Reversal in the Size Dependence of Grain Rotation

DOE PAGES

Zhou, Xiaoling; Tamura, Nobumichi; Mi, Zhongying; ...

2017-03-01

The conventional belief, based on the Read-Shockley model for the grain rotation mechanism, has been that smaller grains rotate more under stress due to the motion of grain boundary dislocations. However, in our high-pressure synchrotron Laue x-ray microdiffraction experiments, 70 nm nickel particles are found to rotate more than any other grain size. We infer that the reversal in the size dependence of the grain rotation arises from the crossover between the grain boundary dislocation-mediated and grain interior dislocation-mediated deformation mechanisms. The dislocation activities in the grain interiors are evidenced by the deformation texture of nickel nanocrystals. This new findingmore » reshapes our view on the mechanism of grain rotation and helps us to better understand the plastic deformation of nanomaterials, particularly of the competing effects of grain boundary and grain interior dislocations.« less

Grain boundary, triple junction and quadruple point mobility controlled normal grain growth

NASA Astrophysics Data System (ADS)

Rios, P. R.; Glicksman, M. E.

2015-07-01

Reduction in stored free energy provides the thermodynamic driving force for grain and bubble growth in polycrystals and foams. Evolution of polycrystalline networks exhibit the additional complication that grain growth may be controlled by several kinetic mechanisms through which the decrease in network energy occurs. Polyhedral boundaries, triple junctions (TJs), and quadruple points (QPs) are the geometrically distinct elements of three dimensional networks that follow Plateau's rules, provided that grain growth is limited by diffusion through, and motion of, cell boundaries. Shvindlerman and co-workers have long recognized the kinetic influences on polycrystalline grain growth of network TJs and QPs. Moreover, the emergence of interesting polycrystalline nanomaterials underscored that TJs can indeed influence grain growth kinetics. Currently there exist few detailed studies concerned either with network distributions of grain size, number of faces per grain, or with 'grain trajectories', when grain growth is limited by the motion of its TJs or QPs. By contrast there exist abundant studies of classical grain growth limited by boundary mobility. This study is focused on a topological/geometrical representation of polycrystals to obtain statistical predictions of the grain size and face number distributions, as well as growth 'trajectories' during steady-state grain growth. Three limits to grain growth are considered, with grain growth kinetics controlled by boundary, TJ, and QP mobilities.

In situ synchrotron investigation of grain growth behavior of nano-grained UO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yinbin; Yao, Tiankai; Lian, Jie

Here, we report on the study of grain growth kinetics in nano-grained UO 2 samples. Dense nano-grained UO 2 samples with well-controlled stoichiometry and grain size were fabricated using the spark plasma sintering technique. To determine the grain growth kinetics at elevated temperatures, a synchrotron wide-angle X-ray scattering (WAXS) study was performed in situ to measure the real-time grain size evolution based on the modified Williamson-Hall analysis. The unique grain growth kinetics of nanocrystalline UO 2 at 730 °C and 820 °C were observed and explained by the difference in mobility of various grain boundaries.

In situ synchrotron investigation of grain growth behavior of nano-grained UO 2

DOE PAGES

Miao, Yinbin; Yao, Tiankai; Lian, Jie; ...

2017-01-09

Here, we report on the study of grain growth kinetics in nano-grained UO 2 samples. Dense nano-grained UO 2 samples with well-controlled stoichiometry and grain size were fabricated using the spark plasma sintering technique. To determine the grain growth kinetics at elevated temperatures, a synchrotron wide-angle X-ray scattering (WAXS) study was performed in situ to measure the real-time grain size evolution based on the modified Williamson-Hall analysis. The unique grain growth kinetics of nanocrystalline UO 2 at 730 °C and 820 °C were observed and explained by the difference in mobility of various grain boundaries.

C-Cr segregation at grain boundary before the carbide nucleation in Alloy 690

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Hui, E-mail: huili@shu.edu.cn; Laboratory for Microstructures, Shanghai University, Shanghai, 200444; Xia Shuang

2012-04-15

The grain boundary segregation in Alloy 690 was investigated by atom probe tomography. B, C and Si segregated at the grain boundary. The high concentration regions for each segregation element form a set of straight arrays that are parallel to each other in the grain boundary plane. The concentration fluctuation has a periodicity of about 7 nm in the grain boundary plane. Before the Cr{sub 23}C{sub 6} nucleation at grain boundaries, the C-Cr co-segregate on one side of the grain boundaries while not the exact grain boundary core regions have been detected. The reasons why grain boundary carbides have coherentmore » orientation relationship only with one side of nearby grain which grain boundary is located at high index crystal plane were discussed. - Highlights: Black-Right-Pointing-Pointer Grain boundary segregation in Alloy 690 was investigated by atom probe tomography. Black-Right-Pointing-Pointer B, C and Si segregate at the grain boundary. Black-Right-Pointing-Pointer Concentration of segregated atoms periodicity fluctuated in the grain boundary plane. Black-Right-Pointing-Pointer C and Cr co-segregate on one side of the grain boundary before carbide nucleation.« less

On the interaction of solutes with grain boundaries

DOE PAGES

Dingreville, Remi Philippe Michel; Berbenni, Stephane

2015-11-01

Solute segregation to grain boundaries is considered by modeling solute atoms as misfitting inclusions within a disclination structural unit model describing the grain boundary structure and its intrinsic stress field. The solute distribution around grain boundaries is described through Fermi–Dirac statistics of site occupancy. The susceptibility of hydrogen segregation to symmetric tilt grain boundaries is discussed in terms of the misorientation angle, the defect type characteristics at the grain boundary, temperature, and the prescribed bulk hydrogen fraction of occupied sites. Through this formalism, it is found that hydrogen trapping on grain boundaries clearly correlates with the grain boundary structure (i.e.more » type of structural unit composing the grain boundary), and the associated grain boundary misorientation. Specifically, for symmetric tilt grain boundaries about the [001] axis, grain boundaries composed of both B and C structural units show a lower segregation susceptibility than other grain boundaries. A direct correlation between the segregation susceptibility and the intrinsic net defect density is provided through the Frank–Bilby formalism. Moreover, the present formulation could prove to be a simple and useful model to identify classes of grain boundaries relevant to grain boundary engineering.« less

On the interaction of solutes with grain boundaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dingreville, Remi Philippe Michel; Berbenni, Stephane

Solute segregation to grain boundaries is considered by modeling solute atoms as misfitting inclusions within a disclination structural unit model describing the grain boundary structure and its intrinsic stress field. The solute distribution around grain boundaries is described through Fermi–Dirac statistics of site occupancy. The susceptibility of hydrogen segregation to symmetric tilt grain boundaries is discussed in terms of the misorientation angle, the defect type characteristics at the grain boundary, temperature, and the prescribed bulk hydrogen fraction of occupied sites. Through this formalism, it is found that hydrogen trapping on grain boundaries clearly correlates with the grain boundary structure (i.e.more » type of structural unit composing the grain boundary), and the associated grain boundary misorientation. Specifically, for symmetric tilt grain boundaries about the [001] axis, grain boundaries composed of both B and C structural units show a lower segregation susceptibility than other grain boundaries. A direct correlation between the segregation susceptibility and the intrinsic net defect density is provided through the Frank–Bilby formalism. Moreover, the present formulation could prove to be a simple and useful model to identify classes of grain boundaries relevant to grain boundary engineering.« less

Influence of attrition milling on nano-grain boundaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rawers, J.; Cook, D.

1999-03-01

Nanostructured materials have a relatively large proportion of their atoms associated with the grain boundary, and the method used to develop the nano-grains has a strong influence on the resulting grain boundary structure. In this study, attrition milling iron powders and blends of iron powders produced micron-size particles composed of nano-size grains. Mechanical cold-working powder resulted in dislocation generation, multiplication, and congealing that produced grain refinement. As the grain size approached nano-dimensions, dislocations were no longer sustained within the grain and once generated, rapidly diffused to the grain boundary. Dislocations on the grain boundary strained the local lattice structure which,more » as the grain size decreased, became the entire grain. Mechanical alloying of substitutional aluminium atoms into iron powder resulted in the aluminium atoms substituting for iron atoms in the grain boundary cells and providing a grain boundary structure similar to that of the iron powder processed in argon. Attrition milling iron powder in nitrogen gas resulted in nitrogen atoms being adsorbed onto the particle surface. Continued mechanical milling infused the nitrogen atoms into interstitial lattice sites on the grain boundary which also contributed to expanding and straining the local lattice.« less

Whole Grains: Hearty Options for a Healthy Diet

MedlinePlus

... called cereals, grains and whole grains are the seeds of grasses cultivated for food. Grains and whole ... from large kernels of popcorn to small quinoa seeds. Whole grains. These grains are either present in ...

78 FR 57261 - Safety Zone; Grain-Shipment and Grain-Shipment Assist Vessels, Columbia and Willamette Rivers

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-18

... 1625-AA00 Safety Zone; Grain-Shipment and Grain-Shipment Assist Vessels, Columbia and Willamette Rivers... temporary safety zone around all inbound and outbound grain-shipment and grain-shipment assist vessels... Columbia and Willamette Rivers and their tributaries. For grain- shipment vessels, this safety zone extends...

Grain size constraints on twin expansion in hexagonal close packed crystals

DOE PAGES

Kumar, Mariyappan Arul; Beyerlein, Irene Jane; Tome, Carlos N.

2016-10-20

Deformation twins are stress-induced transformed domains of lamellar shape that form when polycrystalline hexagonal close packed metals, like Mg, are strained. Several studies have reported that the propensity of deformation twinning reduces as grain size decreases. Here, we use a 3D crystal plasticity based micromechanics model to calculate the effect of grain size on the driving forces responsible for expanding twin lamellae. The calculations reveal that constraints from the neighboring grain where the grain boundary and twin lamella meet induce a stress reversal in the twin lamella. A pronounced grain size effect arises as reductions in grain size cause thesemore » stress-reversal fields from twin/grain boundary junctions to affect twin growth. We further show that the severity of this neighboring grain constraint depends on the crystallographic orientation and plastic response of the neighboring grain. We show that these stress-reversal fields from twin/grain boundary junctions will affect twin growth, below a critical parent grain size. Finally, these results reveal an unconventional yet influential role that grain size and grain neighbors can play on deformation twinning.« less

Irradiation-induced grain growth and defect evolution in nanocrystalline zirconia with doped grain boundaries

DOE PAGES

Dey, Sanchita; Mardinly, John; Wang, Yongqiang; ...

2016-05-27

Grain boundaries are effective sinks for radiation-induced defects, ultimately impacting the radiation tolerance of nanocrystalline materials (dense materials with nanosized grains) against net defect accumulation. However, irradiation-induced grain growth leads to grain boundary area decrease, shortening potential benefits of nanostructures. A possible approach to mitigate this is the introduction of dopants to target a decrease in grain boundary mobility or a reduction in grain boundary energy to eliminate driving forces for grain growth (using similar strategies as to control thermal growth). Here, in this study, we tested this concept in nanocrystalline zirconia doped with lanthanum. Although the dopant is observedmore » to segregate to the grain boundaries, causing grain boundary energy decrease and promoting dragging forces for thermally activated boundary movement, irradiation induced grain growth could not be avoided under heavy ion irradiation, suggesting a different growth mechanism as compared to thermal growth. Furthermore, it is apparent that reducing the grain boundary energy reduced the effectiveness of the grain boundary as sinks, and the number of defects in the doped material is higher than in undoped (La-free) YSZ.« less

A Phase Field Study of the Effect of Microstructure Grain Size Heterogeneity on Grain Growth

NASA Astrophysics Data System (ADS)

Crist, David J. D.

Recent studies conducted with sharp-interface models suggest a link between the spatial distribution of grain size variance and average grain growth rate. This relationship and its effect on grain growth rate was examined using the diffuse-interface Phase Field Method on a series of microstructures with different degrees of grain size gradation. Results from this work indicate that the average grain growth rate has a positive correlation with the average grain size dispersion for phase field simulations, confirming previous observations. It is also shown that the grain growth rate in microstructures with skewed grain size distributions is better measured through the change in the volume-weighted average grain size than statistical mean grain size. This material is based upon work supported by the National Science Foundation under Grant No. 1334283. The NSF project title is "DMREF: Real Time Control of Grain Growth in Metals" and was awarded by the Civil, Mechanical and Manufacturing Innovation division under the Designing Materials to Revolutionize and Engineer our Future (DMREF) program.

Film grain synthesis and its application to re-graining

NASA Astrophysics Data System (ADS)

Schallauer, Peter; Mörzinger, Roland

2006-01-01

Digital film restoration and special effects compositing require more and more automatic procedures for movie regraining. Missing or inhomogeneous grain decreases perceived quality. For the purpose of grain synthesis an existing texture synthesis algorithm has been evaluated and optimized. We show that this algorithm can produce synthetic grain which is perceptually similar to a given grain template, which has high spatial and temporal variation and which can be applied to multi-spectral images. Furthermore a re-grain application framework is proposed, which synthesises based on an input grain template artificial grain and composites this together with the original image content. Due to its modular approach this framework supports manual as well as automatic re-graining applications. Two example applications are presented, one for re-graining an entire movie and one for fully automatic re-graining of image regions produced by restoration algorithms. Low computational cost of the proposed algorithms allows application in industrial grade software.

7 CFR 810.804 - Grades and grade requirements for mixed grain.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 7 2014-01-01 2014-01-01 false Grades and grade requirements for mixed grain. 810.804... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Mixed Grain Grades and Grade Requirements § 810.804 Grades and grade requirements for mixed grain. (a) U.S. Mixed Grain (grade). Mixed grain...

7 CFR 810.804 - Grades and grade requirements for mixed grain.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for mixed grain. 810.804... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Mixed Grain Grades and Grade Requirements § 810.804 Grades and grade requirements for mixed grain. (a) U.S. Mixed Grain (grade). Mixed grain...

7 CFR 810.804 - Grades and grade requirements for mixed grain.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 7 2012-01-01 2012-01-01 false Grades and grade requirements for mixed grain. 810.804... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Mixed Grain Grades and Grade Requirements § 810.804 Grades and grade requirements for mixed grain. (a) U.S. Mixed Grain (grade). Mixed grain...

7 CFR 810.804 - Grades and grade requirements for mixed grain.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 7 2013-01-01 2013-01-01 false Grades and grade requirements for mixed grain. 810.804... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Mixed Grain Grades and Grade Requirements § 810.804 Grades and grade requirements for mixed grain. (a) U.S. Mixed Grain (grade). Mixed grain...

7 CFR 810.804 - Grades and grade requirements for mixed grain.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 7 2011-01-01 2011-01-01 false Grades and grade requirements for mixed grain. 810.804... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Mixed Grain Grades and Grade Requirements § 810.804 Grades and grade requirements for mixed grain. (a) U.S. Mixed Grain (grade). Mixed grain...

78 FR 33224 - Safety Zone; Grain-Shipment and Grain-Shipment Assist Vessels, Columbia and Willamette Rivers

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-04

... 1625-AA00 Safety Zone; Grain-Shipment and Grain-Shipment Assist Vessels, Columbia and Willamette Rivers... Guard is establishing a temporary safety zone around all inbound and outbound grain-shipment and grain-shipment assist vessels involved in commerce with the Columbia Grain facility on the Willamette River in...

Migration of grain boundaries and triple junctions in high-purity aluminum during annealing after slight cold rolling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Wenhong; School of Mechanical Engineering, Shandong University of Technology, Zibo 255049; Wang, Weiguo, E-mail: wang_weiguo@vip.163.com

Grain orientations and grain boundary migrations near triple junctions in a high purity aluminum were analyzed by electron back scattered diffraction. The results indicate that there are good correlations between the Schmid factors or Taylor factors and the misorientation values of point to original point in grains near the triple junctions in a slightly deformed sample. Grains with higher Schmid factors or lower Taylor factors typically correspond to higher misorientation values near the triple junctions. In a subsequent annealing at 400 °C, both grain boundaries and triple junctions migrate, but the former leave ghost lines. During such migration, a grainmore » boundary grows from the grain with lower Schmid factor (higher Taylor factor) into the grain with higher Schmid factor (lower Taylor factor). Usually, the amount of migration of a grain boundary is considerably greater than that of a triple junction, and the grain boundary becomes more curved after migration. These observations indicate that the triple junctions have drag effects on grain boundary migration. - Highlights: • Polycrystalline aluminum with fine grains about 30 μm were used. • Off-line in situ EBSD was used to identify TJs before and after annealing. • Grains with higher SFs have higher misorientation values near TJs after deformation. • Grain boundaries grow from hard grains into soft grains during annealing. • Triple junctions have drag effects on grain boundaries migration.« less

WIDE AND THICK GRAIN 1, which encodes an otubain-like protease with deubiquitination activity, influences grain size and shape in rice.

PubMed

Huang, Ke; Wang, Dekai; Duan, Penggen; Zhang, Baolan; Xu, Ran; Li, Na; Li, Yunhai

2017-09-01

Grain size and shape are two crucial traits that influence grain yield and grain appearance in rice. Although several factors that affect grain size have been described in rice, the molecular mechanisms underlying the determination of grain size and shape are still elusive. In this study we report that WIDE AND THICK GRAIN 1 (WTG1) functions as an important factor determining grain size and shape in rice. The wtg1-1 mutant exhibits wide, thick, short and heavy grains and also shows an increased number of grains per panicle. WTG1 determines grain size and shape mainly by influencing cell expansion. WTG1 encodes an otubain-like protease, which shares similarity with human OTUB1. Biochemical analyses indicate that WTG1 is a functional deubiquitinating enzyme, and the mutant protein (wtg1-1) loses this deubiquitinating activity. WTG1 is expressed in developing grains and panicles, and the GFP-WTG1 fusion protein is present in the nucleus and cytoplasm. Overexpression of WTG1 results in narrow, thin, long grains due to narrow and long cells, further supporting the role of WTG1 in determining grain size and shape. Thus, our findings identify the otubain-like protease WTG1 to be an important factor that determines grain size and shape, suggesting that WTG1 has the potential to improve grain size and shape in rice. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

The Femtosecond Laser Ablation on Ultrafine-Grained Copper

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Ruan, Shuangchen; Guo, Dengji; Du, Chenlin; Liang, Xiong; Wu, Zhaozhi

2018-07-01

To investigate the effects of femtosecond laser ablation on the surface morphology and microstructure of ultrafine-grained copper, point, single-line scanning, and area scanning ablation of ultrafine-grained and coarse-grained copper were performed at room temperature. The ablation threshold gradually increased and materials processing became more difficult with decreasing grain size. In addition, the ablation depth and width of the channels formed by single-line scanning ablation gradually increased with increasing grain size for the same laser pulse energy. The microhardness of the ablated specimens was also evaluated as a function of laser pulse energy using area scanning ablation. The microhardness difference before and after ablation increased with decreasing grain size for the same laser pulse energy. In addition, the microhardness after ablation gradually decreased with increasing laser pulse energy for the ultrafine-grained specimens. However, for the coarse-grained copper specimens, no clear changes of the microhardness were observed after ablation with varying laser pulse energies. The grain sizes of the ultrafine-grained specimens were also surveyed as a function of laser pulse energy using electron backscattered diffraction (EBSD). The heat generated by laser ablation caused recrystallization and grain growth of the ultrafine-grained copper; moreover, the grain size gradually increased with increasing pulse energy. In contrast, no obvious changes in grain size were observed for the coarse-grained copper specimens with increasing pulse energy.

The Femtosecond Laser Ablation on Ultrafine-Grained Copper

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Ruan, Shuangchen; Guo, Dengji; Du, Chenlin; Liang, Xiong; Wu, Zhaozhi

2018-05-01

To investigate the effects of femtosecond laser ablation on the surface morphology and microstructure of ultrafine-grained copper, point, single-line scanning, and area scanning ablation of ultrafine-grained and coarse-grained copper were performed at room temperature. The ablation threshold gradually increased and materials processing became more difficult with decreasing grain size. In addition, the ablation depth and width of the channels formed by single-line scanning ablation gradually increased with increasing grain size for the same laser pulse energy. The microhardness of the ablated specimens was also evaluated as a function of laser pulse energy using area scanning ablation. The microhardness difference before and after ablation increased with decreasing grain size for the same laser pulse energy. In addition, the microhardness after ablation gradually decreased with increasing laser pulse energy for the ultrafine-grained specimens. However, for the coarse-grained copper specimens, no clear changes of the microhardness were observed after ablation with varying laser pulse energies. The grain sizes of the ultrafine-grained specimens were also surveyed as a function of laser pulse energy using electron backscattered diffraction (EBSD). The heat generated by laser ablation caused recrystallization and grain growth of the ultrafine-grained copper; moreover, the grain size gradually increased with increasing pulse energy. In contrast, no obvious changes in grain size were observed for the coarse-grained copper specimens with increasing pulse energy.

The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

NASA Astrophysics Data System (ADS)

Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-09-01

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to identify grain dissection in natural microstructures.

Size effect on the deformation mechanisms of nanocrystalline platinum thin films.

PubMed

Shu, Xinyu; Kong, Deli; Lu, Yan; Long, Haibo; Sun, Shiduo; Sha, Xuechao; Zhou, Hao; Chen, Yanhui; Mao, Shengcheng; Liu, Yinong

2017-10-16

This paper reports a study of time-resolved deformation process at the atomic scale of a nanocrystalline Pt thin film captured in situ under a transmission electron microscope. The main mechanism of plastic deformation was found to evolve from full dislocation activity-enabled plasticity in large grains (with grain size d > 10 nm), to partial dislocation plasticity in smaller grains (with grain size 10 nm < d < 6 nm), and grain boundary-mediated plasticity in the matrix with grain sizes d < 6 nm. The critical grain size for the transition from full dislocation activity to partial dislocation activity was estimated based on consideration of stacking fault energy. For grain boundary-mediated plasticity, the possible contributions to strain rate of grain creep, grain sliding and grain rotation to plastic deformation were estimated using established models. The contribution of grain creep is found to be negligible, the contribution of grain rotation is effective but limited in magnitude, and grain sliding is suggested to be the dominant deformation mechanism in nanocrystalline Pt thin films. This study provided the direct evidence of these deformation processes at the atomic scale.

Phase-field model with plastic flow for grain growth in nanocrystalline material

NASA Astrophysics Data System (ADS)

Steinbach, Ingo; Song, Xiaoyan; Hartmaier, Alexander

2010-01-01

A phase-field model is presented which considers the accumulation of structural defects in grain boundaries by an isotropic eigenstrain associated with the grain boundaries. It is demonstrated that the elastic energy caused by dilatation of the grain boundary with respect to the bulk crystal contributes largely to the grain boundary energy. The sign of this contribution can be both positive and negative dependent on the local stress state in the grain boundary. Self-diffusion of atoms is taken into account to relax the stress caused by the dilatation of the grain boundary. Application of the model to discontinuous grain growth in pure nanocrystalline cobalt material is presented. Linear grain growth is found in the nanocrystalline state, which is explained by the interpretation of grain boundary motion as a diffusive process defining an upper limit of the grain boundary velocity independent of the grain boundary curvature but dependent on temperature. The transition to regular grain growth at a critical temperature, as observed experimentally, is explained by the drop of theoretical grain boundary velocity due to its mean curvature during coarsening of the nanograin structure below the maximum velocity.

Comparison of corrosion behavior between coarse grained and nano/ultrafine grained alloy 690

NASA Astrophysics Data System (ADS)

Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Ting, Guo

2016-01-01

The effect of grain refinement on corrosion resistance of alloy 690 was investigated. The electron work function value of coarse grained alloy 690 was higher than that of nano/ultrafine grained one. The grain refinement reduced the electron work function of alloy 690. The passive films formed on coarse grained and nano/ultrafine grained alloy 690 in borate buffer solution were studied by potentiodynamic curves and electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The results showed that the grain refinement improved corrosion resistance of alloy 690. This was attributed to the fact that grain refinement promoted the enrichment of Cr2O3 and inhibited Cr(OH)3 in the passive film. More Cr2O3 in passive film could significantly improve the corrosion resistance of the nano/ultrafine grained alloy 690.

Grain-grain interaction in stationary dusty plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lampe, Martin; Joyce, Glenn

We present a particle-in-cell simulation study of the steady-state interaction between two stationary dust grains in uniform stationary plasma. Both the electrostatic force and the shadowing force on the grains are calculated explicitly. The electrostatic force is always repulsive. For two grains of the same size, the electrostatic force is very nearly equal to the shielded electric field due to a single isolated grain, acting on the charge of the other grain. For two grains of unequal size, the electrostatic force on the smaller grain is smaller than the isolated-grain field, and the force on the larger grain is largermore » than the isolated-grain field. In all cases, the attractive shadowing force exceeds the repulsive electrostatic force when the grain separation d is greater than an equilibrium separation d{sub 0}. d{sub 0} is found to be between 6λ{sub D} and 9λ{sub D} in all cases. The binding energy is estimated to be between 19 eV and 900 eV for various cases.« less

Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

NASA Astrophysics Data System (ADS)

Kim, Jeong Min; Min, Guensik; Shim, Jae-Hyeok; Lee, Kyung Jong

2018-05-01

The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.

Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

NASA Astrophysics Data System (ADS)

Kim, Jeong Min; Min, Guensik; Shim, Jae-Hyeok; Lee, Kyung Jong

2018-03-01

The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.

Attraction of likely charged nano-sized grains in dust-electron plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vishnyakov, Vladimir I., E-mail: eksvar@ukr.net

2016-01-15

Dust-electron plasma, which contains only the dust grains and electrons, emitted by them, is studied. Assumption of almost uniform spatial electrons distribution, which deviates from the uniformity only near the dust grains, leads to the grain charge division into two parts: first part is the individual for each grain “visible” charge and the second part is the common charge of the neutralized background. The visible grain charge can be both negative and positive, while the total grain charge is only positive. The attraction of likely charged grains is possible, because the grain interaction is determined by the visible charges. Themore » equilibrium state between attraction and repulsion of grains is demonstrated.« less

Atomistic modeling of grain boundary behavior under shear conditions in magnesium and magnesium-based binary alloys

NASA Astrophysics Data System (ADS)

Nahhas, M. K.; Groh, S.

2018-02-01

In this study, the structure, the energetic, and the strength of a { 10 1 bar 1 } < 11 2 bar 0 > symmetric tilt grain boundary in magnesium and magnesium binary alloys were analyzed in the framework of (semi-)empirical potentials. Following a systematic investigation of the transferability and accuracy of the interatomic potentials, atomistic calculations of the grain boundary energy, the grain boundary sliding energy, and the grain boundary strength were performed in pure magnesium and in binary MgX alloys (X = Al, Ca, Gd, Li, Sn, Y, Ag, Nd, and Pb). The data gained in this study were analyzed to identify the most critical material parameters controlling the strength of the grain boundary, and their consequence on atomic shuffling motions occurring at the grain boundary. From the methodology perspective, the role of in-plane and out-of plane relaxation on the grain boundary sliding energy curves was investigated. In pure magnesium, the results showed that in-plane relaxation is critical in activating b2{ 10 1 bar 1 } twinning dislocation resulting in grain boundary migration. In the alloy systems, however, grain boundary migration was disabled as a consequence of the pinning of the grain boundary by segregated elements. Finally, while the grain boundary energy, the shape of the grain boundary sliding energy curves, and the grain boundary sliding energy are critical parameters controlling the grain boundary strength in pure magnesium, only the grain boundary energy and the segregation energy of the alloying elements at the grain boundary were identified as critical material parameters in the alloys system.

[Effects of shading at different phases of grain-filling on wheat grain protein components contents and processing quality].

PubMed

Shi, Yu; Chen, Mao-xue; Yu, Zhen-wen; Xu, Zhen-zhu

2011-10-01

Taking three wheat cultivars Jimai 20 (strong gluten), Taishan 23 (medium gluten), and Ningmai 9 (weak gluten) as test materials, a field experiment was conducted to examine the effects of shading at different phases of grain-filling on the grain protein components contents and processing quality. Four treatments were installed, i. e., no shading (S0), shading at early grain-filling phase (from 0 day after anthesis (DAA) to 11 DAA; S1), shading at medium grain-filling phase (from 12 DAA to 23 DAA; S2), and shading at late grain-filling phase (from 24 DAA to 35 DAA; S3). No significant differences were observed in the grain albumin+globulin contents of the three cultivars among the four treatments. Shading increased the grain HMW-GS, LMW-GS, gluten, glutenin, and total protein contents of Jimai 20 and Taishan 23 significantly, and the increments were higher in treatment S2 than in other shading treatments. Treatments S2 and S3 increased the grain protein components contents of Ningmai 9 significantly. Comparing with the control, shading decreased the grain yield significantly, but increased the dough development time, dough stability time, and sedimentation volume, especially for treatment S2, which suggested that the wheat grain quality had a close relationship with the light intensity at medium phase of grain-filling. Overall, the regulation effect of shading at grain-filling stage on the wheat grain yield, grain protein components contents, and indices values of grain processing quality for the test cultivars was in the order of Jimai 20 > Taishan 23 > Ningmai 9.

Accretion growth of water-ice grains in astrophysically-relevant dusty plasma experiment

NASA Astrophysics Data System (ADS)

Chai, Kil-Byoung; Marshall, Ryan; Bellan, Paul

2016-10-01

The grain growth process in the Caltech water-ice dusty plasma experiment has been studied using a high-speed camera equipped with a long-distance microscope lens. It is found that (i) the ice grain number density decreases four-fold as the average grain length increases from 20 to 80 um, (ii) the ice grain length has a log-normal distribution rather than a power-law dependence, and (iii) no collisions between ice grains are apparent. The grains have a large negative charge so the agglomeration growth is prevented by their strong mutual repulsion. It is concluded that direct accretion of water molecules is in good agreement with the observed ice grain growth. The volumetric packing factor of the ice grains must be less than 0.25 in order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains; this conclusion is consistent with ice grain images showing a fractal character.

Airborne microorganisms associated with grain handling.

PubMed

Swan, J R; Crook, B

1998-01-01

There is substantial evidence that workers handling grain develop allergic respiratory symptoms. Microbiological contaminants are likely to be a significant contributing factor. Worker's exposure to microorganisms contaminating grain dust in the UK was therefore examined. Aerobiological studies were made when grain was being handled on farms and also during bulk handling of grain in dockside terminals. A quantitative and qualitative microbiological examination of the airborne grain dust was carried out. Samples of airborne grain dust were collected and viable bacteria, fungi and actinomycetes were grown, isolated and identified. It was found that workers handling grain or working close to grain at farms and docks were frequently exposed to more than 1 million bacteria and fungi per m3 air, and that airborne bacteria and fungi exceeded 10(4) per m3 air in all areas sampled. The qualitative examination of the samples showed that the predominant microorganisms present differed between freshly harvested grain and stored grain, but not between different types of grain.

Jamming of Cylindrical Grains in Featureless Vertical Channels

NASA Astrophysics Data System (ADS)

Baxter, G. William; Barr, Nicholas; Weible, Seth; Friedl, Nicholas

2013-03-01

We study jamming of low aspect-ratio cylindrical Delrin grains falling through a featureless vertical channel. With a grain height less than the grain diameter, these grains resemble aspirin tablets, poker chips, or coins. Unidisperse grains are allowed to fall under the influence of gravity through a uniform channel of square cross-section where the channel width is greater than the grain size and constant along the length of the channel. Channel widths are chosen so that no combination of grain heights and diameters is equal to the channel width. Collections of grains sometimes form jams, stable structures in which the grains are supported by the channel walls and not by grains or walls beneath them. The probability of a jam occurring and the jam's strength are influenced by the grain dimensions and channel width. We will present experimental measurements of the jamming probability and jam strength and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College

Dietary modeling shows that substitution of whole-grain for refined-grain ingredients of foods commonly consumed by US children and teens can increase intake of whole grains.

PubMed

Keast, Debra R; Rosen, Renee A; Arndt, Elizabeth A; Marquart, Len F

2011-09-01

Currently available whole-grain foods are not frequently consumed, and few children achieve the whole-grain intake recommendation. To investigate the influence on whole-grain consumption of substituting whole-grain for refined-grain ingredients of foods commonly consumed by children. Secondary cross-sectional analysis of publicly available food consumption data collected by the US Department of Agriculture. A nationally representative sample of US children aged 9 to 18 years (n=2,349) providing 24-hour dietary recall data in the 2003-2004 National Health and Nutrition Examination Survey. Whole-grain intake was modeled by replacing varying proportions of refined flour contained in foods such as pizza crust, pasta, breads, and other baked goods with whole-wheat flour, and by replacing a proportion of white rice with brown rice. Replacement levels were based on the acceptability of whole-grain foods tested among children in elementary schools, and ranged from 15% to 50%; the majority were ≤25%. Sample-weighted mean premodeled and postmodeled whole-grain intake, standard errors, and statistical significance of differences between demographic subgroups were determined using SUDAAN (version 9.0.3, 2007, Research Triangle Institute, Research Triangle Park, NC). Whole-grain intake increased 1.7 oz eq per day (from 0.5 to 2.2 oz eq/day). Premodeled and postmodeled whole-grain intakes were 6% and 28%, respectively, of total grain intake (7.7 oz eq/day). Major sources of postmodeled whole-grain intakes were breads/rolls (28.0%); pizza (14.2%); breakfast cereals (11.0%); rice/pasta (10.6%); quick breads such as tortillas, muffins, and waffles (10.8%); other baked goods (9.9%); and grain-based savory snacks other than popcorn (7.3%). Premodeled whole-grain intake differed by poverty level, but postmodeled whole-grain intake did not. The substitution of whole grain for a specific proportion of refined grain ingredients of commonly consumed foods increased whole-grain intake and reduced disparities between demographic subgroups of children and teens. Copyright © 2011 American Dietetic Association. Published by Elsevier Inc. All rights reserved.

Electrical properties of polycrystalline olivine: evidence for grain boundary transport

NASA Astrophysics Data System (ADS)

Ten Grotenhuis, S. M.; Drury, M. R.; Peach, C. J.; Spiers, C. J.

2003-12-01

The physical and chemical properties of grain boundaries are known to play an important role in determining the electrical properties of polycrystalline oxides. Grain boundaries can either enhance conductivity if the transport of charge carriers along the grain boundaries is faster than through the lattice, or grain boundaries can reduce conductivity if the grain boundaries block the transport of charge carriers. The purpose of the experiments presented here is to deduce the mechanisms responsible for electrical conductivity in fine-grained forsterite, the Mg-end member of olivine, in order to get a better understanding of the contribution of grain boundary transport, of the properties of the grain boundaries, and to determine any relation between grain size and conductivity. A relationship between grain size and conductivity at high temperature could potentially be used to interpret zones of anomalous conductivity in the upper mantle. The materials studied consist of fine-grained forsterite (Mg2SiO4) with a minor amount (5%) of enstatite (MgSiO3) added. The electrical conductivity of three melt-free synthetic polycrystalline samples, with grain sizes between 1.1 and 4.7 mm, was measured at temperatures up to 1470° C. The complex impedance plots display one clear arc, indicating a single dominant conduction mechanism. Bulk conductivity is inversely proportional to the grain size of the different samples. This relation suggests that grain boundary diffusion of the charge carriers is controlling the electrical conductivity of the samples. The activation energy for diffusion of the charge carriers lies between 315 and 323 kJ/mol. This resembles previous data on grain boundary diffusion of Mg in forsterite and grain boundary diffusion creep. A geometrical model of less conducting cubic grains and more conducting grain boundaries agrees well with the experimental data. This model is applied to a natural mantle shear zone to predict the conductivity contrast between fine-grained shear zones and less deformed regions in the lithosphere. Upper mantle shear zones are predicted to have 1.5 to 2 orders of magnitude higher conductivity than less deformed regions in the lithosphere. This may mean that fine-grained shear zones can be detected using magnetotelluric methods.

Implications of Grain Size Evolution for the Effective Stress Exponent in Ice

NASA Astrophysics Data System (ADS)

Behn, M. D.; Goldsby, D. L.; Hirth, G.

2016-12-01

Viscous flow in ice has typically been described by the Glen law—a non-Newtonian, power-law relationship between stress and strain-rate with a stress exponent n 3. The Glen law is attributed to grain-size-insensitive dislocation creep; however, laboratory and field studies demonstrate that deformation in ice is strongly dependent on grain size. This has led to the hypothesis that at sufficiently low stresses, ice flow is controlled by grain boundary sliding [1], which explicitly incorporates the grain-size dependence of ice rheology. Yet, neither dislocation creep (n 4), nor grain boundary sliding (n 1.8), have stress exponents that match the value of n 3 for the Glen law. Thus, although the Glen law provides an approximate description of ice flow in glaciers and ice sheets, its functional form cannot be explained by a single deformation mechanism. Here we seek to understand the origin of the n 3 dependence of the Glen law through a new model for grain-size evolution in ice. In our model, grain size evolves in response to the balance between dynamic recrystallization and grain growth. To simulate these processes we adapt the "wattmeter" [2], originally developed within the solid-Earth community to quantify grain size in crustal and mantle rocks. The wattmeter posits that grain size is controlled by a balance between the mechanical work required for grain growth and dynamic grain size reduction. The evolution of grain size in turn controls the relative contributions of dislocation creep and grain boundary sliding, and thus the effective stress exponent for ice flow. Using this approach, we first benchmark our grain size evolution model on experimental data and then calculate grain size in two end-member scenarios: (1) as a function of depth within an ice-sheet, and (2) across an ice-stream margin. We show that the calculated grain sizes match ice core observations for the interior of ice sheets. Furthermore, owing to the influence of grain size on strain rate, the variation in grain size with deformation conditions results in an effective stress exponent intermediate between grain boundary sliding and dislocation creep. [1] Goldsby & Kohlstedt, JGR, 2001; [2] Austin & Evans, Geology, 1997

Static Grain Growth in Contact Metamorphic Calcite: A Cathodoluminescence Study.

NASA Astrophysics Data System (ADS)

Vogt, B.; Heilbronner, R.; Herwegh, M.; Ramseyer, K.

2009-04-01

In the Adamello contact aureole, monomineralic mesozoic limestones were investigated in terms of grain size evolution and compared to results on numerical modeling performed by Elle. The sampled area shows no deformation and therefore represents an appropriate natural laboratory for the study of static grain growth (Herwegh & Berger, 2003). For this purpose, samples were collected at different distances to the contact to the pluton, covering a temperature range between 270 to 630°C. In these marbles, the grain sizes increase with temperature from 5 µm to about 1 cm as one approaches the contact (Herwegh & Berger, 2003). In some samples, photomicrographs show domains of variable cathodoluminescence (CL) intensities, which are interpreted to represent growth zonations. Microstructures show grains that contain cores and in some samples even several growth stages. The cores are usually not centered and the zones not concentric. They may be in touch with grain boundaries. These zonation patterns are consistent within a given aggregate but differ among the samples even if they come from the same location. Relative CL intensities depend on the Mn/Fe ratio. We assume that changes in trace amounts of Mn/Fe must have occurred during the grain size evolution, preserving local geochemical trends and their variations with time. Changes in Mn/Fe ratios can either be explained by (a) locally derived fluids (e.g. hydration reactions of sheet silicate rich marbles in the vicinity) or (b) by the infiltration of the calcite aggregates by externally derived (magmatic?) fluids. At the present stage, we prefer a regional change in fluid composition (b) because the growth zonations only occur at distances of 750-1250 m from the pluton contact (350-450°C). Closer to the contact, neither zonations nor cores were found. At larger distances, CL intensities differ from grain to grain, revealing diagenetic CL patterns that were incompletely recrystallized by grain growth. The role of infiltration of magmatic fluids is also manifest in the vicinity of dikes, where intense zonation patterns are prominent in the marbles. The software Elle was developed to simulate microstructural evolution in rocks. The numerical model with the title "Grain boundary sweeping" was performed by M. Jessell and was found on http://www.materialsknowledge.org/elle. It displays the grain size evolution and the development of growth zonations during grain boundary migration of a 2D foam structure. This simulation was chosen because the driving force is the minimization of isotropic surface energies. It will be compared to the natural microstructures. At the last stage of the simulation the average grain and core sizes have increased. All, even the smallest grains, show growth zonations. Grains can be divided into two groups: (a) initially larger grains, increasing their grain size and maintaining their core size and (b) initially smaller grains with decreasing grain and decreasing core size. Group (a) grains show large areas swept by grain boundaries into the direction of small grains. Grain boundaries between large grains move more slowly. Their cores do not touch any grain boundaries. Cores of group (b) grains are in contact with the grain boundary network and are on the way to be consumed. In the numerical model and in the natural example similar features can be observed: The cores are not necessarily centered, the zonations are not necessarily concentric and some of the cores touch the grain boundary network. In the simulation, grain boundary migration velocity between large grains is smaller than between a large and a small grain. From this we would predict that - given enough time - a well sorted grain size distribution of increased grain size could be generated. But since many small grains occur we infer that this equilibrium has not been obtained. Analytical results of some natural samples that could be analyzed up to now indicate a relatively well sorted grain size distribution suggesting a more mature state of static grain growth. In comparison to the simulation, grain and core boundaries in the marbles are not always straight. For lobate grain boundaries the surface area has not been minimized in respect to the grain size. An explanation for this might be grain boundary pinning or a local dynamic overprint. Some cores and growth zones in the investigated calcites show a continuous change in luminescence. This is interpreted to be an effect of late diffusion within the grain and/or a continuous change of fluid composition and supply. The absence of zonation in samples close to the contact might be explained by fast grain growth due to high temperatures and/or fast fluid transport. Possibly, this is combined with an enhanced component of volume diffusion. Thus concentration variations of Mn/Fe are diminished and not visible in form of a growth zonation. Herwegh M, Berger A (2003) Differences in grain growth of calcite: a field-based modeling approach. Contr. Min. Pet. 145: 600-611

The grain-size lineup: A test of a novel eyewitness identification procedure.

PubMed

Horry, Ruth; Brewer, Neil; Weber, Nathan

2016-04-01

When making a memorial judgment, respondents can regulate their accuracy by adjusting the precision, or grain size, of their responses. In many circumstances, coarse-grained responses are less informative, but more likely to be accurate, than fine-grained responses. This study describes a novel eyewitness identification procedure, the grain-size lineup, in which participants eliminated any number of individuals from the lineup, creating a choice set of variable size. A decision was considered to be fine-grained if no more than 1 individual was left in the choice set or coarse-grained if more than 1 individual was left in the choice set. Participants (N = 384) watched 2 high-quality or low-quality videotaped mock crimes and then completed 4 standard simultaneous lineups or 4 grain-size lineups (2 target-present and 2 target-absent). There was some evidence of strategic regulation of grain size, as the most difficult lineup was associated with a greater proportion of coarse-grained responses than the other lineups. However, the grain-size lineup did not outperform the standard simultaneous lineup. Fine-grained suspect identifications were no more diagnostic than suspect identifications from standard lineups, whereas coarse-grained suspect identifications carried little probative value. Participants were generally reluctant to provide coarse-grained responses, which may have hampered the utility of the procedure. For a grain-size approach to be useful, participants may need to be trained or instructed to use the coarse-grained option effectively. (c) 2016 APA, all rights reserved).

Aeolian Grain Evolution on Mars: Implications for Regolith Origins

NASA Astrophysics Data System (ADS)

Sullivan, R. J.; Cabrol, N. A.; Golombek, M.; Herkenhoff, K. E.; Landis, G.; Mer Athena Science Team

2010-12-01

Early wind tunnel experiments and the Viking Lander experience led to concepts of grain evolution and regolith development on Mars. Wind tunnel experiments showed that 100-150 μm grains are easiest to entrain on Mars, but at 10 times higher wind speeds than on Earth. Even if trajectory speeds of martian saltating grains achieve smaller fractions of entraining wind speeds than on Earth, kinetic energies of these grains would be much higher, with greater potential for damage to the grains during return collisions with the particle bed. On this basis Sagan et al. [1977] JGR 82, 28, 4430 proposed that aeolian grain evolution on Mars followed a “kamikaze” pattern in which an initially coarse grain, entrained only relatively rarely by the strongest winds, would be abraded by high kinetic energy impacts and migrate through successively smaller size-frequencies at an ever-increasing rate (as entrainment became easier and thus more likely) until the grain was essentially turned to dust. On this basis it was proposed that sand-sized grains might be relatively short-lived and perhaps rare on Mars. MER observations motivate adjustments to these concepts, with implications for origins of martian regolith reworked by wind. Along both MER traverses, on opposite sides of the planet, regolith is volumetrically dominated by very fine sand mixed with unresolved finer grains. Sorting probably is poor, based on weakly cohesive remolding by rover wheel cleats. The size-frequency of this material, even if not precisely known, is consistent with grains that have evolved by attrition to sizes smaller than the most easily-moved 100-150 μm interval, to where entrainment becomes more difficult due to the increasing relative importance of inter-particle surface forces. At these smaller sizes also, kinetic energies have been reduced proportionally by the cube of the particle radius, so grain-to-grain attrition is less effective for further evolution to even smaller grain sizes. Characteristics of the most ubiquitous, volumetrically dominant regolith component at both MER sites are consistent with a residuum of grains developed by aeolian grain-to-grain collisions. At both MER sites also: (1) there is a paucity of grains between 300 and 850 μm; and (2) grains >850 μm have participated in creep movements (driven by saltation of finer grains) during past migrations of coarse-grained ripples. These and other observations suggest aeolian grain evolution in which (1) the coarsest grains initially would be driven in creep only, where attrition efficiency might be limited; (2) probability of saltation increases when grain size evolves somewhere below ~900 μm, accelerating further grain evolution to smaller sizes until slowed by decreasing susceptibility to entrainment and (more importantly) decreased collisional effectiveness at grain sizes of <100 μm. We speculate that on a planet where aeolian working of surface materials is common, this grain evolution scenario could have widespread applicability and that regolith grain size-frequency characteristics encountered at both MER sites might be common in many regolith units across the martian surface that have been processed by wind.

The dependence of carbide morphology on grain boundary character in the highly twinned Alloy 690

NASA Astrophysics Data System (ADS)

Li, Hui; Xia, Shuang; Zhou, Bangxin; Chen, Wenjue; Hu, Changliang

2010-04-01

The dependence of morphology of grain boundary carbides on grain boundary character in Alloy 690 (Ni-30Cr-10Fe, mass fraction, %) with high fraction of low Σ coincidence site lattice (CSL) grain boundaries was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Some of the surface grains were removed by means of deep etching. It was observed that carbides grow dendritically at grain boundaries. The carbide bars observed near incoherent twin boundaries and twin related Σ9 grain boundaries are actually secondary dendrites of the carbides on these boundaries. Higher order dendrites could be observed on random grain boundaries, however, no bar-like dendrites were observed near Σ27 grain boundaries and random grain boundaries. The morphology difference of carbides precipitated at grain boundaries with different characters is discussed based on the experimental results in this paper.

Atomic scale study of grain boundary segregation before carbide nucleation in Ni-Cr-Fe Alloys

NASA Astrophysics Data System (ADS)

Li, Hui; Xia, Shuang; Liu, Wenqing; Liu, Tingguang; Zhou, Bangxin

2013-08-01

Three dimensional chemical information concerning grain boundary segregation before carbide nucleation was characterized by atom probe tomography in two Ni-Cr-Fe alloys which were aged at 500 °C for 0.5 h after homogenizing treatment. B, C and Si atoms segregation at grain boundary in Alloy 690 was observed. B, C, N and P atoms segregation at grain boundary in 304 austenitic stainless steel was observed. C atoms co-segregation with Cr atoms at the grain boundaries both in Alloy 690 and 304 austenitic stainless steel was found, and its effect on the carbide nucleation was discussed. The amount of each segregated element at grain boundaries in the two Ni-Cr-Fe alloys were analyzed quantitatively. Comparison of the grain boundary segregation features of the two Ni-Cr-Fe alloys were carried out based on the experimental results. The impurity and solute atoms segregate inhomogeneously in the same grain boundary both in 304 SS and Alloy 690. The grain boundary segregation tendencies (Sav) are B (11.8 ± 1.4) > P (5.4 ± 1.4) > N (4.7 ± 0.3) > C (3.7 ± 0.4) in 304 SS, and B (6.9 ± 0.9) > C (6.7 ± 0.4) > Si (1.5 ± 0.2) in Alloy 690. Cr atoms may co-segregate with C atoms at grain boundaries before carbide nucleation at the grain boundaries both in 304 SS and Alloy 690. Ni atoms generally deplete at grain boundary both in 304 SS and Alloy 690. The literature shows that the Ni atoms may co-segregate with P atoms at grain boundaries [28], but the P atoms segregation do not leads to Ni segregation in the current study. In the current study, Fe atoms may segregate or deplete at grain boundary in Alloy 690. But Fe atoms generally deplete at grain boundary in 304 SS. B atoms have the strongest grain boundary segregation tendency both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of B in 304 SS is higher than in Alloy 690. C atoms are easy to segregate at grain boundaries both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of C in Alloy 690 is higher than in 304 SS, due to the higher bulk C concentration and the site competition of P atoms which segregate at grain boundary [29,30]. It is imply that the segregation tendency is influenced by the bulk concentration of the segregates. Si atoms slightly segregate at grain boundaries in Alloy 690, but do not segregate at grain boundaries in 304 SS. N and P atoms segregate at grain boundary in 304 SS, and their segregation Gibbs free energy are similar. N atoms may be exhausted by the TiN precipitated in the matrix and can not be observed in the grain boundary of Alloy 690 [19]. Mn atoms deplete at grain boundary in 304 SS. This phenomenon is similar to that of proton irradiation induced segregation in 304 SS [32]. B, C, N, P segregation Gibbs energies are similar both in 304 SS and Alloy 690. B and C atoms segregate at grain boundary both in Alloy 690 and 304 SS, P and N segregate at grain boundary in 304 SS. Si atoms segregate at grain boundary in Alloy 690, but do not segregate at grain boundary in 304 SS. Cr enriches at grain boundary both in Alloy 690 and 304 SS, although carbide does not nucleate. Ni and Fe may segregate, deplete or homogeneously distribute at grain boundary in Alloy 690, but they deplete at grain boundary in 304 SS. C and Cr atoms co-segregate at grain boundaries before carbide nucleation in Alloy 690 and 304 SS. Combination with other results in literatures, the evolution of Cr concentration at grain boundary should be enrichment at grain boundary before carbide nucleation, depletion at grain boundary after carbide precipitation, and healing after obvious growth of carbide. After aging treatment at 500 °C for 0.5 h, the total reduction of grain boundary free energy due to segregation is 27.489 kJ/mol for Alloy 690 and 45.207 kJ/mol for 304.

The Effects of Grain Size and Texture on Dynamic Abnormal Grain Growth in Mo

NASA Astrophysics Data System (ADS)

Noell, Philip J.; Taleff, Eric M.

2016-10-01

This is the first report of abnormal grain morphologies specific to a Mo sheet material produced from a commercial-purity arc-melted ingot. Abnormal grains initiated and grew during plastic deformation of this material at temperatures of 1793 K and 1813 K (1520 °C and 1540 °C). This abnormal grain growth during high-temperature plastic deformation is termed dynamic abnormal grain growth, DAGG. DAGG in this material readily consumes nearly all grains near the sheet center while leaving many grains near the sheet surface unconsumed. Crystallographic texture, grain size, and other microstructural features are characterized. After recrystallization, a significant through-thickness variation in crystallographic texture exists in this material but does not appear to directly influence DAGG propagation. Instead, dynamic normal grain growth, which may be influenced by texture, preferentially occurs near the sheet surface prior to DAGG. The large grains thus produced near the sheet surface inhibit the subsequent growth of the abnormal grains produced by DAGG, which preferentially consume the finer grains near the sheet center. This produces abnormal grains that span the sheet center but leave unconsumed polycrystalline microstructure near the sheet surface. Abnormal grains are preferentially oriented with the < 110rangle approximately along the tensile axis. These results provide additional new evidence that boundary curvature is the primary driving force for DAGG in Mo.

Recrystallization and grain growth phenomena in a particle-reinforced aluminum composite

NASA Astrophysics Data System (ADS)

van Aken, D. C.; Krajewski, P. E.; Vyletel, G. M.; Allison, J. E.; Jones, J. W.

1995-06-01

Recrystallization and grain growth in a 2219/TiC/15p composite were investigated as functions of the amount of deformation and deformation temperature. Both cold and hot deformed samples were annealed at the normal solution treatment temperature of 535 °C. It was shown that large recrystallized grain diameters, relative to the interparticle spacing, could be produced in a narrow range of deformation for samples cold-worked and those hot-worked below 450 °C. For cold-worked samples, between 4 to 6 pct deformation, the recrystallized grain diameters varied from 530 to 66 μm as the amount of deformation increased. Subsequent grain growth was not observed in these recrystallized materials and noncompact grain shapes were observed. For deformations greater than 15 pct, recrystallized grain diameters less than the interparticle spacing were observed and subsequent grain growth produced a pinned grain diameter of 27 μm. The pinned grain diameter agreed well with an empirical model based on three dimensional (3-D) Monte Carlo simulations of grain growth and particle pinning in a two-phase material. Tensile properties were determined as a function of grain size, and it was shown that grain size had a weak influence on yield strength. A maximum in the yield strength was observed at a grain size larger than the normal grain growth and particle-pinned diameter.

No effect of 14 day consumption of whole grain diet compared to refined grain diet on antioxidant measures in healthy, young subjects: a pilot study.

PubMed

Enright, Lynda; Slavin, Joanne

2010-03-19

Epidemiological evidence supports that a diet high in whole grains is associated with lowered risk of chronic diseases included coronary heart disease, obesity, type 2 diabetes, and some types of cancer. One potential mechanism for the protective properties of whole grains is their antioxidant content. The aim of this study was to compare differences in antioxidant measures when subjects consumed either refined or whole grain diets. Twenty healthy subjects took part in a randomized, crossover dietary intervention study. Subjects consumed either a refined grain or whole grain diet for 14 days and then the other diet for the next 14 days. Male subjects consumed 8 servings of grains per day and female subjects consumed 6 servings of grains per day. Blood and urine samples were collected at the end of each diet. Antioxidant measures included oxygen radical absorbance capacity (ORAC) in blood, and isoprostanes and thiobarbituric acid reactive substances (TBARS) in urine. The whole grain diet was significantly higher in dietary fiber, vitamin B6, folate, selenium, copper, zinc, iron, magnesium and cystine compared to the refined grain diet. Despite high intakes of whole grains, no significant differences were seen in any of the antioxidant measures between the refined and whole grain diets. No differences in antioxidant measures were found when subjects consumed whole grain diets compared to refined grain diets.

7 CFR 810.801 - Definition of mixed grain.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 7 2011-01-01 2011-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD... GRAIN United States Standards for Mixed Grain Terms Defined § 810.801 Definition of mixed grain. Any...

7 CFR 810.801 - Definition of mixed grain.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 7 2012-01-01 2012-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD... GRAIN United States Standards for Mixed Grain Terms Defined § 810.801 Definition of mixed grain. Any...

7 CFR 810.801 - Definition of mixed grain.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 7 2013-01-01 2013-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD... GRAIN United States Standards for Mixed Grain Terms Defined § 810.801 Definition of mixed grain. Any...

7 CFR 810.801 - Definition of mixed grain.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 7 2014-01-01 2014-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD... GRAIN United States Standards for Mixed Grain Terms Defined § 810.801 Definition of mixed grain. Any...

78 FR 52606 - Notice of National Grain Car Council Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-23

... of National Grain Car Council Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car... rail grain car availability and transportation. Nat'l Grain Car Supply--Conference of Interested...

7 CFR 810.801 - Definition of mixed grain.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 7 2010-01-01 2010-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD... GRAIN United States Standards for Mixed Grain Terms Defined § 810.801 Definition of mixed grain. Any...

Competing Grain Boundary and Interior Deformation Mechanisms with Varying Sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wei; Gao, Yanfei; Nieh, T. G.

In typical coarse-grained alloys, the dominant plastic deformations are dislocation gliding or climbing, and material strengths can be tuned by dislocation interactions with grain boundaries, precipitates, solid solutions, and other defects. With the reduction of grain size, the increase of material strengths follows the classic Hall-Petch relationship up to nano-grained materials. Even at room temperatures, nano-grained materials exhibit strength softening, or called the inverse Hall-Petch effect, as grain boundary processes take over as the dominant deformation mechanisms. On the other hand, at elevated temperatures, grain boundary processes compete with grain interior deformation mechanisms over a wide range of the appliedmore » stress and grain sizes. This book chapter reviews and compares the rate equation model and the microstructure-based finite element simulations. The latter explicitly accounts for the grain boundary sliding, grain boundary diffusion and migration, as well as the grain interior dislocation creep. Therefore the explicit finite element method has clear advantages in problems where microstructural heterogeneities play a critical role, such as in the gradient microstructure in shot peening or weldment. Furthermore, combined with the Hall-Petch effect and its breakdown, the above competing processes help construct deformation mechanism maps by extending from the classic Frost-Ashby type to the ones with the dependence of grain size.« less

Continuum understanding of twin formation near grain boundaries of FCC metals with low stacking fault energy

NASA Astrophysics Data System (ADS)

Jung, Jaimyun; Yoon, Jae Ik; Kim, Jung Gi; Latypov, Marat I.; Kim, Jin You; Kim, Hyoung Seop

2017-12-01

Deformation twinning from grain boundaries is often observed in face-centered cubic metals with low stacking fault energy. One of the possible factors that contribute to twinning origination from grain boundaries is the intergranular interactions during deformation. Nonetheless, the influence of mechanical interaction among grains on twin evolution has not been fully understood. In spite of extensive experimental and modeling efforts on correlating microstructural features with their twinning behavior, a clear relation among the large aggregate of grains is still lacking. In this work, we characterize the micromechanics of grain-to-grain interactions that contribute to twin evolution by investigating the mechanical twins near grain boundaries using a full-field crystal plasticity simulation of a twinning-induced plasticity steel deformed in uniaxial tension at room temperature. Microstructures are first observed through electron backscatter diffraction technique to obtain data to reconstruct a statistically equivalent microstructure through synthetic microstructure building. Grain-to-grain micromechanical response is analyzed to assess the collective twinning behavior of the microstructural volume element under tensile deformation. Examination of the simulated results reveal that grain interactions are capable of changing the local mechanical behavior near grain boundaries by transferring strain across grain boundary or localizing strain near grain boundary.

Several grain dietary patterns are associated with better diet quality and improved shortfall nutrient intakes in US children and adolescents: a study focusing on the 2015-2020 Dietary Guidelines for Americans.

PubMed

Papanikolaou, Yanni; Jones, Julie Miller; Fulgoni, Victor L

2017-02-20

The present study identified the most commonly consumed grain food patterns in US children and adolescents (2-18 years-old; N = 8,367) relative to those not consuming grains and compared diet quality and nutrient intakes, with focus on 2015-2020 Dietary Guidelines for Americans (2015-2020 DGA) shortfall nutrients. Cluster analysis using data from the National Health and Nutrition Examination Survey 2005-2010, identified 8 unique grain food patterns: a) no consumption of main grain groups, b) cakes, cookies and pies, c) yeast bread and rolls, d) cereals, e) pasta, cooked cereals and rice, f) crackers and salty snacks, g) pancakes, waffles and French toast and other grains, and h) quick breads. Energy intake was higher for all grain cluster patterns examined, except 'cereals', compared to no grains. Children and adolescents in the 'yeast bread and rolls', 'cereals', 'pasta, cooked cereals and rice', and 'crackers and salty snacks' patterns had a higher diet quality relative to no grains (all p < 0.01). Energy adjusted (EA) dietary fiber intake was greater in five of the seven grain patterns, ranging from 1.8 - 2.8 g more per day (all p < 0.01), as compared to those consuming no grains. All grain patterns, except cakes, cookies and pies had higher EA daily folate relative to children in the no grains pattern (all p < 0.0001). EA total fat was lower in 'cereals', 'pasta, cooked cereals and rice', and 'pancakes, waffles, French toast and other grains' in comparison to the no grains food pattern (all p < 0.01). EA magnesium intakes were greater in children and adolescents consuming 'yeast bread and rolls', 'pasta, cooked cereals and rice', and 'quick breads', while EA iron was higher in all grain patterns relative to no grains (all p < 0.01). EA vitamin D intake was higher only in children consuming 'cereals' vs. no grain group (p < 0.0001). There were no significant differences in total or added sugar intake across all grain clusters as compared to no grains. Consumption of several, but not all, grain food patterns in children and adolescents were associated with improved 2015-2020 DGA shortfall nutrient intakes and diet quality as compared to those consuming no grains.

Perspective: A Definition for Whole-Grain Food Products-Recommendations from the Healthgrain Forum.

PubMed

Ross, Alastair B; van der Kamp, Jan-Willem; King, Roberto; Lê, Kim-Anne; Mejborn, Heddie; Seal, Chris J; Thielecke, Frank

2017-07-01

Whole grains are a key component of a healthy diet, and enabling consumers to easily choose foods with a high whole-grain content is an important step for better prevention of chronic disease. Several definitions exist for whole-grain foods, yet these do not account for the diversity of food products that contain cereals. With the goal of creating a relatively simple whole-grain food definition that aligns with whole-grain intake recommendations and can be applied across all product categories, the Healthgrain Forum, a not-for-profit consortium of academics and industry working with cereal foods, established a working group to gather input from academics and industry to develop guidance on labeling the whole-grain content of foods. The Healthgrain Forum recommends that a food may be labeled as "whole grain" if it contains ≥30% whole-grain ingredients in the overall product and contains more whole grain than refined grain ingredients, both on a dry-weight basis. For the purposes of calculation, added bran and germ are not considered refined-grain ingredients. Additional recommendations are also made on labeling whole-grain content in mixed-cereal foods, such as pizza and ready meals, and a need to meet healthy nutrition criteria. This definition allows easy comparison across product categories because it is based on dry weight and strongly encourages a move from generic whole-grain labels to reporting the actual percentage of whole grain in a product. Although this definition is for guidance only, we hope that it will encourage more countries to adopt regulation around the labeling of whole grains and stimulate greater awareness and consumption of whole grains in the general population. © 2017 American Society for Nutrition.

The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice Mantles

NASA Astrophysics Data System (ADS)

Pauly, Tyler; Garrod, Robin T.

2016-02-01

Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface-gas interactions.

Technical note: In situ ruminal starch disappearance kinetics of hull-less barley, hulled barley, and corn grains.

PubMed

Ferreira, G; Yang, Y; Teets, C L; Brooks, W S; Griffey, C A

2018-07-01

The objective of this study was to compare ruminal starch disappearance rates of hull-less barley, hulled barley, and corn grains. Five different genotypes were used for each of the 2 barley types. In addition, each of these genotypes was grown in 2 different locations and years, resulting 10 independent barley samples for each of the 2 barley grain types. Five different genotypes of corn grain were obtained from a commercial seed company. After being ground to pass through a 4-mm screen of a cutter mill, 3.6 g of each grain was placed into a porous bag, which was then incubated in the rumen of 2 ruminally cannulated cows for 0, 4, 8, 12, 24, and 48 h. Corn grains had greater instant ruminal starch disappearances than barley grains (22.4 and 8.2%, respectively). Instant ruminal starch disappearances did not differ between hulled and hull-less barley grains. Ruminal starch fractional disappearance rates were greatest for hulled barley grains, moderate for hull-less barley grains, and lowest for corn grains (15.3, 13.9, and 7.1%/h, respectively). Ruminal starch half-life was shortest for hulled and hull-less barley grains (4.4 h) and longest for corn grains (6.6 h). Ruminal starch half-life did not differ between hulled barley and hull-less barley grains. In conclusion, using a holistic experimental design and statistical analysis, this study showed that starch from hull-less barley grains has a ruminal half-life similar to that of hulled barley grains and shorter than that of corn grains. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Whole grains and health: from theory to practice--highlights of The Grains for Health Foundation's Whole Grains Summit 2012.

PubMed

McKeown, Nicola M; Jacques, Paul F; Seal, Chris J; de Vries, Jan; Jonnalagadda, Satya S; Clemens, Roger; Webb, Densie; Murphy, Lee Anne; van Klinken, Jan-Willem; Topping, David; Murray, Robyn; Degeneffe, Dennis; Marquart, Leonard F

2013-05-01

The Grains for Health Foundation's Whole Grains Summit, held May 19-22, 2012 in Minneapolis, was the first meeting of its kind to convene >300 scientists, educators, food technologists, grain breeders, food manufacturers, marketers, health professionals, and regulators from around the world. Its goals were to identify potential avenues for collaborative efforts and formulate new approaches to whole-grains research and health communications that support global public health and business. This paper summarizes some of the challenges and opportunities that researchers and nutrition educators face in expanding the knowledge base on whole grains and health and in translating and disseminating that knowledge to consumers. The consensus of the summit was that effective, long-term, public-private partnerships are needed to reach across the globe and galvanize the whole-grains community to collaborate effectively in translating whole-grains science into strategies that increase the availability and affordability of more healthful, grain-based food products. A prerequisite of that is the need to build trust among diverse multidisciplinary professionals involved in the growing, producing, marketing, and regulating of whole-grain products and between the grain and public health communities.

Whole Grains and Fiber

MedlinePlus

... or another cereal is a grain product. Bread, pasta, oatmeal and grits are all grain products. There ... whole-grain cereal, brown rice, or whole-wheat pasta 5 whole-grain crackers 3 cups unsalted, air- ...

Dietary intake of whole grains.

PubMed

Cleveland, L E; Moshfegh, A J; Albertson, A M; Goldman, J D

2000-06-01

The objective of this study was to provide national estimates of whole-grain intake in the United States, identify major dietary sources of whole grains and compare food and nutrient intakes of whole-grain consumers and nonconsumers. Data were collected from 9,323 individuals age 20 years and older in USDA's 1994-96 Continuing Survey of Food Intakes by Individuals through in-person interviews on two non-consecutive days using a multiple-pass 24-hour recall method. Foods reported by respondents were quantified in servings as defined by the Food Guide Pyramid using a new database developed by the USDA. Whole-grain and nonwhole-grain servings were determined based on the proportion, by weight, of the grain ingredients in each food that were whole grain and nonwhole grain. Sampling weights were applied to provide national probability estimates adjusted for differential rates of selection and nonresponse. Then, t tests were used to assess statistically significant differences in intakes of nutrients and food groups by whole-grain consumers and nonconsumers. According to the 1994-96 survey, U.S. adults consumed an average of 6.7 servings of grain products per day; 1.0 serving was whole grain. Thirty-six percent averaged less than one whole-grain serving per day based on two days of intake data, and only eight percent met the recommendation to eat at least three servings per day. Yeast breads and breakfast cereals each provided almost one-third of the whole-grain servings, grain-based snacks provided about one-fifth, and less than one-tenth came from quick breads, pasta, rice, cakes, cookies, pies, pastries and miscellaneous grains. Whole-grain consumers had significantly better nutrient profiles than nonconsumers, including higher intakes of vitamins and minerals as percentages of 1989 Recommended Dietary Allowances and as nutrients per 1,000 kilocalories, and lower intakes of total fat, saturated fat and added sugars as percentages of food energy. Consumers were significantly more likely than nonconsumers to meet Pyramid recommendations for the grain, fruit and dairy food groups. Consumption of whole-grain foods by U.S. adults falls well below the recommended level. A large proportion of the population could benefit from eating more whole grain, and efforts are needed to encourage consumption.

Whole grain intakes in Irish adults: findings from the National Adults Nutrition Survey (NANS).

PubMed

O'Donovan, Clare B; Devlin, Niamh F; Buffini, Maria; Walton, Janette; Flynn, Albert; Gibney, Michael J; Nugent, Anne P; McNulty, Breige A

2018-01-20

Observational studies link high whole grain intakes to reduced risk of many chronic diseases. This study quantified whole grain intakes in the Irish adult population and examined the major contributing sources. It also investigated potential dietary strategies to improve whole grain intakes. Whole grain intakes were calculated in a nationally representative sample of 1500 Irish adults using data from the most recent national food survey, the National Adult Nutrition Survey (NANS). Food consumption was assessed, at brand level where possible, using a 4-day semi-weighed food diary with whole grain content estimated from labels on a dry matter basis. Mean daily whole grain intakes were 27.8 ± 29.4 g/day, with only 19% of the population meeting the quantity-specific recommendation of 48 g per day. Wheat was the highest contributor to whole grain intake at 66%, followed by oats at 26%. High whole grain intakes were associated with higher dietary intakes of fibre, magnesium, potassium, phosphorus, and a higher alternative Mediterranean Diet Score. Whole grain foods were most frequently eaten at breakfast time. Regression analysis revealed that consumption of an additional 10 g of whole grain containing 'ready-to-eat breakfast cereals', 'rice or pastas', or 'breads' each day would increase intake of whole grains by an extra 5, 3.5, and 2.7 g, respectively. This study reveals low intakes of whole grains in Irish adults. Recommending cereals, breads, and grains with higher whole grain content as part of public health campaigns could improve whole grain intakes.

Evolution of grain boundary character distributions in alloy 825 tubes during high temperature annealing: Is grain boundary engineering achieved through recrystallization or grain growth?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Qin; Zhao, Qing

Grain boundary engineering (GBE) of nickel-based alloy 825 tubes was carried out with different cold drawing deformations by using a draw-bench on a factory production line and subsequent annealing at various temperatures. The microstructure evolution of alloy 825 during thermal-mechanical processing (TMP) was characterized by means of the electron backscatter diffraction (EBSD) technique to study the TMP effects on the grain boundary network and the evolution of grain boundary character distributions during high temperature annealing. The results showed that the proportion of ∑ 3{sup n} coincidence site lattice (CSL) boundaries of alloy 825 tubes could be increased to > 75%more » by the TMP of 5% cold drawing and subsequent annealing at 1050 °C for 10 min. The microstructures of the partially recrystallized samples and the fully recrystallized samples suggested that the proportion of low ∑ CSL grain boundaries depended on the annealing time. The frequency of low ∑ CSL grain boundaries increases rapidly with increasing annealing time associating with the formation of large-size highly-twinned grains-cluster microstructure during recrystallization. However, upon further increasing annealing time, the frequency of low ∑ CSL grain boundaries decreased markedly during grain growth. So it is concluded that grain boundary engineering is achieved through recrystallization rather than grain growth. - Highlights: •The grain boundary engineering (GBE) is applicable to 825 tubes. •GBE is achieved through recrystallization rather than grain growth. •The low ∑ CSL grain boundaries in 825 tubes can be increased to > 75%.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pauly, Tyler; Garrod, Robin T., E-mail: tap74@cornell.edu

Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays amore » significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface–gas interactions.« less

Microstructure and nanohardness distribution in a polycrystalline Zn deformed by high strain rate impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dirras, G., E-mail: dirras@univ-paris13.fr; Ouarem, A.; Couque, H.

