Fiber laser ultrasonic sensors are demonstrated to be capable of measuring acoustic emission generated by cracks in aluminum panels. A single laser sensor is integrated into a riveted lap joint, which is subject to accelerated fatigue. Acoustic emission generated by crack formation in the panel in addition to other acoustic events due to fretting within the joint are clearly resolved by the laser sensor. Localization of an acoustic emission event is demonstrated with a multiplexed array of three laser sensors. This manuscript also calculates the fundamental limit to displacement resolution of the fiber laser sensor and presents measurements of the directional response to Lamb waves. The high measurement resolution and multiplexing capability of the fiber laser ultrasonic sensor makes it an ideal candidate for structural health monitoring applications.

To accurately assess contributions of human activities to nitrogen (N) cycle disruption, we must consider how systems such as food and renewable fuel production are connected. N impacts of food and biofuel systems have been studied separately, but links between them have not been sufficiently considered. Since 2002, corn ethanol production in the United States has increased sixfold, and ethanol coproducts' roles in animal diets have increased similarly. In this study, we estimated virtual N in ethanol fuel and animal products using the commodity-specific Net Anthropogenic Nitrogen Inputs (CSNANI) model, which uses national corn ethanol, crop, and animal production data to estimate animal diets and the corresponding virtual N inputs to agricultural commodities. Virtual N attributable to ethanol fuel was 30 to 35 g N per liter of ethanol. As ethanol coproduct inclusion in animal diets increased from 1997 to 2012, N per kilogram of beef protein decreased by 19% and N per kilogram of milk protein decreased by 13%. With allocation of virtual N between ethanol and ethanol feed coproducts, the virtual N of both ethanol fuel and products from animals consuming ethanol coproducts is reduced relative to estimates from studies that do not consider the connection between these systems.

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One approach to address both the environmental and scarcity issues that occur with phosphorus (P) losses from human systems is to improve understanding of the P demands of bio-based products. Most P demand in the United States is driven by production of crops for animal feed and mineral P feed supplements for animals. In this research, we used the Commodity-Specific Net Anthropogenic Phosphorus and Nitrogen Inputs (CSNAPNI) model to (1) assess the contributions of individual feed products such as corn, soy, and mineral P supplements to the embodied P of animal products and (2) estimate net anthropogenic phosphorus inputs (NAPIs) for the contiguous United States for two animal P-intake scenarios. Results show that P supplements may contribute up to 30% of embodied P in pork and dairy products, up to 60% in chicken, and up to 75% in turkey. Other major contributors to animal product-embodied P are grains, which are responsible for around 60% of embodied P in pork and dairy products, at least 30% in chicken, and at least 20% in turkey products. Results also show that animal P intake is such a significant driver of anthropogenic phosphorus that a reduction of animal P intake by 25% could reduce NAPI to the contiguous United States by 30%.Considering promising research on methods to improve digestibility of both mineral P supplements and grain P in animal diets, these results are encouraging.