Zero-waste preparation of mixed oxides for submicromolar sensing of Bentazone pesticide

Necessity of having simple selective and robust methods for the analysis of environmentally relevant chemicals stimulates the development of new approaches to material preparation. Electrochemical sensing using electroactive substrates has proved efficient in the analysis of a wide range of pesticides and is widely used as a routine analytical method. Recently, mixed oxides showed promising electrocatalytic activity toward hazardous substrates. Prevalence of wet chemical methods in the synthesis of mixed oxides creates a methodological obstacle and inconvenience for their wide utilization. In this work we challenged the common preparation of mixed oxides with simple powder mixing and developed an electrode for bentazone detection with satisfactory detection limit (0.4 μM), recovery rate (≈104%), and a broad linearity range (1-45 μM). The proposed modified carbon paste electrode is highly selective and can be used for determination of bentazone in presence of interfering ions in water samples.

UHECR results of combined analyses of TA and Auger experiments

The origin of ultra-high-energy cosmic rays (UHECRs) is still unknown. Their sources are believed to be within the local universe (a few hundred megaparsecs), but deflections by intergalactic and Galactic magnetic fields prevent us from straightforwardly associating UHECRs to their sources based on their arrival directions, making their angular distribution mostly isotropic. At higher energies, the number of potential source candidates and the magnetic deflections are both expected to be smaller, but so is the available amount of statistics. Hence, it is interesting to perform searches for anisotropies using several different energy thresholds. With a threshold of 8 EeV a dipole modulation has been discovered, and with higher thresholds evidence is mounting for correlations with certain nearby galaxies. Neither of the two main UHECR detectors, the Pierre Auger Observatory and the Telescope Array project, has full-sky coverage. Full-sky searches require combining the datasets of both, and a working group with members of both collaborations has been tasked with this. We present an overview of the challenges encountered in such analyses, recent results from the working group, possible ways of interpreting them, and an outlook for the near future.

Nonlocal Reaction-Diffusion Equations in Biomedical Applications

Nonlocal reaction-diffusion equations describe various biological and biomedical applications. Their mathematical properties are essentially different in comparison with the local equations, and this difference can lead to important biological implications. This review will present the state of the art in the investigation of nonlocal reaction-diffusion models in biomedical applications. We will consider various models arising in mathematical immunology, neuroscience, cancer modelling, and we will discuss their mathematical properties, nonlinear dynamics, resulting spatiotemporal patterns and biological significance.

Adsorption and survival of faecal coliforms, somatic coliphages and F-specific RNA phages in soil irrigated with wastewater

This study was carried out to compare the adsorption and survival of faecal coliforms, somatic coliphages and F-specific RNA phages in soil irrigated with wastewater. Adsorption isotherms showed that 3-10x more faecal coliforms than somatic coliphages were adsorbed from wastewater onto soil. The adsorption behavior of F-specific RNA phages was intermediate between those of these two microorganisms. In wastewater, the inactivation factor of somatic coliphages at 8-22 degrees C was 5-7 lower than those of faecal coliforms. F-specific RNA phages have a decrease close to faecal coliforms. In soil, at temperatures of 8-22 degrees C and at moistures of 15-35%, somatic coliphages survived longer than the two other microorganisms. These results seemed to be confirmed by the soil column experiments. The rate of inactivation of all microorganisms was lower in soil than in wastewater and depended extensively on soil temperature and moisture content. Survival was optimal at low temperature (8 degrees C) and low moisture content (15%). Thus, somatic coliphages seemed to be a better indicator of faecal contamination than faecal coliforms under our experimental conditions and based only on the two criteria tested (survival and adsorption). Somatic coliphages were able to contaminate the soil over greater distances and survive better in both wastewater and soil than faecal coliforms. These results need to be confirmed by studies on several soil columns using different kinds of soil and different kinds of wastewater.

Compression of picosecond pulses from diode lasers using a modified grating-pair compressor

Optical pulses from gain-switched diode lasers were compressed using a grating-pair compressor containing an internal telescope. Original pulses of 20-30 psec were compressed to 5-7 psec, with the largest compression factor ~5. Diode-laser pulse compression is well modeled by transmission of Gaussian pulses with excess bandwidth through a dispersive system.

Theory of bistability in two-segment diode lasers

Optical bistability in two-segment diode lasers with inhomogeneous injection is considered. Analytical solution of the rate-equation model gives a simple bistability condition. Slower carrier recombination in the absorber relative to the gain region is required for bistability when the gain and the absorber optical cross sections are equal. Carrier lifetimes, switch-on and switch-off powers, and currents are investigated for these bistable lasers.

Expressions for the coupling coefficient of a rectangular-waveguide directional coupler

More-accurate expressions are obtained for the coupling coefficient of the dielectric rectangular-waveguide directional coupler. The previous expressions may overestimate the coupling coefficient by as much as a factor of 2 in some cases of interest.