426 research outputs found
On the extra phase correction to the semiclassical spin coherent-state propagator
The problem of an origin of the Solary-Kochetov extra-phase contribution to
the naive semiclassical form of a generalized phase-space propagator is
addressed with the special reference to the su(2) spin case which is the most
important in applications. While the extra-phase correction to a flat
phase-space propagator can straightforwardly be shown to appear as a difference
between the principal and the Weyl symbols of a Hamiltonian in the
next-to-leading order expansion in the semiclassical parameter, the same
statement for the semiclassical spin coherent-state propagator holds provided
the Holstein-Primakoff representation of the su(2) algebra generators is
employed.Comment: 19 pages, no figures; a more general treatment is presented, some
references are added, title is slightly changed; submitted to JM
Electronic properties of disclinated flexible membrane beyond the inextensional limit: Application to graphene
Gauge-theory approach to describe Dirac fermions on a disclinated flexible
membrane beyond the inextensional limit is formulated. The elastic membrane is
considered as an embedding of 2D surface into R^3. The disclination is
incorporated through an SO(2) gauge vortex located at the origin, which results
in a metric with a conical singularity. A smoothing of the conical singularity
is accounted for by replacing a disclinated rigid plane membrane with a
hyperboloid of near-zero curvature pierced at the tip by the SO(2) vortex. The
embedding parameters are chosen to match the solution to the von Karman
equations. A homogeneous part of that solution is shown to stabilize the
theory. The modification of the Landau states and density of electronic states
of the graphene membrane due to elasticity is discussed.Comment: 15 pages, Journal of Physics:Condensed Matter in pres
Dirac fermions on a disclinated flexible surface
A self-consisting gauge-theory approach to describe Dirac fermions on
flexible surfaces with a disclination is formulated. The elastic surfaces are
considered as embeddings into R^3 and a disclination is incorporated through a
topologically nontrivial gauge field of the local SO(3) group which generates
the metric with conical singularity. A smoothing of the conical singularity on
flexible surfaces is naturally accounted for by regarding the upper half of
two-sheet hyperboloid as an elasticity-induced embedding. The availability of
the zero-mode solution to the Dirac equation is analyzed.Comment: 6 page
Termination Reaction in the Anionic Polymerization of Methacrylonitrile
The anionic polymerization of methacrylonitrile initiated by
triethylphosphine in dimethylformamide was studied. Experimental
evidence for two mechanisms of termination reaction was obtained.
By addition of water or alcohol in polymerizing system the rate of
polymerization and molecular weight of polymethacrylon1itrile
decrease, which proves the termination reaction to be bimolecular
and proceed by interaction of the active carbanion with water or
alcohol. The rate constant for termination of free anions with water
was determined, k~,0 = 2.2 x 102 dm3 moP s-1• The termination
reaction could not be excluded by purification and prolonged drying
of all components of the system, which indicates that the second
mechanism of termination is operative as well. Conductivity measurements gave evidence for a monomolecular spontaneous reaction leading to deactivation of the anion
Training of Specialized Teams of Center of Hygiene and Epidemiology in the Republic of Mordovia
Presented are data on the second republican competition of sanitary and epidemiological reconnaissance groups from the Center of Hygiene and Epidemiology in the Republic of Mordovia. The competition was held in conditions that imitated emergency situations of different origin. All stages of the competition were more complicated than those of the first one, two new stages were included in the program, radio transceivers were used to provide interactions in the group
The Experience of Specialized Teams Training in the Republic of Mordovia
Described are the First Republican competitions of the teams of epidemiological reconnaissance carried out on the basis of Center of Hygiene and Epidemiology in the Republic of Mordovia
Starch metabolism in potato <i>Solanum tuberosum</i> L.
Starch is a major storage carbohydrate in plants. It is an important source of calories in the human and animal diet. Also, it is widely used in various industries. Native starch consists of water-insoluble semicrystalline granules formed by natural glucose polymers amylose and amylopectin. The physicochemical properties of starch are determined by the amylose:amylopectin ratio in the granule and degrees of their polymerization and phosphorylation. Potato Solanum tuberosum L. is one of the main starch-producing crops. Growing industrial needs necessitate the breeding of plant varieties with increased starch content and specified starch properties. This task demands detailed information on starch metabolism in the producing plant. It is a complex process, requiring the orchestrated work of many enzymes, transporter and targeting proteins, transcription factors, and other regulators. Two types of starch are recognized with regard to their biological functions. Transitory starch is synthesized in chloroplasts of photosynthetic organs and degraded in the absence of light, providing carbohydrates for cell needs. Storage starch is synthesized and stored in amyloplasts of storage organs: grains and tubers. The main enzymatic reactions of starch biosynthesis and degradation, as well as carbohydrate transport and metabolism, are well known in the case of transitory starch of the model plant Arabidopsis thaliana. Less is known about features of starch metabolism in storage organs, in particular, potato tubers. Several issues remain obscure: the roles of enzyme isoforms and different regulatory factors in tissues at various plant developmental stages and under different environmental conditions; alternative enzymatic processes; targeting and transport proteins. In this review, the key enzymatic reactions of plant carbohydrate metabolism, transitory and storage starch biosynthesis, and starch degradation are discussed, and features specific for potato are outlined. Attention is also paid to the known regulatory factors affecting starch metabolism
Gauge theory of disclinations on fluctuating elastic surfaces
A variant of a gauge theory is formulated to describe disclinations on
Riemannian surfaces that may change both the Gaussian (intrinsic) and mean
(extrinsic) curvatures, which implies that both internal strains and a location
of the surface in R^3 may vary. Besides, originally distributed disclinations
are taken into account. For the flat surface, an extended variant of the
Edelen-Kadic gauge theory is obtained. Within the linear scheme our model
recovers the von Karman equations for membranes, with a disclination-induced
source being generated by gauge fields. For a single disclination on an
arbitrary elastic surface a covariant generalization of the von Karman
equations is derived.Comment: 13 page
Ribonuclease activity as a new prospective disease resistance marker in potato
Disease resistance is an important characteristic for each variety of potato, and the search for pathogen resistance markers is one of the primary tasks of plant breeding. Higher plants possess a wide spectrum of enzymes catalyzing the hydrolysis of nucleic acids; it is believed that protection against pathogens is the most probable function of the enzymes. RNases are actively involved in several immune systems of higher plants, for example, systemic acquired resistance (SAR) and genetic silencing, hence RNase activity in plant leaves, as a relatively easily measured parameter, can serve as a good marker for the selection of pathogen resistant varieties. We have analyzed sixteen varieties of potatoes permitted for use on the territory of the Russian Federation and tested the correlation of the level of varietyspecifc ribonuclease (RNase) activity with such economically valuable traits as maturity and resistance to viruses, late blight and common scab. In general, the level of RNase activity was varietyspecifc, which was confrmed by very small values of average squared error for the majority of tested varieties. We have detected a statistically signifcant positive correlation of RNase activity in potato leaves with increased resistance of varieties to phytopathogenic viruses, a negative correlation with resistance to scab and an absence of a signifcant connection with maturity and resistance to late blight, regardless of the organ affected by the oomycete. Thus, the level of RNase activity in potato leaves can be used as a selective marker for resistance to viruses, while varieties with increased RNase activity should be avoided when selecting resistance to scab
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