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  • 1
    Electronic Resource
    Electronic Resource
    Electrical and optical properties of ZnS0.05Se0.95 nanocrystalline thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5652-5660 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnS0.05Se0.95 nanocrystalline films were deposited onto fused silica and GaAs (100) substrates by the magnetron sputtering technique. The electrical conductivities of the films deposited onto fused silica substrates were measured in the temperature range of 180–300 K. It was observed that the low temperature conductivity could be explained by hopping of the charge carriers in the Coulomb gap while at elevated temperature Mott hopping is the predominant mode of conduction in these films. A distinct cross over from Efros–Shklovoskii to Mott hopping is observed for all the films. Optical spectra were found to be dominated by the combined effects of optical losses due to absorption and scattering. The absorption spectra indicated a blueshift, the extent of which depended on the crystallite size. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370113
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of $\mathsf{\gamma}$ -Fe $\mathsf{_2}$ O $\mathsf{_3}$ nanoparticles coated on silica spheres: Structural and magnetic properties (2003)
    Springer
    The European physical journal 34 (2003), S. 163-171 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The structural and magnetic properties of $\gamma$ -Fe2O3 nanoparticles dispersed on silica spheres prepared by sol-gel method were investigated. The properties of $\gamma$ -Fe2O3 nanoparticles without silica were compared with those on silica spheres. Both the nanoparticle assemblages were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Mössbauer (20, 80 and 300 K) and electron paramagnetic resonance (EPR) (80, 300 K) measurements. The XRD spectra clearly indicated the formation of pure $\gamma$ -Fe2O3 nanoparticles and the absence of any other form of iron oxide. TEM images showed a uniform distribution of the nanoparticles of size $\sim$ 6 nm on the surfaces of silica spheres (diameter $\sim$ 35-60 nm). The size of the individual nanoparticles (without silica) varied within 5-6 nm. The low temperature (20 K) Mössbauer spectra consisted of a partially split sextet superimposed on a doublet. The partial magnetic splitting of the sextet at 20 K revealed the effect of surface magnetization and surface modifications of the $\gamma$ -Fe2O3 nanoparticles coated on silica spheres. The gradual collapse of the partially split sextet into a doublet with increasing temperature indicated the superparamagnetic relaxation exhibited by the $\gamma$ -Fe2O3 nanoparticles with/without silica. The surface magnetization arising out of mis-aligned spins at the surface as evidenced by Mössbauer spectra was further confirmed by electron paramagnetic resonance (EPR) studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00208-2
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on CdS nanoparticles dispersed in silica matrix prepared by sol-gel technique (2003)
    Springer
    The European physical journal 31 (2003), S. 3-9 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 78.20.-e Optical properties of bulk materials and thin films – 81.05.Dz II-VI semiconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: SiO2/CdS-nanoparticle composite films (SiO2:CdS=85:15, 80:20, 75:25 and 70:30) were prepared by the sol-gel route. The films were characterized by studying microstructural (XRD and TEM) and optical (transmittance and photoluminescence) properties. Band gaps of these films annealed at different temperatures (373-473 K) for different times (10-120 min) indicated that the signature of nanocrystallinity is retained throughout the range of our experimental conditions. A thermal diffusion process controlled growth in the crystallite size with increasing annealing time and temperature. The average radii of the nanoparticles varied as the cube root of the annealing time but showed exponential dependence on the inverse of annealing temperature. Photoluminescence (PL) studies of the composite films indicated excitonic transitions. Theoretical analysis of the line shapes of the PL peaks recorded at 300 K and 80 K could be accounted for by the combined effects of size distribution and phonon broadening. It was observed that the deformation potential (E d) effectively controlled the line shapes of the PL measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00001-3
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  • 4
    Electronic Resource
    Electronic Resource
    Shortest Paths in Digraphs of Small Treewidth. Part I: Sequential Algorithms (2000)
    Springer
    Algorithmica 27 (2000), S. 212-226 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Shortest path, Graph theory, Treewidth, Dynamic algorithm.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. We consider the problem of preprocessing an n -vertex digraph with real edge weights so that subsequent queries for the shortest path or distance between any two vertices can be efficiently answered. We give algorithms that depend on the treewidth of the input graph. When the treewidth is a constant, our algorithms can answer distance queries in O(α(n)) time after O(n) preprocessing. This improves upon previously known results for the same problem. We also give a dynamic algorithm which, after a change in an edge weight, updates the data structure in time O(n β ) , for any constant 0 〈 β 〈 1 . Furthermore, an algorithm of independent interest is given: computing a shortest path tree, or finding a negative cycle in linear time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004530010016
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  • 5
    Electronic Resource
    Electronic Resource
    Computing Mimicking Networks (2000)
    Springer
    Algorithmica 26 (2000), S. 31-49 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Network flow, Maximum flow, Minimum cut, Multiterminal network, Realizable external flow, Mimicking network.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. A mimicking network for a k -terminal network, N , is one whose realizable external flows are the same as those of N . Let S(k) denote the minimum size of a mimicking network for a k -terminal network. In this paper we give new constructions of mimicking networks and prove the following results (the values in brackets are the previously best known results): S(4)=5 [2 16 ] , S(5)=6 [2 32 ] . For bounded treewidth networks we show S(k)= O(k) [2^ 2 k ] , and for outerplanar networks we show S(k) $\leq$ 10k-6 [k 2 2 k+2 ] .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004539910003
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  • 6
    Electronic Resource
    Electronic Resource
    The significance of rubidium-strontium age of sedimentary rock (1976)
    Springer
