Kinetic study on the elastic change of vascular endothelial cells on collagen matrices by atomic force microscopy

The elasticity of vascular endothelial cells (HUVEC) was measured with an atomic force microscopy (AFM, Olympus), and analyzed by applying the Hertz model, and those data were compared with ones reported by us previously. The latter elasticity data were measured with AFM Instruments (Seiko) on the basis of the Young's modulus of gelatin gel, which was obtained from the measurement with a tensile tester. The elasticity of HUVEC was concluded to depend on the culture period. The elasticity of the cells cultured on type IV collagen for longer than 4 days led to average elasticity values higher than ca. 10(4)Pa. Moreover, the scattered values of elasticity decreased eminently in the AFM measurement of the cells at room temperature. A few cells, however, appeared to adhere long and tensely on matrix, which seems to one of reasons for relatively high elasticity in our previous works. The possibility of such high elasticity was considered to change in cell adhesion, anchoring on matrix during a long culture period.     

Nitriding of niobium and tantalum with a plasma jet under reduced pressure

The nitriding of niobium and tantalum with argon-nitrogen and argon-nitrogen-hydrogen plasma jets at pressures of 190 and 240 Torr was studied. The reaction kinetics obeyed a parabolic law. Cubic -NbN and cubic -TaN, which were stable phases at high temperature, were easily obtained at higher nitriding rates than those of thermal nitriding at the same temperature. Results obtained are discussed with plasma diagnostics such as emission spectroscopy and electrical double probe techniques.     

Rheological properties of polymethyl methacrylate and polyvinyl acetate in the molten state

Summary Dynamic viscosity, dynamic rigidityG and apparent viscosity _a of fractions and blends of polymethyl methacrylate and of polyvinyl acetate having different molecular weight and distribution have been measured at high temperatures by means of a concentric cylinder-type rheometer which enables us to measure not only dynamic but also steady-flow properties. The values of andG as functions of frequency for each sample at different temperatures can be superposed according to the usual time-temperature superposition principle, giving master curves covering a wide range of frequency. The absolute value of complex viscosity as a function of angular frequency coincides very well with the apparent viscosity as a function of rate of shear, indicating that the empirical law byCox andMerz holds well with the experimental results. The dynamic viscosity curves for various samples unite in one curve above=1000 sec^–1, and this united portion corresponds to the transition region. The effects of branching and bimodal distribution of molecular weight and the variation of frequency dependence of viscosity-molecular weight relation have been discussed, and emphasis has been placed on the significance of intramolecular motion to the flow properties of polymer melts at higher rates of shear or frequency.

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Zusammenfassung Die dynamische Viskosität, der dynamische SchermodulG und die scheinbare Viskosität _a von Fraktionen und Gemischen des Polymethacrylsäuremethylesters und Polyvinylacetat mit verschiedenem Molekulargewicht und verschiedener Verteilung wurden bei hohen Temperaturen mit einem Rotationsrheometer vom konzentrischen Zylindertyp gemessen, das nicht nur dynamische, sondern auch stationäre Fließeigenschaften zu messen gestattet., undG können als Funktionen der Frequenz für jede Probe bei verschiedenen Temperaturen nach dem üblichen Zeit-Temperatur-Superpositionsprinzip überlagert werden und liefern Masterkurven, die einen großen Frequenzbereich überstreichen. Der Absolutwert der komplexen Viskosität als Funktion der Drehfrequenz stimmt gut mit der scheinbaren Viskosität als Funktion der Schergeschwindigkeit überein, was zeigt, daß die empirische Beziehung vonCox undMerz die Versuchsergebnisse gut wiedergibt. Die Kurven für die dynamische Viskosität verschiedener Proben vereinigen sich oberhalb=1000 sec^–1 zu einer Kurve, und dieser gemeinsame Teil entspricht dem Umwandlungsbereich. Der Einfluß von Verzweigungen und bimodalen Molekulargewichtsverteilungen sowie die Änderung der Frequenzabhängigkeit der Viskositäts-Molekulargewichtsbeziehung werden diskutiert und die Bedeutung der intramolekularen Bewegung für die Fließeigenschaften von Polymerschmelzen bei höherer Schergeschwindigkeit oder Frequenz betont.

     

Design and efficient synthesis of 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D3 Analogues, including 2-epi-ED-71 and their 20-epimers with HL-60 cell differentiation activity

A concise and efficient synthetic approach to 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D(3) (4a-c), including 2-epi-ED-71, was developed starting from D-glucose as a chiral template for the construction of the 2 alpha-modified A-ring precursors (11a-c). It was found that the best ligand for the bovine thymus vitamin D receptor (VDR) in this series is 4b, which has 1.8 times greater binding affinity for the bovine thymus VDR than that of the natural hormone 1. Interestingly, potency in the induction of HL-60 cell differentiation for 4a-c was almost the same or weaker than that of 1 despite the strong binding affinity for the VDR. Next, we were interested in the "double modification"of 1 based on 4a-c with C20-epimerization, affording 2 alpha-(omega-hydroxyalkoxy)-20-epi-1 alpha,25-dihydroxyvitamin D(3) (20-epi-4a-c). All three 2 alpha-substituted 20-epi analogues of 1 (20-epi-4a-c) exhibited stronger binding affinities for the VDR, and their conformations in the ligand binding domain of VDR were analyzed by molecular modeling. Double-modified analogues of 20-epi-4a-c showed marked HL-60 cell differentiation activity, and 20-epi-4a possesses an activity 58-fold higher than that of the natural hormone 1.     

Picosecond fluorescence decays from vibrational levels in the S1(n,π*) state of pyridine vapor

Fluorescence lifetimes of pyridine vapor were measured by exciting at various vibrational bands in the lowest-energy region of the S₁(n,π^*) ← S₀ transition. The lifetime varies between 35 and 60 ps, depending on the vibronic level excited. The non-radiative decay from S₁ is characterized by particularly fast S₁ → S₀ internal conversion.     

A new preparation and some reactions of organocopper(I) isonitrile complexes

A new preparation and some reactions of organocopper(I) isonitrile complexes are described. In the presence of isonitrile (RNC), some active hydrogen compounds (R'H) react smoothly with Cu₂O and with metallic copper, evolving H₂O and hydrogen, respectively, to produce organocopper(I) isonitrile complexes, R'Cu(RNC)₂. The isonitrile insertion and the oxidative coupling by iodine of these complexes are described here.     

Mode-dependent coupling between vibration and translation of product CO(2) in CO oxidation on Pd(111)

The vibrational temperatures of product CO(2) were measured in CO oxidation on Pd(111) as a function of the desorption angle by means of infrared chemiluminescence. The antisymmetric vibration temperature was separately determined from the other vibrational modes from the normalized chemiluminescence intensity. The product CO(2) desorption is sharply collimated along the surface normal. The antisymmetric vibrational temperature increased from 1300 to 1600 K as the desorption angle increased from 0 degrees to 30 degrees , whereas the averaged vibrational temperature over bending and symmetric modes decreased from 2450 to 1530 K. From these angle dependences, an energy partitioning model in repulsive desorption is proposed.