bluuebunny/crossref_metadata_2025 huggingface dataset:
Understandings of the nature of science and decision making on science and technology based issues
Authors: Bell Randy L. , Lederman Norman G.
Published: March 2003

The purpose of this investigation was to explicate the role of the nature of science in decision making on science and technology based issues and to delineate factors and reasoning associated with these types of decisions. Twenty‐one volunteer participants purposively selected from the faculty of geographically diverse universities completed an open‐ended questionnaire and follow‐up interview designed to assess their decision making on science and technology based issues. Participants were subsequently placed in one of two groups based upon their divergent views of the nature of science as assessed by a second open‐ended questionnaire and follow‐up interview. Profiles of each group's decision making were then constructed, based on participants' previous responses to the decision making questionnaire and follow‐up interviews. Finally, the two groups' decisions, decision influencing factors, and decision making strategies were compared. No differences were found between the decisions of the two groups, despite their disparate views of the nature of science. Participants in both groups based their decisions primarily on personal values, morals/ethics, and social concerns. While all participants considered scientific evidence in their decision making, most did not require absolute “proof,” even though many participants held absolute conceptions of the nature of science. Overall, the nature of science did not figure prominently in either group's decisions. These findings contrast with basic assumptions of current science education reform efforts and call for a re‐examination of the goals of nature of science instruction. Developing better decision making skills—even on science and technology based issues—may involve other factors, including more value‐based instruction and attention to intellectual/moral development. © 2003 Wiley Periodicals, Inc. Sci Ed 87:352–377, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10063
Innovative science within and against a culture of “achievement”
Authors: Carlone Heidi B.
Published: March 2003

As science educators struggle to reform science education, we need a better understanding of the conundrums associated with the ways educators enact innovative science within and against the “academic,” “rigorous,” and “elite” sociohistorical constructions of science. I ethnographically investigated the meanings of an innovative, reform‐based curriculum (Active Physics) in various micro (classroom) and macro (school and community) contexts. I conducted the study in a high school serving primarily upper middle class students, the majority of whom (97%) planned to attend college. I explored how meanings of the curriculum transformed as the curriculum traveled across space and time. While certain aspects of the context enabled innovative science (e.g., support from the administration, pressure to serve a wider range of students), other aspects of the context constrained the potential of the curriculum (e.g., the need to establish for students, parents, and administrators the legitimacy of Active Physics as “real” and “rigorous” physics). Using practice theory to understand the influence of context and agency in shaping school science practice, this study demonstrates the potential for viewing meanings of science in local settings as partially fluid entities, sometimes reproducing and sometimes contesting sociohistorical legacies. © 2003 Wiley Periodicals, Inc.Sci Ed87:307–328, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10071
Evolution of KL satellite of F in CaF2
Authors: Uda M. , Yamamoto T. , Ogyu Y. , Yamashita D. , Perera R. C. C. , Mukoyama T.
Published: March 2003

Photoexcited F Kα satellite spectra of CaF2 were studied as a function of excitation energy from threshold. The observed spectra show that the intensity evolution of the KL satellite line is not a monotonic function increasing with excitation energy, in contrast to the prediction from the conventional shake model, but has a small bump. Comparison with the Hartree–Fock calculations indicates that the origin of the bump can be ascribed to resonances of multi‐electron excitation processes in photoabsorption. Copyright © 2003 John Wiley & Sons, Ltd.
Calculation of attenuation and x‐ray fluorescence intensities for non‐parallel x‐ray beams
Authors: Malzer Wolfgang , Kanngießer Birgit
Published: March 2003

With the nowadays widespreaded use of x‐ray optics in x‐ray fluorescence analysis, large convergence or divergence angles can occur. This experimental situation violates a basic assumption of the usual fundamental parameter quantification procedure. In order to take beam divergences in micro x‐ray fluorescence analysis into account, a way of calculating fluorescence intensities numerically by Monte Carlo integration is described. For three examples of typical micro‐XRF set‐ups the fluorescence intensities and their deviation from the parallel beam geometry are calculated. Furthermore, we propose a new approach with ‘equivalent angles’ which correct for the beam divergences in fundamental parameter methods. Copyright © 2003 John Wiley & Sons, Ltd.
On the structure theory of the Iwasawa algebra of a p-adic Lie group
Authors: Venjakob Otmar
Published: March 2003

This paper is motivated by the question whether there is a nice structure theory of finitely generated modules over the Iwasawa algebra, i.e. the completed group algebra, 6 of a p-adic analytic group G. For G without any p-torsion element we prove that 6 is an Auslander regular ring. This result enables us to give a good definition of the notion of a pseudo-null 6-module. This is classical when G=Êkp for some integer kS1, but was previously unknown in the non-commutative case. Then the category of 6-modules up to pseudo-isomorphisms is studied and we obtain a weak structure theorem for the Êp-torsion part of a finitely generated 6-module. We also prove a local duality theorem and a version of Auslander-Buchsbaum equality. The arithmetic applications to the Iwasawa theory of abelian varieties are published elsewhere.
An index inequality for embedded pseudoholomorphic curves in symplectizations
Authors: Hutchings Michael
Published: March 2003

