1,350 research outputs found
On describing
No full textThe overarching topic of this dissertation is the semantics and pragmatics of definite descriptions. It focuses on the question whether sentences such as ‘the king of France is bald’ literally assert the existence of a unique king (and therefore are false) or simply presuppose the existence of such a king (and thus fail to express propositions). One immediate obstacle to resolving this question is that immediate truth value judgments about such sentences (sentences with non-denoting descriptions) are particularly unstable; some elicit a clear intuition of falsity whereas others simply seem awkward or strange. Because of these variations, truth value judgments are generally considered unreliable. In the first chapter of the dissertation, an explanation of this phenomenon is developed. It is observed that when these types of sentences are considered in the context of a discourse, a systematic pattern in judgments emerges. This pattern, it is argued, should be explained in terms of certain pragmatic factors, e.g. whether a speaker’s utterance is interpreted as cooperative. A detailed and general explanation of the phenomenon is then presented which draws importantly on recent research in the semantics and pragmatics of questions and focus. It is shown that the behavior of these judgments can be systematically explained, that truth value judgments are not as unreliable as standardly assumed, and that the proposed explanation best supports the conclusion that definite descriptions presuppose rather than assert existence.
In the second chapter, the following problem is investigated. If definite descriptions are assumed to literally assert existence, a sentence such as ‘Hans wants the ghost in his attic to be quiet’ is incorrectly predicted to be true only if Hans wants there to be a (unique) ghost in his attic. This prediction is often considered evidence against Russell’s quantificational analysis and evidence in favor of the referential analysis of Frege and Strawson. Against this claim, it is demonstrated that this problem is a general problem about the existence commitments of natural language determiners, i.e. not an argument in favor of a referential analysis. It is shown that in order to avoid these undesirable predictions, quite radical changes to the semantic framework are required. For example, it must be assumed that a sentence of the form ‘The F is G’ has the open sentence ‘x is G’ as its asserted content. A uniform quantificational and presuppositional analysis of definites and indefinites is outlined which by exploiting certain features of so-called dynamic semantics unproblematically assumes that the asserted contents indeed are open sentences.
In view of the proposed quantificational/presuppositional analysis, the dissertation is concluded by a rejection of the argument put forward by Reimer (1998) and Devitt (2004) that definite descriptions are ambiguous between attributive (quantificational) and referential (indexical) uses. Reimer and Devitt’s argument is (in contrast to Donnellan, 1966) based primarily on the assumption that definite descriptions are conventionally used to communicate singular thoughts and that the conventional meaning of a definite description therefore must be fundamentally indexical/directly referential. I argue that this argument relies crucially on tacit assumptions about semantic processing for which no empirical evidence is provided. I also argue that the argument is too general; if sound, it would be an argument for an indexical treatment of most, if not all, other determiners. I then conclude by demonstrating that the view does not explain any new data and thus has no clear motivation.
In short, this dissertation provides a detailed pragmatic explanation of a long-standing puzzle about truth value judgments and then outlines a novel dynamic semantic analysis of definites and indefinites. This analysis solves a significant problem about existence commitments — a problem that neither Russell’s nor the Frege/Strawson analysis are equipped to handle. This analysis is then defended against the claim that definite descriptions are ambiguous
Paracelsus, sein Leben und Denken : mit einem Titelkupfer
No full textDrei Bücher von Michael Benedict LessingHandschriftliches Exlibris: "Dr. Kirsch" 990021290220205503_0001 Exemplar der ETH-BIBFrühere Signatur: "Bircher 4692" 990021290220205503_0002 Exemplar der ETH-BI
Software for qualitative research: 2. Some thoughts on ‘aiding’ analysis
No full textIn this paper the author examines how Korea's export-oriented economy has laid its new foundation for global competitiveness by deepening interfirm linkages. Korea's interfirm linkages refer mainly to the relationship between large and small firms. Recent corporate restructuring in the large and small firm sectors has caused denser and highly dynamic intercorporate networks to arise. The author argues that the globalizing of economy in Korea is encouraged by efficacious global - local transactions via large - small firm networks, a matter ignored by most analysts. Major foci are on analyzing the forms, structures, governing mechanisms, and function of large - small firm networks
Quadrupole Electric Field for Erasing the Fine Structure Splitting of a Nanowire Quantum Dot Entangled Photon Source
No full textEntanglement is an essential tool in quantum information processing (QIP), for example, to achieve a secure quantum communication network and quantum computing. Semiconductor quantum dots can generate on-demand entangled photon pairs via the biexciton-exciton cascade. These solid-state sources are currently limited in their applications due to two major challenges: first is the collection efficiency since only a fraction of a percent of the emitted photons from the quantum dot can be collected due to its isotropic emission profile; and second is the FSS that causes an energy splitting of the intermediate exciton state —it arises due to strain and structural asymmetry of the quantum dot and degrades its measured entanglement fidelity. Quantum dots have been integrated into photonic structures such as microcavities and nanowires to enhance their collection efficiency by coupling the emitted photons to the cavity or fundamental nanowire waveguide mode. However, the fine structure splitting still remains a major challenge, and although many post growth perturbation techniques have been implemented to tune and completely erase the FSS of a self-assembled Quantum Dot (QD), erasing the FSS of a QD in a photonic structure has not yet been achieved. In this thesis, we propose and then demonstrate for the first time the tuning of the FSS for a indium arsenic phosphide (InAsP) QD in a tapered indium phosphide (InP) nanowire by applying a quadrupole electric field.
