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  • 1
    Electronic Resource
    Electronic Resource
    Measurement of bacterial growth rates in subsurface sediments using the incorporation of tritiated thymidine into DNA (1988)
    Springer
    Microbial ecology 16 (1988), S. 3-16 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microbial growth rates in subsurface sediment from three sites were measured using incorporation of tritiated thymidine into DNA. Sampling sites included Lula, Oklahoma, Traverse City, Michigan, and Summit Lake, Wisconsin. Application of the thymidine method to subsurface sediments required (1) thymidine concentrations greater than 125 nM, (2) incubation periods of less than 4 hours, (3) addition of SDS and EDTA for optimum macromolecular extraction, and (4) DNA purification, in order to accurately measure the rate of thymidine incorporation into DNA. Macromolecule extraction recoveries, as well as the percentage of tritium label incorporated into the DNA fraction, were variable and largely dependent upon sediment composition. In general, sandy sediments yielded higher extraction recoveries and demonstrated a larger percentage of label incorporated into DNA than sediments that contained a high silt-clay component. Reported results also indicate that the acid-base hydrolysis procedure routinely used for macromolecular fractionation in water samples may not be routinely applicable to the modified sediment procedure where addition of SDS and EDTA are required for macromolecule extraction. Growth rates exhibited by subsurface communities are relatively slow, ranging from 5.1 to 10.2×105 cells g−1 day−1. These rates are 2–1,000-fold lower than growth rates measured in surface sediments. These data lend support to the supposition that subsurface microbial communities are nutritionally stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02097401
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  • 2
    Electronic Resource
    Electronic Resource
    Did primitive microorganisms use nonhem iron proteins in place of NAD/P? (1995)
    Springer
    Journal of molecular evolution 40 (1995), S. 559-563 
    Details
    ISSN: 1432-1432
    Keywords: Archaebacteria ; Evolution of metabolism ; Nicotinamide coenzymes ; Nonhem iron proteins ; Redox coenzymes ; Thermophiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are of universal occurrence in living organisms and play a central role in coupling oxidative with reductive reactions. However, the evidence that the origin and early evolution of life occurred at high temperatures (〉95°C) is now strong, and at these temperatures some modern metabolites, including both the reduced and oxidized forms of these coenzymes, are unstable. We believe there is good evidence that indicates that in the most primitive organisms nonhem iron proteins carried out many or all of the functions of NAD/P(H). This has important implications for the way in which investigations of archaebacterial metabolism are conducted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160501
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  • 3
    Electronic Resource
    Electronic Resource
    A hydrothermally precipitated catalytic iron sulphide membrane as a first step toward life (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 231-243 
    Details
    ISSN: 1432-1432
    Keywords: Botryoid ; Chemiosmosis ; Ferredoxin ; Greigite ; Hydrothermal ; Iron sulphides ; Membrane ; Origin of life ; Protocell ; Proton motive force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We propose that life emerged from growing aggregates of iron sulphide bubbles containing alkaline and highly reduced hydrothermal solution. These bubbles were inflated hydrostatically at sulphidic submarine hot springs sited some distance from oceanic spreading centers four billion years ago. The membrane enclosing the bubbles was precipitated in response to contact between the spring waters and the mildly oxidized, acidic and iron-bearing Hadean ocean water. As the gelatinous sulphide bubbles aged and were inflated beyond their strength they budded, producing contiguous daughter bubbles by the precipitation of new membrane. [Fe2S2]+/0 or [Fe4S4]2+/+ clusters, possibly bonded by hydrothermal thiolate ligands as proferredoxins, could have catalyzed oxidation of thiolates to disulphides, thereby modifying membrane properties. We envisage the earliest iron sulphide bubbles (pro botryoids) first growing by hydrostatic inflation with hydrothermal fluid, but evolving to grow mainly by osmosis (the protocellular stage), driven by (1) catabolism of hydrothermal abiogenic organics trapped on the inner walls of the membrane, catalyzed by the iron sulphide clusters; and (2) cleavage of hydrophobic compounds dissolved in the membrane to hydrophilic moieties which were translocated, by the proton motive force inherent in the acidic Hadean ocean, to the alkaline interior of the protocell. The organics were generated first within the hydrothermal convective system feeding the hot springs operating in the oceanic crust and later in the pyritizing mound developing on the sea floor, as a consequence of the reduction of CO, CO2, and formaldehyde by Fe2+- and S2−-bearing minerals. We imagine the physicochemical interactions in and on the membrane to have been sufficiently complex to have engendered auto- and cross-catalytic replication. The membrane may have been constructed in such a way that a “successful” parent could have “informed” the daughters of membrane characteristics functional for the then-current level of evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160147
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular genetic evidence for a founder effect in familial hypercholesterolemia among French Canadians (1992)
    Springer
    Human genetics 〈Berlin〉 88 (1992), S. 529-536 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Familial hypercholesterolemia (FH), at a prevalence of about 1 in 200 in the French-Canadian population, is caused by a 10-kb deletion in the low-density lipoprotein (LDL) receptor gene in 60% of French-Canadian FH heterozygotes. We genotyped 159 FH patients who carry this common mutation and 221 healthy French-Canadian controls for five DNA restriction fragment length polymorphisms (RFLPs) of the LDL receptor gene. The allele numbers for four of the five RFLPs differed significantly (P 〈 0.001) between FH patients and control subjects. Our results suggest that the 10-kb deletion carrier allele is associated with a single haplotype (called the B haplotype). In a family study including a patient homozygous for the 10-kb deletion, we showed that the B haplotype cosegregates with the deletion in affected members and that the B haplotype is also associated with the normal allele in some members of the family. We identified 15 different haplotypes for the normal allele in 10-kb deletion carrier FH heterozygotes. These results offer strong support, at a molecular level, for the hypothesis of a founder effect for the 10-kb deletion in the French-Canadian population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219339
