Estimating canopy cover from color digital camera image of rice field

Canopy cover (CC) is a good predictor variable for plant growth parameters such as leaf area index and aboveground biomass. A nondestructive, low-cost, and convenient method is presented for estimating CC using digital camera image analysis. CC was estimated by the ratio of plant pixels to total pixels of digital camera image of rice field. To determine the criteria for segmenting the rice plant from variable soil background, three mosaic images for rice plant, flooded/bare soil, and algae-infested background were prepared from digital camera images that were taken in various field conditions. An image analysis program was developed in Visual Basic to extract red, green, and blue (RGB) features from the mosaic images, calculate RGB-based color indices, and compute the minimum segmentation error for separating rice plant from background. When judged by the segmentation error, modified excessive green index (MEGI) showed the highest potential for segmenting rice plant from flooded/bare soil background, followed by normalized green (g) and excessive green index (EGI). At the threshold MEGI value of 0.03, the segmentation error was the lowest as 0.13%. Any single index considered was not satisfactory in segmenting rice plant from algae-infested background. However, a discriminant function of 1.2553EGI + 0.01735G − 0.01474B was successful in segmenting rice plant from flooded/bare soil and algaeinfested background with segmentation errors of 0.34 and 1.17%, respectively. CC for four rice varieties from tillering to booting stage was estimated based on the threshold value of MEGI and discriminant function and also manually using commercial software. Both estimates of CC showed good relationship of r² = 0.94, suggesting that a digital camera could be used efficiently for measuring the CC of rice field.     

Why invest in minor projects in sub-Saharan Africa? An exploration of the scale economy and diseconomy of irrigation projects

It is well-known that major irrigation projects have a strong scale economy, handicapping irrigation development in sub-Saharan Africa (SSA) because of the difficulty in formulating large-scale projects. Using project-level investment cost and performance data of major and minor irrigation projects, this paper examines the causes of the economy of scale phenomenon. We find that strong scale economy exists not only for major but also for minor projects, i.e., small- and micro-scale, projects. This is largely because of the existence of indivisible overhead costs such as high-opportunity-cost human resources for planning, designing and engineering management and supervision. We also find that large differences between major and minor projects in the absolute level of overhead as well as construction costs creates a strong scale diseconomy and results in better performance of minor projects. The advantage of minor projects holds even when their higher risk associated with the water source is taken into consideration. We argue that there is an urgent need to promote irrigation development in SSA through developing minor projects, and to reduce the heavy burden of overhead costs by developing the capacity of human resources at the national, local and farmer levels in the fields of irrigation engineering, irrigation agronomy, institutional development, and micro water management technologies.     

Tank performance and multiple uses in Tamil Nadu,South India–comparison of 2 time periods (1996–97 and 2009–10)

Irrigation tanks in India are common property resources. Tanks provide not only for irrigation, but also forestry, fishing, domestic water supply, livestock, and other uses. Using empirical results from a study of tank performance from 80 tanks in Tamil Nadu, South India in two time period: 1996-97 and 2009-10, this paper evaluates tank irrigation system performance in terms of economic output and revenue generation forirrigation and other uses. The results indicate that irrigation and other productive uses put together raised the total value of output at tank level by 12 % in 1996-97 and just 6 % in 2009-10. This may suggest that tank multiple use values are small and getting smaller, and therefore not worth consideration. However, it was also found that, while declining in absolute terms, non-irrigation uses provided the majority of tax revenues and still more than cover government's operation and maintenance expenditure (O&M) budget. This finding provides another reason to consider multiple use values and their linkage with overall system viability.     

Modelling scenarios to identify a combined sediment-water management strategy for the large reservoirs of the Tuyamuyun hydro-complex

This paper introduces a combined modelling approach using a simple water budget model (THC-model) and a 3D reservoir sedimentation model (MOHID Water) to adapt reservoir operation and visualise their effects on the sediment deposition. By this, an effective combined sediment-water management can be identified under semi-arid conditions for dry, median and wet years. Results are presented for the reservoirs of the Tuyamuyun Hydro-Complex (THC), which is located in the lower Amu Darya River. The determination of the actual and usable reservoir storage volume shows that siltation will significantly adversely affect the ability of the in-stream Channel Reservoir to regulate seasonal demand for both irrigation and municipal water supply. However, modelling scenarios results confirm the effectiveness of adapted operation rules for the THC reservoirs and show that the operation of large dams could be modified according to a combined sediment-water management. The experience gained during this study emphasizes the fact that the concept of a combined reservoir management of sediments as well as water can be an efficient measure to improve the sustainable long-term use of reservoirs and to contribute towards a safe water supply in water crisis regions.     

