1,080 research outputs found
Review on String Breaking - the Query in Quest of the Evidence
Considerable progress has been achieved recently in the observation of string
breaking within non-Abelian Higgs models, by use of multi-channel methods
allowing for broken string states. Similarly, in pure gauge theory this
approach has been shown to reveal string breaking for color charges in the
adjoint represaentation. For QCD with dynmical fermions, one needs substantial
progress in noise reduction, however, to render such techniques viable.Comment: June 1999, 6 pages, 11 figures. Plenary talk presented at the 17th
Int. Symposium on Lattice Field Theory (Lattice 99), Pisa, Italy 29 Jun - 3
Jul, 199
Исследование влияние состава и процессов нагрева на эффективность люминесценции люминофоров на основе алюмоиттриевого граната
Investigation of the Electric Field and Charge Density Distribution of pristine and defective 2D WSe by Differential Phase Contrast Imaging
Most properties of solid materials are defined by their internal electric
field and charge density distributions which so far have been difficult to
measure with sufficient spatial resolution. For 2D materials, the electric
field at the atomic level in particular influences the optoelectronic
properties. In this study, the atomic-scale electric field and charge density
distribution of 2D WSe are revealed by using an emerging microscopy
technique, differential phase contrast (DPC) imaging in the scanning
transmission electron microscope (STEM). Combined with high-angle annular
dark-field imaging the charge density distribution of bi- and trilayers of
WSe is mapped. A measured higher positive charge density located at the
selenium atomic columns compared to the tungsten atomic columns is reported,
and possible reasons are discussed. Furthermore, the change in the electric
field distribution of a selenium point defect in a trilayer is investigated
exhibiting a characteristic electric field distribution in the vicinity of the
defect: there are characteristic regions with locally enhanced and with locally
reduced electric field magnitudes compared to the pristine lattice.Comment: 20 pages including the supplementary information, 3 figures in the
main part and additional 2 figures in the supplementary informatio
Discharges of past flood events based on historical river profiles
International audienceThis paper presents a case study to estimate peak discharges of extreme flood events of Neckar River in south-western Germany during the 19th century. It was carried out within the BMBF research project RIMAX (Risk Management of Extreme Flood Events). The discharge estimations were made for the flood events of 1824 and 1882 based on historical cross profiles. The 1-D model Hydrologic Engineering Centers River Analysis System (HEC-RAS) was applied with different roughness coefficients. The results are compared (i) with contemporary historical calculations and (ii) in the case of a flood event in 1824 with the discharge simulation by the water balance model LARSIM (Large Area Runoff Simulation Model). These calculations are matched by the HEC-RAS simulation based on the standard roughness coefficients
Fully adaptive multiresolution schemes for strongly degenerate parabolic equations with discontinuous flux
A fully adaptive finite volume multiresolution scheme for one-dimensional
strongly degenerate parabolic equations with discontinuous flux is presented.
The numerical scheme is based on a finite volume discretization using the
Engquist--Osher approximation for the flux and explicit time--stepping. An
adaptivemultiresolution scheme with cell averages is then used to speed up CPU
time and meet memory requirements. A particular feature of our scheme is the
storage of the multiresolution representation of the solution in a dynamic
graded tree, for the sake of data compression and to facilitate navigation.
Applications to traffic flow with driver reaction and a clarifier--thickener
model illustrate the efficiency of this method
Factors determining microbial colonization of liquid nitrogen storage tanks used for archiving biological samples
The availability of bioresources is a precondition for life science research, medical applications, and diagnostics, but requires a dedicated quality management to guarantee reliable and safe storage. Anecdotal reports of bacterial isolates and sample contamination indicate that organisms may persist in liquid nitrogen (LN) storage tanks. To evaluate the safety status of cryocollections, we systematically screened organisms in the LN phase and in ice layers covering inner surfaces of storage tanks maintained in different biobanking facilities. We applied a culture-independent approach combining cell detection by epifluorescence microscopy with the amplification of group-specific marker genes and high-throughput sequencing of bacterial ribosomal genes. In the LN phase, neither cells nor bacterial 16S rRNA gene copy numbers were detectable (detection limit, 102 cells per ml, 103 gene copies per ml). In several cases, small numbers of bacteria of up to 104 cells per ml and up to 106 gene copies per ml, as well as Mycoplasma, or fungi were detected in the ice phase formed underneath the lids or accumulated at the bottom. The bacteria most likely originated from the stored materials themselves (Elizabethingia, Janthibacterium), the technical environment (Pseudomonas, Acinetobacter, Methylobacterium), or the human microbiome (Bacteroides, Streptococcus, Staphylococcus). In single cases, bacteria, Mycoplasma, fungi, and human cells were detected in the debris at the bottom of the storage tanks. In conclusion, the limited microbial load of the ice phase and in the debris of storage tanks can be effectively avoided by minimizing ice formation and by employing hermetically sealed sample containers
Schwinger Boson Formulation and Solution of the Crow-Kimura and Eigen Models of Quasispecies Theory
We express the Crow-Kimura and Eigen models of quasispecies theory in a
functional integral representation. We formulate the spin coherent state
functional integrals using the Schwinger Boson method. In this formulation, we
are able to deduce the long-time behavior of these models for arbitrary
replication and degradation functions.
We discuss the phase transitions that occur in these models as a function of
mutation rate. We derive for these models the leading order corrections to the
infinite genome length limit.Comment: 37 pages; 4 figures; to appear in J. Stat. Phy
Extraction of thermal and electromagnetic properties in 45Ti
The level density and gamma-ray strength function of 45Ti have been
determined by use of the Oslo method. The particle-gamma coincidences from the
46Ti(p,d gamma)45Ti pick-up reaction with 32 MeV protons are utilized to obtain
gamma-ray spectra as function of excitation energy. The extracted level density
and strength function are compared with models, which are found to describe
these quantities satisfactorily. The data do not reveal any single-particle
energy gaps of the underlying doubly magic 40Ca core, probably due to the
strong quadruple deformation
Single-crossover dynamics: finite versus infinite populations
Populations evolving under the joint influence of recombination and
resampling (traditionally known as genetic drift) are investigated. First, we
summarise and adapt a deterministic approach, as valid for infinite
populations, which assumes continuous time and single crossover events. The
corresponding nonlinear system of differential equations permits a closed
solution, both in terms of the type frequencies and via linkage disequilibria
of all orders. To include stochastic effects, we then consider the
corresponding finite-population model, the Moran model with single crossovers,
and examine it both analytically and by means of simulations. Particular
emphasis is on the connection with the deterministic solution. If there is only
recombination and every pair of recombined offspring replaces their pair of
parents (i.e., there is no resampling), then the {\em expected} type
frequencies in the finite population, of arbitrary size, equal the type
frequencies in the infinite population. If resampling is included, the
stochastic process converges, in the infinite-population limit, to the
deterministic dynamics, which turns out to be a good approximation already for
populations of moderate size.Comment: 21 pages, 4 figure
- …