1,004 research outputs found
Blending of nanoscale and microscale in uniform large-area sculptured thin-film architectures
The combination of large thickness ( m), large--area uniformity (75
mm diameter), high growth rate (up to 0.4 m/min) in assemblies of
complex--shaped nanowires on lithographically defined patterns has been
achieved for the first time. The nanoscale and the microscale have thus been
blended together in sculptured thin films with transverse architectures.
SiO () nanowires were grown by electron--beam evaporation onto
silicon substrates both with and without photoresist lines (1--D arrays) and
checkerboard (2--D arrays) patterns. Atomic self--shadowing due to
oblique--angle deposition enables the nanowires to grow continuously, to change
direction abruptly, and to maintain constant cross--sectional diameter. The
selective growth of nanowire assemblies on the top surfaces of both 1--D and
2--D arrays can be understood and predicted using simple geometrical shadowing
equations.Comment: 17 pages, 9 figure
Matter-gravity couplings and Lorentz violation
The gravitational couplings of matter are studied in the presence of Lorentz
and CPT violation. At leading order in the coefficients for Lorentz violation,
the relativistic quantum hamiltonian is derived from the gravitationally
coupled minimal Standard-Model Extension. For spin-independent effects, the
nonrelativistic quantum hamiltonian and the classical dynamics for test and
source bodies are obtained. A systematic perturbative method is developed to
treat small metric and coefficient fluctuations about a Lorentz-violating and
Minkowski background. The post-newtonian metric and the trajectory of a test
body freely falling under gravity in the presence of Lorentz violation are
established. An illustrative example is presented for a bumblebee model. The
general methodology is used to identify observable signals of Lorentz and CPT
violation in a variety of gravitational experiments and observations, including
gravimeter measurements, laboratory and satellite tests of the weak equivalence
principle, antimatter studies, solar-system observations, and investigations of
the gravitational properties of light. Numerous sensitivities to coefficients
for Lorentz violation can be achieved in existing or near-future experiments at
the level of parts in 10^3 down to parts in 10^{15}. Certain coefficients are
uniquely detectable in gravitational searches and remain unmeasured to date.Comment: 59 pages two-column REVTe
Bounds on Lorentz and CPT Violation from the Earth-Ionosphere Cavity
Electromagnetic resonant cavities form the basis of many tests of Lorentz
invariance involving photons. The effects of some forms of Lorentz violation
scale with cavity size. We investigate possible signals of violations in the
naturally occurring resonances formed in the Earth-ionosphere cavity.
Comparison with observed resonances places the first terrestrial constraints on
coefficients associated with dimension-three Lorentz-violating operators at the
level of 10^{-20} GeV.Comment: 8 pages REVTe
Light and tree size influence belowground development in yellow birch and sugar maple
The effects of light and tree size on the root architecture and mycorrhiza of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh) growing in the understory of deciduous forests in southern Qu
Could One Find Petroleum Using Neutrino Oscillations in Matter?
In neutrino physics, it is now widely believed that neutrino oscillations are
influenced by the presence of matter, modifying the energy spectrum produced by
a neutrino beam traversing the Earth. Here, we will discuss the reverse
problem, i.e. what could be learned about the Earth's interior from a single
neutrino baseline energy spectrum, especially about the Earth's mantle. We will
use a statistical analysis with a low-energy neutrino beam under very
optimistic assumptions. At the end, we will note that it is hard to find
petroleum with such a method, though it is not too far away from technical
feasibility.Comment: 6 pages, 4 figures, EPL LaTeX. Final version to be published in
Europhys. Let
Signals for Lorentz Violation in Post-Newtonian Gravity
The pure-gravity sector of the minimal Standard-Model Extension is studied in
the limit of Riemann spacetime. A method is developed to extract the modified
Einstein field equations in the limit of small metric fluctuations about the
Minkowski vacuum, while allowing for the dynamics of the 20 independent
coefficients for Lorentz violation. The linearized effective equations are
solved to obtain the post-newtonian metric. The corresponding post-newtonian
behavior of a perfect fluid is studied and applied to the gravitating many-body
system. Illustrative examples of the methodology are provided using bumblebee
models. The implications of the general theoretical results are studied for a
variety of existing and proposed gravitational experiments, including lunar and
satellite laser ranging, laboratory experiments with gravimeters and torsion
pendula, measurements of the spin precession of orbiting gyroscopes, timing
studies of signals from binary pulsars, and the classic tests involving the
perihelion precession and the time delay of light. For each type of experiment
considered, estimates of the attainable sensitivities are provided. Numerous
effects of local Lorentz violation can be studied in existing or near-future
experiments at sensitivities ranging from parts in 10^4 down to parts in
10^{15}.Comment: 46 pages two-column REVTeX, accepted in Physical Review
The Intensive Diet and Exercise for Arthritis (IDEA) trial: design and rationale
Background: Obesity is the most modifiable risk factor, and dietary induced weight loss potentially the best nonpharmacologic intervention to prevent or to slow osteoarthritis (OA) disease progression. We are currently conducting a study to test the hypothesis that intensive weight loss will reduce inflammation and joint loads sufficiently to alter disease progression, either with or without exercise. This article describes the intervention, the empirical evidence to support it, and test-retest reliability data. Methods/Design: This is a prospective, single-blind, randomized controlled trial. The study population consists of 450 overweight and obese (BMI = 27-40.5 kg/m2) older (age greater than or equal to 55 yrs) adults with tibiofemoral osteoarthritis. Participants are randomized to one of three 18-month interventions: intensive dietary restriction-plus-exercise; exercise-only; or intensive dietary restriction-only. The primary aims are to compare the effects of these interventions on inflammatory biomarkers and knee joint loads. Secondary aims will examine the effects of these interventions on function, pain, and mobility; the dose response to weight loss on disease progression; if inflammatory biomarkers and knee joint loads are mediators of the interventions; and the association between quadriceps strength and disease progression. Results: Test-retest reliability results indicated that the ICCs for knee joint load variables were excellent, ranging from 0.86 - 0.98. Knee flexion/extension moments were most affected by BMI, with lower reliability with the highest tertile of BMI. The reliability of the semi-quantitative scoring of the knee joint using MRI exceeded previously reported results, ranging from a low of 0.66 for synovitis to a high of 0.99 for bone marrow lesion size. Discussion: The IDEA trial has the potential to enhance our understanding of the OA disease process, refine weight loss and exercise recommendations in this prevalent disease, and reduce the burden of disability. Originally published BMC Musculoskeletal Disorders, Vol. 10, No. 93, July 200
Effect of microstructural evolution on magnetic properties of Ni thin films
Copyright © Indian Academy of Sciences.The magnetic properties of Ni thin films, in the range 20–500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30–50 nm at ambient temperature to 120–150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30–50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature.University Grants Commission for Centre of Advanced Studies in Physic
- …