There is presently a concern because the US Postal Service now has 8 electron beam accelerators to treat mail in locations along the east coast and that a sufficient dosage to destroy Anthrax is also strong enough to darken and weaken the paper in the postal envelopes. In addition to direct photolytic scission of the cellulose chain, irradiation darkens paper, swells pulp fibres, increases hygroscopicity, and renders the cellulose more soluble in alkaline solution and more susceptible to acid hydrolysis. This report will focus on the effect of electron beam irradiation on degradation of cellulose of fine papers. Three reference papers were selected, sorted into postal envelopes and exposed to electron beam irradiation. The results have shown that irradiation at the dosage used to treat mail by the US Postal Service depolymerizes and oxidizes the cellulose. Depolymerization is responsible for a decrease of paper strength while oxidation induces darkening of the paper. Irradiating at high electron beam energy is less damaging than using lower energy. Moreover, linear relationships have been found between the number of chain scission (CSN) in cellulose and the irradiation dosage as well as between CSN and Zero-Span Breaking Length. These relationships make the strength loss predictable.
a-VPO, crystallizes in the tetragonal space group P4/n with a = 6.014(7) and c = 4.434(2) A. The structure, isotypic with that of a-VS05, was refined by full-matrix least-squares method to an R value of 0.089 using 239 independent reflections. The vanadium ion lies on a crystallographic four-fold axis, as does one of the oxygen atoms, and the P on a site of 4 symmetry. A second oxygen atom, as a result of disorder, occurs in two positions which are mirror reflected with respect to the ac plane. The structure consists of highly distorted V 0 6 groups with bond lengths along the c axis of 1.580(11) and 2.853(11) A while the remaining four V-0 bond lengths are all 1.858(8) A. The P-0 bond lengths in the PO4 tetrahedron are 1.541(8) A with the PO4 groups bridging across four chains of V 0 6 groups.L'aVPOs cristallise dans le groupe d'espace tetragonal P4/n avec n = 6.014 (7) [Traduit par le journal]Can.
Abstract. oc-Vl.os(1)Po.9205, tetragonal, P4/n; a = 6.011 (4), c=4.452 (4) A; Z=2, Dealt=3"39 gcm -3, 147 independent reflexions. The structure was refined by full-matrix least-squares methods, R=0.076, with scintillation counter-measured intensities and monochromatized Mo K~ radiation. The composition was determined by varying the occupancy of the tetrahedral site. The vanadyl bond length is 1.578 (9) /k. Unlike stoichiometric 0c-VPO5 no evidence of positional disorder was found.Introduction. Crystals were grown in a Pt crucible in an attempt to produce large single crystals by the Czochralski procedure. The present crystals grew at the interface with the crucible and at the surface of the charge. Crystals offl-VPO5 and some as yet unidentified crystals were found near the centre of the crucible.A crystal with dimensions 0.5 × 0.5 × 0.05 mm was used for data collection with a Syntex P] diffractometer. The data, corrected for Lorentz-polarization and absorption, were used together with the parameters of disordered ~-VPO5 (Jordan & Calvo, 1973)to refine the structure. Convergence of the least-squares refinement yielded an R of 0.12 with residual peaks in the difference Fourier map that indicated that the compound was non-stoichiometric. Subsequent refinements, with weights set as w-1 = 0.9 + 0.20F+ 0.005F 2, and with the extinction parameter varied indicated that 8 (1)% of the tetrahedral sites were occupied by V.
CALVO. Can. J. Chem. 52,2701 (1974 PbV20, crystallizes in the orthorhornbic space group Pnrnn with n = 9.771(10), b = 3.684(4), c = 12.713(13) A, a n d 2 = 4. The s t r~~c t~i r e was determined sing 8 16 reflections measured with an automatic diffracto~neter and refined by full-matrix least squares to an R val~ie oi'0.052. The two unique vanadium ions lie on mirror planes and are each coordinated to five oxygen atoms lying between 1.61 and 2.06 A. The distorted octahedra are completed by a sixth V-O interaction which is 2.73 A for V(I) and is 2.57 A for V(2). The lead ion is coordinated to nine oxygen atoms lying in a spherical shell with inner and outer radii of 2.56 and 2.90 a. The str~ict~ire con- Extensive studies of n M 0 . V 2 0 , systems have established that for n = I the valiadium ion is coordinated to six oxygen atorns in a highly distorted octahedral environment. For higher integral values of n the vanadium is tetrahedrally coordinated except perhaps in Mg2V,0, (1). The nzeta-vanadates investigated to date, MV,O, with M = Mg, Zn, Cd, Cu, Ca show related structures (2-6) and in addition, polymorphic behavior in some cases. Lead as a metavanadate, with an ionic radius intermediate between that required for an interstial site and that of an oxygen ion, would be expected to crystallize a new structural type. Further, because of the nature of the distorted VO, group and the high polarizability of the lead it would be expected to have a high index of refraction. Thus if a non-centrosymmetric phase were obtained, the structure might be of interest in non-linear optics applications. All the data were collected with a Syntex P i automatic diffractometer. Peaks were scanned at a rate dependent upon the peak counting rate and varied between 2 and 24-in 28lmin. Backgrounds were measured on either side of the peaks. Reflections with intensity measures less than zero were discarded and those with v a l~~e s of less than 3 0 were considered unobserved. A data set consisting of 759 unique reflections was collected within a sphere defined by 28 < 50' for the needle shaped crystal. These data were corrected for Lorentz, polarization, and absorption effects (11 = 400 cm-') a s s~~m i n g a cylindrical shape for the crystal. For personal use only. Experiments
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