19,800 research outputs found
Threshold Regression for Survival Analysis: Modeling Event Times by a Stochastic Process Reaching a Boundary
Many researchers have investigated first hitting times as models for survival
data. First hitting times arise naturally in many types of stochastic
processes, ranging from Wiener processes to Markov chains. In a survival
context, the state of the underlying process represents the strength of an item
or the health of an individual. The item fails or the individual experiences a
clinical endpoint when the process reaches an adverse threshold state for the
first time. The time scale can be calendar time or some other operational
measure of degradation or disease progression. In many applications, the
process is latent (i.e., unobservable). Threshold regression refers to
first-hitting-time models with regression structures that accommodate covariate
data. The parameters of the process, threshold state and time scale may depend
on the covariates. This paper reviews aspects of this topic and discusses
fruitful avenues for future research.Comment: Published at http://dx.doi.org/10.1214/088342306000000330 in the
Statistical Science (http://www.imstat.org/sts/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Extremal black holes in D=4 Gauss-Bonnet gravity
We show that four-dimensional Einstein-Maxwell-Dilaton-Gauss-Bonnet gravity
admits asymptotically flat black hole solutions with a degenerate event horizon
of the Reissner-Nordstr\"om type . Such black holes exist for
the dilaton coupling constant within the interval .
Black holes must be endowed with an electric charge and (possibly) with
magnetic charge (dyons) but they can not be purely magnetic. Purely electric
solutions are constructed numerically and the critical dilaton coupling is
determined . For each value of the dilaton
coupling within this interval and for a fixed value of the Gauss--Bonnet
coupling we have a family of black holes parameterized by their
electric charge. Relation between the mass, the electric charge and the dilaton
charge at both ends of the allowed interval of is reminiscent of the BPS
condition for dilaton black holes in the Einstein-Maxwell-Dilaton theory. The
entropy of the DGB extremal black holes is twice the Bekenstein-Hawking
entropy.Comment: New material and references added, errors corrected including higher
decimals in a_cr, figures improve
II. Apples to apples : cluster selection functions for next-generation surveys
We present the cluster selection function for three of the largest
next-generation stage-IV surveys in the optical and infrared:
Euclid-Optimistic, Euclid-Pessimistic and the Large Synoptic Survey Telescope
(LSST). To simulate these surveys, we use the realistic mock catalogues
introduced in the first paper of this series.
We detected galaxy clusters using the Bayesian Cluster Finder (BCF) in the
mock catalogues. We then modeled and calibrated the total cluster stellar mass
observable-theoretical mass () relation using a power
law model, including a possible redshift evolution term. We find a moderate
scatter of of 0.124, 0.135 and 0.136 for Euclid-Optimistic, Euclid-Pessimistic and LSST, respectively,
comparable to other work over more limited ranges of redshift. Moreover, the
three datasets are consistent with negligible evolution with redshift, in
agreement with observational and simulation results in the literature.
We find that Euclid-Optimistic will be able to detect clusters with
completeness and purity down to up to .
At higher redshifts, the same completeness and purity are obtained with the
larger mass threshold of up to . The
Euclid-Pessimistic selection function has a similar shape with
higher mass limit. LSST shows higher mass limit than
Euclid-Optimistic up to and increases afterwards, reaching values of
at . Similar selection functions with
only completeness threshold have been also computed. The complementarity
of these results with selection functions for surveys in other bands is
discussed.Comment: 13 pages, 10 figures, accepted for publication in MNRA
Investment Strategies to Exploit Economic Growth in China
Since the beginning of the economic reforms two decades ago, the economy in China has enjoyed a real growth rate of 9.6 percent per year. We believe that China is only in the early stages of its rapid-growth period. China is likely to enjoy rapid growth for decades to come at rates well above those of any other large country in the world.
BAC-FISH assays delineate complex chromosomal rearrangements in a case of post-Chernobyl childhood thyroid cancer
Structural chromosome aberrations are known hallmarks of many solid tumors. In the papillary form of thyroid
cancer (PTC), for example, activation of the receptor tyrosine kinase (RTK) genes, RET and neurotrophic tyrosine kinase
receptor type I (NTRK1) by intra- and interchromosomal rearrangements has been suggested as a cause of the disease. However,
many phenotypically similar tumors do not carry an activated RET or NTRK-1 gene or express abnormal ret or NTRK-
1 transcripts. Thus, we hypothesize that other cellular RTK-type genes are aberrantly expressed in these tumors. Using fluorescence
in situ hybridization-based methods, we are studying karyotype changes in a relatively rare subgroup of PTCs,
i.e., tumors that arose in children following the 1986 nuclear accident in Chernobyl, Ukraine. Here, we report our technical
developments and progress in deciphering complex chromosome aberrations in case S48TK, an aggressively growing PTC
cell line, which shows an unusual high number of unbalanced translocations
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