A plug and play microfluidic device

Chip-to-world interface is a major issue in the field of microfluidics and its applications. We developed a plug and play microfluidic device composed of a fluid driving unit and a polymer chip containing microfluidic channels and reservoirs. The one and only connection of the device to the external world is a set of electric control lines for the driving unit. Just putting the reagents and samples onto the reservoirs, the chip can be operated for chemical or biochemical reaction and analysis. We demonstrate here that silicon-based micropumps embedded in the present device allow us to achieve flexible fluidic manipulations with minimum time delay and dead volume.     

Pulsed laser deposition of pure fluoroapatite film without OH groups

The relation between O₂ pressure and composition in the pulsed‐laser deposition of fluoroapatite was investigated using both on‐axis and off‐axis methods to determine the optimal conditions for obtaining a pure fluoroapatite film without OH groups. Through this, it was found that an O₂ pressure of 10 Pa, combined with an off‐axis method, results in P/Ca and F/Ca values (0.6 and 0.2, respectively) that match closely with a stoichiometric composition of Ca₁₀(PO₄)₆F₂. Fourier transform infrared spectroscopy analysis confirmed that this optimized film was almost pure fluoroapatite, with no evidence of any OH groups originating from hydroxyapatite. X‐ray diffraction also revealed that this fluoroapatite film crystallizes with a c‐axis orientation perpendicular to its surface.     

Theory and experiment agree: single-walled carbon nanotube caps grow catalyst-free with chirality preference on a SiC surface

High-temperature quantum chemical molecular dynamics simulations have been performed on model systems of thin SiC crystal surfaces with two graphene sheets placed on top of either C or Si face. In agreement with experiment, we find that (a) the C-face-attached graphene layer warps readily to form small diameter, stable nanocaps, suitable for further perpendicular growth of nanotubes, (b) the Si-face-attached graphene sheet does not readily wrap and forms more volatile Si-graphene bonds, and (c) C face nanocaps appear to anneal to dome-shape structures with zigzag chirality.     

Crystal and molecular structure of a new diterpenyl glycoside from Pteris cretica L.

The crystal and molecular structure of a new diterpenyl glycoside, Ptr-1, is presented. The crystal is triclinic, space group P1, with a = 8.2414(8) Å, b = 13.0826(9) Å, c = 6.1427(8) Å, = 95.345(9)°, = 111.589(8)°, = 96.726(7)°, V = 604.9(1) ų, Z = 1. The structure was solved by direct methods and refined by full-matrix least-squares methods to a final R = 0.049 (Rw = 0.099) for 1872 independent reflections. The molecular structure is based on a glycopyranosyl group and a tetracyclic group. The glycopyranosyl group is -D-allopyranosyl group. The tetracyclic group consists of 1 five-membered and 3 six-membered rings.     

S1-state Mn4Ca complex of Photosystem II exists in equilibrium between the two most-stable isomeric substates: XRD and EXAFS evidence

Photosynthetic water oxidation reaction driven by Sun and catalyzed by a unique Mn(4)Ca cluster in Photosystem II (PSII) is known to take place in an oxygen evolving complex (OEC) that cycles five serial redox states, named "Kok's S(i)-states" (i=0-4). Recently, the atomic crystal structure of PSII from Thermosynechococcus vulcanus was resolved by 1.9 ?-resolution XRD data [55]. Interestingly, it revealed an unusual oxo-bridged Mn(4)CaO(5) cluster in the dark stable S(1)-state, e.g. unusual mono-μ(2)-oxo-mono-μ(4)-oxo-mono-μ(2)-carboxylato bridges connecting Mn(a) (terminal) and Mn(b) (central) ions with unusual atomic distance of 2.9 ?. Using the UDFT/B3LYP/lacvp** geometry optimization method and a truncated cluster model of the chemically-complete OEC put in ε=4 dielectric medium, it is shown that the OEC in S(1) must be in thermal equilibrium between the most-stable isomeric substates ("S(1a) and S(1b)") owing to the quasi-reversible structure change induced by proton migration. Coincidentally, it is found that the Mn(a)-Mn(b) distances in the Mn(4)Ca clusters in S(1a) and S(1b) are given by R(ab)=3.32 ? and 2.77 ?, respectively, so that the apparent distance between Mn(a) and Mn(b) ions in isomeric equilibrium is given by 2.94 ?, in agreement with experimental R(ab)~2.9 ?. Concomitantly, the first full-k-range EXAFS spectrum from powdered PSII [45] is used to provide the second experimental evidence for the S(1)-state OEC being in thermal equilibrium between S(1a) and S(1b)-isomers. These OEC-isomers consist of all the chemically-essential 11 amino acid residues, six cofactor ions and nine essential hydrated water molecules in their chemical ionic states around physiological pH 7, thus reasonably satisfying the biochemical charge neutrality with four Mn ions staying at the oxidation states (Mn(a)(III)/Mn(b)(IV)/Mn(c)(III)/Mn(d)(IV)) with the skeleton structures of MT-5J type and T-shaped DD-4J type. These H-bonding water molecules are found to fill a cavity connecting possible substrate/products channels so as to be arranged as an indispensable part of the catalytic Mn(4)Ca cluster in the order of "current-substrates" (W1/W2 bound to Mn(a)(III)), "next-substrates" (W4/W7) and "next-after-next-substrates" (W5/W6 bound to Ca(2+)). Results show that the Jahn-Teller effect due to Mn(a)(III) ion in these isomers can reasonably explain the very-slow-exchange and very-fast-exchange processes observed in S(1) by time-resolved (18)O-exchange mass spectroscopy.     

Variable-precision dominance-based rough set approach and attribute reduction

In this paper, a variable-precision dominance-based rough set approach (VP-DRSA) is proposed together with several VP-DRSA-based approaches to attribute reduction. The properties of VP-DRSA are shown in comparison to previous dominance-based rough set approaches. An advantage of VP-DRSA over variable-consistency dominance-based rough set approach in decision rule induction is emphasized. Some relations among the VP-DRSA-based attribute reduction approaches are investigated.     

Structural and conformational analysis of spiro(1,3-dithiolane-2,3′-indolin)-2′-one: An anticonvulsant analog

The structure was solved by the heavy-atom method, and refined by full-matrix least squares to anR value of 0.037 for 1670 observed reflections. The bond linking the amide to the tetrahedral carbon atom is a single bond. The six-membered ring is perfectly planar, whereas the five-membered ring deviates from planarity. The five- and six-membered rings are inclined to one another at 2.6(1)°, and the dithiolane ring is nearly perpendicular to the indolinone group.