Rotational bands in 181Ta

High-spin states in ¹⁸¹Ta have been studied via the ¹⁷⁶Yb(¹¹B,α2n) reaction at 52 MeV using the PEX array and at 57 MeV using the NORDBALL array, with α-particle detection. The previously known, K^π=(7/2)⁺ ground state band and K^π=(9/2)⁻ band have been extended to spins (29/2)⁺ and (31/2)⁻, respectively. Two new one-quasiparticle bands, the K^π=(5/2)⁺ band built on the known (5/2)⁺ isomer and a K^π=((1/2)⁻) band have been observed. Two other rotational bands with three-quasiparticle structure, K^π=(15/2)⁻ and ((19/2)⁺ with π(7/2)[404]ν²(1/2)[510](9/2)[624] and π(9/2)[514]ν²(1/2)[510](9/2)[624] configurations, respectively, have been newly observed. The half-life of the K^π=((19/2)⁺) bandhead which decays to the head of the (15/2)⁻ band has been measured to be 140(36) ns. However, transitions from the ((19/2)⁺) state to the (15/2)⁻ band have not been observed. Received: 26 August 1998     

Enthalpimetric and thermometric determination of some nitrogen containing bases and some physiologically active alkaloids

Summary The enthalpimetric determination of a series of bases by using the reaction of the bases and sodium tetraphenylboron is described. The accuracy of the method is analytically acceptable, over the range 3×10^–5 moles to 7.5×10^–4 moles. The upper limit is determined by the bulk of the precipitate.Dosage forms of some physiologically active alkaloids contain more than the upper limit of analyte. Yet, preliminary investigations using silicotungstic acid indicate that this is suitable for thermometric titrations.

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Enthalpimetrische und thermometrische Bestimmung stickstoffhaltiger Basen und physiologisch aktiver Alkaloide

Zusammenfassung Die enthalpimetrische Bestimmung einiger N-haltiger Basen erfolgte aufgrund der Reaktion mit Natriumtetraphenyloborat. Die Genauigkeit ist im Bereich von 3 · 10^–5-7,5 · 10^–4 Mol befriedigend. Eine obere Grenze der Anwendbarkeit ergibt sich aus der Menge des anfallenden Niederschlags. Diese wird bei der Bestimmung von Formulierungen einiger physiologisch aktiver Alkaloide überschritten. Jedoch ist in diesem Fall eine thermometrische Titration mit Hilfe von Silicowolframsäure möglich.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany.     

A rapid enthalpimetric method for the assay of the reducing sugar content of some soft drinks

An enthalpimetric method for the rapid, low cost assay of reducing sugars in soft drinks is reported. The assay involves the determination of the sugars by oxidation with copper(III) ions in an alkaline medium. Separation of the various matrix materials, fruit peel, preservatives, etc. is not required. Amounts of glucose in the range 12.5–50 mg per litre of sample have been determined with an average error of 1.5%. The time of assay is less than 2 minutes. The method is capable of being automated for use with semi-skilled operatives. The proposed method has been compared with the Official Method and the results are equally acceptable. The advantages of the proposed method include speed of assay, the potential for automation and the low cost of individual assays.     

Thermometric titrations at elevated temperatures

The oxidizing power of hexacyanoferrate(III) in alkaline conditions is wellknown. Unfortunately many if its oxidation reactions are too slow at room temperatures for direct titrimetric procedures. A method has been developed for the determination of millimolar amounts of selenium(IV), arsenic(III), antimony(III), chromium(III), and thallium(I) using thermometric titrimetry at approximately 330 K. The reproducibility and accuracy of the method are approximately 1%.     

Simple Analytical Model Predicting Some Features of the Electrolytic Steel-Pickling Process

Electrolytic pickling of steel with neutral solutions, to remove the surface scale, reduces the need for the use of strong acids as needed in conventional pickling. This study is a step towards a more in-depth understanding of the factors affecting the former process. A theoretical model, sufficiently simplified to allow analytical solution, is developed and evaluated to provide a first approximation of the potential and current distributions in the electrolyte and steel band. To gain knowledge and validate the model, a small electrolytic pickling cell is constructed, and experiments, including bubble generation and motion observation, are conducted. The experimental work has shown the remarkable bubble production and adherence to the surfaces, and its effects on reducing pickling efficiency and uniformity. The pickling efficiency is about 30%, confirming other researchers" results. The analytical model shows trends very similar to those observed in the experiments, and provides very valuable guidance. It shows, for example, that the current efficiency decreases as the electrode–band distance increases, and it increases with the band thickness and the band-to-electrolyte conductivity ratio. The energy efficiency decreases by orders of magnitude faster than the current efficiency with all of the above-mentioned parameters, because of the correspondingly strong drop in the band–surface potential. A large amount of current is lost due to interelectrode short circuiting.     

