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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 296 (1982), S. 821-825 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sr and Nd isotope ratios are reported for 17 mid-ocean ridge basalts and for 11 oceanic islands and island groups. Data from the Azores, Samoa and the Society Islands diverge significantly from the mantle array. These results are not explained by binary mixing of depleted and undepleted mantle ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In high-alpine soils the maximum temperature is low even during the growing season, and hence mineralisation of nutrients is reduced. The aim of this study was to investigate what sources of nitrogen and phosphorus are available for vascular plants in the alpine nival zone to support growth. Using acetylene reduction assays levels of nitrogenase activity were assessed in sealed pots containing nival zone soil and plants at an altitude above 3000 m, and in bacterial isolates of soil and rhizosphere in the laboratory. Nitrogenase activity could not be detected in bacterial isolates or in the soil containing no plants. Small quantities of ethylen (〈87 nmol·h-1 per pot) were detected in pots with Cerastium uniflorum and Poa laxa. This activity must be attributable to rhizosphere bacteria since no evidence for the presence of cyanobacteria could be obtained. Other sources of nitrogen for the plants were detected in the form of ammonium and nitrate in soil water and in snow melt water. These solutions also contained extractable phosphorus in quantities normally considered to be sufficient for growth. Analyses of the internal concentration of nitrogen and phosphorus also suggested that these elements were present in adequate amounts in these plants. It was considered that soil and snow melt water together may provide sufficient nitrogen and phosphorus to support the extremely small annual growth increment of nival zone plants.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0649
    Keywords: PACS: 82.20.Kh; 82.40.Js; 82.20.Hf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. For the ultrafast photoinduced ring opening of cyclohexadiene the S1 state plays a central role, providing the possibility to rapidly decay to the ground state. In this paper we follow the path of a wavepacket propagating in the reactive coordinate space of the S1 surface. We present a detailed analysis of the corresponding electronic and nuclear motions. With the help of a projection method and a normal-mode analysis, the vibrational modes driving the reaction might be detected experimentally.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Mikrokerntest ; Feldkanzerisierung ; Biomonitoring ; Prävention ; Key words Micronucleus ; Assay ; Fieldcancerisation ; Biomonitoring ; Prevention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract A lot of different endogenous and exogenous factors are accused to promote squamous cell carcinomas in the upper aerodigestive tract. Main risk factors are the chronic tobacco- and alkohol consumption. The fact, that many patients develop syn- or metachronic carcinomas in this area was first described by Slaughter et al. 1953 and explained with the phenomenon of field cancerisation. Concerning to this hypothesis the whole mucosa of the upper aerodigestive-tract is premalignant damaged. In our study the micronucleus-frequency was determined as a biomarker for the genetic injury to prove the fieldcancerisation on the cellular level at 159 people (control-group, abuser, patients with HNSCC). Our results confirm the hypothesis of fieldcancerisation of the mucosa of the upper aerodigestiv-tract at strong tobacco- and alkohol consumers and patients with head and neck squamous cell carcinoma. Furthermore there is a highly statistically significant correlation between increasing micronucleus frequency and increasing tobacco abuse. As a final result of our study the micronucleus assay seems to be of good value to show a genotoxic damage in healthy mucosa at people with a high risk to develop HNSCC, but it's not usable to give any answer if and when such carcinomas arise.
    Notes: Zusammenfassung Unterschiedliche endogene und exogene Faktoren werden für die Entstehung von Plattenepithelkarzinomen des Oropharynx und Larynx verantwortlich gemacht. Die Hauptrisikofaktoren sind jedoch der chronische Tabak- und Alkoholabusus. Viele Patienten mit Mundhöhlen-, Rachen- oder Kehlkopfkarzinomen erkranken an syn- oder metachronen Zweitkarzinomen. Erklärt wurde dieses Phänomen erstmals von Slaughter et al. 1953 mit dem Konzept der Feldkanzerisierung. Hiernach wird die gesamte Schleimhaut des oberen Aerodigestivtraktes durch die oben genannten Schadstoffe als Ergebnis eines mehrstufigen Prozesses von genetischen Fehlern oder Mutationen prämaligne verändert. Statistisch gesehen steigt mit der Anzahl der Mutationen die Wahrscheinlichkeit des Eintretens spezifischer persistierender DNA – Modifikationen in einem für die Kanzerisierung wichtigen DNA-Abschnitt. In der durchgeführten Untersuchung wurde die Mikrokern (MK-)frequenz in der Wangenschleimhaut als Maß für die genetische Schädigung zur Erkennung der Feldkanzerisierung bestimmt. Die Ergebnisse unserer Untersuchung bestätigen die epidemiologischen Erkenntnisse des Zusammenhangs von Tabakabusus und einer Feldkanzerisierung im Kopf-Hals-Bereich. Ebenfalls zeigte sich ein hochsignifikanter Zusammenhang zwischen der Menge und Dauer des Tabakabusus und der Mikrokernbildung. Mit Hilfe der logistischen Regression konnte gezeigt werden, dass das relative Risiko bei rauchenden Probanden mit mehr als 0.0195 MK/Schleimhautzelle an einem Kopf-Hals-Karzinom zu erkranken, um das 8,04fache erhöht ist. Der Mikrokerntest scheint nach unseren Ergebnissen ein geeignetes Verfahren zu sein, im Sinne eines Biomonitorings Veränderungen am genetischen Endpunkt nachzuweisen; er erlaubt aber keine Aussagen, ob und wann es tatsächlich zu einer Entartung kommen wird.
