Kaukasischer Beinwell (Symphytum caucasicum M. BIEB.) und Hidcote-Beinwell (Symphytum x hidcotense P. D. SELL) im Aachener Raum
Ferdinand Wolfgang Bomble
Bruno G. A. Schmitz
- Es werden zwei neophytische Symphytum-Arten aus dem Aachener Raum (Nordrhein-Westfalen) vorgestellt und abgebildet: S. caucasicum M. BIEB. (Kaukasischer Beinwell) und S. x hidcotense P. D. SELL 'Hidcote Blue' (= S. 'Hidcote Blue', S. x uplandicum x grandiflorum, Hidcote-Beinwell).
Eragrostis curvula (SCHRAD.) NEES, das Gebogene Liebesgras, in Nordrhein-Westfalen
- Das aus Südafrika stammende Gebogene Liebesgras (Eragrostis curvula) wurde bisher in Nordrhein-Westfalen
nur vereinzelt gefunden. Die charakteristischen Merkmale der Art werden hier vorgestellt und drei ihrer nordrhein-westfälischen Wuchsorte (Rhein-Herne-Kanal in Bottrop, NSG "Brachter Wald" im Kreis Viersen, Quarzsandgrube in Frechen, Rhein-Erft-Kreis), an denen sie eingebürgert ist, ausführlich beschrieben. Eragrostis curvula gelangte z. T. offensichtlich aus Ansaaten ins Gelände, an anderen Stellen bleibt die Herkunft unklar. Wie langjährige Beobachtungen zeigen, ist die Art in der Lage, sich an offenen Standorten massiv auszubreiten. Durch Mahd und Brand wird die Art offensichtlich gefärdert. Im NSG "Brachter Wald" wird sie zum Erhalt der ursprünglich vorhandenen Arten und der ursprünglichen Vegetation bereits seit einigen Jahren durch verschiedene Maßnahmen erfolgreich zurückgedrängt.
Nanolesions induced by heavy ions in human tissues: experimental and theoretical studies
- The biological effects of energetic heavy ions are attracting increasing interest for their applications in cancer therapy and protection against space radiation. The cascade of events leading to cell death or late effects starts from stochastic energy deposition on the nanometer scale and the corresponding lesions in biological molecules, primarily DNA. We have developed experimental techniques to visualize DNA nanolesions induced by heavy ions. Nanolesions appear in cells as “streaks” which can be visualized by using different DNA repair markers. We have studied the kinetics of repair of these “streaks” also with respect to the chromatin conformation. Initial steps in the modeling of the energy deposition patterns at the micrometer and nanometer scale were made with MCHIT and TRAX models, respectively.
Spontaneous dissociation of Co2(CO)8 and autocatalytic growth of Co on SiO2: A combined experimental and theoretical investigation
Harald O. Jeschke
- We present experimental results and theoretical simulations of the adsorption behavior of the metal–organic precursor Co2(CO)8 on SiO2 surfaces after application of two different pretreatment steps, namely by air plasma cleaning or a focused electron beam pre-irradiation. We observe a spontaneous dissociation of the precursor molecules as well as autodeposition of cobalt on the pretreated SiO2 surfaces. We also find that the differences in metal content and relative stability of these deposits depend on the pretreatment conditions of the substrate. Transport measurements of these deposits are also presented. We are led to assume that the degree of passivation of the SiO2 surface by hydroxyl groups is an important controlling factor in the dissociation process. Our calculations of various slab settings, using dispersion-corrected density functional theory, support this assumption. We observe physisorption of the precursor molecule on a fully hydroxylated SiO2 surface (untreated surface) and chemisorption on a partially hydroxylated SiO2 surface (pretreated surface) with a spontaneous dissociation of the precursor molecule. In view of these calculations, we discuss the origin of this dissociation and the subsequent autocatalysis.
Synthesis and electrical characterization of intrinsic and in situ doped Si nanowires using a novel precursor
- Perchlorinated polysilanes were synthesized by polymerization of tetrachlorosilane under cold plasma conditions with hydrogen as a reducing agent. Subsequent selective cleavage of the resulting polymer yielded oligochlorosilanes SinCl2n+2 (n = 2, 3) from which the octachlorotrisilane (n = 3, Cl8Si3, OCTS) was used as a novel precursor for the synthesis of single-crystalline Si nanowires (NW) by the well-established vapor–liquid–solid (VLS) mechanism. By adding doping agents, specifically BBr3 and PCl3, we achieved highly p- and n-type doped Si-NWs by means of atmospheric-pressure chemical vapor deposition (APCVD). These as grown NWs were investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as electrical measurements of the NWs integrated in four-terminal and back-gated MOSFET modules. The intrinsic NWs appeared to be highly crystalline, with a preferred growth direction of  and a specific resistivity of ρ = 6 kΩ·cm. The doped NWs appeared to be  oriented with a specific resistivity of ρ = 198 mΩ·cm for p-type Si-NWs and ρ = 2.7 mΩ·cm for n-doped Si-NWs, revealing excellent dopant activation.
