Valorization of Glycerol through Plasma-Induced Transformation into Formic Acid.

To cope with climate change issues, a significant shift is required in worldwide energy sources. Hydrogen and bioenergy are being considered as alternatives toward a carbon neutral society, making formic acid - a hydrogen carrying product of glycerol - of interest for the valorization of glycerol. Here we investigate the plasma-induced transformation of glycerol in an aqueous nanosecond repetitively pulsed discharge reactor. We found that the water content in the aqueous mixture fulfilled a crucial role in both the gas phase (as a source of OH radicals) and the liquid phase (as a promotor of the dissolved OH radical's mobility and reactivity). The formic acid produced was linearly proportional to the specific input energy, and the most cost-effective production of formic acid was found with 10 % v/v glycerol in the aqueous mixture. A plausible reaction pathway was proposed, consisting of the OH radical-driven dehydrogenation and dehydration of glycerol. The results provide a fundamental understanding of plasma-induced transformation of glycerol to formic acid and insights for future practical applications.

Discovery of highly immunogenic spleen-resident FCGR3+CD103+ cDC1s differentiated by IL-33-primed ST2+ basophils.

Recombinant interleukin-33 (IL-33) inhibits tumor growth, but the detailed immunological mechanism is still unknown. IL-33-mediated tumor suppression did not occur in Batf3-/- mice, indicating that conventional type 1 dendritic cells (cDC1s) play a key role in IL-33-mediated antitumor immunity. A population of CD103+ cDC1s, which were barely detectable in the spleens of normal mice, increased significantly in the spleens of IL-33-treated mice. The newly emerged splenic CD103+ cDC1s were distinct from conventional splenic cDC1s based on their spleen residency, robust effector T-cell priming ability, and surface expression of FCGR3. DCs and DC precursors did not express Suppressor of Tumorigenicity 2 (ST2). However, recombinant IL-33 induced spleen-resident FCGR3+CD103+ cDC1s, which were found to be differentiated from DC precursors by bystander ST2+ immune cells. Through immune cell fractionation and depletion assays, we found that IL-33-primed ST2+ basophils play a crucial role in the development of FCGR3+CD103+ cDC1s by secreting IL-33-driven extrinsic factors. Recombinant GM-CSF also induced the population of CD103+ cDC1s, but the population neither expressed FCGR3 nor induced any discernable antitumor immunity. The population of FCGR3+CD103+ cDC1s was also generated in vitro culture of Flt3L-mediated bone marrow-derived DCs (FL-BMDCs) when IL-33 was added in a pre-DC stage of culture. FL-BMDCs generated in the presence of IL-33 (FL-33-DCs) offered more potent tumor immunotherapy than control Flt3L-BMDCs (FL-DCs). Human monocyte-derived DCs were also more immunogenic when exposed to IL-33-induced factors. Our findings suggest that recombinant IL-33 or an IL-33-mediated DC vaccine could be an attractive protocol for better tumor immunotherapy.

Electric fields in a counterflow nonpremixed flame: measurement and simulation.

In electric field modified flames, the electric body force on fluid elements can play a role in modifying the flow field, affecting flame characteristics by this modified flow motion. Numerical studies have developed ion kinetic mechanisms and appropriate transport models for charged species, validating them with a voltage-current trend in 1D premixed flames. Recent experimental approaches have measured the electric field by adopting the Electric Field Induced Second Harmonic generation (EFISH) technique. However, the quantification has turned out very challenging due to the inherent distortion in the EFISH signal, as well as inhomogeneous temperature and concentration fields in the combustion field. Here, we propose measurement and calibration schemes to quantify the EFISH signal in a laminar counterflow nonpremixed flame and present comparison with numerical results using an in-house multi-physics CFD (Computational Fluid Dynamics) code. Overall, the quantified electric fields agreed well with those from numerical simulation, specifically capturing null electric fields near the flame in the sub-saturated regime due to the electric field screening effect. In the saturated regime, notable discrepancy was found in a fuel stream when electrons moved through it: experiment indicated a significant number of negative ions in the fuel stream, whereas numerical results predicted negligible negative ions, due to the implemented ion-mechanism. This suggested that the experimentally obtained electric fields may serve as validation data for modeling studies to improve transport models and ion-mechanism. In-situ measurement of charged species in the presence of external electric fields should be a future work.

Kinetic Study for Plasma Assisted Cracking of NH3: Approaches and Challenges.

