4,832 research outputs found
Theory of double resonance magnetometers based on atomic alignment
We present a theoretical study of the spectra produced by
optical-radio-frequency double resonance devices, in which resonant linearly
polarized light is used in the optical pumping and detection processes. We
extend previous work by presenting algebraic results which are valid for atomic
states with arbitrary angular momenta, arbitrary rf intensities, and arbitrary
geometries. The only restriction made is the assumption of low light intensity.
The results are discussed in view of their use in optical magnetometers
A dynamic auto-adaptive predictive maintenance policy for degradation with unknown parameters
International audienceWith the development of monitoring equipment, research on condition-based maintenance (CBM) is rapidly growing. CBM optimization aims to find an optimal CBM policy which minimizes the average cost of the system over a specified duration of time. This paper proposes a dynamic auto-adaptive predictive maintenance policy for single-unit systems whose gradual deterioration is governed by an increasing stochastic process. The parameters of the degradation process are assumed to be unknown and Bayes' theorem is used to update the prior information. The time interval between two successive inspections is scheduled based on the remaining useful life (RUL) of the system and is updated along with the degradation parameters. A procedure is proposed to dynamically adapt the maintenance decision variables accordingly. Finally, different possible maintenance policies are considered and compared to illustrate their performance
Extensive 1-year survey of trace elements and compounds in the airborne suspended particulate matter in Cleveland, Ohio
Concentrations of 75 chemical constituents in the airborne particulate matter were measured in Cleveland, Ohio, during 1971 and 1972. Values covering a 1-year period (45 to 50 sampling days) at each of 16 sites are presented for 60 elements. A lesser number of values is given for sulfate, nitrate, fluoride, acidity, 10 polynuclear aromatic hydrocarbon compounds, and the aliphatic hydrocarbon compounds as a group. Methods used included instrumental neutron activation, emission spectroscopy, gas chromatography, combustion techniques, and colorimetry. Uncertainties in the concentrations associated with the sampling procedures, the analysis methods, the use of several analytical facilities, and samples with concentrations below the detection limits are evaluated in detail. The data is discussed in relation to other studies and source origins. The trace constituent concentrations as a function of wind direction are used to suggest a practical method for air pollution source identification
Symmetry Representations in the Rigged Hilbert Space Formulation of Quantum Mechanics
We discuss some basic properties of Lie group representations in rigged
Hilbert spaces. In particular, we show that a differentiable representation in
a rigged Hilbert space may be obtained as the projective limit of a family of
continuous representations in a nested scale of Hilbert spaces. We also
construct a couple of examples illustrative of the key features of group
representations in rigged Hilbert spaces. Finally, we establish a simple
criterion for the integrability of an operator Lie algebra in a rigged Hilbert
space
Hypermultiplets and hypercomplex geometry from 6 to 3 dimensions
The formulation of hypermultiplets that has been developed for 5-dimensional
matter multiplets is by dimensional reductions translated into the appropriate
spinor language for 6 and 4 dimensions. We also treat the theories without
actions that have the geometrical structure of hypercomplex geometry. The
latter is the generalization of hyper-Kaehler geometry that does not require a
Hermitian metric and hence corresponds to field equations without action. The
translation tables of this paper allow the direct application of superconformal
tensor calculus for the hypermultiplets using the available Weyl multiplets in
6 and 4 dimensions. Furthermore, the hypermultiplets in 3 dimensions that
result from reduction of vector multiplets in 4 dimensions are considered,
leading to a superconformal formulation of the c-map and an expression for the
main geometric quantities of the hyper-Kaehler manifolds in the image of this
map.Comment: 18 pages; v2: several clarifications in text and formulae, version to
appear in Class.Quantum Gravit
Experimental study of laser detected magnetic resonance based on atomic alignment
We present an experimental study of the spectra produced by
optical/radio-frequency double resonance in which resonant linearly polarized
