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111.
Methodi Chetkarov Lachezar Karagyozov Todor Nikolov Dimiter Kolev 《Monatshefte für Chemie / Chemical Monthly》1986,117(8-9):1021-1026
The reaction cellulase (EC 3.2.1.4)—sodium carboxymethylcellulose (Na-CMC) with different degrees of polymerization (n=140, 640 and 900) was investigated by the use of a modifiedMichaelis-Menten equation, valid for enzymatic hydrolysis of linear homopolymers. TheMichaelis-Menten constant [Km (M)=6.31·10–2mol/dm3] and the reaction rate constant (k
+2=4.07·10–6s–1), which correspond to the enzymatic hydrolysis of a single bond in the homopolymer substrates are determined. The free energy (
=101 kJ/mol), which corresponds to the degradation and formation of a single bond in the enzyme—polymer substrate is also estimated. This energy expressed in electronvolt units is
=1.39 eV. The ratio between the effective cross section of the reactive substrate bond and the active enzyme center is =1.22.
Kinetik der enzymkatalysierten Hydrolyse von Natriumcarboxymethylcellulose mit verschiedenem Polymerisationsgrad durch Cellulase
Zusammenfassung Die modifizierte Gleichung nachMichaelis-Menten wird bei der durch Cellulase (EC 3.2.1.4) katalysierten hydrolytischen Spaltung von Natriumcarboxy-methylcellulose (Na-CMC) verschiedenen Polymerisationsgrades (n=140, 640 und 900) angewandt. Es wurde dieMichaelis-Menten-Konstante [Km (M)=6.31·10–2mol/dm3] und die Reaktionsgeschwindigkeitskonstante (k +2=4.07·10–6s–1), die der enzymatischen Hydrolyse einer Einfachbindung im homopolymeren Substrat entspricht, berechnet. Die freie Energie ( =101 kJ/mol), die dem Abbau und der Bildung einer Einfachbindung im Enzym—Polymer-Substrat entspricht, wurde bestimmt. Diese Energie — ausgedrückt in Elektronvolt-Einheiten — beträgt =1.39 eV. Das Verhältnis zwischen den effektiven Querschnitten der reaktiven Substratbindung ( S ) und des aktiven Enzym-Zentrums ( E ) beträgt =1.22.相似文献
112.
A universal and straightforward method for the preparation of polymer brushes via the formation of Si-C bond on silicon substrates through the UV-induced photopolymerization is demonstrated. 相似文献
113.
114.
E. C. Piquette M. Zandian D. D. Edwall J. M. Arias 《Journal of Electronic Materials》2001,30(6):627-631
A semi-empirical constraint to the thermodynamical model for growth of Hg1−xCdxTe (MCT) by molecular beam epitaxy is described. This constraint, derived by forcing the population of Hg atoms in a surface
layer to be proportional to the HgTe fractional growth rate, can determine an optimal total growth rate for specific beam
fluxes and substrate temperature. Utilizing improved growth conditions determined by this model has resulted in MCT layers
with consistently lower visible defect density (e.g., voids). The majority of recent layers grown using the constrained conditions
has achieved defect densities limited by the CdZnTe substrate. On the highest quality substrates, total defect densities have
consistently been reduced to the 100–200 cm−2 range using the improved conditions for compositions x=0.2 to x=0.6. On more typical substrates, the total defect density
is 1000–1500 cm−2. This compares with densities of 3000–5000+ cm−2 for old layers grown under non-optimized conditions. The density of voids has remained about the same upon using the improved
conditions, and is determined primarily by the Te precipitate content of the substrate, but microdefect (hillock) density
has been reduced by almost a factor of ten. 相似文献
115.
116.
Y. Bogumilowicz J.M. Hartmann C. Di Nardo P. Holliger A.-M. Papon G. Rolland T. Billon 《Journal of Crystal Growth》2006,290(2):523-531
We have first of all studied (in reduced pressure–chemical vapour deposition) the high-temperature growth kinetics of SiGe in the 0–100% Ge concentration range. We have then grown very high Ge content (55–100%) SiGe virtual substrates at 850 °C. We have focused on the impact of the final Ge concentration on the SiGe virtual substrates’ structural properties. Polished Si0.5Ge0.5 virtual substrates were used as templates for the growth of the high Ge concentration part of such stacks, in order to minimize the severe surface roughening occurring when ramping up the Ge concentration. The macroscopic degree of strain relaxation increases from 99% up to values close to 104% as the Ge concentration of our SiGe virtual substrates increases from 50% up to 100% (discrepancies in-between the thermal expansion coefficients of Si and SiGe). The surface root mean square roughness increases when the Ge concentration increases, reaching values close to 20 nm for 100% of Ge. Finally, the field (the pile-up) threading dislocations density (TDD) decreases as the Ge concentration increases, from 4×105 cm−2 (1–2×105 cm−2) for [Ge]=50% down to slightly more than 1×105 cm−2 (a few 104 cm−2) for [Ge]=88%. For [Ge]=100%, the field TDD is of the order of 3×106 cm−2, however. 相似文献
117.
