Oxygen Transport Rate Research Articles

Binary Li/Na tungstates modified Mg6MnO8 as redox catalysts for enhanced performance of chemical looping oxidative dehydrogenation of ethane

The present investigation delves into the utilization of Mg6MnO8 modified with binary Li2WO4 and Na2WO4 tungstates as oxygen carriers for the chemical looping oxidative dehydrogenation (CL-ODH) of ethane. The Mg6MnO8-LiNaW2 oxygen carrier demonstrates remarkable performance, achieving up to 77.7 % ethane conversion, 86.5 % ethylene selectivity, and 67.2 % ethylene yield. HRTEM-EDS reveals the formation of a molten binary tungstates layer covering the solid Mg6MnO8 substrate. The molten binary tungstates layer effectively modulates the release of lattice oxygen in a step-wise manner during ODH reactions. XPS analysis reveals that the doping of Li/Na binary tungstates inhibits the formation of OH−/CO32− and Mn4+ species, thus preventing the deep oxidation of ethylene. The Mg6MnO8-LiNaW2 sample maintains stable reactivity and surface morphology throughout 20 redox cycles. DFT calculations further indicate that the modification with Li/Na binary tungstates promotes electron accumulation around the local environment of the Me-O bond, thereby reducing the formation energy (Eo) of oxygen vacancy in Mg6MnO8 and improving the oxygen vacancy concentration within the bulk of the oxygen carriers. The superior ethylene selectivity of the Mg6MnO8-LiNaW2 oxygen carrier can be attributed to the higher oxygen diffusion capability in the bulk of the Mg6MnO8 core, coupled with the lower oxygen transport rate through the molten tungstates layer.

Oxidation of silicon particles suspended in a mullite matrix with dual-mode vacancy diffusion of oxygen

Mullite bond coats filled with silicon particles have recently been proposed for the next generation of environmental barrier coatings (EBC). The sacrificial oxidation of the silicon particles eliminates some of the environmental durability issues associated with traditional EBC designs. To investigate this novel design approach, a mathematical formulation and resulting numerical method have been developed for simulating the oxidation of silicon particles embedded in a mullite matrix. The focus is on the oxidation of the silicon in a dry oxygen environment where the oxidant is presumably oxygen. Oxygen transport from the exterior environment through the mullite is assumed to occur via two lattice defect diffusion mechanisms. As a result, the rate of oxygen transport is dictated by the self-diffusivity of the lattice defects. The numerical method is implemented using the COMSOL Multiphysics® Program. The method is applied to simulate the oxidation of silicon particles in a mullite pellet in recent oxidation experiments. Numerical results compare favorably with the oxidation behavior observed in the oxidation experiments. The numerical method is also used to investigate the effects of various features of the mullite/silicon particle system on the oxidation behavior.

Water and Oxygen Barrier Properties of All-Cellulose Nanocomposites.

Hydroxypropyl cellulose (HPC) is potentially interesting as a biobased, rigid food packaging material, but its stiffness and strength are somewhat low, and its water and oxygen transport rates are too high. To improve these characteristics, we investigated nanocomposites of HPC and cellulose nanocrystals (CNCs). These high-aspect-ratio nanoparticles display high stiffness and strength, and their high crystallinity renders them virtually impermeable. Exchanging the counterions of sulfate-ester decorated CNCs with cetyltrimethylammonium ions affords particles that are dispersible in ethanol (CTA.CNC) and allows solvent casting of HPC/CTA.CNC nanocomposite films, which, even at a CTA.CNC content of 90 wt %, are highly transparent. The introduction of CTA.CNC considerably increases the Young's modulus (Ey) and upper tensile strength (σUTS). For example, in the nanocomposite with 90% CTA.CNC, Ey = 7.6 GPa is increased 20-fold and σUTS = 42.7 MPa is more than doubled in comparison to HPC, whereas the extensibility (1.1%) remains appreciable. Composites with a CTA.CNC content of 70 wt % or less show a lower water vapor permeability (6.4-9.2 × 10-5 g μm m-2 s-1 Pa-1) than the neat HPC (1.5 × 10-4 g μm m-2 s-1 Pa-1), whereas the oxygen permeability (5.6 × 10-7-1.3 × 10-6 cm3 μm m-2 s-1 Pa-1) is reduced by 1 order of magnitude compared to HPC (3.2 × 10-6 cm3 μm m-2 s-1 Pa-1). The biobased nanocomposites retain their mechanical integrity at a relative humidity of 75% but readily disintegrate in water.

