The effect of high dose of gamma-irradiation on residual radicals concentration in ultra-high molecular weight polyethylene (UHMWPE) in the presence of vitamin E

Powder samples of UHMWPE (GUR 1020) containing 0.1% by wt. vitamin E (??-tocopherol, ??-T) were irradiated at room temperature in air for doses of 30-kGy, 65-kGy or 100-kGy (⁶⁰Co). After irradiation, they were stored at ?78.5°C (dry ice temperature) for one year and then opened to air at room temperature. Following the decay of the primary alkyl and allyl radicals (at room temperature in air), growth of the carbon-centered polyenyl R1 (?^·CH?CH=CH?, m ?? 3), and the oxygen-centered dior tri-enyl R2 (?^·OCH?CH=CH? _m , m ?? 3) residual radicals were measured for eight weeks. An X-band electron spin resonance (ESR) spectrometer was used for radical measurements. The initial relative radical concentrations (R2/R1) were found to be 10.13, 4.6 and 3.7 for the 65-kGy, 30-kGy and 100-kGy samples, respectively. R1 and R2 were both found to grow significantly in the 65-kGy samples while they grew only slightly in the 30-kGy and 100-kGy samples. In 65-kGy sample, R1 grew faster than R2 and the relative concentration R2/R1 was reduced from 10.13 to 2.9 for the 65-kGy sample while that for the 30-kGy and 100-kGy samples reduced only slightly, from 4.6 to 3.5 and 3.7 to 3.2, respectively. The behavior of the residual radicals can be explained by Raman spectroscopic data which suggest that the 65-kGy samples had a higher percentage of amorphous regions when compared to the 30-kGy or 100-kGy (21.7% compared to 15.7% or 17.9%) and also suggest a lower percentage of inter-phase regions (16.4% compared to 25.6% or 17.5%) and a lower level of structural disorder (0.26% compared to 0.44% or 0.27%).     

A glow discharge lamp with supplementary excitation by a radio—frequency discharge-preliminary measurements

The emission radiant output of an ordinary glow discharge plasma was increased by several factors through secondary inductively coupled RF excitation produced by an external coil and a 136.2MHz oscillator. The gain factor was determined at several glow discharge currents and voltages in copper alloys and cast iron samples. Improved linear calibration curves were obtained because the RF-boosted glow discharge source decreased the effect of self-absorption.     

Unambiguous identification of three beta-decaying isomers in 70Cu

Using resonant laser ionization, beta-decay studies, and for the first time mass measurements, three beta-decaying states have been unambiguously identified in 70Cu. A mass excess of -62 976.1(1.6) keV and a half-life of 44.5(2) s for the (6-) ground state have been determined. The level energies of the (3-) isomer at 101.1(3) keV with T(1/2)=33(2) s and the 1+ isomer at 242.4(3) keV with T(1/2)=6.6(2) s are confirmed by high-precision mass measurements. The low-lying levels of 70Cu populated in the decay of 70Ni and in transfer reactions compare well with large-scale shell-model calculations, and the wave functions appear to be dominated by one proton-one neutron configurations outside the closed Z=28 shell and N=40 subshell. This does not apply to the 1+ state at 1980 keV which exhibits a particular feeding and deexcitation pattern not reproduced by the shell-model calculations.     

Fourier Invariant Partially Approximating Subalgebras of the Irrational Rotation C*-Algebra

For a dense G-set of parameters, the irrational rotation algebrais shown to contain infinitely many C*-subalgebras satisfyingthe following properties. Each subalgebra is isomorphic to adirect sum of two matrix algebras of the same (perfect square)dimension; the Fourier transform maps each summand onto theother; the corresponding unit projection is approximately central;the compressions of the canonical generators of the irrationalrotation algebra are approximately contained in the subalgebra.2000 Mathematics Subject Classification 46L80, 46L40, 46L35.     

The influence of water content, cooling and warming rate upon survival of embryonic axes of Poncirus trifoliata (L.)

The present study investigated the relative contributions of water content and non-equilibrium cooling and warming rates to the survival of cryopreserved axes of recalcitrant P. trifoliata seeds. Reducing water contents from 1.7 and 0.26 g water per g dry mass is believed to increase cytoplasmic viscosity. Cooling to -196 degree C was done at rates averaging between 0.17 and 1300 degree C per second, and warming at 600 or 1.35 degree C per second. Survival was assessed after 4 weeks in vitro. Rapid warming resulted in higher survival and normal development of axes at all water contents. The effects of cooling rate were dependent on the water content of axes. Cooling rates resulting in >70 percent normal development ranged between 0.17 and about 1300 degree C per second for axes at a water content of 0.26 g water per g dry mass narrowing with increasing hydration to an apparent optimum at about 686 degree C per second in axes at 0.8 g water per g dry mass At 1.7 g water per g dry mass, axes cooled at 0.17 degree C per second yielded nearly 40 percent normal development, whereas faster cooling was deleterious. Results are interpreted in the context of the effect of water content on cytoplasmic viscosity and the rate of intracellular ice formation. At low water contents, the high intracellular viscosity slows ice crystallization making survival independent of cooling rate. At higher water contents, the reduced viscosity requires faster cooling to prevent ice crystal damage. The ability to cool rapidly with increasing hydration is balanced with an increasing limitation to dissipate heat fast enough to prevent severe damage.     

On Fourier Orthogonal Projections in the Rotation Algebra

Projections are constructed in the rotation algebra that areorthogonal to their Fourier transform and which are fixed underthe flip automorphism. Such projections are expected in a constructionof an inductive limit structure for the irrational rotationalgebra that is invariant under the Fourier transform (namely,as two circle algebras of the same dimension, which are swappedby the Fourier transform, plus a few points). The calculationis based on Rieffel's construction of the Schwartz space asan equivalence bimodule of rotation algebras as well as on thetheory of theta functions.     

Sulfur K-edge XAS and DFT calculations on [Fe4S4]2+ clusters: effects of H-bonding and structural distortion on covalency and spin topology

Sulfur K-edge X-ray absorption spectroscopy of a hydrogen-bonded elongated [Fe4S4]2+ cube is reported. The data show that this synthetic cube is less covalent than a normal compressed cube with no hydrogen bonding. DFT calculations reveal that the observed difference in electronic structure has significant contributions from both the cluster distortion and from hydrogen bonding. The elongated and compressed Fe4S4 structures are found to have different spin topologies (i.e., orientation of the delocalized Fe2S2 subclusters which are antiferromagnetically coupled to each other). It is suggested that the H-bonding interaction with the counterion does not contribute to the cluster elongation. A magneto-structural correlation is developed for the Fe4S4 cube that is used to identify the redox-active Fe2S2 subclusters in active sites of HiPIP and ferredoxin proteins involving these clusters.