現代地方分権改革の展開とポスト「平成の大合併」における自治体の再編 : 長野県上小地域・上田市を事例として

departmental bulletin pape

Observation of the Color-Suppressed Decay B̅ 0→D0π0

journal articl

フクセイ シュウケツ リョウイキ ノ ヤクワリ ト フクセイ フォーク シンコウ ソガイ ノ セイブツガク

video/mp4講演者所属: 岡崎国立共同研究機構基礎生物学研究所教授vide

《卒論報告》SNS に関する多様な事例を想定したゲーム型教材の開発

departmental bulletin pape

Site-Isolated Main-Group <i>Tris</i>(2-pyridyl)borate Complexes by Pyridine Substitution and Their Ring-Opening Polymerization Catalysis

Tris(2-pyridyl)­borates are an emerging class of scorpionate ligands, distinguished as exceptionally robust and electron-donating. However, the rapid formation of inert homoleptic complexes with divalent metals has so far limited their catalytic utility. We report site-isolating tris(2-pyridyl)­borate ligands, bearing isopropyl, tert-butyl, and mesityl substituents at the pyridine 6-position to suppress the formation of inert homoleptic complexes. These ligands form the first 1:1 complexes between tris(2-pyridyl)­borates and Mg2+, Zn2+, or Ca2+, with isopropyl-substituted TpyiPrH showing the most generality. Single-crystal X-ray diffraction analysis of the resulting complexes and comparison to density functional theory (DFT) models showed geometric distortions driven by steric repulsion between the pyridine 6-substituents and the hexamethyldisilazide (HMDS–, –N­(SiMe3)2) anion. We show that this steric profile is a feature of the six-membered pyridine ring and contrasts with more established tris(pyrazolyl)­borate and tris(imidazoline)­borate scorpionate complexes. TpyiPrMg­(HMDS) (1) and its zinc analogue are moderately active for the controlled polymerization of l-lactide, ε-caprolactone, and trimethylene carbonate. Furthermore, 1 gives controlled polymerization under more demanding melt-phase polymerization conditions at 100 °C, and block copolymerization of ε-caprolactone and trimethylene carbonate. These results will enable useful catalysis and coordination chemistry studies with tris(2-pyridyl)­borates, and characterizes their structural complementarity to more familiar scorpionate ligands

Ethylene Polymerization with Thermally Robust Vanadium(III) Tris(2-pyridyl)borate Complexes

Despite the useful selectivity offered by vanadium catalysts for olefin polymerization, their implementation under practical conditions remains limited by poor productivity and thermal stability. This report describes phenyl tris(2-pyridyl)borate (Tpy–) complexes of vanadium(III) that are amenable to ethylene polymerization at temperatures approaching industrial conditions (>100 °C). We developed metal tris(2-pyridyl)borate precursors TpyLi, TpyK, and TpyAg, which undergo smooth metathesis with VCl3(THF)3 to provide solvated complexes TpyVCl2(DMF) and TpyVCl2(THF). In contrast, soft deprotonation of TpyH with triethylamine and VCl3(THF)3 gave the anionic complex [TpyVCl3][Et3NH], our optimal precatalyst. Thus, [TpyVCl3][Et3NH] polymerizes ethylene with low dispersity (∼2) and a moderate molecular weight (∼350000) at temperatures up to 135 °C. This work advances the use of tris(2-pyridyl)borates, an emerging ligand class, in catalysis and provides a platform for vanadium catalysis in demanding applications

The cluster lifetime over different values of the reduced modulus and cluster size.

<p>(A, B) ; (C, D) . The surface (A, C) and contour (B, D) plots show that either small cluster size or soft cell/substrate leads to unstable adhesion of molecule bond clusters. In (A), the 4 data points with longest lifetime are subjected to a simulation cutoff .</p

A stochastic-elastic model of focal contact demonstrating the effect of cell/matrix compliance.

<p>(A) A single adhesion patch between two elastic media (cell and extracellular matrix) subjected to a uniform tensile stress directly applied along the interface. In this case, the applied load is nominally equally shared among all bonds, independent of the system elasticity. (B) The elastic recoil at open bonds increasing the surface separation at these bond locations and suppressing receptor/ligand rebinding that is necessary for stable adhesion. (C) Bond transition between closed and open states at force-dependent dissociation and separation-dependent association rates.</p

Failure mode of molecular bond clusters subjected to nominally uniform stress distribution.

<p>Averaged bond survival probability versus bond location (normalized by bond spacing ) for , and . The snapshots indicate that there is no stress concentration in the adhesion domain and the molecular cluster fails in a uniform mode independent of bond location. The fact that 20 events almost break the cluster of 20 bonds suggests that bond rebinding has been rare during the failure process.</p

Effect of bond spacing on bond cooperation/rebinding and adhesion lifetime.

<p>The cluster lifetime is plotted as a function of the bond spacing for different levels of the applied load (, ).</p