Let D be a surface with a symplectic form, let J be a symplectomorphism of D, and let Y be the mapping torus of J. We show that the dimensions of moduli spaces of embedded pseudoholomorphic curves in Â2Y, with cylindrical ends asymptotic to periodic orbits of J or multiple covers thereof, are bounded from above by an additive relative index. We deduce some compactness results for these moduli spaces. This paper establishes some of the foundations for a program with Michael Thaddeus, to understand the Seiberg-Witten Floer homology of Y in terms of such pseudoholomorphic curves. Analogues of our results should also hold in three dimensional contact topology.
EFFECTS OF TWENTY-FIVE YEARS OF FERTILIZER USE ON MAIZE AND WHEAT YIELDS AND QUALITY OF AN ACIDIC SOIL IN THE WESTERN HIMALAYAS
Authors: SHARMA S. P. , SUBEHIA S. K.
Published: March 2003

In a field experiment initiated in the 1972/73 rabi season (November–March) on an acidic soil in the western Himalayas of India, continuous cropping for 25 years with nitrogen fertilizer alone reduced the grain yields of maize (Zea mays) and wheat (Triticum aestivum) to almost zero. Based on five-year moving average values, the application of 100% NP resulted in a reduction of grain yields of maize and wheat crops by 67 and 19% respectively during 1994 to1998 compared with 1973 to 1977. The crops did not respond to K application during the initial years of cropping, but a significant reduction in crop yields was observed in the absence of K after five years of continuous cropping. With the integrated use of chemical fertilizers (100% NPK) and farmyard manure, the pooled grain yields of 25 years were about 4600 and 3300 kg ha−1 for maize and wheat respectively. Corresponding yields with the use of chemical fertilizers and lime (100% NPK + lime) were 4000 and 3100 kg ha−1 respectively. The use of nitrogenous fertilizer alone aggravated the problem of soil acidity by lowering the pH from 5.8 to 4.7 after 25 years. In almost all the treatments, the organic carbon content increased: a marginal decrease occurred in the 100% N and control plots. Even under optimum application rates, the available N and K status decreased with time. Again with the exception of the control plots, the contents of the Diphenyl Triamine Penta Acetic Acid-extractable micronutrients were sufficiently high for the crops in all the treatments. The available sulphur decreased with the use of di-ammonium phosphate as the P source, which drastically reduced the yields of both crops. In the N-alone treatment the weed flora also changed with the change in soil environment. There is a need to review fertilizer recommendations in this region of India.
EFFECTS OF WATER AVAILABILITY AND VINE HARVESTING FREQUENCY ON THE PRODUCTIVITY OF SWEET POTATO IN SOUTHERN MOZAMBIQUE. II. CROP WATER USE
Authors: GOMES F. , CARR M. K. V.
Published: March 2003

In Mozambique, the sweet potato (Ipomoea batatas) is grown in the dry season in areas with a high water table, or as an irrigated crop. It is also grown in the rainy season when short-term droughts can occur. This paper reports the results of experiments designed to evaluate the effects of water availability and vine-harvesting practices on actual crop water use (cv. TIS 2534), during two contrasting seasons in the south of the country. Rain-fed crops extracted water to soil depths (variable sandy loam) of 0.75 m, with most (90%) taken from the top 0.25 m. Well-irrigated crops apparently obtained some (10%) water from below 0.75 m, but most (75%) came from the upper 0.25 m. Total water use from well-watered crops was about 800 mm during the rains, and 550 mm during the dry season. The corresponding values for rain-fed crops were 360 and 180 mm respectively. Peak rates of water use averaged 8 mm d−1 in the rainy season, and 5–6 mm d−1 in the dry season. Water use was not modified by the frequency of vine harvests. Actual rates of evapotranspiration fell below maximum values when the soil water deficit exceeded only 20 mm. By comparison, the maximum depth of extractable water in the root zone was 80–90 mm. The crop coefficients (Kc) for each stage of growth were consistent over both seasons and estimated to be: 0.55–0.7 (crop establishment), 1.1–1.2 (mid-season), and 0.8 (end-season).
EVALUATION OF ON-FARM SOIL FERTILITY RESEARCH IN THE RAINFED LOWLAND RICE FIELDS OF SUKUMALAND, TANZANIA
Authors: MEERTENS H. C. C. , KAJIRU G. J. , NDEGE L. J. , ENSERINK H. J. , BROUWER J.
Published: March 2003

The first ever on-farm soil fertility research in the rainfed lowland rice (Oryza sativa) fields of Sukumaland, in northwest Tanzania, was carried out between 1990 and 1996 in response to farmers' complaints about declining rice yields. From diagnosis to extension, the research approach followed that of the International Maize and Wheat Improvement Center (CIMMYT). In 1990/91, rice yields in the Maswa district increased sharply when nitrogen at a rate of 30 kg ha−1 in the form of urea was broadcast in flooded rice fields at tillering. Similar research was subsequently conducted in other parts of Sukumaland to evaluate this type of low-dose nitrogen application under varying circumstances. In 1995/96, higher doses of nitrogen (60 and 120 kg ha−1) and a high dose of phosphorus (17.5 kg ha−1) were applied for comparison in Sengerema district. Between 1990 and 1996, the average increase in rice yield from the application of 30 kg N ha−1 varied between 463 and 986 kg ha−1. In 1995/96, the same application of N was more economical than both 60 and 120 kg N ha−1, and no phosphorus deficiency was found. The deteriorating ratio between the price of rice at the farm gate and that of urea, however, threatens the adoption of this technology by farmers. Adaptability analysis showed that the relatively small differences in response per field (environment) in all years did not justify a need for multiple different extension messages. Until more detailed recommendations can be made, therefore, a single dose of 30 kg N ha−1, in the form of urea, applied to rice at tillering is recommended for the whole of Sukumaland to reverse the decline in yields. Further on-farm research should concentrate on improving the efficiency of nitrogen fertilization and on determining the optimum rates of other major nutrients to refine this initial recommendation.
FACTORS AFFECTING THE ADOPTION OF LEGUMINOUS COVER CROPS IN NIGERIA AND A COMPARISON WITH THE ADOPTION OF NEW CROP VARIETIES
Authors: MORSE S. , McNAMARA N.
Published: March 2003

