Ring-Opening Polymerization of d,l-Lactide Using Rare-Earth μ-Oxo Isopropoxides as Initiator Systems
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Polymer Interdiffusion near an Attractive Solid Substrate
Neutron reflectometry is used to study interdiffusion in bilayers of hydrogenated and deuterated poly(methyl methacrylate) (PMMA) on silicon substrates where the polymer−substrate interaction energy is strongly attractive. The effect of the polymer−substrate interaction energy on the interdiffusion rate as a function…
Trapping of hydrogen to lattice defects in nickel
The embedded atom method (EAM) potentials for the Ni/Al/H system as previously published contain errors. The corrected potentials are presented here.
Excitons in Semiconductor–Dielectric Nanostructures
Confinement in nanostructures with (some of the) linear dimensions small compared to the exciton radius provides a possibility of enhancement of both the binding energy and the oscillator strength of excitons. Moreover in such structures the possibility arise of controlling the strength of Coulomb interaction, respons…
Rearrangement Reactions in Dinuclear Triple Helicates1
A series of dinuclear M(III) (M = Fe or Ga) catecholate complexes has been prepared using bisbidentate catecholate ligands ( L ). The products contain discrete, dinuclear M 2 ( L ) 3 6- anions featuring pseudo-octahedral coordination centers. The helical nature of the dinuclear complexes has been established by CD spe…
In Situ Studies of the Sol−Gel Synthesis of Materials
The use of in situ methods to study the synthesis of materials from sol−gel precursors is reviewed, with particular emphasis on the formation of crystalline phases from solid gel precursors and the crystallization of zeolitic materials from solution under hydrothermal conditions. A wide range of studies that have been…
Calculating the hopping rate for self-diffusion on rough potential energy surfaces: Cage correlations
We present a method for estimating the hopping rate for Zwanzig’s model of self-diffusion in liquids [R. Zwanzig, J. Chem. Phys. 79, 4507 (1983)]. To obtain this estimate, we introduce the cage correlation function which measures the rate of change of atomic surroundings, and associate the long-time decay of this func…
Subtilisin from psychrophilic antarctic bacteria: characterization and site-directed mutagenesis of residues possibly involved in the adaptation to cold
A subtilisin excreted by the Antarctic Bacillus TA39 has been purified to homogeneity and characterised. Two independent genes subt1 and subt2 are present but only subt1 is expressed significantly in the culture medium. The enzyme displays the usual characteristics of cold enzymes i.e. a high catalytic efficiency at l…
Effects of deposition temperature on the properties of hydrogenated tetrahedral amorphous carbon
The properties of hydrogenated carbon films deposited from a highly ionized hydrocarbon plasma beam are studied as a function of deposition temperature. At low temperatures, the films have high sp3 bonding, density, and compressive stress and are very smooth. Two transition temperatures are observed, a lower transitio…
Collective and non-collective excitations in antiferroelectric and ferrielectric liquid crystals studied by dielectric relaxation spectroscopy and electro-optic measurements
The dynamics of different molecular modes in four antiferroelectric liquid crystal substances have been studied by a combination of spectroscopic methods.The fastest motion is the reorientation around the molecular long axis, here found in the low GHz range by time domain spectroscopy. The reorientation around the sho…
Carbosilane Dendrimers with Perfluoroalkyl End Groups. Core−Shell Macromolecules with Generation-Dependent Order
A series of carbosilane dendrimer generations, G0 to G3, with 4, 12, 36, and 108 end groups, respectively, has been functionalized with perfluorohexyl (C 6 F 13 −) groups on the surface. Quantitative perfluoroalkylation of the dendrimer surface was achieved via free radical addition of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridec…
Synthesis, Characterization, and Catalytic Properties of Colloidal Platinum Nanoparticles Protected by Poly(N-isopropylacrylamide)
We have studied the formation of platinum nanoparticles in an ethanol−water mixture with an ethanol volume fraction of 0.6 by ethanol reduction of PtCl 6 2 - in the presence of poly( N -isopropylacrylamide) (PNIPAAm−Pt) by UV−visible spectrophotometry. As predicted by calculation, a maximum at 215 nm in the absorption…
Noncovalent Synthesis of Layered and Channel Structures involving Sulfur-Mediated Hydrogen Bonds
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTNoncovalent Synthesis of Layered and Channel Structures involving Sulfur-Mediated Hydrogen BondsV. R. Pedireddi, Swati Chatterjee, Anupama Ranganathan, and C. N. R. RaoView Author Information Chemistry & Physics of Materials Unit Jawaharlal Nehru Centre for Advanced Sc…
Preparation and Characterization of Inclusion Complexes of Aliphatic Polyesters with Cyclodextrins
Cyclodextrins (CDs) were found to form inclusion complexes with aliphatic polyesters [−O(CH 2 ) x OCO(CH 2 ) 4 CO] n (where x = 2, 3, or 4) to give crystalline compounds. α- and γ-CD formed complexes with these polyesters in high yields, although β-CD gave complexes in moderate yields. Although the yields of the compl…
High-Resolution Crystal Structures of Δ 5 -3-Ketosteroid Isomerase with and without a Reaction Intermediate Analogue
Bacterial Delta5-3-ketosteroid isomerase (KSI) catalyzes a stereospecific isomerization of steroid substrates at an extremely fast rate, overcoming a large disparity of pKa values between a catalytic residue and its target. The crystal structures of KSI from Pseudomonas putida and of the enzyme in complex with equilen…
Large Dipole Moments of Phosphorus-Containing Dendrimers
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTLarge Dipole Moments of Phosphorus-Containing DendrimersMarie-Laure Lartigue, Bruno Donnadieu, Christophe Galliot, Anne-Marie Caminade, Jean-Pierre Majoral, and Jean-Pierre FayetView Author Information Laboratoire de Chimie de Coord…
Characterization of a 200‐kDa Diatom Protein that is Specifically Associated with a Silica‐Based Substructure of the Cell Wall
The cell wall of a diatom is made up of a silica-based scaffold and organic macromolecules. Proteins located in the cell wall are believed to control morphogenesis of the species-specific silica structures of the scaffold. However, data that correlate distinct silica elements and specific proteins within the diatom ce…
Diffusion-Limited Size-Selective Ion Sensing Based on SAM-Supported Peptide Nanotubes
An approach for the construction of diffusion-limited size-selective sensors is described based on the self-assembly of cyclic peptides into tubular channels in organosulfur self-assembled monolayers on gold films. An eight-residue cyclic peptide of alternating units of d -Leu and l -Trp amino acid residues was incorp…
Electrochemical Li Insertion into Conductive Polymer/ V 2 O 5 Nanocomposites
Electrochemical insertion of Li into a series of “nanocomposites” comprised of alternating V 2 O 5 sheets and conductive polymer layers [polypyrrole (PPY) and polyaniline (PANI)] was examined and compared to the pristine V 2 O 5 material in terms of reversibility, Li site occupancy, and Li diffusion coefficients, and…
Selective Detection of Deoxyribonucleic Acid at Ultralow Concentrations by SERRS
Genetic research programs such as the human genome project have demonstrated the need for selective detection of nucleic acids at ultralow concentrations (McKusik, V. A. FASEB J. 1991, 5, 12−20. Cui, X.; et al. Proc. Natl. Acad. Sci. U.S.A. 1989, 89, 9389−9393). Current detection techniques require amplification of th…