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Significant Gradient (significant + gradient)
Selected AbstractsSimplified System for Absolute Fracture Risk Assessment: Clinical Validation in Canadian Women,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2009William D Leslie Abstract Absolute 10-yr fracture risk based on multiple factors is the preferred method for risk assessment. A simplified risk assessment system from sex, age, DXA, and two clinical risk factors (CRFs),prior fracture and systemic corticosteroid (CS) use-has been used in Canada since 2005. This study was undertaken to evaluate this system in the Canadian female population. A total of 16,205 women ,50 yr of age at the time of baseline BMD (1998,2002) were identified in a database containing all clinical DXA test results for the Province of Manitoba, Canada. Basal 10-yr fracture risk from age and minimum T-score (lumbar spine, femur neck, trochanter, total hip) was categorized as low (<10%), moderate (10,20%), or high (>20%). Health service records since 1987 were assessed for prior fracture codes (N = 5224), recent major CS use (N = 616), and fracture codes after BMD testing (mean, 3.1 yr of follow-up) for the hip, vertebrae, forearm, or humerus (designated osteoporotic, N = 757). Fracture risk predicted from age and minimum T-score alone showed a significant gradient in observed fracture rates (low 5.1 [95% CI, 4.1,6.4], moderate 11.5 [95% CI, 10.1,13.0], high 25.4 [95% CI, 23.2,27.9] per 1000 person-years; p -for-trend <0.0001). There was an incremental increase in incident fracture rates from a prior fracture (13.9 [95% CI, 11.3,16.4] per 1000 person-years) or major CS use (11.2 [95% CI, 4.1,18.2] per 1000 person-years). This simplified fracture risk assessment system provides an assessment of fracture risk that is consistent with observed fracture rates. [source] The Amplatzer Duct Occluder II: A New Device for Percutaneous Ductus Arteriosus ClosureJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 6 2009ZAKHIA SALIBA M.D. Objective: Study the new Amplatzer Duct Occluder II (ADO II). Limitations were encountered with the preexisting devices in nonconical ducts, large ducts, or in small infants. These include failure, residual shunts, protrusion, migration, and vascular damage. Methods: Between June 2008 and March 2009, 20 consecutive patients were enrolled. In cases where different devices were applicable, we favored the use of the ADO II to maximize our experience with this device and prove its superiority. No coils were required in these 20 patients. Results: There were 15 females and 5 males (median age 2 years). ADO II group (n = 16): Immediate complete closure in 75% of the patients, rising to 93.7% at 24 hours. A residual shunt persisted at 3 months in one child. Aortic narrowing from device protrusion was noted in two type E ducts, without any significant gradient, however. ADO I group (n = 4): In two adolescents and in one adult patient, the duct was successfully closed. In a 2-year-old patient with a 6.6 mm type B duct, the ADO I totally obstructed the aortic flow and was retrieved before releasing. The child was sent for surgery. Conclusion: Even though we did not compare the ADO II to other devices, we feel that it has the capacity to substitute most of the coils, and some of the original ADO I indications. Arterial access was sufficient in most patients, but venous delivery is advised in small infants with large or long ducts, to avoid aortic protrusion and residual shunts. [source] The NOAO Fundamental Plane Survey , III.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2006Variations in the stellar populations of red-sequence galaxies from the cluster core to the virial radius ABSTRACT We analyse absorption line-strength indices for ,3000 red-sequence galaxies in 94 nearby clusters to investigate systematic variations of their stellar content with location in the host cluster. The data are drawn from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. Our adopted method is a generalization of that introduced by Nelan et al. to determine the global age,mass and metallicity,mass relations from the same survey. We find strong evidence for a change in galaxy properties, at fixed mass, over a range from the cluster centre to the virial radius, R200. For example, red-sequence galaxies further out in the clusters have weaker Mgb5177 (at ,8, significance) and stronger H, and H, absorption (,3,, ,4,) than galaxies of the same velocity dispersion in the cluster cores. The Fe5270 and Fe5335 indices show only very weak trends with radius. Using a total of 12 indices, the pattern of cluster-centric gradients is considered in light of their different dependences on stellar age and chemical composition. The measured gradients for all 12 indices can be reproduced by a model in which red-sequence galaxies at ,1 R200 have on average younger ages (by 15 ± 4 per cent) and lower ,-element abundance ratios (by 10 ± 2 per cent) than galaxies of the same velocity dispersion but located near the cluster centres. For the total metallicity, Z/H, no significant gradient is found (2 ± 3 per cent larger at R200 than in the cores). There are hints that the age trend may be stronger for galaxies of lower mass and/or for galaxies with more discy morphology. We show, however, that the trends cannot be driven primarily by changes in the morphological mix as a function of radius. The cluster-centric age and [,/Fe] gradients are in the sense expected if galaxies in the cluster core were accreted at an earlier epoch than those at larger radii, and if this earlier accretion contributed to an earlier cessation of star formation. The size of the observed age trend is comparable to predictions from semi-analytic models of hierarchical galaxy formation. [source] Native harvester ants threatened with widespread displacement