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991.
Vinyl phenylboronic acid controlling co‐monomer for nitroxide mediated synthesis of thermoresponsive poly(2‐N morpholinoethyl methacrylate)
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Xeniya Savelyeva David Chondon Milan Marić 《Journal of polymer science. Part A, Polymer chemistry》2016,54(11):1560-1572
Low concentrations of 4‐vinylphenylboronic acid (VPBA) were copolymerized with 2‐N‐morpholinoethyl methacrylate (MEMA) by nitroxide mediated polymerization using BlocBuilder? unimolecular initiator at 80 to 90 °C. The MEMA/VPBA copolymerizations were performed at initial feed compositions (fVPBA,0) of 0.05 to 0.10 VPBA, with fVPBA,0 = 0.10 using dimethylacetamide (DMAc) solvent being most effective, as seen by a linear increase in number average molecular weight, Mn, versus conversion and low dispersity, ? < 1.40. The copolymers were further chain‐extended with a second batch of VPBA, resulting in a block copolymer with monomodal molecular weight distribution and ? = 1.66. For MEMA/VPBA copolymers, increases in VPBA composition and polymer solution concentration resulted in decreases in the cloud point temperature (CPT, typically varied between 27.4–37.8 °C) and CPT increased from 31.2 to 33.8 °C to about 88 °C with decreases in pH from 7 to 4. Rheological tests with small angle light scattering (SALS) confirmed CPTs measured by UV‐Vis and DLS. These copolymers were targeted as models to combine possible glucose‐sensing boronic acid functionality the thermoresponsiveness provided by MEMA groups. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1560–1572 相似文献
992.
Vladimír Danielik Jana Jurišová Pavel Fellner Radka Štefancová Milan Kučera 《Chemical Papers》2018,72(12):3119-3128
The paper deals with the absorption of ammonia in a model fertilizer of ammonium nitrate. Volumetric overall mass transfer coefficient quantitatively characterizing the process was estimated on the basis of experimental data and kinetics modeling. The volumetric overall mass transfer coefficient depends on the temperature, content of water in the fertilizer and hydrodynamic conditions. Different hydrodynamic conditions were simulated by different speeds of the propeller stirrer. The empirical equation describing the volumetric overall mass transfer coefficient was proposed. 相似文献
993.
The article deals with recent failures of the EUSAMA methodology which is used for non-destructive testing of the car chassis without disassembling. Using simulated data, we perform an analysis of false-negative evaluation of car condition which occurs often on cars, which are actually in good technical shape. Suggested analysis is able to evaluate the changes introduced to the testing methodology directly on this particular group of chassis designs. The excitation stroke is identified as one of the main causes of methodology failure. The authors suggest that the stroke does not match the roughness profile of current roads. The authors propose certain adjustments of the EUSAMA methodology which should eliminate growing set of tests with contradictory diagnosis result. Suggested adjustments are tested by simulation as well. These adjustments involve changes either in software or hardware section of methodology. Significantly, the proposed adjustments can be easily applied to most EUSAMA testers already produced. However, it is assumed that the suggested methodology changes will be so significant, that new methodology cannot be labeled as EUSAMA anymore. 相似文献
994.
Linfeng Chen Dr. Michael J. Turo Dr. Milan Gembicky Ruth A. Reinicke Prof. Dr. Alina M. Schimpf 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16752-16758
The Preyssler polyoxoanion, [NaP5W30O110]14− ({P5W30}), is used as a platform for evaluating the role of nonbridging cations in the formation of transition-metal-bridged polyoxometalate (POM) coordination frameworks. Specifically, the assembly architecture of Co2+-bridged frameworks is shown to be dependent on the identity and amount of alkali or alkaline-earth cations present during crystallization. The inclusion of Li+, Na+, K+, Mg2+, or Ca2+ in the framework synthesis is used to selectively synthesize five different Co2+-bridged {P5W30} structures. The influence of the competition between K+ and Co2+ for binding to {P5W30} in dictating framework assembly is evaluated. The role of ion pairing on framework assembly structure and available void volume is discussed. Overall, these results provide insight into factors governing the ability to achieve controlled assembly of POM-based coordination networks. 相似文献
995.
Dr. Milan R. Milovanović Dr. Quentin Dherbassy Dr. Joanna Wencel-Delord Prof. Dr. Françoise Colobert Prof. Dr. Snežana D. Zarić Dr. Jean-Pierre Djukic 《Chemphyschem》2020,21(18):2136-2142
To figure out the possible role of 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) as well as to provide reference thermochemical data in solution, the formation of Lewis acid-base complexes between HFIP (Lewis acid) and a series of 8 different Lewis bases (3 sulfoxides, 3 Nsp2 pyridine derivatives, 1 aromatic amine, 1 cyclic aliphatic ether) was examined by isothermal titration calorimetry (ITC) experiments and static density functional theory augmented with Dispersion (DFT−D) calculations. Measured ITC association enthalpy values (ΔHa) lie between −9.3 and −14 kcal mol−1. Computations including a PCM implicit solvation model produced similar exothermicity of association of all studied systems compared to the ITC data with ΔHa values ranging from −8.5 to −12.7 kcal mol−1. An additional set of calculations combining implicit and explicit solvation by chlorobenzene of the reactants, pointed out the relatively low interference of the solvent with the HFIP-base complexation: its main effect is to slightly enhance the Gibbs energy of the HFIP-Lewis base association. It is speculated that the interactions of bulk HFIP with Lewis bases therefore may significantly intervene in catalytic processes not only via the dynamic microstructuring of the medium but also more explicitly by affecting bonds’ polarization at the Lewis bases. 相似文献
996.
