Instability and noise-induced thermalization of Fermi-Pasta-Ulam recurrence in the nonlinear Schr\"odinger equation

We investigate the spontaneous growth of noise that accompanies the nonlinear evolution of seeded modulation instability into Fermi-Pasta-Ulam recurrence. Results from the Floquet linear stability analysis of periodic solutions of the three-wave truncation are compared with full numerical solutions of the nonlinear Schr\"odinger equation. The predicted initial stage of noise growth is in good agreement with simulations, and is expected to provide further insight in the subsequent dynamics of the field evolution after recurrence breakup

Online monitoring of coffee roasting by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS): towards a real-time process control for a consistent roast profile

A real-time automated process control tool for coffee roasting is presented to consistently and accurately achieve a targeted roast degree. It is based on the online monitoring of volatile organic compounds (VOC) in the off-gas of a drum roaster by proton transfer reaction time-of-flight mass spectrometry at a high time (1Hz) and mass resolution (5,500m/Δm at full width at half-maximum) and high sensitivity (better than parts per billion by volume). Forty-two roasting experiments were performed with the drum roaster being operated either on a low, medium or high hot-air inlet temperature (= energy input) and the coffee (Arabica from Antigua, Guatemala) being roasted to low, medium or dark roast degrees. A principal component analysis (PCA) discriminated, for each one of the three hot-air inlet temperatures, the roast degree with a resolution of better than ±1 Colorette. The 3D space of the three first principal components was defined based on 23 mass spectral profiles of VOCs and their roast degree at the end point of roasting. This provided a very detailed picture of the evolution of the roasting process and allowed establishment of a predictive model that projects the online-monitored VOC profile of the roaster off-gas in real time onto the PCA space defined by the calibration process and, ultimately, to control the coffee roasting process so as to achieve a target roast degree and a consistent roasting. Figure Online monitoring of coffee roasting by real-time analysis of the roaster off-gas using PTR-ToF-MS. In a first phase, 42 calibration experiments were conducted at three different roasting temperatures and to three final roast degrees, to generate the 3D space defined by the three first principle components PC1, PC2 and PC3. Inverted triangles mark the dark roast degree, square medium and circle light, respectively. The hot-air inlet temperature is marked as follows: high (black), medium (grey), low (white). The different hot-air inlet temperatures and roast degrees are clearly separated. In a second phase, an online monitored PTR-ToF-MS spectrum of a roasting process was projected onto the 3D space, allowing following in real-time the roasting process and halting the roasting with a precision better that ± 1 Colorette roast degre

Percutaneous Vertebroplasty: Preliminary Experiences with Rotational Acquisitions and 3D Reconstructions for Therapy Control

Percutaneous vertebroplasty (PVP) is carried out under fluoroscopic control in most centers. The exclusion of implant leakage and the assessment of implant distribution might be difficult to assess based on two-dimensional radiographic projection images only. We evaluated the feasibility of performing a follow-up examination after PVP with rotational acquisitions and volumetric reconstructions in the angio suite. Twenty consecutive patients underwent standard PVP procedures under fluoroscopic control. Immediate postprocedure evaluation of the implant distribution in the angio suite (BV 3000; Philips, The Netherlands) was performed using rotational acquisitions (typical parameters for the image acquisition included a 17-cm field-of-view, 200 acquired images for a total angular range of 180°). Postprocessing of acquired volumetric datasets included multiplanar reconstruction (MPR), maximum intensity projection (MIP), and volume rendering technique (VRT) images that were displayed as two-dimensional slabs or as entire three-dimensional volumes. Image evaluation included lesion and implant assessment with special attention given to implant leakage. Findings from rotational acquisitions were compared to findings from postinterventional CT. The time to perform and to postprocess the rotational acquisitions was in all cases less then 10 min. Assessment of implant distribution after PVP using rotational image acquisition methods and volumetric reconstructions was possible in all patients. Cement distribution and potential leakage sites were visualized best on MIP images presented as slabs. From a total of 33 detected leakages with CT, 30 could be correctly detected by rotational image acquisition. Rotational image acquisitions and volumetric reconstruction methods provided a fast method to control radiographically the result of PVP in our case

Lobar Dementia due to Extreme Widening of Virchow-Robin Spaces in One Hemisphere

Widened perivascular spaces known as Virchow-Robin spaces (VRS) are often seen on MRI and are usually incidental findings. It is unclear if enlarged VRS can be associated with neurological deficits. In this report, we describe a case of lobar dementia associated with unusual VRS widening in one cerebral hemisphere. A 77-year-old woman, seen at a memory clinic, presented with progressive cognitive decline, left hemianopsia, and mild pyramidal signs on the left side. On MRI, unusually wide VRS were visible, predominantly in the right centrum semiovale and the right temporo-occipital white matter. The clinical syndrome was consistent with the extent and location of the abnormally dilated VRS. The high MR signal in white matter bridges between the VRS suggested parenchymal damage, possibly representing gliotic white matter. No evidence for another etiology was found on cerebral MRI and rCBF SPECT. As a conclusion, enlarged VRS in one cerebral hemisphere may be associated with cognitive change and neurological deficits

Experimental Signature of Riemann Wave Shoaling in Optical Fiber

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The Inviscid Burgers' Equation in Nonlinear Fiber Optics

We report on the experimental generation of Riemann waves in an optical fiber system, allowing for the controlled formation of shock waves, as analytically described by a seminal equation of fluid dynamics: the so-called Inviscid Burgers’ Equation

Inviscid Burgers’ Equation and Riemann Waves in Optics

We report on the experimental observation of inviscid Burgers' equation dynamics and Riemann wave formation in a nonlinear fiber. Experimental results clearly show controllable pulse front steepening and shock formation

Experimental Observation of Inviscid Burgers’ Equation Dynamics in Nonlinear Fiber Optics

We report on the experimental observation of inviscid Burgers' equation dynamics, obtained when a properly tailored pulse propagates in an optical fiber. Experimental results show controllable pulse steepening and shock formation in excellent agreement with theory

Laterales Führen. Wenn Hierarchie nur begrenzt zur Verfügung steht

Kühl S, Schnelle W. Laterales Führen. Wenn Hierarchie nur begrenzt zur Verfügung steht. In: Aderhold J, Meyer M, Wetzel R, eds. Modernes Netzwerkmanagement. Anforderungen - Methoden - Anwendungsfelder. Wiesbaden: Gabler; 2005: 185-212

Transient electrical characteristics of silicon heterojunction solar cells under fast transient illumination

For vehicle integrated photovoltaics VIPV there are possibly specific requirements on the speed of maximum power point tracking. However, a certain delay in the response of solar cells to fast irradiance changes might impact those requirements on the MPPT. The subject of this work is therefore the investigation of the transient electrical behaviour of state of the art silicon heterojunction solar cells. We use a fast switchable LED array and an oscilloscope to investigate the cell voltage of silicon heterojunction solar cells under transient illumination. We find that these cells have a switch off delay that is smaller than one millisecond when operated at or close to the maximum power point. This can be assumed to be faster than the time scale on that irradiances change typically occur on a car body while driving. We also find that, after switching off the light source, the transient cell voltage does not show a simple capacitive behaviour, but a more complex characteristic. A theoretical analysis shows that this behaviour can be explained by the nonlinear dependency of the diffusion and depletion capacitance and the minority carrier lifetime on the cell voltag