An Expedient Approach to the Benzopyran Core: Application to Synthesis of the Natural Products(±)-Xyloketals and(±)-Alboatrin

A mild and efficient protocol for the synthesis of the benzopyran ring has been described and a series of chromans compounds is reported, the yield is from 72% to 95%. The diadduct tended to angular product and showed good regioselectivity. This strategy was applied for the benzopyran derived natural products (±)‐xyloketals and (±)‐alboatrin. The crystal of compound 9 exhibited centro‐symmetric space group, containing two isomers in one unit. The relative configurations were 1R,10R,15S and 34S,22R,30S, respectively.     

Evaluation of two methods to minimize the anticlastic curvature of cylindrical bent crystals

A scanning dynamically focusing sagittal X‐ray monochromator accepting 3 mrad × 0.1 mrad from a 6 T wiggler has been designed for XAFS measurements. In the energy range 4.1–12.4 keV, the slope error of the second cylindrical crystal caused by anticlastic bending must be less than 1/5 of the Darwin width of the crystal or the photon flux will decrease drastically. Two methods to minimize the anticlastic bending are proposed. Thin crystals with stiffening ribs and thin crystals with an aspect ratio equal to the `golden value' are evaluated by finite‐element analysis and by long‐trace‐profiler characterization. Both approaches are satisfactory, but the `golden value' approach is preferred in this case for the second crystal of the new monochromator not only because it is easy to manufacture but also because the surface is smoother than the ribbed crystal.     

Large-scale controllable patterning growth of aligned organic nanowires through evaporation-induced self-assembly

Organic one-dimensional nanostructures are attractive building blocks for electronic, optoelectronic, and photonic applications. Achieving aligned organic nanowire arrays that can be patterned on a surface with well-controlled spatial arrangement is highly desirable in the fabrication of high-performance organic devices. We demonstrate a facile one-step method for large-scale controllable patterning growth of ordered single-crystal C(60) nanowires through evaporation-induced self-assembly. The patterning geometry of the nanowire arrays can be tuned by the shape of the covering hats of the confined curve-on-flat geometry. The formation of the pattern arrays is driven by a simple solvent evaporation process, which is controlled by the surface tension of the substrate (glass or Si) and geometry of the evaporation surface. By sandwiching a solvent pool between the substrate and a covering hat, the evaporation surface is confined to along the edge of the solvent pool. The geometry of the formed nanowire pattern is well defined by a surface-tension model of the evaporation channel. This simple method is further established as a general approach that is applicable to two other organic nanostructure systems. The I-V characteristics of such a parallel, organic, nanowire-array device was measured. The results demonstrate that the proposed method for direct growth of nanomaterials on a substrate is a feasible approach to device fabrication, especially to the fabrication of the parallel arrays of devices.     

Synthesis and Characterization of [Ar′GaC(Ph)CH]2 and K2[Ar′GaC(Ph)CH]2⋅OEt2: From Digallene to Digallacyclohexadiene to Digallatabenzene

On a plane : Addition of PhCCH to Ar′GaGaAr′ (Ar′=2,6‐(2,6‐iPr₂C₆H₃)₂C₆H₃) yielded the 1,4‐digallacyclohexadiene [{Ar′GaC(Ph)CH}₂] ( 1 ), which afforded the 1,4‐digallatabenzene dianion [Ar′GaC(Ph)CH]₂^2? ( 2 ) upon reduction with potassium (see scheme; C gray, Ga green, K blue). Structural parameters, DFT calculations, and ¹H NMR spectroscopy support aromatic character of 2 .

     

Effect of substrate temperature on few-layer graphene grown on Al2O3 (0 0 0 1) via direct carbon atoms deposition

Few-layer graphene (FLG) was grown on Al₂O₃ (0 0 0 1) substrates at different temperatures via direct carbon atoms deposition by using solid source molecular beam epitaxy (SSMBE) method. The structural properties were characterized by reflection high energy electron diffraction (RHEED), Raman spectroscopy and near-edge X-ray absorption fine-structure (NEXAFS). The results showed that the FLG started to form at the substrate temperature of 700 °C. When the substrate temperature increased to 1300 °C, the quality of the FLG was the best and the layer number was estimated to be less than 5. At higher substrate temperature (1400 °C or above), the crystalline quality of the FLG would be deteriorated. Our experiment results demonstrated that the substrate temperature played an important role on the FLG layer formation on Al₂O₃ (0 0 0 1) substrates and the related growth mechanism was briefly discussed.     

