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  • Ultrastructure  (348)
  • Lepidoptera  (146)
  • Nitrogen fixation  (118)
  • CR: 5.17  (98)
  • 42.60  (90)
  • Seismology
  • Springer  (806)
  • California Institute of Technology Pasadena  (5)
  • Elsevier  (5)
  • North-Holland  (3)
  • Dover Publ.  (2)
  • Division of Earthsciences, Seismological Laboratory, California Institute of Technology
  • 2010-2014  (4)
  • 1980-1984  (808)
  • 1950-1954  (10)
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  • 1
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    Controls of benthic nitrogen fixation and primary production from nutrient enrichment of oligotrophic, Arctic lakes (2013)
    Springer
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecosystems 16 (2013): 1550-1564, doi:10.1007/s10021-013-9701-0.
    Description: We examined controls of benthic dinitrogen (N2) fixation and primary production in oligotrophic lakes in Arctic Alaska, Toolik Field Station (Arctic Long-Term Ecological Research Site). Primary production in many oligotrophic lakes is limited by nitrogen (N), and benthic processes are important for whole-lake function. Oligotrophic lakes are increasingly susceptible to low-level, non-point source nutrient inputs, yet the effects on benthic processes are not well understood. This study examines the results from a whole-lake fertilization experiment in which N and P were added at a relatively low level (4 times natural loading) in Redfield ratio to a shallow (3 m) and a deep (20 m) oligotrophic lake. The two lakes showed similar responses to fertilization: benthic primary production and respiration (each 50–150 mg C m−2 day−1) remained the same, and benthic N2 fixation declined by a factor of three- to fourfold by the second year of treatment (from ~0.35 to 0.1 mg N m−2 day−1). This showed that the response of benthic N2 fixation was de-coupled from the nutrient limitation status of benthic primary producers and raised questions about the mechanisms, which were examined in separate laboratory experiments. Bioassay experiments in intact cores also showed no response of benthic primary production to added N and P, but contrasted with the whole-lake experiment in that N2 fixation did not respond to added N, either alone or in conjunction with P. This inconsistency was likely a result of nitrogenase activity of existing N2 fixers during the relative short duration (9 days) of the bioassay experiment. N2 fixation showed a positive saturating response when light was increased in the laboratory, but was not statistically related to ambient light level in the field, leading us to conclude that light limitation of the benthos from increasing water-column production was not important. Thus, increased N availability in the sediments through direct uptake likely caused a reduction in N2 fixation. These results show the capacity of the benthos in oligotrophic systems to buffer the whole-system response to nutrient addition by the apparent ability for significant nutrient uptake and the rapid decline in N2 fixation in response to added nutrients. Reduced benthic N2 fixation may be an early indicator of a eutrophication response of lakes which precedes the transition from benthic to water-column-dominated systems.
    Description: This project was supported by NSF-OPP 9732281, NSF-DEB 9810222, NSF-DEB 0423385, and by a Doctoral Dissertation Improvement Grant NSF-DEB 0206173. Additional funding was provided by the Small Grants Program through the NSF-IGERT Program in Biogeochemistry and Environmental Change at Cornell University.
    Keywords: Benthic ; Nitrogen fixation ; Primary production ; Oligotrophic ; Arctic ; Toolik
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Core-mantle boundary topography: seismology (2012)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: n/a
    Description: Published
    Description: 125-127
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: restricted
    Keywords: Core-mantle boundary topography ; Seismology ; 04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 3
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    On the seismogenic increase of the ratio of the ULF geomagnetic field components (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Following the paper by Fraser-Smith et al. (1990), many scientists have focused their research on the ULF geomagnetic field pulsations in the hope of finding possible anomalous signals caused by the seismic activity. Thereafter, many papers have reported ULF geomagnetic field polarization ratio increases which have been claimed to be related to the occurrence of moderate and strong earthquakes. Even if there is no firm evidence of correlation between the polarization ratio increase and seismic events, these publications maintain that these ‘‘anomalous’’ increases are without doubt precursors of pending earthquakes. Furthermore, several researchers suggest that these seismogenic signals may be considered a promising approach towards the possibility of developing short-term earthquake prediction capabilities based on electromagnetic precursory signatures. On the contrary, a part of the scientific community emphasizes the lack of validation of claimed seismogenic anomalies and doubt their association with the seismic activity. Since earthquake prediction is a very important topic of social importance, the authenticity of earthquake precursors needs to be carefully checked. The aim of this paper is to investigate the reliability of the ULF magnetic polarization ratio changes as an earthquakes’ precursor. Several polarization ratio increases of the geomagnetic field, which previous researchers have claimed to have a seismogenic origin, are put into question by a qualitative investigation. The analysis takes into account both the temporal evolution of the geomagnetic field polarization ratio reported in previous papers, and the global geomagnetic activity behaviour. Running averages of the geomagnetic index Kp are plotted onto the original figures from previous publications. Moreover, further quantitative analyses are also reported. Here, nine cases are investigated which include 17 earthquakes. In seven cases it is shown that the suggested association between the geomagnetic field polarization ratio increases and the earthquake preparation process seems to be rather doubtful. More precisely, the claimed seismogenic polarization ratio increases are actually closely related to decreases in the geomagnetic activity level. Furthermore, the last two investigated cases seem to be doubtful as well, although a close correspondence between polarization ratio and geomagnetic activity cannot be unambiguously demonstrated.
    Description: Published
    Description: 19-32
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake precursors ; Short-term earthquake prediction ; Geomagnetic field ; Seismology ; 04. Solid Earth::04.05. Geomagnetism::04.05.99. General or miscellaneous ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Using indirect methods to constrain symbiotic nitrogen fixation rates : a case study from an Amazonian rain forest (2010)
    Springer
    Details
    Publication Date: 2022-05-25
    Description: © The Authors 2009. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License. The definitive version was published in Biogeochemistry 99 (2010): 1-13, doi:10.1007/s10533-009-9392-y.
    Description: Human activities have profoundly altered the global nitrogen (N) cycle. Increases in anthropogenic N have had multiple effects on the atmosphere, on terrestrial, freshwater and marine ecosystems, and even on human health. Unfortunately, methodological limitations challenge our ability to directly measure natural N inputs via biological N fixation (BNF)—the largest natural source of new N to ecosystems. This confounds efforts to quantify the extent of anthropogenic perturbation to the N cycle. To address this gap, we used a pair of indirect methods—analytical modeling and N balance—to generate independent estimates of BNF in a presumed hotspot of N fixation, a tropical rain forest site in central Rondônia in the Brazilian Amazon Basin. Our objectives were to attempt to constrain symbiotic N fixation rates in this site using indirect methods, and to assess strengths and weaknesses of this approach by looking for areas of convergence and disagreement between the estimates. This approach yielded two remarkably similar estimates of N fixation. However, when compared to a previously published bottom-up estimate, our analysis indicated much lower N inputs via symbiotic BNF in the Rondônia site than has been suggested for the tropics as a whole. This discrepancy may reflect errors associated with extrapolating bottom-up fluxes from plot-scale measures, those resulting from the indirect analyses, and/or the relatively low abundance of legumes at the Rondônia site. While indirect methods have some limitations, we suggest that until the technological challenges of directly measuring N fixation are overcome, integrated approaches that employ a combination of model-generated and empirically-derived data offer a promising way of constraining N inputs via BNF in natural ecosystems.
    Description: We acknowledge and are grateful for financial support from the Andrew W. Mellon Foundation (C.C. and B.H.), the National Science Foundation (NSF DEB-0515744 to C.C. and A.T. and DEB-0315656 to C.N.), and the NASA LBA Program (NCC5-285 to C.N.).
    Keywords: Amazon Basin ; Ecosystem modeling ; Mass balance ; Nitrogen fixation ; Nutrient cycling ; Rondonia ; Tropical forest
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Electronic Resource
    Electronic Resource
    A potential method for the biharmonic equation (1984)
    Springer
    Numerische Mathematik 43 (1984), S. 105-119 
    Details
    ISSN: 0945-3245
    Keywords: AMS (MOS): 65N30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary A new formulation of the Dirichlet problem for the biharmonic operator is presented. This gives rise to a simple numerical method to solve the above problem. Convergence is proved in the unidimensional case. Numerical results in one and two dimensional test problems are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01389641
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  • 6
    Electronic Resource
    Electronic Resource
    A uniformly convergent difference scheme for a semilinear singular perturbation problem (1984)
    Springer
    Numerische Mathematik 43 (1984), S. 175-198 
    Details
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65 L 10 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary We present a difference scheme for solving a semilinear singular perturbation problem with any number of turning points of arbitrary orders. It is shown that a solution of the scheme converges, uniformly in a perturbation parameter, to that of the continuous problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01390122
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  • 7
    Electronic Resource
    Electronic Resource
    Une méthode numérique pour les problèmes d'équilibre de corps hyperélastiques compressibles en grandes déformations (1984)
    Springer
    Numerische Mathematik 43 (1984), S. 199-224 
    Details
    ISSN: 0945-3245
    Keywords: AMS (MOS): 65 N 30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Description / Table of Contents: Summary This paper uses Augmented Lagrangian techniques for the numerical solution of equilibrium problems of compressible hyperelastic bodies subjected to large deformations. The resulting method is illustrated by several numerical examples.
    Notes: Résumé Cet article applique les techniques de Lagrangien Augmenté à la résolution numérique des problèmes d'équilibre de corps hyperélastiques compressibles soumis à de grandes déformations. La méthode obtenue est illustrée par plusieurs exemples numériques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01390123
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  • 8
    Electronic Resource
    Electronic Resource
    Sex attractants for the fruit-attacking noctuids Orthosia incerta and Orthosia cruda (1984)
    Springer
    Entomologia experimentalis et applicata 36 (1984), S. 15-16 
    Details
    ISSN: 1570-7458
    Keywords: sex attractants ; Lepidoptera ; Noctuidae ; Orthosia incerta ; Orthosia cruda ; fruit pest ; Z9-14:Ac ; Z9-14:Ald ; Z11-16:Ac ; Z11-16:Ald
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345198
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  • 9
    Electronic Resource
    Electronic Resource
    Factors affecting the dispersive behaviour of larvae of an Australian geometrid moth (1984)
    Springer
    Entomologia experimentalis et applicata 35 (1984), S. 159-167 
    Details
    ISSN: 1570-7458
    Keywords: Lepidoptera ; Geometridae ; Ectropis excursaria ; larval dispersal ; colour polymorphism ; phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Acht Experimente wurden durchgeführt, um einige der Faktoren zu studieren, die das Wanderverhalten der Larven (Raupen) eines polyphagen Geometriden (Ectropis excursaria (Guenée)) beein-flussen. 1. Larven sind positiv phototaktisch. Die positive Phototaxis ist negativ mit Fasten, Alter und Populationsdichte korreliert. Bei hohen Temperaturen ist sie nicht mehr nachweisbar. 2. Das Wanderverhalten der Larven wird durch die Populationsdichte beeinflußt, wodurch annähernd eine konstante Dichte erhalten bleibt. Das Verhalten der individuellen Larven is dabei nicht statistisch homogen. Es gibt ‘Wanderer’ und ‘Nicht-Wanderer’. 3. Diese Verhaltensunderschiede stehen möglicherweise im Zusammenhang mit physiologischen und morphologischen Faktoren, die den individuellen Fortpflanzungserfolg und das überleben beeinflussen können; ‘Wanderer’ sind dunkler, entwickeln sich schneller und das Gewicht ihrer Puppen ist niedriger als das der ‘Nicht-Wanderer’. 4. Eine der larvalen Farbvarianten zeigte eine Präferenz für einen von zwei angebotenen Hintergründen.
