An EPR study of Cu adsorption by clinoptilolite from Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> and SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack> solutions

The concentration and the type of Cu²⁺ species adsorbed on a natural zeolite (Clinoptilolite) was measured and studied by using Electron Paramagnetic Resonance Spectroscopy (EPR). The EPR results together with macroscopic sorption data indicate that the solution ionic strength as well as, the type of electrolyte anion (Cl⁻, NO₃⁻ and SO₄²⁻ ions were examined) affect the amount of Cu adsorbed and the type of Cu surface complexes. The increasing in solution pH affects Cu adsorption quantitatively whereas; the type of surface complexes formed depends mainly on solution ionic strength. For low solution ionic strength, when the inhibition from solution species is limited, the adsorbed Cu is characterized by more than one type of chemical environment. On the contrary, for high solution ionic strength the Cu adsorption is inhomogeneous and EPR spectra show only one type of surface complex. When the anions of the background electrolytes are different, but of equal normality, the results indicate that in the presence of SO₄²⁻ discernible Cu surface complexes are formed whereas, for Cl⁻ and NO₃⁻ these surface formations are obtained only for high Cu adsorbed concentrations.     

A chromotropic acid modified SBA-15 as a highly sensitive fluorescent probe for determination of Fe<Superscript>3+</Superscript> and I<Superscript>−</Superscript> ions in water

A novel organic–inorganic hybrid nanomaterial (SBA-15-CA) was prepared by covalent immobilization of chromotropic acid onto the surface of mesoporous silica material SBA-15. Different techniques such as XRD, TEM, FT-IR, N₂ adsorption–desorption and TGA analyses were employed to characterize the grafting process. The data showed that the organic moiety (0.41 mmol g^?1) was successfully grafted to the SBA-15 and the primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. SBA-15-CA has been realized as a highly sensitive and selective fluorescent probe towards Fe³⁺ and I^? ions in aqueous media. SBA-15-CA exhibited a remarkable fluorescent quenching in the presence of Fe³⁺ ion over other competitive cations including Na⁺, Mg²⁺, Al³⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺ as well as I^? ion among a series of anions including F^?, Cl^?, Br^?, CO₃^2?, HCO₃^?, CN^?, NO₃^?, NO₂^?, SCN^?, SO₄^2?, H₂PO₄^?, HPO₄^2?, and CH₃COO^?. A good linear response was observed between the concentration of the quenchers (Fe³⁺ and I^? ions) and fluorescence intensity of SBA-15-CA with detection limits of 1.5?×?10^?7 M for Fe³⁺ and 0.2?×?10^?7 M for I^?. Moreover, the effects of various pH values on the sensing ability of SBA-15-CA were investigated. Finally, the proposed method was successfully utilized for the determination of Fe³⁺ and I^? ions in river water, well water and tap water samples.     

Effect of amino acids containing sulfur on the corrosion of mild steel in phosphoric acid solutions containing Cl<Superscript>−</Superscript>, F<Superscript>−</Superscript> and Fe<Superscript>3+</Superscript> ions: Behavior under polarization conditions

The effect of cysteine (RSH), methionine (CH₃SR), cystine (RSSR) and N-acetylcysteine (ACC) on the corrosion behavior of mild steel in 40% H₃PO₄ solution without and with Cl⁻, F⁻, Fe^3‰+ and their ternary mixture was studied using both potentiostatic and electrochemical impedance (EIS) techniques under anodic and cathodic polarization conditions. The inorganic additives stimulate the overall corrosion reaction while the amino acids inhibit it with a predominant effect on the dissolution of iron. Both RSH and ACC are adsorbed according to Temkin’s isotherm while adsorption of RSSR and CH₃SR follows Frumkin and Langmuir isotherms respectively. The standard free energy of adsorption (ΔG ) was found to be in the order: RSSR > RSH ≅ ACC > CH₃SR. The binary mixtures of Cl⁻ or F⁻ with RSH or CH₃SR are the best inhibitors (IE > 90%) while those containing ferric ions or blend I and amino acids are not good corrosion inhibitors. EIS measurements showed that the cathodic reaction, hydrogen evolution, is charge transfer controlled while the anodic one, iron dissolution, is a complex process.     

