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Abstract  

Editorial delay, the time between submission and acceptance of scientific manuscripts, was investigated for a set of 4,540 papers published in 13 leading food research journals. Groups of accelerated papers were defined as those that fell in the lower quartile of the distribution of the editorial delay for the journals investigated. Delayed papers are those in the upper quartile of the distribution. Editorial stage is related to the peer review process and two variables were investigated in search of any bias in editorial review that could influence publication delay: countries of origin of the manuscript and authors’ previous publishing experience in the same journal. A ranking of countries was established based on contributions to the leading food research journals in the period 1999–2004 and four categories comprising heavy, medium, light and occasional country producers was established. Chi square tests show significant differences in country provenance of manuscripts only for one journal. The results for influence on editorial delay of cross-national research and international collaboration, conducted by means of the Fisher statistic test, were similar. A two-tailed Student’s t test shows significant differences (p<0.05) in the distribution of experienced and novel authors across the delayed and accelerated groups of papers. Although these results are time and discipline limited, it can be concluded that authors’ publishing experience causes a faster review and acceptance of their papers and that neither country of provenance nor cross-national research influence the time involved in editorial acceptance of the papers.

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The development of local early basal resistance (EBR), is a form of non-specific general defence response of plants to bacteria, greatly depending on temperature. This symptomless defence mechanism is easily detected by its inhibitory action on the hypersensitive response (HR) caused by a subsequent incompatible pathogenic bacterium. Both EBR and HR were investigated at different temperatures ranging from 30 °C to 5 °C. At normal temperatures (30-20 °C) both heat-killed Pseudomonas syringae pv. syringae 61 (polyvirulent to many plants) and Pseudomonas savastanoi pv. phaseolicola S21 (pathogenic to bean) induced EBR in tobacco leaves within a few hours, but below 10 °C it was greatly delayed and at 5 °C usually no EBR response could be detected within 2-3 days. The time required for development of EBR did not depend on the bacterial pathovars or strains. However, the induction time of HR was not as sensitive to low temperatures as that of EBR, instead, it depended on the bacterial pathovars used.

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Abstract  

A 1.85×1011 Bq (5Ci) Am/Be neutron source is being used to investigate the feasibility of applying the absolute method in the elemental analysis of bulk samples by instrumental neutron activation making use of prompt and delayed gamma rays. Among the different factors which might contribute to variations in sensitivity or in the uncertainly associated with the elemental concentration is the presence of hydrogen in the sample. It is the purpose of this study to examine whether the presence of water in bulk samples such as landfill waste produces significant variations in measured elemental concentrations and if so, requires samples to be dried, which can be a time consuming and expensive process. The effect of hydration of samples on the sensitivity of ten elements has there fore been investigated. Samples with different water concentrations in a fixed volume and shape were prepared and used in the analysis in order to obtain a measure and an understanding of the effects involved.

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Abstract  

A detailed theoretical treatment of cyclic activation analysis of thorium and uranium using a 14 MeV neutron generator and delayed neutron counting is presented. Variations of the detector response with sample transfer and total experiment times are examined in order to obtain the optimum cycle periods for the maximum detector response. Cycle optimization for 95% and 90% of the maximum detector response is investigated. Furthermore, elimination of the delayed neutrons produced by the reaction17O(n,p)17N is also considered in optimum cycle timing. Finally, calculations are carried out to estimate detection limits for thorium and uranium. Experimental results will be reported in a subsequent paper.

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Abstract  

Concentrations of uranium and thorium in some West Malaysian limestones have been determined using neutron activation and delayed neutron analyses. These limestones are mainly calcium carbonates and contain uranium and thorium in concentrations of about a few parts per million.

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Abstract  

An attempt was made to apply a delayed coincidence method for the absolute determination of trace quantities of the thorium series. This method is based on selective counting of the relatively short lived nuclide216Po (half-life 145 ms) in the thorium series members. For this purpose, a list mode time analyzing system combined with a liquid scintillation counter was assembled by means of a conventional microcomputer. A multiple time analysis was employed in the processing and data compilation of delayed coincidences to distinguish them from the true coincidences due to random events.From a time spectrum, the decay component of216Po (145 ms) can be selectively measured. Absolute activities of its progenitors,224Ra and228Th as well as220Rn, can be determined even in the presence of the background radiations of the almost equivalent activity-strength of concomitant uranium series.

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Abstract  

A discrete nonautonomous two-species Lotka-Volterra competitive system with delays and feedback controls is proposed and investigated. By using the method of discrete Lyapunov functionals, new sufficient conditions on the permanence of species and global attractivity of the system are established. Particularly, an interesting fact is found in our results, that is, the feedback controls are harmless to the permanence of species for the considered system.

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Abstract  

The International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty will include measurements of Xe fission products. Pacific Northwest National Laboratory has developed an automated system for separating Xe from air which detects Xe fission products using a beta-gamma counting system for 131mXe, 133mXe, 133gXe, and 135gXe. Betas and conversion electrons are detected in a plastic scintillation cell containing the Xe sample. Gamma and X-rays are detected in a NaI(Tl) scintillation detector which surrounds the plastic scintillator sample cell. Two-dimensional pulse-height spectra of gamma-energy versus beta-energy are obtained. The plastic scintillator spectrum in coincidence with the 31-keV X-rays from 131mXe. 133mXe, and 133gXe is a complex mixture of conversion electrons and betas. A new technique to simultaneously measure the delayed coincidence (T 1/2 = 6.27 ns) between beta-particles from 133gXe and conversion electrons depopulating the 81-keV state in 133 Cs is being developed. This technique allows separation of the 133gXe beta spectrum from the conversion electrons due to 131mXe and 133mXe and uniquely quantifies all three nuclides.

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Abstract  

Delayed neutron counting for uranium assay was coupled with -ray spectrometry in order to measure radionuclides of F, Al, Ca and V produced by neutron activation. For this measurement, the delay time required for U determination was exploited. Calibration of the method was provided by standards based on a CaCO3 matrix and validity of results was verified against other analytical methods. A single sample can be analyzed for the five elements in 3 min with a precision of ±10%. The method developed was applied in the exploration of phosphate ores. The measured total concentrations permitted the disclosure of correlations between various elements and constituents in the samples. Chemical and mineralogical properties were obtained as well.

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Abstract  

This paper describes an evaluation of activation analysis by delayed neutron counting to determine uranium and thorium simultaneously in geological materials and to measure235U/238U isotopic ratios. A procedure to isolate the thorium before the irradiation was studied and adapted for use when the interference of uranium makes the nondestructive thorium analysis impossible.235U/238U ratios were determined in standards with235U abundances from about 0.5 to 93%, in milligram size samples. Discussion on precision, accuracy and total error of the method is presented.

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