Improvement effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)on hydrogen storage performance of MgH_(2)

The hydrogen absorption/desorption kinetic properties of MgH_(2)can be effectively enhanced by doping specific catalysts.In this work,MOFs-derived NiCu@C nanoparticles(~15 nm)with regular core-shell structure were successfully prepared and introduced into MgH_(2)(denoted as MgH_(2)-NiCu@C).The onset and peak temperatures of hydrogen desorption of MgH_(2)-11 wt.%NiCu@C are 175.0℃and282.2℃,respectively.The apparent activation energy of dehydrogenated reaction is 77.2±4.5 kJ/mol for MgH_(2)-11 wt.%NiCu@C,which is lower than half of that of the as-milled MgH_(2).Moreover,MgH_(2)-11 wt.%NiCu@C displays great cyclic stability.The strengthening"hydrogen pumping"effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)is proposed to explain the remarkable improvement in hydrogen absorption/desorption kinetic properties of MgH_(2).This work offers a novel perspective for the design of bimetallic nanoparticles and beyond for application in hydrogen storage and other energy related fields.

社会流动感知和预期如何影响居民幸福感?——公共服务满意度的中介作用和社会公平感的调节作用

民众幸福感的提升,不仅源于经济流动(即相对收入的提高),还源于社会流动(即社会地位的改善)。基于2015年中国综合社会调查(CGSS)数据,采用Bootstrap方法检验社会流动感知和预期对居民幸福感的作用机制,研究发现,社会流动感知和社会流动预期均对居民幸福感存在正向影响;公共服务满意度在社会流动预期与幸福感之间具有遮掩效应,在社会流动感知与居民幸福感之间具有中介效应;社会公平感在社会流动感知与幸福感之间、社会流动预期与幸福感之间、社会流动预期与公共服务满意度之间,均发挥着调节作用。该研究不仅揭示了社会流动感知和预期对幸福感的作用机制,还具有新的公共政策价值,即社会政策的目标定位可从弱势群体向非弱势群体拓展,回应社会流动高预期人群对公共服务治理(尤其是公平性)的关切,从而带来提升民众幸福感和获得感之效。

Multi-Agent Deep Deterministic Policy Gradien-Based Task Offloading Resource Allocation Joint Offloading

With the advancement of technology and the continuous innovation of applications, low-latency applications such as drones, online games and virtual reality are gradually becoming popular demands in modern society. However, these applications pose a great challenge to the traditional centralized mobile cloud computing paradigm, and it is obvious that the traditional cloud computing model is already struggling to meet such demands. To address the shortcomings of cloud computing, mobile edge computing has emerged. Mobile edge computing provides users with computing and storage resources by offloading computing tasks to servers at the edge of the network. However, most existing work only considers single-objective performance optimization in terms of latency or energy consumption, but not balanced optimization in terms of latency and energy consumption. To reduce task latency and device energy consumption, the problem of joint optimization of computation offloading and resource allocation in multi-cell, multi-user, multi-server MEC environments is investigated. In this paper, a dynamic computation offloading algorithm based on Multi-Agent Deep Deterministic Policy Gradient (MADDPG) is proposed to obtain the optimal policy. The experimental results show that the algorithm proposed in this paper reduces the delay by 5 ms compared to PPO, 1.5 ms compared to DDPG and 10.7 ms compared to DQN, and reduces the energy consumption by 300 compared to PPO, 760 compared to DDPG and 380 compared to DQN. This fully proves that the algorithm proposed in this paper has excellent performance.

Effectiveness of fire needle combining with moist healing dressing to promote the growth of granulation tissue in chronic wounds:A case report

In this case study,we analyzed the wound-healing process of a patient with a chronic wound who underwent fire needle treatment,and we tracked the coverage of granulation tissue and decrease of slough and exudate.An 85-year-old man had repeated right shoulder and back pain,itching,and skin festering for more than 1.5 years.A fire needle was administered combined with moist dressing once every 5 days to promote wound healing.After six rounds of fire needle treatment,granulation tissue formed over the surface of the wound base,the depth of the wound had become shallow,and the wound area was reduced.No complications occurred during the intervention.Fire needle therapy combined with a moist wound-healing dressing can be an effective alternative approach in managing chronic wounds.

Facet-dependent catalytic activity of two-dimensional Ti_(3)C_(2)T_(x) MXene on hydrogen storage performance of MgH_(2)

Two-dimensional Ti_(3)C_(2)T_(x) MXenes exposing different active facets are introduced into MgH_(2), and their catalytic effects are systematically investigated in depth through experimental and theoretical approaches. Excluding factors such as interlayer space, surface functional groups and experimental contingency, the exposed facets is considered to be the dominant factor for catalytic activity of Ti_(3)C_(2)T_(x) towards MgH_(2).More exposed edge facets of Ti_(3)C_(2)T_(x) displays higher catalytic activity than that with more exposed basal facets, which also leads to different rate-controlling steps of MgH_(2) in the de/hydrogenation process. The low work function, strong hydrogen affinity and high content of in situ metallic Ti for the edge facet contribute the high catalytic activity. This work will give insights into the structural design of two-dimensional Ti_(3)C_(2)T_(x) MXene used for enhancing the catalytic activity in various fields.

