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  • 1
    Digitale Medien
    Digitale Medien
    NMR studies of rotational motion at low viscosity (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 6550-6552 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100354a052
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  • 2
    Digitale Medien
    Digitale Medien
    Optimal algorithms for some intersection radius problems (1994)
    Springer
    Computing 52 (1994), S. 269-279 
    Details
    ISSN: 1436-5057
    Schlagwort(e): 52.A30 ; 52.A10 ; Intersection radius ; prune-and-search ; algorithms ; complexity ; computational geometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Wir bezeichnen als Radius des Durchschnitts einer Menge vonn geometrischen Objekten imd-dimensionalen Euklidischen RaumE d Radius der kleinsten abgeschlossenen Hyperkugel, welche einen nichtleeren Durchschnitt mit allen Objekten besitzt. In der vorliegenden Arbeit beschreiben wir optimale Algorithmen zuer Bestimmung einiger solcher Radien. Zuerst stellen wir einen Algorithmus mit linearem Zeitbedarf vor, wenn die Objekte Hyperebenen inE d mit festemd sind. Er beruht auf der Reduktion des Problems auf eine (d+1)-dimensionale Lineare Optimierungsaufgabe mit 2n linearen Nebenbedingungen. Wir beschreiben auch die Lösung des Durchschnitts-Radius Problems fürn Strecken in der Ebene. Dazu benutzen wir neben Breitensuche die Ersetzung von Halbstrahlen durch Punkte oder Gerade. Bisher waren keine Algorithmen bekannt, welche diese Probleme in den gleichen Zeitschranken lösen.
    Notizen: Abstract The intersection radius of a set ofn geometrical objects in ad-dimensional Euclidean space,E d , is the radius of the smallest closed hypersphere that intersects all the objects of the set. In this paper, we describe optimal algorithms for some intersection radius problems. We first present a linear-time algorithm to determine the smallest closed hypersphere that intersects a set of hyperplanes inE d , assumingd to be a fixed parameter. This is done by reducing the problem to a linear programming problem in a (d+1)-dimensional space, involving 2n linear constraints. We also show how the prune-and-search technique, coupled with the strategy of replacing a ray by a point or a line can be used to solve, in linear time, the intersection radius problem for a set ofn line segments in the plane. Currently, no algorithms are known that solve these intersection radius problems within the same time bounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02246508
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  • 3
    Digitale Medien
    Digitale Medien
    Helly-type theorems for bodies in the plane with common supports (1993)
    Springer
    Geometriae dedicata 45 (1993), S. 289-299 
    Details
    ISSN: 1572-9168
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A theorem of Bisztriczky implies that every pair of disjoint convex bodies in the plane has a common supporting line. In this paper, combinatorial conditions implying the existence of common supporting lines for larger collections of disjoint convex bodies in the plane are exhibited.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01277968
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  • 4
    Digitale Medien
    Digitale Medien
    Continuous marennin production by agar-entrapped Haslea ostrearia using a tubular photobioreactor with internal illumination (2000)
    Springer
    Applied microbiology and biotechnology 54 (2000), S. 634-640 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The marine diatom Haslea ostrearia was immobilized in a tubular agar gel layer introduced into a photobioreactor of original design with internal illumination for the continuous synthesis of marennin, a blue-green pigment of biotechnological interest. Marennin was produced for a long-term period (27–43 days) and the volumetric productivity was maximum (18.7 mg day−1 l−1 gel) at the highest dilution rate (0.25 day−1) and lowest agar layer thickness (3 mm). Heterogeneous cell distribution in the agar layer revealed diffusional limitation of light and nutrients. However, the 3 mm gel thickness led to a more homogeneous cell distribution during incubation and to an increase of the whole biomass in the agar gel layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002530000380
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  • 5
    Digitale Medien
    Digitale Medien
    Subcellular fractionation of the two organelle DNAs of malaria parasites (1992)
    Springer
    Current genetics 21 (1992), S. 405-408 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Malaria ; Organelle ; DNA ; Fractionation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Malaria parasites contain two extrachromosomal DNAs, a 6 kb repetitive linear molecule which is assigned on the basis of its genetic content to the mitochondria, and a 35 kb transcriptionally active circular molecule whose intracellular location is not known. We used the polymerase chain reaction to detect and estimate the numbers of both molecules in sub-cellular fractions derived from the rodent parasite Plasmodium yoelii. The two DNA molecules were not coordinately partitioned by the fractionation process, the 6 kb molecule being more abundant, relative to the 35 kb circle, in a fraction enriched for mitochondria, the converse being true for a less dense fraction of unknown identity. This implies that the two molecules are located in different cellular compartments, and is consistent with other evidence suggesting they have different evolutionary origins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00351702
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  • 6
    Digitale Medien
    Digitale Medien
    Uniparental inheritance of the mitochondrial gene cytochrome b in Plasmodium falciparum (1993)
    Springer
    Current genetics 23 (1993), S. 360-364 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Plasmodium falciparum ; Cytochrome b ; Uniparental inheritance ; Mitochondrial
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The inheritance of an extrachromosomal 6-kb element has been examined in the human malaria parasite Plasmodium falciparum. A single base pair difference in the cytochrome b gene from the 6-kb element of two different cloned lines of the parasite was identified, and used as a marker in a cross in the mosquito stage of the life cycle. Analysis of 59 individual hybrid oocysts resulting from this cross clearly demonstrated that inheritance of the cytochrome b gene was uniparental. This observation makes it possible to investigate the inheritance and evolution of cytoplasmic traits, including certain forms of drug resistance, in natural populations of this parasite.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00310900
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  • 7
    Digitale Medien
    Digitale Medien
    Nocturnal synthesis and diurnal degradation of phytoplankton biomass in surface waters (1989)
    Springer