    Notes: Abstract The dispersive behaviour of larvae of a polyphagous, wide-spread geometrid (Ectropis excursaria (Guenée)) was studied by examining responses to environmental and endogenous variables. It was found that differences in behaviour can be affected by environmental factors such as light, temperature, density, and plant background as well as some physiological and morphological features. The implications of these relationships are discussed as adaptative strategies to a varying environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217535
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  • 10
    Electronic Resource
    Electronic Resource
    Foodplant selection and induction of feeding preference among host and non-host plants in larvae of the tobacco hornworm Manduca sexta (1984)
    Springer
    Entomologia experimentalis et applicata 35 (1984), S. 177-193 
    Details
    ISSN: 1570-7458
    Keywords: induction of feeding preference ; host plants ; non-host plants ; Manduca sexta ; Sphingidae ; Lepidoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Vingt-deux espèces de plantes, dont 10 planteshôtes (Solanées), ont été testés comme plantes alimentaires pour des chenilles de ler stade de Manduca sexta. Sur cet ensemble, seulement 12 plantes (dont 9 plantes hôtes) induisaient la prise de nourriture et permettaient la croissance jusqu'au 5ème stade. La diversité des résultats suggère que les plantes pouvaient être classées en hôtes, non-hôtes acceptables et non-hôtes refusés. En utilisant le test du choix alimentaire préférentiel entre deux rondelles de feuilles, les chenilles néonates de ler stade ont préféré nettement les plantes-hôtes aux autres. Cette préférence initiale pour les plantes-hôtes était préservée quand les cheniles étaient élevées sur plantes-hôtes, mais devenait moins nette ou disparaissait pour des chenilles élevées sur d'autres plantes acceptées. Ainsi l'oligophagie ches M. sexta n'est pas induite, mais doit être héritée. Les chenilles néonates, aussi bien que celles de 5ème stade, présentent des préférences hiérarchisées parmi les plantes hôtes ou non. La seule frontiere nette observée était entre espèces de plantes acceptables ou non. Les hiérarchies préférentielles des chenilles du 5ème stade différaient légèrement lors-qu'elles avaient été élevées sur deux plantes-hôtes différentes. La différence essentielle était l'observation d'une préférence accrue pour l'espèce ayant servi à l'élevage, mais deux autres plantes-hôtes changaient aussi de position hiérarchique. La cause de ces changements de préférence a été approfondie, les chenilles étant élevées sur des feuilles de chaque espèce acceptable (hôte ou non). Leurs préférences alimentaires ont été définies en utilisant des combinaisons diverses (hôte x hôte, hôte x non-hôte acceptable, non-hôte acceptable x non-hôte acceptable). L'induction de la préférence alimentaires a été obtenue dans ces trois associations. Ceci montre que l'induction des choix alimentaires chez M. sexta n'est pas limitée aux plantes-hôtes. Le degré d'induction de la préférence alimentaire variait de très fort à indécelable; il dépendait de l'association examinée. La source de la variabilité de cette induction a été examinée en fonction de la relation entre la force de l'induction et les rapports taxonomiques des plantes associées. La relation obervée était inversée pour M. sexta. L'examen des données de la littérature ont révélé une relation du même type pour les autres espèces de Lépidoptères.
    Notes: Abstract Ten host plant (Solanaceae) and twelve non-host plant species were tested as foodplants for first instar larvae of the tobacco hornworm, Manduca sexta. Only nine host and three non-host plant species elicited feeding and supported growth up to fifth instar. The range of acceptability suggested that plants be divided into hosts, acceptable non-hosts, and unacceptable non-hosts. Using the two-choice feeding preference test we found that the initial preference for hosts was preserved when larvae were reared on hosts, but was less strong or absent for larvae reared on acceptable non-hosts. Thus oligophagy in the tobacco hornworm is not induced, but must be inherited. Newly-hatched first instar larvae and fifth instar larvae showed a preference hierarchy among both hosts and non-hosts. Fifth instar larvae reared separately on two different host species showed slightly different preference hierarchies among hosts. The preference for the rearing plant was increased and also two other host species changed positions in hierarchies. Feeding preferences of larvae reared on hosts or acceptable non-hosts were determined using plant combinations of host vs. host, host vs. acceptable non-host, and acceptable non-host vs. acceptable non-host. Induction of feeding preference was found in all three of these categories. This shows that induction of feeding preference in the tobacco hornworm is not restricted to host plant species. The degree to which feeding preferences were induced ranged from very strong to undetectable and dependend on the plant species paired. The strength of induction in the tobacco hornworm was found to correlate inversely with taxonomic relatedness of the plant species paired. Analysis of induction data from the literature revealed a similar correlation for other lepidopteran species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217537
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  • 11
    Electronic Resource
    Electronic Resource
    Comparison of gravimetry and planimetry in determining dry matter budgets for three species of phytophagous lepidopteran larvae (1984)
    Springer
    Entomologia experimentalis et applicata 35 (1984), S. 255-261 
    Details
    ISSN: 1570-7458
    Keywords: method ; dry matter ; budget ; Lepidoptera ; phytophagous ; gravimetry ; area ; accuracy ; precision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Les budgets en matière sèche consommée par des lépidoptères ont été comparés par les méthodes gravimétrique et planimétrique. La méthode gravimétrique est basée sur le rapport poids sec/poids frais de feuilles consommées par les chenilles. Avec la méthode planimétrique, la quantité d'aliment proposée aux chenilles est déterminée par les tracés de la surface des feuilles et le contenu de matière sèche par unité de surface des feuilles. La méthode de planimétrie permet l'utilisation de plus grands rameaux de feuilles et de cages d'élevage extérieures en gaze. Il n'y avait pas de différence appréciable dans les éléments du budget (croissance, ingestion et déjection), ni aucune différence dans la variabilité observée des données attribuable à la méthode utilisée. Cependant, la variabilité attendue d'après la précision des mesures avec la méthode gravimétrique est inférieure à celle de la méthode planimétrique. est inférieure à celle de la méthode planimétrique. Des éléments expérimentaux, inhérents à la méthode gravimétrique, introduisent une variabilité dans les mesures que l'on n'a pas avec la méthode planimétrique. 30–60% de la variabilité dans la consommation ont été attribués à des paramètres internes à la chenille, même quand elles provenaient toutes de la même ooplaque.
    Notes: Abstract Gravimetric and a combination areal-gravimetric methods for determining dry matter budgets for leaf eating Lepidoptera were compared. The gravimetric method is based on dry weight/live weight ratios of the leaves fed to the larvae. In the areal-gravimetric method, the quantity of food offered to the larvae is determined from the area of leaf tracings and the dry matter content per unit area of the leaves. The areal-gravimetric method permits the use of larger leaf sprays and an open, gauze enclosed rearing chamber. There were no consistent differences in budget factors (growth, ingestion or egestion), nor were there any differences in the observed variability of the data attributable to the method used. However, the expected variability based on instrument precision for the gravimetric method is less than for the areal-gravimetric method. Experimental factors inherent in the gravimetric method introduce variability to the measurements that are not present in the areal method. Thirty to 60% of the variability in budget factors was attributed to intrinsic properties of the larvae, even though the larvae were taken from the same egg masses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369141
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  • 12
    Electronic Resource
    Electronic Resource
    An investigation of laser-induced fluorescence for measuring velocity distributions of neutral atoms using a CW dye laser (1984)
    Springer
    Applied physics 35 (1984), S. 83-93 
    Details
    ISSN: 1432-0649
    Keywords: 32.80 ; 42.60 ; 6.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The velocity distribution of evaporated Zr atoms has been measured by means of laser-induced fluorescence using a cw dye laser by scanning the laser line across the Doppler-broadened absorption line profile of the atoms. It is shown that the experimental data can be explained on the basis of an excitation theory for a three-level system developed from basic principles. It was calculated that the probability for an atom to be in the excited state mainly depends on the radiation-power density of the laser and on the residence time of the atom in the exciting laser light. It was found that the laser frequency must be well stabilized in order to meet the assumptions in the excitation calculation. Otherwise deviations to the theoretical predictions appear in the experimental results due to the jitter of the dye laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697427
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  • 13
    Electronic Resource
    Electronic Resource
    Independently controllable multiline emission from a TEA CO2 laser (1984)
    Springer
    Applied physics 35 (1984), S. 123-126 
    Details
    ISSN: 1432-0649
    Keywords: 42.50 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spatial separation of wavelengths in a CO2-laser resonator helps to avoid competitions. We have achieved this by means of a nearly concentric resonator with a grating or prism in its center. Thus, we demonstrated independent multiline emission with a variety of output spectra. The temporal sequence of the lines was conveniently controlled by varying their losses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697699
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  • 14
    Electronic Resource
    Electronic Resource
    CW and pulsed FIR-CO2 hybrid laser with improved efficiency and amplitude stability at short FIR wavelengths (1984)
    Springer
    Applied physics 33 (1984), S. 23-27 
    Details
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For the first time stable cw output of a FIR-CO2 hybrid laser has been achieved at wavelengths shorter than 300 μm. Due to the saturable absorber characteristic of the FIR laser gas, cw or pulsed emission is observed on both, the CO2 and the FIR laser output, depending on the operating conditions. Results are reported on different resonant lines in CH3OH and the 67 μm Raman line in NH3. The good efficiency of this laser is also demonstrated by the excitation of two new emission lines in CH3OH, namely 49 and 56 μm, pumped by 9R(22) and 9R(24), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690022
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  • 15
    Electronic Resource
    Electronic Resource
    Laser photoion projector (1984)
    Springer
    Applied physics 33 (1984), S. 57-61 
    Details
    ISSN: 1432-0649
    Keywords: 33 ; 42.60 ; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A laser photodesorption microscope has been applied to obtain 4×103-fold images of rhodamine crystals on a tip with a diameter of 66μm. Peculiarities of the formation of these images have been studied with different values of electric field strength on the tip and laser pulse intensities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690026
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  • 16
    Electronic Resource
    Electronic Resource
    Dye-laser frequency stabilization using optical resonators (1984)
    Springer
    Applied physics 33 (1984), S. 179-185 
    Details
    ISSN: 1432-0649
    Keywords: 06 ; 07.60 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe a study, performed using heterodyne techniques, of the frequency fluctuations of two completely independent ring dye lasers locked to independent reference cavities. Single laser linewidths of less than 750 Hz were achieved, the principal limitation being residual vibrations from the noisy laboratory environment. With future design and environmental improvements, ultranarrow linewidths are expected thus providing a useful tool for a great variety of high precision experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688526
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  • 17
    Electronic Resource
    Electronic Resource
    Detection of free NH2(X 2 B 1) radicals by CARS spectroscopy (1984)
    Springer
    Applied physics 33 (1984), S. 213-218 
    Details
    ISSN: 1432-0649
    Keywords: 35 ; 82.40 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract CARS spectra of NH3 and the free NH2-radical in the NH stretch region at 3334 and 3220 cm−1 have been obtained, respectively. The NH2 radicals were generated by laser photolysis of 0.5 mbar NH3 at 193 nm with an ArF-exciplex laser and detected by time resolved CARS spectroscopy.
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    URL: http://dx.doi.org/10.1007/BF00697330
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  • 18
    Electronic Resource
    Electronic Resource
    Frequency measurement chain to 30 THz using FIR schottky diodes and a submillimeter backward wave oscillator (1984)
    Springer
    Applied physics 34 (1984), S. 63-67 
    Details
    ISSN: 1432-0649
    Keywords: 06 ; 07.60 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An infrared frequency measurement chain is reported, the simplicity of which allows phase-coherent frequency measurements up to 30 THz. Frequency measurement is demonstrated on the 10P(28) line of the Lamb-dip stabilized13CO2-laser.
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    Transient orientational grating technique for investigations of fast molecular relaxation processes (1984)
    Springer
    Applied physics 34 (1984), S. 129-137 
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    ISSN: 1432-0649
    Keywords: 33.50 ; 42.10 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A theoretical description of a three-pulse transient grating technique is given where the pump pulses form orientational gratings. Including energy relaxation and angular reorientation the temporal behavior of the diffraction efficiency and energy transmission is discussed with respect to the dependence on the corresponding rate constants and the results are compared with experimental data for Rh6G and RhB. The polarization plane of the pulse diffracted by the grating is found to be rotated in dependence on its initial polarization.
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    Small-signal gain of Free Electron Laser in a resonator Gaussian mode (1984)
    Springer
    Applied physics 35 (1984), S. 163-166 
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    ISSN: 1432-0649
    Keywords: 42.50 ; 42.55 ; 42.60
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    Topics: Physics
    Notes: Abstract We present an analytical expression for the small-signal gain of a Free Electron Laser (FEL) in the presence of a Gaussian mode. To describe the electron beam evolution we use the one-dimensional (1-d) Vlasov equation. Our perturbation result, valid for small values of the parameterq (length of the undulatorL divided by the Rayleigh rangeZ R), can be extrapolated to values ofq≈4÷5.
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    Prospects for vapor-phase dye lasers (1984)
    Springer
    Applied physics 33 (1984), S. 63-74 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 78.30 ; 78.60
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    Topics: Physics
    Notes: Abstract This review covers the field of vapor-phase dye lasers (VPDL) with special emphasis on prospects of gas lasers with optical pumping. Some peculiarities of the gaseous active medium and a possibility to control its density near the critical point are discussed. High specific laser energies (∼0.3J/cm−3), low thresholds, and high efficiencies (20–40%) made it possible to construct a powerful tunable VPDL.
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    A laser optical method for the determination of tropospheric OH concentrations (1984)
    Springer
    Applied physics 33 (1984), S. 103-113 
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    ISSN: 1432-0649
    Keywords: 42.68 ; 42.80 ; 42.60
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    Topics: Physics
    Notes: Abstract A long-path absorption procedure for the determination of tropospheric OH concentrations is described in detail. Initial measurements using this method were carried out in Frankfurt a. M. By including in the evaluation the visible radiation of a frequencydoubled dye laser used in the measurements, it was possible to mathematically reduce the signal fluctuations caused by the scattering and density fluctuations of tropospheric air. The resulting detection limit was 3×106 OH per cm3. SO2 concentrations which had to be simultaneously determined in order to eliminate an interference effect, could be detected in the range of 1–40 ppb on the absorption path.
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    Transverse mode dynamics in a free-electron laser (1984)
    Springer
    Applied physics 33 (1984), S. 9-16 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 42.20 ; 42.55
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    Topics: Physics
    Notes: Abstract We derive the most general equations of motion for the electrons and the electromagnetic field in a free-electron laser including the effects of diffraction and pulse propagation. The field evolution is expressed in terms of the amplitudes and phases of a complete set of transverse modes. The analytic solution is given in the small-signal regime, where the theory is shown to be in excellent agreement with a recent experiment at Orsay.
