We explored N2 fixation and alkaline phosphatase activity (APA) in periphyton from a N-limited stream ecosystem by coupling measurements of these processes with nutrient diffusion substrata (NDS) experiments. We measured periphyton biomass accumulation (as ash-free dry mass [AFDM] and chlorophyll a [CHLA]), N2 fixation, and APA to evaluate the relative importance of N2 fixation as an N source t...

We measured N2 fixation rates from oceanic zones that have traditionally been ignored as sources of biological N2 fixation; the aphotic, fully oxygenated, nitrate (NO(-) 3)-rich, waters of the oligotrophic Levantine Basin (LB) and the Gulf of Aqaba (GA). N2 fixation rates measured from pelagic aphotic waters to depths up to 720 m, during the mixed and stratified periods, ranged from 0.01 nmol N...

The rarity of symbiotic nitrogen-fixing trees in higher-latitude compared to lower-latitude forests is paradoxical because higher-latitude soils are relatively N poor. Using national-scale forest inventories from the United States and Mexico, we show that the latitudinal abundance distribution of N-fixing trees (more than 10 times less abundant poleward of 35 degrees N) coincides with a latitud...

BACKGROUND During the early postoperative period, the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. HYPOTHESIS The initial fixation strength of a double cross pin fixation technique is comparable with the biodegradable interference screw fixation technique. STUDY DESIGN Experimental laboratory study. METHODS The authors examined the ini...

The exploitation of the soybe an [Glycine max (L.) Merr.] -Bradyrhizobium japonicum symbiosis in varied environments requires an understanding of factors that may affect fixed and soil N assimilation. Temperature affects both soybean maturity and N requirement, and soil N availability. Five soybean varieties belonging to four maturity groups (00, IV, VI, and VIII) and their respective nonnodula...

Natural nitrogen isotopic composition (δ(15)N) of suspended particulate organic matter (POM) and nitrogen fixation rates via (15)N(2) assay were measured in surface waters along 120° E from 30° N to 30° S in the Asian marginal seas (the East/South China Seas and the Sulu/Celebes/Java Seas) and the northeastern Indian Ocean in November-December 2005 and March 2006. The POM δ(15)N values ranged f...

During the winter of 2006 we measured nifH gene abundances, dinitrogen (N(2)) fixation rates and carbon fixation rates in the eastern tropical and sub-tropical North Atlantic Ocean. The dominant diazotrophic phylotypes were filamentous cyanobacteria, which may include Trichodesmium and Katagnymene, with up to 10(6) L(-1)nifH gene copies, unicellular group A cyanobacteria with up to 10(5) L(-1)n...

Rising atmospheric carbon dioxide (Ca), a product of fossil fuel burning, land-use change, and cement manufacture, is expected to cause a large carbon sink in land ecosystems, partly mitigating human-driven climate change (1). Increasing biological nitrogen fixation with rising Ca has been invoked as a means to provide the N necessary to support C accumulation (2). As in many short-term experim...

Geochemical estimates of N2 fixation in the North Atlantic often serve as a foundation for estimating global marine diazotrophy. Yet despite being well-studied, estimations of nitrogen fixation rates in this basin vary widely. Here we investigate the variability in published estimates of excess nitrogen accumulation rates in the main thermocline of the subtropical North Atlantic, testing the as...

background: respiratory problems are common after long bone fractures. the objective of the present investigation is to evaluate the effect of early fixation of femoral shaft fracture on the incidence of respiratory problems.   methods: the results of early and late stabilization of femoral shaft fractures were studied in 150 patients. the patients were divided into two groups according to the ...