A new generation of cyanide ion-selective membranes for flow injection application: part II. Comparative study of cyanide flow-injection detectors based on thin electroplated silver chalcogenide membranes

Using induced cathodic electrodeposition a number of silver chalcogenide thin layer membranes of non-trivial composition have been synthesized and their performance as ion-selective flow-injection potentiometric detectors (FIPDs) for free cyanide has been critically estimated in the context of the stringent requirements for toxic cyanide environmental monitoring. AgSCN/Ag₂S, Ag₂S, Ag_2+δSe, Ag_2+δSe_1−xTe_x (0 < δ < 0.25 and x ≈ 0.13), Ag₂Se and Ag₂Se_1−xTe_x electroplated membranes were selected for the present performance-based comparative study in order to obtain a feedback information about the effect of membrane composition. Both silver selenide and Te-doped silver selenide membranes, irrespective of their stoichiometry with respect to silver, exhibit the lowest detection limit for CN⁻ (52 ppb) with linear double-Nernstian response down to 130 ppb. The type of chalcogene anion in the membrane composition proves to exert dominant effect on the general performance characteristics of the newly developed FIPDs. The silver stoichiometry (intrinsic defects factor) and the inclusion of Te-dopant (extrinsic defects factor) have more pronounced effect on the profile of the output signal and exert moderate control on the detectors selectivity and baseline stability. This new generation of CN⁻—ion-selective membranes for FIPDs exhibits high selectivity against the common interferents present in cyanide effluents such as SCN⁻, S₂O₃²⁻, Cl⁻ and do not get poisoned in the presence of S²⁻. Moreover, their long-term stability and signal reproducibility, which make redundant the regular day-to-day calibration, coupled with the cost-effective technology for membranes preparation and easy re-generation make them attractive candidates for incorporation into automated in-field devices for in situ cyanide toxic species monitoring.     

Synthesis of 1,3-aminonaphthols by diastereoselective Betti-type aminoalkylation of dihydroxy naphthalenes; diastereoselectivity,absolute configuration,and application

Dihydroxy naphthalenes have been applied in Betti-type solventless condensation between aldehydes and (S)-phenylethylamine as a chiral auxiliary. A series of chiral 1,3-aminonaphthols has been synthesized and isolated in diastereoisomerically pure form. The absolute configurations of the aminonaphthols synthesized have been determined by means of advanced NMR experiments and confirmed by X-ray crystallography. The new chiral aminonaphthols have been tested as pre-catalysts for the addition of diethyl zinc and alkynyl-Zn-reagents to aldehydes with enantioselectivities of up to 98% ee.     

Relativistically invariant equations (βμ∂μ+ϱ)Ψ(x)=0 with singular ϱ, and detβ0 ≠ 0

We study relativistically invariant equations (β^μ?_μ+?)Ψ(x)=0 with a singular ?. The absence of a simple relation between these equations and their “conjugate” $\text{((β}{}^{\mathrm{\mu }}\text{)}{}^1\text{?}{}_{\mathrm{\mu }}\text{? ?}{}^1\text{)?(x) = 0}$ is pointed out. Assuming that Ψ(x) transforms under an arbitrary finite-dimensional representation of ISL(2,C), the problem of existence is investigated. It is shown that the assumption detβ⁰ ≠ 0 implies: all β^μ are invertible and the representation of ISL(2,C) is even- dimensional. The difficulties in the general treatment of the problem are discussed. A particular class of equations is illustrated by several examples.     

Photoinduced dichroism in additively coloured KCl: Na at room temperature

Spectral and kinetic investigations of the reversible photoinduced dichroism in KCl : Na containing F_A and F_A + F_B centers are done. It is suggested that in presence of F_B centers the observed 〈100〉 and 〈110〉 dichroism is connected with the F_B(II) centers.     

Integrity of endothelium in cryopreserved human cornea

The aim of the present study was to elaborate an optimal method for cryopreservation of human donor cornea for transplantation and to follow the morphological changes in the structure of the endothelial cell layer using scanning electron microscopy (SEM). Sixteen groups, with four donor cornea each, were cryopreserved at cooling rates of 1 degree C per min and 5 degree C per min. Four cryoprotectants (glycerol, dimethyl sulfoxide, 1,2-propanediol, polyethylene glycol-400) in two concentrations (5% and 10% v/v) were prepared on the bases of medium Optisol GS supplied with 20% v/v human serum albumin. Four additional human cornea were used as controls. Endothelial cell recovery of the cornea after thawing and 24 hours culture, was calculated as a percent of the preserved recovered cells. Sufficient recovery of the endothelial cell layer, making the cornea suitable for transplantation was obtained using the cryoprotectants dimethyl sulfoxide and especially polyethylene glycol-400.     

