Replica-Exchange Simulated Tempering Method for Simulations of Frustrated Systems

We propose a new method for the determination of the weight factor for the simulated tempering method. In this method a short replica-exchange simulation is performed and the simulated tempering weight factor is obtained by the multiple-histogram reweighting techniques. The new algorithm is particularly useful for studying frustrated systems with rough energy landscape where the determination of the simulated tempering weight factor by the usual iterative process becomes very difficult. The effectiveness of the method is illustrated by taking an example for protein folding.Comment: 8 pages, (ReVTeX), 5 figures, Chem. Phys. Lett., submitte

On the Liquidus Line of Fe-Mn Alloys

The equilibrium diagram of iron and manganese alloys containing more than 50 per cent of manganese was studied by means of the thermal analysis. The melting point of pure manganese slowly fell with the addition of a small quantity of iron, and the minimum was found at the point of 91 per cent manganese, the temperature being 1240℃. The γ-δ transformation point of pure manganese rapidly rose with the iron content, and realized the peritectic reaction, liquid +δ manganese solid solution ⇄ γ manganese rolid rolution. The β-γ transformation point gradually rose with the iron content, and reached the maximum of 1130℃ with 91 per cent of manganese, and then slowly fell with the further increase of iron to the eutectoid point of 1025℃ with 71 per cent manganese, where the reaction, γ manganese solid solution ⇄ γ iron solid solution +β manganese solid solution, occurred

Generalized-ensemble simulations of spin systems and protein systems

In complex systems such as spin systems and protein systems, conventional simulations in the canonical ensemble will get trapped in states of energy local minima. We employ the generalized-ensemble algorithms in order to overcome this multiple-minima problem. Three well-known generalized-ensemble algorithms, namely, multicanonical algorithm, simulated tempering, and replica-exchange method, are described. We then present three new generalized-ensemble algorithms based on the combinations of the three methods. Effectiveness of the new methods are tested with a Potts model and protein systems.Comment: 12 pages, (LaTeX2e), 6 figures, Computer Physics Communications, in pres

Molecular dynamics of C-peptide of ribonuclease A studied by replica-exchange Monte Carlo method and diffusion theory

Generalized-ensemble algorithm and diffusion theory have been combined in order to compute the dynamical properties monitored by nuclear magnetic resonance experiments from efficient and reliable evaluation of statistical averages. Replica-exchange Monte Carlo simulations have been performed with a C-peptide analogue of ribonuclease A, and Smoluchowski diffusion equations have been applied. A fairly good agreement between the calculated and measured $^1$H-NOESY NMR cross peaks has been obtained. The combination of these advanced and continuously improving statistical tools allows the calculation of a wide variety of dynamical properties routinely obtained by experiments.Comment: 17 pages, 5 figures, (LaTeX); Chemical Physics Letters, in pres

Some Studies of Nodular Graphite Cast Iron

The experiments were carried out on the formation of nodular graphite in cast iron by adding some different kinds of mother alloys to molten cast iron and on the increase of graphite particles caused by annealing treatment. The yield of modified element in cast iron is increased as the content of alloying element in mother alloy or the amount of mother alloy added to molten cast iron decreases. By using many components alloy the structure in which the ground mass consisted fully of ferrite, is obtained. The hardness of modified cast iron decreases rapidly by annealing or with the increase of the diameter of specimen