Change search
Refine search result
4516451745184519452045214522 225901 - 225950 of 1157992
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 225901. Darzentas, N.
    et al.
    Hadzidimitriou, A.
    Murray, Fiona
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
    Hatzi, K.
    Josefsson, P.
    Laoutaris, N.
    Moreno, C.
    Anagnostopoulos, A.
    Jurlander, J.
    Tsaftaris, A.
    Chiorazzi, N.
    Belessi, C.
    Ghia, Paolo
    Rosenquist, Richard
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
    Davi, F.
    Stamatopoulos, K.
    A different ontogenesis for chronic lymphocytic leukemia cases carrying stereotyped antigen receptors: molecular and computational evidence2010In: Leukemia, ISSN 0887-6924, E-ISSN 1476-5551, Vol. 24, no 1, p. 125-132Article in journal (Refereed)
    Abstract [en]

    Chronic lymphocytic leukemia (CLL) is uniquely characterized by the existence of subsets of cases with quasi-identical, 'stereotyped' B-cell receptors (BCRs). Herein we investigate this stereotypy in 2662 patients with CLL, the largest series yet, using purpose-built bioinformatics methods based on sequence pattern discovery. Besides improving the identification of 'stereotyped' cases, we demonstrate that CLL actually consists of two different categories, based on the BCR repertoire, with important biological and ontogenetic differences. The first ( approximately 30% of cases) shows a very restricted repertoire and is characterized by BCR stereotypy (clustered cases), whereas the second includes cases with heterogeneous BCRs (nonclustered cases). Eleven major CLL clusters were identified with antigen-binding sites defined by just a few critically positioned residues, regardless of the actual immunoglobulin (IG) variable gene used. This situation is closely reminiscent of the receptors expressed by cells participating in innate immune responses. On these grounds, we argue that whereas CLL cases with heterogeneous BCRs likely derive from the conventional B-cell pool, cases with stereotyped BCRs could derive from progenitor cells evolutionarily adapted to particular antigenic challenges, perhaps intermediate between a true innate immune system and the conventional adaptive B-cell immune system, functionally similar to what has been suggested previously for mouse B1 cells.

  • 225902.
    Darányi, Sandor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Dobreva, Milena
    Toward a 5M Model of Digital Libraries2010Conference paper (Refereed)
    Abstract [en]

    Whereas the DELOS DRM and the 5S model of digital libraries (DL) addresses the formal side of DL, we argue that a parallel 5M model is emerging as best practice worldwide, integrating multicultural, multilingual, multimodal digital objects with multivariate statistics-based document indexing, categorization and retrieval methods. The fifth M stands for the modeling the information searching behavior of users, and of collection development. We show how an extension of the 5S model to Hilbert space (a) points toward the integration of several Ms; (b) makes the tracking of evolving semantic content feasible, and (c) leads to a field interpretation of word and sentence semantics underlying language change. First experimental results from the Strathprints e-repository verify the mathematical foundations of the 5M model.

  • 225903.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    A computationally and neurologically feasible model of semiosis2004In: From Nature to Psyche. Proceedings from the Imatra International Congresses on Semiotics in 2001 and 2002 / [ed] Eero Tarasti, Helsinki: Acta Semiotica Fennica , 2004, p. 256-264Conference paper (Other academic)
  • 225904.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    Creating a dynamic library in the LIVA project: challenges and solutions2009Conference paper (Other academic)
  • 225905.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    Examples of Formulaity in Narratives and Scientific Communication2010In: Proceedings of the 1st International AMICUS Workshop, October 21, 2010, Vienna, Austria / [ed] Sándor Darányi, Piroska Lendvai, University of Szeged, Hungary , 2010, p. 29-35Conference paper (Refereed)
    Abstract [en]

    The AMICUS project was designed to promote scholarly networking in a topical area, motif recognition in texts, including its automation. Prior to doing so however it is necessary to show the theoretical underpinnings of the research idea. My argument is that evidence from different disciplines amounts to fragmented pieces of a bigger picture. By compiling them like pieces of a puzzle, one can see how the concept of formulaity applies to folklore texts and scholarly communication alike. Regardless of the actual name of the concept (e.g. motif, function, canonical form), what matters is that document parts and whole documents can be characterized by standard sequences of content elements, such formulaic expressions enabling higher-level document indexing and classification by machine learning, plus document retrieval. Information filtering plays a key role in the proposed technology.

  • 225906.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    Factor analysis and the canonical formula: Where do we go from here?2003Conference paper (Refereed)
  • 225907.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    First- and second-order change as symmetry and symmetry breaking in folklore text content evolution: From Heraclitus to Lévi-Strauss2007Conference paper (Refereed)
    Abstract [en]

    We distinguish between first- and second order change and identify the former with perpetual alternation on an existential plane, the second with moving out into existential space. The first type can be demonstrated by two antagonistic processes inherent in a Markov chain of two pairs of complementary values: the chain gradually alternates between the opposite terminal states and the pattern is symmetrical. Such an existential plane catches an essential feature of Heraclitus’ philosophy, and can be illustrated by examples from classical Greek mythology. The same material also exemplifies Lévi-Strauss’ formula of myth, symmetrical in its weak and asymmetrical in 2 its canonical form. Since the weak form equals the orbit of a Klein group, we hypothesize that the canonical form, and thereby symmetry breaking, can be generated by element exchange between two respective Klein groups. The framework for such processes is text variation in folklore, described by ethnosemiotics.

  • 225908.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    HOMO 2003: Information society, cultural heritage and folklore text analysis2003Collection (editor) (Other academic)
  • 225909.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    Language as space2004In: More Space. Proceedings of the "Space, Spatiality and Technology Workshop 2004". Edinburgh: School of Computing, Napier University / [ed] P. Turner, E. Davenport, S. Turner, 2004, p. 60-64Conference paper (Other academic)
  • 225910.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    Látvány és jelentés: Budapesti épuletszobrok elemzése és fejlödéstörténeti modellezése2007Conference paper (Other academic)
  • 225911.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    The importance of context for Digital Libraries2012In: Cuadernos de Gestión de Información, ISSN 2253-8429, Vol. 2, no 1, p. 1-3Article in journal (Other academic)
    Abstract [en]

    The concept of "context" has great importance in digital preservation. This paper analyzes the meaning of context from the point of view of access to digital objects, combining linguistics, terminological disambiguation in information retrieval and text categorization aspects. In these areas, the context is a key element for successful disambiguation and thus get better results. Therefore, the preservation and subsequent access of digital objects should also consider the preservation of appropriate information about the terminology and social context in which these objects were generated.

