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Journal articles on the topic 'Gradient test'

Author: Grafiati

Published: 4 June 2021

Last updated: 11 February 2022

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1

Yu, Jincheng, Jerry Sellwood, Carlton Pryor, Li Chen, and Jinliang Hou. "A test for radial mixing using local star samples." Proceedings of the International Astronomical Union 10, H16 (August 2012): 357. http://dx.doi.org/10.1017/s1743921314011296.

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AbstractWe use samples of local main-sequence stars to show that the radial gradient of [Fe/H] in the thin disk of the Milky Way decreases with mean effective stellar temperature. We use the angular momentum of each star about the Galactic center to eliminate the effects of epicyclic motion, which would otherwise blur the estimated gradients. We use the effective temperatures as a proxy for mean age, and conclude that the decreasing gradient is consistent with the predictions of radial mixing due to transient spiral patterns. We find some evidence that the trend of decreasing gradient with increasing mean age breaks to a constant gradient for samples of stars whose main-sequence life-times exceed the likely age of the thin disk.

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David Suits, L., TC Sheahan, A. Hameiri, and RJ Fannin. "A Cyclic Gradient Ratio Test Device." Geotechnical Testing Journal 25, no. 3 (2002): 9921. http://dx.doi.org/10.1520/gtj11097j.

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3

Khan, M. W., A. R. Dawson, and A. M. Marshall. "A dynamic gradient ratio test apparatus." Geotextiles and Geomembranes 46, no. 6 (December 2018): 782–89. http://dx.doi.org/10.1016/j.geotexmem.2018.07.003.

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4

Rivera, Nelson, and Brian Folt. "Community assembly of glass frogs (Centrolenidae) in a Neotropical wet forest: a test of the river zonation hypothesis." Journal of Tropical Ecology 34, no. 2 (March 2018): 108–20. http://dx.doi.org/10.1017/s0266467418000068.

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Abstract:The river zonation hypothesis predicts that abiotic and biotic conditions along riparian gradients drive variation in animal communities. Glass frogs are a diverse group of Neotropical anurans that use riparian habitats exclusively for oviposition and larval development, but little is known about how glass frog communities are distributed across riparian gradients. Here, we measured glass frog community assembly across a gradient of riparian habitats from first- to fifth-order streams at La Selva Biological Station, Costa Rica. We performed repeated nocturnal frog calling surveys and built occupancy andN-mixture abundance models to test for varying patterns of species occupancy, community assembly, species richness (α-diversity) and species turnover (ß-diversity). We observed significant differences in patterns of species occupancy and community assembly across a stream-order gradient: occupancy of two species increased with stream order (Teratohyla pulverata,Hyalinobatrachium fleischmanni), one species decreased (Teratohyla spinosa), and one species did not vary (Espadarana prosoblepon). We evaluated four a priori hypotheses describing how α- and ß-diversity of centrolenids are shaped across the riparian gradient; our data were most consistent with a pattern of nested assemblages and increasing species richness along the riparian gradient. Species-specific patterns of occupancy and abundance resulted in assemblage-level differences consistent with theoretical predictions for highly aquatic organisms along riparian gradients.

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&NA;. "A TEST GRADIENT SYSTEM FOR OPTIMIZING DENSITY GRADIENT ISOLATION OF PANCREATIC ISLETS." Transplantation 48, no. 2 (August 1989): 354–57. http://dx.doi.org/10.1097/00007890-198908000-00036.

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6

Armas, Cristina, Susana Rodríguez-Echeverría, and Francisco I. Pugnaire. "A field test of the stress-gradient hypothesis along an aridity gradient." Journal of Vegetation Science 22, no. 5 (May 18, 2011): 818–27. http://dx.doi.org/10.1111/j.1654-1103.2011.01301.x.

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7

Lemonte, Artur J., and Silvia L. P. Ferrari. "The local power of the gradient test." Annals of the Institute of Statistical Mathematics 64, no. 2 (October 6, 2010): 373–81. http://dx.doi.org/10.1007/s10463-010-0315-4.

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8

Nardi, Marco. "The Gradient Filter Test to Assess Amblyopia." American Journal of Ophthalmology 111, no. 1 (January 1991): 119–20. http://dx.doi.org/10.1016/s0002-9394(14)76919-3.

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Keech, Ronald V., and Pamela J. Kutschke. "The Gradient Filter Test to Assess Amblyopia." American Journal of Ophthalmology 110, no. 1 (July 1990): 57–61. http://dx.doi.org/10.1016/s0002-9394(14)76938-7.

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10

Říha, Jaromír, and Jan Jandora. "Pressure conditions in the hole erosion test." Canadian Geotechnical Journal 52, no. 1 (January 2015): 114–19. http://dx.doi.org/10.1139/cgj-2013-0474.

