10,627 research outputs found
The Calan-Hertfordshire Extrasolar Planet Search
The detailed study of the exoplanetary systems HD189733 and HD209458 has
given rise to a wealth of exciting information on the physics of exoplanetary
atmospheres. To further our understanding of the make-up and processes within
these atmospheres we require a larger sample of bright transiting planets. We
have began a project to detect more bright transiting planets in the southern
hemisphere by utilising precision radial-velocity measurements. We have
observed a constrained sample of bright, inactive and metal-rich stars using
the HARPS instrument and here we present the current status of this project,
along with our first discoveries which include a brown dwarf/extreme-Jovian
exoplanet found in the brown dwarf desert region around the star HD191760 and
improved orbits for three other exoplanetary systems HD48265, HD143361 and
HD154672. Finally, we briefly discuss the future of this project and the
current prospects we have for discovering more bright transiting planets.Comment: 4 pages, 2 figures, to appear in the conference proceedings "New
Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets"
Shanghai 200
A theoretical and experimental investigation of cylindrical electrostatic probes at arbitrary incidence in flowing plasma
The theory for calculating the current collected by a negatively biased cylindrical electrostatic probe at an arbitrary angle of attack in a weakley ionized flowing plasma is presented. The theory was constructed by considering both random and directed motion simultaneous with dynamic coupling of the flow properties and of the electric field of the probe. This direct approach yielded a theory that is more general than static plasma theories modified to account for flow. Theoretical calculations are compared with experimental electrostatic probe data obtained in the free stream of an arc-heated hypersonic wind tunnel. The theoretical calculations are based on flow conditions and plasma electron densities measured by an independent microwave interferometer technique. In addition, the theory is compared with laboratory and satellite data previously published by other investigators. In each case the comparison gives good agreement
The Magnetic Moments of the Octet Baryons in Quenched Chiral Perturbation Theory
We compute the magnetic moments of the octet baryons up to two orders in
quenched chiral perturbation theory. In addition to the
contributions that arise in QCD, there are lower-order contributions of the
form from loop diagrams involving hairpin interactions.Comment: 18 pages, 3 figures, late
Giant planets around two intermediate-mass evolved stars and confirmation of the planetary nature of HIP67851 c
Precision radial velocities are required to discover and characterize planets
orbiting nearby stars. Optical and near infrared spectra that exhibit many
hundreds of absorption lines can allow the m/s precision levels required for
such work. However, this means that studies have generally focused on
solar-type dwarf stars. After the main-sequence, intermediate-mass stars
(former A-F stars) expand and rotate slower than their progenitors, thus
thousands of narrow absorption lines appear in the optical region, permitting
the search for planetary Doppler signals in the data for these types of stars.
We present the discovery of two giant planets around the intermediate-mass
evolved star HIP65891 and HIP107773. The best Keplerian fit to the HIP65891 and
HIP107773 radial velocities leads to the following orbital parameters: P=1084.5
d; msin = 6.0 M; =0.13 and P=144.3 d; msin = 2.0
M; =0.09, respectively. In addition, we confirm the planetary nature
of the outer object orbiting the giant star HIP67851. The orbital parameters of
HIP67851c are: P=2131.8 d, msin = 6.0 M and =0.17. With
masses of 2.5 M and 2.4 M HIP65891 and HIP107773 are two of the
most massive stars known to host planets. Additionally, HIP67851 is one of five
giant stars that are known to host a planetary system having a close-in planet
( 0.7 AU). Based on the evolutionary states of those five stars, we
conclude that close-in planets do exist in multiple systems around subgiants
and slightly evolved giants stars, but probably they are subsequently destroyed
by the stellar envelope during the ascent of the red giant branch phase. As a
consequence, planetary systems with close-in objects are not found around
horizontal branch stars.Comment: Accepted for publication in A&
Human sensitivity to gearshift loads
This paper describes an investigation of the ability of humans to distinguish different levels of gearlever load. A test rig with a forward-backward moving gearshift lever was constructed using the typical interior dimensions of European B segment automobiles. The rig used a system of weights and pulleys to provide a load which could be varied in steps of 1%. Four reference loads were chosen which were considered representative of automotive gearshift operation: 0.5, 1.0, 2.0 and 5.0 kg. Twenty subjects took part in the study. Using a variation on the psychophysical method of limits, the subjects were asked to respond whether a test load was heavier or lighter
than a reference load. The Weber Fraction was found to decrease monotonically from a value of 0.036 for the 0.5 kg reference load to a value of 0.029 at the 5.0 kg reference load. The average value across all reference loads was 0.032. Measurements of the gearshift force made by means of a knob containing a load cell suggested that the variation in the measured Weber Fraction might be attributable to the time behaviour of the force exchanged between the human subject and the control surface
Mental health: future challenges
The aim of the Foresight Project on Mental Capital and Wellbeing(www.foresight.gov.uk) is to advise the Government on how to achieve the best possible mental development and mental wellbeing for everyone in the UK in the future. The starting point of the Project was to generate an understanding of the science of mental capital and wellbeing (MCW) and to develop a vision for how the size and nature of the challenges exposed by the Project could evolve over the next 20 years. To make this analysis tractable, the work was divided into five broad areas: ● Mental capital through life ● Learning through life ● Mental health ● Wellbeing and work, and ● Learning difficulties. This report presents the findings for “Mental health” and draws upon a comprehensive assessment of the scientific state-of-the art: overall, around 80 reviews have been commissioned across the five areas. Mental health is a term which is used in a number of different ways and which has unfortunately acquired a substantial stigma in all layers of society. While the main focus of this report is on mental ill-health, positive mental health is also vitally important and is also discussed. However, a more comprehensive consideration of positive mental health has been performed in other parts of the Project (as commissioned reviews and in the context of the future of work. This report starts by looking at the situation today, examining the prevalence of important categories of mental disorder. It then considers the risk and protective factors which influence mental ill health, and determines how its prevalence and impact could change in the future, if existing policies and expenditure remain broadly unchanged. An assessment of strategic choices and interventions to meet the future challenges of mental health (and the challenges associated with the other four areas listed above) will be documented in the final Project report which is due for publication in the autumn of 2008
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