589 research outputs found
Global properties of the Skyrme-force-induced nuclear symmetry energy
Large scale calculations are performed to establish the global mass
dependence of the nuclear symmetry energy, , which in turn depends
on two basic ingredients: the mean-level spacing, , and the
effective strength of the isovector mean-potential, . Surprisingly,
our results reveal that in modern parameterizations including SLy4, SkO, SkXc,
and SkP these two basic ingredients of are almost equal after
rescaling them linearly by the isoscalar and the isovector effective masses,
respectively. This result points toward a new fundamental property of the
nuclear interaction that remains to be resolved. In addition, our analysis
determines the ratio of the surface-to-volume contributions to to be
1.6, consistent with hydrodynamical estimates for the static dipole
polarizability as well as the neutron-skin.Comment: 4 pages, 2 figures, 1 tabl
Global nuclear structure effects of tensor interaction
A direct fit of the isoscalar spin-orbit (SO) and both isoscalar and
isovector tensor coupling constants to the f5/2-f7/2 SO splittings in 40Ca,
56Ni, and 48Ca nuclei requires a drastic reduction of the isoscalar SO strength
and strong attractive tensor coupling constants. The aim of this work is to
address further consequences of these strong attractive tensor and weak SO
fields on binding energies, nuclear deformability, and high-spin states. In
particular, we show that contribution to the nuclear binding energy due to the
tensor field shows generic magic structure with tensorial magic numbers at
N(Z)=14, 32, 56, or 90 corresponding to the maximum spin-asymmetries in 1d5/2,
1f7/2-2p3/2, 1g9/2-2d5/2 and 1h11/2-2f7/2 single-particle configurations and
that these numbers are smeared out by pairing correlations and deformation
effects. We also examine the consequences of strong attractive tensor fields
and weak SO interaction on nuclear stability at the drip lines, in particular
close to the tensorial doubly magic nuclei and discuss the possibility of an
entirely new tensor-force driven deformation effect.Comment: replaced with published versio
Global nuclear structure aspects of tensor interaction
A direct fit of the isoscalar spin-orbit and both isoscalar and isovector
tensor coupling constants to the f5/2-f7/2 SO splittings in 40Ca, 56Ni, and
48Ca requires: (i) a significant reduction of the standard isoscalar spin-orbit
strength and (ii) strong attractive tensor coupling constants. The aim of this
paper is to address the consequences of these strong attractive tensor and weak
spin-orbit fields on total binding energies, two-neutron separation energies
and nuclear deformability.Comment: invited talk presented by W. Satula at the XV Nuclear Physics
Workshop, Sept. 24-28, 2008, Kazimierz Dolny, Polan
Performance of a small size telescope (SST-1M) camera for gamma-ray astronomy with the Cherenkov Telescope Array
The foreseen implementations of the Small Size Telescopes (SST) in CTA will
provide unique insights into the highest energy gamma rays offering fundamental
means to discover and under- stand the sources populating the Galaxy and our
local neighborhood. Aiming at such a goal, the SST-1M is one of the three
different implementations that are being prototyped and tested for CTA. SST-1M
is a Davies-Cotton single mirror telescope equipped with a unique camera
technology based on SiPMs with demonstrated advantages over classical
photomultipliers in terms of duty-cycle. In this contribution, we describe the
telescope components, the camera, and the trigger and readout system. The
results of the commissioning of the camera using a dedicated test setup are
then presented. The performances of the camera first prototype in terms of
expected trigger rates and trigger efficiencies for different night-sky
background conditions are presented, and the camera response is compared to
end-to-end simulations.Comment: All CTA contributions at arXiv:1709.0348
Development of a strategy for calibrating the novel SiPM camera of the SST-1M telescope proposed for the Cherenkov Telescope Array
CTA will comprise a sub-array of up to 70 small size telescopes (SSTs) at the
southern array. The SST-1M project, a 4 m-diameter Davies Cotton telescope with
9 degrees FoV and a 1296 pixels SiPM camera, is designed to meet the
requirements of the next generation ground based gamma-ray observatory CTA in
the energy range above 3 TeV. Silicon photomultipliers (SiPM) cameras of
gamma-ray telescopes can achieve good performance even during high night sky
background conditions. Defining a fully automated calibration strategy of SiPM
cameras is of great importance for large scale production validation and online
calibration. The SST-1M sub-consortium developed a software compatible with CTA
pipeline software (CTApipe). The calibration of the SST-1M camera is based on
the Camera Test Setup (CTS), a set of LED boards mounted in front of the
camera. The CTS LEDs are operated in pulsed or continuous mode to emulate
signal and night sky background respectively. Continuous and pulsed light data
analysis allows us to extract single pixel calibration parameters to be used
during CTA operation.Comment: All CTA contributions at arXiv:1709.0348
Endo-(1,4)-beta-Glucanase gene families in the grasses: temporal and spatial Co-transcription of orthologous genes
