Hydrothermal Synthesis of Mixed Oxide Compositions of Cobalt-Zirconium and their Catalytic Activity in the Decomposition of Hydrogen Peroxide

The article presents the results of research on the hydrothermal synthesis of nanoscale oxide of cobalt and zirconium and their mixed oxide compositions. The synthesized samples have been characterized by the X-ray phase, scanning electron microscopy and nitrogen adsorption-desorption methods; the composition of the samples has been determined by chemical analysis methods, and their catalytic activity in the decomposition of hydrogen peroxide has been studied. It has been shown that during synthesis, highly dispersed cobalt and zirconium oxide are formed, and the sample of the composition (mol %): Co₃O₄(88)−ZrO₂(12) has the highest specific surface area (181.2 m²/g) and the highest activity (K=6.18 ⋅ 10⁻² s⁻¹) against the decomposition of hydrogen peroxide. The increasing of the ZrO₂ content in oxide compositions reduces their catalytic activity. The particle size in the synthesized samples is 7–38 nm.     

Generalized Neutrino Equations

I discuss generalized spin-1/2 equations for neutrinos. They have been obtained by means of the Gersten’s method for derivation of arbitrary-spin relativistic equations. Possible physical consequences are discussed.     

Electrostatic Filter Ash from Silane Production as Silicate Substitute in Zeolite Chemistry

This paper is a case study of complete substitution of sodium‐metasilicate in zeolite Na‐A synthesis by an electrostatic filter ash (FA) arising in high amounts during silane waste incineration process. The silicate abundant FA is a suitable material for reinsertion in zeolite chemistry. This is shown in the presented investigation by the development of a model reaction process at low temperatures (50–60 °C) and short times (1.5–4 h). The experiments were performed under addition of NaAlO₂ and variation of the alkalinity and the reaction period. Characterization and fine tuning of the process was mainly done by studying the kinetics of FA digestion and zeolite crystallization by XRD and chemical analyses (ICP‐OES) of solutions and solids. It could be shown that pure FA was mostly dissolved (98 %) in 8 M NaOH already after 1 h. Addition of NaAlO₂ and crystallization for further 60 min under optimized conditions at 50 °C yielded to a suitable product. It consists of zeolite Na‐A (92 % by mass) beside some hydrosodalite (8 % by mass). According to this low temperature short time process this study is a contribution for the development of energy efficient recycling solutions.     

Acoustic variability within and across German, French, and American English vowels: phonetic context effects

Cross-language perception studies report influences of speech style and consonantal context on perceived similarity and discrimination of non-native vowels by inexperienced and experienced listeners. Detailed acoustic comparisons of distributions of vowels produced by native speakers of North German (NG), Parisian French (PF) and New York English (AE) in citation (di)syllables and in sentences (surrounded by labial and alveolar stops) are reported here. Results of within- and cross-language discriminant analyses reveal striking dissimilarities across languages in the spectral/temporal variation of coarticulated vowels. As expected, vocalic duration was most important in differentiating NG vowels; it did not contribute to PF vowel classification. Spectrally, NG long vowels showed little coarticulatory change, but back/low short vowels were fronted/raised in alveolar context. PF vowels showed greater coarticulatory effects overall; back and front rounded vowels were fronted, low and mid-low vowels were raised in both sentence contexts. AE mid to high back vowels were extremely fronted in alveolar contexts, with little change in mid-low and low long vowels. Cross-language discriminant analyses revealed varying patterns of spectral (dis)similarity across speech styles and consonantal contexts that could, in part, account for AE listeners' perception of German and French front rounded vowels, and "similar" mid-high to mid-low vowels.     

A Free-Radical Prompted Barrierless Gas-Phase Synthesis of Pentacene

A representative, low-temperature gas-phase reaction mechanism synthesizing polyacenes via ring annulation exemplified by the formation of pentacene (C₂₂H₁₄) along with its benzo[a]tetracene isomer (C₂₂H₁₄) is unraveled by probing the elementary reaction of the 2-tetracenyl radical (C₁₈H₁₁^.) with vinylacetylene (C₄H₄). The pathway to pentacene—a prototype polyacene and a fundamental molecular building block in graphenes, fullerenes, and carbon nanotubes—is facilitated by a barrierless, vinylacetylene mediated gas-phase process thus disputing conventional hypotheses that synthesis of polycyclic aromatic hydrocarbons (PAHs) solely proceeds at elevated temperatures. This low-temperature pathway can launch isomer-selective routes to aromatic structures through submerged reaction barriers, resonantly stabilized free-radical intermediates, and methodical ring annulation in deep space eventually changing our perception about the chemistry of carbon in our universe.     

