In this report we describe a preliminary concept for a Tritium Removal System (TRS) to remove tritium that is generated in the ⁹⁹Mo production process. Preliminary calculations have been performed to evaluate an approximate size for the system. The concept described utilizes well-established detritiation technology based on catalytic oxidation of tritium and tritiated hydrocarbons to water in a high temperature (400 °C) reactor and capture of water in a molecular sieve bed. The TRS concept involves use of a single system that would cycle through each of the seven online target systems and remove tritium that has been accumulated after one week’s run time. The TRS would perform cleanup operations on each target system for a period of approximately 24 hours. This would occur while the system is still online and just prior to target replacement, so tritium levels would at their minimum values for target replacement. In the concept, during normal operation a small fraction (1%) of the helium recirculating in the system would be diverted through the TRS and returned to the flow loop. With this approach sufficient levels of detritiation can be accomplished in a 24 hour period. In the study it was found that because of the need to maintain low oxygen levels in the system (<100 ppm) this increases the size of the catalytic reactor. As a result of this finding, consideration should be given to other methods for removing tritium from the system. Other methods such as catalytic exchange of tritium with an unsaturated organic compound and subsequent trapping on activated carbon or molecular sieve could offer advantages of reducing reactor size and operation at lower reactor temperature. However the most significant advantage of such an approach would be the ability to operate in very low oxygen environments, which would eliminate any concerns for oxidation of the target.
Performance of a 5A molecular sieve in separating a gaseous mixture of nitrogen and oxygen
Performance of a 5A molecular sieve in separating a gaseous mixture of nitrogen and oxygen
3Effect of Oxygen Pressure on Swimming Activity of Ceriodaphnia Quadrangula
The effect of oxygen pressure on the swimming activity of hemoglobin-rich (red) and hemoglobin-poor (pale) Ceriodaphnia quadrangula was studied at 25?C. The swimming time of red animals until final cessation of antennal movement was constant (38 min) in extremely low oxygen concentration, rapidly increased, and reached 100 min at 4.5 torr. The swimming time of pale animals was constant (24 min) at 3.5 torr, increased gradually, and reached 100 min at 11.7 torr. The swimming time of red animals in nitrogen-saturated water increased on exposure to 3.5 torr and reached a maximum of 35 min at 5.8 torr. The swimming time of pale animals increased above 10.5 torr and reached a maximum of 23 min at 16.3 torr. Hemoglobin commonly occurs in the hemolymph of Ceriodaphnia (Hoshi, 1957; Czeczuga, 1965; Kobayashi and Hoshi, 1983). As in many other cladocerans (Fox et al., 1949, 1953; Green, 1955; Kobayashi and Hoshi, 1982; Kobayashi and Nezu, 1986), the concentration of Ceriodaphnia-hemoglobin varies considerably with environmental oxygen concentration. Hemoglobin-rich (red) animals are normally found in water of low oxygen concentration, while hemoglobin-poor (pale) animals are found in well-aerated water (Czeczuga, 1965; Kobayashi and Hoshi, 1983). In general, the physiological function of hemoglobin in small invertebrates has been estimated from the reduction of oxygen consumption of animals after inactivation of their hemoglobin with carbon monoxide (Prosser, 1973; Weber, 1980). In cladocerans, pale animals have been used as natural controls for comparison with red animals, because of the marked difference in the hemoglobin concentrations between them (Kobayashi, 1974; Kobayashi and Gonoi, 1985). Functional significance of Ceriodaphnia-hemoglobin has been evaluated from the swimming distance in a glass tube (150 cm long) in pale, red, and carbon monoxide-treated red animals (Kobayashi and Yoshida, 1986). The swimming speed (43 cm/min) did not differ between pale and red animals. They both swam a distance of 5 m in oxygen pressure of 2.3 torr. At 4.7 torr, red animals swam more than 80 m, whereas pale animals swam only 7 m. Further increase in oxygen pressure induced an increase in the swimming distance of pale animals which reached 100 m at 21 torr. In red animals treated with carbon monoxide, oxygen pressures demonstrated almost the same effect on the swimming activity as in pale animals. Apparently hemoglobin allowed red animals to take up oxygen in low oxygen environment and to swim a longer distance than pale or carbon monoxide-treated animals even in low oxygen pressure. In oxygen-regulating animals, the critical oxygen concentration (below which the oxygen consumption depends on ambient oxygen concentration) has been determined, to study their responses to low environmental oxygen (Mangum and Van Winkle, 1973; Herreid, 1980; Lubbers, 1980). When the swimming distance was measured by the above-mentioned method (Kobayashi and Yoshida, 1986), the swimming distance was found to increase exponentially with an increase in oxygen concentration and even to exceed the upper limit of measurement. By the use of this method, therefore, it is not possible to estimate the oxygen concentration equivalent to the critical oxygen concentration.
