Quantitative method for analysis of monensin in soil, water, and urine by direct combination of single-drop microextraction with atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry

A simple and selective analytical method for the quantitative determination of low concentrations of monensin in soil, surface water, and human urine has been developed. Prior to atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) analysis, the samples were preconcentrated by using the single-drop microextraction (SDME) technique. Several factors that affect the analyte's extraction, including selection of solvent, microdrop volume, extraction time, and ionic strength, were investigated. Chloroform-toluene (1:1, v/v) was selected as the extraction solvent. Reliable results were obtained using dibenzo-30-crown-10-ether as an internal standard. The proposed method has been successfully applied for the determination of monensin in soil, surface water, and human urine spiked samples. Under the optimized conditions, the limits of quantification of the analyte in surface water, soil, and human urine were 6.7, 12.4 and 7.8 ng/mL, respectively. The intraday and interday precision variation and accuracy of the present method is within the acceptable ranges. The present method avoids the pre- and postderivatization of weak UV absorbing monensin determination using high performance liquid chromatography-ultraviolet detection (HPLC-UV). Furthermore, these techniques are time-consuming, nonreproducible at trace levels, and form undesirable products. The proposed SDME combined with AP-MALDI-MS is simple, fast, and selective for the determination of monensin in environmental and urine samples.     

Effect of Molecular Rotation on Vapor Phase Nucleation: Fullerenes C60 and C70

Abstract

The effect of rotational free energy of fullerenes C₆₀ and C₇₀ on homogeneous nucleation of crystals from vapor phase have been studied. Classical nucleation parameters have been estimated for the case of nucleation and crystal growth of C₆₀ and C₇₀ by Physical Vapor Transport (PVT) method under different supercooling in the range of 20–150 K, keeping the source temperatures constant. The result shows that the growth of large size single crystals is more feasible in the lower supercooling range. The effect of change in interfacial tension on the critical free energy of formation of the nuclei is also studied.     

Cloning and functional expression of Citrobacter amalonaticus Y19 carbon monoxide dehydrogenase in Escherichia coli

Carbon monoxide (CO) is highly toxic but is an abundant carbon source that can be utilized for the production of hydrogen (H₂). CO-dependent H₂ production is catalyzed by a unique enzyme complex composed of carbon monoxide dehydrogenase (CODH) and CO-dependent hydrogenase (CO–H₂ase), both of which contain metal cluster(s). In this study, CODH and the required maturation proteins from the novel facultative anaerobic bacterium Citrobacter amalonaticus Y19 were cloned and heterologously expressed in Escherichia coli. For functional expression of CODH in E. coli, only CooF (ferredoxin-like protein) and CooS (CODH), not the maturation proteins, were needed. The recombinant E. coli BL21(DE3)-cooFS showed a 3.5-fold higher specific CODH activity (4.9 U mg protein⁻¹) compared to C. amalonaticus Y19 (Y19) (1.4 U mg protein⁻¹). Purified heterologous CODH from the soluble cell-free extract of the recombinant E. coli showed a specific activity of 170.6 U mg protein⁻¹. Recombinant E. coli harboring Y19 CODH and maturation proteins did not produce H₂ from CO, suggesting that the native hydrogenases present in E. coli could not substitute the Y19 CO–H₂ase for CO-dependent H₂ production.     

Potassium Phosphate‐Catalyzed Chemoselective Reduction of α‐Keto Amides: Route to Synthesize Passerini Adducts and 3‐Phenyloxindoles

A chemoselective reduction of α‐keto amides to biologically important α‐hydroxy amides (mandelamides) by polymethylhydrosiloxane (PMHS) using 5 mol% potassium phosphate (K₃PO₄) as catalyst has been developed. This transition metal‐free protocol discloses excellent chemoselectivity for the ketone reduction of α‐keto amides in the presence of other reducible functionalities like ketone, nitro, halides, nitrile and amide. Also, the chemoselectively reduced α‐hydroxy amide has been derivatized to isocyanide‐free Passerini adducts. The N‐alkyl‐α‐hydroxy amides have been successfully converted to 3‐phenyloxindole derivatives by treatment with methanesulfonyl cholride and triethylamine.

