What Will Power the Hydrogen Economy? Present and Future Sources of Hydrogen Energy

During the last ten to fifteen years advances in fuel cell technology have spurred an enormous wave of interest in hydrogen. This report first examines various methods for producing hydrogen, including discussion of the production potential for the United States. It then discusses and summarizes hydrogen distribution and delivery options, including a study of the environmental pollutant emissions implications and land and water use impacts of different production options. In addition, potential regional hydrogen production strategies around the U.S., and the potential for regional hydrogen production from renewable sources are discussed. The report concludes with a look at policy implications, particularly in light of the hydrogen production option costs and benefits that are reviewed and described in the report

Spot sputum samples are at least as good as early morning samples for identifying Mycobacterium tuberculosis

Supported by the Global Alliance for TB Drug Development with support from the Bill and Melinda Gates Foundation, the European and Developing Countries Clinical Trials Partnership (Grant IP.2007.32011.011), US Agency for International Development, UK Department for International Development, Directorate General for International Cooperation of the Netherlands, Irish Aid, Australia Department of Foreign Affairs and Trade, National Institutes of Health, AIDS Clinical Trials Group. The study was also supported by grants from the National Institute of Allergy and Infectious Diseases (NIAID) (UM1AI068634, UM1 AI068636, and UM1AI106701) and by NIAID grants to the University of KwaZulu Natal, South Africa, AIDS Clinical Trials Group (ACTG) site 31422 (1U01AI069469); to the Perinatal HIV Research Unit, Chris Hani Baragwanath Hospital, South Africa, ACTG site 12301 (1U01AI069453); and to the Durban International Clinical Trials Unit, South Africa, ACTG site 11201 (1U01AI069426). Bayer Healthcare for donated moxifloxacin and Sanofi donated rifampin.Background:  The use of early morning sputum samples (EMS) to diagnose tuberculosis (TB) can result in treatment delay given the need for the patient to return to the clinic with the EMS, increasing the chance of patients being lost during their diagnostic workup. However, there is little evidence to support the superiority of EMS over spot sputum samples. In this new analysis of the REMoxTB study, we compare the diagnostic accuracy of EMS with spot samples for identifying Mycobacterium tuberculosis pre- and post-treatment. Methods:  Patients who were smear positive at screening were enrolled into the study. Paired sputum samples (one EMS and one spot) were collected at each trial visit pre- and post-treatment. Microscopy and culture on solid LJ and liquid MGIT media were performed on all samples; those missing corresponding paired results were excluded from the analyses. Results:  Data from 1115 pre- and 2995 post-treatment paired samples from 1931 patients enrolled in the REMoxTB study were analysed. Patients were recruited from South Africa (47%), East Africa (21%), India (20%), Asia (11%), and North America (1%); 70% were male, median age 31 years (IQR 24–41), 139 (7%) co-infected with HIV with a median CD4 cell count of 399 cells/μL (IQR 318–535). Pre-treatment spot samples had a higher yield of positive Ziehl–Neelsen smears (98% vs. 97%, P = 0.02) and LJ cultures (87% vs. 82%, P = 0.006) than EMS, but there was no difference for positivity by MGIT (93% vs. 95%, P = 0.18). Contaminated and false-positive MGIT were found more often with EMS rather than spot samples. Surprisingly, pre-treatment EMS had a higher smear grading and shorter time-to-positivity, by 1 day, than spot samples in MGIT culture (4.5 vs. 5.5 days, P < 0.001). There were no differences in time to positivity in pre-treatment LJ culture, or in post-treatment MGIT or LJ cultures. Comparing EMS and spot samples in those with unfavourable outcomes, there were no differences in smear or culture results, and positive results were not detected earlier in Kaplan–Meier analyses in either EMS or spot samples. Conclusions:  Our data do not support the hypothesis that EMS samples are superior to spot sputum samples in a clinical trial of patients with smear positive pulmonary TB. Observed small differences in mycobacterial burden are of uncertain significance and EMS samples do not detect post-treatment positives any sooner than spot samples.Publisher PDFPeer reviewe

Modern optical astronomy: technology and impact of interferometry

The present `state of the art' and the path to future progress in high spatial resolution imaging interferometry is reviewed. The review begins with a treatment of the fundamentals of stellar optical interferometry, the origin, properties, optical effects of turbulence in the Earth's atmosphere, the passive methods that are applied on a single telescope to overcome atmospheric image degradation such as speckle interferometry, and various other techniques. These topics include differential speckle interferometry, speckle spectroscopy and polarimetry, phase diversity, wavefront shearing interferometry, phase-closure methods, dark speckle imaging, as well as the limitations imposed by the detectors on the performance of speckle imaging. A brief account is given of the technological innovation of adaptive-optics (AO) to compensate such atmospheric effects on the image in real time. A major advancement involves the transition from single-aperture to the dilute-aperture interferometry using multiple telescopes. Therefore, the review deals with recent developments involving ground-based, and space-based optical arrays. Emphasis is placed on the problems specific to delay-lines, beam recombination, polarization, dispersion, fringe-tracking, bootstrapping, coherencing and cophasing, and recovery of the visibility functions. The role of AO in enhancing visibilities is also discussed. The applications of interferometry, such as imaging, astrometry, and nulling are described. The mathematical intricacies of the various `post-detection' image-processing techniques are examined critically. The review concludes with a discussion of the astrophysical importance and the perspectives of interferometry.Comment: 65 pages LaTeX file including 23 figures. Reviews of Modern Physics, 2002, to appear in April issu

