Materials Literature
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Resistivity, magnetoresistance, and M\"ossbauer effect of metallic spiral antiferromagnet ${\mathrm{SrFeO}}_{2.95}$ have been examined in the temperature range 4.5--300 K. A large negative magnetoresistance below 50 K is observed. We find hysteresis in resistivity in 0 and 9 T due to the coexistence of antiferromagnet…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTLight-Driven Catalysis within Dendrimers: Designing Amphiphilic Singlet Oxygen SensitizersStefan Hecht and Jean M. J. FréchetView Author Information Department of Chemistry, University of California Berkeley, California 94720-1460 Cite this: J. Am. Chem. Soc. 2001, 123…
Intramolecular Förster-type excitation energy transfer (FRET) processes in a series of first-generation polyphenylene dendrimers substituted with spatially well-separated peryleneimide chromophores and a terryleneimide energy-trapping chromophore at the rim were investigated by steady-state and time-resolved fluoresce…
Monte Carlo simulations combined with the embedded-atom method potential have been employed to investigate the microscopic process of the $\ensuremath{\Sigma}5$ tilt grain boundary sliding in aluminum. We have studied the atomic structures and the grain boundary sliding/migration energy profile at elevated temperature…
BaGa2Sb2 was obtained from a direct element combination reaction in a sealed graphite tube at 950 degrees C, and its structure was determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group Pnma (No. 62) with a = 25.454(5) A, b = 4.4421(9) A, c = 10.273(6) A, and Z = 8. The…
Ultrasmall CdS nanoparticles were prepared by the size-selective photoetching technique. The smallest size of the CdS nanoparticles was obtained by the irradiation with the monochromatic light having the wavelength of 365 nm, while the absorbance of CdS nanoparticles monotonically decreased, for the whole wavelength,…
Novel bolaamphiphiles, consisting of a biphenyl rigid core, polar 2,3-dihydroxypropoxy groups at each terminal end, and an additional long alkyl chain in a lateral position have been synthesized. The structures of these ternary block molecules were systematically changed by variation of the length and position of the…
A new tabulation of atomic form factors is discussed briefly, extending the validity of the isolated atom approximation and serving as a baseline for near-edge solid-state and XAFS investigations. This is detailed by Chantler [J. Phys. Chem. Ref. Data, (2000), 29, 597-1048] and is the latest component of the FFAST tab…
We suggest an approach to account for spatial (composition) and thermal fluctuations in "disordered" magnetic models (e.g. Heisenberg, Ising) with given spatial dependence of magnetic spin-spin interaction. Our approach is based on introduction of fluctuating molecular field (rather than mean field) acting between the…
A transit is the motion of a system from one many-particle potential energy valley to another. We report the observation of transits in molecular dynamics calculations of supercooled liquid argon and sodium. Each transit is a correlated simultaneous shift in the equilibrium positions of a small local group of particle…
It is shown and discussed how the conventional system of hydrodynamic equations for ferrofluids was derived. The set consists of the equation of fluid motion, the Maxwell equations, and the magnetization equation. The latter was recently revised by Felderhof [Phys. Rev. E, v.62, p.3848 (2000)]. His phenomenological ma…
A new magnetization equation recently derived from irreversible thermodynamics is employed to the calculation of an increase of ferrofluid viscosity in a magnetic field. Results of the calculations are compared with those obtained on the basis of two well-known magnetization equations. One of the two was obtained phen…
The contributions of the covalent bond energies of various atom pairs to the cohesive energy of MgB2 and AlB2 are analysed with a variant of our recently developed energy-partitioning scheme for the density-functional total energy. The covalent bond energies are strongest for the intralayer B-B pairs. In contrast to t…
First-principles density functional calculations reveal that aluminum can form planar chains in zigzag and ladder structures. The most stable one has equilateral triangular geometry with four nearest neighbors; the other stable zigzag structure has wide bond angle and allows for two nearest neighbors. An intermediary…
Nonlocal Hamiltonians are used widely in first-principles quantum calculations; the nonlocality stems from eliminating undesired degrees of freedom, e.g. core electrons. To date, attempts to couple nonlocal systems to external electromagnetic (EM) fields have been heuristic or limited to weak or long wavelength fields…
Convective instability in a ferrofluid layer heated from below or from above in the presence of a uniform vertical magnetic field is investigated theoretically. Convection is caused by a magnetic mechanism based on the temperature and concentration dependence of magnetization. An imposed temperature gradient establish…
We report the development of new bioactive coatings of biomaterials based on the alternate deposition of oppositely charged polyelectrolytes. We selected polylysine (PLL) and poly(glutamic acid) (PGA) for the polyelectrolytes and murine melanoma cells as a biological test model system. These cells respond specifically…
Nearly monodisperse (1.7 ± 0.2 nm) palladium nanoparticles were prepared within the interiors of three different generations of hydroxyl-terminated poly(amidoamine) (PAMAM) dendrimers. These dendrimer-encapsulated catalysts (DECs) were used to hydrogenate allyl alcohol and four α-substituted derivatives in a 4:1 metha…
Transition metal nanoparticles used in catalysis in solution are stabilized by capping the surfaces that are supposed to be used for catalysis. Determining how these two properties, that is, the catalytic activity and stability of nanoparticles, change as different capping materials are used is the aim of this work. P…
SBA-15 siliceous materials templated using triblock copolymers have recently received considerable attention because of their potential applications in catalysis and separations of large molecules. SBA-15 materials possess a regular hexagonal array of cylindrical channels of 5−30 nm in diameter and, unless specially t…