Combustion behavior of single iron particles, Part II: A theoretical analysis based on a zero-dimensional model

Following the ignition and solid-to-liquid phase transition of a fine (on the order of 10–100µm in diameter) iron particle, the self-sustained combustion of a liquid-phase droplet of iron and its oxides takes place. The objective of the current work is to develop an interpretive and explanatory model for the liquid-phase combustion of a single fine iron particle. A zero-dimensional physicochemical model is developed assuming fast internal processes, such that the combustion rate is limited by the rate of external oxygen (O2) transport. The model considers a particle covered by a shell of liquid-phase FeO enclosing a core of liquid-phase Fe. Stefan flow and diffusion are considered for the gas-transport of O2, while the gas-transport of gas-phase Fe and FeO are calculated via diffusion only. The outward gas-phase Fe and FeO consume inward-transported O2 to stoichiometrically form hematite (Fe2O3), and the remaining oxygen that reaches the particle surface is entirely consumed to form liquid-phase FeO. The time history of simulated particle temperature shows consistent overprediction of the peak particle temperature when compared to experimental temperature measurements, indicating that the assumption of fast internal kinetics may be incorrect. The model is also unable to capture the apparent slow cooling rate observed in experiments. A further analysis is performed through a heuristic model with a calibrated reaction-rate law, where the internal diffusion of reactive Fe and O ions may become rate-limiting. The calibration of the pre-exponential factor in the Arrhenius term to match the experimental peak temperature yielded good agreement of time to peak temperature, as well as the slow cooling rate. The heuristic model considering internal diffusion predicts a plateau in peak temperature with increasing oxygen concentration. Possible uncertainties of the models, as well as future work, are discussed.

Modelling oxygen-limited and self-sustained smoldering propagation: Thermochemical treatment of food waste in an inert porous medium

Smoldering treatment is emerging as a valuable engineering tool for many processes, including food waste treatment. However, smoldering systems are currently not well-understood nor optimized. Therefore, numerical models provide invaluable insight into the process dynamics, which improves our understanding and supports the development of novel systems. These smoldering models couple heat, mass, and momentum transfer with pyrolysis and oxidation chemical reactions within porous media. While recent models have untangled many aspects of these systems, local oxygen transport rates from bulk flow to the fuel surface are still not well-resolved. In this work, local oxygen-transport equation was approximated by an analytic derivation based on the gas–solid oxygen non-equilibrium hypothesis. With the improved oxygen-transport equation, a 2D model with five-step reaction scheme for smoldering propagation of food waste in sand was developed. Kinetic parameters obtained from TG experiments were incorporated into the bed-scale smoldering propagation model. The developed model was validated with experimental data that stretched from robust to weak smoldering propagation. It was demonstrated that the developed model matches well with experiments. Furthermore, this model revealed: (i) the emergence of non-uniform gas flow in the reactor, (ii) the evolution of the kinetic- and oxygen-transport-limiting regimes, and (iii) valuable insight into the fundamental changes with smoldering robustness.

Modeling and tuning of glucose oxidase‐catalase system incorporating dissolved oxygen concentration

AbstractBACKGROUNDGluconic acid production by a glucose oxidase (GOx) and catalase (CAT) system has been proposed. However, the bioprocess optimal design and operation are limited by the lack of kinetic models of GOx involving oxygen as substrate. Herein, the GOx‐CAT system is modeled considering a continuous oxygen supply at a bioreactor lab scale. Initially, experiments and modeling for parameter estimations of and the individual enzymes were conducted. Then, experiments and modeling for the GOx‐CAT system were performed for final model tuning. Additionally, the model quality was evaluated, allowing for a deeper understanding of the system phenomenology.RESULTSFrom the oxygen transport model tuning, a highly accurate estimation was obtained (>0.98 and confidence interval <2%). The highest oxygen transport rate was obtained for the combined system Buffer‐antifoam‐GOx‐CAT that was 2.5 times larger than that obtained for DI water. Kinetic models for the individual enzymes were very accurate and the parameters were fully identifiable. For the integrated system, the gluconic acid evolution was properly predicted and there was a loss of predictive power for the oxygen model. Parameter identifiability analysis showed that and interpretability was compromised. However, the sensitivity analysis indicated that the model must not be simplified.CONCLUSIONHerein its has been demonstrated that is a complex parameter to be estimated for multi‐enzymatic systems due to its dependency on medium composition, particularly with GOx. Nonetheless, based on the acceptable model predictive power, the calculated parameters could be used for studies on the process design phase. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Going with the flow - how a stream insect, Pteronarcys californica, exploits local flows to increase oxygen availability.

