Phyllotaxis — a new chapter in an old tale about beauty and magic numbers

Phyllotaxis, the regular arrangement of leaves and flowers around the stem, is one of the most fascinating patterning phenomena in biology. Numerous theoretical models, that are based on biochemical, biophysical and other principles, have been proposed to explain the development of the patterns. Recently, auxin has been identified as the inducer of organ formation. An emerging model for phyllotaxis states that polar auxin transport in the plant apex generates local peaks in auxin concentration that determine the site of organ formation and thereby the different phyllotactic patterns found in nature. The PIN proteins play a primary role in auxin transport. These proteins are localized in a polar fashion, reflecting the directionality of polar auxin transport. Recent evidence shows that most aspects of phyllotaxis can be explained by the expression pattern and the dynamic subcellular localization of PIN1.

Ms. Barth. 92 - Sammelhandschrift

Vorbesitzer: Jungo Frosch; Bartholomaeusstift Frankfurt am Main

Pseudospectra in non-Hermitian quantum mechanics

We propose giving the mathematical concept of the pseudospectrum a central role in quantum mechanics with non-Hermitian operators. We relate pseudospectral properties to quasi-Hermiticity, similarity to self-adjoint operators, and basis properties of eigenfunctions. The abstract results are illustrated by unexpected wild properties of operators familiar from PT -symmetric quantum mechanics.

Delayed Thrombus Resolution and Fibroproliferative Vascular Wound Healing From Deficiency of Type III Collagen: a Paradoxical Mechanism for Tissue Fragility

Vascular Ehlers-Danlos syndrome is a heritable disease of connective tissue caused by mutations in COL3A1, conferring a tissue deficiency of type III collagen. Cutaneous wounds heal poorly in these patients, and they are susceptible to spontaneous and catastrophic rupture of expansible hollow organs like the gut, uterus, and medium-sized to large arteries, which leads to premature death. Although the predisposition for organ rupture is often attributed to inherent tissue fragility, investigation of arteries from a haploinsufficient Col3a1 mouse model (Col3a1+/-) demonstrates that mutant arteries withstand even supraphysiologic pressures comparably to wild-type vessels. We hypothesize that injury that elicits occlusive thrombi instead unmasks defective thrombus resolution resulting from impaired production of type III collagen, which causes deranged remodeling of matrix, persistent inflammation, and dysregulated behavior by resident myofibroblasts, culminating in the development of penetrating neovascular channels that disrupt the mechanical integrity of the arterial wall. Vascular injury and thrombus formation following ligation of the carotid artery reveals an abnormal persistence and elevated burden of occlusive thrombi at 21 post-operative days in vessels from Col3a1+/- mice, as opposed to near complete resolution and formation of a patent and mature neointima in wild-type mice. At only 14 days, both groups harbor comparable burdens of resolving thrombi, but wild-type mice increase production of type III collagen in actively resolving tissues, while mutant mice do not. Rather, thrombi in mutant mice contain higher burdens of macrophages and proliferative myofibroblasts, which persist through 21 days while wild-type thrombi, inflammatory cells, and proliferation all regress. At the same time that increased macrophage burdens were observed at 14 and 21 days post ligation, the medial layer of mutant arterial walls concurrently harbored a significantly higher incidence of penetrating neovessels compared with those in wild-type mice. To assess whether limited type III collagen production alters myofibroblast behavior, fibroblasts from vEDS patients with COL3A1 missense mutations were seeded into three-dimensional fibrin gel constructs and stimulated with transforming growth factor-β1 to initiate myofibroblast differentiation. Although early signaling events occur similarly in all cell lines, late extracellular matrix- and mechanically-regulated events like transcriptional upregulation of type I and type III collagen secretion are delayed in mutant cultures, while transcription of genes encoding intracellular contractile machinery is increased. Sophisticated imaging of collagen synthesized de novo by resident myofibroblasts visualizes complex matrix reorganization by control cells but only meager remodeling by COL3A1 mutant cells, concordant with their compensatory contraction to maintain tension in the matrix. Finally, administration of immunosuppressive rapamycin to mice following carotid ligation sufficiently halts the initial inflammatory phase of thrombus resolution and fully prevents both myofibroblast migration into the thrombus and the differential development of neovessels between mutant and wild-type mice, suggesting that pathological defects in mutant arteries develop secondarily to myofibroblast dysfunction and chronic inflammatory stimulation, rather than as a manifestation of tissue fragility. Together these data establish evidence that pathological defects in the vessel wall architecture develop in mutant arteries as sequelae to abnormal healing and remodeling responses activated by arterial injury. Thus, these data support the hypothesis that events threatening the integrity of type III collagen-deficient vessels develop not as a result of inherent tissue weakness and fragility at baseline but instead as an episodic byproduct of abnormally persistent granulation tissue and fibroproliferative intravascular remodeling.

