Ability Of Re Research Articles

Fabrication of uniform and anti-corrosion layered double hydroxides film on Mg-Gd-Y-Zn-Zr alloy through solution pH tailoring

Second phase is generally beneficial to the mechanical properties of magnesium (Mg) alloys. As an electrochemically heterogeneous structure, it leads to the formation of uneven chemical conversion films which are detrimental to corrosion protection. To address this problem for multiphase Mg alloys, a simple hydrothermal method was reported herein for fabricating a layered double hydroxides (LDHs) film with a uniform structure and superior corrosion protection upon Mg-Gd-Y-Zn-Zr alloy through tailoring solution pH. Morphology characterization reveals that high solution pH facilitates the production of LDHs nanosheets with dense and fine features, which is attributed to the high density of hydroxy groups on substrate as nucleation sites for LDHs growth. In addition, the uniformity of films depended on solution pH. The highest pH (13.5) of this study drove even distribution of OH− that in turn circumvented the micro-galvanic effect between second phases and α-Mg matrix. Immersion and electrochemical tests confirmed that corrosion resistance of the sample fabricated at pH of 13.5 outperformed those of the counterparts fabricated at pH 10−12. It is postulated that the high compactness of the LDHs film and the self-healing ability of RE(OH)3 were the driving forces.

Ginsenoside Re Attenuates High Glucose-Induced RF/6A Injury via Regulating PI3K/AKT Inhibited HIF-1α/VEGF Signaling Pathway.

Hyperglycaemia-induced retinal microvascular endothelial cell apoptosis is a critical and principle event in diabetic retinopathy (DR), which involves a series of complex processes such as mitochondrial dysfunction and oxidative stress. Ginsenoside Re (Re), a key ingredients of ginseng, is considered to have various pharmacologic functions, such as antioxidative, inhibition of inflammation and anti-apoptotic properties. However, the effects of Re in DR and the related mechanisms of endothelial cell injury induced by high glucose (HG) exposure remain unclear. The present study was designed to investigate and evaluate the ability of Re to ameliorate HG-induced retinal endothelial RF/6A cell injury and the potential mechanisms involved in the hypoxia-inducible factor-1-alpha (HIF-1α)/vascular endothelial growth factor (VEGF) signaling regulated by phosphoinositide 3-kinase (PI3K)/AKT pathway. Our results showed that preincubation with Re exerted cytoprotective effects by reversing the HG-induced decrease in RF/6A cell viability, downregulation of apoptosis rate and inhibition of oxidative-related enzymes, thereby reducing the excess intracellular reactive oxygen species (ROS) and HG-triggered RF/6A cell injury. In addition, Western blot analysis results showed ginsenoside Re significantly increased HIF-1α expression in the cytoplasm but decreased its expression in the nucleus, suggesting that it reduced the translocation of HIF-1α from the cytoplasm to the nucleus, and downregulated VEGF level. Moreover, this effect is involved in the activation of the PI3K/Akt pathway. LY294002, a PI3K inhibitor, was used to block the Akt pathway. Afterwards, the effects of Re on the regulation of apoptotic related proteins, VEGF and HIF-1α nuclear transcription was partially reversed. These findings suggested the exerting protective effects of ginsenoside Re were associated with regulating of PI3K/AKT and HIF-1α/VEGF signaling pathway, which indicates that ginsenoside Re may ameliorates HG-induced retinal angiogenesis and suggests the potential for the development of Re as a therapeutic for DR.

Ginsenoside Re Inhibits ROS/ASK-1 Dependent Mitochondrial Apoptosis Pathway and Activation of Nrf2-Antioxidant Response in Beta-Amyloid-Challenged SH-SY5Y Cells.

