Ammonia emissions from urine patches amended with N stabilized fertilizer formulations

In rotational grazing systems, it is common practice to apply nitrogen (N) fertiliser within 24 h of grazing thus resulting in addition of N fertiliser to urine patches. However, there is a lack of information on what the potential is, if any, to use this common practice to deliver N stabilisers to urine patches via N fertiliser formulations to reduce N losses to the environment. The objective of this study was to investigate the effect of applying urea fertiliser (with and without N stabilisers) 24 h after urine patch deposition on NH₃ emissions. Treatments included (1) urine, (2) urea, (3) urine + urea, (4) urine + urea with N-(butyl)thiophosphoric triamide (NBPT), (5) urine + urea with dicyandiamide (DCD) and (6) urine + urea with both NBPT and DCD. Treatments were applied on two occasions, May and June, under contrasting soil moisture and meteorological conditions to a temperate grassland site. Urine (569–883 kg N ha^?1) was applied 24 h prior to urea fertiliser application (40 kg N ha^?1). There was no significant reduction or increase in NH₃ emission factors from treatments receiving the two N stabilisers (NBPT and DCD) in the May and June application timings compared to the other treatments. The results of this study suggest that common farm practice of applying N fertiliser the day after grazing in rotational grazing systems offers no reduction in NH₃ emission rates from urine patches where the N stabiliser inclusion rate is designed to reduce the fertiliser-based N losses only.     

The Transfer of Matrix Toughness to Composite Mode I Interlaminar Fracture Toughness in Glass-Fibre/vinyl Ester Composites

The transfer of matrix toughness to composite mode I interlaminar fracture toughness (G _Ic ) has been investigated in unidirectional glass-fibre reinforced composites with brittle and rubber-toughened vinyl ester matrices. Single-edge-notch bend (SENB) and double cantilever beam (DCB) specimens were used for matrix and composite G _Ic characteristion, respectively. The initial crack opening displacement rate was used as the parameter for comparison of G _Ic results. Matrix G _Ic was completely transferred to composite G _Ic for crack initiation (G _Ic-init) in the brittle-matrix composites, but in the toughened composites transfer was only partial due to the presence of fibres. The conclusion is that the maximum contribution to energy absorption by the matrix is more accurately reflected by G _Ic-init, and should be used for further assessment of the enhancing effect of fibre bridging during steady-state crack propagation, instead of matrix G _Ic . A plot of composite G _Ic for steady-state crack propagation, G _Ic-prop versus G _Ic-init indicates that the enhancing effect of fibre bridging is greater in the toughened composites. This enhancement is related to a larger deformation zone size in the toughened matrices.     

Shape optimization of critical stiffener runouts for F-111 airframe life extension

ABSTRACT Optimal rework shapes for the most critical stiffener runout fatigue locations in the F-111 wing pivot fitting have been determined using a recently developed finite-element-based gradient-less shape optimization procedure. The resulting precise free-form shapes render the local notch stress distributions near uniform and typically provide a 30–40% reduction in peak elastic stresses as compared to the current rework shapes that exist for aircraft in service with the Royal Australian Air Force. The present numerical results are also consistent with recent preliminary experimental results, and a significant program of further validation testing is envisaged. Hence it is expected that the stress reductions predicted in the present work will be sufficient to provide a basis for extending inspection intervals by at least a factor of two; from 500 to 1000 h. Implementation of such an extension to the F-111 fleet in service with the Royal Australian Air Force would provide a very significant maintenance cost saving. The anticipated reduction in local crack growth rates would also allow achievement of the planned withdrawal date for the aircraft.     

Analysis and properties of some commercial poly(methylmethacrylate)-based materials

Four commercial crosslinked poly(methacrylate)-based materials have been analysed, and the differences in some of their physical properties from those of the unmodified polymer have been related to the variation in chemical structure. These co-polymers, which are about 95% methylmethacrylate, have different co-monomers which introduce crosslinks and hydrogen bonds into the polymer. The modifications have changed the craze resistance relative to the homopolymer, with in some cases improvements of over 50%. This change in craze resistance is not uniform with change in crazing agent, so showing that the responses of the materials with the change in solubility parameter of the agents are not the same. Likewise the water absorption behaviour shows wide variation, the solubility ranging up to twice that of the homopolymer. Measurements of the fracture properties show that three of the polymers are significantly less ductile than the homopolymer, though this is masked by an increase of the elastic modulus in two.     

Monitoring and analysis of combustion aerosol emissions from fast moving diesel trains

In this paper we report the results of the detailed monitoring and analysis of combustion emissions from fast moving diesel trains. A new highly efficient monitoring methodology is proposed based on the measurements of the total number concentration (TNC) of combustion aerosols at a fixed point (on a bridge overpassing the railway) inside the violently mixing zone created by a fast moving train. Applicability conditions for the proposed methodology are presented, discussed and linked to the formation of the stable and uniform mixing zone. In particular, it is demonstrated that if such a mixing zone is formed, the monitoring results are highly consistent, repeatable (with typically negligible statistical errors and dispersion), stable with respect to the external atmospheric turbulence and result in an unusual pattern of the aerosol evolution with two or three distinct TNC maximums. It is also shown that the stability and uniformity of the created mixing zone (as well as the repeatability of the monitoring results) increase with increasing length of the train (with an estimated critical train length of ~ 10 carriages, at the speed of ~ 150 km/h). The analysis of the obtained evolutionary dependencies of aerosol TNC suggests that the major possible mechanisms responsible for the formation of the distinct concentration maximums are condensation (the second maximum) and thermal fragmentation of solid nanoparticle aggregates (third maximum). The obtained results and the new methodology will be important for monitoring and analysis of combustion emissions from fast moving trains, and for the determination of the impact of rail networks on the atmospheric environment and human exposure to combustion emissions.     

