2,369 research outputs found
A comparison of in-cloud HCl concentrations from the NASA/MSFC MDM to measurements for the space shuttle launch
The Multilevel Diffusion Model (MDM) Version 5 was modified to include features of more recent versions. The MDM was used to predict in-cloud HCl concentrations for the April 12 launch of the space Shuttle (STS-1). The maximum centerline predictions were compared with measurements of maximum gaseous HCl obtained from aircraft passes through two segments of the fragmented shuttle ground cloud. The model over-predicted the maximum values for gaseous HCl in the lower cloud segment and portrayed the same rate of decay with time as the observed values. However, the decay with time of HCl maximum predicted by the MDM was more rapid than the observed decay for the higher cloud segment, causing the model to under-predict concentrations which were measured late in the life of the cloud. The causes of the tendency for the MDM to be conservative in over-estimating the HCl concentrations in the one case while tending to under-predict concentrations in the other case are discussed
The effect of changes in space shuttle parameters on the NASA/MSFC multilayer diffusion model predictions of surface HCl concentrations
A method for formulating these changes into the model input parameters using a preprocessor program run on a programed data processor was implemented. The results indicate that any changes in the input parameters are small enough to be negligible in comparison to meteorological inputs and the limitations of the model and that such changes will not substantially increase the number of meteorological cases for which the model will predict surface hydrogen chloride concentrations exceeding public safety levels
Construction of spin models displaying quantum criticality from quantum field theory
We provide a method for constructing finite temperature states of
one-dimensional spin chains displaying quantum criticality. These models are
constructed using correlators of products of quantum fields and have an
analytical purification. Their properties can be investigated by Monte-Carlo
simulations, which enable us to study the low-temperature phase diagram and to
show that it displays a region of quantum criticality. The mixed states
obtained are shown to be close to the thermal state of a simple nearest
neighbour Hamiltonian.Comment: 10 pages, 6 figure
Lattice effects on Laughlin wave functions and parent Hamiltonians
We investigate lattice effects on wave functions that are lattice analogues
of bosonic and fermionic Laughlin wave functions with number of particles per
flux in the Landau levels. These wave functions are defined
analytically on lattices with particles per lattice site, where may
be different than . We give numerical evidence that these states have the
same topological properties as the corresponding continuum Laughlin states for
different values of and for different fillings . These states define,
in particular, particle-hole symmetric lattice Fractional Quantum Hall states
when the lattice is half-filled. On the square lattice it is observed that for
this particle-hole symmetric state displays the topological
properties of the continuum Laughlin state at filling fraction , while
for larger there is a transition towards long-range ordered
anti-ferromagnets. This effect does not persist if the lattice is deformed from
a square to a triangular lattice, or on the Kagome lattice, in which case the
topological properties of the state are recovered. We then show that changing
the number of particles while keeping the expression of these wave functions
identical gives rise to edge states that have the same correlations in the bulk
as the reference lattice Laughlin states but a different density at the edge.
We derive an exact parent Hamiltonian for which all these edge states are
ground states with different number of particles. In addition this Hamiltonian
admits the reference lattice Laughlin state as its unique ground state of
filling factor . Parent Hamiltonians are also derived for the lattice
Laughlin states at other fillings of the lattice, when or
and when also at half-filling.Comment: 18 pages, 15 figure
Some Integrals Involving Bessel Functions
AbstractA number of new definite integrals involving Bessel functions are presented. These have been derived by finding new integral representations for the product of two Bessel functions of different order and argument in terms of the generalized hypergeometric function with subsequent reduction to special cases. Connection is made with Weber′s second exponential integral and Laplace transforms of products of three Bessel functions
"Can't live without music": engaging and disengaging from music listening
Background: Listening to music is a popular leisure activity. Investigations of music in everyday life are dominated by a functional perspective, drawn from work using the theory of Uses and Gratifications. In so doing, we may have neglected to fully appreciate the value people place on music listening. Therefore, the present study considered if, and why, people value music listening and probed instances when they may not want to listen to music in everyday life.
Aims: This study considered if, and why, people value music listening and also probed instances when they may not want to listen to music in everyday life. This research was therefore guided by two questions: (1) How is the value of music listening expressed? and (2) Are there any times/ situations when people do not want to listen to music?
Methods: A total of 319 university students residing in Australia (76.50% female, Mean age = 20.64 years) completed an online questionnaire. The majority of the sample considered themselves to be ‘non-musicians’; however, the sample reported listening to an average of three hours of
music daily and considered music to be very important in their lives (Mean = 6.14 on a 7-point scale). Participants responded to open-ended questions directly addressing the two research questions and thematic analyses were conducted.
Results: Inductive thematic analysis yielded thirteen themes synthesising how participants valued listening to music, such as appreciation, emotion, time and engagement, cognitive factors and mood regulation. Reasons for not listening to music were summarised by eight themes dominated by interference with activities that required focus or concentration, followed by environmental context, affective responses, music engagement and inversely, a preference for silence or other auditory stimuli. Fifteen percent of participants stated there was never a time they did not want to listen to music.
Conclusion and Implications: By taking a macroscopic approach with the present research, we posit that Uses and Gratifications theory can be interpreted as inhabiting one of two branches of an axiological theory of value, with aesthetics on the other branch. Thus, while Uses and Gratifications is an appropriate framework to understand music listening from the perspective of ‘listening as valued as a means to an end’, it may be less able to interpret music listening’s worth when identified as ‘a means in and of itself’. It is worth noting, however, that within the axiological theory of value the two branches are not mutually exclusive; indeed, the distinction between means and ends is a fuzzy line. We posit that forms of musical engagement, such as music listening, can fall within this intersection
Generating Diffusion MRI scalar maps from T1 weighted images using generative adversarial networks
Diffusion magnetic resonance imaging (diffusion MRI) is a non-invasive
microstructure assessment technique. Scalar measures, such as FA (fractional
anisotropy) and MD (mean diffusivity), quantifying micro-structural tissue
properties can be obtained using diffusion models and data processing
pipelines. However, it is costly and time consuming to collect high quality
diffusion data. Here, we therefore demonstrate how Generative Adversarial
Networks (GANs) can be used to generate synthetic diffusion scalar measures
from structural T1-weighted images in a single optimized step. Specifically, we
train the popular CycleGAN model to learn to map a T1 image to FA or MD, and
vice versa. As an application, we show that synthetic FA images can be used as
a target for non-linear registration, to correct for geometric distortions
common in diffusion MRI
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