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71.
Cellulose acetate was characterized by using enzyme in both digestion and chemical derivation and acetolysis. The fragments were normalised and compared on an anhydroglucose scale, using mass spectrometry to identify the different sized fragments. It was determined that at least two sub-populations for cellulose acetate existed within the parent. The macroscopic effect of this variation in the degree of acetylation will be a modification of the structural properties of the polymer chains. It was found that through comparison with enzyme-based degradation, an estimation of the acetylation topography of the cellulose acetate fraction could be made. Enzyme degradation produced a number of oligosaccharides of more than 10 glucose units, presumably resistant to enzyme degradation because they contained acetate groups. Chemical hydrolysis gave a random ladder of short sequences of mainly 3–4 glucose units some of which had a high methyl ether content, that were analysed by mass and converted to an anhydroglucose mass scale. This approach could be used to demonstrate differences between large biopolymers of cellulose acetate that previously gave an overall average rather than a specific ladder average. 相似文献
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In this paper, we present the sufficient conditions ensuring the instability of the zero solution of an impulsive state dependent delay integrodifferential system for different conditions on the delay function. We assume the instability of the associated linear impulsive system and apply the idea of dichotomies together with Schauder–Tychonoff theorem to establish the sufficient conditions for the unstable solution of the problem. 相似文献
76.
Nasuha Siti Pershaanaa M. Bashir Shahid Ramesh K. Ramesh S. 《Journal of Solid State Electrochemistry》2022,26(8):1733-1746
Journal of Solid State Electrochemistry - Binary metal sulfide–based electrode materials with distinct nanoarchitecture, improved conductivities, and fascinating mechanical stabilities are... 相似文献
77.
M. Shahid Rafique Shazia Bashir Ali Ajami Wolfgang Husinsky 《Applied Physics A: Materials Science & Processing》2010,100(4):1183-1189
We have investigated femtosecond laser irradiation effects on the surface topography, structural changes and nonlinear absorption
properties of CR-39. For this purpose, a CR-39 target was exposed in air to 25 fs, 800 nm Ti: sapphire laser radiation at
fluences ranging from 0.25 J cm−2 to 3.6 J cm−2. The surface of irradiated CR-39 probed by an Atomic Force Microscope (AFM) exhibits the formation of several topographical
structures, like bumps, explosions and nano cavities. Raman spectroscopy is performed to explore chemical and structural modification
of the irradiated target. The spectroscopy reveals changes such as cross linking, bond breaking, formation of new bonds etc.
in the fundamental structure of the polymer after irradiation. In order to establish a correlation between morphological and
structural changes with the changes in the nonlinear absorption of the irradiated CR-39, a Z-scan technique was employed.
A comparison of experimentally obtained data from Z-scan measurements with our calculations predicts the dominance of three-photon
absorption in the case of pristine CR-39, whereas for irradiated targets concurrence of three- and two-photon absorption is
probable. Nonlinear absorption increases with increasing laser fluences and is well correlated by surface and structural changes
revealed by AFM and Raman spectroscopy. 相似文献
78.
AbstractIn the present paper, we focus on a stochastic predator-prey model with stage structure for prey. Firstly, by using the stochastic Lyapunov function method, we obtain sufficient conditions for the existence and uniqueness of an ergodic stationary distribution of the positive solutions to the model. Then we establish sufficient conditions for extinction of the predator population in two cases. Some examples and numerical simulations are carried out to validate our analytical findings. 相似文献
79.
Fractional order nonlinear mixed coupled systems with coupled integro-differential boundary conditions 下载免费PDF全文
Bashir Ahm Ahmed Alsaedi Sotiris K. Ntouyas 《Journal of Applied Analysis & Computation》2020,10(3):892-903
We study the existence and uniqueness of solutions for a class of coupled fractional differential equations involving both Riemann-Liouville and Caputo fractional derivatives, and coupled integro-differential boundary conditions. We derive the desired results with the aid of modern methods of functional analysis. An example illustrating the abstract results is also presented. 相似文献
80.
Dynamical behavior of a stochastic food chain chemostat model with Monod response functions 下载免费PDF全文
Miaomao Gao Daqing Jiang Kai Qi Tasawar Hayat Ahmed Alsaedi Bashir Ahmad 《Journal of Applied Analysis & Computation》2019,9(6):2278-2294
This paper studies a food chain chemostat model with Monod response functions, which is perturbed by white noise. Firstly, we prove the existence and uniqueness of the global positive solution. Then sufficient conditions for the existence of a unique ergodic stationary distribution are established by constructing suitable Lyapunov functions. Moreover, we consider the extinction of microbes in two cases. In the first case, both the predator and prey species are extinct. In the second case, only the predator species is extinct, and the prey species survives. Finally, numerical simulations are carried out to illustrate the theoretical results. 相似文献