Oxygen clamps in gold nanowires

We investigate how the insertion of an oxygen atom in an atomically thin gold nanowire can affect its rupture. We find, using ab initio total energy density functional theory calculations, that O atoms when inserted in gold nanowires form not only stable but also very strong bonds, in such a way that they can extract atoms from a stable tip, serving in this way as a clamp that could be used to pull a string of gold atoms.Comment: 4 pages; 4 figure

The Superconducting Toroid for the New International AXion Observatory (IAXO)

IAXO, the new International AXion Observatory, will feature the most ambitious detector for solar axions to date. Axions are hypothetical particles which were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. This detector aims at achieving a sensitivity to the coupling between axions and photons of one order of magnitude beyond the limits of the current detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap toroids, a large superconducting toroid is being designed. The toroid comprises eight, one meter wide and twenty one meters long racetrack coils. The assembled toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250 tons. The useful field in the bores is 2.5 T while the peak magnetic field in the windings is 5.4 T. At the operational current of 12 kA the stored energy is 500 MJ. The racetrack type of coils are wound with a reinforced Aluminum stabilized NbTi/Cu cable and are conduction cooled. The coils optimization is shortly described as well as new concepts for cryostat, cold mass, supporting structure and the sun tracking system. Materials selection and sizing, conductor, thermal loads, the cryogenics system and the electrical system are described. Lastly, quench simulations are reported to demonstrate the system's safe quench protection scheme.Comment: To appear in IEEE Trans. Appl. Supercond. MT 23 issue. arXiv admin note: substantial text overlap with arXiv:1308.2526, arXiv:1212.463

New Superconducting Toroidal Magnet System for IAXO, the International AXion Observatory

Axions are hypothetical particles that were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. The new International AXion Observatory (IAXO) will incorporate the most promising solar axions detector to date, which is designed to enhance the sensitivity to the axion-photon coupling by one order of magnitude beyond the limits of the current state-of-the-art detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions into X-ray photons. Inspired by the successful realization of the ATLAS barrel and end-cap toroids, a very large superconducting toroid is currently designed at CERN to provide the required magnetic field. This toroid will comprise eight, one meter wide and twenty one meter long, racetrack coils. The system is sized 5.2 m in diameter and 25 m in length. Its peak magnetic field is 5.4 T with a stored energy of 500 MJ. The magnetic field optimization process to arrive at maximum detector yield is described. In addition, materials selection and their structure and sizing has been determined by force and stress calculations. Thermal loads are estimated to size the necessary cryogenic power and the concept of a forced flow supercritical helium based cryogenic system is given. A quench simulation confirmed the quench protection scheme.Comment: Accepted for publication in Adv. Cryo. Eng. (CEC/ICMC 2013 special issue

Collider limits on new physics within micrOMEGAs4.3

Results from the LHC put severe constraints on models of new physics. This includes constraints on the Higgs sector from the precise measurement of the mass and couplings of the 125GeV Higgs boson, as well as limits from searches for other new particles. We present the procedure to use these constraints in micrOMEGAs by interfacing it to the external codes Lilith, HiggsSignals, HiggsBounds and SModelS. A few dedicated modules are also provided. With these new features, micrOMEGAs_4.3 provides a generic framework for evaluating dark matter observables together with collider and non-collider constraints.Comment: 23 page

EFFECTS OF WHOLE-BODY VIBRATION OVER DELAYED-ONSET MUSCLE SORENESS IN PHYSICAL ACTIVE PERSONS

The aim of this study was to investigate the effects of vibratory platform upon delayed-onset muscle soreness in physically active persons. 24 volunteers were recruited and randomly divided in 3 different groups: control, vibratory platform before exercise, vibratory platform after exercise. Volunteers were submitted to physical training to induce muscle pain. Pain sensation and muscular flexibility were valued in 3 consecutive days. Vibratory platform was able to reduce significantly muscle pain in both platform groups and there were no changes in muscular flexibility in any group.   Article visualizations

Temperature dependence of antiferromagnetic susceptibility in ferritin

We show that antiferromagnetic susceptibility in ferritin increases with temperature between 4.2 K and 180 K (i. e. below the N\'{e}el temperature) when taken as the derivative of the magnetization at high fields ($30\times10^4$ Oe). This behavior contrasts with the decrease in temperature previously found, where the susceptibility was determined at lower fields ($5\times10^4$ Oe). At high fields (up to $50 \times10^4$ Oe) the temperature dependence of the antiferromagnetic susceptibility in ferritin nanoparticles approaches the normal behavior of bulk antiferromagnets and nanoparticles considering superantiferromagnetism, this latter leading to a better agreement at high field and low temperature. The contrast with the previous results is due to the insufficient field range used ($< 5 \times10^4$ Oe), not enough to saturate the ferritin uncompensated moment.Comment: 7 pages, 7 figures, accepted in Phys. Rev.

Design Evolution and Properties of Superconducting Parallel-Bar rf-Dipole Detecting and Crabbing Cavities

Deflecting/crabbing cavities serve a variety of purposes in different accelerator applications, primarily in separating a single beam into multiple beams and in rotating bunches for head-on collisions at the interaction point in particle colliders. Deflecting/crabbing cavities are also used for transverse and longitudinal emittance exchange in beams, x-ray pulse compression, and for beam diagnostics. Compact superconducting deflecting/crabbing cavities are under development due to strict dimensional constraints and requirements for higher field gradients with low surface losses. The TEM-like superconducting parallel-bar cavity supports low operating frequencies, thus making the design favorable for many of the deflecting/crabbing cavity applications. The design of the parallel-bar cavity based on cylindrical straight loading elements and rectangular outer conductors has evolved and been adapted to improve the design properties by modifying the design geometry. The improved design with trapezoidal-shaped loading elements and cylindrical outer conductor has attractive properties such as low and well-balanced peak surface fields and high transverse shunt impedance. Additionally, the wide separation of modes in the higher-order mode spectrum and the absence of lower-order mode are advantageous in high current applications. The evolution of the parallel-bar geometry into an rf-dipole geometry is presented with a detailed analysis of the properties for each design

Multipole Field Effects for the Superconducting Parallel-Bar/RF-Dipole Deflecting/Crabbing Cavities

The superconducting parallel-bar deflecting/crabbing cavity is currently being considered as one of the design options in rf separation for the Jefferson Lab 12 GeV upgrade and for the crabbing cavity for the proposed LHC luminosity upgrade. Knowledge of multipole field effects is important for accurate beam dynamics study of rf structures. The multipole components can be accurately determined numerically using the electromagnetic surface field data in the rf structure. This paper discusses the detailed analysis of those components for the fundamental deflecting/crabbing mode and higher order modes in the parallel-bar deflecting/crabbing cavity

Calagem e adubação da laranjeira no estado de Sergipe.

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