Deciphering patterns in whole fish nitrogen isotopes on a continental scale

Nitrogen isotopes (δ15N) have been used as an indicator of anthropogenic nitrogen loading at local and regional scales. We examined δ15N in fish from estuaries across the continental United States. In the summer of 2015, the U.S. Environmental Protection Agency's National Coastal Condition Assessment (NCCA) collected fish in 136 coastal waterbodies throughout the United States. Whole fish were analyzed by NCCA for metals, organic contaminants, and lipids. For this study, we also analyzed these fish for isotopes of nitrogen (N). NCCA collected water quality, nutrients, chlorophyll a, and sediment chemistry at each site. We used these data, along with fish life history and watershed land use, to examine how whole fish δ15N was related to these environmental variables using random forest regression models at national and ecoregional scales. At the national scale, fish δ15N were negatively related to total N:total phosphorous (P) ratios (TN:TP) in surface water and reflected differences between the P-limited, δ15N depleted sites in the Floridian ecoregion to sites in other regions. δ15N was lower on the Atlantic relative to the Pacific coast. When considered by region, TN:TP was an important predictor of fish δ15N in 4 of 9 ecoregions, with higher δ15N observed with increasing N limitation (lower TN:TP) Fish life history was also an important predictor of fish δ15N at both the national and ecoregional scale. Whole fish δ15N was positively associated with bioaccumulative contaminants such as PCBs and mercury. Although land use was related to δ15N in fish, it was location specific. This study showed that N stable isotopes reflected ecological conditions at both regional and continental scales.

Energy procurement in a deregulating United States ‐ Part 2: Key considerations and criteria in long‐term energy commitments

The advent of retail deregulation (liberalisation) in the United States electricity markets provides the major energy users, for the first time, significant choice in energy procurement. With choice comes responsibility for sorting the wide range of potential services, associated risks and variables in price. As deregulation has progressed, the emerging market has not yet reached maturity for retail customers, resulting in significant price volatility and imbalances in supply in some regions. This paper, presented in the Journal in two parts, of which this is the second, explains the fundamentals of energy choice for commercial and industrial energy users and the criteria to be considered in making long‐term energy commitments.

Energy procurement in a deregulating United States ‐ Part 1: The strategies available to corporate occupiers

The advent of retail deregulation (liberalisation) in the United States electricity markets provides major energy users, for the first time, significant choice in energy procurement. With choice comes responsibility for sorting the wide range of potential services, associated risks, and variables in price. As deregulation has progressed, the emerging market has not yet reached maturity for retail consumers, resulting in significant price volatility and imbalances in supply in some regions. This paper, presented in two parts in this and the next issue of the Journal, explains the fundamentals of energy choice for commercial and industrial energy users and the criteria to be considered in making long‐term energy commitments.

Structuring effective real estate outsourcing and preferred provider relationships in the global environment

Companies may seek tremendous advantage through the consolidation of corporate real estate requirements with leading real estate brokers or advisors under a comprehensive service arrangement. Such relationships require crafting the business structure and contract provisions to promote the objectives of both parties. The successful outsourcing relationship must begin with the realisation that each customer and service provider deserves a unique set of terms, founded upon mutual understanding and the realities of the diverse markets in which the services will be performed. Where the parties take the time and care to share common expectations, the scope and quality of service can be articulated in a positive and definitive manner to the personnel responsible for performance. Incentives can be aligned to provide a sufficient and competitive motivation for client and advisor alike. Through this process, the agreement can serve as a platform to the mutually beneficial relationship for which the parties had hoped.

Biomechanics of walking, running, and sprinting

A biomechanical study of 13 runners which consisted of 2 male sprinters, 5 experienced joggers, and 6 elite long-distance runners were studied. We obtained hip, knee, and ankle joints motions in the sagittal plane and electromyographic data from specific muscle groups. As the speed of gait increased, the length of stance phase progressively decreased from 62% for walking to 31% for running and to 22% for sprinting. The sagittal plane motion increased as the speed of gait increased. Generally speaking, the body lowers its center of gravity with the increased speed by increasing flexion of the hips and knees and magnifying dorsiflexion at the ankle joint. Electromyographic activity about the knee demonstrated increased activity in the quadricep muscle group and hamstring group with increased speed. Muscle function about the ankle joint demonstrated that the posterior calf musculature which normally functions during the midstance phase in walking became a late swing phase muscle and was active through the first 80% of stance phase, as compared to 15% in walking. Beside the changes in the electromyographic activity of the muscles, the anterior compartment muscles of the calf undergo a concentric contracture at the time of initial floor contact during running and sprinting but undergo an eccentric contraction during walking.