This article examines how trade effect of non‐tariff measures (NTMs) differs across quality segments of import market. NTMs reduce total import and force exit, while import from continuing partners ...increases, as well as their prices. Such effects are especially large for low‐end varieties. We construct a model to explain the difference between NTMs and tariffs and the various effects of NTMs at the low end of the quality distribution. We model two competing effects. First, NTMs impose minimum quality standard. Second, NTMs also inform consumers about import quality in a way that is particularly advantageous to low‐end varieties. The model predicts how these competing effects can force exit, while also altering market shares of continuing varieties.
Sutton and Trefler (2016) present a model that explains how a country's quality capability simultaneously affects per capita income and the sectoral mix of its exports. The model predicts an ...inverted‐U relationship between an exporter's income and its world market share of export. This paper examines whether the prediction is consistent with the time‐series variations of trade data. We find inverted‐U relationships in all three groups of markets. While market shares do eventually drop as income grows, it happens only when incomes are very high. In addition, exporters' global market progression described in Sutton and Trefler (2016) is accelerated with the presence of a “super” exporter, such as China. Lastly, we confirm the model's implication on how quality capability improvements affect market entry by presenting an inverted‐U relationship between market entry and income in middle‐rank group, with the relationship being negative in low‐rank group and positive in high‐rank group.
A large and growing literature focuses on product quality differentiation and its positive and normative importance for international trade. In this literature, there are a number of approaches that ...attempt to extract a quality ‘signal’ from noisy price or price–quantity data (i.e., unit value and demand residual approach). I propose a simple test for the robustness of these approaches to quality inference: when purchasing goods from a common set of exporters, do two importers agree on which goods are high quality? Results from Spearman's rank correlation tests show that as we use import demand residuals to measure quality, quality estimates become progressively less consistent and worsen the agreement among importers. Such inconsistency cannot be explained by trade cost effects on exporters' quality suggested by Melitz (2003) and Alchian–Allen hypothesis (Hummels and Skiba, 2004). It is also uncorrelated to differences in the compositions of imports. However, demand residual approach produces strong quality ‘signal’ relative to the noise only in highly differentiated products. Further analyses confirm the role of the differences in consumers' preferences and tastes across importers in the distortion of quality signals.
Ionogels have gained increasing attentions as a flexible conductive material. However, it remains a big challenge to integrate multiple functions into one gel that can be widely applied in various ...complex scenes. Herein, a kind of multifunctional ionogels with a combination of desirable properties, including transparency, high stretchability, solvent and temperature resistance, recyclability, high conductivity, underwater self‐healing ability, and underwater adhesiveness is reported. The ionogels are prepared via one‐step photoinitiated polymerization of 2,2,2‐trifluoroethyl acrylate and acrylamide in a hydrophobic ionic liquid. The abundant noncovalent interactions including hydrogen bonding and ion–dipole interactions endow the ionogels with excellent mechanical strength, resilience, and rapid self‐healing capability at room temperature, while the fluorine‐rich polymeric matrix brings in high tolerance against water and various organic solvents, as well as tough underwater adhesion on different substrates. Wearable strain sensors based on the ionogels can sensitively detect and differentiate large body motions, such as bending of limbs, walking and jumping, as well as subtle muscle movements, such as pronunciation and pulse. It is believed that the designed ionogels will show great promises in wearable devices and ionotronics.
A physically crosslinked multifunctional ionogel is designed and prepared via a simple one‐step photoinitiated polymerization of a fluorinated monomer and a hydrogen bond enabling comonomer in a hydrophobic ionic liquid. The ionogels possess excellent comprehensive performance, including high transparency, robust mechanical properties, self‐healing and self‐adhesion in air/underwater, easy recyclability, solvent tolerance, and sensitive and reliable strain sensing.
