23,686 research outputs found
An Induced Natural Selection Heuristic for Finding Optimal Bayesian Experimental Designs
Bayesian optimal experimental design has immense potential to inform the
collection of data so as to subsequently enhance our understanding of a variety
of processes. However, a major impediment is the difficulty in evaluating
optimal designs for problems with large, or high-dimensional, design spaces. We
propose an efficient search heuristic suitable for general optimisation
problems, with a particular focus on optimal Bayesian experimental design
problems. The heuristic evaluates the objective (utility) function at an
initial, randomly generated set of input values. At each generation of the
algorithm, input values are "accepted" if their corresponding objective
(utility) function satisfies some acceptance criteria, and new inputs are
sampled about these accepted points. We demonstrate the new algorithm by
evaluating the optimal Bayesian experimental designs for the previously
considered death, pharmacokinetic and logistic regression models. Comparisons
to the current "gold-standard" method are given to demonstrate the proposed
algorithm as a computationally-efficient alternative for moderately-large
design problems (i.e., up to approximately 40-dimensions)
Land information systems : an overview and outline of software requirements
This thesis looks at some aspects of land information systems. The introduction gives the rationale for this study, and the second chapter outlines the development of land information systems with particular reference to the cadastre. In the third chapter the software requirements for the development of land information systems are considered. Programming language and databases are discussed. The fouth chapter deals with the organisation and hardware needed for a land information system. Finally, in the fifth chapter some of the algorithms used in land information systems are presented. Four appendices cover the programmes which were developed in the course of this study, the software specification for an operational system, an example of LIS-related data in a large organisation, and the syntax of Modula-2, the programming language used for the examples
Genes, pathways and risk prediction in Alzheimer's disease
The failure of recent clinical trials in Alzheimer's disease has highlighted the need for the development of a more complete understanding of the pathogenesis of the disorder and also a belief that therapies may only work if given very early in the disease process before overt symptoms occur. The rare, early onset forms of the disease are all caused by mutations which make amyloid deposition a more likely event. Here we discuss the recent data showing that, in contrast, much of the risk of late onset disease is encoded by loci involved in lipid metabolism and/or encoded by microglia. We discuss these finding and suggest that amyloid induced membrane damage may be a key factor in disease and also review the evidence that genome wide genetic analysis can substantially help in the prediction of those individuals at high risk of disease in the general population
Promoting Partnerships for Student Success: Lessons from the SSPIRE Initiative
The Student Support Partnership Integrating Resources and Education (SSPIRE) initiative aimed to increase the success of young, low-income, and academically underprepared California community college students by helping colleges strengthen their support services and better integrate these services with academic instruction. This report describes what the nine participating community colleges did to meet the goals of SSPIRE and offers lessons for other institutions drawn from MDRC's research on the initiative
Evidence for a circumplanetary disk around protoplanet PDS 70 b
We present the first observational evidence for a circumplanetary disk around
the protoplanet PDS~70~b, based on a new spectrum in the band acquired with
VLT/SINFONI. We tested three hypotheses to explain the spectrum: Atmospheric
emission from the planet with either (1) a single value of extinction or (2)
variable extinction, and (3) a combined atmospheric and circumplanetary disk
model. Goodness-of-fit indicators favour the third option, suggesting
circumplanetary material contributing excess thermal emission --- most
prominent at m. Inferred accretion rates (-- yr) are compatible with observational
constraints based on the H and Br lines. For the planet, we
derive an effective temperature of 1500--1600 K, surface gravity , radius , mass , and possible thick clouds.
Models with variable extinction lead to slightly worse fits. However, the
amplitude (mag) and timescale of variation
(~years) required for the extinction would also suggest
circumplanetary material.Comment: 8 pages, 2 figures, 1 table. This is a pre-copyedited,
author-produced PDF of an article accepted for publication in ApJL on 2019
May 1
Reading instruction in first-grade classrooms: Do basals control teachers?
This study describes first-grade teachers beliefs and practices about reading instruction. Drawing from interview and observational data, 16 teachers from four districts were placed on a continuum from skills-based to literature-based in relationship to their use of the basal. Only 2 teachers were found to rely solely on the basal, while 3 teachers enhanced the basal with literature, and 4 teachers used only literature in their reading instruction. Six teachers enhanced their basal use with additional skills and 1 teacher relied on skills only in her reading instruction. This diversity\u27 of teaching beliefs and practices was corroborated by questionnaire data from a larger sample of teachers. Next, a framework developed by Belenky, Clinchy, Goldberger, and Tarule (1986) was used to categorize teachers\u27 ways of knowing. The findings showed 1 teacher to be a silent knower, 6 were received knowers, 1 was a subjective knower, 7 were procedural knowers, and 1 was a connected knower. Results challenge Shannon\u27s (1987) hypothesis that basals deskill teachers while supporting Sosniak and Stodolskv\u27s (1993) view that teachers are more autonomous in their use of textbook materials
Dipole Perturbations of the Reissner-Nordstrom Solution: The Polar Case
The formalism developed by Chandrasekhar for the linear polar perturbations
of the Reissner-Nordstrom solution is generalized to include the case of dipole
(l=1) perturbations. Then, the perturbed metric coefficients and components of
the Maxwell tensor are computed.Comment: 16 pages, LaTeX, no figures. Submitted for publication in Physical
Review
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