Increasing NO Concentration Research Articles

A fundamental study of hydrogen supplemented natural gas vehicle to meet ULEV

In the present study, investigations were carried out to obtain data on combustion characteristics of methane gas and hydrogen supplemented methane gas in a constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The maximum combustion pressure increases as the initial pressure and hydrogen supplement rate increase, the total burning time is shorten by lowering the initial pressure and by increasing the hydrogen supplement rate. The maximum flame temperature and NO concentration increase by the initial pressure and hydrogen supplement rate increase. The flame propagation processes in near stoichiometric mixture are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate.

Mechanisms mediating the vasodilatory effects of N-hydroxy- l-arginine in coronary arteries

We assessed the mechanisms of action of N G-hydroxy- l-arginine in isolated porcine large coronary arterial rings. Increasing (1, 10 and 100 μM) concentrations of N G-hydroxy- l-arginine evoked endothelium-dependent dilation which was eliminated by 100 μM of N G-nitro- l-arginine methyl ester, but not affected by a cytochrome P 450 inhibitors (miconazole or 7-ethoxyresorufin). At a given concentration, the dilatory response to N G-hydroxy- l-arginine was stronger than that elicited by l-arginine. N G-Hydroxy- l-arginine (100 μM), but not N G-hydroxy- d-arginine, potentiated the endothelium-dependent dilation of calcium ionophore A23187 but had no effect on endothelium-independent dilation evoked by an NO donor. NO release by endothelium-intact porcine coronary arterial rings was measured with a chemiluminescence analyser. A23187 (10 μM), N G-Hydroxy- l-arginine (100 μM), and to a lesser extent N G-hydroxy- d-arginine (100 μM), significantly increased NO concentration over 15 min observation period. When A23187 and N G-hydroxy- l-arginine were combined, NO concentration increased in an additive fashion. Enhanced No release by either A23187, N G-hydroxy- l-arginine or N G-hydroxy- d-arginine was attenuated by N G-nitro- l-arginine methyl ester. We conclude that N G-hydroxy- l-arginine exerts its effects on the contractility of coronary arteries by acting as a substrate for the endothelial nitric oxide synthase leading to enhanced NO production. Cytochrome P 450 were not involved the dilatory response to N G-hydroxy- l-arginine. In this respect, porcine coronary arteries differ significantly from cultured smooth muscle cells in metabolising N G-hydroxy- l-arginine.

N2O Formation from Combustion of Char Particles with NO

Devolatilized coal particles were combusted with NO as the only oxidizing agent. The effect of different NO concentrations in the inlet gas, as well as the effect of changing gas residence time within and after the fixed bed, on the emission of N2O from the char particles burning at single particle conditions is reported. The experiments were carried out in a fixed bed reactor containing quartz sand (SiO2) to support the coal particles. The bituminous coal particles were devolatilized in situ prior to the actual combustion in an argon flow. The inlet gas mixture contained NO and Ar. The NO concentration was varied between 5 and 50% and the inlet gas flow was varied between 395 and 1200 mL(NTP)/min (NTP = 273 K, 1 atm). The bed temperature was 1073 K. The off-gases were analyzed for N2O, CO, and CO2. Extremely high yields of N2O (150−430% of the char nitrogen content) were obtained in all cases when the devolatilized coal particles were combusted with NO. The N2O formation increased with increasing NO concentration in the inlet gas for low NO concentrations (5−20%) and reached a plateau for higher NO concentrations. The N2O formation increased with increasing gas residence time within and after the fixed bed.

Removal of Sulfur Dioxide from Flue Gas by the Absorbent Prepared from Coal Ash: Effects of Nitrogen Oxide and Water Vapor

Removal of SO2 from flue gas by the absorbent prepared from coal fly ash, calcium oxide, and calcium sulfate was studied under different reaction conditions to elucidate the effects of the reaction temperature, water vapor pressure, and coexistence of NO in a flue gas. The SO2 removal activity increased with an increase in NO concentration up to 500 ppm at 130 °C. The SO2 removal activity increased as the water vapor pressure increased until a monolayer coverage with water molecule is achieved. As the adsorbed water exceeded the monolayer coverage, the SO2 removal activity suddenly decreased and calcium sulfite became the main product instead of calcium sulfate. The NO removal activity increased with an increase in SO2 concentration up to 2000 ppm at 130 °C. The NO removal also increased with an increase in water vapor pressure. The NO removal markedly decreased as the adsorbed water exceeded the monolayer coverage.

