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131.
Spontaneous melting of a perfect crystalline graphene model in 2D space is studied via molecular dynamics simulation. Model containing 104 atoms interacted via long-range bond-order potential (LCBOP) is heated up from 50 to 8,450 K in order to see evolution of various thermodynamic quantities, structural characteristics and occurrence of various structural defects. We find that spontaneous melting of our graphene model in 2D space exhibits a first-order behaviour of the transition from solid 2D graphene sheet into a ring-like structure 2D liquid. Occurrence and clustering of Stone–Wales defects are the first step of melting process followed by breaking of C–C bonds, occurrence/growth of various types of vacancies and multi-membered rings. Unlike that found for melting of a 2D crystal with an isotropic bonding, these defects do not occur homogeneously throughout the system, they have a tendency to aggregate into a region and liquid phase initiates/grows from this region via tearing-like or crack-propagation-like mechanism. Spontaneous melting point of our graphene model occurs at Tm = 7,750 K. The validity of classical nucleation theory and Berezinsky–Kosterlitz–Thouless–Nelson–Halperin–Young (BKTNHY) one for the spontaneous melting of our graphene model in strictly 2D space is discussed. 相似文献
132.
We present a low-temperature scanning tunneling microscopy study of the alpha-Sn/Si(111) surface that demonstrates the fluctuating behavior of the Sn adatoms. The dynamical fluctuation model, successfully applied in describing the alpha-Sn/Ge(111) surface, is proposed for the related alpha-Sn/Si(111) surface too, although with a much lower transition temperature. In addition, a new phenomenon appears responsible for the unexpected evidence that the average oscillation frequency remains constant at temperatures lower than 15 K, in contradiction to the Arrhenius law. We explain this phenomenon as quantum tunneling of Sn adatoms. 相似文献
133.
The sensitivity of the torsional pendulum demonstrates the self-shape-memory effect in different types of spider draglines. Here we report the time-resolved noncovalent bonds recovery in the protein structure. The torsional dynamics of such multilevel structure governed by reversible interactions are described in the frame of a nested model. Measurement of three different relaxation times confirms the existence of three energy storage levels in such two protein spidroin systems. Torsion opens the way to further investigations towards unraveling the tiny torque effects in biological molecules. 相似文献
134.
Philippe Pinel Bertrand Thirion Sébastien Meriaux Antoinette Jobert Julien Serres Denis Le Bihan Jean-Baptiste Poline Stanislas Dehaene 《BMC neuroscience》2007,8(1):91
Background
Although cognitive processes such as reading and calculation are associated with reproducible cerebral networks, inter-individual variability is considerable. Understanding the origins of this variability will require the elaboration of large multimodal databases compiling behavioral, anatomical, genetic and functional neuroimaging data over hundreds of subjects. With this goal in mind, we designed a simple and fast acquisition procedure based on a 5-minute functional magnetic resonance imaging (fMRI) sequence that can be run as easily and as systematically as an anatomical scan, and is therefore used in every subject undergoing fMRI in our laboratory. This protocol captures the cerebral bases of auditory and visual perception, motor actions, reading, language comprehension and mental calculation at an individual level. 相似文献135.
Cai Xiang-Ming Shan Jian Le Yun-Lin Luo Yuan Li Ya-Dong 《Journal of Radioanalytical and Nuclear Chemistry》2021,330(3):747-753
Journal of Radioanalytical and Nuclear Chemistry - The rapid measurement of radon progeny concentration is of great significance for improving the efficiency of radon exposure dose evaluation in a... 相似文献
136.
The influence of various surface preparation methods (mechanical polishing, electropolishing and etching) on the passivity and the corrosion behaviour of a duplex stainless steel (UNS S32202) was studied using Auger spectroscopy and the electrochemical microcell technique. From surface analyses, the thickness and chemical compositions (ratios Cr/Fe and O2?/OH?, distribution of chloride and nitrogen) were determined. The corrosion behaviour of samples was investigated from local polarization curves. The presence of oxidation peaks and stable pitting was discussed considering the specimen microstructure and the properties of the passive film. 相似文献
137.
Cover Picture: Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets (Chem. Eur. J. 6/2014) 下载免费PDF全文
138.
139.
Dr. Ryohei Yasukuni Prof. Nordin Félidj Dr. Leïla Boubekeur-Lecaque Stéphanie Lau-Truong Prof. Jean Aubard 《Chemphyschem》2020,21(22):2614-2619
Localized surface plasmon resonance (LSPR) excitation on the photochromic reaction of a diarylethene derivative (DE) was studied by surface enhanced Raman scattering (SERS). UV and visible light irradiations transform reversibly DE between open-form (OF) and closed-form (CF) isomers, respectively. A mixture of PMMA and DE (either OF or CF isomer) was spin-coated onto gold nanorods (GNRs) arrays, designed by electron beam lithography, with two localized surface plasmon resonances (LSPR) at distinct wavelengths, due to their anisotropy. The photochromic reaction rates from CF to OF isomers, under LSPR excitation, were monitored from SERS spectral changes under different polarizations, on the same GNR substrate to compare the effect of LSPR field strength. It appears that the photoisomerization rate was faster when LSPR was excited with the polarization parallel to the GNR long axis. The present results highlight a potential genuine mechanism, from near field LSPR excitation, involved in the photochromic enhancement of diarylethene photochromes. 相似文献
140.
Christian Decker Danielle Decker Trieu Nguyen Thi Viet Hien Le Xuan 《Macromolecular Symposia》1996,102(1):63-71
Different types of tridimensional polymer networks have been synthetised by photoinitiated cationic polymerisation of vinyl ether and epoxy-functionalised oligomers and polymers. The polymerisation kinetics was followed by real-time infrared (RTIR) spectroscopy, a technique that records directly conversion versus time profiles in a timescale as short as 1 s. The addition of a diacrylate monomer was shown to accelerate the ring-opening polymerisation of epoxidized polyisoprene, with formation of interpenetrating polymer networks having well contrasted properties. A dual polymer network has been generated by photocrosslinking of a polyisoprene functionalised with both epoxy and acrylate groups. 相似文献