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The hole erosion test (HET) is used in the study of soil erosion in the case of what is known as “piping” when concentrated leaks occur. The HET enables the determination of soil erosion characteristics such as the critical shear stress along the pre-formed hole (pipe) and the coefficient of soil erosion. Normally, in the HET, the hydraulic gradient is determined from the difference between the piezometric heads measured at the inflow and outflow chambers (upstream and downstream of the soil specimen). Hydraulic analysis shows that such measurements ignore losses at the entrance and exit of the hole, causing the overestimation of the hydraulic gradient along the length of the hole, and thus the calculated shear stress. In this technical note, the results of preliminary analysis using the Bernoulli principle and of numerical study of the pressure conditions in the HET apparatus are shown. The turbulent flow in the HET apparatus was calculated using ANSYS commercial CFD (computational fluid dynamics) software. The analysis was performed for various hole entrance shapes. The conclusion of this note details the differences between traditionally determined hydraulic gradients and those numerically derived along the length of a hole.

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11

Ran, Jin Cheng, Quan Jun Liu, and Zhi Guo Zhang. "Separation Test of Ilmenite in Yunnan." Applied Mechanics and Materials 556-562 (May 2014): 205–8. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.205.

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Because of the low ilmenite grade and fine dissemination size, a lot of low-magnetic flaky phlogopite in the run-of-mine ore and it can not effectively remove the phlogopite by the high gradient magnetic separation, so it is very difficult to sorting. We decided take the process of low intensity magnetic separation – high gradient magnetic separation and gravity separation discarding tailing - high gradient magnetic separation and shaking concentrate. Then we obtained satisfaction index - the grade and the recovery of TiO2 were 43.32% and 74.41% in the ilmenite concentrates, the grade and recovery of Fe were 66.83% and 56.77% in the iron concentrates. It provides a feasible way for such ilmenite separation.

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12

Keech, Ronald V., and Pamela J. Kutschke. "The Gradient Filter Test to Assess Amblyopia :Reply." American Journal of Ophthalmology 111, no. 1 (January 1991): 120–21. http://dx.doi.org/10.1016/s0002-9394(14)76920-x.

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13

Pincus, HJ, RJ Fannin, YP Vaid, and Y. Shi. "A Critical Evaluation of the Gradient Ratio Test." Geotechnical Testing Journal 17, no. 1 (1994): 35. http://dx.doi.org/10.1520/gtj10070j.

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14

Ramasundaram, T., and V. Sangeetha . "Bio-Inspired Gradient Genetic Optimization for Test Suite Generation." International Journal of Computer Sciences and Engineering 7, no. 1 (January 31, 2019): 99–107. http://dx.doi.org/10.26438/ijcse/v7i1.99107.

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15

Villa, F., F. Villa, and A. Luccio. "Test of a High-gradient Low-emittance Electron Gun." Laser and Particle Beams 15, no. 3 (September 1997): 427–47. http://dx.doi.org/10.1017/s0263034600010983.

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A maximum electric field E = 2.65 GV/m with an accelerated electron current of 1 KA has been obtained, for pulse lengths of 130 ps, in an electron gun based on Pulse Power Technology. This is the highest accelerating field ever achieved in the presence of such a large current. Measurements of beam emittance and energy from 0.4 to 2.65 MeV show that the scaling of the invariant emittance with electric field and with beam current is consistent with theoretical predictions. A few applications of high-gradient acceleration are discussed.

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Wang, W., Y. Huang, K. J. Hsia, K. X. Hu, and A. Chandra. "A study of microbend test by strain gradient plasticity." International Journal of Plasticity 19, no. 3 (March 2003): 365–82. http://dx.doi.org/10.1016/s0749-6419(01)00066-3.

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17

Pogue, Nathaniel J., Peter M. McIntyre, Akhdiyor I. Sattarov, and Charles Reece. "Ultra-Gradient Test Cavity for Testing SRF Wafer Samples." IEEE Transactions on Applied Superconductivity 21, no. 3 (June 2011): 1903–7. http://dx.doi.org/10.1109/tasc.2010.2088091.

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A 1.3 GHz test cavity has been designed to test wafer samples of superconducting materials. This mushroom shaped cavity, operating in TE01mode, creates a unique distribution of surface fields. The surface magnetic field on the sample wafer is 3.75 times greater than elsewhere on the Niobium cavity surface. This field design is made possible through dielectrically loading the cavity by locating a hemisphere of ultra-pure sapphire just above the sample wafer. The sapphire pulls the fields away from the walls so the maximum field the Nb surface sees is 25% of the surface field on the sample. In this manner, it should be possible to drive the sample wafer well beyond the BCS limit for Niobium while still maintaining a respectable Q. The sapphire's purity must be tested for its loss tangent and dielectric constant to finalize the design of the mushroom test cavity. A sapphire loaded CEBAF cavity has been constructed and tested. The results on the dielectric constant and loss tangent will be presented.

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18

Xu, Jia-Hao, Cheng-Gang Shao, Jie Luo, Qi Liu, Lin Zhu, and Hui-Hui Zhao. "Effect of gravity gradient in weak equivalence principle test." Chinese Physics B 26, no. 8 (August 2017): 080401. http://dx.doi.org/10.1088/1674-1056/26/8/080401.

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19

Chaney, RC, KR Demars, GR Fischer, AD Maré, and RD Holtz. "Influence of Procedural Variables on the Gradient Ratio Test." Geotechnical Testing Journal 22, no. 1 (1999): 22. http://dx.doi.org/10.1520/gtj11313j.

