12,044 research outputs found
L\'{e}vy flights in quantum transport in quasi-ballistic wires
Conductance fluctuations, localization and statistics of Lyapunov exponents
are studied numerically in pure metallic wires with rough boundaries
(quasi-ballistic wires). We find that the correlation energy of conductance
fluctuations scales anomalously with the sample dimensions, indicating the role
of L\'{e}vy flights. Application of a magnetic field deflects the L\'{e}vy
flights which reduces the localization length. This deflection also breaks the
geometrical flux cancellation and restores the usual Aharonov-Bohm type
magneto-conductance fluctuations.Comment: Available also at http://roberto.fis.uniroma3.it/leadbeat/pub.htm
Location Determinants of Food Manufacturing Investment: Are Non-metropolitan Counties Competitive?
Food manufacturing site selection is determined by infrastructure, agglomeration, product and input markets, labor markets, and fiscal attributes of local communities. This article examines how these factors influence location decisions across the rural-urban continuum in the lower forty-eight states of the U.S. Negative binomial regression and spatial clustering methods are used to forecast new food processor location patterns at the county level, 2000-2004. Remote rural areas are at a comparative disadvantage with respect to attracting food processors, but non-metropolitan counties with economic links to urban core areas may be attractive investment sites for footloose, supply, and demand-oriented food manufacturers.firm location, food manufacturing, negative binomial regression, spatial clustering, Community/Rural/Urban Development, R1, R3,
Granulation across the HR diagram
We have obtained ultra-high quality spectra (R=180,000; S/N>300) with
unprecedented wavelength coverage (4400 to 7400 A) for a number of stars
covering most of the HR diagram in order to test the predictions of models of
stellar surface convection. Line bisectors and core wavelength shifts are both
measured and modeled, allowing us to validate and/or reveal the limitations of
state-of-the-art hydrodynamic model atmospheres of different stellar
parameters. We show the status of our project and preliminary results.Comment: 4 pages, 3 figures; proceedings article for Joint Discussion 10 at
the IAU General Assembly, Rio de Janeiro, Brazil, August 200
Electron spin manipulation and resonator readout in a double quantum dot nano-electromechanical system
Magnetically coupling a nano-mechanical resonator to a double quantum dot
confining two electrons can enable the manipulation of a single electron spin
and the readout of the resonator's natural frequency. When the Larmor frequency
matches the resonator frequency, the electron spin in one of the dots can be
selectively flipped by the magnetised resonator. By simultaneously measuring
the charge state of the two-electron double quantum dots, this transition can
be detected thus enabling the natural frequency of the mechanical resonator to
be determined.Comment: 7 pages, fixed typos, updated figures 4 and
Relationships between different nutritional anthropometric statuses and health-related fitness of South African primary school children
Background A double burden of both under- and over-nutrition exists among South African children. Aim Describe associations between nutritional statuses and health-related fitness test performances. Subjects and methods Height and weight of 10 285 children (6-13 years; n=5604 boys and 4681 girls) were measured and used to calculate: body mass index (BMI), and prevalence of overweight and obesity, stunting, wasting, and underweight. Physical fitness scores for standing long jump, shuttle run, sit-and-reach, sit-up (EUROFIT) and cricket ball throw were assessed. Age and gender specific z-scores were calculated for these variables. Physical fitness for each nutritional status group was compared to children of normal weight. Results Compared to normal weight children, overweight and obese children scored lower on all fitness tests (p<.001), except cricket ball throw (p=.235) and sit-and-reach (p=.015). Stunted and underweight children performed poorer than normal weight children on most fitness tests (p<.001), except sit-and-reach (stunted: p=.829; underweight: p=.538) and shuttle run (underweight: p=.017). Performance of wasted children was not as highly compromised as other undernourished groups, but they performed poorer on the cricket ball throw (p<.001). Conclusions When compared to normal weight children, both under- and over-nourished children performed poorer on some, but not all, health-related fitness tests
The detailed chemical composition of the terrestrial planet host Kepler-10
Chemical abundance studies of the Sun and solar twins have demonstrated that
the solar composition of refractory elements is depleted when compared to
volatile elements, which could be due to the formation of terrestrial planets.
In order to further examine this scenario, we conducted a line-by-line
differential chemical abundance analysis of the terrestrial planet host
Kepler-10 and fourteen of its stellar twins. Stellar parameters and elemental
abundances of Kepler-10 and its stellar twins were obtained with very high
precision using a strictly differential analysis of high quality CFHT, HET and
Magellan spectra. When compared to the majority of thick disc twins, Kepler-10
shows a depletion in the refractory elements relative to the volatile elements,
which could be due to the formation of terrestrial planets in the Kepler-10
system. The average abundance pattern corresponds to ~ 13 Earth masses, while
the two known planets in Kepler-10 system have a combined ~ 20 Earth masses.
For two of the eight thick disc twins, however, no depletion patterns are
found. Although our results demonstrate that several factors (e.g., planet
signature, stellar age, stellar birth location and Galactic chemical evolution)
could lead to or affect abundance trends with condensation temperature, we find
that the trends give further support for the planetary signature hypothesis.Comment: 12 pages, 11 figures, accepted for publication in MNRA
Quantum Spin Fluctuations as a Source of Long-Range Proximity Effects in Diffusive Ferromagnet-Superconductor Structures
We show that quantum spin fluctuations in inhomogeneous ferromagnets
drastically affect the Andreev reflection of electrons and holes at a
ferromagnet-superconductor interface. As a result a strong long-range proximity
effect appears, associated with electron-hole spin triplet correlations and
persisting on a lenght scale typical for non-magnetic materials, but
anomalously large for ferromagnets.Comment: 4 pages, 2 figure
- …