A transition metal-free tandem process for the synthesis of 1,2,4-triazoloquinoxalines was described. The construction of this tricyclic system went through a one-pot condensation/nucleophilic aromatic substitution approach. This methodology applied to a broad range of substrates, which included 2-halogenated or 2-nitro aryl aldehydes and ketones. 相似文献
118.
In this work, the electric charging effect on the spreading of droplet impacting on dielectric substrates has been investigated. The charged water droplets were directed on the paraffin wax and the Teflon-coated plates. The impinging behavior was visualized and recorded using a CCD camera to identify the maximum extent of the flattened droplets. Droplet diameter and velocity approaching the wall were measured as well. The diameter of the electrically charged droplet at the maximum spread turned out to be larger compared to that of neutral droplet (at the maximum spread), and the difference becomes larger with increasing of the electric charge ratio (defined as the ratio of the actual electric charge to the Rayleigh limit). This phenomenon is considered to be due to reduction of effective interfacial tensions between the liquid and the gas and between the liquid and the solid by electric charging. Finally, an improved model was proposed to predict the maximum spreading ratio for electrically charged droplets by introducing correlations on the liquid–gas and the liquid–solid interfacial tensions. 相似文献
119.
Haonan Li Yijing Yang Xun Zhu Hong Wang Dingding Ye Yang Yang Qiang Liao Rong Chen 《Advanced functional materials》2023,33(24):2300308
Flexibly and precisely controlling bubbles is of paramount significance for biological and chemical analysis, reaction engineering, etc. However, the buoyancy force acting on bubbles is significant, making it difficult to precisely manipulate bubbles. Particularly, controlling the anti-buoyancy motion of bubbles remains a fundamental challenge. Herein, a versatile light strategy for manipulating the anti-buoyancy motion of bubbles via a photosensitive substrate is developed. Upon focused laser beam irradiation, an intense Marangoni effect associated with non-uniform temperature distribution is induced underneath the bubble. The created excess Laplace pressure drives the bubble to move against the buoyancy force downward to the focused-laser-acted region, manifesting an excellent phototaxis motion. Theoretical analysis demonstrates that the Marangoni effect is responsible for actuating the anti-buoyancy motion of a bubble. With this light strategy, the bubble collection, transportation, and on-demand release can be flexibly implemented. Moreover, the phototaxis motion of bubbles inspires a manipulation protocol via the integration of 3D-structured design of photosensitive substrate. This light strategy for manipulating bubbles not only possesses sufficiently high accuracy and quick response, but also circumvents the limitation of the liquid volatility and multi-dimensional motion, which provides new ideas for rational control of bubble behaviors. 相似文献
120.
Dr. Yogesh Somasundar Iris C. Lu Dr. Matthew R. Mills Lisa Y. Qian Ximena Olivares Prof. Dr. Alexander D. Ryabov Prof. Dr. Terrence J. Collins 《Chemphyschem》2020,21(11):1083-1086
Understanding the catalysis of oxidative reactions by TAML activators of peroxides, i. e. iron(III) complexes of tetraamide macrocyclic ligands, advocated a spectrophotometric procedure for quantifying the catalytic activity of TAMLs for colorless targets (kII′, M−1 s−1), which is incomparably more advantageous in terms of time, cost, energy, and ecology than NMR, HPLC, UPLC, GC-MS and other similar techniques. Dyes Orange II or Safranin O (S) are catalytically bleached by non-excessive amount of H2O2 in the presence of colorless substrates (S1) according to the rate law: −d[S]/dt=kIkII[H2O2][S][TAML]/(kI[H2O2]+kII[S]+kII′[S1]). The bleaching rate is thus a descending hyperbolic function of S1 : v=ab/(b+[S1]). Values of kII′ found from a and b for phenol and propranolol with commonly used TAML [FeIII{o,o′-C6H4(NCONMe2CO)2CMe2}2(OH2)]+ are consistent with those for S1 (phenol, propranolol) obtained directly by UPLC. The study sends vital messages to enzymologists and environmentalists. 相似文献