Studies on the rheology and oxygen mass transfer in the clavulanic acid production by Streptomyces clavuligerus

Directory of Open Access Journals (Sweden)

E. R. Gouveia

2000-12-01

Full Text Available In the present work rheological characteristics and volumetric oxygen transfer coefficient (kLa were investigated during batch cultivations of Streptomyces clavuligerus NRRL 3585 for production of clavulanic acid. The experimental rheological data could be adequately described in terms of the power law model and logistic equation. Significant changes in the rheological parameters consistency index (K and flow behavior index (n were observed with the fermentation evolution. Interesting correlations between the consistency index (K/biomass concentration (C X and the flow behavior index (n/biomass concentration were proposed. Volumetric oxygen mass transfer coefficient (kLa was determined by the gas balance method. Classical correlation relating the volumetric oxygen mass transfer coefficient to the operating conditions, physical and to transport properties, including apparent viscosity (muap, could be applied to the experimental results.

Development of a model to determine mass transfer coefficient and oxygen solubility in bioreactors

Directory of Open Access Journals (Sweden)

Johnny Lee

2017-02-01

where T is in degree Kelvin, and the subscripts refer to degree Celsius; E, ρ, σ are properties of water. Furthermore, using data from published data on oxygen solubility in water, it was found that solubility bears a linear and inverse relationship with the mass transfer coefficient.

Visualisation of gas-liquid mass transfer around a rising bubble in a quiescent liquid using an oxygen sensitive dye

Science.gov (United States)

Dietrich, Nicolas; Hebrard, Gilles

2018-02-01

An approach for visualizing and measuring the mass transfer around a single bubble rising in a quiescent liquid is reported. A colorimetric technique, developed by (Dietrich et al. Chem Eng Sci 100:172-182, 2013) using an oxygen sensitive redox dye was implemented. It was based on the reduction of the colorimetric indicator in presence of oxygen, this reduction being catalysed by sodium hydroxide and glucose. In this study, resazurin was selected because it offered various reduced forms with colours ranging from transparent (without oxygen) to pink (in presence of oxygen). These advantages made it possible to visualize the spatio-temporal oxygen mass transfer around rising bubbles. Images were recorded by a CCD camera and, after post-processing, the shape, size, and velocity of the bubbles were measured and the colours around the bubbles mapped. A calibration, linking the level of colour with the dissolved oxygen concentration, enabled colour maps to be converted into oxygen concentration fields. A rheoscopic fluid was used to visualize the wake of the bubbles. A calculation method was also developed to determine the transferred oxygen fluxes around bubbles of two sizes (d = 0.82 mm and d = 2.12 mm) and the associated liquid-side mass transfer coefficients. The results compared satisfactorily with classical global measurements made by oxygen micro-sensors or from the classical models. This study thus constitutes a striking example of how this new colorimetric method could become a remarkable tool for exploring gas-liquid mass transfer in fluids.

Oxygen and carbon transfer during solidification of semiconductor grade silicon in different processes

Science.gov (United States)

Ribeyron, P. J.; Durand, F.

2000-03-01

A model is established for comparing the solute distribution resulting from four solidification processes currently applied to semiconductor grade silicon: Czochralski pulling (CZ), floating zone (FZ), 1D solidification and electromagnetic continuous pulling (EMCP). This model takes into account solid-liquid interface exchange, evaporation to or contamination by the gas phase, container dissolution, during steady-state solidification, and in the preliminary preparation of the melt. For simplicity, the transfers are treated in the crude approximation of perfectly mixed liquid and boundary layers. As a consequence, only the axial ( z) distribution can be represented. Published data on oxygen and carbon transfer give a set of acceptable values for the thickness of the boundary layers. In the FZ and EMCP processes, oxygen evaporation can change the asymptotic behaviour of the reference Pfann law. In CZ and in 1D-solidification, a large variety of solute profile curves can be obtained, because they are very sensitive to the balance between crucible dissolution and evaporation. The CZ process clearly brings supplementary degrees of freedom via the geometry of the crucible, important for the dissolution phenomena, and via the rotation rate of the crystal and of the crucible, important for acting on transfer kinetics.

Study of oxygen mass transfer coefficient and oxygen uptake rate in a stirred tank reactor for uranium ore bioleaching

International Nuclear Information System (INIS)

Zokaei-Kadijani, S.; Safdari, J.; Mousavian, M.A.; Rashidi, A.

2013-01-01

Highlights: ► Mass transfer coefficient does not depend on biomass concentration. ► The pulp density has a negative effect on mass transfer coefficient. ► The pulp density is the unique factor that affects maximum OUR. ► In this work, Neale’s correlation is corrected for prediction of mass transfer coefficient. ► Biochemical reaction is a limiting factor in the uranium bioleaching process. - Abstract: In this work, the volumetric oxygen mass transfer coefficient and the oxygen uptake rate (OUR) were studied for uranium ore bioleaching process by Acidthiobacillus ferrooxidans in a stirred tank reactor. The Box-Bohnken design method was used to study the effect of operating parameters on the oxygen mass transfer coefficient. The investigated factors were agitation speed (rpm), aeration rate (vvm) and pulp density (% weight/volume) of the stirred tank reactor. Analysis of experimental results showed that the oxygen mass transfer coefficient had low dependence on biomass concentration but had higher dependence on the agitation speed, aeration rate and pulp density. The obtained biological enhancement factors were equal to ones in experiments. On the other hand, the obtained values for Damkohler number (Da < 0.468) indicated that the process was limited by the biochemical reaction rate. Experimental results obtained for oxygen mass transfer coefficient were correlated with the empirical relations proposed by Garcia-Ochoa and Gomez (2009) and Neale and Pinches (1994). Due to the high relative error in the correlation of Neale and Pinches, that correlation was corrected and the coefficient of determination was calculated to be 89%. The modified correlation has been obtained based on a wide range of operating conditions, which can be used to determine the mass transfer coefficient in a bioreactor

Electron transfer pathways in microbial oxygen biocathodes

Energy Technology Data Exchange (ETDEWEB)

Freguia, Stefano, E-mail: stefano@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan); Tsujimura, Seiya, E-mail: seiya@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan); Kano, Kenji, E-mail: kkano@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan)

2010-01-01

The ability of some bacteria to enhance the rate of cathodic oxygen reduction to water has been recently discovered, opening the way to an entirely renewable and environmentally friendly concept of biocathode. In this study we reveal that several mechanisms may induce catalytic effects by bacteria. These comprise mechanisms that are putatively beneficial to the bacteria as well as mechanisms which are merely side effects, including quinone autoxidation and direct O{sub 2} reduction by heme compounds. Here we showed that 1 muM of ACNQ is able to generate a significant catalytic wave for oxygen reduction, with onset at approximately 0 V vs. SHE. Similarly, adsorption of hemin on a carbon surface catalyses O{sub 2} reduction to H{sub 2}O{sub 2} with an onset of +0.2 V vs. SHE. To evaluate the catalytic pathways of live cells on cathodic oxygen reduction, two species of electrochemically active bacteria were selected as pure cultures, namely Acinetobacter calcoaceticus and Shewanella putrefaciens. The former appears to exploit a self-excreted redox compound with redox characteristics matching those of pyrroloquinoline quinone (PQQ) for extracellular electron transfer. The latter appears to utilise outer membrane-bound redox compounds. Interaction of quinones and cytochromes with the membrane-bound electron transfer chain is yet to be proven.

Mathematical modeling of oxygen transport in solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Svensson, Ann Mari

1997-12-31

This thesis develops mathematical models to describe the electrochemical performance of a solid oxide fuel cell cathode based on electrochemical kinetics and mass transfer. The individual effects of various coupled processes are investigated. A one-dimensional model is developed based on porous electrode theory. Two different mechanisms are investigated for the charge transfer reaction. One of these assumes that intermediately adsorbed oxygen atoms are reduced at the electrode/electrolyte interface, similar to the models proposed for metal electrodes. Simulated polarization curves exhibit limited currents due to depletion of oxygen adsorbates at high cathodic overvoltages. An empirical correlation is confirmed to exist between the limiting current an the oxygen partial pressure, however, a similar correlation often assumed to exist between the measured polarization resistance and the oxygen partial pressure could not be justified. For the other model, oxygen vacancies are assumed to be exchanged directly at the electrode/electrolyte interface. The electrochemical behaviour is improved by reducing the oxygen partial pressure, due to increased vacancy concentration of the electrode material. Simulated polarization curves exhibit Tafel-like slopes in the cathodic direction, which are due to polarization concentration, and not activation polarization in the conventional sense. Anodic limiting currents are predicted due to lack of available free sites for vacancy exchange at the cathode side. The thesis also presents a theoretical treatment of current and potential distributions in simple two-dimensional cell geometries, and a two-dimensional model for a porous electrode-electrolyte system for investigation of the effect of interfacial diffusion of adsorbates along the electrode/electrolyte interface. 172 refs., 60 figs., 11 tabs.

Energy transfers between N_2(A"3Σ) nitrogen metastable molecules and oxygen atoms and molecules

International Nuclear Information System (INIS)

De Souza, Antonio Rogerio

1985-01-01

This research thesis aims at determining reaction coefficients for energy transfers between nitrogen in its metastable status and oxygen atoms and molecules, the variation of these coefficients with respect to temperature (mainly in the 200-400 K range), products formed and more particularly branching rates of O("1S) oxygen and of NO_2. Reaction coefficients are experimentally determined by using the technique of post-discharge in flow. The experimental set-up is described and the study of the best operating conditions is reported. In the next part, the author reports the study of the energy transfer between nitrogen in its metastable status N_2(A) and oxygen molecules. Reaction coefficients are determined for the first three vibrational levels. The author then reports the study of the transfer of N_2(A) molecules on oxygen atoms in their fundamental status. Reactions coefficients and their variations are determined for the three first vibrational levels. The author describes the dissociation method and the method of detection of atomic oxygen. A kinetic model is proposed for the analysis of formed products during a post-discharge in flow, and the branching rate for the formation of O("1S) oxygen between 190 and 365 K is determined. The author finally discusses publications on the role of these reactions in the interpretation of some atmospheric phenomena

Effect of membranes on oxygen transfer rate and consumption within a newly developed three-compartment bioartificial liver device: Advanced experimental and theoretical studies.

Science.gov (United States)

Hilal-Alnaqbi, Ali; Mourad, Abdel-Hamid I; Yousef, Basem F

2014-01-01

A mathematical model is developed to predict oxygen transfer in the fiber-in-fiber (FIF) bioartificial liver device. The model parameters are taken from the constructed and tested FIF modules. We extended the Krogh cylinder model by including one more zone for oxygen transfer. Cellular oxygen uptake was based on Michaelis-Menten kinetics. The effect of varying a number of important model parameters is investigated, including (1) oxygen partial pressure at the inlet, (2) the hydraulic permeability of compartment B (cell region), (3) the hydraulic permeability of the inner membrane, and (4) the oxygen diffusivity of the outer membrane. The mathematical model is validated by comparing its output against the experimentally acquired values of an oxygen transfer rate and the hydrostatic pressure drop. Three governing simultaneous linear differential equations are derived to predict and validate the experimental measurements, e.g., the flow rate and the hydrostatic pressure drop. The model output simulated the experimental measurements to a high degree of accuracy. The model predictions show that the cells in the annulus can be oxygenated well even at high cell density or at a low level of gas phase PG if the value of the oxygen diffusion coefficient Dm is 16 × 10(-5) . The mathematical model also shows that the performance of the FIF improves by increasing the permeability of polypropylene membrane (inner fiber). Moreover, the model predicted that 60% of plasma has access to the cells in the annulus within the first 10% of the FIF bioreactor axial length for a specific polypropylene membrane permeability and can reach 95% within the first 30% of its axial length. © 2013 International Union of Biochemistry and Molecular Biology, Inc.

Modelling of the heat transfer during oxygen atoms recombination on metallic surfaces in a plasma reactor

NARCIS (Netherlands)

Cavadias, S; Cauquot, P; Amouroux, J

1997-01-01

Space shuttle overheating during the re-entry phase, due to catalytic oxygen recombination on the thermal protection system, is a problem of practical and theoretical interest. The energy transfer is characterised by the product of the accommodation and the recombination coefficients. Previous

Oxygen transfer rate during the production of alginate by Azotobacter vinelandii under oxygen-limited and non oxygen-limited conditions

Directory of Open Access Journals (Sweden)

Peña Carlos F

2011-02-01

Full Text Available Abstract Background The oxygen transfer rate (OTR and dissolved oxygen tension (DOT play an important role in determining alginate production and its composition; however, no systematic study has been reported about the independent influence of the OTR and DOT. In this paper, we report a study about alginate production and the evolution of the molecular mass of the polymer produced by a wild-type A. vinelandii strain ATCC 9046, in terms of the maximum oxygen transfer rate (OTRmax in cultures where the dissolved oxygen tension (DOT was kept constant. Results The results revealed that in the two dissolved oxygen conditions evaluated, strictly controlled by gas blending at 0.5 and 5% DOT, an increase in the agitation rate (from 300 to 700 rpm caused a significant increase in the OTRmax (from 17 to 100 mmol L-1 h-1 for DOT of 5% and from 6 to 70 mmol L-1 h-1 for DOT of 0.5%. This increase in the OTRmax improved alginate production, as well as the specific alginate production rate (SAPR, reaching a maximal alginate concentration of 3.1 g L-1 and a SAPR of 0.031 g alg g biom-1 h-1 in the cultures at OTRmax of 100 mmol L-1 h-1. In contrast, the mean molecular mass (MMM of the alginate isolated from cultures developed under non-oxygen limited conditions increased by decreasing the OTRmax, reaching a maximal of 550 kDa at an OTRmax of 17 mmol L-1 h-1 . However, in the cultures developed under oxygen limitation (0.5% DOT, the MMM of the polymer was practically the same (around 200 kDa at 300 and 700 rpm, and this remained constant throughout the cultivation. Conclusions Overall, our results showed that under oxygen-limited and non oxygen-limited conditions, alginate production and its molecular mass are linked to the OTRmax, independently of the DOT of the culture.

Charge transfer induced activity of graphene for oxygen reduction

International Nuclear Information System (INIS)

Shen, Anli; Xia, Weijun; Dou, Shuo; Wang, Shuangyin; Zhang, Lipeng; Xia, Zhenhai

2016-01-01

Tetracyanoethylene (TCNE), with its strong electron-accepting ability, was used to dope graphene as a metal-free electrocatalyst for the oxygen reduction reaction (ORR). The charge transfer process was observed from graphene to TCNE by x-ray photoelectron spectroscopy and Raman characterizations. Our density functional theory calculations found that the charge transfer behavior led to an enhancement of the electrocatalytic activity for the ORR. (paper)

PHOTOINDUCED TRANSFER OF OXYGEN FROM WATER: AN ARTIFICAL PHOTOSYNTHETIC SYSTEM

Energy Technology Data Exchange (ETDEWEB)

Willner, Itamar; Otvos, John W.; Ford, William E.; Mettee, Howard; Calvin, Melvin

1979-11-01

The photoinduced splitting of water into hydrogen and oxygen has evoked great interest in recent years as a means for energy storag eand fuel production. Photoinduced reduction of water to hydrogen, using visible light, has been described using heterogeneous or homogeneous catalysts. However, the complementary part involving the oxidation of water to oxygen is required in order to create a cyclic artificial 'photosynthetic' fuel system. The major difficulty assocaited with the photooxidation of water involves the requirement for a four electron transfer to produce oxygen. A stepwise one-electron oxidation of water is unfavorable due to the implied formation of active hydroxyl radicals. Very recently, it has been reported that RuO{sub 2} can serve as a heterogeneous charge storage catalyst for oxygen production. On the basis of the limited knowledge about natural photosynthesis, in which manganese ions play an important role in oxygen evolution, synthetic manganese complexes, and in particular dimeric complexes, have been proposed as potential catalysts for oxygen production. So far, efforts directed toward this goal have been unsuccessful. Consequently, using a manganese complex, they attempted to perform a photoinduced oxidation of water whereby the active oxygen is transferred to a trapping substrate. In such a way, the requirement for a dimerization process to evolve molecular oxygen is avoided. They wish to report a photoinduced redox cycle sensitized by a manganese porphyrin, 5-(4{prime}-hexadecylpyridium)-10, 15, 20-tri (4{prime}-pyridyl)-porphinatomanganese(III) (abbreciated to Pn-Mn{sup III}) in which the resultant reaction is the oxidation of water and trapping of the single oxygen atom by a substrate (triphenylphosphine).

Accelerated Oxygen Atom Transfer and C-H Bond Oxygenation by Remote Redox Changes in Fe3 Mn-Iodosobenzene Adducts.

Science.gov (United States)

de Ruiter, Graham; Carsch, Kurtis M; Gul, Sheraz; Chatterjee, Ruchira; Thompson, Niklas B; Takase, Michael K; Yano, Junko; Agapie, Theodor

2017-04-18

We report the synthesis, characterization, and reactivity of [LFe 3 (PhPz) 3 OMn( s PhIO)][OTf] x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzene-metal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, 57 Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe III 2 Fe II Mn II vs. Fe III 3 Mn II ) influence oxygen atom transfer in tetranuclear Fe 3 Mn clusters. In particular, a one-electron redox change at a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

3-D Numerical Investigation on Oxygen Transfer in a Horizontal Venturi Flow with Two Holes

Directory of Open Access Journals (Sweden)

Zegao Yin

2018-02-01

Full Text Available In order to investigate the dissolved oxygen increase caused by air suction in a horizontal Venturi flow with two holes, a 3-D computational fluid dynamics model was used to explore the water and bubble mixture flow, coupled with a dissolved oxygen transfer model. A series of experiments were conducted to validate the mathematical model. A relative saturation coefficient correlation was examined factoring in dissolved oxygen concentration at the inlet, water velocity at the inlet, the hole’s diameter, contraction ratio at throat section, and the downstream length of Venturi pipe. It was found that the relative saturation coefficient increases with increasing dissolved oxygen concentration at the inlet and downstream length of Venturi pipe respectively. However, it increases with decreasing water velocity at the inlet and contraction ratio at the throat section to some extent. The hole’s diameter plays a complex role in the relative saturation coefficient. The dimensional analysis method and the least square method were used to deduce a simple formula for the relative saturation coefficient, and this was consistent with related data.

Optimization of perfluorocarbon emulsion properties for enhancing oxygen mass transfer in a bio-artificial liver support system

CSIR Research Space (South Africa)

Moolman, FS

2004-07-29

Full Text Available : With increase in the dispersed phase volume fraction (phi(p)) both the oxygen holding capacity and the viscosity increases. These issues are addressed here using simplified mass transfer models, amenable to analytical solution, for both gas-sparged and membrane...

Promotion of multi-electron transfer for enhanced photocatalysis: A review focused on oxygen reduction reaction

Energy Technology Data Exchange (ETDEWEB)

Wang, Changhua [Centre for Advanced Optoelectronic Functional Materials Research, and Key Laboratory for UV-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, Changchun 130024 (China); College of Chemistry and Biology, Beihua University, Jilin 132013 (China); Zhang, Xintong, E-mail: xtzhang@nenu.edu.cn [Centre for Advanced Optoelectronic Functional Materials Research, and Key Laboratory for UV-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, Changchun 130024 (China); Liu, Yichun [Centre for Advanced Optoelectronic Functional Materials Research, and Key Laboratory for UV-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, Changchun 130024 (China)

2015-12-15

Highlights: • Oxygen reduction reaction (ORR) in photocatalysis process is focused. • Multi-electron transfer ORR is reviewed. • This review provides a guide to access to enhanced photocatalysis via multi-electron transfer. - Abstract: Semiconductor photocatalysis has attracted significant interest for solar light induced environmental remediation and solar fuel generation. As is well known, photocatalytic performance is determined by three steps: photoexcitation, separation and transport of photogenerated charge carriers, and surface reactions. To achieve higher efficiency, significant efforts have been made on improvement of efficiency of above first two steps, which have been well documented in recent review articles. In contrast, this review intends to focus on strategies moving onto the third step of improvement for enhanced photocatalysis wherein active oxygen species including superoxide radical, hydrogen peroxide, hydroxyl radical are in situ detected. Particularly, surface electron-transfer reduction of oxygen over single component photocatalysts is reviewed and systems enabling multi-electron transfer induced oxygen reduction reaction (ORR) are highlighted. It is expected this review could provide a guideline for readers to better understand the critical role of ORR over photocatalyst in charge carrier separation and transfer and obtain reliable results for enhanced aerobic photocatalysis.

Study of magnetic field to promote oxygen transfer and its application in zinc–air fuel cells

International Nuclear Information System (INIS)

Shi, Jicheng; Xu, Hongfeng; Lu, Lu; Sun, Xin

2013-01-01

Highlights: ► High magnetic strength reduces R ct and increases C d in oxygen reduction reaction. ► Oxygen diffusion and transfer coefficient become large in high magnetic strength. ► The magnetic ZAFC discharge performance is better than the nonmagnetic ZAFC. ► Increased NdFeB/C load density improves the magnetic ZAFC discharge performance. ► Excess NdFeB/C load density decreases the magnetic ZAFC discharge performance. -- Abstract: This study investigates the effects of magnetic field on oxygen transfer and the correlations of electrochemical parameters in different magnetic strengths. The discharge performance of zinc–air fuel cell (ZAFC) was tested under magnetic and nonmagnetic conditions using neodymium–iron–boron/carbon (NdFeB/C) magnetic particles in ZAFC cathode. The results showed that the oxygen diffusion coefficient (D Oi ) and transfer coefficient (α i ) increased by 102.14% and 52.38% when the magnetic strength increased from 0 mT to 5.0 mT, respectively. In addition, the electric double-layer capacitance (C d ) increased from 8.16 to 22.46 μF cm −2 , the charge-transfer resistance (R ct ) decreased from 9.43 Ω cm 2 to 6.02 Ω cm 2 , and the oxygen reduction reaction (ORR) current was improved. With the NdFeB/C load density of 2.4 mg cm −2 in ZAFC cathode, the discharge current of magnetic ZAFC increased by 13.86% compared with the nonmagnetic ZAFC at the 0.80 V discharge voltage. These results indicate that magnetic strength has a positive correlation with D Oi , α i , and the ORR current. Under magnetic attractions, the oxygen transfer process is easier at the Pt/C catalytic surface, and the discharge performance of magnetic ZAFC is superior to the nonmagnetic ZAFC. At lower NdFeB/C load density, increasing the NdFeB/C load density facilitates oxygen transfer and improves the discharge performance of ZAFC. However, the magnetic ZAFC discharge performance decreases at a higher NdFeB/C load density because of the blocked oxygen

Modelling of heat and mass transfer processes in neonatology

Energy Technology Data Exchange (ETDEWEB)

Ginalski, Maciej K [FLUENT Europe, Sheffield Business Park, Europa Link, Sheffield S9 1XU (United Kingdom); Nowak, Andrzej J [Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, 44-100 Gliwice (Poland); Wrobel, Luiz C [School of Engineering and Design, Brunel University, Uxbridge UB8 3PH (United Kingdom)], E-mail: maciej.ginalski@ansys.com, E-mail: Andrzej.J.Nowak@polsl.pl, E-mail: luiz.wrobel@brunel.ac.uk

2008-09-01

This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices.

Modelling of heat and mass transfer processes in neonatology

International Nuclear Information System (INIS)

Ginalski, Maciej K; Nowak, Andrzej J; Wrobel, Luiz C

2008-01-01

This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices

Development of a Mass Transfer Model and Its Application to the Behavior of the Cs, Sr, Ba, and Oxygen ions in an Electrolytic Reduction Process for SF

International Nuclear Information System (INIS)

Park, Byung Heung; Kang, Dae Seung; Seo, Chung Seok; Park, Seong Won

2005-01-01

Isotopes of alkali and alkaline earth metals (AM and AEM) are the main contributors to the heat load and the radiotoxicity of spent fuel (SF). These components are separated from the SF and dissolved in a molten LiCl in an electrolytic reduction process. A mass transfer model is developed to describe the diffusion behavior of Cs, Sr, and Ba in the SF into the molten salt. The model is an analytical solution of Fick's second law of diffusion for a cylinder which is the shape of a cathode in the electrolytic reduction process. And the model is also applied to depict the concentration profile of the oxygen ion which is produced by the electrolysis of Li 2 O. The regressed diffusion coefficients of the model correlating the experimentally measured data are evaluated to be greater in the order of Ba, Cs, and Sr for the metal ions and the diffusion of the oxygen ion is slower than the metal ions which implies that different mechanisms govern the diffusion of the metal ions and the oxygen ions in a molten LiCl.

Gas hold-up and oxygen mass transfer in three pneumatic bioreactors operating with sugarcane bagasse suspensions.

Science.gov (United States)

Esperança, M N; Cunha, F M; Cerri, M O; Zangirolami, T C; Farinas, C S; Badino, A C

2014-05-01

Sugarcane bagasse is a low-cost and abundant by-product generated by the bioethanol industry, and is a potential substrate for cellulolytic enzyme production. The aim of this work was to evaluate the effects of air flow rate (QAIR), solids loading (%S), sugarcane bagasse type, and particle size on the gas hold-up (εG) and volumetric oxygen transfer coefficient (kLa) in three different pneumatic bioreactors, using response surface methodology. Concentric tube airlift (CTA), split-cylinder airlift (SCA), and bubble column (BC) bioreactor types were tested. QAIR and %S affected oxygen mass transfer positively and negatively, respectively, while sugarcane bagasse type and particle size (within the range studied) did not influence kLa. Using large particles of untreated sugarcane bagasse, the loop-type bioreactors (CTA and SCA) exhibited higher mass transfer, compared to the BC reactor. At higher %S, SCA presented a higher kLa value (0.0448 s−1) than CTA, and the best operational conditions in terms of oxygen mass transfer were achieved for %S 27.0 L min−1. These results demonstrated that pneumatic bioreactors can provide elevated oxygen transfer in the presence of vegetal biomass, making them an excellent option for use in three-phase systems for cellulolytic enzyme production by filamentous fungi.

Oxygen mass transfer in a stirred tank bioreactor using different impeller configurations for environmental purposes

Science.gov (United States)

2013-01-01

In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581

Gas transfer under breaking waves: experiments and an improved vorticity-based model

Directory of Open Access Journals (Sweden)

V. K. Tsoukala

2008-07-01

Full Text Available In the present paper a modified vorticity-based model for gas transfer under breaking waves in the absence of significant wind forcing is presented. A theoretically valid and practically applicable mathematical expression is suggested for the assessment of the oxygen transfer coefficient in the area of wave-breaking. The proposed model is based on the theory of surface renewal that expresses the oxygen transfer coefficient as a function of both the wave vorticity and the Reynolds wave number for breaking waves. Experimental data were collected in wave flumes of various scales: a small-scale experiments were carried out using both a sloping beach and a rubble-mound breakwater in the wave flume of the Laboratory of Harbor Works, NTUA, Greece; b large-scale experiments were carried out with a sloping beach in the wind-wave flume of Delft Hydraulics, the Netherlands, and with a three-layer rubble mound breakwater in the Schneideberg Wave Flume of the Franzius Institute, University of Hannover, Germany. The experimental data acquired from both the small- and large-scale experiments were in good agreement with the proposed model. Although the apparent transfer coefficients from the large-scale experiments were lower than those determined from the small-scale experiments, the actual oxygen transfer coefficients, as calculated using a discretized form of the transport equation, are in the same order of magnitude for both the small- and large-scale experiments. The validity of the proposed model is compared to experimental results from other researchers. Although the results are encouraging, additional research is needed, to incorporate the influence of bubble mediated gas exchange, before these results are used for an environmental friendly design of harbor works, or for projects involving waste disposal at sea.

Intra-particle oxygen diffusion limitation in solid-state fermentation

NARCIS (Netherlands)

Oostra, J.; Comte, le E.P.; Heuvel, van den J.C.; Tramper, J.; Rinzema, A.

2001-01-01

Oxygen limitation in solid-state fermentation (SSF) has been the topic of modeling studies, but thus far, there has been no experimental elucidation on oxygen-transfer limitation at the particle level. Therefore, intra-particle oxygen transfer was experimentally studied in cultures of Rhizopus

Investigation of tungsten mass transfer in rarefied air oxygen and water vapors

International Nuclear Information System (INIS)

Evsikov, A.S.; Makeev, A.A.; Lyubimova, L.L.; Sinyavskij, V.V.

1989-01-01

The results of experimental investigations of oxygen and water vapor effect on the rate of tungsten evaporation are presented. Methods for carrying out an experiment are presented. The experiments are carried out at the 2600 degC tungsten wire temperature and the pressure of oxygen and water vapors (2x10 -3 -5) Pa. Registration of final products of mass transfer is carried out by the DRON-2.0 diffractometer using a detachable substrate. Empirical dependence taking into account oxygen and water vapor effect on the rate of tungsten evaporation is suggested. It is marked that air oxygen and water vapor increase evaporation rate uniformly the difference is observed only in final products of interaction

Study on low intensity aeration oxygenation model and optimization for shallow water

Science.gov (United States)

Chen, Xiao; Ding, Zhibin; Ding, Jian; Wang, Yi

2018-02-01

Aeration/oxygenation is an effective measure to improve self-purification capacity in shallow water treatment while high energy consumption, high noise and expensive management refrain the development and the application of this process. Based on two-film theory, the theoretical model of the three-dimensional partial differential equation of aeration in shallow water is established. In order to simplify the equation, the basic assumptions of gas-liquid mass transfer in vertical direction and concentration diffusion in horizontal direction are proposed based on engineering practice and are tested by the simulation results of gas holdup which are obtained by simulating the gas-liquid two-phase flow in aeration tank under low-intensity condition. Based on the basic assumptions and the theory of shallow permeability, the model of three-dimensional partial differential equations is simplified and the calculation model of low-intensity aeration oxygenation is obtained. The model is verified through comparing the aeration experiment. Conclusions as follows: (1)The calculation model of gas-liquid mass transfer in vertical direction and concentration diffusion in horizontal direction can reflect the process of aeration well; (2) Under low-intensity conditions, the long-term aeration and oxygenation is theoretically feasible to enhance the self-purification capacity of water bodies; (3) In the case of the same total aeration intensity, the effect of multipoint distributed aeration on the diffusion of oxygen concentration in the horizontal direction is obvious; (4) In the shallow water treatment, reducing the volume of aeration equipment with the methods of miniaturization, array, low-intensity, mobilization to overcome the high energy consumption, large size, noise and other problems can provide a good reference.

Improvement of AD Biosynthesis Response to Enhanced Oxygen Transfer by Oxygen Vectors in Mycobacterium neoaurum TCCC 11979.

Science.gov (United States)

Su, Liqiu; Shen, Yanbing; Gao, Tian; Luo, Jianmei; Wang, Min

2017-08-01

In steroid biotransformation, soybean oil can improve the productivity of steroids by increasing substrate solubility and strengthen the cell membrane permeability. However, little is known of its role as oxygen carrier and its mechanism of promoting the steroid biotransformation. In this work, soybean oil used as oxygen vector for the enhancement of androst-4-ene-3,17-dione (AD) production by Mycobacterium neoaurum TCCC 11979 (MNR) was investigated. Upon the addition of 16% (v/v) soybean oil, the volumetric oxygen transfer coefficient (K L a) value increased by 44%, and the peak molar yield of AD (55.76%) was achieved. Analysis of intracellular cofactor levels showed high NAD + , ATP level, and a low NADH/NAD + ratio. Meanwhile, the two key enzymes of the tricarboxylic acid (TCA) cycle, namely, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, were upregulated after incubation with soybean oil. These enhancements induced by the increasing of oxygen supply showed positive effects on phytosterol (PS) bioconversion. Results could contribute to the understanding of effects of soybean oil as oxygen vector on steroid biotransformation and provided a convenient method for enhancing the efficiency of aerobic steroid biocatalysis.

Low-head hydropower impacts on steam dissolved oxygen

International Nuclear Information System (INIS)

Thene, J.R.; Stefan, H.G.; Daniil, E.I.

1989-01-01

A method to evaluate the effect of hydropower development on downstream dissolved oxygen (DO) is presented for a low head dam. Water, previously aerated during release over spillways and under gates, is diverted through the hydropower facility without further aeration. The oxygen transfer that occurs as a result of air entrainment at the various release points of a dam is measured. Oxygen transfer efficiencies are calculated and incorporated into an oxygen transfer model to predict average release DO concentrations. This model is used to systematically determine the effect of hydropower operation on downstream DO. Operational alternatives are investigated and a simple operational guide is developed to mitigate the effects of hydropower operation. Combinations of reduced generation and optimal releases from the dam allow the hydropower facility to operate within DO standards

Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

Science.gov (United States)

Barklem, P. S.

2018-02-01

Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20 000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates. Data are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57. The data are also available at http://https://github.com/barklem/public-data

Towards a Biohybrid Lung: Endothelial Cells Promote Oxygen Transfer through Gas Permeable Membranes.

Science.gov (United States)

Menzel, Sarah; Finocchiaro, Nicole; Donay, Christine; Thiebes, Anja Lena; Hesselmann, Felix; Arens, Jutta; Djeljadini, Suzana; Wessling, Matthias; Schmitz-Rode, Thomas; Jockenhoevel, Stefan; Cornelissen, Christian Gabriel

2017-01-01

In patients with respiratory failure, extracorporeal lung support can ensure the vital gas exchange via gas permeable membranes but its application is restricted by limited long-term stability and hemocompatibility of the gas permeable membranes, which are in contact with the blood. Endothelial cells lining these membranes promise physiological hemocompatibility and should enable prolonged application. However, the endothelial cells increase the diffusion barrier of the blood-gas interface and thus affect gas transfer. In this study, we evaluated how the endothelial cells affect the gas exchange to optimize performance while maintaining an integral cell layer. Human umbilical vein endothelial cells were seeded on gas permeable cell culture membranes and cultivated in a custom-made bioreactor. Oxygen transfer rates of blank and endothelialized membranes in endothelial culture medium were determined. Cell morphology was assessed by microscopy and immunohistochemistry. Both setups provided oxygenation of the test fluid featuring small standard deviations of the measurements. Throughout the measuring range, the endothelial cells seem to promote gas transfer to a certain extent exceeding the blank membranes gas transfer performance by up to 120%. Although the underlying principles hereof still need to be clarified, the results represent a significant step towards the development of a biohybrid lung.

Kinetics of oxygen uncoupling of a copper based oxygen carrier

International Nuclear Information System (INIS)

Hu, Wenting; Donat, Felix; Scott, S.A.; Dennis, J.S.

2016-01-01

Highlights: • The kinetics of a Cu-based oxygen carrier was determined using a TGA. • A diffusion model was applied to remove mass transfer effects from rate parameters. • Thermodynamics are separated from kinetics, usually difficult for the CLOU reaction. • The rate parameters correctly described the behaviour in a fluidised bed. • The rate parameters can be used to predict performance of large CLOU systems. - Abstract: Here, an oxygen carrier consisting of 60 wt% CuO supported on a mixture of Al_2O_3 and CaO (23 wt% and 17 wt% respectively) was synthesised by wet-mixing powdered CuO, Al(OH)_3 and Ca(OH)_2, followed by calcination at 1000 °C. Its suitability for chemical looping with oxygen uncoupling (CLOU) was investigated. After 25 repeated redox cycles in either a thermogravimetric analyser (TGA) or a laboratory-scale fluidised bed, (with 5 vol% H_2 in N_2 as the fuel, and air as the oxidant) no significant change in either the oxygen uncoupling capacity or the overall oxygen availability of the carrier was found. In the TGA, it was found that the rate of oxygen release from the material was controlled by intrinsic chemical kinetics and external transfer of mass from the surface of the particles to the bulk gas. By modelling the various resistances, values of the rate constant for the decomposition were obtained. The activation energy of the reaction was found to be 59.7 kJ/mol (with a standard error of 5.6 kJ/mol) and the corresponding pre-exponential factor was 632 m"3/mol/s. The local rate of conversion within a particle was assumed to occur either (i) by homogeneous chemical reaction, or (ii) in uniform, non-porous grains, each reacting as a kinetically-controlled shrinking core. Upon cross validation against a batch fluidised bed experiment, the homogeneous reaction model was found to be more plausible. By accurately accounting for the various artefacts (e.g. mass transfer resistances) present in both TGA and fluidised bed experiments, it was

A model for the chain-to-plane charge transfer in YBa2Cu3O6+x

International Nuclear Information System (INIS)

Matic, V. M.; Lazarov, N. Dj.; Milic, M.

2012-01-01

A model for the chain-to-plane charge transfer is proposed to account for the two plateaus, at 60 K and at 90 K, of the T c (x) characteristics of the YBa 2 Cu 3 O 6+x high-T c superconductor. It is assumed that the number of holes transferred from a CuO chain of length l to two nearby CuO 2 sheets is proportional to l (that is, to the number of oxygen atoms in the chain), if the chain length is greater than, or equal to, a certain critical chain length, l cr , that is required to trigger the charge transfer process. No holes are assumed to have been transferred from chains of length l cr . The calculated T c (x) dependence is found to be in excellent agreement with the experimentally reported T c (x). The critical chain length parameter is estimated to be equal to l cr = 11 (eleven oxygen atoms in a chain), which is a greater value than that obtained in the previously proposed model for the chain-to-plane charge transfer (l cr = 4). The results obtained out of the proposed model are briefly discussed

Oxygen permeation modelling of perovskites

NARCIS (Netherlands)

van Hassel, Bart A.; van Hassel, B.A.; Kawada, Tatsuya; Sakai, Natsuko; Yokokawa, Harumi; Dokiya, Masayuki; Bouwmeester, Henricus J.M.

1993-01-01

A point defect model was used to describe the oxygen nonstoichiometry of the perovskites La0.75Sr0.25CrO3, La0.9Sr0.1FeO3, La0.9Sr0.1CoO3 and La0.8Sr0.2MnO3 as a function of the oxygen partial pressure. Form the oxygen vacancy concentration predicte by the point defect model, the ionic conductivity

Oxygen-assisted charge transfer between ZnO quantum dots and graphene.

Science.gov (United States)

Guo, Wenhao; Xu, Shuigang; Wu, Zefei; Wang, Ning; Loy, M M T; Du, Shengwang

2013-09-23

Efficient charge transfer between ZnO quantum dots (QDs) and graphene is demonstrated by decorating ZnO QDs on top of graphene, with the assistance of oxygen molecules from the air. The electrical response of the device to UV light is greatly enhanced, and a photoconductive gain of up to 10(7) can be obtained. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A conceptual design of catalytic gasification fuel cell hybrid power plant with oxygen transfer membrane

Science.gov (United States)

Shi, Wangying; Han, Minfang

2017-09-01

A hybrid power generation system integrating catalytic gasification, solid oxide fuel cell (SOFC), oxygen transfer membrane (OTM) and gas turbine (GT) is established and system energy analysis is performed. In this work, the catalytic gasifier uses steam, recycled anode off-gas and pure oxygen from OTM system to gasify coal, and heated by hot cathode off-gas at the same time. A zero-dimension SOFC model is applied and verified by fitting experimental data. Thermodynamic analysis is performed to investigate the integrated system performance, and system sensitivities on anode off-gas back flow ratio, SOFC fuel utilization, temperature and pressure are discussed. Main conclusions are as follows: (1) System overall electricity efficiency reaches 60.7%(HHV) while the gasifier operates at 700 °C and SOFC at 850 °C with system pressure at 3.04 bar; (2) oxygen enriched combustion simplify the carbon-dioxide capture process, which derives CO2 of 99.2% purity, but results in a penalty of 6.7% on system electricity efficiency; (3) with SOFC fuel utilization or temperature increasing, the power output of SOFC increases while GT power output decreases, and increasing system pressure can improve both the performance of SOFC and GT.

Electrocatalysis of anodic oxygen-transfer reactions at modified lead dioxide electrodes

Energy Technology Data Exchange (ETDEWEB)

Hsiao, Yun-Lin.

1990-09-21

The electrocatalytic activities were compared for pure and chloride-doped beta-PbO{sub 2} (Cl-PbO{sub 2}) films on gold and platinum substrates. Rate constants were increased significantly for oxidations of Mn{sup 2+}, toluene, benzyl alcohol, dimethylsulphoxide (DMSO) and benzaldehyde in acidic media by the incorporation of Cl{sup {minus}} into the oxide films. These reactions are concluded to occur by the electrocatalytic transfer of oxygen from H{sub 2}O to the reaction products. Results of x-ray diffraction studies indicate the Cl-PbO{sub 2} film continues to have the slightly distorted rutile structure of pure beta-PbO{sub 2}. The observed electrocatalytic phenomena are concluded to be the beneficial consequence of surface defects generated when Cl{sup {minus}} serves for charge compensation within the surface matrix and, thereby, increases the number of surface sites capable of adsorbing hydroxyl radicals which are transferred in the electrocatalytic O-transfer reactions. 91 refs., 44 figs., 10 tabs.

Oxygen-Reducing Biocathodes Operating with Passive Oxygen Transfer in Microbial Fuel Cells

KAUST Repository

Xia, Xue

2013-02-19

Oxygen-reducing biocathodes previously developed for microbial fuel cells (MFCs) have required energy-intensive aeration of the catholyte. To avoid the need for aeration, the ability of biocathodes to function with passive oxygen transfer was examined here using air cathode MFCs. Two-chamber, air cathode MFCs with biocathodes produced a maximum power density of 554 ± 0 mW/m 2, which was comparable to that obtained with a Pt cathode (576 ± 16 mW/m2), and 38 times higher than that produced without a catalyst (14 ± 3 mW/m2). The maximum current density with biocathodes in this air-cathode MFC was 1.0 A/m2, compared to 0.49 A/m2 originally produced in a two-chamber MFC with an aqueous cathode (with cathode chamber aeration). Single-chamber, air-cathode MFCs with the same biocathodes initially produced higher voltages than those with Pt cathodes, but after several cycles the catalytic activity of the biocathodes was lost. This change in cathode performance resulted from direct exposure of the cathodes to solutions containing high concentrations of organic matter in the single-chamber configuration. Biocathode performance was not impaired in two-chamber designs where the cathode was kept separated from the anode solution. These results demonstrate that direct-air biocathodes can work very well, but only under conditions that minimize heterotrophic growth of microorganisms on the cathodes. © 2013 American Chemical Society.

Technology Transfer Issues and a New Technology Transfer Model

Science.gov (United States)

Choi, Hee Jun

2009-01-01

The following are major issues that should be considered for efficient and effective technology transfer: conceptions of technology, technological activity and transfer, communication channels, factors affecting transfer, and models of transfer. In particular, a well-developed model of technology transfer could be used as a framework for…

Glacial-interglacial variability in ocean oxygen and phosphorus in a global biogeochemical model

Directory of Open Access Journals (Sweden)

V Palastanga

2013-02-01

Full Text Available Increased transfer of particulate matter from continental shelves to the open ocean during glacials may have had a major impact on the biogeochemistry of the ocean. Here, we assess the response of the coupled oceanic cycles of oxygen, carbon, phosphorus, and iron to the input of particulate organic carbon and reactive phosphorus from shelves. We use a biogeochemical ocean model and specifically focus on the Last Glacial Maximum (LGM. When compared to an interglacial reference run, our glacial scenario with shelf input shows major increases in ocean productivity and phosphorus burial, while mean deep-water oxygen concentrations decline. There is a downward expansion of the oxygen minimum zones (OMZs in the Atlantic and Indian Ocean, while the extension of the OMZ in the Pacific is slightly reduced. Oxygen concentrations below 2000 m also decline but bottom waters do not become anoxic. The model simulations show when shelf input of particulate organic matter and particulate reactive P is considered, low oxygen areas in the glacial ocean expand, but concentrations are not low enough to generate wide scale changes in sediment biogeochemistry and sedimentary phosphorus recycling. Increased reactive phosphorus burial in the open ocean during the LGM in the model is related to dust input, notably over the southwest Atlantic and northwest Pacific, whereas input of material from shelves explains higher burial fluxes in continental slope and rise regions. Our model results are in qualitative agreement with available data and reproduce the strong spatial differences in the response of phosphorus burial to glacial-interglacial change. Our model results also highlight the need for additional sediment core records from all ocean basins to allow further insight into changes in phosphorus, carbon and oxygen dynamics in the ocean on glacial-interglacial timescales.

Experimental evaluation of the oxygen transfer in bubble aeration systems. Full scale experiences in lengthened activated sludge reactors

International Nuclear Information System (INIS)

Andreottola, G.; Ragazzi, M.; Tatano, F.

1999-01-01

The results of some full-scale oxygen transfer measurements conduced at the lengthened activate sludge tanks of two WWTPs of Trentino Region, are presented and discussed. As far at the tests in clean water are concerned, the non-liner regression method seems non accurate; important conclusion on the correlation between oxygen transfer process and typical parameters (i.e., fine-bubble diffusers, specific air flux) are derived. As far as the test in the wastewater is concerned, an increase of α-value from the inlet to the end of aeration tanks has been observed in the 'Andalo' WWTP [it

Computational Investigation of Amine–Oxygen Exciplex Formation

Science.gov (United States)

Haupert, Levi M.; Simpson, Garth J.; Slipchenko, Lyudmila V.

2012-01-01

It has been suggested that fluorescence from amine-containing dendrimer compounds could be the result of a charge transfer between amine groups and molecular oxygen [Chu, C.-C.; Imae, T. Macromol. Rapid Commun. 2009, 30, 89.]. In this paper we employ equation-of-motion coupled cluster computational methods to study the electronic structure of an ammonia–oxygen model complex to examine this possibility. The results reveal several bound electronic states with charge transfer character with emission energies generally consistent with previous observations. However, further work involving confinement, solvent, and amine structure effects will be necessary for more rigorous examination of the charge transfer fluorescence hypothesis. PMID:21812447

Manganese-Oxygen Intermediates in O-O Bond Activation and Hydrogen-Atom Transfer Reactions.

