scholarly journals Uso do LiDAR para avaliar os padrões hídricos de bacias em áreas urbanas: Caracterização fisiográfica da bacia do Rio Beberibe, PE

2020 ◽  
Vol 13 (07) ◽  
pp. 3659
Author(s):  
Gabriel Antonio Silva Soares ◽  
Josiclêda Domiciano Galvíncio
Keyword(s):  
River Basin ◽  
Urban Areas ◽  
Three Dimensional ◽  
Drainage Density ◽  
Sensor Data ◽  
Aerial Photographs ◽  
Sinuosity Index ◽  
Main River ◽  
Circularity Index

A caracterização fisiográfica, consiste no levantamento dos principais parâmetros fisiográficos de uma bacia, que  podem ser extraídos de mapas, fotografias aéreas e imagens de satélite, e se apresenta como uma ferramenta útil ao planejamento e gestão dos recursos hídricos, por existir uma forte correspondência entre as características físicas de uma bacia hidrográfica e seu regime hidrológico. O presente estudo se propõe a caracterizar fisiograficamente a bacia hidrográfica do Rio Beberibe utilizando os dados do sensor LiDAR com resolução espacial de 5 m em uma escala de 1:5000, provenientes do programa PE3D (Pernambuco Tridimensional). Os resultados obtidos sobre os parâmetros geométricos, levaram à conclusão de que a bacia hidrográfica do Rio Beberibe não é naturalmente propensa à ocorrência de enchentes, por possuir uma forma alongada. Sobre os padrões de drenagem, foi possível concluir que a bacia possui uma drenagem rica e escoamento superficial fluido e ágil, que seus canais possuem perfis retilíneos, e que se trata de uma bacia de 6ª ordem. Acerca das características do relevo, foi constatado que a bacia não possui picos de altitudes elevados, porém uma considerável amplitude altimétrica, além de que na declividade da bacia não estão apresentadas inclinações bruscas.  Using LiDAR to evaluate water patterns in urban areas basin: Physiographic characterization of the Rio Beberibe basin, PE A B S T R A C TThe physiographic characterization consists in the survey of the main physiographic parameters of a basin, which can be extracted from maps, aerial photographs and satellite images, and presents itself as a useful tool for planning and management of water resources, as a consequence of the influence between the physical characteristics of a river basin and its hydrological behaviour. The selection of the Beberibe river basin for the development of this research was made due to their importance for the macrodrainage of the state of Pernambuco, and because they are located in an area of strong urban activity. Thus, these areas present strong socioeconomic activity, which configures them as spaces where water planning is crucial for the conscious use of their resources. Faced with this scenario, the present study proposes to physiographically characterize the Beberibe river basin using LiDAR sensor data with a spatial resolution of 5 m on a scale of 1:5000, from the PE3D program (Three-Dimensional Pernambuco). The main morphometric parameters obtained for the Beberibe River basin were grouped into three groups of characteristics. The geometric characteristics, which consist of the following parameters: drainage area (A), basin perimeter (P), axial length (L), compacity coefficient (Kc), shape factor (Kf), and circularity index (IC). The characteristics of the drainage network, which consists in the survey of the following parameters: length of the main river (Lc), total length of the channels (Lt), basin order, drainage density (Dd), hydrographic density (Dh), sinuosity index (Is), and average runoff length (

scholarly journals Morphometric analysis of an Areal Watershed in Taubaté, SP, Brazil

2019 ◽  
Vol 14 (7) ◽  
pp. 1
Author(s):  
Vicente Rodolfo Santos Cezar ◽  
Marcelo Dos Santos Targa ◽  
Celso De Souza Catelani
Keyword(s):  
Land Use ◽  
River Basin ◽  
Morphometric Analysis ◽  
High Surface ◽  
High Capacity ◽  
Sediment Concentration ◽  
Sao Paulo ◽  
São Paulo ◽  
Circularity Index

