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  • Artikel  (359)
  • Springer  (308)
  • Molecular Diversity Preservation International  (51)
  • 2015-2019  (137)
  • 2000-2004  (34)
  • 1995-1999  (104)
  • 1990-1994  (84)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell, tissue and organ culture 26 (1991), S. 75-82 
    ISSN: 1573-5044
    Schlagwort(e): betalamic acid ; betaxanthins ; betaxanthin formation ; cell cultures ; Portulaca grandiflora ; selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cell cultures derived from three yellow flowering Portulaca grandiflora genotypes contained betacyanins rather than betaxanthins. A betaxanthin-producing cell culture was obtained by subculturing orange cell clusters isolated from the red-violet cell culture of a violet flowering P. grandiflora genotype. Selection of the most strongly yellow coloured cell material reduced the portion of betacyanins considerably and resulted in a P. grandiflora cell culture characterized by a high concentration of betaxanthins and the occurrence of free betalamic acid. Vulgaxanthin I was the main compound. Besides these pigments carotenoids and flavonoids were detectable. Betaxanthin biosynthesis strongly dependend on light. Product accumulation reached its maximum during the stationary phase of the growth cycle. Excretion of pigments, especially of betalains, could not be detected. Vulgaxanthin I as found in the cell culture was identical with one of two main betaxanthins in the yellow petals of P. grandiflora. The yellow P. grandiflora cells grew well on solid modified Murashige and Skoog medium but failed to grow in liquid medium after a few subcultures. In contrast, white P. grandiflora suspension cultures could be established repeatedly.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
  • 3
  • 4
    ISSN: 1436-2236
    Schlagwort(e): Key words:Geodia cydonium, Suberites domuncula, sponges, Porifera, aquaculture, CD63, bioactive compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract: Among Metazoa, sponges (phylum Porifera) are the richest source for different bioactive compounds. The availability of the raw material is, however, restricted. To obtain enough of the bioactive compounds for application in human therapy, sponges have to be cultured in in vitro systems. One technique for the establishment of a long-term cell culture from sponges has recently been elaborated. Here, we present a procedure to cultivate tissue samples from sponges in an open system. The species Geodia cydonium, which produces bioactive compounds, has been selected. Tissue samples of approximately 10 g were attached to the bottoms of cultivation trays. After 2 to 3 days, the tissue samples formed a robust contact with the metal support. Subsequently, sets of trays, called tray batteries, either remained in huge aquaria at the Center for Marine Research or were transferred to the vicinity of a fish and mussel farm. The growth rates of the samples remained unchanged within the first month; however, after 3 and 6 months, they increased to 147% and 189%, respectively. In parallel, extracts were prepared from the tissue samples and tested for cytotoxicity in a mouse lymphoma cell assay system. Extracts from cultured tissue initially had a low inhibitory potency; however, after cultivation for 3 or 6 months, values comparable to those of extracts from sponges taken from the biotope were found. In addition, a molecular marker was applied to document the response (health state) of the tissue and the identity of the material in culture. The CD63 molecule was chosen because the expression of this molecule in mammalian systems changes with the age of the animals. The corresponding complementary DNA was isolated from Geodia cydonium. With this probe, the level of expression in cultured tissue samples decreased immediately after starting cultivation; after a cultivation period of 6 months, however, values were similar to those found in controls. These data show that sponge species that produce bioactive compounds can be cultivated in open systems, in which they retain their potency to produce bioactive compounds as well as their health state.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Lasers in medical science 6 (1991), S. 363-366 
    ISSN: 1435-604X
    Schlagwort(e): Laser vascular welding ; Tissue fusion ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Physik , Technik allgemein
    Notizen: Abstract The central problem in microsurgery is the reconstruction of small vessels. The long operating time, foreign body granuloma formation around the suture material as well as aneurysmal alterations of the vessel wall after conventional suture technique make the search for alternatives indispensable. Some of these disadvantages can be avoided as demonstrated by our animal experiments and histological examinations in laser-assisted anastomosing. The aim of this study is to show these aspects in connection with laser application and compare them with conventional suture techniques.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Annals of operations research 54 (1994), S. 119-127 
    ISSN: 1572-9338
    Schlagwort(e): Input-output ; multiple criteria decision making ; environmental policy ; JEL C44 ; C67 ; Q28
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Notizen: Abstract It is often claimed that there is a trade-off between economic goals and the quality of the environment. For this reason, an environmental input-output optimization model with multiple objectives is formulated. The criteria are the minimization of factor costs to produce the Gross National Product and the minimization of net pollution for a given level of final demand. Using the LeChatelier-Samuelson principle, we analyze the changes in the production of the sectors and in the prices of the goods (described by the dual model) due to the change in the preferences of the decision makers. It can be shown that higher weights for the environmental objectives imply — in tendency —non-decreasing production of the sectors andnon-decreasing abatement activities. The changes of prices are ambiguous. The condition for increasing prices is given. To some degree, the opposite results can be achieved, if maximization of the value of final demand (or of private consumption) and minimization of net pollution under the constraints for primary input are taken as objective functions. In this case, increasing weights for environmental goals will leadin tendency tonon-increasing final demand and tonon-increasing net pollution. Under given conditions, higher environmental quality will be achieved bynon-increasing gross production and abatement activities.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 18 (1994), S. 27-45 
    ISSN: 1572-9443
    Schlagwort(e): Markovian queues ; heterogeneous arrivals ; transient analysis ; lattice path ; enumeration ; 05A15 ; 60K25
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract In this paper we consider a discrete time queueing model where the time axis is divided into time slots of unit length. The model satisfies the following assumptions: (i) an event is either an arrival of typei of batch sizeb i, i=1,...,r with probabilityα i or is a depature of a single customer with probabilityγ or zero depending on whether the queue is busy or empty; (ii) no more than one event can occur in a slot, therefore the probability that neither an arrival nor a departure occurs in a slot is 1−γ−⌆i α i or 1−⌆i α i according as the queue is busy or empty; (iii) events in different slots are independent. Using a lattice path representation in higher dimensional space we will derive the time dependent joint distribution of the number of arrivals of various types and the number of completed services. The distribution for the corresponding continuous time model is found by using weak convergence.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 26 (1997), S. 255-267 
    ISSN: 1572-9443
    Schlagwort(e): birth-death processes ; lattice path enumeration ; uniformization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract In this paper we present a combinatorial technique which allows the derivation of the transition functions of general birth-death processes. This method provides a flexible tool for the transient analysis of Markovian queueing systems with state dependent transition rates, like M/M/c models or systems with balking and reneging.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 21 (1991), S. 40-43 
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Mass transfer towards the inner electrode and the wall electrode was studied in an annular cell stirred with an inert gas bubble flow. Experimental data obtained for the wall electrode follow the relationship found previously for circular cells; namely $$Sh = 0.231(ScGa)^{1/3} (L/D_e )^{ - 0.194_\varepsilon0.246}$$ Study of the influence of gas hold-up on the mass transfer rate towards the inner wall electrode has yielded the following relationship: $$Sh_\infty= 0.315(ScGa)^{1/3_\varepsilon0.231}$$
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 25 (1995), S. 273-278 
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The behaviour of regular packings constructed from corrugated metal sheets was investigated since they constitute an attractive packing material for the electrochemical absorption of gases. Mass transfer coefficients for the regular packing contained in a circular electrolytical cell were determined by the electrochemical method with simulation of the absorption process by bubbling nitrogen through the column. Correlations for the mass transfer rate as a function of fluid dynamic parameters and fluid properties are presented.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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