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1.
Tilahun Geleto D. G. Tanner Tekalign Mamo Getinet Gebeyehu 《Nutrient Cycling in Agroecosystems》1995,44(3):195-204
In trials conducted at 2 highland Vertisol sites in Ethiopia in 1990 and 1991, 2 locally popular wheat cultivars, 1 spring bread wheat (Triticum aestivum L.) and 1 durum wheat (T. durum Desf.), were supplied with nitrogen (N) fertilizer at 0, 60 and 120 kg N ha–1 in the form of large granular urea (LGU), standard urea prills or ammonium sulfate. N was applied all at sowing, all at mid-tillering or split-applied between these two stages (1/3:2/3). While durum wheat exhibited the highest N concentration in grain and straw, bread wheat, because of its higher productivity, resulted in a greater grain and total N uptake. In general, split application of N and use of LGU as N source enhanced grain and total N uptake, apparent N recovery and agronomic efficiency of N, particularly under severe water-logging stress. Where significant, the interactions among the experimental factors substantiated the superior responsiveness of the bread wheat cultivar to fertilizer N, and the beneficial effects of split N application and LGU as an N source. Split application of N tended to nullify the positive effects of LGU, presumably by approximating the delayed release of N achieved with LGU. Considering the potential benefits to Ethiopian peasant farmers and consumers, split application of N should be advocated, particularly on water-logged Vertisols; LGU could be an advantageous N source assuming a cost comparable to the conventional N source urea. 相似文献
2.
Tomislav Hengl Johan G. B. Leenaars Keith D. Shepherd Markus G. Walsh Gerard B. M. Heuvelink Tekalign Mamo Helina Tilahun Ezra Berkhout Matthew Cooper Eric Fegraus Ichsani Wheeler Nketia A. Kwabena 《Nutrient Cycling in Agroecosystems》2017,109(1):77-102
Spatial predictions of soil macro and micro-nutrient content across Sub-Saharan Africa at 250 m spatial resolution and for 0–30 cm depth interval are presented. Predictions were produced for 15 target nutrients: organic carbon (C) and total (organic) nitrogen (N), total phosphorus (P), and extractable—phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), aluminum (Al) and boron (B). Model training was performed using soil samples from ca. 59,000 locations (a compilation of soil samples from the AfSIS, EthioSIS, One Acre Fund, VitalSigns and legacy soil data) and an extensive stack of remote sensing covariates in addition to landform, lithologic and land cover maps. An ensemble model was then created for each nutrient from two machine learning algorithms—random forest and gradient boosting, as implemented in R packages ranger and xgboost—and then used to generate predictions in a fully-optimized computing system. Cross-validation revealed that apart from S, P and B, significant models can be produced for most targeted nutrients (R-square between 40–85%). Further comparison with OFRA field trial database shows that soil nutrients are indeed critical for agricultural development, with Mn, Zn, Al, B and Na, appearing as the most important nutrients for predicting crop yield. A limiting factor for mapping nutrients using the existing point data in Africa appears to be (1) the high spatial clustering of sampling locations, and (2) missing more detailed parent material/geological maps. Logical steps towards improving prediction accuracies include: further collection of input (training) point samples, further harmonization of measurement methods, addition of more detailed covariates specific to Africa, and implementation of a full spatio-temporal statistical modeling framework. 相似文献
3.
Tilahun Shimeles Park Do Su Taye Adanech Melaku Jeong Cheon Soon 《Food science and biotechnology》2017,26(2):473-479
Food Science and Biotechnology - This study was conducted to assess the physicochemical changes and overall nutritional implications of greenhouse-grown “TY Megaton” and... 相似文献
4.
