Responses of chlorophyll fluorescence parameters of the facultative halophyte and C-3-CAM intermediate species Mesembryanthemum crystallinum to salinity and high irradiance stress

Mesembryanthemum crystallinum L. (Aizoaceae) is a facultative annual halophyte and a C-3-photosynthesis/crassulacean acid metabolism intermediate species currently used as a model plant in stress physiology. Both salinity and high light irradiance stress are known to induce CAM in this species. The present study was performed to provide a diagnosis of alterations at the photosystem 11 level during salinity and irradiance stress. Plants were subjected for up to 13 days to either 0.4M NaCl salinity or high irradiance of 1000 mu mol m(-2) s(-1), as well as to both stress factors combined (LLSA = low light plus salt; HLCO = high light of 1000 mu mol m(-2)s(-1), no salt; HLSA = high light plus salt). A control of LLCO = low light of 200 mu mol m(-2) s(-1), no salt was used. Parameters of chlorophyll a fluorescence of photosystem 11 (PSII) were measured with a pulse amplitude modulated fluorometer. HLCO and LLSA conditions induced a weak degree of CAM with day/night changes of malate levels (Delta malate) of similar to 12 mM in the course of the experiment, while HLSA induced stronger CAM of Delta malate similar to 20mM. Effective quantum yield of PSII, Delta F/F'(m), was only slightly affected by LLSA, somewhat reduced during the course of the experiment by HLCO and clearly reduced by HLSA. Potential quantum efficiency of PSII, F-v/F-m, at predawn times was not affected by any of the conditions, always remaining at >= 0.8, showing that there was no acute photoinhibition. During the course of the days HL alone (HLCO) also did not elicit photoinhibition; salt alone (LLSA) caused acute photoinhibition which was amplified by the combination of the two stresses (HLSA). Non-photochemical, NPQ, quenching remained low (< 0.5) under LLCO, LLSA and HLCO and increased during the course of the experiment under HLSA to 1-2. Maximum apparent photosynthetic electron transport rates, ETRmax, declined during the daily courses and were reduced by LLSA and to a similar extent by HLSA. It is concluded that A crystallinum expresses effective stress tolerance mechanisms but photosynthetic capacity is reduced by the synergistic effects of salinity and tight irradiance stress combined. (c) 2006 Elsevier GmbH. All rights reserved.

Electroactive layer-by-layer films of iron tetrasulfonated phthalocyanine

Electroactive films of iron tetrasulfonated phthalocyanine (FeTsPc) were assembled via the electrostatic layer-by-layer technique (LBL), in which FeTsPc layers were alternated with the polycationic poly(allylamine hydrochloride) (PAN). The multilayer formation was monitored via UV-Vis spectroscopy by measuring the increase in the Q Band of FeTsPc at 676 nm. Film thickness was estimated by profilometry as ca. 10 Angstrom per bilayer. Fourier transform infrared and UV-Vis absorption spectroscopy suggested specific interactions between FeTsPc and PAR Cyclic voltammograms showed reproducible pairs of oxidation-reduction peaks at 0.92 mV and 0.70 mV, respectively, for a 50-bilayer PAH/FeTsPc film at 50 mV/s (vs Ag/AgNO3).

Effects of the postannealing atmosphere on the dielectric properties of (Ba, Sr)TiO3 capacitors: Evidence of an interfacial space charge layer

The dielectric properties of (Ba, Sr)TiO3 films were found to be remarkably sensitive to the postannealing treatment atmosphere. This study demonstrates that postannealing in an oxygen atmosphere increases the dielectric relaxation phenomenon and that postannealing in a nitrogen atmosphere produces a slight dielectric relaxation. Such dependence of the dielectric relaxation was related both to oxygen vacancies and to the presence of negatively charged oxygen, trapped at the grain boundary and/or at the electrode/dielectric film interface. (C) 2000 American Institute of Physics. [S0003-6951(00)00817-2].

Dynamic scale theory for characterizing surface morphology of layer-by-layer films of poly(o-methoxyaniline)

The dynamic scale theory and fractal concepts are employed in the characterization of surface morphological properties of layer-by-layer (LBL) films from poly(o-methoxyaniline) (POMA) alternated with poly(vinyl sulfonic acid) (PVS). The fractal dimensions are found to depend on the procedures to fabricate the POMA/PVS multilayers, particularly with regard to the drying procedures. LBL films obtained via drying in ambient air show a more homogeneous surface, compared to films dried under vacuum or a flow of nitrogen, due to a uniform rearrangement of polymer molecules during solvent evaporation.

EXAMINATION BY ELISA OF SERA OBTAINED FROM CHICKEN BREEDER AND LAYER FLOCKS SHOWING EVIDENCE OF FOWL TYPHOID OR PULLORUM DISEASE

An indirect ELISA using soluble whole cell antigen was used to screen serum samples obtained from breeder and layer flocks some of which had shown clinical or bacteriological evidence of infection with Salmonella Gallinarum or S. Pullorum. There was good correlation between Salmonella infection and the presence of serum samples showing high optical density (OD) values. Sera from seven flocks showing high values were retested using group D (0-1, 9, 12) lipopolysaccharide (LPS) and g,m-H flagella as detecting antigens. Sera from six flocks produced high OD values with LPS and low values with flagella confirming infection with a non-flagellate, group D Salmonella while one produced high values with both antigens indicating mixed infection with another group D serotype.

