1,168 research outputs found
Higgs Spin Determination in the WW channel and beyond
After the discovery of the 126 GeV resonance at the LHC, the determination of
its features, including its spin, is a very important ongoing task. In order to
distinguish the two most likely spin hypotheses, spin-0 or spin-2, we study the
phenomenology of a light Higgs-like spin-2 resonance produced in different
gluon-fusion and vector-boson-fusion processes at the LHC. Starting from an
effective model for the interaction of a spin-2 particle with the SM gauge
bosons, we calculate cross sections and differential distributions within the
Monte Carlo program Vbfnlo. We find that with specific model parameters such a
spin-2 resonance can mimic SM Higgs rates and transverse-momentum distributions
in , and decays, whereas several distributions allow
to separate spin-2 from spin-0, independently of the spin-2 model parameters.Comment: 14 pages, 7 figure
A free-piston Stirling engine/linear alternator controls and load interaction test facility
A test facility at LeRC was assembled for evaluating free-piston Stirling engine/linear alternator control options, and interaction with various electrical loads. This facility is based on a 'SPIKE' engine/alternator. The engine/alternator, a multi-purpose load system, a digital computer based load and facility control, and a data acquisition system with both steady-periodic and transient capability are described. Preliminary steady-periodic results are included for several operating modes of a digital AC parasitic load control. Preliminary results on the transient response to switching a resistive AC user load are discussed
Genotype-Phenotype Correlations in Autosomal Dominant Osteogenesis Imperfecta
Osteogenesis imperfecta, discussed in Baldridge et al. 2008 is an inherited bone fragility disorder with a wide range of clinical severity that in the majority of cases is caused by mutations in COL1A1 or COL1A2, the genes that encode the two collagen type I alpha chains. Here we describe genotype-phenotype correlations in OI patients who have mutations affecting collagen type I. This paper is based on findings in a large single-centre OI population and a review of the literature
Detection of Xe from the Fukushima nuclear power plant in the upper troposphere above Germany
After the accident in the Japanese Fukushima Dai-ichi nuclear power plant in
March 2011 large amounts of radioactivity were released and distributed in the
atmosphere. Among them were also radioactive noble gas isotopes which can be
used as tracers to test global atmospheric circulation models. This work
presents unique measurements of the radionuclide Xe from Fukushima in
the upper troposphere above Germany. The measurements involve air sampling in a
research jet aircraft followed by chromatographic xenon extraction and
ultra-low background gas counting with miniaturized proportional counters. With
this technique a detection limit of the order of 100 Xe atoms in
litre-scale air samples (corresponding to about 100 mBq/m) is achievable.
Our results provide proof that the Xe-rich ground level air layer from
Fukushima was lifted up to the tropopause and distributed hemispherically.
Moreover, comparisons with ground level air measurements indicate that the
arrival of the radioactive plume at high altitude over Germany occurred several
days before the ground level plume.Comment: 8 pages, 5 figure
A time lens for high resolution neutron time of flight spectrometers
We examine in analytic and numeric ways the imaging effects of temporal
neutron lenses created by traveling magnetic fields. For fields of parabolic
shape we derive the imaging equations, investigate the time-magnification, the
evolution of the phase space element, the gain factor and the effect of finite
beam size. The main aberration effects are calculated numerically. The system
is technologically feasible and should convert neutron time of flight
instruments from pinhole- to imaging configuration in time, thus enhancing
intensity and/or time resolution. New fields of application for high resolution
spectrometry may be opened.Comment: 8 pages, 11 figure
Real time digital control and controlled structures experiments
Viewgraphs covering the following topics are given: controlled structures technology at Grumman Corporate Research Center, active and passive control technology, experiment plans, and vacuum chamber test experiment objectives and setup
A Search for Oxygen in the Low-Density Lyman-alpha Forest Using the Sloan Digital Sky Survey
We use 2167 Sloan Digital Sky Survey (SDSS) quasar spectra to search for
low-density oxygen in the Intergalactic Medium (IGM). Oxygen absorption is
detected on a pixel-by-pixel basis by its correlation with Lyman-alpha forest
absorption. We have developed a novel Locally Calibrated Pixel (LCP) search
method that uses adjacent regions of the spectrum to calibrate interlopers and
spectral artifacts, which would otherwise limit the measurement of OVI
absorption. Despite the challenges presented by searching for weak OVI within
the Lyman-alpha forest in spectra of moderate resolution and signal-to-noise,
we find a highly significant detection of absorption by oxygen at 2.7 < z < 3.2
(the null hypothesis has a chi^2=80 for 9 data points).