2011-05-15

Polycrystalline Zn with an average grain size of about 300 {mu}m was deformed by direct impact Hopkinson pressure bar at a velocity of 29 m/s. An inhomogeneous grain structure was found consisting of a center region having large average grain size of 20 {mu}m surrounded by a fine-grained rim with an average grain size of 6 {mu}m. Transmission electron microscopy investigations showed a significant dislocation density in the large-grained area while in the fine-grained rim the dislocation density was negligible. Most probably, the higher strain yielded recrystallization in the outer ring while in the center only recovery occurred. The hardeningmore » effect of dislocations overwhelms the smaller grain size strengthening in the center part resulting in higher nanohardness in this region than in the outer ring. - Graphical Abstract: (a): EBSD micrograph showing the initial microstructure of polycrystalline Zn that was subsequently submitted to high strain rate impact. (b): an inhomogeneous grain size refinement was obtained which consists of a central coarse-grained area, surrounded by a fine-grained recrystallized rim. The black arrow points to the disc center. Research Highlights: {yields} A polycrystalline Zn specimen was submitted to high strain rate impact loading. {yields} Inhomogeneous grain refinement occurred due to strain gradient in impacted sample. {yields} A fine-grained recrystallized rim surrounded the coarse-grained center of specimen. {yields} The coarse-grained center exhibited higher hardness than the fine-grained rim. {yields} The higher hardness of the center was caused by the higher dislocation density.« less

Transmission Electron Microscopy of Non-Etched Presolar Silicon Carbide

NASA Technical Reports Server (NTRS)

Stroud, Rhonda M.; Nittler, Larry R.; Alexander, Conel M. O'D.; Bernatowicz, Thomas J.; Messenger, Scott R.

2003-01-01

Our solar system formed from nuclei produced in earlier generations of stars. Mixing in the proto-solar nebula isotopically homogenized most of this material, but some grains, called presolar grains, retain their original isotopic composition. The isotopic properties of presolar SiC grains indicate that most of the grains formed in the outflows of carbon-rich Asymptotic Giant Branch (AGB) stars. The microstructure of these presolar grains reflects the conditions of the dust formation and subsequent alteration. Early microstructural studies of SiC grains obtained by acid dissolution from meteorites show that most isotopically anomalous SiC grains have the face-centered cubic b- SiC structure. However, Daulton et al. have shown that a small fraction of sub-micron presolar SiC grains are of the hexagonal 2H polytype (a-SiC). Although the harsh chemical treatments of these grains does not alter their crystal structure, significant alteration of the surface morphology of the grains due to the acid treatments has been observed. In addition, the acid treatments may preferentially remove cracked or fissured grains, and possible sub-grains, such as graphite. By studying SiC grains isolated by physical separation and found in situ, we attempt to obtain a more complete analysis of presolar SiC microstructures, including the surface morphology, in order to address the formation and processing history of the grains. In our prior work, we reported on one in situ SiC grain (hereafter CBIS1). Here we present results from two additional grains, one in situ, and one prepared as a physical separate.

Pleiotropic effects of the wheat domestication gene Q on yield and grain morphology.

PubMed

Xie, Quan; Li, Na; Yang, Yang; Lv, Yulong; Yao, Hongni; Wei, Rong; Sparkes, Debbie L; Ma, Zhengqiang

2018-05-01

Transformation from q to Q during wheat domestication functioned outside the boundary of threshability to increase yield, grains m -2 , grain weight and roundness, but to reduce grains per spike/spikelet. Mutation of the Q gene, well-known affecting wheat spike structure, represents a key domestication step in the formation of today's free-threshing, economically important wheats. In a previous study, multiple yield components and spike characteristics were associated with the Q gene interval in the bread wheat 'Forno' × European spelt 'Oberkulmer' recombinant inbred line population. Here, we reported that this interval was also associated with grain yield, grains m -2 , grain morphology, and spike dry weight at anthesis. To clarify the roles of Q in agronomic trait performance, a functional marker for the Q gene was developed. Analysis of allelic effects showed that the bread wheat Q allele conferred free-threshing habit, soft glumes, and short and compact spikes compared with q. In addition, the Q allele contributed to higher grain yield, more grains m -2 , and higher thousand grain weight, whereas q contributed to more grains per spike/spikelet likely resulting from increased preanthesis spike growth. For grain morphology, the Q allele was associated with reduced ratio of grain length to height, indicating a rounder grain. These results are supported by analysis of four Q mutant lines in the Chinese Spring background. Therefore, the transition from q to Q during wheat domestication had profound effects on grain yield and grain shape evolution as well, being a consequence of pleiotropy.

Probing Cosmic Infrared Sources: A Computer Modeling Approach

DTIC Science & Technology

1992-06-01

developed to study various physical phenomena involving dust grains, e.g., molecule formation on grains, grain formation in expanding circumstellar...EVALUATION OF METHODS OF ANALYSIS IN INFRARED ASTR9?NOMY 16 4.0 THEORETICAL STUDIES INVOLVING DUST GRAINS., 16 4.1 Theory of Molecule Formation on Dust Grains...17 4.2 Modeling Grain Formation in Stellar Outflows 7 18 4.3 Infrared Emission from Fractal Grains * 19 4.4 Photochemistry in Circumstellar Envelopes

Levels of fungi and mycotoxins in the samples of grain and grain dust collected from five various cereal crops in eastern Poland.

PubMed

Krysińska-Traczyk, Ewa; Perkowski, Juliusz; Dutkiewicz, Jacek

2007-01-01

During combine harvesting of 5 various cereal crops (rye, barley, oats, buckwheat, corn) 24 samples of grain and 24 samples of settled grain dust were collected on farms located in the Lublin province of eastern Poland. The samples were examined for the concentration of total microfungi, Fusarium species, deoxynivalenol (DON), nivalenol (NIV), and ochratoxin A (OTA). Microfungi able to grow on malt agar were present in 79.2% of grain samples and in 91.7% of grain dust samples in the concentrations of 1.0-801.3x10(3) cfu/g and 1.5-12440.0x10(3) cfu/g, respectively. The concentration of microfungi in grain dust samples was significantly greater than in grain samples (p<0.01). Fusarium strains were isolated from 54.2% of grain samples and from 58.3% of grain dust samples in the concentrations of 0.1-375.0x10(3) cfu/g and 4.0-7,700.0x10(3) cfu/g, respectively. They were found in all samples of grain and grain dust from rye, barley and corn, but only in 0-16.7% of samples of grain and grain dust from oats and buckwheat. DON was found in 79.2% of grain samples and in 100% of grain dust samples in the concentrations of 0.001-0.18 microg/g and 0.006-0.283 microg/g, respectively. NIV was detected in 62.5% of grain samples and in 94.4% of grain dust samples in the concentrations of 0.004-0.502 microg/g and 0.005-0.339 microg/g, respectively. OTA was detected in 58.3% of grain samples and in 91.7% of grain dust samples in the concentrations of 0.00039- 0.00195 microg/g and 0.00036-0.00285 microg/g, respectively. The concentrations of DON, total fusariotoxins (DON+NIV) and OTA were significantly greater in grain dust samples than in grain samples (p<0.05, p<0.05, and p<0.001, respectively). The concentration of Fusarium poae in the samples of rye grain and dust was significantly correlated with the concentrations of DON (p<0.05), NIV (p<0.01), and total fusariotoxins (p<0.05). Similarly, the concentration of Fusarium culmorum in the samples of barley grain and dust was significantly correlated with the concentration of total fusariotoxins (p<0.05). A significant correlation was also found between the concentration of total fungi grown on malt agar and the concentration of OTA (p<0.05). In conclusion, although the concentration of DON, NIV and OTA in the samples of grain dust collected from 5 various cereals on farms in eastern Poland was not large, the persistent presence of these mycotoxins in over 90% of examined samples poses a potential health risk of chronic respiratory intoxication for exposed grain farmers.

Ancient grains and pseudocereals: chemical compositions, nutritional benefits, and roles in 21st century diets

USDA-ARS?s Scientific Manuscript database

In recent history, refined grains have replaced whole grains in the human diet. However, refined grains have fewer phytochemicals and more starches than whole grain. In addition, studies have shown that inclusion of whole grains in a daily diet results in decreased risk of cancer and cardiovascular ...

Identification of Accretion as Grain Growth Mechanism in Astrophysically Relevant Water&ice Dusty Plasma Experiment

NASA Astrophysics Data System (ADS)

Marshall, Ryan S.; Chai, Kil-Byoung; Bellan, Paul M.

2017-03-01

The grain growth process in the Caltech water-ice dusty plasma experiment has been studied using a high-speed camera and a long-distance microscope lens. It is observed that (I) the ice grain number density decreases fourfold as the average grain major axis increases from 20 to 80 μm, (II) the major axis length has a log-normal distribution rather than a power-law dependence, and (III) no collisions between ice grains are apparent. The grains have a large negative charge resulting in strong mutual repulsion and this, combined with the fractal character of the ice grains, prevents them from agglomerating. In order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains, the volumetric packing factor (I.e., ratio of the actual volume to the volume of a circumscribing ellipsoid) of the ice grains must be less than ˜0.1 depending on the exact relative velocity of the grains in question. Thus, it is concluded that direct accretion of water molecules is very likely to dominate the observed ice grain growth.

Meso-scale anisotropic hydrogen segregation near grain-boundaries in polycrystalline nickel characterized by EBSD/SIMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oudriss, A.; Le Guernic, Solenne; Wang, Zhaoying

2016-02-15

To study anisotropic hydrogen segregation and diffusion in nickel polycrystalline, Secondary Ion Mass Spectrometry (SIMS) and Electron Back Scattered Diffraction (EBSD) are integrated to investigate hydrogen distribution around grain boundaries. Hydrogen distribution in pre-charged samples were correlated with grain boundary character by integrating high-resolution grain microstructure from EBSD inverse pole figure map and low-resolution hydrogen concentration profile map from SIMS. This multimodal imaging instrumentation shows that grain boundaries in nickel can be categorized into two families based on behavior of hydrogen distribution crossing grain boundary: the first one includes random grain boundaries with fast hydrogen diffusivity, showing a sharp gapmore » for hydrogen concentration profile cross the grain boundaries. The second family are special Σ3n grain boundaries with low hydrogen diffusivity, showing a smooth gradient of hydrogen concentration cross the grain boundary. Heterogeneous hydrogen distributions due to grain boundary family revealed by SIMS/EBSD on mesoscale further validate the recent hydrogen permeation data and anisotropic ab-initio calculations in nanoscale. The results highlight the fact that grain boundaries character impacts hydrogen distribution significantly.« less

Effect of Grain Boundary Misorientation on Electromigration in Lead-Free Solder Joints

NASA Astrophysics Data System (ADS)

Tasooji, Amaneh; Lara, Leticia; Lee, Kyuoh

2014-12-01

Reduction in microelectronic interconnect size gives rise to solder bumps consisting of few grains, approaching a single- or bicrystal grain morphology in C4 bumps. Single grain anisotropy, individual grain orientation, presence of easy diffusion paths along grain boundaries, and the increased current density in these small solder bumps aggravate electromigration. This reduces the reliability of the entire microelectronic system. This paper focuses on electromigration behavior in Pb-free solder, specifically the Sn-0.7 wt.%Cu alloy. We discuss the effects of texture, grain orientation, and grain boundary misorientation angle on electromigration (EM) and intermetallic compound formation in EM-tested C4 bumps. The detailed electron backscatter diffraction (EBSD) analysis used in this study reveals the greater influence of grain boundary misorientation on solder bump electromigration compared with the effect associated with individual grain orientation.

Alignment of dust grains in ionized regions

NASA Technical Reports Server (NTRS)

Anderson, Nels; Watson, William D.

1993-01-01

The rate at which charged dust grains in a plasma are torqued by passing ions and electrons is calculated. When photo-emission of electrons is not important, attraction of ions by the grain monopole potential increases the rate at which the grains' spins are dealigned by nearly an order of magnitude. Consequently, the energy density of the magnetic field required to align grains in an H II region may be increased by about an order of magnitude. In contrast, electric dipole and quadrupole moments are unlikely to produce large dealignment rates for grains of modest length-to-width ratio. Nonetheless, for positively charged grains these higher-order moments likely prevent monopole repulsion of ions from reducing the dealignment rate far below that for neutral grains. The presence of positive grain charge therefore does not greatly facilitate grain alignment in an H II region.

Whole grains and health: attitudes to whole grains against a prevailing background of increased marketing and promotion.

PubMed

McMackin, Elaine; Dean, Moira; Woodside, Jayne V; McKinley, Michelle C

2013-04-01

To explore current awareness and perceptions of whole grain foods and perceived barriers and facilitators of whole grain consumption. Focus groups were conducted to investigate consumer attitudes to whole grains. Discussions were transcribed verbatim and analysed thematically. Discussions were held throughout Northern Ireland with adults who were at least partly responsible for food shopping. Seven focus groups were held (n 43; thirty-three females, ten males). All participants were aware of the term 'whole grain' and had a basic level of awareness of their health benefits. Prominent barriers and facilitators of whole grain intake were related to perceptions of the sensory properties (most dominant factor) of whole grains; knowledge of how to locate, identify and use whole grains; and awareness of the health benefits, perceived cost and family influences. Parents of young children appeared to be altruistically motivated with many stating they wanted to ensure their children consumed whole grains in order to establish good eating habits. Participants were generally aware of the term 'whole grain'; however, even against a background of increased availability and promotion of whole grain foods, many key barriers to whole grain consumption were still evident. Alongside general education efforts, opportunities and challenges exist for the food industry to develop novel, but affordable, food products that are able to deliver whole grains in a wide variety of forms, including whole grains 'in disguise' for those who are most resistant to change.

Comparison of microstructure of superplastically deformed synthetic materials and ultramylonite: Coalescence of secondary mineral grains via grain boundary sliding

NASA Astrophysics Data System (ADS)

Hiraga, T.; Miyazaki, T.; Tasaka, M.; Yoshida, H.

2011-12-01

Using very fine-grained aggregates of forsterite containing ~10vol% secondary mineral phase such as periclase and enstatite, we have been able to demonstrate their superplascity, that is, achievement of more than a few 100 % tensile strain (Hiraga et al. 2010). Superplastic deformation is commonly considered to proceed via grain boundary sliding (GBS) which results in grain switching in the samples. Hiraga et al. (2010) succeeded in detecting the operation of GBS from observing the coalescence of grains of secondary phase in superplastically deformed samples. The secondary phase pins the motion of grain boundaries of the primary phase; however, the reduction of the number of the grains of secondary phase due to their coalescence allows grain growth of the primary phase. We analyzed the relationships between grain size of the primary and secondary phases, between strain and grain size, and between strain and the number of coalesced grains in the superplastically deformed samples. The results supports participation of all the grains of the primary phase in grain switching process indicating that the grain boundary sliding accommodates almost entire strain during the deformation. Mechanical properties of these materials such as their stress and grain size exponents of 1-2 do not conflict this conclusion. We applied the relationships obtained from analyzing superplastic materials to the microstructure of the natural samples, which has been considered to have deformed via grain boundary sliding, that is, ultramylonite. The microstructure of greenschist-grade ultramylonite reported by Fliervoet et al. (1997) was analyzed. Distributions of the mineral phases (i.e., quartz, plagioclase, K-feldspar and biotite) show distinct coalescence of the same mineral phases in the direction almost perpendicular to the foliation of the rock. The number of coalesced grains indicates that the strain that rock experienced is > 2. [reference] Hiraga et al. (2010) Nature 468, 1091-1094; Fliervoet et al. (1997) Journal of Structural Geology 19, 1495-1520

Effects of moisture and grain size on the mechanisms of rainsplash transport

NASA Astrophysics Data System (ADS)

Taube, S. R.; Furbish, D. J.

2010-12-01

Desert shrubs accumulate soil mounds beneath their canopies through rainsplash transport. Previous studies of this process have suggested that there is a preferential concentration of smaller grain sizes closer to the base of the shrub, based on the idea that smaller material is more readily splashed inward beneath the shrub. However, our studies have shown that there are two mechanisms of ejection of the grains with moist soil conditions, each preferentially moving either large or small grain sizes. Larger grains tend to be launched from grain-to-grain collisions following drop impact and travel as individual grains. Smaller grains appear to clump together and move as a single large "grain". The medium-sized grains generally had a greater travel distance than the very large or very small grains, potentially because they involve both modes of transport with a greater effective transfer of energy from the raindrop to the grains. The average travel distance is greatest near 100 microns, which is reflected by the data of Leguedois, et al. (2005). Experiments using high-speed imaging reveals that there is a marked difference between the mechanism of transport when the sediment grains are dry versus when they are moist. The dry grains are rapidly deposited about the impact site with a small proportion moving far from the site. However, moist grains tend to clump together to form “blobs” of water and sediment. Immediately after impact, the drop creates a water corona with entrained sediment, which then contracts into water-sediment blobs that are rocketed outwards from the impact, leaving little to no grain mass near the impact site. Varying degrees of moisture content appeared to have little influence on grain dispersal, leading us to believe that once the soil material is moist (but not saturated), its splash behavior is mostly related to details of the drop corona.

Study of the prevalence of chronic, non-specific lung disease and related health problems in the grain-handling industry. Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rankin, J.; Bates, J.; Claremont, A.

1986-10-01

A total of 310 grain handlers was studied, with attention to prevalence and characteristics of clinical, psychological, immunological, radiological, serological blood and urine parameters to determine any apparent effects from grain-dust exposure. Grain handlers had a higher prevalence of respiratory symptoms and signs than did the city workers who comprised the comparison group. Evidence of accumulative respiratory effect due to recurring exposures to grain dust was found. Acute and chronic airway reactions were induced by exposure to grain dust. Wheezing and dyspnea on exposure were related to length of employment. Grain fever syndrome was prevalent. Cases of acute recurrent conjunctivitismore » and rhinitis were found along with skin pruritus, mainly on exposure to barley dust. Pesticide exposure caused temporary disabling symptoms. Lung function was adversely affected by grain-dust exposure. Exposure to grain mites and insects in contaminated cereal grain caused a reaction among grain workers.« less

Grain growth mechanism and magnetic properties in L10-FePt thin films

NASA Astrophysics Data System (ADS)

Li, W.; Chen, L.

2017-08-01

This paper focuses on the grain growth mechanisms and magnetic properties of FePt thin films during an annealing process. The grain size and grain orientation distribution have been quantitatively investigated by electron backscatter diffraction (EBSD), and the grain growth kinetics of thin films were described by the phenomenological kinetic grain growth model. The results show that the grain growth exponent and activation energy of the FePt thin films were 4.26 and 136 kJ/mol respectively, indicating that the grain growth mechanism is mainly controlled by the stochastic jumping of atoms crossing the grain boundaries. X-ray diffraction (XRD) results show that disorder-order transformation was concurrent with grain growth during the annealing process, slowing down the velocity of grain growth. The hysteresis loops reveal that the out-of-plane coercivity and squareness is enhanced with increasing annealing temperature and this can be attributed to the improvement of L10-ordered phase volume fraction and texture intensity.

Influence of SiC grain boundary character on fission product transport in irradiated TRISO fuel

NASA Astrophysics Data System (ADS)

Lillo, T. M.; van Rooyen, I. J.

2016-05-01

In this study, the fission product precipitates at silicon carbide grain boundaries from an irradiated TRISO particle were identified and correlated with the associated grain boundary characteristics. Precession electron diffraction in the transmission electron microscope provided the crystallographic information needed to identify grain boundary misorientation and boundary type (i.e., low angle, random high angle or coincident site lattice (CSL)-related). The silicon carbide layer was found to be composed mainly of twin boundaries and small fractions of random high angle and low angle grain boundaries. Most fission products were found at random, high-angle grain boundaries, with small fractions at low-angle and CSL-related grain boundaries. Palladium (Pd) was found at all types of grain boundaries while Pd-uranium and Pd-silver precipitates were only associated with CSL-related and random, high-angle grain boundaries. Precipitates containing only Ag were found only at random, high-angle grain boundaries, but not at low angle or CSL-related grain boundaries.

Influence of SiC grain boundary character on fission product transport in irradiated TRISO fuel

DOE PAGES

Lillo, T. M.; Rooyen, I. J.

2016-02-26

The relationship between grain boundary character and fission product migration is identified as an important knowledge gap in order to advance the understanding of fission product release from TRISO fuel particles. Precession electron diffraction (PED), a TEM-based technique, was used in this study to quickly and efficiently provide the crystallographic information needed to identify grain boundary misorientation, grain boundary type (low or high angle) and whether the boundary is coincident site lattice (CSL) – related, in irradiated SiC. Analysis of PED data showed the grain structure of the SiC layer in an irradiated TRISO fuel particle from the AGR-1 experimentmore » to be composed mainly of twin boundaries with a small fraction of low angle grain boundaries (<10%). In general, fission products favor precipitation on random, high angle grain boundaries but can precipitate out on low angle and CSL-related grain boundaries to a limited degree. Pd is capable of precipitating out on all types of grain boundaries but most prominently on random, high angle grain boundaries. Pd-U and Pd-Ag precipitates were found on CSL-related as well as random high angle grain boundaries but not on low angle grain boundaries. In contrast, precipitates containing only Ag were found only on random, high angle grain boundaries but not on either low angle or CSL-related grain boundaries.« less

Influence of SiC grain boundary character on fission product transport in irradiated TRISO fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lillo, T. M.; Rooyen, I. J.

The relationship between grain boundary character and fission product migration is identified as an important knowledge gap in order to advance the understanding of fission product release from TRISO fuel particles. Precession electron diffraction (PED), a TEM-based technique, was used in this study to quickly and efficiently provide the crystallographic information needed to identify grain boundary misorientation, grain boundary type (low or high angle) and whether the boundary is coincident site lattice (CSL) – related, in irradiated SiC. Analysis of PED data showed the grain structure of the SiC layer in an irradiated TRISO fuel particle from the AGR-1 experimentmore » to be composed mainly of twin boundaries with a small fraction of low angle grain boundaries (<10%). In general, fission products favor precipitation on random, high angle grain boundaries but can precipitate out on low angle and CSL-related grain boundaries to a limited degree. Pd is capable of precipitating out on all types of grain boundaries but most prominently on random, high angle grain boundaries. Pd-U and Pd-Ag precipitates were found on CSL-related as well as random high angle grain boundaries but not on low angle grain boundaries. In contrast, precipitates containing only Ag were found only on random, high angle grain boundaries but not on either low angle or CSL-related grain boundaries.« less

Improve sensitization and corrosion resistance of an Al-Mg alloy by optimization of grain boundaries

NASA Astrophysics Data System (ADS)

Yan, Jianfeng; Heckman, Nathan M.; Velasco, Leonardo; Hodge, Andrea M.

2016-05-01

The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys. Understanding sensitization requires the review of grain boundary character on the precipitation process which can assist in developing and designing alloys with improved corrosion resistance. This study shows that the degree of precipitation in Al-Mg alloy is dependent on grain boundary misorientation angle, adjacent grain boundary planes and grain boundary types. The results show that the misorientation angle is the most important factor influencing precipitation in grain boundaries of the Al-Mg alloy. Low angle grain boundaries (≤15°) have better immunity to precipitation and grain boundary acid attack. High angle grain boundaries (>15°) are vulnerable to grain boundary acid attack. Grain boundaries with adjacent plane orientations near to {100} have potential for immunity to precipitation and grain boundary acid attack. This work shows that low Σ (Σ ≤ 29) coincident site lattice (CSL) grain boundaries have thinner β precipitates. Modified nitric acid mass loss test and polarization test demonstrated that the global corrosion resistance of sputtered Al-Mg alloy is enhanced. This may be attributed to the increased fractions of low Σ (Σ ≤ 29) CSL grain boundaries after sputtering.

Improving detection probabilities for pests in stored grain.

PubMed

Elmouttie, David; Kiermeier, Andreas; Hamilton, Grant

2010-12-01

The presence of insects in stored grain is a significant problem for grain farmers, bulk grain handlers and distributors worldwide. Inspection of bulk grain commodities is essential to detect pests and thereby to reduce the risk of their presence in exported goods. It has been well documented that insect pests cluster in response to factors such as microclimatic conditions within bulk grain. Statistical sampling methodologies for grain, however, have typically considered pests and pathogens to be homogeneously distributed throughout grain commodities. In this paper, a sampling methodology is demonstrated that accounts for the heterogeneous distribution of insects in bulk grain. It is shown that failure to account for the heterogeneous distribution of pests may lead to overestimates of the capacity for a sampling programme to detect insects in bulk grain. The results indicate the importance of the proportion of grain that is infested in addition to the density of pests within the infested grain. It is also demonstrated that the probability of detecting pests in bulk grain increases as the number of subsamples increases, even when the total volume or mass of grain sampled remains constant. This study underlines the importance of considering an appropriate biological model when developing sampling methodologies for insect pests. Accounting for a heterogeneous distribution of pests leads to a considerable improvement in the detection of pests over traditional sampling models. Copyright © 2010 Society of Chemical Industry.

Detecting rare, abnormally large grains by x-ray diffraction

DOE PAGES

Boyce, Brad L.; Furnish, Timothy Allen; Padilla, H. A.; ...

2015-07-16

Bimodal grain structures are common in many alloys, arising from a number of different causes including incomplete recrystallization and abnormal grain growth. These bimodal grain structures have important technological implications, such as the well-known Goss texture which is now a cornerstone for electrical steels. Yet our ability to detect bimodal grain distributions is largely confined to brute force cross-sectional metallography. The present study presents a new method for rapid detection of unusually large grains embedded in a sea of much finer grains. Traditional X-ray diffraction-based grain size measurement techniques such as Scherrer, Williamson–Hall, or Warren–Averbach rely on peak breadth andmore » shape to extract information regarding the average crystallite size. However, these line broadening techniques are not well suited to identify a very small fraction of abnormally large grains. The present method utilizes statistically anomalous intensity spikes in the Bragg peak to identify regions where abnormally large grains are contributing to diffraction. This needle-in-a-haystack technique is demonstrated on a nanocrystalline Ni–Fe alloy which has undergone fatigue-induced abnormal grain growth. In this demonstration, the technique readily identifies a few large grains that occupy <0.00001 % of the interrogation volume. Finally, while the technique is demonstrated in the current study on nanocrystalline metal, it would likely apply to any bimodal polycrystal including ultrafine grained and fine microcrystalline materials with sufficiently distinct bimodal grain statistics.« less

Grain-size-yield stress relationship: Analysis and computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meyers, M.A.; Benson, D.J.; Fu, H.H.

1999-07-01

The seminal contributions of Julia Weertman to the understanding of the mechanical properties of nanocrystalline materials will be briefly outlined. A constitutive equation predicting the effect of grain size on the yield stress of metals, based on the model proposed by M.A. Meyers and E. Ashworth, is discussed and extended to the nanocrystalline regime. At large grain sizes, it has the Hall-Petch form, and in the nanocrystalline domain the slope gradually decreases until it asymptotically approaches the flow stress of the grain boundaries. The material is envisaged as a composite, comprised of the grain interior, with flow stress {sigma}{sub fB},more » and grain boundary work-hardened layer, with flow stress {sigma}{sub fGB}. Three principal factors contribute to the grain-boundary hardening: (1) the grain boundaries act as barriers to plastic flow; (2) the grain boundaries act as dislocation sources; and (3) elastic anisotropy causes additional stresses in grain-boundary surroundings. The predictions of this model are compared with experimental measurements over the mono, micro, and nanocrystalline domains. Computational predictions are made of plastic flow as a function of grain size incorporating elastic and plastic anisotropy as well as differences of dislocation accumulation rate in grain boundary regions and grain interiors. This is the first plasticity calculation that accounts for grain size effects in a physically-based manner. 58 refs., 7 figs., 1 tab.« less

7 CFR 1412.49 - Apportionment of long and medium grain rice.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 10 2012-01-01 2012-01-01 false Apportionment of long and medium grain rice. 1412.49... and Peanuts 2008 through 2012 § 1412.49 Apportionment of long and medium grain rice. (a) Rice base...) Medium grain rice. Medium grain rice includes short grain rice. (c) Owners on a farm will elect rice base...

7 CFR 1412.49 - Apportionment of long and medium grain rice.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 10 2010-01-01 2010-01-01 false Apportionment of long and medium grain rice. 1412.49... and Peanuts 2008 through 2012 § 1412.49 Apportionment of long and medium grain rice. (a) Rice base...) Medium grain rice. Medium grain rice includes short grain rice. (c) Owners on a farm will elect rice base...

7 CFR 1412.49 - Apportionment of long and medium grain rice.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 10 2013-01-01 2013-01-01 false Apportionment of long and medium grain rice. 1412.49... and Peanuts 2008 Through 2012 § 1412.49 Apportionment of long and medium grain rice. (a) Rice base...) Medium grain rice. Medium grain rice includes short grain rice. (c) Owners on a farm will elect rice base...

7 CFR 1412.49 - Apportionment of long and medium grain rice.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 10 2011-01-01 2011-01-01 false Apportionment of long and medium grain rice. 1412.49... and Peanuts 2008 through 2012 § 1412.49 Apportionment of long and medium grain rice. (a) Rice base...) Medium grain rice. Medium grain rice includes short grain rice. (c) Owners on a farm will elect rice base...

7 CFR 1412.49 - Apportionment of long and medium grain rice.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 10 2014-01-01 2014-01-01 false Apportionment of long and medium grain rice. 1412.49... and Peanuts 2008 Through 2012 § 1412.49 Apportionment of long and medium grain rice. (a) Rice base...) Medium grain rice. Medium grain rice includes short grain rice. (c) Owners on a farm will elect rice base...

Weighing in on whole grains: A review of evidence linking whole grains to body weight

USDA-ARS?s Scientific Manuscript database

U.S. dietary guidelines support the consumption of whole grains in lieu of refined grains. On January 31, 2011, the 2010 Dietary Guidelines for Americans (DGA) were released and the recommendations with respect to grains were for individuals to “Consume at least half of all grains as whole grains” a...

7 CFR 810.805 - Special grades and special grade requirements.

Code of Federal Regulations, 2010 CFR

2010-01-01

... grain. Mixed grain in which barley predominates and that contains more than 4.0 percent of fungus-damaged and/or mold-damaged barley kernels. (b) Ergoty mixed grain. (1) Mixed grain in which rye or wheat... than 0.10 percent ergot. (c) Garlicky mixed grain. (1) Mixed grain in which wheat, rye, or triticale...

Effect of ultrafine grain on tensile behaviour and corrosion resistance of the duplex stainless steel.

PubMed

Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Limin, Dong

2016-05-01

The ultrafine grained 2205 duplex stainless steel was obtained by cold rolling and annealing. The tensile properties were investigated at room temperature. Comparing with coarse grained stainless steel, ultrafine grained sample showed higher strength and plasticity. In addition, grain size changed deformation orientation. The strain induced α'-martensite was observed in coarse grained 2205 duplex stainless steel with large strain. However, the grain refinement inhibited the transformation of α'-martensite;nevertheless, more deformation twins improved the strength and plasticity of ultrafine grained 2205 duplex stainless steel. In addition, the grain refinement improved corrosion resistance of the 2205 duplex stainless steel in sodium chloride solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Strength of Rocks Affected by Deformation Enhanced Grain Growth

NASA Astrophysics Data System (ADS)

Kellermann Slotemaker, A.; de Bresser, H.; Spiers, C.

2005-12-01

One way of looking into the possibility of long-term strength changes in the lithosphere is to study transient effects resulting from modifications of the microstructure of rocks. It is generally accepted that mechanical weakening may occur due to progressive grain size refinement resulting from dynamic recrystallization. A decrease in grain size may induce a switch from creep controlled by grain size insensitive dislocation mechanisms to creep governed by grain size sensitive (GSS) mechanisms involving diffusion and grain boundary sliding processes. This switch forms a well-known scenario to explain localization in the lithosphere. However, fine-grained rocks in localized deformation zones are prone to grain coarsening due to surface energy driven grain boundary migration (SED-GBM). This might harden the rock, affecting its role in localizing strain in the long term. The question has arisen if grain growth by SED-GBM in a rock deforming in the GSS creep field can be significantly affected by strain. The broad aim of this study is to shed more light onto this. We have experimentally investigated the microstructural and strength evolution of fine-grained (~0.6 μm) synthetic forsterite and Fe-bearing olivine aggregates that coarsen in grain size while deforming by GSS creep at elevated pressure (600 MPa) and temperature (850-1000 °C). The materials were prepared by `sol-gel' method and contained 0.3-0.5 wt% water and 5-10 vol% enstatite. We performed i) static heat treatment tests of various time durations involving hot isostatic pressing (HIP), and ii) heat treatment tests starting with HIP and continuing with deformation up to 45% axial strain at strain rates in the range 4x10-7 - 1x10-4 s-1. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. In addition to the experiments, we studied microstructural evolution in simple two-dimensional numerical models, combining deformation and SED-GBM by means of the modeling package ELLE. Synthetic olivine samples that were heat treated without straining showed only minor grain growth. Presumably, the second phase (enstatite) and/or porosity remaining in the starting material after densification slowed down or inhibited SED-GBM in the static situation. In contrast, samples heat treated and deformed for time durations similar to those of the static tests demonstrated, at identical temperature, an increase in grain size with increasing strain up to a value twice that of the static counterpart. This grain coarsening was associated with continuous hardening of the material, witnessed by the stress-strain curves. A random lattice preferred orientation combined with a low stress sensitivity (n~2) suggested dominant GSS creep controlled by grain boundary sliding. A dynamic grain growth model involving an increase in the fraction of non-hexagonal grains, related to grain neighbor switching, appears applicable to the observed grain growth that is held responsible for the hardening. The ELLE numerical modeling demonstrated that a combination of SED-GBM and geometrical deformation of a 2D grain aggregate can indeed result in enhanced grain growth compared to static grain growth tests. The fraction of non-hexagonal grains was found to remain more or less constant during static grain growth but increased during deformation. We suggest that the application of the dynamic grain growth model to the long-term microstructural evolution of fine-grained lithospheric shear zones can further improve our understanding of the transient or permanent character of strain localizations and related rheological behavior.

Effects of local film properties on the nucleation and growth of tin whiskers and hillocks

NASA Astrophysics Data System (ADS)

Sarobol, Pylin

Whiskers and hillocks grow spontaneously on Pb-free Sn electrodeposited films as a response to thin film stresses. Stress relaxation occurs by atom deposition to specific grain boundaries in the plane of the film, with hillocks being formed when grain boundary migration accompanies growth out of the plane of the film. The implication for whisker formation in electronics is serious: whiskers can grow to be millimeters long, sometimes causing short circuiting between adjacent components and, thereby, posing serious electrical reliability risks. In order to develop more effective whisker mitigation strategies, a predictive physics-based model has been needed. A growth model is developed, based on grain boundary faceting, localized Coble creep, as well as grain boundary sliding for whiskers, and grain boundary sliding with shear induced grain boundary migration for hillocks. In this model of whisker formation, two mechanisms are important: accretion of atoms by Coble creep on grain boundary planes normal to the growth direction inducing a grain boundary shear and grain boundary sliding in the direction of whisker growth. The model accurately captures the importance of the geometry of "surface grains"---shallow grains on film surfaces whose depths are significantly less than their in-plane grain sizes. A critical factor in the analysis is the ratio of the grain boundary sliding coefficient to the in-plane film compressive stress. If the accretion-induced shear stresses are not coupled to grain boundary motion and sliding occurs, a whisker forms. If the shear stress is coupled to grain boundary migration, a hillock forms. Based on this model, long whiskers grow from shallow surface grains with easy grain boundary sliding in the direction of growth. Other observed growth morphologies will be discussed in light of our model. Additional insights into the preferred sites for whisker and hillock growth were developed based on elastic anisotropy, local film microstructure, grain misorientation, and elastic strain energy density (ESED) as the driving force for growth. Local grain orientations and strains measured by synchrotron micro-diffraction in regions containing whiskers or hillocks were compared with elastic finite element analysis simulations, including Sn elastic anisotropy. Whisker and hillock grains were observed to have higher crystallographic misorientations with neighboring grains than generally observed in the microstructure. While elastic simulations predicted higher local out-of-plane elastic strains and ESEDs for whisker and hillock grains, synchrotron measurements of out-of-plane strains of whisker and hillock grains after growth showed relaxation, with correspondingly low ESEDs calculated from measured strains. This suggests that, before whisker or hillock formation, highly misoriented grains with high out-of-plane elastic strains and ESEDs relative to their neighbors determined, at least in part, which grains became whiskers or hillocks. Based on the models and experiments in this thesis, a clearer picture emerges of the necessary and sufficient conditions for tin whisker and hillock formation in thin films.

Influence of modes of metal transfer on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, Manidipto; Saha, Saptarshi; Pal, Tapan Kumar, E-mail: tkpal.ju@gmail.com

2015-04-15

The present study elaborately discussed the effect of different modes of metal transfer (i.e., short circuit mode, spray mode and pulse mode) on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals. Electron backscattered diffraction (EBSD) analysis was used to study the grain growth direction and grain structure in weld metals. The changes in grain structure and grain growth direction were found to be essentially varied with the weld pool shape and acting forces induced by modes of metal transfer at a constant welding speed. Short circuit mode of metal transfer owing to highermore » Marangoni force (M{sub a}) and low electromagnetic force (R{sub m}) promotes the lower weld pool volume (Γ) and higher weld pool maximum radius (r{sub m}). Short circuit mode also shows curved and tapered columnar grain structures and the grain growth preferentially occurred in <001> direction. In contrast, spray mode of metal transfer increases the Γ and reduces the r{sub m} values due to very high R{sub m} and typically reveals straight and broad columnar grain structures with preferential growth direction in <111>. In the pulse mode of metal transfer relatively high M{sub a} and R{sub m} simultaneously increase the weld pool width and the primary penetration which might encourage relatively complex grain growth directions in the weld pool and cause a shift of major intensity from <001> to <111> direction. It can also be concluded that the fusion zone grain structure and direction of grain growth are solely dependent on modes of metal transfer and remain constant for a particular mode of metal transfer irrespective of filler wire used. - Highlights: • Welded joints of LNiASS were prepared by varying modes of metal transfer. • Weld pool shape, grain structure and grain growth direction were studied. • Short circuit mode shows curved and tapered grain growth in <001> direction. • Spray mode shows straight and broad columnar grain growth in <111> direction. • Pulse mode shows complex grain growth with a shift in growth direction.« less

What does it mean to be pseudo single domain? Demystifying the PSD state

NASA Astrophysics Data System (ADS)

Lascu, I.; Harrison, R. J.; Einsle, J. F.; Ball, M.

2016-12-01

Until recently, non-interacting stable single domain grains were thought to be the sole reliable paleomagnetic recorders. However most natural samples contain so-called "non-ideal" paleomagnetic recorders, which are either interacting single domain particles, or magnetic grains larger than single domain grains, but smaller than proper multi domain grains, which are poor paleomagnetic recorders. The grain size range for these recorders, which for magnetite comprises grains from 100 nm to a few μm in size, is known as the pseudo single domain (PSD) state. Natural samples containing abundant PSD grains have been shown time and again to reliably record thermomagnetic remanent magnetizations that are stable over billions of years. Here we attempt to shed new light on the PSD state by investigating obsidian varieties found at Glass Butte, Oregon, which present the opportunity to study simple cases of magnetic grains encapsulated in volcanic glass. We do this by combining rock magnetism, scanning electron microscopy (SEM) nanotomography, and finite-element micromagnetic modeling. Using rock magnetism we have identified PSD signatures in these samples via their fingerprint in first-order reversal curve (FORC) diagrams. Tomographic reconstructions obtained by stacking SEM images acquired via sequential milling through sample volumes of a few tens of cubic μm reveal the presence of abundant grains that span the PSD grain size interval. These grains have a variety of shapes, from simple ellipsoidal particles, to more complex morphologies attained through the coalescence of neighboring grains during crystallization, to intricate "rolling snowball" morphologies in larger grains that contain appendices formed as a result of particle growth in a dynamic environment as the flowing lava cooled. Micromagnetic modeling of the simplest morphologies reveals that these grains are in single vortex states, with the remanence controlled by irregularities in grain morphology. Coalesced grains present extreme cases of shape anisotropy, which will control the remanence. The remanence of the largest grains is controlled by the collection of PSD states from areas of the grain with pronounced shape anisotropy. Finally, micromagnetic modeling of realistic grain shapes allows the understanding of PSD signatures in FORC diagrams.

Effects of film growth kinetics on grain coarsening and grain shape.

PubMed

Reis, F D A Aarão

2017-04-01

We study models of grain nucleation and coarsening during the deposition of a thin film using numerical simulations and scaling approaches. The incorporation of new particles in the film is determined by lattice growth models in three different universality classes, with no effect of the grain structure. The first model of grain coarsening is similar to that proposed by Saito and Omura [Phys. Rev. E 84, 021601 (2011)PLEEE81539-375510.1103/PhysRevE.84.021601], in which nucleation occurs only at the substrate, and the grain boundary evolution at the film surface is determined by a probabilistic competition of neighboring grains. The surface grain density has a power-law decay, with an exponent related to the dynamical exponent of the underlying growth kinetics, and the average radius of gyration scales with the film thickness with the same exponent. This model is extended by allowing nucleation of new grains during the deposition, with constant but small rates. The surface grain density crosses over from the initial power law decay to a saturation; at the crossover, the time, grain mass, and surface grain density are estimated as a function of the nucleation rate. The distributions of grain mass, height, and radius of gyration show remarkable power law decays, similar to other systems with coarsening and particle injection, with exponents also related to the dynamical exponent. The scaling of the radius of gyration with the height h relative to the base of the grain show clearly different exponents in growth dominated by surface tension and growth dominated by surface diffusion; thus it may be interesting for investigating the effects of kinetic roughening on grain morphology. In growth dominated by surface diffusion, the increase of grain size with temperature is observed.

[Effects of PASP-KT-NAA on the grain-filling of maize in different accumulated temperature zones of Hilongjiang Province, Norheast China].

PubMed

Xu, Tian-Jun; Dong, Zhi-Qiang; Gao, Jiao; Chen, Chuan-Xiao; Jiao, Liu; Xie, Zhen-Xing

2013-02-01

Taking the two maize varieties Zhengdan 958 and Fengdan 3 grown on the three accumulated temperature zones (I, II and III) in Heilongjiang Provice as test materials, a field investigation was made in 2010 and 2011 to study the effects of PASP-KT-NAA (PKN), a compound of exogenous plant growth regulators, on the grain filling and yield of the varieties under different environmental temperatures. From zone I to III, the air temperature at the grain filling stage had a decreasing trend, with the average minimum temperature being 12.16, 11.40, and 9.56, respectively. The effective accumulated temperature at the mid-ate amt sae stage of grain filling was too low to be sufficient for grain filling, which severely affected the grain filling process. Applying N, P and K promoted the dry matter accumulation of maize grain and the grain filling rate in the three zones, delayed the peak time (Tmax) of the grain filling rate of Fengdan 3 but advanced that of Zhengdan 958, promoted the growth capacity at peak time of grain filling rate and the maximum grain filling rate of the two varieties, and shortened their active grain filling period. Applying N, P, and K increased the grain yield of the two varieties in the three zones obviously, and, as compared with those in zones I and II , the grain yields of Zhengdan 958 and Fengdan 3 in zone III were increased by 8.2% and 5.1% , and 3.4% and 0.8% , respectively. Therefore, applying N, P and K could help maize utilizing the limited accumulation temperature, improve the grain filling rate, decrease the grain water content, and ultimately, increase the maize yield.

Genome wide association mapping for grain shape traits in indica rice.

PubMed

Feng, Yue; Lu, Qing; Zhai, Rongrong; Zhang, Mengchen; Xu, Qun; Yang, Yaolong; Wang, Shan; Yuan, Xiaoping; Yu, Hanyong; Wang, Yiping; Wei, Xinghua

2016-10-01

Using genome-wide association mapping, 47 SNPs within 27 significant loci were identified for four grain shape traits, and 424 candidate genes were predicted from public database. Grain shape is a key determinant of grain yield and quality in rice (Oryza sativa L.). However, our knowledge of genes controlling rice grain shape remains limited. Genome-wide association mapping based on linkage disequilibrium (LD) has recently emerged as an effective approach for identifying genes or quantitative trait loci (QTL) underlying complex traits in plants. In this study, association mapping based on 5291 single nucleotide polymorphisms (SNPs) was conducted to identify significant loci associated with grain shape traits in a global collection of 469 diverse rice accessions. A total of 47 SNPs were located in 27 significant loci for four grain traits, and explained ~44.93-65.90 % of the phenotypic variation for each trait. In total, 424 candidate genes within a 200 kb extension region (±100 kb of each locus) of these loci were predicted. Of them, the cloned genes GS3 and qSW5 showed very strong effects on grain length and grain width in our study. Comparing with previously reported QTLs for grain shape traits, we found 11 novel loci, including 3, 3, 2 and 3 loci for grain length, grain width, grain length-width ratio and thousand grain weight, respectively. Validation of these new loci would be performed in the future studies. These results revealed that besides GS3 and qSW5, multiple novel loci and mechanisms were involved in determining rice grain shape. These findings provided valuable information for understanding of the genetic control of grain shape and molecular marker assistant selection (MAS) breeding in rice.

The electrostatics of a dusty plasma

NASA Technical Reports Server (NTRS)

Whipple, E. C.; Mendis, D. A.; Northrop, T. G.

1986-01-01

The potential distribution in a plasma containing dust grains were derived where the Debye length can be larger or smaller than the average intergrain spacing. Three models were treated for the grain-plasma system, with the assumption that the system of dust and plasma is charge-neutral: a permeable grain model, an impermeable grain model, and a capacitor model that does not require the nearest neighbor approximation of the other two models. A gauge-invariant form of Poisson's equation was used which is linearized about the average potential in the system. The charging currents to a grain are functions of the difference between the grain potential and this average potential. Expressions were obtained for the equilibrium potential of the grain and for the gauge-invariant capacitance between the grain and the plasma. The charge on a grain is determined by the product of this capacitance and the grain-plasma potential difference.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ann N.; Keller, Lindsay P.; Messenger, Scott, E-mail: lan-anh.n.nguyen@nasa.gov

We report the chemical and structural analysis of nine presolar silicate grains and one presolar oxide grain from the ungrouped chondrite Acfer 094 and the CR chondrite Queen Alexandra Range 99177. Oxygen isotopic analyses indicate that five of these grains condensed in the outflows of asymptotic giant branch (AGB) stars, four have supernova (SN) origins, and one grain likely has a nova origin. Transmission electron microscopy studies show that most of the grains are amorphous with widely varying non-stoichiometric chemical compositions. Three crystalline AGB grains were identified: a clinoenstatite-containing grain assemblage, a Fe-rich olivine grain, and a nanocrystalline enstatite grainmore » encased in an amorphous silicate shell. An amorphous stoichiometric enstatite (MgSiO{sub 3}) SN grain likely condensed as a crystal and was later rendered amorphous. We do not observe a systematic difference in the chemistries and mineralogies of presolar silicates from different stellar sources, suggesting that the grains formed under a similar range of conditions.« less

The Role of Grain Boundary Energy on Grain Boundary Complexion Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bojarski, Stephanie A.; Rohrer, Gregory S.

Grain boundary complexions are distinct equilibrium structures and compositions of a grain boundary and complexion transformations are transition from a metastable to an equilibrium complexion at a specific thermodynamic and geometric conditions. Previous work indicates that, in the case of doped alumina, a complexion transition that increased the mobility of transformed boundaries and resulted in abnormal grain growth also caused a decrease in the mean relative grain boundary energy as well as an increase in the anisotropy of the grain boundary character distribution (GBCD). The current work will investigate the hypothesis that the rates of complexion transitions that result inmore » abnormal grain growth (AGG) depend on grain boundary character and energy. Furthermore, the current work expands upon this understanding and tests the hypothesis that it is possible to control when and where a complexion transition occurs by controlling the local grain boundary energy distribution.« less

Microstructural Evaluation of Forging Parameters for Superalloy Disks

NASA Technical Reports Server (NTRS)

Falsey, John R.

2004-01-01

Forgings of nickel base superalloy were formed under several different strain rates and forging temperatures. Samples were taken from each forging condition to find the ASTM grain size, and the as large as grain (ALA). The specimens were mounted in bakelite, polished, etched and then optical microscopy was used to determine grain size. The specimens ASTM grain sizes from each forging condition were plotted against strain rate, forging temperature, and presoak time. Grain sizes increased with increasing forging temperature. Grain sizes also increased with decreasing strain rates and increasing forging presoak time. The ALA had been determined from each forging condition using the ASTM standard method. Each ALA was compared with the ASTM grain size of each forging condition to determine if the grain sizes were uniform or not. The forging condition of a strain rate of .03/sec and supersolvus heat treatment produced non uniform grains indicated by critical grain growth. Other anomalies are noted as well.

Evolution of twinning in extruded AZ31 alloy with bimodal grain structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcés, G., E-mail: ggarces@cenim.csic.es

2017-04-15

Twinning in extruded AZ31 alloy with a bimodal grain structure is studied under compression along the extrusion direction. This study has combined in-situ measurements during the compression tests by Synchrotron Radiation Diffraction and Acoustic Emission techniques and the evaluation of the microstructure and texture in post-mortem compression samples deformed at different strains. The microstructure of the alloy is characterized by the coexistence of large areas of fine dynamic recrystallized grains and coarse non-recrystallized grains elongated along extrusion direction. Twinning occurs initially in large elongated grains before the macroscopic yield stress which is controlled by the twinning in equiaxed dynamically recrystallizedmore » grains. - Highlights: • The AZ31 extruded at low temperature exhibits a bimodal grains structure. • Twinning takes place before macroscopic yielding in coarse non-DRXed grains. • DRXed grains controls the beginning of plasticity in magnesium alloys with bimodal grain structure.« less

Interactive introductory nutrition course focusing on disease prevention increased whole-grain consumption by college students.

PubMed

Ha, Eun-Jeong; Caine-Bish, Natalie

2011-01-01

To estimate current consumption of whole grains in college students and determine whether there would be an increase in whole-grain consumption after the students completed an interactive introductory nutrition course focusing on disease prevention. Eighty college students, 18-24 years old, participated in the study. Grain and whole-grain consumption, whole-grain food sources, and energy intake were measured before and after the nutrition course. Repeated-measures analysis of variance was performed. After the study, whole-grain intake significantly increased from 0.37 ounces (oz) to 1.16 oz (P < .001), whereas total grain intake remained the same (3.07 oz). The number of whole-grain food sources increased from 7 to 11 food items after the intervention. A general nutrition course can be used as an avenue to increase whole-grain intake by college students. Copyright © 2011 Society for Nutrition Education. Published by Elsevier Inc. All rights reserved.

A brittle to ductile transition in NiAl of a critical grain size

NASA Technical Reports Server (NTRS)

Schulson, E. M.; Barker, D. R.

1983-01-01

Tensile tests have been carried out on the strongly ordered B2 aluminide NiAl at 400 C to investigate the effect of the grain size on the ductility of the material. It is found that the ductility is very low and essentially independent of the grain size for aggregates of grains larger than about 20 microns; for finer-grained aggregates, the ductility increases sharply with decreasing grain size. Thus, NiAl exhibits a critical grain size below which polycrystalline aggregates are ductile in tension. For all grain sizes, fracture occurs in a brittle manner through a combination of intergranular decohesion and transgranular cleavage.

Microstructure characterization based on the type of deformed grains in cold-rolled, Cu-added, bake-hardenable steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.S.; Kim, S.I.; Choi, S.-H., E-mail: shihoon@sunchon.ac.kr

2014-06-01

The electron backscatter diffraction technique has been used to characterize the microstructure of deformed grains in cold-rolled, Cu-added, bake-hardenable steel. A new scheme based on the kind and number of average orientations, as determined from a unique grain map of the deformed grains, was developed in order to classify deformed grains by type. The α-fiber components, γ-fiber components and random orientations, those which could not be assigned to either γ-fiber or α-fiber components, were used to define the average orientation of unique grains within individual deformed grains. The microstructures of deformed grains in as-rolled specimens were analyzed based on themore » Taylor factor, stored energy, and misorientation. The relative levels and distributions of the Taylor factor, the stored energy and the misorientation were examined in terms of the types of deformed grains. - Highlights: • We characterized the microstructure of Cu-added BH steel using EBSD. • A new scheme was developed in order to classify deformed grains by type. • Stored energy and misorientation are strongly dependent on the type of deformed grains. • Microstructure was examined in terms of the types of deformed grains.« less

The Role of Grain Orientation and Grain Boundary Characteristics in the Mechanical Twinning Formation in a High Manganese Twinning-Induced Plasticity Steel

NASA Astrophysics Data System (ADS)

Shterner, Vadim; Timokhina, Ilana B.; Rollett, Anthony D.; Beladi, Hossein

2018-04-01

In the current study, the dependence of mechanical twinning on grain orientation and grain boundary characteristics was investigated using quasi in-situ tensile testing. The grains of three main orientations (i.e., <111>, <110>, and <100> parallel to the tensile axis (TA)) and certain characteristics of grain boundaries (i.e., the misorientation angle and the inclination angle between the grain boundary plane normal and the TA) were examined. Among the different orientations, <111> and <100> were the most and the least favored orientations for the formation of mechanical twins, respectively. The <110> orientation was intermediate for twinning. The annealing twin boundaries appeared to be the most favorable grain boundaries for the nucleation of mechanical twinning. No dependence was found for the inclination angle of annealing twin boundaries, but the orientation of grains on either side of the annealing twin boundary exhibited a pronounced effect on the propensity for mechanical twinning. Annealing twin boundaries adjacent to high Taylor factor grains exhibited a pronounced tendency for twinning regardless of their inclination angle. In general, grain orientation has a significant influence on twinning on a specific grain boundary.

Grain Entrapment Pressure on the Torso: Can You Breathe while Buried in Grain?

PubMed

Moore, Kevin G; Jones, Carol L

2017-04-26

The pressure applied to the chest and back of a simulated grain entrapment victim was measured. Pressure sensors were attached to the chest and back of a manikin that was buried in grain in the vertical position. Measurements were made in four grain types at four grain depths ranging from the top of the manikin's shoulders to 0.61 m (24 in.) over the head. The pressure ranged from 1.6 to 4.0 kPa (0.23 to 0.57 psi). Based on available physiological information, this amount of pressure is unlikely to limit the respiration of an otherwise healthy adult male victim. However, other factors, such as the victim's age, gender, and body position in the grain, may influence respiration. The aspiration of grain appears to be the most likely asphyxiation risk during grain bin entrapment. Entering a grain storage bin is inherently dangerous, and Occupational Safety and Health Administration (OSHA) guidelines for permit-required confined spaces and grain handling facilities must be followed. Due to the risk of grain aspiration during engulfment, the development of safety equipment that could help protect the airway of a victim should be investigated. Copyright© by the American Society of Agricultural Engineers.

Gel-free/label-free proteomic analysis of developing rice grains under heat stress.

PubMed

Timabud, Tarinee; Yin, Xiaojian; Pongdontri, Paweena; Komatsu, Setsuko

2016-02-05

High temperature markedly reduces the yields and quality of rice grains. To identify the mechanisms underlying heat stress-induced responses in rice grains, proteomic technique was used. Developing Khao Dawk Mali 105 rice grains at the milky, dough, and mature stages were treated at 40 °C for 3 days. Aromatic compounds were decreased in rice grains under heat stress. The protein abundance involved in glycolysis and tricarboxylic acid cycle, including glyceraldehyde 3-phosphate dehydrogenase and citrate synthase, was changed in milky and dough grains after heat treatment; however, none changes in mature grains. The abundance involved in amino acid metabolism was increased in dough grains, but decreased in milky grains. In addition, the abundance involved in starch and sucrose metabolism, such as starch synthase, ADP-glucose pyrophosphorylase, granule-bound starch synthase, and alpha amylase, was decreased in milky grains, but increased in dough grains. A number of redox homeostasis-related proteins, such as ascorbate peroxidase and peroxiredoxin, were increased in developing rice grains treated with heat stress. These results suggest that in response to heat stress, the abundance of numerous proteins involved in redox homeostasis and carbohydrate biosynthetic pathways may play a major role in the development of KDML105 rice grains. Yield of Khao Dawk Mali 105 rice, which is an economical aromatic rice, was disrupted by environmental stress. Rice grains developed under heat stress caused loss of aroma compound. To identify the mechanism of heat response in rice grain, gel-free/label-free proteomic technique was used. The abundance of proteins involved in glycolysis and tricarboxylic acid cycle was disrupted by heat stress. High temperature limited starch biosynthesis; however, it enhanced sugar biosynthesis in developing rice grains. Redox homeostasis related proteins were disrupted by heat stress. These results suggest that proteins involved in redox homeostasis and carbohydrate pathway might play a major role in developing grains in Khao Dawk Mali 105 rice under heat stress. Copyright © 2015 Elsevier B.V. All rights reserved.

Controls on sediment entrainment shear stress determined from X-Ray CT scans and a 3D moment-balance model

NASA Astrophysics Data System (ADS)

Hodge, R. A.; Voepel, H.; Leyland, J.; Sear, D. A.; Ahmed, S. I.

2017-12-01

The shear stress at which a grain is entrained is determined by the balance between the applied fluid forces, and the resisting forces of the grain. Recent research has tended to focus on the applied fluid forces; calculating the resisting forces requires measurement of the geometry of in-situ sediment grains which has previously been very difficult to measure. We have used CT scanning to measure the grain geometry of in-situ water-worked grains, and from these data have calculated metrics that are relevant to grain entrainment. We use these metrics to parameterise a new, fully 3D, moment-balance model of grain entrainment. Inputs to the model are grain dimensions, exposed area, elevation relative to the velocity profile, the location of grain-grain contact points, and contact area with fine matrix sediment. The new CT data and model mean that assumptions of previous grain-entrainment models (e.g. spherical grains, 1D measurements of protrusion, entrainment in the downstream direction) are no longer necessary. The model calculates the critical shear stress for each possible set of contact points, and outputs the lowest value. Consequently, metrics including pivot angle and the direction of grain entrainment are now model outputs, rather than having to be pre-determined. We use the CT data and model to calculate the critical shear stress of 1092 in-situ grains from baskets that were buried and water-worked in a flume prior to scanning. We find that there is no consistent relationship between relative grain size (D/D50) and pivot angle, whereas there is a negative relationship between D/D50 and protrusion. Out of all measured metrics, critical shear stress is most strongly controlled by protrusion. This finding suggests that grain-scale topographic data could be used to estimate grain protrusion and hence improve estimates of critical shear stress.

Tungsten Carbide Grain Size Computation for WC-Co Dissimilar Welds

NASA Astrophysics Data System (ADS)

Zhou, Dongran; Cui, Haichao; Xu, Peiquan; Lu, Fenggui

2016-06-01

A "two-step" image processing method based on electron backscatter diffraction in scanning electron microscopy was used to compute the tungsten carbide (WC) grain size distribution for tungsten inert gas (TIG) welds and laser welds. Twenty-four images were collected on randomly set fields per sample located at the top, middle, and bottom of a cross-sectional micrograph. Each field contained 500 to 1500 WC grains. The images were recognized through clustering-based image segmentation and WC grain growth recognition. According to the WC grain size computation and experiments, a simple WC-WC interaction model was developed to explain the WC dissolution, grain growth, and aggregation in welded joints. The WC-WC interaction and blunt corners were characterized using scanning and transmission electron microscopy. The WC grain size distribution and the effects of heat input E on grain size distribution for the laser samples were discussed. The results indicate that (1) the grain size distribution follows a Gaussian distribution. Grain sizes at the top of the weld were larger than those near the middle and weld root because of power attenuation. (2) Significant WC grain growth occurred during welding as observed in the as-welded micrographs. The average grain size was 11.47 μm in the TIG samples, which was much larger than that in base metal 1 (BM1 2.13 μm). The grain size distribution curves for the TIG samples revealed a broad particle size distribution without fine grains. The average grain size (1.59 μm) in laser samples was larger than that in base metal 2 (BM2 1.01 μm). (3) WC-WC interaction exhibited complex plane, edge, and blunt corner characteristics during grain growth. A WC ( { 1 {bar{{1}}}00} ) to WC ( {0 1 1 {bar{{0}}}} ) edge disappeared and became a blunt plane WC ( { 10 1 {bar{{0}}}} ) , several grains with two- or three-sided planes and edges disappeared into a multi-edge, and a WC-WC merged.

Rotation-induced grain growth and stagnation in phase-field crystal models.

PubMed

Bjerre, Mathias; Tarp, Jens M; Angheluta, Luiza; Mathiesen, Joachim

2013-08-01

We consider grain growth and stagnation in polycrystalline microstructures. From the phase-field crystal modeling of the coarsening dynamics, we identify a transition from a grain-growth stagnation upon deep quenching below the melting temperature T(m) to a continuous coarsening at shallower quenching near T(m). The grain evolution is mediated by local grain rotations. In the deep quenching regime, the grain assembly typically reaches a metastable state where the kinetic barrier for recrystallization across boundaries is too large and grain rotation with subsequent coalescence or boundary motion is infeasible. For quenching near T(m), we find that the grain growth depends on the average rate of grain rotation, and follows a power-law behavior with time, with a scaling exponent that depends on the quenching depth.

Algorithm based on regional separation for automatic grain boundary extraction using improved mean shift method

NASA Astrophysics Data System (ADS)

Zhenying, Xu; Jiandong, Zhu; Qi, Zhang; Yamba, Philip

2018-06-01

Metallographic microscopy shows that the vast majority of metal materials are composed of many small grains; the grain size of a metal is important for determining the tensile strength, toughness, plasticity, and other mechanical properties. In order to quantitatively evaluate grain size in metals, grain boundaries must be identified in metallographic images. Based on the phenomenon of grain boundary blurring or disconnection in metallographic images, this study develops an algorithm based on regional separation for automatically extracting grain boundaries by an improved mean shift method. Experimental observation shows that the grain boundaries obtained by the proposed algorithm are highly complete and accurate. This research has practical value because the proposed algorithm is suitable for grain boundary extraction from most metallographic images.

Grain boundary and triple junction diffusion in nanocrystalline copper

NASA Astrophysics Data System (ADS)

Wegner, M.; Leuthold, J.; Peterlechner, M.; Song, X.; Divinski, S. V.; Wilde, G.

2014-09-01

Grain boundary and triple junction diffusion in nanocrystalline Cu samples with grain sizes, , of ˜35 and ˜44 nm produced by spark plasma sintering were investigated by the radiotracer method using the 63Ni isotope. The measured diffusivities, Deff, are comparable with those determined previously for Ni grain boundary diffusion in well-annealed, high purity, coarse grained, polycrystalline copper, substantiating the absence of a grain size effect on the kinetic properties of grain boundaries in a nanocrystalline material at grain sizes d ≥ 35 nm. Simultaneously, the analysis predicts that if triple junction diffusion of Ni in Cu is enhanced with respect to the corresponding grain boundary diffusion rate, it is still less than 500ṡDgb within the temperature interval from 420 K to 470 K.

Abnormal grain growth in AISI 304L stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirdel, M., E-mail: mshirdel1989@ut.ac.ir; Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir; Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran

2014-11-15

The microstructural evolution during abnormal grain growth (secondary recrystallization) in 304L stainless steel was studied in a wide range of annealing temperatures and times. At relatively low temperatures, the grain growth mode was identified as normal. However, at homologous temperatures between 0.65 (850 °C) and 0.7 (900 °C), the observed transition in grain growth mode from normal to abnormal, which was also evident from the bimodality in grain size distribution histograms, was detected to be caused by the dissolution/coarsening of carbides. The microstructural features such as dispersed carbides were characterized by optical metallography, X-ray diffraction, scanning electron microscopy, energy dispersivemore » X-ray analysis, and microhardness. Continued annealing to a long time led to the completion of secondary recrystallization and the subsequent reappearance of normal growth mode. Another instance of abnormal grain growth was observed at homologous temperatures higher than 0.8, which may be attributed to the grain boundary faceting/defaceting phenomenon. It was also found that when the size of abnormal grains reached a critical value, their size will not change too much and the grain growth behavior becomes practically stagnant. - Highlights: • Abnormal grain growth (secondary recrystallization) in AISI 304L stainless steel • Exaggerated grain growth due to dissolution/coarsening of carbides • The enrichment of carbide particles by titanium • Abnormal grain growth due to grain boundary faceting at very high temperatures • The stagnancy of abnormal grain growth by annealing beyond a critical time.« less

Three dimensional grain boundary modeling in polycrystalline plasticity

NASA Astrophysics Data System (ADS)

Yalçinkaya, Tuncay; Özdemir, Izzet; Fırat, Ali Osman

2018-05-01

At grain scale, polycrystalline materials develop heterogeneous plastic deformation fields, localizations and stress concentrations due to variation of grain orientations, geometries and defects. Development of inter-granular stresses due to misorientation are crucial for a range of grain boundary (GB) related failure mechanisms, such as stress corrosion cracking (SCC) and fatigue cracking. Local crystal plasticity finite element modelling of polycrystalline metals at micron scale results in stress jumps at the grain boundaries. Moreover, the concepts such as the transmission of dislocations between grains and strength of the grain boundaries are not included in the modelling. The higher order strain gradient crystal plasticity modelling approaches offer the possibility of defining grain boundary conditions. However, these conditions are mostly not dependent on misorientation of grains and can define only extreme cases. For a proper definition of grain boundary behavior in plasticity, a model for grain boundary behavior should be incorporated into the plasticity framework. In this context, a particular grain boundary model ([l]) is incorporated into a strain gradient crystal plasticity framework ([2]). In a 3-D setting, both bulk and grain boundary models are implemented as user-defined elements in Abaqus. The strain gradient crystal plasticity model works in the bulk elements and considers displacements and plastic slips as degree of freedoms. Interface elements model the plastic slip behavior, yet they do not possess any kind of mechanical cohesive behavior. The physical aspects of grain boundaries and the performance of the model are addressed through numerical examples.

Non-Destructive Evaluation of Grain Structure Using Air-Coupled Ultrasonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belvin, A. D.; Burrell, R. K.; Cole, E.G.

2009-08-01

Cast material has a grain structure that is relatively non-uniform. There is a desire to evaluate the grain structure of this material non-destructively. Traditionally, grain size measurement is a destructive process involving the sectioning and metallographic imaging of the material. Generally, this is performed on a representative sample on a periodic basis. Sampling is inefficient and costly. Furthermore, the resulting data may not provide an accurate description of the entire part's average grain size or grain size variation. This project is designed to develop a non-destructive acoustic scanning technique, using Chirp waveforms, to quantify average grain size and grain sizemore » variation across the surface of a cast material. A Chirp is a signal in which the frequency increases or decreases over time (frequency modulation). As a Chirp passes through a material, the material's grains reduce the signal (attenuation) by absorbing the signal energy. Geophysics research has shown a direct correlation with Chirp wave attenuation and mean grain size in geological structures. The goal of this project is to demonstrate that Chirp waveform attenuation can be used to measure grain size and grain variation in cast metals (uranium and other materials of interest). An off-axis ultrasonic inspection technique using air-coupled ultrasonics has been developed to determine grain size in cast materials. The technique gives a uniform response across the volume of the component. This technique has been demonstrated to provide generalized trends of grain variation over the samples investigated.« less

A simple phenomenological model for grain clustering in turbulence

NASA Astrophysics Data System (ADS)

Hopkins, Philip F.

2016-01-01

We propose a simple model for density fluctuations of aerodynamic grains, embedded in a turbulent, gravitating gas disc. The model combines a calculation for the behaviour of a group of grains encountering a single turbulent eddy, with a hierarchical approximation of the eddy statistics. This makes analytic predictions for a range of quantities including: distributions of grain densities, power spectra and correlation functions of fluctuations, and maximum grain densities reached. We predict how these scale as a function of grain drag time ts, spatial scale, grain-to-gas mass ratio tilde{ρ }, strength of turbulence α, and detailed disc properties. We test these against numerical simulations with various turbulence-driving mechanisms. The simulations agree well with the predictions, spanning ts Ω ˜ 10-4-10, tilde{ρ }˜ 0{-}3, α ˜ 10-10-10-2. Results from `turbulent concentration' simulations and laboratory experiments are also predicted as a special case. Vortices on a wide range of scales disperse and concentrate grains hierarchically. For small grains this is most efficient in eddies with turnover time comparable to the stopping time, but fluctuations are also damped by local gas-grain drift. For large grains, shear and gravity lead to a much broader range of eddy scales driving fluctuations, with most power on the largest scales. The grain density distribution has a log-Poisson shape, with fluctuations for large grains up to factors ≳1000. We provide simple analytic expressions for the predictions, and discuss implications for planetesimal formation, grain growth, and the structure of turbulence.

"Coulombic Viscosity" In Granular Materials: Planetary and Astrophysical Implications

NASA Astrophysics Data System (ADS)

Marshall, J. R.

1999-09-01

The term "Coulombic viscosity" is introduced here to define an empirically observed phenomenon from experiments conducted in both microgravity, and in ground-based 1-g conditions. In the latter case, a sand attrition device was employed to test the longevity of aeolian materials by creating two intersecting grain-circulation paths or cells that would lead to most of the grain energy being expended on grain-to-grain collisions (simulating dune systems). In the areas in the device where gravitationally-driven grain-slurries recycled the sand, the slurries moved with a boundary-layer impeded motion down the chamber walls. Excessive electrostatic charging of the grains during these experiments was prevented by the use of an a.c. corona (created by a Tesla coil) through which the grains passed on every cycle. This created both positive and negative ions which neutralized the triboelectrically-generated grain charges. When the corona was switched on, the velocity of the wall-attached slurries increased by a factor of two as approximately determined by direct observation. What appeared to be a freely-flowing slurry of grains impeded only by intergranular mechanical friction, had obviously been significantly retarded in its motion by electrostatic forces between the grains; with the charging reduced, the grains were able to move past one another without a flow "viscosity" imposed by the Coulombic intergranular forces. A similar phenomenon was observed during microgravity experiments aboard Space Shuttle in USML-1 & USML-2 spacelabs where freely-suspended clouds of sand were being investigated for their potential to for-m aggregates. In this environment, the grains were also charged electrostatically (by natural processes prior to flight), but were free from the intervention of gravity in their interactions. The grains were dispersed into dense clouds by bursts of air turbulence and allowed to form aggregates as the ballistic and turbulent motions damped out. During this very brief (30-60 sec) damping period, motion of the grains was observed to be retarded by the electrostatic interactions. The fact that the grains almost instantly formed aggregates was evidence that their ballistic motions had been constrained and redirected by the dipole-dipole interactions that led to filamentary aggregate development. Undoubtedly, the "Coulombic viscosity" of the cloud assisted in damping grain motion so rapidly. The electrostatically-induced grain-cloud viscosity or drag exerted on grain motion, is a complex function of three major parameters: charge magnitude, charge sign, and mean intergranular distance. The above experiments illustrate one particular type of granular behavior. The discussion here will therefore be restricted to drag relationships: (a) between grains that are naturally charged triboelectrically and thus exhibit dipole-dipole attractions between one another even if there are slight net charges present (which can be overwhelmed by dipole coupling at short distances), and (b) between grains that are densely spaced where the intergranular distance varies between zero and some value (usually tens or hundreds of grain diameters) that permits each grain to detect the dipole moment of another grain -- the distance is not so great that other grains appears as neutral electrical "singularities. I. Aeolian transport: During motion of grains in a saltation cloud (on Earth, Mars, or Venus), triboelectric charging must occur as a result of multiple grain contacts, and by friction with the entraining air. A situation might develop that is similar to the one described above in the attrition device: grain motion becoming significantly retarded (reduced flux) as grains find it increasingly difficult to either separate from the surface, or to pass one another without Coulombic retarding forces. A "Coulombic drag" will exist at flux initiation and increase with time to work in direct opposition to the aerodynamic drag that drives the grain motion. It is predicted that this will lead to an increase with time of both the aerodynamic and bed-dilatancy thresholds (3). Because of Paschen discharge effects in the martian atmosphere, the electrostatic charging in a saltation cloud may be partially abated, but this will lead to greater grain mobility, more charging, and thus to a charge-discharge steady state mediated by mechanical interactions. II. Dry colluvial systems: Sand avalanches on dunes, dry debris flows, talus flows, avalanches, and pyroclastic surges are examples of gravity-driven, dense granular flows where rock/grain fragmentation and grain-to-grain interactions cause triboelectrification (sometimes augmented by other electrical charging processes), and where the grain densities of the systems are such that strong dipole-dipole interactions between grains might be expected to be present. Because it is expected that the Coulombic forces between grains will cause a sluggishness or enhanced granular-flow viscosity, the motion of a grain mass will be retarded or damped so that this will assist, ultimately, in terminating the flow. The greatest Coulombic viscosity will be created in the most highly charged systems, which will also be the most energetic. Thus, grain flows have some tendency to be self-limiting by internal energy partitioning; gravitational potential is converted to Coulombic potential, which manifests itself as a drag force between the grains. III. Volcanic eruption plumes and impact ejecta curtains: The violence of these systems leads to powerful electrical charging of particulates. Lightning storms emanating from volcanic plumes are a testimony to the levels of charging. As pyroclastic grains interact forcefully and frequently within eruption plumes, it is reasonable to predict that the internal turbulent motions of the plume will be significantly damped by the Coulombic viscosity exerted by grain charges. Additional information is contained in the original.

