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191.
Adrian Muntean 《Nonlinear Analysis: Real World Applications》2009,10(4):2541-2557
We deal with a one-dimensional coupled system of semi-linear reaction-diffusion equations in two a priori unknown moving phases driven by a non-local kinetic condition. The PDEs system models the penetration of gaseous carbon dioxide in unsaturated porous materials (like concrete). The main issue is that the strong competition between carbon dioxide diffusion and the fast reaction of carbon dioxide with calcium hydroxide–which are the main active reactants–leads to a sudden drop in the alkalinity of concrete near the steel reinforcement. This process–called concrete carbonation–facilitates chemical corrosion and drastically influences the lifetime of the material. We present details of a class of moving-boundary models with kinetic condition at the moving boundary and address the local existence, uniqueness and stability of positive weak solutions. We also point out our concept of global solvability. The application of such moving-boundary systems to the prediction of carbonation penetration into ordinary concrete samples is illustrated numerically. 相似文献
192.
Abdiaziz A. Farah Raluca Voicu Farid Bensebaa Karim Faid 《Applied Surface Science》2006,252(14):5158-5167
A novel alkylthioacetyl-capped hydroxyethyl methacrylate monomer and its corresponding homopolymer have been synthesized and characterized. Direct chemisorption of these moieties have been carried out on gold-coated substrate and found to form a strong surface bonding. The surface coverage and the properties of the resultant self-assembled layers have been investigated by multiple surface characterization techniques (i.e. ellipsometry, GA-FTIR, XPS, AFM, and contact angle measurements). These analyses have all confirmed the occurrence of complete chemisorption reactions with typical n-alkanethiol self-assembled characteristics. 相似文献
193.
194.
Fluorescence fluctuation experiments are performed in single-molecule detection regime if the fluorescence of at most one molecule is registered at a time. Although the significance of such experiments for investigations of complex nonergodic systems like those met in the biosciences has been stressed out by many scientists, the quantitative and accurate determination of the single-molecule detection regime received rather little attention. In this work we present a method based on the photon counting histogram (PCH) analysis, which enables the determination of the average number N of molecules within the observation volume, for which only the fluorescence of individual molecules is detected at a time. Thus, the accurate design of fluorescence fluctuation experiments performed in single-molecule detection regime is possible. Demonstrative fluorescence fluctuation experiments based on two-photon excitation are performed on diluted solutions of coumarin 153, in order to verify the potential of the PCH analysis in experiments on the single-molecule detection level. If the mean number N of molecules within the excitation volume is larger than 0.048, the probability to simultaneously detect the fluorescence of two or more molecules is no longer negligible, i.e., no single-molecule detection regime. If the mean number N of molecules is lower than 0.0057, the detection limit of the method is reached, i.e., the fluorescence signal cannot be distinguished from the background. Consequently, the concentration of coumarin 153 characteristic for the single-molecule detection regime lies in the range 13-110 pmol/l for the given experimental conditions. We also investigate the influence of the molecular brightness, i.e., detected photons per fluorophore molecule and sampling time, on the single-molecule detection regime. 相似文献
195.
Alexandru V. Asimit Raluca Vernic Ricardas Zitikis 《Methodology and Computing in Applied Probability》2016,18(3):805-827
Assuming the multiplicative background risk model, which has been a popular model due to its practical applicability and technical tractability, we develop a general framework for analyzing portfolio performance based on its subportfolios. Since the performance of subportfolios is easier to assess, the herein developed stepwise portfolio construction (SPC) provides a powerful alternative to a number of traditional portfolio construction methods. Within this framework, we discuss a number of multivariate risk models that appear in the actuarial and financial literature. We provide numerical and graphical examples that illustrate the SPC technique and facilitate our understanding of the herein developed general results. 相似文献
196.
This paper is a follow-up of the study realized by Vernic (2014) on the aggregation of dependent random variables joined by Sarmanov’s multivariate distribution, with accent on the particular case of exponentially distributed marginals. More precisely, in this paper we present capital allocation formulas for a portfolio of risks following the just mentioned Sarmanov’s distribution. The overall capital and its allocation to the risk sources are evaluated using the TVaR rule. The resulting formulas are illustrated in some particular cases. 相似文献
197.
