426 research outputs found
Lattice-point enumerators of ellipsoids
Minkowski's second theorem on successive minima asserts that the volume of a
0-symmetric convex body K over the covolume of a lattice \Lambda can be bounded
above by a quantity involving all the successive minima of K with respect to
\Lambda. We will prove here that the number of lattice points inside K can also
accept an upper bound of roughly the same size, in the special case where K is
an ellipsoid. Whether this is also true for all K unconditionally is an open
problem, but there is reasonable hope that the inductive approach used for
ellipsoids could be extended to all cases.Comment: 9 page
Towards a Generic Model for MU-MIMO Analysis Including Mutual Coupling and Multipath Effects
A network model which accounts for antenna mutual coupling and multipath effects in a wireless channel is proposed as a tool to qualitatively evaluate the performance of a multi-user multiple-input multiple-output (MU-MIMO) system. The system performance is assessed when a zero-forcing (ZF) beamformed conventional uniform linear array (ULA) and a sparse array are employed as one sector of a base station antenna (BSA) in a single-cell network. It is shown that highly correlated user equipments (UEs) in a line-of-sight (LOS) scenario can be decorrelated to some extents, by a scattering environment in a non-line-of-sight (NLOS) scenario. This occurs due to increase of the spatial variation by a multipath effect. Furthermore, in both environments a sparse array realized by an increased interelement spacing is also capable for correlation reduction among users due to the narrower beams
Finite-size Scaling and Universality above the Upper Critical Dimensionality
According to renormalization theory, Ising systems above their upper critical
dimensionality d_u = 4 have classical critical behavior and the ratio of
magnetization moments Q = ^2 / has the universal value 0.456947...
However, Monte Carlo simulations of d = 5 Ising models have been reported which
yield strikingly different results, suggesting that the renormalization
scenario is incorrect. We investigate this issue by simulation of a more
general model in which d_u < 4, and a careful analysis of the corrections to
scaling. Our results are in a perfect agreement with the renormalization theory
and provide an explanation of the discrepancy mentioned.Comment: 5 pages RevTeX, 1 PostScript figure. Accepted for publication in
Physical Review Letter
Medium-range interactions and crossover to classical critical behavior
We study the crossover from Ising-like to classical critical behavior as a
function of the range R of interactions. The power-law dependence on R of
several critical amplitudes is calculated from renormalization theory. The
results confirm the predictions of Mon and Binder, which were obtained from
phenomenological scaling arguments. In addition, we calculate the range
dependence of several corrections to scaling. We have tested the results in
Monte Carlo simulations of two-dimensional systems with an extended range of
interaction. An efficient Monte Carlo algorithm enabled us to carry out
simulations for sufficiently large values of R, so that the theoretical
predictions could actually be observed.Comment: 16 pages RevTeX, 8 PostScript figures. Uses epsf.sty. Also available
as PostScript and PDF file at http://www.tn.tudelft.nl/tn/erikpubs.htm
Cost-effectiveness of a multicomponent primary care program targeting frail elderly people
Contains fulltext :
191679.pdf (publisher's version ) (Open Access
Quantum Cosmology and Higher-Order Lagrangian Theories
In this paper the quantum cosmological consequences of introducing a term
cubic in the Ricci curvature scalar into the Einstein--Hilbert action are
investigated. It is argued that this term represents a more generic
perturbation to the action than the quadratic correction usually considered. A
qualitative argument suggests that there exists a region of parameter space in
which neither the tunneling nor the no-boundary boundary conditions predict an
epoch of inflation that can solve the horizon and flatness problems of the big
bang model. This is in contrast to the --theory.Comment: 13 pages, LaTeX, preprint FERMILAB-Pub-94/XXX-A, March 199
Energetic and spatial bonding properties from angular distributions of ultraviolet photoelectrons: application to the GaAs(110) surface
Angle-resolved ultraviolet photoemission spectra are interpreted by combining
the energetics and spatial properties of the contributing states. One-step
calculations are in excellent agreement with new azimuthal experimental data
for GaAs(110). Strong variations caused by the dispersion of the surface bands
permit an accurate mapping of the electronic structure. The delocalization of
the valence states is discussed analogous to photoelectron diffraction. The
spatial origin of the electrons is determined, and found to be strongly energy
dependent, with uv excitation probing the bonding region.Comment: 5 pages, 3 figures, submitted for publicatio
Holographic models for undoped Weyl semimetals
We continue our recently proposed holographic description of single-particle
correlation functions for four-dimensional chiral fermions with Lifshitz
scaling at zero chemical potential, paying particular attention to the
dynamical exponent z = 2. We present new results for the spectral densities and
dispersion relations at non-zero momenta and temperature. In contrast to the
relativistic case with z = 1, we find the existence of a quantum phase
transition from a non-Fermi liquid into a Fermi liquid in which two Fermi
surfaces spontaneously form, even at zero chemical potential. Our findings show
that the boundary system behaves like an undoped Weyl semimetal.Comment: 64 pages, 19 figure
Data-driven prioritization and preclinical evaluation of therapeutic targets in glioblastoma
Background: Patients with glioblastoma (GBM) have a dismal prognosis, and there is an unmet need for new therapeutic options. This study aims to identify new therapeutic targets in GBM. Methods: mRNA expression data of patient-derived GBM (n = 1279) and normal brain tissue (n = 46) samples were collected from Gene Expression Omnibus and The Cancer Genome Atlas. Functional genomic mRNA profiling was applied to capture the downstream effects of genomic alterations on gene expression levels. Next, a class comparison between GBM and normal brain tissue was performed. Significantly upregulated genes in GBM were further prioritized based on (1) known interactions with antineoplastic drugs, (2) current drug development status in humans, and (3) association with biologic pathways known to be involved in GBM. Antineoplastic agents against prioritized targets were validated in vitro and in vivo. Results: We identified 712 significantly upregulated genes in GBM compared to normal brain tissue, of which 27 have a known interaction with antineoplastic agents. Seventeen of the 27 genes, including EGFR and VEGFA, have been clinically evaluated in GBM with limited efficacy. For the remaining 10 genes, RRM2, MAPK9 (JNK2, SAPK1a), and XIAP play a role in GBM development. We demonstrated for the MAPK9 inhibitor RGB-286638 a viability loss in multiple GBM cell culture models. Although no overall survival benefit was observed in vivo, there were indications that RGB-286638 may delay tumor growth. Conclusions: The MAPK9 inhibitor RGB-286638 showed promising in vitro results. Furthermore, in vivo target engagement studies and combination therapies with this compound warrant further exploration
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