5,128 research outputs found
Palaeomagnetism, rock magnetism and AMS of the Cabo Magmatic Province, NE Brazil, and the opening of South Atlantic
P>Reconstruction of the South Atlantic opening has long been a matter of debate and several models have been proposed. One problem in tracing properly the Atlantic history arises from the existence of a long interval without geomagnetic reversals, the Cretaceous Normal Superchron, for which ages are difficult to assign. Palaeomagnetism may help in addressing this issue if high-quality palaeomagnetic poles are available for the two drifting continental blocks, and if precise absolute ages are available. In this work we have investigated the Cabo Magmatic Province, northeastern Brazil, recently dated at 102 +/- 1 Ma (zircon fission tracks, Ar39/Ar40). All volcanic and plutonic rocks showed stable thermal and AF demagnetization patterns, and exhibit primary magnetic signatures. AMS data also support a primary origin for the magnetic fabric and is interpreted to be contemporaneous of the rock formation. The obtained pole is located at 335.9 degrees E/87.9 degrees S (N = 24; A(95) = 2.5; K = 138) and satisfies modern quality criteria, resulting in a reference pole for South America at similar to 100 Ma. This new pole also gives an insight to test and discuss the kinematic models currently proposed for the South Atlantic opening during mid-Cretaceous
Relationships between nutrient composition of flowers and fruit quality in orange trees grown in calcareous soil
A field experiment was conducted in a commercial orange orchard (Citrus sinensis
(L.) Osb. cv. ‘Valencia late’ grafted on Citrange Troyer) established on a calcareous soil in the south of Portugal, to investigate if flower analysis could be used to predict fruit quality.
In April 1996, during full bloom, flowers were collected from 20 trees. In March 1997 the fruits were harvested and their quality evaluated. This procedure was repeated every year during three years.
Principal Component Analysis was used to evaluate the patterns of covariation in the
concentrations of nutrients in flowers and in fruit quality parameters. Stepwise selection procedures wer then used to develop regression models relating fruit quality parameters to the mineral composition of flowers. The predictive power of the regression models was evaluated using an independent set of data.
The mineral composition of flowers at full bloom could be used to predict quality
parameters of fruit in the following year, namely fruit fresh weight and the maturation
index. Magnesium, Ca and Zn registered in flowers were related to fruit fresh weight
estimations and N, P, Mg and Fe were related to fruit maturation index. Reference values
were determined for the mineral composition of flowers, corresponding to trees where
fruits had a diameter > 76 mm
Age, growth and reproduction of the Axilary Seabream, "Pagellus acarne" (Risso, 1827), from the South coast of Portugal
Axillary seabream, Pagellus acarne, caught by longlines in the Algarve (Southern Portugal), were
sampled between August 1995 and August 1996. Age was studied by counting growth increments on otoliths
and the estimated von Bertalanffy parameters were Linf = 28.82 cm, K = 0.29 year-1 and t0 = -1.47 year for
males and Linf = 32.30 cm, K = 0.18 year-1 and t0 = -2.56 year for females. Evidence of the annual periodicity of
the deposition of increments was found by marginal increment analyses. Macroscopic analysis of the
gonads and the gonad somatic index showed that reproduction occurred over an extensive period of
time, from May to November. Lengths at first maturity were 18.10 and 17.60 cm for males and females,
respectively. This species was characterized as being a protandric hermaphrodite.info:eu-repo/semantics/publishedVersio
Identification of Saccharomyces cerevisiae genes involved in the resistance to multiple stresses during Very-High-Gravity and lignocellulosic biomass industrial fermentations
Most of the current processes for bioethanol production are based on the use of Very-High-Gravity (VHG) technology and the processing of lignocellulosic biomass, limited by the high osmotic pressure and ethanol concentration in the fermentation medium, and by inhibitors resulting from biomass pre-treatments, respectively.