This paper presents the results of:

(a) On-farm trials (eight) over a two-year period designed to test the effectiveness of leguminous cover crops in terms of increasing maize yields in Igalaland, Nigeria.

(b) A survey designed to monitor the extent of, and reasons behind, adoption of the leguminous cover crop technology in subsequent years by farmers involved, to varying degrees, in the trial programme.

Particular emphasis was placed on comparing adoption of leguminous cover crops with that of new crop varieties released by a non-governmental organization in the same area since the mid 1980s. While the leguminous cover crop technology boosted maize grain yields by 127 to 136% above an untreated control yield of between 141 and 171 kg ha−1, the adoption rate (number of farmers adopting) was only 18%. By way of contrast, new crop varieties had a highly variable benefit in terms of yield advantage over local varieties, with the best average increase of around 20%. Adoption rates for new crop varieties, assessed as both the number of farmers growing the varieties and the number of plots planted to the varieties, were 40% on average. The paper discusses some key factors influencing adoption of the leguminous cover crop technology, including seed availability. Implications of these results for a local non-governmental organization, the Diocesan Development Services, concerned with promoting the leguminous cover crop technology are also discussed.
EVALUATION OF INTEGRATED STRIGA HERMONTHICA CONTROL TECHNOLOGIES UNDER FARMER MANAGEMENT
Authors: SCHULZ S. , HUSSAINI M. A. , KLING J. G. , BERNER D. K. , IKIE F. O.
Published: March 2003

On-farm trials were conducted in the northern Guinea savanna of Nigeria. The objective was to compare integrated Striga hermonthica control measures (soyabean or cowpea trap crop in the first year followed by maize resistant to Striga in the second year) with farmers' traditional practices (cereal-based cropping systems) under farmer-managed conditions.

Integrated control proved to be highly effective in terms of reducing Striga incidence both in terms of reduced seed density in the soil and decreased infection in maize. Resistant maize following the soyabean trap crop yielded 1.58 t ha−1 of grain and out-yielded local maize following traditional practices by more than 80%. Similarly, the overall productivity over the period of the experiment was highest with the integrated control treatment using soyabean. Conversely, resistant maize after the cowpea trap crop yielded only 0.92 t ha−1 (possibly due to the poor performance of the cowpea crop in the first year), and maize yields were similar to those obtained with farmer practices. Initial Striga seed density in the soil was negatively correlated (r = −0.33) with soil nitrogen, but nitrogen-fertilizer application rates did not seem to affect the level of Striga infection in maize.
PROFESSOR NORMAN SIMMONDS
Authors: Lockwood Rob
Published: March 2003

Norman Simmonds was an outstanding member of the group of British Tropical Agriculturalists who served overseas with great distinction during and immediately after the Second World War. He was then equally successful and influential in British academia and as an internationally respected researcher. He will be remembered as a plant breeder, a geneticist, a teacher and author, and as incisive commentator on current affairs in tropical agriculture. Simmonds had a long association with Experimental Agriculture, serving on its Editorial Board from 1978 to 1998, and as a Book Review Editor from 1978 to 1987.
ON-FARM EXPERIMENTS WITH MAIZE-MUCUNA SYSTEMS IN THE LOS TUXTLAS REGION OF VERACRUZ, SOUTHERN MEXICO. II. MUCUNA VARIETY EVALUATION AND SUBSEQUENT MAIZE GRAIN YIELD
Authors: EILITTÄ M. , SOLLENBERGER L. E. , LITTELL R. C. , HARRINGTON L. W.
Published: March 2003

Despite interest in mucuna (Mucuna pruriens) as a green manure/cover crop, biomass production of its accessions has been poorly quantified, including in the Los Tuxtlas region of Veracruz, Mexico where smallholders have used maize (Zea mays)-mucuna systems increasingly since 1991. This on-farm research compared the biomass production of three mucuna varieties (white-, mottled-, and black seeded) in a rotational maize-mucuna system. Mucuna was sole-cropped during the first season (on eleven and five fields in 1996 and 1997 respectively), and its impact on the second-season maize yield was measured (on seven fields in 1996). White and mottled varieties produced equal biomass (7.92 and 6.74 t ha−1 in 1996 and 1997 respectively), and more than the black variety (6.85 and 4.90 t ha−1 in 1996 and 1997 respectively). Mucuna increased 1996/97 second-season maize grain yields by 50 % (from 0.97 to 1.46 t ha−1). Plots previously cropped with white and mottled varieties produced greater maize yield (1.55 t ha−1) than did black-variety plots (1.29 t ha−1). The research confirmed the higher productivity of the white and mottled varieties and the potential of the rotational system. Allocating the more desirable first-season growth period to mucuna and the riskier second season to maize is problematic, but the system may have potential in the region as a short-term fallow that permits second-season maize production.
ON-FARM EXPERIMENTS WITH MAIZE-MUCUNA SYSTEMS IN THE LOS TUXTLAS REGION OF VERACRUZ, MEXICO. I. MUCUNA BIOMASS AND MAIZE GRAIN YIELD
Authors: EILITTÄ M. , SOLLENBERGER L. E. , LITTELL R. C. , HARRINGTON L. W.
Published: March 2003

