757 research outputs found
Translative lens-based full-field coherent X-ray imaging Detlefs Carsten
No full textA full-field coherent imaging approach suitable for hard X-rays based on a classical (i.e. Galilean) X-ray microscope is described. The method combines a series of low-resolution images acquired at different transverse lens positions into a single high-resolution image, overcoming the spatial resolution limit set by the numerical aperture of the objective lens. The optical principles of the approach are described, the successful reconstruction of simulated phantom data is demonstrated, and aspects of the reconstruction are discussed. The authors believe that this approach offers some potential benefits over conventional scanning X-ray ptychography in terms of spatial bandwidth and radiation dose rate
Determination of magnetic-moment directions using x-ray resonant exchange scattering
No full textWe present determinations of the magnetic structures of NCdNi2B2C and SmN2B2C by means of x-ray resonant exchange scattering (XRES). The integrated intensity of a number of magnetic reflections was measured as a function of the Bragg angle and compared to model calculations for various magnetic structures. The two compounds were found to have the same magnetic modulation wave vector but different moment directions. A resonant feature observed below the Sm L(3)-absorption edge, similar to unexplained effects found in other light rare-earth compounds, is identified as quadrupolar XRES and is used to refine the details of the moment direction.This article is published as Detlefs, Carsten, A. H. M. Z. Islam, A. I. Goldman, C. Stassis, P. C. Canfield, J. P. Hill, and D. Gibbs. "Determination of magnetic-moment directions using x-ray resonant exchange scattering." Physical Review B 55, no. 2 (1997): R680.
DOI: 10.1103/PhysRevB.55.R680.
Copyright 1997 American Physical Society.
Posted with permission
Correction to: When terminology hinders research: the colloquialisms of transitions of control in automated driving (Cognition, Technology & Work, (2022), 10.1007/s10111-022-00705-3)
No full textIn the original article, author affiliation published with error. The correct affiliations are: Davide Maggi—Institute for Transport Studies, Leeds, UK. Richard Romano—Institute for Transport Studies, Leeds, UK. Oliver Carsten—Institute for Transport Studies, Leeds, UK. Joost C. F. De Winter—Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands. The original article has been corrected.Human-Robot Interactio
X-ray resonant exchange scattering of rare-earth nickel borocarbides
No full textThe purpose of this thesis is to investigate the systematics of the microscopic magnetic order within a series of isostructural compounds and, at the same, to develop the relatively young experimental method of x-ray resonant exchange scattering (XRES). In this thesis, the author presents XRES studies of several rare-earth nickel borocarbides, RNi{sub 2}B{sub 2}C. He shows that XRES, similar to the neutron techniques, allows the determination of the orientation of the magnetic moment by measuring the Q-dependence of the scattered intensity of magnetic Bragg reflections. As samples in this study, he chose the recently discovered family of rare-earth nickel borocarbides, RNi{sub 2}B{sub 2}C, which display a wide variety of magnetic structures. Furthermore, in several of these materials, long range magnetic order coexists with superconductivity over some temperature range
Theodor Storm's novelle ''Carsten Curator': An evaluation of the terms "Befreiungsdichtung" and "das Peinliche".
No full textThis thesis undertakes an analysis of two interrelated aspects of Theodor Storm's later prose writing. The Novelle Carsten Curator (1877) has been selected since this work constitutes the most significant example of both "Befreiungsdichtung" and "das Peinliche". A definition of "Befreiungsdichtung" - the artistic projection of personal experience as an act of 'self-liberation' - and the way this is revealed in a series of earlier works is the subject of the first chapter. The following three chapters offer a study of the genesis of Carsten Curator and show by an investigation into Storm's relationship with his eldest son (Chapter 2) the extent of the autobiographical content in the Novelle (Chapter 4) and Storm's awareness of its 'confessional' nature while writing it (Chapter 3). The second part of the thesis concerns itself with artistic problems which thereby arose for Storm. The creative process conditioned Storm's treatment of the thematic complex of heredity, alcoholism and paternal responsibility in Carsten Curator and brought with it a degree of realism which the author and his more sensitive critics found 'unpoetic' and thus 'offensive' (Chapter 5). This constitutes "das Peinliche", which Storm believed detracted from the 'tragic' nature of the central conflict. The following two chapters assess Carsten Curator in the light of Storm's theoretical definitions of "das Tragische" and draw the conclusion that the Novelle is a prime example of his mature tragic art. Chapter 8 discusses the implications of "das Peinliche" for a study of Storm's later Novellen (1877 - 1888), including the development of his realism, the effects of literary censorship on his later treatment of the central themes of Carsten Curator and his knowledge of Naturalist literature, showing the absence of any direct influence where these themes are concerned. The thesis concludes that Storm's continuing preoccupation with the themes of Carsten Curator after 1877 can be attributed only to their 'confessional' nature
Crystallographic investigation of gold nanoparticles embedded in a SrTiO3 thin film for plasmonics applications.
No full textLAUREA MAGISTRALEMetallic nanoparticles represent a widespread subject of study in several different fields of research, such as applied physics (nanotechnology), material science, chemistry and biology.
