585 research outputs found
Dark Energy: Recent Developments
A six parameter cosmological model, involving a vacuum energy density that is
extremely tiny compared to fundamental particle physics scales, describes a
large body of increasingly accurate astronomical data. In a first part of this
brief review we summarize the current situation, emphasizing recent progress.
An almost infinitesimal vacuum energy is only the simplest candidate for a
cosmologically significant nearly homogeneous exotic energy density with
negative pressure, generically called Dark Energy. If general relativity is
assumed to be also valid on cosmological scales, the existence of such a dark
energy component that dominates the recent universe is now almost inevitable.
We shall discuss in a second part the alternative possibility that general
relativity has to be modified on distances comparable to the Hubble scale. It
will turn out that observational data are restricting theoretical speculations
more and more. Moreover, some of the recent proposals have serious defects on a
fundamental level (ghosts, acausalities, superluminal fluctuations).Comment: 19 pages, 5 figures, invited ``brief review'' for Modern Physics
Letters A; to appea
Adaptive data acquisition multiplexing system and method
A reconfigurable telemetry multiplexer is described which includes a monitor-terminal and a plurality of remote terminals. The remote terminals each include signal conditioning for a plurality of sensors for measuring parameters which are converted by an analog to digital converter. CPU's in the remote terminals store instructions for prompting system configuration and reconfiguration commands. The measurements, instructions, and the terminal's present configuration and status data are transmitted to the monitor-terminal and displayed. In response to menu-driven prompts generated and displayed at the monitor-terminal, data generation request commands, status and health commands, and the like are input at the monitor-terminal and transmitted to the remote terminals. The CPU in each remote terminal receives the various commands, stores them in electrically alterable memory, and reacts in accordance with the commands to reconfigure a plurality of aspects of the system. The CPU in each terminal also generates parameter measurements, status and health signals, and transmits these signals of the respective terminals to the monitor-terminal for low data rate operator viewing and to higher rate external transmission/monitor equipment. Reconfiguration may be in real time during the general period of parameter measurement acquisition, and may include alteration of the gain, automatic gain rescaling, bias, and or sampling rates associated with one or more of the parameter measurements made by the remote terminals
On induced CPT-odd Chern-Simons terms in 3+1 effective action
This paper was originally designated as Comment to the paper by R. Jackiw and
V. Alan Kostelecky (hep-ph/9901358). We provide an example of the fermionic
system, the superfluid 3He-A, in which the CPT-odd Chern-Simons terms in the
effective action are unambiguously induced by chiral fermions. In this system
the Lorentz and gauge invariances both are violated at high energy, but the
behavior of the system beyond the cut-off is known. This allows us to construct
the CPT-odd action, which combines the conventional 3+1 Chern-Simons term and
the mixed axial-gravitational Chern-Simons term discussed in hep-ph/9905460.
The influence of Chern-Simons term on the dynamics of the effective gauge field
has been experimentally observed in rotating 3He-A.Comment: RevTex, 3 pages, no figures, extended version of Comment to the paper
by R. Jackiw and V. Alan Kostelecky (hep-ph/9901358), to appear in JETP Let
The Cheshire Cat Bag Model: Color Anomaly and Properties
We show that color can leak from a QCD bag if we allow for pseudoscalar
isoscalar singlet () coupling at the surface. To enforce total
confinement of color an additional boundary term is suggested. New relations
between the mass and decay constant and the QCD gluon condensates are
derived and compared with the empirical parameters.Comment: 7 pages, LaTeX, Nordita - 92/68
Contributions to the Power Spectrum of Cosmic Microwave Background from Fluctuations Caused by Clusters of Galaxies
We estimate the contributions to the cosmic microwave background radiation
(CMBR) power spectrum from the static and kinematic Sunyaev-Zel'dovich (SZ)
effects, and from the moving cluster of galaxies (MCG) effect. We conclude, in
agreement with other studies, that at sufficiently small scales secondary
fluctuations caused by clusters provide important contributions to the CMBR. At
, these secondary fluctuations become important relative to
lensed primordial fluctuations. Gravitational lensing at small angular scales
has been proposed as a way to break the ``geometric degeneracy'' in determining
fundamental cosmological parameters. We show that this method requires the
separation of the static SZ effect, but the kinematic SZ effect and the MCG
effect are less important. The power spectrum of secondary fluctuations caused
by clusters of galaxies, if separated from the spectrum of lensed primordial
fluctuations, might provide an independent constraint on several important
cosmological parameters.Comment: LateX, 41 pages and 10 figures. Accepted for publication in the
Astrophysical Journa
Celestial mechanics in Kerr spacetime
The dynamical parameters conventionally used to specify the orbit of a test
particle in Kerr spacetime are the energy , the axial component of the
angular momentum, , and Carter's constant . These parameters are
obtained by solving the Hamilton-Jacobi equation for the dynamical problem of
geodesic motion. Employing the action-angle variable formalism, on the other
hand, yields a different set of constants of motion, namely, the fundamental
frequencies , and associated with
the radial, polar and azimuthal components of orbital motion. These
frequencies, naturally, determine the time scales of orbital motion and,