Extent: 19p.BACKGROUND Endo-(1,4)-β-glucanase (cellulase) glycosyl hydrolase GH9 enzymes have been implicated in several aspects of cell wall metabolism in higher plants, including cellulose biosynthesis and degradation, modification of other wall polysaccharides that contain contiguous (1,4)-β-glucosyl residues, and wall loosening during cell elongation. RESULTS The endo-(1,4)-β-glucanase gene families from barley (Hordeum vulgare), maize (Zea mays), sorghum (Sorghum bicolor), rice (Oryza sativa) and Brachypodium (Brachypodium distachyon) range in size from 23 to 29 members. Phylogenetic analyses show variations in clade structure between the grasses and Arabidopsis, and indicate differential gene loss and gain during evolution. Map positions and comparative studies of gene structures allow orthologous genes in the five species to be identified and synteny between the grasses is found to be high. It is also possible to differentiate between homoeologues resulting from ancient polyploidizations of the maize genome. Transcript analyses using microarray, massively parallel signature sequencing and quantitative PCR data for barley, rice and maize indicate that certain members of the endo-(1,4)-β-glucanase gene family are transcribed across a wide range of tissues, while others are specifically transcribed in particular tissues. There are strong correlations between transcript levels of several members of the endo-(1,4)-β-glucanase family and the data suggest that evolutionary conservation of transcription exists between orthologues across the grass family. There are also strong correlations between certain members of the endo-(1,4)-β-glucanase family and other genes known to be involved in cell wall loosening and cell expansion, such as expansins and xyloglucan endotransglycosylases. CONCLUSIONS The identification of these groups of genes will now allow us to test hypotheses regarding their functions and joint participation in wall synthesis, re-modelling and degradation, together with their potential role in lignocellulose conversion during biofuel production from grasses and cereal crop residues.Margaret Buchanan, Rachel A Burton, Kanwarpal S Dhugga, Antoni J Rafalski, Scott V Tingey, Neil J Shirley and Geoffrey B Finche
Solution of the Skyrme-Hartree-Fock-Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (VII) HFODD (v2.49t): a new version of the program
We describe the new version (v2.49t) of the code HFODD which solves the
nuclear Skyrme Hartree-Fock (HF) or Skyrme Hartree-Fock-Bogolyubov (HFB)
problem by using the Cartesian deformed harmonic-oscillator basis. In the new
version, we have implemented the following physics features: (i) the isospin
mixing and projection, (ii) the finite temperature formalism for the HFB and
HF+BCS methods, (iii) the Lipkin translational energy correction method, (iv)
the calculation of the shell correction. A number of specific numerical methods
have also been implemented in order to deal with large-scale multi-constraint
calculations and hardware limitations: (i) the two-basis method for the HFB
method, (ii) the Augmented Lagrangian Method (ALM) for multi-constraint
calculations, (iii) the linear constraint method based on the approximation of
the RPA matrix for multi-constraint calculations, (iv) an interface with the
axial and parity-conserving Skyrme-HFB code HFBTHO, (v) the mixing of the HF or
HFB matrix elements instead of the HF fields. Special care has been paid to
using the code on massively parallel leadership class computers. For this
purpose, the following features are now available with this version: (i) the
Message Passing Interface (MPI) framework, (ii) scalable input data routines,
(iii) multi-threading via OpenMP pragmas, (iv) parallel diagonalization of the
HFB matrix in the simplex breaking case using the ScaLAPACK library. Finally,
several little significant errors of the previous published version were
corrected.Comment: Accepted for publication to Computer Physics Communications. Program
files re-submitted to Comp. Phys. Comm. Program Library after correction of
several minor bug
Control Software for the SST-1M Small-Size Telescope prototype for the Cherenkov Telescope Array
The SST-1M is a 4-m Davies--Cotton atmospheric Cherenkov telescope optimized
to provide gamma-ray sensitivity above a few TeV. The SST-1M is proposed as
part of the Small-Size Telescope array for the Cherenkov Telescope Array (CTA),
the first prototype has already been deployed. The SST-1M control software of
all subsystems (active mirror control, drive system, safety system,
photo-detection plane, DigiCam, CCD cameras) and the whole telescope itself
(master controller) uses the standard software design proposed for all CTA
telescopes based on the ALMA Common Software (ACS) developed to control the
Atacama Large Millimeter Array (ALMA). Each subsystem is represented by a
separate ACS component, which handles the communication to and the operation of
the subsystem. Interfacing with the actual hardware is performed via the OPC UA
communication protocol, supported either natively by dedicated industrial
standard servers (PLCs) or separate service applications developed to wrap
lower level protocols (e.g. CAN bus, camera slow control) into OPC UA. Early
operations of the telescope without the camera were already carried out. The
camera is fully assembled and is capable to perform data acquisition using
artificial light source.Comment: In Proceedings of the 35th International Cosmic Ray Conference
(ICRC2017), Busan, Korea. All CTA contributions at arXiv:1709.0348
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