Income distribution and unequal gains from trade

This paper studies welfare gains from trade in a tractable model with a nonhomothetic preference over product quality. We show that the welfare changes due to trade shocks are unequal across consumers and derive a parsimonious formula to measure these welfare changes as in Arkolakis et al. (2012, American Economic Review, 102, 94–130). We find that the welfare changes are larger for consumers with lower income. Moreover, this paper shows that the welfare implications are different between a change in (iceberg-type) variable trade cost and a change in tariff when tariff revenue matters. More importantly, we show that the difference varies across consumers with different income levels.</p

Income distribution and unequal gains from trade

This paper studies welfare gains from trade in a tractable model with a nonhomothetic preference over product quality. We show that the welfare changes due to trade shocks are unequal across consumers and derive a parsimonious formula to measure these welfare changes as in Arkolakis et al. (2012, American Economic Review, 102, 94–130). We find that the welfare changes are larger for consumers with lower income. Moreover, this paper shows that the welfare implications are different between a change in (iceberg-type) variable trade cost and a change in tariff when tariff revenue matters. More importantly, we show that the difference varies across consumers with different income levels.</p

Export quality differentiation in learning from neighbors

This paper explores how learning from neighboring firms affects new exporters’ product quality. We build a Bayesian learning model where new exporters can update their prior beliefs about the quality preference of foreign markets from their neighboring pioneering exporters. Our model shows that a new exporter raises its product quality when it receives a positive signal from its neighbors. The learning process of a firm depends on the number of neighbors, the level and heterogeneity of their export quality, and its own prior knowledge of the market. Using highly disaggregated firm-product-country-level transaction data, we find robust evidences for these predictions. Our results also suggest the impact of neighboring signals on a new exporter’s quality is channeled through the imports of high-quality intermediate inputs and more fixed investment. In addition, we find that the learning effect are heterogeneous across firms and learning can influence other aspects of export performance.</p

Export quality differentiation in learning from neighbors

This paper explores how learning from neighboring firms affects new exporters’ product quality. We build a Bayesian learning model where new exporters can update their prior beliefs about the quality preference of foreign markets from their neighboring pioneering exporters. Our model shows that a new exporter raises its product quality when it receives a positive signal from its neighbors. The learning process of a firm depends on the number of neighbors, the level and heterogeneity of their export quality, and its own prior knowledge of the market. Using highly disaggregated firm-product-country-level transaction data, we find robust evidences for these predictions. Our results also suggest the impact of neighboring signals on a new exporter’s quality is channeled through the imports of high-quality intermediate inputs and more fixed investment. In addition, we find that the learning effect are heterogeneous across firms and learning can influence other aspects of export performance.</p

Portable Smartphone Platform Based on Aggregation-Induced Enhanced Emission Carbon Dots for Ratiometric Quantitative Sensing of Fluoride Ions

The development of an instrument-free, on-site, real-time, sensitive, and visualized fluoride-ion (F–) content rapid detection strategy is crucial to ensuring the health of the population. Smart microdevices that are portable, directly read, and easy to operate have recently attracted much attention. Herein, a ratiometric fluorescent probe (AA-CDs@[Ru(bpy)3]2+)-based smartphone sensing platform was developed for the detection of F–. The red fluorescent ruthenium bipyridine [Ru(bpy)3]2+ molecule was chosen as the reference signal, and the carbon dots (AA-CDs) with Al3+ aggregation-induced enhanced emission (AIE) were designed as the response signal. The ratiometric probe fluorescence changed continuously from red to cyan in response to different concentrations of F–, and the red–green–blue (RGB) channel values of the fluorescence image were extracted through the smartphone color recognition application (APP). There was a linear relationship between the blue–red (B/R) ratio and the F– concentration, with a limit of detection (LOD) of 1.53 μM, far below the allowable content of F– in drinking water prescribed by the World Health Organization. The F– content was rapidly detected on-site with satisfactory repeatability and relative standard deviation using several water and toothpaste samples as the real sample. The platform features low cost, portability, easy operation, and good stability, selectivity, and repeatability, which provides a powerful tool for the visual quantitative detection of smartphone-based microsensing platforms possibly in the fields of environmental protection, diagnosis, and food safety assessment