Science.gov (United States)

Rice, Derek B; Massie, Allyssa A; Jackson, Timothy A

2017-11-21

Biological systems capitalize on the redox versatility of manganese to perform reactions involving dioxygen and its derivatives superoxide, hydrogen peroxide, and water. The reactions of manganese enzymes influence both human health and the global energy cycle. Important examples include the detoxification of reactive oxygen species by manganese superoxide dismutase, biosynthesis by manganese ribonucleotide reductase and manganese lipoxygenase, and water splitting by the oxygen-evolving complex of photosystem II. Although these enzymes perform very different reactions and employ structurally distinct active sites, manganese intermediates with peroxo, hydroxo, and oxo ligation are commonly proposed in catalytic mechanisms. These intermediates are also postulated in mechanisms of synthetic manganese oxidation catalysts, which are of interest due to the earth abundance of manganese. In this Account, we describe our recent efforts toward understanding O-O bond activation pathways of Mn III -peroxo adducts and hydrogen-atom transfer reactivity of Mn IV -oxo and Mn III -hydroxo complexes. In biological and synthetic catalysts, peroxomanganese intermediates are commonly proposed to decay by either Mn-O or O-O cleavage pathways, although it is often unclear how the local coordination environment influences the decay mechanism. To address this matter, we generated a variety of Mn III -peroxo adducts with varied ligand environments. Using parallel-mode EPR and Mn K-edge X-ray absorption techniques, the decay pathway of one Mn III -peroxo complex bearing a bulky macrocylic ligand was investigated. Unlike many Mn III -peroxo model complexes that decay to oxo-bridged-Mn III Mn IV dimers, decay of this Mn III -peroxo adduct yielded mononuclear Mn III -hydroxo and Mn IV -oxo products, potentially resulting from O-O bond activation of the Mn III -peroxo unit. These results highlight the role of ligand sterics in promoting the formation of mononuclear products and mark an important

The determination of oxygen in metals using an impulse heating furnace with a simple transfer lock

International Nuclear Information System (INIS)

Dale, L.S.; de Jong, S.; Kelly, J.W.; Whittem, R.N.

1975-05-01

An impulse heating furnace has been constructed for the determination of low levels of oxygen down to 100 μg g -1 in metals. The furnace is equipped with a sample transfer lock which permits samples to be loaded into outgassed crucibles in a helium atmosphere. As a result, blank levels in the range 2 to 3 μg oxygen are obtained; the modification also results in shorter sample processing time. The apparatus is described, and its suitability for oxygen determinations at these levels has been verified by comparison of results obtained on reference and analysed materials. (author)

Strategies to overcome oxygen transfer limitations during hairy root cultivation of Azadiracta indica for enhanced azadirachtin production.

Science.gov (United States)

Srivastava, Smita; Srivastava, Ashok Kumar

2012-07-01

The vast untapped potential of hairy root cultures as a stable source of biologically active chemicals has focused the attention of scientific community toward its commercial exploitation. However, the major bottleneck remains its successful scale-up. Due to branching, the roots form an interlocked matrix that exhibits resistance to oxygen transfer. Thus, present work was undertaken to develop cultivation strategies like optimization of inlet gas composition (in terms of % (v/v) O(2) in air), air-flow rate and addition of oxygen vectors in the medium, to curb the oxygen transfer limitations during hairy root cultivation of Azadirachta indica for in vitro azadirachtin (a biopesticide) production. It was found that increasing the oxygen fraction in the inlet air (in the range, 20-100% (v/v) O(2) in air) increased the azadirachtin productivity by approximately threefold, to a maximum of 4.42 mg/L per day (at 100% (v/v) O(2) in air) with respect to 1.68 mg/L per day in control (air with no oxygen supplementation). Similarly, increasing the air-flow rate (in the range, 0.3-2 vvm) also increased the azadirachtin productivity to a maximum of 1.84 mg/L per day at 0.8 vvm of air-flow rate. On the contrary, addition of oxygen vectors (in the range, 1-4% (v/v); hydrogen peroxide, toluene, Tween 80, kerosene, silicone oil, and n-hexadecane), decreased the azadirachtin productivity with respect to control (1.76 mg/L per day).

Nonparametric Transfer Function Models

Science.gov (United States)

Liu, Jun M.; Chen, Rong; Yao, Qiwei

2009-01-01

In this paper a class of nonparametric transfer function models is proposed to model nonlinear relationships between ‘input’ and ‘output’ time series. The transfer function is smooth with unknown functional forms, and the noise is assumed to be a stationary autoregressive-moving average (ARMA) process. The nonparametric transfer function is estimated jointly with the ARMA parameters. By modeling the correlation in the noise, the transfer function can be estimated more efficiently. The parsimonious ARMA structure improves the estimation efficiency in finite samples. The asymptotic properties of the estimators are investigated. The finite-sample properties are illustrated through simulations and one empirical example. PMID:20628584

The beneficial role of rubble mound coastal structures on seawater oxygenation

Directory of Open Access Journals (Sweden)

E. I. Daniil

2000-10-01

Full Text Available The beneficial role of rubble mound coastal structures on oxygenation under the effect of waves is discussed, based on analytical considerations and experimental data from laboratory experiments with permeable and impermeable structures. Significant oxygenation of the wave-protected area was observed as a result of horizontal transport through the permeable structure. A two-cell model describing the transport of dissolved oxygen (DO near a rubble mound breakwater structure was developed and used for the determination of the oxygen transfer coefficients from the experimental data. Oxygen transfer through the air–water interface is considered a source term in the transport equation and the oxygen flux through the structure is taken into account. The mass transport equations for both sides of the structure are solved analytically in terms of time evolution of DO concentration. The behaviour of the solution is illustrated for three different characteristic cases of initial conditions. The oxygen transfer through the air-water interface in the wave-influenced area increases the DO content in the area; the resulting oxygen flux through the structure is discussed. The analytical results depend on the initial conditions, the oxygen transfer coefficient and the exchange flow rate through the structure. Experiments with impermeable structures show that air water oxygen transfer in the harbour area is negligible in the absence of waves. In addition the ratio of the horizontal DO flux to the vertical flux into the seaward side tends towards a constant value, independent of the initial conditions.Key words: Oceanography: physical (air-sea interactions; surface waves and tides

Mathematical modeling of dissolved oxygen in fish ponds ...

African Journals Online (AJOL)

Mathematical modeling of dissolved oxygen in fish ponds. WJS Mwegoha, ME Kaseva, SMM Sabai. Abstract. A mathematical model was developed to predict the effects of wind speed, light, pH, Temperature, dissolved carbon dioxide and chemical oxygen demand (COD) on Dissolved Oxygen (DO) in fish ponds. The effects ...

empirical modeling of oxygen modeling of oxygen uptake of flow

African Journals Online (AJOL)

eobe

structure. Keywords: stepped chute, skimming flow, aeration l. 1. INTRODUCTION ..... [3] Toombes, L. and Chanson, H., “Air-water flow and gas transfer at aeration ... of numerical model of the flow behaviour through smooth and stepped.

Mathematical modelling of striation formation in oxygen laser cutting of mild steel

Energy Technology Data Exchange (ETDEWEB)

Ermolaev, G V; Kovalev, O B; Orishich, A M; Fomin, V M [Institute of Theoretical and Applied Mechanics SB RAS, 4/1 Institutskaya Str., Novosibirsk 630090 (Russian Federation)

2006-10-07

A physicomathematical model is proposed for the phenomenon of formation of periodic striations in oxygen laser cutting of mild steel sheets. The mechanism of roughness origination is assumed to be caused by a cyclic reaction of iron-oxygen oxidation. The mathematical description is based on solving the adjoint problems of heat and mass transfer in the liquid phase and in the solid metal with nonlinear moving interfaces between the substances and phase changes. The motion of the boundaries occurs owing to metal melting under the action of focused laser radiation and the heterogeneous chemical reaction of iron oxidation in oxygen. The main feature of iron oxidation is the loss of protective properties of its oxide film due to melting. The general statement of the problem for the nonlinear heat-conduction equation with variable coefficients is formulated by the type of the Stefan problem solved with the use of the difference method with smoothing coefficients at the melting point and the fictitious domain method, which allows obtaining of the solution without explicit identification of the cut boundary and the phase-transition front. Results of numerical simulations of the shape and linear size of roughness as functions of the cutting velocity, purity of oxygen and thickness of the film of the iron oxide being formed are presented.

Heterogeneous electron transfer and oxygen reduction reaction at nanostructured iron(II) phthalocyanine and its MWCNTs nanocomposites

CSIR Research Space (South Africa)

Mamuru, SA

2010-05-01

Full Text Available species within the porous layers of MWCNTs. Electron transfer process is much easier at the EPPGE-MWCNT and EPPGE-MWCNT-nanoFePc compared to the other electrodes. The best response for oxygen reduction reaction was at the EPPGE-MWCNTnanoFePc, yielding a 4...

Biogeochemical modelling of dissolved oxygen in a changing ocean

Science.gov (United States)

Andrews, Oliver; Buitenhuis, Erik; Le Quéré, Corinne; Suntharalingam, Parvadha

2017-08-01

Secular decreases in dissolved oxygen concentration have been observed within the tropical oxygen minimum zones (OMZs) and at mid- to high latitudes over the last approximately 50 years. Earth system model projections indicate that a reduction in the oxygen inventory of the global ocean, termed ocean deoxygenation, is a likely consequence of on-going anthropogenic warming. Current models are, however, unable to consistently reproduce the observed trends and variability of recent decades, particularly within the established tropical OMZs. Here, we conduct a series of targeted hindcast model simulations using a state-of-the-art global ocean biogeochemistry model in order to explore and review biases in model distributions of oceanic oxygen. We show that the largest magnitude of uncertainty is entrained into ocean oxygen response patterns due to model parametrization of pCO2-sensitive C : N ratios in carbon fixation and imposed atmospheric forcing data. Inclusion of a pCO2-sensitive C : N ratio drives historical oxygen depletion within the ocean interior due to increased organic carbon export and subsequent remineralization. Atmospheric forcing is shown to influence simulated interannual variability in ocean oxygen, particularly due to differences in imposed variability of wind stress and heat fluxes. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

Mechanisms of electron transfer from structrual Fe(II) in reduced nontronite to oxygen for production of hydroxyl radicals

Science.gov (United States)

Yuan, Songhu; Liu, Xixiang; Liao, Wenjuan; Zhang, Peng; Wang, Xiaoming; Tong, Man

2018-02-01

Production of hydroxyl radicals (radOH) has been recently revealed upon oxygenation of sediments in redox-dynamic subsurface environments. In particular, Fe(II)-bearing clay minerals are the major sediment components contributing to radOH production upon oxygenation, and the produced radOH can oxidize contaminants and inactivate bacteria. Whereas, the mechanisms of radOH production from oxygenation of Fe(II)-bearing clay minerals remain elusive. The objectives of this study were to identify the structural variation of Fe(II) entities during the oxidation of Fe(II)-bearing clay minerals by O2, and to unravel the mechanisms of electron transfer within the mineral structure and from mineral to O2 for radOH production. Nontronite (NAu-2, 23% Fe) which was chemically reduced to 54.5% Fe(II) in total Fe was used as a model Fe(II)-bearing clay mineral. Production of radOH and oxidation of Fe(II) were measured during the oxidation of reduced NAu-2 by O2. A wide spectrum of spectroscopic techniques, including Fourier transform infrared spectroscopy (FTIR), Fe K-edge X-ray absorption spectroscopy (XAS), Mössbauer spectra, and X-ray photoelectron spectroscopy (XPS), were employed to explore the structural variation of Fe(II) entities in NAu-2 and the electron transfer within NAu-2 and from NAu-2 to O2. For 180 min oxidation of 1 g/L reduced NAu-2, a biphasic radOH production was observed, being quick within the initial 15 min and slow afterwards. Production of radOH correlates well with oxidation of Fe(II) in the reduced NAu-2. Within the initial 15 min, trioctahedral Fe(II)-Fe(II)-Fe(II) entities and edge Fe(II) in the reduced NAu-2 were preferentially and quickly oxidized, and electrons from the interior Fe(II)-Fe(II)-Fe(II) entities were most likely ejected from the basal siloxane plane to O2. Meanwhile, trioctahedral Fe(II)-Fe(II)-Fe(II) entities were mainly transformed to dioctahedral Fe(II)-Fe(II) entities. When the time of oxygenation was longer than 15 min

Biogeochemical Modeling of the Second Rise of Oxygen

Science.gov (United States)

Smith, M. L.; Catling, D.; Claire, M.; Zahnle, K.

2014-03-01

The rise of atmospheric oxygen set the tempo for the evolution of complex life on Earth. Oxygen levels are thought to have increased in two broad steps: one step occurred in the Archean ~ 2.45 Ga (the Great Oxidation Event or GOE), and another step occured in the Neoproterozoic ~750-580 Ma (the Neoprotoerozoic Oxygenation Event or NOE). During the NOE, oxygen levels increased from ~1-10% of the present atmospheric level (PAL) (Holland, 2006), to ~15% PAL in the late Neoproterozoic, to ~100% PAL later in the Phanerozoic. Complex life requires O2, so this transition allowed complex life to evolve. We seek to understand what caused the NOE. To explore causes for the NOE, we build upon the biogeochemical model of Claire et al. (2006), which calculates the redox evolution of the atmosphere, ocean, biosphere, and crust in the Archean through to the early Proterozoic. In this model, the balance between oxygenconsuming and oyxgen-producing fluxes evolves over time such that at ~2.4 Ga, the rapidly acting sources of oxygen outweigh the rapidly-acting sinks. Or, in other words, at ~2.4 Ga, the flux of oxygen from organic carbon burial exceeds the sinks of oxygen from reaction with reduced volcanic and metamoprphic gases. The model is able to drive oxygen levels to 1-10% PAL in the Proterozoic; however, the evolving redox fluxes in the model cannot explain how oxygen levels pushed above 1-10% in the late Proterozoic. The authors suggest that perhaps another buffer, such as sulfur, is needed to describe Proterozoic and Phanerozoic redox evolution. Geologic proxies show that in the Proterozoic, up to 10% of the deep ocean may have been sulfidic. With this ocean chemistry, the global sulfur cycle would have worked differently than it does today. Because the sulfur and oxygen cycles interact, the oxygen concentration could have permanently changed due to an evolving sulfur cycle (in combination with evolving redox fluxes associated with other parts of the oxygen cycle and carbon

A theoretical model for the effects of reduced hemoglobin-oxygen affinity on tumor oxygenation

International Nuclear Information System (INIS)

Kavanagh, Brian D.; Secomb, Timothy W.; Hsu, Richard; Lin, P.-S.; Venitz, Jurgen; Dewhirst, Mark W.

2002-01-01

Purpose: To develop a theoretical model for oxygen delivery to tumors, and to use the model to simulate the effects of changing the affinity of hemoglobin for oxygen on tumor oxygenation. Methods and Materials: Hemoglobin affinity is expressed in terms of P 50 , the partial pressure of oxygen (Po 2 ) at half saturation. Effects of changing P 50 on arterial Po 2 are predicted using an effective vessel approach to describe diffusive oxygen transport in the lungs, assuming fixed systemic oxygen demand and fixed blood flow rate. The decline in oxygen content of blood as it flows through normal tissue before entering the tumor region is assumed fixed. The hypoxic fraction of the tumor region is predicted using a three-dimensional simulation of diffusion from a network of vessels whose geometry is derived from observations of tumor microvasculature in the rat. Results: In air-breathing rats, predicted hypoxic fraction decreases with moderate increases in P 50 , but increases with further increases of P 50 , in agreement with previous experimental results. In rats breathing hyperoxic gases, and in humans breathing either normoxic or hyperoxic gases, increased P 50 is predicted to improve tumor oxygenation. Conclusions: The results support the administration of synthetic agents to increase P 50 during radiation treatment of tumors

Carbon dioxide stripping in aquaculture -- part II: development of gas transfer models

Science.gov (United States)

Colt, John; Watten, Barnaby; Pfeiffer, Tim

2012-01-01

The basic mass transfer equation for gases such as oxygen and carbon dioxide can be derived from integration of the driving force equation. Because of the physical characteristics of the gas transfer processes, slightly different models are used for aerators tested under the non steady-state procedures, than for packed columns, or weirs. It is suggested that the standard condition for carbon dioxide should be 20 °C, 1 atm, CCO2=20 mg/kg, and XCO2=0.000285. The selection of the standard condition for carbon dioxide based on a fixed mole fraction ensures that standardized carbon dioxide transfer rates will be comparable even though the value of C*CO2 in the atmosphere is increasing with time. The computation of mass transfer for carbon dioxide is complicated by the impact of water depth and gas phase enrichment on the saturation concentration within the unit, although the importance of either factor depends strongly on the specific type of aerator. For some types of aerators, the most accurate gas phase model remains to be determined for carbon dioxide. The assumption that carbon dioxide can be treated as a non-reactive gas in packed columns may apply for cold acidic waters but not for warm alkaline waters.

Seasonal transfer of oxygen isotopes from precipitation and soil to the tree ring: source water versus needle water enrichment.

Science.gov (United States)

Treydte, Kerstin; Boda, Sonja; Graf Pannatier, Elisabeth; Fonti, Patrick; Frank, David; Ullrich, Bastian; Saurer, Matthias; Siegwolf, Rolf; Battipaglia, Giovanna; Werner, Willy; Gessler, Arthur

2014-05-01

For accurate interpretation of oxygen isotopes in tree rings (δ(18) O), it is necessary to disentangle the mechanisms underlying the variations in the tree's internal water cycle and to understand the transfer of source versus leaf water δ(18) O to phloem sugars and stem wood. We studied the seasonal transfer of oxygen isotopes from precipitation and soil water through the xylem, needles and phloem to the tree rings of Larix decidua at two alpine sites in the Lötschental (Switzerland). Weekly resolved δ(18) O records of precipitation, soil water, xylem and needle water, phloem organic matter and tree rings were developed. Week-to-week variations in needle-water (18) O enrichment were strongly controlled by weather conditions during the growing season. These short-term variations were, however, not significantly fingerprinted in tree-ring δ(18) O. Instead, seasonal trends in tree-ring δ(18) O predominantly mirrored trends in the source water, including recent precipitation and soil water pools. Modelling results support these findings: seasonal tree-ring δ(18) O variations are captured best when the week-to-week variations of the leaf water signal are suppressed. Our results suggest that climate signals in tree-ring δ(18) O variations should be strongest at temperate sites with humid conditions and precipitation maxima during the growing season. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Functional and biocompatibility performances of an integrated Maglev pump-oxygenator.

Science.gov (United States)

Zhang, Tao; Cheng, Guangming; Koert, Andrew; Zhang, Juntao; Gellman, Barry; Yankey, G Kwame; Satpute, Aditee; Dasse, Kurt A; Gilbert, Richard J; Griffith, Bartley P; Wu, Zhongjun J

2009-01-01

To provide respiratory support for patients with lung failure, a novel compact integrated pump-oxygenator is being developed. The functional and biocompatibility performances of this device are presented. The pump-oxygenator is designed by combining a magnetically levitated pump/rotor with a uniquely configured hollow fiber membrane bundle to create an assembly free, ultracompact, all-in-one system. The hemodynamics, gas transfer and biocompatibility performances of this novel device were investigated both in vitro in a circulatory flow loop and in vivo in an ovine animal model. The in vitro results showed that the device was able to pump blood flow from 2 to 8 L/min against a wide range of pressures and to deliver an oxygen transfer rate more than 300 mL/min at a blood flow of 6 L/min. Blood damage tests demonstrated low hemolysis (normalized index of hemolysis [NIH] approximately 0.04) at a flow rate of 5 L/min against a 100-mm Hg afterload. The data from five animal experiments (4 h to 7 days) demonstrated that the device could bring the venous blood to near fully oxygen-saturated condition (98.6% +/- 1.3%). The highest oxygen transfer rate reached 386 mL/min. The gas transfer performance was stable over the study duration for three 7-day animals. There was no indication of blood damage. The plasma free hemoglobin and platelet count were within the normal ranges. No gross thrombus is found on the explanted pump components and fiber surfaces. Both in vitro and in vivo results demonstrated that the newly developed pump-oxygenator can achieve sufficient blood flow and oxygen transfer with excellent biocompatibility.

Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex.

Science.gov (United States)

Kafentzi, Maria-Chrysanthi; Papadakis, Raffaello; Gennarini, Federica; Kochem, Amélie; Iranzo, Olga; Le Mest, Yves; Le Poul, Nicolas; Tron, Thierry; Faure, Bruno; Simaan, A Jalila; Réglier, Marius

2018-04-06

Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H 2 O as an oxygen source. To date, this strategy has not been reported for copper complexes. Herein, a copper(II) complex, [(RPY2)Cu(OTf) 2 ] (RPY2=N-substituted bis[2-pyridyl(ethylamine)] ligands; R=indane; OTf=triflate), is used. This complex, which contains an oxidizable substrate moiety (indane), is used as a tool to monitor an intramolecular oxygen atom transfer reaction. Electrochemical properties were investigated and, upon electrolysis at 1.30 V versus a normal hydrogen electrode (NHE), both dioxygen production and oxygenation of the indane moiety were observed. The ligand was oxidized in a highly diastereoselective manner, which indicated that the observed reactivity was mediated by metal-centered reactive species. The pH dependence of the reactivity was monitored and correlated with speciation deduced from different techniques, ranging from potentiometric titrations to spectroscopic studies and DFT calculations. Water oxidation for dioxygen production occurs at neutral pH and is probably mediated by the oxidation of a mononuclear copper(II) precursor. It is achieved with a rather low overpotential (280 mV at pH 7), although with limited efficiency. On the other hand, oxygenation is maximum at pH 8-8.5 and is probably mediated by the electrochemical oxidation of an antiferromagnetically coupled dinuclear bis(μ-hydroxo) copper(II) precursor. This constitutes the first example of copper-centered oxidative water activation for a selective oxygenation reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A model for oxygen conservation associated with titration during pediatric oxygen therapy.

Directory of Open Access Journals (Sweden)

Grace Wu

Full Text Available Continuous oxygen treatment is essential for managing children with hypoxemia, but access to oxygen in low-resource countries remains problematic. Given the high burden of pneumonia in these countries and the fact that flow can be gradually reduced as therapy progresses, oxygen conservation through routine titration warrants exploration.To determine the amount of oxygen saved via titration during oxygen therapy for children with hypoxemic pneumonia.Based on published clinical data, we developed a model of oxygen flow rates needed to manage hypoxemia, assuming recommended flow rate at start of therapy, and comparing total oxygen used with routine titration every 3 minutes or once every 24 hours versus no titration.Titration every 3 minutes or every 24 hours provided oxygen savings estimated at 11.7% ± 5.1% and 8.1% ± 5.1% (average ± standard error of the mean, n = 3, respectively. For every 100 patients, 44 or 30 kiloliters would be saved-equivalent to 733 or 500 hours at 1 liter per minute.Ongoing titration can conserve oxygen, even performed once-daily. While clinical validation is necessary, these findings could provide incentive for the routine use of pulse oximeters for patient management, as well as further development of automated systems.

Lateral transfer of tetrahymanol-synthesizing genes has allowed multiple diverse eukaryote lineages to independently adapt to environments without oxygen

Directory of Open Access Journals (Sweden)

Takishita Kiyotaka

2012-02-01

Full Text Available Abstract Sterols are key components of eukaryotic cellular membranes that are synthesized by multi-enzyme pathways that require molecular oxygen. Because prokaryotes fundamentally lack sterols, it is unclear how the vast diversity of bacterivorous eukaryotes that inhabit hypoxic environments obtain, or synthesize, sterols. Here we show that tetrahymanol, a triterpenoid that does not require molecular oxygen for its biosynthesis, likely functions as a surrogate of sterol in eukaryotes inhabiting oxygen-poor environments. Genes encoding the tetrahymanol synthesizing enzyme squalene-tetrahymanol cyclase were found from several phylogenetically diverged eukaryotes that live in oxygen-poor environments and appear to have been laterally transferred among such eukaryotes. Reviewers This article was reviewed by Eric Bapteste and Eugene Koonin.

Prospects for Money Transfer Models

OpenAIRE

Yougui Wang; Ning Ding; Ning Xi

2005-01-01

Recently, in order to explore the mechanism behind wealth or income distribution, several models have been proposed by applying principles of statistical mechanics. These models share some characteristics, such as consisting of a group of individual agents, a pile of money and a specific trading rule. Whatever the trading rule is, the most noteworthy fact is that money is always transferred from one agent to another in the transferring process. So we call them money transfer models. Besides e...

CHROMOSPHERIC MODELS AND THE OXYGEN ABUNDANCE IN GIANT STARS

Energy Technology Data Exchange (ETDEWEB)

Dupree, A. K.; Avrett, E. H.; Kurucz, R. L., E-mail: dupree@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2016-04-10

Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri, which include a chromosphere (CHR), influence the formation of optical lines of O i: the forbidden lines (λ6300, λ6363) and the infrared triplet (λλ7771−7775). One-dimensional semi-empirical non-local thermodynamic equilibrium (LTE) models are constructed based on observed Balmer lines. A full non-LTE formulation is applied for evaluating the line strengths of O i, including photoionization by the Lyman continuum and photoexcitation by Lyα and Lyβ. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than those in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than those produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors of ∼3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate-mass AGB stars contribute to the observed abundance pattern in globular clusters. A change in the oxygen abundance of metal-poor field giants could affect models of deep mixing episodes on the red giant branch. Changes in the oxygen abundance can impact other abundance determinations that are critical to astrophysics, including chemical tagging techniques and galactic chemical evolution.

Characterization of a continuous agitated cell reactor for oxygen dependent biocatalysis

DEFF Research Database (Denmark)

Pedersen, Asbjørn Toftgaard; Teresa de Melo Machado Simoes Carvalho, Ana; Sutherland, Euan

2017-01-01

Biocatalytic oxidation reactions employing molecular oxygen as the electron acceptor are difficult to conduct in a continuous flow reactor because of the requirement for high oxygen transfer rates. In this paper, the oxidation of glucose to glucono-1,5-lactone by glucose oxidase was used as a model...

Oxygen Transport: A Simple Model for Study and Examination.

Science.gov (United States)

Gaar, Kermit A., Jr.

1985-01-01

Describes an oxygen transport model computer program (written in Applesoft BASIC) which uses such variables as amount of time lapse from beginning of the simulation, arterial blood oxygen concentration, alveolar oxygen pressure, and venous blood oxygen concentration and pressure. Includes information on obtaining the program and its documentation.…

Numerical modelling of pyrolysis in normal and reduced oxygen concentration

International Nuclear Information System (INIS)

Kacem, Ahmed

2016-01-01

The predictive capability of computational fluid dynamics (CFD) fire models depends on the accuracy with which the source term due to fuel pyrolysis can be determined. The pyrolysis rate is a key parameter controlling fire behavior, which in turn drives the heat feedback from the flame to the fuel surface. In the present study an in-depth pyrolysis model of a semi-transparent solid fuel (here, clear polymethyl methacrylate or PMMA) with spectrally-resolved radiation and a moving gas/solid interface was coupled with the CFD code ISIS of the IRSN which included turbulence, combustion and radiation for the gas phase. A combined genetic algorithm/pyrolysis model was used with Cone Calorimeter data from a pure pyrolysis experiment to estimate a unique set of kinetic parameters for PMMA pyrolysis. In order to validate the coupled model, ambient air flaming experiments were conducted on square slabs of PMMA with side lengths of 10, 20 and 40 cm. From measurements at the center of the slab, it was found that i) for any sample size, the experimental regression rate becomes almost constant with time, and ii) although the radiative and total heat transfers increase significantly with the sample size, the radiative contribution to the total heat flux remains almost constant (∼80%). Coupled model results show a fairly good agreement with the literature and with current measurements of the heat fluxes, gas temperature and regressing surface rate at the center of the slabs. Discrepancies between predicted and measured total pyrolysis rate are observed, which result from the underestimation of the flame heat flux feedback at the edges of the slab, as confirmed by the comparison between predicted and observed topography of burned samples. Predicted flame heights based on a threshold temperature criterion were found to be close to those deduced from the correlation of Heskestad. Finally, in order to predict the pyrolysis of PMMA under reduced ambient oxygen concentration, a two

Modeling the oxygen microheterogeneity of tumors for photodynamic therapy dosimetry

Science.gov (United States)

Pogue, Brian W.; Paulsen, Keith D.; O'Hara, Julia A.; Hoopes, P. Jack; Swartz, Harold

2000-03-01

Photodynamic theory of tumors uses optical excitation of a sensitizing drug within tissue to produce large deposits of singlet oxygen, which are thought to ultimately cause the tumor destruction. Predicting dose deposition of singlet oxygen in vivo is challenging because measurement of this species in vivo is not easily achieved. But it is possible to follow the concentration of oxygen in vivo, and so measuring the oxygen concentration transients during PDT may provide a viable method of estimating the delivered dose of singlet oxygen. However modeling the microscopic heterogeneity of the oxygen distribution within a tumor is non-trivial, and predicting the microscopic dose deposition requires further study, but this study present the framework and initial calibration needed or modeling oxygen transport in complex geometries. Computational modeling with finite elements provides a versatile structure within which oxygen diffusion and consumption can be modeled within realistic tissue geometries. This study develops the basic tools required to simulate a tumor region, and examines the role of (i) oxygen supply and consumption rates, (ii) inter- capillary spacing, (iii) photosensitizer distribution, and (iv) differences between simulated tumors and those derived directly from histology. The result of these calculations indicate that realistic tumor tissue capillary networks can be simulated using the finite element method, without excessive computational burden for 2D regions near 1 mm2, and 3D regions near 0.1mm3. These simulations can provide fundamental information about tissue and ways to implement appropriate oxygen measurements. These calculations suggest that photodynamic therapy produces the majority of singlet oxygen in and near the blood vessels, because these are the sites of highest oxygen tension. These calculations support the concept that tumor vascular regions are the major targets for PDT dose deposition.

Transference of mass in fermentation process

International Nuclear Information System (INIS)

Rios E, R.; Buitrago H, G

1998-01-01

Based on bibliographical references, in a theoretical model based on a fermentation process, the relationship between the speed of oxygen transfer and the biochemistry demand is implemented, in order to discover the different conditions of aeration and of agitation speed, under those which the microbial growth is not affected by deficiency in the oxygen supply. This correlation was adapted to the cultivation of B. Thuringiensis, and of this form, maximum biomass concentration to the one, which is possible to supply oxygen efficiently with a group of defined operation conditions, could be estimated

A theoretical model for oxygen transport in skeletal muscle under conditions of high oxygen demand.

Science.gov (United States)

McGuire, B J; Secomb, T W

2001-11-01

Oxygen transport from capillaries to exercising skeletal muscle is studied by use of a Krogh-type cylinder model. The goal is to predict oxygen consumption under conditions of high demand, on the basis of a consideration of transport processes occurring at the microvascular level. Effects of the decline in oxygen content of blood flowing along capillaries, intravascular resistance to oxygen diffusion, and myoglobin-facilitated diffusion are included. Parameter values are based on human skeletal muscle. The dependence of oxygen consumption on oxygen demand, perfusion, and capillary density are examined. When demand is moderate, the tissue is well oxygenated and consumption is slightly less than demand. When demand is high, capillary oxygen content declines rapidly with axial distance and radial oxygen transport is limited by diffusion resistance within the capillary and the tissue. Under these conditions, much of the tissue is hypoxic, consumption is substantially less than demand, and consumption is strongly dependent on capillary density. Predicted consumption rates are comparable with experimentally observed maximal rates of oxygen consumption.

A model technology transfer program for independent operators: Kansas Technology Transfer Model (KTTM)

Energy Technology Data Exchange (ETDEWEB)

Schoeling, L.G.

1993-09-01

This report describes the development and testing of the Kansas Technology Transfer Model (KTTM) which is to be utilized as a regional model for the development of other technology transfer programs for independent operators throughout oil-producing regions in the US. It describes the linkage of the regional model with a proposed national technology transfer plan, an evaluation technique for improving and assessing the model, and the methodology which makes it adaptable on a regional basis. The report also describes management concepts helpful in managing a technology transfer program. The original Tertiary Oil Recovery Project (TORP) activities, upon which the KTTM is based, were developed and tested for Kansas and have proved to be effective in assisting independent operators in utilizing technology. Through joint activities of TORP and the Kansas Geological Survey (KGS), the KTTM was developed and documented for application in other oil-producing regions. During the course of developing this model, twelve documents describing the implementation of the KTTM were developed as deliverables to DOE. These include: (1) a problem identification (PI) manual describing the format and results of six PI workshops conducted in different areas of Kansas, (2) three technology workshop participant manuals on advanced waterflooding, reservoir description, and personal computer applications, (3) three technology workshop instructor manuals which provides instructor material for all three workshops, (4) three technologies were documented as demonstration projects which included reservoir management, permeability modification, and utilization of a liquid-level acoustic measuring device, (5) a bibliography of all literature utilized in the documents, and (6) a document which describes the KTTM.

Characterization and modelling of the heat transfers in a pilot-scale reactor during composting under forced aeration

International Nuclear Information System (INIS)

Guardia, A. de; Petiot, C.; Benoist, J.C.; Druilhe, C.

2012-01-01

The paper focused on the modelling of the heat transfers during composting in a pilot-scale reactor under forced aeration. The model took into account the heat production and the transfers by evaporation, convection between material and gas crossing the material, conduction and surface convection between gas and material in bottom and upper parts of the reactor. The model was adjusted thanks to the measurements practised during fifteen composting experiments in which five organic wastes were, each, composted under three constant aeration rates. Heat production was considered proportional to oxygen consumption rate and the enthalpy per mole oxygen consumed was assumed constant. The convective heat transfer coefficients were determined on basis of the continuous measurements of the temperatures of both the lid and the bottom part of the reactor. The model allowed a satisfying prediction of the temperature of the composting material. In most cases, the mean absolute discard between the experimental and the simulated temperatures was inferior to 2.5 °C and the peaks of temperature occurred with less than 8 h delay. For the half of the experiments the temperature discard between the simulated peak and the experimental one was inferior to 5 °C. On basis of the calculation of a stoichiometric production of water through oxidation of the biodegradable organic matter, the simulation of water going out from material as vapour also allowed a rather satisfying prediction of the mass of water in final mixture. The influence of the aeration rate on every type of heat loss was characterized. Finally, the model was used to evaluate the impacts on material temperature caused by the change of the insulation thickness, the ambient temperature, take the lid away, the increase or the decrease of the mass of waste to compost.

Nitrogen-doped graphene prepared by a transfer doping approach for the oxygen reduction reaction application

Science.gov (United States)

Mo, Zaiyong; Zheng, Ruiping; Peng, Hongliang; Liang, Huagen; Liao, Shijun

2014-01-01

Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm-2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity.

The effect of oxygen transfer mechanism on the cathode performance based on proton-conducting solid oxide fuel cells

KAUST Repository

Hou, Jie

2015-01-01

Two types of proton-blocking composites, La2NiO4+δ-LaNi0.6Fe0.4O3-δ (LNO-LNF) and Sm0.2Ce0.8O2-δ-LaNi0.6Fe0.4O3-δ (SDC-LNF), were evaluated as cathode materials for proton-conducting solid oxide fuel cells (H-SOFCs) based on the BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte, in order to compare and investigate the influence of two different oxygen transfer mechanism on the performance of the cathode for H-SOFCs. The X-ray diffraction (XRD) results showed that the chemical compatibility of the components in both compounds was excellent up to 1000°C. Electrochemical studies revealed that LNO-LNF showed lower area specific polarization resistances in symmetrical cells and better electrochemical performance in single cell tests. The single cell with LNO-LNF cathode generated remarkable higher maximum power densities (MPDs) and lower interfacial polarization resistances (Rp) than that with SDC-LNF cathode. Correspondingly, the MPDs of the single cell with the LNO-LNF cathode were 490, 364, 266, 180 mW cm-2 and the Rp were 0.103, 0.279, 0.587, 1.367 Ω cm2 at 700, 650, 600 and 550°C, respectively. Moreover, after the single cell with LNO-LNF cathode optimized with an anode functional layer (AFL) between the anode and electrolyte, the power outputs reached 708 mW cm-2 at 700°C. These results demonstrate that the LNO-LNF composite cathode with the interstitial oxygen transfer mechanism is a more preferable alternative for H-SOFCs than SDC-LNF composite cathode with the oxygen vacancy transfer mechanism.

Oxygen transfer rate identifies priming compounds in parsley cells.

Science.gov (United States)

Schilling, Jana Viola; Schillheim, Britta; Mahr, Stefan; Reufer, Yannik; Sanjoyo, Sandi; Conrath, Uwe; Büchs, Jochen

2015-11-25

In modern agriculture, the call for an alternative crop protection strategy increases because of the desired reduction of fungicide and pesticide use and the continuously evolving resistance of pathogens and pests to agrochemicals. The direct activation of the plant immune system does not provide a promising plant protection measure because of high fitness costs. However, upon treatment with certain natural or synthetic compounds, plant cells can promote to a fitness cost-saving, primed state of enhanced defense. In the primed state, plants respond to biotic and abiotic stress with faster and stronger activation of defense, and this is often associated with immunity and abiotic stress tolerance. Until now, the identification of chemical compounds with priming-inducing activity (so-called plant activators) relied on tedious and invasive approaches, or required the late detection of secreted furanocoumarin phytoalexins in parsley cell cultures. Thus, simple, fast, straightforward, and noninvasive techniques for identifying priming-inducing compounds for plant protection are very welcome. This report demonstrates that a respiration activity-monitoring system (RAMOS) can identify compounds with defense priming-inducing activity in parsley cell suspension in culture. RAMOS relies on the quasi-continuous, noninvasive online determination of the oxygen transfer rate (OTR). Treatment of parsley culture cells with the known plant activator salicylic acid (SA), a natural plant defense signal, resulted in an OTR increase. Addition of the defense elicitor Pep13, a cell wall peptide of Phythophthora sojae, induced two distinctive OTR peaks that were higher in SA-primed cells than in unprimed cells upon Pep13 challenge. Both, the OTR increase after priming with SA and the Pep13 challenge were dose-dependent. Furthermore, there was a close correlation of a compound's activity to enhance the oxygen consumption in parsley cells and its capacity to prime Pep13-induced furanocoumarin

Effects of Agitation, Aeration and Temperature on Production of a Novel Glycoprotein GP-1 by Streptomyces kanasenisi ZX01 and Scale-Up Based on Volumetric Oxygen Transfer Coefficient

Directory of Open Access Journals (Sweden)

Yong Zhou

2018-01-01

Full Text Available The effects of temperature, agitation and aeration on glycoprotein GP-1 production by Streptomyces kanasenisi ZX01 in bench-scale fermentors were systematically investigated. The maximum final GP-1 production was achieved at an agitation speed of 200 rpm, aeration rate of 2.0 vvm and temperature of 30 °C. By using a dynamic gassing out method, the effects of agitation and aeration on volumetric oxygen transfer coefficient (kLa were also studied. The values of volumetric oxygen transfer coefficient in the logarithmic phase increased with increase of agitation speed (from 14.53 to 32.82 h−1 and aeration rate (from 13.21 to 22.43 h−1. In addition, a successful scale-up from bench-scale to pilot-scale was performed based on volumetric oxygen transfer coefficient, resulting in final GP-1 production of 3.92, 4.03, 3.82 and 4.20 mg/L in 5 L, 15 L, 70 L and 500 L fermentors, respectively. These results indicated that constant volumetric oxygen transfer coefficient was appropriate for the scale-up of batch fermentation of glycoprotein GP-1 by Streptomyces kanasenisi ZX01, and this scale-up strategy successfully achieved 100-fold scale-up from bench-scale to pilot-scale fermentor.

Oxygen as a product of water radiolysis in high-LET tracks. II. Radiobiological implications

International Nuclear Information System (INIS)

Baverstock, K.F.; Burns, W.G.

1981-01-01

Consideration is given to the possibility that molecular oxygen generated in the tracks of energetic heavy ions is responsible for the reduction in oxygen enhancement ratio (OER) with increasing linear energy transfer (LET) observed for the loss of reproductive capacity caused by radiation in many cellular organisms. Yields of oxygen relationship of OER to LET for two organisms, Chlamydomonas reinhardii and Shigella flexneri, using a simple diffusion kinetic model for radiobiological action which takes account of the diffusion of oxygen after its formation. The results of these calculations show that the model accounts well for the shape of the OER vs. LET relationship

Effect of low oxygen concentrations on growth and alpha-amylase production of Aspergillus oryzae in model solid-state fermentation systems

NARCIS (Netherlands)

Rahardjo, Y.S.P.; Sie, S.; Weber, F.J.; Tramper, J.; Rinzema, A.

2005-01-01

Oxygen transfer in the fungal mat is a major concern in solid-state fermentation (SSF). Oxygen supply into the mycelial layers is hampered by diffusion limitation. For aerobic fungi, like Aspergillus oryzae, this oxygen depletion can be a severely limiting factor for growth and metabolite

Visual prosthesis wireless energy transfer system optimal modeling.

Science.gov (United States)

Li, Xueping; Yang, Yuan; Gao, Yong

2014-01-16

Wireless energy transfer system is an effective way to solve the visual prosthesis energy supply problems, theoretical modeling of the system is the prerequisite to do optimal energy transfer system design. On the basis of the ideal model of the wireless energy transfer system, according to visual prosthesis application condition, the system modeling is optimized. During the optimal modeling, taking planar spiral coils as the coupling devices between energy transmitter and receiver, the effect of the parasitic capacitance of the transfer coil is considered, and especially the concept of biological capacitance is proposed to consider the influence of biological tissue on the energy transfer efficiency, resulting in the optimal modeling's more accuracy for the actual application. The simulation data of the optimal model in this paper is compared with that of the previous ideal model, the results show that under high frequency condition, the parasitic capacitance of inductance and biological capacitance considered in the optimal model could have great impact on the wireless energy transfer system. The further comparison with the experimental data verifies the validity and accuracy of the optimal model proposed in this paper. The optimal model proposed in this paper has a higher theoretical guiding significance for the wireless energy transfer system's further research, and provide a more precise model reference for solving the power supply problem in visual prosthesis clinical application.

A numerical two layer model for blood oxygenation in lungs

International Nuclear Information System (INIS)

Aminatai, A.

2001-01-01

In the modelling of the simultaneous transport of O 2 and CO 2 in the pulmonary circulation described in our earlier studies, the blood has been treated as a homogeneous layer of haemoglobin solution. Since the size of the erythrocyte is not negligible in comparison with that of the capillary, the blood can no longer be considered as a homogeneous fluid and hence, It is worthwhile to consider the blood flow as a two-phase flow consisting of cells and plasma. In the present study, the heterogeneous nature of blood has been proposed by considering the axial train model for the flow [whitmore (1967)], in order to analyze the effect of cell free plasma layer on the process of blood oxygenation in pulmonary capillaries. The proposed model consists of a core of suspended erythrocytes surrounded by a cell free plasma layer near the wall. The coupled system of convective diffusion equaions together with the physiologically relevant boundary, entrance and interface conditions is solved numerically by a four-point semi-implicit scheme to gether with a fixed point iterative technique. The distance traversed by the blood before getting fully oxygenated is computed. It is shown that the core haematocrit and the thickness of the cell depleted layer affect the oxygenation process significantly. It is found that (i) oxygen takes longest and carbondioxide is the fastest to attain equilibraton, (ii) the blood is completely oxygenated within one-fifth part of its transit and (iii) the rate of oxygenation is smaller in case of homogeneous model than that in heterogenous model in the capillary. Finally, the effect of various physiological parameters on the rate of oxygenation has been examined

Modeling microscale heat transfer using Calore.

Energy Technology Data Exchange (ETDEWEB)

Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley

2005-09-01

Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.

Mathematical Modelling of Intraretinal Oxygen Partial Pressure ...

African Journals Online (AJOL)

Purpose: The aim of our present work is to develop a simple steady state model for intraretinal oxygen partial pressure distribution and to investigate the effect of various model parameters on the partial pressure distribution under adapted conditions of light and darkness.. Method: A simple eight-layered mathematical model ...

Oxygen ordering and superconductivity in the high Tc superconductor YBa2Cu3O6+x

International Nuclear Information System (INIS)

Friis Poulsen, H.

1991-12-01

This report contains the result of an experimental and theoretical investigation of the oxygen ordering process in the High T c superconductor Y Ba 2 Cu 3 O 6+x . Neutron scattering is used in connection with in situ monitoring of the oxygen in-diffusion in a gas-volumetric equipment. Information on the variations of the structural phases, the twin domain sizes, the elastic forces, the chemical potential og oxygen as well as diffusion are provided. Using Monte Carlo simulations we find that a simple two-dimentional lattice gas model of the oxygen ordering process, the ASYNNNI model, gives an excellent description of the vast majority of these data. A systematic study of the relationship between the static and dynamic variations of the superconducting transition temperature, T c , and the corresponding variations of the low temperature oxygen ordering process is performed. Statistics from Monte Carlo simulations based on the ASYNNNI model are combined with experimental data from the literature. The combined static and dynamic analysis makes it evident that within a charge transfer model, a linear T c versus charge transfer relationship can only be rationalized if the description is based on extended coherent ordered domains and if the dynamic co-existence between the Ortho-I and the Ortho-II type of domains inherent to the ASYNNNI model is taken into account. A minimal model is proposed, where the total charge transfer is found as a weighted sum over the areas of the Ortho-I and the Ortho-II domains, and the minimal size of the two types of domains are given by a doubling og their unit cells in both directions. (au) 5 tabs., 35 ills., 108 refs

Bubble column fermenter modeling: a comparison for pressure effects

Energy Technology Data Exchange (ETDEWEB)

Shioya, S; Dang, N D.P.; Dunn, I J

1978-01-01

Two models which describe the oxygen transfer, oxygen uptake, and axial mixing in a bubble column fermenter are described. Model I includes no pressure effects and can be solved analytically. Model II incorporates the influence of hydrostatic pressure on oxygen solubility and gas expansion and must be solved numerically. The liquid phase oxygen concentration profiles from both models are compared to ascertain for what parametric conditions and for what maximum column height Model I is valid. Results show that for many situations Model I can approximate the oxygen profiles in a 10 m column within 20%. As the transfer and uptake rates increase, the deviation of Model I can reach 80% for a 10 m column. 7 figures.

Numerical modeling of hypolimnetic oxygenation by electrolysis of water

Directory of Open Access Journals (Sweden)

Jaćimović Nenad M.

