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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 49 (1993), S. 769-774 
    ISSN: 1420-9071
    Schlagwort(e): Natural and artificial electric and magnetic fields ; possible biological effects of electric and magnetic fields and of atmospherics ; atmospheric small ions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The features and intensities of electric and magnetic fields in the environment are described. Natural as well as technical constant and variable fields are considered in the light of their possible biological effects. The upper limits of the various fields are discussed. Results of laboratory measurements and also of epidemiological investigations are presented. The question is raised whether atmospheric small ions can cause a biological effect.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 42 (1990), S. 91-104 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary Longterm recordings of the O3 concentration at the Zugspitze in 2964 m a.s.l. and at the Wank peak in 1780 m a.s.l. together with continuous daily measurements of cosmogenic radio-nuclides have been analyzed in order to ascertain whether or not a significant trend of O3 exists. Recordings from 1981 to 1988 show definitely that there was no trend of the O3 concentration in the free atmosphere between 1.8 and 3 km a.s.l. However, an increase of 10 ppb occurred 1978 to 1981. A cable car operating between Zugspitze and the valley (in 1000 m a.s.l.) over a two km height difference at the northern border of the Bavarian Alps has been used for atmospheric research. The run of this cable car is rather steep and is mostly suspended far away from the ground. Consequently it is ideal for simulataneously investigating the profiles of meteorlogical and atmospheric electrical parameters, and the ozone concentration. From 1980 to 1982 a total of 1990 ozone profiles have been recorded on fair weather days. The data collected offer a profound basis in order to study the time variations in the lower tropospheric ozone profile depending on the hour of the day during all seasons. The influence of the following atmospheric processes and conditions on the O3 profile pattern has been investigated: Vertical mixing intensity in and above the boundary layer, temperature inversions, photochemical production of ozone or its depletion in the lowermost layers, and stratospheric intrusions based on the measurements of cosmogenic radionuclides on Zugspitze, the upper end of the trail. The penetration depth of stratospheric O3 in the lower troposphere has been investigated and the shape and time behavior of temporarily O3 maxima within the boundary layer has been studied.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 49 (1993), S. 654-664 
    ISSN: 1420-9071
    Schlagwort(e): Pineal gland ; melatonin rhythm ; circadian rhythm ; seasonal reproduction ; melatonin receptors ; biological clock
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The paper briefly reviews the data which shows that the circadian production and secretion of melatonin by the pineal gland can impart both daily, i.e., clock, and seasonal, i.e., calendar, information to the organism. The paper summarizes the 3 patterns of nocturnal melatonin production that have been described. Clearly, regardless of the pattern of nocturnal melatonin production a particular species normally displays, the duration of nightime elevated melatonin is proportional to the duration of the night length. Since daylength under natural conditions changes daily the melatonin rhythm, which adjusts to the photoperiod sends time of year information to the organism. The melatonin receptors which subserve the clock message sent by the pineal gland in the form of a melatonin cycle may reside in the biological clock itself, namely, the suprachiasmatic nuclei (SCN). The melatonin receptors that mediate seasonal changes in reproductive physiology are presumably those that are located on the pars tuberalis cells of the anterior pituitary gland. Besides these receptors which likely mediate clock and calendar information, melatonin receptors have been described in other organs. Interestingly, the distribution of melatonin receptors is highly species-specific. Whereas the clock and calendar information that the melatonin cycle imparts to the organism relies on cell membrane receptors, a fact that is of some interest considering the high lipophilicity of melatonin, recent studies indicate that other functions of melatonin may require no receptor whatsoever.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1573-4935
    Schlagwort(e): deiodinase ; thyroxine ; Swiss mouse ; pineal ; Harderian
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Type II thyroxine 5′-deiodinase (5′-D) activity in both pineal and Harderian glands of the Swiss mouse was studied. Pineal 5′-D activity exhibited a nyctohemeral profile with a maximal peak value at 05.00 h, which coincides with that for pineal melatonin production. However, no rhythm of 5′-D activity in the Harderian gland could be found. In pineal gland, light at night inhibited the nocturnal increase in 5′-D activity, while isoproterenol, a β-adrenergic agonist, could not stimulate the enzyme. In the Harderian gland, neither darkness, nor light at night, or isoproterenol were capable of modifying basal values of 5′-D activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 82 (1991), S. 561-568 
    ISSN: 1432-2242
