Formation of Saddle-Shaped Composite Sheets

Based on the deformation model of an unbalanced multilayer composite, changes in bending curvatures of sheet-type composites with nonsymmetric structure relative to the midplane of the sheet, depending on the moisture of layers, are predicted. The bending curvatures of saddle-shaped sheets of wood-based composites are calculated with regard to the physical and mechanical properties, geometrical dimensions, orientation, and distribution of layers. The analytical results are compared with the bending curvatures found experimentally for a four-layered unbalanced composite made of birch veneer. The applied calculation model enables us to determine the values of bending curvatures of saddle-shaped wood composite sheets, which can be used in elaborating the technological recommendations.     

银纳米粒子上苯甲酸吸收行为的实验(FT-Raman)和理论(DFT)研究(英文)

1IntroductionSurface-enhanced Raman scattering(SERS)has been widely used in studying interaction mecha-nismof the molecules withthesurface of thesubstrateand molecular orientation1-3·However,with thevariation of the characteristics of the surface of thesubstrates,the SERSspectrumof adsorbates will alsobe different,which makes the analyses difficult·Thecommon analytical methodis basedontheshift of Ra-man bands,enhancement or weakness of intensity toguessthe adsorption orientation,geometry…     

Monomolecular sheets of propeller‐shaped triethyl 4,4′,4′′‐[benzene‐1,3,5‐triyltris(ethyne‐2,1‐diyl)]tribenzoate deuterochloroform monosolvate

The title compound, C₃₉H₃₀O₆·CDCl₃, has a chemical threefold axis and an approximately planar structure, with an ethoxycarbonyl substituent on each of the terminal benzenes oriented in the same direction, thus forming a propeller‐shaped molecule. This molecule is of particular interest in the field of metal–organic frameworks (MOFs), where its hydrolyzed analogue forms MOF structures with high surface areas. The benzene ring which occupies the centre of the molecule forms π–π interactions to the equivalent benzene ring at a perpendicular distance of 3.32 (1) Å. Centrosymmetric dimers formed in this way are interconnected by intermolecular C—H...π interactions with a rather short H...CgA distance of 2.51 Å (CgA is the centroid of the central benzene ring). The molecules are arranged in regular parallel sheets. Within a sheet, molecules are interconnected via C—H...O interactions where all carbonyl O atoms participate in weak hydrogen bonds as hydrogen‐bond acceptors. Neighbouring sheets are connected through the above‐mentioned π–π and C—H...π interactions.     

Rapid analysis of cyanuric acid in swimming pool waters by high performance liquid chromatography using porous graphitic carbon

Summary An approach is presented for reducing analysis times of cyanuric acid in swimming pool waters by high performance liquid chromatography (HPLC). The HPLC method exploits the unique selectivity of porous graphitic carbon (PGC) to fully resolve cyanuric acid from other pool interferences within 10 min. By carefully timing the injections, multiple injections can be made before the end of the initial chromatographic run, more than doubling sample throughout. The method utilizes 95% of a 50 mM phosphate buffer solution (pH 9.1) and 5% methanol (v/v) with UV detection at 213 nm. This approach yielded run times rivaling those of the fastest methods using silica columns, and with the benefits of increased sensitivity.     

A compact light sheet generator for flow visualizations

Tomographic flow visualizations by means of plane light sheets are now well known. Previously, a laboratory set-up using sphero-cylindrical lenses was proposed. In this paper a compact optical system generating plane laser sheets whose geometrical parameters are easily adjustable is presented. This optical device is well adapted for an industrial practice.     

Artificial egg stalks made of a recombinantly produced lacewing silk protein

Rigid threads: Lacewings protect their eggs from predators by laying them on small stalks (see picture). The stalks have good mechanical properties and, unlike most other silks, a cross β structure. An artificial egg stalk was produced using a designed recombinant variant of a sequenced lacewing egg stalk protein, and it attained 90?% of the tensile strength of a natural egg stalk.     

