Polyacrylic Acid Supported L-proline as an Effective Heterogeneous Catalyst for the Direct Asymmetric Aldol Reaction.

INTRODUCTION: L-proline is an efficient chiral small-molecule organocatalyst for the direct asymmetric aldol reaction between unmodified acetone and a variety of aldehydes. METHOD: However, it is difficult to separate from the reaction medium for reuse. In this work, polyacrylic acid (PAA) supported The acylation reaction between L-hydroxyproline and PAA prepared l-proline (P(AA-co-PA)) catalysts with various catalyst loadings. Fourier characterized them transforms infrared spectroscopy, nuclear magnetic resonance spectrum, gel permeation chromatography and thermogravimetry analysis. RESULT: These macromolecular catalysts were used to catalyze acetone and benzaldehydes' direct asymmetric aldol reaction. The influence of the catalyst structure on the catalytic performance was studied, and the reaction conditions were optimized. CONCLUSION: The results showed that P(AA-co-PA) with 50 mol% catalyst loading had excellent catalytic performance, much higher than that of L-proline and L-hydroxyproline. Its recovery was achieved by simple filtration. After being reused 7 times, its catalytic performance was still higher than that of L-proline.

SiO x /C Composite Anode of Lithium-Ion Batteries with Enhanced Performances Using Multicomponent Binders.

A silicon suboxide-carbon (SiO x /C, 1 ≤ x ≤ 2) composite anode of lithium-ion batteries (LIBs) with enhanced performance is prepared using an aqueous multicomponent binder technology. Considering the adhesive force, electrolyte absorption, and stability, different binders including sodium alginate (SA), polyacrylamide gel (PAM), polytetrafluoroethylene (PTFE), and their composites are evaluated. It is indicated that compared to other anodes with single- or multicomponent binders, the SiO x /C composite anode with PAM/SA/PTFE663 (PSAP663) binders exhibits strong adhesion, moderate electrolyte absorption ability, and a specific capacity of 427 mA h g-1 charge-discharged at 0.5 A g-1 after 300 cycles. The improvement of electrochemical performance is attributed to the comprehensive effects of composite binders, including the adhesion of active substances, surface protection, solution adsorption, conductive path, and so on. These results show that the PSAP663 binder has promising potential for application, which not only gives alternative practical schemes of the green binders for the SiO x /C anodes but also provides ideas to develop a high-performance adhesive technology for LIBs.

Exposure of Ophthalmologists to Patients' Exhaled Droplets in Clinical Practice: A Numerical Simulation of SARS-CoV-2 Exposure Risk.

Background: Lack of quantification of direct and indirect exposure of ophthalmologists during ophthalmic diagnostic process makes it hard to estimate the infectious risk of aerosol pathogen faced by ophthalmologists at working environment. Methods: Accurate numerical models of thermal manikins and computational fluid dynamics simulations were used to investigate direct (droplet inhalation and mucosal deposition) and indirect exposure (droplets on working equipment) within a half-minute procedure. Three ophthalmic examination or treatment scenarios (direct ophthalmoscopic examination, slit-lamp microscopic examination, and ophthalmic operation) were selected as typical exposure distance, two breathing modes (normal breathing and coughing), three levels of ambient RH (40, 70, and 95%) and three initial droplet sizes (50, 70, and 100 µm) were considered as common working environmental condition. Results: The exposure of an ophthalmologist to a patient's expiratory droplets during a direct ophthalmoscopic examination was found to be 95 times that of a person during normal interpersonal interaction at a distance of 1 m and 12.1, 8.8, and 9.7 times that of an ophthalmologist during a slit-lamp microscopic examination, a surgeon during an ophthalmic operation and an assistant during an ophthalmic operation, respectively. The ophthalmologist's direct exposure to droplets when the patient cough-exhaled was ~7.6 times that when the patient breath-exhaled. Compared with high indoor RH, direct droplet exposure was higher and indirect droplet exposure was lower when the indoor RH was 40%. Conclusion: During the course of performing ophthalmic examinations or treatment, ophthalmologists typically face a high risk of SARS-CoV-2 infection by droplet transmission.