Mixture of HIBA and glycolic acid as eluent for effective separation of yttrium and dysprosium by HPLC

A mixture of 2-hydroxy-2-methylpropanoic acid (HIBA) and glycolic acid, with 1-octanesulfonate (OS) as hydrophobic ion proved to be successful for the separation of rare-earth elements (REE). If the ratio of HIBA and glycolic acid is suitably adjusted, it is possible to separate Y from Dy. The resolution of Y and Dy was further improved by controlling the concentration of HIBA and glycolic acid. The technique was applied successfully to the separation and analysis of highly pure Y₂O₃ and Dy₂O₃. Received: 30 June 1998 / Revised: 3 September 1998 / Accepted: 15 September 1998     

Hydrogen removal by annealing from C-doped InGaAs grown on InP by metalorganic chemical vapor deposition

Hydrogen removal from C-doped InGaAs grown on InP substrate by metalorganic chemical vapor deposition is discussed based on the dependence of hole concentration on various annealing conditions. It is revealed that the hydrogen removal rate becomes higher as the annealing temperature is higher and the activation energy of hydrogen removal is about 1.9 eV regardless of C-doped layer thickness. The hydrogen removal rate is also found to be inversely proportional to C-doped layer thickness, suggesting that the hydrogen removal reaction is mainly governed by hydrogen diffusion.     

Preparation of processable polyaniline doped and complexed with anionic surfactant

Processable polyaniline doped and complexed with dodecylbenzenesulfonic acid was obtained by one-step micellar chemical polymerization of aniline in the presence of dodecylbenzenesulfonic acid. Homogeneous transparent suspension could be made by dispersing processable polyaniline in m-cresol without any precipitation. Polyaniline composite film blended with polymethylmethacrylate (PMMA) exhibits relatively high levels of conductivity at low volume fractions of the polyaniline, while keeping good mechanical properties, equivalent to those of the PMMA. © 1998 John Wiley & Sons, Ltd.     

Detection and grading for esophageal varices in patients with chronic liver damage: comparison of gadolinium-enhanced and unenhanced steady-state coherent MR images

The purpose of this study was to compare observer interpreted steady-state coherent coronal images and gadolinium-enhanced axial images in terms of the detection and grading of esophageal varices. Magnetic resonance imaging (MRI) and gastrointestinal endoscopy were performed within 2 weeks in 90 patients with chronic liver damage, including 55 with untreated esophageal varices, for periodic screening purposes. Two blinded readers retrospectively reviewed T1- and T2-weighted images with gadolinium-enhanced (gadolinium image set) and steady-state coherent (coherent image set) images. Sensitivity for the detection of esophageal varices was higher (P<.001) in the gadolinium image set (76%) than in the coherent image set (35%); on the other hand, specificity was higher (P<.001) in the coherent image set (91%) than in the gadolinium image set (66%). Furthermore, area under the ROC curve was higher for the gadolinium image set (Az=0.823) than the coherent image set (Az=0.761) (P=.48). Moderate and weak positive correlations with endoscopic grades were found for the gadolinium image (r=0.48, P<.01) and coherent image sets (r=0.34, P=.018). The addition of steady-state coherent imaging to the current routine liver imaging protocol did not improve the detection or grading of esophageal varices, whereas gadolinium-enhanced imaging was found to be potentially valuable. Nevertheless, endoscopy was confirmed to be mandatory in patients with esophageal varices suspected by MRI of the liver.     

Reversible haptotropic shift in zirconocene-hexapentaene complexes

Low-valent zirconocene species reacted with 1,1,6,6-tetraalkyl-1,2,3,4,5-hexapentaenes to form both 1-zirconacyclopent-3-ynes and eta2-pi-coordinated complexes according to the alkyl groups (R) and the existence of the neutral ligand (L). Haptotropic interconvertion between these two complexes was observed. It was proposed that double insertion of isocyanide into the Zr-C bond of 1-zirconacyclopent-3-ynes takes place via the isocyanide adduct of the eta2-pi-complex as an intermediate.     

Synthesis of masked haloareneboronic acids via iridium-catalyzed aromatic C-H borylation with 1,8-naphthalenediaminatoborane (danBH)

“Masked” areneboronic acids have been prepared by Ir-catalyzed C-H borylation of arenes. A [Ir(OMe)(cod)]₂ complex with a DPPE ligand showed the highest catalytic activity in the C-H borylation of benzene at 80 °C. The reaction system can be applied to substituted arenes, including halogen-substituted arenes. 1,3-Dihalobenzenes undergo the C-H borylation at their 5-positions in a regioselective fashion, affording 3,5-dihaloareneboronic acid derivatives, which serve as useful coupling modules for the convergent dendrimer synthesis.     