Approach to group decision making based on determining the weights of experts by using projection method

The aim of this paper is to present a new approach for determining weights of experts in the group decision making problems. Group decision making has become a very active research field over the last decade. Especially, the investigation to determine weights of experts for group decision making has attracted great interests from researchers recently and some approaches have been developed. In this paper, the weights of experts are determined in the group decision environment via projection method. First of all, the average decision of all individual decisions is defined as the ideal decision. After that, the weight of expert is determined by the projection of individual decision on the ideal decision. By using the weights of experts, all individual decisions are aggregate into a collective decision. Then an ideal solution of alternatives of the collective decision, expressed by a vector, is determined. Further, the preference order of alternatives are ranked in accordance with the projections of alternatives on the ideal solution. Comparisons with an extended TOPSIS method are also made. Finally, an example is provided to illustrate the developed approach.     

Transfer color to night vision images

Natural color appearance is the key problem of color night vision field. In this paper, the color mood of daytime color image is transferred to the monochromic night vision image. This method gives the night image a natural color appearance. For each pixel in the night vision image, the best matching pixel in the color image is found based on texture similarity measure. Entropy, energy, contrast, homogeneity, and correlation features based on co-occurrence matrix are combined as texture similarity measure to find the corresponding pixels between the two images. We use a genetic algorithm (GA) to find the optimistic weighting factors assigned to the five different features. GA is also employed in searching the matching pixels to make the color transfer algorithm faster. When the best matching pixel in the color image is found, the chromaticity values are transferred to the corresponding pixel of the night vision image. The experiment results demonstrate the efficiency of this natural color transfer technique.     

Biomimetic RNA‐Silencing Nanocomplexes: Overcoming Multidrug Resistance in Cancer Cells

RNA interference (RNAi) is an RNA‐dependent gene silencing approach controlled by an RNA‐induced silencing complex (RISC). Herein, we present a synthetic RISC‐mimic nanocomplex, which can actively cleave its target RNA in a sequence‐specific manner. With high enzymatic stability and efficient self‐delivery to target cells, the designed nanocomplex can selectively and potently induce gene silencing without cytokine activation. These nanocomplexes, which target multidrug resistance, are not only able to bypass the P‐glycoprotein (Pgp) transporter, due to their nano‐size effect, but also effectively suppress Pgp expression, thus resulting in successful restoration of drug sensitivity of OVCAR8/ADR cells to Pgp‐transportable cytotoxic agents. This nanocomplex approach has the potential for both functional genomics and cancer therapy.     

Adsorption behavior of cadmium ion onto synthetic ferrihydrite: effects of pH and natural seawater ligands

Batch experiments were conducted to study the adsorption behavior of cadmium ion onto the synthetic ferrihydrite. The adsorbent was characterized using X-ray diffraction and N₂ adsorption–desorption measurements. The effects of pH value and the major seawater anions (nitrate, carbonate, chloride and sulphate) at their natural concentrations on the adsorption of cadmium ion were investigated. The results showed that the adsorption of cadmium ion was highly pH-dependent and suppressed in the presence of chloride, sulphate and nitrate, while carbonate was found to enhance the adsorption of cadmium ion over the examined range of 4.0–7.5. The maximum percentage of cadmium ion adsorbed can reach 89.96 % at pH 7.5. It is proposed that the competition for binding sites played a key role in the reduction of cadmium ion adsorption by nitrate, chloride and sulphate. X-ray diffraction spectroscopic data for cadmium adsorbed on ferrihydrite showed that CdCO₃(s) was formed on ferrihydrite; the formation of CdCO₃ precipitation or surface precipitation in carbonate system may be the reason for the increase of cadmium adsorption.     

Preparation of Ce‐doped TiO2 Hollow Fibers and Their Photocatalytic Degradation Properties for Dye Compound

Cerium‐doped titanium dioxide (TiO₂) with a hollow fiber structure was successfully prepared using ammonium ceric nitrate and tetrabutyltitanate as precursors and cotton fiber as the template. The effects of cerium (Ce)‐doping on the crystallite sizes, crystal pattern, and optical property of the prepared catalysts were investigated by means of techniques such as scanning electron microscopy (SEM), X‐ray diffraction (XRD), BET surface area, and UV‐vis diffuse absorption spectroscopy. SEM observation showed that the prepared TiO₂ fibers possessed fibrous shape inherited from the cotton fiber and had a hollow structure. As confirmed by XRD and UV‐vis diffuse absorption spectroscopy examinations, Ce‐doping restrained the growth of grain size and extended the photoabsorption edge of TiO₂ hollow fiber into the visible light region. The present photocatalyst showed higher photocatalytic reactivity in photodegradation of highly concentrated methylene blue (MB) solutions than pure TiO₂ under UV and visible light, and the amount of Ce‐doped significantly affected the catalytic property. In the experiment condition, the photocatalytic activity of 0.5 mol% Ce‐doped TiO₂ fiber was optimal of all the prepared samples. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed. The material was easily removed by centrifugal separation. Therefore, using the template method and by doping with cerium, TiO₂ may hopefully become a low‐energy consuming, high activity and green environmentally friendly catalytic material.