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Organic Material (organic + material)
Selected AbstractsPhotobleaching of Dissolved Organic Material from a Tidal Marsh-Estuarine System of the Chesapeake Bay,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Maria Tzortziou ABSTRACT Wetlands and tidal marshes in the Rhode River estuary of the Chesapeake Bay act as important sources of dissolved organic carbon and strongly absorbing dissolved organic matter (DOM) for adjacent estuarine waters. The effects of solar exposure on the photochemical degradation of colored DOM (CDOM) were examined for material derived from different sources (estuarine and freshwater parts of the Rhode River, sub-watershed stream, marshes) in this estuarine ecosystem. Consistent with changes in fluorescence emission, absorption loss upon exposure to different portions of the solar spectrum (i.e. different long-pass cut-off filters) occurred across the entire spectrum but the wavelength of maximum photobleaching decreased as the cut-off wavelength of the filter decreased. Our results illustrate that solar exposure can cause either an increase or a decrease in the CDOM absorption spectral slope, SCDOM, depending on the spectral quality of irradiation and, thus, on the parameters (e.g. atmospheric composition, concentration of UV-absorbing water constituents) that affect the spectral characteristics of the light to which CDOM is exposed. We derived a simple spectral model for describing the effects of solar exposure on CDOM optical quality. The model accurately, and consistently, predicted the observed dependence of CDOM photobleaching on the spectral quality of solar exposure. [source] Nanowires: Fabrication of Sub-10,nm Metallic Lines of Low Line-Width Roughness by Hydrogen Reduction of Patterned Metal,Organic Materials (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Mater. This computer rendered graphic displays direct writing of sub-10 nm metallic wires of low line-width roughness using an electron beam (shown as a sinusoidal wave), as presented by M. S. M. Saifullah, D. J. Kang, U. Steiner, et al. on page 2317. Sub-10 nm metallic wires of good integrity and low line-width roughness were obtained by reducing electron-beam patterned metal naphthenate lines in a hydrogen-rich atmosphere at 500°C for 1 h. [source] Fabrication of Sub-10,nm Metallic Lines of Low Line-Width Roughness by Hydrogen Reduction of Patterned Metal,Organic Materials,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Mihaela Nedelcu Abstract The fabrication of very narrow metal lines by the lift-off technique, especially below sub-10,nm, is challenging due to thinner resist requirements in order to achieve the lithographic resolution. At such small length scales, when the grain size becomes comparable with the line-width, the built-in stress in the metal film can cause a break to occur at a grain boundary. Moreover, the line-width roughness (LWR) from the patterned resist can result in deposited metal lines with a very high LWR, leading to an adverse change in device characteristics. Here a new approach that is not based on the lift-off technique but rather on low temperature hydrogen reduction of electron-beam patterned metal naphthenates is demonstrated. This not only enables the fabrication of sub-10,nm metal lines of good integrity, but also of low LWR, below the limit of 3.2,nm discussed in the International Technology Roadmap for Semiconductors. Using this method, sub-10,nm nickel wires are obtained by reducing patterned nickel naphthenate lines in a hydrogen-rich atmosphere at 500,°C for 1,h. The LWR (i.e., 3 ,LWR) of these nickel nanolines was found to be 2.9,nm. The technique is general and is likely to be suitable for fabrication of nanostructures of most commonly used metals (and their alloys), such as iron, cobalt, nickel, copper, tungsten, molybdenum, and so on, from their respective metal,organic compounds. [source] Charge Transport in Disordered Organic Materials and Its Relevance to Thin-Film Devices: A Tutorial ReviewADVANCED MATERIALS, Issue 27 2009Nir Tessler Abstract Semiconducting polymers and small molecules form an extremely flexible class of amorphous materials that can be used in a wide range of applications, some of which are display, radio-frequency tags, and solar cells. The rapid progress towards functional devices is occurring despite the lack of sufficient understanding of the physical processes and very little experience in device engineering. This tutorial review aims to provide sufficient intuitive background to draw more researchers to look into the fundamental aspects of device physics and engineering. [source] Book Review: Molecular Organic Materials.ADVANCED MATERIALS, Issue 5 2007By Jordi Fraxedas. No abstract is available for this article. [source] Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approachLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2004Ulrich Förstner Abstract Characteristic dynamic features of sediment-related processes in rivers include dramatic effects of stormwater events on particle transport, rapid and far-reaching effects of sulphide oxidation during resuspension, and biological accumulation and potential release of toxic chemicals. Pollutant mobility is the net result of the stabilizing and mobilizing effects in both hydraulic and chemical fields. In practice, emphasis has to be given to fine-grained sediments and suspended matter as these materials exhibit large surface areas and high sorption capacities. Organic materials are highly reactive. Degradation