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  • 1
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (15 Seiten, 842,33 KB) , Illustrationen
    Language: German
    Note: Paralleltitel dem englischen Berichtsblatt entnommen , Förderkennzeichen BMBF 16KIS0618 , Verbundnummer 01175154 , Durchführende Institution dem Berichtsblatt entnommen , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Sprache der Zusammenfassung: Deutsch, Englisch
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  • 2
    Online Resource
    Online Resource
    San Diego :Elsevier,
    Keywords: Electric power production-Developing countries. ; Renewable energy sources-Developing countries. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (444 pages)
    Edition: 1st ed.
    ISBN: 9780323884259
    DDC: 333.793
    Language: English
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  • 3
    Online Resource
    Online Resource
    San Diego :Elsevier Science & Technology,
    Keywords: Perovskite. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (458 pages)
    Edition: 1st ed.
    ISBN: 9780128204009
    Series Statement: Woodhead Publishing Series in Composites Science and Engineering Series
    DDC: 549.528
    Language: English
    Note: Intro -- Hybrid Perovskite Composite Materials: Design to Applications -- Copyright -- Contents -- Contributors -- 1 Nano-crystalline perovskite and its applications -- 1.1 Common material structures -- 1.2 Nonstoichiometry in perovskites -- 1.3 Crystallography and chemistry of perovskite structures -- 1.3.1 Size effects -- 1.3.2 Effect of the composition variation from the ideal ABO3 -- 1.3.3 Single perovskite -- 1.3.4 Double perovskite -- 1.4 Nano-structured perovskite level -- 1.5 Applications for nano-perovskites -- 1.6 Conclusion -- References -- 2 Preparation and processing of nanocomposites of all-inorganic lead halide perovskite nanocrystals -- 2.1 Introduction -- 2.2 Nanocomposites based on conventional semiconductor nanocrystals-Brief overview -- 2.3 Fabrication and processing of nanocomposites of all-inorganic perovskite nanocrystals -- 2.3.1 Preparation of silica, titania, zirconia, and siloxane-based perovskite nanocomposites -- 2.3.1.1 Preparation of nanocomposites of LHP NCs/SiO 2 and SiO 2 -related compounds -- 2.3.1.2 Preparation of LHP NCs/titania (TiO 2) composites -- 2.3.1.3 Preparation of LHP NCs/alumina (Al 2 O 3) composites -- 2.3.1.4 Preparation of LHP NCs/zirconia (ZrO 2) composites -- 2.3.1.5 Miscellaneous -- 2.3.2 Preparation of polymer-based perovskite nanocomposites -- 2.3.2.1 Preparation and properties of CsPbX 3 NCs/poly-methyl-methacrylate (PMMA) composites -- 2.3.2.2 Preparation and properties of CsPbX 3 NCs/polystyrene (PS) composites -- 2.3.2.3 Role of polymeric oligomeric silsesquioxane (POSS) in improving properties of CsPbX 3 NCs -- 2.3.3 Nanocomposites of mixed perovskite phases -- 2.3.4 Miscellaneous -- 2.4 Conclusion and future perspectives -- Acknowledgments -- References -- 3 Thin films for planar solar cells of organic-inorganic perovskite composites -- 3.1 Introduction. , 3.1.1 History of perovskite solar cells -- 3.2 Perovskite solar cells: Architecture, evolution, and thin-film synthesis -- 3.2.1 The architecture of PSCs -- 3.2.2 Evolution of PSC -- 3.2.3 Thin film formation -- 3.2.3.1 Vacuum thermal coevaporation -- 3.2.3.2 Layer-by-layer sequential vacuum sublimation -- 3.2.3.3 Vapor deposition by dual-source -- 3.2.3.4 Spin coating -- 3.2.3.5 Spray coating -- 3.2.3.6 Screen printing -- 3.2.4 Thin-films for perovskite solar cells: A case study -- 3.2.4.1 Fundamentals of photovoltaic devices -- 3.2.4.2 Optical and electrical properties of perovskite solar cells -- 3.3 Future scope of perovskite solar cells -- 3.4 Conclusion -- Acknowledgments -- References -- 