  • 225912.
    Darányi, Sándor
    University of Borås, Swedish School of Library and Information Science.
    The necessity of a European virtual laboratory for the processing of digitized cultural heritage: The HOMO concept2003Conference paper (Refereed)
  • 225913.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Eklund, Johan
    University of Borås, Swedish School of Library and Information Science.
    Automated text categorization of bibliographic records2007In: Svensk biblioteksforskning, ISSN 0284-4354, E-ISSN 1653-5235, Vol. 16, no 2, p. 1-14Article in journal (Refereed)
  • 225914.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Forró, László
    Detecting Multiple Motif Co-occurrences in the Aarne-Thompson- Uther Tale Type Catalog: A Preliminary Survey2012In: Anales de Documentación, ISSN 1575-2437, E-ISSN 1697-7904, Vol. 15, no 1Article in journal (Refereed)
    Abstract [en]

    : Catalogs project subject field experience onto a multidimensional map which is then converted to a hierarchical list. In the case of the Aarne-Thompson-Uther Tale Type Catalog (ATU), this subject field is the global pattern of tale content defining tale types as canonical motif sequences. To extract and visualize such a map, we considered ATU as a corpus and analysed two segments of it, “Supernatural adversaries” (types 300-399) in particular and “Tales of magic” (types 300-749) in general. The two corpora were scrutinized for multiple motif cooccurrences and visualized by two-mode clustering of a bag-of-motif co-occurrences matrix. Findings indicate the presence of canonical content units above motif level as well. The organization scheme of folk narratives utilizing motif sequences is reminiscent of nucleotid sequences in the genetic code.

  • 225915.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Forró, László
    Detecting Multiple Motif Co-occurrences in the Aarne-Thompson-Uther Tale Type Catalog: A Preliminary Survey2011In: Anales de Documentación, ISSN 1575-2437, E-ISSN 1697-7904Article in journal (Other academic)
  • 225916.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Forró, László
    Toward Sequencing Multiple Motif Co-Occurrences2011In: Tanulmányok az örökségmenedzsmentröl 2. Kulturális örökségek kezelése [Studies in Heritage Management 2: The Management of Cultural Heritage]. / [ed] L. Bassa, Információs Társadalomért Alapítvány , 2011, p. 247-260Chapter in book (Refereed)
    Abstract [en]

    Catalogs project subject field experience onto a multidimensional map which is then converted to a hierarchical list. In the case of the Aarne-Thompson-Uther Tale Type Catalog (ATU), this subject field is the global pattern of tale content defining tale types as canonical motif sequences. To extract and visualize such a map, we considered ATU as a corpus and ana-lysed two segments of it, “Supernatural adversaries” (types 300-399) in particular and “Tales of magic” (types 300-749) in general. The two corpora were scru-tinized for multiple motif co-occurrences and visualized by two-mode clustering of a bag-of-motif co-occurrences matrix. Findings indicate the presence of canonical content units above motif level as well. The organization scheme of folk narratives utilizing motif sequences is reminiscent of nucleotid sequences in the genetic code

  • 225917.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Lendvai, Piroska
    Proceedings of the First AMICUS Workshop, October 21, 2010 Vienna, Austria2010Collection (editor) (Other academic)
    Abstract [en]

    In cultural heritage objects, digitized or not, content indicators occurring on higher than word level are often called motifs or their equivalent. Their recognition for document classification and retrieval is largely unresolved. Work on identifying rhetorical, narrative and persuasive elements in scientific texts has been progressing, in several, but largely unconnected tracks. The AMICUS project1 (running between 2009 and 2012) set out to test a possible way to resolve these issues, starting with the identification of Proppian functions in folk tale corpora and adapting the solution to the identification of tale motifs or their functional counterparts. AMICUS has devoted its first project year to listing the corpora, tools, methods and contacts available to address these issues. The initiators of the project have identified a common need in the processing of texts from both the cultural heritage (CH) and scientific communication (SC) domains: to perform automated, large-scale higher-order text analytics, i.e., to reach an advanced level of text understanding so that structured knowledge can be extracted from unstructured text. The four research groups propose to tackle an important aspect of this complex issue by investigating how linguistic elements convey motifs in texts from the CH and the SC domains. Our shared working hypothesis is that the identity of higherorder content-bearing elements, i.e., textual units that are typically designated for e.g. document indexing, classification, enrichment, and the like, strongly depends on community perception.

  • 225918.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Maceviciute, Elena
    University of Borås, Swedish School of Library and Information Science.
    Wilson, Tom
    University of Borås, Swedish School of Library and Information Science.
    The SHAMAN project on digital preservation2012Conference paper (Other academic)
  • 225919.
    Darányi, Sándor
    et al.
    University of Borås, Faculty of Librarianship, Information, Education and IT.
    Wittek, Peter
    University of Borås, Faculty of Librarianship, Information, Education and IT.
    Conceptual machinery of the mythopoetic mind: Attis, a case study2015In: Proceedings of QI-15, 9th International Quantum Interaction Symposium, 2015Conference paper (Refereed)
    Abstract [en]

    In search for the right interpretation regarding a body of related content, we screened a small corpus of myths about Attis, a minor deity from the Hellenistic period in Asia Minor to identify the noncommutativity of key concepts used in storytelling. Looking at the protagonist's typical features, our experiment showed incompatibility with regard to his gender and downfall. A crosscheck for entanglement found no violation of a Bell inequality, its best approximation being on the border of the local polytope.