Increasing concentrations of nitrogen dioxide pollution in rural Wales

Monitoring of nitrogen dioxide pollution was carried out in rural environments throughout Wales during a 1-year survey to quantify any changes in background concentrations and distribution of the pollutant since an earlier survey in 1986. There were 23 sites in the present survey of which 16 had been monitored during the 1986 survey. The remaining 7 sites were based on moorland in mid-Wales within map squares for which critical loads for soil acidification are expected to be exceeded by the year 2005. All sites were chosen so as to be remote from major local sources of NO 2 and the values obtained were deemed to be minimum concentrations for the different regions. Measurements were made using diffusion tubes which aimed to provide mean concentrations of NO 2 for 2-week exposure periods. Concentrations of NO 2 were found to be higher in the winter months for most sites and this is probably related to a greater use of fossil fuels for heating buildings at this time of year. The exception was the high concentrations of NO 2 in May and June for several sites in North Wales, and in July and August for a site on Mount Snowdon. These high summer concentrations in North Wales are thought to be related to increased traffic associated with tourism. It is apparent that there has been a substantial increase in rural concentrations of NO 2 throughout Wales since the earlier survey of 1986. As an average of all 16 sites used in both surveys, there was a 53% increase in the annual mean concentration of NO 2. Also, it is evident that, since 1986, there has been a substantial increase in the area of south-eastern Wales which has a background level in excess of 10 ppb NO 2 and a notable reduction in land area with concentrations below 6 ppb NO 2 as an annual mean concentration. The possible future impact of increasing rural concentrations of NO 2 on Welsh vegetation is discussed with references to estimates of critical levels of NO 2 for adverse effects on plants.

Reaction of char nitrogen during fluidized bed coal combustion—Influence of nitric oxide and oxygen on nitrous oxide

The conditions that favor the formation of nitrous oxide from char under fluidized bed combustion conditions are shown to be the oxidation of the char to make the nitrogen bound in the heterocyclic rings accessible so that it can react heterogeneously either with oxygen to form NO or with nitric oxide to form N 2O. This was demonstrated by measurement of the gas composition when a batch of coal particles was introduced into a fluidized sand bed electrically heated to 1023 K. Oxygen and nitric oxide were added to the fluidizing helium gas in varying concentrations. N 2O was formed in amounts that increased with increasing NO concentration showing the importance of NO for N 2O formation. The N 2O concentration, however, fell to zero when the O 2 supply was interrupted underlying the essential role of oxygen in freeing the organically bound nitrogen so that it can react with NO to form N 2O.

Removal of nitric oxide from flue gas using mixed oxide sorbents

A scheme for denitrification of the flue gas using regenerable mixed oxide sorbents is proposed in this study. The sorption of nitric oxide with several pure and mixed oxides (Na 2O, Co 2O 4, Fe 2O 3) is studied by thermogravimetric analysis. Various sorbent preparation techniques are evaluated with an objective of increasing the capacity and rate of sorption. A freeze drying technique for preparing highly porous and homogeneous sorbents showed an increased capacity (for NO x ) of 12 g NO/100 g sorbent, double that of the classical precipitation method (6 g NO/100 g sorbent) (AVCO, 1969 [1]). A further increase in capacity (26 g NO/100 g sorbent) was achieved by sorbents prepared by pyrolysis of an organic precursor (citric acid) mixed with the sorbent. The results showed that the Na 2O was the only reacting species. The Co 3O 4 and Fe 2O 3, it was proposed, acted as catalysts, promoting an reaction. Sorbents proved regenerable at 700°C and sorption performance increased up to 400°C. The effect of increasing NO concentration was a linear increase in the initial rate. Sorbent performance was successfully modelled using a pellet grain model. The model takes into account diffusion and structural changes.

Diurnal variations of atmospheric nitric oxide: Ground‐based infrared spectroscopic measurements and their interpretation with time‐dependent photochemical model calculations

Total vertical column amounts of NO have been derived from infrared solar absorption spectra recorded near sunrise and sunset with the 0.01‐cm−1 resolution Fourier transform interferometer at the National Solar Observatory on Kitt Peak (elevation 2095 m, latitude 31.9°N) on February 23, 1981. The results show an increase in NO concentration in the morning, late afternoon values about 40% higher than in the morning, and a decrease in NO concentration prior to sunset. The measured diurnal changes in the total vertical column amount are compared with values obtained from time‐dependent photochemical calculations.

Radiation Treatment of Exhaust Gases, (XIII)

The NH3 consumption by electron beam irradiation has been studied in the moist NO-SO2-O2-N2 mixtures containing NH3. The [NH3] decreased linearly with increasing dose at various NH3 initial concentrations. The G(-NH3) increased with NH3 concentration up to about 500 ppm and was held almost constant G(-NH3)=5.8 at 750 ppm NH3) above it. The rate of the NH3 consumption was about 175 ppm/Mrad above 500 ppm NH3 The G(-NH3) increased with H20 and SO2 concentrations. On the contrary, the G(-NH3) decreased with increasing NO concentration and was hardly affected by the presence of 3–19.5% O2. The G(-NH3) became larger with decreasing temperature in the range of 80–150°C. An apparent activation energy of the NH3 consumption was −3.82 kcal/mol. The NH3 is mainly consumed by the reactions of NH3 with HNO3 and H2SO4, leading to the formations of NH4NO3 and (NH4)2SO4 respectively

Radiation treatment of exhaust gases, (XIII). NH3 consumption in moist NO-SO2-O2-N2 mixtures containing NH3.

