Can laboratory-based tennis profiles predict field tests of tennis performance?

The present study examined the impact of physical characteristics of adolescent competitive tennis players (13-18 years) on field tests of tennis performance. Results (n = 33) showed that boys were taller (p = 0.001), possessed greater wingspan (p = 0.030), had greater maximum oxygen consumption (p = 0.001), and performed better on isokinetic strength measurements. Multiple regression analyses controlling for age and sex showed that height (p = 0.025), maximum minute ventilation (p = 0.005), and isokinetic strength measurements significantly and positively affected ball velocity. Knee extension average power was the only variable to positively and significantly affect ball placement (p = 0.040); however, several isokinetic strength measurements negatively affected ball placement. For the nondominant side, down-the-line strokes showed reduced accuracy (p = 0.001) and ball velocity (p = 0.001) compared with cross-court strokes. Given our results, resistance training may be beneficial for the performance of on-court tennis play.     

Which data should be tracked in forward-dynamic optimisation to best predict muscle forces in a pathological co-contraction case?

The choice of the cost-function for predicting muscle forces during a movement remains a challenge, especially in patients with neuromuscular disorders. Forward dynamics-based optimisations mainly track joint kinematics or torques, combined with a least-excitation criterion. Tracking marker trajectories and/or electromyography (EMG) has rarely been proposed. Our objective was to determine the best tracking objective-function to accurately predict the upper-limb muscle forces. A musculoskeletal model was created and EMG was simulated to obtain a reference movement – a shoulder abduction. A Gaussian noise (mean = 0; standard deviation = 15%) was added to the simulated EMG. Another noise – corresponding to the actual soft tissue artefacts (STA) of experimental shoulder abduction movements – was added to the trajectories of the markers placed on the model. Muscle forces were estimated from these noisy data, using forward dynamics assisted by six non-linear least-squared objective-functions. These functions involved the tracking of marker trajectories, joint angles or torques, with and without EMG-tracking. All six approaches used the same musculoskeletal model and were solved using a direct multiple shooting algorithm. Finally, the predicted joint angles, muscle forces and activations were compared to the reference values, using root-mean-square errors (RMSe) and biases. The force RMSe of the approach tracking both marker trajectories and EMG (18.45 ± 12.60 N) was almost five times lower than the one of the approach tracking only joint angles (82.37 ± 66.26 N) or torques (85.10 ± 116.40 N). Therefore, using EMG as a complementary tracking-data in forward dynamics seems to be promising for the estimation of muscle forces.     

Can species traits be used to predict marine macroalgal introductions?

Species traits which facilitate introduction and predominance have been quantitatively ranked using interval arithmetic to search for common patterns among 113 marine macroalgae introduced in Europe. Three main categories were used: dispersal, establishment and ecological impact. These were further subdivided into more specific categories, a total of 13. Introduced species were compared with the same number of native species randomized from the same families as the introduced. Invasive species (i.e. species having a negative ecological or economical impact) were also compared with non-invasive introductions, separately for the three algal groups. In many categories, as well as when adding all species, the introduced species ranked more hazardous than the native species and the invasive species ranked higher than the non-invasive ones. The ranking within the three main categories differed, reflecting different strategies between the species within the three algal groups. When all categories (excluding salinity and temperature) were summed, the top five risk species, all invasive, were, in descending order, Codium fragile spp.tomentosoides, Caulerpa taxifolia, Undaria pinnatifida, Asparagopsis armata and Grateloupia doryphora, while Sargassum muticum ranked eight and Caulerpa racemosa ten. Fifteen of the twenty-six species listed as invasive were among the twenty highest ranked.     

Can species data only be appropriately used to conserve biodiversity?

Despite widely acknowledged handicaps of the species approach to identifying priority conservation areas, many workers continue to use these flawed techniques as the backbone of their analyses. Species-based approaches address only a small part of biological diversity by ignoring different levels of organisation as well as the functional linkages among these levels. These data are often biased and incomplete and are often used in preference to data dealing with higher biological levels of organisation though the latter may be readily available. Within the framework of Noss's [(1990) Conservation Biology 4: 355–364] hierarchical definition of biodiversity (and Scott etal. [(1993) Wildlife Monographs 123: 1–31] gap analysis), we propose a top-down model dealing with broad organisational levels first, and finer-scale species distributions last. Note that we do not discard the latter approach, but merely argue for its use at a stage when, in our opinion, it adds most to the value of the prioritisation exercise. The model is flexible so that additional information, particularly those related to threats to biological diversity, can be added when they are available.     

