Optimal control of magnetization dynamics in ferromagnetic heterostructures by spin--polarized currents

We study the switching-process of the magnetization in a ferromagnetic-normal-metal multilayer system by a spin polarized electrical current via the spin transfer torque. We use a spin drift-diffusion equation (SDDE) and the Landau-Lifshitz-Gilbert equation (LLGE) to capture the coupled dynamics of the spin density and the magnetization dynamic of the heterostructure. Deriving a fully analytic solution of the stationary SDDE we obtain an accurate, robust, and fast self-consistent model for the spin-distribution and spin transfer torque inside general ferromagnetic/normal metal heterostructures. Using optimal control theory we explore the switching and back-switching process of the analyzer magnetization in a seven-layer system. Starting from a Gaussian, we identify a unified current pulse profile which accomplishes both processes within a specified switching time.Comment: 5 figure

Erfahrungen mit "half-dose" photodynamischer Therapie mittels Verteporfin bei Chorioretinopathia centralis serosa

Zusammenfassung: Hintergrund: Chorioretinopathia centralis serosa (CCS) ist eine idiopathische, meist selbstlimitierende Erkrankung gewöhnlich jüngerer Patienten. Charakteristisches Zeichen ist eine seröse Abhebung der neurosensorischen Retina. Die Visusprognose ist gut. In bis zu 30% der Fälle kann die Erkrankung chronisch oder rezidivierend sein. Es gibt das Risiko der Entwicklung einer sekundären choroidalen Neovaskularisation. Therapeutische Optionen sind Laserphotokoagulation oder photodynamische Therapie mit Verteporfin (PDT). In den letzten Jahren ist zur Minimierung von Nebenwirkungen der PDT das Behandlungsprotokoll modifiziert worden. Diese Protokolle werden als "Half-dose-" oder "Reduce-fluence-" bzw. "Low-fluence-PDT" bezeichnet. Patienten und Methoden: Retrospektiv wurden 7Augen von 6 konsekutiven männlichen Patienten mit chronischer CCS ausgewertet. Vor "Half-dose-PDT" und am Ende des Follow-up wurden der bestkorrigierte Visus sowie die Netzhautdicke mittels "spectral-domain" optischer Kohärenztomographie bestimmt. Ergebnisse: Das Durchschnittsalter lag bei 40,7 ± 10,3Jahren. Fünf Augen erhielten 1, 1Auge 2 und 1Auge 3 "Half-dose-PDT". Das durchschnittliche Follow-up lag bei 79,8 ± 104,5Monaten. Der Visus (Snellen) war vor PDT bei 0,4 ± 0,2 und nach PDT bei 0,4 ± 0,3 (p = 0,49). Die Netzhautdicke nahm von 479μm ± 233 auf 242μm ± 60 ab (p = 0,08). Fazit: "Half-dose-PDT" ist eine sichere Behandlungsoption für Patienten mit chronischer CCS. Alle Patienten zeigten eine Abnahme der Netzhautdicke mit zum Teil vollständiger Resorption von subretinaler Flüssigkeit in 6Augen. Fünf Augen zeigten zusätzlich sowohl eine funktionelle als auch eine anatomische Verbesserung durch die Behandlun

On the Permissibility of Homicidal Violence: Perspectives from Former U.S. White Supremacists

Drawing upon in-depth life-history interviews with 91 North American-based former white supremacists, we examine how participants perceive homicidal violence as either an appropriate or inappropriate political strategy. Based on the current findings, participants considered homicidal violence as largely inappropriate due to moral concerns and its politically ineffective nature but also discussed how homicidal violence could be an appropriate defensive measure in RAHOWA (Racial Holy War) or through divine mandate. Capturing how white supremacists frame the permissibility of homicidal violence is a step toward better understanding the “upper limit” or thresholds for violence among members who are trying to construct and negotiate a collective identity that involves violent and aggressive worldviews

Paradigm change in hydrogel sensor manufacturing: From recipe-driven to specification-driven process optimization

The volume production of industrial hydrogel sensors lacks a quality-assuring manufacturing technique for thin polymer films with reproducible properties. Overcoming this problem requires a paradigm change from the current recipe-driven manufacturing process to a specification-driven one. This requires techniques to measure quality-determining hydrogel film properties as well as tools and methods for the control and optimization of the manufacturing process. In this paper we present an approach that comprehensively addresses these issues. The influence of process parameters on the hydrogel film properties and the resulting sensor characteristics have been assessed by means of batch manufacturing tests and the application of several measurement techniques. Based on these investigations, we present novel methods and a tool for the optimization of the cross-linking process step, with the latter being crucial for the sensor sensitivity. Our approach is applicable to various sensor designs with different hydrogels. It has been successfully tested with a sensor solution for surface technology based on PVA/PAA hydrogel as sensing layer and a piezoelectric thickness shear resonator as transducer. Finally, unresolved issues regarding the measurement of hydrogel film parameters are outlined for future research