Accumulation of amyloid-β (Aβ), which results in the formation of senile plaques that cause oxidative damage and neuronal cell death, has been accepted as the major pathological mechanism of Alzheimer’s disease (AD). Hence, inhibition of Aβ-induced oxidative damage and neuronal cell apoptosis represents the effective strategies in combating AD. Ginsenoside Re (Re) has pharmacological effects against Aβ-induced neurotoxicity. However, its molecular mechanism remains elusive. The present study evaluated the effect of Re against Aβ-induced cytotoxicity and apoptosis in SH-SY5Y cells, and investigated the underlying mechanism. We demonstrate that Re inhibits the Aβ-triggered mitochondrial apoptotic pathway, as indicated by maintenance of mitochondrial functional, elevated Bcl-2/Bax ratio, reduced cytochrome c release, and inactivation of caspase-3/9. Re attenuated Aβ-evoked reactive oxygen species (ROS) production, apoptosis signal-regulating kinase 1 (ASK1) phosphorylation, and JNK activation. ROS-scavenging abrogated the ability of Re to alter ASK-1 activation. Simultaneously, inhibition of JNK abolished Re-induced Bax downregulation in Aβ-challenged SH-SY5Y cells. In addition, Re enhanced activation of the nuclear factor-E2-related factor 2 (Nrf2) in Aβ-induced SH-SY5Y cells. Knockdown of Nrf2 by small interfering RNA targeting Nrf2 abolished the protective effect of Re. Our findings indicate that Re could be a potential therapeutic approach for the treatment of AD.

Effects of Re, W and Co on dislocation nucleation at the crack tip in the γ-phase of Ni-based single-crystal superalloys by atomistic simulation.

The effects of Re, W and Co on dislocation nucleation at the crack tip in Ni have been studied by the molecular dynamics method. The results show that the activation energy of dislocation nucleation is lowered by the addition of Re, W and Co; moreover, the activation energy decreases when the alloying element increases from 1 at.% to 2 at.%. The energy landscapes of the atoms are studied to elucidate these effects. Quantification analyses of the bonding strength between Ni and X (X = Re, W or Co) reveal that strong bonding between Ni and X (X = Re, W or Co) in the dislocation nucleation process can suppress the cleavage process and enhance the ability of dislocation nucleation. The surface energy and unstable stacking fault energy are also calculated to understand the alloying effects on the dislocation nucleation process. The results imply that interaction between alloying elements and Ni atoms plays a role in promoting the dislocation nucleation process at the crack tip. The ability of Re, W and Co in improving the ductility of the Ni crack system is in the order W > Re > Co. The results could provide useful information in the design of Ni-based superalloys.

Geochronology of Hydrothermal Processes Leading to the Formation of the Au–U Mineralization at the Rompas Prospect, Peräpohja Belt, Northern Finland: Application of Paired U–Pb Dating of Uraninite and Re–Os Dating of Molybdenite to the Identification of Multiple Hydrothermal Events in a Metamorphic Terrane

The Peräpohja belt comprises a greenschist to amphibolite facies; multiply-folded supracrustal sequence of quartzites; mafic volcanics; carbonate rocks; black shales; mica schists and greywackes deposited from ca. 2.44 Ga to 1.92 Ga; during protracted rifting of the Archaean basement. Metamorphism and multiple folding of the basin fill occurred during the Svecofennian orogeny (1.92–1.80 Ga). The Rompas Au–U mineralization is hosted within deformed and metamorphosed calcsilicate veins in mafic volcanics. Textural evidence suggests that deposition and periods of uraninite re-mobilization were followed by localized hydrocarbon-bearing fluid flow which produced pyrobitumen crusts around grains of uraninite. Gold precipitated during the latest hydrothermal event at around 1.75 Ga. In situ U–Pb dating of uraninite by laser ablation inductively coupled mass spectroscopy (LA-ICP-MS), and Re–Os dating of molybdenite, indicate that primary hydrothermal uranium mineralization forms two age clusters; about 2.03–2.01 and 1.95–1.94 Ga. Resetting of the U–Pb system and precipitation of new generations of uraninite are associated with major deformation and metamorphic stages of the Svecofennian orogeny at 1.91–1.89 Ga, 1.85 Ga, and 1.80 Ga. Gold deposition was synchronous with the emplacement of the 1.75–1.78 Ga late/post-orogenic granitoids. The gold-producing hydrothermal event is also recorded by Re–Os dating of molybdenite from the gold-bearing Mg-metasomatized metasedimentary and metavolcanic units at the Palokas prospect; a few kilometres from Rompas. Results of this study confirm that some domains in the structure of uraninite may preserve the original crystallization age, despite an overprinting amphibolite facies metamorphic and other hydrothermal events. The study supports the utility of in situ U–Pb dating of uraninite and the ability of Re–Os dating to assist in sorting out different hydrothermal events in areas with complex tectonic; magmatic and metamorphic histories.

