Supply chain disruption recovery in the evolving crisis-Evidence from the early COVID-19 outbreak in China.

The speed of recovery from supply chain disruption has been identified as the predominant factor in building a resilient supply chain. However, COVID-19 as an example of an evolving crisis may challenge this assumption. Infection risk concerns may influence production resumption decision-making because any incidents of infection may lead to further shutdowns of production lines and undermine firms' long-term cash flows. Sampling 244 production resumption announcements by Chinese manufacturers in the early COVID-19 crisis (February-March 2020), our analysis shows that, generally, investors react positively to production resumptions. However, investors perceived the earlier production resumptions were higher risk (indicated by declined stock price). Such concerns were exacerbated by more locally confirmed cases of COVID-19 but were less salient for manufacturers with high debts (liquidity pressure). This study calls for a reassessment of the current disruption management mindset in response to new evolving crises (e.g., COVID-19) and provides theoretical, practical, and policy implications for building resilient supply chains.

Macau's sustainability and diversification.

We analyze the socio-economic development of Macau after the return to Chinese sovereignty from the three dimensions of sustainability (economy, society, and environment). Macau's economy has both high growth and high volatility, mainly due to its unbalanced industrial structure and vulnerability to external shocks. During the COVID-19 pandemic, consumer confidence declined, due to the rising and high unemployment rate, while the environment has been relatively good since air quality became better. The overall assessment of sustainable city competitiveness of Macau has slipped gradually. This suggests that Macau's factor endowment structure has reached its upper limit and needs to be changed through internal industrial pluralism and external regional deepening (e.g., Guangdong-Macau In-Depth Cooperation Zone in Hengqin) to promote the moderately diversified and sustainable development of the economy.

Margin purchases, short sales and stock return volatility in China: Evidence from the COVID-19 outbreak.

In this paper, we investigate the effects of margin purchases and short sales on the return volatility in the Chinese stock market during the COVID-19 outbreak. We present two main findings. First, we show that stocks with higher level of margin-trading activity exhibit higher return volatility. The COVID-19 outbreak amplifies the destabilizing effects of margin-trading activity. Second, no evidence shows that short selling destabilizes the stock market in general. However, we observe that intensified short-selling activity is associated with lower return volatility when infection risk is high during the COVID-19 crisis.

The effects of supply chain diversification during the COVID-19 crisis: Evidence from Chinese manufacturers.

Resilience amidst a crisis is vital to survival in the turbulent contemporary business environment. Diversifying the supply chain has been proposed as an important means to build this capability. However, there is insufficient empirical evidence demonstrating the merits of supply chain diversification during a crisis. Sampling 1434 Chinese manufacturing firms amidst the COVID-19 crisis, our two-stage least squares (2SLS) regression analyses show that firms with a diversified supply base are associated with a larger supply stream (increased abnormal inventory) and increased profitability during the COVID-19 crisis, including both the disruption and recovery periods. In addition, firms with a diversified customer base are associated with a larger demand stream (reduced abnormal inventory) during the COVID-19 crisis (both disruption and recovery periods) but show increased profitability only during the recovery period. Our study contributes to the literature on supply chain risk, disruption, diversification, and inventory management. We also discuss the practical implications of supply chain structure design in building resilience.

Prevention of intestinal adhesion and regeneration of abdominal wall tissue with meshes containing an electrostatically spun acellular dermal matrix (ADM)/silk fibroin (SF) fiber composite polypropylene mesh.

The repair of abdominal wall defects often requires the use of polypropylene (PP) as the main material. After a PP mesh is implanted in the body, contact with the intestine can cause adhesions between the intestine and the mesh, leading to serious complications such as intestinal fistula. In this study, we used electrostatic spinning technology to coat one side of PP meshes with an electrostatically spun isolating layer of acellular dermal matrix (ADM)/silk fibroin (SF) hybrid material. These meshes were used to repair abdominal wall defects in model rats and were compared with polycaprolactone (PCL) composite polypropylene meshes and PP meshes. The results showed that the adhesion score and area of ADM/SF-PP meshes were smaller than those of PCL-PP and PP meshes. Immunohistochemical assessment revealed that the ADM/SF meshes could effectively reduce the inflammatory response at the contact surface between the meshes and abdominal organs. The tissues regenerated on the abdominal side were rich in new blood vessels. Furthermore, the ADM/SF meshes could effectively reduce the expression levels of the inflammation-related factors IL-6 and TNF-α. The expression levels of tissue regeneration-related factors, such as VEGF and PAX-7, were also higher after ADM/SF-PP mesh-mediated repair than after PCL-PP mesh and PP mesh repair. Thus, ADM/SF-PP meshes can effectively reduce the inflammatory response at the contact surface between the meshes and abdominal organs and quickly promote regeneration of abdominal surface tissue to prevent and reduce abdominal adhesion and support restoration of the abdominal wall.

