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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3574-3576 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the phase Fe14R2X, where R is a lanthanide and X is either boron or carbon, or a mixture of the two, the extent of stability of the carbides and their miscibility with the borides is traced for the lighter rare-earth metals. Like the borides, the carbides are magnetically hard, but unlike them, they do not normally crystallize from the melt, and this property is exploited to produce intrinsic coercivities above 12 kOe in cast materials without the added special processing step of sintering or melt spinning. The high coercivity is related to a cellular microstructure of Fe14R2X in which the cell size is approximately 1 μm. The cell structure, which originates in a peritectoidlike transformation from primary Fe17R2, is quite stable and does not change during prolonged annealing. The coercivity is sensitive to variations in composition.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 40 (1987), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Symbiotic effectiveness (nitrogen-fixation ability) is not a measure of inter-strain competitiveness, and Rhizobium strains used as inocula frequently compete poorly with indigenous rhizobia for nodulation of the host legume. Competition between rhizobia delimits the use of Rhizobium inoculum in agriculture. We therefore chose to investigate aspects of the gene pool represented by an indigenous population of R. meliloti selected for maximum diversity, particularly for evidence of competitive dominance. This unadapted population was very heterogeneous in terms of plasmid content, somatic antigens and intrinsic antibiotic resistance (IAR). Little tendency towards competitive dominance (measured in terms of nodule occupancy) was observed. Classical methods (serotype, IAR) of characterising strains did not correlate to define dominance of a strain or a group of strains. The data are consistent with a continuum of symbiotically proficient strains under conditions of maximum diversity.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Polar biology 5 (1986), S. 139-143 
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Samples of muscle, liver and kidney of Weddell and crabeater seals, Adélie and emperor penguins, and McCormick's skuas collected in the Weddell Sea in the summer 1982/83 were analysed for cadmium and copper. In general, the study aimed at contributing to the establishment of base-line data on potential pollutants in Antarctic ecosystems. In particular, it aimed at increasing the amount of data on Cd and Cu levels in the same species that that had been collected and analysed two years eralier, thus improving the possibility of statistical analyses into relationships between metal contents and biological parameters or sampling-sites of the animals, but the data basis is still too small for the letter purpose. In all species together, concentration ranges (on dry weight basis) were 0.16–0.77, 3.7–96.8 and 15.6–491 mg cadmium and 1.6–21.4, 14.9–149 and 12.6–47.7 mg copper per kg in muscles, livers and kidneys, respectively. The relatively high levels of both metals in all species analysed, in connexion with the available literature, suggest that levels in marine mammals and birds can only, if at all, to a minor extent reflect differences in environmental concentrations of these metals.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2307
    Keywords: Chronic myeloproliferative disorders ; Thrombocytosis ; Primary Thrombocythaemia ; Granulo ; Erythrocytopoiesis ; Reticulin Fibers ; Circular Deviation ; Histomorphometry ; Bone marrow biopsies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A histomorphometric analysis was performed on trephine biopsies of the bone marrow in 55 patients with chronic myeloproliferative disorders (CMPDs) and marked thrombocytosis (platelet count exceeding 600 × 109/l). This study aimed at discriminating primary (essential) thrombocythaemia (PTH) from the various other subtypes of CMPDs presenting with thrombocytosis. Following the diagnostic requirements postulated by the Polycythemia-vera-Study-Group for PTH and polycythaemia vera rubra (P.vera) and the generally accepted criteria for the establishment of chronic myeloid leukaemia (CML) and agnogenic myeloid metaplasia (AMM), our cohort of 55 patients was divided into the following subgroups: CML (16 cases), P.vera (11 cases), AMM (13 cases) and finally PTH (15 