997.
Tai-Chia?LinEmail author Milivoj?R.?Beli? Milan?S.?Petrovi? Hichem?Hajaiej Goong?Chen 《Calculus of Variations and Partial Differential Equations》2017,56(5):147
The virial theorem is a nice property for the linear Schrödinger equation in atomic and molecular physics as it gives an elegant ratio between the kinetic and potential energies and is useful in assessing the quality of numerically computed eigenvalues. If the governing equation is a nonlinear Schrödinger equation with power-law nonlinearity, then a similar ratio can be obtained but there seems to be no way of getting any eigenvalue estimates. It is surprising as far as we are concerned that when the nonlinearity is either square-root or saturable nonlinearity (not a power-law), one can develop a virial theorem and eigenvalue estimates of nonlinear Schrödinger (NLS) equations in \({{\mathbb {R}}^{2}}\) with square-root and saturable nonlinearity, respectively. Furthermore, we show here that the eigenvalue estimates can be used to obtain the 2nd order term (which is of order \(\ln \Gamma \)) of the lower bound of the ground state energy as the coefficient \(\Gamma \) of the nonlinear term tends to infinity. 相似文献
998.
The catalytic oxidation of a synthetic water-soluble analogue of vitamin E (α-tocopherol, Trolox) by tyrosinase enzyme in the presence of molecular oxygen was studied using electrochemical techniques. This specific enzymatic reaction was exploited for the preparation of a biosensor based on the amperometric reduction of the electroactive product (α-tocoquinone) formed. An electroactive surface of the transducers used was covered with a thin conductive layer of Nafion containing tyrosinase. Significant progress in sensitivity towards polyphenolic compounds such as Trolox was achieved at CPE with carbon nanotubes immobilised on its surface (CPE/CNTs) as electric transducers. The biosensor so developed can be used for the direct determination of total phenolic content (TPC). This important nutrition value can be expressed as the mass equivalent of Trolox, i.e. Trolox equivalent antioxidant capacity (TEAC), which could be used as an alternative to the evaluations currently used based on spectrophotometric methods such as total radical-trapping antioxidant parameter (TRAP), ferric reducing-antioxidant power (FRAP) or 1,1-diphenyl-2-picrylhydrazyl spectrometric assay (DPPH). The effects of the enzyme amount in the Nafion layer (3.0 µg), the influence of the nanoparticles present, the optimal pH value suitable for enzymatic activity (7.0), and the kinetics of enzymatic and electrochemical reactions were studied using cyclic voltammetry (CV). The determination of optimal conditions for amperometry in batch configuration (working potential, speed of stirring, volume of sample, calibration curve, etc.) was not a target of this electrochemical study. 相似文献
999.
Martin Vlk Milan Urban Tomas Elbert Jan Sarek 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1149-1157
The aim of this work was to synthesize deuterated and tritiated analogues of highly oxidized lupane derivatives known from our group. We selected compounds that previously showed very high cytotoxic activity on multiple cancer cell lines in order to further investigate the mechanism of their action. From starting material (compounds 1–4), we obtained benzyl platanate (5) and its reaction with deuteromethyltriphenylphosphonium iodide gave deuterated compound 6. Following benzyl deprotection gave free acid 7 and oxidation with SeO2 gave 30-oxo-[29-2H2]lup-20(29)-en-28-oic acid (8), which is one of the most active compounds synthesized in our group to date (IC50 6 μmol/L on CEM cell line). The alkylation of benzyl 2-hydroxy-3-oxolupa-1,20(29)-dien-28-oate (9) with methyliodide or deuteromethyliodide followed by a series of deprotection and hydrogenation steps gave compounds 10–14, where 2β-[31-2H3]methoxy-3-oxolupan-20(29)-en-28-oic acid (13) is especially interesting, it showed lower activity on CEM cell line (IC50 10 μmol/L) however, it was very active against Ph1—positive human leukemia BV-173 (IC50 0.91 μmol/L) and against human myelogenous leukemia K562 (IC50 0.52 μmol/L). Selectively labelled [3α-2H] and [3α-3H] methyl 3β-acetoxy-21,22-dioxolup-18-en-28-oates 24, 25 were prepared in three steps by reduction of corresponding 3-oxo derivatives and they showed moderate activity on CEM cell line (IC50 10 μmol/L). In total, 11 labelled compounds (6–8, 11, 14, 18, 19, 21, 22, 24 and 25) have not been reported before. 相似文献
1000.
The performance of weak and strong anion- and cation-exchange membrane adsorbents with a grafted gel layer (Sartobind Q, D, S, and C) was investigated using six proteins: bovine serum albumin, human serum albumin, α-lactalbumin, β-lactoglobulin, lysozyme, and myoglobin. Static binding experiments were used to assess the effect of pH and buffer concentration and to determine the adsorption isotherms for selected membrane/protein combinations. The equilibrium data were duly described either by the Langmuir or Freundlich isotherms. Dynamic binding experiments were carried out for the same membrane/protein combinations in a broad range of linear flow velocity. Both the dynamic binding capacity at 10 % breakthrough and the final binding capacity at complete breakthrough were independent of the flow velocity despite strong dispersion of the adsorption zone. A good match between the equilibrium data from static and dynamic experiments was obtained for the anion exchangers. The correlation between the dynamic binding capacity and protein molecule size was observed for the strong cation exchanger. This was due to the different accessibility of the gel layer for the protein molecules. 相似文献