Modélisation des réseaux de microirrigation

La microirrigation est une technique dont l'uniformité de distribution d'eau par les goutteurs est très sensible aux faibles variations de pression. Pour maîtriser ces variations, avec davantage de précision, le présent travail est basé sur une analyse hydraulique approfondie de l'écoulement aboutissant à des équations différentielles aux dérivées partielles dont la pression et la vitesse de l'eau sont des inconnues. Ces équations non linéaires sont résolues en utilisant la méthode d'intégration Runge-Kutta d'ordre quatre. Les modèles développés dans la présente étude permettent de simuler la dynamique de l'eau dans la rampe et dans le réseau et sont utilisés pour déterminer le dimensionnement optimal du réseau. Les résultats obtenus corroborent ceux publiés par d'autres auteurs ayant utilisé la méthode des volumes de contrôle ou la méthode des éléments finis.Micro-irrigation is recommended for use in arid and semi-arid countries such as Algeria. This method consists of accurately providing the right amount of water and mineral nutrients to the plant's root area. The goal is to provide water efficiently by applying it at the correct rate. However, irrigation efficiency is clearly a function of the uniformity of water application.Micro-irrigation is a technique in which a delicate instrument known as an emitter (a terminal element of the network) operating with low pressure is used. The emitter, designed and manufactured with high precision, is a system with hydraulic laws and norms considered as a black box model that discharges water at atmospheric pressure. The emitter is an element of a network that constitutes a unit called a system or physical model. Water and mineral elements are delivered to a localized place, to the level of each plant by the emitters whose discharge is a function of lateral pressure. The precision of the dosage of irrigation, which must exactly satisfy the requirement for cultivation, depends fundamentally on the design of the network. It takes into account the pressure variations, which are due not only to head loss in the lateral branches of the network but also to the land slope and to the characteristics of the emitters. Water and air temperature and the possible plugging of the emitter orifice also influence the discharge of an emitter.The network is designed to satisfy the water needs of all the plants. Uniformity of water distribution is a main criterion for network design. To understand the variations in water distribution with more precision, we based the present work on a hydraulic analysis focussed on the outflow. This approach yields differential equations in which the pressure and the velocity of water in the pipeline network are unknown; the uniformity of water distribution is largely dependent on these variables. The differential second-order equations obtained are non-linear and analytical resolution is impossible, due to the empirical relation of the discharge emitter and the energy loss relation. Thus, the solution is obtained by numerical methods using the Runge Kutta integration method. The conditions in the limit equation modelling the outflow in the lateral pipes are different from those for the submain pipe. For the lateral pipes, the velocity of water at the extremity of the downstream region is inevitably minimal, as the whole region of discharge in the last pipe section is delivered by the last emitter where the pressure is minimal (Hmin). The velocity and pressure are calculated step by step along the lateral pipe until the entrance of water into the network where the pressure is maximal (Hsmax). The algorithm developed to simulate the emitter discharge distribution from the lateral pipes is called the "RK" model, and when it includes the discharge in the submain pipe it is called the "RS" model. These two models are transcribed in Fortran language by a computer program that automates iterations and calculations. Twelve parameters are changed in turn, or per group according to the cases studied, and the choice of the optimal solution of the parameters includes: emitter coefficients (a, y and Cvf); length and diameter of lateral pipes; the submain and main network (Lr, Dr, Ls, Ds, Lp, Dp); the roughness of the pipes (C); the spacing between the emitters (Δxr); the spacing between the lateral pipes (Δxs); and the water temperature. From these data of discharge and available pressure to the level of the parcel, the model precisely describes the distribution of the pressure and the discharges to all network emitters. In this case, the total discharge and the total required pressure, the uniformity of pressure and discharges are determined for each pattern of design. The combination of structural, functional and environmental factors is applied to guarantee an optimal exploitation taking into account the limits imposed by the specific norms for the micro-irrigation and the technical limits of velocity and pressure tolerance.Parameters that influence variations in uniformity are numerous and variable, which is why it is not easy to integrate them into this phase of study. The proposed model has merit as it avoids the complex numerical method of finite elements, recommended by some researchers (BRALTS et al., 1993; KANG and NISHIYAMA, 1994). The finite element method based on matrix structuring requires an important volume of iterations and calculations that could constitute a major constraint in the case of a large network. The model of BRALTS et al. (1993) is of particular interest in this regard ; our results have been confronted with those obtained with their model. Thus, the models presented in this study permit the simulation of water dynamics in micro-irrigation networks and offer the opportunity to determine the optimal design for such networks. Optimization is based on the variation of twelve classical parameters plus the associated geometric structure of the network, which was shown to be a non-negligible parameter. Optimization would not only reduce irrigation water volumes, but also fertilizer use and pumping energy. The example illustrated in Table 4 shows that although the networks deliver the same total discharge and have some similar design characteristics, the consumption of pumping energy changes from one geometric structure to another. Once a network is installed, it is impossible to change its design, so it is important to assure precision of the design calculations.This work shows promise in the simulation of the optimal design of micro-irrigation networks and also constitutes an economic means of making decisions. Moreover, the modelling results can guide field experimentation to explore other methods. Micro-irrigation can potentially solve many water shortage problems, but it requires further research in the safe reuse of low quality water and wastewater, the development of long term sustainability and the minimization salt accumulation and drainage problems

