5,170 research outputs found
Relativistic effects in the production of pseudoscalar and vector doubly heavy mesons from e^+e^- annihilation
On the basis of the perturbative QCD and the relativistic quark model we
investigate the relativistic and bound state effects in the production
processes of a pair of -wave doubly heavy mesons with opposite charge
conjugation consisting of and quarks. All possible relativistic
corrections in the production amplitude including the terms connected with the
transformation law of the bound state wave function to the reference frame of
the moving pseudoscalar and vector mesons are taken
into account. We obtain a growth of the cross section for the reaction
due to considered effects by a factor
in the range of the center-of-mass energy GeV.Comment: 18 pages, 4 figure
Cytological and molecular description of Hamiltosporidium tvaerminnensis gen. et sp. nov., a microsporidian parasite of Daphnia magna, and establishment of Hamiltosporidium magnivora comb. nov.
We describe the new microsporidium Hamiltosporidium tvaerminnensis gen. et sp. nov. with an emphasis on its ultrastructural characteristics and phylogenetic position as inferred from the sequence data of SSU rDNA, alpha-and beta-tubulin. This parasite was previously identified as Octosporea bayeri Jirovec, 1936 and has become a model system to study the ecology, epidemiology, evolution and genomics of microsporidia - host interactions. Here, we present evidence that shows its differences from O. bayeri. Hamiltosporidium tvaerminnensis exclusively infects the adipose tissue, the ovaries and the hypodermis of Daphnia magna and is found only in host populations located in coastal rock pool populations in Finland and Sweden. Merogonial stages of H. tvaerminnensis have isolated nuclei; merozoites are formed by binary fission or by the cleaving of a plasmodium with a small number of nuclei. A sporogonial plasmodium with isolated nuclei yields 8 sporoblasts. Elongated spores are generated by the most finger-like plasmodia. The mature spores are polymorphic in shape and size. Most spores are pyriform (4.9-5.6x2.2-2.3 mu m) and have their polar filament arranged in 12-13 coils. A second, elongated spore type (6.8-12.0x1.6-2.1 mu m) is rod-shaped with blunt ends and measures 6.8-12.0x1.6-2.1 mu m. The envelope of the sporophorous vesicle is thin and fragile, formed at the beginning of the sporogony. Cytological and molecular comparisons with Flabelliforma magnivora, a parasite infecting the same tissues in the same host species, reveal that these two species are very closely related, yet distinct. Moreover, both cytological and molecular data indicate that these species are quite distant from F. montana, the type species of the genus Flabelliforma. We therefore propose that F. magnivora also be placed in Hamiltosporidium gen. nov
Multiple scattering formalism for correlated systems: A KKR+DMFT approach
We present a charge and self-energy self-consistent computational scheme for
correlated systems based on the Korringa-Kohn-Rostoker (KKR) multiple
scattering theory with the many-body effects described by the means of
dynamical mean field theory (DMFT). The corresponding local multi-orbital and
energy dependent self-energy is included into the set of radial differential
equations for the single-site wave functions. The KKR Green's function is
written in terms of the multiple scattering path operator, the later one being
evaluated using the single-site solution for the -matrix that in turn is
determined by the wave functions. An appealing feature of this approach is that
it allows to consider local quantum and disorder fluctuations on the same
footing. Within the Coherent Potential Approximation (CPA) the correlated atoms
are placed into a combined effective medium determined by the dynamical mean
field theory (DMFT) self-consistency condition. Results of corresponding
calculations for pure Fe, Ni and FeNi alloys are presented.Comment: 25 pages, 5 fig. acepted PR
Spontaneous Branching of Anode-Directed Streamers between Planar Electrodes
Non-ionized media subject to strong fields can become locally ionized by
penetration of finger-shaped streamers. We study negative streamers between
planar electrodes in a simple deterministic continuum approximation. We observe
that for sufficiently large fields, the streamer tip can split. This happens
close to Firsov's limit of `ideal conductivity'. Qualitatively the tip
splitting is due to a Laplacian instability quite like in viscous fingering.
