Materials Literature
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This paper presents novel results on the electrical properties of amorphous carbon films prepared by ion-beam sputtering. The conductivity is found to be similar to that seen in evaporated carbon. Over the range approximately 40-300 K, it is well described by the variable range hopping equation with a hopping exponent…
The electron paramagnetic resonance spectrum of Mn 4+ in single-crystal lead titanate has been studied at 9.8 and 33.8 GHz. An axial sextet with g perpendicular to eff =3.7742(1) to g/sub /// eff approximately=2.00 was measured at 9.8 GHz and with g perpendicular to eff =2.7048(15) at 33.8 GHz; a second sextet was obs…
High structural regularity, second-order nonlinear susceptibility, and thermal stability characterize the self-assembled stilbazolium chromophoric multilayers (the structure obtained after the first cycle is shown schematically on the right). A topotactic approach for the stilbazolium chromophore deposition has result…
Enhancement of the phonon density of states due to low-energy floppy modes in crystalline and glassy states of the high-temperature ceramic S${\mathrm{i}}_{3}$${\mathrm{N}}_{4}$ is investigated using the molecular-dynamics method. Floppy modes appear continuously in the glass as the connectivity of the system is reduc…
CuxS nanocrystals (NC’s) are reported. The samples are prepared by a CdS-to-CuxS chemical conversion from the glasses originally containing CdS NC’s. A room-temperature linear absorption of the converted samples shows several well resolved peaks with spectral positions from red to blue. These spectral features are exp…
Thin film ferroelectrics with polarization gradients normal to the growth surface readily form when gradients in temperature, strain, or composition are coupled to the polarization vector in ferroelectric materials. This letter describes the formation of thin films of potassium tantalum niobate with graded polarizatio…
Extremely stiff macromolecules in the form of “hairy rods” or more precisely “molecular bottlebrushes” (without a handle) are easily accessible by the polymerization of polymacromonomers. As anticipated from their high degree of stiffness, these molecules form lyotropic, liquid‐crystalline phases, although they consis…
Cyclic tetrameric units (··Mn-NC-Fe-CN··)4 (depicted on the right) construct the two-dimensional network of the title compound. The layers thus formed are linked together by van der Waals contacts. The compound displays metamagnetism: ferromagnetic coupling is observed within layers and antiferromagnetic coupling betw…
π-Stacking interactions between adjacent aromatic ligand fragments of L− separated by approximately 3.4 Å provides a pathway for weak ferromagnetic coupling in the tetramer [Mn4L4](PF6)4 (1). The cavity of L− is too large for a single MnII ion; instead the tetramer 1 comprises a Mn4 tetrahedron, with a ligand L− attac…
An air bubble trapped in water by an oscillating acoustic field undergoes either spherical or nonspherical pulsations depending on the strength of the forcing pressure. Two different instability mechanisms (the Rayleigh-Taylor instability and parametric instability) cause deviations from sphericity. Distinguishing the…
Novel, polymeric linear chains of Keggin polyoxometalate units PMnW11O39 linked through Mn-O-W bridges (see picture below) are present in the structure of the title compound 1. The chains alternate with layers of the organic donor bis(ethylenedithio)tetrathiafulvalene (ET). Compound 1 promises interesting material pro…
Viscometry and dynamic light scattering (DLS) were used to study suspensions of colloidal particles which interact like hard spheres. The rate of ``structural relaxation'' of microscopic density fluctuations, indicated by the long-time diffusion coefficient measured by DLS at the peak of the static structure factor, w…
We have measured Raman spectra of diamond with nanometer size, called cluster diamond. The Raman bands assigned to sp2 and sp3 clusters have been observed at around 1600 and 1322 cm−1, respectively. This result suggests that the cluster diamond slightly contains the sp2 cluster. The Raman band assigned to sp3 cluster…
A detailed study of doped LaMn${\mathrm{O}}_{3}$ with fixed carrier concentration reveals a direct relationship between the Curie temperature ${T}_{c}$ and the average ionic radius of the La site $〈{r}_{A}〉$, which is varied by substituting different rare earth ions for La. With decreasing $〈{r}_{A}〉$, magnetic order…
Abstract Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′‐[1,4‐phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H 2 SO 4 . Th…
Abstract Six nearly monodisperse substituted poly(styrene) homopolymers, poly(styrene) (PS), poly(2‐methylstyrene) (P2MS), poly(3‐methylstyrene) (P3MS), poly(4‐methylstyrene) (P4MS), poly(tertiary‐butylstyrene) (PtBS), and poly(α‐methylstyrene) (FαMS) were anionically polymerized and subsequently saturated using heter…
Abstract 4,4′‐Binaphthyl‐1,1′,8,8′‐tetracarboxylic dianhydride was synthesized from 4‐chloro‐1,8‐naphthalic anhydride and polymerized with aromatic and pliphatic diamines in m ‐cresol or N ‐methyl‐2‐pyrrolidinone (NMP). The polyimides, except for two derived from p ‐phenylenediamine and hydrazine, are soluble in 1,1,2…
Abstract Three N , N ′‐bis (glycidyl ester imide) of pyromellitic acid (diepoxides) were prepared and were used as chain extenders for poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). The typical reaction conditions for the coupling of the polyester macromolecules were heating with the chai…
It is the intention of this paper to rigorously clarify the role of the occupation numbers in the current practical applications of the density functional formalism. In these calculations one has to decide how to distribute a given, fixed number of electrons over a set of single-particle orbitals. The conventional cho…
There are two stereochemical classes of hydratase-dehydratase enzymes. Those that catalyze the addition of water to alpha, beta-unsaturated thioesters give syn addition-elimination stereochemistry, whereas those that catalyze the addition of water to conjugated carboxylate substrates give anti stereochemistry. This di…