The NH3 consumption by electron beam irradiation has been studied in the moist NO-SO2-O2-N2 mixtures containing NH3. The [NH3] decreased linearly with increasing dose at various NH3 initial concentrations. The G(-NH3) increased with NH3 concentration up to about 500 ppm and was held almost constant G(-NH3)=5.8 at 750 ppm NH3) above it. The rate of the NH3 consumption was about 175 ppm/Mrad above 500 ppm NH3 The G(-NH3) increased with H20 and SO2 concentrations. On the contrary, the G(-NH3) decreased with increasing NO concentration and was hardly affected by the presence of 3–19.5% O2. The G(-NH3) became larger with decreasing temperature in the range of 80–150°C. An apparent activation energy of the NH3 consumption was −3.82 kcal/mol. The NH3 is mainly consumed by the reactions of NH3 with HNO3 and H2SO4, leading to the formations of NH4NO3 and (NH4)2SO4 respectively

Effects of gas composition on sparking characteristics of back discharge — preliminary study

Preliminary studies were made on the mode and sparking characteristics of a back discharge occurring in simulated combustion gases with different O 2 and NO concentrations. Special interest was focused on the effect of NO content, which has a very low ionization potential and high electron affinity. Sparking voltages of back discharge were measured for a wide range of gas mean-free-path, which constitutes two different curves according to the discharge mode. The lower one corresponds to the streamer mode, the higher one to the steady-glow mode. The experimental results show that a decrease in O 2 concentration causes a reduction in the intensity of the streamer to turn into the steady-glow mode in the lower mean-free-path region. It is also shown that, for low NO concentration, propagation of the space streamer is enhanced, so that the sparking voltage curves are lowered to a minimum at NO concentration of 670 ppm. Increase in NO concentration beyond this value, however, results in the change of space streamer to surface and the sparking voltage curves begin to increase.

Geographical variations of NO and O3 in the lower stratosphere

Nitric oxide and ozone concentrations in the lower stratosphere have been measured from a high‐altitude research aircraft using in situ measuring techniques. Results of several geographical surveys are presented along with predictions of two two‐dimensional stratospheric models. Meridional and zonal data were obtained in June 1974 and in June, July, and August 1975. At longitudes 122°–158°W the meridional data taken between 5° and 80°N latitude show an increasing NO concentration with latitude, by a factor of 4 at 21‐km altitude and a less marked increase at 18 km. The minimum NO concentration at 21 km is observed at 5°N latitude and is about 6 × 108 cm−3. Zonal data at latitudes 22°–38°N taken from 55° to 176°N longitude show little variation of the NO and O3 concentrations with longitude.

地磁気の劣化が気候変動を招く可能性について

Some of the possible mechanisms for changes in the earth's surface temperature due to a depression of the geomagnetic field are described and commented upon. For example, as a result of the field depression, charged particles, such as galactic and solar cosmic rays, are expected to impinge upon air molecules in the stratosphere, even at lower latitudes. This may lead to an increase in NO concentration, and a subsequent decrease in ozone content in the atmosphere. Depletion of ozone would cause climatic changes to some extent and/or some biological effects.A brief discussion is also given of some effects of magnetospheric deformation.

PRIMARY METHOXY RADICAL FORMATION IN THE REACTION OF METHANOL VAPOR WITH Hg 6(3P1) ATOMS

A study has been made of the decomposition of methanol vapor by Hg 6(3P1) atoms, under static conditions, at 25 °C. A system constructed entirely of quartz was employed to eliminate the dark reaction between methanol vapor and pyrex glass to form trimethyl borate. Emphasis in this investigation was placed on the determination of the nature of the primary processes operative, and to this end, the reaction was studied in some detail in the presence of nitric oxide.For pure methanol, the major primary products were found to be hydrogen and ethylene glycol. The primary quantum yield for hydrogen was 0.46. Minor products of primary origin were formaldehyde (0.01), ethane (0.005), and dimethyl ether (0.006), with the numbers in parentheses showing the primary quantum yields.In the presence of nitric oxide, the major products became methyl nitrite, nitrous oxide, and water. The quantum yield of methyl nitrite rose steadily with increasing NO concentrations. For a 1:1 CH3OH:NO mixture, the primary quantum yield for methyl nitrite was found to be 0.56. The behavior of the reaction in the presence of NO establishes fairly unequivocally that the major primary process involves O—H bond scission to form methoxy radicals and H atoms. These primary radicals then form hydroxymethyl radicals by abstraction reactions with the substrate. The ethylene glycol product arises by recombination of the secondary hydroxymethyl radicals. These conclusions were further substantiated by mass spectrometric analysis of the products of the decomposition of CD3OH. It was shown that CD3OD is a significant product of the reaction.