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101.
Xavier Fernàndez‐Francos Xavier Ramis Àngels Serra 《Journal of polymer science. Part A, Polymer chemistry》2014,52(1):61-75
The curing kinetics and network buildup during curing of epoxy–anhydride formulations using tertiary amines as initiators are reviewed in this work. A mechanism‐based kinetic and structural model has been defined, showing better prediction capabilities than previous living polymerization and simple regeneration models. The curing kinetics have been analyzed using differential scanning calorimetry (DSC), and the gelation during curing has been determined by combined thermomechanical analysis and DSC. The effect of initiator content and epoxy equivalent weight are taken into account. The network buildup has been modeled using a stochastic network buildup model based on the random combination of primary chains generated by the kinetic model. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 61–75 相似文献
102.
Most developed countries support farming activities through policies that are tailored to meet their specific social, economic and environmental objectives. Economic and environmental efficiency have recently become relevant targets of most of these policies, whose sound implementation can be enhanced by monitoring farm performance from a multidimensional perspective. This paper proposes farm-level technical and environmental efficiency measures that recognize the stochastic conditions in which production takes place. A state-contingent framework is used to model production uncertainty. An implementable representation of the technology is developed using data envelopment analysis. The application focuses on a sample of Catalan arable crop farms. Results suggest that technical efficiency is slightly lower in bad than in good growing conditions. Nitrogen pollution can decrease substantially more under good than bad growing conditions. 相似文献
103.
Esra Korkmaz Kirakli Gökhan Takan Sinan Hoca F. Zümrüt Biber Müftüler Ayfer Yurt Kılçar Serra Arun Kamer 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(3):595-602
The purpose of this study was to assess SPION’s in vitro radiosensitizer effect at 6MV-energies and to calculate nanoparticle enhancement ratio (NER) of SPIONs. Citrate coated-SPION’s were synthesized. Trypan-blue, metabolic activity tests were performed. Cell cultures were irradiated at 0,2,4,6,8 Gy at 6MV-energy. Clonogenic survival assays, NER calculations were carried out. SPIONs were biocompatible. NERs were cell-line specific and dose dependent. The highest radiosensitization were seen in radiosensitive MCF-7 and MDAH-2447 cells at 2 Gy (NER:1.49 and 1.39 respectively), in relatively radioresistant MDA-MB-231 cells at 4 Gy (NER:1.20). By increasing doses radiosensitizer effect disappeared. There is possibility that by synergistic effect, SPIONs may cause dose-dependent and cell-line specific radiosensitization at 6MV. 相似文献
104.
A study of the structure and bonding configuration of the bioactive glasses in the system Na2O–CaO–P2O5–SiO2 by Fourier transform Raman spectroscopy is presented. The assignment of the Raman lines, the changes in the Si–O–Si bond environment and the identification of the non-bridging silicon–oxygen groups (Si–O–NBO) for a wide range of silicate glasses are discussed. The frequency shifting and intensity variations of the Raman lines as a function of the bioactive glass composition are attributed to a decrease of the local symmetry originated by the addition of alkali and alkali earth oxides to the vitreous silica network. Correlation plots for the quantification of the Si–O–NBO groups as a function of the glass composition are also presented. These Raman analyses contribute to a better knowledge of the structural role of the network modifiers in the bioactive glasses and, as a consequence, improve the understanding of the bioactive process and the chemical routes of the CaP layer formation when exposed body fluids. 相似文献
105.
The influence of interdigital multilamination micromixer characteristics on monomer conversions, molecular weights and especially on the polydispersity index of block copolymers synthesized continuously in two microtube reactors is investigated. The micromixers are used to mix, before copolymerization, a polymer solution with different viscosities and the second monomer. Different geometries of micromixer (number of microchannels, characteristic lengths) have been studied. It was found that polydispersity indices of the copolymers follow a linear relationship with the Reynolds number in the micromixer, represented by a form factor. Thus, beside the operating conditions (nature of the first block and comonomer flow rate), the choice of the micromixer geometry and dimension is essential to control the copolymerization in terms of molecular weights and polydispersity indices. This linear correlation allows the prediction of copolymer features. It can also be a new method to optimize existing micromixers or design other geometries so that mixing could be more efficient. 相似文献
106.
Serra B Zhang J Morales MD Guzmán-Vázquez de Prada A Reviejo AJ Pingarrón JM 《Talanta》2008,75(4):1134-1139
The rapid detection of catalase-positive and catalase-negative bacteria in complex culture media has been accomplished by monitoring of hydrogen peroxide consumption or generation with a graphite-Teflon-peroxidase-ferrocene composite electrode. Escherichia coli and Streptococcus pneumoniae have been used as model catalase-positive and catalase-negative bacteria, respectively. Hydrogen peroxide evolution was amperometrically measured at 0.00 V. Experimental conditions, including the working solution composition, the incubation time and the hydrogen peroxide concentration, were optimized. The reusability of the biosensor was improved by placing a nylon membrane on the bioelectrode surface to prevent fouling caused by the bacterial medium. The developed methodology allowed the detection of E. coli and S. pneumoniae at concentration levels of approximately 2x10(6) and 2x10(5) cfu/mL, in assays taking 10 and 15 min, respectively, without any pre-concentration step or pre-enrichment procedure. 相似文献
107.
