16,121 research outputs found
Investigation of nonlinear motion simulator washout schemes
An overview is presented of some of the promising washout schemes which have been devised. The four schemes presented fall into two basic configurations; crossfeed and crossproduct. Various nonlinear modifications further differentiate the four schemes. One nonlinear scheme is discussed in detail. This washout scheme takes advantage of subliminal motions to speed up simulator cab centering. It exploits so-called perceptual indifference thresholds to center the simulator cab at a faster rate whenever the input to the simulator is below the perceptual indifference level. The effect is to reduce the angular and translational simulation motion by comparison with that for the linear washout case. Finally, the conclusions and implications for further research in the area of nonlinear washout filters are presented
Complex joint probabilities as expressions of determinism in quantum mechanics
The density operator of a quantum state can be represented as a complex joint
probability of any two observables whose eigenstates have non-zero mutual
overlap. Transformations to a new basis set are then expressed in terms of
complex conditional probabilities that describe the fundamental relation
between precise statements about the three different observables. Since such
transformations merely change the representation of the quantum state, these
conditional probabilities provide a state-independent definition of the
deterministic relation between the outcomes of different quantum measurements.
In this paper, it is shown how classical reality emerges as an approximation to
the fundamental laws of quantum determinism expressed by complex conditional
probabilities. The quantum mechanical origin of phase spaces and trajectories
is identified and implications for the interpretation of quantum measurements
are considered. It is argued that the transformation laws of quantum
determinism provide a fundamental description of the measurement dependence of
empirical reality.Comment: 12 pages, including 1 figure, updated introduction includes
references to the historical background of complex joint probabilities and to
related work by Lars M. Johanse
Mean first passage time for fission potentials having structure
A schematic model of over-damped motion is presented which permits one to
calculate the mean first passage time for nuclear fission. Its asymptotic value
may exceed considerably the lifetime suggested by Kramers rate formula, which
applies only to very special, favorable potentials and temperatures. The
additional time obtained in the more general case is seen to allow for a
considerable increment in the emission of light particles.Comment: 7 pages, LaTex, 7 postscript figures; Keywords: Decay rate, mean
first passage tim
Neuroenhancement of exposure therapy in anxiety disorders
Although exposure-based treatments and anxiolytic medications are more effective than placebo for treating anxiety disorders, there is still considerable room for further improvement. Interestingly, combining these two modalities is usually not more effective than the monotherapies. Recent translational research has identified a number of novel approaches for treating anxiety disorders using agents that serve as neuroenhancers (also known as cognitive enhancers). Several of these agents have been studied to determine their efficacy at improving treatment outcome for patients with anxiety and other psychiatric disorders. In this review, we examine d-cycloserine, yohimbine, cortisol, catecholamines, oxytocin, modafinil, and nutrients such as caffeine and amino fatty acids as potential neuroenhancers. Of these agents, d-cycloserine shows the most promise as an effective neuroenhancer for extinction learning and exposure therapy. Yet, the optimal dosing and dose timing for drug administration remains uncertain. There is partial support for cortisol, catecholamines, yohimbine and oxytocin for improving extinction learning and exposure therapy. There is less evidence to indicate that modafinil and nutrients such as caffeine and amino fatty acids are effective neuroenhancers. More research is needed to determine their long term efficacy and clinical utility of these agents.R34 MH086668 - NIMH NIH HHS; R01 AT007257 - NCCIH NIH HHS; R21 MH101567 - NIMH NIH HHS; R34 MH099311 - NIMH NIH HHS; R21 MH102646 - NIMH NIH HHS; K23 MH100259 - NIMH NIH HHS; R01 MH099021 - NIMH NIH HH
Attachment style moderates the effects of oxytocin on social behaviors and cognitions during social rejection: applying an RDoC framework to social anxiety
Whereas the DSM categorizes individuals with similar self-reported symptoms, the Research Domain Criteria (RDoC) offers a new approach for classifying mental disorders based on dimensions of observable behaviors and neurobiological measures. The objective of this proof-of-concept study is to adopt this approach by distinguishing individuals based on disorder-related personality traits during an experimental manipulation that targeted a disorder-related biological mechanism. Specifically, we examined whether attachment style moderated the effect of oxytocin administration on social behaviors and cognitions during a social exclusion test in individuals with social anxiety disorder. When receiving oxytocin compared to placebo, only individuals with low attachment avoidance displayed more social affiliation and cooperation, and only those with high attachment avoidance showed faster detection of disgust and neutral faces. Thus, attachment style moderated oxytocin's effects among individuals who shared the same DSM diagnosis. We conclude that neurobiological tests can inform new classification strategies by adopting an RDoC framework.R01 AT007257 - NCCIH NIH HHS; R01 MH078308 - NIMH NIH HH
Observation of Galactic Gamma-ray Sources with VERITAS
We report on VERITAS observations at energies above 200 GeV of known or
potential galactic gamma-ray sources. The observed objects comprise pulsars,
pulsar wind nebulae, high-mass X-ray binaries and gamma-ray sources with
unknown counterparts in other wavelengths. Among the highlights are the
observation of variable gamma-ray emission from the X-ray binary LS I +61 303
and the detection of MGRO J1906+06/HESS J1906+063, an extended gamma-ray source
which could not be associated with any obvious counterpart at lower energies.Comment: Fixed typos in source name
Mean first passage time for nuclear fission and the emission of light particles
The concept of a mean first passage time is used to study the time lapse over
which a fissioning system may emit light particles. The influence of the
"transient" and "saddle to scission times" on this emission are critically
examined. It is argued that within the limits of Kramers' picture of fission no
enhancement over that given by his rate formula need to be considered.Comment: 4 pages, RevTex, 4 postscript figures; with correction of misprints;
appeared in Phys. Rev. Lett.90.13270
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