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External Electric Field Effect on Electrons Transport in Carbon Nanotubes

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World Journal of Condensed Matter Physics 2013年第4期3卷 169-172页

作者： Sulemana S. Abukari Samuel Y. mensah Musah Rabiu kofi W. Adu Natalia G. mensah Kwadwo A. Dompreh Anthony Twum Matthew Amekpewu Department of Applied Physics University for Development Studies Navorongo Ghana Department of Mathematics University of Cape Coast Cape Coast Ghana Department of Physics Laser and Fibre Optics Centre University of Cape Coast Cape Coast Ghana Department of Physics The Pennsylvania State University Altoona USA Materials Research Institute The Pennsylvania State University University Park USA

We consider a simple model of carbon nanotubes (CNTs) subject to external electric field E(t). Using a tight-binding approximation for the description of energy bands of CNTs, together with the standard Boltzmann transport equation and constant relaxation time, we predict the effect of self-induced transparency and absolute negative conductivity. The predicted effects may be useful in diagnostics of carbon nanotubes as well as in the amplification and efficiency conversion of electromagnetic signals.

关键词： Carbon Nanotubes Electric Field Electric Current Density Negative Differential Conductivity

Grazing effects on vegetation dynamics in the savannah ecosystems of the Sahel

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Ecological Processes 2023年第1期12卷 752-763页

作者： Haftay Hailu Gebremedhn Ousmane Ndiaye Sylvanus mensah Cofélas Fassinou Simon Taugourdeau Torbern Tagesson Paulo Salgado African Center of Excellence for Climate-Smart Agriculture and Biodiversity Conservation Haramaya UniversityP.O.Box 138Dire DawaEthiopia Dispositif en Partenariat«Pôle Pastoralisme Et Zones Sèches» Route du Front de Terre BP 2057Pôle de Recherche de HannISRADakarSenegal Centre de Recherches Zootechniques de Dahra Institut Sénégalais de Recherches AgricolesDakarSenegal Laboratoire de Biomathématiques et d’Estimations Forestières Facultédes Sciences AgronomiquesUniversitéd’Abomey-CalaviCotonouBenin Chair of Forest Growth and Dendroecology Albert-Ludwigs-Universität FreiburgFreiburg Im BreisgauGermany Facultédes Sciences et Techniques Département BVUniversitéCheikh-Anta-DiopDakarSenegal UMR SELMET CIRADINRAEInstitut Agro Univ MontpellierMontpellierFrance Department of Physical Geography and Ecosystem Science Lund UniversitySölvegatan 1222362 LundSweden Department of Geosciences and Natural Resource Management University of CopenhagenØster Voldgade 101350 CopenhagenDenmark

Background The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still,their vegetation response to grazing pressure remains poorly *** this study,we analysed the herbaceous plant dynamics,measured by species diversity,composition,cover,and biomass in response to grazing pressure in the savannah ecosystems of *** Senegal,we selected four savannah sites represented with high,moderate,light and no grazing intensity *** survey methods were used for sampling the vegetation data within each of the *** richness and composition were analysed using species accumulation curve and multivariate ***,we used General Linear Models and a piecewise Structural Equation Model(pSEM)to examine the relationships between grazing intensity,vegetation cover,diversity and *** The herbaceous species diversity and composition varied significantly among the different grazing intensity levels(p<0.001).The plant species composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing ***,the attributes of species diversity,herbaceous biomass,and ground cover were higher on sites with low grazing than sites with high and moderate grazing *** all sites,species diversity was positively related to total *** pSEM explained 37%of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species *** Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah *** information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.

关键词： Biomass Biodiversity Diodella sarmentosa Forb Grazing intensity Invasive species Pastoral ecosystem Senegal West Africa

Study on Preparation of Nitrogen-Doped Hierarchically Porous and High-Performance Carbon Materials from Seaweed Biomass

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Journal of Renewable Materials 2022年第2期10卷 541-560页

作者： Kaihan Xie Yamin Hu Stephen Afonaa-mensah Chuan Yuan Bin Cao Shuang Wang Qian Wang School of Energy and Power Engineering Jiangsu UniversityZhenjiangChina Takoradi Technical University TakoradiGhana

Use Enteromorpha clathrate as a carbon and nitrogen precursor could obtain the N-doped porous carbon mate-rials by two-step *** this paper,the exogenous nitrogen(urea,melamine)and activating agents(KOH,ZnCl_(2))were employed for the production of higher-performance carbon materials from seaweed ***,BET,FTIR,XRD,XPS,Raman and ultimate analyses were carried out to investigate the morpho-structural and elemental peculiarities of the carbonaceous ***,cyclic voltammetry(CV),galvanostatic charge-discharge(GCD)and cyclic charge-discharge tests were carried out to examine the electrochemical properties of the *** results showed that electrochemical performance of the carbonaceous materials improved by adding the appropriate nitrogen *** improvement was observed under either condition,when the nitro-gen source and activating agent were melamine and ZnCl_(2) or urea and KOH,***,under the condition with KOH as the activator,the nitrogen content of carbon material without exogenous nitrogen was initially 1.46%.After the addition of urea or melamine,the nitrogen content increased to 4.86%and 6.18%,*** the condition with ZnCl_(2) as the activator,and without exogenous nitrogen,the nitrogen con-tent of carbon materials was initially 3.75%.However,after adding urea or melamine,the nitrogen content increased to 12.11%and 14.76%,*** carbonaceous materials(prepared from urea/KOH and mel-amine/ZnCl_(2))showed excellent gravimetric capacitances of 172 and 151.5 F/g at 1A/***,at a current density of 5 A/g,their specific capacitance retention rate reached 78.3%and 82.6%respectively after 1000 cycles.

