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Ergosterol Effect On The Desaturation Of 14c-Cis-Vaccenate In Tetrahymena, Tiee-Chyau Miin

Masters Theses

Supplement of ergosterol to the growth medium of the ciliated protozoan Tetrahymena pyriformis W leads to incorporation of the foreign sterol within cell membranes and suppression of synthesis of the native sterol-like compound tetrahymanol, as well as to changes in the fatty acid compositions of several major classes of membrane lipid. Alteration of fatty acid composition is thought to represent a regulatory mechanism whereby optimum membrane fluidity is maintained when the slightly dissimilar foreign sterol is added into the phospholipid bilayer of the membranes.

The present study, using several different conditions of growth temperature, substrate concentrations and incubation time, and …

Thermodynamics Of Ion Association In Aqueous Solutions Of Sodium Sulfate, Sodium Carbonate And Sodium Bicarbonate, Yan-Chun Chung

Masters Theses

Stoichiometric association constants of NaSO₄^-, NaCO₃^- and NaHCO₃^- ion-pairs were determined over the temperature range 10 - 40°C at several ionic strengths by using a sodium ion selective electrode. At zero ionic strength values for K°_A,NaSO₄^- are 15.8 ± .4, 8.5 ± .2 and 4.6 ± .3 at 10°, 25° and 40°C, respectively; like values for K°_A,NaCO₃^- are 17.1 ± 1.4, 19.1 ± .6 and 21.0 ± .7. Values for K°_A,NaHCO₃° are 3.35 ± .07 and 6.75 ± .02 at 25°C …

Amperometric Determination Of Chemical Oxygen Demand, Catherine Eckert Hutchins

Masters Theses

A method is described for measuring the low level --5 to 50 ppm-- chemical oxygen demand (COD) of water samples by amperometric titration. The method involves digestion of the sample with potassium dichromate in a 50% sulfuric acid solution using one-fifth the reagents and sample required for the standard COD method. This is followed by an amperometric titration using a standard ferrous ammonium sulfate solution and employing a rotating platinum electrode in a three-electrode potentiostatic system. The titration is carried out at a potential of +0.80 volts versus a saturated calomel electrode, thus eliminating the need for O₂ purging …

Ditertiary Phosphines As Monodentate Ligands In Transition Metal Carbonyl Complexes, Yih-Yau York Sun

Masters Theses

Carbonyl complexes of chromium, molybdenum and tungsten have been synthesized in which two potentially chelating tetraphenyldiphosphinoethane molecules (Ph₂PCH₂CH₂PPh₂) are bound as monodentate ligands. The reaction of trans-(CO)₄M(PPh₂CH=CH₂)₂ (M = Cr, Mo, W) with diphenylphosphine (PPh₂H) in the presence of potassium t-butoxide yields trans-(CO)₄M(PPh₂CH₂CH₂PPh₂)₂. The complexes, which represent the first of this type to be synthesized, have been characterized by ³¹P nmr. From the XAA'X' phosphorus-31 spectra of the …