2017-01-01

Full Text Available The paper presents a novel method for hypolimnetic oxygenation by electrolysis of water. The performance of the method is investigated by the laboratory and the field experiment. The laboratory experiment is conducted in a 90 L vessel, while the field experiment is conducted at the lake Biwa in Japan. In order to provide a better insight into involved processes, a numerical model for simulation of bubble flow is developed with consideration of gas compressibility and oxygen dissolution. The model simultaneously solves 3-D volume averaged two-fluid governing equations. Developed model is firstly verified by simulation of bubble flow experiments, reported in the literature, where good qualitative agreement between measured and simulated results is observed. In the second part, the model is applied for simulation of conducted water electrolysis experiments. The model reproduced the observed oxygen concentration dynamics reasonably well. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 37009

Determining the effect of solid and liquid vectors on the gaseous interfacial area and oxygen transfer rates in two-phase partitioning bioreactors

Energy Technology Data Exchange (ETDEWEB)

Quijano, Guillermo [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Departamento de Biotecnologia y Bioingenieria, Centro de Investigacion y de Estudios, Avanzados del IPN (Cinvestav), Apdo. Postal 14-740, 07360 Mexico, D.F. (Mexico); Rocha-Rios, Jose [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Departamento de Ingenieria de Procesos e Hidraulica (IPH), Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, 09340 Mexico, D.F. (Mexico); Hernandez, Maria; Villaverde, Santiago [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Revah, Sergio [Departamento de Procesos y Tecnologia, Universidad Autonoma Metropolitana-Cuajimalpa, c/o IPH, UAM-Iztapalapa, Av. San Rafael Atlixco No. 186, 09340 Mexico, D.F. (Mexico); Munoz, Raul, E-mail: mutora@iq.uva.es [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Thalasso, Frederic [Departamento de Biotecnologia y Bioingenieria, Centro de Investigacion y de Estudios, Avanzados del IPN (Cinvestav), Apdo. Postal 14-740, 07360 Mexico, D.F. (Mexico)

2010-03-15

The effect of liquid and solid transfer vectors (silicone oil and Desmopan, respectively) on the gaseous interfacial area (a{sub g}) was evaluated in a two-phase partitioning bioreactor (TPPB) using fresh mineral salt medium and the cultivation broth of a toluene degradation culture (Pseudomonas putida DOT-T1E cultures continuously cultivated with and without silicone oil at low toluene loading rates). Higher values of a{sub g} were recorded in the presence of both silicone oil and Desmopan compared to the values obtained in the absence of a vector, regardless of the aqueous medium tested (1.6 and 3 times higher, respectively, using fresh mineral salt medium). These improvements in a{sub g} were well correlated to the oxygen mass transfer enhancements supported by the vectors (1.3 and 2.5 for liquid and solid vectors, respectively, using fresh medium). In this context, oxygen transfer rates of 2.5 g O{sub 2} L{sup -1} h{sup -1} and 1.3 g O{sub 2} L{sup -1} h{sup -1} were recorded in the presence of Desmopan and silicone oil, respectively, which are in agreement with previously reported values in literature. These results suggest that mass transfer enhancements in TPPBs might correspond to an increase in a{sub g} rather than to the establishment of a high-performance gas/vector/water transfer pathway.

Determining the effect of solid and liquid vectors on the gaseous interfacial area and oxygen transfer rates in two-phase partitioning bioreactors

International Nuclear Information System (INIS)

Quijano, Guillermo; Rocha-Rios, Jose; Hernandez, Maria; Villaverde, Santiago; Revah, Sergio; Munoz, Raul; Thalasso, Frederic

2010-01-01

The effect of liquid and solid transfer vectors (silicone oil and Desmopan, respectively) on the gaseous interfacial area (a g ) was evaluated in a two-phase partitioning bioreactor (TPPB) using fresh mineral salt medium and the cultivation broth of a toluene degradation culture (Pseudomonas putida DOT-T1E cultures continuously cultivated with and without silicone oil at low toluene loading rates). Higher values of a g were recorded in the presence of both silicone oil and Desmopan compared to the values obtained in the absence of a vector, regardless of the aqueous medium tested (1.6 and 3 times higher, respectively, using fresh mineral salt medium). These improvements in a g were well correlated to the oxygen mass transfer enhancements supported by the vectors (1.3 and 2.5 for liquid and solid vectors, respectively, using fresh medium). In this context, oxygen transfer rates of 2.5 g O 2 L -1 h -1 and 1.3 g O 2 L -1 h -1 were recorded in the presence of Desmopan and silicone oil, respectively, which are in agreement with previously reported values in literature. These results suggest that mass transfer enhancements in TPPBs might correspond to an increase in a g rather than to the establishment of a high-performance gas/vector/water transfer pathway.

T1 relaxation time constants, influence of oxygen, and the oxygen transfer function of the human lung at 1.5 T—A meta-analysis

Energy Technology Data Exchange (ETDEWEB)

Dietrich, Olaf, E-mail: od@dtrx.net [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany); Gaass, Thomas [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany); Comprehensive Pneumology Center, German Center for Lung Research, Munich (Germany); Reiser, Maximilian F. [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany)

2017-01-15

Purpose: To pool and summarize published data from magnetic resonance longitudinal relaxation measurements of the human lung at 1.5 T to provide a reliable basis of T{sub 1} relaxation time constants of healthy lung tissue both under respiration of room air and of pure oxygen. In particular, the oxygen-induced shortening of T{sub 1} was evaluated. Materials and methods: The PubMed database was comprehensively searched up to June 2016 for original publications in English containing quantitative T{sub 1} data (at least mean values and standard deviations) of the lung parenchyma of healthy subjects (minimum subject number: 3) at 1.5 T. From all included publications, T{sub 1} values of the lung of healthy subjects were extracted (inhaling room air and, if available, inhaling pure oxygen). Weighted mean values and standard deviations of all extracted data and the oxygen transfer function (OTF) were calculated. Results: 22 publications were included with a total number of 188 examined healthy subjects. 103 of these subjects (from 13 studies) were examined while breathing pure oxygen and room air; 85 subjects were examined only under room-air conditions. The weighted mean value (weighted sample standard deviation) of the room-air T{sub 1} values over all 22 studies was 1196 ms (152 ms). Based on studies with room-air and oxygen results, the mean T{sub 1} value at room-air conditions was 1172 ms (161 ms); breathing pure oxygen, the mean T{sub 1} value was reduced to 1054 ms (138 ms). This corresponds to a mean T{sub 1} reduction by 118 ms (35 ms) or 10.0 % (2.3 %) and to a mean OTF value of 1.22 (0.32) × 10{sup −3} s{sup −1}/(%O{sub 2}). Conclusion: This meta-analysis with data from 188 subjects indicates that the average T{sub 1} relaxation time constant of healthy lung tissue at 1.5 T is distributed around 1200 ms with a standard deviation of about 150 ms; breathing pure oxygen reduces this value significantly by 10 % to about 1050 ms.

Structure and charge transfer correlated with oxygen content for a Y0.8Ca0.2Ba2Cu3Oy (y = 6.84 6.32) system: a positron study

Science.gov (United States)

Cao, Shixun; Li, Lingwei; Liu, Fen; Li, Wenfeng; Chi, Changyun; Jing, Chao; Zhang, Jincang

2005-05-01

The structure and charge transfer correlated with oxygen content are studied by measuring the positron lifetime parameters of the Y0.8Ca0.2Ba2Cu3Oy system with a large range of oxygen content (y = 6.84-6.32). The local electron density ne is evaluated from the positron lifetime data. The positron lifetime parameters show a clear change around y = 6.50 where the compounds undergo the orthorhombic-tetragonal phase transition. The effect of ne and oxygen content on the structure, charge transfer and superconductivity are discussed. With the decrease of oxygen content y, O(4) tends to the Cu(1) site, causing carrier localization, and accordingly, the decrease of ne. This would prove that the localized carriers (electrons and holes) in the Cu-O chain region have great influence on the superconductivity by affecting the charge transfer between the reservoir layers and the conducting layers. The positron annihilation mechanism and its relation with superconductivity are also discussed.

Diffusion of oxygen in cork.

Science.gov (United States)

Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Simon, Jean-Marc; Paulin, Christian; Bellat, Jean-Pierre

2012-04-04

This work reports measurements of effective oxygen diffusion coefficient in raw cork. Kinetics of oxygen transfer through cork is studied at 298 K thanks to a homemade manometric device composed of two gas compartments separated by a cork wafer sample. The first compartment contains oxygen, whereas the second one is kept under dynamic vacuum. The pressure decrease in the first compartment is recorded as a function of time. The effective diffusion coefficient D(eff) is obtained by applying Fick's law to transient state using a numerical method based on finite differences. An analytical model derived from Fick's law applied to steady state is also proposed. Results given by these two methods are in close agreement with each other. The harmonic average of the effective diffusion coefficients obtained from the distribution of 15 cork wafers of 3 mm thickness is 1.1 × 10(-9) m(2) s(-1) with a large distribution over four decades. The statistical analysis of the Gaussian distribution obtained on a 3 mm cork wafer is extrapolated to a 48 mm cork wafer, which length corresponds to a full cork stopper. In this case, the probability density distribution gives a mean value of D(eff) equal to 1.6 × 10(-9) m(2) s(-1). This result shows that it is possible to obtain the effective diffusion coefficient of oxygen through cork from short time (few days) measurements performed on a thin cork wafer, whereas months are required to obtain the diffusion coefficient for a full cork stopper. Permeability and oxygen transfer rate are also calculated for comparison with data from other studies.

A model technology transfer program for independent operators

Energy Technology Data Exchange (ETDEWEB)

Schoeling, L.G.

1996-08-01

In August 1992, the Energy Research Center (ERC) at the University of Kansas was awarded a contract by the US Department of Energy (DOE) to develop a technology transfer regional model. This report describes the development and testing of the Kansas Technology Transfer Model (KTTM) which is to be utilized as a regional model for the development of other technology transfer programs for independent operators throughout oil-producing regions in the US. It describes the linkage of the regional model with a proposed national technology transfer plan, an evaluation technique for improving and assessing the model, and the methodology which makes it adaptable on a regional basis. The report also describes management concepts helpful in managing a technology transfer program.

OXYGEN MANAGEMENT DURING ALCOHOLIC FERMENTATION

OpenAIRE

MOENNE VARGAS, MARÍA ISABE

2013-01-01

Oxygen additions are a common practice in winemaking, as oxygen has a positive effect in fermentative kinetics, biomass synthesis and improvement of color, structure and :flavor in treated wines. However, most oxygen additions are carried out heuristically through pump-over operations solely on a know-how basis, which is difficult to manage in terms of the exact quantity of oxygen transferred to the fermenting must. It is important to estímate the amount of oxygen added because...

Characterization of a continuous agitated cell reactor for oxygen dependent biocatalysis.

Science.gov (United States)

Toftgaard Pedersen, Asbjørn; de Carvalho, Teresa Melo; Sutherland, Euan; Rehn, Gustav; Ashe, Robert; Woodley, John M

2017-06-01

Biocatalytic oxidation reactions employing molecular oxygen as the electron acceptor are difficult to conduct in a continuous flow reactor because of the requirement for high oxygen transfer rates. In this paper, the oxidation of glucose to glucono-1,5-lactone by glucose oxidase was used as a model reaction to study a novel continuous agitated cell reactor (ACR). The ACR consists of ten cells interconnected by small channels. An agitator is placed in each cell, which mixes the content of the cell when the reactor body is shaken by lateral movement. Based on tracer experiments, a hydrodynamic model for the ACR was developed. The model consisted of ten tanks-in-series with back-mixing occurring within and between each cell. The back-mixing was a necessary addition to the model in order to explain the observed phenomenon that the ACR behaved as two continuous stirred tank reactors (CSTRs) at low flow rates, while it at high flow rates behaved as the expected ten CSTRs in series. The performance of the ACR was evaluated by comparing the steady state conversion at varying residence times with the conversion observed in a stirred batch reactor of comparable size. It was found that the ACR could more than double the overall reaction rate, which was solely due to an increased oxygen transfer rate in the ACR caused by the intense mixing as a result of the spring agitators. The volumetric oxygen transfer coefficient, k L a, was estimated to be 344 h -1 in the 100 mL ACR, opposed to only 104 h -1 in a batch reactor of comparable working volume. Interestingly, the large deviation from plug flow behavior seen in the tracer experiments was found to have little influence on the conversion in the ACR, since both a plug flow reactor (PFR) model and the backflow cell model described the data sufficiently well. Biotechnol. Bioeng. 2017;114: 1222-1230. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Study on the mass transfer of oxygen in an electrolytic reduction process of ACP

International Nuclear Information System (INIS)

Park, Byung Heung; Park, Sung Bin; Seo, Chung Seok; Park, Seong Won

2005-01-01

The Advanced Spent Fuel Conditioning Process (ACP) is a molten-salt-based back-end fuel cycle technology developed at KAERI. The target fuel type for the process is the oxide fuel unloaded from PWRs which are the main prototype reactor commercially operating in Korea. The volume and the radiotoxicity of the spent fuel decrease to quarters of the initial volume and radiotoxicity after being reduced to metal forms and removing some elements into a molten salt. The reduction of the two properties improves the convenience in managing the spent fuels and makes it possible for disposal sites to be made the best use of. Metallization of the spent oxide fuels is accomplished in an electrolytic reduction cell where a molten LiCl is adopted as an electric medium and Li 2 O is added to increase the activity of the oxygen ion in the system. A porous magnesia filter, a SUS solid conductor, and the metal oxides to be reduced constitute a cathode and anodes are made of platinum. The only cation in the liquid phase is lithium at the first stage and the ion diffuses through the pores of the magnesia filter and then receives electrons to become a metal. The reduced lithium metal snatches oxygen from the metal oxides in the filter and transforms into lithium oxide which diffuses back to the molten salt phase leaving the reduced metal at the inside of the filter. The lithium oxide is dissociated to lithium and oxygen ions once it dissolves in the molten salt if the concentration is within the solubility limit. Hence the actual diffusing element is oxygen in an ionic state rather than the lithium oxide since there is no concentration gradient for the lithium ion to move on - the lithium ion is the main cation in the system though some alkali and alkaline-earth metals dissolve in the molten salt phase to be cations. The analysis of the mass transfer of oxygen in the electrolytic reduction process is, thus, of importance for the metallization process to be completely interpreted

Modeling and experimental methods to predict oxygen distribution in bone defects following cell transplantation.

Science.gov (United States)

Heylman, Christopher M; Santoso, Sharon; Krebs, Melissa D; Saidel, Gerald M; Alsberg, Eben; Muschler, George F

2014-04-01

We have developed a mathematical model that allows simulation of oxygen distribution in a bone defect as a tool to explore the likely effects of local changes in cell concentration, defect size or geometry, local oxygen delivery with oxygen-generating biomaterials (OGBs), and changes in the rate of oxygen consumption by cells within a defect. Experimental data for the oxygen release rate from an OGB and the oxygen consumption rate of a transplanted cell population are incorporated into the model. With these data, model simulations allow prediction of spatiotemporal oxygen concentration within a given defect and the sensitivity of oxygen tension to changes in critical variables. This information may help to minimize the number of experiments in animal models that determine the optimal combinations of cells, scaffolds, and OGBs in the design of current and future bone regeneration strategies. Bone marrow-derived nucleated cell data suggest that oxygen consumption is dependent on oxygen concentration. OGB oxygen release is shown to be a time-dependent function that must be measured for accurate simulation. Simulations quantify the dependency of oxygen gradients in an avascular defect on cell concentration, cell oxygen consumption rate, OGB oxygen generation rate, and OGB geometry.

The Pathway for Oxygen: Tutorial Modelling on Oxygen Transport from Air to Mitochondrion: The Pathway for Oxygen.

Science.gov (United States)

Bassingthwaighte, James B; Raymond, Gary M; Dash, Ranjan K; Beard, Daniel A; Nolan, Margaret

2016-01-01

The 'Pathway for Oxygen' is captured in a set of models describing quantitative relationships between fluxes and driving forces for the flux of oxygen from the external air source to the mitochondrial sink at cytochrome oxidase. The intervening processes involve convection, membrane permeation, diffusion of free and heme-bound O2 and enzymatic reactions. While this system's basic elements are simple: ventilation, alveolar gas exchange with blood, circulation of the blood, perfusion of an organ, uptake by tissue, and consumption by chemical reaction, integration of these pieces quickly becomes complex. This complexity led us to construct a tutorial on the ideas and principles; these first PathwayO2 models are simple but quantitative and cover: (1) a 'one-alveolus lung' with airway resistance, lung volume compliance, (2) bidirectional transport of solute gasses like O2 and CO2, (3) gas exchange between alveolar air and lung capillary blood, (4) gas solubility in blood, and circulation of blood through the capillary syncytium and back to the lung, and (5) blood-tissue gas exchange in capillaries. These open-source models are at Physiome.org and provide background for the many respiratory models there.

Modeling of Cerebral Oxygen Transport Based on In vivo Microscopic Imaging of Microvascular Network Structure, Blood Flow, and Oxygenation.

Science.gov (United States)

Gagnon, Louis; Smith, Amy F; Boas, David A; Devor, Anna; Secomb, Timothy W; Sakadžić, Sava

2016-01-01

Oxygen is delivered to brain tissue by a dense network of microvessels, which actively control cerebral blood flow (CBF) through vasodilation and contraction in response to changing levels of neural activity. Understanding these network-level processes is immediately relevant for (1) interpretation of functional Magnetic Resonance Imaging (fMRI) signals, and (2) investigation of neurological diseases in which a deterioration of neurovascular and neuro-metabolic physiology contributes to motor and cognitive decline. Experimental data on the structure, flow and oxygen levels of microvascular networks are needed, together with theoretical methods to integrate this information and predict physiologically relevant properties that are not directly measurable. Recent progress in optical imaging technologies for high-resolution in vivo measurement of the cerebral microvascular architecture, blood flow, and oxygenation enables construction of detailed computational models of cerebral hemodynamics and oxygen transport based on realistic three-dimensional microvascular networks. In this article, we review state-of-the-art optical microscopy technologies for quantitative in vivo imaging of cerebral microvascular structure, blood flow and oxygenation, and theoretical methods that utilize such data to generate spatially resolved models for blood flow and oxygen transport. These "bottom-up" models are essential for the understanding of the processes governing brain oxygenation in normal and disease states and for eventual translation of the lessons learned from animal studies to humans.

Glacial-interglacial variability in ocean oxygen and phosphorus in a global biogeochemical model

NARCIS (Netherlands)

Palastanga, V.; Slomp, C.P.; Heinze, C.

2013-01-01

Increased transfer of particulate matter from continental shelves to the open ocean during glacials may have had a major impact on the biogeochemistry of the ocean. Here, we assess the response of the coupled oceanic cycles of oxygen, carbon, phosphorus, and iron to the input of particulate organic

The impact of including spatially longitudinal heterogeneities of vessel oxygen content and vascular fraction in 3D tumor oxygenation models on predicted radiation sensitivity.

Science.gov (United States)

Lagerlöf, Jakob H; Kindblom, Jon; Bernhardt, Peter

2014-04-01

Oxygen distribution models have been used to analyze the influences of oxygen tensions on tissue response after radiotherapy. These distributions are often generated assuming constant oxygen tension in the blood vessels. However, as red blood cells progress through the vessels, oxygen is continuously released into the plasma and the surrounding tissue, resulting in longitudinally varying oxygen levels in the blood vessels. In the present study, the authors investigated whether a tumor oxygenation model that incorporated longitudinally varying oxygen levels would provide different predictions of necrotic fractions and radiosensitivity compared to commonly used models with a constant oxygen pressure. Our models simulated oxygen diffusion based on a Green's function approach and oxygen consumption according to the Michaelis-Menten equation. The authors constructed tumor models with different vascular fractions (VFs), from which they generated depth oxygenation curves and a look-up table of oxygen pressure gradients. The authors evaluated models of spherical tumors of various sizes, from 1 to 10(4) mg. The authors compared the results from a model with constant vessel oxygen (CVO) pressure to those from models with longitudinal variations in oxygen saturation and either a constant VF (CVF) or variable VF (VVF) within the tumor tissue. The authors monitored the necrotic fractions, defined as tumor regions with an oxygen pressure below 1 mmHg. Tumor radiation sensitivity was expressed as D99, the homogeneous radiation dose required for a tumor control probability of 0.99. In the CVO saturation model, no necrosis was observed, and decreasing the VF could only decrease the D99 by up to 10%. Furthermore, the D99 vs VF dependence was similar for different tumor masses. Compared to the CVO model, the extended CVF and VVF models provided clearly different results, including pronounced effects of VF and tumor size on the necrotic fraction and D99, necrotic fractions ranging

Application of flexibility model in modeling of flow boiling heat transfer

International Nuclear Information System (INIS)

Peng Jinfeng; Zhao Fuyu

2009-01-01

The mathematical modeling and computer simulation have been widely used in the analysis of system's dynamic characteristics, and often useful for system control. One of the popular methods for this purpose is the lumped parameter method. For flow boiling heat transfer system, the traditional lumped parameter modeling method has a problem that the heat transfer coefficients change suddenly at the boundary of coolant phase change. It can cause error. In this paper, an idea of flexibility model is developed to deal with the boundary problem and to improve the model of flow boiling heat transfer. The segments of coolant phase change's boundary are identified, and the membership functions which are derived from Fuzzy Mathematics are used to derive approximate expressions of heat transfer coefficient in those regions. The continuity of heat transfer coefficient can be described by those expressions. The membership functions are derived from mathematical analysis and transformation. The result shows that this idea is feasible and the conclusion is practicable.

A Privacy Model for RFID Tag Ownership Transfer

Directory of Open Access Journals (Sweden)

Xingchun Yang

2017-01-01

Full Text Available The ownership of RFID tag is often transferred from one owner to another in its life cycle. To address the privacy problem caused by tag ownership transfer, we propose a tag privacy model which captures the adversary’s abilities to get secret information inside readers, to corrupt tags, to authenticate tags, and to observe tag ownership transfer processes. This model gives formal definitions for tag forward privacy and backward privacy and can be used to measure the privacy property of tag ownership transfer scheme. We also present a tag ownership transfer scheme, which is privacy-preserving under the proposed model and satisfies the other common security requirements, in addition to achieving better performance.

Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation

Science.gov (United States)

Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.

2012-01-01

Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.

Oxygen sensitive polymeric nanocapsules for optical dissolved oxygen sensors

Science.gov (United States)

Sun, Zhijuan; Cai, Chenxin; Guo, Fei; Ye, Changhuai; Luo, Yingwu; Ye, Shuming; Luo, Jianchao; Zhu, Fan; Jiang, Chunyue

2018-04-01

Immobilization of the oxygen-sensitive probes (OSPs) in the host matrix greatly impacts the performance and long-term usage of the optical dissolved oxygen (DO) sensors. In this work, fluorescent dyes, as the OSPs, were encapsulated with a crosslinked fluorinated polymer shell by interfacial confined reversible addition fragmentation chain transfer miniemulsion polymerization to fabricate oxygen sensitive polymeric nanocapsules (NCs). The location of fluorescent dyes and the fluorescent properties of the NCs were fully characterized by fourier transform infrared spectrometer, x-ray photoelectron spectrometer and fluorescent spectrum. Dye-encapsulated capacity can be precisely tuned from 0 to 1.3 wt% without self-quenching of the fluorescent dye. The crosslinked fluorinated polymer shell is not only extremely high gas permeability, but also prevents the fluorescent dyes from leakage in aqueous as well as in various organic solvents, such as ethanol, acetone and tetrahydrofuran (THF). An optical DO sensor based on the oxygen sensitive NCs was fabricated, showing high sensitivity, short response time, full reversibility, and long-term operational stability of online monitoring DO. The sensitivity of the optical DO sensor is 7.02 (the ratio of the response value in fully deoxygenated and saturated oxygenated water) in the range 0.96-14.16 mg l-1 and the response time is about 14.3 s. The sensor’s work curve was fit well using the modified Stern-Volmer equation by two-site model, and its response values are hardly affected by pH ranging from 2 to 12 and keep constant during continuous measurement for 3 months. It is believed that the oxygen sensitive polymeric NCs-based optical DO sensor could be particularly useful in long-term online DO monitoring in both aqueous and organic solvent systems.

Effect of different heat transfer models on HCCI engine simulation

International Nuclear Information System (INIS)

Neshat, Elaheh; Saray, Rahim Khoshbakhti

2014-01-01

Highlights: • A new multi zone model is developed for HCCI combustion modeling. • New heat transfer model is used for prediction of heat transfer in HCCI engines. • Model can predict engine combustion, performance and emission characteristics well. • Appropriate mass and heat transfer models cause to accurate prediction of CO, UHC and NOx. - Abstract: Heat transfer from engine walls has an important role on engine combustion, performance and emission characteristics. The main focus of this study is offering a new relation for calculation of convective heat transfer from in-cylinder charge to combustion chamber walls of HCCI engines and providing the ability of new model in comparison with the previous models. Therefore, a multi zone model is developed for homogeneous charge compression ignition engine simulation. Model consists of four different types of zones including core zone, boundary layer zone, outer zones, which are between core and boundary layer, and crevice zone. Conductive heat transfer and mass transfer are considered between neighboring zones. For accurate calculation of initial conditions at inlet valve closing, multi zone model is coupled with a single zone model, which simulates gas exchange process. Various correlations are used as convective heat transfer correlations. Woschni, modified Woschni, Hohenberg and Annand correlations are used as convective heat transfer models. The new convection model, developed by authors, is used, too. Comparative analyses are done to recognize the accurate correlation for prediction of engine combustion, performance and emission characteristics in a wide range of operating conditions. The results indicate that utilization of various heat transfer models, except for new convective heat transfer model, leads to significant differences in prediction of in-cylinder pressure and exhaust emissions. Using Woschni, Chang and new model, convective heat transfer coefficient increases near top dead center, sharply

Electron and Oxygen Atom Transfer Chemistry of Co(II) in a Proton Responsive, Redox Active Ligand Environment.

Science.gov (United States)

Cook, Brian J; Pink, Maren; Pal, Kuntal; Caulton, Kenneth G

2018-05-21

The bis-pyrazolato pyridine complex LCo(PEt 3 ) 2 serves as a masked form of three-coordinate Co II and shows diverse reactivity in its reaction with several potential outer sphere oxidants and oxygen atom transfer reagents. N-Methylmorpholine N-oxide (NMO) oxidizes coordinated PEt 3 from LCo(PEt 3 ) 2 , but the final cobalt product is still divalent cobalt, in LCo(NMO) 2 . The thermodynamics of a variety of oxygen atom transfer reagents, including NMO, are calculated by density functional theory, to rank their oxidizing power. Oxidation of LCo(PEt 3 ) 2 with AgOTf in the presence of LiCl as a trapping nucleophile forms the unusual aggregate [LCo(PEt 3 ) 2 Cl(LiOTf) 2 ] 2 held together by Li + binding to very nucleophilic chloride on Co(III) and triflate binding to those Li + . In contrast, Cp 2 Fe + effects oxidation to trivalent cobalt, to form (HL)Co(PEt 3 ) 2 Cl + ; proton and the chloride originate from solvent in a rare example of CH 2 Cl 2 dehydrochlorination. An unexpected noncomplementary redox reaction is reported involving attack by 2e reductant PEt 3 nucleophile on carbon of the 1e oxidant radical Cp 2 Fe + , forming a P-C bond and H + ; this reaction competes in the reaction of LCo(PEt 3 ) 2 with Cp 2 Fe + .

One-dimensional simulation of stratification and dissolved oxygen in McCook Reservoir, Illinois

Science.gov (United States)

Robertson, Dale M.

2000-01-01

As part of the Chicagoland Underflow Plan/Tunnel and Reservoir Plan, the U.S. Army Corps of Engineers, Chicago District, plans to build McCook Reservoir.a flood-control reservoir to store combined stormwater and raw sewage (combined sewage). To prevent the combined sewage in the reservoir from becoming anoxic and producing hydrogen sulfide gas, a coarse-bubble aeration system will be designed and installed on the basis of results from CUP 0-D, a zero-dimensional model, and MAC3D, a three-dimensional model. Two inherent assumptions in the application of MAC3D are that density stratification in the simulated water body is minimal or not present and that surface heat transfers are unimportant and, therefore, may be neglected. To test these assumptions, the previously tested, one-dimensional Dynamic Lake Model (DLM) was used to simulate changes in temperature and dissolved oxygen in the reservoir after a 1-in-100-year event. Results from model simulations indicate that the assumptions made in MAC3D application are valid as long as the aeration system, with an air-flow rate of 1.2 cubic meters per second or more, is operated while the combined sewage is stored in the reservoir. Results also indicate that the high biochemical oxygen demand of the combined sewage will quickly consume the dissolved oxygen stored in the reservoir and the dissolved oxygen transferred through the surface of the reservoir; therefore, oxygen must be supplied by either the rising bubbles of the aeration system (a process not incorporated in DLM) or some other technique to prevent anoxia.

Batch culture of Azotobacter vinelandii under oxygen limitation conditionS

Energy Technology Data Exchange (ETDEWEB)

Camacho Rubio, F.; Martinez Nieto, L.; Fernandez Serrano, M.; Jimenez Moleon, M.C. [Departamento de Ingenieria Quimica, Universidad de Granada, Granada (Spain)

1996-12-01

The batch culture of Azotobacter vinealandii on glucose under nitrogen-fixing conditions, seeking oxygen limitation conditions, has been studied in order to use it as a Biological Test System for the experimental study of oxygen transfer enhancement methods in aerobic fermenters. overall kinetic parameters for exponential growth and for linear growth (under oxygen limitation) have been determined. It was noted an appreciable influence of the oxygen transfer rate on glucose and oxygen uptake, which seems to be due to alginate production, excreted as a nitrogenase protection mechanisms. (Author) 12 refs.

Combination of On-line pH and Oxygen Transfer Rate Measurement in Shake Flasks by Fiber Optical Technique and Respiration Activity MOnitoring System (RAMOS

Directory of Open Access Journals (Sweden)

Jochen Büchs

2007-12-01

Full Text Available Shake flasks are commonly used for process development in biotechnologyindustry. For this purpose a lot of information is required from the growth conditions duringthe fermentation experiments. Therefore, Anderlei et al. developed the RAMOS technology[1, 2], which proviedes on-line oxygen and carbondioxide transfer rates in shake flasks.Besides oxygen consumption, the pH in the medium also plays an important role for thesuccessful cultivation of micro-organisms and for process development. For online pHmeasurement fiber optical methods based on fluorophores are available. Here a combinationof the on-line Oxygen Transfer Rate (OTR measurements in the RAMOS device with anon-line, fiber optical pH measurement is presented. To demonstrate the application of thecombined measurement techniques, Escherichia coli cultivations were performed and on-line pH measurements were compared with off-line samples. The combination of on-lineOTR and pH measurements gives a lot of information about the cultivation and, therefore, itis a powerful technique for monitoring shake flask experiments as well as for processdevelopment.

Oxygen-atom transfer chemistry and thermolytic properties of a di-tert-butylphosphate-ligated Mn4O4 cubane.

Science.gov (United States)

Van Allsburg, Kurt M; Anzenberg, Eitan; Drisdell, Walter S; Yano, Junko; Tilley, T Don

2015-03-16

[Mn4O4{O2P(OtBu)2}6] (1), an Mn4O4 cubane complex combining the structural inspiration of the photosystem II oxygen-evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen-atom acceptor (PEt3), to give the butterfly complex [Mn4O2{O2P(OtBu)2}6(OPEt3)2]. The cubane structure is restored by reaction of the latter complex with the O-atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X-ray absorption spectroscopy to determine the fate of the Mn4O4 unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn(II) species. Finally, the related butterfly complex [Mn4O2{O2P(pin)}6(bpy)2] (pin = pinacolate) is described. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Approaches to modelling radionuclide transfer in agricultural systems

International Nuclear Information System (INIS)

Mitchell, N. G.

1995-01-01

Radiological dose assessment requires information describing the concentration and distribution of radionuclides in the environment. This information can be obtained from monitoring but is also evaluated with the aid of mathematical models. In such models the pathways of radionuclides from the release point to man are described in terms of transfer between compartments. The main pathways to be considered include: deposition to vegetation and soils; transfer from soil-to-plant; uptake and turnover in domestic animals; and, intake by man. The development of mathematical models for simulating transfer via these pathways depends on: an understanding of the system under study, in particular for those processes that are most important in the overall transfer to man; the availability of data to determine the structure and parameters for the model; the computing systems available; the knowledge of the user of the model; and, the application of the model. (author)

Transfer Function Identification Using Orthogonal Fourier Transform Modeling Functions

Science.gov (United States)

Morelli, Eugene A.

2013-01-01

A method for transfer function identification, including both model structure determination and parameter estimation, was developed and demonstrated. The approach uses orthogonal modeling functions generated from frequency domain data obtained by Fourier transformation of time series data. The method was applied to simulation data to identify continuous-time transfer function models and unsteady aerodynamic models. Model fit error, estimated model parameters, and the associated uncertainties were used to show the effectiveness of the method for identifying accurate transfer function models from noisy data.

Evaluation of multivariate calibration models transferred between spectroscopic instruments

DEFF Research Database (Denmark)

Eskildsen, Carl Emil Aae; Hansen, Per W.; Skov, Thomas

2016-01-01

In a setting where multiple spectroscopic instruments are used for the same measurements it may be convenient to develop the calibration model on a single instrument and then transfer this model to the other instruments. In the ideal scenario, all instruments provide the same predictions for the ......In a setting where multiple spectroscopic instruments are used for the same measurements it may be convenient to develop the calibration model on a single instrument and then transfer this model to the other instruments. In the ideal scenario, all instruments provide the same predictions...... for the same samples using the transferred model. However, sometimes the success of a model transfer is evaluated by comparing the transferred model predictions with the reference values. This is not optimal, as uncertainties in the reference method will impact the evaluation. This paper proposes a new method...... for calibration model transfer evaluation. The new method is based on comparing predictions from different instruments, rather than comparing predictions and reference values. A total of 75 flour samples were available for the study. All samples were measured on ten near infrared (NIR) instruments from two...

Modeling and sensitivity analysis of mass transfer in active multilayer polymeric film for food applications

Science.gov (United States)

Bedane, T.; Di Maio, L.; Scarfato, P.; Incarnato, L.; Marra, F.

2015-12-01

The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction

Solubility is the most important mass transfer factor

International Nuclear Information System (INIS)

Slobodov, A.A.; Zarembo, V.I.

1992-01-01

The existence of the quantitative correlation between mass transfer and equilibrium solubility of corrosion products of construction materials in water circuits of power plants is shown. Thermodynamic and mathematical methods of modeling and calculating for these processes are developed. The results for iron based materials - aqueous solution systems in a wide range of temperature, pH, oxygen-hydrogen concentrations are presented. The optimization conditions for mass transfer, sedimentation of corrosion products for BWR, PWR reactors, etc. have been obtained

Comparison of heat transfer models for reciprocating compressor

International Nuclear Information System (INIS)

Tuhovcak, J.; Hejcik, J.; Jicha, M.

2016-01-01

Highlights: • Comparison of integral heat transfer models. • Influence of heat transfer model on volumetric and isentropic efficiency. • Various gases used as working fluid. - Abstract: One of the main factors affecting the efficiency of reciprocating compressor is heat transfer inside the cylinder. An analysis of heat transfer could be done using numerical models or integral correlations developed mainly from approaches used in combustion engines; however their accuracy is not completely verified due to the complicated experimental set up. The goal of this paper is to analyse the effect of heat transfer on compressor efficiency. Various integral correlations were compared for different compressor settings and fluids. CoolProp library was used in the code to obtain the properties of common coolants and gases. A comparison was done using the in-house code developed in Matlab, based on 1st Law of Thermodynamics.

Mathematical model for dissolved oxygen prediction in Cirata ...

African Journals Online (AJOL)

This paper presents the implementation and performance of mathematical model to predict theconcentration of dissolved oxygen in Cirata Reservoir, West Java by using Artificial Neural Network (ANN). The simulation program was created using Visual Studio 2012 C# software with ANN model implemented in it. Prediction ...

A Comprehensive X-Ray Absorption Model for Atomic Oxygen

Science.gov (United States)

Gorczyca, T. W.; Bautista, M. A.; Hasoglu, M. F.; Garcia, J.; Gatuzz, E.; Kaastra, J. S.; Kallman, T. R.; Manson, S. T.; Mendoza, C.; Raassen, A. J. J.;

Oxygen transport enhancement by functionalized magnetic nanoparticles (FMP) in bioprocesses

Science.gov (United States)

Ataide, Filipe Andre Prata

The enhancement of fluid properties, namely thermal conductivity and mass diffusivity for a wide range of applications, through the use of nanosized particles' suspensions has been gathering increasing interest in the scientific community. In previous studies, Olle et al. (2006) showed an enhancement in oxygen absorption to aqueous solutions of up to 6-fold through the use of functionalized nanosized magnetic particles with oleic acid coating. Krishnamurthy et al. (2006) showed a remarkable 26-fold enhancement in dye diffusion in water. These two publications are landmarks in mass transfer enhancement in chemical systems through the use of nanoparticles. The central goal of this Ph.D. thesis was to develop functionalized magnetic nanoparticles to enhance oxygen transport in bioprocesses. The experimental protocol for magnetic nanoparticles synthesis and purification adopted in this thesis is a modification of that reported by Olle et al. (2006). This is facilitated by employing twice the quantity of ammonia, added at a slower rate, and by filtering the final nanoparticle solution in a cross-flow filtration modulus against 55 volumes of distilled water. This modification in the protocol resulted in improved magnetic nanoparticles with measurably higher mass transfer enhancement. Magnetic nanoparticles with oleic acid and Hitenol-BC coating were screened for oxygen transfer enhancement, since these particles are relatively inexpensive and easy to synthesize. A glass 0.5-liter reactor was custom manufactured specifically for oxygen transport studies in magnetic nanoparticles suspensions. The reactor geometry, baffles and Rushton impeller are of standard dimensions. Mass transfer tests were conducted through the use of the sulphite oxidation method, applying iodometric back-titration. A 3-factor central composite circumscribed design (CCD) was adopted for design of experiments in order to generate sufficiently informative data to model the effect of magnetic

Evaluation of Water Distribution and Oxygen Mass Transfer in Sponge Support Media for a Down-flow Hanging Sponge Reactor

International Nuclear Information System (INIS)

Uemura, S.; Okubo, T.; Maeno, K.; Takahashi, M.; Kubota, K.; Harada, H.

2016-01-01

A down-flow hanging sponge reactor has been developed for sewage treatment, mainly in developing countries. This novel reactor employs polyurethane sponge material as a support medium, which promises a proliferation of a large amount of biomass, offering excellent pollutant removal capability. Three types of sponge medium were evaluated with respect to water distribution and oxygen mass transfer. Water was supplied to the device, which consisted of 40 pieces of sponge media connected in series, and a tracer experiment was carried out. The ratios of actual hydraulic retention time to theoretical hydraulic retention time were in the range of 25-67% depending on the type of support medium. By supplying deoxygenated water from the top of the device, the overall volumetric oxygen transfer coefficient, K L a, was evaluated. Despite the non-aerated conditions, the K L a values of the support media were very high, in the range of 0.56-4.88 (1/min), surpassing those of other mechanically aerated processes. Furthermore, it was found that the suspended solids concentration in the influent played a role in increasing the actual hydraulic retention time/theoretical hydraulic retention time ratio, suggesting that managing the influent suspended solids concentration is prerequisite for preventing clogging problems in the down-flow hanging.

Modeling Fish Growth in Low Dissolved Oxygen

Science.gov (United States)

Neilan, Rachael Miller

2013-01-01

This article describes a computational project designed for undergraduate students as an introduction to mathematical modeling. Students use an ordinary differential equation to describe fish weight and assume the instantaneous growth rate depends on the concentration of dissolved oxygen. Published laboratory experiments suggest that continuous…

Singlet oxygen production and quenching mechanisms in travelling microwave discharges

International Nuclear Information System (INIS)

Savin, Yu V; Goryachev, L V; Adamenkov, Yu A; Rakhimova, T V; Mankelevich, Yu A; Popov, N A; Adamenkov, A A; Egorov, V V; Ilyin, S P; Kolobyanin, Yu V; Kudryashov, E A; Rogozhnikov, G S; Vyskubenko, B A

2004-01-01

Experimental and theoretical studies of singlet oxygen excitation in travelling microwave (TMW) discharges are presented. Singlet oxygen O 2 (a 1 Δ g ) concentrations and atomic oxygen mole fraction have been measured for different pressures, input powers and distances from the MW resonator. It was shown that a steady-state TMW discharge with a coaxial cavity resonator could provide a maximal O 2 (a 1 Δ g ) yield of 22% for 2 Torr of pure oxygen and 27-30% for He : O 2 = 1 : 1 mixture. The two-dimensional (r, z) model developed for calculations of plasma-chemical kinetics, heat and mass transfer was used for simulation of processes in the TMW discharge under study. Effects of gas pressure, gas flow rate and input power are studied and compared with experimental measurements of O 2 (a 1 Δ g ) concentrations and atomic oxygen mole fractions

Towards an Integrative Model of Knowledge Transfer

DEFF Research Database (Denmark)

Turcan, Romeo V.; Heslop, Ben

This paper aims to contribute towards the advancement of an efficient architecture of a single market for knowledge through the development of an integrative model of knowledge transfer. Within this aim, several points of departure can be singled out. One, the article builds on the call of the Eu......This paper aims to contribute towards the advancement of an efficient architecture of a single market for knowledge through the development of an integrative model of knowledge transfer. Within this aim, several points of departure can be singled out. One, the article builds on the call...... business and academia, and implementing the respective legislature are enduring. The research objectives were to explore (i) the process of knowledge transfer in universities, including the nature of tensions, obstacles and incentives, (ii) the relationships between key stakeholders in the KT market...... of the emergent integrative model of knowledge transfer. In an attempt to bring it to a higher level of generalizability, the integrative model of KT is further conceptualized from a ‘sociology of markets’ perspective resulting in an emergent architecture of a single market for knowledge. Future research...

Design and application of new type of oxygen supplier for water and ...

African Journals Online (AJOL)

A new oxygen supplier was designed to inject both ozone and air into the water under high pressure. The oxygen transfer coefficient (KLa) of the system with air and ozone were 0.0264 and 0.4900, respectively. The oxygen transfer efficiencies of the system with ozone and air were 73.58 and 52.17%, respectively.

Removal of copper by oxygenated pyrolytic tire char: kinetics and mechanistic insights.

Science.gov (United States)

Quek, Augustine; Balasubramanian, Rajashekhar

2011-04-01

The kinetics of copper ion (Cu(II)) removal from aqueous solution by pyrolytic tire char was modeled using five different conventional models. A modification to these models was also developed through a modified equation that accounts for precipitation. Conventional first- and second-order reaction models did not fit the copper sorption kinetics well, indicating a lack of simple rate-order dependency on solute concentration. Instead, a reversible first-order rate reaction showed the best fit to the data, indicating a dependence on surface functional groups. Due to the varying solution pH during the sorption process, modified external and internal mass transfer models were employed. Results showed that the sorption of copper onto oxygenated chars was limited by external mass transfer and internal resistance with and without the modification. However, the modification of the sorption process produced very different results for unoxygenated chars, which showed neither internal nor external limitation to sorption. Instead, its slow sorption rate indicates a lack of surface functional groups. The sorption of Cu(II) by oxygenated and unoxygenated chars was also found to occur via three and two distinct stages, respectively. Copyright © 2010 Elsevier Inc. All rights reserved.

Radiative transfer in type I supernovae atmospheres

International Nuclear Information System (INIS)

Isern, J.; Lopez, R.; Simonneau, E.

1987-01-01

Type I Supernovae are thought to be the result of the thermonuclear explosion of a carbon oxygen white dwarf in a close binary system. As the only direct information concerning the physics and the triggering mechanism of supernova explosions comes from the spectrophotometry of the emitted radiation, it is worthwhile to put considerable effort on the understanding of the radiation transfer in the supernovae envelopes in order to set constraints on the theoretical models of such explosions. In this paper we analyze the role played by the layers curvature on the radiative transfer. (Author)

Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

OpenAIRE

Sgouralis, Ioannis; Kett, Michelle M.; Ow, Connie P. C.; Abdelkader, Amany; Layton, Anita T.; Gardiner, Bruce S.; Smith, David W.; Lankadeva, Yugeesh R.; Evans, Roger G.

2016-01-01

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2. Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2. Both intravenous infusion of [Phe2,Ile3,Orn8]-vasopressin and infusion of NG-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8–1...

Comparison between model-predicted tumor oxygenation dynamics and vascular-/flow-related Doppler indices.

Science.gov (United States)

Belfatto, Antonella; Vidal Urbinati, Ailyn M; Ciardo, Delia; Franchi, Dorella; Cattani, Federica; Lazzari, Roberta; Jereczek-Fossa, Barbara A; Orecchia, Roberto; Baroni, Guido; Cerveri, Pietro

2017-05-01

Mathematical modeling is a powerful and flexible method to investigate complex phenomena. It discloses the possibility of reproducing expensive as well as invasive experiments in a safe environment with limited costs. This makes it suitable to mimic tumor evolution and response to radiotherapy although the reliability of the results remains an issue. Complexity reduction is therefore a critical aspect in order to be able to compare model outcomes to clinical data. Among the factors affecting treatment efficacy, tumor oxygenation is known to play a key role in radiotherapy response. In this work, we aim at relating the oxygenation dynamics, predicted by a macroscale model trained on tumor volumetric data of uterine cervical cancer patients, to vascularization and blood flux indices assessed on Ultrasound Doppler images. We propose a macroscale model of tumor evolution based on three dynamics, namely active portion, necrotic portion, and oxygenation. The model parameters were assessed on the volume size of seven cervical cancer patients administered with 28 fractions of intensity modulated radiation therapy (IMRT) (1.8 Gy/fraction). For each patient, five Doppler ultrasound tests were acquired before, during, and after the treatment. The lesion was manually contoured by an expert physician using 4D View ® (General Electric Company - Fairfield, Connecticut, United States), which automatically provided the overall tumor volume size along with three vascularization and/or blood flow indices. Volume data only were fed to the model for training purpose, while the predicted oxygenation was compared a posteriori to the measured Doppler indices. The model was able to fit the tumor volume evolution within 8% error (range: 3-8%). A strong correlation between the intrapatient longitudinal indices from Doppler measurements and oxygen predicted by the model (about 90% or above) was found in three cases. Two patients showed an average correlation value (50-70%) and the remaining

Correlation among Singlet-Oxygen Quenching, Free-Radical Scavenging, and Excited-State Intramolecular-Proton-Transfer Activities in Hydroxyflavones, Anthocyanidins, and 1-Hydroxyanthraquinones.

Science.gov (United States)

Nagaoka, Shin-Ichi; Bandoh, Yuki; Nagashima, Umpei; Ohara, Keishi

2017-10-26

Singlet-oxygen ( 1 O 2 ) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1 O 2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1 O 2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1 O 2 quenching and free-radical scavenging activities negatively correlate to the ESIPT activity. A catechol structure at B-ring is another factor that enhances the free-radical scavenging in hydroxyflavones. In contrast to these hydroxyflavones, 1-hydroxyanthraquinones having an electron-donating OH substituent adjacent to the O-H---O═C moiety susceptible to ESIPT do not show a simple correlation between their 1 O 2 quenching and ESIPT activities, because the OH substitution modulates these reactions.

The development of efficient two-photon singlet oxygen sensitizers

DEFF Research Database (Denmark)

Nielsen, Christian Benedikt

The development of efficient two-photon singlet oxygen sensitizers is addressed focusing on organic synthesis. Photophysical measurements were carried out on new lipophilic molecules, where two-photon absorption cross sections and singlet oxygen quantumyields were measured. Design principles...... for making efficient two-photon singlet oxygen sensitizers were then constructed from these results. Charge-transfer in the excited state of the prepared molecules was shown to play a pivotal role in the generationof singlet oxygen. This was established through studies of substituent effects on both...... the singlet oxygen yield and the two-photon absorption cross section, where it was revealed that a careful balancing of the amount of charge transfer present in theexcited state of the sensitizer is necessary to obtain both a high singlet oxygen quantum yield and a high two-photon cross section. An increasing...

