Residual Oxygen Levels Research Articles

Surface chemical analysis of spatter particles generated in laser powder bed fusion of Hastelloy X in process atmospheres with high and low oxygen content

Additive manufacturing, particularly laser powder bed fusion (LPBF), has received much attention in recent years because of its multiple benefits over traditional manufacturing. One of the key factors affecting the repeatability and performance of the materials is the existence of defects. Defects can be driven by process by‐products called spatters, which consist of particles covered by an oxide layer formed during their travel time in the process atmosphere. As a standard process atmosphere consists of argon containing a residual oxygen level of around 0.1%, one possible way of addressing spatter‐driven defect formation is by reducing the oxygen level, thereby reducing the oxidation of the spatter particles. In this study, Hastelloy X powder was processed by means of LPBF in an argon atmosphere containing 1000‐ppm O2 or 50‐ppm O2. Spatter particles were collected in a controlled manner, allowing sampling particles of different sizes, which were analyzed in terms of their surface chemical composition by means of X‐ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). By combining these two tools, a comprehensive assessment of the surface chemical composition was conducted, taking advantage of XPS for the evaluation of the overall surface chemistry and of Auger nanoprobe analysis for high lateral analytical resolution combined with depth profiling. It is shown that tighter oxygen control will both limit the overall oxidation and affect the surface chemical composition. At regular O2 level in the process atmosphere (1000 ppm), spatter particles are covered by a 70‐nm‐thick oxide layer, on average. The thickness is substantially greater than that measured in spatter particles collected from the process atmosphere containing 50‐ppm oxygen, which averages 6 nm and is comparable with that of the virgin powder, thus revealing a potential for defect mitigation through control of the process atmosphere. Nonetheless, substantial differences in the surface chemical composition were identified between spatters and virgin powder, notably with the appearance of Al‐ and Ti‐oxides on spatter particles, revealing the influence of the manufacturing process on surface characteristics.

Creation of Gases with Interplanetary Oxygen Concentration at Atmospheric Pressure by Nanoparticle Aerosol Scavengers: Implications for Metal Processing from nm to mm Range

A gas purification setup (GPS) is presented that is capable of producing ultrapure inert gases, such as nitrogen, at ambient pressure with residual oxygen concentrations of 10–13 ppm and below. The GPS relies on the interaction of metallic aerosol nanoparticles that capture residual oxygen, resulting in metal oxide particle formation. The finally reached residual oxygen level can be illustrated by the 6.8 billion years needed for the creation of one monolayer of oxygen on a substrate. Consequently, the processing of oxygen-affine materials of any size may be shifted from vacuum processes toward machining steps at atmospheric pressure, maintaining an oxygen-free environment in the future. As an outlook, the presented work includes measurements of the electron work function of nanoparticles under purified (10–13 ppm-level) and unpurified process gas (100 ppm-level), pointing at the strong influence of residual oxygen on nanostructured materials with reference to copper nanoparticles. Future syntheses and applications of nanoscaled structures will be inspired by the opportunity to work with true inert gases at ambient pressure, which has been inaccessible so far.

Oxygen absorbing food packaging made by extrusion compounding of thermoplastic cassava starch with gallic acid

