Exceedingly Fast Copper(II)‐Promoted ortho CH Trifluoromethylation of Arenes using TMSCF3

The direct ortho‐trifluoromethylation of arenes, including heteroarenes, with TMSCF₃ has been accomplished by a copper(II)‐promoted C? H activation reaction which completes within 30 minutes. Mechanistic investigations are consistent with the involvement of C? H activation, rather than a simple electrophilic aromatic substitution (S_EAr), as the key step.     

Turn-on fluorescence sensing of cyanide ions in aqueous solution简

A sensitive fluorescent probe, 2,2＇-bisbenzimidazole （L）, for CN has been developed. This structurally simple receptor displays great selectivity for the cyanide anion over other common inorganic anions in an aqueous environment. In addition, further study demonstrates the lower detection of the fluorescence response of the sensor to CN is in 10 9 mol/L range. Thus, the present probe should be applicable as a practical system for the monitoring of cyanide concentrations in aqueous samples.     

Microbial Leaching of Waste Solder for Recovery of Metal

This study proposes an environment-friendly bioleaching process for recovery of metals from solders. Tin-copper (Sn-Cu), tin-copper-silver (Sn-Cu-Ag), and tin-lead (Sn-Pb) solders were used in the current study. The culture supernatant of Aspergillus niger removed metals faster than the culture supernatant of Acidithiobacillus ferrooxidans. Also, the metal removal by A. niger culture supernatant is faster for Sn-Cu-Ag solder as compared to other solder types. The effect of various process parameters such as shaking speed, temperature, volume of culture supernatant, and increased solder weight on bioleaching of metals was studied. About 99 (±1.75)?% metal dissolution was achieved in 60 h, at 200-rpm shaking speed, 30 °C temperature, and by using 100-ml A. niger culture supernatant. An optimum solder weight for bioleaching was found to be 5 g/l. Addition of sodium hydroxide (NaOH) and sodium chloride (NaCl) in the bioleached solution from Sn-Cu-Ag precipitated tin (85?±?0.35 %) and silver (80?±?0.08 %), respectively. Passing of hydrogen sulfide (H₂S) gas at pH 8.1 selectively precipitated lead (57.18?±?0.13 %) from the Sn-Pb bioleached solution. The proposed innovative bioleaching process provides an alternative technology for recycling waste solders to conserve resources and protect environment.     

Production and Characterization of a Novel Thermostable Extracellular Agarase from Pseudoalteromonas hodoensis Newly Isolated from the West Sea of South Korea

A Gram-negative, aerobic, motile, rod-shaped, agarolytic bacterium, designated as H7, was isolated from a coastal seawater sample. This strain grows at pH 6.0–8.0, temperature of 15–40 °C, and at an NaCl concentration of 1–7 % (w/v). Ubiquinone-8 was the predominant respiratory quinone, and the DNA G+C content was 45.82 mol%. Analysis of the 16S rRNA sequence suggests that strain H7 belongs to the genus Pseudoalteromonas. DNA-DNA hybridization analysis showed DNA relatedness of as low as 55.42 and 40.27 % with its nearest phylogenetic neighbors Pseudoalteromonas atlantica IAM12927^T and Pseudoalteromonas espejiana NCIMB2127^T, respectively, which led us to name H7 Pseudoalteromonas hodoensis sp. nov. The type strain is H7^T (=DSM25967^T = KCTC23887^T). An agarase (AgaA7) was purified to homogeneity from the cell-free culture broth of H7 through many steps of chromatography. Purified AgaA7 had an apparent molecular weight of 35 kDa, with a distinct NH₂-terminal sequence of Ala-Asp-Ala-Thr-X-Pro (X, any amino acid) from the reported proteins, implying that it is a novel enzyme. The optimum pH and temperature for agarase activity were 7.0 and 45 °C, respectively. Thin-layer chromatography analysis, mass spectrometry, and enzyme assay using p-nitrophenyl-α/β-D-galactopyranoside revealed that AgaA7 is both an exo- and endo-type β-agarase that degrades agarose into neoagarotetraose, neoagarohexaose, and neoagarooctaose (minor).     

