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排序方式: 共有1414条查询结果,搜索用时 11 毫秒
41.
Louis Lemahieu Julien Bras Pascal Tiquet Sylvain Augier Alain Dufresne 《大分子材料与工程》2011,296(11):984-991
Cross‐linked alginate capsules a few millimeters in diameter have been formed by immersion in a CaCl2 solution. When adding cellulose whiskers or microfibrillated cellulose to the aqueous alginate solution, nanocomposite capsules containing 40 wt.% cellulosic nanoparticles were obtained. The morphology and compression strength of these capsules were investigated by microscopic observations and crushing tests, respectively. The capsules were extruded with a thermoplastic polymer. Visual inspection of the ensuing films shows a nonhomogeneous dispersion of the capsules that kept their integrity after extrusion. It results in preliminary disappointing mechanical properties of the composite films. However, further investigation is in progress to optimize this simple and ecofriendly process.
42.
Pascal Médéric Julien Ville Jacques Huitric Michel Moan Thierry Aubry 《Polymer Engineering and Science》2011,51(5):969-978
The article deals with the effect of processing procedures and conditions on structural, morphological, and rheological properties of ternary blends composed of polyethylene (PE), polyamide (PA)‐12, and organically modified montmorillonite nanoclay with selective affinity. Samples were prepared from PE/PA and PA/PE blends, either by simultaneous mixing or from a polymer/clay masterbatch, using two processing conditions. The results have shown the existence of a weight fraction threshold, above which no significant processing effect was observed. Below this weight fraction threshold, the results tend to underline the significant role of two parameters that depend on processing procedures and/or conditions: the contact time between PE and PA phases and the contact time between clay and PA. Clay structure, blend morphology, and rheological properties were all shown to depend on these two parameters, and also on the nature of the matrix (PE or PA), because of the selective affinity of clay toward polymer phases. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers 相似文献
43.
Dr. Julien J. Freudenreich Dr. Sean Bartlett Dr. Naomi S. Robertson Dr. Sarah L. Kidd Dr. Suzie Forrest Dr. Hannah F. Sore Dr. Warren R. J. D. Galloway Dr. Martin Welch Prof. David R. Spring 《ChemMedChem》2020,15(14):1289-1293
The cylindrocyclophanes are a family of macrocyclic natural products reported to exhibit antibacterial activity. Little is known about the structural basis of this activity due to the challenges associated with their synthesis or isolation. We hypothesised that structural modification of the cylindrocyclophane scaffold could streamline their synthesis without significant loss of activity. Herein, we report a divergent synthesis of the cylindrocyclophane core enabling access to symmetrical macrocycles by means of a catalytic, domino cross-metathesis-ring-closing metathesis cascade, followed by late-stage diversification. Phenotypic screening identified several novel inhibitors of methicillin-resistant Staphylococcus aureus. The most potent inhibitor has a unique tetrabrominated [7,7]paracyclophane core with no known counterpart in nature. Together these illustrate the potential of divergent synthesis using catalysis and unbiased screening methods in modern antibacterial discovery. 相似文献
44.
Nitin A. Patil Julien Tailhades Richard Anthony Hughes Frances Separovic John D. Wade Mohammed Akhter Hossain 《International journal of molecular sciences》2015,16(1):1791-1805
Bioactive peptides play important roles in metabolic regulation and modulation and many are used as therapeutics. These peptides often possess disulfide bonds, which are important for their structure, function and stability. A systematic network of enzymes—a disulfide bond generating enzyme, a disulfide bond donor enzyme and a redox cofactor—that function inside the cell dictates the formation and maintenance of disulfide bonds. The main pathways that catalyze disulfide bond formation in peptides and proteins in prokaryotes and eukaryotes are remarkably similar and share several mechanistic features. This review summarizes the formation of disulfide bonds in peptides and proteins by cellular and recombinant machinery. 相似文献
45.
Ronan Le Hyaric Hassen Benbelkacem Julien Bollon Rémy Bayard Renaud Escudié Pierre Buffière 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(7):1032-1035
The objective of this study was to evaluate the influence of moisture content on the specific methanogenic activity (SMA) of a fresh dry mesophilic digestate from a municipal solid waste digester plant. For this purpose, SMA tests were performed under mesophilic conditions in 500 mL glass bottles of volume used as batch reactors, during a period of 20–25 days. Cellulose, propionate and acetate were used as substrates (5 gCOD kg?1 digestate) at four different moisture contents, ranging from 65 to 82%. The moisture content strongly influenced the specific methanogenic activity. The highest SMA values were observed at a moisture content of 82% (11.1, 7.8 and 6.0 mgCOD gVS?1 d?1 for cellulose, propionate and acetate spikes, respectively). SMA and moisture content were found to be linearly linked. Dry digestion at low water content is thus detrimental to the biological activity, probably due to physical limitations. Copyright © 2011 Society of Chemical Industry 相似文献
46.
