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  • 1
    Electronic Resource
    Electronic Resource
    Auger electron spectroscopy study of silver incorporation in epitaxial Y–Ba–Cu–O superconducting films grown on MgO by laser ablation (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2078-2080 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied by Auger electron spectroscopy the incorporation of silver in epitaxial YBa2Cu3O7 (YBCO) thin films fabricated by pulsed laser deposition using YBCO+Ag 10% targets. Films were grown on MgO substrates. The silver was found in a thin layer, of approximately 50 nm in depth. X-ray photoelectron spectroscopy confirmed that the Ag is in its metallic form. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115084
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of growth, water use efficiency and δ13C by the nitrogen source in Casuarina equisetifolia Forst. & Forst. (1998)
    Oxford, UK : Blackwell Science Ltd, UK
    Plant, cell & environment 21 (1998), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbon isotope composition (δ13C) was measured in a glasshouse experiment with N2-fixing and NO3–- or NH4+-fed Casuarina equisetifolia Forst. & Forst plants, both under well-watered and drought conditions. The abundance of 13C was higher (more positive δ13C) for NH4+- than for NO3– -grown plants and was lowest for N2-fixing plants. NH4+-fed plants had more leaf area and dry weight and higher water use efficiency (on a biomass basis) than N2- and NO3–-grown plants and had lower water consumption than plants supplied with NO3–, either with high or low water supply. Specific leaf areas and leaf area ratios were higher with NH4+ than with NO3– or N2 as the N source. The difference observed in δ13C between plants grown with different N sources was higher than that predicted by theory and was not in the right direction (NH4+-grown plants with a more negative δ13C) to be explained by differences in plant composition and engagement of the various carboxylation reactions. The more positive δ13C in NH4+- than in NO3–-grown plants is probably due to a decreased ratio of stomatal to carboxylation conductances, which accounts for the lower water cost of C assimilation in NH4+-grown plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1998.00302.x
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  • 3
    Electronic Resource
    Electronic Resource
    Long- and short-term responses of leaf carbohydrate levels and photosynthesis to decreased sink demand in soybean (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Axillary buds and the apical portion of shoots of soybean [Glycine max (L.) Merr. cultivar Turchina] plants were trimmed to investigate long-term regulation of photosynthesis by sink demand at ambient CO2 and 22 °C. Also, in intact and trimmed shoots, the CO2 level was increased to 660 μmol mol−1 and temperature was lowered to 5°C to examine the superimposed short-term responses of photosynthesis to low sink demand. Under growth conditions, trimming the shoots increased leaf photosynthesis and the levels of sucrose, glucose-6-phosphate (G6P) and 3-phosphoglycerate (PGA), as well as the G6P/fructose-6-phosphate (F6P) and sucrose/starch ratios, while it decreased the level of starch and the triose-phosphate (glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, TP)/PGA ratio. Photosynthesis enhancement was accompanied by increased chlorophyll contents and ribulose-l,5-bisphosphate carboxylase oxygenase (Rubisco) activity. Sink removal consistently increased photosynthesis measured under a variety of conditions (growth CO2 or a short-term change to 660 μmol mol-1 CO2; growth temperature or a short-term change to 5 °C), except when low temperature was combined with ambient CO2; the increase in photosynthesis was higher under short-term elevated CO2 than at ambient CO2. In contrast with its effect at ambient CO2, shoot trimming increased the levels of TP and ribulose-1,5-bisphosphate (RuBP) and the TP/PGA ratio under high-CO2 conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00462.x
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  • 4
    Electronic Resource
    Electronic Resource
    Photosynthesis, carbohydrate levels and chlorophyll fluorescence-estimated intercellular CO2 in water-stressed Casuarina equisetifolia Forst. & Forst. (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of long-term water stress on photosynthetic carbon metabolism in Casuarina equisetifolia Forst. & Forst. was analysed by measuring CO2 assimilation, stomatal conductance, the quantum yield of photosystem II (ΦPSII), enzyme activities, and the levels of photosynthetic intermediates and carbohydrates. CO2 assimilation decreased under water stress while the intercellular CO2 concentration (Ci) as estimated by gas exchange measurements remained high. However, the estimates of Ci from measurements of ΦPSII suggest that the decrease in photosynthesis can be explained in terms of stomatal closure. Water stress decreased total stromal fructose-1,6-bisphosphatase activity and did not alter the activities and activation states of ribulose bisphosphate carboxylase oxygenase and NADP-dependent malate dehydrogenase (NADP-MDH). The concentration of photosynthetic metabolites, glucose, fructose and sucrose decreased, whereas starch concentrations increased under drought conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00447.x
