Oxygen-assisted water partial dissociation on copper: a model study.

It is essential to understand and control the O-H bond cleavage on metal surfaces with pre-adsorbed oxygen atoms in heterogeneous catalytic processes. The adsorption and dissociation of water on clean and oxygen-pre-adsorbed copper surfaces, including Cu(111), Cu(110), Cu(100), Cu(210), Cu(211), Cu(310) and Cu(110)-(1 × 2), as well as Cu-ad-row and Cu-ad-atom, have been investigated by the density functional theory-generalized gradient approximation (DFT-GGA) method. The calculation results indicate that the presence of oxygen species significantly promotes the water dissociation. It is found that the promotion effect depends both on the adsorption energy of the pre-adsorbed oxygen and the distance between the pre-adsorbed oxygen and the stripped hydrogen in water: the more strongly the oxygen atom binds to the metal surface, the less the promotion effect it has on the water O-H bond cleavage; the shorter the distance between pre-adsorbed oxygen and hydrogen in water, the greater is the promotion effect. Based on electronic analysis, physical origin of the promotion effect can be attributed to the strong interaction of acid-base pair sites on oxygen-metal systems.

Influence of tube voltage, tube current and newer iterative reconstruction algorithms in CT perfusion imaging in rabbit liver VX2 tumors.

PURPOSE: We aimed to explore the influence of tube voltage, current and iterative reconstruction (IR) in computed tomography perfusion imaging (CTPI) and to compare CTPI parameters with microvessel density (MVD). METHODS: Hepatic CTPI with three CTPI protocols (protocol A, tube voltage/current 80 kV/40 mAs; protocol B, tube voltage/current 80 kV/80 mAs; protocol C: tube voltage/current 100 kV/80 mAs) were performed in 25 rabbit liver VX2 tumor models, and filtered back projection (FBP) and IR were used for reconstruction of raw data. Hepatic arterial perfusion (HAP), hepatic portal perfusion (HPP), total perfusion (TP), hepatic arterial perfusion index (HPI), blood flow (BF) and blood volume (BV) of VX2 tumor and normal hepatic parenchyma were measured. Image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were quantified and radiation dose was recorded. MVD was counted using CD34 stain and compared with CTPI parameters. RESULTS: The highest radiation dose was found in protocol C, followed by protocols B and A. IR lowered image noise and improved SNR and CNR in all three protocols. There was no statistical difference between HAP, HPP, TP, HPI, BF and BV of VX2 tumor and normal hepatic parenchyma among the three protocols (P > 0.05) with FBP or IR reconstruction, and no statistical difference between IR and FBP reconstruction (P > 0.05) in either protocol. MVD had a positive linear correlation with HAP, TP, BF, with best correlation observed with HAP; MVD of VX2 tumor showed no or poor correlation with HPI and BV. CONCLUSION: CTPI parameters are not affected by tube voltage, current or reconstruction algorithm; HAP can best reflect MVD, but no correlation exists between BV and MVD.

The evaluation of coronary artery-to-pulmonary artery fistula in adulthood on 256-slice CT coronary angiography: Comparison with coronary catheter angiography and transthoracic echocardiography.

