7,781 research outputs found
Deflection resistance indicator
Instrument for nondestructively measuring compression resistance of spray foam used as thermal insulation was developed. Cylindrical indicator has probe with coil spring to provide force and indicating dial. Probe is manually pressed against area to be tested until complete foot area contacts foam surfaces
Charge density of a positively charged vector boson may be negative
The charge density of vector particles, for example W, may change sign. The
effect manifests itself even for a free propagation; when the energy of the
W-boson is higher than sqrt{2}m and the standing-wave is considered the charge
density oscillates in space. The charge density of W also changes sign in close
vicinity of a Coulomb center. The dependence of this effect on the g-factor for
an arbitrary vector boson, for example rho-meson, is discussed. An origin of
this surprising effect is traced to the electric quadrupole moment and
spin-orbit interaction of vector particles. Their contributions to the current
have a polarization nature. The charge density of this current, rho = -\nabla
\cdot P, where P is an effective polarization vector that depends on the
quadrupole moment and spin-orbit interaction, oscillates in space, producing
zero contribution to the total charge.Comment: 4 pages, revte
Chen-Ruan cohomology of ADE singularities
We study Ruan's \textit{cohomological crepant resolution conjecture} for
orbifolds with transversal ADE singularities. In the -case we compute both
the Chen-Ruan cohomology ring and the quantum corrected
cohomology ring . The former is achieved in general, the
later up to some additional, technical assumptions. We construct an explicit
isomorphism between and in the -case,
verifying Ruan's conjecture. In the -case, the family
is not defined for . This implies that
the conjecture should be slightly modified. We propose a new conjecture in the
-case which we prove in the -case by constructing an explicit
isomorphism.Comment: This is a short version of my Ph.D. Thesis math.AG/0510528. Version
2: chapters 2,3,4 and 5 has been rewritten using the language of groupoids; a
link with the classical McKay correpondence is given. International Journal
of Mathematics (to appear
Level density of Fe and low-energy enhancement of -strength function
The MnFe differential cross section is measured at
MeV\@. The Fe level density obtained from neutron evaporation spectra is
compared to the level density extracted from the
FeHe,Fe reaction by the Oslo-type technique.
Good agreement is found between the level densities determined by the two
methods. With the level density function obtained from the neutron evaporation
spectra, the Fe -strength function is also determined from the
first-generation matrix of the Oslo experiment. The good agreement
between the past and present results for the -strength function
supports the validity of both methods and is consistent with the low-energy
enhancement of the strength below MeV first discovered by the
Oslo method in iron and molybdenum isotopes.Comment: 7 pages, 5 figure
Relativistic electronic dressing in laser-assisted ionization of atomic hydrogen by electron impact
Within the framework of the coplanar binary geometry where it is justified to
use plane wave solutions for the study of the reaction and in the
presence of a circularly polarized laser field, we introduce as a first step
the DVRPWBA1 (Dirac-Volkov Plane Wave Born Approximation1) where we take into
account only the relativistic dressing of the incident and scattered electrons.
Then, we introduce the DVRPWBA2 (Dirac-Volkov Plane Wave Born Approximation2)
where we take totally into account the relativistic dressing of the incident,
scattered and ejected electrons. We then compare the corresponding triple
differential cross sections for laser-assisted ionization of atomic hydrogen by
electron impact both for the non relativistic and the relativistic regime.Comment: 18 pages, Latex, 7 figure
Density Functional Theory for the Photoionization Dynamics of Uracil
Photoionization dynamics of the RNA base Uracil is studied in the framework
of Density Functional Theory (DFT). The photoionization calculations take
advantage of a newly developed parallel version of a multicentric approach to
the calculation of the electronic continuum spectrum which uses a set of
B-spline radial basis functions and a Kohn-Sham density functional hamiltonian.
