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91.
Syntheses,characterization, and hydrolytic degradation of P(ε‐caprolactone‐co‐δ‐valerolactone) copolymers: Influence of molecular weight 下载免费PDF全文
Biodegradable poly(ε‐caprolactone‐co‐δ‐valerolactone) copolymers were synthesized and investigated to study their behavior in aqueous medium. The copolyesters were produced by ring opening polymerization between ε‐caprolactone (CL) and δ‐valerolactone (VL) in bulk at 140°C using tin(II) octoate as catalyst. They were characterized by using 1H NMR, size exclusion chromatography, differential scanning calorimetry, and MALDI TOF mass spectrometry. Reactivity ratio determination gave an insight on their microstructure. Hydration, hydrolytic degradation, and biocide release of P(CL‐VL) films with different molecular weights values were studied. A one‐order kinetic whose rate constant decreases with copolymer macromolecular weight was observed. Although the molecular weight decrease remained relatively weak after 8 months of immersion, a correlation between molecular weight and hydrolysis rate was shown by high performance liquid chromatography‐mass spectrometry. The ability of the P(CL‐VL) films to release active compounds dispersed in the films was studied by atomic absorption spectroscopy. The release behavior of all copolymers was identical with a zero‐order kinetic. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43007. 相似文献
92.
In order to model the tensile behaviour of flax fibre based composites, the properties of each of the constituents need to be determined. In addition to the fibres, the matrix and the fibre/matrix interface, the fibre/fibre interface present within a bundle of flax fibres is an element which is rather hard to characterize but whose properties also need to be taken into account to understand properly the deformation and rupture modes of the derived composites. In the first part of this study, the protocol used to determine these properties is described; the results of the mechanical tests and the microscopic observations carried out on pairs of fibres are given and exploited to lead to the fibre/fibre interface properties. In the second part, various cohesive zone models will be evaluated using these interface properties and numerical simulations will be performed for the purpose of validation. 相似文献
93.
A temperature fluctuation equation model dedicated to the computation of turbulent thermal layers in high Reynolds internal flows 总被引:1,自引:0,他引:1
Karine Truffin Adlène Benkenida 《International Journal of Heat and Mass Transfer》2008,51(21-22):5160-5174
The paper deals with the modelling of temperature fluctuations in the fresh gases for the simulation of turbulent internal flows. For this purpose, a transport equation for the sensible enthalpy variance is treated. The proposed dynamic model for the scalar dissipation rate incorporates the effect of the turbulent Reynolds number. The wall closure is based on a non-isothermal formulation and accounts for the non-equilibrium state of the boundary layer. The developed models are implemented into the compressible code IFP-C3D. Results of the computations are successfully compared with experiments and DNS data for a slightly heated jet and moderate non-isothermal walls. 相似文献
94.
Andrieux K Lesieur P Lesieur S Ollivon M Grabielle-Madelmont C 《Analytical chemistry》2002,74(20):5217-5226
Fluorescein Isothiocyanate-dextrans of various weight average molecular masses (4,400-487,000) were analyzed in buffer solution for pH, osmolarity, fluorescence intensity as a function of the polymer concentration, average molecular masses, and radii of gyration. Labeling of polymers and conformation of the polymers were characterized by high-performance gel exclusion chromatography (HPLC-GEC) and small-angle X-ray scattering. The fluorescence measurements evidence the absence of fluorescence quenching of the FITC chromophores but the existence of an inner filter effect at high polymer concentration. The conformation of the polymers in buffer is very likely of random coil type, as shown by the relationship between the radii of gyration and the weight-average molecular masses of the dextrans (Mw). The medium used to analyze the FITC-dextrans by HPLC-GEC strongly influences their elution behavior. In buffer medium, they are sieved over the TSK G4000 PW column through a single population according to their Mw. whereas in pure water, they are separated into several species by an exclusion mechanism that depends on the number of labeled sites per dextran molecule. A Monte Carlo simulation was used to analyze the distribution of the fluorescent labels. HPLC-GEC in water could interestingly be applied to yield labeled polymers bearing a known number of functionalized groups. 相似文献
95.
Kishan Radha; Zeelen Ph. Johan; Noble Martin E.M.; Borchert Torben V.; Mainfroid Veronique; Goraj Karine; Martial Joseph A.; Wierenga Rik K. 《Protein engineering, design & selection : PEDS》1994,7(8):945-951
Abstract The crystal structure of a hybrid Escherichia coli triosephosphateisomerase (TIM) has been determined at 2.8 Å resolution.The hybrid TIM (ETIM8CHI) was constructed by replacing the eighthß-unit of E.coli TIM with the equivalent unit of chickenTIM. This replacement involves 10 sequence changes. One of thechanges concerns the mutation of a buried alanine (Ala232 instrand 8) into a phenylalanine. The ETIM8CHI structure showsthat the A232F sequence change can be incorporated by a side-chainrotation of Phe224 (in helix 7). No cavities or strained dihedralsare observed in ETIM8CHI in the region near position 232, whichis in agreement with the observation that ETIM8CHI and E.coliTIM have similar stabilities. The largest CA (C-alpha atom)movements, 3 Å, are seen for the C-terminal end of helix8 (associated with the outward rotation of Phe224) and for theresidues in the loop after helix 1 (associated with sequencechanges in helix 8). From the structure it is not clear whythe kcat of ETIM8CHI is 10 times lower than in wild type E.coliTIM 相似文献
96.
