Small Number Of Clusters Research Articles

On the behaviour of small clusters near the spinodal decomposition

The canonical average of the Boltzmann factor of the interaction potential, as measured by a test particle, is shown to be equal to the inverse of the fraction of the average number \((\bar m_1 )\) of 1-particle Mayer clusters. The potential distribution theory is used to derive an analytic expression for a mean number of small clusters \((\bar m_n {\text{ , 1 }} \leqslant {\text{ }}n < {\text{ }}N,\) 1≤n<N, in anN-particle system) in the mean-field expression. Near the spinodal density, the average number of small clusters undergo a sharp change. Computation of pressure shows that only the first four clusters produce surprisingly good agreement with known pressure even beyond the spinodal density.

Malignant disease of the pleura: a histopathological study with special emphasis on diagnostic criteria and differentiation from reactive mesothelium.

In order to define the histopathological criteria for the diagnosis of malignant neoplasm involving pleura, we studied 11 pleurectomy specimens containing undoubted malignant cells. The most important feature for a diagnosis of malignancy was the pattern of neoplastic infiltration of the fibrous sub-pleural tissue. These criteria were subsequently applied in a re-analysis of 76 pleural needle biopsies with a diagnosis of cancer. The patterns most frequently seen were a multi-pronged growth of at least four clusters of atypical cells in the fibrous sub-pleural tissue, a solid pattern with a large collection of atypical cells and a confluent one where large numbers of small clusters of atypical cells appeared almost fused in the stroma. Less frequently, malignant cells covered the surface of fibromuscular tissue, or were found in an intravascular or intramuscular location, but often associated with any of the three main patterns. Five needle biopsies were considered suspicious and 11, considered benign, contained a prominent mesothelial reaction. The benign control cases showed mesothelial cells mainly in a peripheral growth pattern or as clusters of cells interspersed with fibrin, without any mitotic activity; granulation tissue and lympho-histiocytic infiltrates were more frequently seen in the control group.

Using interdocument similarity information in document retrieval systems

Etude comparative de quatre methodes de constitution de grappes de documents et de leur efficacite lors de la recherche documentaire, testee sur sept collections de documents

Reconstruction of a thyroid gland equivalent from cells and matrix materials.

A living thyroid gland equivalent has been fabricated with a cultivated strain of rat thyroid cells (FRTL), dermal or thyroid fibroblasts, and matrix materials. The mixture becomes tissuelike in vitro by virtue of interactions between fibroblasts and collagen. Initially in vitro the thyroid cells are uniformly distributed as single cells and a small number of clusters containing less than 10 cells. When implanted into thyrodectomized hosts the thyroid cells in the tissue lattice become organized into follicles containing a colloidlike material. The follicles were found in clusters in sizes up to 0.3 mm. The clusters are vascularized. It is thought that they arise within clones rather than by an aggregation process. Using an antithyroglobulin antibody it was shown that both thyroid cells and the colloidlike material within follicles reacted positively. Development of follicles was strictly dependent on whether hosts were thyroidectomized. In nonthyroidectomized hosts no follicles were observed. We conclude that an organotypic structure can develop in vivo from a "gland-equivalent" fabricated with adult cells and matrix materials combined in vitro, and that cells cultivated for years in vitro retain the capacity to express differentiated functions in a reconstituted organ equivalent in vivo.

The main-sequences of NGCs 2 88, 3201, 4590, and 6809

A globular cluster is an admirable object for the study of stellar evolution and theoretical investigations of the isochrones in the colour-magnitude diagram (CMD) have been numerous, with the most recent being that of Vandenberg (1983, Ap. J. Suppl. 51, 29), but there are still uncertainties such as rotation, abundance variations and gravitational settling. The matching observations are in fair agreement. However only a small number of clusters have been observed and the detailed matching is poor. Most of the CMDs are from photoelectrically calibrated photographic photometry which are affected by the variable background found in clusters. Modern detectors suffer less from this problem and are very sensitive. A programme has been underway on a number of clusters using electronographs and CCDs with the SAAO 1.Om telescope and the crowded-field Starlink Aspic software. This paper reports on preliminary results from four of the clusters. The CCD observations were done in collaboration with W.K. Griffiths of Leeds University.

