Evaluation of gadoxetate disodium as a contrast agent for mouse liver imaging: comparison with gadobenate dimeglumine

We investigated the characteristics of gadoxetate disodium (Gd-EOB-DTPA) as a contrast agent for magnetic resonance imaging of the mouse liver. Mice were imaged sequentially under isoflurane anesthesia using a T1-weighted, three-dimensional fast low-angle shot (3D FLASH) sequence after an intravenous injection of Gd-EOB-DTPA or gadobenate dimeglumine (Gd-BOPTA), and the time course of the contrast effect was examined. The time course of the contrast effect of Gd-EOB-DTPA was also assessed after intravenous injection under pentobarbital anesthesia and after subcutaneous injection while awake or under isoflurane or pentobarbital anesthesia. Moreover, different doses of Gd-EOB-DTPA or Gd-BOPTA were injected subcutaneously into conscious mice, and the clarity of the liver border was evaluated visually. Intravenous injection under isoflurane anesthesia caused rapid contrast enhancement in the liver with both Gd-EOB-DTPA and Gd-BOPTA, and the contrast effect was 41% stronger with Gd-EOB-DTPA. Subcutaneous injection of Gd-EOB-DTPA caused delayed but favorable contrast enhancement in the liver. Washout of Gd-EOB-DTPA was faster in mice injected while awake than in those injected under anesthesia. After intravenous injection, washout was faster under pentobarbital anesthesia than under isoflurane anesthesia. The peak liver contrast was 11% and 18% stronger under pentobarbital anesthesia than under isoflurane anesthesia, after intravenous and subcutaneous injections, respectively. Subcutaneous injection of Gd-EOB-DTPA or Gd-BOPTA caused dose-dependent contrast effects in the liver. At a given dose, the contrast effect tended to be stronger and liver demarcation tended to be clearer with Gd-EOB-DTPA than with Gd-BOPTA. In conclusion, intravenous or subcutaneous injection of Gd-EOB-DTPA produces a favorable contrast effects in the mouse liver, indicating its potential in investigating mouse models of liver diseases. The contrast effects vary between conscious mice and anesthetized mice and among anesthetic agents used.     

A note on Markov type constants

We prove that, if a geodesic metric space has Markov type 2 with constant 1, then it is an Alexandrov space of nonnegative curvature. The same technique provides a lower bound of the Markov type 2 constant of a space containing a tripod or a branching point. Received: 28 November 2007     

Fast Enumeration Algorithms for Non-crossing Geometric Graphs

A non-crossing geometric graph is a graph embedded on a set of points in the plane with non-crossing straight line segments. In this paper we present a general framework for enumerating non-crossing geometric graphs on a given point set. Applying our idea to specific enumeration problems, we obtain faster algorithms for enumerating plane straight-line graphs, non-crossing spanning connected graphs, non-crossing spanning trees, and non-crossing minimally rigid graphs. Our idea also produces efficient enumeration algorithms for other graph classes, for which no algorithm has been reported so far, such as non-crossing matchings, non-crossing red-and-blue matchings, non-crossing k-vertex or k-edge connected graphs, or non-crossing directed spanning trees. The proposed idea is relatively simple and potentially applies to various other problems of non-crossing geometric graphs.     

Coordination framework hosts consisting of 4-pyridyl-substituted carboxylic acid (PCA) dimers and 1D chains of Ni2+ and SCN-: a rational structural extension toward coordination framework hosts with large rectangular cavities

