1,271 research outputs found
Modeling the effect of small-scale magnetic turbulence on the X-ray properties of Pulsar Wind Nebulae
Pulsar Wind Nebulae (PWNe) constitute an ideal astrophysical environment to
test our current understanding of relativistic plasma processes. It is well
known that magnetic fields play a crucial role in their dynamics and emission
properties. At present, one of the main issues concerns the level of magnetic
turbulence present in these systems, which in the absence of space resolved
X-ray polarization measures cannot be directly constrained. In this work we
investigate, for the first time using simulated synchrotron maps, the effect of
a small scale fluctuating component of the magnetic field on the emission
properties in X-ray. We illustrate how to include the effects of a turbulent
component in standard emission models for PWNe, and which consequences are
expected in terms of net emissivity and depolarization, showing that the X-ray
surface brightness maps can provide already some rough constraints. We then
apply our analysis to the Crab and Vela nebulae and, by comparing our model
with Chandra and Vela data, we found that the typical energies in the turbulent
component of the magnetic field are about 1.5 to 3 times the one in the ordered
field.Comment: 9 pages, 8 figures, accepted for publication in MNRA
Investigation of the Electromagnetic Radiation Emitted by Sub-GeV Electrons in a Bent Crystal
The radiation emitted by 855 MeV electrons via planar channeling and volume reflection in a 30.5-μm-thick bent Si crystal has been investigated at the MAMI (Mainzer Mikrotron) accelerator. The spectral intensity was much more intense than for an equivalent amorphous material, and peaked in the MeV range in the case of channeling radiation. Differently from a straight crystal, also for an incidence angle larger than the Lindhard angle, the spectral intensity remains nearly as high as for channeling. This is due to volume reflection, for which the intensity remains high at a large incidence angle over the whole angular acceptance, which is equal to the bending angle of the crystal. Monte Carlo simulations demonstrated that incoherent scattering significantly influences both the radiation spectrum and intensity, either for channeling or volume reflection. In the latter case, it has been shown that incoherent scattering increases the radiation intensity due to the contribution of volume-captured particles. As a consequence, the experimental spectrum becomes a mixture of channeling and pure volume reflection radiations. These results allow a better understanding of the radiation emitted by electrons subjected to coherent interactions in bent crystals within a still-unexplored energy range, which is relevant for possible applications for innovative and compact x-ray or γ-ray sources. © 2015 American Physical Society
Influence of incoherent scattering on stochastic deflection of high-energy negative particle beams in bent crystals
An investigation on stochastic deflection of high-energy negatively charged
particles in a bent crystal was carried out. On the basis of analytical
calculation and numerical simulation it was shown that it exists a maximum
angle at which most of the beam is deflected. The existence of a maximum, which
is taken in the correspondence of the optimal radius of curvature, is a novelty
with respect to the case of positively charged particles, for which the
deflection angle can be freely increased by increasing the crystal length. This
difference has to be ascribed to the stronger contribution of incoherent
scattering affecting the dynamics of negative particles that move closer to
atomic nuclei and electrons. We therefore identified the ideal parameters for
the exploitation of axial confinement for negatively charged particle beam
manipulation in future high-energy accelerators, e.g., ILC or muon colliders
Sobrecarga de pacientes en el servicio de urgencias y emergencias
Para lograr un servicio de urgencias verdaderamente eficiente son necesarias, entre otras variables, la rapidez y la calidad en la prestación del servicio. Estas variables se ven afectadas cuando hay una sobre carga de servicio, la cual consiste es un aumento notable en la cantidad de pacientes que asisten al servicio de guardia de urgencias para ser atendidos. Se observa a su vez, que las diversas afecciones por las que asisten los pacientes no entran en los parámetros de urgencias ni emergencias. Ante esta problemática se ve afectada la salud del personal de salud (médicos y enfermeros), los cuales manifiestan agotamiento físico y mental ante tal aumento de trabajo. Una de las tareas para evitar esta situación será educar a las personas con respecto a las patologías, así ellos lograran identificar cuáles son consideradas urgencias y cuáles deben ser atendidas en servicio de consultorio externo. El presente trabajo de investigación tiene como objetivo general determinar cuáles son los factores socioeconómicos y culturales que inciden en la sobrecarga de pacientes del servicio de emergencia del Centro de Salud nº101 José María Méndez, de la cuidad de La Consulta, en el departamento de San Carlos, Mendoza, en el año 2012.
