Organization of measurable thermodynamic quantities and their relevance to analytical chemistry

Summary A short discussion is given of the fundamentals of thermodynamics and of how the large number of measurable thermodynamic quantities can be organized in a clear and self-consistent way. The suggested Thermodynamic Family Tree also undelines the recent introduction of third order derivatives of Gibbs free energy as measurable properties with a sufficient accuracy. Those state functions are so new that they dont have a name nor a symbol yet! Finally some thoughts are given of how one should relate the thermodynamics to a recent discussion of H. Malissa [3] concerning the philosophy of analytical chemistry.

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Organisation meßbarer thermodynamischer Größen und ihre Bedeutung für die Analytische Chemie

Zusammenfassung Die Grundprinzipien der Thermodynamik werden kurz diskutiert und es wird gezeigt, wie die große Zahl meßbarer thermodynamischer Größen in ein klares und folgerichtiges System gebracht werden kann. Der vorgeschlagene thermodynamische Stammbaum zeigt die kürzlich eingeführten dritten Ableitungen der freien Gibbs-Energie als meßbare Eigenschaften mit befriedigender Genauigkeit. Diese Zustandsfunktionen sind so neu, daß sie noch keinen Namen und kein Symbol haben. Abschließend wird ausgeführt, wie die Thermodynamik zu einer kürzlichen Diskussion von Malissa über die Philosophie der analytischen Chemie in Beziehung gebracht werden kann.

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This paper was suggested by Professor Malissa of the Technische Hochschule Wien and should be considered a complement or extension to his important contribution to the discussion on the state and future of Analytical Chemistry (published in Fresenius Z. Anal Chem 305:97 (1981)     

Holographic optical tweezers and their relevance to lab on chip devices

During the last decade, optical tweezers have been transformed by the combined availability of spatial light modulators and the speed of low-cost computing to drive them. Holographic optical tweezers can trap and move many objects simultaneously and their compatibility with other optical techniques, particularly microscopy, means that they are highly appropriate to lab-on-chip systems to enable optical manipulation, actuation and sensing.     

Methodologies for the analysis of rare earth elements and their relevance to reference materials

India has the third largest resources of rare earth elements (REE) in the world. These resources are essentially the monazite sand present in the beaches of southwest, south-east, and mid-eastern coasts of India. Therefore, analytical methodologies for the determination of REE in sea water and high-purity materials were developed. An overview of this work and its relevance to the preparation of standard reference materials of REE in sea water, marine sediments, and high-purity materials in the future is given.     

Methodologies for the analysis of rare earth elements and their relevance to reference materials

India has the third largest resources of rare earth elements (REE) in the world. These resources are essentially the monazite sand present in the beaches of south-west, south-east, and mid-eastern coasts of India. Therefore, analytical methodologies for the determination of REE in sea water and high-purity materials were developed. An overview of this work and its relevance to the preparation of standard reference materials of REE in sea water, marine sediments, and high-purity materials in the future is given.     

Rapid reduction of pentavalent antimony by trypanothione: potential relevance to antimonial activation

The dithiol trypanothione can reduce an antiparasitic pentavalent antimony agent to trivalent rapidly; this reduction process is both pH and temperature dependent and trypanothione may therefore play an important role in the activation of the drug.     

The behaviour and photoresponses of some indolinospiropyrans in monomolecular films

Surface pressure-area isotherms of two spiropyrans were determined under different conditions of illumination. It was found that the photomerocyanine forms produced stable films whilst this was not always the case with the spiro forms. Photomerocyanine monolayers were stabilized by the polar aqueous subphases and photoinduced ring-opening could be effected on the water surface by U. V. irradiation.The ring-closing reaction, however, was inhibited in monolayers.Photomechanical responses occurred as a consequence of the spiropyran photomerocyanine reaction and these were catalysed on acidic subphases. Factors influencing the magnitude of such responses were assessed.Photoregulation of surface tension at the air-water interface was inferred from measurements on stearic acid monolayers spread on photochromic subphases.     

Trends in solid-state NMR spectroscopy and their relevance for bioanalytics

Based on continuous methodical advances and developments, solid-state NMR spectroscopy has become a powerful tool for the investigation of various materials, including polymers, glasses, zeolites, fullerenes, and many others. During the past decade, solid-state NMR spectroscopy also found increasing interest for the study of biomolecules. For example, membrane proteins reconstituted into lipid environments such as bilayers or vesicles, protein aggregates such as amyloid fibrils, as well as carbohydrates can now be studied by solid-state NMR spectroscopy. This review briefly introduces the principles of solid-state NMR spectroscopy and highlights novel methodical trends. Selected applications demonstrate the possibilities of solid-state NMR spectroscopy as a valuable bioanalytical tool.     

Two distinct structures of the sandwich complex of scytonemin with iron and their relevance to astrobiology

Structural Chemistry - Scytonemin is a pigment synthesized by cyanobacteria and found in their sheath. The importance of this biomolecule is its photoprotective function, which is one of the major...     

Some coordination complexes of chromic chloride with aromatic aldehydes and their relevance to the Etard reaction

1:3- and 1:2-complexes of anhydrous chromic chloride with aromatic aldehydes have been prepared. The IR spectra of these complexes are consistent with coordination via carbonyl oxygen and are shown to be identical with the spectra of Etard adducts thus confirming the presence of coordinated aldehyde in the adducts.     

Some niobium(V) complexes and their relevance to the uptake of niobium by ascidians

Ascidians have been reported to absorb many unusual elements, including niobium. A study of some aqueous niobium(V) chemistry is used to identify potential ligating systems. It is proposed from the inorganic chemical evidence that these marine organisms may concentrate other early second and third row transition elements.     

