Constant Oxygen Flow Research Articles

Photocatalytic Degradation of Naproxen: Intermediates and Total Reaction Mechanism.

Photochemical and photocatalytic oxidation of naproxen (NPX) with UV-A light and commercial TiO2 under constant flow of oxygen have been investigated. Adsorption experiments indicated that 90% of the solute remained in the solution. Combined chemical analysis of samples on the photochemical degradation indicated that NPX in an aqueous solution (20 ppm) is efficiently transformed into other species but only 18% of the reactant is mineralized into CO2 and water after three hours of reaction. Performing the photocatalytic oxidation in the presence of TiO2, more than 80% of the organic compounds are mineralized by reactive oxidation species (ROS) within four hours of reaction. Analysis of reaction mixtures by a combination of analytical techniques indicated that naproxen is transformed into several aromatic naphthalene derivatives. These latter compounds are eventually transformed into polyhydroxylated aromatic compounds that are strongly adsorbed onto the TiO2 surface and are quickly oxidized into low-molecular-weight acids by an electron transfer mechanism. Based on this and previous studies on NPX photocatalytic oxidation, a unified and complete degradation mechanism is presented.

Food Industrial Effluent Treatment with Oxygen and Ozone Using Activated Carbon for Catalytic Oxidation

ABSTRACT A catalytic oxidation treatment to remove coloration and chemical oxygen demand (COD) in an effluent from a food industry was carried out using oxygen and ozone as oxidizing agents and activated carbon as a catalytic. Different experiments of oxidation were conducted using 25, 50 and 100 mL of activated carbon bed to treat 100 mL of sample and constant flow of oxygen 7.2 g/min and ozone 0.034 mg/min, maintaining initial pH of industrial effluent. Almost a complete coloration removal and COD reduction of the sample was achieved for catalytic processes; however, time of treatment and agent oxidant doses were different in each case. According to volume of activated carbon beds, ozone doses for discoloration and COD removal were 8.5, 2 and 1.7 mg/L, whereas the oxygen doses were 2860, 770 and 500 g/L, respectively. Consequently, to eliminate the color in the industrial effluent, the dose of oxygen was higher than that of ozone. In addition, the oxidation agents promoted the regeneration of activated carbon, showing that its activity is declined after 60 cycles of effluent treatment with ozone, whereas with oxygen treatment, the total depletion was observed in 18 cycles. In turn, single adsorption showed activated carbon depletion in 5 cycles of effluent treatment.

High-flow nasal cannula oxygen therapy is superior to conventional oxygen therapy but not to non-invasive mechanical ventilation in reducing intubation rate in hypoxia and dyspnea due to acute heart failure: a systematic review and meta-analysis.

High-flow nasal cannula oxygen therapy is superior to conventional oxygen therapy but not to non-invasive mechanical ventilation in reducing intubation rate in hypoxia and dyspnea due to acute heart failure: a systematic review and meta-analysis.

Automatic oxygen titration versus constant oxygen flow rates during walking in COPD: a randomised controlled, double-blind, crossover trial

RationaleIn patients with COPD, oxygen (O2)-supplementation via a constant flow oxygen system (CFOS) can result in insufficient oxygen saturation (SpO2 <90%) during exercise. An automatically titrating O2-system (ATOS) has been...

Injector Effects on Hybrid Polymethylmethacrylate Combustion Assessed by Thermochemical Tomography

In this work, two representative hybrid rocket injector designs, a single-port and an axial showerhead design, were examined experimentally to determine the comparative influence on the development of the downstream combustion zone with polymethylmethacrylate (PMMA) fuel. One-dimensional laser absorption tomography was employed to obtain the thermochemical structure of the PMMA–gaseous oxygen reaction layer via quantitative in situ species and temperature measurements. Optical measurements were performed with tunable semiconductor lasers in the midwave infrared to target absorption features in the fundamental vibrational bands of CO, , and . Planar measurements were conducted at the exit plane of cylindrical fuel grains () at axial distances () ranging from 2 to 11 with a constant gaseous oxygen flow for each of the injectors. Assuming azimuthal symmetry, a Tikhonov-regularized Abel inversion technique was used to obtain the radially resolved absorption coefficient, from which temperature and mole fractions were extracted. One-dimensional measurements over all fuel-grain lengths were consolidated to obtain spatially resolved two-dimensional images of the reaction layer thermochemical structure in a hybrid rocket motor geometry. Significant variations in experimental results were observed between the two injectors, suggesting the importance of injection fluid dynamics in hybrid rocket combustion performance. Explanations of the variations are offered from both a theoretical and a computational analysis.

