While a wide variety of approaches to engineering orthopedic tissues have been proposed, less attention has been paid to the interfaces, the specialized areas that connect two tissues of different biochemical and mechanical properties. The interface tissue plays an important role in transitioning mechanical load between disparate tissues. Thus, the relatively new field of interfacial tissue engineering presents new challenges--to not only consider the regeneration of individual orthopedic tissues, but also to design the biochemical and cellular composition of the linking tissue. Approaches to interfacial tissue engineering may be distinguished based on if the goal is to recreate the interface itself, or generate an entire integrated tissue unit (such as an osteochondral plug). As background for future efforts in engineering orthopedic interfaces, a brief review of the biology and mechanics of each interface (cartilage-bone, ligament-bone, meniscus-bone, and muscle-tendon) is presented, followed by an overview of the state-of-the-art in engineering each tissue, including advances and challenges specific to regenerating the interfaces.

Thrombosis and intimal hyperplasia are the principal causes of small-diameter vascular graft failure. To improve the long-term patency of polyurethane vascular grafts, we have incorporated both poly(ethylene glycol) and a diazeniumdiolate nitric oxide (NO) donor into the backbone of polyurethane to improve thromboresistance. Additionally, we have incorporated the laminin-derived cell adhesive peptide sequence YIGSR to encourage endothelial cell adhesion and migration, while NO release encourages endothelial cell proliferation. NO production by polyurethane films under physiological conditions demonstrated biphasic release, in which an initial burst of 70% of the incorporated NO was released within 2 days, followed by sustained release over 2 months. Endothelial cell proliferation in the presence of the NO-releasing material was increased as compared to control polyurethane, and platelet adhesion to polyethylene glycol-containing polyurethane was decreased significantly with the addition of the NO donor.

Increasing urbanization places cities at the forefront of achieving global sustainability. For cities to become more sustainable, however, the infrastructure on which they rely must also become more productive, efficient and resilient. Unfortunately the current paradigm of urban infrastructure development is fragmented in approach lacking a systems perspective. Urban infrastructure systems are analogous to ecological systems because they are interconnected, complex and adaptive components that exchange material, information and energy among themselves and to and from the environment, and exhibit characteristic scaling properties that can be expressed by Zipf's Law. Analyzing them together as a whole, as one would do for an ecological system, provides a better understanding about their dynamics and interactions, and enables system-level optimization. The adoption of this "infrastructure ecology" approach will result in urban (re)development that requires lower investment of financial and natural resources to build and maintain, is more sustainable (e.g. uses less materials and energy and generates less waste) and resilient, and enables a greater and more equitable opportunities for the creation of wealth and comfort. The 12 guiding principles of infrastructure ecology will provide a set of goals for urban planners, engineers and other decision-makers in an urban system for urban (re)development. Highlights• Infrastructure ecology, a novel paradigm for urban infrastructure development is presented.• Urban infrastructure systems function analogous to natural ecological systems.• Interdependence between infrastructure sectors are identified and assessed.• Infrastructural symbiosis reorganizes the flows within for system-level optimization.• 12 guiding principles of infrastructure ecology are presented for decision makers.

Previously, GIS-based visibility analysis has been conducted mainly in two dimensions, based on the concept of an isovist in the built environment or the concept of a viewshed in terrain and landscape analysis. The Viewsphere, a GIS approach towards 3D visibility analysis is proposed for measuring visible urban space quantitatively in a way that is different from its predecessors, the isovist and the viewshed. A test case of Singapore's urban space was conducted by evaluating the visibility of three alternative urban design scenarios and their potential impacts on the visual quality of open space. Both directional and nondirectional approaches were applied to the mapping of visibility based on the 2D and 3D indices. The proposition that 3D visibility indices are more effective than 2D indices was verified. The findings show that the 3D indices are sensitive to the changes of z-dimension.