Extensive oxygen exchange between carbon dioxide and magnesium oxide surface

Temperature-programmed desorption study of C¹⁸O₂ adsorbed on MgO has revealed that the desorbed carbon dioxide is composed exclusively of C¹⁶O₂, indicating that the adsorbed CO₂ species roll over the MgO surface.     

Fisher information metric and Poisson kernels

A complete Riemannian manifold X with negative curvature satisfying −b²?KX?−a²<0 for some constants a,b, is naturally mapped in the space of probability measures on the ideal boundary ∂X by assigning the Poisson kernels. We show that this map is embedding and the pull-back metric of the Fisher information metric by this embedding coincides with the original metric of X up to constant provided X is a rank one symmetric space of non-compact type. Furthermore, we give a geometric meaning of the embedding.     

Dichloro­(4,4′‐dialkyl‐2,2′‐bipyridine‐κ2N,N′)platinum(II), where alkyl is pentyl and heptyl

Dichloro­(4,4′‐dipentyl‐2,2′‐bipyridine‐κ²N,N′)platinum(II), [PtCl₂(C₂₀H₂₈N₂)], adopts a discrete π–π stacking structure, where the alkyl chains are located in a random manner. In contrast, dichloro­(4,4′‐diheptyl‐2,2′‐bipyridine‐κ²N,N′)platinum(II), [PtCl₂(C₂₄H₃₆N₂)], forms a layer structure comprised of alkyl chain layers and paired coordination sites, as observed for analogous complexes with longer alkyl chains.     

Bench‐Stable Stock Solutions of Silicon Grignard Reagents: Application to Iron‐ and Cobalt‐Catalyzed Radical C(sp3)–Si Cross‐Coupling Reactions

A robust method for the preparation of silicon‐based magnesium reagents is reported. The MgBr₂ used in the lithium‐to‐magnesium transmetalation step is generated in situ from 1,2‐dibromoethane and elemental magnesium in hot THF. No precipitation of MgBr₂ occurs in the heat, and transmetalation at elevated temperature leads to homogeneous stock solutions of the silicon Grignard reagents that are stable and storable in the fridge. This method avoids the preparation of silicon pronucleophiles such as Si?Si and Si?B reagents. The new Grignard reagents were applied to unprecedented iron‐ and cobalt‐catalyzed cross‐coupling reactions of unactivated alkyl bromides. The functional‐group tolerance of these magnesium reagents is excellent.     

Antioxidant effects of photodegradation product of nifedipine

Recently, increasing evidence suggests that the antihypertensive drug nifedipine acts as a protective agent for endothelial cells, and that the activity is unrelated to its calcium channel blocking. Nifedipine is unstable under light and reportedly decomposes to a stable nitrosonifedipine (NO-NIF). NO-NIF has no antihypertensive effect, and it has been recognized as a contaminant of nifedipine. The present study for the first time demonstrated that NO-NIF changed to a NO-NIF radical in a time-dependent manner when it interacted with human umbilical vein endothelial cells (HUVECs). The electron paramagnetic resonance (EPR) signal of NO-NIF radicals in HUVECs showed an asymmetric pattern suggesting that the radicals were located in the membrane. The NO-NIF radicals had radical scavenging activity for 1,1-diphenyl-2-picrylhydrazyl, whereas neither NO-NIF nor nifedipine did. In addition, the NO-NIF radical more effectively quenched lipid peroxides than NO-NIF or nifedipine. Furthermore, NO-NIF attenuated the superoxide-derived free radicals in HUVECs stimulated with LY83583, and suppressed iron-nitrilotriacetic acid (Fe-NTA)-induced cytotoxicity in rat pheochromocytoma (PC12) cells. Our findings suggest that NO-NIF is a candidate for a new class of antioxidative drugs that protect cells against oxidative stress.     