Polyethylene crystals with dislocation networks; their origin structure and relevance to polymer crystallization

Summary A variety of techniques, comprising degradation, low angle X-ray diffraction, and measures of crystallinity, have been applied to polyethylene crystals showing crystallographic contact between constituent layers. The results are analysed in the light of the model proposed in the preceding communication, and defined more concretely in the present paper. This model requires that the short molecules-one to three times the layer thickness in length-which largely constitute these crystals should have their ends at the lamellar surfaces. As a consequence, in the presence of the finite molecular weight spread, these surfaces will have to the rough owing to uneven lengths of the lamellar traverses. This roughness enables intermeshing of layers, which constitutes the observed crystallographic contact. Infra red experiments verify that the ends are at the surfaces; G. P. C. analysis of nitric acid degraded material measures the surface roughness as detected by fluctuations in the depths of the folds.The continuous variation of the layer thickness with crystallization temperature observed by X-rays can be attributed to changes in the proportion of molecules with different numbers of folds.Measurements of heats of fusion, densities, and NMR line widths, reveal a non-crystallographic component comparable with the usual crystals of polyethylene, while the melting points are reduced because of the low molecular weights. As the crystallographic information has to be transmitted from one layer to the next there can be no true amorphous barrier between them. In consequence, the crystallinity deficiency is attributed to the rough surfaces only. Implications for the general problem of amorphous content in single crystals are discussed.

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Zusammenfassung Eine Vielfalt von Techniken, umfassend Abbau, Kleinwinkelstreuung und Messung der Kristallinität, wurden auf Polyäthylenkristalle angewendet, die kristallographischen Kontakt zwischen den Lamellen aufweisen. Die Ergebnisse wurden im Rahmen eines Modells analysiert, wie es in der vorausgegangenen Veröffentlichung vorgeschlagen und in der vorliegenden Arbeit konkretisiert wird. Dieses Modell verlangt, daß im wesentlichen kurze Moleküle-1-3mal so lang, wei es die Schichtdicke verlangt-diese Kristalle aufbauen, so daß viele Enden in Lamellenoberflächen zu leigen kommen. Als eine Folge der Anwesenheit endlicher Molekulargewichte müssen diese Oberflächen rauch sein gemäß den ungleichen Längen für die Lamellenübergänge. Diese Rauhigkeit erlaubt eine Kuppelung der Schichten, welche die beobachteten kristallographischen Kontakte herbeiführen. IR-Experimente zeigen, daß die Enden in der Oberfläche liegen, G. P. C.-Analyse von salpetersäureabgeätztem Material mißt die Oberflächenrauhigkeit, wie sie durch die Fluktuation der Faltentiefen entsteht.Kontinuierliche Variation der Schichtdicken mit Kristallisationstemperature, beobachtet durch Röntgenstreuung, kann den Änderungen des Anteils an Molekülen mit verschiedenen Faltungszahlen zugeschrieben werden.Messungen der Schmelzwärme, Dichten und NMR-Linienweiten zeigen einen nichtkristallographischen Anteil, vergleichbar mit dem von gewöhnlichen Polyäthylenkristallen, wohingegen die Schmelzpunkte wegen des niedrigen Molekulargewichts reduziert sind. Als Folgerung daraus wird der nichtkristalline Anteil allein den rauhen Oberflächen zugeschrieben. Das allgemeine Problem des amorphen Anteils an Einkristallen wird in diesem Zusammenhang diskutiert.

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With 12 figures in 13 details     

Singlet-triplet splittings and their relevance to the spin-dependent exciton formation in light-emitting polymers: an EOM/CCSD study

By employing the coupled-cluster equation of motion method (EOM/CCSD) for excited-state structures, we have investigated the structure dependence of the singlet and triplet exciton splittings, through extensive calculations for polythiophene (PT), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(thienylenevinylene) (PTV), polyparaphenylene vinylene (PPV), MEHPPV, polyparaphenylene ethylene (PPE), polyfluorene (PFO), and ladder-type polyparaphenylene (mLPPP). The results for the polymer are extrapolated through computations for the oligomers with increasing length. Recent investigations have been quite controversial about whether the internal quantum efficiency of electroluminescence could be higher than the 25% spin statistics limit or not in polymeric materials. Using a simple relationship between the exciton formation rate and the excitation energy level, we have discussed the material-dependent ratios of singlet and triplet exciton formation, which are in good agreement with the magnetic-field resonance detected transient spectroscopy measurement by Wohlgenannt et al. for a series of electronic polymers. This provides another piece of evidence to support the view that the internal quantum efficiency for conjugated polymers can exceed the 25% limit.     

Chemical waves in open flows of active media: their relevance to axial segmentation in biology

The boundary forcing of open flows of active media can lead to a variety of spatiotemporal structures, depending on the local kinetics of the medium and on the characteristics of the forcing. Here, we demonstrate that regardless of the local kinetics, the combination of flow and boundary forcing is a powerful method for replacing intrinsic modes with extrinsic ones. This entrainment of dynamics has important implications for biological morphogenesis. During early embryonic development it is frequently observed that stripes of gene expression and segments arise one after the other along a growth-axis. We show that axial growth can be viewed as an open flow of cells away from a growth zone. Based on this realisation, we demonstrate using three generic reaction-diffusion-advection schemes how a space-periodic structure is induced, one "segment" at a time along the growth/flow axis, by a segmental clock that is synchronised within the growth zone. The schemes are investigated in the context of an abrupt and a gradual change in the properties of the segmental clock. Experimental observations provide evidence that the latter is involved in the early development of many vertebrates.     

Material properties of GaPO4 and their relevance for applications

A set of physical constants of gallium(ortho-)phosphate GaPO₄ has been determined in recent years. These constants allow to calculate precisely the properties of the most important applications of GaPO₄ such as BAW and SAW devices.