7,013 research outputs found

    Development of a computer code for calculating the steady super/hypersonic inviscid flow around real configurations. Volume 1: Computational technique

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    A numerical procedure has been developed to compute the inviscid super/hypersonic flow field about complex vehicle geometries accurately and efficiently. A second order accurate finite difference scheme is used to integrate the three dimensional Euler equations in regions of continuous flow, while all shock waves are computed as discontinuities via the Rankine Hugoniot jump conditions. Conformal mappings are used to develop a computational grid. The effects of blunt nose entropy layers are computed in detail. Real gas effects for equilibrium air are included using curve fits of Mollier charts. Typical calculated results for shuttle orbiter, hypersonic transport, and supersonic aircraft configurations are included to demonstrate the usefulness of this tool

    Rubiaceae family: Flora Argentina, history and evolution

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    The Rubiaceae family in Argentina is represented by 41 genera and 146 species, of which 9 spp., 2 subspp., and 1 variety are endemic. The highest concentration and endemism are found in the NE ofthe country, in savannas, rainforests, riverside forests, followed by the NW of Argentina, from sea level to 1000-4000 m in the Andes. They also inhabit the heterogeneous landscape of the Center Region of the country, and few species grow in the Patagonian zone. This work is the contribution to the integral study of the Flora of our country. The beginning of knowledge of Argentina’s vegetation dates back to the mid 19th century, with foreign naturalists attracted by the virgin vegetation of the country. The Academy of Science and the first Institute of Botany were founded in Córdoba, where the herbarium and methodical study of native plants began. The first floristic works were carried out, which were enriched in the 20th century, with the improvement of instruments, development of new methods, which changed the analysis and interpretation of data. Fast means of transportation and communication facilitated the exchange of ideas and the increase in botanical expeditions. Despite the advances in the local botany, a comprehensive work on the country’s flora was still missing. It began with species checklists, regional catalogues and flora from various provinces. At the Instituto Botánica Darwinion (IBODA), the project “Flora Argentina” began methodically with the hand-picking of species bibliography, collection and identification activities. Professor Nélida Bacigalupo began to work there in 1949. She worked for more than 60 years and her publications about Rubiaceae taxa were the first in the country. When we met her, we had the privilege of valuing her predisposition and her wisdom as “Teacher”, which led to the transfer of her knowledge to three generations, for which we express our appreciation and gratitude

    A New Approach for the Analysis of Hyperspectral Data: Theory and Sensitivity Analysis of the Moment Distance Method

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    We present the Moment Distance (MD) method to advance spectral analysis in vegetation studies. It was developed to take advantage of the information latent in the shape of the reflectance curve that is not available from other spectral indices. Being mathematically simple but powerful, the approach does not require any curve transformation, such as smoothing or derivatives. Here, we show the formulation of the MD index (MDI) and demonstrate its potential for vegetation studies. We simulated leaf and canopy reflectance samples derived from the combination of the PROSPECT and SAIL models to understand the sensitivity of the new method to leaf and canopy parameters. We observed reasonable agreements between vegetation parameters and the MDI when using the 600 to 750 nm wavelength range, and we saw stronger agreements in the narrow red-edge region 720 to 730 nm. Results suggest that the MDI is more sensitive to the Chl content, especially at higher amounts (Chl \u3e 40 mg/cm2) compared to other indices such as NDVI, EVI, and WDRVI. Finally, we found an indirect relationship of MDI against the changes of the magnitude of the reflectance around the red trough with differing values of LAI

    Canopy Height Estimation by Characterizing Waveform LiDAR Geometry Based on Shape-Distance Metric

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    There have been few approaches developed for the estimation of height using waveform LiDAR data. Unlike any existing methods, we illustrate how the new Moment Distance (MD) framework can characterize the canopy height based on the geometry and return power of the LiDAR waveform without having to go through curve modeling processes. Our approach offers the possibilities of using the raw waveform data to capture vital information from the variety of complex waveform shapes in LiDAR. We assess the relationship of the MD metrics to the key waveform landmarks—such as locations of peaks, power of returns, canopy heights, and height metrics—using synthetic data and real Laser Vegetation Imaging Sensor (LVIS) data. In order to verify the utility of the new approach, we use field measurements obtained through the DESDynI (Deformation, Ecosystem Structure and Dynamics of Ice) campaign. Our results reveal that the MDI can capture temporal dynamics of canopy and segregate generations of stands based on curve shapes. The method satisfactorily estimates the canopy height using the synthetic (r 2 = 0.40) and the LVIS dataset (r 2 = 0.74). The MDI is also comparable with existing RH75 (relative height at 75%) and RH50 (relative height at 50%) height metrics. Furthermore, the MDI shows better correlations with ground-based measurements than relative height metrics. The MDI performs well at any type of waveform shape. This opens the possibility of looking more closely at single-peaked waveforms that usually carries complex extremes

