Polyelectrolyte Adsorption on Charged Substrate

The behavior of a polyelectrolyte adsorbed on a charged substrate of high-dielectric constant is studied by both Monte-Carlo simulation and analytical methods. It is found that in a low enough ionic strength medium, the adsorption transition is first-order where the substrate surface charge still keeps repulsive. The monomer density at the adsorbed surface is identified as the order parameter. It follows a linear relation with substrate surface charge density because of the electrostatic boundary condition at the charged surface. During the transition, the adsorption layer thickness remains finite. A new scaling law for the layer thickness is derived and verified by simulation.Comment: Proceedings of the 3rd Symposium on Slow Dynamics in Complex Systems, 3-8 November 2003, Sendai, Japa

The effect of self-assembled nanofibrils on the morphology and microstructure of poly(L-lactic acid)

[[abstract]]The morphologies and microstructures of neat 1,3:2,4-dibenzylidene-D-sorbitol (DBS) and DBS/poly(L-lactic acid) (PLLA) samples have been investigated by polarizing optical microscopy (POM) and scanning electron microscopy (SEM). The morphology of neat DBS samples prepared from solution had unspecific structures, and no fibrils formed. In comparison, DBS molecules self-assembled into fibrils with diameters ranging from 100 nm to 1 µm when samples were prepared from the melt. The DBS fibrils were also found in DBS/PLLA systems, but the average diameter was only around 20 nm. The DBS architectures could be well tuned by varying the DBS contents and PLLA crystallization temperatures. Micron-sized fibrillar rings or disks due to the aggregation of DBS nanofibrils were found using SEM in samples with DBS contents more than 3 wt% and crystallized above 120 °C. Meanwhile, “concentric-circled” PLLA spherulites were observed by POM. The DBS nanofibrils largely formed at the circles, but some nanofibrils formed beyond the circles and were dispersed in the PLLA spherulites. These dispersed nanofibrils affected the orientation of PLLA lamellae and caused a change in birefringence, yet the growth rate of PLLA was not significantly influenced by the formation of DBS nanofibrils. In addition, porous PLLA structures could be obtained by solvent extraction of the DBS nanofibrils.[[incitationindex]]SCI[[booktype]]紙

The SL(K+3,C) Symmetry of the Bosonic String Scattering Amplitudes

We discover that the exact string scattering amplitudes (SSA) of three tachyons and one arbitrary string state, or the Lauricella SSA (LSSA), in the 26D open bosonic string theory can be expressed in terms of the basis functions in the infinite dimensional representation space of the SL(K+3,C) group. In addition, we find that the K+2 recurrence relations among the LSSA discovered by the present authors previously can be used to reproduce the Cartan subalgebra and simple root system of the SL(K+3,C) group with rank K+2. As a result, the SL(K+3,C) group can be used to solve all the LSSA and express them in terms of one amplitude. As an application in the hard scattering limit, the SL(K+3,C) group can be used to directly prove Gross conjecture [1-3], which was previously corrected and proved by the method of decoupling of zero norm states [4-10].Comment: 19 pages, no figure. v2: 20 pages, typos corrected and Eqs. added. v3: 24 pages, Examples in sec. II added,"Discussion" added, to be published in Nucl.Phys.

Analysis of olgimetric and subunit sizes of membrane receptors

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