Detection and Identification of Alkylating Agents by Using a Bioinspired “Chemical Nose”

Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical‐warfare agents. The detection and identification of alkylating agents is not a trivial issue because of their high reactivity and simple structure. Herein, we report on a new multispot luminescence‐based approach to the detection and identification of alkylating agents. In order to demonstrate the potential of the approach, seven π‐conjugated oligomers and polymers bearing nucleophilic pyridine groups, 1 – 7 , were adsorbed onto a solid support and exposed to vapors of alkylators 8 – 15 . The alkylation‐induced color‐shift patterns of the seven‐spot array allow clear discrimination of the different alkylators. The spots are sensitive to minute concentrations of alkylators and, because the detection is based on the formation of new covalent bonds, these spots saturate at about 50 ppb.     

Nonadiabatic chemical reaction triggered by electron photodetachment: an ab initio quantum dynamical study

Dynamics following electron photodetachment in a complex of a chloride anion with ammonia is explored by a combination of electronic structure and quantum dynamical methods. This system serves as a prototype for investigating a hitherto unexplored class of chemical reactions-nonadiabatic proton transfer triggered by a detachment of an electron. All the reactive and nonreactive channels of this process are characterized and the respective quantum yields are presented.     

Long term behavior of lithographically prepared in vitro neuronal networks

We measured the long term spontaneous electrical activity of neuronal networks with different sizes, grown on lithographically prepared substrates and recorded with multi-electrode-array technology. The time sequences of synchronized bursting events were used to characterize network dynamics. All networks exhibit scale-invariant Lévy distributions and long-range correlations. These observations suggest that different-size networks self-organize to adjust their activities over many time scales. As predictions of current models differ from our observations, this calls for revised models.     

Electrochemically Predicting Phenolic Substrates’ Suitability for Detection by Amperometric Laccase Biosensors

In this article, a rapid, simple method of electrochemically predicting a given phenolic substrate’s ability to be detected via amperometric laccase biosensors is proposed. Ten selected substrates were analysed by cyclic voltammetry and the relevant electrochemical parameters compared to biosensor kinetic parameters produced through amperometric detection of these substrates. The two major findings of this study were that biosensor detection sensitivities were found to correlate to: (1) peak oxidation potential of a substrate at unmodified electrodes and (2) the apparent Michaelis? Menten constant, K_m, of the biosensor‐substrate system, once corrections accounting for the relative differences in electroreducible product yield are made.     

Structural Transformation of SnS2 to SnS by Mo Doping Produces Electro/Photocatalyst for Hydrogen Production

SnS and SnS₂ are layered semiconductors, with potential promising properties for electro- and photocatalytic hydrogen (H₂) production. The vast knowledge in preparation and modification of layered structures was still not employed successfully in this system to fully maximize its potential. Here, the first report of structural transformation of SnS₂ into SnS with Mo-doping as a bifunctional catalyst for the hydrogen evolution reaction (HER) is reported. The structural phase transition optimized the properties of the material, providing a more delicate morphology with additional catalytic sites. The electrochemical studies showed overpotential of 377 mV at 10 mA cm⁻² for HER with Tafel slopes of 100 mV dec⁻¹ in 0.5 m H₂SO₄ for 10 % Mo-SnS. The same structure acts as an efficient photocatalyst in the generation of H₂ from water under visible illumination with rate of 0.136 mmol g⁻¹ h⁻¹ of H₂, which is 20 times higher than pristine SnS₂ under visible light.     

A Polynomial Number of Random Points Does Not Determine the Volume of a Convex Body

We show that there is no algorithm which, provided a polynomial number of random points uniformly distributed over a convex body in ℝ ⁿ , can approximate the volume of the body up to a constant factor with high probability.     

Biodegradation of Pyridine and Pyridine Derivatives by Soil and Subsurface Microorganisms

Abstract

Large amounts of aromatic compounds are produced by various industries and two thirds of these are heterocyclic chemicals. Compared with the extensive information available on microbial degradation of homocyclic aromatic compounds, relatively little is known on the transformation and biodegradation of heterocyclic chemicals in soil. Recent concerns about the persistence of hazardous pollutants have led to a renewed interest in the biodegradation of heterocyclic compounds. Hence, we investigated the microbial degradation of pyridine and some of its alkylated derivatives under aerobic and anaerobic conditions in groundwater, subsurface sediment, and soil. Results of the investigation revealed that these compounds were degraded predominantly under aerobic conditions and, to a lesser extent, under anaerobic conditions, with nitrate or sulfate serving as electron acceptors. In groundwater polluted with various pyridine derivatives, biodegradation was limited by the absence of oxygen. Therefore, we conclude that, under appropriate conditions, bioremediation is a potentially feasible method for the clean-up of environments contaminated with heterocyclic chemicals and, in particular, pyridine derivatives.     

A characterization of all the static stabilizing controllers for LTI systems

In this article, we give a complete characterization (geared towards a parametrization) of all the static feedbacks of a given LTI system triplet, in terms of the coefficients of some reduced order Riccati equation, with simultaneously stabilizing solutions and structural constraints – on the coefficients.