Low Concentrations Of NO Research Articles

Neem (Azadirachta indica A. Juss) Oil to Tackle Enteropathogenic Escherichia coli.

Neem (Azadirachta indica A. Juss) oil (NO) was assayed against forty-eight isolates of Escherichia coli by standardised disc diffusion test and microdilution test. By molecular biology characterization, fourteen isolates resulted in diarrheagenic E. coli with sixteen primer pairs that specifically amplify unique sequences of virulence genes and of 16S rRNA. The NO showed biological activity against all isolates. The bacterial growth inhibition zone by disc diffusion method (100 µL NO) ranged between 9.50 ± 0.70 and 30.00 ± 1.00 mm. The antibacterial activity was furthermore determined at lower NO concentrations (1 : 10–1 : 10,000). The percent of growth reduction ranged between 23.71 ± 1.00 and 99.70 ± 1.53. The highest bacterial growth reduction was 1 : 10 NO concentration with 50 µL of bacterial suspension (ca. 1 × 106 CFU/mL). There is significant difference between the antibacterial activities against pathogenic and nonpathogenic E. coli, as well as NO and ciprofloxacin activities. Viable cells after the different NO concentration treatments were checked by molecular biology assay using PMA dye. On the basis of the obtained results, NO counteracts E. coli and also influences the virulence of E. coli viable cells after NO treatment. The NO metabolomic composition was obtained using fingerprint HPTLC.

Nanoflower-like weak crystallization manganese oxide for efficient removal of low-concentration NO at room temperature

The efficient removal of low-concentration nitric oxide at room temperature from a semi-closed space is becoming a crucial but challenging issue in the context of increasingly serious air pollution.

Mesostructured amorphous manganese oxides: facile synthesis and highly durable elimination of low-concentration NO at room temperature in air.

At a high space velocity of 120 000 mL g(-1) h(-1) and a relative humidity of 50-90%, 98% removal of 10 ppm NO has been achieved for over 237 h and no sign of deactivation was observed with mesostructured amorphous manganese oxides (AMO), due to the prevention of the catalyst active sites from deactivation.

NO2 Sensing Properties of Thermally or UV Activated In2O3 Nano-octahedra

In the present work, we have synthesized single crystalline In2O3 octahedra via a vapour phase transport at high temperatures over Si/SiO2 substrates. Gas sensing measurements (NO2) have been performed under temperature variations and UV irradiation. Optimum working conditions for each case have been found. A comparison between nanostructured In2O3 and commercial In2O3 powder has been performed in order to show the advantages of using a nanostructured based sensor. As a result, the detection of low concentrations of NO2 (50 ppb) has found to be possible with sensitivities for higher concentrations comparable to those shown in recent publications.

Analysis of Air Purification in a Woodland by Field Observation and Wind Tunnel Experiment

As part of a comprehensive study of the harmonious coexistence between man and nature focusing on woodland, we evaluated the role of the Ryukoku forest in air purification. The Ryukoku forest, located at Seta Hill in Shiga Prefecture, Japan, is composed of a mixture of conifer and deciduous trees. There are two mechanisms in purifying forest air: the deposition of air pollutants onto leaf surfaces and the effect of a tree wind break (air pollutant break). We measured the vertical distributions of nitrogen dioxide (NO2) concentration inside and outside the Ryukoku forest using passive samplers attached to a 25-m-tall observation tower and to the neighbouring university campus buildings, respectively. Wind tunnel experiments that treat atmospheric dispersion in model trees but cannot consider the effect of deposition have been conducted to evaluate the effect of a tree wind break. The observed NO2 concentrations in the Ryukoku forest showed a 5 - 20 percent decrease depending on the season towards the forest floor from the top of the canopy. Within the forest canopy layer, the average NO2 concentration was approximately 30 percent lower than that outside the forest. The results of the wind tunnel experiment showed a similar decrease in the concentration of air pollutants inside the forest. However, the decrease in the concentration of air pollutants towards the forest floor from the top of the canopy was not observed in the wind tunnel experiment. It is deduced that the low NO2 concentration inside the forest compared with that outside is mainly due to tree wind break effect and that the variation in NO2 concentration with height from the forest floor is mainly due to the deposition of air pollutants onto leaf surfaces.

