Asset management modelling framework for irrigation and drainage systems: Principles and case study application

Sustainability of irrigation and drainage infrastructure poses many challenges to many irrigation authorities worldwide due to a mismatch between the actual cost incurred in the provision of irrigation and drainage service and pricing of this service. This shortfall often leads to inadequate expenditure on maintenance in the absence of adequate subsidies from government or other sources.The asset management modelling framework (AMMF) presented in this paper enables the quantification of on-going ownership costs and operation costs. A life cycle cost (LCC) model for the evaluation of alternative irrigation and drainage asset management strategies is also presented. The AMMF is applied to the evaluation of asset ownership costs and LCC for alternative maintenance and interest rate scenarios in the Cu Chi irrigation system, Vietnam. The cost of three renewal strategies was evaluated: linear depreciation, full annuity and partial annuity. The cost ranges between US$ 28.00/ha and US$ 41.00/ha when interest rate varies between 9 and 3%. The average maintenance expenditure during recent years was estimated to be only US$ 1.30/ha which translates into 0.68% of the total asset replacement cost.The application of a simplified LCC model reveals that the least LCC varies with the level of maintenance and interest rate between US$ 353.5/ha for 5% maintenance expenditure and 12% interest rate to US$ 522.3/ha for 3% maintenance expenditure and 6% interest rate. The importance of exercising value judgements in applying the LCC model is also emphasised and discussed.     

The financial viability of irrigation management companies: A case study of Cu Chi irrigation system,Vietnam

A crucial, yet little understood, element in the economic studies of irrigation is the role played by companies who manage the supply of water. Many of these companies are publicly managed as they have the potential to act as monopolists. Possibly as a consequence of their ownership structure, analysts have questioned the economic viability and management of these firms. The case is made that many of these companies do not run profitably, that they rely on government subsidies to survive, that they do not spend enough on maintenance and that they run down their capital base. The purpose in this paper is to specify the measures that allow analysts to examine the financial viability of a publicly owned irrigation management companies and to apply these to a scheme in Vietnam. Of concern and contention in any irrigation scheme is the price that a company should charge for water in order to recover costs in the short-run. It was found that the company under investigation could not operate without subsidies and did run down their assets. It was found that a great disparity exists between what the consumers were charged for water and what the company received for supplying it. To ensure the sustainability of the Irrigation Management Companies in long term, they may have to increase the water fee by 3.75 times the current rate set by the provincial government (US$ 20 per ha).     

Prediction of oriented strand board properties from mat formation and compression operating conditions. Part 1. Horizontal density distribution and vertical density profile

A model is presented to determine the horizontal density distribution (HDD) and vertical density profile (VDP) of oriented strand board (OSB) panels produced by batch pressing. The HDD is simulated using input distributions of flake dimensions and orientation from plant measurements. Many previous HDD models rely on assumed distributions, which may not accurately characterize current manufacturing processes. The model predicts the VDP based on the compression behaviour of cellular materials in combination with temperature and moisture profiles calculated using a previously published heat and mass transport model. A novel empirical approach is applied rather than the time–temperature–moisture superposition method commonly used. The model predictions compare favourably with plant data and exhibit trends similar to previously reported experimental results. This work is the first of a two-part publication. The second part is concerned with stiffness property prediction and an optimization of the OSB manufacturing process. This work is novel in that no comprehensive model including HDD, VDP, stiffness property prediction and optimization has been reported in the literature.     

Cardiac myosin activation: a potential therapeutic approach for systolic heart failure

Decreased cardiac contractility is a central feature of systolic heart failure. Existing drugs increase cardiac contractility indirectly through signaling cascades but are limited by their mechanism-related adverse effects. To avoid these limitations, we previously developed omecamtiv mecarbil, a small-molecule, direct activator of cardiac myosin. Here, we show that it binds to the myosin catalytic domain and operates by an allosteric mechanism to increase the transition rate of myosin into the strongly actin-bound force-generating state. Paradoxically, it inhibits adenosine 5'-triphosphate turnover in the absence of actin, which suggests that it stabilizes an actin-bound conformation of myosin. In animal models, omecamtiv mecarbil increases cardiac function by increasing the duration of ejection without changing the rates of contraction. Cardiac myosin activation may provide a new therapeutic approach for systolic heart failure.     