Some examples on the use of atomic emission spectral analysis in analytical control of the preparation of oxide single crystals

The application of atomic emission spectrometric methods (AES) to the different stages of preparation of white sapphire and neodymium doped yttrium-aluminium garnet (Y₃Al₅O₁₂ : Nd³⁺) single crystals is discussed. Optimum conditions for d.c. arc analysis of NH₄Al(SO₄)₂·12H₂O and Al₂O₃ were established and the detection limits for impurities were determined. The applicability of laser spectral microanalysis for monitoring the distribution of neodymium in the single crystals is shown.     

Low-temperature graft copolymerization of triethylene glycol dimethacrylate with oligomeric butadiene rubber

The kinetics of low-temperature graft copolymerization of triethylene glycol dimethacrylate with Krasol LBH-3000 oligobutadiene rubber was studied in relation to the initial mixture composition at 20°C. The experimental kinetic data were compared with the results of calculation by the suggested equation. The copolymer compositions were calculated from the extraction data in relation to the initial mixture compositions. The binary copolymerization constants were calculated by the analytical and graphical methods.     

Novel pyridyl‐substituted coumarin and its perchlorate salt–crystal structure and spectroscopic properties

The novel pyridyl‐substituted coumarin ( 1 ) and its perchlorate salt ( 2 ) have been synthesized and their structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X‐ray diffraction for 2 , linear‐polarized solid state IR‐spectroscopy, UV‐spectroscopy, TGA, DSC, DTA, and positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The studied compound crystallizes in the centrosymmetric space group P‐1 and exhibits an infinite layered structure with the ions linked by means of the intermolecular N⁺H…OClO₃ (2.795 Å) interactions. The cations are disposed in a manner leading to a significant π‐stacking effect with a distance of 2.980 Å. The effects of N_py protonation on the optical and magnetic properties are elucidated by comparing the data of the protonated and neutral compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of T2 and LASER T2dagger image contrast in a rat model of acute cerebral ischemia

Previous studies have shown that T2(dagger)-weighted magnetic resonance images acquired using localization by adiabatic selective refocusing (LASER) can provide early tissue contrast following ischemia, possibly due to alterations in microscopic susceptibility within the tissue. The purpose of this study was to make a direct in vivo comparison of T2-, T2(dagger)- and diffusion-weighted image contrast during acute ischemia. Acute middle cerebral artery (MCA) occlusion was attempted in 14 rats using a modified Tamura approach incorporating electrocoagulation of the left MCA. T2(dagger)-weighted LASER images (Echo Time [TE]=108 ms), T2-weighted Carr-Purcell-Meiboom-Gill (CPMG) images (TE=110 ms) and diffusion-weighted images (b value=105 s/mm(2)) were acquired at 4 T within 1.5 h of ischemia onset. Tissue contrast in the MCA territory was quantified for histologically verified ischemic tissue (n=6) and in sham controls (n=4). T2(dagger)-weighted LASER images demonstrated greater contrast compared to the T2-weighted CPMG images, and more focal contrast compared to the diffusion-weighted images, suggesting different contrast mechanisms were involved.     

1,10-Phenanthrolinium hydrogensquarate monohydrate—A non-centrosymmetric structure from two non-chiral agents

Four different dimethyltin(IV) complexes of Schiff bases derived from 2-amino-3-hydroxypyridine and different substituted salicylaldehydes have been synthesized. The compounds, with the general formula [Me₂Sn(2-OArCHNC₅H₃NO)], where Ar = –C₆H₃(5-CH₃) [Me₂SnL¹], –C₆H₃(5-NO₂) [Me₂SnL²], –C₆H₂(3,5-Cl₂) [Me₂SnL³], and –C₆H₂(3,5-I₂) [Me₂SnL⁴], were characterized by IR, NMR (¹H and ¹³C), mass spectroscopy and elemental analysis. Me₂SnL³ was also characterized by X-ray diffraction analysis and shows a fivefold C₂NO₂ coordination with distorted square pyramidal geometry. H₃C–Sn–CH₃ angles in the complexes were calculated using Lockhart's equations with the ¹J(^117/119Sn–¹³C) and ²J(^117/119Sn–¹H) values (from the ¹H-NMR and ¹³C-NMR spectra). The in vitro antibacterial and antifungal activities of dimethyltin(IV) complexes were also investigated.