      In 1991, the Integrated Water Resources Management System (SIGRHI) in the State of São Paulo adopted the watershed as a territorial unit for studies, integrated planning and sustainable development. The morphometric analysis of small watersheds, which involves the characterization of geometric parameters, relief, drainage network, combined with land use and occupation, may constitute an important model for environmental analysis of larger watersheds. This study aimed at characterization of the morphometry in the Areal river basin, in the city of Taubaté, São Paulo. The study found 1.89 km² of area, 7.44 km of perimeter and 3.11 km in length of the basin axis, which allowed the calculation of the compactness coefficient (Kc = 1.51), form factor, (F = 0.195) and circularity index (CI = 0.43), indicating that under normal precipitation conditions, this basin is unlikely to be flooded, due to the distance from the unit, leading to smaller concentrate outflow. The results obtained for the Maintenance Coefficient (Cm) indicate that 260 m² is required to maintain each meter of perennial channel. The high values of drainage density (Dd = 3.35 km.km-2) and sinuosity index (Is = 0.95) indicate that drainage channels in the area are rectilinear, thus suggesting the occurrence of a high surface runoff associated with high dissection. The analysis of land use and occupation revealed that, from the seven types of vegetation cover, the dominant cover in the Areal basin is 0.756 km2 (40%) constituted of pasture, while forest represents 0.580 km2 (31%), 0.321 km2 (17%) of the land cover is constituted of degraded forest. In terms of conservation, the Areal basin is conserved because, besides being located in the environmental preservation area of the Una River Basin, it is located at the meeting of two ecological corridors and is occupied by only 8 families of rural producers. On the other hand, the creation of approximately 120 head of cattle in the upper part of the basin and the existence of gully erosion of the order of 0.018 km2 (1%) of the basin area, which led to increased runoff and sediment concentration in the flat areas marginal to the creek of Areal. Based on morphometric analysis, it was concluded that: Areal watershed presents high capacity to form new watercourses and their relief characteristics, with low sinuosity channels and high values of altimetric amplitude, channel gradient, and density. Drainage, allied to the existence of erosive processes, favors sediment flow and transport. Conservation actions are required to control erosion.

scholarly journals Morphotectonic Analysis of Euphrates River Basin/ Iraq

2018 ◽  
Vol 26 (8) ◽  
pp. 217-229
Author(s):  
Zeyad Jameel Al- Saedi ◽  
Mustafa Rashead Al-Obaidi
Keyword(s):  
River Basin ◽  
Drainage Basin ◽  
Active Tectonics ◽  
Drainage Density ◽  
Tectonic Activity ◽  
Euphrates River ◽  
Sinuosity Index ◽  
Hypsometric Integral ◽  
Active Tectonic ◽  
Main Basin

Morphological and morphotectonic analysis have been used to obtain information that influences basis. The study area includes the Euphrates river basin in Iraq. Tectonically this area within a Stable shelf, The Stable Shelf which covers the vast majority of the focal south and west of Iraq reaches out into Syria and Jordan and Southwards into Kuwait and Saudi Arabia. It is separated in Iraq into three considerable structural zones. Discrimination of morphotectonic indices of Euphrates basin by using sevenindices. The Euphrates basin (main basin) was divided into four sub-basin (s.b) Wadi Horan, Wadi Ubaiyidh, Shuab Hwaimy, and Shuab Qusair. Which has been completed for each drainage basin utilizing remote sensing and GIS techniques? So as to identify the tectonic activity, different indices including Drainage density (D), Sinuosity index (S), Hypsometric integral (HI), Drainage basin asymmetry (AF), Basin Shape (BS), Transverse Topographic Symmetry (T) and Active tectonic index (Iat). The study demonstrates that the intensity of tectonic activities in different parts of the basin and sub-basins are different. The values of Drainage density (D) main basin and sub-basins are in high classes which mean that the study area has resultant of slight or impermeable subsurface material, little vegetation as well as a good discharge for water and sediments. The Sinuosity index (S) of all study area are sinuous and its semi-equilibrium. Hypsometric integral (HI) of Horan, Ubaiyidh and shuab Hwaimy sub-basins shows high values of HI which means high rates of geological erosion while the shuab Qusair and main basin shows moderate of erosion rates, HI high values shows that study area is tectonically uplifted. According to the calculation of Drainage basin asymmetry (AF) the study area reflects inactive tectonic activity. The Basin Shape (BS) all of the basins are in third class and it reflects inactive tectonic activity. After computing Transverse Topographic Symmetry (T) index in the area of investigate, the outcome demonstrate that all the subbasins lie in low active tectonics except wadi Horan and the main basin was moderate active tectonics. Based on an Active tectonic index (Iat) all the basins were moderate active tectonics except Horan subbasin is active tectonically. These basins have evolved as a result of plate movements, subsidence, uplift and various erosional processes. The study shows the variable relationship between faulting and valleys but most of the trends of faults are subparallel to the Euphrates River. Faults orientations in the study area are parallel to NE-SW direction and NW-SE direction. And also the type of drainage network in the study area which is varied from dendritic to parallel with SW-NE trending and its indicate that study area may be structurally controlled.

