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The paper investigates how barter can be used to finance imports and restore the creditworthiness of highly indebted countries when reputation as an enforcement mechanism for credit repayment does not work. The authors argue that payments in goods can be used to collateralize a trade credit and thus improve the creditor’s incentives to pursue defaulting debtors. Furthermore, it is shown that barter is particularly advantageous if export revenues of the debtor country are stochastic, even in the absence of risk aversion. The predictions of the model are consistent with data on actual barter contracts. [ABSTRACT FROM AUTHOR]

SUMMARY Since the concentration of free radicals in humic subtances increases at high pH the use of basic solutions for 13C NMR spectroscopy may cause broadening and loss of aromatic signals, with distortion of intensity distributions. No such effects were found in 13C spectra of soil humic and fulvic acid, an aquatic fulvic acid, and two phenolic polymers run in aqueous solutions at different pH values, and in dimethylsulphoxide. With increasing pH, the peak in the carboxyl region shifted in a manner consistent with greater dissociation of carboxyl and phenolic groups, and also certain features in the aliphatic and carboxyl regions were enhanced under some solution conditions. Elevated solution temperature (70°C) caused only slight improvement in the resolution of some lines. Chemical shifts were determined for some known phenolic and benzenecarboxylic acid compounds in DMSO and NaOD. The range for phenolic carbons extended to 173 ppm in NaOD, while some aromatic carbons occurred around 105 ppm, in the same region as anomeric carbons. Thus, even under quantitative acquisition conditions, relative areas may be used only to estimate proportions of different types of carbons and functional groups. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to compare structural characteristics of PMA with those of FA in order to assess the suitability of PMA to serve as a model for FA. Chemical (elemental analyses, CO2H group determinations, increases in OCH3 after methylation, oxidative degradation) and spectroscopic (visible, UV, fluorescence, IR, 13CNMR, and ESR) methods were used for this purpose. While PMA was found to resemble FA in a number of characteristics (water solubility, rich in CO2H groups, dark brown colour), it significantly differed from FA in a number of respects (UV, fluorescence, 13CNMR spectra as well in oxidation products). Compared to FA, PMA appeared to be better organized and more homogeneous at the molecular level, richer in olefinic structures and less aromatic. But the chemical structures of both PMA and FA remain largely unknown. [ABSTRACT FROM AUTHOR]

Leachates from decomposing leaves of four species of deciduous trees were collected after each rainfall during the months of May to September. Determinations were made of the capacity of these leachates to take up iron from iron-saturated Dowex-50 and to withhold this iron from exchange and/or adsorption by exchange resins saturated with H, Al, Ca, and Mn. For both characteristics the leachates ranked maple > poplar > birch > beech. The capacity of ion-saturated resins to remove iron from iron-enriched leachates was as follows: H > Al > Ca = Mn. This behaviour may be related to the variable thicknesses of the horizons of eluviation and deposition of iron in various podzolic soils. These horizons are, in general, thinner in the strongly acidic Podzol soils than in Grey-Brown Podzolic soils more highly saturated with calcium. Potentiometric titrations of metal-free and iron-enriched leachates indicated that titratable acid groups were blocked by the added iron. Apparent pK values of metal-free leachates ranged from 3·6 to 3·9, those of iron-enriched leachates, except poplar, from 4·7 to 5·0. [ABSTRACT FROM AUTHOR]