105,233 research outputs found
Undulators and free-electron lasers
No full textThis book is a reference text for all those working in free-electron laser research as well as being a learning aid for physicists and graduate students who wish an introduction to this field. Only a basic understanding of relativistic mechanics and electromagnetism is presupposed. After an overview of early developments and general principles of operation, the different models that can be used to describe free-electron lasers are presented, organized according to their range of applicability. The relevent conceptual and mathematical constructs are built up from first principles with attention to obtaining the practically important results in a simple but rigorous way. Interaction of the undulator with the driving electron accelerator and the laser cavity and design of undulator magnets are treated and an overview is given of some typical experiments
Rezension: Motz, Markus: Englisch oder Deutsch in Internationalen Studiengängen?
No full textBrandl H. Rezension: Motz, Markus: Englisch oder Deutsch in Internationalen Studiengängen? Info DaF. 2006;(2-3):230-235
Modified finite-difference approximations near the singularitiy in the problem of motz
No full textA simple, modified finite-difference method is described for solving Laplace's equation with boundary singularities of the infinite derivative type. Modified approximations for the derivatives of the Laplacian equation are employed near the singularity. These are developed from a truncated series form of the local analytical solution. The method is applied to the problem of Motz. The numerical results compare favourably with those obtained by other techniques
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
First Row Transition Metal Aminopyridinates – the Missing Complexes
No full textLithiated 4-methyl-2-[(trimethylsilyl)amino]pyridine (Ap(TMS)H) undergoes a salt metathesis reaction with [SCCl(3)(thf)(3)] and FeCl(3), at low temperature in thf, to yield the homoleptic complexes [Sc(Ap(TMS))(3)] (1) and [Fe(Ap(TMS))(3)] (2). An analogous reaction with MnCl(2), CoCl(2) and FeCl(2) using two equivalents of 4-tert-butylpyridine (tBuPy) as additional donor ligand affords the structurally analogous cis complexes [Mn(Ap(TMS))(2)(tBuPy)(2)] (3), [Co(Ap(TMS))(2)(tBuPy)(2)] (4) and [Fe(Ap(TMS))(2)(tBuPy)(2)] (5). If FeCl(3), is used without tBuPy, the highly symmetric trinuclear complex [Fe(3)(Ap(TMS))((6)Li(2)O] (6) is obtained. Furthermore, the use of ZnCl(2) in a reaction with lithiated Ap(TMS)H yields the dimeric complex [Zn(Ap(TMS))(4)] (7) in which two Ap(TMS) ligands bridge the two metals. All complexes have been characterised by X-ray crystal structure analysis. To the best of our knowledge, complexes 1 and 2 and 5 are the first scandium and iron aminopyridinates, respectively, and complex 3 is the first manganese aminopyridinate complex which contains no additional anionic ligand. Complexes 4 and 7 are rare examples of cobalt and zinc aminopyridinates. This study proves that aminopyridinato ligands are highly universal ligands since they are able to stabilize early and late transition metals. Aminopyridinates of every first row transition metal are now available. The magnetic properties of all paramagnetic complexes were investigated. All complexes are high-spin complexes and the trinuclear iron complex 6 exhibits a weak antiferromagnetic coupling. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)Deutsche Forschungsgerneinschaft (DFG
Is heart rate variability an objective parameter with which to manage treatment of infants with heart failure due to left-to-right shunting?
No full textTreatment in heart failure could be guided by additional non-clinical measures, such as neurohumoral levels. Variability in heart rate is known to reflect neurohumoral stimulation. With this in mind, we sought to assess retrospectively the variability in heart rate to guide the treatment of infants in heart failure. We analysed retrospectively the data from 20 infants with a significant left-to-right shunt. All were unsuitable for cardiac surgery or interventional therapy at the time the treatment had commenced. None of the infants improved while receiving diuretics, spironolactone, and digoxin alone, but improved after the addition of propanolol or metoprolol. None of the infants had problems during or after the subsequent operation. Parasympathetic activity reflected by parameters of variability in heart rate, such as the square root of adjacent RR-intervals, and the amount of adjacent RR-Intervals greater than 50 milliseconds, improved in nearly all infants during beta blockade. On the other hand, parameters of variability in heart rate reflecting sympathetic activity did not change. Parasympathetic activity reflected the clinical state of nearly all the infants. These parameters, therefore, seem to be a good non-clinical parameter, showing the optimal treatment for heart failure in an ambulatory setting
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Contribution of Information and Communication Technology (ICT) in Country’S H-Index
No full textThe aim of this study is to examine the effect of Information and Communication Technology (ICT) development on country’s scientific ranking as measured by H-index. Moreover, this study applies ICT development sub-indices including ICT Use, ICT Access and ICT skill to find the distinct effect of these sub-indices on country’s H-index. To this purpose, required data for the panel of 14 Middle East countries over the period 1995 to 2009 is collected. Findings of the current study show that ICT development increases the H-index of the sample countries. The results also indicate that ICT Use and ICT Skill sub-indices positively contribute to higher H-index but the effect of ICT access on country’s H-index is not clear
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