Simulations of Field Driven Domain Wall Interactions in Ferromagnetic Nanowires

The interaction of domain walls in a single ferromagnetic nanowire has been observed with micromagnetic simulation. Domain walls separating domains of opposite magnetization move towards each other when an external field is applied along the long axis of the wire resulting in a collision. The final magnetic state of the wire after the collision will contain either zero (domain wall annihilation) or two (domain wall conservation) domain walls. Here we explore the behavior that determines the final state, showing that it depends on the initial domain wall configuration, the speed the domain walls are moving with before the collision, and the dimensions of the nanowire. A model is also presented which helps to determine the repulsive force the conserved domain walls exert on each other

DOC trail: soil organic matter quality and soil aggregate stability in organic and conventional soils

Conclusion Soil organic matter quality is affected by the agricultural systems of the DOC trial. System effects on the chemical composition, however, were smaller than those on the living organisms in soil and their functions. A close correlation was found between soil structure and microbial biomass indicating that microbes are playing an important role in soil structural stability

Uncovering the molecular basis of compartmentalization as a principle of neuronal organization

Cells are faced with coordinating countless, simultaneous, partly antagonistic biochemical reactions. This is especially true for neurons that must orchestrate the complex task of neurotransmission. One solution to this problem is the formation of specialized compartments. To understand the molecular mechanisms of such compartments this thesis investigates two system in neuronal cells: i. the plasma membrane and its underlying cytoskeleton and ii. synaptic vesicle clusters inside synaptic boutons. Towards this end, a combinatorial approach of computational modeling, single particle tracking and super-resolution microscopy is employed. A periodic array of actin rings in the neuronal axon initial segment has been known to confine membrane protein motion. Still, a local enrichment of ion channels offers an alternative explanation. Using computational modeling this thesis now shows that ion channels, in contrast to actin rings, cannot mediate confinement. Furthermore, by employing single particle tracking and super-resolution microscopy, this work shows that actin rings are close to the plasma membrane and that actin rings confine membrane proteins in several neuronal cell types. Further, it is shown that actin ring disruption leads to a reduction of membrane compartmentalization. Synaptic boutons in the axon of neurons are the location of synaptic vesicle release. Synaptic vesicles form dense clusters inside boutons, that are essential for pre-synaptic function. In vitro experiments have suggested that the soluble phosphoprotein synapsin 1 controls synaptic clustering via liquid liquid phase separation. However, the in vivo mechanism remains elusive. This work now shows via two-color single molecule tracking in live neurons that synapsin 1 drives synaptic vesicle clustering. Furthermore, using a synapsin knock-out model it is shown that synapsin 1 controls the mobility of synaptic vesicles through its intrinsically disordered region, which is responsible for phase separation. By studying the dynamics of compartmentalized systems in neuronal cells this work uncovers two molecular mechanisms: actin rings form membrane diffusion barriers and synapsin 1 controls synaptic vesicle clustering and mobility through liquid liquid phase separation. Thus, this thesis makes important strides towards deepening the understanding of neuronal function by uncovering how compartmentalization operates in both the plasma membrane and the cytosol of neuronal cells.Zellen müssen unzählige, gleichzeitige, teilweise gegensätzliche biochemische Reaktionen koordinieren. Dies gilt insbesondere für Neuronen, die die komplexe Aufgabe der Neurotransmission koordinieren. Eine Lösung für dieses Problem ist die Bildung spezialisierter Kompartimente. Um die molekulare Funktionsweise solcher Kompartimente zu verstehen, werden in dieser Arbeit zwei Systeme in neuronalen Zellen untersucht: i. die Plasmamembran und das darunterliegende Zytoskelett und ii. synaptische Vesikel-Cluster in Boutons. Zu diesem Zweck, wurde ein kombinatorischer Ansatz aus Computermodellierung, Einzelpartikelverfolgung und superauflösender Mikroskopie verwendet. Periodische Aktinringe im neuronalen Axoninitialsegment schränken die Bewegung von Membranproteinen ein. Jedoch liefert eine lokale Anreicherung von Ionenkanälen eine alternative Erklärung. Durch Computermodellierung wird in dieser Arbeit nun gezeigt, dass Ionenkanäle keine Einschränkung der Membranmolekülbewegung bewirken. Darüber hinaus wird durch Einzelpartikelverfolgung und superauflösende Mikroskopie gezeigt, dass Aktinringe nahe der Plasmamembran sind und dass Aktinringe Membranproteine in verschiedenen neuronalen Zelltypen in ihrer Bewegung einschränken. Weiterhin wird gezeigt, dass die Zerstörung der Aktinringe Membrankompartmentalisierung reduziert. Synaptische Boutons im Axon sind der Ort der Freisetzung synaptischer Vesikel. Synaptische Vesikel bilden dichte Cluster in Boutons, welche für die Funktion der Präsynapse essenziell sind. In vitro Experimente haben gezeigt, dass das lösliche Phosphoprotein Synapsin 1 das Clustern durch Flüssig-Flüssig-Phasentrennung steuert, der Mechanismus in vivo ist jedoch unklar. Diese Arbeit zeigt nun mittels Zweifarben-Einzelmolekülverfolgung in lebenden Neuronen, dass Synapsin 1 das Clustern synaptischer Vesikel steuert. Anhand eines Synapsin-Knock-out-Modells wird gezeigt, dass Synapsin 1 die Mobilität synaptischer Vesikel durch seine intrinsisch ungeordnete Region kontrolliert, die für die Phasentrennung verantwortlich ist. Durch Untersuchungen der Dynamik kompartmentalisierter Systeme in neuronalen Zellen deckt diese Arbeit zwei molekulare Mechanismen auf: Aktinringe bilden Membrandiffusionsbarrieren und Synapsin 1 steuert Clustern und Mobilität synaptischer Vesikel durch Flüssig-Flüssig-Phasentrennung. Somit macht diese Arbeit wichtige Fortschritte zum Verständnis der Funktionsweise neuronaler Zellen, indem sie aufdeckt, wie die Kompartmentalisierung der Plasmamembran und des Zytosols gesteuert wird

Iowa Agriculturist 96.01

Special Report Ag Week 1993: Topics of Today and Opportunities for Tomorrow 16 Features Cyclone Stampede 6 Students Find Adverse Conditions, Good Times in International Exchange 8 Soil Compassion 10 ISU Researchers Develop Use for Leaner Pork 12 Adding Some Excitement to the Chores 20 Learn the Whole Story: Farm House Museum 22 Departments Professor Profile 5 Editorials: Grassley: Frustration over Clinton\u27s Indecisiveness . . 14 Harkin: Restructuring the USDA . . . 15 Udderances 18 Photo Tour . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Photo Tour of the 1993 Farm Progress Showhttps://lib.dr.iastate.edu/iowaagriculturist/1008/thumbnail.jp

Controlling Individual Domain Walls in Ferromagnetic Nanowires for Memory and Sensor Applications

Controlled motion of 180o and 360o domain walls along planar nanowires is presented. Standard Landau – Lifshitz micromagnetic modeling has been used to simulate the response of the domain walls to the application of an external magnetic field. A 180o wall is quickly and easily moved with the application of an applied. field along the axis of the wire but a 360odomain wall is stationary in the same case. An oscillatory applied field can be used to continually move the wall along the wires axis. The speed at which the 360o domain wall is found to be several times slower than a similar 180o domain wall and is limited by interaction between the magnetization of the domain wall and the external field