2,758 research outputs found
Enabling Factor Analysis on Thousand-Subject Neuroimaging Datasets
The scale of functional magnetic resonance image data is rapidly increasing
as large multi-subject datasets are becoming widely available and
high-resolution scanners are adopted. The inherent low-dimensionality of the
information in this data has led neuroscientists to consider factor analysis
methods to extract and analyze the underlying brain activity. In this work, we
consider two recent multi-subject factor analysis methods: the Shared Response
Model and Hierarchical Topographic Factor Analysis. We perform analytical,
algorithmic, and code optimization to enable multi-node parallel
implementations to scale. Single-node improvements result in 99x and 1812x
speedups on these two methods, and enables the processing of larger datasets.
Our distributed implementations show strong scaling of 3.3x and 5.5x
respectively with 20 nodes on real datasets. We also demonstrate weak scaling
on a synthetic dataset with 1024 subjects, on up to 1024 nodes and 32,768
cores
Production of a chromium Bose-Einstein condensate
The recent achievement of Bose-Einstein condensation of chromium atoms [1]
has opened longed-for experimental access to a degenerate quantum gas with
long-range and anisotropic interaction. Due to the large magnetic moment of
chromium atoms of 6 {}B, in contrast to other Bose- Einstein condensates
(BECs), magnetic dipole-dipole interaction plays an important role in a
chromium BEC. Many new physical properties of degenerate gases arising from
these magnetic forces have been predicted in the past and can now be studied
experimentally. Besides these phenomena, the large dipole moment leads to a
breakdown of standard methods for the creation of a chromium BEC. Cooling and
trapping methods had to be adapted to the special electronic structure of
chromium to reach the regime of quantum degeneracy. Some of them apply
generally to gases with large dipolar forces. We present here a detailed
discussion of the experimental techniques which are used to create a chromium
BEC and alow us to produce pure condensates with up to {} atoms in an
optical dipole trap. We also describe the methods used to determine the
trapping parameters.Comment: 17 pages, 9 figure
Pathwise Sensitivity Analysis in Transient Regimes
The instantaneous relative entropy (IRE) and the corresponding instanta-
neous Fisher information matrix (IFIM) for transient stochastic processes are
pre- sented in this paper. These novel tools for sensitivity analysis of
stochastic models serve as an extension of the well known relative entropy rate
(RER) and the corre- sponding Fisher information matrix (FIM) that apply to
stationary processes. Three cases are studied here, discrete-time Markov
chains, continuous-time Markov chains and stochastic differential equations. A
biological reaction network is presented as a demonstration numerical example
Sensitivity in Multiobjective Programming by Differential Equations Methods. The Case of Homogeneous Functions
Proceedings of the Second International Conference on Multi-Objective Programming and Goal Programming, Torremolinos, Spain, May 16-18, 1996.The purpose of this paper is to characterize for convex multiobjective programming, the situations in which the sensitivity with respect to the right side vector of the constraints can be obtained as a solution of a dual program.Publicad
An inhibitory pull-push circuit in frontal cortex.
Push-pull is a canonical computation of excitatory cortical circuits. By contrast, we identify a pull-push inhibitory circuit in frontal cortex that originates in vasoactive intestinal polypeptide (VIP)-expressing interneurons. During arousal, VIP cells rapidly and directly inhibit pyramidal neurons; VIP cells also indirectly excite these pyramidal neurons via parallel disinhibition. Thus, arousal exerts a feedback pull-push influence on excitatory neurons-an inversion of the canonical push-pull of feedforward input
Fecundity, spore recruitment and size in Gelidium sesquipedale (Gelidiales,Rhodophyta)
Gelidium sesquipedale fecundity was quantified by counting tetrasporangial sori and cystocarps per meter squared
and by estimating the number of spores contained inside them . These were obtained by regression on a size metric
of reproductive structures . Tetrasporangial sori length and cystocarp thickness were the best estimators of spore
number. To assess spore recruitment, 12 pottery tiles were fixed to the bottom, and the appearance of small fronds
was monitored.
