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991.
U. S. Andropova N. A. Tebeneva A. N. Tarasenkov M. S. Parshin A. A. Askadskii O. A. Serenko A. M. Muzafarov 《Polymer Science Series B》2017,59(2):202-209
Amorphous polyaryleneetherketone tetrakis(phenyldiethoxysiloxy)hafnium or tetrakis(methyldiethoxysiloxy) hafnium are used as precursors of disperse phase of composites. One of the factors determining the morphology of filled polymer films and the size and shape of particles forming in polymer in situ is the activity of alkoxy groups of metal alkoxysiloxane precursor in hydrolysis and condensation reactions. When using tetrakis(phenyldiethoxysiloxy)hafnium instead of tetrakis(methyldiethoxysiloxy)hafnium, nanocomposites obtained via the sol-gel method are characterized by a uniform distribution of spherical particles of disperse phase. 相似文献
992.
K. Wallmann M. Kersten J. Gruber U. Förstner 《International journal of environmental analytical chemistry》2013,93(1-4):187-200
Abstract The binding forms of Co, Cd, Cu, Pb, and Zn in an anoxic, sulfide-bearing sediment were investigated by performing both thermodynamic equilibrium calculations and sequential extractions. Care was taken to maintain oxygen-free conditions during the whole experiment. The calculations suggested that trace metals were bound to sulfidic minerals. Sequential extraction results, however, showed increased importance of exchangeable and reducible fractions in the order Cu < Cd < Pb < Zn < Co. Thermodynamic equilibrium calculations of the chemical reactions during extraction showed that Cd, Co, Pb, and Zn sulfides are to a significant extent soluble in the acetate-exchangeable (step 1 + 2) and oxalate-reducible (step 3) fractions. Neglecting the dissolution of sulfide minerals would lead to a misinterpretation of the experimental results. 相似文献
993.
M. W. F. Nielen J. De Jong R. W. Frei U. A.Th. Brinkman 《International journal of environmental analytical chemistry》2013,93(1-3):37-48
Abstract A strongly basic anion-exchange resin is used for the trace enrichment and automated sample handling of phenol, with subsequent determination by reversed-phase liquid chromatography with fluorescence detection. Because of the presence of high concentrations of ionic compounds in the water samples tested, phenol is first trapped on a relatively long precolumn filled with a highly hydrophobic packing material; during this step, (in) organic anions which are not retained, are flushed to waste. In the next step, phenol is desorbed from this column at high pH and sorbed in a small zone (“peak compression”) on a short precolumn containing the anion exchanger. In the analysis of tap and river water samples, the detection limit was found to be 10ppt (1:1011). 相似文献
994.
Madlene U. Koller Katrina L. Peariso Tina S. Guion Shannon Studer Martinez Charles F. Beam 《合成通讯》2013,43(19):2963-2974
2-, 3-, or 4-Picolyllithium was prepared in excess lithium diiso-propylamide and condensed with several hydroxy-benzaldehydes and 4-hydroxy-acetophenone to afford substituted hydroxyphenyl-pyridyl-ethanols and α-hydroxyphenyl-α-methylpyridineethanols. In two instances. 3-picolyllithium condensed with aldehydes to presumably form the hydroxyphenyl-pyridyl-ethanol, which underwent linear dehydration to the substituted pyridyl-ethylenyl-phenol. 相似文献
995.
996.
P. R. Alapati D. M. Potukuchi N. V. S. Rao V. G. K. M. Pisipati A. S. Paranjpe U. R. K. Rao 《Liquid crystals》2013,40(11):1461-1479
Abstract We report X-ray diffraction, density, ultrasonic velocity and refractive index studies in the N(p-n-pentyloxy benzylidene) p-n-alkylaniline compounds, viz. 50.5, 50.6 and 50.7. The nematic-smectic A (NA) transition is found to be weak first order in 50.6 while it is second order in 50.5 and 50.7. The salient features observed are cybotactic clusters in the nematic phase in all the compounds, molecular tilt which was inferred due to the end alkyl chains tilt causing orienta-tional disorder (smaller orientational order parameters ‘s’ than expected) in smectic A phase, smectic F phase and large tilt angle variation in smectic C phase in a small temperature range in 50.5. The observed results are discussed in the light of available data in other n0.m compounds. 相似文献
997.
Zinc oxide nanoparticles based UV detector was fabricated on thermally oxidized silicon substrate. ZnO nanoparticle films were deposited using sol–gel route. The seed solution was prepared using two different solvents (methanol and isopropyl alcohol (IPA)). The surface morphology of the prepared films was characterized by FESEM. Structural characterization along with optical measurements was carried out using XRD and UV–vis spectroscopy. For the UV photo-detector, ZnO thin film prepared in IPA is selected based on their structural and optical analysis. The changes in photo-response of ZnO thin film with respect to time was studied under the dark and variable UV intensities. It was observed that the photocurrent increased with a factor of 4.82 under 1.16 mW of UV intensity. It is believe that the synthesized ZnO thin films have potential to use in the ultraviolet photo-detector applications. 相似文献
998.
U. Schulze M. Arndt F. Freidanck I. Beulich G. Pompe E. Meyer 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):1037-1044
Abstract The microstructure of ethylene copolymers based on 1-hexene, 1-octene, and norbornene as comonomers was studied and related to its melting, crystallization, and glass transition behavior as well as to tensile strength. 相似文献
999.
Afshan Siddiqui Kajal Singh Kanchan Lata Singh Shailendra Kumar Gupta Mohd Safi Ahmad U. N. Tripathi 《应用有机金属化学》2012,26(5):203-211
Mixed ligand complexes of Iron(III) with aspartic acid and 3(2′‐hydroxy phenyl)‐5‐(4′‐substituted phenyl) pyrazolines of type [Fe(C4O4NH6)2(C15H12N2OX)] and [Fe(C4O4NH6)(C15H12N2OX)2], where (C4O4NH6) = aspartate, (C15H12N2OX) = deprotonated 3(2′‐hydroxyphenyl)‐5‐(4′‐substituted phenyl) pyrazolines (X = H, CH3, OCH3, Cl), have been synthesized. These newly synthesized derivatives have been physicochemically characterized by elemental analysis (C, H, N, Cl and Fe), magnetic moment data, thermogravimetric analysis, molar conductance, cyclic voltammetry, spectral analysis (UV–visible, IR, far IR and fast atom bombardment mass spectrometry). Scanning electron microscopy, transmission electron microscopy and X‐ray powder diffraction studies have been carried out for powdered samples, which show nanometric particles of these derivatives. Antibacterial and antifungal potential of free pyrazoline and some iron(III) complexes have been evaluated. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
1000.
In the present paper, we study a dynamic reaction model in which (i) the predator is provided with an alternative food in addition to the prey species, (ii) the predator is harvested, and (iii) a tax is imposed to regulate the system. The existence of possible steady states along with their local as well as global stability is discussed for both the exploited and unexploited systems. Boundedness of the system is also discussed. It is seen that the system undergoes a Hopf bifurcation by the addition of alternative prey and the criteria for the Hopf-bifurcation is also discussed. Optimal tax policy is discussed using Pontryagin’s maximal principle. Finally, some numerical simulations are given to show the consistency with theoretical analysis. 相似文献