Aiming the optimization of strains for industrial bioethanol production an integrated approach was undertaken to identify genes required for simultaneous yeast resistance to different fermentation-related stresses. The integration of previous chemogenomics data was used to identify eight genes whose expression confers simultaneous resistance to high concentrations of glucose, acetic acid and ethanol, chemical stresses relevant for VHG fermentations; and eleven genes conferring simultaneous resistance to different inhibitors present during lignocellulosic fermentations. The expression of BUD31 and HPR1 lead to the increase of both ethanol yield and fermentation rate, while PHO85, VRP1 and YGL024w expression is required for maximal ethanol production in VHG fermentations. Five genes, ERG2, PRS3, RAV1, RPB4 and VMA8 were found to contribute to the maintenance of cell viability in wheat straw hydrolysate and/or for maximal fermentation rate of this substrate [1]. Moreover, the yeast disruptome was screened for strains with increased susceptibility to inhibitory compounds present in an industrial lignocellulosic hydrolysate obtained from wheat straw. With this genome-wide analysis, 42 determinants of resistance to inhibitors were identified showing a high susceptibility phenotype compared to the parental strain. The identified genes stand as preferential targets for genetic engineering manipulation to generate more robust and efficient industrial strains
(Bio)Sensing Strategies Based on Ionic Liquid-Functionalized Carbon Nanocomposites for Pharmaceuticals: Towards Greener Electrochemical Tools
The interaction of carbon-based nanomaterials and ionic liquids (ILs) has been thoroughly exploited for diverse electroanalytical solutions since the first report in 2003. This combination, either through covalent or non-covalent functionalization, takes advantage of the unique characteristics inherent to each material, resulting in synergistic effects that are conferred to the electrochemical (bio)sensing system. From one side, carbon nanomaterials offer miniaturization capacity with enhanced electron transfer rates at a reduced cost, whereas from the other side, ILs contribute as ecological dispersing media for the nanostructures, improving conductivity and biocompatibility. The present review focuses on the use of this interesting type of nanocomposites for the development of (bio)sensors specifically for pharmaceutical detection, with emphasis on the analytical (bio)sensing features. The literature search displayed the conjugation of more than 20 different ILs and several carbon nanomaterials (MWCNT, SWCNT, graphene, carbon nanofibers, fullerene, and carbon quantum dots, among others) that were applied for a large set (about 60) of pharmaceutical compounds. This great variability causes a straightforward comparison between sensors to be a challenging task. Undoubtedly, electrochemical sensors based on the conjugation of carbon nanomaterials with ILs can potentially be established as sustainable analytical tools and viable alternatives to more traditional methods, especially concerning in situ environmental analysisThis work was financed by FEDER—Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020—Operacional Programme for Competitiveness and Internationalization (POCI), and by Portuguese funds through FCT—Fundação para a Ciência e a Tecnologia in the framework of the project POCI-01-0145-FEDER-029547—PTDC/ASP-PES/29547/2017.
This work received support by UIDB/50006/2020, UIDP/50006/ 2020 and LA/P/0008/2020 by the Fundação para a Ciência e a Tecnologia (FCT), Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds. T.M.B.F. Oliveira thanks the Brazilian agencies CNPq (Proc. 420261/2018-4 and 308108/2020-5) and FUNCAP (Proc. BP4-0172-00111.01.00/20) for their financial support, and he is grateful to UFCA and CAPES (Finance code 001) for supporting his investigations. F.W.P. Ribeiro thanks all support provided by the UFCA’s Pro-Rectory of Research and Innovation and the funding provided by FUNCAP-BPI (Proc. BP4-0172-00150.01.00/20) and CNPq (Proc. 406135/2018-5). P. de Lima-Neto thanks the financial support received from CNPq projects 408626/2018-6 and 304152/2018-8 and FUNCAP project FCT-00141-00011.01.00/18. A. N. Correia thanks the financial support received from CNPq projects: 305136/2018-6 and 405596/2018-9info:eu-repo/semantics/publishedVersio
Sensitive bi-enzymatic biosensor based on polyphenoloxidases–gold nanoparticles–chitosan hybrid film–graphene doped carbon paste electrode for carbamates detection
A bi-enzymatic biosensor (LACC–TYR–AuNPs–CS/GPE) for carbamates was prepared in a single step by electrodeposition of a hybrid film onto a graphene doped carbon paste electrode (GPE). Graphene and the gold nanoparticles (AuNPs) were morphologically characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, dynamic light scattering and laser Doppler velocimetry. The electrodeposited hybrid film was composed of laccase (LACC), tyrosinase (TYR) and AuNPs entrapped in a chitosan (CS) polymeric matrix. Experimental parameters, namely graphene redox state, AuNPs:CS ratio, enzymes concentration, pH and inhibition time were evaluated. LACC–TYR–AuNPs–CS/GPE exhibited an improved Michaelis–Menten kinetic constant (26.9 ± 0.5 M) when compared with LACC–AuNPs–CS/GPE (37.8 ± 0.2 M) and TYR–AuNPs–CS/GPE (52.3 ± 0.4 M). Using 4-aminophenol as substrate at pH 5.5, the device presented wide linear ranges, low detection limits (1.68×10− 9 ± 1.18×10− 10 – 2.15×10− 7 ± 3.41×10− 9 M), high accuracy, sensitivity (1.13×106 ± 8.11×104 – 2.19×108 ± 2.51×107 %inhibition M− 1), repeatability (1.2–5.8% RSD), reproducibility (3.2–6.5% RSD) and stability (ca. twenty days) to determine carbaryl, formetanate hydrochloride, propoxur and ziram in citrus fruits based on their inhibitory capacity on the polyphenoloxidases activity. Recoveries at two fortified levels ranged from 93.8 ± 0.3% (lemon) to 97.8 ± 0.3% (orange). Glucose, citric acid and ascorbic acid do not interfere significantly in the electroanalysis. The proposed electroanalytical procedure can be a promising tool for food safety control
Mudanças no diagnóstico pré-natal cromossómico: indicações clínicas, amostras biológicas, metodologias e cromossomopatias
Introdução: As mudanças no diagnóstico pré-natal de anomalias cromossómicas (DPN) nos últimos 10-15 anos foram contínuas e significativas.
