22,899 research outputs found
Absorbable-susceptor joining of ceramic surfaces
An assembly of ceramic surfaces particularly refractory metal oxides and carbides, abutting a thin sheet of metal susceptor material are placed in a chamber of an enclosure containing inert gas. An RF coil is activated by power supply to melt the susceptor and adjacent zones of the ceramic. Reactive gas such as oxygen or a carbonizing gas is then fed to the chamber and reacts with the susceptor to form compounds which disperse and dissolve in the zones. On cooling, a strong joint is formed. The susceptor may contain inner perforations and outer perforations to aid in distribution of heat
Experimental studies of Strong Electroweak Symmetry Breaking in gauge boson scattering and three gauge boson production
If no light Higgs boson exist, the interaction among the gauge bosons becomes
strong at high energies (~1TeV). The effects of strong electroweak symmetry
breaking (SEWSB) could manifest themselves as anomalous couplings before they
give rise to new physical states, thus measurement of all couplings and their
possible deviation from Standard Model (SM) values could give valuable
information for understanding the true nature of symmetry breaking sector. Here
we present a detailed study of the measurement of quartic gauge couplings in
weak boson scattering processes and a possibility for same measurement in
triple weak boson production. Expected limits on the parameters alpha_4
alpha_5,alpha_6, alpha_7 and alpha_10 in electroweak chiral Lagrangian are
given.Comment: talk presented at LCWS05, Stanford, USA, March 200
A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: Hipparcos-Tycho cool stars
The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is
indicative of very energetic, transient phenomena, associated with energy
release via magnetic reconnection. We present a uniform, large-scale survey of
X-ray flare emission. The XMM-Newton Serendipitous Source Catalogue and its
associated data products provide an excellent basis for a comprehensive and
sensitive survey of stellar flares - both from targeted active stars and from
those observed serendipitously in the half-degree diameter field-of-view of
each observation. The 2XMM Catalogue and the associated time-series
(`light-curve') data products have been used as the basis for a survey of X-ray
flares from cool stars in the Hipparcos Tycho-2 catalogue. In addition, we have
generated and analysed spectrally-resolved (i.e. hardness-ratio), X-ray
light-curves. Where available, we have compared XMM OM UV/optical data with the
X-ray light-curves. Our sample contains ~130 flares with well-observed
profiles; they originate from ~70 stars. The flares range in duration from ~1e3
to ~1e4 s, have peak X-ray fluxes from ~1e-13 to ~1e-11 erg/cm2/s, peak X-ray
luminosities from ~1e29 to ~1e32 erg/s, and X-ray energy output from ~1e32 to
~1e35 erg. Most of the ~30 serendipitously-observed stars have little
previously reported information. The hardness-ratio plots clearly illustrate
the spectral (and hence inferred temperature) variations characteristic of many
flares, and provide an easily accessible overview of the data. We present flare
frequency distributions from both target and serendipitous observations. The
latter provide an unbiased (with respect to stellar activity) study of flare
energetics; in addition, they allow us to predict numbers of stellar flares
that may be detected in future X-ray wide-field surveys. The serendipitous
sample demonstrates the need for care when calculating flaring rates.Comment: 26 pages, 24 figures. Additional tables and figures available as 4
ancillary files. To be published in Astronomy and Astrophysic
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Urban Fathers Asset Building – Final Report
The Urban Fathers Asset Building (UFAB) project demonstrated the potential benefits, as well as limitations, of an innovative nexus between the child support system, fatherhood programs, and the Assets for Independence (AFI) grant-funded services. UFAB was a collaborative initiative of the Texas Office of the Attorney General (OAG), Baylor College of Medicine’s Teen Health Clinic, Covenant Community Capital Corporation (the local AFI grantee), and RAISE Texas, the statewide association of AFI grantees. This Final Report summarizes UFAB’s operational features and outcomes; depicts the demonstration’s challenges and innovative responses; reviews the accomplishments of the ancillary projects supported by BAFF funds; and assesses the prospects for sustaining demonstration practices in the Houston area, as well as extending promising practices to other areas of the state.Texas Office of the Attorney GeneralRay Marshall Center for the Study of Human Resource
Electromagnetic cascade in high energy electron, positron, and photon interactions with intense laser pulses
The interaction of high energy electrons, positrons, and photons with intense
laser pulses is studied in head-on collision geometry. It is shown that
electrons and/or positrons undergo a cascade-type process involving multiple
emissions of photons. These photons can consequently convert into
electron-positron pairs. As a result charged particles quickly lose their
energy developing an exponentially decaying energy distribution, which
suppresses the emission of high energy photons, thus reducing the number of
electron-positron pairs being generated. Therefore, this type of interaction
suppresses the development of the electromagnetic avalanche-type discharge,
i.e., the exponential growth of the number of electrons, positrons, and photons
does not occur in the course of interaction. The suppression will occur when 3D
effects can be neglected in the transverse particle orbits, i.e., for
sufficiently broad laser pulses with intensities that are not too extreme. The
final distributions of electrons, positrons, and photons are calculated for the
case of a high energy e-beam interacting with a counter-streaming, short
intense laser pulse. The energy loss of the e-beam, which requires a
self-consistent quantum description, plays an important role in this process,
as well as provides a clear experimental observable for the transition from the
classical to quantum regime of interaction.Comment: 13 pages, 7 figure
On the t-Term Rank of a Matrix
For t a positive integer, the t-term rank of a (0,1)-matrix A is defined to
be the largest number of 1s in A with at most one 1 in each column and at most
t 1s in each row. Thus the 1-term rank is the ordinary term rank. We generalize
some basic results for the term rank to the t-term rank, including a formula
for the maximum term rank over a nonempty class of (0,1)-matrices with the the
same row sum and column sum vectors. We also show the surprising result that in
such a class there exists a matrix which realizes all of the maximum terms
ranks between 1 and t.Comment: 18 page
Quantum stabilization of Z-strings, a status report on D=3+1 dimensions
We investigate an extension to the phase shift formalism for calculating
one-loop determinants. This extension is motivated by requirements of the
computation of Z-string quantum energies in D=3+1 dimensions. A subtlety that
seems to imply that the vacuum polarization diagram in this formalism is
(erroneously) finite is thoroughly investigated.Comment: Based on talk by O.S. at QFEXT07, Leipzig Sept. 2007. 8 page
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