3,331 research outputs found
Sleep and Cognition
Sleep is an ancestral and primitive behaviour, an important part of life thought to be essential for restoration of body and mind. As adults, we spend approximately a third of our lives asleep and as we progress through life there are certain shifts in sleep architecture, most notably in sleep quantity. These biological or physiological age-dependent changes in sleep are well documented [1], and alongside the shifts in sleep architecture there is an increased susceptibility to certain sleep disorders.
Sleep disturbances and sleep deprivation are common in modern society. Most studies show that since the beginning of the century, populations have been subjected to a steady constant decline in the number of hours devoted to sleep. This is due to changes in a variety of environmental and social conditions (e.g. less dependence on daylight for most activities, extended shift work and 24/7 round-the-clock activities
Spectropolarimetry of the 3.4 micron absorption feature in NGC 1068
In order to test the silicate-core/organic-mantle model of galactic
interstellar dust, we have performed spectropolarimetry of the 3.4 micron C-H
bond stretch that is characteristic of aliphatic hydrocarbons, using the
nucleus of the Seyfert 2 galaxy, NGC 1068, as a bright, dusty background
source. Polarization calculations show that, if the grains in NGC 1068 had the
properties assigned by the core-mantle model to dust in the galactic diffuse
ISM, they would cause a detectable rise in polarization over the 3.4 micron
feature. No such increase is observed. We discuss modifications to the basic
core-mantle model, such as changes in grain size or the existence of additional
non-hydrocarbon aligned grain populations, which could better fit the
observational evidence. However, we emphasize that the absence of polarization
over the 3.4 micron band in NGC 1068 - and, indeed, in every line of sight
examined to date - can be readily explained by a population of small, unaligned
carbonaceous grains with no physical connection to the silicates.Comment: ApJ, accepte
Removing non-stationary, non-harmonic external interference from gravitational wave interferometer data
We describe a procedure to identify and remove a class of non-stationary and
non-harmonic interference lines from gravitational wave interferometer data.
These lines appear to be associated with the external electricity main
supply, but their amplitudes are non-stationary and they do not appear at
harmonics of the fundamental supply frequency. We find an empirical model able
to represent coherently all the non-harmonic lines we have found in the power
spectrum, in terms of an assumed reference signal of the primary supply input
signal. If this signal is not available then it can be reconstructed from the
same data by making use of the coherent line removal algorithm that we have
described elsewhere. All these lines are broadened by frequency changes of the
supply signal, and they corrupt significant frequency ranges of the power
spectrum. The physical process that generates this interference is so far
unknown, but it is highly non-linear and non-stationary. Using our model, we
cancel the interference in the time domain by an adaptive procedure that should
work regardless of the source of the primary interference. We have applied the
method to laser interferometer data from the Glasgow prototype detector, where
all the features we describe in this paper were observed. The algorithm has
been tuned in such a way that the entire series of wide lines corresponding to
the electrical interference are removed, leaving the spectrum clean enough to
detect signals previously masked by them. Single-line signals buried in the
interference can be recovered with at least 75 % of their original signal
amplitude.Comment: 14 pages, 5 figures, Revtex, psfi
ArgoNeuT and the Neutrino-Argon Charged Current Quasi-Elastic Cross Section
ArgoNeuT, a Liquid Argon Time Projection Chamber in the NuMI beamline at
Fermilab, has recently collected thousands of neutrino and anti-neutrino events
between 0.1 and 10 GeV. The experiment will, among other things, measure the
cross section of the neutrino and anti-neutrino Charged Current Quasi-Elastic
interaction and analyze the vertex activity associated with such events. These
topics are discussed along with ArgoNeuT's automated reconstruction software,
currently capable of fully reconstructing the muon and finding the event vertex
in neutrino interactions.Comment: 6 pages, 4 figures, presented at the International Nuclear Physics
Conference, Vancouver, Canada, July 4-9, 2010, to be published in Journal of
Physics: Conference Series (JPCS
Extending the bandwidth of optical-tweezers interferometry
The extension of the bandwidth of optical-tweezers interferometry was discussed. It was found that the detection bandwidth was extended to at least 100 KHz, either by using wavelengths below 850 nm or by using different detectors at longer wavelengths. The power spectral density of the Brownian motion of micron-sized beads in optical tweezers was also measured
Neural Network-Based Equations for Predicting PGA and PGV in Texas, Oklahoma, and Kansas
Parts of Texas, Oklahoma, and Kansas have experienced increased rates of
seismicity in recent years, providing new datasets of earthquake recordings to
develop ground motion prediction models for this particular region of the
Central and Eastern North America (CENA). This paper outlines a framework for
using Artificial Neural Networks (ANNs) to develop attenuation models from the
ground motion recordings in this region. While attenuation models exist for the
CENA, concerns over the increased rate of seismicity in this region necessitate
investigation of ground motions prediction models particular to these states.
To do so, an ANN-based framework is proposed to predict peak ground
acceleration (PGA) and peak ground velocity (PGV) given magnitude, earthquake
source-to-site distance, and shear wave velocity. In this framework,
approximately 4,500 ground motions with magnitude greater than 3.0 recorded in
these three states (Texas, Oklahoma, and Kansas) since 2005 are considered.
