6,228 research outputs found
Transmission-Line Analysis of Epsilon-Near-Zero (ENZ)-Filled Narrow Channels
Following our recent interest in metamaterial-based devices supporting
resonant tunneling, energy squeezing and supercoupling through narrow waveguide
channels and bends, here we analyze the fundamental physical mechanisms behind
this phenomenon using a transmission-line model. These theoretical findings
extend our theory, allowing us to take fully into account frequency dispersion
and losses and revealing the substantial differences between this unique
tunneling phenomenon and higher-frequency Fabry-Perot resonances. Moreover,
they represent the foundations for other possibilities to realize tunneling
through arbitrary waveguide bends, both in E and H planes of polarization,
waveguide connections and sharp abruptions and to obtain analogous effects with
geometries arguably simpler to realize.Comment: 35 pages, 9 figure
POTENTIAL HEALTHCARE SAVINGS FROM PLANT STEROL ENRICHED FOODS IN CANADA
Increased consumption of foods containing plant sterols has the potential to reduce the incidence of coronary heart disease (CHD) and thus reduce costs associated with treating that disease in a significant way. This paper reports the results of an investigation of the potential monetary benefits of allowing foods enriched with plant sterols to be marketed in Canada. The objective of this research was to estimate the annual savings that would accrue to Canada’s single-payer publicly funded health care system if plant sterols were approved for use. If foods containing plant sterols are consumed at a sufficient rate, a reduction in CHD should follow. This research employs a variation of traditional cost-of-illness analysis entailing four steps: (i) estimation of a “success rate” (proportion of persons who would consume plant sterols at the necessary rate); (ii) presumption of blood cholesterol reduction due to plant sterol consumption; (iii) assumption of reduction in CHD that follows from blood cholesterol reduction; (iv) calculation of cost savings associated with reduced incidence of CHD. Calculations were carried out for four scenarios: ideal, optimistic, pessimistic, and very pessimistic. It was estimated that between 2.45 billion (ideal scenario) could be saved annually by Canada’s health care system with plant sterol enriched food products being made available for sale.coronary heart disease, cost of illness analysis, health care costs, success rate, Agricultural and Food Policy, Consumer/Household Economics, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Health Economics and Policy, I18,
89Y NMR Probe of Zn Induced Local Magnetism in YBa2(Cu(1-y)Zn(y))3O(6+x)
We present detailed data and analysis of the effects of Zn substitution on
the planar Cu site in YBaCuO (YBCO) as evidenced from
our Y NMR measurements on oriented powders. For we find
additional NMR lines which are associated with the Zn substitution. From our
data on the intensities and temperature dependence of the shift, width, and
spin-lattice relaxation rate of these resonances, we conclude that the spinless
Zn 3 state induces local moments on the near-neighbour () Cu
atoms. Additionally, we conjecture that the local moments actually extend to
the farther Cu atoms with the magnetization alternating in sign at subsequent
sites. We show that this analysis is compatible with ESR data taken on
dilute Gd doped (on the Y site) and on neutron scattering data reported
recently on Zn substituted YBCO. For optimally doped compounds
Y resonances are not detected, but a large % -dependent
contribution to the Y NMR linewidth is evidenced and is also attributed
to the occurence of a weak induced local moment near the Zn. These results are
compatible with macroscopic magnetic measurements performed on YBCO
samples prepared specifically in order to minimize the content of impurity
phases. We find significant differences between the present results on the
underdoped YBCO samples and Al NMR data taken on Al
substituted on the Cu site in optimally doped LaCuO. Further
experimental work is needed to clarify the detailed evolution of the impurity
induced magnetism with hole content in the cuprates.Comment: To be published in EPJB 15 pages of text and figures in eps forma
Roles of Free Electrons and H2O2 in the Optical Breakdown-Induced Photochemical Reduction of Aqueous [AuCl4]-