In recent years they have been extensively studied by many authors (Kelly et al. [30],
Link and El-Sayed [37], Jackson and Halas [27]) particularly with respect to their optical
properties. These are characterized by the presence of the so called localized surface plasmon
resonance, which earned the study of metal nanoparticles the name of plasmonics. Their
properties have been probed with a wide selection of experimental techniques, ranging
from microscopy (TEM, AFM, STM . . . ) to optical spectroscopy and X-ray diffraction,
and a large variety of fabrication methods (Pelton et al. [44]) have been explored to obtain
systems made up of nanoparticles of various metals. Furthermore, they have been
proved to be promising for many different scientific and practical applications (Prasad [45]
and Bell [3]), for which both the surrounding medium sensitivity of the plasmonic resonance
and the associated local field enhancement play a major role. The morphological and structural
features of the metallic nanoparticles are strictly related to their properties in most of
the applications mentioned above. These features mainly depend on the particular preparation
method exploited for the nanoparticles production: a fundamental understanding of the
atomic-scale processes involved in the nanoparticles formation is thus of great importance.
The samples object of the present work are composed by anisotropic monocrystalline gold
(Au) nanoparticles embedded in a strontium titanate (SrTiO3) thin film. They were prepared
through a novel two-steps deposition process, whose main parameters can be varied in order
to obtain nanoparticles of different size and shape (Christke et al. [13] and Katzer et al.
[29]). This process therefore allows to tune the optical properties of the nanoparticles and it
constitutes a valid alternative to other traditionally used fabrication processes, particularly
for the production of plasmonic active sensors in life sciences. Nanoparticles prepared with
an analogous deposition process have been also exploited as flux pinning centers in high temperature superconducting YBCO thin films (Grosse et al. [23] and Katzer et al. [28]) or for the engineering of YBCO grain boundaries in Josephson junctions (Michalowski et al.[40]).
The study here presented consists of a crystallographic characterization realized through
synchrotron X-ray diffraction. The aim was to determine the preferred crystallographic orientations
of the Au nanocrystals and their interaction with the surrounding SrTiO3 matrix.
It represents the first step of a research project addressing the nanoparticles features (such
as the shape and the dimension) with an impact on their optical properties and the modifications induced in the surrounding matrix. Samples with different amounts of deposited
Au were probed with a hard X-ray beam and two different diffraction setups were used, exploiting
both a two-dimensional and a zero-dimensional detector. The main vertical (normal
to the substrate) growth direction of the nanoparticles was determined for all the samples,
along with the crystalline quality of the SrTiO3 layer. For each vertical growth direction the
in-plane orientation of the Au crystals was measured, in order to fully determine their crystallographic orientation with respect to the substrate. The correlation between the nanoparticles
orientation and the amount of deposited Au was investigated, trying to understand the role
of the SrTiO3 thin film in the nanoparticles formation process. Such a characterization is
not only important in the light of the potential practical applications of the samples, but
it is also valuable in itself. It indeed offers the possibility of a deeper understanding of the
fundamental properties regarding the growth of Au (and transition metals in general) on
ceramic substrates, which are still not well explored.
The present work is organized as explained hereafter. After a general overview of metallic
nanoparticles (Section 1.1), Chapter 1 describes the samples experimentally probed, with
particular focus on the preparation methods used and their potential practical applications
(Section 1.2). Chapter 2 provides the reader with the main theoretical concepts involved
in the measurements presented in the following chapters: Sections 2.1 and 2.2 outline the
basics of the X-ray diffraction technique and the properties of transition (face centered cubic)
metals deposited on ceramic substrate respectively; then, Section 2.3 describes in detail all the
mathematical framework necessary for the description of a diffraction experiment performed
with a CCD area detector. Following the presentation of the experimental setup of Chapter 3,
the main experimental results obtained are discussed. In particular Chapter 4 presents the
preliminary textured analysis undertaken and the main vertical growth direction of the Au
nanoparticles (along with the modification induced in the SrTiO3 thin film). Chapter 5 deals
with the in-plane investigation of the Au crystals, addressing its relation with the presence
of the SrTiO3 layer and the amount of Au deposited. Finally the appendices provide a brief
overview of the properties of synchrotron radiation (Appendix A) and some details about the
program used to performed the CCD diffraction data reduction (Appendix B). In Appendix C
the most important Python scripts used for the data analysis are reported
Corrigendum: Towards an understanding of global brain data governance: ethical positions that underpin global brain data governance discourse
No full textIn the published article, there was an error in the author list arrangement, the corrected author list appears below. Paschal Ochang1*, Damian Eke1 and Bernd Carsten Stahl1,2 The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated
Naturalizing institutions: Evolutionary principles and application on the case of money
No full textIn recent extensions of the Darwinian paradigm into economics, the replicator-interactor duality looms large. I propose a strictly naturalistic approach to this duality in the context of the theory of institutions, which means that its use is seen as being always and necessarily dependent on identifying a physical realization. I introduce a general framework for the analysis of institutions, which synthesizes Searle's and Aoki's theories, especially with regard to the role of public representations (signs) in the coordination of actions, and the function of cognitive processes that underly rule-following as a behavioral disposition. This allows to conceive institutions as causal circuits that connect the population-level dynamics of interactions with cognitive phenomena on the individual level. Those cognitive phenomena ultimately root in neuronal structures. So, I draw on a critical restatement of the concept of the meme by Aunger to propose a new conceptualization of the replicator in the context of institutions, namely, the replicator is a causal conjunction between signs and neuronal structures which undergirds the dispositions that generate rule-following actions. Signs, in turn, are outcomes of population-level interactions. I apply this framework on the case of money, analyzing the emotions that go along with the use of money, and presenting a stylized account of the emergence of money in terms of the naturalized Searle-Aoki model. In this view, money is a neuronally anchored metaphor for emotions relating with social exchange and reciprocity. Money as a meme is physically realized in a replicator which is a causal conjunction of money artefacts and money emotions. --Generalized Darwinism,institutions,replicator/interactor,Searle,Aoki,naturalism,memes,emotions,money
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