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  • 1
    Electronic Resource
    Electronic Resource
    Photoluminescence performance of pulsed-laser deposited Al2O3 thin films with large erbium concentrations (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5120-5125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Erbium doped Al2O3 films with concentrations up to 6×1020 Er cm−3 have been prepared in a single step process by pulsed-laser deposition. Alternate ablation of Al2O3 and Er targets has been used to control the in-depth distribution and in-plane concentration of Er3+ ions independently. The characteristic Er3+ photoluminescence response at 1.53 μm has been studied as a function of the Er3+ distribution. It is found that lifetime values can be greatly increased by increasing the Er3+–Er3+ in-depth separation above 3 nm. This result can be related to a reduced Er3+–Er3+ energy migration process. The in-plane Er3+ concentration was increased by either increasing the number of pulses on the Er target or the laser energy density for ablation. By the latter method in-plane concentrations as high as 1.1×1014 Er cm−2 per layer (corresponding to 2×1020 Er cm−3) were achieved, while keeping lifetime values as high as 6 ms. This result is explained in terms of shallow Er3+ implantation during deposition. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1409575
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  • 2
    Electronic Resource
    Electronic Resource
    Nurse Plants, Mycorrhizae, and Plant Establishment in a Disturbed Area of the Sonoran Desert (1999)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 7 (1999), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Arbuscular-mycorrhizal (AM) fungi stabilize the soil and enhance plant growth by alleviating nutrient and drought stress. Their contributions to agriculture are well known, but their role in desert ecosystems has received less attention. The AM status of perennial plants in disturbed and undisturbed plots were investigated in the Sonoran Desert near La Paz, Baja California Sur, Mexico to determine if AM fungi contribute to resource-island stability and plant establishment. All perennial plants (46 species) in the study plots were AM, but root colonization varied widely (〈10 to〉 70%). Roots of plants that established in greatest numbers in plant-free zones (colonizers) of disturbed areas were highly AM. Plants with trace (〈10%) root colonization (cacti of the tribe Pachycereae: Pachycereus pringlei, Machaerocereus gummosus, and Lemaireocereus thurberi; and Agave datilyo) established preferentially in association with nurse trees. The pachycereid cacti grew under Prosopis articulata and A. datilyo under Olneya tesota canopies. Of the nine species of trees and arborescent shrubs in the area, the mature (〉20 yr) nurse-legumes P. articulata and O. tesota supported the largest number of under-story plants. Younger plants had only occasional associates. AM propagule densities in plant-free areas were lower than under plant canopies (40 vs. 280 propagules/kg soil). Occurrence of soil mounds (islands) under plants owing to soil deposition was related to the nature of the canopies and to the AM status of the roots. Island soils were enmeshed with AM-fungal hyphae, especially in the upper layer (approximately 10 cm). Seedlings of P. pringlei, growing in a screenhouse for six months in soil collected under P. articulata, had a biomass ten times greater than plants growing in bare-area soil. The results are consistent with the proposition that AM fungi contributed to the plant-soil system of our study area by: (1) helping to stabilize windborne soil that settles under dense plant canopies; (2) enhancing the establishment of colonizer plants in bare soils of disturbed areas; and (3) influencing plant associations through differences in the mycotrophic status of the associates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.1999.72027.x
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  • 3
    Electronic Resource
    Electronic Resource
    Genetic differences between natural populations of diploid and tetraploid Dactylis glomerata ssp. izcoi (1997)
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 52 (1997), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Twenty-one natural populations (thirteen tetraploids and eight diploids) of Dactylis glomerata ssp. izcoi (an Iberian endemic) were evaluated in the field for three consecutive years, using two clones per genotype, to separate genetic and environmental factors. Many traits showed significant differences between ploidy levels, but all of them overlapped. Therefore, it is justified to include both cytotypes in a subspecies in which tetraploids could be autopolyploids. In general, however, diploids had shorter stomatal guard cells, lower seed production and were later heading than tetraploids. Within tetraploids, most traits differed significantly between and within populations. There was less inter- and intrapopulation variation in the diploids. The range of plant dimensions exceeded that of former descriptions of the sub-species, bringing it closer to ssp. glomerata. Inland populations were not qualitatively different from one coastal population. Diploid populations showed less risk of hypomagnesemia than tetraploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1997.tb02359.x
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental evidence of a crossover in the vortex dimensionality in high-Tc superconductors : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6589-6591 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum motion of vortices in high-temperature superconductors (HTSCs) was studied via magnetic relaxation measurements performed with a commercial superconducting quantum interference device magnetometer. At a fixed temperature, the field dependence of the time-logarithmic magnetic relaxation rate normalized to the first magnetization value, R=||d(M/M0)/d ln(t)||, was investigated in different polycrystalline HTSCs: TlBaCaCuO (2212 and 2223 single phases), YBaCuO (123 phase), and (Hg,Tl)BaCaCuO (1223 phase). The results obtained for TlBaCaCuO 2223 phase and (Hg,Tl)BaCaCuO show a common trend: R increases linearly with magnetic field up to a certain value, the dimensional crossover field H3D-2D, above which it becomes field-independent. H3D-2D is a characteristic field which depends on the anisotropy parameter and the interlayer spacing of the material. The field dependence of R can be ascribed to a crossover in the dimensionality of the object involved in the quantum process: above H3D-2D, the longitudinal dimension of the tunneling object, Lc, is smaller than the interlayer distance, so the object is of two-dimensional (2D) nature (2D pancake vortices). Below H3D-2D, 2D vortices in neighboring layers become coupled, so the tunneling object becomes three-dimensional (3D) in nature (3D flux-lines). The field dependences of R obtained for TlBaCaCuO 2212 phase and YBaCuO show only the 2D and 3D vortex regimes, respectively. Well agreement between theoretical estimates and experimental values for the dimensional crossover field and normalized relaxation rates is achieved. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362568
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  • 5
    Electronic Resource
    Electronic Resource
