Preparation of a new solid state fluoride ion selective electrode and application

A new solid state fluoride ion selective electrode composed of 70% Ag₂S, 10% Cu₂S and 20% CaF₂ has been developed. An analytically useful potential change occurred, from 1 × 10⁻⁶ to 1 × 10⁻¹ M fluoride ion. The slope of the linear portion (1 × 10⁻¹-1 × 10⁻⁵ M) was about 26 ± 2 mV/10-fold concentration changes in fluoride. It was found that pH change between 1 and 8 had no effect on the potential of the electrode. There was no interference of most common cations such as K^+, Na⁺, Ca²⁺ and Mg²⁺ and anions such as Cl⁻, NO₃⁻, SO₄²⁻ and PO₄³⁻. The lifetime of the electrode was more than 2 years, when used at least 4-5 times a day, and the response time was about 60 s.The measurements were made at constant ionic strength (0.1 M NaNO₃) and at room temperature. This electrode has been used for the determination of fluoride ion in Ankara city tap water and in bottled spring water using standard addition method. The validation of the electrode has been made with a commercial fluoride ion selective electrode (Orion) and high consistency was obtained.     

N,N,N′,N′-Tetrakis(2-hydroxyethyl)ethylenediamine palladium(II) complex as efficient catalyst for the Suzuki/Miyaura reaction in water

A new water soluble palladium(II) complex (2) derived from N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (edteH₄) (1) was synthesized in high yield and characterized by ¹H, ¹³C, HMQC and COSY NMR spectroscopy. X-ray diffraction studies on a single crystal of 2 confirmed the cis square planar geometry; the edteH₄ ligand (1) is κ² (N,N)-coordinated with four pendant CH₂CH₂OH groups. This new complex [PdCl₂(edteH₄)] (2) and the previously synthesized triethanolamine complex [Pd(OCH₂CH₂N(CH₂CH₂OH)₂)₂] (3) were tested as catalysts for the Suzuki/Miyaura cross-coupling reaction of various aryl bromides with phenylboronic acid in water. Electronically activated aryl bromides, such as 4-bromoacetophenone and 4-bromobenzaldehyde undergo the cross-coupling with extremely high turnover numbers (TON) of up to 1,00,000 without organic solvent.     

Fluorescent aminoarylcyclotetraphosphazenes

In the present work, octachlorocyclotetraphosphazatetraene (1), N₄P₄Cl₈, is reacted with aniline (2), 1-napthylamine (4) and 2-aminoanthracene (6) to give octakis(arylamino)cyclotetraphosphazenes (3, 5 and 7). These cyclotetraphosphazene compounds (3, 5 and 7) have been fully characterized by elemental analysis, mass (MS), FT-IR, ¹H and ³¹P NMR spectroscopies. The molecular and crystal structures of 5 have been characterized by X-ray crystallography. The structure of 5 is monoclinic with the space group P21/c. The octakis(1-napthylamino)-(5) and octakis(2-aminoanthracene)-(7) cyclotetraphosphazene compounds have been synthesised for the first time in this study. The fluorescence properties of 3, 5 and 7 have been investigated in tetrahydrofuran (THF) and have been shown to have highly fluorescence behavior. This work also presents the quenching of arylamino substituted cyclotetraphosphazene derivatives (3, 5 and 7) by p-benzoquinone (BQ) or hydroquinone (HQ).     

Crystallographic and conformational analysis of two novel trans-azo benzene compounds

The molecular and crystal structure of (E)-2-Acetyl-4-(2-bromophenyldiazenyl)phenol (1) and (E)-2-Methyl-4-(o-tolyldiazenyl)phenol (2) were characterized and determined by single crystal X-ray diffraction method besides spectroscopic means. The periodic organization of 1 is stabilized by C–H···O type weak H-bond and Br···O type weak halogen bonding and thus, a two dimensional puckered network is established almost parallel to () the plane. Molecules of 2 are linked into C(7) chains generated by translation along the [1 0 1] direction with the aid of O–H···N type H-bonds, and these chains are strengthened by C–H···π interactions involving o-tolylphenol ring. Quantum chemical studies at B3LYP/6-311 ++G(d,p) level reveal that potential barrier of the compounds around Ar–N torsions is of double minimum character unless it is defected by the presence of o-substituent groups in the vicinity of the azo bridge. The results from crystallographic and quantum chemical studies suggest that azo benzene compounds may adapt non-planar geometry apart from the most stable planar conformation, which is located on the secondary minima of double potential barrier regarding rotational motion around Ar–N bonds.     