For insects, life in water is challenging because oxygen supply is typically low compared with in air. Oxygen limitation may occur when oxygen levels or water flows are low or when warm temperatures stimulate metabolic demand for oxygen. A potential mechanism for mitigating oxygen shortages is behavior - moving to cooler, more oxygenated or faster flowing microhabitats. Whether stream insects can make meaningful choices, however, depends on: (i) how temperature, oxygen and flow vary at microspatial scales and (ii) the ability of insects to sense and exploit that variation. To assess the extent of microspatial variation in conditions, we measured temperature, oxygen saturation and flow velocity within riffles of two streams in Montana, USA. In the lab, we then examined preferences of nymphs of the stonefly Pteronarcys californica to experimental gradients based on field-measured values. Temperature and oxygen level varied only slightly within stream riffles. By contrast, flow velocity was highly heterogeneous, often varying by more than 125 cm s-1 within riffles and 44 cm s-1 around individual cobbles. Exploiting micro-variation in flow may thus be the most reliable option for altering rates of oxygen transport. In support of this prediction, P. californica showed little ability to exploit gradients in temperature and oxygen but readily exploited micro-variation in flow - consistently choosing higher flows when conditions were warm or hypoxic. These behaviors may help stream insects mitigate low-oxygen stress from climate change and other anthropogenic disturbances.

Iron based oxygen-carrier-aided oxy-fuel combustion of coal char: Reactivity and oxygen transfer mechanism

Adding an active oxygen carrier to the inert bed material may favor the oxygen distribution in fluidized bed (FB) combustors. This so-called method “Oxygen-carrier-aided combustion, OCAC” has been applied recently to air combustion in FB boilers, but could also be potentially interesting in oxy-fuel combustion. Here we analyze OCAC in oxy-fuel combustion by experimental determination of the reactivity of char from three coals (lignite, bituminous and anthracite coal) using three oxygen carriers (OC, analytical reagent Fe2O3, hematite, and steel slag). The tests were conducted in a micro thermo-gravimetric analyzer (micro-TGA) and the combustion kinetics was determined for the nine combinations of char and OC. Additional tests were conducted in a macro-TGA i.e., much sample in a big ceramic crucible, to evaluate the phase composition and crystal quality using X-ray diffraction (XRD) to the combustion residues collected at various degrees of carbon conversion (0.2, 0.5, and 0.8). The results show that the burnout temperature decreases with OCs as the combustion rate increases, while the ignition temperature hardly changes. The enhancement of the rate of char combustion by OCs is in the following order: steel slag < hematite < AR-Fe2O3. The lower the fuel rank, the stronger the effect of the oxygen carrier. The combustion kinetics of chars using OC has a higher activation energy and pre-exponential factor than pure char. The enlarged lattice constant of Fe2O3 measured by XRD during the char combustion indicates that the redox reactions of Fe2O3 accelerate the oxidization of char by enhancing the rate of oxygen transport to the carbon surface.

