1,445 research outputs found
Soliton stability and collapse in the discrete nonpolynomial Schrodinger equation with dipole-dipole interactions
The stability and collapse of fundamental unstaggered bright solitons in the
discrete Schrodinger equation with the nonpolynomial on-site nonlinearity,
which models a nearly one-dimensional Bose-Einstein condensate trapped in a
deep optical lattice, are studied in the presence of the long-range
dipole-dipole (DD) interactions. The cases of both attractive and repulsive
contact and DD interaction are considered. The results are summarized in the
form of stability/collapse diagrams in the parametric space of the model, which
demonstrate that the the attractive DD interactions stabilize the solitons and
help to prevent the collapse. Mobility of the discrete solitons is briefly
considered too.Comment: 6 figure
Nuclear spirals as feeding channels to the Supermassive Black Hole: the case of the galaxy NGC 6951
We report the discovery of gas streaming motions along nuclear spiral arms
towards the LINER nucleus of the galaxy NGC 6951. The observations, obtained
using the GMOS integral field spectrograph on the Gemini North telescope,
yielded maps of the flux distributions and gas kinematics in the Halpha,
[NII]6584 and [SII]6717,31 emission lines of the inner 7x5 arcsec^2 of the
galaxy. This region includes a circumnuclear star-forming ring with radius
500pc, a nuclear spiral inside the ring and the LINER nucleus. The kinematics
of the ionized gas is dominated by rotation, but subtraction of a kinematic
model of a rotating exponential disk reveals deviations from circular rotation
within the nuclear ring which can be attributed to (1) streaming motions along
the nuclear spiral arms and (2) a bipolar outflow which seems to be associated
to a nuclear jet. On the basis of the observed streaming velocities and
geometry of the spiral arms we estimate a mass inflow rate of ionized gas of
3x10^(-4) Msun/yr, which is of the order of the accretion rate necessary to
power the LINER nucleus of NGC 6951. Similar streaming motions towards the
nucleus of another galaxy with LINER nucleus -- NGC 1097 -- have been reported
by our group in a previous paper. Taken together, these results support a
scenario in which nuclear spirals are channels through which matter is
transferred from galactic scales to the nuclear region to feed the supermassive
black hole.Comment: 25 pages, 6 eps figures, accepted for publication in Ap
Disentangling the multigenic and pleiotropic nature of molecular function
Background:
Biological processes at the molecular level are usually represented by molecular interaction networks. Function is organised and modularity identified based on network topology, however, this approach often fails to account for the dynamic and multifunctional nature of molecular components. For example, a molecule engaging in spatially or temporally independent functions may be inappropriately clustered into a single functional module. To capture biologically meaningful sets of interacting molecules, we use experimentally defined pathways as spatial/temporal units of molecular activity.
Results:
We defined functional profiles of Saccharomyces cerevisiae based on a minimal set of Gene Ontology terms sufficient to represent each pathway's genes. The Gene Ontology terms were used to annotate 271 pathways, accounting for pathway multi-functionality and gene pleiotropy. Pathways were then arranged into a network, linked by shared functionality. Of the genes in our data set, 44% appeared in multiple pathways performing a diverse set of functions. Linking pathways by overlapping functionality revealed a modular network with energy metabolism forming a sparse centre, surrounded by several denser clusters comprised of regulatory and metabolic pathways. Signalling pathways formed a relatively discrete cluster connected to the centre of the network. Genetic interactions were enriched within the clusters of pathways by a factor of 5.5, confirming the organisation of our pathway network is biologically significant.