Analysis of oxygen-enhanced combustion of gas power cycle

Energy Technology Data Exchange (ETDEWEB)

Maidana, Cristiano Frandalozo; Carotenuto, Adriano; Schneider, Paulo Smith [Universidade Federal do Rio Grande do Sul (GESTE/UFRGS), Porto Alegre, RS (Brazil). Grupo de Estudos Termicos e Energeticos], E-mails: cristiano.maidana@ufrgs.br, pss@mecanica.ufrgs.br

2010-07-01

The majority of combustion processes use air as oxidant, roughly taken as 21% O{sub 2} and 79% N{sub 2}, by volume. In many cases, these processes can be enhanced by using an oxidant that contains higher proportion of O{sub 2} than in air. This is known as oxygen-enhanced combustion or OEC, and can bring important benefits like higher thermal efficiencies, lower exhaust gas volumes, higher heat transfer efficiency, reduction fuel consumption, reduced equipment costs and substantially pollutant emissions reduction. Within this scenario, this paper aims to investigate the influence of 21-30% oxygen concentration on the performance of a air-fired natural gas fueled power plant. This power plant operates under a Brayton cycle with models with the help of an air flow splitter after the compressor output in order to dose the oxygen rate of combustion and to keep the flue gas intake of the turbine at a prescribed temperature. Simulations shows that the enhancing of the oxidant stream reduced fuel consumption of about 10%, driven by higher adiabatic flame temperatures, which improves thermal and heat transfer efficiencies. A conclusion obtained is that the use of oxygen in higher proportions can be a challenge to retrofit existing air-fired natural gas power turbine cycles, because of the technological limitation of its materials with higher flame temperatures. (author)

Modelling of a Batch Whey Cultivation of Kluyveromyces marxianus var. lactis MC 5 with Investigation of Mass Transfer Processes in the Bioreactor

Directory of Open Access Journals (Sweden)

Mitko Petrov

2015-04-01

Full Text Available This study presents a mathematical model of a batch fermentation of lactose oxidation from a natural substratum in a cultivation by the strain Kluyweromyces marxianus var. lactis MC 5. In the model of the process, the mass transfer in the bioreactor for oxygen concentration in the gas phase (GP and in the liquid phase (LP is based on the dispersion model of the GP. In addition, perfect mixing in LP is included. Nine models were investigated for specific growth rate and specific oxygen consumptions rate: Monod, Mink, Tessier, Aiba, Andrews, Haldane, Luong, Edward and Han-Levenspiel. In regard to the parameter estimation, the worst observed error was used for all experiments as an objective function. This approach is a special case of multi objective parameter estimation problems allowing the parameter estimation problem to become a min-max problem. The results obtained (values of criteria, relative error and statistics λ for the specific growth rate showed that the best fit to experimental data is achieved when applying the Mink model. In a combination a Mink, and Monod, Mink, Luong, Haldane, and Han-Levenspiel are used for specific oxygen consumptions rate. Based on the investigation, it was discovered that the best fit belonged to the models of Mink and Haldane, Mink and Luong and Mink and Han-Levenspiel. Therefore, these particular models are used for modeling the batch processes.

Advanced k-epsilon modeling of heat transfer

Science.gov (United States)

Kwon, Okey; Ames, Forrest E.

1995-01-01

This report describes two approaches to low Reynolds-number k-epsilon turbulence modeling which formulate the eddy viscosity on the wall-normal component of turbulence and a length scale. The wall-normal component of turbulence is computed via integration of the energy spectrum based on the local dissipation rate and is bounded by the isotropic condition. The models account for the anisotropy of the dissipation and the reduced mixing length due to the high strain rates present in the near-wall region. The turbulent kinetic energy and its dissipation rate were computed from the k and epsilon transport equations of Durbin. The models were tested for a wide range of turbulent flows and proved to be superior to other k-epsilon models, especially for nonequilibrium anisotropic flows. For the prediction of airfoil heat transfer, the models included a set of empirical correlations for predicting laminar-turbulent transition and laminar heat transfer augmentation due to the presence of freestream turbulence. The predictions of surface heat transfer were generally satisfactory.

Atmospheric radiative transfer modeling: a summary of the AER codes

Energy Technology Data Exchange (ETDEWEB)

Clough, S.A. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Shephard, M.W. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States)]. E-mail: mshephar@aer.com; Mlawer, E.J. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Delamere, J.S. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Iacono, M.J. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Cady-Pereira, K. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Boukabara, S. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Brown, P.D. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States)

2005-03-01

The radiative transfer models developed at AER are being used extensively for a wide range of applications in the atmospheric sciences. This communication is intended to provide a coherent summary of the various radiative transfer models and associated databases publicly available from AER (http://www.rtweb.aer.com). Among the communities using the models are the remote sensing community (e.g. TES, IASI), the numerical weather prediction community (e.g. ECMWF, NCEP GFS, WRF, MM5), and the climate community (e.g. ECHAM5). Included in this communication is a description of the central features and recent updates for the following models: the line-by-line radiative transfer model (LBLRTM); the line file creation program (LNFL); the longwave and shortwave rapid radiative transfer models, RRTM{sub L}W and RRTM{sub S}W; the Monochromatic Radiative Transfer Model (MonoRTM); the MT{sub C}KD Continuum; and the Kurucz Solar Source Function. LBLRTM and the associated line parameter database (e.g. HITRAN 2000 with 2001 updates) play a central role in the suite of models. The physics adopted for LBLRTM has been extensively analyzed in the context of closure experiments involving the evaluation of the model inputs (e.g. atmospheric state), spectral radiative measurements and the spectral model output. The rapid radiative transfer models are then developed and evaluated using the validated LBLRTM model.

A DYNAMICAL SYSTEM APPROACH IN MODELING TECHNOLOGY TRANSFER

Directory of Open Access Journals (Sweden)

Hennie Husniah

2016-05-01

Full Text Available In this paper we discuss a mathematical model of two parties technology transfer from a leader to a follower. The model is reconstructed via dynamical system approach from a known standard Raz and Assa model and we found some important conclusion which have not been discussed in the original model. The model assumes that in the absence of technology transfer from a leader to a follower, both the leader and the follower have a capability to grow independently with a known upper limit of the development. We obtain a rich mathematical structure of the steady state solution of the model. We discuss a special situation in which the upper limit of the technological development of the follower is higher than that of the leader, but the leader has started earlier than the follower in implementing the technology. In this case we show a paradox stating that the follower is unable to reach its original upper limit of the technological development could appear whenever the transfer rate is sufficiently high.  We propose a new model to increase realism so that any technological transfer rate could only has a positive effect in accelerating the rate of growth of the follower in reaching its original upper limit of the development.

Residual oxygen time model for oxygen partial pressure near 130 kPa (1.3 atm).

Science.gov (United States)

Shykoff, Barbara E

2015-01-01

A two-part residual oxygen time model predicts the probability of detectible pulmonary oxygen toxicity P(P[O2tox]) after dives with oxygen partial pressure (PO2) approximately 130 kPa, and provides a tool to plan dive series with selected risk of P[O2tox]. Data suggest that pulmonary oxygen injury at this PO2 is additive between dives. Recovery begins after a delay and continues during any following dive. A logistic relation expresses P(P[O2tox]) as a function of dive duration (T(dur)) [hours]: P(P[O2tox]) = 100/[1+exp (3.586-0.49 x T(dur))] This expression maps T(dur) to P(P[O2tox]) or, in the linear mid-portion of the curve, P(P[O2tox]) usefully to T(dur). For multiple dives or during recovery, it maps to an equivalent dive duration, T(eq). T(eq) was found after second dives of duration T(dur 2). Residual time from the first dive t(r) = T(eq) - T(dur2). With known t(r), t and T(dur) a recovery model was fitted. t(r) = T(dur) x exp [-k x((t-5)/T(dur)2], where t = t - 5 hours, k = 0.149 for resting, and 0.047 for exercising divers, and t represents time after surfacing. The fits were assessed for 1,352 man-dives. Standard deviations of the residuals were 8.5% and 18.3% probability for resting or exercise dives, respectively.

Numerical Modeling of Conjugate Heat Transfer in Fluid Network

Science.gov (United States)

Majumdar, Alok

2004-01-01

Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.

OXYGEN PRESSURE REGULATOR DESIGN AND ANALYSIS THROUGH FINITE ELEMENT MODELING

Directory of Open Access Journals (Sweden)

Asterios KOSMARAS

2017-05-01

Full Text Available Oxygen production centers produce oxygen in high pressure that needs to be defused. A regulator is designed and analyzed in the current paper for medical use in oxygen production centers. This study aims to design a new oxygen pressure regulator and perform an analysis using Finite Element Modeling in order to evaluate its working principle. In the design procedure,the main elements and the operating principles of a pressure regulator are taking into account. The regulator is designed and simulations take place in order to assessthe proposed design. Stress analysis results are presented for the main body of the regulator, as well as, flow analysis to determine some important flow characteristics in the inlet and outlet of the regulator.

Species distribution model transferability and model grain size - finer may not always be better.

Science.gov (United States)

Manzoor, Syed Amir; Griffiths, Geoffrey; Lukac, Martin

2018-05-08

Species distribution models have been used to predict the distribution of invasive species for conservation planning. Understanding spatial transferability of niche predictions is critical to promote species-habitat conservation and forecasting areas vulnerable to invasion. Grain size of predictor variables is an important factor affecting the accuracy and transferability of species distribution models. Choice of grain size is often dependent on the type of predictor variables used and the selection of predictors sometimes rely on data availability. This study employed the MAXENT species distribution model to investigate the effect of the grain size on model transferability for an invasive plant species. We modelled the distribution of Rhododendron ponticum in Wales, U.K. and tested model performance and transferability by varying grain size (50 m, 300 m, and 1 km). MAXENT-based models are sensitive to grain size and selection of variables. We found that over-reliance on the commonly used bioclimatic variables may lead to less accurate models as it often compromises the finer grain size of biophysical variables which may be more important determinants of species distribution at small spatial scales. Model accuracy is likely to increase with decreasing grain size. However, successful model transferability may require optimization of model grain size.

Numerical simulation of ion transport membrane reactors: Oxygen permeation and transport and fuel conversion

KAUST Repository

Hong, Jongsup

2012-07-01

Ion transport membrane (ITM) based reactors have been suggested as a novel technology for several applications including fuel reforming and oxy-fuel combustion, which integrates air separation and fuel conversion while reducing complexity and the associated energy penalty. To utilize this technology more effectively, it is necessary to develop a better understanding of the fundamental processes of oxygen transport and fuel conversion in the immediate vicinity of the membrane. In this paper, a numerical model that spatially resolves the gas flow, transport and reactions is presented. The model incorporates detailed gas phase chemistry and transport. The model is used to express the oxygen permeation flux in terms of the oxygen concentrations at the membrane surface given data on the bulk concentration, which is necessary for cases when mass transfer limitations on the permeate side are important and for reactive flow modeling. The simulation results show the dependence of oxygen transport and fuel conversion on the geometry and flow parameters including the membrane temperature, feed and sweep gas flow, oxygen concentration in the feed and fuel concentration in the sweep gas. © 2012 Elsevier B.V.

RRTM: A rapid radiative transfer model

Energy Technology Data Exchange (ETDEWEB)

Mlawer, E.J.; Taubman, S.J.; Clough, S.A. [Atmospheric and Environmental Research, Inc., Cambridge, MA (United States)

1996-04-01

A rapid radiative transfer model (RRTM) for the calculation of longwave clear-sky fluxes and cooling rates has been developed. The model, which uses the correlated-k method, is both accurate and computationally fast. The foundation for RRTM is the line-by-line radiative transfer model (LBLRTM) from which the relevant k-distributions are obtained. LBLRTM, which has been extensively validated against spectral observations e.g., the high-resolution sounder and the Atmospheric Emitted Radiance Interferometer, is used to validate the flux and cooling rate results from RRTM. Validations of RRTM`s results have been performed for the tropical, midlatitude summer, and midlatitude winter atmospheres, as well as for the four Intercomparison of Radiation Codes in Climate Models (ICRCCM) cases from the Spectral Radiance Experiment (SPECTRE). Details of some of these validations are presented below. RRTM has the identical atmospheric input module as LBLRTM, facilitating intercomparisons with LBLRTM and application of the model at the Atmospheric Radiation Measurement Cloud and Radiation Testbed sites.

Heat transfer corrected isothermal model for devolatilization of thermally-thick biomass particles

DEFF Research Database (Denmark)

Luo, Hao; Wu, Hao; Lin, Weigang

Isothermal model used in current computational fluid dynamic (CFD) model neglect the internal heat transfer during biomass devolatilization. This assumption is not reasonable for thermally-thick particles. To solve this issue, a heat transfer corrected isothermal model is introduced. In this model......, two heat transfer corrected coefficients: HT-correction of heat transfer and HR-correction of reaction, are defined to cover the effects of internal heat transfer. A series of single biomass devitalization case have been modeled to validate this model, the results show that devolatilization behaviors...... of both thermally-thick and thermally-thin particles are predicted reasonable by using heat transfer corrected model, while, isothermal model overestimate devolatilization rate and heating rate for thermlly-thick particle.This model probably has better performance than isothermal model when it is coupled...

Computational Modeling of Oxygen Transport in the Microcirculation: From an Experiment-Based Model to Theoretical Analyses

OpenAIRE

Lücker, Adrien

2017-01-01

Oxygen supply to cells by the cardiovascular system involves multiple physical and chemical processes that aim to satisfy fluctuating metabolic demand. Regulation mechanisms range from increased heart rate to minute adaptations in the microvasculature. The challenges and limitations of experimental studies in vivo make computational models an invaluable complement. In this thesis, oxygen transport from capillaries to tissue is investigated using a new numerical model that is tailored for vali...

Oxygen distribution in tumors: A qualitative analysis and modeling study providing a novel Monte Carlo approach

International Nuclear Information System (INIS)

Lagerlöf, Jakob H.; Kindblom, Jon; Bernhardt, Peter

2014-01-01

Purpose: To construct a Monte Carlo (MC)-based simulation model for analyzing the dependence of tumor oxygen distribution on different variables related to tumor vasculature [blood velocity, vessel-to-vessel proximity (vessel proximity), and inflowing oxygen partial pressure (pO 2 )]. Methods: A voxel-based tissue model containing parallel capillaries with square cross-sections (sides of 10 μm) was constructed. Green's function was used for diffusion calculations and Michaelis-Menten's kinetics to manage oxygen consumption. The model was tuned to approximately reproduce the oxygenational status of a renal carcinoma; the depth oxygenation curves (DOC) were fitted with an analytical expression to facilitate rapid MC simulations of tumor oxygen distribution. DOCs were simulated with three variables at three settings each (blood velocity, vessel proximity, and inflowing pO 2 ), which resulted in 27 combinations of conditions. To create a model that simulated variable oxygen distributions, the oxygen tension at a specific point was randomly sampled with trilinear interpolation in the dataset from the first simulation. Six correlations between blood velocity, vessel proximity, and inflowing pO 2 were hypothesized. Variable models with correlated parameters were compared to each other and to a nonvariable, DOC-based model to evaluate the differences in simulated oxygen distributions and tumor radiosensitivities for different tumor sizes. Results: For tumors with radii ranging from 5 to 30 mm, the nonvariable DOC model tended to generate normal or log-normal oxygen distributions, with a cut-off at zero. The pO 2 distributions simulated with the six-variable DOC models were quite different from the distributions generated with the nonvariable DOC model; in the former case the variable models simulated oxygen distributions that were more similar to in vivo results found in the literature. For larger tumors, the oxygen distributions became truncated in the lower

Facial Performance Transfer via Deformable Models and Parametric Correspondence.

Science.gov (United States)

Asthana, Akshay; de la Hunty, Miles; Dhall, Abhinav; Goecke, Roland

2012-09-01

The issue of transferring facial performance from one person's face to another's has been an area of interest for the movie industry and the computer graphics community for quite some time. In recent years, deformable face models, such as the Active Appearance Model (AAM), have made it possible to track and synthesize faces in real time. Not surprisingly, deformable face model-based approaches for facial performance transfer have gained tremendous interest in the computer vision and graphics community. In this paper, we focus on the problem of real-time facial performance transfer using the AAM framework. We propose a novel approach of learning the mapping between the parameters of two completely independent AAMs, using them to facilitate the facial performance transfer in a more realistic manner than previous approaches. The main advantage of modeling this parametric correspondence is that it allows a "meaningful" transfer of both the nonrigid shape and texture across faces irrespective of the speakers' gender, shape, and size of the faces, and illumination conditions. We explore linear and nonlinear methods for modeling the parametric correspondence between the AAMs and show that the sparse linear regression method performs the best. Moreover, we show the utility of the proposed framework for a cross-language facial performance transfer that is an area of interest for the movie dubbing industry.

Functional State Modelling of Cultivation Processes: Dissolved Oxygen Limitation State

Directory of Open Access Journals (Sweden)

Olympia Roeva

2015-04-01

Full Text Available A new functional state, namely dissolved oxygen limitation state for both bacteria Escherichia coli and yeast Saccharomyces cerevisiae fed-batch cultivation processes is presented in this study. Functional state modelling approach is applied to cultivation processes in order to overcome the main disadvantages of using global process model, namely complex model structure and a big number of model parameters. Alongwith the newly introduced dissolved oxygen limitation state, second acetate production state and first acetate production state are recognized during the fed-batch cultivation of E. coli, while mixed oxidative state and first ethanol production state are recognized during the fed-batch cultivation of S. cerevisiae. For all mentioned above functional states both structural and parameter identification is here performed based on experimental data of E. coli and S. cerevisiae fed-batch cultivations.

Numerical Modeling of Ablation Heat Transfer

Science.gov (United States)

Ewing, Mark E.; Laker, Travis S.; Walker, David T.

2013-01-01

A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

Can spatial statistical river temperature models be transferred between catchments?

Science.gov (United States)

Jackson, Faye L.; Fryer, Robert J.; Hannah, David M.; Malcolm, Iain A.

2017-09-01

There has been increasing use of spatial statistical models to understand and predict river temperature (Tw) from landscape covariates. However, it is not financially or logistically feasible to monitor all rivers and the transferability of such models has not been explored. This paper uses Tw data from four river catchments collected in August 2015 to assess how well spatial regression models predict the maximum 7-day rolling mean of daily maximum Tw (Twmax) within and between catchments. Models were fitted for each catchment separately using (1) landscape covariates only (LS models) and (2) landscape covariates and an air temperature (Ta) metric (LS_Ta models). All the LS models included upstream catchment area and three included a river network smoother (RNS) that accounted for unexplained spatial structure. The LS models transferred reasonably to other catchments, at least when predicting relative levels of Twmax. However, the predictions were biased when mean Twmax differed between catchments. The RNS was needed to characterise and predict finer-scale spatially correlated variation. Because the RNS was unique to each catchment and thus non-transferable, predictions were better within catchments than between catchments. A single model fitted to all catchments found no interactions between the landscape covariates and catchment, suggesting that the landscape relationships were transferable. The LS_Ta models transferred less well, with particularly poor performance when the relationship with the Ta metric was physically implausible or required extrapolation outside the range of the data. A single model fitted to all catchments found catchment-specific relationships between Twmax and the Ta metric, indicating that the Ta metric was not transferable. These findings improve our understanding of the transferability of spatial statistical river temperature models and provide a foundation for developing new approaches for predicting Tw at unmonitored locations across

Oxygen transport through soft contact lens and cornea: Lens characterization and metabolic modeling

Science.gov (United States)

Chhabra, Mahendra

The human cornea requires oxygen to sustain metabolic processes critical for its normal functioning. Any restriction to corneal oxygen supply from the external environment (e.g., by wearing a low oxygen-permeability contact lens) can lead to hypoxia, which may cause corneal edema (swelling), limbal hyperemia, neovascularization, and corneal acidosis. The need for adequate oxygen to the cornea is a major driving force for research and development of hypertransmissible soft contact lenses (SCLs). Currently, there is no standard technique for measuring oxygen permeability (Dk) of hypertransmissible silicone-hydrogel SCLs. In this work, an electrochemistry-based polarographic apparatus was designed, built, and operated to measure oxygen permeability in hypertransmissible SCLs. Unlike conventional methods where a range of lens thickness is needed for determining oxygen permeabilities of SCLs, this apparatus requires only a single lens thickness. The single-lens permeameter provides a reliable, efficient, and economic tool for measuring oxygen permeabilities of commercial hypertransmissible SCLs. The single-lens permeameter measures not only the product Dk, but, following modification, it measures separately diffusivity, D, and solubility, k, of oxygen in hypertransmissible SCLs. These properties are critical for designing better lens materials that ensure sufficient oxygen supply to the cornea. Metabolism of oxygen in the cornea is influenced by contact-lens-induced hypoxia, diseases such as diabetes, surgery, and drug treatment, Thus, estimation of the in-vivo corneal oxygen consumption rate is essential for gauging adequate oxygen supply to the cornea. Therefore, we have developed an unsteady-state reactive-diffusion model for the cornea-contact-lens system to determine in-vivo human corneal oxygen-consumption rate. Finally, a metabolic model was developed to determine the relation between contact-lens oxygen transmissibility (Dk/L) and corneal oxygen deficiency. A

A brief clinical case of monitoring of oxygenator performance and patient-machine interdependency during prolonged veno-venous extracorporeal membrane oxygenation.

Science.gov (United States)

Belliato, Mirko; Degani, Antonella; Buffa, Antonino; Sciutti, Fabio; Pagani, Michele; Pellegrini, Carlo; Iotti, Giorgio Antonio

2017-10-01

Monitoring veno-venous extracorporeal membrane oxygenation (vvECMO) during 76 days of continuous support in a 42-years old patient with end-stage pulmonary disease, listed for double-lung transplantation. Applying a new monitor (Landing ® , Eurosets, Medolla, Italy) and describing how measured and calculated parameters can be used to understand the variable interdependency between artificial membrane lung (ML) and patient native lung (NL). During vvECMO, in order to understand how the respiratory function is shared between ML and NL, ideally we should obtain data about oxygen transfer and CO 2 removal, both by ML and NL. Measurements for NL can be made on the mechanical ventilator. Measurements for ML are typically made from gas analysis on blood samples drawn from the ECMO system before and after the oxygenator, and therefore are non-continuous. Differently, the Landing monitor provides a continuous measurement of the oxygen transfer from the ML, combined with hemoglobin level, saturation of drained blood and saturation of reinfused blood. Moreover, the Landing monitor provides hemodynamics data about circulation through the ECMO system, with blood flow, pre-oxygenator pressure and post-oxygenator pressure. Of note, measurements include the drain negative pressure, whose monitoring may be particularly useful to prevent hemolysis. Real-time monitoring of vvECMO provides data helpful to understand the complex picture of a patient with severely damaged lungs on one side and an artificial lung on the other side. Data from vvECMO monitoring may help to adapt the settings of both mechanical ventilator and vvECMO. Data about oxygen transfer by the oxygenator are important to evaluate the performance of the device and may help to avoid unnecessary replacements, thus reducing risks and costs.

A Conceptual Model of Technology Transfer for Public Universities in Mexico

Directory of Open Access Journals (Sweden)

Hugo Necoechea

2013-12-01

Full Text Available Technology transfer from academic and scientific institutions has been transformed into a strategic variable for companies and nations who wish to cope with the challenges of a global economy. Since the early 1970s, many technology transfer models have tried to introduce key factors in the process. Previous studies have shown that technology transfer is influenced by various elements. This study is based on a review of two recent technology transfer models that we have used as basic concepts for developing our own conceptual model. Researcher–firm networks have been considered as key elements in the technology transfer process between public universities and firms. The conceptual model proposed could be useful to improve the efficiency of existing technology transfer mechanisms.

Challenges of transferring models of fish abundance between coral reefs.

Science.gov (United States)

Sequeira, Ana M M; Mellin, Camille; Lozano-Montes, Hector M; Meeuwig, Jessica J; Vanderklift, Mathew A; Haywood, Michael D E; Babcock, Russell C; Caley, M Julian

2018-01-01

Reliable abundance estimates for species are fundamental in ecology, fisheries, and conservation. Consequently, predictive models able to provide reliable estimates for un- or poorly-surveyed locations would prove a valuable tool for management. Based on commonly used environmental and physical predictors, we developed predictive models of total fish abundance and of abundance by fish family for ten representative taxonomic families for the Great Barrier Reef (GBR) using multiple temporal scenarios. We then tested if models developed for the GBR (reference system) could predict fish abundances at Ningaloo Reef (NR; target system), i.e., if these GBR models could be successfully transferred to NR. Models of abundance by fish family resulted in improved performance (e.g., 44.1% fish abundance (9% fish species richness from the GBR to NR, transferability for these fish abundance models was poor. When compared with observations of fish abundance collected in NR, our transferability results had low validation scores ( R 2   0.05). High spatio-temporal variability of patterns in fish abundance at the family and population levels in both reef systems likely affected the transferability of these models. Inclusion of additional predictors with potential direct effects on abundance, such as local fishing effort or topographic complexity, may improve transferability of fish abundance models. However, observations of these local-scale predictors are often not available, and might thereby hinder studies on model transferability and its usefulness for conservation planning and management.

Generation of Triplet Excited States via Photoinduced Electron Transfer in meso-anthra-BODIPY: Fluorogenic Response toward Singlet Oxygen in Solution and in Vitro

KAUST Repository

Filatov, Mikhail A.; Karuthedath, Safakath; Polestshuk, Pavel M.; Savoie, Huguette; Flanagan, Keith J.; Sy, Cindy; Sitte, Elisabeth; Telitchko, Maxime; Laquai, Fré dé ric; Boyle, Ross W.; Senge, Mathias O.

2017-01-01

Heavy atom-free BODIPY-anthracene dyads (BADs) generate locally excited triplet states by way of photoinduced electron transfer (PeT), followed by recombination of the resulting charge-separated states (CSS). Subsequent quenching of the triplet states by molecular oxygen produces singlet oxygen (1O2), which reacts with the anthracene moiety yielding highly fluorescent species. The steric demand of the alkyl substituents in the BODIPY subunit defines the site of 1O2 addition. Novel bis- and tetraepoxides and bicyclic acetal products, arising from rearrangements of anthracene endoperoxides were isolated and characterized. 1O2 generation by BADs in living cells enables visualization of the dyads distribution, promising new imaging applications.

Generation of Triplet Excited States via Photoinduced Electron Transfer in meso-anthra-BODIPY: Fluorogenic Response toward Singlet Oxygen in Solution and in Vitro

KAUST Repository

Filatov, Mikhail A.

2017-04-14

Heavy atom-free BODIPY-anthracene dyads (BADs) generate locally excited triplet states by way of photoinduced electron transfer (PeT), followed by recombination of the resulting charge-separated states (CSS). Subsequent quenching of the triplet states by molecular oxygen produces singlet oxygen (1O2), which reacts with the anthracene moiety yielding highly fluorescent species. The steric demand of the alkyl substituents in the BODIPY subunit defines the site of 1O2 addition. Novel bis- and tetraepoxides and bicyclic acetal products, arising from rearrangements of anthracene endoperoxides were isolated and characterized. 1O2 generation by BADs in living cells enables visualization of the dyads distribution, promising new imaging applications.

Influence of vascular network design on gas transfer in lung assist device technology.

Science.gov (United States)

Bassett, Erik K; Hoganson, David M; Lo, Justin H; Penson, Elliot J N; Vacanti, Joseph P

2011-01-01

Blood oxygenators are vital for the critically ill, but their use is limited to the hospital setting. A portable blood oxygenator or a lung assist device for ambulatory or long-term use would greatly benefit patients with chronic lung disease. In this work, a biomimetic blood oxygenator system was developed which consisted of a microfluidic vascular network covered by a gas permeable silicone membrane. This system was used to determine the influence of key microfluidic parameters-channel size, oxygen exposure length, and blood shear rate-on blood oxygenation and carbon dioxide removal. Total gas transfer increased linearly with flow rate, independent of channel size and oxygen exposure length. On average, CO(2) transfer was 4.3 times higher than oxygen transfer. Blood oxygen saturation was also found to depend on the flow rate per channel but in an inverse manner; oxygenation decreased and approached an asymptote as the flow rate per channel increased. These relationships can be used to optimize future biomimetic vascular networks for specific lung applications: gas transfer for carbon dioxide removal in patients with chronic obstructive pulmonary disease or oxygenation for premature infants requiring complete lung replacement therapy.

Laplace transform analysis of a multiplicative asset transfer model

Science.gov (United States)

Sokolov, Andrey; Melatos, Andrew; Kieu, Tien

2010-07-01

We analyze a simple asset transfer model in which the transfer amount is a fixed fraction f of the giver’s wealth. The model is analyzed in a new way by Laplace transforming the master equation, solving it analytically and numerically for the steady-state distribution, and exploring the solutions for various values of f∈(0,1). The Laplace transform analysis is superior to agent-based simulations as it does not depend on the number of agents, enabling us to study entropy and inequality in regimes that are costly to address with simulations. We demonstrate that Boltzmann entropy is not a suitable (e.g. non-monotonic) measure of disorder in a multiplicative asset transfer system and suggest an asymmetric stochastic process that is equivalent to the asset transfer model.

High cell density fed-batch fermentations for lipase production: feeding strategies and oxygen transfer.

Science.gov (United States)

Salehmin, M N I; Annuar, M S M; Chisti, Y

2013-11-01

This review is focused on the production of microbial lipases by high cell density fermentation. Lipases are among the most widely used of the enzyme catalysts. Although lipases are produced by animals and plants, industrial lipases are sourced almost exclusively from microorganisms. Many of the commercial lipases are produced using recombinant species. Microbial lipases are mostly produced by batch and fed-batch fermentation. Lipases are generally secreted by the cell into the extracellular environment. Thus, a crude preparation of lipases can be obtained by removing the microbial cells from the fermentation broth. This crude cell-free broth may be further concentrated and used as is, or lipases may be purified from it to various levels. For many large volume applications, lipases must be produced at extremely low cost. High cell density fermentation is a promising method for low-cost production: it allows a high concentration of the biomass and the enzyme to be attained rapidly and this eases the downstream recovery of the enzyme. High density fermentation enhances enzyme productivity compared with the traditional submerged culture batch fermentation. In production of enzymes, a high cell density is generally achieved through fed-batch operation, not through perfusion culture which is cumbersome. The feeding strategies used in fed-batch fermentations for producing lipases and the implications of these strategies are discussed. Most lipase-producing microbial fermentations require oxygen. Oxygen transfer in such fermentations is discussed.

Multimillennium changes in dissolved oxygen under global warming: results from an AOGCM and offline ocean biogeochemical model

Science.gov (United States)

Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y.

2016-12-01

Long-term oceanic oxygen change due to global warming is still unclear; most future projections (such as CMIP5) are only performed until 2100. Indeed, few previous studies using conceptual models project oxygen change in the next thousands of years, showing persistent global oxygen reduction by about 30% in the next 2000 years, even after atmospheric carbon dioxide stops rising. Yet, these models cannot sufficiently represent the ocean circulation change: the key driver of oxygen change. Moreover, considering serious effect oxygen reduction has on marine life and biogeochemical cycling, long-term oxygen change should be projected for higher validity. Therefore, we used a coupled atmosphere-ocean general circulation model (AOGCM) and an offline ocean biogeochemical model, investigating realistic long-term changes in oceanic oxygen concentration and ocean circulation. We integrated these models for 2000 years under atmospheric CO2 doubling and quadrupling. After global oxygen reduction in the first 500 years, oxygen concentration in deep ocean globally recovers and overshoots, despite surface oxygen decrease and weaker Atlantic Meridional Overturning Circulation. Deep ocean convection in the Weddell Sea recovers and overshoots, after initial cessation. Thus, enhanced deep convection and associated Antarctic Bottom Water supply oxygen-rich surface waters to deep ocean, resulting global deep ocean oxygenation. We conclude that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in the deep ocean; contrary to past reported long-term oxygen reduction and general expectation. In presentation, we will discuss the mechanism of response of deep ocean convection in the Weddell Sea and show the volume changes of hypoxic waters.

Geometric data transfer between CAD systems: solid models

DEFF Research Database (Denmark)

Kroszynski, Uri; Palstroem, Bjarne; Trostmann, Erik

1989-01-01

The first phase of the ESPRIT project CAD*I resulted in a specification for the exchange of solid models as well as in some pilot implementations of processors based on this specification. The authors summarize the CAD*I approach, addressing the structure of neutral files for solids, entities......, and attributes supporting three kinds of representations: facilities for the transfer of parametric designs; referencing library components; and other general mechanisms. They also describe the current state of the specification and processor implementations and include an example of a CAD*I neutral file....... Results from cycle and intersystem solid model transfer tests are presented, showing the practicality of the CAD*I proposal. B-rep model transfer results are discussed in some detail. The relationship of this work to standardization efforts is outlined...

A passive and active microwave-vector radiative transfer (PAM-VRT) model

International Nuclear Information System (INIS)

Yang, Jun; Min, Qilong

2015-01-01

A passive and active microwave vector radiative transfer (PAM-VRT) package has been developed. This fast and accurate forward microwave model, with flexible and versatile input and output components, self-consistently and realistically simulates measurements/radiation of passive and active microwave sensors. The core PAM-VRT, microwave radiative transfer model, consists of five modules: gas absorption (two line-by-line databases and four fast models); hydrometeor property of water droplets and ice (spherical and nonspherical) particles; surface emissivity (from Community Radiative Transfer Model (CRTM)); vector radiative transfer of successive order of scattering (VSOS); and passive and active microwave simulation. The PAM-VRT package has been validated against other existing models, demonstrating good accuracy. The PAM-VRT not only can be used to simulate or assimilate measurements of existing microwave sensors, but also can be used to simulate observation results at some new microwave sensors. - Highlights: • A novel microwave vector radiative transfer model is developed. • It can simulate passive and active microwave radiative transfer simultaneously. • It can be applied to simulate measurements for different types of viewing geometry. • The accuracy of this model has been validated against other existing models

Heme biomolecule as redox mediator and oxygen shuttle for efficient charging of lithium-oxygen batteries

Science.gov (United States)

Ryu, Won-Hee; Gittleson, Forrest S.; Thomsen, Julianne M.; Li, Jinyang; Schwab, Mark J.; Brudvig, Gary W.; Taylor, André D.

2016-01-01

One of the greatest challenges with lithium-oxygen batteries involves identifying catalysts that facilitate the growth and evolution of cathode species on an oxygen electrode. Heterogeneous solid catalysts cannot adequately address the problematic overpotentials when the surfaces become passivated. However, there exists a class of biomolecules which have been designed by nature to guide complex solution-based oxygen chemistries. Here, we show that the heme molecule, a common porphyrin cofactor in blood, can function as a soluble redox catalyst and oxygen shuttle for efficient oxygen evolution in non-aqueous Li-O2 batteries. The heme's oxygen binding capability facilitates battery recharge by accepting and releasing dissociated oxygen species while benefiting charge transfer with the cathode. We reveal the chemical change of heme redox molecules where synergy exists with the electrolyte species. This study brings focus to the rational design of solution-based catalysts and suggests a sustainable cross-link between biomolecules and advanced energy storage. PMID:27759005

Model Transport: Towards Scalable Transfer Learning on Manifolds

DEFF Research Database (Denmark)

Freifeld, Oren; Hauberg, Søren; Black, Michael J.

2014-01-01

We consider the intersection of two research fields: transfer learning and statistics on manifolds. In particular, we consider, for manifold-valued data, transfer learning of tangent-space models such as Gaussians distributions, PCA, regression, or classifiers. Though one would hope to simply use...... ordinary Rn-transfer learning ideas, the manifold structure prevents it. We overcome this by basing our method on inner-product-preserving parallel transport, a well-known tool widely used in other problems of statistics on manifolds in computer vision. At first, this straightforward idea seems to suffer...... “commutes” with learning. Consequently, our compact framework, applicable to a large class of manifolds, is not restricted by the size of either the training or test sets. We demonstrate the approach by transferring PCA and logistic-regression models of real-world data involving 3D shapes and image...

Oxygen consumption rates by different oenological tannins in a model wine solution.

Science.gov (United States)

Pascual, Olga; Vignault, Adeline; Gombau, Jordi; Navarro, Maria; Gómez-Alonso, Sergio; García-Romero, Esteban; Canals, Joan Miquel; Hermosín-Gutíerrez, Isidro; Teissedre, Pierre-Louis; Zamora, Fernando

2017-11-01

The kinetics of oxygen consumption by different oenological tannins were measured in a model wine solution using the non-invasive method based on luminiscence. The results indicate that the oxygen consumption rate follows second-order kinetics depending on tannin and oxygen concentrations. They also confirm that the oxygen consumption rate is influenced by temperature in accordance with Arrhenius law. The indications are that ellagitannins are the fastest oxygen consumers of the different oenological tannins, followed in decreasing order by quebracho tannins, skin tannins, seed tannins and finally gallotannins. This methodology can therefore be proposed as an index for determining the effectiveness of different commercial tannins in protecting wines against oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Post-dryout heat transfer analysis model with droplet Lagrangian simulation

International Nuclear Information System (INIS)

Keizo Matsuura; Isao Kataoka; Kaichiro Mishima

2005-01-01

Post-dryout heat transfer analysis was carried out considering droplet behavior by using the Lagrangian simulation method. Post-dryout heat transfer is an important heat transfer mechanism in many industrial appliances. Especially in recent Japanese BWR licensing, the standard for assessing the integrity of fuel that has experienced boiling transition is being examined. Although post-dryout heat transfer analysis is important when predicting wall temperature, it is difficult to accurately predict the heat transfer coefficient in the post-dryout regime because of the many heat transfer paths and non-equilibrium status between droplet and vapor. Recently, an analysis model that deals with many heat transfer paths including droplet direct contact heat transfer was developed and its results showed good agreement with experimental results. The model also showed that heat transfer by droplet could not be neglected in the low mass flux condition. However, the model deals with droplet deposition behavior by experimental droplet deposition correlation, so it cannot estimate the effect of droplet flow on turbulent flow field and heat transfer. Therefore, in this study we deal with many droplets separately by using the Lagrangian simulation method and hence estimate the effect of droplet flow on the turbulent flow field. We analyzed post-dryout experimental results and found that they correlated well with the analysis results. (authors)

Heat transfer in Rockwool modelling and method of measurement. Modelling radiative heat transfer in fibrous materials

Energy Technology Data Exchange (ETDEWEB)

Dyrboel, Susanne

1998-05-01

Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the

Improved heat transfer modeling of the eye for electromagnetic wave exposures.

Science.gov (United States)

Hirata, Akimasa

2007-05-01

This study proposed an improved heat transfer model of the eye for exposure to electromagnetic (EM) waves. Particular attention was paid to the difference from the simplified heat transfer model commonly used in this field. From our computational results, the temperature elevation in the eye calculated with the simplified heat transfer model was largely influenced by the EM absorption outside the eyeball, but not when we used our improved model.

BUSINESS MODELS FOR INCREASING TECHNOLOGICAL TRANSFER EFFECTIVENESS

Directory of Open Access Journals (Sweden)

Simina FULGA

2016-05-01

Full Text Available The present paper is devoted to analyze the appropriate recommendations to increase the effectiveness of technology transfer organizations (centers from ReNITT, by using the specific instruments of Business Model Canvas, associated to the technological transfer value chain for the value added services addressed to their clients and according to a continuously improved competitive strategy over competition analysis.

Silicon Micropore-Based Parallel Plate Membrane Oxygenator.

Science.gov (United States)

Dharia, Ajay; Abada, Emily; Feinberg, Benjamin; Yeager, Torin; Moses, Willieford; Park, Jaehyun; Blaha, Charles; Wright, Nathan; Padilla, Benjamin; Roy, Shuvo

2018-02-01

Extracorporeal membrane oxygenation (ECMO) is a life support system that circulates the blood through an oxygenating system to temporarily (days to months) support heart or lung function during cardiopulmonary failure until organ recovery or replacement. Currently, the need for high levels of systemic anticoagulation and the risk for bleeding are main drawbacks of ECMO that can be addressed with a redesigned ECMO system. Our lab has developed an approach using microelectromechanical systems (MEMS) fabrication techniques to create novel gas exchange membranes consisting of a rigid silicon micropore membrane (SμM) support structure bonded to a thin film of gas-permeable polydimethylsiloxane (PDMS). This study details the fabrication process to create silicon membranes with highly uniform micropores that have a high level of pattern fidelity. The oxygen transport across these membranes was tested in a simple water-based bench-top set-up as well in a porcine in vivo model. It was determined that the mass transfer coefficient for the system using SµM-PDMS membranes was 3.03 ± 0.42 mL O 2 min -1 m -2 cm Hg -1 with pure water and 1.71 ± 1.03 mL O 2 min -1 m -2 cm Hg -1 with blood. An analytic model to predict gas transport was developed using data from the bench-top experiments and validated with in vivo testing. This was a proof of concept study showing adequate oxygen transport across a parallel plate SµM-PDMS membrane when used as a membrane oxygenator. This work establishes the tools and the equipoise to develop future generations of silicon micropore membrane oxygenators. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

Directory of Open Access Journals (Sweden)

O. Funk

2003-03-01

Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements. Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

Directory of Open Access Journals (Sweden)

O. Funk

Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements.

Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

Radiation heat transfer model for the SCDAP code

International Nuclear Information System (INIS)

Sohal, M.S.

1984-01-01

A radiation heat transfer model has been developed for severe fuel damage analysis which accounts for anisotropic effects of reflected radiation. The model simplifies the view factor calculation which results in significant savings in computational cost with little loss of accuracy. Radiation heat transfer rates calculated by the isotropic and anisotropic models compare reasonably well with those calculated by other models. The model is applied to an experimental nuclear rod bundle during a slow boiloff of the coolant liquid, a situation encountered during a loss of coolant accident with severe fuel damage. At lower temperatures and also lower temperature gradients in the core, the anisotropic effect was not found to be significant

Comparison of experimental methods for determination of the volumetric mass transfer coefficient in fermentation processes

Energy Technology Data Exchange (ETDEWEB)

Tobajas, M.; Garcia-Calvo, E. [Dept. de Ingenieria Quimica, Univ. de Alcala, Alcala de Henares (Spain)

2000-05-01

Mass transfer in bioreactors has been examined. In the present work, dynamic methods are used for the determination of K{sub L}a values for water, model media and a fermentation broth (Candida utilis) in an airlift reactor. The conventional dynamic method is applied at the end of the microbial process in order to avoid an alteration in the metabolism of the microorganisms. New dynamic methods are used to determine K{sub L}a in an airlift reactor during the microbial growth of Candida utilis on glucose. One of the methods is based on the continuous measurement of carbon dioxide production while the other method is based on the relationship between the oxygen transfer and biomass growth rates. These methods of determining K{sub L}a does not interfere with the microorganisms action. A theoretical mass transfer model has been used for K{sub L}a estimation for the systems described above. Some differences between calculated and measured values are found for fermentation processes due to the model is developed for two-phase air-water systems. Nevertheless, the average deviation between the predicted values and those obtained from the relationship between oxygen transfer and biomass production rates are lower than 25% in any case. (orig.)

Revisiting the mouse model of oxygen-induced retinopathy

Directory of Open Access Journals (Sweden)

Kim CB

2016-05-01

Full Text Available Clifford B Kim,1,2 Patricia A D’Amore,2–4 Kip M Connor1,2 1Angiogenesis Laboratory, Massachusetts Eye and Ear, 2Department of Ophthalmology, Harvard Medical School, 3Schepens Eye Research Institute, Massachusetts Eye and Ear, 4Department of Pathology, Harvard Medical School, Boston, MA, USA Abstract: Abnormal blood vessel growth in the retina is a hallmark of many retinal diseases, such as retinopathy of prematurity (ROP, proliferative diabetic retinopathy, and the wet form of age-related macular degeneration. In particular, ROP has been an important health concern for physicians since the advent of routine supplemental oxygen therapy for premature neonates more than 70 years ago. Since then, researchers have explored several animal models to better understand ROP and retinal vascular development. Of these models, the mouse model of oxygen-induced retinopathy (OIR has become the most widely used, and has played a pivotal role in our understanding of retinal angiogenesis and ocular immunology, as well as in the development of groundbreaking therapeutics such as anti-vascular endothelial growth factor injections for wet age-related macular degeneration. Numerous refinements to the model have been made since its inception in the 1950s, and technological advancements have expanded the use of the model across multiple scientific fields. In this review, we explore the historical developments that have led to the mouse OIR model utilized today, essential concepts of OIR, limitations of the model, and a representative selection of key findings from OIR, with particular emphasis on current research progress. Keywords: ROP, OIR, angiogenesis

Multistate cohort models with proportional transfer rates

DEFF Research Database (Denmark)

Schoen, Robert; Canudas-Romo, Vladimir

2006-01-01

of transfer rates. The two living state case and hierarchical multistate models with any number of living states are analyzed in detail. Applying our approach to 1997 U.S. fertility data, we find that observed rates of parity progression are roughly proportional over age. Our proportional transfer rate...... approach provides trajectories by parity state and facilitates analyses of the implications of changes in parity rate levels and patterns. More women complete childbearing at parity 2 than at any other parity, and parity 2 would be the modal parity in models with total fertility rates (TFRs) of 1.40 to 2......We present a new, broadly applicable approach to summarizing the behavior of a cohort as it moves through a variety of statuses (or states). The approach is based on the assumption that all rates of transfer maintain a constant ratio to one another over age. We present closed-form expressions...

Dietary isothiocyanate sulforaphene induces reactive oxygen ...

African Journals Online (AJOL)

intracellular oxygen species (ROS) measurement, mitochondrial membrane depolarization and western blot analysis were performed in four time-intervals to explore sulforaphene activity. ..... proteins were transferred to PVDF membranes.

Operational Limitations of Arctic Waste Stabilization Ponds: Insights from Modeling Oxygen Dynamics and Carbon Removal

DEFF Research Database (Denmark)

Ragush, Colin M.; Gentleman, Wendy C.; Hansen, Lisbeth Truelstrup

2018-01-01

Presented here is a mechanistic model of the biological dynamics of the photic zone of a single-cell arctic waste stabilization pond (WSP) for the prediction of oxygen concentration and the removal of oxygen-demanding substances. The model is an exploratory model to assess the limiting environmen...

TRANSFER

African Journals Online (AJOL)

This paper reports on further studies on long range energy transfer between curcumine as donor and another thiazine dye, thionine, which is closely related to methylene blue as energy harvester (Figure 1). Since thionine is known to have a higher quantum yield of singlet oxygen sensitization than methylene blue [8], it is ...

Modeling Variable Phanerozoic Oxygen Effects on Physiology and Evolution.

