Adsorption, stability and evolution path of benzene on graphene surface: Size and edge effects

2022 ◽  
Vol 571 ◽  
pp. 151376
Author(s):  
Xinran Zhang ◽  
Jiangang Guo
Author(s):  
William J. Baxter

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.


2019 ◽  
Vol 21 (2) ◽  
pp. 205-217
Author(s):  
Nádson Ricardo Leite de Souza ◽  
Vanessa Vasconcelos da Silva ◽  
Edson Henrique Almeida de Andrade ◽  
Valéria Raquel Porto de Lima

A Mata do Buraquinho consiste no maior remanescente de Mata Atlântica em área urbana do país, é cortada pelo Rio Jaguaribe, um dos afluentes do Rio Paraíba e maior rio urbano de João Pessoa/PB que, represado, forma o Açude do Buraquinho, de onde provém parte da água potável da capital paraibana. O local é declarado uma Área de Preservação Permanente desde 1989, devido à importância ambiental e, desde o ano de 2000, abriga o Jardim Botânico Benjamin Maranhão, que ocupa mais de 65% da área total, criado com a missão de fortalecer as ações de preservação e promover a intensificação dos estudos no representativo ambiente, todavia, a existência de trilhas em seu interior possibilita maior vulnerabilidade à degeneração ecossistêmica, somada aos efeitos de borda no contato com a densa urbanização do entorno. Com o objetivo de analisar os impactos ambientais negativos ocasionados por tais bordas, foram realizadas observações in loco, por meio de inventariações de parcelas concretizadas ao longo das trilhas mais frequentadas, onde se apurou diversos indicativos de degradação florestal. A partir disso, confirmou-se a autenticidade das teorias empregadas sobre os impactos ambientais negativos e a degeneração das espécies habituais, resultantes das ações de caráter antrópico, concluindo-se que a propagação dos efeitos de borda originada pela abertura de trilhas que favorecem o avanço da degradação e fazem-se necessárias ações de conservação mais rigorosas do que as em vigor, mesmo se tratando de uma área legalmente protegida.Palavras-chave: Efeitos de borda; Degeneração ecossistêmica; Mata do Buraquinho. ABSTRACTMata do Buraquinho is the largest remnant of Mata Atlântica in an urban area of the country. It is cut by the Jaguaribe River, - one of the tributaries of the Paraíba River and the largest urban river of João Pessoa/PB – which was dammed up forming the Açude do Buraquinho, from where comes part of the potable water of the capital of Paraíba. The place has been declared a Permanent Preservation Area since 1989. Due to its environmental importance and, since the year of 2000, it has sheltered the Benjamin Maranhão Botanical Garden, which occupies more than 65% of the total area. This garden was created with the mission of strengthening actions of preservation and to promote the intensification of studies in the representative environment. However, the existence of trails inside of it, allows greater vulnerability to the ecosystem degeneration, and combined with effects of border in the contact with the dense urbanization of the surrounding area. In order to analyze the negative environmental impacts caused by such edges, some observations were made in loco, through inventories of concretized plots along the most frequented trails, where several indications of forest degradation were obtained. From this, the authenticity of the theories used on the negative environmental impacts and the degeneration of the habitual species was confirmed. And resulting from actions of anthropic character, it was concluded that the propagation of the edge effects originated by the opening of tracks, favors the advance of the degradation and becomes necessary conservation actions more stringent than those in force, even in the case of a legally protected area. Keywords: Edge effects; Ecosystem Degeneration; Mata do Buraquinho. RESUMENLa “Mata do Buraquinho” es el testimonio más grande del bosque Atlántico en el área urbana de Brasil, es cortado por el Río Jaguaribe, uno de los tributarios del Río Paraíba, además, es el río urbano más grande de João Pessoa/PB, que forma la presa del “Buraquinho”, de donde proviene el suministro de agua potable para la capital del Estado de Paraíba. Esta zona es declarada un Área de Preservación Permanente desde 1989, debido a su importancia ambiental, y desde el año 2000, acoge el Jardín Botánico Benjamin Maranhão, que ocupa más de 65% del área total, creado con la misión de fortalecer las acciones de preservación y promover la intensificación de los estudios en el representativo de ambiente, sin embargo, la existencia de rutas en el interior aumenta la vulnerabilidad a la degeneración ecosistémica, añadidos a los efectos de borde que tienen contacto directo con la densa urbanización de los alrededores. Con el propósito de analizar los impactos ambientales negativos ocasionados por estos bordes, han sido realizadas observaciones "In loco", a través de inventariaciones de parcelas implementadas a lo largo de las rutas más frecuentadas, donde se ha detectado indicios de degradación forestal. Con eso, se ha confirmado la autenticidad de las teorías utilizadas sobre los impactos ambientales negativos y la degeneración de especies habituales, resultantes de acciones antrópicas, se concluye que la propagación de los efectos de borde originada por la apertura de rutas ha favorecido el avance de la degradación, con eso, son necesarias acciones de conservación todavía más estrictas de que las que existen, aún que ya sea un área protegida por la ley.Palabras-clave: Efectos de borde; Degeneración ecosistémica; Mata do Buraquinho.


