2,450 research outputs found
Measurement of Magnetization Dynamics in Single-Molecule Magnets Induced by Pulsed Millimeter-Wave Radiation
We describe an experiment aimed at measuring the spin dynamics of the Fe8
single-molecule magnet in the presence of pulsed microwave radiation. In
earlier work, heating was observed after a 0.2-ms pulse of intense radiation,
indicating that the spin system and the lattice were out of thermal equilibrium
at millisecond time scale [Bal et al., Europhys. Lett. 71, 110 (2005)]. In the
current work, an inductive pick-up loop is used to probe the photon-induced
magnetization dynamics between only two levels of the spin system at much
shorter time scales (from ns to us). The relaxation time for the magnetization,
induced by a pulse of radiation, is found to be on the order of 10 us.Comment: 3 RevTeX pages, including 3 eps figures. The paper will appear in the
Journal of Applied Physics as MMM'05 conference proceeding
The effect of uniaxial pressure on the magnetic anisotropy of the Mn_{12}-Ac single-molecule magnet
We study the effect of uniaxial pressure on the magnetic hysteresis loops of
the single-molecule magnet Mn_{12}-Ac. We find that the application of pressure
along the easy axis increases the fields at which quantum tunneling of
magnetization occurs. The observations are attributed to an increase in the
molecule's magnetic anisotropy constant D of 0.142(1)%/kbar. The increase in D
produces a small, but measurable increase in the effective energy barrier for
magnetization reversal. Density-functional theory calculations also predict an
increase in the barrier with applied pressure.Comment: version accepted by EPL; 6 pages, including 7 figures. Small changes
and added reference
Non-equilibrium Magnetization Dynamics in the Fe_8 Single-Molecule Magnet Induced by High-Intensity Microwave Radiation
Resonant microwave radiation applied to a single crystal of the molecular
magnet Fe_8 induces dramatic changes in the sample's magnetization. Transitions
between excited states are found even though at the nominal system temperature
these levels have negligible population. We find evidence that the sample heats
significantly when the resonance condition is met. In addition, heating is
observed after a short pulse of intense radiation has been turned off,
indicating that the spin system is out of equilibrium with the lattice.Comment: Version to appear in Europhysics Letters. Minor changes and updated
reference
Experimental Upper Bound on Superradiance Emission from Mn12 Acetate
We used a Josephson junction as a radiation detector to look for evidence of
the emission of electromagnetic radiation during magnetization avalanches in a
crystal assembly of Mn_12-Acetate. The crystal assembly exhibits avalanches at
several magnetic fields in the temperature range from 1.8 to 2.6 K with
durations of the order of 1 ms. Although a recent study shows evidence of
electromagnetic radiation bursts during these avalanches [J. Tejada, et al.,
Appl. Phys. Lett. {\bf 84}, 2373 (2004)], we were unable to detect any
significant radiation at well-defined frequencies. A control experiment with
external radiation pulses allows us to determine that the energy released as
radiation during an avalanche is less than 1 part in 10^4 of the total energy
released. In addition, our avalanche data indicates that the magnetization
reversal process does not occur uniformly throughout the sample.Comment: 4 RevTeX pages, 3 eps figure
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An examination of computer-use ethics in Hong Kong and the United States
This study examines differences in individual ethical evaluations of computer-use scenarios between subjects in Hong Kong and the United States in an effort to better understand value differences that may be associated with differences in attitudes toward computer use expectations. Analysis indicates that although Hong Kong subjects generally take a more permissive view of ethical responsibility regarding computer use, they do not necessarily condone violations of ethical behavior. Results are discussed and implications for future research are addressed
A Cross-National Examination of Expected Correlation of Computer Ethical Perceptions and User Computer Attitudes
This study examined computer ethical perceptions and computer use attitudes among three differing groups consisting of nationalities from the United States, Singapore and Hong Kong. The purpose of the study was to determine if computer attitudes have a moderating effect on the perceptions of computer ethical use across multiple cultural backgrounds. Evidence supporting this claim would add additional insight into previously discovered differences. This study found limited support for the suggested hypotheses, but confirmed fundamental cultural differences. Future research should examine other variables to determine if significant effects can be determined from unexamined variable
Discrete reduction patterns of parvalbumin and calbindin D-28k immunoreactivity in the dorsal lateral geniculate nucleus and the striate cortex of adult macaque monkeys after monocular enucleation
We analyzed the immunohistochemical distribution of the two calcium-binding proteins, parvalbumin (PV) and calbindin D-28k (CB), in the primary visual cortex and lateral dorsal geniculate nucleus (dLGN) of monocularly enucleated macaque monkeys (Macaca fascicularis and Macaca nemestrind) in order to determine how the expression of PV and CB is affected by functional inactivity. The monkeys survived 1-17 weeks after monocular enucleation. The distribution pattern of each of the proteins was examined immunocytochemically using monoclonal antibodies and compared with that of the metabolic marker cytochrome oxidase (CO). We recorded manually the number of immunostained neurons and estimated the concentration of immunoreactive staining product using a computerized image-acquisition system. Our results indicate a decrease of approximately 30% in the labeling of PV-immunoreactive (ir) neuropil particularly in those layers of denervated ocular-dominance columns receiving the geniculocortical input. There was no change in the number of PV-ir neurons in any compartment irrespective of the enucleation interval. For CB-ir, we found a 20% decrease in the neuropil labeling in layer 2/3 of the denervated ocular-dominance columns. In addition, a subset of pyramidal CB-ir neurons in layers 2 and 4B, which are weakly stained in control animals, showed decreased labeling. In the dLGN of enucleated animals, PV-ir and CB-ir were decreased only in the neuropil of the denervated layers. From these results, we conclude that cortical interneurons and geniculate projection neurons still express PV and CB in their cell bodies after disruption of the direct functional input from one eye. The only distinct decrease of PV and CB expression is seen in axon terminals from retinal ganglion cells in the dLGN, and in the axons and terminals of both geniculocortical projection cells and cortical interneurons in the cerebral corte
PROCESS-CONTROL EFFECTS FOR TEAM-BASEDCOMPUTER-MEDIATED DECISION ANALYSES
As the evolution of research in Group Support Systems (GSS) continues, focus must begin to shift away from the concentration of GSS groups versus non-GSS groups, and begin to direct scrutiny toward the examination of the group dynamics that influence the experience of the teams that use GSS. The literature has clearly established that GSS improves the quality of certain decisions. The new challenge is to discover what processes within GSS are responsible for decision improvement and how they interact with other group processes extant in work situation
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