Using GPU parallelization to perform realistic simulations of the LPCTrap experiments

We performed classical molecular dynamics (MD) simulations in order to search the conditions for efficient sympathetic cooling of highly charged ions (HCIs) in a linear Paul trap. Small two-component ion Coulomb crystals consisting of laser-cooled ions and HCIs were characterized by the results of the MD simulations. We found that the spatial distribution is determined by not only the charge-to-mass ratio but also the space charge effect. Moreover, the simulation results suggest that the temperature of HCIs do not necessarily decrease with increasing the number of laser-cooled ions in the cases of linear ion crystals. We also determined the cooling limit of sympathetically cooled ¹⁶⁵Ho¹⁴⁺ ions in small linear ion Coulomb crystals. The present results show that sub-milli-Kelvin temperatures of at least 10 Ho¹⁴⁺ ions will be achieved by sympathetic cooling with a single laser-cooled Be⁺.     

Synthesis and photochemistry of pH-sensitive GFP chromophore analogs

GFP chromophore analogs (7a-e, 8, and 10a,b) containing 2-thienyl-, 5-methyl-2-furyl-, 2-pyrryl, and 6-methyl-2-pyridyl-groups were synthesized and their fluorescence spectra recorded in the pH range 1-7. NMR studies showed that protonation of 8 (2-thienyl system) inhibited photoisomerization (Z-E) about the exocyclic double bond but that protonation of 7c (E + Z) (2-pyrryl system) gave only 7cE. Fluorescence studies revealed enhancement of fluorescence intensity of 7c and 7b,e (furyl system) below pH 2.5 and gave a similar result for 10a (pyridyl system) below pH 6. Quantum yields at pH 1 were low, probably due to excited state proton transfer (ESPT).     

Single-molecule force spectroscopy for studying kinetics of enzymatic dextran elongations

Catalytic elongation of dextran by a single molecule of dextransucrase (DSase) was directly monitored by observing the movements of the positions of a rupture peak, which represented the adhesive force between an isomaltoheptaose (dextran 7-mer)-immobilized probe and a DSase-immobilized mica surface. This was initiated with the addition of sucrose monomers. From the histograms of the rupture peaks after elongation reactions on each individual enzyme and the continuous peak shift of certain single enzymes, the catalytic elongation rate constant (k(cat)) was ascertained to be 1.2-2.7 s(-1).     

Pyridinium tribromide catalyzed condensation of indoles and aldehydes to form bisindolylalkanes

An efficient synthetic method for bis(indol-3-yl)alkane derivatives has been developed.In the presence of 5 mol%of pyridinium tribromide(PTB),the condensation of indoles and aldehydes proceeded smoothly under mild conditions,giving rise to the corresponding bis(indol-3-yl)alkanes in good to excellent yields.     

Short sales in Log-robust portfolio management

This paper extends the Log-robust portfolio management approach to the case with short sales, i.e., the case where the manager can sell shares he does not yet own. We model the continuously compounded rates of return, which have been established in the literature as the true drivers of uncertainty, as uncertain parameters belonging to polyhedral uncertainty sets, and maximize the worst-case portfolio wealth over that set in a one-period setting. The degree of the manager’s aversion to ambiguity is incorporated through a single, intuitive parameter, which determines the size of the uncertainty set. The presence of short-selling requires the development of problem-specific techniques, because the optimization problem is not convex. In the case where assets are independent, we show that the robust optimization problem can be solved exactly as a series of linear programming problems; as a result, the approach remains tractable for large numbers of assets. We also provide insights into the structure of the optimal solution. In the case of correlated assets, we develop and test a heuristic where correlation is maintained only between assets invested in. In computational experiments, the proposed approach exhibits superior performance to that of the traditional robust approach.     

Synthesis of transparent aqueous sols of colloidal layered niobate nanocrystals at room temperature

Transparent aqueous sols of colloidal tetramethylammonium niobate nanocrystals were synthesized by mixing tetramethylammonium hydroxide (TMAOH), niobium ethoxide, and water at TMAOH/Nb≥0.7 at room temperature. The X-ray diffraction patterns of the thin films prepared by evaporating the colloidal solutions on a glass substrate indicated that the colloidal niobate had a layered crystalline structure. Two types of layered structures are known as a layered niobate, i.e. M(4)Nb(6)O(17)·nH(2)O and MNb(3)O(8) (M=H, H(3)O, or alkaline metal). Raman spectra and electron diffraction suggested that the niobate nanocrystals were similar in crystal structure to M(4)Nb(6)O(17)·nH(2)O compounds. Moreover, when niobium oxide thin films were fabricated from the niobate colloidal solutions by the sol-gel method, oriented T-Nb(2)O(5) thin films, whose c-axis was parallel to the substrate surface, were obtained. The orientation of the thin films was probably attributed to the layered structure of the colloidal niobate nanocrystals.     

Surfactant-free synthesis of palladium nanoclusters for their use in catalytic cross-coupling reactions

Surfactant-free Pd nanoclusters (Pd NCs) (size: 1-1.5 nm) showed high catalytic activity in the Suzuki-Miyaura cross-coupling and Mizoroki-Heck reactions. The Pd NCs had a high turnover number, up to 6.0 × 10(8), which can be recycled at least five times without loss of catalytic activity.     

Synthesis and in vitro protein tyrosine kinase inhibitory activity of furan-2-yl(phenyl)methanone derivatives

A series of novel furan-2-yl(phenyl)methanone derivatives were synthesized, and their structures were established on the basis of 1H-NMR, 13C-NMR and mass spectral data. All the prepared compounds were screened for their in vitro protein tyrosine kinase inhibitory activity and several new derivatives exhibited promising activity, which, in some cases, was identical to, or even better than that of genistein, a positive reference compound. The preliminary structure-activity relationships of these compounds were investigated and are discussed.