Plankton abundance and feeding characteristics of Thysanoessa raschii from Godthabsfjord, Greenland

Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the Godthabsfjord (64°N, 51°W) SW Greenland, through a combination of fieldwork and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily ration of 1% body C/d. Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 µm, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory behaviour of krill will concentrate and elevate the grazing in specific areas of the euphotic zone.

Gramática para todos : proyecto pedagógico con modalidad a distancia para la terminalidad de estudios de EGB3 y Educación Polimodal EDITEP

Los contenidos de este material de estudio (en torno a las palabras y el sentido) se refieren a la gramática como "sistema que permite describir y explicar oraciones y enunciados sin necesidad de contenerlos todos en un inventario". Están organizados en dos ejes. El eje 1 contiene temas como el sustantivo y su clasificación, el enunciado, los adjetivos, los verbos, los adverbios y los pronombres. El eje 2 se refiere a la sintaxis y el análisis de oraciones. Se editó como material de aprendizaje destinado al personal de seguridad pública de la Provincia de Mendoza en el marco del proyecto pedagógico con modalidad a distancia para la terminalidad de estudios de EGB3 y Educación Polimodal –EDITEP–, implementado a partir de la firma del Convenio entre la Universidad Nacional de Cuyo y el Gobierno de la Provincia de Mendoza, en octubre de 2003.

Telas antigranizo

La vitivinicultura mendocina representa más del 50% del PBI Agrícola Nacional; dada la relevancia económica de esta provincia en la industria vitivinícola, y siendo la caída de granizo una contingencia climática determinante en el volumen y calidad (actual y futura) de la producción de Vid, se ha tratado de analizar la factibilidad financiera de la inversión en Malla Antigranizo, la cual busca disminuir los daños, tanto físicos como económicos, en los oasis productivos que conforman esta provincia. Por lo tanto, el propósito del presente trabajo de investigación es brindar una herramienta que permita analizar la factibilidad económica financiera de colocar malla antigranizo en cada uno de los oasis productivos de la provincia de Mendoza. El tipo de inversión en malla antigranizo a analizar será el sistema Grembuile o Guardapolvo, el cual se coloca en el sistema de conducción de vid en espaldero. Esto permitiría al productor de uva decidir colocar o no la malla antigranizo según: el daño promedio de la caída de granizo por oasis, el tipo de uva sobre la cual quiere colocar la protección contra granizo, el precio de comercialización de dicha uva, el rendimiento promedio en kg/ha de la variedad y el oasis en donde se encuentra la superficie cultivada. Para poder abordar entonces esta investigación, se parte de la hipótesis de que no todas las variedades de uva justifican o permiten, desde el punto de vista económico financiero, la colocación de malla antigranizo. Es decir, no todas las variedades de uva justificarían invertir en malla antigranizo.

Horizontal profiles of longwave and shortwave radiation components over sea ice near Barrow, Alaska during the 2011 melt

An integrated instrument package for measuring and understanding the surface radiation budget of sea ice is presented, along with results from its first deployment. The setup simultaneously measures broadband fluxes of upwelling and downwelling terrestrial and solar radiation (four components separately), spectral fluxes of incident and reflected solar radiation, and supporting data such as air temperature and humidity, surface temperature, and location (GPS), in addition to photographing the sky and observed surface during each measurement. The instruments are mounted on a small sled, allowing measurements of the radiation budget to be made at many locations in the study area to see the effect of small-scale surface processes on the large-scale radiation budget. Such observations have many applications, from calibration and validation of remote sensing products to improving our understanding of surface processes that affect atmosphere-snow-ice interactions and drive feedbacks, ultimately leading to the potential to improve climate modelling of ice-covered regions of the ocean. The photographs, spectral data, and other observations allow for improved analysis of the broadband data. An example of this is shown by using the observations made during a partly cloudy day, which show erratic variations due to passing clouds, and creating a careful estimate of what the radiation budget along the observed line would have been under uniform sky conditions, clear or overcast. Other data from the setup's first deployment, in June 2011 on fast ice near Point Barrow, Alaska, are also shown; these illustrate the rapid changes of the radiation budget during a cold period that led to refreezing and new snow well into the melt season.