2,024 research outputs found
Canonical general relativity: Matter fields in a general linear frame
Building on the results of previous work, we demonstrate how matter fields
are incorporated into the general linear frame approach to general relativity.
When considering the Maxwell one-form field, we find that the system that leads
naturally to canonical vierbein general relativity has the extrinsic curvature
of the Cauchy surface represented by gravitational as well as non-gravitational
degrees of freedom. Nevertheless the metric compatibility conditions are
undisturbed, and this apparent derivative-coupling is seen to be an effect of
working with (possibly orthonormal) linear frames. The formalism is adapted to
consider a Dirac Fermion, where we find that a milder form of this apparent
derivative-coupling appears.Comment: 13 pages; uses AMS-latex style file
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A highly oriented cubic phase formed by lipids under shear
We demonstrate the formation of a macroscopically
oriented inverse bicontinuous cubic (QII) lipid
phase from a sponge (L3) phase by controlled hydration
during shear flow. The L3 phase was the monoolein/
butanediol/water system; the addition of water reduces
the butanediol concentration, inducing the formation of a
diamond (QIID) cubic phase, which is oriented by the shear
flow. The phenomenon was reproduced in both capillary
and Couette geometries, indicating that this represents a
robust general route for the production of highly aligned
bulkQII samples, with applications in nanomaterial templating and protein research
Modelling and Measurement of Charge Transfer in Multiple GEM Structures
Measurements and numerical simulations on the charge transfer in Gas Electron
Multiplier (GEM) foils are presented and their implications for the usage of
GEM foils in Time Projection Chambers are discussed. A small test chamber has
been constructed and operated with up to three GEM foils. The charge transfer
parameters derived from the electrical currents monitored during the
irradiation with an Fe-55 source are compared with numerical simulations. The
performance in magnetic fields up to 2 T is also investigated.Comment: 21 pages, 16 figures, submitted to NIM-
Charge Transfer and Charge Broadening of GEM Structures in High Magnetic Fields
We report on measurements of charge transfer in GEM structures in high
magnetic fields. These were performed in the framework of the R&D work for a
Time Projection Chamber at a future Linear Collider. A small test chamber has
been installed into the aperture of a superconducting magnet with the GEM
structures mounted perpendicular to the B field direction. The charge transfer
is derived from the electrical currents monitored during irradiation with an
Fe source. No severe loss of primary ionisation charge is observed,
but an improved ion feedback suppression is achieved for high magnetic fields.
Additionally, the width of the charge cloud released by individual Fe
photons is measured using a finely segmented strip readout after the triple GEM
structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which
originate from the charge broadening inside the GEM readout. This charge
broadening is only partly suppressed at high magnetic fields.Comment: 11 pages, 9 figure
Implementierung eines verlustleistungsoptimierten Dezimators für kaskadierte Sigma-Delta Analog-Digital Umsetzer
Dieser Beitrag stellt die Implementierung eines neuartigen Ansatzes einer effizienten Dezimator-Architektur für kaskadierte Sigma-Delta Modulatoren vor. Die Rekombinationslogik kaskadierter Modulatoren und die Korrektur des Verstärkungsfehlers zeitkontinuierlicher (CT) Modulatoren werden in die erste Stufe des Dezimators integriert. Eine entsprechende Filtertopologie wird hergeleitet und auf einem Hardware-Emulator der Firma Mentor Graphics implementiert. Der Vergleich der vorgeschlagenen Struktur mit einer herkömmlichen Implementierung zeigt eine nennenswerte Verbesserung der Effizienz
Creation of scalar and Dirac particles in the presence of a time varying electric field in an anisotropic Bianchi I universe
In this article we compute the density of scalar and Dirac particles created
by a cosmological anisotropic Bianchi type I universe in the presence of a time
varying electric field. We show that the particle distribution becomes thermal
when one neglects the electric interaction.Comment: 8 pages, REVTEX 3.0. to appear in Phys. Rev.