Read more183Altering hemoglobin levels changes energy status in maize cells under hypoxia.
Nonsymbiotic hemoglobins are broadly present across the plant kingdom; however, the function of these proteins is unknown. Cultured maize cells have been transformed to constitutively express a barley hemoglobin gene in either the sense (HB+) or antisense (HB-) orientation. Hemoglobin protein in the transformed cell lines correspondingly was higher or lower than in wild-type cells under normal atmospheric conditions. Limiting oxygen availability, by placing the cells in a nitrogen atmosphere for 12 hr, had little effect on the energy status of cells constitutively expressing hemoglobin, but had a pronounced effect on both wild-type and HB- cells, where ATP levels declined by 27% and 61%, respectively. Total adenylates in these cells were approximately 35% lower than in HB+ cells. Energy charge was relatively unaffected by the treatment in HB+ and wild-type cells, but was reduced from 0.91 to 0.73 in HB- cells, suggesting that the latter were incapable of maintaining their energy status under the low oxygen regime. Treatment of the cells grown in an air atmosphere with antimycin A gave essentially the same results. It is suggested that nonsymbiotic hemoglobins act in plants to maintain the energy status of cells in low oxygen environments and that they accomplish this effect by promoting glycolytic flux through NADH oxidation, resulting in increased substrate-level phosphorylation. Hypoxic acclimation of plants is an example of this effect in nature. Nonsymbiotic hemoglobins are likely ancestors of an early form of hemoglobin that sequestered oxygen in low oxygen environments, providing a source of oxygen to oxidize NADH to provide ATP for cell growth and development.
Read more1Characteristics of Psychophysiological Change of Drivers in the Low Pressure and Oxygen Deficient Environment in High Altitude Area
According to the influence of the traffic operation environment on the drivers in high altitude areas, in this chapter we selected the motor vehicle drivers with different driving experience on the highways on Qinghai-Tibet Plateau, collected the heart rate, eye movement, electromyography, blood oxygen saturation and other indicators at different elevations (3,000–5,000 m) through driving simulation tests and real vehicle tests. After analysis and screening, indicators whose heart rate are easy to monitor during the test and less affected by individual differences are selected as the research objects, the change rules of drivers’ perception and operation ability and fatigue characteristics in high altitude and low oxygen environment were analyzed, and the driver heart rate change model and driver fatigue model in low oxygen environment were established, which provides a basis for proposing that driver’s physiological and physiological status affects the geometric design index, parameters and reasonable spacing of service facilities.
