Styrene epoxidation catalyzed by polyoxometalate/quaternary ammonium phase transfer catalysts: The effect of cation size and catalyst deactivation mechanism

Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quaternary ammoniums bearing different cationic sizes,i.e.MTOA+(methyltrioctylammonium,[(C_(8)H_(17))_(3)CH_(3)N]+),HTMA+(hexadecyltrimethylammonium,[(C_(16)H_(33))(CH_(3))_(3)N]+) and DMDOA+(dimethyldioctadecylammonium,[(C_(18)H_(37))_(2)(CH_(3))_(2)N]+) were incorporated with polyoxometalate (POM) anions to prepare phase transfer catalysts (PTCs),which were used in the styrene epoxidations.Among them,(MTOA)_(3)PW_(4)O_(24)exhibits the best catalytic performance judged from the highest styrene conversion rate(52%) and styrene oxide selectivity (93%),during which the styrene epoxidation conditions were optimized.Meanwhile,the deactivation mechanism of this kind of PTCs was proposed firstly,i.e.in the case of low H_(2)O_(2) content,the oxidant can only be used in the styrene epoxidation,in which the catalyst can transform into stable Keggin-type POM.But when the content of H_(2)O_(2) is higher,the excess H_(2)O_(2) can reactivate the Keggin-type POM into active (PW_(4)O_(24))_(3)-anions,which can trigger the ring-opening polymerization of styrene oxide.Consequently,the catalyst is deactivated by adhered poly(styrene oxide)irreversibly,which was determined by NMR spectra.In this situation,the active moiety{PO_(4)[WO(O_(2))_(2)]_(4)}_(3)-in phase-transfer catalytic system can break into some unidentified species with low W/P ratio with the presence of epoxides.This work will be beneficial for the design of new PTCs in alkene epoxidation in fine chemical industry.

Cell cycle regulation through primary cilium:A long-forgotten story

Protruded from cytomembrane,primary cilium is a widespread cell organelle that can be found in almost all cell types in Mammalia.Because of its comprehensive requirement in various cellular activities and various functions in different organs,primary cilium has been a valuable research area of human pathology research since the turn of the millennium.And the potential application of the interaction between primary cilia and cell cycle regulation may be the most promising direction as many primary cilium-caused diseases are found to be caused by cell cycle dysregulation resulted from primary cilia defects.Therefore,a deep understanding of the interaction between primary cilia and the cell cycle is in great need.Hence in this review,we mainly described how the interaction between primary cilia and cell cycle proceeds and demonstrated three hypotheses raised from much different research.These hypotheses include(1)Primary cilium as a cellular signaling hub to regulate the cell cycle,(2)Primary cilium as a reservoir of cell cycle regulation-related factors,and(3)Primary cilium as a cell cycle checkpoint or a brake.Nonetheless,we also call for more attention on research of interaction between cell cycle and primary cilia and tried to point out some possible research directions for those who are interested.

Economic Policy Uncertainty,Heterogeneity of Executives and Enterprise Innovation

This study analyzes how economic policy uncertainty affects corporate innovation,and the moderating effects of executive heterogeneity.A threephase dynamic investment and financing model is first built to analyze the mechanism.Empirical analysis confirms that the increase in the degree of economic policy uncertainty promotes enterprise innovation.Further results show that this promotion effect is more significant in enterprises with male executives,low educational level,no financial experience and political background.Moreover,the positive impact is only found in enterprises with moderate executive ability,and the overconfidence of senior executives plays a positive regulating role in it.