Maize (Zea mays)-mucuna (Mucuna pruriens) systems have been promoted to the smallholder farmers of the Los Tuxtlas region of southeastern Veracruz, Mexico. To determine on-farm performance, an agronomic assessment was conducted in 1995–97 replicating farmer conditions in four fields. Treatments were first- and second-season maize with first-season mucuna (system Zm-Mp/Zm), first-season maize with first- and second-season mucuna (system Zm-Mp/Mp), second-season maize following first-season mucuna (system Mp/Zm), and first- and second-season maize, no mucuna control. Data on mucuna biomass amount and quality as well as maize yield, yield components, and nutrient status were collected. Highest mucuna biomass was obtained in system Mp/Zm (leaf-stem-mulch biomass in 1996/97, 7.34 t ha−1, 147 kg ha−1 N), followed by systems Zm-Mp/Mp (5.06 t ha−1, 101 kg N ha−1) and Zm-Mp/Zm (2.75 t ha−1, 50 kg N ha−1). Second-season maize yield was increased over that of the control by 45–58% (0.15–0.23 t ha−1) in system Zm-Mp/Zm and by 118% (0.60 t ha−1) in system Mp/Zm. Mucuna did not increase first-season maize yield. Climatic constraints make second-season maize production risky and yield increases due to mucuna are low in absolute terms, perhaps not offsetting labour costs (systems Zm-Mp/Zm and Mp/Zm) or loss of first-season maize (Mp/Zm).
ROOT CHARACTERISTICS IN COWPEA RELATED TO DROUGHT TOLERANCE AT THE SEEDLING STAGE
Authors: MATSUI T. , SINGH B. B.
Published: March 2003

Cowpea (Vigna unguiculata) has relatively higher drought tolerance than other legume crops. It is widely grown in semi-arid regions, particularly in West Africa. One objective of the present study was to determine the effects of soil moisture stress on the length, dry matter and distribution of the roots of two cowpea varieties with different drought tolerances. Another objective was to evaluate the pin-board root-box as a method for identifying the role of root characteristics in drought tolerance. Two cowpea varieties, IT96D-604 (drought tolerant) and TVu7778 (drought susceptible), were used in this study. There were three watering treatments, T1 (well-watered), T2 (mild water stress) and T3 (severe water stress). Between varieties, there were no significant differences in shoot and root characteristics except for leaf area in T1. Under T2, the shoot:root ratio (S:R ratio) of IT96D-604 was significantly decreased compared with that under T1 as a result of the increase in root dry matter and decrease in leaf area without significant differences in total dry matter. In addition, the root dry matter per leaf area, which indicates the capacity to absorb water, of IT96D-604 was significantly higher than that of TVu7778. Under T3, the total dry matter of TVu7778 was about one third of those of the other treatments for the same variety, whereas that of IT96D-604 was more than half. Regarding root distribution, the centres of root dry matter and root length density of both varieties moved downwards significantly under water-stress conditions compared with those of the well-watered condition. This tendency was more pronounced in IT96D-604 than in TVu7778. Drought tolerance in IT96D-604 was associated with the increase in root dry matter per leaf area under mild water-stress conditions, and downward movement of roots (increasing access and use of soil moisture in deep soil layers) under mild and severe water stress conditions. In addition, the root-box method was versatile and can be used for studying root responses to edaphic factors relevant to root growth.
Determination of macro elements in alfalfa and white clover by near-infrared reflectance spectroscopy
Authors: MORÓN A. , COZZOLINO D.
Published: March 2003

Near-infrared reflectance spectroscopy was used to assess the mineral composition of both alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.). Alfalfa (n=230) and white clover (n=97) plant samples from different locations in Uruguay representing a wide range of soil types were analysed. The samples were scanned for reflectance in a NIRSystems 6500 monochromator (NIRSystems, Silver Spring, MD, USA). Predictive equations were developed using modified partial least squares (MPLS) with cross validation to avoid overfitting. The coefficients of determination in calibration (R_{\rm cal}^{2}) and the standard errors in cross validation (SECV) were 0·93 (SECV: 1·6), 0·95 (SECV: 1·3), 0·93 (SECV: 1·9), 0·88 (SECV: 2·7), 0·82 (SECV: 0·3) and 0·75 (SECV: 4·7) for alfalfa and 0·98 (SECV: 0·8), 0·52 (SECV: 0·8), 0·97 (SECV: 2·7), 0·83 (SECV: 3·1), 0·82 (SECV: 1·9) and 0·45 (SECV: 2·6) for white clover, for N, Ca, K, P, Mg and S in g/kg on a dry weight respectively. Calcium, nitrogen and potassium were well predicted by NIRS in both alfalfa and white clover samples.
The integration of herbicides with mechanical weeding for weed control in winter wheat
Authors: BLAIR A. M. , JONES P. A. , INGLE R. H. , TILLETT N. D. , HAGUE T.
Published: March 2003

