Ox Reduction Research Articles

Interpretation of decadal-scale ozone production efficiency in the Seoul Metropolitan Area: Implication for ozone abatement

Understanding the drivers of urban ozone (O3) formation is challenging and requires uncovering the non-linear relationship between O3 and its precursors. We used a novel method to differentiate between background O3 levels and local photochemical O3 generation using the observation-based O3 production efficiency (OPE) from decade-long observations including nitrogen dioxide (NO2), nitrogen monoxide (NO), reactive nitrogen compounds (NOy), O3, and 56 volatile organic compounds (VOCs) covering eight years (2009–2016). In this study, we employed Ox (=O3+NO2), and defined OPEx as the number of Ox molecules produced from the oxidation of a single NOx molecule, and estimates the local contribution (in %) to total O3 from the slope of the Ox−NOz(=NOy–NOx) linear regression. We thus identified the local urban O3 formation regime using the relationship of several factors, including nitrogen oxide (NOx), VOC/NOx, NO2, NOz, and long-range transported Ox, and suggested how O3 can be reduced in the Seoul Metropolitan Area (SMA).The results show that the regional background dominates the annual level of Ox with a contribution of about 66 ± 11%, while photochemical production acts as a stronger factor influencing the annual variability of Ox than regional background. Regional background varies by transport evidenced by its good correlation with the west wind fraction, whereas photochemical production depends on the VOC/NOx ratio, which is high in summer and low in winter. The relationship between photochemical production and VOC/NOx indicates that the transition of the Ox formation regime occurs at a VOC/NOx ratio of approximately 4 in the SMA. Urban environments with NOx > 20 ppb typically lie in low VOC/NOx zone, where reduced NO2 emissions lead to decreased NOz but increased OPEx, with no discernible change in photochemical Ox production. Thus, NOx emission reductions in urban environments would have a negligible effect on Ox reduction. In contrast, suburban environments such as usually NOx < 10 ppb are located in the higher VOC/NOx zone, where decreased NO2 leads to decreased OPEx with no discernible change in NOz, consequently suppressing photochemical Ox production. Together, these results suggest that any urban O3 policy in the SMA should consider significant cuts in NOx emissions to allow the O3 regime to shift. The OPEx method can also be applied to other urban areas for the development of effective O3 reduction policies.

Carbon-neutral energy cycles using alcohols

We demonstrated carbon-neutral (CN) energy circulation using glycolic acid (GC)/oxalic acid (OX) redox couple. Here, we report fundamental studies on both catalyst search for power generation process, i.e. GC oxidation, and elemental steps for fuel generation process, i.e. OX reduction, in CN cycle. The catalytic activity test on various transition metals revealed that Rh, Pd, Ir, and Pt have preferable features as a catalyst for electrochemical oxidation of GC. A carbon-supported Pt catalyst in alkaline conditions exhibited higher activity, durability, and product selectivity for electrooxidation of GC rather than those in acidic media. The kinetic study on OX reduction clearly indicated that OX reduction undergoes successive two-electron reductions to form GC. Furthermore, application of TiO2 catalysts with large specific area for electrochemical reduction of OX facilitates the selective formation of GC.

Direct Power Charge and Discharge Using the Glycolic Acid/Oxalic Acid Redox Couple toward Carbon-Neutral Energy Circulation

We demonstrated an electric power circulation method that does not emit CO2 and is based on the glycolic acid (GC)/oxalic acid (OX) redox couple. Electric power charge in GC was achieved through OX electro-reduction with high selectivity (>98%) using purely anatase-type TiO2 spheres in the potential region of -0.5 to -0.7 V vs. RHE at 50 ºC. We also realized GC production via the combination of electrochemical OX reduction and electro-oxidation of water with the help of renewable light energy for the first time. Furthermore, we succeeded in power generation via the selective electro-oxidation of GC to OX without CO2 emission. These results are the first experimental proof of the carbon-neutral power circulation involving an alcohol/carboxylic acid redox couple.