Intelligent Voice Instructor-Assistant System for Collaborative and Interactive Classes

College classes are becoming increasingly large.A critical component in scaling class size is the collaboration and interactions among instructors,teaching assistants,and students.We develop a prototype of an intelligent voice instructorassistant system for supporting large classes,in which Amazon Web Services,Alexa Voice Services,and self-developed services are used.It uses a scraping service for reading the questions and answers from the past and current course discussion boards,organizes the questions in JavaScript object notation format,and stores them in the database,which can be accessed by Amazon web services Alexa skills.When a voice question from a student comes,Alexa is used for translating the voice sentence into texts.Then,Siamese deep long short-term memory model is introduced to calculate the similarity between the question asked and the questions in the database to find the best-matched answer.Questions with no match will be sent to the instructor,and instructor’s answer will be added into the database.Experiments show that the implemented model achieves promising results that can lead to a practical system.Intelligent voice instructor-assistant system starts with a small set of questions.It can grow through learning and improving when more and more questions are asked and answered.

A Coherent Pattern Mining Algorithm Based on All Contiguous Column Bicluster

Microarray contains a large matrix of information and has been widely used by biologists and bio data scientist for monitoring combinations of genes in different organisms.The coherent patterns in all continuous columns are mined in gene microarray data matrices.It is investigated,in this study,the coherent patterns in all continuous columns in gene microarray data matrix by developing the time series similarity measure for the coherent patterns in all continuous columns,as well as the evaluation function for verifying the proposed algorithm and the corresponding biclusters.The continuous time changes are taken into account in the coherent patterns in all continuous columns,and co-expression patterns in time series are searched.In order to use all the common information between sequences,a similarity measure for the coherent patterns in continuous columns is defined in this paper.To validate the efficiency of the similarity measure to mine biological information at continuous time points,an evaluation function is defined to measure biclusters,and an effective algorithm is proposed to mine the biclusters.Simulation experiments are conducted to verify the biological significance of the biclusters,which include synthetic datasets and real gene microarray datasets.The performance of the algorithm is analyzed,and the results show that the algorithm is highly efficient.

Novel magnetic field computation model in pattern classification

Field computation, an emerging computation technique, has inspired passion of intelligence science research. A novel field computation model based on the magnetic field theory is constructed. The proposed magnetic field computation （MFC） model consists of a field simulator, a non-derivative optimization algo- rithm and an auxiliary data processing unit. The mathematical model is deduced and proved that the MFC model is equivalent to a quadratic discriminant function. Furthermore, the finite element prototype is derived, and the simulator is developed, combining with particle swarm optimizer for the field configuration. Two benchmark classification experiments are studied in the numerical experiment, and one notable advantage is demonstrated that less training samples are required and a better generalization can be achieved.

Development of underwater electric manipulator based on interventional autonomous underwater vehicle (AUV)

In applications such as marine rescue,marine science,archaeology,and offshore industries,autonomous underwater vehicles(AUVs)are frequently used for survey missions and monitoring tasks,with most operations being performed by manned submersibles or remotely operated vehicles(ROVs)equipped with robotic arms,as they can be operated remotely for days without problems.However,they require expensive marine vessels and specialist pilots to operate them.Scientists exploring oceans are no longer satisfied with the use of manned submersibles and ROVs.There is a growing desire for seabed exploration to be performed using smarter,more flexible,and automated equipment.By improving the field operation and intervention capability of AUVs,large-scale and long-range seafloor exploration and sampling can be performed without the support of a mother ship,making it a more effective,economical,convenient,and rapid means of seafloor exploration and sampling operations,and playing a critical role in marine resource exploration.In this study,we explored the integration technology of underwater electric robotic arms and AUVs and designed a new set of electric manipulators suitable for water depths greater than 500 m.The reliability of the key components was analyzed by finite element analysis and,based on the theory of robot kinematics and dynamics,simulations were performed to verify the reliability of the key components.Experiments were conducted on land and underwater,trajectory tracking experiments were completed,and the experimental data in air and water were compared and analyzed.Finally,the objectives for further research on the autonomous control of the manipulator underwater were proposed.

The altered PD-1/PD-L1 pathway delivers the ‘one-two punch’ effects to promote the Treg/Th17 imbalance in pre-eclampsia