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    Tritium isotope separation by CO2-laser irradiation at low temperatures (1984)
    Springer
    Applied physics 33 (1984), S. 83-90 
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    ISSN: 1432-0649
    Keywords: 82.50 ; 82.40 ; 42.60
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    Topics: Physics
    Notes: Abstract Tritium isotope separation by CO2-laser induced multiphoton dissociation of CTF3 is investigated. For the optimization of the performance of this working substance, trifluoromethane, the conditions to yield high-selectivity at high-operating pressure and low-critical fluence for complete dissociation are studied using our deconvolution procedure. The irradiation conditions are varied over the following ranges; wavenumber: 1052–1087 cm−1, gas temperature: 25°C to −78°C, CHF3 pressure: 5–205 Torr. The selectivities exceeding 104 are observed for 85–205 Torr CHF3 at −78°C by the irradiation at 1057 cm−1.
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    Directional and wavelength sweep of distributed-feedback dye-laser pulses (1984)
    Springer
    Applied physics 34 (1984), S. 29-31 
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    ISSN: 1432-0649
    Keywords: 42.60
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    Topics: Physics
    Notes: Abstract Directional and wavelength sweep of a pulse train from a distributed-feedback dye laser is studied and found not to be a thermal effect, rather a gain-induced one. The directional sweep can be used for single-pulse selection.
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    Energy transfer in slab dye lasers (1984)
    Springer
    Applied physics 35 (1984), S. 71-75 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55 ; 42.72
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    Topics: Physics
    Notes: Abstract A simple model of the energy transfer between a booster dye and the active dye in a flashlamp pumped planar waveguide dye laser is described. Analytical results are compared with experiments for several dyes in the 600–650 nm region. A twofold increase of laser output was found at a wavelength (630 nm) which is of particular interest for several applications.
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    Simultaneous phase-lock of five CO2 lasers to a primary Cs frequency standard (1984)
    Springer
    Applied physics 35 (1984), S. 119-122 
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    ISSN: 1432-0649
    Keywords: 42.72 ; 42.80 ; 42.60
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    Topics: Physics
    Notes: Abstract The output of a CO2 laser, operating on theP I(18) transition of13C16O2 at 26941 GHz (11.128 μm) was phase-locked to a 5 MHz signal from a primary Cs frequency standard by means of a frequency chain having only CO2 lasers as infrared sources. Simultaneously, four other CO2 lasers in the chain were phase-locked to the 26941 GHz output. This provided CO2 laser frequencies at 26 450 305, 26 940 815, 28 694 625, 29 442 480, and 33 185 715 MHz having zero long-term-average frequency error relative to the Cs standard, and the ±10−13 (≃3 Hz) long-term absolute uncertainty of the standard.
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    Self-phase locking in lasers with homogeneously broadened emission lines (1984)
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    Applied physics 33 (1984), S. 187-193 
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    Keywords: 42.50 ; 42.55 ; 42.60
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    Notes: Abstract It is shown by numerical analysis based on Lamb's equations of motion, that standing-wave lasers with purely homogeneously broadened emission lines exhibit regular multimode oscillations. Specifically, modes lying far from the line centre are quenched due to mode competition, and the amplitudes of the oscillating modes approach steady-state values. The stabilization of the amplitudes is normally accompanied, or followed, by an evolution of the phases towards a phase-locked regime, where the relative phasesψ n = 2φ n −φ n + 1 −φ n − 1 [φ n phase in then th mode, defined by (6)] attain either the value 0 or ± π. The build-up times for the relative phases are found to vary over a wide range.
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    Picosecond gain dynamics of KrF (1984)
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    Applied physics 33 (1984), S. 219-223 
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    Keywords: 42.60
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    Topics: Physics
    Notes: Abstract We describe the generation of excimer-laser pulses of 〈10 ps pulse width and up to 40 mJ pulse energy at 248.5 nm and their use in the measurement of ps gain dynamics in a KrF amplifier. Small-signal gain of 〉2×104, saturation energy density of 2.0 mJ/cm2, and gain recovery time of 4 ns were measured. In contrast to XeCl* no short-gain rcovery time was found in KrF* and the stored inversion could be fully depleted bya single ps pulse.
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    Quantitative lidar at 532 nm for vertical extinction profiles and the effect of relative humidity (1984)
    Springer
    Applied physics 34 (1984), S. 187-189 
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    ISSN: 1432-0649
    Keywords: 42.68 ; 42.60
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    Topics: Physics
    Notes: Abstract An analysis of 532 nm lidar data is presented for the retrieval of vertical extinction profiles. The strong influence of the relative humidity on the extinction-to-backscatter ratio is parametrized for this purpose. A comparison is made between remotely sensed and locally measured extinction coefficients, using reference values in aircraft and at ground level.
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    A subpicosecond dye laser pumped by a xenon ion laser (1984)
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    Applied physics 34 (1984), S. 191-192 
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    Keywords: 42.55 ; 42.60
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    Topics: Physics
    Notes: Abstract A pulsed xenon ion laser has been used to pump a rhodamine 6G dye laser utilizing a ring resonator. The dye laser has been passively mode-locked; a pulsewidth of 0.5 ps and a 50 kW peak power have been obtained.
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    Conditions for the harmonic-like and efficient amplitude modulation of the cw gaussian laser beam by means of a mechanical chopper (1984)
    Springer
    Applied physics 34 (1984), S. 1-4 
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    ISSN: 1432-0649
    Keywords: 42.80 ; 42.60
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    Topics: Physics
    Notes: Abstract The values of the chopping disc slot and mark space widths relative to the radius of the Gaussian beam are found, which achieve optimum harmonic-like and efficient amplitude modulation of the cw laser beam. The simple approximation for the waveform of the modulated laser power valid for these optimum or near optimum values of the chopping disc parameters is presented.
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    On the high-voltage regime of the discharge in hollow-cathode tube (1984)
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    Applied physics 33 (1984), S. 17-21 
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    ISSN: 1432-0649
    Keywords: 52.00 ; 42.60
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    Topics: Physics
    Notes: Abstract A comparison of the operating characteristics of the high-voltage regime of the discharge in a hollow-cathode tube, the hollow-canthode discharge (HCD) and the discharge to a plane cathode are presented. The disappearnce of the hollow-cathode effect and the transition to a high-voltage discharge after inserting several anode rods into the cathode cylinder is exhibited. The similarity between the operating characteristics of such a high-voltage discharge and of a plane cathode discharge is shown. The loss of ions at the anode rods, as well at insulators or floating conductors is believed to be the reason behind the increase of the operating voltage and the disappearance of HCD characteristics. Practical means of increasing the operating voltage are mentioned.
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    Mirror problems of a cw argon-ion laser at high output power (1984)
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    Applied physics 33 (1984), S. 75-77 
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    ISSN: 1432-0649
    Keywords: 42.30 ; 42.60
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    Topics: Physics
    Notes: Abstract We report upon some experiments done on a continuous-wave argon-ion laser which offers 300 W output power in the visible and 34 W in the ultraviolet region of the spectrum, limited by the degradation of the resonator mirrors. To avoid destruction of the outcoupling mirror, a folded three-mirror instead of a two-mirror cavity was tried, resulting in nearly the same output power.
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    Excimer-laser-pumped ps-dye laser (1984)
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    Applied physics 33 (1984), S. 95-98 
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    ISSN: 1432-0649
    Keywords: 42.60
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    Topics: Physics
    Notes: Abstract Generation of single dye laser pulses of 12 ps pulse width (FWHM) and 1.2 mJ pulse energy is described using only one XeCl-excimer laser as pump source. At 1 Hz pulse repetition rate the stability of amplitude and pulse width of these pulses is excellent.
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    Effect of resonant laser light upon a fast-atom charge-exchange source (1984)
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    Applied physics 35 (1984), S. 233-236 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 07.77 ; 34.50
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    Topics: Physics
    Notes: Abstract The effect of resonant laser-light upon a charge-exchange source of eV-range sodium atoms is to decrease the Na kinetic energy by about 2 eV. The mechanism probably involves a reduction of the space charge in the low-energy ion precursors. The reduction is caused by electrons created in collisional ionization of laser-excited atoms. This is related to the well-known optogalvanic effect. A knowledge of the existence of this effect can be important for the design of experiments involving laser driven chemistry.
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    High-order harmonic mixing with Schottky diodes in the FIR region (1984)
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    Applied physics 35 (1984), S. 199-200 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 07.60
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    Topics: Physics
    Notes: Abstract We report results of harmonic mixing experiments between millimetric oscillators and FIR laser radiations up to 3 THz, using micrometer-size Schottky-barrier diodes. Signal-to-noise ratios suitable for precise frequency counting have been obtained for harmonic numbers up to 40.
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    A new blue-green XeF (C→A) excimer laser amplifier concept (1984)
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    Applied physics 35 (1984), S. 227-231 
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    ISSN: 1432-0649
    Keywords: 42.55 ; 42.60
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    Topics: Physics
    Notes: Abstract The feasibility of using the electrically excited XeF(C»A) excimer medium as an efficient wideband amplifier in the blue-green region of the spectrum has been investigated. Calculations show that for an intense blue-green optical flux input the amplification characteristics of XeF(C»A) improve, as a result of both bleaching of the pump induced absorbers and by additional production of XeF(C) level population. The removal of one of the major absorbing species, Xe** in the XeF (C»A) laser mixture by means of a pulsed ruby laser probe beam has been demonstrated.
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    Generation of coherent ultraviolet radiation in the 330 nm region by multiphoton excitation of sodium vapor (1984)
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    Applied physics 33 (1984), S. 155-160 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 42.65
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    Topics: Physics
    Notes: Abstract We report the observation of coherent uv emission at 330.2±0.5 nm when sodium vapor in a heatpipe is irradiated with a pulsed visible dye laser with output wavelength in the 570–595 nm region. It is found that intense uv emission can be produced from Na atoms as well as from Na2 molecules. The excitation functions and their dependence on vapor density and laser power density are presented and the mechanisms for producing the emission are discussed.
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    The evolution of a plant globin gene family (1984)
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    Journal of molecular evolution 21 (1984), S. 19-32 
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    ISSN: 1432-1432
    Keywords: Leghemoglobin ; Gene duplication ; Gene linkage ; Concerted evolution ; Nitrogen fixation ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analyzed the sequences of soybean leghemoglobin genes as an initial step toward understanding their mode of evolution. Alignment of the sequences of plant globin genes with those of animals reveals that (i) based on the proportion of nucleotide substitutions that have occurred at the first, second, and third codon positions, the time of divergence of plant and animal globin gene families appears to be extremely remote (between 900 million and 1.4 billion years ago, if one assumes constancy of evolutionary rate in both the plant and animal lineages) and (ii) in addition to the normal regulatory sequences on the 5′ end, an approximately 30-base-pair sequence, specific to globin genes, that surrounds the cap site is conserved between the plant and animal globin genes. Comparison of the leghemoglobin sequences with one another shows that (i) the relative amount of sequence divergence in various coding and noncoding regions is roughly similar to that found for animal globin genes and (ii) as in animal globin genes, the positions of insertions and deletions in the intervening sequences often coincide with the locations of direct repeats. Thus, the mode of evolution of the plant globin genes appears to resemble, in many ways, that of their animal counterparts. We contrast the overall intergenic organization of the plant globin genes with that of animal genes, and discuss the possibility of the concerted evolution of the leghemoglobin genes.
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    Superconvergence phenomenon in the finite element method arising from averaging gradients (1984)
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    Numerische Mathematik 45 (1984), S. 105-116 
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    ISSN: 0945-3245
    Keywords: AMS(MOS) 65 N 30 ; CR: 5.17
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    Topics: Mathematics
    Notes: Summary We study a superconvergence phenomenon which can be obtained when solving a 2nd order elliptic problem by the usual linear elements. The averaged gradient is a piecewise linear continuous vector field, the value of which at any nodal point is an average of gradients of linear elements on triangles incident with this nodal point. The convergence rate of the averaged gradient to an exact gradient in theL 2-norm can locally be higher even by one than that of the original piecewise constant discrete gradient.
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    Asymptotic bounds on the errors of one-step methods (1984)
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    Numerische Mathematik 45 (1984), S. 201-206 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65L05 ; CR: 5.17
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    Topics: Mathematics
    Notes: Summary Bulirsch and Stoer have shown how to construct asymptotic upper and lower bounds on the true (global) errors resulting from the solution by extrapolation of the initial value problem for a system of ordinary differential equations. It is shown here how to do this for any one-step method endowed with an asymptotically correct local error estimator. The one-step method can be changed at every step.
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    Optical klystron experiments for the ACO storage ring Free Electron Laser (1984)
    Springer
    Applied physics 34 (1984), S. 207-219 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55
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    Topics: Physics
    Notes: Abstract To improve the gain in the Orsay storage ring Free Electron Laser (FEL) experiment, the 17 period permanent magnet undulator has been modified to form an optical klystron (OK). We report the measurement of spontaneous emission and the effects on it of energy spread and angular spread. Gain and laser induced bunch lengthening measurements with the OK are also reported and are in very good agreement with the FEL classical theory. The spontaneous emission spectrum which is easy to measure with good signal to noise ratio, turns out to be a very good diagnostic tool forenergy spread and angular spread measurements on storage rings. The factor of four increase in the small gain obtained by converting the undulator NOEL into an OK was the critical factor in the recent operation of the ACO storage ring laser above threshold.
