10,225 research outputs found
Searches For New Bosons Coupling To e-q Pairs At HERA And Other Colliders
The early observation at HERA of an excess of events compared to the
expectation from the Standard Model in very short distance
deep-inelastic scattering processes has renewed the interest in the search for
new physics which could manifest in electroweak-like interactions. New
preliminary results from the H1 and ZEUS experiments making use of all
available data are reviewed here, with an emphasis on the search for new
bosons possessing Yukawa couplings to lepton-quark pairs. The sensitivity of
HERA to leptoquarks, and to squarks of R-parity violating supersymmetry, is
confronted to existing indirect constraints from rare and forbidden
semi-leptonic decays, atomic parity violation and neutrinoless double-beta
decay, as well as to direct constraints from LEP and Tevatron colliders. The
HERA and Tevatron colliders are found to offer exciting prospects for new
physics, accessing yet unexplored domains of the mass-coupling plane. Possible
striking manifestation of explicit lepton flavour violation is also discussed.Comment: 27 pages, 16 figures. Proceedings of the WEIN'98 Symposium (June
1998
Search for Particles and Forces Beyond the Standard Model at HERA ep and Tevatron p\bar{p} Colliders
A review of searches for physics beyond the Standard Model carried out at
high energy lepton-hadron and hadron-hadron facilities is presented, with
emphasis on topics of interest for future data taking at the upgraded Tevatron
and HERA colliders. The status and discovery prospects are
discussed for leptoquarks, Technicolour and supersymmetry, forbidden lepton and
quark flavour-changing processes, extra gauge bosons, excited states of
composite fermions, generic contact interactions and extra compactified
dimensions.Comment: 64 pages, 34 figures, submitted for publication in "Progress in
Particle and Nuclear Physics
High-speed fluorescent thermal imaging of quench propagation in high temperature superconductor tapes
Fluorescent Microthermographic Imaging, a method using rare-earth fluorescent
coatings with temperature-dependent light emission, was used for quench
investigation in high temperature superconductors (HTS). A fluorophore was
embedded in a polymer matrix and used as a coating on top of an HTS tape, while
being excited with UV light and recorded with a high-speed camera.
Simultaneously, the tape was pulsed with high amplitude, short duration DC
current, and brought to quench with the help of a localized defect. The joule
heating during a quench influences the fluorescent light intensity emitted from
the coating, and by recording the local variations in this intensity over time,
the heating of the tape can be visualized and the developed temperatures can be
calculated. In this paper, the fluorophore Europium
tris[3-(trifluoromethylhydroxymethylene)- (+)-camphorate] (EuTFC) provided
sufficient temperature sensitivity and a usable temperature range from 77 K to
260 K. With the help of high-speed recordings, the normal zone development was
imaged in a 20 \mu m copper stabilized HTS tape held in a liquid nitrogen bath,
and using a calibration curve, the temperatures reached during the quench have
been calculated
Identifying Barriers and Supports to Breastfeeding in the Workplace Experienced by Mothers in the New Hampshire Special Supplemental Nutrition Program for Women, Infants, and Children Utilizing the Total Worker Health Framework
Variations in the barriers and contributors to breastfeeding across industries have not been well characterized for vulnerable populations such as mothers participating in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Our study used the Total Worker Health Framework to characterize workplace factors acting as barriers and/or contributors to breastfeeding among women participating in the New Hampshire WIC. Surveys were collected from WIC mothers (n = 682), which asked about employment, industry, and workplace accommodation and supports related to breastfeeding in the workplace. We found workplace policy factors supporting breastfeeding (i.e., having paid maternity leave, other maternity leave, and a breastfeeding policy) varied by industry. Women in specific service-oriented industries (i.e., accommodation and retail) reported the lowest rates of breastfeeding initiation and workplace supports for breastfeeding and pumping. Further, how a woman hoped to feed and having a private pumping space at work were significantly associated with industry, breastfeeding initiation, and breastfeeding duration. A substantial portion of women reported being not sure about their workplace environment, policies, and culture related to breastfeeding. Additional studies with larger sample sizes of women participating in WIC are needed to further characterize the barriers to breastfeeding associated with specific industries
Self-consistent Modeling of the of HTS Devices: How Accurate do Models Really Need to Be?
Numerical models for computing the effective critical current of devices made
of HTS tapes require the knowledge of the Jc(B,theta) dependence, i.e. of the
way the critical current density Jc depends on the magnetic flux density B and
its orientation theta with respect to the tape. In this paper we present a
numerical model based on the critical state with angular field dependence of Jc
to extract the Jc(B,theta) relation from experimental data. The model takes
into account the self-field created by the tape, which gives an important
contribution when the field applied in the experiments is low. The same model
can also be used to compute the effective critical current of devices composed
of electromagnetically interacting tapes. Three examples are considered here:
two differently current rated Roebel cables composed of REBCO coated conductors
and a power cable prototype composed of Bi-2223 tapes. The critical currents
computed with the numerical model show good agreement with the measured ones.
The simulations reveal also that several parameter sets in the Jc(B,theta) give
an equally good representation of the experimental characterization of the
tapes and that the measured Ic values of cables are subjected to the influence
of experimental conditions, such as Ic degradation due to the manufacturing and
assembling process and non-uniformity of the tape properties. These two aspects
make the determination of a very precise Jc(B,theta) expression probably
unnecessary, as long as that expression is able to reproduce the main features
of the angular dependence. The easiness of use of this model, which can be
straightforwardly implemented in finite-element programs able to solve static
electromagnetic problems, is very attractive both for researchers and devices
manufactures who want to characterize superconducting tapes and calculate the
effective critical current of superconducting devices
Fluorescent thermal imaging of a non-insulated pancake coil wound from high temperature superconductor tape
We have wound a 157-turn, non-insulated pancake coil with an outer diameter
of 85 mm and we cooled it down to 77 K with a combination of conduction and gas
cooling. Using high-speed fluorescent thermal imaging in combination with
electrical measurements we have investigated the coil under load, including
various ramping tests and over-current experiments. We have found found that
the coil does not heat up measurably when being ramped to below its critical
current. Two over-current experiments are presented, where in one case the coil
recovered by itself and in another case a thermal runaway occurred. We have
recorded heating in the bulk of the windings due to local defects, however the
coil remained cryostable even during some over-critical conditions and heated
only to about 82-85 K at certain positions. A thermal runaway was observed at
the center, where the highest magnetic field and a resistive joint create a
natural defect. The maximum temperature, ~100 K, was reached only in the few
innermost windings around the coil former
Perspectives: Les animaux dans l’oeuvre romanesque : l’exemple de Kamouraska
Le bestiaire d’Anne Hébert est considérable. Dans les nouvelles et les romans, on relève
près de 200 occurrences d’animaux particuliers, auxquelles s’ajoutent une cinquantaine de
désignations génériques. Parmi les espèces les plus fréquentes, on remarque le cheval, le chat,
le chien, le corbeau, le coq, qui revêtent souvent un sens symbolique. Le présent article s’intéresse
à l’exemple de Kamouraska et montre comment les animaux participent à la progression
narrative et contribuent au sens de ce roman
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