Materials Literature
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Mesostructured aluminophosphate/dodecyl phosphate composite materials were synthesized under aqueous and alcoholic conditions. The syntheses were monitored by temperature- and time-resolved in-situ small-angle X-ray scattering (SAXS). In the aqueous synthesis, a lamellar mesostructure is formed within the first few mi…
A series of mesoporous siliceous MCM-41 (SiMCM-41) molecular sieves with silicon partially substituted by Al, Ti, and Zr were synthesized hydrothermally. A combination of electron spin resonance (ESR), diffuse reflectance UV−vis spectroscopy (UV−vis), Raman spectroscopy, and temperature-programmed reduction (TPR) was…
2,4,5,7-Tetranitro-9-fluorenone (1b) reacts readily with n-butanethiol in dipolar aprotic solvents with selective substitution of nitro groups by butylsulfanyl groups in positions 2 and 7 (2, 3); the 2,5-isomer 4 was formed only as a minor product (<1%). Condensation of fluorenones 2-4 with malononitrile yielded 9-dic…
Molecular dynamics simulations are used to study the flow of methane, ethane, and ethylene through carbon nanotubes at room temperature. The interatomic forces in the simulations are calculated using a classical, reactive, empirical bond-order hydrocarbon potential coupled to Lennard−Jones potentials. The simulations…
The roughness of vapor-deposited thin films can display a nonmonotonic dependence on film thickness, if the smoothening of the small-scale features of the substrate dominates over growth-induced roughening in the early stage of evolution. We present a detailed analysis of this phenomenon in the framework of the contin…
We investigated the carrier and light trapping in GaInAs/AlGaAs single quantum well laser structures by means of time resolved photoluminescence and Raman spectroscopy. The influence of the shape and depth of the confinement potential and of the cavity geometry was studied by using different AlGaAs/GaAs short-period s…
We describe the use of a near-field scanning microwave microscope to image the permittivity and tunability of bulk and thin film dielectric samples on a length scale of about 1 micron. The microscope is sensitive to the linear permittivity, as well as to nonlinear dielectric terms, which can be measured as a function…
This research was to investigate the conversion of bagasse into a thermomoldable material through esterification of the fiber matrix. For this purpose, bagasse fiber was esterified in the absence of solvent using succinic anhydride. The dimensional stability and mechanical properties of composites prepared from the es…
ADVERTISEMENT RETURN TO ISSUEPREVNoteFluorescence Study of the Coil−Globule Transition of a Poly(ε-caprolactone) Chain Labeled with Pyrenes at Both EndsSusana Piçarra, Pedro T. Gomes, and J. M. G. MartinhoView Author Information Centro de Química-Física Molecular, Instituto Superior Técnico, 1049-001 Lisboa, Portugal,…
NO and O 2 coadsorption on γ-Al 2 O 3 -supported Tb 4 O 7, La 2 O 3, BaO, and MgO has been investigated by in situ infrared spectroscopy coupled with temperature-programmed decomposition and desorption. BaO/γ-Al 2 O 3 and MgO/γ-Al 2 O 3 possess a higher NO x storage capability than Tb 4 O 7 /γ-Al 2 O 3 and La 2 O 3 /γ…
The interaction of three Eu(III) macrocyclic complexes Eu(THED)3+, Eu(ATHC)3+, and Eu(ATHC)3+, and Eu(S-THP)3+ with two 5'-cap model compounds, GpppG and m7GpppG is studied (THED = 1,4,7,10-tetrakis(2-hydroxyethyl)-1,4,7,-10-tetraazacyclododecane, ATHC = 1-(carbamoylmethyl)-4,7,10-tris(2-hydroxyethyl)-1,4,7,10- tetraa…
The synthesis and characterization of the trifluoromethanesulfonate salt of bis(2,6-xylyl isocyanide)tetrakis( p -tolyl)porphyrinatoiron(III), [( p -TTP)Fe(2,6-xylylNC) 2 ]CF 3 SO 3 ( 1 ), is reported. The crystal structure shows that the porphyrinate ring is strongly ruffled. The equatorial Fe−N bond distances averag…
The graft copolymerization of methyl acrylate onto sago starch was carried out by a free radical initiating process. The free radicals were produced by the chemical initiation method in which ceric ammonium nitrate was used as an initiator. It was found that the percentages of grafting, grafting efficiency, and rate o…
This research was to investigate the conversion of bagasse into a thermoformable material through esterification of the fiber matrix. For this purpose, bagasse was esterified in the absence of solvent using succinic anhydride (SA). The reaction parameters of temperature reaction, time, and amount of succinic anhydride…
Static polarizabilities and hyperpolarizabilities have been calculated for the furan homologues including furan (C 4 H 4 O), thiophene (C 4 H 4 S), selenophene (C 4 H 4 Se), and tellurophene (C 4 H 4 Te), at the Hartree−Fock and various correlation levels by ab initio molecular orbital methods. The influence of substi…
The antiferromagnetic insulating cuprate Ba$_3$Cu$_2$O$_4$Cl$_2$ contains folded CuO$_2$ chains with four magnetic copper ions ($S=1/2$) per unit cell. An underlying multiorbital Hubbard model is formulated and the superexchange theory is developed to derive an effective spin Hamiltonian for this cuprate. The resultin…
A reaction mechanism is proposed for the dissolution process of silicon dioxide networks in aqueous HF-based solutions. Etch experiments with thermally grown silicon dioxide were used to create a model for the etch process. Literature data on the etching of other vitreous silicon dioxide materials were used to refine…
A study aimed at understanding the factors that control the optical properties of DNA-linked gold nanoparticle aggregates containing oligonucleotide linkers of varying length (24−72 base pairs) is described. In this system, ∼15 nm diameter Au particles modified with (alkanethiol)-12 base oligomers are hybridized to a…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThree-Dimensional Optical Data Storage Using Photochromic MaterialsSatoshi Kawata and Yoshimasa KawataView Author Information Department of Applied Physics, Osaka University, Suita, Osaka, 565-0871, Japan, and Department of Mechanical Engineering, Shizuoka University, Johoku…
The magnetization process in a square dot of permalloy having a size of 20 μm and 80 nm thickness has been investigated with a focused magneto-optical hysteresigraph. With this apparatus, it is possible to measure in a few seconds the hysteresis loop with a signal-to-noise ratio adequate for the observation of Barkhau…