A regret function for agricultural production systems

Decision-making under uncertainty is a difficult task, involving risks. Since losses are to be expected although not necessarily through the decision-maker's fault, a regret concept is adopted. A regret concept and a regret function, based on a linear programming model, are suggested, using analysis of the sensitivity of the optimal plan to changes in random prices and in the amounts of available resources and estimates of the probabilities that each of the random variables will drop below a critical value. The use of this regret function, as an aid in decision-making, to evaluate the plan at the planning stage is explained and clarified by examples and a case study.     

Design procedure of sprinkling laterals: The mathematical background of a computerized aid

A correctly designed lateral has to meet the infiltration rate of the soil, the crop-water requirements and the existing limitations imposed by the hydraulic network. Several factors are involved in the design of sprinkler laterals aimed at achieving this goal. These factors are interrelated and the design requires non-linear equations.This paper presents the mathematical background of a computerized interactive design procedure. The lateral is defined here as a pipe network and is solved by the Newton-Raphson iterative method. The design procedure is an improvement on existing methods but, at present, is limited to solving laterals with a maximum of 30 sprinklers. The conversational mode and its fast response make the design procedure a practical aid which can be used even by an unskilled person.This work is part of a comprehensive research project carried out by a joint team of the Technion Faculty of Agricultural Engineering and the Israel IBM Scientific Center.     

Certification of sustainable forest management practices: a global perspective on why countries certify

In this paper, we examine national conditions that encourage the growth of a private regulatory environmental system to govern forests. Economic, institutional and social capital variables for 117 countries are used to examine factors determining forest certification under the Forest Stewardship Council and domestic competitor schemes. Although economic factors, such as forest exports and GDP, are important in explaining the likelihood that a country's forest management practices are certified, the regression results support the idea that economic institutions and the social context under which firms and forest landowners seek certification matters. The ability of citizens to influence the political process is also significant; in particular, the likelihood that firms and forest owners will seek to certify their forest practices is significantly reduced if women have little or no effective voice in civil society.     

Sensitivity of Neurospora crassa to a Marine-Derived Aspergillus tubingensis Anhydride Exhibiting Antifungal Activity That Is Mediated by the MAS1 Protein

The fungus Aspergillus tubingensis (strain OY907) was isolated from the Mediterranean marine sponge Ircinia variabilis. Extracellular extracts produced by this strain were found to inhibit the growth of several fungi. Among the secreted extract components, a novel anhydride metabolite, tubingenoic anhydride A (1) as well as the known 2-carboxymethyl-3-hexylmaleic acid anhydride, asperic acid, and campyrone A and C were purified and their structure elucidated. Compound 1 and 2-carboxymethyl-3-hexylmaleic acid anhydride inhibited Neurospora crassa growth (MIC = 330 and 207 μM, respectively) and affected hyphal morphology. We produced a N. crassa mutant exhibiting tolerance to 1 and found that a yet-uncharacterized gene, designated mas-1, whose product is a cytosolic protein, confers sensitivity to this compound. The ∆mas-1 strain showed increased tolerance to sublethal concentrations of the chitin synthase inhibitor polyoxin D, when compared to the wild type. In addition, the expression of chitin synthase genes was highly elevated in the ∆mas-1 strain, suggesting the gene product is involved in cell wall biosynthesis and the novel anhydride interferes with its function.     

Using attraction to light to decrease cannibalism and increase fry production in guppy (Poecilia reticulata Peters) hatcheries. I: phototactic reaction and light colour preference

A substantial proportion of newborns are lost in guppy hatcheries to cannibalism by the broodfish although small‐mesh baskets, which allow passage to small fry only and provide a predation‐free area, are used in breeding tanks. If newborn guppies are attracted by light, illuminating the small‐mesh baskets might enhance aggregation of newborns in the mesh basket and thus mitigate cannibalism effect. In this study, light attraction and light colour preference in newborn guppies were investigated. Testing the attraction to white, blue, green and red LED lights revealed attraction to each of these light types in newborns, but no significant attraction in adult females. Both newborns and adult females exhibited reduced mobility under red LED light. In a preference experiment in which all light colours were presented simultaneously, newborns were most attracted to the white light (52.0% of the newborns) and least attracted to the red light and darkness (6.8% and 6.7% of the newborns respectively). These results support the potential efficacy of using white light to attract newborns into the baskets in guppy breeding tanks and reduce cannibalism effects.     