Control of oxygen levels in package headspace directly preserves quality and safety of packaged foods and beverage. This research aimed to produce oxygen scavenging bio-based plastics to control oxygen contents in food packaging. Thermoplastic starch (TPS) was produced via extrusion compounding with different gallic acid (GA) contents (1–10%) and linear-low-density polyethylene (LLDPE). Morphology, relaxation behavior, surface and mechanical properties and oxygen scavenging capacities were investigated. Increasing GA content plasticized and facilitated starch melting. GA likely induced H-bonding and esterification with the TPS phase, which apparently modified mechanical relaxation behavior and interacted with LLDPE via C–H bonded aromatic rings. Increasing GA to 5% gave more homogeneous microstructures and miscible GA, while a further increase caused clumps that likely reduced surface area available for oxygen. XRD intensity of TPS/LLDPE linearly decreased with increased GA that likely led to increased water vapor permeability possibly due to decreased crystallinity of the polymers. Studies of oxygen scavenging at 4, 25 and 50 °C showed enhanced capacity with increasing temperature that facilitated reaction between GA and oxygen. Minimum residual oxygen level decreased with GA content and temperature, from 4 to 50 °C. Rates of oxygen scavenging increased and residual oxygen decreased linearly with GA content. Compounding bio-based polymers with GA via in-situ extrusion efficiently produced active films which could be used to control oxygen in food packaging. • Novel oxygen absorbing bio-based polymer via extrusion compounding with gallic acid. • Gallic acid bonded starch and LLDPE, improving compatibility and plasticization. • Oxygen scavenging kinetics increased with temperature and gallic acid contents. • Minimum residual oxygen contents as low as 16% was reached by 5 days at 50 °C.

Mitigating oxygen pick-up during laser powder bed fusion of Ti-6Al-4V by limiting heat accumulation

The dissolution of oxygen in Ti-6Al-4V during laser powder bed fusion (L-PBF) is a limitation for the final ductility of the produced components and a challenge for the end-users. In the present work, the effect of the residual oxygen in the process atmosphere of a laboratory scale L-PBF machine, as well as the role of heat accumulation, are studied. It was shown that oxygen content in the as-built Ti-6Al-4V is determined by the size of the scanned area and build time. The heat accumulation aspect was investigated by adjusting the inter-layer time (ILT), by increasing the recoating time or the number of produced parts. The results showed that oxygen pick-up could be limited by reducing residual oxygen level in the atmosphere or heat accumulation. A 400 ppm O2 reduction measured at the top of a 70 mm column was achieved by increasing the ILT manually by 4.5 s, and a 1200 ppm O2 reduction by increasing the scanned area by 7 times. By doing so, the hardness at full height was reduced by approximately 30 HV10. It is shown that design features characterised by high aspect ratio can absorb significant amount of oxygen resulting in increased brittleness.

Argon-helium mixtures as Laser-Powder Bed Fusion atmospheres: Towards increased build rate of Ti-6Al-4V

The effect of the gas thermal properties and density on the laser powder bed fusion (L-PBF) process was investigated by using inert argon, characterized by high density, and helium, characterized by high thermal conductivity and heat capacity, and their gas mixtures. The results highlighted that for L-PBF of Ti-6Al-4V, the effect of residual impurities such as oxygen and nitrogen on the process stability and defect generation is prevailing the type of the process gas. However, by monitoring the residual oxygen level in the process atmosphere, the results showed that using the argon-helium mixtures allows to increase the produced material density upon higher build rates. High density, greater than 99.98 % is indeed achieved using a mixture of 50 % argon and 50 % helium, allowing for a build rate increase of 44 % in comparison to the standard build rate. The analysis of the produced material revealed the presence of thermal residual stresses attributed to an enhanced energy input when using the gas mixtures. The latter offer a positive balance of density and thermal properties, and in turn, probably reduce the accumulation of process by-products at the melt pool that interfere with and attenuate the laser radiation. The possible detrimental effect of the introduced residual stresses is efficiently eliminated by the conventional stress relieving treatment leading to the decomposition of α´martensite into a fine (α + β) microstructure. This study opens the perspective on the development of the gas recipes for improved process stability and increased productivity of L-PBF process.

