Ambient Oxygen Pressure Research Articles

Ambient Species Density and Gas Temperature Radial Profiles Derived from a Schlieren Technique in a Low-Frequency Non-thermal Oxygen Plasma Jet

A quantitative interpretation of the schlieren technique applied to a non-thermal atmospheric-pressure oxygen plasma jet driven at low-frequency (50 Hz) is reported. The jet was operated in the turbulent regime with a hole-diameter based Reynolds number of 13,800. The technique coupled to a simplified kinetic model of the jet effluent region allowed deriving the temporally-averaged values of the gas temperature of the jet by processing the gray-level contrast values of digital schlieren images. The penetration of the ambient air into the jet due to turbulent diffusion was taken into account. The calibration of the optical system was obtained by fitting the sensitivity parameter so that the oxygen fraction at the nozzle exit was unity. The radial profiles of the contrast in the discharge off case were quite symmetric on the whole outflow, but with the discharge on, relatively strong departures from the symmetry were evident in the near field. The time-averaged gas temperature of the jet was relatively high, with a maximum departure of about 55 K from the room temperature; as can be expected owing to the operating molecular gas. The uncertainty in the temperature measurements was within 6 K, primarily derived from errors associated to the Abel inversion procedure. The results showed an increase in the gas temperature of about 8 K close to the nozzle exit; thus suggesting that some fast-gas heating (with a heating rate ~0.3 K/μs) still occurs in the near field of the outflow.

Prolonged transport of rainbow trout fingerlings in plastic bags: Optimization of hauling conditions based on survival and water chemistry

Breeding and seed production of rainbow trout is limited to government operated hatcheries in India, which often necessitates the transport of stock size fish to geographically distant farm units. Therefore, the present field study was carried out to derive suitable conditions for prolonged transport of rainbow trout fingerlings in plastic bags. Critical factors such as starvation period (24 vs. 72h), loading density (13.3, 26.7 and 40g/L), addition of salt (0, 3 and 6g/L) and mild sedation with clove oil (0, 10, 20 and 40μL/L) were evaluated based on fish survival and changes in total ammonia nitrogen (TAN), un-ionized ammonia (NH3-N), CO2 and pH of the transport water. The experimental fish (mean weight 4±2g and mean total length 5.5±1.5cm) were packed in plastic bags containing 6L of stream water and 12L of pressurized oxygen atmosphere, and transported by road in a refrigerated truck, at a constant temperature of 13°C. The total distance covered and duration taken was 750km and 40h, respectively. On the basis of zero fish mortality and least adverse water quality after transport, we suggest that a starvation period of 72h, loading density of 26.7g/L and light sedation of fish with 40μL/L clove oil prior to packing is suitable for transporting rainbow trout juveniles in plastic bags up to 40h. To ascertain the benefit of adding salt to the transport medium, we need to further investigate the aspects of delayed mortality and long term fish welfare.

In situ chemical and morphological characterization of copper under near ambient reduction and oxidation conditions

By using spatially resolved photoelectron spectromicroscopy, we have investigated the formation of Cu(I) oxide phases when a bulk Cu foil is exposed to a near ambient pressure of molecular oxygen. The experiment was performed by using a novel cell for in operando measurements capable to overcome the so called ‘pressure gap’. We have found that the oxidation of Cu proceeds through the formation of Cu(I) oxide domains in the micron and submicron range size, the evolution of which affects the overall morphology of the Cu surface as well. Chemical and morphological changes have been simultaneously detected. It was, surprisingly, found that during the oxidation process in many areas domains having +1 valence state do not spread on the metallic regions which homogenously oxidize; no chemical oxidizing wave was detected by the available lateral resolution and time frame.

Hypoxia Enhances Cell Properties of Human Mesenchymal Stem Cells.