scholarly journals MORPHOMETRY OF THE HYDROGRAPHIC BASINS INSERTED IN THE URBAN AREA OF DOURADOS – MS – BRAZIL

2019 ◽  
Vol 46 (3) ◽  
pp. 75
Author(s):  
Leonardo Lima dos Santos ◽  
Vinícius De Oliveira Ribeiro ◽  
Jonailce Oliveira Diodato
Keyword(s):  
Urban Area ◽  
Drainage Density ◽  
Water Quantity ◽  
Digital Elevation ◽  
Circularity Index ◽  
Physical Variables ◽  
Elevation Model ◽  
Gis Software ◽  
Morphometric Characterization

The morphometric characterization of watersheds has great importance and appliance for the prediction of phenomena such as floods. The objective of this study was to delimitate and characterize morphometrically the hydrographic basins that encompass the urban area of the Municipality of Dourados / MS – Brazil, which derived from estimated physical variables obtained by applying a license-free GIS software. Based on a Digital Elevation Model (DEM), the following microcatchment characteristics were determined: area, perimeter, slope, altitude, and watercourse orders. Four morphometric parameters that express a direct or inverse relationship with the water quantity factors of a hydrographic source were calculated and analyzed, being them: compactness coefficient, shape factor, circularity index, and drainage density. By comparing the studied basin results, it was observed that Água Limpa, Água Boa, and Laranja Azeda basin streams are more susceptible to flooding, especially considering the measurement factor and drainage density.

scholarly journals Caracterização morfométrica da bacia hidrográfica do igarapé da Prata, Capitão Poço – Pará – Brasil

2016 ◽  
Vol 11 (3) ◽  
pp. 143 ◽  
Author(s):  
Rodrigo Silvano Silva Rodrigues ◽  
Lindemberg Lima Fernandes ◽  
Diêgo Lima Crispim ◽  
Artur Sales de Abreu Vieira ◽  
Francisco Carlos Lira Pessoa
Keyword(s):  
Structural Control ◽  
Drainage System ◽  
Drainage Density ◽  
Annual Rainfall ◽  
Digital Elevation ◽  
Circularity Index ◽  
Major Floods ◽  
Elevation Model ◽  
Index Value

<p>Este trabalho teve como objetivo realizar a caracterização morfométrica da bacia hidrográfica do igarapé da Prata, localizado no município de Capitão Poço, Pará. Inicialmente gerou-se o Modelo Digital de Elevação a partir de SRTM com resolução espacial de 30 m, utilizando o sistema de informações geográficas, por meio do software ArcGis 10.1 e da extensão ArcHydro, foram calculados alguns parâmetros morfométricos para o estudo do comportamento hidrológico da bacia. A área de drenagem encontrada foi de 115,283 km² e o perímetro de 70,151 km. A bacia hidrográfica do igarapé da Prata tem formato alongado, coeficiente de compacidade de 1,829, fator de forma de 0,356 e índice de circularidade de 0,294. A densidade de drenagem obtida para a bacia foi de 0,525 km/km², com padrão dendrítico. A forma mais alongada da bacia hidrográfica indica que a precipitação pluviométrica sobre ela se distribui em diferentes pontos. De maneira geral, suas características morfométricas denotam um controle estrutural da drenagem eficiente, bem como menor risco de grandes cheias em condições normais de pluviosidade anual e topografia favorável ao escoamento superficial.</p><p align="center"><strong><em>Morphometric characterization of Prata catchment, Capitão Poço – Pará – Brazil</em></strong></p><p><strong>Abstract:</strong> This study aimed to characterize the morphometric Prata catchment, located in the municipality of the Capitão Poço/PA. In order to do so, a Digital Elevation Model (DEM), spatial resolution of 30 meters, using as database and analysis the system of geographic information, by means of the ArcMap 10.2 and ArcHydro systems. From this, some morphometric parameters of a previous study on the hydrologic behavior of the watershed were calculated. The drainage area was 115,283 km² and 70,151 km in perimeter. The Prata catchment was proven not easily subject to floods as the compacity coefficient was far from the unit (1,829) and its shape factor presented a low value (0,356). Such fact can still be proven by the circularity index value (0,294). The drainage density was 0,525 km/km². The drainage system forms a dendritic pattern. The more elongated watershed shape indicates that the rainwater volume that falls within the watershed is concentrated in different points. The morphometric characteristics denote a structural control of efficient drainage, lower risk of major floods in normal annual rainfall and topography favorable to runoff.</p>

