3,738 research outputs found
Agronomic, economic and ecological aspects of the papaya (Carica papaya) production in Tabasco, Mexico
The cultivation of papaya is important in the tropic because it provides source of income to the farmer within a short time. Statistical data were obtained from farmers located in the Chontalpa, Rios and Centro-Sierra regions; the size of the survey was 67 farmers. The study shows the results of the farmers’ problem in a drastic reduction of their productivity because of the virosis and low prices in commercialization. The farmers were classified into three levels of technology, “low”, “middle” and “high”. The first one covers 88% of the farmers in seasonal conditions in contrast with the high technology that concentrates 4.5% in irrigation conditions. According to the technology used, the fertilizer shows more yields. Economically, the high technology had an internal tax return of 0.43 in comparison with the low technology of 0.25, which means that the investment is recovered with different yields. However, the use of high technology makes the system more competitive. Key words
Low-lying spectra in anharmonic three-body oscillators with a strong short-range repulsion
Three-body Schroedinger equation is studied in one dimension. Its two-body
interactions are assumed composed of the long-range attraction (dominated by
the L-th-power potential) in superposition with a short-range repulsion
(dominated by the (-K)-th-power core) plus further subdominant power-law
components if necessary. This unsolvable and non-separable generalization of
Calogero model (which is a separable and solvable exception at L = K = 2) is
presented in polar Jacobi coordinates. We derive a set of trigonometric
identities for the potentials which generalizes the well known K=2 identity of
Calogero to all integers. This enables us to write down the related partial
differential Schroedinger equation in an amazingly compact form. As a
consequence, we are able to show that all these models become separable and
solvable in the limit of strong repulsion.Comment: 18 pages plus 6 pages of appendices with new auxiliary identitie
Theoretical study of the N N --> N N pi pi reaction
We have developed a model for the N N --> N N pi pi reaction and evaluated
cross sections for the different charged channels. The low energy part of those
channels where the pions can be in an isospin zero state is dominated by N*
excitation, driven by an isoscalar source recently found experimentally,
followed by the decay N* --> N (pi pi, T=0, s-wave). At higher energies, and in
channels where the pions are not in T=0, Delta excitation mechanisms become
relevant. A rough agreement with the experimental data is obtained in most
channels. Repercussions of the present findings for the ABC effect and the p p
--> p p pi0 reaction close to threshold are also suggested.Comment: 22 pages, 12 postscripts figures, revised: a more general N* N pi pi
Lagrangian is considered, to be published in Nucl. Phys.
The two pion decay of the Roper resonance
We evaluate the two pion decay of the Roper resonance in a model where
explicit re-scattering of the two final pions is accounted for by the use of
unitarized chiral perturbation theory. Our model does not include an explicit
or scalar-isoscalar meson decay mode, instead it
generates it dynamically by means of the pion re-scattering. The two ways,
explicit or dynamically generated, of introducing this decay channel have very
different amplitudes.
Nevertheless, through interference with the other terms of the model we are
able to reproduce the same phenomenology as models with explicit consideration
of the meson.Comment: 17 latex pages, 11 eps figures. A few misprints corrected. A few new
references. Version accepted for publication in Phys. Rev.
Absolute agreement and consistency of the OptoGait system and Freemed platform for measuring walking gait
The gait cycle can be divided into four functional rocker units. Although the widespread use of the OptoGait (OG) system and the Freemed (FM) platform, their accuracy has not been tested. An observational study was completed with eighteen healthy volunteers to determine the accuracy of OG and FM for overground walking gait analysis. The pairwise comparison between data obtained from OG, FM and high-speed video analysis revealed significant differences for most of the measurements (p 0.94) for all measures for OG systems compared to video-analysis. When considering FM vs. video-analysis, ICCs showed good absolute agreement for rocker 1 (ICC = 0.86) and 3 (ICC = 0.82), excellent for rocker 2 (ICC = 0.93) and poor (ICC 0.1) while no heteroscedasticity of error was found when using FM (r2 < 0.1). This study indicates that the OG system and the FM platform can provide consistent foot rockers values when walking at a constant velocity. The differences between the systems assessed and their agreement and consistency values advise against their interchangeable use
Identification of an interferon-stimulated gene, isg15, involved in host immune defense against viral infections in gilthead seabream (Sparus aurata L.)
Interferons (IFNs) play a key role in the innate immunity of vertebrates against viral infections by inducing
hundreds of IFN-stimulated genes (ISGs), such as isg15. Isg15 is an ubiquitin-like protein, which can conjugate
cellular and viral proteins in a process called ISGylation, although it can also act as a cytokine-like protein.
Gilthead seabream (Sparus aurata L.) is an important asymptomatic carrier of viral haemorrhagic septicaemia
virus (VHSV) and nodavirus, representing a threat to other co-cultivated susceptible species. In order to better
understand virus-host interactions in this fish species, this study addresses the identification and molecular
characterization of seabream isg15 (sb-isg15). In addition, the modulation of transcript levels of sb-isg15 was
analysed in SAF-1 cells and seabream acidophilic granulocytes (AGs) stimulated in vitro with different pathogenassociated
molecular patterns (PAMPs) or inoculated with VHSV and striped jack nervous necrosis virus
(SJNNV).
The full-length cDNA of sb-isg15 gene, encoding a predicted protein of 155 amino acids, was identified and
seen to share the same characteristics as other fish and mammalian isg15 genes. Here we report the clear induction
of sb-isg15 transcript levels in SAF-1 cells and AGs stimulated with toll-like receptor (TLR) ligands, such
as polyinosinic:polycytidylic acid (poly I:C) or genomic DNA from Vibrio anguillarum (VaDNA), respectively.
Furthermore, VHSV and SJNNV inoculation induced a significant degree of sb-isg15 transcription in SAF-1 cells
and AGs. However, the relative levels of viral RNA transcription showed that SJNNV replication seems to be
more efficient than VHSV in both in vitro systems. Interestingly, sb-isg15 transcript induction elicited by VaDNA
was reduced in VHSV- and SJNNV-inoculated AGs, suggesting an interference prompted by the viruses against
the type I IFN system. Taken together, these findings support the use of seabream AGs as a valuable experimental
system to study virus-host interactions, in which sb-isg15 seems to play an important role.Versión del edito
Comparisons of Production Costs and Profit of Three Different Technology Levels of Papaya Production in Tabasco, Mexico
The survey was carried out from September 2006 to January 2007 in three papaya production sites located in main papaya production zones in Tabasco; SE Mexico. There are differences in size of the cultivated area, in the yield of the papaya as well as in production costs and profit, according to the different technology levels in the farming systems: low, medium and high technology cultivation level. The financial evaluations were carried out in three sites with different productive technologies. The comparison of the agronomic and economic traits results for low technology level in: V AN of 2359.00 USD, BCR in 1.9 and an equilibrium point of 3750.00 USD, TIR of 0.25. In order to avoid loses, a quantity of 10714 kg papaya should be sold. In medium technology VAN is 1605.10 USD, BCR is 1.7, TIR 0.20 and the equilibrium point is 12800.00 USD. 36571 kg of papaya should be yearly sold. In high technology level VAN is 11749.40, BCR is 2.73, TIR 0.43 and the equilibrium point is 12187.50 USD, 34821 kg papaya should be sold yearly. The indicators showed that all three levels are profitable and economically viable
Autofluorescence of stingray skeletal cartilage: hyperspectral imaging as a tool for histological characterization
Tessellated cartilage is a distinctive composite tissue forming the bulk of the skeleton of cartilaginous fishes (e.g. sharks and rays), built from unmineralized cartilage covered at the surface by a thin layer of mineralized tiles called tesserae. The finescale structure and composition of elasmobranch tessellated cartilage has largely been investigated with electron microscopy, micro-computed tomography and histology, but many aspects of tissue structure and composition remain uncharacterized. In our study, we demonstrate that the tessellated cartilage of a stingray exhibits a strong and diverse autofluorescence, a native property of the tissue which can be harnessed as an effective label-free imaging technique. The autofluorescence signal was excited using a broad range of wavelengths in confocal and light sheet microscopy, comparing several sample preparations (fresh; demineralized and paraffin-embedded; non-demineralized and plastic-embedded) and imaging the tissue at different scales. Autofluorescence varied with sample preparation with the signal in both plastic- and paraffin-embedded samples strong enough to allow visualization of finescale (≥ 1 μm) cellular and matrix structures, such as cell nuclei and current and former mineralization fronts, identifiable by globular mineralized tissue. A defined pericellular matrix (PCM) surrounding chondrocytes was also discernible, described here for the first time in elasmobranchs. The presence of a PCM suggests similarities with mammalian cartilage regarding how chondrocytes interact with their environment, the PCM in mammals acting as a transducer for biomechanical and biochemical signals. A posterior analysis of hyperspectral images by an MCR-ALS unmixing algorithm allowed identification of several distinct fluorescence signatures associated to specific regions in the tissue. Some fluorescence signatures identified could be correlated with collagen type II, the most abundant structural molecule of cartilage. Other fluorescence signatures, however, remained unidentified, spotlighting tissue regions that deserve deeper characterization and suggesting the presence of molecules still unidentified in elasmobranch skeletal cartilage. Our results show that autofluorescence can be a powerful exploratory imaging tool for characterizing less-studied skeletal tissues, such as tessellated cartilage. The images obtained are largely comparable with more commonly used techniques, but without the need for complicated sample preparations or external staining reagents standard in histology and electron microscopy (TEM, SEM)
Euclid preparation : XVI. Exploring the ultra-low surface brightness Universe with Euclid/VIS
Context. While Euclid is an ESA mission specifically designed to investigate the nature of dark energy and dark matter, the planned unprecedented combination of survey area (similar to 15000 deg(2)), spatial resolution, low sky-background, and depth also make Euclid an excellent space observatory for the study of the low surface brightness Universe. Scientific exploitation of the extended low surface brightness structures requires dedicated calibration procedures that are yet to be tested. Aims. We investigate the capabilities of Euclid to detect extended low surface brightness structure by identifying and quantifying sky-background sources and stray-light contamination. We test the feasibility of generating sky flat-fields to reduce large-scale residual gradients in order to reveal the extended emission of galaxies observed in the Euclid survey. Methods. We simulated a realistic set of Euclid/VIS observations, taking into account both instrumental and astronomical sources of contamination, including cosmic rays, stray-light, zodiacal light, interstellar medium, and the cosmic infrared background, while simulating the effects of background sources in the field of view. Results. We demonstrate that a combination of calibration lamps, sky flats, and self-calibration would enable recovery of emission at a limiting surface brightness magnitude of mu(lim) = 29.5(-0.27)(+0.08) mag arcsec(-2) (3 sigma, 10 x 10 arcsec(2)) in theWide Survey, and it would reach regions deeper by 2 mag in the Deep Surveys. Conclusions. Euclid/VIS has the potential to be an excellent low surface brightness observatory. Covering the gap between pixel-to-pixel calibration lamp flats and self-calibration observations for large scales, the application of sky flat-fielding will enhance the sensitivity of the VIS detector at scales larger than 1 '', up to the size of the field of view, enabling Euclid to detect extended surface brightness structures below mu(lim) = 31 mag arcsec(-2) and beyond.Peer reviewe
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