Contrast-enhanced MR angiography in rats with hepatobiliary contrast agents

The aim of this animal study was to evaluate the feasibility of contrast-enhanced magnetic resonance (MR) angiography with two hepatobiliary contrast agents, Gd-DTPA-DeA and Gd-EOB-DTPA. Coronal images of the rat abdomen were acquired using a three-dimensional spoiled gradient recalled sequence before and after the administration of Gd-DTPA-DeA, Gd-EOB-DTPA, or Gd-DTPA. Four sets of postcontrast images were collected every 90 s. Contrast ratios were calculated for the abdominal aorta on the source images, and the retention index was defined as the ratio of the contrast ratio on the last imaging to that on the first postcontrast imaging. Partial minimum intensity projection (MIP) images covering the abdominal aorta were generated from the first and second postcontrast imagings, and the image quality was visually evaluated. The contrast ratio on the first postcontrast imaging was the highest for Gd-DTPA-DeA, followed by Gd-EOB-DTPA and Gd-DTPA. Retention indices were higher with Gd-DTPA-DeA than with Gd-EOB-DTPA and Gd-DTPA, implying a prolonged contrast effect with Gd-DTPA-DeA. On the MIP image from the first postcontrast imaging, delineation of the abdominal aorta tended to be better with Gd-DTPA-DeA and Gd-EOB-DTPA than with Gd-DTPA, and the difference was evident at low injection doses. Image quality for the second postcontrast imaging was higher with Gd-DTPA-DeA than with the other two agents, suggesting a longer imaging window for Gd-DTPA-DeA. In conclusion, Gd-DTPA-DeA and Gd-EOB-DTPA showed stronger contrast enhancement for the rat abdominal aorta and provided MR angiograms of higher image quality when compared with Gd-DTPA at the same injection dose. These hepatobiliary agents may make it possible to perform contrast-enhanced MR angiography even at a low injection dose.     

Kinetics and Mechanism of the Gold-Catalyzed Hydroamination of 1,1-Dimethylallene with N-Methylaniline

The mechanism of the intermolecular hydroamination of 3-methylbuta-1,2-diene ( 1 ) with N-methylaniline ( 2 ) catalyzed by (IPr)AuOTf has been studied by employing a combination of kinetic analysis, deuterium labelling studies, and in situ spectral analysis of catalytically active mixtures. The results of these and additional experiments are consistent with a mechanism for hydroamination involving reversible, endergonic displacement of N-methylaniline from [(IPr)Au(NHMePh)]⁺ ( 4 ) by allene to form the cationic gold π-C1,C2-allene complex [(IPr)Au(η²-H₂C=C=CMe₂)]⁺ ( I ), which is in rapid, endergonic equilibrium with the regioisomeric π-C2,C3-allene complex [(IPr)Au(η²-Me₂C=C=CH₂)]⁺ ( I′ ). Rapid and reversible outer-sphere addition of 2 to the terminal allene carbon atom of I′ to form gold vinyl complex (IPr)Au[C(=CH₂)CMe₂NMePh] ( II ) is superimposed on the slower addition of 2 to the terminal allene carbon atom of I to form gold vinyl complex (IPr)Au[C(=CMe₂)CH₂NMePh] ( III ). Selective protodeauration of III releases N-methyl-N-(3-methylbut-2-en-1-yl)aniline ( 3 a ) with regeneration of 4 . At high conversion, gold vinyl complex II is competitively trapped by an (IPr)Au⁺ fragment to form the cationic bis(gold) vinyl complex {[(IPr)Au]₂[C(=CH₂)CMe₂NMePh]}⁺ ( 6 ).     

Synthesis and photochromic properties of quinoxalino[e]-annelated dimethyldihydropyrene with planar chirality

9,10-Diacetyl-2,7-di-tert-butyl-trans-10b,10c-dimethyl-10b,10c-dihydropyrene annelated with a quinoxaline unit (q-DM-DHP, 3) was prepared from 5,13-di-tert-butyl-8,16-dimethyl[2.2]metacyclophane-1,2,9,10-tetraoxide (2) and o-phenylenediamine in two steps. The photochromic isomers of q-DM-DHP 3, closed form 3a and open form 3b, were separated by reverse-phase HPLC, and their isolated UV–visible spectra were estimated. The chiral HPLC analyses of q-DM-DHP 3 indicated their planar chirality, and their CD spectra were measured. The photochromic properties and thermodynamic properties of 3 were also discussed based on their UV–visible, ¹H NMR, CD, and fluorescence spectra.     

