Extended chain crystals of linear high polymers
Abstract
Materials Literature
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Accurate calculations of properties of the two-tube electrostatic lens. I. Improved digital methods for the precise calculation of electric fields and trajectories
Di g it a l me th ods of hi g h prec is ion ha ve bee n de ve loped for th e c alculation of e lec tri c fi e lds a nd tra jectori es in e lec tros tati c le nses a lld a comput e r prog ra m was wri tt e n to app ly th ese me t hods to th e two-tube le ns . Th e ill c reased prec is ion res uit s fro m til(" use of n…
A.C. and D.C. electrical conductivity in amorphous arsenic trisulphide films
It is shown that measurements of a.c. and d.c. conductivity in undoped amorphous As2S3 films differ in several respects from those reported in other chalcogenide glasses. Experiments show conclusively that the a.c. lows in this material are due to a bulk-controlled process. The frequency-dependent but temperature-inde…
Influence of Grain Size on the Portevin-LeChatelier Effect in Al–Mg Alloys
In order to investigate the effect of grain size on Portevin-LeChatelier yielding, tensile tests were performed on Al–0.55 and 1 at% Mg alloys having various grain sizes. In a temperature range of −20°∼+40°C and a strain rate range of 3.3×10−5∼1.7×10−3/sec, the value of activation energy for the P–L effect was found t…
The photochemical oxidation of 4-arylazo-1-naphthols
The 4-arylazo-1-naphthols (1) undergo self-sensitised or dye-sensitised photo-oxidation in solution, giving 1,4-naphthaquinone and the aryl-diazonium ion.
Carbon Thermal Diffusion in the UC 2 ‐C System
Alpha uranium dicarbide disks coated with pyrolytic carbon migrate, relative to the carbon, up a temperature gradient, leaving behind a layer of rejected graphite. A model for the migration process based on solution of carbon at the hot UC 2 ‐C interface, transport across the UC 2 phase by thermal diffusion, and rejec…
Apoverbenone (6,6-dimethylnorpin-3-en-2-one). An investigation into its preparation by dehydrobromination of a sterically hindered bromo-ketone
The dehydrobromination of 3-bromo-6,6-dimethylbicyclo[3,1,1]heptan-2-one has been studied. Treatment with lithium bromide and lithium carbonate in dimethyl sulphoxide gave 6,6-dimethylnorpin-3-en-2-one (apoverbenone) in good yield. From (–)-pin-2(10)-ene, optical purity 91%, we obtained (+)-apoverbenone, [α]D+ 319°(c…
Pyrroles and related compounds. Part XX. Syntheses of coproporphyrins
Coproporphyrin-I has been synthesised by modifications of Fischer's original methods; Coproporphyrin-II has been synthesised by three methods including a variant of the MacDonald method, involving self-condensation of a 5-formylpyrromethane-5′-carboxylic acid. Coproporphyrins-III and -IV and a related porphyrin tricar…
Blue-Green Algae of the Saline Soils of the Punjab
Cultures of blue-green algae of 44 soil samples and 40 samples of naturally growing ones, collected from highly saline soils, moderately saline soils and reclaimed saline soils, were studied in relation to the soil type. It was found that most of the species belonging to Chroococcales, Oscillatoriaceae, Nostoc, Tolypo…
Accurate Calculation of Properties of the Two-Tube Electrostatic Lens II. First-Order Focal Properties and P-Q Curves
Using digital methods, electric fields and paraxial electron trajectories in the two-tube electrostatic lens have been calculated, and the first-order (Gaussian) focal properties accurate to at least 0.1% were obtained for voltage ratios from 1.5 to 50. The results are presented in the form of P-Q (object-image positi…
The Chemistry and Technology of Rubber-Bound and Related Novel Antioxidants
Abstract The discovery that C-nitrosoanilines react with olefins to give p -phenylenediamines has made possible the synthesis of powerful antioxidants from a wide range of naturally occurring and synthetic unsaturated compounds. Simple alkenes, vegetable oils, and factices may be converted to antidegradants whose beha…
X‐Ray and stereochemical studies on xylan diacetate
Abstract By means of x‐ray fiber diffraction, it has been found that xylan diacetate crystallizes with two chains or four residues in a monoclinic cell (space group P 2 1 ): a = 7.64, b = 12.44, c (fiber axis) = 10.31 Å, and γ = 85°. Pairs of residues are related by a twofold screw axis in the c direction. Based on th…
Porphyrins and bile pigments from brominated pyrromethenes
Aetioporphyrin-I (1a) is obtained in 50–60% yield by heating 5-bromo-3,4′-diethyl-3′,4,5′-trimethylpyrromethene perbromide (4a) under reflux in formic acid, surpassing the yields from the established syntheses using the less accessible 5-bromo-5′-bromomethylpyrromethene hydrobromides (2a, b). The 5-bromo-5′-methylpyrr…
Conditions of Formation of Calcite Crystals of Tabular and Acute Rhombohedral Habits
Abstract Calcite crystals are grown under pure conditions by the method of counterdiffusion of calcium and carbonate ions in water. An extension of the diffusion method is used making possible the crystallization of calcite in a medium containing calcium or carbonate ions in excess of their stoichiometric amounts in c…
Toxic products from the combustion and pyrolysis of polyurethane foams
Abstract Products from the thermal decomposition of four polyurethane foams heated to temperatures in the range 220 to 400 °C, in atmospheres of nitrogen, of 6% oxygen in nitrogen and of air were examined for some of the anticipated toxic materials. When phosphorus‐containing inhibitors were added to or chemically inc…
Characteristics of rf Sputtered Barium Titanate Films on Silicon
The physical and electrical properties of barium titanate films approximately 1 μm thick, prepared by rf sputtering onto silicon substrates in both pure argon and 95% argon–5% oxygen glow discharges were investigated. The argon-oxygen mixture was used to minimize oxygen deficiencies in the films resulting from the pos…
NEW FORM SPECIES OF POLLEN FROM SOUTHERN AUSTRALIAN EARLY TERTIARY SEDIMENTS
(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.
Chemistry of soil minerals. Part XI. Hydrothermal transformations of metakaolinite in potassium hydroxide
Metakaolinite, or metakaolinite with added silica, has been treated with potassium hydroxide solutions to yield six zeolites and the two felspathoids kaliophilite and kalsilite. Among the zeolites K–F, K–M (near-phillipsite), and K–G (near-chabazites) were abundantly and consistently formed. The properties of these ze…
Solution Chemistry and Colloid Formation in the Tin Chloride Sensitizing Process
For many years, stannous chloride solutions have been used to prepare surfaces so that they would catalyze deposition from electroless plating solutions. This paper discusses the colloid and solution chemistry of such baths, including the colloid formation, size mediation, and aging processes. The colloid is shown to…
The CBS-Accelerated Sulfuration of Natural Rubber and Cis-1,4-Polybutadiene
Abstract The results of characterization of the natural rubber vulcanizates are consistent with the results of characterization of the sulfidic products from 2-methylpent-2-ene. In both the model olefin system and the rubber system the initially formed crosslinks are polysulfidic but these are subsequently reduced to…