Science.gov (United States)

Graham, Jeffrey B; Jew, Corey J; Wegner, Nicholas C

2016-01-01

Geochemical approximation of Earth's atmospheric O2 level over geologic time prompts hypotheses linking hyper- and hypoxic atmospheres to transformative events in the evolutionary history of the biosphere. Such correlations, however, remain problematic due to the relative imprecision of the timing and scope of oxygen change and the looseness of its overlay on the chronology of key biotic events such as radiations, evolutionary innovation, and extinctions. There are nevertheless general attributions of atmospheric oxygen concentration to key evolutionary changes among groups having a primary dependence upon oxygen diffusion for respiration. These include the occurrence of Devonian hypoxia and the accentuation of air-breathing dependence leading to the origin of vertebrate terrestriality, the occurrence of Carboniferous-Permian hyperoxia and the major radiation of early tetrapods and the origins of insect flight and gigantism, and the Mid-Late Permian oxygen decline accompanying the Permian extinction. However, because of variability between and error within different atmospheric models, there is little basis for postulating correlations outside the Late Paleozoic. Other problems arising in the correlation of paleo-oxygen with significant biological events include tendencies to ignore the role of blood pigment affinity modulation in maintaining homeostasis, the slow rates of O2 change that would have allowed for adaptation, and significant respiratory and circulatory modifications that can and do occur without changes in atmospheric oxygen. The purpose of this paper is thus to refocus thinking about basic questions central to the biological and physiological implications of O2 change over geological time.

Mathematical modeling of dissolved oxygen in fish ponds

African Journals Online (AJOL)

TUOYO

A mathematical model was developed to predict the effects of wind speed, light, pH, Temperature, dissolved carbon dioxide .... chlorophyll, the energy obtained splits water, and oxygen ... is a function of temperature T, light L, substrate, and pH as shown in ..... plants and its relation to the concentration of carbon dioxide and.

Experimental test of a four-level kinetic model for excited-state intramolecular proton transfer dye lasers

Energy Technology Data Exchange (ETDEWEB)

Costela, A; Munnoz, J M; Douhal, A; Figuera, J M; Acuna, A U [Inst. de Quimica Fisica ' ' Rocasolano' ' , C.S.I.C., Madrid (Spain)

1989-11-01

The nanosecond pulses of a dye laser oscillator based on the excited-state intramolecular proton-transfer reaction (IPT) of salicylamide and 2'-hydroxylphenyl benzimidazole dyes have been studied as a function of several experimental parameters. To explain the operation of this laser a numerical four-level kinetic model was developed until the lasing properties of these dyes, in the presence of a variable oxygen concentration and pumped with a double pulse technique, could be reproduced. This was possible only by assuming that the efficiency of the laser is controlled by the absorption cross-section of a transient state with a lifetime in the nanosecond-picosecond range, which was tentatively identified as a ground state tautomeric species. (orig.).

Heat transfer modeling an inductive approach

CERN Document Server

Sidebotham, George

2015-01-01

This innovative text emphasizes a "less-is-more" approach to modeling complicated systems such as heat transfer by treating them first as "1-node lumped models" that yield simple closed-form solutions. The author develops numerical techniques for students to obtain more detail, but also trains them to use the techniques only when simpler approaches fail. Covering all essential methods offered in traditional texts, but with a different order, Professor Sidebotham stresses inductive thinking and problem solving as well as a constructive understanding of modern, computer-based practice. Readers learn to develop their own code in the context of the material, rather than just how to use packaged software, offering a deeper, intrinsic grasp behind models of heat transfer. Developed from over twenty-five years of lecture notes to teach students of mechanical and chemical engineering at The Cooper Union for the Advancement of Science and Art, the book is ideal for students and practitioners across engineering discipl...

A model study of warming-induced phosphorus-oxygen feedbacks in open-ocean oxygen minimum zones on millennial timescales

Science.gov (United States)

Niemeyer, Daniela; Kemena, Tronje P.; Meissner, Katrin J.; Oschlies, Andreas

2017-05-01

Observations indicate an expansion of oxygen minimum zones (OMZs) over the past 50 years, likely related to ongoing deoxygenation caused by reduced oxygen solubility, changes in stratification and circulation, and a potential acceleration of organic matter turnover in a warming climate. The overall area of ocean sediments that are in direct contact with low-oxygen bottom waters also increases with expanding OMZs. This leads to a release of phosphorus from ocean sediments. If anthropogenic carbon dioxide emissions continue unabated, higher temperatures will cause enhanced weathering on land, which, in turn, will increase the phosphorus and alkalinity fluxes into the ocean and therefore raise the ocean's phosphorus inventory even further. A higher availability of phosphorus enhances biological production, remineralisation and oxygen consumption, and might therefore lead to further expansions of OMZs, representing a positive feedback. A negative feedback arises from the enhanced productivity-induced drawdown of carbon and also increased uptake of CO2 due to weathering-induced alkalinity input. This feedback leads to a decrease in atmospheric CO2 and weathering rates. Here, we quantify these two competing feedbacks on millennial timescales for a high CO2 emission scenario. Using the University of Victoria (UVic) Earth System Climate Model of intermediate complexity, our model results suggest that the positive benthic phosphorus release feedback has only a minor impact on the size of OMZs in the next 1000 years. The increase in the marine phosphorus inventory under assumed business-as-usual global warming conditions originates, on millennial timescales, almost exclusively (> 80 %) from the input via terrestrial weathering and causes a 4- to 5-fold expansion of the suboxic water volume in the model.

A model study of warming-induced phosphorus–oxygen feedbacks in open-ocean oxygen minimum zones on millennial timescales

Directory of Open Access Journals (Sweden)

D. Niemeyer

2017-05-01

Full Text Available Observations indicate an expansion of oxygen minimum zones (OMZs over the past 50 years, likely related to ongoing deoxygenation caused by reduced oxygen solubility, changes in stratification and circulation, and a potential acceleration of organic matter turnover in a warming climate. The overall area of ocean sediments that are in direct contact with low-oxygen bottom waters also increases with expanding OMZs. This leads to a release of phosphorus from ocean sediments. If anthropogenic carbon dioxide emissions continue unabated, higher temperatures will cause enhanced weathering on land, which, in turn, will increase the phosphorus and alkalinity fluxes into the ocean and therefore raise the ocean's phosphorus inventory even further. A higher availability of phosphorus enhances biological production, remineralisation and oxygen consumption, and might therefore lead to further expansions of OMZs, representing a positive feedback. A negative feedback arises from the enhanced productivity-induced drawdown of carbon and also increased uptake of CO2 due to weathering-induced alkalinity input. This feedback leads to a decrease in atmospheric CO2 and weathering rates. Here, we quantify these two competing feedbacks on millennial timescales for a high CO2 emission scenario. Using the University of Victoria (UVic Earth System Climate Model of intermediate complexity, our model results suggest that the positive benthic phosphorus release feedback has only a minor impact on the size of OMZs in the next 1000 years. The increase in the marine phosphorus inventory under assumed business-as-usual global warming conditions originates, on millennial timescales, almost exclusively (> 80 % from the input via terrestrial weathering and causes a 4- to 5-fold expansion of the suboxic water volume in the model.

Ceramics for Molten Materials Transfer

Science.gov (United States)

Standish, Evan; Stefanescu, Doru M.; Curreri, Peter A.

2009-01-01

The paper reviews the main issues associated with molten materials transfer and handling on the lunar surface during the operation of a hig h temperature electrowinning cell used to produce oxygen, with molten iron and silicon as byproducts. A combination of existing technolog ies and purposely designed technologies show promise for lunar exploi tation. An important limitation that requires extensive investigation is the performance of refractory currently used for the purpose of m olten metal containment and transfer in the lunar environment associa ted with electrolytic cells. The principles of a laboratory scale uni t at a scale equivalent to the production of 1 metric ton of oxygen p er year are introduced. This implies a mass of molten materials to be transferred consistent with the equivalent of 1kg regolithlhr proces sed.

Modelling the effects of oxygen evolution in the all-vanadium redox flow battery

International Nuclear Information System (INIS)

Al-Fetlawi, H.; Shah, A.A.; Walsh, F.C.

2010-01-01

The impact of oxygen evolution and bubble formation on the performance of an all-vanadium redox flow battery is investigated using a two-dimensional, non-isothermal model. The model is based on mass, charge, energy and momentum conservation, together with a kinetic model for the redox and gas-evolving reactions. The multi-phase mixture model is used to describe the transport of oxygen in the form of gas bubbles. Numerical simulations are compared to experimental data, demonstrating good agreement. Parametric studies are performed to investigate the effects of changes in the operating temperature, electrolyte flow rate and bubble diameter on the extent of oxygen evolution. Increasing the electrolyte flow rate is found to reduce the volume of the oxygen gas evolved in the positive electrode. A larger bubble diameter is demonstrated to increase the buoyancy force exerted on the bubbles, leading to a faster slip velocity and a lower gas volume fraction. Substantial changes are observed over the range of reported bubble diameters. Increasing the operating temperature was found to increase the gas volume as a result of the enhanced rate of O 2 evolution. The charge efficiency of the cell drops markedly as a consequence.

Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

Science.gov (United States)

Kelly, Sean M; Kromer, Brian R; Litwin, Michael M; Rosen, Lee J; Christie, Gervase Maxwell; Wilson, Jamie R; Kosowski, Lawrence W; Robinson, Charles

2014-01-07

A method and apparatus for producing heat used in a synthesis gas production is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the stream reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5.

Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

Science.gov (United States)

Kelly, Sean M.; Kromer, Brian R.; Litwin, Michael M.; Rosen, Lee J.; Christie, Gervase Maxwell; Wilson, Jamie R.; Kosowski, Lawrence W.; Robinson, Charles

2016-01-19

A method and apparatus for producing heat used in a synthesis gas production process is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the steam reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5

Kinetics of oxygen reduction in perovskite cathodes for solid oxide fuel cells: A combined modeling and experimental approach

Science.gov (United States)

Miara, Lincoln James

Solid oxide fuel cells (SOFCs) have the potential to replace conventional stationary power generation technologies; however, there are major obstacles to commercialization, the most problematic of which is poor cathode performance. Commercialization of SOFCs will follow when the mechanisms occurring at the cathode are more thoroughly understood and adapted for market use. The catalytic reduction of oxygen occurring in SOFC cathodes consists of many elementary steps such as gas phase diffusion, chemical and/or electrochemical reactions which lead to the adsorption and dissociation of molecular oxygen onto the cathode surface, mass transport of oxygen species along the surface and/or through the bulk of the cathode, and full reduction and incorporation of the oxygen at the cathode/electrolyte two or three phase boundary. Electrochemical impedance spectroscopy (EIS) is the main technique used to identify the occurrence of these different processes, but when this technique is used without an explicit model describing the kinetics it is difficult to unravel the interdependence of each of these processes. The purpose of this dissertation is to identify the heterogeneous reactions occurring at the cathode of an SOFC by combining experimental EIS results with mathematical models describing the time dependent behavior of the system. This analysis is performed on two different systems. In the first case, experimental EIS results from patterned half cells composed of Ca-doped lanthanum manganite (LCM)| yttria-doped ZrO2 (YSZ) are modeled to investigate the temperature and partial pressure of oxygen, pO2, dependence of oxygen adsorption/dissociation onto the LCM surface, surface diffusion of atomic oxygen, and electrochemical reduction and incorporation of the oxygen into the electrolyte in the vicinity of the triple phase boundary (TPB). This model determines the time-independent state-space equations from which the Faradaic admittance transfer function is obtained. The

Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

Science.gov (United States)

Sgouralis, Ioannis; Kett, Michelle M.; Ow, Connie P. C.; Abdelkader, Amany; Layton, Anita T.; Gardiner, Bruce S.; Smith, David W.; Lankadeva, Yugeesh R.

2016-01-01

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2. Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2. Both intravenous infusion of [Phe2,Ile3,Orn8]-vasopressin and infusion of NG-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8–17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r2 = 0.87–0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2. Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1–0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10–50% of the change in pelvic urine/medullary Po2. Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury. PMID:27385734

Diffusive-dispersive mass transfer in the capillary fringe: Impact of water table fluctuations and heterogeneities

DEFF Research Database (Denmark)

Grathwohl, Peter; Haberer, Cristina; Ye, Yu

Diffusive–dispersive mass transfer in the capillary fringe is important for many groundwater quality issues such as transfer of volatile compounds into (and out of) the groundwater, the supply of oxygen for aerobic degradation of hydrocarbons as well as for precipitation of minerals (e.g. iron...... hydroxides). 2D-laboratory scale experiments were used to investigate the transfer of oxygen into groundwater under non-reactive and reactive conditions, at steady state and with water table fluctuations. Results show that transfer of oxygen is limited by transverse dispersion in the capillary fringe...... and the dispersion coefficients are the same as below the water table. Water table fluctuations cause temporarily increased fluxes of oxygen into groundwater during draining conditions and entrapped air after water table rise. High-permeability inclusions in the capillary fringe enhance mass transfer of oxygen...

Fast radiative transfer models for retrieval of cloud properties in the back-scattering region: application to DSCOVR-EPIC sensor

Science.gov (United States)

Molina Garcia, Victor; Sasi, Sruthy; Efremenko, Dmitry; Doicu, Adrian; Loyola, Diego

2017-04-01

In this work, the requirements for the retrieval of cloud properties in the back-scattering region are described, and their application to the measurements taken by the Earth Polychromatic Imaging Camera (EPIC) on board the Deep Space Climate Observatory (DSCOVR) is shown. Various radiative transfer models and their linearizations are implemented, and their advantages and issues are analyzed. As radiative transfer calculations in the back-scattering region are computationally time-consuming, several acceleration techniques are also studied. The radiative transfer models analyzed include the exact Discrete Ordinate method with Matrix Exponential (DOME), the Matrix Operator method with Matrix Exponential (MOME), and the approximate asymptotic and equivalent Lambertian cloud models. To reduce the computational cost of the line-by-line (LBL) calculations, the k-distribution method, the Principal Component Analysis (PCA) and a combination of the k-distribution method plus PCA are used. The linearized radiative transfer models for retrieval of cloud properties include the Linearized Discrete Ordinate method with Matrix Exponential (LDOME), the Linearized Matrix Operator method with Matrix Exponential (LMOME) and the Forward-Adjoint Discrete Ordinate method with Matrix Exponential (FADOME). These models were applied to the EPIC oxygen-A band absorption channel at 764 nm. It is shown that the approximate asymptotic and equivalent Lambertian cloud models give inaccurate results, so an offline processor for the retrieval of cloud properties in the back-scattering region requires the use of exact models such as DOME and MOME, which behave similarly. The combination of the k-distribution method plus PCA presents similar accuracy to the LBL calculations, but it is up to 360 times faster, and the relative errors for the computed radiances are less than 1.5% compared to the results when the exact phase function is used. Finally, the linearized models studied show similar behavior

Turbulence modeling for mass transfer enhancement by separation and reattachment with two-equation eddy-viscosity models

International Nuclear Information System (INIS)

Xiong Jinbiao; Koshizuka, Seiichi; Sakai, Mikio

2011-01-01

Highlights: → We selected and evaluated five two-equation eddy-viscosity turbulence models for modeling the separated and reattaching flow. → The behavior of the models in the simple flow is not consistent with that in the separated and reattaching flow. → The Abe-Kondoh-Nagano model is the best one among the selected model. → Application of the stress limiter and the Kato-Launder modification in the Abe-Kondoh-Nagano model helps to improve prediction of the peak mass transfer coefficient in the orifice flow. → The value of turbulent Schmidt number is investigated. - Abstract: The prediction of mass transfer rate is one of the key elements for estimation of the flow accelerated corrosion (FAC) rate. Three low Reynolds number (LRN) k-ε models (Lam-Bremhorst (LB), Abe-Kondoh-Nagano (AKN) and Hwang-Lin (HL)), one LRN k-ω (Wilcox, WX) model and the k-ω SST model are tested for the computation of the high Schmidt number mass transfer, especially in the flow through an orifice. The models are tested in the computation of three types of flow: (1) the fully developed pipe flow, (2) the flow over a backward facing step, (3) the flow through an orifice. The HL model shows a good performance in predicting mass transfer in the fully developed pipe flow but fails to give reliable prediction in the flow through an orifice. The WX model and the k-ω SST model underpredict the mass transfer rate in the flow types 1 and 3. The LB model underestimates the mass transfer in the flow type 1, but shows abnormal behavior at the reattaching point in type 3. Synthetically evaluating all the models in all the computed case, the AKN model is the best one; however, the prediction is still not satisfactory. In the evaluation in the flow over a backward facing step shows k-ω SST model shows superior performance. This is interpreted as an implication that the combination of the k-ε model and the stress limiter can improve the model behavior in the recirculation bubble. Both the

Improved Wave-vessel Transfer Functions by Uncertainty Modelling

DEFF Research Database (Denmark)

Nielsen, Ulrik Dam; Fønss Bach, Kasper; Iseki, Toshio

2016-01-01

This paper deals with uncertainty modelling of wave-vessel transfer functions used to calculate or predict wave-induced responses of a ship in a seaway. Although transfer functions, in theory, can be calculated to exactly reflect the behaviour of the ship when exposed to waves, uncertainty in inp...

The mitochondrial outer membrane protein mitoNEET is a redox enzyme catalyzing electron transfer from FMNH2 to oxygen or ubiquinone.

Science.gov (United States)

Wang, Yiming; Landry, Aaron P; Ding, Huangen

2017-06-16

Increasing evidence suggests that mitoNEET, a target of the type II diabetes drug pioglitazone, is a key regulator of energy metabolism in mitochondria. MitoNEET is anchored to the mitochondrial outer membrane via its N-terminal α helix domain and hosts a redox-active [2Fe-2S] cluster in its C-terminal cytosolic region. The mechanism by which mitoNEET regulates energy metabolism in mitochondria, however, is not fully understood. Previous studies have shown that mitoNEET specifically interacts with the reduced flavin mononucleotide (FMNH 2 ) and that FMNH 2 can quickly reduce the mitoNEET [2Fe-2S] clusters. Here we report that the reduced mitoNEET [2Fe-2S] clusters can be readily oxidized by oxygen. In the presence of FMN, NADH, and flavin reductase, which reduces FMN to FMNH 2 using NADH as the electron donor, mitoNEET mediates oxidation of NADH with a concomitant reduction of oxygen. Ubiquinone-2, an analog of ubiquinone-10, can also oxidize the reduced mitoNEET [2Fe-2S] clusters under anaerobic or aerobic conditions. Compared with oxygen, ubiquinone-2 is more efficient in oxidizing the mitoNEET [2Fe-2S] clusters, suggesting that ubiquinone could be an intrinsic electron acceptor of the reduced mitoNEET [2Fe-2S] clusters in mitochondria. Pioglitazone or its analog NL-1 appears to inhibit the electron transfer activity of mitoNEET by forming a unique complex with mitoNEET and FMNH 2 The results suggest that mitoNEET is a redox enzyme that may promote oxidation of NADH to facilitate enhanced glycolysis in the cytosol and that pioglitazone may regulate energy metabolism in mitochondria by inhibiting the electron transfer activity of mitoNEET. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Supporting Students' Knowledge Transfer in Modeling Activities

Science.gov (United States)

Piksööt, Jaanika; Sarapuu, Tago

2014-01-01

This study investigates ways to enhance secondary school students' knowledge transfer in complex science domains by implementing question prompts. Two samples of students applied two web-based models to study molecular genetics--the model of genetic code (n = 258) and translation (n = 245). For each model, the samples were randomly divided into…

Modeling Transfer of Vibrio Parahaemolyticus During Peeling of Raw Shrimp.

Science.gov (United States)

Xiao, Xingning; Pang, Haiying; Wang, Wen; Fang, Weihuan; Fu, Yingchun; Li, Yanbin

2018-03-01

This study aimed to qualify the transfer of Vibrio parahaemolyticus during the shrimp peeling process via gloves under 3 different scenarios. The 1st 2 scenarios provided quantitative information for the probability distribution of bacterial transfer rates from (i) contaminated shrimp (6 log CFU/g) to non-contaminated gloves (Scenario 1) and (ii) contaminated gloves (6 log CFU/per pair) to non-contaminated shrimp (Scenario 2). In Scenario 3, bacterial transfer from contaminated shrimp to non-contaminated shrimp in the shrimp peeling process via gloves was investigated to develop a predictive model for describing the successive bacterial transfer. The range of bacterial transfer rate (%) in Scenarios 1 and 2 was 7% to 91.95% and 0.04% to 12.87%, respectively, indicating that the bacteria can be transferred from shrimp to gloves much easier than that from gloves to shrimp. A Logistic (1.59, 0.14) and Triangle distribution (-1.61, 0.12, 1.32) could be used to describe the bacterial transfer rate in Scenarios 1 and 2, respectively. In Scenario 3, a continuously decay patterning with fluctuations as the peeling progressed has been observed at all inoculation levels of the 1st shrimp (5, 6, and 7 log CFU/g). The bacteria could be transferred easier at 1st few peels, and the decreasing bacterial transfer was found in later phase. Two models (exponential and Weibull) could describe the successive bacterial transfer satisfactorily (pseudo-R 2 > 0.84, RMSE peeling process. The bacterial transfer rate distribution and predictive model derived from this work could be used in risk assessment of V. parahaemolyticus to ensure peeled shrimp safety. © 2018 Institute of Food Technologists®.

Modeling Force Transfer around Openings in Wood-Frame Shear Walls

Science.gov (United States)

Minghao Li; Frank Lam; Borjen Yeh; Tom Skaggs; Doug Rammer; James Wacker

2012-01-01

This paper presented a modeling study on force transfer around openings (FTAO) in wood-frame shear walls detailed for FTAO. To understand the load transfer in the walls, this study used a finite-element model WALL2D, which is able to model individual wall components, including framing members, sheathing panels, oriented panel-frame nailed connections, framing...

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model.

Science.gov (United States)

Park, Marcelo; Mendes, Pedro Vitale; Costa, Eduardo Leite Vieira; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Azevedo, Luciano Cesar Pontes

2016-01-01

The aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure. The factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested. Oxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL). In conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin.

Reduced Moment-Based Models for Oxygen Precipitates and Dislocation Loops in Silicon

Science.gov (United States)

Trzynadlowski, Bart

The demand for ever smaller, higher-performance integrated circuits and more efficient, cost-effective solar cells continues to push the frontiers of process technology. Fabrication of silicon devices requires extremely precise control of impurities and crystallographic defects. Failure to do so not only reduces performance, efficiency, and yield, it threatens the very survival of commercial enterprises in today's fiercely competitive and price-sensitive global market. The presence of oxygen in silicon is an unavoidable consequence of the Czochralski process, which remains the most popular method for large-scale production of single-crystal silicon. Oxygen precipitates that form during thermal processing cause distortion of the surrounding silicon lattice and can lead to the formation of dislocation loops. Localized deformation caused by both of these defects introduces potential wells that trap diffusing impurities such as metal atoms, which is highly desirable if done far away from sensitive device regions. Unfortunately, dislocations also reduce the mechanical strength of silicon, which can cause wafer warpage and breakage. Engineers must negotiate this and other complex tradeoffs when designing fabrication processes. Accomplishing this in a complex, modern process involving a large number of thermal steps is impossible without the aid of computational models. In this dissertation, new models for oxygen precipitation and dislocation loop evolution are described. An oxygen model using kinetic rate equations to evolve the complete precipitate size distribution was developed first. This was then used to create a reduced model tracking only the moments of the size distribution. The moment-based model was found to run significantly faster than its full counterpart while accurately capturing the evolution of oxygen precipitates. The reduced model was fitted to experimental data and a sensitivity analysis was performed to assess the robustness of the results. Source

Incorporation of oxygen contribution by plant roots into classical dissolved oxygen deficit model for a subsurface flow treatment wetland.

Science.gov (United States)

Bezbaruah, Achintya N; Zhang, Tian C

2009-01-01

It has been long established that plants play major roles in a treatment wetland. However, the role of plants has not been incorporated into wetland models. This study tries to incorporate wetland plants into a biochemical oxygen demand (BOD) model so that the relative contributions of the aerobic and anaerobic processes to meeting BOD can be quantitatively determined. The classical dissolved oxygen (DO) deficit model has been modified to simulate the DO curve for a field subsurface flow constructed wetland (SFCW) treating municipal wastewater. Sensitivities of model parameters have been analyzed. Based on the model it is predicted that in the SFCW under study about 64% BOD are degraded through aerobic routes and 36% is degraded anaerobically. While not exhaustive, this preliminary work should serve as a pointer for further research in wetland model development and to determine the values of some of the parameters used in the modified DO deficit and associated BOD model. It should be noted that nitrogen cycle and effects of temperature have not been addressed in these models for simplicity of model formulation. This paper should be read with this caveat in mind.

Modelling radiation-induced cell death and tumour re-oxygenation: local versus global and instant versus delayed cell death

International Nuclear Information System (INIS)

Gago-Arias, Araceli; Espinoza, Ignacio; Sánchez-Nieto, Beatriz; Aguiar, Pablo; Pardo-Montero, Juan

2016-01-01

The resistance of hypoxic cells to radiation, due to the oxygen dependence of radiosensitivity, is well known and must be taken into account to accurately calculate the radiation induced cell death. A proper modelling of the response of tumours to radiation requires deriving the distribution of oxygen at a microscopic scale. This usually involves solving the reaction-diffusion equation in tumour voxels using a vascularization distribution model. Moreover, re-oxygenation arises during the course of radiotherapy, one reason being the increase of available oxygen caused by cell killing, which can turn hypoxic tumours into oxic. In this work we study the effect of cell death kinetics in tumour oxygenation modelling, analysing how it affects the timing of re-oxygenation, surviving fraction and tumour control. Two models of cell death are compared, an instantaneous cell killing, mimicking early apoptosis, and a delayed cell death scenario in which cells can die shortly after being damaged, as well as long after irradiation. For each of these scenarios, the decrease in oxygen consumption due to cell death can be computed globally (macroscopic voxel average) or locally (microscopic). A re-oxygenation model already used in the literature, the so called full re-oxygenation, is also considered. The impact of cell death kinetics and re-oxygenation on tumour responses is illustrated for two radiotherapy fractionation schemes: a conventional schedule, and a hypofractionated treatment. The results show large differences in the doses needed to achieve 50% tumour control for the investigated cell death models. Moreover, the models affect the tumour responses differently depending on the treatment schedule. This corroborates the complex nature of re-oxygenation, showing the need to take into account the kinetics of cell death in radiation response models. (paper)

Stochastic Modelling of Wireless Energy Transfer

Science.gov (United States)

Veilleux, Shaun; Almaghasilah, Ahmed; Abedi, Ali; Wilkerson, DeLisa

2017-01-01

This study investigates the efficiency of a new method of powering remote sensors by the means of wireless energy transfer. The increased use of sensors for data collection comes with the inherent cost of supplying power from sources such as power cables or batteries. Wireless energy transfer technology eliminates the need for power cables or periodic battery replacement. The time and cost of setting up or expanding a sensor network will be reduced while allowing sensors to be placed in areas where running power cables or battery replacement is not feasible. This paper models wireless channels for power and data separately. Smart scheduling for the data channel is proposed to avoid transmitting data on a noisy channel where the probability of data loss is high to improve power efficiency. Analytical models have been developed and verified using simulations.

Separate effects tests for GOTHIC condensation and evaporative heat transfer models

International Nuclear Information System (INIS)

George, T.L.; Singh, A.

1994-01-01

The GOTHIC computer program, under development at EPRI/NAI, is a general purpose thermal hydraulics computer program for design, licensing, safety and operating analysis of nuclear containments and other confinement buildings. The code solves a nine equation model for three dimensional multiphase flow with separate mass, momentum and energy equations for vapor, liquid and drop phases. The vapor phase can be a gas mixture of steam and non-condensing gases. The phase balance equations are coupled by mechanistic and empirical models for interface mass, energy and momentum transfer that cover the entire flow regime from bubbly flow to film/drop flow. A variety of heat transfer correlations are available to model the fluid coupling to active and passive solid conductors. This paper focuses on the application of GOTHIC to two separate effects tests; condensation heat transfer on a vertical flat plate with varying bulk velocity, steam concentration and temperature, and evaporative heat transfer from a hot pool to a dry (superheated) atmosphere. Comparisons with experimental data is included for both tests. Results show the validity of two condensation heat transfer correlations as incorporated into GOTHIC and the interfacial heat and mass transfer models for the range of the experimental test conditions. Comparisons are also made for lumped versus multidimensional modeling for buoyancy controlled flow with evaporative heat transfer. (author). 13 refs., 1 tab., 10 figs

Separate effects tests for GOTHIC condensation and evaporative heat transfer models

International Nuclear Information System (INIS)

George, T.L.; Singh, A.

1996-01-01

The GOTHIC computer program, under development at NAI for EPRI, is a general purpose thermal hydraulics computer program for design, licensing, safety and operating analysis of nuclear containments and other confinement buildings. The code solves a nine-equation model for three-dimensional multiphase flow with separate mass, momentum and energy equations for vapor, liquid and drop phases. The vapor phase can be a gas mixture of steam and non-condensing gases. The phase balance equations are coupled by mechanistic and empirical models for interface mass, energy and momentum transfer that cover the entire flow regime from bubbly flow to film-drop flow. A variety of heat transfer correlations are available to model the fluid coupling to active and passive solid conductors. This paper focuses on the application of GOTHIC to two separate effects tests: condensation heat transfer on a vertical flat plate with varying bulk velocity, steam concentration and temperature, and evaporative heat transfer from a hot pool to a dry (superheated) atmosphere. Comparisons with experimental data are included for both tests. Results show the validity of two condensation heat transfer correlations as incorporated into GOTHIC and the interfacial heat and mass transfer models for the range of the experimental test conditions. Comparisons are also made for lumped vs. multidimensional modeling for buoyancy-controlled flow with evaporative heat transfer. (orig.)

A transfer-matrix method for spatially modulated structures

International Nuclear Information System (INIS)

Surda, A.

1991-03-01

A cluster transfer-matrix method convenient for calculation of spatially modulated structures of a wide class of lattice-gas models is developed. The method formulates the problem of calculation of the partition function in terms of non-linear mapping of effective multi-site fields. It is applied to a lattice-gas model qualitatively describing the system of oxygen atoms in the basal planes of high-temperature superconductors. The properties of an incommensurate structure occurring at intermediate temperatures are discussed in detail. (author). 21 refs, 15 figs

Development of a transfer model for design of sodium purification systems for Fast Breeder Reactors

International Nuclear Information System (INIS)

Khatcheressian, N.

2013-01-01

Operating a Sodium Fast Reactor (SFR) in reliable and safe conditions requires to master the quality of the sodium fluid coolant, regarding oxygen and hydrogen impurities contents. A cold trap is a purification unit in SFR, designed for maintaining oxygen and hydrogen contents within acceptable limits. The purification of these impurities is based on crystallization of sodium hydride on cold walls and sodium oxide or hydride on wire mesh packing. Indeed, as oxygen and hydrogen solubilities are nearly nil at temperatures close to the sodium fusion point, i.e. 97.8 C, on line sodium purification can be performed by crystallization of sodium oxide and hydride from liquid sodium flows. However, the management of cold trap performances is necessary to prevent from unforeseen maintenance operations, which could induce shut-down of the reactor. It is thus essential to understand how a cold trap fills up with impurities crystallization in order to optimize the design of this system and to overcome any problems during nominal operation. The objective is to develop a design and simulation tool for cold traps able to predict the location and the amount of the impurities deposited. Crystallization model involve phenomena coupling in a porous medium with hydrodynamics, heat and mass transfer, distinguishing nucleation and growth phases for each impurity. It enables to understand how thermo hydraulic conditions and growing impurities interact on each other. This analysis will adapt operating and management conditions in order to optimize purification requirements. (author) [fr

Calcium-manganese oxides as structural and functional models for active site in oxygen evolving complex in photosystem II: lessons from simple models.

Science.gov (United States)

Najafpour, Mohammad Mahdi

2011-01-01

The oxygen evolving complex in photosystem II which induces the oxidation of water to dioxygen in plants, algae and certain bacteria contains a cluster of one calcium and four manganese ions. It serves as a model to split water by sunlight. Reports on the mechanism and structure of photosystem II provide a more detailed architecture of the oxygen evolving complex and the surrounding amino acids. One challenge in this field is the development of artificial model compounds to study oxygen evolution reaction outside the complicated environment of the enzyme. Calcium-manganese oxides as structural and functional models for the active site of photosystem II are explained and reviewed in this paper. Because of related structures of these calcium-manganese oxides and the catalytic centers of active site of the oxygen evolving complex of photosystem II, the study may help to understand more about mechanism of oxygen evolution by the oxygen evolving complex of photosystem II. Copyright © 2010 Elsevier B.V. All rights reserved.

Liquid-gas mass transfer at drop structures

DEFF Research Database (Denmark)

Matias, Natércia; Nielsen, Asbjørn Haaning; Vollertsen, Jes

2017-01-01

-water mass transfer, little is known about hydrogen sulfide emission under highly turbulent conditions (e.g., drop structures, hydraulic jumps). In this study, experimental work was carried out to analyze the influence of characteristics of drops on reaeration. Physical models were built, mimicking typical...... sewer drop structures and allowing different types of drops, drop heights, tailwater depths and flow rates. In total, 125 tests were performed. Based on their results, empirical expressions translating the relationship between the mass transfer of oxygen and physical parameters of drop structures were...... established. Then, by applying the two-film theory with two-reference substances, the relation to hydrogen sulfide release was defined. The experiments confirmed that the choice of the type of drop structure is critical to determine the uptake/emission rates. By quantifying the air-water mass transfer rates...

Phenomenological model of photoluminescence degradation and photoinduced defect formation in silicon nanocrystal ensembles under singlet oxygen generation

Energy Technology Data Exchange (ETDEWEB)

Gongalsky, Maxim B., E-mail: mgongalsky@gmail.com; Timoshenko, Victor Yu. [Faculty of Physics, Moscow State M.V. Lomonosov University, 119991 Moscow (Russian Federation)

2014-12-28

We propose a phenomenological model to explain photoluminescence degradation of silicon nanocrystals under singlet oxygen generation in gaseous and liquid systems. The model considers coupled rate equations, which take into account the exciton radiative recombination in silicon nanocrystals, photosensitization of singlet oxygen generation, defect formation on the surface of silicon nanocrystals as well as quenching processes for both excitons and singlet oxygen molecules. The model describes well the experimentally observed power law dependences of the photoluminescence intensity, singlet oxygen concentration, and lifetime versus photoexcitation time. The defect concentration in silicon nanocrystals increases by power law with a fractional exponent, which depends on the singlet oxygen concentration and ambient conditions. The obtained results are discussed in a view of optimization of the photosensitized singlet oxygen generation for biomedical applications.

Verification and Validation of Heat Transfer Model of AGREE Code

Energy Technology Data Exchange (ETDEWEB)

Tak, N. I. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Seker, V.; Drzewiecki, T. J.; Downar, T. J. [Department of Nuclear Engineering and Radiological Sciences, Univ. of Michigan, Michigan (United States); Kelly, J. M. [US Nuclear Regulatory Commission, Washington (United States)

2013-05-15

The AGREE code was originally developed as a multi physics simulation code to perform design and safety analysis of Pebble Bed Reactors (PBR). Currently, additional capability for the analysis of Prismatic Modular Reactor (PMR) core is in progress. Newly implemented fluid model for a PMR core is based on a subchannel approach which has been widely used in the analyses of light water reactor (LWR) cores. A hexagonal fuel (or graphite block) is discretized into triangular prism nodes having effective conductivities. Then, a meso-scale heat transfer model is applied to the unit cell geometry of a prismatic fuel block. Both unit cell geometries of multi-hole and pin-in-hole types of prismatic fuel blocks are considered in AGREE. The main objective of this work is to verify and validate the heat transfer model newly implemented for a PMR core in the AGREE code. The measured data in the HENDEL experiment were used for the validation of the heat transfer model for a pin-in-hole fuel block. However, the HENDEL tests were limited to only steady-state conditions of pin-in-hole fuel blocks. There exist no available experimental data regarding a heat transfer in multi-hole fuel blocks. Therefore, numerical benchmarks using conceptual problems are considered to verify the heat transfer model of AGREE for multi-hole fuel blocks as well as transient conditions. The CORONA and GAMMA+ codes were used to compare the numerical results. In this work, the verification and validation study were performed for the heat transfer model of the AGREE code using the HENDEL experiment and the numerical benchmarks of selected conceptual problems. The results of the present work show that the heat transfer model of AGREE is accurate and reliable for prismatic fuel blocks. Further validation of AGREE is in progress for a whole reactor problem using the HTTR safety test data such as control rod withdrawal tests and loss-of-forced convection tests.

Validation of heat transfer models for gap cooling

International Nuclear Information System (INIS)

Okano, Yukimitsu; Nagae, Takashi; Murase, Michio

2004-01-01

For severe accident assessment of a light water reactor, models of heat transfer in a narrow annular gap between overheated core debris and a reactor pressure vessel are important for evaluating vessel integrity and accident management. The authors developed and improved the models of heat transfer. However, validation was not sufficient for applicability of the gap heat flux correlation to the debris cooling in the vessel lower head and applicability of the local boiling heat flux correlations to the high-pressure conditions. Therefore, in this paper, we evaluated the validity of the heat transfer models and correlations by analyses for ALPHA and LAVA experiments where molten aluminum oxide (Al 2 O 3 ) at about 2700 K was poured into the high pressure water pool in a small-scale simulated vessel lower head. In the heating process of the vessel wall, the calculated heating rate and peak temperature agreed well with the measured values, and the validity of the heat transfer models and gap heat flux correlation was confirmed. In the cooling process of the vessel wall, the calculated cooling rate was compared with the measured value, and the validity of the nucleate boiling heat flux correlation was confirmed. The peak temperatures of the vessel wall in ALPHA and LAVA experiments were lower than the temperature at the minimum heat flux point between film boiling and transition boiling, so the minimum heat flux correlation could not be validated. (author)

A Model of the Antecedents of Training Transfer

Science.gov (United States)

Mohammed Turab, Ghaneemah; Casimir, Gian

2015-01-01

Many organizations have invested heavily in training. However, only a small percentage of what is learnt from training is applied or transferred to the workplace. This study examines factors that influence training transfer. A conceptual model based on the Theory of Reasoned Action is hypothesized and tested. The sample consisted of 123 full-time…

Muon transfer from muonic hydrogen to heavier atoms; Transfert de charge muonique

Energy Technology Data Exchange (ETDEWEB)

Dupays, A

2004-06-01

This work concerns muon transfer from muonic hydrogen to heavier atoms. Recently, a method of measurement of the hyperfine structure of ground-state muonic hydrogen based on the collision energy dependence of the muon transfer rate to oxygen has been proposed. This proposal is based on measurements which where performed at the Paul Scherrer Institute in the early nineties which indicate that the muon transfer from muonic hydrogen to oxygen increases by a factor of 4 going from thermal to 0.12 eV energies. The motivation of our calculations was to confirm this behaviour. To study the collision energy dependence of the muon transfer rate, we have used a time-independent close-coupling method. We have set up an hyperspherical elliptic formalism valid for nonzero total angular momentum which allows accurate computations of state-to-state reactive and charge exchange processes. We have applied this formalism to muon-transfer process to oxygen and neon. The comparison with experimental results is in both cases excellent. Finally, the neon transfer rate dependence with energy suggests to use neon instead of oxygen to perform a measurement of the hyperfine structure of muonic hydrogen. The results of accurate calculations of the muon transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen and neon are also reported. Very good agreement with measured rates is obtained and for the three systems, the isotopic effect is perfectly reproduced. (author)

An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

International Nuclear Information System (INIS)

Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.

1995-01-01

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba's Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to ±5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce0.8Pr0.2O2-delta

OpenAIRE

Chatzichristodoulou, Christodoulos; Hendriksen, Peter Vang

2010-01-01

The oxygen nonstoichiometry (delta) of Ce0.8Pr0.2O2−delta has been measured as a function of PO2 at temperatures between 600 and 900°C by coulometric titration and thermogravimetry. An ideal solution defect model, a regular solution model, and a defect association model, taking into account the association of reduced dopant species and oxygen vacancies, were unable to reproduce the experimental results. However, excellent agreement with the experimentally determined oxygen nonstoichiometry co...

HTCC - a heat transfer model for gas-steam mixtures

International Nuclear Information System (INIS)

Papadimitriou, P.

1983-01-01

The mathematical model HTCC (Heat Transfer Coefficient in Containment) has been developed for RALOC after a loss-of-coolant accident in order to determine the local heat transfer coefficients for transfer between the containment atmosphere and the walls of the reactor building. The model considers the current values of room and wall temperature, the concentration of steam and non-condensible gases, geometry data and those of fluid dynamics together with thermodynamic parameters and from these determines the heat transfer mechanisms due to convection, radiation and condensation. The HTCC is implemented in the RALOC program. Comparative analyses of computed temperature profiles, for HEDL Standard problems A and B on hydrogen distribution, and of computed temperature profiles determined during the heat-up phase in the CSE-A5 experiment show a good agreement with experimental data. (orig.) [de

Micro-oxygenation of red wine: techniques, applications, and outcomes.

Science.gov (United States)

Schmidtke, Leigh M; Clark, Andrew C; Scollary, Geoff R

2011-02-01

Wine micro-oxygenation (MOX) is the controlled addition of oxygen to wine in a manner designed to ensure that complete mass transfer of molecular oxygen from gaseous to dissolved state occurs. MOX was initially developed to improve the body, structure, and fruitfulness in red wines with high concentrations of tannins and anthocyanins, by replicating the ingress of oxygen thought to arise from barrel maturation, but without the need for putting all wine to barrel. This review describes the operational parameters essential for the effective performance of the micro-oxidation process as well as the chemical and microbiological outcomes. The methodologies for introducing oxygen into the wine, the rates of oxygen addition, and their relationship to oxygen solubility in the wine matrix are examined. The review focuses on the techniques used for monitoring the MOX process, including sensory assessment, physicochemical properties, and the critical balance of the rate of oxygen addition in relation to maintaining the sulfur dioxide concentration. The chemistry of oxygen reactivity with wine components, the changes in wine composition that occur as a consequence of MOX, and the potential for wine spoilage if proper monitoring is not adopted are examined. Gaps in existing knowledge are addressed focusing on the limitations associated with the transfer of concepts from research trials in small volume tanks to commercial practice, and the dearth of kinetic data for the various chemical and physical processes that are claimed to occur during MOX.

Interaction cross sections and matter radii of oxygen isotopes using the Glauber model

Science.gov (United States)

Ahmad, Suhel; Usmani, A. A.; Ahmad, Shakeb; Khan, Z. A.

2017-05-01

Using the Coulomb modified correlation expansion for the Glauber model S matrix, we calculate the interaction cross sections of oxygen isotopes (O-2616) on 12C at 1.0 GeV/nucleon. The densities of O-2616 are obtained using (i) the Slater determinants consisting of the harmonic oscillator single-particle wave functions (SDHO) and (ii) the relativistic mean-field approach (RMF). Retaining up to the two-body density term in the correlation expansion, the calculations are performed employing the free as well as the in-medium nucleon-nucleon (N N ) scattering amplitude. The in-medium N N amplitude considers the effects arising due to phase variation, higher momentum transfer components, and Pauli blocking. Our main focus in this work is to reveal how could one make the best use of SDHO densities with reference to the RMF one. The results demonstrate that the SDHO densities, along with the in-medium N N amplitude, are able to provide satisfactory explanation of the experimental data. It is found that, except for O,2423, the predicted SDHO matter rms radii of oxygen isotopes closely agree with those obtained using the RMF densities. However, for O,2423, our results require reasonably larger SDHO matter rms radii than the RMF values, thereby predicting thicker neutron skins in 23O and 24O as compared to RMF ones. In conclusion, the results of the present analysis establish the utility of SDHO densities in predicting fairly reliable estimates of the matter rms radii of neutron-rich nuclei.

Physical-analytical model for cesium/oxygen coadsorption on tungsten

International Nuclear Information System (INIS)

Rasor, N.S.

1992-01-01

In this paper a physical-analytical model is formulated for computing the emission and vaporization properties of a surface immersed in a multi-species vapor. The evaporation and condensation processes are assumed to be identical to those for an equilibrium adsorbed phase in equilibrium with its vapor, permitting statistical mechanical computation of the sticking coefficient for the practical non-equilibrium condensation condition. Two classes of adsorption sites are defined corresponding to superficial and interstitial coadsorption. The work function is computed by a self-consistent summation over the dipole moments of the various coadsorbed species in their mutual electric field. The model adequately describes observed emission and evaporation from tungsten surfaces immersed in pure cesium vapor and in pure oxygen vapor. Using available and estimated properties for 17 species of cesium, oxygen, tungsten and their compounds, the computed work function for tungsten immersed in Cs/O vapor is compared with limited available experimental data, and the basic phenomenology of Cs/O coadsorption electrodes is discussed

Mass transfer models analysis for the structured packings

International Nuclear Information System (INIS)

Suastegui R, A.O.

1997-01-01

The models that have been developing, to understand the mechanism of the mass transfer through the structured packings, present limitations for their application, existing then uncertainty in order to use them in the chemical industrial processes. In this study the main parameters used in the mass transfer are: the hydrodynamic of the bed of the column, the geometry of the bed, physical-chemical properties of the mixture and the flow regime of the operation between the flows liquid-gas. The sensibility of each one of these parameters generate an arduous work to develop right proposals and good interpretation of the phenomenon. With the purpose of showing the importance of these parameters mentioned in the mass transfer, this work is analyzed the process of absorption for the system water-air, using the models to the structured packings in packed columns. The models selected were developed by Bravo and collaborators in 1985 and 1992, in order to determine the parameters previous mentioned for the system water-air, using a structured packing built in the National Institute of Nuclear Research. In this work is showed the results of the models application and their discussion. (Author)

Oxygen transfer rates and requirements in oxidative biocatalysis

DEFF Research Database (Denmark)

Pedersen, Asbjørn Toftgaard; Rehn, Gustav; Woodley, John

2015-01-01

Biocatalytic oxidation reactions offer several important benefits such as regio- and stereoselectivity, avoiding the use of toxic metal based catalysts and replacing oxidizing reagents by allowing the use of oxygen. However, the development of biocatalytic oxidation processes is a complex task......-up is relatively straight forward (Gabelman and Hwang, 1999), and membrane contactors are implemented for various industrial applications (Klaassen et al., 2005)....