Two systems for integrated weed control in winter wheat based around the combination of herbicides with cultural control have been investigated and compared with conventional practice in experiments between 1993 and 2001. These systems were (a) an overall spray of a reduced herbicide dose followed by spring tine harrow weeding and (b) the combination of herbicide applied over the crop row with a novel vision guided inter-row hoe. The latter required wheat to be established with a wider (22 cm) inter-row spacing than standard (12·5 cm). Experiments over 10 sites/seasons indicated that this increased spacing could be achieved without yield loss. Trials to measure the accuracy of hoe blade lateral positioning using the vision guidance system indicated that error was normally distributed with standard deviation of 12 mm and a bias that could be set to within 1 cm. This performance could be maintained through the normal hoeing period and the crop row location and tracking techniques were robust to moderate weed infestation. In the absence of weeds neither overall harrowing nor inter-row hoeing affected winter wheat yield, 1000-seed weight or specific weight in 12·5 or 22 cm rows. When combined with inter-row hoeing, manually targeted banded applications of fluazolate, pendimethalin or isoproturon reduced grass weed levels and increased yields over untreated controls, though better results were obtained using overall herbicides. However, improvements would be possible with more accurately targeted herbicide applications and more effective inter-row grass weed control. The implications and costs of using such an integrated system are discussed and requirements for future developments identified.
Assessing and predicting the local performance of spring wheat varieties
Authors: ÖFVERSTEN J. , JAUHIAINEN L. , NIKANDER H. , SALO Y.
Published: March 2003

Each crop variety has a genotype-specific ability to maintain performance over a wide range of environmental conditions. This ability is usually referred to as the sensitivity or adaptability of a variety. Such an ability is an important property, because farmers naturally want to use varieties which perform well in their own fields. Assessing sensitivity has, however, proved difficult, because of problems involved in defining and measuring the wide diversity of natural environments. These problems often lead to split statistical analyses of trial data or statistical models including explanatory variables with no biological interpretation. That causes ambiguity in statistical inference and prediction. The present study shows how the latest advances in statistical research can be applied to overcome some of these difficulties. A key point is to use the conditional expectation of the yield given the environment as a latent explanatory variable. In this way the predicted yields of different varieties can be estimated at any expected environmental yield level. Discussion is restricted to yield data but similar methods can be applied to other performance characters. The Finnish statutory variety trial data are used to illustrate the methods and the results.
The impact of diversification of a rice–wheat cropping system on crop productivity and soil fertility
Authors: SINGH V. K. , SHARMA B. B. , DWIVEDI B. S.
Published: March 2003

Field experiments were conducted at the Crop Research Centre of Govind Ballabh Pant University of Agriculture and Technology, Pantnagar during 1996/97 and 1997/98. Each experiment comprised 10 crop sequences: (a) wheat–rice, (b) chickpea–rice, (c) lentil–rice, (d) pea–rice, (e) wheat–mungbean green manure–rice, (f) wheat–Sesbania green manure–rice, (g) wheat–fodder–rice, (h) chickpea–fodder–rice, (i) lentil–fodder–rice and (j) pea–fodder–rice, in a randomized block design with four replications. The crop sequences were compared in terms of economic rice equivalent yield (REY), protein production, apparent nutrient balances and effect on soil fertility status. Amongst crop sequences involving two crops each year (200% cropping intensity), chickpea–rice gave highest REY and protein production. Of the sequences involving three crops each year (300% cropping intensity), chickpea–fodder–rice and wheat–fodder–rice were superior to others. The P balances were positive for all sequences, whereas K balances were generally negative except for sequences involving green manure legumes. Green manuring with Sesbania or mungbean helped restore soil fertility, indicating the advantage of green manure for higher productivity and sustainability of rice–wheat system. Chickpea–rice and chickpea–fodder–rice appeared promising alternatives to rice–wheat crop sequence.
Genetic and environmental variation for tocopherol content and composition in sunflower commercial hybrids
Authors: VELASCO L. , FERNÁNDEZ-MARTÍNEZ J. M. , GARCÍA-RUÍZ R. , DOMÍNGUEZ J.
Published: March 2003

Tocopherols are the most important compounds having antioxidant activity in sunflower seeds. The objective of the present research was to study the genetic and environmental variation for tocopherol content and composition in sunflower. Thirty-six sunflower hybrids were grown at 13 locations across all major areas of sunflower cultivation in southern Spain. Seed yield, 100 seed weight, oil content and tocopherol content and composition were determined. Tocopherol content ranged from 314·5 to 1024·5 mg/kg seed and from 562·8 to 1872·8 mg/kg oil. The tocopherol fraction was largely composed of alpha-tocopherol, which accounted for 88·4% to 96·3% of the total tocopherols. Both genotypic and environmental effects were significant for tocopherol content and composition. For alpha-, beta- and total tocopherol content, the effect of the genotype was larger than that of the environment, whereas the latter had a greater effect on gamma-tocopherol content. Genotype×location interaction was significant for alpha-, gamma- and total tocopherol content. Tocopherol content was not correlated with seed oil or seed yield, indicating the possibility of selecting for this trait without affecting the performance of the genotypes.
Correspondence
Authors: Allison M. F. , Fowler J. H. , Allen E. J.
Published: March 2003