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20

Abel, Ernest L. "Gradient of alarm substance in the forced swimming test." Physiology & Behavior 49, no. 2 (February 1991): 321–23. http://dx.doi.org/10.1016/0031-9384(91)90050-x.

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21

Penfold, Guy C., and David Lamb. "A test of the hypothesis of ecological equivalence in an Australian subtropical rain forest." Journal of Tropical Ecology 18, no. 3 (March 26, 2002): 327–52. http://dx.doi.org/10.1017/s0266467402002249.

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We tested the hypothesis that tree species in a subtropical rain forest in south-east Queensland are ecologically equivalent and therefore have identical environmental requirements for their regeneration. We assessed the evidence that juveniles of species differed in their distributions in treefall gap microsites and along gradients of light availability, soil pH, soil PO4-P availability and soil NO3-N availability. Pairwise comparisons were made on a subset of the common species selected on the basis that they showed a relatively high level of positive association, and would therefore, a priori, be expected to have similar regeneration requirements. Detailed comparisons between the species failed to demonstrate evidence for species differentiation with respect to their tolerance of the disturbance associated with gap microsites or to the gradient of NO3-N availability. However, species differed markedly in their distributions along the soil pH gradient and along the gradients of light availability and soil PO4-P availability. The overall level of ecological differentiation between the species is high: seven out of the 10 possible species pairings showed evidence for ecological differentiation. Such niche differentiation amongst the juveniles of tree species may play an important role in maintaining the species richness of rain-forest communities.

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Fwa, T. F., S. A. Tan, and C. T. Chuai. "Permeability Measurement of Base Materials Using Falling-Head Test Apparatus." Transportation Research Record: Journal of the Transportation Research Board 1615, no. 1 (January 1998): 94–99. http://dx.doi.org/10.3141/1615-13.

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The development of a new falling-head procedure for laboratory permeability measurement of pavement base materials is described. The main advantage of the falling-head test over the conventional constant-head test is its ability to determine permeability properties of the test material at different levels of hydraulic gradients in a single test. The test setup is simpler and the test duration is much shorter. Each test takes only a few minutes to complete. A large number of tests have been conducted with the proposed procedure on different materials, including compacted crushed stones, glass spheres, and cement stabilized base materials. The falling-head test results were verified by performing constant-head permeability tests on the same specimens at different hydraulic gradients. Analysis on the falling-head test data revealed that the relationship between specific discharge and hydraulic gradient over the range studied could not be represented by a single linear relationship as stated by Darcy’s law. The proposed approach can be a useful tool for determining the drainage properties of base materials within the range of hydraulic gradients encountered in actual pavements.

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23

Yao, Yu Hong, Jian Feng Wei, Jiang Nan Liu, Zheng Pin Wang, and Yao Hua Jin. "Ageing Embrittlement of 15Cr1Mo1V Steel Welded Joints Evaluated by Small Punch Test." Advanced Materials Research 160-162 (November 2010): 1223–27. http://dx.doi.org/10.4028/www.scientific.net/amr.160-162.1223.

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The microstructure and property of 15Cr1Mo1V steel welded joints after 70,000h service have been researched by OM, SEM, Vickers hardness test and small punch test (SPT). The microstructure of 15Cr1Mo1V steel welded joints after service became coarse and the grain boundary became vague. More carbide particles were observed in welded joints after service. The microhardness gradient curve of 15Cr1Mo1V steel welded joints before service was higher than that after service. The SPT properties gradient curves, including yield strength gradient curve and tensile strength gradient curve by SPT, had the same shape and trend as the microhardness gradient curve before and after service. The SEM fracture appearance of SPT specimens was the characteristic of ductile fracture, irrespectively of before or after service, though the dimple size was a little bit big and deep before service and some cluster particles were observed after service for the ripening of carbides.

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24

Boisse, Philippe, Peng Wang, Nahiene Hamila, Kevin Lemeur, Anton Rusanov, E. Guzman, Manuel Ferretti, Marco D'Agostino, and Angela Madeo. "Bias Extension Test for In-Plane Shear Properties during Forming - Use at High Temperature and Limits of the Test." Key Engineering Materials 651-653 (July 2015): 369–74. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.369.

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The results of in-plane shear tests performed on 5-hardness satin woven carbon/PPS thermoplastic prepregs are described. The experimental analyses are based on bias-extension tests performed in an environmental chamber. The results are given for different temperatures on both side of the melting point. This range of temperature is those of the part during a thermoforming process. In another hand it is shown that second-gradient energy terms allow for an effective prediction of the onset of internal shear boundary layers which are transition zones between two different shear deformation modes. The existence of these boundary layers cannot be described by a simple first-gradient model.

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Liu, Zhipeng, Rui Feng, Xiuhan Li, Wei Wang, and Xiaoling Wu. "Gradient-Sensitive Optimization for Convolutional Neural Networks." Computational Intelligence and Neuroscience 2021 (March 22, 2021): 1–16. http://dx.doi.org/10.1155/2021/6671830.