Free electrons and H2O2 formed in an optical breakdown plasma are found to directly control the kinetics of [AuCl4]− reduction to form Au nanoparticles (AuNPs) during femtosecond laser-assisted synthesis of AuNPs. The formation rates of both free electrons and H2O2 strongly depend on the energy and duration of the 800 nm laser pulses over the ranges of 10−2400 μJ and 30−1500 fs. By monitoring the conversion of [AuCl4]− to AuNPs using in situ UV−vis spectroscopy during laser irradiation, the first- and second-order rate constants in the autocatalytic rate law, k1 and k2, were extracted and compared to the computed free electron densities and experimentally measured H2O2 formation rates. For laser pulse energies of 600 μJ and lower at all pulse durations, the first-order rate constant, k1, was found to be directly proportional to the theoretically calculated plasma volume, in which the electron density exceeds the threshold value of 1.8 × 1020 cm−3. The second-order rate constant, k2, was found to correlate with the measured H2O2 formation rate at all pulse energies and durations, resulting in the empirical relationship k2 ≈ H2O20.5. We have demonstrated that the relative composition of free electrons and H2O2 in the optical breakdown plasma may be controlled by changing the pulse energy and duration, which may make it possible to tune the size and dispersity of AuNPs and other metal nanoparticle products synthesized with femtosecond laser-based methods
Sagebrush Ecosystem Characterization, Monitoring, and Forecasting with Remote Sensing: Quantifying Future Climate and Wildlife Habitat Change
Sagebrush (Artemisia spp.) ecosystems constitute the largest single North American shrub ecosystem and provide vital ecological, hydrological, biological, agricultural, and recreational ecosystem services. Disturbances continue to alter this ecosystem, with climate change possibly representing the greatest future disturbance risk. Improved ways to characterize and monitor gradual change in this ecosystem are vital to its future management. A new remote sensing sagebrush characterization approach was developed in Wyoming which integrates three scales of remote sensing to derive four primary continuous field components (bare ground, herbaceousness, litter, and shrub), and four secondary components (sagebrush, big sagebrush, Wyoming sagebrush, and shrub height) using a regression tree. An independent accuracy assessment of results revealed the primary component root mean square error values ranged from 4.90% to 10.16% for 2.4-m QuickBird, 6.01% to 15.54% for 30-m Landsat, and 6.97% to 16.14% for 56-m AWiFS. The change over time of five of these continuous field components (bare ground, herbaceous, litter, sagebrush, and shrub) was measured on the ground and by satellite across six seasons and four years to validate component change capability. Correlation of ground measurements to remote sensing predictions indicated that annual component predictions tracked ground measurements more closely than seasonal ones, and QuickBird predictions tracked ground measurements more closely than Landsat predictions. Correlation of component predictions to DAYMET precipitation revealed QuickBird components had better response to precipitation patterns than Landsat components. Further in-depth analysis of precipitation and component change patterns was completed from 1984 to 2011 for the same five components. A statistically significant correlation model between vegetation components and precipitation was established, and used to forecast vegetation components response in 2050 using IPCC precipitation scenarios. Bare ground increased under future scenarios, with the remaining components all decreasing. When 2050 future component results were applied to sage-grouse habitat models, a loss of about 12% of nesting habitat and 4% of summer habitat were predicted to occur. Results demonstrate the successful ability of sagebrush components to characterize the sagebrush ecosystem, monitor precipitation driven gradual change, support linear models to forecast future component response, and quantify future habitat impacts on sage-grouse
Self-Organized Criticality Effect on Stability: Magneto-Thermal Oscillations in a Granular YBCO Superconductor
We show that the self-organized criticality of the Bean's state in each of
the grains of a granular superconductor results in magneto-thermal oscillations
preceding a series of subsequent flux jumps. We find that the frequency of
these oscillations is proportional to the external magnetic field sweep rate
and is inversely proportional to the square root of the heat capacity. We
demonstrate experimentally and theoretically the universality of this
dependence that is mainly influenced by the granularity of the superconductor.Comment: submitted to Physical Review Letters, 4 pages, RevTeX, 4 figures
available as uufile
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