2,602 research outputs found
Raft cultures
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43237/1/11022_2004_Article_BF00918296.pd
Positive intergroup contact modulates fusiform gyrus activity to black and white faces.
In this study, we investigated the effect of intergroup contact on processing of own- and other-race faces using functional Magnetic Resonance Imaging (fMRI). Previous studies have shown a neural own-race effect with greater BOLD response to own race compared to other race faces. In our study, white participants completed a social-categorization task and an individuation task while viewing the faces of both black and white strangers after having answered questions about their previous experiences with black people. We found that positive contact modulated BOLD activity in the right fusiform gyrus (rFG) and left inferior occipital gyrus (lIOC), regions associated with face processing. Within these regions, higher positive contact was associated with higher activity when processing black, compared to white faces during the social categorisation task. We also found that in both regions a greater amount of individuating experience with black people was associated with greater activation for black vs. white faces in the individuation task. Quantity of contact, implicit racial bias and negatively valenced contact showed no effects. Our findings suggest that positive contact and individuating experience directly modulate processing of out-group faces in the visual cortex, and illustrate that contact quality rather than mere familiarity is an important factor in reducing the own race face effect
Cosmological perturbations on local systems
We study the effect of cosmological expansion on orbits--galactic, planetary,
or atomic--subject to an inverse-square force law. We obtain the laws of motion
for gravitational or electrical interactions from general relativity--in
particular, we find the gravitational field of a mass distribution in an
expanding universe by applying perturbation theory to the Robertson-Walker
metric. Cosmological expansion induces an ( force where
is the cosmological scale factor. In a locally Newtonian framework, we
show that the term represents the effect of a continuous
distribution of cosmological material in Hubble flow, and that the total force
on an object, due to the cosmological material plus the matter perturbation,
can be represented as the negative gradient of a gravitational potential whose
source is the material actually present. We also consider the effect on local
dynamics of the cosmological constant. We calculate the perihelion precession
of elliptical orbits due to the cosmological constant induced force, and work
out a generalized virial relation applicable to gravitationally bound clusters.Comment: 10 page
Random graphs with arbitrary degree distributions and their applications
Recent work on the structure of social networks and the internet has focussed
attention on graphs with distributions of vertex degree that are significantly
different from the Poisson degree distributions that have been widely studied
in the past. In this paper we develop in detail the theory of random graphs
with arbitrary degree distributions. In addition to simple undirected,
unipartite graphs, we examine the properties of directed and bipartite graphs.
Among other results, we derive exact expressions for the position of the phase
transition at which a giant component first forms, the mean component size, the
size of the giant component if there is one, the mean number of vertices a
certain distance away from a randomly chosen vertex, and the average
vertex-vertex distance within a graph. We apply our theory to some real-world
graphs, including the world-wide web and collaboration graphs of scientists and
Fortune 1000 company directors. We demonstrate that in some cases random graphs
with appropriate distributions of vertex degree predict with surprising
accuracy the behavior of the real world, while in others there is a measurable
discrepancy between theory and reality, perhaps indicating the presence of
additional social structure in the network that is not captured by the random
graph.Comment: 19 pages, 11 figures, some new material added in this version along
with minor updates and correction
QED theory of the nuclear recoil effect in atoms
The quantum electrodynamic theory of the nuclear recoil effect in atoms to
all orders in \alpha Z is formulated. The nuclear recoil corrections for atoms
with one and two electrons over closed shells are considered in detail. The
problem of the composite nuclear structure in the theory of the nuclear recoil
effect is discussed.Comment: 20 pages, 6 figures, Late
Systems biologists seek fuller integration of systems biology approaches in new cancer research programs
Systems biology takes an interdisciplinary approach to the systematic study of complex interactions in biological systems. This approach seeks to decipher the emergent behaviors of complex systems rather than focusing only on their constituent properties. As an increasing number of examples illustrate the value of systems biology approaches to understand the initiation, progression, and treatment of cancer, systems biologists from across Europe and the United States hope for changes in the way their field is currently perceived among cancer researchers. In a recent EU-US workshop, supported by the European Commission, the German Federal Ministry for Education and Research, and the National Cancer Institute of the NIH, the participants discussed the strengths, weaknesses, hurdles, and opportunities in cancer systems biology
A Taxonomy of Causality-Based Biological Properties
We formally characterize a set of causality-based properties of metabolic
networks. This set of properties aims at making precise several notions on the
production of metabolites, which are familiar in the biologists' terminology.
From a theoretical point of view, biochemical reactions are abstractly
represented as causal implications and the produced metabolites as causal
consequences of the implication representing the corresponding reaction. The
fact that a reactant is produced is represented by means of the chain of
reactions that have made it exist. Such representation abstracts away from
quantities, stoichiometric and thermodynamic parameters and constitutes the
basis for the characterization of our properties. Moreover, we propose an
effective method for verifying our properties based on an abstract model of
system dynamics. This consists of a new abstract semantics for the system seen
as a concurrent network and expressed using the Chemical Ground Form calculus.
We illustrate an application of this framework to a portion of a real
metabolic pathway
Positronium S state spectrum: analytic results at O(m alpha^6)
We present an analytic calculation of the O(m alpha^6) recoil and radiative
recoil corrections to energy levels of positronium nS states and their
hyperfine splitting. A complete analytic formula valid to O(m alpha^6) is given
for the spectrum of S states. Technical aspects of the calculation are
discussed in detail. Theoretical predictions are given for various energy
intervals and compared with experimental results.Comment: 29 pages, revte
The prognostic value of Cardiopulmonary Exercise Testing in Idiopathic Pulmonary Fibrosis
Rationale: Idiopathic pulmonary fibrosis (IPF) is characterized by progressive
dyspnea, impaired gas exchange, and ultimate mortality.
Objectives: To test the hypothesis that maximal oxygen uptake
during cardiopulmonary exercise testing at baseline and with
short-term longitudinal measures would predict mortality in
patients with idiopathic pulmonary fibrosis.
Methods: Data from 117 patients with IPF and longitudinal cardiopulmonary
exercise tests were examined retrospectively. Survival
was calculated from the date of the first cardiopulmonary exercise
test.
Measurements and Main Results: Patients with baseline maximal
oxygen uptake less than 8.3 ml/kg/min had an increased risk of
death (n=8; hazard ratio, 3.24; 95% confidence interval, 1.10–9.56;
P = 0.03) after adjusting for age, gender, smoking status, baseline
forced vital capacity, and baseline diffusion capacity for carbon
monoxide. We were unable to define a unit change in maximal
oxygen uptake that predicted survival in our cohort.
Conclusions: We conclude that a threshold maximal oxygen uptake of
8.3 ml/kg/min during cardiopulmonary exercise testing at baseline
adds prognostic information for patients with IPF.Supported by National Institute of Health NHLBI grant P50HL-56402, NHLBI, 2
K24 HL04212, 1 K23 HL68713, and 1K23 HL077719. C.D.F. was supported by
the Alberta Heritage Foundation for Medical Research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91965/1/2009 AJRCCM The prognostic value of Cardiopulmonary Exercise Testing in Idiopathic Pulmonary Fibrosis.pd
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