96 research outputs found
Relativistic structure of one-meson and one-gluon exchange forces and the lower excitation spectrum of the Nucleon and the Delta
The lower excitation spectrum of the nucleon and is calculated in a
relativistic chiral quark model. Corrections to the baryon mass spectrum from
the second order self-energy and exchange diagrams induced by pion and gluon
fields are estimated in the field -theoretical framework. Convergent results
for the self-energy terms are obtained when including the intermediate quark
and antiquark states with a total momentum up to . Relativistic
one-meson and color-magnetic one-gluon exchange forces are shown to generate
spin 0, 1, 2, etc. operators, which couple the lower and the upper components
of the two interacting valence quarks and yield reasonable matrix elements for
the lower excitation spectrum of the Nucleon and Delta. The only contribution
to the ground state nucleon and comes from the spin 1 operators, which
correspond to the exchanged pion or gluon in the l=1 orbit, thus indicating,
that the both pion exchange and color-magnetic gluon exchange forces can
contribute to the spin of baryons. Is is shown also that the contribution of
the color-electric component of the gluon fields to the baryon spectrum is
enormously large (more than 500 MeV with a value ) and one needs
to restrict to very small values of the strong coupling constant or to exclude
completely the gluon-loop corrections to the baryon spectrum. With this
restriction, the calculated spectrum reproduces the main properties of the
data, however needs further contribution from the two-pion exchange and
instanton induced exchange (for the nucleon sector) forces in consistence with
the realistic NN-interaction models.Comment: 15 pages, 4 figures, 7 table
Investigation of correlation of generated nuclearactive particles in the protonantiproton annihilation at momenta 22.4 and 32 GeV / c
Separation of the individual events
corresponding to antiproton-proton annihilation
gives the possibility to carry out the analysis of
multiparticle correlations for generated particles
and to compare them with corresponding data for
inelastic pp and non-annihilation p̃p interactions..
Investigation of correlation of generated nuclearactive particles in the protonantiproton annihilation at momenta 22.4 and 32 GeV / c
Separation of the individual events
corresponding to antiproton-proton annihilation
gives the possibility to carry out the analysis of
multiparticle correlations for generated particles
and to compare them with corresponding data for
inelastic pp and non-annihilation p̃p interactions..
Investigation of risk factors for Echinococcus coproantigen positivity in dogs in the Alay valley, Kyrgyzstan
Echinococcosis caused by the zoonotic cestodes Echinococcus granulosus (sensu lato) and Echinococcus multilocularis is highly endemic in the Central Asian Republic of Kyrgyzstan, and is increasingly being identified as public health problem especially amongst pastoral communities. As domestic dogs are considered to be the main source of human infection in these communities, the identification of potential transmission pathways can be of use when considering implementing a control scheme for echinococcosis. The current report describes the results of an analytic study of canine echinococcosis (based on the results of coproantigen ELISA testing) in the Alay valley of southern Kyrgyzstan prior to the commencement of a praziquantel dosing scheme amongst dogs. A logistic regression model using a form of Bayes modal estimation was used to identify possible risk factors for coproantigen positivity, and the output was interpreted in a Bayesian context (posterior distributions of the coefficients of interest). The study found that sheepdogs had lower odds of coproantigen positivity, as did households with donkeys, some knowledge of echinococcosis, and which did not engage in home slaughtering. There was no evidence of an association between free roaming or previous praziquantel dosing and coproantigen positivity, as has been found in previous studies. Possible reasons for these findings are discussed and suggestions made for further work
