Developing a method to improve SAR change detection under varying illumination angles

Change detection is an important field of application for remote sensing. While many studies rely on optical data, Synthetic Aperture Radar brings the advantage of its potential operability being independent from natural illumination and weather conditions. Particularly in time sensitive situations, this can be a great advantage. However, SAR change detection evokes some challenges that may not be seen in other sensor technologies. One of these challenges includes its dependability on a consistent illumination geometry when applying known 2D change detection methods. False alarms increase with growing difference between the illumination angles of a reference and test image. The characteristics of these false alarms have been studied in this thesis and it has been revealed that they predominantly occur as pairs caused by a single object. This phenomenon has been exploited to develop an algorithm which checks elements of change detection on potential pairs and removes them if a certain agreement between the elements of the pairs is met. The results have shown that the method is able to greatly reduce the occurrence of false alarms, especially in large angular deviations. In smaller angles where current methods perform well, the algorithm retains a majority of the detected changes which are mostly attributable to true changes. Challenges persist in intermediate angles, where false alarms are ample, but pairs are not as pronounced. Nevertheless, the method managed to significantly reduce the false alarm rate in all acquisitions in a circle while retaining the detection rate to a great part

Random Bit Multilevel Algorithms for Stochastic Differential Equations

We study the approximation of expectations \E(f(X)) for solutions $X$ of SDEs and functionals $f \colon C([0,1],\R^r) \to \R$ by means of restricted Monte Carlo algorithms that may only use random bits instead of random numbers. We consider the worst case setting for functionals $f$ from the Lipschitz class w.r.t.\ the supremum norm. We construct a random bit multilevel Euler algorithm and establish upper bounds for its error and cost. Furthermore, we derive matching lower bounds, up to a logarithmic factor, that are valid for all random bit Monte Carlo algorithms, and we show that, for the given quadrature problem, random bit Monte Carlo algorithms are at least almost as powerful as general randomized algorithms

Random Bit Quadrature and Approximation of Distributions on Hilbert Spaces

We study the approximation of expectations \E(f(X)) for Gaussian random elements $X$ with values in a separable Hilbert space $H$ and Lipschitz continuous functionals $f \colon H \to \R$. We consider restricted Monte Carlo algorithms, which may only use random bits instead of random numbers. We determine the asymptotics (in some cases sharp up to multiplicative constants, in the other cases sharp up to logarithmic factors) of the corresponding $n$-th minimal error in terms of the decay of the eigenvalues of the covariance operator of $X$. It turns out that, within the margins from above, restricted Monte Carlo algorithms are not inferior to arbitrary Monte Carlo algorithms, and suitable random bit multilevel algorithms are optimal. The analysis of this problem leads to a variant of the quantization problem, namely, the optimal approximation of probability measures on $H$ by uniform distributions supported by a given, finite number of points. We determine the asymptotics (up to multiplicative constants) of the error of the best approximation for the one-dimensional standard normal distribution, for Gaussian measures as above, and for scalar autonomous SDEs

Learning to Put On a Knit Cap in a Head-Centric Policy Space

Twardon L, Ritter H. Learning to Put On a Knit Cap in a Head-Centric Policy Space. IEEE ROBOTICS AND AUTOMATION LETTERS. 2018;3(2):764-771.Robotic manipulation of such highly deformable objects as clothes is a challenging problem. Robot-assisted dressing adds even more complexity as the garment motions must be aligned with a human body under conditions of strong and variable occlusion. As a step toward solutions for the general task, we consider the example of a dual-arm robot with attached anthropomorphic hands that learns to put a knit cap on a styrofoam head. Our approach avoids modeling the details of the garment and its deformations. Instead, we demonstrate that a head-centric policy parameterization, combined with a suitable objective function for determining the right amount of contact between the cap and the head, enables a direct policy search algorithm to find successful trajectories for this task. We also show how a toy problem that mirrors some of the task constraints can be used to efficiently structure hyperparameter search. Additionally, we suggest a point cloud based algorithm for modeling the head as an ellipsoid which is required for defining the policy space