Application of O2 sensor technology to monitor performance of industrial beef samples packaged on three different vacuum packaging machines

Two optical oxygen sensor systems we applied to monitor the evolution of meat spoilage in vacuum packaged (VP) samples of raw beef meat, which were produced at a large meat processing factory in Ireland under standard industrial settings on three different vacuum packaging machines. After packaging, the samples were put on storage at +1 °C for 90 days, while analysing their quality parameters. Residual oxygen levels and their time profiles, were measured non-destructively with disposable O2 sensors placed in each pack and interrogated with a handheld reader Optech Platinum (Mocon). Total aerobic viable counts (TVC) were measured by destructive sampling on a sensor based platform Greenlight (Agilent). Furthermore, sensory attributes of meat samples were analysed by internal sensory testing panel. The two commercial oxygen sensor-based systems allowed us to assess the performance of the three VP machines and correlate it with quality and safety characteristics of packaged meat products. They provide convenient and versatile tools for simple, rapid and in situ assessment of various packaged products and packaging systems.

Effect of argon and nitrogen atmospheres on the properties of stainless steel 316 L parts produced by laser-powder bed fusion

The role of the inert gas during laser powder bed fusion (L-PBF) is to remove the process by-products and the air that is initially present in the process chamber. On this purpose, different gas supply options are available. The effect of the process gas and its purity, using argon and nitrogen, on the properties of the 316 L stainless steel produced by L-PBF was studied. The results obtained showed that utilization of argon and nitrogen result in residual oxygen levels that vary over the course of the process sequence in the process chamber. It can be concluded that 316 L stainless steel is a robust alloy to process by L-PBF. A limited effect of the residual oxygen or the gas type (argon or nitrogen) on the tensile properties of the 316 L stainless steel parts was registered. The oxygen and nitrogen pick-up within the produced parts are limited. However, when processing 316 L stainless steel with lower purity gas supply such as a nitrogen generator, risks related to powder degradation arise. Out of the available gas options, the findings highlighted that processing with high purity argon ensures limited powder degradation and high toughness of the produced parts.

REAL-TIME BIOFEEDBACK INTEGRATED INTO NEUROMUSCULAR TRAINING INCREASES BRAIN FUNCTIONAL CONNECTIVITY AND REDUCES HIGH-RISK KNEE BIOMECHANICS

