Materials Literature
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Abstract The spontaneous and face‐specific copolymerization of [l.l.l]propellane and maleic anhydride to give the strictly alternating 1:1 copolymer 2 is described. The molecular weight of 2 after transformation into the corresponding diester 5c was determined to be 80.000 (M n ) and 220.000 (M w ), respectively.
Abstract Electron scatterings in the volume and at the surface of a solid are simulated by the Monte Carlo method. The effect on the electron distributions is demonstrated in some typical cases: aluminium, copper and gold covered with a carbonaceous layer.
Abstract Seit einigen Jahren wird versucht, die Synchrotronstrahlung, die eine intensive Röntgenquelle mit hervorragenden Polarisationseigenschaften darstellt, auch zur Untersuchung magnetischer Strukturen zu nutzen. Mit zirkular polarisierter Röntgenstrahlung als Sonde liefert hierzu die spinabhängige Absorptionsspek…
Isocitrate lyase was purified from Phycomyces blakesleeanus N.R.R.L. 1555(-). The native enzyme has an Mr of 240,000. The enzyme appeared to be a tetramer with apparently identical subunits of Mr 62,000. The enzyme requires Mg2+ for activity, and the data suggest that the Mg2(+)-isocitrate complex is the true substrat…
Consider a system of N hard spheres of radii d i > 0 and masses m i < 0, i = 1,…, N. The spheres may interact through elastic pair collisions but move freely otherwise in all of R3. It is shown that (with the exception of a set of initial states of measure zero) there are at most finitely many collisions for any given…
Hard spheres serve as one of the basic models in classical equilibrium statistical mechanics, as well as, in fluid mechanics. Sterically stabilized polymethylmethacrylate (PMMA) spheres suspended in certain organic solvents have interparticle interactions which approximate the hard sphere interaction. Thus the equilib…
The effects of proton irradiation on the electrical and infrared switching properties of vanadium oxides were studied. Bombardments are carried out to fluences typical of long-term space missions. Proton bombardment significantly alters semiconductor phase resistivity, infrared transmissivity, transition temperature a…
A series of neutron diffraction experiments have been used to investigate the properties of liquid, solid and amorphous sulphur. The liquid was studied from 131 degrees C to 230 degrees C, i.e. at conditions around the λ -transition (T λ =159 degrees C). The amorphous sample was studied at -196 degrees C and the cryst…
Die Ringkontraktion eines Porphycenderivats ergibt ein Isocorrolderivat, dessen Ringgerüst deutlich stärker als das von Corrol von der Planarität abweicht. Nach spektroskopischen Befunden hat man es dennoch mit einer aromatischen Verbindung zu tun. 1 und 3 sind die Stammverbindungen Corrol bzw. Isocorrol. magnified im…
Abstract The effect of heating on the water sorption capacity of a La-saturated montmorillonite, La-Mt, has been investigated. Sodium and Li as exchangeable ions have also been included for comparative purposes. XPS of La-Mt shows no migration of La(III) from interlamellar positions to octahedral sites on heating at 3…
Article A neutron powder diffraction study of the β to γ phase transformation in NaFeO2 was published on December 1, 1990 in the journal Zeitschrift für Kristallographie - Crystalline Materials (volume 193, issue 1-4).
Abstract The radiation‐stability of annealed and quenched polyethylene (PE) was estimated by gel, FTIR, and mechanical property (elongation at break) measurements. Although both types of PE showed an equal probability in gel and carbonyl formation, the resistance to γ‐ray irradiation as probed by elongation at break (…
Fine sialon powders (Si 6‐z Al z O z N 8‐z , Z = 0.3, 0.6) were prepared by nitriding combustion. Silicon powders was reacted with AlN and Si 3 N 4 under 10 MPa of nitrogen gas. The reaction temperature reached above 2000°C and single‐phase sialon powders were synthesized within minutes. The obtained powders were full…
A series of monoclinic C2/c pyroxenes was synthesized along the join CaNiSi 2 O 6 -CaMgSi 2 O 6 (diopside). The crystal structures of these pyroxenes were refined indices were in the range 2.7-3.7%. Cell parameters and mean bond lengths vary linearly as a function of composition along the join. However, the derived tr…
Phase transitions among paraelectric, ferroelectric, ferrielectric and antiferroelectric phases in a chiral smectic liquid crystal, MHPOBC, have been investigated by means of circular dichroism (CD). It was found that the helix undergoes a complex variation through the transitions such as discontinuous jumps and hande…
An approach to measure semiconductor structures for nondestructive submicrometer metrology in the scanning electron microscope (SEM) at low accelerating voltage is described utilizing the collection and measurement of only the backscattered electron signal rather than the more commonly used secondary electron signal.…
The three-dimensional distribution of various types of point defects in diamond crystals has been investigated by means of new photoluminescence tomographic techniques. In relatively perfect natural yellow diamonds the zoned distribution of blue luminescent N3 and blue–green luminescent 463·0 nm centres was mapped. Br…
This study evaluated yams produced on the DREF-3 friction spinning machine using varying core inlet sliver linear densities and output yam core proportions. A long staple, medium micronaire, Acala cotton was spun into 74, 54, and 45 tex yams at constant spinning drum and outlet speeds. Inlet sliver of 1.77, 2.47, and…
Die enge strukturelle Verflechtung von Porphyrin‐ und Porphycen‐System wird mit dem [22]Porphyrin(2.2.2.2) 1/2 besonders augenfällig demonstriert: [22]Porphyrin(2.2.2.2) existiert aus Spannungsgründen nicht als das Isomer mit Porphyrin‐Symmetrie ( D 2 h ) 1 , sondern liegt als gestrecktes Porphycen 2 vor. magnified im…
Abstract A comparison between the entirely statistical and the combined kinetic and statistical model for amine‐epoxy networks, both studied previously in the literature is made. The chemistry studied involves the generation of a secondary site which reacts in the network through chainwise addition rather than the ste…