Review of chemical syntheses of 7-keto-Δ<Superscript>5</Superscript>-sterols

Steroids bearing ketone functionality at carbon-7 are found commonly in nature, and the most prevalent of these are the 7-keto-Δ⁵-sterols. These substances have diverse biological properties and are present in biological samples and food products. For the purpose of studying this class of oxysterols, many chemical methods, involving the chemical oxidation of Δ⁵-sterols to the corresponding 7-keto-Δ⁵-sterols derivatives have been developed to produce these compounds. We have undertaken a review and evaluation of chemical methods for the synthesis of these compounds and have endeavored to enhance one of these procedures to yield products for chemical and biological investigations.     

Dioxirane oxidation of 3β-substituted Δ<Superscript>5</Superscript>-steroids

This article reviews the utility of dioxiranes in the oxidation of 3beta-substituted delta5-sterols. Dioxiranes are the smallest cyclic peroxides that contain a carbon atom. They can be generated in situ from Oxone (2KHSO5.KHSO4.K2SO4) and a ketone. Dioxiranes are versatile oxidizing agents. The most common reaction of dioxiranes is epoxidation, with nearly 1:1 ratios of alpha/beta isomer products in all cases. delta5-Steroids with different side chains were epoxidized by dioxiranes generated in situ from several commercially available ketones. Although ketones function as catalyst, they were used in about an equivalent amount or large excess to accelerate the reaction.     

Production and use of vibrocast products from the company “Promresurs”<Superscript>1</Superscript>

An assortment of products made by the young company “Promresurs” for casting steel is presented. It is noted that the products are made with high-quality raw materials, modern technologies, and high-quality equipment. Results are presented from tests of the products at the Nizhniy Tagil Metallurgical Combine.     

Mechanistic Study of the NO + NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> Reaction on H- and Fe/H-BEA Zeolites Using <Superscript>15</Superscript>N and <Superscript>18</Superscript>O Labeled Species

Reduction of NO by NH₃ over metal-promoted zeolites represents the principal reaction in the selective catalytic reduction (SCR) technology for NOx removal from Diesel engine exhausts. It has been established that addition of ammonium nitrate (AN) to the reaction mixture substantially enhances the rate of this reaction, decreasing the temperature necessary for an efficient deNOx process. Nevertheless, the nature of this effect has not been completely elucidated. To investigate the NO?+?AN reaction mechanism, we have used individual reactants labeled with either ¹⁵N or ¹⁸O (or both isotopes), thus obtaining an experimental background for proposing the route of the SCR accelerated by AN addition. For this study, we have used as the catalysts H-BEA and Fe/H-BEA zeolites with various Si/Al ratios and various amounts and states of the iron species.     

Crystallographic studies on the site selectivity of Ca<Superscript>2+</Superscript>, K<Superscript>+</Superscript>, and Rb<Superscript>+</Superscript> ions within zeolite Y (Si/Al = 1.56)

The single-crystals of Ca²⁺, K⁺-exchanged zeolite Y, and Ca²⁺, Rb⁺-exchanged zeolite Y were prepared by using flow method with mixed ion-exchange solution, whose Ca(NO₃)₂:KNO₃ mole ratios were 1:1 (crystal 1) and 1:100 (crystal 2), and Ca(NO₃)₂:RbNO₃ mole ratios were 1:1 (crystal 3) and 1:100 (crystal 4), respectively, with a total concentration of 0.05 M. They were fully dehydrated by vacuum dehydration at 723 K and 1 × 10^?6 Torr for 2 days. Their crystals were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group \(Fd \overline{3}\) m, respectively, and were refined to the final error indices R ₁/wR ₂ = 0.057/0.196, 0.073/0.223, 0.055/0.188, and 0.049/0.175 for crystals 1, 2, 3, and 4, respectively. In the structure of crystal 1 (|Ca₂₃K₂₉|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 23 Ca²⁺ ions per unit cell occupy sites I, II′, and II; 29 K⁺ ions per unit cell are at sites II′, II, and III′. In the structure of crystal 2 (|Ca_18.5K₃₈|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 18.5 Ca²⁺ ions per unit cell occupy sites I, I′, and II; 38 K⁺ ions are at sites I′, II, and III′. In the structure of crystal 3 (|Ca₂₇Rb₂₁|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 27 Ca²⁺ ions per unit cell occupy sites I, II′, and II; 21 Rb⁺ ions per unit cell are at sites II′, II, and III. In the structure of crystal 4 (|Ca₁₈Rb₃₉|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 18 Ca²⁺ ions per unit cell occupy sites I and II; 39 Rb⁺ ions per unit cell are at sites I′, II′, II, III, and III′. In the four crystals, the Ca²⁺ ion which has much smaller size and higher charge than other cations such as K⁺ and Rb⁺ energetically preferred at site I and so the first to be filled on it. Unlike Ca²⁺ ion, no K⁺ and Rb⁺ ions are found at site I, which are clearly less favorable for K⁺ and Rb⁺ ions.     

