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The discovery of superconductors with high critical temperatures (~) has led to a considerable effort to fabricate Josephson junctions operating at temperatures approaching, or even exceeding, 77 K for both scientific investigations and potential applications. Superconductor-normal-superconductor (SNS) devices, with noble or oxide metals as normal interlayers, are perhaps the most widely explored high-~" junction type at present. Although demonstrations of individual high-~ SNS devices exhibiting excellent current-voltage characteristics, high critical current-resistance products, and low noise behavior have been made, reproducible devices suitable for electronic applications are elusive. It is therefore important to ask how well these nominally SAN high-Tc junctions are understood. We review the available data, with emphasis on junction critical currents, and conclude that there is little evidence supporting a conventional proximity effect interpretation in the majority of reported high-, devices. The strongest candidates for SNS behavior are junctions in which N is a superconductor above its transition temperature. We discuss the present experimental and theoretical understanding of SNS junctions with emphasis on the implications for future research and development of these devices.

Abstract:The Sensor Web is a macro-instrument concept that allows for the spatiotemporal understanding of an environment through coordinated efforts between multiple numbers and types of sensing platforms, including both orbital and terrestrial and both fixed and mobile. Each of these platforms, or pods, communicates within their local neighborhood and thus distributes information to the instrument as a whole. Much as intelligence in the brain is a result of the myriad of connections between dendrites, it is anticipated that the Sensor Web will develop a macro-intelligence as a result of its distributed information with the pods reacting and adapting to their environment in a way that is much more than their individual sum. The sharing of data among individual pods will allow for a global perception and purpose of the instrument as a whole. The Sensor Web is to sensors what the Internet is to computers, with different platforms and operating systems communicating via a set of shared, robust protocols. This paper will outline the potential of the Sensor Web concept and describe the Jet Propulsion Laboratory (JPL) Sensor Webs Project (http://sensorwebs.jpl.nasa.gov/). In particular, various fielded Sensor Webs will be discussed.

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Measuring environmental variables at appropriate temporal and spatial scales remains an important challenge in ecological research. New developments in wireless sensors and sensor networks will free ecologists from a wired world and revolutionize our ability to study ecological systems at relevant scales. In addition, sensor networks can analyze and manipulate the data they collect, thereby moving data processing from the end user to the sensor network itself. Such embedded processing will allow sensor networks to perform data analysis procedures, identify outlier data, alter sampling regimes, and ultimately control experimental infrastructure. We illustrate this capability using a wireless sensor network, the Sensor Web, in a study of microclimate variation under shrubs in the Chihuahuan Desert. Using Sensor Web data, we propose simple analytical protocols for assessing data quality “on‐the‐fly” that can be programmed into sensor networks. The ecological community can influence the evolution of environmental sensor networks by working across disciplines to infuse new ideas into sensor network development.