Polyelectrolyte-modified short microchannel for cation separation

Three alkali cations, potassium, sodium, and lithium, have been separated within 15 s in a 1 cm long polymer microchip. The separation microchannel is modified by a polycation, poly(allylammonium chloride), which makes the channel surfaces positively charged leading to a reversed electroosmotic flow (EOF) when compared to bare channels. Due to the decreased apparent mobility of the cations, the separation resolution is improved allowing the use of shorter channels.     

Bond lengths and bond strengths in weak and strong chemisorption: N2, CO,and CO/H on nickel surfaces

New chemical-state-specific scanned-energy mode photoelectron diffraction experiments and density functional theory calculations, applied to CO, CO/H, and N2 adsorption on Ni(100), show that chemisorption bond length changes associated with large changes in bond strength are small, but those associated with changes in bond order are much larger, and are similar to those found in molecular systems. Specifically, halving the bond strength of atop CO to Ni increases the Ni-C distance by 0.06 A, but halving the bond order (atop to bridge site) at fixed bond strength causes an increase of 0.16 A.     

Growth of anthracene thin films by matrix-assisted pulsed-laser evaporation

Thin films of anthracene (C₁₄H₁₀) have been grown by matrix-assisted pulsed-laser evaporation. Frozen solutions of 2 wt% anthracene (solute) in ortho-xylene or in chloroform were used as targets and were irradiated by a frequency-quadrupled Nd:YAG laser (266 nm). The deposited films were studied by the complementary use of infrared absorption and photoluminescence emission. The vibrational bands and fluorescence emission of bulk anthracene were clearly identified in the films. This means that the organic molecules were not modified by photochemical reactions during the laser irradiations, despite the strong absorption of anthracene at 266 nm. Among the growth parameters, the laser fluence was found to be critical in order to avoid the fragmentation of the anthracene molecules. The results show that matrix-assisted pulsed-laser evaporation is suitable for growing thin films of organic materials even if they absorb at the irradiating wavelength. PACS 81.15.Fg; 78.55.Kz; 33.20.Ea; 71.20.Rv     

Neutral and dianionic iron and ruthenium 1,4-diphosphabutadiene complexes

Reaction of a tetraphenyl-1,2-diphosphinyl dianion with [FeCl2(THF)1.5] or [Ru(COD)(acac)2] yields dianionic complexes which further react with Ph3SnCl to afford the corresponding bis(1,4-diphosphabutadiene) complexes.     

Review on contact simulation of beveloid and cycloid gears and application of a modern approach to treat deformations

Gear drives are key components for all kinds of machines as well as of industrial equipment. Therein, beveloid gears and cycloid gears are increasingly used in industry. Gaining a more comprehensive understanding of those types of gears is essential. However, the measurement of the dynamic response of these gears is not an option due to the high cost of the required experiments. Along with the development of computer technology, several numerical tools and methods to study gears with standard and non-standard flank profiles have been introduced. Various works related to standard gears or beveloid and cycloid gears have been published. In this study, a contemporary review about the modelling and contact simulation of beveloid and cycloid gear drives will be given. Some studies will also be introduced to present an efficient approach to simulate contact forces and contact characteristics of gear wheels with standard and non-standard tooth profiles considering deformations too.     

Upper bound for the Lempert function of smooth domains

An upper estimate for the Lempert function of any C ^1+ε -smooth bounded domain in \mathbbCⁿ{\mathbb{C}^n} is found in terms of the boundary distance.     

Microwave-assisted conversion of carbohydrates. State of the art and outlook

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e., lignocellulosic biomass) is nowadays an area of utmost interest. In this context, the implementation of fast, expeditious and cost-effective methodologies for the modification of these naturally occurring compounds is becoming a prerequisite. With this aim, the application of microwaves has gained progressive attention in laboratories for making a range of high-added value sugars derivative scaffolds. The advantages of microwaves are numerous, and include enhancement of reaction rates and yields, combined with improved regio-, chemo- and anomeric selectivities.