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  • Author or Editor: A. Burger x
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Abstract  

The antihypertensive drug substance amlodipine besylate crystallizes in two stable crystal forms, an anhydrate and a hitherto unknown monohydrate. Both forms have been characterized by thermal analysis, X-ray powder diffractometry, FTIR- and FT Raman spectroscopy. Moisture sorption- and desorption investigations reveal their unusual physical stability in a broad range of relative humidities. The monohydrate forms an isomorphic dehydrate upon dehydration, which was elucidated by variable temperature X-ray powder diffractometry. Physico-chemical properties as well as relative stabilities of the crystal forms are described and discussed based on a comprehensive analytical identification, and enable an estimation of practical relevance for manufacturing of amlodipine besylate solid dosage forms.

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Abstract  

One challenge to a potential verification regime for a Fissile Material Cutoff Treaty (FMCT) would be to assure that enrichment plants are not producing highly enriched uranium (HEU) for weapons purposes. Namely in some older enrichment plants, operated in nuclear weapon states, environmental sampling techniques might detect particles from historic HEU production. Determination of the age of these particles would be the most direct confirmation of treaty-compliance. While methods are available to determine the age of nuclear materials based on the concentrations of decay products, micron-sized uranium particles are particularly difficult to analyze. We will review the sensitivity requirements for age determination of HEU particles in an FMCT, and assess the potential of advanced measurement techniques available for this application.

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Journal of Thermal Analysis and Calorimetry
Authors: Maria Kuhnert-Brandstätter and A. Burger

Abstract  

The stearic acid-urea binary system exhibits an unusual phase diagram, which, on the one hand, indicates an incongruently melting inclusion compound and on the other hand a miscibility gap in the liquid phases. The peritectic point lies near the melting point of urea and the unstable congruent melting point of the inclusion compound coincides with the melting point of urea. In addition to the processing of the phase diagram, the pure inclusion compound was prepared and its DSC curve, FTIR spectrum and X-ray diffractogram were recorded.

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Abstract  

Iron injections containing high spin iron(III) complexes may undergo a reductive decomposition during preparation or storage. This process was investigated by the Mössbauer spectroscopy of ice samples prepared by quick-freezing of the injection. The comparison of three model compounds and the correlation between the osmotic pressure of the solutions and their iron(II) concentration formed in the decomposition process and determined by Mössbauer measurements revealed the reason and mechanism of the decomposition.

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Abstract  

Liquids and solutions containing Mössbauer active isotopes when trapped in the capillaries of porous silicate glasses show the Mössbauer effect1 also at room temperature2,3. A model is given for the explanation of this phenomenon.

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Abstract  

A comparison is made between two types of research past performance analysis: the results of bibliometric-indicators and the results of peer judgement. This paper focuses on two case studies: the work of Dutch National Survey Committees on Chemistry and on Biology, both compared with our bibliometric results for research groups in these disciplines at the University of Leiden. The comparison reveals a serious lack of agreement between the two types of past performance analysis. This important, science-policy relevant observation is discussed in this paper.

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Abstract  

An analysis of three major problems in the application of bibliometric research performance indicators is made in three separate sections. In the first section, the influence of field-dependent citation practices is analysed. The results indicate that rankings of publications from different fields, based on citation counts, can be affected seriously by differences between citation characteristics in those fields. If certain assumptions hold, one should expect high (short term) citation levels in Biochemistry, Celbiology and Biophysics. Medium citation levels are to be expected in Experimental and Molecular Physics, Physical and Organic Chemistry, Pharmacology and Plant Physiology, and low citation levels in Mathematics, Taxonomy, Pharmacognosy and Inorganic Solid State Chemistry. In the second section time-dependent factors are studied. It is shown that trend-analyses of output and impact based on bibliometric scores can be disturbed by changes in theSCI-database and in publication and citation practices. One of the disturbing factors is shown to be the inclusion of so called Books into theSCI data-base in 1977. Finally, in the third section a case is presented which illustrates the consequences of operating on incomplete bibliometric data in the evaluation of scientific performance. A completeness percentage of 99% for publication data is proposed as a standard in evaluations of the performance of small university research groups).

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