Special studies of AROD system concepts and designs

Signal to noise ratios in airborne range and orbit determination system, and carrier and range loop performance analyse

Self-sustained spatiotemporal oscillations induced by membrane-bulk coupling

We propose a novel mechanism leading to spatiotemporal oscillations in extended systems that does not rely on local bulk instabilities. Instead, oscillations arise from the interaction of two subsystems of different spatial dimensionality. Specifically, we show that coupling a passive diffusive bulk of dimension d with an excitable membrane of dimension d-1 produces a self-sustained oscillatory behavior. An analytical explanation of the phenomenon is provided for d=1. Moreover, in-phase and anti-phase synchronization of oscillations are found numerically in one and two dimensions. This novel dynamic instability could be used by biological systems such as cells, where the dynamics on the cellular membrane is necessarily different from that of the cytoplasmic bulk.Comment: Accepted for publication in Physical Review Letter

Perforatationstrauma im Gesichtsschädel: Eine ungewöhnliche Verletzung beim Skifahren

Zusammenfassung: Pfählungsverletzungen am Kopf und im Gesicht sind selten. Wir berichten über den Fall eines 48-jährigen Patienten, der sich beim Skifahren eine Pfählungsverletzung des Gesichtschädels mit einem 11cm langen Ast zugezogen hatte. Der Patient präsentierte sich bei der Einlieferung in die Klinik neurologisch unauffällig und kreislaufstabil. In den CT-Untersuchungen des Kopfs konnten Frakturen im Gesichtschädel und ein 11cm langer Fremdkörper, ausgehend vom Sinus maxillaris durch den Gesichtschädel bis paravertebral reichend, ohne Verletzung von Gefäßen nachgewiesen werden. Zusätzlich zog sich der Patient Frakturen an der Hand und an den Rippen zu. Er wurde in ein Zentrum für Kiefer- und Gesichtschirurgie verlegt, mehrfach operiert und konnte 8Monate nach dem Unfall wieder in sein gewohntes privates und berufliches Leben zurückkehre

District-level mineral survey using airborne hyperspectral data, Los Menucos, Argentina

The Los Menucos District, Rio Negro, Argentina, provides an excellent case history of a complex epithermal gold system mapped and explored using a combination of field mapping and multispectral/hyperspectral remote sensing. The district offers a host of argillic and advanced argillic alteration minerals at the surface, many of which are difficult to identify visually. A strategy utilizing regional targeting with Landsat TM to optimize field mapping followed by district-level survey with hyperspectral imaging (HSI) data demonstrates the value added by high-spectral resolution aircraft data. Standardized analysis methods consisting of spatial and spectral data reduction to a few key endmember spectra provides a consistent way to map spectrally active minerals. Minerals identified in the Los Menucos district using the JPL Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) include hematite, goethite, kaolinite, dickite, alunite, pyrophyllite, muscovite/sericite, montmorillonite, calcite, and zeolites. Hyperspectral maps show good correspondence with the results of field reconnaissance verification and spectral measurements acquired using an ASD field spectrometer. Further analysis of Hyperion (satellite-based) hyperspectral data indicates that similar mapping results can be achieved from satellite altitudes. These examples illustrate the high potential of hyperspectral remote sensing for geologic mapping and mineral exploration

Self-organization and Mechanical Properties of Active Filament Bundles

A phenomenological description for active bundles of polar filaments is presented. The activity of the bundle results from crosslinks, that induce relative displacements between the aligned filaments. Our generic description is based on momentum conservation within the bundle. By specifying the internal forces, a simple minimal model for the bundle dynamics is obtained, capturing generic dynamic behaviors. In particular, contracted states as well as solitary and oscillatory waves appear through dynamic instabilities. The introduction of filament adhesion leads to self-organized persistent filament transport. Furthermore, calculating the tension, homogeneous bundles are shown to be able to actively contract and to perform work against external forces. Our description is motivated by dynamic phenomena in the cytoskeleton and could apply to stress-fibers and self-organization phenomena during cell-locomotion.Comment: 19 pages, 10 figure

Perforatationstrauma im Gesichtsschädel. Eine ungewöhnliche Verletzung beim Skifahren

Facial perforation injuries are very rare. We describe a case of a 48-year-old man who sustained a perforation trauma from an 11 cm long wooden tree branch in the middle of the face in a skiing accident. He suffered from additional injuries, such as fractures of the ribs and hand, but was neurologically without pathologic findings and was cardiopulmonary stable.The branch penetrated the head from the sinus maxillaris through the maxilla just missing the internal and external carotid arteries and ending just short of the cervical vertebra. The patient was transported to a center for oral and maxillofacial surgery and underwent several operations.He could return to his normal social and professional life 8 months after the accident