Medical use of cannabis in Switzerland: analysis of approved exceptional licences

In recent years, the Swiss Federal Office of Public Health (FOPH) granted exceptional licenses for the medical use of cannabinoids, typically for 6 months with possible extensions. A systematic review of cannabinoids for medical use commissioned by the FOPH supports the use of cannabinoids for the treatment of chronic pain and spasticity. However, little is known about the patients treated with cannabinoids. We aimed to study medical uses of cannabinoids as part of the FOPH's programme of exceptional licenses.; We examined all requests for medical use of cannabinoids sent to FOPH in 2013 and 2014. A standardised data sheet was developed to extract data from the files of approved requests. We extracted the duration of the licence, the year it was granted, and the payer of the therapy. At the level of the patient we collected the date of birth, sex, region of residence, diagnosis and the indication. Ethical approval was granted by the Ethics Committee of the Canton of Bern.; We analysed 1193 patients licenced for cannabinoid treatment in 2013 or 2014. During 2013, 542 patients were treated under the exceptional licencing programme (332 requesting physicians) compared with 825 in 2014 (446 physicians). Over half of patients (685; 57%) were women. The mean age was 57 years (standard deviation 15.0), chronic pain (49%) and spasticity (40%) were the most common symptoms, and co-medication was reported for 39% of patients. Seventy-eight different diagnoses were recorded, including multiple sclerosis (257 patients, 22%), soft tissue disorders (119, 10%), dorsalgia (97, 8.1%), spinal muscular atrophy (65, 5.5%) and paraplegia/tetraplegia (62, 5.2%). Licence extensions were granted to 143 patients (26.4%) in 2013 and 324 patients (39.3%) in 2014. There were substantial regional variations of the rates of patients treated with cannabinoids. On average, eight patients per 100 000 residents received an exceptional licence. Most patients (1083, 91%) paid out of pocket.; Exceptional licences for medical use of cannabinoids have increased substantially in Switzerland, with the programme including patients with a wide range of conditions

Active Boundary Component Models for Robotic Dressing Assistance

Twardon L, Ritter H. Active Boundary Component Models for Robotic Dressing Assistance. In: 2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). Piscataway, NJ: IEEE; 2016: 2811-2818

Magnetoelastic coupling in triangular lattice antiferromagnet CuCrS2

CuCrS2 is a triangular lattice Heisenberg antiferromagnet with a rhombohedral crystal structure. We report on neutron and synchrotron powder diffraction results which reveal a monoclinic lattice distortion at the magnetic transition and verify a magnetoelastic coupling. CuCrS2 is therefore an interesting material to study the influence of magnetism on the relief of geometrical frustration.Comment: 6 pages, 6 figures, 1 tabl

Simultaneous bilateral hip replacement reveals superior outcome and fewer complications than two-stage procedures: a prospective study including 1819 patients and 5801 follow-ups from a total joint replacement registry

<p>Abstract</p> <p>Background</p> <p>Total joint replacements represent a considerable part of day-to-day orthopaedic routine and a substantial proportion of patients undergoing unilateral total hip arthroplasty require a contralateral treatment after the first operation. This report compares complications and functional outcome of simultaneous versus early and delayed two-stage bilateral THA over a five-year follow-up period.</p> <p>Methods</p> <p>The study is a post hoc analysis of prospectively collected data in the framework of the European IDES hip registry. The database query resulted in 1819 patients with 5801 follow-ups treated with bilateral THA between 1965 and 2002. According to the timing of the two operations the sample was divided into three groups: I) 247 patients with simultaneous bilateral THA, II) 737 patients with two-stage bilateral THA within six months, III) 835 patients with two-stage bilateral THA between six months and five years.</p> <p>Results</p> <p>Whereas postoperative hip pain and flexion did not differ between the groups, the best walking capacity was observed in group I and the worst in group III. The rate of intraoperative complications in the first group was comparable to that of the second. The frequency of postoperative local and systemic complication in group I was the lowest of the three groups. The highest rate of complications was observed in group III.</p> <p>Conclusions</p> <p>From the point of view of possible intra- and postoperative complications, one-stage bilateral THA is equally safe or safer than two-stage interventions. Additionally, from an outcome perspective the one-stage procedure can be considered to be advantageous.</p

