7,748 research outputs found
Gravitationally lensed radio emission associated with SMM J16359+6612, a multiply imaged submillimeter galaxy behind A2218
We report the detection of discrete, lensed radio emission from the multiply
imaged, z=2.516 submillimetre selected galaxy, SMM J16359+6612. All three
images are detected in deep WSRT 1.4 GHz and VLA 8.2 GHz observations, and the
radio positions are coincident with previous sub-mm SCUBA observations of this
system. This is the widest separation lens system to be detected in the radio
so far, and the first time that multiply imaged lensed radio emission has been
detected from a star forming galaxy -- all previous multiply-lensed radio
systems being associated with radio-loud AGN. Taking into account the total
magnification of ~45, the WSRT 1.4 GHz observations suggest a star formation
rate of 500 Solar mass/yr. The source has a steep radio spectrum (alpha -0.7)
and an intrinsic flux density of just 3 microJy at 8.2 GHz. Three other SCUBA
sources in the field are also detected by the WSRT, including SMMJ16359+66118,
a singly imaged (and magnified) arclet at z=1.034. Higher resolution radio
observations of SMMJ16359+6612 (and other highly magnified star forming
galaxies) provide a unique opportunity to study the general properties and
radio morphology of intrinsically faint, distant and obscured star forming
galaxies. They can also help to constrain the technical specification of next
generation radio telescopes, such as the Square Kilometre Array.Comment: 5 pages, 2 figures, to appear in A&A letter
Modelling the dynamics of turbulent floods
Consider the dynamics of turbulent flow in rivers, estuaries and floods. Based on the widely used k-epsilon model for turbulence, we use the techniques of centre manifold theory to derive dynamical models for the evolution of the water depth and of vertically averaged flow velocity and turbulent parameters. This new model for the shallow water dynamics of turbulent flow: resolves the vertical structure of the flow and the turbulence; includes interaction between turbulence and long waves; and gives a rational alternative to classical models for turbulent environmental flows
Hamiltonian formalism and the Garrett-Munk spectrum of internal waves in the ocean
Wave turbulence formalism for long internal waves in a stratified fluid is
developed, based on a natural Hamiltonian description. A kinetic equation
appropriate for the description of spectral energy transfer is derived, and its
self-similar stationary solution corresponding to a direct cascade of energy
toward the short scales is found. This solution is very close to the high
wavenumber limit of the Garrett-Munk spectrum of long internal waves in the
ocean. In fact, a small modification of the Garrett-Munk formalism includes a
spectrum consistent with the one predicted by wave turbulence.Comment: 4 pages latex fil
Design guidelines for assessing and controlling spacecraft charging effects
The need for uniform criteria, or guidelines, to be used in all phases of spacecraft design is discussed. Guidelines were developed for the control of absolute and differential charging of spacecraft surfaces by the lower energy space charged particle environment. Interior charging due to higher energy particles is not considered. A guide to good design practices for assessing and controlling charging effects is presented. Uniform design practices for all space vehicles are outlined
Strict limit on in-plane ordered magnetic dipole moment in URu2Si2
Neutron diffraction is used to examine the polarization of weak static
antiferromagnetism in high quality single crystalline URu2Si2. As previously
documented, elastic Bragg-like diffraction develops for temperature T<T_{HO}=
17.5 K at q=(100) but not at wave vector transfer q=(001). The peak width
indicates correlation lengths \xi_c=230(12) \AA \ and \xi_a=240(15) \AA. The
integrated intensity of the T-dependent peaks corresponds to a sample averaged
c-oriented staggered moment of \mu_{c}=0.022(1) \mu_B at T=1.7 K. The absence
of T-dependent diffraction at q=(001) places a limit \mu_{\perp}<0.0011 \mu_B
on an f- or d-orbital based in-plane staggered magnetic dipole moment, which is
associated with multipolar orders proposed for URu_2Si_2.Comment: 9 pages, 7 figure
Remarks on monopole charge properties within the Generalized Coherent State Model
The Generalized Coherent State Model, proposed previously for a unified
description of magnetic and electric collective properties of nuclear systems,
is used to study the ground state band charge density as well as the E0
transitions from to . The influence of the nuclear