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  • 5
    ISSN: 1433-044X
    Keywords: Schlüsselwörter Knochentransplantate ; Knochendesinfektion ; Knochensterilisation ; Osteoblast ; Biokompatibilität ; Key words Bone graft ; Bone desinfection ; Bone sterilization ; Osteoblast ; Biokompatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract All sterilizatian and desinfection procedures for bone grafts are different in regard to influence of bone graft features, which may influence the function of different cell types. We used an in-vitro approach to assess the influence of bone matrix, which was sterilized or desinfected, on osteoblastic activities in-vitro by simulating a cell-transplant-interface. Primary bovine osteoblast cell cultures were established from periosteum. Bone grafts specimens made of bovine cortical bone (Ø 15 mm, 300 μm thickness) were treated in 5 different ways: autoclaved, ethylen-oxid-sterilized, demineralized and low-temperature-plasma-sterilized (DEM-LTP), chemically sterilized (modified Tutoplast® method), and 80°C-temperature desinfected. The following cell function parameters were assayed: plating efficiency proliferation by measuring the DNA-content, and MTT-activity, soluble protein and extracellular matrix synthesis, alkaline phosphatase, and osteocalcin expression. All desinfected bone grafts were biocompatable with primary periosteal osteoblasts. Measured cell activities upon bone specimens showed better results than cells of the plastic surface control. The DEM-LTP-bone showed better results in comparison to other groups, and stimulated the proliferation and differentiation.
    Notes: Zusammenfassung Unterschiedliche Sterilisations- und Desinfektionsverfahren für Knochentransplantate unterscheiden sich bezüglich ihres Einflusses auf die Eigenschaften des Transplantats, die für den Remodelingprozeß von größter Bedeutung sind. In dieser Arbeit wurde der Einfluß der unterschiedlich sterilisierten und desinfizierten Knochenmatrix auf die Funktion primärer periosaler Osteoblasten in vitro untersucht. Folgende Desinfektionsverfahren wurden getestet: Autoklavierung, von uns modifizierte Tutoplast®-Methode, demineralisiertes Knochentransplantat mit anschließender Niedrig-Temperatur-Plasmasterilisation (DKM-NTP), 80°C-Thermodesinfektion und Ethylenoxidsterilisation. Isolierte bovine Osteoblasten wurden auf behandelten Knochenproben kultiviert. Folgende Parameter wurden geprüft: plating efficiency, Proliferation, DNA-Gehalt, MTT-Aktivität, Aktivität alkalischer Phosphatase, Proteinsynthese und Osteokalzin-Expression. Alle untersuchten Konchentransplantate waren biokompatibel mit primären periostalen Osteoblasten. Eindeutig toxischer Effekt wurde beim ethylenoxidsterilisierten Knoche nach 2tägiger Auslüftung nachgewiesen. Die Differenzierungsparameter zeigten deutlich höhere Werte in allen Testgruppen im Vergleich zur Plastikkontrolloberfläche, wobei die DKM-NTP-Gruppe stets die höchsten Werte aufwies und einen induktiven Effekt auf die Proliferation und die Differenzierung der Osteoblasten in vitro zeigte. Die Untersuchung wurde mit organspezifischen Zellen durchgeführt, die einen unveränderten Osteoblastenphäntyp aufwiesen. Die unterschiedlichen Knochendesinfektionsverfahren sind auf diese Weise zum 1. Mal getestet worden. Ethisch problematische Tierversuche zur Prüfung der Toxizität, der Biokompatibilität und der induktiven Eigenschaften von behandelten Knochentransplantaten können durch Verwendung dieser Methode erspart werden.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 306 (1983), S. 431-436 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Analyses on fresh glass samples of mid-ocean ridge basalt yield a uniform ratio K/U = 12,700 ± 200. In contrast, Th/U increases systematically with Th concentration. From these results we calculate an upper limit (1.5 pW kg−1) and a best estimate (0.6 pW ...
