Harmonic entanglement with second-order nonlinearity

We investigate the second-order nonlinear interaction as a means to generate entanglement between fields of differing wavelengths and show that perfect entanglement can, in principle, be produced between the fundamental and second-harmonic fields in these processes. Neither pure second-harmonic generation nor parametric oscillation optimally produce entanglement; such optimal entanglement is rather produced by an intermediate process.     

Nonlinear frequency conversion in waveguide directional couplers

Nonlinear optical effects for frequency conversion require a phase-matching condition to efficiently generate a coherent field at the new wavelength. We find that the phase-matching condition can be replaced by a resonance condition when the nonlinear effect takes place in a waveguide directional coupler. We apply this theory to second-harmonic generation and find a theoretical conversion efficiency of 100%, equivalent to the perfect phase-matching condition. An example of the design of such waveguide directional coupler is presented.     

A dihydroxo-bridged Fe(II)-Fe(III) complex: a new member of the diiron diamond core family

The first structurally characterized Fe(II)-Fe(III) complex containing a M2(mu-OH)2 diamond core is a Robin and Day class II mixed-valence complex.     

Enabling Aromatic Hydroxylation in a Cytochrome P450 Monooxygenase Enzyme through Protein Engineering

The cytochrome P450 (CYP) family of heme monooxygenases catalyse the selective oxidation of C−H bonds under ambient conditions. The CYP199A4 enzyme from Rhodopseudomonas palustris catalyses aliphatic oxidation of 4-cyclohexylbenzoic acid but not the aromatic oxidation of 4-phenylbenzoic acid, due to the distinct mechanisms of aliphatic and aromatic oxidation. The aromatic substrates 4-benzyl-, 4-phenoxy- and 4-benzoyl-benzoic acid and methoxy-substituted phenylbenzoic acids were assessed to see if they could achieve an orientation more amenable to aromatic oxidation. CYP199A4 could catalyse the efficient benzylic oxidation of 4-benzylbenzoic acid. The methoxy-substituted phenylbenzoic acids were oxidatively demethylated with low activity. However, no aromatic oxidation was observed with any of these substrates. Crystal structures of CYP199A4 with 4-(3′-methoxyphenyl)benzoic acid demonstrated that the substrate binding mode was like that of 4-phenylbenzoic acid. 4-Phenoxy- and 4-benzoyl-benzoic acid bound with the ether or ketone oxygen atom hydrogen-bonded to the heme aqua ligand. We also investigated whether the substitution of phenylalanine residues in the active site could permit aromatic hydroxylation. Mutagenesis of the F298 residue to a valine did not significantly alter the substrate binding position or enable the aromatic oxidation of 4-phenylbenzoic acid; however the F182L mutant was able to catalyse 4-phenylbenzoic acid oxidation generating 2′-hydroxy-, 3′-hydroxy- and 4′-hydroxy metabolites in a 83 : 9 : 8 ratio, respectively. Molecular dynamics simulations, in which the distance and angle of attack were considered, demonstrated that in the F182L variant, in contrast to the wild-type enzyme, the phenyl ring of 4-phenylbenzoic acid attained a productive geometry for aromatic oxidation to occur.     

Benchmark calculations with correlated molecular wave functions XII. Core correlation effects on the homonuclear diatomic molecules B2-F2

Using systematic sequences of the newly developed correlation consistent core-valence basis sets from cc-pCVDZ through cc-pCV6Z, the spectroscopic constants of the homonuclear diatomic molecules containing first row atoms, B–F, are calculated both with and without inclusion of 1s correlation. Internally contracted multireference configuration interaction (IC-MRCI) and singles and doubles coupled cluster (CCSD) theory with a perturbational estimate of connected triple excitations, CCSD(T), have been investigated. By exploiting the convergence of the correlation consistent basis sets, complete basis set (CBS) limits have been estimated for total energies, dissociation energies, equilibrium geometries, and harmonic frequencies. Based on the estimated CBS limits the effects of 1s correlation on D _e (kcal/mol), r _e (?), and ω _e (cm⁻¹) are: +1.1, −0.0070, +10 for B₂; +1.5, −0.0040, +13 for C₂; +0.9, −0.0020, +9 for N₂; +0.3, −0.0020, +6 for O₂; and −0.1, −0.0015, +1 for F₂. Received: 20 January 1997 / Accepted: 6 May 1997     

发光玻璃在X射线实时成像系统中的应用

介绍了以铽（Ｔｂ）激活的高密度发光玻璃和光导纤维发光玻璃的特性。它应用在Ｘ射线实时成像系统中,可大大改善空间分辨能力。用它做的转换屏比一般晶粒状荧光物质做的厚得多,特别适合用于高能Ｘ射线实时成像系统     

ChemInform Abstract: Structure and Heats of Formation of Iodine Fluorides and the Respective Closed‐Shell Ions from CCSD(T) Electronic Structure Calculations and Reliable Prediction of the Steric Activity of the Free‐Valence Electron Pair in ClF6‐, BrF6‐, and IF6‐

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