The Predictive Relationship of Inhibitory Control, Emotion Regulation, Moral Emotions, and Life Stressors on Behavior Problems in School-Aged Children of Incarcerated Mothers
Children whose mothers go to prison are at high risk for poor outcomes of many kinds,including externalizing behaviors, internalizing disorders, school dropout, and eventual criminal activity. Inhibitory control, moral emotions, emotion regulation, and stressful life events were examined as predictors of externalizing and internalizing behaviors in children of incarcerated mothers. Participants were 50 children age 6 to 12 years (M = 9.77 y, SD = 1.54) with mothers currently in prison who attended a faith-based recreational summer camp. Inhibitory control was not impaired in these children, showing that their brains were functioning appropriately in this area of executive functioning. Inhibitory control did not impact emotion regulation as is usually seen, however. As expected, though, poor emotion regulation predicted both internalizing and externalizing behaviors. Lower levels of guilt (a healthy moral emotion) and higher levels of blame (an unhealthy denial of responsibility) predicted externalizing behaviors, while higher levels of shame (an unhealthy self-deprecation) predicted internalizing behaviors. A lower level of guilt also predicted the presence of callous/unemotional traits. Almost half the children experienced four or more life stressors within the past year; stressors predicted feelings of sadness and anxiety as opposed to externalizing problems, and not problems with emotion regulation. Results indicated that children who experienced the incarceration of their mothers have the cognitive and moral tools with which to regulate their emotions, but they do not always use these tools. Poor emotion regulation puts children at risk of difficulties ranging from psychopathy to long-lasting peer and relationship problems. One possibility is that their behaviors are learned and purposeful; perhaps their home and neighborhood environments modeled and reinforced out-of-control behavior. Suggestions for interventions include increasing the understanding of the impact of emotional self-understanding on self-control and behaviors, using strategies that employ both a cognitive and moral focus
Neutrinos from Cosmic Ray Interactions in the Sun as background for dark matter searches
[EN] Neutrino telescopes have been proposed as efficient tools for indirect dark matter searches,
especially using the Sun as source for its good capability to capture dark matter and since we do
not expect high-energy neutrinos from it. However, the last statement should be taken with
caution because high-energy neutrinos may come from cosmic particle interactions in the
atmosphere of the Sun and producing neutrinos. In this work, we describe an analysis of the
ANTARES neutrino telescope optimised for the observation of neutrinos coming from the
atmosphere of the Sun due to cosmic particles interactions. Focusing in the 10 GeV - 10 TeV
energy range and using 2007-2012 data, the sensitivity obtained for the flux is approximately
1012 km-2
y
-1
, whereas the expected flux is two order of magnitudes below. From this, we can
conclude that present high-energy neutrino telescopes dark matter searches in the Sun can
indeed neglect this contribution, but could play a role in future detectors with better neutrino
flux sensitivities in the 10 GeV - 10 TeV energy range and very good angular resolution.We acknowledge the financial support of Plan Estatal de Investigación, ref. FPA2015-65150-C3-1-Pand ref. FPA2015-65150-C3-2-P (MINECO/FEDER), Consolider MultiDark CSD2009-00064 (MINECO) and of the Generalitat Valenciana, Grant PrometeoII/2014/079.Ardid Ramírez, M.; Felis-Enguix, I.; Lotze, M.; Tönnis, C. (2018). Neutrinos from Cosmic Ray Interactions in the Sun as background for dark matter searches. PoS. Proceedings of Science. 301:1-8. https://doi.org/10.22323/1.301.0907S1830
Adaption reveals a neural code for the visual location of orientation change
We apply an adaptation technique to explore the neural code for the visual location of textures defined by modulation of orientation over space. In showing that adaptation to textures modulated around one orientation shifts the perceived location of textures modulated around a different orientation, we demonstrate the existence of a neural code for the location of orientation change that generalises across orientation content. Using competitive adaptation, we characterise the neural processes underlying this code as single-opponent for orientation, that is with concentric excitatory/inhibitory receptive areas tuned to a single orientation.<br /
Electronic Structure and Luminescence of Quasi-Freestanding MoS2 Nanopatches on Au(111)
Monolayers of transition metal dichalcogenides are interesting materials for
optoelectronic devices due to their direct electronic band gaps in the visible
spectral range. Here, we grow single layers of MoS2 on Au(111) and find that
nanometer-sized patches exhibit an electronic structure similar to their
freestanding analogue. We ascribe the electronic decoupling from the Au
substrate to the incorporation of vacancy islands underneath the intact MoS2
layer. Excitation of the patches by electrons from the tip of a scanning
tunneling microscope leads to luminescence of the MoS2 junction and reflects
the one-electron band structure of the quasi-freestanding layer
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