954 research outputs found
High-Dimensional Graphical Model Search with the gRapHD R Package
This paper presents the R package gRapHD for efficient selection of high-dimensional undirected graphical models. The package provides tools for selecting trees, forests, and decomposable models minimizing information criteria such as AIC or BIC, and for displaying the independence graphs of the models. It has also some useful tools for analysing graphical structures. It supports the use of discrete, continuous, or both types of variables.
High-Dimensional Graphical Model Search with the gRapHD R Package
This paper presents the R package gRapHD for efficient selection of high-dimensional undirected graphical models. The package provides tools for selecting trees, forests, and decomposable models minimizing information criteria such as AIC or BIC, and for displaying the independence graphs of the models. It has also some useful tools for analysing graphical structures. It supports the use of discrete, continuous, or both types of variables
Entropy bounds in terms of the w parameter
In a pair of recent articles [PRL 105 (2010) 041302 - arXiv:1005.1132; JHEP
1103 (2011) 056 - arXiv:1012.2867] two of the current authors have developed an
entropy bound for equilibrium uncollapsed matter using only classical general
relativity, basic thermodynamics, and the Unruh effect. An odd feature of that
bound, S <= A/2, was that the proportionality constant, 1/2, was weaker than
that expected from black hole thermodynamics, 1/4. In the current article we
strengthen the previous results by obtaining a bound involving the (suitably
averaged) w parameter. Simple causality arguments restrict this averaged
parameter to be <= 1. When equality holds, the entropy bound saturates at the
value expected based on black hole thermodynamics. We also add some clarifying
comments regarding the (net) positivity of the chemical potential. Overall, we
find that even in the absence of any black hole region, we can nevertheless get
arbitrarily close to the Bekenstein entropy.Comment: V1: 14 pages. V2: One reference added. V3: This version accepted for
publication in JHE
A proposal for the evaluation of the bioeconomic efficiency of beef cattle production systems
Derivation of High Purity Neuronal Progenitors from Human Embryonic Stem Cells
The availability of human neuronal progenitors (hNPs) in high purity would greatly facilitate neuronal drug discovery and developmental studies, as well as cell replacement strategies for neurodegenerative diseases and conditions, such as spinal cord injury, stroke, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Here we describe for the first time a method for producing hNPs in large quantity and high purity from human embryonic stem cells (hESCs) in feeder-free conditions, without the use of exogenous noggin, sonic hedgehog or analogs, rendering the process clinically compliant. The resulting population displays characteristic neuronal-specific markers. When allowed to spontaneously differentiate into neuronal subtypes in vitro, cholinergic, serotonergic, dopaminergic and/or noradrenergic, and medium spiny striatal neurons were observed. When transplanted into the injured spinal cord the hNPs survived, integrated into host tissue, and matured into a variety of neuronal subtypes. Our method of deriving neuronal progenitors from hESCs renders the process amenable to therapeutic and commercial use
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
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