On the leverage of high-fT transistors foradvanced high-speed bipolar circuits

A detailed study on the leverage of high-f_T transistors for advanced high-speed bipolar circuit applications is presented. It is shown that for the standard ECL (emitter-coupled logic) circuit, the leverage of high f_T is limited by the passive resistors (emitter-follower resistor and collector load resistor) and wire delay, especially in the low-power regime. For the standard NTL (nonthreshold logic) circuit, the leverage is higher due to its front-end configuration and lower power supply value. As the passive resistors are decoupled from the delay path in various advanced circuits utilizing active-pull-down schemes, the leverage of high F_T becomes more significant     

Si/SiGe epitaxial-base transistors. I. Materials, physics, andcircuits

A detailed review of SiGe epitaxial base technology is presented, which chronicles the progression of research from materials deposition through device and integration demonstrations, culminating in the first SiGe integrated circuit application. In part I of this paper, the requirements and processes for high-quality SiGe film preparation are discussed, with emphasis on fundamental principles. A detailed overview of SiGe HBT device design and implications for circuit applications is then presented     

Genetic determinants of sensitivity to ethanol in inbred mice.

Mice from 15 inbred strains (n?=?27–40 per strain) differed in sensitivity to ethanol-induced effects on open-field activity, hypothermia, rotarod ataxia, and anesthesia. Sensitivities to the different behavioral responses were generally uncorrelated. This suggests that the genetic determinants of behavioral sensitivity to one domain of ethanol effects are unrelated to those determining other responses. On the other hand, some variables were genetically related. For example, those strains sensitive to the loss of righting reflex induced by higher doses of ethanol showed reduced activity in the open field at lower doses and were more sensitive to ethanol-induced decreases in rearing. More generally, the pattern of results suggests that genetically influenced sensitivity to ethanol is not a monolithic phenomenon. Rather, it is specific to the particular response variable studied. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitivity to ethanol-induced motor incoordination in 5-HT1B receptor null mutant mice is task-dependent: Implications for behavioral assessment of genetically altered mice.

Neuromuscular impairment by ethanol likely involves complex effects on balance, gait, muscle strength, and other features of motor coordination. The present experiments showed that relative sensitivity to ethanol-induced motor impairment in serotonin 1B (5-HT1B) null mutant and control mice was task dependent. We found that ethanol-treated null mutant mice made fewer missteps on a balance beam than did ethanol-treated wild-type mice, and confirmed a previous finding of their lesser ethanol sensitivity in the grid test. The genotypes did not differ in ethanol sensitivity as measured by the screen test, static dowel, fixed-speed rotarod, accelerating rotarod, grip strength, or loss of righting reflex tests. These experiments suggest that within a behavioral domain, alternative tests of function are not equivalent, so multiple assessment tools should be used to avoid misinterpretation of gene function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-mobility modulation-doped SiGe-channel p-MOSFETs

A novel subsurface SiGe-channel p-MOSFET is demonstrated in which modulation doping is used to control the threshold voltage without degrading the channel mobility. A novel device design consisting of a graded SiGe channel, an n⁺ polysilicon gate, and p⁺ modulation doping is used. A boron-doped layer is located underneath the graded and undoped SiGe channel to minimize process sensitivity and maximize transconductance. Low-field hole mobilities of 220 cm²/V-s at 300 K and 980 cm²/V-s at 82 K were achieved in functional submicrometer p-MOSFETs     

On the profile design and optimization of epitaxial Si- andSiGe-base bipolar technology for 77 K applications. II. Circuitperformance issues

For pt.I see ibid., vol.40, no.3, p.525-41 (1993). The circuit performance issues associated with optimizing epitaxial Si- and SiGe-base bipolar technology for the liquid-nitrogen temperature environment are examined in detail. It is conclusively demonstrated that the notion that silicon-based bipolar circuits perform poorly at low temperatures is untrue. Transistor frequency response is examined both theoretically and experimentally, with particular attention given to the differences between SiGe and Si devices as a function of temperature. ECL and NTL ring oscillator circuits were fabricated for each of the four profiles described in pt.I. The minimum ECL gate delay for a SiGe base is essentially unchanged from its room-temperature value. ASTAP models were used to explore circuit operation under typical wire loading. The results indicate that epitaxial-base bipolar technology offers significant leverage for future cryogenic applications     

