A Cartan-Hadamard type result for relatively hyperbolic groups

In this article, we prove that if a finitely presented group has an asymptotic cone which is tree-graded with respect to a precise set of pieces then it is relatively hyperbolic. This answers a question of M. Sapir.Comment: 33 pages, 2 figure

Fabrication and performance of selectively oxidized vertical-cavity lasers

Includes bibliographical references.We report the high yield fabrication and reproducible performance of selectively oxidized vertical-cavity surface emitting lasers. We show that linear oxidation rates of AlGaAs without an induction period allows reproducible fabrication of buried oxide current apertures within monolithic distributed Bragg reflectors. The oxide layers do not induce obvious crystalline defects, and continuous wave operation in excess of 650 h has been obtained. The high yield fabrication enables relatively high laser performance over a wide wavelength span. We observe submilliamp threshold currents over a wavelength range of up to 75 nm, and power conversion efficiencies at 1 mW output power of greater than 20% over a 50-nm wavelength range.The work at Sandia National Laboratories was supported in part by the United States DOE under contract No. DE-AC04-94AL85000

A Critical Appraisal of the UK’s Regulatory Regime for Combustible Façades

The Grenfell Tower fire has brought the regulatory system that permitted combustible materials on high-rise buildings in England into question. At the heart of that system is the BS 8414 test, and the BR 135 criteria used to demonstrate compliance with the Building Regulations. The test is empirical and the criteria arbitrary: there is no scientific link between test performance and how a building will perform in the event of a fire; nor any detailed analysis of why fires spread through façade systems which have passed the test. Following the Grenfell tragedy, the UK government commissioned a series of tests on Grenfell Tower-type facades, using BS 8414. This paper critically analyses BS 8414, the BR 135 criteria and the government tests. It shows that important aspects of the standard are poorly defined: the heat flux imposed on the façade is not measured and the fire load can vary by at least a factor of 2; the ambient ventilation has a significant impact on the thermal attack but is not adequately controlled; judicious location of the cavity barriers can confer compliance or failure on a façade system. As the vehicle for allowing combustible products on tall buildings, the test does not specify the extent of cavity barrier deployment, while ignoring features present in real buildings, such as windows, vents or other openings, despite a test rig height of more than 8 m. There is no restriction on debris, or molten or burning droplets falling from the façade during the test. The BR 135 criteria only specify that the test must run for the full 60 min duration without flames reaching the top, and the temperature rise at thermocouples 5 m above the fire chamber must only remain below 600°C for the first 15 min. It is unclear how the fire safety of the occupants behind the façade system can be ensured, when the criteria specify such a high temperature for such a short period, so early in the test. There is no direct connection between the façade system in the test and the actual façade system the results deem compliant. Worse, “desktop studies”, using large-scale test data, have been allowed to confer compliance on systems which have never been subject to the test. The UK government tests used heavy-duty welded aluminium “window pods”, preventing flames from entering the cavity within the façade. They also used a disproportionately large number of vertical and horizontal cavity barriers of a higher specification than required by statutory guidance. These aids to meeting the criteria are not proscribed by BS 8414-1 but are not commonly found in actual rainscreen system designs

Conceiving time?: women who do or do not conceive

This article explores the importance of time for an understanding of women's experiences of reproductive identity. In order to do this we draw on data from two separate qualitative research projects. The first project is concerned with the experiences of conception, pregnancy, childbirth and early motherhood in primagravidae, whilst the second focuses on the experiences of individuals (especially women) who defined themselves (at the time of the fieldwork, or some time previously) as 'involuntarily childless' and/or 'infertile'. These two areas are usually treated as separate; however this article explores similarities between them in terms of time and medicalisation. Our central concern then is with exploring the similarities of experience for women who do or do not conceive

Next Generation Very Large Array Memo No. 5 Science Working Groups Project Overview