"Coulombic Viscosity" In Granular Materials: Planetary and Astrophysical Implications

NASA Technical Reports Server (NTRS)

Marshall, J. R.

1999-01-01

The term "Coulombic viscosity" is introduced here to define an empirically observed phenomenon from experiments conducted in both microgravity, and in ground-based 1-g conditions. In the latter case, a sand attrition device was employed to test the longevity of aeolian materials by creating two intersecting grain-circulation paths or cells that would lead to most of the grain energy being expended on grain-to-grain collisions (simulating dune systems). In the areas in the device where gravitationally-driven grain-slurries recycled the sand, the slurries moved with a boundary-layer impeded motion down the chamber walls. Excessive electrostatic charging of the grains during these experiments was prevented by the use of an a.c. corona (created by a Tesla coil) through which the grains passed on every cycle. This created both positive and negative ions which neutralized the triboelectrically-generated grain charges. When the corona was switched on, the velocity of the wall-attached slurries increased by a factor of two as approximately determined by direct observation. What appeared to be a freely-flowing slurry of grains impeded only by intergranular mechanical friction, had obviously been significantly retarded in its motion by electrostatic forces between the grains; with the charging reduced, the grains were able to move past one another without a flow "viscosity" imposed by the Coulombic intergranular forces. A similar phenomenon was observed during microgravity experiments aboard Space Shuttle in USML-1 & USML-2 spacelabs where freely-suspended clouds of sand were being investigated for their potential to for-m aggregates. In this environment, the grains were also charged electrostatically (by natural processes prior to flight), but were free from the intervention of gravity in their interactions. The grains were dispersed into dense clouds by bursts of air turbulence and allowed to form aggregates as the ballistic and turbulent motions damped out. During this very brief (30-60 sec) damping period, motion of the grains was observed to be retarded by the electrostatic interactions. The fact that the grains almost instantly formed aggregates was evidence that their ballistic motions had been constrained and redirected by the dipole-dipole interactions that led to filamentary aggregate development. Undoubtedly, the "Coulombic viscosity" of the cloud assisted in damping grain motion so rapidly. The electrostatically-induced grain-cloud viscosity or drag exerted on grain motion, is a complex function of three major parameters: charge magnitude, charge sign, and mean intergranular distance. The above experiments illustrate one particular type of granular behavior. The discussion here will therefore be restricted to drag relationships: (a) between grains that are naturally charged triboelectrically and thus exhibit dipole-dipole attractions between one another even if there are slight net charges present (which can be overwhelmed by dipole coupling at short distances), and (b) between grains that are densely spaced where the intergranular distance varies between zero and some value (usually tens or hundreds of grain diameters) that permits each grain to detect the dipole moment of another grain -- the distance is not so great that other grains appears as neutral electrical "singularities. I. Aeolian transport: During motion of grains in a saltation cloud (on Earth, Mars, or Venus), triboelectric charging must occur as a result of multiple grain contacts, and by friction with the entraining air. A situation might develop that is similar to the one described above in the attrition device: grain motion becoming significantly retarded (reduced flux) as grains find it increasingly difficult to either separate from the surface, or to pass one another without Coulombic retarding forces. A "Coulombic drag" will exist at flux initiation and increase with time to work in direct opposition to the aerodynamic drag that drives the grain motion. It is predicted that this will lead to an increase with time of both the aerodynamic and bed-dilatancy thresholds (3). Because of Paschen discharge effects in the martian atmosphere, the electrostatic charging in a saltation cloud may be partially abated, but this will lead to greater grain mobility, more charging, and thus to a charge-discharge steady state mediated by mechanical interactions. II. Dry colluvial systems: Sand avalanches on dunes, dry debris flows, talus flows, avalanches, and pyroclastic surges are examples of gravity-driven, dense granular flows where rock/grain fragmentation and grain-to-grain interactions cause triboelectrification (sometimes augmented by other electrical charging processes), and where the grain densities of the systems are such that strong dipole-dipole interactions between grains might be expected to be present. Because it is expected that the Coulombic forces between grains will cause a sluggishness or enhanced granular-flow viscosity, the motion of a grain mass will be retarded or damped so that this will assist, ultimately, in terminating the flow. The greatest Coulombic viscosity will be created in the most highly charged systems, which will also be the most energetic. Thus, grain flows have some tendency to be self-limiting by internal energy partitioning; gravitational potential is converted to Coulombic potential, which manifests itself as a drag force between the grains. III. Volcanic eruption plumes and impact ejecta curtains: The violence of these systems leads to powerful electrical charging of particulates. Lightning storms emanating from volcanic plumes are a testimony to the levels of charging. As pyroclastic grains interact forcefully and frequently within eruption plumes, it is reasonable to predict that the internal turbulent motions of the plume will be significantly damped by the Coulombic viscosity exerted by grain charges. Additional information is contained in the original.

Abundances of presolar graphite and SiC from supernovae and AGB stars in the Murchison meteorite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amari, Sachiko; Zinner, Ernst; Gallino, Roberto

2014-05-02

Pesolar graphite grains exhibit a range of densities (1.65 – 2.20 g/cm{sup 3}). We investigated abundances of presolar graphite grains formed in supernovae and in asymptotic giant branch (AGB) stars in the four density fractions KE3, KFA1, KFB1 and KFC1 extracted from the Murchison meteorite to probe dust productions in these stellar sources. Seventy-six and 50% of the grains in the low-density fractions KE3 and KFA1, respectively, are supernova grains, while only 7.2% and 0.9% of the grains in the high-density fractions KFB1 and KFC1 have a supernova origin. Grains of AGB star origin are concentrated in the high-density fractionsmore » KFB1 and KFC1. From the C isotopic distributions of these fractions and the presence of s-process Kr with {sup 86}Kr/{sup 82}Kr = 4.43±0.46 in KFC1, we estimate that 76% and 80% of the grains in KFB1 and KFC1, respectively, formed in AGB stars. From the abundance of graphite grains in the Murchison meteorite, 0.88 ppm, the abundances of graphite from supernovae and AGB stars are 0.24 ppm and 0.44 ppm, respectively: the abundances of graphite in supernovae and AGB stars are comparable. In contrast, it has been known that 1% of SiC grains formed in supernovae and 95% formed in AGB stars in meteorites. Since the abundance of SiC grains is 5.85 ppm in the Murchison meteorite, the abundances of SiC from supernovae and AGB stars are 0.063 ppm and 5.6 ppm, respectively: the dominant source of SiC grains is AGB stars. Since SiC grains are harder and likely to survive better in space than graphite grains, the abundance of supernova graphite grains, which is higher than that of supernova SiC grains, indicates that supernovae proficiently produce graphite grains. Graphite grains from AGB stars are, in contrast, less abundant that SiC grains from AGB stars (0.44 ppm vs. 5.6 ppm). It is difficult to derive firm conclusions for graphite and SiC formation in AGB stars due to the difference in susceptibility to grain destruction. Metallicity of the parent AGB stars of graphite grains is much lower than that of SiC grains and the difference in metallicity might also have affected to the difference in the abundances in the Murchison meteorite.« less

Grain dissection as a grain size reducing mechanism during ice microdynamics

NASA Astrophysics Data System (ADS)

Steinbach, Florian; Kuiper, Ernst N.; Eichler, Jan; Bons, Paul D.; Drury, Martin R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-04-01

Ice sheets are valuable paleo-climate archives, but can lose their integrity by ice flow. An understanding of the microdynamic mechanisms controlling the flow of ice is essential when assessing climatic and environmental developments related to ice sheets and glaciers. For instance, the development of a consistent mechanistic grain size law would support larger scale ice flow models. Recent research made significant progress in numerically modelling deformation and recrystallisation mechanisms in the polycrystalline ice and ice-air aggregate (Llorens et al., 2016a,b; Steinbach et al., 2016). The numerical setup assumed grain size reduction is achieved by the progressive transformation of subgrain boundaries into new high angle grain boundaries splitting an existing grain. This mechanism is usually termed polygonisation. Analogue experiments suggested, that strain induced grain boundary migration can cause bulges to migrate through the whole of a grain separating one region of the grain from another (Jessell, 1986; Urai, 1987). This mechanism of grain dissection could provide an alternative grain size reducing mechanism, but has not yet been observed during ice microdynamics. In this contribution, we present results using an updated numerical approach allowing for grain dissection. The approach is based on coupling the full field theory crystal visco-plasticity code (VPFFT) of Lebensohn (2001) to the multi-process modelling platform Elle (Bons et al., 2008). VPFFT predicts the mechanical fields resulting from short strain increments, dynamic recrystallisation process are implemented in Elle. The novel approach includes improvements to allow for grain dissection, which was topologically impossible during earlier simulations. The simulations are supported by microstructural observations from NEEM (North Greenland Eemian Ice Drilling) ice core. Mappings of c-axis orientations using the automatic fabric analyser and full crystallographic orientations using electron backscatter diffraction (EBSD) are presented. Numerical simulations predict and resolve the microstructural evolution over strain and time. The occurrence of processes such as grain dissection can only be proven using such time resolved movies of microstructure evolution. We will present movies that show grain dissection as a common process during the simulations. Microstructures obtained from NEEM ice core support the observations and we provide evidence for grain dissection in natural ice. Grain dissection is observed to be most efficient relative to polygonisation, when the microstructure approaches steady state grain sizes. This is consistent with analogue experiments observing grain dissection by Jessell (1986) and Urai (1987). Our research suggests a novel grain size reducing mechanisms in ice microdynamics that should be considered when developing a consistent grain size law.

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel

NASA Astrophysics Data System (ADS)

Hayakawa, Yasuyuki

2017-12-01

Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 106 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, Ryan S.; Chai, Kil-Byoung; Bellan, Paul M.

The grain growth process in the Caltech water–ice dusty plasma experiment has been studied using a high-speed camera and a long-distance microscope lens. It is observed that (i) the ice grain number density decreases fourfold as the average grain major axis increases from 20 to 80 μ m, (ii) the major axis length has a log-normal distribution rather than a power-law dependence, and (iii) no collisions between ice grains are apparent. The grains have a large negative charge resulting in strong mutual repulsion and this, combined with the fractal character of the ice grains, prevents them from agglomerating. In ordermore » for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains, the volumetric packing factor (i.e., ratio of the actual volume to the volume of a circumscribing ellipsoid) of the ice grains must be less than ∼0.1 depending on the exact relative velocity of the grains in question. Thus, it is concluded that direct accretion of water molecules is very likely to dominate the observed ice grain growth.« less

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel

PubMed Central

Hayakawa, Yasuyuki

2017-01-01

Abstract Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 106 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model. PMID:28804524

A Rare Allele of GS2 Enhances Grain Size and Grain Yield in Rice.

PubMed

Hu, Jiang; Wang, Yuexing; Fang, Yunxia; Zeng, Longjun; Xu, Jie; Yu, Haiping; Shi, Zhenyuan; Pan, Jiangjie; Zhang, Dong; Kang, Shujing; Zhu, Li; Dong, Guojun; Guo, Longbiao; Zeng, Dali; Zhang, Guangheng; Xie, Lihong; Xiong, Guosheng; Li, Jiayang; Qian, Qian

2015-10-05

Grain size determines grain weight and affects grain quality. Several major quantitative trait loci (QTLs) regulating grain size have been cloned; however, our understanding of the underlying mechanism that regulates the size of rice grains remains fragmentary. Here, we report the cloning and characterization of a dominant QTL, grain size on chromosome 2 (GS2), which encodes Growth-Regulating Factor 4 (OsGRF4), a transcriptional regulator. GS2 localizes to the nucleus and may act as a transcription activator. A rare mutation of GS2 affecting the binding site of a microRNA, OsmiR396c, causes elevated expression of GS2/OsGRF4. The increase in GS2 expression leads to larger cells and increased numbers of cells, which thus enhances grain weight and yield. The introduction of this rare allele of GS2/OsGRF4 into rice cultivars could significantly enhance grain weight and increase grain yield, with possible applications in breeding high-yield rice varieties. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel.

PubMed

Hayakawa, Yasuyuki

2017-01-01

Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 10 6 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model.

Grain formation around carbon stars. 1: Stationary outflow models

NASA Technical Reports Server (NTRS)

Egan, Michael P.; Leung, Chun Ming

1995-01-01

Asymptotic giant branch (AGB) stars are known to be sites of dust formation and undergo significant mass loss. The outflow is believed to be driven by radiation pressure on grains and momentum coupling between the grains and gas. While the physics of shell dynamics and grain formation are closely coupled, most previous models of circumstellar shells have treated the problem separately. Studies of shell dynamics typically assume the existence of grains needed to drive the outflow, while most grain formation models assume a constant veolcity wind in which grains form. Furthermore, models of grain formation have relied primarily on classical nucleation theory instead of using a more realistic approach based on chemical kinetics. To model grain formation in carbon-rich AGB stars, we have coupled the kinetic equations governing small cluster growth to moment equations which determine the growth of large particles. Phenomenological models assuming stationary outflow are presented to demonstrate the differences between the classical nucleation approach and the kinetic equation method. It is found that classical nucleation theory predicts nucleation at a lower supersaturation ratio than is predicted by the kinetic equations, resulting in significant differences in grain properties. Coagulation of clusters larger than monomers is unimportant for grain formation in high mass-loss models but becomes more important to grain growth in low mass-loss situations. The properties of the dust grains are altered considerably if differential drift velocities are ignored in modeling grain formation. The effect of stellar temperature, stellar luminosity, and different outflow velocities are investigated. The models indicate that changing the stellar temperature while keeping the stellar luminosity constant has little effect on the physical parameters of the dust shell formed. Increasing the stellar luminosity while keeping the stellar temperature constant results in large differences in grain properties. For small outflow velocities, grains form at lower supersaturation ratios and close to the stellar photosphere, resulting in larger but fewer grains. The reverse is true when grains form under high outflow velocities, i.e., they form at higher supersaturation ratios, farther from the star, and are much smaller but at larger quantities.

Study on grain quality forecasting method and indicators by using hyperspectral data in wheat

NASA Astrophysics Data System (ADS)

Huang, Wenjiang; Wang, Jihua; Liu, Liangyun; Wang, Zhijie; Tan, Changwei; Song, Xiaoyu; Wang, Jingdi

2005-01-01

Field experiments were conducted to examine the influence factors of cultivar, nitrogen application and irrigation on grain protein content, gluten content and grain hardness in three winter wheat cultivars under four levels of nitrogen and irrigation treatments. Firstly, the influence of cultivars and environment factors on grain quality were studied, the effective factors were cultivars, irrigation, fertilization, et al. Secondly, total nitrogen content around winter wheat anthesis stage was proved to be significant correlative with grain protein content, and spectral vegetation index significantly correlated to total nitrogen content around anthesis stage were the potential indicators for grain protein content. Accumulation of total nitrogen content and its transfer to grain is the physical link to produce the final grain protein, and total nitrogen content at anthesis stage was proved to be an indicator of final grain protein content. The selected normalized photochemical reflectance index (NPRI) was proved to be able to predict of grain protein content on the close correlation between the ratio of total carotenoid to chlorophyll a and total nitrogen content. The method contributes towards developing optimal procedures for predicting wheat grain quality through analysis of their canopy reflected spectrum at anthesis stage. Regression equations were established for forecasting grain protein and dry gluten content by total nitrogen content at anthesis stage, so it is feasible for forecasting grain quality by establishing correlation equations between biochemical constitutes and canopy reflected spectrum.

Whole grain intake, determined by dietary records and plasma alkylresorcinol concentrations, is low among pregnant women in Singapore.

PubMed

Ross, Alastair B; Colega, Marjorelee T; Lim, Ai Lin; Silva-Zolezzi, Irma; Macé, Katherine; Saw, Seang Mei; Kwek, Kenneth; Gluckman, Peter; Godfrey, Keith M; Chong, Yap-Seng; Chong, Mary F F

2015-01-01

To quantify whole grain intake in pregnant women in Singapore in order to provide the first detailed analysis of whole grain intake in an Asian country and in pregnant women. Analysis of 24-h diet recalls in a cross-sectional cohort study and analysis of a biomarker of whole grain intake (plasma alkylresorcinols) in a subset of subjects. The Growing Up in Singapore Towards healthy Outcomes-mother offspring cohort study based in Singapore. 998 pregnant mothers with complete 24-h recalls taken during their 26-28th week of gestation. Plasma samples from a randomly select subset of 100 subjects were analysed for plasma alkylresorcinols. Median (IQR) whole grain intake for the cohort and the 30% who reported eating whole grains were 0 (IQR 0, 9) and 23.6 (IQR 14.6, 44.2) g/day respectively. Plasma alkylresorcinol concentrations were very low [median (IQR)=9 (3, 15) nmol/L], suggesting low intake of whole grain wheat in this population. Plasma alkylresorcinols were correlated with whole grain wheat intake (Spearman's r=0.35; p<0.01). Whole grain intake among pregnant mothers in Singapore was well below the 2-3 (60-95 g) servings of whole grains per day recommended by the Singapore Health Promotion Board. Efforts to increase whole grain intake should be supported to encourage people to choose whole grains over refined grains in their diet.

Increased pericarp cell length underlies a major quantitative trait locus for grain weight in hexaploid wheat.

PubMed

Brinton, Jemima; Simmonds, James; Minter, Francesca; Leverington-Waite, Michelle; Snape, John; Uauy, Cristobal

2017-08-01

Crop yields must increase to address food insecurity. Grain weight, determined by grain length and width, is an important yield component, but our understanding of the underlying genes and mechanisms is limited. We used genetic mapping and near isogenic lines (NILs) to identify, validate and fine-map a major quantitative trait locus (QTL) on wheat chromosome 5A associated with grain weight. Detailed phenotypic characterisation of developing and mature grains from the NILs was performed. We identified a stable and robust QTL associated with a 6.9% increase in grain weight. The positive interval leads to 4.0% longer grains, with differences first visible 12 d after fertilization. This grain length effect was fine-mapped to a 4.3 cM interval. The locus also has a pleiotropic effect on grain width (1.5%) during late grain development that determines the relative magnitude of the grain weight increase. Positive NILs have increased maternal pericarp cell length, an effect which is independent of absolute grain length. These results provide direct genetic evidence that pericarp cell length affects final grain size and weight in polyploid wheat. We propose that combining genes that control distinct biological mechanisms, such as cell expansion and proliferation, will enhance crop yields. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

SILICON CARBIDE GRAIN BOUNDARY DISTRIBUTIONS, IRRADIATION CONDITIONS, AND SILVER RETENTION IN IRRADIATED AGR-1 TRISO FUEL PARTICLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lillo, T. M.; Rooyen, I. J.; Aguiar, J. A.

Precession electron diffraction in the transmission electron microscope was used to map grain orientation and ultimately determine grain boundary misorientation angle distributions, relative fractions of grain boundary types (random high angle, low angle or coincident site lattice (CSL)-related boundaries) and the distributions of CSL-related grain boundaries in the SiC layer of irradiated TRISO-coated fuel particles. Two particles from the AGR-1 experiment exhibiting high Ag-110m retention (>80%) were compared to a particle exhibiting low Ag-110m retention (<19%). Irradiated particles with high Ag-110m retention exhibited a lower fraction of random, high angle grain boundaries compared to the low Ag-110m retention particle. Anmore » inverse relationship between the random, high angle grain boundary fraction and Ag-110m retention is found and is consistent with grain boundary percolation theory. Also, comparison of the grain boundary distributions with previously reported unirradiated grain boundary distributions, based on SEM-based EBSD for similarly fabricated particles, showed only small differences, i.e. a greater low angle grain boundary fraction in unirradiated SiC. It was, thus, concluded that SiC layers with grain boundary distributions susceptible to Ag-110m release were present prior to irradiation. Finally, irradiation parameters were found to have little effect on the association of fission product precipitates with specific grain boundary types.« less

Effects of whole grains on coronary heart disease risk.

PubMed

Harris, Kristina A; Kris-Etherton, Penny M

2010-11-01

Characterizing which types of carbohydrates, including whole grains, reduce the risk for coronary heart disease (CHD) is challenging. Whole grains are characterized as being high in resistant carbohydrates as compared with refined grains, meaning they typically are high in fiber, nutrients, and bound antioxidants. Whole grain intake consistently has been associated with improved cardiovascular disease outcomes, but also with healthy lifestyles, in large observational studies. Intervention studies that assess the effects of whole grains on biomarkers for CHD have mixed results. Due to the varying nutrient compositions of different whole grains, each could potentially affect CHD risk via different mechanisms. Whole grains high in viscous fiber (oats, barley) decrease serum low-density lipoprotein cholesterol and blood pressure and improve glucose and insulin responses. Grains high in insoluble fiber (wheat) moderately lower glucose and blood pressure but also have a prebiotic effect. Obesity is inversely related to whole grain intake, but intervention studies with whole grains have not produced weight loss. Visceral fat, however, may be affected favorably. Grain processing improves palatability and can have varying effects on nutrition (e.g., the process of milling and grinding flour increases glucose availability and decreases phytochemical content whereas thermal processing increases available antioxidants). Understanding how individual grains, in both natural and processed states, affect CHD risk can inform nutrition recommendations and policies and ultimately benefit public health.

Impact of Kansas grain transportation on Kansas highway damage costs

DOT National Transportation Integrated Search

2002-03-01

Changes have occurred in the Kansas grain transportation systems that have increased trucking of grain. Kansas farmers will truck their grain a much greater distance to obtain the higher grain price at the unit train loading location. Farmers will by...

On the theory of dynamics of dust grain in plasma

NASA Astrophysics Data System (ADS)

Stepanenko, A. A.; Krasheninnikov, S. I.

2013-03-01

The dynamics of rotationally symmetric dust grains in plasma embedded in a magnetic field are of concern. The general expressions for forces and torques acting on dust are found. It is shown that dust spinning is determined by torques related to both the Lorentz force (dominant for relatively small grains) and the gyro-motion of plasma particles impinging the grain (which prevails for large grains). The stability of grain spinning is analyzed and it is shown that, for some cases (e.g., oblate spheroid), there is no stable dynamic equilibrium of grain spinning.

Optimization of strength and ductility in nanotwinned ultrafine grained Ag: twin density and grain orientations

DOE PAGES

Ott, R. T.; Geng, J.; Besser, M. F.; ...

2015-06-27

Nanotwinned ultrafine grained Ag thick films with different twin densities and orientations have been synthesized by magnetron sputtering with a wide-range of deposition rates. The twin boundary (TB) spacings and orientations as well as the grain size for the different deposition conditions have been characterized by both synchrotron X-ray scattering and transmission electron microscopy (TEM). Structural characterization combined with uniaxial tensile tests of the free-standing films reveals a large increase in the yield strength for films deposited at high deposition rates without any accompanying change in the TB spacing – a behavior that is in contrast with what has beenmore » reported in the literature. We find that films deposited at lower deposition rates exhibit more randomly oriented grains with a lower overall twin density (averaged over all the grains) than the more heavily twinned grains with strong <111> fiber texture in the films deposited at higher deposition rates. The TB spacing in the twinned grains, however, does not show any significant dependence on the deposition rate. The dependence of the strength and ductility on the twin density and orientations can be described by two different soft deformation modes: 1) untwinned grains and 2) nanowinned grains that are not oriented with <111> along the growth direction. The untwinned grains provide relatively low resistance to slip, and thus decreased strength, while the nanotwinned grains that are not oriented with <111> along the growth direction are softer than nanotwinned grains that are oriented with <111> along the growth direction. We reveal that an ultrafine-grained (150-200 nm) structure consisting of a mixture of nanotwinned (~ 8-12 nm spacing) and untwined grains yields the best combination of high strength and uniform tensile ductility.« less

Developing a Standard Definition of Whole-Grain Foods for Dietary Recommendations: Summary Report of a Multidisciplinary Expert Roundtable Discussion12

PubMed Central

Ferruzzi, Mario G.; Jonnalagadda, Satya S.; Liu, Simin; Marquart, Len; McKeown, Nicola; Reicks, Marla; Riccardi, Gabriele; Seal, Chris; Slavin, Joanne; Thielecke, Frank; van der Kamp, Jan-Willem; Webb, Densie

2014-01-01

Although the term “whole grain” is well defined, there has been no universal standard of what constitutes a “whole-grain food,” creating challenges for researchers, the food industry, regulatory authorities, and consumers around the world. As part of the 2010 Dietary Guidelines for Americans, the U.S. Dietary Guidelines Technical Advisory Committee issued a call to action to develop definitions for whole-grain foods that could be universally accepted and applied to dietary recommendations and planning. The Committee’s call to action, and the lack of a global whole-grain food definition, was the impetus for the Whole Grain Roundtable held 3–5 December 2012 in Chicago, Illinois. The objective was to develop a whole-grain food definition that is consistent with the quartet of needs of science, food product formulation, consumer behavior, and label education. The roundtable’s expert panel represented a broad range of expertise from the United States and Europe, including epidemiology and dietary intervention researchers, consumer educators, government policy makers, and food and nutrition scientists from academia and the grain food industry. Taking into account the totality, quality, and consistency of available scientific evidence, the expert panel recommended that 8 g of whole grain/30 g serving (27 g/100 g), without a fiber requirement, be considered a minimum content of whole grains that is nutritionally meaningful and that a food providing at least 8 g of whole grains/30-g serving be defined as a whole-grain food. Having an established whole-grain food definition will encourage manufacturers to produce foods with meaningful amounts of whole grain, allow consistent product labeling and messaging, and empower consumers to readily identify whole-grain foods and achieve whole-grain dietary recommendations. PMID:24618757

Charging of Interstellar Dust Grains in the out-of-equilibrium Heliosheath Plasma traced by IBEX ENAs

NASA Astrophysics Data System (ADS)

Frisch, P. C.; Ogasawara, K.; Livadiotis, G.; Slavin, J. D.; McComas, D. J.; Funsten, H. O.; Schwadron, N.; Heerikhuisen, J.

2017-12-01

Dusty bow waves are common around stars and anticipated around the heliosphere due to the deficit of low-mass interstellar dust grains in the inner heliosphere. Interstellar grains entering the heliosphere must first cross barriers of non-Maxwellian plasma in the heliosheath regions where collisional charging of grains is highly effective. IBEX measures 0.1-6 keV ENAs in the heliosheath plasma, providing an in situ sample of the heliosheath plasma thermodynamics that can be used for grain-charging calculations. Plasma in three-quarters of the sky can be described with a stationary state kappa-distribution, giving predictions for kappa, kappa-distribution temperature, and plasma density [1]. This thermodynamic description allows a more realistic evaluation of the dominant heliosheath electron and ion currents, and hence also grain gyroradii and exclusion from the heliosphere. At the highest temperatures ion collisional currents dominate grain charging; at lower temperatures collisional electron currents are more important together with the photoelectric ejection of electrons. An absence of data on the thermodynamical state of heliosheath electrons has led to the assumption of similar thermodynamic parameters for the electron and ion populations. The balance between electron, proton and photoionization currents on the grains then yield the equilibrium grain charges. Grain gyroradii calculated based on these charging currents differentiate between interstellar grains able to penetrate the heliosphere, versus those that are excluded, and allow predictions of properties of the dusty bow wave likely to be present around the heliosphere. The smallest grains are excluded and grains at the high latitude edges of the described regions tend to have systematically lower grain potentials. Grain charging calculations utilize the modeling of [2]. [1] Livadiotis et al., ApJ 734, 1 (2011). [2] Weingartner Draine, ApJSS 263 (2001)

Stellar Origin of 15N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

NASA Astrophysics Data System (ADS)

Liu, Nan; Nittler, Larry R.; Pignatari, Marco; O'D. Alexander, Conel M.; Wang, Jianhua

2017-06-01

We report C, N, and Si isotopic data for 59 highly 13C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 15N-rich (14N/15N ≤ solar) AB grains, and their Mg-Al, S, and Ca-Ti isotope data when available. These 37 grains are enriched in 13C, 15N, and 26Al with the PNGs showing more extreme enhancements. The 15N-rich AB grains show systematically higher 26Al and 30Si excesses than the 14N-rich AB grains. Thus, we propose to divide the AB grains into groups 1 (14N/15N < solar) and 2 (14N/15N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found 32S and/or 50Ti enhancements. Interestingly, one AB1 grain had the largest 32S and 50Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the 32S excess and thus the initial presence of radiogenic 32Si (t 1/2 = 153 years). More importantly, we found that the 15N and 26Al excesses of AB1 grains form a trend that extends to the region in the N-Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.

Expansins expression is associated with grain size dynamics in wheat (Triticum aestivum L.)

PubMed Central

Lizana, X. Carolina; Riegel, Ricardo; Gomez, Leonardo D.; Herrera, Jaime; Isla, Adolfo; McQueen-Mason, Simon J.; Calderini, Daniel F.

2010-01-01

Grain weight is one of the most important components of cereal yield and quality. A clearer understanding of the physiological and molecular determinants of this complex trait would provide an insight into the potential benefits for plant breeding. In the present study, the dynamics of dry matter accumulation, water uptake, and grain size in parallel with the expression of expansins during grain growth in wheat were analysed. The stabilized water content of grains showed a strong association with final grain weight (r2=0.88, P <0.01). Grain length was found to be the trait that best correlated with final grain weight (r2=0.98, P <0.01) and volume (r2=0.94, P <0.01). The main events that defined final grain weight occurred during the first third of grain-filling when maternal tissues (the pericarp of grains) undergo considerable expansion. Eight expansin coding sequences were isolated from pericarp RNA and the temporal profiles of accumulation of these transcripts were monitored. Sequences showing high homology with TaExpA6 were notably abundant during early grain expansion and declined as maturity was reached. RNA in situ hybridization studies revealed that the transcript for TaExpA6 was principally found in the pericarp during early growth in grain development and, subsequently, in both the endosperm and pericarp. The signal in these images is likely to be the sum of the transcript levels of all three sequences with high similarity to the TaExpA6 gene. The early part of the expression profile of this putative expansin gene correlates well with the critical periods of early grain expansion, suggesting it as a possible factor in the final determination of grain size. PMID:20080826

Whole grain intake of Australians estimated from a cross-sectional analysis of dietary intake data from the 2011-13 Australian Health Survey.

PubMed

Galea, Leanne M; Beck, Eleanor J; Probst, Yasmine C; Cashman, Chris J

2017-08-01

The Australian Dietary Guidelines recommend Australians choose mostly whole-grain and/or high-fibre varieties within the grains (cereal) foods category, with other groups specifying a whole grain Daily Target Intake of 48 g for Australians aged 9 years or above. The USA and UK report estimates of whole grain intake that are low and declining, and no comprehensive studies on whole grain intake in the Australian population are available. The present study aimed to determine national estimates of whole grain intake, compared with current recommendations. A recently updated whole grain database was applied to the most current population dietary intake data. Single 24 h dietary recall intake data were reviewed against age group, sex, relative to energy intake and whole grain recommendations. Australia. Australians (2-85 years) participating in the 2011-13 Australian Health Survey (n 12 153). The median daily whole grain intake was 21 g for adults (19-85 years) and 17 g for children/adolescents (2-18 years), or 28 and 23 g/10 MJ per d, respectively. Approximately 30 % of children/adolescents consumed no whole grains on the day of the survey. Whole grain intake was lowest for the age group 14-18 years (8·7 g/d). Of all participants aged ≥9 years, 73 % did not reach the recommended Daily Target Intake of 48 g. Whole grain intake in Australia is below recommendations in all age groups. Adolescents may be a key target for campaigns to increase whole grain consumption. This study provides the first quantification of absolute whole grain intake from all food sources in a national sample of Australians.

Local Plasticity of Al Thin Films as Revealed by X-Ray Microdiffraction

NASA Astrophysics Data System (ADS)

Spolenak, R.; Brown, W. L.; Tamura, N.; MacDowell, A. A.; Celestre, R. S.; Padmore, H. A.; Valek, B.; Bravman, J. C.; Marieb, T.; Fujimoto, H.; Batterman, B. W.; Patel, J. R.

2003-03-01

Grain-to-grain interactions dominate the plasticity of Al thin films and establish effective length scales smaller than the grain size. We have measured large strain distributions and their changes under plastic strain in 1.5-μm-thick Al0.5%Cu films using a 0.8-μm-diameter white x-ray probe at the Advanced Light Source. Strain distributions arise not only from the distribution of grain sizes and orientation, but also from the differences in grain shape and from stress environment. Multiple active glide plane domains have been found within single grains. Large grains behave like multiple smaller grains even before a dislocation substructure can evolve.

Behavior of Windblown Sand on Mars: Results from Single-Particle Experiments

NASA Technical Reports Server (NTRS)

Marshall, J. R.; Borucki, J.; Sagan, C.

1999-01-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG&G Program. Because the martian aeolian environment in both high energy and of long duration, the most mobile fractions of windblown sand should have eradicated themselves by attrition, unless sand supply has kept pace with destruction. It is therefore important to understand the rate of grain attrition in order to make sense of the existence of vast dune fields on Mars. Attrition, has been addressed in other studies, but precise data for a single saltating grain striking a loose bed of sand have not been acquired -- the quintessential case to be understood for dunes on Mars. To acquire these data, we are employing a compound crossbow which has the bolt-firing mechanism replaced with a pneumatically-automated sabot system. The sabot can launch individual grains of sand of any size between several millimeters and about 50 microns, at velocities up to 100m/s. This is around the maximum velocity expected for saltating grains on Mars. The sabot sled is equipped with photoelectric sensors for measuring shot velocity. Baffling of the grain's exit orifice has enabled projection of single grains without significant aerodynamic effects from the sabot. Grains are fired into loose beds of sand at about 15 degrees from the horizontal (typical saltation trajectory at impact) while being filmed on high-speed video. High-intensity pulse illumination for the grains is triggered by the solenoid-operated bow trigger. A 45 degree mirror over the impact site provides simultaneous horizontal and vertical images of the impact on each video frame. UV fluorescence is enabling grain and grain-fragment recovery. At 100 m/s, grains of all sizes shatter into many fragments when the sand is replaced with a solid target. Kinetic energy of the grains at this velocity exceeds the critical energy for catastrophic failure of minerals. Although probably exceptional as a grain speed, it suggests that conditions on Mars might elevate materials into an attrition regime not encountered on other planets; individual grains blown across rock pavements on Mars will have short lifespans. When experimental grains impact loose (dune) sand, much, if not most of the kinetic energy is converted into momentum of other grains. Using high-speed filming, the energy involved in splashing grains at the impact site can be derived from the size of the crater, the speed of the splashed grains, and the rebound speed of the impactor. The amount of energy partitioned into material failure (as opposed to momentum) is too small a fraction of the total to be calculated under these circumstances. This does not necessarily mean that little damage occurs to the grains (the full extent of the damage has yet to be determined) because only a small fraction of the impact energy is required for inducing brittle fracture. Damage is orders of magnitude less than during impact against solid surfaces.

Behavior of Windblown Sand on Mars: Results from Single-Particle Experiments

NASA Astrophysics Data System (ADS)

Marshall, J. R.; Borucki, J.; Sagan, C.

1999-09-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG&G Program. Because the martian aeolian environment in both high energy and of long duration, the most mobile fractions of windblown sand should have eradicated themselves by attrition, unless sand supply has kept pace with destruction. It is therefore important to understand the rate of grain attrition in order to make sense of the existence of vast dune fields on Mars. Attrition, has been addressed in other studies, but precise data for a single saltating grain striking a loose bed of sand have not been acquired -- the quintessential case to be understood for dunes on Mars. To acquire these data, we are employing a compound crossbow which has the bolt-firing mechanism replaced with a pneumatically-automated sabot system. The sabot can launch individual grains of sand of any size between several millimeters and about 50 microns, at velocities up to 100m/s. This is around the maximum velocity expected for saltating grains on Mars. The sabot sled is equipped with photoelectric sensors for measuring shot velocity. Baffling of the grain's exit orifice has enabled projection of single grains without significant aerodynamic effects from the sabot. Grains are fired into loose beds of sand at about 15 degrees from the horizontal (typical saltation trajectory at impact) while being filmed on high-speed video. High-intensity pulse illumination for the grains is triggered by the solenoid-operated bow trigger. A 45 degree mirror over the impact site provides simultaneous horizontal and vertical images of the impact on each video frame. UV fluorescence is enabling grain and grain-fragment recovery. At 100 m/s, grains of all sizes shatter into many fragments when the sand is replaced with a solid target. Kinetic energy of the grains at this velocity exceeds the critical energy for catastrophic failure of minerals. Although probably exceptional as a grain speed, it suggests that conditions on Mars might elevate materials into an attrition regime not encountered on other planets; individual grains blown across rock pavements on Mars will have short lifespans. When experimental grains impact loose (dune) sand, much, if not most of the kinetic energy is converted into momentum of other grains. Using high-speed filming, the energy involved in splashing grains at the impact site can be derived from the size of the crater, the speed of the splashed grains, and the rebound speed of the impactor. The amount of energy partitioned into material failure (as opposed to momentum) is too small a fraction of the total to be calculated under these circumstances. This does not necessarily mean that little damage occurs to the grains (the full extent of the damage has yet to be determined) because only a small fraction of the impact energy is required for inducing brittle fracture. Damage is orders of magnitude less than during impact against solid surfaces.

Rotation-limited growth of three-dimensional body-centered-cubic crystals

NASA Astrophysics Data System (ADS)

Tarp, Jens M.; Mathiesen, Joachim

2015-07-01

According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered-cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe, as a function of the quenching depth, a crossover between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescence through rotation and alignment of the lattices of neighboring grains. We show that the grain rotation per volume change of a grain follows a power law with an exponent of -1.25 . The scaling exponent is consistent with theoretical considerations based on the conservation of dislocations.

Cyclic hardening behavior of extruded ZK60 magnesium alloy with different grain sizes

NASA Astrophysics Data System (ADS)

Zhang, Lixin; Zhang, Wencong; Chen, Wenzhen; Wang, Wenke

2018-04-01

Montonic and fully reversed strain-controlled cyclic deformation experiments were conducted on extruded ZK60 magnesium alloy with two different grain sizes in ambient air. Results revealed that the hardening rates of the ZK60 magnesium alloy rods with fine grain and coarse grain in the monotonic deformation and the fully reversed strain-controlled cyclic deformation were opposite along the extrusion direction. Electron Backscatter Diffration analysis revealed that fine grains were more easily rotated than coarse grains under the cyclic deformation. Under the twinning and detwinning process of the cyclic deformation at a large strain amplitude, the coarse grained ZK60 magnesium alloys were more prone to tension twinning {10-12}<10-11> and more residual twins were observed. Texture hardening of coarse grained magnesium alloy was more obvious in cyclic defromation than fine-grained magnesium alloy.

Solid propellant grain design and internal ballistics

NASA Technical Reports Server (NTRS)

1972-01-01

The ballistic aspects of grain design were studied to outline the steps necessary to achieve a successful grain design. The relationships of the grain design to steady-state mass balance and erosive burning are considered. Grain design criteria is reviewed, and recommended design criteria are included.

Mechanical behavior of nanostructured and ultrafine-grained materials under shock wave loadings. experimental data and results of computer simulation

NASA Astrophysics Data System (ADS)

Skripnyak, Vladimir

2012-03-01

Features of mechanical behavior of nanostructured and ultrafine-grained metals under quasistatic and shock wave loadings are discussed. Features of mechanical behavior of nanostructured and ultrafine grained metals over a wide range of strain rates are discussed. A constitutive model for mechanical behavior of metal alloys under shock wave loading including a grain size distribution, a precipitate hardening, and physical mechanisms of shear stress relaxation is presented. Strain rate sensitivity of the yield stress of face-centered-cubic, hexagonal close-packed metal alloys depends on grain size, whereas the Hugoniot elastic limits of ultrafine-grained copper, aluminum, and titanium alloys are close to values of coarse-grained counterparts. At quasi-static loading the yield strength and the tensile strength of titanium alloys with grain size from 300 to 500 nm are twice higher than at coarse-grained counterparts. But the spall strength of the UFG titanium alloys exceeds the value of coarse-grained counterparts only for 10 percents.

Grain dust and the lungs.

PubMed Central

Chan-Yeung, M.; Ashley, M. J.; Grzybowski, S.

1978-01-01

Grain dust is composed of a large number of materials, including various types of grain and their disintegration products, silica, fungi, insects and mites. The clinical syndromes described in relation to exposure to grain dust are chronic bronchitis, grain dust asthma, extrinsic allergic alveolitis, grain fever and silo-filler's lung. Rhinitis and conjunctivitis are also common in grain workers. While the concentration and the quality of dust influence the frequency and the type of clinical syndrome in grain workers, host factors are also important. Of the latter, smoking is the most important factor influencing the frequency of chronic bronchitis. The role of atopy and of bronchial hyperreactivity in grain dust asthma has yet to be assessed. Several well designed studies are currently being carried out in North America not only to delineate the frequency of the respiratory abnormalities, the pathogenetic mechanisms and the host factors, but also to establish a meaningful threshold limit concentration for grain dust. Images p1272-a PMID:348288

Damage Tolerance and Mechanics of Interfaces in Nanostructured Metals

NASA Astrophysics Data System (ADS)

Foley, Daniel J.

The concept of interface driven properties in crystalline metals has been one of the most intensely discussed topics in materials science for decades. Since the 1980s researchers have been exploring the concept of grain boundary engineering as route for tuning properties such as fracture toughness and irradiation resistance. This is especially true in ultra-fine grained and nanocrystalline materials where grain boundary mediated properties become dominant. More recently, materials composed of hierarchical nanostructures, such as amorphous-crystalline nanolaminates, have attracted considerable attention due to their favorable properties, ease of manufacture and highly tunable microstructure. While both grain boundary engineering and hierarchical nanostructures have shown promise there are still questions remaining regarding the role of specific attributes of the microstructure (such as grain boundaries, grain/layer size and inter/intralayer morphology) in determining material properties. This thesis attempts to address these questions by using atomistic simulations to perform deformation and damage loading studies on a series of nanolaminate and bicrystalline structures. During the course of this thesis the roles of layer thickness, interlayer structure and interlayer chemistry on the mechanical properties of Ni-NiX amorphous-crystalline nanolaminates were explored using atomistic simulations. This thesis found that layer thickness/thickness ratio and amorphous layer chemistry play a crucial role in yield strength and Young's modulus. Analysis of the deformation mechanisms at the atomic scale revealed that structures containing single crystalline, crystalline layers undergo plastic deformation when shear transformation zones form in the amorphous layer and impinge on the amorphous-crystalline interface, leading to dislocation emission. However, structures containing nanocrystalline, crystalline layers (both equiaxed and columnar nanocrystalline) undergo plastic deformation through a combination of grain boundary sliding and grain boundary mediated dislocation nucleation. Since grain boundaries were found to play a critical role as sources and sinks for dislocations in amorphous-crystalline nanolaminates a follow-up study on the effect of grain boundary character on damage accumulation/accommodation in copper symmetric tilt grain boundaries was performed. This study found that grain boundaries will become saturated with damage, a state where grain boundary energy and grain boundary free volume oscillate about a plateau during continuous defect loading (vacancy, interstitial and frenkel pair loading were all considered). Further, grain boundary character (specifically equilibrium grain boundary energy) was strongly correlated to the damage accommodation behavior of grain boundaries in copper. Finally, a study that attempted to link grain boundary damage saturation behavior to variations in grain boundary mechanical properties was performed. This study found no direct relationships between grain boundary damage saturation behavior and variations in grain boundary properties. The results of this thesis provide researchers with several strategies for tuning the properties of amorphous-crystalline nanolaminates. These strategies include manipulated bulk attributes such as layer thickness and morphology as well as manipulation of microscale attributes such as grain boundary engineering. Finally, this thesis provides valuable insight into the damage loading/accommodation behavior of FCC symmetric tilt grain boundaries.

O(minus 2) grain boundary diffusion and grain growth in pure dense MgO

NASA Technical Reports Server (NTRS)

Kapadia, C. M.; Leipold, M. H.

1973-01-01

Grain growth behavior in fully dense compacts of MgO of very high purity was studied, and the results compared with other similar behaving materials. The activation energy for the intrinsic self-diffusion of Mg(2minus) is discussed along with the grain boundary diffusion of O(2minus). Grain boundary diffusion of O(2minus) is proposed as the controlling mechanism for grain growth.

Electrical characterization of grain boundaries of CZTS thin films using conductive atomic force microscopy techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muhunthan, N.; Singh, Om Pal; Toutam, Vijaykumar, E-mail: toutamvk@nplindia.org

2015-10-15

Graphical abstract: Experimental setup for conducting AFM (C-AFM). - Highlights: • Cu{sub 2}ZnSnS{sub 4} (CZTS) thin film was grown by reactive co-sputtering. • The electronic properties were probed using conducting atomic force microscope, scanning Kelvin probe microscopy and scanning capacitance microscopy. • C-AFM current flow mainly through grain boundaries rather than grain interiors. • SKPM indicated higher potential along the GBs compared to grain interiors. • The SCM explains that charge separation takes place at the interface of grain and grain boundary. - Abstract: Electrical characterization of grain boundaries (GB) of Cu-deficient CZTS (Copper Zinc Tin Sulfide) thin films wasmore » done using atomic force microscopic (AFM) techniques like Conductive atomic force microscopy (CAFM), Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM). Absorbance spectroscopy was done for optical band gap calculations and Raman, XRD and EDS for structural and compositional characterization. Hall measurements were done for estimation of carrier mobility. CAFM and KPFM measurements showed that the currents flow mainly through grain boundaries (GB) rather than grain interiors. SCM results showed that charge separation mainly occurs at the interface of grain and grain boundaries and not all along the grain boundaries.« less

Microstructures and rheology of a calcite-shale thrust fault

NASA Astrophysics Data System (ADS)

Wells, Rachel K.; Newman, Julie; Wojtal, Steven

2014-08-01

A thin (˜2 cm) layer of extensively sheared fault rock decorates the ˜15 km displacement Copper Creek thrust at an exposure near Knoxville, TN (USA). In these ultrafine-grained (<0.3 μm) fault rocks, interpenetrating calcite grains form an interconnected network around shale clasts. One cm below the fault rock layer, sedimentary laminations in non-penetratively deformed footwall shale are cut by calcite veins, small faults, and stylolites. A 350 μm thick calcite vein separates the fault rocks and footwall shale. The vein is composed of layers of (1) coarse calcite grains (>5 μm) that exhibit a lattice preferred orientation (LPO) with pores at twin-twin and twin-grain boundary intersections, and (2) ultrafine-grained (0.3 μm) calcite that exhibits interpenetrating grain boundaries, four-grain junctions and lacks a LPO. Coarse calcite layers crosscut ultrafine-grained layers indicating intermittent vein formation during shearing. Calcite in the fault rock layer is derived from vein calcite and grain-size reduction of calcite took place by plasticity-induced fracture. The ultrafine-grained calcite deformed primarily by diffusion-accommodated grain boundary sliding and formed an interconnected network around shale clasts within the shear zone. The interconnected network of ultrafine-grained calcite indicates that calcite, not shale, was the weak phase in this fault zone.

Grain growth and pore coarsening in dense nano-crystalline UO 2+x fuel pellets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Tiankai; Mo, Kun; Yun, Di

Dense nano-sized UO 2+x pellets are synthesized by spark plasma sintering with controlled stoichiometries (UO 2.03 and UO 2.11) and grain sizes (~100 nm), and subsequently isothermally annealed to study their effects on grain growth kinetics and microstructure stability. The grain growth kinetics is determined and analyzed focusing on the interaction between grain boundary migration, pore growth and coalescence. Grains grow much bigger in nano-sized UO 2.11 than UO 2.03 upon thermal annealing, consistent with the fact that hyper-stoichiometric UO 2+x is beneficial for sintering due to enhanced U ion diffusion from excessive O ion interstitials. The activation energies ofmore » the grain growth for UO 2.03 and UO 2.11 are determined as ~1.0 and 1.3~2.0 eV, respectively. As compared with the micron-sized UO 2 in which volumetric diffusion dominates the grain coarsening with an activation energy of ~3.0 eV, the enhanced grain growth kinetics in nano-sized UO 2+x suggests that grain boundary diffusion controls grain growth. Lastly, the higher activation energy of more hyper-stoichiometric nano-sized UO 2.11 may be attributed to the excessive O interstitials pinning grain boundary migration.« less

Grain growth and pore coarsening in dense nano-crystalline UO 2+x fuel pellets

DOE PAGES

Yao, Tiankai; Mo, Kun; Yun, Di; ...

2017-03-25

Dense nano-sized UO 2+x pellets are synthesized by spark plasma sintering with controlled stoichiometries (UO 2.03 and UO 2.11) and grain sizes (~100 nm), and subsequently isothermally annealed to study their effects on grain growth kinetics and microstructure stability. The grain growth kinetics is determined and analyzed focusing on the interaction between grain boundary migration, pore growth and coalescence. Grains grow much bigger in nano-sized UO 2.11 than UO 2.03 upon thermal annealing, consistent with the fact that hyper-stoichiometric UO 2+x is beneficial for sintering due to enhanced U ion diffusion from excessive O ion interstitials. The activation energies ofmore » the grain growth for UO 2.03 and UO 2.11 are determined as ~1.0 and 1.3~2.0 eV, respectively. As compared with the micron-sized UO 2 in which volumetric diffusion dominates the grain coarsening with an activation energy of ~3.0 eV, the enhanced grain growth kinetics in nano-sized UO 2+x suggests that grain boundary diffusion controls grain growth. Lastly, the higher activation energy of more hyper-stoichiometric nano-sized UO 2.11 may be attributed to the excessive O interstitials pinning grain boundary migration.« less

Rain-induced spring wheat harvest losses

NASA Technical Reports Server (NTRS)

Bauer, A.; Black, A. L. (Principal Investigator)

1983-01-01

When rain or a combination of rain and high humidity delay wheat harvest, losses can occur in grain yield and/or grain quality. Yield losses can result from shattering, from reduction in test weight, and in the case of windrowed grain, from rooting of sprouting grain at the soil: windrow contact. Losses in grain quality can result from reduction in test weight and from sprouting. Sprouting causes a degradation of grain proteins and starches, hence flour quality is reduced, and the grain price deteriorates to the value of feed grain. Although losses in grain yield and quality are rain-induced, these losses do not necessarily occur because a standing or windrowed crop is wetted by rain. Spike water concentration in hard red spring wheat must be increased to about 45-49% before sprouting is initiated in grain that has overcome dormancy. The time required to overcome this dormancy after the cultivar has dried to 12 to 14% water concentration differs with hard red spring cultivars. The effect of rain on threshing-ready standing and windrowed hard red spring wheat grain yeild and quality was evaluated. A goal was to develop the capability to forecast the extent of expected loss of grain yield and quality from specific climatic events that delay threshing.

Strain Amount Dependent Grain Size and Orientation Developments during Hot Compression of a Polycrystalline Nickel Based Superalloy

PubMed Central

He, Guoai; Tan, Liming; Liu, Feng; Huang, Lan; Huang, Zaiwang; Jiang, Liang

2017-01-01

Controlling grain size in polycrystalline nickel base superalloy is vital for obtaining required mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Strain amount occupied a dominant position in manipulating the dynamic recrystallization (DRX) process and regulating the grain size of the alloy during hot forging. In this article, the high-throughput double cone specimen was introduced to yield wide-range strain in a single sample. Continuous variations of effective strain ranging from 0.23 to 1.65 across the whole sample were achieved after reaching a height reduction of 70%. Grain size is measured to be decreased from the edge to the center of specimen with increase of effective strain. Small misorientation tended to generate near the grain boundaries, which was manifested as piled-up dislocation in micromechanics. After the dislocation density reached a critical value, DRX progress would be initiated at higher deformation region, leading to the refinement of grain size. During this process, the transformations from low angle grain boundaries (LAGBs) to high angle grain boundaries (HAGBs) and from subgrains to DRX grains are found to occur. After the accomplishment of DRX progress, the neonatal grains are presented as having similar orientation inside the grain boundary. PMID:28772514

Grain size evolution and convection regimes of the terrestrial planets

NASA Astrophysics Data System (ADS)

Rozel, A.; Golabek, G. J.; Boutonnet, E.

2011-12-01

A new model of grain size evolution has recently been proposed in Rozel et al. 2010. This new approach stipulates that the grain size dynamics is governed by two additive and simultaneous processes: grain growth and dynamic recrystallization. We use the usual normal grain growth laws for the growth part. For dynamic recrystallization, reducing the mean grain size increases the total area of grain boundaries. Grain boundaries carry some surface tension, so some energy is required to decrease the mean grain size. We consider that this energy is available during mechanical work. It is usually considered to produce some heat via viscous dissipation. A partitioning parameter f is then required to know what amount of energy is dissipated and what part is converted in surface tension. This study gives a new calibration of the partitioning parameter on major Earth materials involved in the dynamic of the terrestrial planets. Our calibration is in adequation with the published piezometric relations available in the literature (equilibrium grain size versus shear stress). We test this new model of grain size evolution in a set of numerical computations of the dynamics of the Earth using stagYY. We show that the grain size evolution has a major effect on the convection regimes of terrestrial planets.

The OsmiR396c-OsGRF4-OsGIF1 regulatory module determines grain size and yield in rice.

PubMed

Li, Shuangcheng; Gao, Fengyan; Xie, Kailong; Zeng, Xiuhong; Cao, Ye; Zeng, Jing; He, Zhongshan; Ren, Yun; Li, Wenbo; Deng, Qiming; Wang, Shiquan; Zheng, Aiping; Zhu, Jun; Liu, Huainian; Wang, Lingxia; Li, Ping

2016-11-01

Grain weight is the most important component of rice yield and is mainly determined by grain size, which is generally controlled by quantitative trait loci (QTLs). Although numerous QTLs that regulate grain weight have been identified, the genetic network that controls grain size remains unclear. Herein, we report the cloning and functional analysis of a dominant QTL, grain length and width 2 (GLW2), which positively regulates grain weight by simultaneously increasing grain length and width. The GLW2 locus encodes OsGRF4 (growth-regulating factor 4) and is regulated by the microRNA miR396c in vivo. The mutation in OsGRF4 perturbs the OsmiR396 target regulation of OsGRF4, generating a larger grain size and enhanced grain yield. We also demonstrate that OsGIF1 (GRF-interacting factors 1) directly interacts with OsGRF4, and increasing its expression improves grain size. Our results suggest that the miR396c-OsGRF4-OsGIF1 regulatory module plays an important role in grain size determination and holds implications for rice yield improvement. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Creep of quartz by dislocation and grain boundary processes

NASA Astrophysics Data System (ADS)

Fukuda, J. I.; Holyoke, C. W., III; Kronenberg, A. K.

2015-12-01

Wet polycrystalline quartz aggregates deformed at temperatures T of 600°-900°C and strain rates of 10-4-10-6 s-1 at a confining pressure Pc of 1.5 GPa exhibit plasticity at low T, governed by dislocation glide and limited recovery, and grain size-sensitive creep at high T, governed by diffusion and sliding at grain boundaries. Quartz aggregates were HIP-synthesized, subjecting natural milky quartz powder to T=900°C and Pc=1.5 GPa, and grain sizes (2 to 25 mm) were varied by annealing at these conditions for up to 10 days. Infrared absorption spectra exhibit a broad OH band at 3400 cm-1 due to molecular water inclusions with a calculated OH content (~4000 ppm, H/106Si) that is unchanged by deformation. Rate-stepping experiments reveal different stress-strain rate functions at different temperatures and grain sizes, which correspond to differing stress-temperature sensitivities. At 600-700°C and grain sizes of 5-10 mm, flow law parameters compare favorably with those for basal plasticity and dislocation creep of wet quartzites (effective stress exponents n of 3 to 6 and activation enthalpy H* ~150 kJ/mol). Deformed samples show undulatory extinction, limited recrystallization, and c-axis maxima parallel to the shortening direction. Similarly fine-grained samples deformed at 800°-900°C exhibit flow parameters n=1.3-2.0 and H*=135-200 kJ/mol corresponding to grain size-sensitive Newtonian creep. Deformed samples show some undulatory extinction and grain sizes change by recrystallization; however, grain boundary deformation processes are indicated by the low value of n. Our experimental results for grain size-sensitive creep can be compared with models of grain boundary diffusion and grain boundary sliding using measured rates of silicon grain boundary diffusion. While many quartz mylonites show microstructural and textural evidence for dislocation creep, results for grain size-sensitive creep may apply to very fine-grained (<10 mm) quartz mylonites.

Dispersal of Volcanic Ash on Mars: Ash Grain Shape Analysis

NASA Astrophysics Data System (ADS)

Langdalen, Z.; Fagents, S. A.; Fitch, E. P.

2017-12-01

Many ash dispersal models use spheres as ash-grain analogs in drag calculations. These simplifications introduce inaccuracies in the treatment of drag coefficients, leading to inaccurate settling velocities and dispersal predictions. Therefore, we are investigating the use of a range of shape parameters, calculated using grain dimensions, to derive a better representation of grain shape and effective grain cross-sectional area. Specifically, our goal is to apply our results to the modeling of ash deposition to investigate the proposed volcanic origin of certain fine-grained deposits on Mars. Therefore, we are documenting the dimensions and shapes of ash grains from terrestrial subplinian to plinian deposits, in eight size divisions from 2 mm to 16 μm, employing a high resolution optical microscope. The optical image capture protocol provides an accurate ash grain outline by taking multiple images at different focus heights prior to combining them into a composite image. Image composite mosaics are then processed through ImageJ, a robust scientific measurement software package, to calculate a range of dimensionless shape parameters. Since ash grains rotate as they fall, drag forces act on a changing cross-sectional area. Therefore, we capture images and calculate shape parameters of each grain positioned in three orthogonal orientations. We find that the difference between maximum and minimum aspect ratios of the three orientations of a given grain best quantifies the degree of elongation of that grain. However, the average aspect ratio calculated for each grain provides a good representation of relative differences among grains. We also find that convexity provides the best representation of surface irregularity. For both shape parameters, natural ash grains display notably different shape parameter values than sphere analogs. Therefore, Mars ash dispersal modeling that incorporates shape parameters will provide more realistic predictions of deposit extents because volcanic ash-grain morphologies differ substantially from simplified geometric shapes.

Complete grain boundaries from incomplete EBSD maps: the influence of segmentation on grain size determinations

NASA Astrophysics Data System (ADS)

Heilbronner, Renée; Kilian, Ruediger

2017-04-01

Grain size analyses are carried out for a number of reasons, for example, the dynamically recrystallized grain size of quartz is used to assess the flow stresses during deformation. Typically a thin section or polished surface is used. If the expected grain size is large enough (10 µm or larger), the images can be obtained on a light microscope, if the grain size is smaller, the SEM is used. The grain boundaries are traced (the process is called segmentation and can be done manually or via image processing) and the size of the cross sectional areas (segments) is determined. From the resulting size distributions, 'the grain size' or 'average grain size', usually a mean diameter or similar, is derived. When carrying out such grain size analyses, a number of aspects are critical for the reproducibility of the result: the resolution of the imaging equipment (light microscope or SEM), the type of images that are used for segmentation (cross polarized, partial or full orientation images, CIP versus EBSD), the segmentation procedure (algorithm) itself, the quality of the segmentation and the mathematical definition and calculation of 'the average grain size'. The quality of the segmentation depends very strongly on the criteria that are used for identifying grain boundaries (for example, angles of misorientation versus shape considerations), on pre- and post-processing (filtering) and on the quality of the recorded images (most notably on the indexing ratio). In this contribution, we consider experimentally deformed Black Hills quartzite with dynamically re-crystallized grain sizes in the range of 2 - 15 µm. We compare two basic methods of segmentations of EBSD maps (orientation based versus shape based) and explore how the choice of methods influences the result of the grain size analysis. We also compare different measures for grain size (mean versus mode versus RMS, and 2D versus 3D) in order to determine which of the definitions of 'average grain size yields the most stable results.

Testing the responses of four wheat crop models to heat stress at anthesis and grain filling.

PubMed

Liu, Bing; Asseng, Senthold; Liu, Leilei; Tang, Liang; Cao, Weixing; Zhu, Yan

2016-05-01

Higher temperatures caused by future climate change will bring more frequent heat stress events and pose an increasing risk to global wheat production. Crop models have been widely used to simulate future crop productivity but are rarely tested with observed heat stress experimental datasets. Four wheat models (DSSAT-CERES-Wheat, DSSAT-Nwheat, APSIM-Wheat, and WheatGrow) were evaluated with 4 years of environment-controlled phytotron experimental datasets with two wheat cultivars under heat stress at anthesis and grain filling stages. Heat stress at anthesis reduced observed grain numbers per unit area and individual grain size, while heat stress during grain filling mainly decreased the size of the individual grains. The observed impact of heat stress on grain filling duration, total aboveground biomass, grain yield, and grain protein concentration (GPC) varied depending on cultivar and accumulated heat stress. For every unit increase of heat degree days (HDD, degree days over 30 °C), grain filling duration was reduced by 0.30-0.60%, total aboveground biomass was reduced by 0.37-0.43%, and grain yield was reduced by 1.0-1.6%, but GPC was increased by 0.50% for cv Yangmai16 and 0.80% for cv Xumai30. The tested crop simulation models could reproduce some of the observed reductions in grain filling duration, final total aboveground biomass, and grain yield, as well as the observed increase in GPC due to heat stress. Most of the crop models tended to reproduce heat stress impacts better during grain filling than at anthesis. Some of the tested models require improvements in the response to heat stress during grain filling, but all models need improvements in simulating heat stress effects on grain set during anthesis. The observed significant genetic variability in the response of wheat to heat stress needs to be considered through cultivar parameters in future simulation studies. © 2016 John Wiley & Sons Ltd.

Origins of GEMS Grains

NASA Technical Reports Server (NTRS)

Messenger, S.; Walker, R. M.

2012-01-01

Interplanetary dust particles (IDPs) collected in the Earth s stratosphere contain high abundances of submicrometer amorphous silicates known as GEMS grains. From their birth as condensates in the outflows of oxygen-rich evolved stars, processing in interstellar space, and incorporation into disks around new stars, amorphous silicates predominate in most astrophysical environments. Amorphous silicates were a major building block of our Solar System and are prominent in infrared spectra of comets. Anhydrous interplanetary dust particles (IDPs) thought to derive from comets contain abundant amorphous silicates known as GEMS (glass with embedded metal and sulfides) grains. GEMS grains have been proposed to be isotopically and chemically homogenized interstellar amorphous silicate dust. We evaluated this hypothesis through coordinated chemical and isotopic analyses of GEMS grains in a suite of IDPs to constrain their origins. GEMS grains show order of magnitude variations in Mg, Fe, Ca, and S abundances. GEMS grains do not match the average element abundances inferred for ISM dust containing on average, too little Mg, Fe, and Ca, and too much S. GEMS grains have complementary compositions to the crystalline components in IDPs suggesting that they formed from the same reservoir. We did not observe any unequivocal microstructural or chemical evidence that GEMS grains experienced prolonged exposure to radiation. We identified four GEMS grains having O isotopic compositions that point to origins in red giant branch or asymptotic giant branch stars and supernovae. Based on their O isotopic compositions, we estimate that 1-6% of GEMS grains are surviving circumstellar grains. The remaining 94-99% of GEMS grains have O isotopic compositions that are indistinguishable from terrestrial materials and carbonaceous chondrites. These isotopically solar GEMS grains either formed in the Solar System or were completely homogenized in the interstellar medium (ISM). However, the chemical compositions of GEMS grains are extremely heterogeneous and seem to rule out this possibility. Based on their solar isotopic compositions and their non-solar elemental compositions we propose that most GEMS grains formed in the nebula as late-stage non-equilibrium condensates.

Life history attributes of Indian meal moth (Lepidoptera: Pyralidae) and Angoumois grain moth (Lepidoptera: Gelechiidae) reared on transgenic corn kernels.

PubMed

Sedlacek, J D; Komaravalli, S R; Hanley, A M; Price, B D; Davis, P M

2001-04-01

The Indian meal moth, Plodia interpunctella (Hübner), and Angoumois grain moth, Sitotroga cerealella (Olivier), are two globally distributed stored-grain pests. Laboratory experiments were conducted to examine the impact that corn (Zea mays L.) kernels (i.e., grain) of some Bacillus thuringiensis Berliner (Bt) corn hybrids containing CrylAb Bt delta-endotoxin have on life history attributes of Indian meal moth and Angoumois grain moth. Stored grain is at risk to damage from Indian meal moth and Angoumois grain moth; therefore, Bt corn may provide a means of protecting this commodity from damage. Thus, the objective of this research was to quantify the effects of transgenic corn seed containing CrylAb delta-endotoxin on Indian meal moth and Angoumois grain moth survival, fecundity, and duration of development. Experiments with Bt grain, non-Bt isolines, and non-Bt grain were conducted in environmental chambers at 27 +/- 1 degrees C and > or = 60% RH in continuous dark. Fifty eggs were placed in ventilated pint jars containing 170 g of cracked or whole corn for the Indian meal moth and Angoumois grain moth, respectively. Emergence and fecundity were observed for 5 wk. Emergence and fecundity of Indian meal moth and emergence of Angoumois grain moth were significantly lower for individuals reared on P33V08 and N6800Bt, MON 810 and Bt-11 transformed hybrids, respectively, than on their non-Bt transformed isolines. Longer developmental times were observed for Indian meal moth reared on P33V08 and N6800Bt than their non-Bt-transformed isolines. These results indicate that MON 810 and Bt-11 CrylAb delta-endotoxin-containing kernels reduce laboratory populations of Indian meal moth and Angoumois grain moth. Thus, storing Bt-transformed grain is a management tactic that warrants bin scale testing and may effectively reduce Indian meal moth and Angoumois grain moth populations in grain without application of synthetic chemicals or pesticides.

Chemical signature of a migrating grain boundaries in polycrystalline olivine

NASA Astrophysics Data System (ADS)

Boneh, Y.; Marquardt, K.; Skemer, P. A.

2017-12-01

Olivine is the most abundant phase and influences strongly the physical and chemical properties of the upper mantle. The structure and chemistry of olivine grain-boundaries is important to understand, as these interfaces provide a reservoir for incompatible elements and partial melt, and serve as a fast pathway for chemical diffusion. This project investigates the chemical characteristics of grain boundaries in an olivine-rich aggregate. The sample is composed of Fo50 olivine crystals with minor amounts of enstatite. It was previously deformed (Hansen et al., 2016) and then annealed (Boneh et al., 2017) to investigate the microstructural changes during recrystallization. This transient microstructure has a bimodal grain size distribution and includes grains that experienced abnormal grain-growth, (porphyroblasts) and highly strained grains with no significant recrystallization or growth (matrix). Using high-resolution transmission electron microscopy (HR-TEM) with energy dispersive X-ray (EDX) at the Bayerisches Geoinstitut (BGI), we characterized boundaries between pairs of porphyroblasts, pairs of matrix grains, and mixed boundaries between porphyroblast and matrix grains. It was found that the boundary between porphyroblasts is enriched in Al and Ca and depleted in Mg, in comparison to grain interiors. However, matrix-matrix boundaries show less chemical segregation of these elements. The relatively high level of chemical segregation to porphyroblast grain boundaries offers different possible interpretations: 1) During grain boundary migration incompatible elements are swept up by the migrating grain boundary. 2) Large angle grain boundaries provide a large density of energetically favorable storage sites for incompatible elements. 3) Diffusion along low angle grain boundaries is too slow to allow for fast chemical equilibration between the different grain boundaries. 4) Dislocations cores serve as an important transport media for impurities (i.e., Cottrell atmosphere). We will further discuss these different interpretations, their feasibility, and implications for the geochemistry of the mantle.

Phloem Transport Of Arsenic Species From Flag Leaf To Grain During Grain Filling

EPA Science Inventory

Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was ...

7 CFR 800.17 - Special inspection and weighing requirements for sacked export grain.

Code of Federal Regulations, 2010 CFR

2010-01-01

... sacked export grain. 800.17 Section 800.17 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE... Requirements § 800.17 Special inspection and weighing requirements for sacked export grain. (a) General...

Association analysis for loci regulating grain quality traits and marker development in the USDA rice collection

USDA-ARS?s Scientific Manuscript database

Uncovering underlying genetics associated with grain quality is important to world food security. Rice is consumed as a whole grain, therefore cooked rice texture, stickiness, chewiness, grain dimensions and grain appearance can affect palatability and marketability. Amylose and protein content play...

Grain Handling and Storage.

ERIC Educational Resources Information Center

Harris, Troy G.; Minor, John

This text for a secondary- or postecondary-level course in grain handling and storage contains ten chapters. Chapter titles are (1) Introduction to Grain Handling and Storage, (2) Elevator Safety, (3) Grain Grading and Seed Identification, (4) Moisture Control, (5) Insect and Rodent Control, (6) Grain Inventory Control, (7) Elevator Maintenance,…

Grain Grading and Handling.

ERIC Educational Resources Information Center

Rendleman, Matt; Legacy, James

This publication provides an introduction to grain grading and handling for adult students in vocational and technical education programs. Organized in five chapters, the booklet provides a brief overview of the jobs performed at a grain elevator and of the techniques used to grade grain. The first chapter introduces the grain industry and…

Predicting Stored Grain Insect Population Densities Using an Electronic Probe Trap

USDA-ARS?s Scientific Manuscript database

Manual sampling of insects in stored grain is a laborious and time consuming process. Automation of grain sampling should help to increase the adoption of stored-grain integrated pest management. A new commercial electronic grain probe trap (OPI Insector™) has recently been marketed. We field tested...

77 FR 50763 - Notice of National Grain Car Council Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-22

... of National Grain Car Council Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car... Transportation Board's predecessor agency, the Interstate Commerce Commission (ICC), in National Grain Car Supply...

75 FR 53736 - Notice of National Grain Car Council Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-01

... of National Grain Car Council Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car... Commerce Commission (ICC), in National Grain Car Supply-- Conference of Interested Parties, EP 519. The...

Supplemental irrigation for grain sorghum production in the US Eastern Coastal Plain

USDA-ARS?s Scientific Manuscript database

Grain sorghum is an important grain crop throughout the world and is generally considered drought tolerant. Recently, in the US eastern Coastal Plain region, there was an emphasis on increasing regional grain production with grain sorghum having an important role. The region soils have low water hol...

Volatile organic compounds of whole grain soft winter wheat

USDA-ARS?s Scientific Manuscript database

The aroma from volatile organic compounds (VOCs) is an indicator of grain soundness and also an important quality attribute of grain foods. To identify the inherent VOCs of wheat grain unaffected by fungal infestation and other extrinsic factors, grains of nine soft wheat varieties were collected at...