No clear seasonal pattern of reproduction was found . Tetraspore production peaked in March 1990 with 10.4
x 106 spores m-2, whereas the carpospore peak was lower, 4.9 x 10 5 spores m-2 in July 1989. Recruitment
followed tetraspore peaks . The probability of a G. sesquipedale tetraspore making the transition to a recruit was
4.7 x 10-5. Frond length was significantly related to tetrasporangial sori number, while cystocarp number was
only related to frond branching order. Minimum size for reproduction was 6.9 cm for gametophytes and 5.4 cm for
tetrasporophytes; very rarely were cystocarpic fronds smaller than 9 cm, while tetrasporic fronds were often longer
than 15 cm . Cystocarpic fronds were significantly shorter and had more branches than tetrasporic fronds
Graviton Vertices and the Mapping of Anomalous Correlators to Momentum Space for a General Conformal Field Theory
We investigate the mapping of conformal correlators and of their anomalies
from configuration to momentum space for general dimensions, focusing on the
anomalous correlators , - involving the energy-momentum tensor
with a vector or a scalar operator () - and the 3-graviton vertex
. We compute the , and one-loop vertex functions in
dimensional regularization for free field theories involving conformal scalar,
fermion and vector fields. Since there are only one or two independent tensor
structures solving all the conformal Ward identities for the or
vertex functions respectively, and three independent tensor structures for the
vertex, and the coefficients of these tensors are known for free fields,
it is possible to identify the corresponding tensors in momentum space from the
computation of the correlators for free fields. This works in general
dimensions for and correlators, but only in 4 dimensions for ,
since vector fields are conformal only in . In this way the general
solution of the Ward identities including anomalous ones for these correlators
in (Euclidean) position space, found by Osborn and Petkou is mapped to the
ordinary diagrammatic one in momentum space. We give simplified expressions of
all these correlators in configuration space which are explicitly Fourier
integrable and provide a diagrammatic interpretation of all the contact terms
arising when two or more of the points coincide. We discuss how the anomalies
arise in each approach [...]Comment: 57 pages, 7 figures. Refs adde
Telecare motivational interviewing for diabetes patient education and support : a randomised controlled trial based in primary care comparing nurse and peer supporter delivery
Background: There is increasing interest in developing peer-led and 'expert patient'-type interventions, particularly to meet the support and informational needs of those with long term conditions, leading to improved clinical outcomes, and pressure relief on mainstream health services. There is also increasing interest in telephone support, due to its greater accessibility and potential availability than face to face provided support. The evidence base for peer telephone interventions is relatively weak, although such services are widely available as support lines provided by user groups and other charitable services.
Methods/Design: In a 3-arm RCT, participants are allocated to either an intervention group with Telecare service provided by a Diabetes Specialist Nurse (DSN), an intervention group with service provided by a peer supporter (also living with diabetes), or a control group receiving routine care only. All supporters underwent a 2-day training in motivational interviewing, empowerment and active listening skills to provide telephone support over a period of up to 6 months to adults with poorly controlled type 2 diabetes who had been recommended a change in diabetes management (i.e. medication and/or lifestyle
changes) by their general practitioner (GP). The primary outcome is self-efficacy; secondary outcomes include HbA1c, total and HDL cholesterol, blood pressure, body mass index, and adherence to treatment. 375 participants (125 in each arm) were sought from GP practices across West Midlands, to detect a difference in self-efficacy scores with an effect size of 0.35, 80% power, and 5% significance level. Adults
living with type 2 diabetes, with an HbA1c > 8% and not taking insulin were initially eligible. A protocol
change 10 months into the recruitment resulted in a change of eligibility by reducing HbA1c to > 7.4%. Several qualitative studies are being conducted alongside the main RCT to describe patient, telecare supporter and practice nurse experience of the trial.
Discussion and implications of the research: With its focus on self-management and telephone peer support, the intervention being trialled has the potential to support improved self-efficacy and patient experience, improved clinical outcomes and a reduction in diabetes-related complications
Oscillations and interactions of dark and dark-bright solitons in Bose-Einstein condensates
Solitons are among the most distinguishing fundamental excitations in a wide
range of non-linear systems such as water in narrow channels, high speed
optical communication, molecular biology and astrophysics. Stabilized by a
balance between spreading and focusing, solitons are wavepackets, which share
some exceptional generic features like form-stability and particle-like
properties. Ultra-cold quantum gases represent very pure and well-controlled
non-linear systems, therefore offering unique possibilities to study soliton
dynamics. Here we report on the first observation of long-lived dark and
dark-bright solitons with lifetimes of up to several seconds as well as their
dynamics in highly stable optically trapped Rb Bose-Einstein
condensates. In particular, our detailed studies of dark and dark-bright
soliton oscillations reveal the particle-like nature of these collective
excitations for the first time. In addition, we discuss the collision between
these two types of solitary excitations in Bose-Einstein condensates.Comment: 9 pages, 4 figure
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