Read more106Influence of hypoxia‐inducible factor 1α on dendritic cell differentiation and migration
Dendritic cells(DCs) are important sentinels of the immune system and frequently reside in areas of low oxygen availability, in particular in the course of inflammatory processes. Hypoxia-inducible transcription factor (HIF)1α is responsible for major alterations in gene expression as part of the cellular adaptation to low oxygen concentration. In this study, we generated mice with a conditional deletion of HIF1α in DCs. Bone marrow-derived DCs from WT and conditional mutant mice expressed elevated levels of major histocompatibility complex class II and CD86 when grown in a hypoxic environment, whereas production of the cytokines interleukin (IL)-12p70, IL-10, IL-6, TNF-α, IL-1β, and IL-23 was reduced, both independent of HIF1α expression. In contrast, secretion of IL-22 was strongly enhanced under hypoxic conditions in an HIF1α-dependent manner. The chemokine receptor CCR7 was expressed at higher levels in wild-type DCs compared with HIF1α-deficient DCs, whereas the production of CCL17 and CCL22 was increased in conditions of low oxygen. Using in vitro as well as in vivo migration assays, we observed an enhanced migratory capability of DCs generated under hypoxia, which was HIF1α-dependent. Taken together, our data indicate that HIF1α plays an important role for DC differentiation and migration in a low oxygen environment.
Read more
35Metabolic profiling reveals potential metabolic markers associated with Hypoxia Inducible Factor-mediated signalling in hypoxic cancer cells
Hypoxia inducible factors (HIFs) plays an important role in oxygen compromised environments and therefore in tumour survival. In this research, metabolomics has been applied to study HIFs metabolic function in two cell models: mouse hepatocellular carcinoma and human colon carcinoma, whereby the metabolism has been profiled for a range of oxygen potentials. Wild type cells have been compared to cells deficient in HIF signalling to reveal its effect on cellular metabolism under normal oxygen conditions as well as low oxygen, hypoxic and anoxic environments. Characteristic responses to hypoxia that were conserved across both cell models involved the anti-correlation between 2-hydroxyglutarate, 2-oxoglutarate, fructose, hexadecanoic acid, hypotaurine, pyruvate and octadecenoic acid with 4-hydroxyproline, aspartate, cysteine, glutamine, lysine, malate and pyroglutamate. Further to this, network-based correlation analysis revealed HIF specific pathway responses to each oxygen condition that were also conserved between cell models. From this, 4-hydroxyproline was revealed as a regulating hub in low oxygen survival of WT cells while fructose appeared to be in HIF deficient cells. Pathways surrounding these hubs were built from the direct connections of correlated metabolites that look beyond traditional pathways in order to understand the mechanism of HIF response to low oxygen environments.
Read more156Regulation of Hypoxia Inducible Factors (HIF) in Hypoxia and Normoxia During Placental Development
Regulation of Hypoxia Inducible Factors (HIF) in Hypoxia and Normoxia During Placental Development
48Modification of embryonic resistance to heat shock in cattle by melatonin and genetic variation in HSPA1L.
Modification of embryonic resistance to heat shock in cattle by melatonin and genetic variation in HSPA1L.
35Reactions of oxygen with VCrTi alloys
Reactions of oxygen with VCrTi alloys
1HELIUM-PURIFICATION UNIT FOR HIGH-PURITY INERT-ATMOSPHERE BOXES
A device for purifying and recycling the helium atmosphere of two dry boxes having a combined volume of 50 ft/sup 3/ is described. Trace impurities are removed by passing the helium through a palladium-catalyst container and a molec ular sieve bed and cooling to - 195 deg C before passing through an activated charcoal bed. Flow rates of 10 scfm and purity levels are estimated. Regeneration procedures are given. Construction prints and a schematic diagram of the heliumpurification unit are shown. (H.G.G.)
Read more38Reversible water capture by a charged metal-free porous polymer
Reversible water capture by a charged metal-free porous polymer
118Root Bending Is Antagonistically Affected by Hypoxia and ERF-Mediated Transcription via Auxin Signaling.