    Marine biology 101 (1989), S. 457-462 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Natural populations of phytoplankton were collected near the Bay of Bourgneuf, France, in spring 1982, and were subjected to natural surface irradiance outdoors. They exhibited exponential growth on time scales of a week, but significant decreases in biomass indicators such as chlorophyll a and particulate nitrogen were observed during daytime. At night, these decreases were more than compensated by increases in the same biomass variables, which could double over 12 h of darkness. These features are characteristic of phytoplankton populations in surface waters which cannot escape high irradiances, and may be representative of situations in incubation bottles held at fixed depths near the surface. Under such conditions, a decrease in biomass during daytime should not necessarily be interpreted as irreversible damage unless growth measurements are carried out over the following night hours to check for possible recovery.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00541647
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  • 8
    Digitale Medien
    Digitale Medien
    Do toxicity and accumulation of copper change during size reduction in the marine pennate diatom Haslea ostrearia? (2000)
    Springer
    Marine biology 136 (2000), S. 323-330 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  One of the best-known features of diatom biology is the reduction in mean cell size during vegetative multiplication by binary fission. We examined changes in copper toxicity and copper accumulation during cell-size reduction in Haslea ostrearia (Simonsen), a pennate diatom responsible for greening in oyster-ponds. We selected three strains with apical axes of different lengths: 40 μm (S40), 65 μm (S65) and 85 μm (S85). Each strain was grown separately in batch culture and exposed to a range of copper overloads (0 to 1.57 μM) that were added to the culture immediately after cell inoculation. Significant differences in sensitivity to copper were observed among the three strains. S85 exhibited highest sensitivity, followed by S40, while S65 displayed the highest tolerance. After 5 to 6 d exposure to 0.47 μM copper, chlorophyll a, carbohydrate, protein and lipid content per g dry weight had not changed in any of the three strains studied, except for a decrease of 16% in chlorophyll a in S85. At the end of the growth period with 0.47 μM copper, the amount of metal per unit surface area was similar for all strains, but the quantity of intracellular copper per g dry weight was lower in S65 cells than in S40 and S85 cells. Notable differences in the kinetics of both adsorbed and intracellular copper were observed between S40 and S85. Our results suggest that tolerance mechanisms may change during the vegetative life of H. ostrearia. The differential sensitivities of the strains suggest that copper pollution may alter the cell composition of natural populations of H. ostrearia by inducing selection for smaller cell size. Since auxosporulation results in the formation of larger cells with a higher sensitivity to copper, H. ostrearia could gradually disappear from copper-contaminated environments. In addition, by inducing smaller cell size, copper contamination would have an impact on filter-feeders such as oysters, whose diet is largely composed of diatoms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002270050690
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  • 9
    Digitale Medien
    Digitale Medien
    The evolutionary origin of the 35 kb circular DNA of Plasmodium falciparum: new evidence supports a possible rhodophyte ancestry (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 249-252 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Malaria ; Plasmodium falciparum ; Plastid extrachromosomal DNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In common with other Apicomplexan parasites, Plasmodium falciparum carries two extrachromosomal DNAs, one of which, the 6 kb element, is undoubtedly mitochondrial. The second, generally referred to as the 35 kb circle, is of unknown provenance, but the nature and organization of its genetic content makes a mitochondrial association unlikely and the molecule has features reminiscent of plastid genomes. We now report the occurrence on the circle of an open reading frame specifying a predicted 470 amino acid protein that shares more than 50% identity with a gene currently known only on the plastome of red algae. This high degree of conservation confirms the 35 kb circle's plastid ancestry, and we speculate that it may have originated from the rhodoplast of an ancient red algal endosymbiont in the progenitor of the Apicomplexa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280323
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  • 10
    Digitale Medien
    Digitale Medien
    The ILWAS model: Formulation and application (1985)
    Springer
    Water, air & soil pollution 26 (1985), S. 425-459 
    Details
    ISSN: 1573-2932
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The Integrated Lake-Watershed Acidification Study (ILWAS) model was developed to predict changes in surface water acidity given changes in the acidity of precipitation and dry deposition. The model routes precipitation through the forest canopy, soil horizons, streams and lakes using mass balance concepts and equations which relate flow to hydraulic gradients. The physical-chemical processes which change the acid-base characteristics of the water are simulated by rate (kinetic) and equilibrium expressions and include mass transfers between gas, liquid and solid phases. The aqueous constituents simulated include: pH, alkalinity, the major cations (Ca2+ Mg2+, K+, Na+, and NH4 +) and anions (SO inf4 sup2− , NO inf3 sup− , Cl−, F−), monomeric Al and its inorganic and organic complexes, organic acid analogues and dissolved inorganic carbon (CT). Since free hydrogen ion (H+) (and hence pH) is not conserved, its concentration is derived from the solution alkalinity and the total concentrations of inorganic C, organic acid, and monomeric Al. The ILWAS model has been used to predict changes in the acidity of Woods Lake (typical lake pH 4.5 to 5.0) and Panther Lake (typical lake pH 6 to 7) given reductions in total atmospheric S loads. The two basins are located within 30 km of each other in the Adirondack Mountains and receive similar acidic deposition. The response to a halving in the total atmospheric S load was basin-specific: In Panther Lake, little pH change occurred even 12 yr after the load reduction; in Woods Lake, the change was considerably larger. Hypothesis testing with the model has shown that the routing of water through soils (shallow versus deep flow) largely determines the extent to which incident precipitation is neutralized. Analysis of the two lake basins using the model and field data showed the watersheds to be net suppliers of base to the through-flowing water, although internal watershed production of strong acidity did occur. This internal production of acidity was approximately two-thirds the amount of the atmospheric load.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280695
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