A high-throughput transient gene expression system for switchgrass (Panicum virgatum L.) seedlings

<p>Abstract</p> <p>Background</p> <p>Grasses are relatively recalcitrant to genetic transformation in comparison to certain dicotyledons, yet they constitute some of the most important biofuel crops. Genetic transformation of switchgrass (<it>Panicum virgatum </it>L.) has previously been reported after cocultivation of explants with <it>Agrobacterium </it>and biolistics of embryogenic calli. Experiments to increase transient gene expression <it>in planta </it>may lead to stable transformation methods with increased efficiency.</p> <p>Results</p> <p>A high-throughput <it>Agrobacterium</it>-mediated transient gene expression system has been developed for <it>in planta </it>inoculation of germinating switchgrass seedlings. Four different <it>Agrobacterium </it>strains were compared for their ability to infect switchgrass seedlings, and strain AGL1 was found to be the most infective. Wounding pretreatments such as sonication, mixing by vortex with carborundum, separation by centrifugation, vacuum infiltration, and high temperature shock significantly increased transient expression of a reporter gene (GUSPlus, a variation of the β-glucuronidase (GUS) gene). The addition of L-cysteine and dithiothreitol in the presence of acetosyringone significantly increased GUS expression compared with control treatments, whereas the addition of 0.1% surfactants such as Silwet L77 or Li700 decreased GUS expression. 4-Methylumbelliferyl beta-D-galactopyranoside (MUG) assays showed a peak of β-glucuronidase (GUS) enzyme activity 3 days after cocultivation with <it>Agrobacterium </it>harboring pCambia1305.2, whereas MUG assays showed a peak of enzyme activity 5 days after cocultivation with <it>Agrobacterium </it>harboring pCambia1305.1.</p> <p>Conclusion</p> <p><it>Agrobacterium </it>strains C58, GV3101 and EHA105 are less able to deliver transfer DNA to switchgrass seedlings (cultivar Alamo) compared with strain AGL1. Transient expression was increased by double or triple wounding treatments such as mixing by vortex with carborundum, sonication, separation by centrifugation, and heat shock. The addition of thiol compounds such as L-cysteine and dithiothreitol in combination with acetosyringone during cocultivation also increased transient expression. The combination of multiple wounding treatments along with the addition of thiol compounds during cocultivation increased transient expression levels from 6% to 54%. There were differences in temporal GUS expression induced by pCambia1305.1 and pCambia1305.2.</p

Extremely powerful and frequency-tunable terahertz pulses from a table-top laser-plasma wiggler

The production of broadband, terawatt terahertz (THz) pulses has been demonstrated by irradiating relativistic lasers on solid targets. However, the generation of extremely powerful, narrow-band, and frequency-Tunable THz pulses remains a challenge. Here, we present a novel approach for such THz pulses, in which a plasma wiggler is elaborated by a tabletop laser and a near-critical density plasma. In such a wiggler, the laser-Accelerated electrons emit THz radiations with a period closely related to the plasma thickness. Theoretical model and numerical simulations predict a THz pulse with a laser-THz energy conversion over 2.0%, an ultra-strong field exceeding 80 GV/m, a divergence angle approximately 20?, and a center-frequency tunable from 4.4 to 1.5 THz, can be generated from a laser of 430 mJ. Furthermore, we demonstrate that this method can work across a wide range of laser and plasma parameters, offering potential for future applications with extremely powerful THz pulse. © 2023 Authors. All rights reserved.11Nsciescopu

Mesoporous Polydopamine Loaded Pirfenidone Target to Fibroblast Activation Protein for Pulmonary Fibrosis Therapy

Recently, fibroblast activation protein (FAP), an overexpressed transmembrane protein of activated fibroblast in pulmonary fibrosis, has been considered as the new target for diagnosing and treating pulmonary fibrosis. In this work, mesoporous polydopamine (MPDA), which is facile prepared and easily modified, is developed as a carrier to load antifibrosis drug pirfenidone (PFD) and linking FAP inhibitor (FAPI) to realize lesion-targeted drug delivery for pulmonary fibrosis therapy. We have found that PFD@MPDA-FAPI is well biocompatible and with good properties of antifibrosis, when ICG labels MPDA-FAPI, the accumulation of the nanodrug at the fibrosis lung in vivo can be observed by NIR imaging, and the antifibrosis properties of PFD@MPDA-FAPI in vivo were also better than those of pure PFD and PFD@MPDA; therefore, the easily produced and biocompatible nanodrug PFD@MPDA-FAPI developed in this study is promising for further clinical translations in pulmonary fibrosis antifibrosis therapy

An experimental and kinetic modeling study on the laminar burning velocity of NH3+N2O+air flames

