The sensitizing effects of NO2and NO on methane low temperature oxidation in a jet stirred reactor

The oxidation of neat methane (CH4) and CH4doped with NO2or NO in argon has been investigated in a jet-stirred reactor at 107 kPa, temperatures between 650 and 1200 K, with a fixed residence time of 1.5 s, and for different equivalence ratios (Φ), ranging from fuel-lean to fuel-rich conditions. Four different diagnostics have been used: gas chromatography (GC), chemiluminescence NOxanalyzer, continuous wave cavity ring-down spectroscopy (cw-CRDS) and Fourier transform infrared spectroscopy (FTIR). In the case of the oxidation of neat methane, the onset temperature for CH4oxidation was above 1025 K, while it is shifted to 825 K with the addition of NO2or NO, independently of equivalence ratio, indicating that the addition of NO2or NO highly promotes CH4oxidation. The consumption rate of CH4exhibits a similar trend with the presence of both NO2and NO. The amount of produced HCN has been quantified and a search for HONO and CH3NO2species has been attempted. A detailed kinetic mechanism, derived from POLIMI kinetic framework, has been used to interpret the experimental data with a good agreement between experimental data and model predictions. Reaction rate and sensitivity analysis have been conducted to illustrate the kinetic regimes. The fact that the addition of NO or NO2seems to have similar effects on promoting CH4oxidation can be explained by the fact that both species are involved in a reaction cycle interchanging them and whose result is 2CH3+ O2= 2CH2O + 2H. Additionally, the direct participation of NO2in the NO2+ CH2O = HONO + HCO reaction has a notable accelerating effect on methane oxidation

Inkjet Metrology: High-Accuracy Mass Measurements of Microdroplets Produced by a Drop-on-Demand Dispenser

We describe gravimetric methods for measuring the mass of droplets generated by a drop-on-demand (DOD) microdispenser. Droplets are deposited, either continuously at a known frequency or as a burst of known number, into a cylinder positioned on a submicrogram balance. Mass measurements are acquired precisely by computer, and results are corrected for evaporation. Capabilities are demonstrated using isobutyl alcohol droplets. For ejection rates greater than 100 Hz, the repeatability of droplet mass measurements was 0.2%, while the combined relative standard uncertainty (uc) was 0.9%. When bursts of droplets were dispensed, the limit of quantitation was 72 μg (1490 droplets) with uc = 1.0%. Individual droplet size in a burst was evaluated by high-speed videography. Diameters were consistent from the tenth droplet onward, and the mass of an individual droplet was best estimated by the average droplet mass with a combined uncertainty of about 1%. Diameters of the first several droplets were anomalous, but their contribution was accounted for when dispensing bursts. Above the limits of quantitation, the gravimetric methods provided statistically equivalent results and permit detailed study of operational factors that influence droplet mass during dispensing, including the development of reliable microassays and standard materials using DOD technologies

Stress granules, RNA-binding proteins and polyglutamine diseases: too much aggregation?

Stress granules (SGs) are membraneless cell compartments formed in response to different stress stimuli, wherein translation factors, mRNAs, RNA-binding proteins (RBPs) and other proteins coalesce together. SGs assembly is crucial for cell survival, since SGs are implicated in the regulation of translation, mRNA storage and stabilization and cell signalling, during stress. One defining feature of SGs is their dynamism, as they are quickly assembled upon stress and then rapidly dispersed after the stress source is no longer present. Recently, SGs dynamics, their components and their functions have begun to be studied in the context of human diseases. Interestingly, the regulated protein self-assembly that mediates SG formation contrasts with the pathological protein aggregation that is a feature of several neurodegenerative diseases. In particular, aberrant protein coalescence is a key feature of polyglutamine (PolyQ) diseases, a group of nine disorders that are caused by an abnormal expansion of PolyQ tract-bearing proteins, which increases the propensity of those proteins to aggregate. Available data concerning the abnormal properties of the mutant PolyQ disease-causing proteins and their involvement in stress response dysregulation strongly suggests an important role for SGs in the pathogenesis of PolyQ disorders. This review aims at discussing the evidence supporting the existence of a link between SGs functionality and PolyQ disorders, by focusing on the biology of SGs and on the way it can be altered in a PolyQ disease context.ALG-01-0145-FEDER-29480, SFRH/BD/133192/2017, SFRH/BD/133192/2017, SFRH/BD/148533/2019info:eu-repo/semantics/publishedVersio

Entwicklung neuer Prozeduren zur Elementbestimmung und Speziation in Vanadium Redox Flow Batterien

Die Vanadium Redox Flow Batterie (VRFB) hat ein großes Potenzial als kommerzielles elektrochemisches Energiespeichersystem eingesetzt zu werden, aufgrund von ausge-zeichneten Eigenschaften wie zum Beispiel einer langen Lebensdauer sowie einer theo-retisch unendlich hohen Kapazität. Die am meiste verwendete Membran in VRFB ist Nafion™ (DuPont), welche neben mehreren positiven Eigenschaften wie einer guten chemischen und mechanischen Stabilität auch eine sehr schlechte Ionenselektivität be-sitzt. Aufgrund dieser schlechten Ionenselektivität werden nicht nur Protonen, sondern auch Vanadium-Ionen durch die Nafion Membran transportiert. Die Folgen dieses Pro-zesses, auch Crossover genannt, sind in der Regel über mehrere Lade-Entlade-Zyklen eine Zunahme der Vanadium-Menge im Positiven Elektrolyten (PE), eine Volumenzu-nahme des PE, die Selbstentladung der Batterie sowie schlussendlich die Abnahme der Kapazität. Die genauen Transportprozesse von Vanadium-Ionen durch die Membran sind noch nicht verstanden. Dies wird unterstrichen durch die publizierten Diffusions-koeffizienten der Vanadium-Spezies. Zum Beispiel befinden sich die veröffentlichten Diffusionskoeffizienten von VII zwischen 3,13 · 10-12 m2s-1 und 9,44 · 10-12 m2s-1. Für ein besseres Verständnis der Transportvorgänge in der Membran einer VRFB, fokussiert sich unsere Arbeit auf die Entwicklung neuer Prozeduren für die Elementbestimmung und Speziation von Vanadium in VRFB mittels Photometrie und Labor-Röntgen-Nah-kanten-Absorptions-Spektroskopie (XANES). In der folgenden Arbeit wird gezeigt, dass Nafion™ 117 bei 18 °C 22,89 ± 0,58 % Wasser aufnimmt und nach einer Konditi-onierung in einem Vanadium-Elektrolyten die wässrige Phase des Nafion™ eine Vana-dium-Konzentration von 1,029 ± 0,024 mol kg-1 aufweist. Der Gehalt auf die hydrierte Membran bezogen beträgt 0,192 ± 0,004 mol kg-1, welcher λ = n(V)/n(SO3) = 0,211 ± 0,005 entspricht. Zusätzlich wird gezeigt, dass sich sowohl die Photometrie als auch die Labor-XANES zur direkten Speziation von Vanadium in Nafion™ eignen