furthermore, the instantaneous gravitational wave spectrum in the adiabatic
approximation. In this article, it is shown that the fundamental frequencies
are geometric invariants and explicit formulas in terms of quadratures are
derived. The numerical evaluation of these formulas in the case of a rapidly
rotating black hole illustrates the behaviour of the fundamental frequencies as
orbital parameters such as the semi-latus rectum , the eccentricity or
the inclination parameter are varied. The limiting cases of
circular, equatorial and Keplerian motion are investigated as well and it is
shown that known results are recovered from the general formulas.Comment: 25 pages (LaTeX), 5 figures, submitted to Class. Quantum Gra
A review of research into business coaching supervision
A systematic search of the coaching literature for original peer-reviewed studies into business coaching supervision yielded seven research reports. Evaluation of these studies showed them to be low in the reporting of methodological rigour. However, as an emerging area of research with great importance for the development of the profession of business coaching these studies provide valuable insights into the functions of supervision and its benefits. Gaps in knowledge and directions for future research are identified. There is a need for future research to be more rigorous in its reporting of methods and analytic procedures, small scale qualitative research that can provide insight into the issues and challenges of coaching supervision in specific contexts, and large scale quantitative research which can provide broader and generalizable understandings into the uses and benefits of supervision
Preinfection in vitro chemotaxis, phagocytosis, oxidative burst, and expression of CD11/CD18 receptors and their predictive capacity on the outcome of mastitis induced in dairy cows with Escherichia coli.
Four to 6 wk after parturition, 12 cows in second, fourth, or fifth lactation were experimentally infected in one gland with Escherichia coli. The capacity of chemotaxis, phagocytosis, oxidative burst, and expression of CD11/CD18 receptors to predict the severity of IMI was measured. Bacterial counts in the infected quarter, expressed as area under the curve, and residual milk production in the uninfected quarters were compared to determine severity of the infection. Although these two outcome parameters were highly negatively correlated, regression models with preinfection tests for leukocyte function fitted best with bacterial counts as an outcome parameter. Of the preinfection tests for leukocyte function, chemotaxis best predicted the outcome of the IMI that had been experimentally induced by E. coli.
The number of circulating peripheral leukocytes just prior to inoculation was used to predict 52 and 45% of the severity of IMI for bacterial counts and residual milk production, respectively. As a categorical variable, parity predicted 75 and 56% of the severity of IMI expressed as bacterial counts and residual milk production, respectively. Because of the strong effect of parity on the outcome of the experimentally induced mastitis, analysis was performed to discriminate between second parity cows and older cows. Significant differences were found for the number of circulating peripheral leukocytes and for the expression of CD11b/CDl8 and CD11c/CD18 receptors between younger and older cows
Behavioral Inhibition as a Risk Factor for the Development of Childhood Anxiety Disorders: A Longitudinal Study
This longitudinal study examined the additive and interactive effects of behavioral inhibition and a wide range of other vulnerability factors in the development of anxiety problems in youths. A sample of 261 children, aged 5 to 8 years, 124 behaviorally inhibited and 137 control children, were followed during a 3-year period. Assessments took place on three occasions to measure children’s level of behavioral inhibition, anxiety disorder symptoms, other psychopathological symptoms, and a number of other vulnerability factors such as insecure attachment, negative parenting styles, adverse life events, and parental anxiety. Results obtained with Structural Equation Modeling indicated that behavioral inhibition primarily acted as a specific risk factor for the development of social anxiety symptoms. Furthermore, the longitudinal model showed additive as well as interactive effects for various vulnerability factors on the development of anxiety symptoms. That is, main effects of anxious rearing and parental trait anxiety were found, whereas behavioral inhibition and attachment had an interactive effect on anxiety symptomatology. Moreover, behavioral inhibition itself was also influenced by some of the vulnerability factors. These results provide support for dynamic, multifactorial models for the etiology of child anxiety problems
Phenomenological analysis of K+ meson production in proton-nucleus collisions
Total and differential cross sections from literature, on the production of
K+ mesons in pA interactions at projectile energies between T=0.8 and 2.9 GeV,
covering the transition across the free nucleon-nucleon threshold at 1.58 GeV,
have been investigated. From the target-mass dependence of the production cross
sections no evidence for the expected change of the dominant reaction mechanism
from two-step to direct kaon production was found. At T=1.0 GeV the A
dependences of the total cross sections and of the most recent data from
COSY-Juelich, differential cross sections measured under forward angles, are
strongly different. The invariant K+ production cross sections show an overall
exponential scaling behavior with the squared four-momentum transfer between
the beam proton and the produced K+ meson for t< -0.05 GeV^2 independent of the
beam energy and emission angle. The data from COSY-Juelich reveal a strongly
different t dependence in the region of t>0 GeV^2. Further data at forward
angles and different beam energies should be taken in order to explore this
region of kinematically extreme conditions.Comment: 9 Pages, 11 Figure
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