Base-selective adsorption of nucleosides to pore-engineered nanocarbon, carbon nanocage

Selective molecular recognition is an important subject in supramolecular science as well as in practical applications such as sensing, drug delivery, and biomedical processes. In this research we have investigated adsorption behavior of nucleosides (adenosine, guanosine, and thymidine) onto various porous supports. When compared with mesoporous silica, porous carbons exhibit superior adsorptive performance. We serendipitously observed a pronounced selectivity between purine-base and pyrimidine-base nucleosides by carbon naonocage. These findings are useful for design of materials for applications in adsorption-based separations and as column stationary phases for separation of costly and important biomolecules.     

Continuous wave cavity ring down spectroscopy measurements of velocity distribution functions of argon ions in a helicon plasma

We report continuous wave cavity ring down spectroscopy (CW-CRDS) measurements of ion velocity distribution functions (VDFs) in low pressure argon helicon plasma (magnetic field strength of 600 G, T(e) ≈ 4 eV and n ≈ 5 × 10(11) cm(-3)). Laser induced fluorescence (LIF) is routinely used to measure VDFs of argon ions, argon neutrals, helium neutrals, and xenon ions in helicon sources. Here, we describe a CW-CRDS diagnostic based on a narrow line width, tunable diode laser as an alternative technique to measure VDFs in similar regimes but where LIF is inapplicable. Being an ultra-sensitive, cavity enhanced absorption spectroscopic technique; CW-CRDS can also provide a direct quantitative measurement of the absolute metastable state density. The proof of principle CW-CRDS measurements presented here are of the Doppler broadened absorption spectrum of Ar II at 668.6138 nm. Extrapolating from these initial measurements, it is expected that this diagnostic is suitable for neutrals and ions in plasmas ranging in density from 1 × 10(9) cm(-3) to 1 × 10(13) cm(-3) and target species temperatures less than 20 eV.     

Functional sites and evolutionary connections of acylhomoserine lactone synthases

Acylhomoserine lactone (AHL) synthases act as chemical communicationsignals or pheromones in Gram-negative bacteria and regulatediverse physiological events in a cell density-dependent manner.The recent crystal structure determination of EsaI, a key enzymein this pathway, shows that the AHL synthase superfamily membersadopt the fold of the N-acetyltransferase superfamily. We suggest,by the identification of intermediate sequences, that the twosuperfamilies are evolutionarily related. Evolutionary traceanalyses of aligned sequences and docking studies have beenused to discuss functionally important residues of EsaI homologues.     

Effect of MgO Grain Size on Thermal Expansion Behavior of Alumina–Magnesia–Carbon Refractory

The effect of MgO grain size on the permanent linear change behavior of resin bonded alumina–magnesia–carbon refractory has been studied in relation to the formation of spinel phase in these refractories as a function of firing time and temperature. From scanning electron microscopic studies, spinelization at the interface of Al₂O₃ and MgO grains has also been studied to determine the reaction kinetics for gaining insight into the process.