Pengaruh Perbedaan Umur Masak Benih Terhadap Hasil Panen Tiga Varietas Lokal Mentimun (Cucumis Sativus L.)

Salah satu faktor penentu keberhasilan budidaya pertanian yaitu kualitas benih yang digunakan. Benih yang berkualitas dicerminkan dari tiga mutu benih, yaitu mutu fisik, mutu genetis dan mutu fisiologis. Jika benih yang digunakan memiliki ketiga mutu benih yang tinggi, maka dapat meng-hasilkan tanaman yang tumbuh kuat dan berproduksi tinggi. Maka dari itu, perlu dilakukan penelitian untuk mengetahui sejauh mana mutu benih, khususnya mutu fisiologis benih mempengaruhi produksi tanaman. Tujuan penelitian ini ialah untuk mengetahui pengaruh perbedaan umur masak benih terhadap hasil panen dan mutu fisiologis benih tiga varietas lokal mentimun. Penelitian dilaksanakan bulan Mei hingga Agustus 2014 di lahan percobaan Sekolah Tinggi penyuluhan per-tanian Malang dan di laboratorium Pemulia-an Tanaman Fakultas Pertanian Universitas Brawijaya Malang, menggunakan metode rancangan acak kelompok faktorial (RAKF) dengan 3 ulangan untuk budidaya mentimun dan 4 ulangan untuk uji mutu fisiologis benih. Penelitian menggunakan 3 varietas (Lokal Malang, Lokal Blitar dan Lokal Jember) dan 4 tingkat umur masak benih yaitu 18 hari setelah polinasi (hsp), 28 hsp, 38 hsp dan 48 hsp. Hasil penelitian menunjukkan terdapat interaksi antara varietas dan umur masak benih terhadap parameter keserempakan tumbuh benih. Namun, pada parameter daya ber-kecambah, laju perkecambahan, kecepatan tumbuh dan indeks vigor, serta pada hasil dan karakteristik hasil seperti diameter buah, panjang buah, bobot buah, bobot buah per tanaman, jumlah buah per tanaman, bobot buah per plot dan jumlah buah per plot hanya dipengaruhi oleh varietas. Sedangkan parameter per-tumbuhan reproduktif dan persentase tanaman tumbuh menunjukkan hasil yang tidak berbeda nyata pada semua perlakuan

