Determination of bismuth, indium and lead in geological samples by electrothermal AAS Part 2. Comparative study of palladium and molybdenum containing chemical modifiers*

A comparative and systematic study has been carried out of the effects of palladium and molybdenum containing chemical modifiers, such as Pd + Rh, Pd + Pt, Pd + Ru, Pd + Rh + Pt, Pd + Rh + Ru, Mo + Pd, Mo + Rh, Mo + Ru and Mo + Pt and additionally tartaric acid (TA) as a reducing agent together with mixed modifiers for the thermal stabilization of Bi, In and Pb in a Zeeman electrothermal atomic absorption spectrometer (ETAAS). The effect of the mass ratios of the mixed modifier components on the maximum pretreatment temperature for the analytes has been determined. The modifier mixtures of Pd + Rh + Pt, Mo + Pd + TA and Mo + Pt + TA were found to be especially powerful for the determination of Bi, In and Pb. These mixed modifiers could increase the ashing temperatures of the analytes up to 1250–1400° C. They were applied to the determination of Bi and Pb in dissolved geological reference samples and accuracy and precision of the method were thereby enhanced. The percent relative error was decreased from 20.0 to 0.4 for Bi and from 10.5 to 0.3 for Pb, depending on the sample type. Received: 9 May 1997 / Revised: 19 August 1997 / Accepted: 20 August 1997     

Cognitive impairment related changes in the elemental concentration in the brain of old rat

In order to evaluate the elemental concentration as a function of learning and memory deficiency, six different structures of the brain were analyzed by total reflection X-ray fluorescence spectrometry with synchrotron radiation (SR-TXRF). To evaluate the cognitive processes, the animals were tested in an adaptation of the Morris water maze. After the test, the animals were divided into two groups: cognitively healthy (control group) and cognitively impaired. The measurements were carried out at XRF beam line at Light Synchrotron Brazilian laboratory, Campinas, Brazil. The following elements were identified: Al, P, S, Cl, K, Ca, Ti, Cr, Fe, Cu, Zn, Br and Rb. K concentration was higher in all regions of the brain studied for control group than the cognitively impaired group. Moreover, the control group presented higher levels for P and Fe in the entorhinal cortex, in the temporal cortex (only P), in the hypothalamus and in the thalamus, than the cognitively impaired group. Br concentration in the animals which presented cognitive impairment was three times larger in the hypothalamus and thalamus, twice larger in temporal cortex and higher in visual cortex than the cognitively healthy group. Cu was more remarkable in the hippocampus and hypothalamus from the animals with cognitive impairment than the control group.We observed that the cognitively impaired group presented highest concentrations of Br and Cu in certain areas than the control group, on the other hand, this group presented highest levels of K for all brain areas studied.     

Synthesis and characterization of oligosalicylaldehyde-based epoxy resins

The synthesis of a new epoxy resin of oligosalicylaldehyde by the reaction with epichlorohydrin is reported. New resin’s epoxy value and chlorine content were determined and found to be 25% and 1%, respectively. The characterization of the new resin was instrumented by FTIR, ¹H NMR, scanning electron microscopy, and thermal gravimetric analyses. TGA results showed that the cured epoxy resin has a good resistance to thermal decomposition. The mass losses of cured epoxy resin were found to be 5%, 10%, 50% at 175°C, 240°C, and 400°C, respectively. On the curing procedure the resin was cured with polyethylenepolyamine at 25 °C for 8 h and 100°C for 1.5 h. The FTIR spectrum of new epoxy resin gave the peak of oxirane ring at ṽ = 918 cm⁻¹. In memory of Professor Dr. Adalet R. Vilayetoğlu     

Synthesis and biological activity of new 2-amino-4-[3-methyl-3-(5,6,7,8-tetrahydro-2-naphthyl)cyclobutyl]thiazole derivatives

2-Amino-4-[3-methyl-3-(5,6,7,8-tetrahydro-2-naphthyl)cyclobutyl]thiazole was synthesized by reaction of 1-methyl-1-(5,6,7,8-tetrahydro-2-naphthyl)-3-chloroacetylcyclobutane with thiourea in ethanol, and its subsequent transformations afforded new derivatives which were tested in vitro for antibacterial activity against some bacteria using the disk diffusion technique.__________From Zhurnal Organicheskoi Khimii, Vol. 40, No. 12, 2004, pp. 1861–1865.Original English Text Copyright © 2004 by Koparr, Cansz, Ahmedzade.The original article was submitted in English.     