Revenue risk management, risk aversion and the use of Livestock Gross Margin for Dairy Cattle insurance

The Livestock Gross Margin Insurance for Dairy Cattle is a federally reinsured insurance program that enables US dairy producers to establish minimum levels of milk income net of feed cost. Given the structure of this program there are an infinite number of possible contract designs based on the choice of deductible level and proportion of production insured. Adding to this complexity, producers vary in their risk preferences, which affect the incentive to insure their margin. It is unclear as to how producers may adopt this program for revenue risk management. This paper investigates the interplay between producer risk preferences, contract design and the subsidization of premium in determining program coverage. We undertook this analysis within an expected utility framework. Optimal contracts under different rates of constant relative rate of risk aversion and subsidies were analyzed using a nonlinear optimization model. We found that total optimal coverage increased significantly with the level of risk of aversion at lower deductibles but as deductible level increased, the level of risk aversion had a lesser impact on total optimal coverages. As expected, at the same deductible and risk aversion levels, inclusion of a premium subsidy increased the total optimal coverage.     

Diet drives convergence in gut microbiome functions across mammalian phylogeny and within humans

Coevolution of mammals and their gut microbiota has profoundly affected their radiation into myriad habitats. We used shotgun sequencing of microbial community DNA and targeted sequencing of bacterial 16S ribosomal RNA genes to gain an understanding of how microbial communities adapt to extremes of diet. We sampled fecal DNA from 33 mammalian species and 18 humans who kept detailed diet records, and we found that the adaptation of the microbiota to diet is similar across different mammalian lineages. Functional repertoires of microbiome genes, such as those encoding carbohydrate-active enzymes and proteases, can be predicted from bacterial species assemblages. These results illustrate the value of characterizing vertebrate gut microbiomes to understand host evolutionary histories at a supraorganismal level.     

The limb bud Shh-Fgf feedback loop is terminated by expansion of former ZPA cells

Vertebrate limb outgrowth is driven by a positive feedback loop involving Sonic Hedgehog (Shh), Gremlin, and Fgf4. By overexpressing individual components of the loop at a time after these genes are normally down-regulated in chicken embryos, we found that Shh no longer maintains Gremlin in the posterior limb. Shh-expressing cells and their descendants cannot express Gremlin. The proliferation of these descendants forms a barrier separating the Shh signal from Gremlin-expressing cells, which breaks down the Shh-Fgf4 loop and thereby affects limb size and provides a mechanism explaining regulative properties of the limb bud.     

Charge transfer equilibria between diamond and an aqueous oxygen electrochemical redox couple

Undoped, high-quality diamond is, under almost all circumstances, one of the best insulators known. However, diamond covered with chemically bound hydrogen shows a pronounced conductivity when exposed to air. This conductivity arises from positive-charge carriers (holes) and is confined to a narrow near-surface region. Although several explanations have been proposed, none has received wide acceptance, and the mechanism remains controversial. Here, we report the interactions of hydrogen-terminated, macroscopic diamonds and diamond powders with aqueous solutions of controlled pH and oxygen concentration. We show that electrons transfer between the diamond and an electrochemical reduction/oxidation couple involving oxygen. This charge transfer is responsible for the surface conductivity and also influences contact angles and zeta potentials. The effect is not confined to diamond and may play a previously unrecognized role in other disparate systems.     

Role of Polo-like kinase CDC5 in programming meiosis I chromosome segregation

Meiosis is a specialized cell division in which two chromosome segregation phases follow a single DNA replication phase. The budding yeast Polo-like kinase Cdc5 was found to be instrumental in establishing the meiosis I chromosome segregation program. Cdc5 was required to phosphorylate and remove meiotic cohesin from chromosomes. Furthermore, in the absence of CDC5 kinetochores were bioriented during meiosis I, and Mam1, a protein essential for coorientation, failed to associate with kinetochores. Thus, sister-kinetochore coorientation and chromosome segregation during meiosis I are coupled through their dependence on CDC5.     

School food environments and the obesity issue: content,structural determinants,and agency in Canadian high schools

To understand the phenomenon of the rapidly increasing prevalence of overweight and obese children and youth, it is especially important to examine the school food environment, the role of structural factors in shaping this environment, and the resulting nutrition and health outcomes. The paper examines research on school food environments in the US and Canada. It notes evidence of widespread availability of poor nutrition products in both environments and delineates reasons for the situation, and examines initiatives presently being undertaken in a number of jurisdictions in both countries to encourage healthy eating in schools. Empirical data are presented from a pilot study of high schools in the Canadian province of Ontario. The study documents the extent of student purchasing of nutrient-poor foods and beverages, and the structural factors internal and external to the school that appear responsible for the availability of such products in food environments in this critical institutional sphere. The paper also examines positive local initiatives in high schools that seek to encourage healthy eating in schools.