Most studies of freshwater dissolved organic matter (DOM) have been conducted in temperate climates where allochthonous organic material is abundant. Because climatic conditions of the Southwestern USA are different than temperate environments, DOM from three freshwater reservoirs (Saguaro Lake, Bartlett Lake and Lake Pleasant) was investigated to determine the importance of allochthonous and a...

Hydrogen stable isotopes (δ2H) have recently been used to complement δ13C and δ15N in food web studies due to their potentially greater power to separate sources of organic matter in aquatic food webs. However, uncertainties remain regarding the use of δ2H, since little is known about the potential variation in the amount of exchangeable hydrogen (Hex) among common sample materials or the patte...

The priming effect refers to quantitative changes in microbial decomposition of recalcitrant organic matter upon addition of labile organic matter and is a phenomenon that mainly has been reported and debated in soil science. Recently, priming effects have been indicated in aquatic ecosystems and have received attention due to the potential significance for ecosystem carbon budgets. Headwater s...

Ecosystems are differentially open to subsidies of energy, material and organisms. This fundamental ecosystem attribute has long been recognized but the influence of this property on community regulation has not been investigated. We propose that this environmental attribute may explain variation in the strength of trophic cascades among ecosystems. Simply because of gravity, we should predict ...

The author has presented an excellent paper describing considerations that went into the development and imple­ mentation of the subject facility. The use of some pho­ tographs in the paper was particularly helpful. The photo on p. 240 shows open structural members around the bottom of the key air pollution control elements. For very little additional capital cost, these areas can be en­ closed...

Nurse staffing and scheduling is a major health human resource issue currently facing healthcare organizations. To increase the capacity of healthcare organizations to address a variety of issues related to nurse staffing and scheduling, a mult-isite collaborative project was undertaken. The primary focus of this project was

Motivated by the GKM picture of the equivariant cohomol-ogy ring for a torus action on an orbifold we define one-skeletons and their corresponding rings, H(Γ, α). We prove that, under a mild gener-icity condition, such a ring is a free S(g *)−module, with generators given by Thom classes of flow-outs of the vertices. We also show that many interesting notions and results in symplectic geometry,...

A photogeologic and physical modeling study indicates that Hebes Chasma, Mars, formed by collapse of the megaregolith. Local heating facilitated drainage of ~105 km3 of brines and entrained particulates through fractures in the chasma fl oor and into a regional aquifer. A megaregolith rich in salts and water is implied by massive, low-gradient allochthonous fl ows that terminate in deep pits an...

We applied natural abundance stable isotope δ13C and radiocarbon ∆14C analyses to investigate trophic linkages between zooplankton and their potential food sources (phytoplankton, submersed plants, and allochthonous organic carbon) in Lake Nam Co, one of the largest oligosaline and oligotrophic lakes in the Tibetan Plateau, in south-west China. The δ13C and ∆14C levels of the calanoid copepod A...