Epidemiological Evaluation of Bacillus cereus-Induced Foodborne Outbreaks — China, 2010–2020

Introduction:Bacillus cereus(B.cereus)is a common gram-positive bacterium that contaminates starch-rich food and can cause outbreaks of foodborne diseases.This study describes characteristics of outbreaks caused by B.cereus in China during 2010–2020 and explore the possible reasons for changes in the number of outbreaks over time.Results of this analysis can efficiently help guide and allocate public resources to prevent B.cereus caused foodborne diseases.Methods:Descriptive statistical methods were used to analysis the data on B.cereus outbreaks in China during this period.The data were identified,reported at all levels in China through National Foodborne Disease Outbreak Surveillance System.Results:From 2010 to 2020,a total of 419 foodborne outbreaks prompted by B.cereus were reported in China,leading to 7,892 cases,2,786 hospital admissions,and 5 fatalities.The bulk of the outbreaks were recorded in the summer,primarily between May and September.The most recurrent food vehicle was linked with rice or flour-based products,notably those made with rice or fried rice.School canteens bore the brunt of the B.cereus outbreaks.In multifactor outbreaks,food contamination was identified as the most common culprit;while in instances where only one factor contributed,improper storage was most frequently implicated.Conclusion:The prevalence of B.cereus outbreaks remained relatively consistent throughout the studied period.Understanding the types of foods,causative factors,and contributing elements leading to B.cereus outbreaks can help inform prevention strategies for foodborne illnesses.The majority of outbreaks were associated with rice-or flour-based foods in school canteens,suggesting contamination and improper storage during food preparation.Consequently,it is essential to prioritize continuous education for canteen staff on food safety,efficacious management,and proper practices.The implementation of comprehensive guidelines,encompassing multiple critical aspects,can potentially reduce the occurrence of B.cereus outbreaks.

pH-sensitive and biodegradable charge-transfer nanocomplex for second near-infrared photoacoustic tumor imaging

The emerging technique of photoacoustic imaging,especially in the near infra-red(NIR)window,permits high resolution,deep-penetration,clinically reliable sensing.However,few contrast agents are available that can specifically respond to intricate biological environments,and which are biodegradable and biocompatible.Herein,we in troduce a new class of pH-sensitive orga nic photoacoustic con trast age nt that operates in the second NIR window(NIR-II,960-1,700 nm),which is derived from the self-assembled charge-transfer nanocomplex(CTN)by 3,3',5,5'-tetramethylbenzidine(TMB)and its dication structure(TMB++).The unique NIR-ll-responsive CTN can specifically respond to pH change in the physiological range and allows noninvasive and sensitive visualization of the tumor acidic microenvironment(e.g.at pH5)in mice with higher signal-to-noise ratio.The CTN is biodegradable under physiological conditions(e.g.pH 7.4),which alleviates the biosafety concern of nan oparticle accumulati on in vivo.These results clearly show the pote ntial of the TMB/TMB++-based CTN as a promisi ng pH-activated and biodegradable molecular probe for specific tumor photoacoustic imaging in the NIR-II region.

Characteristics of Settings and Etiologic Agents of Foodborne Disease Outbreaks—China,2020

Introduction:Foodborne diseases are a growing public health problem and have caused a large burden of disease in China.This study analyzed epidemiological characteristics of foodborne diseases in China in 2020 to provide a scientific basis for prevention and control measures.Methods:Data were collected from 30 of 31 provincial-level administrative divisions(PLADs)in the mainland of China,excluding Xizang(Tibet)Autonomous Region,via the National Foodborne Disease Outbreaks Surveillance System・The number and proportion of outbreaks,illnesses,hospitalizations,deaths by setting,pathogen-food category pairs and etiology were calculated.Results:In 2020,7,073 foodborne disease outbreaks were reported,resulting in 37,454 illnesses and 143 deaths.Among the identified pathogens,microbial pathogens were the most common confirmed etiology,accounting for 41.7%of illnesses.Poisonous mushrooms caused the largest proportion of outbreaks(58.0%)and deaths(57.6%).For venues where foodborne disease outbreaks occur,household had the highest number of outbreaks(4,140)and deaths(128),and catering service locations caused the largest proportion of illnesses(59.9%).Outbreaks occurring between June and September accounted for 62.8%of total outbreaks.Conclusions:Foodborne disease outbreaks mainly occurred in households・Microbial pathogens remained the top cause of outbreak-associated illnesses.Poisonous mushrooms were ranked the top cause of deaths in private homes in China.The supervision and management of food safety and health education should be strengthened to reduce the burden of foodborne diseases・Publicity should be increased to reduce the incidence of mushroom poisonings in families,and supervision and management of food should be strengthened to reduce microbial contamination.