Initial State Fluctuations and Complete Destruction of the Projectile Nucleus in Interactions of Asymmetric Nuclei at High Energies
A study of characteristics of the events of complete destruction of the projectile nucleus in the interactions between asymmetric nuclei for different initial states of the collision, is performed. In the interactions of the sulfur nuclei with heavy emulsion nuclei at energy 200 AGeV, anomalous high number of events the complete destruction of the projectile nuclei, is observed. The high probability of such events depends on the energy of interaction (it is not detected in the interactions of the sulfur nuclei with emulsion nuclei at energy of 3.7 AGeV), on the degree of asymmetry of the interacting nuclei (it is not detected in interactions of the sulfur nuclei with light emulsion nuclei) and on initial state of interaction (it is not detected in peripheral collisions). These events are characterized by high multiplicity of secondary particles and narrow angular distribution at large angles (they form narrow peak in the region of small values of average pseudorapidity)
MXene-containing composite electrodes for hydrogen evolution: material design aspects and approaches for electrode fabrication
This work explores the possibilities for the processing of Ni- and Ti3C2Tx (T = OH, O) MXene-containing composite electrodes, by co-pressing and plastic deformation or by etching of the electrodes prepared directly by self-propagation high-temperature synthesis (SHS). Various material design approaches were also explored. In order to tune the Ti3C2 interlayer distance in Ti3C2Al MAX phase, an introduction of additional Al to form Ti3C2Alz materials with z > 1 was attempted. Self-propagation high-temperature synthesis of powder mixtures with extra Ni and Al content (e.g. Ni:Ti:Al:C = 1:2:3:1) resulted in SHS products containing Ti3C2Alz z > 1 material and Ni–Al alloys. Further etching of these products in 10M NaOH allowed the direct formation of electrodes with active surface containing Ti3C2Tx (T = OH, O) MXene- and Raney nickel-containing composites. The electrochemical studies were focused on hydrogen evolution and showed the potential for boosting the electrochemical reaction in Ni and MXene-containing composite electrodes, especially at high current densities. The guidelines for the processing of such electrodes under fluorine-free conditions are proposed and discussed.publishe
Moscow-type NN-potentials and three-nucleon bound states
A detailed description of Moscow-type (M-type) potential models for the NN
interaction is given. The microscopic foundation of these models, which appear
as a consequence of the composite quark structure of nucleons, is discussed.
M-type models are shown to arise naturally in a coupled channel approach when
compound or bag-like six-quark states, strongly coupled to the NN channel, are
eliminated from the complete multiquark wave function. The role of the
deep-lying bound states that appear in these models is elucidated. By
introducing additional conditions of orthogonality to these compound six-quark
states, a continuous series of almost on-shell equivalent nonlocal interaction
models, characterized by a strong reduction or full absence of a local
repulsive core (M-type models), is generated. The predictions of these
interaction models for 3N systems are analyzed in detail. It is shown that
M-type models give, under certain conditions, a stronger binding of the 3N
system than the original phase-equivalent model with nodeless wave functions.
An analysis of the 3N system with the new versions of the Moscow NN potential
describing also the higher even partial waves is presented. Large deviations
from conventional NN force models are found for the momentum distribution in
the high momentum region. In particular, the Coulomb displacement energy for
nuclei ^3He - ^3H displays a promising agreement with experiment when the ^3H
binding energy is extrapolated to the experimental value.Comment: 23 pages Latex, 9 figures, to appear in Phys.Rev.
