Absence Of Oxide Research Articles

Spectroscopic, SOD, anticancer, antimicrobial, molecular docking and DNA binding properties of bioactive VO(IV), Cu(II), Zn(II), Co(II), Mn(II) and Ni(II) complexes obtained from 3-(2-hydroxy-3-methoxybenzylidene)pentane-2,4-dione

Novel macrocyclic Schiff base complexes [[ML]X; where M = Cu(II), Co(II), Ni(II), Zn(II), Mn(II) and VO(IV); L = macrocyclic ligand; X = Cl2 and SO4 2−] have been synthesized and characterized by microanalytical, 1H, 13C NMR, IR, Mass, UV–Vis, EPR spectral studies, as well as conductivity data. All the complexes exhibit square-planar geometry except vanadium complex. Magnetic susceptibility measurements and high conductance data reveal the monomeric and electrolytic nature of the complexes. Electronic absorption, cyclic voltammetry, viscosity measurements have been carried out on the interaction of the complexes with DNA. The results suggest that the complexes bind to DNA by intercalation via the aromatic ring of the macrocycle into the base pairs of DNA. Using gel electrophoresis experiment in the presence and absence of oxidant (H2O2) the nuclease cleavage activity of the complexes has been performed on plasmid DNA. The results demonstrate that most of the complexes have promising superoxide dismutase (SOD)-mimetic activity. The in vitro cytotoxicity of ligand and its complexes has also been evaluated against human breast and colon carcinoma cells. Binding interactions and energies of ligand and its metal complexes [ML]2+ (M = VO(IV), Mn(II), Co(II), Ni(II), Cu(II), Zn(II)) against the receptors EGFR and HER2 are performed using the Auto dock module. Consequently, it is found that the ligand is strong inhibitor for EGFR and HER2 while [VOL]SO4 is good inhibitor for EGFR and [ZnL]Cl2 is moderate inhibitor for HER2. The antimicrobial activity of the ligand and its complexes against bacteria Salmonella typhi, Staphylococcus aureus, Escherichia coli and Bacillus subtilis and fungi Aspergillus niger, Aspergillus flavus, Candida Albicans and Rhizoctonia bataicola. The complexes have higher activities than the macrocyclic free Schiff base. Communicated by Ramaswamy H. Sarma

AURUBIS Cu-OF

Abstract Aurubis Cu-OF is an oxygen-free, high conductivity copper with 99.95% minimum Cu. It offers the advantages of both electrolytic tough pitch (ETP) copper and phosphorus deoxidized (DHP) copper. Its high purity, with less than 10 ppm (0.001%) oxygen, and the absence of deoxidizers accounts for an electrical conductivity of 100% IACS minimum, as well as no susceptibility to hydrogen embrittlement. Due to the absence of oxides in the structure, Cu-OF is capable of withstanding extra deep drawing and severe forming, and is superior to Cu-ETP in this respect. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: Cu-911. Producer or Source: Aurubis AG.

Replacement reactions of copper sulphides at moderate temperature in acidic solutions

Understanding mineral transformations of composite copper sulphide ores and the associated reaction mechanism at low to medium temperatures in acidic solutions with oxidant restriction is important for in situ recovery operations because natural ore bodies typically comprise multiple sulphide species and their dissolution is oxidant consuming. Here we present experimental observations on mineral replacement reactions of coarse-grained natural bornite (Cu5FeS4)–chalcocite (Cu2S) samples in acidic solutions at 90 °C and in the absence of oxidant. Transformations were found to follow a three-stage reaction sequence for bornite and one stage for chalcocite. Bornite replacement commenced with the formation of digenite (Cu1.8S) along fractures and surfaces. Bornite–digenite interfaces are sharp and digenite rims contain nanochannels that connect to the original bornite. When copper dissolution exceeded 30%, copper-deficient lamellae exsolved from the bornite by solid-state diffusion; this texture appeared only in stronger acidic solutions with extended times and did not occur in the heating experiments without fluid. Chalcocite that was present together with bornite in the unreacted samples transformed into digenite characterized by laminar replacement textures. Finally, all phases were replaced by covellite (CuS) accompanied by the formation of porosity. These replacements showed the concomitant operation of fluid-induced solid-state diffusion and fluid-mediated mineral replacement by coupled dissolution–precipitation reactions. The textures found in the resulting covellite showed a promising increase in porosity that could be beneficial for hard-rock in situ recovery and suggests a pathway for refractory sulfide processing by acid pre-treatment.

