161,740 research outputs found
Computing only minimal answers in disjunctive deductive databases
A method is presented for computing minimal answers in disjunctive deductive
databases under the disjunctive stable model semantics. Such answers are
constructed by repeatedly extending partial answers. Our method is complete (in
that every minimal answer can be computed) and does not admit redundancy (in
the sense that every partial answer generated can be extended to a minimal
answer), whence no non-minimal answer is generated. For stratified databases,
the method does not (necessarily) require the computation of models of the
database in their entirety. Compilation is proposed as a tool by which problems
relating to computational efficiency and the non-existence of disjunctive
stable models can be overcome. The extension of our method to other semantics
is also considered.Comment: 48 page
Nonmonotonic charge occupation in double dots
We study the occupation of two electrostatically-coupled single-level quantum
dots with spinless electrons as a function of gate voltage. While the total
occupation of the double-dot system varies monotonically with gate voltage, we
predict that the competition between tunneling and Coulomb interaction can give
rise to a nonmonotonic filling of the individual quantum dots. This
non-monotonicity is a signature of the correlated nature of the many-body
wavefunction in the reduced Hilbert space of the dots. We identify two
mechanisms for this nonmonotonic behavior, which are associated with changes in
the spectral weights and the positions, respectively, of the excitation spectra
of the individual quantum dots. An experimental setup to test these predictions
is proposed.Comment: 4 pages, 5 figure
Coulomb-Modified Fano Resonance in a One-Lead Quantum Dot
We investigate a tunable Fano interferometer consisting of a quantum dot
coupled via tunneling to a one-dimensional channel. In addition to Fano
resonance, the channel shows strong Coulomb response to the dot, with a single
electron modulating channel conductance by factors of up to 100. Where these
effects coexist, lineshapes with up to four extrema are found. A model of
Coulomb-modified Fano resonance is developed and gives excellent agreement with
experiment.Comment: related papers available at http://marcuslab.harvard.ed
BRCA1 Zinc RING Finger Domain Disruption Alters Caspase Response in Ovarian Surface Epithelial Cells
BACKGROUND: The frequently occurring 185delAG mutation occurs in the amino-terminal zinc RING domain of the breast and ovarian cancer susceptibility gene, BRCA1. We sought to determine differential cell viability and apoptotic response of human ovarian surface epithelial cells with and without the 185delAG mutation. RESULTS: BRCA1wt and BRCA1+ cells were treated with staurosporine. Cell proliferation assays showed BRCA1wt cells grew to a greater extent compared to BRCA1+ cells. Trypan blue exclusion assays confirmed this observation. Western immunoblot analysis revealed that caspase 3 levels were higher after staurosporine treatment in BRCA1+ cells than in wild type cells, while full length DNA Fragmentation Factor 45 levels were lower in BRCA1+ cells. While there was no significant difference in levels of excision repair cross complementing protein1 (ERCC1) with BRCA1 status, BRCA1+ cells demonstrated cleavage of polyribose ADP polymerase (PARP) before wild type cells. CONCLUSIONS: Disruption of the BRCA1 RING domain caused altered cell viability and caspase-dependent apoptotic response after chemotoxic stress
A new puzzle for random interaction
We continue a series of numerical experiments on many-body systems with
random two-body interactions, by examining correlations in ratios in excitation
energies of yrast = 0, 2, 4, 6, 8 states. Previous studies, limited only to
= 0,2,4 states, had shown strong correlations in boson systems but not
fermion systems. By including states and considering different
scatter plots, strong and realistic correlations appear in both boson and
fermion systems. Such correlations are a challenge to explanations of random
interactions.Comment: 4 pages, 4 figure
Psychological Contracts, OCB and Customer Service: An Exploratory Examination
This paper examines the relationships among the psychological contract, fairness, OCB, and customer service. We report on two exploratory studies that provide insight into psychological contract violations and subsequent perceptions of fairness, as well as OCB activity. A linkage is made between psychological contracts and behavior directed internally and those directed externally (i.e., customer service). We extend the current theory to suggest implications for effectively managing customer service employee OCB. Finally, suggestions are made for both practice and future research to be conducted in a multidisciplinary design
Topological gravity localization on a delta-function like Brane
Besides the String Theory context, the quantum General Relativity can be
studied by the use of constrained topological field theories. In the celebrated
Plebanski formalism, the constraints connecting topological field theories and
gravity are imposed in space-times with trivial topology. In the braneworld
context there are two distinct regions of the space-time, namely, the bulk and
the braneworld volume. In this work we show how to construct topological
gravity in a scenario containing one extra dimension and a delta-function like
3-brane which naturally emerges from a spontaneously broken discrete symmetry.
Starting from a D=5 theory we obtain the action for General Relativity in the
Palatini form in the bulk as well as in the braneworld volume. This result is
important for future insights about quantum gravity in brane scenarios.Comment: 4 page
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