Synthesis of Functionalized Heteroleptic Germylene Alkoxides

N-coordinated Ge(II) alkoxides L¹(tBuO)Ge ( 1 ), L²(tBuO)Ge ( 2 ) and [L²(OtBu)Ge ⋅ BH₃] ( 4 ) were prepared. Effect of either chelating ligands L¹ and L² or Ge→B interaction on strength of the Ge−OtBu bond was studied by insertion reaction of PhNCO. As a result, the Ge(II) carbamate L²{[(tBuO)OC](Ph)N}Ge ( 3 ) was isolated. Alcoholysis exchange reactions of 1 and 2 with substituted phenols were studied to find an easy synthetic protocol for a synthesis of functionalized Ge(II) alkoxides. Reactions yielded Ge(II) alkoxides L^1,2(2-Br−C₆H₄O)Ge ( 5 for L¹, 8 for L²), L^1,2(2-MeNH−C₆H₄O)Ge ( 6 for L¹, 9 for L²), L^1,2(2-Ph₂P−C₆H₄O)Ge ( 7 for L¹, 10 for L²), L²(2-Br-3-OH−C₆H₃O)Ge ( 11 ) and L²(2-NC₅H₄O)Ge ( 12 ) containing the additional polar groups Y (Y=Br, MeNH, PPh₂, OH or N). Finally, phosphane decorated Ge(II) alkoxides 7 and 10 were tested as suitable ligands in reactions with (COD)W(CO)₄ and BH₃. As a consequence, new complexes [(κ²- 7 )W(CO)₄] ( 13 ) and [L¹(2-Ph₂P ⋅ {BH₃}-C₆H₄O)Ge ⋅ {BH₃}] ( 14 ) were isolated. All compounds were characterized by NMR and IR spectroscopy, and compounds 3 , 4 , 9 and 11 were additionally characterized by X-ray diffraction analysis.     

Hochschild (co)homology of exterior algebras using algebraic Morse theory

In [1 Han, Y., Xu, Y. (2007). Hochschild (co)homology of exterior algebras. Comm. Algebra 35(1):115–131.[Web of Science ®] , [Google Scholar]], the authors computed the additive and multiplicative structure of HH*(A;A), where A is the n-th exterior algebra over a field. In this paper, we derive all their results using a different method (AMT) as well as calculate the additive structure of HH_k(A;A) and HH^k(A;A) over ?. We provide concise presentations of algebras HH_?(A;A) and HH*(A;A) as well as determine their generators in the Hochschild complex. Finally, we compute an explicit free resolution (spanned by multisets) of the A^e-module A and describe the homotopy equivalence to its bar resolution.     

Laser microsampling and multivariate methods in provenance studies of obsidian artefacts

The provenance of obsidian artefacts and raw materials was studied by the multivariate statistical analysis of forty-five samples using elemental composition data obtained by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). One ICP-MS instrument equipped with a quadrupole mass filter and the other based on a time-of-flight analyser were coupled to the same type of laser ablation device (Nd:YAG 213 nm), thereby affording a comparison of the different mass spectrometers in terms of precision and verification of the consistency of the results. The influence of surface roughness (polished raw material vs artefact) and microinhomogeneity on the LA-ICP-MS signal was studied under the optimised working conditions of the laser ablation device. Principal component analysis, correspondence analysis, independent component analysis, multi-dimensional scaling, Sammon mapping and fuzzy cluster analysis were applied and compared in order to reveal statistically significant compositional differences between particular geological sites and to disclose the provenance of the raw materials used in manufacture of the artefacts. Twenty-seven artefacts and eighteen raw material samples from natural resources in the Czech Republic, Slovakia, Italy, Greece, Syria, Iraq, Turkey, Mexico and Nicaragua were examined with special attention focused on samples from Moravia (Czech Republic) and some Near East sites (Tell Arbid, Tell Asmar). The Carpathian origin of the obsidian artefacts was investigated in the Moravian samples using the Pb, Rb and U contents. The Near East samples were classified according to their Sr, Ba, Zr and REE contents as per-alkaline obsidians (Bingöl A/Nemrut Da?) originating from Southeast Anatolia.     

