31 research outputs found
What happens after the catchment caught the storm? Hydrological processes at the small, semi-arid Weatherley catchment, South-Africa
No full textThe knowledge of water flow pathways and residence times in a catchment are essential for predicting the hydrological response to a rain storm event. Different experimental techniques are available to study these processes, which are briefly reviewed in this paper. To illustrate this, recent findings from the Weatherley catchment a 1.5 km2 semi-arid headwater in South-Africa, are reported in this paper. Beside classical hydrometric measurements of precipitation and runoff different experimental techniques were applied to explore flow paths (i.e. soil moisture and groundwater measurements, natural tracers, and 2-D electrical resistivity tomographies (ERT))
Long-range automaton models of earthquakes: Power-law accelerations, correlation evolution, and mode-switching
No full textWe introduce a conceptual model for the in-plane physics of an earthquake fault. The model employs cellular automaton techniques to simulate tectonic loading, earthquake rupture, and strain redistribution. The impact of a hypothetical crustal elastodynamic Green's function is approximated by a long-range strain redistribution law with a r(-p) dependance. We investigate the influence of the effective elastodynamic interaction range upon the dynamical behaviour of the model by conducting experiments with different values of the exponent (p). The results indicate that this model has two distinct, stable modes of behaviour. The first mode produces a characteristic earthquake distribution with moderate to large events preceeded by an interval of time in which the rate of energy release accelerates. A correlation function analysis reveals that accelerating sequences are associated with a systematic, global evolution of strain energy correlations within the system. The second stable mode produces Gutenberg-Richter statistics, with near-linear energy release and no significant global correlation evolution. A model with effectively short-range interactions preferentially displays Gutenberg-Richter behaviour. However, models with long-range interactions appear to switch between the characteristic and GR modes. As the range of elastodynamic interactions is increased, characteristic behaviour begins to dominate GR behaviour. These models demonstrate that evolution of strain energy correlations may occur within systems with a fixed elastodynamic interaction range. Supposing that similar mode-switching dynamical behaviour occurs within earthquake faults then intermediate-term forecasting of large earthquakes may be feasible for some earthquakes but not for others, in alignment with certain empirical seismological observations. Further numerical investigation of dynamical models of this type may lead to advances in earthquake forecasting research and theoretical seismology
Multi-nuclear Magnetic Resonance Imaging in the Longitudinal Assessment of Idiopathic Pulmonary Fibrosis
No full textComparison of in vivo lung morphometry models from 3D multiple b-value 3He and 129Xe diffusion-weighted MRI
No full textPurpose
To compare in vivo lung morphometry parameters derived from theoretical gas diffusion models, the cylinder model and stretched exponential model, in a range of acinar microstructural length scales encountered in healthy and diseased lungs with 3He and 129Xe diffusion‐weighted MRI.
Methods
Three‐dimensional multiple b‐value 3He and 129Xe diffusion‐weighted MRI was acquired with compressed sensing at 1.5 T from 51 and 31 subjects, respectively, including healthy volunteers, ex‐smokers, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease patients. For each subject, the stretched exponential model–derived mean diffusive length scale (LmD) was calculated from the diffusion signal decay, and was compared with the cylinder model–derived mean chord length (Lm) and mean alveolar diameter (LAlv) in order to determine the relationships among the different lung morphometry parameters.
Results
For both 3He and 129Xe diffusion‐weighted MRI, the mean global LmD value was significantly related (P < .001) to Lm in a nonlinear power relationship, whereas the LAlv demonstrated excellent linear correlation (P < .001) with LmD. A mean bias of +1.0% and urn:x-wiley:07403194:media:mrm27608:mrm27608-math-00012.6% toward LmD was obtained for Bland‐Altman analyses of 3He and 129Xe LmD and LAlv values, suggesting that the two morphometric parameters are equivalent measures of mean acinar dimensions.