    Threading dislocations in silicon layer produced by separation by implanted oxygen process (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2113-2120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Threading dislocations in the silicon layer in three different types of the silicon on insulator samples produced by standard and improved separation by implanted oxygen (SIMOX) processes were investigated by synchrotron x-ray topography, scanning electron microscopy (SEM), and optical microscopy. The densities and Burgers vectors of the dislocations were first determined nondestructively by synchrotron x-ray topography. Then the line directions of the same dislocations were determined by SEM after chemical Secco etching. Some of these results were compared with results obtained from optical microscopy of Secco etched samples. The threading dislocations in the Si layer were found to occur mainly in pairs with densities of the order of 105 cm−2 in standard SIMOX samples and of the order of 104 cm−2 in improved SIMOX samples. These dislocations have an edge character. Other features of these dislocations, such as the distances between two dislocations forming a pair, orientations of these pairs, and dislocations that change their line direction, are also discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363104
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum vortex motion in high-Tc superconductors : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6516-6518 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic relaxation experiments at low temperatures were performed in different zero-field-cooled (ZFC) and field-cooled (FC) high-Tc superconductors (HTSCs): TlBaCaCuO (2212 and 2223 phases, polycrystalline and thin-film samples), (Hg,Tl)BaCaCuO (1223 phase, polycrystalline material), and (Bi,Pb)SrCaCuO (2212 phase, single crystal). For each system and in the whole temperature range investigated, the relaxation curves obtained after both cooling processes are linear with the logarithm of time. The temperature dependence of the relaxation rate normalized to the first magnetization value, R=||d(M/M0)/d ln(t)||, follows a trend which is common to all systems: R decreases linearly with decreasing temperature down to a value, which is called the crossover temperature, below which it levels off to a T-independent plateau. This behavior gives evidence of a transition in the mechanism responsible for the relaxation process at low temperatures, from thermally activated (linear dependence on T) to quantum vortex motion (T-independent regime). The experimental values for the crossover temperatures and normalized relaxation rates compare fairly well to numerical estimates in the framework of the theories of quantum vortex motion in layered HTSCs. Finally, the transition from one regime into another was studied in two samples of the TlBaCaCuO, 2223 phase, system in order to investigate the influence of dissipation on the quantum process. A clear conclusion on this point could not be drawn from these kinds of measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361930
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetization processes in samples with modulated anisotropy under the action of nonuniform magnetic fields (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3961-3964 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we study the magnetic behavior of amorphous ferromagnetic ribbons having helical anisotropy with the helix axis perpendicular to the sample surface. It is shown that the magnetization processes under the action of a longitudinal magnetic field can be controlled by the nonuniform field produced by an alternating current, of the same frequency than the exciting field, flowing through the sample. Hysteresis loops with very different susceptibilities and coercive fields have been obtained by varying the amplitude of the current intensity and the phase differences between the exciting magnetic field and the current through the sample. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359917
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  • 8
    Electronic Resource
    Electronic Resource
    Herpetic whitlow in an AIDS patient (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the European Academy of Dermatology and Venereology 12 (1999), S. 0 
    Details
    ISSN: 1468-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This case confirms that cutaneous herpes simplex virus (HSV) infections in many AIDS patients is important not only for the difficulty in diagnosis of herpetic lesions, but also for the possibility that co-infection by HSV and HIV can adversely affect prognosis in these patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1468-3083.1999.tb01036.x
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of High-pressure Processing on Carotenoid Extractability, Antioxidant Activity, Glucose Diffusion, and Water Binding of Tomato Puree (Lycopersicon esculentum Mill.) (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 66 (2001), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : High-pressure-treated tomato puree was investigated for changes in carotenoid extractability, antioxidant activity, glucose diffusion, and water binding. No effect of pressurization was observed in the total concentrations of the main water-insoluble antioxidants, lycopene and β-carotene, extracted with tetrahydrofuran, but lower recovery of carotenoids with petroleum ether suggested structural changes in the tomato pulp tissue, due to processing. Total antioxidant capacity of the water-soluble fraction was unchanged immediately after pressure treatment, but was better preserved during 21 d at 4 °C, compared with untreated samples. High-pressure treatment resulted also in enhanced water binding. Glucose diffusion through dialysis tubing was lower after high-pressure treatment, leading to a higher glucose retardation index.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2001.tb08231.x
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  • 10
    Electronic Resource
    Electronic Resource
    Genetic diversity in tropical maize inbred lines: heterotic group assignment and hybrid performance determined by RFLP markers (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 119 (2000), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Tropical maize inbred lines, eight derived from a Thai synthetic population (BR-105) and 10 from a Brazilian composite population (BR-106), were assayed for restriction fragment length polymorphisms with 185 clone-enzyme combinations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocation and hybrid performance. Genetic distances (GDs) were on average greater for BR-105×BR-106 lines (0.77) than for BR-106×BR-106 (0.71) and for BR-105×BR-105 (0.69) lines. Cluster analysis resulted in a clear separation of BR-105 and BR-106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for grain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP-based GDs are efficient and reliable to assess and allocate genotypes from tropical maize populations into heterotic groups. However, RFLP-based GDs are not suitable for predicting the performance of line crosses from genetically different heterotic groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0523.2000.00539.x
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