Atmospheric (in vitro) oxygen pressure is around 150mmHg (20% O2), whereas physiologic (in vivo) oxygen pressure ranges between 5 and 50mmHg (0.7-7% O2). The normoxic environment in cell culture does not refer to a physiological stem cell niche. The aim of this study is to investigate the effect of oxygen concentration on cell properties of human mesenchymal stem cells (MSCs). We analyzed cell proliferation rate, senescence, immunophenotype, stemness gene expression and differentiation potency with human urine stem cells (USCs), dental pulp stem cells (DPSCs), amniotic fluid stem cells (AFSCs), and bone marrow stromal cells (BMSCs). USCs, DPSCs, AFSCs and BMSCs were cultured under either 5% O2 hypoxic or 20% O2 normoxic conditions for 5days. MSCs cultured under hypoxia showed significantly increased proliferation rate and high percentage of S-phase cells, compared to normoxic condition. In real-time PCR assay, the cells cultured under hypoxia expressed higher level of Oct4, C-Myc, Nanog, Nestin and HIF-1α. In immunophenotype analysis, MSCs cultured under hypoxia maintained higher level of the MSC surface markers, and lower hematopoietic markers. Senescence was inhibited under hypoxia. Hypoxia enhances osteogenic differentiation efficiency compared to normoxia. Hypoxia showed enhanced cell proliferation rate, retention of stem cell properties, inhibition of senescence, and increased differentiation ability compared to normoxia.

Combustion characteristics of hydrotreated vegetable oil – diesel blend under EGR and supercharged conditions

This paper investigates the effects of Hydrotreated vegetable oil-diesel blend to combustion characteristics under various ambient oxygen concentrations and ambient pressure. Combustion characteristics were investigated using heat release rate analysis, two color method, soot concentration measurement and NOx concentration measurement. The experiments were carried out on a rapid compression expansion machine to simulate the ambient condition of a CI engine at TDC. Synthetic gas with oxygen concentrations of 21 %, 15 % and 10 % were used to simulate EGR conditions. A single hole injector was used with five different fuels: commercial diesel, HVO-commercial diesel blends and HVO. The results showed that increasing HVO blending percentages decreased ignition delay, flame temperature, soot concentration and NOx concentration. Heat release at oxygen concentration of 10 % dramatically dropped due to a shortened ignition delay, which resulted in less combustion. A decreased oxygen concentration from applied EGR conditions not only increased ignition delay, heat release, flame temperature and NOx concentration, but also increased soot concentration. A combination of EGR and supercharged conditions by increasing ambient pressure and decreasing oxygen concentrations resulted in increased heat release, decreased flame temperature, ignition delay and soot concentration, compared to EGR conditions.

Flame spread limits (LOC) of fire resistant fabrics

Selecting fabrics based on their fire resistance is important for professions with substantial fire risk such as firefighters, race car drivers, and astronauts suits. Generally, fire resistant materials are tested under standard atmospheric conditions. However, their flammability properties can change when the ambient conditions deviate from standard atmospheric conditions. Particularly in high altitude locations, aircraft, and spacecraft, the pressure and oxygen concentrations are different than in a standard atmosphere. Also, the presence of external radiation (i.e. overheating component or nearby fire) can reduced the fire resistance of a material. In this work, an experimental study was conducted to analyze the influence of environmental variables such as oxygen concentration, ambient pressure, and external radiant heat flux on the flame spread limits of two different fire resistant fabrics: Nomex HT90-40 and a blend made of Cotton/Nylon/Nomex. Ambient pressure was varied between 40 and 100kPa and ambient oxygen concentrations were decreased until the Limiting Oxygen Concentration (LOC), limiting conditions which would permit flame propagation, were found. Experiments were conducted using no external radiant flux or a radiant flux of 5kW/m2 to examine the influence of the presence of a nearby heat source. Among the results, it was found that as ambient pressure is reduced the oxygen concentration required for the flame to propagate must be increased. The external radiant heat flux acts as an additional source of heat and allows propagation of the flame at lower oxygen concentrations. An analysis of the propagation limits in terms of the partial pressure of oxygen suggest that the LOC of a material is not only determined by heat transfer mechanisms but also by chemical kinetic mechanisms. The information provided in this work helps characterize increased flammability risk of materials when in environments different from the standard atmospheric conditions at which they are typically tested.

Singlet oxygen feedback delayed fluorescence of protoporphyrin IX in organic solutions.

