Economics of Agricultural Water Conservation: Empirical Analysis and Policy Implications

Climate change and recurrent drought in many of the world's dry places continue to inspire the search for economically attractive measures to conserve water. This study analyzes water conservation practices in irrigated agriculture in a sub-basin in North America's Rio Grande. A method is developed to estimate water savings in irrigated agriculture that result from public subsidies to farmers who convert from surface to drip irrigation. The method accounts for economic incentives affecting farmers' choices on irrigation technology, crop mix, water application, and water depletion. Findings show that farmers will invest in technologies that reduce water applications when faced with lower financial costs for converting to drip irrigation. Subsidies for drip irrigation increase farm income, raise the value of food production, and reduce the amount of water applied to crops. However, an unexpected result is that water conservation subsidies that promote conversion to drip irrigation can increase the demand for water depleted by crops. Our findings show that where water rights exist, water rights administrators will need to guard against increased depletion of the water source in the face of growing subsidies for drip irrigation. Our approach for analyzing water conservation programmes can be applied where water is scarce, irrigation is significant, food security is important, and water conservation policies are under debate.     

Numerical integration based on quasi-interpolating splines

In this paper product quadrature rules based on quasi-interpolating splines are proposed and convergence results are proved for bounded integrands. Convergence results are also proved for sequences of Cauchy principal value integrals of these quasiinterpolating splines. Some comparisons with other methods and numerical examples are given.     

Loss of heterozygosity for chromosome 1p in familial neuroblastoma

Loss of heterozygosity (LOH) and deletion of chromosome 1p are very often found in sporadic neuroblastoma. Nevertheless, very few data are available concerning 1p LOH in familial neuroblastoma. Families with recurrent neuroblastoma are rare and analysis of chromosome 1p in these families might give useful information for identifying the putative neuroblastoma suppressor gene. We used combined cytogenetic and molecular techniques to study 1p LOH in two neuroblastoma families. Family M has 2 out of 3 children with neuroblastoma and family C has 2 children, 1 of whom has neuroblastoma and type 1 neurofibromatosis (NF1). All patients of both families showed tumour cells with chromosome 1p deletion (1pdel), but only the patient from family C also had MYCN gene amplification. In all cases the deleted chromosome 1 was of maternal origin.     

An algorithm for one-and two-dimensional quadrature rules

An algorithm is presented which implements one- and two-dimensional quadrature formulas on finite domainsD under the assumption that the function to be integrated, ?(t), is not completely known. We suppose that ? (t) is the product of two functions,w (t) andf (t), such thatw (t) is not given in analytical form but his moments are known in the regionD, whilef (t) is completely given. Moreover error bounds are obtained for these formulas, which appear to be satisfactory in many actual cases.     

Use of highly sensitive sublethal stress responses in the social amoeba Dictyostelium discoideum for an assessment of freshwater quality

In this work, the sensitivity of a battery of tests on the social amoeba Dictyostelium discoideum has been assessed within a freshwater toxicity study. The results obtained from the evaluation of survival and replication rate of D. discoideum were compared to those derived with a series of widely used tests for freshwater toxicity assessment, i. e. bioassays using Vibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata. The effects on sublethal endpoints, i.e. lysosomal membrane stability (LMS) and endocytotic rate, were analysed in conjunction with high-level endpoints to verify the potential to make a typical bioassay more sensitive. The field ecotoxicological investigation employing D. discoideum is part of a monitoring study assessing environmental quality of the Bormida River (Italy), subjected until recently to a chronic industrial pollution. The survey was carried out at several stations (upstream and downstream of a chemical factory outlet) in two different periods. In 2002, the results of chemical analyses performed on river water indicated no contamination. The ecotoxicological data obtained in this period showed that no evidence of biological effects was observed using V. fischeri and D. magna bioassays. In spite of the previous classical acute toxicity tests, significant differences in cell viability of D. discoideum were found. By analysing the effects measured on LMS and endocytotic rate, more relevant changes were observed for these sublethal stress biomarkers compared to survival. The chronic toxicity data showed significant changes in cell growth both of P. subcapitata and D. discoideum. Nevertheless, more sensitive and rapid responses were obtained when assessing the effects of exposure on D. discoideum. The chemical and ecotoxicological data obtained in 2006 indicated a full recovery of the quality of the river water (neither contamination nor toxicity found). Altogether, the results reported in this study underline that the use of a battery of biomarkers in conjunction with high-level endpoints may help follow the pollutant-induced stress syndrome in the organisms from early sublethal effects to starting mortality.     

Deriving Goals from a Use-Case Based Requirements Specification

Use cases and scenarios have emerged as prominent analysis tools during requirements engineering activities due to both their richness and informality. In some instances, for example when a project’s budget or schedule time is reduced at short notice, practitioners have been known to adopt a collection of use cases as a suitable substitute for a requirements specification. Given the challenges inherent in managing large collections of scenarios, this shortcut is cause for concern and deserves focused attention. We describe our experiences during a goal-driven requirements analysis effort for an electronic commerce application. In particular, we identify the specific risks incurred, focusing more on the challenges imposed due to traceability, inconsistent use of terminology, incompleteness and consistency, rather than on traditional software project management risks. We conclude by discussing the impact of the lessons learned for requirements engineering in the context of building quality systems during goal and scenario analysis.     

Occurrence of androgens in sewage treatment plants influents is associated with antagonist activities on other steroid receptors

The occurrence of endocrine disrupting chemicals such as estrogens in raw urban sewage is well documented. By contrast, the presence of other steroidal activities in wastewater has been poorly studied, although they can cause undesirable biological responses in the environment. In this work, extracts of raw wastewater were tested for agonist and antagonist activities on estrogen, androgen, progesterone, mineralocorticoid and glucocorticoid receptors. We detected strong estrogenic activities that correlated well with the concentration of natural estrogens (estrone, estriol and 17β-estradiol) measured by chemical analysis. We also measured strong androgenic activities which were not due to estrogen receptor ligands based on the use of recombinant estrogen receptor α affinity columns. Several molecules with androgenic activities were identified in wastewater samples, testosterone, dihydrotestosterone and epiandrosterone being the most abundant. However, they explain only a small part of the detected androgenic activity, as indicated by the comparison of the detected biological responses with the results of the targeted chemical analysis. Finally, we found that our samples also contained strong antagonist activities on progesterone, glucocorticoid and mineralocorticoid receptors. Very interestingly, we identified pregnenolone (the precursor to all steroid hormones in humans) as a major endocrine disrupting chemical which accounts for most of the anti-mineralocorticoid activities present in raw wastewater. In conclusion, this study demonstrates the occurrence of androgen agonists as well as other steroid receptor antagonists such as pregnenolone in raw wastewater. Further research is needed to assess the fate of such compounds during sewage treatment and their potential effect on living organisms.