Effects of the nitrification inhibitor N-Serve on the utilization of fall-applied urea by wheat

Four-year microplot tests were performed to study the utilization by wheat, in the presence and absence of the nitrification inhibitor N-Serve, of¹⁵N labeled urea spread in fall. The percentages of fertilizer nitrogen taken up by winter wheat (grains and straw) were 18 to 37 percent when urea was spread in fall, 33 to 45 percent when urea plus N-Serve was applied in fall, and 36 to 49 percent when urea was spread in spring. In the 0–30 cm layer of soil there were found, for the treatments listed above, 15 to 23 percent, 24 to 45 percent, and 15 to 47 percent of urea nitrogen after the harvesting of winter wheat. Application of urea plus N-Serve in fall and of urea alone in spring resulted in similar amounts of fertilizer nitrogen being taken up by spring wheat to those taken up by winter wheat. Of the urea nitrogen applied in fall, 20 to 28 percent and 47 to 50 percent were not recovered from the plants and 0–30 cm soil layer with and without additional N-Serve treatment, respectively. The utilization by winter wheat of urea nitrogen spread, with no additional N-Serve, in fall from mid-October onward was considerably lower in those cases where, after fertilizing, weather conditions were such as to favour both nitrification and leaching. On heavy and loamy soil such influences of weather were offset by application of N-Serve.     

Experimental observation of temperature gradients occurring in a single zeolite pellet

An experimental study has been made of temperature profiles incident within a zeolite adsorbent particle in the course of adsorption of n-heptan. Using thermocouple wires 0.1 mm in diameter it has been possible to measure simultaneously the temperatures of the surface and in the centre. It was observed that temperature differences between center of the pellet and ambient stagnant gas may be more than 20°C. The results of this work indicate that the overheating of an adsorbent particle is a very rapid process which is followed by a slow cooling of the hot particle. Experimental data are compared with predictions calculated from the theoretical model.     

Coking kinetics of a Cr2O3/Al2O3 catalyst during 1-butene dehydrogenation: Effect of H2 partial pressure

The influence has been studied of the partial pressure of hydrogen (0–30 kPa) upon the coking rate of a Cr₂O₃/Al₂O₃ commercial catalyst during 1-butene dehydrogenation. Coke deposition has been analysed using a monolayer-multilayer reversible coke growth model (MMRC model). This model provides good fits to the experimental data, within the range of partial pressure of H₂ studied, and allows us to estimate the main kinetic parameters involved in the coking-deactivation process. The results obtained reveal a dual effect of hydrogen: competition against 1-butene for the active sites and the removal of coke precursors from the catalyst surface. Bom effects diminish the coking rate as the H₂ partial pressure is increased.     

A SIMPLE METHOD FOR STUDYING THE KINETICS OF GAS-SOLID REACTIONS IN A FLUIDIZED BED REACTOR

A methodology for studying the kinetics of gas-solid reactions in a fluidized bed reactor is presented. This procedure is based on the analysis of the response of the system (flue gases) when batches of solids of different weight are added to the reactor. The method has been applied to the study of limestone particle calcination. The calcination rate constants obtained are in good agreement with those found in the literature. The method offers the advantage of simplicity and avoids the use of model assumptions or empirical correlations.     

Laser-generated liquid microjets: correlation between bubble dynamics and liquid ejection

Laser-based techniques provide excellent means for liquid microprinting, with several advantages over other more conventional printing techniques, such as being nozzle-free (as opposed to inkjet, for instance) or requiring minimal engineering of the liquid properties in the pre-printing stage. In such techniques, the transfer is usually mediated by liquid jets that contact a receiver substrate placed nearby the liquid source, leading to the deposition of a small droplet. The main cause of jetting lies in a laser-generated bubble produced inside the liquid, whose dynamics dictates the evolution of liquid ejection. However, the detailed relationship between the bubble and the jet is not completely understood, as the studies carried out so far have been mostly focused on the jetting dynamics taking place above the liquid free-surface, without access to the liquid interior and therefore to the behavior of the bubble. In this work, we analyze through time-resolved imaging the film-free laser printing of an aqueous solution by simultaneously visualizing both the bubble evolution and the liquid ejection dynamics, thus making possible the correlation between the two phenomena. We find that the pulsating behavior of the bubble leads to successive jetting events with different jet morphologies arising from the particular geometries that the bubble acquires during its evolution. Finally, we find good agreement between our results and those from studies analyzing the dynamics of cavitation bubbles near the free-surface of a liquid through numerical solution of the fluid dynamics equations.     

