Permeability of Concrete with Recycled Concrete Aggregate and Pozzolanic Materials under Stress.

The research reported herein studied the permeability of concrete containing recycled-concrete aggregate (RA), superfine phosphorous slag (PHS), and ground granulated blast-furnace slag (GGBS) with and without stress. Test results showed that the chloride diffusion coefficient of RA concrete (RAC) without external loads decreased with time, and the permeability of RAC is much lower than that of the reference concrete due to the on-going hydration and the pozzolanic reaction provided by the PHS and GGBS additives in the RAC mixture. The permeability of chloride under flexural load is much more sensitive than that under compressive load due to the differences in porosity and cracking pattern. At low compressive stress levels, the permeability of chloride decreased by the closing of pores and microcracks within RAC specimens. However, in a relatively short time the chloride diffusion coefficient and the chloride content increased rapidly with the increase of compressive stress when it exceeded a threshold stress level of approximate 35% of the ultimate compressive strength. Under flexural stress, the chloride transport capability increased with the increase of stress level and time. At high compressive and flexural stress levels, creep had a significant effect on the permeability of chloride in the RAC specimens due to the damage from the nucleation and propagation of microcracks over time. It is apparent that mortar cracking has more of a significant effect on the chloride transport in concrete than cracking in the interfacial transition zone (ITZ)

Match Probability Statistics and Gamma Ray Burst Recurrences in the BATSE Catalog

We develop match probability statistics to test the recurrences of gamma ray bursts in the BATSE catalog 1B and 2B. We do not find a signal of repetitions at the match level of 1.e-3.Comment: 4 pages, LaTeX, two macros included (kluwer.sty, spacekap.sty) To appear in the proceedings of the Eslab29 symposium, ``gamma ray bursts: toward the source

Spectroscopic characterization of 1.3µm GaInNAs quantum-well structures grown by metal-organic vapor phase epitaxy

We report optical studies of high-quality 1.3 μm strain-compensated GaInNAs/GaAs single-quantum-well structures grown by metalorganic vapor phase epitaxy. Photoluminescence excitation (PLE) spectroscopy shows clearly the electronic structure of the two-dimensional quantum well. The transition energies between quantized states of the electrons and holes are in agreement with theoretical calculations based on the band anti-crossing model in which the localized N states interact with the extended states in the conduction band. We also investigated the polarization properties of the luminescence by polarized edge-emission measurements. Luminescence bands with different polarization characters arising from the electron to heavy-hole and light-hole transitions, respectively, have been identified and verify the transition assignment observed in the PLE spectrum

Crystal Nucleation by Laser-Induced Cavitation\ud

High-speed and high-resolution photography have been used to investigate the relationship between creation, expansion, and collapse of a vapor cavity induced by a 6 ns laser pulse and the subsequent nucleation of crystals. A thin layer of supersaturated aqueous solutions of (NH4)2SO4 and KMnO4 was confined between two glass plates with a separation of 50 and 100 μm. The expansion and collapse of the laser-induced vapor bubble occurred over a total time scale of 200 μs, while the first identifiable crystal appears one second after the laser pulse. Crystals were observed to form on a ring with a diameter of 70 μm centered in the focal point of the laser. The ring is preceded by an optical disturbance observed through the cavity around 30–50 μs after the laser pulse and vapor cavity formation. This ring-shaped optical disturbance originates from changes in refractive index induced by crystal nuclei formation. The formation of the nuclei most probably coincides with the formation of the bubble, when the rate of evaporation and the supersaturation are at their maxima. Apparently, it takes the nuclei around 30–50 μs to grow to a particle size with a visible optical disturbanc

The renormalization transformation of two-type branching models

Article / Letter to editorMathematisch Instituu

Superconducting Order Parameter in Bi-Layer Cuprates: Occurrence of π\pi Phase Shifts in Corner Junctions