2019 ◽  
Vol 33 (31) ◽  
pp. 1950384
Author(s):  
Di Lu ◽  
Yu-E Yang ◽  
Weichun Zhang ◽  
Caixia Wang ◽  
Jining Fang ◽  
...  

We have investigated Raman spectra of the G and 2D lines of a single-layer graphene (SLG) with metallic contacts. The shift of the G and 2D lines is correlated to two different factors. Before performing annealing treatment or annealing under low temperature, the electron transfer on graphene surface is dominated by nonuniform strain effect. As the annealing treatment is enhanced, however, a suitable annealing treatment can eliminate the nonuniform strain effect where the relative work function (WF) between graphene and metal becomes a main factor to determine electronic transfer. Moreover, it is confirmed that the optimized annealing treatment can also decrease effectively the structural defect and induced disorder in graphene due to metallic contacts.


BMC Ecology ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Bertrand Andriatsitohaina ◽  
Daniel Romero-Mujalli ◽  
Malcolm S. Ramsay ◽  
Frederik Kiene ◽  
Solofonirina Rasoloharijaona ◽  
...  

Abstract Background Edge effects can influence species composition and community structure as a result of changes in microenvironment and edaphic variables. We investigated effects of habitat edges on vegetation structure, abundance and body mass of one vulnerable Microcebus species in northwestern Madagascar. We trapped mouse lemurs along four 1000-m transects (total of 2424 trap nights) that ran perpendicular to the forest edge. We installed 16 pairs of 20 m2 vegetation plots along each transect and measured nine vegetation parameters. To determine the responses of the vegetation and animals to an increasing distance to the edge, we tested the fit of four alternative mathematical functions (linear, power, logistic and unimodal) to the data and derived the depth of edge influence (DEI) for all parameters. Results Logistic and unimodal functions best explained edge responses of vegetation parameters, and the logistic function performed best for abundance and body mass of M. ravelobensis. The DEI varied between 50 m (no. of seedlings, no. of liana, dbh of large trees [dbh ≥ 10 cm]) and 460 m (tree height of large trees) for the vegetation parameters, whereas it was 340 m for M. ravelobensis abundance and 390 m for body mass, corresponding best to the DEI of small tree [dbh < 10 cm] density (360 m). Small trees were significantly taller and the density of seedlings was higher in the interior than in the edge habitat. However, there was no significant difference in M. ravelobensis abundance and body mass between interior and edge habitats, suggesting that M. ravelobensis did not show a strong edge response in the study region. Finally, regression analyses revealed three negative (species abundance and three vegetation parameters) and two positive relationships (body mass and two vegetation parameters), suggesting an impact of vegetation structure on M. ravelobensis which may be partly independent of edge effects. Conclusions A comparison of our results with previous findings reveals that edge effects are variable in space in a small nocturnal primate from Madagascar. Such an ecological plasticity could be extremely relevant for mitigating species responses to habitat loss and anthropogenic disturbances.


Author(s):  
Jing-hua Guo ◽  
Jin-Xiang Liu ◽  
Hongbo Wang ◽  
Haiying Liu ◽  
Gang Chen

In this work, combining the first-principles calculations with kinetic Monte Carlo (KMC) simulations, we constructed an irregular carbon bridge on the graphene surface and explored the process of H migration...


Author(s):  
Ling He ◽  
Qing Yang ◽  
Xingxing Liu ◽  
Lingmei Fu ◽  
Jinmei Wang

As the impact factors of the waste Not-In-My-Back Yard (NIMBY) crisis are complex, and the scenario evolution path of it is diverse. Once the crisis is not handled properly, it will bring adverse effects on the construction of waste NIMBY facilities, economic development and social stability. Consequently, based on ground theory, this paper takes the waste NIMBY crisis in China from 2006 to 2019 as typical cases, through coding analysis, scenario evolution factors of waste NIMBY crisis are established. Furtherly, three key scenarios were obtained, namely, external situation (E), situation state (S), emergency management (M), what is more, scenario evolution law of waste NIMBY crisis is revealed. Then, the dynamic Bayesian network theory is used to construct the dynamic scenario evolution network of waste NIMBY crisis. Finally, based on the above models, Xiantao waste NIMBY crisis is taken as a case study, and the dynamic process of scenario evolution network is visually displayed by using Netica. The simulation results show that the scenario evolution network of Xiantao waste NIMBY crisis is basically consistent with the actual incident development process, which confirms the effectiveness and feasibility of the model.


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