of organic matter will induce oxygen depletion and might enhance formation of flocs and biofilms. Study of variations of sediment and water chemistry should predominantly include changes of pH and redox conditions, competition of dissolved ions and processes such as complexation by organic substances. Major questions relate to the potential reduction of sorption sites on minerals and degradation of organic carrier materials. All these processes will influence solution/solid equilibrium conditions and have to be studied prior to modelling the overall effects of pollutants on the water body and aquatic ecosystems. With respect to handling and remediation of contaminated river sediments, either in-place or excavated, a chemical and biological characterization of the material, of the (disposal) site and of the long-term processes is crucial. Passive techniques (e.g. in situ stabilization, subaqueous capping) provide economic advantages as there are no operation costs following their installation. However, the success of these ecological and geochemical engineering approaches is mainly based on an in-depth knowledge of the underlying processes. [source] Impact of wastewater discharge on the channel morphology of ephemeral streamsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2001Marwan A. Hassan Abstract The impact of wastewater flow on the channel bed morphology was evaluated in four ephemeral streams in Israel and the Palestinian Territories: Nahal Og, Nahal Kidron, Nahal Qeult and Nahal Hebron. Channel changes before, during and after the halting of wastewater flow were monitored. The wastewater flow causes a shift from a dry ephemeral channel with intermittent floods to a continuous flow pattern similar to that of humid areas. Within a few months, nutrient-rich wastewater flow leads to rapid development of vegetation along channel and bars. The colonization of part of the active channel by vegetation increases flow resistance as well as bank and bed stability, and limits sediment availability from bars and other sediment stores along the channels. In some cases the established vegetation covers the entire channel width and halts the transport of bed material along the channel. During low and medium size flood events, bars remain stable and the vegetation intact. Extreme events destroy the vegetation and activate the bars. The wastewater flow results in the development of new small bars, which are usually destroyed by flood flows. Due to the vegetation establishment, the active channel width decreases by up to 700 per cent. The deposition of fine sediment and organic material changed the sediment texture within the stable bar surface and the whole bed surface texture in Nahal Hebron. The recovery of Nahal Og after the halting of the wastewater flow was relatively fast; within two flood seasons the channel almost returned to pre-wastewater characteristics. The results of the study could be used to indicate what would happen if wastewater flows were introduced along natural desert streams. Also, the results could be used to predict the consequences of vegetation removal as a result of human intervention within the active channel of humid streams. Copyright © 2001 John Wiley & Sons, Ltd. [source] Fabrication and evaluation of complementary logic circuits using zinc oxide and pentacene thin film transistorELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 9 2009Hiroyuki Iechi Abstract We fabricated hybrid complementary inverters with n-channel zinc oxide (ZnO) transistors as the n-type inorganic material and p-channel organic transistors using pentacene as the p-type organic material. The complementary inverter exhibited a large voltage gain of 10 to 12 and a cutoff frequency of 0.5 kHz. ZnO thin film transistors show n-type semiconducting properties having field-effect mobility of 2.1×10,3 cm2/Vs. On the other hand, pentacene thin film transistors show p-type semiconducting properties having field-effect mobility of 3.2×10,2 cm2/Vs. We describe basic charge transfer characteristics of ZnO thin films. The results obtained here demonstrate that it is important for the transistor using ZnO to be injected charge from electrode to semiconducting material effectively. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(9): 36,42, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10085 [source] Nanostructure and nanomechanics of live Phaeodactylum tricornutum morphotypesENVIRONMENTAL MICROBIOLOGY, Issue 5 2008Grégory Francius Summary The ultrastructure and mechanical properties of the fusiform, triradiate and ovoid morphotypes of Phaeodactylum tricornutum were investigated using atomic force microscopy. Using topographic imaging, we showed that the surface of the ovoid form is rougher than those of the two other specimens, and coated with an outer layer of extracellular polymers. Using spatially resolved force,indentation curves, we found that the valve of the ovoid form is about five times stiffer (Young modulus of ,500 kPa) than those of the other forms (,100 kPa), a finding fully consistent with the fact that only the ovoid form has a silica valve, whereas the valves in the other two consist mostly of organic material. Notably, the girdle region of both fusiform and ovoid forms was five times softer than the valve, suggesting that this region is poor in silica and enriched in organic material. For the triradiate form, we showed the arms to be softer than the core region, presumably as a result of organelle localization. Last, we observed mucilaginous footprints of moderate