Thin-layer chromatography of mycobactins and mycolic acids for the identification of clinical mycobacteria

Forty seven strains of mycobacteria (35 strains isolated from clinical specimens and 12 reference strains) were analyzed for mycobactin and mycolate production by thin-layer chromatography (TLC). Different growth conditions had little or no effect on the production of individual mycobactins and the reproducibility of mycobactin Rf values. Mycolate profiles of isolated strains were compared with those of reference strains. Clinical isolates belonging to the same species showed the same profiles. The combined evaluation of mycobacterial products by TLC allowed the identification of pathogenic and opportunist cultivable mycobacteria. on routine examination, the analysis of mycobactin and mycolate production constitutes an adequate procedure for the characterization and identification of myobacteria.

Layer-by-layer hybrid films of polyaniline and vanadium oxide

Supramolecular structures of polyaniline (PANI) and vanadium oxide (V2O5) have been assembled via the electrostatic layer-by-layer (LBL) technique. The films were characterized by vibrational analyses which indicated that the interactions between the two components lead to different properties in the films when compared to sol-gel films. of the neat compounds. In particular, using surface enhanced Raman scattering we were able to probe LBL film properties that depend on which material comprises the topmost layer.

Turbinatine, a potential key intermediate in the biosynthesis of corynanthean-type indole alkaloids

Extraction of the leaves of Chimarrhis turbinata has led to the isolation of turbinatine (1), a new corynanthean-type indole alkaloid, besides four known indole alkaloids, strictosidine, 5alpha-carboxystrictosidine, vallesiachotamine, and isovallesiachotamine. The structural determination of 1 was based on 1D and 2D spectroscopic data. An evaluation of the DNA-damaging activities of the isolates was performed by means of a bioassay using mutant strains of Saccharomyces cerevisiae, which indicated these compounds were weakly active.

The influence of crystallization route on the properties of lanthanum-doped Bi4Ti3O12 thin films prepared from polymeric precursors

Pure and lanthanum-doped Bi4Ti3O12 thin films were deposited on Pt/Ti/SiO2/Si substrate using a polymeric precursor solution. The spin-coated films were specular and crack-free and crystalline after annealing at 700 degreesC for 2 h. Crystallinity and morphological evaluation were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Multilayered films obtained using the intermediate-crystalline layer route present a dense microstructure with spherical grains. Films obtained using the intermediate-amorphous layer, present elongated grains around 250 nm in size. The dielectric and ferroelectric properties of the lanthanum-doped Bi4Ti3O12 films are strongly affected by the crystallization route. The hysteresis loops are fully saturated with a remnant polarization and drive voltage of the films, heat-treated by the intermediate-crystalline (P-r = 20.2 muC/cm(2) and V = 1.35 V) and for the film heat-treated by amorphous route (P-r = 22.4 muC/cm(2) and V = 2.99 V). (C) 2004 Elsevier B.V. All rights reserved.

Manganese(III) porphyrins: Catalytic activity and intermediate studies in homogeneous systems

We studied how solvent, stirring method, PhIO/MnP molar ratio, presence of water and axial ligand affect the catalytic activities of Mn(TPP)Cl, Mn(MNPP)Cl, Mn(TDCPP)Cl and Mn(TFPP)Cl in the oxidation of cyclohexane by PhIO. A study of the catalytic intermediates in the reaction between Mn(TPP)Cl or Mn(TDCPP)Cl and PhIO was also carried out by UV-Vis and EPR spectroscopies. The reaction of Mn(TPP)Cl with PhIO showed the formation of a mixture of species Mn-IV(OP+ and Mn-V(O)P as intermediates, which were confirmed by the deconvolution of the UV-Vis spectra. Addition of imidazole as cocatalyst favoured the formation of the intermediate species Mn-V(O)P, evidenced by the UV-Vis band at 408 nm. The corresponding EPR spectra gave evidence that in the presence of imidazole, Mn-IV(OP+ species are formed only in very low amounts. For Mn(TDCPP)Cl the dominating intermediate species is Mn-IV(OP+. Addition of imidazole to halogen-substituted MnP systems does not result in increase of the C-ol yields because very stable bis-imidazole-MnP complexes are formed. Anchoring of such MnP on imidazole propyl gel (IPG) results in better catalytic activity because in this case, the catalyst is mono-coordinated to the support and imidazole favours the formation of the intermediate species Mn-V(O)P.

Evaluation of an electroless nickel interlayer on the fatigue & corrosion strength of chromium-plated AISI 4340 steel

Despite the fact that chromium electrodeposition results in protection against wear and corrosion, combined with chemical resistance and good lubricity, the reduction in fatigue strength of base metal and environmental requirements causes one to search for possible alternatives. To improve the fatigue and corrosion resistance of AISI 4340 steel, an experimental study has been made for an intermediate electroless nickel layer deposited on base metal. The objective of this study was to analyze the effect of nickel underplate on the fatigue and corrosion strength of hard-chromium-plated AISI 4340 steel. Deposition of the conventional wear-resistant hard chromium plating leads to a decrease in mechanical properties of the base metal, especially the fatigue strength. Rotating bending fatigue tests results indicate better performance for conventional hard chromium plating. Good corrosion resistance in salt fog exposure was obtained for the accelerated hard chromium plating. Experimental data showed higher fatigue and corrosion resistance for samples prepared with accelerated hard chromium plate over electroless nickel plate, when compared with samples without electroless nickel underplate.