25 research outputs found
New insight on pseudospin doublets in nuclei
The relevance of the pseudospin symmetry in nuclei is considered. New insight
is obtained from looking at the continuous transition from a model satisfying
the spin symmetry to another one satisfying the pseudospin symmetry. This study
suggests that there are models allowing no missing single-particle states in
this transition, contrary to what is usually advocated. It rather points out to
an association of pseudospin partners different from the one usually assumed,
together with a strong violation of the corresponding symmetry. A comparison
with results obtained from some relativistic approaches is made.Comment: 27 pages, 18 figure
Self-Control in Cyberspace: Applying Dual Systems Theory to a Review of Digital Self-Control Tools
Many people struggle to control their use of digital devices. However, our
understanding of the design mechanisms that support user self-control remains
limited. In this paper, we make two contributions to HCI research in this
space: first, we analyse 367 apps and browser extensions from the Google Play,
Chrome Web, and Apple App stores to identify common core design features and
intervention strategies afforded by current tools for digital self-control.
Second, we adapt and apply an integrative dual systems model of self-regulation
as a framework for organising and evaluating the design features found. Our
analysis aims to help the design of better tools in two ways: (i) by
identifying how, through a well-established model of self-regulation, current
tools overlap and differ in how they support self-control; and (ii) by using
the model to reveal underexplored cognitive mechanisms that could aid the
design of new tools.Comment: 11.5 pages (excl. references), 6 figures, 1 tabl
Cavity optomechanics on a microfluidic resonator with water and viscous liquids
Currently, optical- or mechanical-resonances are commonly used in
microfluidic research. However, optomechanical oscillations by light pressure
were not shown with liquids. This is because replacing the surrounding air with
water inherently increases the acoustical impedance and hence the associated
acoustical radiation-losses. Here, we bridge between microfluidics and
optomechanics by fabricating hollow bubble resonators with liquid inside and
optically exciting 100-MHz vibrations with only mW optical-input power. This
constitutes the first time that any microfluidic system is optomechanically
actuated. We further prove the feasibility of microfluidic optomechanics on
liquids by demonstrating vibrations on organic fluids with viscous-dissipation
higher than blood viscosity while measuring density changes in the liquid via
the vibration frequency shift. Our device will enable using cavity
optomechanics for studying non-solid phases of matter
One and two dimensional analysis of 3pi correlations measured in Pb+Pb interactions
3pi- correlations from Pb+Pb collisions at 158 GeV/c per nucleon are
presented as measured by the focusing spectrometer of the NA44 experiment at
CERN. The three-body effect is found to be stronger for PbPb than for SPb. The
two-dimensional three-particle correlation function is also measured and the
longitudinal extension of the source is larger than the transverse extension
Gaia Data Release 2 Observations of solar system objects
CONTEXT: The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs)
since the beginning of its operations. Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs. These
asteroids have been already identified and have been numbered by the Minor Planet Center repository. Positions are provided for each
Gaia observation at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered
G band is also provided for selected observations.
AIMS: We explain the processing of SSO data, and describe the criteria we used to select the sample published in Gaia DR2. We then
explore the data set to assess its quality.
METHODS: To exploit the main data product for the solar system in Gaia DR2, which is the epoch astrometry of asteroids, it is necessary
to take into account the unusual properties of the uncertainty, as the position information is nearly one-dimensional. When this aspect
is handled appropriately, an orbit fit can be obtained with post-fit residuals that are overall consistent with the a-priori error model that
was used to define individual values of the astrometric uncertainty. The role of both random and systematic errors is described. The
distribution of residuals allowed us to identify possible contaminants in the data set (such as stars). Photometry in the G band was
compared to computed values from reference asteroid shapes and to the flux registered at the corresponding epochs by the red and blue
photometers (RP and BP).
RESULTS: The overall astrometric performance is close to the expectations, with an optimal range of brightness G ⌠12 â 17. In this
range, the typical transit-level accuracy is well below 1 mas. For fainter asteroids, the growing photon noise deteriorates the performance.
Asteroids brighter than G ⌠12 are affected by a lower performance of the processing of their signals. The dramatic improvement
brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons to the archive data and by preliminary tests on the detection
of subtle non-gravitational effects
Cerebellocerebral diaschisis is the likely mechanism of postsurgical posterior fossa syndrome in pediatric patients with midline cerebellar tumors
BACKGROUND AND PURPOSE: PFS occurs in approximately 25% of pediatric patients receiving surgery for midline posterior fossa tumors. Increasing evidence suggests that PFS represents a complex supratentorial cortical dysfunction related to surgery-induced disruption of critical cerebellocerebral connections. The purpose of this study was to determine whether a consistent surgical damage pattern may be identified in patients with PFS by early postoperative anatomic imaging analysis of the pECP and to test whether DSC can detect corresponding changes in cerebral cortical perfusion to indicate a secondary, remote functional disturbance, which could suggest a diaschisis-like pathomechanism