4,345 research outputs found
Simulations of Contrail Optical Properties and Radiative Forcing for Various Crystal Shapes
The aim of this study is to investigate the sensitivity of radiative-forcing computations to various contrail
crystal shape models. Contrail optical properties in the shortwave and longwave ranges are derived using
a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods
present good correspondence of the single-scattering albedo and the asymmetry parameter in a transition
range (3–8 µm). There are substantial differences in single-scattering properties among 10 crystal models
investigated here (e.g., hexagonal columns and plates with different aspect ratios, and spherical particles). The
single-scattering albedo and the asymmetry parameter both vary by up to 0.1 among various crystal shapes.
The computed single-scattering properties are incorporated in the moderate-resolution atmospheric radiance
and transmittance model(MODTRAN) radiative transfer code to simulate solar and infrared fluxes at the top
of the atmosphere. Particle shapes have a strong impact on the contrail radiative forcing in both the shortwave
and longwave ranges. The differences in the net radiative forcing among optical models reach 50% with
respect to the mean model value. The hexagonal-column and hexagonal-plate particles show the smallest net
radiative forcing, and the largest forcing is obtained for the spheres. The balance between the shortwave
forcing and longwave forcing is highly sensitive with respect to the assumed crystal shape and may even
change the sign of the net forcing. The optical depth at which the mean diurnal radiative forcing changes sign
from positive to negative varies from 4.5 to 10 for a surface albedo of 0.2 and from 2 to 6.5 for a surface albedo
of 0.05. Contrails are probably never that optically thick (except for some aged contrail cirrus), however, and
so will not have a cooling effect on climate
VELO-TT track reconstruction
The paper describes the track reconstruction in the system of VELO and TT detectors. Two separate algorithms for off-line and on-line approaches were merged. The single algorithm consists of the common code for pattern recognition and two parts specific to off-line and on-line functionalities. The note presents the performance in terms of track reconstruction efficiency and ghost rate
Measurement of g-factor tensor in a quantum dot and disentanglement of exciton spins
We perform polarization-resolved magneto-optical measurements on single InAsP
quantum dots embedded in an InP nanowire. In order to determine all elements of
the electron and hole -factor tensors, we measure in magnetic field with
different orientations. The results of these measurements are in good agreement
with a model based on exchange terms and Zeeman interaction. In our experiment,
polarization analysis delivers a powerful tool that not only significantly
increases the precision of the measurements, but also enables us to probe the
exciton spin state evolution in magnetic fields. We propose a disentangling
scheme of heavy-hole exciton spins enabling a measurement of the electron spin
time
Primary vertex reconstruction
This report reviews the improved method of primary vertex off-line reconstruction. The new method for primary vertex seed finding as well as modified procedure for vertex fit have been briefly described. Results of the primary vertex reconstruction performance are presented and compared to the previous version of the package. Improvement in the primary vertex reconstruction efficiencies is observed. Small but statistically significant bias, coming mostly from the long-living tracks as well as from a bias of the Velo measurements present in the DC06 simulation, affects the determination of the primary vertex position along the beam direction
Head-on collisions of unequal mass black holes in D=5 dimensions
We study head-on collisions of unequal mass black hole binaries in D=5
space-time dimensions, with mass ratios between 1:1 and 1:4. Information about
gravitational radiation is extracted by using the Kodama-Ishibashi
gauge-invariant formalism and details of the apparent horizon of the final
black hole. For the first time, we present waveforms, total integrated energy
and momentum for this process. Our results show surprisingly good agreement,
within 5% or less, with those extrapolated from linearized, point-particle
calculations. Our results also show that consistency with the area theorem
bound requires that the same process in a large number of spacetime dimensions
must display new features.Comment: 10 pages, 5 figures, RevTex4. v2: Published versio
Spin-induced dynamical scalarization, de-scalarization and stealthness in scalar-Gauss-Bonnet gravity during black hole coalescence
Particular couplings between a scalar field and the Gauss-Bonnet invariant lead to spontaneous scalarization of black holes. Here we continue our work on simulating this phenomenon in the context of binary black hole systems. We consider a negative coupling for which the black-hole spin plays a major role in the scalarization process. We find two main phenomena: (i) dynamical descalarization, in which initially scalarized black holes form an unscalarized remnant, and (ii) dynamical scalarization, whereby the late merger of initially unscalarized black holes can cause scalar hair to grow. An important consequence of the latter case is that modifications to the gravitational waveform due to the scalar field may only occur post-merger, as its presence is hidden during the entirety of the inspiral. However, with a sufficiently strong coupling, we find that scalarization can occur before the remnant has even formed. We close with a discussion of observational implications for gravitational-wave tests of general relativity
Numerical relativity for D dimensional axially symmetric space-times: formalism and code tests
The numerical evolution of Einstein's field equations in a generic background
has the potential to answer a variety of important questions in physics: from
applications to the gauge-gravity duality, to modelling black hole production
in TeV gravity scenarios, analysis of the stability of exact solutions and
tests of Cosmic Censorship. In order to investigate these questions, we extend
numerical relativity to more general space-times than those investigated
hitherto, by developing a framework to study the numerical evolution of D
dimensional vacuum space-times with an SO(D-2) isometry group for D\ge 5, or
SO(D-3) for D\ge 6.
Performing a dimensional reduction on a (D-4)-sphere, the D dimensional
vacuum Einstein equations are rewritten as a 3+1 dimensional system with source
terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN)
formulation. This allows the use of existing 3+1 dimensional numerical codes
with small adaptations. Brill-Lindquist initial data are constructed in D
dimensions and a procedure to match them to our 3+1 dimensional evolution
equations is given. We have implemented our framework by adapting the LEAN code
and perform a variety of simulations of non-spinning black hole space-times.
Specifically, we present a modified moving puncture gauge which facilitates
long term stable simulations in D=5. We further demonstrate the internal
consistency of the code by studying convergence and comparing numerical versus
analytic results in the case of geodesic slicing for D=5,6.Comment: 31 pages, 6 figures; v2 Minor changes and added two references.
Matches the published version in PRD
Elevating crop disease resistance with cloned genes
Essentially all plant species exhibit heritable genetic variation for resistance to a variety of plant diseases caused by fungi, bacteria, oomycetes or viruses. Disease losses in crop monocultures are already significant, and would be greater but for applications of disease-controlling agrichemicals. For sustainable intensification of crop production, we argue that disease control should as far as possible be achieved using genetics rather than using costly recurrent chemical sprays. The latter imply CO2 emissions from diesel fuel and potential soil compaction from tractor journeys. Great progress has been made in the past 25 years in our understanding of the molecular basis of plant disease resistance mechanisms, and of how pathogens circumvent them. These insights can inform more sophisticated approaches to elevating disease resistance in crops that help us tip the evolutionary balance in favour of the crop and away from the pathogen. We illustrate this theme with an account of a genetically modified (GM) blight-resistant potato trial in Norwich, using the Rpi-vnt1.1 gene isolated from a wild relative of potato, Solanum venturii, and introduced by GM methods into the potato variety Desiree
Cell Separations and Sorting
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Analytical Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.analchem.9b05357.NIBIB Grant P41-EB020594COBRE Grant 5P20GM13042
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