Kritische und wenig bekannte Gefäßpflanzenarten im Aachener Raum II
Ferdinand Wolfgang Bomble
- Als Weiterführung der im Vorjahr begonnenen Serie ber kritische und wenig bekannte Sippen im Aachener Raum werden hier weitere Sippen vorgestellt. Neu kombiniert werden Bromus mediterraneus (H. SCHOLZ & F. M. VÁZQUEZ) BOMBLE & PATZKE und Sagina leiosperma (THELL.) BOMBLE. Ansonsten werden behandelt: Anthyllis vulneraria s. str., Bromus scholzii BOMBLE & PATZKE ined. (mit E. PATZKE), Eryngium giganteum, Lotus suberectus, Melampyrum pratense, Melampyrum commutatum, Persicaria capitata (= Polygonum capitatum), Sagina micropetala, Sagina x normaniana, Sagina procumbens, Sagina subulata var. glabrata und Solanum luteovirescens (mit B. G. A. SCHMITZ).
Radiation-induced nanostructures: Formation processes and applications
Actomyosin-based Self-organization of cell internalization during C. elegans gastrulation
Julia L. Moore
- Background: Gastrulation is a key transition in embryogenesis; it requires self-organized cellular coordination, which has to be both robust to allow efficient development and plastic to provide adaptability. Despite the conservation of gastrulation as a key event in Metazoan embryogenesis, the morphogenetic mechanisms of self-organization (how global order or coordination can arise from local interactions) are poorly understood.
Results: We report a modular structure of cell internalization in Caenorhabditis elegans gastrulation that reveals mechanisms of self-organization. Cells that internalize during gastrulation show apical contractile flows, which are correlated with centripetal extensions from surrounding cells. These extensions converge to seal over the internalizing cells in the form of rosettes. This process represents a distinct mode of monolayer remodeling, with gradual extrusion of the internalizing cells and simultaneous tissue closure without an actin purse-string. We further report that this self-organizing module can adapt to severe topological alterations, providing evidence of scalability and plasticity of actomyosin-based patterning. Finally, we show that globally, the surface cell layer undergoes coplanar division to thin out and spread over the internalizing mass, which resembles epiboly.
Conclusions: The combination of coplanar division-based spreading and recurrent local modules for piecemeal internalization constitutes a system-level solution of gradual volume rearrangement under spatial constraint. Our results suggest that the mode of C. elegans gastrulation can be unified with the general notions of monolayer remodeling and with distinct cellular mechanisms of actomyosin-based morphogenesis.
"Jüdische Irrlehre" oder exegetisches Experiment? : die Restitution Israels im 16. Jahrhundert
Untangling perceptual memory: hysteresis and adaptation map into separate cortical networks
Caspar Martin Schwiedrzik
Christian C. Ruff
Frauke C. Leitner
- Perception is an active inferential process in which prior knowledge is combined with sensory input, the result of which determines the contents of awareness. Accordingly, previous experience is known to help the brain “decide” what to perceive. However, a critical aspect that has not been addressed is that previous experience can exert 2 opposing effects on perception: An attractive effect, sensitizing the brain to perceive the same again (hysteresis), or a repulsive effect, making it more likely to perceive something else (adaptation). We used functional magnetic resonance imaging and modeling to elucidate how the brain entertains these 2 opposing processes, and what determines the direction of such experience-dependent perceptual effects. We found that although affecting our perception concurrently, hysteresis and adaptation map into distinct cortical networks: a widespread network of higher-order visual and fronto-parietal areas was involved in perceptual stabilization, while adaptation was confined to early visual areas. This areal and hierarchical segregation may explain how the brain maintains the balance between exploiting redundancies and staying sensitive to new information. We provide a Bayesian model that accounts for the coexistence of hysteresis and adaptation by separating their causes into 2 distinct terms: Hysteresis alters the prior, whereas adaptation changes the sensory evidence (the likelihood function).