Electrode Ionomer Accelerated Stress Test Applied to High Oxygen Permeability Ionomer in Fuel Cells

Perfluorosulfonic acid (PFSA) polymer electrolytes are widely used in proton exchange membrane (PEM) fuel cell fabrication for the membrane separator and the electrode binder. The PEM serves to electrically insulate the cathode catalyst layer (CCL) from anode catalyst layer (ACL), provide proton conduction between both CCL and ACL, as well as prevent gas crossover. PFSA ionomers are also used in the CCL and ACL to mechanically bind the catalyst particles into thin-films, provide proton conduction between the PEM and catalyst surface, and produce a high proton reactant concentration at the oxygen reduction reaction catalyst. Despite their versatility to be used as a membrane and catalyst binder, the typical PFSA ionomers pose challenges due to the high oxygen transport resistance that is introduced by the thin ionomer films over the catalyst. In recent years, novel high oxygen permeability ionomers (HOPIs) have been developed as the successor to the traditional Nafion™ PFSA ionomers. Despite their remarkable results as a catalyst binder due to their increased oxygen transport rates, less is known regarding their degradation and functional lifetime. Although accelerated stress tests (ASTs) for platinum (Pt)/Pt-alloy catalysts, carbon supports, and membranes are well-established and commonly applied, there is no standard and easily implemented AST for electrode ionomers. One challenge is that membrane ASTs usually quantify the fluoride emission rate (FER) to assess chemical degradation, which is difficult to apply for electrode PFSA ionomer when also using a PFSA membrane because the FER is overwhelmed by membrane signal. In addition, changes in OCV and H2 crossover are not directly indicative of electrode ionomer degradation. Furthermore, concomitant degradation of the catalyst and support can interfere with interpreting electrode ionomer degradation. Here we present an effective and easily applied electrode ionomer chemical AST protocol that can be used to evaluate degradation in the functionality of the electrode ionomer. The approach borrows the chemical AST conditions of the chemical membrane AST’s open circuit voltage (OCV) hold and avoids excessive potential cycling to minimize catalyst and support degradation that will elicit changes in electrode properties separate from ionomer degradation. During the AST, we measure the cathode’s proton conduction resistance, oxygen permeability, and electrochemically surface area (ECSA) to evaluate the degradation of the ionomer’s functionality. Thus, this protocol can be used to assess if more complex and time consuming analyses of ionomer durability are needed as new chemistries emerge. Here we present results of this AST to both conventional PFSA ionomers and HOPIs.

Rapid Field Approach to Evaluating Natural Source Zone Depletion for a Range of Light Non‐Aqueous Phase Liquid Sites

AbstractMore rapid cost‐effective approaches are required to enable field evaluation of natural source zone depletion (NSZD) at petroleum LNAPL sites. Long and costly cleanups have continued as NSZD has not become widely acceptable as a remedial option. We have developed a low cost rapid field approach (RFA) and expanded the site conceptual models (SCMs) to include NSZD. Results from two sites are presented that illustrate the benefit of the RFA in supplementing existing data and updating SCMs. At present, most NSZD guidelines follow a single generic SCM (aerobic oxidation of methane) as the primary contributor to NSZD. Aerobic oxidation of LNAPL is also possible, and can be documented by subsurface measurements of soil‐gas composition and/or heat generated from biodegradation. The RFA was developed so that sites could be easily separated into those with and without a methane plume overlying LNAPL. This distinction is important as it defines the relative rates of oxygen transport into the soil, and methane generation and release from saturated zone anaerobic biodegradation. For the RFA, evidence for direct LNAPL oxidation is absence of methane (&lt;0.1%‐v) in the unsaturated zone above LNAPL. This measurement can be readily made in the field using existing monitoring wells. The absence of a methane plume above LNAPL would indicate that NSZD is a result of direct biodegradation of LNAPL. This alternative SCM needs to be considered and evaluated prior to implementing more costly data collection or other remediation or site management options.

Biomimetic Nanocatalysts Enhance Oxidative Damage against Cancer Cells

Red blood cells (RBCs) naturally delivery oxygen and kill pathogens through reactive oxygen species (ROS) generated from Fe-protoporphyrin component in hemoglobin, which might be also promising for cancer treatment in terms of relieving tumor hypoxia and inducing oxidative damage against cancer cells. However, the therapy efficacy is far from satisfactory due to the limited oxygen transport and ROS generation rate in tumor tissue. Herein, artificial RBCs (designated as FTP@RBCM) with radical storm production ability is developed for oncotherapy through multi-dimensional reactivity pathways of Fe-protoporphyrin based hybrid metal-organic framework (FTP, as the core), including photodynamic/chemodynamic (PDT/CDT)-like, catalase-like and glutathione (GSH) peroxidase-like activity. Meanwhile, owing to the advantages of reticuloendothelial system (RES) evasion and long circulation abilities of RBCs governed by their cell membranes (RBCMs), FTP with surface further coated with RBCMs (FTP@RBCM) could enormously accumulate at tumor site to achieve remarkably enhanced therapy efficiency.