Food shortage in sub-Saharan Africa is generally considered a function of limited access to food, with little thought to nutritional quality. Analyzing household production of nutrients across farming systems could be valuable in guiding the improvement of those systems. An optimization model was employed to analyze the scenario of human nutrition and cropland allocation in enset (Enset ventricosum)/root crop-based and cereal-based systems of the Ethiopian Highlands. The type and amount of nutrients produced in each system were analyzed, and an optimization model was used to analyze which cropping strategies might improve the nutritional quality of the household using existing resources. Both production systems were in food deficit, in terms of quantity and quality of nutrients, except for iron. The energy supply of resource-poor households in the enset/root crop-based system was only 75% of the recommended daily dietary allowance (RDA) of the World Health Organization (WHO), whereas resource-rich farmers were able to meet their energy, protein, zinc, and thiamine demands. Extremely high deficiency was found in zinc, calcium, vitamin A, and vitamin C, which provided only 26.5%, 34%, 1.78%, and 12%, of the RDA, respectively. The RDA could be satisfied if the land area occupied by enset, kale, and beans were expanded by about 20%, 10%, and 40%, respectively, at the expense of maize and sweet potato. The cereal-based system also had critical nutrient deficits in calcium, vitamin A, and vitamin C, which provided 30%, 2.5%, and 2% of the RDA, respectively. In the cereal system, the RDA could be fully satisfied by reducing cropland allocated to barley by about 50% and expanding the land area occupied by faba beans, kale, and enset. A shift from the cereal/root crop-dominated system to a perennial-enset dominated system would decrease soil erosion by improving the crop factor by about 45%. This shift would also have a very strong positive impact on soil fertility management. However, any policy suggestions for change in cropland allocation should be done through negotiations with households, communities, and district stakeholders. 相似文献
5.
Tilahun Kidanemariam Gelaw Laura Espina Rafael Pagán Diego García-Gonzalo Sílvia De Lamo-Castellví 《Food and Bioprocess Technology》2014,7(7):2084-2092
Attenuated total reflectance infrared microspectroscopy combined with soft independent modeling of class analogy (SIMCA) multivariate technique was used to differentiate between alive, dead, and injured Escherichia coli O157:H7 cells. E. coli O157:H7 cells were suspended in citrate phosphate buffer at pH 4.0 and 7.0 and treated by heat at 54 °C for 5, 10, 20, and 90 min or pulsed electric field (PEF) at 35 kV/cm for 10, 25, 50, and 60 pulses. The SIMCA analysis confirmed that major contribution to the discrimination of the untreated and treated E. coli cells were (1) the amide I band at 1,638 and 1,618 cm?1 corresponding to changes in β-pleated secondary protein structure (heat-treated cells at pH 7.0 and 4.0, and PEF-treated cells at pH 4.0), and (2) the bands at 1,078 and 993 cm?1 corresponding to changes in P?=?O (PO 2 ? ) stretching of phosphodiesters or lipopolysaccharides and C–O–C or C–O stretching of different polysaccharides (PEF-treated cells at pH 7.0). The use of partial least squares regression analysis allowed for correctly predicting the survivors of the thermal treatment. Injured cells could be estimated from the comparison of cell counts predicted in nonselective and selective plating media with sodium chloride and bile salts. The prediction results yielded inactivation values with a coefficient of determination (R 2) of 0.83 or higher and a standard error of cross validation between 0.11 and 0.37 log cycles of inactivation. 相似文献
6.
A Kebede S Taticheff T Bulto W Workneh D Tilahun 《Canadian Metallurgical Quarterly》1993,31(2):127-135
Improvement of the siloxane layer on minerals by using a bisfunctional silane, such as 1,6-bis(trichlorosilyl) hexane and 1,8 bis(trichlorosilyl)octane, and the effects on adhesion of methacrylic resin to glass plates treated with the silanes were studied. The tensile bond strength of the resin to the glass plate treated with bisfunctional silane alone was high (about 20MPa) in spite of the fact that the molecule contains no double bonds. Furthermore, a mixture of bisfunctional silane and 3-methacryloxypropyltrichlorosilane showed an excellent effect for tensile bond strength and water-resistance. Based on the results, it is suggested that the better water resistant adhesion of the mixed silane depends on the higher degree of crosslinking in the siloxane phase and on the formation of an interpenetrating polymer network between the siloxane layer and the matrix resin. 相似文献
7.
Hong Choon Ong Surafel Luleseged Tilahun Wai Soon Lee Jean Meadard T. Ngnotchouye 《Intelligent Automation and Soft Computing》2018,24(2):359-366
Metaheuristic algorithms are found to be promising for difficult and high dimensional problems. Most
of these algorithms are inspired by different natural phenomena. Currently, there are hundreds of
these metaheuristic algorithms introduced and used. The introduction of new algorithm has been one
of the issues researchers focused in the past fifteen years. However, there is a critic that some of the
new algorithms are not in fact new in terms of their search behavior. Hence, a comparative study in
between existing algorithms to highlight their differences and similarity needs to be studied. Apart
from knowing the similarity and difference in search mechanisms of these algorithms it will also help
to set criteria on when to use these algorithms. In this paper a comparative study of prey predator
algorithm and firefly algorithm will be discussed. The discussion will also be supported by simulation
results on selected twenty benchmark problems with different properties. A statistical analysis called
Mann—Whitney U 2 test is used to compare the algorithms. The theoretical as well as simulation
results support that prey predator algorithm is a more generalized search algorithm, whereas firefly
algorithm falls as a special case of prey predator algorithm by fixing some of the parameters of prey
predator algorithm to certain values. 相似文献
8.
