Methane Nitrous Oxide Research Articles

Genetically Modified Rice Is Associated with Hunger, Health, and Climate Resilience.

While nearly one in nine people in the world deals with hunger, one in eight has obesity, and all face the threat of climate change. The production of rice, an important cereal crop and staple food for most of the world's population, faces challenges due to climate change, the increasing global population, and the simultaneous prevalence of hunger and obesity worldwide. These issues could be addressed at least in part by genetically modified rice. Genetic engineering has greatly developed over the century. Genetically modified rice has been approved by the ISAAA's GM approval database as safe for human consumption. The aim behind the development of this rice is to improve the crop yield, nutritional value, and food safety of rice grains. This review article provides a summary of the research data on genetically modified rice and its potential role in improving the double burden of malnutrition, primarily through increasing nutritional quality as well as grain size and yield. It also reviews the potential health benefits of certain bioactive components generated in genetically modified rice. Furthermore, this article discusses potential solutions to these challenges, including the use of genetically modified crops and the identification of quantitative trait loci involved in grain weight and nutritional quality. Specifically, a quantitative trait locus called grain weight on chromosome 6 has been identified, which was amplified by the Kasa allele, resulting in a substantial increase in grain weight and brown grain. An overexpressing a specific gene in rice, Oryza sativa plasma membrane H+-ATPase1, was observed to improve the absorption and assimilation of ammonium in the roots, as well as enhance stomatal opening and photosynthesis rate in the leaves under light exposure. Cloning research has also enabled the identification of several underlying quantitative trait loci involved in grain weight and nutritional quality. Finally, this article discusses the increasing threats of climate change such as methane-nitrous oxide emissions and global warming, and how they may be significantly improved by genetically modified rice through modifying a water-management technique. Taken together, this comprehensive review will be of particular importance to the field of bioactive components of cereal grains and food industries trying to produce high-quality functional cereal foods through genetic engineering.

Entropy Generation and Exergy Assessment of Methane–Nitrous Oxide Diffusion Flames in a Triple-Port Burner

A triple-port burner was used in this study, and a numerical simulation was employed to investigate the entropy generation rate of CH4–N2O diffusion flames at the R ratio = 1 . Here, R ratio refers to the ratio of the oxidizer flow velocity to the fuel flow velocity. In order to scrutinize the decomposition effect of N2O on entropy generation, an oxygen-enriched gas with the same nitrogen to oxygen ratio as N2O (N-to- O = 2 ) was used in CH4–N2–O2 diffusion flames. Besides, because the N2O could decompose into the oxygen-enriched gas, the oxygen-enriched effect was also studied by the CH4–air diffusion flames that were conducted in this research. The entropy generation rate comprises of three items in this study, including heat conduction, mass diffusion, and chemical reaction. As a result, the different reaction pathways would take part in the major reaction pathway in CH4–N2O diffusion flames, causing more entropy generation rate being produced through the more intense reactions in CH4–N2O diffusion flames. The irreversibility in CH4–air diffusion flames are dominated through heat conduction and chemical reaction, which is an identical result in CH4–N2–O2 diffusion flames. However, in CH4–N2O diffusion flames, chemical reactions dominated the irreversibility because of the more intense reaction caused by the thermal effect of N2O decomposition. As a result, the decomposition effect of N2O influences the availability of CH4–N2O diffusion flames.

Methane-unconventional oxidant flames. Laminar burning velocities of nitrogen-diluted methane–N 2 O mixtures

Abstract The flame propagation in nitrogen-diluted CH4–N2O mixtures was monitored by pressure measurements during explosions in a spherical vessel with central ignition. The burning velocities were obtained from experimental measurements of pressure variation during closed vessel explosions and from the detailed modelling of free laminar premixed flames. Lean- and stoichiometric methane–nitrous oxide mixtures (equivalence ratios: 0.8 and 1.0) diluted by various amounts of nitrogen between 40 and 60 vol% were studied at various initial pressures between 0.3 and 1.8 bar and ambient initial temperature. Nitrogen addition to each CH4–N2O mixture results in the decrease of laminar burning velocity and flame temperature, along with the increase of flame width. Examination of burning velocity variation against average flame temperature in experiments at constant initial pressure and various inert concentrations allowed the determination of the overall activation energy; examination of burning velocity dependence on pressure, at constant inert concentration, allowed the determination of the overall reaction orders. For all CH4–N2O–N2 mixtures, the temperature, volumetric rate of heat release and reactive species concentration profiles across the flame front were examined versus similar data characteristic to stoichiometric methane–air mixtures. The most important elementary reactions in CH4–N2O–N2 and CH4–air mixtures were identified by means of sensitivity analysis.