  • 225920.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Connecting the Dots: Mass, Energy, Word Meaning, and Particle-Wave Duality2012Conference paper (Refereed)
    Abstract [en]

    With insight from linguistics that degrees of text cohesion are similar to forces in physics, and the frequent use of the energy concept in text categorization by machine learning, we consider the applicability of particle-wave duality to semantic content inherent in index terms. Wave-like interpretations go back to the regional nature of such content, utilizing functions for its representation, whereas content as a particle can be conveniently modelled by position vectors. Interestingly, wave packets behave like particles, lending credibility to the duality hypothesis. We show in a classical mechanics framework how metaphorical term mass can be computed.

  • 225921.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Demonstrating Conceptual Dynamics in an Evolving Text Collection2013In: Journal of the Association for Information Science and Technology, ISSN 2330-1635, E-ISSN 2330-1643, Vol. 64, no 12, p. 2564-2572Article in journal (Refereed)
    Abstract [en]

    Based on real world user demands, we demonstrate how animated visualisation of evolving text corpora displays the underlying dynamics of semantic content. To interpret the results, one needs a dynamic theory of word meaning. We suggest that conceptual dynamics as the interaction between kinds of intellectual, emotional etc. content, and language, is key for such a theory. We demonstrate our methodology by two-way seriation which is a popular technique to analyse groups of similar instances and their features, as well as the connections between the groups themselves. The two-way seriated data may be visualised as a two-dimensional heat map or as a three-dimensional landscape where colour codes or height correspond to the values in the matrix. In this paper we focus on two-way seriation of sparse data in the Reuters-21568 test collection. To achieve a meaningful visualisation thereof we introduce a compactly supported convolution kernel similar to filter kernels used in image reconstruction and geostatistics. This filter populates the high-dimensional sparse space with values that interpolate nearby elements, and provides insight into the clustering structure. We also extend two-way seriation to deal with online updates of both the row and column spaces, and, combined with the convolution kernel, demonstrate a three-dimensional visualisation of dynamics.

  • 225922.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    On Information, Meaning, Space and Geometry2009In: Exploration of Space, Technology and Spatiality: Interdisciplinary Perspectives / [ed] Susan Turner, E. D. P. Turner, Hersey: Idea Group , 2009Chapter in book (Other academic)
    Abstract [en]

    We offer a few general considerations, with theoretical overtones, working toward the definition and generation of a geometric language for practical purposes, prominently for information retrieval. This chapter is a non-mathematical introduction to the mathematical modelling of meaning of both words and sentences, outlining already existing components of such an endeavour, and hinting at directions of synthesis.

  • 225923.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    The gravity of meaning: Physics as a metaphor to model semantic changes2012Conference paper (Refereed)
    Abstract [en]

    Based on a computed toy example, we offer evidence that by plugging in similarity of word meaning as a force plus a small modification of Newton’s 2nd law, one can acquire specific “mass” values for index terms in a Saltonesque dynamic library environment. The model can describe two types of change which affect the semantic composition of document collections: the expansion of a corpus due to its update, and fluctuations of the gravitational potential energy field generated by normative language use as an attractor juxtaposed with actual language use yielding time-dependent term frequencies. By the evolving semantic potential of a vocabulary and concatenating the respective term “mass” values, one can model sentences or longer strings of symbols as vector-valued functions. Since the line integral of such functions is used to express the work of a particle in a gravitational field, the work equivalent of strings can be calculated.

  • 225924.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Dobreva, Milena
    Position paper: Adding a 5M layer to the 5S model of digital libraries.2010Conference paper (Refereed)
    Abstract [en]

    We expect radical changes in document ( rst and foremost text) representation for digital libraries (DL) leading to new applications for documents processing.

  • 225925.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Dobreva, Milena
    Using wavelet analysis for text categorization in digital libraries: a first experiment with Strathprints2011In: International Journal on Digital Libraries, ISSN 1432-5012, E-ISSN 1432-1300Article in journal (Refereed)
    Abstract [en]

    Digital libraries increasingly bene t from re- search on automated text categorization for improved access. Such research is typically carried out by using standard test collections. In this paper we present a pilot experiment of replacing such test collections by a set of 6000 objects from a real-world digital repos- itory, indexed by Library of Congress Subject Head- ings, and test support vector machines in a supervised learning setting for their ability to reproduce the exist- ing classi cation. To augment the standard approach, we introduce a combination of two novel elements: us- ing functions for document content representation in Hilbert space, and adding extra semantics from lexical resources to the representation. Results suggest that wavelet-based kernels slightly outperformed traditional kernels on classi cation reconstruction from abstracts and vice versa from full-text documents, the latter out- come due to word sense ambiguity. The practical imple- mentation of our methodological framework enhances the analysis and representation of speci c knowledge relevant to large-scale digital collections, in this case the thematic coverage of the collections. Representation of speci c knowledge about digital collections is one of the basic elements of the persistent archives and the less studied one (compared to representations of digital ob- jects and collections). Our research is an initial step in this direction developing further the methodological ap- proach and demonstrating that text categorisation can be applied to analyse the thematic coverage in digital repositories.

  • 225926.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Forró, László
    Toward Sequencing “Narrative DNA”: Tale Types, Motif Strings and Memetic Pathways2012Conference paper (Other academic)
    Abstract [en]

    The Aarne-Thompson-Uther Tale Type Catalog (ATU) is a bibliographic tool which uses metadata from tale content, called motifs, to define tale types as canonical motif sequences. The motifs themselves are listed in another bibliographic tool, the Aarne-Thompson Motif Index (AaTh). Tale types in ATU are defined in an abstracted fashion and can be processed like a corpus. We analyzed 219 types with 1202 motifs from the “Tales of magic” (types 300-749) segment to exemplify that motif sequences show signs of recombination in the storytelling process. Compared to chromosome mutations in genetics, we offer examples for insertion/deletion, duplication and, possibly, transposition, whereas the sample was not sufficient to find inverted motif strings as well. These initial findings encourage efforts to sequence motif strings like DNA in genetics, attempting to find for instance the longest common motif subsequences in tales. Expressing the network of motif connections by graphs suggests that tale plots as consolidated pathways of content help one memorize culturally engraved messages. We anticipate a connection between such networks and addington’s epigenetic landscape.