4 Perovskite-type catalytic materials for water treatment -- 4.1 Introduction -- 4.2 Structure of perovskites -- 4.3 Synthesis methods of perovskites -- 4.3.1 Sol-gel method -- 4.3.2 Coprecipitation method -- 4.3.3 Hydrothermal method -- 4.3.4 Solid-state method -- 4.3.5 Microwave radiation method -- 4.4 Perovskite catalyst for water treatment -- 4.4.1 Process based on advanced oxidation process (AOPs) -- 4.4.1.1 Dye degradation -- 4.4.2 Process based on photocatalysis -- 4.5 Summary and perspective -- Acknowledgments -- References -- 5 Perovskite-based material for sensor applications -- 5.1 Introduction -- 5.2 Synthesis of perovskite materials -- 5.2.1 Solid-state reactions -- 5.2.2 Hydrothermal synthesis -- 5.2.3 Coprecipitation method -- 5.2.4 Sol-gel method -- 5.2.5 Gas phase reaction -- 5.2.6 Microwave synthesis -- 5.2.7 Wet chemical methods -- 5.3 Fabrication of sensors -- 5.3.1 Screen printing -- 5.3.2 Chemical vapor deposition -- 5.3.3 Sol-gel method -- 5.3.4 Spray pyrolysis -- 5.3.5 Physical vapors deposition -- 5.4 Perovskites as sensors -- 5.4.1 Perovskites as temperature sensors. , 5.4.2 Humidity sensors -- 5.4.3 Perovskites as gas sensors -- 5.4.4 Perovskite sensors for explosive species -- 5.5 Conclusions and future outlook -- References -- Further reading -- 6 High-sensitivity piezoelectric perovskites for magnetoelectric composites -- 6.1 Introduction -- 6.2 Historical background of ME coupling -- 6.3 Theoretical background -- 6.3.1 Perovskite oxide -- 6.3.2 Key piezoelectric and magnetostrictive parameters -- 6.3.3 ME effect -- 6.4 Factors influencing performance of ME composites -- 6.4.1 Nature of prominent phases -- 6.4.2 Geometrical configurations -- 6.4.3 Selection criteria for ME composites -- 6.5 Perovskite structure-based ME materials -- 6.5.1 Pb-based composites -- 6.5.2 Green ME composites -- 6.5.2.1 Barium titanate-based ME composites -- 6.5.2.2 Bismuth ferrite-based ME composites -- 6.5.2.3 Potassium niobate-based composites -- 6.6 Applications of ME composites -- 6.6.1 ME nanoparticles in nanomedicine -- 6.6.2 Energy harvesters -- 6.6.3 Magnetic sensors -- 6.7 Future directions -- 6.8 Conclusions -- References -- 7 Spectroscopic parameters of red emitting Eu3 +-doped La2Ba3B4O12 phosphor for display and forensic applicatio ... -- 7.1 Introduction -- 7.2 Synthesis and characterization of prepared phosphor -- 7.2.1 Materials and methods -- 7.2.2 Experimental details -- 7.3 Results and discussion -- 7.3.1 Phase identification and structural refinement -- 7.3.2 FTIR analysis of prepared LBBO:Eu3 + phosphors -- 7.3.3 Morphology -- 7.3.4 PL excitation and emission spectra for LBBO doped with Eu3 + -- 7.3.4.1 PL excitation studies of Eu3 + in LBBO host matrix -- Charge-transfer (CT) transition -- 7.3.4.2 Emission transitions of Eu3 + in LBBO host matrix -- 7.3.4.3 Concentration quenching -- 7.4 Fingerprint detection in different materials -- 7.5 Conclusion -- Acknowledgments. , References -- 8 Perovskite's potential functionality in a composite structure -- 8.1 Introduction -- 8.2 Structure of perovskites -- 8.2.1 Structure of LaCrO3 -- 8.2.2 Structure of LaFeO3 -- 8.3 Methods of synthesis -- 8.3.1 Pechini method -- 8.3.2 Conventional method -- 8.3.3 Citrate method -- 8.3.4 Oxalate method -- 8.3.5 Microwave-aided method -- 8.3.6 Combustion method -- 8.3.7 Sol-gel method -- 8.3.8 Solid-state oxide reaction method -- 8.3.9 Coprecipitation method -- 8.3.10 Solution combustion synthesis (SCS) -- 8.3.11 Polymer precursor method -- 8.4 Applications of perovskite oxides -- 8.5 Conclusion -- References -- 9 Compositional engineering of perovskite materials -- 9.1 Introduction -- 9.2 Synthesis methods for the compositional engineering -- 9.2.1 Solid-state reaction -- 9.2.2 Wet chemical methods -- 9.2.2.1 The chemical coprecipitation