Background: Anterior cruciate ligament (ACL) injury is associated with alterations in the central nervous system and resultant sensorimotor control (Courtney et al., 2005; Grooms et al., 2017). Our prospective data indicates that altered knee-motor functional brain connectivity is associated with increased risk for ACL injury (Diekfuss et al., revisions invited), revealing novel neural targets for neuromuscular training interventions. Specifically, interventions that integrate concomitant sensorimotor feedback with injury prevention techniques have the potential to enhance brain functional connectivity to optimize ACL injury risk reduction strategies. To deliver concomitant sensorimotor feedback, we have developed an augmented neuromuscular training (aNMT) system that utilizes interactive, real-time biofeedback to simultaneously target multiple biomechanical variables associated with ACL injury risk (Bonnette et al., in press; Figure 1A). aNMT calculates and maps key biomechanical parameters to an interactive graphical shape that responds in real time as a function of participants’ movements. Participants are instructed to perform exercises to achieve a goal shape, which equates to producing biomechanical parameters associated with ACL injury risk reduction, while deviations toward injury risk factors result in specific shape distortions. We hypothesized that aNMT would significantly improve biomechanics associated with ACL injury risk and also increase knee-motor functional connectivity. We further predicted that the identified connectivity changes would be associated with the hypothesized changes in biomechanics. Methods: Over six weeks of training, participants (n = 25) performed a series of aNMT-based progressive exercises (e.g., squat, overhead squat, squat jump, tuck jump, single-leg Romanian dead lift, pistol squat) and completed a drop vertical jump (DVJ) task while fully instrumented for 3D motion analysis pre- and post-training. Peak knee abduction moment (pKAM; bilateral average) from the DVJ was used as the biomechanical outcome variable. Resting-state functional magnetic resonance imaging (fMRI) scans were also collected pre- and post-training on a subset of the cohort (n = 17). Thirteen additional participants were recruited to serve as untrained controls and completed the DVJ and resting-state fMRI on two testing sessions separated by approximately 6 weeks. Twenty-five knee-motor regions of interest (ROIs) were created based on the areas of brain activation derived from previously published data (Grooms et al., 2015; Kapreli et al., 2007). Paired-samples t tests with a false discovery rate correction for multiple comparisons determined differences in functional connectivity among these 25 ROIs (post > pre). Fisher-transformed Pearson correlation coefficients between the average residual blood oxygen level dependent (BOLD) signal time series extracted from ROIs that demonstrated significant group level changes were associated with pKAM in DVJ task at pre- and post-training. The pre- and post-training Pearson correlation coefficients were subsequently compared using the cocor package (Diedenhofen & Musch, 2015) to determine if the two relationships were significantly different. Results: Results showed that pKAM in the aNMT group was significantly lower following aNMT (p < .05), while no significant changes were found between the two time points for controls (p > .05). Results also revealed significantly greater functional connectivity between the right supplementary motor area (SMA) and the left thalamus at post-training relative to pre-training for the aNMT group, t(16) = 3.37, p = .04 (Figure 1B). No significant differences between the two time points were observed for the controls (all p > .05). The association between pKAM and the right SMA and left thalamus at pre-training (r = -.22; Figure 1C) was significantly different compared to that at post-training (r = .26; Figure 1D), p < .05, with a positive relationship between pKAM and SMA and thalamus activation following aNMT biofeedback. No similar changes in pKAM and right SMA and left thalamus connectivity were observed for the untrained controls, p > .05. Conclusions/Significance: The right SMA is involved in the planning and coordination of movement, and the left thalamus is associated with neuromotor control. The increased functional connectivity between these regions, combined with the reduction in pKAM, which is associated with reduced risk of ACL injury, indicate a possible neural mechanism for improved motor adaption associated with aNMT biofeedback. These findings have distinct implications for ACL injury prevention strategies. Biofeedback tools such as aNMT can be designed to target specifically the neural drivers of aberrant movement biomechanics underlying increased ACL injury risk. [Figure: see text]

Reduction of Residual Impurities in Homoepitaxial m‐Plane GaN by Using N2 Carrier Gas in Metalorganic Vapor Phase Epitaxy

The reduction of unintentional impurities in m‐plane GaN homoepitaxial layers is demonstrated by using nitrogen (N2), as opposed to hydrogen (H2), as carrier gas in metalorganic vapor phase epitaxy (MOVPE). Secondary ion mass spectrometry (SIMS) analysis shows that the impurity levels of residual oxygen (O), carbon (C), and silicon (Si) are decreased by nearly one order of magnitude in N2‐grown samples. Although the full width at half maximum (FWHM) values for the on‐axis m‐plane X‐ray rocking curves of all specimens are quite similar (around 50 arcsec), plan‐view scanning transmission electron microscopy (STEM) measurements reveal a clear reduction of dislocation densities in N2‐grown films. Their origin is likely related to an initial surface roughening with H2 carrier gas, which also causes surface faceting resulting in the formation of large four‐sided pyramidal hillocks, while using N2 results in smoother surfaces. Hence, MOVPE growth with N2 carrier gas is an effective method to lower the impurity incorporation in m‐plane GaN materials in addition to reducing the formation of defects and improving the surface morphology, which can enable the development of high‐performance GaN‐based devices on non‐polar surfaces.

Oxygen Consumption and Acoustic Activity of Adult Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae: Bruchinae) during Hermetic Storage.

