Turnover of microbial biomass, plant residues and soil humic constituents under field conditions

Includes bibliographical references (pages 156-157).The effects of soil texture and climatic conditions on turnover rates of plant residues were measured under field conditions. Carbon-14- and 15N-labelled straw made it possible to follow degradation rates of the original substrate and of the soil organic constituents formed during the initial degradation process. Subsequent sampling measured the turnover of the active fraction. Carbon dating was used to measure the turnover rates of the more resistant fraction. Fractionation of the soil during the first two years showed greater accumulation of a condensed aromatic moiety (humic acid A) in the medium-textured Luvisolic soil and in the coarse-textured Dark Brown Chernozemic (Kastanozem). High clay grassland soils showed protection of aliphatic nitrogen from further humification. Much of the initial nitrogen and carbon mineralization of soil organic materials produced on decomposition of the straw came from the fulvic acids which contained a predominance of recently synthesized low molecular weight materials. Carbon and nitrogen incorporation into the > 0.2 μm fraction lagged behind incorporation into other fractions. Large quantities of immobilized carbon and nitrogen were contained in the > 0.2 μm fraction as well as in the 0.04 μm sedimentation fraction allowing these two fractions to act as sources of slowly released nitrogen. Residual humic acid carbon and nitrogen turnover was best estimated from carbon dating of the carbon after fractionation of the soil. The nitrogen turnover was calculated utilizing the C/N ratios of the fractions. Acid hydrolysis was found to be the simplest method of fractionation of large quantities of soil for carbon dating and for specific components. Na4P2O7 extraction followed by peptization and sediment analysis proved useful for measuring C and N transformations on a shorter term basis

Fractionation of soil and 15N nitrogen to separate the organic and clay interactions of immobilized N

Includes bibliographical references (pages 211-212).Labelled 15N was added to two soils in cylinders in the field, and allowed to equilibrate for two summers of crop growth. The labelled soils were fractionated to provide information on the effect of organic and inorganic colloids on the stabilization of immobilized, 15N. Organic materials removed by 0.5 N NaOH without pretreatment contained more 15N than those extracted by the same reagent following decalcification and removal of sesquioxides with dithionite and HCl. Both extracts had similar amino acid (contents) and similar degrees of hydrolability. A fractionation system using an initial 0.1 M NaOH–0.1 M Na4P2O7 extraction followed by sonication and peptization in H2O yielded a humic acid fraction and a sedimentation fraction (< 0.04 μm) which differed markedly in degree of hydrolyzability, 15N content and amino acid-N content. The N associated with inorganic colloids < 0.04 μm, and that remaining in solution after the removal of larger particles accounted for 50% of the amino acid-N in a clay soil, and 40% in a fine sandy loam soil. Removal of sesquioxides followed by a second 0.5 N NaOH extraction reduced the N content of the colloidal size fractions of both soils, indicating that amorphous iron and aluminum compounds on the surface of clays are probably the active agents in bonding organic N to inorganic colloids. It is suggested that the nonhydrolytic technique, based largely on dispersion of the inorganic–organic colloids and analyses of the sediment, could be used to interpret the fate of microbiologically immobilized N compounds in the soil. Materials removed by 0.1 M Na4P2O7 were associated with polyvalent cations in the soil. Materials such as cytoplasmic constituents, released from the biomass during ultrasonic vibration or as lytic products would be expected to be adsorbed to inorganic colloids. They should be concentrated in the < 0.04 μm-size fraction. Cell wall and other particulate debris with a faster setting velocity would be expected to appear in larger-sized sedimentation fractions

Thyroid disease in Kenya: Including a general review of thyroid disease in East Africa, a report of endemic goitre in Mwezi, Tanzania, and an account of simple goitre, thyroid carcinoma and thyrotoxicosis in Kenya

Abstract Not Provided

Impact of direct and indirect heating systems in broiler units on environmental conditions and flock performance

peer-reviewedThis study compared the impact of three indirect heating systems to direct gas flame heaters on a selection of flock performance and environmental indicators in commercial broiler units. No statistically significant differences (P≥0.05) were found in flock mortality rates, bird weight, water consumption, stress response, carbon dioxide, ammonia, temperature, relative humidity, litter quality, within-flock Campylobacter levels or mean Campylobacter counts when flock data from any of the three indirect heating systems were compared to flocks reared in houses with direct heating systems. Differences in litter quality were observed between upper and lower litter layers in all houses, regardless of heating type, which may have implications for bird health and welfare. Carbon dioxide concentrations in houses with direct heating systems were significantly higher than those in houses with indirect heating systems during the first 10 days of bird life (P≤0.05). This was due to the increased use of heating systems during this period of the flock cycle. Differences in CO2 concentrations had no effect on flock performance, possibly due to the fact that concentrations did not exceed known safe levels. A statistically significant increase in stress response was observed in birds as a result of partial depopulation (thinning) within houses, irrespective of heating system type used (P≤0.05). Stress associated with thinning may have consequences for bird welfare and food safety. In conclusion, the results of our study suggest that indirect heating systems do not appear to negatively impact on flock performance, stress response, within-flock Campylobacter levels or mean Campylobacter counts and do not appear to significantly alter environmental conditions within broiler houses when compared to houses equipped with direct heating systems. Indirect systems are a viable alternative for heating broiler houses in terms of flock performance, bird welfare and food safety

