7,448 research outputs found
Fitting multilevel multivariate models with missing data in responses and covariates that may include interactions and non-linear terms
The paper extends existing models for multilevel multivariate data with mixed response types to handle quite general types and patterns of missing data values in a wide range of multilevel generalized linear models. It proposes an efficient Bayesian modelling approach that allows missing values in covariates, including models where there are interactions or other functions of covariates such as polynomials. The procedure can also be used to produce multiply imputed complete data sets. A simulation study is presented as well as the analysis of a longitudinal data set. The paper also shows how existing multiprocess models for handling endogeneity can be extended by the framework proposed
Learning in the Repeated Secretary Problem
In the classical secretary problem, one attempts to find the maximum of an
unknown and unlearnable distribution through sequential search. In many
real-world searches, however, distributions are not entirely unknown and can be
learned through experience. To investigate learning in such a repeated
secretary problem we conduct a large-scale behavioral experiment in which
people search repeatedly from fixed distributions. In contrast to prior
investigations that find no evidence for learning in the classical scenario, in
the repeated setting we observe substantial learning resulting in near-optimal
stopping behavior. We conduct a Bayesian comparison of multiple behavioral
models which shows that participants' behavior is best described by a class of
threshold-based models that contains the theoretically optimal strategy.
Fitting such a threshold-based model to data reveals players' estimated
thresholds to be surprisingly close to the optimal thresholds after only a
small number of games
Full Disclosure, Market Discipline, and Risk Taking: Rethinking Confidentiality in Bank Regulation
Differential expression of glycoproteins containing [alpha]--galactosyl groups on normal human breast epithelial cells and MCF-7 human breast carcinoma cells
Cell surface glycoproteins were isolated from the lysates of 125I-labeled normal human mammary epithelial cells (NHMEC) and from the human breast carcinoma cell line MCF-7, of blood-group O phenotype, by affinity chromatography on Griffonia simplicifolia I lectin-Sepharose. Specific elution of glycoproteins from the column with methyl [alpha]--galactoside suggests the presence of [alpha]--galactosyl groups on these moieties. SDS-PAGE analysis of isolated glycoproteins revealed both quantitative and qualitative differences between glycoproteins from normal and malignant cells. Three major glycoproteins of Mr 180 kDa, 85 kDa and the 44 kDa were obtained from MCF-7 cells. The 180-kDa glycoprotein was absent in NHMEC and the 44-kDa glycoprotein was very weakly expressed in these cells. The only glycoprotein which was found in almost equal amount in the lysate from both normal and malignant cells was the 85-kDa glycoprotein. These results indicate differences between normal human mammary epithelial cells and one kind of malignant human mammary epithelial cells, in the expression of glycoproteins containing [alpha]--galactosyl groups, irrespective of blood-group phenotype; they also demonstrate that [alpha]--galactosyl group are expressed in a very restrictive manner on the surface of this tumor cell line.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29093/1/0000129.pd
Velocity Selection for Propagating Fronts in Superconductors
Using the time-dependent Ginzburg-Landau equations we study the propagation
of planar fronts in superconductors, which would appear after a quench to zero
applied magnetic field. Our numerical solutions show that the fronts propagate
at a unique speed which is controlled by the amount of magnetic flux trapped in
the front. For small flux the speed can be determined from the linear marginal
stability hypothesis, while for large flux the speed may be calculated using
matched asymptotic expansions. At a special point the order parameter and
vector potential are dual, leading to an exact solution which is used as the
starting point for a perturbative analysis.Comment: 4 pages, 2 figures; submitted to Phys. Rev. Letter
Near-horizon symmetries of extremal black holes
Recent work has demonstrated an attractor mechanism for extremal rotating
black holes subject to the assumption of a near-horizon SO(2,1) symmetry. We
prove the existence of this symmetry for any extremal black hole with the same
number of rotational symmetries as known four and five dimensional solutions
(including black rings). The result is valid for a general two-derivative
theory of gravity coupled to abelian vectors and uncharged scalars, allowing
for a non-trivial scalar potential. We prove that it remains valid in the
presence of higher-derivative corrections. We show that SO(2,1)-symmetric
near-horizon solutions can be analytically continued to give SU(2)-symmetric
black hole solutions. For example, the near-horizon limit of an extremal 5D
Myers-Perry black hole is related by analytic continuation to a non-extremal
cohomogeneity-1 Myers-Perry solution.Comment: 21 pages, latex. v2: minor improvements v3: Corrected error in
argument excluding de Sitter and Poincare-symmetric cases. Results unaffecte
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