Modeling a weak turbulent flow in a narrow and wavy channel: case of micro-irrigation

The baffle-fitted labyrinth channel is commonly used in micro-irrigation systems. The flow in this labyrinth channel has a rather low-Reynolds number. In addition, emitter clogging, which is the major drawback of the micro-irrigation technique, is significantly related to flow characteristics. In order to design an anti-clogging emitter with a good performance, the hydrodynamics must be understood and analyzed. As CFD modeling is nowadays the most efficient approach for improving emitter geometry, this paper presents assessment of several k–\(\varepsilon\) turbulence models for computation of micro-irrigation emitter hydrodynamics. The objective is to determine the simplest and most efficient model to improve emitter conception, in terms of both discharge/pressure loss and limitation of the areas where low velocity is likely to generate emitter clogging. Low-Reynolds number k–\(\varepsilon\) models are often assumed to be more suitable for the labyrinth-channel flow since these models have no wall functions, they can take into account low turbulence levels and they account for the effect of damped turbulence. The low-Reynolds number k–\(\varepsilon\) models used in the present study are compared to high-Reynolds number k–\(\varepsilon\) models. Very different trends are observed between low-Reynolds number k–\(\varepsilon\) models. Some models reproduce a turbulent behavior, while others reproduce a laminar behavior. The head loss analysis reveals that, contrary to classical smooth pipe flow, the contribution of turbulent dissipation cannot be neglected since its contribution is larger than wall friction ones. This feature explains why different models can induce quite different flow behavior.     

Screening wheat germplasm for seedling root architectural traits under contrasting water regimes: potential sources of variability for drought adaptation

In this study, we selected 180 accessions from different wild relatives of wheat (Aegilops–Triticum species) and tested them in the presence of a tolerant and a sensitive control variety under well-watered and drought-stressed conditions. The results of analysis of variance for dry masses and all measured root traits showed that water regimes, accession and species main effects were highly significant. Drought stress significantly declined shoot dry mass (59.42%), root length (37.85%) and the total number of branch roots (36.25%), but increased the root-to-shoot ratio (75.00%), specific root length (64.19%) and root tissue density (29.46%). Principal component analysis for 182 individuals and 12 species groups identified two components that explained 75.67 and 82.39% of the total variation in dry mass and root traits under drought-stressed conditions, respectively. Taking together, our results identified 12 accessions with superior tolerance to drought stress. Remarkably, four species of wild relatives – Ae. cylindrica (DC genome), Ae. neglecta (UM genome), Ae. speltoides (B genome) and Ae. tauschii (D genome) – responded well to drought stress. The potential of these species could be used for molecular analysis such as marker assisted selection and gene mapping, ultimately aimed at breeding for root traits with improved adaptation to drought environments.     

Effects of different irrigation intervals and weed control on yield and yield components of safflower (Carthamus tinctorius L.)

A two-year (2008–2009) field experiment was conducted to determine the effect of irrigation management and weed control on yield and yield components of safflower. The experiment was conducted as a split-split plot arranged in a randomized blocks design with three replications. There were two treatments (weedy and weed free) and four irrigation interval water managements (7 days for all stages, 15, 22 and 28 days after six-leaf stages). The results indicated that grain yield was 29% higher in weed-free plots than in weedy plots. Weed competition reduced yield components such as primary branches, petal weight and number of capitulum per plant. Increasing the irrigation interval to 15 days at the six-leaf stage had no significant effects on grain yield, but grain yield decreased by 18 and 29.8% with increases in the irrigation interval to 22 and 28 days, respectively. An increased irrigation interval >15 days had negative effects on yield components like number of capitulum per plant, petal weight and number of primary branches. The highest grain yield (3703 kg ha^?1) was obtained in the weed-free plot, and there was no significant difference between 7- and 15-day irrigation intervals.     

Helicobacter pylori SabA adhesin in persistent infection and chronic inflammation

Helicobacter pylori adherence in the human gastric mucosa involves specific bacterial adhesins and cognate host receptors. Here, we identify sialyl-dimeric-Lewis x glycosphingolipid as a receptor for H. pylori and show that H. pylori infection induced formation of sialyl-Lewis x antigens in gastric epithelium in humans and in a Rhesus monkey. The corresponding sialic acid-binding adhesin (SabA) was isolated with the "retagging" method, and the underlying sabA gene (JHP662/HP0725) was identified. The ability of many H. pylori strains to adhere to sialylated glycoconjugates expressed during chronic inflammation might thus contribute to virulence and the extraordinary chronicity of H. pylori infection.     

Proteolytic enzymes reactions on wool yarn and surfactants effects on the enzyme treatment

In this study, the effects of enzymes on wool yarn in the presence of different salts (ammonium sulfate, sodium tetraborate, and di-sodium hydrogen phosphate) were investigated. Alcalase 2,5 LDX and Savinase 16 LEX were selected as proteolytic enzymes. In addition, the effects of surfactants (Sandozin NRW, Irgasol NA, Erkantol NR, and Sandozin EH) on the enzyme treatment of wool yarn were evaluated. The results indicated that the effects of enzymes on wool yarn were greatest in the presence of sodium tetraborate. Furthermore, the properties of wool yarn such as weight loss, strength loss, and hairiness were influenced by these surfactants. The SEM images of the treated samples confirmed the obtained results.     