최근(2010~2012년) 제주지역 대기환경 변화에 관한 기상특성 분석

The characteristics of meteorological conditions related to changes in atmospheric environment on Jeju Island were investigated during recent years (2010-2012). This analysis was performed using the hourly observed data of meteorological variables (air temperature, wind speed and direction) and air pollutants (<TEX>$O_3$</TEX>, <TEX>$PM_{10}$</TEX>, <TEX>$SO_2$</TEX>, <TEX>$NO_2$</TEX>, and CO). Out of 5 pollutants, <TEX>$O_3$</TEX> and <TEX>$PM_{10}$</TEX> concentrations have frequently exceeded national environmental standards in the study area during the study period, with relatively higher concentrations than the others. The concentrations of <TEX>$O_3$</TEX> and <TEX>$PM_{10}$</TEX> in 2010 and 2011 were somewhat higher than those in 2012, and their highest concentrations were mostly observed in spring followed by fall. Nighttime <TEX>$O_3$</TEX> concentrations (with relatively high concentration levels) were almost similar to its daytime concentrations, due to less <TEX>$O_3$</TEX> titration by very low NO concentrations in the target area and in part to <TEX>$O_3$</TEX> increase resulting from atmospheric transport processes. The transport effect related to the concentration variations of <TEX>$O_3$</TEX> and <TEX>$PM_{10}$</TEX> was also clarified in correlation between these pollutants and meteorological variables, e.g. the high exceedance frequency of concentration criteria with strong wind speed and the high concentrations with the westerly/northwesterly winds (e.g., transport from the polluted regions of China). The overall results of this study suggest that the changes in atmospheric environment in the study area were likely to be caused by the transport effect (horizontal and vertical) due to the meteorological conditions rather than the contribution of local emission sources.

Predicting aquatic macrophyte occurrence in soft-water oligotrophic lakes (Pyrenees mountain range)

Distribution of aquatic macrophytes in lakes is related to geographical, morphological, catchment and water chemistry variables as well as human impacts, which modify the original environment. Here, we aim at building statistical models to establish the ecological niches of 11 aquatic macrophytes (10 different phanerogams and the genus Nitella ) from oligotrophic soft-water lakes and infer their ecological requirements and environmental constraints at the southernmost limit of their distribution. Macrophyte occurrence and environmental variables were obtained from 86 non-exploited oligotrophic soft-water lakes from the Pyrenees (Southern Europe; 42o50´N, 1o00´E); macrophytes inhabited 55 of these lakes. Optimum ranges and macrophyte occurrence were predicted in relation to 18 geographical, morphological, catchment and water chemistry variables using univariate and multivariate logistic models. Lakes at low altitude, in vegetated catchments and with low water concentration of NO 3 - and SO 4 -2 , were the most suitable to host macrophytes. In general, individual species of aquatic macrophytes showed clear patterns of segregation along conductivity and pH gradients, although the specific combination of variables selected in the best models explaining their occurrence differed among species. Based on the species response to pH and conductivity, we found Isoetes lacustris have its optimum in waters with low conductivity and pH (i.e. negative monotonic response). In contrast, Callitriche palustris , Ranunculus aquatilis , Subularia aquatica , Nitella spp., and Myriophyllum alterniflorum showed an optimum at intermediate values ( i.e. unimodal response), whereas Potamogeton berchtoldii , Potamogeton alpinus , and Ranunculus trichophyllus as species had their optimum at relatively high water pH and conductivity (i.e. positive monotonic response). This pattern has been observed in other regions for the same species, although with different optima and tolerance ranges. The parsimonious models developed here allowed us to explore niche requirements for each species and to predict the occurrence of macrophytes and of individual species in any particular lake by using only few, easily measured environmental variables. This is of interest to forecast possible changes related to global change and to assist managers in making conservation, management and restoration decisions.

A facile ultrasonic process for the preparation of Co3O4 nanoflowers for room-temperature removal of low-concentration NOx

Co3O4 nanoflowers with high surface areas were synthesized with a facile template-free ultrasonic process and showed high performance on the removal of low-concentration (10ppm) NO at room temperature. By doping Mg2+ in the Co3O4 nanoflowers, improved performances of about 9h for above 50% NO removal were obtained.

SiC Foams Decorated with SnO2 Nanostructures for Room Temperature Gas Sensing

Cell walls of the commercial silicon carbide (SiC)‐based foams were decorated by one‐dimensional tin dioxide (SnO2) nanostructures. Thermal evaporation of SnO2 powder with the assistance of a Au catalyst in inert atmosphere caused the formation of SnO2 nanobelts on the pore surfaces. The room temperature (RT) ammonia (NH3) and nitrogen dioxide (NO2) gas sensing behaviors were investigated systematically in both dry and humid air atmosphere with/without UV activation. The results were compared to those for bare SnO2 and SiC. It was shown that SiC/SnO2 composite was efficient to detect low concentration of NH3 (10–50 ppm) and NO2 (1–5 ppm) under humid air and UV activation at RT.

