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Better Spatial Resolution (good + spatial_resolution)
Selected AbstractsCorrelation between sea surface topography and bathymetry in shallow shelf waters in the Western MediterraneanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2002G. Rodríguez Velasco Summary In this paper, gravimetric and altimetric data are used to assess an estimation of the sea surface topography in the Western Mediterranean Sea. This is a complex area from different points of view, due to the presence of several islands, coastal lines, shallow waters and a peculiar hydrologic equilibrium due to its proximity to the Atlantic water exchange area. First, a gravimetric geoid was computed using the least-squares collocation (LSC) procedure with the classical remove-restore technique. We also present a local mean sea surface generated from repeat ERS-1 altimeter data fitted to TOPEX. We chose this satellite because it offers a better spatial resolution than the TOPEX data. The time span used in the computations is one year. This is a useful interval for averaging out the regular seasonal variations, which are very large in this area. We present the comparisons between the gravimetric geoidal heights and the adjusted sea surface. This is a way to obtain a rough estimation of the sea surface topography (SST) since we also include the errors in the two surfaces and other oceanic signals. The differences obtained are physically reasonable with a mean of 17 cm and standard deviation (s.d.) of 39 cm. A significant similarity is observed between the features reproduced by these differences and the bathymetry in the area, suggesting some sort of correlation between both magnitudes for the studied region. If we accept such correlation, the SST may be described as a function of depth. This procedure lets us filter out the short wavelength part of the geoid from the first SST estimation. [source] Two-photon near-field mapping of local molecular orientations in hexaphenyl nanofibersLASER PHYSICS LETTERS, Issue 10 2005J. Beermann Abstract Two-photon excited near field images of hexaphenyl nanofibers are obtained using a scanning near field optical microscope in transmission configuration. From polarized measurements the orientations of the molecular basis units of the fibers are determined with a resolution of better than 400 nm. The molecular orientation angles obtained are comparable to results from two-photon scanning far-field microscopy, but the present measurements provide a better spatial resolution. From this near-field data it is concluded that the molecules can be oriented either very homogeneously or with some scatter in otherwise similar organic nanoaggregates. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Phase-sensitive cardiac tagging,REALTAGMAGNETIC RESONANCE IN MEDICINE, Issue 1 2007J. Andrew Derbyshire Abstract Fully inverting spins, instead of merely saturating them, provides superior contrast for tagging procedures. The resulting improvement in tag contrast-to-noise ratio (CNR) yields higher-precision tag detection. Also, thinner slices and hence reduced tag separations can be employed, providing displacement and strain measurements with better spatial resolution. Alternatively, the improved tag contrast can be used to obtain cine images covering a greater portion of the cardiac cycle. The use of standard magnitude reconstruction for images of these inversion tags causes rectification of the negative-valued signals from the tags, confounding the image interpretation. Therefore, a phase-sensitive reconstruction scheme of the inverted tags must be employed. Here we demonstrate the implementation of inverted tags with phase-sensitive reconstruction in a ramped-flip-angle, steady-state free precession (SSFP) sequence. Magn Reson Med 58:206,210, 2007. © 2007 Wiley-Liss, Inc. [source] Femtosecond laser ablation elemental mass spectrometryMASS SPECTROMETRY REVIEWS, Issue 4 2006Roland Hergenröder Abstract Laser ablation mass spectrometry (LA-MS) has always been an interesting method for the elemental analysis of solid samples. Chemical analysis with a laser requires small amounts of material. Depending on the analytical detection system, subpicogram quantities may be sufficient. In addition, a focused laser beam permits the spatial characterization of heterogeneity in solid samples typically with micrometer resolution in terms of lateral and depth dimensions. With the advent of high-energy, ultra-short pulse lasers, new possibilities arise. The task of this review is to discuss the principle differences between the ablation process of short (>1 ps) and ultra-short (<1 ps) pulses. Based on the timescales and the energy balance of the process that underlies an ablation event, it will be shown that ultra-short pulses are less thermal and cause less collateral damages than longer pulses. The confinement of the pulse energy to the focal region guarantees a better spatial resolution in all dimensions and improves the analytical figures of merit (e.g., fractionation). Applications that demonstrate these features and that will be presented are in-depth profiling of multi-layer samples and the elemental analysis of biological materials. © 2006 Wiley Periodicals, Inc., Mass Spec Rev 25:551,572, 2006 [source] Identification of shocked quartz by scanning cathodoluminescence imagingMETEORITICS & PLANETARY SCIENCE, Issue 6 2001Sam Boggs Jr. These lamellae appear as remarkably straight, thin, planar features (microstructures) in sets within which lamellae are essentially parallel to each other and spaced , 20 ,m apart. Two or more intersecting sets are typically present. Shock lamellae are commonly recognized and identified by optical methods, by use of the transmission electron microscope (TEM), and by etching polished sections and subsequent examination with a scanning electron microscope (SEM) operated in the secondary electron mode. We present here a method for observing planar microstructures in shocked quartz by using a cathodoluminescence (CL) detector attached to a SEM. The method relies on the fact that planar microstructures in quartz arising as a result of shock display no CL whatever; thus, they show up as distinct, thin, black lines on otherwise luminescent quartz grains. We used scanning CL imaging to study shocked quartz from the Ries Crater, Germany, a well-known impact crater of Miocene age. We demonstrate that shock-produced planar microstructures are clearly displayed in SEM-CL images and can be distinguished from microfractures generated by tectonism, and subsequently filled with quartz, and other similar features not related to impact events. The SEM-CL method provides a powerful supplement to other methods of identifying shocked quartz. It commonly provides better spatial resolution than does standard optical methods, and does not require etching of quartz grains. Further, it is easier and faster to use than are TEM methods, although it is not capable of the fine-scale defect analysis possible with TEM. [source] Use of different proteases working in acidic conditions to improve sequence coverage and resolution in hydrogen/deuterium exchange of large proteinsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2003Laetitia Cravello The combination of hydrogen exchange and mass spectrometry has been widely used in structural biology, providing views on protein structure and protein dynamics. One of the constraints is to use proteases working at low pH and low temperature to limit back-exchange during proteolysis. Although pepsin works in these conditions and is currently used in such experiments, sequence coverage is not always complete especially for large proteins, and the spatial resolution of the exchange rate is limited by the size of the resulting peptides. In this study we tried two other proteases, protease type XIII from Aspergillus saitoi and protease type XVIII from Rhizhopus species. The penicillin-binding protein X (PBP-2X*), a 77-kDa protein, was selected as a model. Like pepsin, neither of these proteases is really specific, but we found very good reproducibility in the digestion pattern. Compared with using pepsin alone, combining the results of the three independent proteolyses increased the coverage for the peptide mapping, thus avoiding missing some potentially interesting regions of the protein. Furthermore, we obtained a better spatial resolution for deuterium incorporation data, specifying accurately the deuterated regions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Polar low le Cygne: Satellite observations and numerical simulationsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 598 2004Chantal Claud Abstract A polar low (PL) which occurred in October 1993 over the Norwegian Sea is investigated from an observational and a numerical point of view. This PL has several unique features: it developed early in the season, it lasted for about 3 days, and its trajectory was such that it passed over weather stations so that ,conventional' observations of the low are available. The conditions of the formation, development and decay of the PL are investigated using a double approach: satellite data from several instruments are used together to document the mesoscale structure of the low, and two versions of a limited-area model are run to investigate the dynamics of the low. Numerical model fields are compared to quantities derived from TIROS-N Operational Vertical Sounder, the Special Sensor Microwave/Imager, and satellite radar altimeter data. In spite of a better spatial resolution of the models, humidity and surface wind speeds are less organized in the simulations than in satellite retrievals. The number of vertical levels, especially for the lowest layers of the atmosphere, appears to be an essential component for a good simulation of the trajectory of the low. There is, however, good overall agreement between modelled and satellite-derived fields, and the good quality of the simulations allows inferences to be made regarding the essential physical and dynamical processes taking place during the formation and development of the PL. We find that the PL was the result of favourable flow conditions at the surface in the form of a shallow arctic front established south of the ice edge, together with an upper-level potential-vorticity anomaly setting the stage for a positive interaction. Later on, the strong surface sensible- and latent-heat fluxes contributed to the extensive vertical development. This study demonstrates the usefulness of the approach adopted here, which relies not only on simulations but also on observations to get a very complete description of such disturbances. Copyright © 2004 Royal Meteorological Society. [source] | ||||||||||||||||