Approximating Probability Densities by Iterated Laplace Approximations

The Laplace approximation is an old, but frequently used method to approximate integrals for Bayesian calculations. In this paper we develop an extension of the Laplace approximation, by applying it iteratively to the residual, i.e., the difference between the current approximation and the true function. The final approximation is thus a linear combination of multivariate normal densities, where the coefficients are chosen to achieve a good fit to the target distribution. We illustrate on real and artificial examples that the proposed procedure is a computationally efficient alternative to current approaches for approximation of multivariate probability densities. The R-package iterLap implementing the methods described in this article is available from the CRAN servers.Comment: to appear in Journal of Computational and Graphical Statistics, http://pubs.amstat.org/loi/jcg

On Landscape Criticism and Literary Criticism

This article explores the adoption of notions and methods of literary criticism to the criticism of non-designed landscapes. As a position paper, it argues that attempts to organise and structure the vast multiplicity of landscape instances should follow the path laid by literary criticism when dealing with the multiplicity of literary works. The case is presented for the adoption of genre, as understood by contemporary literary critics, to serve as a categorisation tool for instances of non-designed landscapes. A distinction between primary and secondary, along the lines proposed by Bakhtin for speech genres, appears promising for organising the variety of landscape genres that can be envisaged. A number of separate landscape discourses may be constructed from individual or from closely related landscape genres; further progress of landscape criticism requires a common ground on which otherwise autonomous discourses could meet and clash

Feasibility study of an Integrated Program for Aerospace vehicle Design (IPAD). Volume 4: IPAD system design

The computing system design of IPAD is described and the requirements which form the basis for the system design are discussed. The system is presented in terms of a functional design description and technical design specifications. The functional design specifications give the detailed description of the system design using top-down structured programming methodology. Human behavioral characteristics, which specify the system design at the user interface, security considerations, and standards for system design, implementation, and maintenance are also part of the technical design specifications. Detailed specifications of the two most common computing system types in use by the major aerospace companies which could support the IPAD system design are presented. The report of a study to investigate migration of IPAD software between the two candidate 3rd generation host computing systems and from these systems to a 4th generation system is included

Interference in Bohmian Mechanics with Complex Action

In recent years, intensive effort has gone into developing numerical tools for exact quantum mechanical calculations that are based on Bohmian mechanics. As part of this effort we have recently developed as alternative formulation of Bohmian mechanics in which the quantum action, S, is taken to be complex [JCP {125}, 231103 (2006)]. In the alternative formulation there is a significant reduction in the magnitude of the quantum force as compared with the conventional Bohmian formulation, at the price of propagating complex trajectories. In this paper we show that Bohmian mechanics with complex action is able to overcome the main computational limitation of conventional Bohmian methods -- the propagation of wavefunctions once nodes set in. In the vicinity of nodes, the quantum force in conventional Bohmian formulations exhibits rapid oscillations that pose severe difficulties for existing numerical schemes. We show that within complex Bohmian mechanics, multiple complex initial conditions can lead to the same real final position, allowing for the description of nodes as a sum of the contribution from two or more crossing trajectories. The idea is illustrated on the reflection amplitude from a one-dimensional Eckart barrier. We believe that trajectory crossing, although in contradiction to the conventional Bohmian trajectory interpretation, provides an important new tool for dealing with the nodal problem in Bohmian methods

Three Decades of Research: The Case for Comprehensive Sex Education

Purpose School-based sex education plays a vital role in the sexual health and well-being of young people. Little is known, however, about the effectiveness of efforts beyond pregnancy and sexually transmitted disease prevention. The authors conducted a systematic literature review of three decades of research on school-based programs to find evidence for the effectiveness of comprehensive sex education. Methods Researchers searched the ERIC, PsycINFO, and MEDLINE. The research team identified papers meeting the systematic literature review criteria. Of 8,058 relevant articles, 218 met specific review criteria. More than 80% focused solely on pregnancy and disease prevention and were excluded, leaving 39. In the next phase, researchers expanded criteria to studies outside the U.S. to identify evidence reflecting the full range of topic areas. Eighty articles constituted the final review. Results Outcomes include an appreciation of sexual diversity, dating and intimate partner violence prevention, development of healthy relationships, prevention of child sex abuse, improved social/emotional learning, and increased media literacy. Substantial evidence supports sex education beginning in elementary school, which is scaffolded and of longer duration, as well as LGBTQ–inclusive education across the school curriculum and a social justice approach to healthy sexuality. Conclusions A review of the literature of the past three decades provides strong support for comprehensive sex education across a range of topics and grade levels. Results provide evidence for the effectiveness of approaches that address a broad definition of sexual health and take positive, affirming, inclusive approaches to human sexuality. Findings strengthen justification for the widespread adoption of the National Sex Education Standards

Three Decades of Research: The Case for Comprehensive Sex Education

Purpose School-based sex education plays a vital role in the sexual health and well-being of young people. Little is known, however, about the effectiveness of efforts beyond pregnancy and sexually transmitted disease prevention. The authors conducted a systematic literature review of three decades of research on school-based programs to find evidence for the effectiveness of comprehensive sex education. Methods Researchers searched the ERIC, PsycINFO, and MEDLINE. The research team identified papers meeting the systematic literature review criteria. Of 8,058 relevant articles, 218 met specific review criteria. More than 80% focused solely on pregnancy and disease prevention and were excluded, leaving 39. In the next phase, researchers expanded criteria to studies outside the U.S. to identify evidence reflecting the full range of topic areas. Eighty articles constituted the final review. Results Outcomes include the appreciation of sexual diversity, dating and intimate partner violence prevention, development of healthy relationships, prevention of child sex abuse, improved social/emotional learning, and increased media literacy. Substantial evidence supports sex education beginning in elementary school, which is scaffolded and of longer duration, as well as LGBTQ–inclusive education across the school curriculum and a social justice approach to healthy sexuality. Conclusions A review of the literature of the past three decades provides strong support for comprehensive sex education across a range of topics and grade levels. Results provide evidence for the effectiveness of approaches that address a broad definition of sexual health and take positive, affirming, inclusive approaches to human sexuality. Findings strengthen justification for the widespread adoption of the National Sex Education Standards

Search Engine Advertising: Channel Substitution when Pricing Ads to Context

We explore substitution patterns across advertising platforms. Using data on the advertising prices paid by lawyers for 139 Google search terms in 195 locations, we exploit a natural experiment in “ambulance-chaser” regulations across states. When lawyers cannot contact clients by mail, advertising prices per click for search engine advertisements are 5%–7% higher. Therefore, online advertising substitutes for offline advertising. This substitution toward online advertising is strongest in markets with fewer customers, suggesting that the relationship between the online and offline media is mediated by the marketers' need to target their communications.NET Institut