Wear behaviour of metals in dry sliding against molybdenum with current collection

The possibility of high electrical conductivity of dry sliding electrical contact against molybdenum counterbody was studied. It was found that metals W and Cu were not able to form a sliding electrical contact with high wear resistance at current density higher 100 A/cm2 . The characteristics of the contacts of iron containing metals were slightly better than the contact characteristics of non-ferrous metals due to weaker adhesion. Using X-ray phase analysis, it was shown the absence of oxides in the sliding zone of non-ferrous metals. This led to their strong wear and contact’s low electrical conductivity. In the contact zone of iron containing samples the formation of FeO was observed that made it possible to reduce wear. This means that high electrical conductivity is unattainable in sliding with current collection against molybdenum.

Microstructural Evolution of the Refractory WCuNi Metallic Alloy

Science and technology of materials are widely interested in the development of new alloys involving tungsten due to its large applicability to the domain of nuclear material transportation. Tungsten is a refractory material and it has many applications in the nuclear industry due to its mechanical properties and excellent cross-section for thermal neutrons, being widely used for shielding of high-energy radiation. Some of the main elements added to tungsten forming alloys are Nb, Cr, Cu, Fe, Ni, Mo, Co, Sn, Ti, and Ta, which are responsible for modifications of the physical and chemical properties of the resulting alloy, interfering on the attenuation of gamma radiation. The main goal of this paper is to present a refractory alloy based on tungsten with embedded infiltrating elements like copper (Cu) and nickel (Ni) and characterize the microstructural evolution of different sintering process during its formation. Such a refractory alloy is submitted to the following characterization process: X-rays diffractometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy, and energy dispersive spectroscopy. The diffractometry exhibit typical standard results for the precursor powders: W, Cu, and Ni demonstrating high degrees of purity accordingly to the crystallographic determined parameters. The TGA for the powder W demonstrated thermal stability until 360 oC, after an increase of mass due to the process of oxidation. The DSC analyze present two endothermal processes at temperatures 350 °C and 450 °C. The microstructural evolution of WCuNi samples presents the absence of oxidation, homogeneous morphology and stability of the binary phase α–β (W and CuNi respectively) for different sintering. These results shall be taken into consideration for future works, particularly on the study of shielding and gamma radiation attenuation.

Enhancing the wash fastness of disperse dyes on wool with oxidants

AbstractDisperse dyes are not currently applied to wool commercially, in large part because of inadequate wash fastness, but they do have potential, especially for wool‐polyester blends. In this study, for the first time hydrogen peroxide was investigated to increase the wash fastness of disperse dyes on wool. In the absence of oxidants, 10 disperse dyes from seven classes imparted colours with a range of depths (K/S 2‐26) with wash fastness (grey scale ratings for colour change) grades of 3 to 4‐5. Hydrogen peroxide had only small effects on colours and gave only small enhancements to wash fastness, which were limited to anthraquinone, nitrodiphenylamine, disazo and coumarin dyes. The bleach activators Prestogen W and citric acid enhanced the bleaching effect of hydrogen peroxide but did not assist with raising wash fastness. Hydrogen peroxide in post‐dyeing scouring made the dyeings brighter but did not significantly enhance wash fastness. Ammonium persulphate, which was included for benchmarking with earlier studies, yellowed the wool and decomposed some dyes. This study extends the range of dye classes whose wash fastness on wool can be improved by ammonium persulphate to now include diazo, coumarin and methine, and confirms that oxidants/free radical initiators have potential for enabling the disperse dyeing of wool.

Potassium‐Cyanide Catalyzed Aerobic Oxidation of Aromatic Aldehydes into Esters

AbstractA simple and efficient procedure for trimerization of aromatic aldehydes mediated by potassium cyanide is described. A variety of aromatic aldehydes reacted efficiently and the corresponding oxidative esterification products were obtained in good to excellent yields in the absence of oxidant, solvent and metal species.

