Low Levels Of NO Research Articles

The effect of SO2 on the sensitive layer of a NOx dosimeter

The accumulating-type or integrating-type NOx sensor works like a dosimeter being well suited for long-term total amount detection of low levels of NO and NO2 while information about the instantaneous NOx concentration is obtained from the signal derivative. A potassium-based lean NOx trap material, known from automotive catalysts, is applied as sensitive material. It accumulates NOx in the form of nitrates and thereby changes its conductivity with the NOx loading state. Since SO2 is known to poison the catalytic properties of LNTs, the effect of SO2 on the sensing characteristics is addressed now. The competition between SO2 and NO2 for the accessible storage sites was found to affect the sensor signal in two ways: due to sulfate formation, the resistance of the LNT material decreases in the presence of SO2 and the accumulating NOx sensing properties are strongly reduced. However, a high reversibility of sulfur poisoning was obtained by desulfurization of the sensitive device at 650°C in H2 containing gas. The results reveal that with the presented setup, SO2 detection is possible with a linear correlation between the conductivity and the exposed SO2 amount. Since at 380°C, the sensitivity to SO2 is about half compared to NOx, cross sensitivities need to be concerned. At higher temperatures nitrates are decomposed and the sensor is selective to SO2.

UP-REGULATING HO-1 IMPROVES POST-INFARCTION HEART FUNCTION OF SPONTANEOUS HYPERTENSIVE RATS VIA ANTI-INFLAMMATION, ANTI-OXIDATION, LOWERING BLOOD GLUCOSE AND IMPROVING ENDOTHELIAL FUNCTION

ObjectivesOur previous results showed that hame oxygenase 1 (HO-1) is involved in the regulation of endothelial function by the modulation of NOS isoforms and control of oxidative stress. HO-1, in...

In vitro immunomodulatory properties of osteogenic and adipogenic differentiated mesenchymal stem cells isolated from three inbred mouse strains

Mesenchymal stem cells (MSCs) are used for cell-based therapies because of their immunomodulatory properties. The immunomodulatory properties of adipogenic (AD) and osteogenic (OS) differentiated adipose tissue-derived MSCs (AD-MSCs) isolated from BALB/c, C57BL/6, and DBA mice were compared. Splenocytes proliferation was suppressed in the presence of AD-MSCs conditioned media in all mice. After OS differentiation, BALB/c AD-MSCs produced higher levels of TGF-β and IL-17 and lower levels of NO than AD-MSCs isolated from C57BL/6 and DBA mice. In addition, OS differentiated AD-MSCs isolated from DBA mice produced lower levels of IL-10 than AD-MSCs isolated from C57BL/6 and DBA mice. After in vitro AD and OD differentiation, AD-MSCs isolated from each mouse produced higher levels of NO and IDO than undifferentiated cells. Additionally, AD-MSCs isolated from C57BL/6 and DBA mice produced higher levels of NO than AD-MSCs isolated from BALB/c mice. Adipose tissue-derived MSCs thus retain their immunomodulatory properties after in vitro OS and AD differentiation in a strain-dependent manner.

Association between T-786C polymorphism of endothelial nitric oxide synthase gene and level of the vessel dilation factor in patients with coronary artery disease

A B S T R A C T Various polymorphisms on endothelial nitric oxide syn thase (eNOs) gene cause reduced production of NO, the endothelial relaxing factor, and may accelerate the process of atherosclerosis. The study designed to investigate the frequency of T -786C polymorphism of the eNOs gene in patients suffering from coronary artery disease (CAD) in north-west of Iran. One hundred twenty subjects including 60 patients with angiographically diagnosed CAD and 60 age and sex matched CAD-free subjects as control were studied. The levels of n itric oxide in the samples were measured with the Griess Method. The genotype studies were carried using allele specific PCR. Comparing with the control, reduced levels of NO were noticed in the patient group (P<0.05). Statistical analysis showed that the genotype TC associated with risk of CAD (OR=2.50, 95% CI: 1.13-5.50, P=0.023). The prevalence of C allele was significantly higher in patients compared to control group (OR=2.04, 95% CI: 1.16-3.57, P=0.013). The low levels of NO and increased frequency of T-786C polymorphism might be a risk factor in progression of coronary artery disease in the studied subjects.