Suppression of ring artefacts when tomographing anisotropically attenuating samples

There are many objects for which the attenuation varies significantly as they are rotated during computerized X‐ray tomography, for example plate samples. This can lead to significant ring artefacts in the subsequent tomographic reconstructions. In this paper a new method is presented that can successfully suppress such ring artefacts and is applicable to both parallel and cone‐beam geometries. Rapid correction is achieved via an analytical formula which involves only a matrix‐vector multiplication, for which the matrix is known and depends on a regularization parameter. The efficacy of the method is demonstrated for a paleontological sample (calcified shark cartilage) and a carbon–carbon composite/Ti–SiC metal matrix composite test sample.     

Synthesis, crystal structure, NMR data and thermogravimetrical properties of novel zirconium fluoride LiK10Zr6F35·2H2O

The synthesis and study (single crystal X-ray diffraction, thermogravimetry, IR- and NMR-spectroscopy) of a novel fluorozirconate LiK₁₀Zr₆F₃₅·2H₂O was performed. The structure of the compound is built from infinite chains _∞[Zr₆F₃₅]¹¹⁻, in which Zr-polyhedra are linked to each other through common edges and vertices. The chains are surrounded by K and Li cations and H₂O molecules. The compound dehydration occurs in the temperature range 453–543 K with maximal rate at 528 K. It was established that zirconium polyhedra chain fragments underwent reorientational motion starting to influence ¹⁹F NMR spectra at temperatures higher than 270 and 180 K in LiK₁₀Zr₆F₃₅·2H₂O and LiK₁₀Zr₆F₃₅, respectively. Above 450–420 K all fluorine sites in both samples participate in fluorine translational diffusion by at least two diffusion paths. Isotropic ¹⁹F NMR chemical shifts from different site types were detected by MAS NMR in the range 125–171 ppm.     

Ag(I)/V(V) Heterobimetallic Frameworks Generated from Novel-Type {Ag(2)(VO(2)F(2))(2)(triazole)(4)} Secondary Building Blocks: A New Aspect in the Design of SVOF Hybrids

A series of new silver(I)-containing MOFs [Ag(2)(tr(2)ad)(2)](ClO(4))(2) (1), [Ag(2)(VO(2)F(2))(2)(tr(2)ad)(2)]·H(2)O (2), [Ag(2)(VO(2)F(2))(2)(tr(2)eth)(2)(H(2)O)(2)] (3), and [Ag(2)(VO(2)F(2))(2)(tr(2)cy)(2)]·4H(2)O (4) supported by 4-substituted bifunctional 1,2,4-triazole ligands (tr(2)ad = 1,3-bis(1,2,4-triazol-4-yl)adamantane, tr(2)eth = 1,2-bis(1,2,4-triazol-4-yl)ethane, tr(2)cy = trans-1,4-bis(1,2,4-triazol-4-yl)cyclohexane) were hydrothermally synthesized and structurally characterized. In these complexes, the triazole heterocycle as an N(1),N(2)-bridge links either two adjacent Ag-Ag or Ag-V centers at short distances forming polynuclear clusters. The crystal structure of compound 1 is based on cationic {Ag(2)(tr)(4)}(2+) fragments connected in a 2D rhombohedral grid network with (4,4) topology. The neighboring layers are tightly packed into a 3D array by means of argentophilic interactions (Ag···Ag 3.28 ?). Bridging between different metal atoms through the triazole groups assists formation of heterobimetallic Ag(I)/V(V) secondary building blocks in a linear V-Ag-Ag-V sequence that is observed in complexes 2-4. These unprecedented tetranuclear {Ag(2)(VO(2)F(2))(2)(tr)(4)} units (the intermetal Ag-Ag and Ag-V distances are 4.24-4.36 and 3.74-3.81 ?, respectively), in which vanadium(V) oxofluoride units possess distorted trigonal bipyramidal environment {VO(2)F(2)N}ˉ, are incorporated into 1D ribbon (2) or 2D square nets (3, 4) using bitopic μ(4)-triazole ligands. The valence bond calculation for vanadium atoms shows +V oxidation state in the corresponding compounds. Thermal stability and photoluminescence properties were studied for all reported coordination polymers.     

Isomeric 3‐Isoxadiazolylcoumarins and Their Derivatives

Here, we represent preparative methods of synthesis of isomeric 3‐isoxadiazolylcoumarins and their derivatives. Two new synthetic methods have been developed for 3‐[1,2,4‐oxadiazol‐5‐yl]coumarins I . The first method is based on a three‐component condensation of coumarin‐;3‐carboxylic acids, 1,1′‐carbonyldiimidazole, and amidoximes. The second method essentially uses the interaction of 5‐cyanomethyl‐1,2,4‐oxadiazoles with salicylic aldehydes. General approach for preparation of 3‐[1,2,4‐oxadiazol‐3‐yl]coumarins II has been worked out. Moreover, aforementioned synthetic ways open the way for the synthesis of 2‐iminoderivatives III and IV not described before, those were diversified by reaction of nucleophilic substitution of 2‐imino group with a numerous amino compounds.