Delayed fluorescence (DF) of protoporphyrin IX (PpIX) has been recently proposed as a tool for monitoring of mitochondrial oxygen tension in vivo as well as for observation of the effectiveness of photodynamic therapy (PDT) [E. G. Mik, Anesth. Analg., 2013, 117, 834-346; F. Piffaretti et al., J. Biomed. Opt., 2012, 17, 115007]. However, the efficiency of the mechanism of thermal activation (E-type DF), which was considered in the papers, is limited due to a large energy gap between the first excited singlet and the first triplet state of PpIX at room or body temperatures. Moreover, the energy gap is roughly equal to other porphyrinoid photosensitizers that generate DF mostly through the Singlet Oxygen Feedback-Induced mechanism (SOFDF) under certain conditions [M. Scholz and R. Dědic, Singlet Oxygen: Applications in Biosciences and Nanosciences, 2016, vol. 2, pp. 63-81]. The mechanisms of delayed fluorescence of PpIX dissolved either in dimethylformamide (DMF) or in the mixture of DMF with ethylene glycol (EG) were investigated at atmospheric partial pressure of oxygen by means of a simultaneous time-resolved detection of 1O2 phosphorescence and PpIX DF which makes a direct comparison of the kinetics and lifetimes of both the luminescence channels possible. Samples of PpIX (100 μM) exhibit concave DF kinetics, which is a typical footprint of the SOFDF mechanism. The dramatic decrease in the DF intensity after adding a selective 1O2 quencher sodium azide (NaN3, 10 mM) proves that >90% of DF is indeed generated through SOFDF. Moreover, the analysis of the DF kinetics in the presence of NaN3 implies that the second significant mechanism of DF generation is the triplet-triplet annihilation (P-type DF). The bimolecular mechanism of DF was further confirmed by the decrease of the DF intensity in the more viscous mixture DMF/EG and by the increase of the ratio of DF to the prompt fluorescence (PF) intensity with the increasing excitation intensity. These results show the significant role of the SOFDF mechanism in the DF of PpIX at high concentrations and at atmospheric partial pressure of oxygen and should be considered when developing diagnostic tools for clinical applications.

Highly c-Axis Oriented Growth and Optical Characterization of ZnO Pore-Like Structures Surrounded by Craters via Pulsed Laser Deposition

This research deals with the deposition and characterization of ZnO nanostructures by the pulsed laser deposition technique at various ambient pressures of oxygen on a silicon substrate at 600 ∘C temperature. X-ray diffraction study shows that the ZnO nanostructure is single crystal in nature and has strong c-axis orientation. The field emission scanning electron microscopic image shows that the formation of pores within the craters is highly sensitive to the oxygen pressure. The atomic force microscopy image reveals the reduction in surface roughness of the nanostructure indicating transformation of pores to particles. A near-band-edge emission peak along with the defect peaks arising from oxygen defects and zinc interstitials are observed in the photoluminescence spectra. The defect related emission due to O 2 vacancy decreases with increasing O 2 pressure due to more incorporation of O 2 during pulsed laser deposition.

Thermodynamic analysis of ZnO nanoparticle formation by wire explosion process and characterization

Zinc Oxide (ZnO) nanoparticles were synthesized by wire explosion process through deposition of different levels of energy to the exploding conductor in oxygen ambience at different pressures. The produced nanoparticles were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and by Brunauer-Emmett-Teller (BET) studies. Energy dependent formation reaction mechanisms were formulated based on Born-Haber cycle. The size dependent gas phase reaction energetics was analyzed by using Hess's diagram. Butler's multicomponent molten oxide model was adopted to predict the surface tension of ZnO. Thermodynamic modelling studies revealed that the amount of energy deposited has an impact on saturation ratio, activation free energy, and nucleation rate of nanoparticles. It is observed based on experimental and modelling studies that the amount of energy deposited to the current carrying conductor, ambient pressure of oxygen and the saturation ratio influence the size of nanoparticle formed.

