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Author(s): Xu, Ming; Daigger, Glen T; Xi, Chuanwu; Liu, Jianguo; Qu, Jiuhui; Alvarez, Pedro J; Biswas, Pratim; Chen, Yongsheng; Dolinoy, Dana; Fan, Ying; Gao, Huaizhu Oliver; Hao, Jiming; He, Hong; Kammen, Daniel M; Lemos, Maria Carmen; Liu, Fudong; Love, Nancy G; Lu, Yonglong; Mauzerall, Denise L; Miller, Shelie A; Ouyang, Zhiyun; Overpeck, Jonathan T; Peng, Wei; Ramaswami, Anu; Ren, Zhiyong; Wang, Aijie; Wu, Brian; Wu, Ye; Zhang, Junfeng; Zheng, Chunmiao; Zhu, Bing; Zhu, Tong; Chen, Wei-Qiang; Liu, Gang; Qu, Shen; Wang, Chunyan; Wang, Yutao; Yu, Xueying; Zhang, Chao; Zhang, Hongliang

Waste paper, an essential substitute for wood and other plant-based fibers in paper making, is an indispensable part of the circular economy; yet, the impacts of China's ban on global waste paper cycles have not been well understood. We modeled the evolution of the global waste paper trade network during 1995-2019. We found that the cumulative trade volume of global waste paper reached 1010 million tons in the last 25 years and showed a downward trend since 2015. The global import center of waste paper experienced a transfer from Europe to East Asia and then to Southeast Asia. The ban has stimulated some developed countries to reduce the exports of unsorted waste paper since 2017, but for many major importers their changes in waste paper trade patterns were related to waste paperboard, which was not banned by China, suggesting that this import change trend may be inevitable and irrespective of China's ban. Besides, India has replaced China to become a new import hub of unsorted waste paper. Our results lay a foundation for exploring the evolution of the future global solid waste cycle under the background of zero import of solid waste increasingly implemented by China and many other developing countries.

In this study, we present a holistic analysis of the stock and emissions of poly- and perfluoroalkyl substances (PFAS) in California carpet in 2000-2030. Our high estimate is that, in 2017, the total PFAS accumulated in in-use carpet stock and landfilled carpet are ∼60 and ∼120 tonnes, respectively, and the resultant PFAS emissions are ∼800 and ∼100 kg, respectively. Among the three subclasses (side-chain polymers, PFAA, and nonpolymeric precursors), side-chain polymers dominate the in-use stock and landfill accumulation, while nonpolymeric precursors dominate the resultant emissions. Our low estimate is typically 8-15% of the high estimate and follows similar trends and subclass breakdowns as the high estimate. California's new Carpet Stewardship Regulations (24% recycling of end-of-life carpet) will reduce the landfilled PFAS by 6% (7 tonnes) at the cost of increasing the in-use stock by 2% (2 tonnes) in 2030. Aggressive PFAS phase-out by carpet manufacturers (i.e., reduce PFAS use by 15% annually starting 2020) could reduce the in-use PFAS stock by 50% by 2030, but its impact on the total landfilled PFAS is limited. The shift toward short-chain PFAS will also significantly reduce the in-use stock of long-chain PFAS in carpet by 2030 (only 25% of the total PFAS will be long-chain). Among the data gaps identified, a key one is the current area-based PFAS emission reporting (i.e., g PFAS emitted/area carpet/time), which leads to the counterintuitive result that reducing the PFAS use in carpet production has no impact on the PFAS emissions from in-use stock and landfills. Future technical studies should either confirm this or consider a mass-based unit (e.g., g PFAS emitted/g PFAS used/time) for better integration into regional substance flow analysis. Other noticeable data gaps include the lack of time-series data on emissions from the in-use stock and on leaching of side-chain polymers from landfills.

How an interfacial superconductivity emerges during the nucleation and epitaxy is of great importance not only for unveiling the physical insights but also for finding a feasible way to tune the superconductivity via interfacial engineering. In this work, we report the nanoscale creation of a robust and relatively homogeneous interfacial superconductivity (TC ≈ 13 K) on the epitaxial FeTe surface, by van der Waals epitaxy of single-quintuple-layer topological insulator Bi2Te3. Our study suggests that the superconductivity in the Bi2Te3/FeTe heterostructure is generated at the interface and that the superconductivity at the interface does not enhance or weaken with the increase of the Bi2Te3 thickness beyond 1 quintuple layer (QL). The observation of the topological surface states crossing Fermi energy in the Bi2Te3/FeTe heterostructure with the average Bi2Te3 thickness of about 20 QL provides further evidence that this heterostructure may potentially host Majorana zero modes.