stiffness (,100 kPa) in the vicinity of ovoid diatoms, which we believe are secreted extracellular polymers. [source] Effects of water hardness and dissolved organic material on bioavailability of selected organic chemicalsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Jarkko Akkanen Abstract The influence of water hardness and dissolved organic matter (DOM) on bioavailability of organic chemicals to Daphnia magna was studied by using benzo[a]pyrene (BaP), pyrene, atrazine, and 3,3,,4,4,-tetrachlorobiphenyl (TCB) as model compounds. Two types of DOM were used, namely Lake Kontiolampi, Joeusuu, Finland water (KL) and Nordic reference fulvic acid (NoFA) dissolved in artificial freshwater. Binding of the four contaminants by KL, DOM decreased with increasing water hardness. Furthermore, increasing hardness reduced the binding of BaP and pyrene to NoFA. The binding of atrazine and TCB by NoFA was low and was not significantly affected by water hardness. In the DOM-free samples, the bioconcentration of the four contaminants in D. magna usually was not affected by water hardness. In the presence of DOM, the bioconcentration factors (BCFs) were lower (except for atrazine) than in the DOM-free controls. In the presence of both types of DOM, increasing water hardness resulted in higher BCFs for BaP. The bioconcentration of pyrene and TCB increased with increasing water hardness in the presence of KL DOM. In conclusion, the effects of DOM and water hardness on bioavailability of hydrophobic chemicals depend on the type of chemical and on the properties of DOM. [source] Determination of refractory organic matter in marine sediments by chemical oxidation, analytical pyrolysis and solid-state 13C nuclear magnetic resonance spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2008J. M. De La Rosa Summary Seeking to quantify the amount of refractory organic matter (ROM), which includes black carbon-like material (BC), in marine sediments, we have applied a two-step procedure that consists of a chemical oxidation with sodium chlorite of the demineralized sediments followed by integration of the aromatic C region in the remaining residues by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The efficacy for lignin removal was tested by analytical pyrolysis in the presence of tetramethyl ammonium hydroxide (TMAH). Riverine, estuarine and offshore marine sediment samples were collected from the southwest Atlantic coast of Spain, a site of geological and environmental interest. Measured contents of BC-like material ranged between 3.0 and 45.7% of the total organic carbon. Greater relative BC contents were found in riverine sediments close to urban areas, which show an elevated input of anthropogenic organic material. The contents of BC-like material in offshore marine sediments (5.5,6.1%) were similar to those previously reported for these kinds of samples. However, NMR and pyrolysis-GC/MS of the isolated ROM reveals that abundant refractory aliphatic organic material remains in most of the marine samples after chlorite oxidation. We suggest that this pool of aliphatic carbon may play an important role as a stable carbon pool within the global C cycle. [source] Carbon and nitrogen isotope composition of bulk soils, particle-size fractions and organic material after treatment with hydrofluoric acidEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2005M. W. I. Schmidt Summary Soils and sediments contain only small amounts of organic matter, and large concentrations of paramagnetic metals can give poor solid-state nuclear magnetic resonance (NMR) spectra of organic matter. Pretreatment of samples with hydrofluoric acid (HF) dissolves significant proportions of the mineral matrix and extracts paramagnetic elements. We investigated the effects of 10% HF treatment on the stable isotope content of carbon (C) and nitrogen (N) of organic matter from soils, composts and shales. Additionally we inferred molecular and isotopic characteristics of lost materials from calculations of isotope mass balances. Treatment with HF enriched C and N in mineral samples substantially (factors 2.5,42.4), except for Podzol B horizons (1.1,1.7) and organic material (1.0,1.3). After treatment most of the C (59.7,91.7%) and N (53.7,86.6%) was recovered, although changing C/N ratios often indicated a preferential loss of N-rich material. Isotope ratios of C and N in the remaining material became more negative when net alterations exceeded 0.3,. The isotope ratios of the lost material contained more 13C (1,2,) and 15N (1,4,) than the initial organic matter. Acid hydrolysis typically removes proteins, amino acids and polysaccharides, all of which are enriched in 13C, and in the case of proteins and amino acids, enriched in 15N as well. We conclude that HF treatment released fresh, soluble, probably microbial, biomass in addition to carbohydrates. Net changes of the bulk chemical composition of organic matter were small for most soils, size fractions and plant material, but not for samples containing little organic matter, or those rich in easily soluble organic matter associated with iron oxides, such as Podzol B horizons. [source] Bacteria in the cold deep-sea benthic boundary layer and sediment,water interface of the NE AtlanticFEMS MICROBIOLOGY ECOLOGY, Issue 2 2000Carol Turley Abstract This is a short review of the current understanding of the role of microorganisms in the biogeochemistry in the deep-sea benthic boundary layer (BBL) and sediment,water interface (SWI) of the NE Atlantic, the gaps in our knowledge and some