High Oxygen Affinity Research Articles

COMPARISON OF THE MECHANICAL RESPONSE OF POROUS TI-6AL-4V ALLOYS PRODUCED BY DIFFERENT COMPACTION TECHNIQUES

Porous Ti-6Al-4V alloys are attractive candidates as implant materials due to their good biocompatibility combined with the porous structure leading to increased osseointegration and decreased stiffness. Accordingly, different processing techniques were employed for the production of Ti-6Al-4V foams in the literature. Among these techniques, sintering with space holder is used to produce porous Ti-6Al-4V alloys in this study. Magnesium was employed as the space holder material because of its relatively low boiling point as well as high oxygen affinity. Two different compaction techniques, die compaction with hydraulic pressing and cold isostatic pressing (CIP), were employed for obtaining green compacts. Both spherical and nonspherical Ti-6Al-4V powders were used to investigate the effect of powder shape on compaction. Processed foams were characterized in terms of both microstructural and mechanical aspects in order to investigate the effect of pressing conditions in combination with powder characteristics. It was observed that NS-CIP foam, which was produced by compacting nonspherical powders by cold isostatic press, has the highest strength. However, the S-DP foam, which was produced by die-pressing of spherical powders, has the highest toughness.

Bioinspired Polydopamine-Coated Hemoglobin as Potential Oxygen Carrier with Antioxidant Properties.

Oxidative side reaction is one of the major factors hindering the development of hemoglobin-based oxygen carriers (HBOCs). To avoid the oxidative toxicity, we designed and synthesized polydopamine-coated hemoglobin (Hb-PDA) nanoparticles via simple one-step assemblage without any toxic reagent. Hb-PDA nanoparticles showed oxidative protection of Hb by inhibiting the generation of methemoglobin (MetHb) and ferryl (Fe IV) Hb, as well as excellent antioxidant properties by scavenging free radicals and reactive oxygen species (ROS). Interestingly, the scavenging rate of Hb-PDA nanoparticles for ABTS+ radical is at most 89%, while for DPPH radical it reaches 49%. In addition, Hb-PDA efficiently reduced the intracellular H2O2-induced ROS generation. Moreover, Hb-PDA nanoparticles exhibited high oxygen affinity, low effect on blood constituents, and low cytotoxicity. The results indicate that polydopamine-coated hemoglobin might be a promising approach for constructing novel oxygen carriers with the capacity to reduce oxidative side reaction.

"Inside-Out" PEGylation of Bovine β-Cross-Linked Hemoglobin.

The development of a blood substitute is urgent due to blood shortages and potential communicable diseases. A novel method, inside-out PEGylation, has been used here to conjugate a multiarm maleimide-PEG (Mal-PEG) to β-cross-linked (βXL-Hb) hemoglobin (Hb) tetramers through the Cys β93 residues. This method produces a polymer with a single PEG backbone that is surrounded by multiple proteins, rather than coating a single protein with multiple PEG chains. Electrophoresis under denaturing conditions showed a large molecular weight species. Gel filtration chromatography and analytical ultracentrifugation determined the most prevalent species had three βXL-Hb to one Mal-PEG. Thermal denaturation studies showed that the cross-linked and PEGylated species were more stable than native Hb. Cross-linking under oxy-conditions produced a high oxygen affinity Hb species (P50 =9.18Torr), but the oxygen affinity was not significantly altered by PEGylation (P50 =9.67Torr). Inside-out PEGylation can be used to produce a hemoglobin-based oxygen carrier and potentially for other multiprotein complexes.

High-Temperature Corrosion of AlCrSiN Film in Ar-1%SO2 Gas

AlCrSiN film with a composition of 29.1Al-17.1Cr-2.1Si-51.7N in at. % was deposited on a steel substrate by cathodic arc ion plating at a thickness of 1.8 μm. It consisted of nanocrystalline hcp-AlN and fcc-CrN, where a small amount of Si was dissolved. Corrosion tests were carried out at 800 °C for 5–200 h in Ar-1%SO2 gas. The major corrosion reaction was oxidation owing to the high oxygen affinity of Al and Cr in the film. The formed oxide scale consisted primarily of (Al,Cr)2O3, within which Fe, Si, and S were dissolved. Even after corrosion for 200 h, the thickness of the scale was about 0.7–1.2 μm, indicating that the film had good corrosion resistance in the SO2-containing atmosphere.

