The single-point active nonlinear microrheology of a colloidal suspension is measured using laser tweezers in the limit that the diameter of the probe particle approaches the diameter of the bath suspension particles. The microviscosity thins as the probe velocity (and corresponding microrheological Péclet number) increases. This thinning behavior correlates with the development of a nonequilibrium suspension microstructure surrounding the probe particle, in which a boundary layer forms on the upstream face of the probe and a wake depleted of bath particles trails the probe. The magnitude of the microviscosities and the thinning behavior are in good agreement with Brownian dynamics simulations reported by Carpen and Brady [J. Rheol. 49, 1483 (2005)]. The microviscosity increment collapses onto a single curve for all volume fractions when scaled by the contact distribution of bath particles around the probe. Scaling the microviscosity increment yields values lower than the dilute theory; furthermore, it plateaus at significantly higher Péclet numbers. The latter effect is corrected by rescaling the Péclet number with the suspension collective diffusion coefficient in place of the bath particle self-diffusivity. The magnitude of the microviscosity increment suggests the theory overestimates the frequency of bath-probe collisions. The presence and role of hydrodynamic interactions and the effect of the soft repulsive potential are discussed.
Die molekularen Parameter von Kopf‐Schwanz‐verknüpften Poly(3‐alkylthiophenen) 1 (R=C6H13, C12H25) wurden rastertunnelmikroskopisch an zweidimensionalen Kristallen bestimmt. Die Polymerfaltungen und ‐konformationen wurden mit submolekularer Auflösung abgebildet (siehe Bild von 1 mit R=C12H25). Darüber hinaus konnte eine elektronische Kopplung zwischen diesen „molekularen Drähten”︁ und denen einer parallel angeordneten zweiten Schicht nachgewiesen werden.
Currently, lymphoma diagnosis is based on a combination of morphology, immunophenotyping, and molecular testing. Using the example of an unusual case of malignant non-Hodgkin lymphoma, we show that improved visualization using digital pathology contributes to the convergence of these complementary diagnostic modalities. A 45-year-old woman presented with skin rash and cervical lymphadenopathy. Histological workup of an excised lymph node showed loss of normal architecture with diffuse infiltration and increased mitotic activity. Immunohistochemistry for CD3/CD5 showed atypical arrangement and infiltration of a T-cell population that dominated over regionally dense, MUM1-positive plasmacellular infiltrates. Expanded CD21/CD23-positive meshworks of follicular dendritic cells were present within and between regressed follicles and the T-cell infiltrate; staining for CD56 and cyclin-D1 was negative. Quantification of Ki-67 staining within the T-, B- and plasmacellular compartments was achieved by digital image conversion, overlay and subsequent quantification algorithms that revealed proliferation within more than 60% of T-cells, over 50% of plasma cells and only 20% of B-cells. Clonality analysis by PCR revealed monoclonal rearrangement for both T-cell receptor gamma chains and immunoglobulin heavy chains. Taken together, we present an unusual combination of an angioimmunoblastic T-cell lymphoma (AITL) and simultaneous plasmacellular lymphoma. This report demonstrates how application of modern tools of digital pathology can visually integrate unusual morphological and molecular findings.
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