cases). Histomorphometric measurements revealed that PTH was distinguishable from the other subtypes of CMPDs with respect to several histological variables: patients with PTH had a normal amount of neutrophilic granulo- and erythrocytopoiesis as well as a non-increased content of reticulin (argyrophilic) fibers in contrast to the findings in CML, P.vera and of course AMM. Moreover, sizes of megakaryocytes and their nuclei were significantly greater in PTH and internalization of haematopoietic cells (emperipolesis) was more frequently encountered in comparison with the other subtypes of CMPDs. Deviation of the circular perimeter of megakaryocyte shape was most prominently expressed in CML and AMM, and consequently generated an increased number of a-nuclear cytoplasmic fragments. In contrast to this feature aberration of the nuclei from a circular outline occurred in a less pronounced way in CML, but was excessive in P.vera, AMM and PTH. Our morphometric evaluation demonstrates that certain histological features may serve as a valuable aid in discriminating PTH from the other occasionally thrombocythaemic subtypes of CMPDs.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 39 (1986), S. 173-181 
    ISSN: 1432-0630
    Keywords: 44.50 ; 78.65 ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Optical reflection measurements are described as a new and simple technique to measure thicknesses and thickness changes of ultrathin organic overlayers on inorganic support. The prime advantages are high sensitivity in thickness measurements (0.1–1 Å), applicability under varying environmental conditions, nondestructiveness, applicability on different supports and high time resolution. These features are assessed theoretically and experimentally studying Langmuir-Blodgett films on SiO2 and Au supports. These films, in this work prepared with the model compound arachidic acid, provide the salient feature of well-defined thicknesses in integer multiples of 26.7 Å. Application of the technique in thermodesorption experiments reveals distinguished binding states with binding energies (73–110 kJ/mol) depending on the counterion (Mg2+ or Cd2+) used in preparing the films and ratios of different states depending on thickness. The binding energy for the main component of multilayers (73 and 81 kJ/mol) with thickness larger than 100 Å is comparable to the heat of evaporation of bulk fatty acids. In addition an analytic expression between layer thicknesses and reflection is derived from the Fresnel equation.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Visual system ; Neuroplasticity ; Axon-sprouting ; Pruning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unilateral lesions of the right superior colliculus (SC) were made in hamsters on the day after birth. In order to quantify the extent of abnormal innervation by left eye fibers in the diencephalon and midbrain, the left eye was removed on postnatal day 12 or 36, and after an appropriate survival time, the brains were stained for degenerating axons and axon terminals with the Fink-Heimer method. In additional cases, anterograde transport of 3H proline-leucine or horseradish peroxidase was used to assess left eye connectivity. In agreement with previous reports we found abnormal projections in the ventral nucleus of the lateral geniculate body (LGv), in the lateral posterior nucleus (LP) of the thalamus, and in the left SC (the ‘recrossing’ pathway). We also noted areas of abnormally heavy terminal fields arranged in patches in coronal sections in the dorsal nucleus of the lateral geniculate body (LGd). These patches arise from columns of dense innervation that are oriented along a rostral-to-caudal axis. If the right SC lesion was made large enough to diminish the recrossing pathway, retinofugal axons establish a significantly smaller distal terminal field in the left SC. In these cases, a corresponding increase in the size of terminal fields in all major proximal structures (LGd, LGv, LP, DTN) was observed. The sum of abnormal proximal growth (“compensatory sprouting”) was found to truly compensate for the distal loss of terminals. The evaluation of hamsters in which left eye connectivity was assessed at the age of 12 days revealed that lesion-induced patches of abnormal growth have already reached their full size by that time. These findings provide evidence for the ‘pruning -effect’ and demonstrate that retinofugal axons support a fixed number of terminal arborizations (the principle of ‘conservation of total axonal arborizations’).
