Voltammetric,potentiometric and amperometric studies with a rotated aluminum wire electrode : A comparison of the baker and morrison cell with the raie.

In the amperometric determination of fluoride at the RAIE a half cell composed of 5% cadmium amalgam in equilibrum with a solution 1 M in cadmium sulfate and saturated with potassium chloride can be used as a reference electrode in a short-circuited cell instead of applying a potential of -0 75 V versus the saturated calomel electrode The standard addition method can be used in the presence of air, although removal of oxygen is recommended Using the Baker and Morrison electrode versus the above half cell and following their directions (10 ml solution, magnetic stirring) proportionality between current and fluoride concentration in a range between 1 · 10^-5 and 1 · 10^-4M was found in oxygen-free solutions Halides and perchlorates do not interfere. The standard addition technique can be used in the determination of fluoride in an unknown.     

Voltammetric,potentiometric and amperometric studies with a rotated aluminum wire electrode: Amperometric determination of fluoride with the raie

A simple and rapid amperometric method is described for the determination of traces of fluoride by measuring the anodic current at the RAIE at —0.75 V vs. SCE. In order to be independent of varying sensitivity of the RAIE, use is made of the standard addition technique. Proportionality between current and concentration is found between 0.2 and 6 p.p.m. of fluoride. Chloride, sulfate, nitrate, alkali and earth alkali ions do not interfere. Phosphate decreases the sensitivity but does not interfere. Aluminum ions interfere but can be made harmless by EDTA. Oxidising agents (including oxygen) must be removed. The method gives excellent results in potable and natural waters.     

Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

Voltammetric,potentiometric and amperometric studies with a rotated aluminum wire electrode: Voltammetric behavior of the r.al.e.

A rotated aluminum wire electrode (R.Al.E.) is described for the determination of voltammograms and potentials. An aluminum electrode is highly polarizable both cathodically and anodically. Of all ions tested only hydroxyl and fluoride ions depolarize it anodically at highly negative potentials. In the absence of fluoride it is not a pH electrode, but it is a pOH electrode in the presence of an excess of hydroxyl ions. Fluoride in acid medium and hydroxyl ions yield well defined anodic diffusion currents. In the absence of fluoride or of an excess of hydroxyl ions the potential is ill defined. In acid medium a trace of fluoride (2.10^-5M or 0.4 p.p.m.) causes the potential to become approximately 600 mV more negative than in the absence of fluoride. At a pH greater than j l the potential varies 66 mV per unit change of pH.     

Voltammetric,potentiometric and amperometric studies with a rotated aluminum wire electrode : Amperometric titration of fluoride with aluminum

The rotated aluminum electrode is a suitable indicator electrode in the amperometric titration of fluoride, Fluoride in concentrations varying between 1.10^-4 and 2.10^-3M was titrated with a standard aluminum nitrate solution in aqueous buffer solutions (pH between 3.6 and 46) Equilibrium was established within 15 mim. The fluoride-aluminum ratio at the (true) end-point was found to increase from 2 2 in 10^-4M fluoride to 28 in. 2.10^-3M fluoride. The titration calculated from the stability constants of the various aluminum-fluoride complexes were found to be in excellent agreement with the experimental curves.From a practical point of view titration in an acetate buffer in 50% alcohol in the presence of 0 5 M potassium or sodium nitrate is recommended. The fluoride-aluminum ratio at the end-point was found to be 5 9 ± 0 1 and independent of the fluoride concentration.     

Effect of substrate temperature on electrical and magnetic properties of epitaxial La1−x Pb x MnO3 films

Epitaxial La_1−x Pb _x MnO₃ (LPMO) thin films, grown on (100) SrTiO₃ substrates by laser ablation technique at different temperatures between 600 and 850°C, have been characterized for electrical and magnetic properties. The temperature dependence of resistivity showed that the metal-insulator transition temperature (T _MI) decreases with increasing substrate temperature, which has been attributed to decrease in Pb content in the filsm. The YBa₂Cu₃O _x /La_1−x MnO₃ heterostructures, exhibiting both superconductivity and ferromagnetism, have been fabricated.