Reagentless biosensor based on glucose oxidase wired by the mediator freely diffusing in enzyme containing membrane

Wiring glucose oxidase in the membrane with an immobilized mediator is possible due to the diffusion ability of the latter, if the enzyme containing membrane is formed according to the proposed protocol, including exposing proteins to water-organic mixtures with the high content of organic solvent. In the course of the study, the new glucose oxidase mediator, unsubstituted phenothiazine, was discovered. The diffusion coefficient of the mediator in the resulting membrane is independent of the presence of enzyme. The cyclic voltammograms of the enzyme electrode after appearance of the only glucose in solution obtain a well-defined catalytic shape, which is normally observed for both the enzyme and the mediator in solution. Analytical performances of the resulting biosensor are comparable to the advanced second generation ones, which, however, require covalent linking of the mediator either to the membrane forming polymer or to the enzyme. Even without such covalent linking, the reported biosensor is characterized by an appropriate long-term operational stability allowing reagentless sensing.     

Engineering of the space-variant linear polarization of vortex-beams in biaxially induced crystals

We considered the propagation of Bessel beams through the biaxially induced birefringent crystal implemented by the mechanical torsion of the uniaxial crystal around its optical axis. Analyzing the solutions to the wave equation in the form of eigenmodes, we found that the system enables us to convert the beams with a uniform distribution of the linear polarization at the beam cross section into radially, azimuthally, and spirally polarized beams. Moreover, we revealed that the above system permits us to convert the beams with the space-variant linear polarization in accordance with the rule -s?s+1, where s is the topological index of the centered polarization singularity.     

Hydroprocessing of Aromatics Using Sulfide Catalysts Supported on Ordered Mesoporous Phenol–Formaldehyde Polymers

Ni–W sulfide catalysts for the hydroprocessing of aromatic hydrocarbons were synthesized by the in situ decomposition of tetrabutylammonium nickel thiotungstate complex supported on ordered mesoporous phenol–formaldehyde polymer. Catalysts obtained with and without additional sulfidation with dimethyl disulfide were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The catalytic activity has been studied using naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, and anthracene as examples. It is shown that the system used in this study proved to be active in hydrogenation and hydrocracking of polyaromatic hydrocarbons.     

Current state of the sponge fauna (Porifera: Lubomirskiidae) of Lake Baikal: Sponge disease and the problem of conservation of diversity

The spatial distribution of healthy and diseased sponges in Lake Baikal was investigated. The endemic sponges were studied in May ? June 2015 at 11 transects within the depth range of 0 to 40 m. More than 500 sponge specimens were collected, and 29 taxa including 12 species and 17 morphospecies (sp. taxa) were identified. Among the 29 taxa, only B. martinsoni specimens and 14 morphospecies were healthy, whereas specimens of the other 11 species and 3 morphospecies were diseased, making up 35% of the total number of specimens (512). The different body forms of sponge found among the specimens were encrusting (66%), globulous (21%), and branched (13%). Sponges with necrosis signs, discolored specimens or covered with violet film or brown spots, were found in all transects under study (37 stations of 68). The percent cover of the bottom (per m²) by various body forms of sponges was evaluated with a sponge faunal state assessment test. Changes in the diversity and abundance of sponges due to their disease may jeopardize the functioning of the entire ecosystem of Lake Baikal which is a World Heritage Site. This baseline data on patterns of sponges, including their spatial distribution and percent cover, will be utilized to support future management and monitoring of Lake Baikal. Data on the current state of Baikal endemic sponge fauna are essential for understanding the causes and prognosis of disease processes of freshwater sponges.     

Inoculum density and buffer capacity are crucial for H2 photoproduction from acetate by purple bacteria

The increase of inoculum density of Rhodobacter sphaeroides B-3059 above 2.0 mg bacteriochlorophyll/l in 15 mM K-phosphate buffer inhibited hydrogen photoproduction but favored PHB synthesis. This inhibition was substrate-specific and was observed on media containing acetate. The inhibition resulted from sharp increase in pH above 10 due evidently to fast acetate consumption. The lower the buffer concentration, the lower the inhibitory inoculum density was. The dependence of H₂ photoproduction from acetate on buffer concentration at low and high inoculum density was different for different strains of purple bacteria. However, conditions were found to provide H₂ production by each of 9 tested strains. Acetate-dependent hydrogen photoproduction in 10 mM K-phosphate buffer was unreliable even with low inoculum density. Ammonium traces and high acetate concentration also facilitated medium alkalization and, consequently, inhibited H₂ production. The increase of buffer concentration above 20 mM helped to prevent pH rise independent of the triggering factor.     

EBSD Characterization of Cryogenically Rolled Type 321 Austenitic Stainless Steel

Metallurgical and Materials Transactions A - Electron backscatter diffraction was applied to investigate microstructure evolution during cryogenic rolling of type 321 metastable austenitic...     

The influence of vegetable puree containing carotenoids on the nutrient composition and structure of milk yoghurt

The aim of this study was to develop technology to produce a mashed pumpkin yoghurt rich in β‐carotene and to check its physicochemical properties and nutritional values. The structural and mechanical properties of the yoghurt product, as well its basic nutrient content and antioxidant activity, were studied. Yoghurt fortified with pumpkin puree has the potential to normalise the commensal intestinal microbiota and has potential as a dietary health supplement. The experimental yoghurt samples that were produced had physicochemical properties comparable to commercially produced yoghurt: the pumpkin‐supplemented samples contained 4.5% fibre, 8.5 mg/100 g vitamin C and 8.9 mg/100 g β‐carotene.     

Chiral Octahedral Complexes of Cobalt(III) as “Organic Catalysts in Disguise” for the Asymmetric Addition of a Glycine Schiff Base Ester to Activated Olefins

Stereochemically inert and positively charged chiral complexes of cobalt(III) prepared from Schiff bases derived from chiral diamines and salicylaldehydes were shown to be efficient catalysts of the benchmark asymmetric phase‐transfer Michael addition of nine activated olefins to O’Donnell’s substrate. The reaction products had enantiomeric purities of up to 96%. DFT calculations were invoked to rationalize the stereochemistry of the addition.

     

Ultrathin single crystal diamond nanomechanical dome resonators

We present the first nanomechanical resonators microfabricated in single-crystal diamond. Shell-type resonators only 70 nm thick, the thinnest single crystal diamond structures produced to date, demonstrate a high-quality factor (Q ≈ 1000 at room temperature, Q ≈ 20?000 at 10 K) at radio frequencies (50-600 MHz). Quality factor dependence on temperature and frequency suggests an extrinsic origin to the dominant dissipation mechanism and methods to further enhance resonator performance.