Nitrogen fixation in waterlogged, soil-straw, and sandday-straw mixtures was measured with the C2H2reduction assay, the I5N-tracer technique, and the Kjeldahl method. The reduction of 6 to 15 moles C2H2 corresponded to the fixation of 1 mole N2. The theoretical ratio is 3 moles C2H2 to 1 mole N2. A ratio of 3 moles C2H2 reduced for each mole of N2 fixed was obtained when samples of sandxlay-str...

Heterocyst differentiation in cyanobacteria filaments is one of the simplest examples of cellular differentiation and pattern formation in multicellular organisms. Despite of the many experimental studies addressing the evolution and sustainment of heterocyst patterns and the knowledge of the genetic circuit underlying the behavior of single cyanobacterium under nitrogen deprivation, there is s...

The role of ammonia toxicity in the production of the hepatic coma syndrome has not been clearly defined. No direct relationship has been demonstrated consistently between arterial or venous blood ammonia-nitrogen concentration or the arteriovenous ammonia-nitrogen difference and the state of cerebral dysfunction in hepatic disease. Recently a direct relationship between an increase in blood pH...

A spatially-explicit, two-dimensional model was developed to evaluate the processes which determine the fate and transport of nitrogen (N) in wetland systems. The wetland soil profile was partitioned into floodwater, and aerobic, and anaerobic soil layers, with diffusion and settling accounting for the transport of N between layers. Nitrogen transformations considered in the model were; enzyme ...

We present a modeling scheme to analyze cagelike silica mesoporous crystals based on in situ X-ray diffraction (XRD) data collected during gas adsorption-desorption (physisorption) processes. Nitrogen physisorption on a silica mesoporous crystal of SBA-16 was directly monitored by using synchrotron in situ powder XRD measurements conducted at SPring-8. SBA-16 is a well-ordered mesoporous silica...

A linear 11-compartment model was developed to describe and simulate the postprandial distribution of dietary nitrogen. The values of its 15 constant diffusion coefficients were estimated from the experimental measurement of (15)N nitrogen kinetics in the intestine, blood, and urine after the oral administration of (15)N-labeled milk protein in humans. Model structure development, parameter est...

The stable nitrogen isotopic composition of nitrate, concentrations of inorganic nitrogen and phosphorus, dissolved oxygen and nitrification rates were determined at six stations ranging from the oligotrophic North Pacific Subtropical Gyre (NPSG) to the more productive Eastern Tropical North Pacific (ETNP). Nitrification rates increased along the transect from a maximum rate of 1 nmol L 1 d 1 a...

OBJECTIVE To determine clinical and biochemical factors influencing cerebral edema formation during diabetic ketoacidosis (DKA) in children. STUDY DESIGN We used magnetic resonance diffusion-weighted imaging to quantify edema formation. We measured the apparent diffusion coefficient (ADC) of brain water during and after DKA treatment in 26 children and correlated ADC changes with clinical and...

Molecular simulations have been used to investigate at the molecular level the suitability of zeolites with different topology on the adsorption, diffusion and separation of a nitrogen-sulfur hexafluoride mixture containing the latter at low concentration. This mixture represents the best alternative for the sulfur hexafluoride in industry since it reduces the use of this powerful greenhouse ga...

The understanding of nitric oxide (NO) signaling has grown substantially since the identification of endothelial derived relaxing factor (EDRF). NO has emerged as a ubiquitous signaling molecule involved in diverse physiological and pathological processes. Perhaps the most significant function, independent of EDRF, is that of NO signaling mediated locally in signaling modules rather than relyin...