The Ensemble Kalman Filter: A Signal Processing Perspective

The ensemble Kalman filter (EnKF) is a Monte Carlo based implementation of the Kalman filter (KF) for extremely high-dimensional, possibly nonlinear and non-Gaussian state estimation problems. Its ability to handle state dimensions in the order of millions has made the EnKF a popular algorithm in different geoscientific disciplines. Despite a similarly vital need for scalable algorithms in signal processing, e.g., to make sense of the ever increasing amount of sensor data, the EnKF is hardly discussed in our field. This self-contained review paper is aimed at signal processing researchers and provides all the knowledge to get started with the EnKF. The algorithm is derived in a KF framework, without the often encountered geoscientific terminology. Algorithmic challenges and required extensions of the EnKF are provided, as well as relations to sigma-point KF and particle filters. The relevant EnKF literature is summarized in an extensive survey and unique simulation examples, including popular benchmark problems, complement the theory with practical insights. The signal processing perspective highlights new directions of research and facilitates the exchange of potentially beneficial ideas, both for the EnKF and high-dimensional nonlinear and non-Gaussian filtering in general

X-ray diffraction microscopy based on refractive optics

We describe a diffraction microscopy technique based on refractive optics to study structural variations in crystals. The X-ray beam diffracted by a crystal was magnified by beryllium parabolic refractive lenses on a 2D X-ray camera. The microscopy setup was integrated into the 6-circle Huber diffractometer at the ESRF beamline ID06. Our setup allowed us to visualize structural imperfections with a resolution of approximately 1 micrometer. The configuration, however, can easily be adapted for sub-micrometer resolution.Comment: 9 pages, 4 figures. Submitted to Journal of Synchrotron Radiation on April 4th 2012. Rejecte

Experimental demonstration of surface plasmon polaritons reflection and transmission effects

Special integrated photonic surface structures composed of a dielectric semicircle ridge and a dielectric block placed on a metal substrate are proposed for the investigation of surface plasmon polariton (SPP) reflection and transmission effects. A fabrication method called microscope projection photolithography was employed for the preparation of the structures. Leakage radiation microscopy was applied for the excitation and observation of surface plasmon polaritons (SPPs). It was observed that SPPs exhibit a remarkable decrease in intensity when impinging onto the rectangular dielectric block. Nevertheless, the transmitted wave out of the dielectric block was always observable. The propagation behavior of both the reflected waves at two boundaries (air/dielectric and dielectric/air) and the transmitted wave inside the dielectric block were demonstrated for different SPP incident conditions. The variation of the angles of reflection and transmission with respect to the incident angle was analytically and experimentally investigated. An agreement between the calculated results and the experimental results was obtained. Our findings might allow for novel applications in sensing and analytics once the structures will be functionalized

No Impact of Functional Connectivity of the Motor System on the Resting Motor Threshold: A Replication Study

The physiological mechanisms of corticospinal excitability and factors influencing its measurement with transcranial magnetic stimulation are still poorly understood. A recent study reported an impact of functional connectivity (FC) between the primary motor cortex (M1) and the dorsal premotor cortex (PMd) on the resting motor threshold (RMT) of the dominant hemisphere. We aimed to replicate these findings in a larger sample of 38 healthy right-handed subjects with data from both hemispheres. Resting-state FC was assessed between the M1 and five a priori defined motor-relevant regions on each hemisphere as well as interhemispherically between both primary motor cortices. Following the procedure by the original authors, we included age, cortical gray matter volume, and coil-to-cortex distance (CCD) as further predictors in the analysis. We report replication models for the dominant hemisphere as well as an extension to data from both hemispheres and support the results with Bayes factors. FC between the M1 and the PMd did not explain the variability in the RMT, and we obtained moderate evidence for the absence of this effect. In contrast, CCD could be confirmed as an important predictor with strong evidence. These findings contradict the previously proposed effect, thus questioning the notion of the PMd playing a major role in modifying corticospinal excitability

UV-LED projection photolithography for high-resolution functional photonic components

The advancement of micro- and nanostructuring techniques in optics is driven by the demand for continuous miniaturization and the high geometrical accuracy of photonic devices and integrated systems. Here, UV-LED projection photolithography is demonstrated as a simple and low-cost approach for rapid generation of two-dimensional optical micro- and nanostructures with high resolution and accuracy using standard optics only. The developed system enables the projection of structure patterns onto a substrate with 1000-fold demagnification. Photonic devices, e.g., waveguides and microring resonators, on rigid or flexible substrates with varied geometrical complexity and overall structure dimensions from the nanometer to centimeter scale were successfully prepared. In particular, high-resolution gratings with feature sizes down to 150 nm and periods as small as 400 nm were realized for the first time by this approach. Waveguides made of doped laser active materials were fabricated, and their spontaneous emission was detected. The demonstrated superior performance of the developed approach may find wide applications in photonics, plasmonics, and optical materials science, among others

Intersektionalität als diskursanalytisches Basiskonzept

Junker C, Roth J. Intersektionalität als diskursanalytisches Basiskonzept. In: Warnke IH, ed. Handbuch Diskurs. Handbücher Sprachwissen. Vol 6. Berlin; Boston: de Gruyter; 2018: 152-170

Tilting refractive x-ray lenses for fine-tuning their focal length

In this work, we measure and model tilted x-ray refractive lenses to investigate their effects on an x-ray beam. The modelling is benchmarked against at-wavelength metrology obtained with x-ray speckle vector tracking experiments (XSVT) at the BM05 beamline at the ESRF-EBS light source, showing very good agreement. This validation permits us to explore possible applications of tilted x-ray lenses in optical design: we demonstrate that tilting 1D lenses around their focusing direction can be used for fine-tuning their focal length with possible applications in beamline optical design.Comment: 15 pages, 13 figures, 38 references to be submitted to Optics Expres

Influence of Gender on Occurrence of Aseptic Loosening and Recurrent PJI after Revision Total Knee Arthroplasty

Background: Periprosthetic joint infection (PJI) is a common yet severe complication after total knee arthroplasty (TKA). Surgical intervention and antibiotic therapy are obligatory to achieve successful, infection-free outcome. Compared to the outcomes after primary TKA, prosthesis failure rates are drastically increased after PJI-dependent revision surgery. Recurrent PJI and aseptic loosening are the most common reasons for prosthesis failure after revision TKA. An open question is the influence of the patients’ gender on long-term prosthesis survival after revision surgery. Additionally, it is unknown whether gender-related parameters and risk factors or differences in treatment are responsible for potential differences in outcome after revision arthroplasty. Patients and Methods: In this report, 109 patients that received TKA revision surgery due to PJI were retrospectively analyzed. We used clinical, paraclinical and radiological examinations to study the influence of gender on the long-term complications aseptic loosening and recurrent PJI after PJI-dependent revision arthroplasty. Results: While overall prosthesis failure rates and risk of recurrent PJI did not differ between genders, the long-term risk of aseptic loosening was significantly elevated in female patients. Postoperative coronal alignment was significantly more varus for women later diagnosed with aseptic loosening. Besides coronal alignment, no gender-dependent differences in clinical presentation or treatment were observed. Conclusions: Female patients displayed a significantly increased risk for aseptic loosening after PJI-dependent revision TKA. The observed gender-dependent differences in long-term outcome in our study support theories surrounding the role of bone metabolism in the development of aseptic loosening. Our data suggest that further research on a female design for PJI-dependent revision prostheses is warranted