suggestions of future directions. The BBL is the layer of water, often tens of meters thick, adjacent to the sea bed and with homogenous properties of temperature and salinity, which sometimes contains resuspended detrital particles. The SWI is the bioreactive interface between the water column and the upper 1 cm of sediment and can include a large layer of detrital material composed of aggregates that have sedimented from the upper mixed layer of the ocean. This material is biologically transformed, over a wide range of time scales, eventually forming the sedimentary record. To understand the microbial ecology of deep-sea bacteria, we need to appreciate the food supply in the upper ocean, its packaging, passage and transformation during the delivery to the sea bed, the seasonality of variability of the supply and the environmental conditions under which the deep-sea bacteria grow. We also need to put into a microbial context recent geochemical findings of vast reservoirs of intrinsically labile organic material sorped onto sediments. These may well become desorped, and once again available to microorganisms, during resuspension events caused by deep ocean currents. As biotechnologists apply their tools in the deep oceans in search of unique bacteria, an increasing knowledge and understanding of the natural processes undertaken and environmental conditions experienced by deep-sea bacteria will facilitate this exploitation. [source] Feeding rates, assimilation efficiencies and growth of two amphipod species on biodeposited material from zebra musselsFRESHWATER BIOLOGY, Issue 12 2008RENÉ GERGS Summary 1. Accumulation of organic material by the zebra mussel Dreissena polymorpha is assumed to be the source of a biodeposition-based food web. However, only little is known about the importance of the biodeposited material as a food source and its contribution to increased abundances of macroinvertebrates in the presence of D. polymorpha. 2. Feeding, assimilation and growth of the amphipods Gammarus roeselii and Dikerogammarus villosus on food sources directly and indirectly associated with D. polymorpha (biodeposited material and chironomids) and on conditioned alder leaves were measured. The stoichiometry of carbon, nitrogen and phosphorus of the diets was measured as an important determining factor of food quality. 3. Chironomids had the highest nitrogen and phosphorus contents, alder leaves were depleted in nitrogen and phosphorus, and the stoichiometry of biodeposited material was intermediate. 4. Both amphipod species had highest feeding rates and assimilation efficiencies on chironomids. Gammarus roeselii fed more on biodeposited material than on alder leaves, but assimilation efficiencies were similar; D. villosus also had similar feeding rates and assimilation efficiencies on the two diets. 5. Both amphipod species had highest growth rates on chironomids and lowest growth rates on alder leaves. Both grew at intermediate rates on biodeposited material of D. polymorpha. The growth rates of the amphipod species were related to food stoichiometry. Overall, the invasive D. villosus grew faster than the indigenous G. roeselii. 6. Food resources directly and indirectly associated with D. polymorpha are potential diets for amphipods, providing further evidence for a D. polymorpha biodeposition-based food web. [source] Pelagic and benthic net production of dissolved inorganic carbon in an unproductive subarctic lakeFRESHWATER BIOLOGY, Issue 3 2007JAN ÅBERG Summary 1. Both the pelagic and benthic net dissolved inorganic carbon (DIC) productions were measured in situ on four occasions from June to September 2004, in the unproductive Lake Diktar-Erik in subarctic Sweden. The stable isotopic signal (,13C) of respired organic material was estimated from hypolimnion water data and data from a laboratory incubation using epilimnion water. 2. Both pelagic and benthic habitats were net heterotrophic during the study period, with a total net DIC production of 416 mg C m,2 day,1, of which the pelagic habitat contributed approximately 85%. The net DIC production decreased with depth both in the pelagic water and in the sediments, and most of the net DIC production occurred in the upper water column. 3. Temporal variations in both pelagic and benthic DIC production were small, although we observed a significant decrease in pelagic net DIC production after the autumn turnover. Water temperature was the single most important factor explaining temporal and vertical variations in pelagic DIC production. No single factor explained more than 10% of the benthic net DIC production, which probably was regulated by several interacting factors. 4. Pelagic DIC production, and thus most of the whole-lake net production of DIC, was mainly due to the respiration of allochthonous organic carbon. Stable isotope data inferred that nearly 100% of accumulated DIC in the hypolimnion water had an allochthonous carbon source. Similarly, in the laboratory incubation using epilimnion water, c. 85% of accumulated DIC was indicated to have an allochthonous organic carbon source. [source] Seasonal and interannual variation of bacterial production in lowland rivers of the Orinoco basinFRESHWATER BIOLOGY, Issue 11 2004María M. Castillo Summary 1. We examined the influence of hydrologic seasonality on temporal variation of planktonic bacterial production (BP) in relatively undisturbed lowland rivers of the middle Orinoco basin, Venezuela. We sampled two clearwater and two blackwater rivers over 2 years for dissolved organic carbon (DOC), chlorophyll, phosphorus and bacterial abundance to determine their relationship to temporal variation in BP. 2. Dissolved organic carbon concentration was greater in blackwater (543,664 ,m) than in clearwater rivers (184,240 ,m), and was generally higher during periods of rising and high water compared with low water. Chlorophyll concentration peaked (3 ,g L,1) during the first year of study when discharge was lowest, particularly in blackwater rivers. Soluble reactive phosphorus (SRP) was very low in the study rivers (<3.8 ,g L,1) and concentration increased during low water. 3. Average BP was higher in clearwater (0.20,0.26 ,g C L,1 h,1) than in blackwater rivers (0.14,0.17 ,g C L,1 h,1), although mean bacterial abundance was similar among rivers (0.6,0.8 × 106 cells mL,1). 4. Periods of higher chlorophyll a concentration (low water) or flushing of terrestrial organic material (rising water) were accompanied by higher BP, while low BP was observed during the period of high water. 5. Interannual variation in BP was influenced by variations in discharge related to El Niño Southern Oscillation events. 6. Seasonal variation in BP in the study rivers and other tropical systems was relatively small compared with seasonal variation in temperate rivers and lakes. In addition to the low seasonal variation of temperature in the tropics, low overall human disturbance could result in less variation in the inputs of nutrients and carbon to the study rivers compared with more disturbed temperate systems. [source] Depositional history and evolution of the Paso del Indio site, Vega Baja, Puerto RicoGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2003Jeffrey J. Clark Potshards discovered during excavation of bridge pilasters for a major expressway over the Rio Indio floodplain, a stream incised within the karsts of north-central Puerto Rico, required large-scale archaeological excavation. Five-meter-deep bridge pilaster excavations in the alluvial valley provide a 4500-year history of deposition. Stratigraphic analysis of the exposed pilaster walls in combination with textural and organic carbon analyses of sediment cores obtained over a much broader area suggest a fluvial system dominated by overbank deposition. Six sequences of alternating light and dark layers of sediment were identified. The darker layers are largely composed of silts and clays, whereas the lighter layers are rich in sand-sized sediment. Archaeological evidence indicates the organic-rich dark layers, believed to be buried A horizons, coincide with pre-historic occupation by Cedrosan Saladoid, Elenan Ostionoid, and Chican Ostionoid, extending from A.D. 450 to A.D. 1500. Lighter layers below the dark soil horizons are interpreted as overbank deposits from large magnitude flood events. The floodplain aggraded discontinuously with rapid deposition of sand followed by gradual accumulation of silt, clay, and organic material. An approximately 1-m-thick layer of coarse sand and gravel halfway up the stratigraphic column represents an episode of more frequent and severe floods. Based on radiocarbon ages, this layer aggraded between A.D. 1000 and A.D. 1100, which is well within the Elenan Ostionoid era (A.D. 900,1200). Rates of sedimentation during this period were approximately 8 mm per year, ten times greater than the estimates of sedimentation rates before and after this flood sequence. The cause for the change in deposition is unknown. Nonetheless the Elenan Ostionoid would have had to endure frequent loss of habitation structures and crops during these events. © 2003 Wiley Periodicals, Inc. [source] Conceptual models for burrow-related, selective dolomitization with textural and isotopic evidence from the Tyndall Stone, CanadaGEOBIOLOGY, Issue 1 2004Murray K. Gingras ABSTRACT The formation of dolomite is generally explained using models that reflect larger-scale processes that describe the relationship between the supply and transport of Mg, and geochemical conditions that are amenable to the formation of dolomite. However, heterogeneities in the substrate, such as those made by bioturbating infauna, may play a more important role in dolomitization than has been previously considered. Burrow-facilitated dolomitization is evident in the Ordovician Tyndall Stone (Red River Group, Selkirk Formation) of central Canada. The diagenetic fabrics present are attributed to dolomitizing fluids that both flowed through and evolved within burrow networks. Petrographic analysis suggests that two phases of dolomite formation took place. The first formed a fine-grained, fabric-destructive type that probably accompanied early burial; the second is a fine- to medium-grained, locally sucrosic dolomite that is interpreted to have precipitated during later burial. Isotopic analysis supports the proposed paragenetic history: (1) an apparent linking of the stable isotopes 13C and 18O strongly suggests that the micrite matrix formed during very early diagenesis and was derived from seawater; (2) the initial phase of dolomitization is potentially microbially mediated, as evidenced by the enrichment of 13C; and (3) isotopic values for the second generation of dolomite reflect the mixing of ground water and resorbed early dolomite. This paper conceptualizes the physical and chemical conditions required for the formation of dolomite in association with burrow fabrics. The proposed model reveals a composite of biological and inorganic reactions that demonstrates the interdependence of sediment fabric, organic content and microbial interactions in the development of burrow-mottled dolomitic limestone. It is suggested that where burrow-associated dolomite occurs, it is most likely to develop in two stages: first, the byproducts of the degradation of organic material in burrows locally increase the permeability and porosity around burrow fabrics in shallow diagenetic depositional environments; and, second, the passing of burrowed media into deeper dysaerobic sediment is accompanied by the establishment of fermenting micro-organisms whose byproducts mediate dolomitization. [source] Carbon emission and sequestration by agricultural land use: a model study for EuropeGLOBAL CHANGE BIOLOGY, Issue 6 2002L. M. Vleeshouwers Abstract A model was developed to calculate carbon fluxes from agricultural soils. The model includes the effects of crop (species, yield and rotation), climate (temperature, rainfall and evapotranspiration) and soil (carbon content and water retention capacity) on the carbon budget of agricultural land. The changes in quality of crop residues and organic material as a result of changes in CO2 concentration and changed management were not considered in this model. The model was parameterized for several arable crops and grassland. Data from agricultural, meteorological, soil, and land use databases were input to the model, and the model was used to evaluate the effects of different carbon dioxide mitigation measures on soil organic carbon in agricultural areas in Europe. Average carbon fluxes under the business as usual scenario in the 2008,2012 commitment period were estimated at 0.52 tC ha,1 y,1 in grassland and ,0.84 tC ha,1 y,1 in arable land. Conversion of arable land to grassland yielded a flux of 1.44 tC ha,1 y,1. Farm management related activities aiming at carbon sequestration ranged from 0.15 tC ha,1 y,1 for the incorporating of straw to 1.50 tC ha,1 y,1 for the application of farmyard manure. Reduced tillage yields a positive flux of 0.25 tC ha,1 y,1. The indirect effect associated with climate was an order of magnitude lower. A temperature rise of 1 °C resulted in a ,0.05 tC ha,1 y,1 change whereas the rising CO2 concentrations gave a 0.01 tC ha,1 y,1 change. Estimates are rendered on a 0.5 × 0.5° grid for the commitment period 2008,2012. The study reveals considerable regional differences in the effectiveness of carbon dioxide abatement measures, resulting from the interaction between crop, soil and climate. Besides, there are substantial differences between the spatial patterns of carbon fluxes that result from different measures. [source] Control of Charge Transport in Iridium(III) Complex-Cored Carbazole Dendrimers by Generation and Structural ModificationADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Salvatore Gambino Abstract Here, the charge transporting properties of a family of highly phosphorescent iridium(III) complex-cored carbazole dendrimers designed to have improved charge transport by incorporating carbazole units into the dendrons are studied. Firstly, the effect of the dendrimer generation and the role of dendron for materials with one dendron per ligand of the core are considered. It is shown, in contrast to previously reported light-emitting dendrimers, that in this case the carbazolyl-based dendrons have an active role in charge transport. Next, the effect on the charge transport of attaching two dendrons per ligand to the dendrimer core is explored. In this latter case, for the so called "double dendron" material a highly non-dispersive charge transport behavior is observed, together with a time-of-flight mobility of the order of 10,3,cm2 V,1,s,1. Furthermore the lowest energetic disorder parameter (,) ever reported for a solution-processed conjugated organic material is found, ,,< ,20 meV. [source] Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007F. Hakim Abstract Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2,nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13,% increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions. [source] Measuring thaw depth beneath peat-lined arctic streams using ground-penetrating radarHYDROLOGICAL PROCESSES, Issue 14 2005John H. Bradford Abstract In arctic streams, depth of thaw beneath the stream channel is likely a significant parameter controlling hyporheic zone hydrology and biogeochemical cycling. As part of an interdisciplinary study of this system, we conducted a field investigation to test the effectiveness of imaging substream permafrost using ground-penetrating radar (GPR). We investigated three sites characterized by low-energy water flow, organic material lining the streambeds, and water depths ranging from 0·2 to 2 m. We acquired data using a 200 MHz pulsed radar system with the antennas mounted in the bottom of a small rubber boat that was pulled across the stream while triggering the radar at a constant rate. We achieved excellent results at all three sites, with a clear continuous image of the permafrost boundary both peripheral to and beneath the stream. Our results demonstrate that GPR can be an effective tool for measuring substream thaw depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Biogenic gas production from major Amazon reservoirs, BrazilHYDROLOGICAL PROCESSES, Issue 7 2003Luiz Pinguelli Rosa Abstract Methane (CH4) and carbon dioxide (CO2) emissions from Brazilian reservoirs were assessed. Point measurements were made during 1998 and 1999 (using inverted funnels for bubbles and air and water concentration gradients for diffusion) in the 559 km2 Samuel reservoir, which was initially flooded in 1988, and the 