Hydride Transfer-Initiated Cross-Dehydrogenative Coupling Reaction to Access Nine-Membered Rings

An unprecedented hydride transfer-triggered cross-dehydrogenative coupling of two C(sp3)–H bonds to target nine-membered rings has been developed. Salient features of this methodology include atom and step economy and metal-free and redox-neutral conditions, with water as the byproduct and proceeding well even with decomposed aldehydes

1,6-Hydride Transfer-Enabled [6 + 1] Annulation to Access Polycyclic 3,4-Fused Azepinoindoles

A [6 + 1] annulation reaction via cascade 1,6-hydride transfer/cyclization is reported to construct a polycyclic 3,4-fused azepinoindole skeleton. The newly designed 4-amino-indole-3-carbaldehyde is applied as a novel six-atom synthon, interacting with arylamines and malononitrile to achieve the [6 + 1] annulation. Notably, the reaction proceeds smoothly under redox-neutral and metal-free conditions, providing a wide range of azepinoindoles in up to 94% yields, with water as the only byproduct. Besides, the advantage of high step- and atom-economy further highlights the practicality of this methodology

Access to Polycyclic Indole-3,4-Fused Nine-Membered Ring via Cascade 1,6-Hydride Transfer/Cyclization

A cascade aldimine condensation/1,6-hydride transfer/Mannich-type cyclization of indole-derived phenylenediamine with aldehydes was developed for one-step construction of a polycyclic indole-3,4-fused skeleton. Aldehyde serves as a key to start the whole process, including 1,6-hydride transfer enabled δ-C­(sp3)–H activation of the secondary amine. The challenges of construction of medium-sized rings are addressed via hydride transfer chemistry

Manganese-Catalyzed Asymmetric Oxidation of Methylene C–H of Spirocyclic Oxindoles and Dihydroquinolinones with Hydrogen Peroxide

A highly efficient strategy for the enantioselective oxidation of methylene C–H of spirocyclic oxindoles and dihydroquinolinones has been established, in which an earth-abundant manganese catalyst and hydrogen peroxide are used. Noteworthy, the manganese catalyst can be applied to the asymmetric hydroxylation of spirocyclic 2,3-dihydroquinolin-4-ones with 94–99% ee

Surface-Enhanced Electrochemiluminescence of Ru@SiO₂ for Ultrasensitive Detection of Carcinoembryonic Antigen

Carcinoembryonic antigen (CEA) is recognized as a disease biomarker to reflect the existence of various cancers and tumors in the human body. Sensitive detection of CEA in body fluid is valuable for clinical diagnosis and treatment assessment of cancers. Herein, we present a new approach for ultrasensitive determination of CEA in human serum based on localized surface plasmon resonance (LSPR) enhanced electrochemiluminescence (ECL) of Ru­(bpy)₃²⁺. In this surface-enhanced ECL (SEECL) sensing scheme, Ru­(bpy)₃²⁺-doped SiO₂ nanoparticles (Ru@SiO₂) act as ECL luminophores, and AuNPs are used as LSPR source to enhance the ECL signal. Two different kinds of aptamers specific to CEA are modified on the surface of Ru@SiO₂ and AuNPs, respectively. In the presence of CEA, a multilayer of Ru@SiO₂–AuNPs nanoarchitectures would be formed. Our investigation reveals that the ECL signal of Ru@SiO₂ can be effectively enhanced by AuNPs. One layer of Ru@SiO₂–AuNPs nanoarchitectures would generate about 3-fold ECL enhancement compared with the ECL of the nanoarchitectures without the presence of AuNPs. As much as 30-fold ECL enhancement could be obtained by a multilayer of Ru@SiO₂–AuNPs nanoarchitectures. Under the optimal conditions, a detection limit of 1.52 × 10^–6 ng/mL of CEA in human serum was achieved. To the best of our knowledge, CEA assays with such a low LOD have never been reported for an ECL sensor