Conclusion
Within the experimental range of parameters considered here for both 3He and 129Xe, the stretched exponential model–derived LmD is related nonlinearly to cylinder model–derived Lm, and demonstrates excellent agreement with the cylinder model–derived LAlv
RNAseq analysis of fast skeletal muscle in restriction-fed transgenic coho salmon (Oncorhynchus kisutch) : an experimental model uncoupling the growth hormone and nutritional signals regulating growth
No full textBackground Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tissues which results in increased appetite and continuous high growth with satiation feeding. Restricting Gh-transgenics to the same lower ration (TR) as wild-type fish (WT) results in similar growth, but with the recruitment of fewer, larger diameter, muscle skeletal fibres to reach a given body size. In order to better understand the genetic mechanisms behind these different patterns of muscle growth and to investigate how the decoupling of Gh and nutritional signals affects gene regulation we used RNA-seq to compare the fast skeletal muscle transcriptome in TR and WT coho salmon. Results Illumina sequencing of individually barcoded libraries from 6 WT and 6 TR coho salmon yielded 704,550,985 paired end reads which were used to construct 323,115 contigs containing 19,093 unique genes of which >10,000 contained >90 % of the coding sequence. Transcripts coding for 31 genes required for myoblast fusion were identified with 22 significantly downregulated in TR relative to WT fish, including 10 (vaspa, cdh15, graf1, crk, crkl, dock1, trio, plekho1a, cdc42a and dock5) associated with signaling through the cell surface protein cadherin. Nineteen out of 44 (43 %) translation initiation factors and 14 of 47 (30 %) protein chaperones were upregulated in TR relative to WT fish. Conclusions TR coho salmon showed increased growth hormone transcripts and gene expression associated with protein synthesis and folding than WT fish even though net rates of protein accretion were similar. The uncoupling of Gh and amino acid signals likely results in additional costs of transcription associated with protein turnover in TR fish. The predicted reduction in the ionic costs of homeostasis in TR fish associated with increased fibre size were shown to involve multiple pathways regulating myotube fusion, particularly cadherin signaling.Peer reviewe
Load-unload response ratio and accelerating moment/energy release critical region scaling and earthquake prediction
No full textThe main idea of the Load-Unload Response Ratio (LURR) is that when a system is stable, its response to loading corresponds to its response to unloading, whereas when the system is approaching an unstable state, the response to loading and unloading becomes quite different. High LURR values and observations of Accelerating Moment/Energy Release (AMR/AER) prior to large earthquakes have led different research groups to suggest intermediate-term earthquake prediction is possible and imply that the LURR and AMR/AER observations may have a similar physical origin. To study this possibility, we conducted a retrospective examination of several Australian and Chinese earthquakes with magnitudes ranging from 5.0 to 7.9, including Australia's deadly Newcastle earthquake and the devastating Tangshan earthquake. Both LURR values and best-fit power-law time-to-failure functions were computed using data within a range of distances from the epicenter. Like the best-fit power-law fits in AMR/AER, the LURR value was optimal using data within a certain epicentral distance implying a critical region for LURR. Furthermore, LURR critical region size scales with mainshock magnitude and is similar to the AMR/AER critical region size. These results suggest a common physical origin for both the AMR/AER and LURR observations. Further research may provide clues that yield an understanding of this mechanism and help lead to a solid foundation for intermediate-term earthquake prediction
Fish population dynamics in tropical waters: a manual for use with programmable calculators
No full textStock assessment, Population dynamics, Multispecies fisheries, Tropics, Computer programmes, Manuals
Time to full publication of studies of anti-cancer medicines for breast cancer, and the potential for publication bias: a short systematic review
No full textObjectives: To identify the expected delay between publication of conference abstracts and full publication of results from trials of new anti-cancer agents for breast cancer and to identify whether there are any apparent biases in publication and reporting.Data sources: Major electronic databases were searched to identify randomised controlled trials (RCTs) of the selected interventions for the treatment of breast cancer.Review methods: A systematic review was conducted according to standard methods. Data were extracted from the included studies using a predesigned and piloted data extraction template.Results: Six anti-cancer treatments for breast cancer were included in the review: docetaxel, paclitaxel, trastuzumab, gemcitabine, lapatinib and bevacizumab. The literature searches generated 1556 references, from which 71 publications were retrieved and screened for inclusion. Screening identified 41 publications of 18 