In the present work, the laminar burning velocities of the NH3+N2O+air flames were measured using the heat flux method at 1 atm and 298 K, with varied equivalence ratios and N2O mixing ratios. For the mixing ratio N2O/(N2O+air) = 0.5, a full range of equivalence ratios was covered. Moreover, at three equivalence ratios an extended range of mixing ratios was investigated. The laminar burning velocity has an approximately linear relationship against the fraction of nitrous oxide in the oxidizer mixture, regardless of the tested equivalence ratios. Several recently published NH3 mechanisms were compared with these new experimental data; among them the models of Nakamura et al. and Stagni et al. show the best performance for NH3+N2O+air flames over the entire range of the mixing ratios. The H/N/O kinetic mechanism of the authors was analyzed and updated focusing on the rate constants of reactions most sensitive in ammonia flame propagation and self-ignition of NH3+O2 and H2+N2O mixtures. The choice of the new rate constants is outlined, however, no modification (adjustment or tuning) of the rate parameters to accommodate experimental results was attempted. The updated mechanism demonstrates significantly improved agreement with all measurements used for the model development and with other experimental data from the literature for ammonia flames and self-ignition. A comparative reaction path analysis for NH3+N2O+air and NH3+air flames revealed that an almost linear increase of the laminar burning velocity with an increased fraction of N2O in the oxidizer originates from the rate controlling reaction N2O+H = N2+OH, which produces OH radicals dominating ammonia oxidation

Comparative Effect of Ammonia Addition on the Laminar Burning Velocities of Methane, n-Heptane, and Iso-octane

Adiabatic laminar burning velocities for methane, n-heptane, and iso-octane blended with ammonia were experimentally determined using the heat flux method. The flames were stabilized at atmospheric pressure and at an initial temperature of 338 K, over equivalence ratios ranging from 0.7 to 1.4 and ammonia blending fractions in the binary fuel mixtures from 0 to 90%. These experiments are essential for the development, validation, and optimization of chemical kinetic models, e.g., for the combustion of gasoline-ammonia fuel mixtures. It was observed that the addition of ammonia to methane, n-heptane, and iso-octane leads to a decrease in the laminar burning velocity that is not proportional to the ammonia mole fraction. In addition, ammonia has the same impact on the burning velocities of n-heptane and iso-octane but a slightly higher effect on those of methane. Such a burning velocity reduction is due to synergistic thermal, kinetic, and indirect transport effects. New experimental results were compared to predictions of the POLIMI detailed chemical kinetic mechanism. An overall good agreement between the measurements and simulated results was observed for the laminar burning velocities over the equivalence ratio and ammonia fraction ranges investigated

SAFT Regimes and Laminar Burning Velocities : A Comparative Study of NH3+ N2+ O2and CH4+ N2+ O2Flames

Super adiabatic flame temperature (SAFT) is a distinctive phenomenon in the adiabatic flame where the local maximum temperature exceeds the adiabatic flame temperature. The flame temperatures exhibiting the extent of SAFT are difficult to measure with low uncertainties in experiments, while the laminar burning velocity also represents global flame features, thus could possibly be related to the SAFT. The present study investigated the SAFT regimes, laminar burning velocities (SL), and their relationships for the CH4+ O2+ N2and NH3+ O2+ N2flames over large equivalence (φ) and oxygen ratio (xO2) ranges. The laminar burning velocities were experimentally measured using the heat flux method at φ = 1.4-1.8 and xO2= 0.22-0.44, where some conditions have never been reported before in the literature. Comparisons were made with simulated SLresults using five CH4mechanisms and five NH3mechanisms, and none of them well reproduce all of the experimental data. From the simulation results, three CH4SAFT regimes (I, II, and III) and two NH3SAFT regimes (I and II) have been identified, among which regime III for CH4and regime II for NH3were found for the first time. The kinetic origins of these regimes were discussed, and different flame features regarding the flame temperature and dominant species were clarified. The relationship between the SAFT extent and the laminar burning velocity is revealed by equation derivation based on the classical flame theories, proving that a mechanism reproducing well the SLand its temperature dependence can at the same time yield accurate predictions of the SAFT. The present study also provided the most sensitive reactions in the SAFT predictions accompanied by the rate constant uncertainties, which can be helpful for further mechanism development since none of the mechanisms reproduces well the present SLexperimental data, let alone the SAFT extent

Experimental and kinetic modeling study of the CH4+H2S+air laminar burning velocities at atmospheric pressure

With the increasing demand for natural gas and depletion of many sweet gas fields, direct usage of sour gas, usually containing a large percentage of hydrogen sulfide (H2S), becomes a more economical choice in recent years. However, the laminar burning velocity (SL) of CH4+H2S flames have seldom been investigated due to the corrosivity and toxicity of H2S, and no available experimental data can be found for these mixtures burnt in the air. In this work, the laminar burning velocities of CH4+H2S+air flames were measured using the heat flux method at 1 atm and 298 K. The experimental data were obtained at various equivalence ratios and xH2S = 0–0.25, where xH2S refers to the mole fraction of H2S in the fuel. Simulations using a detailed mechanism of Mulvihill et al. (2019) were carried out, showing good agreement with the present experimental results. Kinetic analyses of A-factor SL reaction sensitivities, reaction pathways, and dominant intermediate species pointed out the importance of the C- and S-containing species interactions. To overcome the convergence problem of the Mulvihill mechanism, an examination of the unphysical reactions and species was carried out, which could be alleviated by making several reactions that violate the collision limit irreversible, accompanied by updating the heat capacity data. It's also found that substituting the hydrocarbon subset of the Mulvihill mechanism with mechanisms from FFCM-1, Konnov, San Diego, as well as Aramco noticeably deteriorates the simulation results due to the selection of different reaction rate constants