Effect of pump-probe detuning on the Faraday rotation and ellipticity signals of mode-locked spins in InGaAs quantum dots

We have studied the Faraday rotation and ellipticity signals in ensembles of singly-charged (In,Ga)As/GaAs quantum dots by pump-probe spectroscopy. For degenerate pump and probe we observe that the Faraday rotation signal amplitude first grows with increasing the time separation between pump and probe before a decay is observed for large temporal separations. The temporal behavior of the ellipticity signal, on the other hand, is regular: its amplitude decays with the separation. By contrast, for detuned pump and probe the Faraday rotation and ellipticty signals both exhibit similar and conventional behavior. The experimental results are well described in the frame of a recently developed microscopic theory [Phys. Rev. B 80, 104436 (2009)]. The comparison between calculations and experimental data allows us to provide insight into the spectral dependence of the electron spin precession frequencies and extract the electron g-factor dependence on energy.Comment: 9 pages, 7 figure

QCD and electroweak corrections to WZ scattering at the LHC

We present the first computation of the full next-to-leading-order QCD and electroweak corrections to the WZ scattering process at the LHC. All off-shell, gauge-boson-decay, and interference effects are taken into account for the process $\mathrm{p} \mathrm{p} \to \mu^+\mu^-\mathrm{e}^+\nu_\mathrm{e} \mathrm{j} \mathrm{j} + X$ at the orders $\mathcal{O}{\left( \alpha_\mathrm{s} \alpha^6 \right)}$ and $\mathcal{O}{\left( \alpha^7 \right)}$. The electroweak corrections feature the typical Sudakov behaviour towards high energy and amount to $-16\%$ relative to the electroweak contribution to the integrated cross section. Moreover, the corrections induce significant shape distortions in differential distributions. The next-to-leading-order analysis of the quark- and gluon-induced channels is supplemented by a leading-order study of all possible contributions to the full 4\ell+2\mbox{jets} production cross section in a realistic fiducial phase-space volume

Optical control of coherent interactions between quantum dot electron spins

Coherent interactions between spins in quantum dots are a key requirement for quantum gates. We have performed pump-probe experiments in which pulsed lasers emitting at different photon energies manipulate two distinct subsets of electron spins within an inhomogeneous InGaAs quantum dot ensemble. The spin dynamics are monitored through their precession about an external magnetic field. These measurements demonstrate spin precession phase shifts and modulations of the magnitude of one subset of oriented spins after optical orientation of the second subset. The observations are consistent with results from a model using a Heisenberg-like interaction with microeV-strength.Comment: 5 pages, 4 figure

Correcting the polarization effect in low frequency Dielectric Spectroscopy

We demonstrate a simple and robust methodology for measuring and analyzing the polarization impedance appearing at interface between electrodes and ionic solutions, in the frequency range from 1 to $10^6$ Hz. The method assumes no particular behavior of the electrode polarization impedance and it only makes use of the fact that the polarization effect dies out with frequency. The method allows a direct and un-biased measurement of the polarization impedance, whose behavior with the applied voltages and ionic concentration is methodically investigated. Furthermore, based on the previous findings, we propose a protocol for correcting the polarization effect in low frequency Dielectric Spectroscopy measurements of colloids. This could potentially lead to the quantitative resolution of the $\alpha$-dispersion regime of live cells in suspension

Editorial: Eliciting plant defense responses: From basic to applied science for sustainable agriculture

Plants constantly face a diversity of pathogens and insects that affect food production. Synthetic agrochemicals are often use to overcome these challenges. However, current demands for stringent worldwide regulatory policies led to the development of sustainable agriculture strategies, including naturally-derived molecules that elicit plant defense responses (Scariotto et al., 2021). The commercial use of these molecules is still limited, mostly due to poor knowledge on the molecular mechanisms producing their effects on plant metabolism. In recent decades, efforts have been directed toward understanding how individual molecules, such as immune receptors or microbial effectors, enable plants to perceive and respond to pathogens, insects, and other stresses. Furthermore, recent research on plant immunity has revealed high levels of complexity, including regulation mediated by micro-peptides and miRNA. Such knowledge opens the opportunity to link basic and applied science to facilitate using natural elicitors as a sustainable option for crop protection

Relações de causa e efeito entre condições ambientais, urediniósporos e severidade de ferrugem-asiática da soja.

O objetivo deste trabalho foi estabelecer relações entre condições ambientais, o número de urediniósporos de Phakopsora pachyrhizi e a severidade da ferrugem-asiática-da-soja. Para quantificar urediniósporos de P. pachyrhizi, coletores foram instalados em campos de soja, em Itambé e Mandaguari, PR. Avaliações de severidade foram realizadas e dados climáticos foram coletados nos dois locais. As variáveis elaboradas foram: número de dias com umidade favorável (>60%), número de dias com temperatura favorável (18 a 32º C), preciptação acumulada e urediniósporos coletados. Uma variável baseada no controle químico também foi elaborada. Correlações entre as variáveis foram estimadas. A análise de trilha foi empregada para desdobrar as correlações. Cerca de 76% da variação das relações de causa e efeito entre as variáveis foi explicada pela análise de trilha. O número de dias para efetuar o controle químico teve efeito direto sob a severidade. O número de dias com temperatura favorável e as precipitações tiveram efeito indireto na severidade, atuando via manutenção de condições favoráveis de umidade

Inactivation of Genes for Antigenic Variation in the Relapsing Fever Spirochete \u3ci\u3eBorrelia hermsii\u3c/i\u3e Reduces Infectivity in Mice and Transmission by Ticks

Borrelia hermsii, a causative agent of relapsing fever of humans in western North America, is maintained in enzootic cycles that include small mammals and the tick vector Ornithodoros hermsi. In mammals, the spirochetes repeatedly evade the host’s acquired immune response by undergoing antigenic variation of the variable major proteins (Vmps) produced on their outer surface. This mechanism prolongs spirochete circulation in blood, which increases the potential for acquisition by fast-feeding ticks and therefore perpetuation of the spirochete in nature. Antigenic variation also underlies the relapsing disease observed when humans are infected. However, most spirochetes switch off the bloodstream Vmp and produce a different outer surface protein, the variable tick protein (Vtp), during persistent infection in the tick salivary glands. Thus the production of Vmps in mammalian blood versus Vtp in ticks is a dominant feature of the spirochete’s alternating life cycle. We constructed two mutants, one which was unable to produce a Vmp and the other was unable to produce Vtp. The mutant lacking a Vmp constitutively produced Vtp, was attenuated in mice, produced lower cell densities in blood, and was unable to relapse in animals after its initial spirochetemia. This mutant also colonized ticks and was infectious by tick-bite, but remained attenuated compared to wild-type and reconstituted spirochetes. The mutant lacking Vtp also colonized ticks but produced neither Vtp nor a Vmp in tick salivary glands, which rendered the spirochete noninfectious by tick bite. Thus the ability of B. hermsii to produce Vmps prolonged its survival in blood, while the synthesis of Vtp was essential for mammalian infection by the bite of its tick vector