An Automated Approach to Maneuver Campaign Management for SkySats

Planet Labs PBC currently operates a fleet of 21 high-resolution imaging, Low Earth Orbit (LEO) satellites called SkySats comprised of both a sun-synchronous constellation and a lower inclination constellation. Due to their low altitude, operational constraints, and mission-driven requirements on image resolution and coverage, there is a need to perform routine stationkeeping and occasional constellation reconfiguration maneuver campaigns for these satellites. The Mission Systems team at Planet is currently implementing an automated and robust maneuver management system that autonomously plans and executes all SkySat maneuvers in order to reduce operator workload and improve overall constellation management efficiency. This paper describes the architecture of this system and how it has been designed to handle heterogeneous maneuver campaign types under various operational constraints. Finally, results from recent altitude raising campaigns for both constellations are presented

An investigation of high intensity ultrasonication and chemical immersion treatments on Campylobacter jejuni and spoilage bacteria in chicken

High intensity ultrasonication (US) alone or in combination with chemical immersion treatments of lactic acid (3% LA), sodium decanoate (3% SD) and trisodium phosphate (10% TSP) were investigated to reduce populations of Campylobacter jejuni and spoilage organisms in raw chicken. Different experimental conditions were used including a range of temperatures (4°C, 25°C and 54°C) and exposure times (1, 2 and 3min). All combination treatments significantly reduced C. jejuni compared to their individual treatments while only the combination US+SD significantly reduced Total Viable Count (TVC). Multiple linear regression predicted bacterial reductions resulting from changing treatment, temperature and time or each group of microorganisms. Increasing temperature from 4°C to 54°C would enhance C. jejuni, TVC and Total Enterobacteriaceae Count (TEC) reductions by 0.73, 1.02 and 1.37log10cfu/g respectively. Increasing time from 1 to 3min enhanced bacterial dependent of C. jejuni and TEC by 0.49 and 0.31log10cfu/g respectively. Industrial relevance. This study demonstrates the potential application of high intensity ultrasomication alone or in combination with chemical treatments to reduce bacterial contamination of chicken carcasses. Different tempretures and times were investigated to optimize the most effective treatments conditions in chicken abattoirs

Evaluation of chemical immersion treatments to reduce microbial populations in fresh beef

The aim of the current study was to assess the ability of a number of chemicals (acetic Acid (AA), citric acid (CA) lactic acid (LA), sodium decanoate (SD) and trisodium phosphate (TSP)) to reduce microbial populations (total viable count, Campylobacter jejuni, Escherichia coli, Salmonella typhimurium and Listeria monocytogenes) on raw beef using an immersion system. The following concentrations of each chemical were used: 3 & 5% for AA, CA, LA, SD and 10 & 12% for TSP. Possible synergistic effects of using combinations of two chemicals sequentially (LA +CA and LA +AA) were also investigated. L*, a* and b* values were measured before and after treatments and ΔE* values were calculated in order to determine any changes in the color of meat due to the use of these chemicals. In general, all chemical treatments resulted in significantly (p \u3c 0.05) reduced bacterial counts when compared to untreated controls. The greatest reductions were obtained by using LA3%, SD5%, AA5%, LA5% and SD3% for TVC, C. jejuni, E. coli, S. typhimurium and L. monocytogenes, respectively. However, no significant difference in microbial load was observed between the different concentrations of each chemical used (p \u3e 0.05). The application of combinations of chemical immersion treatments (LA3%+AA3% and LA3% + CA3%) did not result in further significant reductions in microbial populations when compared to single chemical treatments (P \u3c 0.05). Assessment of color changes in meat following the application of chemical immersion treatments indicated that using AA or CA at either concentration and LA at 5% led to an increase in the ΔE* value of\u3e 3 immediately after treatment and after 24 h storage. The remaining treatments did not result in significant changes to the color of raw beef

Building Performance and End-user Interaction in Passive Solar and Low Energy Housing Developments in Scotland

In the UK housing sector, changes to building regulations have raised standards for fabric performance, bringing about a demand for affordable, low energy housing. Housing Associations have been at the forefront of adopting these measures, but as owners of long term rented stock it is important for them to understand and evaluate the performance of both ‘as-built’ and ‘as-occupied’ dwellings. This paper describes a detailed evaluation of three new-build social housing demonstration projects located in Glasgow (Scotland). The study included occupant surveys in each scheme, fabric testing and detailed monitoring of environmental conditions, energy consumption, and evaluation of occupancy behaviours in eight dwellings. A particular focus of this paper is the ventilation performance as the homes are ventilated differently using natural, mechanical extract and mechanical heat recovery methods. The results showed a wide discrepancy of energy consumption and poor levels of ventilation, particularly in bedrooms. Causes of this included the design and installation of the ventilation provision but occupant interaction with the systems was also a significant factor. Two sites included sun-spaces that, despite having good potential for preheat ventilation and drying spaces, were underperforming. The study highlights significant impacts of the complex interactions between heating and ventilation systems, and the apparent need for more effective ventilation strategies and systems in bedroom spaces, but also improved strategies for end-user understanding of, and interaction with, both mechanical systems and natural ventilation opportunities. The papers aims to provide robust and credible evidence on which to base critical regulatory and design decisions on the most effective means of ventilating low carbon social housing in Britain