Influence of plasma surface pretreatment and triarylmethane dye on the photocatalytic performance of TiO 2 -chitosan coating on textile

Abstract Treatment of household wastewater loaded with hair colorants by means of solar photocatalysis using TiO 2 -coated polyester/wool textile has been reported recently. In this work, the attributes of immobilized photocatalyst were enhanced; a textile support (polyester/wool blend fabric) was pre-treated by atmospheric and low pressure oxygen plasma prior to coating of the surface. Plasma pre-treatment contributed to hydrophilisation of support and overall resistance to wear of immobilized photocatalyst was improved. Moreover, TiO 2 -chitosan composite coating was modified by the addition of triarylmethane dye (C.I. Basic Blue 1; BB1). The sensitizing effect of the dye was observed during the first 180 min of photocatalytic treatment of greywater polluted by hair colorants under solar irradiation. Adversarially, the rate of photocatalytic degradation of bisphenol A (BPA) model solution under visible light was lower in the presence of BB1 in the photocatalyst formulation. According to the performed study of BB1 chemistry in aqueous solution, it was found that the dye undergoes two distinct photodegradation mechanisms depending on the characteristics of studied system. When dominant, photoreduction of BB1 to leuco-form (BB1-H), provides additional electron capture and consequently ensures decrease in h + − e − recombination rates, resulting in a false sensitizing effect.

Health and productivity of dairy cattle in high altitude cold desert environment of Leh-Ladakh: A review

The environment is usually attributed as the major climatic factor affecting animal health and production system in all agro-climatic zones. There are various environmental components viz. temperature, radiation, snowfall, wind, precipitation, humidity etc. that impact animal health and productivity. Ladakh is a remote and difficult terrain of India for studying the impact of climate change on livestock production. This area is situated at high altitude, which varies from 10,000 to 12,000 feet from mean sea level (MSL) and temperature range is 35° to -35°C. The atmospheric oxygen pressure is 30% short of MSL. Therefore, this region exhibits hypobaric-hypoxia, extreme cold and dry-arid climate for most of the year, which restrict the growth and productivity of the different livestock populations, including dairy cattle. However, demands are very high for milk and milk products by local people, Indian troops deployed in this region and tourists. Availability of fodder and high altitude stress-induced maladies, mountain sickness (brisket edema), stunted growth, infertility, mastitis pneumonia, etc. severely limits the dairy development, which has increased the gap between supply and demand of dairy products in this region. The impact of climate change on livestock production in Ladakh is a relatively ignored research area. Since the literature on the effect of climate change on dairy cattle productivity in Leh-Ladakh is scarce, therefore, the present article reviewed the available reports and presents authors' own observations on how this climate change impacted on health, production and reproduction of dairy cattle in high altitude cold desert.

High-Altitude Pulmonary Vascular Diseases

More than 140 million people permanently reside in high-altitude regions of Asia, South America, North America, and Africa. Another 40 million people travel to these places annually for occupational and recreational reasons, and are thus exposed to the low ambient partial pressure of oxygen. This review will focus on the pulmonary circulatory responses to acute and chronic high-altitude hypoxia, and the various expressions of maladaptation and disease arising from acute pulmonary vasoconstriction and subsequent remodeling of the vasculature when the hypoxic exposure continues. These unique conditions include high-altitude pulmonary edema, high-altitude pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness.

Palladium-catalyzed C–H olefination of uracils and caffeines using molecular oxygen as the sole oxidant

The palladium-catalyzed oxidative C-H olefination of uracils or caffeines with alkenes using an atmospheric pressure of molecular oxygen as the sole oxidant has been disclosed. This novel strategy offers an efficient and environmentally friendly method to biologically important C5-alkene uracil derivatives or C8-alkene caffeine derivatives.

Can the measurement of pulmonary diffusing capacity for nitric oxide replace the measurement of pulmonary diffusing capacity for carbon monoxide?