7 CFR 800.97 - Weighing grain in containers, land carriers, barges, and shiplots.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 7 2010-01-01 2010-01-01 false Weighing grain in containers, land carriers, barges... (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS Weighing Provisions and Procedures § 800.97 Weighing grain in...

Effects of Intergranular Gas Bubbles on Thermal Conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

K. Chockalingam; Paul C. Millett; M. R. Tonks

2012-11-01

Model microstructures obtained from phase-field simulations are used to study the effective heat transfer across bicrys- tals with stationary grain boundary bubble populations. We find that the grain boundary coverage, irrespective of the intergranular bubble radii, is the most relevant parameter to the thermal resistance, which we use to derive effec- tive Kapitza resistances that are dependent on the grain boundary coverage and Kaptiza resistance of the intact grain boundary. We propose a model to predict thermal conductivity as a function of porosity, grain-size, Kaptiza resistance of the intact grain boundary, and grain boundary bubble coverage.

Atomistic simulations of dislocation pileup: Grain boundaries interaction

DOE PAGES

Wang, Jian

2015-05-27

Here, using molecular dynamics (MD) simulations, we studied the dislocation pileup–grain boundary (GB) interactions. Two Σ11 asymmetrical tilt grain boundaries in Al are studied to explore the influence of orientation relationship and interface structure on dislocation activities at grain boundaries. To mimic the reality of a dislocation pileup in a coarse-grained polycrystalline, we optimized the dislocation population in MD simulations and developed a predict-correct method to create a dislocation pileup in MD simulations. MD simulations explored several kinetic processes of dislocations–GB reactions: grain boundary sliding, grain boundary migration, slip transmission, dislocation reflection, reconstruction of grain boundary, and the correlation ofmore » these kinetic processes with the available slip systems across the GB and atomic structures of the GB.« less

On the role of the grain size in the magnetic behavior of sintered permanent magnets

NASA Astrophysics Data System (ADS)

Efthimiadis, K. G.; Ntallis, N.

2018-02-01

In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries.

Relict grains in chondrules: Evidence for chondrule recycling

NASA Technical Reports Server (NTRS)

Jones, R. H.

1994-01-01

The presence of relict grains in chondrules, which offers some insight into the degree to which chondrule material was recycled in the chondrule-forming region, is discussed in this report. Relics are grains that clearly did not crystallize in situ in the host chondrule. They represent coarse-grained precursor material that did not melt during chondrule formation, and provide the only tangible record of chondrule precursor grains. Relics are commonly identified by a large difference in size, textural differences, and/or significant compositional differences compared with normal grains in the host chondrule. Two important types of relics are: (1) 'dusty,' metal-bearing grains of olivine and pyroxene; and (2) forsterite (Mg-rich olivine) grains present in FeO-rich chondrules.

Effect of Grain Refining on Defect Formation in DC Cast Al-Zn-Mg-Cu Alloy Billet

NASA Astrophysics Data System (ADS)

Nadella, Ravi; Eskin, Dmitry; Katgerman, Laurens

In direct chill (DC) casting, the effect of grain refining on the prominent defects such as hot cracking and macrosegregation remains poorly understood, especially for multi-component commercial aluminum alloys. In this work, DC casting experiments were conducted on a 7075 alloy with and without grain refining at two casting speeds. The grain refiner was introduced either in the launder or in the furnace. The concentration profiles of Zn, Cu and Mg, measured along the billet diameter, showed that the increasing casting speed raises the segregation levels but grain refining does not seem to have a noticeable effect. However, hot cracking tendency is significantly reduced with grain refining and it is observed that crack is terminated with the introduction of grain refiner at a lower casting speed. These experimental results are correlated with microstructural observations such as grain size and morphology, and the occurrence of floating grains.

Grain boundary crystallography in polycrystalline yttria-stabilised cubic zirconia

NASA Astrophysics Data System (ADS)

Kini, Maya K.

2018-07-01

Properties of grain boundaries such as grain boundary energy, mobility and diffusion are reported to depend strongly on their crystallography. While studies on ceramic bicrystals with low Σ misorientations have shown highly ordered structures and low energies, studies on dense polycrystalline ceramics often show the significance of grain boundary planes. In the present study, grain boundary plane distributions were studied for yttria-stabilised cubic zirconia with varying grain sizes using Electron Back Scattered Diffraction technique combined with a stereological approach. Despite nearly isotropic grain boundary plane distributions, a highly anisotropic grain boundary character distribution is observed for specific misorientations. Certain low-energy symmetric tilts such as Σ3 and Σ11 are found to occur with high frequencies across the grain size range studied, leading to an inverse correlation between GB energy and frequency of occurrence, consistent with other ceramics studied in literature.

Managing for Multifunctionality in Perennial Grain Crops

PubMed Central

Ryan, Matthew R; Crews, Timothy E; Culman, Steven W; DeHaan, Lee R; Hayes, Richard C; Jungers, Jacob M; Bakker, Matthew G

2018-01-01

Abstract Plant breeders are increasing yields and improving agronomic traits in several perennial grain crops, the first of which is now being incorporated into commercial food products. Integration strategies and management guidelines are needed to optimize production of these new crops, which differ substantially from both annual grain crops and perennial forages. To offset relatively low grain yields, perennial grain cropping systems should be multifunctional. Growing perennial grains for several years to regenerate soil health before rotating to annual crops and growing perennial grains on sloped land and ecologically sensitive areas to reduce soil erosion and nutrient losses are two strategies that can provide ecosystem services and support multifunctionality. Several perennial cereals can be used to produce both grain and forage, and these dual-purpose crops can be intercropped with legumes for additional benefits. Highly diverse perennial grain polycultures can further enhance ecosystem services, but increased management complexity might limit their adoption. PMID:29662249

Re-exchange of Fe and Cu at the interface in sintered Nd-Fe-B magnets: A method to eliminate Fe precipitation at grain boundaries

NASA Astrophysics Data System (ADS)

Yang, YuQi; Si, HengGang; Yang, Hao; Zhang, Lan; Huang, DongFang; Chen, BaiYi; Xu, Fang; Hu, YongMei; Han, BaoJun

2018-01-01

According to the decoupling hypothesis for magnetic grains, the coercivity in sintered Nd-Fe-B magnets is increased after Cu doping, which is due to the formation of non-magnetic grain boundaries. However, this method partially fails, and ferromagnetic Fe-segregation occurs at the grain boundary. We discovered both experimentally and through calculation that the Fe content at the grain boundaries can be tuned across a wide range by introducing another element of Ag. Segregated Fe at high temperature at the grain boundary re-dissolves into Nd2Fe14B grains during annealing at low temperature. Both configurable and magnetic entropies contribute a large driving force for the formation of nonmagnetic grain boundaries. Almost zero Fe content could be achieved at the grain boundaries of sintered Nd-Fe-B magnet.

Experimental research on friction coefficient between grain bulk and bamboo clappers

NASA Astrophysics Data System (ADS)

Tang, Gan; Sun, Ping; Zhao, Yanqi; Yin, Lingfeng; Zhuang, Hong

2017-12-01

A silo is an important piece of storage equipment, especially in the grain industry. The internal friction angle and the friction coefficient between the grain and the silo wall are the main parameters needed for calculating the lateral pressure of the silo wall. Bamboo is used in silo walls, but there are no provisions about the friction coefficient between bulk grain and bamboo clappers in existing codes. In this paper, the material of the silo wall is bamboo. The internal friction of five types of grain and the friction coefficient between the grain and the bamboo clappers were measured with an equal-strain direct shear apparatus. By comparing the experimental result values with the code values, the friction coefficient between the grain bulk and bamboo clappers is lower than that between grain and steel wall and that between grain and concrete wall. The differences in value are 0.21 and 0.09, respectively.

Molecular microelectrostatic view on electronic states near pentacene grain boundaries

NASA Astrophysics Data System (ADS)

Verlaak, Stijn; Heremans, Paul

2007-03-01

Grain boundaries are the most inevitable and pronounced structural defects in pentacene films. To study the effect of those structural defects on the electronic state distribution, the energy levels of a hole on molecules at and near the defect have been calculated using a submolecular self-consistent-polarization-field approach in combination with atomic charge-quadrupole interaction energy calculations. This method has been benchmarked prior to application on four idealized grain boundaries: a grain boundary void, a void with molecules squeezed in between two grains, a boundary between two grains with different crystallographic orientations, and a grain boundary void in which a permanent dipole (e.g., a water molecule) has nested. While idealized, those views highlight different aspects of real grain boundaries. Implications on macroscopic charge transport models are discussed, as well as some relation between growth conditions and the formation of the grain boundary.

Improvement of the Reliability of Dielectrics for MLCC

NASA Astrophysics Data System (ADS)

Nakamura, Tomoyuki; Yao, Takayuki; Ikeda, Jun; Kubodera, Noriyuki; Takagi, Hiroshi

2011-10-01

To achieve enough reliability of monolithic ceramic capacitor, it is important to know the contribution of grain boundary and grain interior to its reliability and insulation resistance. As the number of grain boundaries per layer increased, mean time to failure (MTTF) increased. In addition, as the number of grain boundaries per layer increased, samples showed lower current leakage in the measured electric field range. Using these data, the grain boundary E-J curves were determined by simulation. As a result, temperature and electric field dependence of insulation resistance of grain boundary were very low. The insulation characteristics of one BaTiO3 grain per layer were examined. The resistance and reliability of grain interior were very low. To improve the degradation resistance of grain interior, Ca-doped BaTiO3-based dielectrics were developed. The influence of Ca substitution on MTTF was investigated and it was found out that MTTF increased with the increase of Ca substitution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hak-Sung, E-mail: hslee@kims.re.kr; Park, Chanbum; Oh, Chang-Seok

Highlights: • We model the sample grain boundary of LiCoO2, one of important Li cathode materials. • Rigid body translation was found the asymmetric GB is more stable than symmetric GB. • The vacancy formation energy of Li and O was estimated with first principles calculations. • This model boundary can help to find a new dopant to improve Li diffusions. - Abstract: An atomic structure of LiCoO{sub 2} model grain boundary, Σ2 [1120](1102), is introduced and grain boundary energies with rigid body translations are investigated systematically to find the most stable interface structures. It is found that the coordinatedmore » structures of Co and O in the vicinity of grain boundary are strongly related to grain boundary energy. Examining nonstoichiometry at grain boundary, the defect energetics of Li and O site at grain boundary are estimated. In addition, the effect of grain boundary on Li diffusion is investigated to calculate Li diffusion across grain boundary.« less

Respiratory profiles of grain handlers and sedentary workers.

PubMed Central

Herbert, F. A.; Woytowich, V.; Schram, E.; Baldwin, D.

1981-01-01

During 1978, grain handlers employed at three large inland grain terminals were studied along with an equal number of office workers matched for sex, age and smoking history. Respiratory symptoms and spirometric abnormalities were no more frequent in 16 grain handlers who were non-smokers than in their controls. However, 20 grain handlers who were smokers complained significantly more (P less than 0.01) of grade 1 dyspnea and had significantly lower ratios of forced expiratory volume in the first second to forced vital capacity (P less than 0.05) than their controls. Only 3% of the grain handlers were sensitive to grain dust, and 18% were found to be atopic but to have good lung function. A family history of asthma or allergic rhinitis was no more frequent in the grain handlers than in the control subjects. We conclude that the combination of cigarette smoking and exposure to grain dust causes a deterioration in lung function. PMID:7260809

Whole-grain intake is associated with body mass index in college students.

PubMed

Rose, Nick; Hosig, Kathy; Davy, Brenda; Serrano, Elena; Davis, Linda

2007-01-01

To measure whole-grain intake in college students and determine the association with body mass index (BMI). Cross-sectional convenience sample of college students enrolled in an introductory nutrition course. Large state university. 159 college students, mean age: 19.9. Intake of whole grains, refined grains, calories, and fiber from food records; BMI determined from height and weight measurements. Analysis of variance with linear contrasts; participants grouped by BMI category (P<.05). Average intake of cereal grains was 5.4 servings per day, of which whole-grain intake accounted for an average of 0.7 servings per day. Whole-grain intake was significantly higher in normal weight students than in overweight and obese students (based on BMI). The low intake of whole grains in this population of college students indicates the need for interventions aiming to increase whole-grain intake to the recommended minimum of 3 servings per day. College students who are concerned about their body weight may be motivated to increase their intake of whole-grain foods; however, their intake of whole grains is likely to be influenced by the availability of these food items in campus dining halls and other locations around the college campus.

Electrochemical Behavior Assessment of Micro- and Nano-Grained Commercial Pure Titanium in H2SO4 Solutions

NASA Astrophysics Data System (ADS)

Fattah-alhosseini, Arash; Ansari, Ali Reza; Mazaheri, Yousef; Karimi, Mohsen

2017-02-01

In this study, the electrochemical behavior of commercial pure titanium with both coarse-grained (annealed sample with the average grain size of about 45 µm) and nano-grained microstructure was compared by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis. Nano-grained Ti, which typically has a grain size of about 90 nm, is successfully made by six-cycle accumulative roll-bonding process at room temperature. Potentiodynamic polarization plots and impedance measurements revealed that as a result of grain refinement, the passive behavior of the nano-grained sample was improved compared to that of annealed pure Ti in H2SO4 solutions. Mott-Schottky analysis indicated that the passive films behaved as n-type semiconductors in H2SO4 solutions and grain refinement did not change the semiconductor type of passive films. Also, Mott-Schottky analysis showed that the donor densities decreased as the grain size of the samples reduced. Finally, all electrochemical tests showed that the electrochemical behavior of the nano-grained sample was improved compared to that of annealed pure Ti, mainly due to the formation of thicker and less defective oxide film.

Fingerprints of carbon, nitrogen, and silicon isotopes in small interstellar SiC grains from the Murchison meteorite

NASA Technical Reports Server (NTRS)

Hoppe, Peter; Geiss, Johannes; Buehler, Fritz; Neuenschwander, Juerg; Amari, Sachiko; Lewis, Roy S.

1993-01-01

We report ion microprobe determinations of the carbon, nitrogen, and silicon isotopic compositions of small SiC grains from the Murchison CM2 chondrite. Analyses were made on samples containing variable numbers of grains and on 14 individual grains. In some cases the multiple-grain sample compositions were probably dominated by only one or two grains. Total ranges observed are given. Only a few grains show values near the range limits. Both the total ranges of carbon and nitrogen isotopic compositions, and even the narrower ranges typical for the majority of the grains, are similar to those observed for larger SiC grains. Two rare components appear to be present in the smaller-size fraction, one characterized by C-12/C-13 about 12-16 and the other by very heavy nitrogen. The carbon and nitrogen isotopic compositions qualitatively may reflect hydrostatic H-burning via the CNO cycle and He-burning in red giants, as well as explosive H-burning in novae. The silicon isotopic compositions of most grains qualitatively show what is the signature of He-burning. The silicon isotopic composition of one grain, however, suggests a different process.

Effect of feeding a corn hybrid selected for leafiness as silage or grain to lactating dairy cattle.

PubMed

Clark, P W; Kelm, S; Endres, M I

2002-03-01

A leafy corn hybrid was compared to a grain corn hybrid as silage and high moisture grain to evaluate dry matter intake, milk yield, and milk composition. Sixteen multiparous Holstein cows averaging 97 DIM were used in a feeding trial based on 4 x 4 Latin squares with 21-d periods. Each of four diets contained (dry basis) 8% chopped hay, 42% corn silage, 11% high moisture corn grain, 10% whole, fuzzy cottonseed, and 29% protein concentrate. One diet used leafy corn as both high moisture grain and silage. A second diet contained grain corn hybrid (control) as both high moisture grain and silage. A third diet contained leafy corn for high moisture grain and control corn for silage and the fourth diet used control corn for high moisture grain and leafy corn for silage. Cows fed diets containing leafy silage produced more milk and milk protein and ate more DM than cows fed control silage. The corn hybrid used for high moisture grain did not influence milk yield or composition. Dry matter intake was greater for cows fed the diet containing both leafy high moisture grain and leafy silage than for cows fed both control high moisture grain and control silage, but milk yield and composition were not different. When fed as silage, the leafy corn hybrid used in this experiment supported greater DMI as well as higher milk and protein yields when compared to the grain corn hybrid.

Impact of grain size evolution on necking and pinch-and-swell formation in calcite layers

NASA Astrophysics Data System (ADS)

Schmalholz, Stefan Markus; Duretz, Thibault

2017-04-01

The formation of necking zones and the associated formation of pinch-and-swell structure is one form of strain localization in extending, competent layers. Natural pinch-and-swell structure in centimetre-thick calcite layers typically shows a reduction of grain size from swell towards pinch. However, the impact of grain size evolution on necking and pinch-and-swell formation is incompletely understood. We perform zero-dimensional (0D) and 2D thermo-mechanical numerical simulations to quantify the impact of grain size evolution on necking for extension rates between 10-12s^-1and10^-14 s-1 and temperatures around 350°C. For a combination of diffusion and dislocation creep we calculate grain size evolution according to the paleowattmeter (grain size is proportional to mechanical work rate) or the paleopiezometer (grain size is proportional to stress). Numerical results fit two observations: (i) grain size reduction from swells towards pinches, and (ii) dislocation creep dominated deformation in swells and significant contribution of diffusion creep in pinches. Modelled grain size in pinches (10 to 60 μm) and swells (70 to 800 μm) is close to observed grain size in pinches (15 to 27 μm) and in swells (250 to 1500 μm). Grain size evolution has only a minor impact on necking suggesting that grain size evolution is a consequence, and not the cause of necking. Viscous shear heating and grain size evolution had a negligible thermal impact in the simulations.

Intragranular Recrystallization and Lattice Reorientation of Calcite Grains in Experimentally Deformed Crinoids and Trilobites

NASA Astrophysics Data System (ADS)

Kim, N.; Takahashi, M.; Shigematsu, N.; Ree, J. H.; Jung, H.

2017-12-01

Intragranular recrystallization, including subgrain-rotation-recrystallization (SGR) and nucleation (and growth) of new grains along boundaries of deformation twins and bands, is an important process leading to grain-size reduction and causing rheological change depending on deformation condition. Despite of its importance, the detailed processes of intragranular recrystallization are still somewhat unclear. We deformed a limestone using triaxial testing machine at AIST of Japan at temperature of 500 700 °, strain rate of 10-4 10-5 s-1, confining pressure of 200 MPa and strain of up to 30%, to explore intragranular recrystallization processes of calcite. The limestone contains two abundant fossils, crinoid and trilobite. The crinoids are mono- or poly-crystalline. We focus on the monocrystalline crinoids with a coarser grain size ( 700 μm). The trilobites are polycrystalline and much finer-grained ( 7 μm) with initially a strong c-axis preferred orientation. At a lower temperature condition, subgrains develop both in twin and host domains of crinoids and evolve into new grains by SGR. At a higher temperature, recrystallized grains have irregular grain boundaries and bimodal grain-size distribution, implying grain-boundary migration (GBM) recrystallization. At a lower temperature, new grains nucleating and growing along twin boundaries inherit lattice orientation of twin domain, and with the nucleation site and usually a smaller grain size, they can be distinguished from new grains by SGR. At a higher temperature, however, the distinction is difficult at present due to extensive GBM. For the trilobites, there is only local GBM with no significant change in grain size, and flattening of grains reflects the bulk strain at a lower temperature. At a higher temperature, individual grains of the trilobites are equi-axed with weakened LPO, although the strain of trilobites is higher than bulk strain. These microfabrics suggest that the dominant deformation mechanism of the trilobites is diffusion creep. Although the initial LPO of the trilobites is weakened, the LPO is still preserved up to strain of 30%. This implies that even if the grain size of trilobites and matrix is similar in naturally deformed limestones, the lattice orientation map may be useful in recognizing trilobite fossils.

Increased Night Temperature Negatively Affects Grain Yield, Biomass and Grain Number in Chilean Quinoa

PubMed Central

Lesjak, Jurka; Calderini, Daniel F.

2017-01-01

Quinoa high nutritive value increases interest worldwide, especially as a crop that could potentially feature in different cropping systems, however, climate change, particularly rising temperatures, challenges this and other crop species. Currently, only limited knowledge exists regarding the grain yield and other key traits response to higher temperatures of this crop, especially to increased night temperatures. In this context, the main objective of this study was to evaluate the effect of increased night temperature on quinoa yield, grain number, individual grain weight and processes involved in crop growth under the environmental conditions (control treatment) and night thermal increase at two phases: flowering (T1) and grain filling (T2) in southern Chile. A commercial genotype, Regalona, and a quinoa accession (Cod. BO5, N°191, grain bank from Semillas Baer, hereby referred to as Accession) were used, due to their adaptability to Southern Chilean conditions and contrasting grain yield potential, grain weight and size of plants. Temperature was increased ≈4°C above the ambient from 8 pm until 9 am the next morning. Control treatments reached a high grain yield (600 and 397 g m-2, i.e., Regalona and Accession). Temperature increase reduced grain yield by 31% under T1 treatment and 12% when under T2 in Regalona and 23 and 26% in Accession, respectively. Aboveground biomass was negatively affected by the thermal treatments and a positive linear association was found between grain yield and aboveground biomass across treatments. By contrast, the harvest index was unaffected either by genotype, or by thermal treatments. Grain number was significantly affected between treatments and this key trait was linearly associated with grain yield. On the other hand, grain weight showed a narrow range of variation across treatments. Additionally, leaf area index was not affected, but significant differences were found in SPAD values at the end of T1 treatment, compared to control. Little change was found in the harvest index, individual grain weight, grain protein content or water soluble carbohydrates in response to the increased night temperature in this crop. PMID:28386266

Laboratory Studies of Charging Properties of Dust Grains in Astrophysical/Planetary Environments

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2012-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper we focus on charging of individual micron/submicron dust grains by processes that include: (a) UV photoelectric emissions involving incident photon energies higher than the work function of the material and b) electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). It is well accepted that the charging properties of individual micron/submicron size dust grains are expected to be substantially different from the bulk materials. However, no viable models for calculation of the charging properties of individual micron size dust grains are available at the present time. Therefore, the photoelectric yields, and secondary electron emission yields of micron-size dust grains have to be obtained by experimental methods. Currently, very limited experimental data are available for charging of individual micron-size dust grains. Our experimental results, obtained on individual, micron-size dust grains levitated in an electrodynamic balance facility (at NASA-MSFC), show that: (1) The measured photoelectric yields are substantially higher than the bulk values given in the literature and indicate a particle size dependence with larger particles having order-of-magnitude higher values than for submicron-size grains; (2) dust charging by low energy electron impact is a complex process. Also, our measurements indicate that the electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Laboratory measurements on charging of analogs of the interstellar dust as well as Apollo 11 dust grains conducted at the NASA-MSFC Dusty Plasma Lab. are presented here

Interruption of magnesium supply at heading influenced proteome of peripheral layers and reduced grain dry weight of two wheat (Triticum aestivum L.) genotypes.

PubMed

Qiu, Huiling; Nadaud, Isabelle; Ledoigt, Gérard; Piquet-Pissaloux, Agnès; Branlard, Gérard

2016-06-30

Magnesium (Mg), an indispensable mineral for plant growth, is concentrated in the peripheral layers (PLs) of the mature grain of wheat. The supply of Mg was interrupted from plant heading to maturity and a proteomic approach was used to investigate the PLs at three stages of development. Two genotypes with contrasting concentrations of Mg in the grain were studied: Apache (low Mg) and MgHL (high Mg). The concentration of Mg was significantly reduced in the roots (10-21%), straw (18-50%) and grain (24-10%), respectively. Mg deficiency altered enzymes involved in photosynthesis, glycolysis, respiration, amino acid synthesis, cell division, protein degradation and folding at early stages, especially in MgHL. This latter had smaller grain by reducing grain potential size and dry matter accumulation. By contrast in Apache, few proteins were affected at early stages and proteins related to stress/defense and arginine/proline metabolism were up accumulated resulting in lower number of grains per ear (24.9%). This study showed that Mg in PLs plays an important role in cell division, ATP generation, carbohydrate and amino acid metabolism, and hence may influence grain potential size and assimilates in grain, which determines grain weight. These results should help wheat breeders improve Mg content and hence grain yield. Magnesium (Mg) is an abundant cation and is involved in many cell activities. Its role in determining wheat productivity remains unclear. This study is the first to investigate how Mg deficiency influences the physiological characters of wheat and dry matter in the grain in two genotypes with contrasting Mg content. Moreover, Mg is concentrated in peripheral layers of grain, which are known to play a critical role in grain development. In this study, we investigated proteins in the peripheral layers expressed differentially in three development stages to identify the mechanism by which Mg influences grain development. This study revealed that the supply of Mg influences grain yield and that Mg regulates proteins related to cell metabolism and stress defense in grain. Copyright © 2016 Elsevier B.V. All rights reserved.

Dynamic Grain Growth in Forsterite Aggregates Experimentally Deformed to High Strain

NASA Astrophysics Data System (ADS)

Kellermann Slotemaker, A.; de Bresser, H.; Spiers, C.; Drury, M.

2004-12-01

The dynamics of the outer Earth are largely controlled by olivine rheology. From previous work it has become clear that if olivine rocks are deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that were reduced in grain size during straining by grain size insensitive (dislocation) creep mechanisms. The aim of the present study was to investigate microstructure evolution of fine-grained olivine rocks that coarsen in grain size while deforming by grain size sensitive (GSS) creep. We used fine-grained (~1 μ m) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3). Two types of experiments were carried out: 1) Hot isostatic pressing (HIP) followed by axial compression to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C, 2) HIP treatment without axial deformation. Microstructures were characterized by analyzing full grain size distributions and texture using SEM/EBSD. Our stress-strain curves showed continuous hardening. When samples were temporally unloaded for short time intervals, no difference in flow stress was observed before and after the interruption in straining. Strain rate sensitivity analysis showed a low value of ~1.5 for the stress exponent n. Measured grain sizes show an increase with strain up to a value twice that of the starting value. HIP-only samples showed only minor increase in grain size. A random LPO combined with the low n ~1.5 suggests dominant GSS creep controlled by grain boundary sliding. These results indicate that dynamic grain growth occurs in forsterite aggregates deforming by GSS creep, and we relate the continuous strain hardening to this process. A dynamic grain growth model involving an increase in cellular defect fraction seems best applicable to the grain growth observed in this study. We suggest that the employment of this model to fine-grained olivine rocks can further improve our understanding of the microstructural evolution of this material and related rheological behaviour.

Grain boundary diffusion in olivine (Invited)

NASA Astrophysics Data System (ADS)

Marquardt, K.; Dohmen, R.

2013-12-01

Olivine is the main constituent of Earth's upper mantle. The individual mineral grains are separated by grain boundaries that have very distinct properties compared to those of single crystals and strongly affect large-scale physical and chemical properties of rocks, e.g. viscosity, electrical conductivity and diffusivity. Knowledge on the grain boundary physical and chemical properties, their population and distribution in polycrystalline materials [1] is a prerequisite to understand and model bulk (rock) properties, including their role as pathways for element transport [2] and the potential of grain boundaries as storage sites for incompatible elements [3]. Studies on selected and well characterized single grain boundaries are needed for a detailed understanding of the influence of varying grain boundaries. For instance, the dependence of diffusion on the grain boundary structure (defined by the lattice misfit) and width in silicates is unknown [2, 4], but limited experimental studies in material sciences indicate major effects of grain boundary orientation on diffusion rates. We characterized the effect of grain boundary orientation and temperature on element diffusion in forsterite grain boundaries by transmission electron microscopy (TEM).The site specific TEM-foils were cut using the focused ion beam technique (FIB). To study diffusion we prepared amorphous thin-films of Ni2SiO4 composition perpendicular to the grain boundary using pulsed laser deposition. Annealing (800-1450°C) leads to crystallization of the thin-film and Ni-Mg inter-diffuse into the crystal volume and along the grain boundary. The inter-diffusion profiles were measured using energy dispersive x-ray spectrometry in the TEM, standardized using the Cliff-Lorimer equation and EMPA measurements. We obtain volume diffusion coefficients that are comparable to Ni-Mg inter-diffusion rates in forsterite determined in previous studies at comparable temperatures, with similar activation energies. Grain boundary diffusion perpendicular to the dislocation lines of the small angle grain boundaries proved to be about an order of magnitude faster than volume diffusion, whereas diffusion in high angle grain boundaries is several orders of magnitude faster. We will discuss the variation of element diffusion rates with grain boundary orientation and the temperature- and/or time-induced transition from one diffusion regime to the next regime. This is done using time series experiments and two-dimensional grain boundary diffusion simulations. Finally, we will debate the differences between our data and other data sets that result from different experimental setups, conditions and analyses.

Survival of carbon grains in shocks

NASA Technical Reports Server (NTRS)

Seab, C. Gregory

1990-01-01

Supernova shocks play a significant part in the life of an interstellar grain. In a typical 10 to the 9th power year lifetime, a grain will be hit by an average of 10 shocks of 100 km s(sup -1) or greater velocity, and even more shocks of lower velocity. Evaluation of the results of this frequent shock processing is complicated by a number of uncertainties, but seems to give about 10 percent destruction of silicate grains and about half that for graphite grains. Because of the frequency of shocking, the mineralogy and sizes of the grain population is predominately determined by shock processing effects, and not by the initial grain nucleation and growth environment. One consequence of the significant role played by interstellar shocks is that a certain fraction (up to 5 percent) of the carbon should be transformed into the diamond phase. Diamond transformation is observed in the laboratory at threshold shock pressures easily obtainable in grain-grain collisions in supernova shocks. Yields for transforming graphite, amorphous carbon, glassy carbon, and other nearly pure carbon solids into diamond are quite high. Impurities up to at least the 10 percent level (for oxygen) are tolerated in the process. The typical size diamond expected from shock transformation agrees well with the observed sizes in the Lewis et al. findings in meteoritic material. Isotropic anomalies already contained in the grain are likely to be retained through the conversion process, while others may be implanted by the shock if the grain is close to the supernova. The meteoritic diamonds are likely to be the results of transformation of carbon grains in grain-grain collisions in supernova shock waves.

Combination of Eight Alleles at Four Quantitative Trait Loci Determines Grain Length in Rice

PubMed Central

Zeng, Yuxiang; Ji, Zhijuan; Wen, Zhihua; Liang, Yan; Yang, Changdeng

2016-01-01

Grain length is an important quantitative trait in rice (Oryza sativa L.) that influences both grain yield and exterior quality. Although many quantitative trait loci (QTLs) for grain length have been identified, it is still unclear how different alleles from different QTLs regulate grain length coordinately. To explore the mechanisms of QTL combination in the determination of grain length, five mapping populations, including two F2 populations, an F3 population, an F7 recombinant inbred line (RIL) population, and an F8 RIL population, were developed from the cross between the U.S. tropical japonica variety ‘Lemont’ and the Chinese indica variety ‘Yangdao 4’ and grown under different environmental conditions. Four QTLs (qGL-3-1, qGL-3-2, qGL-4, and qGL-7) for grain length were detected using both composite interval mapping and multiple interval mapping methods in the mapping populations. In each locus, there was an allele from one parent that increased grain length and another allele from another parent that decreased it. The eight alleles in the four QTLs were analyzed to determine whether these alleles act additively across loci, and lead to a linear relationship between the predicted breeding value of QTLs and phenotype. Linear regression analysis suggested that the combination of eight alleles determined grain length. Plants carrying more grain length-increasing alleles had longer grain length than those carrying more grain length-decreasing alleles. This trend was consistent in all five mapping populations and demonstrated the regulation of grain length by the four QTLs. Thus, these QTLs are ideal resources for modifying grain length in rice. PMID:26942914

TEMPERATURE SPECTRA OF INTERSTELLAR DUST GRAINS HEATED BY COSMIC RAYS. I. TRANSLUCENT CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalvāns, Juris, E-mail: juris.kalvans@venta.lv

Heating of whole interstellar dust grains by cosmic-ray (CR) particles affects the gas–grain chemistry in molecular clouds by promoting molecule desorption, diffusion, and chemical reactions on grain surfaces. The frequency of such heating, f{sub T}, s{sup −1}, determines how often a certain temperature T{sub CR}, K, is reached for grains hit by CR particles. This study aims to provide astrochemists with a comprehensive and updated data set on CR-induced whole-grain heating. We present calculations of f{sub T} and T{sub CR} spectra for bare olivine grains with radius a of 0.05, 0.1, and 0.2 μ m and such grains covered withmore » ice mantles of thickness 0.1 a and 0.3 a . Grain shape and structure effects are considered, as well as 30 CR elemental constituents with an updated energy spectrum corresponding to a translucent cloud with A{sub V} = 2 mag. Energy deposition by CRs in grain material was calculated with the srim program. We report full T{sub CR} spectra for all nine grain types and consider initial grain temperatures of 10 K and 20 K. We also provide frequencies for a range of minimum T{sub CR} values. The calculated data set can be simply and flexibly implemented in astrochemical models. The results show that, in the case of translucent clouds, the currently adopted rate for heating of whole grains to temperatures in excess of 70 K is underestimated by approximately two orders of magnitude in astrochemical numerical simulations. Additionally, grains are heated by CRs to modest temperatures (20–30 K) with intervals of a few years, which reduces the possibility of ice chemical explosions.« less

The Role of Grain Dynamics in the Onset of Sediment Transport

NASA Astrophysics Data System (ADS)

Clark, A., IV; Shattuck, M. D.; Ouellette, N. T.; O'Hern, C.

2016-12-01

Despite decades of research, the grain-scale mechanisms that control the onset of sediment transport are still not well understood. A large collection of data, known as the Shields curve, shows that Θ c, which is the minimum dimensionless shear stress at the bed for grains to move, is primarily a function of the shear Reynolds number Re*. To understand this collapse, it is typically assumed that the onset of grain motion is determined by the conditions at which fluid forces violate static equilibrium for surface grains. Re* compares the grain size to the size of the viscous sublayer in the fluid flow, so the relevant fluid lift and drag forces vary with Re*. A complimentary approach, which remains relatively unexplored, is to ask instead when mobilized grains can stop. In this case, Re* is the ratio of two important time scales related to grain motion: (1) the time for a grain to equilibrate to the fluid flow and (2) the time for the shear stress to accelerate a grain over the characteristic bed roughness. Thus, Re* controls whether grains are accelerated significantly between collisions with the bed. To test how this effect relates to the Shields curve, we perform simulations of granular beds sheared by a model fluid flow, where Re* is varied only through the fluid-grain coupling, which alters the grain dynamics. We find good qualitative agreement with the Shields curve, and the quantitative discrepancies are consistent with lift forces calculations at varying Re*. Our results suggest that the onset of sediment transport may be better described as when mobile grains are able to stop, which varies significantly with Re*, and theoretical descriptions that account for this effect may be more successful than those that consider only static equilibrium.

Intakes of whole grain in an Italian sample of children, adolescents and adults.

PubMed

Sette, Stefania; D'Addezio, Laura; Piccinelli, Raffaela; Hopkins, Sinead; Le Donne, Cinzia; Ferrari, Marika; Mistura, Lorenza; Turrini, Aida

2017-03-01

There is wide evidence that regular consumption of whole grain foods may reduce the risk of chronic diseases. The aim of this work was to quantify the intake of whole grains and identify main dietary sources in the Italian population. Whole grain intakes were calculated in a sample of 2830 adults/older adults and of 440 children/adolescents from the last national survey INRAN-SCAI 2005-06. Food consumption was assessed from a 3-day food record. The whole grain content of foods was estimated mainly from quantitative ingredient declarations on labels. Mean whole grain intakes were 3.7 g/day in adults/older adults and 2.1 g/day in children/adolescents. Overall, 23 % of the sample reported consumption of whole grain foods during the survey, among which mean whole grain intakes ranged from 6.0 g/day in female children to 19.1 g/day in female older adults. The main sources of whole grains were breakfast cereals in children/adolescents (32 %) and bread in adults/older adults (46 %). Consumption of whole grain among adults was associated with significantly higher daily intakes and adequacy of dietary fibre, several vitamins (thiamine, riboflavin, vitamin B 6 ) and minerals (iron, calcium, potassium, phosphorus, zinc, magnesium) compared to non-consumption. Among children, whole grain intake was associated with significantly higher intakes of iron and magnesium. The study reveals very low whole grain intakes across all age groups of the Italian population. Considering the positive association in consumers between whole grain intakes and fibre and micro-nutrient intakes, public health strategies to increase whole grain consumption should be considered.

Microstructure of warm rolling and pearlitic transformation of ultrafine-grained GCr15 steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Jun-Jie; Lian, Fu-Liang; Liu, Hong-Ji

2014-09-15

Pearlitic transformation mechanisms have been investigated in ultra-fine grained GCr15 steel. The ultrafine-grained steel, whose grain size was less than 1 μm, was prepared by thermo-mechanical treatment at 873 K and then annealing at 923 K for 2 h. Pearlitic transformation was conducted by reheating the ultra-fine grained samples at 1073 K and 1123 K for different periods of time and then cooling in air. Scanning electron microscope observation shows that normal lamellar pearlite, instead of granular cementite and ferrite, cannot be formed when the grain size is approximately less than 4(± 0.6) μm, which yields a critical grain sizemore » for normal lamellar pearlitic transformations in this chromium alloyed steel. The result confirms that grain size has a great influence on pearlitic transformation by increasing the diffusion rate of carbon atoms in the ultra-fine grained steel, and the addition of chromium element doesn't change this pearlitic phase transformation rule. Meanwhile, the grain growth rate is reduced by chromium alloying, which is beneficial to form fine grains during austenitizing, thus it facilitating pearlitic transformation by divorced eutectoid transformation. Moreover, chromium element can form a relatively high gradient in the frontier of the undissolved carbide, which promotes carbide formation in the frontier of the undissolved carbide, i.e., chromium promotes divorced eutectoid transformation. - Highlights: • Ultrafine-grained GCr15 steel was obtained by warm rolling and annealing technology. • Reduction of grain size makes pearlite morphology from lamellar to granular. • Adding Cr does not change normal pearlitic phase transformation rule in UFG steel. • Cr carbide resists grain growth and facilitates pearlitic transformation by DET.« less

Condensation Temperature in Non-Equilibrium Condensation.

NASA Astrophysics Data System (ADS)

Tanaka, K. K.; Tanaka, H.; Nakazawa, K.

1999-09-01

In investigation of the origins of the presolar grains, it is important to clear the formation process of grains in ejecta of AGB stars or supernovae, where most presolar grains are suggested to be formed. The grain formation has been investigated based on the classical nucleation theory in many previous studies. On the other hand it has been pointed out that the classical nucleation rate is significantly different from that obtained by experiments, and should not be applied to grain formation in astrophysical environments (Donn and Nuth, 1985, ApJ 288, 187-190). Recently Dillmann and Meier (1991, J. Chem. Phys. 94, 3872-3884) proposed new semi-phenomological nucleation model, which achieved excellent agreements with experiments. In this study we applied the nucleation rate in the semi-phenomological model to the grain formation in astrophysical environment in order to make it clear how the grain formation changes due to the new nucleation rate. For various parameters determined by surface energy of grain and cooling time of vapor, we solved equations describing the grain formation. From the comparison between the results obtained by new nucleation rate and that by classical one we found that there is no significant difference in grain number density and grain size, but the condensation temperature is considerably different from the previous one. For example in carbon rich AGB star the condensation temperature of graphite is lower than that obtained by classical one by a few hundreds Kelvin: this means the condensation temperature is lower than the equilibrium condensation temperature by about 500 Kelvin. Furthermore we investigated the condensation of vapor in which grain impurities are already present. We obtained the condition for formation of core-mantle type grains. Our obtained condition would give constraint on the formation of core-mantle type presolar grains.

Computer Modeling of Sand Transport on Mars Using a Compart-Mentalized Fluids Algorithm (CFA)

NASA Technical Reports Server (NTRS)

Marshall, J.; Stratton, D.

1999-01-01

It has been postulated that aeolian transport on Mars may be significantly different from that on Earth. From laboratory experiments simulating martian grain transport [2], it has been observed that (saltating) grains striking the bed can cause hundreds of secondary reptation trajectories when impact occurs at speeds postulated for Mars. Some of the ballistically induced trajectories "die ouf' and effectively join the ranks on the creep population that is merely nudged along by impact. Many of the induced reptation trajectories, however, are sufficiently high for the grains to become part of the saltation load (it is irrelevant to the boundary layer how a grain attained its initial lift force). When these grains, in turn, strike the surface, they too are capable of inducing more reptating grains. This cascading effect has been discussed in connection with terrestrial aeolian transport in an attempt to dispel the notion that sand motion is divisible only into creep and saltation loads. On Earth, only a few grains are splashed by impact. On Mars, it may be hundreds. We developed a computer model to address this phenomenon because there are some important ramifications: First, this ratio may mean that martian aeolian transport is dominated by reptation flux rather than saltation. On Earth, the flux would be a roughly balanced mixture between reptation/creep and saltation. On Venus, there would be no transport other than by saltation. In other words, an understanding of planetary aeolian processes may not be necessarily understood by extrapolating from the "Earth case", with only gravity and atmospheric density/viscosity being considered as variables. Second, the reptation flux on Mars may be self sustaining, so that little input is required by the wind once transport has been initiated. The number of grains saturating the boundary layer near the bed may mean that average grain speed on Mars might conceivably be less than that on Earth. This would say much for models of sand comminution on Mars. A multiple-grain transport model using just the equations of grain motion describing lift and drag is impossible to develop owing to stochastic effects --the very effects we wish to model. Also, unless we were to employ supercomputing techniques and extremely complex computer codes that could deal with millions of grains simultaneously, it would also be difficult to model grain transport if we attempted to consider every grain in motion. No existing computer models were found that satisfactorily used the equations of motion to arrive at transport flux numbers for the different populations of saltation and reptation. Modeling all the grains in a transport system was an intractable problem within our resources, and thus we developed what we believe to be a new modeling approach to simulating grain transport. The CFA deals with grain populations, but considers them to belong to various compartmentalized fluid units in the boundary layer. In this way, the model circumvents the multigrain problem by dealing primarily with the consequences of grain transport --momentum transfer between air and grains, which is the physical essence of a dynamic grain-fluid mixture. We thus chose to model the aeolian transport process as a superposition of fluids. These fluids include the air as well as particle populations of various properties. The prime property distinguishing these fluids is upward and downward grain motion. In a normal saltation trajectory, a grain's downwind velocity increases with time, so a rising grain will have a smaller downwind velocity than a failing grain. Because of this disparity in rising and falling grain proper-ties, it seemed appropriate to track these as two separate grain populations within the same physical space. The air itself can be considered a separate fluid superimposed within and interacting with the various grain-cloud "fluids". Additional informaiton is contained in the original.

Occupational exposure to Aspergillus and aflatoxins among food-grain workers in India.

PubMed

Malik, Abida; Ali, Sana; Shahid, Mohd; Bhargava, Rakesh

2014-01-01

Aflatoxins are a metabolite of Aspergillus molds and are widespread in the natural environment. Workers who handle food grains are at increased risk of exposure to aflatoxins and subsequently certain respiratory conditions. In India, more than half of the employed population is engaged in some type of agricultural work, yet little known about the respiratory problems as a result of exposure to aflatoxins among workers who handle food grains in India. The aim of this study was to determine the risk of occupational exposure to aflatoxins in food-grain workers compared to workers who are not occupationally exposed to food grains. Bronchoalveolar lavage (BAL) and serum samples from 46 food-grain workers and 44 non-food-grain workers were analyzed for the presence of aflatoxins. Microscopy and culture of BAL samples were performed to detect Aspergillus species. Aflatoxins were detected in 32·6% of the food-grain workers and 9·1% of non food grain workers (P<0·01). A significant difference was also found in BAL culture for Aspergillus (P<0·01) between the two groups. About 47·8% of the food-grain workers and 11·4% of non-food-grain workers had chronic respiratory symptoms. Occupational exposure to aflatoxins in food-grain workers was found to be associated with the increased presence of respiratory symptoms.

[Effect of grain-bean package, grain-bean package dietary fiber and single whole grain dietary fiber on dyslipidemia rats].

PubMed

Liu, Yang; Zhai, Chengkai; Sun, Guiju; Zhang, Hong; Jiang, Mingxia; Zhang, Haifeng; Guo, Junling; Lan, Xi

2014-05-01

To observe and compare the effects of grain-bean package, dietary fiber (DF) extracted from grain-bean package, and DF from grain corn on the blood lipids and fatty acid synthase (FAS) activity in high-fat, high-cholesterol feeding induced dyslipidemia rats, and observe its effects on regulation of sterol regulatory element protein-1c (SREBP-1c) mRNA expression in rat liver. Consolidation 50 SD rats of clean grade feeding adaptation for one week, randomly assigned into normal control group, hyperlipidemia model group, grain-bean package group, grain-bean package DF group and grain corn group. Feed with corresponding diets for 8 weeks, and measure the total cholesterol (TC), triglyceridaemia (TG), high density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG), FAS, SREBP-1c mRNA of all groups. Compared with control group, TC, TG, FBG levels of hyperlipidemia model group were significantly increased (P < 0.05). Compared with model group, TC, TG, FBG levels of grain-bean package group, grain-bean package DF group were significantly decreased, HDL-C levels significantly increased, and activity of FAS, regulation of SREBP-1c were significantly decreased (P < 0.05). The Grain-bean package dietary fiber can improve blood lipids levels of dyslipidemia rats, and decrease FAS activity and SREBP-1c mRNA expression.

Impact of high temperature stress on floret fertility and individual grain weight of grain sorghum: sensitive stages and thresholds for temperature and duration

PubMed Central

Prasad, P. V. V.; Djanaguiraman, Maduraimuthu; Perumal, Ramasamy; Ciampitti, Ignacio A.

2015-01-01

Sorghum [Sorghum bicolor (L.) Moench] yield formation is severely affected by high temperature stress during reproductive stages. This study pursues to (i) identify the growth stage(s) most sensitive to high temperature stress during reproductive development, (ii) determine threshold temperature and duration of high temperature stress that decreases floret fertility and individual grain weight, and (iii) quantify impact of high daytime temperature during floret development, flowering and grain filling on reproductive traits and grain yield under field conditions. Periods between 10 and 5 d before anthesis; and between 5 d before- and 5 d after-anthesis were most sensitive to high temperatures causing maximum decreases in floret fertility. Mean daily temperatures >25°C quadratically decreased floret fertility (reaching 0% at 37°C) when imposed at the start of panicle emergence. Temperatures ranging from 25 to 37°C quadratically decreased individual grain weight when imposed at the start of grain filling. Both floret fertility and individual grain weights decreased quadratically with increasing duration (0–35 d or 49 d during floret development or grain filling stage, respectively) of high temperature stress. In field conditions, imposition of temperature stress (using heat tents) during floret development or grain filling stage also decreased floret fertility, individual grain weight, and grain weight per panicle. PMID:26500664

Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis

PubMed Central

Durruty, Ignacio; Aguirrezábal, Luis A. N.; Echarte, María M.

2016-01-01

Grain growth and oil biosynthesis are complex processes that involve various enzymes placed in different sub-cellular compartments of the grain. In order to understand the mechanisms controlling grain weight and composition, we need mathematical models capable of simulating the dynamic behavior of the main components of the grain during the grain filling stage. In this paper, we present a non-structured mechanistic kinetic model developed for sunflower grains. The model was first calibrated for sunflower hybrid ACA855. The calibrated model was able to predict the theoretical amount of carbohydrate equivalents allocated to the grain, grain growth and the dynamics of the oil and non-oil fraction, while considering maintenance requirements and leaf senescence. Incorporating into the model the serial-parallel nature of fatty acid biosynthesis permitted a good representation of the kinetics of palmitic, stearic, oleic, and linoleic acids production. A sensitivity analysis showed that the relative influence of input parameters changed along grain development. Grain growth was mostly affected by the specific growth parameter (μ′) while fatty acid composition strongly depended on their own maximum specific rate parameters. The model was successfully applied to two additional hybrids (MG2 and DK3820). The proposed model can be the first building block toward the development of a more sophisticated model, capable of predicting the effects of environmental conditions on grain weight and composition, in a comprehensive and quantitative way. PMID:27242809

Effect of environment and variety on the relationships of wheat grain physical and chemical characteristics with ethanol yield.

PubMed

Awole, Kedija D; Kettlewell, Peter S; Hare, Martin C; Agu, Reginald C; Brosnan, James M; Bringhurst, Thomas A

2012-02-01

Following the Renewable Transport Fuel Obligation (RTFO), there is an increasing demand for wheat grain for liquid biofuel in the UK. In order to enhance productivity of the bioethanol industry, good quality wheat must be used. A total of 84 grain samples comprising 14 varieties collected from 11 sites in two harvest years were analysed for a range of grain quality parameters and ethanol yield (EY). The grain quality parameters studied were starch and protein concentration, specific weight, grain density, packing efficiency, thousand-grain weight (TGW), grain length, width, length/width ratio and hardness index. Regression analysis was used to establish the relationships between grain quality parameters and EY. Apart from grain length and density, all grain parameters had significant relationships with EY. In the order of importance, protein concentration, TGW, packing efficiency and specific weight showed good relationships with EY. All other parameters, including starch concentration, showed a poor correlation with EY. EY and the relationship with the grain parameters were affected more by environment than by variety. Some sites gave consistently higher EY than others. When site and variety were considered with TGW and protein, a good prediction of EY could be made (variance accounted for = 87%). Combining TGW and protein concentration could be a better indicator of EY than the current practice of specific weight and protein. Copyright © 2011 Society of Chemical Industry.

In situ grain fracture mechanics during uniaxial compaction of granular solids

NASA Astrophysics Data System (ADS)

Hurley, R. C.; Lind, J.; Pagan, D. C.; Akin, M. C.; Herbold, E. B.

2018-03-01

Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

Alignment of Irregular Grains by Mechanical Torques

NASA Astrophysics Data System (ADS)

Hoang, Thiem; Cho, Jungyeon; Lazarian, A.

2018-01-01

We study the alignment of irregular dust grains by mechanical torques due to the drift of grains through the ambient gas. We first calculate mechanical alignment torques (MATs) resulting from specular reflection of gas atoms for seven irregular shapes: one shape of mirror symmetry, three highly irregular shapes (HIS), and three weakly irregular shapes (WIS). We find that the grain with mirror symmetry experiences negligible MATs due to its mirror-symmetry geometry. Three HIS can produce strong MATs, which exhibit some generic properties as radiative torques (RATs), while three WIS produce less efficient MATs. We then study grain alignment by MATs for the different angles between the drift velocity and the ambient magnetic field, for paramagnetic and superparamagnetic grains assuming efficient internal relaxation. We find that for HIS grains, MATs can align subsonically drifting grains in the same way as RATs, with low-J and high-J attractors. For supersonic drift, MATs can align grains with low-J and high-J attractors, analogous to RAT alignment by anisotropic radiation. We also show that the joint action of MATs and magnetic torques in grains with iron inclusions can lead to perfect MAT alignment. Our results point out the potential importance of MAT alignment for HIS grains predicted by the analytical model of Lazarian & Hoang, although more theoretical and observational studies are required due to uncertainty in the shape of interstellar grains. We outline astrophysical environments where MAT alignment is potentially important.

NEW CONSTRAINTS ON THE ABUNDANCES OF SILICATE AND OXIDE STARDUST FROM SUPERNOVAE IN THE ACFER 094 METEORITE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoppe, Peter; Leitner, Jan; Kodolányi, János, E-mail: peter.hoppe@mpic.de

2015-07-20

We studied about 5000 μm{sup 2} of fine-grained matrix material in the Acfer 094 meteorite by high-resolution (nominal 50 nm) NanoSIMS ion imaging for the presence of O-rich presolar (stardust) grains. This approach permits identifying presolar grains down to <100 nm in size, compared to >150 nm in lower-resolution (nominal 100 nm) ion imaging surveys. The number density of identified presolar grains is a about a factor of two to three higher than what was found by lower-resolution ion imaging studies. The abundances of grains of O isotope Group 3 and 4 are higher than previously found. None of themore » presolar grains shows the strong enrichments in {sup 16}O expected from model predictions for the majority of supernova (SN) grains. Other potential O-rich SN grains, the Group 4 and some of the Group 3 grains, make up 33% by number and 19% by mass. This is clearly higher than the ∼10% (by number) inferred before and the 5% (by mass) estimated by a model for stellar dust in the interstellar medium. Our work shows that O-rich SN grains might be more abundant among the population of presolar grains in primitive solar system materials than currently thought, even without the {sup 16}O-rich grains as predominantly expected from SN models.« less

Fabrication and characterization of controllable grain boundary arrays in solution-processed small molecule organic semiconductor films

NASA Astrophysics Data System (ADS)

Wo, Songtao; Headrick, Randall L.; Anthony, John E.

2012-04-01

We have produced solution-processed thin films of 6,13-bis(tri-isopropyl-silylethynyl) pentacene with grain sizes from a few micrometers up to millimeter scale by lateral crystallization from a rectangular stylus. Grains are oriented along the crystallization direction, and the grain size transverse to the crystallization direction depends inversely on the writing speed, hence forming a regular array of oriented grain boundaries with controllable spacing. We utilize these controllable arrays to systematically study the role of large-angle grain boundaries in carrier transport and charge trapping in thin film transistors. The effective mobility scales with the grain size, leading to an estimate of the potential drop at individual large-angle grain boundaries of more than 1 volt. This result indicates that the structure of grain boundaries is not molecularly abrupt, which may be a general feature of solution-processed small molecule organic semiconductor thin films, where relatively high energy grain boundaries are typically formed. Transient measurements after switching from positive to negative gate bias or between large and small negative gate bias reveal reversible charge trapping, with time constants on the order of 10 s and trap densities that are correlated with grain boundary density. We suggest that charge diffusion along grain boundaries and other defects is the rate-determining mechanism of the reversible trapping.

7 CFR 800.30 - Foreign commerce grain business.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 7 2013-01-01 2013-01-01 false Foreign commerce grain business. 800.30 Section 800.30... § 800.30 Foreign commerce grain business. “Foreign commerce grain business” is defined as the business of buying grain for sale in foreign commerce or the business of handling, weighing, or transporting...

7 CFR 800.30 - Foreign commerce grain business.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 7 2011-01-01 2011-01-01 false Foreign commerce grain business. 800.30 Section 800.30... § 800.30 Foreign commerce grain business. “Foreign commerce grain business” is defined as the business of buying grain for sale in foreign commerce or the business of handling, weighing, or transporting...

7 CFR 800.30 - Foreign commerce grain business.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 7 2010-01-01 2010-01-01 false Foreign commerce grain business. 800.30 Section 800.30... § 800.30 Foreign commerce grain business. “Foreign commerce grain business” is defined as the business of buying grain for sale in foreign commerce or the business of handling, weighing, or transporting...

In Vitro Bile-Acid-Binding of Whole vs. Pearled Wheat Grain

USDA-ARS?s Scientific Manuscript database

Health benefits of consuming whole grains help reduce the risk of heart disease, stroke and cancer. The USDA Food Guide pyramid and dietary guidelines recommend the consumption of 6-10 oz of grain products daily and one-half of that is desired to be containing whole grains (2005). Whole grains con...

7 CFR 800.30 - Foreign commerce grain business.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 7 2014-01-01 2014-01-01 false Foreign commerce grain business. 800.30 Section 800.30... § 800.30 Foreign commerce grain business. “Foreign commerce grain business” is defined as the business of buying grain for sale in foreign commerce or the business of handling, weighing, or transporting...

7 CFR 800.30 - Foreign commerce grain business.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 7 2012-01-01 2012-01-01 false Foreign commerce grain business. 800.30 Section 800.30... § 800.30 Foreign commerce grain business. “Foreign commerce grain business” is defined as the business of buying grain for sale in foreign commerce or the business of handling, weighing, or transporting...

Genetic Architecture of Grain Chalk in Rice and Interactions with a Low Phytic Acid Locus

USDA-ARS?s Scientific Manuscript database

Grain quality characteristics have a major impact on the value of the harvested rice crop. In addition to grain dimensions which determine rice grain market classes, translucent milled kernels are also important for assuring the highest grain quality and crop value. Over the last several years, ther...

Whole grain gluten-free egg-free pasta

USDA-ARS?s Scientific Manuscript database

The USDA food guide recommends that at least ½ of all the grains eaten should be whole grains. The FDA allows food Health Claim labels for food containing 51% whole grains and 11 g of dietary fiber. This is the only report demonstrating innovative whole grain gluten free, egg free (no chemicals adde...

78 FR 6209 - Safety Zone; Grain-Shipment Vessels, Columbia and Willamette Rivers

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-30

... 1625-AA00 Safety Zone; Grain-Shipment Vessels, Columbia and Willamette Rivers AGENCY: Coast Guard, DHS... temporary safety zone around all inbound and outbound grain-shipment vessels involved in commerce with the Columbia Grain facility on the Willamette River in Portland, OR, the United Grain Corporation facility on...

77 FR 74587 - Safety Zone; Grain-Shipment Vessels, Columbia and Willamette Rivers

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-17

... 1625-AA00 Safety Zone; Grain-Shipment Vessels, Columbia and Willamette Rivers AGENCY: Coast Guard, DHS... inbound and outbound grain-shipment vessels involved in commerce with the Columbia Grain facility on the Willamette River in Portland, OR, and the United Grain Corporation facility on the Columbia River in...

Grain Cluster Microstructure and Grain Boundary Character Distribution in Alloy 690

NASA Astrophysics Data System (ADS)

Xia, Shuang; Zhou, Bangxin; Chen, Wenjue

2009-12-01

The effects of thermal-mechanical processing (TMP) on microstructure evolution during recrystallization and grain boundary character distribution (GBCD) in aged Alloy 690 were investigated by the electron backscatter diffraction (EBSD) technique and optical microscopy. The original grain boundaries of the deformed microstructure did not play an important role in the manipulation of the proportion of the Σ3 n ( n = 1, 2, 3…) type boundaries. Instead, the grain cluster formed by multiple twinning starting from a single nucleus during recrystallization was the key microstructural feature affecting the GBCD. All of the grains in this kind of cluster had Σ3 n mutual misorientations regardless of whether they were adjacent. A large grain cluster containing 91 grains was found in the sample after a small-strain (5 pct) and a high-temperature (1100 °C) recrystallization anneal, and twin relationships up to the ninth generation (Σ39) were found in this cluster. The ratio of cluster size over grain size (including all types of boundaries as defining individual grains) dictated the proportion of Σ3 n boundaries.

Deformation Twins in Nanocrystalline Body-Centered Cubic Mo as Predicted by Molecular Dynamics Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Tonks; Bulent biner; Yongfeng Zhang

2012-10-01

This work studies deformation twins in nanocrystalline body-centered cubic Mo, including the nucleation and growth mechanisms as well as their effects on ductility, through molecular dynamics simulations. The deformation processes of nanocrystalline Mo are simulated using a columnar grain model with three different orientations. The deformation mechanisms identified, including dislocation slip, grain-boundary-mediated plasticity, deformation twins and martensitic transformation, are in agreement with previous studies. In (1 1 0) columnar grains, the deformation is dominated by twinning, which nucleates primarily from the grain boundaries by successive emission of twinning partials and thickens by jog nucleation in the grain interiors. Upon arrestmore » by a grain boundary, the twin may either produce continuous plastic strain across the grain boundary by activating compatible twinning/slip systems or result in intergranular failure in the absence of compatible twinning/slip systems in the neighboring grain. Multiple twinning systems can be activated in the same grain, and the competition between them favors those capable of producing continuous deformation across the grain boundary.« less

The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

NASA Astrophysics Data System (ADS)

Atapour, Hadi; Mortazavi, Ali

2018-04-01

The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

Influence of CdTe Deposition Temperature and Window Thickness on CdTe Grain Size and Lifetime After CdCl 2 Recrystallization

DOE PAGES

Amarasinghe, Mahisha; Colegrove, Eric; Moutinho, Helio; ...

2018-01-23

Grain structure influences both transport and recombination in CdTe solar cells. Larger grains generally are obtained with higher deposition temperatures, but commercially it is important to avoid softening soda-lime glass. Furthermore, depositing at lower temperatures can enable different substrates and reduced cost in the future. We examine how initial deposition temperatures and morphology influence grain size and lifetime after CdCl 2 recrystallization. Techniques are developed to estimate grain distribution quickly with low-cost optical microscopy, which compares well with electron backscatter diffraction data providing corroborative assessments of exposed CdTe grain structures. Average grain size increases as a function of CdCl 2more » temperature. For lower temperature close-spaced sublimation CdTe depositions, there can be more stress and grain segregation during recrystallization. However, the resulting lifetimes and grain sizes are similar to high-temperature CdTe depositions. The grain structures and lifetimes are largely independent of the presence and/or interdiffusion of Se at the interface, before and after the CdCl 2 treatment.« less

DUST DYNAMICS IN PROTOPLANETARY DISK WINDS DRIVEN BY MAGNETOROTATIONAL TURBULENCE: A MECHANISM FOR FLOATING DUST GRAINS WITH CHARACTERISTIC SIZES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyake, Tomoya; Suzuki, Takeru K.; Inutsuka, Shu-ichiro, E-mail: miyake.tomoya@e.mbox.nagoya-u.ac.jp, E-mail: stakeru@nagoya-u.jp

We investigate the dynamics of dust grains of various sizes in protoplanetary disk winds driven by magnetorotational turbulence, by simulating the time evolution of the dust grain distribution in the vertical direction. Small dust grains, which are well-coupled to the gas, are dragged upward with the upflowing gas, while large grains remain near the midplane of a disk. Intermediate-size grains float near the sonic point of the disk wind located at several scale heights from the midplane, where the grains are loosely coupled to the background gas. For the minimum mass solar nebula at 1 au, dust grains with sizemore » of 25–45 μm float around 4 scale heights from the midplane. Considering the dependence on the distance from the central star, smaller-size grains remain only in an outer region of the disk, while larger-size grains are distributed in a broader region. We also discuss the implications of our result for observations of dusty material around young stellar objects.« less

Influence of CdTe Deposition Temperature and Window Thickness on CdTe Grain Size and Lifetime After CdCl 2 Recrystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amarasinghe, Mahisha; Colegrove, Eric; Moutinho, Helio

Grain structure influences both transport and recombination in CdTe solar cells. Larger grains generally are obtained with higher deposition temperatures, but commercially it is important to avoid softening soda-lime glass. Furthermore, depositing at lower temperatures can enable different substrates and reduced cost in the future. We examine how initial deposition temperatures and morphology influence grain size and lifetime after CdCl 2 recrystallization. Techniques are developed to estimate grain distribution quickly with low-cost optical microscopy, which compares well with electron backscatter diffraction data providing corroborative assessments of exposed CdTe grain structures. Average grain size increases as a function of CdCl 2more » temperature. For lower temperature close-spaced sublimation CdTe depositions, there can be more stress and grain segregation during recrystallization. However, the resulting lifetimes and grain sizes are similar to high-temperature CdTe depositions. The grain structures and lifetimes are largely independent of the presence and/or interdiffusion of Se at the interface, before and after the CdCl 2 treatment.« less

Landau-Lifshitz-Bloch equation for exchange-coupled grains

NASA Astrophysics Data System (ADS)

Vogler, Christoph; Abert, Claas; Bruckner, Florian; Suess, Dieter

2014-12-01

Heat-assisted recording is a promising technique to further increase the storage density in hard disks. Multilayer recording grains with graded Curie temperature is discussed to further assist the write process. Describing the correct magnetization dynamics of these grains, from room temperature to far above the Curie point, during a write process is required for the calculation of bit error rates. We present a coarse-grained approach based on the Landau-Lifshitz-Bloch (LLB) equation to model exchange-coupled grains with low computational effort. The required temperature-dependent material properties such as the zero-field equilibrium magnetization as well as the parallel and normal susceptibilities are obtained by atomistic Landau-Lifshitz-Gilbert simulations. Each grain is described with one magnetization vector. In order to mimic the atomistic exchange interaction between the grains a special treatment of the exchange field in the coarse-grained approach is presented. With the coarse-grained LLB model the switching probability of a recording grain consisting of two layers with graded Curie temperature is investigated in detail by calculating phase diagrams for different applied heat pulses and external magnetic fields.

Jamming of Monodisperse Cylindrical Grains in Featureless Vertical Channels

NASA Astrophysics Data System (ADS)

Friedl, Nicholas; Baxter, G. William

2014-03-01

We study jamming of low aspect-ratio cylindrical Delrin grains falling through a featureless vertical channel under the influence of gravity. These grains have an aspect-ratio less than two (H/D < 2) and resemble aspirin tablets, 35mm film canisters, poker chips, or coins. Monodisperse grains are allowed to fall under the influence of gravity through a uniform channel of square cross-section where the channel width is greater than the grain size and constant along the length of the channel. No combination of grain heights and diameters is equal to the channel width. Collections of grains sometimes form jams, stable structures in which the grains are supported by the channel walls and not by grains or walls beneath them. The probability of a jam occurring and the jam's strength are influenced by the grain dimensions and channel width. We will present experimental measurements of the jamming probability and jam strength and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College.

Bioactive components and functional properties of biologically activated cereal grains: A bibliographic review.

PubMed

Singh, Arashdeep; Sharma, Savita

2017-09-22

Whole grains provide energy, nutrients, fibers, and bioactive compounds that may synergistically contribute to their protective effects. A wide range of these compounds is affected by germination. While some compounds, such as β-glucans are degraded, others, like antioxidants and total phenolics are increased by means of biological activation of grains. The water and oil absorption capacity as well as emulsion and foaming capacity of biologically activated grains are also improved. Application of biological activation of grains is of emerging interest, which may significantly enhance the nutritional, functional, and bioactive content of grains, as well as improve palatability of grain foods in a natural way. Therefore, biological activation of cereals can be a way to produce food grains enriched with health-promoting compounds and enhanced functional attributes.

The balance between keystone clustering and bed roughness in experimental step-pool stabilization

NASA Astrophysics Data System (ADS)

Johnson, J. P.

2016-12-01

Predicting how mountain channels will respond to environmental perturbations such as floods requires an improved quantitative understanding of morphodynamic feedbacks among bed topography, surface grain size and sediment sorting. In boulder-rich gravel streams, transport and sorting often lead to the development of step pool morphologies, which are expressed both in bed topography and coarse grain clustering. Bed stability is difficult to measure, and is sometimes inferred from the presence of step pools. I use scaled flume experiments to explore feedbacks among surface grain sizes, coarse grain clustering, bed roughness and hydraulic roughness during progressive bed stabilization and over a range of sediment transport rates. While grain clusters are sometimes identified by subjective interpretation, I quantify the degree of coarse surface grain clustering using spatial statistics, including a novel normalization of Ripley's K function. This approach is objective and provides information on the strength of clustering over a range of length scales. Flume experiments start with an initial bed surface with a broad grain size distribution and spatially random positions. Flow causes the bed surface to progressively stabilize in response to erosion, surface coarsening, roughening and grain reorganization. At 95% confidence, many but not all beds stabilized with coarse grains becoming more clustered than complete spatial randomness (CSR). I observe a tradeoff between topographic roughness and clustering. Beds that stabilized with higher degrees of coarse-grain clustering were topographically smoother, and vice-versa. Initial conditions influenced the degree of clustering at stability: Beds that happened to have fewer initial coarse grains had more coarse grain reorganization during stabilization, leading to more clustering. Finally, regressions demonstrate that clustering statistics actually predict hydraulic roughness significantly better than does D84 (the size at which 84% of grains are smaller). In the experimental data, the spatial organization of surface grains is a stronger control on flow characteristics than the size of surface grains.

Dislocation creep accommodated Grain Boundary Sliding: A high strain rate/low temperature deformation mechanism in calcite ultramylonites

NASA Astrophysics Data System (ADS)

Rogowitz, Anna; Grasemann, Bernhard

2014-05-01

Grain boundary sliding (GBS) is an important grain size sensitive deformation mechanism that is often associated with extreme strain localization and superplasticity. Another mechanism has to operate simultaneously to GBS in order to prevent overlaps and voids between sliding grains. One of the most common accommodating mechanisms is diffusional creep but, recently, dislocation creep has been reported to operate simultaneous to GBS. Due to the formation of a flanking structure in nearly pure calcite marble on Syros (Cyclades, Greece) at lower greenschist facies conditions, an extremely fine grained ultramylonite developed. The microstructure of the layer is characterized by (1) calcite grains with an average grain size of 3.6 µm (developed by low temperature/high strain rate grain boundary migration recrystallization, BLG), (2) grain boundary triple junctions with nearly 120° angles and (3) small cavities preferentially located at triple junctions and at grain boundaries in extension. These features suggest that the dominant deformation mechanism was GBS. In order to get more information on the accommodation mechanism detailed microstructural and textural analyses have been performed on a FEI Quanta 3D FEG instrument equipped with an EDAX Digiview IV EBSD camera. The misorientation distribution curves for correlated and uncorrelated grains follow almost perfect the calculated theoretical curve for a random distribution, which is typical for polycrystalline material deformed by GBS. However, the crystallographic preferred orientation indicates that dislocation creep might have operated simultaneously. We also report Zener-Stroh cracks resulting from dislocation pile up, indicating that dislocation movement was active. We, therefore, conclude that the dominant deformation mechanism was dislocation creep accommodated grain boundary sliding. This is consistent with the observed grain size range that plots at the field boundary between grain size insensitive and grain size sensitive creep, in a deformation mechanism map for calcite.

Stellar Origin of {sup 15}N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.

We report C, N, and Si isotopic data for 59 highly {sup 13}C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 {sup 15}N-rich ({sup 14}N/{sup 15}N ≤ solar) AB grains, and their Mg–Al, S, and Ca–Ti isotope data when available. These 37 grains are enriched in {sup 13}C, {sup 15}N, and {sup 26}Al with the PNGs showing more extreme enhancements. The {sup 15}N-rich AB grains show systematically higher {sup 26}Al and {sup 30}Si excesses than the {sup 14}N-rich AB grains. Thus, we propose to divide the AB grains into groupsmore » 1 ({sup 14}N/{sup 15}N < solar) and 2 ({sup 14}N/{sup 15}N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found {sup 32}S and/or {sup 50}Ti enhancements. Interestingly, one AB1 grain had the largest {sup 32}S and {sup 50}Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the {sup 32}S excess and thus the initial presence of radiogenic {sup 32}Si ( t {sub 1/2} = 153 years). More importantly, we found that the {sup 15}N and {sup 26}Al excesses of AB1 grains form a trend that extends to the region in the N–Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.« less

Recent Uptrend in Whole-Grain Intake Is Absent for Low-Income Adolescents, National Health and Nutrition Examination Survey, 2005–2012

PubMed Central

Leung, Cindy W.; Leak, Tashara M.; Laraia, Barbara A.