Beta Al5FeSi phase platelets-porosity formation relationship in A319.2 type alloys

The effects of several variables on the precipitation of the β-Al5FeSi phase, and porosity formation in A319.2 alloys were examined in detail. Various techniques were used for microstructural characterization and phase identification, including optical and scanning electron microscopy, electron probe microanalysis coupled with energy-dispersive X-ray and wavelength-dispersive spectroscopy facilities, and thermal analysis. An image analyzer was used in conjunction with the optical microscope for quantification purposes. The results obtained showed that the amount of iron present in the alloy affects the size of the β-Al5FeSi platelets and their distribution, particularly at low solidification rates. Addition of strontium leads to fragmentation of co-eutectic or post-eutectic β-platelets. This effect diminishes with the increase in iron concentration, and further strontium addition leads to the precipitation of Al2Si2Sr phase particles, instead. The porosity observed at any given iron level is the result of the competition between fluidity and β-platelet size and depends on the permeability of the interdendritic regions as solidification proceeds. Although branching of the β-platelets leads to porosity formation, the platelets, on the other hand, also limit pore growth. In general, percentage porosity, maximum pore area and maximum pore length increase with an increase in the average maximum β-Al5FeSi platelet length. In the Sr-modified alloys, porosity formation is frequently associated with strontium oxides (particles or films), as well as the β-Al5FeSi platelets. These oxides (with a stoichiometric composition close to Al2SrO3) are formed during melting, due to the high oxygen affinity of strontium, and are difficult to remove via degassing.

Ag-Sn Bimetallic Catalyst with a Core-Shell Structure for CO2 Reduction.

Converting greenhouse gas carbon dioxide (CO2) to value-added chemicals is an appealing approach to tackle CO2 emission challenges. The chemical transformation of CO2 requires suitable catalysts that can lower the activation energy barrier, thus minimizing the energy penalty associated with the CO2 reduction reaction. First-row transition metals are potential candidates as catalysts for electrochemical CO2 reduction; however, their high oxygen affinity makes them easy to be oxidized, which could, in turn, strongly affect the catalytic properties of metal-based catalysts. In this work, we propose a strategy to synthesize Ag-Sn electrocatalysts with a core-shell nanostructure that contains a bimetallic core responsible for high electronic conductivity and an ultrathin partially oxidized shell for catalytic CO2 conversion. This concept was demonstrated by a series of Ag-Sn bimetallic electrocatalysts. At an optimal SnOx shell thickness of ∼1.7 nm, the catalyst exhibited a high formate Faradaic efficiency of ∼80% and a formate partial current density of ∼16 mA cm-2 at -0.8 V vs RHE, a remarkable performance in comparison to state-of-the-art formate-selective CO2 reduction catalysts. Density-functional theory calculations showed that oxygen vacancies on the SnO (101) surface are stable at highly negative potentials and crucial for CO2 activation. In addition, the adsorption energy of CO2- at these oxygen-vacant sites can be used as the descriptor for catalytic performance because of its linear correlation to OCHO* and COOH*, two critical intermediates for the HCOOH and CO formation pathways, respectively. The volcano-like relationship between catalytic activity toward formate as a function of the bulk Sn concentration arises from the competing effects of favorable stabilization of OCHO* by lattice expansion and the electron conductivity loss due to the increased thickness of the SnOx layer.

Diagnostic approach to hemoglobins with high oxygen affinity: experience from France and Belgium and review of the literature

Congenital causes of erythrocytosis are now more easily identified due to the improvement of the molecular characterization of many of them. Among these causes, hemoglobins with high oxygen affinity take a large place. The aim of this work was to reevaluate the diagnostic approach of these disorders. To assess the current practices, we sent a questionnaire to the expert laboratories in the diagnosis of hemoglobinopathies in France and Belgium. In parallel, we gathered the methods used for the diagnosis of the hemoglobins with high oxygen affinity indexed in the international database HbVar. Even though they remain a rare cause of erythrocytosis (1 to 5 positive diagnosis every year in each of the questioned specialized laboratories), hemoglobins with high oxygen affinity are increasingly suspected by clinicians. Phenotypic assessment by laboratory techniques remains a main step in their diagnosis as it enables the finding of 93% of them in the questioned laboratories (28 of the 30 variants diagnosed during the last 5 years). Among the 96 hemoglobin variants with high oxygen affinity indexed in the international database, 87% could be diagnosed with phenotypic techniques. A direct measure of the p50 with the Hemox-Analyzer is included in the diagnostic approach of half of the laboratories only, because of the poor availability of this apparatus. Comparatively, the estimation of p50 by blood gas analyzers on venous blood is a much more convenient and attractive method but due to the lack of proof as to its effectiveness in the diagnosis of hemoglobins with high oxygen affinity, it requires further investigations. Beta- and alphaglobin genes analysis by molecular biology techniques is essential as it either allows a quick and definite identification of the variant or definitely excludes the diagnosis. It is thus systematically performed as a first or second step method, according to the laboratory practice.

