Materials Literature
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Abstract An extensive series of homopolymers and copolymers has been investigated to test earlier indications of a possible link between resistance to slow crack growth and creep of macroscopic oriented samples. It was found that in the majority of cases a good correlation exists between a single creep parameter and s…
We study the average mobilities and long-time self-diffusion coefficients of a suspension of bimodally distributed spherical particles. Stokesian dynamics is used to calculate the particle trajectories for a monolayer of bimodal-sized spheres. Hydrodynamic forces only are considered and they are calculated using the i…
The determination of chlorophyll-a in algae is still subject to discussions. Literature reports that results for chlorophyll-a obtained by HPLC (high performance liquid chromatography) are too low compared with values obtained by conventional methods such as spectrophotometry or fluorometry. The reason is obvious sinc…
A method is presented for the estimation of the 'time to maximum rate under adiabatic conditions' of autocatalytic decompositions and for their safety assessment. This method is based on the kinetics: a first-order reaction in competition with a Prout-Tompkins step was choosen. Isothermal or temperature-programmed Dif…
The structural and electronic properties of clean and hydrogenated diamond (100) surfaces have been investigated via fully self-consistent ab initio calculations. We find that the clean and the monohydrogenated surfaces reconstruct via the formation of rows of symmetric dimers. Further hydrogenation to a coverage of 1…
In the bacterium Alcaligenes eutrophus, three genes encode the enzymes necessary to catalyze the synthesis of poly[(R)-(-)-3-hydroxybutyrate] (PHB) from acetyl-CoA. In order to target these enzymes into the plastids of higher plants, the genes were modified by addition of DNA fragments encoding a pea chloroplast trans…
Das am stärksten sattelförmig verbogene Porphyrin , das bislang charakterisiert wurde, ist das Dikation [H 4 obrtpp] 2 + (H 2 obrtpp = Octabromtetraphenylporphyrin). Seine Pyrrolringe sind in der Verbindung [H 4 obrtpp][CF 3 COO] 2 .5 CHCI 3 im Kristall um 62° gegeneinander gekippt, und die β‐Pyrrol‐C‐Atome sind mehr…
Abstract Structure/permeability correlations for a family of aromatic polyamide‐imides are presented. The variations in chemical structure lead to significant changes in permeability. The crystallization of PAP results in a very low permeability. The introduction of bulky group tends to increase permeability without a…
Lanthanum-modified lead zirconate titanate (PLZT) specimens with a La content of 2 at. % and a Zr/Ti ratio of 95/5 (PLZT 2/95/5) have been investigated by dielectric spectroscopy, Sawyer–Tower polarization (P-E) measurements, and hot-stage transmission electron microscopy (TEM). La ‘‘impurities’’ have been found to in…
We study the thermally induced shape fluctuations of monodisperse emulsion droplets. The very small amplitude of these fluctuations is clearly resolved by diffusing wave spectroscopy and a theory is derived to describe the measured data. We measure the dependence of the fluctuations on droplet volume fraction $\ensure…
Abstract Cationic starch, an important additive for papermaking and other uses, was prepared from native cornstarch and 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride in aqueous sodium hydroxide using a twin‐screw extruder as the reactor. The effects of physical and chemical reaction variables on reaction efficien…
Abstract Aqueous polyurethane (PU) dispersions were prepared from isophorone diisocyanate (IPDI), polytetramethylene glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and dimethylol propionic acid (DMPA) as anionic center. The effects of the PEG/PTAd mixing ratio, type of polyether polyols, and har…
The relaxor behavior is characteristic of the class of disordered ferroelectrics. These systems possess a high dielectric constant with a broad relaxation peak and a low frequency dispersion. Because of their complexity, there exist various explanations for their dielectric and polarization behavior, but no unifying m…
Vitellogenin of Bombyx mori is a precursor of major yolk protein synthesized in the female fat body at larval-pupal ecdysis. The gene for B. mori vitellogenin is composed of seven exons interspersed by six introns. Developmental profile of the primary transcript of the gene indicated that the biosynthesis of B. mori v…
Abstract Jute fiber‐reinforced polypropylene composites have been produced and characterized in order to investigate the influence of water on their mechanical properties. Being hydrophilic, jute fibers absorb a high amount of water causing swelling of fibers. On the other hand, the thermal shrinkage of polypropylene…
Neutron reflectivity measurements are made on a chemically end-grafted polymer brush swollen over a range of temperatures above and below the theta point. Good agreement between the brush profiles and recent self-consistent field calculations and numerical simulations is obtained for temperatures in the vicinity of th…
High quality vanadium dioxide (VO2) thin films have been successfully deposited by pulsed laser deposition without postannealing on (0001) and (101̄0) sapphire substrates. X-ray diffraction reveals that the films are highly oriented with (010) planes parallel to the surface of the substrate. VO2 thin films on (0001) a…
The electrical resistivity, thermoelectric power (Seebeck coefficient), Hall effect, and thermal conductivity have been measured in Cux(Dy2S3)1−x compounds with the η-orthorhombic structure in the composition range 0.006≤x≤0.15 in order to determine their potential as high temperature (300–1000 °C) thermoelectric mate…
Measurements of dc dielectric breakdown strength were made on polyethylene terephthalate films of 50 μm in thickness at temperatures of 35, 70, and 100 °C under hydrostatic pressure ranging from 50 to 500 bar. It has been found that the electrical breakdown field Eb increases with pressure and decreases with temperatu…
The optical reflectance spectra of various wurtzite-BN (w-BN) specimens prepared by the shock-wave method have been measured in the vacuum-ultraviolet region with synchrotron radiation. The optical constants have been determined by applying the Kramers-Kronig relation. The optical band gap was found to be 8.7\ifmmode\…