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    CVL-pumped dye laser for spectroscopic application (1984)
    Springer
    Applied physics 35 (1984), S. 31-36 
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    ISSN: 1432-0649
    Keywords: 42.60 ; 33 ; 36
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A spectroscopic dye laser system-pumped by a Copper Vapor Laser (CVL)-has been built and optimized for different dye solutions operating in the spectral range from 530 to 890 nm. Conversion efficiencies up to 40% were reached in broad band operation, 24% with a prism expander grating cavity, and 20% in grazing incidence configuration, which operated at typical band widths of 3 GHz. Second harmonic generation (SHG) of the dye laser output produced tunable uv-radiation between 260 and 408 nm at conversion efficiencies ≦5%. Fundamental and SHG output were used for resonant ionization experiments in molecular beams.
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    Vanadium oxidation as a result of cw CO2 laser irradiation in atmospheric air (1984)
    Springer
    Applied physics 35 (1984), S. 103-108 
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    ISSN: 1432-0630
    Keywords: 42.60 ; 68.55 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract New results are reported concerning the vanadium oxidation by cw CO2 laser irradiation in air at atmospheric pressure. Particular emphasis is paid both to the initial stage and the development of the oxidation process under the action of the laser radiation. Some aspects are finally discussed concerning the quantitative theoretical interpretation of the experimentally recorded data.
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    A finite element method for a boundary value problem of mixed type (1984)
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    Numerische Mathematik 44 (1984), S. 191-200 
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    ISSN: 0945-3245
    Keywords: AMS (MOS): Primary 65M05, 65M10, 65M15 ; Secondary: 35M05 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary We consider the numerical solution of the boundary value problem (1) $$(1) Lu = k(y)u_{xx} + u_{yy} - c(x,y)u = f, u|_{\Gamma _0 \cup \Gamma _1 } = 0,$$ where $$k(y) \gtreqless 0$$ for $$y \gtreqless 0$$ Г 0 andГ 1 are parts of the boundary of a bounded simply connected regionG inR 2.G is bounded fory〉0 by a piecewise smooth curveГ 0 which intersects the liney=0 at the pointsA(−1,0) andB(0, 0). Fory〈0,G is bounded by a piecewise smooth curveГ 1 throughA, which meets the characteristic of (1) issued fromB at pointC, and by the curveГ 2 which consists of the portionCB of the characteristic throughB. Using a weak formulation based on different spaces of test and trial functions, we construct a Galerkin procedure for the above boundary value problem. Existence, uniqueness and uniform stability of an approximate solution is proven and a priori error bounds are given.
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    On the convergence of difference schemes for the approximation of solutionsu ∈ W 2 m (m〉0.5) of elliptic equations with mixed derivatives (1984)
    Springer
    Numerische Mathematik 44 (1984), S. 223-232 
    Details
    ISSN: 0945-3245
    Keywords: AMS: 65N10 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary The paper deals with such estimates of the rate of convergence of difference methods, which are compatible with the smoothness of the exact solutionu ∈ W 2 m (Ω),m〉0.5, of elliptic equations with mixed derivatives: The error in the norm of the discrete Sobolev spaceW 2 s (ω), ω denoting the set of grid points, is shown to be of the orderO(|h| m−s), 0≦s〈m.
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    Contractivity of locally one-dimensional splitting methods (1984)
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    Numerische Mathematik 44 (1984), S. 247-259 
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    ISSN: 0945-3245
    Keywords: AMS (MOS): 65L05 ; 65M05 ; 65M20 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary The aim of this paper is to study contractivity properties of two locally one-dimensional splitting methods for non-linear, multi-space dimensional parabolic partial differential equations. The term contractivity means that perturbations shall not propagate in the course of the time integration process. By relating the locally one-dimensional methods with contractive integration formulas for ordinary differential systems it can be shown that the splitting methods define contractive numerical solutions for a large class of non-linear parabolic problems without restrictions on the size of the time step.
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    Monotone explicit iterations of the finite element approximations for the nonlinear boundary value problem (1984)
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    Numerische Mathematik 43 (1984), S. 419-437 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65N30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary In this paper, we consider monotone explicit iterations of the finite element schemes for the nonlinear equations associated with the boundary value problem Δu=bu 2, based on piecewise linear polynomials and the lumping operator. These iterations construct the monotonically decreasing and increasing sequences, and convergence proofs are given. Finally, we present some numerical examples verifying the effectiveness of the theory.
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    Free boundary problems with nonlinear source terms (1984)
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    Numerische Mathematik 43 (1984), S. 463-483 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65N30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary The method of lines is used to semi-discretize the non-linear Poisson equation over a domain with a free boundary. The resulting multipoint free boundary problem is solved with a line Gauss-Seidel method which is shown to converge monotonically. The method of lines solution is then shown to converge to the continuous solution of the variational inequality form of the obstacle problem. Some numerical results for the diffusion-reaction equation indicate that the method is applicable to more general free boundary problems for nonlinear elliptic equations.
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    Finite element solution of diffusion problems with irregular data (1984)
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    Numerische Mathematik 43 (1984), S. 309-327 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65 N 30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary Diffusion problems occuring in practice often involve irregularities in the initial or boundary data resulting in a local break-down of the solution's regularity. This may drastically reduce the accuracy of discretization schemes over the whole interval of integration, unless certain precautions are taken. The diagonal Padé schemes of order 2μ, combined with a standard finite element discretization, usually require an unnatural step size restriction in order to achieve even locally optimal accuracy. It is shown here that this restriction can be avoided by means of a sample damping procedure which preserves the order of the discretization and, in the case μ=1, does not increase the costs.
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    Numerical solution of retarded initial value problems: Local and global error and stepsize control (1984)
    Springer
    Numerische Mathematik 43 (1984), S. 343-360 
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    ISSN: 0945-3245
    Keywords: AMS (MOS): 65L05 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary Retarded initial value problems are routinely replaced by an initial value problem of ordinary differential equations along with an appropriate interpolation scheme. Hence one can control the global error of the modified problem but not directly the actual global error of the original problem. In this paper we give an estimate for the actual global error in terms of controllable quantities. Further we show that the notion of local error as inherited from the theory of ordinary differential equations must be generalized for retarded problems. Along with the new definition we are led to developing a reliable basis for a step selection scheme.
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    Asymptotic stability analysis of θ-methods for functional differential equations (1984)
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    Numerische Mathematik 43 (1984), S. 389-396 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65L20 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary Stability analysis of θ-methods for functional differential equations based on the test equation $$\begin{gathered} y'(t) = ay(t - \lambda ) + by(t),t 〉 0 \hfill \\ y(t) = \psi (t),t \in \left[ { - \lambda ,0} \right] \hfill \\ \end{gathered} $$ λ〉0, is presented. It is known thaty(t)→0 ast→∞ if and only if |b|〈−a and we investigate whether this property is inherited by the numerical solution approximatingy.
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    Feedback and adaptive finite element solution of one-dimensional boundary value problems (1984)
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    Numerische Mathematik 44 (1984), S. 75-102 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65L10 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary This paper examines the concepts of feedback and adaptivity for the Finite Element Method. The model problem concernsC 0 elements of arbitrary, fixed degree for a one-dimensional two-point boundary value problem. Three different feedback methods are introduced and a detailed analysis of their adaptivity is given.
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    Combined finite element and spectral approximation of the Navier-Stokes equations (1984)
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    Numerische Mathematik 44 (1984), S. 201-217 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65N30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Description / Table of Contents: Resumé On présente une méthode d'approximation numérique des équations de Navier-Stokes possédant une direction de périodicité. Dans cette direction une méthode pseudospectrale basée sur des développements en série de Fourier est utilisée, dans les deux autres on applique une méthode d'éléments finis standard. On montre que la convergence est optimale et que les deux paramètres de discrétisation peuvent être choisis de façon indépendante.
    Notes: Summary We present a method for the numerical approximation of Navier-Stokes equations with one direction of periodicity. In this direction a Fourier pseudospectral method is used, in the two others a standard F.E.M. is applied. We prove optimal rate of convergence where the two parameters of discretization intervene independently.
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    On the stability of bilinear-constant velocity-pressure finite elements (1984)
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    Numerische Mathematik 44 (1984), S. 219-222 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65N30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary An analysis of the Babuška stability of bilinear/constant finite element pairs for viscous flow calculations is given. An unstable mode not of the checkerboard type is given for which the stability constant turns out to beO(h). Thus, the indicated spaces are not stable in general for numerical calculation.
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    On numerical asymptotic behavior of finite element solutions for parabolic equations (1984)
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    Numerische Mathematik 44 (1984), S. 285-300 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65N30 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary In this paper, we investigate the numerical asymptotic behavior of the finite element solutions for linear parabolic equations under some appropriate conditions. We also give some results of numerical experiments in the two dimensional problems to indicate the effectiveness of our results.
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    Partitioned adaptive Runge-Kutta methods and their stability (1984)
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    Numerische Mathematik 45 (1984), S. 283-300 
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    ISSN: 0945-3245
    Keywords: AMS(MOS): 65L05 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary This paper deals with the solution of partitioned systems of nonlinear stiff differential equations. Given a differential system, the user may specify some equations to be stiff and others to be nonstiff. For the numerical solution of such a system partitioned adaptive Runge-Kutta methods are studied. Nonstiff equations are integrated by an explicit Runge-Kutta method while an adaptive Runge-Kutta method is used for the stiff part of the system. The paper discusses numerical stability and contractivity as well as the implementation and usage of such compound methods. Test results for three partitioned stiff initial value problems for different tolerances are presented.
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    Asymptotic theory of the global error and some techniques of error estimation (1984)
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    Numerische Mathematik 45 (1984), S. 51-74 
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    ISSN: 0945-3245
    Keywords: MR65 M15 ; CR: 5.17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary The error of the approximate solution obtained by discretising a functional equation can be shown under certain conditions to possess an asymptotic expansion in terms of some parameter which is usually a representative step-length. We consider the case of two-parameter expansions, which is particularly relevant to parabolic equations. We derive results for the existence of the expansion and for the application of the classical difference correction and of defect correction. The theory is illustrated by the discussion of a simple parabolic problem
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    Length and shape of enamel crystals (1984)
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    Calcified tissue international 36 (1984), S. 550-555 
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    ISSN: 1432-0827
    Keywords: Enamel crystals ; Length ; Shape ; Apatite ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An original method for fractionating and preparing isolated crystals of homogeneous size was developed. It was demonstrated that enamel apatite crystals are at least 100 µm long. The flexibility of the very long crystallites was demonstrated. Crystal curvatures, accounting for the irregular course of the prisms through the enamel thickness, were visualized and measured. It was shown that in the deep forming enamel layer, lateral branches may grow out of the crystals and crystal fusing often occurs, inducing the crystallites to assume pyramidal shapes with their wide bases pointing toward the dentino-enamel junction and one or two tops toward Tomes' processes. During the maturation process, the two tops of the still immature crystals also fuse so that the mature crystals acquire a rodlike aspect, with parallel faces and steplike graduations along thec axis, allowing a close contact between the crystals. These results support the hypothesis that the crystallites would be continuous from the dentino-enamel junction to the surface.
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    Nitrogen nutrition and the development of biochemical functions associated with nitrogen fixation and ammonia assimilation of nodules on cowpea seedlings (1984)
    Springer
    Planta 162 (1984), S. 327-333 
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    ISSN: 1432-2048
    Keywords: Ammonia ; Nitrogen fixation ; Nodule ; Senescence (root nodules) ; Ureide ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During early development (up to 18 d after sowing) of nodules of an “effective” cowpea symbiosis (Vigna unguiculata (L.) Walp cv. Vita 3: Rhizobium strain CB756), rapidly increasing nitrogenase (EC 1.7.99.2) activity and leghaemoglobin content were accompanied by rapid increases in activities of glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 2.6.1.53), enzymes of denovo purine synthesis (forming inosine monophosphate) xanthine oxidoreductase (EC 1.2.3.2), urate oxidase (EC 1.7.3.3), phosphoenolpyruvate carboxylase (EC 4.1.1.31) and led to increased export of ureides (allantoin and allantoic acid) to the shoot of the host plant in the xylem. Culturing plants with the nodulated root systems maintained in the absence of N2 (in 80 Ar: 20 O2, v/v) had little effect on the rates of induction and increase in nitrogenase activity and leghaemoglobin content but, in the absence of N2 fixation and consequent ammonia production by bacteroids, there was no stimulation of activity of enzymes of ammonia assimilation or of the synthesis of purines or ureides. Addition of NO 3 - (0.1–0.2 mM) relieved host-plant nitrogen deficiency caused by the Ar: O2 treatment but failed to increase levels of enzymes of N metabolism in either the bacteroid or the plant-cell fractions of the nodule. Premature senescence in Ar: O2-grown nodules occurred at 18–20 d after sowing, and resulted in reduced levels of nitrogenase activity and leghaemoglobin but increased the activity of hydroxybutyrate oxidoreductase (EC 1.1.1.30).