methods include two typical strategies -- 9.2.2.2 The sol-gel method -- 9.2.3 Hydrothermal synthesis method -- 9.3 Compositional engineering in BiFeO3-based perovskites -- 9.4 Compositional engineering in bismuth-layered perovskites -- 9.5 Conclusion -- Acknowledgments -- References -- 10 Development of hybrid organic-inorganic perovskite (HOIP) composites -- 10.1 Introduction -- 10.2 Types of HOIPs -- 10.2.1 Development of ferroelectric HOIPs -- 10.2.1.1 1D-HOIPs -- 10.2.1.2 2D-HOIPs -- 10.2.1.3 3D-HOIPs -- 10.2.2 Development of dielectric HOIPs -- 10.2.3 Development of piezoelectric HOIPs -- 10.2.4 Development of pyroelectric HOIPs -- 10.3 Development in electrochemical and photovoltaic behavior of HOIPs -- 10.4 Conclusions -- References -- Further reading -- 11 Progress in efficiency and stability of hybrid perovskite photovoltaic devices in high reactive environments -- 11.1 Introduction -- 11.2 Progress in efficiency -- 11.3 Progress in stability. , 11.3.1 Factors affecting stability -- 11.3.1.1 Effect of oxygen and moisture -- 11.3.1.2 Effect of Temperature -- 11.3.1.3 Effect of illumination -- 11.3.1.4 Other factors -- 11.4 Summary and future scope -- References -- 12 Enhancement of photoluminescence/phosphorescence properties of Eu3 +-doped Gd2Zr2O7 phosphor -- 12.1 Introduction -- 12.2 Experimental -- 12.3 Results and discussion -- 12.3.1 X-ray diffraction analysis -- 12.3.2 SEM images of phosphor -- 12.3.3 Photoluminescence studies of pure and Eu3 +-doped GZO phosphor -- 12.4 PL studies of Eu3 +-doped GZO phosphor -- 12.4.1 CIE coordinate -- 12.5 Conclusion -- Acknowledgments -- References -- 13 Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications -- 13.1 Introduction and general features -- 13.2 Perovskite and perovskite structure -- 13.3 Three-dimensional organic-inorganic hybrid halide perovskites -- 13.3.1 Gold Schmidt's and tolerance factor concept -- 13.4 Low-dimensional organic-inorganic hybrid layered halide perovskites -- 13.4.1 Dimensionality -- 13.4.2 Two-dimensional perovskite system -- 13.5 Double perovskite structure -- 13.6 Hybrid halide double perovskite -- 13.7 Applications -- 13.7.1 Electronic applications (photovoltaic and solar cells) -- 13.7.2 Optoelectronic applications -- 13.7.2.1 Light-emitting diode -- 13.7.2.2 Lasers -- 13.7.2.3 Photodetectors -- 13.7.2.4 Water-splitting -- 13.7.2.5 Field effect transistors -- 13.8 Conclusion -- 13.9 Vision for the future -- References -- 14 Hybrid perovskite photovoltaic devices: Architecture and fabrication methods based on solution-processed metal oxide tr ... -- 14.1 Introduction -- 14.1.1 Electron transport layer (ETL) -- 14.1.2 Hole transport layer (HTL) -- 14.2 Conclusion -- Acknowledgments -- Conflict of interest -- References. , 15 Composite perovskite-based material for chemical-looping steam methane reforming to hydrogen and syngas.
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  • 4
    Online Resource
    Online Resource
    Millersville, PA :Materials Research Forum LLC,
    Keywords: Thermosphere-Congresses. ; Electronic books.
    Description / Table of Contents: Characterization, design, specific properties and applications of thermoset composites are reported. These composites are presently in high demand because they can be shaped into many-sided segments and structures, and can have a great variety of densities and special physical and mechanical properties. Keywords: Thermoset composites, Polymeric Composites, Fiber Reinforced Composites, Lignocellulosic Composites, Hybrid Bast Fibers, Epoxy Composites, Nano-Carbon/Polymer Composites, Conductive Composites, Polyurethane Composites, Wood Flour Filled Composites, Energy Absorption, Automotive Crashworthiness, Electromagnetic Shielding, Electromagnetic Field Emission Applications.
