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Correlation between types of defects/vacancies of Bi2S3 nanostructures and their transient photocurrent

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Nano Research 2017年第7期10卷 2405-2414页

作者： Mingyang Liu Luqing Wang Pei Dong Liangliang Dong Xifan Wang Jarin Joyner Xiangjian Wan Boris I. Yakobson robert vajtai Pulickel Ajayan PolSpanos Department of Materials Science and Nanoengineeriing Rice University Houston TX 77005 USA Department of Chemistry Rice University Houston TX 77005 USA College of Chemistry Nankai University Tianjin 300071 China

Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of Bi2S3 microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies （VBi） to septuple Bi3＋-sulfur vacancy associates （VBiBiBiSSSS）. Furthermore, the concentration of septuple BiB＋-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that VBiBiBiSSSS strongly absorbs I2（sol）, easily desorbs I-（sol）, and enhances the electrocatalytic activity of the nanostructures.

关键词： Bi2S3 microspheres nanorod assembly defects/vacancies positron annihilationspectrometry transient photocurrent

Synthesis of large-scale atomic-layer SnS2 through chemical vapor deposition

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Nano Research 2017年第7期10卷 2386-2394页

作者： Gonglan Ye Yongji Gong Sidong Lei Yongmin He Bo Li Xiang Zhang Zehua Jin Liangliang Dong Jun Lou robert vajtai Wu Zhou Pulickel M. Ajayan Department of Materials Science & NanoEngineering Rice University Houston Texas 77005 USA Department of Chemistry Rice University Houston Texas 77005 USA Department of Applied Physics Rice University Houston Texas 77005 USA Materials Science & Technology Division Oak Ridge National Lab Oak Ridge TN 37831 USA School of Materials Science and Engineering Beihang University Beijing 100191 China

Two-dimensional layers of metal dichalcogenides have attracted much attention because of their ultrathin thickness and potential applications in electronics and optoelectronics. Monolayer SnS2, with a band gap of -2.6 eV, has an octahedral lattice made of two atomic layers of sulfur and one atomic layer of tin. Till date, there have been limited reports on the growth of large-scale and high quality SnS2 atomic layers and the investigation of their properties as a semiconductor. Here, we report the chemical vapor deposition （CVD） growth of atomic-layer SnS2 with a large crystal size and uniformity. In addition, the number of layers can be changed from a monolayer to few layers and to bulk by changing the growth time. Scanning transmission electron microscopy was used to analyze the atomic structure and demonstrate the 2H stacking poly-type of different layers. The resultant SnS2 crystals is used as a photodetector with external quantum efficiency as high as 150%, suggesting promise for optoelectronic applications.

关键词： metal dichalcogenides tin disulfide two-dimensional materials chemical vapor deposition photodetector

The modulating effect of N coordination on single-atom catalysts researched by Pt-N_(x)-C model through both experimental study and DFT simulation

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Journal of Materials Science & Technology 2021年第32期91卷 160-167页

作者： Mengmeng Fan Jiewu Cui Junjie Zhang Jingjie Wu Shuangming Chen Li Song Zixing Wang Ao Wang robert vajtai Yucheng Wu Pulickel MAjayan Jianchun Jiang Dongping Sun Nanjing Forestry University Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest ResourcesCollege of Chemical EngineeringNanjing 210037China Rice University Department of Materials Science and NanoEngineeringHoustonTX 77005USA Hefei University of Technology School of Materials Science and EngineeringHefei 230009China University of Cincinnati Department of Chemical and Environmental EngineeringCincinnatiOH 45221USA University of Science and Technology of China National Synchrotron Radiation LaboratoryCAS Center for Excellence in NanoscienceHefei 230026China Nanjing University of Science and Technology Chemicobiology and Functional Materials InstituteNanjing 210094China Key Lab of Biomass Energy and Material Jiangsu ProvinceJiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest ResourcesInstitute of Chemical Industry of Forest ProductsChinese Academy of ForestryNanjing 210042China

N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic *** catalytic activity of NC-SACs originates from the coordinating structure between single metal site(M) and the doped nitrogen(N) in carbon matrix by forming M-N_(x)-C structure(1≤x≤4).The M-N4-C structure is widely considered to be the most stable and effective catalytic ***,there is no in-depth research for the "x" modulation in Pt-Nx-C structure and the corresponding catalytic ***,atomically dispersed Pt on N-doped carbon(Pt-NC) with Pt-Nx-C structure(1≤x≤4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen *** carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C *** Pt-NC has the predictable low half-wave potential(E_(1/2)) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81 V due to low Pt ***,the Pt-NC shows a high onset potential(1.10 V vs RHE,determined for j=-0.1 mA cm^(2)) and a high current density of 5.2 mA cm^(-2),more positive and higher than that of Pt/C 20%(0.96 V) and 4.9 mA cm^(-2),*** the structural characterization and DFT simulation confirmed,the reducing PtN coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic ***,the Pt-NC shows high mass activity(172 times higher than that of Pt/C 20%),better stability and methanol crossover resistance.