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    Isolation and characterization of a new coccoid methanogen, Methanogenium tatii spec. nov. from a solfataric field on Mount Tatio (1984)
    Springer
    Archives of microbiology 137 (1984), S. 308-315 
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    ISSN: 1432-072X
    Keywords: Methanogenium tatii ; Ultrastructure ; Physiology ; Glycoproteins ; DNA-DNA Homology ; Taxonomy ; Archaebacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new coccoid methanogen, Methanogenium tatii, was isolated and characterized. The mesophilic isolate can grow on and produce methane from H2:CO2 and formate. For growth acetate is strictly required. The cell shape, the G+C content of 54 mol% and DNA-DNA homology data suggest it to be a Methanogenium species.
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    The relationship between the state of adenylylation of glutamine synthetase I and the export of ammonium in free-living, N2-fixing Rhizobium (1984)
    Springer
    Archives of microbiology 138 (1984), S. 26-30 
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    ISSN: 1432-072X
    Keywords: Ammonium export ; Ammonium assimilation ; Glutamine synthetase ; Nitrogen fixation ; Rhizobium sp. 32H1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between ammonium assimilation and ammonium export has been studied in free-living, N2-fixing Rhizobium sp. 32H1. After 55 to 67 h of microaerobic growth under a gas phase of 0.2% O2 – 1.0% CO2 – 98.8% Ar high levels of nitrogenase were observed concomitant with a slightly adenylylated glutamine synthetase (GSI) and some glutamine synthetase (GSII) activity. However, after growth of 89 h, or longer, GSI became adenylylated and the level of GSII had decreased. When the gas phase was shifted to 0.2% O2 – 1.0% CO2 – 98.8% N2, a lag was observed before ammonium export could be detected in the 55 to 67 h cultures. No lag in ammonium export was observed in the cultures previously grown for 89 h. The onset of ammonium export in the 55 to 67 h cultures was found to correlate with the adenylylation state of GSI. There appeared to be no correlation between the level of GSII and the export of ammonium. Neither an increase in the adenylylation level of GSI nor ammonium export was observed when the 55 to 67 h cultures were maintained under the Ar gas mixture.
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    Fine structure of the knobby spore type of Streptomyces torulosus (1984)
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    Archives of microbiology 138 (1984), S. 229-232 
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    ISSN: 1432-072X
    Keywords: Actinomycetes ; Streptomyces torulosus ; Morphology ; Ultrastructure ; Verrucate spores ; Knobby ornamentation ; Sheath
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The type strain of Streptomyces torulosus Lyons and Pridham (1971) was studied by scanning- and transmission electron microscope. Spore chains were formed in spirals by aerial mycelium. The spores were connected by nozzles in which small channels could be observed. The knobby ornamentations of the spores arised on a thin fibrous sheath, enveloping the spore chains. These irregular blunt projections, called knobs, had varying diameters of 100 to 250 nm. The base of the knob, consisting of globose to flattened electron dense material, was sitting directly on the sheath. It was covered by several small vesicles of the same material. Each hollow vesicle beared a thin bowlshaped shell of electron transparent material. In general, the cupular bowls and their supporting vesicles became easily depressed on their base, but not detached from the surface of the spores. This type of knobby spore ornamentation was suggested to be designated as a verrucate spore type.
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    Organisation of nodulation and nitrogen fixation genes on a Rhizobium trifolii symbiotic plasmid (1984)
    Springer
    Archives of microbiology 139 (1984), S. 151-157 
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    ISSN: 1432-072X
    Keywords: Rhizobium trifolii ; Symbiosis ; Nodulation ; Nitrogen fixation ; Symbiotic genes ; Reiterated sequences ; Plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Rhizobium trifolii symbiotic plasmid specific gene library was constructed and the physical organisation of regions homologous to nifHDK, nifA and nod genes was determined. These symbiotic gene regions were localised to u 25 kb region on the sym-plasmid, pPN1. In addition four copies of a reiterated sequence were identified on this plasmid, with one copy adjacent to nifH. No rearrangement of these reiterated sequences was observed between R. trifolii bacterial and bacteroid DNA. Analysis of a deletion derivative of pPN1 showed that these sequences were spread over a 110 kb region to the left of nifA.
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    Denitrification by Azospirillum brasilense Sp 7 (1984)
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    Archives of microbiology 138 (1984), S. 212-216 
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    ISSN: 1432-072X
    Keywords: Denitrification ; Nitrate respiration ; Nitrous oxide reduction ; Nitrogen fixation ; Azospirillum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrous oxide reduction can consistently be demonstrated with high activities in cells of Azospirillum brasilense Sp 7 which are grown anaerobically in the presence of low amounts of nitrite. Azospirillum can even grow anaerobically with nitrous oxide in the absence of any other respiratory electron acceptor. Nitrous oxide reduction by Azospirillum is inhibited by acetylene, amytal and weakly by carbon monoxide. Azospirillum converts nitrous oxide to molecular nitrogen without the formation of ammonia. The cells must, therefore, be supplied with ammonia from nitrogen fixation during anaerobic growth with nitrous oxide. When no other nitrogen compound besides nitrous oxide is available in the medium, the bacteria synthesize nitrogenase from protein reserves in about 2 h. Nitrogenase synthesis is blocked by chloramphenicol under these conditions. In contrast, the addition of nitrate or nitrite to the medium represses the synthesis of nitrogenase. Nitrous oxide reduction by Azospirillum and other microorganisms is possibly of ecological significance, because the reaction performed by the bacteria may remove nitrous oxide from soils.
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    Membrane-bound nitrite oxidoreductase of Nitrobacter: evidence for a nitrate reductase system (1984)
    Springer
    Archives of microbiology 140 (1984), S. 153-158 
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    ISSN: 1432-072X
    Keywords: Nitrobacter hamburgensis ; Nitrite oxidoreductase ; Nitrate reductase ; Molybdenum iron-sulfur protein ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite oxidoreductase, the essential enzyme complex of nitrite oxidizing membranes, was isolated from cells of the nitrifying bacterium Nitrobacter hamburgensis. The enzyme system was solubilized and purified in the presence of 0.25% sodium deoxycholate. Nitrite oxidoreductase oxidized nitrite to nitrate in the presence of ferricyanide. The pH optimum was 8.0, and the apparent K m value for nitrite amounted to 3.6 mM. With reduced methyl-and benzylviologen nitrite oxidoreductase exhibited nitrate reductase activity with an apparent K m value of 0.9 mM for nitrate. NADH was also a suitable electron donor for nitrate reduction. The pH optimum was 7.0. Treatment with SDS resulted in the dissociation into 3 subunits of 116,000, 65,000 and 32,000. The enzyme complex contained iron, molydbenum, sulfur and copper. A c-type cytochrome was present. Isolated nitrite oxidoreductase is a particle of 95±30 Å in diameter.
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    Glutathione reductase activity in heterocysts and vegetative cells of the cyanobacterium Nostoc muscorum (1984)
    Springer
    Archives of microbiology 140 (1984), S. 215-217 
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    ISSN: 1432-072X
    Keywords: Glutathione reductase ; Cyanobacteria ; Nostoc muscorum ; O2 protection ; Glutathione ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glutathione reductase activity was detected and characterized in heterocysts and vegetative cells of the cyanobacterium Nostoc muscorum. The activity of the enzyme varied between 50 and 150 nmol reduced glutathione· min-1·mg protein-1, and the apparent Km for NADPH was 0.125 and 0.200 mM for heterocysts and vegetative cells, respectively. The enzyme was found to be sensitive to Zn+2 ions, however, preincubation with oxidized glutathione rendered its resistance to Zn+2 inhibition. Nostoc muscorum filaments were found to contain 0.6–0.7mM glutathione, and it is suggested that glutathione reductase can regenerate reduced glutathione in both cell types. The combined activity of glutathione reductase and isocitrate dehydrogenase in heterocysts was as high as 18 nmol reduced glutathione·min-1·mg protein-1. A relatively high superoxide dismutase activity was found in the two cell types; 34.2 and 64.3 enzyme units·min-1·mg protein-1 in heterocysts and vegetative cells, respectively. We suggest that glutathione reductase plays a role in the protection mechanism which removes oxygen radicals in the N2-fixing cyanobacterium Nostoc muscorum.
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    Attraction of male spruce budworm moths,Choristoneura fumiferana (Clemens), to pheromone-baited traps in small-tree thinnings (1984)
    Springer
    Journal of chemical ecology 10 (1984), S. 125-133 
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    ISSN: 1573-1561
    Keywords: Spruce budworm ; Choristoneura fumiferana ; Lepidoptera ; Tortricidae ; sex pheromone ; small-tree thinnings ; temperature ; precipitation ; wind ; attraction distance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Mean catches of spruce budworm,Choristoneura fumiferana (Clemens), moths were not significantly different among four small-tree thinning treatments of young spruce-fir-hemlock regeneration. Significant inverse relationships were found between trap catches and distances to nearby spruce-fir-hemlock overstory. Prevailing wind directions indicated that moths were attracted anemotactically to upwind pheromone sources. No definite trends were detected between catches and temperature or precipitation.
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    Relative kairomonal activities of 2-acylcyclohexane-1,3-diones in eliciting oviposition behavior from parasiteNemeritis canescens (Grav.) (1984)
    Springer
    Journal of chemical ecology 10 (1984), S. 1597-1601 
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    ISSN: 1573-1561
    Keywords: Kairomone ; 2-acylcyclohexane-1,3-diones ; ovipositionEphestia kuehniella Zeller [syn.Anagasta kuehniella (Zeller)] ; Lepidoptera ; Pyralidae ; Nemeritis canenscens (Grav.) [syn.Venturia canescens (Grav.)] ; Hymenoptera ; Ichneumonidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The relative activities of sixteen 2-acylcyclohexane-1,3-diones from the larval mandibular glands ofEphestia (=Anagasta) kuehniella Zeller in causing the parasiteNemeritis (=Venturia) canescens (Grav.) to make oviposition movements are reported.
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    URL: http://dx.doi.org/10.1007/BF00988427
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    Potential for evolution of resistance to pheromones: Interindividual and interpopulational variation in chemical communication system of pink bollworm moth (1984)
    Springer
    Journal of chemical ecology 10 (1984), S. 1551-1565 
    Details
    ISSN: 1573-1561
    Keywords: Resistance ; mating disruption ; sex pheromone ; (Z,Z)-7 ; 11-hexadecadienyl acetate ; (Z,E)-7 ; 11-hexadecadienyl acetate ; Lepidoptera ; Gelechiidae ; pink bollworm ; Pectinophora gossypiella ; cotton ; pheromone collection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract After an extensive examination of the release rates and blend ratios of pheromonal components emitted by field-collected femalePectinophora gossypiella (Saunders), we find no evidence of resistance to pheromones applied to cotton fields to disrupt mating. Females from fields with 3–5 years of exposure to disruptant pheromones as well as those from fields with only minimal exposure to disruptant pheromones emitted (Z,Z)-7,11-hexadecadienyl acetate at a rate of ca. 0.1 ng/min and (Z,E)7,11-hexadecadienyl acetate at ca. 0.06 ng/min. The ratio of pheromonal components was much less variable than the measured emission rate and was centered about a 61:39Z, Z to Z,E ratio. In contrast to the blend ratio emitted by females, the composition of the pheromonal blend used in monitoring populations and disrupting mating is centered about 50:50 Z,Z to Z.E. In general there was a remarkable consistency in the release rate and blend ratio among populations of females throughout southern California and those from a laboratory colony. It would appear that, although resistance to theP. gossypiella pheromone is still a very real possibility when it is used heavily in pest management as a mating disruptant, there are current agricultural practices and conditions which would hinder its development.
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    URL: http://dx.doi.org/10.1007/BF00988424
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    Structure-activity relationships between stimulus molecule and response of a pheromone receptor cell in turnip moth,Agrotis segetum (1984)
    Springer
    Journal of chemical ecology 10 (1984), S. 1661-1675 
    Details
    ISSN: 1573-1561
    Keywords: Structure-activity relationships ; single-cell recordings ; turnip moth ; Agrotis segetum ; Lepidoptera ; Noctuidae ; molecular shape ; dipole moments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The response of an antennal receptor cell of the turnip moth,Agrotis segetum, was recorded during stimulation with a series of (Z)-7-dodecenyl acetate analogs with structural variations of the acetate group. The investigated receptor cell is known to be highly selective to (Z)-7-dodecenyl acetate. All parts of the acetate group were found to be of great importance for full biological activity. The results indicate very strict requirements on the shape of the polar functional group, as well as on its electron distribution for a successful interaction with the antennal receptor cell.