Regionalization on Age Composition by Neighborhoods within Sendai City

Age composition of neighborhoods in urban area are well known to be variated. The purpose of this paper is to analyse both the spatial pattern of such variations and their changes from 1960 to 1975 within Sendai city.The procedure is as follows: firstly, neighborhoods are conveniently defined as small administrative districts (chos) within Sendai city. Twenty six neighborhoods are chosen for analysis as samples representing all of neighborhoods within Sendai city. Secondly, 26 neighborhoods are classified into a small number of clusters on the similarity of age composition, using the method of Cluster Analysis. Spatial arrangements of such clusters are mapped. Thirdly, spatial variations of age composition is compared with those of occupation composition in order to clarify the coincidences between them.The results may be summarized as follows.1) Twenty six neighborhoods were classified into four clusters on the similarity of age composition in 1960. At the same time, the spatial arrangement of four clusters formed a series of circles within Sendai city. That is, the first cluster is characterized by both comparatively high ratio of 15-24 age group and low ratio of 0-14 age group. This comprized only one neighborhood (Higashi-Nibancho) located in CBD. The second one characterized by relatively high ratio of 35-44 age group consisted of neighborhoods located in the zone around CBD (8 blocks). The third which had the relatively high ratio of 25-44 age group included neighborhoods distributed in the inner zone (the old built-up area excluding the above two zone, 11 blocks). The fourth was characterized by both comparatively high ratio of 0-14 age group and low ratio of 15-34 age group, contrasting with the first cluster. Neighborhoods comprized in this cluster spreaded themselves in the outer zone (suburbs, 7 blocks).2) In 1975 period, Sendai city was divided two regions which consisted of the extended CBD and the outer region. The differentiation between CBD and the zone around CBD distinguished in 1960 became to be diminished in 1975. The two zones were combined as the extended CBD. In addition, the differences between the south part of inner zone and the outer zone in 1960 also became a little, and the two zone were able to be grouped into the outer region.3) The same spatial pattern of age composition by neighborhoods were identified in the spatial variations of occupation composition by neighborhoods. So, the Multiple Regression Analysis had been done in order to clear up the relationship between these two spatial variations. As a result, spatial variations of the proportion of persons engaged in both trade and farming were clarified to be closely related to those of age composition in 1960. But in 1975, such a strong relationship between them was not clearly found. The result guessed that it was necessary to analyse on the scale of Sendai Metropolitan Areas. Because residential developments had been done beyond the administrative area of Sendai city after 1960 and areal differentiation had also developed on that scale.

The X-ray spectra of clusters of galaxies

The identification of extended sources of X-ray emission associated with clusters of galaxies has been one of the major achievements of X-ray astronomy. In this paper the present situation regarding the identification of X-ray clusters is reviewed and the relationship between X-ray and optical cluster properties is briefly discussed. Measurements of X-ray extent have been made for a small number of clusters and the status of these observations is described. The nature of the X-ray emission process and the observations which have led to our present understanding of cluster X-ray production are examined in some detail. Observations at other wavelengths that are relevant to this problem are also discussed. The available evidence suggests that the X-ray emission is due to bremsstrahlung from high-temperature (T>2·107 K) gas that is present in the space between cluster galaxies. Current models of the origin of this gas and of its likely heating mechanism are presented.

Electron microscopy investigation of clusters created in nickel by “in situ” rare gas ion irradiation

Irradiations by rare gas ions of 10 to 50 keV have been performed in nickel [10 ppm impurity) at temperatures between 100 and 500 K. The clusters have been observed “in situ” in a conventional electron microscope during irradiation(1).1)Dose effect - Problems of cascade efficiency - For Argon ions of 25 and 50 keV and at irradiation temperatures between 100 and 500 K, the variation of the cluster density as a function of the dose is the same [see fig. 1). Two points are of interest :-the existence of a dose threshold (do) below which no defect is detectable : do ⋍ 1013ions/cm2;the small number of clusters compared to the number of implanted ions [between 1/1000 and 5/1000). This phenomenon has never been observed before for irradiations with metallic ions(2,3).The most likely interpretation is the creation of microclusters [smaller than 10 Å) due to the presence of rare gas ions.

SAMPLING SYSTEMS FOR EUROPEAN RED MITE, PANONYCHUS ULMI (ACARINA: TETRANYCHIDAE), EGGS ON APPLE IN NOVA SCOTIA

AbstractA study was conducted in a mature apple orchard in Nova Scotia to compare the density of eggs of the European red mite, Panonychus ulmi (Koch), over the whole tree to their density on a selected area using a random selection and standard selection technique. Both methods provided nearly equivalent estimates of population densities for generations 2 and 4 but not for generation 3. The population estimates based on sampling from the selected area overestimated the whole tree population.Optimum allocation of sampling resources may be obtained by sampling a small number of clusters from each of a large number of trees.

Possible Applications of the Mass-energy Cycle on a Micro- and Macro-scopic Scale in the Universe

HUGHES1 suggests that the observed expansion of the universe is only apparent, since the mass components of galactic clusters separate but the energy components approach one another. This is not so. Consider a small number of clusters, receding from each other. Photons emitted on the inward side of each cluster will approach photons from other clusters, and perhaps, as Hughes suggests, condense together under gravitational attraction. In any event, there is a limit to their mutual closeness. Photons emitted on the outward sides of clusters, on the other hand, will move in the same direction as the cluster and so will continue to separate indefinitely. The mean positions of photons originating in these clusters will therefore separate as do the mean positions of the particles of mass >0. Eddington's objection is not disposed of.