The impact of simulated soccer match-play on hip and hamstring strength in academy soccer players.

INTRODUCTION: Together, the burden of hamstring and hip and groin injuries in soccer is substantial and the risk of re-injury in these areas is high. Reduced muscle strength has been identified as an important modifiable intrinsic risk factor of injury. However, little is known regarding the within-match changes in hip and hamstring muscle strength in order to inform early detection and management strategies. METHODS: Seventy-one male soccer players (age, 19.2 ± 0.9 yrs; height, 175.9 ± 5.8 cm; weight, 73 ±8.2 kg) from an international academy completed a fixed soccer-specific activity profile (SAFT90). Isometric hip and eccentric hamstring strength were measured after a standardised 5-min warm-up and repeated at half time and full time. Repeated-measures ANOVA were used to determine changes in muscle strength with magnitude-based decisions used to express probabilistic uncertainty. RESULTS: Findings indicate that i) there was likely to very likely substantial changes in isometric hip strength (-9.9-15.7%) and ii) no substantial changes in eccentric hamstring strength (-2.6-5.1%). DISCUSSION: By extrapolating these findings, it can be inferred that reduced isometric hip strength during match play may be one risk factor for injury, especially during periods of fixture congestion and practitioners should routinely assess muscle strength to inform training and match exposure based on player readiness. In doing so, it is likely that practitioners may enhance player availability and minimise injury incidence.

Some possible evolutionary scenarios suggested by 36Cl measurements in Guarani aquifer groundwaters.

The Guarani aquifer underlies 1.2 M km2 in the Paraná sedimentary basin of South America and is an important source of water for industry, agriculture, and domestic supplies. To determine the sustainability of this aquifer we need to understand the dynamics of the groundwater system. This paper describes the first 36Cl measurements on aquifer groundwaters and some measurements on South American rainwaters, thought to be indicative of the recharge water. The results are compared to previous work in the region, including other radioisotope analyses. A simple model is developed, incorporating radioactive decay, allowing scenarios to be developed for mixing different waters at different mixing rates. Thus, mixing scenarios consistent with other hydrogeological and hydrogeochemical data could be assessed. A model that mixes fresh recharging waters with formational waters, that contain elevated chloride levels, but low (in situ) 36Cl levels, can explain most of the results presented here. The expectation that rainwater samples would provide a good end-member for modelling recharge proved problematic, however. As a consequence, it is suggested that either: the recharge waters are not sourced from the same locations as the rains; that the current rainfall and fallout conditions were significantly different in the past; or that the low levels of chloride in rainfall may have allowed some contamination of the samples by old (36Cl-free) chloride during the recharge process.

Electromigration of microspheres in ferroelectric smectic liquid crystals.

When an electric field is applied to microspheres which are dispersed in a ferroelectric smectic liquid crystal, particle translation along the smectic layer plane, i.e., in a direction nearly perpendicular to that of the director, can be observed. Under certain electric field conditions the translation is shown to be linear in time. We have determined the stability regime of linear particle displacement in the parameter space of amplitude and frequency for various applied wave forms. This regime enlarges for increasing electric field amplitude and frequency, with a threshold behavior observed for small parameters. The upper stability boundary is related to the reciprocal ferroelectric switching time. The microspheres translational velocity is independent of the applied electric field amplitude, but increases linearly with applied frequency. The microsphere velocity also increases with increasing temperature, which is indicative of the respective decrease in liquid crystal viscosity. Possible mechanisms of electric-field-induced particle motion are discussed.

A first estimate of ground water ages for the deep aquifer of the Kathmandu Basin, Nepal, using the radioisotope chlorine-36.

