Theory of the Quantum Speed Up

Insofar as quantum computation is faster than classical, it appears to be irreversible. In all quantum algorithms found so far the speed-up depends on the extra-dynamical irreversible projection representing quantum measurement. Quantum measurement performs a computation that dynamical computation cannot accomplish as efficiently.Comment: 10 pages, RevTex, 1 page of 3 figure

Enteropathogen survival in soil from different land-uses is predominantly regulated by microbial community composition

peer-reviewedMicrobial enteropathogens can enter the environment via landspreading of animal slurries and manures. Biotic interactions with the soil microbial community can contribute to their subsequent decay. This study aimed to determine the relative impact of biotic, specifically microbial community structure, and physico-chemical properties associated with soils derived from 12 contrasting land-uses on enteropathogen survival. Phenotypic profiles of microbial communities (via phospholipid fatty acid (PLFA) profiling), and total biomass (by fumigation-extraction), in the soils were determined, as well as a range of physicochemical properties. The persistence of Salmonella Dublin, Listeria monocytogenes, and Escherichia coli was measured over 110 days within soil microcosms. Physicochemical and biotic data were used in stepwise regression analysis to determine the predominant factor related to pathogen-specific death rates. Phenotypic structure, associated with a diverse range of constituent PLFAs, was identified as the most significant factor in pathogen decay for S. Dublin, L. monocytogenes, non-toxigenic E. coli O157 but not for environmentally-persistent E. coli. This demonstrates the importance of entire community-scale interactions in pathogen suppression, and that such interactions are context-specific

Capacity mechanisms and the technology mix in competitive electricity markets

Capacity mechanisms are increasingly used in electricity market design around the world yet their role remains hotly debated. In this paper, we introduce a new benchmark model of a capacity mechanism in a competitive electricity market with many different generation technologies. We consider two policy instruments, a wholesale price cap and a capacity payment, and show which combinations of these instruments induce socially-optimal investment by the market. Changing the price cap or capacity payment affects investment only in peak generation plant, with no equilibrium impact on baseload or mid-merit plant. We obtain a rationale for a capacity mechanism based on the internalization of a system-cost externality – even where the price cap is set at the value of lost load. In extensions, we show how increasing renewables penetration enhances the need for a capacity mechanism, and outline an optimal design of a strategic reserve with a discriminatory capacity payment

Substrate effects on surface magetetism of Fe/W(110) from first principles

Surface magnetic properties of the pseudomorphic Fe(110) monolayer on a W(110) substrate are investigated from first principles as a function of the substrate thickness (up to eight layers). Analyzing the magnetocrystalline anisotropy energies, we find stable (with respect to the number of substrate layers) in-plane easy and hard axes of magnetization along the [1[overline 1]0] and [001] directions, respectively, reaching a value in good agreement with experiment for thick substrates. Additionally, the changes to the magnetic spin moments and the density of the Fe d states are analyzed with respect to the number of substrate layers as well as with respect to the direction of magnetization. With respect to the number of W(110) substrate layers beneath the Fe(110) surface, we find that the first four substrate layers have a large influence on the electronic and magnetic properties of the surface. Beyond the fourth layer, the substrate has only marginal influence on the surface properties.Comment: 8 Pages, 3 Figures, 3 Table

Environmental public health tracking of childhood asthma using California health interview survey, traffic, and outdoor air pollution data.

BackgroundDespite extensive evidence that air pollution affects childhood asthma, state-level and national-level tracking of asthma outcomes in relation to air pollution is limited.ObjectivesOur goals were to evaluate the feasibility of linking the 2001 California Health Interview Survey (CHIS), air monitoring, and traffic data; estimate associations between traffic density (TD) or outdoor air pollutant concentrations and childhood asthma morbidity; and evaluate the usefulness of such databases, linkages, and analyses to Environmental Public Health Tracking (EPHT).MethodsWe estimated TD within 500 feet of residential cross-streets of respondents and annual average pollutant concentrations based on monitoring station measurements. We used logistic regression to examine associations with reported asthma symptoms and emergency department (ED) visits/hospitalizations.ResultsAssignment of TD and air pollution exposures for cross-streets was successful for 82% of children with asthma in Los Angeles and San Diego, California, Counties. Children with asthma living in high ozone areas and areas with high concentrations of particulate matter < 10 microm in aerodynamic diameter experienced symptoms more frequently, and those living close to heavy traffic reported more ED visits/hospitalizations. The advantages of the CHIS for asthma EPHT include a large and representative sample, biennial data collection, and ascertainment of important socio-demographic and residential address information. Disadvantages are its cross-sectional design, reliance on parental reports of diagnoses and symptoms, and lack of information on some potential confounders.ConclusionsDespite limitations, the CHIS provides a useful framework for examining air pollution and childhood asthma morbidity in support of EPHT, especially because later surveys address some noted gaps. We plan to employ CHIS 2003 and 2005 data and novel exposure assessment methods to re-examine the questions raised here

Electrical conductivity for radio-frequency fields in strongly magnetized plasmas with density fluctuations

A general investigation of the electrical conductivity for radio-frequency (RF) fields in strongly magnetized plasmas with small-scale density fluctuations is performed within the cold plasma hydrodynamical approximation. It is shown that in such plasmas an RF phenomenon similar to the Bohm diffusion exists: the presence of stochastic RF electric field in a turbulent plasma can lead to a strong enhancement of the RF currents flowing in the direction of the applied electric field components transverse to the magnetic field. The appearance of these turbulent drift currents favours energy transfer from the RF fields to the plasma and thus leads to their stronger damping. This effect allows us to interpret quantitatively the enhanced damping of the magnetosonic waves observed in several experiments. The magnetized radially inhomogeneous cylindrical plasmas in these experiments are characterized by density fluctuations due to drift instabilities. The theory has also a number of other applications; an example is given of the whistlers damped by the ionospheric density fluctuation