7,835 research outputs found
Three-dimensional implicit lambda methods
This paper derives the three dimensional lambda-formulation equations for a general orthogonal curvilinear coordinate system and provides various block-explicit and block-implicit methods for solving them, numerically. Three model problems, characterized by subsonic, supersonic and transonic flow conditions, are used to assess the reliability and compare the efficiency of the proposed methods
Nonlinear metrology with a quantum interface
We describe nonlinear quantum atom-light interfaces and nonlinear quantum
metrology in the collective continuous variable formalism. We develop a
nonlinear effective Hamiltonian in terms of spin and polarization collective
variables and show that model Hamiltonians of interest for nonlinear quantum
metrology can be produced in Rb ensembles. With these Hamiltonians,
metrologically relevant atomic properties, e.g. the collective spin, can be
measured better than the "Heisenberg limit" . In contrast to other
proposed nonlinear metrology systems, the atom-light interface allows both
linear and non-linear estimation of the same atomic quantities.Comment: 8 pages, 1 figure
Synthetic aperture radar images of ocean waves, theories of imaging physics and experimental tests
The physical mechanism for the synthetic Aperture Radar (SAR) imaging of ocean waves is investigated through the use of analytical models. The models are tested by comparison with data sets from the SEASAT mission and airborne SAR's. Dominant ocean wavelengths from SAR estimates are biased towards longer wavelengths. The quasispecular scattering mechanism agrees with experimental data. The Doppler shift for ship wakes is that of the mean sea surface
Catalog of quasars from the Kilo-Degree Survey Data Release 3
We present a catalog of quasars selected from broad-band photometric ugri
data of the Kilo-Degree Survey Data Release 3 (KiDS DR3). The QSOs are
identified by the random forest (RF) supervised machine learning model, trained
on SDSS DR14 spectroscopic data. We first cleaned the input KiDS data from
entries with excessively noisy, missing or otherwise problematic measurements.
Applying a feature importance analysis, we then tune the algorithm and identify
in the KiDS multiband catalog the 17 most useful features for the
classification, namely magnitudes, colors, magnitude ratios, and the stellarity
index. We used the t-SNE algorithm to map the multi-dimensional photometric
data onto 2D planes and compare the coverage of the training and inference
sets. We limited the inference set to r<22 to avoid extrapolation beyond the
feature space covered by training, as the SDSS spectroscopic sample is
considerably shallower than KiDS. This gives 3.4 million objects in the final
inference sample, from which the random forest identified 190,000 quasar
candidates. Accuracy of 97%, purity of 91%, and completeness of 87%, as derived
from a test set extracted from SDSS and not used in the training, are confirmed
by comparison with external spectroscopic and photometric QSO catalogs
overlapping with the KiDS footprint. The robustness of our results is
strengthened by number counts of the quasar candidates in the r band, as well
as by their mid-infrared colors available from WISE. An analysis of parallaxes
and proper motions of our QSO candidates found also in Gaia DR2 suggests that a
probability cut of p(QSO)>0.8 is optimal for purity, whereas p(QSO)>0.7 is
preferable for better completeness. Our study presents the first comprehensive
quasar selection from deep high-quality KiDS data and will serve as the basis
for versatile studies of the QSO population detected by this survey.Comment: Data available from the KiDS website at
http://kids.strw.leidenuniv.nl/DR3/quasarcatalog.php and the source code from
https://github.com/snakoneczny/kids-quasar
Certified quantum non-demolition measurement of material systems
An extensive debate on quantum non-demolition (QND) measurement, reviewed in
Grangier et al. [Nature, {\bf 396}, 537 (1998)], finds that true QND
measurements must have both non-classical state-preparation capability and
non-classical information-damage tradeoff. Existing figures of merit for these
non-classicality criteria require direct measurement of the signal variable and
are thus difficult to apply to optically-probed material systems. Here we
describe a method to demonstrate both criteria without need for to direct
signal measurements. Using a covariance matrix formalism and a general noise
model, we compute meter observables for QND measurement triples, which suffice
to compute all QND figures of merit. The result will allow certified QND
measurement of atomic spin ensembles using existing techniques.Comment: 11 pages, zero figure
Hemoglobin-Based Oxygen Carrier for Traumatic Hemorrhagic Shock Treatment in a Jehovah’s Witness
Introduction: Treatment of severe hemorrhagic shock due to acute blood loss from traumatic injuries in a Jehovah’s witness (JW) trauma patient is very challenging since hemostatic blood product resuscitation is limited by refusal of the transfusion of allogeneic blood products.