Out of all the post-growth perturbation based FSS erasing techniques, electric fields, and stress fields have been the most successful ones in erasing the FSS of a self-assembled quantum dot. However, implementing them on a nanowire quantum dot source is not a straightforward solution to its FSS problem. Stress field techniques are difficult to implement on a nanowire quantum dot source due to the thick nanowire shell around the quantum dot, where most of the applied external stress field relaxes and therefore doesn't reach the embedded quantum dot. The electric field on the other hand is known for reducing the electron-hole (e-h) overlap and therefore if implemented in its conventional form will reduce the QD brightness while erasing its FSS. Moreover, both stress and electric field techniques require multiple perturbation axes to erase the FSS of a quantum dot with any possible dipole orientation or macroscopic asymmetry. We overcame these problems by developing a novel approach of applying a quadrupole electric field along the plane of an embedded quantum dot inside the nanowire. We show theoretically that a quadrupole electric field corrects for the spatial asymmetry of the excitonic wave function for any quantum dot dipole orientation (θ = 0°, 10°, 20°) inside a nanowire and completely erases its fine structure splitting from 11 μeV to 0.05 μeV while maintaining a strong e-h overlap (β = 99%, 90, for a dot with θ = 0°, 20°) even after applying a correction quadrupole electric field.
To experimentally demonstrate our theory we fabricated two prototypes of electrically gated InAsP/InP QD nanowire devices, with four metal gates precisely positioned around an individual InAsP quantum dot inside a vertically standing InP nanowire. The electrooptical characterization of an electrically gated nanowire quantum dot device shows the FSS tuning from 7 μeV to 4 μeV by application of a quadrupole electric field.
Although we have achieved a FSS tuning in nanowire device, tuning and completely erasing the FSS of a nanowire device will require a significant improvement in the fabricated device design. This will require reducing the dimension of the metal gates and aligning it perfectly to touch the sidewalls of the vertical nanowires. We also observed the degradation in the QD emission while exposing it to 100 kV electron-beam (e-beam). Therefore, we propose a bottom-up approach of fabricating the device by first patterning the metal gates by e-beam lithography on a wafer and then selectively growing the nanowire QD source at its center by the conventional site-selected vapor-liquid-Solid (VLS) growth method. In principle, such an electrically gated device will erase the FSS of a nanowire quantum dot source and will bring it closer to becoming a deterministic source of entangled photons with near-unity fidelity and collection efficiency
A Comprehensive Strategy for Screening for Xenotransplantation-Relevant Viruses in a Second Isolated Population of Göttingen Minipigs
No full textXenotransplantation using pig tissues and organs is under development in order to alleviate the increasing shortage of human transplants. Since xenotransplantation may be associated with the transmission of porcine microorganisms to the human recipient, the donor pigs should be carefully analyzed, especially for the presence of potentially zoonotic viruses. Göttingen Minipigs (GöMP) are potential donors of islet cells for the treatment of diabetes. Despite the fact that all animals produced at Ellegaard Göttingen Minipigs A/S carry porcine endogenous retroviruses (PERVs) in their genome and that very few animals were infected with porcine cytomegalovirus (PCMV), hepatitis E virus (HEV) and porcine lymphotropic herpesvirus (PLHV), no transmission of these viruses was observed in a preclinical trial transplanting GöMP islet cells into cynomolgus monkeys. Using a new comprehensive strategy, we then analyzed an isolated subpopulation of Göttingen Minipigs which remained at the University of Göttingen. We concentrated on 11 xenotransplantation-relevant viruses and combined co-incubation assays with susceptible human target cells and molecular biological methods to evaluate the risk posed by PERV. All animals in Göttingen carry PERV-A, PERV-B, and PERV-C in their genome but they are not infected with PCMV, PLHV and HEV. The difference may be explained by selection of negative animals and/or de novo infection. The PERV copy number was established using ddPCR (93 copies) and a human-tropic PERV-A/C was found released from PBMCs of one animal with a high expression of PERV-C.Peer Reviewe
Observation of strongly entangled photon pairs from a nanowire quantum dot
No full textA bright photon source that combines high-fidelity entanglement, on-demand generation, high extraction efficiency, directional and coherent emission, as well as position control at the nanoscale is required for implementing ambitious schemes in quantum information processing, such as that of a quantum repeater. Still, all of these properties have not yet been achieved in a single device. Semiconductor quantum dots embedded in nanowire waveguides potentially satisfy all of these requirements; however, although theoretically predicted, entanglement has not yet been demonstrated for a nanowire quantum dot. Here, we demonstrate a bright and coherent source of strongly entangled photon pairs from a position-controlled nanowire quantum dot with a fidelity as high as 0.859±0.006 and concurrence of 0.80±0.02. The two-photon quantum state is modified via the nanowire shape. Our new nanoscale entangled photon source can be integrated at desired positions in a quantum photonic circuit, single-electron devices and light-emitting diodes.QN/Quantum NanoscienceApplied Science
Extremely 13C-enriched dolomite records interval of strong methanogenesis following a sulfate decline in the Miocene Ries impact crater lake
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