893 research outputs found
Characterising and Testing Deep UV LEDs for Use in Space Applications
Deep ultraviolet (DUV) light sources are used to neutralise isolated test
masses in highly sensitive space-based gravitational experiments. An example is
the LISA Pathfinder charge management system, which uses low-pressure mercury
lamps. A future gravitational-wave observatory such as eLISA will use UV
light-emitting diodes (UV LEDs), which offer numerous advantages over
traditional discharge lamps. Such devices have limited space heritage but are
are now available from a number of commercial suppliers. Here we report on a
test campaign that was carried out to quantify the general properties of three
types of commercially available UV LEDs and demonstrate their suitability for
use in space. Testing included general electrical and UV output measurements,
spectral stability, pulsed performance, temperature dependence as well as
thermal vacuum, radiation and vibration survivability
The LISA PathFinder DMU and Radiation Monitor
The LISA PathFinder DMU (Data Management Unit) flight model was formally
accepted by ESA and ASD on 11 February 2010, after all hardware and software
tests had been successfully completed. The diagnostics items are scheduled to
be delivered by the end of 2010. In this paper we review the requirements and
performance of this instrumentation, specially focusing on the Radiation
Monitor and the DMU, as well as the status of their programmed use during
mission operations, on which work is ongoing at the time of writing.Comment: 11 pages, 7 figures, prepared for the Proceedings of the 8th
International LISA Symposium, Classical and Quantum Gravit
LISA and LISA PathFinder, the endeavour to detect low frequency GWs
This is a review about LISA and its technology demonstrator, LISA PathFinder.
We first describe the conceptual problems which need to be overcome in order to
set up a working interferometric detector of low frequency Gravitational Waves
(GW), then summarise the solutions to them as currently conceived by the LISA
mission team. This will show that some of these solutions require new
technological abilities which are still under development, and which need
proper test before being fully implemented. LISA PathFinder (LPF) is the the
testbed for such technologies. The final part of the paper will address the
ideas and concepts behind the PathFinder as well as their impact on LISA.Comment: 25 pages, 21 figures, presented at the Spanish Relativity Meeting,
Mallorca September 2006. Will be published in Journal of Physics: Conference
Series, IOP. To be published in Journal of Physics: Conference Series, IO
The Labour Government, the Treasury and the £6 pay policy of July 1975
The 1974-79 Labour Government was elected in a climate of opinion that was fiercely opposed to government intervention in the wage determination process, and was committed to the principles of free collective bargaining in its manifestoes. However, by December 1974 the Treasury was advocating a formal incomes policy, and by July 1975 the government had introduced a £6 flat rate pay norm. With reference to archival sources, the paper demonstrates that TUC and Labour Party opposition to incomes policy was reconciled with the Treasury's advocacy by limiting the Bank of England‟s intervention in the foreign exchange market when sterling came under pressure. This both helped to achieve the Treasury's objective of improving the competitiveness of British industry, and acted as a catalyst for the introduction of incomes policy because the slide could be attributed to a lack of market confidence in British counter-inflation policy
Slip behavior in liquid films on surfaces of patterned wettability: Comparison between continuum and molecular dynamics simulations
We investigate the behavior of the slip length in Newtonian liquids subject
to planar shear bounded by substrates with mixed boundary conditions. The upper
wall, consisting of a homogenous surface of finite or vanishing slip, moves at
a constant speed parallel to a lower stationary wall, whose surface is
patterned with an array of stripes representing alternating regions of no-shear
and finite or no-slip. Velocity fields and effective slip lengths are computed
both from molecular dynamics (MD) simulations and solution of the Stokes
equation for flow configurations either parallel or perpendicular to the
stripes. Excellent agreement between the hydrodynamic and MD results is
obtained when the normalized width of the slip regions, , where is the (fluid) molecular diameter characterizing the
Lennard-Jones interaction. In this regime, the effective slip length increases
monotonically with to a saturation value. For and transverse flow configurations, the non-uniform interaction
potential at the lower wall constitutes a rough surface whose molecular scale
corrugations strongly reduce the effective slip length below the hydrodynamic
results. The translational symmetry for longitudinal flow eliminates the
influence of molecular scale roughness; however, the reduced molecular ordering
above the wetting regions of finite slip for small values of
increases the value of the effective slip length far above the hydrodynamic
predictions. The strong inverse correlation between the effective slip length
and the liquid structure factor representative of the first fluid layer near
the patterned wall illustrates the influence of molecular ordering effects on
slip in non-inertial flows.Comment: 12 pages, 10 figures Web reference added for animations:
http://www.egr.msu.edu/~priezjev/bubble/bubble.htm
Charge Management for Gravitational Wave Observatories using UV LEDs
Accumulation of electrical charge on the end mirrors of gravitational wave
observatories, such as the space-based LISA mission and ground-based LIGO
detectors, can become a source of noise limiting the sensitivity of such
detectors through electronic couplings to nearby surfaces. Torsion balances
provide an ideal means for testing gravitational wave technologies due to their
high sensitivity to small forces. Our torsion pendulum apparatus consists of a
movable Au-coated Cu plate brought near a Au-coated Si plate pendulum suspended
from a non-conducting quartz fiber. A UV LED located near the pendulum
photoejects electrons from the surface, and a UV LED driven electron gun
directs photoelectrons towards the pendulum surface. We have demonstrated both
charging and discharging of the pendulum with equivalent charging rates of
, as well as spectral measurements of the pendulum
charge resulting in a white noise level equivalent to .Comment: 5 pages, submitted to PR
A comparison of match demands using ball-in-play vs. whole match data in elite male youth soccer players
Effective playing time in soccer is typically 90 seconds. This data allows practitioners to gain a deeper understanding of the physical demands imposed on players and plan sessions using targets that better represent match demands
The South Asian genome
Genetics of disease
Microarrays
Variant genotypes
Population genetics
Sequence alignment
AllelesThe genetic sequence variation of people from the Indian subcontinent who comprise one-quarter of the world's population, is not well described. We carried out whole genome sequencing of 168 South Asians, along with whole-exome sequencing of 147 South Asians to provide deeper characterisation of coding regions. We identify 12,962,155 autosomal sequence variants, including 2,946,861 new SNPs and 312,738 novel indels. This catalogue of SNPs and indels amongst South Asians provides the first comprehensive map of genetic variation in this major human population, and reveals evidence for selective pressures on genes involved in skin biology, metabolism, infection and immunity. Our results will accelerate the search for the genetic variants underlying susceptibility to disorders such as type-2 diabetes and cardiovascular disease which are highly prevalent amongst South Asians.Whole genome sequencing to discover genetic variants underlying type-2 diabetes, coronary heart disease and related phenotypes amongst Indian Asians. Imperial College Healthcare NHS Trust cBRC 2011-13 (JS Kooner [PI], JC Chambers)
Form-function relationship in the amplitude and frequency modulations of infant - directed speech: A predictive processing perspective
Infants prefer infant-directed speech (IDS) over adult-directed speech (ADS). IDS is thought to serve specific functions compared to ADS:
- Attracting infant attention to the speech signal
- Conveying clear opportunities for easier word segmentation.
Two independent domains of complexity that are embedded in the speech stream:
- Amplitude complexity: Lower amplitude complexity associates with greater ease in identifying word boundaries
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- ​Frequency complexity: Higher fre q uency complexity associates with more attention eliciting speech attention by inducing uncertaint
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