关键词： Exogenous nitrogen incorporation N-doped porous carbon two-steps pyrolysis enteromorpha clathrate

Carbon nanotube-reinforced elastomeric nanocomposites: a review

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International Journal of Smart and Nano Materials 2015年第4期6卷 211-238页

作者： Bismark mensah Han Gil Kim Jong-Hwan Lee Sivaram Arepalli Changwoon Nah BK21 Haptic Polymer Composite Research Team Department of Polymer-Nano Science and TechnologyChonbuk National UniversityJeonju 561-756Republic of Korea Nano Science Consultants LLC HamptonVA 23666-6701USA

This review is focused on carbon nanotube(CNT)-elastomeric polymer nanocom-posites,which have attracted industrial and academic interest over the years due to their enhanced *** factors notably CNT type,surface modifica-tion,dispersion of CNT,and processing techniques that affect the physical properties of CNT-elastomeric polymer nanocomposites are reviewed,and several key physical properties,including tensile,electrical,and thermal properties,were also included in this *** of the key challenges that undermine the effectiveness of CNTs and their composites with elastomeric polymers,and the potential applications of CNT-elastomeric composites are also captured.

关键词： carbon nanotubes elastomeric polymers nanocomposites surface mod-ification physical properties

Lanthanum-exchanged zeolite and clay as anticorrosive pigments for galvanized steel

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Journal of Rare Earths 2014年第4期32卷 352-359页

作者： S.Roselli N.Bellotti C.Deyá M.Revuelta B.del amo R.Romagnoli CIDEPINT(Centro de Investigación y Desarrollo en Tecnología de Pinturas)(CONICET-CIC)

A wide variety of inhibitive pigments is now being offered as possible alternatives to chromate and lead compounds for painted metals protection. Unfortunately, the most wide spread of these substitute pigments, zinc phosphate, has, at present, raised some environmental concern because phosphate causes the eutrophication of water courses and zinc itself is toxic. The aim of this re-search was to study the anticorrosive performance of a mixture consisting of zinc phosphate, modified zeolite and clay （bentonite） in order to diminish phosphate content in paints. The zeolite and the clay were exchanged with La（III） ions, as inorganic green inhibitor. In the first step, the anticorrosion protection by La（III） ions in solution was assessed by electrochemical tests. In the second step, an epoxy-polyamide paint formulated with the pigment mixture applied on galvanized panels was studied by salt spray test and electro-chemical noise measurements （ENM）. The results showed that it was possible to replace part of the zinc phosphate content in the paint with the exchanged zeolite and the clay.

关键词： exchanged pigments corrosion anticorrosive paints electrochemical noise measurements rare earths

Predicting the Subcellular Localization of Human Proteins Using Machine Learning and Exploratory Data Analysis

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Genomics, Proteomics & Bioinformatics 2006年第2期4卷 120-133页

作者： George K. Acquaah-mensah Sonia M. Leach Chittibabu Guda Department of Pharmaceutical Sciences School of Pharmacy-Worcester Massachusetts College of Pharmacyand Health Sciences Worcester MA 01608-1715 USA Center for Computational Pharmacology Departmentof Pharmacology University of Colorado School of Medicine Aurora CO 80010 USA Gen*NY*Sis Centerfor Excellence in Cancer Genomics Department of Epidemiology and Biostatistics State University of NewYork at Albany Rensselaer NY 12144-3456 USA.

Identifying the subcellular localization of proteins is particularly helpful in the functional annotation of gene products. In this study, we use Machine Learning and Exploratory Data Analysis （EDA） techniques to examine and characterize amino acid sequences of human proteins localized in nine cellular compartments. A dataset of 3,749 protein sequences representing human proteins was extracted from the SWISS-PROT database. Feature vectors were created to capture specific amino acid sequence characteristics. Relative to a Support Vector Machine, a Multi-layer Perceptron, and a Naive Bayes classifier, the C4.5 Decision Tree algorithm was the most consistent performer across all nine compartments in reliably predicting the subcellular localization of proteins based on their amino acid sequences （average Precision=0.88; average Sensitivity=0.86）. Furthermore, EDA graphics characterized essential features of proteins in each compartment. As examples, proteins localized to the plasma membrane had higher proportions of hydrophobic amino acids; cytoplasmic proteins had higher proportions of neutral amino acids; and mitochondrial proteins had higher proportions of neutral amino acids and lower proportions of polar amino acids. These data showed that the C4.5 classifier and EDA tools can be effective for characterizing and predicting the subcellular localization of human proteins based on their amino acid sequences.

