Tareciliosides H-M: further cycloartane glycosides from leaves of Tarenna gracilipes

From the 1-BuOH-soluble fraction of a MeOH extract of leaves of Tarenna gracilipes, collected in Okinawa, six further new cycloartane glycosides, named tareciliosides H-M (1-6), were isolated. Their structures were established through a combination of spectroscopic analyses.     

Acceleration of the reaction OH + CO → H + CO2 by vibrational excitation of OH

The collision complex formed from a vibrationally excited reactant undergoes redissociation to the reactant, intramolecular vibrational relaxation (randomization of vibrational energy), or chemical reaction to the products. If attractive interaction between the reactants is large, efficient vibrational relaxation in the complex prevents redissociation to the reactants with the initial vibrational energy, and the complex decomposes to the reactants with low vibrational energy or converts to the products. In this paper, we have studied the branching ratios between the intramolecular vibrational relaxation and chemical reaction of an adduct HO(v)-CO formed from OH(X(2)Π(i)) in different vibrational levels v = 0-4 and CO. OH(v = 0-4) generated in a gaseous mixture of O(3)/H(2)/CO/He irradiated at 266 nm was detected with laser-induced fluorescence (LIF) via the A(2)Σ(+)-X(2)Π(i) transition, and H atoms were probed by the two-photon excited LIF technique. From the kinetic analysis of the time-resolved LIF intensities of OH(v) and H, we have found that the intramolecular vibrational relaxation is mainly governed by a single quantum change, HO(v)-CO → HO(v-1)-CO, followed by redissociation to OH(v-1) and CO. With the vibrational quantum number v, chemical process from the adduct to H + CO(2) is accelerated, and vibrational relaxation is decelerated. The countertrend is elucidated by the competition between chemical reaction and vibrational relaxation in the adduct HOCO.     

Conformation of curdlan as observed by tapping mode atomic force microscopy

Tapping mode atomic force microscopy was used to study the bacterial polysaccharide curdlan deposited from dimethyl sulfoxide (Me₂SO) and NaOH aqueous solutions. For curdlan in Me₂SO, flexible single chains corresponding to a disordered conformation were observed at a concentration of 5 mg/l, and the chain diameter was measured to be 0.65±0.05 nm, which showed good agreement with the expected value of the single polysaccharide chain. Because the concentration of curdlan increased, the chains became more rigid and aggregated, subsequently, the network structures of curdlan appeared. However, curdlan samples deposited from a 5 mM NaOH solution showed entirely different conformations. The chains observed were almost in the form of micelles of several nanometers, which were supermolecular assemblies. The heterogeneously dense zones were observed as the curdlan concentration increased to 40 mg/l. When the concentration of curdlan was above 100 mg/l, which might cause the real concentration of curdlan on the mica substrate after drying treatment exceeding some critical value of gelation, gel network structures were formed. Keeping on increasing the concentration of curdlan, the image showed a more homogeneous fibrous network.     

Soluble magnesium and titanium catalyst components for ethylene polymerization

The catalyst system comprised of a heptane solution of magnesiumoctoate-H₂O-Tetrabutoxytitanium/diethylaluminumchloride was highly active for ethylene polymerization at a high temperature. High productivity for the catalyst system at a low temperature was achieved by the aging of the catalyst components. The effect of different orders of addition of the catalyst components on productivity was investigated to assume the role of each components in the formation of active species.     

The rise process of the electric birefringence of poly-γ-benzyl-l-glutamate at high fields

Summary The rise process, steady-state and decay process of the birefringence of poly--benzyl-l-glutamate solutions under the action of a rectangular pulse have been studied at 25 °C over a wide range of field strength of 1.5×10³ to 3×10⁴V/cm. The solvent used was a dichloroethane-dimethylformamide mixture of the volume ratio 991. From the decay process the average relaxation time extrapolated to zero concentration and the corresponding rotational diffusion constant were determined. The apparent dipole moment and the optical anisotropy factor were obtained from the field strength dependence of steady-state birefringence. The rise process was analyzed according to our theory which holds for arbitrary high field strength in the initial stage. The n(t)/t versus t curves for various field strengths were found to be linear in the initial stage and pass through the origin. Thus, it was concluded that the electrical orientation of poly--benzyl-l-glutamate in solution is due primarily to the permanent dipole moment. Furthermore, the value of the apparent permanent dipole moment obtained from the rise process was compared with that obtained from the steadystate birefringence.

