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  • NDE  (41)
  • Nitrate
  • Nitrogen fixation
  • Springer  (91)
  • 2025-2025
  • 1990-1994
  • 1980-1984  (91)
  • 1981  (47)
  • 1980  (44)
  • 1929
Collection
Keywords
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  • Springer  (91)
Years
  • 2025-2025
  • 1990-1994
  • 1980-1984  (91)
Year
  • 1
    Electronic Resource
    Electronic Resource
    The roles of nitrate and ammonium in the regulation of the development of nitrate reductase in Chlamydomonas reinhardii (1980)
    Springer
    Planta 150 (1980), S. 13-18 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium ; Chlamydomonas (mutant) ; Nitrate ; Nitrate reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The regulation of the development of nitrate reductase (NR) activity in Chlamydomonas reinhardii has been compared in a wild-type strain and in a mutant (nit-A) which possesses a modified nitrate reductase enzyme that is non-functional in vivo. The modified enzyme cannot use NAD(P)H as an electron donor for nitrate reduction and it differs from wild-type enzyme in that NR activity is not inactivated in vitro by incubation with NAD(P)H and small quantities of cyanide; it is inactivated when reduced benzyl viologen or flavin mononucleotide is present. After short periods of nitrogen starvation mutant organisms contain much higher levels of terminal-NR activity than do similarly treated wild-type ones. Despite the inability of the mutant to utilize nitrate, no nitrate or nitrite was found in nitrogen-starved cultures; it is therefore concluded that the appearance of NR activity is not a consequence of nitrification. After prolonged nitrogen starvation (22 h) the NR level in the mutant is low. It increases rapidly if nitrate is then added and this increase in activity does not occur in the presence of ammonium, tungstate or cycloheximide. Disappearance of preformed NR activity is stimulated by addition of tungstate and even more by addition of ammonium. The results are interpreted as evidence for a continuous turnover of NR in cells of the mutant with ammonium both stimulating NR breakdown and stopping NR synthesis. Nitrate protects the enzyme from breakdown. Reversible inactivation of NR activity is thought to play an insignificant rôle in the mutant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385608
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of combined nitrogen on anapleurotic carbon assimilation and bleeding sap composition in Phaseolus vulgaris L. (1980)
    Springer
    Planta 148 (1980), S. 338-345 
    Details
    ISSN: 1432-2048
    Keywords: Allantoin ; Amino acids ; Bleeding sap ; Nitrogen fixation ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dwarf french beans, Phaseolus vulgaris L., were grown with or without inoculation with rhizobia (strain 3644), and with or without a combined nitrogen source (nitrate or ammonium ions). The distribution of radioactivity into products of dark 14CO2 assimilation was studied in roots or nodules from these plants. A detailed study was also made of the distribution and rates of excretion of nitrogen in xylem bleeding sap in 28 day old plants grown on the various sources of nitrogen. Whereas detached nodules accumulated radioactive glycine, serine and glutamate when incubated with 14CO2, bleeding sap from plants root fed 14CO2 contained low levels of radioactivity in these compounds but higher levels in allantoin. Chemical analysis showed allantoin to be the major compound transported in the xylem of nodulated plants, whether or not they were fed on combined nitrogen. In contrast uninoculated plants accumulated mainly amino acids in the bleeding sap, the amount and chemical composition of which depended on the combined nitrogen source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388121
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  • 3
    Electronic Resource
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    Effect of chemical inhibitors of photorespiration on nitrogenase activity in nodulated alfalfa plants (1980)
    Springer
    Planta 150 (1980), S. 299-302 
    Details
    ISSN: 1432-2048
    Keywords: Glyoxylate ; Isonicotinic acid hydracide ; Medicago ; Nitrogen fixation ; Photorespiration ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen fixation (measured as acetylene reduction) by whole nodulated alfalfa plants was stimulated when the plants were treated with isonicotinic acid hydracide (INH) and glyoxylate, both inhibitors of the glycolate pathway of carbohydrate metabolism, at concentrations of 300 and 100 mM, respectively. Reducing energetic loses caused by photorespiration results in an increase in the symbiotic nitrogen fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384659
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  • 4
    Electronic Resource
    Electronic Resource
    15N2 Incorporation and metabolism in the lichen Peltigera aphthosa Willd (1981)
    Springer
    Planta 152 (1981), S. 544-552 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Lichens ; Nitrogen fixation ; Peltigera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Nostoc in the cephalodia of the lichen Peltigera aphthosa Willd. fixed 15N2 and the bulk of the nitrogen fixed was continuously transferred from it to its eukaryotic partners (a fungus and a green alga, Coccomyxa sp.). Kinetic studies carried out over the first 30 min, after exposure of isolated cephalodia to 15N2, showed that highest initial 15N2-labelling was into NH 4 + . After 12 min little further increase in the NH 4 + label occurred while that in the amide group of glutamine and in glutamate continued to increase. The 15N-labelling of the amino group of glutamine and of aspartate increased more slowly, followed by an increase in the labelling of alanine. When total incorporation of 15N-label was calculated, the overall pattern was found to be rather similar except that, throughout the experiment, the total 15N incorporated into glutamate was about six times greater than that into the amide group of glutamine. Pulse chase experiments, in which 14N2 was added to cephalodia previously exposed to 15N2, showed that the NH 4 + pool rapidly became depleted of 15N-label, followed by decreases in the labelling of glutamate, the amide group of glutamine and aspartate. The 15N-labelling of alanine, however, continued to increase for a period. When isolated cephalodia were treated with L-methionine-SR-sulphoximine, an inhibitor of glutamine synthetase (EC 6.3.1.2), and azaserine, an inhibitor of glutamate synthase (EC 2.6.1.53), there was no detectable labelling in glutamine although the 15N-labelling of glutamate increased unimpaired. On treating the cephalodia with amino-oxyacetate, an inhibitor of aminotransferase activity, the alanine pool decreased. Evidence was obtained that glutamine synthetase and glutamate synthase were located in the Nostoc, and that glutamate dehydrogenase (EC 1.4.1.4) and various amino-transferases were located in the cephalodial fungus. Possible implications of these findings are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380825
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  • 5
    Electronic Resource
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    Relative levels of guanosine 5′-diphosphate 3′-diphosphate (ppGpp) in some N2 fixing bacteria during derepression and repression of nitrogenase (1981)
    Springer
    Archives of microbiology 128 (1981), S. 341-342 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Regulation ; Guanosine 5′-diphosphate 3′-diphosphate (ppGpp)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Addition of ammonium to N2 fixing cultures of Azotobacter vinelandii, Klebsiella pneumoniae and Clostridium pasteurianum rapidly reduced the intracellular levels of guanosine 5′-diphosphate 3′-diphosphate (ppGpp) by 70–90%. This change might reflect a regulatory role of ppGpp in nitrogen metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422542
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  • 6
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    The occurrence of coryneform bacteria in the leaf cavity of Azolla (1980)
    Springer
    Archives of microbiology 127 (1980), S. 163-165 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Arthrobacter ; Corynebacterium ; Anabaena azollae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coryneform bacteria were found associated with the nitrogen fixing blue-green alga, Anabaena azollae in the leaf cavity of Azolla caroliniana. Plate counts indicated ca. 7,400±1,900 bacterial cells per mature leaf cavity or approximately 1 bacterial cell for every algal cell. No other type of bacterium was found in these cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428020
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  • 7
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    Antigenic differences between Anabaena azollae fresh from the Azolla fern leaf cavity and free-living cyanobacteria (1980)
    Springer
    Archives of microbiology 128 (1980), S. 126-129 
    Details
    ISSN: 1432-072X
    Keywords: Fluorescent antibody staining ; Nitrogen fixation ; Symbiosis ; Anabaena azollae ; Azolla caroliniana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluorescent antibody staining indicated differences in surface antigenicity in Anabaena azollae cells fresh from the leaf cavities of the fern, Azolla caroliniana, and algae which were isolated and subcultured from this fern. Such results suggest that either changes in antigenicity occur in this phycobiont during culturing or that isolation selects for an antigenically different mutant strain capable of in vitro growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422316
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  • 8
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    The uptake and hydrolysis of disaccharides by fast-and slow-growing species of Rhizobium (1981)
    Springer
    Archives of microbiology 129 (1981), S. 238-239 
    Details
    ISSN: 1432-072X
    Keywords: Rhizobium ; Disaccharide ; Bacteroid ; Transport ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Slow growing strains of rhizobia appear to lack both uptake systems and catabolic enzymes for disaccharides. In the fast-growing strains of rhizobia there are uptake mechanisms and catabolic enzymes for disaccharide metabolism. In Rhizobium leguminosarum WU 163 and WU235 and R. trifolii WU290, sucrose and maltose uptake appears to be constitutive whereas in R. meliloti WU60 and in cowpea Rhizobium NGR234 uptake of these disaccharides is inducible. There is evidence that there are at least two distinct disaccharide uptake systems in fast-growing rhizobia, one transporting sucrose, maltose and trehalose and the other, lactose. Disaccharide uptake is via an active process since uptake is inhibited by azide, dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone but not by arsenate. Bacteroids of R. leguminosarum WU235 and R. lupini WU8 are unable to accumulate disaccharides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425257
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  • 9
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    Regulation of nitrogenase messenger RNA synthesis and stability in Klebsiella pneumoniae (1981)
    Springer
    Archives of microbiology 130 (1981), S. 38-43 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Gene expression ; Regulation ; Messenger RNA ; Transcription ; Klebsiella pneumoniae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogenase messenger RNA synthesis in Klebsiella pneumoniae was determined by labelling cells with (3H)uracil and isolating total RnA, which was then hybridized to filterbound recombinant plasmid pSA30 DNA carrying the nitrogenase structural genes nifH, D, and K. Derepression of nitrogenase mRNA starts 1.5 h before the onset of nitrogenase activity (as measured by acetylene reduction). Exposure of nif-derepressed cultures to either NH 4 + , air, or high temperatures (39° C) results in a rapid decrease of the synthesis rates both of nitrogenase mRNA and nitrogenase polypeptides. Nitrogenase mRNA is remarkably stable. After blocking transcription with rifampicin, hybridizable and actively translatable nitrogenase mRNA survives with an average half-life of 18 min. Half-lives are considerably shorter when rifampicin-inhibited cultures are simultaneously shifted to conditions which are non-permissive for nitrogenase synthesis, pointing to some posttranscriptional influence on nitrogenase mRNA stability. In all experiments performed there was no evidence for uncoupling of nitrogenase mRNA synthesis from nitrogenase mRNA translation, indicating that nitrogenase synthesis is regulated solely by transcriptional control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527069
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  • 10
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    Nitrogen fixation associated with a hotspring green alga (1980)
    Springer
    Archives of microbiology 124 (1980), S. 161-167 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Photosynthesis ; Green alga ; Chl a and b ; DCMU ; Light and O2 dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A unicellular alga which can grow in the light without a combined nitrogen source was isolated from a hot spring. The cells were almost spherical, usually 5–10 μm in diameter. Absorption spectra of the watersoluble pigments and of the acetone-extracted ones revealed the existence of chlorophyll a and b and the absence of phycobilins. Thin sections examined by electron microscopy revealed an eukaryotic organization with features typical of the coccoid green algae (the Chlorococcales). Cells divided by internal cytokinesis and subsequent liberation of daughter cells from the parental wall, in a way similar to Chlorella. The alga reduced acetylene to ethylene and incorporated 15N2 into cell protoplasm when incubated in a low oxygen atmosphere. Nitrogenase activity was light-dependent, microaerophilic and thermophilic. Although the association of symbiotic nitrogen fixing prokaryotes with the cells may still be possible, any such organisms have not so far been detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427722
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  • 11
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    Expression of klebsiella his and nif genes in serratia marcescens, Erwinia herbicola and Proteus mirabilis (1980)
    Springer
    Archives of microbiology 127 (1980), S. 115-118 
    Details
    ISSN: 1432-072X
