A theory for environmental craze yielding of polymers at low temperatures

It has been recently discovered that polymers craze at low temperatures in the presence of nitrogen or argon. A quantitative theory has been developed which explains (1) the critical temperature above which the phenomenon disappears, (2) the critical stress for nucleating a craze, (3) the effect of strain rate on the yield point and size of crazes, (4) the drop in the load during craze yielding, and (5) the increase in strength of the polymer in N₂ or Ar at high strain rates so that the ultimate strength may exceed that in He or vacuum. The crazing action of the gases is described qualitatively at the molecular level.     

On the mechanism of allylic alkylations catalyzed by palladium

Reults are reported indicating the intermediacy of a symmetrical π-allyl species in the alkylation of an allylic lactone. A previous report indicating that another mechanism was operative is disputed.     

Scattering of Inertial Waves in a Rotating Fluid

The scattering of plane inertial waves by both a flat strip and a circular cylinder whose generators are perpendicular to the rotation vector is examined. The properties of the reflected and diffracted fields, viz. spatial decay, propagation, structure, etc....are contrasted with those of the classical scattering fields in the limit where the wave length is small compared to the size of the scatterer.     

An ion chromatographic separation method for the sequential determination of <Superscript>90</Superscript>Sr, <Superscript>241</Superscript>Am and Pu isotopes in a urine sample

A radiobioassay method has been developed for the sequential determination of ⁹⁰Sr, ²⁴¹Am and Pu isotopes in a urine sample. Unlike the existing methods using multiple extraction chromatographic cartridges, this work demonstrates an application of an automated ion chromatographic (IC) system for the separation of these radionuclides on a single IC column. The method meets the bioassay performance criteria for relative bias and relative precision as recommended by ANSI/HPS N13.30-2011. The detection limits for the radionuclides are found to be satisfactory for medical intervention in case of an accidental exposure scenario. Sample preparation time is less than 11 h.     

Flocks of Infinite Hyperbolic Quadrics

Let K be a field containing a nonsquare and a quadratic extension. Let denote the unique involutory automorphism of F fixing K pointwise. For every field K such that the nonzero squares of K do not form an index 1 or 2 subgroup of , a construction is given which produces large numbers of infinite nearfield and non nearfield flocks of an infinite hyperbolic quadric in PG(3,K).     

The [CoN4(OH)(OH2)]2+ (N4 = trpn,cyclen and tren) promoted hydrolysis of the phosphotriester 2,4–dinitrophenyl diethyl phosphate

The [CoL(OH2)2]3+ (L=trpn, cyclen andtren)promoted hydrolysis of the phosphotriester 2,4–dinitrophenyl diethyl phosphate to give diethyl phosphate and 2,4–dinitrophenolate has been studied in detail over the pH range 3–7.5. The pK values of the various complexes have been determined at 25°C and I=0.1moldm–3 by potentiometric titration. The pH-rate profiles for the reactions are consistent with the hydroxoaqua complex [CoL(OH)(OH2)]2+ being the active species in the hydrolysis. No evidence for saturation kinetics was obtained and values of kcat determined at pH 7 and 25°C (I=0.1moldm–3) are 4.24×10–3dm3mol–1 s–1 (tren)<3.05×10–2dm3mol–1 s–1 (cyclen)<7.5 × 10–1dm3mol–1s–1 (trpn). Studies involving the more reactive phosphonate ester 2,4–dinitrophenyl ethyl methylphosphonate suggest that the rate-determining step in the reaction is the decomposition of the ternary complex between the cobalt(III) complex and the phosphotriester. The rate enhancement using 0.01mol dm–3 Co(trpn)3+ is some 4.6×104 fold at pH7 and 25°C.