Materials Literature
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Abstract High molecular weight, soluble, amorphous, partially aliphatic polyimides were successfully synthesized using an ester acid high‐temperature solution imidization route, which allows one to control desired glass‐transition ( T g ) and processing temperatures. This method involves the prereaction of aromatic di…
We study geometrically controlled twist transitions of a nematic confined between a sinusoidal grating and a flat substrate. In these cells, the transition to the twisted state is driven by surface effects. We have identified the mechanisms responsible for the transition analytically and used exact numerical calculati…
[structure: see text] New chiral terpyridines containing Frechét-type dendrons have been readily synthesized by coupling dendritic benzyl bromide and 4'-[6-(2,2'-dihydroxy-1,1'-binaphthyl)]-2,2':6'2' '-terpyridine. These chiral dendritic terpyridines were used to efficiently construct high molecular weight hybrid meta…
Two new biflavonoids, namely, 6'"-hydroxylophirone B (1) and 6'"-hydroxylophirone B 4"'-O-beta-glucoside (2), were isolated from the stem bark of Ochna integerrima, together with five known compounds. The structures of 1 and 2 were determined by spectral data interpretation.
An original interferometer-based setup for measurements of length of needlelike samples is developed, and thermal expansion of o-TaS(3) crystals is studied. Below the Peierls transition the temperature hysteresis of length L is observed, the width of the hysteresis loop deltaL/L being up to 5 x 10(-5). The behavior of…
The purpose of this study is to clarify experimentally the influence of streaming induced by ultrasonic vibration on heat transfer using a horn-type ultrasonic vibrator. A horn tip of 6 mm diameter and 60.7 kHz resonant frequency was used as the ultrasonic transducer. Heat transfer experiments for a downward-facing ho…
The dynamic mean-field density functional method, driven from the generalized time-dependent Ginzburg–Landau equation, was applied to the mesoscopic dynamics of the multi-arms star block copolymer melts in two-dimensional lattice model. The implicit Gaussian density functional expression of a multi-arms star block cop…
Abstract Novel alternating conjugated copolymers ( P1–P6 ) consisting of an electron‐deficient benzothiadiazole and a variety of electron‐rich thiophene‐arene‐thiophene units were synthesized by palladium‐catalyzed polycondensations (Stille and Suzuki reactions), aiming at processable materials with a reduced optical…
A hypothetical protein encoded by the gene YjeE of Haemophilus influenzae was selected as part of a structural genomics project for X-ray analysis to assist with the functional assignment. The protein is considered essential to bacteria because the gene is present in virtually all bacterial genomes but not in those of…
We study the structural and dynamical characteristics of the sodium atoms inside and outside the ``diffusion channels'' in glassy ${\mathrm{Na}}_{2}\mathrm{O}\ensuremath{-}4{\mathrm{SiO}}_{2}$ (NS4) using classical molecular dynamics. We show that on average neither energetic arguments nor local environment considerat…
The supercooled dynamics of a Lennard-Jones model liquid is numerically investigated studying relevant points of the potential energy surface, i.e., the minima of the square gradient of total potential energy V. The main findings are (i) the number of negative curvatures n of these sampled points appears to extrapolat…
The surface tension of interacting polymers in a good solvent is calculated theoretically and by computer simulations for a planar wall geometry and for the insertion of a single colloidal hard sphere. This is achieved for the planar wall and for the larger spheres by an adsorption method, and for smaller spheres by a…
The N-confused porphyrin complex Mn(II)(NCHPP)Br exhibits a nonplanar porphyrin ring with an inner core C-H on the inverted pyrrole ring. The aerobic metal oxidation promotes the dissociation of an inner-core proton on the inverted pyrrole ring and changes the N-confused porphyrin conformation to a planar porphyrin ri…
We use an integral equation scheme to obtain self-consistently the effective interaction between colloids in salt-free charged colloidal suspensions. The colloid–counterion direct correlation function (DCF) is obtained for the fixed colloid–colloid pair structure by solving the corresponding hypernetted-chain equation…
Morphological changes in single-walled carbon nanotubes (SWNTs) upon bombardment with 3MeV protons were monitored by transmission electron microscopy in a wide range of irradiation doses. Evident morphological alterations were observed at >0.1 mC, such as curving of the nanotubes, a loss of their straight shape, and f…
In support of improved personal armour development, depth of penetration tests have been conducted on four different ceramic materials including alumina, modified alumina, silicon carbide and boron carbide. These experiments consisted of impacting ceramic tiles bonded to aluminum cylinders with 0.50 caliber armour pie…
The dynamic critical behavior of isotropic Heisenberg ferromagnets with a planar free surface is investigated by means of field-theoretic renormalization group techniques and high-precision computer simulations. An appropriate semi-infinite extension of the stochastic model J is constructed. The relevant boundary term…
A first-principles method, based on density functional perturbation theory, is presented for computing the leading order tunability of high-dielectric-constant materials.
We study the effect of a magnetic field on the thermal relaxation of non-interacting small monodomain particle systems particles with a distribution of anisotropy constants and random easy-axes directions. Numerical calculations of the relaxation curves for different distribution widths, and under different magnetic f…
The magnetic structure of the edge sharing cuprate compound Li2CuO2 has been investigated by means of ab initio electronic structure calculations. The first and second neighbor in-chain magnetic interactions are calculated to be -142 K and 22 K, respectively. The ratio between the two parameters is smaller than sugges…