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  • 1
    ISSN: 1432-072X
    Keywords: Key words Cyanobacteria ; Merismopedia ; Synechococcus ; Synechocystis ; Eucapsis ; 16S rDNA ; sequencing ; SDS-PAGE ; Taxonomy ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five Merismopedia-like cyanobacterial strains were collected from microbial mats at Norderney Island, subcultured in the laboratory, and finally grown as unicyanobacterial cultures. As a sixth strain, Merismopedia glauca from the „Sammlung von Algenkulturen“ at Göttingen (SAG) was used for comparisons. According to morphological and physiological characteristics initially observed in the field and during initial subculturing, the five strains were assigned to the species Merismopedia glauca, Merismopedia punctata, or Merismopedia elegans. However, after prolonged maintenance under laboratory conditions, the formation of platelet-like colonies stopped, whereas cell sizes, production of extracellular polymeric substances, and division patterns were stably maintained. These physiological and morphological parameters allowed us to divide the six strains into two clusters. This division was further supported by the profiling of total cell protein and phycobilisomes using SDS-PAGE. The nearly complete 16S rDNA sequence of three of the six isolates was determined. The comparative sequencing analysis revealed an almost 100% identity of these three Merismopedia-like strains. The evolutionary distance dendrogram constructed placed this Merismopedia cluster into a common line of descent with Synechocystis sp. strain PCC6906. Based on the analysis of common stretches of 1,050 nucleotides, the overall similarity between the sequence types of „Merismopedia“ and „Synechocystis“ is 96–97%. The values of the different methods for taxonomic classification of unicyanobacterial strains, the relationship of the cyanobacterial genera Merismopedia, Synechococcus, Synechocystis, and Eucapsis sp., and the functional role of different Merismopedia morphologies within microbial mats are discussed. It is suggested that all analyzed Merismopedia strains be combined into one species, namely Merismopedia punctata Meyen (1839).
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  • 2
    ISSN: 1432-072X
    Keywords: Key words Actinomycetes ; Acidothermus cellulolyticus ; Arthrobacter ; Bacillus ; Frankia ; Geodermatophilus ; Sporichthya polymorpha ; 16S rDNA sequences ; Rock ; varnish ; Multilocular thallus ; Biodiversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an extended study on the biodiversity of rock-dwelling bacteria, the colony and cell morphology, physiology, protein patterns, and 16S rDNA sequences of 17 bacterial strains isolated from different surfaces of rocks, stones, and monuments and from various geographical locations were characterized. All except one strain, which was found to be a Bacillus, were members of the order Actinomycetales. The majority of the strains either were closely related to Geodermatophilus obscurus, which was also analyzed in this study, or formed a closely related sister taxon. All of these strains were isolated from the surface of marble in Namibia and Greece and from limestone from the Negev desert, Israel. One strain, G10, of Namibia origin was equidistantly related to Geodermatophilus obscurus, Frankia alni, Sporichthya polymorpha, and Acidothermus cellulolyticus. Three strains from rock varnish in the Mojave desert, California, were found to be highly related to Arthrobacter (formerly Micrococcus) agilis. All clusters could be confirmed from results of studies on morphological and physiological properties and from banding patterns of whole cell proteins. Based on the results of tests, four additional strains were assigned to the lineage defined by strain G10.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3185-3192 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculated the steady-state recombination rate for two coupled defect levels and implemented the model into a device simulator. This model generalizes the familiar single-level Shockley–Read–Hall (SRH) formula. If the intercenter transition probability vanishes, it reduces to the sum of two individual SRH rates, which are only linked via the band occupancies. The cases, where one of the levels or even both behave like traps in carrier capture, and the case of a rate-limiting intercenter transition are derived from the general expression. The important feature of the model is a possible increased field effect which might lead to large excess currents. The field effect is discussed in terms of tunnel-assisted multiphonon capture or direct tunneling into the levels, respectively. We show by means of numerical simulation that the large ideality factors found for liquid phase epitaxy grown diodes with weak intrinsic fields can be the result of a rapid direct charge transfer between donors and acceptors and the high probability of tunneling into the hydrogenic states. © 1995 American Institute of Physics.
