Analyses of uranium and thorium by delayed neutron counting are described.The experimental system comprises an automatic pneumatic transfer system associatedwith a device made of twelve BF 3 neutron counters. Using homogeneous preparedsolutions of the samples, the analyses were based on a triple cycle each including60-second irradiation followed by 1-second cooling and 60-second counting.In these conditions, the limit of detection of uranium is about 0.3 µgwith a precision of measurement better than 10%. The contributions of possibleperturbations from 17 O(n,p)17 N reactions, followed by simultaneous –disintegration and neutron emission and from (n) reactions, have been studied.
(t) = −µx(t) + g(x(t − 1)) is considered with µ ≥ 0 and a smooth real function g satisfying g(0) = 0. It is shown that the dynamics generated by this simple-looking equation can be very rich. The dynamics is completely
understood only for a small class of nonlinearities. Open problems are formulated.
Authors:Elena Voronezhskaya, Marina Khabarova, L. Nezlin, and E. Ivashkin
Serotonin (5-HT) is known to induce a wide range of short-term and long-term (or delayed) effects. In the present paper we demonstrated that short time-window application of the 5-HT precursor 5-hydroxytryptophan during early cleavage stages results in both irreversible morphological malformation (exogastrulation) and distinct changes in behavior of young animals of the freshwater snail, Lymnaea stagnalis (Mollusca: Gastropoda). Pharmacological and immunocytochemical analysis confirmed that both the increase of intracellular 5-HT level within the cleaved blastomers and activation of membrane 5-HT2-like type receptors are required for the appearence of these phenomena.
Authors:Ed Rinia, Thed. Van Leeuwen, Eppo Bruins, Hendrik Van Vuren, and Anthony Van Raan
As part of a larger project to investigate knowledge flows between fields of science, westudied the differences in speed of knowledge transfer within and across disciplines. The agedistribution of references in three selections of articles was analysed, including almost 800.000references in journal publications of the United Kingdom in 1992, 700.000 references inpublications of Germany in 1992, and more than 11 million references in the world total ofpublications in 1998.The rate of citing documented knowledge from other disciplines appears to differ sharplyamong disciplines. For most of the disciplines the same ratio's are found in the three data sets.Exceptions show interesting differences in the interdisciplinary nature of a field in a country. Wefind a general tendency of a citation delay in case of knowledge transfer between different fieldsof science: citations to work of the own discipline show less of a time lag than citations to work ina foreign discipline. Between disciplines typical differences in the speed of incorporatingknowledge from other disciplines are observed, which appear to be relatively independent of timeand place: for each discipline the same pattern is found in the three data sets. The disciplinespecific characteristics found in the speed of interdisciplinary knowledge transfer may be point ofdeparture for further investigations. Results may contribute to explanations of differences incitation rates of interdisciplinary research.
Delayed neutron activation analysis (DNAA) presents a fast, accurate, and reliable method for quantification of fissile material.
The method has relatively few sources of error and may be accomplished nondestructively. The need for a fast, accurate screening
of materials stems from the necessity to protect cleanroom facilities from widely varying fissile quantities in samples and
from desired gains in efficiency of mass spectrometric analysis by assisting in spike level selection and by removing from
the sample set those materials that are not of interest. During the last several years, many different materials have been
screened or analyzed in support of international safeguards, internal process control for actinide separations, and in uranium
contamination assessments. Swipes from a variety of sources have been analyzed, either before or after dissolution, and comparison
of the DNAA results to mass spectrometry results is generally favorable. A facility characterization of the High Flux Isotope
Reactor was performed using filter paper swipes to demonstrate the utility of the DNAA technique.
Authors:Veronika Bocsi, Tímea Ceglédi, Zsófia Kocsis, Karolina Eszter Kovács, Klára Kovács, Anetta Müller, Katalin Pallay, Barbara Éva Szabó, Fruzsina Szigeti, and Dorina Anna Tóth
during education as a factor leading to the dropout, as it puts a double burden on the students.
The attraction of the labor market is one of the most important reasons for delayed graduation and dropout – stated by the Hungarian analyses as
Based on the simulation study of the publication delay control process [Yu & al., 2005], transfer function models of delay control processes by adjusting the accepted contribution flux and the published
contribution flux are identified using system identification. According to Cybernetics, the feedback control system of the
publication delay is designed and control processes are simulated and analyzed when the average publication delay are regarded
as the controlled object. On the basis of the relation between the average publication delay and the deposited contribution
quantity, another control method is proposed that the deposited contribution quantity is regarded as the controlled object
and the simulation result proves that the method is an excellent means and can help editors expediently manage their journals
and control publication delays.