Search results for "ELF"

Linear scaling exchange gradients for Hartree–Fock and hybrid density functional theory

2000

Abstract A new method is introduced which allows to form the exchange part of self-consistent field energy gradients in a way which scales linearly with molecular size for molecules with a non-vanishing HOMO–LUMO gap. This is not only important for Hartree–Fock but as well for the popular hybrid density functional theory methods. The method preserves the optimized integral-driven structure of conventional direct methods. Efficiency and scaling behavior of the new method are illustrated for DNA fragments.

Janus particles: synthesis, self-assembly, physical properties, and applications.

2013

Crystalline self-assembly induced by aromatic edge-to-face interactions: the crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyc…

2002

The crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyclophane bromide reveals several intermolecular aromatic edge-to-face interactions which are important in the three-dimensional growing of the crystalline structure. Molecular dynamics and semiempirical studies indicate that the conformer found in the crystal is not the most stable in solution confirming the important role that edge-to-face interactions play in the structural arrangement found in the solid state.

Stamping of monomeric SAMs as a route to structured crystallization templates: patterned titania films.

2000

Gold-coated glass slides have be patterned by using self-assembled monolayers (SAM) of alkane thiols. Through the use of a special thiol terminated with a styrene monomer, microstructures of 5 to 10 microm width and 70 A height have been formed on the surface by graft polymerization of styrene. These patterned gold slides have then been used to template the precipitation of thin titania films from ethanolic solutions of titanium isopropoxide to create microstructured architectures in the film. Plasmon resonance spectra have established the presence of different steps in the process and have been used to follow the kinetics of the precipitation of titania on the surface. The structured TiO2 …

Quality characteristics of horchata (a Spanish vegetable beverage) treated with pulsed electric fields during shelf-life

2005

Abstract The application of pulsed electric fields (PEF) is one of the new non-thermal technologies being studied to evaluate their potential as alternative or complementary processes to thermal pasteurization. “Horchata de chufa” (tiger nut milk or earth almond milk) is of high nutritional quality and therefore has great potential in the food market, limited by its very short shelf-life. The present work studies whether PEF can be used to obtain a quality horchata and increase its shelf-life while maintaining its organoleptic characteristics. In order to do so we determined pH, total fat, peroxide index, thiobarbituric acid-reactive substances index, formol index, and peroxidase activity i…

Titelbild: An Unlockable-Relockable Iron Cage by Subcomponent Self-Assembly (Angew. Chem. 43/2008)

2008

Inside Back Cover: Kinetically Controlled Sequential Growth of Surface-Grafted Chiral Supramolecular Copolymers (Angew. Chem. Int. Ed. 25/2016)

2016

Template induced crystallization of biominerals on self-assembled monolayers of alkylthiols

1998

Abstract We have studied the templated crystallization of the three polymorphs of calcium carbonate on self-assembled monolayers of ω -substituted alkylthiols on gold surfaces. Our interest has been to model biomineralization processes by examining the effect of structured organic templates on heterogeneous nucleation at the inorganic–organic interphase. The crystallization of the three polymorphs was carried out from solution at two different temperatures. The crystals that were formed on the surface were examined using scanning electron microscopy. Phase quantification was achieved through Rietveld analysis of the X-ray diffraction profiles. This study provides significant clues on factor…

The reluctant polymorph: investigation into the effect of self-association on the solvent mediated phase transformation and nucleation of theophylline

2015

Little is known concerning the pathway of the crystallization of the thermodynamically stable polymorph of theophylline, form IV. Here we study the reasons why the thermodynamically stable theophylline form IV can be obtained only by slow, solvent mediated phase transformation (SMPT) in specific solvents, and whether the presence of prenucleation aggregates affect the polymorphic outcome. Solution concentration, polymorphic composition and morphology were monitored over time during the transformation from form II to form IV in several solvents. NMR and FTIR spectroscopy were used to detect prenucleation molecular aggregates present in the solutions. It was determined that theophylline self-…

Hydrogen-Bonding Effects in Calix[4]arene Capsules

2000

The synthesis and spectroscopic characterization of self-assembling calix[4]arene based capsules 1a.1a and 1b.1b are described. These compounds feature four urea substituents at the upper rims and four secondary amide fragments at the lower rims that can participate in inter- and intramolecular hydrogen bonding in apolar solution. Communication between the calixarene rims in 1a, b influences the self-assembled cavity's size and shape. Specifically. dimerization results in a perfect cone conformation of the calixarene skeleton in 1a, b and stabilizes a seam of intramolecular amide C=O...H-N hydrogen bonds at the lower rim. This seam is cycloenantiomeric, with either clockwise or counterclock…