Faculty Opinions recommendation of Compositional gradients in Gramineae genes.

2002 ◽  
Author(s):  
Klaus Mayer
Keyword(s):  
Compositional Gradients

The Effect of Specimen Thickness and Probe Size on Aem Analysis of Cr-Depletion Profiles in Sensitized Stainless Steel

1982 ◽  
Vol 40 ◽  
pp. 518-519
Author(s):  
E. L. Hall
Keyword(s):  
Grain Boundaries ◽  
Boundary Region ◽  
Chromium Concentration ◽  
Foil Thickness ◽  
Specimen Thickness ◽  
Probe Size ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Sensitization Process ◽  
Compositional Gradients

Sensitization in stainless steels is caused by the formation of chromium-rich M23C6 carbides at grain boundaries, which depletes the adjacent matrix and boundary region of chromium, and hence leads to rapid intergranular attack. To fully understand the sensitization process, and to test the accuracy of theories proposed to model this process, it is necessary to obtain very accurate measurements of the chromium concentration at grain boundaries in sensitized specimens. Quantitative X-ray spectroscopy in the analytical electron microscope (AEM) enables the chromium concentration profile across these boundaries to be studied directly; however, it has been shown that a strong effect of foil thickness and electron probe size may be present in the analysis of rapidly-changing compositional gradients. The goal of this work is to examine these effects.

Effect of furnace atmosphere and silica content on the consolidation behaviour of magnesia partially stabilised zirconia

1990 ◽  
Vol 48 (4) ◽  
pp. 1056-1057
Author(s):  
J. Drennan ◽  
R.H.J. Hannink ◽  
D.R. Clarke ◽  
T.M. Shaw
Keyword(s):  
Liquid Phase ◽  
Silica Content ◽  
Liquid Phase Sintering ◽  
Furnace Atmosphere ◽  
Boundary Phase ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Series Of Experiments ◽  
Compositional Gradients ◽  
Mobile Liquid

Magnesia partially stabilised zirconia (Mg-PSZ) ceramics are renowned for their excellent nechanical properties. These are effected by processing conditions and purity of starting materials. It has been previously shown that small additions of strontia (SrO) have the effect of removing the major contaminant, silica (SiO2).The mechanism by which this occurs is not fully understood but the strontia appears to form a very mobile liquid phase at the grain boundaries. As the sintering reaches the final stages the liquid phase is expelled to the surface of the ceramic. A series of experiments, to examine the behaviour of the liquid grain boundary phase, were designed to produce compositional gradients across the ceramic bodies. To achieve this, changes in both silica content and furnace atmosphere were implemented. Analytical electron microscope techniques were used to monitor the form and composition of the phases developed. This paper describes the results of our investigation and the presentation will discuss the work with reference to liquid phase sintering of ceramics in general.

Lack of congruence between terrestrial and epiphytic lichen strata in boreal forests

2021 ◽  
Vol 53 (1) ◽  
pp. 149-158
Author(s):  
Robert J. Smith ◽  
Sarah Jovan ◽  
Susan Will-Wolf
Keyword(s):  
Species Richness ◽  
Boreal Forests ◽  
Environmental Gradients ◽  
Ground Layer ◽  
Global Changes ◽  
Layer Versus ◽  
Epiphytic Lichen ◽  
Incremental Change ◽  
Compositional Gradients ◽  
Environmental Responses

AbstractLichens occupy diverse substrates across tremendous ranges of environmental variation. In boreal forests, lichen communities co-occur in ‘strata’ defined by terrestrial or arboreal substrates, but these strata may or may not be interchangeable as bioindicators. Do co-occurring lichen strata have similar community structures and environmental responses? Could one stratum serve as a proxy for the other? We assessed variation in species richness and community compositions between ground-layer versus epiphyte-layer lichen strata in boreal forests and peatlands of interior Alaska. Species richness was lower and more spatially structured in the ground layer than the epiphyte layer. Richness of strata was not correlated. The most compositionally unique ground-layer communities were species-poor but contained regionally rare species not common in other plots. Variation in community compositions (ordination scores) were not congruent between strata (Procrustes congruence < 0.16 on 0–1 scale); the largest departures from congruence occurred where ground layers were species-poor. The best predictors of ground-layer community compositions were hydrological and topographic, whereas epiphytes were most associated with macroclimate and tree abundances. We conclude that lichens on different substrates ‘move in different circles’: compositional gradients did not agree and the environmental gradients most important to each lichen stratum were not the same. The conditions which strongly influence one vegetation stratum may have little bearing upon another. As global changes modify habitats, an incremental change in environment may lead community trajectories to diverge among lichen strata.