    Keywords: Proteus mirabilis ; Serratia marcescens ; Erwinia herbicola ; Nitrogen fixation ; nif genes ; his genes ; Plasmids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plasmid pRD1, an R plasmid of the P incompatibility group which carries his and nif genes from Klebsiella pneumoniae in addition to drug resistance markers derived from RP4, was transferred to His- mutants of Serratia marcescens, Erwinia herbicola and Proteus mirabilis. His+ transconjugants were obtained at low but different frequencies according to recipient genus. Transconjugants all acquired the drug resistance, and were Nif+ in S. marcescens and E. herbicola, having acetylene-reducing activities of the same order of magnitude as the parent K. pneumoniae and fixing 15N2. No evidence for nif expression in P. mirabilis transconjugants was obtained though the nif genes were present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428014
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  • 12
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    Transformations of inorganic nitrogen by Azospirillum spp. (1981)
    Springer
    Archives of microbiology 130 (1981), S. 96-100 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Nitrate respiration ; Denitrification ; Assimilatory nitrate reduction ; Dissimilatory nitrate reduction ; Acetylene reduction ; Azospirillum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Azospirillum spp. participate in all steps of the nitrogen cycle except nitrification. They can fix molecular nitrogen and perform assimilatory nitrate reduction and nitrate respiration. Culture conditions have been defined under which nitrate is used both as terminal respiratory electron acceptor and as nitrogen source for growth. Nitrate and, possibly to a very limited extent, nitrite, but not sulfate, iron or fumarate support anaerobic respiration. Under anaerobic conditions, nitrate can also supply energy for nitrogen fixation but without supporting growth. Nitrate-dependent nitrogenase activity lasts only for 3–4 h until the enzymes of assimilatory nitrate reduction are synthesized. Nitrite accumulates during this period and inhibits nitrogenase activity at concentrations of about 1 mM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411058
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  • 13
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    Stress-wave attenuation in thin structures by ultrasonic through-transmission (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 277-286 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonics ; through-transmission ; composite materials ; attenuation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The steady-state amplitude of the output of an ultrasonic through-transmission measurement is analyzed and the result is given in closed form. Provided that the product of the input and output transduction ratios, the specimen-transducer reflection coefficient, the specimen-transducer phase-shift parameter, and the material phase velocity are known, this analysis gives a means for determining the through-thickness attenuation of an individual thin sample. Multiple stress-wave reflections are taken into account, and so signal echoes do not represent a difficulty. An example is presented for a graphite fiber epoxy composite (Hercules AS/3501-6). Thus, the technique provides a direct method for continuous or intermittent monitoring of through-thickness attenuation of plate structures which may be subject to service structural degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571808
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  • 14
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    A new digital correlation flaw detection system (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 57-63 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; correlation ; pseudorandom codes ; random signals ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new portable digital random signal flaw detection system is described which uses a digital delay line to replace the acoustic delay line of the original random signal system. Using this new system, a comparison was made between the two types of transmit signals which have been used in previous systems—m-sequences and random signals. This comparison has not been possible with these previous correlation flaw detection systems. Results indicated that for high-speed short code operation, the m-sequences produced slightly lower range sidelobes than typical samples of a clipped random signal. For normal long code operation, results indicated that system performance is essentially equivalent in resolution and signal-to-noise ratio using either m-sequences or clipped and sampled random signals. Further results also showed that for normal long code operation, the system produces outputs equivalent in resolution to pulse-echo systems, but with the added benefit of signal-to-noise ratio enhancement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614998
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  • 15
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    Potential and limits of holographic reconstruction algorithms (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 85-111 
    Details
    ISSN: 1573-4862
    Keywords: Holographic reconstruction ; ultrasound ; NDE ; Rayleigh-Sommerfeld formula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract For the purpose of ultrasonic nondestructive testing of materials, holography in connection with digital reconstruction algorithms has been proposed as a modern tool to extract crack sizes from ultrasonic scattering data. Defining the typical holographic reconstruction algorithm as the application of the scalar Kirchhoff diffraction theory to backward wave propagation, we demonstrate its general incapability of reconstructing equivalent sources, and hence, geometries of scattering bodies. Only the special case of a planar measurement recording surface, that is to say, a hologram plane, and a planar crack with perfectly rigid boundary conditions parallel to the hologram plane and perpendicular to the incident field yields a nearly perfect correlation between crack size and reconstructed image; the reconstruction algorithm is then referred to as the Rayleigh-Sommerfeld formula; it therefore represents the optimal case matched to that special geometrical situation and, hence, may be interpreted as a quasi-matched spatial filter. Using integral equation theory and physical optics, we compute synthetic holographic data for a linear cracklike scatterer for both plane and spherical wave incidence, the latter case simulating a synthetic aperture impulse echo situation, thus illustrating how the Rayleigh-Sommerfeld algorithm or its Fresnel approximation increasingly fail for cracks inclined to the hologram plane and excited nonperpendicularly. Furthermore, we point out how the physical data recording process may additionally influence the reconstruction accuracy, and, finally, guidelines for a careful and serious application of these holographic reconstruction algorithms are given. The theoretical results are supported by measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566307
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  • 16
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    Interior imaging using spatial frequency sampling (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 203-207 
    Details
    ISSN: 1573-4862
    Keywords: ultrasonics ; synthetic aperture ; spatial frequency ; interior imaging ; acoustic microscopy ; defect detection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new acoustic synthetic aperture geometry is demonstrated in which the image field is sampled in the spatial frequency domain. This means the sampled field is recorded in a particularly convenient form for presentation to the back propagation algorithms used to reconstruct the field at the object plane. The method has applications in interior visualization. It is difficult to image the interior of solid objects using lens based imaging systems because a different lens geometry must be used for each distinct object material. The system presented here overcomes such problems since both the angular variation of the transmission coefficient at the object-water interface and the aberrations introduced by the velocity mismatch at the object surface may be readily compensated for in the back propagation routine. Experimental results are presented illustrating the detection of four half wavelength diameter defects, spaced by three wavelengths, at a depth of eight wavelengths below the surface of an aluminum block.
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    URL: http://dx.doi.org/10.1007/BF00570732
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  • 17
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    Spherical wave decomposition approach to ultrasonic field calculations (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 241-247 
    Details
    ISSN: 1573-4862
    Keywords: ultrasonic field ; numerical methods ; transducer design ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically analyzing the diffraction field of a continuous wave transducer of arbitrary size, shape, and frequency. Using the extensively studied circular transducer for comparison, numerical results are shown for an unfocused transducer with uniform velocity excitation as well as for a focused transducer with Gaussian velocity excitation. Data concerning the execution time, program size, and convergence of the method are also presented for its implementation as a design tool on a minicomputer system.
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    URL: http://dx.doi.org/10.1007/BF00570736
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  • 18
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    Volumetric inspection of moderately thick austenitic stainless steels by multifrequency eddy currents (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 23-33 
    Details
    ISSN: 1573-4862
    Keywords: austenitic stainless steel ; austenitic stainless steel welds ; eddy current inspection ; eddy current testing ; electromagnetic testing ; ferromagnetic steel inspection ; flaw characterization ; flaw detection ; NDE ; multifrequency eddy current inspection ; weld inspection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes the initial phase of a project to develop eddy-current methods to inspect welds joining sections of austenitic stainless steel pipe having walls up to 13 mm (0.5 in.) thick. The objective of this phase was to demonstrate the feasibility of detecting and characterizing flaws in austenitic stainless steel base metals. These materials and welds present challenging eddy-current problems because of their relatively large thickness and ferromagnetism. Multiparameter analysis shows that a reflection coil probe operated with three discrete driver frequencies and phase detection can locate and size a cracklike defect in a single conductor in the presence of variations in conductor resistivity, permeability, and thickness and in the probe-conductor spacing (liftoff). Experiments were performed with a modular three-frequency instrument. Flat-plate specimens of types 304L and 347 stainless steel machined to 12.7 to 15.9 mm thickness simulated pipe walls; saw-cut slots 10 to 30% of nominal specimen thickness simulated cracklike defects. The same slots were used in duplicate experiments as near-side (directly under the test probe) or far-side (in the face opposite the probe) defects. Flaw detection and characterization capability was demonstrated by a series of experimental measurements fitted to specimen properties by least squares techniques. The quality of the fit determined the expected accuracy of measurement. Comparison of accuracy estimates determined the best choice of operating frequencies. From the 1,2,5 sequence of frequencies between 0.5 and 20 kHz, the optimum set of operating frequencies was selected to be 0.5, 2, and 10 kHz. Estimates of measurement accuracy for combined near- and far-side defect cases were: plate thickness, 0.74 mm; probe liftoff, 0.03 mm; defect location (depth of material above defect), 3.48 mm; and defect size (vertical slot depth), 1.09 mm. A few property values were back-calculated from instrument readings; the errors in these values were somewhat larger than the measurement accuracy estimates because of instrument drift and the absence of calibration circuits.
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    URL: http://dx.doi.org/10.1007/BF00614994
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  • 19
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    Defect identification and sizing by the ultrasonic satellite-pulse technique (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 263-276 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonics ; scattering ; diffraction ; defect characterization ; cracks ; voids ; pattern recognition ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Shape and size are the most important defect characteristics that need to be determined for the reliable prediction of the remaining service lifetime of a defective structure or part. The analytical and supporting experimental results presented in this paper concern a general, pattern recognition-based, ultrasonic defect identification and sizing method. The satellite-pulse technique (SPT) is based on the interpretation, in terms of defect types (shapes) and dimensions, of the separation in time of arrival between the readily detected specularly reflected pulse and its generally ignored tip-diffracted or tangentially scattered “satellite” contained in the received waveform. Calibration procedures were also developed that enable the ultrasonic examiner to read the time scale of the oscilloscope for equivalent crack depth or void diameter as appropriate.
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    URL: http://dx.doi.org/10.1007/BF00571807
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  • 20
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    Acoustic emission and inclusion fracture in 7075 aluminum alloys (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 35-41 
    Details
    ISSN: 1573-4862
    Keywords: acoustic emission ; crack growth ; 7075 aluminum ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract For slow crack growth (da/dn ≈0.1 µm per load cycle) in 7075-T6 aluminum, quantitative agreement was found between the amplitude distribution of burst acoustic emissions and the area size distribution of intermetallic inclusions ≈10 (µm)2 in area as measured on thepolished fracture face. This observation permits the prediction of the amplitude distribution of acoustic emissions due to crack growth in a particular sample of 7075-T6 aluminum directly from a simple, standard metallographic observation performed on the material in question. It was also found that a reduction of the yield stress from that of 7075-T6 aluminum (503 MPa) to that of 7075-0 aluminum (103 MPa) completely eliminated burst acoustic emission activity due to crack advance in the amplitude range studied.
