Silanization of glass in the making of ion-sensitive microelectrodes

The silanization of glass, particularly Pyrex, was studied using reaction conditions that might be applied in the fabrication of ion-sensitive microelectrodes of the liquid-membrane type. The efficacy was tested by measuring the hydrophobicity (contact angle) or electrical resistivity of the treated surface. Aminosilanes, such as trimethyl-(dimethylamino)-silane are better than chlorosilanes, the optimum temperature is 250–330°C, and the reaction comes near to completion in 5 min. Silanization of glass that is newly exposed (as in the pulling of a micropipette) is greatly improved if the surface is treated with acid. There is considerable variation from one kind of glass to another. A recipe for making double-barrelled ion-sensitive microelectrodes is given

Investigation of p53 codon72 polymorphism in oral squamous cell carcinoma (SCC) specimens and normal population by PCR

"nBackground and Aim: A single nucleotide polymorphism at codon 72 of the p53 gene alters the p53 protein structure and affects its activity. This polymorphism depends on geographic regions and race. Also its association with some cancers has been reported. The aim of this study was to investigate this polymorphism in well differentiated oral SCC and normal population in the city of Isfahan. "nMaterials and Methods: In this case-control study, 20 paraffin blocks of non metastatic and well differentiated oral SCC were selected from the archive of oral pathology department of dental school between 2001 and 2005. 20 whole blood samples from normal people were considered as control group. After DNA extraction, p53 codon 72 polymorphism was determined by polymerase chain reaction (PCR) technique using specific primers of Arg and Pro and agarose gel electrophoresis. Data were analyzed by Fisher's exact test with p<0.05 as the level of significance. "nResults: The prevalence of Arg/Arg , Arg/Pro and Pro/Pro genotypes in case group were 45%,45% and 10% respectively compared to 45%,50% and 5% in controls. There was no statistical significant difference in p53 codon 72 genotypes distribution between case and control groups. "nConclusion: Based on the results of this study, p53 polymorphism could not be considered as a genetic predisposing factor for oral SCC development in Isfahan

Light-induced valence-state switching in BaFCl:La and SrFCl:La

A tetragonal La[2+] center (symmetry C[4v]) was identified in single crystals of BaFCl and SrFCl doped with lanthanum with the aid of electron paramagnetic resonance (EPR)/electron-nuclear double resonance (ENDOR). This center forms a donor-acceptor couple with initially present F(F-) centers. Switching takes place by illumination of appropriate wavelength. The kinetics of the process was monitored by EPR as La[2+] and the unswitched F center are paramagnetic. The results of our experimental investigation of this kinetics are presented. A foregoing spectroscopic characterization of the La[2+] center allowed one to identify a d-d (the B[1]-E) transition, a charge-transfer band (for BaFCl at 10 940 cm[-1] and at 17 890 cm[-1], respectively) and to obtain a value of 710 cm[-1] for the spin-orbit coupling constant in the ground state. In order to narrow the choice of possible acceptor-donor partners a detailed EPR/optical search was further done to identify a number of lattice defects and oxygen centers—in addition to a La-oxygen molecular structure