PURITY UPGRADE OF AMMONIUM PERRHENATE SOLUTIONS IN RESPECT OF MOLYBDENUM (VI) AT SORPTION RECOVERY OF RHENIUM (VII) FROM SOLUTIONS CONTAINING MOLYBDENUM (VI)

The study covers the method of additional cleaning of ammonium perrhenate desorbates from molybdenum through sorption recovery of rhenium from Mo-containing solutions with Purolite A170 and A172 weak base anion exchange resins. The dependence of Re(VII) and Mo(VI) sorption using these resins on solution pH was studied under static conditions with the 1 M (NH 4 ) 2 SO 4 solution. It was found that the pH range at which the resins retain the ability of Re(VII) sorption extends to a weak-alkaline area. A significant decrease in Re(VII) adsorption begins when pH exceeds 7,5 Mo(VI) capacity of the resins decreases significantly when solution pH exceeds 5,0, and both anion exchange resins practically stop molybdenum sorption at above pH ~ 7,0. Reduction of Mo(VI) content in rhenium desorbates obtained in sorption recovery of Re(VII) from Mo-containing solutions with weak base anion exchange resins can be achieved as follows. First, major quantity of adsorbed Mo(VI) is desorbed from the loaded resin by ammonium sulfate solution when stirring the mixture and keeping pH constant in the 7,0–7,5 range by dosing the ammonia solution. Then the resin is separated from the Mo(VI)-containing ammonia solution, washed with water, and Re(VII) is desorbed by the ammonia solution in dynamic conditions. The proposed method was verified with anion exchangers loaded in sorption from the model solution with the following composition, g/L: 98 H 2 SO 4 , 4 Mo(VI), 0,5 Re(VII). It was shown that resin treatment with the ammonium sulfate solution removes at least 90 % of adsorbed molybdenum. A ratio of Re(VII) to Mo(VI) concentrations in ammonium perrhenate desorbates increases by 11 times with Purolite A170 resin, and by 20 times with Purolite A172 resin compared to the results obtained without an additional Mo(VI) washing. Re(VII) losses (reversible) with the Mo-containing desorbate are below 5,2 % of the adsorbed Re(VII) amount.

In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Methanol Oxidation on Pt(111) and Pt–Re Alloys

For methanol oxidation reactions, Pt–Re alloy surfaces are found to have better selectivity for CO2 production and less accumulation of surface carbon compared to pure Pt surfaces. The unique activity of the Pt–Re surface is attributed to the increased ability of Re to dissociate oxygen compared to Pt and the ability of Re to diffuse gradually to the surface under reaction conditions. In this work, the oxidation of methanol was studied by ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and mass spectrometry on Pt(111), a Pt–Re surface alloy, and a Re film on Pt(111) as well as Pt(111) and Pt–Re alloy surfaces that were preoxidized before reaction. Methanol oxidation conditions consisted of 200 mTorr of O2/100 mTorr of methanol at temperatures ranging from 300 to 550 K. The activities of all of the surfaces studied are similar in that CO2 and H2O are the main oxidation products, along with formaldehyde, which is produced below 450 K. For reaction on Pt(111), there is a change in selectivity that favors CO and H2 over CO2 at 500 K and above. This shift in selectivity is not as pronounced on the Pt–Re alloy surface and is completely absent on the oxidized Pt–Re alloy surfaces and oxidized Re film. AP-XPS results demonstrate that Pt(111) is more susceptible to poisoning by carbonaceous surface species than any of the Re-containing surfaces. Oxygen-induced diffusion of Re to the surface is believed to occur at elevated temperatures under reaction conditions, based on the increase in the Re/Pt ratio upon heating; density function theory (DFT) calculations confirm that there is a thermodynamic driving force for Re atoms to diffuse to the surface in the presence of oxygen. Furthermore, Re diffuses to the surface when the Pt–Re alloy is exposed to O2 at 450 K before methanol oxidation, and consequently this surface has the highest CO2 production at temperatures below that required for Re diffusion during methanol reaction. Although the oxidized Re film also exhibits high selectivity for CO2 production and minimal carbon deposition, this surface is unstable due to the sublimation of Re2O7; in contrast, the Pt–Re alloy is more resistant to Re sublimation since the majority of Re resides in the subsurface region.