Bisphenol A (BPA), a synthetic organic chemical, is creating a new category of ecological and human health challenges due to unintended leakage. Effectively managing the use and leakage of BPA can benefit from an understanding of the anthropogenic BPA cycles (i.e., the size of BPA flows and stocks). In this work, we provide a dynamic analysis of the anthropogenic BPA cycles in China for 2000-2014. We find that China's BPA consumption has increased 10-fold since 2000, to ∼3 million tonnes/year. With the increasing consumption, China's in-use BPA stock has increased 500-fold to 14.0 million tonnes (i.e., 10.2 kg BPA/capita). It is unclear whether a saturation point has been reached, but in 2004-2014, China's in-use BPA stock has been increasing by 0.8 kg BPA/capita annually. Electronic products are the biggest contributor, responsible for roughly one-third of China's in-use BPA stock. Optical media (DVD/VCD/CDs) is the largest contributor to China's current End-of-Life (EoL) BPA flow, totaling 0.9 million tonnes/year. However, the EoL BPA flow due to e-waste will increase quickly, and will soon become the largest EoL BPA flow. The changing quantities and sources of EoL BPA flows may require a shift in the macroscopic BPA management strategies.

International audience; Based on the combination of the U.S. economic input-output table and the stocks and flows framework for characterizing anthropogenic metal cycles, this study presents a methodology for building material flow networks of bulk metals in the U.S. economy and applies it to aluminum. The results, which we term the Input–Output Material Flow Networks (IO-MFNs), achieve a complete picture of aluminum flow in the entire U.S. economy and for any chosen industrial sector (illustrated for the Automobile Manufacturing sector). The results are compared with information from our former study on U.S. aluminum stocks and flows to demonstrate the robustness and value of this new methodology. We find that the IO-MFN approach has the following advantages: (1) it helps to uncover the network of material flows in the manufacturing stage in the life cycle of metals; (2) it provides a method that may be less time-consuming but more complete and accurate in estimating new scrap generation, process loss, domestic final demand, and trade of final products of metals, than existing material flow analysis approaches; and, most importantly, (3) it enables the analysis of the material flows of metals in the U.S. economy from a network perspective, rather than merely that of a life cycle chain.

Newly defined categories of WEEE have increased the types of China's regulated WEEE from 5 to 14. Identification of the amounts and valuable-resource components of the "new" WEEE generated is critical to solving the e-waste problem, for both governmental policy decisions and recycling enterprise expansions. This study first estimates and predicts China's new WEEE generation for the period of 2010-2030 using material flow analysis and the lifespan model of the Weibull distribution, then determines the amounts of valuable resources (e.g., base materials, precious metals, and rare-earth minerals) encased annually in WEEE, and their dynamic transfer from in-use stock to waste. Main findings include the following: (i) China will generate 15.5 and 28.4 million tons WEEE in 2020 and 2030, respectively, and has already overtaken the U.S. to become the world's leading producer of e-waste; (ii) among all the types of WEEE, air conditioners, desktop personal computers, refrigerators, and washing machines contribute over 70% of total WEEE by weight. The two categories of EEE-electronic devices and electrical appliances-each contribute about half of total WEEE by weight; (iii) more and more valuable resources have been transferred from in-use products to WEEE, significantly enhancing the recycling potential of WEEE from an economic perspective; and (iv) WEEE recycling potential has been evolving from ∼16 (10-22) billion US$ in 2010, to an anticipated ∼42 (26-58) billion US$ in 2020 and ∼73.4 (44.5-103.4) billion US$ by 2030. All the obtained results can improve the knowledge base for closing the loop of WEEE recycling, and contribute to governmental policy making and the recycling industry's business development.

