Novel Electrochemical Microsensor for Hydrogen Peroxide based on Iron‐Ruthenium Hexacyanoferrate Modified Carbon Fiber Electrode

Novel electrochemical microsensor based on mixed iron‐ruthenium hexacyanoferrate (FeRuHCF) modified carbon fiber microelectrode (CFME) is presented for voltammetric and amperometric measurement of hydrogen peroxide at physiological pH. The FeRuHCF coating was electrochemically deposited using a one step procedure onto the substrate carbon fiber microelectrode by cycling the potential between 0.0 and +1.0 V (vs. Ag/AgCl) in a solution containing all precursor salts. The microsensor displayed good stability in neutral and alkaline media and had a nonstop working lifetime of up to 12 hours. The amperometric response time varied from 5 to 15 s depending on the hydrogen peroxide concentration level. The newly developed electrochemical microsensor exhibited a highly linear behavior in the examined concentration range from 5 to 1000 μmol L^?1 (R²=0.999), an LoD (3σ) of 0.9 μmol L^?1, and a favorable reproducibility with a calculated RSD of 2.9% (n= 6) for 100 μmol L^?1 hydrogen peroxide, thus holding great promise for its further application in real samples and its exploitation in combination with biorecognition elements in advanced microbiosensor design.     

Intramolecular photocycloaddition of dioxenones with alkynes: formation of secondary photoproducts from cyclobutene photoadducts

[Reaction: see text] Intramolecular photocycloaddition of 4 leads to the formation of cyclobutene photoadduct 5. Secondary photoreaction of 5 then affords either cyclobutane 19 or the bridged product 7, as a function of R (H or TMS).     

Finite quotients of rings and applications to subgroup separability of linear groups

In this paper we apply results from algebraic number theory to subgroup separability of linear groups. We then state applications to subgroup separability of free products with amalgamation of hyperbolic -manifold groups.

     

Trapping of arsenite by mercaptopropyl-functionalized mesostructured silica with a wormhole framework

Thiol-functionalized mesostructured silica, prepared by direct assembly methods, is an effective trapping agent for the removal of arsenite from water.     

Widely tunable optical parametric generation in a photonic crystal fiber

We report on the observation of widely tunable optical parametric generation in a photonic crystal fiber. The frequency shift of the generated sidebands that arise from modulational instability is strongly dependent on the detuning of the pump from the fiber's zero-dispersion wavelength. We are able to demonstrate experimentally more than 450 nm of sideband tunability as we tune the pump wavelength over 10 nm. Excellent agreement has been found between the experimentally measured and theoretically predicted shifts.     

Permanent refractive-index modification in germanium-doped optical fibers by use of red light

We observed photoinduced birefringence in elliptical-core optical fibers by using a continuous-wave krypton-ion laser. We induced the birefringence by injecting 20 mW of 647-nm or 50 mW of 676-nm light into the fiber at 45 degrees to the slow axis. The rate of change of the refractive index was found to be proportional to the square of the average power. Polarization mode couplers written into the fibers have been stable for more than 2 years and can be erased by use of light polarized perpendicularly to the original writing beam.     

Time Series Forecasting Based on the Logistic Curve

This paper presents a class of models which are designed for forecasting the net sales of a product when the stock of that product is believed to be subject to a saturation level. The forecast function for the stock takes the form of a general modified exponential, a family which includes the logistic as a special case. However, framing the model in terms of the net increase in the product enables a link to be made between the traditional approach to forecasting based on non-linear trend curves and the approach based on ARIMA models.     

A reexamination of the acid catalyzed addition of ethanethiol to naphthoquinone

The reaction of ethanethiol with naphthoquinone under acidic conditions has been shown to proceed by addition to the olefin, analogous to other nucleophiles, and does not yield ketal products as previously reported.     

Comments on renormalization group series

In previous articles by Nauenberg and by Niemeijer and Ruijgrok, the renormalization group approach has been used to obtain series expansions for the free energies of certain one- dimensional spin systems. We investigate here the question of whether this method provides a fundamentally new way of approximating the largest eigenvalue of a transfer matrix or kernel. For the models mentioned above, this is not the case. The partial sums of the series are essentially equivalent to the free energies of a sequence of finite models of increasing size.