Roberge Pasquale; Marchand André; Reinharz Daniel; Marchand Lyne; Cloutier Karine 《Canadian Metallurgical Quarterly》2004,45(3):202
This literature review examines the results of cost-effectiveness studies of cognitive-behaviour therapies published up to June 2003. Cost offsets likely to be derived from effective treatment of anxiety problems are also examined. A summary of results suggests the following: 1) cognitive-behaviour therapy is cost-effective compared to drug therapy for the treatment of panic disorder and social phobia; 2) group treatments and short courses as well as new technologies are promising alternatives to conventional therapy; 3) the existence of cost offsets for anxiety disorders has yet to be ascertained. Research approaches are suggested to cover significant shortcomings in the methodologies of studies conducted to date. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
Jacynthe Pouliot Karine Bédard Donna Kirkwood Bernard Lachance 《Computers & Geosciences》2008,34(5):529-541
Topological relationships between geological objects are of great interest for mining and petroleum exploration. Indeed, adjacency, inclusion and intersection are common relationships between geological objects such as faults, geological units, fractures, mineralized zones and reservoirs. However, in the context of 3D modeling, actual geometric data models used to store those objects are not designed to manage explicit topological relationships. For example, with Gocad© software, topological analyses are possible but they require a series of successive manipulations and are time consuming. This paper presents the development of a 3D topological query prototype, TQuery, compatible with Gocad© modeling platform. It allows the user to export Gocad© objects to a data storage model that regularizes the topological relationships between objects. The development of TQuery was oriented towards the use of volumetric objects that are composed of tetrahedrons. Exported data are then retrieved and used for 3D topological and spatial queries. One of the advantages of TQuery is that different types of objects can be queried at the same time without restricting the operations to voxel regions. TQuery allows the user to analyze data more quickly and efficiently and does not require a 3D modeling specialist to use it, which is particularly attractive in the context of a decision-making aid. The prototype was tested on a 3D GeoModel of a continental red-bed copper deposit in the Silurian Robitaille Formation (Transfiguration property, Québec, Canada). 相似文献
98.
99.
Goraj Karine; Renard Andre; Martial Joseph A. 《Protein engineering, design & selection : PEDS》1990,3(4):259-266
We have attempted to construct an artificial polypeptide thatfolds like the eight-stranded parallel ß-barrel structures.Our approach consists of repeating eight times a unit peptidedesigned to adopt a ß-strand/-helixpattern. A first test sequence for this structuralunit was deduced from a series of parameters defined after ananalysis of three natural /ß-barrel proteins and includingprincipally the lengths of the secondary structure elements,the /ß packing and the fitting on average Garnierprofiles. The gene encoding this structural unit was synthesized,cloned and expressed in Escherichia coli either as a monomeror as direct repeats of 212 units. Preliminary structuralcharacterization of the 7-, 8- and 9-fold unit polypeptidesby circular dichroism measurements indicates the presence ofthe predicted amount of -helix in the three proteins. Furtheranalysis by urea-gradient gel electrophoresis demonstrates that,in the conditions tested, only the 8-fold unit polypeptide formsa compact structure through a cooperative and rapid two-statefolding transition involving long-range molecular interactions. 相似文献
100.
Luana Mendona Dias Túlio Morandin Ferrisse Karine Sousa Medeiros Eduardo Maffud Cilli Ana Claudia Pavarina 《International journal of molecular sciences》2022,23(6)
Considering the challenges related to antimicrobial resistance, other strategies for controlling infections have been suggested, such as antimicrobial photodynamic therapy (aPDT) and antimicrobial peptides (AMP). This study aims to perform a systematic review and meta-analysis to obtain evidence on the antimicrobial effectiveness of aPDT associated with AMP and establish in vitro knowledge on this topic for further study designs. The PubMed, Scopus, Web of Science, Science Direct, Scielo, and Cochrane Library databases were searched. Two independent and calibrated researchers (Kappa = 0.88) performed all the systematic steps according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The odds ratio (OR) was used as the effect measure. The Peto method was used to perform the meta-analysis due to the sparse data. Twenty studies were included in the present review. The result was significant (OR = 0.14/p = 0.0235/I-squared = 0%), showing better outcomes of aPDT associated with peptides than those of aPDT alone for controlling the microbial load. Only 20% of the studies included evaluated this approach in a biofilm culture. Combined treatment with aPDT and AMP highly increased the ability of microbial reduction of Gram-positive and Gram-negative bacteria. However, additional blind studies are required to evaluate the efficacy of this therapy on microbial biofilms. 相似文献