  • 225927.
    Darányi, Sándor
    et al.
    University of Borås, Swedish School of Library and Information Science.
    Wittek, Peter
    University of Borås, Swedish School of Library and Information Science.
    Kitto, Kirsty
    The Sphynx's new riddle: How to relate the canonical formula of myth to quantum interaction2013Conference paper (Refereed)
    Abstract [en]

    We introduce Claude Lévi Strauss' canonical formula (CF), an attempt to rigorously formalise the general narrative structure of myth. This formula utilises the Klein group as its basis, but a recent work draws attention to its natural quaternion form, which opens up the possibility that it may require a quantum inspired interpretation. We present the CF in a form that can be understood by a non-anthropological audience, using the formalisation of a key myth (that of Adonis) to draw attention to its mathematical structure. The future potential formalisation of mythological structure within a quantum inspired framework is proposed and discussed, with a probabilistic interpretation further generalising the formula.

  • 225928.
    Darányi, Sándor
    et al.
    University of Borås, Faculty of Librarianship, Information, Education and IT.
    Wittek, Peter
    University of Borås, Faculty of Librarianship, Information, Education and IT.
    Konstantinidis, K
    CERTH..
    Papadopoulos, S
    CERTH..
    A Potential Surface Underlying Meaning?2015Conference paper (Other academic)
    Abstract [en]

    Machine learning algorithms utilizing gradient descent to identify concepts or more general learnables hint at a so-far ignored possibility, namely that local and global minima represent any vocabulary as a landscape against which evaluation of the results can take place. A simple example to illustrate this idea would be a potential surface underlying gravitation. However, to construct a gravitation-based representation of, e.g., word meaning, only the distance between localized items is a given in the vector space, whereas the equivalents of mass or charge are unknown in semantics. Clearly, the working hypothesis that physical fields could be a useful metaphor to study word and sentence meaning is an option but our current representations are incomplete in this respect.For a starter, consider that an RBF kernel has the capacity to generate a potential surface and hence create the impression of gravity, providing one with distance-based decay of interaction strength, plus a scalar scaling factor for the interaction, but of course no term masses. We are working on an experiment design to change that. Therefore, with certain mechanisms in neural networks that could host such quasi-physical fields, a novel approach to the modeling of mind content seems plausible, subject to scrutiny.Work in progress in another direction of the same idea indicates that by using certain algorithms, already emerged vs. still emerging content is clearly distinguishable, in line with Aristotle’s Metaphysics. The implications are that a model completed by “term mass” or “term charge” would enable the computation of the specific work equivalent of sentences or documents, and that via replacing semantics by other modalities, vector fields of more general symbolic content could exist as well. Also, the perceived hypersurface generated by the dynamics of language use may be a step toward more advanced models, for example addressing the Hamiltonian of expanding semantic systems, or the relationship between reaction paths in quantum chemistry vs. sentence construction by gradient descent.

  • 225929.
    Darányi, Sándor
    et al.
    University of Borås, Faculty of Librarianship, Information, Education and IT.
    Wittek, Peter
    University of Borås, Faculty of Librarianship, Information, Education and IT.
    Konstantinidis, Konstantinos
    Papadopoulos, Symeon
    Kontopoulos, Efstratios
    A Physical Metaphor to Study Semantic Drift2016In: Proceedings of SuCCESS-16, 1st International Workshop on Semantic Change & Evolving Semantics, 2016, Vol. 1695Conference paper (Refereed)
    Abstract [en]

    In accessibility tests for digital preservation, over time we experience drifts of localized and labelled content in statistical models of evolving semantics represented as a vector field. This articulates the need to detect, measure, interpret and model outcomes of knowledge dynamics. To this end we employ a high-performance machine learning algorithm for the training of extremely large emergent self-organizing maps for exploratory data analysis. The working hypothesis we present here is that the dynamics of semantic drifts can be modeled on a relaxed version of Newtonian mechanics called social mechanics. By using term distances as a measure of semantic relatedness vs. their PageRank values indicating social importance and applied as variable ‘term mass’, gravitation as a metaphor to express changes in the semantic content of a vector field lends a new perspective for experimentation. From ‘term gravitation’ over time, one can compute its generating potential whose fluctuations manifest modifications in pairwise term similarity vs. social importance, thereby updating Osgood’s semantic differential. The dataset examined is the public catalog metadata of Tate Galleries, London.

  • 225930.
    Darén, Malin
    et al.
    Umeå University, Faculty of Social Sciences, Basic training programme for Police Officers.
    Dorj, Madeleine
    Umeå University, Faculty of Social Sciences, Basic training programme for Police Officers.
    Tolkar: Ett hot mot rättssäkerheten?2005Independent thesis Basic level (professional degree), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [sv]

    Arbetar man inom polisen eller andra delar av rättssäkerhetskedjan kommer man dagligen i kontakt med tolkar. Deras arbetsuppgift är att göra kommunikationen möjlig mellan till exempel en målsägande och en polisman. Efter att ha hållit förhör under sommaren 2004 på en polismyndighet insåg vi svårigheterna med att få fram frågorna på rätt sätt samt att veta om svaren man fick tillbaka verkligen var rätt formulerade. Med tiden har vi utvecklat tankarna kring dessa svårigheter. Vad har egentligen tolkarna för kunskap om rättssäkerhet? Vad har de för utbildning? Finns det någon förhörsmetod som lämpar sig bäst då man håller förhör genom tolk? För att få svar på dessa frågor kommer vi att intervju bland annat en advokat som uppmärksammat problemet, en förhörsmetodsexpert samt källor inom polisen. Syftet är att undersöka om och i så fall hur polisen kontrollerar tolkens kompetens. Ett annat syfte är att försöka komma fram till en fungerande förhörsmetod som minimerar feltolkningar och som underlättar för alla parter. Detta för att rättssäkerheten ska upprätthållas.

