese. When exposed to fluorescent light at 5 °C and monitored at intervals for 10 days the loss of riboflavin was still greatest at the surface but a trend to lower values than the control was evident throughout the cheese. Vitamin A losses followed a different pattern in both sunlight and fluorescent light. There was a heavy initial loss throughout the cheese. Under fluorescent light this was followed by a period in which further loss was mainly in the surface layer. Vacuum packaging reduced the loss of riboflavin but had no effect on the loss of vitamin A.     

Large modulation depth, single-moded quantum well waveguide modulator operating around 1.57 mu m

The performance of long wavelength single-mode waveguide modulators suitable for monolithic integration with a quantum well laser is reported. The device operated between 1.560 mu m and 1.570 mu m. The guiding layer was formed by a 0.27 mu m quaternary layer at the centre of which were four 50 AA In/sub 0.53/Ga/sub 0.47/As quantum wells separated by 100 AA InP barrier layers. Lateral confinement was obtained by etching ridges in the top InP contact layer. For devices of 500 mu m length, a modulation depth of 19 dB was obtained at a wavelength of 1.568 mu m with a reverse bias voltage of only 3 V and an internal loss of 2.5 dB.<>     

Impurity induced disordering of GaInAs quantum wells with barriers of AlGaInAs or of GaInAsP

Impurity induced disordering of GaInAs quantum well structures with barriers of AlGaInAs and of GaInAsP has been investigated using boron and fluorine. The impurities were introduced by ion implantation followed by thermal annealing. Annealing unimplanted P-based quaternary material at temperatures greater than 500° C caused a blue shift of the exciton peak. At annealing temperatures greater than 650° C red shifts in the exciton peak of unimplanted Al-based quaternary material were observed. Boron implantation caused small blue shifts of the exciton peak in both material systems at low annealing temperatures. Much larger blue shifts were observed in the fluorine implanted samples.     

Broad-area InAs/GaAs quantum dot lasers incorporating intermixed passive waveguide

InAs/GaAs quantum dot lasers incorporating passive waveguide created by post-growth intermixing processing have been studied. Emission wavelength of the passive section shows relative blueshift as high as 135 nm with respect to the emission wavelength of the active section. Intrinsic losses in the section formed by the intermixing are very small. Broad-area lasers with 100 mum stripe width incorporating intermixed section have demonstrated improvements in far-field pattern under both pulsed and continuous wave pumping current     

数据传输速率不断提升的以太网技术

很难想象一种技术利用最初为语音业务设计的铜线，竟然能几乎天衣无缝地使带宽增大2个数量级。本文阐述当今的以太网(Ethernet)如何像20年前那样继续令人惊奇。     

Millimeter-wave low-noise and high-power metamorphic HEMTamplifiers and devices on GaAs substrates

This paper reports on state of-the-art HEMT devices and circuit results utilizing 32% and 60% indium content InGaAs channel metamorphic technology on GaAs substrates. The 60% In metamorphic HEMT (MHEMT) has achieved an excellent 0.61-dB minimum noise figure with 11.8 dB of associated gain at 26 GHz. Using this MHEMT technology, two and three-stage Ka-band low-noise amplifiers (LNAs) have demonstrated <1.4-dB noise figure with 16 dB of gain and <1.7 with 26 dB of gain, respectively. The 32% In MHEMT device has overcome the <3.5-V drain bias limitation of other MHEMT power devices, showing a power density of 650 mW/mm at 35 GHz, with V_ds=6 V     

照亮消费和工业产品 美好前景的光电传感器

光能级的精确检测在汽车、消费以及工业设备的应用中有无限的前景。新一代光电传感器简化了设计师的任务,以最低成本实现色彩分析。