exert localized effects on serpentine grassland plant community compositionOIKOS, Issue 2 2005Halton A. Peters Seed-harvesting ants can influence the abundance and distribution of plant species through both the selective harvesting of seeds and the construction of nutrient-rich nest mounds, but the relative contributions of these two mechanisms have not been addressed by previous studies. Furthermore, the impact of ant seed harvesting in California serpentine grasslands remains unresolved because of divergent results from several previous experiments. This study investigates the influence of harvester ants on serpentine grassland plant species composition by examining two potential signatures of seed harvesting ants on plant community composition: species composition on versus off ant nest mounds, and species abundance as a function of distance from nest mounds. Of the 28 plant species identified in this study, 22 exhibited spatial patterns consistent with effects of seed harvesting, nest construction, or both. Although most species showed significant gradients in abundance with distance from a nest, there were no clear relationships between plant species distributions and previously reported harvester ant seed foraging patterns. Harvester ant nest mounds supported plant communities that were distinct from the surrounding serpentine grassland, with notably higher densities of legumes and invasive annual grasses. Comparison of our results with those of previous studies indicates that the patterns we observed are generally consistent over time, but affect more species and a larger fraction of the grassland than previously reported. Unaffected areas of the grassland seem likely to serve as important refuges for some plant species. [source] Do pathways of water movement and leaf anatomical dimensions allow development of gradients in H218O between veins and the sites of evaporation within leaves?PLANT CELL & ENVIRONMENT, Issue 1 2004M. M. BARBOUR ABSTRACT The oxygen isotope enrichment of bulk leaf water (,L), is often observed to be poorly predicted by the Craig,Gordon-type models developed for evaporative enrichment from a body of water (,e). The discrepancy between ,L and ,e may be explained by gradients in enrichment within the leaf as a result of convection of unenriched water to the sites of evaporation opposing the diffusion of enrichment away from the sites; a Péclet effect. However, this effect is difficult to quantify because the velocities of water movement within the leaf are unknown. This paper attempts to model the complex anatomy of a leaf, and hence such velocities, to assess if the gradients in H218O required for a significant Péclet effect between the vein and the evaporation sites are possible within a leaf. Published dimensions of cells in wheat leaves are used to calculate the cross-sectional areas perpendicular to the flow velocities of water through assumed pathways. By combining the ratio of actual to ,slab' velocities with anatomical lengths, equivalent lengths (L) emerge. In this way, it is concluded that if water moves only through the cell walls, or from cell to cell via either aquaporins or plasmodesmata, and evaporates from mesophyll cells, or the substomatal cells, or from the peristomatal region (a total of 15 combinations of assumptions), then the 15 central estimates of the values of L are between 9 and 200 mm. Each of these central estimates is subject to uncertainty, but overall their magnitude is important and estimates of L are comparable with those made from fitting to isotopic data (8 mm for wheat). It is concluded that significant gradients in enrichment between the vein and the evaporation sites are likely. [source] Gas sensing in microplates with optodes: Influence of oxygen exchange between sample, air, and plate materialBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2005Sarina Arain Abstract Microplates with integrated optical oxygen sensors are a new tool to study metabolic rates and enzyme activities. Precise measurements are possible only if oxygen exchange between the sample and the environment is known. In this study we quantify gas exchange in plastic microplates. Dissolved oxygen was detected using either an oxygen-sensitive film fixed at the bottom of each well or a needle-type sensor. The diffusion of oxygen into wells sealed with different foils, paraffin oil, and paraffin wax, respectively, was quantified. Although foil covers showed the lowest oxygen permeability, they include an inevitable gas phase between sample and sealing and are difficult to manage. The use of oil was found to be critical due to the extensive shaking caused by movement of the plates during measurements in microplate readers. Thus, paraffin wax was the choice material because it avoids convection of the sample and is easy to handle. Furthermore, without shaking, significant gradients in pO2 levels within a single well of a polystyrene microplate covered with paraffin oil were detected with the needle-type sensor. Higher pO2 levels were obtained near the surface of the sample as well as near the wall of the well. A significant diffusion of oxygen through the plastic plate material was found using plates based on polystyrene. Thus, the location of a sensor element within the well has an effect on the measured pO2 level. Using a sensor film fixed on the bottom of a well or using a dissolved pO2 -sensitive indicator results in pO2 offset and in apparently lower respiration rates or enzyme activities. Oxygen diffusion through a polystyrene microplate was simulated for measurements without convection,that is, for samples without oxygen diffusion through the cover and for unshaken measurements using permeable sealings. This mathematical model allows for calculation of the correct kinetic parameters. © 2005 Wiley Periodicals, Inc. [source] | |||||||||||||