RCTs with at least one arm of treatment meeting the inclusion criteria for the review. Of the 18 included RCTs, only four publications (from three RCTs) reported the same outcomes in both an abstract and a full publication. Time between the abstract and full publication was 5 months in two cases, 7 months in one case and 19 months in one case (overall mean delay = 9 months). Eleven trials were identified that have not currently published in a full publication the data presented in an abstract or conference proceeding. The duration between publication of the abstracts and the end of August 2007 varied from 3 months to 38 months (mean delay 16.5 months). The longest delays in publication were for trials investigating gemcitabine (38 months) or bevacizumab (33 months). Observational analysis of the published and unpublished trials did not indicate any particular biases in terms of whether positive results were more likely to be fully published than non-significant ones.Conclusions: It was surprising that only three of the 18 relevant RCTs had one or more full papers that reported the same outcome measures (and stage of analysis) as an earlier conference abstract. However, a limitation of this review is the small number of studies included. With a larger sample size than that in the present report, investigation into the effect of publication delay on decision-making might be feasible. Future research should include extension of this work to other anticancer drugs and investigation into the reasons for lengthy delays to full publication noted for some trials
The safety and effectiveness of different methods of ear wax removal: a systematic review and economic evaluation
No full textEar wax (cerumen) is a natural secretion produced to protect the inner ear from dirt and other fragments by moving these particles towards the outer ear. If this process does not happen properly, wax may build up causing blockage in the ear canal and the possibility of impaction. People with a build up of ear wax may suffer from hearing loss, discomfort and, on occasions, infection. It may present problems in assessing hearing, blocking the view of the ear drum during medical examination and interfering with the fitting or function of hearing aids. Although it is thought to affect between 2% and 6% of the population in the England and Wales, some groups may be at a higher risk, such as those using hearing aids or with small ear canals and/or skin conditions. Recurrence is thought to be high among some of these groups. The consequences of the build up of ear wax in the ear canal are thought to be a common reason for consultation and cost in general practice with over 2 million consultations per year in the NHS.Methods of removal of ear wax include drops, flushing with water in general practice, and removal with suction or probes in specialist clinics. The relative safety and benefits of these different methods of removal remains uncertain. This research will systematically review published and unpublished evidence on the clinical and cost effectiveness of different methods for the removal of ear wax. Where appropriate, it will develop an economic model using data from this systematic review and other relevant sources to estimate the relative costs and benefits of different methods. In addition, the project will provide recommendations for future research to try to help answer any remaining areas of uncertainty
Water relations of cucumber, tomato, and sweet pepper
No full textThe ever increasing importance of water as a critical resource for agricultural production has encouraged more research on water relations in recent years. Most attention has been paid to field crops and less information is available for horticultural crops, especially vegetables. The results of studies on water relations of cucumber, tomato, and pepper are reported and discussed in this thesis.Drying cycle experiments were carried out with tomato, cucumber, and sweet pepper at two temperatures and three light intensities in order to: (1) examine suitability of some plant parameters as criteria for expression of plant water status; (2) investigate which parameter is most suitable as a basis for timing of irrigation; and (3) observe the change of various parameters during a drying cycle as affected by environment. Measurements were carried out on transpiration rate, stomatal diffusive resistance ( rs ), leaf temperature, plant and soil water potentials, and relative water content. The transpiration rate at 25°C was in general higher than that at 21°C due to the higher vapour pressure deficit (vpd) at the former temperature. For all the three species, a more pronounced stomatal closure was demonstrated at 25°C as compared to that at 21°C when drought was imposed on the plants. This result could be due to the fact that at 25°C the vpd and/or the internal CO 2 concentration was higher. Various levels of irradiance did not invoke different responses of stomata or transpiration rates throughout the drying cycles. The difference among the three light intensities used are thought to have been too small to show distinct responses. Moreover, relatively low intensities were used in this series of experiments. The measured rs , values did not always correlate significantly with