关键词： subcellular localization Machine Learning Exploratory Data Analysis Decision Tree

Infrared Polarizabilities of 3d-Transition and Rare-Earth Metals

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Journal of Modern Physics 2018年第2期9卷 287-301页

作者： kofi Nuroh Department of Mathematical Sciences Kent State University Salem OH USA

A transition or rare-earth metal is modeled as the atom immersed in a jellium at intermediate electron gas densities specified by? rs=4.0. The ground states of the spherical jellium atom are constructed based on the Hohenberg-Kohn-Sham density-functional formalism with the inclusion of electron-electron self-interaction corrections of Perdew and Zunger. Static and dynamic polarizabilities of the jellium atom are deduced using time-dependent linear response theory in a local density approximation as formulated by Stott and Zaremba. The calculation is extended to include the intervening elements In, Xe, Cs, and Ba. The calculation demonstrates how the Lindhard dielectric function can be modified to apply to non-simple metals treated in the jellium model.

关键词： Infrared Polarizability Jellium Transition Metals Rare-Earth Metals Electron Self-Interaction Correction

Energy efficiency based joint cell selection and power allocation scheme for HetNets

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Digital Communications and Networks 2016年第4期2卷 184-190页

作者： Kwabena Kobia mensah Rong Chai Denis Bilibashi Feifei Gao Key Lab of Mobile Communication Technology Chongqing University of Posts and Telecommunications Chongqing 400065 PR China Department of Automation Tsinghua University PR China

Heterogeneous networks （HetNets） composed of overlapped cells with different sizes are expected to improve the transmission performance of data service significantly. User equipments （UEs） in the overlapped area of multiple cells might be able to access various base stations （BSs） of the cells, resulting in various transmission performances due to cell heterogeneity. Hence, designing optimal cell selection scheme is of particular importance for it may affect user quality of service （QoS） and network performance significantly. In this paper, we jointly consider cell selection and transmit power allocation problem in a HetNet consisting of multiple cells. For a single UE case, we formulate the energy efficiency of the UE, and propose an energy efficient optimization scheme which selects the optimal cell corresponding to the maximum energy efficiency of the UE. The problem is then extended to multiple UEs case. To achieve joint performance optimization of all the UEs, we formulate an optimization problem with the objective of maximizing the sum energy efficiency of UEs subject to QoS and power constraints. The formulated nonlinear fractional optimization problem is equivalently transformed into two subproblems, i.e., power allocation subproblem of each UE-eell pair, and cell selection subproblem of UEs. The two subproblems are solved respectively through applying Lagrange dual method and Kuhn-Munkres （K- M） algorithm. Numerical results demonstrate the efficiency of the proposed algorithm.

关键词： Energy efficiency HetNets Cellular network Kuhn-Munkres Lagrange

Assessment of the usefulness of integrated disease surveillance and response on suspected ebola cases in the Brong Ahafo Region, Ghana

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Infectious Diseases of Poverty 2015年第1期4卷 168-175页

作者： kofi Issah Kennedy Nartey Richard amoah Emmanuel George Bachan Jacob Aleeba Enuamah Yeetey Timothy Letsa Ghana Health Service Regional Health DirectorateP.O.Box 145SunyaniBrong Ahafo RegionGhana Kintampo Health Centre Ghana Health ServiceKintampoBrong Ahafo RegionGhana

Background:This study assessed the quality,core and support functions of the integrated disease surveillance and response(IDSR)system relating to 18 suspected cases of Ebola virus disease(EVD)in the Brong Ahafo Region,***:Data was collected on selected indicators of the surveillance system relating to 18 suspected cases of EVD,from epidemiological week 19 to 45 of *** conducted in-depth interviews with seven medical directors and two district directors of health services,and also reviewed documentation on the implementation of the core,support and quality functions of the IDSR *** also monitored news in the media and rumours about EVD within the community as well as in health facility surveillance ***:The study identified gaps in the implementation of IDSR relating to 18 suspected cases of *** staff heavily relied on haemorrhage as the only symptom for detection of suspected EVD *** blood samples and a swab of secretions from the mouth of the thirteenth patient(who died)tested negative for EVD using PCR assay in laboratory *** blood samples of three patients were discarded,as they did not fit the case definition for suspected cases,whilst two refused for their blood samples to be *** community-based surveillance(CBS)system has not been given a prominent role in EVD surveillance and response,as demonstrated by CBS volunteers and health staff not receiving any training in these *** was intense public interest in EVD in August and September *** interest has since waned for reasons that have to be formally *** fear of and anxiety about EVD still remain challenges due to a lack of in-depth knowledge about the disease in ***:Ghana has been one of the pioneers in the implementation of IDSR in *** this,gaps have been identified in the implementation of IDSR relating to EVD in the Brong Ahafo *** address these gaps,the CBS system has to activ

关键词： Ebola Disease surveillance Brong Ahafo Ghana