Carbocations and the Complex Flavor and Bouquet of Wine: Mechanistic Aspects of Terpene Biosynthesis in Wine Grapes.

Computational chemistry approaches for studying the formation of terpenes/terpenoids in wines are presented, using five particular terpenes/terpenoids (1,8-cineole, α-ylangene, botrydial, rotundone, and the wine lactone), volatile compounds (or their precursors) found in wine and/or wine grapes, as representative examples. Through these examples, we show how modern computational quantum chemistry can be employed as an effective tool for assessing the validity of proposed mechanisms for terpene/terpenoid formation

Visualization without Vision – How Blind and Visually Impaired Students and Researchers Engage with Molecular Structures

This article examines the tools and techniques currently available that enable blind and visually impaired (BVI) individuals to visualize three-dimensional objects used in learning chemistry concepts. How BVI individuals engage with and visualize molecular structure is discussed and recent tactile (or haptic) and auditory methods for visualization of various chemistry concepts are summarized. Remaining challenges for chemistry education researchers are described with the aim of highlighting the potential value of educational research in further enabling BVI students to pursue careers in science, technology, engineering, and mathematics (STEM) fields

Extending holographic LEED to ordered small unit cell superstructures

Following on the success of the recent application of holographic LEED to the determination of the 3D atomic geometry of Si adatoms on a SiC(111) p(3x3) surface, which enabled that structure to be solved, we show in this paper that a similar technique allows the direct recovery of the local geometry of adsorbates forming superstructures as small as p(2x2), even in the presence of a local substrate reconstruction.Comment: 10 pages, 5 figures postscript included, revtex, Phys. Rev. B in pres

Holographic Image Reconstruction from Electron Diffraction Intensities of Ordered Superstructures

We report on a novel holographic reconstruction of well resolved atomic images from discrete spot intensities appearing in low-energy electron diffraction (LEED) from crystalline surfaces. This opens holographic LEED to the wide field of ordered systems giving access to rather complex surface structures

A first parameterization of the pore-structure dependent kinetic adsorption model for O2 adsorption in biomass conversion modeling

Mass transport properties of the oxidation and gasification agents O2, CO2, and H2O are highly relevant for the modeling of the conversion process of biomasses. Therefore, this study presents experimental investigations on the adsorption kinetics of O2 on a biomass char using a modified gravimetric sorption device. Based on this comprehensive set of adsorption kinetic data, a first parameterization of the pore-structure dependent kinetic adsorption (PSK) model for O2 adsorption is presented. This model intends to account for mass transport during biomass conversion in a more meaningful way as it is considered in conventional conversion models. With this parameterization, the model is capable of describing accurately the adsorption kinetics of O2 as a function of time, temperature, and pressure

Direct reconstruction of three-dimensional atomic adsorption sites by holographic LEED

We report on the application to measured data of an algorithm for holographic low-energy electron diffraction (LEED), which overcomes the two most important limitations of the technique to date: the ‘‘searchlight’’ effect, which tends to highlight only atoms forward scattered by the adsorbates, and the distorting effects on diffuse LEED intensities due to possible long-range order among the adsorbates. The only experimental input required is a set of the most reliably measured diffuse LEED patterns from normally incident electrons. The algorithm is applied to a set of 11 measured diffraction patterns from a K/Ni(001) surface. A fully three-dimensional image is reconstructed from these data by compensating for the anisotropy of the reference wave by an appropriate scattered-wave kernel. © 1996 The American Physical Society