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21.
Glass transition during bulk polymerization was studied in free-radical cross-linking copolymerization (FCC) of methyl methacrylate (MMA) using the steady-state fluorescence (SSF) technique. Naphthalene (N) was used as a monomer and excimer forming probe. Changes in the viscosity of the pregel solutions due to gel formation dramatically enhance both monomer and excimer fluorescent yield of N molecules. The reaction time at which the monomer and excimer intensities exhibit a sudden increase corresponds to the reaction time at which the rate of polymerization becomes maximum resulting from the gel effect. This effect was used to study the gelation of MMA, as a function of time, in various N concentrations. The results were interpreted in the view of percolation theory. The gel fraction, β, and weight average degree of polymerization, γ, exponents β?=?0.40?±?0.02 and γ?=?1.70?±?0.07 were found in agreement with percolation results for both monomer and excimer measurements, respectively. 相似文献
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Mehmet Akdeniz Ismail Yener Demet Dincel Mehmet Firat Dilek Karatas Degirmenci Abdulselam Ertas 《Biomedical chromatography : BMC》2022,36(2):e5263
Public use of Salvia species and their importance in the scientific world is continually increasing. It is known that this use and the importance of Salvia species are mostly due to the terpenoid compounds that they contain. In this context, the terpenoid–steroid–flavonoid contents of extracts of six endemic Salvia (S. kurdica, S. pseudeuphratica, S. rosifolia, S. siirtica, S. cerino-pruinosa var. cerino-pruinosa and S. cerino-pruinosa var. elazigensis) species prepared with different solvents were determined by gas chromatography–mass spectrometry. Within the framework of the ingredient analysis, content analysis of the ethanol extracts of the root, branch, leaf and flower parts of the species collected in the same period between 2015 and 2017 years was performed. In general, extracts prepared with chloroform and ethanol were found to contain a wide variety of compounds while petroleum ether extracts were found to contain much less varied compounds. In addition, in general, root extracts are richer in terpenoid compounds than aerial part extracts. Some species can be used as source species in terms of ferruginol, cryptanol, 6,7-dehydroroyleanone, lup-(20)29-ene-2α-hydroxy-3β-acetate, salvigenin and β-sitosterol contents (52,114.28, 75,979.08, 101,247.41, 40,071.29, 33,952.13 and 34,010.90 μg analyte/g extract, respectively). 相似文献
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We discuss an improved jackknifed Durbin–Watson estimator for the variance parameter from a steady-state simulation. The estimator is based on a combination of standardized time series area and Cramér–von Mises estimators. Various examples demonstrate its efficiency in terms of bias and variance compared to other estimators. 相似文献
24.
Demet Cebe Zerrin Heren Orhan Büyükgüngör 《Molecular Crystals and Liquid Crystals》2018,667(1):112-125
A new complex of diaquabis(5-methoxyindole-2-carboxylato)bis(3-picoline)nickel(II) (Ni(5-MeOI2CA)2(3-pic)2(H2O)2), was synthesized for the first time and characterized by elemental analysis, FT-IR and electronic spectroscopy (UV-Vis) and single-crystal X-ray diffraction (XRD) techniques. The thermal degradation of the Ni(II) complex was investigated using thermogravimetric and differential thermal analyses techniques in oxygen atmosphere. The molecular structure of the complex was determined by single crystal X-ray diffraction technique. Hirshfeld surface analysis (HSA) investigated the packing modes and intermolecular interactions in molecular crystals, as they provide a visual picture of intermolecular interactions. In addition, all computational studies at B3LYP/6-311++G(d,p) were carried out for theoretical characterization of Ni(II) complex. The optimized geometry results, which were well represented the X-ray data, were shown that the chosen of DFT/B3LYP/6-311++G(d,p) was a successful choice for title compound. After a successful optimization, FMOs, chemical activity, non-linear optical properties (NLO), molecular electrostatic potential (MEP), Mulliken population (MPA), natural population analyses (NPA), Fukui function analysis (FFA) and natural bond orbital analysis (NBO), which could not obtained by experimental ways, were calculated and investigated. The computed of net charges and chemical activity studies which helped to identifying the electrophilic/nucleophilic nature. 相似文献
25.
The reaction of lithium diarylcuprate(I) reagents with o‐bromobenzoyl chloride has been investigated. In general, the reaction proceeds well to give synthetically useful o‐bromobenzophenone derivatives as the major product. It is suggested that a minor substituent effect, whereby diarylcuprate reagents containing an ortho or meta substituent react more favourably, may be attributed to small changes in the structure of the organometallic reagent. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
26.
Background
Cytochrome P450 monooxygenases (CYPs) form a vast and diverse enzyme class of particular interest in drug development and a high biotechnological potential. Although very diverse in sequence, they share a common structural fold. For the comprehensive and systematic comparison of protein sequences and structures the Cytochrome P450 Engineering Database (CYPED) was established. It was built up based on an extensible data model that enables its functions readily enhanced. 相似文献27.
Baris Kiskan Demet Colak Ali Ekrem Muftuoglu Ioan Cianga Yusuf Yagci 《Macromolecular rapid communications》2005,26(10):819-824
Summary: Thermally curable benzoxazine ring‐containing polystyrene macromonomers were synthesized and characterized. 1,4‐Dibromo‐2,5‐bis(bromomethyl)benzene and 1,4‐dibromo‐2‐(bromomethyl)benzene were used as initiators in the atom transfer radical polymerization of styrene. The resulting polymers were used in combination with 3‐aminophenylboronic acid hemisulfate, for a Suzuki coupling. The obtained polymers, with amino groups in the middle or end of the chains, were reacted with formaldehyde and phenol to yield benzoxazine ring‐containing macromonomers. In addition to the glass transition temperature of the polystyrene segment observed at ca. 105 °C, differential scanning calorimetry thermograms exhibit an exotherm at ca. 276 °C corresponding to the oxazine thermal polymerization. Both macromonomers undergo thermal curing with the formation of thermosets having polystyrene segments.
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Demet Sezgin Mansuroğlu Hakan Arslan Don VanDerveer Gün Binzet 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):3221-3230
A series of new N-(2,2-diphenylacetyl)-N ′-substituted thiourea derivatives (1–9) have been prepared and characterized by elemental analyses, IR and 1H NMR spectroscopy. N-(2,2-diphenylacetyl)-N ′-(4-chlorophenyl)-thiourea was also characterized by a single crystal X-ray diffraction study. The compound crystallizes in the monoclinic space group P21/c with Z = 4 and a = 9.6551(19) Å, b = 20.060(4) Å, c = 9.894(2) Å, β = 104.29(3)°. The molecular conformation of the compound is stabilized by an intramolecular (N1-H1···O1) hydrogen bond that forms a pseudo-six-membered ring. 相似文献
30.
Demet Binbaşıoǧlu Serkan Demiriz Duran Türkoǧlu 《Journal of Fixed Point Theory and Applications》2016,18(1):213-224
The study of non-Newtonian calculi was started in 1972 by Grossman and Katz. These calculi provide an alternative to the classical calculus and they include the geometric, anageometric and bigeometric calculi, etc. Recently, Çakmak and Ba?ar (2002) have studied the concept of non-Newtonian metric. Also they have given the triangle and Minkowski’s inequalities in the sense of non-Newtonian calculus. In this paper, we introduce a fixed point theory by defining some topological structures of the relevant non-Newtonian metric space. 相似文献