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Convolutional neural networks (CNNs) are effective models for image classification and recognition. Gradient descent optimization (GD) is the basic algorithm for CNN model optimization. Since GD appeared, a series of improved algorithms have been derived. Among these algorithms, adaptive moment estimation (Adam) has been widely recognized. However, local changes are ignored in Adam to some extent. In this paper, we introduce an adaptive learning rate factor based on current and recent gradients. According to this factor, we can dynamically adjust the learning rate of each independent parameter to adaptively adjust the global convergence process. We use the factor to adjust the learning rate for each parameter. The convergence of the proposed algorithm is proven by using the regret bound approach of the online learning framework. In the experimental section, comparisons are conducted between the proposed algorithm and other existing algorithms, such as AdaGrad, RMSprop, Adam, diffGrad, and AdaHMG, on test functions and the MNIST dataset. The results show that Adam and RMSprop combined with our algorithm can not only find the global minimum faster in the experiment using the test function but also have a better convergence curve and higher test set accuracy in experiments using datasets. Our algorithm is a supplement to the existing gradient descent algorithms, which can be combined with many other existing gradient descent algorithms to improve the efficiency of iteration, speed up the convergence of the cost function, and improve the final recognition rate.

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26

Bybee, Karen. "Field Test of a Full-Scale Dual-Gradient Drilling System." Journal of Petroleum Technology 53, no. 11 (November 1, 2001): 34. http://dx.doi.org/10.2118/1101-0034-jpt.

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Saravanan, M., K. Sharma, M. Kumar, H. Vijaykumar, and D. Mondal. "Analysis of Serum Ascites Albumin Gradient Test in Ascitic Dogs." Veterinary World 5, no. 5 (2012): 285. http://dx.doi.org/10.5455/vetworld.2012.285-287.

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Nowicki, A., R. Olszewski, J. Etienne, P. Karłowicz, and J. Adamus. "Assessment of wall velocity gradient imaging using a test phantom." Ultrasound in Medicine & Biology 22, no. 9 (January 1996): 1255–60. http://dx.doi.org/10.1016/s0301-5629(96)00159-7.

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Clarke, S. F. J. "Core-peripheral temperature gradient as a diagnostic test in dyspnoea." Emergency Medicine Journal 22, no. 9 (September 1, 2005): 633–35. http://dx.doi.org/10.1136/emj.2004.017624.

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Okamura, H., G. Yagawa, T. Hidaka, Y. Urabe, M. Satoh, and J. Sano. "A Crack Arrest Test Using a Toughness Gradient Steel Plate." Journal of Pressure Vessel Technology 117, no. 4 (November 1, 1995): 330–34. http://dx.doi.org/10.1115/1.2842131.

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A crack arrest test was carried out using a toughness gradient steel plate with three layers to study the concept of crack arrest toughness. Four-point bending load with thermal shock was applied to the large flat plate specimen with a surface crack. Five crack initiations and arrests were observed during the test and the propagated crack bifurcated. Finally, cracks were arrested at the boundary of the first and the second layer, except for a small segment of the crack. The first crack initiation took place slightly higher than the lower bound of KIc data obtained by ITCT specimens. That is, the KIC concept for brittle crack initiation was verified for heavy section steel plates. The first crack arrest took place within the scatter band of KIa and KId data for the first layer. That is, the KIa concept appears applicable for crack arrest of a short crack jump.

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Lowe, I. J., G. Zhu, and J. F. Shen. "A design and test of homogeneous self-shielding gradient coils." Magnetic Resonance Imaging 5, no. 6 (January 1987): 553. http://dx.doi.org/10.1016/0730-725x(87)90428-0.

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MARINHODASILVA, A. "Captopril test identifies severity of residual pressure gradient in recoartation." American Journal of Hypertension 17, no. 5 (May 2004): S157. http://dx.doi.org/10.1016/j.amjhyper.2004.03.412.

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Weller, Hilary, and Ava Shahrokhi. "Curl-Free Pressure Gradients over Orography in a Solution of the Fully Compressible Euler Equations with Implicit Treatment of Acoustic and Gravity Waves." Monthly Weather Review 142, no. 12 (December 1, 2014): 4439–57. http://dx.doi.org/10.1175/mwr-d-14-00054.1.

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Abstract Steep orography can cause noisy solutions and instability in models of the atmosphere. A new technique for modeling flow over orography is introduced that guarantees curl-free gradients on arbitrary grids, implying that the pressure gradient term is not a spurious source of vorticity. This mimetic property leads to better hydrostatic balance and better energy conservation on test cases using terrain-following grids. Curl-free gradients are achieved by using the covariant components of velocity over orography rather than the usual horizontal and vertical components. In addition, gravity and acoustic waves are treated implicitly without the need for mean and perturbation variables or a hydrostatic reference profile. This enables a straightforward description of the implicit treatment of gravity waves. Results are presented of a resting atmosphere over orography and the curl-free pressure gradient formulation is advantageous. Results of gravity waves over orography are insensitive to the placement of terrain-following layers. The model with implicit gravity waves is stable in strongly stratified conditions, with NΔt up to at least 10 (where N is the Brunt–Väisälä frequency). A warm bubble rising over orography is simulated and the curl-free pressure gradient formulation gives much more accurate results for this test case than a model without this mimetic property.

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He, W. M., and R. M. Callaway. "The potential for misleading correlations in single-factor analysis of complex gradients." Web Ecology 9, no. 1 (December 21, 2009): 77–81. http://dx.doi.org/10.5194/we-9-77-2009.

