Temperature dependence study of two-dimensional electron gas effecton the noise performance of high frequency field effect transistors

We present experimental evidence that the noise figure (NF) and associated gain equal to those achieved with GaAs pseudomorphic high electron mobility transistors (GaAs p-HEMT's) can also be accomplished by ion implanted GaAs metal-semiconductor field-effect transistors (GaAs MESFET's). These measured noise figure results as a function of low temperature for GaAs MESFET's and p-HEMT's clearly suggest that the transport properties of the two-dimensional electron gas in HEMT's and p-HEMT's do not make a significant contribution to the noise reduction at high frequency operation of these devices     

MPEG-2 over ATM for video dial tone networks: issues and strategies

Market growth for PC multimedia and digital video owes largely to the rapid adoption of ISO compression standards by the industry. For video dial tone (VDT) services, the MPEG-2 set of standards have clearly emerged as the preferred coding method for VDT networks. For point-to-point switched video or multimedia connections, ATM has emerged as the technology of choice for switching and transport. This article describes how compressed digital video is transported over a VDT network, what some of the issues are, and how they are being addressed by the industry. It describes a generic VDT reference architecture, and the delivery method of video and multimedia information over such a network     

Comment on new differential flip-flops from Yuan and Svensson

A family of differential latches has recently been proposed by Yuan and Svensson [1996]. The author shows that the proposed flip-flops using the dynamic slave latch suffer from a poor logic-level zero in the presence of glitches on the data inputs     

Arc fusion splices with improved strength (4.8 GPa) approaching thestrength of the fibre

For the first time it has been shown that a median splice strength (4.8 GPa) closely matching that of the fibre can be achieved using a commercial fusion splicer. This is achieved by carefully controlling the stripping process and the environmental conditions     

Citrullinemia: management and clinical course. Apropos of a familial case

The authors report two cases of citrullinemia in siblings which add to 68 observations from the literature. They overview the clinical presentation, diagnosis and therapeutic management of the disease. The prognosis of severe neonatal form remains poor but an early adequate management may contribute to an acceptable outcome.     

Alpha blockaders--first or second line antihypertensive agents?

Alpha-receptor blockers reduce blood pressure by blocking of the alpha 1-receptors in the smooth muscle cells in the arteriolar walls. The heart pump function is not disturbed. Most studies have shown that the alpha-receptor blockers induce a reduction in plasma-triglycerides and an increase in the ratio between HDL- and LDL-cholesterol. They do not interfere with the metabolism of electrolytes, glucose or uric acid and have no negative effect on pulmonary function. Although long-term use does not induce a permanent increase in heart rate, some patients respond to initial therapy with faster heart rate and palpitations. The alpha-receptor blockers should not be used in patients with coronary heart disease if the patient is not on chronic beta-blockade. When these precautions are followed, the alpha-blockers can be used as first-line treatment--just like ACE-inhibitors and calcium-antagonists.     

A rectangular finite element for analysing composite multilayered shallow shells in statics,vibration and buckling

This paper presents a new 32-degree-of-freedom finite element of multilayered composite, moderately thick, shallow shells. The element is a four-node C¹ rectangular element and is built from standard interpolations but with a new kind of kinematics which allows us to exactly ensure the continuity conditions for displacements and stresses at the interfaces between the layers of a laminated structure and the boundary conditions at the upper and lower surfaces of the shell. The transverse shear deformation which is represented by cosine functions is of a higher order and allows us to avoid shear correction factors. The element is evaluated on standard problems and in comparison with exact three-dimensional and analytical solutions for multilayered plates and shells in statics, vibrations and stability.     

Drug resistance of Helicobacter pylori strains isolated from patients with inflammation of stomach mucous membrane and peptic ulcer of stomach and duodenum

Twelve strains of H. pylori were tested. They were isolated from biosamples from 23 patients with stomach inflammation (16 persons) and stomach (3) and duodenum peptic ulcer. By application of solid medium dilution of MIC50 and MIC90-16 antibiotics and antimicrobials were tested. Values of MIC50 and MIC90 for antibiotics from the tetracycline group were, respectively 0.25-0.5 microgram/ml and 0.12-1.0 microgram/ml. Similar results were obtained with macrolide antibiotics. All strains were sensitive to penicillin (MIC 0.03-0.12 microgram/ml, ampicillin (MIC 0.06-0.5 microgram/ml) and amoxicillin and rifampicin (MIC 0.07-0.3 microgram/ml). Ten out of 12 investigated strains were resistant to metronidazole (MIC90 = 30 micrograms/ml). Results of this study may be important for etiotropic treatment of infections with H. pylori.