AC transport in graphene-based Fabry-Perot devices

We report on a theoretical study of the effects of time-dependent fields on electronic transport through graphene nanoribbon devices. The Fabry-P\'{e}rot interference pattern is modified by an ac gating in a way that depends strongly on the shape of the graphene edges. While for armchair edges the patterns are found to be regular and can be controlled very efficiently by tuning the ac field, samples with zigzag edges exhibit a much more complex interference pattern due to their peculiar electronic structure. These studies highlight the main role played by geometric details of graphene nanoribbons within the coherent transport regime. We also extend our analysis to noise power response, identifying under which conditions it is possible to minimize the current fluctuations as well as exploring scaling properties of noise with length and width of the systems

Electromyographic analyses of muscle pre-activation induced by single joint exercise

Objetivo: Verificar se a execução de um exercício monoarticular de baixa intensidade para os extensores do joelho é uma estratégia eficaz para aumentar o número de unidades motoras recrutadas no músculo vasto lateral durante a realização de um exercício multiarticular subsequente. Métodos: Nove sujeitos saudáveis do sexo masculino (23,33±3,46 anos) foram submetidos a rotinas de treinamento nas quais os exercícios cadeira extensora e leg press 45° eram realizados em sequência. Na rotina de baixa intensidade (R30), foram realizadas 15 extensões unilaterais de joelho, seguidas de 15 repetições de leg press 45° com cargas de 30% e 60% de uma repetição máxima (1-RM), respectivamente. Na rotina de alta intensidade (R60), a mesma sequência foi executada, porém a carga dos dois movimentos foi de 60% de 1-RM. Uma série simples de 15 repetições leg press 45° com carga de 60% de 1-RM foi utilizada como exercício controle (RC). A eletromiografia de superfície foi registrada no músculo vasto lateral por meio de um arranjo linear de eletrodos. O valor RMS foi calculado para cada repetição do leg press 45° e, a partir desses resultados, foram calculadas regressões lineares. As inclinações das retas obtidas foram então normalizadas pelos coeficientes lineares das equações de regressão e comparadas por meio da ANOVA de um fator para medidas repetidas. Resultados: As inclinações observadas na rotina RC foram significativamente inferiores às de R30 e às de R60 (p<0,05). Conclusões: Os resultados indicaram um recrutamento mais efetivo de unidades motoras nas rotinas de exercício multiarticular precedidas de exercício monoarticular.Objective: To investigate whether performing a low-intensity, single-joint exercises for knee extensors was an efficient strategy for increasing the number of motor units recruited in the vastus lateralis muscle during a subsequent multi-joint exercises. Methods: Nine healthy male participants (23.33±3.46 yrs) underwent bouts of exercise in which knee extension and 45°, and leg press exercises were performed in sequence. In the low-intensity bout (R30), 15 unilateral knee extensions were performed, followed by 15 repetitions of the leg presses at 30% and 60% of one maximum repetition load (1-MR), respectively. In the high-intensity bout (R60), the same sequence was performed, but the applied load was 60% of 1-MR for both exercises. A single set of 15 repetitions of the leg press at 60% of 1-MR was performed as a control exercise (CR). The surface electromyographic signals of the vastus lateralis muscle were recorded by means of a linear electrode array. The root mean square (RMS) values were determined for each repetition of the leg press, and linear regressions were calculated from these results. The slopes of the straight lines obtained were then normalized using the linear coefficients of the regression equations and compared using one-way ANOVAs for repeated measures. Results: The slopes observed in the CR were significantly lower than those in the R30 and R60 (p<0.05). Conclusions: The results indicated that the recruitment of motor units was more effective when a single-joint exercise preceded the multi-joint exercise

U-Pb zircon dating of ash fall deposits from the paleozoic paran? basin of Brazil and Uruguay: A reevaluation of the stratigraphic correlations

Ash fall layers and vitroclastic-carrying sediments distributed throughout the entire Permian stratigraphic range of the Paraná Basin (Brazil and Uruguay) occur in the Tubarão Supergroup (Rio Bonito Formation) and the Passa Dois Group (Irati, Estrada Nova/Teresina, Corumbataí, and Rio do Rasto Formations), which constitute the Gondwana 1 Supersequence. U-Pb zircon ages, acquired by SHRIMP and isotope-dissolution thermal ionization mass spectrometer (IDTIMS) from tuffs within the Mangrullo and Yaguari Formations of Uruguay, are compatible with a correlation with the Irati and parts of the Teresina and Rio do Rasto Formations, respectively, of Brazil. U-Pb zircon ages suggest maximum depositional ages for the samples: (1) Rio Bonito Formation: ages ranging from 295:8 5 3:1 to 304:0 5 5:6 Ma (Asselian, lowermost Permian), consistent with the age range of the Protohaploxypinus goraiensis subzone; (2) Irati Formation: ages ranging from 279:9 5 4:8 to 280:0 5 3:0 Ma (Artinskian, middle Permian), consistent with the occurrence of species of the Lueckisporites virkkiae zone; (3) Rio do Rasto Formation: ages ranging from 266:7 5 5:4 to 274:6 5 6:3Ma (Wordian to Roadian, middle Permian). All the SHRIMP U-Pb zircon ages are consistent with their superimposition order in the stratigraphy, the latest revisions to the Permian timescale (International Commission of Stratigraphy, 2018 version), and the most recent appraisals of biostratigraphic data. The ID-TIMS U-Pb zircon ages from the Corumbataí Formation suggest that U-Pb ages may be 110% younger than interpreted biostratigraphic ages