Protein secondary structure conformations and associated hydrophobicity scales

We have developed conformational preference functions and a hierarchy of algorithms that can evaluate the success of each hydrophobicity scale in predicting protein secondary conformation. The results of such evaluation are shown for fiftyfive different scales with respect to their ability to predict -helix, -sheet and coil structure in three testing sets of proteins: five integral membrane proteins, twelve -class and sixteen -class soluble proteins. Our scale of conformational parameters is the best predictor of secondary structure segments in membrane proteins and -class proteins. The success rate and correlation coefficient for -helix conformation in membrane proteins are 76% and 0.46 respectively, which is superior to the performance measures attained with other prediction schemes. Evaluation of solution hydrophobicity scales, often used to predict transmembrane segments in membrane proteins, indicated absence of correlation in prediction of helix segments and experimental results for the conformation of membrane proteins. Such scales have better performance (correlation coefficient around 0.30) in predicting sheet conformation in the -class proteins.     

Influence of chemical effect on the Kβ/Kα X-ray intensity ratios for calcium and potassium compounds

K_β/K_α X-ray intensity ratios of some K and Ca compounds were studied. The samples were excited by 5.96 keV γ-rays emitted from (50 mCi ⁵⁵Fe filtered annular) radioisotope source and characteristic K X-ray from the samples were measured by a Si(Li) detector, with a resolution of 0.16 keV at 5.9 keV. The experimental values were compared with the calculated theoretical values for K and Ca.     

Copper ring-disk microelectrodes: fabrication, characterization, and application as an amperometric detector for capillary columns

A novel approach to the fabrication of metal ring-disk (RD) microelectrodes is presented that employs flexible chemical vapor deposition (CVD) and electrode modification techniques. Specifically, the development of a copper ring-disk microelectrode is described utilizing a combination of CVD coating, electroetching, and electroplating. Initially, a 25 μm diameter tungsten wire is concentrically coated by CVD with an insulating layer of silica, a layer of tungsten metal, and finally, a second outer layer of silica. The copper surface was prepared by first creating micrometer cavities by electrochemical etching the tungsten in hydroxide solutions followed by electrodeposition of copper from aqueous solutions of Cu(II). Each step of the process was characterized by scanning electron microscopy, optical microscopy, and cyclic voltammetry, demonstrating the preparation of a viable metal-based dual ring-disk microelectrode system. For the purpose of demonstrating the concept of introducing specific selectivity into the device, amperometric detection of galactose in 0.1 M NaOH was performed at +0.60 V in bulk solution and after flow injection analysis in a capillary column.     

Double armed crown ethers and armed macrocycles as a new series of metal-selective reagents: a review

Various double armed crown ethers and related macrocycles are presented as metal-selective reagents characterized by macrocyclic ligands and metal-ligating sidearms. They exhibit unique metal binding and recognition functions via macroring-sidearm cooperative action. Since they form three dimensional complexes suitable for metal-sensing and separation, we can develop a new series of metal-selective reagents via armed macrocycle strategy. Polymerization and immobilization of the armed macrocycles further enhance the usefulness in analytical science. This review focuses primarily on the molecular design, host-guest chemistry, and analytical applications of the armed macrocycles, and clearly indicates that these macrocycles provide new options in designing a metal-selective reagent.     

Two-dimensional network formation of cardiac myocytes in agar microculture chip with 1480 nm infrared laser photo-thermal etching

We have developed a new method that enables agar microstructures to be used to cultivate cells and that allows cell network patterns to be controlled. The method makes use of non-contact three-dimensional photo-thermal etching with a 1480 nm infrared focused laser beam, which is strongly absorbed by water and agar gel, to form the shapes of agar microstructures. It allows microstructures to be easily formed in an agar layer within a few minutes, with cell-culture holes formed by the spot heating of a 100 mW laser and tunnels by the tracing of a 100 microm s(-1), 40 mW laser. We cultivated rat cardiac myocytes in adjacent microstructures and observed synchronized beating in them 90 min after they had made physical contact. Our results indicate that the system can make and use microstructures for cell-network cultivation in a minimal amount of time without any expensive microfabrication facilities or complicated procedures.     

Synthesis, characterization, catalytic, electrochemical and thermal properties of tetradentate Schiff base complexes

In this study, the Schiff base ligands H₂L¹–H₂L³ and their Cu^II, Co^II, Ni^II, Fe^III Ru^III and VO^IV complexes have been prepared and characterized by spectroscopic and analytical techniques. All the complexes are mononuclear. Keto-enol tautomeric forms of the ligands have been investigated in polar and apolar solvents. The ligands favor the keto-form in the C₇H₈ and C₆H₁₄. The C–C coupling reaction of the 2,6-di-t-butylphenol has been investigated by the Co^II and Cu^II complexes. Thermal properties of the complexes have been assessed using thermal techniques and similar properties were found. In the Fe^III and Ru^III complexes, firstly, the coordinated water molecule is lost from the complex; in the second step, the chloride ion leaves the molecule in the 300–350 °C temperature range. Finally, the complexes decompose to the appropriate metal oxide at the higher temperature ranges. The electrochemical properties of the complexes have been studied in the two different solvents (DMF and CH₃CN).