2017-01-01

Introduction Whole-grain consumption reduces risk of chronic disease, yet adolescents consume suboptimal amounts. It is unclear whether trends in consumption of whole grains have been positive among adolescents, and research assessing disparities by socioeconomic status is limited. The objective of our study was to evaluate recent trends in whole-grain consumption by US adolescents. Methods We examined data on 3,265 adolescents aged 13 to18 years from the National Health and Nutrition Examination Survey (NHANES) 2005–2012. Intake of whole and refined grains was analyzed by using generalized linear models, and odds of no whole-grain intake were examined with logistic regression, adjusting for socioeconomic and demographic factors. We evaluated trends and examined heterogeneity of trends with respect to annual household income. Results Daily whole-grain consumption among adolescents increased overall by about a quarter-ounce–equivalent per day (oz-eq/d) (P trend <.001). We found a significant relationship between whole-grain intake and income. Daily whole grains (recommended as ≥3 oz-eq/d), increased (0.6 to 1.0 oz-eq/d) among high-income adolescents (P trend < .001) but remained at 0.5 oz-eq/d for low-income adolescents. The ratio of whole grains to total grains (recommended to be at least 50%) rose from 7.6% to 14.2% for high-income adolescents (P trend < .001), with no significant trend for the low-income group. Consumption of refined grains did not change. Odds of having no whole grains trended downward, but only for the high-income adolescents (P trend = .01). Conclusion These data show significant (albeit modest) trends toward increased intake of whole grains among high-income adolescents nationwide that are absent among low-income peers. Future interventions and policies should address barriers to whole-grain consumption among this vulnerable group. PMID:28682743

Mechanisms of the effects of grains on insulin and glucose responses.

PubMed

Hallfrisch, J; Facn; Behall, K M

2000-06-01

Consumption of a number of grains and grain extracts has been reported to control or improve glucose tolerance and reduce insulin resistance. The inability of the body to maintain normal glucose levels or to require excessive levels of insulin to do so has been called glucose intolerance, impaired glucose tolerance and insulin resistance. These conditions are associated with obesity and may be preliminary steps in the progression to type 2 diabetes mellitus. Although dietary goals recommend the consumption of three servings of whole grains per day, average consumption in the United States is less than one serving per day. There are a number of mechanisms by which grains may improve glucose metabolism and delay or prevent the progression of impaired glucose tolerance to insulin resistance and diabetes. These mechanisms are related to the physical properties and structure of grains. The composition of the grain, including particle size, amount and type of fiber, viscosity, amylose and amylopectin content all affect the metabolism of carbohydrates from grains. Increasing whole grain intake in the population can result in improved glucose metabolism and delay or reduce the risk of developing type 2 diabetes mellitus. Whole grains can provide a substantial contribution to the improvement of the diets of Americans. A number of whole grain foods and grain fiber sources are beneficial in reduction of insulin resistance and improvement in glucose tolerance. Form, amount and method of cooking of these foods as well as the health characteristics, age and gender of the group of subjects studied are all important factors in the effectiveness of the foods in altering these responses. Dietary recommendations of health organizations suggest consumption of three servings a day of whole grain foods; however, Americans generally fall below this standard. Recent research using various grains and grain products effective in improving insulin resistance or lowering glycemic index will be discussed below by possible mechanisms of action.

Recent Uptrend in Whole-Grain Intake Is Absent for Low-Income Adolescents, National Health and Nutrition Examination Survey, 2005-2012.

PubMed

Tester, June M; Leung, Cindy W; Leak, Tashara M; Laraia, Barbara A

2017-07-06

Whole-grain consumption reduces risk of chronic disease, yet adolescents consume suboptimal amounts. It is unclear whether trends in consumption of whole grains have been positive among adolescents, and research assessing disparities by socioeconomic status is limited. The objective of our study was to evaluate recent trends in whole-grain consumption by US adolescents. We examined data on 3,265 adolescents aged 13 to18 years from the National Health and Nutrition Examination Survey (NHANES) 2005-2012. Intake of whole and refined grains was analyzed by using generalized linear models, and odds of no whole-grain intake were examined with logistic regression, adjusting for socioeconomic and demographic factors. We evaluated trends and examined heterogeneity of trends with respect to annual household income. Daily whole-grain consumption among adolescents increased overall by about a quarter-ounce-equivalent per day (oz-eq/d) (P trend <.001). We found a significant relationship between whole-grain intake and income. Daily whole grains (recommended as ≥3 oz-eq/d), increased (0.6 to 1.0 oz-eq/d) among high-income adolescents (P trend < .001) but remained at 0.5 oz-eq/d for low-income adolescents. The ratio of whole grains to total grains (recommended to be at least 50%) rose from 7.6% to 14.2% for high-income adolescents (P trend < .001), with no significant trend for the low-income group. Consumption of refined grains did not change. Odds of having no whole grains trended downward, but only for the high-income adolescents (P trend = .01). These data show significant (albeit modest) trends toward increased intake of whole grains among high-income adolescents nationwide that are absent among low-income peers. Future interventions and policies should address barriers to whole-grain consumption among this vulnerable group.

Sand-grain micromorphology used as a sediment-source indicator for Kharga Depression dunes (Western Desert, S Egypt)

NASA Astrophysics Data System (ADS)

Woronko, B.; Dłużewski, M.; Woronko, D.

2017-12-01

Roundness and surface-feature characteristics of sand grains collected from two dune ridges in Kharga Depression (southern Egypt) were tested for potential use as source-to-sink indicators of dunes movement. Grain examination was accommodated through Scanning Electron Microscope (SEM) analysis. Five grain types were distinguished: A) fresh; B) sheet precipitated with ;raindrop; structures; C) platy precipitated; D) broken; and E) with chemically etched surfaces-each type diagnostic of a specific geomorphic inheritance. Regarding the level of sphericity, these grains were subdivided into nine roundness classes (0.1-0.9), where angular grains are marked by 0.1 and very well-rounded grains by 0.9. Significant roundness and grain-type surface variations are observed both along dune ridges and between them. Poorly and medium-rounded grain populations dominate, along with sheet-precipitated grains. The contribution of well- and very well-rounded grains is low. The northern part of both eastern and western dune ridges is characterized by grains that represent high-energy aqueous environments with well-rounded grains, whereas platy precipitated grains with a lower level of roundness are concentrated in the middle part of the dune ridges. The southern part of the Kharga Depression is again characterized by sheet-precipitated grains. Our results indicate that the northern part of dune ridges in the Kharga Depression is mainly built of sands that originate from beyond the depression (e.g., Ghard Abu-Maharik) and the weathered deposits of the Nubian and Moghra Sandstones. The dunes in central and southern part of the Kharga Depression also derive sand from a local depression bottom comprised of playa and fluvial deposits. The growing importance of the local sand source may be explained by the lowering of the local groundwater table, which resulted in playa drying. This groundwater loss resulted in the degradation of the vegetation cover, facilitating an increase in wind entrainment of playa sediments.

Longitudinal analysis of pulmonary dysfunction in the initial years of employment in the grain industry.

PubMed

Olfert, S M; Pahwa, P; Dosman, J A

2005-11-01

The negative health effects of exposure to grain dust have previously been examined, but few studies have observed the effects on newly hired employees. Young grain workers are of interest because changes in pulmonary function may occur after a short duration of employment, and because older grain workers may represent a survivor population. The New Grain Workers Study (NGWS), a longitudinal study of 299 newly hired male grain industry workers, was conducted between 1980 and 1985. The objectives were to determine the effects of employment in the grain industry on pulmonary function. Pre-employment physical examinations and pulmonary function tests were conducted on subjects at the Division of Respiratory Medicine, Department of Medicine, Royal University Hospital, University of Saskatchewan. The Grain Dust Medical Surveillance Program (GDMSP) was a Labour Canada program that began in 1978. All subjects were grain workers employed in the grain industry in Saskatchewan. All subjects completed a respiratory symptoms questionnaire and underwent pulmonary function testing. Baseline observations were recorded every three years between 1978 and 1993. Data were available on 2184 grain workers. Generalized estimating equations were used to fit marginal and transitional multivariable regression models to determine the effects of grain dust exposure on pulmonary function. Marginal and transitional models were then compared. Height, exposure weeks, and previous FVC were predictive of FVC in the NGWS, while exposure weeks and previous FEV1 were predictive of FEV1. These models, as well as a transitional regression model built using the GDMSP data, were used to compute predicted mean annual decline inpulmonary function. Non-smoking grain workers in the NGWS had the highest pulmonary function test values, but also had the greatest predicted annual decline in pulmonary function. Ever-smoking grain workers in the GDMSP had the lowest pulmonary function test values. Non-smoking grain workers in the GDMSP had the least predicted annual decline in pulmonary function.

The Relationship Between Microscopic Grain Surface Structure and the Dynamic Capillary-Driven Advance of Water Films over Individual Dry Natural Sand Grains

NASA Astrophysics Data System (ADS)

Kibbey, T. C. G.; Adegbule, A.; Yan, S.

2017-12-01

The movement of nonvolatile solutes in unsaturated porous media at low water contents depends on transport in surface-associated water films. The focus of the work described here was on studying solute movement in water films advancing by capillary forces over initially-dry grain surfaces, to understand how microscopic surface roughness features influence the initial velocity of water film advance. For this work, water containing a non-adsorbing conservative tracer was used to track the movement of advancing water films. A stainless steel capillary tube connected to an external reservoir a fixed distance below the grain surface was used to transmit solution to the grain surface under negative pressure (positive capillary pressure), consistent with conditions that might be expected in the unsaturated zone. The small internal diameter of the capillary prevents solution from draining out of the capillary back into the reservoir. When the capillary is contacted with a grain surface, capillary forces that result from contact between the fluid and the rough grain surface cause water films to wick across the grain surface. Multiple experiments were conducted on the same grain, rotating the grain and varying the capillary contact point around the circumference of the grain. Imaging was conducted at fixed intervals using an automated Extended Depth of Field (EDF) imaging system, and images were analyzed to determine initial velocity. Grain surfaces were then characterized through scanning electron microscope (SEM) imaging, using a hybrid stereoscopic reconstruction method designed to extract maximum detail in creating elevation maps of geologic surfaces from tilted pairs of SEM images. The resulting elevation maps were used to relate surface roughness profiles around the grain with initial velocities. Results suggest that velocity varies significant with contact point around an individual grain, and correlates quantitatively with the local grain surface structure. Preliminary simulation results will also be discussed.

Mechanical Properties of a Superalloy Disk with a Dual Grain Structure

NASA Technical Reports Server (NTRS)

Gayda, John; Gabb, Timothy; Kantzos, Peter

2003-01-01

Mechanical properties from an advanced, nickel-base superalloy disk, with a dual grain structure consisting of a fine grain bore and coarse grain rim, were evaluated. The dual grain structure was produced using NASA's low cost Dual Microstructure Heat Treatment (DMHT) process. The results showed the DMHT disk to have a high strength, fatigue resistant bore comparable to a subsolvus (fine grain) heat treated disk, and a creep resistant rim comparable to a supersolvus (coarse grain) heat treated disk. Additional work on subsolvus solutioning before or after the DMHT conversion appears to be a viable avenue for further improvement in disk properties.

Cyclic Spin Testing of Superalloy Disks With a Dual Grain Microstructure

NASA Technical Reports Server (NTRS)

Gayda, John; Kantzos, Pete

2005-01-01

An aggressive cyclic spin test program was run to verify the reliability of superalloy disks with a dual grain structure, fine grain bore and coarse grain rim, utilizing a disk design with web holes bisecting the grain size transition zone. Results of these tests were compared with conventional disks with uniform grain structures. Analysis of the test results indicated the cyclic performance of disks with a dual grain structure could be estimated to a level of accuracy which does not appear to prohibit the use of this technology in advanced gas turbine engines, although further refinement of lifing methodology is clearly warranted.

Grain Size Threshold for Enhanced Irradiation Resistance in Nanocrystalline and Ultrafine Tungsten

DOE PAGES

El Atwani, Osman; Hinks, Jonathan; Greaves, Graeme; ...

2017-02-21

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess ~10–20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency.

Healthy grocery shopping

MedlinePlus

... BREADS AND GRAINS Choose healthy breads, cereals, and pasta, such as: Whole-grain breads and rolls (read ... per serving.) Whole-wheat or other whole-grain pasta. Other grains such as millet, quinoa, amaranth, and ...

An atypical bHLH protein encoded by POSITIVE REGULATOR OF GRAIN LENGTH 2 is involved in controlling grain length and weight of rice through interaction with a typical bHLH protein APG.

PubMed

Heang, Dany; Sassa, Hidenori

2012-06-01

Grain size is an important yield component in rice, however, genes controlling the trait remain poorly understood. Previously, we have shown that an antagonistic pair of basic helix-loop-helix (bHLH) proteins, POSITIVE REGULATOR OF GRAIN LENGTH 1 (PGL1) and ANTAGONIST OF PGL1 (APG), is involved in controlling rice grain length. Here, we report the involvement of another atypical bHLH protein gene, POSITIVE REGULATOR OF GRAIN LENGTH 2 (PGL2), in the regulation of rice grain length. Over-expression of PGL2 in the lemma/palea increased grain length and weight in correlation with the level of transgene expression. Observation of the inner epidermal cells of lemma of PGL2-overexpressing lines revealed that the long grain size is caused by an increase in cell length. PGL2 interacts with a typical bHLH protein APG, a negative regulator of rice grain length and weight, in vitro and in vivo. It was reported that overexpression of BU1 (BRASSINOSTEROID UPREGULATED 1), the closest homolog of PGL2, caused an increase in grain length. However, we detected no interaction between BU1 and APG. These findings suggest that PGL2 and PGL1 redundantly suppress the function of APG by forming heterodimers to positively regulate the rice grain length, while the pathway through which BU1, the closest homolog of PGL2, controls grain length is independent of APG.

An atypical bHLH protein encoded by POSITIVE REGULATOR OF GRAIN LENGTH 2 is involved in controlling grain length and weight of rice through interaction with a typical bHLH protein APG

PubMed Central

Heang, Dany; Sassa, Hidenori

2012-01-01

Grain size is an important yield component in rice, however, genes controlling the trait remain poorly understood. Previously, we have shown that an antagonistic pair of basic helix-loop-helix (bHLH) proteins, POSITIVE REGULATOR OF GRAIN LENGTH 1 (PGL1) and ANTAGONIST OF PGL1 (APG), is involved in controlling rice grain length. Here, we report the involvement of another atypical bHLH protein gene, POSITIVE REGULATOR OF GRAIN LENGTH 2 (PGL2), in the regulation of rice grain length. Over-expression of PGL2 in the lemma/palea increased grain length and weight in correlation with the level of transgene expression. Observation of the inner epidermal cells of lemma of PGL2-overexpressing lines revealed that the long grain size is caused by an increase in cell length. PGL2 interacts with a typical bHLH protein APG, a negative regulator of rice grain length and weight, in vitro and in vivo. It was reported that overexpression of BU1 (BRASSINOSTEROID UPREGULATED 1), the closest homolog of PGL2, caused an increase in grain length. However, we detected no interaction between BU1 and APG. These findings suggest that PGL2 and PGL1 redundantly suppress the function of APG by forming heterodimers to positively regulate the rice grain length, while the pathway through which BU1, the closest homolog of PGL2, controls grain length is independent of APG. PMID:23136524

Grain-size dynamics beneath mid-ocean ridges: Implications for permeability and melt extraction.

PubMed

Turner, Andrew J; Katz, Richard F; Behn, Mark D

2015-03-01

Grain size is an important control on mantle viscosity and permeability, but is difficult or impossible to measure in situ. We construct a two-dimensional, single phase model for the steady state mean grain size beneath a mid-ocean ridge. The mantle rheology is modeled as a composite of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a plastic stress limiter. The mean grain size is calculated by the paleowattmeter relationship of Austin and Evans (2007). We investigate the sensitivity of our model to global variations in grain growth exponent, potential temperature, spreading-rate, and mantle hydration. We interpret the mean grain-size field in terms of its permeability to melt transport. The permeability structure due to mean grain size may be approximated as a high permeability region beneath a low permeability region. The transition between high and low permeability regions occurs across a boundary that is steeply inclined toward the ridge axis. We hypothesize that such a permeability structure generated from the variability of the mean grain size may focus melt toward the ridge axis, analogous to Sparks and Parmentier (1991)-type focusing. This focusing may, in turn, constrain the region where significant melt fractions are observed by seismic or magnetotelluric surveys. This interpretation of melt focusing via the grain-size permeability structure is consistent with MT observation of the asthenosphere beneath the East Pacific Rise. The grain-size field beneath MORs can vary over orders of magnitude The grain-size field affects the rheology and permeability of the asthenosphere The grain-size field may focus melt toward the ridge axis.

Genetic diversity of bread wheat genotypes in Iran for some nutritional value and baking quality traits.

PubMed

Amiri, Reza; Sasani, Shahryar; Jalali-Honarmand, Saeid; Rasaei, Ali; Seifolahpour, Behnaz; Bahraminejad, Sohbat

2018-02-01

Genetic variation among 78 irrigated bread wheat genotypes was studied for their nutritional value and baking quality traits as well as some agronomic traits. The experiment was conducted in a randomized complete block design with three replicates under normal and terminal drought stress conditions in Kermanshah, Iran during 2012-2013 cropping season. The results of combined ANOVA indicated highly significant genotypic differences for all traits. All studied traits except grain yield, hectoliter weight and grain fiber content were significantly affected by genotype × environment interaction. Drought stress reduced grain yield, thousand kernel weight, gluten index, grain starch content and hectoliter weight and slightly promoted grain protein and fiber contents, falling number, total gluten and ratio of wet gluten to grain protein content. Grain yield by 31.66% and falling number by 9.20% attained the highest decrease and increase due to drought stress. There were negative and significant correlations among grain yield with grain protein and fiber contents under both conditions. Results of cluster analysis showed that newer genotypes had more grain yield and gluten index than older ones, but instead, they had the lower grain protein and fiber contents. It is thought that wheat breeders have bred cultivars with high grain yield, low protein content, and improved bread-making attributes during last seven decades. While older genotypes indicated significantly higher protein contents, and some of them had higher gluten index. We concluded from this study that it is imperative for breeders to pay more attention to improve qualitative traits coordinated to grain yield.

Reformulation of pizza crust in restaurants may increase whole-grain intake among children.

PubMed

Tritt, Aimee; Reicks, Marla; Marquart, Len

2015-06-01

Whole-grain intake among children is well below recommendations. The purpose of the present study was to test the acceptability and liking of pizza made with whole-grain crust compared with refined-grain crust among children in restaurant and school settings. Plate waste data were collected via observation from child restaurant patrons consuming pizza made with either whole-grain or refined-grain crust. Waste was estimated by trained observers over eight months (August 2012-March 2013). Percentage waste was calculated and compared by crust type. A taste test was conducted with school children who tasted pizza made with whole-grain crust alongside pizza made with refined-grain crust and rated their liking of each product. Liking ratings were compared by crust type. Five Green Mill restaurant (a Midwest US chain) locations and one elementary school in the Minneapolis/St. Paul metropolitan area, Minnesota, USA. Child restaurant patrons (n 394) and school children (n 120, grades 3-5). Children consumed as much of the pizza made with whole-grain crust (42·1 %) as the pizza made with refined-grain crust (44·6 %; P=0·55), based on an average serving size of 350-400 g. Liking ratings for both types of pizza were high (>4·5 of 5) and did not differ by crust type (P=0·47). These positive consumption and liking outcomes indicate that whole-grain pizza crust is well accepted among children in a restaurant setting. The impact on whole-grain intake could be substantial if large, national restaurant chains served pizza made with whole-grain crust.

Charging of Individual Micron-Size Interstellar/Planetary Dust Grains by Secondary Electron Emissions

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2012-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper, we discuss experimental results on dust charging by electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Currently, very limited experimental data are available for charging of individual micron-size dust grains, particularly by low energy electron impact. Available theoretical models based on the Sternglass equation (Sternglass, 1954) are applicable for neutral, planar, and bulk surfaces only. However, charging properties of individual micron-size dust grains are expected to be different from the values measured on bulk materials. Our recent experimental results on individual, positively charged, micron-size lunar dust grains levitated in an electrodynamic balance facility (at NASA-MSFC) indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Here we discuss the complex nature of SEE charging properties of individual micron-size lunar dust grains and silica microspheres.

Plagioclase-Rich Itokawa Grains: Space Weathering, Exposure Ages, and Comparison to Lunar Soil Grains

NASA Technical Reports Server (NTRS)

Keller, L. P.; Berge, E.

2017-01-01

Regolith grains returned by the Hayabusa mission to asteroid 25143 Itokawa provide the only samples currently available to study the interaction of chondritic asteroidal material with the space weathering environment. Several studies have documented the surface alterations observed on the regolith grains, but most of these studies involved olivine because of its abundance. Here we focus on the rarer Itokawa plagioclase grains, in order to allow comparisons between Itokawa and lunar soil plagioclase grains for which an extensive data set exists.

Orientation influence on grain size-effects in ultrafine-grained magnesium

DOE PAGES

Fan, Haidong; Aubry, Sylvie; Arsenlis, A.; ...

2014-11-08

The mechanical behavior of ultrafine-grained magnesium was studied by discrete dislocation dynamics (DDD) simulations. Our results show basal slip yields a strong size effect, while prismatic and pyramidal slips produce a weak one. We developed a new size-strength model that considers dislocation transmission across grain boundaries. Good agreement between this model, current DDD simulations and previous experiments is observed. These results reveal that the grain size effect depends on 3 factors: Peierls stress, dislocation source strength and grain boundary strength.

The Grain Structure of Castings: Some Aspects of Modelling

NASA Technical Reports Server (NTRS)

Hellawell, A.

1995-01-01

The efficacy of the modelling of the solidification of castings is typically tested against observed cooling curves and the final grain structures and sizes. Without thermo solutal convection, equiaxed grain formation is promoted by introduction of heterogeneous substrates into the melt, as grain refiners. With efficient thermo solutal convection, dendrite fragments from the mushy zone can act as an intrinsic source of equiaxed grains and resort to grain refining additions is unnecessary. The mechanisms of dendrite fragmentation and transport of these fragments are briefly considered.

Experimental Study of Dust Grain Charging

NASA Technical Reports Server (NTRS)

Spann, James F; Venturini, Catherine C.; Comfort, Richard H.; Mian, Abbas M.

1999-01-01

The results of an experimental study of the charging mechanisms of micron size dust grains are presented. Individual dust grains are electrodynamically suspended and exposed to an electron beam of known energy and flux, and to far ultraviolet radiation of known wavelength and intensity. Changes in the charge-to-mass ratio of the grain are directly measured as a function of incident beam (electron and/or photon), grain size and composition. Comparisons of our results to theoretical models that predict the grain response are presented.

Physical properties of five grain dust types.

PubMed Central

Parnell, C B; Jones, D D; Rutherford, R D; Goforth, K J

1986-01-01

Physical properties of grain dust derived from five grain types (soybean, rice, corn, wheat, and sorghum) were measured and reported. The grain dusts were obtained from dust collection systems of terminal grain handling facilities and were assumed to be representative of grain dust generated during the handling process. The physical properties reported were as follows: particle size distributions and surface area measurements using a Coulter Counter Model TAII; percent dust fractions less than 100 micron of whole dust; bulk density; particle density; and ash content. PMID:3709482

Stress Distribution During Deformation of Polycrystalline Aluminum by Molecular-Dynamics and Finite-Element Modeling

NASA Technical Reports Server (NTRS)

Yamakov, V.; Saether, E.; Phillips, D.; Glaessgen, E. H.

2004-01-01

In this paper, a multiscale modelling strategy is used to study the effect of grain-boundary sliding on stress localization in a polycrystalline microstructure with an uneven distribution of grain size. The development of the molecular dynamics (MD) analysis used to interrogate idealized grain microstructures with various types of grain boundaries and the multiscale modelling strategies for modelling large systems of grains is discussed. Both molecular-dynamics and finite-element (FE) simulations for idealized polycrystalline models of identical geometry are presented with the purpose of demonstrating the effectiveness of the adapted finite-element method using cohesive zone models to reproduce grain-boundary sliding and its effect on the stress distribution in a polycrystalline metal. The yield properties of the grain-boundary interface, used in the FE simulations, are extracted from a MD simulation on a bicrystal. The models allow for the study of the load transfer between adjacent grains of very different size through grain-boundary sliding during deformation. A large-scale FE simulation of 100 grains of a typical microstructure is then presented to reveal that the stress distribution due to grain-boundary sliding during uniform tensile strain can lead to stress localization of two to three times the background stress, thus suggesting a significant effect on the failure properties of the metal.

Classification of rice grain varieties arranged in scattered and heap fashion using image processing

NASA Astrophysics Data System (ADS)

Bhat, Sudhanva; Panat, Sreedath; N, Arunachalam

2017-03-01

Inspection and classification of food grains is a manual process in many of the food grain processing industries. Automation of such a process is going to be beneficial for industries facing shortage of skilled workforce. Machine Vision techniques are some of the popular approaches for developing such automations. Most of the existing works on the topic deal with identification of the rice variety by analyzing images of well separated and isolated rice grains from which a lot of geometrical features can be extracted. This paper proposes techniques to estimate geometrical parameters from the images of scattered as well as heaped rice grains where the grain boundaries are not clearly identifiable. A methodology based on convexity is proposed to separate touching rice grains in the scattered rice grain images and get their geometrical parameters. And in case of heaped arrangement a Pixel-Distance Contribution Function is defined and is used to get points inside rice grains and then to find the boundary points of rice grains. These points are fit with the equation of an ellipse to estimate their lengths and breadths. The proposed techniques are applied on images of scattered and heaped rice grains of different varieties. It is shown that each variety gives a unique set of results.

Marketing whole grain breads in Canada via food labels.

PubMed

Sumanac, Dunja; Mendelson, Rena; Tarasuk, Valerie

2013-03-01

A recommendation for increased whole grain consumption was released in Canada in 2007 to promote adequate intakes of fibre and magnesium. Since then, a proliferation of 'whole grain' claims on food packaging has been observed, but whole grain labelling is voluntary and unregulated in Canada. Through a detailed survey of bread sold in three supermarkets, this study examined how the presence of front-of-package reference to whole grain relates to (i) the presence and nature of whole grain ingredients, (ii) nutrient content, and (iii) price of the product. Twenty-one percent of breads bore a reference to whole grain on the front-of-package and the front-of-package reference to whole grain was a better predictor of fibre content than any information that could be gleaned from the ingredient list. On average, breads with a whole grain reference were higher in fibre and magnesium and lower in sodium. Mean price did not differ by presence of a whole grain reference, but breads with whole grain labelling were less likely to be low in price. Voluntary nutrition labelling may be targeting a discrete market of health-conscious consumers who are willing to pay premium prices for more healthful options. Copyright © 2012 Elsevier Ltd. All rights reserved.

Chemical and microbiological characterisation of kefir grains.

PubMed

Garrote, G L; Abraham, A G; De Antoni, G L

2001-11-01

Chemical and microbiological composition of four Argentinean kefir grains from different sources as well as characteristics of the corresponding fermented milk were studied. Kefir grains CIDCA AGK1, AGK2 and AGK4 did not show significant differences in their chemical and microbiological composition. In contrast, protein and yeast content of AGK3 was higher than in the other grains. Although grain microflora comprised lactobacilli, lactococcus, acetic acid bacteria and yeast, we found an important difference regarding species. Lactococcus lactis subsp. lactis, Lactobacillus kefir, Lactobacillus plantarum, Acetobacter and Saccharomyces were present in all types of kefir grain. While Leuconostoc mesenteroides was only isolated from grains CIDCA AGK1 and Lactococcus lactis subsp. lactis biovar diacetylactis, Lactobacillus parakefir and Kluyveromyces marxianus were only isolated from CIDCA AGK2 grains. All grains produced acid products with pH between 3.5 and 4.0. The apparent viscosity of AGK1 fermented milk was greater than the product obtained with AGK4. All fermented milks had inhibitory power towards Escherichia coli but AGK1 and AGK2 supernatants were able to halt the bacterial growth for at least 25 h. Grain weight increment in AGK1, AGK2 and AGK3 during growth in milk did not show significant differences. Despite their fermenting activity, AGK4 grains did not increase their weight.

Process-scale modelling of microstructure in direct chill casting of aluminium alloys

NASA Astrophysics Data System (ADS)

Bedel, M.; Heyvaert, L.; Založnik, M.; Combeau, H.; Daloz, D.; Lesoult, G.

2015-06-01

The mechanical properties of an alloy being related to its microstructure, the understanding of the mechanisms responsible for the grain structure formation in direct chill casting is crucial. However, the grain size prediction by modelling is difficult since a variety of multi-scale coupled phenomena have to be considered. Nucleation and growth of the grains are interrelated, and the macroscopic transport phenomena such as the motion of grains and inoculant particles with the flow impact the nucleation-gowth competition. Thus we propose to study the grain size distribution of a 5182 alloy industrial scale slab of 510 mm thickness, both non-inoculated and inoculated with Al-3Ti-1B, for which experimental grain size measurements are available. We use a volume-averaged two-phase multi-scale model that describes nucleation from inoculant particles and grain growth, fully coupled with macroscopic transport phenomena: fluid flow induced by natural convection and solidification shrinkage, heat, mass and solute mass transport, grains and inoculant particles motion. We analyze the effect of liquid and grain motion as the effect of grain morphology on microstructure formation and we show in which extent those phenomena are responsible for the grain size distribution observed experimentally. The effect of the refiner level is also studied.

Health benefits of ancient grains. Comparison among bread made with ancient, heritage and modern grain flours in human cultured cells.

PubMed

Valli, Veronica; Taccari, Annalisa; Di Nunzio, Mattia; Danesi, Francesca; Bordoni, Alessandra

2018-05-01

Nowadays the higher nutritional value of whole grains compared to refined grains is recognized. In the last decade, there has been a renewed interest in the ancient wheat varieties for producing high-value food products with enhanced health benefits. This study compared two ancient grains, two heritage grains, and four modern grains grown in the same agronomic conditions considering not only their chemical characteristics, but also their biological effects. Whole grain flours were obtained and used to make bread. Bread was in vitro digested, the digesta were supplemented to HepG2 cells, and the biological effects of supplementation were evaluated. In addition, cells previously supplemented with the different digested bread types were then exposed to inflammatory agents to evidence possible protective effects of the pre-treatments. Despite the impossibility to discriminate bread made with different grains based on their chemical composition, results herein reported evidence that their supplementation to cultured cells exerts different effects, confirming the potential health benefits of ancient grains. This research represents an advancement for the evaluation of the apparent positive effects of ancient grains and the formulation of cereal-based products with added nutritional value. Copyright © 2018 Elsevier Ltd. All rights reserved.

Morphology and composition of gold in a lateritic profile, Fazenda Pison “Garimpo”, Amazon, Brazil

NASA Astrophysics Data System (ADS)

Larizzatti, J. H.; Oliveira, S. M. B.; Butt, C. R. M.

2008-05-01

This study describes the morphological evolution of gold grains in a lateritic weathering profile in an equatorial rainforest climate. Primary sources of gold are quartz veins associated with shallow granophyric intrusion. Gold grains were found in fresh ore, saprolite, transition zones, ferruginous duricrust, red latosol, and yellow latosol. Irregularly shaped grains predominate, with smaller proportions of dendritic and prismatic forms. Gold grains are weathered in the uppermost 10 m of the regolith. Mean gold grain size is maximum in the duricrust (>125 μm) and decreases progressively upward into the yellow latosol (<90 μm). Voids and corrosion pits appear on grain surfaces, and progressive rounding is observed from the bottom of the profile to the top. Gold grains can be classified as either homogeneous or zoned with respect to their chemical composition. Homogeneous grains contain 2-15% Ag (mean 8.3%). Zoned grains have more variable Ag contents; grain cores have means of approximately 10% or 23% Ag, with Ag-poor zones of approximately 3.7% Ag along internal discontinuities and/or outer rims. Formation of Ag-poor rims is due to preferential depletion of silver. Processes responsible for duricrust formation may preserve some grains as large aggregates, but subsequent transformation into latosol further modifies them.

Grain boundary engineering: fatigue fracture

NASA Astrophysics Data System (ADS)

Das, Arpan

2017-04-01

Grain boundary engineering has revealed significant enhancement of material properties by modifying the populations and connectivity of different types of grain boundaries within the polycrystals. The character and connectivity of grain boundaries in polycrystalline microstructures control the corrosion and mechanical behaviour of materials. A comprehensive review of the previous researches has been carried out to understand this philosophy. Present research thoroughly explores the effect of total strain amplitude on phase transformation, fatigue fracture features, grain size, annealing twinning, different grain connectivity and grain boundary network after strain controlled low cycle fatigue deformation of austenitic stainless steel under ambient temperature. Electron backscatter diffraction technique has been used extensively to investigate the grain boundary characteristics and morphologies. The nominal variation of strain amplitude through cyclic plastic deformation is quantitatively demonstrated completely in connection with the grain boundary microstructure and fractographic features to reveal the mechanism of fatigue fracture of polycrystalline austenite. The extent of boundary modifications has been found to be a function of the number of applied loading cycles and strain amplitudes. It is also investigated that cyclic plasticity induced martensitic transformation strongly influences grain boundary characteristics and modifications of the material's microstructure/microtexture as a function of strain amplitudes. The experimental results presented here suggest a path to grain boundary engineering during fatigue fracture of austenite polycrystals.

Theory of grain alignment in molecular clouds

NASA Technical Reports Server (NTRS)

Roberge, Wayne G.

1993-01-01

Research accomplishments are presented and include the following: (1) mathematical theory of grain alignment; (2) super-paramagnetic alignment of molecular cloud grains; and (3) theory of grain alignment by ambipolar diffusion.

Grain-damage hysteresis and plate tectonic states

NASA Astrophysics Data System (ADS)

Bercovici, David; Ricard, Yanick

2016-04-01

Shear localization in the lithosphere is an essential ingredient for understanding how and why plate tectonics is generated from mantle convection on terrestrial planets. The theoretical model for grain-damage and pinning in two-phase polycrystalline rocks provides a frame-work for understanding lithospheric shear weakening and plate-generation, and is consistent with laboratory and field observations of mylonites. Grain size evolves through the competition between coarsening, which drives grain-growth, and damage, which drives grain reduction. The interface between crystalline phases controls Zener pinning, which impedes grain growth. Damage to the interface enhances the Zener pinning effect, which then reduces grain-size, forcing the rheology into the grain-size-dependent diffusion creep regime. This process thus allows damage and rheological weakening to co-exist, providing a necessary positive self-weakening feedback. Moreover, because pinning inhibits grain-growth it promotes shear-zone longevity and plate-boundary inheritance. However, the suppression of interface damage at low interface curvature (wherein inter-grain mixing is inefficient and other energy sinks of deformational work are potentially more facile) causes a hysteresis effect, in which three possible equilibrium grain-sizes for a given stress coexist: (1) a stable, large-grain, weakly-deforming state, (2) a stable, small-grain, rapidly-deforming state analogous to ultramylonites, and (3) an unstable, intermediate grain-size state perhaps comparable to protomylonites. A comparison of the model to field data suggests that shear-localized zones of small-grain mylonites and ultra-mylonites exist at a lower stress than the co-existing large-grain porphyroclasts, rather than, as predicted by paleopiezometers or paleowattmeters, at a much higher stress; this interpretation of field data thus allows localization to relieve instead of accumulate stress. The model also predicts that a lithosphere that deforms at a given stress can acquire two stable deformation regimes indicative of plate-like flows, i.e., it permits the coexistence of both slowly deforming plate interiors, and rapidly deforming plate boundaries. Earth seems to exist squarely inside the hysteresis loop and thus can have coexisting deformation states, while Venus appears to straddle the end of the loop where only the weakly deforming branch exists.

Grain-Size Dynamics Beneath Mid-Ocean Ridges: Implications for Permeability and Melt Extraction

NASA Astrophysics Data System (ADS)

Turner, A. J.; Katz, R. F.; Behn, M. D.

2014-12-01

The permeability structure of the sub-ridge mantle plays an important role in how melt is focused and extracted at mid-ocean ridges. Permeability is controlled by porosity and the grain size of the solid mantle matrix, which is in turn controlled by the deformation conditions. To date, models of grain size evolution and mantle deformation have not been coupled to determine the influence of spatial variations in grain-size on the permeability structure at mid-ocean ridges. Rather, current models typically assume a constant grain size for the whole domain [1]. Here, we use 2-D numerical models to evaluate the influence of grain-size variability on the permeability structure beneath a mid-ocean ridge and use these results to speculate on the consequences for melt focusing and extraction. We construct a two-dimensional, single phase model for the steady-state grain size beneath a mid-ocean ridge. The model employs a composite rheology of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a brittle stress limiter. Grain size is calculated using the "wattmeter" model of Austin and Evans [2]. We investigate the sensitivity of the model to global variations in grain growth exponent, potential temperature, spreading-rate, and grain boundary sliding parameters [3,4]. Our model predicts that permeability varies by two orders of magnitude due to the spatial variability of grain size within the expected melt region of a mid-ocean ridge. The predicted permeability structure suggests grain size may promote focusing of melt towards the ridge axis. Furthermore, the calculated grain size structure should focus melt from a greater depth than models that exclude grain-size variability. Future work will involve evaluating this hypothesis by implementing grain-size dynamics within a two-phase mid-ocean ridge model. The developments of such a model will be discussed. References: [1] R. F. Katz, Journal of Petrology, volume 49, issue 12, page 2099, 2008. [2] N. J. Austin and B. Evans, Geology, 35:354, 2007. [3] G. Hirth and D. Kohlstedt, In Inside the Subduction Factory, volume 138 of AGU Geophysical Monograph, 2003. [4] L. N. Hansen et al., JGR (Solid Earth), 116:B08201, 2011.

The composition, functional components, and physical characteristics of grain from staygreen and senescent sorghum lines grown under variable water availability

USDA-ARS?s Scientific Manuscript database

The inclusion of sorghum into human food and feed is limited by its low digestibility compared to corn, which has been linked to the higher total kafirin levels in sorghum grain. Water stress after pollination reduced grain filling, affects the grain composition, functional components and grain phys...

Substituting whole grains for refined grains in a 6-week randomized trial favorably affects energy balance parameters in healthy men and post-menopausal women

USDA-ARS?s Scientific Manuscript database

Background: The effect of whole grains on the regulation of energy balance remains controversial. Objective: To determine the effects of substituting whole grains for refined grains, independent of body weight change, on energy metabolism parameters and glycemic control. Design: A randomized, con...

76 FR 28726 - Grain Market News Reports; Request for Extension of a Currently Approved Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-18

... Lynch, Chief, Livestock and Grain Market News Branch, Livestock and Seed Program, Agricultural Marketing... grain industry has requested that USDA continue to issue market news reports on grain. These reports are compiled by AMS on a voluntary basis in cooperation with the grain and feed industry. Market news reporting...

Technical Note: Field-observed angles of repose for stored grain in the United States

USDA-ARS?s Scientific Manuscript database

Bulk grain angle of repose (AoR) is a key parameter for inventorying grain, predicting flow characteristics, and designing bins and grain handling systems. The AoR is defined for two cases, piling (dynamic) or emptying (static), and usually varies with grain type. The objective of this study was to ...

Radiative Grain Alignment in Protoplanetary Disks: Implications for Polarimetric Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tazaki, Ryo; Lazarian, Alexandre; Nomura, Hideko, E-mail: rtazaki@kusastro.kyoto-u.ac.jp

2017-04-10

We apply the theory of radiative torque (RAT) alignment for studying protoplanetary disks around a T-Tauri star and perform 3D radiative transfer calculations to provide the expected maps of polarized radiation to be compared with observations, such as with ALMA. We revisit the issue of grain alignment for large grains expected in the protoplanetary disks and find that mm-sized grains at the midplane do not align with the magnetic field since the Larmor precession timescale for such large grains becomes longer than the gaseous damping timescale. Hence, for these grains the RAT theory predicts that the alignment axis is determinedmore » by the grain precession with respect to the radiative flux. As a result, we expect that the polarization will be in the azimuthal direction for a face-on disk. It is also shown that if dust grains have superparamagnetic inclusions, magnetic field alignment is possible for (sub-)micron grains at the surface layer of disks, and this can be tested by mid-infrared polarimetric observations.« less

Role of Grain Boundaries under Long-Time Radiation

NASA Astrophysics Data System (ADS)

Zhu, Yichao; Luo, Jing; Guo, Xu; Xiang, Yang; Chapman, Stephen Jonathan

2018-06-01

Materials containing a high proportion of grain boundaries offer significant potential for the development of radiation-resistant structural materials. However, a proper understanding of the connection between the radiation-induced microstructural behavior of a grain boundary and its impact at long natural time scales is still missing. In this Letter, point defect absorption at interfaces is summarized by a jump Robin-type condition at a coarse-grained level, wherein the role of interface microstructure is effectively taken into account. Then a concise formula linking the sink strength of a polycrystalline aggregate with its grain size is introduced and is well compared with experimental observation. Based on the derived model, a coarse-grained formulation incorporating the coupled evolution of grain boundaries and point defects is proposed, so as to underpin the study of long-time morphological evolution of grains induced by irradiation. Our simulation results suggest that the presence of point defect sources within a grain further accelerates its shrinking process, and radiation tends to trigger the extension of twin boundary sections.

Different Phosphorus Supplies Altered the Accumulations and Quantitative Distributions of Phytic Acid, Zinc, and Iron in Rice (Oryza sativa L.) Grains.

PubMed

Su, Da; Zhou, Lujian; Zhao, Qian; Pan, Gang; Cheng, Fangmin

2018-02-21

Development of rice cultivars with low phytic acid (lpa) is considered as a primary strategy for biofortification of zinc (Zn) and iron (Fe). Here, two rice genotypes (XS110 and its lpa mutant) were used to investigate the effect of P supplies on accumulations and distributions of PA, Zn, and Fe in rice grains by using hydroponics and detached panicle culture system. Results showed that higher P level increased grain PA concentration on dry matter basis (g/kg), but it markedly decreased PA accumulation on per grain basis (mg/grain). Meanwhile, more P supply reduced the amounts and bioavailabilities of Zn and Fe both in milled grains and in brown grains. Comparatively, lpa mutant was more susceptive to exogenous P supply than its wild type. Hence, the appropriate P fertilizer application should be highlighted in order to increase grain microelement (Zn and Fe) contents and improve nutritional quality in rice grains.

Grain Structure Control of Additively Manufactured Metallic Materials

PubMed Central

Faierson, Eric J.

2017-01-01

Grain structure control is challenging for metal additive manufacturing (AM). Grain structure optimization requires the control of grain morphology with grain size refinement, which can improve the mechanical properties of additive manufactured components. This work summarizes methods to promote fine equiaxed grains in both the additive manufacturing process and subsequent heat treatment. Influences of temperature gradient, solidification velocity and alloy composition on grain morphology are discussed. Equiaxed solidification is greatly promoted by introducing a high density of heterogeneous nucleation sites via powder rate control in the direct energy deposition (DED) technique or powder surface treatment for powder-bed techniques. Grain growth/coarsening during post-processing heat treatment can be restricted by presence of nano-scale oxide particles formed in-situ during AM. Grain refinement of martensitic steels can also be achieved by cyclic austenitizing in post-processing heat treatment. Evidently, new alloy powder design is another sustainable method enhancing the capability of AM for high-performance components with desirable microstructures.

Microstructural development of cobalt ferrite ceramics and its influence on magnetic properties

NASA Astrophysics Data System (ADS)

Kim, Gi-Yeop; Jeon, Jae-Ho; Kim, Myong-Ho; Suvorov, Danilo; Choi, Si-Young

2013-11-01

The microstructural evolution and its influence on magnetic properties in cobalt ferrite were investigated. The cobalt ferrite powders were prepared via a solid-state reaction route and then sintered at 1200 °C for 1, 2, and 16 h in air. The microstructures from sintered samples represented a bimodal distribution of grain size, which is associated with abnormal grain growth behavior. And thus, with increasing sintering time, the number and size of abnormal grains accordingly increased but the matrix grains were frozen with stagnant grain growth. In the sample sintered for 16 h, all of the matrix grains were consumed and the abnormal grains consequently impinged on each other. With the appearance of abnormal grains, the magnetic coercivity significantly decreased from 586.3 Oe (1 h sintered sample) to 168.3 Oe (16 h sintered sample). This is due to the magnetization in abnormal grains being easily flipped. In order to achieve high magnetic coercivity of cobalt ferrite, it is thus imperative to fabricate the fine and homogeneous microstructure.

Changes in properties of starch isolated from whole rice grains with brown, black, and red pericarp after storage at different temperatures.

PubMed

Ziegler, Valmor; Ferreira, Cristiano Dietrich; Goebel, Jorge Tiago Schwanz; El Halal, Shanise Lisie Mello; Santetti, Gabriela Soster; Gutkoski, Luiz Carlos; Zavareze, Elessandra da Rosa; Elias, Moacir Cardoso

2017-02-01

The aim of this study was to evaluate the physicochemical, morphological, crystallinity, thermal, and pasting properties of starches isolated from rice grains with brown, black, and red pericarp. Starch was isolated from the rice grains at initial storage time, and after 6months of storage at different storage temperatures (16, 24, 32 and 40°C). Starch isolated from the grains stored for 6months at 40°C showed darker coloration, surface deformation of granules, and a significant reduction in the extraction yield, final viscosity, enthalpy, and crystallinity, independent of the grain pericarp coloration. The time and storage temperature not influence the swelling power and solubility of starch isolated from grains with brown pericarp, while for the grains with black and red pericarp there was reduction in swelling power and solubility of starches isolated of grains stored at 40°C. Grains stored at 16°C showed minimum changes in starch properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microstructural evolution and grain growth kinetics of GZ31 magnesium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roostaei, M., E-mail: miladroustaei68@ut.ac.ir

2016-08-15

Grain growth behavior of Mg–3Gd–1Zn (GZ31) magnesium alloy was studied in a wide range of annealing time and temperature to clarify the kinetics of grain growth, microstructural evolution and related metallurgical phenomena. This material exhibited typical normal grain growth mode under annealing conditions with annealing temperature of lower than 300 °C and soaking time of lower than 240 min. However, the abnormality in grain growth was also evident at annealing temperature of 400 °C and 500 °C. The dependence of abnormal grain growth (AGG) at mentioned annealing temperatures upon microstructural features such as dispersed precipitates, which were rich in Znmore » and Gd, was investigated by optical micrographs, X-ray diffraction patterns, scanning electron microscopy images, and energy dispersive X-ray analysis spectra. The bimodality in grain-size distribution histograms also signified the occurrence of AGG. Based on the experimental data on grain growth obtained by annealing treatments, the grain growth exponent and the activation energy were also figured out.« less

Positive column of a glow discharge in neon with charged dust grains (a review)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polyakov, D. N., E-mail: cryolab@ihed.ras.ru; Shumova, V. V.; Vasilyak, L. M.

The effect of charged micron-size dust grains (microparticles) on the electric parameters of the positive column of a low-pressure dc glow discharge in neon has been studied experimentally and numerically. Numerical analysis is carried out in the diffusion-drift approximation with allowance for the interaction of dust grains with metastable neon atoms. In a discharge with a dust grain cloud, the longitudinal electric field increases. As the number density of dust grains in an axisymmetric cylindrical dust cloud rises, the growth of the electric field saturates. It is shown that the contribution of metastable atoms to ionization is higher in amore » discharge with dust grains, in spite of the quenching of metastable atoms on dust grains. The processes of charging of dust grains and the dust cloud are considered. As the number density of dust grains rises, their charge decreases, while the space charge of the dust cloud increases. The results obtained can be used in plasma technologies involving microparticles.« less

The role of grain size in He bubble formation: Implications for swelling resistance

DOE PAGES

El-Atwani, Osman; Nathaniel, II, James E.; Leff, Asher C.; ...

2016-12-07

Here, nanocrystalline metals are postulated as radiation resistant materials due to their high defect and particle (e.g. Helium) sink density. Here, the performance of nanocrystalline iron films is investigated in-situ in a transmission electron microscope (TEM) using He irradiation at 700 K. Automated crystal orientation mapping is used in concert with in-situ TEM to explore the role of grain orientation and grain boundary character on bubble density trends. Bubble density as a function of three key grain size regimes is demonstrated. While the overall trend revealed an increase in bubble density up to a saturation value, grains with areas rangingmore » from 3000 to 7500 nm 2 show a scattered distribution. An extrapolated swelling resistance based on bubble size and areal density indicated that grains with sizes less than 2000 nm 2 possess the greatest apparent resistance. Moreover, denuded zones are found to be independent of grain size, grain orientation, and grain boundary misorientation angle.« less

Influence of Solute Content and Solidification Parameters on Grain Refinement of Aluminum Weld Metal

NASA Astrophysics Data System (ADS)

Schempp, Philipp; Cross, Carl Edward; Pittner, Andreas; Rethmeier, Michael

2013-07-01

Grain refinement provides an important possibility to enhance the mechanical properties ( e.g., strength and ductility) and the weldability (susceptibility to solidification cracking) of aluminum weld metal. In the current study, a filler metal consisting of aluminum base metal and different amounts of commercial grain refiner Al Ti5B1 was produced. The filler metal was then deposited in the base metal and fused in a GTA welding process. Additions of titanium and boron reduced the weld metal mean grain size considerably and resulted in a transition from columnar to equiaxed grain shape ( CET). In commercial pure aluminum (Alloy 1050A), the grain-refining efficiency was higher than that in the Al alloys 6082 and 5083. Different welding and solidification parameters influenced the grain size response only slightly. Furthermore, the observed grain-size reduction was analyzed by means of the undercooling parameter P and the growth restriction parameter Q, which revealed the influence of solute elements and nucleant particles on grain size.

Structure and transport at grain boundaries in polycrystalline olivine: An atomic-scale perspective

NASA Astrophysics Data System (ADS)

Mantisi, Boris; Sator, Nicolas; Guillot, Bertrand

2017-12-01

Structure and transport properties at grain boundaries in polycrystalline olivine have been investigated at the atomic scale by molecular dynamics simulation (MD) using an empirical ionocovalent interaction potential. On the time scale of the simulation (a few tens of nanoseconds for a system size of ∼650,000 atoms) grain boundaries and grain interior were identified by mapping the atomic displacements along the simulation run. In the investigated temperature range (1300-1700 K) the mean thickness of the grain boundary phase is evaluated between 0.5 and 2 nm, a value which depends on temperature and grain size. The structure of the grain boundary phase is found to be disordered (amorphous-like) and is different from the one exhibited by the supercooled liquid. The self-diffusion coefficients of major elements in the intergranular region range from ∼10-13 to 10-10 m2/s between 1300 and 1700 K (with DSigb < DOgb < DFegb < DMggb) and are only one order of magnitude smaller than those evaluated in the supercooled melt. In using a newly derived expression for the bulk self-diffusion coefficient it is concluded that the latter one is driven by the grain boundary contribution as long as the grain size is smaller than a centimeter. In assuming that the electrical conduction at grain boundaries is purely ionic, the macroscopic grain boundary conductivity is found to be two orders of magnitude lower than in molten olivine, and one order of magnitude higher than the lattice conductivity. A consequence is that the conductivity of the olivine polycrystal is dominated by the grain interior contribution as soon as the grain size is larger than a micrometer or so. The grain boundary viscosity has been evaluated from the Green-Kubo relation expressing the viscosity as function of the stress tensor time correlation function. In spite of a slow convergence of the calculation by MD, the grain boundary viscosity was estimated about ∼105 Pa s at 1500 K, a value in agreement with high-temperature viscoelastic relaxation data. An interesting information gained from MD is that sliding at grain boundaries is essentially controlled by the internal friction between the intergranular phase and the grain edges.

Grain Size Measurements of Eolian Ripples in Gale Crater, Mars

NASA Astrophysics Data System (ADS)

Weitz, C. M.; Sullivan, R. J., Jr.; Lapotre, M. G. A.; Rowland, S. K.; Edgett, K. S.; Grant, J. A., III; Yingst, R. A.

2017-12-01

The Curiosity rover team has explored several different eolian sand targets in Gale crater, including dunes and ripples. Using Curiosity's Mars Hand Lens Imager (MAHLI), we measured the size of grains on or near ripple crests within dunes, ripple fields, and in isolated ripples. The Barby target (Sol 1184) is on the crest of a ripple on the lower stoss slope of the barchan High dune. Flume Ridge (Sol 1604) and Avery Peak (Sol 1651) are smaller ripples on the Nathan Bridges and Mount Desert Island linear dunes. Schoolhouse Ledge (Sol 1688) is an isolated megaripple not associated with either a dune or ripple field. Enchanted Island (Sol 1751) is a ripple contained within a larger ripple field near the Vera Rubin Ridge. Our results show the grains of the Avery Peak and Flume Ridge targets are mostly 75-150 µm in size and grain motion was observed during each MAHLI imaging sequence. Barby is dominated by 250-450 µm grains assumed to be active based upon the lack of a dust coating, though grain motion was not observed. The Enchanted Island target has slightly larger grains than Barby, with most between 300-500 µm. The grains have some dust aggregates on their surfaces, suggesting they have been less active in recent months or years relative to the ripples examined within the Bagnold dune field. Finally, grains along the crest of Schoolhouse Ledge are the largest, 400-600 µm, and all of the grain surfaces have a thin dust coating, indicating the ripple is not currently active. Some of the ripple crests have similar grain sizes on both the stoss and lee sides (Schoolhouse Ledge, Barby) whereas other ripples showed larger grains concentrated on the stoss side (Enchanted Island, Avery Peak, Flume Ridge). Scuffing by the rover's front wheel revealed both Schoolhouse Ledge and Enchanted Island had coarser grains dominating the ripple surface with finer grains within the ripple interior. In general, the surfaces of active sand ripples have smaller grains compared to the inactive ripples which exhibit an armor of larger grains. Our results indicate grain sizes vary widely depending upon such factors as ripple activity, location along the ripple, ripple size, dune type, and orientation relative to the wind direction.

Are grain packing and flow turbulence the keys to predicting bedload transport in steep streams? (Invited)

NASA Astrophysics Data System (ADS)

Yager, E.; Monsalve Sepulveda, A.; Smith, H. J.; Badoux, A.

2013-12-01

Bedload transport rates in steep mountain channels are often over-predicted by orders of magnitude, which has been attributed to a range of processes from grain jamming, roughness drag, changes in fluid turbulence and a limited upstream sediment supply. We hypothesize that such poor predictions occur in part because the grain-scale mechanics (turbulence, particle arrangements) of sediment transport are not well understood or incorporated into simplified reach-averaged calculations. To better quantify how turbulence impacts sediment movement, we measured detailed flow velocities and forces at the onset of motion of a single test grain with a fixed pocket geometry in laboratory flume experiments. Of all measured parameters (e.g. flow velocity, shear stress), the local fluid drag force had the highest statistical correlation with grain motion. Use of flow velocity or shear stress to estimate sediment transport may therefore result in erroneous predictions given their relatively low correlation to the onset of sediment motion. To further understand the role of grain arrangement on bedload transport, we measured in situ grain resisting forces to motion (using a force sensor) for a range of grain sizes and patch classes in the Erlenbach torrent, Switzerland (10% gradient). Such forces varied by over two orders of magnitude for a given grain weight and were statistically greater than those calculated using empirical equations for the friction angle. In addition, when normalized by the grain weight, the resisting forces declined with higher grain protrusion above the surrounding bed sediment. Therefore, resisting forces from grain packing and interlocking are substantial and depend on the amount of grain burial. The onset of motion may be considerably under-estimated when calculated solely from measured grain sizes and friction angles. These packing forces may partly explain why critical Shields stresses are higher in steep channels. Such flow and grain parameters also spatially vary in steep streams because of boulder steps and patches of different grain size distributions. To determine if this spatial variation is important for bedload transport, we incorporated probability density functions of flow turbulence and patch grain size distributions into a simple bedload transport equation. Predicted bedload fluxes were significantly improved when distributions of these parameters, rather than single reach-averaged values, were used.

Grain-Scale Analyses of Curiosity Data at Marias Pass, Gale Crater, Mars: Methods Comparison and Depositional Interpretation

NASA Astrophysics Data System (ADS)

Sacks, L. E.; Edgar, L. A.; Edwards, C. S.; Anderson, R. B.

2016-12-01

Images acquired by the Mars Hand Lens Imager (MAHLI) and the ChemCam Remote Micro Imager (RMI) onboard the Mars Science Laboratory (MSL) Curiosity rover provide grain-scale data that are critical for interpreting sedimentary deposits. At the location informally known as Marias Pass, Curiosity used both cameras to image the nine rock targets used in this study. We used manual point-counts to measure grain size distributions from those images to compare the abilities of the two cameras. The manually derived results were compared to automated grain size data obtained using pyDGS (Digital Grain Size), an open-source python program. Grain size analyses were used to test the lacustrine and aeolian depositional hypotheses for the Murray and Stimson formations at Marias Pass. Results indicate that the MAHLI and RMI instruments, despite their different fields of view and properties, provide comparable grain size measurements. Additionally, pyDGS does not account for grains smaller than a few pixels and thus does not report representative grain size data and should not be used on images with a large fraction of unresolved grains. Finally, the data collected at Marias Pass are consistent with the existing interpretations of the Murray and Stimson formations. The fine-grained results of the Murray formation analyses support lacustrine deposition, while the mean grain size of the Stimson formation is fine to medium sized sand, consistent with aeolian deposition. However, directly above the contact with the Murray formation, larger rip-up clasts of the Murray formation are present in the Stimson formation. It is possible that water was involved at this stage of erosion and re-deposition, prior to aeolian deposition. Additionally, the grain-scale analyses conducted in this study show that the Dust Removal Tool on Curiosity should be used prior to capturing images for grain-scale analysis. Two images of the target informally named Ronan, taken before and after brushing, resulted in dramatically different grain size results, suggesting that the common, thin layer of dust obscured the true grain size distribution. These grain-scale analyses at Marias Pass have important implications for the collection and processing of image data, as well as the depositional environments recorded in Gale crater. Funded by NSF Grant AST-1461200

Bragg coherent diffractive imaging of single-grain defect dynamics in polycrystalline films

NASA Astrophysics Data System (ADS)

Yau, Allison; Cha, Wonsuk; Kanan, Matthew W.; Stephenson, G. Brian; Ulvestad, Andrew

2017-05-01

Polycrystalline material properties depend on the distribution and interactions of their crystalline grains. In particular, grain boundaries and defects are crucial in determining their response to external stimuli. A long-standing challenge is thus to observe individual grains, defects, and strain dynamics inside functional materials. Here we report a technique capable of revealing grain heterogeneity, including strain fields and individual dislocations, that can be used under operando conditions in reactive environments: grain Bragg coherent diffractive imaging (gBCDI). Using a polycrystalline gold thin film subjected to heating, we show how gBCDI resolves grain boundary and dislocation dynamics in individual grains in three-dimensional detail with 10-nanometer spatial and subangstrom displacement field resolution. These results pave the way for understanding polycrystalline material response under external stimuli and, ideally, engineering particular functions.

A comparison between corn and grain sorghum fermentation rates, Distillers Dried Grains with Solubles composition, and lipid profiles.

PubMed

Johnston, David J; Moreau, Robert A

2017-02-01

The aim of this study was to determine if the compositional difference between grain sorghum and corn impact ethanol yields and coproduct value when grain sorghum is incorporated into existing corn ethanol facilities. Fermentation properties of corn and grain sorghum were compared utilizing two fermentation systems (conventional thermal starch liquefaction and native starch hydrolysis). Fermentation results indicated that protease addition influenced the fermentation rate and yield for grain sorghum, improving yields by 1-2% over non-protease treated fermentations. Distillers Dried Grains with Solubles produced from sorghum had a statistically significant higher yields and significantly higher protein content relative to corn. Lipid analysis of the Distillers Dried Grains with Solubles showed statistically significant differences between corn and sorghum in triacylglycerol, diacylglycerol and free fatty acid levels. Published by Elsevier Ltd.

Bragg coherent diffractive imaging of single-grain defect dynamics in polycrystalline films

DOE PAGES

Yau, Allison; Cha, Wonsuk; Kanan, Matthew W.; ...

2017-05-19

Polycrystalline material properties depend on the distribution and interactions of their crystalline grains. In particular, grain boundaries and defects are crucial in determining their response to external stimuli. A long-standing challenge is thus to observe individual grains, defects, and strain dynamics inside functional materials. Here we report a technique capable of revealing grain heterogeneity, including strain fields and individual dislocations, that can be used under operando conditions in reactive environments: grain Bragg coherent diffractive imaging (gBCDI). Using a polycrystalline gold thin film subjected to heating, we show how gBCDI resolves grain boundary and dislocation dynamics in individual grains in three-dimensionalmore » detail with 10-nanometer spatial and subangstrom displacement field resolution. Finally, these results pave the way for understanding polycrystalline material response under external stimuli and, ideally, engineering particular functions.« less

The ultraviolet extinction properties of the 30 Dor Nebula

NASA Astrophysics Data System (ADS)

De Marchi, Guido; Panagia, Nino

2018-01-01

Recent investigation of the extinction law in 30 Dor and the Tarantula Nebula, at optical and near infrared wavelengths, has revealed a ratio of total to selective extinction RV=AV/E(B-V) of about 4.5. This indicates a larger proportion of large grains than in the Galactic diffuse interstellar medium. Possible origins include coalescence of small grains, grain growth, selective destruction of small grains, and fresh injection of large grains. From a study of the ultraviolet extinction properties of three Wolf-Rayet stars in 30 Dor (R 139, R 140, R 145), observed with the International Ultraviolet Explorer, we show that the excess of large grains does not come at the expense of small grains, which are still present. Fresh injection of large grains by supernova explosions appears to be the dominant mechanism.

Prevalence of IgE antibodies to grain and grain dust in grain elevator workers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, D.M.; Romeo, P.A.; Olenchock, S.A.

1986-04-01

IgE-mediated allergic reactions have been postulated to contribute to respiratory reactions seen in workers exposed to grain dusts. In an attempt better to define the prevalence of IgE antibodies in workers exposed to grain dusts, we performed the radioallergosorbent test (RAST) on worker sera using both commercial allergens prepared from grain and worksite allergens prepared from grain dust samples collected at the worksite. We found that the two types of reagents identified different populations with respect to the specificity of IgE antibodies present. The RAST assay performed using worksite allergens correlated well with skin test procedures. These results may allowmore » us to gain better understanding of allergy associated with grain dust exposure, and document the utility of the RAST assay in assessment of occupational allergies.« less

Stellar Origins of C-13 and N-15-Enriched Presolar SiC Grains

NASA Technical Reports Server (NTRS)

Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.; Wang, Jianhua; Pignatari, Marco; Jose, Jordi; Nguyen, Ann

2016-01-01

Extreme excesses of 13 C ( C (12 C/ 13 C<10) and 15 N ( N (14 N/ 15 N< 20) in rare presolar SiC 20) in rare presolar SiClar SiC grains have been considered diagnostic of an origin in classical novae [1], though an origin in core-collapse supernovae (CCSNe) has also been proposed [2]. We report multi-element isotopic data for 19 13 C- and 15 N-enriched presolar SiC grains(12 C/13 C<16 and 14 N/ 15 N<150) from an acid resistant residue of the Murchison meteorite. These grains are enriched in 13 C and15 N, but with quite diverse Si isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures.

Prevalence of IgE antibodies to grain and grain dust in grain elevator workers.

PubMed Central

Lewis, D M; Romeo, P A; Olenchock, S A

1986-01-01

IgE-mediated allergic reactions have been postulated to contribute to respiratory reactions seen in workers exposed to grain dusts. In an attempt better to define the prevalence of IgE antibodies in workers exposed to grain dusts, we performed the radioallergosorbent test (RAST) on worker sera using both commercial allergens prepared from grain and worksite allergens prepared from grain dust samples collected at the worksite. We found that the two types of reagents identified different populations with respect to the specificity of IgE antibodies present. The RAST assay performed using worksite allergens correlated well with skin test procedures. These results may allow us to gain better understanding of allergy associated with grain dust exposure, and document the utility of the RAST assay in assessment of occupational allergies. PMID:3709478

Grain Unloading of Arsenic Species in Rice1[W

PubMed Central

Carey, Anne-Marie; Scheckel, Kirk G.; Lombi, Enzo; Newville, Matt; Choi, Yongseong; Norton, Gareth J.; Charnock, John M.; Feldmann, Joerg; Price, Adam H.; Meharg, Andrew A.

2010-01-01

Rice (Oryza sativa) is the staple food for over half the world's population yet may represent a significant dietary source of inorganic arsenic (As), a nonthreshold, class 1 human carcinogen. Rice grain As is dominated by the inorganic species, and the organic species dimethylarsinic acid (DMA). To investigate how As species are unloaded into grain rice, panicles were excised during grain filling and hydroponically pulsed with arsenite, arsenate, glutathione-complexed As, or DMA. Total As concentrations in flag leaf, grain, and husk, were quantified by inductively coupled plasma mass spectroscopy and As speciation in the fresh grain was determined by x-ray absorption near-edge spectroscopy. The roles of phloem and xylem transport were investigated by applying a ± stem-girdling treatment to a second set of panicles, limiting phloem transport to the grain in panicles pulsed with arsenite or DMA. The results demonstrate that DMA is translocated to the rice grain with over an order magnitude greater efficiency than inorganic species and is more mobile than arsenite in both the phloem and the xylem. Phloem transport accounted for 90% of arsenite, and 55% of DMA, transport to the grain. Synchrotron x-ray fluorescence mapping and fluorescence microtomography revealed marked differences in the pattern of As unloading into the grain between DMA and arsenite-challenged grain. Arsenite was retained in the ovular vascular trace and DMA dispersed throughout the external grain parts and into the endosperm. This study also demonstrates that DMA speciation is altered in planta, potentially through complexation with thiols. PMID:19880610

Transport properties of olivine grain boundaries from electrical conductivity experiments

NASA Astrophysics Data System (ADS)

Pommier, Anne; Kohlstedt, David L.; Hansen, Lars N.; Mackwell, Stephen; Tasaka, Miki; Heidelbach, Florian; Leinenweber, Kurt

2018-05-01

Grain boundary processes contribute significantly to electronic and ionic transports in materials within Earth's interior. We report a novel experimental study of grain boundary conductivity in highly strained olivine aggregates that demonstrates the importance of misorientation angle between adjacent grains on aggregate transport properties. We performed electrical conductivity measurements of melt-free polycrystalline olivine (Fo90) samples that had been previously deformed at 1200 °C and 0.3 GPa to shear strains up to γ = 7.3. The electrical conductivity and anisotropy were measured at 2.8 GPa over the temperature range 700-1400 °C. We observed that (1) the electrical conductivity of samples with a small grain size (3-6 µm) and strong crystallographic preferred orientation produced by dynamic recrystallization during large-strain shear deformation is a factor of 10 or more larger than that measured on coarse-grained samples, (2) the sample deformed to the highest strain is the most conductive even though it does not have the smallest grain size, and (3) conductivity is up to a factor of 4 larger in the direction of shear than normal to the shear plane. Based on these results combined with electrical conductivity data for coarse-grained, polycrystalline olivine and for single crystals, we propose that the electrical conductivity of our fine-grained samples is dominated by grain boundary paths. In addition, the electrical anisotropy results from preferential alignment of higher-conductivity grain boundaries associated with the development of a strong crystallographic preferred orientation of the grains.

Quantitative transmission electron microscopy analysis of multi-variant grains in present L1{sub 0}-FePt based heat assisted magnetic recording media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Hoan, E-mail: hoan.ho@wdc.com; Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213; Zhu, Jingxi, E-mail: jingxiz@andrew.cmu.edu

2014-11-21

We present a study on atomic ordering within individual grains in granular L1{sub 0}-FePt thin films using transmission electron microscopy techniques. The film, used as a medium for heat assisted magnetic recording, consists of a single layer of FePt grains separated by non-magnetic grain boundaries and is grown on an MgO underlayer. Using convergent-beam techniques, diffraction patterns of individual grains are obtained for a large number of crystallites. The study found that although the majority of grains are ordered in the perpendicular direction, more than 15% of them are multi-variant, or of in-plane c-axis orientation, or disordered fcc. It wasmore » also found that these multi-variant and in-plane grains have always grown across MgO grain boundaries separating two or more MgO grains of the underlayer. The in-plane ordered portion within a multi-variant L1{sub 0}-FePt grain always lacks atomic coherence with the MgO directly underneath it, whereas, the perpendicularly ordered portion is always coherent with the underlying MgO grain. Since the existence of multi-variant and in-plane ordered grains are severely detrimental to high density data storage capability, the understanding of their formation mechanism obtained here should make a significant impact on the future development of hard disk drive technology.« less

Location-Control of Large Si Grains by Dual-Beam Excimer-Laser and Thick Oxide Portion

NASA Astrophysics Data System (ADS)

Ishihara, Ryoichi; Burtsev, Artyom; Alkemade, Paul F. A.

2000-07-01

An array of large Si grains was placed at a predetermined position by dual excimer-laser irradiation of a multi-layer structure of silicon (Si), silicon dioxide (SiO2) with an array of bumps and metal on a glass substrate. We have investigated the effects of irradiating energy density and the topology of the structure on the grain size and crystallographic structure by scanning electron microscopy (SEM) and electron back-scattering pattern (EBSP) analysis. In the low-energy-density regime, numerous small grains and petal shaped grains formed on top of the SiO2 bumps. The number of small grains on the bumps decreased with increasing irradiating energy density. At sufficiently high energy densities, one single Si grain as large as 3.5 μm was positioned at the center of the bumps. Although most of the area of the large Si grain has a single crystallographic orientation, twins and low-angle grain boundaries are often formed at the periphery of the grain. There was no preferred crystallographic orientation in the center of the location-controlled Si grain. Numerical analysis of the temperature profile showed that a temperature drop occurs at the center of the bump, during and immediately after laser irradiation. The diameter of the location-controlled Si grain increased with total thickness of the intermediate SiO2 layer, and took the maximum value of 6.2 μm.

TaGW2-6A allelic variation contributes to grain size possibly by regulating the expression of cytokinins and starch-related genes in wheat.

PubMed

Geng, Juan; Li, Liqun; Lv, Qian; Zhao, Yi; Liu, Yan; Zhang, Li; Li, Xuejun

2017-12-01

Functional allelic variants of TaGW2 - 6A produce large grains, possibly via changes in endosperm cells and dry matter by regulating the expression of cytokinins and starch-related genes via the ubiquitin-proteasome system. In wheat, TaGW2-6A coding region allelic variants are closely related to the grain width and weight, but how this region affects grain development has not been fully elucidated; thus, we explored its influence on grain development based mainly on histological and grain filling analyses. We found that the insertion type (NIL31) TaGW2-6A allelic variants exhibited increases in cell numbers and cell size, thereby resulting in a larger (wider) grain size with an accelerated grain milk filling rate, and increases in grain width and weight. We also found that cytokinin (CK) synthesis genes and key starch biosynthesis enzyme AGPase genes were significantly upregulated in the TaGW2-6A allelic variants, while CK degradation genes and starch biosynthesis-negative regulators were downregulated in the TaGW2-6A allelic variants, which was consistent with the changes in cells and grain filling. Thus, we speculate that TaGW2-6A allelic variants are linked with CK signaling, but they also influence the accumulation of starch by regulating the expression of related genes via the ubiquitin-proteasome system to control the grain size and grain weight.

On-Farm Evaluation of Hermetic Technology Against Maize Storage Pests in Kenya.

