Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes

Numerical Cherenkov radiation (NCR) or instability is a detrimental effect frequently found in electromagnetic particle-in-cell (EM-PIC) simulations involving relativistic plasma beams. NCR is caused by spurious coupling between electromagnetic-field modes and multiple beam resonances. This coupling may result from the slow down of poorly-resolved waves due to numerical (grid) dispersion and from aliasing mechanisms. NCR has been studied in the past for finite-difference-based EM-PIC algorithms on regular (structured) meshes with rectangular elements. In this work, we extend the analysis of NCR to finite-element-based EM-PIC algorithms implemented on unstructured meshes. The influence of different mesh element shapes and mesh layouts on NCR is studied. Analytic predictions are compared against results from finite-element-based EM-PIC simulations of relativistic plasma beams on various mesh types.Comment: 31 pages, 20 figure

Irrigação e fertirrigação na cultura do maracujá.

Métodos e sistemas de irrigação; Necessidades hídricas da cultura; Exigências nutricionais; Necessidades de nutrientes para fertirrigação; Marcha de absorção de nutrientes; Cálculo da necessidade de fertilizante; Cálculo da solução fertilizante

Two Superconducting Phases in CeRh_1-xIr_xIn_5

Pressure studies of CeRh_1-xIr_xIn_5 indicate two superconducting phases as a function of x, one with T_c >= 2 K for x < 0.9 and the other with T_c < 1.2 K for x > 0.9. The higher T_c phase, phase-1, emerges in proximity to an antiferromagnetic quantum-critical point; whereas, Cooper pairing in the lower T_c phase-2 is inferred to arise from fluctuations of a yet to be found magnetic state. The T-x-P phase diagram of CeRh_1-xIr_xIn_5, though qualitatively similar, is distinctly different from that of CeCu_2(Si_1-xGe_x)_2.Comment: 5 pages, 3 figure

Acute Cervical Epidural Hematoma: Case Report.

A 74 year-old patient with a nocturnal onset of neck and chest pain was brought to an emergency clinic. Physical examination and cardiac assessment were normal. Three hours after the addmittance, a flaccid paralysis of the four limbs supervened. Suspecting of an unusual onset of central nervous system infection, a lumbar puncture was performed, yielding 20 ml of normal cerebrospinal fluid. Thirty oinutes after the puncture, the patient completely regained neurological funcion. He was then referred to a General Hospital where a computed tomography (CT) scan was done showing a large cervical epidural bleeding in the posterolateral region of C4/C5 extending to C7/Th1, along with a C6 vertebral body hemangioma. A magnetic resonance imaging revealed the same CT findings. A normal selective angiography of vertebral arteries, carotid arteries and thyreocervical trunk was carried out. Spontaneous spinal epidural hematoma (ASSEH) is a rare but dramatic cause of neurological impairment. In this article we report a fortunate case of complete recovery after an unusual spine cord decompression. We also review the current literature concerning diagnosis and treatment of ASSEH.58726-3

Finite Element Time-Domain Body-of-Revolution Maxwell Solver based on Discrete Exterior Calculus

We present a finite-element time-domain (FETD) Maxwell solver for the analysis of body-of-revolution (BOR) geometries based on discrete exterior calculus (DEC) of differential forms and transformation optics (TO) concepts. We explore TO principles to map the original 3-D BOR problem to a 2-D one in the meridian plane based on a Cartesian coordinate system where the cylindrical metric is fully embedded into the constitutive properties of an effective inhomogeneous and anisotropic medium that fills the domain. The proposed solver uses a TE/TM field decomposition and an appropriate set of DEC-based basis functions on an irregular grid discretizing the meridian plane. A symplectic time discretization based on a leap-frog scheme is applied to obtain the full-discrete marching-on-time algorithm. We validate the algorithm by comparing the numerical results against analytical solutions for resonant fields in cylindrical cavities and against pseudo-analytical solutions for fields radiated by cylindrically symmetric antennas in layered media. We also illustrate the application of the algorithm for a particle-in-cell (PIC) simulation of beam-wave interactions inside a high-power backward-wave oscillator.Comment: 42 pages, 19 figure

Sequenciação Total do Genoma no Instituto Ricardo Jorge: um virar de página na Microbiologia Clínica

comunicação oral, CO5Esta comunicação tem como objectivo divulgar à comunidade médico-científica o impacto significativo que a WGS, agora disponível no Instituto Nacional de Saúde Doutor Ricardo Jorge (INSA), terá em termos de Microbiologia Clínica.N/

Measurements and analysis of the upper critical field Hc2H_{c2} on an underdoped and overdoped La2−xSrxCuO4La_{2-x}Sr_xCuO_4 compounds

The upper critical field $H_{c2}$ is one of the many non conventional properties of high-$T_c$ cuprates. It is possible that the $H_{c2}(T)$ anomalies are due to the presence of inhomogeneities in the local charge carrier density $\rho$ of the $CuO_2$ planes. In order to study this point, we have prepared good quality samples of polycrystalline $La_{2-x}Sr_xCuO_{4}$ using the wet-chemical method, which has demonstrated to produce samples with a better cation distribution. In particular, we have studied the temperature dependence of the second critical field, $H_{c2}(T)$, through the magnetization measurements on two samples with opposite average carrier concentration ($\rho_m=x$) and nearly the same critical temperature, namely $\rho_m = 0.08$ (underdoped) and $\rho_m = 0.25$ (overdoped). The results close to $T_c$ do not follow the usual Ginzburg-Landau theory and are interpreted by a theory which takes into account the influence of the inhomogeneities.Comment: Published versio