A Lattice Boltzmann Model of Binary Fluid Mixture

We introduce a lattice Boltzmann for simulating an immiscible binary fluid mixture. Our collision rules are derived from a macroscopic thermodynamic description of the fluid in a way motivated by the Cahn-Hilliard approach to non-equilibrium dynamics. This ensures that a thermodynamically consistent state is reached in equilibrium. The non-equilibrium dynamics is investigated numerically and found to agree with simple analytic predictions in both the one-phase and the two-phase region of the phase diagram.Comment: 12 pages + 4 eps figure

Pulling adsorbed polymers from surfaces with the AFM: stick versus slip, peeling versus gliding

We consider the response of an adsorbed polymer that is pulled by an AFM within a simple geometric framework. We separately consider the cases of i) fixed polymer-surface contact point, ii) sticky case where the polymer is peeled off from the substrate, and iii) slippery case where the polymer glides over the surface. The resultant behavior depends on the value of the surface friction coefficient and the adsorption strength. Our resultant force profiles in principle allow to extract both from non-equilibrium force-spectroscopic data.Comment: 6 pages, 3 figures; accepted for publication in Europhys. Lett., http://www.edpsciences.org/journal/index.cfm?edpsname=ep

Hamiltonian dynamics reveals the existence of quasi-stationary states for long-range systems in contact with a reservoir

We introduce a Hamiltonian dynamics for the description of long-range interacting systems in contact with a thermal bath (i.e., in the canonical ensemble). The dynamics confirms statistical mechanics equilibrium predictions for the Hamiltonian Mean Field model and the equilibrium ensemble equivalence. We find that long-lasting quasi-stationary states persist in presence of the interaction with the environment. Our results indicate that quasi-stationary states are indeed reproducible in real physical experiments.Comment: Title changed, throughout revision of the tex

自記式「健康チェック票THI」による健康に及ぼす喫煙の影響評価－地方都市と大都市の学生間の比較－

キャンパスが群馬県内（Ｉキャンパス）、東京都内（Ｔキャンパス）および愛知県内（Ｎキャンパス）にあるＡ私立大学の学生347人（男子121人、女子226人）を対象に、喫煙が健康に及ぼす影響について、自記式「健康チェック票THI」によって評価した。対象学生の喫煙率は全国平均と比較して、Ｉキャンパスの男子学生がやや高かったことを除くと、ほぼ同程度であった。健康状態は1.2万人の標準グループから得られた尺度得点の分布をもとに、パーセンタイル値で評価した。喫煙者の健康状態は非喫煙者と比較して、身体面およびメンタル面の両方において劣る傾向がみられ、特に、女子学生の方が男子学生より顕著であった。さらに、Ｉキャンパスの学生より、ＴキャンパスやＮキャンパスの学生の方が、メンタル面の症状レベルが高い傾向が認められた。これらの結果は、喫煙が身体面の健康状態に悪影響を及ぼすことを確認するとともに、その影響は地方都市より大都会で学ぶ学生に強く出やすい可能性を示している

Lattice Boltzmann simulations of lamellar and droplet phases

Lattice Boltzmann simulations are used to investigate spinodal decomposition in a two-dimensional binary fluid with equilibrium lamellar and droplet phases. We emphasise the importance of hydrodynamic flow to the phase separation kinetics. For mixtures slightly asymmetric in composition the fluid phase separates into bulk and lamellar phases with the lamellae forming distinctive spiral structures to minimise their elastic energy.Comment: 19 pages, 5 figure

Universal properties of knotted polymer rings

By performing Monte Carlo sampling of $N$-steps self-avoiding polygons embedded on different Bravais lattices we explore the robustness of universality in the entropic, metric and geometrical properties of knotted polymer rings. In particular, by simulating polygons with $N$ up to $10^5$ we furnish a sharp estimate of the asymptotic values of the knot probability ratios and show their independence on the lattice type. This universal feature was previously suggested although with different estimates of the asymptotic values. In addition we show that the scaling behavior of the mean squared radius of gyration of polygons depends on their knot type only through its correction to scaling. Finally, as a measure of the geometrical self-entanglement of the SAPs we consider the standard deviation of the writhe distribution and estimate its power-law behavior in the large $N$ limit. The estimates of the power exponent do depend neither on the lattice nor on the knot type, strongly supporting an extension of the universality property to some features of the geometrical entanglement.Comment: submitted to Phys.Rev.

Tight and loose shapes in flat entangled dense polymers

We investigate the effects of topological constraints (entanglements) on two dimensional polymer loops in the dense phase, and at the collapse transition (Theta point). Previous studies have shown that in the dilute phase the entangled region becomes tight, and is thus localised on a small portion of the polymer. We find that the entropic force favouring tightness is considerably weaker in dense polymers. While the simple figure-eight structure, created by a single crossing in the polymer loop, localises weakly, the trefoil knot and all other prime knots are loosely spread out over the entire chain. In both the dense and Theta conditions, the uncontracted knot configuration is the most likely shape within a scaling analysis. By contrast, a strongly localised figure-eight is the most likely shape for dilute prime knots. Our findings are compared to recent simulations.Comment: 8 pages, 5 figure