Influencia estacional y de las mareas en la variabilidad del óxido nitroso en el estuario del Tajo (Portugal)

In order to evaluate seasonal and tidal influence on the variability of dissolved nitrous oxide (N2O) in the Tagus estuary, Portugal, water sampling was carried out along the salinity gradient (May and November 2006) and during several tidal cycles (February and April 2007) at a fixed site. N2O and other relevant environmental parameters, temperature, salinity, dissolved oxygen and inorganic nitrogen forms (nitrate, nitrite and ammonium) were measured. Dissolved N2O concentrations showed strong tidal and seasonal variability, with the highest values occurring in February 2007 (13.7 nM, spring tide) and November 2006 (18.4 nM, upper estuary), apparently related to major Tagus river discharge. The existence of N2O sources was noticed in middle estuary. During spring tide, the input from external sources may be augmented by water column nitrification, making this process a contributor to the enhancement of N2O concentration in the estuary. Estimated N2O air-sea fluxes to the atmosphere reached a maximum value of ~10.4 μmol m-2 d-1 in February 2007 during spring tide and in May 2006 in the upper and lower (left bank) estuary. Although the Tagus estuary behaves predominantly as a source of atmospheric N2O, it appears to be a weaker source than other, more eutrophic estuaries.Para evaluar la influencia estacional y de las mareas en la variabilidad de óxido de nitrógeno disuelto (N2O) en el estuario del Tajo (Portugal) se han recogido muestras de agua a lo largo del gradiente de salinidad (mayo y noviembre de 2006) y durante varios ciclos de las mareas (febrero y abril 2007) en una estación fija. Han sido medidos N2O y otros parámetros relevantes del medio ambiente, temperatura, salinidad, oxígeno disuelto y las formas de nitrógeno inorgánico (nitrato, nitrito, amonio). Las concentraciones de N2O disuelto mostraron una fuerte variabilidad estacional y de las mareas, observándose los valores más altos en febrero de 2007 (13.7 nM, marea viva) y noviembre de 2006 (18.4 nM, estuario superior), aparentemente relacionados con el mayor caudal del río Tajo. La existencia de fuentes de N2O se observó en el estuario del medio. Durante la marea viva, la entrada de fuentes externas puede ser ampliada por la nitrificación en la columna de agua, haciendo que este proceso contribuya al incremento de la concentración de N2O en el estuario. Los flujos estimados de N2O a la atmósfera alcanzaron un valor máximo de 10.4 μmol m-2 d-1, ya sea en febrero de 2007, durante la marea viva, o en mayo de 2006, en el estuario superior. Aunque el estuario del Tajo se comporta principalmente como una fuente de N2O atmosférico, parece ser una fuente más débil que otros estuarios más eutróficos

Uncertainty estimation and in-house method validation of HPLC analysis of carotenoids for food composition data production

The method for separation and quantitative determination of the main carotenoids in food by high-performance liquid chromatography (HPLC) was in-house validated. Tomato (Lycopersicon esculentum M.) as food matrix was used to demonstrate its linearity, repeatability, intermediate precision, detection and quantification limits, sensitivity and bias. In addition, stability of carotenoids was studied in function of temperature and time. Method accuracy was quantified through measurement uncertainties estimate based on this validation study. Furthermore, a study was conducted to evaluate variability coming from location in an experimental field composed by 12 subfields. The use of two metal free reverse phase columns and an organic mobile phase based on acetonitrile, methanol and dichloromethane enabled the separation of the six target compounds (trans-a-carotene, trans-b-carotene, b-cryptoxanthin, all-lycopene, lutein, zeaxanthin) within a 30 min run; detection at 450 nm and external calibration allowed the quantification of the analytes. Carotenoids concentration and measurement uncertainty, in mg/100 g, in tomato varieties ‘‘lido” and ‘‘for salad” were, respectively, 1.0 ± 0.14 and 0.39 ± 0.056 for trans-b-carotene, 8 ± 2.0 and 2.3 ± 0.57 for all-lycopene and 0.10 ± 0.017 and 0.08 ± 0.015 for lutein; trans-a-carotene, b-cryptoxanthin and zeaxanthin were not detected in both varieties (detection limits, in lg/100 g, 0.81, 0.57 and 0.77, respectively). For b-carotene and lutein, uncertainty associated with the entire process including small-scale within-region variation was statistically different, at a significance level of 5%, from measurement uncertainty (which includes sampling in the laboratory)