Physical model of evolution of oxygen subsystem of PLZT-ceramics at neutron irradiation and annealing

CERN Document Server

Kulikov, D V; Trushin, Y V; Veber, K V; Khumer, K; Bitner, R; Shternberg, A R

2001-01-01

The physical model of evolution of the oxygen subsystem defects of the ferroelectric PLZT-ceramics by the neutron irradiation and isochrone annealing is proposed. The model accounts for the effect the lanthanum content on the material properties. The changes in the oxygen vacancies concentration, calculated by the proposed model, agree well with the polarization experimental behavior by the irradiated material annealing

Influence of oxygen on the chemical stage of radiobiological mechanism

International Nuclear Information System (INIS)

Barilla, Jiří; Lokajíček, Miloš V.; Pisaková, Hana; Simr, Pavel

2016-01-01

The simulation of the chemical stage of radiobiological mechanism may be very helpful in studying the radiobiological effect of ionizing radiation when the water radical clusters formed by the densely ionizing ends of primary or secondary charged particle may form DSBs damaging DNA molecules in living cells. It is possible to study not only the efficiency of individual radicals but also the influence of other species or radiomodifiers (mainly oxygen) being present in water medium during irradiation. The mathematical model based on Continuous Petri nets (proposed by us recently) will be described. It makes it possible to analyze two main processes running at the same time: chemical radical reactions and the diffusion of radical clusters formed during energy transfer. One may study the time change of radical concentrations due to the chemical reactions running during diffusion process. Some orientation results concerning the efficiency of individual radicals in DSB formation (in the case of Co60 radiation) will be presented; the influence of oxygen present in water medium during irradiation will be shown, too. - Highlights: • Creation of the mathematical model. • Realization of the model with the help of Continuous Petri nets. • Obtain the time dependence of changes in the concentration of radicals. • Influence of oxygen on the chemical stage of radiobiological mechanism.

A Computer Model for Analyzing Volatile Removal Assembly

Science.gov (United States)

Guo, Boyun

2010-01-01

A computer model simulates reactional gas/liquid two-phase flow processes in porous media. A typical process is the oxygen/wastewater flow in the Volatile Removal Assembly (VRA) in the Closed Environment Life Support System (CELSS) installed in the International Space Station (ISS). The volatile organics in the wastewater are combusted by oxygen gas to form clean water and carbon dioxide, which is solved in the water phase. The model predicts the oxygen gas concentration profile in the reactor, which is an indicator of reactor performance. In this innovation, a mathematical model is included in the computer model for calculating the mass transfer from the gas phase to the liquid phase. The amount of mass transfer depends on several factors, including gas-phase concentration, distribution, and reaction rate. For a given reactor dimension, these factors depend on pressure and temperature in the reactor and composition and flow rate of the influent.

Modelling and experimental studies on the transfer of radionuclides to fruit

International Nuclear Information System (INIS)

Carini, F.; Atkinson, C.J.; Collins, C.; Coughtrey, P.J.; Eged, K.; Fulker, M.; Green, N.; Kinnersley, R.; Linkov, I.; Mitchell, N.G.; Mourlon, C.; Ould-Dada, Z.; Quinault, J.M.; Robles, B.; Stewart, A.; Sweeck, L.; Venter, A.

2005-01-01

Although fruit is an important component of the diet, the extent to which it contributes to radiological exposure remains unclear, partially as a consequence of uncertainties in models and data used to assess transfer of radionuclides in the food chain. A Fruits Working Group operated as part of the IAEA BIOMASS (BIOsphere Modelling and ASSessment) programme from 1997 to 2000, with the aim of improving the robustness of the models that are used for radiological assessment. The Group completed a number of modelling and experimental activities including: (i) a review of experimental, field and modelling information on the transfer of radionuclides to fruit; (ii) discussion of recently completed or ongoing experimental studies; (iii) development of a database on the transfer of radionuclides to fruit; (iv) development of a conceptual model for fruit and (v) two model intercomparison studies and a model validation study. The Group achieved significant advances in understanding the processes involved in transfer of radionuclides to fruit. The work demonstrated that further experimental and modelling studies are required to ensure that the current generation of models can be applied to a wide range of scenarios

Linear model correction: A method for transferring a near-infrared multivariate calibration model without standard samples

Science.gov (United States)

Liu, Yan; Cai, Wensheng; Shao, Xueguang

2016-12-01

Calibration transfer is essential for practical applications of near infrared (NIR) spectroscopy because the measurements of the spectra may be performed on different instruments and the difference between the instruments must be corrected. For most of calibration transfer methods, standard samples are necessary to construct the transfer model using the spectra of the samples measured on two instruments, named as master and slave instrument, respectively. In this work, a method named as linear model correction (LMC) is proposed for calibration transfer without standard samples. The method is based on the fact that, for the samples with similar physical and chemical properties, the spectra measured on different instruments are linearly correlated. The fact makes the coefficients of the linear models constructed by the spectra measured on different instruments are similar in profile. Therefore, by using the constrained optimization method, the coefficients of the master model can be transferred into that of the slave model with a few spectra measured on slave instrument. Two NIR datasets of corn and plant leaf samples measured with different instruments are used to test the performance of the method. The results show that, for both the datasets, the spectra can be correctly predicted using the transferred partial least squares (PLS) models. Because standard samples are not necessary in the method, it may be more useful in practical uses.

An effective device for gas-liquid oxygen removal in enclosed microalgae culture.

Science.gov (United States)

Su, Zhenfeng; Kang, Ruijuan; Shi, Shaoyuan; Cong, Wei; Cai, Zhaoling

2010-01-01

A high-performance gas-liquid transmission device (HPTD) was described in this paper. To investigate the HPTD mass transfer characteristics, the overall volumetric mass transfer coefficients, K(A)(La,CO(2)) for the absorption of gaseous CO(2) and K(A)(La,O(2)) for the desorption of dissolved O(2) were determined, respectively, by titration and dissolved oxygen electrode. The mass transfer capability of carbon dioxide was compared with that of dissolved oxygen in the device, and the operating conditions were optimized to suit for the large-scale enclosed micro-algae cultivation. Based on the effectiveness evaluation of the HPTD applied in one enclosed flat plate Spirulina culture system, it was confirmed that the HPTD can satisfy the demand of the enclosed system for carbon supplement and excessive oxygen removal.

Oxygen atom transfer from a trans-dioxoruthenium(VI) complex to nitric oxide.

Science.gov (United States)

Man, Wai-Lun; Lam, William W Y; Ng, Siu-Mui; Tsang, Wenny Y K; Lau, Tai-Chu

2012-01-02

In aqueous acidic solutions trans-[Ru(VI)(L)(O)(2)](2+) (L=1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) is rapidly reduced by excess NO to give trans-[Ru(L)(NO)(OH)](2+). When ≤1 mol equiv NO is used, the intermediate Ru(IV) species, trans-[Ru(IV)(L)(O)(OH(2))](2+), can be detected. The reaction of [Ru(VI)(L)(O)(2)](2+) with NO is first order with respect to [Ru(VI)] and [NO], k(2)=(4.13±0.21)×10(1) M(-1) s(-1) at 298.0 K. ΔH(≠) and ΔS(≠) are (12.0±0.3) kcal mol(-1) and -(11±1) cal mol(-1) K(-1), respectively. In CH(3)CN, ΔH(≠) and ΔS(≠) have the same values as in H(2)O; this suggests that the mechanism is the same in both solvents. In CH(3)CN, the reaction of [Ru(VI)(L)(O)(2)](2+) with NO produces a blue-green species with λ(max) at approximately 650 nm, which is characteristic of N(2)O(3). N(2)O(3) is formed by coupling of NO(2) with excess NO; it is relatively stable in CH(3)CN, but undergoes rapid hydrolysis in H(2)O. A mechanism that involves oxygen atom transfer from [Ru(VI)(L)(O)(2)](2+) to NO to produce NO(2) is proposed. The kinetics of the reaction of [Ru(IV)(L)(O)(OH(2))](2+) with NO has also been investigated. In this case, the data are consistent with initial one-electron O(-) transfer from Ru(IV) to NO to produce the nitrito species [Ru(III)(L)(ONO)(OH(2))](2+) (k(2)>10(6) M(-1) s(-1)), followed by a reaction with another molecule of NO to give [Ru(L)(NO)(OH)](2+) and NO(2)(-) (k(2)=54.7 M(-1) s(-1)). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ceramic oxygen transport membrane array reactor and reforming method

Science.gov (United States)

Kelly, Sean M.; Christie, Gervase Maxwell; Robinson, Charles; Wilson, Jamie R; Gonzalez, Javier E.; Doraswami, Uttam R.

2017-10-03

The invention relates to a commercially viable modular ceramic oxygen transport membrane system for utilizing heat generated in reactively-driven oxygen transport membrane tubes to generate steam, heat process fluid and/or provide energy to carry out endothermic chemical reactions. The system provides for improved thermal coupling of oxygen transport membrane tubes to steam generation tubes or process heater tubes or reactor tubes for efficient and effective radiant heat transfer.

Assessment of reflood heat transfer model of COBRA-TIF against ABB-CE evaluation model

Energy Technology Data Exchange (ETDEWEB)

Lee, S. I.; Lee, S. Y.; Park, C. E.; Choi, H. R.; Choi, C. J. [Korea Power Engineering Company Inc., Taejon (Korea, Republic of)

2000-05-01

According to 10 CFR 50 Appendix K, ECCS performance evaluation model should be based on the experimental data of FLECHT and have the conservatism compared with experimental data. To meet this requirement ABB-CE has the complicate code structure as follows: COMPERC-II calculates three reflood rates, and FLELAPC and HTCOF calculate the reflood heat transfer coefficients, and finally STRIKIN-II calculates the cladding temperature using the reflood heat transfer calculated in previous stage. In this paper, to investigate whether or not COBRA-TF satisfies the requirement of Appendix K, the reflood heat transfer coefficient of COBRA-TF was assessed against ABB-CE MOD-2C model. It was found out that COBRA-TF predicts properly the experimental data and has more conservatism than the results of ABB-CE MOD-2C model. Based on these results, it can be concluded that the reflood heat transfer coefficients calculated by COBRA-TF meet the requirement of Appendix K.

A model of knock-out of oxygen by charged particle irradiation of Bi-2212

International Nuclear Information System (INIS)

Bandyopadhyay, S.K.; Sen, Pintu; Barat, P.; Mukherjee, P.; Das, S.K.; Ghosh, B.

1996-01-01

A model of knock-out of oxygen by charged particle (α and proton) irradiation of Bi 2 Sr 2 CaCu 2 O 8+x (Bi-2212) is proposed on the basis of Monte Carlo TRIM calculations. In Bi-2212, the loosely bound excess oxygen is vulnerable to be displaced by particle irradiation. Binding energy and hence, displacement energy of this loosely bound excess oxygen is less compared to that of stoichiometric lattice bound oxygen and other atoms. The displaced or knocked out oxygen goes to pores or intergranular region and generates large pressure inside the sample. Because of porosity of the material, this displaced oxygen diffuses out and there is a net reduction of oxygen content of the sample. The irradiation induced oxygen knock-out is dominant in the bulk where nonionizing energy loss is maximum. (author). 29 refs., 1 fig., 3 tabs

Transfer-function modelling between environmental variation and mesozooplankton in the Baltic Sea [review article

Science.gov (United States)

Vuorinen, I.; Hänninen, J.; Kornilovs, G.

2003-12-01

Time series of freshwater runoff, seawater salinity, temperature and oxygen were used in transfer functions (TF) to model changes of mesozooplankton taxa in the Baltic Sea from the 1960’s to the 1990’s. The models were then compared with long term zooplankton monitoring data from the same period. The TF models for all taxa over the whole Baltic proper and at different depth layers showed statistically significant estimates in t-tests. TF models were further compared using parsimony as a criterion. We present models showing 1) r2 > 0.4, 2) the smallest residual standard error with the combination of exploratory variables, 3) the lowest number of parameters and 4) the highest proportional decrease in error term when the TF model residual standard error was compared with those of the univariate ARIMA model of the same response variable. Most often (7 taxa out of a total of 8), zooplankton taxa were dependent on freshwater runoff and/or seawater salinity. Cladocerans and estuarine copepods were more conveniently modelled through the inclusion of seawater temperature and oxygen data as independent variables. Our modelling, however, explains neither the overall increase in zooplankton abundance nor a simultaneous decrease found in the neritic copepod, Temora longicornis. Therefore, biotic controlling agents (e.g. nutrients, primary production and planktivore diets) are suggested as independent variables for further TF modelling. TF modelling enabled us to put the controlling factors in a time frame. It was then possible, despite the inherent multiple correlation among parameters studied to deduce a chain-of-events from the environmental controls and biotic feedback mechanisms to changes in zooplankton species. We suggest that the documented long-term changes in zooplankton could have been driven by climatic regulation only. The control by climate could be mediated to zooplankton through marine chemical and physical factors, as well as biotic factors if all of these

An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

International Nuclear Information System (INIS)

Boyer, B.D.; Parlatan, Y.; Slovik, G.C.

1995-01-01

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba's Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to ±5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes

An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

Energy Technology Data Exchange (ETDEWEB)

Boyer, B.D.; Parlatan, Y.; Slovik, G.C. [and others

1995-09-01

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {plus_minus}5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.

Kinetic Monte Carlo modeling of chemical reactions coupled with heat transfer.

Science.gov (United States)

Castonguay, Thomas C; Wang, Feng

2008-03-28

In this paper, we describe two types of effective events for describing heat transfer in a kinetic Monte Carlo (KMC) simulation that may involve stochastic chemical reactions. Simulations employing these events are referred to as KMC-TBT and KMC-PHE. In KMC-TBT, heat transfer is modeled as the stochastic transfer of "thermal bits" between adjacent grid points. In KMC-PHE, heat transfer is modeled by integrating the Poisson heat equation for a short time. Either approach is capable of capturing the time dependent system behavior exactly. Both KMC-PHE and KMC-TBT are validated by simulating pure heat transfer in a rod and a square and modeling a heated desorption problem where exact numerical results are available. KMC-PHE is much faster than KMC-TBT and is used to study the endothermic desorption of a lattice gas. Interesting findings from this study are reported.

Mediatorless electron transfer in glucose dehydrogenase/laccase system adsorbed on carbon nanotubes

International Nuclear Information System (INIS)

Ratautas, D.; Marcinkevičienė, L.; Meškys, R.; Kulys, J.

2015-01-01

Highlights: • Glucose dehydrogenase from Ewingella americana (GDH) demonstrated an effective mediatorless oxidation of glucose on single-walled carbon nanotubes (SWCNT). • Laccase from Trichaptum abietinum (LAC) exhibited mediatorless oxygen reduction when the enzyme was adsorbed on SWCNT. • Simultaneous adsorption of GDH and LAC on SWCNT formed an electron transfer chain in which glucose and lactose were oxidized by oxygen in mediatorless manner. - Abstract: A mediatorless electron transfer in the chain of glucose dehydrogenase (GDH) and laccase (LAC) catalysing the oxidation of glucose by molecular oxygen was studied. To demonstrate mediatorless processes, the GDH from Ewingella americana was adsorbed on single-walled carbon nanotubes (SWCNT). The effective mediatorless oxidation of glucose proceeded at 0.2–0.4 V vs. SCE. The electrode was most active at pH 6.1, and generated 0.8 mA cm −2 biocatalytic current in the presence of 50 mM glucose. The electrode showed a bell-shaped pH dependence with pK a values of 4.1 and 7.5. LAC from Trichaptum abietinum adsorbed on SWCNT exhibited mediatorless oxygen reduction at electrode potential less than 0.65 V. The electrode was most active at pH 3.0–4.0 and generated 1.1 mA cm −2 biocatalytic current in the presence of 0.254 mM oxygen, with an apparent pK a of 1.0 and 5.4. The electrodes prepared by simultaneous adsorption of GDH and LAC on SWCNT exhibited glucose oxidation at a potential higher than 0.25 V. The oxygen consumption in the chain was demonstrated using a Clark-type oxygen electrode. The dependence of oxygen consumption on glucose and lactose concentrations as well as activity of the system on pH were measured. A model of the pH dependence as well as mediatorless consecutive glucose oxidation with oxygen catalysed by LAC/GDH system is presented. This work provides a novel approach towards the synthesis of artificial multi enzyme systems by wiring oxidoreductases with SWCNT, and offers a better

Electron loss from multiply protonated lysozyme ions in high energy collisions with molecular oxygen

DEFF Research Database (Denmark)

Hvelplund, P; Nielsen, SB; Sørensen, M

2001-01-01

We report on the electron loss from multiply protonated lysozyme ions Lys-Hn(n)+ (n = 7 - 17) and the concomitant formation of Lys-Hn(n+1)+. in high-energy collisions with molecular oxygen (laboratory kinetic energy = 50 x n keV). The cross section for electron loss increases with the charge state...... of the precursor from n = 7 to n = 11 and then remains constant when n increases further. The absolute size of the cross section ranges from 100 to 200 A2. The electron loss is modeled as an electron transfer process between lysozyme cations and molecular oxygen....

Radiative transfer model for heterogeneous 3-D scenes

Science.gov (United States)

Kimes, D. S.; Kirchner, J. A.

1982-01-01

A general mathematical framework for simulating processes in heterogeneous 3-D scenes is presented. Specifically, a model was designed and coded for application to radiative transfers in vegetative scenes. The model is unique in that it predicts (1) the directional spectral reflectance factors as a function of the sensor's azimuth and zenith angles and the sensor's position above the canopy, (2) the spectral absorption as a function of location within the scene, and (3) the directional spectral radiance as a function of the sensor's location within the scene. The model was shown to follow known physical principles of radiative transfer. Initial verification of the model as applied to a soybean row crop showed that the simulated directional reflectance data corresponded relatively well in gross trends to the measured data. However, the model can be greatly improved by incorporating more sophisticated and realistic anisotropic scattering algorithms

A proposed agglomerate model for oxygen reduction in the catalyst layer of proton exchange membrane fuel cells

International Nuclear Information System (INIS)

Zhang, Xiaoxian; Gao, Yuan; Ostadi, Hossein; Jiang, Kyle; Chen, Rui

2014-01-01

Highlights: • We developed a new agglomerate model to describe oxygen reduction reaction. • We showed how to calculate the model parameters from catalyst layer structure. • We verified the agglomerate model. - Abstract: Oxygen diffusion and reduction in the catalyst layer of PEM fuel cell is an important process in fuel cell modelling, but models able to link the reduction rate to catalyst-layer structure are lack; this paper makes such an effort. We first link the average reduction rate over the agglomerate within a catalyst layer to a probability that an oxygen molecule, which is initially on the agglomerate surface, will enter and remain in the agglomerate at any time in the absence of any electrochemical reaction. We then propose a method to directly calculate distribution function of this probability and apply it to two catalyst layers with contrasting structures. A formula is proposed to describe these calculated distribution functions, from which the agglomerate model is derived. The model has two parameters and both can be independently calculated from catalyst layer structures. We verify the model by first showing that it is an improvement and able to reproduce what the spherical model describes, and then testing it against the average oxygen reductions directly calculated from pore-scale simulations of oxygen diffusion and reaction in the two catalyst layers. The proposed model is simple, but significant as it links the average oxygen reduction to catalyst layer structures, and its two parameters can be directly calculated rather than by calibration

OXYGEN DEPLETION IN THE INTERSTELLAR MEDIUM: IMPLICATIONS FOR GRAIN MODELS AND THE DISTRIBUTION OF ELEMENTAL OXYGEN

International Nuclear Information System (INIS)

Whittet, D. C. B.

2010-01-01

This paper assesses the implications of a recent discovery that atomic oxygen is being depleted from diffuse interstellar gas at a rate that cannot be accounted for by its presence in silicate and metallic oxide particles. To place this discovery in context, the uptake of elemental O into dust is considered over a wide range of environments, from the tenuous intercloud gas and diffuse clouds sampled by the depletion observations to dense clouds where ice mantles and gaseous CO become important reservoirs of O. The distribution of O in these contrasting regions is quantified in terms of a common parameter, the mean number density of hydrogen (n H ). At the interface between diffuse and dense phases (just before the onset of ice-mantle growth) as much as ∼160 ppm of the O abundance is unaccounted for. If this reservoir of depleted oxygen persists to higher densities it has implications for the oxygen budget in molecular clouds, where a shortfall of the same order is observed. Of various potential carriers, the most plausible appears to be a form of O-bearing carbonaceous matter similar to the organics found in cometary particles returned by the Stardust mission. The 'organic refractory' model for interstellar dust is re-examined in the light of these findings, and it is concluded that further observations and laboratory work are needed to determine whether this class of material is present in quantities sufficient to account for a significant fraction of the unidentified depleted oxygen.

Model studies of the transfer of radionuclides in the Finnish environment

International Nuclear Information System (INIS)

Korhonen, R.

1991-01-01

Environmental modelling of the effects of radionuclide releases was studied. A computer model DETl2A was developed for evaluation of radionuclide transfer. The flexible structure of the model made it suitable for a wide range of applications. The model was employed to evaluate the biospheric transfer of radionuclides in two situations: 1) release cases from planned waste repositories in Finland, and 2) deposition due to the Chernobyl accident. The Chernobyl accident provided a good opportunity to test the DETRA model, originally constructed for waste disposal applications. A study was made of some biospheric local, regional and global scale scenarios, to which releases from repositories were assumed. Drinking water from a local well and consumption of fish were the most important dose pathways. The transfer of the Chernobyl deposition in some important Finnish transfer environments was evaluated. Especially the transfer of Cs-137 in the Kymijoki watercourse, including dynamic transfer to non-predatory and predatory fish species was studied. The calculated behaviour was compared with the measured behaviour. Nuclear weapon testing fallout was also considered in the comparison studies. On the basis of validation studies it was concluded that part of the Cs-137 deposition was in insoluble form. These model assumptions give that deposition consisting of soluble Cs-l37 could cause fourfold contamination of fish per unit deposition than deposition due to the Chernobyl accident in the modelled case. Model validation was also performed within international projects, in particular by participating in the BIOMOVS project. This participation will be continued in the VAMP program. In the summary part of the thesis the main attention is paid to modelling questions, whereas in the accompanying publications the results are presented in greater detail

Best estimate radiation heat transfer model developed for TRAC-BD1

International Nuclear Information System (INIS)

Spore, J.W.; Giles, M.M.; Shumway, R.W.

1981-01-01

A best estimate radiation heat transfer model for analysis of BWR fuel bundles has been developed and compared with 8 x 8 fuel bundle data. The model includes surface-to-surface and surface-to-two-phase fluid radiation heat transfer. A simple method of correcting for anisotropic reflection effects has been included in the model

Oxygen Sensing by the Hybrid Langmuir-Blodgett Films of Iridium(III Complexes and Synthetic Saponite on the Basis of Energy Transfer

Directory of Open Access Journals (Sweden)

Hisako Sato

2017-09-01

Full Text Available An ultra-thin hybrid film of amphiphilic iridium(III complexes and synthetic saponite was manipulated by means of the modified Langmuir-Blodgett method. In the film deposited onto a quartz substrate, the external mixed molecular layer of amphiphilic iridium(III complexes was reinforced by the inner layer of exfoliated synthetic saponite. As components of the molecular layer, two iridium(III complexes were used: [Ir(dfppy2(dc9bpy]+ (dfppyH = 2-(4′,6′-difluorophenyl pyridine; dc9bpy = 4,4′-dinonyl-2,2′-bipyridine (denoted as DFPPY and [Ir(piq2(dc9bpy]+ (piqH = 1-phenyisoquinoline denoted as PIQ. The emission spectra from the films changed from blue to red maxima with the decrease of a ratio of DFPPY/PIQ due to the energy transfer from excited DFPPY to PIQ. The intensity of red decreased with the increase of oxygen pressure through the quenching of excited iridium(III complexes, promising a possibility as an oxygen-sensing film.

A Gibbs Energy Minimization Approach for Modeling of Chemical Reactions in a Basic Oxygen Furnace

Science.gov (United States)

Kruskopf, Ari; Visuri, Ville-Valtteri

2017-12-01

In modern steelmaking, the decarburization of hot metal is converted into steel primarily in converter processes, such as the basic oxygen furnace. The objective of this work was to develop a new mathematical model for top blown steel converter, which accounts for the complex reaction equilibria in the impact zone, also known as the hot spot, as well as the associated mass and heat transport. An in-house computer code of the model has been developed in Matlab. The main assumption of the model is that all reactions take place in a specified reaction zone. The mass transfer between the reaction volume, bulk slag, and metal determine the reaction rates for the species. The thermodynamic equilibrium is calculated using the partitioning of Gibbs energy (PGE) method. The activity model for the liquid metal is the unified interaction parameter model and for the liquid slag the modified quasichemical model (MQM). The MQM was validated by calculating iso-activity lines for the liquid slag components. The PGE method together with the MQM was validated by calculating liquidus lines for solid components. The results were compared with measurements from literature. The full chemical reaction model was validated by comparing the metal and slag compositions to measurements from industrial scale converter. The predictions were found to be in good agreement with the measured values. Furthermore, the accuracy of the model was found to compare favorably with the models proposed in the literature. The real-time capability of the proposed model was confirmed in test calculations.

Towards a quantitative understanding of oxygen tension and cell density evolution in fibrin hydrogels.

Science.gov (United States)

Demol, Jan; Lambrechts, Dennis; Geris, Liesbet; Schrooten, Jan; Van Oosterwyck, Hans

2011-01-01

The in vitro culture of hydrogel-based constructs above a critical size is accompanied by problems of unequal cell distribution when diffusion is the primary mode of oxygen transfer. In this study, an experimentally-informed mathematical model was developed to relate cell proliferation and death inside fibrin hydrogels to the local oxygen tension in a quantitative manner. The predictive capacity of the resulting model was tested by comparing its outcomes to the density, distribution and viability of human periosteum derived cells (hPDCs) that were cultured inside fibrin hydrogels in vitro. The model was able to reproduce important experimental findings, such as the formation of a multilayered cell sheet at the hydrogel periphery and the occurrence of a cell density gradient throughout the hydrogel. In addition, the model demonstrated that cell culture in fibrin hydrogels can lead to complete anoxia in the centre of the hydrogel for realistic values of oxygen diffusion and consumption. A sensitivity analysis also identified these two parameters, together with the proliferation parameters of the encapsulated cells, as the governing parameters for the occurrence of anoxia. In conclusion, this study indicates that mathematical models can help to better understand oxygen transport limitations and its influence on cell behaviour during the in vitro culture of cell-seeded hydrogels. Copyright © 2010 Elsevier Ltd. All rights reserved.

A fast infrared radiative transfer model for overlapping clouds

International Nuclear Information System (INIS)

Niu Jianguo; Yang Ping; Huang Hunglung; Davies, James E.; Li Jun; Baum, Bryan A.; Hu, Yong X.

2007-01-01

A fast infrared radiative transfer model (FIRTM2) appropriate for application to both single-layered and overlapping cloud situations is developed for simulating the outgoing infrared spectral radiance at the top of the atmosphere (TOA). In FIRTM2 a pre-computed library of cloud reflectance and transmittance values is employed to account for one or two cloud layers, whereas the background atmospheric optical thickness due to gaseous absorption can be computed from a clear-sky radiative transfer model. FIRTM2 is applicable to three atmospheric conditions: (1) clear-sky (2) single-layered ice or water cloud, and (3) two simultaneous cloud layers in a column (e.g., ice cloud overlying water cloud). Moreover, FIRTM2 outputs the derivatives (i.e., Jacobians) of the TOA brightness temperature with respect to cloud optical thickness and effective particle size. Sensitivity analyses have been carried out to assess the performance of FIRTM2 for two spectral regions, namely the longwave (LW) band (587.3-1179.5 cm -1 ) and the short-to-medium wave (SMW) band (1180.1-2228.9 cm -1 ). The assessment is carried out in terms of brightness temperature differences (BTD) between FIRTM2 and the well-known discrete ordinates radiative transfer model (DISORT), henceforth referred to as BTD (F-D). The BTD (F-D) values for single-layered clouds are generally less than 0.8 K. For the case of two cloud layers (specifically ice cloud over water cloud), the BTD (F-D) values are also generally less than 0.8 K except for the SMW band for the case of a very high altitude (>15 km) cloud comprised of small ice particles. Note that for clear-sky atmospheres, FIRTM2 reduces to the clear-sky radiative transfer model that is incorporated into FIRTM2, and the errors in this case are essentially those of the clear-sky radiative transfer model

Chemical dynamics of the first proton-coupled electron transfer of water oxidation on TiO2 anatase.

Science.gov (United States)

Chen, Jia; Li, Ye-Fei; Sit, Patrick; Selloni, Annabella

2013-12-18

Titanium dioxide (TiO2) is a prototype, water-splitting (photo)catalyst, but its performance is limited by the large overpotential for the oxygen evolution reaction (OER). We report here a first-principles density functional theory study of the chemical dynamics of the first proton-coupled electron transfer (PCET), which is considered responsible for the large OER overpotential on TiO2. We use a periodic model of the TiO2/water interface that includes a slab of anatase TiO2 and explicit water molecules, sample the solvent configurations by first principles molecular dynamics, and determine the energy profiles of the two electronic states involved in the electron transfer (ET) by hybrid functional calculations. Our results suggest that the first PCET is sequential, with the ET following the proton transfer. The ET occurs via an inner sphere process, which is facilitated by a state in which one electronic hole is shared by the two oxygen ions involved in the transfer.

Oxygen diffusion in a network model of the myocardial microcirculation

NARCIS (Netherlands)

Wieringa, P. A.; Stassen, H. G.; van Kan, J. J.; Spaan, J. A.

1993-01-01

Oxygen supply was studied in a three-dimensional capillary network model of the myocardial microcirculation. Capillary networks were generated using one common strategy to locate the capillary branchings and segments, arterioles and venules. Flow paths developed with different capillary flow

Radiative Transfer Modeling in Proto-planetary Disks

Science.gov (United States)

Kasper, David; Jang-Condell, Hannah; Kloster, Dylan

2016-01-01

Young Stellar Objects (YSOs) are rich astronomical research environments. Planets form in circumstellar disks of gas and dust around YSOs. With ever increasing capabilities of the observational instruments designed to look at these proto-planetary disks, most notably GPI, SPHERE, and ALMA, more accurate interfaces must be made to connect modeling of the disks with observation. PaRTY (Parallel Radiative Transfer in YSOs) is a code developed previously to model the observable density and temperature structure of such a disk by self-consistently calculating the structure of the disk based on radiative transfer physics. We present upgrades we are implementing to the PaRTY code to improve its accuracy and flexibility. These upgrades include: creating a two-sided disk model, implementing a spherical coordinate system, and implementing wavelength-dependent opacities. These upgrades will address problems in the PaRTY code of infinite optical thickness, calculation under/over-resolution, and wavelength-independent photon penetration depths, respectively. The upgraded code will be used to better model disk perturbations resulting from planet formation.

Pattern transfer with stabilized nanoparticle etch masks

International Nuclear Information System (INIS)

Hogg, Charles R; Majetich, Sara A; Picard, Yoosuf N; Narasimhan, Amrit; Bain, James A

2013-01-01

Self-assembled nanoparticle monolayer arrays are used as an etch mask for pattern transfer into Si and SiO x substrates. Crack formation within the array is prevented by electron beam curing to fix the nanoparticles to the substrate, followed by a brief oxygen plasma to remove excess carbon. This leaves a dot array of nanoparticle cores with a minimum gap of 2 nm. Deposition and liftoff can transform the dot array mask into an antidot mask, where the gap is determined by the nanoparticle core diameter. Reactive ion etching is used to transfer the dot and antidot patterns into the substrate. The effect of the gap size on the etching rate is modeled and compared with the experimental results. (paper)

Model of Oxygen and Glucose Deprivation in PC12 Cells and Detection of HSP70 Protein

Science.gov (United States)

He, Jinting; Yang, Le; Shao, Yankun

2018-01-01

Objective: PC12 cell was used to set up a ischemia model by OGD and detected HSP70 protein. Methods: Use of PC12 cells induced by NGF stimulation into nerve cells, oxygen and glucose deprivation to build the nerve cells of oxygen and glucose deprivation model; using Western blot analysis of PC12 cells into neuron-like cells and oxygen-glucose deprivation model established. Results: The application of a final concentration of 50 ng / ml of NGF in DMEM complete mediumPC12 cells showed a typical neuronal morphology with the increase in cell culture time. NGF culture time showed a positive correlation, the establishment of oxygen and glucose deprivation (OGD) training environment, the OGD after nerve element appears different degrees of damage, OGD can effectively induce the expression of HSP70. Conclusion: PC12 cell transformed into cells by NGF; the cell model of OGD was established.

Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

KAUST Repository

Hunt, Anton

2015-09-01

© 2015 Elsevier B.V. The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions at extreme temperatures (>800°C). This is especially true when fuels are present at the permeate surface. For both inert and reactive (fuels) operations, solid-state oxygen surface vacancies (δ) are ultimately responsible for driving the oxygen flux, JO2. In the inert case, the value of δ at either surface is a function of the local PO2 and temperature, whilst the magnitude of δ dictates both the JO2 and the inherent stability of the material. In this study values of δ are presented based on experimental measurements under inert (CO2) sweep: using a permeation flux model and local PO2 measurements, collected by means of a local gas-sampling probe in our large-scale reactor, we can determine δ directly. The ITM assessed was La0.9Ca0.1FeO3-δ (LCF); the relative resistances to JO2 were quantified using the pre-defined permeation flux model and local PO2 values. Across a temperature range from 825°C to 1056°C, δ was found to vary from 0.007 to 0.029 (<1%), safely within material stability limits, whilst the permeate surface exchange resistance dominates. An inert JO2 limit was identified owing to a maximum sweep surface δ, δmaxinert. The physical presence of δmaxinert is attributed to a rate limiting step shift from desorption to associative electron transfer steps on the sweep surface as PO2 is reduced. Permeate surface exchange limitations under non-reactive conditions suggest that reactive (fuel) operation is necessary to accelerate surface chemistry for future work, to reduce flux resistance and push δpast δmaxinert in a stable manner.

The transfer function model for dynamic response of wet cooling coils

International Nuclear Information System (INIS)

Yao Ye; Liu Shiqing

2008-01-01

This paper mainly concerned about the dynamic response model of wet cooling coils that is developed by the Laplace transform method. The theoretic equations are firstly established based on the theory of energy conservation. Then, the transfer functions on the transient responses of wet cooling coils have been deduced using the method of Laplace transform. The transfer functions reveal the dynamic relationships between the inlet variables and the outlet ones of the cooling coils. Partial-fraction method and Newton-Raphson method are both used in the inversion of the transfer functions from the s-domain to τ-domain. To make the dynamic model of wet cooling coils more adaptive, RBFNN method is employed to determine the coefficients of heat and mass transfer. Experiments have been done and manifested that the coefficients of heat and mass transfer by RBFNN will be of great value to the validity of the transient response model of wet cooling coils in this study

Oxygen consumption in EPDM irradiated under different oxygen pressures and at different LET

International Nuclear Information System (INIS)

Dely, N.; Ngono-Ravache, Y.; Ramillon, J.-M.; Balanzat, E.

2005-01-01

We conceived a novel set-up for measuring the radiochemical yields of oxygen consumption in polymers. The measurement is based on a sampling of the gas mixture with a mass spectrometer, before and after irradiation. We irradiated an ethylene, propylene and 1,4-hexadiene terpolymer (EPDM) with 1 MeV electron and 10.75 MeV/A carbon beams. Samples were irradiated under oxygen within a wide range of pressure (5-200 mbar). The yields under C irradiation are four times smaller than the yields under electron irradiation. This shows that radiooxidation is very sensitive to the linear energy transfer of the projectiles and hence to the heterogeneity of the energy deposition. The oxygen consumption yields do not vary significantly in the range of pressure investigated; even at 5 mbar, the kinetics is still governed by the bimolecular recombination of peroxy radicals

SCIATRAN 3.1: A new radiative transfer model and retrieval package

Science.gov (United States)

Rozanov, Alexei; Rozanov, Vladimir; Kokhanovsky, Alexander; Burrows, John P.

The SCIATRAN 3.1 package is a result of further development of the SCIATRAN 2.X software family which, similar to previous versions, comprises a radiative transfer model and a retrieval block. After an implementation of the vector radiative transfer model in SCIATRAN 3.0 the spectral range covered by the model has been extended into the thermal infrared ranging to approximately 40 micrometers. Another major improvement has been done accounting for the underlying surface effects. Among others, a sophisticated representation of the water surface with a bidirectional reflection distribution function (BRDF) has been implemented accounting for the Fresnel reflection of the polarized light and for the effect of foam. A newly developed representation for a snow surface allows radiative transfer calculations to be performed within an unpolluted or soiled snow layer. Furthermore, a new approach has been implemented allowing radiative transfer calculations to be performed for a coupled atmosphere-ocean system. This means that, the underlying ocean is not considered as a purely reflecting surface any more. Instead, full radiative transfer calculations are performed within the water allowing the user to simulate the radiance within both the atmosphere and the ocean. Similar to previous versions, the simulations can be performed for any viewing geometry typi-cal for atmospheric observations in the UV-Vis-NIR-TIR spectral range (nadir, limb, off-axis, etc.) as well as for any observer location within or outside the Earth's atmosphere including underwater observations. Similar to the precursor version, the new model is freely available for non-commercial use via the web page of the University of Bremen. In this presentation a short description of the software package, especially of the new features of the radiative transfer model is given, including remarks on the availability for the scientific community. Furthermore, some application examples of the radiative transfer model are

SMRT: A new, modular snow microwave radiative transfer model

Science.gov (United States)

Picard, Ghislain; Sandells, Melody; Löwe, Henning; Dumont, Marie; Essery, Richard; Floury, Nicolas; Kontu, Anna; Lemmetyinen, Juha; Maslanka, William; Mätzler, Christian; Morin, Samuel; Wiesmann, Andreas

2017-04-01

Forward models of radiative transfer processes are needed to interpret remote sensing data and derive measurements of snow properties such as snow mass. A key requirement and challenge for microwave emission and scattering models is an accurate description of the snow microstructure. The snow microwave radiative transfer model (SMRT) was designed to cater for potential future active and/or passive satellite missions and developed to improve understanding of how to parameterize snow microstructure. SMRT is implemented in Python and is modular to allow easy intercomparison of different theoretical approaches. Separate modules are included for the snow microstructure model, electromagnetic module, radiative transfer solver, substrate, interface reflectivities, atmosphere and permittivities. An object-oriented approach is used with carefully specified exchanges between modules to allow future extensibility i.e. without constraining the parameter list requirements. This presentation illustrates the capabilities of SMRT. At present, five different snow microstructure models have been implemented, and direct insertion of the autocorrelation function from microtomography data is also foreseen with SMRT. Three electromagnetic modules are currently available. While DMRT-QCA and Rayleigh models need specific microstructure models, the Improved Born Approximation may be used with any microstructure representation. A discrete ordinates approach with stream connection is used to solve the radiative transfer equations, although future inclusion of 6-flux and 2-flux solvers are envisioned. Wrappers have been included to allow existing microwave emission models (MEMLS, HUT, DMRT-QMS) to be run with the same inputs and minimal extra code (2 lines). Comparisons between theoretical approaches will be shown, and evaluation against field experiments in the frequency range 5-150 GHz. SMRT is simple and elegant to use whilst providing a framework for future development within the

Two-temperature chemically non-equilibrium modelling of transferred arcs

International Nuclear Information System (INIS)

Baeva, M; Kozakov, R; Gorchakov, S; Uhrlandt, D

2012-01-01

A two-temperature chemically non-equilibrium model describing in a self-consistent manner the heat transfer, the plasma chemistry, the electric and magnetic field in a high-current free-burning arc in argon has been developed. The model is aimed at unifying the description of a thermionic tungsten cathode, a flat copper anode, and the arc plasma including the electrode sheath regions. The heat transfer in the electrodes is coupled to the plasma heat transfer considering the energy fluxes onto the electrode boundaries with the plasma. The results of the non-equilibrium model for an arc current of 200 A and an argon flow rate of 12 slpm are presented along with results obtained from a model based on the assumption of local thermodynamic equilibrium (LTE) and from optical emission spectroscopy. The plasma shows a near-LTE behaviour along the arc axis and in a region surrounding the axis which becomes wider towards the anode. In the near-electrode regions, a large deviation from LTE is observed. The results are in good agreement with experimental findings from optical emission spectroscopy. (paper)

Modelling Ecosystem Dynamics of the Oxygen Minimum Zones in the Angola Gyre and the Northern Benguela Upwelling System.

Science.gov (United States)

Schmidt, M.; Eggert, A.

2016-02-01

The Angola Gyre and the Northern Benguela Upwelling System are two major oxygen minimum zones (OMZ) of different kind connected by the system of African Eastern Boundary Currents. We discuss results from a 3-dimensional coupled biogeochemical model covering both oxygen-deficient systems. The biogeochemical model component comprises trophic levels up to zooplankton. Physiological properties of organisms are parameterized from field data gained mainly in the course of the project "Geochemistry and Ecology of the Namibian Upwelling System" (GENUS). The challenge of the modelling effort is the different nature of both systems. The Angola Gyre, located in a "shadow zone" of the tropical Atlantic, has a low productivity and little ventilation, hence a long residence time of water masses. In the northern Benguela Upwelling System, trade winds drive an intermittent, but permanent nutrient supply into the euphotic zone which fuels a high coastal productivity, large particle export and high oxygen consumption from dissimilatory processes. In addition to the local processes, oxygen-deficient water formed in the Angola Gyre is one of the source water masses of the poleward undercurrent, which feeds oxygen depleted water into the Benguela system. In order to simulate the oxygen distribution in the Benguela system, both physical transport as well as local biological processes need to be carefully adjusted in the model. The focus of the analysis is on the time scale and the relative contribution of the different oxygen related processes to the oxygen budgets in both the oxygen minimum zones. Although these are very different in both the OMZ, the model is found as suitable to produce oxygen minimum zones comparable with observations in the Benguela and the Angola Gyre as well. Variability of the oxygen concentration in the Angola Gyre depends strongly on organismic oxygen consumption, whereas the variability of the oxygen concentration on the Namibian shelf is governed mostly by

Evaluation of Advanced Models for PAFS Condensation Heat Transfer in SPACE Code

Energy Technology Data Exchange (ETDEWEB)

Bae, Byoung-Uhn; Kim, Seok; Park, Yu-Sun; Kang, Kyung Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Ahn, Tae-Hwan; Yun, Byong-Jo [Pusan National University, Busan (Korea, Republic of)

2015-10-15

The PAFS (Passive Auxiliary Feedwater System) is operated by the natural circulation to remove the core decay heat through the PCHX (Passive Condensation Heat Exchanger) which is composed of the nearly horizontal tubes. For validation of the cooling and operational performance of the PAFS, PASCAL (PAFS Condensing Heat Removal Assessment Loop) facility was constructed and the condensation heat transfer and natural convection phenomena in the PAFS was experimentally investigated at KAERI (Korea Atomic Energy Research Institute). From the PASCAL experimental result, it was found that conventional system analysis code underestimated the condensation heat transfer. In this study, advanced condensation heat transfer models which can treat the heat transfer mechanisms with the different flow regimes in the nearly horizontal heat exchanger tube were analyzed. The models were implemented in a thermal hydraulic safety analysis code, SPACE (Safety and Performance Analysis Code for Nuclear Power Plant), and it was evaluated with the PASCAL experimental data. With an aim of enhancing the prediction capability for the condensation phenomenon inside the PCHX tube of the PAFS, advanced models for the condensation heat transfer were implemented into the wall condensation model of the SPACE code, so that the PASCAL experimental result was utilized to validate the condensation models. Calculation results showed that the improved model for the condensation heat transfer coefficient enhanced the prediction capability of the SPACE code. This result confirms that the mechanistic modeling for the film condensation in the steam phase and the convection in the condensate liquid contributed to enhance the prediction capability of the wall condensation model of the SPACE code and reduce conservatism in prediction of condensation heat transfer.

Behaviour of oxygen in liquid sodium

International Nuclear Information System (INIS)

Torre Cabezas, M. de la

1975-01-01

In this work, the vacuum distillation method has been used for the determination of oxygen concentration in liquid sodium. During this investigation, more than 800 analyses have been made and a fluctuation of between 15 and 20$ has been noted in the results. The performance of a cold trap to remove oxygen from sodium has been studied and the corresponding mass transfer coefficient evaluated. The value of this coefficient was in good agreement with those achieved by other workers. (Authors) 69 refs

First principles study of dissolved oxygen water adsorption on Fe (001 surfaces

Directory of Open Access Journals (Sweden)

Dong ZHANG

2018-02-01

Full Text Available In order to study the mechanism of dissolved oxygen content on the surface corrosion behavior of Fe-based heat transfer, the first principle is used to study the adsorption of O2 monomolecular, H2O monolayer and dissolved oxygen system on Fe-based heat transfer surface. The GGA/PBE approximation is used to calculate the adsorption energy, state density and population change during the adsorption process. Calculations prove that when the dissolved oxygen is adsorbed on the Fe-based surface, the water molecule tends to adsorb at the top sites, and the oxygen molecule tends to adsorb at Griffiths. When the H2O molecule adsorbs and interacts on the Fe (001 surface, the charge distribution of the interfacial double electric layer changes to cause the Fe atoms to lose electrons, resulting in the change of the surface potential. When the O2 molecule adsorbs on the Fe (001 crystal surfaces, the electrons on the Fe (001 surface are lost and the surface potential increases. O2 molecule and the surface of the Fe atoms are prone to electron transfer, in which O atom's 2p orbit for the adsorption of O2 molecule on Fe (001 crystal surface play a major role. With the increase of the proportion of O2 molecule in the dissolved oxygen water, the absolute value of the adsorption energy increases, and the interaction of the Fe-based heat transfer surface is stronger. This study explores the influence law of different dissolved oxygen on the Fe base heat exchange surface corrosion, and the base metal corrosion mechanism for experimental study provides a theoretical reference.

Photo-excitation of carotenoids causes cytotoxicity via singlet oxygen production

International Nuclear Information System (INIS)

Yoshii, Hiroshi; Yoshii, Yukie; Asai, Tatsuya; Furukawa, Takako; Takaichi, Shinichi; Fujibayashi, Yasuhisa

2012-01-01

Highlights: ► Some photo-excited carotenoids have photosensitizing ability. ► They are able to produce ROS. ► Photo-excited fucoxanthin can produce singlet oxygen through energy transfer. -- Abstract: Carotenoids, natural pigments widely distributed in algae and plants, have a conjugated double bond system. Their excitation energies are correlated with conjugation length. We hypothesized that carotenoids whose energy states are above the singlet excited state of oxygen (singlet oxygen) would possess photosensitizing properties. Here, we demonstrated that human skin melanoma (A375) cells are damaged through the photo-excitation of several carotenoids (neoxanthin, fucoxanthin and siphonaxanthin). In contrast, photo-excitation of carotenoids that possess energy states below that of singlet oxygen, such as β-carotene, lutein, loroxanthin and violaxanthin, did not enhance cell death. Production of reactive oxygen species (ROS) by photo-excited fucoxanthin or neoxanthin was confirmed using a reporter assay for ROS production with HeLa Hyper cells, which express a fluorescent indicator protein for intracellular ROS. Fucoxanthin and neoxanthin also showed high cellular penetration and retention. Electron spin resonance spectra using 2,2,6,6-tetramethil-4-piperidone as a singlet oxygen trapping agent demonstrated that singlet oxygen was produced via energy transfer from photo-excited fucoxanthin to oxygen molecules. These results suggest that carotenoids such as fucoxanthin, which are capable of singlet oxygen production through photo-excitation and show good penetration and retention in target cells, are useful as photosensitizers in photodynamic therapy for skin disease.

