Dynamic mechanical analysis of ethylene/1‐hexene copolymers: The effect of the catalyst type on the short‐chain branching distribution and properties of the amorphous and crystalline phases

Dynamic mechanical analysis was used to study ethylene/1‐hexene copolymers with different compositions, molecular weight distributions, and profiles of short‐chain branching (SCB) versus molecular weight. These copolymers were produced over a highly active supported titanium–magnesium catalyst (TMC), a highly active supported vanadium–magnesium catalysts (VMC), and a supported zirconocene catalyst. A higher fraction of the crystalline phase in the copolymers prepared with VMC was shown to result in higher elastic modulus values. β relaxation was found to be sensitive to the SCB distribution versus the molecular weight. The copolymers prepared with the zirconocene catalyst and VMC were characterized by more uniform SCB distributions and higher temperatures of β relaxation compared to the copolymers prepared with TMC. The mobility of the polymer chains at room temperature in the amorphous phase obtained by the spin‐probe method rose with increasing branch content in the copolymers and was not sensitive to different SCB distribution profiles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44638.     

Phase evolution from Ln2Ti2O7 (Ln=Y and Gd) pyrochlores to brannerites in glass with uranium incorporation

Ln₂Ti₂O₇ (Ln=Y and Gd) pyrochlore glass‐ceramics have been fabricated successfully via internal crystallization. Subsequently, the phase evolution from Ln₂Ti₂O₇ pyrochlores to Ln_0.5U_0.5Ti₂O₆ brannerites in glass with uranium (U) substitutions on the Ln‐site of Ln₂Ti₂O₇ has been investigated using X‐ray diffraction, scanning electron microscope‐electron dispersive spectroscopy, transmission electron microscopy, Raman and diffuse reflectance spectroscopy. Combined characterization by XRD, SEM‐EDS and TEM SAED confirms the structures and phase evolution while Raman spectroscopy reveals characteristic vibration modes for both pyrochlore and brannerite. In addition, DRS of the U⁵⁺ ion has been used to probe the phase evolution, with the corresponding f‐f transition band of ²F_7/2 energy level significantly shifting to longer wavenumbers due to the local coordination environment changing from eightfold coordination in pyrochlore to sixfold coordination in brannerite.     

Combustion Synthesis of Sialon-Based Ceramic Composites

We have studied the process of synthesis of ceramic composites based on β‐sialons under filtration combustion conditions in high-pressure gaseous nitrogen. We have shown that an important role is played by deformation shrinkage in formation of their structure and phase composition. The most favorable conditions for obtaining high-density ceramic are realized in the layer-by-layer regime for combustion of reaction mixtures with high oxide content (synthesis of highly substituted β‐sialons). The synthesized ceramic is characterized by high resistance to thermal loading and to the corrosive action of metallurgical melts.     

Atom Transfer Radical Polymerization with Ti(III) Halides and Alkoxides

Summary Ti(III) compounds (halides and n-butoxide) along with several mono-, bi-, and tridentate ligands have been studied for the first time in the atom transfer radical polymerization (ATRP) of styrene. The important advantage of titanium compounds is the white color of the Ti(IV) ions (Ti in the highest and air stable oxidation state) which ensures the absence of coloring in the final polymer. The better control over polymerization was realized when conditions increasing the reactivity of the intermediate Ti(IV) species and decreasing their steady state concentration were maintained. This occurred when chlorides were replaced with bromides (which decreased the bond strength), and when ligands with low donor ability were employed. Using a sulfide complex of Ti(III) chloride and 1,2-bis(hexylthio)ethane allowed styrene polymerization with kinetic and molecular weight characteristics inherent to ATRP. Received: 2 January 2003 / Accepted: 28 March 2003 Correspondence to Lyudmila M. Bronstein     

Pseudotransient Continuation Method in Extended Period Simulation of Water Distribution Systems

This paper presents and discusses a new static solver that implements the pseudotransient continuation method for the quasi-steady state analysis, or extended-period simulation of water distribution systems. The implementation is based on the concept of virtual tanks and has a clear physical meaning. The steady state solver described in this paper can analyze a pipe network under pressure deficient conditions and is free from some convergence problems that occur in the Newton-Raphson method-based solvers when analyzing a pipe network with control devices. The numerical examples considered in the paper demonstrate the convergence of the proposed method in cases where existing static solvers (e.g., that of the EPANET 2 hydraulic simulator) fail.     