scholarly journals Detection and Geometrical Characterization of a Buried Landfill Site by Integrating Land Use Historical Analysis, Digital Photogrammetry and Airborne Lidar Data

Geosciences ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 348 ◽  
Author(s):  
Giuseppe Esposito ◽  
Fabio Matano ◽  
Marco Sacchi
Keyword(s):  
Urban Areas ◽  
Airborne Lidar ◽  
Landfill Site ◽  
Aerial Photographs ◽  
Topographic Maps ◽  
Campi Flegrei ◽  
Digital Photogrammetry ◽  
Geometrical Characterization ◽  
Starting Point

Abandoned quarries are frequently used as sites of illegal dumping of solid urban waste. These sites often occur nearby or within urban areas so that their detection may turn out to be quite difficult from the surface. This study focuses on the detection and geometrical characterization of a hidden landfill site located along the coastline of the Campi Flegrei, near Naples, Italy. Our approach is based on the analysis of historical topographic maps and aerial photographs, coupled with quantitative comparison of multitemporal digital elevation models obtained by digital photogrammetry and lidar techniques. The comparative analysis of topographic maps and aerial photos clearly shows modifications of the landscape associated with the urban development and quarrying activity, as well as the later filling of the quarry. The change detection analysis reveals that remarkable elevation changes occurred in the study area between 1956 and 2008. The average thickness of the landfill deposits is ca. 8 m, whereas the average volume is ca. 100,000 m3. The results of this work confirm the suitability of the used methodological approach that combines both qualitative and quantitative techniques for the detection of buried landfill sites. The geometric characterization of a landfill represents a fitting starting point for the further planning of geophysical site surveys and direct investigations aimed at the assessment of environmental hazards.

Morphometric and Sinuosity Analysis of Tlawng River Basin: A Geographic Information System Approach

2021 ◽  
Vol 5 (1) ◽  
pp. 22-32
Author(s):  
David Lalramchulloa ◽  
Ch Udaya Bhaskra Rao ◽  
P. Rinawma
Keyword(s):  
River Basin ◽  
Drainage Density ◽  
Alluvial Plain ◽  
Morphometric Parameters ◽  
Positive Relation ◽  
Vegetative Cover ◽  
Bifurcation Ratio ◽  
Sinuosity Index ◽  
Stream Frequency ◽  
And Behavior

Channel plan-form patterns of river Tlawng has been studied which shows that there is variation in the sinuosity index. This variation is a sign of changing characteristics and behavior of the river. The average sinuosity of the river is 1.41. The sinuosity index is higher in the lower course of the river as it flows through alluvial plain. GIS techniques have been used for studying morphometric parameters. There are 6736 streams in the Tlawng river basin which shows that the topography is still undergoing erosion as the number of stream is high (Zaidi, 2011). The river has low bifurcation ratio which indicates less possibilities of flooding. The drainage density indicates the higher permeable subsoil and moderate to thick vegetative cover. The stream frequency value of the Tlawng river basin is 1.30 streams / km2 which shows a positive relation with drainage density.

scholarly journals GEOPHYSICAL CHARACTERIZATION OF AQUIFERS IN THE SALITRE RIVER BASIN, BAHIA STATE, BRAZIL, USING RESISTIVITY SOUNDINGS AND ELECTRICAL TOMOGRAPHIES