Compositional gradients at the nanoscale in substoichiometric thin films deposited by magnetron sputtering at oblique angles: A case study on SiO x thin films

2021 ◽  
Author(s):  
Aurelio Garcia‐Valenzuela ◽  
Antonio M. Alcaide ◽  
Victor Rico ◽  
Francisco J. Ferrer ◽  
German Alcala ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetron Sputtering ◽  
Compositional Gradients

scholarly journals Feldspar megacrysts and anorthosite xenolith-bearing dykes in the Narssarssuaq area, South Greenland

1992 ◽  
Vol 154 ◽  
pp. 49-59
Author(s):  
T Winther
Keyword(s):  
Open Systems ◽  
Early Stage ◽  
Rift System ◽  
Magma Chambers ◽  
Degree Of Contamination ◽  
Magma Reservoirs ◽  
Incompatible Elements ◽  
Low Degree ◽  
Alkaline Magmas ◽  
Compositional Gradients

Numerous dyke intrusions are found in the Narssarssuaq area of the Gardar province, a Mid-Proterozoic intracontinental rift system. Ten to fifteen percent of these dykes, which range in composition from trachybasalt to phonolite and rhyolite, contain significant proportions of feldspar megacrysts and occasionally anorthosite xenoliths. Two groups of dykes are distinguished; the older group is more alkaline, richer in incompatible elements and contains more anorthosite xenoliths than the younger. It is probable that the main reason for the differences is variation in magma production through time and from one area to another. Chemical zonation in the dykes reflects compositional gradients in the feeding magma reservoirs; the magma reservoirs acting as open systems in which crystal fractionation was an important controlling process. The anorthosite xenoliths are not strictly cognate with their hosts, but were derived from comparable alkaline magmas with a composition roughly corresponding to the most primitive of the dykes. The plagioclase megacrysts were presumably formed at an early stage of the development of the magma chambers. Rb-Sr dating of one of the dykes from the older group of dykes gives an age of 1206 ± 20 Ma and an initial 87Sr/86Sr ratio of 0.7028 ± 0.0001 supporting a low degree of contamination with upper crustal Sr.

Modeling of the Interface of Functionally Graded Superelastic Zones in Compliant Deployable Structures

2018 ◽  
Author(s):  
Jovana Jovanova ◽  
Simona Domazetovska ◽  
Mary Frecker
Keyword(s):  
Compliant Mechanisms ◽  
Step Change ◽  
Functionally Graded ◽  
Deployable Structures ◽  
Additive Manufacturing Technology ◽  
Compositional Gradients ◽  
Local Compliance ◽  
Transformation Stress ◽  
Gradient Change ◽  
Compact Shape

Functionally graded compliant mechanisms can be fabricated with additive manufacturing technology by engineering the microstructural and compositional gradients at selected locations resulting in compositionally graded zones of higher and lower flexibility. The local compliance depends on the geometry of the structure as well as the material property in the selected region. As Nitinol (NiTi) is well suited for applications requiring compliance, the critical transformation stress and the superelastic modulus of elasticity are crucial parameters for defining the local compliance. To understand the behavior at the interface between two different material compositions, three models of gradient change between the alloys are analyzed: step change, linear and polynomial gradients. In addition to localize the deformation in the interface, three different flexure designs in the interface are analyzed. This paper will address a methodology for modeling and parametrization of material properties and transition at the interface, for different flexure designs. The combined effort in the interface of the functional grading and the geometry will be used for the design of monolithic self-deployable structures, initially folded in compact shape. The design motivation comes from the self-deploying mechanisms inspired by insects’ wings.

scholarly journals Influence of Atomic Scale Compositional Gradients on Colossal Ionic Conductivity in Highly Strained YSZ/STO Heterostructures

2013 ◽  
Vol 19 (S2) ◽  
pp. 1094-1095
Author(s):  
D.W. McComb ◽  
F.J. Scheltens ◽  
J. Santamaria ◽  
C. Leon ◽  
A. Rivera
Keyword(s):  
Ionic Conductivity ◽  
Atomic Scale ◽  
Compositional Gradients ◽  
Highly Strained

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

scholarly journals Charged domain walls in lithium tantalate with compositional gradients produced by partial VTE process

2019 ◽  
Vol 699 ◽  
pp. 012015
Author(s):  
E D Greshnyakov ◽  
B I Lisjikh ◽  
V I Pryakhina ◽  
M S Nebogatikov ◽  
V Ya Shur
Keyword(s):  
Domain Walls ◽  
Lithium Tantalate ◽  
Compositional Gradients
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