PubMed

Likhayo, Paddy; Bruce, Anani Y; Mutambuki, Kimondo; Tefera, Tadele; Mueke, Jones

2016-08-01

On-farm trial with a total of 32 farmers in eight villages of Naivasha and Nakuru areas of Kenya was conducted between December 2013 and September 2014 to evaluate hermetic grain storage technologies under farmers' management conditions. The storage technologies evaluated were metal silo and SuperGrain IV-R bag alongside the standard woven polypropylene bag with or without Actellic super dust. Moisture content, insect population, grain discoloration, and weight loss were analyzed 90, 180, and 270 d after storage. Grain moisture content remained stable over the storage period. Both metal silo and SuperGrain IV-R bag suppressed insect population, prevented grain loss and cross-infestation of insects from the surrounding environment. On the contrary, polypropylene bags allowed rapid build up of insect population and re-infestation from the surrounding environment. Grain weight losses were 1.5% in the metal silo and 1.8% in the SuperGrain IV-R bags compared to 32% in the polypropylene bags without Actellic Super dust, 270 d after storage. The present study, therefore, demonstrates that storing grains either in metal silo or SuperGrain IV-R bags would benefit farmers in reducing grain losses and improving quality. The study was of great interest to the farmers, grain storage scientists, and food security experts. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Mineralogy of Circumstellar Silicates Preserved in Cometary Dust

NASA Technical Reports Server (NTRS)

Keller, L. P.; Messenger, S.

2010-01-01

Interplanetary dust particles (IDPs) contain a record of the building blocks of the solar system including presolar grains, molecular cloud material, and materials formed in the early solar nebula. Cometary IDPs have remained relatively unaltered since their accretion because of the lack of parent body thermal and aqueous alteration. We are using coordinated transmission electron microscope (TEM) and ion microprobe studies to establish the origins of the various components within cometary IDPs. Of particular interest is the nature and abundance of presolar silicates in these particles because astronomical observations suggest that crystalline and amorphous silicates are the dominant grain types produced in young main sequence stars and evolved O-rich stars. Five circumstellar grains have been identified including three amorphous silicate grains and two polycrystalline aggregates. All of these grains are between 0.2 and 0.5 micrometers in size. The isotopic compositions of all five presolar silicate grains fall within the range of presolar oxides and silicates, having large (17)O-enrichments and normal (18)O/(16)O ratios (Group 1 grains from AGB and RG stars). The amorphous silicates are chemically heterogeneous and contain nanophase FeNi metal and FeS grains in a Mg-silicate matrix. Two of the amorphous silicate grains are aggregates with subgrains showing variable Mg/Si ratios in chemical maps. The polycrystalline grains show annealed textures (equilibrium grains boundaries, uniform Mg/Fe ratios), and consist of 50-100 nm enstatite and pyrrhotite grains with lesser forsterite. One of the polycrystalline aggregates contains a subgrain of diopside. The polycrystalline aggregates form by subsolidus annealing of amorphous precursors. The bulk compositions of the five grains span a wide range in Mg/Si ratios from 0.4 to 1.2 (avg. 0.86). The average Fe/Si (0.40) and S/Si (0.21) ratios show a much narrower range of values and are approximately 50% of their solar abundances. The latter observation may indicate a decoupling of the silicate and sulfide components in grains that condense in stellar outflows. The amorphous silicate grains described here were not extensively affected by irradiation, sputtering, or thermal processing and may represent relatively pristine circumstellar grains. They are strong candidates for the "dirty silicates" in astronomical observations of circumstellar dust shells. The polycrystalline grains were originally amorphous silicate grains that were likely annealed in the early solar nebula but the processing was not sufficient to erase their anomalous oxygen isotopic compositions.

The cause of ‘weak-link’ grain boundary behaviour in polycrystalline Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 superconductors

NASA Astrophysics Data System (ADS)

Wang, Guanmei; Raine, Mark J.; Hampshire, Damian P.

2018-02-01

The detrimental effects of grain boundaries have long been considered responsible for the low critical current densities ({J}{{c}}) in high temperature superconductors. In this paper, we apply the quantitative approach used to identify the cause of the ‘weak-link’ grain boundary behaviour in YBa2Cu3O7 (Wang et al 2017 Supercond. Sci Technol. 30 104001), to the Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 materials that we have fabricated. Magnetic and transport measurements are used to characterise the grain and grain boundary properties of micro- and nanocrystalline materials. Magnetisation measurements on all nanocrystalline materials show non-Bean-like behaviour and are consistent with surface pinning. Bi2Sr2CaCu2O8: our microcrystalline material has very low grain boundary resistivity ({ρ }{{GB}}), which is similar to that of the grains ({ρ }{{G}}) such that {ρ }{{GB}}≈ {ρ }{{G}}=2× {10}-5 {{Ω }}{{m}} (assuming a grain boundary thickness (d) of 1 nm) equivalent to an areal resistivity of {ρ }{{G}}=2× {10}-14 {{{Ω }}{{m}}}2. The transport {J}{{c}} values are consistent with well-connected grains and very weak grain boundary pinning. However, unlike low temperature superconductors (LTS) in which decreasing grain size increases the pinning along the grain boundary channels, any increase in pinning produced by making the grains in our Bi2Sr2CaCu2O8 materials nanocrystalline was completely offset by a decrease in the depairing current density of the grain boundaries caused by their high resistivity. We suggest a different approach to increasing {J}{{c}} from that used in LTS materials, namely incorporating additional strong grain and grain boundary pinning sites in microcrystalline materials to produce high {J}{{c}} values. Bi2Sr2Ca2Cu3O10: both our micro- and nanocrystalline samples have {ρ }{{GB}}/{ρ }{{G}} of at least 103. This causes strong suppression of {J}{{c}} across the grain boundaries, which explains the low transport {J}{{c}} values we find experimentally. Our calculations show that low {J}{{c}} in untextured polycrystalline Bi2Sr2Ca2Cu3O10 material is to be expected and the significant effort in the community in texturing samples and removing grain boundaries altogether is well-founded.

Influence of Aluminum Content on Grain Refinement and Strength of AZ31 Magnesium GTA Weld Metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babu, N. Kishore; Cross, Carl E.

2012-06-28

The goal is to characterize the effect of Al content on AZ31 weld metal, the grain size and strength, and examine role of Al on grain refinement. The approach is to systematically vary the aluminum content of AZ31 weld metal, Measure average grain size in weld metal, and Measure cross-weld tensile properties and hardness. Conclusions are that: (1) increased Al content in AZ31 weld metal results in grain refinement Reason: higher undercooling during solidification; (2) weld metal grain refinement resulted in increased strength & hardness Reason: grain boundary strengthening; and (3) weld metal strength can be raised to wrought basemore » metal levels.« less

Microstructural Evolution at Micro/Meso-Scale in an Ultrafine-Grained Pure Aluminum Processed by Equal-Channel Angular Pressing with Subsequent Annealing Treatment.

PubMed

Xu, Jie; Li, Jianwei; Zhu, Xiaocheng; Fan, Guohua; Shan, Debin; Guo, Bin

2015-11-04

Micro-forming with ultrafine-grained (UFG) materials is a promising direction for the fabrication of micro-electro-mechanical systems (MEMS) components due to the improved formability, good surface quality, and excellent mechanical properties it provides. In this paper, micro-compression tests were performed using UFG pure aluminum processed by equal-channel angular pressing (ECAP) with subsequent annealing treatment. Microstructural evolution was investigated by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that microstructural evolutions during compression tests at the micro/meso-scale in UFG pure Al are absolutely different from the coarse-grained (CG) materials. A lot of low-angle grain boundaries (LAGBs) and recrystallized fine grains are formed inside of the original large grains in CG pure aluminum after micro-compression. By contrast, ultrafine grains are kept with few sub-grain boundaries inside the grains in UFG pure aluminum, which are similar to the original microstructure before micro-compression. The surface roughness and coordinated deformation ability can be signmicrostructure; micro/meso-forming; ultrafine grains; ECAP; aluminumificantly improved with UFG pure aluminum, which demonstrates that the UFG materials have a strong potential application in micro/meso-forming.

Grain-scale modeling and splash parametrization for aeolian sand transport.

PubMed

Lämmel, Marc; Dzikowski, Kamil; Kroy, Klaus; Oger, Luc; Valance, Alexandre

2017-02-01

The collision of a spherical grain with a granular bed is commonly parametrized by the splash function, which provides the velocity of the rebounding grain and the velocity distribution and number of ejected grains. Starting from elementary geometric considerations and physical principles, like momentum conservation and energy dissipation in inelastic pair collisions, we derive a rebound parametrization for the collision of a spherical grain with a granular bed. Combined with a recently proposed energy-splitting model [Ho et al., Phys. Rev. E 85, 052301 (2012)PLEEE81539-375510.1103/PhysRevE.85.052301] that predicts how the impact energy is distributed among the bed grains, this yields a coarse-grained but complete characterization of the splash as a function of the impact velocity and the impactor-bed grain-size ratio. The predicted mean values of the rebound angle, total and vertical restitution, ejection speed, and number of ejected grains are in excellent agreement with experimental literature data and with our own discrete-element computer simulations. We extract a set of analytical asymptotic relations for shallow impact geometries, which can readily be used in coarse-grained analytical modeling or computer simulations of geophysical particle-laden flows.

Constitutive expression of cell wall invertase genes increases grain yield and starch content in maize.

PubMed

Li, Bei; Liu, Hua; Zhang, Yue; Kang, Tao; Zhang, Li; Tong, Jianhua; Xiao, Langtao; Zhang, Hongxia

2013-12-01

Grain size, number and starch content are important determinants of grain yield and quality. One of the most important biological processes that determine these components is the carbon partitioning during the early grain filling, which requires the function of cell wall invertase. Here, we showed the constitutive expression of cell wall invertase-encoding gene from Arabidopsis, rice (Oryza sativa) or maize (Zea mays), driven by the cauliflower mosaic virus (CaMV) 35S promoter, all increased cell wall invertase activities in different tissues and organs, including leaves and developing seeds, and substantially improved grain yield up to 145.3% in transgenic maize plants as compared to the wild-type plants, an effect that was reproduced in our 2-year field trials at different locations. The dramatically increased grain yield is due to the enlarged ears with both enhanced grain size and grain number. Constitutive expression of the invertase-encoding gene also increased total starch content up to 20% in the transgenic kernels. Our results suggest that cell wall invertase gene can be genetically engineered to improve both grain yield and grain quality in crop plants. © 2013 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Determination and controlling of grain structure of metals after laser incidence: Theoretical approach

PubMed Central

Dezfoli, Amir Reza Ansari; Hwang, Weng-Sing; Huang, Wei-Chin; Tsai, Tsung-Wen

2017-01-01

There are serious questions about the grain structure of metals after laser melting and the ways that it can be controlled. In this regard, the current paper explains the grain structure of metals after laser melting using a new model based on combination of 3D finite element (FE) and cellular automaton (CA) models validated by experimental observation. Competitive grain growth, relation between heat flows and grain orientation and the effect of laser scanning speed on final micro structure are discussed with details. Grains structure after laser melting is founded to be columnar with a tilt angle toward the direction of the laser movement. Furthermore, this investigation shows that the grain orientation is a function of conduction heat flux at molten pool boundary. Moreover, using the secondary laser heat source (SLHS) as a new approach to control the grain structure during the laser melting is presented. The results proved that the grain structure can be controlled and improved significantly using SLHS. Using SLHS, the grain orientation and uniformity can be change easily. In fact, this method can help us to produce materials with different local mechanical properties during laser processing according to their application requirements. PMID:28134347

Crystalline orientation dependent photoresponse and heterogeneous behaviors of grain boundaries in perovskite solar cells

NASA Astrophysics Data System (ADS)

Jiang, Chuanpeng; Zhang, Pengpeng

2018-02-01

Using photoconductive atomic force microscopy and Kelvin probe force microscopy, we characterize the local electrical properties of grains and grain boundaries of organic-inorganic hybrid perovskite (CH3NH3PbI3) thin films on top of a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS)/ITO substrate. Three discrete photoconductivity levels are identified among perovskite grains, likely corresponding to the crystal orientation of each grain. Local J-V curves recorded on these grains further suggest an anti-correlation behavior between the short circuit current (JSC) and open circuit voltage (VOC). This phenomenon can be attributed to diffusion-limited surface recombination at the non-selective perovskite-tip contact, where a higher carrier mobility established in the perovskite grain results in an enhanced surface recombination and thus a lower VOC. In addition, the photoresponse of perovskite films displays a pronounced heterogeneity across the grain boundaries, with the boundaries formed between grains of the same photoconductivity level displaying even enhanced photocurrent and open circuit voltage compared to those of the adjacent grain interiors. These observations highlight the significance of controlling the microstructure of perovskite thin films, which will be a necessary route for further improving the efficiency of perovskite solar cells.

Empirical Study on the Sustainability of China's Grain Quality Improvement: The Role of Transportation, Labor, and Agricultural Machinery.

PubMed

Zhang, Ming; Duan, Fang; Mao, Zisen

2018-02-05

As a major part of farming sustainability, the issues of grain production and its quality improvement have been important in many countries. This paper aims to address these issues in China. Based on the data from the main production provinces and by applying the stochastic frontier analysis methodology, we find that the improvement of transportation and the use of agricultural machinery have become the main driving forces for grain quality improvement in China. After further studying different provinces' potentials of grain quality improvement, we show that grain quality has increased steadily. Therefore, we can conclude China's grain quality improvement is indeed sustainable. Furthermore, different grains like rice, wheat, and corn share similar characteristics in terms of quality improvement, but the improvement rate for rice is relatively low, while those of corn and wheat are relatively high. Moreover, the overall change of efficiency gain of grain quality improvement is not significant for different provinces. The efficiency gains of the quality improvements for rice and wheat even decrease slightly. In addition, we find that only expanding grain quality improvement potential can simultaneously achieve the dual objectives of improving grain quality and increasing yield.

SMALL GRAIN 1, which encodes a mitogen-activated protein kinase kinase 4, influences grain size in rice.

PubMed

Duan, Penggen; Rao, Yuchun; Zeng, Dali; Yang, Yaolong; Xu, Ran; Zhang, Baolan; Dong, Guojun; Qian, Qian; Li, Yunhai

2014-02-01

Although grain size is one of the most important components of grain yield, little information is known about the mechanisms that determine final grain size in crops. Here we characterize rice small grain1 (smg1) mutants, which exhibit small and light grains, dense and erect panicles and comparatively slightly shorter plants. The short grain and panicle phenotypes of smg1 mutants are caused by a defect in cell proliferation. The smg1 mutations were identified, using a map-based cloning approach, in mitogen-activated protein kinase kinase 4 (OsMKK4). Relatively higher expression of OsMKK4/SMG1 was detected in younger organs than in older ones, consistent with its role in cell proliferation. Green fluorescent protein (GFP)-OsMKK4/SMG1 fusion proteins appear to be distributed ubiquitously in plant cells. Further results revealed that OsMKK4 influenced brassinosteroid (BR) responses and the expression of BR-related genes. Thus, our findings have identified OsMKK4 as a factor for grain size, and suggest a possible link between the MAPK pathways and BRs in grain growth. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

Empirical Study on the Sustainability of China’s Grain Quality Improvement: The Role of Transportation, Labor, and Agricultural Machinery

PubMed Central

Zhang, Ming; Duan, Fang; Mao, Zisen

2018-01-01

As a major part of farming sustainability, the issues of grain production and its quality improvement have been important in many countries. This paper aims to address these issues in China. Based on the data from the main production provinces and by applying the stochastic frontier analysis methodology, we find that the improvement of transportation and the use of agricultural machinery have become the main driving forces for grain quality improvement in China. After further studying different provinces’ potentials of grain quality improvement, we show that grain quality has increased steadily. Therefore, we can conclude China’s grain quality improvement is indeed sustainable. Furthermore, different grains like rice, wheat, and corn share similar characteristics in terms of quality improvement, but the improvement rate for rice is relatively low, while those of corn and wheat are relatively high. Moreover, the overall change of efficiency gain of grain quality improvement is not significant for different provinces. The efficiency gains of the quality improvements for rice and wheat even decrease slightly. In addition, we find that only expanding grain quality improvement potential can simultaneously achieve the dual objectives of improving grain quality and increasing yield. PMID:29401727

Identification of Genomic Regions and the Isoamylase Gene for Reduced Grain Chalkiness in Rice

PubMed Central

Sun, Wenqian; Zhou, Qiaoling; Yao, Yue; Qiu, Xianjin; Xie, Kun; Yu, Sibin

2015-01-01

Grain chalkiness is an important grain quality related to starch granules in the endosperm. A high percentage of grain chalkiness is a major problem because it diminishes grain quality in rice. Here, we report quantitative trait loci identification for grain chalkiness using high-throughput single nucleotide polymorphism genotyping of a chromosomal segment substitution line population in which each line carried one or a few introduced japonica cultivar Nipponbare segments in the genetic background of the indica cultivar ZS97. Ten quantitative trait loci regions were commonly identified for the percentage of grain chalkiness and the degree of endosperm chalkiness. The allelic effects at nine of these quantitative trait loci reduced grain chalkiness. Furthermore, a quantitative trait locus (qPGC8-2) on chromosome 8 was validated in a chromosomal segment substitution line–derived segregation population, and had a stable effect on chalkiness in a multiple-environment evaluation of the near-isogenic lines. Residing on the qPGC8-2 region, the isoamylase gene (ISA1) was preferentially expressed in the endosperm and revealed some nucleotide polymorphisms between two varieties, Nipponbare and ZS97. Transgenic lines with suppression of ISA1 by RNA interference produced grains with 20% more chalkiness than the control. The results support that the gene may underlie qPGC8-2 for grain chalkiness. The multiple-environment trials of the near-isogenic lines also show that combination of the favorable alleles such as the ISA1 gene for low chalkiness and the GS3 gene for long grains considerably improved grain quality of ZS97, which proves useful for grain quality improvement in rice breeding programs. PMID:25790260

Influence of grain size and texture prior to warm rolling on microstructure, texture and magnetic properties of Fe-6.5 wt% Si steel

NASA Astrophysics Data System (ADS)

Xu, H. J.; Xu, Y. B.; Jiao, H. T.; Cheng, S. F.; Misra, R. D. K.; Li, J. P.

2018-05-01

Fe-6.5 wt% Si steel hot bands with different initial grain size and texture were obtained through different annealing treatment. These bands were then warm rolled and annealed. An analysis on the evolution of microstructure and texture, particularly the formation of recrystallization texture was studied. The results indicated that initial grain size and texture had a significant effect on texture evolution and magnetic properties. Large initial grains led to coarse deformed grains with dense and long shear bands after warm rolling. Such long shear bands resulted in growth advantage for {1 1 3} 〈3 6 1〉 oriented grains during recrystallization. On the other hand, sharp {11 h} 〈1, 2, 1/h〉 (α∗-fiber) texture in the coarse-grained sample led to dominant {1 1 2} 〈1 1 0〉 texture after warm rolling. Such {1 1 2} 〈1 1 0〉 deformed grains provided massive nucleation sites for {1 1 3} 〈3 6 1〉 oriented grains during subsequent recrystallization. These {1 1 3} 〈3 6 1〉 grains were confirmed to exhibit an advantage on grain growth compared to γ-fiber grains. As a result, significant {1 1 3} 〈3 6 1〉 texture was developed and unfavorable γ-fiber texture was inhibited in the final annealed sheet. Both these aspects led to superior magnetic properties in the sample with largest initial grain size. The magnetic induction B8 was 1.36 T and the high frequency core loss P10/400 was 17.07 W/kg.

Numerical Study of Splash Detail Due to Grain Impact on Granular Bed

NASA Astrophysics Data System (ADS)

Tanabe, Takahiro; Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku

2017-04-01

Massive sediment transport phenomena, such as sand storm and drifting snow, pose a considerable threat to human life. Further, the formation of geomorphological patterns on sand-desert and snowfield surfaces as a result of sediment transport, such as dunes and ripples, is of considerable research interest. Because the major component of the grain entrainment into the air is caused by both the collision and ejection, it is necessary to focus on the collisions between wind-blown grains and surface of sand field along with the resultant ejection grains from the surfaces, which processes are, as a whole, called a splash process. However, because of complexity of jumping grains over the ground surface, detailed measurement is very hard. Therefore, to investigate the splash process, we simulate detailed process of splash caused by 1-grain impact onto a randomly packed granular bed using discrete element method. As a result, we obtained good correspondence between our numerical results and the findings of previous experiments for the movement of ejected grains. Furthermore, the distributions of the ejection angle and the vertical ejection speed for individual grains vary depending on the relative timing at which the grains are ejected after the initial impact. Obvious differences are observed between the distributions of grains ejected during the earlier and later splash periods: the form of the vertical ejection-speed distribution varies from a power-law form to a lognormal form with time, and this difference is related to the grain trajectory after ejection [1]. In addition, we focus on the bulk dynamics inside the granular bed to relate the ejected grains behavior to the force propagations from the first impact to the ejection of each grain. [1] T. Tanabe, T. Shimada, N. Ito, and, H. Nishimori, (submitted)

Climate and the Soviet Grain Crisis of 1928

NASA Astrophysics Data System (ADS)

Welker, Jean Edward

1995-01-01

This dissertation tests the premise that peasant hoarding of surplus grain supplies and the refusal of the rural Soviet peasants to sell grain to state procurement apparatus during the late New Economic Policy period, caused the Grain Crisis of 1928. The peasants' reluctance to sell grain and claims of peasant hoarding could only occur if sufficient grain surpluses existed during this period. The existence of these assumed grain surpluses is shown to be highly improbable. First, the large but inconsistent body of 1920s grain statistics was evaluated per se and related to two periods of pre-WWI data, the Witte and Stolypin years, on a practical comparison whenever possible. For both these pre-World War I periods, intensive links between rapid industrialization and agriculture had been established similar to the conditions of the 1920s. The climatic conditions of the two imperial and one Soviet period in the 1920s, especially drought in 1927, was analyzed, and its impact on grain production estimated and interpreted. The conclusion was reached that the cause of drop in grain production in 1927 was due to a long-term and persistent trend of regional drought affecting spring wheat yields, especially in the areas of the Middle Volga and Kazakhstan. Second, the resultant conclusion was reached that there was insufficient bread grain on a national basis in 1927 to meet the essential needs of the rural peasants, much less the increasing demands of the government procurements. Third, the government's 1927 policy of monopolizing all available "surpluses" on the grain market under the false assumption that these surpluses were abundant, demonstrated either naivete and incompetence, or political expediency. This monopolization contributed to a breakdown in the marketing distribution of available grain, and generally exacerbated the poor procurement situation which was publically and incorrectly blamed on the peasants' hoarding.

Understanding the impact of grain structure in austenitic stainless steel from a nanograined regime to a coarse-grained regime on osteoblast functions using a novel metal deformation-annealing sequence.

PubMed

Misra, R D K; Nune, C; Pesacreta, T C; Somani, M C; Karjalainen, L P

2013-04-01

Metallic biomedical devices with nanometer-sized grains (NGs) provide surfaces that are different from their coarse-grained (CG) (tens of micrometer) counterparts in terms of increased fraction of grain boundaries (NG>50%; CG<2-3%). The novel concept of 'phase-reversion' involving a controlled deformation-annealing sequence is used to obtain a wide range of grain structures, starting from the NG regime to the CG regime, to demonstrate that the grain structure significantly impacts cellular interactions and osteoblast functions. The uniqueness of this concept is the ability to address the critical aspect of cellular activity in nanostructured materials, because a range of grain sizes from NG to CG are obtained in a single material using an identical set of parameters. This is in addition to a high strength/weight ratio and superior wear and corrosion resistance. These multiple attributes are important for the long-term stability of biomedical devices. Experiments on the interplay between grain structure from the NG regime to CG in austenitic stainless steel on osteoblast functions indicated that cell attachment, proliferation, viability, morphology and spread varied with grain size and were favorably modulated on the NG and ultrafine-grain structure. Furthermore, immunofluorescence studies demonstrated stronger vinculin signals associated with actin stress fibers in the outer regions of the cells and cellular extensions on the NG surface. The differences in the cellular response with change in grain structure are attributed to grain structure and degree of hydrophilicity. The study lays the foundation for a new branch of nanostructured materials for biomedical applications. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Rheology of ice I at low stress and elevated confining pressure

USGS Publications Warehouse

Durham, W.B.; Stern, L.A.; Kirby, S.H.

2001-01-01

Triaxial compression testing of pure, polycrystalline water ice I at conditions relevant to planetary interiors and near-surface environments (differential stresses 0.45 to 10 MPa, temperatures 200 to 250 K, confining pressure 50 MPa) reveals that a complex variety of rheologies and grain structures may exist for ice and that rheology of ice appears to depend strongly on the grain structures. The creep of polycrystalline ice I with average grain size of 0.25 mm and larger is consistent with previously published dislocation creep laws, which are now extended to strain rates as low as 2 ?? 10-8s-1. When ice I is reduced to very fine and uniform grain size by rapid pressure release from the ice II stability field, the rheology changes dramatically. At 200 and 220 K the rheology matches the grain-size-sensitive rheology measured by Goldsby and Kohlstedt [1997, this issue] at 1 atm. This finding dispels concerns that the Goldsby and Kohlstedt results were influenced by mechanisms such as microfracturing and cavitation, processes not expected to operate at elevated pressures in planetary interiors. At 233 K and above, grain growth causes the fine-grained ice to become more creep resistant. Scanning electron microscopy investigation of some of these deformed samples shows that grains have markedly coarsened and the strain hardening can be modeled by normal grain growth and the Goldsby and Kohlstedt rheology. Several samples also displayed very heterogeneous grain sizes and high aspect ratio grain shapes. Grain-size-sensitive creep and dislocation creep coincidentally contribute roughly equal amounts of strain rate at conditions of stress, temperature, and grain size that are typical of terrestrial and planetary settings, so modeling ice dynamics in these settings must include both mechanisms. Copyright 2001 by the American Geophysical Union.

Effects of polymorphic variations in tumor necrosis factor alpha and occupational exposure to grain dust on longitudinal decline in pulmonary function.

PubMed

Pahwa, Punam; Nakagawa, Kazuko; Koehncke, Niels; McDuffie, Helen H

2009-01-01

Longitudinal declines in pulmonary function are associated with individuals experiencing occupational exposure to organic dusts in combination with lifestyle factors such as cigarette smoking and with genetic factors, and interactions between these factors. To investigate the relationship between polymorphism of genes encoding Tumor Necrosis Factor Alpha (TNF-alpha) and longitudinal lung function decline in grain workers exposed to grain dust. Male grain handlers who participated in the Saskatchewan Grain Workers Surveillance Program from 2002 through 2005 provided demographic, occupational, lifestyle, and respiratory symptoms information as well as pulmonary function measurements and DNA for genotyping. Marginal models using the generalized estimating equations approach were fitted by using a SAS PROC GENMOD to predict the annual decline in Forced Expired Volume in one second (FEV(1)) and Forced Vital Capacity (FVC). Smoking intensity contributed to the decline in FEV(1.)Among *1/*1 homozygotes and *1/*2 heterozygotes, grain workers with <10 years in the grain industry had significantly lower FEV(1)declines compared to those of the other two exposure groups (>10 and < or =20 years, and >20 years in the grain industry). The annual declines in FEV(1)for grain workers who were either *1/*1 homozygote or *1/*2 heterozygote and had been in the grain industry for <10 years were lower by comparison to those of grain workers who were *2/*2 genotype and had been in the industry for <10 years. This research demonstrates that years in the grain industry is an effect modifier between TNF-alpha 308 genotype and longitudinal decline in FEV(1)in male subjects exposed to grain dust.

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Atwani, Osman; Hinks, Jonathan; Greaves, Graeme

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess ~10–20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency.

Grain dryer temperature field analysis

NASA Astrophysics Data System (ADS)

Li, Shizhuang; Cao, Shukun; Meng, Wenjing; Ma, Lingran

2017-09-01

Taking into account the drying process in the hot air temperature on the grain temperature has a great impact, and grain temperature and determines the quality of food after baking, so in order to ensure that the grain drying temperature in the safe range, the use of ANSYS FLUENT module of grain The temperature field was simulated in the drying process. The horizontal spacing of the angle box was 200mm and the vertical spacing was 240mm. At this time, the grain temperature distribution was more uniform and the drying was more adequate.

Grain size control of rhenium strip

NASA Technical Reports Server (NTRS)

Schuster, Gary B.

1991-01-01

Ensuring the desired grain size in the pure Re strip employed by the SP-100 space nuclear reactor design entails the establishment of an initial grain size in the as-received strip and the avoidance of excessive grain growth during subsequent fabrication. Pure Re tapered tensile specimens have been fabricated and tested in order to quantify the effects of grain-boundary migration. Grain size could be rendered fine and uniform by means of a rolling procedure that uses rather large reductions between short intermediate anneals. The critical strain regime varies inversely with annealing temperature.

Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial.

PubMed

Roager, Henrik Munch; Vogt, Josef K; Kristensen, Mette; Hansen, Lea Benedicte S; Ibrügger, Sabine; Mærkedahl, Rasmus B; Bahl, Martin Iain; Lind, Mads Vendelbo; Nielsen, Rikke L; Frøkiær, Hanne; Gøbel, Rikke Juul; Landberg, Rikard; Ross, Alastair B; Brix, Susanne; Holck, Jesper; Meyer, Anne S; Sparholt, Morten H; Christensen, Anders F; Carvalho, Vera; Hartmann, Bolette; Holst, Jens Juul; Rumessen, Jüri Johannes; Linneberg, Allan; Sicheritz-Pontén, Thomas; Dalgaard, Marlene D; Blennow, Andreas; Frandsen, Henrik Lauritz; Villas-Bôas, Silas; Kristiansen, Karsten; Vestergaard, Henrik; Hansen, Torben; Ekstrøm, Claus T; Ritz, Christian; Nielsen, Henrik Bjørn; Pedersen, Oluf Borbye; Gupta, Ramneek; Lauritzen, Lotte; Licht, Tine Rask

2017-11-01

To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality. 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week dietary intervention periods comprising whole grain diet and refined grain diet, separated by a washout period of ≥6 weeks. The response to the interventions on the gut microbiome composition and insulin sensitivity as well on measures of glucose and lipid metabolism, gut functionality, inflammatory markers, anthropometry and urine metabolomics were assessed. 50 participants completed both periods with a whole grain intake of 179±50 g/day and 13±10 g/day in the whole grain and refined grain period, respectively. Compliance was confirmed by a difference in plasma alkylresorcinols (p<0.0001). Compared with refined grain, whole grain did not significantly alter glucose homeostasis and did not induce major changes in the faecal microbiome. Also, breath hydrogen levels, plasma short-chain fatty acids, intestinal integrity and intestinal transit time were not affected. The whole grain diet did, however, compared with the refined grain diet, decrease body weight (p<0.0001), serum inflammatory markers, interleukin (IL)-6 (p=0.009) and C-reactive protein (p=0.003). The reduction in body weight was consistent with a reduction in energy intake, and IL-6 reduction was associated with the amount of whole grain consumed, in particular with intake of rye. Compared with refined grain diet, whole grain diet did not alter insulin sensitivity and gut microbiome but reduced body weight and systemic low-grade inflammation. NCT01731366; Results. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Computational study of deformation mechanisms and grain size evolution in granulites - Implications for the rheology of the lower crust

NASA Astrophysics Data System (ADS)

Maierová, Petra; Lexa, Ondrej; Jeřábek, Petr; Schulmann, Karel; Franěk, Jan

2017-05-01

Most of granulite terrains worldwide are characterized by large mean grain sizes of 1 mm or more. An important exception are the high-pressure felsic granulites in the Bohemian Massif, the European Variscan belt. There, recrystallization of original coarse-grained ternary feldspar led to formation of a fine-grained (∼100 μm) mixed matrix dominated by plagioclase and K-feldspar. This change occurred at temperatures of ∼850 °C and was probably caused by chemically induced decomposition related to slight cooling and enhanced by deformation during continental collision. The resulting microstructure shows indications of diffusion creep assisted by melt-enhanced grain-boundary sliding. Further on, minor coarsening occurred associated with deformation by dislocation creep and aggregation of mineral phases. Using a thermodynamics-based model of grain size evolution we show that stability of the fine-grained microstructure crucially depends on Zener pinning in the two-phase mineral matrix. Pinning efficiently hinders grain growth, and the small grain size that resulted from the ternary feldspar decomposition can be stable even at high temperatures. The late switch from the grain-size-sensitive creep to dislocation creep is rather difficult to explain by temperature and strain rate (or stress) changes only. However, a simple incorporation of melt solidification can successfully simulate this behavior. Alternatively, the switch and the associated grain size growth can be related to mineral phase aggregation at lower pressure-temperature conditions resulting into a decrease of pinning efficiency. This study suggests that the fine grain size of the Bohemian granulites, in contrast to the common coarse-grained type, stems from abrupt recrystallization during the high-pressure high-temperature conditions, and pinning in the fine-grained matrix. Such a process may in some cases significantly and suddenly reduce the strength of the lower continental crust and allow for its efficient redistribution.

Investigating selective transport and abrasion on an alluvial fan using quantitative grain size and shape analysis

NASA Astrophysics Data System (ADS)

Litwin, K. L.; Jerolmack, D. J.

2011-12-01

Selective sorting and abrasion are the two major fluvial processes that are attributed to the downstream fining of sediments in rivers and alluvial fans. Selective transport is the process by which smaller grains are preferentially transported downstream while larger grains are deposited closer to the source. Abrasion is defined by the production of fine sediments and sand that occurs by saltation of gravel, where particle-to-particle collisions supply the energy required to break apart grains. We hypothesize that abrasion results in the gradual fining of large grains and the production of fine sands and silts, while sorting accounts for the differences in transport of these two grain-size fractions produced from abrasion, thereby creating the abrupt gravel-sand transition observed in many channel systems. In this research, we explore both selective transport and abrasion processes on the Dog Canyon alluvial fan near Alamogordo, New Mexico. We complete an extensive grain size analysis down the main channel of the fan employing an image-based technique that utilizes an autocorrelation process. We also characterize changes in grain shape using standard shape parameters, as well as Fourier analysis, which allows the study of contributions of grain roughness on a variety of length scales. Sorting appears to dominate the upper portion of the fan; the grain-size distribution narrows moving downstream until reaching a point of equal mobility, at which point sorting ceases. Abrasion exerts a subtle but persistent effect on grains during transport down the fan. Shape analysis reveals that particles become more rounded by the removal of small-scale textural features, a process that is expected to only modestly influence grain size of gravel, but should produce significant quantities of sand. This study provides a better understanding of the importance of grain abrasion and sorting on the downstream fining of channel grains in an alluvial fan, as well as an improved knowledge about the abrupt gravel-sand transition observed in a majority of alluvial fans.

Plate-tectonic boundary formation by grain-damage and pinning

NASA Astrophysics Data System (ADS)

Bercovici, David

2015-04-01

Shear weakening in the lithosphere is an essential ingredient for understanding how and why plate tectonics is generated from mantle convection on terrestrial planets. I present continued work on a theoretical model for lithospheric shear-localization and plate generation through damage, grain evolution and Zener pinning in two-phase (polycrystalline) lithospheric rocks. Grain size evolves through the competition between coarsening, which drives grain-growth, with damage, which drives grain reduction. The interface between phases controls Zener pinning, which impedes grain growth. Damage to the interface enhances the Zener pinning effect, which then reduces grain-size, forcing the rheology into the grain-size-dependent diffusion creep regime. This process thus allows damage and rheological weakening to co-exist, providing a necessary shear-localizing feedback. Moreover, because pinning inhibits grain-growth it promotes shear-zone longevity and plate-boundary inheritance. This theory has been applied recently to the emergence of plate tectonics in the Archean by transient subduction and accumulation of plate boundaries over 1Gyr, as well as to rapid slab detachment and abrupt tectonic changes. New work explores the saturation of interface damage at low interface curvature (e.g., because it is associated with larger grains that take up more of the damage, and/or because interface area is reduced). This effect allows three possible equilibrium grain-sizes for a given stress; a small-grain-size high-shear state in diffusion creep, a large grain-size low shear state in dislocation creep, and an intermediate state (often near the deformation map phase-boundary). The low and high grain-size states are stable, while the intermediate one is unstable. This implies that a material deformed at a given stress can acquire two stable deformation regimes, a low- and high- shear state; these are indicative of plate-like flows, i.e, the coexistence of both slowly deforming plates and rapidly deforming plate boundaries.

Photophoretic Levitation and Trapping of Dust in the Inner Regions of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

McNally, Colin P.; McClure, Melissa K.

2017-01-01

In protoplanetary disks, the differential gravity-driven settling of dust grains with respect to gas and with respect to grains of varying sizes determines the observability of grains, and sets the conditions for grain growth and eventually planet formation. In this work, we explore the effect of photophoresis on the settling of large dust grains in the inner regions of actively accreting protoplanetary disks. Photophoretic forces on dust grains result from the collision of gas molecules with differentially heated grains. We undertake one-dimensional dust settling calculations to determine the equilibrium vertical distribution of dust grains in each column of the disk. In the process we introduce a new treatment of the photophoresis force which is consistent at all optical depths with the representation of the radiative intensity field in a two-stream radiative transfer approximation. The levitation of large dust grains creates a photophoretic dust trap several scale heights above the mid-plane in the inner regions of the disk where the dissipation of accretion energy is significant. We find that differential settling of dust grains is radically altered in these regions of the disk, with large dust grains trapped in a layer below the stellar irradiation surface, where the dust to gas mass ratio can be enhanced by a factor of a hundred for the relevant particles. The photophoretic trapping effect has a strong dependence on particle size and porosity.

Effect of Hot Rolling on the Microstructure and Mechanical Properties of Nitrogen Alloyed Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Chenna Krishna, S.; Karthick, N. K.; Jha, Abhay K.; Pant, Bhanu; Cherian, Roy M.

2018-05-01

In the present investigation, the effect of multi-pass hot rolling in the temperature range of 700-1000 °C on the microstructure and mechanical properties of nitrogen alloyed austenitic stainless steel was studied with the aid of optical microscopy, tensile testing and x-ray diffraction measurements. The microstructural changes that occurred in the hot rolled specimens were elongation of grains in rolling direction, nucleation of new grains at the grain boundaries of elongated grains and growth of nucleated grains to form fully recrystallized grains. Elongated grains formed at lower rolling temperature (700-800 °C) due to inadequate strain/temperature for the initiation of dynamic recrystallization. At higher rolling temperature (900-1000 °C), fine grains formed due to dynamic recrystallization. Tensile properties showed strong dependency on the rolling temperature. Tensile strength increased with the decrease in the rolling temperature at the cost of ductility. Maximum strength was observed in samples hot rolled at 700 °C with yield strength of 917 MPa and ductility of 25%. This variation in the tensile properties with the rolling temperature is attributed to changes in the dislocation density and grain structure. The estimated yield strength from the dislocation density, solid solution and grain boundary strengthening closely matched with experimentally determined yield strength confirming the role of dislocation density and grain size in the strengthening.

The Role of Carbon in Grain Refinement of Cast CrFeCoNi High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Liu, X. W.; Liu, L.; Liu, G.; Wu, X. X.; Lu, D. H.; Yao, J. Q.; Jiang, W. M.; Fan, Z. T.; Zhang, W. B.

2018-03-01

As a promising engineering material, high-entropy alloys (HEAs) CrFeCoNi system has attracted extensive attention worldwide. Their cast alloys are of great importance because of their great formability of complex components, which can be further improved through the transition of the columnar to equiaxed grains and grain refinement. In the current work, the influence of C contents on the grain structures and mechanical properties of the as-cast high-entropy alloy CrFeCoNi was chosen as the target and systematically studied via a hybrid approach of the experiments and thermodynamic calculations. The alloys with various C additions were prepared by arc melting and drop cast. The as-cast macrostructure and microstructure were characterized using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The cast HEAs transform from coarse columnar grains into equiaxed grains with the C level increased to ≥ 2 at. pct and the size of equiaxed grains is further decreased with the increasing C addition. It is revealed that the interdendritic segregation of Cr and C results in grain boundary precipitation of M23C6 carbides. The grain refinement is attributed to the additional constitutional supercoiling from the C addition. The yield stress and tensile strength at room temperature are improved due to the transition of columnar to equiaxed grains and grain refinement.

The Effect of Grain Size on the Strain Hardening Behavior for Extruded ZK61 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Zhang, Lixin; Zhang, Wencong; Chen, Wenzhen; Duan, Junpeng; Wang, Wenke; Wang, Erde

2017-12-01

The effects of grain size on the tensile and compressive strain hardening behaviors for extruded ZK61 alloys have been investigated by uniaxial tensile and compressive tests along the extrusion directions. Cylindrical tension and compression specimens of extruded ZK61 alloys with various sized grain were fabricated by annealing treatments. Tensile and compressive tests at ambient temperature were conducted at a strain rate of 0.5 × 10-3 s-1. The results indicate that both tensile strain hardening and compressive strain hardening of ZK61 alloys with different grain sizes have an athermal regime of dislocation accumulation in early deformation. The threshold stress value caused dynamic recovery is predominantly related to grain size in tensile strain hardening, but the threshold stress values for different grain sizes are almost identical in compressive strain hardening. There are obvious transition points on the tensile strain hardening curves which indicate the occurrence of dynamic recrystallization (DRX). The tensile strain hardening rate of the coarse-grained alloy obviously decreases faster than that of fine-grained alloys before DRX and the tensile strain hardening curves of different grain sizes basically tend to parallel after DRX. The compressive strain hardening rate of the fine-grained alloy obviously increases faster than that of coarse-grained alloy for twin-induced strain hardening, but compressive strain hardening curves also tend to parallel after twinning is exhausted.

Detection and validation of QTLs for milky-white grains caused by high temperature during the ripening period in Japonica rice

PubMed Central

Miyahara, Katsunori; Wada, Takuya; Sonoda, Jun-ya; Tsukaguchi, Tadashi; Miyazaki, Masayuki; Tsubone, Masao; Yamaguchi, Osamu; Ishibashi, Masafumi; Iwasawa, Norio; Umemoto, Takayuki; Kondo, Motohiko

2017-01-01

The occurrence of chalky rice (Oryza sativa L.) grains caused by high temperature is a serious problem in rice production. Of the several kinds of chalky grains, milky-white grains are not well analyzed. The milky-white rice grain phenomenon is caused by genetic factors as well as environmental and nutritional conditions. To analyze the genetic control system for rice grain quality, we raised recombinant inbred lines from progeny produced from ‘Tsukushiroman’ (high temperature sensitive) and ‘Chikushi 52’ (high temperature tolerant) cultivars. Quantitative trait locus (QTL) analysis revealed that the QTL on chromosome 4, linked to the simple sequence repeat marker RM16424, contributed substantially to the occurrence of milky-white grains, as it was detected over two experimental years. To validate the effect of the QTL, we developed near isogenic lines that have the ‘Chikushi 52’ segment on the short arm of chromosome 4 in the ‘Tsukushiroman’ genetic background, and that had a lower milky-white grain ratio than that of ‘Tsukushiroman’ when exposed to high temperatures during the ripening period. These results suggest that the ‘Chikushi 52’ allele on chromosome 4 suppresses the occurrence of milky-white grains and improves rice grain quality under heat stress during the grain ripening period. PMID:29085242

Effect of Hot Rolling on the Microstructure and Mechanical Properties of Nitrogen Alloyed Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Chenna Krishna, S.; Karthick, N. K.; Jha, Abhay K.; Pant, Bhanu; Cherian, Roy M.

2018-04-01

In the present investigation, the effect of multi-pass hot rolling in the temperature range of 700-1000 °C on the microstructure and mechanical properties of nitrogen alloyed austenitic stainless steel was studied with the aid of optical microscopy, tensile testing and x-ray diffraction measurements. The microstructural changes that occurred in the hot rolled specimens were elongation of grains in rolling direction, nucleation of new grains at the grain boundaries of elongated grains and growth of nucleated grains to form fully recrystallized grains. Elongated grains formed at lower rolling temperature (700-800 °C) due to inadequate strain/temperature for the initiation of dynamic recrystallization. At higher rolling temperature (900-1000 °C), fine grains formed due to dynamic recrystallization. Tensile properties showed strong dependency on the rolling temperature. Tensile strength increased with the decrease in the rolling temperature at the cost of ductility. Maximum strength was observed in samples hot rolled at 700 °C with yield strength of 917 MPa and ductility of 25%. This variation in the tensile properties with the rolling temperature is attributed to changes in the dislocation density and grain structure. The estimated yield strength from the dislocation density, solid solution and grain boundary strengthening closely matched with experimentally determined yield strength confirming the role of dislocation density and grain size in the strengthening.

The Role of Carbon in Grain Refinement of Cast CrFeCoNi High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Liu, X. W.; Liu, L.; Liu, G.; Wu, X. X.; Lu, D. H.; Yao, J. Q.; Jiang, W. M.; Fan, Z. T.; Zhang, W. B.

2018-06-01

As a promising engineering material, high-entropy alloys (HEAs) CrFeCoNi system has attracted extensive attention worldwide. Their cast alloys are of great importance because of their great formability of complex components, which can be further improved through the transition of the columnar to equiaxed grains and grain refinement. In the current work, the influence of C contents on the grain structures and mechanical properties of the as-cast high-entropy alloy CrFeCoNi was chosen as the target and systematically studied via a hybrid approach of the experiments and thermodynamic calculations. The alloys with various C additions were prepared by arc melting and drop cast. The as-cast macrostructure and microstructure were characterized using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The cast HEAs transform from coarse columnar grains into equiaxed grains with the C level increased to ≥ 2 at. pct and the size of equiaxed grains is further decreased with the increasing C addition. It is revealed that the interdendritic segregation of Cr and C results in grain boundary precipitation of M23C6 carbides. The grain refinement is attributed to the additional constitutional supercoiling from the C addition. The yield stress and tensile strength at room temperature are improved due to the transition of columnar to equiaxed grains and grain refinement.

Effects of Favorable Alleles for Water-Soluble Carbohydrates at Grain Filling on Grain Weight under Drought and Heat Stresses in Wheat

PubMed Central

Chang, Xiaoping; Li, Runzhi; Jing, Ruilian

2014-01-01

Drought, heat and other abiotic stresses during grain filling can result in reductions in grain weight. Conserved water-soluble carbohydrates (WSC) at early grain filling play an important role in partial compensation of reduced carbon supply. A diverse population of 262 historical winter wheat accessions was used in the present study. There were significant correlations between 1000-grain weight (TGW) and four types of WSC, viz. (1) total WSC at the mid-grain filling stage (14 days after flowering) produced by leaves and non-leaf organs; (2) WSC contributed by current leaf assimilation during the mid-grain filling; (3) WSC in non-leaf organs at the mid-grain filling, excluding the current leaf assimilation; and (4) WSC used for respiration and remobilization during the mid-grain filling. Association and favorable allele analyses of 209 genome-wide SSR markers and the four types of WSC were conducted using a mixed linear model. Seven novel favorable WSC alleles exhibited positive individual contributions to TGW, which were verified under 16 environments. Dosage effects of pyramided favorable WSC alleles and significantly linear correlations between the number of favorable WSC alleles and TGW were observed. Our results suggested that pyramiding more favorable WSC alleles was effective for improving both WSC and grain weight in future wheat breeding programs. PMID:25036550

The Relationship between Polyamines and Hormones in the Regulation of Wheat Grain Filling

PubMed Central

Liu, Yang; Gu, Dandan; Wu, Wei; Wen, Xiaoxia; Liao, Yuncheng

2013-01-01

The grain weight of wheat is strongly influenced by filling. Polyamines (PA) are involved in regulating plant growth. However, the effects of PA on wheat grain filling and its mechanism of action are unclear. The objective of the present study was to investigate the relationship between PAs and hormones in the regulation of wheat grain filling. Three PAs, spermidine (Spd), spermine (Spm), and putrescine (Put), were exogenously applied, and the grain filling characteristics and changes in endogenous PA and hormones, i.e., indole-3-acetic acid (IAA), zeatin (Z) + zeatin riboside (ZR), abscisic acid (ABA), ethylene (ETH) and gibberellin 1+4 (GAs), were quantified during wheat grain filling. Exogenous applications of Spd and Spm significantly increased the grain filling rate and weight, but exogenous Put had no significant effects on these measures. Exogenous Spd and Spm significantly increased the endogenous Spd, Spm, Z+ZR, ABA, and IAA contents and significantly decreased ETH evolution in grains. The endogenous Spd, Spm and Z+ZR contents were positively and significantly correlated with the grain filling rate and weight of wheat, and the endogenous ETH evolution was negatively and significantly correlated with the wheat grain filling rate and weight. Based upon these results, we concluded that PAs were involved in the balance of hormones that regulated the grain filling of wheat. PMID:24205154

Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

USGS Publications Warehouse

Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

2011-01-01

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

Study of composite thin films for applications in high density data storage

NASA Astrophysics Data System (ADS)

Yuan, Hua

Granular Co-alloy + oxide thin films are currently used as the magnetic recording layer of perpendicular media in hard disk drives. The microstructure of these films is composed mainly of fine (7--10 nm) magnetic grains physically surrounded by oxide phases, which produce magnetic isolation of the grains. As a result, the magnetic switching volume is maintained as small as the physical grain size. Consequently, ample number of magnetic switching units can be obtained in one recording bit, in other words, higher signal to noise ratios (SNR) can be achieved. Therefore, a good understanding and control of the microstructure of the films is very important for high areal density magnetic recording media. Interlayers and seedlayers play important roles in controlling the microstructure in terms of grain size, grain size distribution, oxide segregation and orientation dispersion of the crystallographic texture. Developing novel interlayers or seedlayers with smaller grain size is a key approach to produce smaller grain size in the recording layer. This study focuses on how to achieve smaller grain sizes in the recording layer through novel interlayer/seedlayer materials and processes. It also discusses the resulting microstructure in smaller-grain-size thin films. Metal + oxide (e.g. Ru + SiO2) composite thin films were chosen as interlayer and seedlayer materials due to their unique segregated microstructure. Such layers can be grown epitaxially on top of fcc metal seedlayers with good orientation. It can also provide an epitaxial growth template for the subsequent magnetic layer (recording layer). The metal and oxide phases in the composite thin films are immiscible. The final microstructure of the interlayer depends on factors, such as, sputtering pressure, oxide species, oxide volume fraction, thickness, alloy composition, temperature etc. Moreover, it has been found that the microstructure of the composite thin films is affected mostly by two important factors---oxide volume fraction and sputtering pressure. The latter affects grain size and grain segregation through surface-diffusion modification and the self-shadowing effect. The composite Ru + oxide interlayers were found to have various microstructures under various sputtering conditions. Four characteristic microstructure zones can be identified as a function of oxide volume fraction and sputtering pressure---"percolated" (A), "maze" (T), "granular" (B) and "embedded" (C), based on which, a new structural zone model (SZM) is established for composite thin films. The granular microstructure of zone B is of particular interest for recording media application. The grain size of interlayers is a strong function of pressure, oxide species and oxide volume fraction. Magnetic layers grown on top of these interlayers were found to be significantly affected by the interlayer microstructure. One-to-one grain epitaxial growth is very difficult to achieve when the grain size is too small. As a result, the magnetic properties of smaller grain size magnetic layers deteriorate due to poor growth. This presents a huge challenge to high areal density magnetic recording media. A novel approach of Ar-ion etched Ru seedlayer, which can improve epitaxy between interlayer and magnetic layer is proposed. This method produces interlayer thin films of: (1) smaller grain size and higher nucleation density due to both a rougher seedlayer surface and an oxide addition in the interlayer; (2) good (00.2) texture due to the growth on top of the low pressure deposited Ru seedlayer; (3) dome-shape grain morphology due to the high pressure deposition. Therefore, a significant Ru grain size reduction with enhanced granular morphology and improved grain-to-grain epitaxy with the magnetic layer was achieved. High resolution transmission electron microscopy (TEM) techniques, such as, electron energy loss spectroscopy (EELS), energy-filtered TEM (EFTEM), energy-dispersive X-ray spectroscopy (EDS) and mapping, and high angle annular dark field (HAADF) imaging have been utilized to investigate elemental distribution and grain morphology in composite magnetic thin films of different grain sizes. An oxygen-rich grain shell of about 0.5 ˜ 1 nm thickness is often observed for most media with different grain sizes. Reducing the grain size increases surface to volume ratio. With more surface area, smaller grains are more vulnerable to oxidization, resulting in even greater influence of the oxide on the magnetic properties of the grains.

Austenite grain growth simulation considering the solute-drag effect and pinning effect.

PubMed

Fujiyama, Naoto; Nishibata, Toshinobu; Seki, Akira; Hirata, Hiroyuki; Kojima, Kazuhiro; Ogawa, Kazuhiro

2017-01-01

The pinning effect is useful for restraining austenite grain growth in low alloy steel and improving heat affected zone toughness in welded joints. We propose a new calculation model for predicting austenite grain growth behavior. The model is mainly comprised of two theories: the solute-drag effect and the pinning effect of TiN precipitates. The calculation of the solute-drag effect is based on the hypothesis that the width of each austenite grain boundary is constant and that the element content maintains equilibrium segregation at the austenite grain boundaries. We used Hillert's law under the assumption that the austenite grain boundary phase is a liquid so that we could estimate the equilibrium solute concentration at the austenite grain boundaries. The equilibrium solute concentration was calculated using the Thermo-Calc software. Pinning effect was estimated by Nishizawa's equation. The calculated austenite grain growth at 1473-1673 K showed excellent correspondence with the experimental results.

Structure and phase composition of ultrafine-grained TiNb alloy after high-temperature annealings

NASA Astrophysics Data System (ADS)

Eroshenko, Anna Yu.; Glukhov, Ivan A.; Mairambekova, Aikol; Tolmachev, Alexey I.; Sharkeev, Yurii P.

2017-12-01

The paper presents the experimental data observed in the microstructure and phase composition of ultrafine-grained Ti-40 mass % Nb (Ti40Nb) alloy after high-temperature annealings. The ultrafine-grained Ti40Nb alloy is produced by severe plastic deformation (SPD). This method includes multiple abc-pressing and multi-pass rolling followed by further pre-recrystallizing annealing which, in its turn, enhances the formation of ultrafine-grained structures with mean size of 0.28 µm involving stable β- and α-phase and metastable nanosized ω-phase in the alloy. It is shown that annealing at 500°C preserves the ultrafine-grained structure and phase composition. In cases of annealing at 800°C the ultrafine-grained state transforms into the coarse-grained state. The stable β-phase and the nanosized metastable ω-phase have been identified in the coarse-grained structure.

Effects of grain size on the properties of bulk nanocrystalline Co-Ni alloys

NASA Astrophysics Data System (ADS)

Qiao, Gui-Ying; Xiao, Fu-Ren

2017-08-01

Bulk nanocrystalline Co78Ni22 alloys with grain size ranging from 5 nm to 35 nm were prepared by high-speed jet electrodeposition (HSJED) and annealing. Microhardness and magnetic properties of these alloys were investigated by microhardness tester and vibrating sample magnetometer. Effects of grain size on these characteristics were also discussed. Results show that the microhardness of nanocrystalline Co78Ni22 alloys increases following a d -1/2-power law with decreasing grain size d. This phenomenon fits the Hall-Petch law when the grain size ranges from 5 nm to 35 nm. However, coercivity H c increases following a 1/d-power law with increasing grain size when the grain size ranges from 5 nm to 15.9 nm. Coercivity H c decreases again for grain sizes above 16.6 nm according to the d 6-power law.

Automatic vision-based grain optimization and analysis of multi-crystalline solar wafers using hierarchical region growing

NASA Astrophysics Data System (ADS)

Fan, Shu-Kai S.; Tsai, Du-Ming; Chuang, Wei-Che

2017-04-01

Solar power has become an attractive alternative source of energy. The multi-crystalline solar cell has been widely accepted in the market because it has a relatively low manufacturing cost. Multi-crystalline solar wafers with larger grain sizes and fewer grain boundaries are higher quality and convert energy more efficiently than mono-crystalline solar cells. In this article, a new image processing method is proposed for assessing the wafer quality. An adaptive segmentation algorithm based on region growing is developed to separate the closed regions of individual grains. Using the proposed method, the shape and size of each grain in the wafer image can be precisely evaluated. Two measures of average grain size are taken from the literature and modified to estimate the average grain size. The resulting average grain size estimate dictates the quality of the crystalline solar wafers and can be considered a viable quantitative indicator of conversion efficiency.

Effect of Strain Restored Energy on Abnormal Grain Growth in Mg Alloy Simulated by Phase Field Methods

NASA Astrophysics Data System (ADS)

Wu, Yan; Huang, Yuan-yuan

2018-03-01

Abnormal grain growth of single phase AZ31 Mg alloy in the spatio-temporal process has been simulated by phase field models, and the influencing factors of abnormal grain growth are studied in order to find the ways to control secondary recrystallization in the microstructure. The study aims to find out the mechanisms for abnormal grain growth in real alloys. It is shown from the simulated results that the abnormal grain growth can be controlled by the strain restored energy. Secondary recrystallization after an annealing treatment can be induced if there are grains of a certain orientation in the microstructure with local high restored energy. However, if the value of the local restored energy at a certain grain orientation is not greater than 1.1E 0, there may be no abnormal grain growth in the microstructure.

Role of grain and grain boundary on the electrical and thermal conductivity of Bi0.9Y0.1Fe0.9Mn0.1O3 ceramics

NASA Astrophysics Data System (ADS)

Pandey, Rabichandra; Panda, Chandrakanta; Kumar, Pawan; Pradhan, Lagen Kumar; Kar, Manoranjan

2017-05-01

Role of grain and grain boundary on electrical and thermal conductivity of Bi0.9Y0.1Fe0.9Mn0.1O3 ceramic was investigated systematically. Tartaric acid modified sol gel method was used to synthesize the compound. X-ray diffraction technique was used to confirm the formation of single phase orthorhombic (Pbnm) structure. Electrical properties of the sample were measured with a wide frequency range from 100Hz to 10MHz at different temperature from 40°C to 250°C. AC impedance studies indicate the presence of grain and grain boundary effect. The negative temperature coefficient of resistance (NTCR) behaviour of the compound has been confirmed by the cole-cole plot. DC electrical and thermal conductivities of the compound were explained on the basis of grain and grain boundaries.

Swash mark and grain flow

USGS Publications Warehouse

Sallenger,, Asbury H.

1981-01-01

Swash marks composed entirely of coarse sand are commonly found on coarse-sand beaches. These swash marks are 10 to 30 centimeters in width and a few millimeters to one centimeter in height. Previous observations, mostly on finer-sand beaches, indicate swash marks are seldom over a few millimeters in height and are commonly composed of material readily floated by surface tension (e.g., mica flakes and shell fragments). Swash marks composed of coarse sand have both fining seaward and fining with depth trends in grain size. Apparently, the leading margin of a wave upwash drives a highly concentrated flow of grains in which both grain size and grain velocity decrease with depth. Therefore, large grains are transported at greater velocities than are smaller grains. Thus, at the maximum advance of an upwash, a swash mark is deposited which has the observed fining seaward and fining with depth trends in grain size.

Photoconductivity induced by nanoparticle segregated grain-boundary in spark plasma sintered BiFeO3

NASA Astrophysics Data System (ADS)

Nandy, Subhajit; Mocherla, Pavana S. V.; Sudakar, C.

2017-05-01

Photoconductivity studies on spark plasma sintered BiFeO3 samples with two contrasting morphologies, viz., nanoparticle-segregated grain boundary (BFO-AP) and clean grain boundary (BFO-AA), show that their photo-response is largely influenced by the grain boundary defects. Impedance analyses at 300 K and 573 K clearly demarcate the contributions from grain, grain-boundary, and the nanoparticle-segregated grain-boundary conductivities. I-V characteristics under 1 sun illumination show one order of higher conductivity for BFO-AP, whereas conductivity decreases for BFO-AA sample. Larger photocurrent in BFO-AP is attributed to the extra conduction path provided by oxygen vacancies on the nanoparticle surfaces residing at the grain boundaries. Creation of photo-induced traps under illumination and the absence of surface conduction channels in BFO-AA are surmised to result in a decreased conductivity on illumination.

Grain-scale supercharging and breakdown on airless regoliths

NASA Astrophysics Data System (ADS)

Zimmerman, M. I.; Farrell, W. M.; Hartzell, C. M.; Wang, X.; Horanyi, M.; Hurley, D. M.; Hibbitts, K.

2016-10-01

Interactions of the solar wind and emitted photoelectrons with airless bodies have been studied extensively. However, the details of how charged particles interact with the regolith at the scale of a single grain have remained largely uncharacterized. Recent efforts have focused upon determining total surface charge under photoemission and solar wind bombardment and the associated electric field and potential. In this work, theory and simulations are used to show that grain-grain charge differences can exceed classical sheath predictions by several orders of magnitude, sometimes reaching dielectric breakdown levels. Temperature-dependent electrical conductivity works against supercharging by allowing current to leak through individual grains; the balance between internal conduction and surface charging controls the maximum possible grain-to-grain electric field. Understanding the finer details of regolith grain charging, conductive equilibrium, and dielectric breakdown will improve future numerical studies of space weathering and dust levitation on airless bodies.

Comments on 'Extinct radioactivities: Trapped residuals of presolar grains'

NASA Technical Reports Server (NTRS)

Trivedi, B. M. P.

1977-01-01

It has recently been suggested that extinct I-129 and Pu-244 were trapped in primitive-solar-nebula ('presolar') grains and decayed into radiogenic Xe-129 and fission Xe before the grains were incorporated into meteorite bodies. This idea is reconsidered in light of the thermal and metamorphic history of meteorites. The criteria that parent and daughter species should never separate and that minerals or grains containing the anomalous xenon should not be subjected to temperatures exceeding 500 C are applied to iron meteorites, achondrites, and chondrites to determine whether presolar grains could be the carriers of rare-gas anomalies to meteorites. The results strongly indicate that the xenon anomaly could not have originated in presolar grains. Other difficulties with the presolar-grain model are discussed, including insufficiently small grain sizes, large variations in Xe-129/I-127 ratios in various meteorites, and apparently unrealistic meteorite formation times and locations.

Automated grain mapping using wide angle convergent beam electron diffraction in transmission electron microscope for nanomaterials.

PubMed

Kumar, Vineet

2011-12-01

The grain size statistics, commonly derived from the grain map of a material sample, are important microstructure characteristics that greatly influence its properties. The grain map for nanomaterials is usually obtained manually by visual inspection of the transmission electron microscope (TEM) micrographs because automated methods do not perform satisfactorily. While the visual inspection method provides reliable results, it is a labor intensive process and is often prone to human errors. In this article, an automated grain mapping method is developed using TEM diffraction patterns. The presented method uses wide angle convergent beam diffraction in the TEM. The automated technique was applied on a platinum thin film sample to obtain the grain map and subsequently derive grain size statistics from it. The grain size statistics obtained with the automated method were found in good agreement with the visual inspection method.

Influence of grain size distribution on the mechanical behavior of light alloys in wide range of strain rates

NASA Astrophysics Data System (ADS)

Skripnyak, Vladimir A.; Skripnyak, Natalia V.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.

2017-01-01

Inelastic deformation and damage at the mesoscale level of ultrafine grained (UFG) light alloys with distribution of grain size were investigated in wide loading conditions by experimental and computer simulation methods. The computational multiscale models of representative volume element (RVE) with the unimodal and bimodal grain size distributions were developed using the data of structure researches aluminum and magnesium UFG alloys. The critical fracture stress of UFG alloys on mesoscale level depends on relative volumes of coarse grains. Microcracks nucleation at quasi-static and dynamic loading is associated with strain localization in UFG partial volumes with bimodal grain size distribution. Microcracks arise in the vicinity of coarse and ultrafine grains boundaries. It is revealed that the occurrence of bimodal grain size distributions causes the increasing of UFG alloys ductility, but decreasing of the tensile strength.

GIS-based spatial decision support system for grain logistics management

NASA Astrophysics Data System (ADS)

Zhen, Tong; Ge, Hongyi; Jiang, Yuying; Che, Yi

2010-07-01

Grain logistics is the important component of the social logistics, which can be attributed to frequent circulation and the great quantity. At present time, there is no modern grain logistics distribution management system, and the logistics cost is the high. Geographic Information Systems (GIS) have been widely used for spatial data manipulation and model operations and provide effective decision support through its spatial database management capabilities and cartographic visualization. In the present paper, a spatial decision support system (SDSS) is proposed to support policy makers and to reduce the cost of grain logistics. The system is composed of two major components: grain logistics goods tracking model and vehicle routing problem optimization model and also allows incorporation of data coming from external sources. The proposed system is an effective tool to manage grain logistics in order to increase the speed of grain logistics and reduce the grain circulation cost.

Grain-Scale Supercharging and Breakdown on Airless Regoliths

NASA Technical Reports Server (NTRS)

Zimmerman, M. I.; Farrell, W. M.; Hartzell, C.M.; Wang, X.; Horanyi, M.; Hurley, D. M.; Hibbitts, K.

2016-01-01

Interactions of the solar wind and emitted photoelectrons with airless bodies have been studied extensively. However, the details of how charged particles interact with the regolith at the scale of a single grain have remained largely uncharacterized. Recent efforts have focused upon determining total surface charge under photoemission and solar wind bombardment and the associated electric field and potential. In this work, theory and simulations are used to show that grain-grain charge differences can exceed classical sheath predictions by several orders of magnitude, sometimes reaching dielectric breakdown levels. Temperature-dependent electrical conductivity works against supercharging by allowing current to leak through individual grains; the balance between internal conduction and surface charging controls the maximum possible grain-to-grain electric field. Understanding the finer details of regolith grain charging, conductive equilibrium, and dielectric breakdown will improve future numerical studies of space weathering and dust levitation on airless bodies.

Search for Large Presolar Silicate Grains in the QUE 99177 CR Chondrite

NASA Technical Reports Server (NTRS)

Nguyen, A. N.; Messenger, S.

2012-01-01

Silicates are among the most abundant pre-solar grain type, and their diverse chemical and isotopic compos-tions preserve detailed constraints on their stellar origins, condensation conditions, and nucleosynthetic and interstellar processes. Yet, owing to their small sizes, relatively few grains have been measured for isotopic compositions besides O and Si, and their mineralogy is poorly characterized. The average grain size (approx 270 nm) limits the number of analyses that can be conducted on a given grain, and their identification among solar system silicates introduces contaminating signal. These difficulties can be overcome by identifying large presolar silicate grains. However, such grains are very rare and only two approx 1 micron grains have been discovered. We are conducting a dedicated search for large presolar silicates in size-separated QUE 99177 matrix material. This primitive meteorite has among the highest abundance of presolar silicates

Grain-Boundary Roughening in Colloidal Crystals

NASA Astrophysics Data System (ADS)

Liao, Maijia; Xiao, Xiao; Chui, Siu Tat; Han, Yilong

2018-04-01

In polycrystals, faceted grains may become round and rough at high temperatures. Such a roughening phenomenon remains poorly understood, partly because of the lack of experimental observations. Here, we directly visualize the roughening dynamics of grain boundaries inside thin-film colloidal crystals at the single-particle level using video microscopy. The thermal fluctuations of grain boundaries appear to exhibit both static and dynamic critical-like behaviors, in contrast to the Kosterlitz-Thouless transition in typical free surface roughening. The roughening point shifts towards the melting point as the grain boundary's mismatch angle θ decreases and is preempted by melting when θ <18 ° . Counterintuitively, the amplitude of grain-boundary fluctuations decreases above the roughening point. This could be attributed to the observed widening of the grain boundary. The roughening strongly affects the mobility of the grain boundary but not the stiffness. These results provide new guidance for the control of microstructures in polycrystals and further development of roughening theory.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krasheninnikov, S. I.

The equations of motion of a dust grain with non-spherical shape in plasma are generalized by incorporating the effects associated with propeller-like features of the grain's shape. For the grain shape close to rotationally symmetric, the stability of “stationary” (in terms of variables used in the grain dynamic equations) solutions are considered. It is found that propeller-like features of the grain's shape can crucially alter stability of such “stationary” states.

Whole-Grain Intake and Mortality from All Causes, Cardiovascular Disease, and Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies.

PubMed

Benisi-Kohansal, Sanaz; Saneei, Parvane; Salehi-Marzijarani, Mohammad; Larijani, Bagher; Esmaillzadeh, Ahmad

2016-11-01

No conclusive information is available about the relation between the consumption of whole grains and the risk of mortality. We aimed to conduct a meta-analysis of prospective cohort studies to summarize the relation between whole-grain intake and risk of mortality from all causes, cardiovascular disease, and total and specific cancers. A systematic search of the literature published earlier than March 2015 was conducted in Medline and PubMed, SCOPUS, EMBASE, and Cochrane Library to identify relevant articles. Prospective cohort studies that examined the association of total whole-grain intake or specific whole-grain foods with risk of mortality from all causes, cardiovascular disease, and total and specific cancers were considered. Twenty prospective cohort studies were included in the systematic review: 9 studies reported total whole-grain intake and 11 others reported specific whole-grain food intake. In a follow-up period of 5.5 to 26 y, there were 191,979 deaths (25,595 from cardiovascular disease, 32,746 from total cancers, and 2671 from specific cancers) in 2,282,603 participants. A greater intake of both total whole grains and specific whole-grain foods was significantly associated with a lower risk of all-cause mortality in the meta-analysis. The pooled RR for all-cause mortality for an increase of 3 servings total whole grains/d (90 g/d) was 0.83 (95% CI: 0.79, 0.88). Total whole-grain intake (0.84; 95% CI: 0.76, 0.93) and specific whole-grain foods (0.82; 95% CI: 0.75, 0.90) were also associated with a reduced risk of mortality from cardiovascular disease. Each additional 3 servings total whole grains/d was associated with a 25% lower risk of mortality from cardiovascular disease. An inverse association was observed between whole-grain intake and risk of mortality from total cancers (0.94; 95% CI: 0.91, 0.98). We found an inverse association between whole-grain intake and mortality from all causes, cardiovascular disease, and total cancers. © 2016 American Society for Nutrition.

Whole-Grain Intake and Mortality from All Causes, Cardiovascular Disease, and Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies123

PubMed Central

Benisi-Kohansal, Sanaz; Saneei, Parvane; Salehi-Marzijarani, Mohammad; Larijani, Bagher; Esmaillzadeh, Ahmad

2016-01-01

No conclusive information is available about the relation between the consumption of whole grains and the risk of mortality. We aimed to conduct a meta-analysis of prospective cohort studies to summarize the relation between whole-grain intake and risk of mortality from all causes, cardiovascular disease, and total and specific cancers. A systematic search of the literature published earlier than March 2015 was conducted in Medline and PubMed, SCOPUS, EMBASE, and Cochrane Library to identify relevant articles. Prospective cohort studies that examined the association of total whole-grain intake or specific whole-grain foods with risk of mortality from all causes, cardiovascular disease, and total and specific cancers were considered. Twenty prospective cohort studies were included in the systematic review: 9 studies reported total whole-grain intake and 11 others reported specific whole-grain food intake. In a follow-up period of 5.5 to 26 y, there were 191,979 deaths (25,595 from cardiovascular disease, 32,746 from total cancers, and 2671 from specific cancers) in 2,282,603 participants. A greater intake of both total whole grains and specific whole-grain foods was significantly associated with a lower risk of all-cause mortality in the meta-analysis. The pooled RR for all-cause mortality for an increase of 3 servings total whole grains/d (90 g/d) was 0.83 (95% CI: 0.79, 0.88). Total whole-grain intake (0.84; 95% CI: 0.76, 0.93) and specific whole-grain foods (0.82; 95% CI: 0.75, 0.90) were also associated with a reduced risk of mortality from cardiovascular disease. Each additional 3 servings total whole grains/d was associated with a 25% lower risk of mortality from cardiovascular disease. An inverse association was observed between whole-grain intake and risk of mortality from total cancers (0.94; 95% CI: 0.91, 0.98). We found an inverse association between whole-grain intake and mortality from all causes, cardiovascular disease, and total cancers. PMID:28140323

SEM Characterization of Extinguished Grains from Plasma-Ignited M30 Charges

NASA Technical Reports Server (NTRS)

Kinkennon, A.; Birk, A.; DelGuercio, M.; Kaste, P.; Lieb, R.; Newberry, J.; Pesce-Rodriguez, R.; Schroeder, M.