When plants encounter soil water logging or flooding, roots are the first organs to be confronted with reduced gas diffusion resulting in limited oxygen supply. Since roots do not generate photosynthetic oxygen, they are rapidly faced with oxygen shortage rendering roots particularly prone to damage. While metabolic adaptations to low oxygen conditions, which ensure basic energy supply, have been well characterized, adaptation of root growth and development have received less attention. In this study, we show that hypoxic conditions cause the primary root to grow sidewise in a low oxygen environment, possibly to escape soil patches with reduced oxygen availability. This growth behavior is reversible in that gravitropic growth resumes when seedlings are returned to normoxic conditions. Hypoxic root bending is inhibited by the group VII ethylene response factor (ERFVII) RAP2.12, as rap2.12-1 seedlings show exaggerated primary root bending. Furthermore, overexpression of the ERFVII member HRE2 inhibits root bending, suggesting that primary root growth direction at hypoxic conditions is antagonistically regulated by hypoxia and hypoxia-activated ERFVIIs. Root bending is preceded by the establishment of an auxin gradient across the root tip as quantified with DII-VENUS and is synergistically enhanced by hypoxia and the auxin transport inhibitor naphthylphthalamic acid. The protein abundance of the auxin efflux carrier PIN2 is reduced at hypoxic conditions, a response that is suppressed by RAP2.12 overexpression, suggesting antagonistic control of auxin flux by hypoxia and ERFVII. Taken together, we show that hypoxia triggers an escape response of the primary root that is controlled by ERFVII activity and mediated by auxin signaling in the root tip.
Read more31Influence of Oxygen on High Temperature Aqueous Corrosion of Iron
The corrosion of pure iron in distilled water was investigated over a range of temperature (50-315 C) and oxygen content of the water (&lt;0.1 —540 ppm). A uniform brown-black coating formed in water of low oxygen content at 260 C. The corrosion rate was low after the initial period. Severe pitting of the iron was encountered in water containing intermediate concentrations of oxygen over the entire range of temperature. The average metal loss rates were also much higher than that obtained in a low oxygen environment. A thin protective film formed when adequate oxygen was present. No significant pitting was noted. The total corrosion at 30 days’ exposure was lower for samples in a 260C-540 ppm oxygen test than for those with very little oxygen at the same temperature. The protective film forming ability of iron in a pitting oxygen-water environment was improved by alloying, particularly with chromium and carbon. The improved corrosion performance of some mild and low alloy steels over pure iron at intermediate oxygen concentrations was also noted. The thin films formed on pure iron in adequately oxygenated water were composed of α-Fe2O3 (hematite) as contrasted with the Fe3O4 (magnetite) coatings produced in deoxygenated water. Distinctive growth habits for the various iron oxides were found on the outer surfaces of the protective coatings.
Read more14Oxygen enhances the recovery of Potamogeton maackianus from prolonged exposure to very low irradiance
Oxygen enhances the recovery of Potamogeton maackianus from prolonged exposure to very low irradiance
3HIF1α is dispensable for oocyte development and female fertility in mice
BackgroundIt has been thought that oocyte may develop in a low oxygen environment, as changes in follicle structure and formation of a fluid-filled antrum. The survival of hypoxic tissues is controlled by hypoxia-inducible factors (HIFs) that are activated in a low oxygen state. HIF1α is expressed in mature mouse oocytes and continues to be expressed after fertilization, from the 2-cell to blastocyst stage. However, the physiological roles of HIF pathway during oogenesis and embryogenesis have still not been elucidated in detail.MethodsMutant mice with oocyte-specific HIF1α deletion were generated by crossing Hif1αfl/fl mice with transgenic mice expressing Gdf9-promoter-mediated Cre recombinase. Breeding assay was carried out to detect female fertility. In vitro fertilization and embryo culture were used to assess early embryo development. Oocyte meiotic progression was also examined. Quantitative RT-PCR was used for analyzing of candidate genes expression.ResultsWe successfully generated mutant mice with oocyte-specific deletion of HIF1α. Oocytes loss of HIF1α did not affect female fertility, ovulation and early embryo development. Moreover, oocytes can mature in vitro, and form well-organized spindle in the absence of HIF1α. In addition, pronounced differences in Hif2α and Hif3α mRNA expression were not observed in HIF1α-deleted oocytes. These results revealed that HIF pathway in oocytes is not essential for female fertility.
Read more
Copyright 2026 Cactus Communications. All rights reserved.