2430 km2 Tucuruí reservoir, which was flooded in 1984, and the data were evaluated with respect to historical measurements in other Brazilian reservoirs. Bubble emissions of CH4 were higher in Samuel (ranging from 2 to 70 mgCH4 m,2 day,1) than in Tucuruí (ranging from 0·5 to 30 mgCH4 m,2 day,1), with the highest values occurring the shallowest regions in each reservoir. CH4 from diffusion for the Tucuruí reservoir ranged from 5 to 30 mgCH4 m,2 day,1, which is lower than that for the Samuel reservoir, which ranged from 10 to 80 mgCH4 m,2 day,1. The smaller emissions in Tucuruí compared with Samuel are attributed to a larger depletion in the source organic material that was present when the reservoir was filled. The CO2 concentration was similar for each reservoir, and ranged from 1000 to 10 000 mgCO2 m,2 day,1. Copyright © 2003 John Wiley & Sons, Ltd. [source] A conceptual model of preferential flow systems in forested hillslopes: evidence of self-organizationHYDROLOGICAL PROCESSES, Issue 10 2001Roy C. Sidle Abstract Preferential flow paths are known to be important conduits of subsurface stormflow in forest hillslopes. Earlier research on preferential flow paths focused on vertical transport; however, lateral transport is also evident in steep forested slopes underlain by bedrock or till. Macropores consisting of decayed and live roots, subsurface erosion, surface bedrock fractures, and animal burrows form the basis of a ,backbone' for lateral preferential flow in such sites. Evidence from field studies in Japan indicates that although individual macropore segments are generally <0·5 m in length, they have a tendency to self-organize into larger preferential flow systems as sites become wetter. Staining tests show clear evidence of interconnected macropore flow segments, including: flow within decayed root channels and subsurface erosion cavities; flow in small depressions of the bedrock substrate; fracture flow in weathered bedrock; exchange between macropores and mesopores; and flow at the organic horizon,mineral soil interface and in buried pockets of organic material and loose soil. Here we develop a three-dimensional model for preferential flow systems based on distributed attributes of macropores and potential connecting nodes (e.g. zones of loose soil and buried organic matter). We postulate that the spatially variable and non-linear preferential flow response observed at our Japan field site, as well as at other sites, is attributed to discrete segments of macropores connecting at various nodes within the regolith. Each node is activated by local soil water conditions and is influenced strongly by soil depth, permeability, pore size, organic matter distribution, surface and substrate topography, and possibly momentum dissipation. This study represents the first attempt to characterize the spatially distributed nature of preferential flow paths at the hillslope scale and presents strong evidence that these networks exhibit complex system behaviour. Copyright © 2001 John Wiley & Sons, Ltd. [source] Nanostructured Materials: Microstructural and Biochemical Characterization of the Nanoporous Sucker Rings from Dosidicus gigas (Adv. Mater.ADVANCED MATERIALS, Issue 4 20094/2009) The cover image shows an SEM image of a squid tentacle, revealing the individual sucker rings. These toothed ringlike structures within the suckers provide additional gripping power during prey capture and handling. The background image depicts the nanoscale network of parallel tubular elements from which the rings are constructed. The structural, mechanical and biochemical properties of this wholly organic material is discussed in detail by David Kisailus, Henrik Birkedal, and co-workers on p. 401. [source] Microstructural and Biochemical Characterization of the Nanoporous Sucker Rings from Dosidicus gigasADVANCED MATERIALS, Issue 4 2009Ali Miserez The individual toothed sucker rings of squid tentacles (highlighted in blue) provide additional gripping power during prey capture and handling. These rings comprise a nanoscale network of parallel tubular elements, as shown in the background image. The structural, mechanical, and biochemical properties of this wholly organic material are discussed in detail. [source] Room temperature photoluminescence of the Li2ZnTi3O8 spinel: Experimental and theoretical studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005M. S. C. Câmara Abstract This article describes the characterization of intense photoluminescence observed at room temperature of the Li2ZnTi3O8 spinel phase, obtained by the polymeric precursor method. The evolution of visible photoluminescence is demonstrated by measurement of the photoluminescence signal as a function of the annealing treatment time. The evolution indicates that PL can be attributed to the presence of an inorganic disordered phase. In addition, increased annealing treatment times cause not only a decrease in the total residual content of organic material in the samples, but also an intensified photoluminescence. We discuss the nature of visible photoluminescence at room temperature of the Li2ZnTi3O8 spinel phase in the light of results of both recent experimental and quantum mechanical theoretical studies. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Participatory research methods in environmental science: local and scientific knowledge of a limnological phenomenon in the Pantanal wetland of BrazilJOURNAL OF APPLIED ECOLOGY, Issue 4 2000D.F. Calheiros Summary 1.,Participatory research methodologies incorporating local knowledge are important to the success of ecological research and the sustainable management of natural systems. However, methods of this type are not commonly employed in the natural sciences. 