Rapid analysis of dosage forms of some pharmaceuticals by nonaqueous thermometric titrimetry

The use of the technique of solution thermochemistry is proposed for the rapid assay for quality control and quality assurance of dosage amounts of some ethical formulations of some antimalarial drugs. The active ingredients are chloroquine, hydroxychloroquine, dapsone, proguanil hydrochloride, and pyrimethamine.Assay is done without the separation of the excipients and without isolation or derivatisation of the analytes. The titrations are done in glacial acetic acid and utilise the catalysed hydrolysis of acetic anhydride by perchloric acid to indicate the endpoint of the reactions.The time taken for a typical assay, of a typical dosage amount is about 3–5 minutes. The reproducibility is of the order of 1% for the milligramme amounts of analyte present in the dosage amounts of the drugs.

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Zusammenfassung Es wird die Anwendung eines lösungsthermochemischen Verfahrens zu Schnellbestimmungen bei der Qualitätskontrolle und — sicherung von Wirkstoffeinsatzmengen einiger rezeptpflichtiger Präparate von einigen antimalarischen Arzneimitteln empfohlen. Die aktiven Bestandteile sind Chloroquin, Hydroxychloroquin, Dapson, Proguanilhydrochlorid und Pyrimethamin.Die Bestimmungen werden ohne jegliche Abtrennung der Bindestoffe und ohne Isolierung oder Derivatisierung der zu bestimmenden Substanzen durchgeführt. Die Titrierungen werden in Eisessig durchgeführt und bedienen sich der katalytischen Hydrolyse von Essigsäureanhydrid durch Perchlorsäure als Endpunktindikation der Reaktion.Die Dauer für eine typische Probe bei einer typischen Wirkstoffmenge beträgt etwa 3–5 Minuten. Die Reproduzierbarkeit liegt in der Größenordnung von 1% für Milligrammengen der zu analysierenden Stoffe im Arzneimittel.

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We acknowledge the Nigerian Government for the provision of a grant to one of us (S.I.A.). We acknowledge the following for the gifts of samples of the authentic drugs and the tablets assayed in this work: Imperial Chemical Industries plc; May and Baker plc; Winthrop Laboratories plc; Wellcome Foundation (Medical Division).     

Thermodynamic characterization of different actin isoforms

Summary The thermodynamic properties of the cardiac and skeletal a-actin isoforms were studied to characterize the molecular bases of the functional differences between them with the method of differential scanning calorimetry (DSC). The thermal properties of the actin filaments were described in the presence of calcium and magnesium ions as well. Based on the calculated free energy changes the α-cardiac actin filaments appeared to be more stable in its physiologically more relevant, magnesium saturated form. The magnesium saturated form of the α-cardiac actin filaments seemed to be more stable compared to the calcium saturated form of it. The enthalpy and entropy changes could differentiate between the α-cardiac and α-skeletal actin isoforms and between the calcium and magnesium saturated cardiac actin isoforms as well. Our results can demonstrate that the few differences between the amino acid sequences of the α-actin isoforms have an influence on the thermal properties and maybe on the function of these proteins as well.     

Some aspects of the reactions between selenium-containing ligands and platinum group metals

2-(2-Pyridyl)benzo[b]selenophene has been investigated as a possible reagent for palladium. From a consideration of its reactions with diverse metal ions, and the probable structure of the complex formed between the compound and palladium(II) it is postulated that the group may be highly selective for palladium. From the experimental evidence it is suggested that the delocalization of the metal electron density by pi-bond formation between the palladium and selenium atoms is a major factor in determining the stability of the chelated complex.     

Application of an artificial neural network (ANN) and piezoelectric chemical sensor array for identification of volatile organic compounds

A piezoelectric chemical sensor array was developed using four quartz crystals. Gas chromatographic stationary phases were used as sensing materials and the array was connected to an artificial neural network (ANN). The application of the ANN method proved to be particularly advantageous if the measured property (mass, concentration, etc.) should not be connected exactly to the signal of the transducers of the piezoelectric sensor. The optimum structure of neural network was determined by a trial and error method. Different structures were tried with several neurons in the hidden layer and the total error was calculated. The optimum values of primary weight factors, learning rate (η=0.15), momentum term (μ=0.9), and the sigmoid parameter (β=1) were determined. Finally, three hidden neurons and 900 training cycles were applied. After the teaching process the network was used for identification of taught analytes (acetone, benzene, chloroform, pentane). Mixtures of organic compounds were also analysed and the ANN method proved to be a reliable way of differentiating the sensing materials and identifying the volatile compounds.     

Diodes as sensors in solution thermochemistry

The advantages of using diodes as thermal sensors in solution thermochemistry are discussed and a simple, low-cost circuit for the use of diodes as temperature sensors is reported. In preliminary studies, the titration of TRIS and hydrochloric acid is used to compare the precision of thermistors and diodes in thermometric titrimetry. Several systems are assayed at various temperatures by enthalpimetric methods to illustrate the advantages of diodes as sensors for monitoring thermal methods capable of being used in quality control system.