Orthogonal packing of enantiomerically pure helical silver coordination networks

The combination of the chiral tecton based on the (R)-6,6'-dibromo-1,1'-binaphthyl moiety bearing two isonicotinoyl groups with AgX (X = BF4-, CF3SO3-, PF6-) leads to the formation of enantiomerically pure helical strands with orthogonal packing in the rare space group I2(1)3.     

On-line dynamic fractionation and automatic determination of inorganic phosphorus in environmental solid substrates exploiting sequential injection microcolumn extraction and flow injection analysis

Sequential injection microcolumn extraction (SI-MCE) based on the implementation of a soil-containing microcartridge as external reactor in a sequential injection network is, for the first time, proposed for dynamic fractionation of macronutrients in environmental solids, as exemplified by the partitioning of inorganic phosphorus in agricultural soils. The on-line fractionation method capitalises on the accurate metering and sequential exposure of the various extractants to the solid sample by application of programmable flow as precisely coordinated by a syringe pump.

Three different soil phase associations for phosphorus, that is, exchangeable, Al- and Fe-bound, and Ca-bound fractions, were elucidated by accommodation in the flow manifold of the three steps of the Hieltjes–Lijklema (HL) scheme involving the use of 1.0 M NH₄Cl, 0.1 M NaOH and 0.5 M HCl, respectively, as sequential leaching reagents. The precise timing and versatility of SI for tailoring various operational extraction modes were utilized for investigating the extractability and the extent of phosphorus re-distribution for variable partitioning times.

Automatic spectrophotometric determination of soluble reactive phosphorus in soil extracts was performed by a flow injection (FI) analyser based on the Molybdenum Blue (MB) chemistry. The 3σ detection limit was 0.02 mg P L⁻¹ while the linear dynamic range extended up to 20 mg P L⁻¹ regardless of the extracting media. Despite the variable chemical composition of the HL extracts, a single FI set-up was assembled with no need for either manifold re-configuration or modification of chemical composition of reagents.

The mobilization of trace elements, such as Cd, often present in grazed pastures as a result of the application of phosphate fertilizers, was also explored in the HL fractions by electrothermal atomic absorption spectrometry.     

Nano-structured lead dioxide as a novel stationary phase for solid-phase microextraction

The first study on the high efficiency of nano-structured lead dioxide as a new fiber for solid-phase microextraction (SPME) purposes has been reported. The size of the PbO2 particles was in the range of 34-136 nm. Lead dioxide-based fibers were prepared via electrochemical deposition on a platinum wire. The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using headspace solid-phase microextraction (HS-SPME) mode coupled to gas chromatography-flame ionization detection (GC-FID). The results obtained proved the suitability of proposed fibers for the sampling of organic compounds from water. The extraction procedure was optimized by selecting the appropriate extraction parameters, including preparation conditions of coating, salt concentration, time and temperature of adsorption and desorption and stirring rate. The calibration graphs were linear in a concentration range of 0.1-100 microg l(-1) (R2 > 0.994) with detection limits below 0.012 microg l(-1) level. Single fiber repeatability and fiber-to-fiber reproducibility were less than 10.0 and 12.5%, respectively. The PbO2 coating was proved to be very stable at relatively high temperatures (up to 300 degrees C) with a high extraction capacity and long lifespan (more than 50 times). Higher chemical resistance and lower cost are among the advantages of PbO2 fibers over commercially available SPME fibers. Good recoveries (81-108%) were obtained when environmental samples were analyzed.     

Synthesis and characterization of nanostructured-segmented block copolyetheramide based on nylon6 and poly(ethylene oxide)

<正>Segmented block copolymer based on nylon6(N6) and polyethylene oxide(PEO) with stochiometric ratio was synthesized via a two-step process.The first step represents end capping of N6 in the presence of adipic acid leading to carboxy terminated N6,and the second one is polycondensation of the latter product with PEO in the presence of catalyst and thermostabilizer to form a high molecular weight multi-block copolymer.Several methods were applied to characterize the synthesized copolymer such as Fourier transform infrared spectroscopy,proton nuclear magnetic resonance spectroscopy,differential thermal analysis,differential scanning calorimetry,X-ray diffraction and atomic force microscopy. The obtained results confirmed the multi-block structure for copolymer with a very high degree of micro-phase separation. Atomic force microscopy micrographs indicated that the morphology was the dispersion of high stiffness nanostructured polyamide(PA) domains in the amorphous region of PEO matrix,which can be very important in their performance for membrane processes.     

Extensions of some polynomial inequalities to the polar derivative

Let p(z) be a polynomial of degree n and for any real or complex number α, let Dαp(z)=np(z)+(α−z)p^′(z) denote the polar derivative of the polynomial p(z) with respect to α. In this paper, we obtain inequalities for the polar derivative of a polynomial having all its zeros inside or outside a circle. Our results shall generalize and sharpen some well-known polynomial inequalities.     

Liquid chromatographic determination of benomyl in water samples after dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method combined with solvolysis reaction for extraction of the carbamate fungicide benomyl as carbendazim from water samples is described. The method is based on the extraction of benomyl from acidified sample solution and its conversion into carbendazim via solvolysis reaction with DMF as organic solvent. The proposed DLLME method was followed by HPLC with fluorimetric detection for determination of benomyl. The proposed method has good linearity (0.998) with wide linear dynamic range (0.01–25 mg/L) and low detection limit (0.0033 mg/L), making it suitable for benomyl determination in water samples.     

Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L⁻¹) and low detection limit (0.03 μg L⁻¹), which makes it suitable for determination of PCP in water samples.      

The BV Formalization of Chern-Simons Theory on Deformed Superspace

In this paper we will study non-abelian Chern-Simons theory on a deformed superspace. We will deform the superspace in such a way that it includes the noncommutativity between bosonic and fermionic coordinates. We will first analyse the BRST and the anti-BRST symmetries of the Chern-Simons theory on this deformed superspace. Then we will analyse the extended BRST and the extended anti-BRST symmetries of this theory in the Batalin-Vilkovisky (BV) formalism. Finally, we will express these extended BRST and extended anti-BRST symmetries in extended superspace formalism by introducing new Grassmann coordinates.     

Diffraction phase microscopy with white light

We present white light diffraction phase microscopy (wDPM) as a quantitative phase imaging method that combines the single shot measurement benefit associated with off-axis methods, high temporal phase stability associated with common path geometries, and high spatial phase sensitivity due to the white light illumination. We propose a spatiotemporal filtering method that pushes the limit of the pathlength sensitivity to the subangstrom level at practical spatial and temporal bandwidths. We illustrate the utility of wDPM with measurements on red blood cell morphology and HeLa cell growth over 18 hours.