226 research outputs found
Decomposition of Differences
This paper examines methods of decomposing a difference in levels between groups for a dependent variable such as income. Applied to regression equations, this technique estimates the contribution to the difference from divergent characteristics and divergent rates of converting characteristics into the dependent variable. The consequences of an "interaction" component being present in the decomposition is examined. The paper, using data from the 1960 Census, shows how ignoring the interaction term can influence results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68707/2/10.1177_004912417500300306.pd
Massive IIA supergravity from the topologically massive D-2-brane
The superfield equations of massive IIA supergravity, in the form of
constraints on the superspace geometry, are shown to be implied by
-symmetry of the topologically massive D-2-brane.Comment: 19 pp. Minor corrections. To appear in PL
Large-N supersymmetric beta-functions
We present calculations of the leading and O(1/N) terms in a large-N
expansion of the \beta-functions for various supersymmetric theories: a
Wess-Zumino model, supersymmetric QED and a non-abelian supersymmetric gauge
theory. In all cases N is the number of a class of the chiral superfields in
the theory.Comment: 9 pages, tex, five figures. Uses harvmac and epsf. Revised to include
a discussion of higher loop DRED ambiguities. Some references added, and
notation clarifie
Impact of mutant beta-catenin on ABCB1 expression and therapy response in colon cancer cells
Background: Colorectal cancers are often chemoresistant toward antitumour drugs that are substrates for ABCB1-mediated multidrug resistance (MDR). Activation of the Wnt/beta-catenin pathway is frequently observed in colorectal cancers. This study investigates the impact of activated, gain-of-function beta-catenin on the chemoresistant phenotype. Methods: The effect of mutant (mut) beta-catenin on ABCB1 expression and promoter activity was examined using HCT116 human colon cancer cells and isogenic sublines harbouring gain-of-function or wild-type beta-catenin, and patients' tumours. Chemosensitivity towards 24 anticancer drugs was determined by high throughput screening. Results: Cell lines with mut beta-catenin showed high ABCB1 promoter activity and expression. Transfection and siRNA studies demonstrated a dominant role for the mutant allele in activating ABCB1 expression. Patients' primary colon cancer tumours shown to express the same mut beta-catenin allele also expressed high ABCB1 levels. However, cell line chemosensitivities towards 24 MDR-related and non-related antitumour drugs did not differ despite different beta-catenin genotypes. Conclusion: Although ABCB1 is dominantly regulated by mut beta-catenin, this did not lead to drug resistance in the isogenic cell line model studied. In patient samples, the same beta-catenin mutation was detected. The functional significance of the mutation for predicting patients' therapy response or for individualisation of chemotherapy regimens remains to be established
Initial State Interactions for -Proton Radiative Capture
The effects of the initial state interactions on the radiative
capture branching ratios are examined and found to be quite sizable. A general
coupled-channel formalism for both strong and electromagnetic channels using a
particle basis is presented, and applied to all the low energy data
with the exception of the {\it 1s} atomic level shift. Satisfactory fits are
obtained using vertex coupling constants for the electromagnetic channels that
are close to their expected SU(3) values.Comment: 16 pages, uses revte
SUSY-QCD Decays of Squarks and Gluinos
The partial widths are determined for squark decays to gluinos and quarks,
and gluino decays to squarks and quarks, respectively. The widths are
calculated including one-loop SUSY-QCD corrections. The corrections amount to
30\% to 50\% for squark decays and 10\% to 10\% for gluino decays.
We have derived the results in the \DR ~and \MS ~renormalization schemes, and
we have demonstrated explicitly that the one-loop effective and q\sq\gl
couplings are equal in the limit of exact supersymmetry.Comment: 11 pages, Latex2e, 2 figures (uses epsfig). Complete postscript file
available at http://www.desy.de/pub/preprints/desy/1996/desy96-022.p
Soft parton radiation in polarized vector boson production: theoretical issues
Accurate measurement of spin-dependent parton distributions in production of
electroweak bosons with polarized proton beams at the Relativistic Heavy Ion
Collider depends on good understanding of QCD radiation at small transverse
momenta of vector bosons. We present a theoretical formalism for
small- resummation of the cross sections for production of virtual
photons, W, and Z bosons, with the subsequent decay of these bosons into lepton
pairs, for arbitrary longitudinal polarizations of the proton beams.Comment: 35 pages, 2 figures; minor modifications; bibliography references
adde
Vibrational Properties of Nanoscale Materials: From Nanoparticles to Nanocrystalline Materials
The vibrational density of states (VDOS) of nanoclusters and nanocrystalline
materials are derived from molecular-dynamics simulations using empirical
tight-binding potentials. The results show that the VDOS inside nanoclusters
can be understood as that of the corresponding bulk system compressed by the
capillary pressure. At the surface of the nanoparticles the VDOS exhibits a
strong enhancement at low energies and shows structures similar to that found
near flat crystalline surfaces. For the nanocrystalline materials an increased
VDOS is found at high and low phonon energies, in agreement with experimental
findings. The individual VDOS contributions from the grain centers, grain
boundaries, and internal surfaces show that, in the nanocrystalline materials,
the VDOS enhancements are mainly caused by the grain-boundary contributions and
that surface atoms play only a minor role. Although capillary pressures are
also present inside the grains of nanocrystalline materials, their effect on
the VDOS is different than in the cluster case which is probably due to the
inter-grain coupling of the modes via the grain-boundaries.Comment: 10 pages, 7 figures, accepted for publication in Phys. Rev.
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
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