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排序方式: 共有2505条查询结果,搜索用时 10 毫秒
71.
S. A. Yakimov D. A. Knyaz’kov T. A. Bol’shova A. G. Shmakov O. P. Korobeinichev F. Qi 《Combustion, Explosion, and Shock Waves》2012,48(5):609-619
Molecular beam mass spectrometry with photoionizationby synchrotron radiation was used to study the structure of flat premixed flames of C2H4/O2/Ar and C2H4/C2H5OH/O2/Ar at a pressure of 30 torr (4 kPa) with equivalence ratios ϕ = 1 and 2. It was shown that the replacement of part of ethylene with ethanol in the starting mixture lowered the concentration of a number of intermediate flame species, including soot precursors C3H3 and C6H6. These data are important for the development, analysis, and further improvement of detailed kinetic mechanisms for combustion of mixtures of hydrocarbon and oxygenated fuels. 相似文献
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Karla Čech Barabaszová Sylva Holešová Marianna Hundáková Erich Pazdziora Michal Ritz 《Journal of Inorganic and Organometallic Polymers and Materials》2017,27(4):986-995
Polyethylene (PE) nanocomposites with the zinc oxide-nanoparticles/vermiculite nanofiller were prepared in two-steps. In first step, the ZnO-np/V nanofiller were prepared by the mechanochemical method followed by a heat treatment at 650?°C for 90 min. In second step, this nanofiller was used in concentration 3, 6, 10 and 15 wt% for PE nanocomposites preparation via melt compounding technique, the nanocomposites plates were pressed. The particles morphology of the ZnO-np/V nanofiller, arrangement of the ZnO-np/V nanofiller and surface of the PE plates were studied using scanning electron microscopy, optical light microscopy and atomic force microscopy. The surface roughness of the PE plates was evaluated from AFM measurements. Structural changes of the ZnO-np/V nanofiller in PE nanocomposites were monitored using X-ray diffraction analysis and Fourier transform infrared analysis. The gradual and long-term antibacterial effect of PE nanocomposites was tested on the Gram positive bacteria E. faecalis by counting the colony forming units number. 相似文献
74.
Petr Ryšánek Marek Malý Pavla Čapková Martin Kormunda Zdeňka Kolská Milan Gryndler Ondřej Novák Lucie Hocelíková Lukáš Bystrianský Marcela Munzarová 《Journal of Polymer Research》2017,24(11):208
Antibacterial nylon 6 (PA6) nanofibers have been prepared in one-step procedure using Nanospider technology. Chlorhexidine (CHX), 1-dodecyltrimethylamonium bromide (DTAB) and benzyltrimethylamonium bromide (BTAB) have been used as antibacterial agents. Samples were characterized by a series of analytical and testing methods to investigate the surface chemistry, zeta potential, structure, morphology, phase composition, mechanical properties and antibacterial activity. Experimental characterization has been combined with molecular modeling to analyze the interaction of nanofibers with modifying molecules for better understanding the effect of nanofibers modification on their properties. Antibacterial modification of PA6 led to significant changes of zeta potential (from -31 mV for PA 6 up to -49 mV for PA6/BTAB), changes in phase composition (decrease of alpha phase content and increase of gamma phase content for PA6/BTAB and PA6/CHX) and to significant increase of fiber diameter for PA6/BTAB. Antibacterial modification resulted in the straightening of nanofibers and to higher permeability of nanofiber textile for all investigated samples. Tensile tests showed the the increase of Young modulus for all the investigated samples. All the modified samples: PA6/DTAB, PA6/BTAB and PA6/CHX exhibit good antibacterial activity. 相似文献
75.
