Spectroscopic studies on the inclusion complex of 2-naphthol-6-sulfonate with beta-cyclodextrin

The photophysical properties of 2-naphthol-6-sulfonate (2-NOH-6-S) in various solvents and in aqueous beta-cyclodextrin solution have been investigated. The fluorescence quantum yields in non-aqueous solvents are approximately 0.20+/-0.02, while in water the yield is higher. The fluorescence quantum yield in water was found to depend on the pH value of the medium and increases as the pH increase up to a pH value of 4.0 where it comes to be constant. Absorption and fluorescence measurements show 1:1 inclusion of 2-NOH-6-S in the beta-cyclodextrin cavity. The association constant of 2-NOH-6-S-beta-cyclodextrin complex based on fluorescence measurements was calculated using Benesi-Hildbrand relationship and found to be 330+/-30M(-1). (1)H NMR studies are used to confirm the inclusion and to provide information on the geometry of 2-NOH-6-S inside the cavity of beta-cyclodextrin.     

Verification of Mason and Smythe equations for electrical treeing breakdown at the tip of charged particle tracks in ECE polycarbonate detectors

There are two different equations to describe enhancement of field strength at the track tip in ECE polycarbonate detectors: Mason and Smythe equations. In order to evaluate the equations, PC detectors with different thicknesses were exposed to 1 MeV alpha and/or fast neutron. The response of the detectors was studied as a function of applied voltage and average field strength. The ratio of critical voltages for different detectors was estimated experimentally and compared with calculated values. The experimental results are in good agreement with Smythe's equation. The results show that the track density and mean track diameter in the different detectors have the same behaviour, when the macroscopic field strength increases, and also that the field strength at the tip of tracks is proportional to macroscopic field strength.     

New adjuvant design using layered double hydroxide for production of polyclonal antibodies in radioimmunoassay techniques

Various adjuvants have been used to enhance the immune response against specific antigens. So the objective of this work describes the immune stimulating activity of layered double hydroxide (LDH) particles incorporate with mineral oil as a new formulation of adjuvant as compared to known Freund’s adjuvant for production of alpha-fetoprotein polyclonal antibody (anti-AFP) for estimation of alpha fetoprotein (AFP) in human serum by radioimmunoassay technique. In this concern, the study comprised two groups of white New Zealand rabbits, 2?2.5 kg body weight and each group comprised three rabbits. The first group vaccinated with AFP antigen emulsified with Freund’s adjuvant and the second group vaccinated with AFP antigen emulsified with LDH formulation. The obtained data show that the highest displacement using LDH adjuvant reached (74.2, 61.7 and 66.5 %) while the corresponding values with Freund’s adjuvant recorded (64.8, 60.3 and 54.6 %) which indicates that the use of LDH adjuvant as a cellular vehicle is a more suitable choice. Also, the preparation of AFP tracer using lactoperoxidase oxidation method and its purification using gel chromatography on PD-10 column were carried out. Different factors affecting the optimization of the assay process were studied. Validation testes of the assay were carried out. The reproducibility as measured by the intra- and inter- assay variations is satisfactory. The recovery and dilution testes indicated accurate calibration and appropriate matrix. The present technique agreed well with the currently used commercial kit (Siemens, IRMA kit). In conclusion, the liquid phase double antibody RIA technique proved to be sensitive, specific, precis and accurate for routine laboratory use.     

Micellar catalysis by perfluorooctanoic acid

Rates of acidic hydrolysis of hexano-, octano-, and decanohydroxamic acids and of 4-bromophenylaceto- and phenylacetohydroxamic acids have been determined in aqueous perfluorooctanoic acid—a reactive counterion surfactant system. Typical micellar catalysis was observed for the hydrolyses of the n-alkyl hydroxamic acids but not for the arylacetohydroxamic acids. The Arrhenius activation energy for hydrolysis of octano-hydroxamic acid is smaller above the cmc of the surfactant than it is below the cmc.     

Structural, magnetic and electronic transport properties of MnxGe1−x/Ge(0 0 1) films grown by MBE at 350 °C

We report on the structural, magnetic and electronic transport properties of thin Mn_xGe_1−x films grown at 350 °C. Isolated Mn₅Ge₃ nanoclusters, about 100 nm in size, were formed at the top surface of the film, dominating the magnetic properties of the whole film. Electronic transport properties show Mn doping effect indicating the presence of substitutional Mn ions dispersed in the Ge host, contributing to the formation of a Mn_xGe_1−x diluted phase. Electrical behaviour indicates a saturation effect with the raise of the nominal Mn concentration in the film, above x ≅ 0.03.