RETRACTED ARTICLE: Imperialism in Bioethics: How Policies of Profit Negate Engagement of Developing World Bioethicists and Undermine Global Bioethics

How do bioethics gatekeepers located in wealthy nations treat bioethics workers from developing countries? Can the policies of leading international bioeth- ics journals—based on a concern for profit that effectively restrictsaccessfor mostresearchersfrom developingcoun- tries—be ethically justified? We examined these policies focusing on the way they influence the ability of re- searchers in resource-poor countries to participate in the development of the field of bioethics. Eight of the fourteen leading bioethics journals are published by three transna- tional publishing houses, all of which are based in wealthy nations. None of these eight journals participates in the Health InterNetwork Access to Research Initiative (HINARI) of the World Health Organization, a program that provides free or very low-cost online access to the major journals by researchers in developing countries. Lack of access to these essential resources makes it ex- tremely difficult, if not impossible, for bioethicists in de- veloping countries to learn from, and engage in, the global bioethics dialogue. Thus, exclusionary practices of leading bioethics journals sustain the hegemony of Western bio- ethics, raising serious questions about professed aspira- tions to create a truly Bglobal^ bioethics. This phenome- non indicates lack of empathy and moral imagination of

Effect of Substituent Groups in Rhenium Bipyridine Complexes on Photocatalytic CO2 Reduction

We synthesized four different rhenium complexes, Re(bpy-R)(CO)3Cl (bpy = 2,2-bipyridine and R = H, CH3, COOH, or CN), as photocatalysts that selectively reduce CO2 to CO and investigated the effect of substituent groups (Rs) on the absorption and photocatalystic properties for CO2 reduction under 365-nm light irradiation. The Re(bpy-R)(CO)3Cl (R = H or CH3 or COOH) reduced CO2 to CO in CO2-saturated DMF-triethanolamine solution, which was irradiated with 365-nm light. The amount of CO produced by CO2 reduction differed, depending on the introduced Rs in the bipyridine moiety. We found that the ability of Re(bpy-R)(CO)3Cl (R = H or CH3 or COOH) to produce CO has a linear relationship to molar absorption coefficients of rhenium complexes at the irradiated light wavelength. Introduction of the COOH group, which has the highest molar absorption coefficient among four rhenium complexes, enhanced CO2-to-CO reduction capacity (6.59 mol/cat-mol2h) five times that of Re(bpy-H)(CO)3Cl with no R.

Effect of remelting treatment on glass forming ability of RE (Gd, Sm)56Al26Co18 alloys

The bulk metallic glasses (BMGs) were prepared by a copper mold suction casting method, denoted by Gd56Al26Co18 (1) and Sm56Al26Co18 (1). Then, the obtained metallic glasses mentioned above were remelted and injected to copper mold, and the metallic glasses were prepared by remelting, denoted by Gd56Al26Co18 (2) and Sm56Al26Co18 (2). The glass forming ability and thermal expansion behavior were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), dilatometer and high resolution transmission electron microscopy (HRTEM). The results showed that the remelting treatment can improve the glass forming ability of the alloys. In addition, it was found that the average thermal expansion coefficients of the BMGs prepared by remelting were smaller than the BMGs prepared by first-time melting for Gd56Al26Co18 and Sm56Al26Co18 alloys, which indicated the remelting treatment can enhance the thermal stability of the Gd56Al26Co18 and Sm56Al26Co18 BMGs.

The mechanism of oxide ion conductivity in bismuth rhenium oxide, Bi28Re2O49

We have carried out a combined experimental and computational study of oxide ion conductor Bi28Re2O49, with the aim of elucidating the conductivity mechanisms and pathways in this material. Single crystals of Bi28Re2O49 were grown from melt and the structure was investigated for the first time by single crystal X-ray diffraction. The structural model obtained is consistent with the Re atoms in Bi28Re2O49 being both four- and six-coordinate, in a 3:1 ratio, in agreement with previous EXAFS and IR spectroscopy studies. The thermal displacement parameters of the oxygen atoms bonded to Re suggest substantial disorder of the Re coordination polyhedra. Ab-initio molecular dynamics simulations were performed to probe the oxide ion migration pathways in Bi28Re2O49 and the roles of the Bisingle bondO and Resingle bondO sublattices. The key conclusion is that the ability of Re to support variable coordination environments is vitally important in Bi28Re2O49; it provides a mechanism for ‘self-doping’ of the structure, i.e. the creation of O2 − vacancies in the fluorite-like Bisingle bondO sublattice by exchange of O atoms with the Resingle bondO sublattice, and the subsequent increase of the average coordination number of Re. All three crystallographically unique oxygen sites in the Bisingle bondO sublattice play roles in the ionic migration processes, by facilitating the O2 − exchange between the ReOx groups and by contributing to the O2 − diffusion via the vacancy-hopping mechanisms.

Harnessing Redox-Active Ligands for Low-Barrier Radical Addition at Oxorhenium Complexes

The addition of an [X](+) electrophile to the five-coordinate oxorhenium(V) anion [Re(V)(O)(ap(Ph))(2)](-) {[ap(Ph)](2-) = 2,4-di-tert-butyl-6-(phenylamido)phenolate} gives new products containing Re-X bonds. The Re-X bond-forming reaction is analogous to oxo transfer to [Re(V)(O)(ap(Ph))(2)](-) in that both are 2e(-) redox processes, but the electronic structures of the products are different. Whereas oxo addition to [Re(V)(O)(ap(Ph))(2)](-) yields a closed-shell [Re(VII)(O)(2)(ap(Ph))(2)](-) product of 2e(-) metal oxidation, [Cl](+) addition gives a diradical Re(VI)(O)(ap(Ph))(isq(Ph))Cl product ([isq(Ph)](•-) = 2,4-di-tert-butyl-6-(phenylimino)semiquinonate) with 1e(-) in a Re d orbital and 1e(-) on a redox-active ligand. The differences in electronic structure are ascribed to differences in the π basicity of [O](2-) and Cl(-) ligands. The observation of ligand radicals in Re(VI)(O)(ap(Ph))(isq(Ph))X provides experimental support for the capacity of redox-active ligands to deliver electrons in other bond-forming reactions at [Re(V)(O)(ap(Ph))(2)](-), including radical additions of O(2) or TEMPO(•) to make Re-O bonds. Attempts to prepare the electron-transfer series monomers between Re(VI)(O)(ap(Ph))(isq(Ph))X and [Re(V)(O)(ap(Ph))(2)](-) yielded a symmetric bis(μ-oxo)dirhenium complex. Formation of this dimer suggested that Re(VI)(O)(ap(Ph))(isq(Ph))Cl may be a source of an oxyl metal fragment. The ability of Re(VI)(O)(ap(Ph))(isq(Ph))Cl to undergo radical coupling at oxo was revealed in its reaction with Ph(3)C(•), which affords Ph(3)COH and deoxygenated metal products. This reactivity is surprising because Re(VI)(O)(ap(Ph))(isq(Ph))Cl is not a strong outer-sphere oxidant or oxo-transfer reagent. We postulate that the unique ability of Re(VI)(O)(ap(Ph))(isq(Ph))Cl to effect oxo transfer to Ph(3)C(•) arises from symmetry-allowed mixing of a populated Re≡O π bond with a ligand-centered [isq(Ph)](•-) ligand radical, which gives oxyl radical character to the oxo ligand. This allows the closed-shell oxo ligand to undergo a net 2e(-) oxo-transfer reaction to Ph(3)C(•) via kinetically facile redox-active ligand-mediated radical steps. Harnessing intraligand charge transfer for radical reactions at closed-shell oxo ligands is a new strategy to exploit redox-active ligands for small-molecule activation and functionalization. The implications for the design of new oxidants that utilize low-barrier radical steps for selective multielectron transformations are discussed.

Poly(4-vinylpyridine) resins towards perrhenate sorption and desorption

The series of the 4-vinylpyridine and divinylbenzene cationic polymers (4-VP/DVB) in the presence of toluene or toluene and heptane (100 wt.% in respect to the monomers mixture) were synthesised in order to obtain weak base anion exchangers with gel or macroporous structure. The strong base anion exchangers were obtained by its quaternization with alkyl iodide: propyl iodide, butyl iodide and pentyl iodide. The FTIR spectra of anion exchangers were useful to characterize resins and degree of quaternization. The sorption and desorption ability of rhenium, Re(VII), as perrhenate anion from acid solution (sulphuric or hydrochloric acid 0.1 M) were tested in batch and dynamic methods. The sorption of Re(VII) from the solution of 50 mg Re/L reached about 60 mg/g of dry resin in batch method. All the investigated anion exchangers characterize with high selectivity of perrhenate from multicomponent solution containing chlorocomplexes of PGM metals (Pt, Pd) and Au. The sorption ability of PGM metals and Re(VII) is on the same level as from the solution containing only one ion. The dynamic method of sorption allowed to reach the sorption of Re(VII) up 200 mg/g of resin. The desorption of Re(VII) by ammonium (5 wt.%), with the yield about 97%, was possible only from the weak base anion exchangers, where the degree of sorption and desorption is on the same level in the second and other cycles. The sorption ability of Re(VII) on new anion exchanger is comparable to commercial anion exchangers, like Reillex HP.

Charge donation to and dearomatization of benzene attending complexation: DFT estimates of binding energies of TpMXO(L) with benzene, for Tp = hydridotris(pyrazolyl) borate, MXO = MoNO, ReCO, and WNO, and L = ammonia, N‐methylimidazole, pyridine, phosphine, methyl isocyanide, and carbon monoxide

By density functional methods we characterize the bonding and charge distribution in complexes of benzene with dearomatizing agents tpReCO(L), tpMoNO(L), and tpWNO(L), where tp = hydrido Tris (pyrazolyl)borate), for a range of ligands L. Our LSDA and B3LYP density functional calculations use the Spartan LACVP+ basis and pseudopotential on Re, Mo, and W and 6-31G* on light atoms. The binding energy is strongly dependent on the nature of the ligand L, being greatest for L = ammonia and N-methylimidazole and weakest for CH3NC and CO. We find a correlation between strength of binding and electron transfer from the dearomatizing agents toward benzene. For the most strongly bound systems we find substantial (up to 500 millielectrons) charge transfer towards benzene, while for the most weakly bound systems charge is withdrawn from benzene. Structural details illustrate the ability of Re, Mo, and W species to dearomatize complexed benzene, which is extensive for all but the most weakly bound species with L = MeNC and CO. Re and W dearomatizing agents, which are computed and observed to form stable complexes with benzene, may be economic alternatives to osmium dearomatizing agents.

The Saccharomyces cerevisiae recombination enhancer biases recombination during interchromosomal mating-type switching but not in interchromosomal homologous recombination.

Haploid Saccharomyces can change mating type through HO-endonuclease cleavage of an expressor locus, MAT, followed by gene conversion using one of two repository loci, HML or HMR, as donor. The mating type of a cell dictates which repository locus is used as donor, with a cells using HML and alpha cells using HMR. This preference is established in part by RE, a locus on the left arm of chromosome III that activates the surrounding region, including HML, for recombination in a cells, an activity suppressed by alpha 2 protein in alpha cells. We have examined the ability of RE to stimulate different forms of interchromosomal recombination. We found that RE exerted an effect on interchromosomal mating-type switching and on intrachromosomal homologous recombination but not on interchromosomal homologous recombination. Also, even in the absence of RE, MAT alpha still influenced donor preference in interchromosomal mating-type switching, supporting a role of alpha 2 in donor preference independent of RE. These results suggest a model in which RE affects competition between productive and nonproductive recombination outcomes. In interchromosome gene conversion, RE enhances both productive and nonproductive pathways, whereas in intrachromosomal gene conversion and mating-type switching, RE enhances only the productive pathway.