Enantioenriched α-exo-methylene γ-butyrolactones have been obtained via a two-step sequence consisting of a highly enantioselective chromium-catalyzed carbonyl 2-(alkoxycarbonyl)allylation and lactonization. A variety of functional groups are compatible under the mild reaction conditions. The synthetic utility of this methodology was demonstrated by two short derivatization transformations and the enantioselective synthesis of (+)-methylenolactocin.

Nanoformulations show many therapeutic advantages over conventional formulations. We seek to develop traceable nanoformulations in order to closely monitor delivery. Herein, we developed a new drug delivery system (DDS) using tetraphenylethene (TPE) to fabricate a self-assembly micelle with aggregation-induced emission (AIE micelle). AIE makes the nanocarriers visible for high-quality imaging, and the switching on and off of the AIE is intrinsically controlled by the assembly and disassembly of the micelles. This DDS was tested for doxorubicin (DOX) delivery and intracellular imaging. For the DOX-loaded micelles (TPED), the DOX content reached as much as 15.3% by weight, and the anticancer efficiency was higher than for free DOX. Meanwhile, high-quality imaging was obtained to trace the intracellular delivery of the TPED.

Tetraphenylethylene (TPE), an archetypal luminogen with aggregation-induced emission (AIE), was grafted to a salt-responsive peptide to yield a yet luminescent hydrogelator. After testing different parameters, we found that only in the presence of salt rather than temperature, pH, and solvent, did the monodisperse hydrogelators self-assemble into a hydrogel network with bright emission turned on. The induced luminescence was a dynamic change and enabled real time monitoring of hydrogel formation. Grating AIE molecules to stimuli-responsive peptides is a promising approach for the development of self-revealing soft materials for biological applications.

A cycle is the quantitative characterization of the flows of a specific material into, within, and from a given system. An anthropogenic elemental cycle can be static (for a point in time) or dynamic (over a time interval). The about 350 publications collected for this review contain a total of 1074 individual cycle determinations, 989 static and 85 dynamic, for 59 elements; more than 90% of the publications have appeared since 2000. The cycles are of varying quality and completeness, with about 80% at country- or territory-level, addressing 45 elements, and 5% at global-level, addressing 30 elements. Despite their limitations, cycles have often been successful in revealing otherwise unknown information. Most of the elements for which no cycles exist are radioactively unstable or are used rarely and in small amounts. For a variety of reasons, the anthropogenic cycles of only perhaps a dozen elements are well characterized. For all the others, with cycles limited or nonexistent, our knowledge of types of uses, lifetimes in those uses, international trade, losses to the environment, and rates of recycling is quite limited, thereby making attempts to evaluate resource sustainability particularly problematic.

The nonlinear optical properties of the size-controlled trans-4-[4-(dimethylamino)-N-methylstilbazolium] p-tosylate (DAST) organic nanocrystals (ONCs) have been investigated. The size and monoclinic crystal structure have been demonstrated by the scanning electron microscope, transmission electron microscope, and X-ray diffraction measurement. The DAST ONCs exhibited 6-fold enhanced fluorescence quantum yield and prolonged fluorescence lifetime compared to DAST molecular solution. The evaluations of two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) microscopes have been implemented for investigating the optical nonlinearities of DAST nanocrystals. The TPEF intensity of DAST ONCs was improved by a factor of 37.3 compared to DAST molecular solution. The extraordinary large two-photon absorption cross section up to 1.72 × 106 GM was observed. DAST ONC was demonstrated as a single crystal from the four-lobe polarization response in the SHG microscope. These results would provide DAST...

A new low-bandgap π-conjugated D–A copolymer of squaraine and pyridopyrazine (P1) and a new small molecule squaraine–pyridopyrazine model compound (P2) were synthesized and compared. P1 and P2 exhibit strong NIR absorption and low bandgap (1–1.3 eV). P2 in solution shows an intense and sharp absorption peak at 764 nm, while P1 in solution exhibits a red-shifted and broad absorption peak at 808 nm. The HOMO and LUMO levels of P1 were estimated to be −5.02 and −4.15 eV, while the HOMO and LUMO levels of P2 were estimated to be −5.27 and −3.22 eV, respectively. Polymer P1 exhibits strong two-photon absorption (2PA) at telecommunication wavelengths with 2PA cross sections per repeat unit as high as 2300 GM, 3–5 times that for the small molecule P2. The higher HOMO, the lower LUMO levels, lower bandgap, red-shifted absorption, and stronger two-photon absorption of P1 are attributed to higher degree of conjugation and delocalization of π-electrons in the polymer.