  • 225931.
    Daréus, Emma
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Suhr, Hektor
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    En undersökning av sambandet mellan kronisk inflammation och lungcancer2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Cancer is a big health problem in Sweden and one of the leading causesof death. As of recently there has been an increase in the interest in thecancer research community in how chronic inflammation influences theemergence of cancer tumors. In this paper we intend to investigate therelationship between markers of chronic inflammation and lung cancer.We will also look in to the possibility that sialic acid may be a marker oflung cancer.Lung cancer is one of the most common types of cancers in Sweden andhas a high mortality rate compared to other cancers. Reasons for thisbeing both from the fact that it is usually discovered at a later stage and islocated in a sensitive organ make it harder to treat.To do this we will use sialic acid as a marker of inflammation from acohort study done during the early sixties, it will be cross referenced withthe Swedish Cancer Registry from Socialstyrelsen. BMI and age will alsobe used as variables of interest.The method for the paper will use Cox Proportional Hazard Model toestimate the risk of sialic acid relating to the emergence of lung cancer.Sensitivity analysis will be used to consider the effects of smoking as aconfounder variable.The results show that there are reasons to believe that chronicinflammation may have a role in the emergence of lung cancer tumors.There is no evidence in this study that suggest that sialic acid is a goodmarker for an individual having lung cancer. Furthermore, BMI seems tohave a protective effect against lung cancer, but this would need furtherstudy to draw any real conclusions from.

  • 225932.
    Das, A.
    et al.
    Indian Institute of Science.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sharma, P.K.
    Luleå University of Technology.
    Natarajan, K.A.
    Indian Institute of Science.
    Forssberg, Eric
    Surface chemical and adsorption studies using Thiobacillus ferrooxidans with reference to bacterial adhesion to sulfide minerals1999In: Biohydrometallurgy and the Environment toward the Mining of the 21st century: Proceedings of the International Biohydrometallurgy Symposium IBS 1999, Madrid, Spain / [ed] R. Amils; A. Ballester, Elsevier, 1999, Vol. Part A: Bioleaching, Microbiology, p. 697-707Conference paper (Refereed)
  • 225933. Das, Anup
    et al.
    Zachariah, Dave
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Stoica, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Comparison of two hyperparameter-free sparse signal processing methods for direction-of-arrival tracking in the HF97 ocean acoustic experiment2018In: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 43, no 3, p. 725-734Article in journal (Refereed)
  • 225934.
    Das, Arindam
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alam, Rauful
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereocontrol in Synthesis of Homoallylic Amines. Syn Selective Direct Allylation of Hydrazones with Allylboronic Acids2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 14, p. 3808-3811Article in journal (Refereed)
    Abstract [en]

    Allylboronic acids directly react with acyl hydrazones, affording homoallylic amine derivatives. The reaction proceeds with very high syn selectivity, which is the opposite of the stereochemistry observed for allylboration of imines. The reaction can be carried out with both aromatic and aliphatic acyl hydrazones. Based on our studies the excellent syn stereochemistry can be explained by chelation control of the acyl hydrazone and the B(OH)(2) moiety.

  • 225935.
    Das, Arindam
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wang, Dong
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Belhomme, Marie-Charlotte
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-Catalyzed Cross-Coupling of Allylboronic Acids with alpha-Diazoketones2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 19, p. 4754-4757Article in journal (Refereed)
    Abstract [en]

    Copper-catalyzed cross-coupling of substituted allylboronic acids with alpha-diazoketones was studied. This allylation reaction is highly regioselective, providing the branched allylic product. The process involves creation of a new C(sp(3))-C(sp(3)) bond by retaining the keto functional group of the alpha-diazoketone precursor.

  • 225936.
    Das Arulsamy, Andrew
    et al.
    Condensed Matter Grp, Div Interdisciplinary Sci, Ampang 68000, Selangor De, Malaysia.
    Kregar, Zlatko
    Inst Phys, HR-10000 Zagreb.
    Elersic, Kristina
    Jozef Stefan Inst, SI-1000 Ljubljana.
    Modic, Martina
    Jozef Stefan Inst, SI-1000 Ljubljana.
    Subramani, Uma Shankar
    Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 33, p. 15175-15181Article in journal (Refereed)
    Abstract [en]

    Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue-and red-shifting O-H covalent bonds within a single water molecule adsorbed on the MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on the MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the first-order electronic-phase transition temperature.

  • 225937. Das, B
    et al.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Reddy, M. V.
    Chowdari, B. V. R.
    High performance metal nitrides, MN (M = Cr, Co) nanoparticles for non-aqueous hybrid supercapacitors2015In: Advanced Powder Technology, ISSN 0921-8831, E-ISSN 1568-5527, Vol. 26, no 3, p. 783-788Article in journal (Refereed)
    Abstract [en]

    In this study, metal nitrides MN (M = Cr, Co) nanoparticles of particle size similar to 20-30 nm have been prepared under NH3 + N-2 atmosphere at relatively low temperature. The Cr-urea complex was directly converted to CrN with an intermediate formation of Cr2O3, whereas CoN was prepared from Co3O4. These compounds were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) techniques. The electrochemical properties were evaluated by galvanostatic cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical performance of the resultant MN nanoparticles showed that they can be used as potential electrode materials for non-aqueous hybrid electrochemical supercapacitors (HESCs). The MN/AC showed high specific capacitance of 75 and 37 F g (1) for M = Cr, Co, respectively when cycled at 30 mA g (1) in non-aqueous electrolyte.

  • 225938.
    Das, Bibhash
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Technical Due Diligence Assessment and Bayesian Belief Networks Methodology for Wind Power Projects2013Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    A Technical Due Diligence (TDD) investigation is an important step in the process of obtaining financing, or in mergers and acquisitions, for a wind power project. The investigation, the scope of which varies depending on the stage and nature of the project, involves reviewing important documentation relating to different aspects of the project, assessing potential risks in terms of the quality of the information available and suggesting mitigation or other risk management measures where required.

