We investigate the evolution of the fractions of late type cluster galaxies as a function of redshift, using one of the largest, most uniform cluster samples available. The sample consists of 514 clusters of galaxies in the range 0.02≤z≤0.3 from the Sloan Digital Sky Survey Cut & Enhance galaxy cluster catalog. This catalog was created using a single automated cluster finding algorithm applied to uniform data from a single telescope, with accurate CCD photometry, thus, minimizing selection biases. We use four independent methods to analyze the evolution of the late type galaxy fraction. Specifically, we select late type galaxies based on: restframe g −r color, u−r color, galaxy profile fitting and concentration index. The first criterion corresponds to 1 the one used in the classical Butcher-Oemler analyses. The last two criteria are more sensitive to the morphological type of the galaxies. In all the four cases, we find an increase in the fraction of late type galaxies with increasing redshift, significant at the 99.9% level. The results confirm that cluster galaxies do change colors with redshift (the Butcher-Oemler effect) and, in addition, they change their morphology to latertype toward higher redshift -indicating a morphological equivalent of the Butcher-Oemler effect. We also find a tendency of richer clusters to have lower fractions of late type galaxies. The trend is consistent with a ram pressure stripping model, where galaxies in richer clusters are affected by stronger ram pressure due to higher temperature of clusters.

Abstract. We present the first algorithms for processing graphs in the slidingwindow model. The sliding window model, introduced by Datar et al. (SICOMP 2002), has become a popular model for processing infinite data streams in small space when older data items (i.e., those that predate a sliding window containing the most recent data items) are considered "stale" and should implicitly be ignored. While processing massive graph streams is an active area of research, it was hitherto unknown whether it was possible to analyze graphs in the slidingwindow model. We present an extensive set of positive results including algorithms for constructing basic graph synopses like combinatorial sparsifiers and spanners as well as approximating classic graph properties such as the size of a graph matching or minimum spanning tree.

Phenotypic characterization of lymphoid cell subpopulations in gingivitis associated with the deciduous dentition in children was carried out. Biopsies were obtained from 10 children aged between 5 and 9 years. The tissues were processed for either histochemistry or for immunofluorescence. T‐cells were identified by their T‐enzyme staining pattern and lack of immunoglobulin. B‐cells on the other hand were identified by their lack of T‐cell enzymes and presence of surface or cytoplasmic immunoglobulin. Morphologically the lesions consisted of approximately 70 % lymphocytes, between 11 and 26 % macrophages and fewer numbers of polymorphonuclear leukocytes and plasma cells. The majority of lymphocytes (approximately 70 %) were T‐enzyme positive/Ig negative indicative of a Tcell population. Approximately 12 % of the infiltrating cells were immunoglobulin positive. These results showed that gingivitis in children is essentially a T‐cell lesion and supports the hypothesis that the conversion from a stable to a progressive lesion involves shifts in cell populations.

Monoclonal antibodies made against lymphocyte differentiation antigens were used to characterize phenotypically the lymphoid cell subpopulations in sections of human lymphoid tissue and inflamed gingival tissue associated with the deciduous dentition in children. Four monoclonal antibodies designated FMC 1, FMC 4, FMC 7, and UCHT1 were used. These antibodies are specific for B‐cells, p28,33 (la‐like) antigen, a B‐cell subset, and peripheral T‐cells respectively. FMC 1 and FMC 4 positive cells (B‐cells) were found mainly in the secondary follicles while UCHT1 positive cells (T‐cells) were found in the parafollicular areas of human tonsils. Cells in some, but not all, secondary follicles in the tonsils were FMC 7 positive. In the gingival tissue only 12.6 % of the infiltrating cells were FMC 1 positive, 12.2 % were FMC 4 positive, and 4.8 % FMC 7 positive. On the other hand over 75 % of cells appeared to be UCHT1 positive. These results indicate that the majority of inflammatory cells in gingivitis associated with the deciduous dentition in children have the phenotype B‐cell antigen‐/p28,33 (lalike) antigen‐/B‐cell subset antigen‐ and possibly T‐cell antigen+. Such a phenotype is, at least by exclusion, suggestive of T‐cells and as such confirms earlier studies using T‐cell enzyme markers.