Can the past predict the future? Experimental tests of historically based population models

A frequently advocated approach for forecasting the population‐level impacts of climate change is to project models based on historical, observational relationships between climate and demographic rates. Despite the potential pitfalls of this approach, few historically based population models have been experimentally validated. We conducted a precipitation manipulation experiment to test population models fit to observational data collected from the 1930s to the 1970s for six prairie forb species. We used the historical population models to predict experimental responses to the precipitation manipulations, and compared these predictions to ones generated by a statistical model fit directly to the experimental data. For three species, a sensitivity analysis of the effects of precipitation and grass cover on forb population growth showed consistent results for the historical population models and the contemporary statistical models. Furthermore, the historical population models predicted population growth rates in the experimental plots as well or better than the statistical models, ignoring variation explained by spatial random effects and local density‐dependence. However, for the remaining three species, the sensitivity analyses showed that the historical and statistical models predicted opposite effects of precipitation on population growth, and the historical models were very poor predictors of experimental responses. For these species, historical observations were not well replicated in space, and for two of them the historical precipitation‐demography correlations were weak. Our results highlight the strengths and weaknesses of observational and experimental approaches, and increase our confidence in extrapolating historical relationships to predict population responses to climate change, at least when the historical correlations are strong and based on well‐replicated observations.     

Sanctions and mutualism stability: when should less beneficial mutualists be tolerated?

Why do mutualists perform costly behaviours that benefit individuals of a different species? One of the factors that may stabilize mutualistic interactions is when individuals preferentially reward more mutualistic (beneficial) behaviour and/or punish less mutualistic (more parasitic) behaviour. We develop a model that shows how such sanctions provide a fitness benefit to the individuals that carry them out. Although this approach could be applied to a number of symbioses, we focus on how it could be applied to the legume‐rhizobia interaction. Specifically, we demonstrate how plants can be selected to supply preferentially more resources to (or be less likely to senesce) nodules that are fixing more N₂ (termed plant sanctions). We have previously argued that appreciable levels of N₂ fixation by rhizobia are only likely to be selected for in response to plant sanctions. Therefore, by showing that plant sanctions can also be favoured by natural selection, we are able to provide an explanation for the stability of the plant‐legume mutualism.     

Can assignment tests measure dispersal?

Individual-based assignment tests are now standard tools in molecular ecology and have several applications, including the study of dispersal. The measurement of natal dispersal is vital to understanding the ecology of many species, yet the accuracy of assignment tests in situations where natal dispersal is common remains untested in the field. We studied a metapopulation of the grand skink, Oligosoma grande, a large territorial lizard from southern New Zealand. Skink populations occur on isolated, regularly spaced rock outcrops and are characterized by frequent interpopulation dispersal. We examined the accuracy of assignment tests at four replicate sites by comparing long-term mark-and-recapture records of natal dispersal with the results of assignment tests based on microsatellite DNA data. Assignment tests correctly identified the natal population of most individuals (65-100%, depending on the method of assignment), even when interpopulation dispersal was common (5-20% dispersers). They also provided similar estimates of the proportions of skinks dispersing to those estimated by the long-term mark-and-recapture data. Fully and partially Bayesian assignment methods were equally accurate but their accuracy depended on the stringency applied, the degree of genetic differentiation between populations, and the number of loci used. In addition, when assignments required high confidence, the method of assignment (fully or partially Bayesian) had a large bearing on the number of individuals that could be assigned. Because assignment tests require significantly less fieldwork than traditional mark-and-recapture approaches (in this study < 3 months vs. > 7 years), they will provide useful dispersal data in many applied and theoretical situations.     

Can screening Chlamydia trachomatis by serological tests predict tubal damage in infertile patients?