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  • 4
    ISSN: 1573-8590
    Keywords: evaporitic ; sedimentation ; microbial mats ; salina ; salt production ; egypt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract A salina system along the Mediterranean coast of Egypt was investigated. Five sedimentary facies are described. For each facies, the evaporitic sedimentation and the biological conditions are considered. Comparisons of evaporite precipitates in the salina with ancient deposits are made.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Aerobiologia 11 (1995), S. 205-211 
    ISSN: 1573-3025
    Keywords: Atmospheric (passat) dust ; Blood rain-blood snow ; Geomicrobiology ; Microgeology ; Paper meteorites ; Infusoria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Christian Gottfried Ehrenberg can be considered to be the founder of the science of air-borne micro-organisms and thus aerobiology. The bicentennial of his birth (he was born on Easter Sunday, April 19th, 1795), however marks the beginning of several sciences and fields of science. He is the founder of geomicrobiology, protistology, co-founder of microbiology, scientific microscopy, neurobiology, and last not least of the theory of the Earth as a living entity, including rocks and rock deposits. The number of genera and species of bacteria, spirochaetes, fungi, diatoms, radiolaria, protozoa, and rotifera which were first described by him is in the hundreds. He is known as the discoverer and detailed describer of some of the most common bioluminescent marine organisms (Noctiluca miliaris andPeridinium), as well as the person who first deciphered the secret of the bloody hostia (Monas orBacterium prodigiosum, or more correctlySerratia marcescens), of the red snow and of the ‘meteor paper’ or ‘paper meteorites’. In this commemorative paper his work on air-borne dust and air-borne micro-organisms is reviewed.
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  • 6
    ISSN: 1572-9699
    Keywords: black yeasts ; microcolonial fungi ; taxonomy ; microbial damage ; stone monuments ; marble
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new meristematic black yeast species, Sarcinomyces petricola, is described. All strains known to date were isolated from sun-exposed marble in the Mediterranean basin. On the basis of PCR-ribotyping and nutritional physiology, the species is classified as an anamorph member of the ascomycete family Herpotrichiellaceae (Chaetothyriales).
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  • 7
    ISSN: 1572-9699
    Keywords: phylogeny ; taxonomy ; rock fungi ; MCF ; meristematic fungi ; Coniosporium ; Sarcinomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coniosporium perforans and C. apollinis, orginating from marble in the Mediterranean basin, are described as new species of rock inhabiting microcolonial fungi. The morphologically similar species Monodictys castaneae (Wallr.) S. Hughes, Phaeosclera dematioides Sigler et al., and a Coniosporium-like strain are compared using 18S rDNA phylogeny and Restriction Length Fragment Polymorphism analysis of Internal Transcribed Spacer regions. Sarcinomyces crustaceus Lindner is additionally compared on the basis of 18S rDNA sequencing data. Phylogenetic analysis suggests that Phaeosclera dematioides is related to the ascomycetous order Dothideales and Monodictys castaneae to the Pleosporales, whereas the three Coniosporium species studied are a sister group to the Herpotrichiellaceae (Chaetothyriales). A similar affinity was suggested previously for the recently described meristematic rock-fungus Sarcinomyces petricola Wollenzien & de Hoog. Sarcinomyces crustaceus appears unrelated to this group, and hence the present new taxa cannot be described in this genus.
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The "passivated emitter and rear locally diffused'' (PERL) silicon solar cell structure presently demonstrates the highest terrestrial performance of any silicon-based solar cell. This paper presents a detailed investigation of the limiting loss mechanisms in PERL cells exhibiting independently confirmed 1-sun efficiencies of up to 23.0%. Optical, resistive, and recombinative losses are all analyzed under the full range of solar cell operating conditions with the aid of two-dimensional (2D) device simulations. The analysis is based on measurements of the reflectance, quantum efficiency, dark and illuminated current–voltage (I–V) characteristics, and properties of the Si–SiO2 interfaces employed on these cells for surface passivation. Through the use of the 2D simulations, particular attention has been paid to the magnitudes of the spatially resolved recombination losses in these cells. It is shown that approximately 50% of the recombination losses at the 1-sun maximum power point occur in the base of the cells, followed by recombination losses at the rear and front oxidized surfaces (25% and 〈25%, respectively). The relatively low fill factors of PERL cells are principally a result of resistive losses; however, the recombination behavior in the base and at the rear surface also contributes. This work predicts that the efficiency of 23% PERL cells could be increased by about 0.7% absolute if ohmic losses were eliminated, a further 1.1% absolute if there were no reflection losses at the nonmetallized front surface regions, about 2.0% by introducing ideal light trapping and eliminating shading losses due to the front metallization, and by about 3.7% absolute if the device had no defect-related recombination losses. New design rules for future efficiency improvements, evident from this analysis, are also presented. © 1995 American Institute of Physics.
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