University of Arkansas

About: University of Arkansas is a education organization based out in Fayetteville, Arkansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17225 authors who have published 33329 publications receiving 941102 citations. The organization is also known as: Arkansas & UA.

Integrating legacy soil phosphorus into sustainable nutrient management strategies for future food, bioenergy and water security

Abstract: Legacy phosphorus (P) that has accumulated in soils from past inputs of fertilizers and manures is a large secondary global source of P that could substitute manufactured fertilizers, help preserve critical reserves of finite phosphate rock to ensure future food and bioenergy supply, and gradually improve water quality. We explore the issues and management options to better utilize legacy soil P and conclude that it represents a valuable and largely accessible P resource. The future value and period over which legacy soil P can be accessed depends on the amount present and its distribution, its availability to crops and rates of drawdown determined by the cropping system. Full exploitation of legacy P requires a transition to a more holistic system approach to nutrient management based on technological advances in precision farming, plant breeding and microbial engineering together with a greater reliance on recovered and recycled P. We propose the term ‘agro-engineering’ to encompass this integrated approach. Smaller targeted applications of fertilizer P may still be needed to optimize crop yields where legacy soil P cannot fully meet crop demands. Farm profitability margins, the need to recycle animal manures and the extent of local eutrophication problems will dictate when, where and how quickly legacy P is best exploited. Based on our analysis, we outline the stages and drivers in a transition to the full utilization of legacy soil P as part of more sustainable regional and global nutrient management.

Silicon Carbide Power MOSFET Model and Parameter Extraction Sequence

Abstract: A compact circuit simulator model is used to describe the performance of a 2-kV, 5-A 4-H silicon carbide (SiC) power DiMOSFET and to perform a detailed comparison with the performance of a widely used 400-V, 5-A Si power MOSFET. The model's channel current expressions are unique in that they include the channel regions at the corners of the square or hexagonal cells that turn on at lower gate voltages and the enhanced linear region transconductance due to diffusion in the nonuniformly doped channel. It is shown that the model accurately describes the static and dynamic performance of both the Si and SiC devices and that the diffusion-enhanced channel conductance is essential to describe the SiC DiMOSFET on-state characteristics. The detailed device comparisons reveal that both the on-state performance and switching performance at 25degC are similar between the 400-V Si and 2-kV SiC MOSFETs, with the exception that the SiC device requires twice the gate drive voltage. The main difference between the devices is that the SiC has a five times higher voltage rating without an increase in the specific on-resistance. At higher temperatures (above 100degC), the Si device has a severe reduction in conduction capability, whereas the SiC on-resistance is only minimally affected

Sperm Mobility: A Primary Determinant of Fertility in the Domestic Fowl (Gallus domesticus)

Abstract: Previous research demonstrated that sperm mobility is a quantitative trait of the domestic fowl. The trait is quantified by measuring the absorbance of an Accudenz solution after overlay with a sperm suspension and brief incubation at body temperature. In the present work, average and high sperm mobility phenotypes (n = 30 males per phenotype) were selected from a base population. Differences were found between sperm oxygen consumption (p < 0.0001), acylcarnitine content (p < 0.05), linear velocity (p < 0.001), and straightness (p < 0.001), a trajectory variable measured with the Hobson SpermTracker. Oxygen consumption and stearoylcarnitine content of sperm from the high-mobility phenotype were twice those observed with sperm from average males, implying a pivotal role for mitochondria. On the basis of these results, a graded relationship was predicted between fertility and sperm mobility. Males (n = 48) were chosen at random from another base population, sperm mobility was measured per male, and each ejaculate was used to inseminate 8-12 hens (8 x 10(7) viable sperm per hen). When fertility was plotted as a function of sperm mobility, data points approximated a skewed logistic function. The hypothesis that vaginal immunoglobulins constitute an immunological barrier to sperm transport was tested and rejected. Therefore, we concluded that sperm mobility is a primary determinant of fertility in the fowl.

Measuring Water-Extractable Phosphorus in Manure as an Indicator of Phosphorus in Runoff

Abstract: Water-extractable P (WEP) in manure is correlated with P concentration in runoff from soils amended with manure and is, thus, an effective indicator of environmental P loss. This study sought to elucidate methodological factors affecting WEP measurement in manure and to quantify errors related to two established methods of manure WEP measurement. Dairy cow (Bos taurus) manure, poultry (Gallus gallus domesticus L.) (layer) manure, and swine (Sus scrofa domestica L.) slurry were used. Varying dry matter/distilled water ratios (1 to 20:200) revealed that greater dilution of manure dry matter increased WEP (mean 1.8-5.4 g kg -1 ), likely because of the dissolution of calcium phosphates. Increasing shaking time from 1 min to 24 h, increased manure WEP concentration (average 3.7-8.2 g kg -1 ). Filtration with Whatman 1 paper filters resulted in significantly higher WEP measurements in-dairy and poultry manure (4.1 g kg -1 ) than with a 0.45-μm filtration (3.7 g kg -1 ). No significant difference was observed in the swine slurry. A rainfall-runoff experiment using simulated rainfall was conducted to determine the effect of the individual factors on predicting dissolved-reactive P (DRP) concentration in runoff. Comparison of regression coefficients relating manure WEP to runoff DRP concentration revealed an optimum shaking time between 30 min and 2 h, but did not support any single manure/distilled water ratio or filtration method. Replication of two established methods of manure WEP measurement resulted in coefficients of variation of 0.01 to 0.12. Results of this study support the use of a single method with a fixed manure/distilled water ratio for liquid and dry manures.

Natural Antioxidant Extract from Fenugreek (Trigonella foenumgraecum) for Ground Beef Patties

Abstract: Ground beef patties (75% lean) containing synthetic antioxidants, or Fenugreek (Trigonella foenumgraecum) extracts were cooked to internal temperature 70°C, and evaluated for storage stability at 4°C. Thiobarbituric acid values of raw or cooked samples containing fenugreek extracts were lower than controls (P<0.05). Fenugreek extracts delayed the induction period of oxidative rancidity. No differences were observed in psychrotrophic bacterial counts, and samples containing fenugreek extracts had lower Hunterlab “a” and higher “b” values. Samples with Fenugreek extracts had better oxidative stability and Fenugreek may be a promising natural antioxidant source.