부산지역 오존농도의 주말 효과 특성

This study analyzes the characteristics of ozone weekend effect(OWE) in Busan. concentration on Sunday was over 10% higher than that on weekdays in all areas except for Kwangbokdong, Taejongdae, and Joadong. Such a difference was higher in the industrial area than in the residential area. generation was facilitated by the decrease in emission on Sunday in VOC-limited regime where the VOC/ ratio is low. Low NO concentration in the Sunday morning decreased inhibition of . NO- crossover time on Sunday was shorter than that on weekdays which in turn extended the accumulated duration of . Future studies can include whether the entire Busan is VOCS-limited or the coastal area is VOCS-limited while the inland area is -limited.

High-performance chemical sensing using Schottky-contacted chemical vapor deposition grown monolayer MoS2 transistors.

Trace chemical detection is important for a wide range of practical applications. Recently emerged two-dimensional (2D) crystals offer unique advantages as potential sensing materials with high sensitivity, owing to their very high surface-to-bulk atom ratios and semiconducting properties. Here, we report the first use of Schottky-contacted chemical vapor deposition grown monolayer MoS2 as high-performance room temperature chemical sensors. The Schottky-contacted MoS2 transistors show current changes by 2-3 orders of magnitude upon exposure to very low concentrations of NO2 and NH3. Specifically, the MoS2 sensors show clear detection of NO2 and NH3 down to 20 ppb and 1 ppm, respectively. We attribute the observed high sensitivity to both well-known charger transfer mechanism and, more importantly, the Schottky barrier modulation upon analyte molecule adsorption, the latter of which is made possible by the Schottky contacts in the transistors and is not reported previously for MoS2 sensors. This study shows the potential of 2D semiconductors as high-performance sensors and also benefits the fundamental studies of interfacial phenomena and interactions between chemical species and monolayer 2D semiconductors.

Light-activated gas sensing of Bi2O3-core/ZnO-shell nanobelt gas sensors

Bi2O3 is highly sensitive to low concentrations of NO2 in ambient air but almost insensitive to most other common gasses. On the other hand, its sensing performance and detection limit need to be improved before it can be used more widely. This study examined the NO2 gas sensing properties of β-Bi2O3 nanobelts encapsulated with ZnO. Bi2O3-core/ZnO-shell nanobelts were fabricated using a two-step process involving the thermal evaporation of Bi powders and the atomic layer deposition of ZnO. The core–shell nanobelts were 100 to 300nm in diameter with lengths ranging from a few tens to a few hundreds of micrometers with a mean shell layer thickness of ~20nm. Multiple networked Bi2O3-core/ZnO-shell nanobelt sensors showed responses of 113–198% and 227–665% to 1–5ppm NO2 at room temperature in the dark and under UV illumination, respectively. These responses were 1.2–1.9 and 2.4–6.3 times larger, respectively, than those of pristine Bi2O3 nanobelt sensors at 1–5ppm NO2. The underlying mechanism of the enhanced response of the Bi2O3 nanobelts to NO2 gas by ZnO encapsulation and UV irradiation is discussed.

Design, synthesis and biological evaluation of D-ring opened galantamine analogs as multifunctional anti-Alzheimer agents

Facing the multifactorial nature of Alzheimer's disease, twelve dibenzofuran/carbazole derivatives, which can be considered as the D-ring opened analogs of galantamine, have been designed and synthesized as multifunctional anti-Alzheimer agents. In vitro tests revealed that compounds 3 and 5, which bear a nitrate moiety in the molecule, showed a potent inhibition activity towards AChE and compound 3 showed a good Aβ42 aggregation inhibitory activity. Moreover, 3 and 5 could also release a relative low concentration of NO in vitro and they did not show toxicity to neuronal cells, while exerted a neuroprotective effect against the Aβ-induced toxicity. More importantly, compound 3 showed a significant spatial memory improving effect in vivo, and a good safety in the ex vivo toxicity study.