Черепно-мозговая травма и горы

Today, the traumatic epidemic is gaining momentum around the world. Having a complex pathogenesis, many aspects of the development and impact of traumatic brain injury (TBI) on the body remain undescribed. In particular, there is practically no information about the state of the body after a traumatic brain injury received in the highlands. The aim of the study is to establish the features of animal behavior, homeostatic blood parameters and functional morphology of the cerebellum in TBI in the highlands. The work was performed on 46 white male mongrel rats. The low-mountain series of experiments was modeled at an altitude of 760 m above sea level (Kyrgyzstan, Bishkek), the high-mountain series — at the Tuya-Ashu pass — 3200 m above sea level (Kyrgyzstan). The Weight Drop Method shock model was used to reproduce a traumatic brain injury. The ethology of animals was evaluated in the Open Field test. The lactic acid level was determined in the AQUA LAB (Bishkek). The microcirculation of the cerebellum was examined under the Olympus B×40 microscope (Japan). Statistical data processing was carried out in the SPSS 16.0 program. The visit to the outer squares of the field during TBI decreases (P&lt;0.001) regardless of the height of the experiments, the number of racks in the highlands decreases by 60% (P &lt; 0.001), the number of peeks into minks — by 76 % (P&lt;0.01). The number of acts of defecation after TBI increases. The biochemical parameters of blood in TBI are characterized by an increase in the deficit of buffer bases to −3.8 mmol/l, a drop in the rate of oxygen consumption to 2.5 ml/min, an increase in the ratio between the rate of oxygen transport by arterial blood and the rate of its consumption to 4.8 rel. unit, and the concentration of lactic acid in the blood is up to 5 mmol/l. The microcirculatory bed of the cerebellum in TBI in the highlands is characterized by increased tortuosity, the appearance of swellings and interceptions along the course of blood vessels, activation of anastomoses, increased vascular porosity, hypercapillarization with erythrocyte sludge, parietal standing of leukocytes, the formation of blood clots in all parts of the vascular bed. There is vasogenic swelling of the cerebellum with the phenomena of dislocation of layers.

Climate-smart crops: key root anatomical traits that confer flooding tolerance.

Plants require water, but a deficit or excess of water can negatively impact their growth and functioning. Soil flooding, in which root-zone is filled with excess water, restricts oxygen diffusion into the soil. Global climate change is increasing the risk of crop yield loss caused by flooding, and the development of flooding tolerant crops is urgently needed. Root anatomical traits are essential for plants to adapt to drought and flooding, as they determine the balance between the rates of water and oxygen transport. The stele contains xylem and the cortex contains aerenchyma (gas spaces), which respectively contribute to water uptake from the soil and oxygen supply to the roots; this implies that there is a trade-off between the ratio of cortex and stele sizes with respect to adaptation to drought or flooding. In this review, we analyze recent advances in the understanding of root anatomical traits that confer drought and/or flooding tolerance to plants and illustrate the trade-off between cortex and stele sizes. Moreover, we introduce the progress that has been made in modelling and fully automated analyses of root anatomical traits and discuss how key root anatomical traits can be used to improve crop tolerance to soil flooding.

Enhancing the Heterologous Fructosyltransferase Activity of Kluyveromyces lactis: Developing a Scaled-Up Process and Abolishing Invertase by CRISPR/Cas9 Genome Editing.

