Chemoselective Catalytic Conjugate Addition of Alcohols over Amines

A highly chemoselective conjugate addition of alcohols in the presence of amines is described. The cooperative nature of the catalyst enabled chemoselective activation of alcohols over amines, allowing the conjugate addition to soft Lewis basic α,β‐unsaturated nitriles. Divergent transformation of the nitrile functionality highlights the utility of the present catalysis.     

Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques

There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next‐generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X‐ray absorption fine structure) method and by a quick‐XAFS(QXAFS) method. Information on the site‐preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro‐crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation.     

Determination of alkaline-earth metals in foetus bones by inductively-coupled plasma atomic-emission spectrometry

Alkaline-earth metals in human bone samples have been determined simultaneously by inductively-coupled plasma atomic-emission spectrometry (ICP-AES). Results obtained by atomic-absorption spectrometry for Mg, Sr and Ba, and complexometry for Ca, have been compared with those by ICP-AES for a laboratory-control bone sample. Accuracy and precision were examined by analysing the IAEA animal bone standard (H-5). Agreement with the certified values to within 5% was obtained. The concentrations of the elements in foetal bone have also been determined.     

Stabilization of High‐Valence Ruthenium with Silicotungstate Ligands: Preparation,Structural Characterization,and Redox Studies of Ruthenium(III)‐Substituted α‐Keggin‐Type Silicotungstates with Pyridine Ligands, [SiW11O39RuIII(Py)]5−

Ruthenium(III)‐substituted α‐Keggin‐type silicotungstates with pyridine‐based ligands, [SiW₁₁O₃₉Ru^III(Py)]^5?, (Py: pyridine ( 1 ), 4‐pyridine‐carboxylic acid ( 2 ), 4,4′‐bipyridine ( 3 ), 4‐pyridine‐acetamide ( 4 ), and 4‐pyridine‐methanol ( 5 )) were prepared by reacting [SiW₁₁O₃₉Ru^III(H₂O)]^5? with the pyridine derivatives in water at 80 °C and then isolated as their hydrated cesium salts. These compounds were characterized using cyclic voltammetry (CV), UV/Vis, IR, and ¹H NMR spectroscopy, elemental analysis, titration, and X‐ray absorption near‐edge structure (XANES) analysis (Ru K‐edge and L₃‐edge). Single‐crystal X‐ray analysis of compounds 2 , 3 , and 4 revealed that Ru^III was incorporated in the α‐Keggin framework and was coordinated by pyridine derivatives through a Ru? N bond. In the solid state, compounds 2 and 3 formed a dimer through π? π interaction of the pyridine moieties, whereas they existed as monomers in solution. CV indicated that the incorporated Ru^III–Py was reversibly oxidized into the Ru^IV–Py derivative and reduced into the Ru^II–Py derivative.     

Strategy for structural elucidation of drugs and drug metabolites using (MS)n fragmentation in an electrospray ion trap

Triple-stage quadrupole (TSQ) electrospray ionization (ESI) tandem mass spectrometry (MS/MS) and ion trap ESI-MS/MS can be used to cleave protonated molecules to produce carbocations and neutral molecules in the positive ion mode. Dissociation products which correspond to protonated forms of neutral fragment molecules can also be trapped and detected. These protonated molecules in turn can cleave via carbocation cleavage, ipso cleavage, onium cleavage or McLafferty or related rearrangements. One can elucidate the structures of metabolites from the differences in m/z ratios of the fragments arising from the original drug compound and its metabolite. This strategy for structural elucidation is further facilitated by estimates of the reactivity of drugs with oxygen diradicals involved in cytochrome P-450 cycles.     

AC 1 make or break lemma

Mañé suggested the following question: Consider aC ^r flow on a compact manifold without boundary and suppose that the ω-limit set of a pointp intersets the α-limit set ofq, i.e. ω(p)∩α(q)≠Ø. Can the flow beC ^r-perturbed so that either (a)p is connected toq (p andq in the same orbit) or (b) ω(p)∩α(q)=Ø for the new flow? Here we solve positively a stronger version of this problem forC ¹ small perturbations of the original flow.     

Evolution of long-period stacking order (LPSO) in Mg97Zn1Gd2 cast alloys viewed by HAADF-STEM multi-scale electron tomography

We have studied three-dimensional (3D) structures and growth processes of 14H-type long-period stacking order (LPSO) formed in Mg₉₇Zn₁Gd₂ cast alloys by single tilt-axis electron tomography (ET) using high-angle annular dark-field scanning transmission electron microscopy. Evolution of the solute-enriched stacking faults (SFs) and the 14H LPSO by ageing were visualised in 3D with a high spatial resolution in multi-scale fields of views from a few nanometres to ~10 μm. Lateral growth of the solute-enriched SFs and the LPSO in the (0?0?0?1)_Mg plane is notable compared to the out-of-plane growth in the [0?0?0?1]_Mg direction. The 14H LPSO grows at the cost of decomposition of the (Mg, Zn)₃Gd-type precipitates, and accompany a change of in-plane edge angles from 30 to 60°. We have updated the Time–Temperature–Transformation diagram for precipitation in Mg₉₇Zn₁Gd₂ alloys: starting temperatures of both solute-enriched SFs and LPSO formation shifted to a shorter time side than those in the previous diagram.