New fluorophores with rod-shaped polycyano pi-conjugated structures: synthesis and photophysical properties

[reaction: see text] Novel rod-shaped polycyano-oligo(phenyleneethynylene)s were synthesized by Pd cross-coupling reaction. Polycyano groups were found to greatly improve the emission efficiency (Phi(f)) of OPEs. By the end donor modification, we achieved the creation of very intense blue light-emitting fluorophore with the SMe group (Phi(f) = 0.972, log epsilon 4.89, lambda(em) 455 nm) and very intense yellow light-emitting fluorophore with the NMe(2) group (Phi(f) = 0.999, log epsilon 4.75, lambda(em) 555 nm). Contrasting Phi(f) solvent dependency of 6 and 7 and a linear relationship between Phi(f) and sigma(p)-X over the whole region of sigma(p)-X were also found.     

Volumetric study on the inclusion complex formation of α- and β-cyclodextrin with 1-alkanols at different temperatures

The partial molar volumes (V_a) of 1-alkanols (carbon number, m=5, 6, 7) in - and -cyclodextrin (CD) solutions at 5.00 mmol kg^–1 have been determined as a function of alkanol concentration (C_a) between 293.2 and 308.2 K by using a dilatometer. It has been observed that with an increase in C_a, V_a increased in -CD solution but decreased in -CD solution, asymptotically to a value of V_a in CD-free water. The dependence of V_a on C_a provided the binding constant (K) of 1:1 complex, the volume change in complex formation, and the partial molar volume of complex itself. The complex formation mechanism has been discussed on the basis of these values and their carbon number dependences in the respect of geometric behavior, hydrophobic interaction, and van der Waals interaction. It is concluded that the CD cavity in water is not rigid but flexible for fitting in nicely with guest molecule.     

Core temperature and density profile measurements in inertial confinement fusion implosions

We have measured time-integrated and time-gated electron temperature (T_e) and density (N_e) spatial profiles from indirect-drive implosions. In our experiments, we used a multiple-pinhole two-dimensional imaging spectrometer to obtain multispectral X-ray images of the imploded core. Quantitative comparisons between quasi-monochromatic images in different energy bands allowed T_e and N_e spatial profiles to be determined using two independent and validated techniques: a multi-objective search and reconstruction analysis, and an analytical analysis. We then compared the results to a simple one-dimensional (1D) mix-free hydrodynamics simulation in order to evaluate the ability of such a model to predict our experiments. Our data show spatial T_e profiles that are qualitatively consistent with the predictions of our 1D simulations, but we observe central cores that are 10–25% cooler and emit X-rays as late as 200 ps after peak compression. We infer time-gated spatial N_e profiles that are consistent with our 1D simulations near the times of peak compression, but we find significant disagreement between time-integrated data and 1D simulation predictions at large radii. Careful analysis of the time-gated and time-integrated T_e and N_e spatial profiles, together with streaked X-ray emission spectra from core and shell dopants, suggests mixing of shell material into the core is an important process that our 1D hydrodynamics simulations fail to capture, and comparison between image data and a simple analytical model suggests that 2–5 μm of the initial inner shell thickness mixes into the core during the time period of significant X-ray emission. This mix width is consistent with the predictions of a growth-factor analysis that treats instability growth seeded by capsule surface roughness, and points to the need to consider time-dependent mixing effects when interpreting T_e and N_e spatial profiles derived from multispectral X-ray image data, particularly at large radii where mixing effects will be most significant.     

A Two-Dimensional Network Model to Simulate Permeability Decrease Under Hydrodynamic Effect of Particle Release and Capture

A model was developed to simulate permeability decrease induced by hydrodynamic effects when injecting a fluid in a reservoir with respect to particle release and capture mechanisms and the parameters of the fluid–rock system. The kinetics of particle release and capture were integrated after computing the initial permeability of the porous medium with a square lattice of a two–dimensional network model. The rate of particle release is related to the difference between a microscopic velocity of the fluid and a critical velocity. The permeability decrease shows a direct link to the reduction of pore throat radii by three mechanisms of particle capture: straining and particle accumulation through direct interception or diffusion. Comparison between the simulations and the experimental results shows that the model reproduces the physics of the permeability decrease phenomenon, although the values are overestimated. The difference between the two sets of results can be explained by the fact that the simulations are realized at constant pressure whereas the experiments are realized at constant flow rate, and that re–entrainment of the trapped particles was not taken into account in the model.     

