Inhabiting infrastructure: exploring the interactional spaces of urban cycling

Contemporary cities are thick with infrastructure. In recognition of this fact a great deal of recent work within urban studies and urban geography has focused on transformations in the governance and ownership of infrastructural elements within cities. Less attention has been paid to the practices through which urban infrastructures are inhabited by urban dwellers. Yet in all sorts of ways infrastructures are realised through their use and inhabitation. This paper argues for the importance of attending to the ways that infrastructures are reinterpreted through use. Focusing on a case study of commuter cyclists in London, it explores the ways in which cyclists accommodate themselves to (and are in turn accommodated by) the infrastructural orderings of London’s streets. Confronted by the obduracy of a road infrastructure designed primarily for motorised traffic, cyclists show a diverse range of approaches to negotiating movement through the city on bikes. The paper describes how this negotiation can be understood in terms of the more or less skilful processes of navigation, rule following, rule making, and rule bending. This involves a polymorphous mix of practices, some common to driving, others to walking, and yet others unique to cycling. In conclusion, the paper suggests that transformations of infrastructures found within cities need to be understood as much through emergent changes between their elements, and that close attention to how infrastructures come to be inhabited offers productive avenues for thinking about ways to improve them

FDDI data link development

and efficiency. The advent of fiber optics, large-scale integrated circuits, and related technologies makes it possible to provide a relatively low-cost, high-speed local area network (LAN) with large physical extent and connectivity. One LAN standard is the fiber distributed data interface (FDDI), a 100-megabit-per-second token ring that uses an optical fiber medium. The scope of FDDI spans the data link layer and the physical layer. The FDDI data link provides its users with communication services on a multiaccess LAN for transmitting and receiving frames with best-effort delivery service (also called the datagram service). The development of the FDDI data link encountered several significant challenges, including the instability of the standard, unproven technology and protocols, and an order of magnitude increase in speed from the International Standards The fiber distributed data interface (FDDI) data link is based on the ANSI X3T9.5 FDDI standards with Digital's enhancements to provide greater performance, reliability, and robustness. The FDDI project team encountered significant challenges, including the evolving ANSI X3T9.5 FDDI standards and the development of the technology to implement the data link, coupled with time-to-market pressure. Appropriate considerations and design trade-offs were made to design complexity, performance, risk, cost, and schedule, when deciding functional partitioning and semiconductor technology. Extensive simulations and a novel test approach were used to verify the algorithms, the functional models comprising the chips, and the physical chips themselves

GIGAswitch System: A High-Performance Packet-Switching Platform

The GIGAswitch system is a high-performance packet-switching platform built on a 36-port 100 Mb/s crossbar switching fabric. The crossbar is data link independent and is capable of making 6.25 million connections per second. Digital’s first GIGAswitch system product uses 2-port FDDI line cards to construct a 22-port IEEE 802.1d FDDI bridge. The FDDI bridge implements distributed forwarding in hardware to yield forwarding rates in excess of 200,000 packets per second per port. The GIGAswitch system is highly available and provides robust operation in the presence of overload. The GIGAswitch system is a multiport packetswitching platform that combines distributed forwarding hardware and crossbar switching to attain very high network performance. When a packet is received, the receiving line card decides where to forward the packet autonomously. The ports on a GIGAswitch system are fully interconnected with a custom-designed, very large-scale integration (VLSI) crossbar that permits up to 36 simultaneous conversations. Data flows through 100 megabits per second (Mb/s) point-to-point connections, rather than through any shared media. Movement of unicast packets through the GIGAswitch system is accomplished completely by hardware. The GIGAswitch system can be used to eliminate network hierarchy and concomitant delay. It can aggregate traffic from local area networks (LANs) and be used to construct workstation farms. The use of LAN and wide area network (WAN) line cards makes the GIGAswitch system suitable for building, campus, and metropolitan interconnects. The GIGAswitch system provides robustness and availability features useful in high-availability applications like financial networks and enterprise backbones. In this paper, we present an overview of the switch architecture and discuss the principles influencing its design. We then describe the implementation of an FDDI bridge on the GIGAswitch syste

Endothelial-Specific Loss of Sphingosine-1-Phosphate Receptor 1 Increases Vascular Permeability and Exacerbates Bleomycin-induced Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease which leads to significant morbidity and mortality from respiratory failure. The two drugs currently approved for clinical use slow the rate of decline in lung function but have not been shown to halt disease progression or reverse established fibrosis. Thus, new therapeutic targets are needed. Endothelial injury and the resultant vascular permeability are critical components in the response to tissue injury and are present in patients with IPF. However, it remains unclear how vascular permeability affects lung repair and fibrosis following injury. Lipid mediators such as sphingosine-1-phosphate (S1P) are known to regulate multiple homeostatic processes in the lung including vascular permeability. We demonstrate that endothelial cell–(EC) specific deletion of the S1P receptor 1 (S1PR1) in mice (EC-S1pr1(−/−)) results in increased lung vascular permeability at baseline. Following a low-dose intratracheal bleomycin challenge, EC-S1pr1(−/−) mice had increased and persistent vascular permeability compared with wild-type mice, which was strongly correlated with the amount and localization of resulting pulmonary fibrosis. EC-S1pr1(−/−) mice also had increased immune cell infiltration and activation of the coagulation cascade within the lung. However, increased circulating S1P ligand in ApoM-overexpressing mice was insufficient to protect against bleomycin-induced pulmonary fibrosis. Overall, these data demonstrate that endothelial cell S1PR1 controls vascular permeability in the lung, is associated with changes in immune cell infiltration and extravascular coagulation, and modulates the fibrotic response to lung injury