soil water potentials because rs , measurements were carried out on single leaves at only one point in the photoperiod and the measurements were also affected by other environmental factors, such as humidity, prevailing during the measurements. Calculated rs , values showed better correlations with soil water potential, presumably because transpiration rates of the whole plants over the entire photoperiod were used for their calculation. Relative water content and leaf water potential correlated significantly with soil water potential. Among the plant parameters studied, the plant water potential as measured with the pressure chamber, was judged as the most suitable parameter expressing plant water status.Some physical aspects of the internal plant water relations were considered for the three species. The measured parameters were relative water content, sap electrical conductivity, and leaf water potential and its components (osmotic, pressure, and matric potentials). The contribution of matric potential to the total plant water potential was considerable. Neglecting the matric component would result in unrealistically low levels of pressure potential for the three species. Tomato was considered to have the best osmotic and matric adjustments, followed by cucumber and pepper. Sap osmotic potential and electrical conductivity were found to be significantly correlated with leaf water potential. Electrical conductivity was considered as an easy and accurate method to determine the osmotic potential indirectly. From the regression of relative water content on leaf water potential, cucumber, tomato, and pepper showed, in this order, decreasing drought resistance. Examination of some other parameters, however, such as osmotic and matric adjustments and reduction of photosynthesis in stress conditions, confirmed a better drought resistance property to tomato, followed by cucumber and pepper. Relative position of cucumber and tomato in drought resistance was discussed. For all the criteria examined, pepper was considered to be the least drought resistant. It was concluded that a better understanding of the drought resistance mechanisms in plants is required.Carbon dioxide exchange and transpiration rates were measured in a gas exchange assembly in two series of experiments. In the first series, measurements were carried out on cucumber and pepper at light saturation and in darkness. In the second series, photosynthesis-light curves for cucumber, tomato, and pepper were obtained. For both series, well-watered as well as stressed plants were used. Both photosynthesis and transpiration were reduced as stress set in. It was shown that both stomatal and nonstomatal mechanisms were involved in the reduction of photosynthesis. For all the three species, an increase in mesophyll resistance was observed as a result of water stress. In experiments with different levels of irradiance, it was observed that the stressinduced reduction of photosynthesis was more pronounced at light saturation compared to low light. After showing some initial opening reaction to light, the stomata of stressed plants showed a closing pattern, especially for cucumber and pepper, regardless of irradiance levels. It was proposed that the closing effect of drought overrode the opening effect of light. Severely stressed plants of cucumber and pepper were rewatered to study their recovery. Photosynthesis did not reach the pre-stress level one day after rewatering, this was due to an aftereffect of drought on stomata in cucumber and pepper and a damage to the photosynthetic system in pepper.Diurnal changes in water relations parameters were measured in a glasshouse for tomato and pepper. In a constant environmental condition, gas exchange rates were monitored throughout the photoperiod for cucumber, pepper, and two cultivars of tomato. Both well-watered and stressed plants were used for the above measurements. In the glasshouse, transpiration, leaf water potential, stomatal diffusive resistance, as well as the diurnal changes in environmental factors such as radiation, temperature, vpd, and evaporation were measured. It was observed that the diurnal variation in leaf water potential followed that of transpiration. Changes in the whole plant transpiration were not necessarily accounted for by the rs values measured on single leaves. Multiple regression relationships were obtained for plant water potentials on radiation and temperature and suggestions were made to their use in timing of irrigation. In a constant environmental condition, all species showed maximum rates of transpiration and photosynthesis during the first hour of the photoperiod. The rates steadily declined thereafter, and the decline was more pronounced in stressed plants. A decrease in leaf water potential could not account for these diurnal phenomena, and other internal control mechanisms were thought to be involved. It has been suggested that photorespiration increased under the high irradiance employed. Internal CO 2 levels then increased, causing stomatal closure, leading to a decline in transpiration. Photosynthesis also decreased through both stomatal closure and a decrease in the CO 2 gradient. Increases in mesophyll. resistance in the case of cucumber and pepper also occurred.<p/
