Farm-scale carbon and nitrogen fluxes in pastoral dairy production systems using different nitrogen fertilizer regimes

Nutrient Cycling in Agroecosystems - The nitrogen (N) fertilizer application rate (kg ha?1 year?1) in pastoral dairy systems affects the flow of N through the soil,...     

Identification of straight-chain fatty acids in coal extracts and their geochemical relation with straight-chain alkanes

Mono-carboxylic, straight-chain fatty acids are present in extracts of lignite and subbituminous coal (0.4–1.0 wt%, daf basis), but not in those of a bituminous coal. They are removed with nearly equal ease by both solvent and supercritical gas (SCG) extraction. Octacosanoic acid is the major constituent, and values of the carbon preference index (even over odd) lie between 2 and 6. Solvent extraction of the coals also removes small quantities (< 0.08 wt%) of straight-chain alkanes which are closely related in composition to the straight-chain fatty acids and are probably derived from them during maturation. However, previous SCG extraction of the coals yielded much larger quantities of straight-chain alkanes (0.3–0.7 wt%). Pyrolysis experiments with a lignite fatty acid fraction and with tetracosanoic acid show that these acids largely survive SCG extraction and, therefore, are not the main source of the relatively large quantity of straight-chain alkanes in these extracts.     

Molecular mass calibration in size-exclusion chromatography of coal derivatives

A number of procedures have been investigated for the calibration of a size-exclusion chromatography (s.e.c.) column in the determination of molecular mass (MM) distributions of coal derivatives. The behaviour of narrow fractions of coal extracts in the MM range 200–3000 was compared with a variety of the more generally available calibration standards. Calibration with preparative s.e.c. subfractions of materials similar to those under study has been recommended. Polystyrene standards are satisfactory, however, for MM < 1000, but above this range other polymer standards should be sought. Universal and molar volume calibration do not apply to coal-derived materials.     

Who will drive technological advance?

Electronic materials and packaging have been inexorably drawn along with the relentless march of technology. The complexity and capability of electronics increases with technology, yet it reduces the size and simplifies the shape of the materials and components that go to make up electronics. Whilst basic research into materials and packaging can be targeted into the areas of concern the main thrust for improvements is, of necessity, controlled by the specific needs of the product and the market.     

便携式照片打印机:让你的生活更轻松

曾几何时,在我们的书桌上少掉几张泛黄的合影照片,总是感觉遗憾。有人说,从现在开始,所有的回忆,包括声音与画面,都注定会被数字化。那么,为了避免这种遗憾,就让便携式照片打印机成为我们“家具”的一部分吧!     

Elbow extension in the C5 quadriplegic using functionalneuromuscular stimulation

A system has been designed to provide overhead reach in C5/6 quadriplegic subjects using functional neuromuscular stimulation (FNS) for control of the triceps muscle. The system uses the position of the arm in space as the input command, relieving the user from having to supply a conscious command signal. By measuring the position of the arm, the magnitude of the gravitational and passive torques opposing elbow extension can be calculated. This torque is counteracted by electrical activation of the triceps muscle, with the appropriate stimulus parameters determined from the recruitment characteristics of each electrode. Sufficient stimulus is applied to produce full elbow extension. Intermediate elbow angles are achieved using voluntary elbow flexor torque to counteract the effects of the stimulation. System performance was tested in two subjects. Subjects were asked to reach targets with and without stimulation, with loads up to 500 g in the hand. Using the FNS system, subjects were able to successfully reach the target positions above the horizontal that were inaccessible without stimulation.     

Coke Formation from Aircraft Engine Oils: Part II—Effects of Oil Formulation and Surface Composition

This is the second of two papers giving the results of a study undertaken to determine how aircraft engine oil degrades to form coke on oil-wetted surfaces. In part 2 the authors address the impacts of additives (which is related to oil types) and surface materials upon the oil coking process.

In Part 1 of this study, the authors showed that simple laboratory tests involving thin films of oil heated for specified timesltemperatures in open glass vials produced polymer and coke similar to the deposits seen on failed face seals taken from the operating aircraft engines and polymers isolated from used engine oils. Antioxidants inhibit and delay the coke producing reactions. After the antioxidant package is depleted to approximately 10 percent of the original level, the ester basestock undergoes accelerated oxidation to form oil-soluble polymers. As the oil spends additional time at elevated temperature, these polymers increase in molecular weight and undergo minor compositional changes becoming insoluble in the oil, producing deposits. If the time that a thin oil layer spends on a hot surface at elevated temperature can be limited so that the antioxidant does not deplete completely, coking can be prevented. This shifts the focus from coke minimization to coke prevention.

The authors results in Part 2 indicate that oil choice—which is largely a choice of antioxidant package—makes a large difference in how long oil can remain on a hot surface without forming polymer/coke deposits. For the oils studied in Part 2, the capabilities of the oils' antioxidant packages to inhibit coke formation varied 15 fold.

Surface material choice has minimal effect upon the rate of antioxidant depletion. However, once the antioxidant in the oil in a thin layer has become ineffective in inhibiting accelerated oxidation (approximately 10 percent of original concentration), the material the oil resides upon strongly effects the rate of the polymer/coke formation processes. Stainless steel speeds the process compared to a glass substrate.     

Organizational Vision and System Influences on Employee Inspiration and Organizational Performance

A model integrating multiple levels of leadership, leader charisma and organizational system influences on employee vision inspiration (motivation to help achieve their organizations' visions) was proposed and tested. The study employed data from 1,662 employees across 15 organizations. Results indicated that leader charisma was significantly and sizably related to employee inspiration, but differentially for different levels (executive versus supervisory) of leaders. Similarly, organizational system factors were significantly related to levels of employee inspiration, which significantly predicted multiple criteria for organizational performance. Practical and scientific implications of the results are considered.