关键词： Modulating effect N coordination Single-atom catalysts Pt-N_(x)-C model DFT simulation

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Carbon nanotube micropillars trigger guided growth of complex human neural stem cells networks

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Nano Research 2019年第11期12卷 2894-2899页

作者： Gabriela S.Lorite Laura Yla-Outinen Lauriane Janssen Olli Pitkanen Tiina Joki Janne T.Koivisto Minna Kellomaki robert vajtai Susanna Narkilahti Krisztian Kordas Microelectronics Research Unit University of OuluOuluPO BOX 4500FI 90014Finland NeuroGroup BioMediTech and Faculty of Medicine and Health technologyTampere UniversityArvo Ylpön katu 34TampereFI 33520Finland Biomaterials&Tissue Engineering Group BioMediTechFaculty of Medicine and Health TechnologyTampere UniversityPO Box 527TampereFI 33101Finland Department of Materials Science and Nanoengineering Rice UniversityP.O.Box 1892HoustonTX77251-1892USA

New strategies for spatially controlled growth of human neurons may provide viable solutions to treat and recover peripheral or spinal cord *** topography cues are known to promote attachment and direct proliferation of many cell types,guided outgrowth of human neurites has been found difficult to achieve so ***,three-dimensional(3D)micropatterned carbon nanotube(CNT)templates are used to effectively direct human neurite stem cell *** exploiting the mechanical flexibility,electrically conductivity and texture of the 3D CNT micropillars,a perfect environment is created to achieve specific guidance of human neurites,which may lead to enhanced therapeutic effects within the injured spinal cord or peripheral *** is found that the 3D CNT micropillars grant excellent anchoring for adjacent neurites to form seamless neuronal networks that can be grown to any arbitrary shape and *** from clear practical relevance in regenerative medicine,these results using the CNT based templates on Si chips also can pave the road for new types of microelectrode arrays to study cell network electrophysiology.

关键词： carbon nanotubes multiple cues guided neurite outgrowth human neural stem cells neuronal networks

Predicting the coefficient of friction in a sliding contact by applying machine learning to acoustic emission data

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Friction 2024年第6期12卷 1299-1321页

作者： robert GUTIERREZ Tianshi FANG robert MAINWARING Tom REDDYHOFF Tribology Group Department of Mechanical EngineeringImperial College LondonExhibition RoadLondon SW72AZUK Shell Global Solutions(US)Inc.Shell Technology Center Houston 3333 Highway 6 SouthHoustonTX 77082USA Shell International Petroleum Company Limited Shell CentreYork RoadLondon SE17NAUK

It is increasingly important to monitor sliding interfaces within machines,since this is where both energy is lost,and failures *** emission(AE)techniques offer a way to monitor contacts remotely without requiring transparent or electrically conductive ***,acoustic data from sliding contacts is notoriously complex and difficult to ***,we simultaneously measure coefficient of friction(with a conventional force transducer)and acoustic emission(with a piezoelectric sensor and high acquisition rate digitizer)produced by a steel‒steel rubbing *** data is then used to train machine learning(ML)algorithms(e.g.,Gaussian process regression(GPR)and support vector machine(SVM))to correlated acoustic emission with *** training requires the dense AE data to first be reduced in size and a range of processing techniques are assessed for this(e.g.,down-sampling,averaging,fast Fourier transforms(FFTs),histograms).Next,fresh,unseen AE data is given to the trained model and the resulting friction predictions are compared with the directly measured *** is excellent agreement between the measured and predicted friction when the GPR model is used on AE histogram data,with root mean square(RMS)errors as low as 0.03 and Pearson correlation coefficients reaching ***,predictions remain accurate despite changes in test conditions such as normal load,reciprocating frequency,and stroke *** paves the way for remote,acoustic measurements of friction in inaccessible locations within machinery to increase mechanical efficiency and avoid costly failure/needless maintenance.

关键词： acoustic emission condition monitoring friction machine learning Gaussian process regression support vector machine

Necrotic enteritis and antibiotic-free production of broiler chickens:Challenges in testing and using alternative products

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Animal Nutrition 2024年第1期16卷 288-298页

作者： robert J.Moore School of Science RMIT University

The global trend towards raising broiler chickens without the use of in-feed antibiotics(IFAs) means that there is an ongoing need to develop alternative treatments capable of delivering the benefits that IFAs previously provided. IFAs supported the productivity performance of chickens and played a key role in maintaining their health. Necrotic enteritis(NE) is an important disease of broilers that affects health,productivity, and welfare, and was previously well controlled by IFAs. However, with the reduction in IFA use, NE is resurgent in some countries. Vaccines and various feed additives, including pre-, pro-, and postbiotics, phytobiotics, fatty acids, and phage therapies have been introduced as alternative methods of NE control. While some of these feed additives have specific activity against the NE pathogen, Clostridium perfringens, most have the more general goal of reinforcing gut health. Extensive reviews of the effects of many of these feed additives on gut health have been published recently. Hence, rather than cover previously well reviewed areas of research this review focuses on the challenges and pitfalls in undertaking experimental assessment of alternative NE treatments and translating laboratory research to real world commercial production settings. The review is based on the author's particular experience,reading, thoughts, and analysis of the available information and inevitably presents a particular understanding that is likely to be at odds with others thinking on these issues. It is put forward to stimulate thinking and discussion on the issues covered.