Effectiveness of screening Chlamydia trachomatis (CT) antibody to predict tubal damage was assessed in this prospective study which was performed in a teaching hospital between September 2003 and September 2004. The study group consisted of 152 patients who underwent laparoscopy for infertility and the control group consisted of 80 fertile women who gave birth in the same hospital. CT antibody levels were measured by IFA (Indirect Fluorescence Assay for CT). Adhesions were defined by Gomel's classification system. Rate of seropositivity of CT was 34.6% in the study group and 22.5% in the control group (p>0.05). In the study group, the sensitivity, specifity, positive predictive and negative predictive values of CT positivity for tubal damage were 40%, 69.5%, 50% and 60.2% respectively. In the infertile group, the rate of tubal adhesion in the CT positive group was 50% and in the CT negative group it was 39.7% (p>0.05). However, there was a positive correlation between the severity of tubo-peritoneal adhesions and seropositivity for CT. In this study, we found out that tubo-peritoneal adhesions could not be predicted by the presence of CT inserum. There was a positive correlation between high CT seropositivity and high degree of adhesions.     

How should clinical data be included in experimental studies of cancer immunology?

Patients diagnosed with the same malignant disease are often heterogeneous with regard to age, complications, malignant cell morphology and tumor histology, disease stage, prognostic parameters, and previous therapy. Many of these factors can affect immunocompetent cells or influence the malignant cell susceptibility to immunotherapy. Summaries of relevant clinical information should therefore be included in cancer immunology studies to increase the present as well as the future scientific impact. Guidelines for selection of relevant information are suggested in the article.     

Can we predict perceived risk?

This paper examines the possibility that we may be able to use subjective measures of perceived risk in order to assess the relative safety of different shift systems. A large-scale survey of safety-critical engineers included three items relating to risk on each shift, namely alertness, likelihood of making a mistake and confidence in driving home after it. These three measures were found to load on a separate factor for each shift. Hierarchical regression analyses indicated that perceived night shift risk could be predicted on the basis of circadian type, the extent to which the engineers could control their work schedule, and a number of features of the scheduled shift system. In most cases the relationships observed were reasonably consistent with established trends in either performance capability or accident and injury frequency. However, there were exceptions to this indicating that results based on measures of perceived risk should be interpreted with the utmost caution.     

Can root electrical capacitance be used to predict root mass in soil?

Background

Electrical capacitance, measured between an electrode inserted at the base of a plant and an electrode in the rooting substrate, is often linearly correlated with root mass. Electrical capacitance has often been used as an assay for root mass, and is conventionally interpreted using an electrical model in which roots behave as cylindrical capacitors wired in parallel. Recent experiments in hydroponics show that this interpretation is incorrect and a new model has been proposed. Here, the new model is tested in solid substrates.

Methods

The capacitances of compost and soil were determined as a function of water content, and the capacitances of cereal plants growing in sand or potting compost in the glasshouse, or in the field, were measured under contrasting irrigation regimes.

Key Results

Capacitances of compost and soil increased with increasing water content. At water contents approaching field capacity, compost and soil had capacitances at least an order of magnitude greater than those of plant tissues. For plants growing in solid substrates, wetting the substrate locally around the stem base was both necessary and sufficient to record maximum capacitance, which was correlated with stem cross-sectional area: capacitance of excised stem tissue equalled that of the plant in wet soil. Capacitance measured between two electrodes could be modelled as an electrical circuit in which component capacitors (plant tissue or rooting substrate) are wired in series.

Conclusions

The results were consistent with the new physical interpretation of plant capacitance. Substrate capacitance and plant capacitance combine according to standard physical laws. For plants growing in wet substrate, the capacitance measured is largely determined by the tissue between the surface of the substrate and the electrode attached to the plant. Whilst the measured capacitance can, in some circumstances, be correlated with root mass, it is not a direct assay of root mass.     

Can iron be teratogenic?

Several kinds of evidence indicate that elevated iron during the 3–8 week embryonic (organogenesis) period of human gestation may be teratogenic. (1) In the embryonic period, the natural maternal absorption of food iron is 30% below the estimated daily iron loss. (2) As compared with maternal serum, embryonic fetal coelomic fluid contains only one-fourth as much iron but nearly six times the quantity of the iron withholding protein, ferritin. (3) In the embryonic period, intraplacental oxygen pressure is 2–3 times lower than in the subsequent fetal growth period. (4) Iron is a strong inducer of emesis which peaks in the embryonic period. (5) In a murine gestation model, iron was neurotoxic at a sharp peak of 8–9 days. Thus it would be prudent, in human pregnancy, to delay any needed iron supplementation until the embryonic period has been completed.