laser light is used in the optical pumping and detection processes. We show
that the experimental spectra obtained for cesium are in excellent agreement
with a very general theoretical model developed in our group and we investigate
the limitations of this model. Finally, the results are discussed in view of
their use in the study of relaxation processes in aligned alkali vapors.Comment: 8 pages, 9 figures. Submitted to Phys. Rev. A. Related to
physics/060523
A nonstationary form of the range refraction parabolic equation and its application as an artificial boundary condition for the wave equation in a waveguide
The time-dependent form of Tappert's range refraction parabolic equation is
derived using Daletskiy-Krein formula form noncommutative analysis and proposed
as an artificial boundary condition for the wave equation in a waveguide. The
numerical comparison with Higdon's absorbing boundary conditions shows
sufficiently good quality of the new boundary condition at low computational
cost.Comment: 12 pages, 9 figure
Expression of Complement and Toll-Like Receptor Pathway Genes is Associated with Malaria Severity in Mali: A Pilot Case Control Study
Background: The host response to infection by Plasmodium falciparum, the parasite most often responsible for severe malaria, ranges from asymptomatic parasitaemia to death. The clinical trajectory of malaria is influenced by host genetics and parasite load, but the factors determining why some infections produce uncomplicated malaria and some proceed to severe disease remain incompletely understood. Methods: To identify molecular markers of severe falciparum malaria, human gene expression patterns were compared between children aged 6 months to 5 years with severe and uncomplicated malaria who were enrolled in a case–control study in Bandiagara, Mali. Microarrays were used to obtain expression data on severe cases and uncomplicated controls at the time of acute disease presentation (five uncomplicated and five severe), 1 week after presentation (three uncomplicated and three severe) and treatment initiation, and in the subsequent dry season (late convalescence, four uncomplicated and four severe). This is a pilot study for the first use of microarray technology in Mali
Physico-chemistry of continental Bentonites and Kaolin for ceramic applications
Growing demand for bentonite and kaolin applications in the ceramic industry motivated this study which aimed at physico-chemically characterizing some selected continental clayey materials from Botswana, Mozambique, Pakistan, Senegal, South Africa and the United States of America. The hydrogen ion concentration (pH), electrical conductivity (EC), cation exchange capacitance (CEC), specific surface area (SSA) and color were determined. The results depicted that the pH values were between 5.8 and 10.5, EC values ranged from 200 ìS/cm to 6501 ìS/cm, CEC values occurred between 3.5 meq/100 g and 105 meq/100 g, and the SSA values were between 4 m2g-1 and 19 m2g-1. Raw clay color ranged from white to black with most samples having a greyish-like appearance. These values are in conformity with those obtained by other researchers, and based on their physico-chemical characteristics, the clayey materials were found to be suitable for use in the ceramic industry
Heavy Fermion Quantum Criticality and Destruction of the Kondo Effect in a Nickel Oxypnictide
A quantum critical point arises at a continuous transformation between
distinct phases of matter at zero temperature. Studies in antiferromagnetic
heavy fermion materials have revealed that quantum criticality has several
classes, with an unconventional type that involves a critical destruction of
the Kondo entanglement. In order to understand such varieties, it is important
to extend the materials basis beyond the usual setting of intermetallic
compounds. Here we show that a nickel oxypnictide, CeNiAsO, displays a
heavy-fermion antiferromagnetic quantum critical point as a function of either
pressure or P/As substitution. At the quantum critical point, non-Fermi liquid
behavior appears, which is accompanied by a divergent effective carrier mass.
Across the quantum critical point, the low-temperature Hall coefficient
undergoes a rapid sign change, suggesting a sudden jump of the Fermi surface
and a destruction of the Kondo effect. Our results imply that the enormous
materials basis for the oxypnictides, which has been so crucial to the search
for high temperature superconductivity, will also play a vital role in the
effort to establish the universality classes of quantum criticality in strongly
correlated electron systems.Comment: 4 figures, Supplementary Information on NPG websit
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