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排序方式: 共有193条查询结果,搜索用时 15 毫秒
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The multicritical points of the O(N)-invariant N vector model in the large-N limit are re-examined. Of particular interest are the subtleties involved in the stability of the phase structure at critical dimensions. In the limit N → ∞ while the coupling g → gc in a correlated manner (the double scaling limit) a massless bound state O(N) singlet is formed and powers of 1/N are compensated by IR singularities. The persistence of the N → ∞ results beyond the leading order is then studied with particular interest in the possible existence of a phase with propagating small mass vector fields and a massless singlet bound state. We point out that under certain conditions the double scaled theory of the singlet field is non-interacting in critical dimensions. 相似文献
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A new strain of the fungusMorchella nov. ES-1 (ATCC 20951) that produces blue pigment in submerged culture has been isolated. The blue pigment was extracted by chloroform or ethyl acetate treatment. The crude extract when chromatographed yielded three fractions; a blue one has been identified by mass spectrometry as indigotin. Fermentation studies using enriched media revealed that maximum accumulation of indigotin in culture was approx 24 mg/L in 168 h. 相似文献
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Size‐dependent mechanical properties of glassy polymer nanofibers via molecular dynamics simulations 下载免费PDF全文
Shengwei Deng Arkadii Arinstein Eyal Zussman 《Journal of Polymer Science.Polymer Physics》2017,55(6):506-514
The microstructure of polymer matrix under cylindrical confinement is key to understanding the size‐dependent thermomechanical behavior of electrospun nanofibers. Coarse‐grained molecular dynamics simulation was applied here to probe polymer systems under cylindrical confinement, prepared with or without pre‐stretching. Simulation results showed that below a certain radius, a noticeable increase of the elastic modulus is observed with the decrease of the radius of cylindrical confinement. This size‐dependent mechanical behavior correlated to the degree of polymer chain orientation. Modulation of density and bond orientation in the radial direction was observed: the density and bond orientation began to oscillate, increasing the oscillation amplitudes with decreases in the radius. Such behavior suggests that the cylindrical confinement enhances the bond alignment of the entire fiber and not in the near‐surface layers only. The unstretched fibers had uniform density distribution along the fiber axis, while the stretched fibers demonstrated a fluctuation in density distribution. The crossover radius of size‐dependent behavior was two orders of magnitude smaller than observed in real experiments, demonstrating that the confinement affects some internal fiber scale, which exceeds the scale of individual macromolecules, and this internal scale may be related to supramolecular structures of the polymer matrix rather than the individual macromolecules. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 506–514 相似文献
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Eyal Jakobs Yael Hanein 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):33-40
A novel method for fabricating micrometer sized gel patterns is described. The presented method involves spin-coating a pre-gel solution on a surface that was chemically treated to modulate its surface energy, creating highly hydrophobic areas on a hydrophilic substrate. Following spin-coating, the gel solution self organizes on the hydrophilic sites. This method offers the advantages of high resolution, self-alignment to pre-patterned electrodes, and a simple straightforward fabrication process. Minimum feature size achieved was approximately 20 μm. The characteristic shrinking and swelling times of gel patterns were measured and found to be around 0.6 s for swelling and 2 s for shrinking (for a 60 μm diameter gel) in agreement with the reduced response time expected for scaled down gel patterns. These results suggest the suitability of these gel patterns as valves or actuators in microfluidic devices. Micron-size gel patterns were also incorporated into microfluidic channels thus demonstrating a new approach to create simple, affordable, microfluidic devices, which incorporate “smart” hydrogels as building elements in a simple fashion. 相似文献
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Pressure-driven flow in microfluidic channels is characterized by a distribution of velocities. This distribution makes it difficult to implement conventional flow cytometry data analysis. We have demonstrated a method to measure velocity as an independent parameter when performing microfluidic flow cytometry. This method allows velocity-independent analysis of particles such as beads or cells, and allows flow cytometry analysis of extended objects, such as long DNA molecules. It allows accurate flow cytometry in transient and nonuniform flows. This general measurement method could be used in the future to measure the velocity of particles in a variety of existing microfluidic devices without the need for changes in their design. 相似文献
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Angular distributions for one-neutron and many-nucleon transfer reactions were measured in the systems 17, 18O and 12, 13C at c.m. energies between 12.6 to 14.0 MeV. All the cross sections were analyzed in terms of the full-recoil finite-range DWBA model. For multi-nucleon transfer processes an inert cluster transfer was assumed. The sensitivity of DWBA calculations to various parameter sets is discussed, and the effect of the no-recoil approximation on the phase and magnitude of the transfer amplitude is studied. For one-neutron transfer reactions the forward part of the angular distributions was reproduced reasonably well by the DWBA model, yielding satisfactory spectroscopic information. The rise of the cross section at the backward angles was not reproduced by the DWBA model. Possible contributions of cluster-exchange and compound-nucleus reactions are discussed. For multi-nucleon transfer reactions poorer fits were obtained, particularly in the 18O+12C system. 相似文献
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Reaction of the organoactinide complexes (C5Me5)2AnMe2 (An = Th, U) with catecholborane yields an inclusion complex where the actinide is encapsulated inside a 15-membered, hexaoxo, trianionic macrocycle built from alternating catechol and catecholborate fragments. In the presence of LiOH, a dimer of two encapsulated actinide macrocycles is formed. The X-ray molecular structure for all the complexes is presented. 相似文献
10.
Due to the apolar nature of the lipid bilayer, the weak Calpha-H...O H-bond is thought to contribute significantly toward the stability of transmembrane helical bundles such as glycophorin A (GPA). Here for the first time we measured the strength of such a bond, using vibrational frequency shifts of a dimeric and nondimeric variants of GPA containing a Gly CD2 label. Although the resulting estimated bond strength of 0.88 kcal/mol is relatively weak, several such bonds could contribute significantly toward bundle stabilization. 相似文献