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The composition of vinyl acetate–butyl acrylate copolymers obtained with batch emulsion polymerization have been studied by 1H-NMR. Using the integrated copolymerization Meyer–Lowry equation, the apparent reactivity ratios of the two monomers were calculated as 10.67 for r1, the reactivity ratio of butyl acrylate (BA), and 0.024 for r2, the reactivity ratio of vinyl acetate (VAC). These results were compared with those obtained by other methods. 相似文献
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The photochemistry of various Roussin's red ester compounds of the general formula Fe(2)(SR)(2)(NO)(4), where R = CH(3), CH(2)CH(3), CH(2)C(6)H(5), CH(2)CH(2)OH, and CH(2)CH(2)SO(3)(-), were investigated. Continuous photolyses of these ester compounds in aerated solutions led to the release of NO with moderate quantum yields for the photodecomposition of the ester (Phi(RSE) = 0.02-0.13). Electrochemical studies using an NO electrode demonstrated that 4 mol of NO are generated for each mole of ester undergoing photodecomposition. Nanosecond flash photolysis studies of Fe(2)(SR)(2)(NO)(4) (where R = CH(2)CH(2)OH and CH(2)CH(2)SO(3)(-)) indicate that the initial photoreaction is the reversible dissociation of NO. In the absence of oxygen, the presumed intermediate, Fe(2)(SR)(2)(NO)(3), undergoes second-order reaction with NO to regenerate the parent cluster with a rate constant of k(NO) = 1.1 x 10(9) M(-1) s(-1) for R = CH(2)CH(2)OH. Under aerated conditions the intermediate reacts with oxygen to give permanent photochemistry. 相似文献
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In this paper, linear stability and chaotic motion of a time-delayednonlinear vehicle system are studied. The stability is determined bycomputing the spectrum associated with a system of linear retardedfunctional differential equations, which reveals that a loss ofstability occurs following a Hopf bifurcation. Beyond the critical valuefor linear stability, the system exhibits limit cycle motions.Subharmonic, quasi-periodic and chaotic motions are observed for asystem excited by a periodic disturbance. 相似文献
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In this study, we investigate the hydration of three different functional groups present on cellulose nanocrystal (CNC) surfaces: hydroxyls, carboxylates and sulphates by means of quantum chemical calculation. The performance of several density functional theory (DFT) functionals in reproducing, against higher level MP2 benchmark calculations, relevant non-covalent CNC interactions is also assessed. The effect of a sodium ion on the hydration of the surface functional groups was also investigated. Major restructuring of the hydrogen-bonding network within cellulose was found in the presence of a sodium ion. The calculated binding energy of water with a surface group ion pair was also greater, which indicates a greater hydrophilicity of CNC surfaces in the presence of adsorbed sodium. Cellulose hydrophilic surfaces (1 1 0) and (1 ?1 0) were also calculated using DFT methods. The results indicate that the surfaces possess different electrostatic potential maps. Hydrogen bond restructuring is found on the chemically modified surfaces. The adsorption energy of water and electrolyte is also found to be different on each surface. 相似文献
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Vadim?V.?KrongauzEmail author Yann-Per?Lee Anthony?Bourassa 《Journal of Thermal Analysis and Calorimetry》2011,106(1):139-149
Extensively studied thermal degradation of polyvinyl chloride (PVC) occurs with formation of free hydrogen chloride and conjugated
double bonds absorbing light in visible region. Thermogravimetric monitoring of PVC blends degradation kinetics by the loss
of HCl is often complicated by evaporation and degradation of plasticizers and additives. Spectroscopic PVC degradation kinetics
monitoring by absorbance of forming conjugated polyenes is specific and should not be affected by plasticizers loss. The kinetics
of isothermal degradation monitored by thermal gravimetric analysis in real time was compared with batch data obtained by
UV/Visible absorption spectroscopy. Effects of plasticizer on kinetics of polyene formation were examined. Thermal degradation
of PVC films plasticized with di-(2-ethylhexyl) phthalate (DEHP) and 1,2,4-benzenedicarboxylic acid, tri-(3-ethylhexyl) ester
(TOTM) was monitored by conjugated double bonds light absorption at 350 nm at 160, 180, and 200 °C. Plasticizer-free PVC powder
degradation kinetics and that of plasticized films were also obtained thermogravimetrically at temperatures ranging from 160
to 220 °C. Plasticizer-free PVC powder degradation and spectroscopically monitored degradation of plasticized PVC films occurred
with the same apparent activation energy of ≈150 kJ mol−1. No difference in degradation kinetics of films plasticized with DEHP and TOTM was detected. 相似文献
7.