OBJECTIVE: To review the imaging features of coronary artery-to-pulmonary artery fistula (CPAF) on CT coronary angiography (CTCA) and evaluate its diagnostic performance compared with coronary catheter angiography (CCA) and transthoracic echocardiography (TTE). MATERIALS AND METHODS: We retrospectively reviewed with a diagnosis of CPAF from among 19855 consecutive CCTA performed with 256-slice MDCT scanner for suspected coronary artery disease. CT images were evaluated for - origin, number, size and course (tubular/worm-like dilation/significant aneurysm formation/wall attachment sign) of fistula vessels, drainage site, drainage site imaging features (pierced sign, isodensity sign, smoke sign, jet sign), and main pulmonary artery (MPA) enlargement. 25 patients of CPAF also underwent CCA and 47 patients underwent TTE. RESULTS: There were 72 patients with CPAF (0.36%) in our study, of which 44 were men and 28 were women, with mean age of 55.8 ±â€¯13.2 years (range 22-85 years). CPAF originated from conus artery, left anterior descending artery (LAD), combined conus artery and LAD in 55, 67, 50 cases, respectively. Tubular dilation, worm-like dilation and aneurysm was seen in 14, 58 and 35 cases, respectively. Wall attachment sign was noted in 69 cases. All the cases demonstrated only a single drainage site, with left lateral wall, left anterolateral, anterior, right lateral and right anterolateral walls of MPA in 44, 21, 5, 1 and 1 cases, respectively. The mean diameter of the fistula drainage site was 2.6 ±â€¯1.3 mm. Pierced sign, jet sign, smoke sign, isodensity sign was seen in 72, 46, 41 and 24 cases, respectively. MPA enlargement was seen in 20 patients. CCA showed CPAF in only 20 cases among 25 patients; while TTE showed CPAF in only 9 patients among 47 patients. CONCLUSION: CTCA is competent in detecting and characterizing CPAF with an excellent diagnostic performance as the first imaging modality of choice, which is valuable for giving a distinct and intuitive explanation to patients and physicians and making an objective and exact assessment for further management.

Tetrakis(mu-anthracene-9-carboxylato)-kappa4O:O';kappa3O,O':O';kappa3O:O,O'-bis[(anthracene-9-carboxylato-kappa2O,O')(1,10-phenanthroline-kappa2N,N')erbium(III)]: effects of a noncoordinating anthracene ligand ring system on the final structure of a coordination complex.

The title complex, [Er(2)(C(15)H(9)O(2))(6)(C(12)H(8)N(2))(2)], has a centrosymmetric binuclear cage structure in which the two Er(III) atoms are both nine-coordinated and are bridged by four bulky anthracene-9-carboxylate (L) ligands, with a nonbonding Er...Er separation of 3.9041 (2) A. The L groups coordinate each Er(III) atom in three different ways. The results reported here reveal that the bulky anthracene skeleton of the L ligand plays an important role in the formation of the complex by virtue of intra- and intermolecular pi-pi stacking and C-H...pi interactions.

Comparison of microvascular perfusion evaluation among IVIM-DWI, CT perfusion imaging and histological microvessel density in rabbit liver VX2 tumors.

OBJECT: To explore microcirculation features with intravoxel incoherent motion (IVIM) and to compare IVIM with CT perfusion imaging (CTPI) and microvessel density (MVD). MATERIALS AND METHODS: Hepatic CTPI and IVIM were performed in 16 rabbit liver VX2 tumor models. Hepatic arterial perfusion (HAP), hepatic arterial perfusion index (HPI), Blood flow (BF), and blood volume (BV) from CTPI were measured. Apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion fraction (f), and pseudo-diffusion coefficient (D*) from IVIM were measured. MVD was counted with CD34 stain. The microcirculation features with IVIM were compared with CTPI parameters and MVD. RESULTS: Strong linear correlations were found between D value (0.89±0.21×10-3mm2/s) and HAP (15.83±6.97ml/min/100mg) (r=0.755, P=0.001) and between f value (12.64±6.66%) and BV (9.74±5.04ml/100mg) (r=0.693, P=0.004). Moderate linear correlations were observed between ADC (1.07±0.32×10-3mm2/s) and HAP (r=0.538, P=0.039), respectively; and between D value and MVD (9.31±2.57 vessels at 400×magnification) (r=0.509, P=0.044). No correlations were found between D* (119.90±37.67×10-3mm2/s) and HAP, HPI (68.34±12.91%), BF (4.95±2.16ml/min/100mg), BV. CONCLUSION: IVIM parameters can characterize microcirculation to certain extent and separate it from pure water molecular diffusion. There is fair correlation between D or ADC value and CTPI parameters or MVD, but no correlation between D* or f value and CTPI parameters or MVD except f value and BV, which is still unclear and need further clinical studies to validate.

catena-Poly[[diazido-manganese(II)]bis-[µ-1-(4-pyridylmeth-yl)-1H-benzimidazole]].

