Nonsequential Double Ionization with Polarization-gated Pulses

We investigate laser-induced nonsequential double ionization by a polarization-gated laser pulse, constructed employing two counter-rotating circularly polarized few cycle pulses with a time delay $T_{d}$. We address the problem within a classical framework, and mimic the behavior of the quantum-mechanical electronic wave packet by means of an ensemble of classical electron trajectories. These trajectories are initially weighted with the quasi-static tunneling rate, and with suitably chosen distributions for the momentum components parallel and perpendicular to the laser-field polarization, in the temporal region for which it is nearly linearly polarized. We show that, if the time delay $T_{d}$ is of the order of the pulse length, the electron-momentum distributions, as functions of the parallel momentum components, are highly asymmetric and dependent on the carrier-envelope (CE) phase. As this delay is decreased, this asymmetry gradually vanishes. We explain this behavior in terms of the available phase space, the quasi-static tunneling rate and the recollision rate for the first electron, for different sets of trajectories. Our results show that polarization-gating technique may provide an efficient way to study the NSDI dynamics in the single-cycle limit, without employing few-cycle pulses.Comment: 17 pages, 6 figure

Parametric Competition in non-autonomous Hamiltonian Systems

In this work we use the formalism of chord functions (\emph{i.e.} characteristic functions) to analytically solve quadratic non-autonomous Hamiltonians coupled to a reservoir composed by an infinity set of oscillators, with Gaussian initial state. We analytically obtain a solution for the characteristic function under dissipation, and therefore for the determinant of the covariance matrix and the von Neumann entropy, where the latter is the physical quantity of interest. We study in details two examples that are known to show dynamical squeezing and instability effects: the inverted harmonic oscillator and an oscillator with time dependent frequency. We show that it will appear in both cases a clear competition between instability and dissipation. If the dissipation is small when compared to the instability, the squeezing generation is dominant and one can see an increasing in the von Neumann entropy. When the dissipation is large enough, the dynamical squeezing generation in one of the quadratures is retained, thence the growth in the von Neumann entropy is contained

Erratum: Martins, M.S., et al. Wideband and wIde beam polyvinylidene difluoride (PVDF) acoustic transducer for broadband underwater. Sensors 2019, 19, 3991

The authors wish to make the following erratum to this paper [...].info:eu-repo/semantics/publishedVersio

A role for the small GTPases RAC1 and RAC1b in the modulation of NIS expression: potentiation of therapy with radioactive iodine in differentiated thyroid carcinoma

Introduction or Background: The Sodium Iodide Symporter (NIS) is responsible for active transport of iodide into thyroid follicular cells. The retention of its functional expression in most of the well-differentiated thyroid carcinomas (DTCs) enables the use of radioactive iodine (RAI) for treatment of metastatic disease. Still, about 30% of patients with advanced forms of DTC became refractory to RAI which makes their management very challenging. The main reason for impaired iodide uptake in refractory-DTC is the defective functional expression of NIS. Several molecular players have been described as critical for TSH-induced NIS expression, an example being the p38 mitogenic kinase. In breast cancer cells, the small GTPase RAC1 was shown to mediate the positive impact of p38 kinase activity on NIS expression. We, on the other hand, have previously shown that overexpression of RAC1b, a tumor-related splicing variant of RAC1, is associated with worse outcomes in DTC and correlates with the MAPK-activating BRAFV600E mutation, which has been related to the loss of NIS. Since RAC1 and RAC1b may act in an antagonistic fashion to regulate specific cellular responses, we asked if RAC1b would be implicated in NIS downregulation observed in DTCs. Methods Section: NIS expression levels were analyzed by RT-qPCR in a RAC1/RAC1b expression model system developed in non-transformed thyroid cell lines. A non-radioactive iodide influx assay was used to confirm the impact of RAC1-signaling on the efficacy of iodide uptake. Results Section: We demonstrate that ectopic overexpression of RAC1b is sufficient to decrease TSH-induced NIS expression, antagonizing the positive effect of RAC1 GTPase. Moreover, we clearly document, for the first time in thyroid cells, that both NIS expression and iodide uptake are downregulated upon RAC1 inhibition, supporting the role of canonical RAC1 signaling in promoting TSH-induced NIS expression. Conclusion: Our findings provide evidence that RAC1 and RAC1b signaling are implicated in the regulation of NIS expression in thyroid cells and suggest that RAC1b overexpression may be one of the mechanisms contributing to the low levels of NIS observed in some subgroups of DTCs, antagonizing RAC1 stimulatory effect on the TSH/cAMP-mediated induction of NIS expression.FCT - PTDC/BIAMOL/31787/2017N/

Genetic diversity of Lusitano horse in Brazil using pedigree information

This study aimed to evaluate population parameters and to describe the genetic diversity of the Lusitano breed in Brazil using pedigree data. Two populations were evaluated: total population (TP) containing 18,922 animals, and reference population (RP) composed of a part of TP containing 8,329 animals, representing the last generation. The generation interval (10.1 ± 5.1 years) was in the range for horse populations. Pedigree completeness in RP shows almost 100% filling in the three most recent generations, indicating improvement in the pedigree data and accuracy of the results, and the inbreeding coefficient (4.46%) and average relatedness (5.97%) for RP, indicating control on the part of breeders. The effective population size was 89 (TP) and 90 (RP). The effective number of founders (fe) were 33 and 29, effective number of ancestors (fa) were 30 and 26, and effective number of founder genomes (fg) were 19 and 15 for TP and RP, respectively, indicating a reduction of genetic variability in the last generations. The total number of ancestors that explains 100% of the genetic diversity in the Lusitano breed in Brazil was 427 (TP) and 341 (RP). The reproductive parameters, probabilities of gene origin showing loss of variability in the last generations, and the genetic contributions of ancestors suggest the need to monitor genetic diversity over time in breeding programs to allow control of the next generations and to increase their variability.info:eu-repo/semantics/publishedVersio

Causality and quantum interference in time-delayed laser-induced nonsequential double ionization

We perform a detailed analysis of the importance of causality within the strong-field approximation and the steepest-descent framework for the recollision-excitation with subsequent tunneling ionization (RESI) pathway in laser-induced nonsequential double ionization (NSDI). In this time-delayed pathway, an electron returns to its parent ion and, by recolliding with the core, gives part of its kinetic energy to excite a second electron at a time t′. The second electron then reaches the continuum at a later time t by tunneling ionization. We show that, if t′ and t are complex, the condition that recollision of the first electron occurs before tunnel ionization of the second electron translates into boundary conditions for the steepest-descent contours and thus puts constraints on the saddles to be taken when computing the RESI transition amplitudes. We also show that this generalized causality condition has a dramatic effect on the shapes of the RESI electron momentum distributions for few-cycle laser pulses. Physically, causality determines how the dominant sets of orbits of an electron returning to its parent ion can be combined with the dominant orbits of a second electron tunneling from an excited state. All features encountered are analyzed in terms of such orbits and their quantum interference

Finding Out The Neurological Consequences Of Covid-19

t- Introduction: Since the first official case of COVID-19 in China in December 2019, researchers have been trying to uncover the mechanism of action of the severe acute respiratory syndrome Coronavirus 2 (Sars-CoV-2), which attacks several organs in addition to the lungs and causes circulatory changes that can lead to death not only from lung failure but also due to commitment of other organs. Objective: The aim of this study is to find out the neurological consequences of COVID-19. Material and methods: A systematic review of the literature was concretised by mobilizing the descriptors: "Sars-Cov-2", "coronavirus infections" and "Neurological Consequences". Databases were selected and seven articles were included for analysis. Results and discussion: Although the effects of Sars-CoV-2 on the lung are exemplary and frightening, the long-term effects on the nervous system may be greater and even more overwhelming, as the regeneration of nerve tissue is difficult and can lead to general disability, as the nervous system coordinates the functions of the entire body. All studies show the presence of any kind of injury (mild or severe) to Central Nervous System, but some of them highlight the need for further studies to have great certainty. Conclusion: It can be said that the studies all agree on the possibility of existing neurological sequelae and a majority agree on the need for other studies.info:eu-repo/semantics/publishedVersio

Electronic reconstruction of hexagonal FeS: a view from density functional dynamical mean-field theory

We present a detailed study of correlation- and pressure-induced electronic reconstruction in hexagonal iron monosulfide, a system which is widely found in meteorites and one of the components of Earth's core. Based on a perusal of experimental data, we stress the importance of multi-orbital electron-electron interactions in concert with first-principles band structure calculations for a consistent understanding of its intrinsic Mott–Hubbard insulating state. We explain the anomalous nature of pressure-induced insulator-metal-insulator transition seen in experiment, showing that it is driven by dynamical spectral weight transfer in response to changes in the crystal-field splittings under pressure. As a byproduct of this analysis, we confirm that the electronic transitions observed in pristine FeS at moderated pressures are triggered by changes in the spin state which causes orbital-selective Kondo quasiparticle electronic reconstruction at low energies