11,373 research outputs found
Chemical origin of the Venusian clouds Final report
Chemical analysis of cloud components in upper atmosphere of Venu
Chemical origin of the Venusian clouds Interim report, 1 Oct. 1966 - 30 Jan. 1967
Chemical reactions between solar hydrogen and carbon monoxide in Venus atmospher
Holography and Cosmological Singularities
Certain null singularities in ten dimensional supergravity have natural
holographic duals in terms of Matrix Theory and generalizations of the AdS/CFT
correspondence. In many situations the holographic duals appear to be well
defined in regions where the supergravity develops singularities. We describe
some recent progress in this area.Comment: Anomaly equation corrected. References adde
LIMS Instrument Package (LIP) balloon experiment: Nimbus 7 satellite correlative temperature, ozone, water vapor, and nitric acid measurements
The Limb Infrared Monitor of the Stratosphere (LIMS) LIP balloon experiment was used to obtain correlative temperature, ozone, water vapor, and nitric acid data at altitudes between 10 and 36 kilometers. The performance of the LIMS sensor flown on the Nimbus 7 Satellite was assessed. The LIP consists of the modified electrochemical concentration cell ozonesonde, the ultraviolet absorption photometric of ozone, the water vapor infrared radiometer sonde, the chemical absorption filter instrument for nitric acid vapor, and the infrared radiometer for nitric acid vapor. The limb instrument package (LIP), its correlative sensors, and the resulting data obtained from an engineering and four correlative flights are described
Geometric phases and anholonomy for a class of chaotic classical systems
Berry's phase may be viewed as arising from the parallel transport of a
quantal state around a loop in parameter space. In this Letter, the classical
limit of this transport is obtained for a particular class of chaotic systems.
It is shown that this ``classical parallel transport'' is anholonomic ---
transport around a closed curve in parameter space does not bring a point in
phase space back to itself --- and is intimately related to the Robbins-Berry
classical two-form.Comment: Revtex, 11 pages, no figures
Unified Description of Aging and Rate Effects in Yield of Glassy Solids
The competing effects of slow structural relaxations (aging) and deformation
at constant strain rate on the shear yield stress of simple model
glasses are examined using molecular simulations. At long times, aging leads to
a logarithmic increase in density and . The yield stress also rises
logarithmically with rate, but shows a sharp transition in slope at a rate that
decreases with increasing age. We present a simple phenomenological model that
includes both intrinsic rate dependence and the change in properties with the
total age of the system at yield. As predicted by the model, all data for each
temperature collapse onto a universal curve.Comment: 4 pages, 3 figure
Sex Differences in the Arousal of Need for Affiliation
This study reports that the Pelto Projective Pictures when scored by the Atkinson-Heyns-Veroff procedure is a valid instrument for measuring n affiliation. The hypothesis that an experimental group of junior-high-school students exposed to a stimulus would display a significantly higher mean n affiliation score than a control group was rejected. A sex difference was involved in the failure to reject the null hypothesis. There is strong evidence that n affiliation was aroused in an experimental group of females, but not in an experimental group of males. The Pelto Projective Pictures were successful in discriminating this difference. Moreover, the scoring procedure, developed for use with the TAT, appears to be applicable to other projective techniques
Impaired awareness of action-outcome contingency and causality during healthy ageing and following ventromedial prefrontal cortex lesions
Detecting causal relationships between actions and their outcomes is fundamental to guiding goal-directed behaviour. The ventromedial prefrontal cortex (vmPFC) has been extensively implicated in computing these environmental contingencies, via animal lesion models and human neuroimaging. However, whether the vmPFC is critical for contingency learning, and whether it can occur without subjective awareness of those contingencies, has not been established. To address this, we measured response adaption to contingency and subjective awareness of action-outcome relationships in individuals with vmPFC lesions and healthy elderly subjects. We showed that in both vmPFC damage and ageing, successful behavioural adaptation to variations in action-outcome contingencies was maintained, but subjective awareness of these contingencies was reduced. These results highlight two contexts where performance and awareness have been dissociated, and show that learning response-outcome contingencies to guide behaviour can occur without subjective awareness. Preserved responding in the vmPFC group suggests that this region is not critical for computing action-outcome contingencies to guide behaviour. In contrast, our findings highlight a critical role for the vmPFC in supporting awareness, or metacognitive ability, during learning. We further advance the hypothesis that responding to changing environmental contingencies, whilst simultaneously maintaining conscious awareness of those statistical regularities, is a form of dual-tasking that is impaired in ageing due to reduced prefrontal function.Recruitment and characterisation of individuals with brain lesions was made possible by the Cambridge Cognitive Neuroscience Research Panel at the MRC Cognition and Brain Sciences Unit, Cambridge. We acknowledge the contribution of Dr Sharon Erzinçlioğlu, Prof. Facundo Manes and Dr Tilak Das (consultant radiologist, Addenbroke’s Hospital) for their involvement in co-ordinating the panel, lesion tracing, and referral to the panel.
This research was funded by a Wellcome Trust Senior Investigator Award (104631/Z/14/Z) to TWR. Work was completed at the Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK, supported by a joint award from the Medical Research Council and Wellcome Trust (G00001354). CO is supported by a National Health and Medical Research Council Neil Hamilton Fairley Fellowship (GNT 1091310). MMV is supported by a Pinsent Darwin Scholarship in Mental Pathology and Angharad Dodds John Bursary in Mental Health and Neuropsychiatry
Quantum indistinguishability from general representations of SU(2n)
A treatment of the spin-statistics relation in nonrelativistic quantum
mechanics due to Berry and Robbins [Proc. R. Soc. Lond. A (1997) 453,
1771-1790] is generalised within a group-theoretical framework. The
construction of Berry and Robbins is re-formulated in terms of certain locally
flat vector bundles over n-particle configuration space. It is shown how
families of such bundles can be constructed from irreducible representations of
the group SU(2n). The construction of Berry and Robbins, which leads to a
definite connection between spin and statistics (the physically correct
connection), is shown to correspond to the completely symmetric
representations. The spin-statistics connection is typically broken for general
SU(2n) representations, which may admit, for a given value of spin, both bose
and fermi statistics, as well as parastatistics. The determination of the
allowed values of the spin and statistics reduces to the decomposition of
certain zero-weight representations of a (generalised) Weyl group of SU(2n). A
formula for this decomposition is obtained using the Littlewood-Richardson
theorem for the decomposition of representations of U(m+n) into representations
of U(m)*U(n).Comment: 32 pages, added example section 4.
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