Heterogeneous studies in pulping of wood: Modelling mass transfer of alkali

OpenAIRE

Simão, João P. F.; Egas, Ana P. V.; Carvalho, M. Graça; Baptista, Cristina M. S. G.; Castro, José Almiro A. M.

2008-01-01

In this paper a heterogeneous lumped parameter model is proposed to describe the mass transfer of effective alkali during the kraft pulping of wood. This model, based on the spatial mean of the concentration profile of effective alkali along the chip thickness, enables the estimation of the effective diffusion coefficient that characterizes the internal resistance to mass transfer and the contribution of the external resistance to mass transfer which has often been neglected. http://www.sc...

Modeling of atmospheric pollutant transfers

International Nuclear Information System (INIS)

Jourdain, F.

2007-01-01

Modeling is today a common tool for the evaluation of the environmental impact of atmospheric pollution events, for the design of air monitoring networks or for the calculation of pollutant concentrations in the ambient air. It is even necessary for the a priori evaluation of the consequences of a pollution plume. A large choice of atmospheric transfer codes exist but no ideal tool is available which allows to model all kinds of situations. The present day approach consists in combining different types of modeling according to the requested results and simulations. The CEA has a solid experience in this domain and has developed independent tools for the impact and safety studies relative to industrial facilities and to the management of crisis situations. (J.S.)

Dissolved oxygen analysis, TMDL model comparison, and particulate matter shunting—Preliminary results from three model scenarios for the Klamath River upstream of Keno Dam, Oregon

Science.gov (United States)

Sullivan, Annett B.; Rounds, Stewart A.; Deas, Michael L.; Sogutlugil, I. Ertugrul

2012-01-01

Efforts are underway to identify actions that would improve water quality in the Link River to Keno Dam reach of the Upper Klamath River in south-central Oregon. To provide further insight into water-quality improvement options, three scenarios were developed, run, and analyzed using previously calibrated CE-QUAL-W2 hydrodynamic and water-quality models. Additional scenarios are under development as part of this ongoing study. Most of these scenarios evaluate changes relative to a "current conditions" model, but in some cases a "natural conditions" model was used that simulated the reach without the effect of point and nonpoint sources and set Upper Klamath Lake at its Total Maximum Daily Load (TMDL) targets. These scenarios were simulated using a model developed by the U.S. Geological Survey (USGS) and Watercourse Engineering, Inc. for the years 2006–09, referred to here as the "USGS model." Another model of the reach was developed by Tetra Tech, Inc. for years 2000 and 2002 to support the Klamath River TMDL process; that model is referred to here as the "TMDL model." The three scenarios described in this report included (1) an analysis of whether this reach of the Upper Klamath River would be in compliance with dissolved oxygen standards if sources met TMDL allocations, (2) an application of more recent datasets to the TMDL model with comparison to results from the USGS model, and (3) an examination of the effect on dissolved oxygen in the Klamath River if particulate material were stopped from entering Klamath Project diversion canals. Updates and modifications to the USGS model are in progress, so in the future these scenarios will be reanalyzed with the updated model and the interim results presented here will be superseded. Significant findings from this phase of the investigation include: * The TMDL analysis used depth-averaged dissolved oxygen concentrations from model output for comparison with dissolved oxygen standards. The Oregon dissolved oxygen

Diffusive oxygen shunting between vessels in the preglomerular renal vasculature: anatomic observations and computational modeling.

Science.gov (United States)

Gardiner, Bruce S; Thompson, Sarah L; Ngo, Jennifer P; Smith, David W; Abdelkader, Amany; Broughton, Brad R S; Bertram, John F; Evans, Roger G

2012-09-01

To understand how geometric factors affect arterial-to-venous (AV) oxygen shunting, a mathematical model of diffusive oxygen transport in the renal cortex was developed. Preglomerular vascular geometry was investigated using light microscopy (providing vein shape, AV separation, and capillary density near arteries) and published micro-computed tomography (CT) data (providing vessel size and AV separation; Nordsletten DA, Blackett S, Bentley MD, Ritman EL, Smith NP. IUPS Physiome Project. http://www.physiome.org.nz/publications/nordsletten_blackett_ritman_bentley_smith_2005/folder_contents). A "U-shaped" relationship was observed between the arterial radius and the distance between the arterial and venous lumens. Veins were found to partially wrap around the artery more consistently for larger rather than smaller arteries. Intrarenal arteries were surrounded by an area of fibrous tissue, lacking capillaries, the thickness of which increased from ∼5 μm for the smallest arteries (200-μm diameter). Capillary density was greater near smaller arteries than larger arteries. No capillaries were observed between wrapped AV vessel pairs. The computational model comprised a single AV pair in cross section. Geometric parameters critical in renal oxygen transport were altered according to variations observed by CT and light microscopy. Lumen separation and wrapping of the vein around the artery were found to be the critical geometric factors determining the amount of oxygen shunted between AV pairs. AV oxygen shunting increases both as lumen separation decreases and as the degree of wrapping increases. The model also predicts that capillaries not only deliver oxygen, but can also remove oxygen from the cortical parenchyma close to an AV pair. Thus the presence of oxygen sinks (capillaries or tubules) near arteries would reduce the effectiveness of AV oxygen shunting. Collectively, these data suggest that AV oxygen shunting would be favored in larger vessels common to the

Metro passengers’ route choice model and its application considering perceived transfer threshold

Science.gov (United States)

Jin, Fanglei; Zhang, Yongsheng; Liu, Shasha

2017-01-01

With the rapid development of the Metro network in China, the greatly increased route alternatives make passengers’ route choice behavior and passenger flow assignment more complicated, which presents challenges to the operation management. In this paper, a path sized logit model is adopted to analyze passengers’ route choice preferences considering such parameters as in-vehicle time, number of transfers, and transfer time. Moreover, the “perceived transfer threshold” is defined and included in the utility function to reflect the penalty difference caused by transfer time on passengers’ perceived utility under various numbers of transfers. Next, based on the revealed preference data collected in the Guangzhou Metro, the proposed model is calibrated. The appropriate perceived transfer threshold value and the route choice preferences are analyzed. Finally, the model is applied to a personalized route planning case to demonstrate the engineering practicability of route choice behavior analysis. The results show that the introduction of the perceived transfer threshold is helpful to improve the model’s explanatory abilities. In addition, personalized route planning based on route choice preferences can meet passengers’ diversified travel demands. PMID:28957376

Third Radiation Transfer Model Intercomparison (RAMI) exercise : Documenting progress in canopy reflectance models

NARCIS (Netherlands)

Widlowski, J.-L.; Taberner, M.; Pinty, B.; Bruniquel-Pinel, V.; Disney, M.; Fernandes, R.; Gastellu-Etchegorry, J.P.; Gobron, N.; Kuusk, A.; Lavergne, T.; Leblanc, S.; Lewis, P.E.; Martin, E.; Mottus, M.; North, P.R.J.; Qin, W.; Robustelli, M.; Rochdi, N.; Ruiloba, R.; Soler, C.; Thompson, R.; Verhoef, W.; Xie, D.; Thompson, R.

2007-01-01

The Radiation Transfer Model Intercomparison (RAMI) initiative benchmarks canopy reflectance models under well‐controlled experimental conditions. Launched for the first time in 1999, this triennial community exercise encourages the systematic evaluation of canopy reflectance models on a voluntary

Heat Transfer Modelling of Glass Media within TPV Systems

Science.gov (United States)

Bauer, Thomas; Forbes, Ian; Penlington, Roger; Pearsall, Nicola

2004-11-01

Understanding and optimisation of heat transfer, and in particular radiative heat transfer in terms of spectral, angular and spatial radiation distributions is important to achieve high system efficiencies and high electrical power densities for thermophtovoltaics (TPV). This work reviews heat transfer models and uses the Discrete Ordinates method. Firstly one-dimensional heat transfer in fused silica (quartz glass) shields was examined for the common arrangement, radiator-air-glass-air-PV cell. It has been concluded that an alternative arrangement radiator-glass-air-PV cell with increased thickness of fused silica should have advantages in terms of improved transmission of convertible radiation and enhanced suppression of non-convertible radiation.

Ocean (de)oxygenation from the Last Glacial Maximum to the twenty-first century: insights from Earth System models

Science.gov (United States)

Bopp, L.; Resplandy, L.; Untersee, A.; Le Mezo, P.; Kageyama, M.

2017-08-01

All Earth System models project a consistent decrease in the oxygen content of oceans for the coming decades because of ocean warming, reduced ventilation and increased stratification. But large uncertainties for these future projections of ocean deoxygenation remain for the subsurface tropical oceans where the major oxygen minimum zones are located. Here, we combine global warming projections, model-based estimates of natural short-term variability, as well as data and model estimates of the Last Glacial Maximum (LGM) ocean oxygenation to gain some insights into the major mechanisms of oxygenation changes across these different time scales. We show that the primary uncertainty on future ocean deoxygenation in the subsurface tropical oceans is in fact controlled by a robust compensation between decreasing oxygen saturation (O2sat) due to warming and decreasing apparent oxygen utilization (AOU) due to increased ventilation of the corresponding water masses. Modelled short-term natural variability in subsurface oxygen levels also reveals a compensation between O2sat and AOU, controlled by the latter. Finally, using a model simulation of the LGM, reproducing data-based reconstructions of past ocean (de)oxygenation, we show that the deoxygenation trend of the subsurface ocean during deglaciation was controlled by a combination of warming-induced decreasing O2sat and increasing AOU driven by a reduced ventilation of tropical subsurface waters. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

Ocean (de)oxygenation from the Last Glacial Maximum to the twenty-first century: insights from Earth System models.

Science.gov (United States)

Bopp, L; Resplandy, L; Untersee, A; Le Mezo, P; Kageyama, M

2017-09-13

All Earth System models project a consistent decrease in the oxygen content of oceans for the coming decades because of ocean warming, reduced ventilation and increased stratification. But large uncertainties for these future projections of ocean deoxygenation remain for the subsurface tropical oceans where the major oxygen minimum zones are located. Here, we combine global warming projections, model-based estimates of natural short-term variability, as well as data and model estimates of the Last Glacial Maximum (LGM) ocean oxygenation to gain some insights into the major mechanisms of oxygenation changes across these different time scales. We show that the primary uncertainty on future ocean deoxygenation in the subsurface tropical oceans is in fact controlled by a robust compensation between decreasing oxygen saturation (O 2sat ) due to warming and decreasing apparent oxygen utilization (AOU) due to increased ventilation of the corresponding water masses. Modelled short-term natural variability in subsurface oxygen levels also reveals a compensation between O 2sat and AOU, controlled by the latter. Finally, using a model simulation of the LGM, reproducing data-based reconstructions of past ocean (de)oxygenation, we show that the deoxygenation trend of the subsurface ocean during deglaciation was controlled by a combination of warming-induced decreasing O 2sat and increasing AOU driven by a reduced ventilation of tropical subsurface waters.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

Constitutive modeling of intrinsic and oxygen-contaminated silicon monocrystals in easy glide

Science.gov (United States)

Cochard, J.; Yonenaga, I.; Gouttebroze, S.; M'Hamdi, M.; Zhang, Z. L.

2010-11-01

We generalize in this work the constitutive model for silicon crystals of Alexander and Haasen. Strain-rate and temperature dependency of the mechanical behavior of intrinsic crystals are correctly accounted for into stage I of hardening. We show that the steady-state of deformation in stage I is very well reproduced in a wide range of temperature and strain rate. The case of extrinsic crystals containing high levels of dissolved oxygen is examined. The introduction of an effective density of mobile dislocations dependent on the unlocking stress created by oxygen atoms gathered at the dislocation cores is combined to an alteration of the dislocation multiplication rate, due to pinning of the dislocation line by oxygen atoms. This increases the upper yield stress with the bulk oxygen concentration in agreement with experimental observations. The fraction of effectively mobile dislocations is found to decay exponentially with the unlocking stress. Finally, the influence of oxygen migration back onto the dislocations from the bulk on the stress distribution in silicon bars is investigated.

Validation of the TASS/SMR-S Code for the PRHRS Condensation Heat Transfer Model

International Nuclear Information System (INIS)

Jun, In Sub; Yang, Soo Hyoung; Chung, Young Jong; Lee, Won Jae

2011-01-01

When some accidents or events are occurred in the SMART, the secondary system is used to remove the core decay heat for the long time such as a feedwater system. But if the feedwater system can't remove the residual core heat because of its malfunction, the core decay heat is removed using the Passive Residual Heat Removal System (PRHRS). The PRHRS is passive type safety system adopted to enhance the safety of the SMART. It can fundamentally eliminate the uncertainty of operator action. TASS/SMR-S (Transient And Setpoint Simulation/ System-integrated Modular Reactor-Safety) code has various heat transfer models reflecting the design features of the SMART. One of the heat transfer models is the PRHRS condensation heat transfer model. The role of this model is to calculate the heat transfer coefficient in the heat exchanger (H/X) tube side using the relevant heat transfer correlations for all of the heat transfer modes. In this paper, the validation of the condensation heat transfer model was carried out using the POSTECH H/X heat transfer test

Are Model Transferability And Complexity Antithetical? Insights From Validation of a Variable-Complexity Empirical Snow Model in Space and Time

Science.gov (United States)

Lute, A. C.; Luce, Charles H.

2017-11-01

The related challenges of predictions in ungauged basins and predictions in ungauged climates point to the need to develop environmental models that are transferable across both space and time. Hydrologic modeling has historically focused on modelling one or only a few basins using highly parameterized conceptual or physically based models. However, model parameters and structures have been shown to change significantly when calibrated to new basins or time periods, suggesting that model complexity and model transferability may be antithetical. Empirical space-for-time models provide a framework within which to assess model transferability and any tradeoff with model complexity. Using 497 SNOTEL sites in the western U.S., we develop space-for-time models of April 1 SWE and Snow Residence Time based on mean winter temperature and cumulative winter precipitation. The transferability of the models to new conditions (in both space and time) is assessed using non-random cross-validation tests with consideration of the influence of model complexity on transferability. As others have noted, the algorithmic empirical models transfer best when minimal extrapolation in input variables is required. Temporal split-sample validations use pseudoreplicated samples, resulting in the selection of overly complex models, which has implications for the design of hydrologic model validation tests. Finally, we show that low to moderate complexity models transfer most successfully to new conditions in space and time, providing empirical confirmation of the parsimony principal.

Modeling the oxygen diffusion of nanocomposite-based food packaging films.

Science.gov (United States)

Bhunia, Kanishka; Dhawan, Sumeet; Sablani, Shyam S

2012-07-01

Polymer-layered silicate nanocomposites have been shown to improve the gas barrier properties of food packaging polymers. This study developed a computer simulation model using the commercial software, COMSOL Multiphysics to analyze changes in oxygen barrier properties in terms of relative diffusivity, as influenced by configuration and structural parameters that include volume fraction (φ), aspect ratio (α), intercalation width (W), and orientation angle (θ) of nanoparticles. The simulation was performed at different φ (1%, 3%, 5%, and 7%), α (50, 100, 500, and 1000), and W (1, 3, 5, and 7 nm). The θ value was varied from 0° to 85°. Results show that diffusivity decreases with increasing volume fraction, but beyond φ = 5% and α = 500, diffusivity remained almost constant at W values of 1 and 3 nm. Higher relative diffusivity coincided with increasing W and decreasing α value for the same volume fraction of nanoparticles. Diffusivity increased as the rotational angle increased, gradually diminishing the influence of nanoparticles. Diffusivity increased drastically as θ changed from 15° to 30° (relative increment in relative diffusivity was almost 3.5 times). Nanoparticles with exfoliation configuration exhibited better oxygen barrier properties compared to intercalation. The finite element model developed in this study provides insight into oxygen barrier properties for nanocomposite with a wide range of structural parameters. This model can be used to design and manufacture an ideal nanocomposite-based food packaging film with improved gas barrier properties for industrial applications. The model will assist in designing nanocomposite polymeric structures of desired gas barrier properties for food packaging applications. In addition, this study will be helpful in formulating a combination of nanoparticle structural parameters for designing nanocomposite membranes with selective permeability for the industrial applications including membrane

Biofilm structure and mass transfer in a gas phase trickle-bed biofilter.

Science.gov (United States)

Zhu, X; Suidan, M T; Alonso, C; Yu, T; Kim, B J; Kim, B R

2001-01-01

Mass transport phenomena occurring in the biofilms of gas phase trickle-bed biofilters are investigated in this study. The effect of biofilm structure on mass transfer mechanisms is examined using experimental observation from the operating of biofilters, microelectrode techniques and microscopic examination. Since the biofilms of biofilters used for waste gas treatment are not completely saturated with water, there is not a distinguishable liquid layer outside the biofilm. Results suggest that due to this characteristic, gas phase substrates (such as oxygen or volatile organic compounds) may not be limited by the aqueous phase because transport of the compound into the biofilm can occur directly through non-wetted areas. On the other hand, for substrates that are present only in the liquid phase, such as nitrate, the mass transfer limitation is more serious because of the limited liquid supply. Microscopic observations show that a layered structure with void spaces exists within the biofilm. Oxygen concentration distributions along the depth of the biofilms are examined using an oxygen microelectrode. Results indicate that there are some high dissolved oxygen zones inside the biofilm, which suggests the existence of passages for oxygen transfer into the deeper sections of the biofilm in a gas phase trickle-bed biofilter. Both the low gas-liquid mass transfer resistance and the resulting internal structure contribute to the high oxygen penetration within the biofilms in gas phase trickle-bed biofilters.

Modelling of Multi Input Transfer Function for Rainfall Forecasting in Batu City

OpenAIRE

Priska Arindya Purnama

2017-01-01

The aim of this research is to model and forecast the rainfall in Batu City using multi input transfer function model based on air temperature, humidity, wind speed and cloud. Transfer function model is a multivariate time series model which consists of an output series (Yt) sequence expected to be effected by an input series (Xt) and other inputs in a group called a noise series (Nt). Multi input transfer function model obtained is (b1,s1,r1) (b2,s2,r2) (b3,s3,r3) (b4,s4,r4)(pn,qn) = (0,0,0)...

Dynamic modeling of fixed-bed adsorption of flue gas using a variable mass transfer model

International Nuclear Information System (INIS)

Park, Jehun; Lee, Jae W.

2016-01-01

This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 .deg. C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen.

Oxidative degradation of alternative gasoline oxygenates in aqueous solution by ultrasonic irradiation: Mechanistic study

Energy Technology Data Exchange (ETDEWEB)

Kim, Duk Kyung, E-mail: dkim@aum.edu [Department of Physical Science, Auburn University Montgomery, Montgomery, AL 36117 (United States); O' Shea, Kevin E., E-mail: osheak@fiu.edu [Department of Chemistry and Biochemistry, Florida International University, University Park, Miami, FL 33199 (United States); Cooper, William J. [Department of Civil and Environmental Engineering, Urban Water Research Center, University of California Irvine, Irvine, CA 92697-2175 (United States)

2012-07-15

Widespread pollution has been associated with gasoline oxygenates of branched ethers methyl tert-butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), and tert-amyl ether (TAME) which enter groundwater. The contaminated plume develops rapidly and treatment for the removal/destruction of these ethers is difficult when using conventional methods. Degradation of MTBE, with biological methods and advanced oxidation processes, are rather well known; however, fewer studies have been reported for degradation of alternative oxygenates. Degradation of alternative gasoline oxygenates (DIPE, ETBE, and TAME) by ultrasonic irradiation in aqueous oxygen saturation was investigated to elucidate degradation pathways. Detailed degradation mechanisms are proposed for each gasoline oxygenate. The common major degradation pathways are proposed to involve abstraction of {alpha}-hydrogen atoms by hydroxyl radicals generated during ultrasound cavitation and low temperature pyrolytic degradation of ETBE and TAME. Even some of the products from {beta}-H abstraction overlap with those from high temperature pyrolysis, the effect of {beta}-H abstraction was not shown clearly from product study because of possible 1,5 H-transfer inside cavitating bubbles. Formation of hydrogen peroxide and organic peroxides was also determined during sonolysis. These data provide a better understanding of the degradation pathways of gasoline oxygenates by sonolysis in aqueous solutions. The approach may also serve as a model for others interested in the details of sonolysis. - Highlights: Black-Right-Pointing-Pointer Gasoline oxygenates (ETBE, TAME, DIPE) were completely degraded after 6 hours under ultrasonic irradiation in O{sub 2} saturation. Black-Right-Pointing-Pointer The major degradation pathways were proposed to involve abstraction of {alpha}-hydrogen atoms by hydroxyl radicals and low temperature pyrolytic degradation. Black-Right-Pointing-Pointer The effect of {beta

A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.

Science.gov (United States)

de Jong, J A; Wijnant, Y H; de Boer, A

2014-03-01

A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.

A forced convective heat transfer model for two-phase hydrogen systems

International Nuclear Information System (INIS)

Pasch, J.; Anghaie, S.

2007-01-01

A consistent event in the use of hydrogen in nuclear thermal propulsion is film boiling, in which the wall heat is so large that liquid can not exist at the wall. Instead, vapor interfaces with the wall and liquid flows in the core of the duct. To better understand heat transfer under these conditions, a select set of hydrogen test data from these conditions are analyzed. This paper presents the results of an extensive literature search for film boiling heat transfer models. A representative cross-section of these models is then applied to the data. The heat transfer coefficient data were found difficult to predict and highly dependent upon the flow regime. Pre-critical heat flux correlations completely fail to predict the heat transfer of inverted film boiling conditions. Pool boiling models for inverted film boiling also are inappropriate. Current force convection models for inverted film boiling, while far better than the previous two classes of models, still generate large predictive errors. It is recommended that for the inverted annular film boiling flow regime the modified equilibrium bulk Dittus-Boelter model be used. For agitated inverted annular film boiling and dispersed film boiling regimes associated with positive equilibrium qualities, the Hendricks model should be used. (A.C.)

Predicting Biological Information Flow in a Model Oxygen Minimum Zone

Science.gov (United States)

Louca, S.; Hawley, A. K.; Katsev, S.; Beltran, M. T.; Bhatia, M. P.; Michiels, C.; Capelle, D.; Lavik, G.; Doebeli, M.; Crowe, S.; Hallam, S. J.

2016-02-01

Microbial activity drives marine biochemical fluxes and nutrient cycling at global scales. Geochemical measurements as well as molecular techniques such as metagenomics, metatranscriptomics and metaproteomics provide great insight into microbial activity. However, an integration of molecular and geochemical data into mechanistic biogeochemical models is still lacking. Recent work suggests that microbial metabolic pathways are, at the ecosystem level, strongly shaped by stoichiometric and energetic constraints. Hence, models rooted in fluxes of matter and energy may yield a holistic understanding of biogeochemistry. Furthermore, such pathway-centric models would allow a direct consolidation with meta'omic data. Here we present a pathway-centric biogeochemical model for the seasonal oxygen minimum zone in Saanich Inlet, a fjord off the coast of Vancouver Island. The model considers key dissimilatory nitrogen and sulfur fluxes, as well as the population dynamics of the genes that mediate them. By assuming a direct translation of biocatalyzed energy fluxes to biosynthesis rates, we make predictions about the distribution and activity of the corresponding genes. A comparison of the model to molecular measurements indicates that the model explains observed DNA, RNA, protein and cell depth profiles. This suggests that microbial activity in marine ecosystems such as oxygen minimum zones is well described by DNA abundance, which, in conjunction with geochemical constraints, determines pathway expression and process rates. Our work further demonstrates how meta'omic data can be mechanistically linked to environmental redox conditions and biogeochemical processes.

Two dimensional finite element heat transfer models for softwood

Science.gov (United States)

Hongmei Gu; John F. Hunt

2004-01-01

The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential directions and have not differentiated the effects of cellular alignment, earlywood/latewood...

CO2 Mass transfer model for carbonic anhydrase-enhanced aqueous MDEA solutions

DEFF Research Database (Denmark)

Gladis, Arne Berthold; Deslauriers, Maria Gundersen; Neerup, Randi

2018-01-01

In this study a CO2 mass transfer model was developed for carbonic anhydrase-enhanced MDEA solutions based on a mechanistic kinetic enzyme model. Four different enzyme models were compared in their ability to predict the liquid side mass transfer coefficient at temperatures in the range of 298...

Economical analyses of build-operate-transfer model in establishing alternative power plants

Energy Technology Data Exchange (ETDEWEB)

Yumurtaci, Zehra [Yildiz Technical University, Department of Mechanical Engineering, Y.T.U. Mak. Fak. Mak. Muh. Bolumu, Besiktas, 34349 Istanbul (Turkey)]. E-mail: zyumur@yildiz.edu.tr; Erdem, Hasan Hueseyin [Yildiz Technical University, Department of Mechanical Engineering, Y.T.U. Mak. Fak. Mak. Muh. Bolumu, Besiktas, 34349 Istanbul (Turkey)

2007-01-15

The most widely employed method to meet the increasing electricity demand is building new power plants. The most important issue in building new power plants is to find financial funds. Various models are employed, especially in developing countries, in order to overcome this problem and to find a financial source. One of these models is the build-operate-transfer (BOT) model. In this model, the investor raises all the funds for mandatory expenses and provides financing, builds the plant and, after a certain plant operation period, transfers the plant to the national power organization. In this model, the object is to decrease the burden of power plants on the state budget. The most important issue in the BOT model is the dependence of the unit electricity cost on the transfer period. In this study, the model giving the unit electricity cost depending on the transfer of the plants established according to the BOT model, has been discussed. Unit electricity investment cost and unit electricity cost in relation to transfer period for plant types have been determined. Furthermore, unit electricity cost change depending on load factor, which is one of the parameters affecting annual electricity production, has been determined, and the results have been analyzed. This method can be employed for comparing the production costs of different plants that are planned to be established according to the BOT model, or it can be employed to determine the appropriateness of the BOT model.

Economical analyses of build-operate-transfer model in establishing alternative power plants

International Nuclear Information System (INIS)

Yumurtaci, Zehra; Erdem, Hasan Hueseyin

2007-01-01

The most widely employed method to meet the increasing electricity demand is building new power plants. The most important issue in building new power plants is to find financial funds. Various models are employed, especially in developing countries, in order to overcome this problem and to find a financial source. One of these models is the build-operate-transfer (BOT) model. In this model, the investor raises all the funds for mandatory expenses and provides financing, builds the plant and, after a certain plant operation period, transfers the plant to the national power organization. In this model, the object is to decrease the burden of power plants on the state budget. The most important issue in the BOT model is the dependence of the unit electricity cost on the transfer period. In this study, the model giving the unit electricity cost depending on the transfer of the plants established according to the BOT model, has been discussed. Unit electricity investment cost and unit electricity cost in relation to transfer period for plant types have been determined. Furthermore, unit electricity cost change depending on load factor, which is one of the parameters affecting annual electricity production, has been determined, and the results have been analyzed. This method can be employed for comparing the production costs of different plants that are planned to be established according to the BOT model, or it can be employed to determine the appropriateness of the BOT model

Development of a UF{sub 6} cylinder transient heat transfer/stress analysis model

Energy Technology Data Exchange (ETDEWEB)

Williams, W.R. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)

1991-12-31

A heat transfer/stress analysis model is being developed to simulate the heating to a point of rupture of a cylinder containing UF{sub 6} when it is exposed to a fire. The assumptions underlying the heat transfer portion of the model, which has been the focus of work to date, will be discussed. A key aspect of this model is a lumped parameter approach to modeling heat transfer. Preliminary results and future efforts to develop an integrated thermal/stress model will be outlined.

Discussion on the Heat and Mass Transfer Model on the Pool Surface

Energy Technology Data Exchange (ETDEWEB)

Hong, Soon-Joon; Choo, Yeon-Jun [FNC Tech., Yongin (Korea, Republic of); Ha, Sang-Jun [KHNP Central Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Heat transfer on the pool surface involves the evaporation and condensation of steam in the presence of non-condensable gas. It is a kind of inter-phase heat transfer. This phenomenon has been regarded as less important on the thermal hydraulic behaviors such as pressure, temperature, hydrogen distribution, and so on in the nuclear reactor containment building. As a matter of fact, several RAIs (requests for additional information) during the licensing review of the developed CAP have been presented. And early in 2000s the steam condensation on the water surface of IRWST was a concern of APR1400 design. Such an increased concern is believed because it is a newly adopted system. This study discusses the pool surface heat transfer by reviewing the models of several well-known containment analysis codes, and conducting the sensitivities. This study discussed the pool surface heat transfer. The related models of CAP, GOTHIC, CONTEMPT-LT, and CONTEMPT4 were compared. The sensitivity of heat transfer coefficient for SKN3 and 4 using conventional code CONTEMPT-LT/028-A showed little effect. And the sensitivity of relative humidity and heat transfer area for latent heat transfer shows that CAP locates between GOTHIC and CONTEMPT4/MOD. The sensitivity for sensible heat transfer also shows similar trend. Conclusively, current CAP model of pool surface heat transfer has no fatal defect.

Discussion on the Heat and Mass Transfer Model on the Pool Surface

International Nuclear Information System (INIS)

Hong, Soon-Joon; Choo, Yeon-Jun; Ha, Sang-Jun

2016-01-01

Heat transfer on the pool surface involves the evaporation and condensation of steam in the presence of non-condensable gas. It is a kind of inter-phase heat transfer. This phenomenon has been regarded as less important on the thermal hydraulic behaviors such as pressure, temperature, hydrogen distribution, and so on in the nuclear reactor containment building. As a matter of fact, several RAIs (requests for additional information) during the licensing review of the developed CAP have been presented. And early in 2000s the steam condensation on the water surface of IRWST was a concern of APR1400 design. Such an increased concern is believed because it is a newly adopted system. This study discusses the pool surface heat transfer by reviewing the models of several well-known containment analysis codes, and conducting the sensitivities. This study discussed the pool surface heat transfer. The related models of CAP, GOTHIC, CONTEMPT-LT, and CONTEMPT4 were compared. The sensitivity of heat transfer coefficient for SKN3 and 4 using conventional code CONTEMPT-LT/028-A showed little effect. And the sensitivity of relative humidity and heat transfer area for latent heat transfer shows that CAP locates between GOTHIC and CONTEMPT4/MOD. The sensitivity for sensible heat transfer also shows similar trend. Conclusively, current CAP model of pool surface heat transfer has no fatal defect

A model for dispersed flow heat transfer in rod bundles during reflood

International Nuclear Information System (INIS)

Wong, S.

1980-01-01

The present model calculates the heat transfer characteristics of the non-equilibrium dispersed droplet flow regime above the quench front during reflood by solving simultaneously the wall-to-vapor interactions, wall-to-droplet interactions and vapor-to-droplet interactions by an iterative numerical method. The unique feature in the present study is various heat transfer mechanisms are combined in an overall energy balance equation, and the convective heat transfer to vapor is obtained by calculating the vapor temperature distributions at the heated walls. The reactor rod bundle geometry, axial variations of vapor temperature and flow properties, radiative heat transfers, and enhancement of heat transfer due to turbulence are considered carefully, so that the present model could be used to predict PWR (Pressurized Water Reactor) reflood heat transfers, and hence the fuel cladding wall temperature transients. In order to achieve closure of the problem formulations, the droplet size and its motion are determined from the FLECHT (Full Length Emergency Cooling Heat Transfer Program) low flooding rate series consine axial power shape test data. The model is then verified by comparing the heat transfer predictions with FLECHT low flooding rate series skewed axial power shape test data. Comparisons of predictions with data show satisfactory agreements

MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS

Energy Technology Data Exchange (ETDEWEB)

Leishear, R.

2009-09-09

Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.

MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS

International Nuclear Information System (INIS)

Leishear, R.

2009-01-01

Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels

Modeling of oxygen transport and cellular energetics explains observations on in vivo cardiac energy metabolism.

Directory of Open Access Journals (Sweden)

Daniel A Beard

2006-09-01

Full Text Available Observations on the relationship between cardiac work rate and the levels of energy metabolites adenosine triphosphate (ATP, adenosine diphosphate (ADP, and phosphocreatine (CrP have not been satisfactorily explained by theoretical models of cardiac energy metabolism. Specifically, the in vivo stability of ATP, ADP, and CrP levels in response to changes in work and respiratory rate has eluded explanation. Here a previously developed model of mitochondrial oxidative phosphorylation, which was developed based on data obtained from isolated cardiac mitochondria, is integrated with a spatially distributed model of oxygen transport in the myocardium to analyze data obtained from several laboratories over the past two decades. The model includes the components of the respiratory chain, the F0F1-ATPase, adenine nucleotide translocase, and the mitochondrial phosphate transporter at the mitochondrial level; adenylate kinase, creatine kinase, and ATP consumption in the cytoplasm; and oxygen transport between capillaries, interstitial fluid, and cardiomyocytes. The integrated model is able to reproduce experimental observations on ATP, ADP, CrP, and inorganic phosphate levels in canine hearts over a range of workload and during coronary hypoperfusion and predicts that cytoplasmic inorganic phosphate level is a key regulator of the rate of mitochondrial respiration at workloads for which the rate of cardiac oxygen consumption is less than or equal to approximately 12 mumol per minute per gram of tissue. At work rates corresponding to oxygen consumption higher than 12 mumol min(-1 g(-1, model predictions deviate from the experimental data, indicating that at high work rates, additional regulatory mechanisms that are not currently incorporated into the model may be important. Nevertheless, the integrated model explains metabolite levels observed at low to moderate workloads and the changes in metabolite levels and tissue oxygenation observed during graded

Pollinators, geitonogamy and a model of pollen transfer

International Nuclear Information System (INIS)

Di Pasquale, C.

1995-12-01

A model of pollination that considers the amount of geitonogamous pollen transfer in different flowers and plants is presented. We assumed in this work self-incompatible plant species and we studied how pollination is affected by different round trips described by pollinator from its nest, taking into account the fraction geitonogamy and the fraction pollen export. A deterministic model and a stochastic model of pollen transfer were developed from which we found that when pollinators describe a uniform sequence (visit the same number of flowers in each plant), individuals receive the maximum outcross pollen or minimum self pollen. That is, from the point of view of fertilization, the optimal number of flowers visited in each plant depends on the number of flowers of the plant, the length of the visit and the number of individuals. (author). 18 refs, 1 fig

Enhanced kinetics of hole transfer and electrocatalysis during photocatalytic oxygen evolution by cocatalyst tuning

KAUST Repository

Nurlaela, Ela; Wang, Hai; Shinagawa, Tatsuya; Flanagan, Sean; Ould-Chikh, Samy; Qureshi, Muhammad; Mics, Zoltan; Sautet, Philippe; Le Bahers, Tangui; Canovas, Enrique; Bonn, Mischa; Takanabe, Kazuhiro

2016-01-01

Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic effi-ciency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the ef-fects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm2 V-1 s-1), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

Enhanced kinetics of hole transfer and electrocatalysis during photocatalytic oxygen evolution by cocatalyst tuning

KAUST Repository

Nurlaela, Ela

2016-05-23

Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic effi-ciency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the ef-fects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm2 V-1 s-1), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

An analytical model for annular flow boiling heat transfer in microchannel heat sinks

International Nuclear Information System (INIS)

Megahed, A.; Hassan, I.

2009-01-01

An analytical model has been developed to predict flow boiling heat transfer coefficient in microchannel heat sinks. The new analytical model is proposed to predict the two-phase heat transfer coefficient during annular flow regime based on the separated model. Opposing to the majority of annular flow heat transfer models, the model is based on fundamental conservation principles. The model considers the characteristics of microchannel heat sink during annular flow and eliminates using any empirical closure relations. Comparison with limited experimental data was found to validate the usefulness of this analytical model. The model predicts the experimental data with a mean absolute error 8%. (author)

Bridging the Radiative Transfer Models for Meteorology and Solar Energy Applications

Science.gov (United States)

Xie, Y.; Sengupta, M.

2017-12-01

Radiative transfer models are used to compute solar radiation reaching the earth surface and play an important role in both meteorology and solar energy studies. Therefore, they are designed to meet the needs of specialized applications. For instance, radiative transfer models for meteorology seek to provide more accurate cloudy-sky radiation compared to models used in solar energy that are geared towards accuracy in clear-sky conditions associated with the maximum solar resource. However, models for solar energy applications are often computationally faster, as the complex solution of the radiative transfer equation is parameterized by atmospheric properties that can be acquired from surface- or satellite-based observations. This study introduces the National Renewable Energy Laboratory's (NREL's) recent efforts to combine the advantages of radiative transfer models designed for meteorology and solar energy applictions. A fast all-sky radiation model, FARMS-NIT, was developed to efficiently compute narrowband all-sky irradiances over inclined photovoltaic (PV) panels. This new model utilizes the optical preperties from a solar energy model, SMARTS, to computes surface radiation by considering all possible paths of photon transmission and the relevent scattering and absorption attenuation. For cloudy-sky conditions, cloud bidirectional transmittance functions (BTDFs) are provided by a precomputed lookup table (LUT) by LibRadtran. Our initial results indicate that FARMS-NIT has an accuracy that is similar to LibRadtran, a highly accurate multi-stream model, but is significantly more efficient. The development and validation of this model will be presented.

Heat transfer model for quenching by submerging

International Nuclear Information System (INIS)

Passarella, D N; Varas, F; MartIn, E B

2011-01-01

In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.

Heat transfer model for quenching by submerging

Energy Technology Data Exchange (ETDEWEB)

Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)

2011-05-01

In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.

Simplified analytical model for thermal transfer in vertical hollow brick

Energy Technology Data Exchange (ETDEWEB)

Lorente, S [Lab. d` Etudes Thermiques et Mecaniques, INSA, UPS, Toulouse (France); Petit, M [Lab. d` Etudes Thermiques et Mecaniques, INSA, UPS, Toulouse (France); Javelas, R [Lab. d` Etudes Thermiques et Mecaniques, INSA, UPS, Toulouse (France)

1996-12-01

A modern building envelope has a lot of little cavities. Most of them are vertical with a high height to thickness ratio. We present here the conception of a software to determine heat transfer through terra-cotta bricks full of large vertical cavities. After a bibliographic study on convective heat transfer in such cavities, we made an analytical model based on Karman-Polhausen`s method for convection and on the radiosity method for radiative heat transfer. We used a test apparatus of a single cavity to determine the temperature field inside the cavity. Using these experimental results, we showed that the exchange was two-dimensional. We also realised heat flux measurements. Then we expose our theoretical study: We propose relations between central core temperatures and active face temperatures, then between outside and inside active face temperatures. We calculate convective superficial heat transfer because we noticed we have boundary layers along the active faces. We realise a heat flux balance between convective plus radiative heat transfer and conductive heat transfer, so we propose an algorithm to calculate global heat transfer through a single cavity. Finally, we extend our model to a whole hollow brick with lined-up cavities and propose an algorithm to calculate heat flux and thermal resistance with a good accuracy ({approx}7.5%) compared to previous experimental results. (orig.)

The electrode kinetics of the evolution and dissolution of oxygen at the urania-zirconia interfaces

International Nuclear Information System (INIS)

Badwal, S.P.S.; Bevan, D.J.M.; Bockris, J.O'M.

1980-01-01

In order to assess the potential of urania-yttria fluorite-type solid solutions as electrodes for high-temperature electrolysis of steam, oxygen evolution and dissolution reactions have been studied at the (Usub(0.7)Ysub(0.3))Osub (2+x)/YSZ interface. A current-interruption technique was used to separate overpotential and resistive potential drop. In oxygen and air the overpotential-current curves obey the Tafel law, suggesting that a charge-transfer process is rate determining. Activation energies of 120 kJ mole -1 and 165 kJ mole -1 were obtained for the cathodic reaction in oxygen and air respectively. The capacitance obtained from galvanostatic transients varied with potential, temperature, and oxygen partial pressure. The average value of n, the number of electrons involved in the overall charge-transfer reaction, was determined to be 4.01 from reversible potential measurements. The overpotential losses are small for porous electrodes at high psub(O 2 ). A mechanism for the oxygen transfer reaction has been proposed and its limitations discussed. (author)

Gas exchange efficiency of an oxygenator with integrated pulsatile displacement blood pump for neonatal patients.

Science.gov (United States)

Schlanstein, Peter C; Borchardt, Ralf; Mager, Ilona; Schmitz-Rode, Thomas; Steinseifer, Ulrich; Arens, Jutta

2014-01-01

Oxygenators have been used in neonatal extracorporeal membrane oxygenation (ECMO) since the 1970s. The need to develop a more effective oxygenator for this patient cohort exists due to their size and blood volume limitations. This study sought to validate the next design iteration of a novel oxygenator for neonatal ECMO with an integrated pulsatile displacement pump, thereby superseding an additional blood pump. Pulsating blood flow within the oxygenator is generated by synchronized active air flow expansion and contraction of integrated silicone pump tubes and hose pinching valves located at the oxygenator inlet and outlet. The current redesign improved upon previous prototypes by optimizing silicone pump tube distribution within the oxygenator fiber bundle; introduction of an oval shaped inner fiber bundle core, and housing; and a higher fiber packing density, all of which in combination reduced the priming volume by about 50% (50 to 27 mL and 41 to 20 mL, respectively). Gas exchange efficiency was tested for two new oxygenators manufactured with different fiber materials: one with coating and one with smaller pore size, both capable of long-term use (OXYPLUS® and CELGARD®). Results demonstrated that the oxygen transfer for both oxygenators was 5.3-24.7 mlO2/min for blood flow ranges of 100-500 mlblood/min. Carbon dioxide transfer for both oxygenators was 3.7-26.3 mlCO2/min for the same blood flow range. These preliminary results validated the oxygenator redesign by demonstrating an increase in packing density and thus in gas transfer, an increase in pumping capacity and a reduction in priming volume.

Isotopic effects in the muon transfer from pmu and dmu to heavier atoms.

Science.gov (United States)

Dupays, Arnaud

2004-07-23

The results of accurate hyperspherical calculations of the muon-transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen, and neon are reported. Very good agreement with measured rates is obtained and, for the three systems, the isotopic effect is perfectly reproduced. The transfer rate is higher for deuterium in the cases of nitrogen and neon due to constructive interferences between two transfer paths. The lower transfer rate for deuterium in the case of oxygen results from a large resonant contribution. Copyright 2004 The American Physical Society

Modeling heat transfer in supercritical fluid using the lattice Boltzmann method.

Science.gov (United States)

Házi, Gábor; Márkus, Attila

2008-02-01

A lattice Boltzmann model has been developed to simulate heat transfer in supercritical fluids. A supercritical viscous fluid layer between two plates heated from the bottom has been studied. It is demonstrated that the model can be used to study heat transfer near the critical point where the so-called piston effect speeds up the transfer of heat and results in homogeneous heating in the bulk of the layer. We have also studied the onset of convection in a Rayleigh-Bénard configuration. It is shown that our model can well predict qualitatively the onset of convection near the critical point, where there is a crossover between the Rayleigh and Schwarzschild criteria.

An in silico analysis of oxygen uptake of a mild COPD patient during rest and exercise using a portable oxygen concentrator

Directory of Open Access Journals (Sweden)

Katz I

2016-09-01

Full Text Available Ira Katz,1,2 Marine Pichelin,1 Spyridon Montesantos,1 Min-Yeong Kang,3 Bernard Sapoval,3,4 Kaixian Zhu,5 Charles-Philippe Thevenin,5 Robert McCoy,6 Andrew R Martin,7 Georges Caillibotte1 1Medical R&D, Air Liquide Santé International, Centre de Recherche Paris-Saclay, Les Loges-en-Josas, France; 2Department of Mechanical Engineering, Lafayette College, Easton, PA, USA; 3Physique de la Matière Condensée, CNRS, Ecole Polytechnique, Palaiseau, 4Centre de Mathématiques et de leurs Applications, CNRS, UniverSud, Cachan, 5Centre Explor!, Air Liquide Healthcare, Gentilly, France; 6Valley Inspired Products, Inc, Apple Valley, MN, USA; 7Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada Abstract: Oxygen treatment based on intermittent-flow devices with pulse delivery modes available from portable oxygen concentrators (POCs depends on the characteristics of the delivered pulse such as volume, pulse width (the time of the pulse to be delivered, and pulse delay (the time for the pulse to be initiated from the start of inhalation as well as a patient’s breathing characteristics, disease state, and respiratory morphology. This article presents a physiological-based analysis of the performance, in terms of blood oxygenation, of a commercial POC at different settings using an in silico model of a COPD patient at rest and during exercise. The analysis encompasses experimental measurements of pulse volume, width, and time delay of the POC at three different settings and two breathing rates related to rest and exercise. These experimental data of device performance are inputs to a physiological-based model of oxygen uptake that takes into account the real dynamic nature of gas exchange to illustrate how device- and patient-specific factors can affect patient oxygenation. This type of physiological analysis that considers the true effectiveness of oxygen transfer to the blood, as opposed to delivery to the nose (or mouth, can be

Modelling of Multi Input Transfer Function for Rainfall Forecasting in Batu City

Directory of Open Access Journals (Sweden)

Priska Arindya Purnama

2017-11-01

Full Text Available The aim of this research is to model and forecast the rainfall in Batu City using multi input transfer function model based on air temperature, humidity, wind speed and cloud. Transfer function model is a multivariate time series model which consists of an output series (Yt sequence expected to be effected by an input series (Xt and other inputs in a group called a noise series (Nt. Multi input transfer function model obtained is (b1,s1,r1 (b2,s2,r2 (b3,s3,r3 (b4,s4,r4(pn,qn = (0,0,0 (23,0,0 (1,2,0 (0,0,0 ([5,8],2 and shows that air temperature on t-day affects rainfall on t-day, rainfall on t-day is influenced by air humidity in the previous 23 days, rainfall on t-day is affected by wind speed in the previous day , and rainfall on day t is affected by clouds on day t. The results of rainfall forecasting in Batu City with multi input transfer function model can be said to be accurate, because it produces relatively small RMSE value. The value of RMSE data forecasting training is 7.7921 while forecasting data testing is 4.2184. Multi-input transfer function model is suitable for rainfall in Batu City.