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Abstract. Gradient analysis is an important tool for describing patterns in ecology. Natural environmental gradients are complex combinations of factors, suggesting that gradientsshould, when possible, be analyzed in multi-factorial ways. We searched papers published in Ecology, Global Change Biology, Journal of Ecology, Oecologia, Oikos, and Journal of Vegetation Science from January 2001 to December 2005, and found 133 papers matching two keywords: “gradient analysis” and “environmental gradient”. Of these, 86 utilized single-factor correlation analyses between ecological entities and natural environmental gradients. Thus the use of single-factor correlations in studies of natural environmental gradients is widespread despite the potential of this approach to overemphasize the importance of the particular factor chosen. We reanalyzed a data set from the literature, provided a example of contrasting analyses, and analyzed our own data with both single- and multiple-factor analyses to demonstrate how single-factor correlation can result in correlations that provide incomplete analysis. Integrated multi-factor approaches to studying natural environmental gradients cannot solve all analytical problems when two or more important variables are correlated, but are likely to better test the relative importance of factors driving ecological patterns.

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Aguirre-Tamaral, Adrián, and Isabel Guerrero. "Improving the understanding of cytoneme-mediated morphogen gradients by in silico modeling." PLOS Computational Biology 17, no. 8 (August 3, 2021): e1009245. http://dx.doi.org/10.1371/journal.pcbi.1009245.

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Morphogen gradients are crucial for the development of organisms. The biochemical properties of many morphogens prevent their extracellular free diffusion, indicating the need of an active mechanism for transport. The involvement of filopodial structures (cytonemes) has been proposed for morphogen signaling. Here, we describe an in silico model based on the main general features of cytoneme-meditated gradient formation and its implementation into Cytomorph, an open software tool. We have tested the spatial and temporal adaptability of our model quantifying Hedgehog (Hh) gradient formation in two Drosophila tissues. Cytomorph is able to reproduce the gradient and explain the different scaling between the two epithelia. After experimental validation, we studied the predicted impact of a range of features such as length, size, density, dynamics and contact behavior of cytonemes on Hh morphogen distribution. Our results illustrate Cytomorph as an adaptive tool to test different morphogen gradients and to generate hypotheses that are difficult to study experimentally.

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Joshaghani, Alireza, and Dan G. Zollinger. "Assessment of Concrete Pavement Set Gradient Based on Analysis of Slab Behavior and Field Test Data." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 6 (May 16, 2019): 512–23. http://dx.doi.org/10.1177/0361198119849900.

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This paper discusses how the set gradient in a jointed concrete slab is related to the cracking performance and its effects on fatigue crack model calibration. The role of curing quality on-set and how curing quality parameters are related to the set gradient is also discussed. To assess the impacts of curing practices on the set gradient of a newly constructed concrete slab, a field investigation was undertaken at the Florida Department of Transportation State Materials Office in Gainesville, Florida. This study investigated early age concrete pavement behavior with respect to the development of the set gradient. In this research, four test slabs were placed and cured under different conditions to create different states of stress and creep behavior during and after hardening of the concrete. Early age concrete temperature and moisture history are key factors that affect the slab curling and warping behavior as they pertain to the resulting set gradient. This paper elaborates on the details of the cracking performance data analysis of test data associated with the development of the set gradient.

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Shang, H. M., G. S. Tan, and W. C. M. Tan. "Effects of Prestrain With Strain Gradient Present on Sheet Metal Formability." Journal of Engineering Materials and Technology 107, no. 4 (October 1, 1985): 298–306. http://dx.doi.org/10.1115/1.3225823.

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In this investigation, two double-stage forming processes are used to study the effects of prestrain on sheet metal formability. The processes chosen are the bulge test and the plunger test using a die throat to punch diameter ratio of 2.42. It is seen that during the second stage of forming, deformation and shape of the deformed shell are influenced by the level of prestrain and strain gradients on the prestrained workpiece. An improved formability is observed when the workpiece for the plunger test is prestrained by hydroforming, but the formability is reduced when the prestraining process becomes the plunger test. The present results also imply that care should be taken in utilizing the forming limit diagram even if it is constructed from double-stage forming, in which strain gradient on the prestrained workpiece is generally absent.

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38

Fudge, Douglas S., James S. Ballantyne, and E. Don Stevens. "A test of biochemical symmorphosis in a heterothermic tissue: bluefin tuna white muscle." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 280, no. 1 (January 1, 2001): R108—R114. http://dx.doi.org/10.1152/ajpregu.2001.280.1.r108.

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To test predictions of biochemical symmorphosis, we measured the activity of seven consecutive glycolytic enzymes at three positions along the heterothermic white muscle of the bluefin tuna. Biochemical symmorphosis predicts that adjustments in sequential enzyme concentrations along a thermal gradient should occur as a function of the thermal sensitivity of the enzymes to ensure that no one enzyme in the pathway is in excess at any point along the gradient. We found no evidence for adjustments in enzyme quantity or quality along the thermal gradient, as well as no evidence for the prediction that the more temperature-sensitive enzymes would exhibit more dramatic compensation. Conservation of glycolytic flux in the cold exterior and warm interior muscle may be achieved by the near insensitivity of glyceraldehyde-3-phosphate dehydrogenase to temperature in this tissue. This may have the added benefit of moderating flux during seasonal or transient changes in the thermal gradient. According to the strictest application of biochemical symmorphosis, such a mechanism represents adequate, yet suboptimal design.

