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  • 2000-2004  (12)
  • 1935-1939  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Preparation and transport properties of polycrystalline Bi and Bi–SiO2 nanocomposites (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3269-3275 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bismuth–silica nanocomposites and polycrystalline bismuth were prepared via powder metallurgy in order to study the influence of silica inclusions on the thermoelectric properties of bismuth. Bi–SiO2 powders containing from 0.5 to 15 vol. % of silica and pure Bi powders were produced by an arc-plasma processing. Transmission electron microscopy investigations revealed the presence of a nanometric silica shell around the Bi grains. The powders were cold pressed and sintered close to the melting temperature of bismuth. The bulk microstructures are very different for the bismuth and the Bi–SiO2 nanocomposites because silica, which is primarily dispersed at grain boundaries, inhibits the grain growth during sintering. The electrical resistivity was measured from 5 to 300 K, while the thermoelectric power and the thermal conductivity were measured from 65 to 300 K on both polycrystalline bismuth and Bi–SiO2 samples containing 0.5, 4, and 15 vol. % of silica, respectively. The transport properties are mainly discussed with regard to the microstructures. In spite of a strong reduction of the thermal conductivity for the nanocomposites, the thermoelectric figure of merit is not improved compared to bismuth due to a dominating concurrent increase of the electrical resistivity resulting from a finite-size effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289079
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  • 2
    Electronic Resource
    Electronic Resource
    Calculation of the magnetic properties of CoN clusters on Pd(111) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4894-4896 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of CoN clusters (N≤7) deposited on Pd(111) have been determined in the framework of a self-consistent d-band model Hamiltonian. Results are given for the spin and orbital magnetic moments and for the magnetic anisotropy energy for different structures of the CoN clusters. We find that the magnetic orbital contribution to the total magnetic moment can be of the order of 20%. The magnetization direction of CoN changes in most cases from in-plane to off-plane upon deposition. We observe that the main contribution to the magnetic anisotropy energy results from the cluster–substrate interface. Comparison of the magnetic properties between deposited and free clusters is also provided. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373194
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetism of RhN clusters (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4906-4908 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The size and structural dependence of the magnetic properties of RhN clusters (3≤N≤27) are studied by using a d-electron tight-binding Hamiltonian which includes hybridizations, Coulomb interactions, and spin–orbit coupling on the same electronic level. We show that the spin (S) and orbital (L) magnetic moments depend strongly on the local environment of the atoms and that their behavior as a function of the cluster size present oscillations which are in good qualitative agreement with experiment. The magnetic anisotropy energy and the anisotropy in L are quantified by considering different directions of the spin magnetization S within the cluster. We conclude that orbital contributions to the average magnetization in RhN clusters could be important for precise comparison with experiment. Bond-length relaxation effects are also briefly discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373198
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced hysteresis in the semiconductor-to-metal phase transition of VO2 precipitates formed in SiO2 by ion implantation (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3161-3163 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A strongly enhanced hysteresis with a width of 〉34 °C has been observed in the semiconductor-to-metal phase transition of submicron-scale VO2 precipitates formed in the near-surface region of amorphous SiO2 by the stoichiometric coimplantation of vanadium and oxygen and subsequent thermal processing. This width is approximately an order of magnitude larger than that reported previously for the phase transition of VO2 particles formed in Al2O3 by a similar technique. The phase transition is accompanied by a significant change in infrared transmission. The anomalously wide hysteresis loop observed here for the VO2/SiO2 system can be exploited in optical data storage and switching applications in the infrared region. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415768
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  • 5
    Electronic Resource
    Electronic Resource