Preliminary Study of Zirconium Carbide Ceramic Deposition on Austenitic Stainless Steel by Pulsed Laser Deposition

Coating Zirconium Carbide (ZrC) on the stainless steel (SS) will increase the corrosion resistance of SS which suffer from the intergranular attacks during operation as construction materials in reactors. ZrC coating have been partially deposited on Austenitic 316L SS by Pulsed Laser Deposition (PLD) at 800°C temperature substrate with constant oxygen flow injection of 40 sccm (Standard Cubic Centimeters per Minute), chamber pressure around 229-244 mTorr and 105 the numbers of laser shots. The sample was analyzed using X-Ray Diffraction (XRD), Microscope Optic (MO), Scanning Electron Microscope – Energy Dispersive X-Ray Spectroscope (SEM-EDS), and Atomic Force Microscope (AFM) to characterize the phase, morphology, thickness of the films and surface topography. The results showed that the thickness of the thin film around 4.93-8.10 µm with 49.6 nm surface roughness. The film surface was very smooth. The present of Zr and C was detected in SEM & EDS results but not appeared in XRD pattern, possibly due to diminish tension of the thin films on the substrates caused by low lattice mismatch between ZrC and Austenitic 316L SS substrate. Furthermore, ZrO2 phase has been found on the substrate which is predicted because of the interaction between ZrC target and oxygen background gas.

Photolytic and photocatalytic degradation of doxazosin in aqueous solution

Doxazosin (DOX), a selective alpha blocker, is widely used in medical therapy as an effective antihypertensive agent. It is a frequently prescribed drug and for this reason, environmental and ecotoxicological research is of great importance in terms of exposure and risk for both aquatic species and humans. In this study we focused on photolytic and TiO2 photocatalytic degradation processes of doxazosin under different simulated conditions, with the emphasis on identification of degradation products. Photolytic (without TiO2) experiments were performed in the presence and absence of oxygen, while photocatalytic degradation of doxazosin aqueous solution has been carried out under constant oxygen flow. DOX degradation was more efficient in the TiO2/UVA photocatalytic experiment than during photolytic processes (UVA and UVC, UVC-N2).LC-HRMS analyses with electrospray ionization allowed observing the formation of several major degradation products depending on the reaction conditions (presence or absence of oxygen, photocatalysis). The transformation products were identified based on exact mass measurements, isotopic distribution, and fragmentation pattern. Among them, dominated C17H21N5O3 and C17H23N5O4 (cleavage of the dioxane cycle), and C23H25N5O7 (hydroxylation). The detailed degradation pathway has been proposed.Toxicity testing with V. fischeri luminescent bacteria revealed higher toxicity of samples in photolytic rather than photocatalytic experiments which might be attributed to the formation of different products.

Photocatalytic degradation of diclofenac sodium salt: adsorption and reaction kinetic studies