Design parameters and operation of small, and medium size municipal reverse osmosis North America

The design, construction and operation of 1,000 to 250,000 gallon per day reverse osmosis systems requires a different approach than larger multi-million gallon per day systems. Smaller modular units are based on actual proven installations. The units are pre-engineexed, and factory tested in their entirety. The unit concept of reverse osmosis design allows for more reliable systems, easily and quickly installed, with a minimum of operation and maintenance attention. Small and medium size reverse osmosis systems have been running for many years. A seawater single pass reverse osmosis system has been producing potable water for over 18 months with little operator attention and maintenance.Construction and operation of small and medium size municipal reverse osmosis systems present some unique areas of consideration which differentiates these units from much larger installations. By small and medium we mean from 1000 gallons to 250,000 gallons per day capacities. The ultimate objectives of any water treating system is to obtain the quality and quantity of water desired with a minimum of operating effort and maintenance. In general, where dissolved solids are to be removed from a feedwater source, reverse osmosis is presently recognized as the most efficient method available.Large reverse osmosis systems are usually engineered on an individual basis to meet the users needs and, include on-site analysis of the raw feedwater and climate conditions. In addition, engineering consultants as well as the ultimate customers preferences need to be considered. Large quantities of time are consumed in the initial engineering, preparation of drawings and design changes. Equipment housing facilities need to be designed around the type of system selected and engineered separately. Large amounts of time are used in the construction of the system components. Membrane racks are erected individually with membranes shipped separately. Large amounts of piping needs to be cut and installed on-site. High pressure pumps, membrane cleaning systems, electrical controls and pretreatment equipment are separately built, shipped individually, and assembled on location.     

Rapid development of tolerance to the hypothermic effect of ethanol in mice

The hypothermic response to i.p. injection of ethanol (2.0-4.0 g/kg) in mice was found to be attenuated by a single equivalent ethanol injection given 24 hr earlier. The diminished hypothermic response was not an artifact since it could not be attributed to changes in body weight and was independent of familiarity with test environment and procedures. A parallel shift in the dose-response curve was found. It appears, therefore, that the reduced change in body temperature is indicative of tolerance. If the second ethanol injection was given 48 or 72 hr later, tolerance could no longer be seen. With injections spaced 24 hr apart, a third administration of ethanol did not further increase the tolerance seen after the second injection. Since blood ethanol levels did not differ in tolerant and nontolerant mice, and since tolerance was already present 10 min after the second ethanol injection, a functional rather than a metabolic tolerance is likely.     

Effect of mutations of murine lens alphaB crystallin on transfected neural cell viability and cellular translocation in response to stress

The relationship between exercise-induced lowering of plasma glutamine concentrations and proliferation of peripheral lymphocytes was investigated in male Wistar rats. The T-lymphocyte proliferative responses to the mitogen, concanavalin A, were determined by incorporation of radiolabelled thymidine into the DNA in vitro. The rats ran 2 h x day(-1), 6 days x week(-1) for 4 weeks. Analysis immediately after the final period of exercise showed T-lymphocyte proliferation to be significantly depressed, together with a marked decrease in plasma glutamine concentrations. There were also significant increases in serum corticosterone concentrations immediately after exercise. However, following 24-h recovery, this exercise-induced immunosuppression was not statistically significant when compared with the age-matched control group. In the second experiment, in order to clarify the importance of glutamine for immunological function in vivo, methionine sulfoximine, an effective inhibitor of glutamine synthetase was injected intraperitoneally (12.5 mg x kg body mass[-1]). Plasma glutamine concentrations were decreased 4 h after the injection, compared with the placebo control group, and this resulted in a significant decrease in the rate of T-lymphocyte proliferation. This treatment had no effects on serum corticosterone concentrations. These results would suggest that the chronic exercise-induced reduction in proliferation of peripheral T-lymphocytes is a transient reversible phenomenon, which returns to normal levels within 24 h of the final training period. It is also conceivable that this exercise-induced immunosuppression is associated with a decrease in circulating glutamine concentrations.