Application of a new algorithm using Doppler information to retrieve complex wind fields over the Black Sea from ENVISAT SAR images

Several algorithms have been proposed to retrieve near-surface wind fields from C-band synthetic aperture radar (SAR) images acquired over the ocean. They mainly differ in the way they retrieve the wind direction. Conventionally, the wind direction is taken from atmospheric models or is extracted from the linear features sometimes visible in SAR images. Recently, a new wind retrieval algorithm has been proposed, which also includes the Doppler shift induced by motions of the sea surface. In this article, we apply three wind retrieval algorithms, including the one using Doppler information, to three complex wind events encountered over the Black Sea and compare the SAR-derived wind fields with model wind fields calculated using the high-resolution weather research and forecasting (WRF) model. It is shown that the new algorithm is very efficient in resolving the 180° ambiguity in the wind direction, which is often a problem in the streak-based wind retrieval algorithms. However, the Doppler-based algorithm only yields good results for wind directions that have a significant component in the look direction of the SAR antenna. Furthermore, it is dependent on good separation of the contributions to the Doppler shift induced by surface currents and wind-related effects (wind drift and wind-sea components of the ocean wave spectrum). We conclude that an optimum wind retrieval algorithm should consist of a combination of the algorithms based on linear features and Doppler information.     

Reduced myofibroblast differentiation on femtosecond laser treated 316LS stainless steel

In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell–surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 μm. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis.     

Direct comparison between hot pressing and electric field-assisted sintering of submicron alumina

This study compares hot pressing (HP) and the electric field-assisted sintering technique (FAST) of two different electrically insulating Al₂O₃ submicron powders with median particle sizes of 150 and 500 nm. Sample geometry, heating schedule, applied pressure and atmosphere were identical for both sintering methods. The densification behavior and characterization of the microstructure revealed that FAST sintered samples reached a higher density compared with HP, in particular for the finer powder. It was found that an increase in dwell time was required to reach the same final density by HP. However, analysis of the sintering curves showed that the densification mechanism for both sintering methods was grain boundary diffusion. Increasing the heating rate up to 150 K min^?1 did not modify the densification mechanism. The sintering trajectory showed that the grain size was only dependent on density and was insensitive to the sintering method, in addition to showing a lack of preferential grain orientation.     

Vorwort der Herausgeber

Ohne Zusammenfassung     

Cognitive interpersonal problem-solving skills and the maintenance of treatment success in heroin addicts.

Discusses an unexpected outcome of heroin addiction treatment; namely, the failure inherent in successfully removing patients from illicit drug use, only to find that in doing so, expectations on the part of clients regarding their ability to effectively function in society have risen beyond their ability to realistically attain their goals. Recidivism becomes likely when addicts cannot cope with the stress of low status employment, specific situations of the nondrug world, recreational drug use of straight co-workers, and the effort of maintaining gains made in treatment. Cognitive interpersonal problem-solving skills are recommended as a means of focusing the addict on developing habitual thinking on alternatives, consequences, means and ends, different perspectives, and social influences on the addict's own actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An Analysis of the Sensitivity of Digital Modulation Techniques to Frequency-Selective Fading

This Paper investigates the sensitivity to frequency-selective fading of different modulation techniques commonly used in digital radio systems. The modulation methods considered are phase-shift-keying (Mary PSK), nonoffset and offset quadrature amplitude modulation (M-ary QAM), and quadrature partial response signaling (QPRS). The performances of these methods during multipath fading are compared on the basis of the "signatures" calculated for idealized systems. Results are presented from which the relative outage probability was determined, assuming a propagation channel with frequency-selective Rician fading.     

Infrared Evidence for the Existence of Nitrate Species on Cu-ZSM5 During Isothermal Rate Oscillations in the Decomposition of N2O

Isothermal oscillations in the rate of decomposition of N₂O were studied on an over-exchanged Cu-ZSM-5 catalyst by mass spectroscopy and in situ transient FTIR. Oscillations in the production of O₂ and N₂ were observed to occur in a temperature range of 410–490°C at a total pressure of 1.0 Torr pure N₂O. FTIR has provided the first spectroscopic evidence that surface nitrate species are present under oscillatory conditions. This study confirmed a previously proposed model that predicts a slow build-up of surface nitrates, followed by a rapid nitrate decomposition coupled with an increase in the rate of N₂O decomposition. The IR signature of the surface nitrates suggests they are monodentate nitrate species bound to Cu²⁺ ions. Temperature-programmed desorption studies reveal a strong correlation between the stability of the surface nitrate species and the temperature range in which oscillations occur.     

Material property requirements for analysis and design of UHTC components in hypersonic applications

Analytical modeling of thermal and mechanical response is a fundamental step in the design process for ultra-high-temperature ceramic components, such as nose tips and wing leading edges for hypersonic applications. The purpose of the analyses is to understand the response of test articles to high-enthalpy flows in ground tests and to predict component performance in particular flight environments. Performing these analyses and evaluating the results require comprehensive and accurate physical, thermal, and mechanical properties. In this paper, we explain the nature of the analyses, highlight the essential material properties that are required and why they are important, and describe the impact of property accuracy and uncertainty on the design process.     

Consideration of heat transfer in pore network modelling of convective drying

The influence of heat transfer on the drying behaviour of capillary porous media saturated with water is studied. To overcome the limitations of continuum approaches, a pore network model based on statistical physics and invasion percolation is used. The presented non-isothermal model is the first of its kind to describe free evolution of temperatures in convective drying. Gas-side mass transfer is modelled by a discretised boundary layer. Model assumptions are purely conductive heat transfer in the network and negligible viscosity. Vapour condensation is partially modelled. Simulations are conducted on two-dimensional square lattice networks. Overall drying rates and corresponding evolution of phase distributions and temperature fields are presented for mono- and bi-modal pore structures. The influence of heat transfer on phase distributions and drying behaviour is discussed in comparison with isothermal simulations.