The photocatalytic oxidation of diclofenac, which is a non-steroidal anti-inflammatory medication, with TiO2 illuminated with UV-A light under constant flow of pure oxygen has been investigated in our laboratories to evaluate the effect of initial reactant concentration on the reaction rate. Diclofenac adsorption experiments under dark conditions were also carried out to get information about the interaction between the organic molecule and the solid catalyst. Adsorption experiments at natural pH under dark conditions confirmed that the negatively charged diclofenac molecule is easily adsorbed on the positively charged surface of titania reaching equilibrium in less than 50 min. According to the Langmuir isotherm, the adsorption constant (Keq) and the maximum uptake of diclofenac (qm) on the surface of commercial TiO2 are 21.1401 L mMol−1DFC and 0.04013 mMoles DFC g−1 TiO2, respectively. Experimental results also indicate that the initial reaction rate of the photocatalytic degradation of diclofenac obeys the Langmuir–Hinshelwood–Hougen–Watson model with a kinetic constant K1 = 0.08489 min−1 and an adsorption parameter K2 = 14.12821 mM−1L. Combined chemical analysis of the reaction samples by HPLC, TOC, and UV–vis spectroscopy indicated that the diclofenac is efficiently mineralized by photocatalysis via hydroxylation of the aromatic rings to form 2-aminophenol, catechol, benzene-triol, 2,6-dichloroaniline, and fumaric acid, which in turn are completely mineralized to CO2 and water.

Metalorganic-aerosol-deposited Au nanoparticles for the characterization of ultrathin films by surface-enhanced Raman spectroscopy

An alternative approach for ultrathin film characterization by means of Surface-Enhanced Raman Spectroscopy was realized and applied to the characterization of nanocrystalline TiO2 films. The vacuum-free metalorganic aerosol deposition (MAD) technique was used to grow gold nanoparticles onto the surface of thin TiO2 films. An averaged enhancement factor of 107, as well as the characterization of a 3 nm thin film, was accomplished. Since the thin film acts as a substrate itself, this technique can be used for the characterization of a variety of solid thin film materials. Furthermore, MAD-based nanoparticle growth can be of special interest for oxide films due to the high oxygen partial pressure and the constant oxygen flow during the deposition.

DEPOSITION OF YTTRIA-STABILIZED ZIRCONIA CERAMIC ON SS316L BY PULSED SOLID-STATE ND:YAG LASER

Austenitic stainless steel in general has a limited service temperature up to 600°C. Nevertheless, service temperature more than that temperature are one of the key feature of advanced nuclear reactors to gain higher thermal efficiency which is related to economic beneficial, and also to withstand from abnormal condition. However, austenitic stainless steel such as SS316 class is well-known structure material for nuclear power reactors and other power plants. Therefore, one of the key issue is to modify SS316 so that has capability to service higher temperature. One of the technique for that purpose is ceramic-coated SS316L. In this preliminary study, thin films of zirconia-based ceramic i.e. YSZ (Yttria-Stabilized Zirconia) have been deposited on a SS316L using Plasma-Pulsed Laser Deposition (PLD) at Center For Science and Technology of Advanced Materials laboratory – National Nuclear Energy Agency of Indonesia (BATAN). Thin film was deposited with the constant oxygen flow injection of 20 and 40 sccm (Standard Cubic Centimeters per Minute) that produce a chamber pressure of 60 and 200 mTorr for the numbers of laser shots of 7.2×104 and 14.4×104, respectively. The substrate temperature during deposition was of 850oC. Afterward, the samples were analyzed using Optical Microscope, Scanning Electron Microscope – Energy Dispersive X-ray Spectroscope (SEM-EDS) and Atomic Force Microscope (AFM). The results showed that the YSZ could homogeneously and sticky deposited on the surface of the SS316L surface. The surfaces were very smoothly formed with the surface roughness in the nano-meter scale range of 20-90 nm.

Direct growth of ZnSnO nano-wires by thermal evaporation technique for thermoelectric applications

In this research, we have successfully grown the ZnSnO nano-wires by simple thermal evaporation technique and reported the highest Seebeck coefficient and power factor for first time. The ZTO nano-structures were grown by a simple thermal evaporation method using direct evaporation of Zinc and Tin metal powders under constant oxygen flow rate of 100 sccm in a tube furnace. The post growth annealing was performed in the temperature ranges of 600–900 °C with a step of 100 °C in the programmable muffle furnace. The structural, electrical, morphological and thermoelectric properties of as grown and annealed samples were analyzed by X-Ray Diffraction, Raman spectroscopy, Scanning Electron Microscopy, Hall data and Seebeck effect. The XRD results confirmed the formation of Wurtzite hexagonal structure and the vibrational mode of ZTO at 437 cm−1 is verified by Raman spectroscopy measurements. It was also observed that the crystal structure of ZTO was improved with annealing temperature. SEM micrographs showed the nanowires like morphology of the un-annealed sample but it transformed into nano-crystalline grains by post growth annealing. Seebeck data demonstrated that the values of Seebeck coefficient, electrical conductivity and power factors were found to be increased with annealing temperature because Sn atoms get more thermal energy at high temperature and contribute in the carrier concentration.