Mixture Preparation Effects on Distributed Combustion for Gas Turbine Applications

Distributed combustion is now known to provide significantly improved performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NOx emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion requires controlled mixing between the injected air, fuel, and hot reactive gasses from within the combustor prior to mixture ignition. The mixing process impacts spontaneous ignition of the mixture to result in improved distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed, or nonpremixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near term goal is to develop a high intensity combustor with ultralow emissions of NOx and CO, and a much improved pattern factor and eventual goal of near zero emission combustor. Experimental results are reported for a cylindrical geometry combustor for different modes of fuel injection with emphasis on the resulting pollutants emission. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra low NOx emissions were found for both the premixed and nonpremixed combustion modes for the geometries investigated here. Results showed very low levels of NO (∼10 ppm) and CO (∼21 ppm) emissions under nonpremixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m3-atm. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion.

Low calorific value fuelled distributed combustion with swirl for gas turbine applications

Distributed combustion offers significant performance improvement with near zero emissions for industrial gas turbine applications. Our efforts to further develop zero emission distributed combustion are explored here by utilizing swirl to the flow. The beneficial aspects of distributed swirl combustion using a cylindrical geometry combustor has shown low emissions of NO and CO, and significantly improved pattern factor using methane as the fuel at high thermal intensity. Biofuels, syngas and landfill gases offer superior use in gas turbine combustion. However, they are characterized by their low calorific value. Results are presented here from the distributed swirl combustor with simulated low calorific value fuels with defined mixture of methane diluted with nitrogen. The calorific value of the fuel obtained provided comparable adiabatic flame temperature and flame speed to those characteristic of low to medium calorific value syngas fuels. The results are compared with the methane fueled combustor. Experimental results from the distributed swirl combustor using methane fuel at an equivalence ratio of 0.6 and a heat release intensity of 27MW/m3-atm showed low levels of NO (∼9PPM) and low CO (∼21PPM) under non-premixed conditions. Novel Premixed Combustion design demonstrated 4PPM of NO and 11PPM of CO. In contrast methane diluted with nitrogen resulted in a dramatic decrease of NO emissions (30–50%), to provide NO emission of 7PPM (for non-premixed case) and 2.8PPM (premixed case), at the same conditions, with minimal impact on CO for all the conditions examined here. The combustor provided no instability or flame flashback at higher fuel flow rates (to maintain the same thermal load as with methane fuel). Results obtained with different calorific value fuels on the emissions of NO and CO, lean stability limit and OH* chemiluminescence are presented. The results showed favorable operation of the distributed swirl combustor for applications with both high and low calorific value fuels, such as, methane, synfuel and landfill gases to power the gas turbines without any combustor modifications.

T-786C Polymorphism of Endothelial Nitric Oxide Synthase Gene and Serum Level of Nitric Oxide in Nonsmoker and Nondiabetic Patients Suffering from Coronary Artery Disease

Background: Various mutations on endothelial nitric oxide synthase (eNOs) gene cause reduced production of NO, the endothelial relaxing factor, and may accelerate the process of atherosclerosis. The study designed to investigate the frequency of T-786C polymorphism of the gene in patients suffering from CAD in North West of Iran. Material and methods: One hundred twenty subjects including 60 patients with angiographically diagnosed CAD and 60 age and sex matched CAD-free subjects as control were studied. The levels of Nitric oxide in the samples were measured with the Griess Method. The genotype studies were carried using allele specific PCR. Results:Comparing with the control reduced levels of NO was noticed in the patient group (P<0.05) and significantly high frequency of eNOs -786C genotype was found in CAD patients (P<0.05). Conclusions:The low levels of NO and increased frequency of T-786C polymorphism might be a risk factor in progression of coronary artery disease in the studied subjects.