Soil salinization in marshes : study case: Samborombón Bay wetland, Argentina

En el sector sur de la Bahía de Samborombón (Buenos Aires, Argentina) se desarrolla una extensa marisma que forma un humedal intermareal. En ella se realizaron distintas obras de ingeniería con el fin de evitar el ingreso del flujo mareal y lograr una mayor extensión del área de pastoreo. El objetivo del trabajo es evaluar si la regulación de los flujos mareales ocasiona una modificación en el contenido de cloruros en los sedimentos superficiales, afectando la salinidad de los suelos del humedal. Se realizaron interpretaciones de imágenes satelitales, relevamientos de campo, muestreos de sedimentos y mediciones de niveles y conductividad eléctrica del agua superficial y subterránea. Los resultados obtenidos permitieron reconocer cómo las obras de ingeniería (terraplenes de contención y caminos internos) alteran el comportamiento hidrológico natural y en consecuencia el contenido de cloruros en el sedimento. Problemas de salinización de suelos se reconocen en sectores donde el agua mareal se acumula y luego se evapora formando precipitados de halita. Las futuras obras deberán planificarse de forma tal de minimizar la alteración de los flujos de agua con el fin de lograr un manejo sustentable de los recursos naturales en el humedal.The southern sector of the Samborombón Bay (Buenos Aires, Argentina) is an extensive marsh that is associated with an intertidal wetland environment. Different engineering works were built to avoid tidal inflow and to increase the livestock grazing areas. The objective of this work is to assess if the regulation of tidal inflow causes a chloride content change in the surface sediments, affecting the soil salinity of the wetland. Interpretation of satellite images, field surveys, sampling of sediments, and electrical conductivity and levels measurements of surface and groundwater were carried out. The results allowed us to recognize how engineering works (embankments and internal roads) alter the natural hydrological behavior, and, therefore the chloride content in the sediment. Soil salinization problems are recognized in areas where the tidal water accumulates and then evaporates forming halite precipitates. Future engineering works should be planned so as to minimize the alteration of the water flow in order to achieve a sustainable management of natural resources in the wetland.Fil: Carol, Eleonora S.. Universidad Nacional de La PlataFil: Kruse, Eduardo E.. Universidad Nacional de La PlataFil: Cellone, Francisco A.. Universidad Nacional de La Plat

Morphogen Transport in Epithelia

We present a general theoretical framework to discuss mechanisms of morphogen transport and gradient formation in a cell layer. Trafficking events on the cellular scale lead to transport on larger scales. We discuss in particular the case of transcytosis where morphogens undergo repeated rounds of internalization into cells and recycling. Based on a description on the cellular scale, we derive effective nonlinear transport equations in one and two dimensions which are valid on larger scales. We derive analytic expressions for the concentration dependence of the effective diffusion coefficient and the effective degradation rate. We discuss the effects of a directional bias on morphogen transport and those of the coupling of the morphogen and receptor kinetics. Furthermore, we discuss general properties of cellular transport processes such as the robustness of gradients and relate our results to recent experiments on the morphogen Decapentaplegic (Dpp) that acts in the fruit fly Drosophila

Extraction of quantitative surface characteristics from AIRSAR data for Death Valley, California

Polarimetric Airborne Synthetic Aperture Radar (AIRSAR) data were collected for the Geologic Remote Sensing Field Experiment (GRSFE) over Death Valley, California, USA, in Sep. 1989. AIRSAR is a four-look, quad-polarization, three frequency instrument. It collects measurements at C-band (5.66 cm), L-band (23.98 cm), and P-band (68.13 cm), and has a GIFOV of 10 meters and a swath width of 12 kilometers. Because the radar measures at three wavelengths, different scales of surface roughness are measured. Also, dielectric constants can be calculated from the data. The AIRSAR data were calibrated using in-scene trihedral corner reflectors to remove cross-talk; and to calibrate the phase, amplitude, and co-channel gain imbalance. The calibration allows for the extraction of accurate values of rms surface roughness, dielectric constants, sigma(sub 0) backscatter, and polarization information. The radar data sets allow quantitative characterization of small scale surface structure of geologic units, providing information about the physical and chemical processes that control the surface morphology. Combining the quantitative information extracted from the radar data with other remotely sensed data sets allows discrimination, identification and mapping of geologic units that may be difficult to discern using conventional techniques