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Takano, Jun, and Tsutomu Sugiyama. "Genetic analysis of developmental mechanisms in hydra." Development 90, no. 1 (December 1, 1985): 123–38. http://dx.doi.org/10.1242/dev.90.1.123.

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Effect of food was examined on the budding rate and the developmental gradients of a mutant hydra strain L4. This mutant strain has very high levels of head-inhibition potential gradient along its body axis (Takano & Sugiyama, 1983). It also has a reduced budding capacity when it is cultured using brine shrimp nauplii as food, but its budding capacity is significantly improved when a small amount of tubifex worm tissue is added to its diet of brine shrimp (Takano, 1984). To test whether or not this change of budding rate is correlated with the change in the levels of the head-activation or head-inhibition potential gradients, L4 animals were cultured on the diet of brine shrimp with or without addition of tubifex worm tissue and the budding rates and the gradient levels were examined in these animals. The results showed that food affected the budding rate in L4 without affecting its gradient levels. This suggests that the gradient levels and the budding rate in L4 are uncorrelated to each other, and that therefore the high levels of head-inhibition potential are not the cause for the low budding rate in this strain (cf., Takano & Sugiyama, 1983).

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LIANG, Wei, Tieping WEI, and Xiaoxiang YANG. "Constitutive Model of Thin Metal Sheet in Bulging Test Considering Strain Gradient Hardening." Materials Science 26, no. 4 (August 17, 2020): 415–25. http://dx.doi.org/10.5755/j01.ms.26.4.22201.

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The study of the size effect was one of the most important subjects in the field of micro-forming. To investigate the stress of the thin sheet in the bulging test with the second order size effect, a constitutive equation considering the strain gradient hardening was proposed. Based on the equation, the stress of the thin sheet during the bulging test was calculated by the finite element method. The bulging tests with various thicknesses of brass sheets and radiuses of punching balls were performed to verify the proposed equation. The results showed that the constitutive equation could capture the stress variations, while the simulation using the constitutive equation from the conventional theory of plasticity showed the results with large deviation from those of the experiment. It was found that the stress was sensitive to the thickness of the sheet and the radius of the punching ball in bulging test of thin brass sheet. The bulging of the thin brass sheet with a thickness below ten times of its material intrinsic length would cause the generation of the geometrically necessary dislocations, which induced the strain gradient hardening. Besides that, the decrement of the punching ball radius would also increase the inhomogeneous deformation and enhance the strain gradient hardening during the thin sheet bulging process. The strain gradient hardening during the thin sheet bulging test was related to the strain of the sheet. The hardening effect of the strain gradient was obvious when the strain was small. The strain gradient hardening should be considered in the thin sheet bulging test with the second order size effect.

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Jenkins, Gavin, and Paul Tupper. "A Dynamic Neural Gradient Model of Two-Item and Intermediate Transposition." Neural Computation 30, no. 7 (July 2018): 1961–82. http://dx.doi.org/10.1162/neco_a_01093.

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Transposition is a tendency for organisms to generalize relationships between stimuli in situations where training does not objectively reward relationships over absolute, static associations. Transposition has most commonly been explained as either conceptual understanding of relationships (Köhler, 1938) as nonconceptual effects of neural memory gradients (as in Spence's stimulus discrimination theory, 1937 ). Most behavioral evidence can be explained by the gradient account, but a key finding unexplained by gradients is intermediate transposition, where a central (of three) stimulus, “relationally correct response,” is generalized from training to test. Here, we introduce a dynamic neural field (DNF) model that captures intermediate transposition effects while using neural mechanisms closely resembling those of Spence's original proposal. The DNF model operates on dynamic rather than linear neural relationships, but it still functions by way of gradient interactions, and it does not invoke relational conceptual understanding in order to explain transposition behaviors. In addition to intermediate transposition, the DNF model also replicates the predictions of stimulus discrimination theory with respect to basic two-stimulus transposition. Effects of wider test item spacing were additionally captured. Overall, the DNF model captures a wider range of effects in transposition than stimulus discrimination theory, uses more fully specified neural mechanics, and integrates transposition into a wider modeling effort across cognitive tasks and phenomena. At the same time, the model features a similar low-level focus and emphasis on gradient interactions as Spence's, serving as a conceptual continuation and updating of Spence's work in the field of transposition.

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Campos-Cerqueira, Marconi, and T. Mitchell Aide. "Changes in the acoustic structure and composition along a tropical elevational gradient." Journal of Ecoacoustics 1, no. 1 (December 6, 2017): 1. http://dx.doi.org/10.22261/jea.pnco7i.