Objetivos específicos: medir y cuantificar la asistencia de los pacientes a dicho servicio; identificar sobrecarga en el servicio de urgencia; identificar factores geográficos, económicos y culturales que generan un incremento de consultas en el servicio de emergencias sin ser las mismas,
verdaderas emergencias médicas; comprender modos de comportamiento y costumbres de los pacientes en el sistema de salud; identificar conocimientos de la población sobre problemas médicos de urgencias.Fil: Bandiera B., Graciana L.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Escuela de Enfermería..Fil: Garín, Belén A.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Escuela de Enfermería.
Planar channeling and quasichanneling oscillations in a bent crystal
Particles passing through a crystal under planar channeling experience
transverse oscillations in their motion. As channeled particles approach the
atomic planes of a crystal, they are likely to be dechanneled. This effect was
used in ion-beam analysis with MeV energy. We studied this effect in a bent
crystal for positive and negative particles within a wide range of energies in
sight of application of such crystals at accelerators. We found the conditions
for the appearance or not of channeling oscillations. Indeed a new kind of
oscillations, strictly related to the motion of over-barrier particles, i.e.
quasichanneling particles, has been predicted. Such oscillations, named planar
quasichanneling oscillations, possess a different nature than channeling
oscillations. Through computer simulation, we studied this effect and provided
a theoretical interpretation for them. We show that channeling oscillations can
be observed only for positive particles while quasichanneling oscillations can
exist for particles with either sign. The conditions for experimental
observation of channeling and quasichanneling oscillations at existing
accelerators with available crystal has been found and optimized.Comment: 25 pages, 11 figure
simulation code for modeling of coherent effects of radiation generation in oriented crystals
We present the crystalrad simulation code, combining all the features of the crystal simulation code for simulations of charged particles trajectories in a bent crystal and the radcharm++ code for calculation of the radiation spectrum. The crystalrad code is based on Monte Carlo simulations of trajectories in the planar and axial electric field either in a straight, bent, or periodically bent crystal taking into account multiple and single Coulomb scattering on nuclei and electrons, nuclear scattering and ionization energy losses. The trajectories simulated are used for calculation of radiation spectra by the Baier-Katkov method. We compare our simulations with experimental data taken at MAMI (MAinzer MIkrotron) as well as give an example for a possible future study with sub-GeV electrons interacting with Si bent crystals
Recovery of a medieval Brucella melitensis genome using shotgun metagenomics
Shotgun metagenomics provides a powerful assumption-free approach to the recovery of pathogen genomes from contemporary and historical material. We sequenced the metagenome of a calcified nodule from the skeleton of a 14th-century middle-aged male excavated from the medieval Sardinian settlement of Geridu. We obtained 6.5-fold coverage of a Brucella melitensis genome. Sequence reads from this genome showed signatures typical of ancient or aged DNA. Despite the relatively low coverage, we were able to use information from single-nucleotide polymorphisms to place the medieval pathogen genome within a clade of B. melitensis strains that included the well-studied Ether strain and two other recent Italian isolates. We confirmed this placement using information from deletions and IS711 insertions. We conclude that metagenomics stands ready to document past and present infections, shedding light on the emergence, evolution, and spread of microbial pathogens
Electromagnetic dipole moments of charged baryons with bent crystals at the LHC
We propose a unique program of measurements of electric and magnetic dipole
moments of charm, beauty and strange charged baryons at the LHC, based on the
phenomenon of spin precession of channeled particles in bent crystals. Studies
of crystal channeling and spin precession of positively- and negatively-charged
particles are presented, along with feasibility studies and expected
sensitivities for the proposed experiment using a layout based on the LHCb
detector.Comment: 19 pages, 13 figure
- …