A 68 ka precipitation record from the hyperarid core of the Atacama Desert in northern Chile

[Abstract] The Atacama Desert in northern Chile is one of the driest deserts on Earth. Hyperaridity persists at least since the Miocene and was punctuated by pluvial phases. However, very little is known about the timing, regional spread and intensities of precipitation changes. Here, we present a new precipitation record from a sedimentary sequence recovered in a tectonically blocked endorheic basin that is located in the hyperarid core of the Atacama Desert. The chronostratigraphic framework of the record is given by a multi-disciplinary dating approach, suggesting an age of ca. 68 ka BP for the core base. The sequence consists of three sediment types, whose sedimentological and geochemical characteristics suggest different depositional processes that reflect different degrees in humidity. First, particularly fine-grained sediments with high clastic but low calcium sulfate and carbonate contents reflect a particularly dry climate with only sporadic precipitation events and fluvial supply via channel systems. Second, more coarse-grained sediments with lower clastic and higher calcium sulfate and carbonate contents reflect more moist conditions with stronger precipitation events that lead to fluvial activity not restricted to the channels but involving the slopes and plains in the catchment. Third, normally graded layers with an equally high proportion of calcium sulfate and carbonate reflect occasional high-precipitation events that caused sediment supply also from most distant parts of the catchment via severe flash floods. The sedimentary succession suggests that precipitation changes took place on orbital but also on millennial time scales. Rather moist periods occurred during most of MIS 2, several shorter periods within MIS 3 and parts of MIS 4. Comparison of the findings from the Huara record with selected climate records from continental and marine sites in South America suggests a strong precipitation heterogeneity across the Atacama. This heterogeneity is caused by pronounced differences in the dominating climate patterns and a shift from predominant summer rain in the north to winter rain in the south. Precipitation supply to the Huara clay plan is controlled by the atmospheric circulation rather than the surface temperature of the adjacent ocean

Oxford Phase 3 unicompartmental knee arthroplasty: medium-term results of a minimally invasive surgical procedure

PURPOSE: In the last decade, a major increase in the use of and interest in unicompartmental knee arthroplasty (UKA) has developed. The Oxford Phase 3 UKA is implanted with a minimally invasive technique using newly developed instruments. The objective of this prospective study was to evaluate the outcome of UKA in patients with medial osteoarthritis of the knee in a high-volume unit. METHODS: Two-hundred and forty-four UKAs were performed with a minimally invasive approach. The median age was 72 (43-91) years. The median follow-up was 4.2 years (range 1-10.4 years). Fourteen patients died, and nine were considered to be lost to follow-up, but all had a well-functioning prosthesis in situ until their last follow-up. Pain, function and health-related quality of life were evaluated pre- and postoperatively using patient- and assessor-based outcome scores, as well as radiographic evidence. RESULTS: The mean Knee Society knee and function scores, WOMAC-scores, Oxford-score and VAS pain and satisfaction all improved. Nine knees required revision. Eleven patients required an additional arthroscopic procedure due to persisting pain secondary to intra-articular pathology, and four patients required manipulation under anaesthesia because of limited range of motion. The 7-year cumulative survival rate of the arthroplasty was 94.4%. A low incidence (21%) of a radiolucent line beneath the tibial component was observed at 5 years of follow-up. CONCLUSION: This study showed a high survival rate of the Oxford Phase 3 UKA. Patient satisfaction and functional performance were also very high. Major complication rate was low; in addition, the incidence of radiolucency under the tibial component, when compared to present literature, was low. When strict indication criteria are followed, excellent, durable, and in our opinion reliable, results can be expected for this procedur