Acceptorless Alcohol Dehydrogenation Catalysed by Pd/C.

Although the selective oxidation of alcohols to carbonyl compounds is a critical reaction, it is often plagued by several challenges related to sustainability. Here, the continuous, acceptorless dehydrogenation of alcohols to carbonyl compounds over heterogeneous catalysts was demonstrated, in the absence of oxidants, bases or acceptor molecules. In addition to improving selectivity and atom efficiency, the absence of an acceptor resulted in the co-production of molecular H2 , a clean energy source, and permitted dehydrogenation to proceed at >98 % selectivity at turnover frequency values amongst the highest in the literature. Moreover, excellent durability was observed during continuous operation over 48 h, reaching space-time yields of 0.683 g(product) mL-1 h-1 , better than the state of the art by over two orders of magnitude. Alongside these breakthroughs, the basic kinetic parameters of the reaction were also determined, allowing some of the elementary reaction steps to be identified.

Utilization of formic acid in nanoscale zero valent iron-catalyzed Fenton system for carbon tetrachloride degradation

Although the utilization of formic acid (FA) as a target compound for modeling the kinetic and mechanism in several Fenton processes has been previously reported, this study explored the potential of FA as an efficient hydroxyl radical (HO) scavenger to generate reductive carbon dioxide radical (CO2−) for carbon tetrachloride (CT) degradation in nanoscale zero valent iron (nZVI) suspension in the presence and absence of oxidant. The results showed that the presence of 3.12 mM FA enhanced CT removal from 11.4% to 85.0% within 60 min in oxygenated 0.5 g/L nZVI suspension. Meanwhile, the presence of 3.12 mM FA improved Fe2+ elution by 5 folds under pH = 3. The generation of H2O2 in oxygenated nZVI suspension was also monitored. Hence, it was hypothesized that the rapid CT degradation in nZVI/FA system was initiated by reductive CO2− radical. In anaerobic nZVI/oxidant/FA system, CT degradation of 69.3% and 75.1% was achieved when using H2O2 or calcium peroxide (CP) as the oxidant, respectively. The addition of oxidant at 10 min reaction performed the best for CT removal as enough Fe2+ has been released after the dissolution of nZVI. These results demonstrated that a suitable dose of released Fe2+ was the key factor to enhance HO and CO2− radical generation in nZVI/oxidant/FA system. This study provided new information about effective usage of nZVI and FA for enhancing CT degradation in heterogeneous Fenton system.

N-Acetyl-L-cysteine Protects Human Retinal Pigment Epithelial Cells from Oxidative Damage: Implications for Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) involves the loss of retinal pigment epithelium (RPE) and photoreceptors and is one of the leading causes of blindness in the elderly. Oxidative damage to proteins, lipids, and DNA has been associated with RPE dysfunction and AMD. In this study, we evaluated oxidative stress in AMD and the efficacy of antioxidant, N-acetyl-L-cysteine (NAC), in protecting RPE from oxidative damage. To test this idea, primary cultures of RPE from human donors with AMD (n = 32) or without AMD (No AMD, n = 21) were examined for expression of NADPH oxidase (NOX) genes, a source of reactive oxygen species (ROS). Additionally, the cells were pretreated with NAC for 2 hours and then treated with either hydrogen peroxide (H2O2) or tert-butyl hydroperoxide (t-BHP) to induce cellular oxidation. Twenty-four hours after treatment, ROS production, cell survival, the content of glutathione (GSH) and adenosine triphosphate (ATP), and cellular bioenergetics were measured. We found increased expression of p22phox, a NOX regulator, in AMD cells compared to No AMD cells (p = 0.02). In both AMD and No AMD cells, NAC pretreatment reduced t-BHP-induced ROS production and protected from H2O2-induced cell death and ATP depletion. In the absence of oxidation, NAC treatment improved mitochondrial function in both groups (p < 0.01). Conversely, the protective response exhibited by NAC was disease-dependent for some parameters. In the absence of oxidation, NAC significantly reduced ROS production (p < 0.001) and increased GSH content (p = 0.02) only in RPE from AMD donors. Additionally, NAC-mediated protection from H2O2-induced GSH depletion (p = 0.04) and mitochondrial dysfunction (p < 0.05) was more pronounced in AMD cells compared with No AMD cells. These results demonstrate the therapeutic benefit of NAC by mitigating oxidative damage in RPE. Additionally, the favorable outcomes observed for AMD RPE support NAC's relevance and the potential therapeutic value in treating AMD.