Mechanism of NO-SCR by methane over Co,H-ZSM-5 and Co,H-mordenite catalysts

Results of X-ray photoelectron spectroscopic (XPS) examination and temperature-programmed reduction measurements by H2 (H2-TPR) showed that the Co-zeolite catalysts, which were found most active in the selective catalytic reduction of NO by methane to N2 in the presence of excess O2 (NO-SCR), contain both Co2+/[Co-OH]+/H+ exchange cations, Co-oxo species and cobalt oxide clusters. Using operando Diffuse Reflectance Infrared Fourier Transform Spectroscopic method (DRIFTS method) the NO-SCR reaction was shown to proceed in consecutive steps via bifunctional mechanism over active sites (i) promoting the oxidation of NO by O2 to NO2 (NO-COX reaction), and sites (ii) whereon disproportionation and charge separation of 2NO2 generates activated surface intermediate NO3−/NO+ ion pair. Latter process was found to require Co2+ zeolite cations. The NO-COX reaction was shown to proceed over Co-oxo species and cobalt oxide, if present, and also over Brønsted acid sites but at a significantly lower rate. In the reaction of methane and the NO3−/NO+ ion pair CO2, H2O, and N2 was formed and the active Co2+ sites were recovered (CH4/NO-SCR reaction). The surface concentration of the NO3−/NO+ ion pair must have been controlled by the relative magnitude of the apparent rate constants of the consecutive NO-COX and CH4/NO-SCR reactions. Below about 700K reaction temperature latter reaction governed the rate of the consecutive NO reduction process. Above about 700K combustion became the main reaction of methane. Because of the low equilibrium NO2 concentration at these high temperatures the NO-COX reaction took over the control over the rate of the NO-SCR process. Under steady state reaction conditions a temperature-dependent fraction of the Co2+ active sites was always poisoned by adsorbed H2O formed in the CH4 oxidation reaction.

Indoor Pollutant Exposures Modify the Effect of Airborne Endotoxin on Asthma in Urban Children

The effect of endotoxin on asthma morbidity in urban populations is unclear. To determine if indoor pollutant exposure modifies the relationships between indoor airborne endotoxin and asthma health and morbidity. One hundred forty-six children and adolescents with persistent asthma underwent repeated clinical assessments at 0, 3, 6, 9, and 12 months. Home visits were conducted at the same time points for assessment of airborne nicotine, endotoxin, and nitrogen dioxide (NO2) concentrations. The effect of concomitant pollutant exposure on relationships between endotoxin and asthma outcomes were examined in stratified analyses and statistical models with interaction terms. Both air nicotine and NO2 concentrations modified the relationships between airborne endotoxin and asthma outcomes. Among children living in homes with no detectable air nicotine, higher endotoxin was inversely associated with acute visits and oral corticosteroid bursts, whereas among those in homes with detectable air nicotine, endotoxin was positively associated with these outcomes (interaction P value = 0.004 and 0.07, respectively). Among children living in homes with lower NO2 concentrations (<20 ppb), higher endotoxin was positively associated with acute visits, whereas among those living in homes with higher NO2 concentrations, endotoxin was negatively associated with acute visit (interaction P value = 0.05). NO2 also modified the effect of endotoxin on asthma symptom outcomes in a similar manner. The effects of household airborne endotoxin exposure on asthma are modified by coexposure to air nicotine and NO2, and these pollutants have opposite effects on the relationships between endotoxin and asthma-related outcomes.

On mechanisms of formation of environmentally harmful compounds in homogeneous combustors

A kinetic model is developed for calculating the emission characteristics of homogeneous combustors using methane and synthesis gas (syngas) as a fuel. The model is validated over a large set of experimental data on concentrations of NO, CO, and OH in laminar flames and in the Bunsen burner and on concentrations of OH, NO, and CO in a homogeneous combustor operating on a mixture of syngas with air. At an identical temperature of combustion products, i.e., identical thermodynamic efficiency, the combustor operating on syngas is demonstrated to emit a greater amount of NO, CO, and CO2, as compared with the combustor operating on methane. Though the use of syngas allows one to organize stable combustion of ultralean mixtures and to obtain extremely low concentrations of NO and CO at the combustor exit (≈1–3 ppm), the amount of CO2 in the exhaust of even extremely lean mixtures (α ≈ 3) is appreciably greater than that in the case of using methane.

Effects of local, synoptic and large‐scale climate conditions on daily nitrogen dioxide concentrations in Auckland, New Zealand

