334 research outputs found
DEVELOPING THE METHODS OF FOOD PRESERVATIVES EXTRACTION FROM COMPLEX MATRICES FOR BIOASSAY PURPOSE
The presence of food additives in food products may be associated with the risk of their toxic effects on human body. Therefore, the study of approaches to testing their safety seems to be a particularly urgent task. The aim of this study was to determine the conditions for extracting food preservatives from the samples of preserved pureed vegetables for further bioassay of the extract obtained in the Allium test. Onion roots were used as a test object in this method. Two extraction methods of benzoic and sorbic acids added to pureed vegetables have been developed. Distilled water and acetone were used as extracting solutions. The extraction efficiency was evaluated on Shimadzu Prominence LC-20 liquid chromatograph (Japan) in the ultraviolet range, wavelength 235 nm (benzoic acid), 285 nm (sorbic acid). According to the results of studies using both water and acetone as extractants, the degree of preservatives extraction was approximately the same and quite high. In the quantitative calculation of the preservatives content in pureed vegetables, the value of the correction factor was 0.8. However, due to certain production characteristics of this product, i. e. the stage of cauliflower homogenization, obtaining an extract with acetone seems to be more acceptable for the Allium test conditions.The presence of food additives in food products may be associated with the risk of their toxic effects on human body. Therefore, the study of approaches to testing their safety seems to be a particularly urgent task. The aim of this study was to determine the conditions for extracting food preservatives from the samples of preserved pureed vegetables for further bioassay of the extract obtained in the Allium test. Onion roots were used as a test object in this method. Two extraction methods of benzoic and sorbic acids added to pureed vegetables have been developed. Distilled water and acetone were used as extracting solutions. The extraction efficiency was evaluated on Shimadzu Prominence LC-20 liquid chromatograph (Japan) in the ultraviolet range, wavelength 235 nm (benzoic acid), 285 nm (sorbic acid). According to the results of studies using both water and acetone as extractants, the degree of preservatives extraction was approximately the same and quite high. In the quantitative calculation of the preservatives content in pureed vegetables, the value of the correction factor was 0.8. However, due to certain production characteristics of this product, i. e. the stage of cauliflower homogenization, obtaining an extract with acetone seems to be more acceptable for the Allium test conditions
Infrared studies of a La_(0.67)Ca_(0.33)MnO_3 single crystal: Optical magnetoconductivity in a half-metallic ferromagnet
The infrared reflectivity of a La_(0.67)Ca_(0.33)MnO_3 single crystal is studied over a broad range of temperatures (78–340 K), magnetic fields (0–16 T), and wave numbers (20–9000cm^(-1)). The optical conductivity gradually changes from a Drude-like behavior to a broad peak feature near 5000cm-1 in the ferromagnetic state below the Curie temperature T_C=307K. Various features of the optical conductivity bear striking resemblance to recent theoretical predictions based on the interplay between the double exchange interaction and the Jahn-Teller electron-phonon coupling. A large optical magnetoconductivity is observed near T_C
Infrared Studies of a La_{0.67}Ca_{0.33}MnO_3 Single Crystal: Optical Magnetoconductivity in a Half-Metallic Ferromagnet
The infrared reflectivity of a single crystal
is studied over a broad range of temperatures (78-340 K), magnetic fields (0-16
T), and wavenumbers (20-9000 cm). The optical conductivity gradually
changes from a Drude-like behavior to a broad peak feature near 5000 cm
in the ferromagnetic state below the Curie temperature . Various
features of the optical conductivity bear striking resemblance to recent
theoretical predictions based on the interplay between the double exchange
interaction and the Jahn-Teller electron-phonon coupling. A large optical
magnetoconductivity is observed near .Comment: 4 pages, 4 figures, Latex, PostScript; The 7th Joint MMM-Intermag
Conference,San Francisco, January 6-9, 1998; The Int. Conf. on Strongly
Correlated Electron Systems, Paris, July 15-18,199
Steps in the Negative-Differential-Conductivity Regime of a Superconductor
Current-voltage characteristics were measured in the mixed state of
Y1Ba2Cu3O(7-delta) superconducting films in the regime where flux flow becomes
unstable and the differential conductivity dj/dE becomes negative. Under
conditions where its negative slope is steep, the j(E) curve develops a
pronounced staircase like pattern. We attribute the steps in j(E) to the
formation of a dynamical phase consisting of the succesive nucleation of
quantized distortions in the local vortex velocity and flux distribution within
the moving flux matter.Comment: 5 pages, 3 figure
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..
Vitrification and Glass Transition of Water: Insights from Spin Probe ESR
Three long standing problems related to the physics of water viz, the
possibility of vitrifying bulk water by rapid quenching, its glass transition,
and the supposed impossibility of obtaining supercooled water between 150 and
233 K, the so-called 'no man's land'of its phase diagram, are studied using the
highly sensitive technique of spin probe ESR. Our results suggest that water
can indeed be vitrified by rapid quenching, it undergoes a glass transition at
\~ 135 K, and the relaxation behavior studied using this method between 165 K
and 233 K closely follows the predictions of the Adam-Gibbs model.Comment: 13 pages, 3 figures; results on slow cooled water added; four figures
compressed in to thre
Features of carnitine metabolism in young athletes
Objective: to study the indicators of carnitine metabolism in young athletes of various specializations.Materials and methods: This study involved 46 people with different levels of physical activity aged 15 to 18 years. The first group consisted of 18 girls professionally involved in field hockey (mean age, 16.17 ± 0.31 years). The second group included 21 swimmers (10 girls and 11 boys, mean age 17.00 ± 0.26 years). The control group included 7 young men with a standard mode of motor activity, not involved in sports (the age of the subjects was 16 years). In the course of the study, the method of liquid tandem chromatography-mass spectrometry with ionization in an electrospray was used. The material for research is capillary blood. As a result of the analysis of the material, the concentrations of bound carnitine (acylcarnitines) and free carnitine were determined in µmol/l.Results: Comparative blood analysis between the three groups showed differences in free carnitine levels. It was shown that the concentration of free carnitine in the blood plasma of field hockey athletes was significantly lower than in the groups of swimmers and non-athletes (p < 0.001). At the same time, the values of indicators of bound carnitine did not differ significantly between all subjects. We also studied that the values of the carnitine coefficient were significantly higher in the group of hockey players compared to other groups (p < 0.001).Conclusion: The decrease in free carnitine levels in the group of hockey players is probably the result of long-term adaptation of the body to conditions in which glucose is the main energy substrate for working muscles. Further studies are needed to clarify the exact mechanisms of development of this phenomenon
Double sign reversal of the vortex Hall effect in YBa2Cu3O7-delta thin films in the strong pinning limit of low magnetic fields
Measurements of the Hall effect and the resistivity in twinned
YBa2Cu3O7-delta thin films in magnetic fields B oriented parallel to the
crystallographic c-axis and to the twin boundaries reveal a double sign
reversal of the Hall coefficient for B below 1 T. In high transport current
densities, or with B tilted off the twin boundaries by 5 degrees, the second
sign reversal vanishes. The power-law scaling of the Hall conductivity to the
longitudinal conductivity in the mixed state is strongly modified in the regime
of the second sign reversal. Our observations are interpreted as strong,
disorder-type dependent vortex pinning and confirm that the Hall conductivity
in high temperature superconductors is not independent of pinning.Comment: 4 pages, 4 figure
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