A D&T roundtable: challenges for low-power and high-performancechips

Microprocessor and other lC performance continues to improve at historic rates, with no visible end in sight for the next 10 years. However, we are starting to encounter a power wall. This is true for high-performance components as well as for low-power chips with a very limited energy budget offered by batteries. We need to find ways to manage power and energy consumption on all fronts-technology, design, and architecture-without compromising performance. Otherwise, we may face discontinuation of Moore's law for the semiconductor industry in the near future. This would be triggered not by any difficulty in the scaling of process technology but by formidable barriers posed by packaging and cooling, inefficacy of power delivery, and energy constraints dictated by battery technology, which is advancing at a very lukewarm pace     

Human catalase is imported and assembled in peroxisomes of Saccharomyces cerevisiae

To study the conservation of peroxisomal targeting signals, we have determined the intracellular localization of human peroxisomal catalase when expressed in yeast. Using immunofluorescence, differential centrifugation and immunoelectron microscopy, we show that the protein is targeted to the peroxisomes of the heterologous cell and assembled in its active tetrameric form. These data show the conservation of the catalase targeting signal and import specificity between human and yeast peroxisomes.     

The relationship of individual and family factors to the psychological well-being of junior high school students living in urban poverty

This study examined the contribution of individual and family factors to psychological adjustment in a sample of junior high school students living in urban poverty. Identity development and perceived parental treatment were hypothesized to serve as mediating, or protective, factors between economic hardship and levels of self-esteem, depression, and loneliness. Consistent with the hypotheses, identity development did serve as a mediator between poverty and psychological adjustment. While perceived parental treatment was not related to economic hardship, it was clearly associated with well-being in this sample. Findings are discussed in terms of the differing contributions of family and individual development, as well as the importance of mediators in assessing the effects of poverty on young adolescents.     

A note on closed-loop balanced truncation

Closed-loop balanced truncation is a model reduction method that aims at preserving the closed-loop properties of the original controller. We show that this method is equivalent to frequency-weighted balanced truncation with certain weighting and that for observer-based controllers, a significant amount of computation can be saved because of the observer-state feedback structure of the controller     

Electrochemical,FTIR and morphological study of polypyrrole—Polystyrenesulphonate conducting films

The electrochemical behaviour, FTIR spectrum and the morphology of polypyrrole-polystyrenesulphonate (PPy-PSS) films obtained potentiostatically at 0.6 V in a 0.05m Py + 1.7 × 10^?2m NaPSS medium have been analysed. Different electrochemical parameters have been modified in order to establish the first polaron formation, the reversibility of the redox process and the doping mechanism. The FTIR spectrum confirms the existence of C?O groups in the film structure and two possible explanations are suggested. SEM reveals a higher homogeneity in these films than in PPy films doped with smaller counterions.     

Isolation of single yeast cells by optical trapping

Individual yeast cells can be successfully isolated and recultured on plates with a new isolation method making use of optical trapping with infrared laser light. The cells can be selected on morphological criteria by high resolution microscopy. The isolation device is constructed from two coverslips separated by spacers, in which selected cells are transferred to a plastic capillary, using the optical trap. To test the procedure, selection experiments were done with a mixture of two Saccharomyces cerevisiae strains, distinguishable both in fluorescence microscopy and on agar plates. These experiments showed that only selected cells were isolated, and close to 100% of the isolated stationary-phase cells formed colonies on agar plates, indicating a high recovery. A lower recovery was obtained with exponential-phase cells, possibly because of a higher sensitivity to laser irradiation. Applications for this method may include the isolation of mutants with altered morphology and the isolation of subpopulations of yeast cultures, for their separate investigation or for the initiation of pure cultures.     

The new Eurotransplant Kidney Allocation System: report one year after implementation. Eurotransplant International Foundation

BACKGROUND: Upon the availability of a cadaveric donor kidney, a delicate allocation process precedes every transplantation. A remodeled Eurotransplant Kidney Allocation System (ETKAS)-derived from simulation studies-was installed in March 1996. The purpose was to adjust long waiting times and international exchange balances, while aiming at an optimal HLA-mismatch distribution. The new ETKAS consisted of a point-score system that was 100% patient oriented. METHODS: The impact of the new ETKAS on the composition of the waiting list, and the outcome of the allocation procedures during its first year, were evaluated and compared with the results obtained in 1995. RESULTS: The percentage of long-waiting patients and of patients with poorly matchable HLA phenotype increased significantly, from 9% to 19% and from 19% to 29%, respectively. Zero HLA-A-, HLA-B-, HLA-DR-mismatched patients still comprised 23% of the kidney transplant activity. The kidney exchange of the different Eurotransplant countries became balanced within 4 months; this persisted during the rest of the year. Pediatric patients had a high transplantation rate due to an assignment of extra points. The composition of the waiting list showed, after 1 year, fewer long-waiting patients and fewer patients with rare HLA phenotypes. CONCLUSIONS: The new ETKAS was able in its first year to meet the goals set at its introduction. In comparison with the old ETKAS, there was a better trade-off between HLA matching and waiting time. The value of computer simulation studies has been demonstrated impressively in the context of organ allocation.     

Hybrid cam mechanisms

This paper investigates the problem of driving a machine with several reciprocating heavy inertias. The drive should also realize some programmable flexibility of the motion, so that the operation of the machine, e,g., synchronization between different motions and duration of standstills, can easily be modified. The use of a single servomotor for every motion is not the best solution, since it does not allow for energy recuperation. This means that the installed servomotor power will be much higher than the required net peak power for the machine as a whole. The presented solution, however, reduces the servomotor peak torque and power by one order of magnitude, and makes energy transfer between the motions possible. The hybrid cam mechanism consists of a hybrid drive, which is a combination of a servomotor, a constant velocity motor and a cam follower mechanism. The operation principle exploits the nonlinear characteristics of the cam to add flexibility at low cost of energy. The hybrid solution is particularly successful for motions involving high peak acceleration. In addition, the concept can be used to reject disturbances. Simulations show the performance of the hybrid cam mechanism.