2000-01-01

M30 propellant grains that had been ignited in interrupted closed bomb experiments were characterize by scanning electron microscopy (SEM). Previous chemical analysis of extinguished grains had given no indications of plasma-propellant chemical interactions that could explain the increased burning rates that had been previously observed in full-pressure closed bomb experiments. (This does not mean that there is no unique chemistry occurring with plasma ignition. It may occur very early in the ignition event and then become obscured by the burning chemistry.) In this work, SEM was used to look at grain morphologies to determine if there were increases in the surface areas of the plasma-ignited grains which would contribute to the apparent increase in the burning rate. Charges were made using 30 propellant grains (approximately 32 grams) stacked in two tiers and in two concentric circles around a plastic straw. Each grain was notched so that, when the grains were expelled from the bomb during extinguishment, it could be determined in which tier and which circle each grain was originally packed. Charges were ignited in a closed bomb by either a nickel wire/Mylar-capillary plasma or black powder. The bomb contained a blowout disk that ruptured when the pressure reached 35 MPa, and the propellant was vented into a collection chamber packed with polyurethane foam. SEM analysis of the grains fired with a conventional black powder igniter showed no signs of unusual burning characteristics. The surfaces seemed to be evenly burned on the exteriors of the grains and in the perforations. Grains that had been subjected to plasma ignition, however, had pits, gouges, chasms, and cracks in the surfaces. The sides of the grains closest to the plasma had the greatest amount of damage, but even surfaces facing the outer wall of the bomb had small pits. The perforations contained gouges and abnormally burned regions (wormholes) that extended into the web. The SEM photos indicated that a grain from the top tier, which was farther away from the plasma ignition source, sustained more plasma-induced damage to the perforations and the web than did the grains on the bottom tier.

Carbon, nitrogen, magnesium, silicon, and titanium isotopic compositions of single interstellar silicon carbide grains from the Murchison carbonaceous chondrite

NASA Technical Reports Server (NTRS)

Hoppe, Peter; Amari, Sachiko; Zinner, Ernst; Ireland, Trevor; Lewis, Roy S.

1994-01-01

Seven hundred and twenty SiC grains from the Murchison CM2 chondrite, ranging in size from 1 to 10 micrometers, were analyzed by ion microprobe mass spectrometry for their C-isotopic compositions. Subsets of the grains were also analyzed for N (450 grains), Si (183 grains), Mg (179 grains), and Ti (28 grains) isotopes. These results are compared with previous measurements on 41 larger SiC grains (up to 15 x 26 micrometers) from a different sample of Murchison analyzed by Virag et al. (1992) and Ireland, Zinner, & Amari (1991a). All grains of the present study are isotopically anomalous with C-12/C-13 ratios ranging from 0.022 to 28.4 x solar, N-14/N-15 ratios from 0.046 to 30 x solar, Si-29/Si-28 from 0.54 to 1.20 x solar, Si-30/Si-28 from 0.42 to 1.14 x solar, Ti-49/Ti-48 from 0.96 to 1.95 x solar, and Ti-50/Ti-48 from 0.94 to 1.39 x solar. Many grains have large Mg-26 excesses from the decay of Al-26 with inferred Al-26/Al-27 ratios ranging up to 0.61, or 12,200 x the ratio of 5 x 10(exp -5) inferred for the early solar system. Several groups can be distinguished among the SiC grains. Most of the grains have C-13 and N-14 excesses, and their Si isotopic compositions (mostly excesses in Si-29 and Si-30) plot close to a slope 1.34 line on a Delta Si-29/Si-28 versus Delta Si-30/Si-28 three-isotope plot. Grains with small C-12/C-13 ratios (less than 10) tend to have smaller or no N-14 excesses and high Al-26/Al-27 ratios (up to 0.01). Grains with C-12/C-13 greater than 150 fall into two groups: grains X have N-15 excesses and Si-29 and Si-30 deficits and the highest (0.1 to 0.6) Al-26/Al-27 ratios; grains Y have N-14 excesses and plot on a slope 0.35 line on a Si three-isotope plot. In addition, large SiC grains of the Virag et al. (1992) study fall into three-distinct clusters according to their C-, Si-, and Ti-isotopic compositions. The isotopic diversity of the grains and the clustering of their isotopic compositions imply distinct and multiple stellar sources. The C- and N-isotopic compositions of most grains are consistent with H-burning in the CNO cycle. These and s-process Kr, Xe, Ba, and Nd suggest asymptotic giant branch (AGB) or Wolf-Rayet stars as likely sources for the grains, but existing models of nucleosynthesis in these stellar sites fail to account in detail for all the observed isotopic compositions. Special problems are posed by grains with C-12/C-13 less than 10 and almost normal and heavy N-isotopic compositions. Also the Si- and Ti-isotopic compositions, with excesses in Si-29 and Si-30 relative to Si-28 and excesses in all Ti isotopes relative to Ti-48, do not precisely conform with the compositions predicted for slow neutron capture. Additional theoretical efforts are needed to achieve an understanding of the isotopic composition of the SiC grains and their stellar sources.

Microstructural characterization and electron backscatter diffraction analysis across the welded interface of duplex stainless steel

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Gao, Zhanqi; Zhao, Lei; Zhang, Jianli

2017-08-01

The microstructural evolution, orientation relationships, boundary characteristics, grain type, local deformation, and microhardness across the welded interface of duplex stainless steel (DSS) were investigated. The DSS welded joint consisted of four typical zones: base metal (BM), low-temperature heat-affected zone (LTHAZ), high-temperature heat-affected zone (HTHAZ), and weld metal (WM). The apparent microstructural changes in the HTHAZ and LTHAZ were secondary austenite and Cr2N precipitation. A modified cooperative precipitation mechanism of secondary austenite and Cr2N at the interface was proposed. Furthermore, the ferrite in both the HTHAZ and LTHAZ maintained the same distribution as the ferrite texture in the BM, while this ferrite texture disappeared completely in the WM. Different austenite grains in the different zones exhibited different orientation relationships with the ferrite matrix. Special grain boundaries were mainly distributed between the austenite grains, while the ferrite grains primarily contained random grain boundaries. Austenite twins constituted the largest proportion of the special boundaries. The special austenite grain boundaries in the BM and LTHAZ were higher in relative frequency than those in the HTHAZ and WM. The ferrite grains in the HTHAZ and WM mainly consisted of substructured grains. In the BM, the recrystallization degree of ferrite was significantly lower than that of austenite grains. The local deformations were mainly generated in the grain boundaries and within the deformed grains. The HTHAZ exhibited the highest hardness, while the BM had the lowest hardness. The LTHAZ had a lower hardness than the HTHAZ and higher hardness than the BM.

Formation of Nanostructures in Severely Deformed High-Strength Steel Induced by High-Frequency Ultrasonic Impact Treatment

NASA Astrophysics Data System (ADS)

Dutta, R. K.; Malet, L.; Gao, H.; Hermans, M. J. M.; Godet, S.; Richardson, I. M.

2015-02-01

Surface modification by the generation of a nanostructured surface layer induced via ultrasonic impact treatment was performed at the weld toe of a welded high-strength quenched and tempered structural steel, S690QL1 (Fe-0.16C-0.2Si-0.87Mn-0.33Cr-0.21Mo (wt pct)). Such high-frequency peening techniques are known to improve the fatigue life of welded components. The nanocrystallized structure as a function of depth from the top-treated surface was characterized via a recently developed automated crystal orientation mapping in transmission electron microscopy. Based on the experimental observations, a grain refinement mechanism induced by plastic deformation during the ultrasonic impact treatment is proposed. It involves the formation of low-angle misoriented lamellae displaying a high density of dislocations followed by the subdivision of microbands into blocks and the resulting formation of polygonal submicronic grains. These submicronic grains further breakdown into nano grains. The results show the presence of retained austenite even after severe surface plastic deformation. The average grain size of the retained austenite and martensite is 17 and 35 nm, respectively. The in-grain deformation mechanisms are different in larger and smaller grains. Larger grains show long-range lattice rotations, while smaller grains show plastic deformation through grain rotation. Also the smaller nano grains exhibit the presence of short-range disorder. Surface nanocrystallization also leads to an increased fraction of low angle and low energy coincident site lattice boundaries especially in the smaller grains ( nm).

Elevated CO2 Reduced Floret Death in Wheat Under Warmer Average Temperatures and Terminal Drought

PubMed Central

Dias de Oliveira, Eduardo; Palta, Jairo A.; Bramley, Helen; Stefanova, Katia; Siddique, Kadambot H. M.

2015-01-01

Elevated CO2 often increases grain yield in wheat by enhancing grain number per ear, which can result from an increase in the potential number of florets or a reduction in the death of developed florets. The hypotheses that elevated CO2 reduces floret death rather than increases floret development, and that grain size in a genotype with more grains per unit area is limited by the rate of grain filling, were tested in a pair of sister lines contrasting in tillering capacity (restricted- vs. free-tillering). The hypotheses were tested under elevated CO2, combined with +3°C above ambient temperature and terminal drought, using specialized field tunnel houses. Elevated CO2 increased net leaf photosynthetic rates and likely the availability of carbon assimilates, which significantly reduced the rates of floret death and increased the potential number of grains at anthesis in both sister lines by an average of 42%. The restricted-tillering line had faster grain-filling rates than the free-tillering line because the free-tillering line had more grains to fill. Furthermore, grain-filling rates were faster under elevated CO2 and +3°C above ambient. Terminal drought reduced grain yield in both lines by 19%. Elevated CO2 alone increased the potential number of grains, but a trade-off in yield components limited grain yield in the free-tillering line. This emphasizes the need for breeding cultivars with a greater potential number of florets, since this was not affected by the predicted future climate variables. PMID:26635837

Microstructural and petrophysical characterization of a "structurally oversimplified" fault zone in poorly lithified sands: evidence for a coseismic rupture?

NASA Astrophysics Data System (ADS)

Balsamo, Fabrizio; Storti, Fabrizio

2010-05-01

We studied an extensional fault zone developed in poorly lithified, quartz-rich high porosity sandy sediments of the seismically active Crotone basin (southern Italy). The fault zone cuts across interlayered fine- to coarse-grained sands and consists of a cm-thick, discrete fault core embedded in virtually undeformed wall sediments. Consequently, it can be described as "structurally oversimplified" due to the lack of footwall and hanging wall damage zones. We acquired microstructural, grain size, grain shape, porosity, mineralogical and permeability data to investigate the influence of initial sedimentological characteristics of sands on the final faulted granular products and related hydrologic properties. Faulting evolves by a general grain size and porosity reduction with a combination of intragranular fracturing, spalling, and flaking of grain edges, irrespective of grain mineralogy. The dominance of cataclasis, also confirmed by fractal dimensions >2.6, is generally not expected at a deformation depth <1 km. Coarse-grained sand shows a much higher comminution intensity, grain shape variations and permeability drop than fine-grained sands. This is because coarser aggregates have (i) fewer grain-to-grain contacts for a given area, which results in higher stress concentration at contact points, and (ii) a higher probability of pre-existing intragranular microstructural defects that result in a lower grain strength. The peculiar structural architecture, the dominance of cataclasis over non-destructive particulate flow, and the compositional variations of clay minerals in the fault core, strongly suggest that the studied fault zone developed by a coseismic rupture.

Systematic and simulation-free coarse graining of homopolymer melts: a relative-entropy-based study.

PubMed

Yang, Delian; Wang, Qiang

2015-09-28

We applied the systematic and simulation-free strategy proposed in our previous work (D. Yang and Q. Wang, J. Chem. Phys., 2015, 142, 054905) to the relative-entropy-based (RE-based) coarse graining of homopolymer melts. RE-based coarse graining provides a quantitative measure of the coarse-graining performance and can be used to select the appropriate analytic functional forms of the pair potentials between coarse-grained (CG) segments, which are more convenient to use than the tabulated (numerical) CG potentials obtained from structure-based coarse graining. In our general coarse-graining strategy for homopolymer melts using the RE framework proposed here, the bonding and non-bonded CG potentials are coupled and need to be solved simultaneously. Taking the hard-core Gaussian thread model (K. S. Schweizer and J. G. Curro, Chem. Phys., 1990, 149, 105) as the original system, we performed RE-based coarse graining using the polymer reference interaction site model theory under the assumption that the intrachain segment pair correlation functions of CG systems are the same as those in the original system, which de-couples the bonding and non-bonded CG potentials and simplifies our calculations (that is, we only calculated the latter). We compared the performance of various analytic functional forms of non-bonded CG pair potential and closures for CG systems in RE-based coarse graining, as well as the structural and thermodynamic properties of original and CG systems at various coarse-graining levels. Our results obtained from RE-based coarse graining are also compared with those from structure-based coarse graining.

Survival of refractory presolar grain analogs during Stardust-like impact into Al foils: Implications for Wild 2 presolar grain abundances and study of the cometary fine fraction

NASA Astrophysics Data System (ADS)

Croat, T. K.; Floss, C.; Haas, B. A.; Burchell, M. J.; Kearsley, A. T.

2015-08-01

We present results of FIB-TEM studies of 12 Stardust analog Al foil craters which were created by firing refractory Si and Ti carbide and nitride grains into Al foils at 6.05 km s-1 with a light-gas gun to simulate capture of cometary grains by the Stardust mission. These foils were prepared primarily to understand the low presolar grain abundances (both SiC and silicates) measured by SIMS in Stardust Al foil samples. Our results demonstrate the intact survival of submicron SiC, TiC, TiN, and less-refractory Si3N4 grains. In small (<2 μm) craters that are formed by single grain impacts, the entire impacting crystalline grain is often preserved intact with minimal modification. While they also survive in crystalline form, grains at the bottom of larger craters (>5 μm) are typically fragmented and are somewhat flattened in the direction of impact due to partial melting and/or plastic deformation. The low presolar grain abundance estimates derived from SIMS measurements of large craters (mostly >50 μm) likely result from greater modification of these impactors (i.e., melting and isotopic dilution), due to higher peak temperatures/pressures in these crater impacts. The better survivability of grains in smaller craters suggests that more accurate presolar grain estimates may be achievable through measurement of such craters. It also suggests small craters can provide a complementary method of study of the Wild 2 fine fraction, especially for refractory CAI-like minerals.

The onset and evolution of fatigue-induced abnormal grain growth in nanocrystalline Ni–Fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furnish, T. A.; Mehta, A.; Van Campen, D.

Conventional structural metals suffer from fatigue-crack initiation through dislocation activity which forms persistent slip bands leading to notch-like extrusions and intrusions. Ultrafine-grained and nanocrystalline metals can potentially exhibit superior fatigue-crack initiation resistance by suppressing these cumulative dislocation activities. Prior studies on these metals have confirmed improved high-cycle fatigue performance. In the case of nano-grained metals, analyses of subsurface crack initiation sites have indicated that the crack nucleation is associated with abnormally large grains. But, these post-mortem analyses have led to only speculation about when abnormal grain growth occurs (e.g., during fatigue, after crack initiation, or during crack growth). In thismore » study, a recently developed synchrotron X-ray diffraction technique was used to detect the onset and progression of abnormal grain growth during stress-controlled fatigue loading. Our study provides the first direct evidence that the grain coarsening is cyclically induced and occurs well before final fatigue failure—our results indicate that the first half of the fatigue life was spent prior to the detectable onset of abnormal grain growth, while the second half was spent coarsening the nanocrystalline structure and cyclically deforming the abnormally large grains until crack initiation. Post-mortem fractography, coupled with cycle-dependent diffraction data, provides the first details regarding the kinetics of this abnormal grain growth process during high-cycle fatigue testing. Finally, precession electron diffraction images collected in a transmission electron microscope after the in situ fatigue experiment also confirm the X-ray evidence that the abnormally large grains contain substantial misorientation gradients and sub-grain boundaries.« less

The onset and evolution of fatigue-induced abnormal grain growth in nanocrystalline Ni–Fe

DOE PAGES

Furnish, T. A.; Mehta, A.; Van Campen, D.; ...

2016-10-11

Conventional structural metals suffer from fatigue-crack initiation through dislocation activity which forms persistent slip bands leading to notch-like extrusions and intrusions. Ultrafine-grained and nanocrystalline metals can potentially exhibit superior fatigue-crack initiation resistance by suppressing these cumulative dislocation activities. Prior studies on these metals have confirmed improved high-cycle fatigue performance. In the case of nano-grained metals, analyses of subsurface crack initiation sites have indicated that the crack nucleation is associated with abnormally large grains. But, these post-mortem analyses have led to only speculation about when abnormal grain growth occurs (e.g., during fatigue, after crack initiation, or during crack growth). In thismore » study, a recently developed synchrotron X-ray diffraction technique was used to detect the onset and progression of abnormal grain growth during stress-controlled fatigue loading. Our study provides the first direct evidence that the grain coarsening is cyclically induced and occurs well before final fatigue failure—our results indicate that the first half of the fatigue life was spent prior to the detectable onset of abnormal grain growth, while the second half was spent coarsening the nanocrystalline structure and cyclically deforming the abnormally large grains until crack initiation. Post-mortem fractography, coupled with cycle-dependent diffraction data, provides the first details regarding the kinetics of this abnormal grain growth process during high-cycle fatigue testing. Finally, precession electron diffraction images collected in a transmission electron microscope after the in situ fatigue experiment also confirm the X-ray evidence that the abnormally large grains contain substantial misorientation gradients and sub-grain boundaries.« less

Splash detail due to a single grain incident on a granular bed.

PubMed

Tanabe, Takahiro; Shimada, Takashi; Ito, Nobuyasu; Nishimori, Hiraku

2017-02-01

Using the discrete element method, we study the splash processes induced by the impact of a grain on a randomly packed bed. Good correspondence is obtained between our numerical results and the findings of previous experiments for the movement of ejected grains. Furthermore, the distributions of the ejection angle and ejection speed for individual grains vary depending on the relative timing at which the grains are ejected after the initial impact. Obvious differences are observed between the distributions of grains ejected during the earlier and later splash periods: the form of the vertical ejection-speed distribution varies from a power-law form to a lognormal form with time; this difference may determine grain trajectory after ejection.

Behavior of Windblown Sand on Mars: Results From Single-Particle Experiments

NASA Astrophysics Data System (ADS)

Marshall, J. R.; Borucki, J.; Sagan, C.

1996-03-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG & G Program.

Grain boundary oxidation and its effects on high temperature fatigue life

NASA Technical Reports Server (NTRS)

Liu, H. W.; Oshida, Yoshiki

1986-01-01

Fatigue lives at elevated temperatures are often shortened by creep and/or oxidation. Creep causes grain boundary void nucleation and grain boundary cavitation. Grain boundary voids and cavities will accelerate fatigue crack nucleation and propagation, and thereby shorten fatigue life. The functional relationships between the damage rate of fatigue crack nucleation and propagation and the kinetic process of oxygen diffusion depend on the detailed physical processes. The kinetics of grain boundary oxidation penetration was investigated. The statistical distribution of grain boundary penetration depth was analyzed. Its effect on high temperature fatigue life are discussed. A model of intermittent micro-ruptures of grain boundary oxide was proposed for high temperature fatigue crack growth. The details of these studies are reported.

The effect of the ambient plasma conditions on the variation of charge on dust grains

NASA Astrophysics Data System (ADS)

Chakraborty, M.; Kausik, S. S.; Saikia, B. K.; Kakati, M.; Bujarbarua, S.

2003-02-01

An experimental study has been performed into the variation of charge on dust grains with change in the ambient plasma conditons. A dust beam containing submicron sized silver grains was passed through plasma. The dust grains were charged by the plasma particles as well as by primary electrons from the filament. An increase in the filament current increased both the plasma density and the number density of the primary electrons. The grain charge was found out both from the deflection of the dust grains and also from the floating potential. The experimental observations shows that the secondary emission caused by the primary electrons significantly influenced and played a prominent role in the establishment of charge on the grains.

Grain-Boundary Resistance in Copper Interconnects: From an Atomistic Model to a Neural Network

NASA Astrophysics Data System (ADS)

Valencia, Daniel; Wilson, Evan; Jiang, Zhengping; Valencia-Zapata, Gustavo A.; Wang, Kuang-Chung; Klimeck, Gerhard; Povolotskyi, Michael

2018-04-01

Orientation effects on the specific resistance of copper grain boundaries are studied systematically with two different atomistic tight-binding methods. A methodology is developed to model the specific resistance of grain boundaries in the ballistic limit using the embedded atom model, tight- binding methods, and nonequilibrium Green's functions. The methodology is validated against first-principles calculations for thin films with a single coincident grain boundary, with 6.4% deviation in the specific resistance. A statistical ensemble of 600 large, random structures with grains is studied. For structures with three grains, it is found that the distribution of specific resistances is close to normal. Finally, a compact model for grain-boundary-specific resistance is constructed based on a neural network.

40 CFR 180.207 - Trifluralin; tolerances for residues.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Peppermint, oil 2.0 Peppermint, tops 0.05 Rapeseed, seed 0.05 Safflower, seed 0.05 Sorghum, grain, forage 0.05 Sorghum, grain, grain 0.05 Sorghum, grain, stover 0.05 Spearmint, oil 2.0 Spearmint, tops 0.05...

7 CFR 800.195 - Delegations.

Code of Federal Regulations, 2013 CFR

2013-01-01

... grain do not exceed, as determined by the Administrator, 5 per centum of the total amount of grain... Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS Delegations...

7 CFR 800.195 - Delegations.

Code of Federal Regulations, 2012 CFR

2012-01-01

... grain do not exceed, as determined by the Administrator, 5 per centum of the total amount of grain... Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS Delegations...

7 CFR 800.195 - Delegations.

Code of Federal Regulations, 2014 CFR

2014-01-01

... grain do not exceed, as determined by the Administrator, 5 per centum of the total amount of grain... Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS Delegations...

Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

NASA Technical Reports Server (NTRS)

Marshall, John R.

1999-01-01

Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a dense saltation population of many tens or hundreds of grains for each single high-speed saltation percussion of the bed. Impact cascading will lead to near-surface distortion of the boundary layer, and choked flow formed by a dense "slurry" of sand, with the majority of grains mobilized by repercussive forces rather than by aerodynamic lift. This proceeds until a fully-matured transport layer imposes self- limitations as grain-population density constrains the free-path motion of individual grains.

Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

NASA Technical Reports Server (NTRS)

Marshall, John R.

1999-01-01

Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 um-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a dense saltation population of many tens or hundreds of grains for each single high-speed saltation percussion of the bed. Impact cascading will lead to near-surface distortion of the boundary layer, and choked flow formed by a dense "slurry" of sand, with the majority of grains mobilized by repercussive forces rather than by aerodynamic lift. This proceeds until a fully-matured transport layer imposes self-limitations as grain-population density constrains the free-path motion of individial grains.

Triple bag hermetic technology for controlling a bruchid (Spermophagus sp.) (Coleoptera, Chrysomelidae) in stored Hibiscus sabdariffa grain.

PubMed

Amadou, L; Baoua, I B; Baributsa, D; Williams, S B; Murdock, L L

2016-10-01

We assessed the performance of hermetic triple layer Purdue Improved Crop Storage (PICS) bags for protecting Hibiscus sabdariffa grain against storage insects. The major storage pest in the grain was a bruchid, Spermophagus sp.. When we stored infested H. sabdariffa grain for six months in the woven polypropylene bags typically used by farmers, the Spermophagus population increased 33-fold over that initially present. The mean number of emergence holes per 100 seeds increased from 3.3 holes to 35.4 holes during this time period, while grain held for the same length of time in PICS bags experienced no increase in the numbers of holes. Grain weight loss in the woven control bags was 8.6% while no weight loss was observed in the PICS bags. Seed germination rates of grain held in woven bags for six months dropped significantly while germination of grain held in PICS bags did not change from the initial value. PICS bags can be used to safely store Hibiscus grain after harvest to protect against a major insect pest.

Coesite in suevites from the Chesapeake Bay impact structure

USGS Publications Warehouse

Jackson, John C.; Horton, J. Wright; Chou, I-Ming; Belkin, Harvey E.

2016-01-01

The occurrence of coesite in suevites from the Chesapeake Bay impact structure is confirmed within a variety of textural domains in situ by Raman spectroscopy for the first time and in mechanically separated grains by X-ray diffraction. Microtextures of coesite identified in situ investigated under transmitted light and by scanning electron microscope reveal coesite as micrometer-sized grains (1–3 μm) within amorphous silica of impact-melt clasts and as submicrometer-sized grains and polycrystalline aggregates within shocked quartz grains. Coesite-bearing quartz grains are present both idiomorphically with original grain margins intact and as highly strained grains that underwent shock-produced plastic deformation. Coesite commonly occurs in plastically deformed quartz grains within domains that appear brown (toasted) in transmitted light and rarely within quartz of spheroidal texture. The coesite likely developed by a mechanism of solid-state transformation from precursor quartz. Raman spectroscopy also showed a series of unidentified peaks associated with shocked quartz grains that likely represent unidentified silica phases, possibly including a moganite-like phase that has not previously been associated with coesite.

Annealing of Silicate Dust by Nebular Shocks at 10 AU

NASA Technical Reports Server (NTRS)

Harker, David E.; Desch, Steven J.; DeVincenzi, D. (Technical Monitor)

2001-01-01

Silicate dust grains in the interstellar medium are known to be mostly amorphous, yet crystalline silicate grains have been observed in many long-period comets and in protoplanetary disks. Annealing of amorphous silicate grains into crystalline grains requires temperatures greater than or approximately equal to 1000 K, but exposure of dust grains in comets to such high temperatures is apparently incompatible with the generally low temperatures experienced by comets. This has led to the proposal of models in which dust grains were thermally processed near the protoSun, then underwent considerable radial transport until they reached the gas giant planet region where the long-period comets originated. We hypothesize instead that silicate dust grains were annealed in situ, by shock waves triggered by gravitational instabilities. We assume a shock speed of 5 km/s, a plausible value for shocks driven by gravitational instabilities. We calculate the peak temperatures of pyroxene grains under conditions typical in protoplanetary disks at 5-10 AU. We show that in situ annealing of micron-sized dust grains can occur, obviating the need for large-scale radial transport.

The Coupling of Macrosegregation with Grain Nucleation, Growth and Motion in DC Cast Aluminum Alloy Ingots

NASA Astrophysics Data System (ADS)

Založnik, Miha; Kumar, Arvind; Combeau, Hervé; Bedel, Marie; Jarry, Philippe; Waz, Emmanuel

The phenomena responsible for the formation of macrosegregations, and grain structures during solidification are closely intertwined. We present a model study of the formation of macrosegregation and grain structure in an industrial sized (350 mm thick) direct chill (DC) cast aluminum alloy slab. The modeling of these phenomena in DC casting is a challenging problem mainly due to the size of the products, the variety of the phenomena to be accounted for, and the non-linearities involved. We used a volume-averaged multiscale model that describes nucleation on grain refiner particles and grain growth, coupled with macroscopic transport: fluid flow driven by natural convection and shrinkage, transport of free-floating globular equiaxed grains, heat transfer, and solute transport. We analyze the heat and mass transfer in the slurry moving-grain zone that is a result of the coupling of the fluid flow and of the grain nucleation, growth and motion. We discuss the impact of the flow structure in the slurry zone and of the grain packing fraction on the macrosegregation.

[Concordance among analysts from Latin-American laboratories for rice grain appearance determination using a gallery of digital images].

PubMed

Avila, Manuel; Graterol, Eduardo; Alezones, Jesús; Criollo, Beisy; Castillo, Dámaso; Kuri, Victoria; Oviedo, Norman; Moquete, Cesar; Romero, Marbella; Hanley, Zaida; Taylor, Margie

2012-06-01

The appearance of rice grain is a key aspect in quality determination. Mainly, this analysis is performed by expert analysts through visual observation; however, due to the subjective nature of the analysis, the results may vary among analysts. In order to evaluate the concordance between analysts from Latin-American rice quality laboratories for rice grain appearance through digital images, an inter-laboratory test was performed with ten analysts and images of 90 grains captured with a high resolution scanner. Rice grains were classified in four categories including translucent, chalky, white belly, and damaged grain. Data was categorized using statistic parameters like mode and its frequency, the relative concordance, and the reproducibility parameter kappa. Additionally, a referential image gallery of typical grain for each category was constructed based on mode frequency. Results showed a Kappa value of 0.49, corresponding to a moderate reproducibility, attributable to subjectivity in the visual analysis of grain images. These results reveal the need for standardize the evaluation criteria among analysts to improve the confidence of the determination of rice grain appearance.

Suppression of Twinning and Phase Transformation in an Ultrafine Grained 2 GPa Strong Metastable Austenitic Steel: Experiment and Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Yongfeng; Jia, Nan; Wang, Y. D.

2015-07-17

An ultrafine-grained 304 austenitic 18 wt.%Cr-8 wt.%Ni stainless steel with a grain size of ~270 nm was synthesized by accumulative rolling (67 % total reduction) and annealing (550 °C, 150s). Uniaxial tensile testing at room temperature reveals an extremely high yield strength of 1890 ± 50MPa and a tensile strength of 2050 ± 30MPa, while the elongation reaches 6 ± 1%. Experimental characterization on samples with different grain sizes between 270 nm and 35 μm indicates that both, deformation twinning and martensitic phase transformation are significantly retarded with increasing grain refinement. A crystal plasticity finite element model incorporating a constitutivemore » law reflecting the grain size-controlled dislocation slip and deformation twinning captures the micromechanical behavior of the steels with different grain sizes. Comparison of simulation and experiment shows that the deformation of ultrafine-grained 304 steels is dominated by the slip of partial dislocations, whereas for coarse-grained steels dislocation slip, twinning and martensite formation jointly contribute to the shape change.« less

Does Whole Grain Consumption Alter Gut Microbiota and Satiety?

PubMed Central

Cooper, Danielle N.; Martin, Roy J.; Keim, Nancy L.

2015-01-01

This review summarizes recent studies examining whole grain consumption and its effect on gut microbiota and satiety in healthy humans. Studies comparing whole grains to their refined grain counterparts were considered, as were studies comparing different grain types. Possible mechanisms linking microbial metabolism and satiety are described. Clinical trials show that whole grain wheat, maize, and barley alter the human gut microbiota, but these findings are based on a few studies that do not include satiety components, so no functional claims between microbiota and satiety can be made. Ten satiety trials were evaluated and provide evidence that whole oats, barley, and rye can increase satiety, whereas the evidence for whole wheat and maize is not compelling. There are many gaps in the literature; no one clinical trial has examined the effects of whole grains on satiety and gut microbiota together. Once understanding the impact of whole grains on satiety and microbiota is more developed, then particular grains might be used for better appetite control. With this information at hand, healthcare professionals could make individual dietary recommendations that promote satiety and contribute to weight control. PMID:27417768

Grain boundary character distribution in nanocrystalline metals produced by different processing routes

DOE PAGES

Bober, David B.; Kumar, Mukal; Rupert, Timothy J.; ...

2015-12-28

Nanocrystalline materials are defined by their fine grain size, but details of the grain boundary character distribution should also be important. Grain boundary character distributions are reported for ball-milled, sputter-deposited, and electrodeposited Ni and Ni-based alloys, all with average grain sizes of ~20 nm, to study the influence of processing route. The two deposited materials had nearly identical grain boundary character distributions, both marked by a Σ3 length percentage of 23 to 25 pct. In contrast, the ball-milled material had only 3 pct Σ3-type grain boundaries and a large fraction of low-angle boundaries (16 pct), with the remainder being predominantlymore » random high angle (73 pct). Furthermore, these grain boundary character measurements are connected to the physical events that control their respective processing routes. Consequences for material properties are also discussed with a focus on nanocrystalline corrosion. As a whole, the results presented here show that grain boundary character distribution, which has often been overlooked in nanocrystalline metals, can vary significantly and influence material properties in profound ways.« less

Determination of Entrapment Victim Extrication Forces with and without Use of a Grain Rescue Tube.

PubMed

Roberts, M J; Field, W E; Maier, D E; Stroshine, R L

2015-04-01

The forces required to extricate a test mannequin from a grain mass when buried at different depths with and without a grain restraint system were determined. When there was no grain restraint system in place, the vertical force required to pull the mannequin from the grain when it was buried waist deep and to the underarms was 1259 and 1766 N (283 and 397 lb(f)), respectively. It increased to 1584 N (356 lb(f)) (+26%) and 2153 N (484 lb(f)) (+22%), respectively, with the restraint in place due to the changes in grain properties brought about by the insertion of the rescue tube. It was concluded that the use of a grain restraint during extrication of a victim does not reduce the forces required and that forcefully pulling an entrapped victim, especially with mechanical assistance, with or without a grain restraint system could result in severe injuries and possible death due to the forces exerted on the victim. The authors recommend that these findings be incorporated into current grain extrication training for emergency first responders.

Physical characteristics of cometary dust from optical studies

NASA Technical Reports Server (NTRS)

Hanner, M. S.

1980-01-01

Observations of the sunlight scattered and thermal emission from cometary dust, which may be used to infer the physical properties of the dust grains, are reviewed. Consideration is given to the observed wavelength dependence of the scattered light from cometary coma and tails, the average scattering function of the dust grains, the average grain Bond albedo, the polarization of the scattered light, and grain temperatures deduced from thermal infrared emission. The thermal properties of dust grains are illustrated for models based on magnetite or olivine grain materials, with consideration given to the variation of thermal properties with particle radius and heliocentric distance. Comparison of the models with observations indicates that a disordered or amorphous olivine composition can give a reasonable fit to the data for appropriate grain sizes and temperatures. The observations acquired are noted to indicate an optically important particle size of 1 micron, with silicate particles not larger than a few microns usually present although pure silicate grains can not be responsible for the thermal emission, and the cometary dust grains are most likely not spherical. Further observations needed in the infrared are indicated.

Enhancement of ductility and improvement of abnormal Goss grain growth of magnetostrictive Fe-Ga rolled alloys

NASA Astrophysics Data System (ADS)

Li, Ji-heng; Yuan, Chao; Mu, Xing; Bao, Xiao-qian; Gao, Xue-xu

2018-04-01

The influences of initial microstructures on the mechanical properties and the recrystallization texture of magnetostrictive 0.1at% NbC-doped Fe83Ga17 alloys were investigated. The directionally solidified columnar-grained structure substantially enhanced the tensile elongation at intermediate temperatures by suppressing fracture along the transverse boundaries. Compared with tensile elongations of 1.0% at 300°C and 12.0% at 500°C of the hot-forged equiaxed-grained alloys, the columnar-grained alloys exhibited substantially increased tensile elongations of 21.6% at 300°C and 46.6% at 500°C. In the slabs for rolling, the introduction of <001>-oriented columnar grains also promotes the secondary recrystallization of Goss grains in the finally annealed sheets, resulting in an improvement of the saturation magnetostriction. For the columnar-grained specimens, the inhomogeneous microstructure and disadvantage in number and size of Goss grains are improved in the primarily annealed sheets, which is beneficial to the abnormal growth of Goss grains during the final annealing process.

Nanoscale Investigation of Grain Growth in RF-Sputtered Indium Tin Oxide Thin Films by Scanning Probe Microscopy

NASA Astrophysics Data System (ADS)

Lamsal, B. S.; Dubey, M.; Swaminathan, V.; Huh, Y.; Galipeau, D.; Qiao, Q.; Fan, Q. H.

2014-11-01

This work studied the electronic characteristics of the grains and grain boundaries of indium tin oxide (ITO) thin films using electrostatic and Kelvin probe force microscopy. Two types of ITO films were compared, deposited using radiofrequency magnetron sputtering in pure argon or 99% argon + 1% oxygen, respectively. The average grain size and surface roughness increased with substrate temperature for the films deposited in pure argon. With the addition of 1% oxygen, the increase in the grain size was inhibited above 150°C, which was suggested to be due to passivation of the grains by the excess oxygen. Electrostatic force microscopy and Kelvin probe force microscopy (KPFM) images confirmed that the grain growth was defect mediated and occurred at defective interfaces at high temperatures. Films deposited at room temperature with 1% oxygen showed crystalline nature, while films deposited with pure argon at room temperature were amorphous as observed from KPFM images. The potential drop across the grain and grain boundary was determined by taking surface potential line profiles to evaluate the electronic properties.

Natural Variations in SLG7 Regulate Grain Shape in Rice

PubMed Central

Zhou, Yong; Miao, Jun; Gu, Haiyong; Peng, Xiurong; Leburu, Mamotshewa; Yuan, Fuhai; Gu, Houwen; Gao, Yun; Tao, Yajun; Zhu, Jinyan; Gong, Zhiyun; Yi, Chuandeng; Gu, Minghong; Yang, Zefeng; Liang, Guohua

2015-01-01

Rice (Oryza sativa) grain shape, which is controlled by quantitative trait loci (QTL), has a strong effect on yield production and quality. However, the molecular basis for grain development remains largely unknown. In this study, we identified a novel QTL, Slender grain on chromosome 7 (SLG7), that is responsible for grain shape, using backcross introgression lines derived from 9311 and Azucena. The SLG7 allele from Azucena produces longer and thinner grains, although it has no influence on grain weight and yield production. SLG7 encodes a protein homologous to LONGIFOLIA 1 and LONGIFOLIA 2, both of which increase organ length in Arabidopsis. SLG7 is constitutively expressed in various tissues in rice, and the SLG7 protein is located in plasma membrane. Morphological and cellular analyses suggested that SLG7 produces slender grains by longitudinally increasing cell length, while transversely decreasing cell width, which is independent from cell division. Our findings show that the functions of SLG7 family members are conserved across monocots and dicots and that the SLG7 allele could be applied in breeding to modify rice grain appearance. PMID:26434724

The OsSPL16-GW7 regulatory module determines grain shape and simultaneously improves rice yield and grain quality.

PubMed

Wang, Shaokui; Li, Shan; Liu, Qian; Wu, Kun; Zhang, Jianqing; Wang, Shuansuo; Wang, Yi; Chen, Xiangbin; Zhang, Yi; Gao, Caixia; Wang, Feng; Huang, Haixiang; Fu, Xiangdong

2015-08-01

The deployment of heterosis in the form of hybrid rice varieties has boosted grain yield, but grain quality improvement still remains a challenge. Here we show that a quantitative trait locus for rice grain quality, qGW7, reflects allelic variation of GW7, a gene encoding a TONNEAU1-recruiting motif protein with similarity to C-terminal motifs of the human centrosomal protein CAP350. Upregulation of GW7 expression was correlated with the production of more slender grains, as a result of increased cell division in the longitudinal direction and decreased cell division in the transverse direction. OsSPL16 (GW8), an SBP-domain transcription factor that regulates grain width, bound directly to the GW7 promoter and repressed its expression. The presence of a semidominant GW7(TFA) allele from tropical japonica rice was associated with higher grain quality without the yield penalty imposed by the Basmati gw8 allele. Manipulation of the OsSPL16-GW7 module thus represents a new strategy to simultaneously improve rice yield and grain quality.

GEMS Revealed: Spectrum Imaging of Aggregate Grains in Interplanetary Dust

NASA Technical Reports Server (NTRS)

Keller, L. P.; Messenger, S.; Christoffersen, R.

2005-01-01

Anhydrous interplanetary dust particles (IDPs) of cometary origin contain abundant materials that formed in the early solar nebula. These materials were transported outward and subsequently mixed with molecular cloud materials and presolar grains in the region where comets accreted [1]. GEMS (glass with embedded metal and sulfides) grains are a major component of these primitive anhydrous IDPs, along with crystalline Mg-rich silicates, Fe-Ni sulfides, carbonaceous material, and other trace phases. Some GEMS grains (5%) are demonstrably presolar based on their oxygen isotopic compositions [2]. However, most GEMS grains are isotopically solar and have bulk chemical compositions that are incompatible with inferred compositions of interstellar dust, suggesting a solar system origin [3]. An alternative hypothesis is that GEMS grains represent highly irradiated interstellar grains whose oxygen isotopic compositions were homogenized through processing in the interstellar medium (ISM) [4]. We have obtained the first quantitative X-ray maps (spectrum images) showing the distribution of major and minor elements in individual GEMS grains. Nanometer-scale chemical maps provide critical data required to evaluate the differing models regarding the origin of GEMS grains.

Structural and technological characteristics of starch isolated from sorghum as a function of drying temperature and storage time.

PubMed

Cruz, David Bandeira da; Silva, Wagner Schellin Vieira da; Santos, Ivonir Petrarca Dos; Zavareze, Elessandra da Rosa; Elias, Moacir Cardoso

2015-11-20

The quality of sorghum grains can vary according to the conditions of the drying temperature and storage time. The objective of this study was to evaluate the effects of the drying temperature and storage time of sorghum grain on the structure and technological properties of starch. The sorghum grains were dried at 45, 65, and 85°C and stored for six months. The grains were stored in an environment with a controlled temperature and humidity, and the starch from sorghum grains was isolated in initial time, after three and six months. The sorghum starches grains dried at 45 and 65°C present higher relative crystallinity than the starches of sorghum grains dried at 85°C in three months of storage. A reduction in the solubility of the starches of the sorghum grains dried at 85°C was observed when the grains were stored during six months. The breakdown and swelling power of the starches were reduced with the increase of the drying temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

In vivo indices for predicting acidosis risk of grains in cattle: Comparison with in vitro methods.

PubMed

Lean, I J; Golder, H M; Black, J L; King, R; Rabiee, A R

2013-06-01

Our objective was to evaluate a near-infrared reflectance spectroscopy (NIRS) used in the feed industry to estimate the potential for grains to increase the risk of ruminal acidosis. The existing NIRS calibration was developed from in sacco and in vitro measures in cattle and grain chemical composition measurements. To evaluate the existing model, 20 cultivars of 5 grain types were fed to 40 Holstein heifers using a grain challenge protocol and changes in rumen VFA, ammonia, lactic acids, and pH that are associated with acidosis were measured. A method development study was performed to determine a grain feeding rate sufficient to induce non-life threatening but substantial ruminal changes during grain challenge. Feeding grain at a rate of 1.2% of BW met these criteria, lowering rumen pH (P = 0.01) and increasing valerate (P < 0.01) and propionate concentrations (P = 0.01). Valerate was the most discriminatory measure indicating ruminal change during challenge. Heifers were assigned using a row by column design in an in vivo study to 1 of 20 grain cultivars and were reassigned after a 9 d period (n = 4 cattle/treatment). The test grains were dry rolled oats (n = 3), wheat (n = 6), barley (n = 4), triticale (n = 4), and sorghum (n = 3) cultivars. Cattle were adapted to the test grain and had ad libitum access to grass silage 11 d before the challenge. Feed was withheld for 14 h before challenge feeding with 0.3 kg DM of silage followed by the respective test grain fed at 1.2% of BW. A rumen sample was taken by stomach tube 5, 65, 110, 155, and 200 min after grain consumption. The rumen is not homogenous and samples of rumen fluid obtained by stomach tube will differ from those gained by other methods. Rumen pH was measured immediately; individual VFA, ammonia, and D- and L-lactate concentrations were analyzed later. Rumen pH (P = 0.002) and all concentrations of fermentation products differed among grains (P = 0.001). A previously defined discriminant score calculated at 200 min after challenge was used to rank grains for acidosis risk. A significant correlation between the discriminant score and the NIRS ranking (r = 0.731, P = 0.003) demonstrated the potential for using NIRS calibrations for predicting acidosis risk of grains in cattle. The overall rankings of grains for acidosis risk were wheat > triticale > barley > oats > sorghum.

Understanding the mechanical and acoustical characteristics of sand aggregates compacting under triaxial conditions

NASA Astrophysics Data System (ADS)

Hangx, Suzanne; Brantut, Nicolas

2016-04-01

Mechanisms such as grain rearrangement, coupled with elastic deformation, grain breakage, grain rearrangement, grain rotation, and intergranular sliding, play a key role in determining porosity and permeability reduction during burial of clastic sediments. Similarly, in poorly consolidated, highly porous sands and sandstones, grain rotation, intergranular sliding, grain failure, and pore collapse often lead to significant reduction in porosity through the development of compaction bands, with the reduced porosity and permeability of such bands producing natural barriers to flow within reservoir rocks. Such time-independent compaction processes operating in highly porous water- and hydrocarbon-bearing clastic reservoirs can exert important controls on production-related reservoir deformation, subsidence, and induced seismicity. We performed triaxial compression experiments on sand aggregates consisting of well-rounded Ottawa sand (d = 300-400 μm; φ = 36.1-36.4%) at room temperature, to systematically investigate the effect of confining pressure (Pceff = 5-100 MPa), strain rate (10-6-10-4 s-1) and chemical environment (decane vs. water; Pf = 5 MPa) on compaction. For a limited number of experiments grain size distribution (d = 180-500 μm) and grain shape (subangular Beaujean sand; d = 180-300 μm) were varied to study their effect. Acoustic emission statistics and location, combined with microstructural and grain size analysis, were used to verify the operating microphysical compaction mechanisms. All tests showed significant pre-compaction during the initial hydrostatic (set-up) phase, with quasi-elastic loading behaviour accompanied by permanent deformation during the differential loading stage. This permanent volumetric strain involved elastic grain contact distortion, particle rearrangement, and grain failure. From the acoustic data and grain size analysis, it was evident that at low confining pressure grain rearrangement controlled compaction, with grain failure being present but occurring to a relatively limited extent. Acoustic emission localization showed that failure was focussed along a broad shear plane. At higher confining pressure pervasive grain failure clearly accommodated compaction, though no strain localization was observed and failure appeared to be through cataclastic flow. Chemical environment, i.e. chemically inert decane vs. water as a pore fluid, had no significant effect on compaction in the strain rate range tested. Grain size distribution or grain shape also appeared to not affect the observed mechanical behaviour. Our results can be used to better understand the compaction behaviour of poorly consolidated sandstones. Future research will focus on understanding the effect of cementation on strain localization in deforming artificial Ottawa sandstone.

7 CFR 810.803 - Basis of determination.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Mixed Grain Principles Governing the Application of Standards § 810...

7 CFR 800.60 - Deceptive actions and practices.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS Grain Handling... official personnel, any action or practice, including the loading, weighing, handling, or sampling of grain...

7 CFR 810.1601 - Definition of soybeans.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Soybeans Terms Defined § 810.1601 Definition of soybeans. Grain that...

7 CFR 810.601 - Definition of flaxseed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Flaxseed Terms Defined § 810.601 Definition of flaxseed. Grain that...

7 CFR 810.201 - Definition of barley.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Barley Terms Defined § 810.201 Definition of barley. Grain that...

The effect of high-pressure torsion on the microstructure and properties of magnesium

NASA Astrophysics Data System (ADS)

Figueiredo, Roberto B.; Sabbaghianrad, Shima; Langdon, Terence G.

2017-05-01

High-pressure torsion provides the opportunity to introduce significant plastic strain at room temperature in magnesium and its alloys. It is now established that this processing operation produces ultrafine-grained structures and changes the properties of these materials. The present paper shows that the mechanism of grain refinement differs from f.c.c. and b.c.c. materials. It is shown that fine grains are formed at the grain boundaries of coarse grains and gradually consume the whole structure. Also, the processed material exhibits unusual mechanical properties due to the activation of grain boundary sliding at room temperature.

The plague under Commodus as an unintended consequence of Roman grain market regulation.

PubMed

Silver, Morris

2012-01-01

This paper begins with a review of Roman grain market policies. It is argued that policies such as forced sales and maximum prices made urban consumers hesitant to rely on the market for secure access to grain. Consequently, consumers hoarded grain in their homes. The hoarded grain formed a volatile fuel ready to be ignited by the arrival of the bubonic plague bacillus. This scenario fits events in the city of Rome under Commodus. Attested grain market interventions were followed by a severe epidemic, arguably bubonic plague, which decimated the city's population.

Astrophysical dust grains in stars, the interstellar medium, and the solar system

NASA Technical Reports Server (NTRS)

Gehrz, Robert D.

1991-01-01

Studies of astrophysical dust grains in circumstellar shells, the interstellar medium, and the solar system may provide information about stellar evolution and about physical conditions in the primitive solar nebula. The following subject areas are covered: (1) the cycling of dust in stellar evolution and the formation of planetary systems; (2) astrophysical dust grains in circumstellar environments; (3) circumstellar grain formation and mass loss; (4) interstellar dust grains; (5) comet dust and the zodiacal cloud; (6) the survival of dust grains during stellar evolution; and (7) establishing connections between stardust and dust in the solar system.

Modeling of the Coupling of Microstructure and Macrosegregation in a Direct Chill Cast Al-Cu Billet

NASA Astrophysics Data System (ADS)

Heyvaert, Laurent; Bedel, Marie; Založnik, Miha; Combeau, Hervé

2017-10-01

The macroscopic multiphase flow and the growth of the solidification microstructures in the mushy zone of a direct chill (DC) casting are closely coupled. These couplings are the key to the understanding of the formation of the macrosegregation and of the non-uniform microstructure of the casting. In the present paper we use a multiphase and multiscale model to provide a fully coupled picture of the links between macrosegregation and microstructure in a DC cast billet. The model describes nucleation from inoculant particles and growth of dendritic and globular equiaxed crystal grains, fully coupled with macroscopic transport phenomena: fluid flow induced by natural convection and solidification shrinkage, heat, mass, and solute mass transport, motion of free-floating equiaxed grains, and of grain refiner particles. We compare our simulations to experiments on grain-refined and non-grain-refined industrial size billets from literature. We show that a transition between dendritic and globular grain morphology triggered by the grain refinement is the key to the explanation of the differences between the macrosegregation patterns in the two billets. We further show that the grain size and morphology are strongly affected by the macroscopic transport of free-floating equiaxed grains and of grain refiner particles.

Determination of the five parameter grain boundary character distribution of nanocrystalline alpha-zirconium thin films using transmission electron microscopy

DOE PAGES

Ghamarian, I.; Samani, P.; Rohrer, G. S.; ...

2017-03-24

Grain boundary engineering and other fundamental materials science problems (e.g., phase transformations and physical properties) require an improvement in the understanding of the type and population of grain boundaries in a given system – yet, databases are limited in number and spare in detail, including for hcp crystals such as zirconium. One way to rapidly obtain databases to analyze is to use small-grained materials and high spatial resolution orientation microscopy techniques, such as ASTAR™/precession electron diffraction. To demonstrate this, a study of grain boundary character distributions was conducted for α-zirconium deposited at room temperature on fused silica substrates using physicalmore » vapor deposition. The orientation maps of the nanocrystalline thin films were acquired by the ASTARα/precession electron diffraction technique, a new transmission electron microscope based orientation microscopy method. The reconstructed grain boundaries were classified as pure tilt, pure twist, 180°-twist and 180°-tilt grain boundaries based on the distribution of grain boundary planes with respect to the angle/axis of misorientation associated with grain boundaries. The results of the current study were compared to the results of a similar study on α-titanium and the molecular dynamics results of grain boundary energy for α-titanium.« less

Effect of processing sorghum grain on dairy calf performance.

PubMed

Abdelgadir, I E; Morrill, J L

1995-09-01

Two trials evaluated the effect of sorghum grain processing on dairy calf performance. In trial 1, Holstein calves (n = 76; .5 to 8 wk of age) were fed one of three calf starters that contained either raw, roasted (exit temperature of 135 degrees C), or conglomerated sorghum grain. The conglomeration process consisted of grinding the grain, adding water, pelleting the mixture, and then roasting it. Raw and roasted sorghum grains were ground through a 3.2-mm screen and then included in complete pelleted starters; conglomerated sorghum grain pellets were mixed with the other pelleted ingredients of the starter. Processing did not enhance calf performance or affect selected ruminal and blood metabolites. In trial 2, roasted and conglomerated sorghum grains were ground through a 3.2-mm screen, and each was included in a pelleted starter fed for ad libitum intake to Holstein calves (n = 48) from .5 to 8 wk of age. Calf performance was not affected by method of grain processing, and ruminal and blood metabolites were similar; however, 22% of calves on the conglomerated sorghum grain starter bloated during the postweaning period, which probably resulted in reduced feed intake from wk 6 to 8. Measures to prevent bloat may be necessary to realize a potential benefit of conglomerating sorghum grain for calves.

Activation of Big Grain1 significantly improves grain size by regulating auxin transport in rice.

PubMed

Liu, Linchuan; Tong, Hongning; Xiao, Yunhua; Che, Ronghui; Xu, Fan; Hu, Bin; Liang, Chengzhen; Chu, Jinfang; Li, Jiayang; Chu, Chengcai

2015-09-01

Grain size is one of the key factors determining grain yield. However, it remains largely unknown how grain size is regulated by developmental signals. Here, we report the identification and characterization of a dominant mutant big grain1 (Bg1-D) that shows an extra-large grain phenotype from our rice T-DNA insertion population. Overexpression of BG1 leads to significantly increased grain size, and the severe lines exhibit obviously perturbed gravitropism. In addition, the mutant has increased sensitivities to both auxin and N-1-naphthylphthalamic acid, an auxin transport inhibitor, whereas knockdown of BG1 results in decreased sensitivities and smaller grains. Moreover, BG1 is specifically induced by auxin treatment, preferentially expresses in the vascular tissue of culms and young panicles, and encodes a novel membrane-localized protein, strongly suggesting its role in regulating auxin transport. Consistent with this finding, the mutant has increased auxin basipetal transport and altered auxin distribution, whereas the knockdown plants have decreased auxin transport. Manipulation of BG1 in both rice and Arabidopsis can enhance plant biomass, seed weight, and yield. Taking these data together, we identify a novel positive regulator of auxin response and transport in a crop plant and demonstrate its role in regulating grain size, thus illuminating a new strategy to improve plant productivity.

Effect of canning on color, protein and phenolic profile of grains from kidney bean, field pea and chickpea.

PubMed

Parmar, Naincy; Singh, Narpinder; Kaur, Amritpal; Virdi, Amardeep Singh; Thakur, Sheetal

2016-11-01

The aim of the present study was to evaluate the effect of canning on color, protein and phenolic profile of grains of kidney bean, field pea and chickpea varieties/accession. Color of grains of different pulses was enhanced after canning. Grains L* (lightness) decreased while a* (redness to yellowness) and b* (greenness to blueness) increased after canning in all the pulses. Protein profiling of grains of different pulses after canning revealed that kidney bean and chickpea, respectively, had the least and the most thermally susceptible polypeptides. Kidney bean and chickpea showed higher Percentage washed drained weight (PWDW) than field pea. Pulse with more grain hardness and PWDW showed higher degree of grain splitting during canning. Grain splitting was also higher in dark colored accessions/varieties as compared to the light colored. Ferulic acid was the most predominant compound present in raw grains of different pulses. Raw kidney bean grains showed higher accumulation of catechin, chlorogenic, protocatechuic acid, p-coumaric acid and ferulic acid than those of chickpea and field pea. Canning caused reduction in all the phenolic compounds except gallic acid and most prominent effect of canning on protocatechuic acid, chlorogenic and ferulic acid was observed. Copyright © 2016. Published by Elsevier Ltd.

Influences of granular constraints and surface effects on the heterogeneity of elastic, superelastic, and plastic responses of polycrystalline shape memory alloys

DOE PAGES

Paranjape, Harshad M.; Paul, Partha P.; Sharma, Hemant; ...

2017-02-16

Deformation heterogeneities at the microstructural length-scale developed in polycrystalline shape memory alloys (SMAs) during superelastic loading are studied using both experiments and simulations. In situ X-ray diffraction, specifically the far-field high energy diffraction microscopy (ff-HEDM) technique, was used to non-destructively measure the grain-averaged statistics of position, crystal orientation, elastic strain tensor, and volume for hundreds of austenite grains in a superelastically loaded nickel-titanium (NiTi) SMA. These experimental data were also used to create a synthetic microstructure within a finite element model. The development of intragranular stresses were then simulated during tensile loading of the model using anisotropic elasticity. Driving forcesmore » for phase transformation and slip were calculated from these stresses. The grain-average responses of individual austenite crystals examined before and after multiple stress-induced transformation events showed that grains in the specimen interior carry more axial stress than the surface grains as the superelastic response "shakes down". Examination of the heterogeneity within individual grains showed that regions near grain boundaries exhibit larger stress variation compared to the grain interiors. As a result, this intragranular heterogeneity is more strongly driven by the constraints of neighboring grains than the initial stress state and orientation of the individual grains.« less

Phosphorus reduces the zinc concentration in cereals pot-grown on calcareous Vertisols from southern Spain.

PubMed

Sánchez-Rodríguez, Antonio Rafael; Del Campillo, María Carmen; Torrent, José

2017-08-01

Zinc deficiency, a major problem in crops grown on soils low in available Zn, is even more important in phosphorus-rich soils. This work aimed to elucidate the effects of soil P and Zn levels, and of fertilizer application, on yield and Zn concentration in cereal grains. Wheat and barley were successively pot-grown on 20 calcareous Vertisols low in available Zn and ranging widely in available P. Grain yield in the plants grown on the native soils was positively correlated with Olsen P but not with diethylenetriaminepentaacetic acid (DTPA)-extractable Zn except for wheat on P-rich soils. Grain Zn concentration was negatively correlated with Olsen P. Grain Zn uptake differed little among soils. Application of P to the soils increased grain yield insignificantly and P concentration significantly; however, it reduced grain Zn concentration (particularly at low Olsen P values). Applying Zn alone only increased grain Zn concentration, whereas applying P and Zn in combination increased yield and grain Zn concentration at low and high Olsen P values, respectively. Applying P alone to plants grown on calcareous Vertisols low in available P and Zn may in practice reduce grain Zn concentrations while not increasing grain yield significantly. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Microbiological study of lactic acid bacteria in kefir grains by culture-dependent and culture-independent methods.

PubMed

Chen, Hsi-Chia; Wang, Sheng-Yao; Chen, Ming-Ju

2008-05-01

Lactic acid bacteria (LAB) in different original kefir grains were first assessed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) by a culture-dependent way, and were further confirmed by DNA sequencing techniques. Results indicated that a combined method of cultivation with PCR-DGGE and subsequent DNA sequencing could successfully identify four LAB strains from three kefir grains from Taiwan (named Hsinchu, Mongolia and Ilan). Lactobacillus kefiri accounted, in the three kefir grains, for at least half of the isolated colonies while Lb. kefiranofaciens was the second most frequently isolated species. Leuconostoc mesenteroides was less frequently found but still in the three kefir grains conversely to Lactococcus lactis which based on culture-dependent isolation was only found in two of the kefir grains. It was interesting to find that all three kefir grains contain similar LAB species. Furthermore, the DGGE as a culture-independent method was also applied to detect the LAB strains. Results indicated that Lb. kefiranofaciens was found in all three kefir grains, whereas Lb. kefiri was only observed in Hsinchu kefir grain and Lc. lactis was found in both Mongolia and Ilan samples. Two additional strains, Pseudomonas spp. and E. coli, were also detected in kefir grains.

Energetics and structural properties of twist grain boundaries in Cu

NASA Technical Reports Server (NTRS)

Karimi, Majid

1992-01-01

Structural and energetics properties of atoms near a grain boundary are of great importance from theoretical and experimental standpoints. From various experimental work it is concluded that diffusion at low temperatures at polycrystalline materials take place near grain boundary. Experimental and theoretical results also indicate changes of up to 70 percent in physical properties near a grain boundary. The Embedded Atom Method (EAM) calculations on structural properties of Au twist grain boundaries are in quite good agreement with their experimental counterparts. The EAM is believed to predict reliable values for the single vacancy formation energy as well as migration energy. However, it is not clear whether the EAM functions which are fitted to the bulk properties of a perfect crystalline solid can produce reliable results on grain boundaries. One of the objectives of this work is to construct the EAM functions for Cu and use them in conjunction with the molecular static simulation to study structures and energetics of atoms near twist grain boundaries in Cu. This provides tests of the EAM functions near a grain boundary. In particular, we determine structure, single vacancy formation energy, migration energy, single vacancy activation energy, and interlayer spacing as a function of distance from grain boundary. Our results are compared with the available experimental and theoretical results from grain boundaries and bulk.

Influences of granular constraints and surface effects on the heterogeneity of elastic, superelastic, and plastic responses of polycrystalline shape memory alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paranjape, Harshad M.; Paul, Partha P.; Sharma, Hemant

Deformation heterogeneities at the microstructural length-scale developed in polycrystalline shape memory alloys (SMAs) during superelastic loading are studied using both experiments and simulations. In situ X-ray diffraction, specifically the far-field high energy diffraction microscopy (ff-HEDM) technique, was used to non-destructively measure the grain-averaged statistics of position, crystal orientation, elastic strain tensor, and volume for hundreds of austenite grains in a superelastically loaded nickel-titanium (NiTi) SMA. These experimental data were also used to create a synthetic microstructure within a finite element model. The development of intragranular stresses were then simulated during tensile loading of the model using anisotropic elasticity. Driving forcesmore » for phase transformation and slip were calculated from these stresses. The grain-average responses of individual austenite crystals examined before and after multiple stress-induced transformation events showed that grains in the specimen interior carry more axial stress than the surface grains as the superelastic response "shakes down". Examination of the heterogeneity within individual grains showed that regions near grain boundaries exhibit larger stress variation compared to the grain interiors. As a result, this intragranular heterogeneity is more strongly driven by the constraints of neighboring grains than the initial stress state and orientation of the individual grains.« less

Quantifying grain shape with MorpheoLV: A case study using Holocene glacial marine sediments

NASA Astrophysics Data System (ADS)

Charpentier, Isabelle; Staszyc, Alicia B.; Wellner, Julia S.; Alejandro, Vanessa

2017-06-01

As demonstrated in earlier works, quantitative grain shape analysis has revealed to be a strong proxy for determining sediment transport history and depositional environments. MorpheoLV, devoted to the calculation of roughness coefficients from pictures of unique clastic sediment grains using Fourier analysis, drives computations for a collection of samples of grain images. This process may be applied to sedimentary deposits assuming core/interval/image archives for the storage of samples collected along depth. This study uses a 25.8 m jumbo piston core, NBP1203 JPC36, taken from a 100 m thick sedimentary drift deposit from Perseverance Drift on the northern Antarctic Peninsula continental shelf. Changes in ocean and ice conditions throughout the Holocene recorded in this sedimentary archive can be assessed by studying grain shape, grain texture, and other proxies. Ninety six intervals were sampled and a total of 2319 individual particle images were used. Microtextures of individual grains observed by SEM show a very high abundance of authigenically precipitated silica that obscures the original grain shape. Grain roughness, computed along depth with MorpheoLV, only shows small variation confirming the qualitative observation deduced from the SEM. Despite this, trends can be seen confirming the reliability of MorpheoLV as a tool for quantitative grain shape analysis.

Effect of initial grain size on inhomogeneous plastic deformation and twinning behavior in high manganese austenitic steel with a polycrystalline microstructure

NASA Astrophysics Data System (ADS)

Ueji, R.; Tsuchida, N.; Harada, K.; Takaki, K.; Fujii, H.

2015-08-01

The grain size effect on the deformation twinning in a high manganese austenitic steel which is so-called TWIP (twining induced plastic deformation) steel was studied in order to understand how to control deformation twinning. The 31wt%Mn-3%Al-3% Si steel was cold rolled and annealed at various temperatures to obtain fully recrystallized structures with different mean grain sizes. These annealed sheets were examined by room temperature tensile tests at a strain rate of 10-4/s. The coarse grained sample (grain size: 49.6μm) showed many deformation twins and the deformation twinning was preferentially found in the grains in which the tensile axis is parallel near to [111]. On the other hand, the sample with finer grains (1.8 μm) had few grains with twinning even after the tensile deformation. The electron back scattering diffraction (EB SD) measurements clarified the relationship between the anisotropy of deformation twinning and that of inhomogeneous plastic deformation. Based on the EBSD analysis, the mechanism of the suppression of deformation twinning by grain refinement was discussed with the concept of the slip pattern competition between the slip system governed by a grain boundary and that activated by the macroscopic load.

FORMATION AND ALIGNMENT OF ELONGATED, FRACTAL-LIKE WATER-ICE GRAINS IN EXTREMELY COLD, WEAKLY IONIZED PLASMA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chai, Kil-Byoung; Bellan, Paul M., E-mail: kbchai@caltech.edu, E-mail: pbellan@caltech.edu

2015-04-01

Elongated, fractal-like water-ice grains are observed to form spontaneously when water vapor is injected into a weakly ionized laboratory plasma formed in a background gas cooled to an astrophysically relevant temperature. The water-ice grains form in 1–2 minutes, levitate with regular spacing, and are aligned parallel to the sheath electric field. Water-ice grains formed in plasma where the neutrals and ions have low mass, such as hydrogen and helium, are larger, more elongated, and more fractal-like than water-ice grains formed in plasmas where the neutrals and ions have high mass such as argon and krypton. Typical aspect ratios (length tomore » width ratio) are as great as 5 while typical fractal dimensions are ∼1.7. Water-ice grain lengths in plasmas with low neutral and ion masses can be several hundred microns long. Infrared absorption spectroscopy reveals that the water-ice grains are crystalline and so are similar in constitution to the water-ice grains in protoplanetary disks, Saturn’s rings, and mesospheric clouds. The properties and behavior of these laboratory water-ice grains may provide insights into morphology and alignment behavior of water-ice grains in astrophysical dusty plasmas.« less

SALT-RESPONSIVE ERF1 is a negative regulator of grain filling and gibberellin-mediated seedling establishment in rice.

PubMed

Schmidt, Romy; Schippers, Jos H M; Mieulet, Delphine; Watanabe, Mutsumi; Hoefgen, Rainer; Guiderdoni, Emmanuel; Mueller-Roeber, Bernd

2014-02-01

Grain quality is an important agricultural trait that is mainly determined by grain size and composition. Here, we characterize the role of the rice transcription factor (TF) SALT-RESPONSIVE ERF1 (SERF1) during grain development. Through genome-wide expression profiling and chromatin immunoprecipitation, we found that SERF1 directly regulates RICE PROLAMIN-BOX BINDING FACTOR (RPBF), a TF that functions as a positive regulator of grain filling. Loss of SERF1 enhances RPBF expression resulting in larger grains with increased starch content, while SERF1 overexpression represses RPBF resulting in smaller grains. Consistently, during grain filling, starch biosynthesis genes such as GRANULE-BOUND STARCH SYNTHASEI (GBSSI), STARCH SYNTHASEI (SSI), SSIIIa, and ADP-GLUCOSE PYROPHOSPHORYLASE LARGE SUBUNIT2 (AGPL2) are up-regulated in SERF1 knockout grains. Moreover, SERF1 is a direct upstream regulator of GBSSI. In addition, SERF1 negatively regulates germination by controlling RPBF expression, which mediates the gibberellic acid (GA)-induced expression of RICE AMYLASE1A (RAmy1A). Loss of SERF1 results in more rapid seedling establishment, while SERF1 overexpression has the opposite effect. Our study reveals that SERF1 represents a negative regulator of grain filling and seedling establishment by timing the expression of RPBF.

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

DOE PAGES

El Atwani, Osman; Nathaniel, James; Leff, Asher C.; ...

2017-05-12

Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0 /2 [111] Burgers vector were directly observed asmore » a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. Lastly, a relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.« less

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Atwani, Osman; Nathaniel, James; Leff, Asher C.

Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0 /2 [111] Burgers vector were directly observed asmore » a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. Lastly, a relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.« less

The water kefir grain inoculum determines the characteristics of the resulting water kefir fermentation process.

PubMed

Laureys, D; De Vuyst, L

2017-03-01

To investigate the influence of the water kefir grain inoculum on the characteristics of the water kefir fermentation process. Three water kefir fermentation processes were started with different water kefir grain inocula and followed as a function of time regarding microbial species diversity, community dynamics, substrate consumption profile and metabolite production course. The inoculum determined the water kefir grain growth, the viable counts on the grains, the time until total carbohydrate exhaustion, the final metabolite concentrations and the microbial species diversity. There were always 2-10 lactic acid bacterial cells for every yeast cell and the majority of these micro-organisms was always present on the grains. Lactobacillus paracasei, Lactobacillus hilgardii, Lactobacillus nagelii and Saccharomyces cerevisiae were always present and may be the key micro-organisms during water kefir fermentation. Low water kefir grain growth was associated with small grains with high viable counts of micro-organisms, fast fermentation and low pH values, and was not caused by the absence of exopolysaccharide-producing lactic acid bacteria. The water kefir grain inoculum influences the microbial species diversity and characteristics of the fermentation process. A select group of key micro-organisms was always present during fermentation. This study allows a rational selection of a water kefir grain inoculum. © 2016 The Society for Applied Microbiology.

Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

NASA Technical Reports Server (NTRS)

Marshall, J. R.; Borucki, J.; Bratton, C.

1999-01-01

The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. Elastic energy deposited in the bed by the impacting grain creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains from closed to open packing, and grains are consequently able to eject themselves forcefully from the impact site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. There is a great temptation to draw parallels with cratering produced by meteorite impacts, but a rigorous search for common modelling ground between the two phenomena has not been conducted at this time. For every impact of an aerodynamically energized grain, there are several hundred grains ejected into the wind for the high-energy transport that might occur on Mars. Many of these grains will themselves become subject to the boundary layer's aerodynamic lift forces (their motion will not immediately die and add to the creep population), and these grains will become indistinguishable from those lifted entirely by aerodynamic forces. As each grain impacts the bed, it will eject even more grains into the flow. A cascading effect will take place, but because it must be finite in its growth, damping will occur as the number of grains set in motion causes mid-air collisions that prevent much of the impact energy from reaching the surface of the bed -thus creating a dynamic equilibrium in a high-density saltation cloud. It is apparent that for a given impact energy, the stress field permits a smaller volume of grains to convert to open packing as the size of the bed grains increases, or as the energy of the "percussive" grain decreases (by decrease in velocity or mass). Thus, the mass of the "repercussive" grain population that is ejected from the impact site becomes a function of the scale of the stress field in relation to the scale of the bed material (self-similarity being applicable if both bed size and energy are simultaneously adjusted). In other words, in a very high energy aeolian system where an aerodynamically raised grain can ballistically raise many more grains, the amount of material lifted into the wind becomes largely a function of a dilatancy threshold. If this threshold is exceeded, grains are repercussively injected into the saltation cloud. The "dilatancy threshold" may be defined in terms of the saltation percussive force required to convert the bed, through elastic response, from a closed to an open packing system. If open packing cannot be created, the grains cannot escape from the impact site, even though the elastic deformation and percussive force may be able to reorganize the grains with respect to one another. As the crossbow experiments showed, for an ever-increasing bed grain size, a point is reached when no material can be moved because the energy of the percussive grain is insufficient to dilate the relatively coarse bed. Although this seems to be stating the obvious -- that too little energy will not cause the bed to splash -- the consequences of exceeding the "splash threshold" by dilatancy are not so obvious for high-energy aeolian transport. It is noted that the force required to elastically dilate the bed has to overcome Coulombic grain attractions such as dipole-dipole coupling, dielectric, monopole, contact-induced dipole attractions, van der Waals forces, molecular monolayer capillary forces, as well as the mechanical interlocking frictional resistance of the grains. On Mars, it is predicted that the dilatancy threshold may be the prime control of grain flux. Additional information is contained in the original.

Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

NASA Astrophysics Data System (ADS)

Marshall, J. R.; Borucki, J.; Bratton, C.

