132 research outputs found
Nonlinear ac susceptibility studies of high- rings: Influence of the structuring method and determination of the flux creep exponent
We have studied the influence of the patterning procedure on the critical
current density of high- YBaCuO thin rings using the
nonlinear ac susceptibility method. At no applied dc magnetic field we have
found that laser ablation degrades strongly the critical current density
whereas ion beam etching has only a weak influence on it. From the measurements
at different frequencies and dc magnetic fields we analyzed the influence of
flux creep and obtained the field dependence of the flux creep exponent. Our
data reconfirm the recently observed scaling relation for the nonlinear
susceptibility response of type-II superconductors.Comment: 10 pages, 12 figure
Biosynthese und Funktion von Naturstoffen aus Mortierella alpina
In dieser Arbeit wurde anhand des Modellorganismus Mortierella alpina gezeigt, dass basale Pilze wohl zu ausgedehnter Naturstoffbiosyntese befähigt sind. So konnte für die Biosynthese der Malpinine, der Malpicycline, der Malpibaldine sowie das Calpinactam jeweils eine zugehörige Nicht-ribosomale Peptidsynthetase (NRPSen) identifziert werden. Bei den jeweils zugrundeliegenden Biosynthesegenen malA, mpbA, calA und mpcA handelt es sich um pilzliche Gene, die jedoch bakteriellen Ursprungs sind und durch horizontalen Gentransfer auf M. alpina übertragen worden sind. Zusätzlich wurde die biologische Funktion sowie mögliche pharmazeutische Anwendungsmöglichkeiten untersucht
Higher harmonics of ac voltage response in narrow strips of YBa2Cu3O7 thin films: Evidence for strong thermal fluctuations
We report on measurements of higher harmonics of the ac voltage response in
strips of YBa2Cu3O7 thin films as a function of temperature, frequency and ac
current amplitude. The third (fifth) harmonic of the local voltage is found to
exhibit a negative (positive) peak at the superconducting transition
temperature and their amplitudes are closely related to the slope (derivative)
of the first (Ohmic) harmonic. The peaks practically do not depend on frequency
and no even (second or fourth) harmonics are detected. The observed data can be
interpreted in terms of ac current induced thermal modulation of the sample
temperature added to strong thermally activated fluctuations in the transition
region.Comment: 9 pages, 4 figures (PDF file
Microstructure and flow properties of lyophilized mango pulp with maltodextrin.
<div><p>ABSTRACT The present study had as objective to determine the flow properties and behavior of lyophilized mango pulp powder as a function of different concentrations of maltodextrin. In the samples of the powders contain 5, 10 and 15% of maltodextrin the angle of effective internal friction, wall friction angle, flow index and bulk density were determined. The microstructure was evaluated by scanning electron microscopy. The freeze-dried samples are characterized as having an amorphous structure, and the drying aid used modified the surface of the particles. The flow index was 3.19, 4.28 and 4.53 for samples containing, respectively, 5, 10 and 15% maltodextrin. Increasing the concentration of maltodextrin in the mango pulp decreased the effective angles of internal friction and wall friction. The bulk density of the powders increased with increasing concentration of maltodextrin for the samples containing 5, 10 and 15% of the maltodextrin, being equal to 597.8, 689.8 and 691.3 kg m-3, respectively. Thus, it was concluded that the addition of maltodextrin modified the shape of the particles, decreased segregation, affected the flow properties of the mango powders, facilitating flow and increasing their bulk density.</p></div
Stability and microstructure of powdered pulp of the Palmer mango obtained by the process of lyophilisation.
ABSTRACT The aim of this work was to study the stability of powdered mango pulp obtained through the process of lyophilisation, as well as its structural characteristics using electron microscopy analysis. In response to an earlier experimental design using maltodextrin concentrations of 0%, 10%, 20% and 30% and periods of 24 and 30 hours, the condition of 20% maltodextrin and 24 hours drying was chosen as the best for drying mango in a freeze dryer. The stability study was therefore carried out using powdered mango pulp obtained under the above best-drying conditions, stored for 90 days and monitored every two weeks by analysis of the moisture, ascorbic acid content, b* colorimetric parameter and hygroscopicity. Storage was at room temperature (27 °C) in vacuum and non-vacuum laminated packaging, and in non-vacuum plastic packaging. The vacuum laminated packaging maintained the initial characteristics of the stored product for longer, especially the ascorbic acid content, hygroscopicity and b* colour parameter. The microstructure of the sample was then studied under different concentrations of maltodextrin (0%, 10%, 20% and 30%) so as to understand the effect of the drying agent on the final product. Close-up images of the powder revealed the porous surface formation and the effect of the agent on particle size, where higher concentrations of maltodextrin resulted in more porous powders with smaller particles.</div
Effective Area-Elasticity and Tension of Micro-manipulated Membranes
We evaluate the effective Hamiltonian governing, at the optically resolved
scale, the elastic properties of micro-manipulated membranes. We identify
floppy, entropic-tense and stretched-tense regimes, representing different
behaviors of the effective area-elasticity of the membrane. The corresponding
effective tension depends on the microscopic parameters (total area, bending
rigidity) and on the optically visible area, which is controlled by the imposed
external constraints. We successfully compare our predictions with recent data
on micropipette experiments.Comment: To be published in Phys. Rev. Let
Evaluation of thermal and non-thermal processing effect on non-prebiotic and prebiotic acerola juices using 1HqNMR and GC - MS coupled to chemometrics.
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