Chemical structures and hepatoprotective effects of constituents from the leaves of Salacia chinensis

The methanolic extract from the leaves of Salacia chinensis collected in Thailand was found to show a protective effect on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes. From the methanolic extract, eight new glycosides, named foliachinenosides E, F, G, H, and I, and foliasalaciosides J, K and L, were isolated together with 26 known constituents. The structures of new glycosides were determined on the basis of physicochemical and chemical evidence. In addition, the hepatoprotective effects of the isolated compounds on D-galactosamine-induced cytotoxicity were examined. Among them, lignans, eleutheroside E? and 7R,8S-dihydrodehydrodiconiferyl alcohol 4-O-β-D-glucopyranoside, were found to show the protective effects [inhibition (%) 41.4 ± 3.6 (p < 0.01), 45.5 ± 2.7 (p < 0.01) at 100 μM, respectively].     

Thermomechanical properties and phase structure of epoxy/silica nano‐hybrid materials constructed from a linear silicone oligomer

Epoxy‐grafted silicone oligomer (ESO), which has a linear silicone chain in the backbone moiety, was synthesized from a trifunctional alkoxysilane via a sol–gel reaction. Characterization of ESO was performed with ¹H and ²⁹Si NMR, Fourier transform infrared, and gel permeation chromatography. The number‐average molecular weight of ESO was 3300. By adding the silicone oligomer as the inorganic source in the curing process of the epoxy resin, novel epoxy/silica hybrid materials were prepared. It was observed by transmission electron microscope that fine silica‐rich domains of about 5‐nm diameter were uniformly dispersed in the cured epoxy matrix. Thermomechanical properties of the hybrid materials were also investigated. The storage modulus in the rubbery region and the peak area of the tan δ curve at the glass‐transition region increased and decreased, respectively, with the hybridization of the silica network. The mobility of the epoxy network chains should be considerably suppressed by the hybridization with the silica network. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1631–1639, 2005     

Influence of the loading rate on liquid‐crystalline epoxy resin systems

The fracture toughness of liquid‐crystalline epoxy systems, which had a nematic polydomain structure (domain size about 40 μm), with an increasing loading rate was evaluated. In this system, the fracture toughness dramatically decreased from 1.96 to 0.22 MN/m^3/2 with an increasing loading rate (0.1–5 mm/min). The network orientation near the fracture surface of different loading rate systems was investigated with polarized optical microscopy and polarized infrared spectroscopy. As a result, a large oriented region of mesogenic groups was observed near the fracture surface in the relatively low loading rate (0.1 and 0.5 mm/min) systems, but such a phenomenon was not observed in the high loading rate (2 and 5 mm/min) systems. These results showed that the high fracture toughness of the system at the low loading rate was due to the magnitude and region of the reorientation of the mesogenic groups in the fracture process and that high toughness could not be achieved at a high loading rate because the loading rate was too fast to allow orientation of the networks containing the mesogenic groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1296–1302, 2005     

Simultaneous production of96Tc and111In by α-particle irradiation of stacked Nb and Ag foils,and their carrier-free separations

In order to produce routinely carrier-free⁹⁶Tc and¹¹¹In, their simultaneous production was examined by means of the stacked foil method. Both niobium and silver foils were arranged on the target holder so as the desired nuclear reactions took place effectively. Simultaneous irradiation of the target with 35 MeV -particles produced effectively¹¹¹In and⁹⁶Tc by the¹⁰⁹Ag(, 2n)¹¹¹In and⁹³Nb(, n)⁹⁶Tc reactions, respectively. Sufficient amounts of radioactivities for tracer uses are obtained by the irradiation at 5 A current for 2 hrs. In addition, carrier-free⁹⁶TcO₄ ^– in a perchloric acid solution could be prepared by the combined use of precipitation and anion-exchange methods. Separation of carrier-free¹¹¹In from the silver matrix was done by means of solvent extraction using acetylacetone as a chelating agent.