•This paper provides the first causal estimates of the impact of internal migrant peers on the academic performance of local students in developing countries.•It exploits the random assignment of ...students to classes within a school.•Migrant peers in the classroom negatively affect the academic performance of local students in China, especially for boys and for local students in large cities.•The negative migrant spillover effects may come from the worsened learning environment or from the adjustment of teachers’ pedagogical practices.
This paper provides the first causal estimates of the impact of internal migrant peers on the academic performance of local students in developing countries. By exploiting the random assignment of students to classes within a school, I find that migrant peers have large and negative effects on the academic performance of local students in China and the negative spillover effects are concentrated among male students and among local students in large cities. The investigation of the underlying mechanisms suggests that the negative migrant spillover effects may come from the worsened learning environment or from the adjustment of teachers’ pedagogical practices in response to the migrant composition in the classroom.
Isoxazoles are important five‐membered aromatic heterocycles in organic chemistry. Recently, many exciting advances in the synthesis and functionalization of isoxazoles have been reported. New ...transition metal‐catalyzed reactions have resulted in the development of attractive and highly efficient synthetic approaches to densely functionalized isoxazoles. Complete control of regioselectivity can be achieved on the basis of a judicious choice of metal catalyst and reaction partners using dipolar cycloaddition and cycloisomerization reactions, while more recent studies have focused on the site‐selective functionalization of isoxazoles via CH functionalization. New strategies for the use of isoxazoles as scaffolding templates in asymmetric synthesis have emerged, thus opening new prospects for the synthesis of enantioenriched motifs under the conditions that are orthogonal to other transformations. In this review, recent advances involving the synthesis and reactivity of isoxazoles are summarized. The review covers the period from January 2005 to June 2015.
Heating and cooling represent a significant portion of overall energy consumption of our society. Due to the diffusive nature of thermal energy, thermal insulation is critical for energy management ...to reduce energy waste and improve energy efficiency. Thermal insulation relies on the reduction of thermal conductivity of appropriate materials that are engineerable in compositions and structures. Hollow‐structured materials (HSMs) show a great promise in thermal insulation since the existence of high‐density gaseous voids breaks the continuity of heat‐transport pathways in the HSMs to lower their thermal conductivities efficiently. Herein, a timely overview of the recent progress in developing HSMs for thermal insulation is presented, with the focus on summarizing the strategies for creating gaseous voids in solid materials and thus synthesizing various HSMs. Systematic analysis of the documented results reveals the relationship of thermal conductivities of the HSMs and the size and density of voids, i.e., reducing the void size below ≈350 nm is more favorable to decrease the thermal conductivity of the HSMs because of the possible confinement effect originated from the nanometer‐sized voids. The challenges and promises of the HSMs faced in future research are also discussed.
A comprehensive overview of hollowstructured materials (HSMs) for thermal insulation is presented to identify the dependence of their thermal conductivity on voids confined in the HSMs. The presence of gaseous voids with small sizes and high density in HSMs represents the most promising strategy to suppress thermal conduction significantly, especially when the voids are smaller than ≈350 nm.
This review presents the research progresses on CCMPs made in the past decades, including various synthesis methodologies, structural features and relevant applications with regard to their ...photochromism, photoluminescence and magnetic properties.
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•Organic inorganic hybrid POMs with remarkable physical and chemical properties.•Organic carboxylic acid ligands can directly covalently graft to the POM skeletons.•A new kind of structurally diverse organic inorganic POM-based materials.•Displaying potential applications in optics, electrochromism and photochromism.
Polyoxometalates (POMs) have demonstrated strong potential in various fields, such as catalysis, magnetism, medicine, photochemistry and materials science, for their remarkable physical and chemical properties. Through the introduction of organic functional moieties to the POM systems via self-assembly, grafting, doping or intercalation strategies, advantages from both the POMs and organic moieties are well maintained, resulting in many new properties. Among all the existing organo-functionalized POMs, carboxylate covalently modified POMs (CCMPs, carboxylic acid ligands covalently grafted to the POM skeletons) attract intensive research efforts. The carboxylic acid ligands not only help to enrich the structural diversities of the CCMPs, but also facilitate the tuning of redox behaviors and photoreduction activities of the CCMPs because of the possible electron transfer between the organic ligands and the POM units. Encouraged by the impressive structural diversities and potential applications in optics, magnetism and materials science, the design and exploration of new CCMP complexes have become some of the most compelling and challenging areas in POM chemistry. In this review, we herein discuss the research progress achieved for CCMPs in the past decades in the areas of synthesis methodologies, structural features and relevant applications (photochromism, photoluminescence and magnetism, etc.). In addition, some personal insights are also presented in the last section of the paper with sincere wishes for continuous exploration of the undiscovered world of CCMPs.