Results from this study suggest that existing ground motion prediction models
developed for CENA do not accurately predict the ground motion intensity
measures for earthquakes in this region, especially for those with low
source-to-site distances or on very soft soil conditions. The proposed ANN
models provide much more accurate prediction of the ground motion intensity
measures at all distances and magnitudes. The proposed ANN models are also
converted to relatively simple mathematical equations so that engineers can
easily use them to predict the ground motion intensity measures for future
events. Finally, through a sensitivity analysis, the contributions of the
predictive parameters to the prediction of the considered intensity measures
are investigated.Comment: 5th Geotechnical Earthquake Engineering and Soil Dynamics Conference,
Austin, TX, USA, June 10-13. (2018
ACR testing of a dedicated head SPECT unit
Physics testing necessary for program accreditation is rigorously defined by the ACR. This testing is easily applied to most conventional SPECT systems based on gamma camera technology. The inSPira HD is a dedicated head SPECT system based on a rotating dual clamshell design that acquires data in a dual-spiral geometry. The unique geometry and configuration force alterations of the standard ACR physics testing protocol. Various tests, such as intrinsic planar uniformity and/or resolution, do not apply. The Data Spectrum Deluxe Phantom used for conventional SPECT testing cannot fit in the inSPira HD scanner bore, making (currently) unapproved use of the Small Deluxe SPECT Phantom necessary. Matrix size, collimator type, scanning time, reconstruction method, and attenuation correction were all varied from the typically prescribed ACR instructions. Visible spheres, sphere contrast, visible rod groups, uniformity, and root mean square (RMS) noise were measured. The acquired SPECT images surpassed the minimum ACR requirements for both spatial resolution (9.5 mm spheres resolved) and contrast (6.4 mm rod groups resolved). Sphere contrast was generally high. Integral uniformity was 4% and RMS noise was 1.7%. Noise appeared more correlated than in images from a conventional SPECT scanner. Attenuation-corrected images produced from direct CT scanning of the phantom and a manufacturer supplied model of the phantom demonstrated negligible differences
Exploring Spirituality in Teaching Within a Christian School Context Through Collaborative Action Research
This article reports on a collaborative action research project conducted in New Zealand, during 2012, exploring spirituality in teaching within a Christian school context. The experienced primary school teacher participant chose to take action around the issue of personal fear and insecurity which were believed to be hindering professional growth and relationships. Through self-directed inquiry, critical reflective journaling, Bible study, fellowship and prayer with trusted friends, the teacher experienced a renewed sense of peace and freedom in Christ. This personal transformation was believed to be influential on subsequent professional practice, assisting the teacher to become more relational, responsive and compassionate. The findings provide a rich description of the participantâs spirituality, the lived reality of a personâs spiritual life. This report will be of interest to teachers, teacher-leaders and teacher-educators who desire to explore Christian spirituality through practitioner-led inquiry
Gravitational-Wave Stochastic Background Detection with Resonant-Mass Detectors
In this paper we discuss how the standard optimal Wiener filter theory can be
applied, within a linear approximation, to the detection of an isotropic
stochastic gravitational-wave background with two or more detectors. We apply
then the method to the AURIGA-NAUTILUS pair of ultra low temperature bar
detectors, near to operate in coincidence in Italy, obtaining an estimate for
the sensitivity to the background spectral density of $\simeq 10^{-49}\
Hz^{-1}\simeq 8\times10^{-5}\times\rho_c\rho_c\simeq1.9 \times 10^{-26}\
kg/m^3\simeq 6
\times10^{-5}\times\rho_c\simeq 2\times10^{-5}\times
\rho_c\simeq 2 \times10^{-6}\rho_c$.Comment: 32 pages, postscript file, also available at
http://axln01.lnl.infn.it/reports/stoch.htm
Spectropolarimetric observations of the transiting planetary system of the K dwarf HD 189733
With a Jupiter-mass planet orbiting at a distance of only 0.031 AU, the
active K2 dwarf HD 189733 is a potential candidate in which to study the
magnetospheric interactions of a cool star with its recently-discovered
close-orbiting giant planet. We decided to explore the strength and topology of
the large-scale magnetosphere of HD 189733, as a future benchmark for
quantitative studies for models of the star/planet magnetic interactions. To
this end, we used ESPaDOnS, the new generation spectropolarimeter at the
Canada-France-Hawaii 3.6m telescope, to look for Zeeman circular polarisation
signatures in the line profiles of HD 189733 in 2006 June and August. Zeeman
signatures in the line profiles of HD 189733 are clearly detected in all
spectra, demonstrating that a field is indeed present at the surface of the
star. The Zeeman signatures are not modulated with the planet's orbital period
but apparently vary with the stellar rotation cycle. The reconstructed
large-scale magnetic field, whose strength reaches a few tens of G, is
significantly more complex than that of the Sun; it involves in particular a
significant toroidal component and contributions from magnetic multipoles of
order up to 5. The CaII H & K lines clearly feature core emission, whose
intensity is apparently varying mostly with rotation phase. Our data suggest
that the photosphere and magnetic field of HD 189733 are sheared by a
significant amount of differential rotation. Our initial study confirms that HD
189733 is an optimal target for investigating activity enhancements induced by
closely orbiting planets. More data are needed, densely covering both the
orbital and rotation cycles, to investigate whether and how much the planet
contributes to the overall activity level of HD 189733.Comment: Accepted in Astronomy and Astrophysics, 12 page
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