Search results:
Found 18
Listing 1 - 10 of 18 | << page >> |
Sort by
|
Choose an application
Two fixed bed reactors for nitrification with either polyethylene/clay sinter lamellas (FBR A) or porous ceramic rings (FBR B) were continously run for treating synthetic saline wastewater. Seawater from Hafen Büsum was used as an inoculums. The performance of the system was evaluated under different operating conditions. A better overall nitrification without nitrite accumulation was observed in FBR B during continuous incubation. However, in term of ammonia (AOR) and nitrite oxidation rates (NOR) that were determined in batch incubations, FBR A revealed a higher AOR and NOR of 6 and 7 mg N L-1 h-1, compared to the AOR and NOR of 5 and 5.9 mg N L-1 h-1 in FBR B, respectively. For studies of the effect of fluctuating salinity on the nitrification, polyethylene/clay sinter lamellas or porous ceramic rings from FBR A and B, respectively, were used as a source of immobilized nitrifiers. Salt concentrations were decreased from 3.5% to 0.03% via 2, 1 and 0.5% and increased from 3.5% to 5, 7 and 9%. A similar result for AOR and NOR during batch incubation was obtained for both substrata in FBR A and FBR B. The salinity changes influenced more the nitrite oxidizing bacteria (NOB) than the ammonia oxidizing bacteria (AOB). Measurement of oxidation rates during changing conditions show that the NORs were always higher than the AORs in all reactors, especially in initial phase. However, NORs were more sensitive to the salinity fluctuation than AORs, especially at lower salinity. The AORs remained constant for 0.5-3.5% NaCl and dropped to 70% and 68.5% after the salt concentration was brought to 0.034 or 5%, respectively. The NORs decreased significantly to 62% and 87.5% of initial rates after the salt concentration was changed to 2 and 5%, respectively.Non-halotolerant nitrifiers reactors with fresh polyethylene/clay as supporting material were inoculated with water samples taken from a ""Brackwasser""-location at the North Sea and were continuously run. The salt content in medium was 0% at the start and was then increased up to 10.5%. Increases of the salt concentration in a non-salt-adapted FBR suppressed more to NOR than AOR. When salinity was increased from 0.03% to 0.5, 1 and 2%, AORs remained constant. The AORs were approx. 90% of initial rates after the salt concentrations were increased stepwise to 3.5%, whereas the NORs decreased to 85, 52 and 36% of initial rate after salinity was increased to 1, 2 and 3.5%, respectively.
Choose an application
A mathematical model has been developed for the description of the transport process for low-pressure carbonitriding with ammonia and acetylene. As an example the case hardening steel 18CrNi8 was used. It can be shown that the concentration profiles of carbon and nitrogen as well as the ammonia exhaust gas concentration are described well. Based on the modelling, first simulation runs could be carried out for further optimization of the heat treatment process.
Choose an application
Endocrinological research early recognized the importance of intercellular interactions and realized the importance of glutamatergic and GABAergic signaling. In turn this signalling depends on elaborate interactions between astrocytes and neurons, without which neurons would be unable to produce, reuse and metabolize transmitter glutamate and GABA. Details of these subjects are described in this Research Topic by key investigators in this field. It focuses on the intricate and extremely swift pathway producing these amino acid transmitters from glucose in brain but also discusses difficulties in determining expression of some of the necessary genes in astrocytes and related processes in pancreatic islets. However, it does not discuss how closely associated astrocytes and neurons are anatomically, enabling these interactions. This is elegantly shown in this cover image, kindly provided by Professor Andreas Reichenbach (University of Leipzig, Germany).