Objetivos: Propômo-nos analisar essa evolução: mudanças nas indicações clínicas; introdução das biópsias de vilosidades coriónicas (BVC); utilização do diagnóstico rápido de aneuploidias (DRA); estudos por microarray; alterações cromossómicas encontradas.
Metodologia: Fez-se a avaliação retrospetiva nas gestações com amostras estudadas nos triénios 2004-2006 e 2014-2016. Analisaram-se os parâmetros indicação clínica, tipo de amostra, metodologias utilizadas e resultados.
Resultados: Identificaram-se 68 fetos com cariotipo anormal em 2210 cariotipos (3,1%) em 2004-2006 e 208 fetos com cariotipo anormal em 2315 cariotipos (9,0%) em 2014-2016.
A maior frequência de anomalias encontrou-se nos casos de rastreios ecográficos e combinados indicativos de risco acrescido de anomalia numérica e de progenitores portadores de alterações cromossómicas.
As BVC permitiram respostas precoces nas gestações com anomalias numéricas e, adicionalmente, um aumento desses cariotipos (7.5% das amostras).
O DRA permitiu ter uma resposta rápida nas anomalias numéricas mais frequentes (2 dias).
As anomalias estruturais foram menos preponderantes nos cariotipos anormais (32,4% em 2004-2006 e 14.4% em 2014-2016).
Discussão e conclusões: O DRA reduziu o tempo de resposta e das decisões sobre o futuro das gestações. O microarray permitiu identificar alterações sindromáticas em situações não resolúveis por outras metodologias.
A utilização de BVC permite estabelecer uma melhor correlação fenotipo-genotipo em menores idades gestacionais.
No entanto, as gestações com anomalias numéricas têm algum risco de perda fetal no primeiro e início do segundo trimestres. Assim, algumas BVC com cariotipos anormais resultariam em perdas espontâneas, o que poderia disponibilizar outros casos para DPN.
Por outro lado, o menor número de anomalias estruturais equilibradas encontrado pode reduzir o conhecimento da variação genética nas famílias e na população.
Um novo paradigma resulta da implementação dos testes não invasivos no DPN, para os quais ainda não conhecemos todas as limitações e repercussões.N/
Chromosomal disorders and male infertility
Male factor infertility is considered a complex disorder with a largely unknown etiology that affects about 7% of men. In general, genetic abnormalities account for 15%-30% of condition and Y chromosome microdeletions are also frequent.
The study, based on our casuistic, aimed at contributing to a better understanding of the genetic causes of infertility.
A group of 410 idiopathic infertile men with non-obstructive azoospermia, oligozoospermia, or unknown semen quality (based on clinical evaluation and/or sperm counts) was retrospectively selected. Conventional karyotype was performed in all samples; Y microdeletion screen was performed in 247 samples.
Forty two abnormal karyotypes (10.2%) were found, indicating an elevated frequency of chromosome abnormalities among the selected infertile men, as compared to that of newborn populations (≈0.4%). This frequency is higher than that reported in most similar studies that pointed to frequencies ranging from 2.2%-14.3%.
Klinefelter´s syndrome was the most common chromosome disorder (4.9%). There were 18 cases with 47,XXY karyotype and 2 cases of mosaicism involving lines 47,XXY and 46,XY. Reciprocal translocations were identified in 10 cases (2.4%), particularly in men with unknown semen quality. Overall, reciprocal translocations have been found in approximately 1% of the infertile men and more commonly in azoospermics than in oligozoospermics. However, this type of association was not found in the present study.
On the other hand, Y microdeletions were identified in 16/247 cases (6.5%), more frequently in azoospermics (13.3%, corresponding to 8/60 azoospermics). Among these 8 cases, 7 presented deletions at the AZFc region.
The marked presence of chromosomal abnormalities and Y microdeletions enphasizes the relevance of studying both factors in infertile men to improve genetic counseling, to allow the development of appropriate therapies, and to expand the knowledge about the ethiology of male infertility
Crack Closure Effects on Fatigue Crack Propagation Rates: Application of a Proposed Theoretical Model
Structural design taking into account fatigue damage requires a thorough knowledge of the behaviour of materials. In addition to the monotonic behaviour of the materials, it is also important to assess their cyclic response and fatigue crack propagation behaviour under constant and variable amplitude loading. Materials whenever subjected to fatigue cracking may exhibit mean stress effects as well as crack closure effects. In this paper, a theoretical model based on the same initial assumptions of the analytical models proposed by Hudak and Davidson and Ellyin is proposed to estimate the influence of the crack closure effects. This proposal based further on Walker’s propagation law was applied to the P355NL1 steel using an inverse analysis (back-extrapolation) of experimental fatigue crack propagation results. Based on this proposed model it is possible to estimate the crack opening stress intensity factor, Kop, the relationship between U=ΔKeff/ΔK quantity and the stress intensity factor, the crack length, and the stress ratio. This allows the evaluation of the influence of the crack closure effects for different stress ratio levels, in the fatigue crack propagation rates. Finally, a good agreement is found between the proposed theoretical model and the analytical models presented in the literature
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