Metals, environment and life interference of vanadium in living systems and their contextualization in teaching experimental sciences

The ammonium metavanadate (V + 5), widely used in chemical industry is a toxic compound which is involved in several cases of enzyme inhibition. The alkaline phosphatase (ALP) a zincglycoenzyme implicated in cell growth and apoptosis can be affected by the presence of metals like vanadium. The main objective of this study was to interest young students to the toxicity of metals, exploring the effects of vanadium on the ALP activity, using Saccharomyces cerevisiae as biological model. This activity was developed by a pilot group of students from Dom Manuel Martins high school of Setúbal, Portugal, which follow the yeast growth at 640nm and obtained cell extracts from S. cerevisiae growing at 28 ◦C in YPD medium (glucose 2% (w / v)) in absence and presence of 25 or 75mM NH4VO3, for the quantification of proteins at 720nm by Lowry’s method and ALP activity determination at 405 nm, using pNPP as substrate. The young people observed a growth inhibition of yeast cells exposed to vanadium as well as a decrease of total proteins and ALP activity level, facts which put in evidence a sharp toxicological effect of vanadium in eukaryotic cell. The average score obtained before and after the experimental activity (41%) and (63%), respectively, using the same set of questionsproblem, revealed an overall positive performance of skills developed by students, in the scope of metals toxicological effects in eukaryote cells. In more detail, it was also observed a positive and significant effect in each experimental phase (p < 0.05), before and after the development of the action. The assessment of skills developed by students showed an improvement of their compliance level, thereby acquiring a significant learning. The results for the opinion survey showed that most respondents classified the activity and its difficulty degree as good

On the error of calculation of heat gains through walls by methods using constant decrement factor and time lag values

A transient heat transfer model was developed to numerically predict the thermal behaviour of the external walls of a room under realistic outdoor conditions. The excitation is not simply sinusoidal even though it is considered to have daily periodicity. The numerical model is based on the finite difference method and handles one-dimensional heat conduction through multilayered walls. The boundary condition at the outer surface of the wall is described with the sol-air temperature concept. The temperatures of indoor air and of other internal surfaces in the room are assumed to be equal and constant. The numerical results were used to calculate values of the decrement factor and time lag of several walls. The calculation followed two methods found in literature, in which these parameters are assumed constant, distinguished by the temperature evolution used: the sol-air or the wall's outer surface. Additionally, the inner surface temperature is used in both methods. The walls investigated range from low to high mass construction, face towards various directions and have light or dark coloured sunlit outer surfaces. The heat fluxes at the inner surface of the walls predicted by numerical modelling and estimated by the simplified methods are compared in detail to conclude on the validity of these simplified methods. As a by-product it is also possible to conclude on the dependence of the decrement factor and of the time lag on the outer surface colour and on the orientation of different types of walls. The results show that both simplified methods have poor accuracy in a significant number of cases. Also, it was found that the wall's azimuth significantly affects the time lag

Seroprevalence of antibodies against SARS-CoV-2 among health care workers in a Portuguese hospital

"Background: Health care workers (HCW) are presumably exposed to a higher risk of infection by SARS-CoV-2 and could possibly represent a source of transmission to susceptible patients. Thus, characterization of SARS-CoV-2 infection among HCW is necessary to better understand the determinants of viral transmission and properly implement strategies to prevent dissemination and protect HCW and vulnerable patients. The aim of this study was to estimate the seroprevalence of antibodies against SARS-CoV-2 in a Portuguese tertiary hospital, in the period of July 2020 to March 2021, before the generalized use of the SARS-CoV-2 vaccine, characterize its evolution over time, and identify risk factors associated with seroconversion. Methods: HCW were approached to collect serum samples for qualitative SARS-CoV-2 antibody testing and completion of an online survey capturing demographics, previous symptoms, and details of health care and community exposure. Odds ratio with bivariable and multivariable logistic regression was used to assess characteristics associated with seroprevalence. Results: One thousand HCW were included for analysis. Two hundred nineteen HCW (22%) were seropositive for immunoglobulin G against SARS-CoV-2, and 166 (17%) were seropositive for immunoglobulin M, most of whom reported a previous diagnosis of SARS-CoV-2 infection. The risk factors associated with seroconversion included a previous COVID-19 diagnosis, contact with patients, occupational contact with colleagues, and outside contact. However, in a multivariate logistic regression analysis, only a previous diagnosis and outside contact were associated with seroconversion. Seropositivity decreased over time, especially 28 weeks after infection. Conclusion: HCWs have a high seroprevalence for SARS-CoV-2 infection, probably due to a combination of health care and community exposure. Seropositivity decreases over time, but further studies are needed to better understand our adaptive immune response.

