Electronic Conductivity Enhancement of (La,Sr)TiO3 with Nb‐Doping on B‐Site

B‐site doped, A‐site deficient strontium titanates with general formula La_xSr_1–3x/2+γxNb_yTi_1–yO_3–δ (x = 0.2, 0.25, 0.3, 0.35, 0.4; y = 0, 0.02, 0.03; γ = 0.03) were produced by flame spray synthesis and the electrical conductivity of dense ceramic bars sintered under reducing conditions measured over broad temperature and oxygen concentration ranges. As‐synthesized powders were nano‐scale and slightly reduced, while it was observed that sinterability was promoted by both La substitution and Nb doping. Electrical conductivity measurements on dense bars under reducing conditions revealed that stoichiometric substitution of Ti⁴⁺ by Nb⁵⁺ raised conductivity by ∼ 40%, with a maximum value of 226 S cm⁻¹ observed at 900 °C. This was attributed to a higher concentration of defects, due to concurrent and enhanced oxygen vacancy ( ) formation under reducing conditions. The electronic properties of a slightly porous bar sample of the La_0.3Sr_0.559Nb_0.02Ti_0.98O_3–δ composition were found to be stable over one redox cycle.     

Determining the characteristics of systems with multiple inputs and multiple outputs

A simple and computationally efficient method of determining the transfer function and other characteristics of systems with multiple inputs and multiple outputs (MIMO systems) described by autoregression equations is proposed. The method is based on the use of the discrete Fourier transformation. The algorithm is highly suitable for computer implementation. The efficiency and simplicity of the method are illustrated using the example of a system with three inputs and three outputs. The proposed concept may be applied to systems described by the autoregression sliding mean.     

Ultrasonic air-coupled testing of square-shape CFRP composite rods by means of guided waves

In aerospace industry, one of the most important parts of gliders and motor-gliders is a lightweight longeron reinforcement made of carbon fibre reinforced plastics (CFRP) rods, known as Graphlite SM315 composite. During manufacturing, the rods as constructional elements are glued together in epoxy-filled matrix in order to build the arbitrary spar profile. The defects present in single rods such as breakage of fibres, multiple delaminations due to the lack of bonding between fibres and reduction in density affect essentially the strength and the fail-safety of the overall construction.The aim of the present work is to investigate the effects (transmission, reflection, scattering and mode conversion) of guided waves propagation along a square-shape CFRP rod in the case of contactless excitation/reception and interaction with region of multiple delaminations applying the numerical model and performing experiments.The square-shape CFRP composite rods possessing internal artificial delamination type defects have been investigated by numerical modelling and experiments employing the developed air-coupled technique (pitch-catch set-up) for cases of conventional transmission and advanced back-scattering configurations. Numerical predictions of guided wave interaction with a multiple delamination type defect in a CFRP composite rod have been made and the interaction mechanism explained. It is possible to conclude, that the actual sizes of the internal defects have been clearly detected using reception of the back-scattered waves over the edges of the defective regions only.     

Phosphoinositide 3-kinase regulates phospholipase Cgamma-mediated calcium signaling

It has been demonstrated that the lipid products of the phosphoinositide 3-kinase (PI3K) can associate with the Src homology 2 (SH2) domains of specific signaling molecules and modify their actions. In the current experiments, phosphatidylinositol 3,4, 5-trisphosphate (PtdIns-3,4,5-P3) was found to bind to the C-terminal SH2 domain of phospholipase Cgamma (PLCgamma) with an apparent Kd of 2.4 microM and to displace the C-terminal SH2 domain from the activated platelet-derived growth factor receptor (PDGFR). To investigate the in vivo relevance of this observation, intracellular inositol trisphosphate (IP3) generation and calcium release were examined in HepG2 cells expressing a series of PDGFR mutants that activate PLCgamma with or without receptor association with PI3K. Coactivation of PLCgamma and PI3K resulted in an approximately 40% increase in both intracellular IP3 generation and intracellular calcium release as compared with selective activation of PLCgamma. Similarly, the addition of wortmannin or LY294002 to cells expressing the wild-type PDGFR inhibited the release of intracellular calcium. Thus, generation of PtdIns-3,4,5-P3 by receptor-associated PI3K causes an increase in IP3 production and intracellular calcium release, potentially via enhanced PtdIns-4, 5-P2 substrate availability due to PtdIns-3,4,5-P3-mediated recruitment of PLCgamma to the lipid bilayer.     

Tyrosines 1021 and 1009 are phosphorylation sites in the carboxy terminus of the platelet-derived growth factor receptor beta subunit and are required for binding of phospholipase C gamma and a 64-kilodalton protein, respectively

Squalene synthase is the first pathway-specific enzyme in the cholesterol biosynthetic pathway. The gene (ERG9) encoding squalene synthase in Saccharomyces cerevisiae has been isolated and characterized (S. M. Jennings, Y. H. Tsay, T. M. Fisch, and G. W. Robinson, 1991, Proc. Natl. Acad. Sci. USA 88, 6038-6042: M. Fegueur, L. Richard, A. D. Charles, F. Karst, 1991, Curr. Genet. 20, 365-372). The structural gene for the enzyme was modified by the polymerase chain reaction to remove a hydrophobic C-terminal domain, and the open reading frame for the truncated protein was cloned into yeast and Escherichia coli expression vectors. In E. coli, overexpressed truncated squalene synthase was soluble and constituted 2-5% of total cellular protein. The recombinant enzyme was purified to > 95% homogeneity in two steps by chromatography on hydroxyapatite and phenyl-Superose. Soluble truncated squalene synthase is monomeric and catalyzes the two-step conversion of farnesyl diphosphate (FPP) to squalene via presqualene diphosphate in the presence of Mg2+ and NADPH. The concentration of FPP needed for half-maximal activity was 40 microM. At higher concentrations, FPP was an inhibitor. The activity of squalene synthase was stimulated by detergents and reached a maximal value of kcat = 3.3 s-1 at 100 microM FPP in the presence of 1% (v/v) Tween 80.     

