Evaluation of Three Organic Products With Three Doses for Boat Control (Phytophthora Infestans) in Potato Cultivation (Solanum Tuberosum cv. Fripapa) Riobamba Canton, Chimborazo Province

This research proposes to evaluate three ecological products with three doses for the control disease (Phytophthora infestans) in the potato crop (Solanum tuberosum cv. Fripapa) in the Riobamba canton, Chimborazo province. Three ecological products helped: Citrubact, Fosficarben, and Bioplus in high medium and low doses recommended by the producers, making applications every two weeks in this crop, to determine the best product in both the P. infestans control and performance of growing marginal rate. A design of randomized complete blocks (RCBD) in bifactorial combinations with 9 treatments, 4 replications and a control were used. As a result, the lower incidence of the disease was obtained by Fosficarben treatment in high doses (4cc/Lt) with 8.33%, due to the component ion phosphite, which has a direct effect on the fungal metabolism. The same behaviour was observed in the intensity where Fosficarben in high doses (4cc/Lt) obtained 12,83%, being the lower intensity of the research. The treatment with better performance was also Fosficarben in high doses with 21496, 80l<h/ha. According to the economic analysis the treatment composed by Citrubact in low-doses (lcc/Lt) got a higher marginal rate of return in relation to other treatments of 798.97% and a net income of 2631.28 USD and a variable cost, followed by the Bioplus treatmentdue in medium doses (4cc/Lt) with 765.14% of marginal rate. In conclusion, it is possible to control P. infestans in the potato crop by using ecological products, obtaining a good performance, a healthy product and economic income. Keywords: ecological products, potato crop, control disease. Resumen La presente investigación propone: evaluar tres productos ecológicos con tres dosis para el control de lancha (Phytophthora infestans) en el cultivo de papa (Solanum tuberosum cv. Fripapa) Cantón Riobamba, Provincia de Chimborazo. Ayudándonos de tres productos ecológicos: Citrubact. Fosficarben y Bioplus, en dosis alta media y baja recomendadas por las empresas productoras, realizando aplicaciones cada dos semanas en este cultivo, para determinar el mejor producto, tanto en el control de P. infestans, como en rendimiento del cultivo y tasa de retorno marginal. Se utilizó un diseño de bloques completos al azar (DBCA) en arreglo bifactorial combinatorio, con 9 tratamientos, 4 repeticiones y un testigo. Resultando que la menor incidencia de la enfermedad la obtuvo el tratamiento formado por Fosficarben en dosis alta (4cc/lt) con 8,33%, esto se debe a que contiene ion fosfito, que ejerce un efecto directo sobre el metabolismo fúngico. El mismo comportamiento se pudo observar en la intensidad donde Fosficarben en dosis alta (4cc/lt) obtuvo 12,83% siendo la menor intensidad del estudio. El tratamiento con mayor rendimiento también fue Fosficarben en dosis alta (4cc/lt) con 21496,80 kg/ha. En al análisis económico el tratamiento formado por Citrubact en dosis baja (1 cc/lt) obtuvo una mayor tasa de retorno marginal en relación al resto de tratamientos de 798,97%, con un beneficio neto de 2631,28 USD y un costo variable de 177,55 USD; debido a su dosis baja, es el más rentable de los tratamientos en estudio, seguido por el tratamiento conformado por Bioplus en dosis media (4 cc/lt) con 765,14% de tasa de retorno marginal. En conclusión se puede controlar a P. infestans en el cultivo de papa utilizando productos ecológicos, obteniendo un buen rendimiento, un producto sano y generando ingresos económicos. Palabras clave: productos ecológicos, cosecha de papas, control de enfermedades

Significance of solutions of the inverse Biot-Savart problem in thick superconductors

The evaluation of current distributions in thick superconductors from field profiles near the sample surface is investigated theoretically. A simple model of a cylindrical sample, in which only circular currents are flowing, reduces the inversion to a linear least squares problem, which is analyzed by singular value decomposition. Without additional assumptions about the current distribution (e.g. constant current over the sample thickness), the condition of the problem is very bad, leading to unrealistic results. However, any additional assumption strongly influences the solution and thus renders the solutions again questionable. These difficulties are unfortunately inherent to the inverse Biot-Savart problem in thick superconductors and cannot be avoided by any models or algorithms

A survey of hard spectrum ROSAT sources 1: X-ray source catalogue

We present a catalogue of 147 serendipitous X-ray sources selected to have hard spectra (alpha < 0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. We have used Monte Carlo simulations to verify that our technique is very efficient at selecting hard sources: the survey has > 10 times as much effective area to hard sources as it has to soft sources above a 0.5 - 2 keV flux level of 10^-14 erg/cm^2/s. The distribution of best fit spectral slopes of the hard sources suggests that a typical ROSAT hard source in our survey has a spectral slope alpha ~0. The hard sources have a steep number flux relation (dN/dS propto S^-gamma with a best fit value of gamma = 2.72 +- 0.12) and make up about 15% of all 0.5 - 2 keV sources with S > 10^-14 erg/cm^2/s. If their N(S) continues to fainter fluxes, the hard sources will comprise ~ 40% of sources with 5 10^-15 < S < 10^-14. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S < 10^-14. They probably make a strong contribution to the X-ray background at faint fluxes and could be the solution to the X-ray background spectral paradox.Comment: 13 pages, 6 figures, Accepted for publication in MNRA

XMM-Newton spectra of hard spectrum Rosat AGN: X-ray absorption and optical reddening

We present the XMM-Newton spectra of three low-redshift intermediate Seyferts (one Sy1.5, and two Sy1.8), from our survey of hard spectrum Rosat sources. The three AGN are well fitted by absorbed powerlaws, with intrinsic nuclear photoelectric absorption from column densities between 1.3 and 4.0e21 cm-2. In the brightest object the X-ray spectrum is good enough to show that the absorber is not significantly ionized. For all three objects the powerlaw slopes appear to be somewhat flatter (Gamma~1.3-1.6) than those found in typical unabsorbed Seyferts. The constraints from optical and X-ray emission lines imply that all three objects are Compton-thin. For the two fainter objects, the reddening deduced from the optical broad emission lines in one of them, and the optical continuum in the other, are similar to those expected from the X-ray absorption, if we assume a Galactic gas-to-dust ratio and reddening curve. The broad line region Balmer decrement of our brightest object is larger than expected from its X-ray absorption, which can be explained either by an intrinsic Balmer decrement with standard gas-to-dust ratio, or by a >Galactic gas-to-dust ratio. These >=Galactic ratios of extinction to photoelectric absorption cannot extend to the high redshift, high luminosity, broad line AGN in our sample, because they have column densities >1e22 cm-2, and so their broad line regions would be totally obscured. This means that some effect (e.g., luminosity dependence, or evolution) needs to be present in order to explain the whole population of absorbed AGN.Comment: LaTeX, 10 pages and 7 figures, A&A accepte

A survey of hard spectrum ROSAT sources 2: optical identification of hard sources

We have surveyed 188 ROSAT PSPC fields for X-ray sources with hard spectra (alpha<0.5); such sources must be major contributors to the X-ray background at faint fluxes. In this paper we present optical identifications for 62 of these sources: 28 AGN which show broad lines in their optical spectra (BLAGN), 13 narrow emission line galaxies (NELGs), 5 galaxies with no visible emission lines, 8 clusters and 8 Galactic stars. The BLAGN, NELGs and galaxies have similar distributions of X-ray flux and spectra. Their ROSAT spectra are consistent with their being AGN obscured by columns of 20.5<log(NH/cm^2)<23. The hard spectrum BLAGN have a distribution of X-ray to optical ratios which is similar to that found for AGN from soft X-ray surveys (1<alpha_OX<2). However, a relatively large proportion (15%) of the BLAGN, NELGs and galaxies are radio loud. This could be because the radio jets in these objects produce intrinsically hard X-ray emission, or if their hardness is due to absorption, it could be because radio loud objects are more X-ray luminous than radio quiet objects. The 8 hard sources identified as clusters of galaxies are the brightest, and softest group of sources and hence clusters are unlikely to be an important component of the hard, faint population. We propose that BLAGN are likely to constitute a significant fraction of the faint, hard, 0.5 - 2 keV population and could be important to reproducing the shape of the X-ray background, because they are the most numerous type of object in our sample (comprising almost half the identified sources), and because all our high redshift (z>1) identified hard sources have broad lines.Comment: 10 pages, 6 figures, accepted for publication in MNRA

The XMM deep survey in the CDF-S. X. X-ray variability of bright sources

We aim to study the variability properties of bright hard X-ray selected Active Galactic Nuclei (AGN) with redshift between 0.3 and 1.6 detected in the Chandra Deep Field South (XMM-CDFS) by a long XMM observation. Taking advantage of the good count statistics in the XMM CDFS we search for flux and spectral variability using the hardness ratio techniques. We also investigated spectral variability of different spectral components. The spectra were merged in six epochs (defined as adjacent observations) and in high and low flux states to understand whether the flux transitions are accompanied by spectral changes. The flux variability is significant in all the sources investigated. The hardness ratios in general are not as variable as the fluxes. Only one source displays a variable HR, anti-correlated with the flux (source 337). The spectral analysis in the available epochs confirms the steeper when brighter trend consistent with Comptonisation models only in this source. Finding this trend in one out of seven unabsorbed sources is consistent, within the statistical limits, with the 15 % of unabsorbed AGN in previous deep surveys. No significant variability in the column densities, nor in the Compton reflection component, has been detected across the epochs considered. The high and low states display in general different normalisations but consistent spectral properties. X-ray flux fluctuations are ubiquitous in AGN. In general, the significant flux variations are not associated with a spectral variability: photon index and column densities are not significantly variable in nine out of the ten AGN over long timescales (from 3 to 6.5 years). The photon index variability is found only in one source (which is steeper when brighter) out of seven unabsorbed AGN. These results are consistent with previous deep samples.Comment: 14 pages, 11 figures. Accepted in A&

Acoustic assessment and distribution of the main pelagic fish species in ICES Subdivision 9a South during the ECOCADIZ-RECLUTAS 2018-10 Spanish survey (October 2017).

The present working document summarises the main results obtained during the ECOCADIZ-RECLUTAS 2018-10 Spanish (pelagic ecosystem-) acoustic survey. The survey was conducted by IEO between 10th and 29th October 2018 in the Portuguese and Spanish shelf waters (20-200 m isobaths) off the Gulf of Cadiz onboard the R/V Ramón Margalef. The survey’s main objective is the acoustic assessment of anchovy and sardine juveniles (age 0 fish) in the recruitment areas of the Gulf of Cadiz. The 21 foreseen acoustic transects were sampled. A total of 25 valid fishing hauls were carried out for echo-trace ground-truthing purposes. Chub mackerel was the most frequent species in those hauls, followed by sardine, anchovy, horse mackerel, mackerel, bogue and Mediterranean horse mackerel. Acoustic sampling was carried out with the recently installed Simrad™ EK80 echo-sounder working in multi-frequency and in CW mode. A misconfiguration of the range of the acoustic active layer entailed to slow down the ping rate (1.5-2.0 seconds) in relation to the standard values (at about 0.3 seconds), resulting an acoustic sampling rate much lower than it should be. Therefore, the results from this acoustic sampling and the resulting estimates from this survey should be considered with caution. Anchovy abundance and biomass were of 953 million fish and 10 493 t. The abundance and biomass of age-0 anchovies were estimated at 543 million fish and 3 834 t, 57% and 36% of the total population abundance and biomass, respectively. Despite the methodological problems, these estimates seem to suggest a recent decrease in relation to previous years. The estimates for Gulf of Cadiz sardine in the surveyed area were of 1 134 million fish and 20 679 t. Estimates of age-0 sardine were of 1 036 million fish and 15 224 t, 91% and 74% of the total estimated abundance and biomass, respectively. Even taking into account a possible underestimation for the abovementioned methodological problems, the values reached in 2018 were above the historical mean for the total population and recruits abundance and for the recruit biomass, and they might suggest a relatively stable situation since the maxima registered in 2016

The Luminosity Function Evolution of Soft X--ray selected AGN in the RIXOS survey

A sample of 198 soft X--ray selected active galactic nuclei (AGN) from the ROSAT International X--ray Optical Survey (RIXOS), is used to investigate the X--ray luminosity function and its evolution. RIXOS, with a flux limit of 3E-14 erg s-1 cm-2 (0.5 to 2.0 keV), samples a broad range in redshift over 20 deg^2 of sky, and is almost completely identified; it is used in combination with the Einstein Extended Medium Sensitivity Survey (EMSS), to give a total sample of over 600 AGN. We find the evolution of AGN with redshift to be consistent with pure luminosity evolution (PLE) models in which the rate of evolution slows markedly or stops at high redshifts z>1.8. We find that this result is not affected by the inclusion, or exclusion, of narrow emission line galaxies at low redshift in the RIXOS and EMSS samples, and is insensitive to uncertainties in the conversion between flux values measured with ROSAT and Einstein. We confirm, using a model independent Ve/Va test, that our survey is consistent with no evolution at high redshifts.Comment: 10 pages, LaTeX file, PS figures and mn.sty. Accepted in MNRA

X-ray Spectra of the RIXOS source sample

We present results of an extensive study of the X-ray spectral properties of sources detected in the RIXOS survey, that is nearly complete down to a flux limit of 3e-14 cgs (0.5-2 keV). We show that for X-ray surveys containing sources with low count rate spectral slopes estimated using simple hardness ratios in the ROSAT band can be biased. Instead we analyse three-colour X-ray data using statistical techniques appropriate to the Poisson regime which removes the effects of this bias. We have then applied this technique to the RIXOS survey to study the spectral properties of the sample. For the AGN we find an average energy index of 1.05+-0.05 with no evidence for spectral evolution with redshift. Individual AGN are shown to have a range of properties including soft X-ray excesses and intrinsic absorption. Narrow Emission Line Galaxies also seem to fit to a power-law spectrum, which may indicate a non-thermal origin for their X-ray emission. We infer that most of the clusters in the sample have a bremsstrahlung temperature >3 keV, although some show evidence for a cooling flow. The stars deviate strongly from a power-law model but fit to a thermal model. Finally, we have analysed the whole RIXOS sample containing 1762 sources. We find that the mean spectral slope of the sources hardens at lower fluxes in agreement with results from other samples. However, a study of the individual sources demonstrates that the hardening of the mean is caused by the appearance of a population of very hard sources at the lowest fluxes. This has implications for the nature of the soft X-ray background.Comment: 31,LaTeX file, 2 PS files with Table 2 and 22 PS figures. MNRAS in pres