For the expansion of a rectangular cavity (RC) defined by two isonicotinic acid (isoH) dimers as bridging ligands and two SCN bridges, we conducted a structural extension based on the elongation of the bridging ligands by the replacement of isoH with longer 4-pyridyl-substituted carboxylic acid (PCA). For this purpose, the following three PCAs have been employed: trans-3-(4-pyridyl)propenoic acid (acrylH), 4-(4-pyridyl)benzoic acid (pybenH), and trans-3-(4-(4-pyridyl)phenyl)propenoic acid (pppeH). Self-assembly of Ni2+, SCN-, and each of four PCAs involving isoH, acrylH, pybenH, and pppeH in the presence of an aromatic guest gave four inclusion compounds formulated as [Ni(SCN)2(isoH)2].1/2(benz[a]anthracene) (1), [Ni(SCN)2(acrylH)2].1/2(benz[a]anthracene) (2), [Ni(SCN)2(pybenH)2].(pyrene) (3), and [Ni(SCN)2(pppeH)2](3/)(2).(benz[a]anthracene) (4). X-ray crystal structural determination of 1-4 revealed that the proposed structural extension was successful. Their crystal structures are layered structures of two-dimensional (2D) grid-type coordination frameworks (2D host layers) framed with bridging ligands of the corresponding PCA dimers and 1D chains consisting of Ni2+ ions and mu(1,3)-SCN- ions. The lengths of the PCA dimers are 12.269(5) A (isoH dimer), 16.890(4) A (acrylH dimer), 20.89(2) A (pybenH dimer), 25.387(3) A (pppeH dimer A), and 25.527(4) A (pppeH dimer B). Each 2D host layer has RCs defined by the two corresponding PCA dimers and the two SCN bridges. The dimensions of RCs are expanded in proportion to the increase in the lengths of the PCA dimers: 29.52 x 5.60-7.20 A2 (4) > 24.95 x 5.46-7.38 A2 (3) > 20.88 x 5.49-7.25 A2 (2) > 16.41 x 5.53-7.43 A2 (1). These expansions reflect the number of aromatic guests that can be included in RCs. RC of 1 include only one molecule of benz[a]anthracene, whereas RCs of 3 or 4 includes two molecules of pyrene or benz[a]anthracene, respectively. Comparison of the lengths between the PCA dimers and 4,4'-bipyridine-type ligands demonstrated that a design strategy-the preparation of a bridging ligand through self-assembly of two PCAs-is both efficient and particularly suitable for the preparation of very long bridging ligands.     

Ion chromatographic measurement of sulfide, methanethiolate, sulfite and sulfate in aqueous and air samples

Simultaneous measurement of sulfur species was investigated using ion chromatography. Sulfide, methanethiolate, sulfite and sulfate are representative of sulfur species. The aqueous sulfur species were simultaneously measured using a two-detector system: suppressor-type conductivity detector for sulfite and sulfate, and fluorometric or electrochemical detector for the reduced sulfur compounds. The major sulfur-containing gases, hydrogen sulfide, methyl mercaptan and sulfur dioxide are collected into aqueous solution as the species listed above. Collection of sulfur gases using a membrane-based cylindrical diffusion scrubber was investigated. Atmospheric hydrogen sulfide and sulfur dioxide are measured by the diffusion scrubber collection and subsequent measurement by ion chromatography without an enrichment column. In addition to the two gases, methyl mercaptan was also determined using a dual scrubber system.     

Temporal formation of optical anisotropy and surface relief during polarization holographic recording in polymethylmethacrylate with azobenzene side groups

The formation of polarization holographic gratings with both optical anisotropy and surface relief (SR) deformation was studied for polymethylmethacrylate with azobenzene side groups. Temporal contributions of isotropic and anisotropic phase gratings were simultaneously determined by observing transitional intensity and polarization states of the diffraction beams and characterizing by means of Jones calculus. To clarify the mechanism of SR deformation, cross sections of SR were characterized based on the optical gradient force model; experimental observations were in good agreement with the theoretical expectation. We clarified that the anisotropic phase change originating in the reorientation of the azobenzene side groups was induced immediately at the beginning of the holographic recording, while the response time of the isotropic phase change originating in the molecular migration due to the optical gradient force was relatively slow.     

The Active Phase of Nickel/Ordered Ce(2) Zr(2) O(x) Catalysts with a Discontinuity (x=7-8) in Methane Steam Reforming

Breaking news: A unique discontinuous property and an active phase of Ni/ordered Ce(2) Zr(2) O(x) (x=7-8) solid-solution catalysts were observed during methane steam reforming. The catalytic performance of Ni/Ce(2) Zr(2) O(x) strongly depended on the phase and oxygen content of the Ce(2) Zr(2) O(x) support.     

Multiferroics by rational design: implementing ferroelectricity in molecule-based magnets

Multiferroic materials: A novel class of multiferroics based on organic-inorganic hybrid materials is synthesized. The ferromagnetic properties originate from the coordination network, whereas the ferroelectricity results from the polar organic ions (see picture, M=magnetization and P=polarization).     

Color change (yellow \documentclass{article}\pagestyle{empty}\begin{document}$\rightleftharpoons$\end{document} orange) of 4,6,7-tri(alkoxy-substituted aryl)-1,2,5-thiadiazolo[3,4-c]pyridines in the solid phase

Reversible color change of 4,6,7-tri(alkoxy-substituted phenyl)-1,2,5-thiadiazolo[3,4-c]pyridines 5 in the solid state was observed: on grinding, yellow crystals of 5 became an orange amorphous solid which, on heating or washing with an appropriate solvent, gave the original yellow crystals.     

Temperature and matrix effects on competitive intermolecular and intramolecular reaction of benzylchlorocarbenes in ethanol

Benzylchlorocarbenes generated photolytically from diazirines in EtOH afford chlorostyrenes and acetals, whose distributions are sensitive to the reaction temperature.