In the title polymeric compound, [Mn(N(3))(2)(C(13)H(11)N(3))(2)](n), each Mn(II) centre is six-coordinated in an octahedral geometry by six N atoms from four 1-(4-pyridylmeth-yl)-1H-benzimidazole (L) ligands and two azide anions (N(3) (-)). Each of the Mn(II) ions lies on an inversion centre. The L ligands and N(3) (-) anions bridge adjacent Mn(II) centres, generating a polymeric chain running along the [110] direction. Adjacent polymeric chains are arranged in a two-dimensional network parallel to the (001) plane, linked by C-H⋯N hydrogen bonds.

Tetra-kis(µ-anthracene-9-carboxyl-ato)bis-[(anthracene-9-carboxyl-ato)(2,2'-bipyrid-yl)lanthanum(III)].

The title complex, [La(2)(C(15)H(9)O(2))(6)(C(10)H(8)N(2))(2)], has a centrosymmetric binuclear cage structure in which two La(III )atoms are both nine-coordinated and bridged by four anthracene-9-carboxyl-ate ligands, with an La⋯La separation of 4.0880 (4) Å. The remaining coordination sites are occupied by two N atoms of a 2,2'-bipyridine (bipy) and two O atoms of an anthracene-9-carboxyl-ate ligand. The six anthracene-9-carboxyl-ate groups coordinate each La(III )atom in three different ways. Adjacent discrete dinuclear units are arranged into a one-dimensional chain along the [111] direction by inter-molecular π-π stacking inter-actions, with a centroid-centroid separation of 3.704 (7) Å.

Copper(II), cobalt(II), and nickel(II) complexes with a bulky anthracene-based carboxylic ligand: syntheses, crystal structures, and magnetic properties.

To systematically explore the influence of the bulky aromatic ring skeleton with a large conjugated pi-system on the structures and properties of their complexes, six CuII, CoII, and NiII complexes with the anthracene-based carboxylic ligand anthracene-9-carboxylic acid (HL1), were synthesized and characterized, sometimes incorporating different auxiliary ligands: [Cu2(L1)4(CH3OH)2](CH3OH) (1), [Cu4(L1)6(L2)4](NO3)2(H2O)2 (2), {[Cu2(L1)4(L3)](CH3OH)0.25}infinity (3), [Co2(L1)4(L4)2(micro-H2O)](CH3OH) (4), {[Co(L1)2(L5)(CH3OH)2]}infinity (5), and {[Ni(L1)2(L5)(CH3OH)2]}infinity (6) (L2 = 2,2'-bipyridine, L3 = 1,4-diazabicyclo[2.2.2]octane, L4 = 1,10-phenanthroline, and L5 = 4,4'-bipyridine). 1 has a dinuclear structure that is further assembled to form a one-dimensional (1D) chain and then a two-dimensional (2D) network by the C-H...O H-bonding and pi...pi stacking interactions jointly. 2 takes a tetranuclear structure due to the existence of the chelating L2 ligand. 3 possesses a 1D chain structure by incorporating the related auxiliary ligand L3, which is further interlinked via interchain pi...pi stacking, resulting in a three-dimensional (3D) network. 4 also has a dinuclear structure and then forms a higher-dimensional supramolecular network through intermolecular pi...pi stacking and/or C-H...pi interactions. 5 and 6 are isostructural complexes, except they involve different metal ions, showing 1D chain structures, which are also assembled into 2D networks from the different crystallographic directions by interchain pi...pi stacking and C-H...pi interactions, respectively. The results reveal that the steric bulk of the anthracene ring in HL1 plays an important role in the formation of 1-6. The magnetic properties of the complexes were investigated, and the very long intermetallic distances result in weak magnetic coupling, with the exception of 1 and 3, which adopt the typical paddle-wheel structure of copper acetate and are thus strongly coupled.