Faster-than-light effects and negative group delays in optics and electronics, and their applications

Recent manifestations of apparently faster-than-light effects confirmed our predictions that the group velocity in transparent optical media can exceed c. Special relativity is not violated by these phenomena. Moreover, in the electronic domain, the causality principle does not forbid negative group delays of analytic signals in electronic circuits, in which the peak of an output pulse leaves the exit port of a circuit before the peak of the input pulse enters the input port. Furthermore, pulse distortion for these superluminal analytic signals can be negligible in both the optical and electronic domains. Here we suggest an extension of these ideas to the microelectronic domain. The underlying principle is that negative feedback can be used to produce negative group delays. Such negative group delays can be used to cancel out the positive group delays due to transistor latency (e.g., the finite RC rise time of MOSFETS caused by their intrinsic gate capacitance), as well as the propagation delays due to the interconnects between transistors. Using this principle, it is possible to speed up computer systems.Comment: 13 pages, 5 figures, 2001 Photonic West Plenary Tal

Locating Cities and Their Governments in Multi-Level Sustainability Governance

Cities and their governments are increasingly recognized as important actors in global sustainability governance. With the adoption of the 2030 Agenda for Sustainable Development, their role in the global endeavor to foster sustainability has once again been put in the spotlight. Several scholars have highlighted pioneering local strategies and policies to implement the Sustainable Development Goals and render urban areas more sustainable. However, the question of how such urban sustainability actions are embedded in complex interactions between public and private actors operating at different levels has not been studied in enough detail. Building upon a multi-level governance approach, this article explores the entanglement and interconnectedness of cities and local governments with actors and institutions at various levels and scales to better capture the potential and limitations of urban policymaking contributing to global sustainability. The article finds that on the one hand cities and their governments are well positioned to engage other actors into a policy dialogue. On the other hand, local authorities face considerable budgetary and institutional capacity constraints, and they heavily rely on support from actors at other governmental levels and societal scales to carry out effective sustainability actions in urban areas

Children's verbalizations of motion events in German

Recent studies in language acquisition have paid much attention to linguistic diversity and have begun to show that language properties may have an impact on how children construct and organize their representations. With respect to motion events, Talmy (2000) has proposed a typological distinction between satellite-framed (S) languages that encode PATH in satellites, leaving the verb root free for the expression of MANNER, and verb-framed (V) languages that encode PATH in the verb, requiring MANNER to be expressed in the periphery of the sentence. This distinction has lead to the hypothesis (Slobin 1996) that MANNER should be more salient for children learning S-languages, who should have no difficulty combining it with PATH, as compared to those learning V-languages. This hypothesis was tested in a corpus elicited from German children and adults who had to verbalize short animated cartoons showing motion events, and the results are compared with previous analyses of French and English corpora elicited in an identical situation (Hickmann et al. 2009). As predicted, and as previously found for English, German children from three years on systematically express both MANNER (in the verb root) and PATH (in particles), in sharp contrast to French children, who rarely package MANNER and PATH together. These results suggest that, when they are engaged in communication, children construct spatial representations in accordance with the particular properties of their mother tongue. Future research is necessary to determine the extent to which cross-linguistic differences in production may reflect deeper differences in the allocation of attention and in conceptual organization