Parasites and diseases of the grey mullet (Mugilidae) with special reference to the seas of the Near East

Comprehensive information on the parasite fauna of mullets is still restricted to a few regions: 15 species of parasites have been listed from Black Sea mullets, 34 from the eastern Mediterranean, 20 from the northern Red Sea and 19 from the northern Gulf of Mexico. Parasites listed include flagellates, myxosporidians and ciliates, as well as monogeneans, trematode adults and metacercariae, acanthocephalans, copepods and isopods. Mortality records of wild mullet populations are scarce. Mortalities due to environmental stress of temperature, salinity and pollution have been reported from the southern United States, Israel, and the northern Sinai. An epizootic among wild populations has been recorded in the northern Black Sea, due to the parasitic myxosporidian Myxobolus exiguus. Mortalities associated with heavy infection of the monogenean Benedenia sp. (n.sp.) were recently observed in a lagoon connected to the Gulf of Suez. In the eastern Mediterranean, the copepods Ergasilus lizae and Caligus pageti as well as Pseudocaligus apodus caused skin sores, emaciation and mortality in brackish- and sea-water ponds. The monogenean Benedenia sp. caused severe injuries and death to Red Sea mullets stocked in experimental holding tanks. Numerous forms (over 12) of metacercariae of trematodes, predominantly Heterophyiidea, are particularly common in mullets of the Near and Far East. In these regions, these metacercariae (which encyst in the muscles of mullets) are of considerable public health importance. Trematodes which develop from these larvae cause intestinal diseases in humans who consume infected fish.     

Purification and characterization of a Bacillus cereus collagenolytic/proteolytic enzyme and its effect on Meloidogyne javanica cuticular proteins

A novel collagenolytic/proteolytic enzyme isolated from the bacterium Bacillus cereus was purified and characterized. The extracellular enzyme was secreted into the growth medium only after induction by collagen. It was purified by two-step chromatography, consisting of gel filtration through a Sephadex G-100 column and then through an anion-exchange column. Molecular mass, as determined by SDS-PAGE was 42.8. The 42.8-kDa collagenase band was eluted from the gel to obtain the purified enzyme. The enzyme was found to have a very wide range of optimal pHs for activity (5.4 – 8.2), and was stable at temperatures between 4 and 40 °C. In addition to its collagenolytic property, the enzyme revealed very strong proteolytic activity, demonstrated by its ability to digest bovine serum albumin. The enzyme's ability to damage nematode cuticles was demonstrated by the digestion of collagens extracted from intact cuticles of second-stage juveniles of the root-knot nematode Meloidogyne javanica.     

Properties and inhibition of Sclerotium rolfsii chitin synthetase

A chitin synthetase (CS) preparation was obtained from mycelium of the plant pathogen Sclerotium rolfsii and partially characterised. The CS activity was stimulated by N-acetyl-D-glucosamine and magnesium cations with an optimum temperature of 30°C and an optimum pH of 6.4. The enzyme required proteolytic activation and so apparently existed in a zymogenic form. The fungal CS was strongly inhibited by the nucleoside-peptide antibiotics polyoxin-D and nikkomycin, and weakly inhibited by the terpenoyl benzimidazole, 1-geranyl-2-methylbenzimidazole. It was insensitive to captan and to insecticidal benzoylphenyl ureas. Disrupted chitin formation caused by polyoxin-D showed as swollen hyphae containing numerous depressions. The antibiotic also reduced formation of sclerotia and the few that did form were large, irregular in shape and light coloured.