Both valence and core ionizations are considered. Scattering resonances in
selected single-particle ionization channels are classified by the symmetry of
the resonant state and the peak energy position in the photoelectron kinetic
energy scale; the present results highlight once more the site specificity of
core ionization processes. We further suggest that the resonant structures
previously characterized in low-energy electron collision experiments are
partly shifted below threshold by the photoionization processes. A critical
evaluation of the theoretical results providing a guide for future experimental
work on similar biosystems
Heteronuclear ionizing collisions between laser-cooled metastable helium atoms
We have investigated cold ionizing heteronuclear collisions in dilute
mixtures of metastable (2 3S1) 3He and 4He atoms, extending our previous work
on the analogous homonuclear collisions [R. J. W. Stas et al., PRA 73, 032713
(2006)]. A simple theoretical model of such collisions enables us to calculate
the heteronuclear ionization rate coefficient, for our quasi-unpolarized gas,
in the absence of resonant light (T = 1.2 mK): K34(th) = 2.4*10^-10 cm^3/s.
This calculation is supported by a measurement of K34 using magneto-optically
trapped mixtures containing about 1*10^8 atoms of each species, K34(exp) =
2.5(8)*10^-10 cm^3/s. Theory and experiment show good agreement.Comment: 8 pages, 6 figure
The effects of charge transfer inefficiency (CTI) on galaxy shape measurements
(Abridged) We examine the effects of charge transfer inefficiency (CTI)
during CCD readout on galaxy shape measurements required by studies of weak
gravitational lensing. We simulate a CCD readout with CTI such as that caused
by charged particle radiation damage. We verify our simulations on data from
laboratory-irradiated CCDs. Only charge traps with time constants of the same
order as the time between row transfers during readout affect galaxy shape
measurements. We characterize the effects of CTI on various galaxy populations.
We baseline our study around p-channel CCDs that have been shown to have charge
transfer efficiency up to an order of magnitude better than several models of
n-channel CCDs designed for space applications. We predict that for galaxies
furthest from the readout registers, bias in the measurement of galaxy shapes,
Delta(e), will increase at a rate of 2.65 +/- 0.02 x 10^(-4) per year at L2 for
accumulated radiation exposure averaged over the solar cycle. If uncorrected,
this will consume the entire shape measurement error budget of a dark energy
mission within about 4 years. Software mitigation techniques demonstrated
elsewhere can reduce this by a factor of ~10, bringing the effect well below
mission requirements. CCDs with higher CTI than the ones we studeied may not
meet the requirements of future dark energy missions. We discuss ways in which
hardware could be designed to further minimize the impact of CTI.Comment: 11 pages, 6 figures, and 2 tables. Accepted for publication in PAS
Transnational social capital: the socio‐spatialities of civil society
Civil society remains a contested concept, but one that is widely embedded in global development processes. Transnationalism within civil society scholarship is often described dichotomously, either through hierarchical dependency relations or as a more amorphous networked global civil society. These two contrasting spatial imaginaries produce very particular ideas about how transnational relations contribute to civil society. Drawing on empirical material from research with civil society organizations in Barbados and Grenada, in this article I contend that civil society groups use forms of transnational social capital in their work. This does not, however, resonate with the horizontal relations associated with grassroots globalization or vertical chains of dependence. These social relations are imbued with power and agency and are entangled in situated historical, geographical and personal contexts. I conclude that the diverse transnational social relations that are part of civil society activity offer hope and possibilities for continued civil society action in these unexpected spatial arrangements
Search for LBV Candidates in the M33 Galaxy
A total of 185 luminous blue variable (LBV) candidates with V < 18.5 and B-V
< 0.35 are selected based on the photometrical Survey of Local Group Galaxies
made by P. Massey et al. 2006. The candidates were selected using aperture
photometry of H-alpha images. The primary selection criterion is that the
prospective candidate should be a blue star with H-aplha emission. In order not
to miss appreciably reddened LBV candidates, we compose an additional list of
25 presumably reddened (0.35 < B-V < 1.2, V < 18.5) emission star candidates. A
comparison with the list of known variables in the M33 galaxy showed 29% of our
selected candidates to be photometrically variable. We also find our list to
agree well with the lists of emission-line objects obtained in earlier papers
using different methods.Comment: 6 figure
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