可溶性汞化苯乙烯－丙烯酸甲酯共聚物的合成

用自由基溶液降合方法制备一系列苯乙烯－丙烯酸甲酯线型共聚物，用核磁共振测定了苯基在共聚物中的百分比，在该共聚物的四氢呋喃溶液中，用三氟乙酸汞在共聚物的苯环上进行亲电取代反应，得到可溶性汞化共聚物，由于这类泵化共的可溶于四氢呋喃，二氯甲烷等溶剂，用重沉淀法多次提纯，得到了纯度很高，溶解性较好的含重金属二价汞的共聚物，用红外光谱仪测定共聚物上的汞基团，用原子吸收定量测试共聚中的汞的百分聚代率，结果表明     

The central cell model: a mesoscopic hopping model for the study of the displacement autocorrelation function

On the mesoscale, the molecular motion in a microporous material can be represented as a sequence of hops between different pore locations and from one pore to the other. On the same scale, the memory effects in the motion of a tagged particle are embedded in the displacement autocorrelation function (DACF), the discrete counterpart of the velocity autocorrelation function (VACF). In this paper, a mesoscopic hopping model, based on a lattice-gas automata dynamics, is presented for the coarse-grained modeling of the DACF in a microporous material under conditions of thermodynamic equilibrium. In our model, that we will refer to as central cell model, the motion of one tagged particle is mimicked through probabilistic hops from one location to the other in a small lattice of cells where all the other particles are indistinguishable; the cells closest to the one containing the tagged particle are simulated explicitly in the canonical ensemble, whereas the border cells are treated as mean-field cells in the grand-canonical ensemble. In the present paper, numerical simulation of the central cell model are shown to provide the same results as a traditional lattice-gas simulation. Along with this a mean-field theory of self-diffusion which incorporates time correlations is discussed.     

Introducing a cellular automaton as an empirical model to study static and dynamic properties of molecules adsorbed in zeolites

A new lattice gas cellular automaton (LGCA) simulation approach to study static and dynamic properties of molecules adsorbed in zeolites is proposed. The motivation for the present work arises from the ongoing effort to develop efficient numerical tools where conventional approaches like molecular dynamics and Monte Carlo have been revealed as inefficient for a real extension of length and time scales in such inhomogeneous systems. Our LGCA is constituted by a constant number of interacting identical particles, distributed among a fixed number of identical cells arranged in a three-dimensional cubic network and performing a synchronous random walk at constant temperature. The main input for our model comes from data such as (i) local density dependent mean-field potentials and transition probabilities obtained from atomistic simulations that will be used as the starting point to derive adsorption and diffusion properties and (ii) thermodynamic and kinetic data obtained from experiments and/or other simulation methods. Our numerically less demanding LGCA has been tested over three different systems. The obtained results are in excellent agreement with the experimental and theoretical reported data.     

Diffusion in tight confinement: a lattice-gas cellular automaton approach. I. Structural equilibrium properties

The thermodynamic and transport properties of diffusing species in microporous materials are strongly influenced by their interactions with the confining framework, which provide the energy landscape for the transport process. The simple topology and the cellular nature of the alpha cages of a ZK4 zeolite suggest that it is appropriate to apply to the study of the problem of diffusion in tight confinement a time-space discrete model such as a lattice-gas cellular automaton (LGCA). In this paper we investigate the properties of an equilibrium LGCA constituted by a constant number of noninteracting identical particles, distributed among a fixed number of identical cells arranged in a three-dimensional cubic network and performing a synchronous random walk at constant temperature. Each cell of this network is characterized by a finite number of two types of adsorption sites: the exit sites available to particle transfer and the inner sites not available to such transfers. We represent the particle-framework interactions by assuming a differentiation in binding energy of the two types of sites. This leads to a strong dependence of equilibrium and transport properties on loading and temperature. The evolution rule of our LGCA model is constituted by two operations (randomization, in which the number of particles which will be able to try a jump to neighboring cells is determined, and propagation, in which the allowed jumps are performed), each one applied synchronously to all of the cells. The authors study the equilibrium distribution of states and the adsorption isotherm of the model under various conditions of loading and temperature. In connection with the differentiation in energy between exit and inner sites, the adsorption isotherm is described by a conventional Langmuir isotherm at high temperature and by a dual-site Langmuir isotherm at low temperature, while a first order diffuse phase transition takes place at very low temperature.     

Axisymmetric trawl cod-ends made from netting of a generalized mesh shape

The equations governing the geometry of axisymmetric trawl cod-endsmade from netting of meshes of a particular generalized structureare derived. From this, by suitable setting of the initial meshbar lengths, the equations governing the geometry of cod-endsthat are of importance to the fishing industry can be readilydeduced. It is assumed that arbitrary membrane forces act normalto the edges of the mesh elements, that there is no shear forceacting on the edge of a mesh element and that the twine thatmakes up the netting is extensible. The case where there isslackness in the mesh bars in the circumferential directionis dealt with and it is demonstrated how the finite structureof a knot can be taken into account. The case where the membraneforces arise solely as a result of and can be expressed by theappropriate components of the tensions in the mesh bars is alsoexamined and numerical solutions are found for a range of examples.     

A lattice-gas cellular automaton to model diffusion in restricted geometries

Topological constraints play a fundamental role in problems involving the transfer of heat, matter, or information in a discrete network. Flows in microporous media are the most common cases in which the thermodynamic and transport properties of adsorbate are strongly influenced by its interactions with the confining medium. Combining two local Monte Carlo operations and a Lattice-Gas Cellular Automaton, we constructed an equilibrium synchronous network of cells highly sensitive to the state of their neighborhood and able to capture the effects of confinement by means of few flexible local parameters and a parallel, local evolution rule. Results of an application of the model to the specific problem of geometrical restricted long-range diffusion are used to interpret the behaviors of particles in tight confinement.     

Diffusion in tight confinement: a lattice-gas cellular automaton approach. II. Transport properties

In this second paper the authors study the transport properties of the lattice-gas cellular automaton presented in Paper I [J. Chem. Phys. 126, 194709 (2007)] to model adsorption and dynamics of particles in a lattice of confining cells. Their work shows how a surprisingly simple parallel rule applied to a static network of cells joined by links set in space and time can generate a wide range of dynamical behaviors. In their model the cells are the elementary constituent objects of the network. They are a portion of space structured in sites which are energetically different. Each cell can accommodate a given maximum number of particles, and each pair of neighboring cells can exchange at most one particle at a time. The predictions of the model are in qualitative agreement with both experimental observations and molecular dynamics simulation results.