Monjurul Haq Adane Tilahun Getachew Periaswamy Sivagnanam Saravana Yeon-Jin Cho Seul-Ki Park Min-Jung Kim Byung-Soo Chun 《Korean Journal of Chemical Engineering》2017,34(8):2255-2264
Supercritical carbon dioxide (SC-CO2) extracted Atlantic salmon frame bone oil (SFBO) was used for Eicosapentaenoic acid and Docosahexaenoic acid (EPA-DHA) concentrate production by urea complexation. Urea/fatty acids (2.5 to 4.0 w/w), crystallization temperature (?24 to ?8 °C) and crystallization time (8 to 24 h) were studied by Box-Behnken Design (BBD) to maximize EPA-DHA content. Highest EPA-DHA content was 60.63% at urea/fatty acids 4.0 w/w, crystallization temperature ?15.67 °C and crystallization time 8 h. EPA-DHA concentrate showed improvement of EPA-DHA from 6.39% in SFBO to 62.34%, increase of astaxanthin content from 21.33 μg/g in SFBO to 44.69 μg/g in EPA-DHA concentrate, no residual urea and reduction of many off-flavor compounds. The EPA-DHA yield showed an inverse relation with the urea/fatty acids, whereas its concentration increased proportionally with urea/fatty acids. Therefore, EPA-DHA concentrate produced from SFBO by urea complexation may be an efficient technique to provide ω-3 polyunsaturated fatty acids to the consumers. 相似文献
9.
Potential of DMSO as greener solvent for PES ultra‐ and nanofiltration membrane preparation
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In this article, the performance of polyethersulfone (PES) ultra‐ and nanofiltration membranes, prepared with the non‐toxic solvent dimethyl sulfoxide (DMSO), was investigated. The membranes were prepared by immersion precipitation via phase inversion. Experimental results proved that DMSO is a better alternative to N‐methyl‐2‐pyrrolidone (NMP) as solvent for PES ultrafiltration membranes as the membranes had a higher permeability and rejection of bovine serum albumin (BSA). An explanation was found based on experimental cloud point data and scanning electron microscopy images showing the morphology. The rejection of BSA and rose Bengal (RB) was proportional to the polymer concentration. On the contrary, the permeability decreased with increasing polymer concentration. For a casting thickness of 250 µm, an optimal balance between permeability and rejection of macromolecules for ultrafiltration was found at 24 wt % PES. The permeability was inversely proportional to the casting thickness, but a small decrease in rejection was observed when lowering the thickness. A good balance between permeability and rejection of RB was found, using a reference nanofiltration membrane of 28.5 wt % PES with 150 µm casting thickness. This membrane achieved a RB rejection of 95.3% and a pure water flux of 2.03 L m?2 h?1 bar?1. The membrane thickness and polymer concentration did not have a clear influence on the hydrophilicity of the membranes. It can be concluded that DMSO is a benign alternative as compared to traditional solvents such as NMP and also results in better PES membrane performances. DMSO is a perfectly suitable solvent for ultrafiltration applications and has potential to be used for nanofiltration applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46494. 相似文献
10.
Abel Tilahun 《Computational statistics & data analysis》2007,51(9):4152-4163
The evaluation of surrogate endpoints is thought to be first studied by Prentice, who presented a definition of a surrogate as well as a set of criteria. These criteria were later supplemented with the so-called proportion explained after notifying some drawbacks in Prentice's approach. Subsequently, the evaluation exercise was framed within a meta-analytic setting, thereby overcoming difficulties that necessarily surround evaluation efforts based on a single trial. The meta-analytic approach for continuous outcomes is briefly reviewed. Advantages and problems are highlighted by means of two case studies, one in schizophrenia and one in ophthalmology, and a simulation study.One of the critical issues for the broad adoption of methodology like the one presented here is the availability of flexible implementations in standard statistical software. Generically applicable SAS macros and R functions are developed and made available to the reader. 相似文献