    Carbon radio recombination lines from gigahertz to megahertz frequencies towards Orion A

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    Context. The combined use of carbon radio recombination lines (CRRLs) and the 158 μ\mum-[CII] line is a powerful tool for the study of the energetics and physical conditions (e.g., temperature and density) of photodissociation regions (PDRs). However, there are few observational studies that exploit this synergy. Aims. Here we explore the relation between CRRLs and the 158 μ\mum-[CII] line in light of new observations and models. Methods. We present new and existing observations of CRRLs in the frequency range 0.15--230 GHz with ALMA, VLA, the GBT, Effelsberg 100m, and LOFAR towards Orion~A (M42). We complement these observations with SOFIA observations of the 158 μ\mum-[CII] line. We studied two PDRs: the foreground atomic gas, known as the Veil, and the dense PDR between the HII region and the background molecular cloud. Results. In the Veil we are able to determine the gas temperature and electron density, which we use to measure the ionization parameter and the photoelectric heating efficiency. In the dense PDR, we are able to identify a layered PDR structure at the surface of the molecular cloud to the south of the Trapezium cluster. There we find that the radio lines trace the colder portion of the ionized carbon layer, the C+^{+}/C/CO interface. By modeling the emission of the 158158~μ\mum-[CII] line and CRRLs as arising from a PDR we derive a thermal pressure >5×107>5\times10^{7} K cm3^{-3} and a radiation field G0105G_{0}\approx10^{5} close to the Trapezium. Conclusions. This work provides additional observational support for the use of CRRLs and the 158 μ\mum-[CII] line as complementary tools to study dense and diffuse PDRs, and highlights the usefulness of CRRLs as probes of the C+^{+}/C/CO interface.Comment: 18 pages, 16 figures, accepted for publication in A&

    The Apical Submembrane Cytoskeleton Participates in the Organization of the Apical Pole in Epithelial Cells

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    In a previous publication (Rodriguez, M.L., M. Brignoni, and P.J.I. Salas. 1994. J. Cell Sci. 107: 3145–3151), we described the existence of a terminal web-like structure in nonbrush border cells, which comprises a specifically apical cytokeratin, presumably cytokeratin 19. In the present study we confirmed the apical distribution of cytokeratin 19 and expanded that observation to other epithelial cells in tissue culture and in vivo. In tissue culture, subconfluent cell stocks under continuous treatment with two different 21-mer phosphorothioate oligodeoxy nucleotides that targeted cytokeratin 19 mRNA enabled us to obtain confluent monolayers with a partial (40–70%) and transitory reduction in this protein. The expression of other cytoskeletal proteins was undisturbed. This downregulation of cytokeratin 19 resulted in (a) decrease in the number of microvilli; (b) disorganization of the apical (but not lateral or basal) filamentous actin and abnormal apical microtubules; and (c) depletion or redistribution of apical membrane proteins as determined by differential apical–basolateral biotinylation. In fact, a subset of detergent-insoluble proteins was not expressed on the cell surface in cells with lower levels of cytokeratin 19. Apical proteins purified in the detergent phase of Triton X-114 (typically integral membrane proteins) and those differentially extracted in Triton X-100 at 37°C or in n-octyl-β-d-glycoside at 4°C (representative of GPIanchored proteins), appeared partially redistributed to the basolateral domain. A transmembrane apical protein, sucrase isomaltase, was found mispolarized in a subpopulation of the cells treated with antisense oligonucleotides, while the basolateral polarity of Na+– K+ATPase was not affected. Both sucrase isomaltase and alkaline phosphatase (a GPI-anchored protein) appeared partially depolarized in A19 treated CACO-2 monolayers as determined by differential biotinylation, affinity purification, and immunoblot. These results suggest that an apical submembrane cytoskeleton of intermediate filaments is expressed in a number of epithelia, including those without a brush border, although it may not be universal. In addition, these data indicate that this structure is involved in the organization of the apical region of the cytoplasm and the apical membrane

    A Redescription of Pericapritermes ceylonicus (Holmgren, 1911) (Blattodea, Isoptera, Termitidae) and First Record from India

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    Until now, the occurrence of Pericapritermes ceylonicus (Holmgren) was not confirmed in the Indian mainland. Here, we document the occurrence of this species from Karnataka state constituting its first report from India. The species was identified based on the soldier caste, and the worker characters were described for the first time, including the digestive tube and enteric valve armature. The enteric valve was characterized by the presence of gradually reducing triangular spines. The study provides the basis for further taxonomic characterization of Pericapritermes occurring in India using gut morphology of workers
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