Master alloys in powder metallurgy: the challenge of exploring new alloying compositions

ABSTRACTSintering of steels containing oxidation-sensitive elements such as Cr, Mn and Si is a big challenge for the powder metallurgy (PM) industry but also a chance that could open the door to a new variety of compositions, properties and prices. However, even when very small amounts of these elements are mixed with an iron base powder, the chemical reactions taking place during sintering can be changed significantly. Application of high purity sintering atmospheres is not sufficient to avoid the formation of stable oxides on the surface of the alloying particles, since the source of oxygen can be – and in general is – the base powder itself. This is because the gaseous reaction products from the reduction of the oxides covering the base powder particles act as oxidising agents for elements with higher oxygen affinity. In this study, thermoanalytical techniques have been applied in a systematic study about the influence of different alloying additions either as elemental powders (Cr, Mn, Si) or as master alloys. While Si shows to be relatively inert up to 900°C, Cr and especially Mn present high tendency to act as ‘oxygen-getters’ already at 400–500°C. When these elements are added in the form of a master alloy, their reactivity decreases, alleviating considerably the gettering effect. Moreover, reduction of the iron oxide layers with H2 at 400°C shows positive results, however, from 400°C Mn shows an important tendency to oxidation by reaction with the sintering atmosphere.This paper is part of a special issue on the Advances in Materials and Processing Technologies (AMPT) 2015 and has subsequently been revised and extended before publication in Powder Metallurgy.

Gel filtration of dilute human embryonic hemoglobins reveals basis for their increased oxygen binding

This report establishes a correlation between two known properties of the human embryonic hemoglobins-- their weak subunit assemblies as demonstrated here by gel filtration at very dilute protein concentrations and their high oxygen affinities and reduced cooperativities reported previously by others but without a mechanistic basis. We demonstrate here that their high oxygen affinities are a consequence of their weak assemblies. Weak vs strong hemoglobin tetramers represent a regulatory mechanism to modulate oxygen binding capacity by altering the equilibrium between the various steps in the assembly process that can be described as an inverse allosteric effect.

Study of Traverse Speed Effects on Residual Stress State and Cavitation Erosion Behavior of Arc-Sprayed Aluminum Bronze Coatings

Within a research project regarding cavitation erosion-resistant coatings, arc spraying was used with different traverse speeds to influence heat transfer and the resulting residual stress state. The major reason for this study is the lack of knowledge concerning the influence of residual stress distribution on mechanical properties and coating adhesion, especially with respect to heterogeneous aluminum bronze alloys. The materials used for spray experiments were the highly cavitation erosion-resistant propeller alloys CuAl9Ni5Fe4Mn (Ni-Al-Bronze) and CuMn13Al8Fe3Ni2 (Mn-Al-Bronze). Analyses of cavitation erosion behavior were carried out to evaluate the suitability for use in marine environments. Further microstructural, chemical and mechanical analyses were realized to examine adhesive and cohesive coating properties. Residual stress distribution was measured by modified hole drilling method using electronic speckle pattern interferometry (ESPI). It was found that the highest traverse speed led to higher tensile residual stresses near the surface and less cavitation erosion resistance of the coatings. Moreover, high oxygen affinity of main alloying element aluminum was identified to severely influence the microstructures by the formation of large oxides and hence the coating properties. Overall, Mn-Al-Bronze coatings showed lower residual stresses, a more homogeneous pore and oxide distribution and less material loss by cavitation than Ni-Al-Bronze coatings.

