Effect of Adsorbed Nitrogen on the Thermionic Emission from Lanthanum Hexaboride

The emission properties of lanthanum hexaboride in an atmosphere of nitrogen were investigated. The emitter was not poisoned by adsorbed nitrogen. This result should have application to magnetohydrodynamic devices in which electron flow from channel walls is required

Experiments in Steady State Crossed-Field Acceleration of Plasma

No abstract availabl

Physical growth of schoolchildren from the Jequitinhonha Valley, Minas Gerais, Brazil: Comparison with the CDC-2000 reference using the LMS method

Objective: To analyse the physical growth of a representative school population sample from the Jequitinhonha Valley, Minas Gerais, Brazil, in comparison with the reference proposed by the Centre for Disease Control and Prevention (CDC-2000). Methods: The sample was composed of 5100 individuals (2730 girls and 2370 boys), aged 6-18 years. Body weight-for-age and height-for-age percentiles were obtained using the LMS method. Statistical and graphical comparisons were made with the corresponding percentiles of the CDC-2000 reference, estimated using the same method. Results: Overall, the calculated values of the L (asymmetry) and the S (variability) parameters were quite similar to the CDC-2000 reference values. However, M(median) was substantially different from the reference used in the study, mainly in schoolchildren over 12-13 years of age of both genders. The magnitude of the deficits of height-for-age and body weight-for-age observed in the schoolchildren from the Jequitinhonha Valley, Minas Gerais, Brazil, varied from 4 to 6 cm and from 3 to 6 kg, respectively. Conclusion: The body weight-for-age and height-for-age percentiles of schoolchildren population in the Jequitinhonha Valley, Minas Gerais, Brazil differed substantially from those referenced

A Theoretical Treatment of the Steady-Flow, Linear, Crossed-Field, Direct-Current Plasma Accelerator for Inviscid, Adiabatic, Isothermal, Constant-Area Flow

The theory is developed from the individual equations of motion of the three components of the plasma. The effect of the ion cyclotron angle (omega tau), which is the product of the ion cyclotron frequency and the ion mean free time between collisions with neutral particles and which is proportional to the axial component of the ion slip velocity, on both Joule heating rate and accelerator length is included in the results and is shown to be small only for values of about 10(exp -3) radian or less

Quantum Backreaction on ``Classical'' Variables

A mathematically consistent procedure for coupling quasiclassical and quantum variables through coupled Hamilton-Heisenberg equations of motion is derived from a variational principle. During evolution, the quasiclassical variables become entangled with the quantum variables with the result that the value of the quasiclassical variables depends on the quantum state. This provides a formalism to compute the backreaction of any quantum system on a quasiclassical one. In particular, it leads to a natural candidate for a theory of gravity coupled to quantized matter in which the gravitational field is not quantized.Comment: LaTeX, 10 pp. title change, minor improvement of presentatio

Search for a Correlation Between Very-High-Energy Gamma Rays and Giant Radio Pulses in the Crab Pulsar

We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays (E γ \u3e 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On ~8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits

Técnicas microbiológicas y moleculares para la identificación de Salmonella sp en la industria avícola: una revisión sistemática de alcance

A systematic review of the diagnostic methods described in the literature for the identification and characterization of species of the genus Salmonella was carried out. The review was carried out using publications from 2015 to 2021 registered in the NCBI/PubMed, ScienceDirect, Scopus, SciELO, Google Scholar and Springer databases and applying the PRISMA methodology. In total, 61 articles were analysed, grouping the data according to country of origin, type of sample, technique, microbiology protocol and genes used in molecular tests. The microbiology protocols are based on performing pre-enrichment in peptone water and enrichment in tetrathionate (TT) and Rappaport-Vassiliadis (RV) broths, especially with faecal or environmental samples, to subsequently carry out isolations in selective and differential media. The identification of some Salmonella sp serovars that cause disease in poultry is mainly done with molecular techniques such as conventional PCR and multiplex PCR, based on the detection of genes such as invA, hilA, fliC, sefA, spvC, pefA, speC y glgC. Molecular tools are an alternative to traditional microbiology and serotyping techniques with the White-Kauffmann-Le Minor methodology, as they require less time and can identify serovars; however, microbiological tools such as enrichment contribute to the step prior to the use of other diagnostic tools.Se realizó una revisión sistemática de los métodos de diagnóstico descritos en la literatura para la identificación y caracterización de especies del género Salmonella. La revisión se realizó utilizando publicaciones de 2015 a 2021 registradas en las bases de datos de NCBI/PubMed, ScienceDirect, Scopus, SciELO, Google Scholar y Springer, aplicando la metodología PRISMA. Se analizaron 61 artículos, agrupando los datos según el país de origen, tipo de muestra, técnica utilizada, protocolo de microbiología empleado y genes utilizados en las pruebas moleculares. Los protocolos de microbiología se basan en pruebas de pre-enriquecimiento en agua peptonada y enriquecimiento en caldos de tetrationato (TT) y Rappaport-Vassiliadis (RV), especialmente con muestras de heces o muestras ambientales, para posteriormente realizar los aislamientos en medios selectivos y diferenciales. La identificación de algunas serovariedades de Salmonella sp que causan enfermedad en las aves se realiza principalmente con técnicas moleculares (PCR convencional y PCR multiplex), basándose en la detección de genes como invA, hilA, fliC, sefA, spvC, pefA, speC y glgC. Las herramientas moleculares son una alternativa a las técnicas tradicionales de microbiología y serotipificación con la metodología White-Kauffmann–Le Minor, por requerir de menos tiempo y poder identificar a los serovares; sin embargo, las herramientas microbiológicas como el enriquecimiento contribuyen en el paso previo al empleo de otras herramientas diagnósticas

Geometrical Hyperbolic Systems for General Relativity and Gauge Theories

The evolution equations of Einstein's theory and of Maxwell's theory---the latter used as a simple model to illustrate the former--- are written in gauge covariant first order symmetric hyperbolic form with only physically natural characteristic directions and speeds for the dynamical variables. Quantities representing gauge degrees of freedom [the spatial shift vector $\beta^{i}(t,x^{j})$ and the spatial scalar potential $\phi(t,x^{j})$, respectively] are not among the dynamical variables: the gauge and the physical quantities in the evolution equations are effectively decoupled. For example, the gauge quantities could be obtained as functions of $(t,x^{j})$ from subsidiary equations that are not part of the evolution equations. Propagation of certain (``radiative'') dynamical variables along the physical light cone is gauge invariant while the remaining dynamical variables are dragged along the axes orthogonal to the spacelike time slices by the propagating variables. We obtain these results by $(1)$ taking a further time derivative of the equation of motion of the canonical momentum, and $(2)$ adding a covariant spatial derivative of the momentum constraints of general relativity (Lagrange multiplier $\beta^{i}$) or of the Gauss's law constraint of electromagnetism (Lagrange multiplier $\phi$). General relativity also requires a harmonic time slicing condition or a specific generalization of it that brings in the Hamiltonian constraint when we pass to first order symmetric form. The dynamically propagating gravity fields straightforwardly determine the ``electric'' or ``tidal'' parts of the Riemann tensor.Comment: 24 pages, latex, no figure