We summarize the design, capabilities, and some of the priority science goals of a next generation Very Large Array (ngVLA). The ngVLA is an interferometric array with 10x larger effective collecting area and 10x higher spatial resolution than the current VLA and the Atacama Large Millimeter Array (ALMA), optimized for operation in the wavelength range 0.3cm to 3cm. The ngVLA opens a new window on the Universe through ultra-sensitive imaging of thermal line and continuum emission down to milliarcecond resolution, as well as unprecedented broad band continuum polarimetric imaging of non-thermal processes. The continuum resolution will reach 9mas at 1cm, with a brightness temperature sensitivity of 6K in 1 hour. For spectral lines, the array at 1" resolution will reach 0.3K surface brightness sensitivity at 1cm and 10 km s^(-1) spectral resolution in 1 hour. These capabilities are the only means with which to answer a broad range of critical scientific questions in modern astronomy, including direct imaging of planet formation in the terrestrial-zone, studies of dust-obscured star formation and the cosmic baryon cycle down to pc-scales out to the Virgo cluster, making a cosmic census of the molecular gas which fuels star formation back to first light and cosmic reionization, and novel techniques for exploring temporal phenomena from milliseconds to years. The ngVLA is optimized for observations at wavelengths between the superb performance of ALMA at submm wavelengths, and the future SKA1 at few centimeter and longer wavelengths. This memo introduces the project. The science capabilities are outlined in a parallel series of white papers. We emphasize that this initial set of science goals are simply a starting point for the project. We invite comment on these programs, as well as new ideas, through our public forum link on the ngVLA web page: https://science.nrao.edu/futures/ngvl

Characteristics of transposable element exonization within human and mouse

Insertion of transposed elements within mammalian genes is thought to be an important contributor to mammalian evolution and speciation. Insertion of transposed elements into introns can lead to their activation as alternatively spliced cassette exons, an event called exonization. Elucidation of the evolutionary constraints that have shaped fixation of transposed elements within human and mouse protein coding genes and subsequent exonization is important for understanding of how the exonization process has affected transcriptome and proteome complexities. Here we show that exonization of transposed elements is biased towards the beginning of the coding sequence in both human and mouse genes. Analysis of single nucleotide polymorphisms (SNPs) revealed that exonization of transposed elements can be population-specific, implying that exonizations may enhance divergence and lead to speciation. SNP density analysis revealed differences between Alu and other transposed elements. Finally, we identified cases of primate-specific Alu elements that depend on RNA editing for their exonization. These results shed light on TE fixation and the exonization process within human and mouse genes.Comment: 11 pages, 4 figure

Semantics of Database Transformations

Database transformations arise in many different settings including database integration, evolution of database systems, and implementing user views and data entry tools. This paper surveys approaches that have been taken to problems in these settings, assesses their strengths and weaknesses, and develops require ments on a formal model for specifying and implementing database transformations. We also consider the problem of insuring the correctness of database transformations. In particular, we demonstrate that the usefulness of correctness conditions such as information preservation is hindered by the interactions of transformations and database constraints, and the limited expressive power of established database constraint languages. We conclude that more general notions of correctness are required, and that there is a need for a uniform formalism for expressing both database transformations and constraints, and reasoning about their interactions, Finally we introduce WOL, a declarative language for specifying and implementing database transformations and constraints. We briefly describe the WOL language and its semantics, and argue that it addresses many of the requirements on a formalism for dealing with general database transformations

Describing the profile of diagnostic features in autistic adults using an abbreviated version of the Diagnostic Interview for Social and Communication Disorders (DISCO-Abbreviated)

The rate of diagnosis of autism in adults has increased over recent years; however, the profile of behaviours in these individuals is less understood than the profile seen in those diagnosed in childhood. Better understanding of this profile will be essential to identify and remove potential barriers to diagnosis. Using an abbreviated form of the Diagnostic Interview for Social and Communication Disorders, comparisons were drawn between the profile of a sample of able adults diagnosed in adulthood and the profile of a sample of able children. Results revealed both similarities and differences. A relative strength in non-verbal communication highlighted a potential barrier to diagnosis according to DSM-5 criteria for the adult sample, which may also have prevented them from being diagnosed as children