331 research outputs found
Ground-state baryons in nonperturbative quark dynamics
We review the results obtained in an Effective Hamiltonian (EH) approach for
the three-quark systems. The EH is derived starting from the Feynman--Schwinger
representation for the gauge-invariant Green function of the three quarks
propagating in the nonperturbative QCD vacuum and assuming the minimal area law
for the asymptotic of the Wilson loop. It furnishes the QCD consistent
framework within which to study baryons. The EH has the form of the
nonrelativistic three-quark Hamiltonian with the perturbative Coulomb-like and
nonperturbative string interactions and the specific mass term. After outlining
the approach, methods of calculations of the baryon eigenenergies and some
simple applications are explained in details. With only two parameters: the
string tension and the strong coupling constant
a unified quantitative description of the ground state light
and heavy baryons is achieved. The prediction of masses of the doubly heavy
baryons not discovered yet are also given. In particular, a mass of
for the lightest baryon is found by employing the hyperspherical
formalism to the three quark confining potential with the string junction.Comment: 25 pages, 4 figures included, LaTeX 2e; to be published in Phys.
Atom. Nuc
Pentaquarks in the Jaffe-Wilczek approximation
The masses of , and pentaquarks are
evaluated in a framework of both the Effective Hamiltonian approach to QCD and
spinless Salpeter using the Jaffe--Wilczek diquark approximation and the string
interaction for the diquark--diquark--antiquark system. The pentaquark masses
are found to be in the region above 2 GeV. That indicates that the Goldstone
boson exchange effects may play an important role in the light pentaquarks. The
same calculations yield the mass of pentaquark 3250 MeV
and pentaquark 6509 MeV.Comment: 14 pages, 2 tables, LaTeX2e. References correcte
Spectroscopy of Baryons Containing Two Heavy Quarks in Nonperturbative Quark Dynamics
We have studied the three quark systems in an Effective Hamiltonian approach
in QCD. With only two parameters: the string tension sigma and the strong
coupling constant alpha_s we obtain a good description of the ground state
light and heavy baryons. The prediction of masses of the doubly heavy baryons
not discovered yet are also given. In particular, a mass of 3620 MeV for the
lightest (ccu) baryon is found by employing the hyperspherical formalism to the
three quark confining potential with the string junction.Comment: 8 pages, LaTe
Yield performance and stability of modern breeding stock of spring durum wheat (Triticum durum Desf.) from Russia and Kazakhstan
Identifcation of adaptive responses of breeding material, developed in different breeding centers, helps to purposefully correct these traits where it is necessary. Thus, 42 modern breeding lines from eight institutions of Russia and Kazakhstan were studied in comparison with the historical standard Bezenchukskaya 139 in trails of 16-17 and 18 KASIB-SDW (Kazakhstan-Siberian net for wheat improvement, spring durum wheat) in 2015–2017. Field experiments and yield measurements in each ecological cite were similar. To solve these tasks of the experiment, two-factor ANOVA, methods for adaptability assessment cluster analysis and principle component method were applied. As a result, it was established that 1) genotype and genotype – environment interaction (overall 15.8–23.5 % of total dispersion) had signifcant effect on yield variability; 2) genotype – environment interactions were of linear nature and had no destabilizing effect; 3) all the genotypes tested can be distributed in three clusters, the frst one for locally adapted varieties, the third for varieties of a wide areal, the second included genotypes with intermediate characteristics; 4) breeding centers of the Federal Altai Scientifc Centre of Agro-Biotechnologies and of the Research Institute of Agriculture of South-East produced predominantly varieties of local importance, the Samara Research Institute of Agriculture – varieties of wide area; 5) a stable trend of increased mean yield compared to historical standard Bezenchukskaya 139 over ecological sites was observed only for Samara varieties; 6) varieties of all the breeding centers had no stable difference from Bezenchukskaya 139 concerning stability and responsiveness, which can be explained by an incomplete breeding process for these parameters and confrms the importance of the KASIB program; 7) a trend of yield increase compared to Bezenchukskaya 139 under testing in defnite local environments had more stable parameters with the largest progress observed in the Altai Research Institute of Agriculture (135.4 and 163.2 % to Bezenchukskaya 139), which can be explained by a high efciency of breeding of locally adapted varieties in the breeding center
Comment on the proper QCD string dynamics in a heavy-light system
The string correction to the inter-quark interaction at large distances is
derived using the field theory approach to a heavy-light quark-antiquark system
in the modified Fock-Schwinger gauge.Comment: LaTeX2e, 6 pages, no figures, to appear in JETP Let
A Thin-Layer Chromatography Method for the Determination of Essential Oil Components in Anise and Fennel Fruits