Two new low-bandgap, conjugated donor (D)−acceptor (A) copolymers of porphyrin with 2,3-bis(4-trifluoromethylphenyl)pyrido[3,4-b]pyrazine (P1) and perylene diimide (P2) were synthesized by Sonogashira coupling polymerization and compared with porphyrin−dithienothiophene D−D copolymer (P3). All these polymers possess good thermal stability with decomposition temperatures over 300 °C. Polymers P1 and P2 in films exhibit strong absorption in near-IR (820−950 nm) with optical bandgaps as low as 1.15 eV; their Q-bands red shift 60−190 nm compared to that of P3, while the Soret bands are similar. The HOMO (−5.3 to −5.4 eV) and LUMO (−3.6 to −4.0 eV) of the D−A polymers are lower than that of the D−D polymer. Two-photon absorption (2PA) properties of the polymers were investigated by the femtosecond Z-scan method. The D−A polymer P2 exhibits 2PA cross sections over 7000 GM/repeat unit at telecommunication wavelengths (1320 and 1520 nm), larger than that of P1 and P3, due to the very strong, rigid, and coplanar p...

The first bis(BF(2)) core complex containing a 1,8-naphthyridin derivative (1,2-bis(5,7-dimethyl-1,8-naphthyridin-2-yl)hydrazine) and with yellow-green emission as well as a high quantum yield was synthesized and structurally characterized, and the compound exhibits two-photon absorption and excited fluorescence properties.

Ceramide kinase (CERK) is essential for production of ceramide-1-phosphate (C1P), a bioactive lipid whose formation critically modulates ceramide levels. To explore how CERK is regulated, we used insect cell-expressed, recombinant hCERK and searched for post-translational modifications, using mass-spectrometry techniques. This led to identification of two phosphorylated serine residues, at positions 340 and 408. Point mutations preventing phosphorylation at either of these sites did not lead to detectable changes in subcellular localization or activity. However, preventing phosphorylation at S340 resulted in CERK instability as revealed by the behavior of the S340A mutant protein under various assay conditions in vitro. Phosphorylation of a cognate serine residue in sphingosine kinases was previously shown to be important. Therefore, phosphorylation within a conserved "regulation loop" downstream of the catalytic domain emerges as a new paradigm for regulation of kinases of the diacylglycerol kinase family. This "regulation loop" is reminiscent of the "activation loop" that controls AGC protein kinases, being a similar distance from the critical ATP binding site determinants in the primary sequence.

We propose a novel method for probing aggregation of dendrimers by investigating the isomerization equilibrium between pink zwitterionic form (Z-form) and colorless lactonic form (L-form) of rhodamine B (RhB) molecules in dilute solution. Investigation using carbosiloxane dendrimers (CSiO-D) with different generations as the model dendrimer molecules showed that the equilibrium constant of isomerization of RhB increased dramatically at the critical aggregation concentration (CAC) of dendrimers. The redox potential differences between isomers of RhB indicated that aggregation of CSiO-D accelerated the isomerization of RhB and stabilized the L-form of RhB. The data on Gibbs energy and electrolytic conductivity provided further evidence for confirming the CAC of dendrimers in dilute solution and showed good agreement with our other experimental results. The proposed method is effective in estimating the CAC of dendrimers in dilute solution.

Systematic work on differential protein expression in mitosis is limited, and we therefore used neuroblastoma cells (N1E-115) incubated with either colcemid or nocodazole to arrest mitosis. Proteins were identified by MALDI-TOF/TOF and nano-LC-ESI-MS/MS with subsequent quantification of spot volumes with specific software. Immunoblotting was used for verification of selected proteins. Levels of 10 individual proteins were increased and levels of 6 proteins were decreased concordantly by both treatments. These proteins were constituents of heat shock and chaperone, cytoskeleton, proteasomal, heterochromatin, and DNA replication signaling as well as housekeeping and metabolic systems. Identification of mitosis-dependent proteins is of importance for the interpretation of previous work and for designing future experiments.