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Abstract The source of dust in the global atmosphere is an important factor to better understand the role of dust aerosols in the climate system. However, it is a difficult task to attribute the airborne dust over the remote land and ocean regions to their origins since dust from various sources are mixed during long‐range transport. Recently, a multi‐model experiment, namely the AeroCom‐III Dust Source Attribution (DUSA), has been conducted to estimate the relative contribution of dust in various locations from different sources with tagged simulations from seven participating global models. The BASE run and a series of runs with nine tagged regions were made to estimate the contribution of dust emitted in East‐ and West‐Africa, Middle East, Central‐ and East‐Asia, North America, the Southern Hemisphere, and the prominent dust hot spots of the Bodélé and Taklimakan Deserts. The models generally agree in large scale mean dust distributions, however models show large diversity in dust source attribution. The inter‐model differences are significant with the global model dust diversity in 30%–50%, but the differences in regional and seasonal scales are even larger. The multi‐model analysis estimates that North Africa contributes 60% of global atmospheric dust loading, followed by Middle East and Central Asia sources (24%). Southern hemispheric sources account for 10% of global dust loading, however it contributes more than 70% of dust over the Southern Hemisphere. The study provides quantitative estimates of the impact of dust emitted from different source regions on the globe and various receptor regions including remote land, ocean, and the polar regions synthesized from the seven models. 

Copper(I) halides are often added to olefin metathesis reactions to inhibit catalyst degradation, control product isomerization, enhance catalyst activation, or facilitate catalyst dimerization. In each of these examples, the copper salt is presumed to operate as an independent species, separate from the ruthenium center. We have discovered, however, that certain copper salts can form complexes with the ruthenium catalyst itself, forming hetero-bimetallic copper-ruthenium olefin metathesis catalysts. We confirmed the formation of two complexes through single-crystal X-ray crystallography and NMR spectroscopy. The crystal structure revealed the presence of a four-member ring containing ruthenium, carbon, copper, and chlorine or bromine. The hetero-bimetallic catalyst displayed higher latency and lower activity in the ring-opening metathesis polymerization (ROMP) of norbornene compared to analogous monometallic catalysts. For example, norbornene polymerization catalyzed by the monometallic complex reached 80 % conversion after 4 h, but only 12% conversion when catalyzed by the hetero-bimetallic copper-ruthenium complex under the same conditions. Conversion increased to 63 % when the temperature increased to 50 °C for 1 h, indicating that the bimetallic complex retains activity but requires a higher temperature to activate. The formation of these copper-ruthenium bimetallic complexes suggests the possibility of multi-metallic olefin metathesis catalysts, potentially with different activity and properties than their traditional monometallic counterparts. 

We describe the theory and application of SEC-MALS with minimal equations and a focus on synthetic polymer characterization. 

Abstract Atmospheric aerosol and chemistry modules are key elements in Earth system models (ESMs), as they predict air pollutant concentrations and properties that can impact human health, weather, and climate. The current uncertainty in climate projections is partly due to the inaccurate representation of aerosol direct and indirect forcing. Aerosol/chemistry parameterizations used within ESMs and other atmospheric models span large structural and parameter uncertainties that are difficult to assess independently of their host models. Moreover, there is a strong need for a standardized interface between aerosol/chemistry modules and the host model to facilitate portability of aerosol/chemistry parameterizations from one model to another, allowing not only a comparison between different parameterizations within the same modeling framework, but also quantifying the impact of different model frameworks on aerosol/chemistry predictions. To address this need, we have initiated a new community effort to coordinate the construction of a Generalized Aerosol/Chemistry Interface (GIANT) for use across weather and climate models. We aim to organize a series of community workshops and hackathons to design and build GIANT, which will serve as the interface between a range of aerosol/chemistry modules and the physics and dynamics components of atmospheric host models. GIANT will leverage ongoing efforts at the U.S. modeling centers focused on building next-generation ESMs and the international AeroCom initiative to implement this common aerosol/chemistry interface. GIANT will create transformative opportunities for scientists and students to conduct innovative research to better characterize structural and parametric uncertainties in aerosol/chemistry modules, and to develop a common set of aerosol/chemistry parameterizations. 

We synthesized bottlebrush polymers with polyaziridine brushes and a polynorbornene backbone by a grafting-through approach. Polyaziridine macromonomers were synthesized by aza-anoinic polymerization of an N -tosylaziridine, initiated with a norbornene-functionalized sulfonamide anion. These macromonomers were then polymerized by ring-opening metathesis polymerization (ROMP) in dichloromethane to produce bottlebrush polymers with molecular weights of 136–456 kDa. To investigate potential macromonomer aggregation that would hinder grafting-through polymerization, we used dynamic light scattering (DLS) to measure the change in macromonomer aggregation and the growth of bottlebrush chains during ROMP. We observed that the macromonomers aggregate in solution, but once ROMP is initiated, these aggregates disperse over the course of the polymerization. This solution behavior appears to be an example of polymerization-induced deaggregation. 

We have measured differential yields for double capture and double capture accompanied by ionization in 75 keV p + Ar collisions. Data were taken for two different transverse projectile coherence lengths. A small effect of the projectile coherence properties on the yields were found for double capture, but not for double capture plus ionization. The results suggest that multiple projectile–target interactions can lead to a significant weakening of projectile coherence effects.