Propagation indices of methane-nitrous oxide flames in the presence of inert additives

The propagation indices (explosion pressures, rates of pressure rise, severity factors and explosion times) of CH4-N2O flames in the presence of inert gases (He, Ar, N2 and CO2) were determined by experiments performed in a spherical vessel with central ignition. Lean-and stoichiometric mixtures (φ = 0.8 and 1.0) with a variable inert gas concentration between 40 and 60% were studied, at variable initial pressures within 0.50 and 1.75 bar. Inert gas addition to each of the studied CH4−N2O mixtures results in the decrease of both experimental and adiabatic explosion pressure and of the maximum rate of pressure rise, along with the increase of the explosion time. CO2 was found to be the most efficient inert additive, followed by N2, Ar and He. The measured and computed propagation properties are examined as functions of the total initial pressure and the inert gas concentration. The correlation of peak explosion pressures with the initial pressures, derived from the heat balance of the isochoric combustion of a fuel-oxidizer mixture under non-adiabatic conditions, is used to evaluate the heat losses during the closed vessel combustion, dependent on the initial CH4/N2O ratio and on inert concentration of the flammable mixtures.

An experimental investigation of an inertization effectiveness of fluorinated hydrocarbons in relation to premixed H2–N2O and CH4–N2O flames

An experimental investigation of an influence of trifluoromethane CHF3, pentafluoroethane C2HF5 and perfluorobutane C4F10 on near-limit hydrogen-nitrous oxide and methane-nitrous oxide premixed flames was performed. Flammability limits, a maximum explosion pressure ΔPmax, maximum rate of pressure rise (dP/dt)max, and a laminar burning velocity Su were determined. The flammability area in the case of N2O as an oxidizer is substantially wider than for the case of the oxidizer which is the mixture of oxygen and nitrogen with the O2 content 25% (vol.). The dependences of Su, ΔPmax and (dP/dt)max on concentration of the fluorinated hydrocarbons are characterizing by an availability of maxima which positions are close to the peak concentrations of the flammability regions. A qualitative interpretation of the results obtained is given.

The biochar debate: charcoal's potential to reverse climate change and build soil fertility

Introduction: Charcoal and biochar A visit to India The players. An overall view: Carbon The atmosphere The land Limited resources Geo-engineering Downsides Predictions. The Amazon civilisation: Dark soil (terra preta). Biochar and agriculture: Soil Productivity Peak oil Peak phosphorus Pandemics Introduction of biochar Where, and how much? Permanence in soil Application. Pilot schemes: The banana grower SCAD Southern France Carbon Gold in Belize Ghana Poultry farm Cameroon Microwave Carbon Capture and Storage (CCS). Science: Photosynthesis Carbon dioxide Methane Nitrous Oxide Safe level for greenhouse gases Biochar Nutrient qualities. Carbon credits: Cap-and-trade The global economy Experience Europe Biochar Twin solutions CMF: the Carbon Maintenance Fee. Summary. Selected bibliography.

Hydrogen- and C 1–C 3 Hydrocarbon-Nitrous Oxide Kinetics in Freely Propagating and Burner-Stabilized Flames, Shock Tubes, and Flow Reactors

A detailed, chemical mechanism has been compiled for modeling the combustion of C 1–C 3 hydrocarbon-nitrous oxide mixtures. The compiled, chemical mechanism has been compared and validated against available data in the literature, including flame structure measurements of hydrogen-nitrous oxide and ammonia-nitrous oxide flames, flow reactor data on hydrogen-nitrous oxide and moist, nitrous oxide decomposition mixtures, shock tube ignition delay data on hydrogen- and methane-nitrous oxide mixtures, experimental flame speed data on carbon monoxide-nitrous oxide mixtures, and experimental, laminar flame speed data for hydrogen-, methane-, acetylene-, and propane-nitrous oxide mixtures. Feature sensitivity studies and reaction path analyses have been employed to elucidate important pathways to the overall reaction rate for these systems, and include the nitrous oxide decomposition step (N 2 O(+M) ⇌ N 2 + O(+M)) and nitrous oxide reactions with H atoms (N 2 O + H ⇌ N 2 + OH and N 2 O + H ⇌ NH + NO). Modifications to the compiled mechanism were considered on the basis of the most sensitive reactions with the highest apparent rate constant uncertainty, to closely predict the various experimental data considered.

