N-nitrosamines formation from secondary amines by nitrogen fixation on the surface of activated carbon

Our previous study demonstrated that many commercial activated carbon (AC) particles may catalyze transformation of secondary amines to yield trace levels of N-nitrosamines under ambient aerobic conditions. Because of the widespread usage of AC materials in numerous analytical and environmental applications, it is imperative to understand the reaction mechanism responsible for formation of nitrosamine on the surface of ACs to minimize their occurrence in water treatment systems and during analytical methods employing ACs. The study results show that the AC-catalyzed nitrosamine formation requires both atmospheric oxygen and nitrogen. AC's surface reactive sites react with molecular oxygen to form reactive oxygen species (ROS), which facilitate fixation of molecular nitrogen on the carbon surfaces to generate reactive nitrogen species (RNS) likely nitrous oxide and hydroxylamine that can react with adsorbed amines to form nitrosamines. AC's properties play a crucial role as more nitrosamine formation is associated with carbon surfaces with higher surface area, more surface defects, reduced surface properties, higher O(2) uptake capacity, and higher carbonyl group content. This study is a first of its kind on the nitrosamine formation mechanism involving nitrogen fixation on AC surfaces, and the information will be useful for minimization of nitrosamines in AC-based processes.     

Novel indium(III) complexes with sterically hindered o-iminobenzoquinone

The first examples of indium(III) derivatives based on sterically hindered 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone (imQ) were synthesized and characterized in details. The interaction of sodium o-iminobenzosemiquinolate with indium(III) iodide produces bis[4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzosemiquinonato]-iodo-indium(III) (1). The same product 1 was obtained by the reactions of imQ with InI or imQ disodium derivative with indium(III) iodide. The interaction of imQ with InI₃ results in the formation of indium(III) compound (2) containing neutral form of o-iminobenzoquinone ligand. Structures of complexes 1 and 2 were determined by X-ray diffraction analysis.     

Photon arrival time quantum random number generation

We present an efficient random number generator based on the randomness present in photon emission and detection. The interval between successive photons from a light source with Poissonian statistics is separated into individual time bins, which are then used to create several random bits per detection event. Using a single-photon counter and FPGA-based data processing allows for a cost-efficient and convenient implementation that outputs data at rates of roughly 40 Mbit s^?1.     

Carbon Nanotubes on Polymeric Microcapsules: Free‐Standing Structures and Point‐Wise Laser Openings

Single‐wall carbon nanotubes modified by anionic polyelectrolyte molecules are embedded into the shells of microcapsules. Carbon nanotubes serve as rigid rods in a softer polymeric capsule, which forms a free‐standing shell upon treatment with glutaraldehyde and subsequent drying. The embedded carbon nanotubes exhibit a broad absorption in the UV–near‐infrared part of the spectrum, and that allows point‐wise activation and opening of the microcapsules by laser. Raman signal analysis shows changes of carbon‐nanotube‐specific lines after high‐power laser irradiation, which is characteristic of the formation of disordered carbonlike structures. These polyelectrolyte/carbon nanotube composite capsules represent a novel light‐addressable type of microcontainers.     

A structural study of cadmium interaction with aquatic microorganisms

The molecular mechanisms of cadmium toxicity for aquatic phototrophic microorganisms, reversible adsorption on the surface, and cellular uptake during growth were investigated by combining batch macroscopic experiments with atomic-level in situ Cd K-edge X-ray absorption fine structure spectroscopy. The following species were examined: marine planktonic (Skeletonema costatum, Thalassiossira weissflogil) and freshwater periphytic (Navicula minima, Achnanthidium minutissum) diatoms, cyanobacteria (Gloeocapsa sp.), anoxygenic phototrophic bacteria (Rhodopseudomonas palustris), and freshwater diatom-dominated biofilms. Upon short-term adsorption at the freshwater diatoms and cyanobacteria cell surface from a NaNO3 or NaCl solution, Cd is octahedrally coordinated by oxygen at an average distance of 2.27 +/- 0.02 angstroms and is associated with carboxylate groups. The atomic environment of cadmium incorporated into freshwater diatoms during long-term growth (operationally defined as Cd nonextracted by EDTA) is similar to that of adsorbed metal in terms of Cd-O first-shell distances and coordination numbers. Contrasting speciation is found for Cd incorporated into marine diatoms and adsorbed onto phototrophic anoxygenic bacteria R. palustris, where Cd is coordinated with three to five oxygen/nitrogen atoms and one to three sulfur atoms in the first atomic shell, likely in the form of cysteine/hystidine complexes or Cd-thiolate clusters. The Cd association with sulfhydryl groups in marine planktonic diatoms and anoxygenic bacteria is an important feature of Cd binding which can be useful for assessing the bioavailability of this metal.     

Antioxidant coating of micronsize droplets for prevention of lipid peroxidation in oil-in-water emulsion

Fast lipid peroxidation in emulsified oils results in carcinogens formation and product rancidity. Prevention of oxidative degradation in oil-in-water emulsion has been achieved by encapsulating of each droplet of dispersed phase in antioxidant multilayer coating shell. The fabrication comprised placing a surface-active ionic emulsifier at the oil/water interface followed by stepwise alternate adsorption a biocompatible polyelectrolyte and antioxidant layers. Uncoupled polyelectrolyte macromolecules and antioxidant were thoroughly removed from formulation, thus the protection was entirely attributed to the droplets' shell. The experiments were performed using linseed oil, the richest source of highly unstable omega-3 alpha linolenic essential fatty acid. Bovine serum albumin (BSA) was exploited as an anionic emulsifier. The biodegradable coating shell was formed of poly-l-arginine (PARG) and dextran sulfate (DS) applied as a polycation and a polyanion respectively. Tannic acid (TA) known as a natural antioxidant and possessing antimicrobial properties was used as a protective remedy. Oil microdroplets coated with TA-containing shell displayed physical-chemical and mechanical stability in aqueous phase and over freeze-drying process as determined by ζ-potential measurements, dynamic light scattering (DLS), and confocal laser scanning microscopy (CLSM). Oxidation of emulsified oil was monitored by formation of malondialdehyde (MDA) in the samples quantified by Thiobarbituric Acid Reactive Substances (TBARS) assay. Coating shell with an incorporated layer of TA effectively suppressed oxidation in water-dispersed oil droplets and affected iron-catalyzed oxidation over 15 days of incubation at 37 °C in 0.3 mM FeBr2 solution. Antioxidant activity of TA-containing shell assembled around each oil droplet was found to be higher than that of mixed tocopherols (MT) added to linseed oil in concentration of 10000 ppm.