ABSTRACTAs with many urban centres around the world, nitrogen dioxide (NO2) is of concern in Auckland, New Zealand because of its possible link to respiratory and heart disease. It has also been associated with the frequent occurrence of brown haze in the region. This article examines quantitatively the differential effects of the local‐, synoptic‐ and large‐scale (El Niño‐Southern Oscillation—ENSO, Southern Annular Mode—SAM) climate conditions on daily NO2 concentrations in urban Auckland under the framework of generalized linear models. The local meteorology is found to be the most important driver of the daily NO2 concentrations in Auckland, primarily through the coupling of local‐scale atmospheric flow and stability conditions with local emissions and chemical processes. Both the synoptic circulation and large‐scale climate modes play significant roles in determining the local air pollution. Synoptic circulations, even after controlling for the local meteorological conditions, modulate the daily NO2 at a regional level via two main mechanisms: (1) blocking types facilitate the transport of clean oceanic air over the Auckland landmass, leading to generally low NO2 concentrations; (2) westerly cyclonic types contribute to region‐wide increases in NO2 concentrations due to the enhanced mixing‐in and/or downward transport of ozone (O3) from the upper troposphere or stratosphere. The large‐scale climate modes, ENSO and SAM, modulate the regional air quality through changing the frequency of occurrence and air‐mass characteristics of synoptic systems over New Zealand. Overall, this study demonstrates a holistic approach to understand how atmospheric circulations of different scales affect local air quality and thus provides useful information for the formulation of effective public health management and planning strategies in response to future climate variability and change.

Flexible NO2gas sensor using multilayer graphene films by chemical vapor deposition

We report a highly sensitive NO2 gas sensor based on multi-layer graphene (MLG) films synthesized by a chemical vapor deposition method on a microheater-embedded flexible substrate. The MLG could detect low-concentration NO2 even at sub-ppm (<200 ppb) levels. It also exhibited a high resistance change of ~6% when it was exposed to 1 ppm NO2 gas at room temperature for 1 min. The exceptionally high sensitivity could be attributed to the large number of NO2 molecule adsorption sites on the MLG due to its a large surface area and various defect-sites, and to the high mobility of carriers transferred between the MLG films and the adsorbed gas molecules. Although desorption of the NO 2 molecules was slow, it could be enhanced by an additional annealing process using an embedded Au microheater. The outstanding mechanical flexibility of the graphene film ensures the stable sensing re sponse of the device under extreme bending stress. Our large-scale and easily reproducible MLG films can provide a proof-of-concept for future flexible NO 2 gas sensor devices.

Low Concentrations of Hydrogen Peroxide or Nitrite Induced of Paracoccidioides brasiliensis Cell Proliferation in a Ras-Dependent Manner

Paracoccidioides brasiliensis, a causative agent of paracoccidioidomycosis (PCM), should be able to adapt to dramatic environmental changes inside the infected host after inhalation of air-borne conidia and transition to pathogenic yeasts. Proteins with antioxidant functions may protect fungal cells against reactive oxygen (ROS) and nitrogen (RNS) species generated by phagocytic cells, thus acting as potential virulence factors. Ras GTPases are involved in stress responses, cell morphology, and differentiation in a range of organisms. Ras, in its activated form, interacts with effector proteins and can initiate a kinase cascade. In lower eukaryotes, Byr2 kinase represents a Ras target. The present study investigated the role of Ras in P. brasiliensis after in vitro stimulus with ROS or RNS. We have demonstrated that low concentrations of H2O2 (0.1 mM) or NO2 (0.1–0.25 µM) stimulated P. brasiliensis yeast cell proliferation and that was not observed when yeast cells were pre-incubated with farnesyltransferase inhibitor. We constructed an expression plasmid containing the Byr2 Ras-binding domain (RBD) fused with GST (RBD-Byr2-GST) to detect the Ras active form. After stimulation with low concentrations of H2O2 or NO2, the Ras active form was observed in fungal extracts. Besides, NO2 induced a rapid increase in S-nitrosylated Ras levels. This alternative posttranslational modification of Ras, probably in residue Cys123, would lead to an exchange of GDP for GTP and consequent GTPase activation in P. brasiliensis. In conclusion, low concentrations of H2O2 or NO2 stimulated P. brasiliensis proliferation through Ras activation.

CO and NO2 Selective Monitoring by ZnO-Based Sensors

ZnO nanomaterials with different shapes were synthesized, characterized and tested in the selective monitoring of low concentration of CO and NO2 in air. ZnO nanoparticles (NPs) and nanofibers (NFs) were synthesized by a modified sol-gel method in supercritical conditions and electrospinning technique, respectively. CO and NO2 sensing tests have demonstrated that the annealing temperature and shape of zinc oxide nanomaterials are the key factors in modulating the electrical and sensing properties. Specifically, ZnO NPs annealed at high temperature (700 °C) have been found sensitive to CO, while they displayed negligible response to NO2. The opposite behavior has been registered for the one-dimensional ZnO NFs annealed at medium temperature (400 °C). Due to their adaptable sensitivity/selectivity characteristics, the developed sensors show promising applications in dual air quality control systems for closed ambient such as automotive cabin, parking garage and tunnels.