Beveling of fine micropipette electrodes by a rapid precision method

A technique has been developed for embedding alumina particles 0.05 micrometer in size in the surface of a polyurethane film laid on glass. This abrasive surface is used for rapid, precise, and reliable beveling of Pyrex micropipettes with tip diameters at least as small as 0.1 micrometer. In the snapping turtle retina the beveled electrodes give much better cell penetration and intracellular response stability than unbeveled electrodes of considerably higher proach to this problem.     

A risk efficiency analysis of backgrounding and finishing steers on pasture in Saskatchewan, Canada

This paper combines an agricultural production decision support tool, GrassGro, with economic risk efficiency theory to examine several cattle feeding options that include various grazing systems for three climatic environments in Saskatchewan, Canada. Historical weather data were used to simulate a distribution of forage and cattle production data for each of several grazing systems during a 21-year period, 1978–1998. Price variability was included by varying year 2000 prices using historical price margin changes between the buying and selling weights of cattle. The risk efficiency analysis was completed using the Mean Standard Deviation (MSD) framework, and stochastic dominance principles.

Results of the study suggested that feeding systems, which included grazing, were economically competitive with traditional feedlot feeding systems and grain farming. Finishing cattle on pasture with the addition of a barley supplement was an attractive option, especially when high pasture productivity can be achieved. In all locations, more intense systems that included pasture fertilization and provision of an energy supplement, improved production and risk efficiency. Although the average net returns of all these feeding simulations were negative, the returns of traditional grain crops were even more negative. It is these negative returns in grain operations that lead to the incentive for producers to diversify into cattle production. Despite the negative net returns, the cash flow (range −$15.59 to $407.54 ha⁻¹) was mostly positive in all three locations.     

Carotene, tocopherol, and ascorbate contents in subspecies of Brassica oleracea

Cruciferous vegetables contain high levels of vitamins that can act as antioxidants, compounds that may protect against several degenerative diseases. The edible portions of 50 broccoli and 13 cabbage, kale, cauliflower, and Brussels sprouts accessions were assayed to determine variation in alpha-carotene, beta-carotene, alpha-tocopherol, gamma-tocopherol, and ascorbate contents within and between subspecies of Brassica oleracea. Ascorbate content was estimated in fresh samples using HPLC. Tissues for carotene and tocopherol analysis were lyophilized prior to extraction. Carotene and tocopherol concentrations were simultaneously measured using a reverse phase HPLC system. Results indicate that there is substantial variation both within and between subspecies. Kale had the highest levels of vitamins, followed by broccoli and Brussels sprouts with intermediate levels and then by cabbage and cauliflower, with comparatively low concentrations. Variability in vitamin content among the broccoli accessions suggests that potential health benefits that accrue with consumption are genotype dependent.     

The movement of metals applied to soils in sewage effluent

Water, Air, & Soil Pollution - Land treatment is increasingly being utilized as a method of waste disposal for both sewage effluent and sludges. While there has been considerable attention...     

Volatilization of 1,3-Dichloropropene under Different Application Methods

Atmospheric emission of volatilepesticides can be a significant source of airpollution. A field study was conducted to reduce1,3-dichloropropene (1,3-D) emission by applying thechemical via subsurface drip irrigation with a reduceddosage (4.7 g m^-2 or 47 kg ha^-1). Comparisons were made between ashallow drip application with the plot covered with apolyethylene film, a deep drip application and aconventional shank injection (at 11.2 g m^-2) withthe plots left as bare soil surface. For eachtreatment, seven replicated active flux chambers wereused continuously to measure 1,3-D loss until nomeasurable emission was found. Results indicated thattotal 1,3-D emission loss was over 90% for the shankinjection, and 66 and 57% for the shallow and deepdrip plots, respectively. The emission loss wasextremely high for shank injection since about 80%were lost from the bed furrows where the slantedshanks left uncompacted fractures. On mass basis, theshank plot lost 10.4 g m^-2, whereas the shallow-and deep-drip plots lost 3.1 and 2.7 g m^-2,respectively. Applying 1,3-D using subsurface dripirrigation with reduced dosage has a great potentialfor emission reduction.     

RothCUK – a dynamic modelling system for estimating changes in soil C from mineral soils at 1-km resolution in the UK

We describe the development and application of an integrated data and modelling system for estimating soil carbon (C) fluxes from mineral soils caused by changes in climate, land use and land management at 1‐km resolution in the UK (RothCUK). The system was developed with the aim of improving methods for United Nations Framework Convention on Climate Change (UNFCCC) and Kyoto Protocol accounting and integrates national scale data sets of soil properties, land use and climate with the Rothamsted carbon model (RothC). A preliminary estimate of soil C fluxes because of land use change (LUC) over the period 1990–2000 is presented as an example application of the system. RothCUK shows LUC to be a net source of CO₂ from 1990 to 2000 although the RothC estimate was smaller (6488 kt C) than the estimate from the single exponential model (SEM) method currently used to calculate C fluxes due to LUC for the UK National Greenhouse Gas Inventory (mean: 9412 kt C). Based on previous studies, an uncertainty range in our estimates of ±50–100% seems plausible. In agreement with the SEM, RothCUK suggests that the largest single contributor to soil C fluxes from LUC was conversion of grassland to arable land. Differences between the results may be attributed to differences in the two models and the assumptions and underlying data used in making the calculations. The RothCUK system provides a powerful method for estimating changes in soil C stocks, enabling areas and management systems with particularly large changes in soil C stocks to be located at fine resolution.     

Microbiology of roots infected with the take-all fungus (Gaeumannomyces graminis var. tritici) in phased sequences of winter wheat

Bacteria with possible relevance to the growth of the take-all fungus were counted from surfaces of lesioned and healthy roots of wheat growing in soil from a field monoculture system. Numbers showed short-term seasonal and long-term monocultural changes, which seemed to be genuinely associated with the monoculture. Bacteria were more numerous on lesioned than healthy roots. Only bacteria inhibitory to growth of Gaeumannomyces graminis on agar and Pseudomonas spp showed consistent changes irrespective of the source of the roots. Relationships were considered between the microflora on lesioned tissue and (a) severity of disease on roots supplying the lesions, and (b) infection produced on axenic seedlings inoculated with the lesioned tissue. Only total bacterial counts on the lesions from tillering and mature plants were positively correlated with disease on the donor roots. Only inhibitory bacteria on lesions from tillering and mature plants were positively correlated with disease on test seedlings. Pseudomonas spp showed no correlations. Interpretation of data differed with age of plant and the sequence in the monoculture from which plants or soil came.