-Studies of chemical ecology of an organism are founded on the isolation and identification of a semiochemical, often comprised of two or more synergistic compounds (each synergist alone has little activity, but presented together they are bioactive). Chromatographic fractionation and bioassay methods of binary splitting, additive combination, and subtractive combination are compared for effici...

Zircon (ZrSiO4) is the most commonly used mineral in U–Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion of zircon involves thermal annealing followed by relatively low temperature partial dissolution in HF acid. It was specifically developed ...

Field-flow fractionation (FFF) is a powerful alternative to column-based polymer fractionation methods such as size-exclusion chromatography (SEC) or interaction chromatography (IC). The most common polymer fractionation method, SEC, has its limitations when polymers with very high molar masses or complex structures must be analysed. Another limitation of all column-based methods is that the sa...

The study used 276 urban soils and 447 rural soils collected from in and around the UK town of Northampton and focussed on the fractionation of Pb. The Pb fractionation obtained from total element data was compared to the fractionation of Pb in a subset of 10 urban soils obtained using a sequential extraction method. The fractionation of the Pb from the total element data and from the sequentia...

Introduction: Recently, the classic theory of stable isotope fractionation of the Bigeleisen-Mayer equation [1] has been expanded by the original author to include the mass-independent term named the nuclear field shift effect [2]. The improved theory successfully explained the observed non-linear isotope effect on U in a chemical exchange system [2]. Since then, researchers have applied the ne...

A suite of 47 carbonaceous, enstatite, and ordinary chondrites are examined for Re-Os isotopic systematics. There are significant differences in the Re/Os and Os/Os ratios of carbonaceous chondrites compared with ordinary and enstatite chondrites. The average Re/Os for carbonaceous chondrites is 0.392 0.015 (excluding the CK chondrite, Karoonda), compared with 0.422 0.025 and 0.421 0.013 for or...

[1] Experimental data for alteration of synthetic Martian basalts at pH = 0–1 indicate that chemical fractionations at low pH are vastly different from those observed during terrestrial weathering. Rock surface analyses from Gusev crater are well described by the relationships apparent from low-pH experimental alteration data. A model for rock surface alteration is developed, which indicates th...

Although the particulate fraction of egg yolk (yolk granules) has attracted the attention of investigators since Miescher (1) and Hoppe-Seyler (2)) reliable information concerning the distribution of the yolk constituents between its soluble phase and the granules is lacking. Separation of both phases is difficult, owing to the high viscosity of egg yolk. For this reason, all information concer...

A screening of marine bacteria for antimicrobial activity resulted in the isolation of Bacillus pumilus (SP21) from a sediment sample collected in the Bahamas. A bioassayguided fractionation led to the isolation of five surfactin analogs, glycocholic acid, amicoumacins A and B in addition to three new compounds named lipoamides A–C. The chemical structure of all the bioactive compounds was eluc...