A novel non-enzymatic glucose sensor based on Cu nanoparticle modified graphene sheets electrode

A novel, stable and sensitive non-enzymatic glucose sensor was developed by potentiostatically electrodepositing metallic Cu nanoparticles on graphene sheets. The electrochemical performance of the Cu-graphene sheets electrode for detection of glucose was investigated by cyclic voltammetry and chronamperometry. The Cu-graphene sheets electrode displayed a synergistic effect of copper nanoparticles and graphene sheets towards the oxidation of glucose in alkaline solution, showing higher oxidation current and negative shift in peak potential. At detection potential of 500 mV, the Cu-graphene electrode sensor presented a wide linear range up to 4.5 mM glucose with a detection limit of 0.5 μM (signal/noise = 3). In addition, the sensor responds very quickly (<2 s) with addition of glucose. Furthermore, the Cu-graphene sheets electrode exhibits high stability and selectivity to glucose, and the poisoning by chloride ion as well as interference from the oxidation of common interfering species (ascorbic, dopamine, uric acid and carbohydrate) are effectively avoided. The Cu-graphene sheets electrode allows highly selective and sensitive, stable and fast amperometric sensing of glucose, which is promising for the development of non-enzymatic glucose sensor.     

Facile synthesis of graphene hybrid tube-like structure for simultaneous detection of ascorbic acid,dopamine, uric acid and tryptophan

In the present work, a tube-like structure of graphene hybrid as modifier to fabricate electrode for simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp) was reported. The hybrid was synthesized by a simple method based on graphene sheets (GS) and 3,4,9,10-perylenetetracarboxylic acid (PTCA) via π–π stacking interaction under ultrasonic condition. The combination of GS and PTCA could effectively improve the dispersion of GS, owing to PTCA with the carboxylic-functionalized interface. Comparing with pure GS or PTCA modified electrode, GS–PTCA displayed high catalytic activity and selectivity toward the oxidation of AA, DA, UA, and Trp. Moreover, cyclic voltammetry, different pulse voltammetry and scanning electron microscopy were employed to characterize the sensors. The experiment results showed that the linear response range for simultaneous detection of AA, DA, UA, and Trp were 20–420 μM, 0.40–374 μM, 4–544 μM and 0.40–138 μM, respectively, and the detection limits were 5.60 μM, 0.13 μM, 0.92 μM and 0.06 μM (S/N = 3). Importantly, the proposed method offers promise for simple, rapid, selective and cost-effective analysis of small biomolecules.     

Sonochemical fabrication of gold nanoparticles–boron nitride sheets nanocomposites for enzymeless hydrogen peroxide detection

A simple sonochemical route was developed for the preparation of gold nanoparticles/boron nitride sheets (AuNPs/BNS) nanocomposites without using reducing or stabilizing agents. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and UV–vis absorption spectra were used to characterize the structure and morphology of the nanocomposites. The experimental results showed that AuNPs with approximately 20 nm were uniformly attached onto the BNS surface. It was found that the AuNPs/BNS nanocomposites exhibited good catalytic activity for the reduction of H₂O₂. The modified electrochemical sensor showed a linear range from 0.04 to 50 mM with a detection limit of 8.3 μM at a signal-to-noise ratio of 3. The findings provide a low-cost approach to the production of stable aqueous dispersions of nanoparticles/BNS nanocomposites.     

On the Limit as the Density Ratio Tends to Zero for Two Perfect Incompressible Fluids Separated by a Surface of Discontinuity

We study the asymptotic limit as the density ratio ρ^?/ρ⁺ → 0, where ρ⁺ and ρ^? are the densities of two perfect incompressible 2-D/3-D fluids, separated by a surface of discontinuity along which the pressure jump is proportional to the mean curvature of the moving surface. Mathematically, the fluid motion is governed by the two-phase incompressible Euler equations with vortex sheet data. By rescaling, we assume the density ρ⁺ of the inner fluid is fixed, while the density ρ^? of the outer fluid is set to ε. We prove that solutions of the free-boundary Euler equations in vacuum are obtained in the limit as ε → 0.