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Small Aggregates (small + aggregate)
Selected AbstractsFine-needle aspiration cytology of giant cell fibroblastoma: Case report and review of the literatureDIAGNOSTIC CYTOPATHOLOGY, Issue 6 2002Lester J. Layfield M.D. Abstract Giant cell fibroblastoma is an uncommon soft tissue neoplasm occurring in childhood. It appears to be the juvenile form of dermatofibrosarcoma protuberans, with which it shares some histologic, cytogenetic, and immunohistochemical features. We report, to our knowledge, the second description of the cytologic features of giant cell fibroblastoma. The present case represents a recurrent lesion in the soft tissues of the scrotum of a 17-yr-old male. The aspirate produced moderately cellular smears containing mononuclear cells, usually lying singly, but occasionally forming clusters. The majority of the individual cells possessed scanty bipolar cytoplasm or were devoid of cytoplasm. The nuclei were bland, with small nucleoli. Nuclear membranes frequently contained notches, creases, or folds. Small fragments of metachromatic stroma were present in the background and were often associated with small aggregates of cells. Rare multinucleated giant cells containing bland oval or basillary-shaped nuclei were admixed with the spindle-cell component. Necrosis and mitotic figures were not a component of the smears. Surgical resection of the mass confirmed the diagnosis of giant cell fibroblastoma. We review the characteristic cytologic features of giant cell fibroblastoma and compare them with other soft tissue tumors in the differential diagnosis. Diagn. Cytopathol. 2002;26:398,403. © 2002 Wiley-Liss, Inc. [source] A novel flow cytometric analysis for platelet activation on immobilized von Willebrand factor or fibrillar collagenJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2003S. Kao Summary., Under flow conditions, platelets adhere singly or in small aggregates on von Willebrand factor (VWF)-coated surfaces, but form large aggregates on immobilized fibrillar collagen. We developed a novel flow cytometric analysis to study the mechanisms underlying these distinct platelet deposition patterns. Flow cytometry was used to measure platelet activation after platelet adherence onto microspheres coated with either VWF or collagen fibrils. Two representative indices were calculated to quantify activated GpIIb,IIIa and P-selectin expression on adherent platelets. The signaling pathways responsible for platelet activation after interacting with fibrillar collagen were elucidated using various inhibitors. An in vitro endothelial cell wound model was also used to study the roles of VWF and fibrillar collagen in platelet deposition onto subendothelial matrixes. The adherent platelets on fibrillar collagen express more activated GpIIb,IIIa and P-selectin than those on VWF. Activation of GpIIb,IIIa and expression of P-selectin after platelet interaction with collagen occur via different intracellular signaling pathways; however, Ca2+ released from intracellular pools is common to both phenomena. Platelets were deposited singly or formed small aggregates on the endothelial cell wounded area, and this deposition pattern was dependent on VWF molecules secreted by endothelial cells and the absence of subendothelial collagen fibrils. As less activated GpIIb,IIIa and P-selectin are expressed after platelets interact with immobilized VWF alone, subsequent flowing platelet recruitment is minimal. Collagen fibrils, however, can activate adherent platelets sufficiently to promote the formation of large platelet aggregates. [source] A new smoothed aggregation multigrid method for anisotropic problemsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 1 2009Michael W. Gee Abstract A new prolongator is proposed for smoothed aggregation (SA) multigrid. The proposed prolongator addresses a limitation of standard SA when it is applied to anisotropic problems. For anisotropic problems, it is fairly standard to generate small aggregates (used to mimic semi-coarsening) in order to coarsen only in directions of strong coupling. Although beneficial to convergence, this can lead to a prohibitively large number of non-zeros in the standard SA prolongator and the corresponding coarse discretization operator. To avoid this, the new prolongator modifies the standard prolongator by shifting support (non-zeros within a prolongator column) from one aggregate to another to satisfy a specified non-zero pattern. This leads to a sparser operator that can be used effectively within a multigrid V-cycle. The key to this algorithm is that it preserves certain null space interpolation properties that are central to SA for both scalar and systems of partial differential equations (PDEs). We present two-dimensional and three-dimensional numerical experiments to demonstrate that the new method is competitive with standard SA for scalar problems, and significantly better for problems arising from PDE systems. Copyright © 2008 John Wiley & Sons, Ltd. [source] On-line Determination of Aggregate Size and Morphology in SuspensionsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2004Frédéric Gruy Abstract Information concerning the aggregation state of fine solid particles is an important element for process control and monitoring of product quality in many applications of industrial slurries. This work deals with the application of different in-line methods to the characterization of silica aggregate size and morphology. All of these methods exploit turbidity signals, obtained by various means including: from analysis of turbidity fluctuations in homogeneous suspension and from overall turbidity decrease during particle settling. This work also presents the opportunity to report progress in morphological and optical models of small aggregates. As a result of these models, the morphological characteristics of the aggregates along with the number of their constituting particles are derived from experimental results. Similarities between the different methods are examined and discussed. [source] Intracerebral schwannoma in a child with infiltration along perivascular spaces resembling meningioangiomatosisPATHOLOGY INTERNATIONAL, Issue 8 2009Misa Ishihara Schwannoma arising within brain parenchyma is a rare lesion, usually found in children. Reported herein is a case of intracerebral schwannoma in a 5-year-old boy, with a review of the English-language literature on the subject, in which 47 cases were found. Few detailed histological reviews of intracerebral schwannoma exist. The tumor had a distinctive plexiform growth pattern, and small aggregates of Schwann cells spread extensively into the surrounding brain tissue along perivascular spaces adjacent to the tumor nodule. Histological differential diagnoses included perivascular schwannosis and meningioangiomatosis. A few intratumoral axons, seen on immunostaining for neurofilament protein, were trapped at the periphery of the main lesion, but there was no evidence of intralesional axons in the multiple nodules of Schwann cell proliferations that extended into the perivascular spaces, suggesting that the lesions are neoplastic. Because Schwann cells are not a natural component of the central nervous system, the origin of intracerebral schwannomas remains unknown. The histology suggests that Schwann cells of the perivascular nerve plexus are a likely site of origin. [source] | ||||||||||