Impact of amorphous Ge thin layer at the amorphous Si/Al interface on Al-induced crystallization

We investigated the impact of an amorphous Ge (a-Ge) thin layer inserted at the amorphous Si (a-Si)/Al interface on Al-induced crystallization. In situ observation of the growth process clarified that the nucleation rate is drastically reduced by insertion of a-Ge, which led to increase in the average size of crystal grains. This was interpreted as resulting from decrease in the driving force of crystallization, mainly due to the larger solubility of Ge in Al than that of Si in Al. The obtained films were SiGe alloys with lateral distribution of Ge content, and its origin is discussed based on the two-step nucleation process.     

Synthesis of tetrasubstituted and functionalized enol ethers by E-selective olefination of esters with ynolates

We have developed the E-selective olefination of ester carbonyls to afford tetrasubstituted, functionalized olefins and the C-S insertion of thiol esters to give beta-keto thiol esters via ynolates.     

Similarity rules of magnetic minor hysteresis loops in Fe and Ni metals

We have studied similarity rules of quasistatic minor hysteresis loops for Fe and Ni single crystals in the wide temperature range from 10 to 600 K. Two similarity rules of M_R*/M_a*∼3/4 and W_R*/W_F*∼1/6, were found in a medium field range where irreversible movement of Bloch walls plays a crucial role for magnetization; M_a*, M_R*, W_F*, and W_R* are magnetization, remanence, hysteresis loss, and remanence work of a minor hysteresis loop. The similarity rules hold true, being almost independent of kinds of ferromagnets, applied stress, and temperature. The origin was discussed from the viewpoint of pinning effects due to dislocations as well as eddy current effects which become predominant at low temperatures for samples with low dislocation density.     

Effect of cocrystallization due to bile acid on molecular-ion sensitivity of biological phospholipids in Bi cluster time-of-flight secondary ion mass spectrometry measurements

Bi cluster time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a useful method for evaluating organic surfaces. However, its ability to detect large molecules is limited. One of the problems is that the sensitivities of macromolecules are lower than those of small molecules because larger molecules tend to exhibit lower ionization efficiencies and/or higher probabilities of fragmentation. Matrix-enhanced (ME)-SIMS is a sensitivity enhancement technique for intact molecular ions. The crystal structure of a mixed substance composed of an analyte and a matrix is known to affect the sensitivity of the analysis target. In this study, the effect of cocrystallization, which occurs due to the presence of bile acid, on the molecular-ion sensitivity was investigated using Bi cluster TOF-SIMS. Biological phospholipids and bile acids, which exhibit surfactant behaviors, were selected as the evaluated molecules and additives, respectively. The mass spectra indicated that the secondary-ion yields of phospholipids with bile acid were substantially greater than those of the pristine lipid. Specifically, samples with an analyte/bile acid ratio of 1:100 achieved approximately 60–100-fold sensitivity enhancement of [M + H]⁺ and [2M + H]⁺ molecular ions than the sensitivity achieved with the pristine samples. In the evaluation of molecular distribution, higher signal counts of intact ions were obtained from the cocrystallization area, although less-fragmented ions were emitted from these regions. Consequently, the results indicate that the cocrystallization due to the presence of bile acid provides an effective crystal structure for facilitating emission of larger molecules.     

In situ time-resolved XAFS study of the reaction mechanism of bromobenzene homocoupling mediated by [Ni(cod)(bpy)

A homocoupling reaction mechanism of bromobenzene mediated by the [Ni(cod)(bpy)] (cod = 1,5-cyclooctadiene; bpy = 2,2'-bipyridine) complex was investigated by means of in situ time-resolved X-ray absorption fine structure (XAFS) and factor analysis. A dimer intermediate [Ni(bpy)(Ph)Br](2) proposed in the previous studies by other groups is too dilute to observe with the XAFS technique; however, the structures and concentrations on the time course of a reactant [Ni(cod)(bpy)], an intermediate [Ni(bpy)(Ph)Br(dmf)(2)], and a byproduct [Ni(bpy)Br(2)(dmf)] during reaction are revealed by this combination.