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 36 (2000), S. 127-133 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The theory of the cross-flow heat exchanger first was treated by Nußelt [1, 2] on the base of heat balances for the two interacting fluids over an exchanging area element. This leads to a partial differential equation. But the solution was an infinite row which could not be expressed in a compact formula. In this paper it will be shown that a compact formula for the infinite row is possible. All temperatures of the interacting fluids, for example the local fluid temperatures and the mean outlet temperatures as well as the local temperature difference and the mean temperature difference over the complete exchanger are now being available in simple formulae which have the form of an infinite sum. The summation has to be stopped at a finite value with a negligible deviation. As all variables in the formulae are dimensionless, normalized diagrams are developed which are generally valid and give a good overview over a wide range of exchanger conditions.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Der Schmerz 14 (2000), S. 264-265 
    ISSN: 1432-2129
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 84 (1983), S. 382-389 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract This paper presents a method for the systematic trace element modelling of a cogenetic suite of lavas. It is based on the geochemical inversion technique of Allègre and coworkers and utilizes the variations in the trace element concentrations of the lavas to calculate initial concentrations and source mineralogy. We reduce this inversion to a simple, step-by-step procedure: (1) correcting for fractional crystallization; (2) testing the inferred primary melt compositions for consistency with a model of equilibrium partial melts (with constant partition coefficients) formed from identical sources; (3) estimating the proportions of mineral phases entering the melt; (4) computing concentrations and bulk partition coefficients in the initial source relative to the concentration of a common reference element; (5) estimating relative mineral abundances in the source. Except for the fractionation correction, the calculations are done element by element using a direct analytic solution. For the purpose of comparison we apply this method to the same set of data used by Minster and Allègre (1978), a suite of lavas from Grenada (lesser Antilles) originally analyzed by Shimizu and Arculus (1975). The results of both methods agree well for the source abundances of the light REE, whereas the heavy REE abundances are shown to be poorly constrained by the data. Both methods require residual clinopyroxene and garnet in the source, but the ratio of these minerals is not well constrained. We are unable to reproduce the shape of D0 pattern (=bulk partition coefficients of the initial source) given by Minster and Allègre. The reason for this cannot be evaluated without repeating their calculations in detail. The set of data from Grenada is useful for comparison of the methods only, because it is now known from isotopic data that the samples are not truly cogenetic. Possibly better suited sets of samples for petrogenetic modelling are presented in parts II and III of this series.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1439-0973
    Keywords: Key Words GBV-C/HGV infection ; HIV infection ; Seroprevalence ; Male homosexuals ; Sexual transmission ; Age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Background: The objective of this cross-sectional, non-randomized, prospective study was to generate data on the prevalence of GB virus C (GBV-C)/hepatitis G virus (HGV) in a cohort of HIV-infected homosexuals from Munich. Patients and Methods: A total of 71 HIV-infected homosexual men were analyzed for prevalence of GBV-C RNA and antibodies to the E2 envelope glycoprotein (E2Ab). 475 healthy volunteer blood donors in southern Bavaria served as a control group. Results: The prevalence of GBV-C RNA was 27% (control group: 2.3%) and the prevalence of E2Ab was 35% (control group: 6%). The total prevalence for present and past infection was 62%. The differences between the HIV-infected patients and the control group were significantly (p 〈 0.0001). GBV-C RNA and E2Ab were not detected simultaneously in any serum sample. The E2Ab positive patients were older than the GBV-C RNA positives (mean 46 years versus 39 years, p = 0.0350). The GBV-C RNA and E2Ab negative patients were older than the GBV-C RNA positives (mean 47 years versus 39 years, p = 0.0236). The E2Ab positive patients had suffered sexually transmittet diseases more frequently than the patients negative for markers of GBV-C infection (p = 0.0308). E2Ab positive patients also had higher mean levels of alanine aminotransferase compared to patients without evidence of GBV-C infection (p = 0.0164). 59.4% of all individuals were anti-HBc IgG positive. Conclusion: The data can be interpreted as indirect evidence for sexual transmission of GBV-C.
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