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In this article neutron-scattering experiments using the backscattering instrument IN13 on the glass-forming polymer polybutadiene are reported. As compared to other neutron spectrometers IN13 has a large range of wave vectors Q accessible. Therefore, a better statement can be made about the spatial extent of the obse…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSynthesis of Model 3-Miktoarm Star Terpolymers of Styrene, Isoprene, and Methyl MethacrylateStella Sioula, Yiannis Tselikas, and Nikos HadjichristidisView Author Information Department of Chemistry, University of Athens, Panepistimi…
The Dawson-type P(2)W(15)Nb(3)O(62)(9)(-) polyoxoanion-supported Re(CO)(3)(+) complex, [Re(CO)(3).P(2)W(15)Nb(3)O(62)](8)(-) (1), has been synthesized and characterized in two different counter-cation compositions. The [(n-C(4)H(9))(4)N](8)(8+) complex provides a highly soluble compound which exists as a single isomer…
The preparation and purification of the heterocyclic diradical benzo-1,2:4,5-bis(1,3,2-dithiazolyl) (BBDTA) is described. Crystals of BBDTA, grown by fractional sublimation at 120−180 °C/10 -3 Torr, are monoclinic, space group P 2 1 / c, with a = 4.144(2), b = 9.0344(13), and c = 10.7424(16) Å, β = 91.11(3)°, and Z =…
The magnetic couplings in insulating ${\mathrm{LaMnO}}_{3}$, ${\mathrm{CaMnO}}_{3}$, and the planar analogs ${\mathrm{La}}_{\mathrm{n}+1}$${\mathrm{Mn}}_{\mathrm{n}}$${\mathrm{O}}_{3\mathrm{n}+1}$ are estimated using standard superexchange arguments. The orbital ordering observed in ${\mathrm{LaMnO}}_{3}$ is found to…
As in the case of uracil, a complete set of vibrational spectra of thymine and its N-deuterated species, obtained from several spectroscopic techniques, i.e., neutron inelastic scattering (NIS), Raman scattering, and infrared absorption (IR), has been used in order to assign the vibrational modes on the basis of an ab…
With age, the proximal sections of turkey leg tendons become calcified, and this phenomenon has led to their use as a model for collagen mineralization. Mineralizing turkey leg tendon was used in this study to characterize further the composition and cross-linking of collagen in calcified tissues. The cross-link profi…
Conformational analysis of highly substituted porphyrins has potential implications for modeling the behavior of macrocycles in tetrapyrrole-containing protein complexes and during catalytic reactions. In order to study the influence of different substituent patterns on the conformation of the porphyrin macrocycle, a…
The analysis of multilayered interference coatings by coupled-mode theory is considered to be an approximation useful for small index, gain, and/or loss modulations. In this paper, we show that an exact analysis of a multilayer coating with coupled-mode theory is possible by redefining the coupling and detuning coeffi…
We studied the glass transition dynamics of polystyrene micronetwork colloids with an average cross-link density of 1:50 (inverse number of monomer units between cross-links) and a hydrodynamic radius of about 100 nm by dynamic light scattering. Special emphasis was put on extracting correct intermediate scattering fu…
The flow properties of aqueous suspensions of silica particles with diameters ranging from 117 to 780 nm were measured as a function of volume fraction, ionic strength, and continuous phase composition. Dense, aqueous suspensions of all sizes displayed similar behavior with a yield stress in the limit of low shear rat…
We have calculated the electronic structures of five different manganese-oxo dimer complexes using density functional methods combined with the broken symmetry and spin projection concepts. The number of carboxylate, oxo, and peroxo bridging ligands was varied, and the terminal ligands were triazacyclononane (TACN). T…
Globular proteins can be crystallized by the addition of electrolyte or nonadsorbing polymer. Too much additive, however, gives rise to amorphous precipitates. By comparing existing data on various proteins with previous work on a model colloid-polymer mixture, we suggest an explanation for noncrystallization in terms…
Weblike aggregates of coalesced Si nanocrystals are produced by a laser vaporization−controlled condensation technique. SEM micrographs show particles with ∼10 nm diameter but the Raman shift suggests the presence of particles as small as ∼4 nm. FTIR of the freshly prepared particles shows weak peaks due to the stretc…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTThermal Derivatization of Porous Silicon with AlcoholsNamyong Y. Kim and Paul E. LaibinisView Author Information Departments of Chemistry and Chemical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 Cite this: J. Am. Chem. Soc. 1997, 11…
The crystallization of oxyethylene/oxybutylene (E/B) diblock copolymers has been studied by simultaneous SAXS and WAXS. The copolymers crystallized from their melts (disordered, lamellar, or hexagonal) with folded E blocks. Rapid crystallization (quench) of lamellar melts was accompanied by a change in length scale an…
The protonated form of the ligand 2,6-bis(1'-methylbenzimidazol-2'-yl)pyridine crystallizes as its perchlorate salt (HL(1))ClO(4) (1) in the orthorhombic system Pbca, with a = 13.976(3) Å, b = 14.423(3) Å, c = 19.529(4) Å, Z = 8. The proton is located on one benzimidazole N-atom, and the two N-methyl substituents lie…
The X-ray structure of the &mgr;-carboxylate-&mgr;(1,1)-azido-bridged compound {[Cu(Hpht)(N(3))].H(2)O}(n)() has been determined (Hpht = hydrogen phthalate). Crystal data: formula C(8)H(7)CuN(3)O(5), monoclinic, P2(1)/m (No. 11), a = 7.383(3) Å, b = 6.568(4) Å, c = 10.659(4) Å, beta = 93.38(3) degrees, Z = 2. The comp…
We have measured the dc magnetization at low temperatures of tetragonal crystals of ${\mathrm{Mn}}_{12}$ acetate complex [${\mathrm{Mn}}_{12}$ ${\mathrm{O}}_{12}$ (${\mathrm{CH}}_{3}$ COO${)}_{16}$ (${\mathrm{H}}_{2}$ O${)}_{4}$ ], a material composed of a large (Avogadro's) number of identical magnetic molecules, eac…
A purification procedure for single-walled nanotubes is presented in this report. A novel purification method that incorporates the hydrothermal treatment along with other treatments such as extraction of fullerenes and oxidation and dissolution of metal particles is used in this study. The effects of each treatment i…