Biochar is a porous carbonaceous material with high alkalinity and rich minerals, making it possible for CO2 capture. In this study, biochars derived from pig manure, sewage sludge, and wheat straw ...were evaluated for their CO2 sorption behavior. All three biochars showed high sorption abilities for CO2, with the maximum capacities reaching 18.2–34.4 mg g−1 at 25 °C. Elevating sorption temperature and moisture content promoted the transition of CO2 uptake from physical to chemical process. Mineral components such as Mg, Ca, Fe, K, etc. in biochar induced the chemical sorption of CO2 via the mineralogical reactions which occupied 17.7%–50.9% of the total sorption. FeOOH in sewage sludge biochar was transformed by sorbed CO2 into Fe(OH)2CO3, while the sorbed CO2 in pig manure biochar was precipitated as K2Ca(CO3)2 and CaMg(CO3)2, which resulted in a dominant increase of insoluble inorganic carbon in both biochars. For wheat straw biochar, sorbed CO2 induced CaCO3 transformed into soluble Ca(HCO3)2, which led to a dominant increase of soluble inorganic carbons. The results obtained from this study demonstrated that biochar as a unique carbonaceous material could distinctly be a promising sorbent for CO2 capture in which chemical sorption induced by mineralogical reactions played an important role.
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•Biochar is distinctly effective for CO2 capture through both physical and chemical processes.•Elevating temperature and moisture enhance chemisorption of CO2 by biochar.•Rich minerals and high alkalinity of biochar favor CO2 chemisorption.•Mineralogical reactions in biochar promote CO2 transformation into carbonates.
Rich minerals and high alkalinity of biochar favor CO2 chemisorption in which mineralogical reactions promote CO2 transformation into carbonates.
Abstract Gelatin methacryloyl (GelMA) hydrogels have been widely used for various biomedical applications due to their suitable biological properties and tunable physical characteristics. GelMA ...hydrogels closely resemble some essential properties of native extracellular matrix (ECM) due to the presence of cell-attaching and matrix metalloproteinase responsive peptide motifs, which allow cells to proliferate and spread in GelMA-based scaffolds. GelMA is also versatile from a processing perspective. It crosslinks when exposed to light irradiation to form hydrogels with tunable mechanical properties. It can also be microfabricated using different methodologies including micromolding, photomasking, bioprinting, self-assembly, and microfluidic techniques to generate constructs with controlled architectures. Hybrid hydrogel systems can also be formed by mixing GelMA with nanoparticles such as carbon nanotubes and graphene oxide, and other polymers to form networks with desired combined properties and characteristics for specific biological applications. Recent research has demonstrated the proficiency of GelMA-based hydrogels in a wide range of tissue engineering applications including engineering of bone, cartilage, cardiac, and vascular tissues, among others. Other applications of GelMA hydrogels, besides tissue engineering, include fundamental cell research, cell signaling, drug and gene delivery, and bio-sensing.
Current in vitro antitumor drug screening strategies insufficiently mimic biological systems. They tend to lack true perfusion and draining microcirculation systems, which may post significant ...limitations in explicitly reproducing the transport kinetics of cancer therapeutics. Herein, the fabrication of an improved tumor model consisting of a bioprinted hollow blood vessel and a lymphatic vessel pair, hosted in a 3D tumor microenvironment‐mimetic hydrogel matrix is reported, termed as the tumor‐on‐a‐chip with a bioprinted blood and a lymphatic vessel pair (TOC‐BBL). The bioprinted blood vessel is a perfusable channel with an opening on both ends, while the bioprinted lymphatic vessel is blinded on one end, both of which are embedded in a hydrogel tumor mass, with vessel permeability individually tunable through optimization of the compositions of the bioinks. It is demonstrated that systems with different combinations of these bioprinted blood/lymphatic vessels exhibit varying levels of diffusion profiles for biomolecules and anticancer drugs. The results suggest that this unique in vitro tumor model containing the bioprinted blood/lymphatic vessel pair may have the capacity of simulating the complex transport mechanisms of certain pharmaceutical compounds inside the tumor microenvironment, potentially providing improved accuracy in future cancer drug screening.
A tumor model consisting of a bioprinted hollow blood vessel and a lymphatic vessel pair hosted in a 3D hydrogel matrix is fabricated, which may have the capacity to simulate the complex transport mechanisms of pharmaceutical compounds inside the tumor microenvironment, potentially providing improved accuracy in future cancer drug screening.