Evaluation of ice‐tea quality by DART‐TOF/MS

DART (Direct Analysis in Real Time) coupled with Time‐of‐Flight Mass Spectrometry (TOF/MS) has been used for analyses of ice‐teas. The article focuses on quality and authenticity of ice‐teas as one of the most important tea‐based products on the market. Twenty‐one samples of ice‐teas (black and green) were analysed. Selected compounds of ice‐teas were determined: theobromine, caffeine, total phenolic compounds, total soluble solids, total amino acid concentration, preservatives and saccharides were determined. Fingerprints of DART‐TOF/MS spectra were used for comprehensive assessment of the ice‐tea samples. The DART‐TOF/MS method was used for monitoring the following compounds: citric acid, caffeine, saccharides, artificial sweeteners (saccharin, acesulphame K), and preservatives (sorbic and benzoic acid), phosphoric acid and phenolic compounds. The measured data were subjected to a principal components analysis. The HPLC and DART‐TOF/MS methods were compared in terms of determination of selected compounds (caffeine, benzoic acid, sorbic acid and saccharides) in the ice‐teas. The DART‐TOF/MS technique seems to be a suitable method for fast screening, testing quality and authenticity of tea‐based products. Copyright © 2015 John Wiley & Sons, Ltd.     

Universal Scalings in Homoclinic Doubling Cascades

Cascades of period doubling bifurcations are found in one parameter families of differential equations in ℝ³. When varying a second parameter, the periodic orbits in the period doubling cascade can disappear in homoclinic bifurcations. In one of the possible scenarios one finds cascades of homoclinic doubling bifurcations. Relevant aspects of this scenario can be understood from a study of interval maps close to x↦p+r(1 −x ^β)², β∈ (?,1). We study a renormalization operator for such maps. For values of β close to ?, we prove the existence of a fixed point of the renormalization operator, whose linearization at the fixed point has two unstable eigenvalues. This is in marked contrast to renormalization theory for period doubling cascades, where one unstable eigenvalue appears. From the renormalization theory we derive consequences for universal scalings in the bifurcation diagrams in the parameter plane. Received: 16 June 1999 / Accepted: 24 April 2001     

A Geometric Criterion for Positive Topological Entropy¶II: Homoclinic Tangencies

In a series of important papers [GS1,GS2] Gavrilov and Shilnikov established a topological conjugacy between a surface diffeomorphism having a dissipative hyperbolic periodic point with certain types of quadratic homoclinic tangencies and the full shift on two symbols, thus exhibiting horseshoes near a tangential homoclinic point. In this note, which should be viewed of as an addendum to [BW] we extend this result by showing that such a diffeomorphism with a one-sided isolated homoclinic tangency having any order contact, possible with infinite order contact, possesses a horseshoe near the homoclinic point. Received: 2 March 1999 / Accepted: 14 May 1999     

Intramolecularly Coordinated Gallium Sulfides: Suitable Single Source Precursors for GaS Thin Films

Our studies have been focused on the synthesis of N→Ga coordinated organogallium sulfides [L¹Ga(μ‐S)]₃ ( 1 ) and [L²Ga(μ‐S)]₂ ( 2 ) containing either N,C,N‐ or C,N‐chelating ligands L¹ or L² (L¹ is {2,6‐(Me₂NCH₂)₂C₆H₃}^? and L² is {2‐(Et₂NCH₂)‐4,6‐tBu₂‐C₆H₂}^?). As the result of the different ligands, compounds 1 and 2 differ mutually in their structure. To change the Ga/S ratio, unusually N→Ga coordinated organogallium tetrasulfide L¹Ga(κ²‐S₄) ( 3 ) was prepared and the unprecedented complex [{2‐[CH{(CH₂)₃CH₃}(μ‐OH)]‐6‐CH₂NMe₂}C₆H₃]GaS ( 4 ) was also isolated as the minor by‐product of the reaction. Compounds 1 – 3 were further studied as potential single‐source precursors for amorphous GaS thin film deposition by spin‐coating.     

Effect of waste tires addition on a low-temperature hydrovisbreaking process of vacuum residue

Most of the resources used for energy have a fossil origin and they are non-renewable materials. Using mixtures of waste materials with the currently used non-renewable materials can improve the renewability of the energy production. The goal of this work was to explore the effect of waste tire addition on a hydrovisbreaking process at low temperature. Four tests were carried out at 300 °C in H₂ with different feedstocks: (1) vacuum residue; (2) tires; (3) 37.5wt% tires + 62.5wt% vacuum residue; (4) 15wt% tires + 85wt% vacuum residue. Dynamic viscosity, simulated distillation, density, elemental analysis (C, H, N, S% content) by ICP and analysis of gaseous products by GC–MS were carried out for all products. Content of insoluble compounds in hexane was estimated for the products from test (1) and vacuum residue. TGA analyses of the tires were carried out. The addition of tires to the vacuum residue brought a positive effect to increasing the yield of lighter products in the final liquid product. Densities and composition determinated by elemental analyses were similar for feedstock and products. The dynamic viscosity (60 °C) decreased from 24,550 to 17,700 mPa s for test (1) and to 1640 mPa s for test (3).