Current Performance and Preliminary Results of a New14C Extraction Line for Meteorites at the University of Bern

AbstractHere, we introduce a new radiocarbon (14C) extraction line operating at the University of Bern, which was designed and built for the extraction of in situ14C from meteorites. With this system, we achieved two important developments compared to other systems. First, using the MICADAS gas-interface system,14C can directly be measured from the collected CO2gas, i.e., without graphitization of the sample. Second, meteorite sample masses as low as ~0.05 g can be used for high precision and reproducibility. Prior to extraction in an oxygen atmosphere held at a pressure of ~20–30 mbar in an iridium crucible at 1600°C for 40 min, samples were preheated for 1 h in a constant oxygen flow at 500°C and continuous pumping. Gas purification followed the method described previously (e.g., Hippe et al. 2009). While the blank levels for preheated samples are low (&lt;2×104 14C atoms), the blanks for non-preheated samples are high, therefore those results cannot be used. We also report preliminary results for the L-chondrite JaH 073. The terrestrial age of 17.7±0.4 ka is in good agreement with previous results for the same sample of this meteorite, confirming that the extraction line, the gas purification system, and the AMS measurements are all reliable.

Nebulized Heparin Attenuates Pulmonary Coagulopathy and Inflammation through Alveolar Macrophages in a Rat Model of Acute Lung Injury.

Objective Alveolar macrophages play a key role in the development and resolution of acute respiratory distress syndrome (ARDS), modulating the inflammatory response and the coagulation cascade in lungs. Anti-coagulants may be helpful in the treatment of ARDS. This study investigated the effects of nebulized heparin on the role of alveolar macrophages in limiting lung coagulation and inflammatory response in an animal model of acute lung injury (ALI). Methods Rats were randomized to four experimental groups. In three groups, ALI was induced by intratracheal instillation of lipopolysaccharide (LPS) and heparin was nebulized at constant oxygen flow: the LPS/Hep group received nebulized heparin 4 and 8 hours after injury; the Hep/LPS/Hep group received nebulized heparin 30 minutes before and 4 and 8 hours after LPS-induced injury; the LPS/Sal group received nebulized saline 4 and 8 hours after injury. The control group received only saline. Animals were exsanguinated 24 hours after LPS instillation. Lung tissue, bronchoalveolar lavage fluid (BALF) and alveolar macrophages isolated from BALF were analysed. Results LPS increased protein concentration, oedema and neutrophils in BALF as well as procoagulant and proinflammatory mediators in lung tissue and alveolar macrophages. In lung tissue, nebulized heparin attenuated ALI through decreasing procoagulant (tissue factor, thrombin–anti-thrombin complexes, fibrin degradation products) and proinflammatory (interleukin 6, tumour necrosis factor alpha) pathways. In alveolar macrophages, nebulized heparin reduced expression of procoagulant genes and the effectors of transforming growth factor beta (Smad 2, Smad 3) and nuclear factor kappa B (p-selectin, CCL-2). Pre-treatment resulted in more pronounced attenuation. Conclusion Nebulized heparin reduced pulmonary coagulopathy and inflammation without producing systemic bleeding, partly by modulating alveolar macrophages.

