Cluster model of the glass transition

A cluster model of the glass transition has been developed, treating the relative size of the cluster as an order parameter. The model accounts for some of the features of the glass transition.

High pressure transport behaviour of AgI-Ag2O-MoO3 glasses and the cluster model

The effect of pressure on the conductivity of fast ion conducting AgI-Ag2O-MoO3 glasses has been investigated down to 150 K. The observed variation of conductivities appears to support the application of cluster model to the ionic glasses.

Glass transition. A new approach based on cluster model of glasses

The structure of real glasses has been considered to be microheterogeneous, composed of clusters and connective tissue. Particles in the cluster are assumed to be highly correlated in positions. The tissue is considered to have a truly amorphous structure with its particles vibrating in highly anharmonic potentials. Glass transition is recognized as corresponding to the melting of clusters. A simple mathematical model has been developed which accounts for various known features associated with glass transition, such as range of glass transition temperature,T g, variation ofT g with pressure, etc. Expressions for configurational thermodynamic properties and transport properties of glass forming systems are derived from the model. The relevence and limitations of the model are also discussed.

Baryon magnetic moment and beta decay ratio in colored quark cluster model

Baryon magnetic moments of p, n, Sigma(+), Sigma(-), Xi(0), Xi(-) and the beta decay ratios (G(A)/G(V)) of n -> p, Sigma(-) -> n and Xi(0) -> Sigma(+) are calculated in a colored quark cluster model. With SU(3) breaking, the model gives a good fit to the experimental values of those baryon magnetic moments and the beta decay ratios. Our results show that the orbital motion has a significant contribution to the spin and magnetic moments of those baryons and the strange component. in nucleon is small.

Performance of correlation functionals in ab initio chemisorption cluster-model calculations: Alkali metals on Si(111)

The performance of different correlation functionals has been tested for alkali metals, Li to Cs, interacting with cluster models simulating different active sites of the Si(111) surface. In all cases, the ab initio Hartree-Fock density has been obtained and used as a starting point. The electronic correlation energy is then introduced as an a posteriori correction to the Hartree-Fock energy using different correlation functionals. By making use of the ionic nature of the interaction and of different dissociation limits we have been able to prove that all functionals tested introduce the right correlation energy, although to a different extent. Hence, correlation functionals appear as an effective and easy way to introduce electronic correlation in the ab initio Hartree-Fock description of the chemisorption bond in complex systems where conventional configuration interaction techniques cannot be used. However, the calculated energies may differ by some tens of eV. Therefore, these methods can be employed to get a qualitative idea of how important correlation effects are, but they have some limitations if accurate binding energies are to be obtained.

CLUSTER MODEL FOR REACTIONS INDUCED BY WEAKLY BOUND AND/OR EXOTIC HALO NUCLEI WITH MEDIUM-MASS TARGETS

An experimental overview of reactions induced by the stable, but weakly-bound nuclei (6)Li, (7)Li and (9)Be, and by the exotic, halo nuclei (6)He, (8)B, (11)Be and (17)F On medium-mass targets, such as (58)Ni, (59)Co or (64)Zn, is presented. Existing data on elastic scattering, total reaction cross sections, fusion, breakup and transfer channels are discussed in the framework of a CDCC approach taking into account the breakup degree of freedom.

Test of nucleon-nucleon quark cluster model

The description of the short-range part of the nucleon forces in terms of quark degrees of freedom is tested by supplementing, to the short range quark cluster model, a long range mesonic force well founded theoretically.

Testing the quark cluster model in nucleon-nucleon scattering

The description of the short-range part of the nucleon-nucleon forces in terms of quark degrees of freedom is tested against experimental observables. We consider, for this purpose, a model where the short-range part of the forces is given by the quark cluster model and the long- and medium-range forces by well established meson exchanges. The investigation is performed using different quark cluster models coming from different sets of quark-quark interactions. The predictions of this model are compared not only with the phase shifts but also directly with the experimental observables. Agreement with the existing pp and np world set of data is poor. This suggests that the current description of the nucleon-nucleon interaction, at short distances, in the framework of the nonrelativistic quark models, is at present only qualitative.

A CLUSTER MODEL FOR HYBRIDS

A model for describing hybrid spectroscopy similar to the diquark model for baryons is presented. Mass and r.m.s. radii are calculated and compared with experimental results.

Factors that cause genotype by environment interaction and use of a multiple-trait herd-cluster model for milk yield of Holstein cattle from Brazil and Colombia

Descriptive herd variables (DVHE) were used to explain genotype by environment interactions (G x E) for milk yield (MY) in Brazilian and Colombian production environments and to develop a herd-cluster model to estimate covariance components and genetic parameters for each herd environment group. Data consisted of 180,522 lactation records of 94,558 Holstein cows from 937 Brazilian and 400 Colombian herds. Herds in both countries were jointly grouped in thirds according to 8 DVHE: production level, phenotypic variability, age at first calving, calving interval, percentage of imported semen, lactation length, and herd size. For each DVHE, REML bivariate animal model analyses were used to estimate genetic correlations for MY between upper and lower thirds of the data. Based on estimates of genetic correlations, weights were assigned to each DVHE to group herds in a cluster analysis using the FASTCLUS procedure in SAS. Three clusters were defined, and genetic and residual variance components were heterogeneous among herd clusters. Estimates of heritability in clusters 1 and 3 were 0.28 and 0.29, respectively, but the estimate was larger (0.39) in Cluster 2. The genetic correlations of MY from different clusters ranged from 0.89 to 0.97. The herd-cluster model based on DVHE properly takes into account G x E by grouping similar environments accordingly and seems to be an alternative to simply considering country borders to distinguish between environments.

The alpha-cluster model applied to 74Ge.

There are few studies using cluster models in the nuclei around the intermediate and heavy mass regions. The alpha-cluster model is based on the interaction between an alpha particle and a nucleus chosen as a core. This model can be applied to nuclear system where alpha-cluster stability is expected and the application in light and intermediate mass nuclei was able to give consistent descriptions of experimental data.

The cluster effect in China: Real or imagined?

Policy makers, urban planners and economic geographers readily acknowledge the potential value of industrial clustering. Clusters attract policy makers’ interest because it is widely held that they are a way of connecting agglomeration to innovation and human capital to investment. Urban planners view clustering as a way of enticing creative human capital, the so-called ‘creative class’, that is, creative people are predisposed to live where there is a range of cultural infrastructure and amenities. Economists and geographers have contrived to promote clustering as a solution to stalled regional development. In the People’s Republic of China, over the past decade the cluster has become the default setting of the cultural and creative industries, the latter a composite term applied to the quantifiable outputs of artists, designers and media workers as well as related service sectors such as tourism, advertising and management. The thinking behind many cluster projects is to ‘pick winners’. In this sense the rapid expansion in the number of cultural and creative clusters in China over the past decade is not so very different from the early 1990s, a period that saw an outbreak of innovation parks, most of which inevitably failed to deliver measurable innovation and ultimately served as revenue-generating sources for district governments via real estate speculation. Since the early years of the first decade of the new millennium the cluster model has been pressed into the service of cultural development.