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Elevational gradients influence the distribution and composition of animal species and can provide useful information for the development of conservation strategies in the context of climate change. Despite an increase in studies of species diversity along elevational gradients, there is still a lack of information about community responses to environmental gradients, in part because of the logistical limitations of sampling multiple taxa simultaneously. One solution is to use passive acoustic monitoring (PAM) to acquire and analyze information from different animal taxa simultaneously along an entire elevational gradient. To improve our understanding of how environmental gradients influence patterns of animal communities and to test the relationship between soundscapes and animal composition we investigated how variation in bird and anuran composition affect the acoustic structure and composition of the soundscapes along an elevation gradient. We used PAM deploying portable acoustic recorders along three elevational transects in the Luquillo Mountains (LM), Puerto Rico. We found that elevation plays a major role in structuring the acoustic community and that the soundscape composition reflected the same patterns of anuran and bird distribution and composition along the elevational gradient. This study shows how different animal taxa respond to environmental gradients and provide strong evidence for the use of soundscapes as a tool to describe and compare species distribution and composition across large spatial scales.

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Hirano, Tetsuo, Toshiaki Yoneyama, Hiroko Matsuzaki, and Takainitsu Sekine. "Simple method for preparing a concentration gradient of serum components by freezing and thawing." Clinical Chemistry 37, no. 7 (July 1, 1991): 1225–29. http://dx.doi.org/10.1093/clinchem/37.7.1225.

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Abstract We created a simple method for obtaining a series of successively more-concentrated samples from a serum without changing the ratio of its components. We froze a pooled serum and then allowed it to thaw undisturbed. The serum components formed a gradient of increasing concentration from the top of the sample to the bottom. We found that (a) in test results, each fraction of serum in the gradient showed almost the same relative concentrations of components (i.e., inorganic and organic compounds, proteins, metals, and hormones), irrespective of atomic or molecular mass; (b) the concentration gradient depended on the thawing temperature but not on the freezing temperature; (c) when we thawed the frozen sample with centrifugation, the slope of the concentration gradient increased with increasing centrifugal force; (d) when the thawed sample was fractionated into 10 fractions from the top to the bottom, the original serum concentration was always maintained between the sixth and seventh fractions from the top; and (e) the concentration gradient became steeper with repeated freezing and thawing. By using this method, one can easily prepare serum samples at gradients of concentration useful in the clinical laboratory, although the mechanism of gradient formation is still unclear.

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Linden, Rafael. "Dendritic competition in the developing retina: Ganglion cell density gradients and laterally displaced dendrites." Visual Neuroscience 10, no. 2 (March 1993): 313–24. http://dx.doi.org/10.1017/s0952523800003710.

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AbstractDendrites of retinal ganglion cells (RGCs) tend to be distributed preferentially toward areas of reduced RGC density. This, however, does not occur in the retina of normal pigmented rats, in which it has been suggested that the centro-peripheral gradient of RGC density is too shallow to provide directional guidance to growing dendrites. In this study, laterally displaced dendrites of RGCs retrogradely labeled with horseradish peroxidase were related to cell density gradients induced experimentally in the rat retina. Neonatal unilateral lesions of the optic tract produced retrograde degeneration of contralaterally projecting RGCs, but spared ipsilaterally projecting neurons in the same retina. These lesions created an anomalous temporal to nasal gradient of cell density across the decussation line, opposite to the nasal to temporal gradient found along the same axis in either normal rats or rats that had the contralateral eye removed at birth. RGCs in rats that received optic tract lesions had their dendrites displaced laterally toward the depleted nasal retina, while in either normal or enucleated rats there was no naso-temporal asymmetry. The lateral displacement affected both primary dendrites and higher-order branches. However, the gradient of cell density after optic tract lesions was less steep than the gradient in either normal or enucleated rats. To test for the presence of steeper gradients at early stages of development, RGC density gradients were also examined at postnatal day 5 (P5). In normal rats, the RGCs were homogeneously distributed throughout the retina, while rats given optic tract lesions at birth already showed a temporo-nasal density gradient at P5. Still, this anomalous gradient was less steep than that found in normal adults. It is concluded that the time course, rather than the steepness of the RGC density gradient, is the major determinant of the lateral displacement of dendritic arbors with respect to the soma in developing RGCs. The data are consistent with the idea that the overall shape of dendritic arbors depends in part on dendritic competition during retinal development.

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Colville, Jonathan F., Colin M. Beale, Félix Forest, Res Altwegg, Brian Huntley, and Richard M. Cowling. "Plant richness, turnover, and evolutionary diversity track gradients of stability and ecological opportunity in a megadiversity center." Proceedings of the National Academy of Sciences 117, no. 33 (August 5, 2020): 20027–37. http://dx.doi.org/10.1073/pnas.1915646117.

