We have studied a sample of 809 Mg ii absorption systems with 1.0 ≤zabs≤ 1.86 in the spectra of Sloan Digital Sky Survey quasi‐stellar objects (QSOs), with the aim of understanding the nature and abundance of the dust and the chemical abundances in the intervening absorbers. Normalized, composite spectra were derived, for abundance measurements, for the full sample and several subsamples, chosen on the basis of the line strengths and other absorber and QSO properties. Average extinction curves were obtained for the subsamples by comparing their geometric mean spectra with those of matching samples of QSOs without absorbers in their spectra. There is clear evidence for the presence of dust in the intervening absorbers. The 2175‐Å feature is not present in the extinction curves, for any of the subsamples. The extinction curves are similar to the Small Magellanic Cloud (SMC) extinction curve with a rising ultraviolet (UV) extinction below 2200 Å. The absorber rest‐frame colour excess, E(B−V), derived from the extinction curves, depends on the absorber properties and ranges from <0.001 to 0.085 for various subsamples. The column densities of Mg ii, Al ii, Si ii, Ca ii, Ti ii, Cr ii, Mn ii, Fe ii, Co ii, Ni ii and Zn ii do not show such a correspondingly large variation. The overall depletions in the high E(B−V) samples are consistent with those found for individual damped Lyman α systems, the depletion pattern being similar to halo clouds in the Galaxy. Assuming an SMC gas‐to‐dust ratio, we find a trend of increasing abundance with decreasing extinction; systems with NH I∼ 1020 cm−2 show solar abundance of Zn. The large velocity spread of strong Mg ii systems seems to be mimicked by weak lines of other elements. The ionization of the absorbers, in general appears to be low: the ratio of the column densities of Al iii to Al ii is always less than 1/2. QSOs with absorbers are, in general, at least three times as likely to have highly reddened spectra as compared to QSOs without any absorption systems in their spectra.

SARS‐CoV‐2 and other respiratory viruses spread via aerosols generated by infected people. Face masks can limit transmission. However, widespread use of disposable masks consumes tremendous resources and generates waste. Here, a novel material for treating blown polypropylene filtration media used in medical‐grade masks to impart antimicrobial activity is reported. To produce thin copper@ZIF‐8 core‐shell nanowires (Cu@ZIF‐8 NWs), Cu NWs are stabilized using a pluronic F‐127 block copolymer, followed by growth of ZIF‐8 to obtain uniform core‐shell structures. The Cu@ZIF‐8 NWs are applied to filtration media by dip coating. Aerosol filtration efficiency decreases upon exposure to ethanol (solvent for dip‐coating), but increases with addition of Cu@ZIF‐8 NWs. Cu@ZIF‐8 NWs shows enhanced antibacterial activity, compared to Cu NWs or ZIF‐8 alone, against Streptococcus mutans and Escherichia coli . Antiviral activity against SARS‐CoV‐2 is assayed using virus‐infected Vero E6 cells, demonstrating 55% inhibition of virus replication after 48 h by 1 µg of Cu@ZIF‐8 NWs per well. Cu@ZIF‐8 NWs’ cytotoxicity is tested against four cell lines, and their effect on inflammatory response in A549 cells is examined, demonstrating good biocompatibility. This low‐cost, scalable synthesis and straightforward deposition of Cu@ZIF‐8 NWs onto filter media has great potential to reduce disease transmission, resource consumption, and environmental impact of waste.

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We review the synthesis, characterization, and applications of one-dimensional palladium-based nanostructures and provide perspectives on future directions in this field.

We propose a simple model where dark matter (DM) carries top flavor and couples to the Standard Model through the top quark within a framework of minimal flavor violation (MFV).Top-flavored DM can explain the anomalous top forward-backward asymmetry observed at the Tevatron, while remaining consistent with other top observables at colliders. By virtue of its large coupling to top, DM acquires a sizable loop coupling to the Z boson, and the relic density is set by annihilation through the Z. We also discuss contraints from current direct detection searches, emphasizing the role of spin-dependent searches to probe this scenario. * Electronic address: abhishek@triumf.ca † Electronic address: tulin@umich.edu