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    URL: http://dx.doi.org/10.1007/BF00614995
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  • 21
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    Static finite element stress intensity factors for annular cracks (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 119-124 
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    ISSN: 1573-4862
    Keywords: Stress intensity factor ; annular crack ; finite element methods ; fatigue ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Results of finite element static stress intensity factor calculations for an annular crack around a spherical inclusion (void) are presented and compared with those from approximate analytical methods.
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    URL: http://dx.doi.org/10.1007/BF00566309
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    Note on ultrasonic tomography (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 147-149 
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    ISSN: 1573-4862
    Keywords: Ultrasonic tomography ; residual stress ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Ultrasonic tomography is being explored as a potential tool to map residual stresses in solids. The angular scanning required in tomography imposed limitations on the stress configuration adaptable to such a treatment. These are discussed in the following note.
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    Ill-posed and well-posed problems in inverse elastodynamic scattering for nondestructive evaluation (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 161-172 
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    Keywords: elastodynamic inverse scattering ; ultrasonics ; data reduction ; ill-posed problems ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The practical significance of ill-posedness in a data reduction problem is reviewed. Inverse elastodynamic scattering is shown to be ill-posed in general, although suitably restricted problems may be well-posed. These results underscore the need to analyze carefully the errors of data reduction problems in NDE, and to focus attention on final results of an NDE exercise, rather than on intermediate steps.
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    Effects of sinusoidal crack-face perturbations on scattering of elastic waves (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 153-159 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; scattering ; cracks ; periodic surface perturbation ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The scattering of a plane longitudinal wave from a two-dimensional crack, with a sinusoidal surface perturbation whose amplitude and wavelength are much smaller than the length of the crack, is investigated. The amplitude of the cylindrical body waves in the far field are calculated from a Kirchhoff approximation that utilizes the solution to the reflection from the sinusoidal surface profile of a semiinfinite solid. The results are compared to those for a flat crack, and conditions for significant differences of the amplitude as a function of the angle of observation are discussed. Characteristic changes in the scattered field produced by profiles with different amplitudes and periods are explained.
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    Parasitic voltages induced by artificial flaws when measured using the ac field technique (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 195-202 
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    ISSN: 1573-4862
    Keywords: ac potential difference ; fatigue crack measurement ; slots ; artificial flaws ; parasitic voltages ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The development of a successful and accurate instrument for measuring surface-breaking cracks in metals using the ac field technique has raised several interesting theoretical problems. Measurements with the instrument, known as the Crack Microgauge, do not rely on any prior calibration against an artificial flaw such as a saw-cut in a test block, but some users accustomed to such a calibration from other devices have nevertheless wished to use the instrument in that fashion and have in some instances reported erroneous results. In this paper, we develop a simple theory to explain and quantify this phenomenon. We calculate the parasitic voltages induced in the instrument probe due to the finite opening possessed by an artificial flaw, and we use these results to reinterpret the instrument readings. Controlled experimental measurements on artificial flaws of rectangular cross-section made in aluminum and in steel are found to be in good agreement with the theory. It is shown, however, that application of the theory requires additional information about the internal phase shift associated with the instrument. To enhance the accuracy of the theory, the effect of the corners of the artificial flaws was also considered, although it was not very influential in this work.
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    Remaining fatigue life prediction in the initiation regime using SAW NDE (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 3-9 
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    ISSN: 1573-4862
    Keywords: harmonic generation ; fatigue ; microcracks ; aluminum ; surface acoustic waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Harmonic generation of surface acoustic waves (SAW) is shown to be a useful tool for the detection of the initiation of surface cracks during fatigue of high strength aluminum alloys. A model that relates the length and density of microcracks to the amplitude of a SAW harmonic signal is described, and an associated coefficient of generation efficiency for the second harmonic amplitude is derived. A correlation between experimentally measured harmonic amplitude and remaining fatigue life is then demonstrated, which allows the mean remaining fatigue lifetime to be estimated to within 5% over the last 50% of the fatigue life for an Al 7075 alloy if the cyclic stress amplitude, but not the duration of fatigue, is known.
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    Ultrasonic diffraction technique for characterization of fatigue cracks (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 11-19 
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    ISSN: 1573-4862
    Keywords: ultrasonic diffraction ; fatigue cracks ; crack closure ; crack surfaces ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes an ultrasonic diffraction technique for characterizing fatigue cracks. The angular field of energy scattered from a crack tip was computed. Using the theoretically predicted and experimentally verified optimum range of angles, we measured the crack profiles by the ultrasonic diffraction technique. Ultrasonic measurements agreed very well with direct destructive measurements. In addition, fatigue crack closure was detected and information on crack surfaces was obtained.
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    Methods for determining the depth of near-surface defects (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 21-36 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; surface defects ; defect depth ; deconvolution ; correlation ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In previous work by the authors,(1,6) it was demonstrated that the presence of near-surface defects could be detected reliably, even though the defect echo was contained within the near-surface echo. The algorithm consists of examining the variation in the composite (near-surface plus defect) response after it has been deconvolved from a near-surface response known to be defect-free. This paper presents two algorithms that have been developed subsequent to the work presented in ref. (6) for estimating thedepth of a near-surface defect, given that its presence has already been detected. One algorithm uses complex frequency domain techniques, and the other uses time domain analysis. Both procedures operate on the surface-plus-defect signal, using reference signals containing surface-only and defect-only responses. The defect signal is extracted from the composite signal. Defect depth is then computed from the time difference between the centers of the front-surface and extracted defect responses. A mean absolute depth error of 0.015 in. was obtained by applying the algorithms to experimental data containing depths from 0.020 to 0.130 in. below the near-surface.
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    Accept/reject decisions and failure prediction for structural ceramics: Application to failure from voids (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 37-52 
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    ISSN: 1573-4862
    Keywords: failure prediction ; accept/reject decisions ; ceramic materials ; ultrasonics ; fracture ; probabilistic model ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A general probabilistic method for reaching accept/reject decisions and failure prediction based on nondestructive evaluation procedures is described. The method is illustrated for ceramic materials that fail by the activation of microcracks located at void surfaces. The inspection procedure used for the analysis is the long wavelength ultrasonic method. The analysis indicates influences on the decision level and on the false-reject probability of variations in the signal-to-noise ratio and in the preexistent void population. The ultrasonic inspection is shown to exert a relatively minor influence on the false-reject probability, even for low signal-to-noise ratios, low stresses, and a widely dispersed void population, because of the intrinsic variability of the selected failure process. More encouraging results concerning the utility of NDE are anticipated to apply to other failure mechanisms in ceramics.
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    Analytical representation of transient ultrasonic phased-array near- and far-fields (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 53-66 
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    ISSN: 1573-4862
    Keywords: ultrasonic transducers ; phased array ; ultrasonic imaging ; impulse response ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The present contribution provides a method for the derivation of analytical near- and far-field expressions for the pressure step-function response of nonuniformly excited ultrasonic transducers modeled as pistons of arbitrary shape in an infinite rigid baffle. Explicit inversion of the Laplace transformed ultrasonic field using Cagniard's idea results in elementary functions or definite integrals of elementary functions, depending on the assumed nonuniform aperture distribution. The basic signal distortion is illustrated in terms of three-dimensional space-time plots of the pressure unit step-function response of a rectangular uniform aperture. The corresponding results for a phased-array transducer are also given. In addition, we investigate the pressure profile on the axis perpendicular to a uniform rectangular piston and its horizontal radiation pattern for different bandwidths of the exciting impulse.
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    Acoustic measurements of stress fields and microstructure (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 67-77 
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    ISSN: 1573-4862
    Keywords: stress fields ; microstructure ; J integral ; stress intensity factor ; harness acoustic velocity ; acoustic elasticity ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A very precise system for measuring two-dimensional velocity fields in solid samples has been used for nondestructive measurements of both externally applied and residual inhomogeneous stresses in solids,J integrals, stress intensity factors of cracks, and hardness of quenched steel. The longitudinal velocity measurement is based on precise determination of the propagation transit time through the stressed solid specimen using a small diameter, water-coupled acoutic transducer, which is scanned mechanically over the sample. Changes in velocity are then related to changes of stress in the sample by the theory of acoustoelasticity. Similar measurements show a high degree of correlation between longitudinal velocity changes and changes in microstructure in steel samples. Applications to problems of solid mechanics and material science illustrate the utility of this nondestructive measuring technique.
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    The relationship between radiating body forces and equivalent surface stresses: Analysis and application to EMAT design (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 79-85 
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    ISSN: 1573-4862
    Keywords: ultrasonic waves ; EMAT ; surface stress ; NDE ; Green's function
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An analysis of the radiation from a body force shows that it is equivalent to the radiation from a series of surface stresses defined by the moments of the body force taken with respect to the depth coordinate. As the body force becomes localized near the surface, the zeroth moment of the force dominates the radiation and is often thought of as an equivalent surface stress. However, under certain conditions, this can vanish, and the other moments must be considered. It is found that, as the order of the moment of a particular force component increases, the resulting radiation patterns alternate between those characteristic of a compressive surface stress and those characteristic of a shear surface stress, which have considerably different angular variations. Results of experiments in the development of EMAT transducers for nondestructive testing that support these results are cited, and important consequences in the design of inspection systems are indicated.
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    An acoustic emission energy analysis and its use to study damage in laminated composites (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 225-233 
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    ISSN: 1573-4862
    Keywords: Acoustic emission ; energy analysis ; composite materials ; strength ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new technique which uses the output of a true RMS voltmeter to measure the acoustic emission energy output of a transducer is presented. To demonstrate its use in a typical case, this procedure is used to measure acoustic emission energy during tensile tests on [0°/±30°/90°]s glass-epoxy laminate uniaxial and 10° off-axis tensile coupons. The test results were compared with numerical predictions of laminate response and acoustic emission energy. The experiments indicate that acoustic emission energy can be used to indicate the onset of ply and interlaminar failure.
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    Defect characterization in the short-wavelength regime (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 235-247 
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    ISSN: 1573-4862
    Keywords: Ultrasonics ; acoustic waves ; scattering ; diffraction ; defect characterization ; silicon nitride ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The scattering of acoustic waves by different types of spherical defects in a silicon nitride matrix is calculated by using Ying and Truell's scattering theory. The theoretical scattering results are interpreted using a ray tracing approach. Experiments were carried out at a high frequency (150–450 MHz) to characterize defects in silicon nitride. Time and space averaging, Wiener filtering, diffraction, and propagation loss corrections were used to remove the effect of the transducer response and propagation loss in the material from the scattered signal. Our experimental results indicate the presence of a new type of defect in silicon nitride. They give the type and size of voids, cracks, and Si inclusions in good agreement with measurements obtained after sectioning.
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    Rayleigh wave propagation in a solid with a cold-worked surface layer (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 43-49 
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    ISSN: 1573-4862
    Keywords: Rayleigh wave dispersion ; higher mode generation ; cold-working ; rail ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The propagation of the Rayleigh surface wave is experimentally studied along the top surface of used railroad rail under conditions where ultrasonic pulses have carrier frequencies ranging from 0.4 to 3.0 MHz and approximately 10 µs duration. The generation of the first higher (M 21 or Sezawa) mode as well as the fundamental (M 11) mode and their dispersion properties are observed. These phenomena are attributable to the presence of the cold-worked surface layer caused by the wheel passage. It is shown that a theoretical model of a single layer overlying a half space, whose elastic constants are determined by a destructive method, yields results which agree with the dispersion curves obtained experimentally. On the basis of this one-layered model, an inversion method to estimate the layer thickness and its elastic constants is discussed.