Redesign of EAF Peg Hb As an Oxygen Transfer Catalyst for Improved Tissue Oxygenation of Hypoxic Areas: A Therapeutic for Anemia and Sickle Cell Disease

BackgroundSurface decoration of Hb with PEG chains has been advanced as an approach to attenuate the vasoconstrictive activity of acellular Hb in circulation. PEGylated Hbs with higher oxygen affinities relative to unmodified Hb has an advantage when designing blood substitutes in achieving targeted transport of O2 from lungs to tissues. Extension Arm Facilitated (EAF) PEGylation of Hb with six copies of PEG 5K (EAF P5K6 Hb) was advanced as an optimum level of PEGylation that does not induce weakening of interdimeric interactions in the quaternary structure of Hb. EAF P5K6 Hb at 4 gm % is an O2 carrying colloidal plasma expander. However, a prototype of EAF P5K6 Hb, developed by Sangart as MP4, did not increase microvascular oxygen delivery or improve tissue oxygenation in models of extreme hemodilution,whereas the EAF P5K6 Hb and P5K2 did better than the non-oxygen carrying semisynthetic colloidal plasma expander and EAF P5K6 albumin.Also, P5K2 Hb does a better tissue oxygenation even though its oxygen affinity is comparable to that of EAF P5K6 Hb1.As PEG chains increases from 2 to 10 copies, there is a lesser effect in the oxygen affinity of PEG Hbs in the presence of allosteric effectors like IHP and L-35. This suggests that higher degree of PEGylation preferentially stabilize the oxy conformation of PEG Hb, decreasing the efficacy of O2 release in the circulation. We attributed this decreased efficiency to the larger PEG shell which might lower the diffusion of O2out to the plasma. We reasoned that we could reduce the size of the PEG shell using six copies of PEG 3K and that we could use this new PEG Hb (EAF P3K6 Hb) at 6 gm% to get nearly the same viscosity as 4 gm % EAF P5K6 Hb. We compared tissue oxygenation by EAF P3K6 Hb with EAF P5K6 Hb and P5K2 Hb in an experimentally induced anemia model and tested its therapeutic efficacy in attenuating the experimentally induced acute crisis in a mild murine model of SCD, NY1DD.MethodsEAF P3K6 Hb was prepared with PEG3K and characterized as EAF P5K6 Hb2. Molecular models and the shapes of PEG Hbs have been developed using InsightII program (Accelrys). Tissue oxygenation studies were carried out in the extreme hemodilution hamster model as described previously.1 Acute vaso-occlusion was studied using intravital microscopy in the venules of cremaster muscles of NY1DD SCD mice subjected to hypoxia-reoxygenation (18 hrs of hypoxia with 8% O2 and then normoxia).3The efficacy was measured after treatment with 10% top load of 6 gm % solution of EAF P3K6 Hb, given at the transitioning stage from hypoxia to normoxiaResultsPEG 3K chains reduced the molecular radius and volume while increased the packing density of PEG shell of EAF P3K6 Hb as compared to EAF P5K6 Hb (Table 1). The packing of the PEG chains induced a globular shape to the EAF P3K6 Hb vs ellipsoidal shape to EAF P5K6 Hb (Fig 1). Oxygen affinity of EAF P3K6 was comparable to that of EAF P5K6 Hb. In the extreme hemodilution hamster model of anemia, the efficacy of EAF P3K6 Hb to increase tissue oxygenation was comparable to that of P5K2 Hb (Fig 2). From the intravital micrographs of cremaster muscles (Fig 3), P3K6 Hb markedly attenuated the induced vaso-occlusive crisis in NY1DD mice.Discussion and ConclusionsWe have previously shown that EAF P3K6 Hb is effective in normalizing the chronic state of vaso-occlusion in BERK sickle mice. We demonstrate here that EAF P3K6 Hb protects NY1DD sickle mice from developing acute vaso-occlusion. These studies suggest that a smaller compact PEG shell around Hb increases the ability of the PEG Hb to oxygenate the tissues. NY1DD mice are not very anemic (Hb > 10 gm/dl); a 10% top load of 6 gm% high oxygen affinity Hb represents no significant increase in Hb level (≈0.06 gm %). We suggest that the ability of such a miniscule amount of PEG Hb in the plasma to protect the animal from hypoxia is due to its enhanced ability to deliver O2 under anemic and hypoxic conditions. We suggest that EAF P3K6 Hb facilitates improved extraction of O2 from RBC to plasma and to the subsequent diffusion to tissues, i.e. small amount of PEG Hb in plasma acts as a catalyst for O2 transfer while the oxyHb in RBC serves as the local reservoir for O2. This improved O2 extractionmay be effective in anemia in general, and have a unique application in sickle cell disease.

