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  • Springer  (43)
  • Wiley  (16)
  • American Institute of Physics (AIP)  (5)
  • Oxford University Press  (2)
  • American Physical Society (APS)
  • 1995-1999  (66)
  • 1
    Electronic Resource
    Electronic Resource
    Liposome-Based Optochemical Nanosensors (1999)
    Springer
    Microchimica acta 131 (1999), S. 57-64 
    Details
    ISSN: 1436-5073
    Keywords: Key words: dye-encapsulating liposomes; pH sensing; oxygen sensing; optochemical nanosensors.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  This paper describes the optochemical pH and oxygen sensing properties of dye-encapsulating and fluorescently labeled nano-sized unilamellar liposomes. To prepare the oxygen sensitive liposomes a lipid mixture consisting of dimyristoylphospatidylcholine, cholesterol, and dihexadecyl phosphate (molar ratio 5:4:1) all dissolved in dry isopropyl alcohol is injected into a sensing dye solution. The mixture is then sonicated with a liposome maker to form dye-encapsulating liposomes. A lipid mixture consisting of dimyristoylphospatidylcholine, N-(fluorescein-5-thiocarbamoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (fluorescein DHPE), cholesterol, and dihexadecyl phosphate (molar ratio 20:1:16:4) is used to prepare the pH sensitive liposomes by the same sonication technique. Fluorescein labeled DHPE phospholipids are combined with DMPC phospholipids in a 1:20 ratio to incorporate the sensing dye directly into the bilayer membrane, virtually eliminating any instability due to dye leakage. Oxygen sensing liposomes are created by encapsulating the oxygen sensitive ruthenium tris(1,10)-phenanthroline complex [Ru(phen)3]. The dye is believed to exist both in free solution within the liposome, and as an adherent on the inner membrane of the liposome. High uniformity of the liposomes is realized by extruding them back and forth through a 100 nm pore-size polycarbonate membrane. TEM images of the liposomes, stained with uranyl acetate, show that the liposomes are unilamellar, spherical in shape, maintain high structural integrity, and average 70 nm in diameter. The liposomes show high stability with respect to dye leaking at room temperature for 8 days, and high photostability when exposed to the excitation light. Individual liposomes are used to monitor the pH and oxygen level in their vicinity during the enzymatic oxidation of glucose by the enzyme glucose oxidase. The newly prepared environmentally sensitive liposomes can be applied for non-invasive pH and oxygen determination in tissues and single biological cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s006040050009
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  • 2
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    Liposome-Based Optochemical Nanosensors (1999)
    Springer
    Details
    Publication Date: 1999-06-24
    Print ISSN: 0026-3672
    Electronic ISSN: 1436-5073
    Topics: Chemistry and Pharmacology
    Published by Springer
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    PAPER CURRENT
  • 3
    Electronic Resource
    Electronic Resource
    Optical gain and spontaneous emission in InGaAs/GaAs multiple quantum well laser diodes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 582-584 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present gain and spontaneous emission measurements in In0.35Ga0.65As/GaAs multiple quantum well lasers. First, the gain is extracted from measured amplified spontaneous emission through a laser facet. Second, unamplified spontaneous emission is detected through the transparent GaAs-substrate. Taking advantage of the fundamental relationship between gain and spontaneous emission, the separation of the electron and hole quasi-Fermi levels, ΔEF, at various bias currents below laser threshold is accurately determined. Theoretically, ΔEF is calculated utilizing a simple two-subband structure model. Fitting the theoretical predictions to the experimental data allows us to determine the threshold carrier density (nth=2.0×1018 cm−3), the in-plane hole effective mass (mv1=0.21m0), and the amount of band gap shrinkage at threshold (ΔEg,th=33 meV). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362721
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  • 4
    Electronic Resource
    Electronic Resource
    A new method for the synthesis of magnetoliposomes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5699-5701 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new method for the synthesis of magnetoliposomes, i.e., nanosized magnetic particles coated by a phospholipid membrane, is presented. Magnetoliposomes are prepared by directly using the phospholipid vesicles as nanoreactors for the precipitation of the magnetic particles. The magnetoliposomes have been characterized using transmission electron microscopy imaging and x-ray powder diffraction. The magnetic properties of the magnetoliposomes have been investigated with a superconducting quantum interference device magnetometer. Our results indicate that the magnetoliposomes contain approximately spherical maghemite nanoparticles averaging 25 nm in diameter. The occurrence of a phospholipid bilayer surrounding the magnetic particles is confirmed both by transmission electron micrographs of samples negatively stained with uranyl acetate and by digital fluorescence imaging microscopy measurements of magnetoliposomes labeled with fluorescein. The temperature dependence of the zero field cooled and field cooled susceptibilities of the magnetoliposomes is consistent with their expected superparamagnetic nature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370256
