Atmospheric boundary layer development over a narrow coastal plain during onshore flow

A study of the structure of the daytime atmospheric boundary layer during onshore flow over a narrow coastal plain is presented. The main emphasis of the study is on the nature and causes of heating and cooling observed in the boundary layer temperature profiles. Measurements included vertical temperature profiles above at least two sites derived from radiosondes and aircraft, as well as surface estimates of radiative and sensible heat fluxes. Surface meteorological and pilot balloon data were also available, providing further evidence of short-term changes in atmospheric boundary layer structure. The Manawatu case was representative of autumnal anticyclonic conditions with weak pressure gradients, and illustrated typical diurnal development of a convective boundary layer over a coastal plain bordered by mountain ranges, with a transition from a stable nocturnal situation to a well-mixed profile in the afternoon. The profiles show surface input of heat propagating upwards through the boundary layer during the day, as well as entrainment of heat at the top associated with shear induced turbulence and/or penetrative convection. Applying a one-dimensional model, estimates of boundary layer heat budget components were obtained for four time periods during the day. Later periods were affected by cumulus cloud development at the top of the boundary layer, resulting in significant changes in individual components. Input of sensible heat from the surface decreased, while the addition of heat to the boundary layer from both cloud condensation and advection increased.

Cutaneous stimulation from patella tape causes a differential increase in vasti muscle activity in people with patellofemoral pain

Patella taping reduces pain ill individuals with patellofemoral pain (PFP), although the mechanism remains unclear. One possibility is that patella taping modifies vasti muscle activity via stimulation of cutaneous afferents. The aim of this study was to investigate the effect of stretching the skin over the patella on vasti Muscle activity in people with PFP. Electromyographic activity (EMG) of individual motor units in vastus medialis obliquus (VMO) was recorded via a needle electrode and from Surface electrodes placed over VMO and vastus lateralis (VL). A tape was applied to the skin directly over the patella and stretch was applied via the tape in three directions, while subjects maintained a gentle isometric knee extension effort at constant force. Recordings were made from five separate motor units in each direction. Stretch applied to the skin over the patella increased VMO surface EMG and was greatest with lateral stretch. There was no change in VL surface EMG activity. While there was no net increase in motor unit firing rate, it was increased in the majority of motor units during lateral stretch. Application of stretch to the skin over VMO via the tape can increase VMO activity, suggesting that cutaneous stimulation may be one mechanism by which patella taping produces a clinical effect. (c) 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.

The Y2K scare: causes, costs and cures

The worldwide scare over the 'Y2K bug' resulted in the expenditure of hundreds of billions of dollars on Y2K compliance and conversion policies. Most of this expenditure can be seen, in retrospect, to have been unproductive or, at least, misdirected. In this article, the technological and institutional factors leading to the adoption of these policies are considered, along with suggestions as to how such policy failures could be avoided in future.

Identifying causes for N2O accumulation in a lab-scale sequencing batch reactor performing simultaneous nitrification, denitrification and phosphorus removal

The recently described process of simultaneous nitrification, denitrification and phosphorus removal (SNDPR) has a great potential to save capital and operating costs for wastewater treatment plants. However, the presence of glycogen-accumulating organisms (GAOs) and the accumulation of nitrous oxide (N2O) can severely compromise the advantages of this process. In this study, these two issues were investigated using a lab-scale sequencing batch reactor performing SNDPR over a 5-month period. The reactor was highly enriched in polyphosphate-accumulating organisms (PAOs) and GAOs representing around 70% of the total microbial community. PAOs were the dominant population at all times and their abundance increased, while GAOs population decreased over the study period. Anoxic batch tests demonstrated that GAOs rather than denitrifying PAOs were responsible for denitrification. NO accumulated from denitrification and more than half of the nitrogen supplied in a reactor cycle was released into the atmosphere as NO. After mixing SNDPR sludge with other denitrifying sludge, N2O present in the bulk liquid was reduced immediately if external carbon was added. We therefore suggest that the N2O accumulation observed in the SNDPR reactor is an artefact of the low microbial diversity facilitated by the use of synthetic wastewater with only a single carbon source. (C) 2005 Elsevier B.V. All rights reserved.

Identification of the causes of subsoil ammonium accumulations in southeastern Queensland

Unusually high concentrations of exchangeable-NH4+ (up to 270 kg-N/ha) were observed in a Vertisol below 1 m in southeast Queensland. This study aimed to identify the source of this NH4+. Preliminary sampling of native vegetation and cropping areas had found that elevated NH4+was only present under cropped soil, indicating that clearing was linked to the NH4+formation. Mechanisms of NH4+formation that may have occurred in the subsoil after clearing were hypothesised to be a) mineralisation of organic-N; b) NO3- reduction to NH4+; and/or c) the release of fixed-NH4+. In addition it was proposed that nitrification was inhibited in the subsoil, and that this allowed any NH4+formed to accumulate over time. Incubation experiments to examine nitrification rates revealed that nitrification was undetectable, and appeared to be limited by a combination of subsoil acidity and low numbers of nitrifying organisms. Mineralisation studies also revealed that the mineralisation of organic-N was undetectable, and that mineralising organisms were limited by acidity. A small amount of nitrate ammonification could be observed with the aid of a 15N tracer if the soil was waterlogged. However, this NH4+was insufficient to account for the overall NH4+accumulation, and these waterlogged conditions were not observed in the field. Concentrations of fixed- NH4+ measured were also too low to have been responsible for the accumulation of exchangeable-NH4+. It was concluded that none of the proposed hypotheses of NH4+formation could account for the NH4+accumulation observed.