关键词： Necrotic enteritis Clostridium perfringens Vaccines Feed additive Farm management

A detailed rock density model of the Hong Kong territories

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Geodesy and Geodynamics 2024年第1期15卷 75-81页

作者： Albertini Nsiah Ababio robert Tenzer Department of Land Surveying and Geo-Informatics Hong Kong Polytechnic UniversityHong KongChina

We used the geological map and published rock density measurements to compile the digital rock density model for the Hong Kong *** then estimated the average density for the whole *** to our result,the rock density values in Hong Kong vary from 2101 to 2681 kg·m^(-3).These density values are typically smaller than the average density of 2670 kg·m^(-3),often adopted to represent the average density of the upper continental crust in physical geodesy and gravimetric geophysics *** finding reflects that the geological configuration in Hong Kong is mainly formed by light volcanic formations and lava flows with overlying sedimentary deposits at many locations,while the percentage of heavier metamorphic rocks is very low(less than 1%).This product will improve the accuracy of a detailed geoid model and orthometric heights.

关键词： Density model Rock types Gravimetric modeling Hong Kong

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The concept of gene therapy for glaucoma:the dream that has not come true yet

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Neural Regeneration Research 2024年第1期19卷 92-99页

作者： robert Sulak Xiaonan Liu Adrian Smedowski Department of Physiology Faculty of Medical Sciences in KatowiceMedical University of Silesia in KatowiceKatowicePoland Institute of Biotechnology HiLIFEUniversity of HelsinkiHelsinkiFinland GlaucoTech Co. KatowicePoland

Gene therapies,despite of being a relatively new therapeutic approach,have a potential to become an important alternative to current treatment strategies in *** glaucoma is not considered a single gene disease,the identified goals of gene therapy would be rather to provide neuroprotection of retinal ganglion cells,especially,in intraocular-pressure-independent *** most commonly reported type of vector for gene delivery in glaucoma studies is adeno-associated virus serotype 2 that has a high tro pism to retinal ganglion cells,res ulting in long-term expression and low immunogenic *** gene thera py studies recruit inducible and genetic animal models of optic neuropathy,like DBA/2J mice model of high-tension glaucoma and the optic nerve *** gene therapy-based neuroprotection of retinal ganglion cells is targeting specific genes translating to growth factors(i.e.,brain derived neurotrophic factor,and its receptor TrkB),regulation of apoptosis and neurodegeneration(i.e.,Bcl-xl,Xiap,FAS system,nicotinamide mononucleotide adenylyl transferase 2,Digit3 and Sarm1),immunomodulation(i.e.,Crry,C3 complement),modulation of neuroinflammation(i.e.,e rythropoietin),reduction of excitotoxicity(i.e.,Com KIlα)and transcription regulation(i.e.,Max,Nrf2).On the other hand,some of gene therapy studies focus on lowering intra ocular pressure,by impacting genes involved in both,decreasing aqueous humor production(i.e.,aquaporin 1),and increasing outflow facility(i.e.,COX2,prostaglandin F2a receptor,RhoA/RhoA kinase signaling pathway,MMP1,Myocilin).The goal of this review is to summarize the current stateof-art and the direction of development of gene therapy strategies for glaucomatous neuropathy.

关键词： adeno-associated virus gene editing gene therapy glaucoma IOP lowering IOP-independent mechanisms neuroprotection optic nerve optic neuropathy retinal ganglion cells

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Optimization of product characteristics of porous carbon agglomerates using a design of experiments in fluidized bed agglomeration

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Particuology 2024年第6期89卷 258-269页

作者： Martin Oelofse robert Rack Marcelle Hilden Peter Langguth Department of Pharmaceutical Technology and Biopharmaceutics Johannes Gutenberg UniversityMainzGermany Carbon Advanced Solutions GmbH HeuchelheimGermany

Spraying parameters during particle agglomeration processes can affect the agglomeration kinetics and particle *** study was conducted to better understand the influence of the spraying parameters in a fluidized bed wet agglomeration process,and the influence on the stability characteristics of carbon tablets.A formulation based on fine carbon and peroxide powder,as well as carboxymethyl cellulose as a binder,was used to produce agglomerates in a first production *** in a second production step carbon tablets with a high porosity were molded for the customer goods *** optimization of the compressive strength of these carbon tablets was the goal of the *** agglomerates were produced with a laboratory scale granulator called“ProCell”and were compressed with a five-cavity mechanical *** screening of the agglomeration process parameters and their influence on the agglomerates quality,as well as the performance characteristics of the carbon tablets,were investigated using a multilevel factorial *** experimental runs were done by varying atomized air pressure and feed rate of the *** was determined by the design *** findings of the statistical trials showed that low atomized air pressure and a low feed rate lead to a higher tablet compressive strength.

关键词： Wet agglomeration Fluidized bed Design of experiments Carbon agglomerates and tablets