New global communication process in thermodynamics: impact on quality of published experimental data

Thermodynamic data are a key resource in the search for new relationships between properties of chemical systems that constitutes the basis of the scientific discovery process. In addition, thermodynamic information is critical for development and improvement of all chemical process technologies. Historically, peer-reviewed journals are the major source of this information obtained by experimental measurement or prediction. Technological advances in measurement science have propelled enormous growth in the scale of published thermodynamic data (almost doubling every 10 years). This expansion has created new challenges in data validation at all stages of the data delivery process. Despite the peer-review process, problems in data validation have led, in many instances, to publication of data that are grossly erroneous and, at times, inconsistent with the fundamental laws of nature. This article describes a new global data communication process in thermodynamics and its impact in addressing these challenges as well as in streamlining the delivery of the thermodynamic data from "data producers" to "data users". We believe that the prolific growth of scientific data in numerous and diverse fields outside thermodynamics, together with the demonstrated effectiveness and versatility of the process described in this article, will foster development of such processes in other scientific fields.     

Internal kink instability during off-axis electron cyclotron current drive in the DIII-D tokamak

Experimental evidence is reported of an internal kink instability driven by a new mechanism: barely trapped suprathermal electrons produced by off-axis electron cyclotron heating on the DIII-D tokamak. It occurs in plasmas with an evolving safety factor profile q(r) when q(min) approaches 1. This instability is most active when ECCD is applied on the high field side of the flux surface. It has a bursting behavior with poloidal/toroidal mode number = m/n = 1/1. In positive magnetic shear plasmas, this mode becomes the fishbone instability. This observation can be qualitatively explained by the drift reversal of the barely trapped suprathermal electrons.     

Apparent spin polarization decay in Cu-dusted Co/Al2O3/Co tunnel junctions

Co/Al2O3/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated with in situ growth characterization and ex situ magnetotransport measurements. Cu interlayers grown on Co give an approximately exponential decay of the tunneling magnetoresistance with xi approximately 0.26 nm while those grown on Al2O3 have a decay length of 0.70 nm. The difference in decay lengths can be explained by different growth morphologies, and in this way clarifies a present disagreement in the literature. For monolayer coverage of Cu, we show that the tunneling spin polarization is suppressed by at least a factor of 2 compared to Co and beyond approximately 5 ML it becomes vanishingly small.     

Identification and quantification of inorganic and organic selenium compounds with highperformance liquid chromatography

Selenium appears in the natural selenium cycle in the form of several organic and inorganic compounds. The biologically beneficial and deterimental effects of ‘selenium’ must be ascribed to particular selenium compounds. The identification and quantification of selenium compounds in biological and environmental samples is required for an understanding of the role of selenium. The high-performance liquid-chromatographic (HPLC) methods for the separation, identification and quantification of selenite, selenate, hydrogen selenide, methaneselenol, bis(organothio) selenides, trimethylselenonium salts, selenonamino-acids, selenium derivatives of carbohydrates, selenoproteins, selenonucleosides and other miscellaneous selenium compounds are summarized (193 references) and pertinent detection modes discussed. Advantages and disadvantages of the methods are pointed out. The literature is covered since 1974, the year of the first publication in this field.     

Determination of lead and cadmium in biological samples by potentiometric stripping analysis

Summary The determination of lead and cadmium in biological materials was carried out by potentiometric stripping analysis. Supporting electrolyte was a mixture of NaCl and HCl. In the presence of 4% lumatom in methanol, oxidation potentials of –0.46 V for Pb and –0.68 V for Cd were found (vs. SCE). The method was applied to different standard reference materials (leaves, needles, hair) and was also compared with the differential pulse anodic stripping technique. The latter presented considerable difficulties, in particular by the interference of oxygen.

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Bestimmung von Blei und Cadmium in biologischem Material durch potentiometrische Stripping-Analyse

Zusammenfassung Als Trägerelektrolyt diente bei diesem Verfahren ein Gemisch von NaCl und HCl. In Gegenwart von 4% Lumatom in Methanol wurden Oxidationspotentiale von –0,46 V für Pb und –0,68 V für Cd (gegen SKE) erhalten. Die Methode wurde auf verschiedene Referenzmaterialien (Laub, Nadeln, Haar) angewendet und auch mit der Differentialpuls-Anodic Stripping-Analyse verglichen. Bei der letzteren ergaben sich größere Schwierigkeiten, hauptsächlich durch störenden Sauerstoff.

     

C13 N.M.R. spectroscopy on butyltin compounds containing N-, O- and S- ligands.

¹³C NMR data are reported for a range of tributyl and dibutyl-tin complexes containing O, N and S ligands. The coupling constant J¹ appears to be indicative of the coordination state of the tin atom. Using J¹, shift values and other supporting evidence, structure for a number of the compounds are proposed.     

A DTA study of phenols

A comprehensive DTA study is reported of eight methyl-phenols, 4-methoxy-phenol and four methyl-halo-phenols and of the correspondingp-nitrobenzoylchloride, 3,5-dinitrobenzoylchloride andp-phenylazobenzoylchloride derivatives, prepared in situ by heating intimate mixtures of phenol and acid chloride in a DTA system. The thermal analysis data, in particular, the derivative formation temperatures, are interpreted in terms of the inductive, mesomeric and steric effects associated with the ring substituents of the phenol and acid chloride and the extent of inter- and intramolecular hydrogen-bonding existing in these systems. The DTA data collectively, provide a comprehensive data base for the identification and characterisation of these phenols via DTA.

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Zusammenfassung An durch Erhitzen inniger Mischungen aus Phenol und Säurechloriden in einem DTA-System hergestellten acht Methylphenolen, an 4-Methoxyphenol, an vier Methylhalophenolen und an den entsprechendenp-Nitrobenzoylchlorid-, 3,5-Dinitrobenzoylchlorid- undp-Phenylazobenzoylchloridderivaten wurden ausführliche DTA-Untersuchungen durchgeführt. Thermoanalytische Ergebnisse, insbesondere die Bildungstemperatur der Derivate wurden als Ausdruck des induktiven, mesomeren und sterischen Effektes bezüglich der Substituenten am Phenolring und des Säurechlorides sowie des Ausmaßes der in diesem System existierenden inter- und intramolekularen Wasserstoffbrückenbindungen gewertet. Die Gesamtheit der DTA-Daten ist gleichzeitig eine ausführliche Datenreferenz zur Identifizierung und Charakterisierung dieser Phenole mittels DTA.

     

Substituent effects in reactions of benzenes with 5-tert-butyl-3H-pyrazolylidene

The effects of substituents on the conversions of benzenes by 5-tert-butyl-3$\text{H}$-pyrazolylidene to (substituted phenyl)pyrazoles and pyrazolo[1,5-$\text{a}$azocines are described.     

Improved Parameterization for Combined Isotopomer Analysis of Diatomic Spectra and Its Application to HF and DF

A new way of representing vibration-rotation term values for multiple isotopomers of a given electronic state of a diatomic molecule is presented which resolves problems associated with the way the conventional combined isotopomer expansion represents the atomic mass-dependent JWKB and Born-Oppenheimer breakdown correction terms. Its application to infrared and microwave data for HF and DF yields new Dunham expansion coefficients and Born-Oppenheimer breakdown correction terms for this species. This procedure is implemented in a generally available computer program for fitting to various types of data involving one or several electronic states of multiple isotopomers of a diatomic molecule. Copyright 1999 Academic Press.