A “Sliding Scale Rule” for Selectivity among NO, CO, and O2 by Heme Protein Sensors

Selectivity among NO, CO, and O₂ is crucial for the physiological function of most heme proteins. Although there is a million-fold variation in equilibrium dissociation constants (K(D)), the ratios for NO:CO:O₂ binding stay roughly the same, 1:~10(3):~10(6), when the proximal ligand is a histidine and the distal site is apolar. For these proteins, there is a "sliding scale rule" for plots of log(K(D)) versus ligand type that allows predictions of K(D) values if one or two are missing. The predicted K(D) for binding of O₂to Ns H-NOX coincides with the value determined experimentally at high pressures. Active site hydrogen bond donors break the rule and selectively increase O₂ affinity with little effect on CO and NO binding. Strong field proximal ligands such as thiolate, tyrosinate, and imidazolate exert a "leveling" effect on ligand binding affinity. The reported picomolar K(D) for binding of NO to sGC deviates even more dramatically from the sliding scale rule, showing a NO:CO K(D) ratio of 1:~10(8). This deviation is explained by a complex, multistep process, in which an initial low-affinity hexacoordinate NO complex with a measured K(D) of ≈54 nM, matching that predicted from the sliding scale rule, is formed initially and then is converted to a high-affinity pentacoordinate complex. This multistep six-coordinate to five-coordinate mechanism appears to be common to all NO sensors that exclude O₂ binding to capture a lower level of cellular NO and prevent its consumption by dioxygenation.

Combined fish oil and astaxanthin supplementation modulates rat lymphocyte function

Higher intakes of n-3 polyunsaturated fatty acids that are abundant in marine fishes have been long described as a "good nutritional intervention" with increasing clinical benefits to cardiovascular health, inflammation, mental, and neurodegenerative diseases. The present study was designed to investigate the effect of daily fish oil (FO-10 mg EPA/kg body weight (BW) and 7 mg DHA/kg BW) intake by oral gavage associated with the antioxidant astaxanthin (ASTA-1 mg/kg BW) on the redox metabolism and the functional properties of lymphocytes from rat lymph nodes. This study was conducted by measurements of lymphocyte proliferation capacity, ROS production [superoxide (O₂(•-)) and hydrogen peroxide (H₂O₂)], nitric oxide (NO(•)) generation, intracellular calcium release, oxidative damage to lipids and proteins, activities of major antioxidant enzymes, GSH/GSSG content, and cytokines release. After 45 days of FO + ASTA supplementation, the proliferation capacity of activated T- and B-lymphocytes was significantly diminished followed by lower levels of O₂(•-), H₂O₂ and NO(•) production, and increased activities of total/SOD, GR and GPx, and calcium release in cytosol. ASTA was able to prevent oxidative modification in cell structures through the suppression of the oxidative stress condition imposed by FO. L: -selectin was increased by FO, and IL-1β was decreased only by ASTA supplementation. We can propose that association of ASTA with FO could be a good strategy to prevent oxidative stress induced by polyunsaturated fatty acids and also to potentiate immuno-modulatory effects of FO.

P1-439 Effect of regular exercise on the nitric oxide levels in saliva

IntroductionNitric oxide (NO) regulates blood flow and both muscle contraction and metabolism during exercise. The plasma levels of NO increase after exercise. However, studies that determined the association between the...

No pharmacodynamic (PD) and pharmacokinetic (PK) interaction of riociguat (BAY 63-2521) and aspirin

Objectives Riociguat, an oral soluble guanylate cyclase (sGC) stimulator, is a new candidate for treatment of pulmonary hypertension (PH). Riociguat increases cGMP production through a novel dual mode of action: direct NOindependent stimulation of sGC and increasing sensitivity of sGC to low levels of NO. Another sGC stimulator, BAY 41-2272, has shown anti-platelet activity in animal models, as have BAY 41-2272 and riociguat in washed human platelets, although bleeding has not been noted as an adverse event (AE) in riociguat clinical studies [1,2]. As riociguat and aspirin are likely to be used together in PH, it was of interest to investigate potential PD and PK interactions.