Effects of Dietary Lipid Levels on Growth,Survival, and Molting of Yearling Narrow Clawed Crayfish,Astacus leptodactylus

The influence of dietary lipid level was evaluated on growth, survival, and molting of yearling narrow clawed crayfish, Astacus leptodactylus. Yearling crayfish were fed five isonitrogenous diets (35% protein), formulated to contain 4%, 7%, 10%, 13%, or 16% lipid. Crayfish (10.1 ± 1.6 g) were reared for 56 days in 60-L fiberglass tanks at 23 ± 1.7 °C, with flow-through water and continuous aeration. At the end of the trial, crayfish fed 13% lipid had the highest weight gain and specific growth rate, significantly different from crayfish fed 4% and 7% lipid (p < 0.05). Crayfish fed 13% lipid had a significantly higher survival rate (86.7%) than the animals fed 4% lipid (71%) (p < 0.05). Molting was not affected by lipid level (p > 0.05). We recommend 13% dietary lipid level for optimum growth and survival of Astacus leptodactylus in intensive cultivation.     

Influence of zinc sulfate and municipal solid waste compost on chemical forms of zinc in calcareous soils

Zinc (Zn) is an essential micronutrient for crop growth. This metal can be found in chemical forms or fractions in the soil. The objective of this study was to investigate the distribution of Zn in special chemical forms using the sequential extraction method after treating eight calcareous soils by zinc sulfate and municipal solid waste (MSW) compost. Zn was separated in seven defined forms as exchangeable (Ex), carbonate (Car), organic (Om), manganese oxide bound (MnOX), amorphous iron oxide bound (FeAOX), crystalline iron oxide bound (FeCOX), and residual (Res). According to the results, the mean concentrations of Zn in chemical forms in untreated soils from higher to lower were 31.84, 8.13, 2.64, 2.57, 0.45, 0.39, and 0.16?mg?kg^?1 for the Res, FeCOX, Car, FeAOX, Om, MnOX, and Ex forms, respectively. The total applied Zn to the studied soils from both the sources of zinc sulfate and MSW compost after incubation for 30 days was converted to chemical forms in the following order: Car?>?Res?>?FeCOX?>?Om?>?FeAOX?>?MnOX?>?Ex. On average, 30.3% of total Zn from zinc sulfate and 28.8% of total Zn in the MSW compost were converted into the Car form. The high content of calcium carbonate (CaCO₃) in the studied soils is an important factor affecting the conversion of Zn forms, mostly in the Car form through the application of both the inorganic and the organic sources of Zn.     

Maize growth and yield as affected by wheat residues and irrigation management in a no-tillage system

Determining the proper rate of wheat residues incorporation into the soil under a wheat–maize double cropping system is an important issue in southern parts of Iran, where these two irrigated crops are consecutively grown. A 2-year experiment (2010–2011) was conducted to evaluate the effect of wheat residue incorporation rates (25%, 50% and 75%) and irrigation intervals (12, 16 and 20 days) on yield and growth of maize under no-tillage system compared to control without residue and under conventional tillage (CT) at the College of Agriculture, Shiraz University, Shiraz, Iran. The experiment was conducted as a split plot arranged in randomized complete block design with three replications. The results showed that increased irrigation intervals reduced the plant height (14.6%), leaf-area index (12.9%), rows (10.1%) and grains per ear (29.8%), thousand grain weight (6.9%), grain (33.8%) and biological yield (24.2) and harvest index (23.2%). Water deficit had no significant effect on soil organic matter and carbon-to-nitrogen ratio. Under 12 and 20 days irrigation intervals, the highest grain yields were obtained with 12.7 and 8.6 t ha^?1 in CT and 25% residue incorporation into soil, respectively. Therefore, according to the results of this 2-year study, realized incorporation of 25% wheat residue soil covering percentage is recommended for this area with limited water resources.     

Collaborative modelling to support forest management: Qualitative systems analysis at Lumut Mountain,Indonesia

Complex ecological and social processes in tropical forests imply that observations on any single element of the system do not provide an adequate basis for sound forest management. A collaborative modelling process engaging all relevant stakeholders led to a shared understanding of how to manage forests around Lumut Mountain, Pasir District, East Kalimantan. The model was developed by identifying forest management objectives, building a conceptual model using a causal loop diagram, and defining performance indicators. The model was then used to explore future scenarios to improve the well-being of local stakeholders while maintaining forest quality. Finally, roles needed to implement the chosen scenarios were defined and assigned to individual participants. This qualitative modelling process was found to be an effective way to assist the development of a collaborative action plan. The authors wish to acknowledge that this paper has been produced with financial support from Department for International Development of UK, the Asian Development Bank under RETA Grant 5812 and CIFOR. The views expressed contained herein are solely of the authors and do not necessarily reflect official views of the donors or of CIFOR. The authors would like to thank Richard Dudley and Bruce Campbell for their inputs to the paper.