In Volume 136, 407–426, you published a paper entitled ‘Responses of potato (Solanum tuberosum) to potassium fertilizers’ by M. F. Allison, J. H. Fowler and E. J. Allen. We consider that the authors' conclusions were not justified and they have mis-interpreted and criticized earlier published work. One of their criticisms is levelled at the use of exchangeable potassium (Kex – rapidly plant-available K) to categorize soils on the basis of the likely response of crops to an application of potassium (K) fertilizer. While Kex is not perfect, it is the best rapid method currently available (Johnston & Goulding 1990). To support their contention about Kex, the authors quote in Table 15 data from Rothamsted experiments done in the late 1950s and early 1960s. They state that despite the large amounts of K applied in fertilizers and manures the effect on Kex was relatively small. This comment fails to recognize that it is the K balance (K applied minus K removed) that must be related to Kex, not the K applied, and the inevitable transfer of part of the K balance from Kex to fixed K (less readily available K). Warren & Johnston (1962) showed that on these soil types as much as 60% of the K balance is rapidly transferred to fixed K.
Effects of slurry application method and timing on grass silage quality
Authors: LAWS J. A. , SMITH K. A. , JACKSON D. R. , PAIN B. F.
Published: March 2003

Small-scale silos (60-litre polyethylene barrels) were used to examine the chemical composition of grass silage after the application of slurry, at 40 m3/ha, at a range of timings, at two sites with contrasting rainfall; North Wyke, in Devon (high rainfall) and Reaseheath College, Cheshire (low rainfall). Grass plots (60 m2) received cattle slurry via surface broadcast (S), shallow injection (I) or surface placement by trailing shoe (T) techniques at 10, 6 or 2 weeks before an early silage (first) cut in May/June, and 6 or 2 weeks before a second cut in June/July. Control plots (C) received no slurry treatment. The harvested grass was compressed and sealed in the experimental silos and samples of the herbage at ensiling and of ensilage (after >100-day fermentation) were analysed for various chemical components. Herbage yield was measured when the harvests were taken. Wetter than average weather conditions in both years resulted in silages with variable DM content (range 140–277 g/kg) being made at both sites. Generally, silages were poorly preserved with high pH and NH4+-N and low lactic acid contents. In particular, the silages from treatment S where slurry was applied 2 weeks prior to harvest exhibited characteristics indicative of clostridial growth, with high pH (range 4·0–5·2) and NH4+-N (106–213 g/kg total N) and low lactic acid (16–86 g/kg DM) contents. Damage to herbage caused by the injection tines on taller swards (treatments I at 6 and 2 weeks before cutting) was evident and the injection process was impeded by tall grass. This contributed to herbage contamination with soil and slurry on these treatments and, consequently, to poor silage fermentation. Silages made with slurry application method T at all timings showed improved fermentation characteristics compared with the other treatments, particularly at North Wyke. The results indicate that silage quality is unlikely to be compromised by slurry applications made in early spring, during February, March or even in April, where these are at agronomically sensible rates. Such practice will enable better utilization of slurry nitrogen (N), reducing risks of nutrient losses via leaching or surface runoff. Furthermore, shallow injection and, particularly, trailing shoe slurry application techniques may be used to increase flexibility of slurry management by allowing more immediate spreading before cutting than with conventional surface broadcasting, without detriment to silage quality.
Uptake from soil and distribution of 95Zr in Chinese cabbage
Authors: SHI J. , GUO J.
Published: March 2003

In order to quantify the radiation hazard to humans through food, both migration and distribution of 95Zr in Chinese cabbage/soil system were examined by using the radioisotope tracer technique. When 95Zr was administered with simulated irrigation or simulated rainfall, 95Zr was detected in every part of Chinese cabbage, which indicated that 95Zr could be translocated to above-ground parts. Although concentrations of 95Zr in different parts of Chinese cabbage were different in the two treatments used in the present study, the patterns of 95Zr distribution in different parts of the plant were similar. Concentration of 95Zr in each part of Chinese cabbage followed the order of root>leaf>lower part of petiole>upper part of petiole>bud in the case of simulated irrigation. Moreover, the 95Zr could be accumulated in leaves after being taken up by roots. In the simulated irrigation treatment, 95Zr concentrations were 1·7 and 2·9 times higher in the leaf than in the petiole and bud, respectively. In the case of simulated rainfall, a portion of applied 95Zr precipitated on the above-ground parts of Chinese cabbage, which led to a higher concentration here than in the case of simulated irrigation. The results of the present study clearly indicate that there is a distinct possibility that foodstuffs produced in the 95Zr-contaminated area are radioactively contaminated. More than 90% of total 95Zr in soil was retained in the upper layer (0–8 cm), which indicated 95Zr could not easily move downwards because of strong adsorption to soil.
Vibration-induced drop atomization and the
numerical simulation of low-frequency
single-droplet ejection
Authors: JAMES ASHLEY J. , SMITH MARC K. , GLEZER ARI
Published: March 2003