Retrospective Study of High Hemoglobin Levels in 56 Young Adults

▪Introduction. Erythrocytosis is a common reason for a hematology consultation. Most of the patients are over 50 years of age. The diagnostic approach is already well established, but determining the etiology of erythrocytosis in the young adult may be a real diagnostic challenge. Hereditary causes are often first suspected, but the real etiologic panorama of erythrocytosis in this population is still poorly understood.Methods. This Canadian single-center retrospective observational study was conducted in a Québec university hospital over a period of 20 years (1995 - 2015). Data were collected by a single investigator in a standardized database. From a computer-generated query over a chosen period of time, all patients between 16 and 35 years of age with high levels of hemoglobin or hematocrit were selected (hemoglobin > 185 g/L and/or hematocrit > 0.52 in men; hemoglobin > 165 g/L and/or hematocrit > 0.48 in women). Files were analyzed after approval from the scientific and ethical committees.Results. 426 patients fulfilled the above criteria (on a total of 113 453 complete blood counts conducted in the same age range during the analysis period), but only 56 benefitted from further investigations. Only those cases were included in the study. The male-to-female ratio was 5 : 3. Among them, 59% were smokers, 11% had a high alcohol intake and 27% were using drugs on a regular basis. Obesity was present in 43% of patients (morbid obesity in nearly one third of cases). More than half of the patients had one visit or less with a specialist for investigation of their erythrocytosis. Among those who had a medical follow-up, the median length is 42 months. Erythropoietin was measured in 23% of cases and the JAK2 mutation was screened in 18% of cases. The diagnosis of an acquired polycythemia was made in 41% of cases: hypoxemia (n= 13), renal disorders (n = 6) and drug-induced (n= 4). No case of myeloproliferative syndrome was identified. Two cases were associated with congenital polycythemia (high oxygen affinity hemoglobinopathy). Diagnosis of relative polycythemia was made in slightly over 10% of cases (n= 7). In 24 patients, no conclusive cause could be identified. One third of those patients (n= 8) were hospitalised for mental health decompensation or self-induced intoxication when high hemoglobin levels were detected. When JAK2 mutation testing was not available, the complete blood count was further analyzed and it did not provide any evidence for myeloproliferative syndrome. One in five patients received treatment for their polycythemia, whatever the cause: aspirin (n= 7) and phlebotomy (n= 5). There has been no reported patient death associated with polycythemia or its treatment. Only two major complications occurred: thrombosis (n =1) and bleeding (n= 1).Conclusion. This is the first study to specifically analyze erythrocytosis in young adults. Despite the retrospective design, it demonstrates patient management often inconsistent with the actual recommendations and a lack of follow-up after initial investigations. Congenital polycythemia deserves to be systematically evoked in this age range, but represents only a small part of cases. Acquired polycythemia dominates the etiologies whereas myeloproliferative syndromes were not depicted in this study. Harmonisation of patient care for young adults with erythrocytosis is therefore highly desirable. DisclosuresNo relevant conflicts of interest to declare.

Sintered Structural Steels Containing Mn, Cr And Mo – The Summary of the Investigations

AbstractThe paper is presented the development and method of production of modern, Ni-free sintered structural steels which contain carbide forming alloying elements (Cr) with high affinity for oxygen (Cr, Mn) and the much smaller additive of an expensive alloying element (Mo), enabling the production of structural sintered steels in commercial belt furnaces, using safe sintering atmospheres. The investigations reported deal with the analysis of microstructure and mechanical properties of these sintered structural steels produced in different processing conditions, especially modification of chemical composition of sintering atmosphere and also the connections between the microstructure of sintered material and its mechanical properties. This analysis was done to propose the appropriate chemical composition of sintered Ni-free steels with properties which are comparable or even better than those of sintered structural steels containing rich and carcinogenic nickel. The investigations of PM Mn- Cr-Mo steels were preceded by those on Mn steels.