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    URL: http://dx.doi.org/10.1007/BF00987353
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    Plant-determined variation in the cardenolide content, thin-layer chromatography profiles, and emetic potency of monarch butterflies,Danaus plexippus L. Reared on milkweed plants in California: 2.Asclepias speciosa (1984)
    Springer
    Journal of chemical ecology 10 (1984), S. 601-639 
    Details
    ISSN: 1573-1561
    Keywords: Danaus plexippus ; Lepidoptera ; Danaidae ; monarch butterflies ; Asdepias speciosa ; Asclepiadaceae ; milkweeds ; ecological chemistry ; plant-insect interactions ; chemical ecology ; chemical defense ; coevolution ; thin-layer chromatography ; cardenolide fingerprints ; cardenolides ; cardiac glycosides ; desglucosyrioside ; labriformin ; labriformidin ; syriogenin ; uzarigenin ; emetic potency ; emesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The pattern of variation in gross cardenolide concentration of 111Asclepias speciosa plants collected in six different areas of California is a positively skewed distribution which ranges from 19 to 344 μg of cardenolide per 0.1 g dry weight with a mean of 90 μg per 0.1 g. Butterflies reared individually on these plants in their native habitats ranged from 41 to 547 μg of cardenolide per 0.1 g dry weight with a mean of 179 μg. Total cardenolide per butterfly ranged from 54 to 1279 μg with a mean of 319 μg. Differences in concentrations and total cardenolide contents in the butterflies from the six geographic areas appeared minor, and there were no differences between the males and the females, although the males did weigh significantly more than females. The uptake of cardenolide by the butterflies was found to be a logarithmic function of the plant concentration. This results in regulation: larvae which feed on low-concentration plants produce butterflies with increased cardenolide concentrations relative to those of the plants, and those which feed on high-concentration plants produce butterflies with decreased concentrations. No evidence was adduced that high concentrations of cardenolides in the plants affected the fitness of the butterflies. The mean emetic potencies of the powdered plant and butterfly material were 5.62 and 5.25 blue jay emetic dose fifty units per milligram of cardenolide and the number of ED50 units per butterfly ranged from 0.28 to 6.7 with a mean of 1.67. Monarchs reared onA. speciosa, on average, are only about one tenth as emetic as those reared onA. eriocarpa. UnlikeA. eriocarpa which is limited to California,A. speciosa ranges from California to the Great Plains and is replaced eastwards byA. syriaca L. These two latter milkweed species appear to have a similar array of chemically identical cardenolides, and therefore both must produce butterflies of relatively low emetic potency to birds, with important ecological implications. About 80% of the lower emetic potency of monarchs reared on A. speciosa compared to those reared onA. eriocarpa appears attributable to the higher polarity of the cardenolides inA. speciosa. Thin-layer Chromatographie separation of the cardenolides in two different solvent systems showed that there are 23 cardenolides in theA. speciosa plants of which 20 are stored by the butterflies. There were no differences in the cardenolide spot patterns due either to geographic origin or the sex of the butterflies. As when reared onA. eriocarpa, the butterflies did not store the plant cardenolides withR f values greater than digitoxigenin. However, metabolic transformation of the cardenolides by the larvae appeared minor in comparison to when they were reared onA. eriocarpa. AlthoughA. eriocarpa andA. speciosa contain similar numbers of cardenolides and both contain desglucosyrioside, the cardenolides ofA. speciosa overall are more polar. ThusA. speciosa has no or only small amounts of the nonpolar labriformin and labriformidin, whereas both occur in high concentrations inA. eriocarpa. A. speciosa plants and butterflies also contain uzarigen, syriogenin, and possibly other polar cardenolides withR f values lower than digitoxin. The cardenolide concentration in the leaves is not only considerably less than inA. eriocarpa, but the latex has little to immeasurable cardenolide, whereas that ofA. eriocarpa has very high concentrations of several cardenolides. Quantitative analysis ofR f values of the cardenolide spots, their intensities, and their probabilities of occurrence in the chloroform-methanol-formamide TLC system produced a cardenolide fingerprint pattern very different from that previously established for monarchs reared onA. eriocarpa. This dispels recently published skepticism about the predictibility of chemical fingerprints based upon ingested secondary plant chemicals.
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    Metabolism of uscharidin, a milkweed cardenolide, by tissue homogenates of monarch butterfly larvae,Danaus plexippus L. (1984)
    Springer
    Journal of chemical ecology 10 (1984), S. 945-956 
    Details
    ISSN: 1573-1561
    Keywords: Cardenolide ; uscharidin ; metabolism ; monarch butterfly ; Danaus plexippus ; Lepidoptera ; Danaidae ; milkweed ; Asclepias ; N-demethylation ; mixed function oxidase ; monooxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Midgut and fat body homogenates of monarch butterfly larvae,Danaus plexippus L. (Lepidoptera:Danaidae), were examined for microsomal monooxygenase activity usingp-chloro-N-methylanilineN-demethylation and for the ability to metabolize a milkweed (Asclepias spp.) cardenolide (C23 steroid glycoside), uscharidin. All homogenates tested had bothN-demethylation and uscharidin biotransformation activities. Both transformations required NADPH. The monooxygenase inhibitors sesamex, SKF525A, and carbon monoxide inhibitedN-demethylation but not uscharidin biotransformation. Subsequent subcellular fractionation revealed the uscharidin biotransformation occurs in the soluble fraction and not the microsomal fraction, whileN-demethylation occurs in the microsomal fraction and not the soluble fraction. The larval NADPH-dependent microsomal monooxygenase apparently is not involved in the metabolism of uscharidin.
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    Nitrogen nutrition and the development and senescence of nodules on cowpea seedlings (1984)
    Springer
    Planta 162 (1984), S. 316-326 
    Details
    ISSN: 1432-2048
    Keywords: Nitrogen fixation ; Nodule development ; Senescence (nodules) ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cowpea (Vigna unguiculata (L.) Walp cv. Vita 3) seedlings inoculated with Rhizobium strain CB756 were cultured with their root systems maintained in air or in Ar: O2 (80:20, v/v) during early nodule development (up to 24 d after sowing). Compared with those in air, seedlings in Ar:O2 showed progressive N deficiency with inhibited shoot growth, reduced ribulose-1,5-bisphosphate carboxylase and total protein levels and loss of chlorophyll in the leaves. Nodule initiation, differentiation of infected and uninfected nodule tissues and the ultrastructure of bacteriod-containing cells were similar in the air and Ar: O2 treatments up to 16 d after sowing. Thereafter the Ar: O2 treatment caused cessation of growth and development of nodules, reduced protein levels in bacteroids and nodule plant cells, and progressive degeneration of nodule ultrastructure leading to premature senescence of these organs. Provision of NO 3 - (0.1–0.2 mM) to Ar: O2-grown seedlings overcame the abovementioned consequences of N2 deficiency on nodule and plant growth, but merely delayed the degenerative effects of Ar: O2 treatment on nodule structure and senescence. Treatment of Ar: O2-grown seedlings with NO 3 - greatly increased the protein level of nodules but the increase was largely restricted to the plant cell fraction as opposed to the bacteroids. By contrast, NO 3 - treatment of air-grown seedlings increased protein of bacteroid and host nodule fractions to the same relative extents when compared with air-grown plants not supplemented with NO 3 - . These findings, taken together with studies of the distribution of N in nodules of symbiotically effective plants grown from 15N-labeled seed, indicate that direct incorporation of fixation products by bacteroids may be a critical feature in the establishment and continued growth of an effective symbiosis in the cowpea seedling.
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    URL: http://dx.doi.org/10.1007/BF00396743
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    Ultrastructure of gill epithelial cells of Diopatra neapolitana (Annelida, Polychaeta) (1984)
    Springer
    Zoomorphology 104 (1984), S. 304-309 
    Details
    ISSN: 1432-234X
    Keywords: Ultrastructure ; Gills ; Epithelial cells ; Polychaeta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of gill epidermal cells of Diopatra neapolitana and their relationship with blood spaces are described. The existence of a basal infolding complex, related to the blood spaces, is also reported. A possible involvement of these cells in osmoregulation and ion interchange, apart from their well-known role in respiration, is suggested.
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    Unequal distribution of plastids during generative cell formation in Impatiens (1984)
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    Theoretical and applied genetics 68 (1984), S. 305-309 
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    ISSN: 1432-2242
    Keywords: Impatiens ; Microspore mitosis ; Plastid distribution ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper describes the unequal distribution of plastids in the developing microspores of Impatiens walleriana and Impatiens glandulifera which leads to the exclusion of plastids from the generative cell. During the development from young microspore to the onset of mitosis a change in the organization of the cytoplasm and distribution of organelles is gradually established. This includes the formation of vacuoles at the poles of the elongate-shaped microspores, the movement of the nucleus to a position near the microspore wall in the central part of the cell, and the accumulation of the plastids to a position near the wall at the opposite side of the cell. In Impatiens walleriana, the accumulated plastids are separated from each other by ER cisterns, and some mitochondria are also accumulated. In both Impatiens species, the portion of the microspore in which the generative cell will be formed is completely devoid of plastids at the time mitosis starts.
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    URL: http://dx.doi.org/10.1007/BF00267882
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    Degenerative regression of the digestive tract in the colonial ascidian Botryllus schlossen (Pallas) (1984)
    Springer
    Cell & tissue research 235 (1984), S. 309-318 
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    ISSN: 1432-0878
    Keywords: Ascidian ; Gut ; Cell involution ; Ultrastructure ; Phagocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Degenerative changes in the digestive tract of zooids of Botryllus schlosseri were studied by light and electron microscopy. Three main processes occurred in the tissues: contraction, involution and phagocytosis. The contraction of epidermis and peribranchial epithelium in which cytoplasmic microfilaments probably participate, seemed to have a special role in compressing the underlying organs. During contraction most of the body cavities collapsed, the branchial walls disintegrated and the fragments were rapidly taken up by large phagocytes. The gut epithelium retained its apparent continuity longer, though isolated phagocytes infiltrated it to eliminate single cells. Cell degeneration came about chiefly either through swelling and lysis of cells or through loss of water and condensation of cytoplasm and nucleus. The fate of all regressed tissues was to be engulfed and digested by wandering phagocytes. However, it was also observed that numerous cells of different epithelia could act as fixed phagocytes by engulfing cell debris and entire cells into heterophagic vacuoles.
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    The pig blastocyst: Its ultrastructure and the uptake of protein macromolecules (1984)
    Springer
    Cell & tissue research 235 (1984), S. 347-356 
    Details
    ISSN: 1432-0878
    Keywords: Blastocyst ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Between days 8 and 11 of pregnancy spherical blastocysts from 0.3 to 10 mm in diameter were flushed from the uterine horns of Dutch Landrace pigs. A description of their ultrastructure is given, and the uptake of horseradish peroxidase and ferritin is demonstrated. The ultrastructure of the trophoblast was similar at all ages studied. The trophoblast which has many apical microvilli is able to take up and digest the macromolecules which were offered in the in vitro incubation medium. The hypoblast consists of flattened cells. In blastocysts 2 mm and larger, compact cells bearing microvilli are found below the embryoblast. Cell organelles indicating protein synthesis are found within hypoblast cells of such blastocysts. In the embryoblast, local concentrations of cell organelles are visible, indicating that differentiation has started. After the disappearance of Rauber's layer, which takes place when the blastocyst reaches a diameter of about 2 mm, superficial embryoblast cells develop short microvilli. The cells do not absorb ferritin or peroxidase but are dependent on the trophoblast for their food requirements. All cell layers in the blastocyst contain mitochondria that have characteristics of those found in steroidproducing cells. The significance of the uptake and digestion of macromolecules by trophoblast cells, the synthesis of protein by hypoblast cells and the possible synthesis of steroids is discussed with respect to the relationship between the cell layers of the blastocyst and in the context of conceptomaternal relationships.
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    Changes in human skeletal muscle induced by long-term eccentric exercise (1984)
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    Cell & tissue research 236 (1984), S. 365-372 
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    ISSN: 1432-0878
    Keywords: Skeletal muscles ; Myofibrils ; Ultrastructure ; Exertion ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of muscle fibres from m. vastus lateralis of nine healthy males (mean age 26 years) was investigated. Four individuals constituted non-exercised controls while five subjects participated in a two-months eccentric muscular training program. Specimens from the controls showed a well-preserved, regular myofibrillar band pattern while changes in the myofibrillar architecture were constantly found in specimens taken after the training program. These changes consisted of Z-band alterations, Z-bands being out of register, extra sarcomeres, Z-band extensions and bisected Z-bands. Between the separated Z-band halves, thin and thick myofilaments as well as abundant glycogen particles and/or ribosomes, were observed. Type-2 (fast-twitch) fibres were predominantly affected. Contrary to the controls the trained individuals constantly showed a greater variation in sarcomere lengths in Type-2 fibres than in Type-1 fibres. It is concluded that muscular work of high tension can induce fine-structural alterations. When repeated over a long period of time, extreme tension demands seem to initiate reorganization in the muscle fibres, predominantly in the, ultrastructurally defined, Type-2 fibres. This adaptation probably results in a better stretchability of the muscle fibres, reduces the risk for mechanical damage and brings about an optimal overlap between actin and myosin filaments.
