2,040 research outputs found

    Union Catalogs for Poets

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    The Andrew W. Mellon Foundation and the National Library of Estonia organized a Conference on Union Catalogs which took place in Tallinn, in the National Library of Estonia on October 17–19, 2002. The Conference presented and discussed analytical papers dealing with various aspects of designing and implementing union catalogs and shared cataloging systems as revealed through the experiences of Eastern European, Baltic and South African research libraries. Here you can find the texts of the conference papers and the list of contributors and participants.The Andrew W. Mellon Foundation and the National Library of Estonia organized a Conference on Union Catalogs which took place in Tallinn, in the National Library of Estonia on October 17–19, 2002. The Conference presented and discussed analytical papers dealing with various aspects of designing and implementing union catalogs and shared cataloging systems as revealed through the experiences of Eastern European, Baltic and South African research libraries. Here you can find the texts of the conference papers and the list of contributors and participants

    From Periodic to Dilute Anderson Models

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    Actinide- and Lanthanide based compounds are often considered as heavy Fermion (HF) systems. The essential ingredient for these systems is a localized d- or f-shell electron per lattice site which hybridizes with a non-interacting conduction band of p- or d-shell electrons. For temperatures below the so called coherence temperature Tc, the localized electrons stop to act like mag- netic scatterers known from the Kondo effect. There the conduction band electrons screen the local magnetic moments coherently. As a main effect the conduction electrons build a Fermi liquid (FL) of quasiparticles with strongly enhanced masses which exceed 10-1000 times the mass of the original electrons. These enhancements can be seen experimentally in an increased heat capacity coefficient and Pauli susceptibility. In this work we employ the periodic Anderson model (PAM) to describe the paramagnetic phase of the heavy Fermion compounds. To solve the compli- cated many body problem the dynamical mean-field theory is adopted with the numerical renormalization group technique as impurity solver. We find that for low conduction band fillings Tc decreases drastically, which is in accordance with the exhaustion effect predicted by Nozières [5]. Additionally we find, that the form of the free conduction band density of states is decisive to obtain a FL or a Mott insulating (MI) phase for strongly depleted conduction band fillings. Furthermore we investigate the PAM on a bipartite lattice, the coherence temperatures for each sublattice and especially the case of vanishing hybridiza- tion for one sublattice. In the latter case the system resembles a conduction band with only half the localized moment sites coupled to it. Our results show that it depends strongly on the chosen parameters if there is only one scale for the whole lattice or two distinct scales for each sublattice. Especially decoupling one sublattice leads to two separated scales. In the last part the attention is focused on the two-impurity Anderson model and its solution via the DMFT method. We investigate the Anderson model and compare results to direct NRG calculations. Importantly, the two-impurity DMFT method can be easier extended to multi-impurity systems than the NRG on its own. This might lead to a method to efficiently examine multi- impurity systems

    Molecular and Genetic Analysis of Flower Development in Arabidopsis thaliana and the Diploid Strawberry, Fragaria vesca

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    In a world with a warming climate and a rapidly growing population, plant biology is becoming a field of increasing importance. Deciphering the molecular and genetic mechanisms behind the development of the flower, the fruit and seed progenitor, will enhance the agricultural productivity needed to ensure a sustainable food supply. My PhD research ties in with this need by furthering the basic knowledge of the mechanisms underlying flower development in two ways. First, using Arabidopsis thaliana, the classic model plant, I investigated the regulation of a gene, SPATULA (SPT), necessary for the proper development of the gynoecium, the female flower organ that, upon fertilization, directly gives rise to fruit. For flower and fruit to properly develop, the expression of SPT, must be tightly regulated both spatially and temporally. My research examined the mechanism of transcriptional repression of SPT in the sepals and petals by several interacting transcription factors (LEUNIG, SEUSS, APETALA2) and the molecular and genetic interaction between ETTIN and SPT in patterning gynoecium. The second focus of my research was to develop Fragaria vesca (the diploid strawberry), as a model Rosaceae for the study of flower and fruit development. Arabidopsis has much value as a small, fast growing, flowering plant with a multitude of genetic and genomic resources, however the flower of this mustard family weed is not representative of all crop flowers. The Rosaceae family, including many agriculturally important fruit trees such as apple, peach, blackberry, and strawberry, warrants its own model plant to investigate the distinct mechanisms behind their unique reproductive biology. Toward developing F. vesca as the model plant for studying Rosaceae flowers, I characterized and described developmental progression of F. vesca flowers morphologically through scanning electron microscopy and histological analysis as well as molecularly through transcriptomes and in situ hybridization. In addition, I pioneered a small-scale mutagenesis screen of F. vesca that will lead to future genetic resources. My thesis work places the groundwork for future discoveries in F. vesca and Rosaceae and benefits research, education, and agricultural applications for the Rosaceae and the plant biology communities

    Physical Illness: The Family and the Physician

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    When confronted by the specific stress of a close relative\u27s illness, the family members\u27 reactions may be schematically divided into three stages: 1) disorganization; 2) reintegration; and 3) adjustment. Either disorganization can be intensified or adjustment can be fostered, depending on the physician\u27s understanding of the feelings the family members experience and his willingness and ability to be helpful. The family members\u27 responses, in turn, will influence the patient\u27s reaction to illness or his recovery and rehabilitation. Accordingly, good medical practice requires that the physician include the family in his total treatment plan whenever possible

    Who will Take Over the Libraries of the New Europe ?

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    Intervention au 36e congrès LIBER qui s\u27est tenu à Varsovie du 3 au 7 juillet 2007. Situation des bibliothèques chez les nouveaux entrants dans la Communauté européenne du point de vue du management et des nouveaux profils professionnels

    The Computational Complexity of Finding Stationary Points in Non-Convex Optimization

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    Finding approximate stationary points, i.e., points where the gradient is approximately zero, of non-convex but smooth objective functions ff over unrestricted dd-dimensional domains is one of the most fundamental problems in classical non-convex optimization. Nevertheless, the computational and query complexity of this problem are still not well understood when the dimension dd of the problem is independent of the approximation error. In this paper, we show the following computational and query complexity results: 1. The problem of finding approximate stationary points over unrestricted domains is PLS-complete. 2. For d=2d = 2, we provide a zero-order algorithm for finding ε\varepsilon-approximate stationary points that requires at most O(1/ε)O(1/\varepsilon) value queries to the objective function. 3. We show that any algorithm needs at least Ω(1/ε)\Omega(1/\varepsilon) queries to the objective function and/or its gradient to find ε\varepsilon-approximate stationary points when d=2d=2. Combined with the above, this characterizes the query complexity of this problem to be Θ(1/ε)\Theta(1/\varepsilon). 4. For d=2d = 2, we provide a zero-order algorithm for finding ε\varepsilon-KKT points in constrained optimization problems that requires at most O(1/ε)O(1/\sqrt{\varepsilon}) value queries to the objective function. This closes the gap between the works of Bubeck and Mikulincer [2020] and Vavasis [1993] and characterizes the query complexity of this problem to be Θ(1/ε)\Theta(1/\sqrt{\varepsilon}). 5. Combining our results with the recent result of Fearnley et al. [2022], we show that finding approximate KKT points in constrained optimization is reducible to finding approximate stationary points in unconstrained optimization but the converse is impossible.Comment: Full version of COLT 2023 extended abstrac
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