Relations for supermatrices in hartree-fock-roothaan equation

Relations have been proved by which the double summations over symmetry subspecies appearing in J- and K- supermatrices of the Hartree-Fock-Roothaan equation are reduced to a single summation.     

A mechanistic dichotomy in concerted versus stepwise pathways in hydride and hydrogen transfer reactions of NADH analogues

A mechanistic dichotomy of one‐step versus stepwise pathways in hydride and hydrogen transfer reactions of NADH analogues is discussed including the relation between two pathways: a continuous change versus a discontinuous change of the mechanism. Examples of stepwise electron–proton–electron transfer through a charge transfer (CT) complex in hydride transfer from NADH analogues to hydride acceptors are presented including the detection and the reactivity of the intermediate, that is, radical cations of NADH analogues. The relation between stepwise versus one‐step mechanisms of hydride and hydrogen transfer reaction of NADH analogues is also clarified by showing examples of the change of the mechanism including the borderline. Copyright © 2008 John Wiley & Sons, Ltd.     

Hot electron plasmas trapped in helical magnetic surfaces

Experimental studies on nonneutral (pure electron) plasmas of finite temperature, trapped in helical closed magnetic surfaces have been conducted. The helical electron plasmas are produced with thermal electrons launched from the outside of the last closed flux surface (LCFS). About 150 μs after the electron injection, the plasmas reach equilibrium state. Around the LCFS, a steep gradient of plasma space potential φ _s is formed. The corresponding radial electric field is about 2.5 kV/m. On the other hand, around the magnetic axis of helical magnetic surfaces, φ _s is almost constant, indicating that there are little electrons there. The volume-averaged electron density is on the order of 10¹³ m^–3, smaller than the Brillouin density limit. The confinement time seems to be limited by a disruptive instability, and is so far about 1.5 ms.      

Search for novel amorphous alloys with high crystallization temperature by combinatorial arc plasma deposition

This paper describes a combinatorial search for novel amorphous alloys with high crystallization temperatures (T_x) using combinatorial arc plasma deposition (CAPD). The CAPD technique can deposit 1089 (33 × 33) thin film samples with different compositions on a substrate at one time. These 1089 samples on the substrate are individually referred to as CAPD samples and collectively referred to as a thin film library. Thin film libraries of Ir-Zr-Fe, Ir-Zr-Al, Mo-Zr-Al, Mo-Zr-Si, Ru-Zr-Fe and Ru-Zr-Si were deposited by CAPD. The compositions and phases of the CAPD samples were measured by energy dispersive X-ray fluorescence spectrometry and X-ray diffractometry, respectively. The results revealed that each library included amorphous CAPD samples. Since it is impossible to measure the T_x, fracture strength, fracture strain and Young's modulus of the CAPD samples by conventional measurement methods, larger samples having the same compositions as the amorphous CAPD samples were fabricated by a sputtering system. Since all CAPD samples of Ir-Zr-Fe and Ir-Zr-Al were too brittle, their corresponding sputter-deposited samples were not prepared. Sputter-deposited Mo-Zr-Al, Mo-Zr-Si, Ru-Zr-Fe and Ru-Zr-Si samples with ∼50 at.% Mo- or Ru-content were fabricated, and T_x and mechanical properties of these sputter-deposited samples were evaluated. All the sputter-deposited samples of Mo-Zr-Al and Mo-Zr-Si showed high T_x exceeding 973 K and as well as brittle characteristics. Ru₅₀Zr₃₅Fe₁₀ samples showed high T_x exceeding 1273 K and a low fracture strength of 0.26 GPa. Samples of Ru₅₁Zr₅Si₄₄ showed a high T_x of 923 K and a high fracture strength of 1.25 GPa.     

EPR and ENDOR studies of the distal site coordination of shark heart myoglobin

The coordination of small molecules and ions at the sixth position of ferric myoglobins (Mb) from the heart muscle of two species of shark,Lamna ditropis (LD) andPrionace glauca (PG), was studied in frozen solution by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy. The results were compared with those of horse heart Mb (EQMb). From our preliminary studies of the absorption spectra and partial amino acid sequences of PGMb and LDMb, we expected PGMb to have glutamine (Gln E7) in place of the distal His E7 that is highly conserved in most animals and present in LDMb. Here, we have used proton ENDOR to show that a water molecule coordinates to the ferric ion in both LDMb and PGMb at pH 6.3. The observed proton hyperfine coupling constant of the coordinating water molecule of PGMb is smaller than those of LDMb and EQMb, which suggests weaker coordination of the water molecule in PGMb, consistent with the absent distal His (E7). Coordination of several exogenous ligands at the distal site was examined by EPR. PGMb showed a coordination behavior different from that of LDMb and EQMb for 1-methylimidazole, 4-methylimidazole and SCN^?, suggesting that its distal site is less sterically hindered. On the basis of the ENDOR and EPR results, we assigned the distal residues of PGMb and LDMb as Gln and His, respectively.     

Synthesis of Nitrogen-Containing Polyaromatics by Aza-Annulative π-Extension of Unfunctionalized Aromatics

Nitrogen-containing polycyclic aromatic compounds (N-PACs) are an important class of compounds in materials science. Reported here is a new aza-annulative π-extension (aza-APEX) reaction that allows rapid access to a range of N-PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow-up oxidative treatment with p-chloranil affords structurally diverse N-PACs, which are very difficult to synthesize. DFT calculations reveal that the aza-APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N-PACs into nitrogen-doped nanographenes and their photophysical properties are also described.     

Theoretical study on the sound absorption of electrolytic solutions. I. Theoretical formulation

A theory is formulated that describes the sound absorption of electrolytic solutions due to the relative motion of ions, including the formation of ion pairs. The theory is based on the Kubo-Green formula for the bulk viscosity. The time correlation function of the pressure is projected onto the bilinear product of the density modes of ions. The time development of the product of density modes is described by the diffusive limit of the generalized Langevin equation, and approximate expressions for the three- and four-body correlation functions required are given with the hypernetted-chain integral equation theory. Calculations on the aqueous solutions of model electrolytes are performed. It is demonstrated that the theory describes both the activated barrier crossing between contact and solvent-separated ion pairs and the Coulombic correlation between ions.     

Total synthesis of (-)-sarain A

This article describes the details of our synthetic studies toward the complex marine alkaloid sarain A. Various strategies were conceived, setbacks encountered, and solutions developed, ultimately leading to a successful enantioselective total synthesis. Our route to (-)-sarain A features a number of key steps, including an asymmetric Michael addition to install the C4'-C3'-C7' stereotriad, an enoxysilane-N-sulfonyliminium ion cyclization to set the C3 quaternary carbon stereocenter, and assemble the diazatricycloundecane core, a ring-closing metathesis to construct the 13-membered ring, an intramolecular Stille coupling to fashion the unsaturated 14-membered macrocycle, and a late-stage installation of the tertiary amine-aldehyde proximity interaction.