    Type of Medium: Online Resource
    Pages: 1 online resource (350 pages)
    Edition: 1st ed.
    ISBN: 9781945291876
    Series Statement: Materials Research Foundations Series ; v.38
    DDC: 551.514
    Language: English
    Note: Intro -- front-matter -- Thermoset Composites: Preparation, Properties and Applications -- Table of Contents -- Preface -- 1 -- Energy Absorption of Natural Fibre Reinforced Thermoset Polymer Composites Materials for Automotive Crashworthiness: A Review -- 1.1 Introduction -- 1.2 Materials -- 1.3 Thermoset and thermoplastic composites -- 1.4 Matrix -- 1.5 Test methodologies -- 1.5.1 Quasi-static test -- 1.5.2 Dynamic test -- 1.6 Crashworthiness design -- 1.7 Crashworthiness prerequisites -- 1.8 Energy-absorbing thermoset composite structures -- 1.9 Assessing factors of energy absorption capability -- 1.9.1 Crush force efficiency (CFE) -- 1.9.2 Stroke efficiency (SE) -- 1.9.3 Initial failure indictor (IFI) -- 1.9.4 Specific energy absorption ES -- 1.10 Volumetric Energy absorption capability -- 1.11 Energy absorption -- 1.12 Literature survey -- 1.13 Conclusions -- Acknowledgments -- References -- 2 -- Wood Flour Filled Thermoset Composites -- 2.1 Introduction -- 2.2 Wood polymer composites -- 2.3 Wood flour composites (WFCs) -- 2.3.1 Processing of WFCs -- 2.3.2 Properties of WFCs -- 2.3.2.1 Mechanical properties -- 2.3.2.2 Surface roughness and wettability -- 2.3.2.3 Water absorption tests -- 2.3.2.4 Thermo-gravimetric analysis (TGA) -- 2.3.2.5 Differential scanning calorimetry (DSC) -- 2.3.2.6 Dynamic mechanical tests (DMA) -- 2.3.2.7 Creep test -- 2.3.2.8 Flammability characteristics -- 2.3.2.9 Tomography -- 2.3.3 Scanning electron microscopy (SEM) analysis -- 2.4 Practical applications -- Conclusions -- References -- 3 -- Experimental and Analysis of Jute Fabric with Silk Fabric Reinforced Polymer Composites -- 3.1 Introduction -- 3.2 Materials and methods -- 3.3 Preparation of composites -- 3.4 Experimentation -- 3.5 Results and discussions on experimentation -- 3.6 Analysis -- Conclusion -- References -- 4. , Biosourced Thermosets for Lignocellulosic Composites -- 4.1 Introduction -- 4.2 Urea, also a natural material for wood adhesives -- 4.3 Tannin thermoset binders for wood adhesives -- 4.4 New technologies for industrial tannin adhesives -- 4.5 Tannin-Hexamethylenetetramine (Hexamine) adhesives and adhesives with alternative aldehydes -- 4.6 Hardening by tannins autocondensation -- 4.7 Lignin adhesives -- 4.8 Protein adhesives -- 4.9 Carbohydrate adhesives -- 4.10 Unsaturated oil adhesives -- Conclusions -- References -- 5 -- Hybrid Bast Fibre Strengthened Thermoset Composites -- 5.1 Introduction -- 5.2 Bast fibre -- 5.2.1 Surface morphology and elemental composition analysis -- 5.2.2 Structural composition and the physical properties of the bast fibre -- 5.2.3 Composition and the properties of the different bast fibre -- 5.3 Advantage and limitation of bast fibre as reinforcing material -- 5.4 Surface modification of bast fibres -- 5.5 Methods for surface modification of natural fibres -- 5.3.1 Physical methods -- 5.5.2 Chemical methods -- 5.5.2.1 Alkali treatment -- 5.5.2.2 Graft copolymerization -- 5.5.2.3 Acetylation -- 5.5.2.4 Treatment with isocyanate -- 5.5.2.5 Other chemical treatments -- Conclusions -- References -- 6 -- Nano-Carbon/Polymer Composites for Electromagnetic Shielding, Structural Mechanical and Field Emission Applications -- 6.1 Introduction -- 6.2 Shielding parameters of GNCs/Polyurethane nanocomposites -- 6.2.2 Characterizations and measurements -- 6.2.3 Analysis of microwave parameters -- 6.2.4 E cient microwave absorbing properties: -- 6.3 Nanocomposite approach for structural engineering -- 6.3.1 GNCs as effective nanofiller -- 6.3.2 Dispersibility investigations: homogeneous distribution vs agglomeration and interfacial adhesion of GNCs -- 6.3.3 Raman mapping of GNCs nanocomposites -- 6.3.4 Optical imaging. , 6.3.5 Mechanical properties of GNCs/nanocomposites -- 6.3.3 Fracture mechanisms using fractography -- 6.3.4 Thermal and physical properties -- 6.4 MWNTs/nylon composite nanofibers by electrospinning -- 6.4.1 Synthesis of composite -- 6.4.2 Characterizations -- 6.4.3 I-V characteristic of the nanofiber composite -- 