1,126 research outputs found
Space-by-time manifold representation of dynamic facial expressions for emotion categorization
Visual categorization is the brain computation that reduces high-dimensional information in the visual environment into a smaller set of meaningful categories. An important problem in visual neuroscience is to identify the visual information that the brain must represent and then use to categorize visual inputs. Here we introduce a new mathematical formalism—termed space-by-time manifold decomposition—that describes this information as a low-dimensional manifold separable in space and time. We use this decomposition to characterize the representations used by observers to categorize the six classic facial expressions of emotion (happy, surprise, fear, disgust, anger, and sad). By means of a Generative Face Grammar, we presented random dynamic facial movements on each experimental trial and used subjective human perception to identify the facial movements that correlate with each emotion category. When the random movements projected onto the categorization manifold region corresponding to one of the emotion categories, observers categorized the stimulus accordingly; otherwise they selected “other.” Using this information, we determined both the Action Unit and temporal components whose linear combinations lead to reliable categorization of each emotion. In a validation experiment, we confirmed the psychological validity of the resulting space-by-time manifold representation. Finally, we demonstrated the importance of temporal sequencing for accurate emotion categorization and identified the temporal dynamics of Action Unit components that cause typical confusions between specific emotions (e.g., fear and surprise) as well as those resolving these confusions
TIMASSS : The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey: Tentative Detection of Deuterated Methyl Formate (DCOOCH3)
High deuterium fractionation is observed in various types of environment such
as prestellar cores, hot cores and hot corinos. It has proven to be an
efficient probe to study the physical and chemical conditions of these
environments. The study of the deuteration of different molecules helps us to
understand their formation. This is especially interesting for complex
molecules such as methanol and bigger molecules for which it may allow to
differentiate between gas-phase and solid-state formation pathways. Methanol
exhibits a high deuterium fractionation in hot corinos. Since CH3OH is thought
to be a precursor of methyl formate we expect that deuterated methyl formate is
produced in such environments. We have searched for the singly-deuterated
isotopologue of methyl formate, DCOOCH3, in IRAS 16293-2422, a hot corino
well-known for its high degree of methanol deuteration. We have used the
IRAM/JCMT unbiased spectral survey of IRAS 16293-2422 which allows us to search
for the DCOOCH3 rotational transitions within the survey spectral range (80-280
GHz, 328-366 GHz). The expected emission of deuterated methyl formate is
modelled at LTE and compared with the observations.} We have tentatively
detected DCOOCH3 in the protostar IRAS 16293-2422. We assign eight lines
detected in the IRAM survey to DCOOCH3. Three of these lines are affected by
blending problems and one line is affected by calibration uncertainties,
nevertheless the LTE emission model is compatible with the observations. A
simple LTE modelling of the two cores in IRAS 16293-2422, based on a previous
interferometric study of HCOOCH3, allows us to estimate the amount of DCOOCH3
in IRAS 16293-2422. Adopting an excitation temperature of 100 K and a source
size of 2\arcsec and 1\farcs5 for the A and B cores, respectively, we find that
N(A,DCOOCH3) = N(B,DCOOCH3) ~ 6.10^14 /cm2. The derived deuterium fractionation
is ~ 15%, consistent with values for other deuterated species in this source
and much greater than that expected from the deuterium cosmic abundance.
DCOOCH3, if its tentative detection is confirmed, should now be considered in
theoretical models that study complex molecule formation and their deuteration
mechanisms. Experimental work is also needed to investigate the different
chemical routes leading to the formation of deuterated methyl formate
Temperature dependent fluctuations in the two-dimensional XY model
We present a detailed investigation of the probability density function (PDF)
of order parameter fluctuations in the finite two-dimensional XY (2dXY) model.