We interpret our results using synthetic spectra generated from a lognormal
density field assuming a mixed quasar-galaxy photoionizing background (Haardt &
Madau 2001) and that it dominates the ionization fraction of detected OVI. The
LCP search data can be fit by a constant metallicity model with [O/H] =
-2.15_(-0.09)^(+0.07), but also by models in which low-density regions are
unenriched and higher density regions have a higher metallicity. The
density-dependent enrichment model by Aguirre et al. (2008) is also an
acceptable fit. All our successful models have similar mass-weighted oxygen
abundance, corresponding to [_MW] = -2.45+-0.06. This result can be used
to find the cosmic oxygen density in the Lyman-alpha forest, Omega_(Oxy, IGM) =
1.4(+-0.2)x10^(-6) = 3x10^(-4) Omega_b. This is the tightest constraint on the
mass-weighted mean oxygen abundance and the cosmic oxygen density in the
Lyman-alpha forest to date and indicates that it contains approximately 16% of
metals produced by star formation (Bouch\'e et al. 2008) up to z = 3.Comment: 12 pages, 9 figures. Accepted by ApJ (minor changes
Entrepreneurial Intentions of Teams: Sub-Dimensions of Machiavellianism Interact With Team Resilience
Machiavellians are often seen as manipulative people who contribute negatively to teams and ventures. However, recent work has shown that Machiavellians can also cooperate and act in pro-social ways in a team context. Thus, some aspects of Machiavellianism might be conducive for teams and team members’ intentions to start a business venture. Most studies in this area have failed to (a) assess the effect of Machiavellianism at the team level, (b) take into account the dimensional nature of Machiavellianism, and (c) assess moderators of these effects. We propose that the combination of Machiavellianism and resilience in teams predict team entrepreneurial intentions (EI). Moreover, we propose that different team level dimensions of Machiavellianism (amoral manipulation, desire for status, desire for control, distrust of others) are differentially related to EI. More specifically, we expect at the team level that amoral manipulation and desire for status are positively related to changes in EI (as teams high on these dimensions feel that they can use unethical practices that give them an advantage in being successful), whereas desire for control and distrust of others should be negatively related to changes in EI (as entrepreneurial teams usually work in less structured situations and need to closely work together). Furthermore, all sub-dimensions of Machiavellianism should interact positively with team resilience as resilience acts as a buffer that protects teams from potential negative effects of Machiavellianism. In a multi-wave study among newly formed teams engaged in entrepreneurship projects, controlling for psychopathy and narcissism, we found partial support for our hypotheses. Results supported our expectations for the “amoral manipulation” and “desire for control” sub-dimensions, but not for the “desire for status” and the “distrust of others” sub-dimensions of Machiavellianism, with distrust of others showing unexpectedly opposite effects. This study contributes to the literature by looking at the dimensions of Machiavellianism at the level of entrepreneurial teams in conjunction with the more positive team characteristic, resilience. Our results indicate that the relationship between Machiavellianism and EI is more complex than previously hypothesized, as the sub-dimensions are s
Enhanced accretion rates of stars on Super-massive Black Holes by star-disk interactions in galactic nuclei
We investigate the dynamical interaction of a central star cluster
surrounding a super-massive black hole and a central accretion disk. The
dissipative force acting on stars in the disk leads to an enhanced mass flow
towards the super-massive black hole and to an asymmetry in the phase space
distribution due to the rotating accretion disk. The accretion disk is
considered as a stationary Keplerian rotating disk, which is vertically
extended in order to employ a fully self-consistent treatment of stellar
dynamics including the dissipative force originating from star-gas ram pressure
effects. The stellar system is treated with a direct high-accuracy N-body
integration code. A star-by-star representation, desirable in N-body
simulations, cannot be extended to real particle numbers yet. Hence, we
carefully discuss the scaling behavior of our model with regard to particle
number and tidal accretion radius. The main idea is to find a family of models
for which the ratio of two-body relaxation time and dissipation time (for
kinetic energy of stellar orbits) is constant, which then allows us to
extrapolate our results to real parameters of galactic nuclei. Our model is
derived from basic physical principles and as such it provides insight into the
role of physical processes in galactic nuclei, but it should be regarded as a
first step towards more realistic and more comprehensive simulations.
Nevertheless, the following conclusions appear to be robust: the star accretion
rate onto the accretion disk and subsequently onto the super-massive black hole
is enhanced by a significant factor compared to purely stellar dynamical
systems neglecting the disk. This process leads to enhanced fueling of central
disks in active galactic nuclei and to an enhanced rate of tidal stellar
disruptions. [Abridged]Comment: 17 pages, 6 figures (with 9 panels), 2 tables, accepted for
publication in Ap
Cholesterol dependence of HTLV-I infection
Cholesterol-rich plasma membrane microdomains are important for entry of many viruses, including retro-viruses. Depletion of cholesterol with 2-hydroxypropyl-β-cyclodextrin inhibits entry of human T cell leukemia virus type I (HTLV-1) and HTLV-I envelope pseudotyped lentivirus particles. Using a soluble fusion protein of the HTLV-I surface envelope protein with the immunoglobulin Fc domain, the HTLV-I receptor was found to colocalize with a raft-associated marker and to cluster in specific plasma membrane microdomains. Depletion of cholesterol did not alter receptor binding activity, suggesting a requirement for cholesterol in a postbinding virus entry step
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