2.,We adopted a scientifically rigorous ethnographic research methodology to incorporate local knowledge into understanding a natural limnological phenomenon in the Brazilian Pantanal. Known locally as ,dequada', it is associated with fish kills. 3.,Using primarily open-ended questions and semi-structured interviews, 30 older head-of-household men were interviewed, by the same interviewer, in a small community representative of the few local riverside settlements. Their opinions were then contrasted with current scientific knowledge. 4.,In concordance with the scientific community, the local community cited decomposition of organic material as the principal cause of fish mortality due to the dequada. Local people therefore can have a well-founded understanding of their environment. 5.,This study demonstrates the importance of incorporating local knowledge to corroborate and, often, to guide the process of scientific inquiry. In this case, local knowledge added to scientific knowledge by providing a more complete understanding of the management and conservation of a natural system. We recommend that ecologists should be ready to acknowledge that local understanding can be greater than that of ,outsiders'. [source] Hydrolysis and microbial community analyses in two-stage anaerobic digestion of energy cropsJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007D.G. Cirne Abstract Aims:, The roles of the diverse populations of micro-organisms responsible for biodegradation of organic matter to form methane and carbon dioxide are rudimentarily understood. To expand the knowledge on links between microbial communities and the rate limiting, hydrolytic stage of two-stage biogas production from energy crops, this study was performed. Methods and Results:, The process performance and microbial communities (as determined by fluorescence in situ hybridization) in two separate two-stage batch digestions of sugar beets and grass/clover were studied. The microbial populations developed in the hydrolytic stage of anaerobic digestion of beets and grass/clover showed very few similarities, despite that the hydrolysis dynamics were similar. In both substrates, the solubilization of organic material was rapid for the first 10 days and accompanied by a build-up of volatile fatty acids (VFAs) and lactate. Between days 10 and 15, VFA and lactate concentrations decreased, as did the solubilization rates. For both substrates, Archaea started to appear in the hydrolytic stage between days 10 and 15, and the fraction of Bacteria decreased. The major bacterial group detected in the leachate fraction for beets was Alphaproteobacteria, whereas for grass/clover it was Firmicutes. The number of cells that bound to probes specifically targeting bacteria with cellulolytic activity was higher in the digestion of grass than in the digestion of beet. Conclusions:, This study allowed the identification of the general bacterial groups involved, and the identification of a clear shift in the microbial population when hydrolysis rate became limiting for each of the substrates investigated. Significance and Impact of the Study:, The findings from this study could be considered as a first step towards the development of strategies to stimulate hydrolysis further and ultimately increasing the methane production rates and yields from reactor-based digestion of these substrates. [source] Effects of Leuconostoc mesenteroides Starter Culture on Fermentation of Cabbage with Reduced Salt ConcentrationsJOURNAL OF FOOD SCIENCE, Issue 5 2007Suzanne Johanningsmeier ABSTRACT:, Sauerkraut fermentations rely upon selection of naturally occurring lactic acid bacteria by addition of 2.0% to 2.25% granulated sodium chloride (NaCl) to shredded cabbage. Excess brine generated is a waste product with high levels of organic material (BOD) and nonbiodegradable NaCl. The objective was to determine whether addition of Leuconostoc mesenteroides starter culture to reduced-salt cabbage fermentations would yield sauerkraut with reproducible and acceptable chemical composition and sensory qualities. Shredded cabbage was salted with 0.5%, 1.0%, or 2.0% NaCl (wt/wt) at 2 starter culture levels, none or L. mesenteroides strain LA 81, ATCC 8293 (106 CFU/g). Fermentation products were quantified by high-performance liquid chromatography, and pH was measured during the initial stages of fermentation and after 10 mo storage at 18 °C. A trained descriptive sensory panel used category scales to rate the flavor and texture of selected sauerkrauts. A modified Kramer shear test was used to measure firmness. Cabbage fermented with L. mesenteroides consistently resulted in sauerkraut with firm texture and reduced off-flavors across all salt levels (P < 0.05). Conversely, sauerkraut quality was highly variable, with softening and off-flavors occurring as salt concentrations were decreased in natural fermentations (P < 0.05). Fermentations were rapid, with a more uniform decline in pH when starter culture was added. L. mesenteroides addition to cabbage fermentations ensured that texture and flavor quality were retained, while allowing 50% NaCl reduction. Application of this technology to commercial sauerkraut production could improve the uniformity of fermentations and substantially reduce generation of nonbiodegradable chloride waste. [source] | ||||||||||||||||||||||||||||||||||||||||||||||