The melting transition of small clusters composed of 13 particles interacting via the Lennard-Jones 6-12 potential has been investigated by means of extensive Metropolis Monte Carlo simulations. The results indicate that whereas the cluster evaporates in vacuum, in a confined pore the cluster undergoes a smooth melting transition from an icosahedral microcrystal to an inhomogeneous liquid phase, with a specific heat peak centered at 39 K. No evidence was found to support the suggestion of a solid-liquid transition in vacuum at 29 K. 相似文献
A novel comb‐like derivative CPEG‐g‐DNQ was prepared by incorporating light responsive 2‐diazo‐1,2‐naphthoquinone (DNQ) groups into the structure of comb‐like poly(ethylene glycol) (CPEG). DLS and TEM results showed that CPEG‐g‐DNQ self‐assembled into spherical micelles with an average size of about 135 nm in water. Upon exposure to light, the micelles could be disrupted because of the conversion of hydrophobic DNQ to hydrophilic 3‐indenecarboylic acid. Additionally, hydrophobic coumarin 102 was successfully loaded into the micelles and photo‐induced ON‐OFF release was demonstrated by fluorescence spectroscopy. MTT assay revealed that the micelles are biocompatible. These photo‐responsive micelles might have great potential for controlled release of hydrophobic drugs.
This paper describes the self‐assembly of rod–coil inclusion complexes, polyethylenimine–poly(ethylene glycol)–α‐cyclodextrin (PEI–PEG–α‐CD). It is demonstrated that α‐CDs should exclusively thread on the PEG block in PEI–PEG copolymers and the resulting complexes have both rigid block (PEG–α‐CD) and coil block (protonated PEI). By varying the rigid block fraction, aggregates with hollow spheres or rod‐like particles could be formed simply by self‐assembly in aqueous solution. 相似文献
The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance. 相似文献
In this paper, the design of low-loss tapered waveguides by applying photonic-crystal-based microlenses is presented. The
microlenses are realized by using two-dimensional photonic crystal (PhC) structures with a hexagonal periodic lattice of air-holes.
In order to make the PhC structures behave as homogeneous and isotropic microlenses, the PhC structures are designed to operate
in the low-frequency domain with light wavelength sufficiently larger than the PhC lattice constant. The effective indices
of the PhC are calculated and the structures are properly arranged in microlenslike shapes. By monolithically integrating
the effective microlenses in the tapered area between the two optical waveguides with different core dimensions, the wavefront
of the eigenmode can be coupled from the larger core to the smaller core effectively and also the radiation loss in the tapered
area between the two connected optical waveguides can be effectively suppressed. The results show that the PhC-based microlens
in the telescopic structure can serve as an optical element in the tapered waveguide with the advantages of low loss, high
efficiency and compactness. 相似文献