We report synthesis of hierarchically porous polymers (HPPs) consisting of micropores and well-defined 3D continuous mesopores by combination of hyper-cross-linking and block polymer self-assembly. Copolymerization of 4-vinylbenzyl chloride (VBzCl) with divinylbenzene (DVB) in the presence of polylactide (PLA) macro-chain-transfer agent produced a cross-linked block polymer precursor PLA-b-P(VBzCl-co-DVB) via reversible addition-fragmentation chain transfer polymerization. A nanoscopic bicontinuous morphology containing PLA and P(VBzCl-co-DVB) microdomains was obtained as a result of polymerization-induced microphase separation. While a basic treatment of the precursor selectively removed PLA to yield a reticulated mesoporous polymer, hyper-cross-linking of the precursor by FeCl3 generated micropores in the P(VBzCl-co-DVB) microdomain via Friedel-Crafts alkylation and simultaneously degraded PLA to produce the HPP containing micropores in the mesoporous framework. The mesopore size of the HPP could be precisely controlled from 6 to 15 nm by controlling the molar mass of PLA. We demonstrate acceleration in adsorption rate in the HPP compared to a hyper-cross-linked microporous polymer.
Historically, in Alzheimer's disease research, a lot of attention has been paid to the development of highly selective fluorophores for beta amyloid plaques. With a shift in the understanding of the disease and the importance of a network of cross-talk interactions, the development of small-molecule fluorescent dyes with high selectivity for (hyperphosphorylated) tau protein aggregates in neurofibrillary tangles has been gaining increasing attention. Fluorescent dyes for the selective labelling of tau aggregates in histological AD brain sections have been described, spanning the entire visible range of the electromagnetic spectrum. Despite the relatively early stages of the development of the field, a large diversity in probe architectures has been reported. Importantly, a handful of near-infrared-emissive dyes have been described as well, and some of these have exhibited good pharmacological profiles, with a significant blood-brain-barrier permeability, and a demonstrated ability to label tau tangles in vivo in small-animal models of Alzheimer's disease and other tauopathies. The developments summarized in the current work are expected to aid the unravelling of the diverse set of players in the etiology of Alzheimer's disease. In this tutorial review, we seek to provide the reader with an overview of the most important recent developments and hope to provide some guidelines for the design of future probes.
The warming (solar insolation) and freshening (sea ice melting and riverine water inputs) of the Arctic Ocean during summer increase stratification and suppress the upward mixing of nutrients into the euphotic zone (Codispoti et al., 2013). However, sea ice is now thinner and less compact (Kwok, 2018; Perovich et al., 2020); thus, the Arctic Ocean is more responsive to wind stress (Kwok et al., 2013), which enhances the nutrient supply (Bluhm et al., 2015). Shelf-break upwelling is becoming more prominent in the Arctic as the sea ice edge retreats poleward with ongoing climate change, exposing the shelf break to more direct wind forcing (Arrigo et al., 2014; Carmack & Chapman, 2003; Tremblay et al., 2011). Recently, Lewis et al. (2020) reported that annual net primary production (NPP) increased by 57% over the Arctic Ocean between 1998 and 2018. They also found that increased chlorophyll-a (Chl-a) was responsible for the sustained increase in annual NPP between 2009 and 2018, particularly along the interior shelf break. These results suggest that additional nutrients were supplied from increased vertical mixing near the shelf break into the nutrient-depleted upper euphotic zone (Arrigo & van Dijken, 2015; Lewis et al., 2020) and that the changes in ocean circulation in response to recent sea ice loss and increased wind mixing could significantly influence biological production (Ardyna & Arrigo, 2020). The Arctic Ocean is experiencing radical modifications in its hydrographic properties and in its overall circulation (Ardyna & Arrigo, 2020). For example, Polyakov et al. (2017) reported that the recent increase in Abstract Atlantic-origin cold saline water has previously not been considered an important contributor to the nutrient supply in the Pacific Arctic due to the effective insulation by the overlying Pacific-origin waters that separate the surface mixed layer from the deeper Atlantic Water. Based on hydrographic observations in the northwestern Chukchi Sea from 2015 to 2017, we demonstrate that the intrusion of Atlantic-origin cold saline water into the halocline boundary between Pacific and Atlanticorigin waters in 2017 lifted Pacific-origin nutrients up to the surface layer. We find that the cyclonic atmospheric circulation in 2017 was considerably strengthened, leading to lateral intrusions of two bodies of cold halocline water from the Eurasian marginal seas into the northwestern Chukchi Sea. Our results reveal that the intrusions of cold halocline waters caused unprecedented shoaling of the nutricline and anomalously high surface phytoplankton blooms in typically highly oligotrophic surface waters in the region during summer. Plain Language Summary Nutrient depletion, especially nitrogen, in Arctic surface waters during the summer is common due to biological uptake and intense stratification caused by sea ice melting and riverine water inputs, which restricts the upward mixing of nutrients into the euphotic zone. Although Atlantic-origin cold saline water has previously not been considered an important ...
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