    Contributions to mineralogy and petrology 59 (1976), S. 161-170 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The isotopic composition of strontium and the rubidium and strontium contents were measured for samples of the Lower Permian Havensville Shale collected at four different localities across a distance of approximately 200 miles in Kansas and northern Oklahoma. The Rb-Sr dates ranged from 320 m.y. to 395 m.y. The initial Sr87/Sr86 ratios were between 0.709 and 0.717. The ages are interpreted to be intermediate between the age of the source material and the time of sedimentation and, therefore, are not indicative of any geologic event. A model has been proposed to explain the colinearity of the Rb-Sr data and the evolution of different Rb-Sr dates for the same stratigraphic unit at different localities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371305
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  • 7
    Electronic Resource
    Electronic Resource
    Sex specific chromosome polymorphisms in the common Indian Krait, Bungarus caeruleus Schneider (Ophidia, Elapidae) (1979)
    Springer
    Chromosoma 73 (1979), S. 93-108 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Chromosome analyses of common Indian Krait, B. caeuleus from three geographical regions of India have revealed variable diploid numbers of 43, 44 and 45 in different female individuals but a constant diploid number of 44 in the males. C-banding and in situ hybridization studies, using radio labelled W sex chromosome specific satellite DNA as a probe, have shown that C-banding and sex chromosome associated satellite DNA's are exclusively localised in the W chromosome. The W chromosome is involved in reciprocal translocations either with a medium sized macroautosome or with a microchromosome resulting in a multiple sex chromosome constitution of Z1Z1Z2Z2♂/Z1Z2W♀ type. In some female individuals dissociation of the W has resulted in multiple W chromosomes, W1 and W2. These polymorphisms are uniquely confined to the female sex only. A predominance of polymorphic females, involving particularly the translocation of a medium sized macrochromosome, in all three geeographical regions and the restriction of the females having the original chromosome constitution (ZW) to one geographical region suggests that polymorphic individuals have adaptive flexibility and higher fecundity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294849
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of prior-austenite grain size and fracture mode on the fracture toughness of 12% Cr steel (1976)
    Springer
    International journal of fracture 12 (1976), S. 101-106 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé En modifiant la température d'austénitisation d'un acier à 12% Cr, on a fait varier son grain austénitique primaire et l'on a étudié l'effet de ces variations sur la ténacité à la rupture K Ic dans l'état brut de trempe et après des revenus allant jusqu'à 550°C. Pour ces divers traitements thermiques, on a constaté des modes de rupture différents, ce qui a permis d'évaluer les effets de variations de la taille du grain sur la ténacité à la rupture, pour des morphologies de rupture bien spécifiques.
    Notes: Abstract The prior-austenite grain size of a 12% Cr steel has been varied by altering the austenitising temperature. The effect of these variations on the K Ic fracture toughness has been studied for the as-quenched condition and after subsequently tempering at temperatures up to 550°C. The fact that different fracture modes occurred within this range of heat-treatment has allowed the effect of grain size variations on fracture toughness to be compared for specific fracture morphologies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00036013
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  • 9
    Electronic Resource
    Electronic Resource
    Development of Anti-Reflection (AR) Coating on Plastic Panels for Display Applications (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 77-82 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel coating ; AR coating ; optical coating ; optical thin film ; anti-reflection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Traditionally, various vacuum-based processes have been used for producing interference-type anti-reflection (AR) coatings on large area substrates for different commercial applications. In this paper, the development of sol-gel derived AR coating on large plastic substrates for display application is presented. The sol-gel dip coating process was used to deposit thin films on large size plastic panels. By developing sols with different refractive indices, multi-layer thin-film AR coating stacks were designed and fabricated. These coatings possess good uniformity and meet stringent automotive specifications. This technology has been commercialized successfully for dashboard instrument panel application in Toyota's new hybrid engine car, named Prius. In this paper, AR coatings prepared by the sol-gel process are reviewed. The basic design concept for an AR coating, the coating preparation procedure, and important parameters of the solution coating process are discussed. Optical constants of the coating materials were characterized by using spectroscopic ellipsometry. Optical, mechanical and environmental tests were performed on the sol-gel derived AR coating stack. The sol-gel derived AR coating possesses equivalent or superior properties when compared to the major commercially available AR coating products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008714205813
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  • 10
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance and Mössbauer spectroscopy of transition metal ion doped mullite (2000)
    Springer
    Journal of materials science 35 (2000), S. 4735-4741 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Appreciable difference in the properties of undoped and oxide-doped mullite are observed. The oxidation state of cation, its concentration and the position of the mullite lattice occupied by it appear to be the responsible factors. Mullite has, therefore, been doped with four transition metal ions, Mn, Fe, Cr and Ti. With the help of EPR and Mössbauer spectroscopy (supplimented by X-ray diffractometry) the oxidation states of these ions and the mullite lattice sites where they enter has been investigated. It was observed that Mn ion was present in Mn2+ and Mn3+ states, the former remained as clusters and the latter occupied the octahedral sites in the mullite lattice. Only Fe3+ ion was detected and conclusive evidence was obtained for the entry of Fe3+ in the octahedral lattice position of mullite from the analysis of Mössbauer spectra with the help of a specially written computer programme. The Cr ion entered the mullite structure only in the Cr3+ state. The change in lattice parameters of Cr doped mullite were measured by the XRD technique. The results showed that the expansion of b-axis was more than that of the a-axis which supported the presence of Cr3+ ion in the octahedral site of mullite lattice. The absence of signal in the EPR spectra of Ti doped mullite suggested the presence of only Ti4+ (3d0) ion. Very low electrical resistivity of Ti doped mullite and close similarity between mullite and Al2TiO5 structures stood as evidence for incorporation of Ti4+ ion in the octahedral site of mullite lattice by replacing Al3+ ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004863309464
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