The programmed cell death-1(PD-1)/PD-ligand 1(PD-L1)pathway is critical for normal pregnancy by promoting regulatory T(Treg)cell development and inhibiting the Th17 response.However,the relationship between the PD-1/PD-L1 pathway and the Treg/Th17 imbalance in pre-eclampsia(PE)is an enigma.In this study,decreased PD-1 and PD-L1 expression and a Treg/Th17 imbalance were observed at the maternal-fetal interface in PE.The regulatory effects of the PD-1/PD-L1 pathway on the Treg and Th17 cell quantities were determined in vitro by targeting T-cell proliferation,differentiation and transdifferentiation.First,decreased PD-1 expression might contribute to a higher Th17 cell frequency by promoting proliferation in PE.Second,the percentages of Treg but not Th17 cells differentiated from peripheral naive CD4+T cells were increased by PD-L1 Fc administration.This effect was accompanied by decreased PI3K/AKT/m-TOR and increased PTEN mRNA expression and was completely reversed by PD-1 blockade.Finally,the percentage of IL-17-producing Treg cells increased and was positively associated with the Th17 cell frequency in PE.Increased RORγt and IL-17 but not Foxp3 and IL-10 mRNA expression by Treg cells was observed with PD-1 blockade.Similar findings occurred when Treg cells were exposed to IL-6/IL-23/IL-1βand were reversed by PD-L1 Fc.Taken together,our findings indicate that the PD-1/PD-L1 pathway contributes to the Treg/Th17 imbalance via‘one-two punch’approaches:(i)promoting Th17 cell proliferation,(ii)inhibiting Treg cell differentiation and(iii)enhancing Treg cell plasticity into Th17 cells in PE.The therapeutic value of PD-L1 Fc for PE treatment will be explored in the future.

In situ atomic-scale observation of monolayer graphene growth from SiC

Because of its high compatibility with conventional microfabrication processing technology, epitaxial graphene （EG） grown on SiC shows exceptional promise for graphene-based electronics. However, to date, a detailed understanding of the transformation from three-layer SiC to monolayer graphene is still lacking. Here, we demonstrate the direct atomic-scale observation of EG growth on a SiC （11^-00） surface at 1,000℃ by in situ transmission electron microscopy in combination with ab initio molecular dynamics （AIMD） simulations. Our detailed analysis of the growth dynamics of monolayer graphene reveals that three SiC （11^-00） layers decompose successively to form one graphene layer. Sublimation of the first layer causes the formation of carbon clusters containing short chains and hexagonal rings, which can be considered as the nuclei for graphene growth. Decomposition of the second layer results in the appearance of new chains connecting to the as-formed clusters and the formation of a network with large pores. Finally, the carbon atoms released from the third layer lead to the disappearance of the chains and large pores in the network, resulting in a whole graphene layer. Our study presents a clear picture of the epitaxial growth of the monolayer graphene from SiC and provides valuable information for future developments in SiC-derived EG technology.

Air-stable magnesium nickel hydride with autocatalytic and self-protective effect for reversible hydrogen storage

Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In this work,a novel method,namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure,was proposed to synthesize air stable and autocatalytic magnesium nickel hydride(Mg2NiH4),which shows excellent hydrogen absorption/desorption kinetics,capacity retention and oxidation resistance.The short-term-milled Mg2NiH4 can desorb 2.97 wt.%hydrogen within 500 s at 230℃.Even after exposure under air atmosphere for 67 days,it can still desorb 2.88 wt.%hydrogen within 500 s at 230℃.The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere.However,the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics,and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning,which we called autocatalytic and self-protective effect.Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4.Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.

Assisting Ni catalysis by CeO_(2) with oxygen vacancy to optimize the hydrogen storage properties of MgH_(2)

Although MgH_(2) has been widely regarded as a promising material for solid-state hydrogen storage,its high operating temperature and slow kinetics pose a major bottleneck to its practical application.Here,a nanocomposite catalyst with interfacial coupling and oxygen defects,Ni/CeO_(2),is fabricated to promote H_(2) desorption and absorption properties of MgH_(2).The interface of Ni/CeO_(2) contributes to both strong mechanical coupling towards stabilizing partial Ni and electronic coupling towards inducing a high con-centration of oxygen vacancies in CeO_(2).Theoretical calculations evidence that CeO_(2) with oxygen vacancy assist Ni in weakening the energy of Mg-H bond as well as enhancing the adsorption energy of Ni upon hydrogen atoms,and the extent of this assistance surprisingly increases with increasing oxygen vacancies concentration.As a result,an impressive performance is achieved by MgH_(2)-5 wt.%Ni/CeO_(2) with onset desorption temperature of only 165°C,and it absorbs approximately 80%hydrogen in just 800 s at 125°C.The generation mechanism of intermediate active species concerning Ni/CeO_(2) in different states has been analyzed for the first time,and the relationship between interfacial coupling and phase evolution has been elucidated.Therefore,a mechanism of the catalysis-assisting effect regarding oxygen defects is proposed.It is believed that this work provides a unique perspective on the mechanism of interfacial coupling and the generation of defects in composite catalysts.

Structure of SARS-CoV-2 main protease in the apo state

Dear Editor,Coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-Co V-2)has been a global pandemic that severely threatens global health with concordant economic damage.However,there is currently no clinically approved vaccines or drugs against COVID-19(Lu et al.,2020).

A Convenient Preparation of Fluorinating Reagent F-TEDA Bearing Bisphenylsulfonylimide Counterion and Its Fluorination to Oxindoles

The direct preparation of a kind of fluorinating reagent 1[F-TEDA-N(SO_(2)Ph)_(2)]was realized in high yield via the complexation of N-fluorobenzenesulfonimide(NFSI)with 1-(chloromethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium N',N'-bis-(benzenesulfonylimide)salt.In its fluorination to oxindoles,the fluorinating products 6 were afforded in moderate to high yields.