6,787 research outputs found
Ballistic thermal conductance limited by phonon roughness scattering: A comparison of power-law and Gaussian roughness
In this work, we have investigated the influence of power-law roughness on the ballistic thermal conductance KTH for a nanosized beam adiabatically connected between two heat reservoirs. The sideways wall beam roughness is assumed to be power-law type, which is described by the roughness amplitude w, the in-plane roughness correlation length ξ and the roughness exponent 0≤H≤1. Distinct differences occur in between power-law and Gaussian wall roughness. For power-law roughness with low roughness exponents H (<0.5), the influence of phonon scattering can be rather destructive leading to significant deviations from the universal conductance value for flat beam walls. On the other hand for large roughness exponents (H>0.5) the conductance drop is significantly smaller than that of Gaussian roughness assuming similar roughness ratios w/ξ.
A New Light Higgs Boson and Short-Baseline Neutrino Anomalies
The low-energy excesses observed by the MiniBooNE experiment have, to date,
defied a convinc- ing explanation under the standard model even with
accommodation for non-zero neutrino mass. In this paper we explore a new
oscillation mechanism to explain these anomalies, invoking a light neu-
trinophilic Higgs boson, conceived to induce a low Dirac neutrino mass in
accord with experimental limits. Beam neutrinos forward-scattering off of a
locally over-dense relic neutrino background give rise to a novel matter-effect
with an energy-specific resonance. An enhanced oscillation around this
resonance peak produces flavor transitions which are highly consistent with the
MiniBooNE neutrino- and antineutrino-mode data sets. The model provides
substantially improved values beyond either the no-oscillation
hypothesis or the more commonly explored 3+1 sterile neutrino hy- pothesis.
This mechanism would introduce distinctive signatures at each baseline in the
upcoming SBN program at Fermilab, presenting opportunities for further
exploration.Comment: 11 pages, 6 figures, submitted to PR
Concept design and alternate arrangements of orbiter mid-deck habitability features
The evaluations and recommendations for habitability features in the space shuttle orbiter mid-deck are summarized. The orbiter mission plans, the mid-deck dimensions and baseline arrangements along with crew compliments and typical activities were defined. Female and male anthropometric data based on zero-g operations were also defined. Evaluations of baseline and alternate feasible concepts provided several recommendations which are discussed
Population Trends of Quails in North America
We used North American Breeding Bird Survey data (1966-91) to estimate distribution, relative abundance, and population trends of quails. Population trends in grassland/shrub birds sympatric with northern bobwhite (Colinus virginianus) were also examined. Northern bobwhite and scaled quail (Callipepl,a squamata) populations have declined since 1966. Rates of decline for these quails have increased during the past decade. California quail (C. califomica), Gambel\u27s quail (C. gambelii), and mountain quail (Oreortyx pictus) populations have been stable over the long-term (1966-91). However, the short-term (1982-91) trend for California quail is positive, whereas Gambel\u27s quail appear to be declining. Patterns in trends indicate similar factors may be negatively affecting breeding populations of grassland/shrub birds throughout the bobwhite\u27s range. We discuss plausible hypotheses to explain population trends and recommend future action
The Impact of Atmospheric Fluctuations on Degree-scale Imaging of the Cosmic Microwave Background
Fluctuations in the brightness of the Earth's atmosphere originating from
water vapor are an important source of noise for ground-based instruments
attempting to measure anisotropy in the Cosmic Microwave Background. This paper
presents a model for the atmospheric fluctuations and derives simple
expressions to predict the contribution of the atmosphere to experimental
measurements. Data from the South Pole and from the Atacama Desert in Chile,
two of the driest places on Earth, are used to assess the level of fluctuations
at each site.Comment: 29 pages, 7 figures, 1 table, appears in The Astrophysical Journa
Initial beam-profiling tests with the NML prototype station at the Fermilab A0 Photoinjector
The beam-profile diagnostics station prototype for the superconducting rf
electron linac being constructed at Fermilab at the New Muon Lab has been
tested. The station uses intercepting radiation converter screens for the
low-power beam mode: either a 100-\mu m thick YAG:Ce single crystal
scintillator or a 1-\mu m thin Al optical transition radiation (OTR) foil. The
screens are oriented with the surface perpendicular to the beam direction. A
downstream mirror with its surface at 45 degrees to the beam direction is used
to direct the radiation into the optical transport. The optical system has
better than 20 (10) \mu m rms spatial resolution when covering a vertical field
of view of 18 (5) mm. The initial tests were performed at the A0 Photoinjector
at a beam energy of ~15 MeV and with micropulse charges from 25 to 500 pC for
beam sizes of 45 to 250 microns. Example results will be presented.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1
Apr 2011. New York, US
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