Apresentação do dossiê "O mar no imaginário religioso: cultos, espaços e representações

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Evaluation and validation of detailed and simplified models of the uncertainty of unified pHabsH2O measurements in aqueous solutions

Highlights • First detailed evaluation of the uncertainty of pHabsH2O measurements. • Bottom-up uncertainty evaluations proven valid for 95% confidence. • Monte Carlo Simulation of pHabsH2O measurement ladder with least-squares minimisation. • Described simplified and detailed bottom-up uncertainty evaluations are equivalent. • Measurements from 2 to 10 pHabsH2O with a 95% expanded uncertainty of 0.26–0.51.The use of the unified pH concept, pHabsH2O, applicable to aqueous and non-aqueous solutions, which allows interpreting and comparison of the acidity of different types of solutions, requires reliable and objective determination. The pHabsH2O can be determined by a single differential potentiometry measurement referenced to an aqueous reference buffer or by a ladder of differential potentiometric measurements that allows minimisation of inconsistencies of various determinations. This work describes and assesses bottom-up evaluations of the uncertainty of these measurements, where uncertainty components are combined by the Monte Carlo Method (MCM) or Taylor Series Approximation (TSM). The MCM allows a detailed simulation of the measurements, including an iterative process involving in minimising ladder deviations. On the other hand, the TSM requires the approximate determination of minimisation uncertainty. The uncertainty evaluation was successfully applied to measuring aqueous buffers with pH of 2.00, 4.00, 7.00, and 10.00, with a standard uncertainty of 0.01. The reference and estimated values from both approaches are metrologically compatible for a 95% confidence level even when a negligible contribution of liquid junction potential uncertainty is assumed. The MCM estimated pH values with an expanded uncertainty, for the 95% confidence level, between 0.26 and 0.51, depending on the pH value and ladder inconsistencies. The minimisation uncertainty is negligible or responsible for up to 87% of the measurement uncertainty. The TSM quantified measurement uncertainties on average only 0.05 units larger than the MCM estimated ones. Additional experimental tests should be performed to test these uncertainty models for analysis performed in other laboratories and on non-aqueous solutions

Global Women’s Breakfast (GWB): #UnidaspelaQuímica

Global Women’s Breakfast (GWB): #BoundbyChemistry. Global Women’s Breakfast is an initiative of the International Union of Pure and Applied Chemistry, aiming to give women scientists, from all over the world, the opportunity to know each other, communicating virtually and sharing their experiences. Many countries joined this initiative and Portugal was not an exception, with its participation already at the first Networking Breakfast in 2011, celebrating the year of the centenaries of Marie Curie Nobel Prize in Chemistry, the Portuguese Chemical Society and the Faculdade de Ciências da Universidade de Lisboa as well. The success of these networking breakfasts, involving students, young researchers, and scientists, encouraged its further organization in Portugal, annually since 2019. This article describes the interventions of Portuguese women scientists, coming from Institutions throughout Portugal, in the Global Women’s Breakfast as partners in their mission as scientists, creative and open to international collaborations. Global Women's Breakfast é uma iniciativa criada pela International Union of Pure and Applied Chemistry para dar oportunidade às mulheres cientistas de todo o mundo de se conhecerem, comunicando virtualmente e compartilhando as suas experiências. A adesão dos países foi muito elevada e Portugal não foi exceção, participando já no primeiro Networking Breakfast em 2011, Ano Internacional da Química, no qual se celebraram os centenários do Prémio Nobel da Química a Marie Curie, da Sociedade Portuguesa de Química e da Faculdade de Ciências da Universidade de Lisboa. O sucesso destes pequenos-almoços em rede, que envolvem estudantes, jovens investigadoras e cientistas, encorajou a continuação da participação de Portugal anualmente, desde 2019. Este artigo descreve a intervenção de mulheres cientistas portuguesas, pertencentes a instituições de Norte a Sul do país, no Global Women’s Breakfast, cúmplices na sua missão de cientistas, criativas e abertas à colaboração internacional

