2,717 research outputs found
Negative Refraction Gives Rise to the Klein Paradox
Electromagnetic negative refraction in metamaterials has attracted
increasingly great interest, since its first experimental verification in 2001.
It potentially leads to the applications superior to conventional devices
including compact antennas for mobile stations, imaging beyond the diffraction
limit, and high-resolution radars, not to mention the anamolous wave
propagation in fundamental optics. Here, we report how metamaterials could be
used to simulate the "negative refraction of spin-zero particles interacting
with a strong potential barrier", which gives rise to the Klein paradox--a
counterintuitive relativistic process. We address the underlying physics of
analogous wave propagation behaviours in those two entirely different domains
of quantum and classical.Comment: 4 journal pages, 2 figure
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Ozone reactions in unoccupied spaces of residences
Ozone has the potential to cause many health problems. Most of the human population exposure to ozone occurs indoors. It has been previously reported that the average ozone penetration factor into the occupied space is 0.79. However, this value does not account for the pathway by which ozone enters the occupied space. A model to determine the amount that unoccupied spaces contribute to the ozone concentration in the occupied space is presented in this thesis. A literature review was then performed to identify parameters for the model as well as gaps that exist in the literature pertaining to the model developed. One of the biggest gaps was the lack of ozone decay rates in unoccupied spaces, such as garages, attics and crawl spaces. Because of this, a field study was designed and completed to determine the ozone decay rate in garages. It was determined that the average ozone decay rate in garages is 2.7 (± 1.1) hr-1. This value is comparable to previous data for occupied space ozone decay rates. Using these data as well as other published data, it was determined that, under normal conditions, ozone penetration through unoccupied spaces to the occupied space is not a significant pathway. However, there are some conditions for which unoccupied spaces may be a major pathway for ozone entry into homes. One example of this is when both the garage door and the door connecting to garage to the occupied space is opened for a long time. Under these conditions, the occupied space can reach an indoor/outdoor (IO) concentration of 0.46. As can be seen, under this condition, unoccupied spaces do provide substantial contribution of ozone to the occupied spaceCivil, Architectural, and Environmental Engineerin
The Partisan Politics of New Social Risks in Advanced Postindustrial Democracies: Social Protection for Labor Market Outsiders
Advanced postindustrialization generates numerous challenges for the European social model. Central among these challenges is declining income, unstable employment, and inadequate training of semi- and unskilled workers. In this chapter, I assess the partisan basis of support for social policies that address the needs of these marginalized workers. I specifically consider the impacts of postindustrial cleavages among core constituencies of social democratic parties on the capacity of these parties to pursue inclusive social policies. I argue – and find support for in empirical analyses – that encompassing labor organization is the most important factor in strengthening the ability of left parties to build successful coalitions in support of outsider-friendly policies. I go beyond existing work on the topic by considering the full array of postindustrial cleavages facing left parties, by more fully elaborating why encompassing labor organization is crucial, and by considering a more complete set of measures of outsider policies than extant work. I compare my arguments and findings to important new work that stresses coalition building and partisan politics but minimizes the role of class organization
Analysis of Generalized Grover's Quantum Search Algorithms Using Recursion Equations
The recursion equation analysis of Grover's quantum search algorithm
presented by Biham et al. [PRA 60, 2742 (1999)] is generalized. It is applied
to the large class of Grover's type algorithms in which the Hadamard transform
is replaced by any other unitary transformation and the phase inversion is
replaced by a rotation by an arbitrary angle. The time evolution of the
amplitudes of the marked and unmarked states, for any initial complex amplitude
distribution is expressed using first order linear difference equations. These
equations are solved exactly. The solution provides the number of iterations T
after which the probability of finding a marked state upon measurement is the
highest, as well as the value of this probability, P_max. Both T and P_max are
found to depend on the averages and variances of the initial amplitude
distributions of the marked and unmarked states, but not on higher moments.Comment: 8 pages, no figures. To appear in Phys. Rev.
Opening the black box of energy throughputs in farm systems: A decomposition analysis between the energy returns to external inputs, internal biomass reuses and total inputs consumed (the Vallès County, Catalonia, c.1860 and 1999)
We present an energy analysis of past and present farm systems aimed to contribute to their sustainability assessment. Looking at agroecosystems as a set of energy loops between nature and society, and adopting a farm-operator standpoint at landscape level to set the system boundaries, enthalpy values of energy carriers are accounted for net Final Produce going outside as well as for Biomass Reused cycling inside, and External Inputs are accounted using embodied values. Human Labour is accounted for the fraction of the energy intake of labouring people devoted to perform farm work, considering the local or external origin of their food basket. In this approach the proportion of internal Biomass Reused becomes a hallmark of organic farm systems that tend to save External Inputs, whereas industrial farming and livestock breeding in feedlots tend to get rid of reuses replacing them with inputs coming from outside. Hence, decomposing the internal or external energy throughputs may bring to light their contrasting sociometabolic profiles. A Catalan case study in 1860 and 1990 is used as a test bench to show how revealing this decomposing analysis may be to plot the energy profiles of farm systems and their possible improvement pathways
Widening the analysis of Energy Return on Investment (EROI) in agro-ecosystems: Socio-ecological transitions to industrialized farm systems (the Vallès County, Catalonia, c.1860 and 1999)
Energy balances of farm systems have overlooked the role of energy flows that remain within agro-ecosystems. Yet, such internal flows fulfil important socio-ecological functions, including maintenance of farmers themselves and agro-ecosystem structures. Farming can either give rise to complex landscapes that favour associated biodiversity, or the opposite. This variability can be understood by assessing several types of Energy Returns on Investment (EROI). Applying these measures to a farm system in Catalonia, Spain in 1860 and in 1999, reveals the expected decrease in the ratio of final energy output to total and external inputs. The transition from solar-based to a fossil fuel based agro-ecosystem was further accompanied by an increase in the ratio of final energy output to biomass reused, as well as an absolute increase of Unharvested Phytomass grown in derelict forestland. The study reveals an apparent link between reuse of biomass and the decrease of landscape heterogeneity along with its associated biodiversity
The electric double layer has a life of its own
Using molecular dynamics simulations with recently developed importance
sampling methods, we show that the differential capacitance of a model ionic
liquid based double-layer capacitor exhibits an anomalous dependence on the
applied electrical potential. Such behavior is qualitatively incompatible with
standard mean-field theories of the electrical double layer, but is consistent
with observations made in experiment. The anomalous response results from
structural changes induced in the interfacial region of the ionic liquid as it
develops a charge density to screen the charge induced on the electrode
surface. These structural changes are strongly influenced by the out-of-plane
layering of the electrolyte and are multifaceted, including an abrupt local
ordering of the ions adsorbed in the plane of the electrode surface,
reorientation of molecular ions, and the spontaneous exchange of ions between
different layers of the electrolyte close to the electrode surface. The local
ordering exhibits signatures of a first-order phase transition, which would
indicate a singular charge-density transition in a macroscopic limit
Search for Higgs Bosons in e+e- Collisions at 183 GeV
The data collected by the OPAL experiment at sqrts=183 GeV were used to
search for Higgs bosons which are predicted by the Standard Model and various
extensions, such as general models with two Higgs field doublets and the
Minimal Supersymmetric Standard Model (MSSM). The data correspond to an
integrated luminosity of approximately 54pb-1. None of the searches for neutral
and charged Higgs bosons have revealed an excess of events beyond the expected
background. This negative outcome, in combination with similar results from
searches at lower energies, leads to new limits for the Higgs boson masses and
other model parameters. In particular, the 95% confidence level lower limit for
the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons
can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA >
72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and
soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for
minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM
parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European
Physical Journal
A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays
The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where
Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL
detector at LEP. Lambda_b are selected by the presence of energetic Lambda
particles in bottom events tagged by the presence of displaced secondary
vertices. A fit to the momenta of the Lambda particles separates signal from B
meson and fragmentation backgrounds. The measured product branching ratio is
f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))%
Combined with a previous OPAL measurement, one obtains
f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European
Physical Journal
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