Dr. Wenhui Niu Dr. Yubin Fu Gianluca Serra Kun Liu Jörn Droste Yeonju Lee Zhitian Ling Dr. Fugui Xu Dr. José D. Cojal González Dr. Andrea Lucotti Prof. Dr. Jürgen P. Rabe Prof. Dr. Michael Ryan Hansen Prof. Dr. Wojciech Pisula Prof. Dr. Paul W. M. Blom Prof. Dr. Carlos-Andres Palma Prof. Dr. Matteo Tommasini Prof. Dr. Yiyong Mai Dr. Ji Ma Prof. Dr. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2023,62(35):e202305737
The incorporation of nanopores into graphene nanostructures has been demonstrated as an efficient tool in tuning their band gaps and electronic structures. However, precisely embedding the uniform nanopores into graphene nanoribbons (GNRs) at the atomic level remains underdeveloped especially for in-solution synthesis due to the lack of efficient synthetic strategies. Herein we report the first case of solution-synthesized porous GNR ( pGNR ) with a fully conjugated backbone via the efficient Scholl reaction of tailor-made polyphenylene precursor ( P1 ) bearing pre-installed hexagonal nanopores. The resultant pGNR features periodic subnanometer pores with a uniform diameter of 0.6 nm and an adjacent-pores-distance of 1.7 nm. To solidify our design strategy, two porous model compounds ( 1 a , 1 b ) containing the same pore size as the shortcuts of pGNR , are successfully synthesized. The chemical structure and photophysical properties of pGNR are investigated by various spectroscopic analyses. Notably, the embedded periodic nanopores largely reduce the π-conjugation degree and alleviate the inter-ribbon π–π interactions, compared to the nonporous GNRs with similar widths, affording pGNR with a notably enlarged band gap and enhanced liquid-phase processability. 相似文献
108.
The natural flavors 2-acetyl-1-pyrroline 1a, 2-propionyl-1-pyrroline 1b, 2-acetyl-3,4,5,6-tetrahydropyridine 1c, 2-acetyl-2-thiazoline 1d, 2-propionyl-2-thiazoline 1e, and the artificial flavor 2-acetyl-5,6-dihydro-4H-1,3-thiazine 1f have been prepared by catalytic SeO2 oxidation of the corresponding cyclic imines 6a-c and sulfur cyclic imines 7a-c using TBHP as co-oxidant. The oxidation of the pyrrolines 1a and b is completely regioselective. Professional olfactory evaluation together with the odor threshold of the new flavor 1f is reported. 相似文献
109.
Serra D Bosch A Russo DM Rodríguez ME Zorreguieta A Schmitt J Naumann D Yantorno O 《Analytical and bioanalytical chemistry》2007,387(5):1759-1767
This work describes the application of several analytical techniques to characterize the development of Bordetella pertussis biofilms and to examine, in particular, the contribution of virulence factors in this development. Growth of surface-attached
virulent and avirulent B. pertussis strains was monitored in continuous-flow chambers by techniques such as the crystal violet method, and nondestructive methodologies
like fluorescence microscopy and Fourier transform (FT) IR spectroscopy. Additionally, B. pertussis virulent and avirulent strains expressing green fluorescent protein were grown adhered to the base of a glass chamber of
1-μm thickness. Three-dimensional images of mature biofilms, acquired by confocal laser scanning microscopy, were quantitatively
analysed by means of the computer program COMSTAT. Our results indicate that only the virulent (Bvg+) phase of B. pertussis is able to attach to surfaces and develop a mature biofilm. In the virulent phase these bacteria are capable of producing
a biofilm consisting of microcolonies of approximately 200 μm in diameter and 24 μm in depth. FTIR spectroscopy allowed us
not only to follow the dynamics of biofilm growth through specific biomass and biofilm marker absorption bands, but also to
monitor the maturation of the biofilm by means of the increase of the carbohydrate-to-protein ratio. 相似文献
110.
The benzannulation reactions of substituted 3-alkoxycarbonyl-3,5-hexadienoic and 3-alkoxycarbonylhex-3-en-5-ynoic acids offer a straightforward access to various polysubstituted aromatic compounds. The process is very flexible, and can be applied to the regiospecific preparation of oligoaryls, naphthalenes, ring-fused heterocycles, chiral tetrahydronaphthalenes, C-aryl-glycosides and many natural products of different structure. In this Concept article, we highlight the potential of this annulation reaction by illustration of our recent contribution to this field, as well as the studies previous reported by others. 相似文献