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    Ultrastructure and morphometry of the stomach muscle of Amphiuma tridactylum (1984)
    Springer
    Cell & tissue research 236 (1984), S. 393-397 
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    ISSN: 1432-0878
    Keywords: Smooth muscle ; Salamander, Amphiuma ; Ultrastructure ; Stereology ; Volume: surface area ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural and stereological examination was performed on stomach smooth muscle of the salamander Amphiuma. This tissue has very large cells, ranging up to 12×1500 μm when relaxed. The extracellular space is 31% of the tissue volume, and the tissue contains 84.6% water. These values are similar to those of other amphibian and mammalian gastrointestinal smooth muscle. The cells possess the usual smooth muscle organelles. Thick, thin and intermediate filaments are present, along with membrane-associated and cytoplasmic dense regions. There is a well-developed sarcoplasmic reticulum and many microtubules. Caveolae are found in rows along the cellular surface; the caveolae increase the cellular surface area by about 70%. The ratio mean volume: surface area of the cells is 1.26 μm. This tissue appears to be typical of gastrointestinal smooth muscle, with the exception of the very large size of the cells.
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    Reproduction and sexual development in a freshwater gastrotrich (1984)
    Springer
    Cell & tissue research 236 (1984), S. 619-628 
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    ISSN: 1432-0878
    Keywords: Gastrotricha, freshwater ; Sperm, reduced ; Ultrastructure ; Spermatogenesis ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Spermatogenesis and spermiogenesis in Lepidodermella squammata are confined to the postparthenogenic phase of the life cycle and coincide with developmental changes in the bilateral female gonads. Male stages are bilateral but asynchronous, in the lateral abdomen anterior to the female gonads. Maximum observed sperm production is two packets per side, or 64 sperm. Sperm formation occurs more rapidly at 27° C than at 20° C (p〈0.001), requiring as little as 1 day. Two spermatogonial mitotic divisions produce a clone of four primary spermatocytes connected by bridges (stage 1). Centrioles are absent. Development occurs within a cyst. Meiotic divisions produce 16 spermatids (stage 2), each containing a dense, elongate, tapered nucleus. Cytoplasmic membranes enclose one end of the nuclear rod, excluding all other organelles. Completion of this process results in stage 3, a packet of 16 sperm associated with one dense sphere, a modified ‘residual body’ containing cytoplasmic debris. The residual body then disappears, leaving the sperm packet of stage 4. Each mature sperm is a dense nuclear rod with surrounding membranes, lacking acrosome, mitochondrion, centrioles, and flagellum. Function of sperm has not been demonstrated. The spermatozoa are of a reduced type not previously described.
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    Reproduction and sexual development in a freshwater gastrotrich (1984)
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    Cell & tissue research 236 (1984), S. 629-636 
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    ISSN: 1432-0878
    Keywords: Oocytes, primary ; Gastrotricha, freshwater ; Ultrastructure ; Synaptonemal complex ; X-body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Six small cells are present in each of the bilateral gonads of parthenogenically reproductive Lepidodermella squammata. Early in the extended postparthenogenic phase of the life history, these cells undergo limited proliferation followed by differentiation. Primary oocytes of three types are present 0.3 days after deposition of the final parthenogenic egg: small oocytes with presynaptic nuclei; intermediate oocytes with nuclei containing synaptonemal complexes; and larger oocytes with a germinal vesicle. Oocytes persist without further development at least until day four of the postparthenogenic phase. Older isolated animals may contain and even deposit an enlarged egg, but successful progeny does not result. Oocytes are located at the anterior pole of each of the bilateral gonads, adjacent to developing male tissues producing sperm. More posterior cells in the gonad are initially undifferentated in the postparthenogenic phase. Dorsal and central cells first show specialization for secretory activity, and by day four contain peripheral layers of RER and central accumulations of polymorphic secretion droplets. The posterior and ventral cells produce secretion droplets that aggregate into an enlarging bilobed structure called the X-body. Two or three cells in each gonad contribute secretions to the X-body, which is intracellular in a secondary syncytium formed by the contributing cells. Functions for the postparthenogenic gametes and for the X-body are not yet demonstrated.
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    Arachnoid mater of the bullfrog, Rana catesbeiana (1984)
    Springer
    Cell & tissue research 236 (1984), S. 693-697 
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    ISSN: 1432-0878
    Keywords: Intermediate filaments ; Microtubules ; Caveolae ; Bullfrog ; Arachnoid mater ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the bullfrog, the meninges surrounding the central nervous system include an arachnoid mater that contains layers of cells with abundant intermediate filaments (IFs) having unique organizational characteristics. This membrane contains an inner lamina of cells that resemble fibroblasts and an outer lamina of flattened cells that are almost filled with IFs. The IFs of the outer arachnoid are arranged in compact, arching bundles that lie parallel to the outer surface of the central nervous system. Thus, sections cut tangentially to the membrane reveal bending of filament bundles, whereas transverse sections do not. In some cells bordering the subdural space, bundles of filaments are organized into highly-ordered spiral arrays. Attachments to the numerous desmosomes and, apparently, to the nuclear envelope suggest anchoring of cytoplasmic structures by the IF system. Microtubules occur primarily near the plasma membrane and the nucleus. Numerous caveolae also are associated with the plasma membrane. The unusual abundance, organization, and cytoplasmic relations of IFs in the bullfrog arachnoid suggest that this membrane may serve as an important model for study of fundamental cytoskeletal relations and function.
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    Ultrastructure and innervation of the swimbladder of Tetractenos glaber (Tetraodontidae) (1984)
    Springer
    Cell & tissue research 237 (1984), S. 277-284 
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    ISSN: 1432-0878
    Keywords: Swimbladder ; Teleost ; Cholinergic nerves ; Adrenergic nerves ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The general structure, ultrastructure and innervation of the swimbladder of the smooth toadfish, Tetractenos glaber, were examined with light-microscopic, fluorescence-histochemical, and transmission electron-microscopic techniques. The structure of the swimbladder is similar to that of other euphysoclists. Fluorescence histochemistry showed adrenergic fibres in both the secretory and resorptive areas of the swimbladder. Transmission electron microscopy revealed two morphologically distinct axon profiles type-I profiles containing many small, flattened vesicles; type-II profiles containing both large, granular vesicles and rounded, small clear vesicles in varying proportions. The gas-gland cells and surrounding muscularis mucosae are innervated by both type-I and type-II fibres. Type-I fibres also innervate pre-rete arteries. The rete- and gas-gland capillaries do not appear to be innervated. Arteries running to the resorptive area are innervated by type-I fibres. Both type-I and type-II profiles make contact with the muscularis mucosae in the resorptive area. Only type-I fibres innervate the radial dilator muscle in the oval sphincter region, whereas only type II fibres innervate the circular muscle of the oval sphincter. Type-I fibres took up α-methyl-noradrenaline, and could not be found after pre-treatment with 6-hydroxydopamine. They are, therefore, assumed to be adrenergic. Type-II fibres were tentatively identified, by exclusion, as cholinergic.
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    Fine structure of regenerating scales and their associated cells in the cichlid Hemichromis bimaculatus (Gill) (1984)
    Springer
    Cell & tissue research 237 (1984), S. 537-547 
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    ISSN: 1432-0878
    Keywords: Scale ; Regeneration ; Ultrastructure ; Cichlid ; Hemichromis bimaculatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scale regeneration has been studied in Hemichromis bimaculatus. The removed scale, which serves as a control, is covered by its surrounding scleroblasts as can be seen with scanning electron microscopy. Subsequently, during regeneration, a population of scleroblasts arises in the empty dermal pocket as shown with transmission electron microscopy. At first, an elongated papilla of regeneration forms, probably from the differentiation of dermal fibroblasts. A scale anlage composed of the osseous layer appears in the middle of the papilla, which becomes a regenerating bag. All the surrounding large scleroblasts are involved in scale formation, although later three populations of scleroblasts specialize according to their location around the scale. Superficial scleroblasts flatten when the final thickness of the osseous layer of the scale is attained; the deep scleroblasts are responsible for the formation of the basal plate whereas marginal scleroblasts increase the diameter of the osseous layer of the scale. During scale regeneration, scleroblasts are more numerous and larger than during scale ontogenesis. In particular, deep scleroblasts form a columnar epithelium when the basal plate is laid down, a feature which is not found during scale ontogenesis. Moreover, the regenerated basal plate exhibits an orthogonal “plywood” arrangement that is never seen in the embryonic scale where the “plywood” is of the intermediate type.
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    Ultrastructure of the epididymis of the tammar, Macropus eugenii, and its relationship to sperm maturation (1984)
    Springer
    Cell & tissue research 237 (1984), S. 525-535 
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    ISSN: 1432-0878
    Keywords: Epididymis (marsupials) ; Ultrastructure ; Sperm maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ductus epididymidis of the tammar is lined by an epithelium composed of principal, mitochondria-rich, apical and basal cells, and intraepithelial leucocytes. The epithelium is structurally differentiated into 6 zones referred to as the initial segment, middle segment (3 subdivisions) and terminal segment (2 subdivisions). The occurrence of the initial, middle and terminal segments corresponds quite closely to the anatomical differentiation of the epididymis into a head, body and tail. The initial segment epithelium in the tammar is lower and has shorter and more slender stereocilia than in other mammals which have been described. Otherwise, the structure of the epithelium has similar characteristics in the tammar to that described in other mammals. Spermatozoa begin to develop the capacity for motility within the initial segment, but only show structural signs of maturation in the middle segment. The sperm head rotates through 90 degrees in the proximal subdivision of the middle segment. The cytoplasmic droplet is detached and spermatozoa develop the capacity for motility in the middle subdivision of the middle segment. The cytoplasmic droplets are phagocytosed by the epididymal epithelium of the middle segment. Sperm storage appears to be the main function of the terminal segment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228437
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    Ultrastructural immunocytochemical evidence for peptidergic neurotransmission in the pond snail Lymnaea stagnalis (1984)
    Springer
    Cell & tissue research 238 (1984), S. 197-201 
    Details
    ISSN: 1432-0878
    Keywords: Peptidergic neurotransmission ; Lymnaea stagnalis ; Immunocytochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Three neuronal systems of the pond snail Lymnaea stagnalis were immunocytochemically investigated at the ultrastructural level with the unlabeled peroxidase-antiperoxidase technique. Preliminary electrophysiological and cell-filling investigations have shown that a cluster of neurons which reacts positively with an antiserum against the molluscan cardio-active peptide FMRFamide, sends axons to the penis retractor muscle. In this muscle anti-FMRF-amide (aFM) positive axons form neuro-muscular synapses with (smooth) muscle fibers. The morphological observations suggest the aFM immunoreactive system to be involved in peptidergic neurotransmission. In the right parietal ganglion a large neuron (LYAC) is penetrated by aFM positive axons which form synapse-like structures (SLS) with the LYAC. The assumption that the SLS represent the morphological basis for peptidergic transmission is sustained by the observation that iontophoretical application of synthetic FMRFamide depolarizes the LYAC. The axons of a group of pedal anti-vasopressin (aVP) positive cells run in close vicinity to the cerebral ovulation (neuro-)-hormone producing cell system (CDC system) Synapses or SLS between the two systems were not observed. The fact that (bath) application of arg-vasopressin induces bursting in the CDC, may indicate that the vasopressin-like substance of the aVP cells is released non-synaptically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215162
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  • 89
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    Influence of photoperiod on the ultrastructure of the hypophysial pars tuberalis of the Djungarian hamster, Phodopus sungorus (1984)
    Springer
    Cell & tissue research 238 (1984), S. 213-216 
    Details
    ISSN: 1432-0878
    Keywords: Photoperiods ; Pituitary gland, pars tuberalis ; Ultrastructure ; Phodopus sungorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Conspicuous cytological differences are found between specific secretory cells of the hypophysial pars tuberalis of Djungarian hamsters exposed to long and short photoperiods. The cells differ with respect to the shapes of perikarya and nuclei and show diverse amounts of secretory granules, lysosome-like bodies and glycogen.
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    URL: http://dx.doi.org/10.1007/BF00215166
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  • 90
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    Ultrastructure and immunolabeling of gonadotrops and thyrotrops in the pituitary of the African catfish, Clarias lazera (1984)
    Springer
    Cell & tissue research 238 (1984), S. 95-103 
    Details
    ISSN: 1432-0878
    Keywords: Pituitary gland, pars anterior (distalis) ; Gonadotrops ; Thyrotrops ; Ultrastructure ; Immunolabeling ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pituitaries of the African catfish (Clarias lazera) were studied with immunocytochemical methods, at the light-microscopic and ultrastructural levels, for the characterization and localization of gonadotropic and thyrotropic cells. Two immunostaining procedures with the use of different markers were carried out: (i) with peroxidase-antiperoxidase, (ii) with protein A-gold. In routinely stained sections for light microscopy two types of basophils were identified in the proximal pars distalis: (1) large, round, purple cells, and (2) small, angular, light-blue cells. Both types were immunolabeled with antibodies against Clarias α,β-gonadotropin (GTH) and salmon G100-GTH. Only the large basophils were immunolabeled with anti-carp β-GTH, whereas the small basophils were the only cells immunolabeled with anti-human thyrotropin beta subunit (anti-h TSH-β). It was concluded that the large basophils represent the gonadotrops and the small basophils the thyrotrops. At the ultrastructural level the immunostaining of the GTH-cells was confined to three types of inclusions: (i) secretory vesicles, (ii) globules, and (iii) electron-dense, membrane-bound irregular masses. Especially the protein A- gold method, in combination with the use of a highly diluted homologous antiserum, resulted in a distinct localization of GTH. The presence of two types of nerve fibres, synaptically contacting the gonadotrops, is discussed with regard to the presence of a peptidergic (stimulatory) and an aminergic (inhibitory) control of GTH-secretion.
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    URL: http://dx.doi.org/10.1007/BF00215149
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  • 91
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    Ultrastructural immunocytochemical demonstration of D2-protein in adrenal medulla (1984)
    Springer
    Cell & tissue research 238 (1984), S. 497-502 
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    ISSN: 1432-0878
    Keywords: D2 glycoprotein ; Adrenal gland ; Immunocytochemistry ; Ultrastructure ; Cell adhesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural localization of the glycoprotein D2 in rat adrenal gland was investigated using immunohistochemical methods, and D2 localization in cultures of adult bovine chromaffin cells was studied by immunofluorescence. D2 was found to be situated on nerve fibers passing through the adrenal cortex and in the medulla zone, and also on the surface of all chromaffin cells. In addition, it was strongly expressed on the surface of glial (Schwann) cells. Cortical cells were unreactive to the antiserum. In cultures, all adrenalin and noradrenalin [dopamine-β-hydroxylase (DBH)-positive] cells were surface labelled for D2. A less frequent second cell type was recognized in vitro which was DBH negative but D2 positive. Such cells were presumed to be Schwann cells. These data are discussed in terms of the developmental origin of the cells and with regard to the putative functional rôle of D2 in cell adhesion phenomena.
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    URL: http://dx.doi.org/10.1007/BF00219864
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  • 92
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    The spatial organization of nucleolar DNA in phytohemagglutinin-stimulated lymphocytes of the guinea pig (1984)
    Springer
    Cell & tissue research 235 (1984), S. 65-70 
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    ISSN: 1432-0878
    Keywords: Lymphocytes ; Phytohemagglutinin stimulation ; Nucleolar organizer region ; Three-dimensional reconstruction ; Ultrastructure ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural changes in the spatial organization of nucleolar DNA in lymphocytes during phytohemagglutinin (PHA) stimulation was studied in guinea pigs by means of oxidized diaminobenzidine (DAB) at low pH as a differentially contrasting stain for nucleic acids and by the use of reconstruction of serial sections. The extended DNA filaments situated inside the fibrillar area originate from a large aggregation of heterochromatin, which is closely associated with the nucleolus, and from the perinucleolar shell of condensed chromatin. It is suggested that these two distinct regions of chromatin might be associated with different functions.
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    URL: http://dx.doi.org/10.1007/BF00213724
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  • 93
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    Diurnal variations in myeloid bodies of the newt retinal pigment epithelium (1984)
    Springer
    Cell & tissue research 235 (1984), S. 177-186 
    Details
    ISSN: 1432-0878
    Keywords: Retinal pigment epithelium ; Myeloid bodies ; Diurnal variation ; Morphometrics ; Ultrastructure ; Lipid metabolism ; Endoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Myeloid bodies (MBs) occur in the newt (Notophthalmus viridescens) retinal pigment epithelium (RPE) and are similar to areas of specialized endoplasmic reticulum found in a variety of other cell types. The function of these structures is unknown, although a role in lipid metabolism has been strongly suggested. Random samples from conventionally-fixed and sectioned newt RPE, obtained over a 24-hr cycle (LD 12∶12), were examined by electron microscopy. Myeloid bodies appear as stacks of flattened endoplasmic reticulum-associated saccules which increase in length and number as the RPE accumulates shed outer segment material, prior to increase in the amount of stored lipid. Associations of MBs with the nuclear envelope can be related to this increased length. Myeloid bodies decrease numerically in the cell as phagosomes are removed from the cytoplasm, but a decrease in mean sectional MB area, seen in the light phase, is counteracted in darkness where individual MBs are larger than those found in the light. The total sectional area of MBs within a cell and their mean length varied depending on the lighting condition; differences were also found between eyes after extended periods of continuous light and dark. Ribosomes were found in association with the surfaces of both flattened and circular MBs, but they were consistently more densely associated with the shorter concave surfaces of curved regions. A new hypothesis for MB function is presented, which is concerned with their role in isolating toxic lipids such as retinoids, which are accumulated during phagocytosis of shed outer segment tips, and which are capable of disrupting membrane-bound systems necessary for their eventual metabolism and safe storage.
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    URL: http://dx.doi.org/10.1007/BF00213738
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    Plasma cells in adult Atlantic hagfish, Myxine glutinosa (1984)
    Springer
    Cell & tissue research 235 (1984), S. 691-693 
    Details
    ISSN: 1432-0878
    Keywords: Plasma cells ; Ultrastructure ; Immunology ; Myxinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hagfishes, the most primitive vertebrates, are of special interest for the evolution of immune responses. Eptatretus stoutii, the Pacific hagfish, is able to mount cellular and humoral immune responses but all attempts to demonstrate in them the presence of plasma cells have failed. In the present study we demonstrate for the first time plasma cells identifiable by ultrastructural criteria in the pronephros, a primitive lymphohaemopoietic organ, of Myxine glutinosa, the Atlantic hagfish.
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    URL: http://dx.doi.org/10.1007/BF00226970
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    A tubular configuration of the granular endoplasmic reticulum forming a raft-like parallel array in the pinealocytes of two species of Japanese moles (Mogera kobeae and M. wogura) (1984)
    Springer
    Cell & tissue research 236 (1984), S. 15-18 
    Details
    ISSN: 1432-0878
    Keywords: Granular endoplasmic reticulum ; Ultrastructure ; Pinealocyte ; Mole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ten or more straight tubules, each of which consists of a double unit membrane of granular endoplasmic reticulum with a cylindrical profile, are joined side by side in a raft-like configuration in the cytoplasm of the pinealocytes of Japanese moles. They measure about 60 nm and 100 nm in their inner and outer diameters, respectively, and are often partially connected to unspecialized granular endoplasmic reticulum. Cisterns held between the inner and outer unit membranes with cylindrical profiles vary from 15 nm to 30 nm in width. Ensheathed portions of the cytoplasm are contiguous with cytoplasm outside the tubular units. The inner unit membranes of the tubules bear fewer ribosomal particles than the outer ones.
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    URL: http://dx.doi.org/10.1007/BF00216507
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    Satellite cells in the tail muscles of the urodelan larvae during development (1984)
    Springer
    Cell & tissue research 236 (1984), S. 431-438 
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    ISSN: 1432-0878
    Keywords: Satellite cells ; Satellite fibres ; Tail muscle ; Urodela ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The incidence and ultrastructure of satellite cells in the tail muscles of urodelan larvae were examined during development during which the number of satellite cells is gradually reduced. They are found more frequently in red than in the white fibres in all four stages examined (stage 53, 64, 66+ and juvenile). As development proceeds, intercellular space between satellite cell and muscle fibre is in general gradually extended and is mostly filled with basal lamina. Small muscle cells, satellite fibres, which are situated under the basal lamina of the parent fibre, are morphologically similar to satellite cells but contain a small amount of myofibrils. Three types of satellite fibres are distinguishable on the basis of differences in K2-EDTA-treated ATPase activity, width of Z line, and parent fibre type. Neuromuscular junctions are visible in satellite fibres.
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    URL: http://dx.doi.org/10.1007/BF00214247
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  • 97
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    Morphometric analysis of loading-induced changes in collagen-fibril populations in young tendons (1984)
    Springer
    Cell & tissue research 236 (1984), S. 465-470 
    Details
    ISSN: 1432-0878
    Keywords: Tendon ; Collagen fibrils ; Morphometry ; Ultrastructure ; Loading ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This study was designed to gain more detailed morphological information on skeletal tendons in the course of adaptation to physical loading. The effect on collagen fibrils was investigated in 6-week-old mice by means of electron microscopy. Physical loading was performed on a treadmill 5 days a week for 1, 3, 5, 7 and 10 weeks. Morphometric analysis of collagen fibrils revealed the mean diameter, the diameter distribution, the number and the cross-sectional area. The principal observations included: 1. After one week of physical loading an increase in mean fibril diameter (30%, p≦0.01), in number (15%, p≦ 0.05), and in cross-sectional area (15%, p≦0.05), as well as a change in mean fibril diameter distribution. 2. From the third to the seventh week a fall under the level of the controls in mean diameter (26%, p≦0.01), in number (26%, p≦0.01), and a reduced cross-sectional area (17%, p≦0.01), accompanied by signs of splitting of individual collagen fibrils. 3. In the long-term study an increase in fibril number (29%, p≦0.01), a fall in mean diameter from 189 nm in the controls to 179 nm (p≦0.05) but no statistically significant change in the relative cross-sectional area (32%) per unit in comparison to unloaded tendons. The possible physiological implications of the findings are discussed in the light of several regulatory mechanisms known to appear during the course of physical loading in connective tissues.
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    URL: http://dx.doi.org/10.1007/BF00214251
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    Changes in metabolism and hepatic ultrastructure induced by estradiol and testosterone in immature female Epinephelus akaara (Teleostei, Serranidae) (1984)
    Springer
    Cell & tissue research 236 (1984), S. 651-659 
    Details
    ISSN: 1432-0878
    Keywords: Steroids ; Vitellogenesis ; Metabolism ; Ultrastructure ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Estradiol injections increase serum level of calcium, amino acid, glucose, protein, ammonia and creatinine in immature Epinephelus akaara, and also increase levels of total lipid, cholesterol, phospholipid and esterified fatty acids. Hepatic protein, glycogen and lipid concentrations also rise after estradiol treatment, and some hepatic enzymes participating in the metabolism of nitrogen, lipid and carbohydrate, show increased activity. Serum vitellogenin levels are increased. Testosterone treatment increases serum protein, total lipid, cholesterol, amino acid and ammonia levels, and also hepatic glycogen content, but in contrast to estradiol treatment, testosterone does not change serum vitellogenin, glucose, calcium, phospholipid, esterified fatty acid and creatinine levels, nor the hepatic lipid and protein content. A small number of hepatic enzymes shows an increased activity. Vitellogenic fish show biochemical changes similar to that of estradiol-treated fish, but are different from those of immature fish. Estradiol treatment induces ultrastructural changes in the hepatocytes of immature fish that are similar to those found in vitellogenic fish. These include a proliferation of rough endoplasmic reticulum and Golgi apparatus, and an increase in glycogen and lipid, all indicative of enhanced metabolic activity.
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    URL: http://dx.doi.org/10.1007/BF00217235
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    Synaptic organization of a multifunctional interneuron in the central nervous system of Helix pomatia L. (1984)
    Springer
    Cell & tissue research 236 (1984), S. 677-683 
    Details
    ISSN: 1432-0878
    Keywords: Interneuron ; Synaptology ; Ultrastructure ; Horseradish peroxidase ; Helix pomatia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology, axonal arborization and ultrastructure of synaptic connections of the V21 giant neuron in the visceral ganglion of the snail Helix pomatia has been investigated following intracellular labelling with horseradish peroxidase. The V21 neuron establishes several afferent and efferent axo-axonic connections, mainly along the first half of the primary axon. Collaterals of 200–300 μm length originate from the primary axon, which shows further arborization, and both afferent and efferent synaptic contacts are formed on these fine axon profiles. Afferent and efferent contacts of the cell occur within very short distances of a few micrometers. On the basis of ultrastructure and vesicle and granule content, several afferent terminals can be distinguished on V21 labelled axon profiles. The majority of these afferent terminals resembles peptidergic-(neurosecretory)-like terminals. This finding supports the possible transmitter role of neuropeptides in the central nervous system of gastropods. Our results are consistent with and provide morphological evidence for recent electrophysiological observations suggesting that, in addition to integrating input, the V21 neuron functions as an interneuron in Helix central nervous system.
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    URL: http://dx.doi.org/10.1007/BF00217238
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    Interactions between immature porcine Leydig and Sertoli cells in vitro (1984)
    Springer
    Cell & tissue research 237 (1984), S. 357-362 
    Details
    ISSN: 1432-0878
    Keywords: Leydig-Sertoli cell interaction ; FSH stimulation ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Interactions between Leydig and Sertoli cells, as well as a stimulatory effect of FSH on Leydig cell activity, have been reported in many studies. In order to investigate these interactions, the ultrastructure of immature pig Leydig cells under different culture conditions has been studied. When cultured alone in a chemically defined medium, there is a marked regression of the Leydig cell smooth endoplasmic reticulum and a swelling of the mitochondria. Addition of FSH or hCG does not prevent these phenomena. Co-culturing of Leydig cells with Sertoli cells from the same animal maintains the smooth endoplasmic reticulum at the level seen in vivo and in freshly isolated Leydig cells. The addition of FSH to the co-culture stimulates its development and increases Leydig cell activity, as assessed by an increase in hCG binding sites and an increased steroidogenic response to hCG. These results suggest that Sertoli cells exert a trophic effect on Leydig cells, and that the stimulatory effect of FSH on Leydig cell function is mediated via the Sertoli cells. These results reinforce the concept of a local regulatory control of Leydig cell steroidogenesis.
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    URL: http://dx.doi.org/10.1007/BF00217157
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