Organic-Inorganic Sol-Gel Hybrids with Ionic Properties

Summary.  A hybrid silicon precursor (ICS-PPG) obtained by reaction of 3-isocyanatopropyltriethoxy silane with poly-(propyleneglycol)-bis-(2-aminopropyl ether) was recognized as a potential host for various salts and molecular species. It has been used for electrochromic, gasochromic, photovoltaic, and fuel cell applications. This focuses on proton conducting gels (PWA/ICS-PPG, SiWA/ICS-PPG, and W-PTA/ICS-PPG) obtained after the incorporation of polyoxometalates in the ICS-PPG host. IR spectroscopic measurements are used to reveal the entrapment, the aggregation, and the interactions of W-PTA, PWA, or SiWA with the sol-gel derived network. The proton conductivity of the composites, measured using impedance spectroscopy, increases with increasing concentration of the polyoxometalates from 10⁻⁶ to 10⁻³ S/cm. Received June 23, 2000. Accepted (revised) September 18, 2000     

Existence and stability of entropy solutions for the hyperbolic systems of isentropic gas dynamics in Eulerian and Lagrangian coordinates

We prove the existence and compactness (stability) of entropy solutions for the hyperbolic systems of conservation laws corresponding to the isentropic gas dynamics, where the pressure and density are related by a γ-law, for any γ > 1. Our results considerably extend and simplify the program initiated by DiPerna and provide a complete existence proof. Our methods are based on the compensated compactness and the kinetic formulation of systems of conservation laws. © 1996 John Wiley & Sons, Inc.     

Carbazolevinylene‐based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis,photophysics, and electroluminescence

Two new soluble alternating carbazolevinylene‐based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5‐diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (T_g) than their corresponding model compounds. The samples showed absorption maximum at 364–403 nm with optical band gap of 2.62–2.82 eV. They emitted blue‐green light with photoluminescence (PL) emission maximum at 450–501 nm and PL quantum yields in THF solution of 0.15–0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue‐shifted as compared to those of POXD and MOXD . The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m^?2. POXD and PTPA exhibited 25.4, and 96.3 cd m^?2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592–5603, 2008     

Design and synthesis of some new pyranoxanthenones with cytotoxic activity

As part of a research program directed towards the design and synthesis of pyranoxanthones structurally related to acronycine, we present here the synthesis and cytotoxic activity of the pyranoxanthones 3 and 4 (X= H, Br; R= H, OMe; R'= H, Ac). Some of these compounds inhibit L1210 cell proliferation.     

Some attributes of cold hardiness of the gregarious ectoparasitoid Colpoclypeus florus (Hymenoptera: Eulophidae)

Cold hardiness of diapause and non-diapause larvae of the parasitoid Colpoclypeus florus Walker (Hymenoptera: Eulophidae) was examined in the laboratory. Mean supercooling point (SCP) for diapausing larvae was -26.7 degree C and for non-diapausing larvae immediately after their larval development, was -16.2 degree C. Mean SCP for non-diapause larvae at the prepupa stage was -19.1 degree C. A short period of acclimation (1 week at 5 degree C) had no influence on the mean SCPs of both diapause and non-diapause larvae. Pre-freeze mortality for diapause and non-diapause larvae was also studied. A constant exposure of diapause larvae to -6 degree C resulted in high mortality (70.7 percent) after a period of 40 days. In contrast, 6 days at -6 degree C were sufficient to cause the same level of mortality in non-diapause larvae. After exposure of 15 days at -9 degree C, mortality for non-diapause larvae was 70 percent, whereas after 20 days at the same temperature mortality of diapause larvae was 25 percent. The importance of these findings for the cryobiology of C. florus is discussed.     

Collagen fibril diameter in relation to bone site. a quantitative ultrastructural study

The collagen fibril diameter was measured in cortical bone samples from the femoral neck, rear and front tibia of rats using electron microscopy analysis. Statistically significant differences (0.001<p<0.04) in mean fibril diameter values between different bone sites were detected demonstrating a dependence upon bone use.     

Addendum to: “Dissipative and Entropy Solutions to Non-Isotropic Degenerate Parabolic Balance Laws”

This note generalizes the notion of dissipative solutions to non-isotropic degenerate parabolic balance laws introduced in [3]. The new definition allows us to use a larger class of test functions than the one used in [3] to study the equivalence between dissipative and entropy solutions. As a result, it is possible to study general relaxation-type approximations (limits).Arch. Rational Mech. Anal. 170 (2003) 359–370 Digital Object Identifier (DOI) 10.1007/s00205-003-0282-5 Published online September 30, 2003Acknowledgement This work was partially supported by HYKE programme HPRN-CT-2002-00282 (http://www.hyke.org), and PANAGIOTIS E. SOUGANIDIS by the National Science Foundation.     

The use of models in the study of stresses during soil compaction

In the present study, it is described the experimental method for measuring the direction and the magnitude of stresses during mechanical soil compaction. These stresses result in an increase in soil density. The greatest effect during the compaction results from developing a vertical component of stress in the soil. This component of stress can be measured experimentally. This stress is a function of many soil factors and the characteristics of the compaction machine. Considering the particular and, in many aspects, unknown processes of these effects on the compaction, the determination of soil compaction with models becomes very difficult. The system equation in the model is obtained by means of dimensional and numerical analysis using special computer programs.