521 research outputs found
Spurious Shell Closures in the Relativistic Mean Field Model
Following a systematic theoretical study of the ground-state properties of
over 7000 nuclei from the proton drip line to the neutron drip line in the
relativistic mean field model [Prog. Theor. Phys. 113 (2005) 785], which is in
fair agreement with existing experimental data, we observe a few spurious shell
closures, i.e. proton shell closures at Z=58 and Z=92. These spurious shell
closures are found to persist in all the effective forces of the relativistic
mean field model, e.g. TMA, NL3, PKDD and DD-ME2.Comment: 3 pages, to appear in Chinese Physics Letter
Projection and ground state correlations made simple
We develop and test efficient approximations to estimate ground state
correlations associated with low- and zero-energy modes. The scheme is an
extension of the generator-coordinate-method (GCM) within Gaussian overlap
approximation (GOA). We show that GOA fails in non-Cartesian topologies and
present a topologically correct generalization of GOA (topGOA). An RPA-like
correction is derived as the small amplitude limit of topGOA, called topRPA.
Using exactly solvable models, the topGOA and topRPA schemes are compared with
conventional approaches (GCM-GOA, RPA, Lipkin-Nogami projection) for
rotational-vibrational motion and for particle number projection. The results
shows that the new schemes perform very well in all regimes of coupling.Comment: RevTex, 12 pages, 7 eps figure
On the coefficients of the liquid drop model mass formulae and nuclear radii
The coefficients of different mass formulae derived from the liquid drop
model and including or not the curvature energy, the diffuseness correction to
the Coulomb energy, the charge exchange correction term, different forms of the
Wigner term and different powers of the relative neutron excess
have been determined by a least square fitting procedure to 2027 experimental
atomic masses. The Coulomb diffuseness correction term or the charge
exchange correction term plays the main role to improve the
accuracy of the mass formula. The Wigner term and the curvature energy can also
be used separately for the same purpose. The introduction of an
dependence in the surface and volume energies improves slightly the efficiency
of the expansion and is more effective than an dependence. Different
expressions reproducing the experimental nuclear charge radius are provided.
The different fits lead to a surface energy coefficient of around 17-18 MeV and
a relative equivalent rms charge radius r of 1.22-1.23 fm.Comment: 19 pages, 1 figure, accepted for publication in Nuclear Physics
Adjustment studies in self-consistent relativistic mean-field models
We investigate the influence of the adjustment procedure and the set of
measured observables on the properties and predictive power of relativistic
self-consistent mean-field models for the nuclear ground state. These studies
are performed with the point-coupling variant of the relativistic mean-field
model. We recommend optimal adjustment algorithms for the general two-part
problem and we identify various trends and dependencies as well as deficiencies
of current models. Consequences for model improvements are presented.Comment: 18 pages, 6 figures, revised version, accepted for publication in
Nuclear Physics
Using sea cucumbers to illustrate the basics of zoological nomenclature
In addition to a brief account of the need to have unique and unambiguous scientific names for taxa, this paper, annotated with examples of sea cucumbers, explains the basics of zoological nomenclature. In doing so it aims to reduce the confusion that exists among various breeds of end-users of taxonomists who may not fully understand the seemingly arbitrary and often volatile nature of scientific names. This paper also aims to provide teachers and students with a comprehensible account of the basic principles of zoological nomenclature
First Experiences with the New Law on DUID in Belgium: Alcohol and Medicines in Drug Negative Cases
Abstract In March 1999 a new law prohibiting driving while impaired by illegal drugs was introduced in Belgium. The legal procedure consists of a) a field impairment test, b) a urine immunoassay for 4 drug groups and c) ultimate proof by plasma analysis (GC-MS with fixed cut-offs). Over about two years the analysis of 896 blood samples revealed the presence of illicit drug(s) above cut-off in 85% of the cases. For the 15% "false positives" (failed impairment test and positive urine assay without confirmation in plasma) we investigated the possible reasons for impaired behavior. The presence of alcohol and psychoactive medication stands for an important number of our 'false positives'. The results adduce arguments for introducing psychotropic medicines in our traffic law. Our findings further suggest that false positive cases can be reduced by minimizing the delay before blood sampling and optimizing sample preservation. Harmonization of the strategy for detection and penalization of impaired drivers (alcohol and/or drugs) is highly recommended. Introduction In March 1999 a new law on driving under the influence of illegal drugs was introduced in Belgium. The legal procedure is a three-step process: a) a field impairment test, i.e. the assessment of external signs of the presence of drugs by a standardized test battery, b) an onsite immunoassay for amphetamines, cannabinoids, cocaine metabolites or opiates in urine and c) blood sampling for plasma GC/MS analysis with the following analytical cut-offs: THC (tetrahydrocannabinol) 2 ng/mL, free morphine 20 ng/mL, amphetamine, MDMA (ecstasy), MDEA, MBDB, benzoylecgonine (BE) or cocaine 50 ng/mL. The urine test resp. the plasma analysis are performed on the condition that the driver fails the preceding test(s) (1,2). In 2000-2001 the analysis of 896 blood samples revealed the presence of one or more illicit drug(s) above cut-off in 85% of the cases (2). We investigated the 15% 'false positives', i.e. cases where the driver failed the field impairment test and the urine immunoassay test was positive for at least one drug group, but where the plasma GC-MS analysis revealed no prohibited drug above cut-off. In such cases the full legal procedure for driving under the influence of illicit drugs was completed but the driver was not fined or penalized
Using XDAQ in Application Scenarios of the CMS Experiment
XDAQ is a generic data acquisition software environment that emerged from a
rich set of of use-cases encountered in the CMS experiment. They cover not the
deployment for multiple sub-detectors and the operation of different processing
and networking equipment as well as a distributed collaboration of users with
different needs. The use of the software in various application scenarios
demonstrated the viability of the approach. We discuss two applications, the
tracker local DAQ system for front-end commissioning and the muon chamber
validation system. The description is completed by a brief overview of XDAQ.Comment: Conference CHEP 2003 (Computing in High Energy and Nuclear Physics,
La Jolla, CA
The CMS Event Builder
The data acquisition system of the CMS experiment at the Large Hadron
Collider will employ an event builder which will combine data from about 500
data sources into full events at an aggregate throughput of 100 GByte/s.
Several architectures and switch technologies have been evaluated for the DAQ
Technical Design Report by measurements with test benches and by simulation.
This paper describes studies of an EVB test-bench based on 64 PCs acting as
data sources and data consumers and employing both Gigabit Ethernet and Myrinet
technologies as the interconnect. In the case of Ethernet, protocols based on
Layer-2 frames and on TCP/IP are evaluated. Results from ongoing studies,
including measurements on throughput and scaling are presented.
The architecture of the baseline CMS event builder will be outlined. The
event builder is organised into two stages with intelligent buffers in between.
The first stage contains 64 switches performing a first level of data
concentration by building super-fragments from fragments of 8 data sources. The
second stage combines the 64 super-fragments into full events. This
architecture allows installation of the second stage of the event builder in
steps, with the overall throughput scaling linearly with the number of switches
in the second stage. Possible implementations of the components of the event
builder are discussed and the expected performance of the full event builder is
outlined.Comment: Conference CHEP0
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