How to inflate a wind-blown bubble

ABSTRACT Stellar winds are one of several ways that massive stars can affect the star formation process on local and galactic scales. In this paper, we investigate the numerical resolution needed to inflate an energy-driven stellar wind bubble in an external medium. We find that the radius of the wind injection region, rinj, must be below a maximum value, rinj,max, in order for a bubble to be produced, but must be significantly below this value if the bubble properties are to closely agree with analytical predictions. The final bubble momentum is within 25 per cent of the value from a higher resolution reference model if χ = rinj/rinj,max = 0.1. Our work has significance for the amount of radial momentum that a wind-blown bubble can impart to the ambient medium in simulations, and thus on the relative importance of stellar wind feedback.

Passive plasma membrane transporters play a critical role in perception of carbon availability in yeast

Recently, our lab found that the canonical glucose/galactose regulation pathway in yeast makes the decision to metabolize galactose based on the ratio of glucose to galactose concentrations in the external medium. This led to the question of where and how the ratio-sensing is achieved. Here, we consider the possibilities of an intracellular, extracellular, or membrane bound ratio sensing mechanisms. We show that hexose transporters in the plasma membrane are mainly responsible for glucose/galactose ratio-sensing in yeast. Further, while the glucose sensors Gpr1, Snf3, and Rgt2 are not required for ratio sensing, they help modulate the ratio sensing phenotype by regulating the expression of individual transporters in different environments. Our study provides an example of an unexpected, but potentially widespread, mechanism for making essential decisions.

Effect of Antioxidant and Buffering Agent Mixture on Dentin Shear Bond Strengths of Laminate Veneer and pH Change of External Medium After Intracoronal Bleaching

Aim: To investigate the effect of sodium ascorbate (SA), an antioxidant and calcium hydroxide (Ca(OH)2), a buffering agent mixture, on the shear bond strength of a luting resin to dentin, and pH changes of the extraradicular medium solution after intracoronal bleaching with hydrogen peroxide. Materials and Methods: In this in vitro study, 60 human maxillary central incisors were randomly assigned into six groups ( n: 10): Group 1: restored, no bleach; group 2: bleached, bonded immediately; group 3: bleached, treated with 10% SA applications before bonding; group 4: bleached, treated with calcium hydroxide applications before bonding; group 5: bleached, treated with CaOH2 and SA mixture applications before bonding; group 6: delay bonding by seven days. For bleach treatment in groups 2 to 6, intracoronal bleaching was performed with 35% hydrogen peroxide for four days. SA or CaOH2 or mixture of SA and CaOH2 were left in the access cavity for four days. Hybrid blocks, 4 mm × 4 mm wide × 2–mm thick, were luted with resin cements on dentin surface and then the specimens were subjected to shear bond strength testing. Analysis of variance and Tukey post hoc multiple comparison tests were applied ( P < .05). Results: G2 and G4 showed significantly low bond strength values and they were lower than the other groups ( P < .05). There were no significant differences between G1, G3, and G6 ( P > .05). The pH values had risen markedly in the groups containing calcium hydroxide (G4 and G5) after four days ( P < .05). Conclusion: The application of 10% SA or 10% SA and CaOH2 mixture were effective at reversing bleaching effects on bond strength. CaOH2 or CaOH2 and 10% SA mixture increased the external medium pH and were effective for alkalinization after intracoronal bleaching.

Roles of proteins containing immunoglobulin-like domains in the conjugation of bacterial plasmids.

Horizontal transfer of bacterial plasmids generates genetic variability and contributes to the dissemination of the genes that enable bacterial cells to develop antimicrobial resistance (AMR). Several aspects of the conjugative process have long been known, namely, those related to the proteins that participate in the establishment of cell-to-cell contact and to the enzymatic processes associated with the processing of plasmid DNA and its transfer to the recipient cell. In this work, we describe the role of newly identified proteins that influence the conjugation of several plasmids. Genes encoding high-molecular-weight proteins that contain one or several immunoglobulin-like domains (Big) are located in the transfer regions of several plasmids that usually harbor AMR determinants. These Big proteins are exported to the external medium and target two extracellular organelles: the flagella and the conjugative pili. The plasmid-encoded Big proteins facilitate conjugation by reducing cell motility (by binding to flagella) and facilitating cell-to-cell contact (by binding to the conjugative pilus). They use the same export machinery as that used by the conjugative pilus components. In the examples characterized in this paper, these proteins influence conjugation at environmental temperatures (i.e., 25C). This suggests that they may play relevant roles in the dissemination of plasmids in natural environments. As they are located in outer surface organelles, they could be targeted to control the dissemination of different bacterial plasmids carrying AMR determinants.

Downregulation of high-affinity potassium and sodium symporter gene, EcHKT1;1, in Eucalyptus roots enhances salt tolerance

Engineering for restricted root Na+ uptake could potentially enhance salt tolerance in Eucalyptus. High-affinity K+ transporters (HKTs) have been implicated in Na+ uptake from the external medium as in the case of TaHKT2;1 or in the unloading of Na+ from xylem like in AtHKT1;1. To rapidly determine the in planta role of EcHKT1:1, composite transgenics in which EcHKT1:1 was specifically downregulated via RNAi in the roots were generated. Compared to the controls that failed to survive at 350 mM NaCl, 33 % of the composite transgenic plantlets generated using the EcHKT1;1 silencing construct were able to tolerate up to 400 mM NaCl. In these composite transgenics, EcHKT1;1 downregulation ranged from 37 % to 74 %. The average shoot to root ratio of sodium was 4.9 folds lower than the controls indicating restricted translocation of Na+ to the shoots. Relative expression analysis in the leaves of two non-transgenic genotypes contrasting for their salt tolerance also showed downregulated EcHKT1;1 expression in the tolerant clone. The study thus determined that EcHKT1;1 is a major gene determining Na+ transport from the roots to shoots. This study also demonstrated the utility of the composite transgenic approach for screening genes conferring salt tolerance in tree species.

Influence of Rugate Filters on the Spectral Manifestation of Tamm Plasmon Polaritons

This study theoretically investigated light reflection and transmission in a system composed of a thin metal layer (Ag) adjacent to a rugate filter (RF) having a harmonic refractive index profile. Narrow dips in reflectance and peaks in transmittance in the RF band gap were obtained due to the excitation of a Tamm plasmon polariton (TPP) at the Ag–RF interface. It is shown that the spectral position and magnitude of the TPP dips/peaks in the RF band gap depend on the harmonic profile parameters of the RF refractive index, the metal layer thickness, and the external medium refractive index. The obtained dependences for reflectance and transmittance allow selecting parameters of the system which can be optimized for various applications.

Создание и определение чувствительности волоконно-оптического рефрактометра на основе поверхностного плазмонного резонанса

A fiber-optic refractive index sensor using the phenomenon of surface plasmon resonance has been developed. A 1 nm layer of chromium and a 50 nm gold film were applied to a section of a standard multimode optical fiber with a partially protected shell. The transmission spectra were measured as a function of the refractive index of the external medium into which the sensor was immersed. When the refractive index of the external medium changed, the minimum in the transmission spectrum caused by the excitation of the surface plasmon-polariton at the boundary between the gold film and the analyte shifted. The sensor sensitivity was 1400 nm/RU.

On the significance of relativistically hot pairs in the jets of FR II radio galaxies

ABSTRACT The energetic composition of radio lobes in the FR II galaxies – estimated by comparing their radio luminosities with the powers required to inflate cavities in the external medium – seems to exclude the possibility of their energetic domination by protons. Furthermore, if the jets were dominated by the kinetic energy of cold protons, it would be difficult to efficiently accelerate leptons in the jets’ terminal shocks. Assuming that the relative energy contents of leptons, protons, and magnetic fields are preserved across the shocks, the above implies that the large-scale jets should also be energetically dominated by leptons: Pe,j ≳ Pp,j. On the other hand, previous studies of small-scale jets in blazars and radio cores suggest a pair content (number of electrons and positrons per proton) of the order of ne/np ∼ 20. Assuming further that the particle composition of jets does not evolve beyond the blazar scales, we show that this implies an average random Lorentz factor of leptons in large-scale jets of $\bar{\gamma }_{\rm e,j} \gtrsim 70(1+\chi _{\rm p})(20n_{\rm p}/n_{\rm e})$, and that the protons should be mildly relativistic with χp ≡ (ϵp + pp)/ρpc2 ≲ 2, pp the pressure of protons, ϵp the internal energy density of protons, and ρpc2 the rest-mass energy density of protons. We derive the necessary conditions for loading the inner jets by electron–positron pairs and proton–electron plasma, and provide arguments that heating of leptons in jets is dominated by magnetic reconnection.

The cubic root unscented kalman filter to estimate the position and orientation of mobile robot trajectory

In this paper we introduce a Cubic Root Unscented Kalman Filter (CRUKF) compared to the Unscented Kalman Filter (UKF) for calculating the covariance cubic matrix and covariance matrix within a sensor fusion algorithm to estimate the measurements of an omnidirectional mobile robot trajectory. We study the fusion of the data obtained by the position and orientation with a good precision to localize the robot in an external medium; we apply the techniques of Kalman Filter (KF) to the estimation of the trajectory. We suppose a movement of mobile robot on a plan in two dimensions. The sensor approach is based on the Cubic Root Unscented Kalman Filter (CRUKF) and too on the standard Unscented Kalman Filter (UKF) which are modified to handle measurements from the position and orientation. A real-time implementation is done on a three-wheeled omnidirectional mobile robot, using a dynamic model with trajectories. The algorithm is analyzed and validated with simulations.