Gas chromatography in water analysis—II selective detection methods

Gas chromatographic methods using selective detectors have been applied successfully to the determination of haloforms, herbicides and chlorophosphate esters in water extracts.

Electron capture detection has been used for the determination of the four haloforms, CHCl₃, CHCl₂Br, CHClBr₂ and CHBr₃ in pentane extracts. The very low detection limits render both the extracts and calibration solutions highly susceptible to contamination, and precautions necessary for their handling and storage are described.

Mass spectrometric single ion monitoring of gas chromatographic effluents has been used for the determination of the herbicides MCPA, MCPB and Mecoprop in methylated ether extracts. Possible interference from other components of the water extracts is discussed, and it is concluded that more than one ion should be monitored for each herbicide to minimise the interference.

A flame photometric method involving detection at 528 nm has been developed for the determination of chlorophosphate esters in dichloromethane extracts. The method is extremely specific for phosphorus compounds, but some interference from sulphur compounds may be observed. This can be minimised by the use of high efficiency capillary columns.

Detection limits and linear response ranges for the methods are given, and detector selectivities are discussed. Typical chromatograms are shown, and representative results for raw and treated waters are also given.     

Gas chromatography in water analysis—I organic profiles of water sources

A method has been developed and used extensively for the routine chromatographic scanning of water sources for trace organic compounds. The method involves solvent extraction of the water with dichloromethane, followed by analysis of the concentrated extract by gas chromatography on a glass SCOT capillary column with flame ionisation detection to yield a water profile. Over 600 extracts from rivers, canals, reservoirs and various stages of water treatment, collected between January 1979 and October 1980 as part of a potability study, were examined. The profiles were quantified using n-paraffin standards and a computerised data system. Components were detected at levels as low as 0.01 μg 1⁻¹ in the water samples.

A Kratos MS-30 double-beam mass spectrometer equipped with a DS-50 data system was used in conjunction with gas chromatography to identify chemical types in over 60 of the organic extracts. Components were generally identified at levels as low as 0.1 μg 1⁻¹ in the water samples. Many components did not give molecular ions and reference spectra were generally unavailable. In such cases, accurate mass measurement using the double-beam technique, which allowed the calculation of atomic compositions for fragment and molecular ions, was particularly valuable.     

Investigation of nitrogen compounds in coal tar products. 2. Basic fractions

Gas chromatography (g.c.), in conjunction with nitrogen-selective alkali flame detection (AFD) and mass spectrometry (m.s.), has been used for the detailed examination of nitrogen compounds in basic fractions from an anthracene oil and a low-temperature coal tar. The compounds identified were mainly aza species, but some di-nitrogen and mixed heteroatomic compounds were detected in the anthracene oil bases. Nitrogen-selective g.c.—AFD chromatograms of the extraction residues showed complex mixtures of non-basic nitrogen compounds; the major peaks were identified, but further g.c.-m.s. investigation of these compounds will require the preparation of hydrocarbon-free fractions.     

Detection of colorectal cancer cells in peripheral blood by reverse-transcriptase polymerase chain reaction for cytokeratin 20

In this study we have determined systemic and local antibody responses against different Helicobacter pylori antigens in H. pylori-infected and noninfected subjects. In addition, we studied whether differences in antibody responses between patients with duodenal ulcers and asymptomatic H. pylori carriers might explain the different outcomes of infection. Sera and in most instances gastric aspirates were collected from 19 duodenal ulcer patients, 15 asymptomatic H. pylori carriers, and 20 noninfected subjects and assayed for specific antibodies against different H. pylori antigens, i.e., whole membrane proteins (MP), lipopolysaccharides, flagellin, urease, the neuraminyllactose binding hemagglutinin HpaA, and a 26-kDa protein, by enzyme-linked immunosorbent assay. The H. pylori-infected subjects had significantly higher antibody titers against MP, flagellin, and urease in both sera and gastric aspirates compared with the noninfected subjects. Furthermore, the antibody titers against HpaA were significantly elevated in sera but not in gastric aspirates from the infected subjects. However, no differences in antibody titers against any of the tested antigens could be detected between the duodenal ulcer patients and the asymptomatic H. pylori carriers, either in sera or in gastric aspirates.     

Curing kinetics and thermal properties of vinyl ester resins

The curing kinetics of dimethacrylate-based vinyl ester resins were studied by scanning and isothermal DSC, gel time studies, and by DMTA. The rate of polymerization was raised by increased methyl ethyl ketone peroxide (MEKP) concentration but the cocatalyst, cobalt octoate, retarded the reaction rate, except at very low concentrations. By contrast, the gel time was reduced for all increases in either peroxide or cobalt concentration. This contradictory behavior was explained by a kinetic scheme in which the cobalt species play a dual role of catalyzing the formation of radicals from MEKP and of destroying the primary and polymeric radicals. The scanning DSC curves exhibited multiple peaks as observed by other workers, but in the present work, these peaks were attributed to the individual influence of temperature on each of fundamental reaction steps in the free radical polymerization. Physical aging appeared to occur during the isothermal polymerization of samples cured below the “fully cured” glass transition temperature (T_g). For these undercured materials, the difference between the DSC T_g and the isothermal curing temperature was approximately 11°C. Dynamic mechanical analysis of a partially cured sample exhibited anomalous behavior caused by the reinitiation of cure of the sample during the DMTA experiment. For partially cured resins, the DSC T_g increased monotonically with the degree of cure, and this dependence was fitted to an equation related to the Couchman and DiBenedetto equations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 769–781, 1997