Ta?ana?Vacková Jaroslav?Kratochvíl Aleksandra?Ostafinska Sabina?Krej?íková Martina?Nevoralová Miroslav?SloufEmail authorView authors OrcID profile 《Polymer Bulletin》2017,74(2):445-464
Crystallization kinetics of polycaprolactone (PCL) filled with TiO2-based particles (TiX) was shown to depend on the TiX particle type and concentration, which were associated with a slight polymer matrix degradation. The partially degraded, shorter, and more mobile polymer chains increased the overall crystallization rate at the initial stage of crystallization, while at the later stages, the non-nucleating TiX particles acted as a sterical hindrance, slowing down the crystallization process. The PCL/TiX composites were prepared by melt-mixing and contained 2.5 and 5 wt% of the filler. The investigated TiX particles included isometric anatase microparticles (mTiO2) and titanate nanotubes with high-aspect ratio (TiNT). Light and electron microscopy showed very homogeneous dispersion of the mTiO2 particles in the PCL matrix, while the TiNT formed large agglomerates. In situ polarized light microscopy displayed faster isothermal crystallization of all PCL/TiX composites, but the micrographs indicated that the TiX particles did not act as nucleation centres. Isothermal DSC experiments, evaluated in terms of Avrami theory, confirmed the PLM results and showed that the overall rate of isothermal crystallization increased in the following order: PCL <PCL/TiNT <PCL/mTiO2. Non-isothermal DSC and rheological measurements revealed the correlation between the crystallization rate and the polymer matrix degradation—the well-dispersed mTiO2 particles with high specific surface caused the highest PCL degradation and, consequently, the earliest start of non-isothermal crystallization as well as the fastest isothermal crystallization. Microindentation hardness measurements confirmed that the partial degradation of the polymer matrix did not have a significant impact on the mechanical performance of PCL/mTiO2 composites. 相似文献
76.
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78.
Dr. Veronika Papoušková Dr. Pavel Kadeřávek Olga Otrusinová Alžbeta Rabatinová Dr. Hana Šanderová Jiří Nováček Dr. Libor Krásný Prof. Vladimír Sklenář Dr. Lukáš Žídek 《Chembiochem : a European journal of chemical biology》2013,14(14):1772-1779
The partially disordered δ subunit of RNA polymerase was studied by various NMR techniques. The structure of the well‐folded N‐terminal domain was determined based on inter‐proton distances in NOESY spectra. The obtained structural model was compared to the previously determined structure of a truncated construct (lacking the C‐terminal domain). Only marginal differences were identified, thus indicating that the first structural model was not significantly compromised by the absence of the C‐terminal domain. Various 15N relaxation experiments were employed to describe the flexibility of both domains. The relaxation data revealed that the C‐terminal domain is more flexible, but its flexibility is not uniform. By using paramagnetic labels, transient contacts of the C‐terminal tail with the N‐terminal domain and with itself were identified. A propensity of the C‐terminal domain to form β‐type structures was obtained by chemical shift analysis. Comparison with the paramagnetic relaxation enhancement indicated a well‐balanced interplay of repulsive and attractive electrostatic interactions governing the conformational behavior of the C‐terminal domain. The results showed that the δ subunit consists of a well‐ordered N‐terminal domain and a flexible C‐terminal domain that exhibits a complex hierarchy of partial ordering. 相似文献
79.
The complexation of charged compounds by humic acids represents the process of exceptional environmental importance. Nevertheless, traditional methods utilized in the complexation studies do not address the way, how these interactions affect the transport of ions in humic-rich environments. To overcome this dilemma, the diffusion cells technique is proposed as an innovative reactivity mapping technique. Using this method, the diffusion of methylene blue was studied in aqueous solutions and in agarose gels with and without the addition of humic acids. Experimental results clearly illustrate the immobilizing effects of humic acids on the transport of methylene blue in gels. The partitioning of methylene blue at the solution-gel interface and the specific interactions between methylene blue and humic acids is discussed on the basis of experimental data. Effective structural parameters of hydrogels (effective porosity, tortuosity factor) were calculated, as well as some standard diffusion and interaction parameters (diffusion and partition coefficients and apparent equilibrium constants). 相似文献
80.
Zdeňka Sedláková Josef Pleštil Josef Baldrian Miroslav Šlouf Pavel Holub 《Polymer Bulletin》2009,63(3):365-384
A series of novel polystyrene and poly(butyl methacrylate) montmorillonites (MMT-Na) nanocomposite latexes have been successfully
prepared by emulsion polymerization. First of all, chemical modification of MMT-Na with a reactive coupling agent (MMT-QS)
has been employed for the synthesis of hybrids. Subsequently, in situ seeded emulsion polymerization of hydrophobic vinyl
monomers, such as butyl methacrylate and styrene, using sodium dodecyl sulfate (SDS) and ammonium persulfate (APS) as surfactant
and initiator, respectively, were used for nanocomposite preparation. This technique allowed preparing of stable nanocomposite
latexes with high (30–45 wt.%) solids contents and with loading of inorganic particles up to 5 wt.%. The prepared wet dispersions
were subsequently characterized by light scattering method. In order to characterize the microstructure of the clay layers,
and that of the organoclay in polystyrene and poly(butyl methacrylate) nanocomposites, wide and small angle X-ray analyses
(WAXS, SAXS) and transmission electron microscopy (TEM) techniques were used. 相似文献