Vortex core switching by coherent excitation with single in-plane magnetic field pulses

The bistability of the core magnetization of nano-scaled magnets with a magnetic vortex configuration has great potential for data storage applications. To exploit this, reliable switching between the two possible states is needed. Time resolved x-ray microscopy was used to study the response of the vortex core to excitation pulses at sub-ns timescales and image the vortex core switching. A reliable switching process by coherent excitation with leading and trailing edges of in-plane magnetic field pulses was found and compared with micromagnetic simulations.Comment: 4 pages, 3 figure

X-ray Crystallography of Inositol Dehydrogenase Enzymes

Lactobacillus casei BL23 expresses two enzymes encoded by the genes iolG1 and iolG2. They have been putatively assigned as myo-inositol dehydrogenases by sequence comparison. The enzyme catalyzes the reversible conversion of myo-inositol to scyllo-inosose and the concurrent reduction of NAD+ to NADH. iolG1 was subsequently determined to be a myo-inositol dehydrogenase but iolG2 was determined to be a scyllo-inositol dehydrogenase. Sequence analysis and kinetics by themselves did not provide insight as to why the enzymes are functionally different. This manuscript provides a structural rationalization for the differences in stereoisomer selectivity by X- ray crystal structure analysis and comparison. High resolution apo, binary, and ternary crystal structures for iolG1 and iolG2 wild type enzymes were determined. For iolG1 the ternary structures were determined for myo-inositol and d-chiro-inositol and for iolG2 the scyllo-inositol bound structure was determined. The high resolution structure information revealed the composition of their respective active sites and showed that subtle differences in critical amino acids for each enzyme define the orientation of the inositol stereoisomer for inline transfer of a hydride to NAD+. Mutagenesis studies of a closely related myo-inositol dehydrogenase from Bacillus subtilis were carried out. The wild type structure for BsIDH had already been determined and characterized. A portion of the results in this manuscript briefly explore structures of dehydrogenase mutants which validate the structural role of residues involved in cofactor selectivit

Wakefield damping in a distributed coupling linear accelerator

The number of cells in a π-mode standing wave (SW) accelerating structure for the Compact Linear Collider (CLIC) project is limited by mode overlap with nearby modes. The distributed coupling scheme avoids mode overlap by treating each cell as independent. Designs of cells suitable for distributed coupling with strong wakefield suppression by waveguide damping have not previously been studied. In this paper we develop a SW cell to be used in a distributed coupling structure that can satisfy the CLIC transverse wake potential limit. From the middle cell of the CLIC-G* traveling wave (TW) structure, a SW cell is designed and then adapted to perform as a cell in a distributed coupling structure. Its wake potentials in an ideal case of open boundaries are reduced to satisfy the wake potential threshold. An electric boundary is added to the model to simulate total reflection at the distribution network. A horizontal coupler cell that connects to the distribution network such that the reflected wakefields remain similar to the open boundary case is simulated. A triplet module which takes advantage of cell-to-cell coupling to reduce reflected wake potential is presented.The number of cells in a $\pi$-mode standing wave (SW) accelerating structure for the Compact linear Collider (CLIC) project is limited by mode overlap with nearby modes. The distributed coupling scheme avoids mode overlap by treating each cell as independent. Designs of cells suitable for distributed coupling with strong wakefield damping have not previously been studied. In this paper we develop a SW cell to be used in a distributed coupling structure that can satisfy the CLIC transverse wakepotential limit. From the middle cell of the CLIC-G* travelling wave (TW) structure, a SW cell is designed. The cell is adapted to be suitable for distributed coupling. Its wakepotentials in an ideal case of open boundaries are reduced to satisfy the wakepotential threshold. An electric boundary is added to the model to simulate total reflection at the distribution network. A horizontal coupler cell that connects to the distribution network such that the reflected wakefields remain similar to the open boundary case is simulated. A triplet module which takes advantage of cell-to-cell coupling to reduce reflected wakepotential is presented

Wakefield damping in a distributed coupling LINAC

The number of cells in a π-mode standing wave (SW) accelerating structure for the Compact linear Collider (CLIC) project is limited by mode overlap with nearby modes. The distributed coupling scheme avoids mode overlap by treating each cell as independent. Designs of cells suitable for distributed coupling with strong wakefield damping have not previously been studied. In this paper we develop a SW cell to be used in a distributed coupling structure that can satisfy the CLIC transverse wakepotential limit. From the middle cell of the CLIC-G travelling wave (TW) structure, a SW cell is designed. The cell is adapted to be suitable for distributed coupling. Its wakepotentials in an ideal case of open boundaries are reduced to satisfy the wakepotential threshold. An electric boundary is added to the model to simulate total reflection at the distribution network. A horizontal coupler cell that connects to the distribution network such that the reflected wakefields remain similar to the open boundary case is simulated. A triplet module which takes advantage of cell-to-cell coupling to reduce reflected wakepotential is presented

Nanoscale Chemical Imaging of the Reduction Behavior of a Single Catalyst Particle

A closer look: Investigation of the reduction properties of a single Fischer-Tropsch catalyst particle, using in situ scanning transmission X-ray microscopy with spatial resolution of 35 nm, reveals a heterogeneous distribution of Fe0, Fe2+, and Fe3+ species. Regions of different reduction properties are defined and explained on the basis of local chemical interactions and catalyst morpholog

Nanoscale Chemical Imaging of the Reduction Behavior of a Single Catalyst Particle

A closer look: Investigation of the reduction properties of a single Fischer-Tropsch catalyst particle, using in situ scanning transmission X-ray microscopy with spatial resolution of 35 nm, reveals a heterogeneous distribution of Fe0, Fe2+, and Fe3+ species. Regions of different reduction properties are defined and explained on the basis of local chemical interactions and catalyst morpholog