Knowledge for games, games for knowledge: designing a digital roll-and-move board game for a law of torts class

published_or_final_versio

Zero-Emission Vehicle Scenario Cost Analysis Using A Fuzzy Set-Based Framework

In this study, potential vehicle manufacturing costs, lifecycle costs, infrastructure support costs, and emission-related costs are compared for three potential zero-emission vehicle (ZEV) technology development and deployment scenarios. These scenarios include production of mid-sized battery electric vehicles direct-hydrogen fuel cell vehicles, and direct methanol fuel cell vehicles from 2003 to 2026, and operation of the vehicles in California's South Coast Air Basin (SCAB) from 2003 to 2043. The study focuses on potential manufacturing cost reductions for electric motors, motor controllers, battery systems, hydrogen storage tanks, and fuel cell systems, due to the combined forces of production scale economies and technological progress.Vehicle manufacturing and lifecycle costs are calculated by integrating vehicle component cost functions with a detailed vehicle performance and cost spreadsheet model. Fleet-level costs for vehicle operation, infrastructure development, and criteria pollutant and greenhouse gas emissions are calculated using a MATLAB/Simulink model developed by the author. In this regional-scale, fleet-level model, fuzzy set theory is used to characterize uncertainty in key input variables, and to propagate uncertainty through the calculation of vehicle, infrastructure, and emissions costs.Findings are that estimated ZEV purchase prices drop steadily with production volume and technological progress, but that even in future, high-volume production the estimated purchase prices for all three ZEV types remain above those of comparable conventional vehicles. However, lifecycle costs for ZEVs in some cases become competitive with those of comparable conventional vehicles, especially for direct-hydrogen fuel cell vehicles. When infrastructure and emission-related costs are considered for vehicles used in the SCAB, total lifecycle costs for direct-hydrogen fuel cell vehicles are found to be below those of even low-emission gasoline vehicles by 2026, under central case assumptions. Meanwhile, total lifecycle costs for battery EVs and direct-methanol fuel cell vehicles are found to be between those of conventional and low-emission gasoline vehicles, again in the year 2026 central case. In general, the overall level of uncertainty in the calculation of total scenario net present values is considerable, and this level of uncertainty prevents the unequivocal determination of a least-cost ZEV technology pathway for the SCAB

The Cost of Manufacturing Electric Vehicle Drivetrains

Propulsion systems designed specifically for electric vehicles (EVs) are currently produced in small volumes and sold at high costs, although some components used in hybrid EVs are beginning to see production in higher volumes. At present, there are two primary choices of motor technology for use in EV drivetrains. Most vehicles in pilot-scale production today use alternating current (AC) induction systems, but some vehicles, such as the Toyota RA V4, use systems based on brushless permanent magnet (BPM) motors. Both AC induction and BPM systems offer similar advantages over conventional direct current (DC) brush motors. These include lighter motor weights, higher efficiencies, and lower service requirements (the brushes in DC brush motors wear out and require replacement). In general, AC induction motors provide high efficiencies over a wide range of operation, while BPM motors provide higher peak efficiencies. BPM motors also tend to be lighter, but they use rare earth magnets that are somewhat costly at present. Both of these motor types require complicated control systems relative to DC brush motors, in order to operate from a DC source. We analyze both AC induction and BPM systems because both are good choices for use in EVs, and it is not clear which system will prove to be the most popular. The control systems needed for these types of motors are costly and complex, but the necessary electronics, particularly insulated-gate bipolar transistor (IGBT) power switching devices, have been improving rapidly. Continued progress in IGBT technology is expected, particularly with regard to the saturation characteristics of the devices and their switching energies, and inverters in general are expected to progress in terms of not only the cost and performance of the IGBT silicon chips, but also in packaging, controls, processors, and transducers (Hodkinson, 1997). Recent statements by EV project managers at GM and Ford reflect the progress that has been made in reducing the cost and complexity of EV motor controllers over the past few years. Bob Purcell of GM reports that the second generation EV-1 motor controller has only three IGBTs, while the first generation had six. The new IGBTs have twice the power handling capability of the old ones, with equal precision levels. Overall, the new electric drive control system has half the mass, one-third fewer parts, and half the cost of the first generation system (Purcell, 1998). John Wallace of Ford reports similar progress in the development of its system (Wallace, 1998