Unlocking the Lithium Storage Capacity of Aluminum by Molecular Immobilization and Purification

Aluminum is regarded as a promising alternative for graphite anode in next-generation lithium-ion batteries, but its application is hindered by the simultaneous presence of aluminum oxide and the huge volume changes. Herein, hydrogenation-induced self-assembly of robust Al nanocrystals with high purity that are uniformly anchored on graphene is demonstrated. The strong molecular interaction between Al and graphene can not only thermodynamically facilitate the homogenous distribution of Al on graphene but also effectively alleviate the volume changes and preserve the structural integrity of the electrode. More importantly, density functional theory calculations reveal that the absence of oxidation can lower the energy barrier for Li diffusion inside the Al matrix to less than 1/6 of that in an Al matrix with only one monolayer coverage of oxygen. These unique structural features enable the aluminum/graphene nanosheets (Al@GNs) electrode to realize a high reversible capacity of 1219 mAh g-1 and an excellent cycling stability with capacity of 766 mAh g-1 after 1000 cycles at the 3 A g-1 rate. Furthermore, a full cell, comprising an Al@GNs anode and LiFePO4 cathode, exhibits remarkable capacity retention of 96.4% after 100 cycles at the 0.5 A g-1 rate.

Hydrothermal treatment of pharmaceutical wastewater

ABSTRACTThe effective disposal of industrial pharmaceutical waste waters with the desired quality has become a challenge. Supercritical water oxidation which involves water beyond critical point has been preferred due to its near complete conversions. This research work made an attempt to degrade the organic matter into fuel gases by gasifying the pharmaceutical waste water stream over sub- to supercritical temperature range (200–400°C). A maximum of 126.5 mmol/L of H2 gas yield was obtained at 400°C for 45 min. To achieve complete conversion, supercritical experiments have been performed in the presence of H2O2. The experiments resulted near complete conversion of 99.5% for an oxidation coefficient of 4 at 400°C in 5 min. The experimental results conveyed that useful products (H2, CO and CH4) can be attained with gasification in the absence of oxidant, while complete conversion can be achieved in the presence of oxidant in supercritical water.

Novel 3‐Hydroxy‐2‐naphthoic hydrazone and Ni(II), Co(II) and Cu(II) Complexes: Synthesis, Spectroscopic Characterization, Antimicrobial, DNA Cleavage and Computational Studies

A novel hydrazone ligand derived from condensation reaction of 3‐hydroxy‐2‐naphthoic hydrazide with dehydroacetic acid, and its Ni(II), Cu(II) and Co(II) complexes were synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility and conductivity methods, and screened for antimicrobial, DNA binding and cleavage properties. Spectroscopic analysis and elemental analyses indicated the formula, [MLCl2], for the complexes; square planar geometry for the nickel, and tetrahedral geometry for copper and cobalt complexes. The non‐electrolytic natures of the complexes in Dimethyl Sulphoxide (DMSO) were confirmed by their molar conductance values in the range of 6.11–14.01 Ω−1cm2mol−1. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA, by agarose gel electrophoresis, in the presence and absence of oxidant (H2O2) and free radical scavenger (DMSO), indicated no activity for the ligand, and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H2O2. When the complexes were evaluated for antibacterial and A‐DNA activity using Molecular docking technique, the copper complex was found to be most effective against Gram‐positive (S. aureus) bacteria. [CuLCl2] showed good hydrogen bonding interaction with the major‐groove (C2.G13 base pair) of A‐DNA. Density functional theory (DFT) calculations of the structural and electronic properties of the complexes revealed that [CuLCl2] had a smaller HOMO‐LUMO gap, suggesting a higher tendency to donate electrons to electron‐accepting species of biological targets.