Charge transfer in the atomic structure of Ge (1 0 5)

The atomic structure and charge transfer on the Ge (1 0 5) surface formed on Si substrates are studied using scanning tunneling microscopy and spectroscopy (STM and STS). The bias-dependent STM images of the whole Ge (1 0 5) facets formed on a Ge “hut” structure on Si (0 0 1) are observed, which are well explained by the recently confirmed structure model. The local surface density of states on the Ge (1 0 5) surface is measured by STS. The localization of the electronic states expected from charge transfer mechanism is observed in the dI/dV spectra. The surface band gap is estimated as 0.8-0.9 eV, which is even wider than the bulk bandgap of Ge, indicating the strong charge transfer effect to make the dangling bonds stable. The shape of normalized tunnel conductance agrees with the theoretical band structure published recently by Hashimoto et al.     

Molecular gas dynamics approaches to interfacial phenomena accompanied with condensation

This paper deals with the condensation coefficient of methanol, which is evaluated from a condensation rate at the vapor–liquid interface. Film condensation is induced on the endwall of a vapor-filled shock tube, when a shock wave is reflected at the endwall and the vapor becomes supersaturated there. The liquid film grows with the lapse of time. The evolution in time of the liquid film thickness is measured by an optical interferometer with a high accuracy, and thereby the net condensation mass flux at the interface is obtained. The mass flux is incorporated into the kinetic boundary condition (KBC) at the interface for the Gaussian–BGK Boltzmann equation. Such a treatment of the boundary condition makes it possible to formally eliminate the evaporation and condensation coefficients in KBC and to obtain the unique numerical solution of the vapor–liquid system. In this way, the instantaneous condensation coefficient is accurately evaluated from the conformity with experiment and numerical solution. It is found that the values of condensation coefficient are, near vapor–liquid equilibrium states, close to those evaluated by molecular dynamics simulations.     

Definition of road roughness parameters for tire vibration noise control

Road roughness plays an important role in the generation of tire vibration noise. However, it is unclear which kinds of road roughness parameters should be controlled to reduce the noise. In this paper, we define the essential road roughness parameters that govern tire tread vibration and provide information on tire/road noise abatement. The detailed effects of road roughness parameters on tire tread vibration are estimated using a tire/road contact model. The results reveal that pavement asperity height itself is not an essential parameter, but asperity height unevenness, asperity radius, and asperity spacing are important for the abatement of tire vibration noise.     

The alignment of nematic liquid crystals on photolithographic micro-groove patterns

The alignment of nematic liquid crystals on micro-groove patterns was studied. It has been found that the order of the alignments is determined by the edge shape, spacing, and line pitch of the micro-groove patterns. On coarse patterns, with pitches greater than 2 μm, striped patterns of the liquid crystal alignment were observed using polarized light which manifested different orientations of the liquid crystals on the top, edge, and bottom of the grooves, respectively. On fine patterns, with pitches less than 2 μm, a uniform device-quality alignment has been realized, with which twisted nematic cells were constructed in combination with the rubbed alignment layer on the opposite substrate. Their viewing angle characteristics and tilt orientations of the director were also investigated.     

Highly efficient heterogeneous acylations of aromatic compounds with acid anhydrides and carboxylic acids by montmorillonite-enwrapped titanium as a solid acid catalyst

Montmorillonite-enwrapped titanium hydroxide species (Ti⁴⁺-mont) acted as a highly efficient heterogeneous acid catalyst for the acylation of aromatic compounds with acid anhydrides or carboxylic acids. The catalytic activity of the Ti⁴⁺-mont was higher than those of other acid catalysts such as zeolites, SO ₄ ^2? /ZrO₂ and p-toluenesulfonic acid. For example, the reaction of anisole with dodecanoic acid in the presence of the Ti⁴⁺-mont catalyst gave 1-(4-methoxyphenyl)-1-dodecanone in 97% yield. Furthermore, the Ti⁴⁺-mont catalyst was easily separated from the reaction mixture and was recyclable.     

Highly efficient C-C bond-forming reactions in aqueous media catalyzed by monomeric vanadate species in an apatite framework

A calcium vanadate apatite (VAp), in which PO4(3-) of hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is completely substituted by VO4(3-) in the apatite framework, was synthesized. Physicochemical analysis of the VAp reveals the presence of isolated VO4 tetrahedron units with a pentavalent oxidation state. The VAp acts as a high-performance heterogeneous base catalyst for various carbon-carbon bond-forming reactions such as Michael and aldol reactions in aqueous media and the H-D exchange reactions using deuterium oxide. For example, a 200-mmol-scale Michael reaction under triphasic conditions proceeded rapidly, with an extremely high turnover number of up to 260 400 and an excellent turnover frequency of 48 s(-1). No vanadium leaching was detected during the above reactions, and the catalyst was readily recycled with no loss of activity.