Droughts in semi-arid cereal regions of Algeria

The droughts in the semi-arid Algeria’s cereal regions are evaluated by studying the average monthly rainfall, from September to June, over the period (1941-2011), based on the firstorder Markov chain. This method traces rainy and dry days, cumulative rainfall and the probability of receiving rainfall above the thresholds of 0,1, 5, 10, 20 and 30 mm, in conjunction with the cereal development cycle. The rains analysed showed that the distribution of rainy days at the chosen thresholds did not exceed the variable averages of 6 to 9 days per month. These days are characterized by random cumulative rainfall, with probabilities fluctuating between + 40% and + 80%. Hard droughts affect seeding dates and yield factors for rainfed cereals.Keywords: Algeria, rainfall, Sowing, Markov Chai

HIV subtype and drug resistance patterns among drug naïve persons in Jos, Nigeria

To determine HIV-1 subtypes and antiretroviral drug resistance mutations for 16 infected, pregnant women in Jos, Nigeria, part of pol (1040 bp) was amplified from patient PBMC DNA, sequenced andanalyzed. Eight of the samples were subtype G, three were CRF02_AG and 2 were unique recombinant forms (URF) between G and CRF02_AG. The remaining consisted of 3 different strains: one was subtypeC, and the other 2 were unrelated URF. Nearly full-length genome sequences were completed for 6 of the strains: 4 subtype G and 2 CRF02_AG. In the 14 drug-naïve subjects, no primary resistance-associated mutations were found, but secondary mutations were identified in 7 different codons of the gene coding for protease: PR K20I, M36I, L63A/P/V, V82I, L10M/I and I93L. In addition, the K238R mutation was identified in the reverse transcriptase gene of 3 viruses. The PR K20I and M36I mutations occurred in all of the strains, and the L10M and V82I mutations occurred only in subtype G. The mutation, I93L, was carried by subtype C viruses. Two of the women that had prior niverapine treatment, had primary resistance-associated mutations, RT M184V and K103N, archived in their proviral DNA several months after treatment cessation. The study reports a predominance of clade G and CRF02_AG, and provides many more examples of nearly full-length genome sequences for subtype G viruses from Nigeria. The ubiquitous presence of PI secondary resistance-associated mutations, as well as primary resistanceassociatedmutations in 2 previously treated women, underscores the need to ensure adherence compliance to treatment

Analysis of CC chemokine and chemokine receptor expression in solid ovarian tumours

To understand the chemokine network in a tissue, both chemokine and chemokine receptor expression should be studied. Human epithelial ovarian tumours express a range of chemokines but little is known about the expression and localisation of chemokine receptors. With the aim of understanding chemokine action in this cancer, we investigated receptors for CC–chemokines and their ligands in 25 biopsies of human ovarian cancer. CC–chemokine receptor mRNA was generally absent from solid tumours, the exception being CCR1 which was detected in samples from 75% of patients. CCR1 mRNA localised to macrophages and lymphocytes and there was a correlation between numbers of CD8+ and CCR1 expressing cells (P = 0.031). mRNA for 6 CC-chemokines was expressed in a majority of tumour samples. In a monocytic cell line in vitro, we found that CCR1 mRNA expression was increased 5-fold by hypoxia. We suggest that the CC-chemokine network in ovarian cancer is controlled at the level of CC-chemokine receptors and this may account for the phenotypes of infiltrating cells found in these tumours. The leukocyte infiltrate may contribute to tumour growth and spread by providing growth survival factors and matrix metalloproteases. Thus, CCR1 may be a novel therapeutic target in ovarian cancer. http://www.bjcancer.com © 2001 Cancer Research Campaignhttp://www.bjcancer.co

