Speculative Parallelization of Sequential Loops on Multicores

The advent of multicores presents a promising opportunity for speeding up the execution of sequential programs through their parallelization. In this paper we present a novel solution for efficiently supporting software-based speculative parallelization of sequential loops on multicore processors. The execution model we employ is based upon state separation, an approach for separately maintaining the speculative state of parallel threads and non-speculative state of the computation. If speculation is successful, the results produced by parallel threads in speculative state are committed by copying them into the computation’s non-speculative state. If misspeculation is detected, no costly state recovery mechanisms are needed as the speculative state can be simply discarded. Techniques are proposed to reduce the cost of data copying between non-speculative and speculative state and efficiently carrying out misspeculation detection. We apply the above approach to speculative parallelization of loops in several sequential programs which results in significant speedups on a Dell PowerEdge 1900 server with two Intel Xeon quad-core processors.     

Ultrafast exciton relaxation in the B850 antenna complex of Rhodobacter sphaeroides

Spectral changes were measured with femtosecond resolution following low-intensity, broad-band excitation of the peripheral antenna complex of the purple photosynthetic bacterium Rhodobacter sphaeroides. Absorption anisotropy decays also were measured. We identified a 35-fs relaxation of the absorption and emission spectra of the excited state, as well as a 20-fs anisotropy decay. We interpret these results as interlevel relaxation and dephasing, respectively, of extensively delocalized exciton states of the circular bacteriochlorophyll aggregate.     

High-speed single-quantum-well InGaAs/GaAs laser design andexperiment

Summary form only given. The authors report damping factors an order of magnitude lower than previously reported for SQW lasers. They also report bandwidths of 15 GHz obtained in SQW (single quantum well) lasers as a result of proper design of the quantum-well structure. The laser samples were grown on (100) n-type GaAs by molecular beam epitaxy (MBE). The SQW lasers had a minimum broad area threshold of 125 A/cm². A self-aligned technique was used to fabricate the narrow-ridge waveguide lasers. The ridges were dry-etched using Cl₂ . A model was developed that quantitatively explains the large enhancement in the dynamic response in the SQW lasers compared to those reported previously. This leads to an optimal design of quantum-well lasers for large-modulation bandwidths     

A note on weight-based load balancing on SONET rings

In a recent paper, Cosares and Saniee [2] introduced the problem of balancing loads on SONET [1] rings. This note gives a counterexample to one of their results and then states the correct result.     

Structural studies on Fe-substituted Y-Ba-Cu-O superconductors by Mössbauer spectroscopy

In this paper we report preparation and structural aspects of YBa₂Cu_2·97Fe_0·03O_7?x with different oxygen stoichiometry. The samples were prepared by standard solid-state reaction. The samples were characterized by X-ray powder diffraction and oxygen contents were estimated from iodometric titration method. The superconducting transition temperatureT _c is measured using the standard four-probe technique. Mössbauer studies of YBa₂Cu_2·97Fe_0·03O_7?x with different oxygen stoichiometry were carried out and the results show that Fe substitutes both Cu(2) and Cu(1) sites and clear asymmetry in the doublets except for the tetragonal case. Also our results show the progressive oxygenation inb-axis as oxygen stoichiometry is increased.     

Benchmarking the perioperative process: III. Effects of regional anesthesia clinical pathway techniques on process efficiency and recovery profiles in ambulatory orthopedic surgery

STUDY OBJECTIVES: (1) To incorporate regional anesthesia options for common outpatient orthopedic surgery into clinical pathways; (2) to use the clinical pathway format and the Procedural Times Glossary published by the Association of Anesthesia Clinical Directors (AACD) as management tools to measure postoperative same-day surgery processes and discharge outcomes; and (3) to determine the effects of general, regional, and combined general-regional anesthesia on these processes and outcomes. DESIGN: Hospital database and patient chart review of consecutive patients undergoing anterior cruciate ligament reconstruction (ACLR) during academic years (AY) 1995-1996 and 1996-1997. Patient data from AY 1995-1996, during which no intraoperative anesthesia clinical pathway existed, served as historical controls. Data from AY 1996-1997, during which intraoperative anesthesia clinical pathways were used, served as the treatment group. SETTING: Ambulatory surgery center in a teaching hospital. MEASUREMENTS AND MAIN RESULTS: The records of 503 ASA physical status I and II patients were reviewed. 1996-1997 patients selected general anesthesia (+/- femoral nerve block) or epidural anesthesia, after which the remainder of the perioperative anesthesia process was standardized with respect to the drugs and equipment used. 1995-1996 patients did not necessarily have a choice in anesthesia technique and did not have a standardized perioperative anesthetic course with respect to specific drugs and supplies. Intervals described in the AACD Procedural Times Glossary, anesthesia drug and supply costs, and patient outcome variables (postoperative nursing interventions required and unexpected admissions), as influenced by anesthesia technique used, were measured. Combined general-regional anesthesia care for ACLR in 1996-1997, when compared with general anesthesia alone, led to increased pharmacy and materials costs and increased turnover time. However, patients with the combined technique showed improved recovery profiles and lower unexpected admission rates, and they required fewer nursing interventions for common postoperative symptoms. Patients receiving epidural anesthesia showed discharge outcomes similar to those patients receiving general anesthesia with femoral nerve block. Postanesthesia care unit bypass (fast-tracking) was more likely in clinical pathway regional anesthesia patients, when compared with the clinical pathway general anesthesia used. CONCLUSIONS: Clinical pathway regional anesthesia care for outpatient orthopedics may have a significant role in simultaneously containing costs and improving both process efficiency and patient outcomes.     

Performance,emission and combustion studies of a DI diesel engine using Distilled Tyre pyrolysis oil-diesel blends

Increase in energy demand, stringent emission norms and depletion of oil resources led the researchers to find alternative fuels for internal combustion engines. Many alternate fuels like Alcohols, Biodiesel, LPG, CNG etc have been already commercialized in the transport sector. In this context, pyrolysis of solid waste is currently receiving renewed interest. The disposal of waste tyres can be simplified to some extent by pyrolysis. The properties of the Tyre pyrolysis oil (TPO) derived from waste automobile tyres were analyzed and compared with the petroleum products and found that it can also be used as a fuel for compression ignition engine. However, the crude TPO has a higher viscosity and sulphur content. The crude TPO was desulphurised and then distilled through vacuum distillation. In the present work, DTPO-diesel blends were used as an alternate fuel in a diesel engine without any engine modification. This paper presents the studies on the performance, emission and combustion characteristics of a single cylinder four stroke air cooled DI diesel engine running with the Distilled Tyre pyrolysis oil (DTPO).