287 research outputs found
Astrophysical Probes of Fundamental Physics
I review the theoretical motivation for varying fundamental couplings and
discuss how these measurements can be used to constrain a number of fundamental
physics scenarios that would otherwise be inacessible to experiment. As a case
study I will focus on the relation between varying couplings and dark energy,
and explain how varying coupling measurements can be used to probe the nature
of dark energy, with important advantages over the standard methods. Assuming
that the current observational evidence for varying and is
correct, a several-sigma detection of dynamical dark energy is feasible within
a few years, using currently operational ground-based facilities. With
forthcoming instruments like CODEX, a high-accuracy reconstruction of the
equation of state may be possible all the way up to redshift .Comment: Invited Review talk at the ESO Precision Spectroscopy in Astrophysics
conference, to appear in the proceeding
Culture change in a professional sports team: Shaping environmental contexts and regulating power
Although high performing cultures are crucial for the enduring success of professional sport performance teams, theoretical and practical understanding of how they are established and sustained is lacking. To develop knowledge in this area, a case study was undertaken to examine the key mechanisms and processes of a successful culture change programme at English Rugby Unionâs Leeds Carnegie. Exploring the change process from a 360 degree perspective, semi-structured interviews were conducted with team management, one specialist coach, six players, and the CEO. Analysed and explained through decentred theory, results revealed that culture change was effectively facilitated by team management: a) subtly and covertly shaping the physical, structural, and psychosocial context in which support staff and players made performance-impacting choices, and b) regulating the âto and froâ of power which characterises professional sport performance teams. Decentred theory is also supported as an effective framework for culture change study
Search for Possible Variation of the Fine Structure Constant
Determination of the fine structure constant alpha and search for its
possible variation are considered. We focus on a role of the fine structure
constant in modern physics and discuss precision tests of quantum
electrodynamics. Different methods of a search for possible variations of
fundamental constants are compared and those related to optical measurements
are considered in detail.Comment: An invited talk at HYPER symposium (Paris, 2002
Evolution of the infrared luminosity density and star formation history up to z~1: preliminary results from MIPS
Using deep observations of the Chandra Deep Field South obtained with MIPS at
24mic, we present our preliminary estimates on the evolution of the infrared
(IR) luminosity density of the Universe from z=0 to z~1. We find that a pure
density evolution of the IR luminosity function is clearly excluded by the
data. The characteristic luminosity L_IR* evolves at least by (1+z)^3.5 with
lookback time, but our monochromatic approach does not allow us to break the
degeneracy between a pure evolution in luminosity or an evolution in both
density and luminosity. Our results imply that IR luminous systems (L_IR >
10^11 L_sol) become the dominant population contributing to the comoving IR
energy density beyond z~0.5-0.6. The uncertainties affecting our measurements
are largely dominated by the poor constraints on the spectral energy
distributions that are used to translate the observed 24mic flux into
luminosities.Comment: 4 pages, 2 figures. To be published in "Starbursts: From 30 Doradus
to Lyman Break Galaxies", held in Cambridge, 6-10 September 2004, Ed. R. de
Grijs & R. M. Gonzalez Delgad
Antihydrogen formation dynamics in a multipolar neutral anti-atom trap
Antihydrogen production in a neutral atom trap formed by an octupole-based
magnetic field minimum is demonstrated using field-ionization of weakly bound
anti-atoms. Using our unique annihilation imaging detector, we correlate
antihydrogen detection by imaging and by field-ionization for the first time.
We further establish how field-ionization causes radial redistribution of the
antiprotons during antihydrogen formation and use this effect for the first
simultaneous measurements of strongly and weakly bound antihydrogen atoms.
Distinguishing between these provides critical information needed in the
process of optimizing for trappable antihydrogen. These observations are of
crucial importance to the ultimate goal of performing CPT tests involving
antihydrogen, which likely depends upon trapping the anti-atom
Constraining fundamental constants of physics with quasar absorption line systems
We summarize the attempts by our group and others to derive constraints on
variations of fundamental constants over cosmic time using quasar absorption
lines. Most upper limits reside in the range 0.5-1.5x10-5 at the 3sigma level
over a redshift range of approximately 0.5-2.5 for the fine-structure constant,
alpha, the proton-to-electron mass ratio, mu, and a combination of the proton
gyromagnetic factor and the two previous constants, gp(alpha^2/mu)^nu, for only
one claimed variation of alpha. It is therefore very important to perform new
measurements to improve the sensitivity of the numerous methods to at least
<0.1x10-5 which should be possible in the next few years. Future
instrumentations on ELTs in the optical and/or ALMA, EVLA and SKA pathfinders
in the radio will undoutedly boost this field by allowing to reach much better
signal-to-noise ratios at higher spectral resolution and to perform
measurements on molecules in the ISM of high redshift galaxies.Comment: 11 pages, 3 figure
Search For Trapped Antihydrogen
We present the results of an experiment to search for trapped antihydrogen
atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator.