Ammonia is considered as one of the promising hydrogen carriers toward a sustainable world. Plasma assisted decomposition of NH3 could provide cost- and energy-effective, low-temperature, on-demand (partial) cracking of NH3 into H2. Here, we presented a temperature-dependent plasma-chemical kinetic study to investigate the role of both electron-induced reactions and thermally induced reactions on the decomposition of NH3. We employed a plasma-chemical kinetic model (KAUSTKin), developed a plasma-chemical reaction mechanism for the numerical analysis, and introduced a temperature-controlled dielectric barrier discharge reactor for the experimental investigation using 1 mol % NH3 diluted in N2. As a result, we observed the plasma significantly lowered the cracking temperature and found that the plasma-chemical mechanism should be further improved to better predict the experiment. The commonly used rates for the key NH3 pyrolysis reaction (NH3 + M ↔ NH2 + H + M) significantly overpredicted the recombination rate at temperatures below 600 K. Furthermore, the other identified shortcomings in the available data are (i) thermal hydrazine chemistry, (ii) electron-scattering cross-section data of NxHy, (iii) electron-impact dissociation of N2, and (iv) dissociative quenching of excited states of N2. We believe that the present study will spark fundamental interest to address these shortcomings and contribute to technical advancements in plasma assisted NH3 cracking technology.

Synthesis of Copper and Copper Oxide Nanomaterials by Pulsed Electric Field in Water with Various Electrical Conductivities.

Nanomaterial synthesis is a hot research subject that has been extensively studied in the last two decades. Recently, plasmas in liquid systems have been proposed as an efficient means of synthesizing various types of nanomaterials. The formation processes implicate many physical and chemical phenomena that take place at the electrode surface, as well as in the plasma volume, which renders it difficult to fully understand the underlying mechanisms. In this study, we assess the effect of electric field on nanomaterial synthesis in a system composed of two copper electrodes immersed in water, in the absence of an electrical discharge. The obtained results indicate that various nanostructures, including copper nanoparticles, copper oxide nanowires, and/or hollow nanoparticles, may be produced, depending on the electrical conductivity of the solution (adjusted by adding highly diluted HCl to deionized water). The materials synthesized herein are collected and characterized, and a formation mechanism is proposed. Overall, our results provide insight into the physical and chemical phenomena underlying nanomaterial synthesis in plasmas in liquid.

Plasma-based multi-reforming for Gas-To-Liquid: tuning the plasma chemistry towards methanol.

Because of its unique properties, plasma technology has gained much prominence in the microelectronics industry. Recently, environmental and energy applications of plasmas have gained a lot of attention. In this area, the focus is on converting CO2 and reforming hydrocarbons, with the goal of developing an efficient single-step 'gas-to-liquid' (GTL) process. Here we show that applying tri-reforming principles to plasma-further called 'plasma-based multi-reforming'-allows us to better control the plasma chemistry and thus the formed products. To demonstrate this, we used chemical kinetics calculations supported by experiments and reveal that better control of the plasma chemistry can be achieved by adding O2 or H2O to a mixture containing CH4 and CO2 (diluted in N2). Moreover, by adding O2 and H2O simultaneously, we can tune the plasma chemistry even further, improving the conversions, thermal efficiency and methanol yield. Unlike thermocatalytic reforming, plasma-based reforming is capable of producing methanol in a single step; and compared with traditional plasma-based dry reforming, plasma-based multi-reforming increases the methanol yield by more than seven times and the thermal efficiency by 49%, as revealed by our model calculations. Thus, we believe that by using plasma-based multi-reforming, 'gas-to-liquid' conversion may be made efficient and scalable.

Development of oral CTL vaccine using a CTP-integrated Sabin 1 poliovirus-based vector system.

We developed a CTL vaccine vector by modification of the RPS-Vax system, a mucosal vaccine vector derived from a poliovirus Sabin 1 strain, and generated an oral CTL vaccine against HIV-1. A DNA fragment encoding a cytoplasmic transduction peptide (CTP) was integrated into the RPS-Vax system to generate RPS-CTP, a CTL vaccine vector. An HIV-1 p24 cDNA fragment was introduced into the RPS-CTP vector system and a recombinant poliovirus (rec-PV) named vRPS-CTP/p24 was produced. vRPS-CTP/p24 was genetically stable and efficiently induced Th1 immunity and p24-specific CTLs in immunized poliovirus receptor-transgenic (PVR-Tg) mice. In challenge experiments, PVR-Tg mice that were pre-immunized orally with vRPS-CTP/p24 were resistant to challenge with a lethal dose of p24-expressing recombinant vaccinia virus (rMVA-p24). These results suggested that the RPS-CTP vector system had potential for developing oral CTL vaccines against infectious diseases.