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Research on global patterns of diversity has been dominated by studies seeking explanations for the equator-to-poles decline in richness of most groups of organisms, namely the latitudinal diversity gradient. A problem with this gradient is that it conflates two key explanations, namely biome stability (age and area) and productivity (ecological opportunity). Investigating longitudinal gradients in diversity can overcome this problem. Here we investigate a longitudinal gradient in plant diversity in the megadiverse Cape Floristic Region (CFR). We test predictions of the age and area and ecological opportunity hypotheses using metrics for both taxonomic and phylogenetic diversity and turnover. Our plant dataset includes modeled occurrences for 4,813 species and dated molecular phylogenies for 21 clades endemic to the CFR. Climate and biome stability were quantified over the past 140,000 y for testing the age and area hypothesis, and measures of topographic diversity, rainfall seasonality, and productivity were used to test the ecological opportunity hypothesis. Results from our spatial regression models showed biome stability, rainfall seasonality, and topographic heterogeneity were the strongest predictors of taxonomic diversity. Biome stability alone was the strongest predictor of all diversity metrics, and productivity played only a marginal role. We argue that age and area in conjunction with non–productivity-based measures of ecological opportunity explain the CFR’s longitudinal diversity gradient. We suggest that this model may possibly be a general explanation for global diversity patterns, unconstrained as it is by the collinearities underpinning the latitudinal diversity gradient.

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Ahmed, Ola, and Peter F. Lovibond. "Rule-based processes in generalisation and peak shift in human fear conditioning." Quarterly Journal of Experimental Psychology 72, no. 2 (March 30, 2018): 118–31. http://dx.doi.org/10.1177/1747021818766461.

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Two experiments explored the role of verbalisable rules in generalisation of human differential fear conditioning with electric shock as the aversive stimulus. Two circles of different sizes served as conditioned stimuli (CS+ and CS–), before testing with a range of circle sizes. In Experiment 1, shock expectancy ratings followed a peak-shifted unimodal gradient, with maximum ratings at a test value further along the dimension from CS+ in the opposite direction to CS–. However, differentiable gradients were observed when participants were divided on the basis of the rules they reported using during the task (linear and similarity). Experiment 2 was designed to counter the contradictory feedback arising from extinction testing by removing the shock electrodes during the test phase. A more linear overall gradient was observed, and sub-groups defined by self-reported rules showed distinct gradients that were congruent with their rules. These results indicate that rule-based processes are influential in generalisation of conditioned fear along simple stimulus dimensions, and may help explain generalisation phenomena that have traditionally been attributed to automatic, similarity-based processes.

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Veznik, Z., D. Svecova, A. Zajicova, Z. Reckova, and J. Rubes. "The interrelationship between quality parameters of sperm before and after separation by gradient centrifugation." Veterinární Medicína 52, No. 10 (January 7, 2008): 423–29. http://dx.doi.org/10.17221/2051-vetmed.

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Significance of a short-time survival test for the prediction of quality parameters of sperm obtained by gradient centrifugation was evaluated from an aspect of their functional resistance. Frozen semen samples from 27 bulls before and after separation were assessed by a 120-min survival test. The evaluation of morphological examination of ejaculates was carried out using the SASMO computer program. Statistically significant interrelationship between sperm quality parameters in the initial insemination doses, the amounts of obtained sperm after separation and their functional and vital resistance in the survival test was documented.

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Ülger Toprak, Nurver, Öncü Akgül, Güven Kelekçi, and Güner Söyletir. "İstanbul’da İki Merkeze ait Prevotella Türlerinin Gradiyent Test Yöntemiyle Belirlenen Antimikrobiyal İlaç Duyarlılığı." Mikrobiyoloji Bulteni 54, no. 2 (April 15, 2020): 246–56. http://dx.doi.org/10.5578/mb.69309.

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Mislevy, S. P., and T. Wang. "The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 1—Mean Quantities." Journal of Turbomachinery 118, no. 4 (October 1, 1996): 717–27. http://dx.doi.org/10.1115/1.2840927.

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The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6 percent. The acceleration parameter, K, was kept constant along the test section. Both surface heat transfer and boundary layer measurements were conducted. The boundary layer measurements were conducted with a three-wire probe (two velocity wires and one temperature wire) for two representative cases, K1 = −0.51 × 10−6 and K2 = −1.05 × 10−6. The surface heat transfer measurements were conducted for K values ranging from −0.045 × 10−6 to −1.44 × 10−6 over five divergent wall angles. The Stanton numbers of the cases with adverse pressure gradients were greater than that of the zero-pressure-gradient turbulent correlation in the low-Reynolds-number turbulent flow, and the difference increased as the adverse pressure gradient was increased. The adverse pressure gradient caused earlier transition onset and shorter transition length based on Rex, Reδ*, and Reθ in comparison to zero-pressure-gradient conditions. As expected, there was a reduction in skin friction as the adverse pressure gradient increased. In the U+−Y+ coordinates, the adverse pressure gradients had a significant effect on the mean velocity profiles in the near-wall region for the late-laminar and early transition stations. The mean temperature profile was observed to precede the velocity profile in starting and ending the transition process, opposite to what occurred in favorable pressure gradient cases in previous studies. A curve fit of the turbulent temperature profile in the log-linear region for the K2 case gave a conduction layer thickness of Y+ = 9.8 and an average Prt = 0.71. In addition, the wake region of the turbulent mean temperature profile was significantly suppressed.

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Andres, S. Verdu, M. Garlasche, R. Bonomi, U. Amaldi, A. Degiovanni, and R. Wegner. "203 THE TERA HIGH GRADIENT TEST PROGRAM FOR HADRON THERAPY LINACS." Radiotherapy and Oncology 102 (March 2012): S99—S100. http://dx.doi.org/10.1016/s0167-8140(12)70173-1.

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