CHARACTERISTICS OF DRY SLIDING ELECTRIC CONTACT OF METALS IN CONDITIONS OF CATASTROPHIC WEARING

The authors have studied the relation between wear intensity, average contact temperature and phase composition of the surface layers ofAISI 1020 steel, copper and NiTi alloy in dry sliding against the steel counterbody under electric current of density higher than 100 A/cm2 . These contact characteristics are considered carefully at the beginning of catastrophic wear, when the surface layers transit to the utmost state. It was noted that relaxation of stresses in the surface layers was due to the structural transformation in normal wear regime. It leads to tribolayers formation. The high strength of the copper tribolayer is first of all due to the formation of FeO oxide on the sliding surface, which prevents adhesion in contact. In addition, signs of a liquid phase were observed on the copper contact surface. It promoted the low rate of formation and accumulation of structural defects. Emergence of areas of melt and FeO oxide on the sliding surface provides high contact wear resistance. These factors, combined with the high thermal copper conductivity, have caused the tribolayer transition to the limit state at high current density and low contact temperature. The absence of oxides on the sliding surface of the NiTi alloy has caused strong adhesion in the contact, high rate of formation and accumulation of structural defects. Therefore, the tribolayer quickly deteriorates and high wear intensity and rapid increase in the contact temperature are observed with current density increase. Therefore, the catastrophic wear of the NiTi alloy begins at a temperature about 350 °C and at low current density. The sliding surface of AISI 1020 steel contained FeO oxide, therefore strong adhesion is not manifested. Formation of FCC-Fe in tribolayer of AISI steel 1020 is detected, that promotes its accelerated deterioration. Therefore, the tribolayer of AISI steel 1020 transites to the utmost state at a relatively low current density and at a higher temperature. The presented contact temperatures corresponding to the beginning stages of the utmost state of the tribolayer do not exceed 350 °С. Comparison of these temperatures with the known contact temperatures of other metals made it possible to assert that raising of the contact temperature of any metal higher than 400 °С leads to its utmost state. Therefore the characteristics of metals contact at temperatures of sliding contact higher than 500 °С is not of practical interest.

Role of CO2 methanation into the kinetics of preferential CO oxidation on Cu/Co3O4

In the present study, cobalt oxide (Co3O4) and Cu substituted Co3O4 were synthesized using sonochemical method. The role of Cu substitution was studied for CO oxidation in absence of H2 as well as in H2 rich conditions (PrOx). The synthesized catalysts were characterized by XRD, XPS, TEM and BET. The role of side reactions such as H2 oxidation and CO2 methanation in inhibiting the CO oxidation reaction were discussed. H2 – TPR and in situ FTIR were conducted to understand the reducible nature of the support and reaction mechanism. The intermediate species such as carbonates, bicarbonates, formates play an important role for CO oxidation under H2 rich conditions. Further, the utilization of atomic hydrogen by surface CO2 species, enhanced the methane formation. A detailed reaction mechanism was proposed for both CO oxidation and PrOx conditions with the insights obtained from in situ FTIR. 3% Cu/Co3O4 showed high stability for CO oxidation under hydrogen rich conditions for 50 h at 170 °C as well as in methanation prone region at 200 °C.

Gallic acid degradation by electron beam irradiation under various conditions.

In this study, aqueous solutions of gallic acid (GA) were irradiated in an electron beam (EB) accelerator under different experimental conditions (various initial GA concentrations, presence or absence of oxidant and oxygen). For an initial GA concentration of 50μM, complete GA degradation was achieved with an absorbed dose of 850Gy in the presence of dissolved oxygen. Both GA removal and mineralization are favored when oxygen is present. The addition of persulfate anions (S2O82-) or hydrogen peroxide (H2O2) also increased the efficiency of GA degradation and mineralization. For an absorbed dose of 14kGy, GA mineralization reached approximately 45%, 55%, and 72% for the EB, EB/H2O2, and EB/S2O82-systems, respectively. Three transformation products were tentatively identified in the presence of oxygen, these are the result of hydroxylation and ring opening reactions. No specific transformation product was found for the sulfate radical anion (SO4-●) reaction. Four additional compounds, including a dimer, were identified in oxygen-free solutions. These findings demonstrate that water radiolysis based on EB irradiation is an efficient process to activate H2O2 and S2O82- anions and is an advanced oxidation process (AOP).

