University of Madeira

About: University of Madeira is a education organization based out in Funchal, Portugal. It is known for research contribution in the topics: Population & Dendrimer. The organization has 1014 authors who have published 2759 publications receiving 59457 citations.

High-Throughput Analytical Strategy Based on Modified QuEChERS Extraction and Dispersive Solid-Phase Extraction Clean-up Followed by Liquid Chromatography-Triple-Quadrupole Tandem Mass Spectrometry for Quantification of Multiclass Mycotoxins in Cereals

Abstract: A simple, reliable, efficient, selective and sensitive QuEChERS-based (quick, easy, cheap, effective, rugged and safe) sample preparation strategy, involving an initial partitioning step using acidified acetonitrile (ACN), MgSO4, NaCl and citrate buffer salts, combined with dispersive solid-phase extraction (d-SPE) clean-up, is proposed for the simultaneous multiclass mycotoxins quantification, including aflatoxins, ochratoxins, fumonisins, trichothecenes and zearalenone, in cereals. The final clear extracts were concentrated under vacuum to near dryness and taken-up with the initial mobile phase (MeOH:H2O;70:30, v/v) previous to reversed-phase liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) analysis. Careful optimization of the LC-ESI-MS/MS parameters was achieved in order to attain a fast separation and increased sensitivity. The detection was carried out on a triple-quadrupole tandem mass spectrometry (MS/MS) by electrospray ionization in positive ion mode (ESI+) with multiple reaction monitoring (MRM). Tandem MS conditions were optimised in order to increase selectivity, selecting the best transitions (parent ion to quantifier and qualifier ions) for quantification and identification. The performance of the method was assessed and compared to European Commission (EC) Regulations, by studying the selectivity, specificity, limits of detection (LOD) and quantification (LOQ), linear dynamic range (LDR), matrix effect, accuracy, precision, and uncertainty. Good linearity (r 2 > 0.9713) was achieved for all mycotoxins investigated, and LODs (S/N = 3) and LOQs (S/N = 10) were below the tolerance levels of mycotoxins set by EC. Recoveries of the extraction process, obtained with different spiked concentrations, ranged from 72.9 to 120.6 %, with relative standard deviations (RSD) lower than 23.0 %. Only in 6 % of all combinations did the RSD values exceed 15 %. Matrix effects were observed by comparing the slope of matrix-matched standard calibration with that of the solvent. The developed method was applied to evaluate the co-occurrence of multiclass mycotoxins in cereals collected at the importation points and consumer habitations at Madeira Island. Samples collected at importation points (15 wheat samples, 4 maize samples and 2 rice samples) showed the presence of DON in three wheat samples, and FB1 and HT-2 in one wheat sample. Three maize samples were detected with FB1 (two samples) and AFG2 (one sample) whereas one rice sample was detected with ZEN. The results revealed the absence of target mycotoxins on the rice samples collected at consumer habitations. None of the studied cereal samples exceeded the maximum permissible limits or indicative levels set by the EC which means that the particular Madeira Island subtropical climate conditions do not represent a major risk for cereal contamination, taking into account the investigated mycotoxins.

Meta-Theories in Research: Positivism, Postmodernism, and Critical Realism

Abstract: No scholar or researcher is able to provide robust evidences that counter the scant reflection on meta-theory - mostly ontology and epistemology - underlying management studies in general, and industrial marketing and purchasing research in particular This paper is a contribution to the indispensable discussion of meta-theoretical alternatives in research and, most importantly, the strengths and shortcomings thereof, and respective implications on research questions, objectives, and findings

Evaluation of the maize ( Zea mays L.) diversity on the Archipelago of Madeira

Abstract: The variability of 43 open-pollinated populations of maize (Zea mays L.), representing a wide range of ecological conditions on the Archipelago of Madeira, was evaluated based on the morphological and reproductive traits. Individual data of 41 traits related to earliness, plant and tassel structure and the shape of the ear and grain were analysed using multivariate analysis. The populations belonging to two major maize varieties were grouped into four groups by their degree of dissimilarity, based on discriminant analysis. The dissimilarity of these groups was confirmed by the values of the Tukey test. The racial rank of these groups was proposed and a brief description of the maize landraces was presented. This work represents the first morphological characterization and analysis of diversity of maize germplasm for the Archipelago of Madeira where the traditional agricultural practices are still keeping this Portuguese region free from corn hybrids. The description of the Madeiran corn landraces allows us to preserve the existing corn biodiversity and could be used for their registration as conservation landraces or for conservation and breeding proposes worldwide.

Modelling current transfer to cathodes in metal halide plasmas

Abstract: This work is concerned with investigation of the main features of current transfer to cathodes under conditions characteristic of metal halide (MH) lamps. It is found that the presence of MHs in the gas phase results in a small decrease of the cathode surface temperature and of the near-cathode voltage drop in the diffuse mode of current transfer; the range of stability of the diffuse mode expands. Effects caused by a variation of the work function of the cathode surface owing to formation of a monolayer of alkali metal atoms on the surface are studied for particular cases where the monolayer is composed of sodium or caesium. It is found that the formation of the sodium monolayer affects the diffuse mode of current transfer only moderately and in the same direction that the presence of metal atoms in the gas phase affects it. Formation of the caesium monolayer produces a dramatic effect: the cathode surface temperature decreases very strongly, the diffuse-mode current–voltage characteristic becomes N–S-shaped.

Evaluation of two methods for computational HLA haplotypes inference using a real dataset

Abstract: HLA haplotype analysis has been used in population genetics and in the investigation of disease-susceptibility locus, due to its high polymorphism. Several methods for inferring haplotype genotypic data have been proposed, but it is unclear how accurate each of the methods is or which method is superior. The accuracy of two of the leading methods of computational haplotype inference – Expectation-Maximization algorithm based (implemented in Arlequin V3.0) and Bayesian algorithm based (implemented in PHASE V2.1.1) – was compared using a set of 122 HLA haplotypes (A-B-Cw-DQB1-DRB1) determined through direct counting. The accuracy was measured with the Mean Squared Error (MSE), Similarity Index (I F ) and Haplotype Identification Index (I H ). None of the methods inferred all of the known haplotypes and some differences were observed in the accuracy of the two methods in terms of both haplotype determination and haplotype frequencies estimation. Working with haplotypes composed by low polymorphic sites, present in more than one individual, increased the confidence in the assignment of haplotypes and in the estimation of the haplotype frequencies generated by both programs. The PHASE v2.1.1 implemented method had the best overall performance both in haplotype construction and frequency calculation, although the differences between the two methods were insubstantial. To our knowledge this was the first work aiming to test statistical methods using real haplotypic data from the HLA region.