Hybrid systems of hydrogels and metals with tough bonding may find widespread applications. Here, a simple and universal method to obtain strong adhesion between hydrogels and diverse metal surfaces, ...such as titanium, steel, nickel, tantalum, argentum, and aluminum, with adhesion energy up to >1000 J m−2 is reported. To achieve such, the metal surfaces are instantly modified with a linker molecule via soaking, dip‐coating, or drop‐casting. The designed linker molecule has a carboxylic acid group to bind with a metal surface, and a methacrylic group to crosslink with a hydrogel, thus bridging the interface between them. In addition, by introducing a stimulus‐responsive disulfide bond into the linker molecule, the on‐demand debonding between toughly bonded hydrogel and metal surface, which is enabled by reductive cleavage of the disulfide chemical linkage, is also demonstrated. More interestingly, after the reductive debonding, the resulting metal surface with free thiol groups can be easily rebonded with a second hydrogel without any further surface modification. The strategy may provide unique opportunities in designing hybrid devices that are suitable for complex and dynamic environments.
Strong adhesion between hydrogels and diverse metal surfaces through a linker molecule is obtained through a simple method. By introducing a stimulus‐responsive moiety into the linker molecule, on‐demand debonding between toughly bonded hydrogels and metal surfaces and facile rebonding is further achieved. This strategy provides unique opportunities in designing hybrid devices that are suitable for complex and dynamic environments.
Abstract Despite the significant technological advancement in tissue engineering, challenges still exist towards the development of complex and fully functional tissue constructs that mimic their ...natural counterparts. To address these challenges, bioprinting has emerged as an enabling technology to create highly organized three-dimensional (3D) vascular networks within engineered tissue constructs to promote the transport of oxygen, nutrients, and waste products, which can hardly be realized using conventional microfabrication techniques. Here, we report the development of a versatile 3D bioprinting strategy that employs biomimetic biomaterials and an advanced extrusion system to deposit perfusable vascular structures with highly ordered arrangements in a single-step process. In particular, a specially designed cell-responsive bioink consisting of gelatin methacryloyl (GelMA), sodium alginate, and 4-arm poly(ethylene glycol)-tetra-acrylate (PEGTA) was used in combination with a multilayered coaxial extrusion system to achieve direct 3D bioprinting. This blend bioink could be first ionically crosslinked by calcium ions followed by covalent photocrosslinking of GelMA and PEGTA to form stable constructs. The rheological properties of the bioink and the mechanical strengths of the resulting constructs were tuned by the introduction of PEGTA, which facilitated the precise deposition of complex multilayered 3D perfusable hollow tubes. This blend bioink also displayed favorable biological characteristics that supported the spreading and proliferation of encapsulated endothelial and stem cells in the bioprinted constructs, leading to the formation of biologically relevant, highly organized, perfusable vessels. These characteristics make this novel 3D bioprinting technique superior to conventional microfabrication or sacrificial templating approaches for fabrication of the perfusable vasculature. We envision that our advanced bioprinting technology and bioink formulation may also have significant potentials in engineering large-scale vascularized tissue constructs towards applications in organ transplantation and repair.
Soft ionic conductors hold great potential for soft ionotronics, such as ionic skin, human–machine interface and soft luminescent device. However, most hydrogel and ionogel‐based soft ionic ...conductors suffer from freezing, evaporation and liquid leakage problems, which limit their use in complex environments. Herein, a class of liquid‐free ionic conductive elastomers (ICEs) is reported as an alternative soft ionic conductor in soft ionotronics. These liquid‐free ICEs offer a combination of desirable properties, including extraordinary stretchability (up to 1913%), toughness (up to 1.08 MJ cm−3), Young's modulus (up to 0.67 MPa), rapid fully self‐healing capability at room temperature, and good conductivity (up to 1.01 × 10−5 S cm−1). The application of these ICEs is demonstrated by creating a wearable sensor that can detect and discriminate minimal deformations and human body movements, such as finger or elbow joint flexion, walking, running, etc. In addition, self‐healing soft ionotronic devices are demonstrated to confront mechanical breakdown, such as an ionic skin and an alternating‐current electroluminescent device that can reuse from damage. It is believed that these liquid‐free ICEs hold great promises for applications in wearable devices and soft ionotronics.
High‐performance multifunctional liquid‐free ionic conductive elastomers enhanced by three non‐covalent interactions are described, which are applied in various types of flexible ionotronic devices, such as strain sensors, capacitive‐type sensors, and electroluminescent devices.
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