C-H Insertion by Alkylidene Carbenes To Form 1,2,3-Triazines and Anionic [3 + 2] Dipolar Cycloadditions To Form Tetrazoles: Crucial Roles of Stereoelectronic and Steric Effects.

The synthesis of 1,2,3-triazines and bicyclic tetrazoles from α-azido ketones is described. The common intermediate generated from lithiated trimethylsilyldiazomethane and α-azido ketones diverges depending on the steric bulk of the substituents. The formation of 1,2,3-triazines via a C-H insertion of alkylidene carbene to form 3-azidocyclopropene, followed by its rearrangement, is supported by density functional theory calculations. Tetrazole formation proceeds via a facile anionic [3 + 2] dipolar cycloaddition between a lithiated diazo moiety and an azido group facilitated by the chelation of a lithium ion.

Silver-Catalyzed Selective Multicomponent Coupling Reactions of Arynes with Nitriles and Isonitriles.

Pathway selective aryne-based novel multicomponent coupling reactions with isonitriles and nitriles are described. Crucial to these reactions is the formation of a silver-aryne complex, which shows differential reactivity toward isonitriles and nitriles to form two different forms of ortho-nitrilium organosilver arene species. Interception of the nitrilium of an aryne-isonitrile adduct with another isonitrile leads to the formation of benzocyclobutene-1,2-diimines, whereas the nitrilium of an aryne-nitrile adduct renders selective formation of 3H-indol-3-imines or 3-iminoindolin-2-ol depending on the structure of the nitrile employed.

Silver-Catalyzed Annulation of Arynes with Nitriles for Synthesis of Structurally Diverse Quinazolines.

An efficient silver catalyzed annulation reaction of aryne with nitriles to generate quinazolines is described. Arynes generated from triynes or tetraynes through a hexadehydro Diels-Alder reaction readily participated in an [A + 2B] mode of annulation with nitriles in the presence of AgSbF6 catalyst. The mechanism was explored by DFT calculations, which supports the silver-catalyzed formation of nitrilium ion as a key intermediate. This annulation generates an array of polysubstituted novel quinazoline derivatives with excellent regioselectivity.

The mechanism of the gold-catalyzed intramolecular [3 + 2]-cycloaddition of 1,6-diynes: a DFT study.

The gold-catalyzed [3 + 2] cycloaddition of areneyne-yne functionalities represents one of the most efficient methodologies for the construction of tricyclic ring systems under mild conditions. In the current report, a detailed mechanistic understanding of the reaction was achieved by DFT calculations. It was found that under the catalysis of gold(i), the initial cyclization occurs more favorably between the two alkynyl moieties via the 6-exo-dig pathway other than the arene-yne addition, which is the selectivity-determining step of the whole reaction and leads eventually to the [3 + 2] cycloadduct irreversibly by following the steps of arene-cation cyclization and proton transfer. Electronic and geometric factors are analyzed to better understand the calculation results.

Alder-ene reactions driven by high steric strain and bond angle distortion to form benzocyclobutenes.

A unique aryne-based Alder-ene reaction to form benzocyclobutene is described. In this process, the thermodynamic barrier to form a four-membered ring is compensated by the relief of the strain energy of an aryne intermediate. On the other hand, the driving force to overcome the high kinetic barrier is provided by the gearing effect of the bulky substituent at the ortho-position of the ene-donor alkene. To maximize the steric strain by the ortho-substituent, a structural element for internal hydrogen bonding is installed, which plays a crucial role for both the hexadehydro Diels-Alder and the Alder-ene reactions. DFT calculations show that the bulky hydrogen bonding element lowers the activation barrier for the Alder-ene reaction by destabilizing the intermediate, which is due to the severe bond angle distortion. The preferred formation of cis-isomers can also be explained by the extent of bond angle distortion.

Consecutive Lossen rearrangement/transamidation reaction of hydroxamic acids under catalyst- and additive-free conditions.

The Lossen rearrangement is a classic process for transforming activated hydroxamic acids into isocyanate under basic or thermal conditions. In the current report we disclosed a consecutive Lossen rearrangement/transamidation reaction in which unactivated hydroxamic acids were converted into N-substituted formamides in a one-pot manner under catalyst- and additive-free conditions. One feature of this novel transformation is that the formamide plays triple roles in the reaction by acting as a readily available solvent, a promoter for additive-free Lossen rearrangement, and a source of the formyl group in the final products. Acyl groups other than formyl could also be introduced into the product when changing the solvent to other low molecular weight aliphatic amide derivatives. The solvent-promoted Lossen rearrangement was better understood by DFT calculations, and the intermediacy of isocyanate and amine was supported well by experiments, in which the desired products were obtained in excellent yields under similar conditions. Not only monosubstituted formamides were synthesized from hydroxamic acids, but also N,N-disubstituted formamides were obtained when secondary amines were used as precursors.