    Density and binding forces in diatomics (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1788-1799 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In a recently reported method, the molecular density is partitioned in minimally deformed atomic contributions, which are expanded in spherical harmonics times radial factors. Here we use this representation to express the electrostatic potential of the molecule, the force on its nuclei, and the conformational variations of energy in terms of some simple integrals of the atomic radial factors. As a first application, we analyze the relationship between the density and the binding forces (and the bonding energy) in the diatomic molecules of the first row atoms. Two types of forces act on each nucleus: the self-pulling exerted by its own cloud and the external force due to the remaining atoms. The self-pulling comes only from the dipole type term of the atomic density. The external force comes from the other clouds and nuclei and is dominated by the effective charges which depend on the outermost region of the charge term. Analyzing the progressive deformations of the atoms when they approach each other, the forces associated with these deformations and their contributions to the energy, one has a detailed description of the chemical bond which is complementary, and in many aspects more appealing, than the conventional ones. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1420403
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  • 6
    Electronic Resource
    Electronic Resource
    Differential capacity of CD8α+ or CD8α− dendritic cell subsets to prime for eosinophilic airway inflammation in the T-helper type 2-prone milieu of the lung (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 34 (2004), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Different subsets of dendritic cells (DCs), identified in mouse spleen by their differential expression of CD8α, can induce different T-helper (Th) responses after systemic administration. CD8α− DCs have been shown to preferentially induce Th type 2 (Th2) responses whereas CD8α+ DCs induce Th1 responses.Objective To study if these DC subsets can still induce different Th responses in the Th2-prone milieu of the lung and differentially prime for eosinophilic airway inflammation, typical of asthma.Methods Donor mice first received daily Flt3L injections to expand DC numbers. Purified CD8α+ or CD8α− splenic DCs were pulsed with ovalbumin (OVA) or phosphate-buffered saline and injected intratracheally into recipient mice in which carboxyfluorescein diacetate succinimidyl ester-labelled OVA-specific T cell receptor transgenic T cells had been injected intravenously 2 days earlier. T cell proliferation and cytokine production of Ag-specific T cells were evaluated in the mediastinal lymph nodes (MLNs) 4 days later. The capacity of both subsets of DCs, to prime for eosinophilic airway inflammation was determined by challenging the mice with OVA aerosol 10 days later.Results CD8α− DCs migrated to the MLN and induced a vigorous proliferative T cell response accompanied by high-level production of IL-4, IL-5, IL-10 and also IFN-γ during the primary response and during challenge with aerosol, leading to eosinophilic airway inflammation. In the absence of migration to the MLN, CD8α+ DCs still induced a proliferative response with identical levels of IFN-γ but reduced Th2 cytokines compared with CD8α− DCs, which led to weak eosinophilic airway inflammation upon OVA aerosol challenge. Unpulsed DCs did not induce proliferation or cytokine production in Ag-specific T cells.Conclusion CD8α− DCs are superior compared with CD8α+ DCs in inducing Th2 responses and eosinophilic airway inflammation in the Th2-prone environment of the lung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2004.02133.x
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  • 7
    Electronic Resource
    Electronic Resource
    Epidemiology of necrotizing ulcerative gingival lesions in adolescents (2002)
    Oxford, UK : Munksgaard International Publishers
    Journal of periodontal research 37 (2002), S. 0 
    Details
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective and background:   Relatively little is known about the epidemiology of necrotizing ulcerative gingival lesions (NUG) in adolescent populations. Most studies have comprised special target groups, such as military recruits, HIV patients, or severely malnourished subjects.Methods:  A multistage random cluster sampling scheme was used to obtain a sample of 9203 students aged 12–21 years from 98 of a total of 618 high schools in Santiago, Chile. Students were given a clinical oral examination and questionnaire information was obtained on smoking and oral hygiene habits, dental attendance patterns, and diabetic status. The diagnostic criteria for NUG were the presence of necrosis and ulceration of at least one interproximal papillae.Results:  The estimated prevalence of NUG was 6.7% (95% CI = [6.2; 7.3]). A multivariable logistic regression analysis showed that last seeing a dentist more than 1 year ago (OR = 1.60), or never (OR = 1.93), and reporting diabetes (OR = 2.12) showed a significant positive association with the presence of NUG; whereas neither gender nor smoking were important predictors. Students aged 18-21 years were more, albeit statistically insignificantly, likely to have NUG than were younger students (OR = 1.40).Conclusions:  Our observation that reporting to be diabetic was positively associated with the presence of NUG is interesting, as diabetes has never been addressed as a possible risk factor. As the association between diabetes and periodontitis in adults is thought to relate to impaired function of neutrophils, microangiopathy, and impaired wound healing this finding suggests a significant role of the host response also for the occurrence of NUG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0765.2002.01377.x