We study the order parameter symmetry in bi-layer cuprates such as YBaCuO, where interesting $\pi$ phase shifts have been observed in Josephson junctions. Taking models which represent the measured spin fluctuation spectra of this cuprate, as well as more general models of Coulomb correlation effects, we classify the allowed symmetries and determine their associated physical properties. $\pi$ phase shifts are shown to be a general consequence of repulsive interactions, independent of whether a magnetic mechanism is operative. While it is known to occur in d-states, this behavior can also be associated with (orthorhombic) s-symmetry when the two sub-band gaps have opposite phase. Implications for the magnitude of $T_c$ are discussed.Comment: 5 pages, RevTeX 3.0, 9 figures (available upon request

Phonon thermal conductivity in doped La2CuO4\rm\bf La_2CuO_4: Relevant scattering mechanisms

Results of in-plane and out-of-plane thermal conductivity measurements on $\rm La_{1.8-x}Eu_{0.2}Sr_xCuO_4$ ($0\leq x\leq0.2$) single crystals are presented. The most characteristic features of the temperature dependence are a pronounced phonon peak at low temperatures and a steplike anomaly at $T_{LT}$, i.e., at the transition to the low temperature tetragonal phase (LTT-phase), which gradually decrease with increasing Sr-content. Comparison of these findings with the thermal conductivity of $\rm La_{2-x}Sr_xCuO_4$ and $\rm La_2NiO_4$ clearly reveals that in $\rm La_{2-x}Sr_xCuO_4$ the most effective mechanism for phonon scattering is impurity-scattering (dopants), as well as scattering by soft phonons that are associated with the lattice instability in the low temperature orthorhombic phase (LTO-phase). There is no evidence that stripe correlations play a major role in suppressing the phonon peak in the thermal conductivity of $\rm La_{2-x}Sr_xCuO_4$.Comment: 7 pages, 4 figure

Paclitaxel-octreotide conjugates inhibit growth of human non-small cell lung cancer cells in vitro

Aim: To evaluate the effects of paclitaxel-octreotide conjugates on the growth of cultured non-small cell lung cancer cells. Methods: RT-PCR was performed to detect mRNA for the subtypes of the human somatostatin receptor (SSTR) using specific primers. MTT-based cytotoxicity assay was used to evaluate the cell viability after treatment with paclitaxel and the conjugates. Cell cycle perturbations were determined using a Fluorescence-Activated Cell Sorter. Results: Non-small cell lung cancer A549 and Calu-6 cells expressed mRNA for SSTR2 and SSTR5. Paclitaxel and the conjugates effectively inhibited the growth of A549 and Calu-6 cells in a concentration- and time-dependent manner. In SSTR-negative fibroblasts, the conjugates were less cytotoxic than paclitaxel. The conjugates and paclitaxel could induce the increase of G2/M phase ratio in A549 cells. Conclusion: The paclitaxel-octreotide conjugates can be used as selective-targeted chemotherapeutic agents for treating non-small cell lung cancer.Цель: оценить эффект конъюгатов паклитаксела-октреотида на рост культивированных клеток немелкоклеточного рака легкого человека. Методы: для определения мРНК подтипов рецептора соматостатина человека (SSTR) применяли ОT-ПЦР. Анализ цитотоксичности в МТТ-тесте применяли для оценки выживаемости клеток после их инкубации с паклитакселом и конъюгатами. Нарушения клеточного цикла определяли с применением FACS — клеточного сортера. Результаты: установлено, что клеточные линии немелкоклеточного рака легкого A549 и Calu-6 экспрессируют SSTR2 и SSTR5 мРНК. Отмечено эффективное дозо- и времязависимое угнетение роста клеток A549 и Calu-6 паклитакселом и конъюгатами. Для SSTR-негативных фибробластов конъюгаты менее цитотоксичны, чем паклитаксел. Конъюгаты и паклитаксел могут индуцировать повышение соотношения фаз G2 /M в клетках A549. Выводы: конъюгаты паклитаксел-октреотида могут быть использованы как селективные химиотерапевтические агенты для воздействия на немелкоклеточный рак легкого