The complex between protoporphyrin IX and zinc was immobilized on nanocarbon paste and on nanodiamond paste to design two stochastic microsensors. The microsensors were used for the recognition and analysis of antibiotics: amoxicillin, ampicillin, and biotin in water samples. Stochastic sensors provided different signatures for the three antibiotics making possible their simultaneous recognition and assay in water samples. Low limits of determination 0.3 pg/mL for amoxicillin and ampicillin, and 0.21 pg/mL for biotin were obtained when nanocarbon paste was used, and 0.03 pg/mL for amoxicillin, 0.30 pg/mL for ampicillin, and 2.14 fg/mL for biotin were obtained when nanodiamond paste was used. Recoveries higher than 99.32 % with RSD lower than 1.00 % were obtained for the assay of the antibiotics in water samples. 相似文献
198.
Guillaume Freychet Mireille Maret Marta Fernandez-Regulez Raluca Tiron Ahmed Gharbi Celia Nicolet Patrice Gergaud 《Journal of polymer science. Part A, Polymer chemistry》2020,58(15):2041-2050
The morphologies of poly(lactide)-block-poly(dimethylsiloxane)-block-polylactide (PLA-b-PDMS-b-PLA) triblock copolymer films were studied using a combination of grazing-incidence small-angle X-ray scattering, X-ray reflectivity and scanning electron microscopy. This block copolymer is characterized by a high Flory–Huggins interaction parameter which leads to the self-assembly of periodic high-resolution nanodomains. In this article, we performed a detailed analysis of GISAXS patterns, in the frame of the Distorted Wave Born Approximation, in order to determine the morphology of blocks and their spatial arrangement. For a low volume fraction of PLA (17%), a three-dimensional hexagonal lattice of PLA spherical blocks is revealed, while, for a PLA fraction twice larger, in-plane (parallel) PLA lying cylinders adopt a two-dimensional centered rectangular lattice. Moreover, the in-depth electron density profile of the polymer film for the cylindrical morphology was extracted from the XRR data, revealing the presence of interfacial layers at the top surface and at the interface with the Si substrate. 相似文献
199.
Theoretical Investigation on the PCP(O) Linear Moiety: How to Stabilize Diphosphaallenic Derivatives
Raluca Septelean Petronela M. Petrar Gabriela Nemes Jean Escudié Ioan Silaghi-Dumitrescu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2321-2331
Abstract Density functional theory calculations on phosphavinylidene(oxo)phosphorane RP?C?P(?O)R′ I are reported, where the R and R′ groups represent substituents with various electron-donor or electron-acceptor properties and different steric hindrance: H, F, Cl, OMe, SiH3, SiMe3, Me, Ph, Mes (2,4,6-trimethylphenyl), and Mes* (2,4,6-tri-tert-butylphenyl) and RF 2,4,6-tris(trifluoromethyl)-phenyl. The investigations provide information about the groups that seem to be the best choice for the stabilization of such systems. The influence of the substituents’ nature on the geometrical parameters and Wiberg bond orders for the P?C bonds are discussed. Two isomers of I with a PCPO linkage (P≡C?P(?O)RR′ II and O?P?C≡PRR′ III) have also been studied. GRAPHICAL ABSTRACT 相似文献
200.
Raluca Nicoleta Darie Ruxandra Bodirlau Carmen Alice Teaca Joanna Macyszyn Marek Kozlowski Iuliana Spiridon 《International Journal of Polymer Analysis and Characterization》2013,18(4):315-327
In the view of producing environmentally friendly materials without compromising properties, new composites containing polypropylene as a matrix and eucalyptus wood, with or without 15% of polylactic acid, were melt processed. In order to improve compatibility between components, a chemical modification of wood with toluene-2,4-diisocyanate (TDI) was realized and evidenced by changes in FT-IR and XPS spectra. The morphological, mechanical, and thermal characterizations of the obtained composites were evaluated before and after accelerating weathering. The results showed that the material comprising 15% TDI-modified wood, PP, and 15% PLA exhibited the best properties. 相似文献