Distributed swirl combustion for gas turbine application

Colorless distributed combustion (CDC) has been shown to provide significant improvement in gas turbine combustor performance. Colorless distributed combustion with swirl is investigated here to develop ultra-low emissions of NO and CO, and significantly improved pattern factor. Experimental investigations have been performed using a cylindrical geometry combustor with swirling air injection and axial hot gas exit stream from the combustor. Air was injected tangentially to impart swirl to the flow inside the combustor. The results obtained from the combustor have demonstrated very low levels of NO (∼3 PPM) and CO (∼70 PPM) emissions at an equivalence ratio of 0.7 and a high heat release intensity of 36 MW/m 3-atm under non-premixed combustion. To further simulate gas turbine operating conditions, inlet air to the combustor was preheated to 600 K temperature and the combustor operated at 2 atm pressure. Results showed very low levels of CO (∼10 PPM) but the NO increased somewhat to ∼10 PPM at an equivalence ratio of 0.5 and heat release intensity of 22.5 MW/m 3-atm under non-premixed combustion conditions. For premixed combustion, the combustor demonstrated low levels of both NO (5 PPM) and CO (8 PPM) at an equivalence ratio of 0.6 and a heat release intensity of 27 MW/m 3-atm. Results are reported at different equivalence ratios on the emission of NO and CO, lean stability limit and OH * chemiluminescence. These results suggest that further performance improvement can be achieved with improved fuel mixture preparation prior to the ignition of fuel at higher operational pressures using swirling combustor design for our quest to develop ultra low emission high intensity combustor for gas turbine application.

Swirling distributed combustion for clean energy conversion in gas turbine applications

Distributed combustion provides significant performance improvement of gas turbine combustors. Key features of distributed combustion includes uniform thermal field in the entire combustion chamber, thus avoiding hot-spot regions that promote NO x emissions (from thermal NO x ) and significantly improved pattern factor. Rapid mixing between the injected fuel and hot oxidizer has been carefully explored for spontaneous ignition of the mixture to achieve distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed or non-premixed modes of combustor operation with sufficient entrainment of hot and active species present in the flame and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here for our quest to explore the beneficial aspects of such flows on clean combustion in simulated gas turbine combustion conditions. The goal is to develop high intensity combustor with ultra low emissions of NO and CO, and much improved pattern factor. Experimental results are reported from a cylindrical geometry combustor with different modes of fuel injection and gas exit stream location in the combustor. In all the configurations, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra-low NO x emissions were found for both the premixed and non-premixed combustion modes for the geometries investigated here. Swirling flow configuration, wherein the product gas exits axially resulted in characteristics closest to premixed combustion mode. Change in fuel injection location resulted in changing the combustion characteristics from traditional diffusion mode to distributed combustion regime. Results showed very low levels of NO (∼3 PPM) and CO (∼70 PPM) emissions even at rather high equivalence ratio of 0.7 at a high heat release intensity of 36 MW/m 3-atm with non-premixed mode of combustion. Results are also reported on lean stability limit and OH * chemiluminescence under both premixed and non-premixed conditions for determining the extent of distribution combustion conditions.

Sickle cell anemia pathophysiology: Back to the data

Sickle cell anemia pathophysiology: Back to the data

Respiratory Health among Korean Pupils in Relation to Home, School and Outdoor Environment

There are few studies about school-environment in relation to pupils' respiratory health, and Korean school-environment has not been characterized. All pupils in 4th grade in 12 selected schools in three urban cities in Korea received a questionnaire (n = 2,453), 96% participated. Gaseous pollutants and ultrafine particles (UFPs) were measured indoors (n = 34) and outdoors (n = 12) during winter, 2004. Indoor dampness at home was investigated by the questionnaire. To evaluate associations between respiratory health and environment, multiple logistic- and multi-level regression models were applied adjusting for potential confounders. The mean age of pupils was 10 yr and 49% were boys. No school had mechanical ventilation and CO2-levels exceeded 1,000 ppm in all except one of the classrooms. The indoor mean concentrations of SO2, NO2, O3 and formaldehyde were 0.6 µg/m3, 19 µg/m3, 8 µg/m3 and 28 µg/m3, respectively. The average level of UFPs was 18,230 pt/cm3 in the classrooms and 16,480 pt/cm3 outdoors. There were positive associations between wheeze and outdoor NO2, and between current asthma and outdoor UFPs. With dampness at home, pupils had more wheeze. In conclusion, outdoor UFPs and even low levels of NO2 may adversely contribute to respiratory health in children. High CO2-levels in classrooms and indoor dampness/mold at home should be reduced.