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  • 5
    Electronic Resource
    Electronic Resource
    Analytical criteria for nonlinear instability of thermal structures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 4127-4133 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analytical criteria for supercritical and asymptotic stability and for subcritical and superexponential instability are obtained for slab-like, spherical, and cylindrical thermal structures. It is assumed that both, the thermal conductivity κ(T) and the gain/loss function Q(T), can be written as continuous functions of the temperature and they have continuous derivatives. Conditions on κ and Q under which the symmetry of the structure determines the kind of instability (or stability) are obtained. Additionally, it is found that the response of the structure not only depends on the amplitude of the disturbance, but also on whether the disturbance increases or decreases the initial steady temperature. In particular, the threshold value for the amplitude of the disturbances beyond which a linearly stable configuration destabilizes, and explicit conditions for catastrophic heating or cooling are obtained. Applications to structures constituted by atomic and molecular gas are outlined. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871036
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and carrier density dependence of carrier lifetime in InGaAs/GaAs multiple-quantum-well lasers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3158-3160 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The carrier lifetime in undoped and p-doped mesa and ridge waveguide In0.35Ga0.65As/GaAs multiple-quantum-well lasers is extracted from the frequency response of the spontaneous emission. The radiative recombination coefficient is found to be the same for mesa and ridge waveguide lasers, and is nearly independent of the doping level. For ridge waveguide lasers, a simple method is proposed to obtain the lateral broadening of the active region due to carrier diffusion. When the corrected active region width is considered, the threshold carrier densities for both undoped and p-doped lasers are independent of the lateral structure and cavity width. Further, the surface recombination velocity in mesa lasers is determined. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116814
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  • 7
    Electronic Resource
    Electronic Resource
    Carrier profile for In0.35Ga0.65As/GaAs multiquantum well lasers from capacitance–voltage measurements (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1138-1140 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The carrier profile for MBE grown In0.35Ga0.65As/GaAs multiquantum well laser structures with nominally undoped and beryllium-doped active regions was determined by using the capacitance–voltage (C–V) technique at room temperature. A simple theoretical model was used to extract the impurity concentration and the quantum-well carrier density from the experimental profiles. We obtained a high carrier concentration in nominally undoped devices caused by a strong growth temperature dependent Be diffusion from the p-cladding layer, and no difference between doped samples with different nominal dopant location. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115738
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  • 8
    Electronic Resource
    Electronic Resource
    Testing CERES-Wheat with Free-Air Carbon Dioxide Enrichment (FACE) Experiment Data: CO2 and Water Interactions (1999)
    Springer
    Semigroup forum 91 (1999), S. 247-255 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: 2 concentration and associated climate change on crop yields. Such model predictions are largely untested in the field, for lack of experimental data. We tested the CERES-Wheat model, modified to include leaf-level photosynthesis response to elevated CO2 using field data from 2 yr of Free-Air Carbon Dioxide Enrichment (FACE) experiments with spring wheat (Triticum aestivum L. cv. Yecora Rojo) in Maricopa, AZ. Two irrigation treatments (well-watered, WW; water-deficit stressed, WS) and two atmospheric CO2 concentrations (ambient, 350 μmol mol-1, elevated, 550 μmol mol-1) were simulated. The model was evaluated using measurements of crop phenology, aboveground dry matter (DM) production, grain yield, and evapotranspiration (ET). Model calculations of crop phenology were within 2 to 3 d of observed values under WW, ambient CO2 conditions in both years. The model did not simulate the accelerated crop phenology (5-8 d at physiological maturity) observed in the WW and elevated CO2 treatments, indicating the need to include effects of increased stomatal resistance on canopy temperature. Simulations of DM and grain yield were within 10% of measured values, except for