P. M. Bell

An improved calibration curve of the pressure shift of the ruby R 1 emission line was obtained under quasi‐hydrostatic conditions in the diamond‐window, high‐pressure cell to 800 kbar. Argon was the pressure‐transmitting medium. Metallic copper, as a standard, was studied in situ by X ray diffraction. The reference pressure was determined by calibration against known equations of state of the copper sample and by previously obtained data on silver.

The wavelength shift with pressure of the ruby R1 fluorescence line (Δλ) has been calibrated in the diamond-window pressure cell from 0.06 to 1 Mbar. This was done by simultaneously making specific volume measurements of four metals (Cu, Mo, Ag, and Pd) and referring these results to isothermal equations of state derived from shock-wave experiments. The result is P (Mbar) = (19.04/5) {[(λ0+Δλ)/λ0]5−1}, where λ0 is the wavelength measured at 1 bar.

Lyngbya wollei (Farlow ex Gomont) comb. nov., a perennial mat-forming filamentous cyanobacterium prevalent in lakes and reservoirs of the southeastern United States, was found to produce a potent, acutely lethal neurotoxin when tested in the mouse bioassay. Signs of poisoning were similar to those of paralytic shellfish poisoning. As part of the Tennessee Valley Authority master plan for Guntersville Reservoir, the mat-forming filamentous cyanobacterium L. wollei, a species that had recently invaded from other areas of the southern United States, was studied to determine if it could produce any of the known cyanotoxins. Of the 91 field samples collected at 10 locations at Guntersville Reservoir, Ala., on the Tennessee River, over a 3-year period, 72.5% were toxic. The minimum 100% lethal doses of the toxic samples ranged from 150 to 1,500 mg kg of lyophilized L. wollei cells-1, with the majority of samples being toxic at 500 mg kg-1. Samples bioassayed for paralytic shellfish toxins by the Association of Official Analytical Chemists method exhibited saxitoxin equivalents ranging from 0 to 58 micrograms g (dry weight)-1. Characteristics of the neurotoxic compound(s), such as the lack of adsorption by C18 solid-phase extraction columns, the short retention times on C18 high-performance liquid chromatography (HPLC) columns, the interaction of the neurotoxins with saxiphilin (a soluble saxitoxin-binding protein), and external blockage of voltage-sensitive sodium channels, led to our discovery that this neurotoxin(s) is related to the saxitoxins, the compounds responsible for paralytic shellfish poisonings. The major saxitoxin compounds thus far identified by comparison of HPLC fluorescence retention times are decarbamoyl gonyautoxins 2 and 3. There was no evidence of paralytic shellfish poison C toxins being produced by L. wollei. Fifty field samples were placed in unialgal culture and grown under defined culture conditions. Toxicity and signs of poisoning for these laboratory-grown strains of L. wollei were similar to those of the field collection samples.

The volume equations of state for MgO and ε Fe determined under calibrated static pressure conditions to 1 Mbar are given by V / V 0 = [1 + 2.85(3) P (Mbar)] −0.219(3) (for MgO) where V 0 = 11.25(2) cm 3 /mol and V (cm 3 /mol) = 6.74(3)[1 + 3.4(3)P(Mbar)] −0.185(7) (for ε Fe). The random error of V is 0.3%, and the maximum systematic error of V (caused by the uncertainty of the pressure scale) is 1%. These equations can be employed in geophysical models of the mantle‐core boundary.