12,976 research outputs found
Direction-Projection-Permutation for High Dimensional Hypothesis Tests
Motivated by the prevalence of high dimensional low sample size datasets in
modern statistical applications, we propose a general nonparametric framework,
Direction-Projection-Permutation (DiProPerm), for testing high dimensional
hypotheses. The method is aimed at rigorous testing of whether lower
dimensional visual differences are statistically significant. Theoretical
analysis under the non-classical asymptotic regime of dimension going to
infinity for fixed sample size reveals that certain natural variations of
DiProPerm can have very different behaviors. An empirical power study both
confirms the theoretical results and suggests DiProPerm is a powerful test in
many settings. Finally DiProPerm is applied to a high dimensional gene
expression dataset
Comparison of bacterioneuston and bacterioplankton dynamics during a phytoplankton bloom in a fjord mesocosm
The bacterioneuston is the community of Bacteria present in surface microlayers, the
thin surface film that forms the interface between aquatic environments and the
atmosphere. In this study we compared bacterial cell abundance and bacterial
community structure of the bacterioneuston and the bacterioplankton (from the
subsurface water column) during a phytoplankton bloom mesocosm experiment.
Bacterial cell abundance, determined by flow cytometry, followed a typical
bacterioplankton response to a phytoplankton bloom, with Synechococcus and high
nucleic acid (HNA) bacterial cell numbers initially falling, probably due to selective
protist grazing. Subsequently HNA and low nucleic acid (LNA) bacterial cells
increased in abundance but Synechococcus did not. There was no significant
difference between bacterioneuston and bacterioplankton cell abundances during the
experiment. Conversely, distinct and consistent differences between the
bacterioneuston and the bacterioplankton community structure were observed. This
was monitored simultaneously by Bacteria 16S rRNA gene terminal restriction
fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis
(DGGE). The conserved patterns of community structure observed in all of the
mesocosms indicate that the bacterioneuston is distinctive and non-random
Binge Eating Disorder Mediates Links between Symptoms of Depression and Anxiety and Caloric Intake in Obese Women
Despite considerable comorbidity between mood disorders, binge eating disorder (BED), and obesity, the underlying mechanisms remain unresolved. Therefore, the purpose of this study was to examine models by which internalizing behaviors of depression and anxiety influence food intake in overweight/obese women. Thirty-two women (15 BED, 17 controls) participated in a laboratory eating-episode and completed questionnaires assessing symptoms of anxiety and depression. Path analysis was used to test mediation and moderation models to determine the mechanisms by which internalizing symptoms influenced kilocalorie (kcal) intake. The BED group endorsed significantly more symptoms of depression (10.1 versus 4.8, P=0.005 ) and anxiety (8.5 versus 2.7, P=0.003). Linear regression indicated that BED diagnosis and internalizing symptoms accounted for 30% of the variance in kcal intake. Results from path analysis suggested that BED mediates the influence of internalizing symptoms on total kcal intake. The associations between internalizing symptoms and food intake are best described as operating indirectly through a BED diagnosis. This suggests that symptoms of depression and anxiety influence whether one engages in binge eating, which influences kcal intake. Greater understanding of the mechanisms underlying the associations between mood, binge eating, and food intake will facilitate the development of more effective prevention and treatment strategies for both BED and obesity
Melting-freezing cycles in a relatively sheared pair of crystalline monolayers
The nonequilibrium dynamical behaviour that arises when two ordered
two-dimensional monolayers of particles are sheared over each other is studied
in Brownian dynamics simulations. A curious sequence of nonequilibrium states
is observed as the driving rate is increased, the most striking of which is a
sliding state with irregular alternation between disordered and ordered states.
We comment on possible mechanisms underlying these cycles, and experiments that
could observe them.Comment: 7 pages, 8 figures, minor changes in text and figures, references
adde
A second anniversary operational review of the OmniTRACS(R): The first two-way mobile Ku-band satellite communications system
A novel two-way mobile satellite communications and vehicle position reporting system that is currently operational in the United States and Europe is described. The system characteristics and service operations are described in detail. Technical descriptions of the equipment and signal processing techniques are provided
Investigations of excitation energy transfer and intramolecular interactions in a nitrogen corded distrylbenzene dendrimer system.
The photophysics of an amino-styrylbenzene dendrimer (A-DSB) system is probed by time-resolved and steady state luminescence spectroscopy. For two different generations of this dendrimer, steady state absorption, emission, and photoluminescence excitation spectra are reported and show that the efficiency of energy transfer from the dendrons to the core is very close to 100%. Ultrafast time-resolved fluorescence measurements at a range of excitation and detection wavelengths suggest rapid (and hence efficient) energy transfer from the dendron to the core. Ultrafast fluorescence anisotropy decay for different dendrimer generations is described in order to probe the energy migration processes. A femtosecond time-scale fluorescence depolarization was observed with the zero and second generation dendrimers. Energy transfer process from the dendrons to the core can be described by a Förster mechanism (hopping dynamics) while the interbranch interaction in A-DSB core was found to be very strong indicating the crossover to exciton dynamics
- …