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of nitrogen supply and sink strength on changes in leaf nitrogen compounds during senescence in two wheat cultivars (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in various nitrogen compounds during senescence of the fourth leaf were studied in two cultivars of spring wheat (Triticum aestivum L.). One of the cultivars (Yecora) was supplied with two N levels; the other (Tauro) was grown with the high N level and pruned above the fourth leaf, whereas the control was left intact. In both cultivars grown with high N supply, net nitrogen export from the fourth leaf did not occur until 35 days after sowing (DAS). Loss of leaf soluble proteins started earlier than that of chlorophylis, and coincided initially with an increase in insoluble protein. In N deficient plants the level of total N, soluble protein, and the activity of nitrate reductase (NRA. EC 1.6.6.1) started to decrease about 5 days earlier, and along with chlorophyll, continued to decrease at a faster rate, than in high N plants. Also, with low N supply, the large subunit (LSU, 58 kDa) of ribulose-1.5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) decreased in greater proportion than other soluble proteins, while with high N supply the decrease in Rubisco LSU was similar to that of other soluble proteins. Nitrogen deficiency caused a greater decrease in soluble proteins than in insoluble proteins, and NRA relative to soluble proteins. The faster senescing Tauro cultivar had lower levels of most parameters, especially NRA, soluble protein and, after 35 DAS. Rubisco LSU as a proportion of soluble protein. The decrease in sink strength due to shoot pruning did generally not affect the level of the various nitrogenous compounds until 35 DAS; thereafter the levels of most parameters, especially soluble protein, Rubisco LSU and, at late stages of senescence, insoluble protein, were higher in pruned than in control shoots. Thus, shoot pruning slows down senescence. The 56- and 78-kDa polypeptides increased, rather than decreased, with leaf age; the level of these two polypeptides showed a negative relationship with Rubisco LSU (r = -0.933 and r = -0.758, respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00807.x
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  • 6
    Electronic Resource
    Electronic Resource
    A cellulase gene from a new alkalophilic Bacillus sp. (strain N186-1). Its cloning, nucleotide sequence and expression in Escherichia coli (1996)
    Springer
    Applied microbiology and biotechnology 46 (1996), S. 149-155 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Several alkalophilic Bacillus spp. strains were selected for their capacity to produce alkaline cellulases. Culture supernatants of these strains showed optimal cellulase activities between pH 8 and 9 and they were stable from pH 6 to pH 12. A cellulase gene (celB1) from the alkalophilic Bacillus sp. strain N186-1 was cloned in Escherichia coli using polymerase chain reaction techniques. The cloned gene was present in a 2.539-bp HindIII fragment and its nucleotide sequence was determined. The coding sequence showed an open-reading frame encoding 389 amino acids. The amino acid sequence, deduced from the nucleotide sequence, permitted us to include it in family 5 (or A) of the glycosyl hydrolases. The complete open-reading frame of celB1 was cloned in the plasmid pET-11d and expressed in E. coli BL21 (DE3), in which a protein of 39 kDa was obtained in the cytoplasm; however, no endoglucanase activity was detected. A second construction in pET-12a allowed the production of a 39-kDa protein located in the periplasmic space of E. coli that had endoglucanase activity. The protein produced has optimal activity at pH 7 and 50°C and it retains more than 70% of its activity after incubation for 1 h at pH 12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050797
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  • 7
    Electronic Resource
    Electronic Resource
    W Mass Measurement at LEP 2 (1997)
    Springer
    Europhysics news 28 (1997), S. 48-49 
    Details
    ISSN: 1432-1092
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00770-997-0048-y
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrogen bonding and dissociation effects on the gas phase proton transfer reactions of ozone (1998)
    Springer
    Theoretical chemistry accounts 99 (1998), S. 60-63 
    Details
    ISSN: 1432-2234
    Keywords: Key words: Gas phase proton transfer reactions ; H-bonding effects ; Dissociation effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. Recently, the proton affinity (PA) of ozone was experimentally determined by Cacace and Speranza [Science (1994) 265: 208] using a bracketing technique that involved the proton transfer (PT) reactions: O3H++B⇒O3+BH+; for different Brönsted bases B. These authors showed that the simple collision model is not adequate to describe PT. We now present a theoretical model reflecting this bracketing procedure by explicitly introducing H-bonding complexing, dissociation and PT contributions, to discuss the kinetic model that assumes that PT occurs through one elementary step. The methods used include semiempirical density functional theory and ab initio Hartree-Fock methods. The procedure is gauged by using estimated PA of ozone obtained from deprotonation reactions including the Brönsted bases B NH3, H2O, HOCl, SO2, CH3F and Kr. The PA-obtained range was from 145.3 to 160.3 kcal/mol, in fair agreement with the experimental value of 148.0±3 kcal/mol. The model seems to be fairly independent of the reference bases used to evaluate the PA. H-bonding effects appear to be a determining factor to explain collision efficiencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050303
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  • 9
    Electronic Resource
    Electronic Resource
    Oxidation behavior of a Ni3Al PM alloy (1997)
    Springer
    Oxidation of metals 48 (1997), S. 143-170 
    Details
    ISSN: 1573-4889
    Keywords: Ni3Al ; oxidation kinetics ; spallation ; scale roughening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of a Ni3Al powder-metallurgical (PM) alloy doped with boron was investigated by means of discontinuous isothermal tests in the temperature range of 535° to 1020°C for exposures of up to 150 hr. The oxidation kinetics were characterized by a sharp decrease in the oxidation rate at about 730°C which is associated with a change in the oxidation mechanism. Below 730°C, the scale exhibited an outer NiO layer and an internal-oxidation zone consisting of a fine dispersion of alumina in a diluted Ni-Al solid solution. Between these two layers a very thin layer of nickel could be observed. Above 730°C, a three-layered scale was observed consisting of an outer NiO layer, an intermediate layer that depending on temperature consisted of a mixture of nickel and aluminum oxides or NiAl2O4, and an inner layer of Al2O3, which accounts for the higher oxidation resistance. Oxidation at the higher temperatures resulted in extensive void formation at the scale/metal interface which led to poorly adherent scales. It is worth noting that at the early oxidation stage the scale was characterized by planar interfaces. Roughening of the air/scale and, specially, the scale/metal interfaces after long exposures at the low-temperature range or after short times at higher temperatures could be related to the formation of the inner Al2O3 layer at the grain boundaries which favor oxygen penetration through the grain interior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01675266
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of Powder Particle Size on the Oxidation Behavior of a PM Ni3Al Alloy (1998)
    Springer
    Oxidation of metals 49 (1998), S. 485-507 
    Details
    ISSN: 1573-4889
    Keywords: INTERMETALLICS ; Ni3AL PARTICLE SIZE ; OXIDATION KINETICS ; POWDER METALLURGY
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of particle size on the oxidationbehavior of Ni3Al prepared by powdermetallurgy (PM) was investigated in the temperaturerange of 535 to 1020°C for exposures up to 200 hr.Four alloys were obtained, each one processed with a differentpowder particle size fraction (〈25, 25-50, 50-100,and 100-200 μm). For temperatures below 730°C,the scale consists of an outer NiO layer, a thindiscontinuous intermediate nickel layer, and an internaloxidation zone. The lowest oxidation rate corresponds tothe material with the smallest particle size. Thisresults from its higher grain-boundary density; the boundaries act as easy-diffusion paths foraluminum leading to the rapid formation of a continuousinner alumina layer. At temperatures above 730°C, athree layered scale is observed consisting of an outer NiO layer, an intermediate layer that,depending on temperature, consisted of a mixture ofnickel and aluminum oxides orNiAl2O4, and an inner layer ofAl2O3, which accounts for thehigher oxidation resistance. The oxidation attack is characterized byintrusions of the scale into the alloy, the intrusionnumber increasing as the particle size decreases. It isassumed that oxide particles and impurities present at the original particle boundaries facilitatealumina growth along these regions. Thus, the lowestoxidation rate for the highest temperature rangecorresponds to the largest particle-sizematerial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018898812184
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