1,721,065 research outputs found
Correlation of upper-Khuff equivalent Palaeotethyan sediments of the Alborz Mountains, northern Iran
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Copolymerization of chiral and chromophoric comonomers: a pathway to optically active functional polymers
No full textOptically active polymers containing side-chain azobenzene moieties. Synthesis and chiroptical properties of copolymers of (-)-menthyl acrylate with trans-4-(phenylazo)-1-naphthyl acrylate and trans-4-(naphthylazo)-1-phenyl acrylate
No full textPhotochromic behavior and photoisomerization kinetics of optically active copolymers of trans-N-(4-azobenzene) maleimide (ABM) with (-)-menthyl vinyl ether (MtVE) and (+)(S) -2-methylbutyl vinyl ether were studied by UV spectroscopy under irradiation at 348 nm. The resulting data have been compared with those of the corresponding copolymers containing also trans-N-( 4-azobenzene) maleamic acid co-units as well as of low molecular weight model compounds. The photoresponsive behavior has been also investigated by circular dichroism measurements at various extents of photoisomerization. The results are discussed in terms of structural requirements of the macromolecules
Photoresponsive properties of optically active (meth)acrylic homopolymers with pendant L-lactic acid or L-alanine residues connected to 4-amino-azobenzene
No full textThe photochromic behaviour and photoisomerization kinetics of optically active homopolymers of trans-(S)-4-N-(2-methacryloyloxypropanoyl)aminoazobenzene and trans-(S)-4-N-(2-acryloyloxypropanoyl)aminoazobenzene were studied by u.v. spectroscopy under irradiation at 366 nm. The resulting data are compared with those obtained for the corresponding low molecular weight structural models trans-(S)-4-N-(2-pivaloyloxypropanoyl)aminoazobenzene and trans-(S)-4-N-(2-isobutyroyloxypropanoyl)aminoazobenzene. The photoresponsive behaviour of the above polymeric systems was also investigated by circular dichroism measurements at various extents of photoisomerization. The results are discussed in terms of the structural requirements of the macromolecules
Lopingian brachiopods from the Abadeh section (Central Iran) and their biostratigraphic implications
No full textThe Abadeh section is one of the most important Neotethyan sections, as it records a continuous marine sedimentary succession across the Permian-Triassic boundary. Although this succession yields a rich brachiopod fauna, this has never been studied in detail. Instead, most of the studies carried out so far have been focused on the position of the Permian-Triassic boundary, which is still debated. Here, we present a systematic study of the brachiopod fauna from the Hambast Formation, which comprises 30 species of the orders Productida, Orthotetida, Orthida, Athyridida and Spiriferida. Brachiopod biodiversity is relatively high and constant in the Wuchiapingian
part of the section. But in Changhsingian, just a single species occurs: Paracrurithyris pygmaea. Also, species of bivalves of the genus Claraia occur within an upper Griesbachian bed of the Elikah Formation.
Using the Unitary Associations method, we compared the stratigraphic distribution of the brachiopods in the Abadeh section with those in the Julfa section, another important Permian-Triassic succession in North-West Iran. Based on this analysis, three Wuchiapingian brachiopod biozones and one Changhsingian brachiopod biozone have been detected and correlated to the conodont biozonation; these biozones are the Araxilevis intermedius-Leptodus nobilis Biozone, the Permophricodothyris ovata-Araxathyris quadrilobata Biozone, and the Haydenella
kiangsiensis-Transcaucasathyris minor Biozone in the Wuchiapingian, and the Paracrurithyris pygmaea Biozone in the Changhsingian. Most of the biozones can be correlate
Brachiopod fabric, classes and biogeochemistry: Implications for the reconstruction and interpretation of seawater carbon-isotope curves and records
No full textShell calcite of modern and ancient brachiopods is an important proxy in reconstructing oceanographic conditions of seawater. Our investigation reveals significant magnesium and carbon isotope relationships between two classes of ancient brachiopods. Brachiopods of the extinct Class Strophomenata constructed two- or three-layer shells with a primary layer of randomized granular calcite, a secondary layer of cross-bladed laminar calcite and, at times, a tertiary layer of large prismatic calcite. Contemporaneous, but extant, Rhynchonellata also have two- or three-layer shells, but their secondary layer consists of calcite fibers instead of cross-bladed laminar calcite. Furthermore, inter-crystalline space is limited in between the fibers of the secondary layer of the Rhynchonellata but higher in the laminar secondary layer of Strophomenata. δ18O values of the two classes of brachiopods from the same stratigraphic interval of the Lopingian Nesen Formation of North Iran show a considerable overlap with no significant difference (p=0.263). In contrast, carbon isotope values are significantly different (p=0.001) between contemporaneous Strophomenata (mean: +2.18‰) and Rhynchonellata (mean: +4.13‰). An evaluation of literature data of Permian (Asselian) and Carboniferous (Visean and Serpukhovian) Strophomenata (mean: +2.32‰, N=59) and Rhynchonellata (mean: +4.94‰, N=105) confirms a similar differentiation in their carbon isotope values.Its higher magnesium contents suggest that the Strophomenata probably secreted shell calcite at a faster rate than their coeval Rhynchonellata. This process may account for the δ13C differentiation observed between specimens of these two brachiopod classes. However, the different amount and composition of the organic matter of the Strophomenata may also play a role in shaping their more negative carbon isotope signature. Thus, the class of brachiopod and their associated different fabric must be adjusted for in their δ13C results and taken into consideration during the reconstruction of Paleozoic global δ13C carbonate-based seawater curves. Invariably, in some earlier studies undetected impacts imposed by the class-fabric on δ13C may account for some of the variation or trends documented in Deep-Time seawater-13C curves reconstructed with brachiopod populations from North America, Europe and Russia. © 2014 Elsevier B.V
Success and demise of exceptionally preserved terebratulide brachiopod accumulations in a Jurassic (early Pliensbachian) tropical lagoonal setting (Southern Alps, Italy): brachiopod response to environmental changes
No full textDuring the Early Jurassic, the shallow marine carbonate platforms of the western-Tethys margins were characterized by highly diverse benthos including larger foraminifera, sponges, bivalves, gastropods, brachiopods, echinoderms, and dasycladalean calcareous algae. In this paper, we document examples of such assemblages within the lower Pliensbachian part of the Rotzo Formation (upper Orbitopsella Zone) of the Southern Alps, Italy. This carbonate succession was deposited in a complex mosaic of marine and brackish habitats within a tropical lagoon of the Trento Platform area. Large terebratulide brachiopod shells form autochthonous accumulations comprising exceptionally well-preserved monospecific assemblages of Lychnothyris rotzoana. These brachiopod-bearing successions were analysed in terms of biotic components, microfacies analysis, shell biofabric (three-dimensional arrangement of skeletal elements), and taphonomic signatures to understand brachiopod response to changing conditions within a highly variable lagoonal palaeoecosystem. Findings show that terebratulide shell accumulations are dominated by adult specimens and juveniles are rare. The brachiopods thrived during low energy conditions that resulted in the accumulation of highly temporally-condensed shell beds. Stabilized by microbialite encrustations, the shells were not re-oriented during the subsequent rapid burial. The abrupt demise of these communities was possibly related to rapid environmental change, and causal factors are discussed. The medium-term response of brachiopods to the relatively instable ecosystem of the tropical lagoon shows that they were not able to adapt to continuous perturbations, and that continuing stress severely compromised the resilience of benthic taxa
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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