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  • 1
    Electronic Resource
    Electronic Resource
    Nucleic acid content of Synechococcus spp. during growth in continuous light and light/dark cycles (1998)
    Springer
    Archives of microbiology 170 (1998), S. 201-207 
    Details
    ISSN: 1432-072X
    Keywords: Key words Cyanobacteria ; Nucleic acid content ; Circadian rhythms ; Cell division ; Ribosomal RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-limited batch cultures of Synechococcus spp. strains PCC 6301 and WH 8103 exhibited a positive correlation between the specific growth rate and the cellular content of both RNA and DNA. The ratio of RNA to DNA increased with the growth rate in Synechococcus sp. strain WH 8103, as it does in heterotrophic bacteria, but remained constant in Synechococcus sp. strain PCC 6301. The cellular content of nucleic acids decreased during light periods and increased during dark periods in Synechococcus sp. strain PCC 6301 entrained by 12-h light/ 12-h dark (diurnal) cycles. This result was unexpected in light of experiments demonstrating a circadian increase in transcriptional activity during the subjective light periods and a decrease in transcriptional activity during subjective dark periods. The cyclical variation in cellular nucleic acid content during diurnal cycles appears to be in part a function of the timing of cell division and will influence estimates of in situ growth rates or relative abundances of cyanobacteria using oligonucleotide probes complementary to 16S rRNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050634
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  • 2
    Electronic Resource
    Electronic Resource
    Stacking fault effects in pure and n-type doped GaAs (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 907-909 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using ab initio total-energy calculations, we investigate the effects of stacking faults on the properties of dopants in pure and n-type doped GaAs. We find that the Si impurity segregates towards a GaAs stacking fault. A Si atom at a Ga site in the stacking fault, in either a neutral or a negative charge state, is energetically favorable as compared to a Si atom at a Ga site in a crystalline environment by as much as 0.2 eV. We also find that a Si impurity in the stacking fault cannot occupy metastable positions, as occurs in the formation of DX centers. Thus, stacking faults can prevent the formation of DX-like centers in GaAs. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347005
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  • 3
    Electronic Resource
    Electronic Resource
    DX centers in GaAs/Si-δ/AlAs heterostructure (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1999-2001 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microscopic mechanisms of impurity spreading in GaAs/Si-δ/AlAs heterostructure have been investigated using an ab initio pseudopotential total energy calculation. Our results showed that silicon atoms can move from the δ-doped plane occupying interstitial positions, favored by the high doped concentration, forming DX centers. The silicon impurity position, out of the δ plane in the AlAs layers, presents an energetically stable configuration, and in the GaAs layers, presents a metastable configuration. As a consequence a silicon doping limit is reached due to the presence of localized deep states inside the band gap, when silicon atoms are in interstitial positions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123726
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  • 4
    Electronic Resource
    Electronic Resource
    Solving the structural model for the Si(001)–In(4×3) surface (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 203-205 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The atomic geometry, energetic, and scanning tunneling microscopy (STM) simulations of the In-induced Si(001)-(4×3) surface have been investigated using first-principles total energy calculations. We have studied three distinct (4×3) structural models, which have been proposed based on STM and x-ray diffraction experiments. The energetic stability calculations indicate that the (4×3) model formed by In–Si–In mixed trimer is the most stable structure. In addition, we have simulated the STM images (for occupied states) of these three models. Our STM image for the In–Si–In mixed trimer structure presents a good agreement with the experimentally observed single central protrusion localized on the top-layer Si atom. Also, the calculated equilibrium atomic geometry of the In–Si–In mixed trimer model presents a good agreement with the experimentally obtained x-ray diffraction results. The other two proposed models are energetically less favorable by as much as 0.2 eV/(1×1) compared to the mixed trimer model. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383275
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon doping of GaAs: Compensation effects (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2715-2717 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the carbon substitutional impurity in GaAs at both cation and anion sites. We use first-principle nonlocal pseudopotentials, and we find for the acceptor CAs impurity the expected shallow-level defect behavior. The CGa impurity, however, behaves as a deep amphoteric impurity, not as a shallow donor, and in the neutral and negative charge states should cause virtually no lattice shrinking. We expect that this unusual behavior is the reason why the center was not directly detected up to now, although compensating for the shallow acceptor is known to occur with high carbon concentrations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113498
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  • 6
    Electronic Resource
    Electronic Resource
    Towards microbial data integration (1997)
    Springer
    Journal of industrial microbiology and biotechnology 18 (1997), S. 68-72 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: database; integration; microbes; phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There are currently 100–200 microbiology-related databases in existence, although it is impossible to find answers to queries that span even a few of these. The Center for Microbial Ecology (CME) at Michigan State University seeks to change this situation by coordinating the creation of an Integrated Microbial Database (IMD), accessible through the World Wide Web (WWW). Such a system will contain up-to-date phylogeny and taxonomy, gene sequences (including genomes), biochemical data, metabolic models, ecological and phenotypic data. Current main obstacles to creation of an IMD are the lack of a single freely available organismal nomenclature with synonyms and the availability of much critical data. An IMD will have major impacts on microbial biology: currently intractable fundamental questions might be answered, experiments could be refocused, and new commercial possibilities created. An IMD should remain freely available and be created under an open development model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900366
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic and structural properties of defects in c-BN (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 941-946 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a molecular cluster with 71 atoms, we studied the electronic and structural properties of nitrogen vacancy, boron antisite, and oxygen in cubic boron nitride through an ab initio Hartree-Fock calculation. We found that all defects introduce a deep state above the middle-energy gap. These defects present a C3v local symmetry. In the case of nitrogen vacancy, the possibility of the F-center formation is discussed. All the calculations were performed using the program code GAMESS.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 941-946, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic structure of periodically Si-δ-doped GaAs (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 203-206 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculation of periodically Si-δ-doped GaAs was performed in the regime of high-donor concentration. The electronic confinement exhibit a quasi-2D behavior even for small periods (p = 45 Å). The electronic properties of the clustering SiGa—SAs also was studied. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560821
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  • 9
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    DX centers in GaAs/Si-δ/AlAs heterostructure (1999)
    American Institute of Physics
    Details
    Publication Date: 1999-04-05
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Perennial grasslands enhance biodiversity and multiple ecosystem services in bioenergy landscapes (2014)
    National Academy of Sciences
    Details
    Publication Date: 2014-01-13
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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