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    Resonance testing of cast iron (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 65-74 
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    ISSN: 1573-4862
    Keywords: NDE ; cast iron ; vibration analysis ; modulus ; strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An outline is given of the existing nondestructive vibration tests for cast irons and their drawbacks in terms of the dimensional accuracy of the components. A proposal is made for a new test based on the change of resonant frequency with vibration amplitude exhibited by cast irons. This proposal is evaluated using material data obtained from dynamic tests of a wide range of cast iron specimens. A test rig is described suitable for testing cylindrical cast bars, and typical results are presented in relation to material strength. There is also a brief description of preliminary testing on cast products.
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    Detection of strength limiting defects in cellular glasses by dielectric measurements (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 113-118 
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    ISSN: 1573-4862
    Keywords: Capacitance ; dielectric constant ; voids ; cellular glasses ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Cellular (foamed) glasses are a prime candidate for certain structural applications, such as support of the silvered glass concentrator mirrors in solar thermal energy systems. An economical nondestructive measurement of strength-limiting defects in these materials would permit development of designs in which the material is subjected to a higher working stress level and maintains the same probability of failure. This would result in weight and cost savings for any application. A method of measuring the capacitance of well-defined regions of a specimen was investigated. Large voids were found to produce significant localized changes in the capacitance of the specimen. The feasibility of locating the large, strength limiting defects in this porous material has been demonstrated for one type of cellular glass. Means of producing an image from this type of data and an implementation scheme for on-line production measurements are discussed.
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    Nondestructive testing of materials using 14 MeV neutrons and a pulse-shape analyzer system (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 139-146 
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    ISSN: 1573-4862
    Keywords: Material defects ; 14 MeV neutrons ; pulse-shape analyzer system ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A 14 MeV neutron generator and fast neutron spectrometer consisting of an organic scintillation detector and a pulse-shape analyzer are used for the nondestructive testing of materials. The 14.6 MeV peak (in the 12.7–15.7 MeV region) is observed to change as a function of both the kind of testing material and the defect condition inside the material. The number of neutron counts under the 14.6 MeV peak for lighter testing materials (e.g., plastic, brass, and aluminum) with a defect will increase, as compared to the number of neutron counts under the same peak region of an identical testing material but with no defect. For heavier testing materials (e.g., steel and lead), the inverse is observed. The method is feasible even with defects of size 0.25 cm3 (i.e., a cylindrical cavity 0.4 cm in diameter and 2.0 cm in length), although quantitative evaluation of the size of the defect as a function of the change of the number of neutron counts under the 14.6 MeV peak region is difficult due to instability of the 14 MeV neutron output.
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    Surface acoustic wave measurements of surface cracks in ceramics (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 219-229 
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    ISSN: 1573-4862
    Keywords: acoustics ; surface acoustic waves ; Rayleigh waves ; ceramics ; surface cracks ; residual stresses ; crack extension ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An investigation of scattering from surface cracks has been conducted. In particular, the change in the reflection coefficient of a Rayleigh wave incident on a surface indentation crack has been measured as the sample is stressed to fracture. The acoustic measurements have been correlated with the stable crack extension that precedes final failure. The crack extension behavior of as-indented specimens was found to differ appreciably from that of annealed specimens. Cracks in the annealed samples exhibited partial crack tip closure, but little stable extension, whereas cracks in the as-indented samples displayed both crack closure and irreversible crack growth. This behavior has been rationalized by invoking concepts based upon the residual stresses created by indentation.
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    Love wave propagation in a solid with a cold-worked surface layer (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 51-55 
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    ISSN: 1573-4862
    Keywords: Love wave dispersion ; surface layer ; work hardening ; rail ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In this paper, experiments show Love wave generation along the top surface of used railroad rail, where the shear wave velocity has been slightly reduced by the cold-working of wheel passage for years. The rf pulses used in the experiments have about 10 µs duration and a relatively narrow frequency spectrum. The group velocity of the Love wave is found to have a strong dependence on the carrier frequency over the tested range of 0.45–3.1 MHz. Application of the seismological one-layered model to the experimental measurements yields an NDE technique for the elastic properties and the thickness of the cold-worked surface layer. The results are interpreted on the basis of a destructive observation by micro-Vickers hardness testing.
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    Digital ultrasonic image construction using electronic ordered dither techniques (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 75-84 
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    ISSN: 1573-4862
    Keywords: digital signal processing ; microprocessor based system ; binary display ; ordered dither ; ultrasonic C-scan ; image magnification ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The use of a digital microprocessor based system for the acquisition of ultrasonic C-scan information is investigated. The C-scan information is displayed on a binary display device using electronic ordered dither techniques to represent gray levels. The digital system with a binary display increases system flexibility and yields better reproducibility and constant image quality independent of the display medium. Images may be stored on magnetic tape or disk for later retrieval and image processing. The techniques which are described allow for image magnification and a reduction in scan time by replacing the mechanical linkage between the scanner and the display with digital signals. A detailed comparison is made between two dither signals, and the advantages of each are discussed. The combination of digital signal processing and imaging techniques produces results which utilize the capabilities of ultrasonic inspection to the point where the transducer becomes the limiting factor.
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    SOL-X: An on-line nondestructive method for measuring grain size with x-rays (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 133-138 
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    Keywords: X-rays ; diffraction ; grain size determination ; NDE
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract It is shown that the grain size of commercial materials can be estimated by x-rays with little or no sample preparation. The method is readily automated and can be employed on-line, for example, in a rolling mill.
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    Computerized evaluation of acoustic images utilizing a method of averaging (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 173-188 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; acoustic imaging ; computer image analysis ; failure prediction ; inhomogeneous materials ; accept/reject criteria ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A computerized technique is presented which has been developed for analyzing acoustic images of an inhomogeneous material. The acoustic imaging system is briefly described with emphasis on its adaptation to billets of graphite for atmospheric reentry body use. Ultrasonic images of such inhomogeneous material contain a nonuniform distribution of anomalies and few, if any, geometrically regular features which can be assessed to establish material integrity. Results obtained with our new algorithms show, for certain discriminants, a high degree of correlation between the numerical accept/reject values obtained from acoustic image processing and the time-to-failure of the graphitic material in simulated atmospheric reentry tests.
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    Propagation of elastic waves in honeycomb panels for application to rapid inspection techniques (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 209-217 
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    ISSN: 1573-4862
    Keywords: honeycomb panels ; acoustic inspection ; leaky waves ; SH and Lamb waves ; line scan ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper considers the properties of elastic waves guided by an aluminum plate bonded to a honeycomb core for application to rapid inspection of honeycomb panels. Current acoustic inspection techniques involve the transmission of a signal between a pair of small transducers located on opposite sides of the panel. Scanning the transducers in raster fashion results in a high resolution inspection of the panel, but is very time consuming. An alternative technique would simultaneously inspect all points along a line between two widely spaced transducers located on the same side of the panel. Scanning the pair once over the panel permits rapid inspection, although with decreased resolution. Studies presented here indicate that such a method of inspection is feasible and that the flexural mode is probably the most useful.
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    Frequency domain methods for reducing transducer variability (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 101-109 
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    ISSN: 1573-4862
    Keywords: ultrasonic transducers ; NDE ; deconvolution ; signal processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A major objective of quantitative nondestructive evaluation is to formulate defect detection, classification, and sizing algorithms that are insensitive to variations in transducer characteristics, material type, and defect depth. With the data used in this research, ultrasonic signals were found to vary significantly with changes in the transducer and only secondarily with changes in material and depth. It is shown that the method for minimizing signal variations due to transducer and material changes is to deconvolve the test signal with respect to the transducer response from a reference defect in a block of the same material. Since depth variation primarily affects signal amplitude and has minor impact on shape, detection, classification, and sizing, insensitivity to depth is achieved by avoiding the use of amplitude-dependent parameters. The notion of a “standard transducer” is introduced. Its mathematical properties and methods of realization are given. It is shown how the effects of variability from different test transducers can be removed by signal processing. When these procedures are applied to the test transducer, the effect is to cause it to resemble the standard transducer and, thereby, to place all ultrasonic waveforms on a common basis.
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    URL: http://dx.doi.org/10.1007/BF00566118
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    Ultrasonic attenuation and velocity in AS/3501-6 graphite fiber composite (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 137-148 
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    ISSN: 1573-4862
    Keywords: composite material ; ultrasonic velocity ; ultrasonic attenuation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The ultrasonic group velocity and attenuation were measured as a function of frequency for longitudinal and shear waves in the Hercules epoxy matrix (3501-6) and in the principal directions of the unidirectional Hercules graphite fiber epoxy composite (AS/3501-6). Tests were conducted in the frequency ranges 0.25–14 MHz and 0.5–3 MHz for longitudinal and shear wave modes, respectively. While the attenuation increased with frequency for all wave modes, the group velocity was independent of frequency for all wave modes. In studying the effects of transducer-specimen interface couplant and pressure, it was found that for each transducer, there exists a frequency-dependent “saturation pressure” corresponding to the maximum output amplitude of the signal.
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    URL: http://dx.doi.org/10.1007/BF00566121
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    On the acoustic emission due to the fracture of brittle inclusions (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 149-155 
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    ISSN: 1573-4862
    Keywords: acoustic emission ; fracture ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The far-field characteristics of the emission from a theoretical model for the fracture of brittle inclusions are presented in detail. The model is a circular crack growing at constant speed from zero size until it attains a prescribed size. The far-field radiation pattern is the same as that of a simple combination of force doublets, and some qualitative similarities between force doublets and acoustic dipoles are noted. The initial shape of the far-field pulses due to the growing stage and the stopping is determined, but difficulties arise in accounting for the diffraction of a surface wave on the crack faces generated by the stopping of the crack.
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    URL: http://dx.doi.org/10.1007/BF00567088
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    Elastic wave emission from damage processes (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 215-224 
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    ISSN: 1573-4862
    Keywords: Acoustic emission ; slip ; microcracking ; deformations ; displacement field ; elastic waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The theory of elastic wave emission (i.e., acoustic emission; AE) from damage processes such as slip and microcracking is discussed. Analogous developments in the literature on earth-quake seismology and dynamic dislocation theory are noted and utilized. A general representation of the displacement field of an AE event is given in terms of the double-couple response to a distribution of “moment density tensor” in the source region. Results are specialized to a point source model and to a general far-field analysis of outgoing elastic waves, and conditions for validity of such representations and their low-frequency specializations are noted. Emitted wave fields are compared for tensile opening and slip events, and procedures which might enable the approximate determination of the size or area increase of tensile microcracks are discussed.
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    URL: http://dx.doi.org/10.1007/BF00571803
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    Half-space radiation by EMATs (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 157-181 
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    ISSN: 1573-4862
    Keywords: EMAT ; radiation pattern ; transducer ; shear waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A Green's function calculation of the far-field radiation patterns of EMATs is presented. The approach is based on (a) closed form expressions for the eddy current and static magnetic field distributions, established by the EMATs, which react to produce the driving Lorentz forces, and (b) a Green's function derived from the steepest descent approximation to the far-field response of an arbitrary surface point force on a half space. Numerical results are presented, illustrating the radiation patterns of the three common EMAT designs. Included are vertically polarized shear waves as radiated by both meander coil and periodic magnet EMATs and horizontally polarized shear waves as radiated by the latter.
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    URL: http://dx.doi.org/10.1007/BF00567089
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    Fatigue lifetime prediction with the aid of SAW NDE (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 123-136 
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    ISSN: 1573-4862
    Keywords: fatigue life ; acoustic surface waves ; NDE ; ultrasonics ; cracks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The present studies concentrated on predicting the remaining fatigue life for single fatigue cracks in the Paris regime of macrocrack propagation. Acoustic surface waves were used to interrogate the crack during cyclic fatigue. The inversion of the obtained scattering data provided crack depth and crack length as a function of the number of cycles applied in tension-tension fatigue. Auxiliary experiments were conducted to study the acoustic response of the crack to tensile and compressive loads, thought to open and close the crack. The technique may allow for new insights into the physics of the “crack closure” effect.
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    URL: http://dx.doi.org/10.1007/BF00566120
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    Fracture mechanics transfer function for two-dimensional noncircular flaws (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 201-206 
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    ISSN: 1573-4862
    Keywords: fracture mechanics ; noncircular crack ; fatigue life ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A transfer function that converts an irregularly shaped two-dimensional crack into an equivalent circular crack of equal propagation lifetime is proposed. The methodology extends the exact elliptical to circular crack transfer function to other noncircular cracks with geometries that slightly deviate from the elliptical. Results for rectangular, symmetric dumbbell, and asymmetric dumbbell cracks are presented.
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    URL: http://dx.doi.org/10.1007/BF00567092
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    Ultrasonic evaluation of geometrical and surface parameters of rough defects in solids (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 249-261 
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    ISSN: 1573-4862
    Keywords: Ultrasonics ; cracks ; surface roughness ; diffraction ; scattering ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Ultrasonic measurements from rough cracks were carried out using both broad-band and narrow-band methods. An analysis is suggested to determine parameters of the crack quantitatively such as size, shape, rms surface roughness, and distribution function of the surface roughness. Ultrasonic measurements of the parameters compare very well with the actual parameters of the defect.
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    URL: http://dx.doi.org/10.1007/BF00571806
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    Photoacoustic microscopy of ceramic engine hardware (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 287-293 
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    ISSN: 1573-4862
    Keywords: Photoacoustic microscopy ; SPAM ; silicon nitride ; surface crack ; turbine vanes ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Scanning photoacoustic microscopy (SPAM) was applied to silicon nitride turbine hardware for purposes of detecting fabrication defects. SPAM traces in selected areas of complex-shaped turbine stator vanes were obtained and indicate that surface-crack detection of the order of tens of microns is possible. Means were devised to allow for multiple scans in areas previously inaccessible to other nondestructive techniques capable of detecting defects in the 25- to 100-µm range. The results show that SPAM is applicable to reaction-bonded silicon nitride turbine components and capable of detecting small surface-related defects.
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    URL: http://dx.doi.org/10.1007/BF00571809
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  • 54
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    Effect of long-term fertilizer treatments on groundnut yield, nodulation, and nutrient uptake at Samaru, Nigeria (1980)
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    Plant and soil 55 (1980), S. 171-180 
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    ISSN: 1573-5036
    Keywords: Groundnut fertilization ; Nigeria ; Nitrogen fixation ; Nodulation ; Nutrient uptake ; Tropical soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract It was observed in a long-term fertility study that P application results in better nodulation and seed yield. The N yield per plant increased significantly with P, K, and B application, but the promoting effect of K and B on N content per plant was not reflected in the final yield. Data on mean nutrient uptake indicate that about 63% of N, 68% of P, 23% of K, 4% of Ca and 24% of Mg were present in the kernels, the remainder being in the haulm and shells. Soil will be exhausted fast if the nutrient rich groundnut residues are completely exported from the field and not compensated by adequate fertilizer application. Judicious use of fertilizers on groundnut has been shown to yield more than 100 kg of biologically fixed N per hectare.
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    URL: http://dx.doi.org/10.1007/BF02181796
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    Forest-floor nitrogen dynamics in a 60-year-old paper birch ecosystem in interior Alaska (1980)
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    Plant and soil 54 (1980), S. 359-381 
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    ISSN: 1573-5036
    Keywords: Alaska ; Ammonium ; Birch ; Forest-floor ; Isotopedilution ; Kinetics ; Nitrate ; Nitrogen pool
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An analysis was conducted of nitrogen dynamics in the forest floor of a paper birch forest in subarctic Alaska. Low addition levels of high enrichment isotope (〈1% of the total nitrogen pool with 95 to 99 atom percent excess15N) and isotope dilution analysis, were used to establish the kinetics of nitrogen flow. The pools examined were NH4, NO3+NO2, soluble organic-N and forest floor organic matter. This approach allows a more realistic assessment of rates of N movement at the levels of nitrogen concentration encountered in natural systems.
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    URL: http://dx.doi.org/10.1007/BF02181831
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    Seasonal and diurnal variations in nitrate reductase activity of soybean (Glycine max (L.) Merr.) (1980)
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    Plant and soil 56 (1980), S. 27-32 
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    ISSN: 1573-5036
    Keywords: Nitrate ; Nitrate reductase ; Nitrogen nutrition ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The seasonal and diurnal variations in nitrate reductase (NR) activity of field grown ‘Altona’ soybean, with and without applied nitrogen, were determined. The NR activity in the fortnightly collected leaf samples was, on the average, 20 percent higher throughout the season in N-treated plants, the highest being early in the season and declining gradually in the samples of subsequent dates. Diurnal variations were marked by increase in the NR activity from 7 a.m. to 7 p.m. and then declining gradually to a minimum at 7 a.m. the next morning.
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    URL: http://dx.doi.org/10.1007/BF02197949
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    Effect of soil moisture stress on yield, nodulation and nitrogenase activity ofMacroptilium atropurpureum cv. Siratro andDesmodium intortum cv. Greenleaf (1980)
    Springer
    Plant and soil 57 (1980), S. 187-194 
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    ISSN: 1573-5036
    Keywords: Moisture stress ; Nitrogen fixation ; Tropical forage legume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of soil moisture stress on growth, nodulation and nitrogenase activity of two tropical forage legumes,Macroptilium atropurpureum cv. Siratro andDesmodium intortum cv. Greenleaf was studied in a pot experiment. After ten weeks growth, the highest moisture stress (20 per cent water holding capacity) significantly reduced only the top weight of both plants. Moisture stress progressively retarded top growth in the two legumes. Similar trends were also observed in defoliated plants. Moisture stress had little or no effect on the nodulation or nitrogenase activity of the plants.
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    Nodulation and N2-fixation byInga jinicuil, a woody legume in coffee plantations (1981)
    Springer
    Plant and soil 59 (1981), S. 201-206 
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    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Coffee plantation ; Inga jinicuil ; Nitrogen fixation ; Nodule biomass ; Woody legume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nodule biomass and yearly C2H2 reduction rates are reported forInga jinicuil, a leguminous tree used for shade in Mexican coffee plantations. Annual fixation by this species approximates 35 kg ha−1; which, when compared to nitrogen additions from fertilizers, represents an important nitrogen input to the coffee ecosystem.
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    URL: http://dx.doi.org/10.1007/BF02184193
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    Respiratory stress in cucumber roots treated with ammonium or nitrate nitrogen (1981)
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    Plant and soil 60 (1981), S. 195-204 
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    ISSN: 1573-5036
    Keywords: Ammonium ; Nitrate ; Cucumber ; Respiration ; Stress ; Root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Characteristic differences in growth and metabolic responses were observed following treatment of cucumber (Cucumis sativus, cv Suisei No. 2) roots with NH4 + or NO3 − as the sole source of N in solution culture. The most significant differences were: 1. Plant growth was more rapid with NO3 − as the nitrogen source. The plants generally appeared healthier, and pH of the nutrient solution was more stable. 2. Free ammonia appeared in the tissues of roots grown in NH4 + media within 3 hr after introduction of the ammonium ion. A rapid accumulation of amide-N and amino-N in root tissue followed within the next 3 h. 3. Characteristic symptoms of ‘rotten root’ appeared on plants growing in ammonium salts, with increasing severity as the volume of solution accessible to each plant diminished. ‘Rotten root’ symptoms were not observed on plants grown in 20 ppm nitrate-N regardless of the solution volume. 4. Root oxygen uptake was clearly higher in plants grown with NH4 + ion than in those grown in NO3 − ion. 5. Increased levels of mitochondrial enzyme activity were observed in NH4 + grown roots. Malate dehydrogenase, NADH oxidase, succinate dehydrogenase, succinate: cytochrome c oxidoreductase, and NADH: cytochrome c oxidoreductase were all higher in the NH4 + grown plants, even when under anoxic conditions. NADH diaphorase, however, was not significantly increased.
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    Gnotobiotic cultures of rice plants up to ear stage in the absence of combined nitrogen source but in the presence of free living nitrogen fixing bacteriaAzotobacter vinelandii andRhodopseudomonas capsulata (1981)
    Springer
    Plant and soil 60 (1981), S. 85-97 
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    ISSN: 1573-5036
    Keywords: Azotobacter vinelandii ; Gnotobiotic cultures ; Nitrogen fixation ; Oryza sativa Rhodopseudomonas capsulata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An all glass tight growth chamber, entirely sterilizable, has been constructed to carry out axenic and gnotobiotic cultures of rice plants (Oryza sativa L.). When grown in liquid medium and in the absence of combined nitrogen but in the presence of the diazotrophsAzotobacter vinelandii andRhodopseudomonas capsulata, rice plants exhibited a complete biological cycle from germination up to ear stage, during a period of time similar to the one encountered in french paddy soil of Camargue. In one experiment, mannitol was given to rice culture medium together withAzotobacter vinelandii andRhodopseudomonas capsulata. In another experiment, mannitol was not given together with Rhodopseudomonas, and still positive nitrogen gain was obtained, although it was less than culture with mannitol. When15N labeled cells of Rhodopseudomonas were added in rice culture medium,15N was partly transferred to rice plant. Among the nitrogen substances excreted from the bacteria in the rhizosphere medium, large organic molecules were shown to be the most abundant in our experimental conditions. Moreover, the concentration of free ammonia or aminoacids present in the rice rhizosphere were always compatible with a bacterial nitrogenase activity.
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    A comparison of nitrogen-fixing ability of peanut, cowpea and siratro plants nodulated by different strains of Rhizobium (1981)
    Springer
    Plant and soil 60 (1981), S. 317-319 
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    ISSN: 1573-5036
    Keywords: Bacteroids ; Cowpea ; Nitrogen fixation ; Peanut ; Rhizobium ; Siratro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Acetylene reduction activity and nitrogen accumulation in the plant top per unit nodule mass were compared among peanut, cowpea and siratro plants nodulated by six different strains of Rhizobium. Peanut was found to have several fold higher values than cowpea and siratro for both parameters for all strains of Rhizobium which nodulated it effectively, but the bacteroid content of the peanut nodules was similar to those of cowpea and siratro.
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    The effect of ammonium and nitrate nitrogen sources on copper uptake and amino acid status of cereals (1981)
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    Plant and soil 62 (1981), S. 279-290 
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    ISSN: 1573-5036
    Keywords: Amino acids ; Ammonium ; Copper ; Barley ; Nitrate ; Nitrogen ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of different nitrogen sources (NH4, NO3, and NH4 NO3) on the uptake of copper by wheat and barley growing in solution culture were compared in three experiments. Both the copper concentration and weight gain of shoots and roots were found to decrease in the order NO3〉NH4 NO3〉NH4 irrespective of the solution copper concentration. Ammonium nitrogen was also found to decrease the copper concentration of wheat grown on a copper deficient soil compared with a nitrate source of nitrogen. Increasing concentrations of ammonium ions in solution culture caused ammonium toxicity and reduced both plant copper concentrations and vegetative yield. Biochemical investigations using paper chromatography revealed that the amino acid asparagine was the major detoxification product of ammonia in wheat. Copper deficient plants were found to have elevated levels of amino acids compared with controls, irrespective of the nitrogen source.
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    The effect of sulfur on the response of cotton to urea under alkali soil conditions in pot experiments (1981)
    Springer
    Plant and soil 62 (1981), S. 255-263 
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    ISSN: 1573-5036
    Keywords: Alkalin soil ; Ammonium ; Ammonium nitrate ; Ammonium sulfate ; Application method ; Cotton cultivars ; Incubation ; Nitrate ; N loss ; Phytotoxic effect ; Sulfur ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of sulfur (S) placement and S rate on the efficiency of urea (U) relative to ammonium sulfate (AS) and ammonium nitrate (AN) for cotton were examined in a pot experiment using sandy clay loam soil (pH 7.9). The results showed that AS and AN application in the absence of S increased the yield than U partly because U-induced damage to plants. The combined application of the N sources with S increased the yields and that, the placement of S in the seed horizon in contact with N was more effective than mixing throughout the soil especially with U. These effects were observed with three cotton cultivars. The addition of S to a maximum of 1.5 g/pot gave further increases in yields or the N content of leaves for U, AS or AN. Using the least squares method, it was found that the presence of S significantly increased the efficiency of U than AS or AN. Incubation of S and the N sources with S in the soil was carried out to understand the growth conditions of cotton fertilized by U in alkalin soil. In the case of U-soil system, the pH increased. NO2−N accumulated and considerable loss of N took place. The pH, NO2−N accumulation and the loss of N decreased with S increments.
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    Differences in nitrate uptake of species from habitats rich or poor in nitrogen when grown at low nitrate concentrations, using a new growth technique (1981)
    Springer
    Plant and soil 62 (1981), S. 265-278 
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    ISSN: 1573-5036
    Keywords: Competition ; Ecophysiology ; Hypochaeris radicata ; Nitrate ; Nitrate uptake ; Urtica dioica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method is described for culturing plants at extremely low nutrient concentrations. Using a Braun infusion pump, a fixed amount of nitrate or ammonium was supplied continuously to plants growing in a culture vessel at a rate limiting the uptake of the plants. At a very low nitrogen concentration an equilibrium was established where uptake rate of the plants is equal to the rate of supply by the infusion pump. The nitrogen concentrations reached appeared to be in the order of 1 μM. The method compared the nitrate uptake byHypochaeris radicata L.ssp.radicata, H. radicata ssp.ericetorum Van Soest andUrtica dioica L. and ammonium uptake byH. radicata ssp.radicata andH. radicata ssp.ericetorum. Plants were cultivated in monocultures or in mixed cultures (two species per culture vessel). For the mixed cultures competition for nitrate (or ammonium) between the species was maintained for long periods. The capacities of the uptake systems of two subspecies ofH. radicata from places different in nitrogen supply and pH were adapted equally well to both low nitrate and low ammonium concentrations. Apparently factors other than nitrogen uptake play a part in the distribution of the subspecies. The capacity of the uptake system ofU. dioica, a nitrophilous species, was lower than that ofH. radicata ssp.radicata, a species from places poorer in nitrogen. This difference is related to the different distribution of the two species in the field. The present results are compared with those of previous experiments where Km and Vmax were measured and the significance of both parameters is discussed.
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    A further extension of the method for independently measuring the amount of nitrogen fixed by a legume crop (1981)
    Springer
    Plant and soil 62 (1981), S. 331-336 
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    ISSN: 1573-5036
    Keywords: Legumes ; Nitrogen fixation ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The combination of using15N for determining the amount of nitrogen fixed by a legume crop in field experiments and the labelling of only one treatment at a time in each treatment combination is shown to be conceptually and experimentally valid for determining the effect of cultural practices on the amount of nitrogen fixed by a legume crop.
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    Ectomycorrhizae in coastal miombo woodland of Tanzania (1981)
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    Plant and soil 63 (1981), S. 283-289 
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    ISSN: 1573-5036
    Keywords: Afzelia quanzensis ; Brachystegia spiciformis ; Ectomycorrhiza ; Miombo woodland ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ectomycorrhizae were found in root samples of the treesAfzelia quanzensis Welw. andBrachystegia spiciformis Benth. (Caesalpiniaceae), collected in the coastal miombo type woodland 50 km west of Dar-es-Salaam, Tanzania. Root nodules with a structure resembling that of nitrogen-fixing root nodules of other leguminous plants were observed in theA. quanzensis material. The climate of the locality is rather dry, and strongly seasonal. In the tropics, ectomycorrhizae have previously been found only in humid or rain forest climate zones.
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    Loss of nitrate nitrogen in the soil surface layer in Japanese grassland during the heavy rainfall season and its enhancement by the root mat (1980)
    Springer
    Plant and soil 55 (1980), S. 147-151 
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    ISSN: 1573-5036
    Keywords: Chloride ; Grassland ; Leaching ; Nitrate ; N loss ; Root mat ; Surface layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Measurement of nitrate and chloride in the soil profile have been made in a grassland field at the National Grassland Research Institute, Tochigi, which received heavy applications at the rate of 60 kg/ha of nitrogen and chloride as potassium nitrate and calcium chloride respectively, at 5 days intervals in the summer wet season. The chloride anion was utilized as a tracer of the nitrate anion. Compared with the plots without a root-mat zone (0–2.5 cm), those with a root-mat zone had a lower NO3−N/Cl ratio in the soil surface layer (0–15 cm). Under intensive rainfall (17th July to 5th Sept., 519 mm) and high temperature (23°C), the surface root zone of the grass sward was assumed to be in a significantly reducing condition. From the change of NO3−N/Cl ratio in the soil profile and the plant uptake of nitrogen and chloride, considerable reduction of NO3−N and its loss from the root-mat zone was suggested.
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    URL: http://dx.doi.org/10.1007/BF02149718
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    A pellet method to demonstrate nitrogen fixation by free-living rhizobia (1980)
    Springer
    Plant and soil 55 (1980), S. 163-165 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Nitrogen fixation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method is described to demonstrate nitrogen fixation by free-living Rhizobium cells. After aerobic growth in a nutrient solution, the bacteria are centrifuged. Acetylene reduction by the rhizobial cells in the pellet can be measured within a few days. Hydrogen gas frequently stimulates acetylene reduction.
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    URL: http://dx.doi.org/10.1007/BF02149721
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    Influence of phosphorus and sulfur nutrition on composition ofClitoria ternatea L. (1980)
    Springer
    Plant and soil 55 (1980), S. 251-259 
    Details
    ISSN: 1573-5036
    Keywords: Nodulation ; Nitrate ; N-fertilization ; Plant P, S, N ; Sugar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A greenhouse experiment on a silt loam surface soil (Typic Hapludult) was done to investigate effects of P and S on yield, quality aspects and sugar reserves in the tropical forage legumeClitoria ternatea L. Four levels of P and two N treatments (NH4NO3 vs symbiotic) were arranged in a factorial design with four replications. After the first cutting two levels of S were imposed on this design. Phosphorus enhanced dry matter yield in the first cutting. Its effect was smaller in the second cutting. Amount of P required to produce maximum plant yield dropped from 200 mg/kg soil (or more) at the first cutting to 50–100 mg/kg at the second. Added S improved growth at suboptimal levels of P. At optimal P and S, symbiotic and +N plants yielded alike. Phosphorus and S fertilization caused several changes in plant composition. Nitrogen concentration was raised by S treatment and lowered by P. Combined addition of P and S lowered plant nitrate content. In symbiotic plants, soluble sugar concentrations were higher than in N-treated plants, and were increased by P and S treatment. In N-treated plants, neither P nor S increased reducing sugar concentration, but they increased total sugar.
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    URL: http://dx.doi.org/10.1007/BF02181805
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    Effect of calcium carbonate on ammonium and urea nutrition of young tea plants (Camellia sinensis L.) grown in sand culture (1980)
    Springer
    Plant and soil 55 (1980), S. 455-463 
    Details
    ISSN: 1573-5036
    Keywords: Acidity control ; Ammonium sulphate ; Calcium carbonate ; Nitrate ; Nitrification ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary When calcium carbonate incorporated nutrient solution containing ammonium sulphate was added to sand in pots marked nitrification of the added ammonium was noted. It resulted in improved growth of tea plants and the toxicity effects of ammonium ions were completely eliminated. Where urea was used as the form of N supply, moderate (50%) nitrification was observed to occur even in the absence of calcium carbonate, however it was very rapid in its presence.
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    URL: http://dx.doi.org/10.1007/BF02182705
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    Nitrogen fixation in hardwood forests of the northeastern United States (1980)
    Springer
    Plant and soil 54 (1980), S. 33-44 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Harwood forests ; Nitrogen cycle ; Nitrogen fixation ; United States ; Wood litter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen-fixing activity in hardwood forests of the northeastern United States occurred in wood litter, greater than 2 cm in diameter. Activity in large dead wood was independent of species, in the case of deciduous wood litter, but was restricted to partially decayed wood with a high moisture content. Maximum rates of activity were observed in the summer months, minimum rates in the winter. Evidence from six stands of varying ages showed that fixation in large wood litter occurred in only 25% of the samples assayed. Fixation was highest in the youngest, 4 years, and oldest, over 200 years, stands; being about 2 kg/ha/yr. The quantity of nitrogen fixed appears to be related to the biomass of dead wood. Large amounts of wood litter in the youngest stands were from slash left after cutting. As the supply of slash is exhausted by decay, nitrogen fixation decreases, with a low around year 20. Fixation then gradually increases as natural thinning adds wood to the litter compartment. Apparently, the amount of nitrogen fixed in dead wood the first 20 years following clearcutting can only replace a modest fraction of the amount lost as a result of the cutting and product removal. Finally, the results indicate that nitrogen fixation in wood litter does not equal nitrogen fixation in a northern hardwood forest calculated using a mass balance approach, suggesting that additional nitrogen inputs exist.
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    URL: http://dx.doi.org/10.1007/BF02181997
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    Influence of ammonium and nitrate nitrogen on nitrogenase activity of pea plants as affected by light intensity and sugar addition (1980)
    Springer
    Plant and soil 54 (1980), S. 271-282 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Ammonium ; Bacteroids ; Carbohydrate supply ; Nitrate ; Nitrogenase ; Pea ; Pisum sativum ; Rhizobium leguminosarum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Addition of ammonium chloride or potassium nitrate to nodulated pea plants resulted in a decrease in acetylene-reducing activity. Both nodule growth and specific activity of the nodules were diminished. Acetylene-reducing activity of isolated bacteroids, treated with EDTA-toluene and supplied with ATP and dithionite, had not decreased after a 3-day treatment of the plants with NH4Cl or KNO3. The effect of combined nitrogen could be counteracted by raising the light intensity or by the addition of sucrose to the growth medium. The latter treatment reduced the nitrogen uptake by the plants. It is concluded that combined nitrogen affects symbiotic nitrogen fixation via the carbohydrate supply to the bacteroids.
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    URL: http://dx.doi.org/10.1007/BF02181853
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    The influence of mineral amendments on the changes in the organic nitrogen components of composts (1980)
    Springer
    Plant and soil 54 (1980), S. 259-270 
    Details
    ISSN: 1573-5036
    Keywords: Amino acid ; Amino sugar ; Ammonium ; Bentonite ; Clay ; Compost ; Decomposition ; Galactosamine ; Glucosamine ; Immobilization ; Kaolinite ; Muramic acid ; Nitrate ; Straw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A series of straw composts, containing two levels of ammonium nitrate, were incubated with mineral amendments. Rate of decomposition was at a maximum over the first twenty days and was not influenced by the level of added nitrogne. The presence of bentonite and kaolinite reduced the loss of organic material slightly over the period of 150 days. In the low-N series, all the added inorganic nitrogen was immediately immobilized but in the high-N series inorganic N was slightly in excess of the microorganisms requirements. Little or no remineralization occurred. As a result of immobilization there was a rapid increase in amino acid and amino sugar nitrogen over the first 30 days and the values then remained fairly constant. The amino acid and amino sugar levels were slightly higher in the composts containing bentonite and kaolinite. In the early stages of the composting process, approximately half the organic nitrogen was soluble in phosphate buffer but the amount decreased with time of composting. Similarly, the amount of extracted nitrogen which could be hydrolysed by proteolytic enzymes, decreased with time. The composition of amino sugars liberated by acid hydrolysis suggested that chitin, probably of fungal origin, accounted for much of the amino sugar nitrogen and there is some evidence from oxidation studies for this. As composting proceeded, the amount of galactosamine increased and eventually muramic acid was identified indicating an increase in the bacterial flora.
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    URL: http://dx.doi.org/10.1007/BF02181852
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    Effect of nutrient medium pH on symbiotic nitrogen fixation byRhizobium leguminosarum andPisum sativum (1980)
    Springer
    Plant and soil 56 (1980), S. 71-80 
    Details
    ISSN: 1573-5036
    Keywords: Acid-sensitive step ; Nitrogen content ; Nitrogen fixation ; Pisum sativum ; Rhizobium leguminosarum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experiments were performed to measure the pH-sensitive steps in nodulation and symbiotic fixation byPisum sativum and isolate RP-212-1 ofRhizobium leguminosarum. An aeroponic system with rigorous pH control was used to obtain numerous effective nodules. After exposure to various pH levels, the following responses were measured: (1) legume root growth and development, (2) survival and growth rate of a single effective bacterial isolate, (3) degree of nodulation, (4) rate of nitrogen fixation, (5) plant biomass, and (6) nitrogen content of plants. Both bacterial growth and root development were adequate at all pH levels from 4.4 to 6.6, but efficient nodulation and nitrogen fixation did not occur at pH 4.8 and below. The processes required for symbiosis were about 10 times as sensitive to acidity as either bacterial growth or root growth alone. Nodulation was the most acid-sensitive step.
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    URL: http://dx.doi.org/10.1007/BF02197954
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    Association of cation and organic anion accumulation with iron chlorosis of Scots pine on prairie soils (1980)
    Springer
    Plant and soil 56 (1980), S. 293-300 
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    ISSN: 1573-5036
    Keywords: Calcareous soils ; Calcium ; Cation-anion balance ; Induced-iron chlorosis ; Nitrate ; Organic anions ; Pinus sylvestris L ; Prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Iron chlorosis of 4 year old Scots pine (Pinus sylvestris L.) in comparison to areas of adjacent healthy growth on calcareous prairie soil, was associated with slight increases in the soluble ion content of the saturation paste extract. Such increases in soluble ions (mainly calcium sulphate) were associated with significant increases in ash, cation (including iron) and organic anion content of the chlorotic needles. Increasing levels of available soil nitrate were also related to increase in organic anions. Nitrogen and phosphorus assimilation was adversely affected under conditions of iron chlorosis. These observations support the theory of induced iron deficiency associated with elevated levels of organic anions or translocated cations and are applicable to plantings of conifers on prairie soils.
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    URL: http://dx.doi.org/10.1007/BF02205858
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    Non-destructive semi-quantitative determination of acetylene reduction in the field (1980)
    Springer
    Plant and soil 56 (1980), S. 335-340 
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    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Field method ; Nitrogen fixation ; Non-destructive ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Direct injection of acetylene into soil around plant roots, followed by determination of ethylene/acetylene ratios in the soil atmosphere has been tested as a rapid, non-destructive method of estimating acetylene reducing activity. In pots of artificial media as well as in field soil, the ratios determined within 10 min. after injection were significantly correlated with the rates of acetylenedependent ethylene production in detached roots. The method may be useful in preliminary screening of large numbers of plant-bacteria combinations.
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    URL: http://dx.doi.org/10.1007/BF02205862
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    Effects of boron on nitrogen metabolism and sugar levels of sugar beet (1980)
    Springer
    Plant and soil 57 (1980), S. 3-9 
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    ISSN: 1573-5036
    Keywords: B-deficient ; B-toxic ; Corrections ; Growth ; Leaf ; Metabolism ; Molybdenum ; Nitrate ; NRase ; Potassium ; Root ; Sap ; Sugar ; Yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of deficient and toxic levels of boron on various aspects of nitrogen metabolism in sugar beet are studied. Plant analysis shows a nitrate ion accumulation, a decrease in the activity of the nitrate reductase enzyme and a lower molybdenum absorption. The effect of boron levels on the plant and root sugar concentration has also been studied.
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    URL: http://dx.doi.org/10.1007/BF02139636
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    Heterotrophic nitrogen fixation (acetylene reduction) associated to flooded rice: A modified measurement technique in the field (1980)
    Springer
    Plant and soil 57 (1980), S. 439-453 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Nitrogen fixation ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A modifiedin situ technique for measuring heterotrophic nitrogen fixing (acetylene reducing) activity associated to rice is proposed. Ethylene evolution rates measured in opaque cylinders covering the stems of rice plants which have been cut 10 cm over the water level were found independent of the diurnal cycle. Cutting of the leaves resulted in decreased variation between plants and suppression of the acceleration of ethylene evolution rate after 12 h incubation as compared to intact plants. In both systems ethylene evolved was swept by a current of methane and the molar ratio between methane and ethylene was stabilized after 12 h. Methane evolution rates remained stable during 12 h and more than 24 h in whole plants and cut plants respectively. It is suggested that alteration in the active gas transport system after 12 h incubation under 10% acetylene may lead to erroneous evaluation of the actual ethylene production in the root's environment. The average values of ethylene evolution rates by cut plants between 12 and 24 h of incubation may be used for comparative studies of nitrogen fixing activity associated to flooded rice.
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    URL: http://dx.doi.org/10.1007/BF02211701
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    Nitrate reductase activity in corn seedlings as influenced byArthrobacter sp. (1980)
    Springer
    Plant and soil 57 (1980), S. 481-485 
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    ISSN: 1573-5036
    Keywords: Arthrobacter sp. ; Corn seedlings GA3 ; IAA ; IPA ; Nitrate ; Nitrate reductase activity ; Phytohormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrate reductase activity has been assayed in corn seedlings grown in a nutrient solution containing different concentrations of nitrate and inoculated withArthrobacter sp. The enzymatic activity was greatly enhanced especially at the levels of NO3-ions suboptimal for the maximum induction. The ability of synthetic phytohormones (IAA, IPA and GA3) in inducting nitrate reductase activity has been also texted.
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    Net assimilation rate and relative nitrogen assimilation rate in relation to the dry matter production of alfalfa cultivars (1981)
    Springer
    Plant and soil 59 (1981), S. 185-192 
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    ISSN: 1573-5036
    Keywords: Alfalfa ; Correlation coefficient ; Factor analysis ; Leaf area ratio ; Nitrogen fixation ; Net assimilation rate ; Path-coefficient analysis ; Relative growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Twelve alfalfa cultivars inoculated with an indigenous strain (RM9) ofRhizobium meliloti, were compared for their seedling morphological characters, and growth characters, including net assimilation rate (NAR), relative growth rate (RGR), leaf area ratio (LAR) and relative nitrogen assimilation rate (RN). Highly significant differences were obtained between cultivars for most characters. Simple correlation showed that NAR influenced RGR (r=0.91) more than leaf area ratio (LAR) (r=−0.44), and that most characters measured were highly correlated with seedling dry weight. Factor analysis showed that NAR, RGR and RN contributed 25% of the total variation in the dependence structure. The grouping indicated that the higher the NAR and RN the greater was the RGR. Path-coefficient analysis showed that NAR had more important direct and indirect effects than RN in dry matter accumulation. The relationship implied that selection for plants with high NAR, or high efficiency in converting light energy to dry matter production could contribute greater N2 fixation in alfalfa.
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    URL: http://dx.doi.org/10.1007/BF02184191
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    Influence of hexachlorocyclohexane on the nitrogenase activity of rice rhizosphere soil (1981)
    Springer
    Plant and soil 59 (1981), S. 473-477 
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    ISSN: 1573-5036
    Keywords: Hexachloroxyclohexane ; Nitrogenase activity ; Nitrogen fixation ; Redox potential ; Rhizosphere ; Rice plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of application of hexachlorocyclohexane (HCH=gamma BHC), to a submerged tropical field soil at rates equivalent to recommended field rates (1–2.5kg a.i./ha) and twice this level, upon the rhizosphere soil nitrogenase, nitrogen fixers, and soil redox potential (Eh) was investigated. The rhizosphere soil from HCH-treated field exhibited significantly higher nitrogenase activity than that from untreated fields. HCH retarded the drop in redox potential of the field soil upto 80 days after transplantation under submerged conditions. Populations of nitrogen-fixingAzospirillum sp. and Azotobacter, to a greater extent, and anaerobic organisms, to a lesser extent, were stimulated in HCH-treated soils. Results indicate the stimulation of heterotrophic nitrogen-fixing bacteria by HCH in submerged paddy soils.
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    URL: http://dx.doi.org/10.1007/BF02184551
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    Cross-inoculation specificity ofPsophocarpus tetragonolobus (L.) DC (1981)
    Springer
    Plant and soil 60 (1981), S. 139-142 
    Details
    ISSN: 1573-5036
    Keywords: Legumes ; Nitrogen fixation ; Nodulation ; Winged beans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Only legumes of the cowpea cross-inoculation group, including the winged bean (Psophocarpus tetragonolobus) were found to form nodules in a temperate zone soil with no previous history of legume cropping. Isolates from root nodules from uninoculated winged beans grown in the field only nodulated legumes in the cowpea cross-inoculation group.Rhizobium japonicum formed ineffective nodules with the winged bean.
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    URL: http://dx.doi.org/10.1007/BF02377119
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    Dark CO2 fixation in leaves of tomato plants grown with ammonium and nitrate as nitrogen sources (1981)
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    Plant and soil 60 (1981), S. 213-222 
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    ISSN: 1573-5036
    Keywords: Ammonium ; Anaplerotic ; Dark CO2 fixation ; Lycopersicon ; Nitrate ; PEP carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The dark (non-photosynthetic) CO2 fixation was studied in the leaves of ammonium-fed and nitratefed tomato plants. The ability to fix14CO2 in the dark of ammonium-fed plants was remarkably lower as compared with nitrate-fed plants, supporting the previous finding that the synthesis of C4-compounds from C3-compounds was reduced in the leaves of ammonium-fed plants. There was no difference in the activity of PEP carboxylase in extracts prepared from the leaves between both the plants during an early period of the treatment. However, the enzyme activity began to decrease rapidly in ammonium-fed plants 4 days after the treatment. By long-term treatments, the enzyme activity in ammonium-fed plants became half as high as that of nitrate-fed plants. The decreased PEP carboxylase activity in ammonium-fed plants was not associated with the presence of NH4-N and the absence of NO3-N in the leaf extract, and was not restored by the addition of the leaf extract from nitrate-fed plants. It is concluded that the decreased rate of synthesis of C4-compounds from C3-compounds in ammonium-fed plants is closely associated with a decrease in the dark fixation involving PEP carboxylase.
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    Growth and nitrogen fixation ofAeschynomene under water stressed conditions (1981)
    Springer
    Plant and soil 60 (1981), S. 309-315 
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    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Aeschynomene americana ; Flooding ; Leaf water potential ; Nitrogen fixation ; Soil moisture deficits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Studies on the tolerance ofAeschynomene americana L. to periods of flooding or soil moisture deficit were conducted in an attempt to elucidate nitrogen fixation as affected by soil moisture. Nitrogenase activity was not reduced significantly in pot-grown Aeschynomene plants subjected to flooding in greenhouse conditions. After 20 days of withholding water from the soil, nitrogenase activities of the drought-stressed plants were much lower than those of either the well-watered or flooded plants. Leaf water potentials were similar in flooded and control plants; however, the droughted plants had leaf water potentials that were 4 bars lower than those of the control plants. Aeschynomene plants were tolerant to long-term periods of flooding, but exhibited a reduction in nitrogenase activity and leaf water status when subjected to soil moisture deficits.
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    Reduction of the nodulation barrier inMedicago laciniata by alteration of the root temperature (1981)
    Springer
    Plant and soil 61 (1981), S. 93-111 
    Details
    ISSN: 1573-5036
    Keywords: Ineffective nodules ; Medicago laciniata ; Nitrogen fixation ; Nodulation ; Root temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Medicago laciniata, an annual leguminous plant of Saharo-Sindian origin, is particularly refractory to root nodulation by most strains ofRhizobium meliloti. Using a series of such bacterial strains belonging to the 8 groups of Brockwell and Hely, and a variety of environmental conditions, it was noted that several normally non-nodulating strains (at 20°C) produced ineffective nodules at root temperatures of 24°C to 28°C. Nodulation at 20°C failed to occur in the presence of a wide variety of test compounds and physical conditions. No phytoalexins or anti-Rhizobium growth inhibitors were isolated from inoculated root tissue at any temperature. Temperature shift experiments indicated no infection of the root hairs at 20°C, and infection threads produced at the permissive root temperature failed to elongate after transfer to 20°C. However, if meristematic activity had been initiated in the inner root-cortical cells as a result of infection thread penetration at 28°C, no blockage of nodule maturation occurred upon subsequent transfer to 20°C root temperature. Nodules produced at 28°C were completely devoid of nitrogenase activity, although the apical (but not the distal) regions contained normal-appearing bacteriods, surrounded by enclosing membranes, and possessed a fully functional leghaemoglobin. A shortage of metabolic energy did not appear to be involved in the ineffective response. A hypothesis to explain the nodulation phenomenon observed was based on the observation in the roots of 2 factors present at 20°C but not at 28°C.
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    Respiration and nitrogen fixation in nodulated roots of soya bean and pea (1981)
    Springer
    Plant and soil 61 (1981), S. 135-143 
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    ISSN: 1573-5036
    Keywords: Hydrogen ; Nitrogen fixation ; Nodulated roots ; Pea ; Respiration ; Soya bean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Oxygen uptake, carbon dioxide evolution and nitrogenase activity, measured either as hydrogen evolution (under argon 80%, oxygen 20%) or as the reduction of acetylene to ethylene, were assayed over the same time period by a direct mass-spectrometric method. When carbon dioxide evolution was used to estimate carbohydrate consumption, the results agreed with other work on whole plants. The RQ values obtained in these experiments were always less than 1.0 and thus the carbohydrate consumption calculated from oxygen uptake suggests that previous estimates, using carbon dioxide evolution as a measure of the cost of nitrogen fixation may be underestimates. Lag periods observed in the reduction of acetylene to ethylene suggest that there is a resistance to diffusion of gases in the root nodules.
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    Salinity tolerance of the tree legumes: Mesquite (Prosopis glandulosa var.torreyana, P. velutina andP. articulata) Algarrobo (P. chilensis), Kiawe (P. pallida) and Tamarugo (P. tamarugo) grown in sand culture on nitrogen-free media (1981)
    Springer
    Plant and soil 61 (1981), S. 311-317 
    Details
    ISSN: 1573-5036
    Keywords: Biofuel ; Leguminous trees ; Nitrogen fixation ; Semi-arid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sand culture pot experiments were carried out with Proposis seedlings in the greenhouse on a nitrogen free nutrient solution with increasing levels of sodium chloride. All species tolerated a 6,000 mg/l salinity with no reduction in growth.P. velutina was the only species that poorly tolerated the 12,000 mg/l salinity level.P. articulata, P. pallida, andP. tamarugo tolerated 18,000 mg/l NaCl with little reduction in growth and grew slightly in a salinity (36,000 mg/l NaCl) greater than seawater. This is the first legume known to grown in salinities equivalent to seawater.
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    Characteristics of nitrogen-fixingKlebsiella oxytoca isolated from wheat roots (1981)
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    Plant and soil 61 (1981), S. 53-63 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Inoculation ; Klebsiella oxytoca ; Nitrogen fixation ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Of 45 fermentative gram negative bacterial isolates examined from wheat roots, three were capable of fixing atmospheric nitrogen as determined by the acetylene reduction technique and by protein contents of cells. A gram negative non-motile facultatively anaerobic bacterial strain capable of N2 fixation was identified asKlebsiella oxytoca ZMK-2. Optimal growth and N2 fixation occurred at pH 6.5. The optimum temperatures for growth under anaerobic conditions ranged between 30°–37°C. Acetylene reduction by intact cells was strikingly inhibited by 0.1 atm. or greater partial pressure of O2. Furthermore, the accumulation of H2 in the gas phase over cultures ofKlebsiella oxytoca ZMK-2 at partial pressures greater than 0.02 atm. resulted in a striking inhibition in the rate of C2H2 reduction. The addition of suspensions of eitherKlebsiella oxytoca ZMK-2 orAzotobacter vinelandii or a mixed culture of these two organisms to axenic cultures of wheat plants produced no significant increase in plant growth as measured by plant dry weight or nitrogen content of plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277362
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  • 89
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    Effect of Azospirillum inoculation on some growth parameters and n-content of wheat, sorghum and panicum (1981)
    Springer
    Plant and soil 61 (1981), S. 65-70 
    Details
    ISSN: 1573-5036
    Keywords: Azospirillum brasilense ; Cereals ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The potential of the nitrogen fixing bacteriumAzospirillum brasilense to enhance development and increase growth of several gramineae was investigated. In both sterilized and non-sterilized systems heading and flowering occurred earlier in the inoculated plants as compared to the noninoculated ones. Total shoot and root weights, total-N content, plant height and leaf length were significantly increased by inoculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277363
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  • 90
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    Effect of host plant selection and temperature on the structure of root nodules of red clover (Trifolium pratense L.) (1981)
    Springer
    Plant and soil 61 (1981), S. 113-124 
    Details
    ISSN: 1573-5036
    Keywords: Host selection ; Nitrogen fixation ; Nodule structure ; Rhizobium trifolii ; TemperatureTrifolium pratense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary 1. Nodule structure was examined in the red clover cultivar S123 and in lines (designated H2) separately bred for high yield withRhizobium trifolii strains RCR 0403 and RCR 5. Plants were grown at 16/11, 22/17 and 27/22°C in a 16 h day at 25,000 lux. 2. The larger yields of bred lines compared with S123 were directly correlated with larger aggregate nodule size, larger infected zones and with more bacteroid tissue. Over all treatments the correlation of plant dry weight with aggregate areas of bacteroid tissue, assessed in median longitudinal section, accounted for 79% of the variance. 3. Yields were unrelated to the proportion of uninfected cells and vacuoles within the bacteroid zone. 4. Effects of host type and strain on nodule structure and yield were greatest at the moderate temperature and least and most irregular at high temperature. 5. Bacteriod tissue degenerated more rapidly in S123 than in the bred lines, more rapidly with RCR 0403 than RCR 5 and more rapidly at the high temperature than at moderate or low temperatures. 6. Aggregate nodule size irrespective of treatment was correlated with the aggregate sizes of nodule meristem and differentiating tissues. Nodule comtex comprised a larger proportion of the nodule section at 17 days than subsequently. Other than as specified above, the size relationships of the different tissues of the nodule were unaffected by host selection, temperature, bacterial strain or plant age. 7. At 22/17°C over a 17–25 day period the increment in dry matter per mm2 active nodule tissue was similar for H2 and S123 plants and was less for RCR 0403 (3.33 mg) than for RCR 5 (6.87 mg). At 27/22°C the effeciency of bacteroid tissue was much less,viz. 0.67 and 1.23 mg per mm2 respectively. 8. Nodule tissue areas and volumes were closely related so that unit volumes of active bacteriod tissue in general promoted similar dry matter increment in S123 and bred lines,viz. about 50.5 mg mm−3 at 22/17° for RCR 0403 and 80.8 mg mm−3 for RCR 5. The latter was associated with a fixation rate of 0.157 mg N mm−3 active tissue day−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277368
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  • 91
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    Electronic Resource
    Influence of inoculation on yield ofAlnus glutinosa in the Netherlands (1981)
    Springer
    Plant and soil 61 (1981), S. 189-202 
    Details
    ISSN: 1573-5036
    Keywords: Actinomycete symbiosis ; Alder ; Alnus glutinosa ; Endophyte ; Farmyard manure ; Forestry ; Frankia ; Inoculation ; Nitrogen fixation ; Nodulation ; Root nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The occurrence and the infectivity of Frankia, the root-nodule endophyte ofAlnus glutinosa, were studied in different kinds of soil in the Netherlands. Both field and pot experiments indicated that many soils, on which alders have not been grown before, had low numbers of endogenous Frankia or none at all. Inoculation of these soils usually enhanced growth and nodulation of alders. The effect of fertilizer treatments on growth and nodulation ofA. glutinosa were studied in experimental plots. Alders grown in sandy soils, dressed with farmyard manure had the highest yield and the most nodules. The influence of inoculation with homogenates of Sp(+) and Sp(−) nodules and with a pure culture of Frankia AvcIl were studied in pot experiments. The quantity of different kinds of inoculum needed to obtain good growth and nodulation of alder was estimated. The results indicated that addition of a nodule homogenate of 90 g fresh AvcIl Sp(+) nodules is sufficient to inoculate one hectare of nursery soil to produce 10 nodules per plant, while a thousand times larger amount of inoculum is necessary when Sp(−) nodules are used. The limitations and the potentials of using nodule homogenates and pure cultures of Frankia for inoculation in forestry are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277374
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