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Furans are a major class of volatile organic compounds emitted from biomass burning. Their high reactivity with atmospheric oxidants leads to the formation of secondary organic aerosol (SOA), including secondary brown carbon (BrC) that can affect global climate via interactions with solar radiation. Here, we investigate the optical properties and chemical composition of SOA generated via photooxidation of furfural, 2‐methylfuran, and 3‐methylfuran under dry (RH < 5%) and humid (RH ∼ 50%) conditions in the presence of nitrogen oxides (NOx) and ammonium sulfate seed aerosol. Dry furfural oxidation has the greatest BrC formation, including reduced nitrogen‐containing organic compounds (NOCs) in SOA, which are dominated by amines and amides formed from reactions between carbonyls and ammonia/ammonium. Based on the products detected, we propose novel formation pathways of NOCs in furfural photooxidation, which can contribute to BrC via accretion reactions during the photochemical aging of biomass burning plumes. Plain Language Summary: Biomass burning is a substantial source of both gas‐ and particle‐phase carbon to the atmosphere, including light‐absorbing aerosol known as brown carbon. Brown carbon can be emitted directly from combustion activities and also formed through the oxidation of gas‐phase carbon, known as secondary brown carbon. In this study, we investigate secondary brown aerosol formation from furans (chemicals with a five‐membered aromatic ring with four carbon atoms and one oxygen atom), one of the major classes of gaseous compounds emitted from biomass burning. We find that furfural is an important subset of furans that generates substantial brown carbon during oxidation, with corresponding formation of nitrogen‐containing organic compounds. Key Points: Photooxidation of furans in the presence of NOx and ammonium sulfate aerosol leads to secondary brown carbon formationOptical properties of secondary brown carbon from furfural photooxidation are comparable to ambient biomass burning observationsReduced nitrogen species are associated with brown carbon formation from furfural photooxidation and are enhanced under dry conditions [ABSTRACT FROM AUTHOR]

A delta-sigma (ΔΣ) digitised polar RF transmitter with a CMOS switching power amplifier is presented. The proposed power amplifier consists of a class-E amplifier with a modulating current source which allows high efficiency and high linearity. A current source is introduced in the proposed power amplifier to achieve ΔΣ digitised amplitude modulation. The current mode amplitude modulation is suitable for a high speed modulated signal such as an oversampled ΔΣ signal. [ABSTRACT FROM AUTHOR]

One of the most challenging fundamental problems in establishing prebiotically plausible routes for phosphorylation reactions using phosphate is that they are thermodynamically unfavorable in aqueous conditions. Diamidophosphate (DAP), a potentially prebiotically relevant compound, was shown to phosphorylate nucleosides in aqueous medium, albeit at a very slow rate (days/weeks). Here, we demonstrate that performing these reactions within an aerosol environment, a suitable model for the early Earth ocean-air interface, yields higher reaction rates when compared to bulk solution, thus overcoming these rate limitations. As a proof-of-concept, we demonstrate the effective conversion (~6.5–10%) of uridine to uridine-2′,3′-cyclophosphate in less than 1 h. These results suggest that aerosol environments are a possible scenario in which prebiotic phosphorylation could have occurred despite unfavorable rates in bulk solution. [ABSTRACT FROM AUTHOR]

Ferromagnetic Bi–Cu codoped ZnO nanowires were fabricated at temperatures as low as 300 °C via a vapor phase transport using the mixture of Zn, BiI3 and CuI powders. They are grown as a bicrystal, along the [0112] direction, have a width of 40–150 nm, and a length of a few microns. The investigation of the growth mechanism proposes that the synergy of BiCu and iodine/iodide induces the formation of bicrystallinity. The photoluminescence measurement shows the cooperative effect of Bi and Cu ions. The ferromagnetism observed in this study is the result of the combined effect of structural defects, the substitution of Cu into Zn site along the c axis, and codoping of Bi. [ABSTRACT FROM AUTHOR]

We report on photoluminescence (PL) spectra of ZnO films grown by low pressure metalorganic vapor phase epitaxy. For PL measurements, high quality ZnO thin films were epitaxially grown on A1[sub 2]O[sub 3](0001) substrates. Time-integrated PL spectra of the films at 10 K clearly exhibited free A and B excitons at 3.376 and 3.382 eV and bound exciton peaks at 3.360, 3.364, and 3.367 eV. With increasing temperature, intensities of the bound exciton peaks drastically decreased and a free exciton peak was dominant above 40 K. Furthermore, time-resolved PL measurements at the free exciton peak were carried out at room temperature. The decay profiles were of double-exponential form, and the decay time constants of 180 ps and 1.0 ns were obtained using a least-square fit of the data. [ABSTRACT FROM AUTHOR]