Pulmonary diffusing capacity for carbon monoxide (DLCO) has been an important pulmonary function test used since the 1950’s. It measures the uptake of CO from the alveolar space into pulmonary capillary blood, following the same path as oxygen. It’s used to evaluate/follow the progress of various lung diseases. In the eighties, a new test was developed similar to the DLCO test: pulmonary diffusing capacity for nitric oxide (DLNO). About 81–90% of the variance in DLNO is shared by DLCO in patients with cardiopulmonary disease and in healthy subjects. When DLNO is abnormally low, so is DLCO, and when DLNO is normal, so is DLCO (Kappa Statistic=0.69, n=251). The probability that DLNO and DLCO will be abnormally low when a cardiopulmonary disease is present (sensitivity) is 79% and 68%, respectively. The DLNO test avoids many technical issues associated with the measurement of DLCO: (1) DLNO is relatively unaffected by inspired oxygen concentration or ambient pressure, (2) DLNO is unaffected by carboxyhemoglobin, (3) DLNO is minimally affected by hemoglobin (Hb) concentration, thus correcting for Hb is not needed. (4) DLNO is more affected by lung volume compared to DLCO, thus DLNO divided by alveolar volume (KNO) is a better measure than KCO in those with restrictive lung disease, and (5) DLNO is a more stable measure over time compared to DLCO. Therefore, DLNO has several advantages over DLCO in the management of patients and could replace the DLCO test in most cases moving forward.

Influencia de la presión de oxígeno ambiental sobre la regeneración ósea guiada

ObjectiveTo evaluate the influence of the variation in ambient oxygen pressure on guided bone regeneration in guinea pigs. Material and methodA total of 32 male guinea pigs weighing 750±50g were assigned into two groups of 16 (group A: studied at 150 metres above sea level in the city of Lima and oxygen pressure of 157mmHg; group B: was at 3230 meters above sea level in the city of Jauja and an oxygen pressure of 107mmHg). Bone defects of 5×6mm were induced in the jaw in both groups through extra-oral surgical access. The defect in 8 guinea pigs of each group were covered with a porcine resorbable collagen membrane, but not in the other animals. The osteoblast and osteocyte cell counts were evaluated at 15 and 30 days post-operatively. ResultsAt 15 and 30 days, in the groups studied at height and with the membrane applied, the osteoblast count was 71±12.1 cells/field, and 83±7.2 cells/field, respectively, and an osteocyte count of 34.5±6.6 cells/field, and 25±7.6 cells/field, respectively. These groups had a higher number of bone cells in all the comparisons, but there were no statistically significant differences (P>.05). ConclusionThere was a tendency to form a greater amount of bone cells was found in the samples treated with bone regeneration and exposed to altitude compared to those at sea level.

Heterogeneous (Cu-Ti) colliding plasma dynamics

Laser ablated copper-titanium colliding plasma plume expansion at 10−4, 10−2, and 100 mbar of oxygen ambient pressures has been investigated with a view to understanding heterogeneous colliding plasma plume dynamics and the formation of multi-element stagnation layers using optical emission spectroscopy and fast imaging of plume. The observation of Cu2(A−X) and TiO−γ bands and their ambient pressure dependent emission intensity opens up the possibility of the stoichiometrically controlled formation of nanoclusters/nanocomposites.

Preparation and characterization of YBaCo4–y Cu y O7 + x compounds

Phase formation processes along the YBa(Co, Cu)4O7 + x section of the Y–Ba–Co–Cu–O system have been studied in the temperature range 900–1150°C under atmospheric oxygen pressure. We have located the boundaries of the homogeneity range of the YBaCo4–y Cu y O7 + x (114) phase and determined the temperature- dependent copper solubility in this phase, y max(t) (y max ≈ 0 at 900°C; the highest solubility is y max ≈ 0.7, at t = 1000–1050°C). Using X-ray diffraction data for quenched samples, we have identified the phases that coexist with YBaCo4–y Cu y O7 + x in the phase regions adjacent to its homogeneity range. The results demonstrate that, if the percentage of copper in a starting mixture, y 0, exceeds the copper solubility limit in the 114 phase at a given synthesis temperature, the excess copper concentrates in copper-rich phases: YBaCo2–y Cu y O5 + x (112), Co1–y Cu y O1 + x (001), and Y2Cu2O5 + x (202). At temperatures in the range 900 ≤ t ≤ 1050°C and compositions in the range y 0 ≤ 0.9, the system can be thought of as ternary, with a constant Y: Ba ratio of 1: 1 (that is, only the 114, 112, and 001 phases are present at equilibrium). Beyond this region, phases with other Y: Ba ratios appear.