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  • 5
    Electronic Resource
    Electronic Resource
    Electron transport in sub-micron GaAs channels at 300 K (1983)
    Springer
    Applied physics 31 (1983), S. 65-70 
    Details
    ISSN: 1432-0630
    Keywords: 72.20 ; 72.60 ; 85.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Transient velocity-field characteristics have been computed for GaAs channels having lengths of 0.1, 0.2, 0.5, 1, and 20 μm for electric fields between 1 and 50 kV/cm at 300 K. The results are compared with earlier calculations and the significant features of the computed results are discussed. It is found that the electron motion for all channel lengths and for all fields is significantly affected by collisions. The threshold field for negative differential mobility increases, and the magnitude of the differential mobility decreases with decrease in the length of the sample. The maximum steady-state velocity increases with decrease in the length and may be as high as 5.4×107 cm/s for 0.1 μm samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616306
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  • 6
    Electronic Resource
    Electronic Resource
    High-field transport properties of In0.765Ga0.235As0.5P0.5 (1983)
    Springer
    Applied physics 32 (1983), S. 39-43 
    Details
    ISSN: 1432-0630
    Keywords: 72 ; 72.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Monte-Carlo results on the velocity-field characteristics, ac diffusion-constant and thermal-noise voltages are presented for In0.765Ga0.235As0.5P0.5 at 300K. Recently available values of physical constants have been used in the calculations. The values of diffusion constants are close to those of InP but the thermal noise voltages are found to increase faster with the field. The peak velocity is 1.9 × 107 cm/s and the threshold field for negative differential mobility is about 6 kV/cm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626132
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  • 7
    Electronic Resource
    Electronic Resource
    Noise current spectrum in submicrometer samples (1986)
    Springer
    Applied physics 41 (1986), S. 197-199 
    Details
    ISSN: 1432-0630
    Keywords: 72.20 ; 72.70
    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 noise current spectral density in submicrometer samples is computed using the Monte Carlo method. The normalized spectral density is found to decrease with sample length and increase with the field. The high-field noise is like shot noise and increases with current in agreement with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616840
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray and thermal properties of (Sm1−x Gd x )2(MoO4)3 (1988)
    Springer
    Journal of materials science 7 (1988), S. 769-771 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00722094
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of the effect of rare earth doping on the electrical and photovoltaic properties of chromotrope 2R thin film devices (1998)
    Springer
    Journal of materials science 9 (1998), S. 91-97 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Praseodymium (Pr) doped and Samarium (Sm) doped chromotrope 2R (CHR) were used for the fabrication of Schottky devices, by the spin coating technique. The diode in which doped CHR behaves as an n-type organic semiconductor exhibits rectification behaviour in the dark. Doping with rare earths imparts an accelerated improvement in the n-type conductivity as well as in the rectification effect. The observed rectification effects are explained by n-type semiconductivity of the doped CHR thin films. The formation of a blocking contact (Schottky barrier) indium tin oxide with (ITO) electrode and an ohmic contact with Al or ln, also confirms its n-type behaviour. The position of the Fermi level shifts toward the conduction band edge on rare earth doping. Additionally, the concentration of free carriers and mobility of electrons also increase upon doping, with the simultaneous decrease in trap concentration. Various electrical parameters such as barrier height (φb), density of ionized donor (Ns) and depletion layer width (W) were calculated from the detail capacitance–voltage analysis of (C–V) characteristics. The photo-action spectra of the devices and absorption spectra of doped CHR layer reveal the formation of a Schottky barrier at the ITO-doped CHR interface and an Ohmic contact at the Al-doped CHR interface. Photovoltaic measurements of these devices provide parameters such as short circuit photocurrent (Jsc), open circuit voltage (Voc), fill factor (FF) and power conversion efficiency (η). The effect of rare earth doping on the electrical and photovoltaic parameters are discussed in detail. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008849120080
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of ITO/ZnPc/CHR/In p-n junction-photovoltaic device using J–V, C–V and photoaction measurements (1999)
    Springer
    Journal of materials science 10 (1999), S. 539-544 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The electrical and photovoltaic properties of a newly designed two-layered photocell having the configuration ITO/ZnPc/CHR/In p-n junction were investigated. The rectification effect observed in the device is due to an energy barrier formed between the CHR and ZnPc layer. The depletion layer characteristics of the device were investigated by measuring the temperature variation of capacitance. These measurements indicate that a depletion layer of width 190 nm as well as potential barrier height of about 0.78 eV, decreases with temperature. The current–voltage characteristics of the device yield a barrier height of about 0.74 eV formed between ZnPc and CHR. The device showed a response to light over the whole visible region extending from 400 nm to 800 nm. The comparison of photoaction spectra with the absorption spectra also indicates the formation of an energy barrier between CHR and ZnPc. The dissociation of excitons induced by the built-in field potential existing between the CHR and ZnPc layers is responsible for photogeneration of the carriers. Various photovoltaic parameters were calculated and are discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008948622871
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