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Multicycle differential scanning calorimetry

Thermophysical procedures for research, development, and quality control of substances and materials

Journal of Thermal Analysis and Calorimetry
Authors: E. Marti, E. Kaisersberger, and E. Füglein

Abstract  

Multicycle Differential Scanning Calorimetry (MCDSC) is a procedure where repeated temperature cycles are executed and the measured data are superimposed for a selected number of cycles. Temperature cycles with a single sample are executed under selected experimental conditions in one of these procedures, namely, the MCDSCs. The second one, MCDSCm is a procedure in which every identical temperature cycle starts with a new sample of the same substance of a similar mass. The procedure MCDSCs using the same sample for a number of cycles is only applicable for substances and materials which are chemically and physically stable under the selected experimental conditions. The application of MCDSC enhances two extremely important qualities of a DSC measurement, namely, the sensitivity and the statistical base, both qualities with respect to the final data elucidated. Another possibility by MCDSC also related to the enhanced sensitivity can lead the discovery of a phenomenon which hitherto has not been observed. The most important result of any MCDSC application is the determination of the mean DSC curve within the temperature interval of interest by superimposing the single curves point by point and by the division of the calorimetric values obtained with the number of scans evaluated. The signal-to-noise-ratio (SNR) for the mean curve can be compared with the value determined for one or even for all the single curves measured yielding the improvement factor achieved with a MCDSC measurement. This experimentally determined improvement of the SNR can be compared with the value given on a statistical consideration by Gauss as the square root of the number of cycles evaluated. The main aims of this article are to prove the practical application of the procedure and the efficiency in case of rather small sample masses. Substances were selected with known enthalpy transitions and, in addition, polystyrene was taken for a determination of the data for the glass transition by MCDSC. Rather small sample masses in the order of micrograms as well as the experimental conditions have been selected for the measurements with 4,4′-azoxyanisole and n-hexatriacontane with the expectation to get a value of SNR for the single curves of about unity or even below. Two aims should be achieved with these experiments. First, the multicycle procedures and the data evaluation developed should be capable of establishing, after performing of a certain number of cycles, a mean curve showing an improvement over the SNR with respect to the single curves. Second, we should be able to get a rough estimation of the lower limit of the SNR for a single curve, below the instrumental noise level of the DSC used, necessary to achieve with a MCDSC experiment a mean curve with a clearly visible peak.

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Different sampling strategies are simulated by changing quadrat size, quadrat shape, sample size and the arrangement of quadrats in a tropical rain forest of Hainan (South China). The simulation uses enumeration data of trees, and derived variables such as species richness, species importance, and species population density, to compare the efficiency of the sampling. The results verify that greater sampling efficiency is to be expected using systematic sampling than random sampling. Quadrat size has substantial influence on parameter estimation, but quadrat shape has negligible effect except when the quadrat is extremely long and narrow.

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Abstract  

We compare a new method for measuring research leadership with the traditional method. Both methods are objective and reliable, utilize standard citation databases, and are easily replicated. The traditional method uses partitions of science based on journal categories, and has been extensively used to measure national leadership patterns in science, including those appearing in the NSF Science & Engineering Indicators Reports and in prominent journals such as Science and Nature. Our new method is based on co-citation techniques at the paper level. It was developed with the specific intent of measuring research leadership at a university, and was then extended to examine national patterns of research leadership. A comparison of these two methods provides compelling evidence that the traditional method grossly underestimates research leadership in most countries. The new method more accurately portrays the actual patterns of research leadership at the national level.

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Abstract  

A description is given of the systematic errors which can be introduced when applying absolute or comparator standardization techniques to RNAA or ENAA at irradiation sites with a deviating 1/E1+α epithermal neutron flux distribution. A simple correction formula for a≠0 is presented and a survey is given of the present state-of-the-art for experimentala-monitoring and for the calculation or experimental determination of the effective resonance energy Ēr. Extensive error calculation leads to the conclusion that, with careful selection ofa monitors and of the nuclear data involved, the rather large errors (∼10% or more) are reduced, after correction fora, to uncertainties of about 2%.

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Orvosi Hetilap
Authors: Anna Fábián, Renáta Bor, Anita Bálint, Klaudia Farkas, Ágnes Milassin, Mariann Rutka, László Tiszlavicz, Ferenc Nagy, Tamás Molnár, and Zoltán Szepes

Zhao, Y. L., Cao, D. M., Zhou, Q. C., et al.: Accuracy of endorectal endoscopic ultrasound (EUS) for Locally Advanced Rectal Cancer (LARC) restaging after neoadjuvant chemoradiotherapy (NAT): a meta

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acceleration on the benchmarks of the II. levelling of high accuracy at the territory of Croatia, Bosnia and Hercegovina, Monte Negro, Slovenia and Vojvodina (in Croatian). Faculty of Geodesy, University of Zagreb, Zagreb

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ISO (1994a): Accuracy (trueness and precision) of results — Part 1: general principles and definitions . International Standard. No 5725-1 Accuracy (trueness and precision) of results — Part 1

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’, Bratislava, Slovak Republic, 122–127. Zimová R, Pešt’ák J, Veverka B 2006: Historical Military Mapping of Czech Lands — Positional Accuracy of Old Maps. GIM International, Vol. 20,Issue 10, 21

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Evaluation of a GPS CORS Network for Real Time Centimetric Positioning — The Victoria GPSnet, IGNSS Symposium, Australia Häkli P 2004: Practical Test on Accuracy and Usability of Virtual Reference Station Method in Finland. FIG

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