Sensitive diagnostics of the temperatures, sizes, and densities of the trapped
antiproton and positron plasmas have been developed, which in turn permitted
development of techniques to precisely and reproducibly control the initial
experimental parameters. The use of a position-sensitive annihilation vertex
detector, together with the capability of controllably quenching the
superconducting magnetic minimum trap, enabled us to carry out a
high-sensitivity and low-background search for trapped synthesised antihydrogen
atoms. We aim to identify the annihilations of antihydrogen atoms held for at
least 130 ms in the trap before being released over ~30 ms. After a three-week
experimental run in 2009 involving mixing of 10^7 antiprotons with 1.3 10^9
positrons to produce 6 10^5 antihydrogen atoms, we have identified six
antiproton annihilation events that are consistent with the release of trapped
antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts,
is incompatible with this observation at a significance of 5.6 sigma. Extensive
simulations predict that an alternative source of annihilations, the escape of
mirror-trapped antiprotons, is highly unlikely, though this possibility has not
yet been ruled out experimentally.Comment: 12 pages, 7 figure
Surface antigen profiles of leukocytes and melanoma cells in lymph node metastases are associated with survival in AJCC stage III melanoma patients
There is an urgent need to identify more accurate prognostic biomarkers in melanoma patients, particularly in those with metastatic disease. This study aimed to identify melanoma and leukocyte surface antigens predictive of survival in a prospective series of AJCC stage IIIb/c melanoma patients (n = 29). Live cell suspensions were prepared from melanoma metastases within lymph nodes (LN). The suspensions were immuno-magnetically separated into CD45+ (leukocyte) and CD45â (non-hematopoietic, enriched melanoma cell) fractions. Surface antigens on CD45â and CD45+ cell populations were profiled using DotScanâą microarrays (Medsaic Pty. Ltd.) and showed differential abundance levels for 52 and 78 antigens respectively. Associations of the surface profiles with clinicopathologic and outcome data (median follow-up 35.4 months post LN resection) were sought using univariate (log-rank test) and multivariate (Waldâs test; modelled with patientâs age, gender and AJCC staging at LN recurrence) survival models. CD9 (p = 0.036), CD39 (p = 0.004) and CD55 (p = 0.005) on CD45+ leukocytes were independently associated with distant metastasis-free survival using multivariate analysis. Leukocytes with high CD39 levels were also significantly associated with increased overall survival (OS) in multivariate analysis (p = 0.016). LNs containing leukocytes expressing CD11b (p = 0.025), CD49d (p = 0.043) and CD79b (p = 0.044) were associated with reduced OS on univariate analysis. For enriched melanoma cells (CD45â cell populations), 11 surface antigens were significantly correlated with the disease-free interval (DFI) between diagnosis of culprit primary melanoma and LN metastasis resection. Nine antigens on CD45+ leukocytes also correlated with DFI. Following validation in independent datasets, surface markers identified here should enable more accurate determination of prognosis in stage III melanoma patients and provide better risk stratification of patients entering clinical trials
Search for varying constants of nature from astronomical observation of molecules
The status of searches for possible variation in the constants of nature from
astronomical observation of molecules is reviewed, focusing on the
dimensionless constant representing the proton-electron mass ratio
. The optical detection of H and CO molecules with large
ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as
the detection of H with the Cosmic Origins Spectrograph aboard the Hubble
Space Telescope is discussed in the context of varying constants, and in
connection to different theoretical scenarios. Radio astronomy provides an
alternative search strategy bearing the advantage that molecules as NH
(ammonia) and CHOH (methanol) can be used, which are much more sensitive to
a varying than diatomic molecules. Current constraints are
for redshift , corresponding to
look-back times of 10-12.5 Gyrs, and for
, corresponding to half the age of the Universe (both at 3
statistical significance). Existing bottlenecks and prospects for future
improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the
International Space Science Institute, Bern 201
Comparison of depression and anxiety symptom networks in reporters and non-reporters of lifetime trauma in two samples of differing severity
Background: Reported trauma is associated with differences in the course and outcomes of depression and anxiety. However, no research has explored the association between reported trauma and patterns of clinically relevant symptoms of both depression and anxiety. Methods: We used network analysis to investigate associations between reported trauma and depression and anxiety symptom interactions in affected individuals from the Genetic Links to Anxiety and Depression (GLAD) Study (n = 17720), and population volunteers from the UK Biobank (n = 11120). Participants with current moderate symptoms of depression or anxiety were grouped into reporters and non-reporters of lifetime trauma. Networks of 16 depression and anxiety symptoms in the two groups were compared using the network comparison test. Results: In the GLAD Study, networks of reporters and non-reporters of lifetime trauma did not differ on any metric. In the UK Biobank, the symptom network of reporters had significantly greater density (7.80) than the network of non-reporters (7.05). Limitations: The data collected in the GLAD Study and the UK Biobank are self-reported with validated or semi-validated questionnaires. Conclusions: Reported lifetime trauma was associated with stronger interactions between symptoms of depression and anxiety in population volunteers. Differences between reporters and non-reporters may not be observed in individuals with severe depression and/or anxiety due to limited variance in the presentation of disorder
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