Analysis of electrical parameters of organic thin film transistors based on thickness variation in semi‐conducting and dielectric layers

This research study analyses the impact of semi-conductor (t osc) and dielectric (t ox) thicknesses on top contact (TC) and bottom contact (BC) organic thin film transistors (OTFTs) using Atlas 2-D numerical device simulation. Thickness of each layer is varied from 20 to 150 nm. The parameters such as electric field, charge carrier distribution and trap density are analysed from device physics point of view with variations in organic semi-conductor layer and dielectric thicknesses. A decrease of 22% in TC to BC current ratio is observed for maximum increase in t osc, whereas, it remains almost constant at unity with variations in t ox. Furthermore, the maximum mobility for TC is achieved at t osc of 20 nm and reduces monotonically with further increase in thickness because of lowering of average charge. However, its highest value is obtained at 60 nm for BC structure that declines with positive or negative change in t osc. Besides this, the threshold voltage (V t) shows a reduction of 50% for both the structures on scaling down t ox from 150 to 20 nm. Furthermore, the ON to OFF current ratio is found to be more dependent on t osc as compared with t ox. This is because of a dominant impact of t osc reduction on OFF current as compared with impact of t ox reduction on the ON current. Additionally, a decrease in contact resistance (R C) is observed in TC structure for thicker active layer while operating at lower Vgs . However, at high gate voltage, t osc maps to the access resistance that results in higher R C values.

GW24-e1136 Shear stress affects the uptake of oxidised low-density lipoprotein by human vascular endothelial cells

ObjectivesIn vivo, vascular endothelial cells are constantly subjected to and sensitive to fluid shear stress. Shear stress may be the most crucial local factor affecting atherogenesis. Atherosclerotic lesions preferentially develop...

Efficacy and safety of Oxalobacter formigenes to reduce urinary oxalate in primary hyperoxaluria

Primary hyperoxaluria (PH) is a rare genetic disease, in which high urinary oxalate (Uox) cause recurrent kidney stones and/or progressive nephrocalcinosis, often followed by early end-stage renal disease, as well as extremely high plasma oxalate, systemic oxalosis and premature death. Oxalobacter formigenes, an anaerobic oxalate degrading bacterium, naturally colonizes the colon of most humans. Orally administered O. formigenes (Oxabact) was found to significantly reduce urine and plasma oxalate. We aimed to evaluate its effect and safety in a randomized, double-blind, placebo-controlled multicenter study. Oral Oxabact was given to PH patients (>5 years old, Uox > 1.0 mmol/1.73 m(2)/day, glomerular filtration rate (GFR) > 50 mL/min) at nine PH referral sites worldwide. Primary endpoint was the change from baseline in Uox (mmol/1.73 m(2)/day) after 24 weeks of treatment (>20% reduction). Of the 43 subjects randomized, 42 patients received either placebo (23 subjects) or Oxabact (19 subjects). The change in Uox was <20% and not different between groups (P = 0.616). Ad hoc analysis was performed in 37 patients compliant with medication and urine processing. Change in Uox was -19% in subjects given Oxabact and -10% in placebo, (P = 0.288), but -21 and -7% with Uox expressed as molar creatinine ratio (Ox:Cr, mmol/mol, P = 0.06). Reduction of Ox:Cr was more obvious for patients with higher baseline values (>160 mmol/mol, Oxabact -28%, placebo -6%; P < 0.082). No serious adverse events were reported. Oxabact was safe and well tolerated. However, as no significant change in Uox was seen, further studies to evaluate the efficacy of Oxabact treatment are needed.

Recombinant glucose oxidase from Penicillium amagasakiense for efficient bioelectrochemical applications in physiological conditions

GOX is the most widely used enzyme for the development of electrochemical glucose biosensors and biofuel cell in physiological conditions. The present work describes the production of a recombinant glucose oxidase from Penicillium amagasakiense (yGOXpenag) displaying a more efficient glucose catalysis ( k cat/ K M(glucose) = 93 μM −1 s −1) than the native GOX from Aspergillus niger (nGOXaspng), which is the most industrially used ( k cat/ K M(glucose) = 27 μM −1 s −1). Expression in Pichia pastoris allowed easy production and purification of the recombinant active enzyme, without overglycosylation. Its biotechnological interest was further evaluated by measuring kinetics of ferrocinium–methanol (FM ox) reduction, which is commonly used for electron transfer to the electrode surface. Despite their homologies in sequence and structure, pH-dependant FM ox reduction was different between the two enzymes. At physiological pH and temperature, we observed that electron transfer to the redox mediator is also more efficient for yGOXpenag than for nGOXaspng( k cat/ K M(FM ox) = 27 μM −1 s −1 and 17 μM −1 s −1 respectively). In our model system, the catalytic current observed in the presence of blood glucose concentration (5 mM) was two times higher with yGOXpenag than with nGOXaspng. All our results indicated that yGOXpenag is a better candidate for industrial development of efficient bioelectrochemical devices used in physiological conditions.