Single Pt Atoms Supported on Oxidized Graphene as a Promising Catalyst for Hydrolysis of Ammonia Borane

Based on density functional theory calculations,the full hydrolysis of per NH3BH3 molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene(Pt1/Gr-O)is investigated.It is suggested that the first hydrogen molecule is produced by the combination of two hydrogen atoms from two successive B-H bonds breaking.Then one H2O molecule attacks the left*BHNH3 group(*represents adsorbed state)to form*BH(H2O)NH3 and the elongated O-H bond is easily broken to produce*BH(OH)NH3.The second H2O molecule attacks*BH(OH)NH3 to form*BH(OH)(H2O)NH3 and the breaking of O-H bond pointing to the plane of Pt1/Gr-O results in the desorption of BH(OH)2NH3.The second hydrogen molecule is produced from two hydrogen atoms coming from two H2O molecules and Pt1/Gr-O is recovered after the releasing of hydrogen molecule.The third hydrogen molecule is generated by the further hydrolysis of BH(OH)2NH3 in water solution.The rate-limiting step of the whole process is the combination of one H2O molecule and*BHNH3 with an energy barrier of 16.1 kcal/mol.Thus,Pt1/Gr-O is suggested to be a promising catalyst for hydrolysis of NH3BH3 at room temperature.

Longitudinal associations of cardiovascular health and vascular events with incident dementia

Introduction Evidence supporting cardiovascular diseases could increase the risk of dementia remains fragmented.A comprehensive study to illuminate the distinctive associations across different dementia types is still lacking.This study is sought to:(1)determine the clinical validity of Framingham General Cardiovascular Risk Score(FGCRS)for dementia assessment and(2)examine the associations between cardiovascular diseases and the risk of dementia.Methods A total of 432079 dementia-free individuals at baseline from UK Biobank were included.Multivariable Cox proportional hazard models were used to investigate the prospective associations for FGCRS and a series of cardiovascular diseases with all-cause dementia(ACD)and its major components,Alzheimer’s disease(AD)and vascular dementia(VaD).Results During a median follow-up of 110.1 months,4711 individuals were diagnosed with dementia.FGCRS was associated with increased risks across the dementia spectrum.In stratification analysis,high-risk groups have demonstrated the greatest dementia burdens,particularly to VaD.Over 74 traits,9 adverse associations,such as chronic ischaemic heart disease(ACD:HR=1.354;AD:HR=1.269;VaD:HR=1.768),atrioventricular block(ACD:HR=1.562;AD:HR=1.556;VaD:HR=2.069),heart failure(ACD:HR=1.639;AD:HR=1.543;VaD:HR=2.141)and hypotension(ACD:HR=2.912;AD:HR=2.361;VaD:HR=3.315)were observed.Several distinctions were also found,with atrial fibrillation,cerebral infarction,and haemorrhage only associated with greater risks of ACD and VaD.Discussion By identifying distinctive associations between cardiovascular diseases and dementia,this study has established a comprehensive‘mapping’that may untangle the long-standing discrepancy.FGCRS has demonstrated its predictivity beyond cardiovascular diseases burdens,suggesting potential opportunities for implantation.

Big Data Modeling and Analysis of Microblog Ecosystem

Recent progress of Web 2.0 applications has witnessed the rapid development of microblog in China, which has already been one of the most important ways for online communications, especially on sharing information. This paper tries to make an in-depth investigation on the big data modeling and analysis of microblog ecosystem in China by using a real dataset containing over17 million records of SinaWeibo users. First, we present the detailed geography, gender, authentication, education and age analysis of microblog users in this dataset. Then we conduct the numerical features distribution analysis, propose the user influence formula and calculate the influences for different kinds of microblog users. Finally, user content intention analysis is performed to reveal users most concerns in their daily life.

Cobalt nanoparticle decorated N-doped carbons derived from a cobalt covalent organic framework for oxygen electrochemistry

The low cost and highly efficient construction of electrocatalysts has attracted significant attention owing to the use of clean and sustainable energy technologies.In this work,cobalt nanoparticle decorated N-doped carbons(Co@NC)are synthesized by the pyrolysis of a cobalt covalent organic framework under an inert atmosphere.The Co@NC demonstrates improved electrocatalytic capabilities compared to N-doped carbon without the addition of Co nanoparticles,indicating the important role of cobalt.The well-dispersed active sites(Co-Nx)and the synergistic effect between the carbon matrix and Co nanoparticles greatly enhance the electrocatalytic activity for the oxygen reduction reaction.In addition,the Co content has a significant effect on the catalytic activity.The resulting Co@NC-0.86 exhibits a superb electrocatalytic activity for the oxygen reduction reaction in an alkaline electrolyte in terms of the onset potential(0.90 V),half-wave potential(0.80 V)and the limiting current density(4.84 mA·cm^(−2)),and a high selectivity,as well as a strong methanol tolerance and superior durability,these results are comparable to those of the Pt/C catalyst.Furthermore,the superior bifunctional activity of Co@NC-0.86 was also confirmed in a home-built Zn-air battery,signifying the possibility for application in electrode materials and in current energy conversion and storage devices.