Acoustic monitoring was applied to consider hermetic exposure durations and oxygen levels required to stop adult Callosobruchus maculatus activity and economic damage on cowpea. A 15-d study was conducted with six treatments of 25, 50, and 100 C. maculatus adults in 500 and 1000 mL jars using acoustic probes inserted through stoppers sealing the jars. Acoustic activity as a result of locomotion, mating, and egg-laying was measured by identifying sound impulses with frequency spectra representative of known insect sounds, and counting trains (bursts) of impulses separated by intervals of <200 ms, that typically are produced only by insects. By the end of the first week of storage in all treatments, oxygen levels declined to levels below 4%, which has been demonstrated to cause mortality in previous studies. Concomitantly, insect sound burst rates dropped below an acoustic detection threshold of 0.02 bursts s−1, indicating that the insects had ceased feeding. Statistically significant relationships were obtained between two different measures of the acoustic activity and the residual oxygen level. Based on the experimental results, a simple equation can be used to estimate the time needed for oxygen to decline to levels that limit insect feeding damage and thus grain losses in hermetic storage containers of different insect population levels and various volumes.

Terahertz Electroluminescence of Shallow Impurities in AlGaN/GaN Heterostructures at Temperatures above 80 K

In this work terahertz (THz) electroluminescence of shallow impurities in AlGaN/GaN high electron mobility transitor (HEMT) structures are studied at temperatures above 80 K. The samples are excited with electric field pulses of up to 300 V cm−1 and duration of ms. The THz emission spectra are measured in vacuumed environment by means of infrared Fourier transform spectroscopy. Resonant 1s − 2p electron transitions in energy levels of residual oxygen and silicon impurities are observed at temperatures above 80 K. A comparison of the area under the shallow impurities electroluminescence signal correlates with the growth conditions of the AlGaN/GaN heterostructures. In such a way a method to monitor the ratio between ionized shallow impurities in unintentionally doped AlGaN/GaN HEMT structures in the THz frequency range is proposed. In addition, the resonant electroluminescence signals are found intermixed with the THz emission caused by the hot electron transitions from conduction band to shallow donors as well as the black‐body radiation of heated AlGaN/GaN HEMT channel. It is found that the temperature increase of the conductive channel greatly suppressed the electroluminescence signal. Therefore, a proper cooling of the sample should be provided in advance.

Effects of Hermetic Storage on Adult Sitophilus oryzae L. (Coleoptera: Curculionidae) Acoustic Activity Patterns and Mortality.

Hermetic storage is of interest to farmers and warehouse managers as a method to control insect pests in small storage facilities. To develop improved understanding of effects of hermetic storage on insect pest activity and mortality over time, oxygen levels, acoustic signals, and observations of visual movement were recorded from replicates of 25, 50, and 100 adult Sitophilus oryzae (L.) (Coleoptera: Curculionidae) hermetically sealed in 500- and 1,000-ml glass jars. Recordings were done for 28 d; twice daily for the first 6 d and twice weekly thereafter. Insect sounds were analyzed as short bursts (trains) of impulses with spectra that matched average spectra (profiles) of previously verified insect sound impulses. Oxygen consumption was highest in treatments of 100 insects/500-ml jar and lowest in 25/1000-ml jars. The rates of bursts per insect, number of impulses per burst, and rates of burst impulses per insect decreased as the residual oxygen levels decreased in each treatment. Activity rates <0.02 bursts s−1, the acoustic detection threshold, typically occurred as oxygen fell below 5%. Mortality was observed at 2% levels. The time to obtain these levels of insect activity and oxygen depletion ranged from 3–14 d depending on initial infestation levels. Acoustic detection made it possible to estimate the duration required for reduction of insect activity to levels resulting in negligible damage to the stored product under hermetic conditions. Such information is of value to farmers and warehouse managers attempting to reduce pest damage in stored crops.

Determination of critical levels of residual oxygen to minimize discoloration of sliced packaged Norwegian salami under light display

Discoloration of sliced packaged salami is contributing to rejection of the product, food waste and economical loss. A combination of residual O2 in the headspace of packages and light is causing photooxidation and deterioration of colour. The aim of this study was to establish maximum tolerable concentrations of residual O2 in packages of salami slices with 100% N2 under light display at 4 and 20°C. Salami sausages had variable inherent O2 consumption rate. Storage of salami in 1% O2 in darkness did not induce discoloration. The upper limits for O2 for avoiding discoloration under light were variable in the range 0.1–1.0%, depending on temperature and type of salami. Display at 20°C increased the rate of O2 depletion compared to 4°C. To minimize discoloration, sliced and packaged salami should be stored in darkness at approximately 20°C until the level of residual O2 is reduced below a critical limit.

