2‐Acetyl‐4,6,8,10,12‐Pentanitro‐Hexaazaisowurtzitane (PNAIW) Preparation and Properties

2‐Acetyl‐4,6,8,10,12‐pentanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (PNAIW) is formed in the last step of nitration of acetyl isowurtzitane derivatives. The amount of the PNAIW formed depends on the conditions of the nitration reaction (temperature, time, and nitrating mixture used) and on the type of the starting acetyl intermediate. The highest PNAIW yields (30 %) were obtained by nitrating 2,6,8,12‐tetraacetylhexaazaisowurtzitane (TAIW) at 60 °C for half an hour using HNO₃/H₂SO₄ nitrating mixture. HPLC, NMR, FTIR, and DSC measurements were used in the study and their results are reported.     

A Multiplex Assay to Assess the Transaminase Activity toward Chemically Diverse Amine Donors

The development of methods to engineer and immobilize amine transaminases (ATAs) to improve their functionality and operational stability is gaining momentum. The quest for robust, fast, and easy-to-use methods to screen the activity of large collections of transaminases, is essential. This work presents a novel and multiplex fluorescence-based kinetic assay to assess ATA activity using 4-dimethylamino-1-naphthaldehyde as an amine acceptor. The developed assay allowed us to screen a battery of amine donors using free and immobilized ATAs from different microbial sources as biocatalysts. As a result, using chromatographic methods, 4-hydroxybenzylamine was identified as the best amine donor for the amination of 5-(hydroxymethyl)furfural. Finally, we adapted this method to determine the apparent Michaelis-Menten parameters of a model immobilized ATA at the microscopic (single-particle) level. Our studies promote the use of this multiplex, multidimensional assay to screen ATAs for further improvement.     

Network structure/mechanical property relationship in crosslinked dimethacrylates of different chain lengths

In this article, the syntheses of three novel dimethacrylates of different chain lengths as well as the mechanical and thermal properties of their copolymers with methyl methacrylate and styrene were studied. The monomers were prepared by the reaction of glycidyl methacrylate with dicarboxylic acid esters obtained from maleic anhydride and ethylene, 1,4‐butylene and 1,6‐hexylene glycols. The addition reaction of glycidyl methacrylate and the acidic compound was carried out in the presence of basic catalyst, tetraethylammonium bromide. The monomers were UV‐copolymerized with methyl methacrylate and styrene in the presence of a photoinitiator which was 2,2‐dimethoxy‐2‐phenyloacetophenone. The prepared polymers were subjected to different studies concerning evaluation of their flexural properties, thermal stability, dynamic mechanical behavior as well as qualitative estimation of the content of unreacted double bonds. The dependence of glass transition temperatures (T_g) as well as degree of inhomogeneity on the crosslinking density has been examined in different copolymer systems. Evidence that the dependence of the T_g on the crosslinking density is not straightforward is presented. Dynamic mechanical measurements have demonstrated that the heterogeneity of the crosslinked polymers depends strongly on the crosslinking density of the system and the nature of methacrylate monomers used. Depending on the monomer size as well as its functionality, the resultant polymer may have features such as crosslinks or residual unsaturations that influence and define the properties of the materials. It is proved that the new dimethacrylates change their functionality in copolymerization with different monovinyl monomers. Also, the degree of unsaturated bonds conversion was found to be growing with the amount of monovinyl in the copolymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of metal cations on betanin stability in aqueous-organic solutions

An effect of metal cations on betanin stability was investigated in aqueous and organic-aqueous solutions. The presence of organic solvents (methanol, ethanol, and acetonitrile) affects substantially the pigments decomposition in acidic media induced by metal cations whose degrading action in such media is significantly higher than in aqueous solutions. The influence of Cu²⁺ on the stability was studied by spectrophotometry in more detailed manner, because of its ability to form complexes with betanin. The possibility of a complex formation between betanin and Ni²⁺ was also stated at pH 7–8; its relatively high stability in aqueous samples was observed. A presence of numerous products of betanin decomposition was detected in the wavelength range 380–500 nm in spectra obtained for most of metal cations investigated, especially for higher concentrations of the organic solvents.     

Levels of 13 multi-class pesticide residues in Polish honeys determined by LC-ESI-MS/MS

Levels of 13 pesticides in 40 honey samples form Poland are reported. A rapid and sensitive method was developed for the LC-ESI-MS/MS determination of multi-class pesticide residues in honey samples. Liquid–liquid extraction (LLE) on a diatomaceous earth support (requiring the use of small amounts of organic solvent), followed by chromatographic separation on a C₁₈ column and gradient elution were employed. The method quantifies over a dynamic linear range from respective MQLs (0.06–1.3 ng/g) to 5 ng/g. Matrix effects were evaluated by comparing the slopes of matrix-matched and solvent-based calibration curves. The mean recoveries obtained for three fortification levels (0.5, 1.0 and 4.0 ng/g) were 63–117% for most compounds, with an expanded uncertainty of <10%. The results for real honey samples collected from five regions of Poland (Pomerania, Wielkopolska, Lublin Region, Lower and Upper Silesia), showed that residue concentrations were <5 ng/g and did not pose a threat to human health.     

Enhanced stress durability of nano resonators with scandium doped electrodes

To explore mechanical stress durability of thin aluminum–scandium (AlSc) films, 0.86 GHz nano resonators with AlSc electrodes have been manufactured. Four different samples have been prepared altering the Sc content in the alloy between 0.0% and 2.5%. A final lift-off step accomplished manufacture procedure of the devices. The resonators have been operated with heavy load to determine power durability. The resonators with AlSc electrodes show increased power durability compared to conventional Al metallized devices. Texture and grain structure of all films have been investigated by means of electron backscatter diffraction (EBSD) and atomic force microscopy (AFM). Material fatigue of electrodes has been visualized by scanning electron microscopy (SEM). The refined grain structure of these alloys can explain the enhanced mechanical stress durability of AlSc electrodes.     

Development of a Mullite-Corundum Mortar for Cementing Mullite-Corundum Components

Studies are conducted to develop the optimum composition of a mullite-corundum mortar for cementing mullite-corundum engineering components. It is shown that the optimum composition for cementing vibrocast components of complex configuration is the MMK85-1-grade mullite-corundum mortar (TU U 14-7-178–99 Specifications) based on a phosphate binder. A technique is proposed by which unburnt components, preliminarily dried and calcined, are cemented into a one-piece product of particularly complex configuration.     

Influence of the lubricant on temperature distribution in the forging dies

Experimental and theoretical analysis of the influence of the lubricant on the temperature distribution in the tool during forging is presented. Finite element solution of the general diffusion equation is used to calculate the heat transfer contact between the die and the hot workpiece and during the interpass times. The results of calculations are compared with the results of measurements carried out using thermocouples inserted in the die. Two ways of modelling heat transfer through the contact surface are considered. The first treats a lubricant as a separate layer with the relevant thermal properties. The second assumes a temperature discontinuity at the interface and introduces the heat transfer coefficient. Insulating properties of various lubricants are compared. White-water lubricant shows the best insulating properties. The values of the heat transfer coefficient obtained from the inverse analysis vary from 2600 (without lubrication) to 1500 W/m²K (white lubricant).