Photoresponse of epitaxial YBa2Cu3O7-x ultrathin films

The voltage photoresponse of YBa2CH307_ x/SrTiO3 10 nm-tlfick films\ud on laser irradiation is studied using the low temperature scanning laser\ud microscopy (LTSLM) teclmique. The irradiation wavelength is 633 run.\ud The spatial response dependencies via temperature (4-100 K), beam\ud intensity modulation frequency (0-150 kHz) and bias current are\ud examined. The bolometric and non-bolometric components are\ud separated. The amplitude of the non-bolometric component at 4.2 K is\ud about 10 times higher than that of bolometric one measured near the\ud midpoint of the superconducting transition. The non-bolometric\ud component is presumably associated with weak links in the film due to\ud interdiffusion of SrTiO3 into YBCO layer. The spatial irregularity in\ud superconducting parameters is not resolved by the LTSLM method\ud since the spacing between weak links is appeared to be less than 1 um

Electric-field effect devices made of YBa2Cu3O7-x/SrTiO3 epitaxial multilayers

Three terminal superconducting electric-field effect devices, consisting of a bufferlayer of PrBa2Cu3O7-x, an ultrathin layer of YBa2Cu3O7-x and a SrTiO3 gate isolation layer were fabricated and successfully operated. Transmission electron microscopy and laser scanning microscopy showed that all layers are highly epitaxial and uniform over the device area. This is essentially important in the analysis of the mechanism of the electric field effect and for the reproducible fabrication of devices. With a 5 nm thick YBa2Cu3O7-x layer and an applied electric field of 0.85 MV/cm the critical current was decreased by 5% at low temperatures and up to 36% close to Tc. Also enhancement was obtained

A HREM study of the atomic structure and the growth mechanism of the YBa2Cu3O7/YSZ interface

The interface between yttria-stabilized zirconia (YSZ) substrate and YBa2Cu3O7 (YBCO) film was studied by high-resolution electron microscopy. In all specimens we have observed an intermediate layer of BaZrO3 located between the substrate YSZ and YBCO. The BaZrO3 layer is composed of almost equally aligned domains being 4¿8 nm in the lateral directions. Reaction products such as Y and Cu oxides were never observed in or close to the BaZrO3 reaction layer but they do occur in the YBCO film. The stacking sequence of BaZrO3/YBCO is predominantly (BaZrO3)-ZrO2-BaO/CuO-BaO-(YBCO) with CuO layer as the beginning YBCO layer. Sometimes a stacking sequence (BaZrO3)-ZrO2-BaO/BaO-CuO2-(YBCO) with a BaO layer as the beginning YBCO layer was observed. This stacking is related to a dislocation with Burgers vector a'/2 [111], where a' = 0.42 nm is the lattice constant of the cubic BaZrO3. Three main epitaxial relations (0°, 45°, 9°) between YSZ and YBCO were observed. These can be explained by near-coincidence site lattices ¿ = 25, ¿ = 49 and ¿ = 13 (for a YSZ substrate). Usually the (001) plane of the YBCO film is parallel to the (001) plane of the BaZrO3 layer and parallel to the substrate surface. In case YBCO is grown on an inclined YSZ substrate, the (001) plane of the YBCO film is parallel to the substrate surface and thus not parallel to the (001) plane of the YSZ substrate

Decline and decadence in Iraq and Syria after the age of Avicenna? : ʿAbd al-Laṭīf al-Baghdādī (1162–1231) between myth and history

‘Abd al-Laṭīf al-Baghdādī’s (d. 1231) work Book of the Two Pieces of Advice (Kitāb al Nasīḥatayn) challenges the idea that Islamic medicine declined after the twelfth century AD. Moreover, it offers some interesting insights into the social history of medicine. ‘Abd al-Laṭīf advocated using the framework of Greek medical epistemology to criticize the rationalist physicians of his day; he argued that female and itinerant practitioners, relying on experience, were superior to some rationalists. He lambasted contemporaneous medical education because it put too much faith in a restricted number of textbooks such as the Canon by Ibn Sīnā (Avicenna, d. 1037) or imperfect abridgments

Anchoring Innovation in the Platonic Axiochus

As the youngest work in the Platonic corpus, the Axiochus interacts with other texts in the corpus as well as with its contemporary philosophical milieu. How it does so, however, and what the purpose of the work is, is still unclear. This paper proposes a new theoretical approach to this text, arguing that the Axiochus anchors a number of innovations. It discusses three innovations in particular: the introduction of philosophical therapy in Platonism, the use of Epicurean arguments in Academic philosophy, and a renovated Platonism on the contemporary philosophical scene. The Axiochus aims, so this paper argues, to make these innovations acceptable to different audiences by anchoring them in the Socratic dialogue and the therapeutic paradigm of philosophy, respectively

Self-knowledge and Politics in the Alcibiades I

This paper offers a case for recognizing the Alcibiades i as a contribution to political philosophy. In so doing, it also shows that the dialogue is much more unified than it is usually considered to be in the scholarly literature. The paper focuses on the connection between two passages: the apparently aporetic passage of 124e1–127d5, in which Socrates questions Alcibiades about the content of political expertise; and Socrates’ exhortation to Alcibiades to get to know himself as his soul (127e9–133c6). The section on self-knowledge provides central conceptual tools that help us articulate the political philosophy that is implicit in the aporetic passage. First, knowledge of one’s humanity is key to politics, understood as an expertise that has people as its proper object. Second, politics deals with human beings qua human beings, not in accidental specialisations. Third, the section on self-knowledge instantiates political rule in the conversation between Socrates and Alcibiades. Fourth, the later section helps resolve the dilemma between friendship as unanimity and friendship as justice that brought 124e-127d to its aporetic close. Finally, the combination of the two passages yields two scenarios of political rule: one of education and one of cooperation. It shows, in essence, what is involved in Alcibiades’ description of politics as an expertise that deals with people: it is rule of fellow rulers

Olympiodorus’ View of Civic Self-Knowledge

This chapter examines Olympiodorus’ conception of civic self-knowledge (gnônai heauton politikôs). It explores the ‘affective’, ‘particularist’ and ‘personal’ aspects involved in this mode of knowing oneself: on this level, self-knowledge concerns one’s dealings with feelings and emotions, with particular situations, but also with others in personal interaction. The concept is hard to pin down, however, which this chapter argues is evidence that it is inherently ‘transitory’. This last aspect suits the intermediary role of civic self-knowledge in ethical development, and makes it a suitable target for the Alcibiades I, the first dialogue of the Platonic curriculum in Neoplatonism

Introduction

This introduction presents Olympiodorus as a committed Platonic teacher whose exegetical work combines a loyalty to his tradition with an emphasis on independent thought. It positions the chapters of this volume in four areas of interest: the profile of the philosopher that we find in Olympiodorus’ work; his interest in perception and knowledge of oneself; his concern with the form of philosophical communication; and his position vis-à-vis his Christian surroundings