Static energy reduction techniques for microprocessor caches

Microprocessor performance has been improved by increasing the capacity of on-chip caches. However, the performance gain comes at the price of static energy consumption due to subthreshold leakage current in cache memory arrays. This paper compares three techniques for reducing static energy consumption in on-chip level-1 and level-2 caches. One technique employs low-leakage transistors in the memory cell. Another technique, power supply switching, can be used to turn off memory cells and discard their contents. A third alternative is dynamic threshold modulation, which places memory cells in a standby state that preserves cell contents. In our experiments, we explore the energy and performance tradeoffs of these techniques. We also investigate the sensitivity of microprocessor performance and energy consumption to additional cache latency caused by leakage-reduction techniques.     

Breastfeeding provides passive and likely long-lasting active immunity

OBJECTIVES: The reader of this review will learn about the mechanisms through which breastfeeding protects against infections during and most likely after lactation, as well as possibly against certain immunologic diseases, including allergy. DATA SOURCES: I have followed the literature in the area closely for the last 30 to 40 years and have made repeated literature searches through MEDLINE, most recently in 1998. Textbooks and peer-reviewed journals have been sought for, as well as books representing meeting reports in English, French, German, and Spanish. RESULTS: Human milk protects against infections in the breastfed offspring mainly via the secretory IgA antibodies, but also most likely via several other factors like the bactericidal lactoferrin. It is striking that the defense factors of human milk function without causing inflammation, some components are even directly anti-inflammatory. Protection against infections has been well evidenced during lactation against, e.g., acute and prolonged diarrhea, respiratory tract infections, otitis media, urinary tract infection, neonatal septicemia, and necrotizing enterocolitis. There is also interesting evidence for an enhanced protection remaining for years after lactation against diarrhea, respiratory tract infections, otitis media, Haemophilus influenzae type b infections, and wheezing illness. In several instances the protection seems to improve with the duration of breastfeeding. Some, but not all studies have shown better vaccine responses among breastfed than non-breastfed infants. A few factors in milk like anti-antibodies (anti-idiotypic antibodies) and T and B lymphocytes have in some experimental models been able to transfer priming of the breastfed offspring. This together with transfer of numerous cytokines and growth factors via milk may add to an active stimulation of the infant's immune system. Consequently, the infant might respond better to both infections and vaccines. Such an enhanced function could also explain why breastfeeding may protect against immunologic diseases like coeliac disease and possibly allergy. Suggestions of protection against autoimmune diseases and tumors have also been published, but need confirmation. CONCLUSIONS: Breastfeeding may, in addition to the well-known passive protection against infections during lactation, have a unique capacity to stimulate the immune system of the offspring possibly with several long-term positive effects.     

In vivo validation of a thermodilution system designed to measure peripheral blood flow

A 5F triple-lumen thermodilution catheter was evaluated in a canine vena cava model to determine whether this catheter and the thermodilution technique provide valid in vivo determinations of blood flow. Our ultimate goal is to develop methods for studying limb blood flow in humans. Seven dogs were studied. Blood flow was provided and regulated by a calibrated roller pump. Flow rate determinations by thermodilution were made over a range of 0.5 to 5.01 1/minute. Excellent correlation (r = 0.98, r2 = 0.96, P less than 0.01) was found between actual flow and flow measured by thermodilution. The mean (+/- SD) coefficient of variation for the thermodilution method was 9.97 +/- 5.72 per cent over the flow range tested. The coefficient of variation tended to be higher at low flow rates. The thermodilution technique with this catheter provides valid in vivo determinations of blood flow through large vessels. This technology can be rationally applied to the study of limb blood flow in humans.     

Evaluating the solar resource: a review of problems resulting from temporal, spatial and angular variations

Accurate assessment of the availability of solar energy at the Earth's surface is hampered by difficulties associated with the variability of solar radiation in space and time and with the angular position in the sky hemisphere. This paper assesses each of these problem areas by highlighting the difficulties and the attempts to offset them. Major emphasis is placed on extrapolation and interpolation procedures, the sensitivity of inclined surfaces to variations in the solar input, numerical models for calculating the irradiance of inclined surfaces and the time scales for which these computations are valid.Finally, the reader is urged to consider the significance of these difficulties in light of both radiation measurement errors and the sensitivity of the application to imprecise determinations of the radiation environment.     

Immunoreactivity of Brazilian HIV isolates with different V3 motifs

The influence of noncompetitive (MK-801), competitive (AP-7) and the antagonist of polyamines site of NMDA receptor (arcaine) on the central activity of angiotensin II (A II) was studied. The open field test, conditioning of active avoidance responses (CARs) and passive avoidance situation was used to investigate learning and memory in rats. All used antagonists decreased beneficial action of A II on these processes.     