a tendency to overcalculate DM response to CO2 by 10 to 15% in Year 1 for WS treatments. The model undercalculated cumulative ET under WW conditions by 15%; model sensitivity analyses suggest that simulation of potential evapotranspiration (PET) was too low for this arid site. The model reproduced measured dynamics of CO2-water interactions. Simulated reductions in water loss due to elevated CO2 were about 4%, in agreement with measurements. The model simulated larger increases in DM production and yield due to elevated CO2 under WS than under WW conditions. In Year 1, simulated crop response to CO2 was 2% larger (measured:3%) under WS than under WW conditions; in Year 2, it was 11% larger (measured: to be further evaluated with additional experimental datasets, is an important attribute of models used to project crop yields under elevated CO2 and climate change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 9
    Electronic Resource
    Electronic Resource
    Key results and implications from phase 1(c) of the Project for Intercomparison of Land-surface Parametrization Schemes (1999)
    Springer
    Climate dynamics 15 (1999), S. 673-684 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract  Using atmospheric forcing data generated from a general circulation climate model, sixteen land surface schemes participating in the Project for the Intercomparison of Land-surface Parametrization Schemes (PILPS) were run off-line to equilibrium using forcing data from a GCM representative of a tropical forest and a mid-latitude grassland grid point. The values for each land surface parameter (roughness length, minimum stomatal resistance, soil depth etc.) were provided. Results were quality controlled and analyzed, focusing on the scatter simulated amongst the models. There were large differences in how the models’ partitioned available energy between sensible and latent heat. Annually averaged, simulations for the tropical forest ranged by 79 1 3;W m-2 for the sensible heat flux and 80 W m-2 for the latent heat flux. For the grassland, simulations ranged by 34 W m-2 for the sensible heat flux and 27 W m-2 for the latent heat flux. Similarly large differences were found for simulated runoff and soil moisture and at the monthly time scale. The models’ simulation of annually averaged effective radiative temperature varied with a range, between all the models, of 1.4 K for tropical forest and 2.2 K for the grassland. The simulation of latent and sensible heat fluxes by a standard ‘bucket’ models was anomalous although this could be corrected by an additional resistance term. These results imply that the current land surface models do not agree on the land surface climate when the atmospheric forcing and surface parameters are prescribed. The nature of the experimental design, it being offline and with artificial forcing, generally precludes judgements concerning the relative quality of any specific model. Although these results were produced de-coupled from a host model, they do cast doubt on the reliability of land surface schemes. It is therefore a priority to resolve the disparity in the simulations, understand the reasons behind the scatter and to determine whether this lack of agreement in de-coupled tests is reproduced in coupled experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050309
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  • 10
    Electronic Resource
    Electronic Resource
    Ferribacterium limneticum, gen. nov., sp. nov., an Fe(III)-reducing microorganism isolated from mining-impacted freshwater lake sediments (1999)
    Springer
    Archives of microbiology 171 (1999), S. 183-188 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsFerribacterium limneticum ; Dissimilatory ; iron reduction ; Mine wastes ; Lake Coeur d’Alene ; Idaho
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dissimilatory Fe(III)-reducing bacterium was isolated from mining-impacted lake sediments and designated strain CdA-1. The strain was isolated from a 4-month enrichment culture with acetate and Fe(III)-oxyhydroxide. Strain CdA-1 is a motile, obligately anaerobic rod, capable of coupling the oxidation of acetate and other organic acids to the reduction of ferric iron. Fe(III) reduction was not observed using methanol, ethanol, isopropanol, propionate, succinate, fumarate, H2, citrate, glucose, or phenol as potential electron donors. With acetate as an electron donor, strain CdA-1 also grew by reducing nitrate or fumarate. Growth was not observed with acetate as electron donor and O2, sulfoxyanions, nitrite, trimethylamine N-oxide, Mn(IV), As(V), or Se(VI) as potential terminal electron acceptors. Comparative 16 S rRNA gene sequence analyses show strain CdA-1 to be most closely related (93.6% sequence similarity) to Rhodocyclus tenuis. However, R. tenuis did not grow heterotrophically by Fe(III) reduction, nor did strain CdA-1 grow photrophically. We propose that strain CdA-1 represents a new genus and species, Ferribacterium limneticum. Strain CdA-1 represents the first dissimilatory Fe(III) reducer in the β subclass of Proteobacteria, as well as the first Fe(III) reducer isolated from mine wastes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050697
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