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.     

Light streak tracking of optically trapped thin microdisks

Nonspherical particles can uniquely probe soft system dynamics. We show that laser tweezers stably trap thin coinlike microdisks in 3D with an edge-on orientation. Scattered light forms a streak that we track using a fast camera to measure the disk's angular displacement. Linearly polarized tweezers rotationally trap a birefringent disk, and we measure its harmonically bound Brownian rotation over 5 decades in time. Near a surface, the disk exhibits a translational-orientational switchback oscillation. Circularly polarized tweezers rotate the disk and streak, yielding a colloidal lighthouse.     

Measurements of the cross section for e(+)e(-) --> hadrons at center-of-mass energies from 2 to 5 GeV

We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.     

An Micro-Bandpasss (6.3≈7.6μm) Filter for the Multichannel Scanning Radiometer

Optical coatings are designed and produced for the multichannel scanning radiometer meteorological space instrument operating in the spectral range 6.37.6m. First the choice of substrates and layers materials is discussed. Then the substrate temperatures dependent effects of three different Te-enriched PbTe single layers on the dispersion and absorption characteristics and carrier concentration are studied. The experimental results demonstrate that the performance of the coating made using PbTe + 0.3 at. % Te material is better than that of the others. Finally, details of the spectral design and manufacture of such a filter which meets the demanding bandwidth and transparency requirements of the application are presented. This design model is based on the optical and semiconductor properties of a multilayer filter containing PbTe layer materials in combination with the dielectric dispersion of ZnSe deposited on the a Ge substrate. Comparisons between the computed spectral performance of the model and spectral measurements from manufactured coatings over a wavelength range of 6.37.6m are presented.     

ICF瞄准定位系统的设计

将"神光Ⅱ"装置的原瞄准定位系统改为全反射式,可以用各波长的三倍频激光打靶.本文介绍一个双球面的反射系统的光学设计和测试结果.     

A three-dimensional renormalization group bubble merger model for Rayleigh-Taylor mixing

In this paper we formulate a model for the merger of bubbles at the edge of an unstable acceleration driven (Rayleigh-Taylor) mixing layer. Steady acceleration defines a self-similar mixing process, with a time-dependent inverse cascade of structures of increasing size. The time evolution is itself a renormalization group (RNG) evolution, and so the large time asymptotics define a RNG fixed point. We solve the model introduced here at this fixed point. The model predicts the growth rate of a Rayleigh-Taylor chaotic fluid mixing layer. The model has three main components: the velocity of a single bubble in this unstable flow regime, an envelope velocity, which describes collective excitations in the mixing region, and a merger process, which drives an inverse cascade, with a steady increase of bubble size. The present model differs from an earlier two-dimensional (2-D) merger model in several important ways. Beyond the extension of the model to three dimensions, the present model contains one phenomenological parameter, the variance of the bubble radii at fixed time. The model also predicts several experimental numbers: the bubble mixing rate, alpha(b)=h(b)/Agt(2) approximately 0.05-0.06, the mean bubble radius, and the bubble height separation at the time of merger. From these we also obtain the bubble height to the radius aspect ratio. Using the experimental results of Smeeton and Youngs (AWE Report No. O 35/87, 1987) to fix a value for the radius variance, we determine alpha(b) within the range of experimental uncertainty. We also obtain the experimental values for the bubble height to width aspect ratio in agreement with experimental values. (c) 2002 American Institute of Physics.     

Conformational differences between O- and C-glycosides: the alpha-O-man-(1-->1)-beta-Gal/alpha-C-Man-(1-->1)-beta-Gal case--a decisive demonstration of the importance of the exo-anomeric effect on the conformation of glycosides

The conformational behavior of alpha-O-Man-(1-->1)-beta-Gal (1) and its C-analogue (2) has been studied using J/NOE NMR data, molecular mechanics, molecular dynamics, and ab initio calculations. The population distribution around the glycosidic linkages of 1 and 2 is rather different, especially for the alpha-Man linkage. A lower limit for the exo-anomeric effect in water has been experimentally determined.     

Molecular Design of Liquid-Crystalline Block Molecules: Semifluorinated Pentaerythritol Tetrabenzoates Exhibiting Lamellar, Columnar, and Cubic Mesophases

Fluid assemblies of star-shaped molecules like 1 form a range of thermotropic liquid crystalline phases, and represent a borderline case between anisometric mesogens, surfactants, and block copolymers. The low molecular mass molecules (<5.5 kDa) consist of a semipolar central core and a shell of semifluorinated chains.     

Synthesis of Optically Active beta-Amino Acid N-Carboxyanhydrides

Methodology has been developed for the general synthesis of optically active beta-amino acid N-carboxyanhydrides (beta-NCAs) through cyclization of N(beta)-Boc or N(beta)-Cbz beta-amino acids using phosphorus tribromide. The formation of beta-NCAs was confirmed by spectroscopy as well as an X-ray structural determination of beta-homoalanine-N-carboxyanhydride. The beta-NCA molecules could be polymerized in good yield to give optically active poly(beta-peptides) that adopt stable chiral conformations in solution. For example, helical oligo(L-beta-homophenylalanine) was synthesized by polymerization of L-beta-homophenylalanine-N-carboxyanhydride.