Expression of Constitutive Nitric Oxide Synthase Isoforms in Varicose Vein Wall; Preliminary Results

There are conflicting findings in literature about the structural changes of the primary varicose veins. NO (a potent vasodilatator) is synthesized by nitric oxide synthase (NOS). From 3 known NOS isoforms the two are constitutional: eNOS (endothelial NOS) and nNOS (neuronal NOS). 10 varicose and 10 control vein samples were processed by standard light microscopy and immuno-histochemica techniques using rabbit polyclonal antibodies against eNOS and nNOS. Antibodies expression was evaluated semiquantitatively and proved morphometrically by 2D-image analysis. total area of NOS isoforms expressions was determined by color analysis and color digital subtraction. The results showed discontinuous and significantly lower expression of both NOS isoforms the in the tunica media of varicose veins compared with the control group. For the statistical analysis the unpaired t-test was used. Our results suppose lower NO levels in varicose vein wall, deducing that varicose dilatation is due to other mechanism, and they contradict the results of previously published similar works.

Emission of impinging swirling and non-swirling inverse diffusion flames

The overall pollutants emission from impinging swirling and non-swirling inverse diffusion flames (IDFs) was evaluated quantitatively by the ‘hood’ method. The results of in-flame volumetric concentrations of CO and NO x and overall pollutants emission of CO and NO x in terms of emission index were reported. The in-flame volumetric concentrations of CO and NO x were measured through a small hole drilled on the impingement plate. In comparison with the corresponding open flame, the CO and NO x concentrations for the impinging swirling IDF are greatly lowered due to the entrainment of much more ambient air which is related to the increased flame surface area. For the swirling and non-swirling IDFs, the EINO x increases as the nozzle-to-plate distance ( H) increases because more space is available for the development of the high-temperature zone in the free jet portion of the impinging flame, which favors the thermal NO formation. The variation of EICO with H is different for the impinging swirling and non-swirling IDFs because they have different flame structures. For both flames, the EICO is high when their main reaction zone or inner reaction cone is impinged and quenched by the copper plate. The parameters of air jet Reynolds number, overall equivalence ratio and nozzle-to-plate distance have significant influence on the overall pollutants emission of the impinging swirling and non-swirling IDFs and the comparison shows that the swirling IDF emits less NO x and CO under most of the experimental conditions tested. Furthermore, it is found that compared with the open flames, the impinging flames emit lower level of NO x and higher level of CO.

A comparison of the thermal, emission and heat transfer characteristics of swirl-stabilized premixed and inverse diffusion flames

Abstract Two swirl-stabilized flames, a premixed flame (PMF-s) and an inverse diffusion flame (IDF-s), were investigated experimentally in order to obtain information on their thermal, emission and heat transfer characteristics. The two flames, having different global air/fuel mixing mechanisms, were compared under identical air and fuel flow rates. Results showed that the two flames have similar visual features such as flame shape, size and structure because the Reynolds number and the swirl number which are important parameters representative of the aerodynamic characteristics of a swirling jet flow, are almost the same for the two flames. The minor dissimilarity in flame color and flame length indicates that the IDF-s is more diffusional. Both the PMF-s and IDF-s are stabilized by the internal recirculation zone (IRZ) and the IDF-s is more stable. Flame temperature is uniformly distributed in the IRZ due to the strong mixing caused by flow recirculation. The highest flame temperature is achieved at the main reaction zone and it is higher for the PMF-s due to more rapid and localized heat release. For the IDF-s, the thermal NO mechanism dominates the NO x formation. For the PMF-s, both the thermal and prompt mechanisms tend to play important roles in the global NO x emission under rich conditions. The comparison of EINO x and EICO shows that the PMF-s has lower level of NO x emission under lean combustion and lower level of CO emission under all conditions. The reason is that the air/fuel premixing in the PMF-s significantly enhances the mixedness of the supplied air/fuel mixture. The analysis of the behaviors of the impinging PMF-s and IDF-s heat transfer reveals that because the PMF-s has more rapid and localized heat release at the main reaction zone, the peak heat flux is higher than that of the IDF-s and the IDF-s has more uniform heating effect. A comparison of the overall heat transfer rates shows that, due to more complete combustion, the PMF-s has higher overall heat transfer.