Global warming and rice based cropping system

International Pannel for Climate Change approximates that the global temperature would rise between 1.50 and 4.50 Celsius by some time in twenty-first century. Since the advent of the industrial revolution in the 1700s, human beings have devised many inventions that burn fossil fuels. Burning these fossil fuels as well as other activities such as clearing land for agriculture or urban settlements, releases some of the gases that trap heat in the atmosphere leading to global warming. Carbon dioxide, methane Nitrous oxide chloro-fluoro-carbons comprises the green house gases. Soil in the earth surface is viewed both as source and sink for most of the green house gases. Agricultural practices such as rice cultivation and clearing of the biomass results in the emission of green house gases. It is always not too late for good beginning, so knowledge and research is emphasized for understanding the green house gases emission and its reduction from agricultural practices. 
 
 Journal of AGRICULTURE AND ENVIRONMENT Vol. 8, 2007, pp. 62-65

Basis set superposition error in MP2 and density-functional theory: A case of methane-nitric oxide association

A systematic study of basis set superposition error (BSSE) behavior in H(3)C-H[ellipsis (horizontal)][NO] complexes for both -H...N- and -H...O- orientations were carried out using MP2 and density-functional theory with Pople's [6-31G(d,p),6-311++G(nd,nd), where n=1,2,3, and 6-311++G(3df,3pd)] and Dunning's augmented correlation consistent basis sets [aug-cc-pVXZ (X=D and T)]. Corrected and uncorrected counterpoise potential-energy surfaces (PESs) were explored and differences obtained between them indicate that reliable optimizations of these molecular interactions must be carried out in a PES free of BSSE, even in the case of large basis sets and popularly used functionals such as B3LYP. Although all basis used could be always considered within a margin of approximation for representing molecular orbitals and show important values of BSSE, 6-311++G(2d,2p) basis set shows the best results in uncorrected PES with respect to the corrected ones. B3LYP functional produces erratic results: complexes appear repulsive and the intermolecular distances are always large, evidencing the lack of a correct dispersive forces treatment in the original parameterization. According to the MP2 results, the -H...N- interactions appear as slightly more stable than those of the -H...O- orientation.

A note on chemiluminescence in low-pressure hydrogen and methane–nitrous oxide flames

Absolute OH(A) and CH(A) concentrations were determined in low-pressure H 2–air and CH 4–N 2O flames, respectively, by measuring absolute chemiluminescence yields at 310 and 430 nm. From spatial profiles and intensities in these and other flames, we deduce that two reactions are responsible in each case, and derive rate constants for all.

Evidence of NCN as a flame intermediate for prompt NO

NCN is detected by laser-induced fluorescence of the A-X transition at 329 nm in low pressure methane–air and methane–nitrous oxide flames. The excitation wavelengths, signal intensities, spatial height profiles above the burner, fluorescence quenching lifetimes, and highly resonant fluorescence wavelength are all consistent with this assignment. The spectral features require the presence of hydrocarbon fuel and nitrogen, and do not gain added intensity under reburn conditions of NO seeding. The resulting arguments and evidence favoring NCN as the initial intermediate in prompt NO formation are discussed.

Flammability limits, ignition energy, and flame speeds in H 2–CH 4–NH 3–N 2O–O 2–N 2 mixtures

Experiments on flammability limits, ignition energies, and flame speeds were carried out in a 11.25- and a 400-liter combustion vessel at initial pressures and temperatures of 100 kPa and 295 K, respectively. Flammability maps of hydrogen–nitrous oxide–nitrogen, methane–nitrous oxide–nitrogen, ammonia–nitrous oxide–nitrogen, and ammonia–nitrous oxide–air, as well as lean flammability limits of various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures were determined. Ignition energy bounds of methane–nitrous oxide, ammonia–nitrous oxide, and ammonia–nitrous oxide–nitrogen mixtures have been determined and the influence of small amounts of oxygen on the flammability of methane–nitrous oxide–nitrogen mixtures has been investigated. Flame speeds have been measured and laminar burning velocities have been determined for ammonia–air–nitrous oxide and various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures. Lower and upper flammability limits (mixing fan on, turbulent conditions) for ignition energies of 8 J are: H 2–N 2O: 4.5 ∼ 5.0% H 2(LFL), 76 ∼ 80% H 2(UFL); CH 4–N 2O: 2.5 ∼ 3.0% CH 4(LFL), 43 ∼ 50% CH 4(UFL); NH 3–N 2O: 5.0 ∼ 5.2% NH 3(LFL), 67.5 ∼ 68% NH 3(UFL). Inerting concentrations are: H 2–N 2O–N 2: 76% N 2; CH 4–N 2O–N 2: 70.5% N 2; NH 3–N 2O–N 2: 61% N 2; NH 3–N 2O–air: 85% air. Flammability limits of methane–nitrous oxide–nitrogen mixtures show no pronounced dependence on small amounts of oxygen (<5%). Generally speaking, flammable gases with large initial amounts of nitrous oxide or ammonia show a strong dependence of flammability limits on ignition energy.