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Traceability of pH to the Mole

Free acidity of aqueous solutions was initially defined in 1909 by Søren Peter Lauritz Sørensen as pH = −lgcH+ (c/mol·dm−3 or m/mol·kg−1 of the free hydrogen ions in solution, H+) soon (1910) was changed to pH = paH+ = −lgaH+, integrating the new concepts of activity, ai and activity coefficient γi, for the ionic species i under concern, H+ in this case; it is ai = −lg(miγi). Since individual ions do not exist alone in solution, primary pH values cannot be assigned solely by experimental measurements, requiring extra thermodynamic model assumptions for the activity coefficient, γH+, which has put pH in a unique situation of not being fully traceable to the International System of Units (SI). Also the concept of activity is often not felt to be as perceptible as that of concentration which may present difficulties, namely with the interpretation of data. pH measurements on unknown samples rely on calibration of the measuring setup with adequate reference pH buffers. In this work, the assignment of pH values to buffers closely matching the samples, e.g., seawater, is revisited. An approach is presented to assess the quantity pmH+ = −lgmH+ profiting from the fact that, contrary to single ion activity coefficients, mean activity coefficients,   can be assessed based on experimentally assessed quantities alone, γExp ±, thus ensuring traceability to the mole, the SI base unit for amount of substance. Compatibility between γExp ± and mean activity coefficient calculated by means of Pitzer model equations, γPtz ±, validates the model for its intended use

Influence of geographical conditions on carotenoid content of Portuguese cabbage

Rationale and objectives. Carotenoid content of food plants often varies not only with species and variety but also with natural factors such as light exposition, soil and temperature. The extent of this variation is not established since many non-controllable factors are involved for a long period of time and these factors may affect different plants in different manners. The objective of this work is to study the carotenoid content of the variety Portuguese cabbage in three landraces of three country regions and to contribute to the definition of the respective sampling plan. Materials and methods. Three different samples of Portuguese cabbage (Brassica oleracea L. var. costata D.C.) landraces, Valhascos, glória de Portugal and penca respectively from Ribatejo (centre), Beira Alta (inland north) and Minho (north) were studied in relation to their carotenoid content which was quantified, after extraction, by a reversed phase HPLC method. Analytical measurement uncertainty was estimated based on data from the in-house method validation. The between samples variance was compared with the measurement uncertainty through an F-test. Results. Lutein and all-trans- -carotene content in Portuguese cabbage samples were, in mg/100 g, respectively 4.7 and 3.6 for Valhascos, 0.52 and 0.46 for glória de Portugal, and 3.3 and 2.8 for penca. Relative analytical measurement uncertainty was 0.19 and 0.21, respectively, for lutein and all-trans- - carotene. At a significance level of 5%, Valhascos and penca landraces did not present statistically significant differences. However, glória de Portugal landrace was statistically different from the last two. Conclusions. The analysed Portuguese cabbages are very good sources of lutein and -carotene presenting diet advantages. The results show that carotenoid content of Portuguese cabbage varies with the geographical region of production easily overshadowing contributions from the analytical process. That factor should be addressed in the production of data for Food Composition Data Bases and based on this study, for the group of Valhascos and penca, and for lutein, 5 primary samples are necessary to estimate the population’s mean value, with a 95% confidence and 10% accuracy. Keywords. Carotenoid, Uncertainty evaluation, Sampling, HPLC, Foo