Simultaneous separate and group determination of tylosin and tilmicosin in foodstuffs using single antibody-based immunoassay

An approach to modify the specificity of competitive indirect ELISA for determination of veterinary macrolides tylosin (TYL) and tilmicosin (TMN) using different structural design of coating antigen is described. The homologous and heterologous assay formats using rabbit antiserum against BSA-TYL conjugate were developed. The first format allowed selective determination of TYL (cross-reactivity for TMN was negligible). Heterologous hapten desmycosin (DMN) based conjugate being immobilised on the plates changed the specificity to group recognition (cross-reactivity for TMN was 103.4%). Using two coating antigens but single antibody and the same TYL standard solutions the described tandem test was capable for simultaneous determination of the respective analytes with their possible differentiation. The detection limit of assay that was far below the current MRLs and achieved 0.07 ng mL⁻¹ for TYL and 0.14 ng mL⁻¹ for TMN allowed to minimise matrix effect by sample dilution. The ELISAs of antibiotics in milk, eggs, honey and chicken muscle were optimised and showed acceptable recovery rate. A range of foodstuff samples was analysed using the developed tandem test.     

Rb掺杂Li4Ti5O12作为锂离子电池负极材料的合成及电化学性能

合成了不同Rb掺杂量的钛酸锂（Li_4-xRb_xTi₅O₁₂; x = 0.010, 0.015, 0.020）作为锂离子电池的负极材料。测试结果显示,Rb离子掺杂有效增强了钛酸锂的电子电导率。相同的测试条件下,相比于未掺杂样品和高Rb含量掺杂样品（x = 0.015, 0.020）,适量的Rb掺杂钛酸锂（Li_3.99Rb_0.01Ti₅O₁₂; x = 0.010）表现出最优的电化学性能。Li_3.99Rb_0.01Ti₅O₁₂材料表现出161.2 mA∙h/g的初始容量,且在1 C下经过1000次循环后容量保持率可达90.9%。此外,全电池Li_3.99Rb_0.01Ti₅O₁₂ // LiFePO₄在0.5 C条件下首次放电容量为144 mA∙h/g,经过150次循环后,容量保持率为78.8%。     

Preparation of Starch Carbamates in Homogeneous Phase using Different Mixing Conditions

The preparation of starch carbamates of wrinkled pea starch in homogeneous phase catalysed by dibutyltin dilaurate in DMSO as solvent is described. The empfloyed isocyanates have linear alkyl chains with 7, 9, 11, 15 or 18 carbon atoms. Starch carbamates with equal degrees of substitution and different alkyl chains lengths were synthesised in a reaction flask. The preparation of carbamates with equal alkyl chain length and different degrees of substitution was also possible. The structures of the polymers were characterised by elemental analysis, IR‐ and ¹H‐NMR‐spectroscopy. The behaviour of the prepared starch carbamates under thermal loading was investigated by using Differential Scanning Calorimetry (DSC) and a hot press. In addition, for 1‐undecyl isocyanate the starch carbamate was prepared both in a kneader and an extruder. The differences in reaction conditions and the results were discussed.     

Improved bioluminescent assay of somatic cell counts in raw milk

Somatic cell count (SCC) in milk is considered to be a valuable indicator of cow mastitis. For assessment of SCC in milk, the bioluminescent assay based on determination of ATP from somatic cells ([ATPsom]) in milk was proposed earlier. However, this assay is still not widely used in practice owing to lower reliability compared with conventional methods such as direct microscopy and flow cytometry. We revised the bioluminescent SCC assay and developed a simple protocol based on determination of the total non-bacterial ATP concentration in milk. It was shown that the novel ATP-releasing agent Neonol-10 (oxy-ethylated iso-nonyl phenol) has superior performance providing 100% lysis of somatic cells while not disrupting bacterial cells of milk at a concentration of 1.5% w/w. There was high correlation (R2=0.99) between measured bioluminescence and SCC as measured by direct microscopy. The observed detection limit of the bioluminescent milk SCC assay was as low as 900 cell/ml, time of analysis was 2-3 min per sample. The proposed method has high potential for on-site mastitis diagnostics.     

Retardation effect of jojoba chain length on the chemical reactivity of the liquid wax

Jojoba wax and its derivatives are slow-reacting compounds. To elucidate the reasons for this phenomenon, we reacted jojoba mono- and bis-epoxide and trans-jojoba bis-epoxide (C₃₈–C₄₄ long-chain esters), as well as side chain esters of three steroid skeleton mono-epoxide derivatives with NaI under acidic conditions to yield the corresponding iodohydrins, which then formed the respective bis-keto (or mono-ketone) derivatives. The kinetics, activation energies, and thermodynamic parameters of activation of nucleophilic epoxide opening and pinacol rearrangement were determined for all these compounds. The reaction rates of the jojoba derivatives were similar to those of two of the epoxides derived from the steroid skeleton compounds, and in the third case the steroid derivative reacted somewhat faster than all the rest. This pattern of rate retardation could stem either from folding of the long jojoba chain, resulting in steric hindrance around the reaction centers, or from repeated unproductive collisions along the long hydrocarbon chain of the jojoba wax (statistical effect). Our results appear to suggest that the multiple unsuccessful collisions were the dominant factor, although steric hindrance cannot be ruled out.