Case Presentation: We describe a multifaceted approach to the clinical care of a severely anemic JW trauma patient including the early administration of a bovine hemoglobin-based oxygen carrier (HBOC) as a bridge to resolution of critical anemia (nadir hemoglobin 3.9 g/dL). Hemoglobin-based oxygen carrier infusions were used to supplement oxygen delivery until endogenous erythropoiesis could restore adequate red blood cell mass. Subsequent endogenous bone marrow recovery was supported by early administration of high-dose erythropoiesis-stimulating agents and iron supplementation.
Conclusions: Early HBOC administration can be used in the treatment of severe hemorrhagic shock in trauma patients who refuse allogeneic blood
How do we treat life‐threatening anemia in a J ehovah's W itness patient?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109968/1/trf12888.pd
Evolution of central dark matter of early-type galaxies up to z ~ 0.8
We investigate the evolution of dark and luminous matter in the central
regions of early-type galaxies (ETGs) up to z ~ 0.8. We use a spectroscopically
selected sample of 154 cluster and field galaxies from the EDisCS survey,
covering a wide range in redshifts (z ~ 0.4-0.8), stellar masses ( ~ 10.5-11.5 dex) and velocity dispersions
( ~ 100-300 \, km/s). We obtain central dark matter (DM)
fractions by determining the dynamical masses from Jeans modelling of galaxy
aperture velocity dispersions and the from galaxy colours, and
compare the results with local samples. We discuss how the correlations of
central DM with galaxy size (i.e. the effective radius, ),
and evolve as a function of redshift, finding
clear indications that local galaxies are, on average, more DM dominated than
their counterparts at larger redshift. This DM fraction evolution with can
be only partially interpreted as a consequence of the size-redshift evolution.
We discuss our results within galaxy formation scenarios, and conclude that the
growth in size and DM content which we measure within the last 7 Gyr is
incompatible with passive evolution, while it is well reproduced in the
multiple minor merger scenario. We also discuss the impact of the IMF on our DM
inferences and argue that this can be non-universal with the lookback time. In
particular, we find the Salpeter IMF can be better accommodated by low redshift
systems, while producing stellar masses at high- which are unphysically
larger than the estimated dynamical masses (particularly for
lower- systems).Comment: 14 pages, 6 figures, 3 tables, MNRAS in pres
Stochastic gradient approach for energy and supply optimisation in water systems management
Under conditions of water scarcity, energy saving in operation of water pumping plants and the minimisation of water deficit for users and activities are frequently contrasting requirements, which should be considered when optimising large-scale multi-reservoirs and multi-users water supply systems. Undoubtedly, a high uncertainty level in predicted water resources due to hydrologic input variability and water demand behaviour characterizes this problem. The aim of this paper is to provide an efficient decision support system considering emergency water pumping plants activation schedules. The obtained results should allow the water system’s authority to adopt a robust decision policy, minimising the risk of harmful future decisions concerning the water resource management. The model has been here developed to manage this problem, in order to reduce the damages due to shortage of water and the energy-cost requirements of pumping plants. Particularly, in optimisation, we look for optimal rules considering both historical and generated synthetic scenarios of hydrologic inputs to reservoirs. Hence, using synthetic series, we can analyse climate change impacts and optimise the activation rules considering future hydrologic occurrences. A simulation model has been coupled with an optimization module using the stochastic gradient method to get robust pumping activation thresholds. This method allows to solve complex problems, solving efficiently large size real cases due to high number of data and variables. Thresholds values are identified in terms of critical storage levels in supply-reservoirs. Application of the modelling approach has been developed on a real case study in a water-shortage prone area in south-Sardinia (Italy), characterized by Mediterranean climate and high annual variability in hydrological input to reservoirs. By applying the combined simulation procedure, a robust decision strategy in pumping activation was obtained. Developing the stochastic gradient model, a main programming supports has been built by MATLAB efficiently interfaced with CPLEX for optimisation and Excel for inputs and results representation
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