Appetite Regulation --- Astrocyte-oligdendrocyte interaction --- Astrocytic gene expression --- Brain ammonia --- Brain aspartate --- Brain glutamate --- Brain glutamine --- brain metabolism --- GABA --- pancreatic islets
Choose an application
Climate change is one of the main threats to modern society. This phenomenon is associated with an increase in greenhouse gas (GHGs, mainly carbon dioxide—CO2) emissions due to anthropogenic activities. The main causes are the burning of fossil fuels and land use change (deforestation). Climate change impacts are associated with risks to basic needs (health, food security, and clean water), as well as risks to development (jobs, economic growth, and the cost of living). The processes involving CO2 capture and storage are gaining attention in the scientific community as an alternative for decreasing CO2 emissions, reducing its concentration in ambient air. The carbon capture and storage (CCS) methodologies comprise three steps: CO2 capture, CO2 transportation, and CO2 storage. Despite the high research activity within this topic, several technological, economic, and environmental issues as well as safety problems remain to be solved, such as the following needs: increase of CO2 capture efficiency, reduction of process costs, and verification of the environmental sustainability of CO2 storage.
CO2 separation --- TBAB --- IGCC --- anti-agglomerant --- micromorphology --- hydrate --- carbon capture and storage --- knowledge mapping --- technological evolution --- CiteSpace --- carbon storage --- the Loess Plateau --- InVEST --- carbon density --- normalized difference vegetation index (NDVI) --- supercritical CO2 --- flow instability --- stability map --- CO2 pipeline --- carbon capture and storage (CCS) --- CO2 capture and utilization --- energy dependence --- power-to-methane --- synthetic natural gas --- renewable power --- fossil fuels --- electricity production --- carbon capture --- calcium looping --- life cycle assessment --- GHG mitigation --- CCS --- cement --- techno-economic analysis --- MEA-based absorption --- chilled ammonia --- membrane-assisted CO2 liquefaction --- oxyfuel --- calcium looping --- CO2 capture --- cement production with CO2 capture --- CO2 capture in industry --- CO2 capture retrofitability --- oxyfuel --- chilled ammonia --- membrane-assisted CO2 liquefaction --- calcium looping
Choose an application
The most efficient process to reduce NOx emissions from lean exhaust gases, selective catalytic reduction (SCR) with ammonia, has undergone tremendous development over the past decades. Originally only applied in stationary power plants and industrial installations, SCR systems are now installed in millions of mobile diesel engines, ranging from off-road machineries, to heavy-duty and light-duty trucks and passenger cars, to locomotives and ships. All of these applications involve specific challenges due to tighter emission limits, new internal combustion engine technologies, or alternative fuels.Three review articles and 14 research articles in this book describe recent results and research trends of various aspects of the SCR process. Reaction engineering aspects, such as the proper dosage of ammonia or urea, respectively, are as important as further developments of the different SCR catalysts, by deepening the understanding of their functionality or by systematic improvements of their properties, such as low-temperature activity, selectivity, or poisoning-resistance. Another covered aspect is cost reduction through the use of cheaper base materials for the production is active and stable SCR catalysts. Finally, research efforts are reported to develop SCR processes with different reducing agents, which would open doors to new applications in the future. The range of topics addressed in this book will stimulate the reader’s interest as well as provide a valuable source of information for researchers in academia and industry.
Selective catalytic reduction (SCR) with ammonia/urea --- SCR in diesel vehicles, stationary power plants and industrial installations --- SCR catalyst research and development on V-based systems, Fe-zeolites and Cu-zeolites --- Catalyst deactivation --- SCR reaction mechanisms --- SCR kinetics and modelling --- Structure-function relationships in SCR catalysts --- Control, dosage and decomposition of reducing agents for SCR
Choose an application
The Special Edition 'Compounds with Polar Metallic Bonding' is a collection of eight original research reports presenting a broad variety of chemical systems, analytical methods, preparative pathways and theoretical descriptions of bonding situations, with the common aim of understanding the complex interplay of conduction electrons in intermetallic compounds that possess different types of dipoles. Coulombic dipoles introduced by electronegativity differences, electric or magnetic dipoles, polarity induced by symmetry reduction—all the possible facets of the term 'polarity'—can be observed in polar intermetallic phases and have their own and, in most cases, unique consequences on the physical and chemical behaviour. Elucidation of the structure–property relationships in compounds with polar metallic bonding is a modern and growing scientific field which combines solid state physics, preparative chemistry, metallurgy, modern analytic methods, crystallography, theoretical calculations of the electronic state and many more disciplines.