Acylglycerols (=Glycerides) from the Glandular Trichome Exudate on the Leaves of Paulownia tomentosa

Chemical investigations of the glandular trichome exudates on the leaves of Paulownia tomentosa (Scrophulariaceae) led to the identification of the thirty acylglycerols (=glycerides) 1 – 30 , including five known ones ( 2, 3, 6, 9 , and 15 ) (Fig. 1). Spectroscopic analysis combined with GC/MS studies of the glycerides and the liberated fatty acids, in the form of trimethylsilyl ether derivatives and trimethylsilylated methyl esters, respectively, established that the constituents belonged to 1,3‐di‐O‐acetyl‐2‐O‐(fatty acyl)glycerols, 1‐O‐acetyl‐2‐O‐(fatty acyl)‐sn‐glycerols, and 2‐O‐(fatty acyl)glycerols, wherein the fatty acyl moiety was either an eicosanoyl or an octadecanoyl group bearing OH and/or AcO groups at the 3‐, 3,6‐, 3,7‐, 3,8‐, or 3,9‐positions. The 1‐O‐acetyl‐2‐O‐[(3R,6S)‐3‐(acetyloxy)‐6‐hydroxyeicosanoyl]‐sn‐glycerol ( 12 ; 20% of the total glycerides), 2‐O‐[(3R,8R)‐3,8‐bis(acetyloxy)eicosanoyl]glycerol ( 17 ; 14%), 2‐O‐[(3R,9R)‐3,9‐bis(acetyloxy)eicosanoyl]glycerol ( 18 ; 12%), and 2‐O‐[(3R)‐3‐(acetyloxy)eicosanoyl]glycerol ( 10 ; 12%) were relatively abundant constituents. The configurations of the stereogenic centers of the fatty acyl moieties were determined by ¹H‐NMR analysis of the monoesters obtained from (R)‐ and (S)‐2‐(naphthalen‐2‐yl)‐2‐methoxyacetic acid ((R)‐ and (S)‐2NMA? OH and the hydroxy‐substituted fatty acid methyl esters (Fig. 2). The configuration at C(2) of the glycerol moiety of the 1‐O‐acetyl‐2‐O‐(fatty acyl)glycerols was determined to be (2S) by chemical conversion of, e.g., G‐2 (= 2 / 3 1 : 10) to (+)‐3‐O‐[tert‐butyl)diphenylsilyl]‐sn glycerol of known absolute configuration.     

Oligothiophene Self‐Assembly on the Surface of ZnO Nanorods: Toward Coaxial p–n Hybrid Heterojunctions

We describe herein the design, synthesis and detailed structural characterization of hybrid 1D nanostructures. They are prepared by supramolecular self‐assembly of oligothiophene molecules on the surface of zinc oxide nanorods in solution at room temperature. Electronic absorption spectroscopy and X‐ray diffraction show that both organic and inorganic components in the coaxial p–n heterojunctions are crystalline. Especially, it is demonstrated that the organic compounds form a self‐assembled monolayer at the surface of the nanorods, which is not the case when zinc oxide quantum dots are instead used. As a result of their hybrid nature, the 1D nanostructures lead to ambipolar semiconducting nanostructured materials as active layers in field‐effect transistors.     

Analysis on heat stress-induced hyperphosphorylation of stathmin at serine 37 in Jurkat cells by means of two-dimensional gel electrophoresis and tandem mass spectrometry

Two-dimensional gel electrophoresis (2-DE) and tandem mass spectrometry were successfully used for determination of a phosphorylation site of stathmin induced by heat stress to Jurkat cells of a human T lymphoblastic cell line. The cells were incubated for 30 min at 41 degrees C up to 45 degrees C in a serum free 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffered culture medium. The intracellular soluble proteins were separated by 2-DE, and some of the proteins increased their abundance by heat stress. Those proteins were identified to be calmodulin, protein kinase C substrate, thymosin beta-4 and F-actin capping protein beta-subunit by peptide mass fingerprinting (PMF) with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). On the contrary, protein phosphatase 2C gamma-isoform, nucleophosmin, translationally controlled tumor protein, Rho GDP-dissociation inhibitor-1, eukaryotic translation initiation factors 5A and 3A subunit 2, ubiquitin-like protein SMT 3B and chloride intracellular channel protein-1 were decreased their abundance. A protein spot of M(r) 18,000 and pI 5.9 was markedly increased at temperatures higher than 43 degrees C at which the cells were led to apoptosis. The spot was identified to be stathmin of a signal relay protein which has a function of sequestering microtubule. MALDI-quadrupole ion trap (QIT)-TOF-MS/MS and immunoblotting with a monoclonal antibody specific for a phosphorylation site of stathmin showed that the spot was a phosphorylated stathmin at serine 37 (Ser 37). The phosphorylation was suppressed by treatment of cells with olomoucine of an inhibitor specific for cyclin dependent kinase (Cdk-1). These results strongly suggest that heat stress activates Cdk-1 which phosphorylates Ser 37 on the stathmin molecule. The phosphorylation may cause the functional loss of stathmin for dynamic microtubule assembly and leads Jurkat cells to cell cycle arrest and apoptosis.