Modification of magnetic anisotropy in metallic glasses using high-energy ion beam irradiation

Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe₄₀Ni₄₀B₂₀ and Fe₄₀Ni₃₈Mo₄B₁₈ metallic glass ribbons. 90 MeV ¹²⁷I beam was used for the irradiations. Irradiation doses were 5×10¹³ and 7.5×10¹³ ions/cm². The relative intensity ratios D ₂₃ of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy.     

Use of the magnetic suspension balance for the study of polymersolutions

The method involves the isothermal gravimetric determination of the absorption of an organic vapour into a thin film of liquid polymer spread upon an inert particulate support. Results are presented for the absorption of benzene and cyclohexane at 25°C in poly (dimethylsiloxane), and the concentration variation of the interaction parameter determined is compared with that found by other workers.The determination of the partial molar enthalpy of mixing was also examined by studying the absorption of hexane in poly (dimethylsiloxane) over the temperature range of 25 to 35°C, and comparing the value obtained with published values.     

X-ray structure of fac-[RuH(1,5-cod)(NH2NMe2)3][PF6]: Stabilization of coordinated substituted hydrazines by hydrogen bonding

The structure of [RuH(cod)(NH₂NMe₂)₃][PF₆] has been solved by X-ray diffraction methods and shows the cation to contain a facial arrangement of N,N-dimethylhydrazine ligands, coordinated via the NH₂ nitrogen atoms, and held together by hydrogen bonds.     

An optical calcium ion sensor

An optical fibre calcium ion sensor is described which utilises the chromogenic crown ether, (5-(4′-nitrophenylazo)-2-hydroxy-1,3-xylyl-18-crown-5), immobilised on a styrene/divinylbenzene copolymer at the tip of an optical fibre. The sensor is sensitive to calcium ions in the concentration range 5–50 mM.     

Automatic coulometric micro-determination of unsaturation with kinetic proof of real equivalence-point

Summary A fully automatic coulometric method has been applied successfully to the determination of unsaturated compounds on the micro-scale. Results are quoted which show a reproducibility of ± 0.3% for monoolefinic hydrocarbons. It is possible to control by means of a simple operation whether the addition reaction is complete and unaccompanied by side reactions. It has been shown that the concentrations of olefines in a mixture can be determined when their bromination speeds differ sufficiently from each other.

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Zusammenfassung Eine für kinetische Zwecke entwickelte vollautomatische, coulometrische Methode wurde mit Erfolg auf die Bromtitration ungesättigter Verbindungen im Mikromaßstab angewandt. Die angeführten Testuntersuchungen zeigen, daß bei monoolefinischen Kohlenwasserstoffen und ähnlichen Verbindungen die erreichbare Reproduzierbarkeit besser ist als ± 0,3%. Die Anordnung ermöglicht auf einfache Weise die Feststellung, ob die Addition vollständig abgelaufen ist und ob der Titrationswert nicht durch eine Nebenreaktion verfälscht wird. An Beispielen wird gezeigt, wie bei Gemischen olefinischer Verbindungen, die Bestandteile ausreichend verschiedener Reaktivität enthalten, die einzelnen Anteile nebeneinander bestimmt werden können.

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Résumé Les auteurs ont appliqué avec succès une méthode coulométrique entièrement automatique pour le dosage des composés non saturés à l'échelle microanalytique. Les résultats obtenus sont reproductibles à ± 0,3% près pour les hydrocarbures mono-oléfiniques. Une opération simple permet de contrôler que la réaction d'addition est complète et qu'elle n'est pas accompagnée par des réactions secondaires. Les auteurs ont montré également qu'il était possible de déterminer les concentrations de diverses oléfines dans un mélange lorsque leurs vitesses de fixation du brome diffèrent suffisamment les unes des autres.

     

The Bioconversion of (3RS,E)- and (3RS,Z)-Nerolidol into Oxygenated Products by Streptomyces cinnamonensis. Possible Implications for the Biosynthesis of the Polyether Antibiotic Monensin A??

The ability of the monensin-producing organism Streptomyces cinnamonensis to bioconvert the (E)-and (Z)-isomers of nerolidol (= 3,7,1 1-trimethyldodeca-1,6,10-trien-3-ol) into new oxygenated products has been investigated. When a ³H-labelled racemic form of each sesquiterpene was added to fermentations of S. cinnamonensis, several new ³H-labelled products could be detected. Two products were isolated from bioconversion of (E)-nerolidol, the amide 8 and the 9 (Scheme 2), whereas four products were isolated from the bioconversion of (Z)-nerolidol, the epoxydiol 10 , triols 11 and 12 , and the tetrahydrofuryl alcohol 13 (Scheme 4). Products 9 – 13 were obtained as a 1 : 1 mixture of diastereoisomers, and 12 was shown to arise by the overall anti addition of two OH groups to the trisubstituted (Z)-double bond of (Z)-nerolidol. Both isomers of nerolidol as well as the acetylene 7 are inhibitors of monensin production in shake cultures of S. cinnamonensis.     

On-line nuclear orientation and relaxation studies of Cs isotopes

The hyperfine field of CsFe has been measured to be (+)40.8(0.7)T, using the technique of on-line low temperature nuclear orientation. The time dependent relaxation of¹²¹Cs^m Fe has also been investigated using a new technique, giving a Korringa constant C_k of 0.059 (15) sK. From this, an effective relaxation time of 3.0 (0.8)s can be deduced for the short lived¹¹⁸Cs^m(T_1/2=17s). This value has then been used to extract the magnetic moment of¹¹⁸Cs^m to be |μ|=5.4 (1.1) nm.     

The influence of a transverse magnetic field on a subnormal glow discharge in air

In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G) some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed in these oscillations.     

Nuclear orientation below 1 mK: Development and applications

The Oxford top-loading PrNi₅ nuclear demagnetisation stage /1/ has been further developed to reach temperatures below 1 mK. The hyperfine field for⁷¹As in nickel has been measured by low temperature nuclear orientation as 14.61(36)T. Measurements on transitions in⁷¹Ge yield spin values 3/2 (1299 kev and 1139 kev) and 5/2 (1027 kev) and 5 E2/M1 mixing ratios are given.