intermetallics --- crystal structure --- group-subgroup --- magnetic properties --- XPS --- coloring problem --- band structure --- structure optimizations --- polar intermetallics --- ternary Laves phases --- electronic structure --- X-ray diffraction --- total energy --- stannides --- plumbides --- alkaline-earth --- polar intermetallics --- symmetry reduction --- chemical bond --- Zintl --- Ca14AlSb11 --- polar intermetallic --- thermoelectric --- COHP method --- bonding analyses --- intermetallic compounds --- nitridometalate --- crystal structure --- powder diffraction --- magnetism --- Zintl compounds --- liquid ammonia --- crystal structure --- n/a
Choose an application
Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, methane conversion into higher hydrocarbons or oxygenates. It is also widely used for air pollution control (e.g., VOC
plasma catalysis --- mode transition --- packed-bed dielectric barrier discharge --- particle-in- cell/Monte Carlo collision method --- surface filament --- gas composition --- self-cooling --- dielectric barrier discharge --- CO2 decomposition --- CO selectivity --- packing materials --- toluene --- CeO2 --- mineralization --- in plasma-catalysis --- post plasma-catalysis --- relative humidity --- plasmas-catalysis --- non-thermal plasmas --- perovskite catalysts --- nonstoichiometry --- H2S oxidation --- plasma catalysis --- gallium --- indium --- Ga–In alloys --- radiofrequency plasma --- ammonia synthesis --- rotating gliding arc plasma --- tar destruction --- toluene --- naphthalene --- phenanthrene --- catalyst --- dielectric barrier discharge (DBD) --- isotope labelling --- methane reforming --- ammonia synthesis --- plasma catalysis --- dry reforming of methane --- dielectric barrier discharge --- packing materials --- plasma catalysis --- VOC abatement --- air pollution --- zeolites --- adsorption-plasma catalysis --- NOx conversion --- DBD plasma --- Manganese --- bimetal --- nanocatalyst --- plasma catalysis --- catalyst preparation --- NH3 decomposition --- H2 generation --- nonequilibrium plasma --- plasma catalysis --- gas temperature --- calcium carbonate decomposition
Choose an application
This Special Issue is aimed at presenting the state of the art of the multidisciplinary science concerning all aspects of volcanic plumes, of relevance to the volcanology, climatology, atmospheric science, and remote sensing communities.
calcium carbonate --- crystallization --- hydrogels --- alginate --- xanthan --- SEM --- X-ray diffraction --- carbonation --- micromechanics --- CaCO3 --- cement --- ammonia bicarbonate --- carbon dioxide --- mass-transfer coefficient --- capture --- bubble-column scrubber --- calcium carbonate --- alginate --- Lessonia nigrescens --- electrocrystallization --- multi-wall carbon nanotubes --- potentiometric titration --- calcium carbonate --- phosphorylated chitin --- electrocrystallization --- potentiometric titration --- gas diffusion method --- sedimentary model --- Callovian-Oxfordian --- Amu Darya Basin --- reservoir --- main controlling factors --- MICP --- Sporosarcina pasteurii --- Bacillus subtilis --- bacterial extracellular secretion --- urease --- calcite --- contact angle --- surface energy --- biomineralization --- calcite --- aragonite --- sericin --- nacre --- CO2 --- composite --- hierarchic structure
Choose an application
Kinetics and reactor modeling for heterogeneous catalytic reactions are prominent tools for investigating and understanding catalyst functionalities at nanoscale and the related rates of complex reaction networks. This book illustrates some examples related to the transformation of simple to more complex feedstocks, including different types of reactor designs, i.e., steady-state, transient plug flow reactors, and TAP reactors for which there is sometimes a strong gap in the operating conditions from ultra-high-vacuum to high-pressure conditions. In conjunction, new methodologies have emerged, giving rise to more robust microkinetics models. As exemplified, they include the kinetics and the dynamics of the reactors and span a large range of length and time scales. The objective of this Special Issue is to provide contributions that can illustrate recent advances and novel methodologies for elucidating the kinetics of heterogeneous reactions and the necessary multiscale approach for optimizing the reactor design. This book is dedicated to postgraduate and scientific researchers, and experts in heterogeneous catalysis. It may also serve as a source of original information for the elaboration of lessons on catalysis for Master students.
