Volatile fingerprints of artemisinin-rich Artemisia annua cultivars by headspace solid-phase microextraction gas chromatography/ mass spectrometry

The cultivar Anamed (A3) is a hybrid of Artemisia annua with a high content of the secondary metabolite artemisinin, a well-known antimalarial drug. Here we report for the first time the volatile profile of fresh leaves of this hybrid in comparison with that of Artemisia annua L. wild-type species. Evaluation and comparison of the volatile profiles of A. annua genotypes with different content in artemisinin were carried out by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography/mass spectrometry (GC/MS) that was performed on fresh leaves of the plants under investigation using a polydimethylsiloxane (PDMS) fiber. The chromatograms obtained from hybrids with a high content of artemisinin (A. annua cv. Anamed A3 and A. annua cv. Artemis F2) reveal the total absence of artemisia ketone, one of the major and characteristic compounds of the wild-type A. annua L., along with a significantly lower variety of volatile compounds. In conclusion, HS-SPME coupled with GC/MS is a very useful, non-destructive and efficient method to describe the volatile pattern of Artemisia annua cultivars. It represents a rapid screening method for the evaluation of volatile biomarkers like artemisia ketone, whose absence is typical of artemisinin-rich A. annua cultivars.     

A Kirkwood-Buff Derived Force Field for Aqueous Alkali Halides

A classical nonpolarizable force field is presented for the simulation of aqueous alkali halide solutions (MX), where M = Li(+), Na(+), K(+), Rb(+), Cs(+) and X = F(-), Cl(-), Br(-), I(-), and their interactions with biomolecules. The models are specifically designed to reproduce the experimental Kirkwood-Buff integrals, and thereby the solution salt activities, as a function of salt concentration. Additionally, we demonstrate that these models reasonably reproduce other experimental properties including ion diffusion constants, dielectric decrements, and the excess heats of mixing. The parameters are developed by considering the properties of aqueous NaX and MCl solutions using a previously established model for NaCl. Transferability of the parameters to other salts is then established by the successful simulation of additional aqueous salt solutions, KI and CsBr, not originally included in the parameterization procedure.     

Mild and tunable benzoic acid catalysts for rearrangement reactions of allylic alcohols

An efficient and simple catalytic method for the isomerization of readily prepared allylic alcohols is described. We focus particularly on cyclic examples and the synthesis of unusual enyne and dienols. The benzoic acid catalysts employed are commercially available and very inexpensive and can be tuned for reactivity and substrate sensitivity.     

Surface functionalization of electro-deposited nickel

A new in situ electrochemical method of functionalizing an oxide-free Ni surface is demonstrated using octanethiol. Initial adsorption results in a multilayer molecular film, which blocks both the hydrogen evolution reaction (HER) and re-oxidation of the Ni by ambient oxygen. However, excess octanethiol can be removed by rinsing with ethanol, leaving behind a monolayer that continues to protect against re-oxidation but gives rise to an unexpected enhancement in the HER, with a greater enhancement for longer film formation times. The presence of an octanethiol monolayer on the surface was confirmed by spectroscopic observation of the CH(2), CH(3) and thiolate groups using infra red spectroscopy, while X-ray photo-electron spectroscopy demonstrated the effectiveness of the thiol layer as a barrier to surface oxidation. The electrochemically prepared octanethiol film impedes oxidation of the Ni in air more effectively than a film formed by immersion in a solution of octanethiol in ethanol.     

Martensite Strain Memory in the Shape Memory Alloy Nickel-Titanium Under Mechanical Cycling

This paper describes an experimental study of stress-induced martensitic phase transformation in the SMA Nickel-Titanium. The rich local thermo-mechanical interactions that underlie transformation are examined using three-dimensional Digital Image Correlation (strain fields) and infrared imaging (thermal fields). We quantify the complex local interactions between released/absorbed latent heat and the extent of transformation, and explore the characteristics of the phase fronts and the evolution of martensitic volume fraction. We also quantify a strong strain memory in the martensite that forms in the wake of the phase transformation front. The accommodated strain in the martensite will remain constant during loading, even as the existing phase front propagates. There also exists a remarkable strain memory in the martensite that persists from cycle to cycle, indicating that the local elastic stress fields in the martensite are driven by a dislocation structure and martensitic nuclei that largely stabilize during the first loading cycle.     

Novel nitration of estrone by metal nitrates

Nitration of estrone has been investigated with different types of metal salts in the presence of solid surfaces under various conditions.     

Diameter control of electrospun polyacrylonitrile/iron acetylacetonate ultrafine nanofibers

Electrospinning is the process of producing ultrafine fibers by overcoming the surface tension of a polymer solution using high voltage. In this work, the effects of both solution properties (viscosity, conductivity, and surface tension) and operational conditions (voltage, feed rate, and spinneret‐collector distance), on the structure of electrospun polyacrylonitrile nanofibers, were systematically investigated. Iron acetylacetonate was added to the electrospinning solution to control fiber diameter by selectively adjusting solution properties. It was found that, with increased salt concentration, the fiber diameter increases and then passes through a maximum due to changes in solution viscosity, conductivity, and surface tension. In addition, the fiber diameter increases with increase in voltage, feed rate, and spinneret‐collector distance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1611–1618, 2008