Iron-based pre-catalyst supported on polyformamidine for C-C bond formation

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In the present study the incorporation of iron into an organic polymer, composed of formamidine subunits [R–N[double bond, length as m-dash]C(H)–NH–R], has been examined. The catalytic ability of the recyclable material was investigated in the iron-catalyzed formation of C–C bonds. After optimization of the reaction conditions, excellent yields and chemoselectivities were feasible.DFG, EXC 314, Unifying Concepts in Catalysi

Bridging the ensemble Kalman and particle filters

In many applications of Monte Carlo nonlinear filtering, the propagation step is computationally expensive, and hence the sample size is limited. With small sample sizes, the update step becomes crucial. Particle filtering suffers from the well-known problem of sample degeneracy. Ensemble Kalman filtering avoids this, at the expense of treating non-Gaussian features of the forecast distribution incorrectly. Here we introduce a procedure that makes a continuous transition indexed by γ∈[0,1] between the ensemble and the particle filter update. We propose automatic choices of the parameter γ such that the update stays as close as possible to the particle filter update subject to avoiding degeneracy. In various examples, we show that this procedure leads to updates that are able to handle non-Gaussian features of the forecast sample even in high-dimensional situation

C-N coupling in the gas-phase reactions of ammonia and [M(CH)](+) (M = Ni, Pd, Pt): a combined experimental/computational exercise

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Electrospray ionization (ESI) of methanolic solutions of monomeric nickel(II) acetate, [Ni(CH3COO)2], and tetrameric platinum(II) acetate, [Pt4(CH3COO)8], leads to the formation of the corresponding methylidyne complexes [M(CH)]+ (M = Ni, Pt), which react with ammonia under C–N coupling. While the product couples M/[CH4N]+ and [M(CH2N)]+/H2 are observed for both metals, hydrogen-atom expulsion to generate [M(CHNH2)]+/H is only observed in the case of the nickel-containing system, and the proton transfer leading to M/[NH4]+ is limited to platinum. Attempts to conduct related experiments with [Pd(CH)]+/NH3 failed. The mechanisms that explain the experimentally observed reaction channels have been investigated computationally using the B3LYP functional for all metals of the nickel group (M = Ni, Pd, Pt). In line with labeling experiments using the reaction pairs [M(CD)]+/NH3 and [M(CH)]+/ND3 (M = Ni, Pt), two different mechanistic scenarios of the dehydrogenation process are operative for the Ni and Pt systems, respectively.DFG, EXC 314, Unifying Concepts in Catalysi

On some properties of T0−ordered reflection

[EN] In [12], the authors give an explicit construction of the T0−ordered reflection of an ordered topological space (X, τ,≤) . All ordered topological spaces such that whose T0−ordered reflections are T1−ordered spaces are characterized. In this paper, some properties of the T0−ordered reflection of a given ordered topological space (X, τ,≤) are studies. The class of morphisms in ORDTOP orthogonal to all T0−ordered topological space is characterized.Lazaar, S.; Mhemdi, A. (2014). On some properties of T0−ordered reflection. Applied General Topology. 15(1):43-54. https://doi.org/10.4995/agt.2014.21444354151A. Ayache, O. Echi, The envelope of a subcategory in Topology and group theory, Int. J. Math. Math. Sci. 21 (2005), 3787-3404.Belaid, K., Echi, O., & Lazaar, S. (2004). T(α,β)-spaces and the Wallman compactification. International Journal of Mathematics and Mathematical Sciences, 2004(68), 3717-3735. doi:10.1155/s0161171204404050Casacuberta, C., Frei, A., & Tan, G. C. (1995). Extending localization functors. Journal of Pure and Applied Algebra, 103(2), 149-165. doi:10.1016/0022-4049(94)00099-5A. Deleanu, A. Frei, and P. Hilton, Generalized Adams completion, Cah. Topologie Géom. Différ. Catég.15 (1974), 61-82.R. El Bashir and J. Velebil, Simultaneously reflective and coreflective subcategories of presheaves, Theory Appl. Categ. 10 (2002), 410-423.Freyd, P. J., & Kelly, G. M. (1972). Categories of continuous functors, I. Journal of Pure and Applied Algebra, 2(3), 169-191. doi:10.1016/0022-4049(72)90001-1A. Grothendieck and J. Dieudonné, Eléments de géométrie algébrique, Springer-Verlag (1971).J. M. Harvey, Reflective subcategories, Ill. J. Math. 29 (1985), 365-369.Herrlich, H., & Strecker, G. (1997). Categorical Topology — Its Origins, as Exemplified by the Unfolding of the Theory of Topological Reflections and Coreflections before 1971. History of Topology, 255-341. doi:10.1007/978-94-017-0468-7_15Herrlich, H., & Strecker, G. E. (1968). H-closed spaces and reflective subcategories. Mathematische Annalen, 177(4), 302-309. doi:10.1007/bf01350722Künzi, H.-P. A., & Richmond, T. A. (2005). Ti-ordered reflections. Applied General Topology, 6(2), 207. doi:10.4995/agt.2005.1955H-P. A. Künzi, A. E. Mccluskey and T. A. Richmond, Ordered separation axioms and the Wallman ordered compactification, Publ. Math. Debrecen 73/3-4 (2008), 361-377.Lane, S. M. (1971). Categories for the Working Mathematician. Graduate Texts in Mathematics. doi:10.1007/978-1-4612-9839-7Tholen, W. (1987). Reflective subcategories. Topology and its Applications, 27(2), 201-212. doi:10.1016/0166-8641(87)90105-