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Zusammenfassung Der Einschaltvorgang, der stationäre Zustand und das Abklingen der Doppelbrechung bei Poly--benzyl-l-glutamat-Lösungen mit einem elektrischen Impuls von rechteckiger Form werden bei 25 °C über einem großen Feldstärkebereich von 1.5×10³–3×10⁴V/cm untersucht. Als Lösungsmittel wird die Dichloräthan/Dimethylformamid-Mischung im Volumenverhältnis 991 verwendet. Aus dem Abklingvorgang werden die zur Konzentration 0 extrapolierte mittlere Relaxationszeit und die entsprechende Rotationsdiffusionskonstante bestimmt. Das scheinbare permanente Dipolmoment und der optische Anisotropiefaktor werden aus der Feldstärkeabhängigkeit der stationären Doppelbrechung ermittelt. Der Einschaltvorgang wird nach unserer Theorie, die für beliebige hohe Feldstärken im Anfangsverlauf gültig ist, analysiert. Die n(t)/t gegen t-Kurven für verschiedene Feldstärken sind geradlinig im Anfangsverlauf und laufen durch den Ursprung. Hieraus zeigt sich, daß die elektrische Orientierung von Poly--benzyl-l-glutamat in Lösungen hauptsächlich durch das permanente Dipolmoment bedingt ist. Überdies wird der aus dem Einschaltvorgang gewonnene Wert des scheinbaren permanenten Dipolmomentes mit dem aus der stationären Doppelbrechung ermittelten Wert verglichen.

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With 7 figures     

Tissue gadolinium deposition in renally impaired rats exposed to different gadolinium-based MRI contrast agents: Evaluation with inductively coupled plasma mass spectrometry (ICP-MS)

ObjectivesTo quantify tissue gadolinium (Gd) deposition in renally impaired rats exposed to Gd-EOB-DTPA and other Gd-based MRI contrast agents by means of inductively coupled plasma mass spectrometry (ICP-MS), and to compare the differences in distribution among major organs as possible triggers for nephrogenic systemic fibrosis (NSF).MethodsA total of 15 renally impaired rats were injected with Gd-EOB-DTPA, Gd-DTPA-BMA and Gd-HP-DO3A. Gd contents of skin, liver, kidney, lung, heart, spleen, diaphragm and femoral muscle were measured by inductively coupled plasma mass spectrometry (ICP-MS). Histological assessment was also conducted.ResultsTissue Gd deposition in all organs was significantly higher (P = 0.005 ~ 0.009) in the Gd-DTPA-BMA group than in the Gd-HP-DO3A and Gd-EOB-DTPA groups. In the Gd-DTPA-BMA group, Gd was predominantly deposited in kidney (1306 ± 605.7 μg/g), followed by skin, liver, lung, spleen, femoral muscle, diaphragm and heart. Comparing Gd-HP-DO3A and Gd-EOB-DTPA groups, Gd depositions in the kidney, liver and lung were significantly lower (P = 0.009 ~ 0.011) in the Gd-EOB-DTPA group than in the Gd-HP-DO3A group although no significant differences were seen for any other organs.ConclusionsGd-EOB-DTPA is a stable and safe Gd-based contrast agent (GBCA) showing lower Gd deposition in major organs in renally impaired rats, compared with other GBCAs. This fact suggests that the risk of NSF onset would be low in the use of Gd-EOB-DTPA.     

Effects of high-concentration phosphorus doping on crystal quality and lattice strain in SiGe HBTs

A high-concentration in-situ phosphorus-doping technique for silicon low-temperature epitaxial growth with Si₂H₆ has been developed. Growth temperature has an impact on the crystal quality and on lattice strain of phosphorus-doped silicon layers. Resistivity, micro-Raman spectroscopy, and high-resolution X-ray diffraction indicated that good crystal quality was achieved at a growth temperature of 525 °C. On the other hand, growth pressure has little influence on crystal quality or on lattice strain except for surface morphology. By optimizing epitaxial growth conditions, an extremely high concentration of phosphorous doping was achieved without a high-temperature activation annealing, and the resultant good crystal quality of the phosphorus-doped silicon layer gave a very low resistivity. Accordingly, the high-concentration in-situ phosphorus doping is a powerful technique to fabricate future ultra-high-speed SiGe HBTs.     

Tareciliosides A--G: Cycloartane glycosides from leaves of Tarenna gracilipes (HAY.) OHWI

From the 1-BuOH-soluble fraction of a MeOH extract of leaves of Tarenna gracilipes, collected in Okinawa, seven new cycloartane glycosides, named tareciliosides A--G (4--10), were isolated together with three known compounds, D-mannitol (1), (R)-linalool 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (2), and mussaenoside (3). Their structures were elucidated through a combination of spectroscopic analyses.