Organodioxygen complexes of some heavy metal ions and their oxygen transfer reactions

International Nuclear Information System (INIS)

Tarafder, M.T.H.; Mei Ling; Gino Mariotto

2003-09-01

Several novel organodioxygen complexes of lanthanide ions, viz., lanthanum(m) and cerium(IV) have been synthesized containing a number of organic co- ligands. The complexes characterized were, [La(0 2 )(det)(N0 3 ) 2 ] (1), [La(O 2 )(tet)(NO 3 ) 2 ] (2), [La(O 2 )(C 5 H 5 N)2NO 3 ] (3), [La(O 2 )(C 6 H 18 N 3 PO) 2 (NO 3 ) 2 ] (4), [La(0 2 )(OPPh 3 ) 2 (N0 3 ) 2 ] (5), [La(O 2 ) 2 (NH 2 CH 2 CH 2 NH 2 ) 2 NO 3 ] (6), [La(O 2 )(PPh 3 ) 2 (NO 3 ) 2 ] (7) and [Ce(O 2 )(C 6 H 18 N 3 PO) 2 (NO 3 ) 3 ] (8). IR and Raman spectra revealed that (3) was a peroxo complex while the others were, in particular, superoxo type. The IR spectrum of (3) gives V 1 (O-O) at 851 cm -1 while the Raman spectra of (4), (5), (7) and (8) give V 1 (O 2 ) bands at 1046 cm -1 , 1032 cm 1 , 1100 cm -1 and 1046 cm -1 , respectively. The oxygen transfer reactions of two selected complexes were carried out under stoichiometric conditions. The complex containing a bidentate ligand, (6), was found to oxidize triphenylphosphine and trans-stilbene to their oxides while the complex containing tridentate ligand (1) was stable and inert towards oxidation. (author)

Linearized vector radiative transfer model MCC++ for a spherical atmosphere

International Nuclear Information System (INIS)

Postylyakov, O.V.

2004-01-01

Application of radiative transfer models has shown that optical remote sensing requires extra characteristics of radiance field in addition to the radiance intensity itself. Simulation of spectral measurements, analysis of retrieval errors and development of retrieval algorithms are in need of derivatives of radiance with respect to atmospheric constituents under investigation. The presented vector spherical radiative transfer model MCC++ was linearized, which allows the calculation of derivatives of all elements of the Stokes vector with respect to the volume absorption coefficient simultaneously with radiance calculation. The model MCC++ employs Monte Carlo algorithm for radiative transfer simulation and takes into account aerosol and molecular scattering, gas and aerosol absorption, and Lambertian surface albedo. The model treats a spherically symmetrical atmosphere. Relation of the estimated derivatives with other forms of radiance derivatives: the weighting functions used in gas retrieval and the air mass factors used in the DOAS retrieval algorithms, is obtained. Validation of the model against other radiative models is overviewed. The computing time of the intensity for the MCC++ model is about that for radiative models treating sphericity of the atmosphere approximately and is significantly shorter than that for the full spherical models used in the comparisons. The simultaneous calculation of all derivatives (i.e. with respect to absorption in all model atmosphere layers) and the intensity is only 1.2-2 times longer than the calculation of the intensity only

Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions

Energy Technology Data Exchange (ETDEWEB)

Simpson, Brett Kimball [Iowa State Univ., Ames, IA (United States)

2002-01-01

Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO₂ films] revealed that MnO₂ film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO₂ films with Fe(III) further enhanced electrode activity. Reasons for this increase are believed to involve the adsorption of DMSO by the Fe(III) sites. The investigation into anodic O-transfer reactions at undoped and Fe(III)-doped RuO₂ films showed that the Fe(III)-doped RuO₂-film electrodes are applicable for anodic detection of sulfur compounds. The Fe(III) sites in the Fe-RuO₂ films are speculated to act as adsorption sites for the sulfur species while the Ru(IV) sites function for anodic discharge of H₂O to generate the adsorbed OH species. The investigation into cathodic H-transfer reactions, specifically nitrate reduction, at various pure metals and their alloys demonstrated that the incorporation of metals into alloy materials can create a material that exhibits bifunctional properties for the various steps involved in the overall nitrate reduction reaction. The Sb₁₀Sn₂₀Ti₇₀, Cu₆₃Ni₃₇ and Cu₂₅Ni₇₅ alloy electrodes exhibited improved activity for nitrate reduction as compared to their pure component metals. The Cu₆₃Ni₃₇ alloy displayed the highest activity for nitrate reduction. The final investigation was a detailed study of the electrocatalytic activity of cathodic H-transfer reactions (nitrate reduction) at various compositions of Cu-Ni alloy electrodes. Voltammetric response for NO₃^- at the Cu-Ni alloy electrode is superior to

Thermochemical modeling of nuclear fuel and the effects of oxygen potential buffers

Energy Technology Data Exchange (ETDEWEB)

Loukusa, Henri, E-mail: henri.loukusa@vtt.fi; Ikonen, Timo; Valtavirta, Ville; Tulkki, Ville

2016-12-01

The elemental and chemical composition of nuclear fuel pellets are key factors influencing the material properties of the pellets. The oxidation state of the fuel is one of the most important chemical properties influencing the material properties of the fuel, and it can only be determined with the knowledge of the chemical composition. A measure of the oxidation state is the oxygen chemical potential of the fuel. It can be buffered by redox pairs, such as the well-known Mo/MoO{sub 2} pair. In this work, the elemental composition of the fuel is obtained from a burnup calculation and the temperature and pressure calculated with a fuel performance code. An estimate of the oxygen potential of fuel is calculated with Gibbs energy minimization. The results are compared against experimental data from the literature. The significance of the UMoO{sub 6} compound and its buffering effect on the oxygen potential is emphasized. - Highlights: • A Gibbs energy minimization routine has been developed for nuclear fuel modeling. • The initial stoichiometry affects the development of the oxygen potential of fuel. • UMoO{sub 6} is found to buffer the oxygen potential of nuclear fuel.

Validation of the community radiative transfer model

International Nuclear Information System (INIS)

Ding Shouguo; Yang Ping; Weng Fuzhong; Liu Quanhua; Han Yong; Delst, Paul van; Li Jun; Baum, Bryan

2011-01-01

To validate the Community Radiative Transfer Model (CRTM) developed by the U.S. Joint Center for Satellite Data Assimilation (JCSDA), the discrete ordinate radiative transfer (DISORT) model and the line-by-line radiative transfer model (LBLRTM) are combined in order to provide a reference benchmark. Compared with the benchmark, the CRTM appears quite accurate for both clear sky and ice cloud radiance simulations with RMS errors below 0.2 K, except for clouds with small ice particles. In a computer CPU run time comparison, the CRTM is faster than DISORT by approximately two orders of magnitude. Using the operational MODIS cloud products and the European Center for Medium-range Weather Forecasting (ECMWF) atmospheric profiles as an input, the CRTM is employed to simulate the Atmospheric Infrared Sounder (AIRS) radiances. The CRTM simulations are shown to be in reasonably close agreement with the AIRS measurements (the discrepancies are within 2 K in terms of brightness temperature difference). Furthermore, the impact of uncertainties in the input cloud properties and atmospheric profiles on the CRTM simulations has been assessed. The CRTM-based brightness temperatures (BTs) at the top of the atmosphere (TOA), for both thin (τ 30) clouds, are highly sensitive to uncertainties in atmospheric temperature and cloud top pressure. However, for an optically thick cloud, the CRTM-based BTs are not sensitive to the uncertainties of cloud optical thickness, effective particle size, and atmospheric humidity profiles. On the contrary, the uncertainties of the CRTM-based TOA BTs resulting from effective particle size and optical thickness are not negligible in an optically thin cloud.

A MODEL OF OXYGEN CONDITIONS IN A SCHOOL OF FISH BASED ON EXPERIMENTAL RESPIROMETRY

DEFF Research Database (Denmark)

Steffensen, John Fleng

2010-01-01

with a logging YSI CTD from a fixed position on the net cage at a depth of one meter. The data did not show lower oxygen levels in the vicinity oflhe fish compared to a position on the edge of the pen. In the near future we hope to be able to verify the model by measuring oxygen levels in large schools...... of Atlantic herring with a ROV instrumented with cameras and a logging YSJ CTD as well as an acoustic Oxyguard oxygen transmitter....

Fluid flow and heat transfer modeling for castings

International Nuclear Information System (INIS)

Domanus, H.M.; Liu, Y.Y.; Sha, W.T.

1986-01-01

Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach. In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process. 14 refs., 13 figs

Radiative heat transfer in coal-fired furnaces and oxycoal retrofit considerations

Energy Technology Data Exchange (ETDEWEB)

Erfurth, Jens

2012-07-01

Oxycoal combustion is the combustion of coal using a mixture of oxygen and cooled recycled flue gas in place of air. In the last years it has gained interest as a means of CO{sub 2} capture from stationary point sources. In particular, under emission mitigation regimes the retrofit of existing coal-fired power plants may help avoid ''stranded assets'' through lower emissions and thus costs if certain technical criteria can be met. Among these is the need to keep total heat transfer in the boiler constant while not raising the furnace exit temperature. The altered gas composition in oxycoal combustion leads to changes in both convective and radiative heat transfer, of which the latter, while of overwhelming importance in the furnace, poses a particular challenge to modellers. This work is thus primarily concerned with the simulation of radiative heat transfer. After a short introduction to oxycoal combustion, a general discussion of Computational Fluid Dynamics (CFD) models for coal combustion is given. Emphasis is placed on the physics of molecular gas band radiation, respective modelling approaches and their application within a CFD context. Based on this analysis, it is concluded that for the purposes of this work, a non-grey CFD implementation of the Exponential Wide Band Model is most suitable. Then the results of CFD simulations of the furnace of a state-of-the-art coal-fired USC boiler with a thermal power of 1,210 MW are presented, which were carried out using the commercial software FLUENT {sup registered} 6.3, combined with some User-Defined Functions. In addition to air combustion, the cases studied include variations of the burner oxygen concentration and the mode of flue gas recycling (wet and dry), the two additional parameters that present themselves in oxycoal combustion to meet the retrofit criteria. The same burner geometry optimised for oxycoal combustion was used in all cases, while the overall boiler geometry designed for air

A first-principles study of oxygen adsorption on Ir(111) surface

Energy Technology Data Exchange (ETDEWEB)

Gao, Hengjiao, E-mail: gaohengjiao@163.com; Xiong, Yuqing, E-mail: xiongyq@hotmail.com; Liu, Xiaoli, E-mail: shantianzi@126.com; Zhao, Dongcai, E-mail: zhaodongc@163.com; Feng, Yudong, E-mail: yudong_feng@sina.com; Wang, Lanxi, E-mail: wanglanxi@live.com; Wang, Jinxiao, E-mail: coldwind716@gmail.com

2016-12-15

Highlights: • Adsorption of oxygen on Ir(111) surface was studied by density functional theory. • The most stable adsorption site was determined by adsorption energy calculation. • Adsorption of oxygen at bridge and top site on Ir surface was the most stable ones. • Interaction of O 2p and Ir 5d orbits is relatively strong and formed hybridization. - Abstract: In order to understand deposition mechanism of iridium thin film by atomic layer deposition, the adsorption of oxygen on Ir(111) surface was studied by use of density functional theory and a periodical slab model. By calculating the adsorption energy and structure of oxygen at four adsorption sites (top, bridge, fcc-hollow and hcp-hollow) on Ir(111) surface, the most stable adsorption site was determined. On this basis, the banding mechanism of O and Ir atoms was studied by density of states of oxygen and iridium atoms. Oxygen adsorbed at hcp(parallel) site on Ir(111) surface was the most stable one according to the adsorption energy calculation results. Orbital charge analysis indicate that charge transferred from 5p and 5d orbit to 2p orbit of adsorbed O atoms, and 6s orbit of iridium atoms. Meanwhile, density of state study indicated that adsorption of oxygen on Ir(111) surface is mainly due to the interaction between 2p orbit of O atoms and 5d orbit of iridium atoms.

Diffusion of oxygen through cork stopper: is it a Knudsen or a Fickian mechanism?

Science.gov (United States)

Lagorce-Tachon, Aurélie; Karbowiak, Thomas; Simon, Jean-Marc; Gougeon, Régis; Bellat, Jean-Pierre

2014-09-17

The aim of this work is to identify which law governs oxygen transfer through cork: Knudsen or Fickian mechanism. This is important to better understand wine oxidation during post-bottling aging. Oxygen transfer through cork wafers is measured at 298 K using a manometric permeation technique. Depending on the mechanism, we can extract the transport coefficients. Increasing the initial pressure of oxygen from 50 to 800 hPa leads to a change in the values of the transport coefficients. This implies that oxygen transport through cork does not obey the Knudsen law. From these results, we conclude that the limiting step of oxygen transport through cork occurs in the cell wall following Fickian law. From the diffusion dependence's coefficients with pressure, we also extract by applying transition state theory an apparent activation volume of 45 ± 4 nm(3). This high value indicates that oxygen molecules also diffuse from one site to another by passing through a gas phase.

No oxygen isotope exchange between water and APS-sulfate at surface temperature: Evidence from quantum chemical modeling and triple-oxygen isotope experiments

Science.gov (United States)

Kohl, Issaku E.; Asatryan, Rubik; Bao, Huiming

2012-10-01

In both laboratory experiments and natural environments where microbial dissimilatory sulfate reduction (MDSR) occurs in a closed system, the δ34S ((34S/32S)sample/(34S/32S)standard - 1) for dissolved SO42- has been found to follow a typical Rayleigh-Distillation path. In contrast, the corresponding δ18O ((18O/16O)sample/(18O/16O)standard) - 1) is seen to plateau with an apparent enrichment of between 23‰ and 29‰ relative to that of ambient water under surface conditions. This apparent steady-state in the observed difference between δ18O and δ18OO can be attributed to any of these three steps: (1) the formation of adenosine-5'-phosphosulfate (APS) from ATP and SO42-, (2) oxygen exchange between sulfite (or other downstream sulfoxy-anions) and water later in the MDSR reaction chain and its back reaction to APS and sulfate, and (3) the re-oxidation of produced H2S or precursor sulfoxy-anions to sulfate in environments containing Fe(III) or O2. This study examines the first step as a potential pathway for water oxygen incorporation into sulfate. We examined the structures and process of APS formation using B3LYP/6-31G(d,p) hybrid density functional theory, implemented in the Gaussian-03 program suite, to predict the potential for oxygen exchange. We conducted a set of in vitro, enzyme-catalyzed, APS formation experiments (with no further reduction to sulfite) to determine the degree of oxygen isotope exchange between the APS-sulfate and water. Triple-oxygen-isotope labeled water was used in the reactor solutions to monitor oxygen isotope exchange between water and APS sulfate. The formation and hydrolysis of APS were identified as potential steps for oxygen exchange with water to occur. Quantum chemical modeling indicates that the combination of sulfate with ATP has effects on bond strength and symmetry of the sulfate. However, these small effects impart little influence on the integrity of the SO42- tetrahedron due to the high activation energy required for

A Summary of Interfacial Heat Transfer Models and Correlations

Energy Technology Data Exchange (ETDEWEB)

Bae, Sung Won; Cho, Hyung Kyu; Lee, Young Jin; Kim, Hee Chul; Jung, Young Jong; Kim, K. D. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2007-10-15

A long term project has been launched in October 2006 to develop a plant safety analysis code. 5 organizations are joining together for the harmonious coworking to build up the code. In this project, KAERI takes the charge of the building up the physical models and correlations about the transport phenomena. The momentum and energy transfer terms as well as the mass are surveyed from the RELAP5/MOD3, RELAP5-3D, CATHARE, and TRAC-M does. Also the recent papers are surveyed. Among these resources, most of the CATHARE models are based on their own experiment and test results. Thus, the CATHARE models are only used as the comparison purposes. In this paper, a summary of the models and the correlations about the interfacial heat transfer are represented. These surveyed models and correlations will be tested numerically and one correlation is selected finally.

Evaluation of empirical heat transfer models using TFG heat flux sensors

International Nuclear Information System (INIS)

De Cuyper, T.; Broekaert, S.; Chana, K.; De Paepe, M.; Verhelst, S.

2017-01-01

Thermodynamic engine cycle models are used to support the development of the internal combustion engine (ICE) in a cost and time effective manner. The sub model which describes the in-cylinder heat transfer from the working gases to the combustion chamber walls plays an important role in the accuracy of these simulation tools. The heat transfer affects the power output, engine efficiency and emissions of the engine. The most common heat transfer models in engine research are the models of Annand and Woschni. These models provide an instantaneous spatial averaged heat flux. In this research, prototype thin film gauge (TFG) heat flux sensors are used to capture the transient in-cylinder heat flux behavior within a production spark ignition (SI) engine as they are small, robust and able to capture the highly transient temperature swings. An inlet valve and two different zones of the cylinder head are instrumented with multiple TFG sensors. The heat flux traces are used to calculate the convection coefficient which includes all information of the convective heat transfer phenomena inside the combustion chamber. The implementation of TFG sensors inside the combustion chamber and the signal processing technique are discussed. The heat transfer measurements are used to analyze the spatial variation in heat flux under motored and fired operation. Spatial variation in peak heat flux was observed even under motored operation. Under fired operation the observed spatial variation is mainly driven by the flame propagation. Next, the paper evaluates the models of Annand and Woschni. These models fail to predict the total heat loss even with calibration of the models coefficients using a reference motored operating condition. The effect of engine speed and inlet pressure is analyzed under motored operation after calibration of the models. The models are able to predict the trend in peak heat flux value for a varying engine speed and inlet pressure. Next, the accuracy of the

Modelling Fungal Fermentations for Enzyme Production

DEFF Research Database (Denmark)

Albæk, Mads Orla; Gernaey, Krist; Hansen, Morten S.

We have developed a process model of fungal fed-batch fermentations for enzyme production. In these processes, oxygen transfer rate is limiting and controls the substrate feeding rate. The model has been shown to describe cultivations of both Aspergillus oryzae and Trichoderma reesei strains in 550......L stirred tank pilot plant reactors well. For each strain, 8 biological parameters are needed as well as a correlation of viscosity, as viscosity has a major influence on oxygen transfer. The parameters were measured averages of at least 9 batches for each strain. The model is successfully able...... to cover a wide range of process conditions (0.3-2 vvm of aeration, 0.2-10.0 kW/m3 of specific agitation power input, and 0.1-1.3 barg head space pressure). Uncertainty and sensitivity analysis have shown that the uncertainty of the model is mainly due to difficulties surrounding the estimation...

Experimental Waterflow Determination of the Dynamic Hydraulic Transfer Function for the J-2X Oxidizer Turbopump. Part Two; Results and Interpretation

Science.gov (United States)

Zoladz, Tom; Patel, Sandeep; Lee, Erik; Karon, Dave

2011-01-01

Experimental results describing the hydraulic dynamic pump transfer matrix (Yp) for a cavitating J-2X oxidizer turbopump inducer+impeller tested in subscale waterflow are presented. The transfer function is required for integrated vehicle pogo stability analysis as well as optimization of local inducer pumping stability. Dynamic transfer functions across widely varying pump hydrodynamic inlet conditions are extracted from measured data in conjunction with 1D-model based corrections. Derived Dynamic transfer functions are initially interpreted relative to traditional Pogo pump equations. Water-to-liquid oxygen scaling of measured cavitation characteristics are discussed. Comparison of key dynamic transfer matrix terms derived from waterflow testing are made with those implemented in preliminary Ares Upper Stage Pogo stability modeling. Alternate cavitating pump hydraulic dynamic equations are suggested which better reflect frequency dependencies of measured transfer matrices.

Heat Transfer Modeling and Validation for Optically Thick Alumina Fibrous Insulation

Science.gov (United States)

Daryabeigi, Kamran

2009-01-01

Combined radiation/conduction heat transfer through unbonded alumina fibrous insulation was modeled using the diffusion approximation for modeling the radiation component of heat transfer in the optically thick insulation. The validity of the heat transfer model was investigated by comparison to previously reported experimental effective thermal conductivity data over the insulation density range of 24 to 96 kg/cu m, with a pressure range of 0.001 to 750 torr (0.1 to 101.3 x 10(exp 3) Pa), and test sample hot side temperature range of 530 to 1360 K. The model was further validated by comparison to thermal conductivity measurements using the transient step heating technique on an insulation sample at a density of 144 kg/cu m over a pressure range of 0.001 to 760 torr, and temperature range of 290 to 1090 K.

Kinetics of oxygen species in an electrically driven singlet oxygen generator

Science.gov (United States)

Azyazov, V. N.; Torbin, A. P.; Pershin, A. A.; Mikheyev, P. A.; Heaven, M. C.

2015-12-01

The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O3(υ) formed in O + O2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O2(a1Δ), oxygen atom removal and ozone formation. It is shown that the process O3(υ ⩾ 2) + O2(a1Δ) → 2O2 + O is the main O2(a1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O2(a1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

Interrogation of metabolic and oxygen states of tumors with fiber-based luminescence lifetime spectroscopy.

Science.gov (United States)

Lukina, Maria; Orlova, Anna; Shirmanova, Marina; Shirokov, Daniil; Pavlikov, Anton; Neubauer, Antje; Studier, Hauke; Becker, Wolfgang; Zagaynova, Elena; Yoshihara, Toshitada; Tobita, Seiji; Shcheslavskiy, Vladislav

2017-02-15

The study of metabolic and oxygen states of cells in a tumor in vivo is crucial for understanding of the mechanisms responsible for tumor development and provides background for the relevant tumor's treatment. Here, we show that a specially designed implantable fiber-optic probe provides a promising tool for optical interrogation of metabolic and oxygen states of a tumor in vivo. In our experiments, the excitation light from a ps diode laser source is delivered to the sample through an exchangeable tip via a multimode fiber, and the emission light is transferred to the detector by another multimode fiber. Fluorescence lifetime of a nicotinamid adenine dinucleotide (NAD(P)H) and phosphorescence lifetime of an oxygen sensor based on an iridium (III) complex of enzothienylpyridine (BTPDM1) are explored both in model experiment in solutions and in living mice.

Heat transfer modelling in thermophotovoltaic cavities using glass media

Energy Technology Data Exchange (ETDEWEB)

Bauer, T.; Forbes, I.; Penlington, R.; Pearsall, N. [Northumbria University, Newcastle upon Tyne (United Kingdom). School of Engineering and Technology

2005-08-15

Optimisation of heat transfer, and in particular radiative heat transfer in terms of the spectral, angular and spatial radiation distributions, is required to achieve high efficiencies and high electrical power densities for thermophotovoltaic (TPV) conversion. This work examines heat transfer from the radiator to the PV cell in an infinite plate arrangement using three different arrangements of participating dielectric media. The modelling applies the Discrete Ordinates method and assumes fused silica (quartz glass) as the dielectric medium. The arrangement radiator-glass-PV cell (also termed dielectric photon concentration) was found to be superior in terms of efficiency and power density. (author)

Oxygen Effects in Anaerobic Digestion

Directory of Open Access Journals (Sweden)

Deshai Botheju

2009-10-01

Full Text Available Interaction of free oxygen in bio-gasification is a sparsely studied area, apart from the common argument of oxygen being toxic and inhibitory for anaerobic micro-cultures. Some studies have, however, revealed increased solubilisation of organic matter in the presence of some free oxygen in anaerobic digestion. This article analyses these counterbalancing phenomena with a mathematical modelling approach using the widely accepted biochemical model ADM 1. Aerobic oxidation of soluble carbon and inhibition of obligatory anaerobic organisms are modelled using standard saturation type kinetics. Biomass dependent first order hydrolysis kinetics is used to relate the increased hydrolysis rate with oxygen induced increase in biomass growth. The amended model, ADM 1-Ox (oxygen, has 25 state variables and 22 biochemical processes, presented in matrix form. The computer aided simulation tool AQUASIM 2.1 is used to simulate the developed model. Simulation predictions are evaluated against experimental data obtained using a laboratory batch test array comprising miniature anaerobic bio-reactors of 100 ml total volume each, operated under different initial air headspaces giving rise to the different oxygen loading conditions. The reactors were initially fed with a glucose solution and incubated at 35 Celsius, for 563 hours. Under the oxygen load conditions of 22, 44 and 88 mg/L, the ADM1-Ox model simulations predicted the experimental methane potentials quite adequately. Both the experimental data and the simulations suggest a linear reduction of methane potential with respect to the increase in oxygen load within this range.

SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

International Nuclear Information System (INIS)

Coryell, E.W.; Siefken, L.J.; Paik, S.

1998-01-01

Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and non-porous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of non-porous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. A design is also described for implementing a model of heat transfer by radiation from debris to the interstitial fluid. A design is described for implementation of models for flow losses and interphase drag in porous debris. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region

The third RAdiation transfer Model Intercomparison (RAMI) exercise: Documenting progress in canopy reflectance models

NARCIS (Netherlands)

Widlowski, J.L.; Taberner, M.; Pinty, B.; Bruniquel-Pinel, V.; Disney, M.I.; Fernandes, R.; Gastellu-Etchegorry, J.P.; Gobron, N.; Kuusk, A.; Lavergne, T.; LeBlanc, S.; Lewis, P.E.; Martin, E.; Mõttus, M.; North, P.R.J.; Qin, W.; Robustelli, M.; Rochdi, N.; Ruiloba, R.; Thompson, R.; Verhoef, W.; Verstraete, M.M.; Xie, D.

2007-01-01

[1] The Radiation Transfer Model Intercomparison ( RAMI) initiative benchmarks canopy reflectance models under well-controlled experimental conditions. Launched for the first time in 1999, this triennial community exercise encourages the systematic evaluation of canopy reflectance models on a

FARMLAND: model for transfer of radionuclides through terrestrial foodchains

International Nuclear Information System (INIS)

Brown, John

1995-01-01

Models to stimulate the transfer of radionuclides through terrestrial foodchains have been developed at the Board and regularly used over the last 20 years. The foodchain model is named FARMLAND (Food Activity from Radionuclide Movement on LAND) and it contains a suite of submodels, each of which simulates radionuclide transfer through a different part of the foodchain. These models can be combined in various orders so that they can be used for different situations of radiological interest. The main foods considered are: green vegetables; grain products; root vegetables; fruit; milk, meat and offal from cattle; meat and offal from sheep. A large variety of elements can be considered, although the degree of complexity with which some are modelled is greater than that for others; isotopes of caesium, strontium and iodine are treated in greatest detail. (Author)

Modelling mass and heat transfer in nano-based cancer hyperthermia.

Science.gov (United States)

Nabil, M; Decuzzi, P; Zunino, P

2015-10-01

We derive a sophisticated mathematical model for coupled heat and mass transport in the tumour microenvironment and we apply it to study nanoparticle delivery and hyperthermic treatment of cancer. The model has the unique ability of combining the following features: (i) realistic vasculature; (ii) coupled capillary and interstitial flow; (iii) coupled capillary and interstitial mass transfer applied to nanoparticles; and (iv) coupled capillary and interstitial heat transfer, which are the fundamental mechanisms governing nano-based hyperthermic treatment. This is an improvement with respect to previous modelling approaches, where the effect of blood perfusion on heat transfer is modelled in a spatially averaged form. We analyse the time evolution and the spatial distribution of particles and temperature in a tumour mass treated with superparamagnetic nanoparticles excited by an alternating magnetic field. By means of numerical experiments, we synthesize scaling laws that illustrate how nano-based hyperthermia depends on tumour size and vascularity. In particular, we identify two distinct mechanisms that regulate the distribution of particle and temperature, which are characterized by perfusion and diffusion, respectively.

Modeling of Heat Transfer in Rooms in the Modelica "Buildings" Library

Energy Technology Data Exchange (ETDEWEB)

Wetter, Michael [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zuo, Wangda [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nouidui, Thierry Stephane [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2011-11-01

This paper describes the implementation of the room heat transfer model in the free open-source Modelica \\Buildings" library. The model can be used as a single room or to compose a multizone building model. We discuss how the model is decomposed into submodels for the individual heat transfer phenomena. We also discuss the main physical assumptions. The room model can be parameterized to use different modeling assumptions, leading to linear or non-linear differential algebraic systems of equations. We present numerical experiments that show how these assumptions affect computing time and accuracy for selected cases of the ANSI/ASHRAE Standard 140- 2007 envelop validation tests.

The improvement of the heat transfer model for sodium-water reaction jet code

International Nuclear Information System (INIS)

Hashiguchi, Yoshirou; Yamamoto, Hajime; Kamoshida, Norio; Murata, Shuuichi

2001-02-01

For confirming the reasonable DBL (Design Base Leak) on steam generator (SG), it is necessary to evaluate phenomena of sodium-water reaction (SWR) in an actual steam generator realistically. The improvement of a heat transfer model on sodium-water reaction (SWR) jet code (LEAP-JET ver.1.40) and application analysis to the water injection tests for confirmation of propriety for the code were performed. On the improvement of the code, the heat transfer model between a inside fluid and a tube wall was introduced instead of the prior model which was heat capacity model including both heat capacity of the tube wall and inside fluid. And it was considered that the fluid of inside the heat exchange tube was able to treat as water or sodium and typical heat transfer equations used in SG design were also introduced in the new heat transfer model. Further additional work was carried out in order to improve the stability of the calculation for long calculation time. The test calculation using the improved code (LEAP-JET ver.1.50) were carried out with conditions of the SWAT-IR·Run-HT-2 test. It was confirmed that the SWR jet behavior on the result and the influence to the result of the heat transfer model were reasonable. And also on the improved code (LEAP-JET ver.1.50), user's manual was revised with additional I/O manual and explanation of the heat transfer model and new variable name. (author)

TURBULENT OXYGEN FLAMES IN TYPE Ia SUPERNOVAE

International Nuclear Information System (INIS)

Aspden, A. J.; Bell, J. B.; Woosley, S. E.

2011-01-01

In previous studies, we examined turbulence-flame interactions in carbon-burning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damkoehler numbers (Da 16 ) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when Da 16 16 >1, turbulence enhances heat transfer and drives the propagation of a flame that is narrower than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen turbulent flame with complex compound structure. The simulations do not appear to support the possibility of a transition to detonation in the oxygen flame, but do not preclude it either.

A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers

NARCIS (Netherlands)

de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries

2014-01-01

A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic

Social Support and Motivation to Transfer as Predictors of Training Transfer: Testing Full and Partial Mediation Using Meta-Analytic Structural Equation Modelling

Science.gov (United States)

Reinhold, Sarah; Gegenfurtner, Andreas; Lewalter, Doris

2018-01-01

Social support and motivation to transfer are important components in conceptual models on transfer of training. Previous research indicates that both support and motivation influence transfer. To date, however, it is not yet clear if social support influences transfer of training directly, or if this influence is mediated by motivation to…

Modelling heat transfer during flow through a random packed bed of spheres

Science.gov (United States)

Burström, Per E. C.; Frishfelds, Vilnis; Ljung, Anna-Lena; Lundström, T. Staffan; Marjavaara, B. Daniel

2018-04-01

Heat transfer in a random packed bed of monosized iron ore pellets is modelled with both a discrete three-dimensional system of spheres and a continuous Computational Fluid Dynamics (CFD) model. Results show a good agreement between the two models for average values over a cross section of the bed for an even temperature profiles at the inlet. The advantage with the discrete model is that it captures local effects such as decreased heat transfer in sections with low speed. The disadvantage is that it is computationally heavy for larger systems of pellets. If averaged values are sufficient, the CFD model is an attractive alternative that is easy to couple to the physics up- and downstream the packed bed. The good agreement between the discrete and continuous model furthermore indicates that the discrete model may be used also on non-Stokian flow in the transitional region between laminar and turbulent flow, as turbulent effects show little influence of the overall heat transfer rates in the continuous model.

Modelling radiative heat transfer inside a basin type solar still

International Nuclear Information System (INIS)

Madhlopa, A.

2014-01-01

Radiative heat transfer inside a basin type solar still has been investigated using two models with (model 1) and without (model 2) taking into account optical view factors. The coefficient of radiative heat exchange (h r,w-gc ) between the water and cover surfaces of a practical solar still was computed using the two models. Simulation results show that model 1 yields lower values of h r,w-gc and the root mean square error than model 2. It is therefore concluded that the accuracy of modelling the performance of a basin-type solar still can be improved by incorporating view factors. - Highlights: • Radiative heat transfer in a basin type solar still has been investigated. • Two models with and without view factors were used. • The model with view factors exhibits a lower magnitude of root mean square error. • View factors affect the accuracy of modelling the performance of the solar still

cis-Stilbene and (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)benzene as mechanistic probes in the Mn(III)(salen)-catalyzed epoxidation: influence of the oxygen source and the counterion on the diastereoselectivity of the competitive concerted and radical-type oxygen transfer.

Science.gov (United States)

Adam, Waldemar; Roschmann, Konrad J; Saha-Möller, Chantu R; Seebach, Dieter

2002-05-08

cis-Stilbene (1) has been epoxidized by a set of diverse oxygen donors [OxD], catalyzed by the Mn(III)(salen)X complexes 3 (X = Cl, PF(6)), to afford a mixture of cis- and trans-epoxides 2. The cis/trans ratios range from 29:71 (extensive isomerization) to 92:8, which depends both on the oxygen source [OxD] and on the counterion X of the catalyst. When (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)-benzene (4) is used as substrate, a mechanistic probe which differentiates between radical and cationic intermediates, no cationic ring-opening products are found in this epoxidation reaction; thus, isomerized epoxide product arises from intermediary radicals. The dependence of the diastereoselectivity on the oxygen source is rationalized in terms of a bifurcation step in the catalytic cycle, in which concerted Lewis-acid-activated oxygen transfer competes with stepwise epoxidation by the established Mn(V)(oxo) species. The experimental counterion effect is attributed to the computationally assessed ligand-dependent reaction profiles and stereoselectivities of the singlet, triplet, and quintet spin states available to the manganese species.

Lattice Boltzmann heat transfer model for permeable voxels

Science.gov (United States)

Pereira, Gerald G.; Wu, Bisheng; Ahmed, Shakil

2017-12-01

We develop a gray-scale lattice Boltzmann (LB) model to study fluid flow combined with heat transfer for flow through porous media where voxels may be partially solid (or void). Heat transfer in rocks may lead to deformation, which in turn can modulate the fluid flow and so has significant contribution to rock permeability. The LB temperature field is compared to a finite difference solution of the continuum partial differential equations for fluid flow in a channel. Excellent quantitative agreement is found for both Poiseuille channel flow and Brinkman flow. The LB model is then applied to sample porous media such as packed beds and also more realistic sandstone rock sample, and both the convective and diffusive regimes are recovered when varying the thermal diffusivity. It is found that while the rock permeability can be comparatively small (order milli-Darcy), the temperature field can show significant variation depending on the thermal convection of the fluid. This LB method has significant advantages over other numerical methods such as finite and boundary element methods in dealing with coupled fluid flow and heat transfer in rocks which have irregular and nonsmooth pore spaces.

Measurement and modeling of interface heat transfer coefficients

International Nuclear Information System (INIS)

Rollett, A.D.; Lewis, H.D.; Dunn, P.S.

1985-01-01

The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m 2 /K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, epsilon = 0.2, of the solidified metal

Influence of methanol/sorbitol co-feeding rate on pAOX1 induction in a Pichia pastoris Mut+ strain in bioreactor with limited oxygen transfer rate.

Science.gov (United States)

Carly, F; Niu, H; Delvigne, F; Fickers, P

2016-04-01

High Pichia pastoris biomass density could be obtained using high co-feeding rate of methanol and sorbitol in a fed-batch or continuous culture, while further higher feeding rate finally leads to oxygen limitation in bioreactor. In the literature, there is lack of report about AOX1 promoter regulation with regard to dissolved oxygen level (DO). Therefore, in this work, chemostat cultures were performed to investigate the cell growth, metabolism and regulation of the AOX1 promoter (pAOX1) regarding co-feeding rate of optimized methanol/sorbitol mixture (methanol fraction 0.60 C-mol/C-mol) using a P. pastoris Mut+/pAOX1-lacZ strain. The oxygen transfer rates (OTR) in bioreactor were kept in the range of typical values of large bioreactor, i.e., 4-8 g/(L h) if DO equals 30 % saturation or 5-10 g/(L h) if DO nears zero. For DO >0, an increase of the carbon fed led to an increase of pAOX1 induction. By contrast, when dissolved oxygen was completely depleted, methanol accumulated, causing a 30 % decrease of pAOX1 induction. However, this decrease is more likely to be lined to methanol accumulation than to low level of dissolved oxygen (sorbitol co-feeding allowed cells to adapt to oxygen transient limitations that often occur at industrial scale with reduced effect on pAOX1 induction. The optimal feeding rate tested here was 6.6 mmol C (DCW h)(-1) at an OTR of 8.28 g O2(L h)(-1) with over fivefold pAOX1 induction (probably directly associated with target protein productivity) compared with previous work.

Influence of dissolved oxygen on the nitrification kinetics in a circulating bed biofilm reactor

Energy Technology Data Exchange (ETDEWEB)

Nogueira, R.; Melo, L.F. [University of Minho, Braga (Portugal). Dept. Bioengineering; Lazarova, V.; Manem, J. [Centre of International Research for Water and Environment (CIRSEE), Lyonnaise des Eaux, Le Pecq (France)

1998-12-01

The influence of dissolved oxygen concentration on the nitrification kinetics was studied in the circulating bed reactor (CBR). The study was partly performed at laboratory scale with synthetic water, and partly at pilot scale with secondary effluent as feed water. The nitrification kinetics of the laboratory CBR as a function of the oxygen concentration can be described according to the half order and zero order rate equations of the diffusion-reaction model applied to porous catalysts. When oxygen was the rate limiting substrate, the nitrification rate was close to a half order function of the oxygen concentration. The average oxygen diffusion coefficient estimated by fitting the diffusion-reaction model to the experimental results was around 66% of the respective value in water. The experimental results showed that either the ammonia or the oxygen concentration could be limiting for the nitrification kinetics. The latter occurred for an oxygen to ammonia concentration ratio below 1.5-2 gO{sub 2}/gN-NH{sub 4}{sup +} for both laboratory and pilot scale reactors. The volumetric oxygen mass transfer coefficient (k{sub L}a) determined in the laboratory scale reactor was 0.017 s{sup -1} for a superficial air velocity of 0.02 m s{sup -1}, and the one determined in the pilot scale reactor was 0.040 s{sup -1} for a superficial air velocity of 0.031 m s{sup -1}. The k{sub L}a for the pilot scale reactor did not change significantly after biofilm development, compared to the value measured without biofilm. (orig.) With 7 figs., 5 tabs., 24 refs.

Fuel element transfer cask modelling using MCNP technique

International Nuclear Information System (INIS)

Rosli Darmawan

2009-01-01

Full text: After operating for more than 25 years, some of the Reaktor TRIGA PUSPATI (RTP) fuel elements would have been depleted. A few addition and fuel reconfiguration exercises have to be conducted in order to maintain RTP capacity. Presently, RTP spent fuels are stored at the storage area inside RTP tank. The need to transfer the fuel element outside of RTP tank may be prevalence in the near future. The preparation shall be started from now. A fuel element transfer cask has been designed according to the recommendation by the fuel manufacturer and experience of other countries. A modelling using MCNP code has been conducted to analyse the design. The result shows that the design of transfer cask fuel element is safe for handling outside the RTP tank according to recent regulatory requirement. (author)

Fuel Element Transfer Cask Modelling Using MCNP Technique

International Nuclear Information System (INIS)

Darmawan, Rosli; Topah, Budiman Naim

2010-01-01

After operating for more than 25 years, some of the Reaktor TRIGA Puspati (RTP) fuel elements would have been depleted. A few addition and fuel reconfiguration exercises have to be conducted in order to maintain RTP capacity. Presently, RTP spent fuels are stored at the storage area inside RTP tank. The need to transfer the fuel element outside of RTP tank may be prevalence in the near future. The preparation shall be started from now. A fuel element transfer cask has been designed according to the recommendation by the fuel manufacturer and experience of other countries. A modelling using MCNP code has been conducted to analyse the design. The result shows that the design of transfer cask fuel element is safe for handling outside the RTP tank according to recent regulatory requirement.

Determination of oxygen content in steel using activation analysis with 14 MeV neutron

International Nuclear Information System (INIS)

Calado, C.E.

1978-01-01

In the quantitative analysis of oxygen in steel by fast neutron activation analysis the oxygen content is evaluated from the measured activity of 16 N produced. Steel s mples are irradiated in 14 MeV neutron flux. After irradiation the samples are pneumatically transfered to the counting terminal where activity is measured. Oxygen concentrations, are obtained by comparison with standards of specified oxygen content [pt

Dynamic modeling system for the transfer of radioactivity in terrestrial food chains

International Nuclear Information System (INIS)

Simmonds, J.R.; Linsley, G.S.

1981-01-01

A dynamic modeling system is described for the transfer of radionuclides in terrestrial food chains. The main features of the system are its ability to predict the time dependence of the major transfer processes and its flexibility and applicability to a range of contamination scenarios. The modeling system is regarded as a basic framework on which more realistic models can be based, given the availability of reliable environmental transfer data. An example of such a development is included for 90 Sr in the pasture-cow-milk pathway. The model predicts annual average concentrations of 90 Sr in milk caused by fallout in the United Kingdom to within 15% of measured values for over most of the 20-y period for which data exist. It makes possible the evaluation of the time dependence of the contributions of various transfer processes. Following acute releases to the atmosphere or releases in any other contamination scenario where direct deposition is absent, certain pathways often not considered in food-chain models, such as the external contamination of plants caused by resuspension processes or the ingestion of contaminants together with soil by grazing animals, are shown to be potentially important in the transfer of activity to man. The main application of dynamic food-chain models is the prediction of the consequences of accidental releases to the terrestrial environment. The predictions can be used in planning countermeasures and in assessing the health, economic, and social impacts of accidental release

One-neutron transfer reaction: a toy model in one dimension

International Nuclear Information System (INIS)

G. Galilei, Padova, Italy INFN, Sezione di Padova, Padova (Italy))" data-affiliation=" (Dipartimento di Fisica e Astronomia G. Galilei, Padova, Italy INFN, Sezione di Padova, Padova (Italy))" >Moschini, L

2014-01-01

A simple 1D toy model to study one-neutron transfer reactions is developed. It is based on the solution of the time dependent Schroedinger equation for a particle initially bound by a fixed potential well, perturbed by a second moving potential, which accounts for the second partner of the reaction. At the end of the time evolution it is possible to evaluate the probability of the transfer of the particle from a potential to the other, as well as the transfer to continuum states in the case of weakly-bound systems. Although rather simple, the model accounts for most of the physical characteristics of these kind of reactions: such as the existence of an optimum Q-value and the dependence on the parameters defining the relative motion of the two potentials

A high-resolution non-invasive approach to quantify oxygen transport across the capillary fringe and within the underlying groundwater.

Science.gov (United States)

Haberer, Christina M; Rolle, Massimo; Liu, Sanheng; Cirpka, Olaf A; Grathwohl, Peter

2011-03-25

Oxygen transport across the capillary fringe is relevant for many biogeochemical processes. We present a non-invasive technique, based on optode technology, to measure high-resolution concentration profiles of oxygen across the unsaturated/saturated interface. By conducting a series of quasi two-dimensional flow-through laboratory experiments, we show that vertical hydrodynamic dispersion in the water-saturated part of the capillary fringe is the process limiting the mass transfer of oxygen. A number of experimental conditions were tested in order to investigate the influence of grain size and horizontal flow velocity on transverse vertical dispersion in the capillary fringe. In the same setup, analogous experiments were simultaneously carried out in the fully water-saturated zone, therefore allowing a direct comparison with oxygen transfer across the capillary fringe. The outcomes of the experiments under various conditions show that oxygen transport in the two zones of interest (i.e., the unsaturated/saturated interface and the saturated zone) is characterized by very similar transverse dispersion coefficients. An influence of the capillary fringe morphology on oxygen transport has not been observed. These results may be explained by the narrow grain size distribution used in the experiments, leading to a steep decline in water saturation at the unsaturated/saturated interface and to the absence of trapped gas in this transition zone. We also modeled flow (applying the van Genuchten and the Brooks-Corey relationships) and two-dimensional transport across the capillary fringe, obtaining simulated profiles of equivalent aqueous oxygen concentration that were in good agreement with the observations. Copyright © 2010 Elsevier B.V. All rights reserved.

New flow boiling heat transfer model for hydrocarbons evaporating inside horizontal tubes

International Nuclear Information System (INIS)

Chen, G. F.; Gong, M. Q.; Wu, J. F.; Zou, X.; Wang, S.

2014-01-01

Hydrocarbons have high thermodynamic performances, belong to the group of natural refrigerants, and they are the main components in mixture Joule-Thomson low temperature refrigerators (MJTR). New evaluations of nucleate boiling contribution and nucleate boiling suppression factor in flow boiling heat transfer have been proposed for hydrocarbons. A forced convection heat transfer enhancement factor correlation incorporating liquid velocity has also been proposed. In addition, the comparisons of the new model and other classic models were made to evaluate its accuracy in heat transfer prediction

CFD modelling wall heat transfer inside a combustion chamber using ANSYS forte

Science.gov (United States)

Plengsa-ard, C.; Kaewbumrung, M.

2018-01-01

A computational model has been performed to analyze a wall heat transfer in a single cylinder, direct injection and four-stroke diesel engine. A direct integration using detailed chemistry CHEMKIN is employed in a combustion model and the Reynolds Averaged Navier Stokes (RANS) turbulence model is used to simulate the flow in the cylinder. To obtain heat flux results, a modified classical variable-density wall heat transfer model is also performed. The model is validated using experimental data from a CUMMINs engine operated with a conventional diesel combustion. One operating engine condition is simulated. Comparisons of simulated in-cylinder pressure and heat release rates with experimental data shows that the model predicts the cylinder pressure and heat release rates reasonably well. The contour plot of instantaneous temperature are presented. Also, the contours of predicted heat flux results are shown. The magnitude of peak heat fluxes as predicted by the wall heat transfer model is in the range of the typical measure values in diesel combustion.

Fast kinetics of the oxygen effect in irradiated mammalian cells

International Nuclear Information System (INIS)

Watts, M.E.; Maughan, R.L.; Michael, B.D.

1978-01-01

A technique using a fast gas transfer with a single pulse of electrons (the gas-explosion technique) has been used to investigate the time-dependence of the dose-modifying action of oxygen in irradiated V79 Chinese hamster cells. Oxygen did not significantly alter the shapes of the survival curves. The dose-modifying factor between the fully oxic and fully hypoxic (oxygen at 9000 ms) curve was 2.6. The dose-modifying factor for the survival curve drawn for oxygen contact at 0.3 ms after irradiation was 1.5 relative to the hypoxic curve. The duration of the post-effect (oxygen contact after irradiation) indicated that oxygen-dependent damage has a lifetime extending into the ms time-range. In the pre-effect time region (oxygen contact before irradiation) 1 to 2 ms oxygen contact was required to achieve the full sensitization. The results are discussed with reference to the diffusion time for oxygen to reach the sensitive site within the cell. (U.K.)

SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris