428 research outputs found
Validation of a liquid chromatography method for the simultaneous quantification of ochratoxin A and its analogues in red wines
A validated high-performance liquid chromatography (HPLC) method with
fluorescence detection for the simultaneous quantification of ochratoxin A (OTA) and
its analogues (ochratoxin B (OTB), ochratoxin C (OTC) and methyl ochratoxin A
(MeOTA)) in red wine at trace levels is described. Before their analysis by HPLC-FLD,
ochratoxins were extracted and purified with immunoaffinity columns from 50 mL of
red wine at pH = 7.2. Validation of the analytical method was based on the following
parameters: selectivity, linearity, robustness, limits of detection and quantification,
precision (within-day and between-day variability), recovery and stability. The limits of
detection (LOD) in red wine were established at 0.16, 0.32, 0.27 and 0.17 ng L-1 for
OTA, OTB, MeOTA and OTC, respectively. The limit of quantification (LOQ) was
established as 0.50 ng L-1 for all of the ochratoxins. The LOD and LOQ obtained are the
lowest found for OTA in the reference literature up to now. Recovery values were 93.5,
81.7, 76.0 and 73.4% for OTA, OTB, MeOTA and OTC, respectively. For the first time,
this validated method permits the investigation of the co-occurrence of ochratoxins A,
B, C and methyl ochratoxin A in 20 red wine samples from Spain
Quantification of ochratoxin A and five analogs in Navarra red wines
Ochratoxin A (OTA), B (OTB) and their methyl (MeOTA, MeOTB) and ethyl (OTC,
EtOTB) esters were evaluated in 51 red wine samples from Navarra (Spain). Detectable
levels of OTA and OTB were found in 100% of the samples, and 71% showed the
presence of OTC. The six ochratoxins appeared simultaneously in 18% of the samples.
Results indicated that OTC is hydrolyzed to OTA in red wine. Therefore, ochratoxin
intake from wine can be underestimated when only assessed by OTA analysis.
Analyzed Navarra wines are scarcely contaminated with ochratoxins and their
contribution to human intake is low, with the worst case being 4.7% and 6.6% of the
provisional tolerable weekly intake (PTWI) for OTA and for the sum of ochratoxins,
respectively. No significant differences were generally found between vintages. With
the exception of OTA, no significant differences were observed between organic and
traditional farming. Levels of ochratoxins were positively correlated with temperature
and inversely correlated with humidity and rainfall
Levels of ochratoxins in Mediterranean red wines
The co-occurrence of ochratoxin A (OTA) and its five analogs (OTB, OTC, MeOTA, MeOTB and EtOTB) in 96 red wine samples from Mediterranean countries has been demonstrated, for the first time, in this study.
OTA was detected in 99 % of the samples (<LOD-455 ng·L-1). This mycotoxin
appeared simultaneously with OTB (2.05 - 119 ng·L-1) in all the samples and in 89.6%
of them OTC (<LOD - 31.5 ng·L-1) also accompanied both. OTB appears at comparable
levels and incidence just like OTA does, and OTC median concentration is
approximately 10 % of that of OTA. A high statistical association was found between
the concentrations of OTA-OTB and OTA-OTC. MeOTA, MeOTB and EtOTB were
detected in 62.5, 83.3 and 83.3 % of the samples, respectively. In 44.8 % of the wines,
the 6 ochratoxins appeared simultaneously.
There was no evidence for ochratoxin A levels being greater in wines from
Southern Europe than those described from North Europe. Samples from North Africa
presented statistically the highest values for OTA, OTB, OTC and EtOTB
Co-occurrence of aflatoxins, ochratoxin A and zearalenone in breakfast cereals from spanish market
Forty-six breakfast cereal samples from the Spanish market have been analyzed for the
occurrence of aflatoxins (AFB1, AFG1, AFB2 and AFG2), ochratoxin A (OTA) and
zearalenone (ZEA). According to the results, 9% of the samples were contaminated with
AFB1 although no sample exceeded the LOQ (0.2 μg kg-1), and no sample presented
detectable levels of the other aflatoxins (AFB2, AFG1 and AFG2). Zearalenone and
OTA contaminated 48 and 39% of the samples, respectively, with mean values of the
samples having quantification levels of 25.40 and 0.37 μg kg-1, respectively. The co23
occurrence of OTA and ZEA was observed in 28% of the samples. Aflatoxin B1
appeared only in the corn-based breakfast cereals, whereas ZEA and OTA showed the
highest contamination rates in the samples containing wheat and wheat and rice,
respectively. No sample of high-fiber content was contaminated with AFB1, whereas
OTA and ZEA occurred with higher incidence in high-fiber content samples. Moreover,
the daily exposure to AFB1, OTA and ZEA is discussed
Ellipsometric Study of SiO x Thin Films by Thermal Evaporation
Abstract This paper presents a study of amorphous SiO x thin films by means of Variable Angle Spectroscopic Ellipsometry (VASE) technique. Tauc Lorentz, Lorentz and Cauchy models have been used to obtain physical thickness and complex refractive index (n and k) from experimental data. In order to obtain a wide range to x stoichiometry values, the films were prepared by vacuum thermal evaporation of SiO on glass substrates, under different and controlled deposition conditions
El Servicio de Validación de Copernicus EMS como vector de mejora de la cartografía de emergencias basada en Sentinel
[EN] The Copernicus Emergency Management Service (CEMS) is coordinated by the European Commission and “provides all actors involved in the management of natural disasters, man-made emergency situations, and humanitarian crises with timely and accurate geo-spatial information derived from satellite remote sensing and complemented by available in situ or open data sources”. It includes two components, Early Warning and Monitoring and Mapping. The latter provides on demand geo-spatial information derived from satellite imagery during all phases of the disaster management cycle. It includes 3 systems, Rapid Mapping (RM), Risk and Recovery Mapping (RRM), and a Validation Service. RM provides geospatial information immediately after a disaster to assess its impact; RRM in the prevention, preparation and reconstruction phases; and the Validation Service is in charge of validating and verifying the products generated by both, and of collecting and analyzing users’ feedback. The wide spectrum of activities framed in the Validation Service has allowed it to become a vector to improve the Mapping component through the testing of new methodologies, data input type, or approach for the creation of emergency cartography in the frame of the CEMS. The present paper introduces the main investigation lines based on Sentinel-1 and 2 for flood and fire monitoring that could be implemented in the CEMS services taking into consideration the characteristics of the Mapping component in terms of products to create and time constraints. The applicability of Sentinel-1 for flood monitoring based on the backscattering, the MultiTemporal Coherence (MTC), and dual polarization; and for burnt area delineation based on MTC was studied, while Sentinel-2 was used for burnt area delineation based on vegetation indices. Results indicate that proposed methodologies might be appropriate for the creation of crisis information products in large areas, due to the relative easy and fast implementation compared to classic photo interpretation, although further applicability analyses should be carried out.[ES] El Servicio de Gestión de Emergencias de Copernicus (CEMS), está coordinado por la Comisión Europea y “provee de información geoespacial precisa y oportuna derivada de la teledetección satelital y completada por fuentes de datos disponibles in situ o abiertas a todos los actores involucrados en la gestión de emergencias, bien sean derivadas de desastres naturales o producidos por el hombre, o de crisis humanitarias”. El servicio tiene dos componentes, uno de alerta temprana y monitoreo y otro de creación de mapas. El servicio de mapeo se encarga de proveer, bajo demanda, a los diferentes agentes de emergencias de información geoespacial derivada de imágenes de satélite en todas las fases de la gestión de emergencias, consta de 3 sistemas, Rapid Mapping (RM), Risk and Recovery Mapping (RRM), y Validation. RM aporta información inmediatamente después de un desastre para evaluar su impacto; RRM en las fases de prevención, preparación y reconstrucción; y la Validación se encarga de validar y verificar los productos generados por ambos, y de recoger y analizar los comentarios de los usuarios. El amplio espectro de actividades enmarcadas en él le ha permitido ser vector de mejora de los servicios de mapeo de emergencias mediante el testeo de nuevas metodologías, tipos de datos, o enfoques para la creación de cartografías de emergencias en el marco de CEMS. El presente artículo describe las principales líneas de investigación en el uso de datos Sentinel-1 y 2 para la monitorización de inundaciones e incendios, que se podrían implementar en el futuro en el marco de CEMS. La aplicabilidad de Sentinel-1 para el monitoreo de inundaciones basado en la retrodispersión, la coherencia multitemporal (MTC) y la polarización dual; y se estudió la delimitación del área quemada basada en MTC. Sentinel-2 se usó para delimitar áreas quemadas en base a índices de vegetación. Los resultados indican que las metodologías propuestas podrían ser apropiadas para la creación de productos de información de crisis en grandes áreas, debido a la implementación relativamente fácil y rápida en comparación con la fotointerpretación clásica, aunque deberían realizarse más análisis para su aplicación en el marco de CEMS.The authors gratefully acknowledge the contribution of Massimiliano Rossi and Antigoni Maistrali
for the preparation of the materials analysed in this
work.Donezar-Hoyos, U.; Albizua-Huarte, L.; Amezketa-Lizarraga, E.; Barinagarrementeria-Arrese, I.; Ciriza, R.; De Blas-Corral, T.; Larrañaga-Urien, A.... (2020). The Copernicus EMS Validation service as a vector for improving the emergency mapping based on Sentinel data. Revista de Teledetección. 0(56):23-34. https://doi.org/10.4995/raet.2020.13770OJS233405
Measurements of differential cross sections of Z/gamma*+jets+X events in proton anti-proton collisions at sqrt{s}=1.96 TeV
We present cross section measurements for Z/gamma*+jets+X production,
differential in the transverse momenta of the three leading jets. The data
sample was collected with the D0 detector at the Fermilab Tevatron proton
anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to
an integrated luminosity of 1 fb-1. Leading and next-to-leading order
perturbative QCD predictions are compared with the measurements, and agreement
is found within the theoretical and experimental uncertainties. We also make
comparisons with the predictions of four event generators. Two
parton-shower-based generators show significant shape and normalization
differences with respect to the data. In contrast, two generators combining
tree-level matrix elements with a parton shower give a reasonable description
of the the shapes observed in data, but the predicted normalizations show
significant differences with respect to the data, reflecting large scale
uncertainties. For specific choices of scales, the normalizations for either
generator can be made to agree with the measurements.Comment: Published in PLB. 11 pages, 3 figure
Dependence of the production cross section on the transverse momentum of the top quark
We present a measurement of the differential cross section for
events produced in collisions at TeV as a function
of the transverse momentum () of the top quark. The selected events
contain a high- lepton (), four or more jets, and a large imbalance
in , and correspond to 1 fb of integrated luminosity recorded
with the D0 detector. Each event must have at least one candidate for a
jet. Objects in the event are associated through a constrained kinematic fit to
the process. Results
from next-to-leading-order perturbative QCD calculations agree with the
measured differential cross section. Comparisons are also provided to
predictions from Monte Carlo event generators using QCD calculations at
different levels of precision.Comment: 8 pages, 6 figures, 4 tables, updated to reflect the published
versio
Measurement of the W boson mass
We present a measurement of the W boson mass in W -> ev decays using 1 fb^-1
of data collected with the D0 detector during Run II of the Fermilab Tevatron
collider. With a sample of 499830 W -> ev candidate events, we measure M_W =
80.401 +- 0.043 GeV. This is the most precise measurement from a single
experiment.Comment: As published in PR
Measurement of the t-channel single top quark production cross section
The D0 collaboration reports direct evidence for electroweak production of
single top quarks through the t-channel exchange of a virtual W boson. This is
the first analysis to isolate an individual single top quark production
channel. We select events containing an isolated electron or muon, missing
transverse energy, and two, three or four jets from 2.3 fb^-1 of ppbar
collisions at the Fermilab Tevatron Collider. One or two of the jets are
identified as containing a b hadron. We combine three multivariate techniques
optimized for the t-channel process to measure the t- and s-channel cross
sections simultaneously. We measure cross sections of 3.14 +0.94 -0.80 pb for
the t-channel and 1.05 +-0.81 pb for the s-channel. The measured t-channel
result is found to have a significance of 4.8 standard deviations and is
consistent with the standard model prediction.Comment: 7 pages, 6 figure
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