315 research outputs found
Dark Matter Disc Enhanced Neutrino Fluxes from the Sun and Earth
As disc galaxies form in a hierarchical cosmology, massive merging satellites
are preferentially dragged towards the disc plane. The material accreted from
these satellites forms a dark matter disc that contributes 0.25 - 1.5 times the
non-rotating halo density at the solar position. Here, we show the importance
of the dark disc for indirect dark matter detection in neutrino telescopes.
Previous predictions of the neutrino flux from WIMP annihilation in the Earth
and the Sun have assumed that Galactic dark matter is spherically distributed
with a Gaussian velocity distribution, the standard halo model. Although the
dark disc has a local density comparable to the dark halo, its higher phase
space density at low velocities greatly enhances capture rates in the Sun and
Earth. For typical dark disc properties, the resulting muon flux from the Earth
is increased by three orders of magnitude over the SHM, while for the Sun the
increase is an order of magnitude. This significantly increases the sensitivity
of neutrino telescopes to fix or constrain parameters in WIMP models. The flux
from the Earth is extremely sensitive to the detailed properties of the dark
disc, while the flux from the Sun is more robust. The enhancement of the muon
flux from the dark disc puts the search for WIMP annihilation in the Earth on
the same level as the Sun for WIMP masses < 100 GeV.Comment: 7 pages, 4 figures, added a short paragraph to the discussion
section, conclusions unchanged, published versio
Non-invasive electrophysiological assessment of the optimal configuration of quadripolar lead vectors on ventricular activation times
High Force Unimanual Handgrip Contractions Increase Ipsilateral Sensorimotor Activation and Functional Connectivity
Imaging and brain stimulation studies seem to correct the classical understanding of how brain networks, rather than contralateral focal areas, control the generation of unimanual voluntary force. However, the scaling and hemispheric-specificity of network activation remain less understood. Using fMRI, we examined the effects of parametrically increasing right-handgrip force on activation and functional connectivity among the sensorimotor network bilaterally with 25%, 50%, and 75% maximal voluntary contractions (MVC). High force (75% MVC) unimanual handgrip contractions resulted in greater ipsilateral motor activation and functional connectivity with the contralateral hemisphere compared to a low force 25% MVC condition. The ipsilateral motor cortex activation and network strength correlated with relative handgrip force (% MVC). Increases in unimanual handgrip force resulted in greater ipsilateral sensorimotor activation and greater functional connectivity between hemispheres within the sensorimotor network. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved
A Three-Pronged Analysis of the Proposal for a United States Space Force
On June 18, 2018, at a meeting of the newly revived National Space Council, President Trump announced that he had directed the Department of Defense and the Pentagon “to immediately begin the process necessary to establish a space force as the sixth branch of the armed forces.” This paper will discuss a three-pronged analysis of the proposal for the United States Space Force. The three topics discussed are legal, political, and military issues that the creation of Space Oriented branch will encounter. The paper has been broken up into four teams consisting of two partners, which comes to a total of nine with one lead overseeing all the teams. The four teams are the legal team which will discuss the legislative components, the military team which will discuss the logistical transfer from the Air Force to the Space Force, the political team which will discuss the effect that the new branch will have on world politics, and the recommendation team which will make the final edits to ensure the entire format, citation, and sources are correct. The paper will be published through the university and hopefully be used in consideration for the creation of the Space Force
Semiclassical transition in \phi^4 theory
We have shown an example of semiclassical transition in theory
with positive coupling constant. This process can be described by the classical
-invariant solution, considered on a contour in the complex time plane.
The transition is technically analogous to the one-instanton transition in the
electroweak model. It is suppressed by the factor , where
is Lipatov instanton action. This process describes a semiclassical
transition between two coherent states with much smaller number of particles in
the initial state than in the final state. Therefore, it could be relevant to
the problem of calculation of amplitudes for multiparticle production in
-type models.Comment: 26 pages, JHU-TIPAC-930013, (correct 2 typos, some notations
Autonomic modulation in patients with heart failure increases beat-to-beat variability of ventricular action potential duration
Background: Exaggerated beat-to-beat variability of ventricular action potential duration (APD) is linked to arrhythmogenesis. Sympathetic stimulation has been shown to increase QT interval variability, but its effect on ventricular APD in humans has not been determined.Methods and Results: Eleven heart failure patients with implanted bi-ventricular pacing devices had activation–recovery intervals (ARI, surrogate for APD) recorded from LV epicardial electrodes under constant RV pacing. Sympathetic activity was increased using a standard autonomic challenge (Valsalva) and baroreceptor indices were applied to determine changes in sympathetic stimulation. Two Valsalvas were performed for each study and were repeated, both off and on bisoprolol. In addition sympathetic nerve activity (SNA) was measured from skin electrodes on the thorax using a novel validated method. Autonomic modulation significantly increased mean short-term variability in ARI; off bisoprolol mean STV increased from 3.73 ± 1.3 to 5.27 ± 1.04 ms (p = 0.01), on bisoprolol mean STV of ARI increased from 4.15 ± 1.14 to 4.62 ± 1 ms (p = 0.14). Adrenergic indices of the Valsalva demonstrated significantly reduced beta-adrenergic function when on bisoprolol (Δ pressure recovery time, p = 0.04; Δ systolic overshoot in Phase IV, p = 0.05). Corresponding increases in SNA from rest both off (1.4 uV, p < 0.01) and on (0.7 uV, p < 0.01) bisoprolol were also seen.Conclusions: Beat-to-beat variability of ventricular APD increases during brief periods of increased sympathetic activity in patients with heart failure. Bisoprolol reduces, but does not eliminate, these effects. This may be important in the genesis of ventricular arrhythmias in heart failure patients
