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131.
An inverse coefficient problem for a quasilinear parabolic equation with periodic boundary and integral overdetermination condition 下载免费PDF全文
In this paper, the inverse problem of finding the time‐dependent coefficient of heat capacity together with the solution periodic boundary and integral overdetermination conditions is considered. Under some natural regularity and consistency conditions on the input data, the existence, uniqueness, and continuous dependence upon the data of the solution are shown. Some considerations on the numerical solution for this inverse problem are presented with an example. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
132.
Xia Liu Yuanbiao Zhang Haiping Shi Xiaoqing Deng 《Mathematical Methods in the Applied Sciences》2015,38(1):1-10
By using the critical point method, some new criteria are obtained for the existence and multiplicity of periodic solutions for fourth-order nonlinear functional difference equations. The proof is based on the linking theorem in combination with variational technique. Recent results in the literature are generalized and significantly improved. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
133.
本文研究一类二维非线性的广义sine-Gordon(简称SG)方程的有限差分格式.首先构造三层时间的紧致交替方向隐式差分格式,并用能量分析法证明格式具有二阶时间精度和四阶空间精度.然后应用改进的Richardson外推算法将时间精度提高到四阶.最后,数值算例证实改进后的算法在空间和时间上均达到四阶精度. 相似文献
135.
Saroj K. Rout David Rhyner Roland Riek Jason Greenwald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(3):e202103841
The prebiotic emergence of molecules capable both of self-replication and of storing information was a defining event at the dawn of life. Still, no plausible prebiotic self-replication of biologically relevant molecules has been demonstrated. Building upon the known templating nature of amyloids, we present two systems in which the products of a peptide-bond-forming reaction act as self-replicators to enhance the yield and stereoselectivity of their formation. This first report of an amino acid condensation that can undergo autocatalysis further supports the potential role of amyloids in prebiotic molecular evolution as an environment-responsive and information-coding system capable of self-replication. 相似文献
136.
Dr. Mohammad Kamal Hossain Dr. Qasem Ahmed Drmosh Amar Kamal Mohamedkhair 《化学:亚洲杂志》2021,16(13):1807-1819
A new route has been developed to design plasmonic pollen grain-like nanostructures (PGNSs) as surface-enhanced Raman scattering (SERS)-active substrate. The nanostructures consisting of silver (Ag) and gold (Au) nanoparticles along with zinc oxide (ZnO) nanoclusters as spacers were found highly SERS-active. The morphology of PGNSs and those obtained in the intermediate stage along with each elemental evolution has been investigated by a high-resolution field emission scanning electron microscopy. The optical band gaps and crystal structure have been identified by UV-vis absorption and X-ray powder diffraction (XRD) measurements, respectively. For PGNSs specimen, three distinct absorption bands related to constituent elements Ag, Au, and ZnO were observed, whereas XRD peaks confirmed the existence of Ag, Au, and ZnO within the composition of PGNSs. SERS-activity of PGNSs was confirmed using Rhodamine 6G (R6G) as Raman-active dyes. Air-cooled solid-state laser kits of 532 nm were used as excitation sources in SERS measurements. SERS enhancement factor was estimated for PGNSs specimen and was found as high as 3.5×106. Finite difference time domain analysis was carried out to correlate the electromagnetic (EM) near-field distributions with the experiment results achieved under this investigation. EM near-field distributions at different planes were extracted for s-, p- and 45° of incident polarizations. EM near-field distributions for such nanostructures as well as current density distributions under different circumstances were demonstrated and plausible scenarios were elucidated given SERS enhancements. Such generic fabrication route as well as correlated investigation is not only indispensable to realize the potential of SERS applications but also unveil the underneath plasmonic characteristics of complex SERS-active nanostructures. 相似文献
137.
Luk Petera Klaudia Mrazikova Lukas Nejdl Kristyna Zemankova Marketa Vaculovicova Adam Pastorek Svatopluk Civis Petr Kubelik Alan Heays Giuseppe Cassone Jiri Sponer Martin Ferus Judit Sponer 《Molecules (Basel, Switzerland)》2021,26(8)
Synthesis of RNA nucleobases from formamide is one of the recurring topics of prebiotic chemistry research. Earlier reports suggest that thymine, the substitute for uracil in DNA, may also be synthesized from formamide in the presence of catalysts enabling conversion of formamide to formaldehyde. In the current paper, we show that to a lesser extent conversion of uracil to thymine may occur even in the absence of catalysts. This is enabled by the presence of formic acid in the reaction mixture that forms as the hydrolysis product of formamide. Under the reaction conditions of our study, the disproportionation of formic acid may produce formaldehyde that hydroxymethylates uracil in the first step of the conversion process. The experiments are supplemented by quantum chemical modeling of the reaction pathway, supporting the plausibility of the mechanism suggested by Saladino and coworkers. 相似文献
138.
Tiziana Forleo Alessandro Zappi Dora Melucci Martina Ciriaci Francesco Griffoni Simone Bacchiocchi Melania Siracusa Tamara Tavoloni Arianna Piersanti 《Molecules (Basel, Switzerland)》2021,26(9)
The international seafood trade is based on food safety, quality, sustainability, and traceability. Mussels are bio-accumulative sessile organisms that need regular control to guarantee their safe consumption. However, no well-established and validated methods exist to trace mussel origin, even if several attempts have been made over the years. Recently, an inorganic multi-elemental fingerprint coupled to multivariate statistics has increasingly been applied in food quality control. The mussel shell can be an excellent reservoir of foreign inorganic chemical species, allowing recording long-term environmental changes. The present work investigates the multi-elemental composition of mussel shells, including Al, Cu, Cr, Zn, Mn, Cd, Co, U, Ba, Ni, Pb, Mg, Sr, and Ca, determined by inductively-coupled plasma mass-spectrometry in Mytilus galloprovincialis collected along the Central Adriatic Coast (Marche Region, Italy) at 25 different sampling sites (18 farms and 7 natural banks) located in seven areas. The experimental data, coupled with chemometric approaches (principal components analysis and linear discriminant analysis), were used to create a statistical model able to discriminate samples as a function of their production site. The LDA model is suitable for achieving a correct assignment of >90% of individuals sampled to their respective harvesting locations and for being applied to counteract fraud. 相似文献
139.
以“常见物质的检验”的教学为例,运用化学史料帮助学生自主建构知识体系,促进学生追寻知识本原,实现思维进阶,发展核心素养,并阐述运用化学史料构建高中化学生命课堂的实施策略。 相似文献
140.