Materials Literature
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The likelihood-based approach to density modification [Terwilliger (2000), Acta Cryst. D56, 965-972] is extended to include the recognition of patterns of electron density. Once a region of electron density in a map is recognized as corresponding to a known structural element, the likelihood of the map is reformulated…
The important role of alkali additives in heterogeneous catalysis is, to a large extent, related to the high promotion effect they have on many fundamental reactions. The wide application of alkali additives in industry does not, however, reflect a thorough understanding of the mechanism of their promotional abilities…
We describe and analyze selected surface impedance data recently obtained by different groups on cuprate, ruthenate and diboride superconducting films on metallic and dielectric substrates for fundamental studies and microwave applications. The discussion includes a first review of microwave data on MgB2, the weak-lin…
The structure of the antiphase domain boundaries of strontium titanate ${\mathrm{SrTiO}}_{3}$ that exist at temperatures below the antiferrodistortive transition, is analyzed. It is found that some boundaries are similar to N\'eel domain walls, as an additional component of the order parameter develops within them. We…
We report the observation of a field-induced transformation from the easy-plane antiferromagnetic structure to the easy-axis ferrimagnetic structure in a single crystal of TbFe_4.4Al_7.6 (tetragonal ThMn_12 structure) at 5 K. Such a field-induced, irreversible transition has been identified for the first time. This tr…
Results of X-ray diffraction experiments on solid oxygen at low temperature and at pressures up to 10 GPa are presented.A careful sample preparation and annealing around 240 K allowed to obtain very good diffraction patterns in the orthorhombic delta-phase. This phase is stable at low temperature, in contrast to some…
In quasicrystals, there are not only conventional, but also phason displacement fields and associated Burgers vectors. We have calculated approximate solutions for the elastic fields induced by two-, three- and fivefold straight screw- and edge-dislocations in infinite icosahedral quasicrystals by means of a generaliz…
A simple and convenient procedure for chemoselectively protecting the amino groups of chitosan has been developed to provide N-phthaloyl-chitosan that is indispensable as a soluble N-protected precursor for further controlled modification reactions of chitosan. Although the conventional N-phthaloylation of chitosan in…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymers with Complex Architecture by Living Anionic PolymerizationNikos Hadjichristidis, Marinos Pitsikalis, Stergios Pispas, and Hermis IatrouView Author Information Department of Chemistry, University of Athens, Panepistimiopolis Zografou, 15771 Athens, Greece Cite this:…
В обзоре рассматриваются основные принципы получения хитина и его производных из разных сырьевых источников. Основное внимание уделено проблеме извлечения хитин- и хитозансодержащих комплексов из мицелиальных грибов. Приведены данные по исследованию химического состава и физико-химических свойств исходного мицелиально…
We present the experimental results of the magnetic viscosity, demagnetization curve and recoil loop for isotropic nanocrystalline Pr 12 Fe 82 B 6 ribbons prepared by melt-spinning. The thermal fluctuation field, activation volume and irreversible demagnetization are discussed. The coercivity mechanism is mainly deter…
Abstract In the last 20 years, much interest has been focused on conducting polymers to find new materials to transfer from research to industry. However, in many cases, as for elastomers for which intrinsically conducting materials are unavailable, it is necessary to use conducting particles that are physically mixed…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTKubas Complexes Revisited: Novel Dihydride Complexes of TungstenD. Michael Heinekey, James K. Law, and Steven M. SchultzView Author Information Department of Chemistry, University of Washington Box 351700, Seattle, Washington 98195-1700 Cite this: J. Am. Chem. Soc. 200…
Abstract Despite the industrial significance of poly(bisphenol A carbonate), there is a scarcity of open literature on the equilibrium of the melt‐phase process. In fact, the equilibrium constant ( K eq ) for this reaction has never been measured directly. This article describes a process on the basis of NMR for the m…
Abstract Measurements of the change of the pour point depression (Δ T PP ) were performed for the wax solutions made of four solvent mixtures: ethyl acetate/hexane (EA/HEX), 1,2‐dichloroethane/cyclohexane (DCE/CYH), butanone/heptane (MEK/HEP), and acetone/chloroform (AC/CF) doped with EVA polymers. The values of Δ T P…
Abstract The reaction of wheat straw hemicelluloses with succinic anhydride in aqueous alkaline systems was studied. The products showed a rather low degree of substitution, ranging from 0.017 to 0.21. The effects of reaction times of 0.5–16 h, temperatures of 25–45°C, and molar ratios of succinic anhydride to anhydro…
The preparation and crystal structure of 5-cyanofuran-2-[1,2,3,5-diselenadiazolyl], [RCN(2)Se(2)] (R = 5-cyanofuran), is reported. Crystal data for C(6)H(2)ON(3)Se(2): monoclinic, space group P2(1), a = 7.1121(7), b= 20.541(2), c =20.923(2) A, beta = 99.785(1) degrees, Z = 16. The crystal structure consists of diselen…
This paper describes the first successful application of the novel technique of X-ray microbeam diffraction to the study of wood cell walls in developing xylem tissue. The method enabled us to obtain quantitative diffraction diagrams from single cell walls. It was further combined with selected area electron diffracti…
Submonolayer Sn deposits on Pt(111) and Sn incorporated in a $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ Sn/Pt(111) surface alloy were oxidized by ${\mathrm{NO}}_{2}$ under ultrahigh-vacuum conditions. The oxide films formed were characterized by Auger-electron spectros…
The dynamics of the fragile glass-forming orthoterphenyl have been investigated by transient grating experiments with an heterodyne detection technique. We measured the relaxation processes of this glass former over more than six decades in time with an excellent signal-to-noise ratio. Acoustic, structural, and therma…