Analysis of exoskeleton triglycerides ofLeptinotarsa decemlineata say

The exoskeleton triglyceride fraction isolated from the Colorado beetle,Leptinotarsa decemlineata Say, was studied. Analysis of the hydrolysis products and direct capillary column gas chromatography showed that, apart from triglycerides, the fraction contained no diol lipids. The composition of the natural triacylglccerol mixture was assessed by gas chromatography and by field desorption and electron impact mass spectrometry. Triglycerides isolated from the Colorado beetle are typical glycerol triesters, with long chain (mainly oleic or palmitic) fatty acids. The structures of two major components (91%), i.e., trioleoyl glycerol and 1,2-dioleoyl-3-palmitoyl glycerol, were determined.     

Stroboscopic determination of settling velocity, size and porosity of activated sludge flocs

A multi-exposure photographic method was developed for the combined measurement of the settling velocity and size of activated sludge flocs. The proposed method mainly differs from the previous stroboscopic tests by introducing a new experimental arrangement which ensures sharp images of flocs on photographs.The relationships between individual floc-settling velocity and the floc size were found to be linear or fractional power functions. All these relationships were well correlated.Based on a simplified floc structure assumption and results of experimental measurements of floc-settling velocity and size, the floc porosity was determined. The porosity increased at two distinct rates as the floc size increased.     

Large Eddy Simulation of mixing effects on the course of parallel chemical reactions and comparison with k-? modeling

The way in which reagents are mixed can have a large influence on the product distribution of chemical reactions. To model effects of mixing on various scales on the course of chemical reactions the method of Large Eddy Simulation (LES) of non-premixed, turbulent reactive flows of incompressible fluids is considered in this work. The subgrid modeling of chemical reaction is based on a beta distribution of the mixture fraction in combination with a conditional moment closure based on linear interpolation of local instantaneous reactant concentration values. The predictions obtained with LES are compared with experimental data for fast parallel chemical reactions, the fluid velocity measured using Particle Image Velocity (PIV) technique and the passive tracer concentration measured using the Planar Laser Induced Fluorescence (PLIF) technique. Predictions of the model based on LES are compared as well with results obtained using the non-equilibrium multiple-time-scale mixing model combined with a standard k-? model and employing similar conditional moment closure as LES, applied, however, at larger scale. All comparisons show a very good performance of the model based on LES.     

Structural and magnetic properties of C15 HoMn2 hydrides

Powder samples of cubic HoMn₂H_x hydrides, with 0 ≤ x ≤ 4.3, have been investigated by X-ray diffraction and AC/DC magnetometry as a function of temperature and external magnetic field. Hydrogen is demonstrated to strongly modify structural and magnetic properties. X-ray studies revealed many structural transformations placed at low temperatures. In particular, a transformation from the cubic to the monoclinic structure was detected, which so far has not been reported for other cubic RMn₂H_x (R - rare earth or Yttrium) compounds. The structural transformations are reflected in the magnetic behavior. The change in ordering temperatures implies a very strong relationship between the magnetic interactions and the Mn-Mn distance modified at hydrogen absorption. Tentative magnetic and structural phase diagrams are proposed. The presented results are compared with the properties of other cubic and hexagonal RMn₂H_x hydrides.     

Transamination Reactivity of Ti(NMe2)4 and Zr(NMe2)4 with 1,3,4,5,6-Pentamethyl-2-aminoborazine and Aryl Amines. Model Chemistry for the Formation of Metalloborazine Preceramic Polymers and MN/BN (M?=?Ti, Zr) Ceramic Composites