Scientific relevance. The State Pharmacopoeia of the Russian Federation, edition XIV, requires the identification of aniseed and fennel fruits by the same thin-layer chromatography (TLC) procedure using Sudan III and menthol. These markers are neither specific nor related to the therapeutic effects of these herbal drug products. The visual interpretation of chromatograms is complicated because of the low intensity of adsorption zones. Moreover, the corresponding compendial monographs do not characterise the adsorption zones specific to each of the plants. The most abundant component in aniseed and fennel essential oils, trans-anethole, would make a better reference standard from a methodological point of view.Aim. This study aimed to optimise the TLC procedure for essential oil determination in herbal drugs and herbal medicinal products of aniseed and fennel fruits and subsequently recommend it for inclusion in the relevant compendial monographs.Materials and methods. The study examined samples from several batches of herbal drugs, including aniseed and common fennel fruits, sourced from Russian manufacturers. The reference standards comprised commercial reagents, including trans-anethole, anise oil, and linalool, as well as fresh essential oils that had been steam distilled from the test samples in a Clevenger apparatus. The study was conducted by TLC. Sample preparation involved using Merck aluminium TLC plates, an IKA KS-501 digital orbital shaker, and a CAMAG Linomat 5 semi-automatic sample application system. The authors heated the plates in either a Binder ED53 drying oven or a CAMAG TLC plate heater. For visualisation, the authors selected a CAMAG TLC VISUALIZER 2 UV imaging and documentation system.Results. The informational and experimental research showed the feasibility of using trans-anethole as an identification reference standard for common anise and fennel fruits. The authors selected the optimal solvent for extracting active substances from the test products (hexane) and a detection reagent for improving visual evaluation of the chromatograms (1% sulfovanillin). The authors established characteristic adsorption zones for differentiating between aniseed and fennel fruits.Conclusions. The optimised procedure identifies the main components in the essential oils of aniseed and fennel fruits with a specific reference standard. This procedure may be recommended for inclusion in draft monographs for the corresponding herbal medicinal products
Analytic Quantization of the QCD String
We perform an analytic semi-classical quantization of the straight QCD string
with one end fixed and a massless quark on the other, in the limits of orbital
and radial dominant motion. We compare our results to the exact numerical
semi-classical quantization. We observe that the numerical semi-classical
quantization agrees well with our exact numerical canonical quantization.Comment: RevTeX, 10 pages, 9 figure
Theoretical Research on the Pipe Rolling Process in Order to Determine the Deformation of the Pipe Billet and the Load on the Rolling Tool
The technology of the shell case rolling into the rough pipe on an automatic mill of the pipe-rolling plant PRP 220 was considered. In case of the pipe rear end stability losing for a special thin-walled assortment of rolling products the theoretical research was carried out based on the FEM. As the result of the research the nature of such flaw as a "fin" on the end of the pipe was investigated, the evaluation of the loading on the automatic mill for the PRP 220 was obtained for different process parameters. © Published under licence by IOP Publishing Ltd
Determination of the Total Alkaloid Content of Thermopsis Dry Extract by HPTLC-Densitometry
When used to quantify alkaloids in thermopsis dry extract, acidimetric titration has several limitations, including insufficient specificity of the method and arbitrary selection of a titration endpoint. Different parts of the Thermopsis lanceolata plant produce alkaloids in different proportions: the herb is rich in thermopsine, whereas the seeds are rich in cytisine. Since thermopsine and cytisine have different pharmacological effects, it is important to identify and quantify individual alkaloids in thermopsis dry extract.The aim of the study was to develop and validate an analytical procedure for identifying and quantifying total alkaloids in thermopsis dry extract by high-performance thin-layer chromatography (HPTLC) with densitometric detection.Materials and methods. The study included samples from two pilot-scale batches of thermopsis dry extract and reference standards for cytisine and thermopsine. The authors used Merck HPTLС Silica Gel 60 F254 20×10 cm plates for chromato-graphic separation and analysed the results with a CAMAG® TLC Scanner 4 densitometer and the winCATS software.Results. The authors identified thermopsis dry extract using HPTLC separation followed by spectrodensitometry. The alkaloid-specific solution applied to chromatography plates helped to identify the three most abundant and four minor alkaloids of thermopsis. The most abundant alkaloids were thermopsine, cytisine, and an unidentified alkaloid with a retention factor of approximately 0.2. These three alkaloids accounted for almost 80% of the total alkaloid content of the dry extract. The authors quantified cytisine, thermopsine, and total alkaloids expressed as thermopsine.Conclusions. The authors developed and validated an analytical procedure for identifying and quantifying total alkaloids in thermopsis dry extract. This procedure offers the possibility of reducing the analysis time from 4–5 hours to 2–2.5 hours
Di-Pion Decays of Heavy Quarkonium in the Field Correlator Method
Mechanism of di-pion transitions in
bottomonium and charmonium is studied with the use of the chiral
string-breaking Lagrangian allowing for the emission of any number of
and not containing fitting parameters. The transition amplitude
contains two terms, , where first term (a) refers to subsequent one-pion
emission: and second term
(b) refers to two-pion emission: . The one-parameter formula for the di-pion mass
distribution is derived, (phase space) , where
. The
parameter dependent on the process is calculated, using SHO wave
functions and imposing PCAC restrictions (Adler zero) on amplitudes a,b. The
resulting di-pion mass distributions are in agreement with experimental data.Comment: 62 pages,8 tables,7 figure
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