2014 ◽  
Vol 32 (4) ◽  
pp. 637
Author(s):  
Olivar Antônio Lima de Lima
Keyword(s):  
River Basin ◽  
Water Table ◽  
Industrial Development ◽  
Karst Aquifer ◽  
Three Dimensional ◽  
Northeastern Brazil ◽  
Karst Water ◽  
Aquifer System ◽  
Tomographic Section

ABSTRACT. The Salitre River basin, which is located in the semi-arid land of northeastern Brazil, is annually faced with severe surface-water scarcity. Twomain aquifersystems, which are distributed in depth, can be exploited to supply the water needs of the population and its present agro-industrial development: (i) a fractured-karst,water-table component, totally developed within the upper carbonate sequence of the Salitre Formation; and (ii) a fractured-clastic, semi-confined component, mostlikely associating lower Salitre limestones with the meta-sandstones of the Morro do Chap´eu Formation. Geophysical efforts have been useful in developing a regional,three-dimensional characterization of these two aquifer components of the Salitre river aquifer system and in detailing a useful electric tomographic scheme to implementtheir exploration. The geophysical survey, which comprised 64 Schlumberger electrical soundings of resistivity and five tomographic sections, was combined with welldata to define the geometric and hydraulic characteristics of these aquifer components. The inversion of the resistivity data, under the control of the well data, was usefulto reduce electrical ambiguities and to better define the depth of the water table and that of the thick, impervious aquifer substrate. The lateral and depth boundaries of thefracture-karst aquifer zones were outlined, allowing the estimation of a total reserve of approximately 100 billion m3 of groundwater. Chemical analysis of water samplescollected at production wells was used to define a water quality zoning within the basin. These results are very important to define an optimum exploration regime for thegroundwater available in the basin.Keywords: electrical sounding, tomographic section, Salitre aquifer system. RESUMO. A bacia hidrogáafica do rio Salitre faz parte da região semiárida da Bahia e, por isso, apresenta severa escassez de água superficial. Dois principais componentes aquíferos, distribuídos em profundidade, podem ser explorados para suprir as necessidades hídricas da população humana e de seu incipiente desenvolvimento agroindustrial: (i) um componente cárstico-fraturado, de natureza livre, desenvolvido nas rochas carbonáticas superiores da Formação Salitre; e (ii) um componentefraturado, semi-confinado, combinando rocha basais da sequência Salitre e unidades meta-quartzíticas da Formação Morro do Chapéu. Foram executadas 64 sondagens elétricas verticais usando o arranjo Schlumberger de eletrodos, centradas em pontos selecionados da bacia, e cinco seções tomográficas de resistividade, para detalhara estrutura subsuperficial de locais selecionados. A inversão dos dados de resistividade aparente, com controle de informações de poços, foi útil para reduzir ambiguidades elétricas e melhor definir as profundidades do nível estático e do topo do espesso substrato impermeável do sistema aquífero Salitre. Esses estudos permitiramavaliar, regionalmente, os recursos hídricos subterrâneos da bacia, em termos de geometria e características hidráulicas, bem como propor um procedimento para efetuar tomografia elétrica bidimensional, visando sua efetiva exploração por meio de poços. Os limites laterais e em profundidade das zonas de maior carstificação e de densos fraturamentos foram delineados, possibilitando estimar uma reserva total de água no sistema do rio Salitre em cerca de 220 bilhões de m3. Análises físico-químicas deamostras de água coletadas em poços foram usadas para caracterizar a variabilidade na qualidade da água subterrânea na bacia. Tais resultados podem ser usados paraplanejar um regime de exploração eficiente e conservativo das reservas de água subterrânea disponíveis.Palavras-chave: sondagem elétrica, seção tomográfica, sistema aquífero Salitre.

scholarly journals GEOPROCESSAMENTO APLICADO NA CARACTERIZAÇÃO MORFOMÉTRICA DA MICROBACIA DO RIBEIRÃO DESCALVADO – BOTUCATU, SP

Irriga ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 52-65
Author(s):  
Sergio Campos ◽  
Andrea Cardador Felipe ◽  
Marcelo Campos ◽  
Aline Minarelli Reche
Keyword(s):  
Drainage Density ◽  
Sao Paulo ◽  
Water Infiltration ◽  
Roughness Coefficient ◽  
Environmental Restoration ◽  
São Paulo ◽  
Circularity Index ◽  
E Mail ◽  
Morphometric Characterization

