Asymmetric,Stereodivergent Synthesis of (−)‐Clusianone Utilizing a Biomimetic Cationic Cyclization

We report a stereodivergent, asymmetric total synthesis of (?)‐clusianone in six steps from commercial materials. We implement a challenging cationic cyclization forging a bond between two sterically encumbered quaternary carbon atoms. Mechanistic studies point to the unique ability of formic acid to mediate the cyclization forming the clusianone framework.     

Negative refraction

Light bends the wrong way in materials where both ε and μ are negative as was pointed out in 1968, but the absence of natural materials with this property led to neglect of the subject until 1999 when it was shown how to make artificial materials, metamaterials, with negative μ. The rapid advance of the subject since that date, both in theory and experiment, is reflected in the exponential growth of publications now at the 200 per year level and still growing. This interest is explained by the sudden availability of a qualitatively different class of electromagnetic materials combined with the quite startling properties which these materials appear to have; all of which provokes debate as each new facet of their behaviour is revealed. Experiment has been vital to resolution of controversy and has chiefly been in the microwave region of the spectrum though there is potential in the optical region currently being explored by several groups.     

Bioelectrochemical signaling in green plants induced by photosensory systems

Plants generate various types of intracellular and intercellular electrical events in response to environmental stress. The generation of electrophysiological responses induced by blue and red photosensory systems was observed in soybean plants. A phototropic response is a sequence of the following four processes: reception of a directional light signal, signal transduction, transformation of the signal into a physiological response, and the production of a directional growth response. It was found that the irradiation of soybean plants at 450+/-50, 670, and 730 nm induces action potentials with duration times and amplitudes of approximately 0.3 ms and 60 mV respectively.     

Indirect spectrophotometric detection of inorganic anions in ion-exchange capillary electrochromatography

The application of indirect spectrophotometric detection was investigated for a capillary electrochromatographic system in which an anion-exchange stationary phase (in the form of aminated latex particles) was coated onto the wall of a fused-silica capillary. The study has focused on the choice of the type and concentration of the absorbing coion (probe) added to the background electrolyte and the role of this species in manipulating the ion-exchange contributions to the separation with a view to controlling the selectivity of the separation. Common inorganic anions were used as analytes and nitrate, p-toluenesulfonate, nicotinate, and chromate were investigated as probes. It was found that most of these probes produced only a limited range of separation selectivities when their concentration was varied over the practically accessible range. p-Toluenesulfonate provided the greatest variation in selectivity, but peak distortion due to electromigration dispersion was evident for the faster ions. When variation of the separation selectivity - from predominantly electrophoretic in nature to predominantly ion-exchange in nature - was desired, this was best achieved by varying the type of probe rather than its concentration. For example, the nitrate probe provided predominantly electrophoretic separations with good peak shapes and high efficiencies. A comprehensive list of probes, ranked in order of ion-exchange selectivity coefficients determined by ion chromatography, was compiled and this proved to be a useful tool to assist in the selection of a probe for a desired separation selectivity. The limits of detection for the analytes and probes studied ranged from 20-55 micromol for the chromate system to 230-600 micromol for the nicotinate system, with nitrate and p-toluenesulfonate giving intermediate values.     

Determination of long-lived fission products and actinides in Savannah River Site HLW sludge and glass for waste acceptance

Savannah River Site (SRS) is immobilizing the radioactive, high-level waste sludge in Tank 51 into a borosilicate glass for disposal in a geologic repository. A requirement for repository aceeptance is that SRS report the concentrations of certain fission product and actinide radionuclides in the glass. This paper presents measurements of many of these concentrations in both Tank 51 sludge and the final glass. The radionuclides were measured by inductively coupled plasma mass spectrometry and α, β, and γ counting methods. Examples of the radionuclides are⁹⁰Sr,¹³⁷Cs,²³⁸U and,²³⁹Pu. Concentrations in the glass are 3.1 times lower due to dilution of the sludge with a nonradio-active glass forming frit in the vitrification process. Results also indicated that in both the sludge and glass the relative concentrations of the long lived fission products insoluble in caustic are in proportion to their yields from the fission of²³⁵U waste in the SRS reactors. This allowed the calculation of a fission yield scaling factor. This factor in addition to the sludge dilution factor can be used to estimate concentrations of waste acceptance radionuclides that cannot be measured in the glass. Examples of these radionuclides are⁷⁹Se,⁹³Zr, and¹⁰⁷Pd.