This study employs science mapping and bibliometric analysis to chart the knowledge structure and research trajectory of enterprise green environment literature from 2002 to 2022. Despite rising ...interest, comprehensive analyses of this field's research landscapes and dynamics remain scarce. Through advanced techniques including discipline mapping, journal co-citation analysis, author co-citation analysis, and keyword co-occurrence analysis, this work elucidates the prominent disciplines, publications, authors, and research foci in enterprise of green environment scholarship over the past two decades. The results provide vital insights into the current status, influential leaders, core journals, knowledge gaps, and future directions of this rapidly evolving field. This science mapping analysis offers a valuable quantitative overview of green environment research enterprise that can inform scholars worldwide in producing impactful work on this critical area. The findings reveal profound implications for the developing structure and frontiers of sustainability-focused business and management research.
The expansion of shrubs across the Arctic tundra may fundamentally modify land–atmosphere interactions. However, it remains unclear how shrub expansion pattern is linked with key environmental ...drivers, such as climate change and fire disturbance. Here we used 40+ years of high‐resolution (~1.0 m) aerial and satellite imagery to estimate shrub‐cover change in 114 study sites across four burned and unburned upland (ice‐poor) and lowland (ice‐rich) tundra ecosystems in northern Alaska. Validated with data from four additional upland and lowland tundra fires, our results reveal that summer precipitation was the most important climatic driver (r = 0.67, p < 0.001), responsible for 30.8% of shrub expansion in the upland tundra between 1971 and 2016. Shrub expansion in the uplands was largely enhanced by wildfire (p < 0.001) and it exhibited positive correlation with fire severity (r = 0.83, p < 0.001). Three decades after fire disturbance, the upland shrub cover increased by 1077.2 ± 83.6 m2 ha−1, ~7 times the amount identified in adjacent unburned upland tundra (155.1 ± 55.4 m2 ha−1). In contrast, shrub cover markedly decreased in lowland tundra after fire disturbance, which triggered thermokarst‐associated water impounding and resulted in 52.4% loss of shrub cover over three decades. No correlation was found between lowland shrub cover with fire severity (r = 0.01). Mean summer air temperature (MSAT) was the principal factor driving lowland shrub‐cover dynamics between 1951 and 2007. Warmer MSAT facilitated shrub expansion in unburned lowlands (r = 0.78, p < 0.001), but accelerated shrub‐cover losses in burned lowlands (r = −0.82, p < 0.001). These results highlight divergent pathways of shrub‐cover responses to fire disturbance and climate change, depending on near‐surface permafrost and drainage conditions. Our study offers new insights into the land–atmosphere interactions as climate warming and burning intensify in high latitudes.
More than four decades' remote sensing observation in upland and lowland tundra revealed divergent pathways of shrub‐cover responses to fire disturbance and climate change, depending on near‐surface permafrost and drainage conditions. Shrub expansion in the well‐drained uplands was largely enhanced by fire disturbance, and it showed positive correlation with fire severity. In contrast, shrub cover markedly decreased in lowland tundra after fire, which triggered thermokarst‐associated water impounding and resulted in ~50% loss of shrub cover over three decades.
0D/2D heterojunctions, especially quantum dots (QDs)/nanosheets (NSs) have attracted significant attention for use of photoexcited electrons/holes due to their high charge mobility. Herein, ...unprecedent heterojunctions of vanadate (AgVO3, BiVO4, InVO4 and CuV2O6) QDs/graphitic carbon nitride (g‐C3N4) NSs exhibiting multiple unique advances beyond traditional 0D/2D composites have been developed. The photoactive contribution, up‐conversion absorption, and nitrogen coordinating sites of g‐C3N4 NSs, highly dispersed vanadate nanocrystals, as well as the strong coupling and band alignment between them lead to superior visible‐light‐driven photoelectrochemical (PEC) and photocatalytic performance, competing with the best reported photocatalysts. This work is expected to provide a new concept to construct multifunctional 0D/2D nanocomposites for a large variety of opto‐electronic applications, not limited in photocatalysis.