GEOPROCESSAMENTO APLICADO NA CARACTERIZAÇÃO MORFOMÉTRICA DA MICROBACIA DO RIBEIRÃO DESCALVADO – BOTUCATU, SP SÉRGIO CAMPOS1; ANDREA CARDADOR FELIPE1 E MARCELO CAMPOS2, ALINE MINARELLI RECHE1  1 Departamento de Engenharia Rural, Faculdade de Ciências Agronômicas - FCA - UNESP - Botucatu - São Paulo - Brasil.  E-mail: [email protected] Departamento de Engenharia de Biossistemas, UNESP - Tupã - São Paulo - Brasil.  E-mail: [email protected]  1 RESUMO Esse trabalho objetivou a aplicação de geoprocessamento na  caracterização morfométrica da  microbacia do Ribeirão Descalvado – Botucatu (SP) através do Sistema de Informação Geográfica – Selva, visando a preservação, racionalização do seu uso e recuperação ambiental.   A microbacia apresenta uma área de 2228,61ha e está localizada entre os paralelos 22o 50' 05" a 22o 54' 26" de latitude S e 48o 22' 29" a 48o 26' 36"  de longitude W Gr.  A base cartográfica utilizada foi a carta planialtimétrica de Botucatu (SP), em escala 1:50000 (IBGE, 1969) na  extração das curvas de nível, da hidrografia e da topografia, para determinação dos índices morfométricos. Os resultados mostram que os baixos valores da densidade de drenagem, associados à presença de rochas permeáveis, facilitam a infiltração da água no solo, diminuindo o escoamento superficial e o risco de erosão e da degradação ambiental, bem como o baixo valor do fator  de forma amparado pelo índice de circularidade indicam que a microbacia é mais alongada e com menor susceptibilidade à ocorrência  de enchentes mais  acentuadas. O parâmetro ambiental de coeficiente de rugosidade permitiu classificar a microbacia para vocação com floresta e reflorestamento. Palavras-chave: morfometria, hidrografia e SIG  CAMPOS, S,;  FELIPE, A.C.; GARCIA, Y.M.; CAMPOS, M.; FERREIRA, L.T.L. GEOPROCESSING APPLIED TO  MORPHOMETRIC CHARACTERIZATION OF THE RIBEIRÃO DESCALVADO  MICRO WATERSHED - BOTUCATU, SP   2 ABSTRACT The objective of this study was to evaluate  geoprocessing  to morphometrically characterize the Ribeirão Descalvado micro watershed – Botucatu, SP by the Geographic Information System (GIS) – Selva for preservation, rationalization of its use and environmental restoration.   The micro watershed is 2,228.61 ha   between the geographic coordinates: 22° 50' 05" to 22° 54' 26 "  latitude  S  and 48° 22' 29" to  48° 26' 36"  longitude W Gr.  The cartographic basis was the planialtimetric chart of Botucatu (SP), 1: 50000 scale (IBGE, 1969) , used for extraction of level, hydrography and topography curves  to determine morphometric indices.   The results showed that  low values of drainage density associated with the presence of permeable rocks facilitates ground water infiltration which decreases surface runoff, erosion risks and environmental degradation.  The low value of the shape factor supported by the circularity index shows that the micro watershed is more elongated and at lower risk of   more pronounced floods.   The   roughness coefficient environmental parameter   classified the micro watershed for forest and reforestation. Keywords: Morphometry, hydrography and GIS

Characterization of photosystem II with the atomic-force microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1146-1147
Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon
Keyword(s):  
Photosystem Ii ◽  
Atomic Force Microscope ◽  
Three Dimensional ◽  
Biologically Active ◽  
Atomic Force ◽  
Freeze Etching ◽  
Image Averaging ◽  
Oxygen Evolving ◽  
Averaging Techniques

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.

convergent-beam diffraction from surfaces

1987 ◽  
Vol 45 ◽  
pp. 30-33
Author(s):  
J. A. Eades ◽  
A. E. Smith ◽  
D. F. Lynch
Keyword(s):  
Reciprocal Lattice ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Three Dimensions ◽  
Plane Figure ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.

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