1999-09-01

The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. Elastic energy deposited in the bed by the impacting grain creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains from closed to open packing, and grains are consequently able to eject themselves forcefully from the impact site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. There is a great temptation to draw parallels with cratering produced by meteorite impacts, but a rigorous search for common modelling ground between the two phenomena has not been conducted at this time. For every impact of an aerodynamically energized grain, there are several hundred grains ejected into the wind for the high-energy transport that might occur on Mars. Many of these grains will themselves become subject to the boundary layer's aerodynamic lift forces (their motion will not immediately die and add to the creep population), and these grains will become indistinguishable from those lifted entirely by aerodynamic forces. As each grain impacts the bed, it will eject even more grains into the flow. A cascading effect will take place, but because it must be finite in its growth, damping will occur as the number of grains set in motion causes mid-air collisions that prevent much of the impact energy from reaching the surface of the bed -thus creating a dynamic equilibrium in a high-density saltation cloud. It is apparent that for a given impact energy, the stress field permits a smaller volume of grains to convert to open packing as the size of the bed grains increases, or as the energy of the "percussive" grain decreases (by decrease in velocity or mass). Thus, the mass of the "repercussive" grain population that is ejected from the impact site becomes a function of the scale of the stress field in relation to the scale of the bed material (self-similarity being applicable if both bed size and energy are simultaneously adjusted). In other words, in a very high energy aeolian system where an aerodynamically raised grain can ballistically raise many more grains, the amount of material lifted into the wind becomes largely a function of a dilatancy threshold. If this threshold is exceeded, grains are repercussively injected into the saltation cloud. The "dilatancy threshold" may be defined in terms of the saltation percussive force required to convert the bed, through elastic response, from a closed to an open packing system. If open packing cannot be created, the grains cannot escape from the impact site, even though the elastic deformation and percussive force may be able to reorganize the grains with respect to one another. As the crossbow experiments showed, for an ever-increasing bed grain size, a point is reached when no material can be moved because the energy of the percussive grain is insufficient to dilate the relatively coarse bed. Although this seems to be stating the obvious -- that too little energy will not cause the bed to splash -- the consequences of exceeding the "splash threshold" by dilatancy are not so obvious for high-energy aeolian transport. It is noted that the force required to elastically dilate the bed has to overcome Coulombic grain attractions such as dipole-dipole coupling, dielectric, monopole, contact-induced dipole attractions, van der Waals forces, molecular monolayer capillary forces, as well as the mechanical interlocking frictional resistance of the grains. On Mars, it is predicted that the dilatancy threshold may be the prime control of grain flux. Additional information is contained in the original.

Computational Investigation of Effects of Grain Size on Ballistic Performance of Copper

NASA Astrophysics Data System (ADS)

He, Ge; Dou, Yangqing; Guo, Xiang; Liu, Yucheng

2018-01-01

Numerical simulations were conducted to compare ballistic performance and penetration mechanism of copper (Cu) with four representative grain sizes. Ballistic limit velocities for coarse-grained (CG) copper (grain size ≈ 90 µm), regular copper (grain size ≈ 30 µm), fine-grained (FG) copper (grain size ≈ 890 nm), and ultrafine-grained (UG) copper (grain size ≈ 200 nm) were determined for the first time through the simulations. It was found that the copper with reduced grain size would offer higher strength and better ductility, and therefore renders improved ballistic performance than the CG and regular copper. High speed impact and penetration behavior of the FG and UG copper was also compared with the CG coppers strengthened by nanotwinned (NT) regions. The comparison results showed the impact and penetration resistance of UG copper is comparable to the CG copper strengthened by NT regions with the minimum twin spacing. Therefore, besides the NT-strengthened copper, the single phase copper with nanoscale grain size could also be a strong candidate material for better ballistic protection. A computational modeling and simulation framework was proposed for this study, in which Johnson-Cook (JC) constitutive model is used to predict the plastic deformation of Cu; the JC damage model is to capture the penetration and fragmentation behavior of Cu; Bao-Wierzbicki (B-W) failure criterion defines the material's failure mechanisms; and temperature increase during this adiabatic penetration process is given by the Taylor-Quinney method.

PHOTOPHORETIC LEVITATION AND TRAPPING OF DUST IN THE INNER REGIONS OF PROTOPLANETARY DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

McNally, Colin P.; McClure, Melissa K., E-mail: cmcnally@nbi.dk, E-mail: mmcclure@eso.org

In protoplanetary disks, the differential gravity-driven settling of dust grains with respect to gas and with respect to grains of varying sizes determines the observability of grains, and sets the conditions for grain growth and eventually planet formation. In this work, we explore the effect of photophoresis on the settling of large dust grains in the inner regions of actively accreting protoplanetary disks. Photophoretic forces on dust grains result from the collision of gas molecules with differentially heated grains. We undertake one-dimensional dust settling calculations to determine the equilibrium vertical distribution of dust grains in each column of the disk.more » In the process we introduce a new treatment of the photophoresis force which is consistent at all optical depths with the representation of the radiative intensity field in a two-stream radiative transfer approximation. The levitation of large dust grains creates a photophoretic dust trap several scale heights above the mid-plane in the inner regions of the disk where the dissipation of accretion energy is significant. We find that differential settling of dust grains is radically altered in these regions of the disk, with large dust grains trapped in a layer below the stellar irradiation surface, where the dust to gas mass ratio can be enhanced by a factor of a hundred for the relevant particles. The photophoretic trapping effect has a strong dependence on particle size and porosity.« less

Microstructure evolution in the fusion zone of laser-welded Mg–Gd–Y–Zr alloy during solution and aging treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lyuyuan

The microstructure evolution in the fusion zone of laser-welded Mg-Gd-Y-Zr alloy during solution and aging treatment is investigated. The morphology of the Mg{sub 24}(Gd,Y){sub 5} in the divorced eutectic at the grain boundary transforms from a continuous network to disconnected and fragmentized islands and then to spheroidal particles before complete dissolution during the solution treatment at 430 °C. During the subsequent aging treatment at 225 °C, the precipitation sequence in the fusion zone follows the order of supersaturated solid solution (SSSS) → βʺ(D0{sub 19}) → βʹ(cbco) → β{sub 1}(fcc) → β(fcc). High-density precipitates are present at the original grain boundariesmore » of the fusion zone from the welded structure but there are less precipitates in the interior of the original grains. The grain growth during the solution treatment at 430 °C comprises the slowly increasing stage, rapidly increasing stage, and stable stage. The network-distributed Mg{sub 24}(Gd,Y){sub 5} impedes migration of the grain boundaries, restricts grain growth in the first slowly increasing stage, and segregation of zirconium near the grain boundaries also affects migration of the grain boundaries. - Highlights: •Different quantities of precipitates are present at different location of grain. •The network-distributed Mg{sub 24}(Gd,Y){sub 5} restricts grain growth. •Segregation of Zr affects migration of grain boundaries.« less

Computer based experimental studies of the Fry method of strain analysis on 2- and 3- dimensional grain populations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longiaru, S.; Bhattacharyya, T.

1985-01-01

Inherent in Fry's (1979) all-object separation method of strain analysis are the subtle conditions that 1) the grains or phenocrysts being counted are of equal diameter and 2) that the true centers of such grains lie within the plane of measurement. When such conditions are met, the technique yields accurate, easily interpreted voids within all-object separation (AOS) plots for both deformed and non-deformed populations. Natural grain or phenocryst populations generally do not conform to these limitation and practical application of the technique from either a cut rock surface or thin section often yields diffuse patterns that are not easily interpreted.more » The authors examine the effect of grain size variation and grain/matrix ratio on AOS diagrams developed from computer generated spherical grain populations constructed in both two and three dimensions. They employ a random number generator and simple fitting algorithm to develop grain populations with known statistical parameters. Such control allows for the modeling of many types of natural grain size populations such as fluvial sandstones, porphyritic ash flow tuffs, augen gneisses, etc. They show that significant grain size variation in a two dimensional population contributes substantial noise in to the AOS diagram and that an additional level of noise is encountered when dealing with slices through populations modeled in three dimensions. Some of this noise can be eliminated by rigorous sampling of only subsets of the total grain population.« less

Grain-size variations on a longitudinal dune and a barchan dune

NASA Astrophysics Data System (ADS)

Watson, Andrew

1986-01-01

The grain-size characteristics of the sand upon two dunes—a 40 m high longitudinal dune in the central Namib Desert and a 6.0 m high barchan in the Jafurah sand sea of Saudi Arabia—vary with position on the dunes. On the longitudinal dune, median grain size decreases, sorting improves and the grain-size distributions are less skewed and more normalized toward the crest. Though sand at the windward toe is distinct, elsewhere on the dune the changes in grain-size characteristics are gradual. An abrupt change in grain size and sorting near the crest—as described by Bagnold (1941, pp. 226-229)—is not well represented on this dune. Coarse grains remain as a lag on concave slope units and small particles are winnowed from the sand on the steepest windward slopes near the crest. Avalanching down slipfaces at the crest acts only as a supplementary grading mechanism. On the barchan dune median grain size also decreases near the crest, but sorting becomes poorer, though the grain-size distributions are more symmetric and more normalized. The dune profile is a Gaussian curve with a broad convex zone at the apex upon which topset beds had accreted prior to sampling. Grain size increases and sorting improves down the dune's slipface. However, this grading mechanism does not influence sand on the whole dune because variations in wind regime bring about different modes of dune accretion. On both dunes, height and morphology appear to influence significantly the grain-size characteristics.

Correlated NanoSIMS, TEM, and XANES Studies of Presolar Grains

NASA Astrophysics Data System (ADS)

Groopman, Evan Edward

The objective of this thesis is to describe the correlated study of individual presolar grains via Nano-scale Secondary Ion Mass Spectrometry (NanoSIMS), Transmission Electron Microscopy (TEM), and Scanning Transmission X-ray Microscopy (STXM) utilizing X-ray Absorption Near Edge Structure (XANES), with a focus on connecting these correlated laboratory studies to astrophysical phenomena. The correlated isotopic, chemical, and microstructural studies of individual presolar grains provide the most detailed description of their formation environments, and help to inform astrophysical models and observations of stellar objects. As a part of this thesis I have developed and improved upon laboratory techniques for micromanipulating presolar grains and embedding them in resin for ultramicrotomy after NanoSIMS analyses and prior to TEM characterization. The new methods have yielded a 100% success rate and allow for the specific correlation of microstructural and isotopic properties of individual grains. Knowing these properties allows for inferences to be made regarding the condensation sequences and the origins of the stellar material that condensed to form these grains. NanoSIMS studies of ultramicrotomed sections of presolar graphite grains have revealed complex isotopic heterogeneities that appear to be primary products of the grains' formation environments and not secondary processing during the grains' lifetimes. Correlated excesses in 15N and 18O were identified as being carried by TiC subgrains within presolar graphite grains from supernovae (SNe). These spatially-correlated isotopic anomalies pinpoint the origin of the material that formed these grains: the inner He/C zone. Complex microstructures and isotopic heterogeneities also provide evidence for mixing in globular SN ejecta, which is corroborated by models and telescopic observations. In addition to these significant isotopic discoveries, I have also observed the first reported nanocrystalline core surrounded by turbostratic graphite within a low-density SN graphite grain. Nanocrystalline cores consisting of randomly-oriented 2-4 nm sheets of graphene and surrounded by concentric shells of graphite have been observed in high-density presolar graphite grains from Asymptotic Giant Branch stars, whose grains are typically microstructurally distinct from SN graphite grains. These vastly different stellar environments briefly formed similar nanocrystalline structures before diverging in the structure of their mantling graphite to be typical of AGB and SN grains. While relatively few correlated NanoSIMS and TEM studies have been performed previously, which this research thesis aims to expand, my collaborators and I also endeavored to add a third correlated technique, STXM/XANES, which had previously not been applied to presolar grains. XANES allows for the investigation of molecular bonds, which we used to help infer physical and chemical properties of stellar ejecta. I investigated the C K-edge and Ti L-edge of molecular bonds in both presolar graphite grains and their TiC subgrains. The presolar graphite grains, while overwhelmingly composed of aromatic C molecules, host a wide variety of minor organic molecules. Considering the large isotopic anomalies in the grains, these minor components are not likely due to contamination. I also investigated the valence state of Ti in Ti-rich subgrains and plan to work towards illuminating the effect that V in solid solution has upon the TiC bonds.

40 CFR 180.507 - Azoxystrobin; tolerances for residues.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Sapote, mamey 2.0 Sapote, white 2.0 Sorghum, grain, forage 25 Sorghum, grain, grain 11 Sorghum, grain... Sugarcane, cane 0.2 Sunflower subgroup 20B 0.5 Tamarind 2.0 Tomato, paste 0.6 Tomato subgroup 8-10A 0.2...

40 CFR 180.507 - Azoxystrobin; tolerances for residues.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Sapote, mamey 2.0 Sapote, white 2.0 Sorghum, grain, forage 25 Sorghum, grain, grain 11 Sorghum, grain... Sugarcane, cane 0.2 Sunflower subgroup 20B 0.5 Tamarind 2.0 Tomato, paste 0.6 Tomato subgroup 8-10A 0.2...

7 CFR 810.1201 - Definition of rye.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Rye Terms Defined § 810.1201 Definition of rye. Grain that, before the...

7 CFR 800.16 - Certification requirements for export grain.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 7 2010-01-01 2010-01-01 false Certification requirements for export grain. 800.16 Section 800.16 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL...

7 CFR 810.1001 - Definition of oats.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Oats Terms Defined § 810.1001 Definition of oats. Grain that consists...

77 FR 65855 - Cancellation of Indianapolis Grain Inspection & Weighing Service, Inc. Designation; Selection of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-31

... DEPARTMENT OF AGRICULTURE Grain Inspection, Packers and Stockyards Administration Cancellation of Indianapolis Grain Inspection & Weighing Service, Inc. Designation; Selection of Interim Provider; Opportunity for Designation in the Indianapolis, IN Area AGENCY: Grain Inspection, Packers and Stockyards...

Grain boundary stability governs hardening and softening in extremely fine nanograined metals

NASA Astrophysics Data System (ADS)

Hu, J.; Shi, Y. N.; Sauvage, X.; Sha, G.; Lu, K.

2017-03-01

Conventional metals become harder with decreasing grain sizes, following the classical Hall-Petch relationship. However, this relationship fails and softening occurs at some grain sizes in the nanometer regime for some alloys. In this study, we discovered that plastic deformation mechanism of extremely fine nanograined metals and their hardness are adjustable through tailoring grain boundary (GB) stability. The electrodeposited nanograined nickel-molybdenum (Ni-Mo) samples become softened for grain sizes below 10 nanometers because of GB-mediated processes. With GB stabilization through relaxation and Mo segregation, ultrahigh hardness is achieved in the nanograined samples with a plastic deformation mechanism dominated by generation of extended partial dislocations. Grain boundary stability provides an alternative dimension, in addition to grain size, for producing novel nanograined metals with extraordinary properties.

Grain size distribution in sheared polycrystals

NASA Astrophysics Data System (ADS)

Sarkar, Tanmoy; Biswas, Santidan; Chaudhuri, Pinaki; Sain, Anirban

2017-12-01

Plastic deformation in solids induced by external stresses is of both fundamental and practical interest. Using both phase field crystal modeling and molecular dynamics simulations, we study the shear response of monocomponent polycrystalline solids. We subject mesocale polycrystalline samples to constant strain rates in a planar Couette flow geometry for studying its plastic flow, in particular its grain deformation dynamics. As opposed to equilibrium solids where grain dynamics is mainly driven by thermal diffusion, external stress/strain induce a much higher level of grain deformation activity in the form of grain rotation, coalescence, and breakage, mediated by dislocations. Despite this, the grain size distribution of this driven system shows only a weak power-law correction to its equilibrium log-normal behavior. We interpret the grain reorganization dynamics using a stochastic model.

Whole grain for whom and why?

PubMed Central

Frølich, Wenche; Åman, Per

2010-01-01

A definition of whole grain is a critical first step in investigating health claims for whole grain and its products. Today, there is no internationally accepted definition of whole grain. Some existing definitions are broad and commodity-based, including grains with similar end uses, while others are more restricted. Scientific knowledge must be the basis for inclusion of certain grains. It is better to start with a restricted list of grains (a precautionary principle) and extend this as more knowledge becomes available. An exact definition of the raw materials (milled, cracked, crushed, rolled, or flaked) and knowledge of the components providing health effects would appear to be crucial issues for the European authorities when approving health claims. It is important that health claims are evidence-based, sustainable, and officially validated. PMID:20300475

Effects of grain size on the corrosion resistance of pure magnesium by cooling rate-controlled solidification

NASA Astrophysics Data System (ADS)

Liu, Yichi; Liu, Debao; You, Chen; Chen, Minfang

2015-09-01

The aim of this study was to investigate the effect of grain size on the corrosion resistance of pure magnesium developed for biomedical applications. High-purity magnesium samples with different grain size were prepared by the cooling rate-controlled solidification. Electrochemical and immersion tests were employed to measure the corrosion resistance of pure magnesium with different grain size. The electrochemical polarization curves indicated that the corrosion susceptibility increased as the grain size decrease. However, the electrochemical impedance spectroscopy (EIS) and immersion tests indicated that the corrosion resistance of pure magnesium is improved as the grain size decreases. The improvement in the corrosion resistance is attributed to refine grain can produce more uniform and density film on the surface of sample.

The role of endotoxin in grain dust exposure and airway obstruction.

PubMed

Von Essen, S

1997-05-01

Grain dust exposure is a common cause of respiratory symptoms in grain workers, feed mill employees, and farmers. Many of these workers develop wheezing and acute and chronic bronchitis symptoms, which can be associated with obstructive changes on pulmonary function testing. It has recently been demonstrated that grain dust exposure causes neutrophilic airways inflammation and systemic symptoms related to release of interleukin-1, tumor necrosis factor, interleukin-6, and other mediators of inflammation. Although grain dust is a heterogenous substance, endotoxin has received the greatest amount of attention as a possible cause of the airway inflammation that occurs after grain dust exposure. Although endotoxin undoubtedly causes a portion of the changes seen after grain dust exposure, it is becoming clear that other substances play a role as well.

Effects of grain dust on lungs prior to and following dust remediation.

PubMed

Pahwa, Punam; Dosman, James A; McDuffie, Helen H

2008-12-01

To determine longitudinal estimates of pulmonary function decline in Canadian grain elevator workers before and after dust control by analyzing data collected from five regions of Canada over 15 years. Declines in forced expired volume in one second and forced vital capacity before and after dust control were estimated by using a generalized estimating equations approach. For grain workers who were in the grain industry for 20 or more years both before and after dust control: the mean annual loss of forced expired volume in one second was greatest among current smoking grain workers followed by ex-smokers and nonsmokers, respectively. Similar results were obtained for forced vital capacity. Grain dust control was effective in reducing decline in the lung function measurements among grain workers in all smoking and exposure categories.

Characteristics and origin of coarse gold in Late Pleistocene sediments of the Cariboo placer mining district, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Eyles, N.

1995-02-01

The Cariboo placer mining district (1000 km 2) sited in the Interior Plateau of central British Columbia, Canada, is the premier placer gold mining district of the Province. Gold is recovered from three Late Pleistocene sedimentary facies: postglacial fluvial gravels (< 10 Ka), Late Wisconsin till (ca. 25-10 Ka), and "older" fluvial gravels (>25 Ka). This study reports the morphology (size, roundness, sphericity) of 1636 gold grains, ranging in size from 0.25 to 17 mm, recovered from 19 placer mines. Older gravels contain the smallest gold grains (mean grani size 1.53 mm), grains of intermediate size occur in till (2.23 mm) and the coarsest gold occurs in postglacial gravels (2.34 mm) with a mean of 1.93 mm for the mining district as a whole. The most common grain shapes are sub-rounded, discoidal (14.73% of the grain population), sub-angular, discoidal (10.88%), and sub-rounded, sub-discoidal (9.59%); the most angular grains occur in postglacial gravels. In-situ growth of coarse, angular grains is indicated by a "composite" grain structure, consisting of aggregates of gold particles welded together by high-grade (Ag = < 2%) filamentous gold; in-situ coarsening may be reliant on organic complexing agents produced below a dense forest cover. An evolutionary sequence of grain form, from angular aggregates to rounded "pumpkin seed" grains, is suggested. Rounded grains commonly show a crystalline structure which may result from the cold hammering of gold during transport; fracturing along crystal boundaries is common. Gold grains may undergo cycles of coarsening, rounding, diagenesis and breakup in response to repeated recycling through Pleistocene sedimentary environments.

In Situ Characterization of Twin Nucleation in Pure Ti Using 3D-XRD

NASA Astrophysics Data System (ADS)

Bieler, Thomas R.; Wang, Leyun; Beaudoin, Armand J.; Kenesei, Peter; Lienert, Ulrich

2014-01-01

A small tensile specimen of grade 1 commercially pure titanium was deformed to a few percent strain with concurrent synchrotron X-ray diffraction measurements to identify subsurface {102} twin nucleation events. This sample was from the same piece of material in which a prior study showed that twin nucleation stimulated by slip transfer across a grain boundary accounted for many instances of twin nucleation. The sample had a strong c-axis texture of about eight times random aligned with the tensile axis. After 1.5 pct tensile strain, three twin nucleation events were observed in grains where the c-axis was nearly parallel to the tensile direction. Far-field 3-D X-ray diffraction data were analyzed to obtain the positional center of mass, the average lattice strain, and stress tensors in each grain and twin. In one case where the parent grain was mostly surrounded by hard grain orientations, the twin system with the highest resolved shear stress (RSS) among the six {102} twin variants was activated and the stress in the parent grain decreased after twin nucleation. In two other parent grains with a majority of softer neighboring grain orientations, the observed twins did not occur on the twin system with the highest RSS. Their nucleation could be geometrically attributed to slip transfer from neighboring grains with geometrically favorable basal slip systems, and the stress in the parent grain increased after twin nucleation. In all three twin events, the stress in the twin was 10 to 30 pct lower than the stress in the parent grain, indicating load partitioning between the hard-oriented parent grain and the soft-oriented twin.

Genetic diversity for grain nutrients in wild emmer wheat: potential for wheat improvement

PubMed Central

Chatzav, Merav; Peleg, Zvi; Ozturk, Levent; Yazici, Atilla; Fahima, Tzion; Cakmak, Ismail; Saranga, Yehoshua

2010-01-01

Background and Aims Micronutrient malnutrition, particularly zinc and iron deficiency, afflicts over three billion people worldwide due to low dietary intake. In the current study, wild emmer wheat (Triticum turgidum ssp. dicoccoides), the progenitor of domesticated wheat, was tested for (1) genetic diversity in grain nutrient concentrations, (2) associations among grain nutrients and their relationships with plant productivity, and (3) the association of grain nutrients with the eco-geographical origin of wild emmer accessions. Methods A total of 154 genotypes, including wild emmer accessions from across the Near Eastern Fertile Crescent and diverse wheat cultivars, were characterized in this 2-year field study for grain protein, micronutrient (zinc, iron, copper and manganese) and macronutrient (calcium, magnesium, potassium, phosphorus and sulphur) concentrations. Key Results Wide genetic diversity was found among the wild emmer accessions for all grain nutrients. The concentrations of grain zinc, iron and protein in wild accessions were about two-fold greater than in the domesticated genotypes. Concentrations of these compounds were positively correlated with one another, with no clear association with plant productivity, suggesting that all three nutrients can be improved concurrently with no yield penalty. A subset of 12 populations revealed significant genetic variation between and within populations for all minerals. Association between soil characteristics at the site of collection and grain nutrient concentrations showed negative associations between soil clay content and grain protein and between soil-extractable zinc and grain zinc, the latter suggesting that the greatest potential for grain nutrient minerals lies in populations from micronutrient-deficient soils. Conclusions Wild emmer wheat germplasm offers unique opportunities to exploit favourable alleles for grain nutrient properties that were excluded from the domesticated wheat gene pool. PMID:20202969

Productivity of clay tailings from phosphate mining: 3. Grain crops. [Zea mays; Helianthus annuus; Sorghum bicolor; Glycine max

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mislevy, P.; Blue, W.G.; Roessler, C.E.

A split-fold field experiment was conducted to study forage and grain yield, forage quality, plant nutrient concentrations, changes in soil nutrients, and {sup 226}Ra contents of four grain crops in various rotations. The crop rotations (1) corn (Zea mays L. Jacques 247)-sunflower (Helianthus annuus L. Cargil 205), (2) sunflower-grain sorghum (Sorghum bicolor L, Moench Northrup King Savanna 5), (3) soybean (Glycine max L. Merr. Williams 80)-grain sorghum, and (4) grain sorghum-soybean (University of Florida V-1) were grown on a dry phosphatic clay with and without a 50-mm surface layer of quartz-sand tailings. Results show that corn and grain sorghum producedmore » highest forage yields and highest grain yields per harvest, respectively. Soybean harvested for forage (Crop 1) contained the highest crude protein and in vitro organic matter digestibility. Concentrations of P, K, Ca, Mg, and Fe in most of the forages were adequate for the diets of beef cattle, while those of Mn, Cu and Zn were low. Mehlich I-extractable soil, Ca, and Mg were considered very high and changed little over the 4-yr production period. Application of 50 mm of sand tailings tended to increase Mehlich I-extractable P, Ca, Mn, Cu, Zn, and Fe. Radium-226 concentration in the forage of all grain crops averaged 8.5 Bq kg{sup {minus}1}, which was about 17 times higher than that in the grain of the same crops. Concentrations of {sup 226}Ra in the forage and grain were 1.1% and 0.09% of the concentration in clay respectively. These data indicate that phosphatic clays can be a valuable resource for the production of corn and sorghum grain that contain low concentrations of {sup 226}Ra.« less

Post Deformation at Room and Cryogenic Temperature Cooling Media on Severely Deformed 1050-Aluminum

NASA Astrophysics Data System (ADS)

Khorrami, M. Sarkari; Kazeminezhad, M.

2018-03-01

The annealed 1050-aluminum sheets were initially subjected to the severe plastic deformation through two passes of constrained groove pressing (CGP) process. The obtained specimens were post-deformed by friction stir processing at room and cryogenic temperature cooling media. The microstructure evolutions during mentioned processes in terms of grain structure, misorientation distribution, and grain orientation spread (GOS) were characterized using electron backscattered diffraction. The annealed sample contained a large number of "recrystallized" grains and relatively large fraction (78%) of high-angle grain boundaries (HAGBs). When CGP process was applied on the annealed specimen, the elongated grains with interior substructure were developed, which was responsible for the formation of 80% low-angle grain boundaries. The GOS map of the severely deformed specimen manifested the formation of 43% "distorted" and 51% "substructured" grains. The post deformation of severely deformed aluminum at room temperature led to the increase in the fraction of HAGBs from 20 to 60%. Also, it gave rise to the formation of "recrystallized" grains with the average size of 13 μm, which were coarser than the grains predicted by Zener-Hollomon parameter. This was attributed to the occurrence of appreciable grain growth during post deformation. In the case of post deformation at cryogenic temperature cooling medium, the grain size was decreased, which was in well agreement with the predicted grain size. The cumulative distribution of misorientation was the same for both processing routes. Mechanical properties characterizations in terms of nano-indentation and tensile tests revealed that the post deformation process led to the reduction in hardness, yield stress, and ultimate tensile strength of the severely deformed aluminum.

Wheat grain hardness results from highly conserved mutations in the friabilin components puroindoline a and b

PubMed Central

Giroux, Michael J.; Morris, Craig F.

1998-01-01

“Soft” and “hard” are the two main market classes of wheat (Triticum aestivum L.) and are distinguished by expression of the Hardness gene. Friabilin, a marker protein for grain softness (Ha), consists of two proteins, puroindoline a and b (pinA and pinB, respectively). We previously demonstrated that a glycine to serine mutation in pinB is linked inseparably to grain hardness. Here, we report that the pinB serine mutation is present in 9 of 13 additional randomly selected hard wheats and in none of 10 soft wheats. The four exceptional hard wheats not containing the serine mutation in pinB express no pinA, the remaining component of the marker protein friabilin. The absence of pinA protein was linked inseparably to grain hardness among 44 near-isogenic lines created between the soft variety Heron and the hard variety Falcon. Both pinA and pinB apparently are required for the expression of grain softness. The absence of pinA protein and transcript and a glycine-to-serine mutation in pinB are two highly conserved mutations associated with grain hardness, and these friabilin genes are the suggested tightly linked components of the Hardness gene. A previously described grain hardness related gene termed “GSP-1” (grain softness protein) is not controlled by chromosome 5D and is apparently not involved in grain hardness. The association of grain hardness with mutations in both pinA or pinB indicates that these two proteins alone may function together to effect grain softness. Elucidation of the molecular basis for grain hardness opens the way to understanding and eventually manipulating this wheat endosperm property. PMID:9600953

Experimental Investigations of the Physical and Optical Properties of Individual Micron/Submicron-Size Dust Grains in Astrophysical Environments

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Tankosic, D.; LeClair, A.

2014-01-01

Dust grains constitute a significant component of matter in the universe, and play an important and crucial role in the formation and evolution of the stellar/planetary systems in interstellar dust clouds. Knowledge of physical and optical properties of dust grains is required for understanding of a variety of processes in astrophysical and planetary environments. The currently available and generally employed data on the properties of dust grains is based on bulk materials, with analytical models employed to deduce the corresponding values for individual small micron/submicron-size dust grains. However, it has been well-recognized over a long period, that the properties of individual smallsize dust grains may be very different from those deduced from bulk materials. This has been validated by a series of experimental investigations carried out over the last few years, on a laboratory facility based on an Electrodynamic Balance at NASA, which permits levitation of single small-size dust grains of desired composition and size, in vacuum, in simulated space environments. In this paper, we present a brief review of the results of a series of selected investigations carried out on the analogs of interstellar and planetary dust grains, as well as dust grains obtained by Apollo-l1-17 lunar missions. The selected investigations, with analytical results and discussions, include: (a) Direct measurements of radiation on individual dust grains (b) Rotation and alignments of dust grains by radiative torque (c) Charging properties of dust grains by: (i) UV Photo-electric emissions (ii) Electron Impact. The results from these experiments are examined in the light of the current theories of the processes involved.

Level of Fluoride in Soil, Grain and Water in Jalgaon District, Maharashtra, India.

PubMed

Naik, Rahul Gaybarao; Dodamani, Arun Suresh; Vishwakarma, Prashanth; Jadhav, Harish Chaitram; Khairnar, Mahesh Ravindra; Deshmukh, Manjiri Abhay; Wadgave, Umesh

2017-02-01

Fluoride has an influence on both oral as well as systemic health. The major source of fluoride to body is through drinking water as well as through diet. Staple diet mainly depends on local environmental factors, food grains grown locally, its availability etc. Determination of fluoride level in these food grains is important. So, estimation of the amount of fluoride in grains and its relation to the sources of fluoride used for their cultivation viz., soil and water is important. To estimate the relation of fluoride concentration in grains (Jowar) with respect to that of soil and water used for their cultivation. Fifteen samples each of soil, water and grains were collected using standardized method from the same farm fields of randomly selected villages of Jalgaon district. Fluoride ion concentration was determined in laboratory using SPADNS technique. Mean difference in fluoride levels in between the groups were analyzed using ANOVA and Post-Hoc Tukey test. Linear regression method was applied to analyse the association of the fluoride content of grain with water and soil. There was a significant difference in between mean fluoride levels of soil and water (p<0.001) and in between soil and grain (p<0.001); however, difference in between mean fluoride levels of water and grain was found to be non significant (p=0.591). Also fluoride levels in all the three groups showed significant association with each other. Fluoride level of soil, grains and water should be adjusted to an optimum level. Soil has positive correlation with respect to uptake of fluoride by Jowar grains. So, Jowar grains with optimum fluoride content should be made available in the commercial markets so that oral and general health can be benefitted.

Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wakita, Shigeru; Nozawa, Takaya; Hasegawa, Yasuhiro, E-mail: shigeru@cfca.jp

Presolar grains are small particles found in meteorites through their isotopic compositions, which are considerably different from those of materials in the solar system. If some isotopes in presolar grains diffused out beyond their grain sizes when they were embedded in parent bodies of meteorites, their isotopic compositions could be washed out, and hence the grains could no longer be identified as presolar grains. We explore this possibility for the first time by self-consistently simulating the thermal evolution of planetesimals and the diffusion length of {sup 18}O in presolar silicate grains. Our results show that presolar silicate grains smaller thanmore » ∼0.03 μ m cannot keep their original isotopic compositions even if the host planetesimals experienced a maximum temperature as low as 600 °C. Since this temperature corresponds to that experienced by petrologic type 3 chondrites, isotopic diffusion can constrain the size of presolar silicate grains discovered in such chondrites to be larger than ∼0.03 μ m. We also find that the diffusion length of {sup 18}O reaches ∼0.3–2 μ m in planetesimals that were heated up to 700–800°C. This indicates that, if the original size of presolar grains spans a range from ∼0.001 μ m to ∼0.3 μ m like that in the interstellar medium, then the isotopic records of the presolar grains may be almost completely lost in such highly thermalized parent bodies. We propose that isotopic diffusion could be a key process to control the size distribution and abundance of presolar grains in some types of chondrites.« less

Wettable and Unsinkable: The Hydrodynamics of Saccate Pollen Grains in Relation to the Pollination Mechanism in the Two New Zealand Species of Prumnopitys Phil. (Podocarpaceae)

PubMed Central

SALTER, JOSHUA; MURRAY, BRIAN G.; BRAGGINS, JOHN E.

2002-01-01

The pollination mechanism of most genera of the Podocarpaceae involves inverted ovules, a pollination drop and bisaccate pollen grains. Saccate grains have sometimes been referred to as ‘non‐wettable’ due to their buoyant properties, while non‐saccate pollen grains have been described as ‘wettable’. The hydrodynamic properties of saccate pollen grains of seven podocarp species in five genera, Dacrydium Sol. ex G. Forst., Dacrycarpus (Endl.) de Laub., Manoao Molloy, Podocarpus L‘Hér. ex Pers. and Prumnopitys Phil. have been tested in water, together with saccate and non‐saccate pollen of four other conifer genera, Cedrus Trew (Pinaceae), Cephalotaxus Siebold & Zucc. ex Endl. (Cephalotaxaceae), Cupressus L. (Cupressaceae) and Phyllocladus Rich. ex Mirb. (Phyllocladaceae), and spores of three fern species and one lycopod species. All four spore types studied were non‐wettable, whereas the bisaccate and trisaccate pollen types, like all other conifer pollen types, were wettable, enabling the grains to cross the surface tension barrier of water. Once past this barrier, grain behaviour was governed by presence or absence of sacci. Non‐saccate and vestigially saccate grains sank, whereas saccate grains behaved like air bubbles, floating up to the highest point. In addition, the grains were observed to float in water with sacci uppermost, consistent with the suggestion that distally placed sacci serve to orientate the germinal furrow of the pollen grain towards the nucellus of an inverted ovule. Observations of pollen grains in the pollen chambers of naturally pollinated Prumnopitys ovules confirmed this. The combination of buoyancy and wettability in saccate pollen has implications for the efficiency of the typical podocarp pollination mechanism. PMID:12099344

Whole Grain Intakes in the Diets Of Malaysian Children and Adolescents--Findings from the MyBreakfast Study.

PubMed

Ak, Norimah; Koo, H C; Hamid Jan, J M; Mohd Nasir, M T; Tan, S Y; Appukutty, Mahenderan; Appukutty, Mahendran; Nurliyana, A R; Thielecke, Frank; Hopkins, Sinead; Ong, M K; Ning, C; Tee, E S

2015-01-01

Diets rich in whole grain are associated with several health benefits. Little is known however, about whole grain consumption patterns in Malaysia. The aim of this study was to assess whole grain intakes and dietary source in Malaysian children and adolescents. This analysis is from the MyBreakfast study, a national cross sectional study investigating eating habits among primary and secondary school children throughout Malaysia, conducted in 2013. Children (n = 5,165) and adolescents (n = 2,947) who completed two days of dietary assessment using a food record or recall respectively were included. The whole grain content of foods was estimated mainly through the use of quantitative ingredient declarations on food labels. All wholegrain foods were considered irrespective of the amount of whole grain they contained. Overall, only 25% of children and 19% of adolescents were wholegrain consumers. Mean daily intakes in the total sample were 2.3g/d (SD 5.8 g/d) in children and 1.7 g/d (SD 4.7 g/d) in adolescents and in the consumer's only sample, mean intakes reached 9.1g/d (SD 8.6) and 9.2g/d (SD 7.1g/d) respectively. Wheat was the main grain source of whole grain while ready to eat breakfast cereals and hot cereals were the main food contributors. Less than 3% of the children and adolescents reached the US quantitative whole grain recommendation of 48 g/day. Whole grain is consumed by only a minority of Malaysian children and adolescents and even among consumers, intakes are well below recommendations. Efforts are needed to firstly understand the barriers to whole grain consumption among Malaysian children in order to design effective health promotion initiatives to promote an increase in whole grain consumption.

Zn uptake, translocation and grain Zn loading in rice (Oryza sativa L.) genotypes selected for Zn deficiency tolerance and high grain Zn

PubMed Central

Impa, Somayanda M.; Morete, Mark J.; Ismail, Abdelbagi M.; Schulin, Rainer; Johnson-Beebout, Sarah E.

2013-01-01

Zn deficiency is a widespread problem in rice (Oryza sativa L.) grown under flooded conditions, limiting growth and grain Zn accumulation. Genotypes with Zn deficiency tolerance or high grain Zn have been identified in breeding programmes, but little is known about the physiological mechanisms conferring these traits. A protocol was developed for growing rice to maturity in agar nutrient solution (ANS), with optimum Zn-sufficient growth achieved at 1.5 μM ZnSO4.7H2O. The redox potential in ANS showed a decrease from +350 mV to −200 mV, mimicking the reduced conditions of flooded paddy soils. In subsequent experiments, rice genotypes contrasting for Zn deficiency tolerance and grain Zn were grown in ANS with sufficient and deficient Zn to assess differences in root uptake of Zn, root-to-shoot Zn translocation, and in the predominant sources of Zn accumulation in the grain. Zn efficiency of a genotype was highly influenced by root-to-shoot translocation of Zn and total Zn uptake. Translocation of Zn from root to shoot was more limiting at later growth stages than at the vegetative stage. Under Zn-sufficient conditions, continued root uptake during the grain-filling stage was the predominant source of grain Zn loading in rice, whereas, under Zn-deficient conditions, some genotypes demonstrated remobilization of Zn from shoot and root to grain in addition to root uptake. Understanding the mechanisms of grain Zn loading in rice is crucial in selecting high grain Zn donors for target-specific breeding and also to establish fertilizer and water management strategies for achieving high grain Zn. PMID:23698631

Limitation of Unloading in the Developing Grains Is a Possible Cause Responsible for Low Stem Non-structural Carbohydrate Translocation and Poor Grain Yield Formation in Rice through Verification of Recombinant Inbred Lines

PubMed Central

Li, Guohui; Pan, Junfeng; Cui, Kehui; Yuan, Musong; Hu, Qiuqian; Wang, Wencheng; Mohapatra, Pravat K.; Nie, Lixiao; Huang, Jianliang; Peng, Shaobing

2017-01-01

Remobilisation of non-structural carbohydrates (NSC) from leaves and stems and unloading into developing grains are essential for yield formation of rice. In present study, three recombinant inbred lines of rice, R91, R156 and R201 have been tested for source-flow-sink related attributes determining the nature of NSC accumulation and translocation at two nitrogen levels in the field. Compared to R91 and R156, R201 had lower grain filling percentage, harvest index, and grain yield. Meanwhile, R201 had significantly lower stem NSC translocation during grain filling stage. Grain filling percentage, harvest index, and grain yield showed the consistent trend with stem NSC translocation among the three lines. In comparison with R91 and R156, R201 had similarity in leaf area index, specific leaf weight, stem NSC concentration at heading, biomass, panicles m-2, spikelets per panicle, remobilization capability of assimilation in stems, sink capacity, sink activity, number and cross sectional area of small vascular bundles, greater number and cross sectional area of large vascular bundles, and higher SPAD, suggesting that source, flow, and sink were not the limiting factors for low stem NSC translocation and grain filling percentage of R201. However, R201 had significant higher stem and rachis NSC concentrations at maturity, which implied that unloading in the developing grains might result in low NSC translocation in R201. The results indicate that stem NSC translocation could be beneficial for enhancement of grain yield potential, and poor unloading into caryopsis may be the possible cause of low stem NSC translocation, poor grain filling and yield formation in R201. PMID:28848573

Grain growth kinetics of ringwoodite and majorite garnet mixtures and implications for the rheology of the transition zone

NASA Astrophysics Data System (ADS)

Ezad, I.; Dobson, D. P.; Brodholt, J. P.; Thomson, A.; Hunt, S.

2017-12-01

The grain size of the transition zone is a poorly known but important geophysical parameter. Among others, the grain size may control the rheology, seismic attenuation and radiative thermal conductivity of the mantle. However, the grain size of the transition zone minerals ringwoodite (Mg,Fe)2SiO4 and majorite garnet MgSiO3 under appropriate zone conditions is currently unknown and there are very few experiments with which to constrain it. In order to determine the grain size of the transition zone, the grain growth kinetics must be determined for a range of mantle compositions. We have, therefore, experimentally determined the grain growth kinetics of the lowermost transition zone minerals through multi anvil experiments at University College London (UCL). This is achieved through a comprehensive set of time series experiments at pressures of 21 GPa and temperatures relevant to the transition zone. We have also determined the effect of varying water content, oxygen fugacity, iron content and aluminium content also discussed by Dobson and Mariani., (2014). Our initial grain growth experiments conducted at 1200°C and 1400°C at 18 GPa show extremely slow grain growth kinetics; time series experiments extended to 105.8 seconds are unable to produce grains larger than 100 nm. This suggests that fine-grained material at the base of the transition zone will persist on geological timescales. Such small grains size suggests that diffusion creep might be the dominant deformation mechanism in this region. Reference: Dobson, D.P., Mariani, E., 2014. The kinetics of the reaction of majorite plus ferropericlase to ringwoodite: Implications for mantle upwellings crossing the 660 km discontinuity. Earth Planet. Sci. Lett. 408, 110-118. doi:10.1016/j.epsl.2014.10.009

Grain size distribution and microstructures of experimentally sheared granitoid gouge at coseismic slip rates - Criteria to distinguish seismic and aseismic faults?

NASA Astrophysics Data System (ADS)

Stünitz, Holger; Keulen, Nynke; Hirose, Takehiro; Heilbronner, Renée

2010-01-01

Microstructures and grain size distribution from high velocity friction experiments are compared with those of slow deformation experiments of Keulen et al. (2007, 2008) for the same material (Verzasca granitoid). The mechanical behavior of granitoid gouge in fast velocity friction experiments at slip rates of 0.65 and 1.28 m/s and normal stresses of 0.4-0.9 MPa is characterized by slip weakening in a typical exponential friction coefficient vs displacement relationship. The grain size distributions yield similar D-values (slope of frequency versus grain size curve = 2.2-2.3) as those of slow deformation experiments (D = 2.0-2.3) for grain sizes larger than 1 μm. These values are independent of the total displacement above a shear strain of about γ = 20. The D-values are also independent of the displacement rates in the range of ˜1 μm/s to ˜1.3 m/s and do not vary in the normal stress range between 0.5 MPa and 500 MPa. With increasing displacement, grain shapes evolve towards more rounded and less serrated grains. While the grain size distribution remains constant, the progressive grain shape evolution suggests that grain comminution takes place by attrition at clast boundaries. Attrition produces a range of very small grain sizes by crushing with a D <-value = 1. The results of the study demonstrate that most cataclastic and gouge fault zones may have resulted from seismic deformation but the distinction of seismic and aseismic deformation cannot be made on the basis of grain size distribution.

Genetic evaluation of recombinant inbred lines of rice (Oryza sativa L.) for grain zinc concentrations, yield related traits and identification of associated SSR markers.

PubMed

Bekele, Berhanu D; Naveen, G K; Rakhi, S; Shashidhar, H E

2013-12-01

The objectives of the present study were to evaluate genetic variability parameters, correlations that exist for grain Zn concentration and yield related traits and identification of SSR markers linked to these traits in rice. One hundred seventy six Recombinant Inbred Lines (RILs) of Azucena X Moromutant were grown at University of Agricultural Sciences, Bangalore in augmented experimental design during wet seasons of 2010 and 2011. The study revealed significant genetic variability for all the traits. Grain yield per plant and grain zinc concentration showed higher phenotypic and genotypic co-efficient of variation. Significant positive correlation was observed for grain yield per plant with number of productive tillers per plant (r = 0.5) and number of tillers per plant (r = 0.4). Grain zinc concentration showed negative correlation with grain yield per plant (r = - 0.27). The path-coefficient analysis indicated the positive direct effect of number of productive tillers per plant on grain yield per plant (0.514). Grain zinc concentration showed negative direct effect on grain yield per plant (-0.186). Single-marker analysis using 26 SSR markers on RILs mapping population showed that RM212, RM263, RM6832, RM152, RM21, RM234 and RM3331 had association with grain zinc concentration and other yield related traits. But validation of these markers on fifty two rice genotypes showed that only three markers RM263, RM152 and RM21 had association with grain zinc concentration. Therefore, the genetic information generated and molecular markers identified from this study could be used for zinc biofortification programmes in rice.

Spread of the dust temperature distribution in circumstellar disks

NASA Astrophysics Data System (ADS)

Heese, S.; Wolf, S.; Dutrey, A.; Guilloteau, S.

2017-07-01

Context. Accurate temperature calculations for circumstellar disks are particularly important for their chemical evolution. Their temperature distribution is determined by the optical properties of the dust grains, which, among other parameters, depend on their radius. However, in most disk studies, only average optical properties and thus an average temperature is assumed to account for an ensemble of grains with different radii. Aims: We investigate the impact of subdividing the grain radius distribution into multiple sub-intervals on the resulting dust temperature distribution and spectral energy distribution (SED). Methods: The temperature distribution, the relative grain surface below a certain temperature, the freeze-out radius, and the SED were computed for two different scenarios: (1) Radius distribution represented by 16 logarithmically distributed radius intervals, and (2) radius distribution represented by a single grain species with averaged optical properties (reference). Results: Within the considered parameter range, I.e., of grain radii between 5 nm and 1 mm and an optically thin and thick disk with a parameterized density distribution, we obtain the following results: in optically thin disk regions, the temperature spread can be as large as 63% and the relative grain surface below a certain temperature is lower than in the reference disk. With increasing optical depth, the difference in the midplane temperature and the relative grain surface below a certain temperature decreases. Furthermore, below 20 K, this fraction is higher for the reference disk than for the case of multiple grain radii, while it shows the opposite behavior for temperatures above this threshold. The thermal emission in the case of multiple grain radii at short wavelengths is stronger than for the reference disk. The freeze-out radius (snowline) is a function of grain radius, spanning a radial range between the coldest and warmest grain species of 30 AU.

Solar Ion Processing of Itokawa Grains: Constraints on Surface Exposure Times

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Keller, L. P.

2015-01-01

Analytical TEM observations obtained to date reveal that a significant sub-population of grains returned from the surface of asteroid Itokawa have had their outer 30-100 nm processed by space weathering effects. Although the effects include some surface deposition of condensed impact vapor and isolated impact melt splashes, much of the width of the space weathered outer margins or "rims" on grains is derived from solar wind processing of the original host grain. Similar to what has long been reported for some lunar grains, the ion-processed rims on Itokawa grains exhibit varing degrees and depths of penetration of atomic-displacement ion damage, resulting in complete amorphization for some rims (particularly in plagioclase), or formation of highly defective but still crystalline structures in others (particularly in pyroxene and olivine). Possibly different from lunar grains, however, is the presence of isolated internal cavities or voids in Itokawa grain rims, which may be implantation "bubbles" due to accumulating implanted solar wind H and/or He. For a given mineral exposed at a particular set of long term solar wind conditions, the level of ion damage in a given grain rim, the depth of damage penetration represented by the rim width, and the formation or lack of formation of implantation bubbles can all be linked to the time spent by the grain in an uncovered state on the topmost, space-exposed, regolith surface. For the lunar case, we have previously shown that with reasonable assumptions about solar wind characteristics over time, a model can be developed to estimate this exposure time based on the width of amorphous rims on lunar grains. Here we report on an expansion of the model to cover exposure time information contained in the array of solar ion-induced features in Itokawa grains.

Genetic dissection of sorghum grain quality traits using diverse and segregating populations.

PubMed

Boyles, Richard E; Pfeiffer, Brian K; Cooper, Elizabeth A; Rauh, Bradley L; Zielinski, Kelsey J; Myers, Matthew T; Brenton, Zachary; Rooney, William L; Kresovich, Stephen

2017-04-01

Coordinated association and linkage mapping identified 25 grain quality QTLs in multiple environments, and fine mapping of the Wx locus supports the use of high-density genetic markers in linkage mapping. There is a wide range of end-use products made from cereal grains, and these products often demand different grain characteristics. Fortunately, cereal crop species including sorghum [Sorghum bicolor (L.) Moench] contain high phenotypic variation for traits influencing grain quality. Identifying genetic variants underlying this phenotypic variation allows plant breeders to develop genotypes with grain attributes optimized for their intended usage. Multiple sorghum mapping populations were rigorously phenotyped across two environments (SC Coastal Plain and Central TX) in 2 years for five major grain quality traits: amylose, starch, crude protein, crude fat, and gross energy. Coordinated association and linkage mapping revealed several robust QTLs that make prime targets to improve grain quality for food, feed, and fuel products. Although the amylose QTL interval spanned many megabases, the marker with greatest significance was located just 12 kb from waxy (Wx), the primary gene regulating amylose production in cereal grains. This suggests higher resolution mapping in recombinant inbred line (RIL) populations can be obtained when genotyped at a high marker density. The major QTL for crude fat content, identified in both a RIL population and grain sorghum diversity panel, encompassed the DGAT1 locus, a critical gene involved in maize lipid biosynthesis. Another QTL on chromosome 1 was consistently mapped in both RIL populations for multiple grain quality traits including starch, crude protein, and gross energy. Collectively, these genetic regions offer excellent opportunities to manipulate grain composition and set up future studies for gene validation.

Source tracking of prokaryotic communities in fermented grain of Chinese strong-flavor liquor.

PubMed

Wang, Xueshan; Du, Hai; Xu, Yan

2017-03-06

The fermentation process of Chinese strong-flavor liquor involves numerous microbes originating from Daqu and pit mud. Daqu is the starter of fermentation, and pit mud acts as another source of inoculum of microbes in the liquor-making process. However, the contribution of microbes in pit mud and Daqu to fermented grain, and the sources of microbes in fermented grain are still waiting to be defined clearly. In this study, prokaryotic communities in fermented grain, pit mud and Daqu were identified via next generation sequencing of the V4 region of 16S rRNA gene. Principal-coordinate analysis indicated that Daqu had stronger influence on the prokaryotic communities in fermented grain at the prophase of fermentation, but pit mud influenced the fermented grain continuously during the whole fermentation process. Totally, 299 genera were detected in all fermented grain, pit mud and Daqu samples. Among them, 204 genera were detected in 3days' fermented grain. Ten genera (Lactobacillus, Leuconostoc, Staphylococcus, Gluconobacter, Acetobacter, Petrimonas, Clostridium, Ruminococcus, Methanobacterium and Methanobrevibacter) were dominant, and accounted for 84.31%-87.13% relative abundance of the total prokaryotic community in fermented grain. Venn analysis indicated Daqu was the main source of strict aerobes and facultative aerobes, which took up over 74% of prokaryotic communities in fermented grain. Conversely, pit mud was the sustained-release source of anaerobes, which accounted for over 14% of prokaryotic communities in fermented grain. In addition, part of anaerobes originated from both Daqu and pit mud. This study could help track the source of prokaryotic communities in fermented grain, and improve the quality and controllability in liquor production. Copyright © 2017 Elsevier B.V. All rights reserved.

Euhedral metallic-Fe-Ni grains in extraterrestrial samples

NASA Technical Reports Server (NTRS)

Rubin, Alan E.

1993-01-01

Metallic Fe-Ni is rare in terrestrial rocks, being largely restricted to serpentinized peridotites and volcanic rocks that assimilated carbonaceous material. In contrast, metallic Fe-Ni is nearly ubiquitous among extraterrestrial samples (i.e., meteorites, lunar rocks, and interplanetary dust particles). Anhedral grains are common. For example, in eucrites and lunar basalts, most of the metallic Fe-Ni occurs interstitially between silicate grains and thus tends to have irregular morphologies. In many porphyritic chondrules, metallic Fe-Ni and troilite form rounded blebs in the mesostasis because their precursors were immiscible droplets. In metamorphosed ordinary chondrites, metallic Fe-Ni and troilite form coarse anhedral grains. Some of the metallic Fe-Ni and troilite grains has also been mobilized and injected into fractures in adjacent silicate grains where local shock-reheating temperatures reached the Fe-FeS eutectic (988 C). In interplanetary dust particles metallic Fe-Ni most commonly occurs along with sulfide as spheroids and fragments. Euhedral metallic Fe-Ni grains are extremely rare. Several conditions must be met before such grains can form: (1) grain growth must occur at free surfaces, restricting euhedral metallic Fe-Ni grains to systems that are igneous or undergoing vapor-deposition; (2) the metal (+/-) sulfide assemblage must have an appropriate bulk composition so that taenite is the liquidus phase in igneous systems or the stable condensate phase in vapor-deposition systems; and (3) metallic Fe-Ni grains must remain underformed during subsequent compaction, thermal metamorphism, and shock. Because of these restrictions, the occurrence of euhedral metallic Fe-Ni grains in an object can potentially provide important petrogenetic information. Despite its rarity, euhedral metallic Fe-Ni occurs in a wide variety of extraterrestrial materials. Some of these materials formed in the solar nebula; others formed on parent body surfaces by meteoroid impacts.

Effect of Aluminum on the Microstructure and Properties of Two Refractory High-Entropy Alloys (Postprint)

DTIC Science & Technology

2014-04-01

The chemical compositions of the recrystallized ic release; distribution unlimited. Fig. 5. (a) Equiaxed grain structure of the annealed...deformation bands crossing a grain boundary; (c) fine recrystallized grains formed at grain boundaries; (d) a higher magnification image shows the...presence of nano-precipitates at the boundaries of the recrystallized grains. 220 O.N. Senkov et al. / Acta Materialia 68 (2014) 214–228and non

Work Plan: Phase II Investigation at the Former CCC/USDA Grain Storage Facility in Montgomery City, Missouri

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaFreniere, Lorraine M

From September 1949 until September 1966, the Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) leased property at the southeastern end of Montgomery City, Missouri, for the operation of a grain storage facility. During this time, commercial grain fumigants containing carbon tetrachloride were commonly used by the CCC/USDA and the private grain storage industry to preserve grain in their facilities.

Combined Near and Far Field High Energy Diffraction Microscopy Dataset for Ti-7Al Tensile Specimen Elastically Loaded In Situ

DOE Data Explorer

Turner, Todd J.; Shade, Paul A; Bernier, Joel V.; Li, Shiu Fai; Schuren, Jay C.; Lind, Jonathan F.; Lienert, Ulrich; Kenesei, Peter; Suter, Robert; Blank, Basil; Almer, Jonathan

2016-01-01

We present both near-field HEDM data that maps out the grain morphology and intragranular crystallographic orientations and far-field HEDM data that provides the grain centroid, grain average crystallographic orientation, and grain average elastic strain tensor for each grain. Finally, we provide a finite element mesh that can be utilized to simulate deformation in the volume of this Ti-7Al specimen.

Computer Modeling of Electrostatic Aggregation of Granular Materials in Planetary and Astrophysical Settings

NASA Technical Reports Server (NTRS)

Marshall, J.; Sauke, T.

1999-01-01

Electrostatic forces strongly influence the behavior of granular materials in both dispersed (cloud) systems and semi-packed systems. These forces can cause aggregation or dispersion of particles and are important in a variety of astrophysical and planetary settings. There are also many industrial and commercial settings where granular matter and electrostatics become partners for both good and bad. This partnership is important for human exploration on Mars where dust adheres to suits, machines, and habitats. Long-range Coulombic (electrostatic) forces, as opposed to contact-induced dipoles and van der Waals attractions, are generally regarded as resulting from net charge. We have proposed that in addition to net charge interactions, randomly distributed charge carriers on grains will result in a dipole moment regardless of any net charge. If grains are unconfined, or fluidized, they will rotate so that the dipole always induces attraction between grains. Aggregates are readily formed, and Coulombic polarity resulting from the dipole produces end-to-end stacking of grains to form filamentary aggregates. This has been demonstrated in USML experiments on Space Shuttle where microgravity facilitated the unmasking of static forces. It has also been demonstrated in a computer model using grains with charge carriers of both sign. Model results very closely resembled micro-g results with actual sand grains. Further computer modeling of the aggregation process has been conducted to improve our understanding of the aggregation process, and to provide a predictive tool for microgravity experiments slated for Space Station. These experiments will attempt to prove the dipole concept as outlined above. We have considerably enhanced the original computer model: refinements to the algorithm have improved the fidelity of grain behavior during grain contact, special attention has been paid to simulation time steps to enable establishment of a meaningful, quantitative time axis, and calibration of rounding accuracies have been conducted to test cumulative numerical influences in the model. The model has been run for larger grain populations, variable initial cloud densities, and we have introduced random net charging to individual grains, as well as a net charge to the cloud as a whole. The model uses 3 positive and 3 negative charges randomly distributed on each grain, with up to 160 grains contained within various size "boxes" that define the initial number densities in the clouds. Each charge represents localized charged region on a grain, but does not necessarily imply single quantized charge carriers. The Coulomb equations are then allowed to interact for each monopole: dipoles and any higher order charge coupling is a natural product of these "free" interactions over which the modeler exerts no influence. The charges are placed on surfaces of grains at random locations. A series of runs was conducted for neutral grains that had a perfect balance of negative and positive char carriers. Runs were also conducted with grains having additional fractional charges ranging between 0 and 1. By adding fractional charges of one sign, the model created grain populations in which all grains had excess charges the same sign, giving the cloud an overall net charge. This simulates clouds subjected to ionizing radiation (e. protoplanetary debris disk around a protosun), or any other process of charge biasing in a grain population (e.g., volcanic plumes). In another run series, random fractional charges of either sign were added to the grains so th some grains had a slight net positive charge while others had a slight net negative charge. This simulates triboelectrically-charged grain populations in which acquisition of an electron by one surface is at the expense creating a hole elsewhere. This dual sign charging was applied in two ways: in one case the cloud remained neutral by ensuring that all grain excess charges added to zero; in the other case, the cloud was permitted slight net char by not imposing a charge-balance condition. Additional information is contained in the original.

Reactive oxygen species induced by heat stress during grain filling of rice (Oryza sativa L.) are involved in occurrence of grain chalkiness.

PubMed

Suriyasak, Chetphilin; Harano, Keisuke; Tanamachi, Koichiro; Matsuo, Kazuhiro; Tamada, Aina; Iwaya-Inoue, Mari; Ishibashi, Yushi

2017-09-01

Heat stress during grain filling increases rice grain chalkiness due to increased activity of α-amylase, which hydrolyzes starch. In rice and barley seeds, reactive oxygen species (ROS) produced after imbibition induce α-amylase activity via regulation of gibberellin (GA) and abscisic acid (ABA) levels during seed germination. Here, we examined whether ROS is involved in induction of grain chalkiness by α-amylase in developing rice grains under heat stress. To elucidate the role of ROS in grain chalkiness, we grew post-anthesis rice plants (Oryza sativa L. cv. Koshihikari) under control (25°C) or heat stress (30°C) conditions with or without antioxidant (dithiothreitol) treatment. The developing grains were analyzed for expression of NADPH oxidases, GA biosynthesis genes (OsGA3ox1, OsGA20ox1), ABA catabolism genes (OsABA8'OH1, OsABA8'OH2) and an α-amylase gene (OsAmy3E), endogenous H 2 O 2 content and the grain quality. In grains exposed to heat stress, the expression of NADPH oxidase genes (especially, OsRbohB, OsRbohD, OsRbohF and OsRbohI) and the ROS content increased. Heat stress also increased the expression of OsGA3ox1, OsGA20ox1, OsABA8'OH1, OsABA8'OH2 and OsAmy3E. On the other hand, dithiothreitol treatment reduced the effects of heat stress on the expression of these genes and significantly reduced grain chalkiness induced by heat stress. These results suggest that, similar to cereal seed germination mechanism, ROS produced under heat stress is involved in α-amylase induction in maturating rice grains through GA/ABA metabolism, and consequently caused grain chalkiness. Copyright © 2017 Elsevier GmbH. All rights reserved.

Grain Flow at High Stresses

NASA Astrophysics Data System (ADS)

McSaveney, M. J.

2015-12-01

The transport mechanism of rapid long-runout rock avalanches was a hotly debated topic when I came on the scene in 1967. So how come it is still debated today? My explanation is that it is the expected outcome of peer review, poor comprehension, and technological advances outpacing intellectual advances. Why think about the problem when we can model it! So let us think about the problem. Shreve thought that rock avalanches fell upon and trapped a layer of air. What physics was he thinking about? It is how feathers and tissue papers fall. When my rock avalanches fly, they fly like unlubricated bricks using the physics of projectiles and ballistics. But the main transport mechanism is not flight. The dominant impression from watching a rock avalanche in motion is of fluid flow, as Heim described it in 1882. A rock avalanche is a very large grain flow. Bagnold studied dispersive grain flows, but why should one assume that rock avalanches are dispersive grain flows as many do. The more common grain flow type is a dense grain flow and rock avalanches are dense grain flows in which the weight can and does generate very high stresses at grain contacts. Brittle rock deforms elastically up to its compressive strength, whereupon it breaks, releasing elastic strain as transient elastic strain (seismic energy to a seismologist, acoustic energy to a physicist). Melosh and others have shown that acoustic energy can fluidize a grain mass. There is no exotic physics behind grain flow at high stress. When grains break, the released elastic strain has to go somewhere, and it goes somewhere principally by transmission though grain contacts. Depending on the state of stress at the grain contact, the contact will pass the stress or will slip at conventional values of Coulomb friction. Enough thinking! A physical model of the entire process is too big for any laboratory. So whose numerical model will do it?

Isotopic Composition of Molybdenum and Barium in Single Presolar Silicon Carbide Grains of Type A+B

NASA Technical Reports Server (NTRS)

Savina, M. R.; Tripa, C. E.; Pellin, M. J.; Davis, A. M.; Clayton, R. N.; Lewis, R. S.; Amari, S.

2003-01-01

Presolar SiC grains fall into several groups based on C, N, and Si isotopic compositions. Approximately 93% are defined as mainstream, having 10 less than C-12/C-13 less than 100 and N-14/N-15 ranging from 50 to 20,000. A number of studies have shown that the most likely sources of mainstream grains are low mass asymptotic giant branch stars. Models of nucleosynthesis in AGB stars reproduce the s-process enhancements seen in the heavy elements in mainstream SiC grains. Among the less common grains, A+B grains, which comprise approximately 3-4% of presolar SiC, are perhaps the least well understood. Recent studies by Amari et al. show that A+B grains can be divided into at least 4 groups based on their trace element concentration patterns. Of 20 grains studied, 7 showed trace element patterns consistent with condensation from a gas of solar system composition, while the rest had varying degrees of process enhancements. Our previous measurements on 3 A+B grains showed Mo of solar isotopic composition, but Zr with a strong enhancement in 96Zr, which is an r-process isotope but can be made in an sprocess if the neutron density is high enough to bridge the unstable Zr-95 (T(sub 1/2)= 64 d). The observation of Mo with solar system isotopic composition in the same grains is puzzling however. Meyer et al. have recently shown that a neutron burst mechanism can produce a high Zr-96/Zr-94 without enhancing Mo-100, however this model leads to enhancements in Mo-95 and Mo-97 not observed in A+B grains. We report here results of Mo measurements on 7 additional A+B grains, and Ba measurements on 2 A+B grains, and compare these to the previous studies.

A generalized self-consistent polycrystal model for the yield strength of nanocrystalline materials

NASA Astrophysics Data System (ADS)

Jiang, B.; Weng, G. J.

2004-05-01

Inspired by recent molecular dynamic simulations of nanocrystalline solids, a generalized self-consistent polycrystal model is proposed to study the transition of yield strength of polycrystalline metals as the grain size decreases from the traditional coarse grain to the nanometer scale. These atomic simulations revealed that a significant portion of atoms resides in the grain boundaries and the plastic flow of the grain-boundary region is responsible for the unique characteristics displayed by such materials. The proposed model takes each oriented grain and its immediate grain boundary to form a pair, which in turn is embedded in the infinite effective medium with a property representing the orientational average of all these pairs. We make use of the linear comparison composite to determine the nonlinear behavior of the nanocrystalline polycrystal through the concept of secant moduli. To this end an auxiliary problem of Christensen and Lo (J. Mech. Phys. Solids 27 (1979) 315) superimposed on the eigenstrain field of Luo and Weng (Mech. Mater. 6 (1987) 347) is first considered, and then the nonlinear elastoplastic polycrystal problem is addressed. The plastic flow of each grain is calculated from its crystallographic slips, but the plastic behavior of the grain-boundary phase is modeled as that of an amorphous material. The calculated yield stress for Cu is found to follow the classic Hall-Petch relation initially, but as the gain size decreases it begins to depart from it. The yield strength eventually attains a maximum at a critical grain size and then the Hall-Petch slope turns negative in the nano-range. It is also found that, when the Hall-Petch relation is observed, the plastic behavior of the polycrystal is governed by crystallographic slips in the grains, but when the slope is negative it is governed by the grain boundaries. During the transition both grains and grain boundaries contribute competitively.

Anomalous permittivity in fine-grain barium titanate

NASA Astrophysics Data System (ADS)

Ostrander, Steven Paul

Fine-grain barium titanate capacitors exhibit anomalously large permittivity. It is often observed that these materials will double or quadruple the room temperature permittivity of a coarse-grain counterpart. However, aside from a general consensus on this permittivity enhancement, the properties of the fine-grain material are poorly understood. This thesis examines the effect of grain size on dielectric properties of a self-consistent set of high density undoped barium titanate capacitors. This set included samples with grain sizes ranging from submicron to ˜20 microns, and with densities generally above 95% of the theoretical. A single batch of well characterized powder was milled, dry-pressed then isostatically-pressed. Compacts were fast-fired, but sintering temperature alone was used to control the grain size. With this approach, the extrinsic influences are minimized within the set of samples, but more importantly, they are normalized between samples. That is, with a single batch of powder and with identical green processing, uniform impurity concentration is expected. The fine-grain capacitors exhibited a room temperature permittivity of ˜5500 and dielectric losses of ˜2%. The Curie-temperature decreased by {˜}5sp°C from that of the coarse-grain material, and the two ferroelectric-ferroelectric phase transition temperatures increased by {˜}10sp°C. The grain size induced permittivity enhancement was only active in the tetragonal and orthorhombic phases. Strong dielectric anomalies were observed in samples with grain size as small as {˜}0.4\\ mum. It is suggested that the strong first-order character observed in the present data is related to control of microstructure and stoichiometry. Grain size effects on conductivity losses, ferroelectric losses, ferroelectric dispersion, Maxwell-Wagner dispersion, and dielectric aging of permittivity and loss were observed. For the fine-grain material, these observations suggest the suppression of domain wall motion below the Curie transition, and the suppression of conductivity above the Curie transition.

In-situ EBSD study of deformation behavior of retained austenite in a low-carbon quenching and partitioning steel via uniaxial tensile tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wan-song

Through using in-situ electron back-scattered diffraction and uniaxial tensile tests, this work mainly focuses on the deformation behavior of retained austenite (RA) in a low-carbon quenching and partitioning (Q&P) steel. In this paper, three different types of RA can be distinguished from different locations, respectively, RA grains at the triple edges, twinned austenite and RA grains positioned between martensite. The results have shown that grains at the triple edges and twinned austenite could transform easily with increasing strain, i.e. are less stable when compared with RA grains distributed between martensite that could resist a larger plastic deformation. Meanwhile, the strainmore » leads to rotations of RA grains distributed at the triple edges and between martensite. Moreover, RA grains with a similar orientation undergone similar rotations with the same true strain. These RA grains rotated along a specific slip plane and slip direction and the grain rotation is taken as a significant factor to improve the ductility of steel. In addition, grain sizes of RA decreased gradually with an increase of true strain and smaller (0–0.2 μm) grains were more capable of resisting the deformation. According to kernel average misorientation (KAM) analysis, it can be found that strain distribution is preferentially localized near martensite–austenite phase boundaries and in the interior of martensite. The average KAM values increased continuously with increasing true strain. - Highlights: •The in-situ and ex-situ tensile specimens differ to some extent in mechanical properties. •Retained austenite grains at the triple edges and twinned austenite transformed easily at the early stage of true strain. •Film-like retained austenite grains only rotated prior to the transformation during straining. •Retained austenite grains having with a similar orientation experienced similar rotations during the same true strain.« less

Evaluation of ground grain versus pre- and post-pellet whole grain additions to poultry diets via a response surface design.

PubMed

Moss, Amy F; Chrystal, Peter V; Truong, Ha H; Selle, Peter H; Liu, Sonia Yun

2017-12-01

1. The objective of this study was to compare the effects of pre- and post-pellet whole grain wheat additions to diets on growth performance, gizzard and pancreas development, nutrient utilisation and starch and protein (N) digestibility coefficients in broiler chickens via an equilateral triangle response surface design. 2. The three apical treatments of the equilateral triangle comprised (1A) a standard diet containing 600 g/kg ground wheat, (2B) the same diet containing 600 g/kg pre-pellet whole wheat and (3C) the same diet containing 300 g/kg ground wheat and 300 g/kg post-pellet whole wheat. Seven blends of the three apical diets were located within the triangle to complete the design and a total of 360 male Ross 308 chicks were offered the ten experimental diets from 7 to 28 d post-hatch. Model prediction and response surface plots were generated with R 3.0.3 software. 3. The most efficient FCR of 1.466 was observed in birds offered an almost equal mixture of the pre- and post-pellet whole grain apical dietary treatments, which corresponded to 172 g/kg ground grain, 256 g/kg pre-pellet whole grain, 172 g/kg post-pellet whole grain in a diet containing 600 g/kg wheat. 4. The most efficient energy utilisation (ME:GE ratio of 0.766) was observed in birds offered a blend of the ground grain and pre-pellet whole grain apical dietary treatments which corresponded to a mixture of 384 g/kg pre-pellet whole grain and 216 g/kg ground grain. 5. Pre-pellet whole grain feeding generated the most pronounced responses in increased relative gizzard contents, reduced gizzard pH and increased relative pancreas weights. Consideration is given to the likely differences between pre- and post-pellet whole grain feeding.

Kuiper Belt Dust Grains as a Source of Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Zook, Herbert A.; Dermott, Stanley F.

1996-01-01

The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce dust grains that may contribute significantly to the interplanetary dust population. In this paper, the orbital evolution of dust grains, of diameters 1 to 9 microns, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged dust grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small dust grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads dust grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter dust grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type dust particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary dust particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar dust grains are considered, however, Kuiper belt dust grains around 9 microns appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 microns. Therefore, Kuiper belt dust grains within this range may not be a significant part of the interplanetary dust complex in the inner Solar System.