Effect of Alkalinity in Irrigation Water on Selected Greenhouse Crops. (August 2004) Luis Alonso Valdez Aguilar, B.S., Universidad Aut??noma de Nuevo Le??n, Mexico; M.S., Universidad Aut??noma Chapingo, Mexico Chair of Advisory Committee: Dr. David Wm. Reed Bicarbonate (HCO3-) and carbonate (CO32-) are the most important ions that determine alkalinity. When the carbonates accumulate in a growing medium, the growing medium solution pH reaches levels that cause plant growth inhibition, which is caused primarily by the transformation of soluble forms of Fe into insoluble forms. The general objective of this research was to provide information about the limits of tolerance to alkalinity in ornamental plants, and to study the interaction of ions such as ammonium (NH4+) and nitrate (NO3-) on the response of plants to alkalinity, as well as the effect of the counter-ions potassium (K+), sodium (Na+), cesium (Cs+), ammonium (NH4+) and rubidium (Rb+). The maximum SPAD index was estimated to occur at 0 mM of NaHCO3 in chrysanthemum, mini-rose, and hibiscus ??Bimini Breeze?? and ??Mango Breeze??. For vinca it was set at 2.64 mM. A 15% decrease from the maximum SPAD index was considered the threshold to declare the toxic concentration of NaHCO3, which was calculated based on the maximum SPAD index predicted by the models. The toxic concentration of NaHCO3 was set at 4.1, 1.1, 6.7, 3.1, and 6.3 mM of NaHCO3 in chrysanthemum, mini-rose, vinca, and hibiscus ??Mango Breeze?? and ??Bimini Breeze??, respectively. Hibiscus ??Bimini Breeze?? was considered tolerant to alkalinity, due to increased Fe-reduction capacity and acidification of the growing medium. In the hydroponic experiment, results showed that the NH4+:NO3- ratio altered the response of sunflower plants to alkalinity. Sunflower plants grew better in solutions containing 5 mM NaHCO3 prepared with a 0.25:0.75 NH4+:NO3- ratio. This was possible due to the reaction of NH4+ with the HCO3-, which reduced its buffering capacity. The response to HCO3--induced alkalinity was modified by the counter-cation of HCO3-. In bean plants, at low-to-intermediate levels of Na+ and HCO3- induced approximately same growth decrease. At high concentration, Na+ induced a decrease on shoot growth that exceeded the toxic effects of HCO3-. Thus, the toxic effect of Na+ is higher than that of HCO3- when its concentration is high. Rubidium was extremely toxic at concentrations of 7.5 mM.

Thèse de doctorat : Sciences chimiques. Chimie-physique : Bordeaux 1 : 2008. / Titre provenant de l'écran-titre.

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Lehigh University, 2002. / Includes vita. Includes bibliographical references (leaves 128-134).

The first example of an N,N'-chelated [beta]-diketiminato phosphenium salt has been isolated by careful tuning of both the ligand architecture and the electronic characteristics of the phosphorus containing moiety. Using a two-electron reduction approach, the first example of a phosphinidene valence isomer has been isolated and structurally characterized. The mechanism of formation of this valence isomer was elucidated via Density Functional Theory (DFT) calculations. These calculations revealed that the formation of this valence isomer involves the intermediacy of a triplet diradical. In turn, the triplet diradical decays by two further steps to generate the observed product. A cationic phosphinous acid has been prepared via the hydrolysis of a cationic phosphenium complex in basic solution. DFT calculations reveals that the introduction of a positive charge stabilizes the phosphinous acid form. Two N,C-bonded phosphenium cation salts have also been obtained, the crystal structures of which reveal that the formation of these compounds involves C-H activation of a methyl group on the [beta]-diketiminate ligand. Three synthetic methods, namely halide abstraction, aluminum/boron halide exchange process and salt metathesis, have been explored for the preparation of boron cations supported by [beta]-diketiminate ligands. The first structurally characterized boron cation supported by a [beta]-diketiminate ligand has been isolated as its [Al₂Cl₇]⁻ salt. A Ga-Fe organometallic complex supported by a [beta]-diketiminate ligand has also been synthesized via salt metathesis reaction and fully characterized. Finally, several bisamidinate supported boron complexes have been synthesized and structurally characterized. Such complexes may have applications as bifunctional catalysts or as building blocks for novel polymers.

No description available.

Despite many drawn parallels between carbon and phosphorus, the development of catena-phosphorus chemistry is superficially explored when compared to carbon. This lack of progression is especially highlighted for cationic phosphorus frameworks, as neutral and anionic phosphorus frameworks have been studied to a much greater extent. This stresses cationic catena-phosphorus frameworks as important molecules for an improved understanding of fundamental phosphorus chemistry. Recent advancements in synthetic methods demonstrate that phosphorus frameworks of this type are viable target molecules. Furthermore, the precedence of a variety of new cationic catena-phosphorus frameworks by such methods exemplify their versatility. Here, novel 1,3-diphosphino-2-phosphonium [R2P-PR2-PR2]+, 2-phosphino-1,3-diphosphonium [R3P-PR-PR3]+ and cyclo-triphosphinophosphonium [R2P(RP)3]+ cations have been isolated and characterized in order to study the insertion of phosphenium cations into the phosphorus-phosphorus bonds of catena-phosphines.

No description available.

Experiments were conducted to investigate the effect of reducing dietary anion-cation balance (AC-balance), defined as meq $ sp circ$(Sodium + Potassium)-(Chloride + Sulfur) S, on calcium (Ca) metabolism. Reducing the dietary AC-balance from +314 to $-22$ (meq kg$ sp{-1}$ dry matter (DM)) did not affect plasma Ca level but reduced Ca retention mainly due to a 10-fold increase in urinary Ca excretion with similar rate of apparent absorption. It also decreased urine pH and titratable acidity. The response to induced hypocalcemia created by the infusion of 4.6% EDTA solution revealed that reducing dietary AC-balance from +354 to +37 (meq kg$ sp{-1}$DM) did not affect the volume of the compartment, within which there was rapid equilibration of free Ca but tended to increase the rate of Ca mobilization from it during the infusion. The Ca kinetic study with a four-compartment model indicated that reducing dietary AC-balance from +338 to $-127$ (meq kg$ sp{-1}$DM) during the eucalcemic period and from +429 to $-147$ (meq kg$ sp{-1}$DM) during an EGTA-infusion period (simulated lactational Ca loss) caused hypercalciuria and increased ionized form of plasma Ca. Increased true intestinal Ca absorption and reduced bone accretion were observed in the lowest AC-balance diet only during the EGTA-infusion period. There were no differences in the size of total exchangeable Ca pool but the amount of Ca movement between them tended to increase in reduced AC-balance diets during both periods. Results indicated that feeding reduced AC-balanced diet may have a beneficial role in preventing parturient paresis (milk fever) by increasing Ca flux through the exchangeable Ca pool and Ca mobilization capability.

This thesis represents results of experiments involved in ultra-high resolution x-ray crystal structures of DNA. Detailed analysis of DNA coordinates of increased accuracy, refinement of individual anisotropic B-factors, visualization of disorder, counterions and hydration are presumably facilitated by the increased information of ultra-high resolution structures. However, recent survey of available DNA crystal structures with the data that extends beyond 1Ã... has brought a few areas of considerations; local conformational flexibility of DNA and counterions and how they have been interpreted in previous studies. While the results given here demonstrate both structural and surrounding details of DNA that may be undetected at lower resolution, some of the technical aspects of interpreting ultra-high resolution data is also addressed.