Nutritional effects on sweetpotato storage root surface chemistry

Plant surface chemistry is known to have a pronounced effect on the behavior of many agriculturally important insects. We assessed the qualitative and quantitative effects of N and K nutrition on storage root surface chemistry of three sweetpotato [Ipomoea batatas (L.) Lam.] cultivars: two displaying moderate resistance (Jewel and Regal), and one susceptible (Centennial) to the sweetpotato weevil, Cylas formcarius (Summers). One field and one pot experiments were conducted, Boehmerol and boehmeryl acetate identified by GC‐MS were found on the surface of Centennial but not Jewel or Regal roots. Another compound, previously identified as “peak 4”;, was found on Regal with a retention time very close to that of boehmeryl acetate. In the field, boehmerol increased quadratically with increases in K rate (0, 112, or 224 kg K/ha); the same was true for boehmeryl acetate, but at 112 kg N/ha only. “Peak 4”; increased linearly (pot experiment) or quadratically (field experiment) with increases in the K rate, while N did not have a significant effect. Nutrition was found to affect storage root surface chemistry and may be a significant factor modulating differences in weevil susceptibility over location and time. The effect may in part explain inconsistencies in published estimates of field resistance to the weevil. Nitrogen and K nutrition should be taken into account when selecting progeny for boehmeryl acetate content in a breeding program.     

The Use of PCR to Detect a Pathogen in Compost

Testing compost for pathogens can be very difficult, time consuming and expensive. A method to purify DNA from compost for amplification by polymerase chain reaction (PCR) was sought. The published techniques used to purify DNA from soils or sediments did not work with compost samples in our laboratory. We have devised an extraction protocol specifically for compost samples. In a series of Escherichia coli-spiked compost samples, ranging from 10⁸ to 10³ organisms per gram of compost, the removal of substances that inhibit PCR amplification of DNA was accomplished by extracting the organisms from the compost and treating the extract with base resin. After cell lysis, the collected DNA was further purified on a 1 percent low melt agarose gel. A 260 base-pair region of the lac Z gene, unique to E. coli, was successfully amplified by PCR in the DNA extracted from the gel. The technique was sensitive to the level of 10⁴ E. coli cells per gram of compost.     

Influence of variable organic matter retention on nutrient availability in a 10-year-old loblolly pine plantation

The effects of varying forest floor and slash retention at time of regeneration were evaluated 10 years after the establishment of a loblolly pine plantation near Millport, Alabama. Treatments included removing, leaving unaltered, or doubling the forest floor and slash material. Forest floor and litterfall mass and nutrient concentrations, available soil N, foliar nutrient concentrations and stand yield were all impacted by the treatments. Forest floor mass and nutrient contents in the doubled treatment were significantly greater than the other two treatments. The doubled treatment accumulated 25, 45 and 350% more forest floor mass and 56, 56, and 310% more N than the control treatment in the Oi, Oe, and Oa layers, respectively. The other nutrients followed similar patterns. Potentially mineralized NO₃⁻-N in the mineral soil was also significantly higher in the doubled treatment. The positive effect of doubling the forest floor on soil N availability was reflected in greater foliage production, 30% more litterfall and 25% more stand yield for this treatment. This study shows that increasing the forest floor retention has resulted in increased nutrient availability and improved tree growth.     

Haematological values of post-laying Arrau turtle (Podocnemis expansa) in the Orinoco River, Venezuela

The Arrau turtle (Podocnemis expansa) is an endangered species, as a result of long-lasting, unsustainable exploitation. To obtain reference haematological values from the wild Podocnemis expansa during post-laying, 20 turtles were captured in the Orinoco River. Blood was obtained from the dorsal cervical sinus in lithium heparin tubes. Red blood cells (RBC), white blood cells (WBC), thrombocytes (TC), packed cell volume (PCV), plasmatic protein (PP), haemoglobin (Hgb), mean corpuscular volume (MCV) and differential leukocyte count were determined. Haematological values were: RBC 0.9×10(9)/L, WBC 5.7×10(9)/L, TC 5.4×10(9)/L, PCV 35.6%, PP 4.2g/dL, Hgb 11.8g/dL, MCV 411fL. The differential leukocyte count comprised: 71% heterophils, 23% lymphocytes, 3% eosinophils, 1.6% basophils, and 1% monocytes. The reports of reference haematology values for the wild P. expansa are limited; therefore, the results presented herein contrast with those values obtained in captivity. This study represents a contribution to the referential haematological values of the wild P. expansa.