Ruimte, rust en stilte; beleving door burgers en indicaties voor beheer en beleid

In een landelijke enqulte is het maatschappelijk belang van ruimte, rust en stilte vastgesteld. Hoewel deze kwaliteiten nog steeds te vinden zijn in het landschap, worden ze wel bedreigd. Rust en stilte worden verschillend ervaren: rust is meer innerlijk, stilte meer uiterlijk. Een gevoel van ruimte is niet gebonden aan openheid; je kunt het ook in een bos hebben. De beleving van ruimte hangt sterk samen met die van rust. Gebiedsvreemd lawaai, vervuiling en niet-passende elementen in het landschap doen afbreuk aan beide. Verschillende typen groene omgevingen hebben een eigen verwachting van ruimte, rust en stilte. Dit maakt beheer en beleid omgevingsspecifiek en de identiteit van een landschap een belangrijk beleidsuitgangspunt - identiteit zowel inruimte als in tijd gezien

Self-interference fluorescence microscopy: three dimensional fluorescence imaging without depth scanning

We present a new method for high-resolution, three-dimensional fluorescence imaging. In contrast to beam-scanning confocal microscopy, where the laser focus must be scanned both laterally and axially to collect a volume, we obtain depth information without the necessity of depth scanning. In this method, the emitted fluorescence is collected in the backward direction and is sent through a phase plate that encodes the depth information into the phase of a spectrally resolved interference pattern. We demonstrate that decoding this phase information allows for depth localization accuracy better than 4 μm over a 500 μm depth-of-field. In a high numerical aperture configuration with a much smaller depth of field, a localization accuracy of tens of nanometers can be achieved. This approach is ideally suited for miniature endoscopes, where space limitations at the endoscope tip render depth scanning difficult. We illustrate the potential for 3D visualization of complex biological samples by constructing a threedimensional volume of the microvasculature of ex vivo murine heart tissue from a single 2D scan. © 2012 Optical Society of America

Angiography of the retina and the choroid with phase-resolved OCT using interval-optimized backstitched B-scans

In conventional phase-resolved OCT blood flow is detected from phase changes between successive A-scans. Especially in high-speed OCT systems this results in a short evaluation time interval. This method is therefore often unable to visualize complete vascular networks since low flow velocities cause insufficient phase changes. This problem was solved by comparing B-scans instead of successive A-scans to enlarge the time interval. In this paper a detailed phase-noise analysis of our OCT system is presented in order to calculate the optimal time intervals for visualization of the vasculature of the human retina and choroid. High-resolution images of the vasculature of a healthy volunteer taken with various time intervals are presented to confirm this analysis. The imaging was performed with a backstitched B-scan in which pairs of small repeated B-scans are stitched together to independently control the time interval and the imaged lateral field size. A time interval of ≥2.5 ms was found effective to image the retinal vasculature down to the capillary level. The higher flow velocities of the choroid allowed a time interval of 0.64 ms to reveal its dense vasculature. Finally we analyzed depth-resolved histograms of volumetric phase-difference data to assess changes in amount of blood flow with depth. This analysis indicated different flow regimes in the retina and the choroid. © 2012 Optical Society of America

An implicit and explicit solver for contact problems

The interaction of rolling tyres with road surfaces is one of the major contributions to road traffic noise. The generation mechanisms of tyre/road noise are usually separated in structure borne and airborne noise. In both mechanisms the contact zone is important. In order to reduce tyre/road noise at the source, accurate (numerical) prediction models are needed. For accurate results, the tyre has to be modelled by a threedimensional finite element model, accounting for complex rubber material behaviour, tread profiles and a detailed tyre construction. A dynamic analysis of a tyre in contact can then be carried out in the time domain. The Structural Dynamics and Acoustics group of the University of Twente has developed an alternative contact solver. The solver, in which the contact condition is always satisfied, is successfully applied to an implicit and explicit three-dimensional finite element model. As a consequence there is no need for contact\ud elements or contact parameters. The finite element model is valid for large translations and rotations, in which different material models and friction models can be added. This paper explains the solver for an implicit and explicit scheme and presents some examples. In one of the examples a deformable rubber ring is modelled, which is rolling on a rigid surface at a slip angle. The results are compared to the finite element package Abaqus. The examples show the robustness and potential of the algorithm

The unified coordination language UnCL.

In this paper we show how to use a (subset) of UML as an Unified Coordination Language (UnCL) that is based on a separation of concerns between coordination and computation. As such UnCL provides a general language for the coordination of, in particular, object-oriented applications. The basic idea of UnCL is to use UML as a formalism to specify the `glue code' in terms of state-machines which are added to the classes of the underlying applications. These state-machines describe the coordination of the objects of the underlying applications in terms of sending and receiving events. We introduce a formal semantics of UnCL and discuss its implementation using a new tool for the transformation of XML data which is based on a new Rule Markup Language (RML). Finally, we discuss the incorporation of a more high-level coordination mechanism called MoCha, an exogenous coordination framework for (distributed) communication and collaboration using mobile channels as its mediu

Polarization-sensitive spectral-domain optical coherence tomography using a single line scan camera

Polarization-sensitive optical coherence tomography can be used to measure the birefringence of biological tissue such as the human retina. Previous measurements with a time-domain polarization-sensitive optical coherence tomography system revealed that the birefringence of the human retinal nerve fiber layer is not constant, but varies as a function of location around the optic nerve head. Here we present a spectral-domain polarization-sensitive optical coherence tomography system that uses a spectrometer configuration with a single line scan camera and a Wollaston prism in the detection arm. Since only one camera has to be synchronized with other components in the system, the design is simplified considerably. This system is 60 times faster than a time-domain polarization-sensitive optical coherence tomography system. Data was acquired using concentric circular scans around the optic nerve head of a young healthy volunteer and the acquisition time for 12 circular scans was reduced from 72 s to 1.2 s. The acquired data sets demonstrate variations in retinal thickness and double pass phase retardation per unit depth that were similar to data from the same volunteer taken with a time-domain polarization-sensitive system. The double pass phase retardation per unit depth of the retinal nerve fiber layer varied between 0.18 and 0.40 degrees/μm, equivalent to a birefringence of 2.2 · 1