A High Luminosity e+e- Collider to study the Higgs Boson

A strong candidate for the Standard Model Scalar boson, H(126), has been discovered by the Large Hadron Collider (LHC) experiments. In order to study this fundamental particle with unprecedented precision, and to perform precision tests of the closure of the Standard Model, we investigate the possibilities offered by An e+e- storage ring collider. We use a design inspired by the B-factories, taking into account the performance achieved at LEP2, and imposing a synchrotron radiation power limit of 100 MW. At the most relevant centre-of-mass energy of 240 GeV, near-constant luminosities of 10^34 cm^{-2}s^{-1} are possible in up to four collision points for a ring of 27km circumference. The achievable luminosity increases with the bending radius, and for 80km circumference, a luminosity of 5 10^34 cm^{-2}s^{-1} in four collision points appears feasible. Beamstrahlung becomes relevant at these high luminosities, leading to a design requirement of large momentum acceptance both in the accelerating system and in the optics. The larger machine could reach the top quark threshold, would yield luminosities per interaction point of 10^36 cm^{-2}s^{-1} at the Z pole (91 GeV) and 2 10^35 cm^{-2}s^{-1} at the W pair production threshold (80 GeV per beam). The energy spread is reduced in the larger ring with respect to what is was at LEP, giving confidence that beam polarization for energy calibration purposes should be available up to the W pair threshold. The capabilities in term of physics performance are outlined.Comment: Submitted to the European Strategy Preparatory Group 01-04-2013 new version as re-submitted to PRSTA

Controlling Window Protocols for Time-Constrained Communication in a Multiple Access Environment

For many time-constrained communication applications, such as packetized voice, a critical performance measure is the percentage of messages which are transmitted within a given amount of time after their arrival at a sending station. We examine the use of a group random access protocol based on time windows for achieving time-constrained communication in a multiple access environment. First, we formulate a policy for controlling protocol operation in order to minimize the percentage of messages with waiting times greater than some given bound. A semi-Markov decision model is then developed for protocol operation and three of the four optimal control elements of this policy are then determined. Although the semi-Markov decision model can also be used to obtain performance results, the procedure is too computationally expensive to be of practical use. Thus, an alternate performance model based on a centralized queueing system with impatient customers is developed. Protocol performance under the optimal elements of the control policy shows significant improvements over cases in which the protocol is not controlled in this manner. Simulation results are also presented to corroborate the analytic results

Production of w's and study of deep inelastic reactions by very high energy neutrinos

A spark chamber and scintillation counter experiment using very high energy neutrinos is proposed using a total of 2 x 10{sup 18} protons at 500 GeV in Area 1 at NAL. The purposes are simultaneously (1) to search for {nu} + Z {yields} Z + {mu}{sup -} + W{sup +}; W{sup +} {yields} {mu}{sup +}{nu}, e{sup +}{nu}, and various hadron decay modes, (2) to analyze {nu} + A {yields} {mu}{sup -} + {Gamma} ({Gamma} = hadronic products) for large energy and momentum transfers and (3) to search with an unrestricted trigger and good analyzing power for low cross section or exotic reactions in this new energy region

Three-dimensional structure of β-cell-specific zinc transporter, ZnT-8, predicted from the type 2 diabetes-associated gene variant SLC30A8 R325W

<p>Abstract</p> <p>Background</p> <p>We examined the effects of the R325W mutation on the three-dimensional (3D) structure of the β-cell-specific Zn²⁺(zinc) transporter ZnT-8.</p> <p>Methods</p> <p>A model of the C-terminal domain of the human ZnT-8 protein was generated by homology modeling based on the known crystal structure of the <it>Escherichia coli </it>(<it>E. coli</it>) zinc transporter YiiP at 3.8 Å resolution.</p> <p>Results</p> <p>The homodimer ZnT-8 protein structure exists as a Y-shaped architecture with Arg325 located at the ultimate bottom of this motif at approximately 13.5 Å from the transmembrane domain juncture. The C-terminal domain sequences of the human ZnT-8 protein and the <it>E. coli </it>zinc transporter YiiP share 12.3% identical and 39.5% homologous residues resulting in an overall homology of 51.8%. Validation statistics of the homology model showed a reasonable quality of the model. The C-terminal domain exhibited an αββαβ fold with Arg325 as the penultimate N-terminal residue of the α2-helix. The side chains of both Arg325 and Trp325 point away from the interface with the other monomer, whereas the ε-NH₃⁺group of Arg325 is predicted to form an ionic interaction with the β-COO^-group of Asp326 as well as Asp295. An amino acid alignment of the β2-α2 C-terminal loop domain revealed a variety of neutral amino acids at position 325 of different ZnT-8 proteins.</p> <p>Conclusions</p> <p>Our validated homology models predict that both Arg325 and Trp325, amino acids with a helix-forming behavior, and penultimate N-terminal residues in the α2-helix of the C-terminal domain, are shielded by the planar surface of the three cytoplasmic β-strands and hence unable to affect the sensing capacity of the C-terminal domain. Moreover, the amino acid residue at position 325 is too far removed from the docking and transporter parts of ZnT-8 to affect their local protein conformations. These data indicate that the inherited R325W abnormality in SLC30A8 may be tolerated and results in adequate zinc transfer to the correct sites in the pancreatic islet cells and are consistent with the observation that the <it>SLC30A8 </it>gene variant R325W has a low predicted value for future type 2 diabetes at population-based level.</p

First superburst from a classical low-mass X-ray binary transient

We report the analysis of the first superburst from a transiently accreting neutron star system with the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer. The superburst occurred 55 days after the onset of an accretion outburst in 4U 1608-522. During that time interval, the accretion rate was at least 7% of the Eddington limit. The peak flux of the superburst is 22 to 45% of the Eddington limit, and its radiation energy output is between 4e41 and 9e41 erg for a distance of 3.2 kpc. Fits of cooling models to the superburst light curve indicate an ignition column depth between 1.5e12 and 4.1e12 g/cm2. Extrapolating the accretion history observed by the ASM, we derive that this column was accreted over a period of 26 to 72 years. The superburst characteristics are consistent with those seen in other superbursting low-mass X-ray binaries. However, the transient nature of the hosting binary presents significant challenges for superburst theory, requiring additional ingredients for the models. The carbon that fuels the superburst is thought to be produced mostly during the accretion outbursts and destroyed in the frequent type-I X-ray bursts. Mixing and sedimentation of the elements in the neutron star envelope may significantly influence the balance between the creation and destruction of carbon. Furthermore, predictions for the temperature of the neutron star crust fail to reach the values required for the ignition of carbon at the inferred column depth.Comment: 12 pages, 8 figures, accepted for publication in A&

Comparative analysis of genome-wide association studies signals for lipids, diabetes, and coronary heart disease: Cardiovascular Biomarker Genetics Collaboration

To evaluate the associations of emergent genome-wide-association study-derived coronary heart disease (CHD)-associated single nucleotide polymorphisms (SNPs) with established and emerging risk factors, and the association of genome-wide-association study-derived lipid-associated SNPs with other risk factors and CHD events