     

Future carbon regulations and current investments in alternative coal-fired power plant technologies

We analyze how uncertain future US carbon regulations shape the current choice of the type of power plant to build. Our focus is on two coal-fired technologies, pulverized coal (PC) and integrated coal gasification combined cycle technology (IGCC). The PC technology is cheapest—assuming there is no need to control carbon emissions. The IGCC technology may be cheaper if carbon must be captured. Since power plants last many years and future regulations are uncertain, a US electric utility faces a standard decision under uncertainty. A company will confront the range of possible outcomes, assigning its best estimate of the probability of each scenario, averaging the results and determining the power plant technology with the lowest possible cost inclusive of expected future carbon related costs, whether those costs be in the form of emissions charges paid or capital expenditures for retrofitting to capture carbon. If the company assigns high probability to no regulation or to less stringent regulation of carbon, then it makes sense for it to build the PC plant. But if it assigns sufficient probability to scenarios with more stringent regulation, then the IGCC technology is warranted. We provide some useful benchmarks for possible future regulation and show how these relate back to the relative costs of the two technologies and the optimal technology choice. Few of the policy proposals widely referenced in the public discussion warrant the choice of the IGCC technology. Instead, the PC technology remains the least costly. However, recent carbon prices in the European Emissions Trading System are higher than these benchmarks. If it is any guide to possible future penalties for emissions in the US, then current investment in the IGCC technology is warranted. Of course, other factors need to be factored into the decision as well.     

探索BS25999国际性营运持续管理标准（BCM）

BS25999-2007是英国标准协会(BSI)所提出的国际性营运持续管理规范标准,其前身是2006年发布的BS 25999-1.企业在营运活动中断后的复原能力已被公认为营运策略的重要一环,因此,许多企业希望了解新的营运持续管理标准BS 25999-2007及该标准所界定的BCM(业务持续管理管理)流程.本文根据已发布的文件草案,列出相关信息,以协助读者更快地掌握该标准的精髓.     

Mechanical and Wear Properties of Al–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Metal Matrix Composites Fabricated by the Combined Effect of Stir and Squeeze Casting Method

The effects of nano particles on double shear strength and tribological properties of A356 alloy reinforced with Al₂O₃ nano particles of size 30 nm were investigated. The percentage inclusions of Al₂O₃ were varied from 0.5 to 1.5 wt%. The particles were added with stirring at 400 rpm and squeeze casting at 750 °C and pressure of 600 MPa in a squeeze casting machine. Comparison of the performance of as cast samples of A356/Al₂O₃ nano composite was conducted. The tribological properties of the samples were also investigated by pin-on-disk tests at 10, 30 and 50 N load, sliding speed 0.534 m/s and sliding distance 1100 m in dry condition. SEM images of microstructure analysis of the composite, Al₂O₃ (0.5 and 1 %) particles were well dispersed in the A356 alloy matrix. Partial agglomeration was observed in metal matrix composite with higher (1.5 %) Al₂O₃ particle contents. The nano dispersed composites containing 0.5 and 1 wt% of Al₂O₃ nano particles exhibited the highest double shear strength, lesser wear loss and coefficient of friction.     

Rhodium(III)‐Catalyzed in situ Oxidizing Directing Group‐ Assisted C?H Bond Activation and Olefination: A Route to 2‐Vinylanilines

A new and efficient method for the synthesis of 2‐vinylanilines from the reaction of arylhydrazine hydrochlorides with alkenes and diethyl ketone via a rhodium‐catalyzed C H activation is described. The oxidant‐free olefination reaction involves the in situ generation of an  N NCR¹R² moiety as the oxidizing directing group thus providing an easy access to 2‐vinylanilines.

     

Optimization of electric discharge machining using simulated annealing

This paper proposes an optimization methodology for the selection of best process parameters in electro-discharge machining. Regular cutting experiments are carried out on die-sinking machine under different conditions of process parameters. The system model is created using counter-propagation neural network using experimental data. This system model is employed to simultaneously maximize the material removal rate as well as minimize the surface roughness using simulated annealing scheme. Finally consistency of the method is tested with several initial trail values. Results are shown in the form of tables and figures.     

Cyber security in New Space

International Journal of Information Security - Developments in technologies, attitudes and investment are transforming the space environment, achieving greater accessibility for an increasing...