Visible-Light-Induced ortho-Selective Migration on Pyridyl Ring: Trifluoromethylative Pyridylation of Unactivated Alkenes

The photocatalyzed ortho-selective migration on a pyridyl ring has been achieved for the site-selective trifluoromethylative pyridylation of unactivated alkenes. The overall process is initiated by the selective addition of a CF₃ radical to the alkene to provide a nucleophilic alkyl radical intermediate, which enables an intramolecular endo addition exclusively to the ortho-position of the pyridinium salt. Both secondary and tertiary alkyl radicals are well-suited for addition to the C2-position of pyridinium salts to ultimately provide synthetically valuable C2-fluoroalkyl functionalized pyridines. Moreover, the method was successfully applied to the reaction with P-centered radicals. The utility of this transformation was further demonstrated by the late-stage functionalization of complex bioactive molecules.     

Packing of three copies of a graph

A graph of order n is said to be 3-placeable if there are three edge-disjoint copies of this graph in K_n. An (n, n − 1)-graph is a graph of order n with n − 1 edges. In this paper we characterize all the (n, n − 1)-graphs which contain no cycles of length 3 or 4 and which are 3-placeable. © 1996 John Wiley & Sons, Inc.     

A New Molecular Crystal: Urea Tartrate

Urea tartrate, CO(NH₂)₂(+)C₄H₆O₆ (hereafter abbraviated as UT) is reported for the first time. Large Single Crystals have been grown by the cooling method from aqueous solution. Some of its physical properties have been measured. The second harmonic generation of powder specimens is about three times larger than that of KH₂PO₄.     

Design of aromatic copolyesters for use in microelectronic devices

The next generation of microelectronic devices will require design of new kinds of polymers which are tailored to display a dielectric constant as low as 2.0, a coefficient of thermal expansion (CTE) which matches the metal circuitry as well as the silicon substrate, moisture and chemical resistance, and dimensional stability at processing temperatures of 300-400°C which are required to form an adhesive bond between laminates. In our program, we have made significant progress in all of these areas through the use of liquid crystalline copolyesters (LCP's) laminated with a newly developed crosslinkable copolyester. In this paper, data are presented which illustrate how films and coatings of either system can be made to adhere in the solid state by interchain transesterification reactions (ITR) at the interface. Ability to foam the crosslinkable copolyester films provides direct control over the dielectric constant. The effect of pore size and distribution on the dielectric constant will be discussed. The potential to dramatically increase the melting point of the LCP's through high temperature annealing is also discussed.     

Kinetic model of living radical polymerization

This work studies the kinetics of living radical polymerization by means of both the nonsteady state approach and the quasi-stationary state method. Expressions for the numberand weight-average degress of polymerization and the polydispersity index were derived. Numerical results show that the concentration of residual initiator seriously influences the polydispersity index of the resulting polymer. The calculated outcomes of the non-steady state approach are evidently different from those of the quasi-stationary state method when the magnitude of the rate constant of termination is comparable with that of the propagation rate constant, and the difference becomes negligible if the rate constant of the termination (k_t) is much larger than that of propagation (k_p). The polydispersity index of the resulting polymer increases with decreasing ratios of k_t to k_p or M_O to I_O (initial concentrations of monomer and initiator).     

天然气管道泄漏可调谐二极管激光遥感探测的研究

天然气管道泄漏不仅造成经济损失而且是危险之源。传统的天然气管道泄漏检测技术效率低、速度慢,难以满足实际应用的需要。近年来以近红外二极管激光吸收光谱为基础的光学传感器由于具有灵敏度高、体积小、重量轻和无需维护等优点而得到了广泛的应用。文章以可调谐二极管激光吸收光谱和谐波探测技术为基础进行天然气管道泄漏遥感探测技术的研究,采用二次谐波与一次谐波信号的比值作为系统浓度标定,结果显示浓度与比值之间具有较好的一致性。文章还就不同地形散射体对探测结果的影响进行了测量和分析,实验结果表明二次谐波与一次谐波信号比值标定技术对便携式二极管激光光学测量能够很好的满足实际应用的需要。