Zero-temperature properties of randomly self-interacting polymers

We study the zero-temperature behavior of several simple models for randomly self-interacting polymers in one and 1+1 dimensions. Results are based on exact enumeration and closed-form expressions.     

Study of the reactione + e −→K + K − in the energy range1350 \leqq \sqrt s \leqq 2400 MeV

Thee ⁺ e ^?→K ⁺ K ^? cross section has been measured from about 750 events in the energy interval \(1350 \leqq \sqrt s \leqq 2400 MeV\) with the DM2 detector at DCI. TheK ^± form factor |F _F ^±| cannot be explained by the ρ, ω, ? and ρ′(1600). An additional resonant amplitude at 1650 MeV has to be added as suggested by a previous experiment.     

Dynamics of polymer packaging

We use the stochastic rotation dynamics algorithm to investigate the packaging of flexible and semiflexible polymers into a capsid that is permeable to solvent molecules. The model takes into account hydrodynamic interactions arising due to local flow. The flexible chain maintains a random configuration as it is being fed into the capsid, in contrast to the semiflexible chain, whose configuration is initially spool-like, becoming more random at high packing. We measure the packing rate, which is found to decrease with the percentage of the chain packed and highlight the difference between the flexible and semiflexible chains. Reflecting experiments, we find pauses in the packing process for individual chains as the motor loses grip of the fluctuating beads. We also find that hydrodynamics is important, in that the packaging rate is faster when flow is included.     

Synthesis and analysis of [4−14C] phenylbutazone

[4?¹⁴C] phenylbutazone (4-butyl-1,2-diphenyl-3,5-[4?¹⁴C] pyrazolidinedione) has been synthesised on the 5 mmole scale. [2?¹⁴C] Diethyl malonate was reacted with n-butyl bromide and the product condensed with hydrazobenzene in the same reaction vessel. The radiochemical yield of highly purified product was 48%. It is proposed that care should be taken in analyses for metabolic products, particularly by TLC, since 4-hydroxyphenylbutazone was shown to be an oxidation product of phenylbutazone in solution and on TLC plates under quite mild conditions. A pure sample of 4-hydroxy [4?¹⁴C] phenylbutazone was isolated.     

Anisotropy of domain growth in nematic liquid crystals

We have studied domain growth in nematic liquid crystals using a lattice Boltzmann algorithm to solve the full, three-dimensional equations of hydrodynamics. An initially cylindrical V (bend) domain in an H (splay) state grows or shrinks anisotropically in agreement with experiment. A disclination loop forms at the mid-point of the wall surrounding the domain. We argue that different director configurations at different points on the loop lead to velocity anisotropy and show that both elastic effects and backflow are relevant. We discuss the dependence of the domain wall velocity on surface tilt and on the magnitude of an applied electric field.     

Polymer collapse in the presence of hydrodynamic interactions

We investigate numerically the dynamical behaviour of a polymer chain collapsing in a dilute solution. The rate of collapse is measured with and without the presence of hydrodynamic interactions. We find that hydrodynamic interactions both accelerate polymer collapse and alter the folding pathway.     

Small-angle X-ray scattering study of liquid crystalline polycarbonates based on α-methyl stilbene mesogen and methylene-containing flexible spacer

Crystallization and melting behavior are studied by small-angle X-ray scattering (SAXS) for a series of recently synthesized monotropic liquid crystalline polycarbonates based on α-methyl stilbene mesogen and methylene flexible spacer. The one-dimensional electron density correlation function is used to obtain long period, crystal thickness, and linear crystallinity from the Lorentz-corrected SAXS intensity. Changes in these parameters during nonisothermal crystallization and melting are explained by a model of dual crystal populations. The primary crystals form first using the liquid crystalline phase as crystal nuclei, while smaller and less perfect crystals form later from the isotropic phase at low temperature. The results of the real-time SAXS study of isothermal crystallization also support the view that the nematic phase serves as crystal nuclei for fast crystallization. An odd-even effect in crystal thickness and linear crystallinity is observed in all the SAXS experiments mentioned above. The results of this study and our complementary wide-angle X-ray scattering (WAXS) investigation show clearly that the difference in the position of the neighboring carbonate dipoles on a chain affects structural organization both at the unit cell level and at the level of the crystal in these monotropic LCPs. © 1995 John Wiley & Sons, Inc.