16,457 research outputs found
Spectral Energy Distributions of Passive T Tauri Disks: Inclination
We compute spectral energy distributions (SEDs) for passive T Tauri disks
viewed at arbitrary inclinations. Semi-analytic models of disks in radiative
and hydrostatic equilibrium are employed. Over viewing angles for which the
flared disk does not occult the central star, the SED varies negligibly with
inclination. For such aspects, the SED shortward of ~80 microns is particularly
insensitive to orientation, since short wavelength disk emission is dominated
by superheated surface layers which are optically thin. The SED of a nearly
edge-on disk is that of a class I source. The outer disk occults inner disk
regions, and emission shortward of ~30 microns is dramatically extinguished.
Spectral features from dust grains may appear in absorption. However,
millimeter wavelength fluxes decrease by at most a factor of 2 from face-on to
edge-on orientations.
We present illustrative applications of our SED models. The class I source
04108+2803B is considered a T Tauri star hidden from view by an inclined
circumstellar disk. Fits to its observed SED yield model-dependent values for
the disk mass of ~0.015 solar masses and a disk inclination of ~65 degrees
relative to face-on. The class II source GM Aur represents a T Tauri star
unobscured by its circumstellar disk. Fitted parameters include a disk mass of
\~0.050 solar masses and an inclination of ~60 degrees.Comment: Accepted to ApJ, 20 pages, 7 figures, aaspp4.st
Phase analysis of the cosmic microwave background from an incomplete sky coverage
Phases of the spherical harmonic analysis of full-sky cosmic microwave
background (CMB) temperature data contain useful information complementary to
the ubiquitous angular power spectrum. In this letter we present a new method
of phase analysis on incomplete sky maps. It is based on Fourier phases of
equal-latitude pixel rings of the map, which are related to the mean angle of
the trigonometric moments from the full-sky phases. They have an advantage for
probing regions of interest without tapping polluted Galactic plane area, and
can localize non-Gaussian features and departure from statistical isotropy in
the CMB.Comment: 5 pages, 3 figures submitted to MNRAS Letters, replaced with minor
change
A theoretical study of heterojunction and graded band gap type solar cells
The work performed concentrated on including multisun effects, high temperature effects, and electron irradiation effects into the computer analysis program for heterojunction and graded bandgap solar cells. These objectives were accomplished and the program is now available for such calculations
Lepton Flavor Violating Radiative Decays in EW-Scale Model: An Update
We perform an updated analysis for the one-loop induced lepton flavor
violating radiative decays in an extended mirror model.
Mixing effects of the neutrinos and charged leptons constructed with a
horizontal symmetry are also taken into account. Current experimental
limit and projected sensitivity on the branching ratio of
are used to constrain the parameter space of the model. Calculations of two
related observables, the electric and magnetic dipole moments of the leptons,
are included. Implications concerning the possible detection of mirror leptons
at the LHC and the ILC are also discussed.Comment: 9 figures, 36 single-side pages. Updated email addresses and
referenc
The Influence of Federal Laboratory R&D on Industrial Research
Over the past 60 years the United States has created the world's largest system of government laboratories. The impact of the laboratories on the private economy has been little studied though their research accounts for 14% of total U.S. R&D, more than the R&D of all colleges and universities combined. In this paper we study the influence of federal laboratory R&D on industrial research using a sample of industrial laboratories. In head-to-head comparisons with alternative measures, we find that Cooperative Research and Development Agreements or CRADAs, are the primary channel by which federal laboratories increase the patenting and R&D of industrial laboratories. With a CRADA industrial laboratories patent more, spend more on company-financed R&D and spend more of their own money on federal laboratories. Without a CRADA patenting stays about the same and only federally funded R&D increases, mostly because of direct subsidies by government. These results are consistent with the literature on endogenous R&D spillovers, which emphasizes that knowledge spills over when recipients work at making it spill over. CRADAs are legal agreements between federal laboratories and firms to work together on joint research. They are backed by real budgets and accompanied by cost sharing that could bind the parties together in joint research. Moreover, the CRADA instrument is the main form of such agreements. Thus, both in theory and in fact CRADAs may be more beneficial to firms than other public- private interactions, precisely because of the mutual effort that they require of firms and government laboratories.
Top Quark Rare Decays via Loop-Induced FCNC Interactions in Extended Mirror Fermion Model
Flavor changing neutral current (FCNC) interactions for a top quark
decays into with represents a neutral gauge or Higgs boson, and a
up- or charm-quark are highly suppressed in the Standard Model (SM) due to the
Glashow-Iliopoulos-Miami mechanism. Whilst current limits on the branching
ratios of these processes have been established at the order of from
the Large Hadron Collider experiments, SM predictions are at least nine orders
of magnitude below. In this work, we study some of these FCNC processes in the
context of an extended mirror fermion model, originally proposed to implement
the electroweak scale seesaw mechanism for non-sterile right-handed neutrinos.
We show that one can probe the process for a wide range of parameter
space with branching ratios varying from to , comparable
with various new physics models including the general two Higgs doublet model
with or without flavor violations at tree level, minimal supersymmetric
standard model with or without -parity, and extra dimension model.Comment: 30 pages, 8 figures, 2 tables and 1 appendix. Version to appear in
NP
The Influence of Federal Laboratory R&D on Industrial Research
This paper studies the influence of R&D in the federal laboratory system, the world's largest, on firm research. Our results are based on a sample of 220 industrial research laboratories that work with a variety of federal laboratories and agencies and are owned by 115 firms in the chemicals, machinery, electrical equipment, and motor vehicles industries. Using an indicator of their importance to R&D managers, we find that Cooperative Research and Development Agreements or CRADAs dominate other channels of technology transfer from federal laboratories to firms. With a CRADA industry laboratories patent more, spend more on company-financed R&D, and devote more resources to their federal counterparts. Without this influence patenting stays about the same, and only federally funded R&D increases, mostly because of government support. The Stevenson-Wydler Act and amendments during the 1980s introduced CRADAs, which legally bind federal laboratories and firms together in joint research. In theory the agreements could capitalize on complementarities between public and private research. Our results support this perspective and suggest that CRADAs may be more beneficial to firms than other interactions with federal laboratories, precisely because of the mutual effort that they demand from both parties.
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