Eliciting spoken interruptions to inform proactive speech agent design
Current speech agent interactions are typically user-initiated, limiting the interactions they can deliver. Future functionality will require agents to be proactive, sometimes interrupting users. Little is known about how these spoken interruptions should be designed, especially in urgent interruption contexts. We look to inform design of proactive agent interruptions through investigating how people interrupt others engaged in complex tasks. We therefore developed a new technique to elicit human spoken interruptions of people engaged in other tasks. We found that people interrupted sooner when interruptions were urgent. Some participants used access rituals to forewarn interruptions, but most rarely used them. People balanced speed and accuracy in timing interruptions, often using cues from the task they interrupted. People also varied phrasing and delivery of interruptions to reflect urgency. We discuss how our findings can inform speech agent design and how our paradigm can help gain insight into human interruptions in new contexts
Interpretable Deep Models for Cardiac Resynchronisation Therapy Response Prediction
Advances in deep learning (DL) have resulted in impressive accuracy in some
medical image classification tasks, but often deep models lack
interpretability. The ability of these models to explain their decisions is
important for fostering clinical trust and facilitating clinical translation.
Furthermore, for many problems in medicine there is a wealth of existing
clinical knowledge to draw upon, which may be useful in generating
explanations, but it is not obvious how this knowledge can be encoded into DL
models - most models are learnt either from scratch or using transfer learning
from a different domain. In this paper we address both of these issues. We
propose a novel DL framework for image-based classification based on a
variational autoencoder (VAE). The framework allows prediction of the output of
interest from the latent space of the autoencoder, as well as visualisation (in
the image domain) of the effects of crossing the decision boundary, thus
enhancing the interpretability of the classifier. Our key contribution is that
the VAE disentangles the latent space based on `explanations' drawn from
existing clinical knowledge. The framework can predict outputs as well as
explanations for these outputs, and also raises the possibility of discovering
new biomarkers that are separate (or disentangled) from the existing knowledge.
We demonstrate our framework on the problem of predicting response of patients
with cardiomyopathy to cardiac resynchronization therapy (CRT) from cine
cardiac magnetic resonance images. The sensitivity and specificity of the
proposed model on the task of CRT response prediction are 88.43% and 84.39%
respectively, and we showcase the potential of our model in enhancing
understanding of the factors contributing to CRT response.Comment: MICCAI 2020 conferenc
KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star
We present the discovery of KELT-1b, the first transiting low-mass companion
from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North)
survey. The V=10.7 primary is a mildly evolved, solar-metallicity, mid-F star.
The companion is a low-mass brown dwarf or super-massive planet with mass of
27.23+/-0.50 MJ and radius of 1.110+0.037-0.024 RJ, on a very short period
(P=1.21750007) circular orbit. KELT-1b receives a large amount of stellar
insolation, with an equilibrium temperature assuming zero albedo and perfect
redistribution of 2422 K. Upper limits on the secondary eclipse depth indicate
that either the companion must have a non-zero albedo, or it must experience
some energy redistribution. Comparison with standard evolutionary models for
brown dwarfs suggests that the radius of KELT-1b is significantly inflated.
Adaptive optics imaging reveals a candidate stellar companion to KELT-1, which
is consistent with an M dwarf if bound. The projected spin-orbit alignment
angle is consistent with zero stellar obliquity, and the vsini of the primary
is consistent with tidal synchronization. Given the extreme parameters of the
KELT-1 system, we expect it to provide an important testbed for theories of the
emplacement and evolution of short-period companions, and theories of tidal
dissipation and irradiated brown dwarf atmospheres.Comment: 30 pages, 19 figures. Submitted to Ap
A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray Luminous Classical Nova to Date
It has recently been discovered that some, if not all, classical novae emit
GeV gamma rays during outburst, but the mechanisms involved in the production
of the gamma rays are still not well understood. We present here a
comprehensive multi-wavelength dataset---from radio to X-rays---for the most
gamma-ray luminous classical nova to-date, V1324 Sco. Using this dataset, we
show that V1324 Sco is a canonical dusty Fe-II type nova, with a maximum ejecta
velocity of 2600 km s and an ejecta mass of few
M. There is also evidence for complex shock interactions, including a
double-peaked radio light curve which shows high brightness temperatures at
early times. To explore why V1324~Sco was so gamma-ray luminous, we present a
model of the nova ejecta featuring strong internal shocks, and find that higher
gamma-ray luminosities result from higher ejecta velocities and/or mass-loss
rates. Comparison of V1324~Sco with other gamma-ray detected novae does not
show clear signatures of either, and we conclude that a larger sample of
similarly well-observed novae is needed to understand the origin and variation
of gamma rays in novae.Comment: 26 pages, 13 figure
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