Genome-wide analyses reveal a highly conserved Dengue virus envelope peptide which is critical for virus viability and antigenic in humans.

Targeting regions of proteins that show a high degree of structural conservation has been proposed as a method of developing immunotherapies and vaccines that may bypass the wide genetic variability of RNA viruses. Despite several attempts, a vaccine that protects evenly against the four circulating Dengue virus (DV) serotypes remains elusive. To find critical conserved amino acids in dengue viruses, 120 complete genomes of each serotype were selected at random and used to calculate conservation scores for nucleotide and amino acid sequences. The identified peptide sequences were analysed for their structural conservation and localisation using crystallographic data. The longest, surface exposed, highly conserved peptide of Envelope protein was found to correspond to amino acid residues 250 to 270. Mutation of this peptide in DV1 was lethal, since no replication of the mutant virus was detected in human cells. Antibodies against this peptide were detected in DV naturally infected patients indicating its potential antigenicity. Hence, this study has identified a highly conserved, critical peptide in DV that is a target of antibodies in infected humans

LC‐HRMS for the Identification of β‐Carboline and Canthinone Alkaloids Isolated from Natural Sources

β-carboline and canthinone alkaloids are widely distributed in the Angiosperms. Due to their diverse biological activities, the structures of these alkaloids have been used as important models for the synthesis of novel therapeutic drugs. Combining high-performance liquid chromatography (HPLC) with high-resolution mass spectrometry (HRMS) has provided a valuable tool in the analysis of these alkaloids in, for example, plants, insects, marine creatures, human tissues and body fluids. In this review, we summarized the main β-carboline and canthinone alkaloids studied by liquid chromatography high-resolution mass spectrometry (LC-HRMS) associated with mass analyzers, molecular weight information, mass fragmentation and biological activities, presenting an overview of increasing interest for carboline alkaloids study by LC-HRMS

Two Notch Ligands, Dll1 and Jag1, Are Differently Restricted in Their Range of Action to Control Neurogenesis in the Mammalian Spinal Cord

Notch signalling regulates neuronal differentiation in the vertebrate nervous system. In addition to a widespread function in maintaining neural progenitors, Notch signalling has also been involved in specific neuronal fate decisions. These functions are likely mediated by distinct Notch ligands, which show restricted expression patterns in the developing nervous system. Two ligands, in particular, are expressed in non-overlapping complementary domains of the embryonic spinal cord, with Jag1 being restricted to the V1 and dI6 progenitor domains, while Dll1 is expressed in the remaining domains. However, the specific contribution of different ligands to regulate neurogenesis in vertebrate embryos is still poorly understood.In this work, we investigated the role of Jag1 and Dll1 during spinal cord neurogenesis, using conditional knockout mice where the two genes are deleted in the neuroepithelium, singly or in combination. Our analysis showed that Jag1 deletion leads to a modest increase in V1 interneurons, while dI6 neurogenesis was unaltered. This mild Jag1 phenotype contrasts with the strong neurogenic phenotype detected in Dll1 mutants and led us to hypothesize that neighbouring Dll1-expressing cells signal to V1 and dI6 progenitors and restore neurogenesis in the absence of Jag1. Analysis of double Dll1;Jag1 mutant embryos revealed a stronger increase in V1-derived interneurons and overproduction of dI6 interneurons. In the presence of a functional Dll1 allele, V1 neurogenesis is restored to the levels detected in single Jag1 mutants, while dI6 neurogenesis returns to normal, thereby confirming that Dll1-mediated signalling compensates for Jag1 deletion in V1 and dI6 domains.Our results reveal that Dll1 and Jag1 are functionally equivalent in controlling the rate of neurogenesis within their expression domains. However, Jag1 can only activate Notch signalling within the V1 and dI6 domains, whereas Dll1 can signal to neural progenitors both inside and outside its domains of expression