Vanadate quantum dots including AgVO3, BiVO4, InVO4, and CuV2O6 were strongly coupled with graphitic carbon nitride nanosheets using an in situ growth strategy. These quantum dots displayed a much better visible‐light‐driven photoelectrochemical activity and photocatalytic degradation efficiency than single vanadate quantum dots, carbon nitride nanosheets or previously reported highly active photocatalysts.
microRNAs (miRNAs) are small noncoding RNAs that play important regulatory roles in plants, animals and viruses. Measuring miRNA activity in vivo remains a big challenge. Here, using an ...miRNA-mediated single guide RNA (sgRNA)-releasing strategy and dCas9-VPR to drive a transgene red fluorescent protein, we create an miRNA sensor that can faithfully measure miRNA activity at cellular levels and use it to monitor differentiation status of stem cells. Furthermore, by designing sgRNAs to target endogenous loci, we adapted this system to control the expression of endogenous genes or mutate specific DNA bases upon induction by cell-type-specific miRNAs. Finally, by miRNA sensor library screening, we discover a previously undefined layer of heterogeneity associated with miR-21a activity in mouse embryonic stem cells. Together, these results highlight the utility of an miRNA-induced CRISPR-Cas9 system as miRNA sensors and cell-type-specific genome regulation tools.
Annual production of crop residues has reached nearly 4 billion metric tons globally. Retention of this large amount of residues on agricultural land can be beneficial to soil C sequestration. Such ...potential impacts, however, may be offset if residue retention substantially increases soil emissions of N2O, a potent greenhouse gas and ozone depletion substance. Residue effects on soil N2O emissions have gained considerable attention since early 1990s; yet, it is still a great challenge to predict the magnitude and direction of soil N2O emissions following residue amendment. Here, we used a meta‐analysis to assess residue impacts on soil N2O emissions in relation to soil and residue attributes, i.e., soil pH, soil texture, soil water content, residue C and N input, and residue C : N ratio. Residue effects were negatively associated with C : N ratios, but generally residue amendment could not reduce soil N2O emissions, even for C : N ratios well above ca. 30, the threshold for net N immobilization. Residue effects were also comparable to, if not greater than, those of synthetic N fertilizers. In addition, residue effects on soil N2O emissions were positively related to the amounts of residue C input as well as residue effects on soil CO2 respiration. Furthermore, most significant and stimulatory effects occurred at 60–90% soil water‐filled pore space and soil pH 7.1–7.8. Stimulatory effects were also present for all soil textures except sand or clay content ≤10%. However, inhibitory effects were found for soils with >90% water‐filled pore space. Altogether, our meta‐analysis suggests that crop residues played roles beyond N supply for N2O production. Perhaps, by stimulating microbial respiration, crop residues enhanced oxygen depletion and therefore promoted anaerobic conditions for denitrification and N2O production. Our meta‐analysis highlights the necessity to connect the quantity and quality of crop residues with soil properties for predicting soil N2O emissions.
Abstract
Rational regulation of electrochemical reconfiguration and exploration of activity origin are important foundations for realizing the optimization of electrocatalyst activity, but rather ...challenging. Herein, we potentially develop a rapid complete reconfiguration strategy for the heterostructures of CoC
2
O
4
coated by MXene nanosheets (CoC
2
O
4
@MXene) during the hydrogen evolution reaction (HER) process. The self-assembled CoC
2
O
4
@MXene nanotubular structure has high electronic accessibility and abundant electrolyte diffusion channels, which favor the rapid complete reconfiguration. Such rapid reconfiguration creates new actual catalytic active species of Co(OH)
2
transformed from CoC
2
O
4
, which is coupled with MXene to facilitate charge transfer and decrease the free energy of the Volmer step toward fast HER kinetics. The reconfigured components require low overpotentials of 28 and 216 mV at 10 and 1000 mA cm
−2
in alkaline conditions and decent activity and stability in natural seawater. This work gives new insights for understanding the actual active species formation during HER and opens up a new way toward high-performance electrocatalysts.
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