2,7-Bis(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine: an ultrasensitive fluorescent probe for glucopyranoside

[structure: see text] A push-pull conjugated molecule, 2,7-bis(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine (BPN), has been designed to bind selectively with octyl glucopyranoside (OGU). The BPN/OGU quadruple hydrogen-bonding complex adopts a rigid BPN conformation in which the proton donor (d) and acceptor (a) relays (daad) are resonantly conjugated through the ethynyl bridge, inducing pi-electron delocalization, i.e., a charge transfer effect. The excellent photophysical properties make BPN a highly sensitive probe for monitoring glucopyranoside to a detection limit of approximately 100 pM.     

Polyferrocenylsilane microspheres: synthesis,mechanism of formation,size and charge tunability,electrostatic self-assembly,and pyrolysis to spherical magnetic ceramic particles

Pt(0)-catalyzed ring-opening precipitation copolymerization of [1]silaferrocenophanes fcSiMe(2) (3) and the spirocyclic cross-linker fcSi(CH(2))(3) (4) (fc = Fe(eta(5)-C(5)H(4))(2)) was used to prepare polyferrocenylsilane microspheres (PFSMSs) under mild conditions. By varying the reaction conditions, a wide variety of other morphologies was obtained. The effects of temperature, monomer ratio, solvent composition, catalyst concentration, and time on the observed morphology were investigated and interpreted in terms of a mechanism for microsphere formation. The most well-defined particles were formed using equimolar amounts of 3 and 4, in a 50:50 mixture of xylenes and decane at 60 degrees C with gentle agitation. Chemical oxidation of the polymeric microspheres led to positively charged particles (OPFSMSs) which underwent electrostatically driven self-assembly with negatively charged silica microspheres to form core-corona composite particles. Redox titration with controlled amounts of the one-electron oxidant [N(C(6)H(4)Br-p)(3)][PF(6)] in acetonitrile led to the oxidation of the outer 0.15 microm (ca. 32%) of the PFSMSs. The resulting OPFSMSs were reduced back to their neutral form by reaction with hydrazine in methanol. Pyrolysis of the PFSMSs led to spherical magnetic ceramic replicas with tunable magnetic properties that organize into ordered 2-D arrays at the air-water interface under the influence of a magnetic field.     

Electron-hole coupling and the charge density wave transition in TiSe2

Angle-resolved photoemission is employed to measure the band structure of TiSe2 in order to clarify the nature of the ( 2 x 2 x 2) charge density wave transition. The results show a very small indirect gap in the normal phase transforming into a larger indirect gap at a different location in the Brillouin zone. Fermi surface topology is irrelevant in this case. Instead, electron-hole coupling together with a novel indirect Jahn-Teller effect drives the transition.     

Effect of the Interface Component on Current-voltage Curves of a Composite Bipolar Membrane for Water and Methanol Solutions

The current-voltage curves of a composite bipolar membrane (CBM) were experimentally measured by varying the interface component between cation- and anion-exchange membranes for water and methanol solutions. In each solution system, 0.05 mol/l LiCl was used as the electrolyte. The interface component was varied by pasting the polymers or installing the thin membranes in the intermediate region of the CBM. The measured results show that the functional groups of the polymers and thin membranes enhanced the water and methanol splitting effect. This phenomenon can be explained by the protonation-deprotonation reactions occurring between these functional groups and the water or methanol molecules in the intermediate region of the CBM. The effect of transition metal compounds existing in the intermediate region of the CBM was also experimentally examined in this study. It was found that the effect of transition metal compounds on water or methanol splitting was not obvious. Copyright 1999 Academic Press.     

Multiple-channel wavelength conversion by use of engineered quasi-phase-matching structures in LiNbO(3) waveguides

We report difference frequency generation-based wavelength converters with multiple phase-matching wavelengths that use engineered quasi-phase-matching structures in LiNbO(3) waveguides. Multiple-channel wavelength conversion is demonstrated within the 1.5-mum band and between the 1.3- and 1.5-mum bands. With simultaneous use of M pump wavelengths, these devices can also be used to perform wavelength broadcasting, in which each of N input signals is converted into M output wavelengths.     

Boundary effects on granular shear flows of smooth disks

Summary We obtain boundary conditions for two-dimensional flows of identical, nearly elastic, circular disks that interact with a flat wall to which identical, evenly spaced half-disks have been attached. Expressions for the transfer of momentum and energy from the boundary to the flow are obtained by statistical averaging over all possible wall-flow disk collisions. We improve upon the expressions derived by Jenkins and Richman [1986] by employing in the averaging process a more elaborate velocity distribution function obtained through the method of moments. In addition we expand the distribution function about a point near the flat wall that guarantees positive slip velocities. With these boundary conditions, we analyze a two-dimensional shear flow driven by parallel bumpy boundaries. The constitutive theory employed includes both the effects of particle collisions and particle transport on the transfer of momentum and energy throughout the flow. We demonstrate how the resulting profiles of velocity, granular temperature, and solid fraction are affected by changes in the geometry of the boundary. We also predict how the induced stresses vary with the geometry of the boundary and the average solid fraction within the flow.

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Zusammenfassung Wir erhalten die Randbedingungen für die zweidimensionale Strömung identischer, beinahe elastischer, runder Scheiben, die sich in Wechselwirkung mit einer geraden Wand befinden, an der in gleichmäßigen Abständen Halbscheiben angebracht sind. Es werden Ausdrücke für die Übertragung von Impuls und Energie vom Rand auf den Strom aufgestellt, die durch den statisch errechneten Durchschnitt aller möglichen Scheibenkollisionen Wand-Strom erhalten werden. Wir verbessern die von Jenkins und Richman (1986) entwickelten Ausdrücke dadurch, daß bei der Berechnung der Mittelwerte eine erweiterte Geschwindigkeitsverteilung, die auf der Momentmethode beruht, einbezogen wurde. Außerdem entwickeln wir die Verteilungsfunktion an einem Punkt so nahe an der Wand, daß positive Gleitgeschwindigkeiten garantiert sind. Wir untersuchen eine zweidimensionale Scherströmung mit diesen Randbedingungen, die durch die parallelen unebenen Ränder getrieben wird. Die konstitutive Theorie, die wir anwenden, beinhaltet sowohl den Einfluß der Teilchenkollisionen als auch den des Teilchentransports auf die Übertragung von Impuls und Energie innerhalb der Strömung. Wir zeigen, wie die Profile der Geschwindigkeit, der Granu-lartemperatur und des Festkörperanteils, die sich ergeben, durch Veränderungen der Randgeometrie beeinflußt werden. Weiterhin können wir voraussagen, wie die erzeugten Spannungen sich mit der Randgeometrie und dem im Strom enthaltenen Festkörperanteil verändern.

     

A Simple and Rapid Separation of Preservatives and Artificial Sweeteners by Polyamide Layer Chromatography

A simple and rapid polyamide chromatographic method for the detection of 12 kinds of preservatives and 3 kinds of artificial sweeteners were reported. The results indicated that the method was good in sensitivity, separability and reproducibility.     

Study of cylindrical stress waves generated by exploding wires

An experimental technique utilizing high-pressure gas from an exploding wire is used to load long, hollow, thick-walled cylinders from the inside. Resulting plane-strain cylindrical stress waves are one-dimensional in nature. Asimultaneity of impact is studied with methods of high-speed photography and dynamic photoelasticity.