For future quantitative analytical progress, our stability analysis of planar
fronts identifies the screening length as a regularization mechanism.Comment: 4 pages, 6 figures, submitted to PRL on Nov. 16, 2001, revised
version of March 10, 200
Observation and theoretical description of the pure Fano-effect in the valence-band photo-emission of ferromagnets
The pure Fano-effect in angle-integrated valence-band photo-emission of
ferromagnets has been observed for the first time. A contribution of the
intrinsic spin polarization to the spin polarization of the photo-electrons has
been avoided by an appropriate choice of the experimental parameters. The
theoretical description of the resulting spectra reveals a complete analogy to
the Fano-effect observed before for paramagnetic transition metals. While the
theoretical photo-current and spin difference spectra are found in good
quantitative agreement with experiment in the case of Fe and Co only a
qualitative agreement could be achieved in the case of Ni by calculations on
the basis of plain local spin density approximation (LSDA). Agreement with
experimental data could be improved in this case in a very substantial way by a
treatment of correlation effects on the basis of dynamical mean field theory
(DMFT).Comment: 11 pages, 3 figures accepted by PR
Pion condensation in quark matter with finite baryon density
The phase structure of the Nambu -- Jona-Lasinio model at zero temperature
and in the presence of baryon- and isospin chemical potentials is investigated.
It is shown that in the chiral limit and for a wide range of model parameters
there exist two different phases with pion condensation. In the first, ordinary
phase, quarks are gapped particles. In the second, gapless pion condensation
phase, there is no energy cost for creating only - or both and
quarks, and the density of baryons is nonzero.Comment: 7 pages, 6 figures; two references adde
Involvement of family physicians in structured programs for chronic diseases or multi-morbidity in Switzerland.
The increasing prevalence of chronic diseases and multi-morbidity represents challenges for health systems worldwide. In that perspective, the current organization of healthcare delivery, fragmentation of care, limited use of evidence-based guidelines and patients'insufficient empowerment are some reasons explaining the current limited effectiveness of the management of chronically ill patients.
Based on theoretical models such as the Chronic Care Model (CCM), initiatives targeting improvements in the care of patients with chronic diseases have been implemented worldwide since more than a decade. Their development in Switzerland, a health system where more than half of practices are still single handed [6], is only recent and infrequent. Structured programs for patients with chronic diseases or multimorbidity usually propose patient-centered interventions and consider an integrative multidisciplinary approach. Currently, little is known on the existence of such programs and on the role of family physicians (FPs)within these programs, in Switzerland. The objective of this study was to identify and describe current structured programs targeting chronic diseases or multi-morbidity in Switzerland. This may help in examining innovative approaches that are only developed locally but would deserve wider interest for further implementation. We conducted a telephone-based survey between June and November 2013 and contacted systematically key institutions, informants and stakeholders nationwide and in the 26 cantons..
Distribution Archaeology: Survey, Mapping, and Analysis of Surface Archaeological Materials in the Green River Basin, Wyoming
Archaeology in America today is in a quandary. This is especially true for that portion of the profession responsible for investigating and managing the surface archaeology of large tracts of land. The quandary concerns how to maximize the amount of information about the archaeology of an area given finite budgets. Predictive modeling, a technique for projecting knowledge derived from a sample to its universe, has been proposed as one response to this dilemma. We shall present another response, distributional archaeology, which is designed to collect quality information about the archaeological record and is consistent with the formation and structure of that data base. Inherent in all archaeological modeling attempts are assumptions about the nature of the archaeological record. These assumptions must be questioned in light of the formation processes that are responsible for the archaeology potentially available to us. Before examining how the archaeological record is formed, we briefly examine some of the prejudgments archaeologists make about their data
Distribution Archaeology: Survey, Mapping, and Analysis of Surface Archaeological Materials in the Green River Basin, Wyoming
Archaeology in America today is in a quandary. This is especially true for that portion of the profession responsible for investigating and managing the surface archaeology of large tracts of land. The quandary concerns how to maximize the amount of information about the archaeology of an area given finite budgets. Predictive modeling, a technique for projecting knowledge derived from a sample to its universe, has been proposed as one response to this dilemma. We shall present another response, distributional archaeology, which is designed to collect quality information about the archaeological record and is consistent with the formation and structure of that data base. Inherent in all archaeological modeling attempts are assumptions about the nature of the archaeological record. These assumptions must be questioned in light of the formation processes that are responsible for the archaeology potentially available to us. Before examining how the archaeological record is formed, we briefly examine some of the prejudgments archaeologists make about their data
- …