Atmospheric pressure plasma assisted calcination of composite submicron fibers

The plasma assisted calcination of composite organic/inorganic submicron fibers for the preparation of inorganic fibers in submicron scale was studied. Aluminium butoxide/polyvinylpyrrolidone fibers prepared by electrospinning were treated using low-temperature plasma generated by special type of dielectric barrier discharge, so called diffuse coplanar surface barrier discharge (DCSBD) at atmospheric pressure in ambient air, synthetic air, oxygen and nitrogen. Effect of plasma treatment on base polymer removal was investigated by using Attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy. Influence of working gas on the base polymer reduction was studied by energy-dispersive X-ray spectroscopy (EDX) and CHNS elemental analysis. Changes in fibers morphology were observed by scanning electron microscopy (SEM). High efficiency of organic template removal without any degradation of fibers was observed after plasma treatment in ambient air. Due to the low-temperature approach and short exposure time, the plasma assisted calcination is a promising alternative to the conventional thermal calcination.

Abstract 737: Transcriptome of glioma growing in the brain is simulated by tumor cells cultured under low oxygen pressure

Abstract Introduction Studies using cultured tumor cells are frequently used to generate large scale data. However, the discrepancy between culture media conditions and host microenvironment factors prevent adequate translation to the clinical reality. Since culturing tumor cells in atmospheric oxygen pressure (20% O2) significantly differs from oxygen pressure within different organs (5-7% O2). We investigated whether the transcriptome of glioma cells cultured under oxygen concentration that is similar to the lesion in the brain (0.5-2% O2) can simulate the transcriptome of tumors growing in vivo. Materials and Methods Human glioma, LN229, cells were cultured in MEM supplemented with 10% FBS under 20%, 6% and 1% oxygen pressure. Glioma growing in the brain was established by stereotactic injection of 1×105 LN229 cells into the brain of nude mice, subcutaneous tumors were established by injection of 1×105 cells. Gene microarray was performed using Illumina Human HT-12_v4_BeadChip microarray and data were collected by using an Illumina bead Array Reader confocal scanner (BeadStation 500GXDW; Illumina). Array data processing and analysis were performed using Illumina BeadStudio software. All statistical analysis was performed using BRB Arraytools Version 4.4.1 under the R language environment. Cluster analysis was performed and Heat Map was generated by Tree view. Results Brain and subcutaneous tumors were harvested 3 weeks post injection. RNA was extracted and processed for gene microarray that identified 2187 genes as brain specific transcriptome. Determination of common genes (same direction) between the transcriptome of glioma growing in the brain and cells growing in culture under 20%, 6%, and 1% O2 identified 23, 5, and 174 specific genes, respectively. Ingenuity pathway analysis and gene set enrichment analysis of the 174 common genes (from cells growing in 1% O2) revealed cluster of genes related to cancer and neurologic diseases, cell death/survival, cell-to-cell signaling. Up-regulation of genes associated with survival and resistance such as AKT, MAPK, NFêB1A, VEGF, and GSTA5 were also commonly identified in glioma growing in the brain and LN229 cells cultured under 1% oxygen. Conclusion Culturing glioma cells under different oxygen pressures induces different transcriptomes and cells cultured under 1% O2 express transcriptome most similar to cells growing in the brain. These data demonstrate that, to simulate clinical relevance, the oxygen tension of cultures should approximate those found in organs. Citation Format: Ho Jeong Lee, Hyun Kyung Yu, Seung Wook Kim, Sung Il Choi, Junqin He, Isaiah J. Fidler, Sun Jin Kim. Transcriptome of glioma growing in the brain is simulated by tumor cells cultured under low oxygen pressure. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 737.

Aqueous Oxidation of Sugars into Sugar Acids Using Hydrotalcite-supported Gold Nanoparticle Catalyst under Atmospheric Molecular Oxygen

Hydrotalcite-supported gold nanoparticles show good activity as a heterogeneous catalyst for the oxidation of monosaccharides (xylose, ribose, galactose and mannose) and disaccharides (lactose and cellobiose) into the corresponding sugar acids under external base-free conditions in water solvent using atmospheric pressure of molecular oxygen. The produced sugar acids were thoroughly identified by 1H-, 13C-, and HMQC-NMR and ESI-FT-ICR MS spectroscopic techniques.