Vibration-induced droplet ejection is a novel way to create a spray. In this method,
a liquid drop is placed on a vertically vibrating solid surface. The vibration leads to
the formation of waves on the free surface. Secondary droplets break off from the
wave crests when the forcing amplitude is above a critical value. When the forcing
frequency is small, only low-order axisymmetric wave modes are excited, and a single
secondary droplet is ejected from the tip of the primary drop. When the forcing
frequency is high, many high-order non-axisymmetric modes are excited, the motion
is chaotic, and numerous small secondary droplets are ejected simultaneously from
across the surface of the primary drop. In both frequency regimes a crater may
form that collapses to create a liquid spike from which droplet ejection occurs. An
axisymmetric, incompressible, Navier–Stokes solver was developed to simulate the
low-frequency ejection process. A volume-of-fluid method was used to track the free
surface, with surface tension incorporated using the continuum-surface-force method.
A time sequence of the simulated interface shape compared favourably with an
experimental sequence. The dynamics of the droplet ejection process was investigated,
and the conditions under which ejection occurs and the effect of the system parameters
on the process were determined.
Direct initiation of detonation with a multi-step
reaction scheme
Authors: NG HOI DICK , LEE JOHN H. S.
Published: March 2003

The problem of direct initiation of detonation, where a powerful ignition source drives
a blast wave into a gaseous combustible mixture to generate a Chapman–Jouguet (CJ)
detonation, is investigated numerically by using a three-step chain-branching chemical
kinetic model. The reaction scheme consists sequentially of a chain-initiation and
a chain-branching step, followed by a temperature-independent chain termination.
The three regimes of direct initiation i.e. subcritical, critical and supercritical, are
numerically simulated for planar, cylindrical and spherical geometries using the
present three-step chemical kinetic model. It is shown that the use of a more detailed
reaction mechanism allows a well-defined value for the critical initiation energy to
be determined. The numerical results demonstrate that detonation instability plays
an important role in the initiation process. The effect of curvature for cylindrical and
spherical geometries has been found to enhance the instability of the detonation wave
and thus influence the initiation process. The results of these simulations are also
used to provide further verification of some existing theories of direct initiation of
detonation. It appears that these theories are satisfactory only for stable detonation
waves and start to break down for highly unstable detonations because they are
based on simple blast wave theory and do not include a parameter to model the
detonation instability. This study suggests that a stability parameter, such as the ratio
between the induction and reaction length, should be considered and a more complex
chemistry should be included in future development of a more rigorous theory for
direct initiation of detonation.
Drag, deformation and lateral migration of a
buoyant drop moving near a wall
Authors: MAGNAUDET JACQUES , TAKAGI SHU , LEGENDRE DOMINIQUE
Published: March 2003

The problem of a drop of arbitrary density and viscosity moving close to a vertical
wall under the effect of buoyancy is analysed theoretically. The case where the
suspending fluid is at rest far from the drop and that of a linear shear flow are
both considered. Effects of inertia and deformation are assumed to be small but of
comparable magnitude, so that both of them contribute to the lateral migration of the
drop. Expressions for the drag, deformation and migration valid down to separation
distances from the wall of a few drop radii are established and discussed. Inertial
and deformation-induced corrections to the drag force and slip velocity of a buoyant
drop moving in a linear shear flow near a horizontal wall are also derived.
Flow along streamwise corners revisited
Authors: RIDHA A.
Published: March 2003

In this paper we investigate the three-dimensional laminar incompressible steady flow
along a corner formed by joining two similar quarter-infinite unswept wedges along
a side-edge. We show that a four-region construction of the potential flow arises
naturally for this flow problem, the formulation being generally valid for a corner of
an arbitrary angle (π−2α), including the limiting cases of semi- and quarter-infinite
flat-plate configurations. This construction leads to five distinct three-dimensional
boundary-layer regions, whereby both the spanwise length and velocity scales of the
blending intermediate layers are O(δ), with Re−1/2 [Lt ] δ [Lt ] 1, Re being a reference
Reynolds number supposed to be large. This reveals crucial differences between
concave and convex corner flows. For the latter flow regime, the corner-layer motion
is shown to be mainly controlled by the secondary flow which effectively reduces to
that past sharp wedges with solutions being unique and existing only for favourable
streamwise pressure gradients. In this regime, the corner-layer thickness is shown
to be O(Re−0.5+α/π/δ2α/π), −½π [les ] α [les ] 0, which is much smaller than O(Re−1/2) for
concave corner flows.

Crucially, our numerical results show conclusively that, for α ≠ 0, closed streamwise
symmetrically disposed vortices are generated inside the intermediate layers, confirming
thus the prediction made by Moore (1956) for a rectangular corner, which has so
far remained unconfirmed in the literature.

For almost planar corners, three-dimensional corner boundary-layer features are
shown, as in (Smith 1975), to arise when α ∼ O(1/ln Re). On the other hand, we
show that the flow past a quarter-infinite flat plate would be attained when both
values of the streamwise pressure gradient and external corner angle (π+2α) become
O(1/ln Re) or smaller.

