100,382 research outputs found
Erbium-doped ion-exchanged waveguide lasers in BK-7 glass
No full textIon exchange in glass is a simple, flexible, technique to realize optical fiber compatible planar waveguide devices. Recently, neodymium-doped waveguide lasers operating at 1060 and 1300 nm have been demonstrated in this technology. Lasers operating at 1540 nm are desirable for telecommunication applications and we report here, for the first time, ion-exchanged waveguide lasers in erbium-doped glass emitting at this wavelength. Lasers in BK-7 glass doped with 0.5 wt% Er2O3 and pumped at 980 nm exhibited launched pump power thresholds of 150 mW and slope efficiencies of 0.55%. The waveguides operated in a single transverse mode at the lasing wavelength
Dynamic mechanical response in epoxy nanocomposites incorporating various nano-silica architectures
No full textThis paper is a continuation of the previous work where the dielectric response (BDS) of epoxy nanocomposites filled with three types of nano-silica architectures, namely core (SiO 2 ), core-shell (SiO 2 )-(SiO 2 ) and hollow (h-SiO 2 ). was investigated. These samples were filled based on their respective nanoparticle surface area, keeping it theoretically constant across all samples. The aim is to better understand the molecular dynamics and physical mechanisms in dielectric nanocomposites to contribute towards developing materials with tailored properties. The samples were characterised based on their dynamic mechanical behaviour (DMA) and their T g was measured by DSC. Unlike BDS, there is no additional relaxation peak observed in DMA thermographs besides the conventionally known α and β. The T g of the samples increases as the size of the nanoparticles decreases. Analysis of the height, width and intensity of the tan δ of α relaxation peak suggests reduction in the localised modes of motion as the size of the nanoparticles reveals a internally plasticised nanocomposite system. The T g values obtained from DSC do not vary significantly across the samples. These key findings are discussed in details and demonstrate by providing further evidence that the additional relaxation observed in BDS measurements is potentially due to the presence of hydrogen bond interactions between the polymer matrix and the fillers. However, no significant impact on the viscoelastic-mechanical properties of the nanocomposites is evident
Did the Medieval West Receive a “Complete Model” of Education from Classical Islam? Reconsidering George Makdisi (1920–2002) and his Hypothesis
No full textGeelhaar T. Did the Medieval West Receive a “Complete Model” of Education from Classical Islam? Reconsidering George Makdisi (1920–2002) and his Hypothesis. In: Feuchter J, Hoffmann F, Yun B, eds. Cultural Transfers in Dispute Representations in Asia, Europe and the Arab World since the Middle Ages. Eigene und fremde Welten. Vol 23. Frankfurt ; New York: Campus; 2011: 98-120
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Morphological structure and mechanical properties of a nucleated Polyoxymethylene (POM) homopolymer resin processed under conventional injection molding conditions
No full textWhen injection molding semi-crystalline polymers, it is known that the resulting morphological and mechanical properties are strongly dependent on the processing conditions. Selectively influencing the performance of the final part as early as during processing is of great interest for industrial applications. To investigate the processing-structure-property correlation for a POM hompolymer resin, tensile specimens were manufactured under conventional injection molding conditions following a Design of Experimets (DoE). Morphological characterization was carried out by microscopy and X-ray measurements. Crystallinity was also measured by differential scanning calorimetry (DSC). Additionally, the (fracture) mechanical behaviour of the samples was assessed. Influences of the processing parameters on the crystalline structure and orientations within the material were identified. Furthermore, tensile tests were found to be sensitive to changes in morphology and processing, whereas the fracture behaviour did not change significantly despite the structural changes within the samples
Fluorescent lifetime of Er<sup>3+</sup> <sup>3</sup>I<sub>13/2</sub> level in BK-7 borosilicate glass
No full textIt is established that the B3+ ions exist only in the form of [BO4] units in BK-7 borosilicate glass. This limits the maximum vibrational energy at peak to 1200 /cm rather than 1400 /cm, as is found in borate glasses, and explains the long lifetime of the Er3+ 4I13/2 level observed in BK-7 borosilicate glass
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
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