Quantification of photocatalytic hydrogen evolution

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A new photoreactor with defined irradiation geometry was developed and tested for the water reduction reaction using carbon nitride (“C3N4”) as a photocatalyst. The hydrogen evolution rate was investigated with a sun simulator (I = 1000 W m−2) in two different operation modes: circulation and stirring of the catalyst dispersion. Only in the stirred mode, where shear stress is lower, a stable hydrogen evolution rate of about 0.41 L m−2 h−1 is obtained. It is confirmed by experiments with D2O that hydrogen is obtained from the water splitting process and not by dehydrogenation of the sacrificial agent. The obtained rate results in an efficiency of <0.1% based on a reference experiment with a photovoltaic-powered electrolysis setup. The change from distilled water to tap or simulated sea water results in a lower hydrogen evolution rate of about 50%.BMBF, 03IS2071D, Light2Hydroge

Enhanced catalysis of the electrochemical hydrogen evolution reaction using composites of molybdenum-based compounds, gold nanoparticles and carbon

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Molybdenum nitride has been recently reported to interact synergistically with gold to show an enhanced activity for the electrochemical hydrogen evolution reaction (2H(+) + 2e(-) -> H-2, HER). In this work, we elucidated the roles of nitrogen, carbon, molybdenum and gold on this observed phenomenon. Composites of Mo-based compounds, carbon black (black pearl 2000) and/or Au nanoparticles (Au-NP) were prepared, and their activities for the HER in a 0.5 M H2SO4 electrolyte were measured using linear sweep voltammetry. We show and discuss here for the first time that, while the presence of carbon is necessary for the synergy phenomenon, the nitrogen atoms present in the compounds play no apparent role in this synergy. In fact, all the compounds containing Mo, namely Mo2N, MoB and metallic Mo-0, exhibited extensive synergy with Au for the HER. A hypothesis for the enhanced catalysis of H-2 evolution by the mixed metal composites is proposed and discussed

Microsolvation of the acetanilide cation (AA(+)) in a nonpolar solvent: IR spectra of AA(+)-L-n clusters (L = He, Ar, N-2; n <= 10)

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Infrared photodissociation (IRPD) spectra of mass-selected cluster ions of acetanilide (N-phenylacetamide), AA+–Ln, with the ligands L = He (n = 1–2), Ar (n = 1–7), and N2 (n = 1–10) are recorded in the hydride stretch (amide A, νNH, νCH) and fingerprint (amide I–III) ranges of AA+ in its 2A′′ ground electronic state. Cold AA+–Ln clusters are generated in an electron impact ion source, which predominantly produces the most stable isomer of a given cluster ion. Systematic vibrational frequency shifts of the N–H stretch fundamentals (νNH) provide detailed information about the sequential microsolvation process of AA+ in a nonpolar (L = He and Ar) and quadrupolar (L = N2) solvent. In the most stable AA+–Ln clusters, the first ligand forms a hydrogen bond (H-bond) with the N–H proton of trans-AA+ (t-AA+), whereas further ligands bind weakly to the aromatic ring (π-stacking). There is no experimental evidence for complexes with the less stable cis-AA+ isomer. Quantum chemical calculations at the M06-2X/aug-cc-pVTZ level confirm the cluster growth sequence derived from the IR spectra. The calculated binding energies of De(H) = 720 and 1227 cm−1 for H-bonded and De(π) = 585 and 715 cm−1 for π-bonded Ar and N2 ligands in t-AA+–L are consistent with the observed photofragmentation branching ratios of AA+–Ln. Comparison between charged and neutral AA(+)–L dimers indicates that ionization switches the preferred ion–ligand binding motif from π-stacking to H-bonding. Electron removal from the HOMO of AA+ delocalized over both the aromatic ring and the amide group significantly strengthens the C[double bond, length as m-dash]O bond and weakens the N–H bond of the amide group

Adriamycin/cyclophosphamide and adriamycin/melphalan in advanced L1210 leukaemia.

Adriamycin and cyclophosphamide are active agents in human and experimental tumours. Using the L1210 murine leukaemia, their effectiveness alone and in combination was studied. The combination is highly synergistic in this tumour, resulting in a greater than 50% survival rate when the agents used alone at optimal doses are not curative. DNA synthesis by tumour cells is substantially inhibited and the total ascitic population much reduced. In contrast, DNA synthesis in sensitive host tissues is less disturbed. There is no major difference in the pharmacology of the agents whether given alone or in combination. In very advanced disease the combination is no better than treatment with cyclophosphamide alone. The combination of adriamycin and melphalan in L1210 leukaemia also produces superior results to those obtained using either drug alone at its optimal dosage

Truth or Meaning: Ricoeur versus Frei on Biblical Narrative

Of the theologians and philosophers now writing on biblical narrative, Hans Frei and Paul Ricoeur are probably the most prominent. It is significant that their views converge on important issues. Both are uncomfortable with hermeneutic theories that convert the text into an abstract philosophical system, an ideal typological structure, or a mere occasion for existential decision. Frei and Ricoeur seem knit together in a common enterprise; they appear to be building a single narrative theology. I argue that the appearance of symmetry is an illusion. There is a fundamental conflict between the ‘pure narrativism’ of Frei and the ‘impure narrativism’ of Ricoeur. I give reasons for thinking that Ricoeur’s is the stronger position