Numerical results for all these flow regimes are presented and discussed.
Flow past a rotating cylinder
Authors: MITTAL SANJAY , KUMAR BHASKAR
Published: March 2003

Flow past a spinning circular cylinder placed in a uniform stream is investigated via
two-dimensional computations. A stabilized finite element method is utilized to solve
the incompressible Navier–Stokes equations in the primitive variables formulation.
The Reynolds number based on the cylinder diameter and free-stream speed of the
flow is 200. The non-dimensional rotation rate, α (ratio of the surface speed and freestream
speed), is varied between 0 and 5. The time integration of the flow equations is
carried out for very large dimensionless time. Vortex shedding is observed for α < 1.91.
For higher rotation rates the flow achieves a steady state except for 4.34 < α < 4:70
where the flow is unstable again. In the second region of instability, only one-sided
vortex shedding takes place. To ascertain the instability of flow as a function of α a
stabilized finite element formulation is proposed to carry out a global, non-parallel
stability analysis of the two-dimensional steady-state flow for small disturbances. The
formulation and its implementation are validated by predicting the Hopf bifurcation
for flow past a non-rotating cylinder. The results from the stability analysis for
the rotating cylinder are in very good agreement with those from direct numerical
simulations. For large rotation rates, very large lift coefficients can be obtained via
the Magnus effect. However, the power requirement for rotating the cylinder increases
rapidly with rotation rate.
Detonation ignition from a temperature
gradient for a two-step chain-branching
kinetics model
Authors: SHARPE GARY J. , SHORT MARK
Published: March 2003

The evolution from a linear temperature gradient to a detonation is investigated for
combustible materials whose chemistry is governed by chain-branching kinetics, using
a combination of high-activation-temperature asymptotics and numerical simulations.
A two-step chemical model is used, which captures the main properties of detonations
in chain-branching fuels. The first step is a thermally neutral induction time, representing
chain initiation and branching, which has a temperature-sensitive Arrhenius
form of the reaction rate. At the end of the induction time is a transition point where
the fuel is instantaneously converted into chain-radicals. The second step is the main
exothermic reaction, representing chain termination, assumed to be temperature insensitive.
Emphasis is on comparing and contrasting the results with previous studies
that used simple one-step kinetics. It is shown that the largest temperature gradient
for which a detonation can be successfully ignited depends on the heat release rate
of the main reaction. The slower the heat release compared to the initial induction
time, the shallower the gradient has to be for successful ignition. For example, when
the rate of heat release is moderate or slow on the initial induction time scale, it was
found that the path of the transition point marking the end of the induction stage
should move supersonically, in which case its speed is determined only by the initial
temperature gradient. For steeper gradients such that the transition point propagates
subsonically from the outset, the rate of heat release must be very high for a detonation
to be ignited. Detonation ignition for the two-step case apparently does not
involve the formation of secondary shocks, unlike some cases when one-step kinetics is used.
Compressible bubbles in Stokes flow
Authors: CROWDY DARREN G.
Published: March 2003

The problem of a two-dimensional inviscid compressible bubble evolving in Stokes
flow is considered. By generalizing the work of Tanveer & Vasconcelos (1995) it
is shown that for certain classes of initial condition the quasi-steady free boundary
problem for the bubble shape evolution is reducible to a finite set of coupled nonlinear
ordinary differential equations, the form of which depends on the equation of state
governing the relationship between the bubble pressure and its area. Recent numerical
calculations by Pozrikidis (2001) using boundary integral methods are retrieved and
extended. If the ambient pressures are small enough, it is shown that bubbles can
expand significantly. It is also shown that a bubble evolving adiabatically is less likely
to expand than an isothermal bubble.
Elliptic and triangular instabilities in
rotating cylinders
Authors: ELOY CHRISTOPHE , LE GAL PATRICE , LE DIZÈS STÉPHANE
Published: March 2003

In this article, the multipolar vortex instability of the flow in a finite cylinder is
addressed. The experimental study uses a rotating elastic deformable tube filled
with water which is elliptically or triangularly deformed by two or three rollers.
The experimental control parameters are the cylinder aspect ratio and the Reynolds
number based on the angular frequency.

For Reynolds numbers close to threshold, different instability modes are visualized
using anisotropic particles, according to the value of the aspect ratio. These modes
are compared with those predicted by an asymptotic stability theory in the limit
of small deformations and large Reynolds numbers. A very good agreement is
obtained which confirms the instability mechanism; for both elliptic and triangular
configurations, the instability is due to the resonance of two normal modes (Kelvin
modes) of the underlying rotating flow with the deformation field. At least four
different elliptic instability modes, including combinations of Kelvin modes with
azimuthal wavenumbers m = 0 and m = 2 and Kelvin modes m = 1 and m = 3 are
visualized. Two different triangular instability modes which are a combination of
Kelvin modes m = −1 and m = 2 and a combination of Kelvin modes m = 0 and
m = 3 are also evidenced.

The nonlinear dynamics of a particular elliptic instability mode, which corresponds
to the combination of two stationary Kelvin modes m = −1 and m = 1, is examined
in more detail using particle image velocimetry (PIV). The dynamics of the phase and
amplitude of the instability mode is shown to be predicted well by the weakly nonlinear
analysis for moderate Reynolds numbers. For larger Reynolds number, a secondary
instability is observed. Below a Reynolds number threshold, the amplitude of this
instability mode saturates and its frequency is shown to agree with the predictions
of Kerswell (1999). Above this threshold, a more complex dynamic develops which is
only sustained during a finite time. Eventually, the two-dimensional stationary elliptic
flow is reestablished and the destabilization process starts again.