37,031 research outputs found
Beyond the Standard Model for Montaneros
These notes cover (i) electroweak symmetry breaking in the Standard Model
(SM) and the Higgs boson, (ii) alternatives to the SM Higgs boson including an
introduction to composite Higgs models and Higgsless models that invoke extra
dimensions, (iii) the theory and phenomenology of supersymmetry, and (iv)
various further beyond topics, including Grand Unification, proton decay and
neutrino masses, supergravity, superstrings and extra dimensions.Comment: Based on lectures by John Ellis at the 5th CERN-Latin-American School
of High-Energy Physics, Recinto Quirama, Colombia, 15 - 28 Mar 2009, 84
pages, 35 figure
Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning
A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range
Design and fabrication of a radiative actively cooled honeycomb sandwich structural panel for a hypersonic aircraft
The panel assembly consisted of an external thermal protection system (metallic heat shields and insulation blankets) and an aluminum honeycomb structure. The structure was cooled to temperature 442K (300 F) by circulating a 60/40 mass solution of ethylene glycol and water through dee shaped coolant tubes nested in the honeycomb and adhesively bonded to the outer skin. Rene'41 heat shields were designed to sustain 5000 cycles of a uniform pressure of + or - 6.89kPa (+ or - 1.0 psi) and aerodynamic heating conditions equivalent to 136 kW sq m (12 Btu sq ft sec) to a 422K (300 F) surface temperature. High temperature flexible insulation blankets were encased in stainless steel foil to protect them from moisture and other potential contaminates. The aluminum actively cooled honeycomb sandwich structural panel was designed to sustain 5000 cycles of cyclic in-plane loading of + or - 210 kN/m (+ or - 1200 lbf/in.) combined with a uniform panel pressure of + or - 6.89 kPa (?1.0 psi)
Graphite/copper alloy interfacial energies determined using the sessile drop method
Graphite surfaces are not wet by pure copper. This lack of wetting is responsible for a debonding phenomenon that was found in continuous graphite fiber/copper matrix composites materials subjected to elevated temperatures. By suitably alloying copper, its capability to wet graphite surfaces can be enhanced. In situ measurements of graphite/copper alloy wetting angles were made using the sessile drop method. Interfacial energy values were calculated based upon these measurements
B-Meson Observables in the Maximally CP-Violating MSSM with Minimal Flavour Violation
Additional sources of CP violation in the MSSM may affect B-meson mixings and
decays, even in scenarios with minimal flavour violation (MFV). We formulate
the maximally CP-violating and minimally flavour-violating (MCPMFV) variant of
the MSSM, which has 19 parameters, including 6 phases that violate CP. We then
develop a manifestly flavour-covariant effective Lagrangian formalism for
calculating Higgs-mediated FCNC observables in the MSSM at large tan(beta), and
analyze within the MCPMFV framework FCNC and other processes involving B
mesons. We include a new class of dominant subleading contributions due to
non-decoupling effects of the third-generation quarks. We present illustrative
numerical results that include effects of the CP-odd MCPMFV parameters on Higgs
and sparticle masses, the B_s and B_d mass differences, and on the decays B_s
--> mu+ mu-, B_u --> tau nu and b --> s gamma. We use these results to derive
illustrative constraints on the MCPMFV parameters imposed by D0, CDF, BELLE and
BABAR measurements of B mesons, demonstrating how a potentially observable
contribution to the CP asymmetry in the b --> s gamma decay may arise in the
MSSM with MCPMFV.Comment: 47 pages, 8 eps figures, comments and references added, accepted for
publication in Physical Review D, Eq.(3.2) correcte
Production and processing of Cu-Cr-Nb alloys
A new Cu-based alloy possessing high strength, high conductivity, and good stability at elevated temperatures was recently produced. This paper details the melting of the master alloys, production of rapidly solidified ribbon, and processing of the ribbon to sheet by hot pressing and hot rolling
Physics opportunities with future proton accelerators at CERN
We analyze the physics opportunities that would be made possible by upgrades
of CERN's proton accelerator complex. These include the new physics possible
with luminosity or energy upgrades of the LHC, options for a possible future
neutrino complex at CERN, and opportunities in other physics including rare
kaon decays, other fixed-target experiments, nuclear physics and antiproton
physics, among other possibilities. We stress the importance of inputs from
initial LHC running and planned neutrino experiments, and summarize the
principal detector R&D issues.Comment: 39 page, word document, full resolution version available from
http://cern.ch/pofpa/POFPA-arXive.pd
Baryon Magnetic Moments and Proton Spin: A Model with Collective Quark Rotation
We analyse the baryon magnetic moments in a model that relates them to the
parton spins , , , and includes a contribution
from orbital angular momentum. The specific assumption is the existence of a
3-quark correlation (such as a flux string) that rotates with angular momentum
around the proton spin axis. A fit to the baryon magnetic
moments, constrained by the measured values of the axial vector coupling
constants , , yields , , where the error is a theoretical
estimate. A second fit, under slightly different assumptions, gives , with no constraint on . The
model provides a consistent description of axial vector couplings, magnetic
moments and the quark polarization measured in deep
inelastic scattering. The fits suggest that a significant part of the angular
momentum of the proton may reside in a collective rotation of the constituent
quarks.Comment: 16 pages, 3 ps-figures, uses RevTeX. Abstract, Sec. II, III and IV
have been expande
Kinetics and Inhibition Studies of the L205R Mutant of cAMP-Dependent Protein Kinase Involved in Cushing’s Syndrome
Overproduction of cortisol by the hypothalamus–pituitary–adrenal hormone system results in the clinical disorder known as Cushing\u27s syndrome. Genomics studies have identified a key mutation (L205R) in the α‐isoform of the catalytic subunit of cAMP‐dependent protein kinase (PKACα) in adrenal adenomas of patients with adrenocorticotropic hormone‐independent Cushing\u27s syndrome. Here, we conducted kinetics and inhibition studies on the L205R‐PKACα mutant. We have found that the L205R mutation affects the kinetics of both Kemptide and ATP as substrates, decreasing the catalytic efficiency (kcat/KM) for each substrate by 12‐fold and 4.5‐fold, respectively. We have also determined the IC50 and Ki for the peptide substrate‐competitive inhibitor PKI(5–24) and the ATP‐competitive inhibitor H89. The L205R mutation had no effect on the potency of H89, but causes a \u3e 250‐fold loss in potency for PKI(5–24). Collectively, these data provide insights for the development of L205R‐PKACα inhibitors as potential therapeutics
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