Paradigm change in hydrogel sensor manufacturing: from recipe-driven to specification-driven process optimization

The volume production of industrial hydrogel sensors lacks a quality-assuring manufacturing technique for thin polymer films with reproducible properties. Overcoming this problem requires a paradigm change from the current recipe-driven manufacturing process to a specification-driven one. This requires techniques to measure quality-determining hydrogel film properties as well as tools and methods for the control and optimization of the manufacturing process. In this paper we present an approach that comprehensively addresses these issues. The influence of process parameters on the hydrogel film properties and the resulting sensor characteristics have been assessed by means of batch manufacturing tests and the application of several measurement techniques. Based on these investigations, we present novel methods and a tool for the optimization of the cross-linking process step, with the latter being crucial for the sensor sensitivity. Our approach is applicable to various sensor designs with different hydrogels. It has been successfully tested with a sensor solution for surface technology based on PVA/PAA hydrogel as sensing layer and a piezoelectric thickness shear resonator as transducer. Finally, unresolved issues regarding the measurement of hydrogel film parameters are outlined for future research

Transition-metal interactions in aluminum-rich intermetallics

The extension of the first-principles generalized pseudopotential theory (GPT) to transition-metal (TM) aluminides produces pair and many-body interactions that allow efficient calculations of total energies. In aluminum-rich systems treated at the pair-potential level, one practical limitation is a transition-metal over-binding that creates an unrealistic TM-TM attraction at short separations in the absence of balancing many-body contributions. Even with this limitation, the GPT pair potentials have been used effectively in total-energy calculations for Al-TM systems with TM atoms at separations greater than 4 AA. An additional potential term may be added for systems with shorter TM atom separations, formally folding repulsive contributions of the three- and higher-body interactions into the pair potentials, resulting in structure-dependent TM-TM potentials. Towards this end, we have performed numerical ab-initio total-energy calculations using VASP (Vienna Ab Initio Simulation Package) for an Al-Co-Ni compound in a particular quasicrystalline approximant structure. The results allow us to fit a short-ranged, many-body correction of the form a(r_0/r)^{b} to the GPT pair potentials for Co-Co, Co-Ni, and Ni-Ni interactions.Comment: 18 pages, 5 figures, submitted to PR

Precision Measurement of the 29Si, 33S, and 36Cl Binding Energies

The binding energies of 29Si, 33S, and 36Cl have been measured with a relative uncertainty $< 0.59 \times 10^{-6}$ using a flat-crystal spectrometer. The unique features of these measurements are 1) nearly perfect crystals whose lattice spacing is known in meters, 2) a highly precise angle scale that is derived from first principles, and 3) a gamma-ray measurement facility that is coupled to a high flux reactor with near-core source capability. The binding energy is obtained by measuring all gamma-rays in a cascade scheme connecting the capture and ground states. The measurements require the extension of precision flat-crystal diffraction techniques to the 5 to 6 MeV energy region, a significant precision measurement challenge. The binding energies determined from these gamma-ray measurements are consistent with recent highly accurate atomic mass measurements within a relative uncertainty of $4.3 \times 10^{-7}$. The gamma-ray measurement uncertainties are the dominant contributors to the uncertainty of this consistency test. The measured gamma-ray energies are in agreement with earlier precision gamma-ray measurements.Comment: 13 pages, 4 figure

A performance comparison of the contiguous allocation strategies in 3D mesh connected multicomputers

The performance of contiguous allocation strategies can be significantly affected by the distribution of job execution times. In this paper, the performance of the existing contiguous allocation strategies for 3D mesh multicomputers is re-visited in the context of heavy-tailed distributions (e.g., a Bounded Pareto distribution). The strategies are evaluated and compared using simulation experiments for both First-Come-First-Served (FCFS) and Shortest-Service-Demand (SSD) scheduling strategies under a variety of system loads and system sizes. The results show that the performance of the allocation strategies degrades considerably when job execution times follow a heavy-tailed distribution. Moreover, SSD copes much better than FCFS scheduling strategy in the presence of heavy-tailed job execution times. The results also show that the strategies that depend on a list of allocated sub-meshes for both allocation and deallocation have lower allocation overhead and deliver good system performance in terms of average turnaround time and mean system utilization