    Schlagwort(e): Zea mays ; Restriction fragment length polymorphisms (RFLPs)-Phosphorus (P) stress-quantitative trait loci (QTLs)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An understanding of the genetic nature underlying tolerance to low-phosphorus (low-P) stress could aid in the efficient development of tolerant plant strains. The objective of this study was to identify the number of loci in a maize (Zea mays L.) population segregating for tolerance to low-P stress, their approximate location, and the magnitude of their effect. Seventy-seven restriction fragment length polymorphisms (RFLPs) were identified and scored in a maize F2 population derived from a cross between line NY821 and line H99. The F2 individuals were self-pollinated to produce F3 families. Ninety F3 families were grown in a sand-alumina system, which simulated diffusion-limited, low-P soil conditions. The F3 families were evaluated for vegetative growth in a controlled-environment experiment. To identify quantitative trait loci (QTLs) underlying tolerance to low-P stress, the mean phenotypic performances of the F3 families were contrasted based on genotypic classification at each of 77 RFLP marker loci. Six RFLP marker loci were significantly associated with performance under low-P stress (P〈0.01). One marker locus accounted for 25% of the total phenotypic variation. Additive gene action was predominant for all of the QTLs identified. Significant marker loci were located on four separate chromosomes representing five unlinked genomic regions. Two marker loci were associated with an additive by additive epistatic interaction. A multiple regression model including three marker loci and the significant epistatic interaction accounted for 46% of the total phenotypic variation. Heterozygosity per se was not predictive of phenotypic performance.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The Harderian gland blood supply of female and male hamsters was studied using light and electron microscopy. A profuse vascularization surrounding secretory acini was observed. Among the blood vessels, the existence of large and irregular sinusoidal capillaries was apparent. These sinusoids appeared in close association to the basal aspect of the secretory cells. Typical, small, fenestrated capillaries were also observed within the connective tissue. The existence of this particular vascularization together with other morphological features of the secretory cell basal pole suggest a possible endocrine function of these orbital glands.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 44 (1993), S. 449-453 
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Metastable iron-manganese alloys - new weld materials used in valve manufactureThe application of protective claddings by weld surfacing is the only possibility of effectively and economically increasing the reliability and service life of components subject to wear. In the case of exposure to adhesive and abrasive wear under high surface contact force, such as that which occurs in the sealing surface area of valves, newly developed austenitic iron-manganese weld surfacing alloys can be substituted for iron-chromium-nickel materials, as well as copper-, nickel-, and cobalt-based materials hitherto employed. These economical materials, which exhibit good working properties from a welding engineering standpoint, form an optimal load-bearing edge layer under load because of a metastable state; this layer is constantly reproduced during exposure to wear. Frictional and wear characteristics, surface structure, and corrosion resistance, as well as the closely associated service life, thus in part considerably exceed that of conventional materials.
    Notizen: Das Auftragschweißen von Schutzschichten ist häufig die einzige Möglichkeit, die Zuverlässigkeit und Lebensdauer von verschleißbeanspruchten Bauteilen mit geringen Kosten wesentlich zu erhöhen. Für Beanspruchungen adhäsiven und abrasiven Verschleißes unter höchsten Flächenpressungen, wie sie z. B. im Dichtflächenbereich von Armaturen auftreten, können neu entwickelte austenitische Eisen-Manganlegierungen bisher verwendete Eisen-Chrom-Nickel-Werkstoffe sowie Kupfer-, Nickel- und Kobaltbasiswerkstoffe gut substituieren. Diese preisgünstigen, auch schweißtechnisch gut verarbeitbaren Werkstoffe bilden aufgrund eines metastabilen Zustandes unter Belastung einen optimal beanspruchungsgerechten Randschichtaufbau aus, der sich bei Verschleiß ständig reproduziert. Reibungs- und Verschleißverhalten, Oberflächenausbildung und Korrosionsbeständigkeit und die damit primär beeinflußte Standzeit übertreffen dadurch die der konventionellen Werkstoffe teilweise erheblich.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 15 (1994), S. 427-437 
    ISSN: 0197-8462
    Schlagwort(e): electric field exposure ; electromagnetic fields ; pineal function ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Sprague-Dawley male rats, maintained in a 14:10 h light:dark cycl were exposed for 30 days (starting at 56 days of age) to a 65 kV/m, 60 Hz electric field or to a sham field for 20 h/day beginning at dark onset. Pineal N-acetyltransferase (NAT), hydroxy-indole-o-methyl transferase (HIOMT), and melatonin as well as serum melatonin were assayed. Preliminary data on unexposed animals indicated that samples obtained 4 h into the dark period would reveal either a phase delay or depression in circadian melatonin synthesis and secretion. Exposure to electric fields for 30 days did not alter the expected nighttime increase in pineal NAT, HIOMT, or melatonin. Serum melatonin levels were also increased at night, but the electric field-exposed animals had lower levels than the sham-exposed animals. Concurrent exposure to red light and the electric field or exposure to the electric field at a different time of the day-night period did not reduce melatonin synthesis. These data do not support the hypothesis that chronic electric field exposure reduces pineal melatonin synthesis in young adult male rats. However, serum melatonin levels were reduced by electric field exposure, suggesting the possibility that degradation or tissue uptake of melatonin is stimulated by exposure to electric fields. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 1993-08-01
    Print ISSN: 0014-4754
    Thema: Biologie , Medizin
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 1993-09-01
    Print ISSN: 0014-4754
    Thema: Biologie , Medizin
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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