10,000 publications from this institution
MultiChord is a new variant of the Chord namespace management algorithm [7] that includes lightweight mechanismsfor accommodating a limited rate of change, specifically, process joins and failures. This paper describes thealgorithm formally and evaluates its performance, using both simulation and analysis. Our main result is that lookupsare provably correctÂthat is, each lookup returns results that are consistent with a hypothetical ideal system that differsfrom the actual system only in entries corresponding to recent joins and failuresÂin the presence of a limited rateof change. In particular, if the number of joins and failures that occur during a given time interval in a given regionof system are bounded, then all lookups are correct. A second result is a guaranteed upper bound for the latency of alookup operation in the absence of any other lookups in the system. Finally, we establish a relationship between thedeterministic assumptions of bounded joins and failures and the probabilistic assumptions (which are often used tomodel large scale networks). In particular, we derive a lower bound for the mean time between two violations of thedeterministic assumptions in a steady state system where joins and failures are modeled by Poisson processes.
The qualitative nature of the time evolution in a piecewiselinear lossy resonant circuit driven by a sinusoidal voltage source is investigated by computer-aided analysis using exact analytical formulas. A surprising wealth of different nonlinear phenomena is discovered. They are: stable and unstable harmonics, subharmonics, and even apparently completely disordered aperiodic "chaotic" motions. In the latter case, the hyperbolicity, strange attractor, and broad-band frequency spectrum normally associated with chaotic motions have all been observed using nearly exact piecewise-linear solutions. These results represent the most reliable numerical confirmation to date of chaotic motions in a real physical circuit.
Barry Eichengreen, professor de Economia e Ciencia Politica na Universidade da California, considera cada vez mais dificil de ler o futuro da economia.
Inter-coflow scheduling improves application-level communication performance in data-parallel clusters. However, existing efficient schedulers require a priori coflow information and ignore cluster dynamics like pipelining, task failures, and speculative executions, which limit their applicability. Schedulers without prior knowledge compromise on performance to avoid head-of-line blocking. In this paper, we present Aalo that strikes a balance and efficiently schedules coflows without prior knowledge. Aalo employs Discretized Coflow-Aware Least-Attained Service (D-CLAS) to separate coflows into a small number of priority queues based on how much they have already sent across the cluster. By performing prioritization across queues and by scheduling coflows in the FIFO order within each queue, Aalo's non-clairvoyant scheduler reduces coflow completion times while guaranteeing starvation freedom. EC2 deployments and trace-driven simulations show that communication stages complete 1.93X faster on average and 3.59X faster at the 95th percentile using Aalo in comparison to per-flow mechanisms. Aalo's performance is comparable to that of solutions using prior knowledge, and Aalo outperforms them in presence of cluster dynamics.
Direct measurement of de novo lipogenesis has not previously been possible in humans. We measured de novo hepatic lipogenesis in normal men by means of stable isotopes and by combining the acetylated-xenobiotic probe technique with mass isotopomer analysis of secreted very low density lipoprotein-fatty acids (VLDL-FA). Sulfamethoxazole (SMX) was administered with [13C]acetate during an overnight fast followed by refeeding with intravenous glucose (7-10 mg/kg of weight per min), oral Ensure (7-10 mg of carbohydrate/kg of weight per min), or a high-carbohydrate mixed-meal breakfast (3.5 g of carbohydrate/kg of weight). Respiratory quotients remained less than 1.0. High-performance liquid chromatography/mass spectrometry-determined enrichments in SMX-acetate attained stable plateau values, and hepatic acetyl-coenzyme A (CoA) dilution rate did not increase with refeeding (approximately 0.024 mmol/kg per min). The fraction of VLDL-palmitate derived from de novo lipogenesis was only 0.91 +/- 0.27% (fasted) and 1.64-1.97% (fed). For stearate, this was 0.37 +/- 0.08% and 0.47-0.64%. Precursor enrichments predicted from isotopomer ratios were close to measured SMX-acetate enrichments, indicating that SMX-acetate samples the true lipogenic acetyl-CoA pool. Stearate synthesis was less than palmitate and the two did not move in parallel. Estimated total VLDL-FA synthesis is less than 500 mg/day. Thus, de novo hepatic lipogenesis is a quantitatively minor pathway, consistent with gas exchange estimates; fatty acid futile cycling (oxidation/resynthesis) is not thermogenically significant; and synthesis rates of different nonessential fatty acids by human liver are not identical in nonoverfed normal men. The contribution and regulation of de novo lipogenesis in other settings can be studied using this technique.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
We adopt a statistical mechanical approach toward the optics of textured and inhomogeneous optical sheets. As a general rule, the local light intensity in such a medium will tend to be <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 n^{2}(x)</tex> times greater than the externally incident light intensity, where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n(x)</tex> is the local index of refraction in the sheet. This enhancement can contribute toward a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4 n^{2}(x)</tex> increase in the effective absorption of indirect-gap semiconductors like crystalline silicon.