The transamination reactions between Ti(NMe₂)₄ and 1,3,4,5,6-pentamethyl-2-aminoborazine, (Me)₃N₃(Me)₂B₃(NH₂), and diphenylamine (Ph₂NH) and between [Zr(NMe₂)₄]₂ and 1,3,4,5,6-pentamethyl-2-aminoborazine, aniline (PhNH₂) and diphenylamine have been studied and the molecular product species have been isolated, spectroscopically characterized and single crystal X-ray structure analyses completed. The results of these studies have been used to interpret the outcome of reactions of Ti(NMe₂)₄ and Zr(NMe₂)₄ with borazinylamine preceramic polymers that, upon pyrolysis, produce TiN/BN, ZrN/BN and ZrH_0.6N/BN composite powders. The transamination reactivity of a two-point poly(borazinylamine) oligomer having terminal –NH₂ amino groups with Ti(NMe₂)₄ and Zr(NMe₂)₄ has been used to obtain metallated preceramic oligomers that, upon pyrolysis, give TiN/BN and ZrN/ZrH_0.6N/BN nanocomposites. Model reactions of 1,3,4,5,6-pentamethyl-2-amino borazine, aniline and Ph₂NH₂ with Ti(NMe₂)₄ and Zr(NMe₂)₄ are also described as models for the formation of the metallated oligomers. Molecular structure determinations for the metal amides are presented. We dedicate this paper to Professor Christopher W. Allen in recognition of his distinguished career and his accomplishments in inorganic ring and polymer chemistry.     

Relation between phase composition of compound zone and growth kinetics of diffusion zone during nitriding of steel

The present work is devoted to an investigation of the influence of the micro-structural evolution of the compound zone (iron (carbo)nitrides zone) upon the development of hardness profiles in the diffusion zone. A different phase structure of iron (carbo)nitrides zone on steel as compared to iron, further changing with the process, may result in upsetting of the quasi-equilibrium of nitrogen concentration in the iron (carbo)nitrides zone/diffusion zone interface. This, as a result, may have an impact on the kinetics of this layer's growth. The research carried out was aimed at solving this problem. It was to evaluate the influence of (carbo)nitrides zone, with an intentionally created diametrically different phase composition, on hardness profiles in the diffusion zone. The nitrided layers were characterised by a light optical microscopy, X-ray diffraction and measurements of hardness. It was observed that the evolution of the phase structure and phase composition of the compound zone contributes significantly, regardless of nitrogen potential and temperature, to the formation of the diffusion zone and in particular to its effective thickness. It makes this complex picture of nitrided case development on steel even more intricate.     

Effect of selected substances on the properties of frozen myofibril preparation obtained from mechanically recovered poultry meat

The experimental material was a myofibrillar preparation obtained from mechanically recovered poultry meat by the washing and separation of fat and connective tissues. Changes occurring during frozen storage were investigated in the preparation without and with the addition of the following substances: 2 g/kg carrageen, 2.5 g/kg sodium tripolyphosphate (TPP) mixture and 80 g/kg polydextrose, and 3 g/kg enzymatic preparation (ACTIVA WM) containing microbial transglutaminase (MTG). Samples with the addition of MTG were pre-incubated at the temperature of 7 ± 1 °C for 1, 3, 5, 24 h. All samples were stored at the temperature of approx. −23 °C for 2, 30, 60, 90 days. The smallest change in protein solubility was observed in samples with added TPP and polydextrose. Along with the extension of pre-incubation time of samples containing the enzyme a gradual decrease was found in the amount of soluble protein. Also the results of the investigations obtained using the DSC technique showed the most advantageous protective effect, i.e., causing the smallest decrease in enthalpy values of samples during freezer storage, in case of the addition of TPP and polydextrose mixture. Analysis of thermal drip volume from gels showed that carrageen was the most advantageous addition to the myofibrillar preparation. Moreover, a gradual increase was observed in the volume of thermal drip along with the extension of pre-incubation time of the protein isolate with enzymatic preparation. Results of gel texture testing indicated that the most advantageous effect on gel quality was found for ACTIVA applied in 3 and 5 h pre-incubation with the myofibrils. Assuming that among the analyzed properties the most important were thermal drip and gel texture, 3 g/kg MTG at pre-incubation time of 3 h was considered the most advantageous additive.     

Synthesis and characterization of carbonaceous replicas of multilayered vesicular siliceous materials

Synthesis of novel, carbon porous replicas of vesicular siliceous materials has been described. The original siliceous materials consist of small, spherical structures resembling onions, known in the literature as multilamellar vesicles (MLVs). They have been characterized with a number of analytical methods that allow one to determine its 3-D structure and basic parameters of the pore system. Carbonaceous materials, made similarly of onion-like porous structures, have been obtained using a standard procedure to form replicas. They have been characterized by the same methods as those applied to the parent materials.