13,188 research outputs found
Quark-Gluon String Model Description of Baryon Production in K^{\pm}N Interactions
The process of baryon production in K p collisions at high energies is
considered in the framework of the Quark-Gluon String Model. The contribution
of the string-junction mechanism to the strange baryon production is analysed.
The results of numerical calculations are in reasonable agreement with the data
on inclusive spectra of p, Lambda, bar{Lambda}, and on the bar{Lambda}/Lambda
asymmetry. The predictions for Xi and Omega baryons are presented.Comment: 19 pages, 7 figure
Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance
Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma
State Transition Algorithm
In terms of the concepts of state and state transition, a new heuristic
random search algorithm named state transition algorithm is proposed. For
continuous function optimization problems, four special transformation
operators called rotation, translation, expansion and axesion are designed.
Adjusting measures of the transformations are mainly studied to keep the
balance of exploration and exploitation. Convergence analysis is also discussed
about the algorithm based on random search theory. In the meanwhile, to
strengthen the search ability in high dimensional space, communication strategy
is introduced into the basic algorithm and intermittent exchange is presented
to prevent premature convergence. Finally, experiments are carried out for the
algorithms. With 10 common benchmark unconstrained continuous functions used to
test the performance, the results show that state transition algorithms are
promising algorithms due to their good global search capability and convergence
property when compared with some popular algorithms.Comment: 18 pages, 28 figure
Conversion of the Mycotoxin Patulin to the Less Toxic Desoxypatulinic Acid by the Biocontrol Yeast Rhodosporidium kratochvilovae Strain LS11
Se describe en este artículo el descubrimiento de la degradación de la micotoxina patulina por una levaduraThe infection of stored apples by the fungus Penicillium expansum causes the contamination of fruits and fruit-derived
products with the mycotoxin patulin, which is a major issue in food safety. Fungal attack can be prevented by beneficial
microorganisms, so-called biocontrol agents. Previous time-course thin layer chromatography analyses showed that the aerobic
incubation of patulin with the biocontrol yeast Rhodosporidium kratochvilovae strain LS11 leads to the disappearance of the
mycotoxin spot and the parallel emergence of two new spots, one of which disappears over time. In this work, we analyzed the
biodegradation of patulin effected by LS11 through HPLC. The more stable of the two compounds was purified and characterized by
nuclear magnetic resonance as desoxypatulinic acid, whose formation was also quantitated in patulin degradation experiments. After
R. kratochvilovae LS11 had been incubated in the presence of 13C-labeled patulin, label was traced to desoxypatulinic acid, thus
proving that this compound derives from the metabolization of patulin by the yeast. Desoxypatulinic acid was much less toxic than
patulin to human lymphocytes and, in contrast to patulin, did not react in vitro with the thiol-bearing tripeptide glutathione. The
lower toxicity of desoxypatulinic acid is proposed to be a consequence of the hydrolysis of the lactone ring and the loss of functional
groups that react with thiol groups. The formation of desoxypatulinic acid from patulin represents a novel biodegradation pathway
that is also a detoxification process
Affine modifications and affine hypersurfaces with a very transitive automorphism group
We study a kind of modification of an affine domain which produces another
affine domain. First appeared in passing in the basic paper of O. Zariski
(1942), it was further considered by E.D. Davis (1967). The first named author
applied its geometric counterpart to construct contractible smooth affine
varieties non-isomorphic to Euclidean spaces. Here we provide certain
conditions which guarantee preservation of the topology under a modification.
As an application, we show that the group of biregular automorphisms of the
affine hypersurface given by the equation
where acts transitively on the
smooth part reg of for any We present examples of such
hypersurfaces diffeomorphic to Euclidean spaces.Comment: 39 Pages, LaTeX; a revised version with minor changes and correction
Nucleon electromagnetic form factors
Elastic electromagnetic nucleon form factors have long provided vital
information about the structure and composition of these most basic elements of
nuclear physics. The form factors are a measurable and physical manifestation
of the nature of the nucleons' constituents and the dynamics that binds them
together. Accurate form factor data obtained in recent years using modern
experimental facilities has spurred a significant reevaluation of the nucleon
and pictures of its structure; e.g., the role of quark orbital angular
momentum, the scale at which perturbative QCD effects should become evident,
the strangeness content, and meson-cloud effects. We provide a succinct survey
of the experimental studies and theoretical interpretation of nucleon
electromagnetic form factors.Comment: Topical review invited by Journal of Physics G: Nuclear and Particle
Physics; 34 pages (contents listed on page 34), 11 figure
Graphene Photonics and Optoelectronics
The richness of optical and electronic properties of graphene attracts
enormous interest. Graphene has high mobility and optical transparency, in
addition to flexibility, robustness and environmental stability. So far, the
main focus has been on fundamental physics and electronic devices. However, we
believe its true potential to be in photonics and optoelectronics, where the
combination of its unique optical and electronic properties can be fully
exploited, even in the absence of a bandgap, and the linear dispersion of the
Dirac electrons enables ultra-wide-band tunability. The rise of graphene in
photonics and optoelectronics is shown by several recent results, ranging from
solar cells and light emitting devices, to touch screens, photodetectors and
ultrafast lasers. Here we review the state of the art in this emerging field.Comment: Review Nature Photonics, in pres
- …