Effect of Potassium Periodate Oxidizer on Germanium Chemical Mechanical Planarization Using Fumed Silica as Abrasive

The chemical mechanical planarization (CMP) removal rate (RR) of germanium using potassium periodate as oxidizer with fumed silica based slurries have been investigated. Static etch rate (ER) of germanium was performed as a function of solution temperature, pH and concentration of potassium periodate. Change in the enthalpy (ΔHact) and entropy (ΔSact) of activation for the Ge in the proposed oxidizer was found to be 11.029 kJ/mol and −271.06 J/mol.K, respectively. The values suggest that the dissolution of germanium in the proposed oxidizer is endothermic in nature and the etching is controlled by activation complex. The effect of slurry pH, KIO4 concentration, turntable speed and down pressure on Ge RR were studied. ER and RR of Ge was found to increase with pH. In the absence of oxidizer, polishing of germanium with 3 wt% fumed silica showed almost zero removal. With the addition of 1 wt% KIO4 + 0.1M KOH to 3 wt% fumed silica slurry, significant increase in the RR of Ge was observed for complete range of pH. Ge is oxidized to form germanium dioxide in the presence of KIO4, which on subsequent oxidation resulted in the formation of soluble species.

Direct Evidence for Ferrous Ion Oxidation and Incorporation in the Absence of Oxidants by Dps from Marinobacter hydrocarbonoclasticus.

Dps proteins (DNA-binding protein from starved cells) are hollow-sphere-shaped, dodecameric enzymes found in bacteria and archaeal species. They can oxidize ferrous iron in a controlled manner using hydrogen peroxide or molecular oxygen as co-substrate, and most of them confer physical protection through DNA binding. Oxidized iron is stored, as a mineral core, in a central cavity. Direct evidence is now provided that, furthermore, Dps proteins containing small mineral cores can oxidize and mineralize toxic ferrous ions in anaerobic conditions and in the absence of any additional aqueous oxidant co-substrate. Dps proteins containing cores of 24 irons per dodecamer can oxidize about 5 ferrous irons per dodecamer, with that number approximately doubling for protein particles containing in average 96 irons per protein. This additional activity carries importance as it can be a detoxification mechanism present during anaerobic or oxygen-limited growth conditions.

Transition Metal Catalyzed Direct Oxidative Borylation of C—H Bonds

AbstractOrganoboron is well‐developed and broadly utilized organometallic reagents in organic synthesis due to its extraordinary performances in transition‐metal catalyzed C‐C and C‐X bonds construction. Catalytic C—H borylation and further transformations catalyzed by transition metal catalysts in the absence of oxidants were well studied in decades. However, as known, transition metal catalyzed oxidative C—H borylations were not reviewed up to date. In this article the oxidative borylation of C(sp2)‐H and C(sp3)‐H bonds were summarized and their mechanisms were also accounted.

A novel method for generating tricolor emission for white LED application

Copper sulphide (CuS) and tin antimonide (Sn2Sb3) are prepared by simple co-precipitation method. The prepared samples are pulverized in the ratio of 1:1 for stipulated number of rotations. X-Ray Diffractogram (XRD) is employed to analyze the structure. Both CuS and Sn2Sb3 systems exhibit hexagonal crystal structure. Thermal gravimetric and differential thermal gravimetric analysis (TG-DTG) is conducted to ensure the absence of oxidation and sulphur evolution in the samples. Ultraviolet–Visible spectroscopy (UV–Vis) and Photoluminescence characterizations were carried out to study the optical properties of the compounds. The band gap obtained from the Tauc plot for CuS, Sn2Sb3 and pulverized CuS:Sn2Sb3 are 2.50, 3.50 and 2.80 eV where the pulverized sample shows an intermediate value between CuS and Sn2Sb3. The photoluminescence studies are carried out for all the samples and the pulverized sample CuS:Sn2Sb3 showed emission over the visible region yielding better results of RGB (Red, Green, Blue) emission.