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The problem of endogenous Research and Development (R&D) timing when technological innovations are sporadic events in a synamic framework, which requires that an exhaustible resource be substituted with an alternative technology resource, is analyzed. Given normal conditions, the pattern of exploitation of the two energy alternatives are characterized and compared. However, uncertain considerations might delay the undertaking of R&D and therefore lead to rapid resource depletion.

This paper expands upon J. Hartwick's 1990 research that considers how to explicitly incorporate natural resources depletion into standard national income accounting. He argues for the deduction of natural resource asset depreciation from the Gross National Product to arrive at a correct estimate of the Net National Product. This paper describes methods of accounting for the durability of exhaustible resources, uncertainty and pollution stock disutility.

The black carp,Mylopharyngodon piceus, is used for biological control of freshwater mollusks in various parts of the World. Fish-borne zoonotic trematodes (FZTs) are a public health concern in Vietnam and we suggest using black carp in nursery ponds, which are important for FZT transmission, to control snails serving as first intermediate hosts. However, the use of large juvenile (>2 kg) black carp in nursery ponds could be problematic and we decided to determine consumption rates by black carp of various sizes and their choice of different sizes of selected snail species found in aquaculture ponds in northern Vietnam. Furthermore, shell strength of common snails was assessed. Average daily consumption as percentage of fish weight ranged from 8.12% for smaller fish (100–250 g) to 4.68% in the larger fish (610–1250 g).Bithynia fuchsiana, the intermediate host ofClonorchis sinensis, and some intestinal trematodes were readily consumed by even the smallest black carp tested. The proportion ofMelanoides tuberculata, an important host for intestinal trematodes, declined with an increase in its shell height. The same was observed for two viviparid snail species,Angulyagra polyzonataandSinotaia aeruginosa; these species do not serve as first intermediate host for FZTs. Small black carp (100–250 g) consumed 50.4% of the second largest size class (26–30 mm) and 19% of the largest size class (>30 mm), while medium-sized black carp consumed 49.6% of the largestM. tuberculataand almost all snails of other size classes. Large black carp consumed 75% of the largest size class (>30 mm) ofM. tuberculata. Crush resistance (loge-transformed) increased linearly with shell size (loge-transformed) in most species tested. Crush resistance was the lowest inB. fuchsiana, while there was an overlap betweenM. tuberculataand the viviparid snails. We concluded that black carp of smaller size preferentially fed onM. tuberculata. [ABSTRACT FROM PUBLISHER]

In this paper, we analyse the problem of optimal domestic credit expansion for a small open economy. We show that (i) the transition from the fixed to the flexible exchange rate regime proceeds smoothly with no speculative attack on the central bank's foreign reserves; (ii) once the exchange rate has floated, it will never be optimal to repeg it afterward; (iii) even under uncertainty, there will not be any speculative attack; however, the optimal rate of credit expansion jumps discontinuously at the date of complete depletion of the known stock of foreign reserves. [ABSTRACT FROM AUTHOR]

This paper is an attempt to deal rigorously with some fundamental mathematical problems arising from the consideration of natural resources in the neoclassical framework of optimal economic growth. The theory of optimal economic growth initiated by Ramsey and developed by many others has benefited considerably from an optimal control formulation (see for example [1] and [22]). Incidentally it posed two interesting problems which seem to be typical of these economic models. [ABSTRACT FROM AUTHOR]