Colour stability of cooked ham packed under modified atmospheres in polyamide nanocomposite blends

Two novel blends containing a low-density polyethylene (LDPE) and a neat polyamide (PA) or a polyamide nanocomposite (PAN) layers were fabricated and their technological potential was evaluated during the refrigeration of cooked ham in modified atmospheres (MAP). Nanoclays were homogeneously distributed and nearly exfoliated, and they lowered significantly the oxygen transmission rate (OTR) of the PAN films. Due to the lower OTR, the headspace oxygen level in PAN pouches do not rise above 0.26% but it approached 2% in PA pouches at day 20. The residual oxygen levels were key for colour change during MAP storage of cooked ham. Cooked ham redness and reflectivity were stable during 27 days in PAN pouches while a strong colour deterioration took place after day 7 in PA pouches. Other parameters such as moisture content and water activity remained unaltered, and pH development was related to microbial growth and independent of the packaging polymer. The evolution of cooked ham colour in PAN was comparable to a high-barrier commercial polymer, and was acceptable for commercial sale for 27 days, showing excellent perspectives for polyamide nanocomposites in the storage of cooked ham.

Aluminum Deoxidation Equilibria in Liquid Iron: Part I. Experimental

In order to provide accurate information for refining of steel containing more than 1 mass pct Al, previously known information about Al deoxidation equilibria in liquid iron was critically reviewed. New Al deoxidation equilibria, Al and O contents in liquid iron in equilibrium with solid Al2O3 were measured at 1873 K and 1923 K (1600 °C and 1650 °C) over the whole Al composition range, 0.0027 < [pct Al] < 100. In order to secure the deoxidation equilibria, in the present study, the Al deoxidation experiments were carried out by employing three different methods: (1) traditional Al deoxidation by the addition of Al into Fe-O alloys, (2) oxidation of Al in Fe-Al alloys by the addition of Fe2O3 as an oxygen source, and (3) addition of CaO flux for an effective removal of suspended Al2O3 inclusions in liquid alloys containing high Al. In addition, in the present study, the O solubility limit in pure Al melt in equilibrium with solid Al2O3 was also measured in the temperature range from 1673 K to 1873 K (1400 °C to 1600 °C). The present experimental results provide a complete set of Al deoxidation equilibria in liquid iron which may be useful for the estimation of residual oxygen level and alumina inclusion formation in high Al steel processing. Interaction parameter formalism, which was originally proposed by Wagner and Chipman and has been widely used to interpret the Al deoxidation equilibria in liquid iron, was found to be inapplicable. Limitation of the interaction parameter formalism at high Al content in liquid Fe was discussed.

Preparation, Characterization and Deoxygenation Performance of Modified Sponge Iron

A modified sponge iron was prepared by chemical replacement copper plating using hydroxyl ethidene phosphonic acid (HEDP) as Cu(II) complexing agent in this paper. The morphology, chemical composition and surface area were characterized by scanning electron microscopy, energy dispersive spectrometer and Brunauer–Emmett–Teller area test, respectively. The results show that the sponge iron deoxygenation performance can be improved obviously by modifying with chemical replacement copper plating. The deoxygenation performance at first increases, and then reaches a maximum before decreasing as the modifying condition. Generally, the residual dissolved oxygen levels decrease with increased copper content rather than surface area. The maximum performance correlates well with maximum copper content, a condition which is realized when selecting optimal values of concentrations, temperature and contact time during the copper plating procedure with the aid of orthogonal experiments. The optimum modifying conditions are [CuSO4] 40 g/L, [HEDP] 80 g/L, [H2SO4] 10 ml/L, modifying times 15 s and plating bath temperature 30 °C. In addition, the copper content on the optimum modified sponge iron is up to 44.22 %.

