Materials Literature
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The levels of two aspartokinase isozymes, a lysine-sensitive enzyme and an aspartokinase that is inhibited synergistically by lysine plus threonine, differ strikingly in different strains of Bacillus subtilis. In derivatives of B. subtilis 168 growing in minimal medium, the predominant isozyme is the lysine-sensitive…
A systematic study of the role of the composition of polysilane homo‐, co‐, and terpolymers on their pyrolysis yield to silicon carbide (SiC) was performed. The ceramic yield was found to increase as the poly(dimethylsilane) structure was substituted with hexyl and, especially, phenyl groups. the best improvement in S…
We have examined the effects of inhibitors of proton transport systems on osteoclastic bone resorption using an in vitro bone slice assay, where osteoclasts (OCs) are free from the influence of other bone cells. Amiloride (AM) and dimethylamiloride (DMA), inhibitors of the Na+/H+ antiporter, were potent inhibitors of…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn efficient synthesis of .alpha.-silylacetates having various types of functional groups in the moleculesYasuyuki Kita, Junichi Sekihachi, Yoshikazu Hayashi, Yong Zhong Da, Miki Yamamoto, and Shuji AkaiCite this: J. Org. Chem. 1990, 55, 3, 1108–1112Publication Date (Print):…
Ionic transport behavior across an electropolymerized polypyrrole/polyazulene composite film was investigated by using ac impedance analysis, and its charge‐discharge characteristics were also studied. Co‐electropolymerization of pyrrole and azulene was well defined and fairly stoichiometric in propylene carbonate sol…
A method of calculating the expected bond valences from the connectivity matrix of complex crystals is described. The method is exact (does not require iteration) and is suitable for implementation on a microcomputer.
The pitting susceptibility of a range of austenitic stainless steels with different molybdenum contents was evaluated in both chloride and bromide solutions at elevated temperatures, using electrochemical polarization techniques. It is found that there is a less beneficial effect of molybdenum in solutions containing…
Monoclonal antibody technology allows the specificity of an antibody for its antigen to be used in targeting cancer cells. The conjugation of metals, particularly radionuclides such as 90Y or 67Cu, to monoclonal antibodies results in agents for radioimmunotherapy and other medical applications. Chelators that can hold…
For the thermotropic cholesteric mesophase of tri-o-(β-methoxyethoxy)ethyl cellulose (DP = 11), cholesteric pitches larger than 2 μm were precisely determined by microscopic observation and their temperature dependence was examined in the temperature range from 80°C to 140°C. In the initial temperature region of 80°C…
We measure the surface order parameter ${S}_{s}$ at the interface between the nematic liquid crystal p-methoxy-benzylidine-p-n-butyl-aniline and a rough glass plate. Roughness is induced by oblique evaporation of SiO. We observe a critical decrease of ${S}_{s}$ when the surface roughness increases, just above the tran…
Abstract The behavior of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) on water aging has been studied above and below the glass transition temperature ( T g ). The aging process is caused by: degradation of the matrix and an increase in crystallinity above T g , and microcavitation at the…
A “diagonal relationship” between technetium(VII) and osmium(VIII) can be proposed based on the properties of the newly synthesized title compounds. Like the valence‐isoelectronic OsO 4 , MeTcO 3 adds olefins to form metallacycles (→ cis ‐diols), whereas the formally analogous MeReO 3 epoxidates olefins in the presenc…
Functional organic materials have been developed over the last twenty‐five years which compete for applications in optical, electrical and magnetic technologies with the more traditional inorganic network solids. In the first article of a regular series Joel Miller of DuPont describes some applications of these molecu…
A number of commercially available SiC and Si 3 N 4 materials were exposed to 1000°C for 40 h in a high‐velocity, pressurized burner rig as a simulation of an aircraft turbine environment. Na impurities (2 ppm) added to the burner flame resulted in molten Na 2 SO 4 deposition, attack of the SiC and Si 3 N 4 , and form…
Collagen intended for use as a dermal implant may be crosslinked to increase its strength and persistence in vivo. Sheets of rat fibrous dermal collagen were crosslinked with either glutaraldehyde or dimethylsuberimidate and the cytotoxicity to human dermal fibroblasts resulting from these treatments was measured by f…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn NMR study of plasticization and antiplasticization of a polymeric glassY. Liu, A. K. Roy, A. A. Jones, P. T. Inglefield, and P. OgdenCite this: Macromolecules 1990, 23, 4, 968–977Publication Date (Print):February 1, 1990Publication History Published online1 May 2002Publis…
Abstract A series of semi‐interpenetrating polymer networks (semi‐IPNs) based on polyurethane and polydimethylsiloxane were prepared. They are formed by crosslinking the polydimethylsiloxane prepolymer with 3‐aminopropyltriethoxysilane in the presence of linear polyurethane. Investigations were carried out by swelling…
The relaxation of electric birefringence in dilute solutions of a polyelectrolyte is shown to be consistent with a stretched-exponential form, exp[-(t/\ensuremath{\tau}${)}^{\ensuremath{\alpha}}$]. The exponent \ensuremath{\alpha} depends on polymer length L and solvent ionic strength only through the ratio x==L/${L}_…
Lactate dehydrogenase was isolated from the extreme thermophilic eubacterium Thermotoga maritima. The enzyme is stereospecific for L(+)-lactate. It represents a homotetramer of 144 kDa molecular mass, with a sedimentation coefficient of s20,w approximately 7 S. Under physiological temperature conditions, the enzyme sh…
We present experimental results on bistable elements with liquid crystals as nonlinear elements showing that, under cw illumination, sequences of spatial structures occur. Index fluctuations, as a particular characteristic of this class of material, seem to play a central role in this effect. We describe the system an…