Materials Literature
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We calculate the temperature dependence of the fluorescence Stokes shift and the fluorescence decay time in linear Frenkel exciton systems resulting from the thermal redistribution of exciton population over the band states. The following factors, relevant to common experimental conditions, are accounted for in our ki…
A detailed investigation of mesoscopic magnetic and crystallographic phase separation in ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{MnO}}_{3},$ $0.00<~x<~0.20,$ is reported. Neutron powder diffraction and dc-magnetization techniques have been used to isolate the different roles played by electron…
Neutron measurements on ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{MnO}}_{3}$ $(0.00<~x<~0.20)$ reveal the development of magnetic droplets showing a liquidlike intercluster spatial distribution. The average size of the droplets is $\ensuremath{\sim}10\mathrm{\AA{}},$ the concentration of which i…
It is argued that both transitions observed in 50% doped manganites, at the Néel temperature (T(N)) and the so-called charge ordering temperature (T(CO)), are magnetic. T(N) corresponds to the order-disorder transition, which takes place between ferromagnetic zigzag chains, while the coherent motion of spins within th…
We show that two major carrier excitation mechanisms are present in II-VI self-assembled quantum dots. The first one is related to direct excited state - ground state transition. It manifests itself by the presence of sharp and intense lines in the excitation spectrum measured from single quantum dots. Apart from thes…
We model the optical dynamics in linear Frenkel exciton systems governed by scattering on static disorder and lattice vibrations, and calculate the temperature dependent fluorescence spectrum and lifetime. The fluorescence Stokes shift shows a nonmonotonic behavior with temperature, which derives from the interplay of…
Energy transfer from the translational degrees of freedom to phonon modes is studied for isolated systems of two coaxial carbon nanotubes, which may serve as a nearly frictionless nano-oscillator. It is found that for oscillators with short nanotubes (less than 30 A) a rocking motion, occurring when the inner tube is…
This paper accompanies a lecture given at the 2003 CCP4 Study Weekend on experimental phasing. The first part is an overview of the fundamentals of Patterson methods and direct methods with the audience of the CCP4 Study Weekend in mind. In the second part, a new hybrid substructure search is outlined.
The steady-state photoluminescence (PL) properties of cadmium selenide quantum dots (QDs) with a zinc sulfide overlayer [(CdSe)ZnS] can be strongly dependent on temperature in the range from 100 to 315 K. The PL intensity from 50 to 55 Å (CdSe)ZnS QDs in poly(lauryl methacrylate) matrices increases by a factor of ∼5 w…
A major challenge in nanoscience and nanotechnology is the rational assembly of nanoscale objects. Here we report that gold nanorods, aspect ratio 18, can be functionalized with a biotin disulfide, and subsequent addition of streptavidin links the rods together in an end-to-end manner much more often than expected.
Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbable devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of…
Die selektive und permanente Titration von Protonen mit organischen Basen (2,6‐Di‐ tert ‐butylpyridin oder Pyridin) liefert ein genaues Maß für die Dispersion von Keggin‐Strukturen während der katalytischen Oxidation von Methanol. Die Titration ermöglicht die systematische Steuerung der Redox‐ und Säureeigenschaften v…
In the crystal structure of dihydroxydiphthalatotricobalt(II), [Co(3)(C(8)H(4)O(4))(2)(OH)(2)](n), two of the four independent Co atoms lie at special positions of site symmetry 2. The hydroxy groups link three Co atoms to form a pyramidal Co(3)O unit, and adjacent Co(3)O units are linked through the Co base atoms int…
The paper outlines some approaches that should be considered in the calculation of partition coefficients based on Langmuir, Freundlich and Linear isotherms. It was found that the Langmuir partition coefficient (K Lg ), whose calculation involved the maximal amount of lead (Pb) and zinc (Zn) adsorbed and their appropr…
Picture this: The simultaneous growth of many single grains of catalyst culminating in polymer particles can be observed by videomicroscopy, and single-grain kinetics can be studied. The gas-phase polymerization of ethylene on 40 particles was examined in an autoclave equipped with a glass window by automatic image pr…
The structure of a new synthetic compound, diammonium tetrahydroxydecaborate monohydrate, has been determined by single-crystal X-ray diffraction. It crystallizes in triclinic space group P-1 and all atoms occupy general sites. The title compound is composed of [B(10)O(15)(OH)(4)](4-) ions as the fundamental building…
The 6-methyl-2-(2-pyridyl)-benzimidazole (biz) ligand coordinates with the actinide species in solution, and the complexes display efficient intramolecular energy-transfer processes. The energy transfer in the Cm(III)-biz system proceeds in a nonradiative mode, whereas a radiative mode is the principal mechanism in th…
Lightly cross-linked, swellable poly(divinylbenzene- alt -maleic anhydride) microgels were allowed to self-assemble at the oil−water interfaces of a propyl acetate−water suspension and covalently fixed in place using polyamines to form novel, flexible microgel capsules. The capsule wall morphology was studied by optic…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTHierarchical Order in a Side-Group Liquid Crystalline Block CopolymerI. A. Ansari, V. Castelletto, T. Mykhaylyk, I. W. Hamley, Z. B. Lu, T. Itoh, and C. T. ImrieView Author Information Department of Chemistry, University of Leeds, Leeds LS2 9JT, UK Department of Chemistry, Univ…
Kinetic modeling of catalytic combustion of ethyl acetate and benzene over Cr-ZSM-5 (Si/Al = 240) is reported. Ethyl acetate was more reactive than benzene and could suppress benzene conversion in the binary mixture while water vapor retarded the conversion of both organics. Kinetic data obtained in the differential r…