Materials Literature
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Without a doubt, photochemically induced electron transfer in 1 proceeds stepwise. Triad 1 is one of the latest models of the photosynthetic reaction center. The rates of the individual steps in the electron transfer relay have been determined by ultra-fast laser spectroscopy.
Syntheses of a series of conjugated donor-acceptor chromophores, based on a strongly electron-withdrawing heterocyclic acceptor, have led to compounds with large second-order optical nonlinearities. Incorporation of one of these chromophores into polycarbonate at 20 percent weight loading yielded, after poling at 150…
The crosslinking reaction of poly(vinyl alcohol) (PVA) with 3,3′,4,4′-tetracarboxybenzophenone dianhydride, pyromellitic carboxylic acid anhydride, and Epiclon B-4400 as hardeners was studied either in solution or by differential scanning calorimetry. A catalyst agent had to be used in all cases. Depending on the conc…
Several microcrystalline celluloses prepared from viscose staple, bagasse, ramie, and cotton were evaluated by viscosimetry, X-ray diffraction and scanning and transmission electron microscopies. The changes in crystallinity, size of crystallites, grain-size distribution, morphological features, and degree of polymeri…
The conductivity mechanism for a carbon black (CB) filled high-density polyethylene (HDPE) compound was investigated in this work. From the experimental results obtained, it can be seen that the relation between electrical current density (J) and applied voltage across the sample (V) coincides with Simmons's equation…
A novel dry-spinning method for the preparation of zein fiber without using formaldehyde is presented. The fiber thus obtained had good stability to boiling aqueous acetic acid solution with breaking tenacity and elongation of 1.0 g/d and 30%, respectively. Citric acid and butanetetracarboxylic acid were used as nonfo…
Large TlInSe2 single crystals are grown by the Bridgman-Stockbarger method, starting from stoichiometric melts. Current–voltage (I–V) characterstics of symmetric In/p-TlInSe2/In structures exhibit two distinct regions: an ohmic region at low current densities and a non-linear region (S-shaped) having negative differen…
A model describing the excitation of UHF signals by current pulses in a waveguide is developed using dyadic Green's functions. This model relates to UHF signals used for the detection of partial discharge (PD) caused by defects in gas-insulated substations (GIS). Application of the theory is demonstrated by compa…
The structure of disodium bis[μ-oxo-tri-μ3-oxopentakis(μ-propionato-κO:κO′) tris(propionato-κO)-0.5-chromium-0.5-irontrimolybdenum](3 Mo-Mo), Na2[Cr0.5Fe0.5Mo3O4(C3H5O2)8]2, consists of a centrosymmetric cluster anion, [(EtCO2)8Mo3O4CrFeO4Mo3(O2CEt)8]2−, in which two Mo3O4 units are joined by the Fe and Cr atoms to co…
In order to understand the effects of density fluctuations in composite systems, we have studied the effects of compression rate on the final density and density variations in a system of hard spheres. Systems of 900 and 1800 mono-sized spheres are placed in a box with periodic boundary conditions in the x and y direc…
Packing polymorphism and conformational disorder of poly(hexamethylene terephthalate) were analyzed by x-ray diffraction technique. The measurements were performed in the temperature range from 20 to 135°C. At high temperature, several unassignable reflections were found to disappear, and all reflections were satisfac…
The basic deformation properties of pseudoelasticity and shape memory effect due to martensitic transformation and R-phase transformation were investigated experi-mentally for TiNi shape memory alloy (SMA) wire subjected to various maximum strains. The properties of transformation temperature were discussed based on d…
Polymeric carboxylic acids such as poly(acrylic acid) and copoly(acrylic—maleic acid)s are widely used as cobuilders in detergent powder formulations. They were introduced in the early 1980s in combination with zeolites as partial replacements for polyphosphates, which were removed from detergent formulations because…
Electromigration-induced void growth in Al metallization was investigated by comparing it with the electrical resistance change and the thermographically measured change in temperature distribution. Constant current flowing through two different-width interconnects in series consistently induced void growth at their j…
Poly(vinylamine) is of interest because of its pH-dependent cationic nature and its reactive primary amine functionality. The preparation of poly(vinylamines) of various molecular weights via the synthesis and hydrolysis of poly(N-ethenylformamide) (PNEF) is readily accomplished. Solution properties of poly(vinylamine…
Magnetic properties of amorphous carbon materials, prepared by pyrolysis of trialkylboranes, were examined using the superconducting quantum interference device and the electron spin resonance (ESR) methods. It is found that the observed magnetic properties could be greatly affected by pyrolysis temperature and the an…
The reaction of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines with benzoyl peroxide (acceptor radical) and with N-ethylmaleimide (acceptor) was investigated. It was shown that benzoyl peroxide adds to monomers 1a and 1b, giving the corresponding linear diester amides 1a and 1b respectively. The oxazolidi…
The transport of fluids in the semicrystalline polymer, poly(aryl ether ether ketone) (PEEK), was investigated. Both solubility and rate of penetration of toluene into PEEK are markedly increased by the application of an external stress. The induction period (i.e., the time for the sorption to begin) is a function of…
Colloidal suspensions of InP quantum dots (diameters 25 and 35 Å) show steplike absorption spectra which are blue-shifted by about 1 eV with respect to bulk material. Time resolved femtosecond spectroscopy at room temperature identifies the first quantum confined state. The nonlinear bleaching signal rises within 300…
We investigate the properties of II–VI short period superlattice (SPSL) blue light-emitting diodes grown by molecular beam epitaxy. The device consists of a ZnSe active layer, SPSL MgZnSSe cladding layers, and a ZnSeTe digital graded contact. The SPSL structure is made of alternating layers of MgSe, ZnSe, ZnS, and ZnS…