In the low temperature critical phase of this model, the PDF approaches a
universal non-Gaussian limit distribution in the limit T-->0. Our analysis
resolves the question of temperature dependence of the PDF in this regime, for
which conflicting results have been reported. We show analytically that a weak
temperature dependence results from the inclusion of multiple loop graphs in a
previously-derived graphical expansion. This is confirmed by numerical
simulations on two controlled approximations to the 2dXY model: the Harmonic
and ``Harmonic XY'' models. The Harmonic model has no
Kosterlitz-Thouless-Berezinskii (KTB) transition and the PDF becomes
progressively less skewed with increasing temperature until it closely
approximates a Gaussian function above T ~ 4\pi. Near to that temperature we
find some evidence of a phase transition, although our observations appear to
exclude a thermodynamic singularity.Comment: 15 pages, 5 figures and 1 tabl
On the Second Law of thermodynamics and the piston problem
The piston problem is investigated in the case where the length of the
cylinder is infinite (on both sides) and the ratio is a very small
parameter, where is the mass of one particle of the gaz and is the mass
of the piston. Introducing initial conditions such that the stochastic motion
of the piston remains in the average at the origin (no drift), it is shown that
the time evolution of the fluids, analytically derived from Liouville equation,
agrees with the Second Law of thermodynamics.
We thus have a non equilibrium microscopical model whose evolution can be
explicitly shown to obey the two laws of thermodynamics.Comment: 29 pages, 9 figures submitted to Journal of Statistical Physics
(2003
D-dimensional Ideal Quantum Gases in Potential
The paper is concerned with thermostatistics of both -dimensional Bose and
Fermi ideal gases in a confining potential of type . The
investigation is performed in the framework of the semiclassical approximation.
Some physical quantities for such systems are derived, like density of states,
density profiles and number of particles. Bose-Einstein condensation (BEC) is
discussed in the high and low temperature regimes.Comment: 13 pages, Late
Mechanisms for collaboration: a design and evaluation framework for multi-user interfaces
Multi-user interfaces are said to provide “natural” interaction in supporting collaboration, compared to individual and noncolocated technologies. We identify three mechanisms accounting for the success of such interfaces: high awareness of others' actions and intentions, high control over the interface, and high availability of background information. We challenge the idea that interaction over such interfaces is necessarily “natural” and argue that everyday interaction involves constraints on awareness, control, and availability. These constraints help people interact more smoothly. We draw from social developmental psychology to characterize the design of multi-user interfaces in terms of how constraints on these mechanisms can be best used to promote collaboration. We use this framework of mechanisms and constraints to explain the successes and failures of existing designs, then apply it to three case studies of design, and finally derive from them a set of questions to consider when designing and analysing multi-user interfaces for collaboration
Molecular Clouds as Ensembles of Transient Cores
We construct models of molecular clouds that are considered as ensembles of
transient cores. Each core is assumed to develop in the background gas of the
cloud, grow to high density and decay into the background. The chemistry in
each core responds to the dynamical state of the gas and to the gas-dust
interaction. Ices are deposited on the dust grains in the core's dense phase,
and this material is returned to the gas as the core expands to low density.
The cores of the ensemble number typically one thousand and are placed randomly
in position within the cloud, and are assigned a random evolutionary phase.
The models are used to generate molecular line contour maps of a typical dark
cloud. These maps are found to represent extremely well the characteristic
features of observed maps of the dark cloud L673, which has been observed at
both low and high resolutions. The computed maps are found to exhibit the
general morphology of the observed maps, and to generate similar sizes of
emitting regions, molecular column densities, and the separations between peaks
of emissions of various molecular species. The models give insight into the
nature of molecular clouds and the dynamical processes occurring within them,
and significantly constrain dynamical and chemical processes in the
interstellar medium.Comment: 29 pages, 8 figures. Accepted for publication in Ap
Examination of Antibody Responses as a Measure of Exposure to Malaria in the Indigenous Batwa and Their Non-Indigenous Neighbors in Southwestern Uganda
Understanding variations in malaria transmission and exposure is critical to identify populations at risk and enable better targeting of interventions. The indigenous Batwa of southwestern Uganda have a disproportionate burden of malaria infection compared with their non-indigenous neighbors. To better understand the individual- and community-level determinants of malaria exposure, a seroepidemiological study was conducted in 10 local council cells in Kanungu District, Uganda, in April 2014. The Batwa had twice the odds of being seropositive to two Plasmodium falciparum–specific antigens, apical membrane antigen-1 and merozoite surface protein-119, compared with the non-indigenous Bakiga (odds ratio = 2.08, 95% confidence interval = 1.51–2.88). This trend was found irrespective of altitude level and after controlling for cell location. Seroconversion rates in the Batwa were more than twice those observed in the Bakiga. For the Batwa, multiple factors may be associated with higher exposure to malaria and antibody levels relative to their non-indigenous neighbors
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