The Kathmandu Basin in Nepal contains up to 550 m of Pliocene-Quaternary fluvio-lacustrine sediments which have formed a dual aquifer system. The unconfined sand and gravel aquifer is separated by a clay aquitard, up to 200 m thick, from the deeper, confined aquifer, comprised of Pliocene sand and gravel beds, intercalated with clay, peat, and lignite. The confined aquifer currently provides an important water supply to the central urban area but there are increasing concerns about its sustainability due to overexploitation. A limited number of determinations of the radioisotope 36Cl have been made on bore waters in the basin, allowing us to postulate on the age of ground water in the deeper, confined aquifer. Ground water evolution scenarios based on radioisotope decay, gradual dissolution of formational salts as the ground waters move downgradient, and flow velocity estimations produce comparable ground water ages for the deep waters, ranging from 200,000 to 400,000 years. From these ages, we deduce a mean ground water flow velocity of only 45 mm/year from recharge in the northeast to the main extraction region 15 km to the southwest. We thus estimate current recharge at about 5 to 15 mm/year, contributing 40,000 to 1.2 million m3/year to the ground water system. Current ground water extraction is estimated to be 20 times this amount. The low specific discharge confirms that the resource is being mined, and, based on current projections, reserves will be used up within 100 years.

Accelerator mass spectrometry for the detection of ultra-low levels of plutonium in urine, including that excreted after the ingestion of Irish sea sediments.

Currently, most methods for the quantitative assessment of (239)Pu have minimum detection levels (25 microBq for alpha-particle spectrometry) that are much higher than the levels of this isotope in many human bioassay and environmental samples. Accordingly, a priority has existed to develop methods that are more sensitive. Fission-track and ICP-MS methods have been used, but these can suffer either from an uncertain level of removal and/or recovery of uranium or from isobaric mass interferences. Accelerator mass spectrometry (AMS) has no such disadvantages, and its demonstrated detection limits for plutonium isotopes approach levels of attograms, equivalent to about 500 nBq for (239)Pu. This paper describes the application of AMS to the measurement of (239)Pu in urine produced by youths living in London (3.5 microBq day(-1)) and by adults (approximately 2-260 microBq day(-1)), some of whom were exposed occupationally. In addition, an experiment was undertaken to measure the fasted absorbed fraction of ingested plutonium after the ingestion of 15 g of Irish Sea sediment by a volunteer. The measured absorbed fraction was 4.5 x 10(-5). It is concluded that accelerator mass spectrometry is a suitable method for the ultra-trace detection of plutonium.

Kinetics of uptake and elimination of silicic acid by a human subject: a novel application of 32Si and accelerator mass spectrometry.

Silicon is possibly important in human physiology in protecting against the toxic effects of aluminium, but the kinetics of uptake and excretion of silicic acid, the bioavailable form, are not well characterised. We have used 32Si as a tracer in a human uptake experiment to determine a gastrointestinal uptake factor for silicic acid, and to elucidate the kinetics of renal elimination. Urine collections were made for extending intervals from 2 to 12 h over 2 days following ingestion by a single human subject of a neutral silicic acid solution containing tracer levels of 32Si (t1/2 approximately 150 y). Silicon was isolated as SiO2 and the 32Si content determined by accelerator mass spectrometry (AMS), using a gas-filled magnet technique to eliminate a prolific isobaric interference from 32S. Silicon uptake appears to have been essentially complete within 2 h of ingestion. Elimination occurred by two simultaneous first-order processes with half-lives of 2.7 and 11.3 h, representing around 90% and 10%, respectively, of the total output. The rapidly eliminated 32Si was probably retained in the extracellular fluid volume, whilst the slower component may represent intracellular uptake and release. Elimination of absorbed 32Si was essentially complete after 48 h and was equivalent to 36% of the ingested dose. This establishes only a lower limit for gastrointestinal absorption as, although there was no evidence for longer term retention of additional 32Si, the possibility could not be excluded by these results.

Determination of aluminium-26 in biological materials by accelerator mass spectrometry.

Studies of the biological chemistry of aluminium can gain significantly from the use of the long-lived isotope 26Al as a tracer, although the cost of the isotope often precludes its determination by radiochemical counting techniques. Accelerator mass spectrometry (AMS) provides an ultra-sensitive method of determination, free from isobaric interference from atomic (26Mg) or molecular species. The source materials for AMS can be aluminium oxide or phosphate, both of which can be readily prepared at a sufficient level of purity from biological substrates. Natural aluminium (27Al, 100%) is added to the preparations as a chemical yield monitor and to provide the reference for the isotope ratio measurement. 26Al/27Al ratios can be determined over the range 10(-14)-10(-7), implying a limit of detection for 26Al of around 10(-18) g. The precision of measurement and long-term reproducibility are < 5% and < 7% (RSD), respectively. Chemical methodologies for routine measurements on blood and urine samples have been developed.