The enzymatic production of prebiotic fructo-oligosaccharides (FOS) from sucrose involves fructosyltransferases (FFTs) and invertases, both of which catalyze forward (transferase) and reverse (hydrolysis) reactions. FOS yields can therefore be increased by favoring the forward reaction. We investigated process conditions that favored transferase activity in the yeast strain Kluyveromyces lactis GG799, which expresses a native invertase and a heterologous FFT from Aspergillus terreus. To maximize transferase activity while minimizing native invertase activity in a scaled-up process, we evaluated two reactor systems in terms of oxygen input capacity in relation to the cell dry weight. In the 0.5-L reactor, we found that galactose was superior to lactose for the induction of the LAC4 promoter, and we optimized the induction time and induction to carbon source ratio using a response surface model. Based on the critical parameter of oxygen supply, we scaled up the process to 7 L using geometric similarity and a higher oxygen transport rate, which boosted the transferase activity by 159%. To favor the forward reaction even more, we deleted the native invertase gene by CRISPR/Cas9 genome editing and compared the ΔInv mutant to the original production strain in batch and fed-batch reactions. In fed-batch mode, we found that the ΔInv mutant increased the transferase activity by a further 66.9%. The enhanced mutant strain therefore provides the basis for a highly efficient and scalable fed-batch process for the production of FOS.

Fluid dynamic conditions and oxygen availability effects on microbial cultures in STBR: An overview

Bioprocesses are often carried out in stirred tank bioreactors. Due to the need of mixing, homogenization and interphase transports, cultures are usually agitated by mechanical, hydraulic or pneumatic means. The increasing in agitation decreases mixing time, improves homogeneity, mass and heat transfer rates and, accordingly, the metabolism and the biochemical reaction rates are also influenced. The power input into the system is essentially required in order to increase the mass transfer rate, the oxygen transport rate in aerobic bioprocesses, but also the shear forces are increased and consequently the concentration of some compounds in the liquid phase (oxygen in the aerobic bioprocess) with the corresponding effects on the cellular metabolism and the cellular structures due to fluid dynamics into the bioreactor. Hydrodynamic conditions in STBR are given by the broth characteristic (mainly viscosity), the vessel geometry, including the stirrer and sparger design, and the agitation and gas flow rate. Thus, shear effects would take place, affecting the culture performance, provoking cell damage in some occasions. The primary goal of this work is to describe up to date knowledge on these concepts: fluid dynamic conditions, hydrodynamic stress and oxygen availability influence affecting the microbial processes performance.

CO2‐resistant SDC‐SSAF oxygen selective dual‐phase hollow fiber membranes

AbstractCe0.85Sm0.15O1.925–Sm0.6Sr0.4Al0.3Fe0.7O3‐δ (SDC‐SSAF) hollow fiber membranes aimed for oxyfuel application are fabricated via a phase inversion‐sintering technique using powders synthesized from EDTA–citrate complex method. Oxygen ions transport is revealed to be the limiting step that determines the overall oxygen transport rate in SDC‐SSAF. SDC‐SSAF hollow fiber membrane attained a maximum flux of 2.6 ml min−1 cm−2 at 950°C under an oxygen partial pressure difference of 1/0.02 atm (feed/permeate). Variation in oxygen partial pressure on the permeate side exerts larger influence on the oxygen permeation flux relative to the change on the feed side. Stability tests over 100 h demonstrate stable oxygen permeation flux under both He and CO2 sweep conditions.

Oxygen diffusion in Mg-doped Sm and Gd zirconates with pyrochlore structure

Oxides with pyrochlore structure are promising materials for SOFCs, oxygen and hydrogen separation membranes, and other devices. Ln zirconates attract interest due to their oxygen and protonic mobility. In this work, oxygen transport mechanism in Mg-doped Sm and Gd zirconates was studied. Sm1.9Mg0.1Zr2O6.95 and Gd1.9Mg0.1Zr2O6.95 oxides have been prepared via the mechanical activation and characterized by XRD, TGA, and SEM. Oxygen transport features were studied by the oxygen isotope exchange with C18O2. Isotope substitution of bulk oxygen was demonstrated to be described by the 2D diffusion model. Very fast diffusion within grain boundaries provides fast isotope label distribution over the oxide domains, then tracer distributes due to a slower diffusion within domains’ bulk. Three forms of oxygen were distinguished within grains’ bulk. Very fast diffusion along grain boundaries (Dgb ~ 10−7 cm2/s at 700 °C) can provide high rates of oxygen transport in oxygen separation membranes.