Conclusions:
Our representation of molecular function according to pathway relationships enables analysis of gene/protein activity in the context of specific functional roles, as an alternative to typical molecule-centric graph-based methods. The pathway network demonstrates the cooperation of multiple pathways to perform biological processes and organises pathways into functionally related clusters with interdependent outcomes
Effect of electron-electron scattering on magnetointersubband resistance oscillations of two-dimensional electrons in GaAs quantum wells
The low-temperature( K) magnetotransport ( T) of
two-dimensional electrons occupying two subbands (with energy and )
is investigated in GaAs single quantum well with AlAs/GaAs superlattice
barriers. Two series of Shubnikov-de Haas oscillations are found to be
accompanied by magnetointersubband (MIS) oscillations, periodic in the inverse
magnetic field. The period of the MIS oscillations obeys condition
, where is the
subband energy separation, is the cyclotron frequency, and is
the positive integer. At =4.2 K the oscillations manifest themselves up to
=100. Strong temperature suppression of the magnetointersubband oscillations
is observed. We show that the suppression is a result of electron-electron
scattering. Our results are in good agreement with recent experiments,
indicating that the sensitivity to electron-electron interaction is the
fundamental property of magnetoresistance oscillations, originating from the
second-order Dingle factor.Comment: 6 pages, 4 figure
Temperature Dependence of Magnetophonon Resistance Oscillations in GaAs/AlAs Heterostructures at High Filling Factors
The temperature dependence of phonon-induced resistance oscillations has been
investigated in two-dimensional electron system with moderate mobility at large
filling factors at temperature range T = 7.4 - 25.4 K. The amplitude of
phonon-induced oscillations has been found to be governed by quantum relaxation
time which is determined by electron-electron interaction effects. This is in
agreement with results recently obtained in ultra-high mobility two-dimensional
electron system with low electron density [A. T. Hatke et al., Phys. Rev. Lett.
102, 086808 (2009)]. The shift of the main maximum of the magnetophonon
resistance oscillations to higher magnetic fields with increasing temperature
is observed.Comment: 5 pages, 4 figure
Multidisciplinary Protocol for the Management of Violent Patients and Promotion of Workplace Safety in the Intensive Care Unit
Introduction: Workplace violence is a prevalent issue in healthcare, yet limited evidence informs management options to improve workplace safety associated with violent patients and families. Even less is known about reducing violence in intensive care units (ICUs), a healthcare setting that commonly serves patients at high risk of aggressive behaviors. Multifaceted, interdisciplinary and institution-specific interventions are recommended to address workplace safety.
Methods: Our institution developed four interventions to address the issue of violent patients in our ICUs. The interventions included a Disruptive/Aggressive Behavior Algorithm, Code Grey Box, Rapid Sedation Protocol and a Customer Service Representative. Security calls to the ICUs were the primary measure used to assess effectiveness of the interventions.
Results: Security calls to the ICUs decreased from October 2013 to August 2016, after the implementation of the four interventions.
Discussion: The implementation of four interventions decreased the calls to security, despite encouraging early escalation to security for potentially violent patients. The trend may represent a decrease in violent episodes, increased staff confidence in managing violent patients, or improved early recognition of high-risk patients.
Conclusions: Violent patients and families in the ICU is an understudied workplace safety issue. Our institution used a multifaceted interdisciplinary approach to create and implement interventions which led to a reduction in the need for security personnel response to threats of ICU staff safety. These interventions serve as a guide for other institutions with the aim to decrease workplace violence and promote workplace safety
Inter-subband resistance oscillations in crossed electric and magnetic fields
Quantum oscillations of nonlinear resistance are investigated in response to
electric current and magnetic field applied perpendicular to single GaAs
quantum wells with two populated subbands. At small magnetic fields
current-induced oscillations appear as Landau-Zener transitions between Landau
levels inside the lowest subband. Period of these oscillations is proportional
to the magnetic field. At high magnetic fields different kind of quantum
oscillations emerges with a period,which is independent of the magnetic field.
At a fixed current the oscillations are periodic in inverse magnetic field with
a period that is independent of the dc bias. The proposed model considers these
oscillations as a result of spatial variations of the energy separation between
two subbands induced by the electric current.Comment: 9 Pages, 10 Figure
Reconciling Supersymmetry and Left-Right Symmetry
We construct the minimal supersymmetric left-right theory and show that at
the renormalizable level it requires the existence of an intermediate
breaking scale. The subsequent symmetry breaking down to MSSM automatically
preserves R-symmetry. Furthermore, unlike in the nonsupersymmetric version of
the theory, the see-saw mechanism takes its canonical form. The theory predicts
the existence of a triplet of Higgs scalars much lighter than the
breaking scale.Comment: 4 pages, revtex, no figure
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