6.5 Carbon nanotube composite: Dispersion routes and field emission parameters -- 6.5.1 Synthesis of thin multiwall carbon nanotube composite -- 6.5.2 Characterization -- 6.3.3 Field emission parameters for the t-MWCNT-composite -- Summary -- References -- 7 -- Conductive Thermoset Composites -- 7.1 Introduction -- 7.2 Historical background of thermoset polymers -- 7.3 Method of Composite processing -- 7.4 Different types of CTC -- 7.4.1 Epoxy Based CTC -- 7.4.2 Polyurethane based CTC -- 7.4.3 Polyester based CTC -- 7.4.4 Polybenzoxanines based CTC -- 7.5 Properties of CTC -- 7.5.1 Thermal properties -- 7.5.2 Mechanical properties -- 7.5.3 Electrical properties -- 7.6 Applications of conductive thermoset composites -- 7.6.1 Electromagnetic interference (EMI) shielding -- 7.6.2 Anti-corrosive coatings -- 7.6.3 Shape memory application -- 7.6.4 Other applications -- 7.7 Problems and solution associated with CTC -- Conclusion -- Acknowledgment -- References -- 8 -- Waterborne Thermosetting Polyurethane Composites -- 8.1 Introduction -- 8.2 PUD thermosetting composites -- 8.2.1 Inorganic oxide based PUD thermosetting composites -- 8.2.1.1 Silica-based PUD thermosetting composites -- 8.2.1.2 Titania (TiO2) based PUD thermosetting composites -- 8.2.1.3 Zinc oxide (ZnO) based PUD thermosetting composites -- 8.2.1.4 Other inorganic oxide-based PUD thermosetting composites -- 8.2.2 PUD thermosetting composites with metal (Ag and Au) nanoparticles -- 8.2.3 PUD/clay thermosetting composites -- 8.2.4 PUD/Carbohydrate thermosetting composites. , 8.2.4.1 Cellulose-based PUD thermosetting composites -- 8.2.4.2 Starch reinforced PUD thermosetting composites -- 8.2.5 PUD thermosetting composites reinforced with nanocarbon materials -- 8.2.5.1 Graphene oxide (GO), and reduced graphene oxide (rGO) based PUD thermosetting composites -- 8.2.5.2 Carbon nanotubes (CNTs) reinforced PUD thermosetting composites -- Summary -- Abbreviations -- References -- 9 -- Classical Thermoset Epoxy Composites for Structural Purposes: Designing, Preparation, Properties and Applications -- 9.1 Introduction -- 9.2 Methods for modifying liquid epoxy compositions -- 9.2.1 Chemical modification of liquid epoxy compositions -- 9.2.2 Physico-chemical modification of liquid epoxy compositions -- 9.2.3 Methods of physical modification of liquid epoxy compositions -- 9.3 Physico-chemical aspects of the modification of epoxy polymers by dispersed and continuous fibrous fillers -- 9.3.1 Features of the formation of clusters in a polymer composite -- 9.3.2 Analysis of the surface interaction of fillers with epoxy oligomers -- 9.3.2.1 Surface interaction of inorganic fillers with epoxy oligomers -- 9.3.2.2 Surface interaction of organic fillers with epoxy oligomers -- 9.3.2.3 The mechanism of molecular interaction between epoxy polymer and filler -- 9.4 Effect of ultrasonic treatment regimes on the properties of epoxy polymers -- 9.4.1 Technological and operational properties of epoxy polymers -- 9.4.2 Physico-mechanical and technological properties of sonificated epoxy matrices -- 9.5 Ultrasonic intensification of prepregs formation -- 9.5.1 Process of capillary impregnation -- 9.5.2 Effect of ultrasonic modification regimes on the kinetics of impregnation of continuous fibrous fillers -- 9.6 Ultrasonic processing devices for liquid polymer systems -- 9.7 Modeling of the structure of oriented and woven fibrous materials. , 9.7.1 Physical models of a capillary-porous medium based on oriented fibrous fillers -- 9.8 Modeling of technical means for production of polymer composite materials -- 9.8.1 The technology of ultrasonic production of long-length epoxy composites -- 9.8.2 Modeling of technical means for thermoplastic production -- 9.9 Other applications of ultrasonic in the production of thermosets and thermoplastic -- 9.9.1 The effectiveness of ultrasonic treatment for the production of epoxy nanocomposites -- 9.9.2 Pepair technologies for the maintenance and restoration of polyethylene pipelines -- Conclusions -- References -- 10 -- A Review on Tribological Performance of Polymeric Composites Based on Natural Fibres -- 10.1 Introduction -- 10.2 Natural fibres -- 10.3 Polymer -- 10.4 Composite -- 10.5 Tribology -- 10.6 Friction and wear -- Summary -- Future Developments -- References -- back-matter -- Keyword Index -- About the Editors.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd
    Journal of advanced nursing 36 (2001), S. 0 
    ISSN: 1365-2648
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Mental health nurses’ perceptions of nurse prescribing Aims. This study aimed to ascertain mental health nurses’ perceptions of the advantages and disadvantages of nurse prescribing and to identify the educational needs of mental health nurse prescribers. Design. A questionnaire was designed and administered to a convenience sample in the UK of 73 mental health nurses in clinical practice, 14 working in in-patient settings and 59 in the community. Questions included both closed and open-ended items. Descriptive statistics were used for numerical data, and category analysis of the open-ended questions was undertaken by two of the researchers independently and then conjointly. Findings. The majority of respondents felt that mental health nurse prescribing would significantly improve clients’ access to medication, improve compliance, prevent relapse and prove cost effective. However, many were anxious that they did not have sufficient knowledge and skills to assume responsibility for prescribing. Conclusions. Although there would be benefits to clients and patients, further training, rigorous supervision and the co-operation of doctors will be required if mental health nurse prescribing is to yield the anticipated benefits.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 44 (1997), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The Miocene-Pliocene Siwalik Group records changing fluvial environments in the Himalayan foreland basin. The Nagri and Dhok Pathan Formations of this Group in the eastern Potwar Plateau, northern Pakistan, comprise relatively thick (tens of metres) sandstone bodies and mudstones that contain thinner sandstone bodies (metres thick) and palaeosols. Thick sandstone bodies extend for kilometres normal to palaeoflow, and are composed of large-scale stratasets (storeys) stacked laterally and vertically adjacent to each other. Sandstone bodies represent single or superimposed braided-channel belts, and large-scale stratasets represent channel bars and fills. Channel belts had widths of km, bankfull discharges on the order of 103 cumecs and braiding parameter up to about 3. Individual channel segments had bankfull widths, maximum depths, and slopes on the order of 102 m, 101 m and 10−4 respectively, and sinuosities around 1-1. These rivers are comparable to many of those flowing over the megafans of the modern Indo-Gangetic basin, and a similar depositional setting is likely. Thin sandstone bodies within mudstone sequences extend laterally for on the order of 102 m and have lobe, wedge, sheet and channel-form geometries: they represent crevasse splays, levees and floodplain channels. Mudstones are relatively bioturbated/disrupted and represent mainly floodbasin and lacustrine deposition. Mudstones and sandstones are extremely disrupted in places, showing evidence of prolonged pedogenesis. These ‘mature’ palaeosols are m thick and extend laterally for km. Lateral and vertical variations in the nature of their horizons apparently depend mainly on deposition rate.The 500 m-thick Nagri Formation has a greater proportion and thicker sandstone bodies than the overlying 700 m-thick Dhok Pathan Formation. The thick sandstone bodies and their large-scale stratasets thicken and coarsen through the Nagri Formation, then thin and fine at the base of the Dhok Pathan Formation. Compacted deposition rates increase with sandstone proportion (0-53 mm/year for Nagri, 0-24 mm/year for Dhok Pathan), and palaeosols are not as well developed where deposition rates are high. Within both formations there are 100 m-scale variations (representing on the order of 105 years) in the proportion and thickness of thick sandstone bodies, and tens-of-m-scale alternations of thick sandstone bodies and mudstone-sandstone strata that represent on the order of 104 years. Formation-scale stratal variations extend across the Potwar Plateau for at least 100 km, although they may be diachronous: however, 100-m and smaller scale variations can only be traced laterally for up to tens of km.Alluvial architecture models indicate that increases in the proportion and thickness of thick sandstone bodies can be explained by increasing channel-belt sizes (mainly), average deposition rate and avulsion frequency on a megafan comparable in size to modern examples. 