Measurement of Oxygen Transport through Separators in Flooded Batteries

An in-depth understanding of oxygen transport in flooded lead acid batteries is necessary to better understand and mitigate water loss in the next generation of batteries for start-stop vehicle applications. The presence of the oxygen cycle leads to a lower rate of water loss observed during intermittent drive cycle testing compared to the gassing that would be calculated from the integrated overcharge current into the battery [1]. A model of the oxygen cycle in flooded lead acid batteries has been proposed [2] but until recently the oxygen transport through the separator-electrolyte system hasn’t been measured.A method for measuring oxygen transport through the separator-electrolyte system has been developed which uses electrodes harvested from commercial batteries. In this method, the separator is sealed between two chambers of a test cell, one containing the positive electrode and the other containing the negative electrode plus a reference. A constant stream of oxygen is delivered to the positive side of the cell using an air pump and diffuser. The negative side is purged, sealed and constantly stirred. The cell is charged and allowed to rest at OCV. Oxygen diffuses from the constant source on the positive side to the negative side where it oxidizes some of the negative active mass. This creates a measurable capacity change at the negative electrode which can be measured during a potentiostatically-controlled recharge cycle.We will report on measurements of oxygen transport through the separator-electrolyte system for different separator materials in a flooded cell using commercial lead acid electrodes. Results are compared with modeling of the oxygen cycle and related to factors in the separator which influence the oxygen transport rate, such as porosity, pore size distribution and tortuosity,.[1] Wirth, 16ELBC, 07 September 2018, Vienna Austria[2] Meissner, Scientific Workshop: High-Temperature Durability Tests for Advanced Lead 12-V Batteries, 30 January 2017, Kloster Eberbach, Germany

The role of oxygen transport in atherosclerosis and vascular disease.

Atherosclerosis and vascular disease of larger arteries are often associated with hypoxia within the layers of the vascular wall. In this review, we begin with a brief overview of the molecular changes in vascular cells associated with hypoxia and then emphasize the transport mechanisms that bring oxygen to cells within the vascular wall. We focus on fluid mechanical factors that control oxygen transport from lumenal blood flow to the intima and inner media layers of the artery, and solid mechanical factors that influence oxygen transport to the adventitia and outer media via the wall's microvascular system—the vasa vasorum (VV). Many cardiovascular risk factors are associated with VV compression that reduces VV perfusion and oxygenation. Dysfunctional VV neovascularization in response to hypoxia contributes to plaque inflammation and growth. Disturbed blood flow in vascular bifurcations and curvatures leads to reduced oxygen transport from blood to the inner layers of the wall and contributes to the development of atherosclerotic plaques in these regions. Recent studies have shown that hypoxia-inducible factor-1α (HIF-1α), a critical transcription factor associated with hypoxia, is also activated in disturbed flow by a mechanism that is independent of hypoxia. A final section of the review emphasizes hypoxia in vascular stenting that is used to enlarge vessels occluded by plaques. Stenting can compress the VV leading to hypoxia and associated intimal hyperplasia. To enhance oxygen transport during stenting, new stent designs with helical centrelines have been developed to increase blood phase oxygen transport rates and reduce intimal hyperplasia. Further study of the mechanisms controlling hypoxia in the artery wall may contribute to the development of therapeutic strategies for vascular diseases.

Oxygen Monitor to Study Vascularization of Medical Devices

Prevascularized medical devices can improve cell therapy. Such devices may replace whole organ transplantation with hosting only the necessary therapeutic cells. We have developed a noninvasive optical technology to study the vascularization into such medical devices. In our technique, oxygen partial pressure within a device is monitored by Oxygen Sensitive Tubes (OSTs), comprising oxygen permeable silicone tubing with inner luminal surfaces coated by an oxygen-sensitive porphyrin dye. OSTs were placed within a PDMS device and transplanted into the subcutaneous space of athymic nude mice. An optical probe placed over the skin excites the OSTs with a pulse of light and detects the luminescent lifetime of emitted light, which is uniquely related to oxygen partial pressure. Furthermore, we developed a Dynamic Inhalation Gas Test (DIGT) to determine the oxygen transport rate between the microvasculature and the device. DIGT works by monitoring oxygen partial pressure in a device following a step change in inhaled-gas oxygen content. We report DIGT oxygen dynamics measured intermittently over eight weeks. Our study shows DIGT dynamics are unique to each implant, supporting the important role of the host tissue response in the availability of oxygen over time.