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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 16 (1968), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: In the first part, the author, recalling the principle of d/c current measurements, shows by means of some examples, different experimental results relative to the induced polarization phenomenon. He presents the case of the negative induced polarization which can be explained by geometric effects. He gives some examples of saturation curves and discusses the problem of the linearity of the I.P. phenomenon. Then he shows some aspects which demonstrate that I.P. decay curves do not always conform to the general law. He concludes by showing the influence of the current electrodes, the position of which, relative to the polarizable bodies, may alter the shape of the I.P. anomalies.In the second part, the author presents different case histories of I.P. mineral surveys where I.P. is compared to other geophysical methods and drilling results.
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  • 12
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 17 (1969), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: This paper deals with electromagnetic fields in the so called “Transient Induced Polarization Technique”. Field equations are integrated in the case of a polarizable sphere inbedded in a sterile overburden. The existence of a remanent polarization vector P which slowly decays once the charging current has been cut off is taken as the initial condition. When the surface between the air and overburden is (as a first step) disregarded, the Laplace transform of the EM fields is given. The integral of the electric field (which is fairly often the result of prospection work) is independent of the various time constants related to electrochemical processes, but it stands as a good measurement of the total electrostatic dipole created by the charging current.We investigate the geometrical circumstances that can bring negative values of I.P. signal. Such negative values can be found in two cases: 1. The discharge currents are. distorted by the ground surface. 2. The I.P. signal is picked up by electrodes inside the polarizable material.The last part is dedicated to an account of experimental work performed on models and of an actual case history.The mathematical derivations are included in an appendix.
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  • 13
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 115 (1996), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A field experiment was designed to compare control with tissue culture-derived plants of rice, and to study the effects of natural selection pressure applied to the first generation (R0) of in vitro plants on the performance of their progeny. Control- and R0 in vitro plants of four rice varieties from middle altitude in Burundi, i.e. Facagro 57′, Facagro 76′, ‘Kirundo 3’ and ‘Kirundo 9’, were cultivated at four different altitudes (800, 1380, 1650 and 1900 m). Several parameters concerning tillering capacity, plant height development and seed production were measured. The means for most measured parameters were higher in control plants than in the in vitro plants, while the higher variation coefficients and most extreme values were usually found in the in vitro plants. For each variety, the 20 control plants and 20 in vitro plants having the highest production were selected at each altitude of 1380 and 1650 m, and their progenies were cultivated on the same site at 1580 m. Among the plants arising from 1650 m, most maximum values, higher variation coefficients and, in some cases, higher means were found in the in vitro plants. In contrast, among the plants arising from 1380 m, higher means most usually corresponded to control plants, while the tendency for maximum values and variation coefficients were unclear. These results indicate the positive effect of natural selection pressure applied in the first generation to plants rising from tissue culture. They also demonstrate that considerable variation may be generated in vitro. The interest for plant breeding purposes is discussed.
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  • 14
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Several R2 somaclonal families were derived from plants regenerated from a salt-resistant callus of the salt-sensitive rice cultivar ‘I Kong Pao’ (IKP). The family R2-1-23, in the presence of NaCl exhibited higher yield performances than the initial cultivar. This improvement in salinity resistance, however, was not transmitted to following generations; despite a higher number of spikelets per plant, family R3-1-23 did not perform better than the initial cultivar because of a very low seed set. This somaclonal family, its initial being the cultivar IKP, the breeding line IR31785 (extremely salt-sensitive) and the cultivar ‘Aiwu’ (moderately salt-resistant), were used as parents for production ofhybrids. Four crosses, IKP×R3-1-23, IR31785 ×R3-1-23, IR31785× IKP and IKP בAiwu’, were performed. Most of the F1 hybrids cultivated in the absence of salt exhibited increased performances compared with the mid-parent, suggesting an heterosis effect for yield-related parameters. F2 populations were screened for salinity resistance and a clear improvement for yield in stress conditions was recorded for populations derived from IK×R3-1-23, IR31785×R3-1-23 and IR31785×IKP, although the mean level of increase over the mid-parent (RIMP) varied depending on the population, the presence or absence of stress, and the quantified parameters. The results are discussed in relation to the usefulness of in vitro selection for obtaining interesting somaclonal variants useful to be integrated in classical breeding programmes for salinity resistance in rice.
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  • 15
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Anaerobic digestion of olive mill wastewaters is generally performed in anaerobic contact bioreactors where the removal of toxic phenols is often unsatisfactory. In the present work we show that a granular activated carbon packed-bed biofilm reactor can be successfully used to achieve effective and reproducible wastewater decontamination even at high organic loads. A comparison of 16S rRNA gene sequences of the inoculum and of biomass samples from different districts of the reactor revealed enrichment of specific microbial populations, probably minor members of the inoculum and/or of the olive mill wastewaters. They mainly consisted of the members of Proteobacteria, Flexibacter-Cytophaga-Bacteroides, and sulphate-reducing bacteria. The dominant sequence among Archaea (70% of clones) was closely related to Methanobacterium formicicum.
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  • 16
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 115 (1996), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Excised leaves of four rice varieties, ‘Facagro 57’, ‘Facagro 76’, ‘Kirundo 3’, ‘Kirundo 9’, were chilled for six days at 10/5°C day/night, along with 11 somaclonal families arising from three of these varieties, which had been selected over four generations for improved chilling tolerance. At the end of the chilling treatment, electrolyte leakage from leaf pieces was followed for 12 h and compared with an unchilled control. With unchilled leaves, no varietal differences nor a rise in leakage over time were observed. Chilling induced higher leakages in all varieties, except in ‘Kirundo 3’ at the time of first measurement, and a continuous rise over time was found in all varieties. Varietal differences were detected, ‘Kirundo 3’ being the least affected, followed by ‘Kirundo 9’ and ‘Facagro 76’, and finally ‘Facagro 57’, which coincides with their ranking for chilling tolerance established through chilling survival tests. The leakages were generally lower in the somaclonal families than in the variety they originated from in ‘Kirundo 9’ and ‘Facagro 76’, while the opposite was observed in ‘Kirundo 3’. The significance and usefulness of electrolyte leakage measurement for chilling tolerance screening, and the potentials of somaclonal variation for chilling tolerance improvement are discussed.
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  • 17
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 21 (1998), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In a laboratory study, we investigated the monoterpene emissions from Quercus ilex, an evergreen sclerophyllous Mediterranean oak species whose emissions are light dependent. We examined the light and temperature responses of individual monoterpenes emitted from leaves under various conditions, the effect of heat stress on emissions, and the emission-onset during leaf development. Emission rate increased 10-fold during leaf growth, with slight changes in the composition. At 30 °C and saturating light, the monoterpene emission rate from mature leaves averaged 4·1 nmol m–2 s–1, of which α-pinene, sabinene and β-pinene accounted for 85%. The light dependence of emission was similar for all monoterpenes: it resembled the light saturation curve of CO2 assimilation, although monoterpene emission continued in the dark. Temperature dependence differed among emitted compounds: most of them exhibited an exponential increase up to 35 °C, a maximum at 42 °C, and a slight decline at higher temperatures. However, the two acyclic isomers cis-β-ocimene and trans-β-ocimene were hardly detected below 35 °C, but their emission rates increased above this temperature as the emission rates of other compounds fell, so that total emission of monoterpenes exponentially increased from 5 to 45 °C. The ratio between ocimene isomers and other compounds increased with both absolute temperature and time of heat exposure. The light dependence of emission was insensitive to the temperature at which it was measured, and vice versa the temperature dependence was insensitive to the light regime. The results demonstrated that none of the models currently applied to simulate isoprene or monoterpene emissions correctly predicts the short-term effects of light and temperature on Q. ilex emissions. The percentage of fixed carbon lost immediately as monoterpenes ranged between 0·1 and 6·0% depending on temperature, but rose up to 20% when leaves were continuously exposed to temperatures between 40 and 45 °C.
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  • 18
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 773 (1995), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 19
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 45 (1980), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper a distributed parameter model is proposed for the discontinuous drying operation of a tunnel-drier. This model is more complete than the previous ones in which continuous loading is currently assumed. The model is used for spherical fruits placed in a California tunnel of the parallel flow type. Numerical results are in good agreement with experimental information. The model can be used for optimum designing and automatic control.
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  • 20
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 27 (2003), S. 0 
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Flagellar motility helps bacteria to reach the most favourable environments and to successfully compete with other micro-organisms. These complex organelles also play an important role in adhesion to substrates, biofilm formation and virulence process. In addition, because their synthesis and functioning are very expensive for the cell (about 2% of biosynthetic energy expenditure in Escherichia coli) and may induce a strong immune response in the host organism, the expression of flagellar genes is highly regulated by environmental conditions. In the past few years, many data have been published about the regulation of motility in polarly and laterally flagellated bacteria. However, the mechanism of motility control by environmental factors and by some regulatory proteins remains largely unknown. In this respect, recent experimental data suggest that the master regulatory protein-encoding genes at the first level of the cascade are the main target for many environmental factors. This mechanism might require DNA topology alterations of their regulatory regions. Finally, despite some differences the polar and lateral flagellar cascades share many functional similarities, including a similar hierarchical organisation of flagellar systems. The remarkable parallelism in the functional organisation of flagellar systems suggests an evolutionary conservation of regulatory mechanisms in Gram-negative bacteria.
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