Fundamental investigation of NO x formation during oxy-fuel combustion of pulverized coal

NO x formation was measured during combustion of pulverized coals and pulverized coal char in N 2 and CO 2 environments under isothermal and nearly constant oxygen conditions (i.e. using dilute coal loading). Three different oxygen concentrations (12% O 2, 24% O 2, and 36% O 2) and two representative US coals were investigated, at a gas temperature of 1050 °C. To investigate the importance of NO reburn reactions, experiments were also performed with an elevated concentration (550 ppm) of NO in the gases into which the coal was introduced. For low levels of background NO, the fractional fuel-nitrogen conversion to NO x increases dramatically with increasing bath gas oxygen content, for both N 2 and CO 2 environments, though the fuel conversion is generally lower in CO 2 environments. Char N conversion is lower than volatile N conversion, especially for elevated O 2 concentrations. These results highlight the importance of the volatile flame and char combustion temperatures on NO x formation. For the high background NO x condition, net NO x production is only observed in the 36% O 2 environment. Under these dilute loading conditions, NO reburn is found to be between 20% and 40%, depending on the type of coal, the use of N 2 or CO 2 diluent, the bulk O 2 concentration, and whether or not one considers reburn of volatile-NO x . This dataset provides a unique opportunity to understand and differentiate the different sources and sinks of NO x under oxy-fuel combustion conditions.

HOx Regeneration in the Oxidation of Isoprene III: Theoretical Study of the key Isomerisation of the Z‐δ‐hydroxy‐peroxy Isoprene Radicals

As a sequel to our communication on a proposed new isoprene oxidation mechanism aiming to rationalize the unexpectedly high OH and HO(2) levels observed in isoprene-rich areas (J. Peeters, T. L. Nguyen, L. Vereecken, Phys. Chem. Chem. Phys. 2009, 11, 5935), we report herein the detailed quantum chemical and statistical kinetics characterization of the crucial 1,6-H shifts in the two Z-δ-hydroxy-peroxy radicals from isoprene. Geometries, energies and vibration frequencies of all conformers of the reactant radicals and transition states are computed at the B3LYP/6-31+G(d,p) level of theory and the energies of the lowest-lying conformers are then refined at various higher levels of theory, including CBS-QB3, IRCMax(CBS-QB3//B3LYP) and CBS-APNO. The rate coefficients over a wide temperature range are calculated using multi-conformer transition state theory with WKB tunneling factors evaluated for the barrier shape found by CBS-QB3//B3LYP IRC analyses. The WKB tunneling factors for these allyl-stabilisation-assisted reactions are about 25 at ambient temperatures. The rate coefficients can be represented by Arrhenius expressions over the 250-350 K range: k(T)=1.4×10(9) exp(-6380/T) s(-1) for the Z-1-OH-4-OO(·)-isoprene radical, and k(T)=0.72×10(9) exp(-5520/T) s(-1) for Z-1-OH-4-OO(·)-isoprene. With the k(1,6-H) of order 1 s(-1) at ambient temperatures, these isomerisations can compete with and even outrun the traditional peroxy reactions at low and moderate NO levels. The importance of these reactions as key processes in the newly proposed, OH-regenerating isoprene oxidation scheme is discussed.