Fractography of Sinteraustempered and Sinterhardened Fe-3Mn-0.8C PM Steels

Abstract Sintered steels with the addition of manganese are widely used in industry because of their attractive mechanical properties. The main problem of using manganese in powder metallurgy steel production is its high affinity for oxygen. The choice of proper sintering parameters can significantly improve the properties of the final product. For the present investigations Höganäs iron powder grade NC 100.24, low-carbon (1.3%C) ferromanganese Elkem (Eramet Norway Sauda – formerly Elkem Manganese Sauda) and graphite powder grade C-UF were used as the starting powders. Mixture of powders, containing 3% Mn and 0.8% C, was prepared in Turbula mixer for 30 minutes. Following mixing, “dog bone” compacts were pressed at 660 MPa according to PN-EN ISO 2740 standard. Sintering of compacts was carried out in the laboratory tube furnace at 1120 and 1250°C for 60 minutes in air or pure nitrogen (99.999%N2). The present investigation deals with the comparison of two heat treatment routes: sinterhardening (SH) and sinteraustempering (SAT), carried out both in air and pure nitrogen. Mechanically tested steels were investigated using JEOL JSM 700F completed with EDS. Metallography tests were carried out on 3% Nital etched samples. In this paper the results of mechanical tests and metallography and fractography investigations are shown. According to the results obtained, it can be assumed that for sinteraustempering higher temperature does not influence mechanical properties of sintered steels. For both methods using pure nitrogen as sintering atmosphere gave better results.

Influence of Oxides on Porosity Formation in Sr-Treated Alloys

The aim of the present study has been to investigate the metallurgical parameters controlling the microstructural evolution and porosity formation in Al–Si–Mg and Al–Si–Cu alloys, through a study of the microstructural characteristics of directionally solidified A356 and 319 type alloys as a function of iron content, Sr addition (~250 ppm), and solidification rate. In the Sr-modified alloys, porosity formation is frequently associated with strontium oxides (particles or films), as well as β-Al5FeSi phase platelets. These oxides (with a stoichiometric composition close to Al2SrO3) are formed during melting, due to the high oxygen affinity of strontium, and are difficult to remove via degassing. The pore morphology (round or irregular) is determined by the form of the oxide, i.e. fine dispersed particles or thick films. Round pores are also observed surrounded by Al–Si eutectic regions. Aluminum oxide films trapped in the molten metal lead to the formation of coarser and deeper pores than those formed due to the strontium oxides. These pores can also link with each other and are characterized by the presence of solidified metal trapped within the aluminum oxide films, close to the periphery. The form of these pores is controlled by the amount of gases trapped within the pores during solidification.

Reactivity and analytical performance of oxygen as cell gas in inductively coupled plasma tandem mass spectrometry

The reactivity and analytical performance of O2 as cell gas in inductively coupled plasma tandem mass spectrometry was investigated. Selected analytes in a wide mass range were divided in three groups according to their reactivity: G1 represents elements with high oxygen affinity (Ce, La, P, Sc, Ti, and Y), G2 contains elements that may partially react with oxygen (As, Ba, Mo, Si, Sr, and V), and G3 comprises elements expected to be less reactive towards oxygen (Al, Bi, Cu, Mg, Pb, and Pd). On-mass and mass-shift modes were evaluated by monitoring atomic and metal oxide ions, respectively. Analytical signal profiles, oxide percentages, sensitivities and limits of detection for oxygen flow rates varying from 0.1 to 1.0mLmin−1 were also studied. Group 1 elements plus As and V presented better sensitivities and LODs when measuring oxides, which were the major species for all flow rates evaluated. Molybdenum and Si oxides presented intermediate behavior and MoO fraction was up to 47% and limit of detection was the same as that obtained in on-mass mode. For others G2 and G3 elements, on-mass mode presented higher sensitivity and better LODs, with estimated oxide contents lower than 10%. In most cases, increasing oxygen flow rates led to lower sensitivities and worse LODs.

Thorium effect on the oxidation of uranium: Photoelectron spectroscopy (XPS/UPS) and cyclic voltammetry (CV) investigation on (U1 − xThx)O2 (x = 0 to 1) thin films