Non-Kolmogorov spectrum scintillation aspects of dark hollow and flat topped beams

The scintillation aspects of dark hollow (DH) and flat topped (FT) beams propagating in the turbulent atmosphere containing the non-Kolmogorov power spectrum are investigated. It is found that low scintillations will occur when the exponent of the power spectrum is just above the numeric value of 3. Initially, the rises in scintillations will take place as the exponent becomes larger, but later the scintillation reductions will be experienced as the exponent grows further, eventually minimum scintillations will be seen when the exponent has reached the value of 4. This will be the case, for scintillation variations against propagation distance, source size, wavelength, inner and outer scales of turbulence. Furthermore, it is found that at the small source sizes, DH beams will offer less scintillation than FT beams, while at the large source sizes, the reverse will be applicable.     

Histopathological Changes in Liver and Heart Tissue Associated with Experimental Ultraviolet Radiation A and B Exposure on Wistar Albino Rats

This study aims to evaluate the influences of ultraviolet radiation A and B ( UVA + B) exposure on the liver and heart organs of albino rats. Female Wistar Albino rats, whose hair of the dorsal skin was shaved, were exposed to a combined UVA + B radiation for 2 h/day, for 4 weeks in order to be compared with the control group. Histopathological findings in vital organs (liver and heart) were evaluated. Tissues were fixed in 10% buffered formalin (pH = 7.2) and embedded in paraffin. The histopathological findings were examined on the H&E stained sections with light microscopy. The results show that the liver and the heart were injured in the UVA + B group. Liver tissue in the UVA + B group showed minimal vacuolation, enlargement of hepatocytes and bile duct proliferation, and the heart tissue showed hibernomas; uniform large cells resembling brown fat with coarsely granular to multivacuolated cytoplasm that is eosinophilic or pale with a small central nucleus. The number of hibernoma cases was significantly higher in the UVA + B group compared with the control group (P = 0.021). The control group showed normal liver and heart histology with normal adipose tissue in the pericardium. As a result, UVA + B exposure has toxic effects, especially on the liver and the heart of Wistar albino rats. UV radiation may cause such adverse effects in humans. Therefore, protection against the harmful effects of UV radiation is of significant importance for skin and organs.     

On the Computation of the Macroscopic Tangent for Multiscale Volumetric Homogenization Problems

For the computation of the macroscopic tangent that is required in multiscale volumetric homogenization techniques, two methods are summarized. First, a condensation approach is followed where the linearity of variational terms associated with the penalty enforcement of boundary conditions is explored in order to extract a macroscopic tangent at any stage of the Newton–Raphson iterations of a microstructural testing procedure. As an alternative approach, a second method is explored that requires only the knowledge of infinitesimally close macroscopic deformation states. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetic adsorption of drugs using carbon nanofibers in simulated gastric and intestinal fluids

Two different classes of drugs were selected to test the adsorption capacity of carbon nanofibers as a greener new generation alternative adsorbent in simulated gastric and intestinal fluids. Kinetics of the promethazine and trimethoprim adsorption were analyzed using Lagergren first order and Pseudo second order models. Intraparticle diffusion graphs were also plotted to discuss the adsorption mechanism. Kinetic data showed the significance of boundary layer effect for both of the drugs and the presence of intraparticle diffusion as the other rate controlling step for the promethazine adsorption. Giles isotherms showed the high affinity of drug molecules to the adsorbent. Maximum adsorption capacity of drugs was calculated using Langmuir model as 18.35 and 41.15 mg/g for trimethoprim and 95.24 and 80.65 mg/g for promethazine in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), respectively. Trimethoprim adsorption was under favor of hydrophobic interaction and π-π dispersion interactions while promethazine adsorption was through cation exchange where the electrostatic attraction is an important force with the contribution of dispersion interactions.