831 research outputs found
The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs
The performance and cost of the 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States were determined. The regional insolation data base is discussed. A range for the forecast cost of conventional electricity by region and nationally over the next several cades are presented
The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs
The performance and cost of four 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States was studied. Each region has different insolation characteristics which result in varying collector field areas, plant performance, capital costs and energy costs. The regional variation in solar plant performance was assessed in relation to the expected rise in the future cost of residential and commercial electricity supplied by conventional utility power systems in the same regions. A discussion of the regional insolation data base is presented along with a description of the solar systems performance and costs. A range for the forecast cost of conventional electricity by region and nationally over the next several decades is given
Bacteriological conversion in twenty urinary tuberculosis patients treated with ofloxacin, rifampin and isoniazid: a 10-year follow-up study
Twenty patients withuri nary tuberculosis were treated withofloxac in (200 mg/day, 6 months), rifampin (600 mg/day, 3 months) and isoniazid (300 mg/day, 3 months) between 1989 and 1990. All patients were new cases, diagnosed by observation and/or isolation of Mycobacterium tuberculosis in one of the three morning urine samples. Bacteriological culture conversion (negativization) was assessed as a clinical guide of efficacy, comparing it, as the only parameter, against a control group (150 patients) withurina ry tuberculosis who received conventional therapy. Bacteriological follow-up studies were performed in bothgroups monthly for 6 months, then again 6 months later and then every year for 10 years after completion of treatment. In the 20 patients, the initial culture was positive with over 100 colonies per culture (>50%); the smear was positive in 45% of the patients (most were 2+). All strains were susceptible to rifampin, isoniazid and ofloxacin. Two patients discontinued treatment. Beginning withth e first monthof treatment, the bacteriological conversion was 100%, 89.5% and 100% in the remaining controls. In the control group, which received conventional treatment, the conversion was: 90%, 87%, 93% and 100% in the remaining controls. Treatment withofloxacin resulted in a bacteriological conversion similar to that following conventional treatment (p>0.05, Fisher’s exact test). After 10 years of patient follow-up, we conclude that ofloxacin, in combination withrifampin and isoniazid (bothfor 3 months only is effective against M. tuberculosis, providing satisfactory bacteriological and clinical efficacy
Cigarette sources for teens by grade: Implications for prevention and intervention
Objective: To identify at-risk teen populations and their sources of cigarettes, in order to help target future efforts in prevention of teen smoking. Methods: Analysis of smoking behavior questions for students in grades 6, 7, 9 and 12 from the 1997 Pennsylvania Biennial Youth Risk Survey. Results: Current smoking prevalence was 20.9% overall. The number of ninth grade smokers was almost five times higher than the number of sixth grade smokers (30.6% vs. 6.6%). Seventy-three percent of the teens identified friends as a source of tobacco. Stores became the most common source for twelfth graders only. Conclusion: Teenage smoking remains a serious public health concern and easy access to tobacco persists, despite recent legislation. The significant increase in smoking between 6th and 9th graders and the high social availability of cigarettes demonstrate the need for continued attempts to limit teen\u27s access to tobacco and emphasis on prevention efforts in younger adolescents
Brain magnetic resonance elastography based on Rayleigh damping material model
1-pageThis research study focuses on application of the subzone based Magnetic Resonance Elastography (MRE) using Rayleigh damped (RD) material model to quantify shear stiffness, damping behavior and elastic energy attenuation mechanism of the intracranial tissue in the in vivo healthy brain. The octahedral shear strain (OSS) SNR calculation confirmed significant attenuation of the shear strain waves in the deeper brain region. The measurement of brain viscoelastic properties revealed that ventricles exhibits much lower elasticity (0.8 kPa) than the surrounding white and gray matter (2.6 kPa). We conclude that RD MRE show promise for potential in vivo determination of different brain tissue types, and the possibility of providing additional diagnostic tools
Controlling the quantum dynamics of a mesoscopic spin bath in diamond
Understanding and mitigating decoherence is a key challenge for quantum
science and technology. The main source of decoherence for solid-state spin
systems is the uncontrolled spin bath environment. Here, we demonstrate quantum
control of a mesoscopic spin bath in diamond at room temperature that is
composed of electron spins of substitutional nitrogen impurities. The resulting
spin bath dynamics are probed using a single nitrogen-vacancy (NV) centre
electron spin as a magnetic field sensor. We exploit the spin bath control to
dynamically suppress dephasing of the NV spin by the spin bath. Furthermore, by
combining spin bath control with dynamical decoupling, we directly measure the
coherence and temporal correlations of different groups of bath spins. These
results uncover a new arena for fundamental studies on decoherence and enable
novel avenues for spin-based magnetometry and quantum information processing
Comparison of bacteria found on the hands of homemakers and neonatal intensive care unit nurses
http://deepblue.lib.umich.edu/bitstream/2027.42/55404/1/a comparison of the bacteris found.pd
Full coherent control of nuclear spins in an optically pumped single quantum dot
Highly polarized nuclear spins within a semiconductor quantum dot (QD) induce
effective magnetic (Overhauser) fields of up to several Tesla acting on the
electron spin or up to a few hundred mT for the hole spin. Recently this has
been recognized as a resource for intrinsic control of QD-based spin quantum
bits. However, only static long-lived Overhauser fields could be used. Here we
demonstrate fast redirection on the microsecond time-scale of Overhauser fields
of the order of 0.5 T experienced by a single electron spin in an optically
pumped GaAs quantum dot. This has been achieved using full coherent control of
an ensemble of 10^3-10^4 optically polarized nuclear spins by sequences of
short radio-frequency (rf) pulses. These results open the way to a new class of
experiments using rf techniques to achieve highly-correlated nuclear spins in
quantum dots, such as adiabatic demagnetization in the rotating frame leading
to sub-micro K nuclear spin temperatures, rapid adiabatic passage, and spin
squeezing
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