Effect of Microwave Plasma Power on Topographical Change in Epoxy Composites

The effect of the microwave (2.45 GHz) plasma power on the surface topography was evaluated on a commercially available epoxy composite. The plasma treatment was performed by varying the microwave plasma power from 200 W to 500 W at a constant oxygen flow rate at 20 sccm for one min treatment. Based on the Atomic Force Microscopy analysis, the surface roughness root mean square was changed from -2% to 21% by increasing the plasma power from 200 W to 500 W. In oxygen plasma, the interaction of plasma ions with the substrate surface leads to oxidation and etching of surface materials. More plasma ion density and ion current can be produced by increasing the plasma power. As a result, more interaction between plasma ion and substrate surface using high plasma power. The surface roughness can be considerably increased by plasma treatment using power above 400 W.

Enhancement in optical characteristics of c-axis-oriented radio frequency–sputtered ZnO thin films through growth ambient and annealing temperature optimization

High-quality radio frequency–sputtered ZnO were grown on Si substrates at 400°C at various partial gas pressures (Ar/Ar+O2). Subsequently, to remove as-grown defects, high temperature annealing from 700 to 900°C on as-grown samples in constant oxygen flow for 10s was performed. X-ray diffraction study confirmed the formation of highly crystalline films with a dominant peak at (002). The sample grown in 50% Ar and 50% O2 ambient exhibited the lowest linewidth (2θ=~0.2728°) and highest stoichiometry. Grain size of the as grown samples decreased with increase in the partial pressure of oxygen till a certain ratio (1:1), and photoluminescence (PL) improved with increase in annealing temperature. Low-temperature (18K) PL measurements showed a near-band-edge emission peak at 3.37eV, and the highest peak intensity (more than six orders compared to others with narrow linewidth of ~0.01272eV) was exhibited by the sample annealed at 900°C and was six orders higher than that of the as-grown sample. All as-grown samples exhibited dominant visible-range peaks due to emission from defect states.

Investigation on the Electrical and Methane Gas-Sensing Properties of ZnO Thin Films Produced by Different Methods

In this work, the influence of deposition method on the structural, electrical, and methane gas-sensing properties of ZnO thin films is investigated. Sol–gel spin coating, direct current (DC) magnetron sputtering, and e-beam evaporation techniques are employed for production of Zn thin films post-annealed at 500°C with a constant flow of oxygen. Detailed morphological, chemical, and structural investigations are carried out on all samples by field emission electron microscopy (FESEM) and x-ray diffraction (XRD) analyses. DC electrical resistivity of the samples was measured using a four-point probe instrument while a Hall effect instrument was used for the Hall effect measurements. The sensing performance was optimized with respect to the deposition method as well as the operating temperature. Detection limit, reproducibility, and stability of all samples produced using different methods are also identified. An optimum operating temperature of 350°C is obtained. The best sensitivity was attributed to the deposited film by the e-beam evaporation method due to its different surface morphology, which provided a larger ratio of surface-to-bulk area, and a lower carrier concentration, which caused higher electrical resistance. All ZnO thin films deposited by different methods also showed good reproducibility and stability.

Four ways to ventilate during cardiopulmonary resuscitation in a porcine model: a randomized study

BackgroundThe optimal method for out-of-hospital ventilation during cardiopulmonary rescue (CPR) is controversial.The aim of this study was to test different modes of ventilation during CPR for a prolonged period of 60 min.MethodsPigs were randomized to four groups after the induction of ventricular fibrillation, which was followed by one hour of mechanical cardiac compressions. The study comprised five pigs treated with free airways, five pigs treated with ventilators, six pigs treated with a constant oxygen flow into the tube, and six pigs treated with apnoeic oxygenation.ResultsThe free airway group was tested for 1 h, but in the first 15 min, the median PaO2 had already dropped to 5.1 kPa.The ventilator group was tested for 1 h and still had an acceptable median PaO2 of 10.3 kPa in the last 15 min. The group was slightly hyperventilated, with PaCO2 at 3.8 kPa, even though the ventilator volumes were unchanged from those before induction of cardiac arrest.In the group with constant oxygen flowing into the tube, one pig was excluded after 47 min due to blood pressure below 25 mmHg. For the remaining 5 pigs, the median PaO2 in the last 15 min was still 14.3 kPa, and the median PaCO2 was 6.2 kPa.The group with apnoeic oxygenation for 1 h had a resulting median PaO2 of 10.2 kPa and a median PaCO2 of 12.3 kPa in the last 15 min.DiscussionExcept for the free airway group, the other methods resulted in PaO2 above 10 kPa and PaCO2 between 3.8 and 12.3 kPa after one hour.ConclusionConstant oxgen flow and apnoeic oxygenation seemed to be useable alternatives to ventilator treatment.