The effect of high pressure and residual oxygen on the color stability of minced cured restructured ham at different levels of drying, pH, and NaCl

Color stability of minced cured restructured ham was studied by considering the effects of high pressure (HP) (600MPa, 13°C, 5min), raw meat pH24 (low, normal, high), salt content (15, 30g/kg), drying (20%, 50% weight loss), and residual oxygen level (0.02%–0.30%). Raw hams were selected by pH24 in Semimembranosus, mixed with additives, frozen, sliced, and dried by the Quick-Dry-Slice® (QDS) process followed by HP treatment or not (control). Packaging and storage simulated industrial packaging: modified atmosphere containing 80% N2, 20% CO2, and residual O2 in one of three intervals: <0.1%, 0.1%–0.2%, or 0.2%–0.3%, and retail storage conditions: chill storage, 12h light, 12h darkness. HP improved the stability of the redness of 20% QDS hams, while the stabilizing effect on 50% QDS hams was smaller, concluding that water has the dominating role. Raw meat pH24, salt content, and residual oxygen level had varying effects on the stability of the red color.

Release of Microparticles During Blood Storage Is Influenced by Residual Platelets, Leukocytes and Oxygen Levels

Abstract 3435 IntroductionPacked red blood cells in blood bank undergo a series of changes and this so-called “storage lesions” increases with time. It is believed that longer storage is associated with adverse transfusion-related complications, but the reason for this is not clear. Many bioactive substances are generated during blood storage and one or more of them may be responsible for adverse events. Among them, red cell microparticles (RMP) are a leading candidate for adverse effects, but conditions influencing their release are not well identified. Elucidation of these conditions is an important step toward minimizing storage lesions. Methods(I) MP generation: Non-leukoreduced and leukoreduced PC of known blood types (A+, B+, AB+, O+) were obtained from the blood bank within 2–4 days of collection, then stored at 4°C. Time of receipt was defined as day 0. At days 0, 10, 20, 30, and 40, forty mL samples were centrifuged at 1000×g for 20 min to remove cells. The supernatants were then assayed for subtypes of MP by flow cytometry comprising (a) RMP assessed by CD235a, (b) leukocyte MP (LMP) by CD45, (c) platelet MP (PMP) by CD41, and (d) generic MP by Ulex Europaeus (Ulex) or annexin V (AnV); MP-mediated procoagulant and proinflammatory activities were determined by TEG and CD11b expression, respectively. (II) Storage under anaerobic conditions: Anaerobic test units were processed by an OCDD (Oxygen Carbon dioxide Depletion Device) to deplete O2 and CO2, then stored anaerobically in an Anaerobic Storage Bag (ASB) [Transfusion 2011:51S, SP89]. After 42 days, MP were assayed as above. Results (a)Time of storage: In non-leukoreduced RBC, multiple MP types (PMP, LMP, RMP) were detected and seen to increase with time, but at distinctive rates. RMP increased little until day 10 when they rose exponentially; PMP counts rose steadily from day 0 and peaked at day 20; LMP showed little change until day 20 when they began to increase, then rose sharply after day 30. Levels of PMP (days 0 to 20) and RMP (days 20 to 40) correlated with increasing MP-mediated procoagulant and inflammatory markers. (b) Leukoreduction: Pre-storage leukoreduction decreased RMP generation by 20–40% and completely suppressed PMP and LMP generation. Leukoreduction decreased total MP-mediated procoagulant and inflammatory markers by 40–60%. This suggests that residual leukocytes and/or platelets potentiate RMP generation. (c) Residual platelet concentrations: We added increasing numbers of platelets to leukoreduced RBC, and then evaluated RMP generation during storage. The levels of RMP released were proportional to platelet counts in the storage bags. (d) Residual oxygen: We observed that storage of leukoreduced RBC under anaerobic conditions resulted in 40 – 60% reductions in RMP and annexin V+ MP generation measured at 42 days. ConclusionsMultiple MP species (RMP, PMP, LMP) are released during storage of non-leukoreduced PC and increased with time. Procoagulant and proinflammatory activities increased in parallel. Leukoreduction eliminates LMP and PMP generation and reduces RMP generation by 40–50%. This was accompanied by reduction of procoagulant and proinflammatory activities by 60%. We have identified residual platelets, leukocytes, and oxygen levels as important factors governing MP release in stored blood. Reduction or elimination of factors influencing MP generation such as residual platelets, leukocytes and oxygen levels would improve future blood storage condition. Disclosures:No relevant conflicts of interest to declare.