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 73 (1988), S. 595-605 
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Brain stimulation ; Orienting behavior ; Defensive behavior ; Hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Syrian golden hamsters were implanted with fixed or moveable stimulating electrodes aimed at the superior colliculus (SC). Behavior was observed in response to trains of 0.1 ms pulses at 200 Hz while the animals were moving freely in an open arena or in their home cages. At threshold stimulating currents, the responses consisted almost entirely of freezing or contraversive turning, which occurred in two forms: fast turns, resembling orienting movements to sunflower seeds, and slow turns that were smooth and continuous. Other responses, including head raising and lowering, ipsiversive turning and backing movements were seen occasionally. Increasing the stimulating current usually gave a variety of responses, including circling movements, prolonged freezing, ipsilateral movements and running escape behavior. The sites in SC giving freezes at threshold tended to be located superficially (SO and above), or deep (SGP and below), while sites giving turns were in the intermediate layers. Most freeze sites occurred in the rostro-medial SC that represents the upper visual field, while turn sites occurred predominantly in caudo-lateral SC. Apart from the turns, most of the stimulated responses resembled natural defensive behavior, supporting the view that SC in rodents plays a role in organizing responses to predators, as well as in orienting behavior.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 71 (1988), S. 365-376 
    ISSN: 1432-1106
    Keywords: Gangliosides ; Brain damage ; Axonal sprouting ; Secondary degeneration ; Retinotectal system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of exogenous gangliosides on sprouting of optic tract axons was studied in hamsters which, after a right tectal lesion on the day after birth (P1), had an abnormal retinotectal projection from the left eye to the left superior colliculus (SC). Sprouting of these axons was induced by removing the competing input by right eye removal on postnatal day 9 (P9). Intraperitoneal GM1, given daily and started on P9, significantly stimulated the sprouting response. This was demonstrated by Fink-Heimer silver staining of anterograde axonal degeneration three days after the left eye was removed on P36. Terminal fields in the left SC were, in average, twice as large compared to controls. An estimate of the total number of terminals (silver stained particles) revealed a value of 7.9×106 for GM1 and 3.2×106 for control hamsters, respectively. Diencephalic structures which also receive collateral input from the sprouting optic tract did not show any alterations in the size of the terminal field due to GM1-treatment, suggesting that, in vivo, gangliosides fail to initiate sprouting in areas that have not previously been denervated. Unexpectedly, GM1-treated hamsters also had significantly smaller right SC damage and less left damage near the midline. Subsequent reanalysis of the data based on a lesion-matching procedure indicates that effects on reducing atrophy were independent of the GM1-enhanced sprouting of retinofugal axons. These findings provide the first direct evidence that exogenous GM1 stimulates lesion-induced axon sprouting in the mammalian brain.
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  • 9
    ISSN: 1432-2013
    Keywords: Patch-clamp ; Chloride channels ; Pulmonary epithelium ; Cultured epithelial cells ; Cystic fibrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The properties of ion channels in patches from the luminal membrane of cultured monolayers of type II alveolar epithelial cells from adult rat lung have been studied. In excised patches, prepared as described to yield the “outside-out” configuration (with cesium ions in the bathing solutions to suppress currents arising from potassium channels), we observed anion-selective channels with a conductance of 350–400 pS, and burst lengths lasting seconds. When patches were bathed in solutions with equal chloride concentrations, channels opened and closed spontaneously at membrane voltages close to zero, but tended to close when the potential was shifted by ±10 mV, particularly in the negative direction. Other anions could pass through these channels with a permeability sequence of I(1.5)〉Br(1.02)=〉Cl(1.00)〉NO3(0.9)〉gluconate(0.6) but there was a very low permeability for sodium (P Na/P Cl=0.015±0.006). Calcium ions reduced channel conductance. The channels probably have a role to play in salt absorption by this epithelium, but insufficient information is available about how sodium crosses it for the role of the anion channels in transport to be defined with confidence.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 100 (1989), S. 507-514 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The population dynamics, ammonia and inorganic phosphate excretion, and nutrient regeneration of the common jellyfish Aurelia aurita was investigated from 1982 to 1984 in the Kiel Bight, western Baltic Sea. During summer 1982, medusae abundance ranged between 14 and 23 individuals 100 m-3, biomass was estimated at about 5 g C 100 m-3 and the mean final diameter of individuals was 22 cm. Abundance, based on numbers, in 1983 and 1984 was an order of magnitude lower; biomass was less than 2 g C 100 m-3 and jellyfish grew to 30 cm. During the summers of 1983 and 1984, A. aurita biomass constituted roughly 40% of that of the total zooplankton〉200 μm. In 1982, for which zooplankton data were lacking, it was assumed that medusae biomass was greater than that of all other zooplankton groups. Total ammonia excretion ranged between 6.5 and 36 μmol h-1 individual-1, whereas inorganic phosphate release was 1.4 to 5.7 μmol h-1 individual-1. Allometric equations were calculated and exponents of 0.93 for NH4−N release and 0.87 for PO4−P excretion were determined. Nitrogen and phosphorus turnover rates were 5.4 and 14.6% d-1, respectively. In 1982, the medusae population released 1 100 μmol NH4−N m-2 d-1, about 11% of the nitrogen requirements of the phytoplankton. The inorganic phosphate excretion (150 μmol m-2 d-1) sustained 23% of the nutrient demands of the primary producers. In the other two years the nutrient cycling of the medusae was much less important, and satisfied only 3 to 6% of the nutrient demands. It is suggested that in some years A. aurita is the second most important source of regenerated nutrients in Kiel Bight, next to sediment.
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