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  • 8
    Electronic Resource
    Electronic Resource
    Astaxanthin Extraction From Shrimp Waste by Lactic Fermentation and Enzymatic Hydrolysis of the Carotenoprotein Complex (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 67 (2002), 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: : Natural carotenoids are an alternative to synthetic orange-red pigments. They are present in crustaceans as a protein-pigment complex. In order to extract this highly unstable pigment, crustacean waste must be stabilized; lactic fermentation is a simple and environmentally friendly method to achieve this goal. Shrimp wastes were inoculated with Lactobacillus bacterial cultures. Carotenoids were then extracted with an organic solvent system. Protein-pigment splitting was carried out using a mixture of 4 commercial enzymes; and the protein was separated from the pigment by ultrafiltration. Electrophoretograms showed that the pigment was attached to a 265-kDa protein. Splitting the protein-pigment complex allows studies on pigment absorption, stability and application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2002.tb09443.x
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  • 9
    Electronic Resource
    Electronic Resource
    Impaired type-1 activity and increased NK cells in Gleich's syndrome (2001)
    Copenhagen : Munksgaard International Publishers
    Allergy 56 (2001), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: An altered production of cytokines has been described in Gleich's syndrome. Our aim was to study the cytokine production at the single-cell level in a patient with Gleich's syndrome and to determine whether it changed during a flare episode. Methods: Blood samples were obtained from a 30-year-old woman diagnosed with Gleich's syndrome before and during the subsequent flare of edema of trunk and arms and weight gain. The major lymphoid subsets (CD4+, CD8+, and CD19+) and natural killer (NK) cells were measured by flow cytometry. Cytokine-producing T cells (IL-2, IFN-γ, and IL-4) were quantified in whole blood by intracellular staining with specific monoclonal antibodies and flow cytometry analysis after polyclonal stimulation with phorbol 12-myristate 13-acetate and ionomycin. Results: Increased numbers of immature CD4+CD8+ T cells and NK cells were observed in peripheral blood during the asymptomatic period. The latter population significantly decreased during the flare. Type-1 cells were decreased in both asymptomatic and, more markedly, during the attack with respect to healthy subjects. Conclusions: The decreased type-1 response demonstrated in this patient might be the basis of the hypereosinophilia of Gleich's syndrome. Besides, the NK cells might play a role in the pathogenesis of these inflammatory episodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1398-9995.2001.00287.x
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  • 10
    Electronic Resource
    Electronic Resource
    Importance of including Blomia tropicalis in the routine diagnosis of Venezuelan patients with persistent allergic symptoms (2004)
    Oxford, UK : Munksgaard International Publishers
    Allergy 59 (2004), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  Blomia tropicalis is a common mite found in the house dust of many tropical countries including Venezuela. The prevalence of skin test and specific serum immunoglobulin (Ig)E reactivity to B. tropicalis in Venezuela has not been previously evaluated.Methods:  In the present study we evaluated the skin reactivity by skin prick test and specific IgE by a multiple antigen blot assay, against B. tropicalis and Dermatophagoides pteronyssinus, in a group of 115 subjects who attended the Allergy Clinic of the Institute of Biomedicine, Caracas, Venezuela, and we studied possible cross reactions between similar proteins of these two mites.Results:  One hundred and six patients with persistent allergic respiratory symptoms showed a positive skin prick test to at least one of the mite extracts, with the frequency of positive reactions to B. tropicalis being as high as to D. pteronyssinus. Twelve patients reacted only to D. pteronyssinus and 13 different patients only to B. tropicalis. Specific IgE to each of the mite extracts was found with similar frequency, and the results coincided with the skin test reactivity.Conclusions:  The study indicated the importance of including B. tropicalis in routine diagnostic testing in tropical and sub-tropical situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1398-9995.2004.00454.x
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