Study of etch rate characteristics of SF6/He plasmas byresponse-surface methodology: effects of interelectrode spacing

The characteristics of SF₆/He plasmas which are used to etch Si₃N₄ have been examined with experimental design and modeled empirically by response-surface methodology using a Lam Research Autoetch 480 single-wafer system. The effects of variations of process gas flow rate (20-380 sccm), reactor pressure (300-900 mtorr). RF power (50-450 W at 13.56 MHz), and interelectrode spacing (8-25 mm) on the etch rates of LPCVD (low-pressure chemical vapor deposition) Si₃N₄, thermal SiO₂, and photoresist were examined at 22±2°C. Whereas the etch rate of photoresist increases with interelectrode spacing between 8 and 19 mm and then declines between 19 and 25 mm, the etch rate of Si₃N ₄ increases smoothly from 8 to 25 mm, while the etch rate of thermal SiO₂ shows no dependence on spacing between 8 and 25 mm. The etch rates of all three films decrease with increasing reactor pressure. Contour plots of the response surfaces for etch rate and etch uniformity of Si₃N₄ as a function of spacing and flow rate at constant RF power (250 W) display complex behavior at fixed reactor pressures. A satisfactory balance of etch rate and etch uniformity for Si₃N₄ is predicted at low reactor pressure (~300 mtorr), large electrode spacing (12-25 mm), and moderate process gas flow rates (20-250 sccm)     

Is insurance for children enough? The link between parents'' and children''s health care use revisited

The gutless hydrothermal tubeworm Riftia pachyptila Jones relies mainly on its chemoautotrophic bacterial symbionts to supply nutrients in the form of secreted organic compounds resulting from fixation and incorporation of CO2. In this study, symbionts were purified, tested for viability, and incubated in the presence of labeled CO2. We demonstrated that purified symbionts can be used as a viable alternative to experiments with bacterial cultures. Several organic acids, sugars, and amino acids were labeled, but their fraction of the total label stayed generally constant during the incubation times used. However, increasing fractions of succinate and, to a lesser degree, glutamate were excreted into the incubation medium, indicating that these are probably the main carbon-containing compounds transferred from the symbionts to the host. Glutamate could also account for the transport of nitrogen from the symbionts to the host.     

Male european corn borer,Ostrinia nubilalis (Hübner), antennal responses to analogs of its sex pheromone

Experiments were conducted to (1) determine whether the electroantennogram (EAG) can detect differences among the responses of antennae from males derived from the three strains ofOstrinia nubilalis (Hübner), and (2) characterize the EAG responses of each strain to isomeric forms of the natural pheromone, (E)- and (Z)-11-tetradecen-1-ol acetate (TDA), and analogs possessing differences in the terminal alkyl group, cyclopropyl (CPA), ortert-butyl (TBA).EAG responses differed among the strains in two ways: (1) Antennae fromZZ males always produced an EAG to (Z)-TDA with an extended duration of response. This signature EAG response was found to be unique to the antennal response ofZZ males to (Z)-TDA, thus providing a relatively easy method of distinguishing liveZZ males fromEE orZE males. Correlated with this longer EAG response was a longer disadaptation time, i.e., the EAG response ofZZ antennae disadapted more slowly (ca. 10 min) than the response ofEE antennae. (2) Strain differences in the relative EAG amplitudes to isomers and analogs were observed at the stimulus amounts eliciting the peak EAG amplitude as follows: TDA CPA > TBA forZZ males and both isomers; TDA > CPA TBA and CPA TDA > TBA forEE males and theE andZ isomers, respectively; CPA > TBA TDA forZE males and both isomers. Dose—response relationships were seen for all compounds if amplitude (peak height) of the EAG was used as a measure of response. However, if width of the EAG at half the peak height (peak width) was used, then only theZZ antennal response to (Z)-TDA resulted in a meaningful dose-response relationship. For all strains, the EAG amplitudes elicited by theZ isomers of any of the tested compounds were greater than those elicited by the correspondingE isomers. Therefore, correlations between the relative EAG and upwind flight responses were observed in theZZ (r = 0.86) andZE (r = 0.80) strains but were not correlated in theEE strain (r = 0.18). Temporal studies showed that adaptation, not postexcision deterioration, was responsible for the observed decreases in the EAG amplitude after repetitive stimulation or after stimulation with amounts in a descending order. Disa-daptation required at least 20 min for a moderate dose (10 g for 1 sec). Developmental studies showed that antennae from 2-day-old adults had the greatest EAG response.     

Dynamic variable depth of cut machining using piezoelectric actuators

This paper describes the design of a piezoelectric actuated cutting tool and implementation of digital servo controls for machining surfaces with dynamically varying depth of cut. Through a flexure hinge, the tool holder could generate 50 μm travel at the tip of the cutting insert. Tool motion errors of less than 0.5 μm were achieved in tracking cyclic waveforms by employing a digital repetitive servo control. When applied to turning aluminum and steel workpieces with variable depth of cut using carbide tools, less than 5 μm machined surface errors were measured.     

Taking control of web browsing

Adherence to accessibility guidelines for Web pages does not necessarily guarantee a usable or satisfying Web experience for all persons with disabilities. The needs of many of these individuals fall outside the guidelines for accessible content that most Web authors take into consideration. Many of these users wish, for example, that they simply could ‘enlarge’ what is on a Web page. They also express the wish that pages would be ‘less confusing’. To meet these needs, Web browsers and various software applications provide for a variety of ways in which page presentations can be altered. The effects of these alterations often have unexpected consequences. Some designs accommodate these alterations better than others. This article discusses one such application that allows users to control features of Web page presentation and explores design features that facilitate such control.