Vacuum stability with spontaneous violation of lepton number

The vacuum of the Standard Model is known to be unstable for the measured values of the top and Higgs masses. Here we show how vacuum stability can be achieved naturally if lepton number is violated spontaneously at the TeV scale. More precise Higgs measurements in the next LHC run should provide a crucial test of our symmetry breaking scenario. In addition, these schemes typically lead to enhanced rates for processes involving lepton flavour violation .Comment: 9 pages, 4+2 figures; some references added, some textual modifications: 2 figures added, appendices added. Results unchanged. Matches published versio

Impact of knee marker misplacement on gait kinematics of children with cerebral palsy using the Conventional Gait Model — a sensitivity study

Clinical gait analysis is widely used in clinical routine to assess the function of patients with motor disorders. The proper assessment of the patient’s function relies greatly on the repeatability between the measurements. Marker misplacement has been reported as the largest source of variability between measurements and its impact on kinematics is not fully understood. Thus, the purpose of this study was: 1) to evaluate the impact of the misplacement of the lateral femoral epicondyle marker on lower limb kinematics, and 2) evaluate if such impact can be predicted. The kinematic data of 10 children with cerebral palsy and 10 aged-match typical developing children were included. The lateral femoral epicondyle marker was virtually misplaced around its measured position at different magnitudes and directions. The outcome to represent the impact of each marker misplacement on the lower limb was the root mean square deviations between the resultant kinematics from each simulated misplacement and the originally calculated kinematics. Correlation and regression equations were estimated between the root mean square deviation and the magnitude of the misplacement expressed in percentage of leg length. Results indicated that the lower-limb kinematics is highly sensitive to the lateral femoral epicondyle marker misplacement in the anterior-posterior direction. The joint angles most impacted by the anterior-posterior misplacement were the hip internal-external rotation (5.3° per 10 mm), the ankle internal-external rotation (4.4° per 10 mm) and the knee flexion-extension (4.2° per 10 mm). Finally, it was observed that the lower the leg length, the higher the impact of misplacement on kinematics. This impact was predicted by regression equations using the magnitude of misplacement expressed in percentage of leg length. An error below 5° on all joints requires a marker placement repeatability under 1.2% of the leg length. In conclusion, the placement of the lateral femoral epicondyle marker in the antero-posterior direction plays a crucial role on the reliability of gait measurements with the Conventional Gait Model

Whirling Waves and the Aharonov-Bohm Effect for Relativistic Spinning Particles

The formulation of Berry for the Aharonov-Bohm effect is generalized to the relativistic regime. Then, the problem of finding the self-adjoint extensions of the (2+1)-dimensional Dirac Hamiltonian, in an Aharonov-Bohm background potential, is solved in a novel way. The same treatment also solves the problem of finding the self-adjoint extensions of the Dirac Hamiltonian in a background Aharonov-Casher

Susceptibilidade da lagarta-do-cartucho do milho, Spodoptera frugiperda, a diferentes isolados de Bacillus thuringiensis.

Este trabalho foi dividido em três bioensaios. No primeiro, usaram-se 17 subespécies do Bacillus thuringiensis, que foram testadas em larvas de Spodoptera frugiperda. As cepas foram crescidas em meio de cultura líquido enriquecido com sais. Folhas de milho foram imersas na suspensão e oferecidas a lagartas sadias de dois dias de idade. Os resultados mostraram que a maior mortalidade de larvas foi causada pelo B. thuringiensis tolworthi (T09) (95,8%) e a menor, causada pelo B. thuringiensis kurstaki (2,7%). No segundo bioensaio, o B. thuringiensis tolworthi, numa mistura liofilizada de esporo e cristal em pó, foi incorporado na dieta artificial numa concentração única de 0,8 mg da toxina por grama de dieta artificial e testado em larvas de S. frugiperda de diferentes idades. Os resultados mostraram que a mortalidade das larvas decresceu à medida em que a idade das larvas aumentou. A maior mortalidade ocorreu com larvas entre três e seis dias de idade (100%). No terceiro bioensaio, uma mistura de esporo e cristal do B. thuringiensis tolworthi, que foi diluido em suspensão aquosa em diferentes tempos de exposição (24, 48 e 72 horas), foi testado em larvas de dois dias de idade, submetidas a diferentes concentrações da toxina. A maior mortalidade de larvas ocorreu com a concentração de 500 mg da mistura de esporo e cristal diluídos em 1 ml de água, para o tempo de exposição de 72 horas. A análise de probit mostrou que a concentração letal 50 (CL50) da cepa B. thuringiensis tolworthi foi de 271,1 mg ml-1, para larvas de dois dias de idade, por um período de exposição à toxina de 72 horas. Já a cepa SA11 (B. thuringiensis kurstaki) foi avaliada separadamente e a análise de probit mostrou que a LC50 para larvas de dois dias de idade foi de apenas 57,5 µg ml-1, por um período de exposição de 72 hora

Beam loading in the nonlinear regime of plasma-based acceleration

A theory that describes how to load negative charge into a nonlinear, three-dimensional plasma wakefield is presented. In this regime, a laser or an electron beam blows out the plasma electrons and creates a nearly spherical ion channel, which is modified by the presence of the beam load. Analytical solutions for the fields and the shape of the ion channel are derived. It is shown that very high beam-loading efficiency can be achieved, while the energy spread of the bunch is conserved. The theoretical results are verified with the Particle-In-Cell code OSIRIS.Comment: 5 pages, 2 figures, to appear in Physical Review Letter

A global simulation for laser driven MeV electrons in 50μm50\mu m-diameter fast ignition targets

The results from 2.5-dimensional Particle-in-Cell simulations for the interaction of a picosecond-long ignition laser pulse with a plasma pellet of 50-$\mu m$ diameter and 40 critical density are presented. The high density pellet is surrounded by an underdense corona and is isolated by a vacuum region from the simulation box boundary. The laser pulse is shown to filament and create density channels on the laser-plasma interface. The density channels increase the laser absorption efficiency and help generate an energetic electron distribution with a large angular spread. The combined distribution of the forward-going energetic electrons and the induced return electrons is marginally unstable to the current filament instability. The ions play an important role in neutralizing the space charges induced by the the temperature disparity between different electron groups. No global coalescing of the current filaments resulted from the instability is observed, consistent with the observed large angular spread of the energetic electrons.Comment: 9 pages, 6 figures, to appear in Physics of Plasmas (May 2006

Uma tentativa de cultivo de rotavírus humano em cultura de leucócitos humano (Nota Prévia)

Experimentos preliminares da permissividade de cultura de leucócitos humanos estimulados com mitógeno frente a infecção pelo rotavirus humano foram realizados por microscopia eletrônica. Observamos que, células mo-nonucleadas, mantidas em cultura, após estimulação com fitohemaglutinina (PHA) colhidas 36 horas pós-infecção apresentavam muitas partículas virais no citoplasma. Verificamos, também, muitas partículas virais associadas a fragmentos celulares, várias células em degeneração e alguns linfócitos pequenos intactos. Não presenciamos partículas virais em células colhidas previamente (12 e 24 horas p.i.) e nas culturas controle (sem tratamento com PHA). Sugerimos que o rotavirus humano pode se replicar em culturas de leucócitos humanos estimulados com PHA