Interferon-α Abrogates Tolerance Induction by Human Tolerogenic Dendritic Cells

BACKGROUND: Administration of interferon-α (IFN-α) represents an approved adjuvant therapy as reported for malignancies like melanoma and several viral infections. In malignant diseases, tolerance processes are critically involved in tumor progression. In this study, the effect of IFN-α on tolerance induction by human tolerogenic dendritic cells (DC) was analyzed. We focussed on tolerogenic IL-10-modulated DC (IL-10 DC) that are known to induce anergic regulatory T cells (iTregs). METHODOLOGY/PRINCIPAL FINDINGS: IFN-α promoted an enhanced maturation of IL-10 DC as demonstrated by upregulation of the differentiation marker CD83 as well as costimulatory molecules. IFN-α treatment resulted in an increased capacity of DC to stimulate T cell activation compared to control tolerogenic DC. We observed a strengthened T cell proliferation and increased IFN-γ production of CD4(+) and CD8(+) T cells stimulated by IFN-α-DC, demonstrating a restoration of the immunogenic capacity of tolerogenic DC in the presence of IFN-α. Notably, restimulation experiments revealed that IFN-α treatment of tolerogenic DC abolished the induction of T cell anergy and suppressor function of iTregs. In contrast, IFN-α neither affected the priming of iTregs nor converted iTregs into effector T cells. CONCLUSIONS/SIGNIFICANCE: IFN-α inhibits the induction of T cell tolerance by reversing the tolerogenic function of human DC

Intestinal microbiota in human health and disease: the impact of probiotics

The complex communities of microorganisms that colonise the human gastrointestinal tract play an important role in human health. The development of culture-independent molecular techniques has provided new insights in the composition and diversity of the intestinal microbiota. Here, we summarise the present state of the art on the intestinal microbiota with specific attention for the application of high-throughput functional microbiomic approaches to determine the contribution of the intestinal microbiota to human health. Moreover, we review the association between dysbiosis of the microbiota and both intestinal and extra-intestinal diseases. Finally, we discuss the potential of probiotic microorganism to modulate the intestinal microbiota and thereby contribute to health and well-being. The effects of probiotic consumption on the intestinal microbiota are addressed, as well as the development of tailor-made probiotics designed for specific aberrations that are associated with microbial dysbiosis

Vitamin D Deficiency and Its Health Consequences in Africa

Africa is heterogeneous in latitude, geography, climate, food availability, religious and cultural practices, and skin pigmentation. It is expected, therefore, that prevalence of vitamin D deficiency varies widely, in line with influences on skin exposure to UVB sunshine. Furthermore, low calcium intakes and heavy burden of infectious disease common in many countries may increase vitamin D utilization and turnover. Studies of plasma 25OHD concentration indicate a spectrum from clinical deficiency to values at the high end of the physiological range; however, data are limited. Representative studies of status in different countries, using comparable analytical techniques, and of relationships between vitamin D status and risk of infectious and chronic diseases relevant to the African context are needed. Public health measures to secure vitamin D adequacy cannot encompass the whole continent and need to be developed locally

ORIGIN AND PREVALENCE OF HUMAN T-LYMPHOTROPIC VIRUS TYPE 1 (HTLV-1) AND TYPE 2 (HTLV-2) AMONG INDIGENOUS POPULATIONS IN THE AMERICAS

Human T-lymphotropic virus type 1 (HTLV-1) is found in indigenous peoples of the Pacific Islands and the Americas, whereas type 2 (HTLV-2) is widely distributed among the indigenous peoples of the Americas, where it appears to be more prevalent than HTLV-1, and in some tribes of Central Africa. HTLV-2 is considered ancestral in the Americas and is transmitted to the general population and injection drug users from the indigenous population. In the Americas, HTLV-1 has more than one origin, being brought by immigrants in the Paleolithic period through the Bering Strait, through slave trade during the colonial period, and through Japanese immigration from the early 20th century, whereas HTLV-2 was only brought by immigrants through the Bering Strait. The endemicity of HTLV-2 among the indigenous people of Brazil makes the Brazilian Amazon the largest endemic area in the world for its occurrence. A review of HTLV-1 in all Brazilian tribes supports the African origin of HTLV-1 in Brazil. The risk of hyperendemicity in these epidemiologically closed populations and transmission to other populations reinforces the importance of public health interventions for HTLV control, including the recognition of the infection among reportable diseases and events