A short and convenient chemical route to optically pure 2-methyl chromanmethanols. Total asymmetric synthesis of beta-, gamma-, and delta-tocotrienols

With use of inexpensive commercially available raw materials, chromanmethanol precursors to the natural beta-, gamma-, and delta-tocotrienols have been prepared in high yield. Enzymatic resolution afforded chiral chromanmethanols in high enantiomeric excess. Subsequent attachment of the farnesyl side chain was high yielding, thus allowing the preparation of asymmetric beta-, gamma-, and delta-tocotrienols in one final step wherein simultaneous deprotection of the phenol and removal of the sulfone group occurs. This chemistry provides the first synthesis of natural-series beta-tocotrienol.     

Curved laser-sheet for conformal surface flow diagnostics

Three-dimensional surface illumination using curved laser-sheet techniques is introduced for optical flow measurements in conformal curved surfaces. The illumination method is applicable to many different optical-based flow measurement techniques, with this paper focusing on application to flow visualization and particle image velocimetry. A brief discussion and example of curved laser-sheet generation is given followed by an example of the technique applied to PIV of low Reynolds number transitional flow around a low-pressure turbine blade.     

Structure and effects of annealing in colloidal matrix‐free Ge quantum dots

The structure of small (2–5 nm) Ge quantum dots prepared by the colloidal synthesis route is examined. Samples were synthesized using either GeO₂ or GeCl₄ as precursor. As‐prepared samples were further annealed under Ar or H₂/Ar atmosphere at different temperatures in order to understand the effect of annealing on their structure. It was found that as‐prepared samples possess distinctly different structures depending on their synthesis route as indicated by their long‐range ordering. An appreciable amount of oxygen was found to be bound to Ge in samples prepared with GeO₂ as a precursor; however, not for GeCl₄. Based on combined transmission electron microscope, Raman, X‐ray diffraction and X‐ray absorption measurements, it is suggested that as‐prepared samples are best described by the core‐shell model with a small nano‐crystalline core and an amorphous outer layer terminated either with oxygen or hydrogen depending on the synthesis route. Annealing in an H₂Ar atmosphere leads to sample crystallization and further nanoparticle growth, while at the same time reducing the Ge—O bonding. X‐ray diffraction measurements for as‐prepared and annealed samples indicate that diamond‐type and metastable phases are present.     

Antiproton cloud compression in the ALPHA apparatus at CERN

We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ～ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime.     

Adsorption kinetics, capacity and mechanism of arsenate and phosphate on a bifunctional TiO2-Fe2O3 bi-composite

Mixed oxide TiO(2)-Fe(2)O(3) bi-composites have been recognised as efficient and economical sorbents with great promise for arsenic removal from groundwater. In this study, we use a fast, simple and inexpensive synthesis method for this type of bi-composite and assess its adsorption performance. The kinetics of arsenate and phosphate adsorption onto the bi-composite are determined, demonstrating rapid and stable uptake of both oxy-anions over several days and with improved performance compared to the widely used TiO(2) sorbent. A modified pseudo-second order rate equation is introduced, which allows the adsorption kinetics to be modelled as two simultaneous, parallel reaction pathways with separate kinetic parameters. This equation reproduces the experimental observations accurately across a wide range of timescales from minutes to days. Our experimental data agrees with previous interpretations of the adsorption mechanism including the formation of mono-dentate and bi-dentate inner-sphere surface complexes. The arsenate and phosphate uptake capacities of the bi-composite are reported. Equilibrium studies were conducted between pH 5 and 9 and interpreted within the Langmuir, Freundlich and Dubinin-Radushkevich isotherm models.     

Alkaline phosphatase assay using a near-infrared fluorescent substrate merocyanine 700 phosphate

Alkaline phosphatase (ALP) is a phosphomonoester hydrolase that is commonly used as a conjugating enzyme in biological research. A wide variety of substrates have been developed to assay its activity. In this study, we developed an ALP assay method utilizing merocyanine 700 (MC700) based substrate MC700 phosphate (MC700p). MC700 is a near-infrared fluorescent merocyanine dye, and has excitation/emission maxima at 686 nm/722 nm in ALP assay buffer. Upon hydrolysis by ALP, MC700p is converted to MC700. The fluorescence of MC700 is dependent on the pH and detergent concentration in the buffer. The fluorescence signal produced by MC700p hydrolysis is linearly related to the ALP amount and substrate concentration. A stop solution containing EDTA could be used to stop the ALP/MC700p reaction. It was also demonstrated that MC700p could substitute pNpp as the ALP substrate in a commercial 17β-Estradiol enzyme immunoassay kit.     

Identification of “Known Unknowns” Utilizing Accurate Mass Data and Chemical Abstracts Service Databases

In many cases, an unknown to an investigator is actually known in the chemical literature. We refer to these types of compounds as “known unknowns.” Chemical Abstracts Service (CAS) Registry is a particularly good source of these substances as it contains over 54 million entries. Accurate mass measurements can be used to query the CAS Registry by either molecular formulae or average molecular weights. Searching the database by the web-based version of SciFinder is the preferred approach when molecular formulae are available. However, if a definitive molecular formula cannot be ascertained, searching the database with STN Express by average molecular weights is a viable alternative. The results from either approach are refined by employing the number of associated references or minimal sample history as orthogonal filters. These approaches were shown to be successful in identifying “known unknowns” noted in LC-MS and even GC-MS analyses in our laboratory. In addition, they were demonstrated in the identification of a variety of compounds of interest to others.