100-m-scale variations in thick sandstone-body proportion and thickness could result from ‘regional’ shifts in the position of major channels, possibly associated with ‘fan lobes’on a single megafan or with separate megafans. However, such variations could also be related to local changes in subsidence rate or changes in sediment supply to the megafan system.Formation-scale and 100-m-scale stratal variations are probably associated with interelated changes in tectonic uplift, sediment supply and basin subsidence. Increased rates of hinterland uplift, sediment supply and basin subsidence, recorded by the Nagri Formation, may have resulted in diversion of a relatively large river to the area. Alternatively, changing river sizes and sediment supply rates may be related to climate changes affecting the hinterland (possibly linked to tectonic uplift). Climate during deposition of the Siwalik Group was monsoonal. Although the deposits contain no direct evidence for climate change, independent evidence indicates global cooling throughout the Miocene, and the possibility of glacial periods (e.g. around 10-8 Ma, corresponding to base of Nagri Formation). If the higher Himalayas were periodically glaciated, a mechanism would exist for varying sediment supply to megafans on time scales of 104-105 years. Although eustatic sea-level changes are related to global climatic change, they are not directly related to Siwalik stratigraphic changes, because the shoreline was many 100 km away during the Miocene.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Agrobacterium tumefaciens produces flagella that are arranged circumthecally near one end of the bacilliform cell. The flagella are required for motility to facilitate reaching the root surface, and possibly aid in orientating the bacterial cells at various sites for infection. We have identified three flagella genes designated flaA, flaB, and flaC. Mutations in flaA, flaB and flaC result in abberant swimming behaviour. Electron microscopic examination of these mutants revealed the defective flagella. A non-motile, bald mutant strain was generated by deleting all three fla genes. Nucleotide sequencing of flaA, flaB, and flaC showed that they have a potential coding capacity for polypeptides of 307, 321, and 314 amino acid residues, respectively. The predicted amino acid sequences of the A. tumefaciens FlaA and FlaB proteins are similar (66% average identity) to the FlaA and FlaB proteins encoded by flaA and flaB genes, respectively, in Rhizobium meliloti. There was no counterpart FlaC protein reported in R. meliloti, but the A. tumefaciens FlaC is similar in amino acid sequence to the R. meliloti FlaA (59.8% identity) and FlaB (66.7% identity). Distinct from FlaA and FlaB of R. meliloti is the absence of histidine and cysteine residues and their shorter length (by 88 amino acid residues fewer than FlaA and FlaB of R. meliloti ). The transcriptional start sites of each fla gene determined by primer extension revealed consensus-sequence boxes representing potential binding sites for σ28 RNA polymerase (RNAP) upstream of the transcriptional start of each fla gene. Besides the potential σ28-binding site upstream of flaC, also present are additional putative conserved sequences, GC at −11 and GG at −21 from the transcriptional start, that resemble potential binding motifs for σ54. Because the σ54 promoter is associated with genes regulated by physiological changes in various bacteria, the flaC gene might be similarly regulated in response to A. tumefaciens responding to host plant stimuli. Virulence studies showed that the bald strain was consistently reduced in virulence below that of the parental wild-type strain by at least 38%. The difference is statistically significant and suggests that the flagella may play a role in facilitating virulence.
    Type of Medium: Electronic Resource
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