Распространение и сезонная динамика токсокароза у собак в Республике Таджикистан
The purpose of the research is to study the spread and seasonal dynamics of toxocarosis in domestic and police dogs in the Republic of Tajikistan.Materials and methods. In order to study the period of maximum Toxocara sp. infection and seasonal dynamics of toxocarosis, monthly records were kept for dogs diagnosed with toxocarosis in a population of both domestic and police dogs from September 2016 to February 2019. We examined 70 dogs, of these 41 were police dogs and 29 were domestic dogs. 334 fecal specimens of police dogs and 221 fecal specimens of domestic dogs were examined by the Fulleborn flotation method.Results and discussion. 75 (22.3%) fecal specimens of police dogs from 336 fecal specimens studied were found to have Toxocara sp. eggs, and Toxocara sp. eggs were found in 28 (12.6%) fecal specimens of domestic dogs from 221 dogs studied. Toxocarosis in domestic dogs was reported throughout the year. The maximum Toxocara sp. infection in dogs was established in winter (28.5%) and summer (29.6%) 2017, and in summer (38.0%) and spring (31.8%) 2018, and in spring (28.5%) 2019. Toxocara sp. occurrence in police dogs and dogs belonging to breeding kennels of various institutions accounts for 4–8 age group. Dogs of younger age were infected with Toxocara sp. to a lesser degree.Цель исследований: изучить распространение и сезонную динамику токсокароза среди домашних и служебных собак в Республике Таджикистан.Материалы и методы. Для изучения периода максимального инвазирования токсокарами и сезонной динамики токсокароза проводили ежемесячный учет собак с диагнозом на токсокароз с сентября 2016 по февраль 2019 гг. как в популяции домашних, так и служебных собак. Всего было исследовано 70 собак, из них 41 служебная и 29 домашних собак. Исследовано 334 проб фекалий служебных и 221 – домашних собак методом флотации по Фюллеборну.Результаты и обсуждение. В 75 (22,3%) пробах фекалий служебных собак из 336 исследованных обнаружены яйца токсокар, а в 221 пробе фекалий домашних собак яйца токсокар обнаружены в 28 (12,6%). Токсокароз у домашних собак регистрировали в течение всего года. В 2017 г. наибольшая инвазированность собак токсокарами установлена в зимний (28,5%) и летний (29,6%) периоды, в 2018 г. – в летний (38,0%) и весенний (31,8%), в 2019 г. – в весенний (28,5%) период. Заболеваемость токсокарами среди служебных и собак, принадлежащих питомникам различных учреждений, приходится на возрастную группу 4–8 лет. Собаки младшего возраста были заражены токсокарами в меньшей степени
Fragmentation and Multifragmentation of 10.6A GeV Gold Nuclei
We present the results of a study performed on the interactions of 10.6A GeV
gold nuclei in nuclear emulsions. In a minimum bias sample of 1311 interac-
tions, 5260 helium nuclei and 2622 heavy fragments were observed as Au projec-
tile fragments. The experimental data are analyzed with particular emphasis of
target separation interactions in emulsions and study of criticalexponents.
Multiplicity distributions of the fast-moving projectile fragments are inves-
tigated. Charged fragment moments, conditional moments as well as two and three
-body asymmetries of the fast moving projectile particles are determined in
terms of the total charge remaining bound in the multiply charged projectile
fragments. Some differences in the average yields of helium nuclei and heavier
fragments are observed, which may be attributed to a target effect. However,
two and three-body asymmetries and conditional moments indicate that the
breakup mechanism of the projectile seems to be independent of target mass. We
looked for evidence of critical point observable in finite nuclei by study the
resulting charged fragments distributions. We have obtained the values for the
critical exponents gamma, beta and tau and compare our results with those at
lower energy experiment (1.0A GeV data). The values suggest that a phase
transition like behavior, is observed.Comment: latex, revtex, 28 pages, 12 figures, 3tables, submitted to Europysics
Journal
Dibaryon model for nuclear force and the properties of the system
The dibaryon model for interaction, which implies the formation of an
intermediate six-quark bag dressed by a -field, is applied to the
system, where it results in a new three-body force of scalar nature between the
six-quark bag and a third nucleon. A new multicomponent formalism is developed
to describe three-body systems with nonstatic pairwise interactions and
non-nucleonic degrees of freedom. Precise variational calculations of
bound states are carried out in the dressed-bag model including the new scalar
three-body force. The unified coupling constants and form factors for and
force operators are used in the present approach, in a sharp contrast to
conventional meson-exchange models. It is shown that this three-body force
gives at least half the total binding energy, while the weight of
non-nucleonic components in the H and He wavefunctions can exceed 10%.
The new force model provides a very good description of bound states with
a reasonable magnitude of the coupling constant. A new Coulomb
force between the third nucleon and dibaryon is found to be very important for
a correct description of the Coulomb energy and r.m.s. charge radius in He.
In view of the new results for Coulomb displacement energy obtained here for
A=3 nuclei, an explanation for the long-term Nolen--Schiffer paradox in nuclear
physics is suggested. The role of the charge-symmetry-breaking effects in the
nuclear force is discussed.Comment: 64 pages, 7 figures, LaTeX, to be published in Phys. At. Nucl. (2005
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