Differences in Δ<Superscript>9</Superscript> desaturase activity between jersey-and limousin-sired cattle

An experiment examined Δ⁹ desaturase activity and FA composition in subcutaneous adipose tissue in two differing breeds of cattle. Jersey-sired cattle had significantly higher rates of desaturase activity than Limousin-sired cattle (1.55 vs. 0.75 nmol/mg protein/min). This difference was also demonstrated by a lower concentration of individual (e.g. 18∶0) and total saturated FA (38.3 vs. 45.1 wt%), and a higher concentration of individual (e.g., 16∶1) and total monounsaturated FA (58.2 vs. 52.7 wt%) in the Jersey animals. Other indices of desaturation calculated from the FA composition showed this same difference. The slip point of adipose tissue of Jersey cattle (36.8°C) was significantly lower than that of Limousin cattle (39.2°C), but Jersey adipose tissue had a greater content of β-carotene. The positive relationship between adipose tissue β-carotene and desaturation opposes the negative relationship between dietary β-carotene and desaturation determined elsewhere. These results, however, lead to the hypothesis that some cattle have a reduced capacity to metabolize β-carotene to various forms of vitamin A, a compound that can reduce Δ⁹ desaturase enzyme activity. In addition, the higher level of intramuscular fat in Jersey cattle (6.97 vs. 3.82%) is possibly related to a lack of inhibition of the adipocyte differentiation genes by vitamin A.     

Studies of Bone-Bonding Ability and Antibacterial Properties of Ag<Superscript>+</Superscript>, Cu<Superscript>2+</Superscript> or Zn<Superscript>2+</Superscript> ions Doping within Hench’s Bioglass and Glass-Ceramic Derivatives

Derived Hench’s bioglasses with specific ionic dopants Ag⁺, Cu²⁺, or Zn²⁺ have been prepared. The bone-boding ability or bioactivity behavior for the prepared glasses and their glass-ceramic derivatives has been investigated after immersion in phosphate solution for two weeks. Collective Fourier transform infrared absorption spectra (FTIR) and scanning electron microscopic (SEM) studies were conducted in order to study the in-vitro bioactivity behavior. X-ray diffraction (XRD) analysis was carried out to identify the crystallized phases upon thermal heat treatment through a two-step regime. The glasses and their glass-ceramic derivatives were tested to study their antibacterial or antifungal efficiency responding to the doped metal ions. FTIR spectra revealed the generation of two split peaks at about 560 and 605 cm^?1, after immersion in (0.2 M) sodium phosphate solution (Na₃PO₄), signifying the formation of a crystalline calcium phosphate phase, leading to hydroxyapatite formation. SEM examinations show characteristic rounded or nodular microcrystals for hydroxyapatite which support the FTIR data. X-ray diffraction analysis indicated crystallization of the main soda-lime silicate phase (1Na₂O.2CaO.3SiO₂) besides a secondary silicon phosphate phase (SiO₂.P₂O₅) in the studied glass ceramics. The route of crystallization is discussed on the basis of the presence of 6% P₂O_5; which facilitates the formation of phase separation and voluminous bulk crystallization of the main soda-lime silicate phase. The introduction of dopants is identified to cause no changes in the precipitated phases, with only minor changes in the percent of the crystalline phases. Experimental data indicate that the glass-ceramic samples are effective in bioactivity and antimicrobial efficiency.     