Thin films of U1−xThxO2 (x=0 to 1) have been deposited via reactive DC sputter technique and characterized by X-ray/Ultra-violet Photoelectron Spectroscopy (XPS/UPS), X-ray Powder Diffractometer (XRD) and Cyclic Voltammetry (CV) in order to understand the effect of Thorium on the oxidation mechanism. During the deposition, the competition between uranium and thorium for oxidation showed that thorium has a much higher affinity for oxygen. Deposition conditions, time and temperature were also the subject of this study, to look at the homogeneity and the stability of the films. While core level and valence band spectra were not altered by the time of deposition, temperature was affecting the oxidation state of uranium and the valence band due to the mobility increase of oxygen through the film. X-ray diffraction patterns, core level spectra obtained for U1−xThxO2 versus the composition showed that lattice parameters follow the Vegard's law and together with the binding energies of U-4f and Th-4f are in good agreement with literature data obtained on bulk compounds. To study the effect of thorium on the oxidation of U1−xThxO2 films, we used CV experiments at neutral pH of a NaCl solution in contact with air. The results indicated that thorium has an effect on the uranium oxidation as demonstrated by the decrease of the current of the oxidation peak of uranium. XPS measurements made before and after the CV, showed a relative enrichment of thorium at the extent of uranium at the surface supporting the formation at a longer term of a thorium protective layer at the surface of uranium-thorium mixed oxide.

The physiological basis of bird flight.

Flapping flight is energetically more costly than running, although it is less costly to fly a given body mass a given distance per unit time than it is for a similar mass to run the same distance per unit time. This is mainly because birds can fly faster than they can run. Oxygen transfer and transport are enhanced in migrating birds compared with those in non-migrators: at the gas-exchange regions of the lungs the effective area is greater and the diffusion distance smaller. Also, migrating birds have larger hearts and haemoglobin concentrations in the blood, and capillary density in the flight muscles tends to be higher. Species like bar-headed geese migrate at high altitudes, where the availability of oxygen is reduced and the energy cost of flapping flight increased compared with those at sea level. Physiological adaptations to these conditions include haemoglobin with a higher affinity for oxygen than that in lowland birds, a greater effective ventilation of the gas-exchange surface of the lungs and a greater capillary-to-muscle fibre ratio. Migrating birds use fatty acids as their source of energy, so they have to be transported at a sufficient rate to meet the high demand. Since fatty acids are insoluble in water, birds maintain high concentrations of fatty acid-binding proteins to transport fatty acids across the cell membrane and within the cytoplasm. The concentrations of these proteins, together with that of a key enzyme in the β-oxidation of fatty acids, increase before migration.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.

Aeration optimization through operation at low dissolved oxygen concentrations: Evaluation of oxygen mass transfer dynamics in different activated sludge systems

In wastewater treatment plants (WWTPs) using the activated sludge process, two methods are widely used to improve aeration efficiency — use of high-efficiency aeration devices and optimizing the aeration control strategy. Aeration efficiency is closely linked to sludge characteristics (such as concentrations of mixed liquor suspended solids (MLSS) and microbial communities) and operating conditions (such as air flow rate and operational dissolved oxygen (DO) concentrations). Moreover, operational DO is closely linked to effluent quality. This study, which is in reference to WWTP discharge class A Chinese standard effluent criteria, determined the growth kinetics parameters of nitrifiers at different DO levels in small-scale tests. Results showed that the activated sludge system could meet effluent criteria when DO was as low as 0.3mg/L, and that nitrifier communities cultivated under low DO conditions had higher oxygen affinity than those cultivated under high DO conditions, as indicated by the oxygen half-saturation constant and nitrification ability. Based on nitrifier growth kinetics and on the oxygen mass transfer dynamic model (determined using different air flow rate (Q′air) and mixed liquor volatile suspended solids (MLVSS) values), theoretical analysis indicated limited potential for energy saving by improving aeration diffuser performance when the activated sludge system had low oxygen consumption; however, operating at low DO and low MLVSS could significantly reduce energy consumption. Finally, a control strategy coupling sludge retention time and MLVSS to minimize the DO level was discussed, which is critical to appropriate setting of the oxygen point and to the operation of low DO treatment technology.

High oxygen affinity hemoglobins

High oxygen affinity hemoglobins are responsible for rare and heterogeneous autosomic dominant genetic diseases. They cause pure erythrocytosis, sometimes accountable for hyperviscosity and thrombosis, or hemolysis. Differential diagnoses must be first ruled out. The diagnosis is based on the identification of a decreased P50, and their possible characterization by cation exchange-high performance liquid chromatography and capillary electrophoresis. Finally, genetic studies of the responsible globin chain gene will confirm the mutation. The prognosis mainly relies on the P50 decrease rate and on the hemoglobin cooperativity impairment. Disease management should be personalized, and it should primarily depend on smoking cessation and physical activity. Phlebotomy and platelet aggregation inhibitors’ prescriptions can be discussed. There is no contraindication to flights, high-altitude conditions, or pregnancy. Nevertheless, blood donation must be prohibited.