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Intricate Patterns (intricate + pattern)
Selected AbstractsCovariance-based subdivision of the human striatum using T1-weighted MRIEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2008Michael X Cohen Abstract The striatum plays a key role in many cognitive and emotional processes, and displays an intricate pattern of connectivity with cortical and subcortical structures. Invasive tracing work in rats and non-human primates demonstrates that the striatum can be segregated into subregions based on similar clustering of input and output fibers. In contrast, the human striatum is typically segregated according to local anatomical landmarks without considering natural boundaries formed by functional/anatomical networks. Here, we used non-invasive magnetic resonance (MR) imaging in young, healthy adults to define subregions of the human striatum based on volume correlations with other subcortical and cortical structures. We present three methods to delineate anatomical volumetric correlations based on gray matter content estimated from T1-weighted MR images. We observed both consistencies with and divergences from invasive tracing work in animals, suggesting that magnetic resonance imaging (MRI)-based covariance likely does not correspond to direct anatomical connections, although it might index other forms of connectivity or tissue type similarity. These novel approaches may be useful in understanding connectivity of other regions, and changes in connectivity in patient or ageing populations. [source] Rapid tunnel-valley formation beneath the receding Late Weichselian ice sheet in Vendsyssel, DenmarkBOREAS, Issue 4 2009PETER B. E. SANDERSEN Interpretation of Transient ElectroMagnetic (TEM) data and wire-line logs has led to the delineation of an intricate pattern of buried tunnel valleys, along with new evidence of glaciotectonically dislocated layers in recessional moraines in the central part of Vendsyssel, Denmark. The TEM data have been compared with recent results of stratigraphical investigations based on lithological and biostratigraphical analyses of borehole samples and dating with Optically Stimulated Luminescence (OSL) and radiocarbon. This has provided an overview of the spatial distribution of the late Quaternary lithostratigraphical formations, and the age of the tunnel valleys has been estimated. The tunnel valleys are typically 5,10 km long, 1 km wide and are locally eroded to depths of more than 180 m b.s.l. The valleys are interpreted to have been formed by subglacial meltwater erosion beneath the outermost part of the ice sheet during temporary standstills and minor re-advances during the overall Late Weichselian recession of the Scandinavian Ice Sheet. The formation of the tunnel valleys occurred after the retreat of the Main ice advance c. 20 kyr BP and before the Lateglacial marine inundation c. 18 kyr BP. Based on the occurrence of the tunnel valleys and the topography, four ice-marginal positions related to the recession of the northeastern Main advance and seven ice-marginal positions related to the recession from the following eastern re-advance across Vendsyssel are delineated. All the tunnel valleys were formed within a time interval of a few thousand years, giving only a few hundred years or less for the formation of the tunnel valleys at each ice-marginal position. [source] Myosin-mediated cytoskeleton contraction and Rho GTPases regulate laminin-5 matrix assemblyCYTOSKELETON, Issue 2 2004Gregory W. deHart Abstract Laminin-5 is a major structural element of epithelial tissue basement membranes. In the matrix of cultured epithelial cells, laminin-5 is arranged into intricate patterns. Here we tested a hypothesis that myosin II-mediated actin contraction is necessary for the proper assembly of a laminin-5 matrix by cultured SCC12 epithelial cells. To do so, the cells were treated with ML-7, a myosin II light chain kinase inhibitor, or Y-27632, an inhibitor of Rho-kinase (ROCK), both of which block actomyosin contraction. Under these conditions, laminin-5 shows an aberrant localization in dense patches at the cell periphery. Since ROCK activity is regulated by the small GTPase Rho, this suggests that members of the Rho family of GTPases may also be important for laminin-5 matrix assembly by SCC12 cells. We confirmed this hypothesis since SCC12 cells expressing mutant proteins that inhibit RhoA, Rac, and Cdc42 assemble the same aberrant laminin-5 protein arrays as drug-treated cells. We have also evaluated the organization of the laminin-5 receptors ,3,1 and ,6,4 integrin and hemidesmosome proteins in ML-7- and Y-27632-treated cells or in cells in which RhoA, Rac, and Cdc42 activity were inhibited. In all instances, ,3,1 and ,6,4 integrin heterodimers, as well as hemidesmosome proteins, localize precisely with laminin-5 in the matrix of the cells. In summary, our results provide evidence that myosin II-mediated actin contraction and the activity of Rho GTPases are necessary for the proper organization of a laminin-5 matrix and localization of hemidesmosome protein arrays in epithelial cells. Cell Motil. Cytoskeleton 57:107,117, 2004. © 2004 Wiley-Liss, Inc. [source] Climatology of near-surface wind patterns over SwitzerlandINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2001Rudolf O. Weber Abstract Over complex, mountainous terrain the near-surface winds can form intricate patterns as large-scale winds and locally forced wind systems interplay. Switzerland, with its mountainous topography and dense meteorological network of 115 automated surface stations, ideally serves as a study area for such wind system interactions. Applying an automated classification scheme to the wind data of one single year (1995), 16 distinct near-surface flow patterns were found. These patterns also show characteristic distributions in magnitude and areal extent of temperature, global radiation and precipitation. An 18-year climatology of flow patterns was created with an identification method for fewer stations. This allowed the determination of annual and diurnal variations in the frequencies of occurrence of the different flow patterns, revealing pronounced daytime and night-time classes characterized by thermally forced winds. Transition probabilities between the flow patterns were computed as well. The relationship between the near-surface wind patterns and the synoptic flow situation was investigated with a comparison with synoptic weather types defined for the Alpine region. The results show clear but not unequivocal interdependencies between the synoptic weather type and the near-surface flow pattern. Copyright © 2001 Royal Meteorological Society [source] BIOCHEMISTRY OF SILICA BIOMINERALIZATION IN DIATOMSJOURNAL OF PHYCOLOGY, Issue 2000M. Sumper Diatoms are well known for the intricate patterns of their silica-based cell walls. The complex structures of diatom cell walls are species specific and become precisely reproduced during each cell division cycle, indicating a genetic control of silica biomineralization. Therefore, the formation of the diatom cell wall has been regarded as a paradigm for controlled production of nanostructured silica. However, the mechanisms allowing biosilicification to proceed at ambient temperature at high rates have remained enigmatic. Recently, we have shown that a set of highly cationic peptides (called silaffins) isolated from Cylindrotheca fusiformis shells are able to generate networks of silica nanospheres within seconds when added to a solution of silicic acid. Different silaffin species produce different morphologies of the precipitated silica. Silaffins contain covalently modified Lys-Lys elements. One of these lysine residues bears a novel type of protein modification, a polyamine consisting of 6,11 repeats of the N-methyl-propylamine unit. In addition to the silaffins, additional polyamine-containing substances have been isolated from a number of diatom species that may be involved in the control of biosilica morphology. Scanning electron microscopic analysis of diatom shells isolated in statu nascendi provide insights into the processes of pattern formation in biosilica. A model will be discussed that explains production of nanostructured biosilica in diatoms on the basis of these experimental results. [source] | |||||||||||||