Application of a Nickel-Bispidine Complex as Pre-Catalyst for C(<Emphasis Type="Italic">sp</Emphasis><Superscript>2</Superscript>)–C(<Emphasis Type="Italic">sp</Emphasis><Superscript>3</Superscript>) Bond Formations

Abstract  

In the present study, the nickel-catalyzed cross coupling of aryl halides with benzyl zinc bromides or dialkyl zinc reagents to create C(sp ²)–C(sp ³) bonds has been explored. As pre-catalyst the well-defined and easy-accessible (bispidine)Ni(NO₃)₂ complex has been applied. After investigation of different reaction parameters a broad scope of C(sp ²)–C(sp ³) bond formations were feasible under mild reaction conditions.     

Hydrothermal Synthesis of Mn–Fe Nano Oxides and Their Composite for Removal of Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> from Simulated Radioactive Waste

A study on the sorption of Zn²⁺, Ni²⁺ and Co²⁺ onto mixed oxide of Mn and Fe obtained at different hydrothermal conditions and its organic hybrid film modified with polyacrylamide (Mn–Fe oxide/PAM) has been examined. The characterization of inorganic oxides and its composite samples were performed using XRD, SEM, FTIR, XRF and DTA-TGA techniques. The percent sorption of Zn²⁺, Ni²⁺ and Co²⁺ on Mn–Fe oxide at pH 4.5 was 97, 11.85 and 10 % respectively with selectivity order Zn²⁺ ? Ni²⁺ > Co²⁺. The sorption value of Zn²⁺ at pH 4.5 onto Fe–Mn oxide reached nearly the same value of Zn²⁺ onto its composite. So, the new compound of Fe–Mn oxide has promising uses for separation of zinc ions while its composite can be used for removal all of these cations.     

Structure of Ca–Sr–Ba Sodium–Borosilicate Glasses according to <Superscript>11</Superscript>B and <Superscript>29</Superscript>Si NMR Spectroscopy

The structure of borosilicate glasses is studied with ¹¹B and ²⁹Si NMR spectroscopy in order to investigate the influence of replacement of Na₂O by oxides of alkali earth metals on their local structure. The quantitative data are analyzed with respect to their correspondence to the criterion of the average charge of the structural unit. The reasons for the deviation between the experimental results and this criterion are considered. It is shown that, in the case of glass devoid of borate structural units with nonbridging oxygen atoms, the corrected contents of these units are consistent with the predictions of thermodynamic modeling of the structure and properties of oxide glasses.     

A Novel Bimetallic Chain Based on [Mo(CN)<Subscript>8</Subscript>]<Superscript>3−</Superscript> and Yb<Superscript>3+</Superscript> Ions as Building Blocks in Which Containing Many Intriguing Structural Features

A novel Mo^V–Yb^III bimetallic chain, {[Yb^III(bpy)₂(DMF)(H₂O)][Mo^V(CN)₈]·0.5bpy·4.5H₂O}_n (1) (DMF = N,N′-dimethylformamide; bpy = 2,2′-bipyridine), has been constructed by the reaction of [Mo(CN)₈]³⁻ with Yb³⁺ and 2,2′-bipyridine. Complex 1 is confirmed as a host–guest supramolecular structure by X-ray structural analysis. The neighboring chains interact with each other with two types of hydrogen bonds and two types of π···π interactions. Thus complex 1 has a unique 3D network. Magnetic analysis of 1 indicates the presence of a strong Yb^III single-ion effect owing to spin–orbital coupling within this system.     

Influence of Nafion<Superscript>®</Superscript> ionomer on carbon corrosion

Corrosion of the three carbon black materials which differ in their textural, sub-structural, and morphological characteristics is studied in H₂SO₄ electrolyte at 80 °C at positive polarization. Impregnation of carbon blacks with Nafion^® ionomer is found to strongly affect their susceptibility to corrosion, which varies non-monotonically as a function of the Nafion^® loading. Low temperature nitrogen adsorption is applied to study the distribution of the ionomer molecules in the carbon matrix.     