On the corrosion resistance of AISI 316L-type stainless steel coated with manganese and annealed with flow of oxygen

AISI 316L-type stainless steel was coated with 300-nm-thick Mn thin films and post-annealed at 673 K with a constant flow of oxygen (250 cm3/min). The films crystallographic and morphological structures were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM) before corrosion test and scanning electron microscopy (SEM) after corrosion test. Corrosion behavior of the samples in 0.3, 0.5 and 0.6 M NaCl solutions was investigated by means of potentiodynamic and electrochemical impedance spectroscopy (EIS) techniques. Results showed that the corrosion inhibition of annealed Mn/SS316L in all NaCl solutions with different concentrations is higher than that of bare SS316L. A correlation is achieved between the structural variation of the films with the potentiodynamic and EIS corrosion results.

Peroxidised dietary lipids impair intestinal function and morphology of the small intestine villi of nursery pigs in a dose-dependent manner.

The objective of this study was to investigate the effect of increasing degrees of lipid peroxidation on structure and function of the small intestine of nursery pigs. A total of 216 pigs (mean body weight was 6·5 kg) were randomly allotted within weight blocks and sex and fed one of five experimental diets for 35 d (eleven pens per treatment with three to four pigs per pen). Treatments included a control diet without added lipid, and diets supplemented with 6 % soyabean oil that was exposed to heat (80°C) and constant oxygen flow (1 litre/min) for 0, 6, 9 and 12 d. Increasing lipid peroxidation linearly reduced feed intake (P<0·001) and weight gain (P=0·024). Apparent faecal digestibility of gross energy (P=0·001) and fat (P<0·001) decreased linearly as the degree of peroxidation increased. Absorption of mannitol (linear, P=0·097) and d-xylose (linear, P=0·089), measured in serum 2 h post gavage with a solution containing 0·2 g/ml of d-xylose and 0·3 g/ml of mannitol, tended to decrease progressively as the peroxidation level increased. Increasing peroxidation also resulted in increased villi height (linear, P<0·001) and crypt depth (quadratic, P=0·005) in the jejunum. Increasing peroxidation increased malondialdehyde concentrations (quadratic, P=0·035) and reduced the total antioxidant capacity (linear, P=0·044) in the jejunal mucosa. In conclusion, lipid peroxidation progressively diminished animal performance and modified the function and morphology of the small intestine of nursery pigs. Detrimental effects were related with the disruption of redox environment of the intestinal mucosa.

INVESTIGATION OF THERMAL DEGRADATION OF POULTRY PROCESSING DEWATERED SLUDGE USING THERMOGRAVIMETRIC ANALYSIS METHOD

Thermal degradation of Poultry Processing Dewatered Sludge (PPDS) was studied using thermogravimetric analysis (TGA) method. The effect of particle size on PPDS samples and operational condition such as heating rates were investigated. The non-isothermal TGA was run under a constant flow of oxygen at a rate of 30 mL/min with temperature ranging from 30ºC to 800ºC. Four sample particle sizes ranging between 0.425 mm to 2 mm, and heating rate between 5 K/min to 20 K/min were used in this study. The TGA results showed that particle size does not have any significant effect on the thermogravimetry (TG) curves at the initial stage, but the TG curves started to separate explicitly at the second stage. Particle size may affect the reactivity of sample and combustion performance due to the heat transfer and temperature gradient. The TG and peak of derivative thermogravimetry (DTG) curves tend to alter at high temperature when heating rate is increased most likely due to the limitation of mass transfer and the delay of degradation process.