366 research outputs found
Transverse instability of the antiproton beam in the Recycler Ring
The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is
limited by a transverse instability. This instability has occurred during the
extraction process to the Tevatron for large stacks of antiprotons even with
dampers in operation. This paper describes observed features of the
instability, introduces the threshold phase density to characterize the beam
stability, and finds the results to be in agreement with a resistive wall
instability model. Effective exclusion of the longitudinal tails from Landau
damping by decreasing the depth of the RF potential well is observed to lower
the threshold density by up to a factor of two.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1
Apr 2011. New York, US
Information entropy and nucleon correlations in nuclei
The information entropies in coordinate and momentum spaces and their sum
(, , ) are evaluated for many nuclei using "experimental"
densities or/and momentum distributions. The results are compared with the
harmonic oscillator model and with the short-range correlated distributions. It
is found that depends strongly on and does not depend very much
on the model. The behaviour of is opposite. The various cases we consider
can be classified according to either the quantity of the experimental data we
use or by the values of , i.e., the increase of the quality of the density
and of the momentum distributions leads to an increase of the values of . In
all cases, apart from the linear relation , the linear relation
also holds. V is the mean volume of the nucleus. If is
considered as an ensemble entropy, a relation between or and the
ensemble volume can be found. Finally, comparing different electron scattering
experiments for the same nucleus, it is found that the larger the momentum
transfer ranges, the larger the information entropy is. It is concluded that
could be used to compare different experiments for the same nucleus and to
choose the most reliable one.Comment: 14 pages, 4 figures, 2 table
Superscaling and Neutral Current Quasielastic Neutrino-Nucleus Scattering beyond the Relativistic Fermi Gas Model
The superscaling analysis is extended to include quasielastic (QE) scattering
via the weak neutral current of neutrinos and antineutrinos from nuclei. The
scaling function obtained within the coherent density fluctuation model (used
previously in calculations of QE inclusive electron and charge-changing (CC)
neutrino scattering) is applied to neutral current neutrino and antineutrino
scattering with energies of 1 GeV from C with a proton and neutron
knockout (u-channel inclusive processes). The results are compared with those
obtained using the scaling function from the relativistic Fermi gas model and
the scaling function as determined from the superscaling analysis (SuSA) of QE
electron scattering.Comment: 10 pages, 6 figures, published in Phys. Rev.
Superscaling in Nuclei: A Search for Scaling Function Beyond the Relativistic Fermi Gas Model
We construct a scaling function for inclusive electron
scattering from nuclei within the Coherent Density Fluctuation Model (CDFM).
The latter is a natural extension to finite nuclei of the Relativistic Fermi
Gas (RFG) model within which the scaling variable was
introduced by Donnelly and collaborators. The calculations show that the
high-momentum components of the nucleon momentum distribution in the CDFM and
their similarity for different nuclei lead to quantitative description of the
superscaling in nuclei. The results are in good agreement with the experimental
data for different transfer momenta showing superscaling for negative values of
, including those smaller than -1.Comment: 16 pages, 5 figures, submitted for publication to Phys. Rev.
Antibacterial effect of nisin in vitro
Results of experimental studies of antimicrobial action of gel compositions containing active substance nisin are presented in the article. It is shown that increasing concentration of nisin at constant concentrations of the other components in the mixture inhibits growth of Staphylococcus aureus and Pseudomonas aeruginosa. The optimal concentration of nisin at which the process of pathogens growth inhibition is the most effective was determined in the experiment
Transverse Instabilities in the Fermilab Recycler
Transverse instabilities of the antiproton beam have been observed in the
Recycler ring soon after its commissioning. After installation of transverse
dampers, the threshold for the instability limit increased significantly but
the instability is still found to limit the brightness of the antiprotons
extracted from the Recycler for Tevatron shots. In this paper, we describe
observations of the instabilities during the extraction process as well as
during dedicated studies. The measured instability threshold phase density
agrees with the prediction of the rigid beam model within a factor of 2. Also,
we conclude that the instability threshold can be significantly lowered for a
bunch contained in a narrow and shallow potential well due to effective
exclusion of the longitudinal tails from Landau damping.Comment: 17 pages, 'Technical' Note, Use of 'internal' jargon and reference
Investigation of physico-chemical characteristics of carboxymethylcellulose colloidal carriers for medical preparations
Introduction. Physico-chemical peculiarities of processes of preparation and aging of colloidal carriers (gels) based on carboxymethylcellulose (CMC) for medical preparations which are planned to be used as a treatment for burn wounds are considered in the article. Studies were conducted in the Central Scientific Research Laboratory of theKharkivNationalMedicalUniversity in 2019.The objectives of the study. The objective was to study the applicability of CMC solutions and their modified analogues for the gel-based pharmaceutical preparations.Material and methods. Experimental studies were carried out under laboratory conditions using equipment for viscosity and pH measuring.Results. The influence of concentration, temperature, and acidity on viscosity of gels was investigated. The gels were tested on aging during storage. The stability of these solutions and syneresis process were investigated. The influence of added modifiers – glycerol and ascorbic acid on the consistency, acidity, susceptibility to contamination and term of storage of the gels was determined.Conclusions. It is shown that unmodified solutions have the highest viscosity and the greatest stability. Increasing of temperature reduces duration of dissolution of CMC and viscosity of the gels. Modification by ascorbic acid significantly reduces viscosity and pH of gels, while addition of glycerol does not affect the stability but increases susceptibility of these solutions to contamination. Storage of obtained solutions for three months under normal conditions at room temperature leads to syneresis and total loss of initial consistency. The gels modified by ascorbic acid are shown to be the least stable. Graphic dependences of these processes are obtained and functions are calculated on the basis of experimental research with the use of mathematical modeling methods. The obtained models will allow to predict physical and chemical properties of gels in order to define the necessary parameters of preparation at the stage of development
Study of He+C Elastic Scattering Using a Microscopic Optical Potential
The He+C elastic scattering data at beam energies of 3, 38.3 and
41.6 MeV/nucleon are studied utilizing the microscopic optical potentials
obtained by a double-folding procedure and also by using those inherent in the
high-energy approximation. The calculated optical potentials are based on the
neutron and proton density distributions of colliding nuclei established in an
appropriate model for He and obtained from the electron scattering form
factors for C. The depths of the real and imaginary parts of the
microscopic optical potentials are considered as fitting parameters. At low
energy the volume optical potentials reproduce sufficiently well the
experimental data. At higher energies, generally, additional surface terms
having form of a derivative of the imaginary part of the microscopic optical
potential are needed. The problem of ambiguity of adjusted optical potentials
is resolved requiring the respective volume integrals to obey the determined
dependence on the collision energy. Estimations of the Pauli blocking effects
on the optical potentials and cross sections are also given and discussed.
Conclusions on the role of the aforesaid effects and on the mechanism of the
considered processes are made.Comment: 12 pages, 9 figures, accepted for publication in Physical Review
- …