The bioavailability of 26Al-labelled aluminium citrate and aluminium hydroxide in volunteers.

A study was undertaken to determine the fraction of ingested aluminium taken up by two male volunteers, following their ingestion of either aluminium citrate or aluminium hydroxide. In addition, the effects of simultaneous citrate ingestion on the gastrointestinal absorption of aluminium from its hydroxide was studied. Volunteers received three oral doses of 26Al-labelled aluminium compound in water. The doses were administered directly into the stomach using a paediatric feeding tube. Blood samples were collected from the volunteers at 1, 4 and 24 h after administration, and their daily output of urine and faeces was collected for 6 days. These samples were analysed for their 26Al content using either coincidence gamma-counting or accelerator mass spectrometry. The uptake of aluminium was greatest following its administration in the citrate form and was least following intake as the aluminium hydroxide suspension. The co-administration of citrate, with the aluminium hydroxide suspension, was found to enhance the levels of 26Al uptake in both volunteers. Using a urinary excretion factor based on the results of previous studies, the fractional aluminium uptake from each of the species was calculated: aluminium citrate, 5.23 x 10(-3); aluminium hydroxide, 1.04 x 10(-4); aluminium hydroxide with citrate, 1.36 x 10(-3).

An economic and technical assessment of the use of plant cell cultures for natural product synthesis on an industrial scale.

Plant cell cultures may be used as an alternative source of established natural products, as a source of novel 'lead' compounds or as a source of enzymes for modification of precursors. Only a few plant cell processes are operating commercially and their performance characteristics are industrial secrets. The economic aspects of natural product synthesis in plant cell cultures are presented on the basis of data derived from work on a pilot plant with bioreactors of 5-80 litres in which cells are grown in batch liquid culture. Cost analysis shows that the labour costs of operating plant cell culture processes are much higher than those for microbial processes, which reflects the longer process times of plant systems. These can be reduced by increasing the cell growth rate, the biomass yield and/or the product yield. Higher yields can be obtained by optimizing media conditions, but there are no standard guidelines for this. Each system has to be developed individually. Reducing the number of production runs a year, usually by increasing the number of days for which each batch of cells is synthesizing product, can markedly decrease costs. Economic assessment of the viability of production in plant cell cultures must consider not only production costs but also the expected market price of the product and the volume of sales.

EFFECTS OF NITROGEN DEPRIVATION ON RATES OF UPTAKE OF NITROGENOUS COMPOUNDS BY THE DIATOM, PHAEODACTYLUM TRICORNUTUM BOHLIN.

A culture of Phaeodactylum tricornutum was suspended in nitrogen-free growth medium under conditions which favoured photosynthesis. Nitrogen deprivation was continued for 60 h and, over this period, samples were removed for measurement of rates of uptake of arginine, guanine, nitrate, nitrite, lysine, methylammonium and urea. In another experiment, the effect of nitrogen deprivation on the ability to take up methylammonium and ammonium was compared. Cells developed, or increased, their abilities to take up all of these nitrogen compounds during nitrogen deprivation but ability to take up the two amino acids increased only slowly whereas the ability to take up the other compounds increased markedly during the first few hours of deprivation. The maximum rates of uptake developed were some 50-100 × higher for methylammonium and ammonium than they were for the other compounds. The rates of uptake are compared with those necessary to sustain growth.

Sodium-dependent uptake of nitrate and urea by a marine diatom.

Uptake of nitrate and urea by Phaeodactylum tricornutum is shown to be a sodium dependent process inhibited by lithium or potassium. The half-saturation constant for sodium (KNa) was 2.6 mM for nitrate uptake and 71 mM for urea uptake. It is suggested that sodium dependent uptake mechanisms may be characteristic of marine plants.

Organ culture of Eucalyptus grandis L.

Organ culture of nodes of Eucalyptus grandis permitted the rooting of nodes from much beyond No. 14, the highest node from which rooting has been described so far, namely up to node No. 80, the cotyledonary node being No. 1. Plantlets which were obtained from node 50 have been successfully transferred to the field.