2,612 research outputs found
Conservatism implications of shock test tailoring for multiple design environments
A method for analyzing shock conservation in test specifications that have been tailored to qualify a structure for multiple design environments is discussed. Shock test conservation is qualified for shock response spectra, shock intensity spectra and ranked peak acceleration data in terms of an Index of Conservation (IOC) and an Overtest Factor (OTF). The multi-environment conservation analysis addresses the issue of both absolute and average conservation. The method is demonstrated in a case where four laboratory tests have been specified to qualify a component which must survive seven different field environments. Final judgment of the tailored test specification is shown to require an understanding of the predominant failure modes of the test item
Magnons in Ferromagnetic Metallic Manganites
Ferromagnetic (FM) manganites, a group of likely half-metallic oxides, are of
special interest not only because they are a testing ground of the classical
doubleexchange interaction mechanism for the colossal magnetoresistance, but
also because they exhibit an extraordinary arena of emergent phenomena. These
emergent phenomena are related to the complexity associated with strong
interplay between charge, spin, orbital, and lattice. In this review, we focus
on the use of inelastic neutron scattering to study the spin dynamics, mainly
the magnon excitations in this class of FM metallic materials. In particular,
we discussed the unusual magnon softening and damping near the Brillouin zone
boundary in relatively narrow band compounds with strong Jahn-Teller lattice
distortion and charge/orbital correlations. The anomalous behaviors of magnons
in these compounds indicate the likelihood of cooperative excitations involving
spin, lattice, as well as orbital degrees of freedom.Comment: published in J. Phys.: Cond. Matt. 20 figure
Quantum Phase Transition in the Itinerant Antiferromagnet (V0.9Ti0.1)2O3
Quantum-critical behavior of the itinerant electron antiferromagnet
(V0.9Ti0.1)2O3 has been studied by single-crystal neutron scattering. By
directly observing antiferromagnetic spin fluctuations in the paramagnetic
phase, we have shown that the characteristic energy depends on temperature as
c_1 + c_2 T^{3/2}, where c_1 and c_2 are constants. This T^{3/2} dependence
demonstrates that the present strongly correlated d-electron antiferromagnet
clearly shows the criticality of the spin-density-wave quantum phase transition
in three space dimensions.Comment: 4 pages, 4 figure
Magnetic Interaction in the Geometrically Frustrated Triangular Lattice Antiferromagnet
The spin wave excitations of the geometrically frustrated triangular lattice
antiferromagnet (TLA) have been measured using high resolution
inelastic neutron scattering. Antiferromagnetic interactions up to third
nearest neighbors in the ab plane (J_1, J_2, J_3, with
and ), as well as out-of-plane coupling (J_z, with
) are required to describe the spin wave dispersion
relations, indicating a three dimensional character of the magnetic
interactions. Two energy dips in the spin wave dispersion occur at the
incommensurate wavevectors associated with multiferroic phase, and can be
interpreted as dynamic precursors to the magnetoelectric behavior in this
system.Comment: 4 pages, 4 figures, published in Phys. Rev. Let
Effect of pressure on the quantum spin ladder material IPA-CuCl3
Inelastic neutron scattering and bulk magnetic susceptibility studies of the
quantum S=1/2 spin ladder system IPA-CuCl3 are performed under hydrostatic
pressure. The pressure dependence of the spin gap is determined. At
GPa it is reduced to meV from meV at
ambient pressure. The results allow us to predict a soft-mode quantum phase
transition in this system at P GPa. The measurements are
complicated by a proximity of a structural phase transition that leads to a
deterioration of the sample.Comment: 5 pages, 4 figure
Cells electric charge analyses define specific properties for cancer cells activity
The surface electrical charge of cells is conditioned by the ionic medium in which they are immersed. This
charge is specific for each cell type and is especially important in tumour cells because it determines their
state of aggregation and their adhesion in the different organs. This study analyses the variations in surface
charge of cells when pH, electrolytes, and their concentration are modified. The modification of these
factors leads to changes in the surface charge of tumour cells; therefore, their states of aggregation and
behaviour can be modified. This may even have a use in the prognosis and treatment of various tumours.
Some studies conclude that the activity associated with the glycolysis process is accompanied by a
change in the surface charge of cells. Notably, there is a high rate of glycolysis in tumours. Our results
show that surface charge of cells strongly depends on nature of ionic medium in which they are found,
with the valence of the majority ion being the most important factor. When ionic strength was high, the
charge decreased dramatically. On the other hand, charge becomes zero or positive in an acidic pH, while
in a basic pH, the negative charge increases.University of Jaen CTS 44
A comparison between mobile and stationary gas chromatography–mass spectrometry devices for analysis of complex volatile profiles (advance online)
On-site analysis of volatile organic compounds (VOCs) with miniaturized gas chromatography–mass spectrometry (GC–MS)systems is a very rapidly developing field of application. While, on the one hand, major technological advances are improv-ing the availability of these systems on the market, on the other hand, systematic studies to assess the performance of suchinstruments are still lacking. To fill this gap, we compared three portable GC–MS devices to a state-of-the-art benchtop(stationary) system for analysis of a standard mixture of 18 VOCs. We systematically compared analytical parameters suchas the sensitivity and similarity of the signal response pattern and the quality of the obtained mass spectra. We found that theinvestigated mobile instruments (i) showed different response profiles with a generally lower number of identified analytes.Also, (ii) mass spectral reproducibility (% relative standard deviation (RSD) of the relative abundance of selective fragments)was generally worse in the mobile devices (mean RSD for all targeted fragments~9.7% vs. ~3.5% in the stationary system).Furthermore, mobile devices (iii) showed a poorer mass spectral similarity to commercial reference library spectra (>20%deviation of fragment ion relative intensity vs. ~10% in the stationary GC–MS), suggesting a less reliable identification ofanalytes by library search. Indeed, (iv) the performance was better with higher-mass and/or more abundant fragments, whichshould be considered to improve the results of library searches for substance identification. Finally, (v) the estimation ofthe signal-to-noise ratio (S/N) in mobile instruments as a measure of sensitivity revealed a significantly lower performancecompared to the benchtop lab equipment (with a ratio among medians of~8 times lower). Overall, our study reveals not only apoor signal-to-noise ratio and poor reproducibility of the data obtained from mobile instruments, but also unfavorable resultswith respect to a reliable identification of substances when they are applied for complex mixtures of volatiles
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