2,3-Butanediol dehydration --- 1,3-Butadiene --- Methyl Ethyl Ketone --- amorphous calcium phosphate --- reactor modeling --- pilot-scale fixed-bed reactor --- gas-phase oxidation --- HNO3 --- hierarchical graphite felts --- selective oxidation --- H2S --- heats of adsorption --- FTIR spectroscopy --- AEIR method --- Temkin model --- kinetics --- kinetic model --- microkinetics --- cracking --- methanol-to-olefins (MTO) --- zeolite --- ZSM-5 --- ZSM-23 --- SAPO-18 --- SAPO-34 --- transient kinetics --- TAP reactor --- temporal analysis of products --- ammonia decomposition --- internal effectiveness factor --- effective diffusion coefficient --- N2O --- catalytic decomposition --- cobalt mixed oxide --- alkali metal --- promoter --- power-law --- Langmuir–Hinshelwood --- kinetic modeling --- Pd/?-Al2O3 --- catalytic combustion --- automation --- digitalization --- mechanism analysis --- rhodium --- methane --- n/a
Choose an application
The majority of carbon stored in the soils of the world is stored in forests. The refractory nature of some portions of forest soil organic matter also provides the slow, gradual release of organic nitrogen and phosphorus to sustain long term forest productivity. Contemporary and future disturbances, such as climatic warming, deforestation, short rotation sylviculture, the invasion of exotic species, and fire, all place strains on the integrity of this homeostatic system of C, N, and P cycling. On the other hand, the CO2 fertilization effect may partially offset losses of soil organic matter, but many have questioned the ability of N and P stocks to sustain the CO2 fertilization effect.
carbon distribution index --- moisture gradient --- soil organic matter fraction --- soil degradation --- soil available nitrogen --- soil available phosphorus --- temperature --- stand density --- charcoal --- forest soil --- carbon mineralization --- microbial activity --- nitrification --- polyphenols --- temperature --- soil microbial communities --- PLFA --- seasons --- nitrogen dynamics --- gross nitrogen transformations --- Daxing’an Mountains --- climatic factors --- soil nutrients --- forest types --- principal component analyses --- soil structure --- soil pH --- Oxisol --- variable-charge soils --- aluminum accumulator --- seasonal trends --- beech forests --- soil enzymes --- organic matter --- multilevel models --- near natural forest management --- Pinus massoniana plantation --- Cunninghamia lanceolata plantation --- soil greenhouse gas flux --- biolability --- tree-DOM --- dissolved organic matter (DOM) --- carbon --- dissolved organic carbon (DOC) --- stemflow --- throughfall --- alpine forest --- ammonia-oxidizing bacteria --- ammonia-oxidizing archaea --- ammonium --- nitrate --- revegetation --- microbial biomass --- chloroform fumigation extraction --- enzyme activities --- stoichiometric homeostasis --- the Three Gorges Reservoir --- Eucalyptus sp. --- wood volume --- second production cycle --- annual increment average --- soil fertility --- nutrient cycling --- Chamaecyparis forest --- humic substances --- 31P nuclear magnetic resonance spectroscopy (31P NMR) --- P species --- topography --- net primary productivity --- climate zone --- climate --- soil N --- litter N --- climate change --- manuring --- manure pelleting --- northern temperate --- pyrolysis --- information review --- leaf N:P ratio --- P resorption efficiency --- soil P fractions --- P stock --- stand age
Listing 1 - 10 of 18 | << page >> |
Sort by
|