Use of optical oxygen sensors to monitor residual oxygen in pre- and post-pasteurised bottled beer and its effect on sensory attributes and product acceptability during simulated commercial storage

Disposable optical oxygen sensors were used to non-destructively assess the levels of residual oxygen in the headspace of commercially produced Lager beer in 330 ml clear glass bottles. Monitored before and after pasteurisation, oxygen concentration was observed to drop as oxygen diffused into the beer. Oxygen levels between 0% and 5% were present in the bottle headspace pre-pasteurisation. Oxygen diffusion into the beer was monitored over time under refrigeration (∼4 °C) and a sensory panel was used to determine the effect of residual oxygen on the sensory quality of the beer. The headspace in the bottles was also monitored over time where oxygen increased to a level of ∼0.5% on average over the course of the shelf life. Interestingly, results showed that beer samples possessing higher levels of oxygen present prior to pasteurisation also possessed the most negative sensory attributes associated with the beer, particularly those consistent with beer staling. The developed optical sensor was shown to act as a predictor of sensory quality and may have on-line applications in the beer packaging sector.

Hemoglobin enhances oxygen uptake in larval zebrafish (Danio rerio) but only under conditions of extreme hypoxia

The role of hemoglobin (Hb) in O(2) uptake by zebrafish larvae ranging in age from 5 to 42 days postfertilization was assessed under conditions of normoxia, moderate hypoxia and extreme hypoxia. This was achieved by exposing larvae with and without functional Hb to continuously declining oxygen levels (P(O(2))) in closed-system respirometers. Exposure to 5% CO for 2-4 h was used to render Hb effectively non-functional in terms of its ability to transport O(2). Routine metabolic rate (rM(O(2))), critical dissolved oxygen level (P(c)) and residual oxygen level (P(r)) were determined and used, respectively, as indicators of response in normoxia, moderate hypoxia and extreme hypoxia. rM(O(2)) was defined as the average rate of O(2) uptake before O(2) became limiting (i.e. at high P(O(2))s). P(c) is the P(O(2)) at which rM(O(2)) first becomes O(2)-limited and P(r) is the P(O(2)) below which larvae are no longer able to extract O(2) from the ambient medium. CO poisoning had no significant impact on rM(O(2)) or P(c) at any age, indicating that the lack of functional Hb does not impair routine O(2) usage in normoxia or at moderate levels of hypoxia [down to at least 25-50 torr (1 torr approximately 0.133 kPa), depending on age]. P(r), however, was significantly lower overall for control larvae (6.7+/-1.1 torr; mean +/- 95%CI) than for CO-poisoned larvae (11.2+/-2.1 torr). It would appear that the presence of functional Hb allows zebrafish larvae to extract O(2) from water down to lower P(O(2))s under conditions of extreme hypoxia. This is the first documented (as opposed to inferred) benefit of Hb in developing zebrafish. However, given the relatively small magnitude of the effect it is unclear if this benefit on its own is sufficient to balance the costs associated with Hb production and maintenance.