Renormalization of the inverse square potential

The quantum-mechanical D-dimensional inverse square potential is analyzed using field-theoretic renormalization techniques. A solution is presented for both the bound-state and scattering sectors of the theory using cutoff and dimensional regularization. In the renormalized version of the theory, there is a strong-coupling regime where quantum-mechanical breaking of scale symmetry takes place through dimensional transmutation, with the creation of a single bound state and of an energy-dependent s-wave scattering matrix element.     

Total structure determination of apratoxin A, a potent novel cytotoxin from the marine cyanobacterium Lyngbya majuscula

Apratoxin A (1), a potent cytotoxin with a novel skeleton, has been isolated from the marine cyanobacterium Lyngbya majuscula Harvey ex Gomont. This cyclodepsipeptide of mixed peptide-polyketide biogenesis bears a thiazoline ring flanked by polyketide portions, one of which possesses an unusual methylation pattern. Its gross structure has been elucidated by spectral analysis, including various 2D NMR techniques. The absolute configurations of the amino acid-derived units were determined by chiral HPLC analysis of hydrolysis products. The relative stereochemistry of the new dihydroxylated fatty acid unit, 3,7-dihydroxy-2,5,8,8-tetramethylnonanoic acid, was elucidated by successful application of the J-based configuration analysis originally developed for acyclic organic compounds using carbon-proton spin-coupling constants ((2,3)J(C,H)) and proton-proton spin-coupling constants ((3)J(H,H)); its absolute stereochemistry was established by Mosher analysis. The conformation of 1 in solution was mimicked by molecular modeling, employing a combination of distance geometry and restrained molecular dynamics. Apratoxin A (1) possesses IC(50) values for in vitro cytotoxicity against human tumor cell lines ranging from 0.36 to 0.52 nM; however, it was only marginally active in vivo against a colon tumor and ineffective against a mammary tumor.     

Transformation of AeIn4 Indides (Ae=Ba, Sr) into an AeAu2In2 structure type through gold substitution

The title compounds were prepared from the elements by high-temperature solid-state synthesis techniques. X-ray structural analyses shows that BaAu2In2 (1) and SrAu2In2 (2) crystallize in a new orthorhombic structure, Pnma, Z=4 (a=8.755(2), 8.530(2) A; b=4.712(1), 4.598(1) A; c=12.368(3), 12.283(4) A, respectively). Gold substitutes for 50% of the indium atoms in the tetragonal BaIn4 and monoclinic SrIn4 parents to give this new and more flexible orthorhombic structure. The Ae atoms in this structure are contained within chains of hexagonal prisms built of alternating In and Au that have additional augmenting atoms around their waists from further condensation of parallel displaced chains. The driving forces for these structural changes are in part the shorter Au-In distances (2.72 and 2.69 A) relative to d(In-In) in the parents, presumably because of relativistic contractions with Au. Generalities about such centered prismatic building blocks and their condensation modes in these and related phases are described. Band structure calculations (EHTB) demonstrate that the two compounds are metallic, which is confirmed by measurements of the resistivity of 1 and the magnetic susceptibilities of both.     

Aluminosilicate Catalysis of Chalcone Diels–Alder Reactions

Previously unreported Diels–Alder adducts of substituted chalcones with isoprene and myrcene have been formed at more than 0°C by employing a nanoporous aluminosilicate catalyst. This catalyst eliminates problems with diene polymerization that are encountered with many other Lewis acids. The chalcone component has some size restrictions.     

Exploratory syntheses and structures of SrAu(4.3)In(1.7) and CaAg(3.5)In(1.9): electron-poor intermetallics with diversified polyanionic frameworks that are derived from the CaAu4In2 approximant

The phase regions around quasicrystals and approximants (QC/ACs) are rich pools for electron-poor intermetallics with novel, complex structures, and bonding patterns. The present SrAu(4.30(1))In(1.70(1)) (1) and CaAg(3.54(1))In(1.88(1)) (2) were synthesized through chemical tunings of the model CaAu(4)In(2) (YCd(6)-Type) AC. Single crystal X-ray diffraction analyses reveals that crystal 1 has Pnma (CeCu(6)-type) symmetry, with a = 9.102(1) ?, b = 5.6379(9) ?, and c = 11.515(2) ?. The building block in 1 is a 19-vertex cluster Sr@Au(9)In(4)M(6) (M = Au/In), which vividly mimics Ca@(Au,In)(18) in Ca(3)Au(12.4)In(6.1) (YCd(6)-type) in geometry. These clusters aggregate into one-dimensional columns extending along the b axis. Crystal 2 (P6/mmm, a = 20.660(3) ?, c = 9.410(2) ?) is closely related to Na(26)Cd(141) (hP167) and Y(13)Pd(40)Sn(31) (hP168), which are differentiated by the selective occupation of Wyckoff 1a (0 0 0) or 2d (1/3 2/3 1/2) sites by Cd or Pd. Crystal 2 adopts the Na(26)Cd(141) structure, but the 1a site is split into two partially occupied sites. The synergistic disorder in the hexagonal tunnels along c is a major property. The valence electron count per atom (e/a) values for 1 and 2 are 1.63 and 1.74, respectively, the lowest among any other ternary phases in each system. These values are close to those of ACs in the Ca-Au-M (M = Ga, In) systems. Electronic structures for both are discussed in terms of the results of TB-LMTO-ASA calculations.     

分子内结构环境对解离能的影响

为了理解化学键的这一结构效应, 本文对具有相同化学键而分子内结构环境不同的系列分子进行了计算研究, 讨论了化学键结构环境对解离能的影响.     

ChemInform Abstract: Contrasts in Structural and Bonding Representations among Polar Intermetallic Compounds. Strongly Differentiated Hamilton Populations for Three Related Condensed Cluster Halides of the Rare-Earth Elements.

The crystal and electronic structures of three related Ln₃MX₃ (Ln: lanthanoid; M: transition metal; X: Cl, I) phases, Pr₃RuI₃ (space group P2₁/m), Gd₃MnI₃ (P2₁/m), and Pr₃RuCl₃ (Pnma) containing extended mixed-metal chains are compared and contrasted using LMTO-ASA calculations with local spin density approximation and crystal orbital Hamilton population analyses.