    A TDD assessment can greatly benefit from increased objectivity in terms of the reviewed aspects as it enables a sharper focus on the important risk elements and also provides a better appreciation of the investigated parameters. This master’s thesis has been an attempt to introduce more objectivity in the technical due diligence process followed at the host company. Thereafter, a points-based scoring system was devised to quantify the answered questions. The different aspects under investigation have a complex interrelationship and the resulting risks can be viewed as an outcome of a causal framework.

    To identify this causal framework the concept of Bayesian Belief Networks has been assessed. The resulting Bayesian Networks can be considered to provide a holistic framework for risk analysis within the TDD assessment process. The importance of accurate analysis of likelihood information for accurate analysis of Bayesian analysis has been identified. The statistical data set for the right framework needs to be generated to have the right correct setting for Bayesian analysis in the future studies.

    The objectiveness of the TDD process can be further enhanced by taking into consideration the capability of the investing body to handle the identified risks and also benchmarking risky aspects with industry standards or historical precedence.

  • 225939. Das, Biswanath
    et al.
    Daver, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pyrkosz-Bulska, Monika
    Gumienna-Kontecka, Elzbieta
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    An Unsymmetric Ligand with a N5O2 Donor Set and Its Corresponding Dizinc Complex: A Structural and Functional Phosphoesterase Model2018In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 36, p. 4004-4013Article in journal (Refereed)
    Abstract [en]

    To mimic the active sites of the hydrolytic enzyme zinc phosphotriesterase, a new dinucleating unsymmetric ligand, PICIMP (2-{[2-hydroxy-5-methyl-3-({[(1-methyl-1H-imidazol-2-yl)methyl](pyridin-2-ylmethyl)amino}methyl)benzyl][(1-methyl-1H-imidazol-2-yl)methyl]amino}acetic acid), has been synthesized and characterized. The hydrolytic efficacy of the complex solution (PICIMP/ZnCl2 = 1:2) has been investigated using bis-(2,4-dinitrophenyl)phosphate (BDNPP), a DNA analogue substrate. Speciation studies were undertaken by potentiometric titrations at varying pH for both the ligand and the corresponding dizinc complex to elucidate the formation of the active hydrolysis catalyst; these studies reveal that the dinuclear zinc(II) complexes, [Zn-2(PICIMP)](2+) and [Zn-2(PICIMP)(OH)](+) predominate in solution above pH 4. The obtained pK(a) of 7.44 for the deprotonation of water suggests formation of a bridging hydroxide between the two Zn-II ions. Kinetic investigations of BDNPP hydrolysis over the pH range 5.5-10.5 have been performed. The cumulative results indicate the hydroxo-bridged dinuclear Zn-II complex [Zn-2(PICIMP)(mu-OH)](+) as the effective catalyst. Density functional theory calculations were performed to investigate the detailed reaction mechanism. The calculations suggest that the bridging hydroxide becomes terminally coordinated to one of the zinc ions before performing the nucleophilic attack in the reaction.

  • 225940. Das, Biswanath
    et al.
    Daver, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pyrkosz-Bulska, Monika
    Persch, Elke
    Barman, Suman K.
    Mukherjee, Rabindranath
    Gumienna-Kontecka, Elzbieta
    Jarenmark, Martin
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    A dinuclear zinc(II) complex of a new unsymmetric ligand with an N(5)0(2) donor set; A structural and functional model for the active site of zinc phosphoesterases2014In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 132, p. 6-17Article in journal (Refereed)
    Abstract [en]

    The dinuclear complex [Zn-2(DPCPMP)(pivalate)](C10(4)), where DPCPMP is the new unsymmetrical ligand [2-(N-(3-((bis((pyridin-2-yl)methyl)amino)methyl)-2-hydroxy-5-methylbenzyl)-N-((pyridin2-y1)methyl)amino)acetic acid], has been synthesized and characterized. The complex is a functional model for zinc phosphoesterases with dinuclear active sites. The hydrolytic efficacy of the complex has been investigated using bis-(2,4-dinitrophenyl)phosphate(BDNPP), a DNA analog, as substrate. Speciation studies using potentiometric titrations have been performed for both the ligand and the corresponding dizinc complex to elucidate the formation of the active hydrolysis catalyst; they reveals that the dinuclear zinc(II) complexes, [Zn-2(DPCPMP)](2) and [Zn-2(DPCPMP)(OH)1 predominate the solution above pH 4. The relatively high pKa of 8.38 for water deprotonation suggests that a terminal hydroxide complex is formed. Kinetic investigations of BDNPP hydrolysis over the pH range 5.5-11.0 and with varying metal to ligand ratio (metal salt:ligand = 0.5:1 to 3:1) have been performed. Variable temperature studies gave the activation parameters triangle H double dagger = 95.6 kJ mol(-1), triangle S double dagger = 44.8 J mo1(-1) K-1, and 6,triangle G double dagger = 108.0 kJ mo1-1. The cumulative results indicate the hydroxido-bridged dinuclear Zn(II) complex [Zn-2(DPCPMP)(mu-OH)] (+) as the effective catalyst. The mechanism of hydrolysis has been probed by computational modeling using density functional theory (DFF). Calculations show that the reaction goes through one concerted step (S(N)2 type) in which the bridging hydroxide in the transition state becomes terminal and performs a nucleophilic attack on the BDNPP phosphorus; the leaving group dissociates simultaneously in an overall inner sphere type activation. The calculated free energy barrier is in good agreement with the experimentally determined activation parameters.

