9,673 research outputs found
A class of multivariate distribution-free tests of independence based on graphs
AbstractA class of distribution-free tests is proposed for the independence of two subsets of response coordinates. The tests are based on the pairwise distances across subjects within each subset of the response. A complete graph is induced by each subset of response coordinates, with the sample points as nodes and the pairwise distances as the edge weights. The proposed test statistic depends only on the rank order of edges in these complete graphs. The response vector may be of any dimensions. In particular, the number of samples may be smaller than the dimensions of the response. The test statistic is shown to have a normal limiting distribution with known expectation and variance under the null hypothesis of independence. The exact distribution free null distribution of the test statistic is given for a sample of size 14, and its Monte-Carlo approximation is considered for larger sample sizes. We demonstrate in simulations that this new class of tests has good power properties for very general alternatives
Cross‐campus Collaboration: A Scientometric and Network Case Study of Publication Activity Across Two Campuses of a Single Institution
Team science and collaboration have become crucial to addressing key research questions confronting society. Institutions that are spread across multiple geographic locations face additional challenges. To better understand the nature of cross‐campus collaboration within a single institution and the effects of institutional efforts to spark collaboration, we conducted a case study of collaboration at Cornell University using scientometric and network analyses. Results suggest that cross‐campus collaboration is increasingly common, but is accounted for primarily by a relatively small number of departments and individual researchers. Specific researchers involved in many collaborative projects are identified, and their unique characteristics are described. Institutional efforts, such as seed grants and topical retreats, have some effect for researchers who are central in the collaboration network, but were less clearly effective for others
Phase-space correlations of chaotic eigenstates
It is shown that the Husimi representations of chaotic eigenstates are
strongly correlated along classical trajectories. These correlations extend
across the whole system size and, unlike the corresponding eigenfunction
correlations in configuration space, they persist in the semiclassical limit. A
quantitative theory is developed on the basis of Gaussian wavepacket dynamics
and random-matrix arguments. The role of symmetries is discussed for the
example of time-reversal invariance.Comment: Published version with minor corrections to version
The Arbitrary Trajectory Quantization Method
The arbitrary trajectory quantization method (ATQM) is a time dependent
approach to quasiclassical quantization based on the approximate dual
relationship that exists between the quantum energy spectra and classical
periodic orbits. It has recently been shown however, that, for polygonal
billiards, the periodicity criterion must be relaxed to include closed
almost-periodic (CAP) orbit families in this relationship. In light of this
result, we reinvestigate the ATQM and show that at finite energies, a
smoothened quasiclassical kernel corresponds to the modified formula that
includes CAP families while the delta function kernel corresponding to the
periodic orbit formula is recovered at high energies. Several clarifications
are also provided.Comment: revtex, ps figure
Plasmid Injection and Application of Electric Pulses Alter Endogenous mRNA and Protein Expression in B16.F10 Mouse Melanomas
The application of electric pulses to tissues causes cell membrane destabilization, allowing exogenous molecules to enter the cells. This delivery technique can be used for plasmid gene therapy. Reporter gene expression after plasmid delivery with eight representative published protocols was compared in B16.F10 mouse melanoma tumors. This expression varied significantly based on the pulse parameters utilized for delivery. To observe the possible influence of plasmid injection and/or pulse application on endogenous gene expression, levels of stress-related mRNAs 4 and 24 h after delivery were determined by PCR array. Increases in mRNA levels for several inflammatory chemokines and cytokines were observed in response to plasmid injection, electric pulses alone or the combination. This upregulation was confirmed by individual real-time reverse transcription TaqMan PCR assays. Proteins were extracted at the same time points from identically treated tumors and inflammatory protein levels were assayed by enzyme-linked immunosorbent assay and by a custom multiplex bead array. Increases in inflammatory protein levels generally paralleled mRNA levels. Some differences were observed, which may have been due to differing expression kinetics. The observed upregulated expression of these cytokines and chemokines may aid or inhibit the therapeutic effectiveness of immune-based cancer gene therapies
Microscopic eigenvalue correlations in QCD with imaginary isospin chemical potential
We consider the chiral limit of QCD subjected to an imaginary isospin
chemical potential. In the epsilon-regime of the theory we can perform precise
analytical calculations based on the zero-momentum Goldstone modes in the
low-energy effective theory. We present results for the spectral correlation
functions of the associated Dirac operators.Comment: 13 pages, 2 figures, RevTe
Hall of Mirrors Scattering from an Impurity in a Quantum Wire
This paper develops a scattering theory to examine how point impurities
affect transport through quantum wires. While some of our new results apply
specifically to hard-walled wires, others--for example, an effective optical
theorem for two-dimensional waveguides--are more general. We apply the method
of images to the hard-walled guide, explicitly showing how scattering from an
impurity affects the wire's conductance. We express the effective cross section
of a confined scatterer entirely in terms of the empty waveguide's Green's
function, suggesting a way in which to use semiclassical methods to understand
transport properties of smooth wires. In addition to predicting some new
phenomena, our approach provides a simple physical picture for previously
observed effects such as conductance dips and confinement-induced resonances.Comment: 19 pages, 8 figures. Accepted for publication in Physical Review B.
Minor additions to text, added reference
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