Homogeneous Catalyzed Ozone Decomposition in the Presence of Co(II).

The homogeneous decomposition of ozone in the presence of a Co(II) catalyst has been investigated in aqueous solution. Under the conditions investigated (Co(II) concentration: 0.0 – 2.0?ppm, pH: 1.6- 8.4, O₃ concentration: 5 10^?5 – 2.0 10⁴?M) the process can be assumed to follow pseudo first order kinetics with respect to ozone. Cobalt concentration dependency also obeys first order kinetics although it may be considered to reach a steady state concentration. pH exerts a positive influence on the decomposition rate from 1.6 to 7.1, the process leveling off at pH 8.4. An Arrhenius analysis of the temperature effect gave a moderate activation energy of the global reaction (E=10917?cal mol^?1). A more detailed radical mechanism than a simple pseudo first order reaction can be postulated for simulation purposes. By numerical optimization of some unknown kinetic constants the influence of several operating variables can be adequately predicted.     

Zinc nutrition in young Chilean adults

To evaluate the effect of dietary factors on plasma zinc levels, dietary zinc intake was estimated and plasma levels were measured in 37 healthy young adults of low and middle socioeconomic status. Our study included 16 males aged 29 +/- 7 and 21 females aged 26 +/- 6 years. Dietary intake of zinc and protein was determined from a 24-hour dietary recall survey. Plasma zinc was measured by atomic absorption spectrophotometry. Alkaline phosphatase (AP) in plasma was also measured and the weight/height percentage for each subject calculated according to Jelliffe's standards. The average diet was composed of cereals, legumes, eggs, bread and noodles, caloric intake was 2051 +/- 154 kcal/day for men and 1767 +/- 158 (x +/- SD) kcal/day for women. The daily intake of zinc was 8.3 +/- 3.0 mg/day for males, and 9.7 +/- 2.0 mg/day for females. Cereals were the main source of zinc for men, while egg and dairy products were for women. Plasma zinc values were 82 +/- 22 micrograms/dl for men and 94 +/- 19 micrograms/dl for women (p less than 0.01). For the whole group plasma zinc concentration was 89 +/- 21 micrograms/dl. Seven males and two females had low plasma zinc values (70 micrograms/dl or less). Alkaline phosphatase (AP) levels were 110 +/- 10 IU for males and 71 +/- 4 IU for females (p less than 0.001). These values did not correlate with the zinc levels. Average weight/height was 99 +/- 18 for men, and 108 +/- 18 for females. Results indicate that on the average, in our study group plasma zinc levels were within the normal range, although they were significantly lower in men. Dietary intake of zinc was below the recommendations, being higher for women as related to values presented by men. The observed low plasma levels of zinc may be caused by a low intake, and/or poor bioavailability.     

A review of the unique features of HDL apoproteins

The human plasma high density lipoproteins (HDL) are a heterogeneous ensemble of five proteins associated with both neutral and polar lipids. The sequences of all five proteins are known. ApoA-I and apoA-II are the major protein components; apoC-I, apoC-II and apoC-III are the minor protein components. All these apoproteins spontaneously recombine with phospholipids to give stable lipid-protein complexes and freely exchange between the two major HDL subclasses, HDL₂ and HDL₃. In addition, ApoC-I, apoC-II, and apoC-III exchange between HDL and very low density lipoproteins. Furthermore, certain HDL apoproteins are activators for plasma enzymes that are important in lipid metabolism. ApoA-I and apoC-I activate lecithin/cholesterol acyltransferase; apoC-II is an activator of lipoprotein lipase. The regions of apoC-I and apoC-II that are involved in the activation of these enzymes have been localized with synthetic peptides. Studies of synthetic and native fragments of apoA-II, apoC-I, apoC-II, and apoC-III as well as model lipid-binding peptides have identified specific regions with structural features common to lipid-binding proteins. These special properties, which include helical potential, sequences with a critical amphipathic length, and high hydrophobicity of the nonpolar side of the amphipathic helix, are the determinants of HDL structure and metabolism.