Conversion of two-micron radiation into visible light using glass and ceramics based on ZBLAN: Но<Superscript>3+</Superscript> and ZBLAN: Ho<Superscript>3+</Superscript> + Yb<Superscript>3+</Superscript>

Visualization of infrared radiation of Tm:YLF-laser at the wavelength of 1908 nm has been investigated in the glass and ceramics samples with compositions of 53ZrF₄ · 20 BaF₂ · 1HoF₃ · 3YbF₃ · 3AlF₃ · 20NaF and 53ZrF₄ · 20BaF₂ · 3LaF₃ · 1HoF₃ · 3AlF₃ · 20NaF (mol %). In luminescence spectra of ZBLAN samples doped with Но³⁺, the bands at the wavelengths of 480, 540, and 650 nm were observed, which correspond to ⁵ F ₃ → ⁵ I ₈, ⁵ S ₂, ⁵ F ₄ → ⁵ I ₈, and ⁵ F ₅ → ⁵ I ₈ electron transitions in Но³⁺ ions with the maximum intensity of the red band (650 nm). Occupancy of the ⁵ S ₂ and ⁵ F ₄ levels in the ZBLAN: 1% Но³⁺ samples is related to the sequential absorption of the exciting radiation quanta. The level of ⁵ F ₅ is filled mainly due to the ionic interaction. Additional doping with the Yb³⁺ ions led to the change of the luminescence color to green and a decrease in the threshold radiation power density of the Tm:YLF-laser in ceramic samples up to 2 W/cm².     

Enhancement of combustion of a hydrogen-air mixture by excitation of O<Subscript>2</Subscript> molecules to the <Emphasis Type="Italic">a</Emphasis><Superscript>1</Superscript>Δ<Subscript><Emphasis Type="Italic">g</Emphasis></Subscript> state

The possibility of increasing the laminar flame velocity in a hydrogen-air mixture by excitation of O₂ molecules into the a ¹Δ _g singlet state. The presence of 10% of O₂(a ¹Δ _g ) molecules in oxygen is demonstrated to result in noticeable (up to 50%) enhancement of mixture burning. The temperature of combustion products and also the concentrations of H₂O, NO, and other constituents increase. The greatest effect of O₂(a ¹Δ _g ) molecules is manifested in combustion of lean mixtures; the least pronounced effect is observed in rich mixtures. These effects are caused by intensification of the chain mechanism in the presence of a super-equilibrium amount of excited O₂(a ¹Δ _g ) molecules in a hydrogen-air mixture. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 4, pp. 3–12, July–August, 2008.     

Methodology for the In Vivo Measurement of the Δ<Superscript>9</Superscript>-Desaturation of Myristic,Palmitic, and Stearic Acids in Lactating Dairy Cattle

There is limited methodology available to quantitatively assess the activity of the Δ⁹-desaturase enzyme in vivo without chemically inhibiting the enzyme or using radioactively labeled substrates. The objective of these experiments was to develop methodology to determine the incorporation and desaturation of ¹³C-labeled fatty acids into milk lipids. In a preliminary experiment, 3.7 g [1-¹³C]myristic acid ([1-¹³C]14:0), 19.5 g [1-¹³C]palmitic acid ([1-¹³C]16:0), 20.0 g [1-¹³C]stearic acid ([1-¹³C]18:0) were combined and infused into the duodenum of a cow over 24 h. In a following experiment, 5.0 g [1-¹³C]14:0, 40.0 g [1-¹³C]16:0, and 50.0 g [1-¹³C]18:0 were infused into the abomasums of separate cows as a bolus over 20 min or continuously over 24 h. Milk fat was extracted using chloroform:methanol. Fatty acids were methylated, and fatty acid methyl esters (FAME) were converted to dimethyl disulfide derivatives (DMDS). The FAME and DMDS were analyzed by gas chromatography mass spectrometry. In the preliminary experiment, ¹³C enrichment in 14:0 but not 16:0 or 18:0 was observed. When dosage amounts were increased in the following experiment, peak enrichments from the bolus infusion were observed at 8 h. Enrichments for continuous infusion peaked at 16 h for 14:0 and 18:0, and at 24 h for 16:0. The Δ⁹-desaturase products of these fatty acids were estimated to be 90% of cis-9 14:1, 50% of cis-9 16:1, and 59% of cis-9 18:1. This study demonstrates that ¹³C-labeled fatty acids may be utilized in vivo to measure the activity of the Δ⁹-desaturase enzyme.