Two photon decay of π0\pi^0 and η\eta at finite temperature and density

A comparative study of the anomalous decays $\pi^0, \eta \to\gamma\gamma$, at finite temperature and at finite density, is performed in the framework of the three--flavor Nambu--Jona-Lasinio. The similarities and differences between both scenarios are discussed. In both cases the lifetimes of these mesons decrease significantly at the critical point, although this might not be sufficient to observe enhancement of these decays in heavy-ion collisions.Comment: 5 pages, 1 figure. Talk given at Strange Quark Matter 2004, Cape Town, South Africa, 15-20 September, 200

Caracterização dos argissolos amarelos com adição de resíduos de madeira: uma alternativa de uso como cobertura em solos da Amazônia paraense.

Em solos altamente intemperizados, como ocorre nos trópicos, a razão de seu empobrecimento está relacionada à lixiviação dos nutrientes das camadas superficiais. Uma alternativa para minimizar esta perda de nutrientes seria a utilização de coberturas orgânicas verdes ou mortas (mulch) nestes solos. Nesse sentido, com o intuito de caracterizar os aspectos morfológicos, físicos e químicos dos solos com e sem adição de resíduos de madeira como cobertura, sob as culturas de paricá (Schizolobium amazonicum) e pupunha (Bactris gasipaes), foram selecionados e coletados 32 amostras de 4 perfis de solo das áreas de plantio de paricá e pupunha com e sem adição de resíduos de madeira. A utilização de resíduos de madeira como cobertura favoreceu a diminuição da densidade, com valores entre 1,19 a 1,33 kg.dm-3 para os solos com adição de resíduos, e de 1,19 a 1,67 kg.dm-3 para os solos sem adição. A mesma influência pode ser percebida no aumento da porosidade nos solos com adição de material, com valores de 0,48 a 0,46 m3.m-3 nos horizontes superficiais, enquanto que os solos sem resíduos demonstraram resultados de 0,35 a 0,38 m3.m-3. Os resultados de pH em água, nos solos com cobertura de resíduos de madeira, variaram de 4,6 a 6 e, os solos sem adição, de 4,6 a 5,2, podendo ser verificado que a adição de resíduos de madeira favoreceu o aumento do pH no solo. Os valores mais elevados para a saturação de bases foram observados também para os solos com utilização de resíduos de madeira como cobertura, cujos valores variaram entre 26% a 54%, enquanto que os perfis sem adição de material orgânico apresentaram variação entre 26% a 39%. O uso adequado de resíduos de madeira no solo desempenhou papel importante na disponibilidade de alguns nutrientes, como o cálcio e o magnésio, e diminuiu a acidez dos solos. Assim, a utilização de resíduos de madeira como cobertura no solo em sistemas agroflorestais é satisfatória por permitir uma destinação adequada para estes materiais, além de melhorar as condições ambientais dos solos amazônicos

Influence of the rainfall in the content of nutrients in litter in agroforestry systems managed with burning and without burning in Amazon.