Paul Leplay Julien Réthoré Sylvain Meille Marie-Christine Baietto 《Journal of the European Ceramic Society》2012,32(15):3949-3958
The mechanical characterization of ceramics can be very challenging. Depending on their composition and fabrication process, ceramic materials may exhibit at room temperature different types of mechanical behaviours, ranging from linear elastic to quasi-brittle, like rocks, concrete or plasters. At elevated temperature, they may present a non-linear behaviour, due for instance to the presence of a vitreous phase. However, estimating the evolution of their behaviour from room temperature to elevated temperature is a challenging topic, especially when there is an asymmetry between tension and compression. A methodology based on Digital Image Correlation is presented in this paper where four point bending tests are analysed for temperatures ranging from 25 °C to 900 °C. For a ceramic mainly made of aluminium titanate, the evolution of an asymmetric constitutive law is identified with a strong link with microstructural observations using SEM images. 相似文献
47.
This study aims at investigating and characterizing the interphase in Polyethylene (PE)/Polyamide (PA) blends with nodular morphology, filled with organically modified Montmorillonite (C30B), using structural and rheological experimental techniques. PE/PA/C30B blends have been prepared by simultaneous mixing at a dispersed phase fraction (PE or PA) of 20% and a clay fraction ranging from 1 to 6%. Structural properties of the interphase have been investigated using XRD combined with TEM micrographs. The presence of numerous interphase defects is evidenced, and the effect of interphase disorder is discussed. Linear viscoelastic properties show the contribution of the interphase in PE matrix ternary blends at all clay fractions, whereas interphase effects are masked by the contribution of dispersed nanoclay particles in PA matrix ternary blends. 相似文献
48.
Dense and homogeneous multi-walled carbon nanotube/metal composites are prepared by powder metallurgy. The distribution of the nano-reinforcements in the matrix is studied by scanning electron microscopy and Raman spectroscopy. The mechanical properties of the composites are determined by means of static tensile tests and Vickers micro-hardness measurements. We show that a homogeneous dispersion of the nanotubes at the micron scale is required in order to improve the mechanical properties of the metal matrix composite. This can be achieved using ball-milling through the mechanisms of plastic deformation and cold-welding. Accordingly, we report significant improvements to the mechanical properties of composites prepared with a high-performance aluminium alloy AA5083 matrix. 相似文献
49.
Dr. Shinpei Uno Dr. Alexander H. Harkiss Dr. Roy Chowdhury Dr. Stuart T. Caldwell Tracy A. Prime Dr. Andrew M. James Dr. Brendan Gallagher Dr. Julien Prudent Prof. Dr. Richard C. Hartley Prof. Dr. Michael P. Murphy 《Chembiochem : a European journal of chemical biology》2023,24(11):e202200774
The targeting of bioactive molecules and probes to mitochondria can be achieved by coupling to the lipophilic triphenyl phosphonium (TPP) cation, which accumulates several hundred-fold within mitochondria in response to the mitochondrial membrane potential (Δψm). Typically, a simple alkane links the TPP to its “cargo”, increasing overall hydrophobicity. As it would be beneficial to enhance the water solubility of mitochondria-targeted compounds we explored the effects of replacing the alkyl linker with a polyethylene glycol (PEG). We found that the use of PEG led to compounds that were readily taken up by isolated mitochondria and by mitochondria inside cells. Within mitochondria the PEG linker greatly decreased adsorption of the TPP constructs to the matrix-facing face of the mitochondrial inner membrane. These findings will allow the distribution of mitochondria-targeted TPP compounds within mitochondria to be fine-tuned. 相似文献
50.
Copolymerization of norbornene with norbornene terminated polystyrene macromonomer in the presence of Ni-based/MAO catalytic systems 总被引:1,自引:0,他引:1
Copolymerization of -norbornenyl polystyrene macromonomer (NBE-PS) with norbornene (NBE) using Ni-based catalysts in combination with methylaluminoxane (MAO) was investigated. The nature of the catalyst, the
of the polystyrene macromonomer as well as the [NBE-PS]/[NBE] ratio have been shown to be important parameters to obtain graft copolymers with high NBE-PS incorporation (up to 43 wt%). The compatibilization ability of these graft copolymers has been checked for PS/PNBE blends. The length of the grafts was proved not to be an important parameter to consider compatibilization of the PS/PNBE blend. 相似文献