Concentration effects on emission of bay-substituted perylene diimide derivatives in a polymer matrix

Reduction of emission quenching in a gain medium based on a dye-doped organic matrix at high doping concentrations is of crucial importance for achieving efficient lasing with a low threshold. In this study, concentration effects on emission properties of bay-substituted perylene diimide derivatives, considered to be promising for lasing application, are reported. Dynamics of emission spectra, quantum yield, lifetime, amplified spontaneous emission, amplified spontaneous emission threshold and photostability of the bromo-, 2,4-di(trifluoromethyl)phenyl- and 4-pyridyl-substituted perylene diimide derivatives in polystyrene films are explored in a wide range of diimide concentrations from 0.06 wt % to 8 wt %. For comparison, emission properties of an unsubstituted perylene diimide derivative are also investigated. An importance of the bay substitution in the perylene diimides is emphasized through i) reduction of emission concentration quenching, which allows for 3-4 times higher doping levels as compared to the doping with an unsubstituted perylene diimide, ii) observation of amplified spontaneous emission at one order of magnitude higher concentrations with reasonable thresholds (up to 200-300 kW/cm²), and iii) high photostability, which is one order of magnitude higher than that of other bay-substituted perylene diimides and various organic compounds. The results imply potential of the perylene diimide substitution at the bay position for tailoring molecular packing and emission properties via steric hindrance effects, and suggest the bay-substituted perylene diimides may be useful as active media for lasing applications.     

Application of the ultrasonic pulse-echo technique for quality control of the multi-layered plastic materials

The main aim of the ultrasonic pulse-echo technique application for quality control is to characterize the internal structure of the object under investigation. The advantage of such technique is a possibility to perform non-contact and one-side access measurements, and to investigate the internal structure of multi-layered materials as well. The presented novel application of the ultrasonic pulse-echo technique for characterization of the multi-layered plastic materials covers the complete attenuation measurement in the frequency domain and is based on ill-posed Tikhonov regularization task for each layer separately. The law of the frequency-dependent attenuation has been estimated from the inverse transfer function approximation in the frequency domain. Phase velocity dispersion curves have been estimated in two ways: from the experimental signal phase spectra and from the causal Kramers–Kronig relations. The developed method enables to predict waveforms of the reflected signals from the interfaces of the individual layers in on-line mode.According to this approach, the step-by-step iterative analysis has been performed for each layer using the information about the previous layers. During each step, the acoustic properties of an individual layer, such as density, absorption, ultrasound velocity and phase velocity dispersion, have been recovered using numerical optimization. Optimization has been performed comparing the real ultrasonic signal, reflected by multi-layered object, with the simulated response of the model. The comparison of the predicted waveforms with the experimental ones has shown a good correspondence.     

Src-like adaptor protein (Slap) is a negative regulator of mitogenesis

The Src-like adaptor protein (Slap) is a recently identified adaptor protein containing Src homology 3 (SH3) and SH2 domains. Slap is found in a wide range of cell types and was shown to interact with the Eck receptor tyrosine kinase in a yeast two-hybrid interaction screen [1]. Here, we found that Slap is expressed in NIH3T3 cells and could associate with the activated platelet-derived growth factor (PDGF) receptor. Using mutated versions of the PDGF receptor and phosphopeptide competition experiments, we determined that Slap has the highest affinity for the Src-binding site of the PDGF receptor. Our inability to produce cell lines that stably expressed Slap suggested that Slap inhibited cell growth. We further investigated this issue by transiently expressing Slap by microinjection. Overexpression of Slap by this method inhibited DNA synthesis induced by PDGF and serum, whereas overexpression of the adaptor proteins Grb2 and Shc did not. Finally, microinjection of a Slap antibody into NIH3T3 cells that had been stimulated with suboptimal doses of growth factors potentiated the effects of the growth factors. These data suggest that, unlike other adaptor proteins, Slap is a negative regulator of signalling initiated by growth factors.     

Photostability of phenothiazinyl-substituted ethylenes

Photostability of phenothiazinyl-substituted ethylenes in both solution and in solid state (thin films) was investigated as a function of UV exposure time. Fluorescence intensity and spectral variation measurements in the presence and absence of ambient air were used to determine the effect of oxygen on the degradation of the compounds. The observed reduction in the fluorescence efficiency of air-saturated solutions and thin films subjected to UV was attributed to permanent photo-oxidative degradation. Photostability was higher in the cases of molecules that contained two bulky phenothiazinyl groups as compared to those containing only one phenothiazinyl group and a smaller phenyl substituent. Fully reversible fluorescence intensity decay in the degassed phenothiazine solutions was attributed to photo-isomerization, whereas the partially reversible changes in fluorescence intensity that were observed for films in the absence of air were ascribed to both photoexcited carrier capture by deep-traps acting as exciton quenching centres and degradation imparted by UV-induced bond scission.