Some results for operators on a model space

We investigate some problems for truncated Toeplitz operators. Namely, the solvability of the Riccati operator equation on the set of all truncated Toeplitz operators on the model space K _θ = H²ΘθH² is studied. We study in terms of Berezin symbols invertibility of model operators. We also prove some results for the Berezin number of the truncated Toeplitz operators. Moreover, we study some property for H²-functions in terms of noncyclicity of co-analytic Toeplitz operators and hypercyclicity of model operators.     

Measurement of isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions induced by bremsstrahlung

We measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions were (4.95 ± 0.51) × 10^?4, (5.72 ± 0.72) × 10^?4, (6.03 ± 0.50) × 10^?4, and (9.27 ± 0.83) × 10^?4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.     

Chloride ion conduction without water coordination in the pore of ClC protein

In the present work, we have found by an atomistic molecular dynamics simulation that hydrogen atoms originating from the residues of a prokaryotic ClC protein (EcClC) stabilize the chloride ion without water molecules in the pore of ClC protein. When the chloride ion conduction is simulated by pulling a chloride ion along the pore axis, the free energy barrier for chloride ion conduction is calculated to be low (4 kcal/mol), although the chloride ion is stripped of its hydration shell as it passes through the dehydrated pore region. The calculation of the number of hydrogen atoms surrounding the chloride ion reveals that water molecules hydrating the chloride ion are replaced by polar and non‐polar hydrogen atoms protruding from the protein residues. From the analysis of the pair interaction energy between the chloride ion and these hydrogen atoms, it is realized that the hydrogen atoms from the protein residues stabilize the chloride ion at the dehydrated region instead of water molecules, by which the energetic penalty for detaching water molecules from the permeating ion is compensated. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

A molecular-clip-based approach to cofacial zinc-porphyrin complexes

We have synthesized molecular-clip-based cofacial zinc-porphyrin complexes. The complexes are shown to be new efficient receptors for the complexation of 1,4-diazabicyclo[2,2,2]octane, acridinium ions, 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA) and 1,2,4,5-benzenetetracarboxylic dianhydride (BTDA). Large binding constants (K_asso) in the range of 2.0 × 10⁴-1.1 × 10⁸ M⁻¹ were obtained for the 1:1 complexes of molecular tweezers (3) and rectangle (8) by inserting the hosts between the two porphyrin rings. The values of K and the spectroscopic results suggest that 3 and 8 serve as effective building blocks to capture the hosts. Semi-empirical calculations show that the guests position themselves within the cleft of the bis-porphyrins.     

Preconcentration of cadmium and nickel using the bioadsorbent Geobacillus thermoleovorans subsp. stromboliensis immobilized on Amberlite XAD-4

Cadmium and nickel ions have been preconcentrated on Geobacillus thermoleovorans subsp. stromboliensis, immobilized on Amberlite XAD-4, and were determined by flame atomic absorption spectrometry (FAAS). Parameters such as pH, amount of adsorbent, eluent type and volume, flow rate of solution and the matrix interference effect on retention have been studied, and extraction conditions were optimized. Elution of Cd(II) and Ni(II) from minicolumns was carried out with 1.0 M hydrochloric acid or nitric acid with recoveries from 97 to 100%. The sorption capacity is 0.0373 and 0.0557 mmol g^?1 for Cd(II) and Ni(II), respectively. The detection limits were 0.24 μg L^?1 for cadmium and 0.3 μg L^?1 for nickel. The relative standard deviations of the procedure were below 10%. The procedure was validated by analyzing certified reference materials and applied to the determination of Cd(II) and Ni(II) in natural water and food samples.     

Efficient rearrangement of epoxides catalyzed by a mixed-valent iron trifluoroacetate [Fe3O(O2CCF3)6(H2O)3]

The mixed-valent oxo-centered triiron(III, III, II) trifluoroacetate complex [Fe₂^IIIFe^IIO(O₂CCF₃)₆(H₂O)₃] was prepared by reacting anhydrous iron(III) chloride with boiling trifluoroacetic acid under nitrogen. The non-hygroscopic and readily available mixed-valent triiron trifluoroacetate complex was found to be an efficient catalyst for the regioselective rearrangement of epoxides. A number of carbonyl compounds formed via the rearrangement of epoxides could be obtained by a simple filtration of the reaction mixture through a short plug of silica gel.     

Synthesis,Crystal Structures,and Vibrational Spectra of Novel Azidopalladates of the Alkali Metals Cs2[Pd(N3)4] and Rb2[Pd(N3)4]·2/3H2O

The transparent dark orange compounds Cs₂[Pd(N₃)₄] and Rb₂[Pd(N₃)₄]·²/₃H₂O are synthesized by reaction of the respective binary alkali metal azides with K₂PdCl₄ in aqueous solutions. According to single‐crystal X‐ray diffraction investigations, the novel ternary azidopalladates(II) crystallize in the monoclinic space group P2₁/c (no. 14) with a = 705.7(2) pm, b = 717.3(2) pm, c = 1125.2(5) pm, β = 104.58(2)°, mP30 for Cs₂[Pd(N₃)₄] and a = 1041.4(1) pm, b = 1292.9(2) pm, c = 1198.7(1) pm, β = 91.93(1)°, mP102 for Rb₂[Pd(N₃)₄]·²/₃H₂O, respectively. Predominant structural features of both compounds are discrete [Pd^II(N₃)₄]^2– anions with palladium in a planar coordination by nitrogen, but differing in point group symmetries., The vibrational spectra of the compounds are analyzed based on the idealized point group C_4h of the spectroscopically relevant unit, [Pd(N₃)₄]^2– taking into account the site symmetry splitting due to the symmetry reduction in the solid phase.