Studies of Counterflow Diffusion Flames at Low Pressures

Methane-oxygen, methane-nitrous oxide and carbon monoxide-nitrous oxide counterflow diffusion flames have been studied at low pressures. Species concentrations have been measured using probe extraction and gas chromatography, and temperatures have been measured using thermo-couples. Measurements have been compared to predictions of a computer model. The chemical kinetic mechanism input into these models has been found to be successful in predicting essential features of the structures of these flames. However, improvement are still needed to predict some of the structural features of the flames more accurately. For the methane-nitrous oxide flame, rate generation analysis was performed to identify which chemistry is most essential in predicting the methane-nitrous oxide flame structure. The results of this analysis were compared to rate generation analysis of a premixed methane-nitrous oxide flame. The differenoes between these analyses have been noted. The rate generation analysis results can be used to help guide the formulation of chemical kinetic mechanisms of reduced size, which are required by global propellant modelers.

Raman and fluorescence spectroscopy in a methane-nitrous oxide laminar flame

Using the prism selected lines of argon and krypton lasers, temperature and concentration profiles through the reaction zone of a premixed laminar methane-nitrous oxide flame have been obtained from the Raman signals for N2, H2O, and CH4. Fluorescence signals from NH, OH, CN, and NCO have also been observed. These signals have been assigned to specific pumping transitions where possible, and also converted to relative concentration profiles. Estimates of the absolute concentrations are also determined. The experimentally determined temperatures and species concentrations are compared with thermochemical equilibrium calculations.

Selective detection of polyaromatic and polychlorinated isomers in aerosol extracts by capillary gas chromatography combined with negative-ion detection

High-resolution gas chromatography combined with negative-ion chemical ionization mass spectrometry has been used to analyse air extracts for polyaromatic and polychlorinated isomeric compounds. Nanogram amounts of isomers could be differentiated by using methane-nitrous oxide reaction gas mixtures. Resonance electron-capture ionization is a very useful technique for the detection of nitrated polyaromatics. The total ion current chromatograms are compared with those obtained by electron-capture detection.

Shock Induced Reactions of Methane with Nitrous and Nitric Oxides

Abstract Reflected shock waves, generated in a 5×3 inch shock tube, have been used to ignite mixtures of methane-nitrous oxide and methane-nitric oxide. Monochromators, a pressure transducer and an oscilloscope were used to determine the induction period to ignition (τ) after the reflected wave passed the window. A flash lamp and spectrograph were also used to obtain spectra before and after explosion. For CH4-N2O mixtures it was found that the plot of log(τ[N2O]p5) against inverse temperature was linear and the activation energy was about 60 kcal/mol. This indicates that the rate controlling process was the reaction N2O(+M)→N2+O(+M). However, the reaction CH3+N2O→CH2+N2+OH may also be important. The results for CH4-NO mixtures could be expressed by log(τ[NO]p5)=−10.2+49000⁄4.58T which suggests to the reaction CH2+NO→CH+HNO may be rate controlling. Spectrographic plates showed that CN and OH were present during the induction period but only OH was detected after explosion. This indicates that the reactions CH+NO→CN+OH and CN+NO→N2+CO may be a significant mechanism for achieving the reduction of nitric oxide.

The quenching of premixed flames by volatile inhibitors

Quenching of premixed fuel-oxidizer flames by volatile additives was studied; the change in quenching diameter with inhibitor concentration was used to measure inhibitor effectiveness. The fuel-oxidizer combinations studied comprised methane-air, methane-nitrogen dioxide, methane-nitrogen dioxide-air and methane-nitric oxide. The experimental results indicate that the nature of the oxidizer is the most important oxidizer seem to be susceptible to chemical inhibition.

The ignition of combustible gases by flames

The ignition of a stoichiometric methane-nitric oxide mixture by stationary pilot flames has been investigated. These pilot flames can be burned indefinitely in the surrounding explosive mixture without causing ignition if the temperature or mass flow of the pilot is insufficient. For very small pilot flames the condition for ignition is a minimum energy flow (cal/s), whereas for large pilots a minimum temperature is necessary. This minimum ignition temperature is little related to the spontaneous ignition temperature. Ignition does not occur close to the burning zone of the pilot, but at the end of a luminous reacting column in which reaction rates, diffusion processes and heat conduction are the determining processes.