Materials Literature
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The elastic constants, magnetic susceptibility, refractive index and density are reported for p,p'-diheptylazobenzene. The behaviour of the elastic constants of this non polar compound is very similar to that of related polar compounds. The anisotropy of both the static and the high-frequency permittivity is proportio…
The reaction of [SiW12O40]4–(1.5 × 10–5 mol dm–3) with excess of hydroxide ion at an ionic strength of 1.0 mol dm–3 MCl, to form [SiO4]4– and [WO4]2–, has been studied. The reaction proceeds in three distinct stages, the intermediates being [SiW11O39]8– and [SiW9O34]10–. The first stage proceeds via a base-dependent p…
In nematics, the simple shear flow may become unstable when the director is perpendicular to the shear plane. Here we study the non-linear regime above the threshold of the Homogeneous Instability [1]. We use a perturbative approach derived from exact equations within the framework of the Frank-Ericksen-Leslie continu…
A hot-stamping brass immune to dezincijication has been developed. The recommended composition is 35·0–37·0% zinc, 1·7–2·7% lead, 0·08–0·12% arsenic, remainder copper. The alloy contains sufficient beta phase at the hot working temperature (∼820°c) to ensure adequate formability. After stamping, a heat treatment, usua…
The photochemistry of periodate and periodic acid in aqueous solution was studied (i) by quantum yield measurements at low light intensity (ii) by flash photolysis, and (iii) by photolysis of glassy samples at 77 K. The photochemical studies were supplemented with pulse radiolysis studies of aqueous periodate solution…
High resolution 125Te and 123Te F.T. n.m.r. spectroscopy have been used to identify all members of the series [TenSe4–n]2+(n= 1–4) in the Te–Se–oleum system.
The temperature dependence of the permittivity of BTF 2 ceramic has been measured. Three singularities have been observed, of which two at 898°C and 752°C correspond to displacive phase transitions leading to the sequence paraelectricm ↔ ferroelectric ↔ ferroelectric. The third feature, around 400°C, is tentatively as…
Fission cross-section ratio measurements were made in the 2- to 3-MeV region using 235U samples with 234U and 236U samples containing ∼10% 235U. Atom ratios were obtained from measured thermal fission ratios and the isotopic analysis and also by alpha counting. Shape measurements were made from threshold to 10 MeV usi…
Temperature dependences of the optical rotatory power ρs 3 in the ferroelectric phase, the field-induced optical rotatory power ρ3(E 3) in the paraelectric phase and of the initial permittivity ε33 have been measured. These results show that dρ3/dE 3 fulfils the Curie-Weiss law being proportional to the value of ε33.…
Previous studies on eutectoid steel have demonstrated that strength and toughness are essentially independently varying parameters, with the former primarily controlled by the pearlite interlamellar spacing and the latter primarily controlled by the prior austenite grain size. The work has now been extended to study t…
The enzymatic defects in a number of Bacillus subtilis mutants of the alpha-ketoglutarate dehydrogenase complex lacking activity have been investigated. Mutants in the citK locus, as well as a series of deletions of unknown length covering the citK locus, are deficient in E1 of the complex, alpha-ketoglutarate dehydro…
The kinetics of the reaction OH + NO(+ M)→ HNO2(+ M) have been studied, using flash photolysis to generate OH radicals and time-resolved resonance absorptions to observe the rate of their removal. Effective second-order rate constants, k1=(– d ln [OH]/dt)/[NO], have been determined at four temperatures, T= 233, 296, 4…
Abstract A series of methyl methacrylate (MMA)–methacrylic acid (MAA) copolymers containing up to 50% methacrylic acid and the respective homopolymers were reproducibly pyrolyzed at 900°C and the fragments identified by gas chromatography (GC) or GC–mass spectroscopy. It was shown that PMMA and the MMA portions of blo…
Abstract Coalescence in vertical close packed dispersions . Models are presented for the description of growing, decomposing, and steady‐state dispersions. They contain the velocity of the dispersed phase V 0 , the initial drop diameter Φ 0 , the hold‐up ε , and the coalescence times between the drops τ and at the fre…
Transmission electron microscopy (TEM) has been widely used to study point defect clusters in metals following quenching and irradiation. As a result of this work considerable progress has been made in our understanding of the nucleation, morphology, and growth of clusters and this paper reviews the current state of t…
Photochromic (Z)-1-methylpropylidene(diphenylmethylene)succinic anhydride undergoes photochemical conrotatory ring closure and thermal disrotatory ring closure reactions to form red 1,8a-dihydronaphthalene intermediates (1,8a-DHNs) which undergo a facile thermal 1,5-H shift to yield colourless 1,2-DHNs. Yellow (E)-3,5…
Abstract Electrically polarized and unpolarized films of polyacrylonitrile (PAN) have been investigated by both infrared attenuated total reflection (ATR) and thermally stimulated discharge (TSD). ATR analysis of PAN films has been aimed at explaining the molecular origin of thermally stimulated currents, and conseque…
Dielectric measurements of the ceramic samples of Bi2MoO6 show that this crystal is ferroelectric with the Curie temperature Tc ≈ 570°C. According to the empirical relation between cation shift and ferroelectric Curie temperature the approximate magnitude of Mo6+ cations displacement equal to Δz = 0.21 Å.
Single crystals of Ca 3 (VO 4 ) 2 with diameters up to 25 mm and lengths of 60 mm have been grown by the Czochralski technique from a stoichiometric melt. Elastic, thermoelastic, piezoelectric, linear electrooptic, dielectric and pyroelectric properties have been measured. Ca 3 (VO 4 ) 2 exhibits much smaller elastic…
Treatment of the phaeofarnesins (4) isolated from the Chlorobium chlorophylls-660 (ex. Chloropseudomonas ethylicum) with sulphuric acid in methanol gives the methyl phaeophorbides (1) which can be dehydrated by refluxing in benzene in the presence of acid to afford the 2-vinyl derivatives (2); prolonged refluxing give…