  • 225941. Das, Biswanath
    et al.
    Daver, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Singh, Amrendra
    Singh, Reena
    Haukka, Matti
    Demeshko, Serhiy
    Meyer, Franc
    Lisensky, George
    Jarenmark, Martin
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    A Heterobimetallic FeIIIMnII Complex of an Unsymmetrical Dinucleating Ligand: A Structural and Functional Model Complex for the Active Site of Purple Acid Phosphatase of Sweet Potato2014In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2014, no 13, p. 2204-2212Article in journal (Refereed)
    Abstract [en]

    The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)(2)Cl] (1) {H2ICIMP = 2-(N-carboxylmethyl)-[N-(N-methylimidazolyl-2-methyl)aminomethyl]-[6-(N-isopropylmethyl)-[N-(N-methylimidazolyl-2-methyl)]aminomethyl-4-methylphenol], an unsymmetrical N4O2 donor ligand} has been synthesized and fully characterized by several spectroscopic techniques as well as by X-ray crystallography. The crystal structure of the complex reveals that both metal centers in 1 are six-coordinate with the chloride ion occupying the sixth coordination site of the Mn-II ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mossbauer spectroscopy shows that the iron ion in 1 is high-spin Fe-III. Two quasi-reversible redox reactions for the complex, attributed to the (FeMnII)-Mn-III/(FeMnII)-Mn-II (at -0.67 V versus Fc/Fc(+)) and (FeMnII)-Mn-III/(FeMnIII)-Mn-III (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe-III-Mn-II distance of 3.58 angstrom, may serve as a model for the mixed-valence oxidation state of purple acid phosphatase from sweet potato. The capability of the complex to effect organophosphate hydrolysis (phosphatase activity) has been investigated at different pH levels (5.5-11) by using bis(2,4-dinitrophenyl)phosphate (BDNPP) as the substrate. Density functional theory calculations indicate that the substrate coordinates to the Mn-II ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the Fe-III ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group.

  • 225942.
    Das, Biswanath
    et al.
    Lund University, Sweden.
    Lee, Bao-Lin
    Stockholm University, Sweden.
    Karlsson, Erik A.
    Stockholm University, Sweden.
    Akermark, Torbjorn
    Stockholm University, Sweden.
    Shatskiy, Andrey
    Stockholm University, Sweden.
    Demeshko, Serhiy
    University of Gottingen, Germany.
    Liao, Rong-Zhen
    Huazhong University of Science and Technology, Peoples R China.
    Laine, Tanja M.
    Stockholm University, Sweden.
    Haukka, Matti
    University of Jyvaskyla, Finland.
    Zeglio, Erica
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Abdel-Magied, Ahmed F.
    Stockholm University, Sweden.
    Siegbahn, Per E. M.
    Stockholm University, Sweden.
    Meyer, Franc
    University of Gottingen, Germany.
    Karkas, Markus D.
    Stockholm University, Sweden.
    Johnston, Eric V.
    Stockholm University, Sweden.
    Nordlander, Ebbe
    Lund University, Sweden.
    Åkermark, Bjorn
    Stockholm University, Sweden.
    Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 34, p. 13289-13293Article in journal (Refereed)
    Abstract [en]

    The synthesis of two molecular iron complexes, a dinuclear iron(III,III) complex and a nonanuclear iron complex, based on the di-nucleating ligand 2,2-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)(3)](3+).

  • 225943. Das, Biswanath
    et al.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Demeshko, Serhiy
    Liao, Rong-Zhen
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Haukka, Matti
    Zeglio, Erica
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Meyer, Franc
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 34, p. 13289-13293Article in journal (Refereed)
    Abstract [en]

    The synthesis of two molecular iron complexes, a dinuclear iron(III,III) complex and a nonanuclear iron complex, based on the di-nucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)(3)](3+).

  • 225944.
    Das, Biswanath
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Iron Pentapyridyl Complexes as Molecular WaterOxidation Catalysts: Strong Influence of a Chloride Ligandand pH in Altering the Mechanism2016In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 10, p. 1178-1186Article in journal (Refereed)
    Abstract [en]

    The development of molecular water oxidation catalysts basedon earth-abundant, non-noble metals is essential for artificial photosynthesis research. Iron, which is the most abundant transition metal in the earth's crust, is a prospective candidate for this purpose. Herein, we report two iron complexes based on the polypyridyl ligand Py5OH (Py5OH=pyridine-2,6-diylbis[di(pyridin-2-yl)methanol]) that can catalyse water oxidation to produce O2 in RuIII-induced (at pH 8, highest turnover number (TON)=26.5; turnover frequency (TOF)=2.2 s-1), CeIV-induced(at pH 1.5 highest TON=16; TOF=0.75 s-1) and photo-induced(at pH 8, highest TON=43.5; TOF=0.6 s-1) reactions. A chloride ligand in one of the iron complexes is shown to affect the activity strongly, improve stability and, thereby, the performance at pH 8 but it inhibits oxygen evolution at pH 1.5. The observations are consistent with a change in mechanism for catalytic water oxidation with the Fe(Py5OH) complexes between acidic (CeIV) and near-neutral pH (RuIII).

  • 225945.
    Das, Biswanath
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Water oxidation catalysed by a mononuclear CoII polypyridine complex; possible reaction intermediates and the role of the chloride ligand2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 66, p. 13074-13077Article in journal (Refereed)
    Abstract [en]

    A mononuclear cobalt(II) complex as a homogeneous molecular catalyst for photochemically, electrochemically and chemically induced oxygen evolution reactions is presented. Experimental evidence points towards the presence of a chloride ligand at the cobalt centre throughout the catalytic cycle, and the temporary detachment of a pyridine ligand to open a coordination site for substrate binding.

  • 225946.
    Das, Biswanath
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Water oxidation catalyzed by mononuclear iron and cobalt polypyridine complexes2017In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 22, no Supplement: 1, p. S259-S259Article in journal (Other academic)
  • 225947.
    Das Burman, Anindita
    University of Skövde, School of Life Sciences.
    TGF-β (BETA) AND PERIOSTIN MODULATE EACH OTHER’S EXPRESSION IN BOTH BREAST STROMA AND TUMOR CELLS2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Breast cancer is the most common cancer in female population worldwide. In addition to mutations, the breast tumor microenvironment especially the tumor cell - stroma interactions through extracellular matrix components and multiple growth factors have been shown to promote tumor progression. Among those, increases in both TGF-β (transforming growth factor beta) activities and periostin expression were associated with tumor cell survival, proliferation and metastasis. TGF-β role in breast cancer progression including its ability to promote periostin expression has been extensively studied. In contrast, the role of periostin in cancer progression remains to be fully understood. Thus, the present study aimed to determine whether TGF-β and periostin have effect on each other’s expressions in breast tumor and stroma cells using in vitro cell models. Through Western blot analyses and ELISAs, the periostin and TGF-β expressions of both stroma and tumor cells were analyzed following TGF-β and periostin treatments, respectively. The results indicate that TGF-β treatments led to significant increase in periostin expression in fibroblasts (p<0.05). In addition, periostin was differentially expressed by human breast cancer cells following TGF-β1 treatment. The TGF-β activities involved activation of pSMAD2 in both L929 fibroblasts and MCF10A mammary cells. Taken together, all experimental data indicate that within the breast tumor TGF-β and periostin likely participate in a regulation loop. Whether this putative regulation loop is critical to metastasis remains to be determined. Should periostin play a critical role in breast cancer progression, it could become a specific target in the preventive and/or therapeutic development of breast cancer patients.

