5,634 research outputs found
Multi-mode mediated exchange coupling in cavity QED
Microwave cavities with high quality factors enable coherent coupling of
distant quantum systems. Virtual photons lead to a transverse exchange
interaction between qubits, when they are non-resonant with the cavity but
resonant with each other. We experimentally probe the inverse scaling of the
inter-qubit coupling with the detuning from a cavity mode and its
proportionality to the qubit-cavity interaction strength. We demonstrate that
the enhanced coupling at higher frequencies is mediated by multiple
higher-harmonic cavity modes. Moreover, in the case of resonant qubits, the
symmetry properties of the system lead to an allowed two-photon transition to
the doubly excited qubit state and the formation of a dark state.Comment: 9 pages, 6 figure
Non-Fermi-liquid scattering rates and anomalous band dispersion in ferropnictides
Angle-resolved photoemission spectroscopy (ARPES) is used to study the band
dispersion and the quasiparticle scattering rates in two ferropnictides
systems. Our ARPES results show linear-in-energy dependent scattering rates
which are constant in a wide range of control parameter and which depend on the
orbital character of the bands. We demonstrate that the linear energy
dependence gives rise to weakly dispersing band with a strong mass enhancement
when the band maximum crosses the chemical potential. In the superconducting
phase the related small effective Fermi energy favors a
Bardeen-Cooper-Schrieffer (BCS)\,\cite{Bardeen1957}-Bose-Einstein
(BE)\,\cite{Bose1924} crossover state.Comment: 5 pages, 4 figures Supplement 4 pages, 6 figure
Optical tomography of Fock state superpositions
We consider optical tomography of photon Fock state superpositions in
connection with recent experimental achievements. The emphasis is put on the
fact that it suffices to represent the measured tomogram as a main result of
the experiment. We suggest a test for checking the correctness of experimental
data. Explicit expressions for optical tomograms of Fock state superpositions
are given in terms of Hermite polynomials. Particular cases of vacuum and low
photon-number state superposition are considered as well as influence of
thermal noise on state purity is studied.Comment: 5 pages, 2 figure
Industrial mining and HIV risk: evidence from 39 mine openings across 16 countries in sub-Saharan Africa
OBJECTIVES: The aim of this study was to assess the impact of natural resource extraction projects on HIV transmission risks in local communities in sub-Saharan Africa. DESIGN: Difference-in-differences design using repeated cross-sectional data from around newly opened mines. METHODS: We combined data on mine openings with HIV data from the Demographic and Health Surveys (DHS). Using logistic regression models, we compared HIV related indicators between mining (i.e. up to 10 km distance from the mine) and comparison (i.e. 10-50 km) areas before and after mine opening to identify their impact on HIV prevalence, sexual behavior and HIV knowledge. RESULTS: A total of 33,086 individuals across 39 mine openings were analyzed. Adjusting for baseline differences and temporal trends in the study regions, mine opening increased the odds of HIV infection almost two-fold (odds ratio (OR): 1.93, 95% confidence interval (CI): 1.19-3.14). Strongest effects were seen in high-prevalence countries and in the 20-29 years age group. In mining communities around operational mines there was a tendency towards lower HIV knowledge (OR: 0.81, 95% CI: 0.63-1.04). New mine openings increased the odds of risky sexual behaviors, such as having multiple sex partners (OR: 1.61, 95% CI: 1.02-2.55), high-risk sexual partners (OR: 1.45, 95% CI: 1.03-2.05) and unprotected sex with high-risk partners (OR: 1.77, 95% CI: 1.18-2.67). CONCLUSION: The findings suggest that in our sample of households surrounding industrial mines, HIV infection risks substantially increase upon mine opening. Existing strategies for addressing mining-related risks for HIV transmission seem to be insufficient. Further efforts for mitigating and monitoring impacts of mines are needed. Video Abstract: http://links.lww.com/QAD/C557
Short-term effects of national-level natural resource rents on life expectancy: a cross-country panel data analysis
While a substantial amount of literature addresses the relationship between natural resources and economic growth, relatively little is known regarding the relationship between natural resource endowment and health at the population level. We construct a 5-year cross-country panel to assess the impact of natural resource rents on changes in life expectancy at birth as a proxy indicator for population health during the period 1970-2015. To estimate the causal effects of interest, we use global commodity prices as instrumental variables for natural resource rent incomes in two-stage-least squares regressions. Controlling for country and year fixed effects, we show that each standard deviation increase in resource rents results in life expectancy increase of 6.72% (CI: 2.01%, 11.44%). This corresponds to approximately one additional year of life expectancy gained over five years. We find a larger positive effect of rents on life expectancy in sub-Saharan Africa (SSA) compared to other world regions. We do not find short-term effects of rents on economic growth, but show that increases in resource rents result in sizeable increases in government revenues in the short run, which likely translate into increased spending across government sectors. This suggests that natural resources can help governments finance health and other development-oriented programs needed to improve population health
Metro-Line Crossing Minimization: Hardness, Approximations, and Tractable Cases
Crossing minimization is one of the central problems in graph drawing.
Recently, there has been an increased interest in the problem of minimizing
crossings between paths in drawings of graphs. This is the metro-line crossing
minimization problem (MLCM): Given an embedded graph and a set L of simple
paths, called lines, order the lines on each edge so that the total number of
crossings is minimized. So far, the complexity of MLCM has been an open
problem. In contrast, the problem variant in which line ends must be placed in
outermost position on their edges (MLCM-P) is known to be NP-hard. Our main
results answer two open questions: (i) We show that MLCM is NP-hard. (ii) We
give an -approximation algorithm for MLCM-P
Influence of magnetic field on paramagnetic-ferromagnetic transition in LaCaMnO () crystal: ultrasonic and transport studies
The ultrasonic properties of LaCaMnO ()
with the Curie temperature about 200 K are studied. Temperature
dependences of longitudinal and transverse sound velocities were measured in
zero magnetic field and for different constant magnetic fields as well. The
ultrasonic study is supported by magnetic, resistive, magnetoresistive,
structural and other measurements of the sample that facilitate interpretation
of the results obtained. The magnetic field influence on sound properties found
in this study presents some new features of the interplay between the elastic
and magnetic properties of these compounds. It is shown that the
paramagnetic-ferromagnetic transition in the sample studied is first order, but
can become second order under the influence of applied magnetic field.Comment: submitted to Phys. Rev.
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