deformation and of angular momentum projection on the charge density is
investigated. The monopole transition amplitude has been calculated for ten
nuclei. The results are compared with some previous theoretical studies and
with the available experimental data. Our results concerning angular momentum
projection are consistent with those of previous microscopic calculations for
the ground state density. The calculations for the E0 transitions agree quite
well with the experimental data. Issues like how the shape transitions or shape
coexistence are reflected in the behavior are also addressed.Comment: 32 pages, 7 figure
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Household and family structure in England and Wales (1851-1911): Continuities and change
AbstractThis article produces the first findings on changes in household and family structure in England and Wales during 1851–1911, using the recently available Integrated Census Microdata (I-CeM) – a complete count database of individual-level data extending to some 188 million records. As such, it extends and updates the important overview article published inContinuity and Changeby Michael Anderson in 1988. The I-CeM data shed new light on transitions in household structure and family life during this period, illustrating both continuities and change in a number of key areas: family composition; single parent families; living alone; extended households; childhood; leaving home and marriage patterns.</jats:p
Thinking territory historically.
BACKGROUND:
While the randomised controlled trial (RCT) is generally regarded as the design of
choice for assessing the effects of health care, within the social sciences there is
considerable debate about the relative suitability of RCTs and non-randomised
studies (NRSs) for evaluating public policy interventions.
// OBJECTIVES:
To determine whether RCTs lead to the same effect size and variance as NRSs of
similar policy interventions; and whether these findings can be explained by other
factors associated with the interventions or their evaluation.
// METHODS:
Analyses of methodological studies, empirical reviews, and individual health and
social services studies investigated the relationship between randomisation and
effect size of policy interventions by:
1) Comparing controlled trials that are identical in all respects other than the use of
randomisation by 'breaking' the randomisation in a trial to create non-randomised
trials (re-sampling studies).
2) Comparing randomised and non-randomised arms of controlled trials mounted
simultaneously in the field (replication studies).
3) Comparing similar controlled trials drawn from systematic reviews that include
both randomised and non-randomised studies (structured narrative reviews and
sensitivity analyses within meta-analyses).
4) Investigating associations between randomisation and effect size using a pool of
more diverse RCTs and NRSs within broadly similar areas (meta-epidemiology).
// RESULTS:
Prior methodological reviews and meta-analyses of existing reviews comparing
effects from RCTs and nRCTs suggested that effect sizes from RCTs and nRCTs
may indeed differ in some circumstances and that these differences may well be
associated with factors confounded with design.
Re-sampling studies offer no evidence that the absence of randomisation directly
influences the effect size of policy interventions in a systematic way. No consistent
explanations were found for randomisation being associated with changes in effect
sizes of policy interventions in field trials
AGN and starbursts at high redshift: High resolution EVN radio observations of the Hubble Deep Field
We present deep, wide-field European VLBI Network (EVN) 1.6 GHz observations
of the Hubble Deep Field (HDF) region with a resolution of 0.025 arcseconds.
Above the 210 microJy/beam (5sigma) detection level, the EVN clearly detects
two radio sources in a field that encompasses the HDF and part of the Hubble
Flanking Fields (HFF). The sources detected are: VLA J123644+621133 (a z=1.013,
low-luminosity FR-I radio source located within the HDF itself) and VLA
J123642+621331 (a dust enshrouded, optically faint, z=4.424 starburst system).
A third radio source, J123646+621404, is detected at the 4sigma level. The VLBI
detections of all three sources suggest that most of the radio emission of
these particular sources (including the dusty starburst) is generated by an
embedded AGN.Comment: 4 pages, 1 figure; Accepted by Astron. & Astrophys Letters ... See
http://www.nfra.nl/~mag/hdf_evn.htm
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