This study evaluated the nutrient content of the litter, testing different treatments with burning and no burning, of the vegetation, to identify which one provides better efficiency in operation and production of nutrients in different seasonal conditions. The study area is located on the property of the family farmer, initially selected by a diagnosis socioeconomic, community Benjamin Constant, in northeastern Para. Litter was collected during two periods: dry season (November) and rainy (March) in 2009. For the collection of litter samples, we used collectors measuring (0.25 × 0.25 m2), which were placed directly on the soil surface. The collected material was stored in paper bags and taken to the laboratory for Chemical Analysis of the Brazilian Agricultural Research Corporation (EMBRAPA), which was determined by analyses of macronutrients (N, P, K, Ca, Mg, Na) and micronutrients (Fe, Cu, Mn, Zn). The highest concentrations of macronutrients were found in N for agroforestry systems with and without burning in two seasons (wet and dry). All macronutrients showed influence of seasonality, which was verified by the wide variation in nutritional behavior. The decreasing concentration of nutrients was presented N > Ca > Mg > Na > K > P in agroforestry system with burning, with maximum values of all nutrients in the rainy season, and N, P, K, Ca, Na in higher concentrations in agroforestry system without burning, and showed only the Mg peak in agroforestry system with burning. The behavior of the concentration of nutrients was opposite to that observed one, for all elements analyzed showed a reduction in the concentrations of nutrients in the dry season. The decreasing concentration of nutrients was presented Fe > Mn > Zn > Cu

Microbial biomass and soil chemical properties under different land use systems in Northeastern Pará.

parte, à expansão da fronteira agrícola, utilizando áreas já antropizadas ou avançando sobre a vegetação primária. Ao mesmo tempo, os sistemas agrícolas, na pequena produção, continuam utilizando o fogo no preparo da área, o que leva à perda da capacidade produtiva dos solos em curto espaço de tempo, forçando a abertura de novas áreas. Este trabalho avaliou o efeito de métodos de preparo do solo e tempo de pousio que envolvem queima e trituração da vegetação, com permanência na superfície ou incorporada ao solo, com ou sem adubação mineral, em duas épocas do ano sobre os atributos químicos e biológicos do solo. O experimento foi instalado em 1995 em um Latossolo Amarelo do campo experimental da Embrapa Amazônia Oriental, no nordeste do Estado do Pará. O delineamento experimental foi em blocos casualizados, arranjados em esquema fatorial 2 x 6, sendo dois sistemas de manejo e seis tratamentos, estudados em duas épocas de coleta. Os sistemas de manejo envolveram as culturas de arroz (Oriza sativa), seguido de feijão-caupi (Vigna unguiculata) e mandioca (Manihot esculenta). Um sistema constou de dois ciclos de cultivo seguidos, deixando em pousio por três anos; e o outro, de um ciclo de cultivo, deixando em pousio por três anos. Os tratamentos foram: corte e queima da vegetação, com adubação NPK (Q+NPK); corte e queima da vegetação, sem adubação NPK (Q-NPK); corte e trituração da vegetação, deixando-a na superfície do solo, com adubação NPK (C+NPK); corte e trituração da vegetação, deixando-a na superfície do solo, sem adubação NPK (C-NPK); corte e trituração da vegetação, com incorporação e com adubação NPK (I+NPK); e corte e trituração da vegetação, com incorporação e sem adubação NPK (I-NPK). As coletas de solo foram realizadas na estação mais chuvosa (abril de 2006) e na menos chuvosa (setembro de 2006), na profundidade de 0,0?0,1 m. Em cada parcela, foram coletadas 10 amostras simples para compor uma amostra composta. O sistema de manejo mais intensivo apresentou maiores teores de C microbiano (Cmic) e N microbiano (Nmic), ao passo que o sistema menos intensivo mostrou maio teor de C orgânico. Os tratamentos que apresentaram maior teor de Cmic e Nmic foram aqueles em que houve corte, trituração e deposição da biomassa na superfície do solo. Os atributos químicos nos dois sistemas de manejo encontram-se em faixas que enquadram os solos como de baixa fertilidade; no entanto, P e K (no período chuvoso) foram mais elevados no sistema de manejo menos intensivo

The QCD critical end point in the PNJL model

We investigate the role played by the Polyakov loop in the dynamics of the chiral phase transition in the framework of the so-called PNJL model in the SU(2)sector. We present the phase diagram where the inclusion of the Polyakov loop moves the critical points to higher temperatures, compared with the NJL model results. The critical properties of physical observables, such as the baryon number susceptibility and the specific heat, are analyzed in the vicinity of the critical end point, with special focus on their critical exponents. The results with the PNJL model are closer to lattice results and we also recover the universal behavior of the critical exponents of both the baryon susceptibility and the specific heat.Comment: 12 pages, 3 figures, EPL versio