J. Truitt Wiensz Adam E. Bourassa Nick D. Lloyd Aldona Wiacek Randall V. Martin Doug A. Degenstein 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(8):582-593
The scattering of visible light by ice crystals and dust in radiative transfer models is challenging in part due to the large amount of scattering in the forward direction. We introduce a technique that ensures numerical conservation of photons in any radiative transfer model and that quantifies the integration error associated with highly asymmetric phase functions. When applied to a successive-orders of scatter model, the technique illustrates the high accuracy obtained in numerical integration of molecular and aerosol scattering. As well, a phase function truncation and renormalization technique is applied to scattering by ice crystals with very large size parameters, between 100 and 1000, and the scaled radiative transfer equation is solved with the spherical successive-orders model, SASKTRAN. Since computations shown this work are performed in a fully spherical model atmosphere, the computed radiances are not subject to the discontinuity at the horizon that is inherent in models using a plane–parallel assumption. The methods introduced in this work are of particular interest in modeling limb radiances in the presence of thin cirrus clouds. 相似文献
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Nonlinear oscillations and chaotic motions in a road vehicle system with driver steering control 总被引:5,自引:0,他引:5
The nonlinear dynamics of a differential system describing the motion of a vehicle driven by a pilot is examined. In a first step, the stability of the system near the critical speed is analyzed by the bifurcation method in order to characterize its behavior after a loss of stability. It is shown that a Hopf bifurcation takes place, the stability of limit cycles depending mainly on the vehicle and pilot model parameters. In a second step, the front wheels of the vehicle are assumed to be subjected to a periodic disturbance. Chaotic and hyperchaotic motions are found to occur for some range of the speed parameter. Numerical simulations, such as bifurcation diagrams, Poincaré maps, Fourier spectrums, projection of trajectories, and Lyapunov exponents are used to establish the existence of chaotic attractors. Multiple attractors may coexist for some values of the speed, and basins of attraction for such attractors are shown to have fractal geometries. 相似文献
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Stabilization of Aliphatic Phosphines by Auxiliary Phosphine Sulfides Offers Zeptomolar Affinity and Unprecedented Selectivity for Probing Biological CuI
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Dr. M. Thomas Morgan Dr. Bo Yang Dr. Shefali Harankhedkar Arielle Nabatilan Dr. Daisy Bourassa Dr. Adam M. McCallum Fangxu Sun Prof. Dr. Ronghu Wu Prof. Dr. Craig R. Forest Prof. Dr. Christoph J. Fahrni 《Angewandte Chemie (International ed. in English)》2018,57(31):9711-9715
Full elucidation of the functions and homeostatic pathways of biological copper requires tools that can selectively recognize and manipulate this trace nutrient within living cells and tissues, where it exists primarily as CuI. Buffered at attomolar concentrations, intracellular CuI is, however, not readily accessible to commonly employed amine and thioether‐based chelators. Herein, we reveal a chelator design strategy in which phosphine sulfides aid in CuI coordination while simultaneously stabilizing aliphatic phosphine donors, producing a charge‐neutral ligand with low‐zeptomolar dissociation constant and 1017‐fold selectivity for CuI over ZnII, FeII, and MnII. As illustrated by reversing ATP7A trafficking in cells and blocking long‐term potentiation of neurons in mouse hippocampal brain tissue, the ligand is capable of intercepting copper‐dependent processes. The phosphine sulfide‐stabilized phosphine (PSP) design approach, which confers resistance towards protonation, dioxygen, and disulfides, could be readily expanded towards ligands and probes with tailored properties for exploring CuI in a broad range of biological systems. 相似文献
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