  • 225948. Das, D. K.
    et al.
    Roy, M.
    Singh, V.
    Joshi, S. V.
    Microstructural degradation of plain and platinum aluminide coatings on superalloy CM247 during isothermal oxidation1999In: Materials Science and Technology, Vol. 15, no 10, p. 1199-1208Article in journal (Refereed)
    Abstract [en]

    Isothermal oxidation at 1100°C of a high activity plain aluminide coating and a platinum aluminide coating, developed by the pack cementation technique, on cast nickel base superalloy CM247 has been carried out with the primary objective of systematically understanding the coating degradation process during oxidation. While the weight gains during oxidation for both plain aluminide and platinum aluminide coatings follow parabolic kinetics from the very beginning of oxidation exposure, the bare alloy was seen to exhibit a considerably long initial transient oxidation period (∼20 h), beyond which the parabolic law was followed. The parabolic rate constant for the platinum aluminide coating was found to be nearly two orders of magnitude lower than that for the plain aluminide coating. Alumina was identified as the only oxide phase that formed on both plain aluminide and platinum aluminide coatings during most of the oxidation exposure, although NiAl2O4 was also found in the case of the plain aluminide coating beyond ∼200 h. The oxide layer on the bare alloy, however, was found to consist of Al2O3, Cr2O3, and NiAl2O4. The microstructural degradation of both the plain aluminide and platinum aluminide coatings during oxidation was seen to occur in three distinct stages which, however, differed for each coating. This stagewise degradation, which involves final obliteration of the interdiffusion layer in each case, is discussed in detail. © 1999 IoM Communications Ltd.

  • 225949. Das, D. K.
    et al.
    Singh, V.
    Joshi, S. V.
    Effect of Al content on microstructure and cyclic oxidation performance of Pt-aluminide coatings2002In: Oxidation of Metals, Vol. 57, no 3-4, p. 245-266Article in journal (Refereed)
    Abstract [en]

    The effect of Al content, i.e., the amount of Al picked up during aluminizing, on the microstructure and cyclic oxidation properties of Pt-aluminide coatings has been investigated. The cast Ni-base superalloy CM-247 was used as the substrate material and a single-step, high-activity pack aluminizing process was used to produce the Pt-aluminide coatings. The Al content of these coatings was varied by using packs with different compositions of the Al source. Pt-aluminide coatings having three different Al contents, namely 6.5, 16, and 21 mg cm-2, were evaluated for their cyclic oxidation resistance at 1200°C in air. It was found that the Pt-aluminide coatings, irrespective of their Al contents, evolve in the same manner during aluminizing and result in a three-layer structure with an outer PtAl2 + NiAl two-phase layer, an intermediate NiAl layer, and the inner interdiffusion layer. The stability of this three-layer coating structure over long periods of aluminizing, however, is dependent on the availability of Al from the pack during this period. Below a certain threshold Al availability, the two-phase outer layer transforms to a single-phase NiAl structure causing the coating to change from its three-layer structure to a two-layer one. Cyclic oxidation results indicate that, while a minimum Al content in Pt-aluminide coatings is essential for deriving the best oxidation performance, increasing the Al content beyond a certain level does not significantly enhance oxidation behavior. The effect of Al content on aspects, such as coating degradation and nature of coating-surface damage during cyclic oxidation, is also discussed.

  • 225950. Das, D. K.
    et al.
    Singh, V.
    Joshi, S. V.
    Effect of prealuminizing diffusion treatment on microstructural evolution of high-activity pt-aluminide coatings2000In: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, Vol. 31, no 8, p. 2037-2047Article in journal (Refereed)
    Abstract [en]

    The effect of prealuminizing (or prior) diffusion treatment on the evolution of Pt-aluminide coatings on the Ni-based superalloy CM-247 has been studied by using a single-step, high-activity aluminizing process. Coatings generated without any prior diffusion treatment, as well as those formed by adopting two extreme prior-diffusion schedules (at 850 °C for 0.5 hours and at 1034 °C for 5 hours), were investigated by analyzing the coating structures at various stages of aluminizing. When the dilution of the Pt layer, caused by its interdiffusion with the substrate during the prior diffusion treatment, is only marginal (as in the case of no prior diffusion and diffusion at 850 °C for 0.5 hours), the equilibrium Pt-aluminide coating structure evolves through the formation of two transient layers during the initial stages of aluminizing. In contrast, for diffusion at 1034 °C for 5 hours, which results in extensive dilution of the Pt layer, the two-phase equilibrium structure (PtAl2 in a matrix of NiAl) in the outer layer of the coating is found to develop during very early stages of aluminizing and remains unchanged, even over extended periods of aluminizing. Further, in the case of prior diffusion at 1034 °C for 5 hours, Pt is found to remain distributed to a greater extent over the entire thickness of the coating than in the cases of limited prior diffusion treatment. The present findings underline the significance of the nature of the prior-diffusion schedule on the microstructural evolution of Pt-aluminide coatings. It has also been found that a prealuminizing diffusion treatment is particularly important for Pt-aluminide coatings from the point of view of coating adhesion to the substrate.

4516451745184519452045214522 225901 - 225950 of 1157992
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf