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.

Mechanical and thermal properties of high density polyethylene – dried distillers grains with solubles composites

USDA-ARS?s Scientific Manuscript database

Dried Distillers Grain with Solubles (DDGS) is evaluated as a bio-based fiber reinforcement. Injection molded composites of high density polyethylene (HDPE), 25% by weight of DDGS, and either 5% of 0% by weight of maleated polyethylene (MAPE) were produced by twin screw compounding and injection mo...

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.

A Direct Grain-Boundary-Activity Correlation for CO Electroreduction on Cu Nanoparticles

PubMed Central

2016-01-01

Copper catalyzes the electrochemical reduction of CO to valuable C2+ products including ethanol, acetate, propanol, and ethylene. These reactions could be very useful for converting renewable energy into fuels and chemicals, but conventional Cu electrodes are energetically inefficient and have poor selectivity for CO vs H2O reduction. Efforts to design improved catalysts have been impeded by the lack of experimentally validated, quantitative structure–activity relationships. Here we show that CO reduction activity is directly correlated to the density of grain boundaries (GBs) in Cu nanoparticles (NPs). We prepared electrodes of Cu NPs on carbon nanotubes (Cu/CNT) with different average GB densities quantified by transmission electron microscopy. At potentials ranging from −0.3 V to −0.5 V vs the reversible hydrogen electrode, the specific activity for CO reduction to ethanol and acetate was linearly proportional to the fraction of NP surfaces comprised of GB surface terminations. Our results provide a design principle for CO reduction to ethanol and acetate on Cu. GB-rich Cu/CNT electrodes are the first NP catalysts with significant CO reduction activity at moderate overpotential, reaching a mass activity of up to ∼1.5 A per gram of Cu and a Faradaic efficiency >70% at −0.3 V. PMID:27163043

A Direct Grain-Boundary-Activity Correlation for CO Electroreduction on Cu Nanoparticles.

PubMed

Feng, Xiaofeng; Jiang, Kaili; Fan, Shoushan; Kanan, Matthew W

2016-03-23

Copper catalyzes the electrochemical reduction of CO to valuable C2+ products including ethanol, acetate, propanol, and ethylene. These reactions could be very useful for converting renewable energy into fuels and chemicals, but conventional Cu electrodes are energetically inefficient and have poor selectivity for CO vs H2O reduction. Efforts to design improved catalysts have been impeded by the lack of experimentally validated, quantitative structure-activity relationships. Here we show that CO reduction activity is directly correlated to the density of grain boundaries (GBs) in Cu nanoparticles (NPs). We prepared electrodes of Cu NPs on carbon nanotubes (Cu/CNT) with different average GB densities quantified by transmission electron microscopy. At potentials ranging from -0.3 V to -0.5 V vs the reversible hydrogen electrode, the specific activity for CO reduction to ethanol and acetate was linearly proportional to the fraction of NP surfaces comprised of GB surface terminations. Our results provide a design principle for CO reduction to ethanol and acetate on Cu. GB-rich Cu/CNT electrodes are the first NP catalysts with significant CO reduction activity at moderate overpotential, reaching a mass activity of up to ∼1.5 A per gram of Cu and a Faradaic efficiency >70% at -0.3 V.

Keypoint Density-Based Region Proposal for Fine-Grained Object Detection and Classification Using Regions with Convolutional Neural Network Features

DTIC Science & Technology

2015-12-15

Keypoint Density-based Region Proposal for Fine-Grained Object Detection and Classification using Regions with Convolutional Neural Network ... Convolutional Neural Networks (CNNs) enable them to outperform conventional techniques on standard object detection and classification tasks, their...detection accuracy and speed on the fine-grained Caltech UCSD bird dataset (Wah et al., 2011). Recently, Convolutional Neural Networks (CNNs), a deep

Light scattering by low-density agglomerates of micron-sized grains with the PROGRA2 experiment

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Renard, J.-B.; Lasue, J.; Levasseur-Regourd, A. C.; Blum, J.; Schraepler, R.

2007-07-01

This work was carried out with the PROGRA2 experiment, specifically developed to measure the angular dependence of the polarization of light scattered by dust particles. The samples are small agglomerates of micron-sized grains and huge, low number density agglomerates of the same grains. The constituent grains (spherical or irregularly shaped) are made of different non-absorbing and absorbing materials. The small agglomerates, in a size range of a few microns, are lifted by an air draught. The huge centimeter-sized agglomerates, produced by random ballistic deposition of the grains, are deposited on a flat surface. The phase curves obtained for monodisperse, micron-sized spheres in agglomerates are obviously not comparable to the ‘smooth’ phase curves obtained by remote observations of cometary dust or asteroidal regoliths but they are used for comparison with numerical calculations to a better understanding of the light scattering processes. The phase curves obtained for irregular grains in agglomerates are similar to those obtained by remote observations, with a negative branch at phase angles smaller than 20° and a maximum polarization decreasing with increasing albedo. These results, coupled with remote observations in the solar system, should provide a better understanding of the physical properties of solid particles and their variation in cometary comae and asteroidal regoliths.

Potent antioxidant and radical-scavenging activities of traditional Japanese cereal grains.

PubMed

Higashi-Okai, Kiyoka; Ishida, Emi; Nakamura, Yumiko; Fujiwara, Satomi; Okai, Yasuji

2008-12-01

To estimate the preventive potential of Japanese traditional cereals against oxygen radical-related chronic diseases such as cardiovascular diseases and diabetes, antioxidant and radical-scavenging activities in the extracts of five Japanese traditional cereal grains were analyzed by using an assay system of lipid peroxidation and a radical compound, 1,1-diphenyl-2-picrylhydrazyl (DPPH). DPPH radical-scavenging activities in the extracts of Japanese cereal grains were divided into two groups. One group including Japanese sorghum, black rice and red rice showed strong radical-scavenging activities, but the other group including Japanese barnyard millet and foxtail millet did not exhibit significant radical-scavenging activities. The DPPH radical-scavenging activities of these extracts were closely correlated to the contents of phenolic compound in the extracts, but not to the sugar or protein content in the extracts. In contrast, all the methanol and water extracts of the cereal grains caused significant antioxidant activities against hydroperoxide generation in the peroxidation of linoleic acid, in which the water extracts of these cereal grains caused much higher antioxidant activities than the methanol extracts of the same cereals. These results suggest that Japanese traditional cereals contain qualitatively different principles associated with antioxidant and radical-scavenging activities, and possible principles responsible for the antioxidant and radical-scavenging activities in the cereal grains are discussed.

Aspergillus ficuum phytase activity is inhibited by cereal grain components.

PubMed

Bekalu, Zelalem Eshetu; Madsen, Claus Krogh; Dionisio, Giuseppe; Brinch-Pedersen, Henrik

2017-01-01

In the current study, we report for the first time that grain components of barley, rice, wheat and maize can inhibit the activity of Aspergillus ficuum phytase. The phytase inhibition is dose dependent and varies significantly between cereal species, between cultivars of barley and cultivars of wheat and between Fusarium graminearum infected and non-infected wheat grains. The highest endpoint level of phytase activity inhibition was 90%, observed with grain protein extracts (GPE) from F. graminearum infected wheat. Wheat GPE from grains infected with F. graminearum inhibits phytase activity significantly more than GPE from non-infected grains. For four barley cultivars studied, the IC50 value ranged from 0.978 ± 0.271 to 3.616 ± 0.087 mg×ml-1. For two non-infected wheat cultivars investigated, the IC50 values were varying from 2.478 ± 0.114 to 3.038 ± 0.097 mg×ml-1. The maize and rice cultivars tested gaveIC50 values on 0.983 ± 0.205 and 1.972 ± 0.019 mg×ml-1, respectively. After purifying the inhibitor from barley grains via Superdex G200, an approximately 30-35 kDa protein was identified. No clear trend for the mechanism of inhibition could be identified via Michaelis-Menten kinetics and Lineweaver-Burk plots. However, testing of the purified phytase inhibitor together with the A. ficuum phytase and the specific protease inhibitors pepstatin A, E64, EDTA and PMSF revealed that pepstatin A repealed the phytase inhibition. This indicates that the observed inhibition of A. ficuum phytase by cereal grain extracts is caused by protease activity of the aspartic proteinase type.

Aspergillus ficuum phytase activity is inhibited by cereal grain components

PubMed Central

Bekalu, Zelalem Eshetu; Madsen, Claus Krogh; Dionisio, Giuseppe

2017-01-01

In the current study, we report for the first time that grain components of barley, rice, wheat and maize can inhibit the activity of Aspergillus ficuum phytase. The phytase inhibition is dose dependent and varies significantly between cereal species, between cultivars of barley and cultivars of wheat and between Fusarium graminearum infected and non-infected wheat grains. The highest endpoint level of phytase activity inhibition was 90%, observed with grain protein extracts (GPE) from F. graminearum infected wheat. Wheat GPE from grains infected with F. graminearum inhibits phytase activity significantly more than GPE from non-infected grains. For four barley cultivars studied, the IC50 value ranged from 0.978 ± 0.271 to 3.616 ± 0.087 mg×ml-1. For two non-infected wheat cultivars investigated, the IC50 values were varying from 2.478 ± 0.114 to 3.038 ± 0.097 mg×ml-1. The maize and rice cultivars tested gaveIC50 values on 0.983 ± 0.205 and 1.972 ± 0.019 mg×ml-1, respectively. After purifying the inhibitor from barley grains via Superdex G200, an approximately 30–35 kDa protein was identified. No clear trend for the mechanism of inhibition could be identified via Michaelis-Menten kinetics and Lineweaver-Burk plots. However, testing of the purified phytase inhibitor together with the A. ficuum phytase and the specific protease inhibitors pepstatin A, E64, EDTA and PMSF revealed that pepstatin A repealed the phytase inhibition. This indicates that the observed inhibition of A. ficuum phytase by cereal grain extracts is caused by protease activity of the aspartic proteinase type. PMID:28472144

Comparative study of He bubble formation in nanostructured reduced activation steel and its coarsen-grained counterpart

NASA Astrophysics Data System (ADS)

Liu, W. B.; Zhang, J. H.; Ji, Y. Z.; Xia, L. D.; Liu, H. P.; Yun, D.; He, C. H.; Zhang, C.; Yang, Z. G.

2018-03-01

High temperature (550 °C) He ions irradiation was performed on nanostructured (NS) and coarsen-grained (CG) reduced activation steel to investigate the effects of GBs/interfaces on the formation of bubbles during irradiation. Experimental results showed that He bubbles were preferentially trapped at dislocations and/or grain boundaries (GBs) for both of the samples. Void denuded zones (VDZs) were observed in the CG samples, while VDZs near GBs were unobvious in NS sample. However, both the average bubble size and the bubble density in peak damage region of the CG sample were significantly larger than that observed in the NS sample, which indicated that GBs play an important role during the irradiation, and the NS steel had better irradiation resistance than its CG counterpart.

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.

Shear-Coupled Grain Growth and Texture Development in a Nanocrystalline Ni-Fe Alloy during Cold Rolling

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

Li, Li; Ungár, Tamás; Toth, Laszlo S.

The evolution of texture, grain size, grain shape, dislocation and twin density has been determined by synchrotron X-ray diffraction and line profile analysis in a nanocrystalline Ni- Fe alloy after cold rolling along different directions related to the initial fiber and the long axis of grains. The texture evolution has been simulated by the Taylor-type relaxed constraints viscoplastic polycrystal model. The simulations were based on the activity of partial dislocations in correlation with the experimental results of dislocation density determination. The concept of stress-induced shear-coupling is supported and strengthened by both the texture simulations and the experimentally determined evolution ofmore » the microstructure parameters. Grain-growth and texture evolution are shown to proceed by the shear-coupling mechanism supported by dislocation activity as long as the grain size is not smaller than about 20 nm.« less

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

Variability of bulk density of distillers dried grains with solubles (DDGS) during gravity-driven discharge.

PubMed

Clementson, C L; Ileleji, K E

2010-07-01

Loading railcars with consistent tonnage has immense cost implications for the shipping of distillers' dried grains with soluble (DDGS) product. Therefore, this study was designed to investigate the bulk density variability of DDGS during filling of railcar hoppers. An apparatus was developed similar to a spinning riffler sampler in order to simulate the filling of railcars at an ethanol plant. There was significant difference (P<0.05) between the initial and final measures of bulk density and particle size as the hoppers were emptied in both mass and funnel flow patterns. Particle segregation that takes place during filling of hoppers contributed to the bulk density variation and was explained by particle size variation. This phenomenon is most likely the same throughout the industry and an appropriate sampling procedure should be adopted for measuring the bulk density of DDGS stored silos or transported in railcar hoppers. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Activated carbon from pyrolysis of brewer's spent grain: Production and adsorption properties.

PubMed

Vanreppelen, Kenny; Vanderheyden, Sara; Kuppens, Tom; Schreurs, Sonja; Yperman, Jan; Carleer, Robert

2014-07-01

Brewer's spent grain is a low cost residue generated by the brewing industry. Its chemical composition (high nitrogen content 4.35 wt.%, fibres, etc.) makes it very useful for the production of added value in situ nitrogenised activated carbon. The composition of brewer's spent grain revealed high amounts of cellulose (20.8 wt.%), hemicellulose (48.78 wt.%) and lignin (11.3 wt.%). The fat, ethanol extractives and ash accounted for 8.17 wt.%, 4.7 wt.% and 3.2 wt.%, respectively. Different activated carbons were produced in a lab-scale pyrolysis/activation reactor by applying several heat and steam activation profiles on brewer's spent grain. Activated carbon yields from 16.1 to 23.6 wt.% with high N-contents (> 2 wt.%) were obtained. The efficiency of the prepared activated carbons for phenol adsorption was studied as a function of different parameters: pH, contact time and carbon dosage relative to two commercial activated carbons. The equilibrium isotherms were described by the non-linear Langmuir and Freundlich models, and the kinetic results were fitted using the pseudo-first-order model and the pseudo-second-order model. The feasibility of an activated carbon production facility (onsite and offsite) that processes brewer's spent grain for different input feeds is evaluated based on a techno-economic model for estimating the net present value. Even though the model assumptions start from a rather pessimistic scenario, encouraging results for a profitable production of activated carbon using brewer's spent grain are obtained. © The Author(s) 2014.

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

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...

The Effects of Atmosphere on the Sintering of Ultrafine-Grained Tungsten with Ti

NASA Astrophysics Data System (ADS)

Ren, Chai; Koopman, Mark; Fang, Z. Zak; Zhang, Huan

2016-11-01

Tungsten (W) is a brittle material at room temperature making it very difficult to fabricate. Although the lack of ductility remains a difficult challenge, nano-sized and ultrafine-grained (UFG) structures offer the potential to overcome tungsten's room-temperature brittleness. One way to manufacture UFG W is to compact and sinter nano-sized W powder. It is challenging, however, to control grain growth during sintering. As one method to inhibit grain growth, the effect of Ti-based additives on the densification and grain growth of nano-W powders was investigated in this study. Addition of 1% Ti into tungsten led to more than a 63% decrease in average grain size of sintered samples at comparable density levels. It was found that sintering in Ar yielded a finer grain size than sintering in H2 at similar densities. The active diffusion mechanisms during sintering were different for W-1% Ti nano powders sintered in Ar and H2.

Microstructural changes in Beta-silicon nitride grains upon crystallizing the grain-boundary glass

NASA Technical Reports Server (NTRS)

Lee, William E.; Hilmas, Gregory E.; Lange, F. F. (Editor)

1991-01-01

Crystallizing the grain boundary glass of a liquid phase sintered Si3N4 ceramic for 2 h or less at 1500 C led to formation of gamma Y2Si2O7. After 5 h at 1500 C, the gamma Y2Si2O7 had transformed to beta Y2Si2O7 with a concurrent dramatic increase in dislocation density within beta Si3N4 grains. Reasons for the increased dislocation density is discussed. Annealing for 20 h at 1500 C reduced dislocation densities to the levels found in as-sintered materials.

Density-cluster NMA: A new protein decomposition technique for coarse-grained normal mode analysis.

PubMed

Demerdash, Omar N A; Mitchell, Julie C

2012-07-01

Normal mode analysis has emerged as a useful technique for investigating protein motions on long time scales. This is largely due to the advent of coarse-graining techniques, particularly Hooke's Law-based potentials and the rotational-translational blocking (RTB) method for reducing the size of the force-constant matrix, the Hessian. Here we present a new method for domain decomposition for use in RTB that is based on hierarchical clustering of atomic density gradients, which we call Density-Cluster RTB (DCRTB). The method reduces the number of degrees of freedom by 85-90% compared with the standard blocking approaches. We compared the normal modes from DCRTB against standard RTB using 1-4 residues in sequence in a single block, with good agreement between the two methods. We also show that Density-Cluster RTB and standard RTB perform well in capturing the experimentally determined direction of conformational change. Significantly, we report superior correlation of DCRTB with B-factors compared with 1-4 residue per block RTB. Finally, we show significant reduction in computational cost for Density-Cluster RTB that is nearly 100-fold for many examples. Copyright © 2012 Wiley Periodicals, Inc.

Permeation of oxygen through high purity, large grain silver

NASA Technical Reports Server (NTRS)

Outlaw, R. A.; Peregoy, W. K.; Hoflund, Gar B.

1987-01-01

The permeation of high purity, large grain Ag membranes by oxygen has been studied over the temperature range 400 to 800 C. The permeability was found to be quite linear and repeatable, but the magnitude was 3.2 times smaller than that determined by past research. Since previous investigators studied substantially less pure Ag and conducted experiments within much poorer vacuum environments (which indicates that their grain boundary density was much greater), the data presented here suggest oxygen transport through the membrane is primarily by grain boundary diffusion. The diffusivity measurements were found to exhibit two distinct linear regions, one above and one below a critical temperature of 630 C. The high-temperature data have an activation energy (11.1 kcal/mole) similar to that reported by others, but the low-temperature data have a higher activation energy (15.3 kcal/mole), which can be explained by impurity trapping in the grain boundaries. Vacuum desorption of the oxygen-saturated Ag was found to occur at a threshold of 630 C, which is consistent with the onset of increased mobility within the grain boundaries.

Refractory Organic Compounds in Enceladus' Ice Grains and Hydrothermal Activity

NASA Astrophysics Data System (ADS)

Postberg, F.; Khawaja, N.; Hsu, H. W.; Sekine, Y.; Shibuya, T.

2015-12-01

Cassini's Cosmic Dust Analyzer (CDA) generates time-of-flight mass spectra of individual grains impinging on the instruments target-plate. Following the analysis of salt rich ice grains emitted by Enceladus that indicated a salt-water ocean in contact with the moon's rocky core [1,2] a recent CDA analysis of nano-phase silica particles pointed at hydrothermal activity at the moon's rock/water interface [3]. The results imply temperatures above 80 - 90°C and alkaline pH values around 10 reminiscent of alkaline hydrothermal vents on Earth like the Lost City Hydrothermal Field. In this context the compositional analysis of organic components in CDA mass spectra of the ejected ice grains is of particular relevance. A multitude of volatile organic species has already been identified in the gas component of the plume [4]. As expected, we find more complex organic molecules in ice grains than in the gas indicating aromatic species, amines, and carbonyl group species. The composition of organic-bearing ice grains displays a great diversity indicating a variety of different organic species in varying concentrations. Recent spatially resolved CDA in situ measurements inside Enceladus' plume indicate that these organic compounds are especially frequent in 'young' ice grains that have just been ejected by high velocity jets. We investigate the implications of our findings with respect to ice grain formation at the water surface and inside the icy vents. We constrain the generation of organic compounds at the rock/water interface in the light of hydrothermal activity and the potential for the formation of life precursor molecules in Enceladus' ocean. Ref:[1] Postberg et al., Nature 459, 1098-1101 (2009). [2] Postberg et al., Nature 474, 620-622 (2011). [3]. Hsu, Postberg, Sekine et al., Nature, 519, 207-210 (2015). [4] Waite et al., Nature 460, 487-490 (2009).

Maternal antibody transfer to broiler progeny varies among strains and is affected by grain source and cage density.

PubMed

Leandro, N M; Ali, R; Koci, M; Moraes, V; Eusebio-Balcazar, P E; Jornigan, J; Malheiros, R D; Wineland, M J; Brake, J; Oviedo-Rondón, E O

2011-12-01

Two experiments were conducted to examine the effects of broiler breeder dietary grain source and cage density on maternal antibody (MatAb) transfer to progeny in 2 genetic strains (A and B). Broiler breeders were assigned to 16 litter floor pens and fed either corn- or wheat-based diets. Breeders were administered 4 live vaccines against Newcastle disease virus (NDV). At 23 wk of age, pullets and cocks, which reflected the full BW distribution from each treatment, were moved to a cage breeder house and placed at 1 or 2 hens/cage. Breeders were artificially inseminated at 44 wk (experiment 1) and 52 wk of age (experiment 2). Eggs were collected for 8 d, incubated, and placed in individual pedigree bags at d 19 of incubation. Blood samples from 5 chicks per treatment combination were collected at hatch in both experiments. Spleen and bursa were collected from the same chicks for histomorphometry analyses in experiment 2. In the second experiment, 12 chicks per treatment were placed in cages. Progeny were provided diets based on the same grain (corn or wheat) as their parents. Serum samples were collected at 5, 9, and 13 d of age and analyzed for anti-NDV MatAb. Data were analyzed as a 2 × 2 × 2 factorial design considering strain, dietary grain source, and cage density as main factors. Interaction effects were observed in breeders and progeny. Experiment 1 showed that strain A chicks had lower levels of MatAb when hens were housed at 2 hens/cage rather than 1 hen/cage. The MatAb levels of strain B chickens were not affected by cage density in either experiment. Experiment 2 demonstrated similar effects of cage density on MatAb levels and the area of bursa follicles for both strains. Progeny of breeders fed corn-based diets had smaller spleen white pulp only when hens were housed at 2 hens/cage compared with 1 hen/cage. The results of these experiments suggest that breeder strain and cage-density conditions affected MatAb transfer to progeny and embryo development

Fracture density and grain size controls on the relief structure of threshold landscapes

NASA Astrophysics Data System (ADS)

DiBiase, R.; Rossi, M. W.; Neely, A.

2015-12-01

A central goal in geomorphology is to untangle the competing controls of climate, tectonics, and rock strength on the topography and relief structure of mountain ranges. This is important for deciphering the history of climate and tectonics encoded in landscapes, predicting natural hazards, and quantifying critical zone processes. Incorporating rock strength into landscape evolution models has been a particularly challenging problem, because the factors that determine rock strength vary in importance depending on process. Here we propose a mechanism of hillslope-channel coupling by which tectonically-induced fracturing influences the relief structure of steep, rocky "threshold" landscapes by leading to A) increased fracture density in exposed bedrock outcrops, thereby limiting hillslope relief, and B) decreased grain size of channel bed material, thereby reducing the magnitude of fluvial incision thresholds and increasing the erosional efficiency of bedrock rivers. To test this hypothesis, we compare two contrasting landscapes in southern California—the eastern San Gabriel Mountains and the northern San Jacinto Mountains. The eastern San Gabriel Mountains rise 2 km in relief and exhibit high uplift and erosion rates due to active faulting along the Cucamonga thrust fault. Although bedrock on hillslopes is common, the exposed granitic and metamorphic basement rock is highly fractured at the decimeter or finer scale, and river channels are mantled with a thin layer of gravel-cobble alluvium. The northern San Jacinto Mountains, 80 km to the southeast, experience similar mean runoff and daily runoff variability, and are underlain by similar bedrock. Yet, despite an absence of active faulting, and erosion rates slower than the eastern San Gabriel Mountains by a factor of 5, the northern San Jacinto Mountains preserve one of the steepest escarpments in the contiguous US (2-3 km high), characterized by massive bedrock outcrops on hillslopes with meter-scale or larger

Two-Step Sintering Behavior of Sol-Gel Derived Dense and Submicron-Grained YIG Ceramics

NASA Astrophysics Data System (ADS)

Chen, Ruoyuan; Zhou, Jijun; Zheng, Liang; Zheng, Hui; Zheng, Peng; Ying, Zhihua; Deng, Jiangxia

2018-04-01

In this work, dense and submicron-grain yttrium iron garnet (YIG, Y3Fe5O12) ceramics were fabricated by a two-step sintering (TSS) method using nano-size YIG powder prepared by a citrate sol-gel method. The densification, microstructure, magnetic properties and ferromagnetic resonance (FMR) linewidth of the ceramics were investigated. The sample prepared at 1300°C in T 1, 1225°C in T 2 and 18 h holding time has a density higher than 98% of the theoretical value and exhibits a homogeneous microstructure with fine grain size (0.975 μm). In addition, the saturation magnetization ( M S) of this sample reaches 27.18 emu/g. High density and small grain size can also achieve small FMR linewidth. Consequently, these results show that the sol-gel process combined with the TSS process can effectively suppress grain-boundary migration while maintaining active grain-boundary diffusion to obtain dense and fine-grained YIG ceramics with appropriate magnetic properties.

TEM Analyses of Itokawa Regolith Grains and Lunar Soil Grains to Directly Determine Space Weathering Rates on Airless Bodies

NASA Technical Reports Server (NTRS)

Berger, Eve L.; Keller, Lindsay P.; Christoffersen, Roy

2016-01-01

Samples returned from the moon and Asteroid Itokawa by NASA's Apollo Missions and JAXA's Hayabusa Mission, respectively, provide a unique record of their interaction with the space environment. Space weathering effects result from micrometeorite impact activity and interactions with the solar wind. While the effects of solar wind interactions, ion implantation and solar flare particle track accumulation, have been studied extensively, the rate at which these effects accumulate in samples on airless bodies has not been conclusively determined. Results of numerical modeling and experimental simulations do not converge with observations from natural samples. We measured track densities and rim thicknesses of three olivine grains from Itokawa and multiple olivine and anorthite grains from lunar soils of varying exposure ages. Samples were prepared for analysis using a Leica EM UC6 ultramicrotome and an FEI Quanta 3D dual beam focused ion beam scanning electron microscope (FIB-SEM). Transmission electron microscope (TEM) analyses were performed on the JEOL 2500SE 200kV field emission STEM. The solar wind damaged rims on lunar anorthite grains are amorphous, lack inclusions, and are compositionally similar to the host grain. The rim width increases as a smooth function of exposure age until it levels off at approximately 180 nm after approximately 20 My (Fig. 1). While solar wind ion damage can only accumulate while the grain is in a direct line of sight to the Sun, solar flare particles can penetrate to mm-depths. To assess whether the track density accurately predicts surface exposure, we measured the rim width and track density in olivine and anorthite from the surface of rock 64455, which was never buried and has a surface exposure age of 2 My based on isotopic measurements. The rim width from 64455 (60-70nm) plots within error of the well-defined trend for solar wind amorphized rims in Fig. 1. Measured solar flare track densities are accurately reflecting the

Enhanced neutrophil chemotactic activity after bronchial challenge in subjects with grain dust-induced asthma.

PubMed

Park, H S; Jung, K S

1998-03-01

There have been few reports suggesting involvement of neutrophils in induction of bronchoconstriction after inhalation of grain dust. To understand the role of neutrophils in pathogenesis of grain dust-induced asthma. We observed serum neutrophil chemotactic activity during grain dust-bronchoprovocation tests in six asthmatic subjects with positive bronchial challenges (group I). They were compared with those of six symptomatic subjects from the same workplace with negative bronchial challenges (group II). After grain dust inhalation, serum neutrophil chemotactic activity significantly increased at 30 minutes (P = .028), and then decreased to baseline level at 240 minutes (P = .028) in five subjects of group I having isolated early asthmatic responses. Enhanced neutrophil chemotactic activity was persistent for up to 240 minutes in one asthmatic subject having both early and late asthmatic responses. There was, however, no significant change in serum neutrophil chemotactic activity during bronchial challenges in subjects of group II. Pre-incubation of sera with anti-interleukin-8 (IL-8) antibody did not affect the neutrophil chemotactic activity results of group I subjects. These results suggest that enhanced neutrophil chemotactic activity distinct from IL-8 may contribute to significant bronchoconstriction induced by grain dust.

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.

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.

Strain localization in ultramylonitic calcite marbles by dislocation creep-accommodated grain boundary sliding

NASA Astrophysics Data System (ADS)

Rogowitz, Anna; Grasemann, Bernhard; Clancy White, Joseph

2015-04-01

Strain localization in monomineralic rocks is often associated with brittle precursors, resulting in stress and strain concentration, followed by grain size reduction and activation of grain-size-sensitive deformation mechanisms such as diffusion creep, grain boundary sliding and cataclastic flow. The aforementioned mechanisms typically tend to produce a random crystallographic orientation or a decrease in intensity of a pre-existing texture. However, reports of fine grained polycrystalline materials showing a preferred crystallographic orientation indicate a need for subsequent grain re-organization by either static annealing or the activation of additional deformation mechanisms in conjunction with grain boundary sliding. We present observations from an almost pure calcite marble layer from Syros Island (Cyclades, Greece) deformed in lower greenschist facies conditions. The presence of a crack (i.e. cross-cutting element) that rotated during shear resulted in the formation of a flanking structure. At the location of maximum displacement (120 cm) along the cross-cutting element, the marble is extremely fine grained (3 µm) leading to anticipation of deformation by grain-size-sensitive mechanisms. Detailed microstructural analysis of the highly strained (80 < gamma < 1000) calcite ultramylonite by optical microscopy, electron backscatter diffraction and scanning transmission electron microscopy show that recrystallization by bulging results in small, strain-free grains. The change in grain size appears to be concomitant with increased activity of independent grain boundary sliding as indicated by a random misorientation angle distribution. At the same time, dislocation multiplication through Frank-Read sources produces high mean dislocation density (~ 5x10^13 m^-2) as well as a weak primary CPO; the latter all argue that grain boundary sliding was accommodated by dislocation activity. Theoretical and experimental determined relationships (paleowattmeter

Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing

NASA Astrophysics Data System (ADS)

Adamczyk, Krzysztof; Søndenâ, Rune; Stokkan, Gaute; Looney, Erin; Jensen, Mallory; Lai, Barry; Rinio, Markus; Di Sabatino, Marisa

2018-02-01

In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.

Elevated tropospheric ozone increased grain protein and amino acid content of a hybrid rice without manipulation by planting density.

PubMed

Zhou, Xiaodong; Zhou, Juan; Wang, Yunxia; Peng, Bin; Zhu, Jianguo; Yang, Lianxin; Wang, Yulong

2015-01-01

Rising tropospheric ozone affects crop yield and quality. Rice protein concentration, which is closely associated with eating/cooking quality, is of critical importance to nutritional quality. The ozone effect on amino acids of rice grains was little known, especially grown under different cultivation conditions. A hybrid rice cultivar Shanyou 63 was grown in 2010 and 2011 to investigate the interactive effect of ozone exposure and planting density on rice protein quality in a free-air ozone enrichment system. The content of protein, total amino acids (TAA), total essential (TEAA) and non-essential amino acids (TNEAA) in rice grain was increased by 12-14% with elevated ozone. A similar significant response to ozone was observed for concentrations of the seven essential and eight non-essential amino acids. In contrast, elevated ozone caused a small but significant decrease in percentage of TEAA to TAA. The year effect was significant for all measured traits; however, interactions of ozone with year or planting density were not detected. The study suggested that season-long elevation of ozone concentration to projected 2050 levels will increase protein and amino acids of Shanyou 63, and crop management such as changing planting density might not alter the impact. © 2014 Society of Chemical Industry.

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

Effect of grain-boundary flux pinning in MgB 2 with columnar structure

NASA Astrophysics Data System (ADS)

Kim, D. H.; Hwang, T. J.; Cha, Y. J.; Seong, W. K.; Kang, W. N.

2009-10-01

We studied the flux pinning properties by grain boundaries in MgB 2 films prepared by using a hybrid physical chemical vapor deposition method on the c-axis oriented sapphire substrates. All the films we report here had the columnar grains with the growth direction perpendicular to the substrates and the grain sizes in the range of a few hundred nanometers. At very low magnetic fields, no discernable grain-boundary (GB) pinning effect was observed in all measuring temperatures, but above those fields, the effect of GB flux pinning was observed as enhanced critical current densities ( Jcs) and reduced resistances when an external magnetic field ( B) was aligned parallel to the c-axis. We interpret the B dependence of Jc in the terms of flux line lattice shear inside the columnar grains activated by dislocations of Frank-Read source while the flux lines pinned by GB act as anchors for dislocations. Magnetic field dependence of flux pinning force density for B parallel to the c-axis was reasonably explained by the above model.

Reduced SnO2 Porous Nanowires with a High Density of Grain Boundaries as Catalysts for Efficient Electrochemical CO2 -into-HCOOH Conversion.

PubMed

Kumar, Bijandra; Atla, Veerendra; Brian, J Patrick; Kumari, Sudesh; Nguyen, Tu Quang; Sunkara, Mahendra; Spurgeon, Joshua M

2017-03-20

Electrochemical conversion of CO 2 into energy-dense liquids, such as formic acid, is desirable as a hydrogen carrier and a chemical feedstock. SnO x is one of the few catalysts that reduce CO 2 into formic acid with high selectivity but at high overpotential and low current density. We show that an electrochemically reduced SnO 2 porous nanowire catalyst (Sn-pNWs) with a high density of grain boundaries (GBs) exhibits an energy conversion efficiency of CO 2 -into-HCOOH higher than analogous catalysts. HCOOH formation begins at lower overpotential (350 mV) and reaches a steady Faradaic efficiency of ca. 80 % at only -0.8 V vs. RHE. A comparison with commercial SnO 2 nanoparticles confirms that the improved CO 2 reduction performance of Sn-pNWs is due to the density of GBs within the porous structure, which introduce new catalytically active sites. Produced with a scalable plasma synthesis technology, the catalysts have potential for application in the CO 2 conversion industry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coarse-grained molecular dynamics simulation of activated penetrant transport in glassy polymers.

PubMed

Zhang, Kai; Meng, Dong; Müller-Plathe, Florian; Kumar, Sanat K

2018-01-17

Membrane separations of gas mixtures strive to maximize the permeability of a desired species while keeping out undesired ones. Permeability vs. selectivity data from many polymer membranes for a given gas pair with diameters d A and d B are typically collected in a "Robeson plot"', and are bound from above by a line with a slope λ = (d B /d A ) 2 - 1. A microscopic understanding of this relationship, especially λ, is still missing. We perform molecular dynamics simulations of penetrant diffusion using three different coarse-grained polymer models over a wide range of penetrant sizes, temperatures, and monomer densities. The empirically relevant λ = (d B /d A ) 2 - 1 is only found for polymers that are either supercooled liquids with caged segmental dynamics or glasses and when the penetrant size is approximately half the Kuhn length of the chains, for which the penetrant diffusion is an activated process.

On the AU Microscopii debris disk. Density profiles, grain properties, and dust dynamics

NASA Astrophysics Data System (ADS)

Augereau, J.-C.; Beust, H.

2006-09-01

Context: . AU Mic is a young M-type star surrounded by an edge-on optically thin debris disk that shares many common observational properties with the disk around β Pictoris. In particular, the scattered light surface brightness profile falls off as ˜ r-5 outside 120 AU for β Pictoris and 35 AU for AU Mic. In both cases, the disk color rises as the distance increases beyond these reference radii. Aims: . In this paper, we present the first comprehensive analysis of the AU Mic disk properties since the system was resolved by Kalas et al. (2004, Science, 303, 1990). We explore whether the dynamical model, which successfully reproduces the β Pictoris brightness profile (e.g., Augereau et al. 2001, A&A, 370, 447), could apply to AU Mic. Methods: . We calculate the surface density profile of the AU Mic disk by performing the inversion of the near-IR and visible scattered light brightness profiles measured by Liu (2004, Science, 305, 1442) and Krist et al. (2005, AJ, 129, 1008), respectively. We discuss the grain properties by analysing the blue color of the disk in the visible (Krist et al. 2005) and by fitting the disk spectral energy distribution. Finally, we evaluate the radiation and wind forces on the grains. The impact of the recurrent X-ray and UV-flares on the dust dynamics is also discussed. Results: . We show that irrespective of the mean scattering asymmetry factor of the grains, most of the emission arises from an asymmetric, collisionally-dominated region that peaks close to the surface brightness break around 35 AU. The elementary scatterers at visible wavelengths are found to be sub-micronic, but the inferred size distribution underestimates the number of large grains, resulting in sub-millimeter emissions that are too low compared to the observations. From our inversion procedure, we find that the V- to H-band scattering cross sections ratio increases outside 40 AU, in line with the observed color gradient of the disk. This behavior is expected if

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

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

Vo, Truong Quoc; Kim, BoHung, E-mail: muratbarisik@iyte.edu.tr, E-mail: bohungk@ulsan.ac.kr; Barisik, Murat, E-mail: muratbarisik@iyte.edu.tr, E-mail: bohungk@ulsan.ac.kr

2016-05-21

This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, threemore » distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

NASA Astrophysics Data System (ADS)

Vo, Truong Quoc; Barisik, Murat; Kim, BoHung

2016-05-01

This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, three distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR. Thus, an

Anti-inflammatory Activity of Grains of Paradise (Aframomum melegueta Schum) Extract

PubMed Central

2015-01-01

The ethanolic extract of grains of paradise (Aframomum melegueta Schum, Zingiberaceae) has been evaluated for inhibitory activity on cyclooxygenase-2 (COX-2) enzyme, in vivo for the anti-inflammatory activity and expression of several pro-inflammatory genes. Bioactivity-guided fractionation showed that the most active COX-2 inhibitory compound in the extract was [6]-paradol. [6]-Shogaol, another compound from the extract, was the most active inhibitory compound in pro-inflammatory gene expression assays. In a rat paw edema model, the whole extract reduced inflammation by 49% at 1000 mg/kg. Major gingerols from the extract [6]-paradol, [6]-gingerol, and [6]-shogaol reduced inflammation by 20, 25 and 38%. respectively when administered individually at a dose of 150 mg/kg. [6]-Shogaol efficacy was at the level of aspirin, used as a positive control. Grains of paradise extract has demonstrated an anti-inflammatory activity, which is in part due to the inhibition of COX-2 enzyme activity and expression of pro-inflammatory genes. PMID:25293633

Effects of starter nitrogen fertilizer on soybean root activity, leaf photosynthesis and grain yield

PubMed Central

Gai, Zhijia; Zhang, Jingtao; Li, Caifeng

2017-01-01

The objective of this study was to examine the impact of starter nitrogen fertilizer on soybean root activity, leaf photosynthesis, grain yield and their relationship. To achieve this objective, field experiments were conducted in 2013 and 2014, using a randomized complete block design, with three replications. Nitrogen was applied at planting at rates of 0, 25, 50, and 75 kg N ha-1. In both years, starter nitrogen fertilizer benefited root activity, leaf photosynthesis, and consequently its yield. Statistically significant correlation was found among root activity, leaf photosynthetic rate, and grain yield at the developmental stage. The application of N25, N50, and N75 increased grain yield by 1.28%, 2.47%, and 1.58% in 2013 and by 0.62%, 2.77%, and 2.06% in 2014 compared to the N0 treatment. Maximum grain yield of 3238.91 kg ha-1 in 2013 and 3086.87 kg ha-1 in 2014 were recorded for N50 treatment. Grain yield was greater for 2013 than 2014, possibly due to more favorable environmental conditions. This research indicated that applying nitrogen as starter is necessary to increase soybean yield in Sangjiang River Plain in China. PMID:28388620

Reduction of pyruvate orthophosphate dikinase activity is associated with high temperature-induced chalkiness in rice grains.

PubMed

Wang, Zhen-mei; Li, Hai-xia; Liu, Xiong-feng; He, Ying; Zeng, Han-lai

2015-04-01

Global warming affects both rice (Oryza sativa) yields and grain quality. Rice chalkiness due to high temperature during grain filling would lower the grain quality. The biochemical and molecular mechanisms responsible for the increased occurrence of chalkiness under high temperature are not fully understood. Previous research suggested that cytosolic pyruvate orthophosphate dikinase (cyPPDK, EC 2.7.9.1) in rice modulates carbon metabolism. The objective of this study was to determine the relationship between cyPPDK and high temperature-induced chalkiness. High temperature treatments were applied during the grain filling of two rice cultivars (9311 and TXZ-25) which had different sensitivity of chalkiness to high temperature. Chalkiness was increased significantly under high temperature treatment, especially for TXZ-25. A shortened grain filling duration and a decreased grain weight in both cultivars were caused by high temperature treatment. A reduction in PPDK activities due to high temperature was observed during the middle and late grain filling periods, accompanied by down regulated cyPPDK mRNA and protein levels. The temperature effects on the developmental regulation of PPDK activity were confirmed at transcription, translation and post-translational levels. PPDK activities were insensitive to variation in PPDK levels, suggesting the rapid phosphorylation mechanism of this protein. The two varieties showed similar responses to the high temperature treatment in both PPDK activities and chalkiness. We concluded that high temperature-induced chalkiness was associated with the reduction of PPDK activity. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Active Free Surface Density Maps

NASA Astrophysics Data System (ADS)

Çelen, S.

2016-10-01

Percolation problems were occupied to many physical problems after their establishment in 1957 by Broadbent and Hammersley. They can be used to solve complex systems such as bone remodeling. Volume fraction method was adopted to set some algorithms in the literature. However, different rate of osteoporosis could be observed for different microstructures which have the same mass density, mechanical stimuli, hormonal stimuli and nutrition. Thus it was emphasized that the bone might have identical porosity with different specific surfaces. Active free surface density of bone refers the used total area for its effective free surface. The purpose of this manuscript is to consolidate a mathematical approach which can be called as “active free surface density maps” for different surface patterns and derive their formulations. Active free surface density ratios were calculated for different Archimedean lattice models according to Helmholtz free energy and they were compared with their site and bond percolation thresholds from the background studies to derive their potential probability for bone remodeling.

Milk-cereal and whole-grain dietary patterns protect against low bone mineral density among male adolescents and young adults.

PubMed

Shin, S; Kim, S-H; Joung, H; Park, M J

2017-09-01

Evidence supporting the possible effect of dietary factors on adult bone health has emerged in recent decades. The purpose of this study was to ascertain the influence of different dietary patterns on bone mineral density (BMD) among Korean male youth. Data were extracted from the Korean National Health and Nutrition Examination Survey (KNHANES) during 2008-2011. The subjects included 1351 male aged 10-25 years. We defined 'low BMD group' as subjects with a BMD Z-score of -2.0 or less. Dietary patterns were derived from 20 food groups via factor analysis. Three dietary patterns-meat and vegetable, white rice and kimchi, milk-cereal and whole grain-were derived. The 'milk-cereal and whole-grain' dietary pattern score showed positive association with energy, protein, fat, calcium, phosphorus, potassium, riboflavin and vitamin C intakes. Participants in the top tertile of the milk-cereal and whole-grain pattern were less likely to have low BMD, compared with subjects in the bottom tertile (odds ratio=0.36, 95% confidence interval=0.16-0.81, P=0.018). Our findings suggest that the milk-cereal and whole-grain dietary pattern may have a benign influence on bone health in the Korean male youth.

Radical formation, chemical processing, and explosion of interstellar grains

NASA Technical Reports Server (NTRS)

Greenberg, J. M.

1976-01-01

The ultraviolet radiation in interstellar space is shown to create a sufficient steady-state density of free radicals in the grain mantle material consisting of oxygen, carbon, nitrogen, and hydrogen to satisfy the critical condition for initiation of chain reactions. The criterion for minimum critical particle size for maintaining the chain reaction is of the order of the larger grain sizes in a distribution satisfying the average extinction and polarization measures. The triggering of the explosion of interstellar grains leading to the ejection of complex interstellar molecules is shown to be most probable where the grains are largest and where radiation is suddenly introduced; i.e., in regions of new star formation. Similar conditions prevail at the boundaries between very dark clouds and H II regions. When the energy released by the chemical activity of the free radicals is inadequate to explode the grain, the resulting mantle material must consist of extremely large organic molecules which are much more resistant to the hostile environment of H II regions than the classical dirty-ice mantles made up of water, methane, and ammonia.

Methanol extract of grain dust shows complement fixing activity and other characteristics similar to tannic acid.

PubMed Central

Skea, D; Broder, I

1986-01-01

We have found several similarities between tannic acid and grain dust extract prepared with methanol. Both formed a precipitate with IgG, and these interactions were inhibited by albumin. In addition, both preparations fixed complement; this activity was heat stable and was removed by prior adsorption of the preparations with hide powder. Adsorption with polyvinyl polypyrrolidone reduced the complement-fixing activity of tannic acid but not that of the methanol grain dust extract. The similarities between tannic acid and the methanol grain dust extract are consistent with the presence of a tannin or tanninlike material in grain dust. Images FIGURE 1. PMID:3709479

Study on Iron Distribution and Electrical Activities at Grain Boundaries in Polycrystalline Silicon Substrate for Solar Cells

NASA Astrophysics Data System (ADS)

Arafune, Koji; Ohishi, Eichiro; Sai, Hitoshi; Terada, Yasuko; Ohshita, Yoshio; Yamaguchi, Masafumi

2006-08-01

To clarify the role of grain boundaries in iron sinks and carrier recombination centers, iron distributions and their chemical states were studied before and after gettering. They were measured by the X-ray microprobe fluorescence and the X-ray absorption in the near-edge structure using the beamline 37XU at the SPring-8 third-generation synchrotron facility. To determine the crystallographic orientation of the grain boundaries, electron backscatter diffraction measurements were performed. The distribution of electric active defects was characterized by electron-beam-induced current measurements. Before gettering, the iron was distributed in the small grain and its chemical state was similar to that of iron oxide. After gettering, the iron was redistributed along the small angle grain boundary, and its chemical state was similar to the iron silicide complexed with the iron oxide. Regarding the electrical activity, high carrier recombination was observed along the small-angle grain boundary. On the contrary, Σ 3 grain boundaries were relatively weak impurity sinks and showed low recombination activity.

Inverse grading and hydraulic equivalence in grain-flow deposits

USGS Publications Warehouse

Sallenger, A. H.

1979-01-01

Inversely graded grain-flow deposits are characterized by a hydraulic equivalence that differs from that based on settling velocities or entrainment. Dispersive equivalence, derived from the dispersive pressure hypothesis on how inverse grading develops, was found to agree reasonably well with observed relationships between grain sizes and densities in grain-flow deposits. Furthermore, observed relationships in deposits formed in subaerial and subaqueous environments were found to be independent of fluid density as is required by dispersive equivalence. The results suggest that dispersive pressure controls the development of the inverse grading common to beach foreshore laminations, slip-face foreset strata, the basal parts of some coarse-grained turbidites, and other diverse deposits.

Significantly enhanced critical current density in nano-MgB2 grains rapidly formed at low temperature with homogeneous carbon doping

NASA Astrophysics Data System (ADS)

Liu, Yongchang; Lan, Feng; Ma, Zongqing; Chen, Ning; Li, Huijun; Barua, Shaon; Patel, Dipak; Shahriar, M.; Hossain, Al; Acar, S.; Kim, Jung Ho; Xue Dou, Shi

2015-05-01

High performance MgB2 bulks using carbon-coated amorphous boron as a boron precursor were fabricated by Cu-activated sintering at low temperature (600 °C, below the Mg melting point). Dense nano-MgB2 grains with a high level of homogeneous carbon doping were formed in these MgB2 samples. This type of microstructure can provide a stronger flux pinning force, together with depressed volatility and oxidation of Mg owing to the low-temperature Cu-activated sintering, leading to a significant improvement of critical current density (Jc) in the as-prepared samples. In particular, the value of Jc for the carbon-coated (Mg1.1B2)Cu0.05 sample prepared here is even above 1 × 105 A cm-2 at 20 K, 2 T. The results herein suggest that the combination of low-temperature Cu-activated sintering and employment of carbon-coated amorphous boron as a precursor could be a promising technique for the industrial production of practical MgB2 bulks or wires with excellent Jc, as the carbon-coated amorphous boron powder can be produced commercially at low cost, while the addition of Cu is very convenient and inexpensive.

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.

Grain Boundary Effect on Charge Transport in Pentacene Thin Films

NASA Astrophysics Data System (ADS)

Weis, Martin; Gmucová, Katarína; Nádaždy, Vojtech; Majková, Eva; Haško, Daniel; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2011-04-01

We report on charge transport properties of polycrystalline pentacene films with variable average grain size in the range from 0.1 to 0.3 µm controlled by the preparation technology. We illustrate with the organic field-effect transistors decrease of the effective mobility and presence of traps with decrease of the grain size. Analysis of the charge transfer excitons reveals decrease of the mobile charge density and the steady-state voltammetry showed significant increase of oxygen- and hydrogen-related defects. We also briefly discuss accumulation of the defects on the grain boundary and show relation between the defect density and grain boundary length.

Canopy Chlorophyll Density Based Index for Estimating Nitrogen Status and Predicting Grain Yield in Rice

PubMed Central

Liu, Xiaojun; Zhang, Ke; Zhang, Zeyu; Cao, Qiang; Lv, Zunfu; Yuan, Zhaofeng; Tian, Yongchao; Cao, Weixing; Zhu, Yan

2017-01-01

Canopy chlorophyll density (Chl) has a pivotal role in diagnosing crop growth and nutrition status. The purpose of this study was to develop Chl based models for estimating N status and predicting grain yield of rice (Oryza sativa L.) with Leaf area index (LAI) and Chlorophyll concentration of the upper leaves. Six field experiments were conducted in Jiangsu Province of East China during 2007, 2008, 2009, 2013, and 2014. Different N rates were applied to generate contrasting conditions of N availability in six Japonica cultivars (9915, 27123, Wuxiangjing 14, Wuyunjing 19, Yongyou 8, and Wuyunjing 24) and two Indica cultivars (Liangyoupei 9, YLiangyou 1). The SPAD values of the four uppermost leaves and LAI were measured from tillering to flowering growth stages. Two N indicators, leaf N accumulation (LNA) and plant N accumulation (PNA) were measured. The LAI estimated by LAI-2000 and LI-3050C were compared and calibrated with a conversion equation. A linear regression analysis showed significant relationships between Chl value and N indicators, the equations were as follows: PNA = (0.092 × Chl) − 1.179 (R2 = 0.94, P < 0.001, relative root mean square error (RRMSE) = 0.196), LNA = (0.052 × Chl) − 0.269 (R2 = 0.93, P < 0.001, RRMSE = 0.185). Standardized method was used to quantity the correlation between Chl value and grain yield, normalized yield = (0.601 × normalized Chl) + 0.400 (R2 = 0.81, P < 0.001, RRMSE = 0.078). Independent experimental data also validated the use of Chl value to accurately estimate rice N status and predict grain yield. PMID:29163568

Formation of intra-island grain boundaries in pentacene monolayers.

PubMed

Zhang, Jian; Wu, Yu; Duhm, Steffen; Rabe, Jürgen P; Rudolf, Petra; Koch, Norbert

2011-12-21

To assess the formation of intra-island grain boundaries during the early stages of pentacene film growth, we studied sub-monolayers of pentacene on pristine silicon oxide and silicon oxide with high pinning centre density (induced by UV/O(3) treatment). We investigated the influence of the kinetic energy of the impinging molecules on the sub-monolayer growth by comparing organic molecular beam deposition (OMBD) and supersonic molecular beam deposition (SuMBD). For pentacene films fabricated by OMBD, higher pentacene island-density and higher polycrystalline island density were observed on UV/O(3)-treated silicon oxide as compared to pristine silicon oxide. Pentacene films deposited by SuMBD exhibited about one order of magnitude lower island- and polycrystalline island densities compared to OMBD, on both types of substrates. Our results suggest that polycrystalline growth of single islands on amorphous silicon oxide is facilitated by structural/chemical surface pinning centres, which act as nucleation centres for multiple grain formation in a single island. Furthermore, the overall lower intra-island grain boundary density in pentacene films fabricated by SuMBD reduces the number of charge carrier trapping sites specific to grain boundaries and should thus help achieving higher charge carrier mobilities, which are advantageous for their use in organic thin-film transistors.

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-grain ready-to-eat oat cereal, as part of a dietary program for weight loss, reduces low-density lipoprotein cholesterol in adults with overweight and obesity more than a dietary program including low-fiber control foods.

PubMed

Maki, Kevin C; Beiseigel, Jeannemarie M; Jonnalagadda, Satya S; Gugger, Carolyn K; Reeves, Matthew S; Farmer, Mildred V; Kaden, Valerie N; Rains, Tia M

2010-02-01

Weight loss and consumption of viscous fibers both lower low-density lipoprotein (LDL) cholesterol levels. We evaluated whether or not a whole-grain, ready-to-eat (RTE) oat cereal containing viscous fiber, as part of a dietary program for weight loss, lowers LDL cholesterol levels and improves other cardiovascular disease risk markers more than a dietary program alone. Randomized, parallel-arm, controlled trial. Free-living, overweight and obese adults (N=204, body mass index 25 to 45) with baseline LDL cholesterol levels 130 to 200 mg/dL (3.4 to 5.2 mmol/L) were randomized; 144 were included in the main analysis of participants who completed the trial without significant protocol violations. Two portions per day of whole-grain RTE oat cereal (3 g/day oat b-glucan) or energy-matched low-fiber foods (control), as part of a reduced energy ( approximately 500 kcal/day deficit) dietary program that encouraged limiting consumption of foods high in energy and fat, portion control, and regular physical activity. Fasting lipoprotein levels, waist circumference, triceps skinfold thickness, and body weight were measured at baseline and weeks 4, 8, 10, and 12. LDL cholesterol level was reduced significantly more with whole-grain RTE oat cereal vs control (-8.7+/-1.0 vs -4.3+/-1.1%, P=0.005). Total cholesterol (-5.4+/-0.8 vs -2.9+/-0.9%, P=0.038) and non-high-density lipoprotein-cholesterol (-6.3+/-1.0 vs -3.3+/-1.1%, P=0.046) were also lowered significantly more with whole-grain RTE oat cereal, whereas high-density lipoprotein and triglyceride responses did not differ between groups. Weight loss was not different between groups (-2.2+/-0.3 vs -1.7+/-0.3 kg, P=0.325), but waist circumference decreased more (-3.3+/-0.4 vs -1.9+/-0.4 cm, P=0.012) with whole-grain RTE oat cereal. Larger reductions in LDL, total, and non-high-density lipoprotein cholesterol levels and waist circumference were evident as early as week 4 in the whole-grain RTE oat cereal group. Consumption of a

Antioxidant Activity of Individual Steryl Ferulates from Various Cereal Grain Sources.

PubMed

Zhu, Dan; Sánchez-Ferrer, Antoni; Nyström, Laura

2016-02-26

Steryl ferulates (SFs) are a subclass of bioactive lipids contributing to the health-promoting effects of whole grains. Most related studies focus on γ-oryzanol, a SF mixture from rice, since individual steryl ferulates are not commercially available. There is little evidence that individual SFs may vary in their bioactivity. The aim of this study was to evaluate the antioxidant activity of eight individual SFs by determining their radical scavenging capacity. Additional molecular properties of the individual SFs were determined by molecular simulation in order to identify correlations with their antioxidant activities. Our study demonstrates that individual SFs exhibit 1,1-diphenyl-2-picrylhydrazyl radical, hydroxyl radical, and superoxide anion radical scavenging abilities with subtle differences that were highly dependent on the kind of reaction taking place. The grouping of SFs by principle component analysis was mainly attributed to molecular properties, not antioxidant activities. Solvation energy was significantly correlated with some experimental observations. To our knowledge, this is the first study to evaluate the antioxidant activity of eight individual steryl ferulates from different sources. Results of this work will provide better insight into the antioxidant activity of SFs and the health benefits of whole grains.

Bio-oil and bio-char from low temperature pyrolysis of spent grains using activated alumina.

PubMed

Sanna, Aimaro; Li, Sujing; Linforth, Rob; Smart, Katherine A; Andrésen, John M

2011-11-01

The pyrolysis of wheat and barley spent grains resulting from bio-ethanol and beer production respectively was investigated at temperatures between 460 and 540 °C using an activated alumina bed. The results showed that the bio-oil yield and quality depend principally on the applied temperature where pyrolysis at 460 °C leaves a bio-oil with lower nitrogen content in comparison with the original spent grains and low oxygen content. The viscosity profile of the spent grains indicated that activated alumina could promote liquefaction and prevent charring of the structure between 400 and 460 °C. The biochar contains about 10-12% of original carbon and 13-20% of starting nitrogen resulting very attractive as a soil amendment and for carbon sequestration. Overall, value can be added to the spent grains opening a new market in bio-fuel production without the needs of external energy. The bio-oil from spent grains could meet about 9% of the renewable obligation in the UK. Copyright © 2011 Elsevier Ltd. All rights reserved.

Physical Activity and Change in Mammographic Density

PubMed Central

Conroy, Shannon M.; Butler, Lesley M.; Harvey, Danielle; Gold, Ellen B.; Sternfeld, Barbara; Oestreicher, Nina; Greendale, Gail A.; Habel, Laurel A.

2010-01-01

One potential mechanism by which physical activity may protect against breast cancer is by decreasing mammographic density. Percent mammographic density, the proportion of dense breast tissue area to total breast area, declines with age and is a strong risk factor for breast cancer. The authors hypothesized that women who were more physically active would have a greater decline in percent mammographic density with age, compared with less physically active women. The authors tested this hypothesis using longitudinal data (1996–2004) from 722 participants in the Study of Women's Health Across the Nation (SWAN), a multiethnic cohort of women who were pre- and early perimenopausal at baseline, with multivariable, repeated-measures linear regression analyses. During an average of 5.6 years, the mean annual decline in percent mammographic density was 1.1% (standard deviation = 0.1). A 1-unit increase in total physical activity score was associated with a weaker annual decline in percent mammographic density by 0.09% (standard error = 0.03; P = 0.01). Physical activity was inversely associated with the change in nondense breast area (P < 0.01) and not associated with the change in dense breast area (P = 0.17). Study results do not support the hypothesis that physical activity reduces breast cancer through a mechanism that includes reduced mammographic density. PMID:20354074

Technical Note: Stored grain volume measurement using a low density point cloud

USDA-ARS?s Scientific Manuscript database

The mass of stored grain is often determined from volume measurements by crop insurers, government auditors, and stored grain managers conducting inventories. Recent increases in bin size have accentuated the difficulty of accounting for irregularities and variations in surface conditions in calcula...

Microstructure stability of ultra-fine grained magnesium alloy AZ31 processed by extrusion and equal-channel angular pressing (EX–ECAP)

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

Stráská, Jitka, E-mail: straska.jitka@gmail.com; Janeček, Miloš, E-mail: janecek@met.mff.cuni.cz; Čížek, Jakub, E-mail: jcizek@mbox.troja.mff.cuni.cz

Thermal stability of the ultra-fine grained (UFG) microstructure of magnesium AZ31 alloy was investigated. UFG microstructure was achieved by a combined two-step severe plastic deformation process: the extrusion (EX) and subsequent equal-channel angular pressing (ECAP). This combined process leads to refined microstructure and enhanced microhardness. Specimens with UFG microstructure were annealed isochronally at temperatures 150–500 °C for 1 h. The evolution of microstructure, mechanical properties and dislocation density was studied by electron backscatter diffraction (EBSD), microhardness measurements and positron annihilation spectroscopy (PAS). The coarsening of the fine-grained structure at higher temperatures was accompanied by a gradual decrease of the microhardnessmore » and decrease of dislocation density. Mechanism of grain growth was studied by general equation for grain growth and Arrhenius equation. Activation energies for grain growth were calculated to be 115, 33 and 164 kJ/mol in temperature ranges of 170–210 °C, 210–400 °C and 400–500 °C (443–483 K, 483–673 K and 673–773 K), respectively. - Highlights: • Microhardness of UFG AZ31 alloy decreases with increasing annealing temperature. • This fact has two reasons: dislocation annihilations and/or grain growth. • The activation energies for grain growth were calculated for all temperature ranges.« less

Rates of Space Weathering in Lunar Regolith Grains

NASA Technical Reports Server (NTRS)

Zhang, S.; Keller, L. P.

2012-01-01

While the processes and products of lunar space weathering are reasonably well-studied, their accumulation rates in lunar soils are poorly constrained. Previously, we showed that the thickness of solar wind irradiated rims on soil grains is a smooth function of their solar flare particle track density, whereas the thickness of vapor-deposited rims was largely independent of track density [1]. Here, we have extended these preliminary results with data on additional grains from other mature soils.

Advantageous grain boundaries in iron pnictide superconductors

PubMed Central

Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

2011-01-01

High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries—the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θGB) were systematically investigated for cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (JcBGB) remained high (>1 MA cm−2) and nearly constant up to a critical angle θc of ∼9°, which is substantially larger than the θc of ∼5° for YBa2Cu3O7–δ. Even at θGB>θc, the decay of JcBGB was much slower than that of YBa2Cu3O7–δ. PMID:21811238

Presynaptic Active Zone Density during Development and Synaptic Plasticity.

PubMed

Clarke, Gwenaëlle L; Chen, Jie; Nishimune, Hiroshi

2012-01-01

Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated.

Presynaptic Active Zone Density during Development and Synaptic Plasticity

PubMed Central

Clarke, Gwenaëlle L.; Chen, Jie; Nishimune, Hiroshi

2012-01-01

Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated. PMID:22438837

Active Space Dependence in Multiconfiguration Pair-Density Functional Theory.

PubMed

Sharma, Prachi; Truhlar, Donald G; Gagliardi, Laura

2018-02-13

In multiconfiguration pair-density functional theory (MC-PDFT), multiconfiguration self-consistent-field calculations and on-top density functionals are combined to describe both static and dynamic correlation. Here, we investigate how the MC-PDFT total energy and its components depend on the active space choice in the case of the H 2 and N 2 molecules. The active space dependence of the on-top pair density, the total density, the ratio of on-top pair density to half the square of the electron density, and the satisfaction of the virial theorem are also explored. We find that the density and on-top pair density do not change significantly with changes in the active space. However, the on-top ratio does change significantly with respect to active space change, and this affects the on-top energy. This study provides a foundation for designing on-top density functionals and automatizing the active space choice in MC-PDFT.

Downstream lightening and upward heavying, sorting of sediments of uniform grain size but differing in density

NASA Astrophysics Data System (ADS)

Viparelli, E.; Solari, L.; Hill, K. M.

2014-12-01

Downstream fining, i.e. the tendency for a gradual decrease in grain size in the downstream direction, has been observed and studied in alluvial rivers and in laboratory flumes. Laboratory experiments and field observations show that the vertical sorting pattern over a small Gilbert delta front is characterized by an upward fining profile, with preferential deposition of coarse particles in the lowermost part of the deposit. The present work is an attempt to answer the following questions. Are there analogous sorting patterns in mixtures of sediment particles having the same grain size but differing density? To investigate this, we performed experiments at the Hydrosystems Laboratory at the University of Illinois at Urbana-Champaign. During the experiments a Gilbert delta formed and migrated downstream allowing for the study of transport and sorting processes on the surface and within the deposit. The experimental results show 1) preferential deposition of heavy particles in the upstream part of the deposit associated with a pattern of "downstream lightening"; and 2) a vertical sorting pattern over the delta front characterized by a pattern of "upward heavying" with preferential deposition of light particles in the lowermost part of the deposit. The observed downstream lightening is analogous of the downstream fining with preferential deposition of heavy (coarse) particles in the upstream part of the deposit. The observed upward heavying was unexpected because, considering the particle mass alone, the heavy (coarse) particles should have been preferentially deposited in the lowermost part of the deposit. Further, the application of classical fractional bedload transport relations suggests that in the case of mixtures of particles of uniform size and different densities equal mobility is not approached. We hypothesize that granular physics mechanisms traditionally associated with sheared granular flows may be responsible for the observed upward heavying and for the

Unfolding grain size effects in barium titanate ferroelectric ceramics

PubMed Central

Tan, Yongqiang; Zhang, Jialiang; Wu, Yanqing; Wang, Chunlei; Koval, Vladimir; Shi, Baogui; Ye, Haitao; McKinnon, Ruth; Viola, Giuseppe; Yan, Haixue

2015-01-01

Grain size effects on the physical properties of polycrystalline ferroelectrics have been extensively studied for decades; however there are still major controversies regarding the dependence of the piezoelectric and ferroelectric properties on the grain size. Dense BaTiO3 ceramics with different grain sizes were fabricated by either conventional sintering or spark plasma sintering using micro- and nano-sized powders. The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used. A peak in the permittivity is observed in all the ceramics with a grain size near 1 μm and can be attributed to a maximum domain wall density and mobility. The piezoelectric coefficient d33 and remnant polarization Pr show diverse grain size effects depending on the particle size of the starting powder and sintering temperature. This suggests that besides domain wall density, other factors such as back fields and point defects, which influence the domain wall mobility, could be responsible for the different grain size dependence observed in the dielectric and piezoelectric/ferroelectric properties. In cases where point defects are not the dominant contributor, the piezoelectric constant d33 and the remnant polarization Pr increase with increasing grain size. PMID:25951408

Strain induced grain boundary migration effects on grain growth of an austenitic stainless steel during static and metadynamic recrystallization

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

Paggi, A., E-mail: alpaggi@tenaris.com; Angella, G.; Donnini, R.

Static and metadynamic recrystallization of an AISI 304L austenitic stainless steel was investigated at 1100 °C and 10{sup −} {sup 2} s{sup −} {sup 1} strain rate. The kinetics of recrystallization was determined through double hit compression tests. Two strain levels were selected for the first compression hit: ε{sub f} = 0.15 for static recrystallization (SRX) and 0.25 for metadynamic recrystallization (MDRX). Both the as-deformed and the recrystallized microstructures were investigated through optical microscopy and electron back-scattered diffraction (EBSD) technique. During deformation, strain induced grain boundary migration appeared to be significant, producing a square-like grain boundary structure aligned along themore » directions of the maximum shear stresses in compression. EBSD analysis revealed to be as a fundamental technique that the dislocation density was distributed heterogeneously in the deformed grains. Grain growth driven by surface energy reduction was also investigated, finding that it was too slow to explain the experimental data. Based on microstructural results, it was concluded that saturation of the nucleation sites occurred in the first stages of recrystallization, while grain growth driven by strain induced grain boundary migration (SIGBM) dominated the subsequent stages. - Highlights: • Recrystallization behavior of a stainless steel was investigated at 1100 °C. • EBSD revealed that the dislocation density distribution was heterogeneous during deformation. • Saturation of nucleation sites occurred in the first stages of recrystallization. • Strain induced grain boundary migration (SIGBM) effects were significant. • Grain growth driven by SIGBM dominated the subsequent stages.« less

Microwave sintering of nanophase ceramics without concomitant grain growth

DOEpatents

Eastman, Jeffrey A.; Sickafus, Kurt E.; Katz, Joel D.

1993-01-01

A method of sintering nanocrystalline material is disclosed wherein the nanocrystalline material is microwaved to heat the material to a temperature less than about 70% of the melting point of the nanocrystalline material expressed in degrees K. This method produces sintered nanocrystalline material having a density greater than about 95% of theoretical and an average grain size not more than about 3 times the average grain size of the nanocrystalline material before sintering. Rutile TiO.sub.2 as well as various other ceramics have been prepared. Grain growth of as little as 1.67 times has resulted with densities of about 90% of theoretical.

Defect and grain boundary scattering in tungsten: A combined theoretical and experimental study

NASA Astrophysics Data System (ADS)

Lanzillo, Nicholas A.; Dixit, Hemant; Milosevic, Erik; Niu, Chengyu; Carr, Adra V.; Oldiges, Phil; Raymond, Mark V.; Cho, Jin; Standaert, Theodorus E.; Kamineni, Vimal K.

2018-04-01

Several major electron scattering mechanisms in tungsten (W) are evaluated using a combination of first-principles density functional theory, a Non-Equilibrium Green's Function formalism, and thin film Kelvin 4-point sheet resistance measurements. The impact of grain boundary scattering is found to be roughly an order of magnitude larger than the impact of defect scattering. Ab initio simulations predict average grain boundary reflection coefficients for a number of twin grain boundaries to lie in the range r = 0.47 to r = 0.62, while experimental data can be fit to the empirical Mayadas-Schatzkes model with a comparable but slightly larger value of r = 0.69. The experimental and simulation data for grain boundary resistivity as a function of grain size show excellent agreement. These results provide crucial insights for understanding the impact of scaling of W-based contacts between active devices and back-end-of-line interconnects in next-generation semiconductor technology.

Simulation of electron transport across charged grain boundaries

NASA Astrophysics Data System (ADS)

Srikant, V.; Clarke, D. R.; Evans, P. V.

1996-09-01

The I-V (current density-electric field) characteristics of low-angle grain boundaries consisting of periodic arrays of charged dislocations are computed using a quasiclassical molecular dynamics approach. Below a critical value of the grain boundary misorientation, the computed I-V characteristics are linear whereas above they are nonlinear. The degree of nonlinearity and the voltage onset of nonlinearity are found to be dependent on the grain boundary misorientation.

Effect of freeze-thaw cycling on grain size of biochar.

PubMed

Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A; Wahab, Leila M; Gonnermann, Helge M; Nittrouer, Jeffrey A

2018-01-01

Biochar may improve soil hydrology by altering soil porosity, density, hydraulic conductivity, and water-holding capacity. These properties are associated with the grain size distributions of both soil and biochar, and therefore may change as biochar weathers. Here we report how freeze-thaw (F-T) cycling impacts the grain size of pine, mesquite, miscanthus, and sewage waste biochars under two drainage conditions: undrained (all biochars) and a gravity-drained experiment (mesquite biochar only). In the undrained experiment plant biochars showed a decrease in median grain size and a change in grain-size distribution consistent with the flaking off of thin layers from the biochar surface. Biochar grain size distribution changed from unimodal to bimodal, with lower peaks and wider distributions. For plant biochars the median grain size decreased by up to 45.8% and the grain aspect ratio increased by up to 22.4% after 20 F-T cycles. F-T cycling did not change the grain size or aspect ratio of sewage waste biochar. We also observed changes in the skeletal density of biochars (maximum increase of 1.3%), envelope density (maximum decrease of 12.2%), and intraporosity (porosity inside particles, maximum increase of 3.2%). In the drained experiment, mesquite biochar exhibited a decrease of median grain size (up to 4.2%) and no change of aspect ratio after 10 F-T cycles. We also document a positive relationship between grain size decrease and initial water content, suggesting that, biochar properties that increase water content, like high intraporosity and pore connectivity large intrapores, and hydrophilicity, combined with undrained conditions and frequent F-T cycles may increase biochar breakdown. The observed changes in biochar particle size and shape can be expected to alter hydrologic properties, and thus may impact both plant growth and the hydrologic cycle.

Effect of freeze-thaw cycling on grain size of biochar

PubMed Central

Dugan, Brandon; Masiello, Caroline A.; Wahab, Leila M.; Gonnermann, Helge M.; Nittrouer, Jeffrey A.

2018-01-01

Biochar may improve soil hydrology by altering soil porosity, density, hydraulic conductivity, and water-holding capacity. These properties are associated with the grain size distributions of both soil and biochar, and therefore may change as biochar weathers. Here we report how freeze-thaw (F-T) cycling impacts the grain size of pine, mesquite, miscanthus, and sewage waste biochars under two drainage conditions: undrained (all biochars) and a gravity-drained experiment (mesquite biochar only). In the undrained experiment plant biochars showed a decrease in median grain size and a change in grain-size distribution consistent with the flaking off of thin layers from the biochar surface. Biochar grain size distribution changed from unimodal to bimodal, with lower peaks and wider distributions. For plant biochars the median grain size decreased by up to 45.8% and the grain aspect ratio increased by up to 22.4% after 20 F-T cycles. F-T cycling did not change the grain size or aspect ratio of sewage waste biochar. We also observed changes in the skeletal density of biochars (maximum increase of 1.3%), envelope density (maximum decrease of 12.2%), and intraporosity (porosity inside particles, maximum increase of 3.2%). In the drained experiment, mesquite biochar exhibited a decrease of median grain size (up to 4.2%) and no change of aspect ratio after 10 F-T cycles. We also document a positive relationship between grain size decrease and initial water content, suggesting that, biochar properties that increase water content, like high intraporosity and pore connectivity large intrapores, and hydrophilicity, combined with undrained conditions and frequent F-T cycles may increase biochar breakdown. The observed changes in biochar particle size and shape can be expected to alter hydrologic properties, and thus may impact both plant growth and the hydrologic cycle. PMID:29329343

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.

Nonideal detonation regimes in low density explosives

NASA Astrophysics Data System (ADS)

Ershov, A. P.; Kashkarov, A. O.; Pruuel, E. R.; Satonkina, N. P.; Sil'vestrov, V. V.; Yunoshev, A. S.; Plastinin, A. V.

2016-02-01

Measurements using Velocity Interferometer System for Any Reflector (VISAR) were performed for three high explosives at densities slightly above the natural loose-packed densities. The velocity histories at the explosive/window interface demonstrate that the grain size of the explosives plays an important role. Fine-grained materials produced rather smooth records with reduced von Neumann spike amplitudes. For commercial coarse-grained specimens, the chemical spike (if detectable) was more pronounced. This difference can be explained as a manifestation of partial burn up. In fine-grained explosives, which are more sensitive, the reaction can proceed partly within the compression front, which leads to a lower initial shock amplitude. The reaction zone was shorter in fine-grained materials because of higher density of hot spots. The noise level was generally higher for the coarse-grained explosives, which is a natural stochastic effect of the highly non-uniform flow of the heterogeneous medium. These results correlate with our previous data of electrical conductivity diagnostics. Instead of the classical Zel'dovich-von Neumann-Döring profiles, violent oscillations around the Chapman-Jouguet level were observed in about half of the shots using coarse-grained materials. We suggest that these unusual records may point to a different detonation wave propagation mechanism.

Trajectories and distribution of interstellar dust grains in the heliosphere

DOE PAGES

Slavin, Jonathan D.; Frisch, Priscilla C.; Müller, Hans-Reinhard; ...

2012-11-01

The solar wind carves a bubble in the surrounding interstellar medium (ISM) known as the heliosphere. Charged interstellar dust grains (ISDG) encountering the heliosphere may be diverted around the heliopause or penetrate it depending on their charge-to-mass ratio. Here, we present new calculations of trajectories of ISDG in the heliosphere, and the dust density distributions that result. We include up-to-date grain charging calculations using a realistic UV radiation field and full three-dimensional magnetohydrodynamic fluid + kinetic models for the heliosphere. Models with two different (constant) polarities for the solar wind magnetic field (SWMF) are used, with the grain trajectory calculationsmore » done separately for each polarity. Small grains a gr ≲ 0.01 μm are completely excluded from the inner heliosphere. Large grains, a gr ≳ 1.0 μm, pass into the inner solar system and are concentrated near the Sun by its gravity. Trajectories of intermediate size grains depend strongly on the SWMF polarity. When the field has magnetic north pointing to ecliptic north, the field de-focuses the grains resulting in low densities in the inner heliosphere, while for the opposite polarity the dust is focused near the Sun. The ISDG density outside the heliosphere inferred from applying the model results to in situ dust measurements is inconsistent with local ISM depletion data for both SWMF polarities but is bracketed by them. Our result points to the need to include the time variation in the SWMF polarity during grain propagation. This provides valuable insights for interpretation of the in situ dust observations from Ulysses.« less

Grain boundaries in bcc-Fe: a density-functional theory and tight-binding study

NASA Astrophysics Data System (ADS)

Wang, Jingliang; Madsen, Georg K. H.; Drautz, Ralf

2018-02-01

Grain boundaries (GBs) have a significant influence on material properties. In the present paper, we calculate the energies of eleven low-Σ ({{Σ }}≤slant 13) symmetrical tilt GBs and two twist GBs in ferromagnetic bcc iron using first-principles density functional theory (DFT) calculations. The results demonstrate the importance of a sufficient sampling of initial rigid body translations in all three directions. We show that the relative GB energies can be explained by the miscoordination of atoms at the GB region. While the main features of the studied GB structures were captured by previous empirical interatomic potential calculations, it is shown that the absolute values of GB energies calculated were substantially underestimated. Based on DFT-calculated GB structures and energies, we construct a new d-band orthogonal tight-binding (TB) model for bcc iron. The TB model is validated by its predictive power on all the studied GBs. We apply the TB model to block boundaries in lath martensite and demonstrate that the experimentally observed GB character distribution can be explained from the viewpoint of interface energy.

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

Electrical resistivity of ultrafine-grained copper with nanoscale growth twins

NASA Astrophysics Data System (ADS)

Chen, X. H.; Lu, L.; Lu, K.

2007-10-01

We have investigated electrical resistivities of high-purity ultrafine-grained Cu containing different concentrations of nanoscale growth twins, but having identical grain size. The samples were synthesized by pulsed electrodeposition, wherein the density of twins was varied systematically by adjusting the processing parameters. The electrical resistivity of the Cu specimen with a twin spacing of 15nm at room temperature (RT) is 1.75μΩcm (the conductivity is about 97% IACS), which is comparable to that of coarse-grained (CG) pure Cu specimen. A reduction in twin density for the same grain size (with twin lamellar spacings of 35 and 90nm, respectively) results in an increment in electrical resistivity from 1.75to2.12μΩcm. However, the temperature coefficient of resistivity at RT for these Cu specimens is insensitive to the twin spacing and shows a consistent value of ˜3.78×10-3/K, which is slightly smaller than that of CG Cu (3.98×10-3/K). The increased electrical resistivities of the Cu samples were ascribed dominantly to the intrinsic grain boundary (GB) scattering, while the GB defects and GB energy would decrease with increasing twin density. Transmission electron microscope observations revealed the GB configuration difference from the Cu samples with various twin densities. Plastic deformation would induce an apparent increase in the resistivity. The higher of the twin density, the higher increment of RT resistivity was detected in the Cu specimens subjected to 40% rolling strain. Both the deviated twin boundaries and strained GBs may give rise to an increase in the resistivity.

Size and density distribution of very small dust grains in the Barnard 5 cloud

NASA Technical Reports Server (NTRS)

Lis, Dariusz C.; Leung, Chun Ming

1991-01-01

The effects of the temperature fluctuations in small graphite grains on the energy spectrum and the IR surface brightness of an isolated dust cloud heated externally by the interstellar radiation field were investigated using a series of models based on a radiation transport computer code. This code treats self-consistently the thermal coupling between the transient heating of very small dust grains and the equilibrium heating of conventional large grains. The model results were compared with the IRAS observations of the Barnard 5 (B5) cloud, showing that the 25-micron emission of the cloud must be produced by small grains with a 6-10 A radius, which also contribute about 50 percent to the observed 12-micron emission. The remaining 12 micron flux may be produced by the polycyclic aromatic hydrocarbons. The 60-and 100-micron radiation is dominated by emission from large grains heated under equilibrium conditions.

Dust grains in the coma of 67P/Churyumov-Gerasimenko - link with surface properties and cometary activity

NASA Astrophysics Data System (ADS)

Capria, M. T.; Ivanovski, S.; Zakharov, W.; Capaccioni, F.; Filacchione, G.; De Sanctis, M. C.; Rotundi, A.; Della Corte, V.; Longobardo, A.; Palomba, E.; Colangeli, L.; Bockelee-Morvan, D.; Erard, S.; Leyrat, C.

2016-11-01

The imaging spectrometer VIRTIS and the dust analyzer GIADA, onboard Rosetta, made an extensive observation of the dust particles in the coma of the comet 67P/Churyumov-Gerasimenko. From the analysis of GIADA data, two different kind of particles have been revealed, compact and fluffy with different compositions and dynamical properties. Compact particles are characterized by densities of about 10E3 kg/m3, while fluffy particles have an almost fractal nature, with densities less than 1 kg/m3. In this work we present the initial results of a model linking the dust flux distribution, as obtained from a theoretical thermal nucleus model, with a model describing the dynamics of aspherical grains in the coma. The results are discussed in the context of the latest observations from VIRTIS and GIADA instruments. The 2D nucleus thermal model, when applied to the real shape of the comet, provides the size distribution and physical properties of the emitted grains at different times and location on the surface. The thermal model can simulate grains of various size distribution, composition and physical properties. This information is used as an input for the dust dynamical model that follows the emitted particles in the coma. The main source of heating is the solar illumination. In the dust dynamical model, the grain trajectory of emitted particles remains in a plane perpendicular to the rotational axis and the direction of illumination is taken to be in the same plane (i.e. does not cause transversal forces). The dust particles are assumed to be isothermal convex bodies and temperature changes only induce modest changes in the aerodynamic force (twice higher temperature changes aerodynamic force less than 30%). This study reviews the theoretical values at which temperature difference starts to play a role on the dynamics. We discuss to what extent the particle's temperature affects the terminal velocities of the dust grains in the 67P coma in dependence on their mass and

Dust grains in the coma of 67P/Churyumov-Gerasimenko - link with surface properties and cometary activity

NASA Astrophysics Data System (ADS)

Capria, Maria Teresa; Ivanovski, Stavro; Zakharov, Vladimir; Capaccioni, Fabrizio; Filacchione, Gianrico; De Sanctis, Maria Cristina; rotundi, alessandra; della corte, vincenzo; Longobardo, Andrea; Palomba, Ernesto; colangeli, luigi; Bockelee-Morvan, Dominique; Érard, Stéphane; Leyrat, Cedric; VIRTIS, GIADA

2016-10-01

The imaging spectrometer VIRTIS and the dust analyzer GIADA, onboard Rosetta, made an extensive observation of the dust particles in the coma of the comet 67P/Churyumov-Gerasimenko. From the analysis of GIADA data, two different kind of particles have been revealed, compact and fluffy with different compositions and dynamical properties. Compact particles are characterized by densities of about 103 kg/m3, while fluffy particles have an almost fractal nature, with densities less than 1 kg/m3.In this work we present the initial results of a model linking the dust flux distribution, as obtained from a theoretical thermal nucleus model, with a model describing the dynamics of aspherical grains in the coma. The results are discussed in the context of the latest observations from VIRTIS and GIADA instruments.The 2D nucleus thermal model, when applied to the real shape of the comet, provides the size distribution and physical properties of the emitted grains at different times and location on the surface. The thermal model can simulate grains of various size distribution, composition and physical properties. This information is used as an input for the dust dynamical model that follows the emitted particles in the coma. The main source of heating is the solar illumination. In the dust dynamical model, the grain trajectory of emitted particles remains in a plane perpendicular to the rotational axis and the direction of illumination is taken to be in the same plane (i.e. does not cause transversal forces). The dust particles are assumed to be isothermal convex bodies and temperature changes only induce modest changes in the aerodynamic force (twice higher temperature changes aerodynamic force less than ~30%). This study reviews the theoretical values at which temperature difference starts to play a role on the dynamics. We discuss to what extent the particle's temperature affects the terminal velocities of the dust grains in the 67P coma in dependence on their mass and

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.

Total phenolic content and antioxidant activities of pomegranate juice and whey based novel beverage fermented by kefir grains.

PubMed

Sabokbar, Nayereh; Khodaiyan, Faramarz

2016-01-01

Mixture of pomegranate juice and whey was evaluated as a potential substrate for production of a novel beverage by kefir grains. The effects of two different variables, fermentation, temperature (19 and 25 °C) and kefir grain amount (5 %w/v and 8 %w/v), on total phenolic content (TPC) and antioxidant activities of beverage were examined during a fermentation time of 32 h. TPC and antioxidant activities including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, reducing power, inhibition effect upon linoleic acid autoxidation and inhibition effect upon ascorbate autoxidation increased significantly (p < 0.05) during fermentation, but metal chelating effect showed no significant difference. The highest increases were observed when the temperature of 25 °C and kefir grain amount of 8 %w/v were applied. Results proved antioxidant activities of beverages were desirable and fermentation by kefir grains has the ability to enhance these antioxidant activities, as compared with unfermented beverage. Also pomegranate juice and whey were suitable media for producing a novel dairy-juice beverage.

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.

Areal density optimizations for heat-assisted magnetic recording of high-density media

NASA Astrophysics Data System (ADS)

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

2016-06-01

Heat-assisted magnetic recording (HAMR) is hoped to be the future recording technique for high-density storage devices. Nevertheless, there exist several realization strategies. With a coarse-grained Landau-Lifshitz-Bloch model, we investigate in detail the benefits and disadvantages of a continuous and pulsed laser spot recording of shingled and conventional bit-patterned media. Additionally, we compare single-phase grains and bits having a bilayer structure with graded Curie temperature, consisting of a hard magnetic layer with high TC and a soft magnetic one with low TC, respectively. To describe the whole write process as realistically as possible, a distribution of the grain sizes and Curie temperatures, a displacement jitter of the head, and the bit positions are considered. For all these cases, we calculate bit error rates of various grain patterns, temperatures, and write head positions to optimize the achievable areal storage density. Within our analysis, shingled HAMR with a continuous laser pulse moving over the medium reaches the best results and thus has the highest potential to become the next-generation storage device.

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.

Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

NASA Technical Reports Server (NTRS)

Ruggles, Timothy; Hochhalter, Jacob; Homer, Eric

2016-01-01

Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction.

Examining the influence of grain size on radiation tolerance in the nanocrystalline regime

DOE PAGES

Barr, Christopher M.; Li, Nan; Boyce, Brad L.; ...

2018-05-01

Here, nanocrystalline materials have been proposed as superior radiation tolerant materials in comparison to coarse grain counterparts. However, there is still a limited understanding whether a particular nanocrystalline grain size is required to obtain significant improvements in key deleterious effects resulting from energetic irradiation. This work employs the use of in-situ heavy ion irradiation transmission electron microscopy experiments coupled with quantitative defect characterization and precession electron diffraction to explore the sensitivity of defect size and density within the nanocrystalline regime in platinum. Under the explored experimental conditions, no significant change in either the defect size or density between grain sizesmore » of 20 and 100 nm was observed. Furthermore, the in-situ transmission electron microscopy irradiations illustrate stable sessile defect clusters of 1–3 nm adjacent to most grain boundaries, which are traditionally treated as strong defect sinks. The stability of these sessile defects observed in-situ in small, 20–40 nm, grains is the proposed primary mechanism for a lack of defect density trends. Lastly, this scaling breakdown in radiation improvement with decreasing grain size has practical importance on nanoscale grain boundary engineering approaches for proposed radiation tolerant alloys.« less

Examining the influence of grain size on radiation tolerance in the nanocrystalline regime

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

Barr, Christopher M.; Li, Nan; Boyce, Brad L.

Here, nanocrystalline materials have been proposed as superior radiation tolerant materials in comparison to coarse grain counterparts. However, there is still a limited understanding whether a particular nanocrystalline grain size is required to obtain significant improvements in key deleterious effects resulting from energetic irradiation. This work employs the use of in-situ heavy ion irradiation transmission electron microscopy experiments coupled with quantitative defect characterization and precession electron diffraction to explore the sensitivity of defect size and density within the nanocrystalline regime in platinum. Under the explored experimental conditions, no significant change in either the defect size or density between grain sizesmore » of 20 and 100 nm was observed. Furthermore, the in-situ transmission electron microscopy irradiations illustrate stable sessile defect clusters of 1–3 nm adjacent to most grain boundaries, which are traditionally treated as strong defect sinks. The stability of these sessile defects observed in-situ in small, 20–40 nm, grains is the proposed primary mechanism for a lack of defect density trends. Lastly, this scaling breakdown in radiation improvement with decreasing grain size has practical importance on nanoscale grain boundary engineering approaches for proposed radiation tolerant alloys.« less

Coagulation of grains in static and collapsing protostellar clouds

NASA Technical Reports Server (NTRS)

Weidenschilling, S. J.; Ruzmaikina, T. V.

1994-01-01

We simulate collisional evolution of grains in dense turbulent molecular cloud cores (or Bok globules) in static equilibrium and free-fall collapse, assuming spherical symmetry. Relative velocities are due to thermal motions, differential settling, and turbulence, with the latter dominant for sonic turbulence with an assumed Kolmogorov spectrum. Realistic criteria are used to determine outcomes of collisions (coagulation vs. destruction) as functions of particle size and velocity. Results are presented for a variety of cloud parameters (radial density profile, turbulent velocity) and particle properties (density, impact strength). Results are sensitive to the assumed mechanical properties (density and impact strength) of grain aggregates. Particle growth is enhanced if aggregates have low density or fractal structures. On a timescale of a few Myr, an initial population of 0.1 micrometers grains may produce dense compact particles approximately 1 micrometer in size, or fluffy aggregates approximately 100 micrometers. For impact strengths less than or equal to 10(exp 6) ergs/g, a steady state is reached between coagulation of small grains and collisional disruption of larger aggregates. Formation of macroscopic aggregates requires high mechanical strengths and low aggregate densities. We assume sonic turbulence during collapse, with varied eddy size scales determining the dissipation rate or turbulence strength. The degree of collisional evolution during collapse is sensitive to the assumed small-scale structure (inner sc ale) of the turbulence. Weak turbulence results in few collisions and preserves the precollapse particle size distribution with little change. Strong turbulence tends to produce net destruction, rather than particle growth, during infall, unless inpact strengths are greater than 10(exp 6)ergs/g.

Physical Activity and Bone Density in Women

NASA Technical Reports Server (NTRS)

Bowley, Susan M.; Whalen, R. T.

2000-01-01

A mathematical model of bone density regulation as a function of the daily tissue "effective" stress has been derived. Using the model, the influence of daily activity in the form of a daily loading history has been related to bone density of the calcaneus. The theory incorporates a stress exponent m to account for differences in the importance of magnitude and number of load cycles experienced during daily activity. We have derived a parameter from the model, the "Bone Density Index" (BDI). We have developed a method of collecting daily habitual loading histories using an insole force sensor interfaced to a portable digital data logger carried in a fanny pack. Our goal for this study was to determine a stress exponent, m, relating GRFz history to Calcaneal Bone Mineral Density (CBMD).

Influence of Temperature and Water Activity on Deleterious Fungi and Mycotoxin Production during Grain Storage

PubMed Central

Mannaa, Mohamed

2017-01-01

Cereal grains are the most important food source for humans. As the global population continues to grow exponentially, the need for the enhanced yield and minimal loss of agricultural crops, mainly cereal grains, is increasing. In general, harvested grains are stored for specific time periods to guarantee their continuous supply throughout the year. During storage, economic losses due to reduction in quality and quantity of grains can become very significant. Grain loss is usually the result of its deterioration due to fungal contamination that can occur from preharvest to postharvest stages. The deleterious fungi can be classified based on predominance at different stages of crop growth and harvest that are affected by environmental factors such as water activity (aw) and eco-physiological requirements. These fungi include species such as those belonging to the genera Aspergillus and Penicillium that can produce mycotoxins harmful to animals and humans. The grain type and condition, environment, and biological factors can also influence the occurrence and predominance of mycotoxigenic fungi in stored grains. The main environmental factors influencing grain fungi and mycotoxins are temperature and aw. This review discusses the effects of temperature and aw on fungal growth and mycotoxin production in stored grains. The focus is on the occurrence and optimum and minimum growth requirements for grain fungi and mycotoxin production. The environmental influence on aflatoxin production and hypothesized mechanisms of its molecular suppression in response to environmental changes are also discussed. In addition, the use of controlled or modified atmosphere as an environmentally safe alternative to harmful agricultural chemicals is discussed and recommended future research issues are highlighted. PMID:29371792

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.

Determination of grain size distribution function using two-dimensional Fourier transforms of tone pulse encoded images

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1986-01-01

Microstructural images may be tone pulse encoded and subsequently Fourier transformed to determine the two-dimensional density of frequency components. A theory is developed relating the density of frequency components to the density of length components. The density of length components corresponds directly to the actual grain size distribution function from which the mean grain shape, size, and orientation can be obtained.

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

A fully-active fine-grained detector with three readout views

NASA Astrophysics Data System (ADS)

Blondel, A.; Cadoux, F.; Fedotov, S.; Khabibullin, M.; Khotjantsev, A.; Korzenev, A.; Kostin, A.; Kudenko, Y.; Longhin, A.; Mefodiev, A.; Mermod, P.; Mineev, O.; Noah, E.; Sgalaberna, D.; Smirnov, A.; Yershov, N.

2018-02-01

This paper describes a novel idea of a fine-grained fully-active plastic scintillator detector made of many optically independent 1×1×1 cm3 cubes with readout on three orthogonal projections by wavelength shifting fibers. The original purpose of this detector is to serve as an active neutrino target for the detection, measurement and identification of the final state particles down to a few tenths MeV kinetic energies. The three readout views as well as the fine granularity ensure powerful localization and measurement of the deposited energy combined with good timing properties and isotropic acceptance. The possible application as a new active target for the T2K near detector, initial simulation studies and R&D test results are reported.

Application of paclobutrazol affect maize grain yield by regulating root morphological and physiological characteristics under a semi-arid region.

PubMed

Kamran, Muhammad; Wennan, Su; Ahmad, Irshad; Xiangping, Meng; Wenwen, Cui; Xudong, Zhang; Siwei, Mou; Khan, Aaqil; Qingfang, Han; Tiening, Liu

2018-03-19

A field experiment was conducted to investigate the effects of paclobutrazol on ear characteristics and grain yield by regulating root growth and root-bleeding sap of maize crop. Seed-soaking at rate of 0 (CK1), 200 (S1), 300 (S2), and 400 (S3) mg L -1 , and seed-dressing at rate of 0 (CK2), 1.5 (D1), 2.5 (D2), and 3.5 (D3) g kg -1 were used. Our results showed that paclobutrazol improved the ear characteristics and grain yield, and were consistently higher than control during 2015-2016. The average grain yield of S1, S2 and S3 were 18.9%, 61.3%, and 45.9% higher, while for D1, D2 and D3 were 20.2%, 33.3%, and 45.2%, compared to CK, respectively. Moreover, paclobutrazol-treated maize had improved root-length density (RLD), root-surface area density (RSD) and root-weight density (RWD) at most of the soil profiles (0-70 cm for seed-soaking, 0-60 cm for seed-dressing) and was attributed to enhancing the grain yield. In addition, root-activity, root-bleeding sap, root dry weight, diameter and root/shoot ratio increased by paclobutrazol, with highest values achieved in S2 and D3 treatments, across the whole growth stages in 2015-2016. Our results suggested that paclobutrazol could efficiently be used to enhance root-physiological and morphological characteristics, resulting in higher grain yield.

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

Constraints on Grain Formation Around Carbon Stars from Laboratory Studies of Presolar Graphite

NASA Technical Reports Server (NTRS)

Bernatowicz, T. J.; Akande, O. W.; Croat, T. K.; Cowsik, R.

2005-01-01

We report the results of an investigation into the physical conditions in the mass outflows of asymptotic giant branch (AGB) carbon stars that are required for the formation of micron-sized presolar graphite grains, either with or without internal crystals of titanium carbide (TiC). In addition to providing detailed information about stellar nucleosynthesis, the structure and composition of presolar grains give unique information about the conditions of grain formation. In the present work we use laboratory observations of presolar graphite to gain insight into the physical conditions in circumstellar outflows from carbon AGB stars. The periodic pulsation of AGB stars enhances the gas density through shocks in the stellar atmosphere above the photosphere, promoting the condensation of dust grains. Copious mass outflow occurs largely because grains are coupled to the radiation field of the star, which accelerates them by radiation pressure; momentum is in turn transferred to gas molecules by collisions with grains. The dust/gas mixture is effectively a two-component fluid whose motion depends on atmospheric structure and which, in turn, influences that structure. In particular, the radiation pressure on the grains determines the velocity field of the outflow and thus the density distribution, while the density distribution itself determines the conditions of radiative transfer within the outflow and thus the effective radiation pressure.

Stored grain pack factors for wheat: comparison of three methods to field measurements

USDA-ARS?s Scientific Manuscript database

Storing grain in bulk storage units results in grain packing from overbearing pressure, which increases grain bulk density and storage-unit capacity. This study compared pack factors of hard red winter (HRW) wheat in vertical storage bins using different methods: the existing packing model (WPACKING...

An Analysis of Hole Trapping at Grain Boundary or Poly-Si Floating-Body MOSFET.

PubMed

Jang, Taejin; Baek, Myung-Hyun; Kim, Hyungjin; Park, Byung-Gook

2018-09-01

In this paper, we demonstrate the characteristics of the floating body effect of poly-silicon with grain boundary by SENTAURUS™ TCAD simulation. As drain voltage increases, impact ionization occurs at the drain-channel junction. And these holes created by impact ionization are deposited on the bottom of the body to change the threshold voltage. This feature, the kink effect, is also observed in fully depleted silicon on insulator because grain boundary of the poly-silicon serve as a storage to trap the holes. We simulate the transfer curve depending on the density and position of the grain boundary. The trap density of the grain boundary affects the device characteristics significantly. However similar properties appear except where the grain boundary is located on the drain side.

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.

A fruit, milk and whole grain dietary pattern is positively associated with bone mineral density in Korean healthy adults.

PubMed

Shin, S; Sung, J; Joung, H

2015-04-01

Osteoporosis is a major health problem that will grow in burden with ageing of the global population. Modifiable risk factors for osteoporosis, including diet, have significant implications for disease prevention. We examined associations between dietary patterns and bone mineral density (BMD) in a Korean adult population. In total, 1828 individuals from the Healthy Twin Cohort were included as subjects. Information on general characteristics, lifestyles and health status was obtained through a health examination, and BMD was assessed using DEXA. Dietary intake was assessed using a 3-day food record, and dietary patterns were examined by factor analysis. Associations between dietary patterns and BMD were examined using mixed linear regression, adjusting for family and twin structure as well as other potential risk factors for bone health. Four dietary patterns were identified (Rice and kimchi; eggs, meat and flour; Fruit, milk and whole grains; and Fast food and soda). The 'Fruit, milk and whole grains' pattern was associated with a reduced risk of having low BMD in men (odds ratio (OR)=0.38; 95% confidence interval (CI)=0.22-0.67) and women (OR=0.45; 95% CI=0.28-0.72) and was positively associated with BMD at multiple sites. The 'rice and kimchi' pattern had a positive association with only whole-arm BMD in men and women. Our results suggest that a dietary pattern with high intake of dairy products, fruits and whole grains may contribute positively to bone health in a Korean adult population, and dietary pattern-based strategies could have potential in promoting bone health.

In situ synchrotron study of electromigration induced grain rotations in Sn solder joints

NASA Astrophysics Data System (ADS)

Shen, Hao; Zhu, Wenxin; Li, Yao; Tamura, Nobumichi; Chen, Kai

2016-04-01

Here we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction. With this technique, crystal orientation evolution is monitored at intragranular levels with high spatial and angular resolution. During the entire experiment, no crystal growth is detected, and rigid grain rotation is observed only in the two grains within the current crowding region, where high density and divergence of electric current occur. Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in the grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains. A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.

In situ synchrotron study of electromigration induced grain rotations in Sn solder joints

DOE PAGES

Shen, Hao; Zhu, Wenxin; Li, Yao; ...

2016-04-18

In this paper we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction. With this technique, crystal orientation evolution is monitored at intragranular levels with high spatial and angular resolution. During the entire experiment, no crystal growth is detected, and rigid grain rotation is observed only in the two grains within the current crowding region, where high density and divergence of electric current occur. Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in themore » grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains. A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.« less

Comparison between measured and computed magnetic flux density distribution of simulated transformer core joints assembled from grain-oriented and non-oriented electrical steel

NASA Astrophysics Data System (ADS)

Shahrouzi, Hamid; Moses, Anthony J.; Anderson, Philip I.; Li, Guobao; Hu, Zhuochao

2018-04-01

The flux distribution in an overlapped linear joint constructed in the central region of an Epstein Square was studied experimentally and results compared with those obtained using a computational magnetic field solver. High permeability grain-oriented (GO) and low permeability non-oriented (NO) electrical steels were compared at a nominal core flux density of 1.60 T at 50 Hz. It was found that the experimental results only agreed well at flux densities at which the reluctance of different paths of the flux are similar. Also it was revealed that the flux becomes more uniform when the working point of the electrical steel is close to the knee point of the B-H curve of the steel.

High capacitance of coarse-grained carbide derived carbon electrodes

NASA Astrophysics Data System (ADS)

Dyatkin, Boris; Gogotsi, Oleksiy; Malinovskiy, Bohdan; Zozulya, Yuliya; Simon, Patrice; Gogotsi, Yury

2016-02-01

We report exceptional electrochemical properties of supercapacitor electrodes composed of large, granular carbide-derived carbon (CDC) particles. Using a titanium carbide (TiC) precursor, we synthesized 70-250 μm sized particles with high surface area and a narrow pore size distribution. Electrochemical cycling of these coarse-grained powders defied conventional wisdom that a small particle size is strictly required for supercapacitor electrodes and allowed high charge storage densities, rapid transport, and good rate handling ability. The material showcased capacitance above 100 F g-1 at sweep rates as high as 250 mV s-1 in organic electrolyte. 250-1000 micron thick dense CDC films with up to 80 mg cm-2 loading showed superior areal capacitances. The material significantly outperformed its activated carbon counterpart in organic electrolytes and ionic liquids. Furthermore, large internal/external surface ratio of coarse-grained carbons allowed the resulting electrodes to maintain high electrochemical stability up to 3.1 V in ionic liquid electrolyte. In addition to presenting novel insights into the electrosorption process, these coarse-grained carbons offer a pathway to low-cost, high-performance implementation of supercapacitors in automotive and grid-storage applications.

Supplying materials needed for grain growth characterizations of nano-grained UO 2

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

Mo, Kun; Miao, Yinbin; Yun, Di

2015-09-30

This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructuremore » based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize our preliminary synchrotron radiation experiments at APS to determine the grain size of nanograin UO 2. The methodology and experimental setup developed in this experiment can directly apply to the proposed in-situ grain growth measurements. The investigation of the grain growth kinetics was conducted based on isothermal annealing and grain growth characterization as functions of duration and temperature. The kinetic parameters such as activation energy for grain growth for UO 2 with different stoichiometry are obtained and compared with molecular dynamics (MD) simulations.« less

Density of steam-flaked sorghum grain, roughage level, and feeding regimen for feedlot steers.

PubMed

Xiong, Y; Bartle, S J; Preston, R L

1991-04-01

Two hundred fifty-two steers (366 kg) were assigned to a 3 x 2 x 2 factorial arrangement of three densities of steam-flaked sorghum grain (bulk [flake] density of 437, 360, and 283 g/liter, B34, B28, and B22, respectively), two roughage levels (9 [R9] and 18% [R18]) and two feeding strategies (ad libitum [AD] or multiple of maintenance [MM], 2.3, 2.5, and 2.7 MM for wk 1, 2, and 3, and 2.9 MM thereafter). Steers fed R18-AD gained faster than steers fed R18-MM (1.59 vs 1.52 kg/d, P = .10); for R9 diets, no difference (P greater than .25) was found between steers fed AD and MM (interaction, P = .07). Flake density did not affect ADG (1.53 kg, P greater than .2). Dry matter intake decreased (9.8, 9.3, and 9.0 kg/d, linear, P less than .001) and gain efficiency (G/DMI, kg of gain/100 kg of DMI) increased (15.7, 16.5, and 16.9, linear, P less than .001; quadratic, P = .19) as processing degree increased (B34 to B22). Percentage of choice carcasses for B34 (67.0%) was higher (linear, P = .05) than for B28 (51.9%) and B22 (52.3%). Fecal starch and pH were 10.8, 5.7, and 4.0%, and 6.11, 6.23, and 6.37 for B34, B28, and B22, respectively (linear, P less than .001). The correlation between fecal starch and pH was -.51 (P less than .001, n = 252). Enzymatic glucose release, in vitro 6-h gas production, microbial protein synthesis, and protein degradability were 375, 483, and 559 mg/g; 24.7, 28.2, and 31.1 ml/.2 g; 6.15, 6.88, and 7.84 g/100g; and 61.4, 56.6, and 42.2% for B34, B28, and B22, respectively (linear, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Shock fabrics in fine-grained micrometeorites

NASA Astrophysics Data System (ADS)

Suttle, M. D.; Genge, M. J.; Russell, S. S.

2017-10-01

The orientations of dehydration cracks and fracture networks in fine-grained, unmelted micrometeorites were analyzed using rose diagrams and entropy calculations. As cracks exploit pre-existing anisotropies, analysis of their orientation provides a mechanism with which to study the subtle petrofabrics preserved within fine-grained and amorphous materials. Both uniaxial and biaxial fabrics are discovered, often with a relatively wide spread in orientations (40°-60°). Brittle deformation cataclasis and rotated olivine grains are reported from a single micrometeorite. This paper provides the first evidence for impact-induced shock deformation in fine-grained micrometeorites. The presence of pervasive, low-grade shock features in CM chondrites and CM-like dust, anomalously low-density measurements for C-type asteroids, and impact experiments which suggest CM chondrites are highly prone to disruption all imply that CM parent bodies are unlikely to have remained intact and instead exist as a collection of loosely aggregated rubble-pile asteroids, composed of primitive shocked clasts.

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.

Explosive desorption of icy grain mantles in dense clouds

NASA Technical Reports Server (NTRS)

Schutte, W. A.; Greenberg, J. M.

1991-01-01

The cycling of the condensible material in dense clouds between the gas phase and the icy grain mantles is investigated. In the model studied, desorption of the ice occurs due to grain mantle explosions when photochemically stored energy is released after transient heating by a cosmic ray particle. It is shown that, depending on the grain size distribution in dense clouds, explosive desorption can maintain up to about eight percent of the carbon in the form of CO in the gas phase at typical cloud densities.

High-Density Amorphous Ice, the Frost on Interstellar Grains

NASA Technical Reports Server (NTRS)

Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

1995-01-01

Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

Whole grains, refined grains and fortified refined grains: What's the difference?

PubMed

Slavin, J L

2000-09-01

Dietary guidance universally supports the importance of grains in the diet. The United States Department of Agriculture pyramid suggests that Americans consume from six to 11 servings of grains per day, with three of these servings being whole grain products. Whole grain contains the bran, germ and endosperm, while refined grain includes only endosperm. Both refined and whole grains can be fortified with nutrients to improve the nutrient profile of the product. Most grains consumed in developed countries are subjected to some type of processing to optimize flavor and provide shelf-stable products. Grains provide important sources of dietary fibre, plant protein, phytochemicals and needed vitamins and minerals. Additionally, in the United States grains have been chosen as the best vehicle to fortify our diets with vitamins and minerals that are typically in short supply. These nutrients include iron, thiamin, niacin, riboflavin and, more recently, folic acid and calcium. Grains contain antioxidants, including vitamins, trace minerals and non-nutrients such as phenolic acids, lignans and phytic acid, which are thought to protect against cardiovascular disease and cancer. Additionally, grains are our most dependable source of phytoestrogens, plant compounds known to protect against cancers such as breast and prostate. Grains are rich sources of oligosaccharides and resistant starch, carbohydrates that function like dietary fibre and enhance the intestinal environment and help improve immune function. Epidemiological studies find that whole grains are more protective than refined grains in the prevention of chronic disease, although instruments to define intake of refined, whole and fortified grains are limited. Nutritional guidance should support whole grain products over refined, with fortification of nutrients improving the nutrient profile of both refined and whole grain products.

OsMAPK6, a mitogen-activated protein kinase, influences rice grain size and biomass production.

PubMed

Liu, Shuying; Hua, Lei; Dong, Sujun; Chen, Hongqi; Zhu, Xudong; Jiang, Jun'e; Zhang, Fang; Li, Yunhai; Fang, Xiaohua; Chen, Fan

2015-11-01

Grain size is an important agronomic trait in determining grain yield. However, the molecular mechanisms that determine the final grain size are not well understood. Here, we report the functional analysis of a rice (Oryza sativa L.) mutant, dwarf and small grain1 (dsg1), which displays pleiotropic phenotypes, including small grains, dwarfism and erect leaves. Cytological observations revealed that the small grain and dwarfism of dsg1 were mainly caused by the inhibition of cell proliferation. Map-based cloning revealed that DSG1 encoded a mitogen-activated protein kinase (MAPK), OsMAPK6. OsMAPK6 was mainly located in the nucleus and cytoplasm, and was ubiquitously distributed in various organs, predominately in spikelets and spikelet hulls, consistent with its role in grain size and biomass production. As a functional kinase, OsMAPK6 interacts strongly with OsMKK4, indicating that OsMKK4 is likely to be the upstream MAPK kinase of OsMAPK6 in rice. In addition, hormone sensitivity tests indicated that the dsg1 mutant was less sensitive to brassinosteroids (BRs). The endogenous BR levels were reduced in dsg1, and the expression of several BR signaling pathway genes and feedback-inhibited genes was altered in the dsg1 mutant, with or without exogenous BRs, indicating that OsMAPK6 may contribute to influence BR homeostasis and signaling. Thus, OsMAPK6, a MAPK, plays a pivotal role in grain size in rice, via cell proliferation, and BR signaling and homeostasis. © 2015 The Authors The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

Nucleotide Polymorphism in the Wheat Transcriptional Activator Spa Influences Its Pattern of Expression and Has Pleiotropic Effects on Grain Protein Composition, Dough Viscoelasticity, and Grain Hardness[W][OA

PubMed Central

Ravel, Catherine; Martre, Pierre; Romeuf, Isabelle; Dardevet, Mireille; El-Malki, Redouane; Bordes, Jacques; Duchateau, Nathalie; Brunel, Dominique; Balfourier, François; Charmet, Gilles

2009-01-01

Storage protein activator (SPA) is a key regulator of the transcription of wheat (Triticum aestivum) grain storage protein genes and belongs to the Opaque2 transcription factor subfamily. We analyzed the sequence polymorphism of the three homoeologous Spa genes in hexaploid wheat. The level of polymorphism in these genes was high particularly in the promoter. The deduced protein sequences of each homoeolog and haplotype show greater than 93% identity. Two major haplotypes were studied for each Spa gene. The three Spa homoeologs have similar patterns of expression during grain development, with a peak in expression around 300 degree days after anthesis. On average, Spa-B is 10 and seven times more strongly expressed than Spa-A and Spa-D, respectively. The haplotypes are associated with significant quantitative differences in Spa expression, especially for Spa-A and Spa-D. Significant differences were found in the quantity of total grain nitrogen allocated to the gliadin protein fractions for the Spa-A haplotypes, whereas the synthesis of glutenins is not modified. Genetic association analysis between Spa and dough viscoelasticity revealed that Spa polymorphisms are associated with dough tenacity, extensibility, and strength. Except for Spa-A, these associations can be explained by differences in grain hardness. No association was found between Spa markers and the average single grain dry mass or grain protein concentration. These results demonstrate that in planta Spa is involved in the regulation of grain storage protein synthesis. The associations between Spa and dough viscoelasticity and grain hardness strongly suggest that Spa has complex pleiotropic functions during grain development. PMID:19828671

On the applicability of density dependent effective interactions in cluster-forming systems

NASA Astrophysics Data System (ADS)

Montes-Saralegui, Marta; Kahl, Gerhard; Nikoubashman, Arash

2017-02-01

We systematically studied the validity and transferability of the force-matching algorithm for computing effective pair potentials in a system of dendritic polymers, i.e., a particular class of ultrasoft colloids. We focused on amphiphilic dendrimers, macromolecules which can aggregate into clusters of overlapping particles to minimize the contact area with the surrounding implicit solvent. Simulations were performed for both the monomeric and coarse-grained models in the liquid phase at densities ranging from infinite dilution up to values close to the freezing point. The effective pair potentials for the coarse-grained simulations were computed from the monomeric simulations both in the zero-density limit (Φeff0) and at each investigated finite density (Φeff). Conducting the coarse-grained simulations with Φeff0 at higher densities is not appropriate as they failed at reproducing the structural properties of the monomeric simulations. In contrast, we found excellent agreement between the spatial dendrimer distributions obtained from the coarse-grained simulations with Φeff and the microscopically detailed simulations at low densities, where the macromolecules were distributed homogeneously in the system. However, the reliability of the coarse-grained simulations deteriorated significantly as the density was increased further and the cluster occupation became more polydisperse. Under these conditions, the effective pair potential of the coarse-grained model can no longer be computed by averaging over the whole system, but the local density needs to be taken into account instead.

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.

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.

Barley HvPAPhy_a as transgene provides high and stable phytase activities in mature barley straw and in grains.

PubMed

Holme, Inger Baeksted; Dionisio, Giuseppe; Madsen, Claus Krogh; Brinch-Pedersen, Henrik

2017-04-01

The phytase purple acid phosphatase (HvPAPhy_a) expressed during barley seed development was evaluated as transgene for overexpression in barley. The phytase was expressed constitutively driven by the cauliflower mosaic virus 35S-promoter, and the phytase activity was measured in the mature grains, the green leaves and in the dry mature vegetative plant parts left after harvest of the grains. The T 2 -generation of HvPAPhy_a transformed barley showed phytase activity increases up to 19-fold (29 000 phytase units (FTU) per kg in mature grains). Moreover, also in green leaves and mature dry straw, phytase activities were increased significantly by 110-fold (52 000 FTU/kg) and 57-fold (51 000 FTU/kg), respectively. The HvPAPhy_a-transformed barley plants with high phytase activities possess triple potential utilities for the improvement of phosphate bioavailability. First of all, the utilization of the mature grains as feed to increase the release of bio-available phosphate and minerals bound to the phytate of the grains; secondly, the utilization of the powdered straw either directly or phytase extracted hereof as a supplement to high phytate feed or food; and finally, the use of the stubble to be ploughed into the soil for mobilizing phytate-bound phosphate for plant growth. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Structure-based coarse-graining for inhomogeneous liquid polymer systems.

PubMed

Fukuda, Motoo; Zhang, Hedong; Ishiguro, Takahiro; Fukuzawa, Kenji; Itoh, Shintaro

2013-08-07

The iterative Boltzmann inversion (IBI) method is used to derive interaction potentials for coarse-grained (CG) systems by matching structural properties of a reference atomistic system. However, because it depends on such thermodynamic conditions as density and pressure of the reference system, the derived CG nonbonded potential is probably not applicable to inhomogeneous systems containing different density regimes. In this paper, we propose a structure-based coarse-graining scheme to devise CG nonbonded potentials that are applicable to different density bulk systems and inhomogeneous systems with interfaces. Similar to the IBI, the radial distribution function (RDF) of a reference atomistic bulk system is used for iteratively refining the CG nonbonded potential. In contrast to the IBI, however, our scheme employs an appropriately estimated initial guess and a small amount of refinement to suppress transfer of the many-body interaction effects included in the reference RDF into the CG nonbonded potential. To demonstrate the application of our approach to inhomogeneous systems, we perform coarse-graining for a liquid perfluoropolyether (PFPE) film coated on a carbon surface. The constructed CG PFPE model favorably reproduces structural and density distribution functions, not only for bulk systems, but also at the liquid-vacuum and liquid-solid interfaces, demonstrating that our CG scheme offers an easy and practical way to accurately determine nonbonded potentials for inhomogeneous systems.

Fate of Ice Grains in Saturn's Ionosphere

NASA Astrophysics Data System (ADS)

Hamil, O.; Cravens, T. E.; Reedy, N. L.; Sakai, S.

2018-02-01

It has been proposed that the rings of Saturn can contribute both material (i.e., water) and energy to its upper atmosphere and ionosphere. Ionospheric models require the presence of molecular species such as water that can chemically remove ionospheric protons, which otherwise are associated with electron densities that greatly exceed those from observation. These models adopt topside fluxes of water molecules. Other models have shown that ice grains from Saturn's rings can impact the atmosphere, but the effects of these grains have not been previously studied. In the current paper, we model how ice grains deposit both material and energy in Saturn's upper atmosphere as a function of grain size, initial velocity (at the "top" of the atmosphere, defined at an altitude above the cloud tops of 3,000 km), and incident angle. Typical grain speeds are expected to be roughly 15-25 km/s. Grains with radii on the order of 1-10 nm deposit most of their energy in the altitude range of 1,700-1,900 km, and can vaporize, depending on initial velocity and impact angle, contributing water mass to the upper atmosphere. We show that grains in this radius range do not significantly vaporize in our model at initial velocities lower than about 20 km/s.

Grain growth in U–7Mo alloy: A combined first-principles and phase field study

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

Mei, Zhi-Gang; Liang, Linyun; Kim, Yeon Soo

2016-05-01

Grain size is an important factor in controlling the swelling behavior in irradiated U-Mo dispersion fuels. Increasing the grain size in UeMo fuel particles by heat treatment is believed to delay the fuel swelling at high fission density. In this work, a multiscale simulation approach combining first-principles calculation and phase field modeling is used to investigate the grain growth behavior in U-7Mo alloy. The density functional theory based first-principles calculations were used to predict the material properties of U-7Mo alloy. The obtained grain boundary energies were then adopted as an input parameter for mesoscale phase field simulations. The effects ofmore » annealing temperature, annealing time and initial grain structures of fuel particles on the grain growth in U-7Mo alloy were examined. The predicted grain growth rate compares well with the empirical correlation derived from experiments. (C) 2016 Elsevier B.V. All rights reserved.« less

Coarse-grained density functional theories for metallic alloys: Generalized coherent-potential approximations and charge-excess functional theory

NASA Astrophysics Data System (ADS)

Bruno, Ezio; Mammano, Francesco; Fiorino, Antonino; Morabito, Emanuela V.

2008-04-01

The class of the generalized coherent-potential approximations (GCPAs) to the density functional theory (DFT) is introduced within the multiple scattering theory formalism with the aim of dealing with ordered or disordered metallic alloys. All GCPA theories are based on a common ansatz for the kinetic part of the Hohenberg-Kohn functional and each theory of the class is specified by an external model concerning the potential reconstruction. Most existing DFT implementations of CPA-based theories belong to the GCPA class. The analysis of the formal properties of the density functional defined by GCPA theories shows that it consists of marginally coupled local contributions. Furthermore, it is shown that the GCPA functional does not depend on the details of the charge density and that it can be exactly rewritten as a function of the appropriate charge multipole moments to be associated with each lattice site. A general procedure based on the integration of the qV laws is described that allows for the explicit construction of the same function. The coarse-grained nature of the GCPA density functional implies a great deal of computational advantages and is connected with the O(N) scalability of GCPA algorithms. Moreover, it is shown that a convenient truncated series expansion of the GCPA functional leads to the charge-excess functional (CEF) theory [E. Bruno , Phys. Rev. Lett. 91, 166401 (2003)], which here is offered in a generalized version that includes multipolar interactions. CEF and the GCPA numerical results are compared with status of art linearized augmented plane wave (LAPW) full-potential density functional calculations for 62 bcc- and fcc-based ordered CuZn alloys, in all the range of concentrations. Two facts clearly emerge from these extensive tests. In the first place, the discrepancies between GCPA and CEF results are always within the numerical accuracy of the calculations, both for the site charges and the total energies. In the second place, the

The Gas-Grain Chemistry of Galactic Translucent Clouds

NASA Astrophysics Data System (ADS)

Maffucci, Dominique M.; Herbst, Eric

2016-01-01

We employ a combination of traditional and modified rate equation approaches to simulate the time-dependent gas-grain chemistry that pertains to molecular species observed in absorption in Galactic translucent clouds towards Sgr B2(N). We solve the kinetic rate laws over a range of relevant physical conditions (gas and grain temperatures, particle density, visual extinction, cosmic ray ionization rate) characteristic of translucent clouds by implementing a new grid module that allows for parallelization of the astrochemical simulations. Gas-phase and grain-surface synthetic pathways, chemical timescales, and associated physical sensitivities are discussed for selected classes of species including the cyanopolyynes, complex cyanides, and simple aldehydes.

The effect of grain size on aluminum anodes for Al-air batteries in alkaline electrolytes

NASA Astrophysics Data System (ADS)

Fan, Liang; Lu, Huimin

2015-06-01

Aluminum is an ideal material for metallic fuel cells. In this research, different grain sizes of aluminum anodes are prepared by equal channel angular pressing (ECAP) at room temperature. Microstructure of the anodes is examined by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Hydrogen corrosion rates of the Al anodes in 4 mol L-1 NaOH are determined by hydrogen collection method. The electrochemical properties of the aluminum anodes are investigated in the same electrolyte using electrochemical impedance spectroscopy (EIS) and polarization curves. Battery performance is also tested by constant current discharge at different current densities. Results confirm that the electrochemical properties of the aluminum anodes are related to grain size. Finer grain size anode restrains hydrogen evolution, improves electrochemical activity and increases anodic utilization rate. The proposed method is shown to effectively improve the performance of Al-air batteries.

Effects of Reduced Terrestrial LiDAR Point Density on High-Resolution Grain Crop Surface Models in Precision Agriculture

PubMed Central

Hämmerle, Martin; Höfle, Bernhard

2014-01-01

3D geodata play an increasingly important role in precision agriculture, e.g., for modeling in-field variations of grain crop features such as height or biomass. A common data capturing method is LiDAR, which often requires expensive equipment and produces large datasets. This study contributes to the improvement of 3D geodata capturing efficiency by assessing the effect of reduced scanning resolution on crop surface models (CSMs). The analysis is based on high-end LiDAR point clouds of grain crop fields of different varieties (rye and wheat) and nitrogen fertilization stages (100%, 50%, 10%). Lower scanning resolutions are simulated by keeping every n-th laser beam with increasing step widths n. For each iteration step, high-resolution CSMs (0.01 m2 cells) are derived and assessed regarding their coverage relative to a seamless CSM derived from the original point cloud, standard deviation of elevation and mean elevation. Reducing the resolution to, e.g., 25% still leads to a coverage of >90% and a mean CSM elevation of >96% of measured crop height. CSM types (maximum elevation or 90th-percentile elevation) react differently to reduced scanning resolutions in different crops (variety, density). The results can help to assess the trade-off between CSM quality and minimum requirements regarding equipment and capturing set-up. PMID:25521383

Multichannel Porous TiO2 Hollow Nanofibers with Rich Oxygen Vacancies and High Grain Boundary Density Enabling Superior Sodium Storage Performance.

PubMed

Wu, Ying; Jiang, Yu; Shi, Jinan; Gu, Lin; Yu, Yan

2017-06-01

TiO 2 as an anode for sodium-ion batteries (NIBs) has attracted much recent attention, but poor cyclability and rate performance remain problematic owing to the intrinsic electronic conductivity and the sluggish diffusivity of Na ions in the TiO 2 matrix. Herein, a simple process is demonstrated to improve the sodium storage performance of TiO 2 by fabricating a 1D, multichannel, porous binary-phase anatase-TiO 2 -rutile-TiO 2 composite with oxygen-deficient and high grain-boundary density (denoted as a-TiO 2- x /r-TiO 2- x ) via electrospinning and subsequent vacuum treatment. The introduction of oxygen vacancies in the TiO 2 matrix enables enhanced intrinsic electronic conductivity and fast sodium-ion diffusion kinetics. The porous structure offers easy access of the liquid electrolyte and a short transport path of Na + through the pores toward the TiO 2 nanoparticle. Furthermore, the high density of grain boundaries between the anatase TiO 2 and rutile TiO 2 offer more interfaces for a novel interfacial storage. The a-TiO 2- x /r-TiO 2- x shows excellent long cycling stability (134 mAh g -1 at 10 C after 4500 cycles) and superior rate performance (93 mAh g -1 after 4500 cycles at 20 C) for sodium-ion batteries. This simple and effective process could serve as a model for the modification of other materials applied in energy storage systems and other fields. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unstable plastic deformation of ultrafine-grained copper at 0.5 K

NASA Astrophysics Data System (ADS)

Isaev, N. V.; Grigorova, T. V.; Shumilin, S. E.; Polishchuk, S. S.; Davydenko, O. A.

2017-12-01

We investigate the relation between the strain-hardening rate and flow instability of polycrystalline Cu-OF deformed by tension at a constant rate in a liquid 3He atmosphere. The microstructure of the ultrafine-grained crystal, obtained by the equal-channel angular hydro-extrusion method, was varied by annealing at recovery and recrystallization temperatures and was monitored by x-ray diffraction. It is shown that that the flow instability, manifesting itself as macroscopic stress serrations on the tension curve, appears at a threshold tension sufficient for activation of a dynamic recovery that leads to a decrease of the strain-hardening coefficient. We discuss the effect of grain size and the initial dislocation density on the evolution of the dislocation structure that determines the scale and the statistical properties of the flow instability in the investigated crystals at low temperature.

ON THE ACTIVE REGION BRIGHT GRAINS OBSERVED IN THE TRANSITION REGION IMAGING CHANNELS OF IRIS

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

Skogsrud, H.; Voort, L. Rouppe van der; Pontieu, B. De

The Interface Region Imaging Spectrograph (IRIS) provides spectroscopy and narrow band slit-jaw (SJI) imaging of the solar chromosphere and transition region at unprecedented spatial and temporal resolutions. Combined with high-resolution context spectral imaging of the photosphere and chromosphere as provided by the Swedish 1 m Solar Telescope (SST), we can now effectively trace dynamic phenomena through large parts of the solar atmosphere in both space and time. IRIS SJI 1400 images from active regions, which primarily sample the transition region with the Si iv 1394 and 1403 Å lines, reveal ubiquitous bright “grains” which are short-lived (two to five minute)more » bright roundish small patches of sizes 0.″5–1.″7 that generally move limbward with velocities up to about 30 km s{sup −1}. In this paper, we show that many bright grains are the result of chromospheric shocks impacting the transition region. These shocks are associated with dynamic fibrils (DFs), most commonly observed in Hα. We find that the grains show the strongest emission in the ascending phase of the DF, that the emission is strongest toward the top of the DF, and that the grains correspond to a blueshift and broadening of the Si iv lines. We note that the SJI 1400 grains can also be observed in the SJI 1330 channel which is dominated by C ii lines. Our observations show that a significant part of the active region transition region dynamics is driven from the chromosphere below rather than from coronal activity above. We conclude that the shocks that drive DFs also play an important role in the heating of the upper chromosphere and lower transition region.« less

Role of translational entropy in spatially inhomogeneous, coarse-grained models

NASA Astrophysics Data System (ADS)

Langenberg, Marcel; Jackson, Nicholas E.; de Pablo, Juan J.; Müller, Marcus

2018-03-01

Coarse-grained models of polymer and biomolecular systems have enabled the computational study of cooperative phenomena, e.g., self-assembly, by lumping multiple atomistic degrees of freedom along the backbone of a polymer, lipid, or DNA molecule into one effective coarse-grained interaction center. Such a coarse-graining strategy leaves the number of molecules unaltered. In order to treat the surrounding solvent or counterions on the same coarse-grained level of description, one can also stochastically group several of those small molecules into an effective, coarse-grained solvent bead or "fluid element." Such a procedure reduces the number of molecules, and we discuss how to compensate the concomitant loss of translational entropy by density-dependent interactions in spatially inhomogeneous systems.

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.

Role of electron temperature on charging of dust grains

NASA Astrophysics Data System (ADS)

Kausik, S. S.; Chakraborty, M.; Saikia, B. K.

2007-02-01

Dust grains are produced by evaporation of silver in an experimental setup consisting of a dust chamber, a plasma chamber, and a deflection chamber. Due to differential pressure between the dust and plasma chambers, the dust grains move upward and after passing through plasma they become negatively charged. These charged dust grains are then deflected by a dc field applied across a pair of deflector plates in the deflection chamber. Both from the amount of deflection and also from the floating potential, the number of charges collected on the dust grains is calculated. As the gas pressure is changed, the plasma density and the electron temperature changes. Dust charge is then calculated at each value of pressure from the deflection and floating potential. It is found that the electron temperature has a profound effect in the accumulation of charge on dust 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.

A high plant density reduces the ability of maize to use soil nitrogen

PubMed Central

Yan, Peng; Pan, Junxiao; Zhang, Wenjie; Shi, Junfang; Chen, Xinping; Cui, Zhenling

2017-01-01

Understanding the physiological changes associated with high grain yield and high N use efficiency (NUE) is important when increasing the plant density and N rate to develop optimal agronomic management. We tested the hypothesis that high plant densities resulting in crowding stress reduce the ability of plants to use the N supply post-silking, thus decreasing the grain yield and NUE. In 2013 and 2014, a field experiment, with five N-application rates and three plant densities (6.0, 7.5, and 9.0 plants m–2), was conducted in the North China Plain (NCP). The calculated maximum grain yield and agronomic use efficiency (AEN) at a density of 7.5 plants m–2 were 12.4 Mg ha–1 and 39.3 kg kg–1, respectively, which were significantly higher than the values obtained at densities of 6.0 (11.3 Mg ha–1 and 30.2 kg kg–1) and 9.0 plant m–2 (11.7 Mg ha–1 and 27.8 kg kg–1). A high plant density of 9.0 plants m–2 decreased the post-silking N accumulation, leaf N concentration and net photosynthesis, which reduced the post-silking dry matter production, resulting in a low yield and NUE. Although a relatively low grain yield was observed at a density of 9.0 plants m–2, the optimal N rate increased from 150 to 186 kg N ha-1 at a density of 7.5 plants m–2. These results indicate that high plant densities with crowding stress reduce the ability of plants to use soil N during the post-silking period, and high rate of N fertilizer was needed to increase grain yield. We conclude that selecting the appropriate plant density combined with optimal N management could increase grain yields and the NUE in the NCP. PMID:28234970

Film grain noise modeling in advanced video coding

NASA Astrophysics Data System (ADS)

Oh, Byung Tae; Kuo, C.-C. Jay; Sun, Shijun; Lei, Shawmin

2007-01-01

A new technique for film grain noise extraction, modeling and synthesis is proposed and applied to the coding of high definition video in this work. The film grain noise is viewed as a part of artistic presentation by people in the movie industry. On one hand, since the film grain noise can boost the natural appearance of pictures in high definition video, it should be preserved in high-fidelity video processing systems. On the other hand, video coding with film grain noise is expensive. It is desirable to extract film grain noise from the input video as a pre-processing step at the encoder and re-synthesize the film grain noise and add it back to the decoded video as a post-processing step at the decoder. Under this framework, the coding gain of the denoised video is higher while the quality of the final reconstructed video can still be well preserved. Following this idea, we present a method to remove film grain noise from image/video without distorting its original content. Besides, we describe a parametric model containing a small set of parameters to represent the extracted film grain noise. The proposed model generates the film grain noise that is close to the real one in terms of power spectral density and cross-channel spectral correlation. Experimental results are shown to demonstrate the efficiency of the proposed scheme.

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.

3-D Characterization of Detrital Zircon Grains and its Implications for Fluvial Transport, Mixing, and Preservation Bias

NASA Astrophysics Data System (ADS)

Markwitz, V.; Kirkland, C. L.; Mehnert, A.; Gessner, K.; Shaw, J.

2017-12-01

Detrital zircon studies can suffer from selective loss of provenance information due to U-Pb age discordance, metamictization, metamorphic overprinting and fluviatile transport processes. The relationship between isotopic composition and zircon grain shape, and how grain shape is modified during transport, is largely unknown. We combine X-ray tomography with U-Pb geochronology to quantify how fluvial transport affects 3-D zircon shape, detrital age signature, and grain density along the Murchison River, whose catchment comprises Eoarchean to Early Paleozoic source rocks in Western Australia. We acquired tomographic volumes and isotopic data from 373 detrital zircons to document changes in size, shape and density in transport direction, and explore how grain shape, age spectra and the proportion of discordant material vary along the channel. Results show that shape characteristics are sensitive to transport distance, stream gradient, proximity to source material, and whether the source consists of primary or recycled zircons. With increasing transport distance, grain lengths decrease more than their widths. Furthermore, the loss of metamict grains occurs at a near constant rate, resulting in a linear increase of mean calculated zircon density by ca. 0.03 g/cm3 per 100 km transport distance. 3-D grain shape is therefore strongly linked to detrital age signature, and mean grain density is a function of the absolute transport distance. 3-D shape characteristics provide valuable information on detrital zircon populations, including the interaction between source materials with fluvial transport processes, which significantly affects preservation bias and, by inference, the representativeness of the sampled data.

High capacitance of coarse-grained carbide derived carbon electrodes

DOE PAGES

Dyatkin, Boris; Gogotsi, Oleksiy; Malinovskiy, Bohdan; ...

2016-01-01

Here, we report exceptional electrochemical properties of supercapacitor electrodes composed of large, granular carbide-derived carbon (CDC) particles. We synthesized 70–250 μm sized particles with high surface area and a narrow pore size distribution, using a titanium carbide (TiC) precursor. Electrochemical cycling of these coarse-grained powders defied conventional wisdom that a small particle size is strictly required for supercapacitor electrodes and allowed high charge storage densities, rapid transport, and good rate handling ability. Moreover, the material showcased capacitance above 100 F g -1 at sweep rates as high as 250 mV s -1 in organic electrolyte. 250–1000 micron thick dense CDCmore » films with up to 80 mg cm -2 loading showed superior areal capacitances. The material significantly outperformed its activated carbon counterpart in organic electrolytes and ionic liquids. Furthermore, large internal/external surface ratio of coarse-grained carbons allowed the resulting electrodes to maintain high electrochemical stability up to 3.1 V in ionic liquid electrolyte. In addition to presenting novel insights into the electrosorption process, these coarse-grained carbons offer a pathway to low-cost, high-performance implementation of supercapacitors in automotive and grid-storage applications.« less

Grain growth in uranium nitride prepared by spark plasma sintering

NASA Astrophysics Data System (ADS)

Johnson, Kyle D.; Lopes, Denise Adorno

2018-05-01

Uranium mononitride (UN) has long been considered a potential high density, high performance fuel candidate for light water reactor (LWR) and fast reactor (FR) applications. However, deployability of this fuel has been limited by the notable resistance to sintering and subsequent difficulty in producing a desirable microstructure, the high costs associated with 15N enrichment, as well as the known proclivity to oxidation and interaction with steam. In this study, the stimulation of grain growth in UN pellets sintered using SPS has been investigated. The results reveal that by using SPS and controlling temperature, time, and holding pressure, grain growth can be stimulated and controlled to produce a material featuring both a desired porosity and grain size, at least within the range of interest for nuclear fuel candidates. Grain sizes up to 31 μm were obtained using temperatures of 1650 °C and hold times of 15 min. Evaluation by EBSD reveal grain rotation and coalescence as the dominant mechanism in grain growth, which is suppressed by the application of higher external pressure. Moreover, complete closure of the porosity of the material was observed at relative densities of 96% TD, resulting in a material with sufficient porosity to accommodate LWR burnup. These results indicate that a method exists for the economic fabrication of an 15N-bearing uranium mononitride fuel with favorable microstructural characteristics compatible with use in a light water-cooled nuclear reactor.

Can a grain size-dependent viscosity help yielding realistic seismic velocities of LLSVPs?

NASA Astrophysics Data System (ADS)

Schierjott, J.; Cheng, K. W.; Rozel, A.; Tackley, P. J.

2017-12-01

Seismic studies show two antipodal regions of low shear velocity at the core-mantle boundary (CMB), one beneath the Pacific and one beneath Africa. These regions, called Large Low Shear Velocity Provinces (LLSVPs), are thought to be thermally and chemically distinct and thus have a different density and viscosity. Whereas there is some general consensus about the density of the LLSVPs the viscosity is still a very debated topic. So far, in numerical studies the viscosity is treated as either depth- and/or temperature- dependent but the potential grain size- dependence of the viscosity is neglected most of the time. In this study we use a self-consistent convection model which includes a grain size- dependent rheology based on the approach by Rozel et al. (2011) and Rozel (2012). Further, we consider a primordial layer and a time-dependent basalt production at the surface to dynamically form the present-day chemical heterogeneities, similar to earlier studies, e.g by Nakagawa & Tackley (2014). With this model we perform a parameter study which includes different densities and viscosities of the imposed primordial layer. We detect possible thermochemical piles based on different criterions, compute their average effective viscosity, density, rheology and grain size and investigate which detecting criterion yields the most realistic results. Our preliminary results show that a higher density and/or viscosity of the piles is needed to keep them at the core-mantle boundary (CMB). Relatively to the ambient mantle grain size is high in the piles but due to the temperature at the CMB the viscosity is not remarkably different than the one of ordinary plumes. We observe that grain size is lower if the density of the LLSVP is lower than the one of our MORB material. In that case the average temperature of the LLSVP is also reduced. Interestingly, changing the reference viscosity is responsible for a change in the average viscosity of the LLSVP but not for a different average

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.

[Characteristics and its forming mechanism on grain size distribution of suspended matter at Changjiang Estuary].

PubMed

Pang, Chong-guang; Yu, Wei; Yang, Yang

2010-03-01

In July of 2008, under the natural condition of sea water, the Laser in-situ scattering and transmissometry (LISST-100X Type C) was used to measure grain size distribution spectrum and volume concentration of total suspended matter in the sea water, including flocs at different layers of 24 sampling stations at Changjiang Estuary and its adjacent sea. The characteristics and its forming mechanism on grain size distribution of total suspended matter were analyzed based on the observation data of LISST-100X Type C, and combining with the temperature, salinity and turbidity of sea water, simultaneously observed by Alec AAQ1183. The observation data showed that the average median grain size of total suspended matter was about 4.69 phi in the whole measured sea area, and the characteristics of grain size distribution was relatively poor sorted, wide kurtosis, and basically symmetrical. The conclusion could be drawn that vertically average volume concentration decreased with the distance from the coastline, while median grain size had an increase trend with the distance, for example, at 31.0 degrees N section, the depth-average median grain size had been increased from 11 microm up to 60 microm. With the increasing of distance from the coast, the concentration of fine suspended sediment reduced distinctly, nevertheless some relatively big organic matter or big flocs appeared in quantity, so its grain size would rise. The observation data indicated that the effective density was ranged from 246 kg/m3 to 1334 kg/m, with average was 613 kg/m3. When the concentration of total suspended matter was relatively high, median grain size of total suspended matter increased with the water depth, while effective density decreased with the depth, because of the faster settling velocity and less effective density of large flocs that of small flocs. As for station 37 and 44, their correlation coefficients between effective density and median grain size were larger than 0.9.

Influence of Pulsed Current on Superplasticity of Fine Grained 1420 Al-Li Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yanling; Hou, Hongliang; Bi, Jing; Wang, Yaoqi

2018-01-01

The effects of an externally applied electropulse on the superplastic deformation behavior and microstructure of 1420 Al-Li alloy were studied. The flow stress of superplastic deformation was reduced by the high-density electropulse while the elongation was increased. The optimal electrical parameters for superplastic deformation were 192A/mm2 of current density, 150Hz of frequency and 30s of duration at 480°C and 0.001s-1. The elongation raised by 68% compared to that without electropulse. Furthermore, the grain was refined and the average grain size was reduced after superplastic deformation with the optimal electropulse. It is noted that the electropulse promoted the recrystallization and restrained the grain growth.

Defect character at grain boundary facet junctions: Analysis of an asymmetric Σ = 5 grain boundary in Fe

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

Medlin, D. L.; Hattar, K.; Zimmerman, J. A.

Grain boundaries often develop faceted morphologies in systems for which the interfacial free energy depends on the boundary inclination. Although the mesoscale thermodynamic basis for such morphological evolution has been extensively studied, the influence of line defects, such as secondary grain boundary dislocations, on the facet configurations has not been thoroughly explored. In this paper, through a combination of atomistic simulations and electron microscopic observations, we examine in detail the structure of an asymmetric Σ = 5 [001] grain boundary in well-annealed, body-centered cubic (BCC) Fe. The observed boundary forms with a hill-and-valley morphology composed of nanoscale {310} and {210}more » facets. Our analysis clarifies the atomic structure of the {310}/{210} facet junctions and identifies the presence of an array of secondary grain boundary dislocations that are localized to these junctions. Analysis of the Burgers vectors of the grain boundary dislocations, which are of type (1/5)<310> and (1/5)<120>, shows that the defect density is consistent with that required to accommodate a small observed angular deviation from the exact Σ = 5 orientation relationship. As a result, these observations and analysis suggest a crucial role for secondary grain boundary dislocations in dictating the length-scale of grain boundary facets, a consideration which has not been included in prior analyses of facet evolution and equilibrium facet length.« less

Defect character at grain boundary facet junctions: Analysis of an asymmetric Σ = 5 grain boundary in Fe

DOE PAGES

Medlin, D. L.; Hattar, K.; Zimmerman, J. A.; ...

2016-11-16

Grain boundaries often develop faceted morphologies in systems for which the interfacial free energy depends on the boundary inclination. Although the mesoscale thermodynamic basis for such morphological evolution has been extensively studied, the influence of line defects, such as secondary grain boundary dislocations, on the facet configurations has not been thoroughly explored. In this paper, through a combination of atomistic simulations and electron microscopic observations, we examine in detail the structure of an asymmetric Σ = 5 [001] grain boundary in well-annealed, body-centered cubic (BCC) Fe. The observed boundary forms with a hill-and-valley morphology composed of nanoscale {310} and {210}more » facets. Our analysis clarifies the atomic structure of the {310}/{210} facet junctions and identifies the presence of an array of secondary grain boundary dislocations that are localized to these junctions. Analysis of the Burgers vectors of the grain boundary dislocations, which are of type (1/5)<310> and (1/5)<120>, shows that the defect density is consistent with that required to accommodate a small observed angular deviation from the exact Σ = 5 orientation relationship. As a result, these observations and analysis suggest a crucial role for secondary grain boundary dislocations in dictating the length-scale of grain boundary facets, a consideration which has not been included in prior analyses of facet evolution and equilibrium facet length.« less

Developing a bubble number-density paleoclimatic indicator for glacier ice

USGS Publications Warehouse

Spencer, M.K.; Alley, R.B.; Fitzpatrick, J.J.

2006-01-01

Past accumulation rate can be estimated from the measured number-density of bubbles in an ice core and the reconstructed paleotemperature, using a new technique. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. An empirical model of these processes, optimized to fit published data on recently formed bubbles, reconstructs accumulation rates using recent temperatures with an uncertainty of 41% (P < 0.05). For modern sites considered here, no statistically significant trend exists between mean annual temperature and the ratio of bubble number-density to grain number-density at the time of pore close-off; optimum modeled accumulation-rate estimates require an eventual ???2.02 ?? 0.08 (P < 0.05) bubbles per close-off grain. Bubble number-density in the GRIP (Greenland) ice core is qualitatively consistent with independent estimates for a combined temperature decrease and accumulation-rate increase there during the last 5 kyr.

PROPERTIES OF DUST GRAINS PROBED WITH EXTINCTION CURVES

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

Nozawa, Takaya; Fukugita, Masataka

Modern data of the extinction curve from the ultraviolet to the near-infrared are revisited to study properties of dust grains in the Milky Way (MW) and the Small Magellanic Cloud (SMC). We confirm that the graphite-silicate mixture of grains yields the observed extinction curve with the simple power-law distribution of the grain size but with a cutoff at some maximal size: the parameters are tightly constrained to be q = 3.5 {+-} 0.2 for the size distribution a {sup -q} and the maximum radius a{sub max} = 0.24 {+-} 0.05 {mu}m, for both MW and SMC. The abundance of grains,more » and hence the elemental abundance, is constrained from the reddening versus hydrogen column density, E(B - V)/N{sub H}. If we take the solar elemental abundance as the standard for the MW, >56% of carbon should be in graphite dust, while it is <40% in the SMC using its available abundance estimate. This disparity and the relative abundance of C to Si explain the difference of the two curves. We find that 50%-60% of carbon may not necessarily be in graphite but in the amorphous or glassy phase. Iron may also be in the metallic phase or up to {approx}80% in magnetite rather than in silicates, so that the Mg/Fe ratio in astronomical olivine is arbitrary. With these substitutions, the parameters of the grain size remain unchanged. The mass density of dust grains relative to hydrogen is {rho}{sub dust}/{rho}{sub H}= 1 / (120{sup +10}{sub -16}) for the MW and 1 / (760{sup +70}{sub -90}) for the SMC under the elemental abundance constraints. We underline the importance of the wavelength dependence of the extinction curve in the near-infrared in constructing the dust model: if A{sub {lambda}}{proportional_to}{lambda}{sup -{gamma}} with {gamma} {approx_equal} 1.6, the power-law grain-size model fails, whereas it works if {gamma} {approx_equal} 1.8-2.0.« less

Impact of volunteer rice infestation on yield and grain quality of rice.

PubMed

Singh, Vijay; Burgos, Nilda R; Singh, Shilpa; Gealy, David R; Gbur, Edward E; Caicedo, Ana L

2017-03-01

Volunteer rice (Oryza sativa L.) grains may differ in physicochemical traits from cultivated rice, which may reduce the quality of harvested rice grain. To evaluate the effect of volunteer rice on cultivated rice, fields were surveyed in Arkansas in 2012. Cropping history that included hybrid cultivars in the previous two years (2010 and 2011) had higher volunteer rice infestation (20%) compared with fields planted previously with inbred rice (5.5%). The total grain yield of rice was reduced by 0.4% for every 1% increase in volunteer rice density. The grain quality did not change in fields planted with the same cultivar for three years. Volunteer rice density of at least 7.6% negatively impacted the head rice and when infestation reached 17.7%, it also reduced the rice grain yield. The protein and amylose contents of rice were not affected until volunteer rice infestation exceeded 30%. Crop rotation systems that include hybrid rice are expected to have higher volunteer rice infestation than systems without hybrid rice. It is predicted that, at 8% infestation, volunteer rice will start to impact head rice yield and will reduce total yield at 18% infestation. It could alter the chemical quality of rice grain at >30% infestation. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

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

United States Department of Agriculture-Agricultural Research Service stored-grain areawide integrated pest management program.

PubMed

Flinn, Paul W; Hagstrum, David W; Reed, Carl; Phillips, Tom W

2003-01-01

The USDA Agricultural Research Service (ARS) funded a demonstration project (1998-2002) for areawide IPM for stored wheat in Kansas and Oklahoma. This project was a collaboration of researchers at the ARS Grain Marketing and Production Research Center in Manhattan, Kansas, Kansas State University, and Oklahoma State University. The project utilized two elevator networks, one in each state, for a total of 28 grain elevators. These elevators stored approximately 31 million bushels of wheat, which is approximately 1.2% of the annual national production. Stored wheat was followed as it moved from farm to the country elevator and finally to the terminal elevator. During this study, thousands of grain samples were taken in concrete elevator silos. Wheat stored at elevators was frequently infested by several insect species, which sometimes reached high numbers and damaged the grain. Fumigation using aluminum phosphide pellets was the main method for managing these insect pests in elevators in the USA. Fumigation decisions tended to be based on past experience with controlling stored-grain insects, or were calendar based. Integrated pest management (IPM) requires sampling and risk benefit analysis. We found that the best sampling method for estimating insect density, without turning the grain from one bin to another, was the vacuum probe sampler. Decision support software, Stored Grain Advisor Pro (SGA Pro) was developed that interprets insect sampling data, and provides grain managers with a risk analysis report detailing which bins are at low, moderate or high risk for insect-caused economic losses. Insect density was predicted up to three months in the future based on current insect density, grain temperature and moisture. Because sampling costs money, there is a trade-off between frequency of sampling and the cost of fumigation. The insect growth model in SGA Pro reduces the need to sample as often, thereby making the program more cost-effective. SGA Pro was validated

Intermittent gravity-driven flow of grains through narrow pipes

NASA Astrophysics Data System (ADS)

Alvarez, Carlos A.; de Moraes Franklin, Erick

2017-01-01

Grain flows through pipes are frequently found in various settings, such as in pharmaceutical, chemical, petroleum, mining and food industries. In the case of size-constrained gravitational flows, density waves consisting of alternating high- and low-compactness regions may appear. This study investigates experimentally the dynamics of density waves that appear in gravitational flows of fine grains through vertical and slightly inclined pipes. The experimental device consisted of a transparent glass pipe through which different populations of glass spheres flowed driven by gravity. Our experiments were performed under controlled ambient temperature and relative humidity, and the granular flow was filmed with a high-speed camera. Experimental results concerning the length scales and celerities of density waves are presented, together with a one-dimensional model and a linear stability analysis. The analysis exhibits the presence of a long-wavelength instability, with the most unstable mode and a cut-off wavenumber whose values are in agreement with the experimental results.

Certain Grain Foods Can Be Meaningful Contributors to Nutrient Density in the Diets of U.S. Children and Adolescents: Data from the National Health and Nutrition Examination Survey, 2009-2012.

PubMed

Papanikolaou, Yanni; Fulgoni, Victor L

2017-02-20

Grain foods may play an important role in delivering nutrients to the diet of children and adolescents. The present study determined grain food sources of energy/nutrients in U.S. children and adolescents using data from the National Health and Nutrition Examination Survey, 2009-2012. Analyses of grain food sources were conducted using a 24-h recall in participants 2-18 years old ( N = 6109). Sources of nutrients contained in grain foods were determined using U.S. Department of Agriculture nutrient composition databases and excluded mixed dishes. Mean energy and nutrient intakes from the total diet and from various grain foods were adjusted for the sample design using appropriate weights. All grains provided 14% ± 0.2% kcal/day (263 ± 5 kcal/day), 22.5% ± 0.3% (3 ± 0.1 g/day) dietary fiber, 39.3% ± 0.5% (238 ± 7 dietary folate equivalents (DFE)/day) folate and 34.9% ± 0.5% (5.6 ± 0.1 mg/day) iron in the total diet in children and adolescents. The current analyses showed that certain grain foods, in particular breads, rolls and tortillas, ready-to-eat cereals and quick breads and bread products, are meaningful contributors of folate, iron, thiamin, niacin and dietary fiber, a nutrient of public health concern as outlined by the 2015-2020 Dietary Guidelines for Americans. Thus, specific grain foods contribute to nutrient density and have the potential to increase the consumption of several under-consumed nutrients in children and adolescents.

Activity of slip in amphibolite facies, fine-grained recrystallized quartz aggregates: high differential stress during high-T creep of quartz?

NASA Astrophysics Data System (ADS)

Viegas, G.; Menegon, L. M.; Archanjo, C. J.

2016-12-01

Quartz axis fabrics are a valuable tool to investigate strain partitioning/distribution in both naturally- and experimentally deformed quartz. Previous works have shown that slip dominates at high temperatures (> 600º C) and water-rich, commonly sub-magmatic conditions, typically associated with large grain sizes and grain boundary migration microstructures. In the Pernambuco shear zone, sheared quartz veins from a protomylonitic granitoid formed during the main amphibolite facies event constrained at mid-crustal conditions (550-600ºC, 5 kbar). The veins contain heterogeneously-deformed primary quartz grains, which typically form both flattened and elongated ribbons as well as more equant porphyroclasts surrounded by aggregates of fine-grained (ca. 20 µm) recrystallized aggregates. Recrystallized quartz with the same fine grain size may also occur in intracrystalline bands within the porphyroclasts. Chessboard extinction is widely observed in the porphyroclasts, and subgrain boundaries are either parallel or normal to the (0001) direction, suggesting slip on both basal and prismatic planes during recrystallization. Crystallographic preferred orientations (CPOs) of porphyroclasts (≥ 100 µm) show maxima of (0001) axes subparallel to Z and X, suggesting coeval glide along both basal and prism planes during shearing. In the recrystallized aggregates, fabric strength tends to become weaker, but still records glide along and directions. These preliminary results suggest that naturally deformed quartz veins record coeval activity of and slip during dynamic recrystallization under amphibolite facies conditions. The microstructure suggests that the CPO of the fine-grained aggregates is host-controlled and results from dominant subgrain rotation recrystallization. To our knowledge, activity of slip in fine-grained recrystallized aggregates has never been reported before. Thus, these preliminary results call into question the general view that slip is expected to be

The QTL GNP1 Encodes GA20ox1, Which Increases Grain Number and Yield by Increasing Cytokinin Activity in Rice Panicle Meristems.

PubMed

Wu, Yuan; Wang, Yun; Mi, Xue-Fei; Shan, Jun-Xiang; Li, Xin-Min; Xu, Jian-Long; Lin, Hong-Xuan

2016-10-01

Cytokinins and gibberellins (GAs) play antagonistic roles in regulating reproductive meristem activity. Cytokinins have positive effects on meristem activity and maintenance. During inflorescence meristem development, cytokinin biosynthesis is activated via a KNOX-mediated pathway. Increased cytokinin activity leads to higher grain number, whereas GAs negatively affect meristem activity. The GA biosynthesis genes GA20oxs are negatively regulated by KNOX proteins. KNOX proteins function as modulators, balancing cytokinin and GA activity in the meristem. However, little is known about the crosstalk among cytokinin and GA regulators together with KNOX proteins and how KNOX-mediated dynamic balancing of hormonal activity functions. Through map-based cloning of QTLs, we cloned a GA biosynthesis gene, Grain Number per Panicle1 (GNP1), which encodes rice GA20ox1. The grain number and yield of NIL-GNP1TQ were significantly higher than those of isogenic control (Lemont). Sequence variations in its promoter region increased the levels of GNP1 transcripts, which were enriched in the apical regions of inflorescence meristems in NIL-GNP1TQ. We propose that cytokinin activity increased due to a KNOX-mediated transcriptional feedback loop resulting from the higher GNP1 transcript levels, in turn leading to increased expression of the GA catabolism genes GA2oxs and reduced GA1 and GA3 accumulation. This rebalancing process increased cytokinin activity, thereby increasing grain number and grain yield in rice. These findings uncover important, novel roles of GAs in rice florescence meristem development and provide new insights into the crosstalk between cytokinin and GA underlying development process.

Measuring Density Stratification and Understanding its Impact on Sediment Transport in Fine-grained Rivers, Based on Observations from the Lower Yellow River, China

NASA Astrophysics Data System (ADS)

Moodie, A. J.; Nittrouer, J. A.; Ma, H.; Lamb, M. P.; Carlson, B.; Kineke, G. C.; Parker, G.

2017-12-01

High concentrations of suspended sediment in channelized fluid flow produces density stratification that can alter the turbulent flow structure, thus limiting fluid momentum redistribution and affecting sediment transport capacity. A low channel-bed slope and large flow depth are hypothesized to be additional important factors contributing to density stratification. However, there are limited observations of density stratification in large rivers, especially those that carry significant fluxes of mud, and so the conditions leading to the development of density stratification are poorly constrained. The Yellow River, China, is a fine-grained and low-sloping river that maintains some of the highest suspended sediment concentrations in large rivers worldwide, making it an ideal natural laboratory for studying density stratification and its impact on sediment transport. Suspended sediment samples from the lower Yellow River, collected over a range of discharge conditions, produced sediment concentration profiles that are used in conjunction with velocity profiles to determine the threshold shear velocity for density stratification effects to develop. Comparing measured and predicted concentration and velocity profiles demonstrates that, there is no significant density stratification for base flow conditions; however, above a shear velocity value of 0.05 m/s, there is a progressive offset between the measured and predicted profiles, indicating that density stratification is increasingly important with higher shear stress values. The analyses further indicate that sediment entrainment from the bed and sediment diffusivity within the water column are significantly impacted by density stratification, suggesting that shear stress and sediment transport rates are inhibited by the development of density stratification. Near-bed concentration measurements are used to assess a stress-to-entrainment relationship, accounting for density stratification. These measurements are

Nanograin Density Outside Saturn’s A Ring

NASA Astrophysics Data System (ADS)

Johnson, Robert E.; Tseng, Wei-Ling; Elrod, M. K.; Persoon, A. M.

2017-01-01

The observed disparity between the radial dependence of the ion and electron densities measured by the Cassini plasma (CAPS) and radio (RPWS) science instruments are used to show that the region between the outer edge of Saturn’s main rings and its tenuous G ring is permeated with small charged grains (nanograins). These grains emanate from the edge of the A ring and from the tenuous F and G rings. This is a region of Saturn’s magnetosphere that is relatively unexplored, but will be a focus of Cassini’s F ring orbits prior to the end of mission in 2017 September. Confirmation of the grain densities predicted here will enhance our ability to describe the formation and destruction of material in this important region of Saturn’s magnetosphere.

Effect of high temperature on grain filling period, yield, amylose content and activity of starch biosynthesis enzymes in endosperm of basmati rice.

PubMed

Ahmed, Nisar; Tetlow, Ian J; Nawaz, Sehar; Iqbal, Ahsan; Mubin, Muhammad; Nawaz ul Rehman, Muhammad Shah; Butt, Aisha; Lightfoot, David A; Maekawa, Masahiko

2015-08-30

High temperature during grain filling affects yield, starch amylose content and activity of starch biosynthesis enzymes in basmati rice. To investigate the physiological mechanisms underpinning the effects of high temperature on rice grain, basmati rice was grown under two temperature conditions - 32 and 22 °C - during grain filling. High temperature decreased the grain filling period from 32 to 26 days, reducing yield by 6%, and caused a reduction in total starch (3.1%) and amylose content (22%). Measurable activities of key enzymes involved in sucrose to starch conversion, sucrose synthase, ADP-glucose pyrophosphorylase, starch phosphorylase and soluble starch synthase in endosperms developed at 32 °C were lower than those at 22 °C compared with similar ripening stage on an endosperm basis. In particular, granule-bound starch synthase (GBSS) activity was significantly lower than corresponding activity in endosperms developing at 22 °C during all developmental stages analyzed. Results suggest changes in amylose/amylopectin ratio observed in plants grown at 32 °C was attributable to a reduction in activity of GBSS, the sole enzyme responsible for amylose biosynthesis. © 2014 Society of Chemical Industry.

Dust Grains and the Luminosity of Circumnuclear Water Masers in Active Galaxies

NASA Technical Reports Server (NTRS)

Collison, Alan J.; Watson, William D.

1995-01-01

In previous calculations for the luminosities of 22 GHz water masers, the pumping is reduced and ultimately quenched with increasing depth into the gas because of trapping of the infrared (approximately equals 30-150 micrometers), spectral line radiation of the water molecule. When the absorption (and reemission) of infrared radiation by dust grains is included, we demonstrate that the pumping is no longer quenched but remains constant with increasing optical depth. A temperature difference between the grains and the gas is required. Such conditions are expected to occur, for example, in the circumnuclear masing environments created by X-rays in active galaxies. Here, the calculated 22 GHz maser luminosities are increased by more than an order of magnitude. Application to the well-studied, circumnuclear masing disk in the galaxy NGC 4258 yields a maser luminosity near that inferred from observations if the observed X-ray flux is assumed to be incident onto only the inner surface of the disk.

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.

Phytase-active yeasts from grain-based food and beer.

PubMed

Nuobariene, L; Hansen, A S; Jespersen, L; Arneborg, N

2011-06-01

To screen yeast strains isolated from grain-based food and beer for phytase activity to identify high phytase-active strains. The screening of phytase-positive strains was carried out at conditions optimal for leavening of bread dough (pH 5·5 and 30°C), in order to identify strains that could be used for the baking industry. Two growth-based tests were used for the initial testing of phytase-active strains. Tested strains belonged to six species: Saccharomyces cerevisiae, Saccharomyces pastorianus, Saccharomyces bayanus, Kazachstania exigua (former name Saccharomyces exiguus), Candida krusei (teleomorph Issachenkia orientalis) and Arxula adeninivorans. On the basis of initial testing results, 14 strains were selected for the further determination of extracellular and intracellular (cytoplasmic and/or cell-wall bound) phytase activities. The most prominent strains for extracellular phytase production were found to be S. pastorianus KVL008 (a lager beer strain), followed by S. cerevisiae KVL015 (an ale beer strain) and C. krusei P2 (isolated from sorghum beer). Intracellular phytase activities were relatively low in all tested strains. Herein, for the first time, beer-related strains of S. pastorianus and S. cerevisiae are reported as phytase-positive strains. The high level of extracellular phytase activity by the strains mentioned previously suggests them to be strains for the production of wholemeal bread with high content of bioavailable minerals. © 2011 The Authors. Journal of Applied Microbiology © 2011 The Society for Applied Microbiology.

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

The interaction of hydrogen with the {010} surfaces of Mg and Fe olivine as models for interstellar dust grains: a density functional theory study

PubMed Central

Downing, C. A.; Ahmady, B.; Catlow, C. R. A.; de Leeuw, N. H.

2013-01-01

There is no consensus as yet to account for the significant presence of water on the terrestrial planets, but suggested sources include direct hydrogen adsorption from the parent molecular cloud after the planets’ formation, and delivery of hydrous material via comets or asteroids external to the zone of the terrestrial planets. Alternatively, a more recent idea is that water may have directly adsorbed onto the interstellar dust grains involved in planetary formation. In this work, we use electronic structure calculations based on the density functional theory to investigate and compare the bulk and {010} surface structures of the magnesium and iron end-members of the silicate mineral olivine, namely forsterite and fayalite, respectively. We also report our results on the adsorption of atomic hydrogen at the mineral surfaces, where our calculations show that there is no activation barrier to the adsorption of atomic hydrogen at these surfaces. Furthermore, different surface sites activate the atom to form either adsorbed hydride or proton species in the form of hydroxy groups on the same surface, which indicates that these mineral surfaces may have acted as catalytic sites in the immobilization and reaction of hydrogen atoms to form dihydrogen gas or water molecules. PMID:23734054

Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F-Coronal Brightness

NASA Technical Reports Server (NTRS)

Ragot, B. R.; Kahler, S. W.

2003-01-01

The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Solar Radius. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of the CME/dust interactions we consider the dominant forces, with and without CMEs. acting on the dust in the 3-5 Solar Radius region. Dust grain orbits are then computed to compare the drift rates from 5 to 3 Solar Radius. for periods of minimum and maximum solar activity, where a simple CME model is adopted to distinguish between the two periods. The ion-drag force, even in the quiet solar wind, reduces the drift time by a significant factor from its value estimated with the Poynting-Robertson drag force alone. The ion-drag effects of CMEs result in even shorter drift times of the large (greater than or approx. 3 microns) dust grains. hence faster depletion rates and lower dust-pain densities, at solar maxima. If dominated by thermal emission, the near-infrared brightness will thus display solar cycle variations close to the dust plane of symmetry. While trapping the smallest of the grains, the CME magnetic fields also scatter the grains of intermediate size (0.1-3 microns) in latitude. If light scattering by small grains close to the Sun dominates the optical brightness. the scattering by the CME magnetic fields will result in a solar cycle variation of the optical brightness distribution not exceeding 100% at high latitudes, with a higher isotropy reached at solar maxima. A good degree of latitudinal isotropy is already reached at low solar activity since the magnetic fields of the quiet solar wind so close to the Sun are able to scatter the small (less than or approx. 3 microns) grains up to the polar regions in only a few days or less, producing strong perturbations of their trajectories in less than half their orbital

Stability and electronic structure of the low- Σ grain boundaries in CdTe: a density functional study

DOE PAGES

Park, Ji-Sang; Kang, Joongoo; Yang, Ji-Hui; ...

2015-01-15

Using first-principles density functional calculations, we investigate the relative stability and electronic structure of the grain boundaries (GBs) in zinc-blende CdTe. Among the low-Σ-value symmetric tilt Σ3 (111), Σ3 (112), Σ5 (120), and Σ5 (130) GBs, we show that the Σ3 (111)GB is always the most stable due to the absence of dangling bonds and wrong bonds. The Σ5 (120) GBs, however, are shown to be more stable than the Σ3 (112) GBs, even though the former has a higher Σ value, and the latter is often used as a model system to study GB effects in zinc-blende semiconductors. Furthermore,more » we find that although containing wrong bonds, the Σ5 (120) GBs are electrically benign due to the short wrong bond lengths, and thus are not as harmful as the Σ3 (112) GBs also having wrong bonds but with longer bond lengths.« less

Characterization of mutagenic activity in grain-based coffee-substitute blends and instant coffees

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

Johansson, M.A.E.; Knize, M.G.; Felton, J.S.

1994-06-01

Several grain-based coffee-substitute blends and instant coffees showed a mutagenic response in the Ames/Salmonella test using TA98, YG1024 and YG1O29 with metabolic activation. The beverage powders contained 150 to 500 TA98 and 1150 to 4050 YG1024 revertant colonies/gram, respectively. The mutagenic activity in the beverage powders was shown to be stable to heat and the products varied in resistance to acid nitrite treatment. Characterization of the mutagenic activity, using HPLC-and the Ames test of the collected fractions, showed the coffee-substitutes and instant coffees contain several mutagenic compounds, which are most likely aromatic amines.

Oxygen Reduction Reaction Activity of Platinum Thin Films with Different Densities

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

Ergul, Busra; Begum, Mahbuba; Kariuki, Nancy

Platinum thin films with different densities were grown on glassy carbon electrodes by high pressure sputtering deposition and evaluated as oxygen reduction reaction catalysts for polymer electrolyte fuel cells using cyclic voltammetry and rotating disk electrode techniques in aqueous perchloric acid electrolyte. The electrochemically active surface area, ORR mass activity (MA) and specific activity (SA) of the thin film electrodes were obtained. MA and SA were found to be higher for low-density films than for high-density film.

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.

Spectroscopic infrared extinction mapping as a probe of grain growth in IRDCs

NASA Astrophysics Data System (ADS)

Lim, Wanggi; Carey, Sean J.

2014-07-01

We present photometric and spectroscopic tests of MIR to FIR extinction laws toward IRDC G028.36+00.07, a potential site of massive star formation. Lim & Tan (2014, hereafter LT14) developed methods of FIR extinction mapping of this source using Spitzer-MIPS 24 micron and Herschel-PACS 70 micron images, and extending the MIR 8 micron mapping methods of (Butler & Tan 2012, hereafter BT12), finding evidence for grain growth in the highest mass surface density regions. Here we present initial results of spectroscopic infrared extinction (SIREX) mapping using Spitzer-IRS (14 to 38 micron) data of the same IRDC. These methods allow us to measure the SED of the diffuse Galactic ISM, which we compare to theoretical models of Draine & Li (2007), as well as to search for opacity law variations with mass surface density within the IRDC. By comparison with theoretical dust models, e.g., Ossenkopf & Henning (1994) and Ormel et al. (2011), we are able to search for compositional signatures of the grain ices, such as water and methanol. We find evidence for generally flatter MIR to FIR extinction laws as mass surface density increases, strengthening the evidence for grain and ice mantle growth in higher density regions.

Toward unraveling a secret of the lower mantle: Detecting and characterizing piles using a grain size-dependent, composite rheology

NASA Astrophysics Data System (ADS)

Schierjott, Jana; Rozel, Antoine; Tackley, Paul

2017-04-01

Seismic studies show two antipodal regions of low shear velocity at the core-mantle boundary (CMB), one beneath the Pacific and one beneath Africa. These regions, called Large Low Shear Velocity Provinces (LLSVPs), are thought to be thermally and chemically distinct and thus have a different density and viscosity. Whereas there is some general consensus about the density of the LLSVPs, their viscosity is still debated. So far, in numerical studies the viscosity is treated as either depth- and/or temperature- dependent but the potential grain size-dependence of the viscosity is neglected most of the time. In this study we use a self-consistent convection model which includes a grain size- dependent rheology based on the approach by Rozel et al. (2011). Further, we consider a basal primordial layer and a time-dependent basalt production to dynamically form the present-day chemical heterogeneities, similar to earlier studies, e.g by Nakagawa & Tackley (2014). Our study comprises three main parts: 1) We perform a parameter study which includes different densities and viscosities of the imposed primordial layer. 2) We detect possible piles and compute their average effective viscosity, density, rheology and grain size. 3) We test the influence of grain size evolution on the development and morphology of piles and compare it to non-grain size models. Our preliminary results show that a higher density and/or viscosity of the piles is needed to keep them at the core-mantle boundary (CMB). Relatively to the ambient mantle grain size is high in the piles but due to the temperature at the CMB the viscosity is not remarkably different than the one of ordinary plumes. We observe that grain size is lower if the density of the imposed primordial material is lower than basalt. In that case the average temperature of the pile is also reduced. Interestingly, changing the reference viscosity is responsible for a change in the average viscosity of the pile but not for a different

Reversal in the Size Dependence of Grain Rotation

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

Zhou, Xiaoling; Tamura, Nobumichi; Mi, Zhongying

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

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

Certain Grain Foods Can Be Meaningful Contributors to Nutrient Density in the Diets of U.S. Children and Adolescents: Data from the National Health and Nutrition Examination Survey, 2009–2012

PubMed Central

Papanikolaou, Yanni; Fulgoni, Victor L.

2017-01-01

Grain foods may play an important role in delivering nutrients to the diet of children and adolescents. The present study determined grain food sources of energy/nutrients in U.S. children and adolescents using data from the National Health and Nutrition Examination Survey, 2009–2012. Analyses of grain food sources were conducted using a 24-h recall in participants 2–18 years old (N = 6109). Sources of nutrients contained in grain foods were determined using U.S. Department of Agriculture nutrient composition databases and excluded mixed dishes. Mean energy and nutrient intakes from the total diet and from various grain foods were adjusted for the sample design using appropriate weights. All grains provided 14% ± 0.2% kcal/day (263 ± 5 kcal/day), 22.5% ± 0.3% (3 ± 0.1 g/day) dietary fiber, 39.3% ± 0.5% (238 ± 7 dietary folate equivalents (DFE)/day) folate and 34.9% ± 0.5% (5.6 ± 0.1 mg/day) iron in the total diet in children and adolescents. The current analyses showed that certain grain foods, in particular breads, rolls and tortillas, ready-to-eat cereals and quick breads and bread products, are meaningful contributors of folate, iron, thiamin, niacin and dietary fiber, a nutrient of public health concern as outlined by the 2015–2020 Dietary Guidelines for Americans. Thus, specific grain foods contribute to nutrient density and have the potential to increase the consumption of several under-consumed nutrients in children and adolescents. PMID:28230731

Quantum theory of multiscale coarse-graining.

PubMed

Han, Yining; Jin, Jaehyeok; Wagner, Jacob W; Voth, Gregory A

2018-03-14

Coarse-grained (CG) models serve as a powerful tool to simulate molecular systems at much longer temporal and spatial scales. Previously, CG models and methods have been built upon classical statistical mechanics. The present paper develops a theory and numerical methodology for coarse-graining in quantum statistical mechanics, by generalizing the multiscale coarse-graining (MS-CG) method to quantum Boltzmann statistics. A rigorous derivation of the sufficient thermodynamic consistency condition is first presented via imaginary time Feynman path integrals. It identifies the optimal choice of CG action functional and effective quantum CG (qCG) force field to generate a quantum MS-CG (qMS-CG) description of the equilibrium system that is consistent with the quantum fine-grained model projected onto the CG variables. A variational principle then provides a class of algorithms for optimally approximating the qMS-CG force fields. Specifically, a variational method based on force matching, which was also adopted in the classical MS-CG theory, is generalized to quantum Boltzmann statistics. The qMS-CG numerical algorithms and practical issues in implementing this variational minimization procedure are also discussed. Then, two numerical examples are presented to demonstrate the method. Finally, as an alternative strategy, a quasi-classical approximation for the thermal density matrix expressed in the CG variables is derived. This approach provides an interesting physical picture for coarse-graining in quantum Boltzmann statistical mechanics in which the consistency with the quantum particle delocalization is obviously manifest, and it opens up an avenue for using path integral centroid-based effective classical force fields in a coarse-graining methodology.

NANOGRAIN DENSITY OUTSIDE SATURN’S A RING

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

Johnson, Robert E.; Tseng, Wei-Ling; Elrod, M. K.

The observed disparity between the radial dependence of the ion and electron densities measured by the Cassini plasma (CAPS) and radio (RPWS) science instruments are used to show that the region between the outer edge of Saturn’s main rings and its tenuous G ring is permeated with small charged grains (nanograins). These grains emanate from the edge of the A ring and from the tenuous F and G rings. This is a region of Saturn’s magnetosphere that is relatively unexplored, but will be a focus of Cassini ’s F ring orbits prior to the end of mission in 2017 September.more » Confirmation of the grain densities predicted here will enhance our ability to describe the formation and destruction of material in this important region of Saturn’s magnetosphere.« less

Coarse-grained forms for equations describing the microscopic motion of particles in a fluid.

PubMed

Das, Shankar P; Yoshimori, Akira

2013-10-01

Exact equations of motion for the microscopically defined collective density ρ(x,t) and the momentum density ĝ(x,t) of a fluid have been obtained in the past starting from the corresponding Langevin equations representing the dynamics of the fluid particles. In the present work we average these exact equations of microscopic dynamics over the local equilibrium distribution to obtain stochastic partial differential equations for the coarse-grained densities with smooth spatial and temporal dependence. In particular, we consider Dean's exact balance equation for the microscopic density of a system of interacting Brownian particles to obtain the basic equation of the dynamic density functional theory with noise. Our analysis demonstrates that on thermal averaging the dependence of the exact equations on the bare interaction potential is converted to dependence on the corresponding thermodynamic direct correlation functions in the coarse-grained equations.

Interaction between solar energetic particles and interplanetary grains

NASA Astrophysics Data System (ADS)

Strazzulla, G.; Calcagno, L.; Foti, G.; Sheng, K. L.

Some laboratory-studied effects induced by the fluence of fast ions on frosts of astrophysical interest are summarized. The results are applied to the interaction between energetic solar ions and interplanetary dust grains assumed to be cometary debris which spends about one-million yr before being collected in the earth's atmosphere or colliding on the moon's surface. The importance of erosion by particles to the stability of ice grains is confirmed. The build up of carbonaceous material by ion fluence on hydrocarbon containing grains is discussed. It is suggested that these new materials could be the glue which cements submicron silicate particles to form a complex agglomeration whose density increases with increasing proton fluence (packing effect). The IR spectra of laboratory synthesized carbonaceous material are compared with those observed in some carbonaceous meteoritic extracts.

Chemical Composition of the Semi-Volatile Grains of Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Wurz, P.; Altwegg, K.; Balsiger, H. R.; Berthelier, J. J.; De Keyser, J.; Fiethe, B.; Fuselier, S. A.; Gasc, S.; Gombosi, T. I.; Korth, A.; Mall, U.; Reme, H.; Rubin, M.; Tzou, C. Y.

2017-12-01

Rosetta was in orbit of comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016. On board is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) experiment that has been continuously collecting data on the chemical composition and activity of the coma from 3.5 AU to pericentre at 1.24 AU and out again to 3.5 AU. ROSINA consists of two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron-type Time-Of-Flight (RTOF), as well as the COmet Pressure Sensor (COPS). ROSINA recorded the neutral gas and thermal plasma in the comet's coma. The two mass spectrometers have high dynamic ranges and complement each other with high mass resolution, and high time resolution and large mass range. COPS measures total gas densities, bulk velocities, and gas temperatures. Occasionally, a dust grain of cometary origin enters the ion source of a ROSINA instrument where the volatile part evaporates since these ion sources are hot. The release of volatiles from cometary dust grains was observed with all three ROSINA instruments on several occasions. Because the volatile content of such a dust grain is completely evaporated after a few seconds, the RTOF instrument is best suited for the investigation of its chemical composition since complete mass spectra are recorded during this time. During the mission 9 dust grains were observed with RTOF during the October 2014 to July 2016 time period. It is estimated that these grains contain about 10-15 g of volatiles. The mass spectra were interpreted with a set of 75 molecules, with the major groups of chemical species being hydrocarbons, oxygenated hydrocarbons, nitrogen-bearing molecules, sulphur-bearing molecules, halogenated molecules and others. About 70% of these grains are depleted in water compared to the comet coma, thus, can be considered as semi-volatile dust grains, and the other about 30% are water grains. The chemical composition varies considerably from grain to grain

Loop and void damage during heavy ion irradiation on nanocrystalline and coarse grained tungsten: Microstructure, effect of dpa rate, temperature, and grain size

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

El-Atwani, O.; Esquivel, E.; Efe, M.

Displacement damage, through heavy ion irradiation was studied on two tungsten grades (coarse grained tungsten (CGW) and nanocrystalline and ultrafine grained tungsten (NCW)) using different displacement per atom rates and different irradiation temperatures (RT and 1050 K). Percentage of <111> and <100> type loops at the irradiation conditions was determined. Irradiation damage in the microstructure was quantified using average loop areas and densities (method A) and loop areal fraction in the grain matrices under 2-beam diffraction conditions (method B). Average values of <111> and <100> loops were calculated from method A. Loop coalescence was shown to occur for CGW atmore » 0.25 dpa. Using both methods of quantifying microstructural damage, no effect of dpa rate was observed and damage in CGW was shown to be the same at RT and 1050 K. Swelling from voids observed at 1050 K was quantified. The loop damage in NCW was compared to CGW at the same diffraction and imaging conditions. NCW was shown to possess enhanced irradiation resistance at RT regarding loop damage and higher swelling resistance at 1050 K compared to CGW. For irradiation at 1050 K, the NCW was shown to have a similar defect densities to the CGW which is attributed to higher surface effects in the CGW, vacancy loop growth to voids and a better sink efficiency in the CGW deduced from the vacancy distribution profiles from Kinetic Monte Carlo simulations. Loop density and swelling was shown to have similar values in grains sizes that range from 80-600 nm. No loop or void denuded zones occurred at any of the irradiation conditions. This work has a collection of experiments and conclusions that are of vital importance to materials and nuclear communities.« less

Loop and void damage during heavy ion irradiation on nanocrystalline and coarse grained tungsten: Microstructure, effect of dpa rate, temperature, and grain size

DOE PAGES

El-Atwani, O.; Esquivel, E.; Efe, M.; ...

2018-02-20

Displacement damage, through heavy ion irradiation was studied on two tungsten grades (coarse grained tungsten (CGW) and nanocrystalline and ultrafine grained tungsten (NCW)) using different displacement per atom rates and different irradiation temperatures (RT and 1050 K). Percentage of <111> and <100> type loops at the irradiation conditions was determined. Irradiation damage in the microstructure was quantified using average loop areas and densities (method A) and loop areal fraction in the grain matrices under 2-beam diffraction conditions (method B). Average values of <111> and <100> loops were calculated from method A. Loop coalescence was shown to occur for CGW atmore » 0.25 dpa. Using both methods of quantifying microstructural damage, no effect of dpa rate was observed and damage in CGW was shown to be the same at RT and 1050 K. Swelling from voids observed at 1050 K was quantified. The loop damage in NCW was compared to CGW at the same diffraction and imaging conditions. NCW was shown to possess enhanced irradiation resistance at RT regarding loop damage and higher swelling resistance at 1050 K compared to CGW. For irradiation at 1050 K, the NCW was shown to have a similar defect densities to the CGW which is attributed to higher surface effects in the CGW, vacancy loop growth to voids and a better sink efficiency in the CGW deduced from the vacancy distribution profiles from Kinetic Monte Carlo simulations. Loop density and swelling was shown to have similar values in grains sizes that range from 80-600 nm. No loop or void denuded zones occurred at any of the irradiation conditions. This work has a collection of experiments and conclusions that are of vital importance to materials and nuclear communities.« less

AC conductivity scaling behavior in grain and grain boundary response regime of fast lithium ionic conductors

NASA Astrophysics Data System (ADS)

Mariappan, C. R.

2014-05-01

AC conductivity spectra of Li-analogues NASICON-type Li1.5Al0.5Ge1.5P3O12 (LAGP), Li-Al-Ti-P-O (LATP) glass-ceramics and garnet-type Li7La2Ta2O13 (LLTO) ceramic are analyzed by universal power law and Summerfield scaling approaches. The activation energies and pre-exponential factors of total and grain conductivities are following the Meyer-Neldel (M-N) rule for NASICON-type materials. However, the garnet-type LLTO material deviates from the M-N rule line of NASICON-type materials. The frequency- and temperature-dependent conductivity spectra of LAGP and LLTO are superimposed by Summerfield scaling. The scaled conductivity curves of LATP are not superimposed at the grain boundary response region. The superimposed conductivity curves are observed at cross-over frequencies of grain boundary response region for LATP by incorporating the exp ( {{{ - (EAt - EAg )} {{{ - (EAt - EAg )} {kT}}} ) factor along with Summerfield scaling factors on the frequency axis, where EAt and EAg are the activation energies of total and grain conductivities, respectively.

Effect of non-metallic precipitates and grain size on core loss of non-oriented electrical silicon steels

NASA Astrophysics Data System (ADS)

Wang, Jiayi; Ren, Qiang; Luo, Yan; Zhang, Lifeng

2018-04-01

In the current study, the number density and size of non-metallic precipitates and the size of grains on the core loss of the 50W800 non-oriented electrical silicon steel sheets were investigated. The number density and size of precipitates and grains were statistically analyzed using an automatic scanning electron microscope (ASPEX) and an optical microscope. Hypothesis models were established to reveal the physical feature for the function of grain size and precipitates on the core loss of the steel. Most precipitates in the steel were AlN particles smaller than 1 μm so that were detrimental to the core loss of the steel. These finer AlN particles distributed on the surface of the steel sheet. The relationship between the number density of precipitates (x in number/mm2 steel area) and the core loss (P1.5/50 in W/kg) was regressed as P1.5/50 = 4.150 + 0.002 x. The average grain size was approximately 25-35 μm. The relationship between the core loss and grain size (d in μm) was P1.5/50 = 3.851 + 20.001 d-1 + 60.000 d-2.

Grain Foods Are Contributors of Nutrient Density for American Adults and Help Close Nutrient Recommendation Gaps: Data from the National Health and Nutrition Examination Survey, 2009-2012.

PubMed

Papanikolaou, Yanni; Fulgoni, Victor L

2017-08-14

limit. Cumulatively, a variety of grain food groups consumed by American adults contribute to nutrient density in the total diet and have the potential to increase consumption of shortfall nutrients as identified by 2015-2020 DGA, particularly dietary fiber, folate, and iron.

Grain Growth in Nanocrystalline Mg-Al Thin Films

DOE PAGES

Kruska, Karen; Rohatgi, Aashish; Vemuri, Rama S.; ...

2017-10-05

We report that an improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing ~10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull.more » The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. In conclusion, the low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.« less

Grain Growth in Nanocrystalline Mg-Al Thin Films

NASA Astrophysics Data System (ADS)

Kruska, Karen; Rohatgi, Aashish; Vemuri, Rama S.; Kovarik, Libor; Moser, Trevor H.; Evans, James E.; Browning, Nigel D.

2017-12-01

An improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing 10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. The low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.

High density of (pseudo) periodic twin-grain boundaries in molecular beam epitaxy-grown van der Waals heterostructure: MoTe{sub 2}/MoS{sub 2}

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

Diaz, Horacio Coy; Ma, Yujing; Chaghi, Redhouane

2016-05-09

Growth of transition metal dichalcogenide heterostructures by molecular beam epitaxy (MBE) promises synthesis of artificial van der Waals materials with controllable layer compositions and separations. Here, we show that MBE growth of 2H-MoTe{sub 2} monolayers on MoS{sub 2} substrates results in a high density of mirror-twins within the films. The grain boundaries are tellurium deficient, suggesting that Te-deficiency during growth causes their formation. Scanning tunneling microscopy and spectroscopy reveal that the grain boundaries arrange in a pseudo periodic “wagon wheel” pattern with only ∼2.6 nm repetition length. Defect states from these domain boundaries fill the band gap and thus give themore » monolayer an almost metallic property. The band gap states pin the Fermi-level in MoTe{sub 2} and thus determine the band-alignment in the MoTe{sub 2}/MoS{sub 2} interface.« less

Study of Ferrite During Refinement of Prior Austenite Grains in Microalloyed Steel Continuous Casting

NASA Astrophysics Data System (ADS)

Liu, Jiang; Wen, Guanghua; Tang, Ping

2017-12-01

The formation of coarse prior austenite grain is a key factor to promote transverse crack, and the susceptibility to the transverse crack can be reduced by refining the austenite grain size. In the present study, the high-temperature confocal laser scanning microscope (CLSM) was used to simulate two types of double phase-transformation technologies. The distribution and morphology of ferrites under different cooling conditions were analyzed, and the effects of ferrite distribution and morphology on the double phase-transformation technologies were explored to obtain the suitable double phase-change technology for the continuous casting process. The results indicate that, under the thermal cycle TH0 [the specimens were cooled down to 913 K (640 °C) at a cooling rate of 5.0 K/s (5.0 °C/s)], the width of prior austenite grain boundaries was thick, and the dislocation density at grain boundaries was high. It had strong inhibition effect on crack propagation; under the thermal cycle TH1 [the specimens were cooled down to 1073 K (800 °C) at a cooling rate of 5.0 K/s (5.0 °C/s) and then to 913 K (640 °C) at a cooling rate of 1.0 K/s (1.0 °C/s)], the width of prior austenite grain boundary was thin, and the dislocation density at grain boundaries was low. It was beneficial to crack propagation. After the first phase change, the developed film-like ferrite along the austenite grain boundaries improved the nucleation conditions of new austenitic grains and removed the inhibition effect of the prior austenite grain boundaries on the austenite grain size.

Phenolic acids and antioxidant activity of distillers dried grains with solubles (DDGS) as compared with corn

USDA-ARS?s Scientific Manuscript database

Sample sets of ground corn and the corresponding distillers dried grains with solubles (DDGS) were collected from three commercial plants in Iowa. Phenolic acids were analyzed by high performance liquid chromatography coupled with diode array and/or mass spectrometry. The antioxidant activity was ...

Antioxidative activities and phenolic compounds of pumpkin (Cucurbita pepo) seeds and amaranth (Amaranthus caudatus) grain extracts.

PubMed

Peiretti, Pier Giorgio; Meineri, Giorgia; Gai, Francesco; Longato, Erica; Amarowicz, Ryszard

2017-09-01

Phenolic compounds were extracted from pumpkin (Cucurbita pepo) seed and amaranth (Amaranthus caudatus) grain into 80% (v/v) methanol. The extracts obtained were characterised by the contents of total phenolic compounds (TPC), trolox equivalent antioxidant capacity (TEAC), ferric-reducing antioxidant power (FRAP) and antiradical activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH · ) radical. The content of individual phenolic compounds was determined by HPLC-DAD method. Pumpkin seeds showed the higher content of TPC than that from amaranth. The TEAC values of both extracts were similar each other. The lower value of FRAP was observed for pumpkin seed. Phenolic compound present in amaranth grain exhibited strongest antiradical properties against DPPH radical. Several peaks were present on the HPLC chromatograms of two extracts. The UV-DAD spectra confirmed the presence of vanillic acid derivatives in the amaranth grain. The three main phenolic compound present in pumpkin seed were characterised by UV-DAD spectra with maximum at 258, 266 and 278 nm.

Proteomics analysis of maize (Zea mays L.) grain based on iTRAQ reveals molecular mechanisms of poor grain filling in inferior grains.

PubMed

Yu, Tao; Li, Geng; Liu, Peng; Dong, Shuting; Zhang, Jiwang; Zhao, Bin

2017-06-01

In maize, inferior grains (IG) located on the upper part of the ear have poor grain filling process compared to superior grains (SG) located on the middle and lower parts of the ear. This difference limits satisfactory yield and quality; however, the underlying molecular mechanisms remain unknown. Here, using the isobaric tag for relative and absolute quantification (iTRAQ) technology, the proteomes of IG and SG during early and middle grain filling stages were investigated. In total, 4720 proteins were identified in maize grain and 305 differentially accumulated proteins (DiAPs) were detected between IG and SG. These DiAPs were involved in diverse cellular and metabolic processes with preferred distribution in protein synthesis/destination and metabolism. Compared to SG, DiAPs related to cell growth/division and starch synthesis were lag-accumulated and down-regulated in IG, respectively, resulting in smaller sink sizes and lower sink activities in IG. Meanwhile, impediment of the glycolysis pathway in IG may lead to reduce energy supply and building materials for substance synthesis. Additionally, reactive oxygen species (ROS) homeostasis and the defense system were disturbed in IG, which might lead to reduce protection against various environmental stresses. The present study provides new information on the proteomic differences between IG and SG, and explains possible molecular mechanisms for poor grain filling in IG. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Correlated NanoSIMS, TEM, and XANES Studies of Presolar Grains

NASA Astrophysics Data System (ADS)

Groopman, Evan Edward

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.

Gas-phase chemistry in dense interstellar clouds including grain surface molecular depletion and desorption

NASA Technical Reports Server (NTRS)

Bergin, E. A.; Langer, W. D.; Goldsmith, P. F.

1995-01-01

We present time-dependent models of the chemical evolution of molecular clouds which include depletion of atoms and molecules onto grain surfaces and desorption, as well as gas-phase interactions. We have included three mechanisms to remove species from the grain mantles: thermal evaporation, cosmic-ray-induced heating, and photodesorption. A wide range of parameter space has been explored to examine the abundance of species present both on the grain mantles and in the gas phase as a function of both position in the cloud (visual extinction) and of evolutionary state (time). The dominant mechanism that removes molecules from the grain mantles is cosmic-ray desorption. At times greater than the depletion timescale, the abundances of some simple species agree with abundances observed in the cold dark cloud TMC-1. Even though cosmic-ray desorption preserves the gas-phase chemistry at late times, molecules do show significant depletions from the gas phase. Examination of the dependence of depletion as a function of density shows that when the density increases from 10(exp 3)/cc to 10(exp 5)/cc several species including HCO(+), HCN, and CN show gas-phase abundance reductions of over an order of magnitude. The CO: H2O ratio in the grain mantles for our standard model is on the order of 10:1, in reasonable agreement with observations of nonpolar CO ice features in rho Ophiuchus and Serpens. We have also examined the interdependence of CO depletion with the space density of molecular hydrogen and binding energy to the grain surface. We find that the observed depletion of CO in Taurus in inconsistent with CO bonding in an H2O rich mantle, in agreement with observations. We suggest that if interstellar grains consist of an outer layer of CO ice, then the binding energies for many species to the grain mantle may be lower than commonly used, and a significant portion of molecular material may be maintained in the gas phase.

A note on coarse-grained gravity-flow deposits within proterozoic lacustrine sedimentary rocks, Transvaal sequence, South Africa

NASA Astrophysics Data System (ADS)

Eriksson, P. G.

A widely developed, thin, coarse-matrix conglomerate occurs within early Proterozoic lacustrine mudrocks in the Transvaal Sequence, South Africa. The poorly sorted tabular chert clasts, alternation of a planar clast fabric with disorientated zones, plus normal and inverse grading in the former rock type suggest deposition by density-modified grain-flow and high density turbidity currents. The lower fan-delta slope palæenvironment inferred for the conglomerate is consistent with the lacustrine interpretation for the enclosing mudrock facies. This intracratonic setting contrasts with the marine environment generally associated with density-modified grain-flow deposits.

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

A combined coarse-grained and all-atom simulation of TRPV1 channel gating and heat activation

PubMed Central

Qin, Feng

2015-01-01

The transient receptor potential (TRP) channels act as key sensors of various chemical and physical stimuli in eukaryotic cells. Despite years of study, the molecular mechanisms of TRP channel activation remain unclear. To elucidate the structural, dynamic, and energetic basis of gating in TRPV1 (a founding member of the TRPV subfamily), we performed coarse-grained modeling and all-atom molecular dynamics (MD) simulation based on the recently solved high resolution structures of the open and closed form of TRPV1. Our coarse-grained normal mode analysis captures two key modes of collective motions involved in the TRPV1 gating transition, featuring a quaternary twist motion of the transmembrane domains (TMDs) relative to the intracellular domains (ICDs). Our transition pathway modeling predicts a sequence of structural movements that propagate from the ICDs to the TMDs via key interface domains (including the membrane proximal domain and the C-terminal domain), leading to sequential opening of the selectivity filter followed by the lower gate in the channel pore (confirmed by modeling conformational changes induced by the activation of ICDs). The above findings of coarse-grained modeling are robust to perturbation by lipids. Finally, our MD simulation of the ICD identifies key residues that contribute differently to the nonpolar energy of the open and closed state, and these residues are predicted to control the temperature sensitivity of TRPV1 gating. These computational predictions offer new insights to the mechanism for heat activation of TRPV1 gating, and will guide our future electrophysiology and mutagenesis studies. PMID:25918362

Active learning for noisy oracle via density power divergence.

PubMed

Sogawa, Yasuhiro; Ueno, Tsuyoshi; Kawahara, Yoshinobu; Washio, Takashi

2013-10-01

The accuracy of active learning is critically influenced by the existence of noisy labels given by a noisy oracle. In this paper, we propose a novel pool-based active learning framework through robust measures based on density power divergence. By minimizing density power divergence, such as β-divergence and γ-divergence, one can estimate the model accurately even under the existence of noisy labels within data. Accordingly, we develop query selecting measures for pool-based active learning using these divergences. In addition, we propose an evaluation scheme for these measures based on asymptotic statistical analyses, which enables us to perform active learning by evaluating an estimation error directly. Experiments with benchmark datasets and real-world image datasets show that our active learning scheme performs better than several baseline methods. Copyright © 2013 Elsevier Ltd. All rights reserved.

Polyamines and ethylene interact in rice grains in response to soil drying during grain filling.

PubMed

Chen, Tingting; Xu, Yunji; Wang, Jingchao; Wang, Zhiqin; Yang, Jianchang; Zhang, Jianhua

2013-05-01

This study tested the hypothesis that the interaction between polyamines and ethylene may mediate the effects of soil drying on grain filling of rice (Oryza sativa L.). Two rice cultivars were pot grown. Three treatments, well-watered, moderate soil drying (MD), and severe soil drying (SD), were imposed from 8 d post-anthesis until maturity. The endosperm cell division rate, grain-filling rate, and grain weight of earlier flowering superior spikelets showed no significant differences among the three treatments. However, those of the later flowering inferior spikelets were significantly increased under MD and significantly reduced under SD when compared with those which were well watered. The two cultivars showed the same tendencies. MD increased the contents of free spermidine (Spd) and free spermine (Spm), the activities of S-adenosyl-L-methionine decarboxylase and Spd synthase, and expression levels of polyamine synthesis genes, and decreased the ethylene evolution rate, the contents of 1-aminocylopropane-1-carboxylic acid (ACC) and hydrogen peroxide, the activities of ACC synthase, ACC oxidase, and polyamine oxidase, and the expression levels of ethylene synthesis genes in inferior spikelets. SD exhibited the opposite effects. Application of Spd, Spm, or an inhibitor of ethylene synthesis to rice panicles significantly reduced ethylene and ACC levels, but significantly increased Spd and Spm contents, grain-filling rate, and grain weight of inferior spikelets. The results were reversed when ACC or an inhibitor of Spd and Spm synthesis was applied. The results suggest that a potential metabolic interaction between polyamines and ethylene biosynthesis responds to soil drying and mediates the grain filling of inferior spikelets in rice.

Pollen density on the stigma affects endogenous gibberellin metabolism, seed and fruit set, and fruit quality in Pyrus pyrifolia.

PubMed

Zhang, Caixi; Tateishi, Naoya; Tanabe, Kenji

2010-10-01

To clarify the relationship between pollen density and gametophytic competition in Pyrus pyrifolia, gametophytic performance, gibberellin metabolism, fruit set, and fruit quality were investigated by modifying P. pyrifolia pollen grain number and density with Lycopodium spores. Higher levels of pollen density improved seed viability, fruit set, and fruit quality. Treatments with the highest pollen density showed a significantly increased fruit growth rate and larger fruit at harvest. High pollen density increased germination rate and gave a faster pollen tube growth, both in vivo and in vitro. Endogenous gibberellin (GA) concentrations increased in pollen tubes soon after germination and the concentration of two growth-active GAs, GA(3), and GA(4), was positively correlated to final fruit size, cell numbers in the mesocarp, and pollen tube growth rate. These two GAs appear to be biosynthesized de novo in pollen tube and are the main pollen-derived bioactive GAs found after pollen germination. GA(1) levels in the pollen tube appear to be related to a pollen-style interaction that occurred after the pollen grains landed on the stigma.

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

Excitation of Kelvin Helmholtz instability by an ion beam in a plasma with negatively charged dust grains

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

Rani, Kavita; Sharma, Suresh C.

2015-02-15

An ion beam propagating through a magnetized dusty plasma drives Kelvin Helmholtz Instability (KHI) via Cerenkov interaction. The frequency of the unstable wave increases with the relative density of negatively charged dust grains. It is observed that the beam has stabilizing effect on the growth rate of KHI for low shear parameter, but for high shear parameter, the instability is destabilized with relative density of negatively charged dust grains.

Cellular response of preosteoblasts to nanograined/ultrafine-grained structures.

PubMed

Misra, R D K; Thein-Han, W W; Pesacreta, T C; Hasenstein, K H; Somani, M C; Karjalainen, L P

2009-06-01

Metallic materials with submicron- to nanometer-sized grains provide surfaces that are different from conventional polycrystalline materials because of the large proportion of grain boundaries with high free energy. In the study described here, the combination of cellular and molecular biology, materials science and engineering advances our understanding of cell-substrate interactions, especially the cellular activity between preosteoblasts and nanostructured metallic surfaces. Experiments on the effect of nano-/ultrafine grains have shown that cell attachment, proliferation, viability, morphology and spread are favorably modulated and significantly different from conventional coarse-grained structures. Additionally, immunofluorescence studies demonstrated stronger vinculin signals associated with actin stress fibers in the outer regions of the cells and cellular extensions on nanograined/ultrafine-grained substrate. These observations suggest enhanced cell-substrate interaction and activity. The differences in the cellular response on nanograined/ultrafine-grained and coarse-grained substrates are attributed to grain size and degree of hydrophilicity. The outcomes of the study are expected to reduce challenges to engineer bulk nanostructured materials with specific physical and surface properties for medical devices with improved cellular attachment and response. The data lay the foundation for a new branch of nanostructured materials for biomedical applications.

Development of High Sensitivity Nuclear Emulsion and Fine Grained Emulsion

NASA Astrophysics Data System (ADS)

Kawahara, H.; Asada, T.; Naka, T.; Naganawa, N.; Kuwabara, K.; Nakamura, M.

2014-08-01

Nuclear emulsion is a particle detector having high spacial resolution and angular resolution. It became useful for large statistics experiment thanks to the development of automatic scanning system. In 2010, a facility for emulsion production was introduced and R&D of nuclear emulsion began at Nagoya university. In this paper, we present results of development of the high sensitivity emulsion and fine grained emulsion for dark matter search experiment. Improvement of sensitivity is achieved by raising density of silver halide crystals and doping well-adjusted amount of chemicals. Production of fine grained emulsion was difficult because of unexpected crystal condensation. By mixing polyvinyl alcohol (PVA) to gelatin as a binder, we succeeded in making a stable fine grained emulsion.

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.

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.

Physical and chemical effects of grain aggregates on the Palos Verdes margin, southern California

USGS Publications Warehouse

Drake, D.E.; Eganhouse, R.; McArthur, W.

2002-01-01

Large discharges of wastewater and particulate matter from the outfalls of the Los Angeles County Sanitation Districts onto the Palos Verdes shelf since 1937 have produced an effluent-affected sediment deposit characterized by low bulk density, elevated organic matter content, and a high percentage of fine silt and clay particles relative to underlying native sands and sandy silts. Comparison of the results of grain-size analyses using a gentle wet-sieving technique that preserves certain grain aggregates to the results of standard size analyses of disaggregated particles shows that high percentages (up to 50%) of the silt and clay fractions of the effluent-affected mud are incorporated in aggregates having intermediate diameters in the fine-to-medium sand size range (63-500 ??m), Scanning electron microscope images of the aggregates show that they are predominantly oval fecal pellets or irregularly shaped fragments of pellets. Deposit-feeding polychaete worms such as Capitella sp. and Mediomastus sp., abundant in the mud-rich effluent-affected sediment on Palos Verdes shelf, are probably responsible for most of the grain aggregates through fecal pellet production. Particle settling rates and densities, and the concentrations of organic carbon and p,p???-DDE, a metabolite of the hydrophobic pesticide DDT, were determined for seven grain-size fractions in the effluent-affected sediment. Fecal pellet grain densities ranged from about 1.2 to 1.5 g/cc, and their average settling rates were reduced to the equivalent of about one phi size relative to spherical quartz grains of the same diameter. However, repackaging of fine silt and clay grains into the sand-sized fecal pellets causes an effective settling rate increase of up to 3 orders of magnitude for the smallest particles incorporated in the pellets. Moreover, organic carbon and p,p???-DDE exhibit a bimodal distribution with relatively high concentrations in the finest size fraction (0-20 ??m), as expected, and a

In-situ TEM observation of the response of ultrafine- and nanocrystalline-grained tungsten to extreme irradiation environments

PubMed Central

El-Atwani, O.; Hinks, J. A.; Greaves, G.; Gonderman, S.; Qiu, T.; Efe, M.; Allain, J. P.

2014-01-01

The accumulation of defects, and in particular He bubbles, can have significant implications for the performance of materials exposed to the plasma in magnetic-confinement nuclear fusion reactors. Some of the most promising candidates for deployment into such environments are nanocrystalline materials as the engineering of grain boundary density offers the possibility of tailoring their radiation resistance properties. In order to investigate the microstructural evolution of ultrafine- and nanocrystalline-grained tungsten under conditions similar to those in a reactor, a transmission electron microscopy study with in situ 2 keV He+ ion irradiation at 950°C has been completed. A dynamic and complex evolution in the microstructure was observed including the formation of defect clusters, dislocations and bubbles. Nanocrystalline grains with dimensions less than around 60 nm demonstrated lower bubble density and greater bubble size than larger nanocrystalline (60–100 nm) and ultrafine (100–500 nm) grains. In grains over 100 nm, uniform distributions of bubbles and defects were formed. At higher fluences, large faceted bubbles were observed on the grain boundaries, especially on those of nanocrystalline grains, indicating the important role grain boundaries can play in trapping He and thus in giving rise to the enhanced radiation tolerance of nanocrystalline materials. PMID:24796578

Protective antifungal activity of essential oils extracted from Buddleja perfoliata and Pelargonium graveolens against fungi isolated from stored grains.

PubMed

Juárez, Z N; Bach, H; Sánchez-Arreola, E; Bach, H; Hernández, L R

2016-05-01

The chemical composition and antifungal activity of essential oils extracted from Buddleja perfoliata and Pelargonium graveolens were analysed to assess their efficacy as a potential alternative to synthetic chemical fungicides to protect stored grain. Essential oils were obtained by hydrodistillation, while GC-MS were used to characterize the components of theses oils. The main components identified from the essential oil of B. perfoliata were cubenol, eudesmol, germacrene D-4-ol and cis-verbenol; whereas (-)-aristolene, β-citronellol and geraniol, were identified in P. graveolens. These essential oils were tested against a panel of fungal strains isolated from stored grains. Toxicity of the essential oils was assessed using two models represented by human-derived macrophages and the brine shrimp assay. Moreover, inflammatory response of the oils was assessed by measuring secretion of the pro-inflammatory cytokines IL-6 and TNF-α using a human-derived macrophage cell line. Results show potent antifungal activity against a collection of fungi, with minimal inhibitory concentrations ranging from 0·3 to 50 μg ml(-1) for both plants. A moderated cytotoxicity was observed, but no inflammatory responses. These oils can be used as an alternative for synthetic chemical fungicides used to protect stored grains. Synthetic chemical fungicides are used to protect stored grains, but their broad use raises concerns about effects on the environment and human health. The impact of the present report is that the use of essential oils is an eco-friendly alternative for fungal control in postharvest grains with a low impact to the environment. © 2016 The Society for Applied Microbiology.

Physics of grain boundaries in polycrystalline photovoltaic semiconductors

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

Yan, Yanfa, E-mail: yanfa.yan@utoledo.edu; Yin, Wan-Jian; Wu, Yelong

2015-03-21

Thin-film solar cells based on polycrystalline Cu(In,Ga)Se{sub 2} (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this paper, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. However, in each solar cell device, the GBs can bemore » chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. Therefore, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.« less

Physics of grain boundaries in polycrystalline photovoltaic semiconductors

DOE PAGES

Yan, Yanfa; Yin, Wan-Jian; Wu, Yelong; ...

2015-03-16

Thin-film solar cells based on polycrystalline Cu(In,Ga)Se 2 (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this study, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. Although, in each solar cell device, the GBs can bemore » chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. In conclusion, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.« less

Erosion and deposition by supercritical density flows during channel avulsion and backfilling: Field examples from coarse-grained deepwater channel-levée complexes (Sandino Forearc Basin, southern Central America)

NASA Astrophysics Data System (ADS)

Lang, Jörg; Brandes, Christian; Winsemann, Jutta

2017-03-01

Erosion and deposition by supercritical density flows can strongly impact the facies distribution and architecture of submarine fans. Field examples from coarse-grained channel-levée complexes from the Sandino Forearc Basin (southern Central America) show that cyclic-step and antidune deposits represent common sedimentary facies of these depositional systems and relate to the different stages of avulsion, bypass, levée construction and channel backfilling. During channel avulsion, large-scale scour-fill complexes (18 to 29 m deep, 18 to 25 m wide, 60 to > 120 m long) were incised by supercritical density flows. The multi-storey infill of the large-scale scour-fill complexes comprises amalgamated massive, normally coarse-tail graded or widely spaced subhorizontally stratified conglomerates and pebbly sandstones, interpreted as deposits of the hydraulic-jump zone of cyclic steps. The large-scale scour-fill complexes can be distinguished from small-scale channel fills based on the preservation of a steep upper margin and a coarse-grained infill comprising mainly amalgamated hydraulic-jump zone deposits. Channel fills include repeated successions deposited by cyclic steps with superimposed antidunes. The deposits of the hydraulic-jump zone of cyclic steps comprise regularly spaced scours (0.2 to 2.6 m deep, 0.8 to 23 m long) infilled by intraclast-rich conglomerates or pebbly sandstones, displaying normal coarse-tail grading or backsets. These deposits are laterally and vertically associated with subhorizontally stratified, low-angle cross-stratified or sinusoidally stratified sandstones and pebbly sandstones, which were deposited by antidunes on the stoss side of the cyclic steps during flow re-acceleration. The field examples indicate that so-called spaced stratified deposits may commonly represent antidune deposits with varying stratification styles controlled by the aggradation rate, grain-size distribution and amalgamation. The deposits of small-scale cyclic

Becoming Proactive With the Whole-Grains Message.

PubMed

Jones, Julie Miller; Reicks, Marla; Adams, Judi; Fulcher, Gary; Marquart, Len

2004-01-01

Whole-grain foods have always been considered a healthy part of the diet. Only recently have epidemiologic and other data shown that whole grains have a role in preventing cardiovascular disease, diabetes, some types of cancer, and even obesity. What nearly all consumers and most health professionals fail to realize is that whole grains deliver as many if not more phytochemicals and antioxidants than do fruits and vegetables. Healthy People 2010 (DHHS) recommends 3 servings of whole grains per day. Because the average intake in the United States is less than 1 serving per day, health professionals must mount an active campaign to help consumers better understand the important health benefits of whole grains and work to increase their intake in the diet.

Grain Foods Are Contributors of Nutrient Density for American Adults and Help Close Nutrient Recommendation Gaps: Data from the National Health and Nutrition Examination Survey, 2009–2012

PubMed Central

Papanikolaou, Yanni; Fulgoni, Victor L.

2017-01-01

to limit. Cumulatively, a variety of grain food groups consumed by American adults contribute to nutrient density in the total diet and have the potential to increase consumption of shortfall nutrients as identified by 2015–2020 DGA, particularly dietary fiber, folate, and iron. PMID:28805734

Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems

PubMed Central

Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

2016-01-01

In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy. PMID:26923713

Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems.

PubMed

Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

2016-02-29

In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy.

Temperature and population density effects on locomotor activity of Musca domestica (Diptera: Muscidae).

PubMed

Schou, T M; Faurby, S; Kjærsgaard, A; Pertoldi, C; Loeschcke, V; Hald, B; Bahrndorff, S

2013-12-01

The behavior of ectotherm organisms is affected by both abiotic and biotic factors. However, a limited number of studies have investigated the synergistic effects on behavioral traits. This study examined the effect of temperature and density on locomotor activity of Musca domestica (L.). Locomotor activity was measured for both sexes and at four densities (with mixed sexes) during a full light and dark (L:D) cycle at temperatures ranging from 10 to 40°C. Locomotor activity during daytime increased with temperature at all densities until reaching 30°C and then decreased. High-density treatments significantly reduced the locomotor activity per fly, except at 15°C. For both sexes, daytime activity also increased with temperature until reaching 30 and 35°C for males and females, respectively, and thereafter decreased. Furthermore, males showed a significantly higher and more predictable locomotor activity than females. During nighttime, locomotor activity was considerably lower for all treatments. Altogether the results of the current study show that there is a significant interaction of temperature and density on daytime locomotor activity of M. domestica and that houseflies are likely to show significant changes in locomotor activity with change in temperature.

Genotype by environment interaction for plant density response in maize

USDA-ARS?s Scientific Manuscript database

Increased adaptation to high plant density has been an important factor in improvements in grain yield in maize. Despite extensive public literature on variation in plant density response among maize varieties, almost no public information is available on environmental effects on plant density respo...

Estimating the settling velocity of bioclastic sediment using common grain-size analysis techniques

USGS Publications Warehouse

Cuttler, Michael V. W.; Lowe, Ryan J.; Falter, James L.; Buscombe, Daniel D.

2017-01-01

Most techniques for estimating settling velocities of natural particles have been developed for siliciclastic sediments. Therefore, to understand how these techniques apply to bioclastic environments, measured settling velocities of bioclastic sedimentary deposits sampled from a nearshore fringing reef in Western Australia were compared with settling velocities calculated using results from several common grain-size analysis techniques (sieve, laser diffraction and image analysis) and established models. The effects of sediment density and shape were also examined using a range of density values and three different models of settling velocity. Sediment density was found to have a significant effect on calculated settling velocity, causing a range in normalized root-mean-square error of up to 28%, depending upon settling velocity model and grain-size method. Accounting for particle shape reduced errors in predicted settling velocity by 3% to 6% and removed any velocity-dependent bias, which is particularly important for the fastest settling fractions. When shape was accounted for and measured density was used, normalized root-mean-square errors were 4%, 10% and 18% for laser diffraction, sieve and image analysis, respectively. The results of this study show that established models of settling velocity that account for particle shape can be used to estimate settling velocity of irregularly shaped, sand-sized bioclastic sediments from sieve, laser diffraction, or image analysis-derived measures of grain size with a limited amount of error. Collectively, these findings will allow for grain-size data measured with different methods to be accurately converted to settling velocity for comparison. This will facilitate greater understanding of the hydraulic properties of bioclastic sediment which can help to increase our general knowledge of sediment dynamics in these environments.

Influence of grain boundaries on the distribution of components in binary alloys

NASA Astrophysics Data System (ADS)

L'vov, P. E.; Svetukhin, V. V.

2017-12-01

Based on the free-energy density functional method (the Cahn-Hilliard equation), a phenomenological model that describes the influence of grain boundaries on the distribution of components in binary alloys has been developed. The model is built on the assumption of the difference between the interaction parameters of solid solution components in the bulk and at the grain boundary. The difference scheme based on the spectral method is proposed to solve the Cahn-Hilliard equation with interaction parameters depending on coordinates. Depending on the ratio between the interaction parameters in the bulk and at the grain boundary, temperature, and alloy composition, the model can give rise to different types of distribution of a dissolved component, namely, either depletion or enrichment of the grain-boundary area, preferential grainboundary precipitation, competitive precipitation in the bulk and at the grain boundary, etc.

Dependence of Grain Size on the Performance of a Polysilicon Channel TFT for 3D NAND Flash Memory.

PubMed

Kim, Seung-Yoon; Park, Jong Kyung; Hwang, Wan Sik; Lee, Seung-Jun; Lee, Ki-Hong; Pyi, Seung Ho; Cho, Byung Jin

2016-05-01

We investigated the dependence of grain size on the performance of a polycrystalline silicon (poly-Si) channel TFT for application to 3D NAND Flash memory devices. It has been found that the device performance and memory characteristics are strongly affected by the grain size of the poly-Si channel. Higher on-state current, faster program speed, and poor endurance/reliability properties are observed when the poly-Si grain size is large. These are mainly attributed to the different local electric field induced by an oxide valley at the interface between the poly-Si channel and the gate oxide. In addition, the trap density at the gate oxide interface was successfully measured using a charge pumping method by the separation between the gate oxide interface traps and traps at the grain boundaries in the poly-Si channel. The poly-Si channel with larger grain size has lower interface trap density.

Observations of dusty plasmas with magnetized dust grains

NASA Astrophysics Data System (ADS)

Luo, Q.-Z.; D'Angelo, N.

2000-11-01

We report a newly observed phenomenon in a dusty plasma device of the \\mbox{Q-machine} type. At low plasma densities the time required by the plasma to return to its no-dust conditions, after the dust dispenser is turned off, can be as long as many tens of seconds or longer. A tentative interpretation of this observation in terms of magnetized dust grains is advanced. It appears that an important loss mechanism of fine dust grains is by ion drag along the magnetic field lines. The effect of ion drag is somewhat counteracted by the -µ∇B force present when the magnetic field has a mirror geometry.

Debris flow rheology: Experimental analysis of fine-grained slurries

USGS Publications Warehouse

Major, Jon J.; Pierson, Thomas C.

1992-01-01

The rheology of slurries consisting of ≤2-mm sediment from a natural debris flow deposit was measured using a wide-gap concentric-cylinder viscometer. The influence of sediment concentration and size and distribution of grains on the bulk rheological behavior of the slurries was evaluated at concentrations ranging from 0.44 to 0.66. The slurries exhibit diverse rheological behavior. At shear rates above 5 s−1 the behavior approaches that of a Bingham material; below 5 s−1, sand exerts more influence and slurry behavior deviates from the Bingham idealization. Sand grain interactions dominate the mechanical behavior when sand concentration exceeds 0.2; transient fluctuations in measured torque, time-dependent decay of torque, and hysteresis effects are observed. Grain rubbing, interlocking, and collision cause changes in packing density, particle distribution, grain orientation, and formation and destruction of grain clusters, which may explain the observed behavior. Yield strength and plastic viscosity exhibit order-of-magnitude variation when sediment concentration changes as little as 2–4%. Owing to these complexities, it is unlikely that debris flows can be characterized by a single rheological model.

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

NASA Astrophysics Data System (ADS)

Zhao, H.; Palmiere, E. J.

2017-07-01

Although there has been much research regarding the effect of austenite deformation on accelerated cooled microstructures in microalloyed steels, there is still a lack of accurate data on boundary densities and effective grain sizes. Previous results observed from optical micrographs are not accurate enough, because, for displacive transformation products, a substantial part of the boundaries have disorientation angles below 15 deg. Therefore, in this research, a niobium microalloyed steel was used and electron backscattering diffraction mappings were performed on all of the transformed microstructures to obtain accurate results on boundary densities and grain refinement. It was found that with strain rising from 0 to 0.5, a transition from bainitic ferrite to acicular ferrite occurs and the effective grain size reduces from 5.7 to 3.1 μm. When further increasing strain from 0.5 to 0.7, dynamic recrystallization was triggered and postdynamic softening occurred during the accelerated cooling, leading to an inhomogeneous and coarse transformed microstructure. In the entire strain range, the density changes of boundaries with different disorientation angles are distinct, due to different boundary formation mechanisms. Finally, the controversial influence of austenite deformation on effective grain size of low-temperature transformation products was argued to be related to the differences in transformation conditions and final microstructures.

Grain growth effects on magnetic properties of Ni0.6Zn0.4Fe2O4 material prepared using mechanically alloyed nanoparticles

NASA Astrophysics Data System (ADS)

Syazwan, M. M.; Hapishah, A. N.; Azis, R. S.; Abbas, Z.; Hamidon, M. N.

2018-06-01

The effect of grain growth via sintering temperature on some magnetic properties is reported in this research. Ni0.6Zn0.4Fe2O4 nanoparticles were mechanically alloyed for 6 h and the sintering process starting from 600 to 1200 °C with 25 °C increment with only one sample subjected to all sintering scheme. The resulting change in the material was observed after each sintering. Single phase has been formed at 600 °C and above and the intensity peaks increased with sintering temperature as well as crystallinity increment. The morphological studies showed grain size increment as the sintering temperature increased. Moreover, the density increased while the porosity decreased with increasing sintering temperature. The saturation induction, Bs increased with the increased of grain size. On the other hand, the coercivity-vs-grain size plot reveals the critical single-domain-to-multidomain grain size to be about ∼400 nm. The initial permeability, μi value was increased with grain size enhancement. The microstructural grain growth, as exposed for the first time by this research, is shown as a process of multiple activation energy barriers.

Continuous modeling of a grain boundary in MgO and its disclination induced grain-boundary migration mechanism

NASA Astrophysics Data System (ADS)

Cordier, P.; Sun, X.; Taupin, V.; Fressengeas, C.

2016-12-01

Grain boundaries (GBs) are thin material layers where the lattice rotates from one orientation to the next one within a few nanometers. Because they treat these layers as infinitely thin interfaces, large-scale polycrystalline representations fail to describe their structure. Conversely, atomistic representations provide a detailed description of the GBs, but their character remains discrete and not prone to coarse-graining procedures. Continuum descriptions based on kinematic and crystal defect fields defined at interatomic scale are appealing because they can provide smooth and thorough descriptions of GBs, recovering in some sense the atomistic description and potentially serving as a basis for coarse-grained polycrystalline representations. In this work, a crossover between atomistic description and continuous representation of a MgO tilt boundary in polycrystals is set-up to model the periodic arrays of structural units by using dislocation and disclination dipole arrays along GBs. The strain, rotation, curvature, disclination and dislocation density fields are determined in the boundary area by using the discrete atomic positions generated by molecular dynamics simulations. Then, this continuous disclination/dislocation model is used as part of the initial conditions in elasto-plastic continuum mechanics simulations to investigate the shear-coupled boundary migration of tilt boundaries. The present study leads to better understanding of the structure and mechanical architecture of grain boundaries.

The influence of grain size, grain color, and suspended-sediment concentration on light attenuation: why fine-grained terrestrial sediment is bad for coral reef ecosystems

USGS Publications Warehouse

Storlazzi, Curt; Norris, Benjamin; Rosenberger, Kurt

2015-01-01

Sediment has been shown to be a major stressor to coral reefs globally. Although many researchers have tested the impact of sedimentation on coral reef ecosystems in both the laboratory and the field and some have measured the impact of suspended sediment on the photosynthetic response of corals, there has yet to be a detailed investigation on how properties of the sediment itself can affect light availability for photosynthesis. We show that finer-grained and darker-colored sediment at higher suspended-sediment concentrations attenuates photosynthetically active radiation (PAR) significantly more than coarser, lighter-colored sediment at lower concentrations and provide PAR attenuation coefficients for various grain sizes, colors, and suspended-sediment concentrations that are needed for biophysical modeling. Because finer-grained sediment particles settle more slowly and are more susceptible to resuspension, they remain in the water column longer, thus causing greater net impact by reducing light essential for photosynthesis over a greater duration. This indicates that coral reef monitoring studies investigating sediment impacts should concentrate on measuring fine-grained lateritic and volcanic soils, as opposed to coarser-grained siliceous and carbonate sediment. Similarly, coastal restoration efforts and engineering solutions addressing long-term coral reef ecosystem health should focus on preferentially retaining those fine-grained soils rather than coarse silt and sand particles.

Grain boundary premelting and activated sintering in binary refractory alloys

NASA Astrophysics Data System (ADS)

Shi, Xiaomeng

Quasi-liquid intergranular film (IGF) which has been widely observed in ceramic systems can persist into sub-solidus region whereby an analogy to Grain boundary (GB) premelting can be made. In this work, a grain boundary (GB) premelting/prewetting model in a metallic system was firstly built based on the Benedictus' model and computational thermodynamics, predicting that GB disordering can start at 60-85% of the bulk solidus temperatures in selected systems. This model quantitatively explains the long-standing mystery of subsolidus activated sintering in W-Pd, W-Ni, W-Co, W-Fe and W-Cu, and it has broad applications for understanding GB-controlled transport kinetics and physical properties. Furthermore, this study demonstrates the necessity of developing GB phase diagrams as a tool for materials design. Subsequently, Grain boundary (GB) wetting and prewetting in Ni-doped Mo are systematically evaluated via characterizing well-quenched specimens and thermodynamic modeling. In contrast to prior reports, the delta-NiMo phase does not wet Mo GBs in the solid state. In the solid-liquid two-phase region, the Ni-rich liquid wets Mo GBs completely. Furthermore, high-resolution transmission electron microscopy demonstrates that nanometer-thick quasi-liquid IGFs persist at GBs into the single-phase region where the bulk liquid phase is no longer stable; this is interpreted as a case of GB prewetting. An analytical thermodynamic model is developed and validated, and this model can be extended to other systems. Furthermore, the analytical model was refined based upon Beneditus' model with correction in determining interaction contribution of interfacial energy. A calculation-based GB phase diagram for Ni-Mo binary system was created and validated by comparing with GB diffusivities determined through a series of controlled sintering experiments. The dependence of GB diffusivity on doping level and temperature was examined and compared with model-predicted GB phase diagram. The

Effect of thermal treatment on the bio-corrosion and mechanical properties of ultrafine-grained ZK60 magnesium alloy.

PubMed

Choi, H Y; Kim, W J

2015-11-01

The combination of solid solution heat treatments and severe plastic deformation by high-ratio differential speed rolling (HRDSR) resulted in the formation of an ultrafine-grained microstructure with high thermal stability in a Mg-5Zn-0.5Zr (ZK60) alloy. When the precipitate particle distribution was uniform in the matrix, the internal stresses and dislocation density could be effectively removed without significant grain growth during the annealing treatment (after HRDSR), leading to enhancement of corrosion resistance. When the particle distribution was non-uniform, rapid grain growth occurred in local areas where the particle density was low during annealing, leading to development of a bimodal grain size distribution. The bimodal grain size distribution accelerated corrosion by forming a galvanic corrosion couple between the fine-grained and coarse-grained regions. The HRDSR-processed ZK60 alloy with high thermal stability exhibited high corrosion resistance, high strength and high ductility, and excellent superplasticity, which allow the fabrication of biodegradable magnesium devices with complicated designs that have a high mechanical integrity throughout the service life in the human body. Copyright © 2015 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.

The Dynamic Density Bottle: A Make-and-Take, Guided Inquiry Activity on Density

ERIC Educational Resources Information Center

Kuntzleman, Thomas S.

2015-01-01

An activity is described wherein students observe dynamic floating and sinking behavior of plastic pieces in various liquids. The liquids and solids are all contained within a plastic bottle; the entire assembly is called a "density bottle". After completing a series of experiments that guides students to think about the relative…

Enhancing critical current density of cuprate superconductors

DOEpatents

Chaudhari, Praveen

2015-06-16

The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.

Synthesis of large single-crystal hexagonal boron nitride grains on Cu-Ni alloy

NASA Astrophysics Data System (ADS)

Lu, Guangyuan; Wu, Tianru; Yuan, Qinghong; Wang, Huishan; Wang, Haomin; Ding, Feng; Xie, Xiaoming; Jiang, Mianheng

2015-01-01

Hexagonal boron nitride (h-BN) has attracted significant attention because of its superior properties as well as its potential as an ideal dielectric layer for graphene-based devices. The h-BN films obtained via chemical vapour deposition in earlier reports are always polycrystalline with small grains because of high nucleation density on substrates. Here we report the successful synthesis of large single-crystal h-BN grains on rational designed Cu-Ni alloy foils. It is found that the nucleation density can be greatly reduced to 60 per mm2 by optimizing Ni ratio in substrates. The strategy enables the growth of single-crystal h-BN grains up to 7,500 μm2, approximately two orders larger than that in previous reports. This work not only provides valuable information for understanding h-BN nucleation and growth mechanisms, but also gives an effective alternative to exfoliated h-BN as a high-quality dielectric layer for large-scale nanoelectronic applications.

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.

The First Discovery of Presolar Graphite Grains from the Highly Reducing Qingzhen (EH3) Meteorite

NASA Astrophysics Data System (ADS)

Xu, Yuchen; Lin, Yangting; Zhang, Jianchao; Hao, Jialong

2016-07-01

Presolar graphite grains have been extensively studied, but are limited in carbonaceous chondrites, particularly in Murchison (CM2) and Orgueil (CI1), which sampled materials from the oxidizing regions in the solar nebula. Here, we report the first discovery of presolar graphite grains from the Qingzhen (EH3) enstatite chondrite which formed under a highly reducing condition. Eighteen presolar graphite grains were identified by C-isotope mapping of the low-density fraction (1.75-1.85 g cm-3) from Qingzhen acid residue. Another 58 graphite spherules were found in different areas of the same sample mount using a scanning electron microscope and were classified into three morphologies, including cauliflower, onion, and cauliflower-onion. The Raman spectra of these spherules vary from ordered, disordered, and glassy to kerogen-like, suggestive of a wide range of thermal metamorphisms. NanoSIMS analysis of the C- and Si-isotopes of these graphite spherules confirmed 23 presolar grains. The other 35 graphite spherules have no significant isotopic anomalies, but they share similar morphologies and Raman spectra with the presolar ones. Another three grains were identified during NanoSIMS analysis. Of all the 44 presolar graphite grains identified, six grains show 28Si-excesses, suggestive of supernovae origins, and four grains are 12C- and 29,30Si-rich, consistent with low-metallicity asymptotic giant branch star origins. Another two graphite spherules have extremely low 12C/13C ratios with marginal solar Si-isotopes. The morphologies, Raman spectra, and C- and Si-isotopic distributions of the presolar graphite grains from the Qingzhen enstatite chondrite are similar to those of the low-density fractions from Murchison carbonaceous chondrites. This study suggests a homogeneous distribution of presolar graphite grains in the solar nebula.

THE FIRST DISCOVERY OF PRESOLAR GRAPHITE GRAINS FROM THE HIGHLY REDUCING QINGZHEN (EH3) METEORITE

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

Xu, Yuchen; Lin, Yangting; Zhang, Jianchao

Presolar graphite grains have been extensively studied, but are limited in carbonaceous chondrites, particularly in Murchison (CM2) and Orgueil (CI1), which sampled materials from the oxidizing regions in the solar nebula. Here, we report the first discovery of presolar graphite grains from the Qingzhen (EH3) enstatite chondrite which formed under a highly reducing condition. Eighteen presolar graphite grains were identified by C-isotope mapping of the low-density fraction (1.75–1.85 g cm{sup 3}) from Qingzhen acid residue. Another 58 graphite spherules were found in different areas of the same sample mount using a scanning electron microscope and were classified into three morphologies,more » including cauliflower, onion, and cauliflower–onion. The Raman spectra of these spherules vary from ordered, disordered, and glassy to kerogen-like, suggestive of a wide range of thermal metamorphisms. NanoSIMS analysis of the C- and Si-isotopes of these graphite spherules confirmed 23 presolar grains. The other 35 graphite spherules have no significant isotopic anomalies, but they share similar morphologies and Raman spectra with the presolar ones. Another three grains were identified during NanoSIMS analysis. Of all the 44 presolar graphite grains identified, six grains show {sup 28}Si-excesses, suggestive of supernovae origins, and four grains are {sup 12}C- and {sup 29,30}Si-rich, consistent with low-metallicity asymptotic giant branch star origins. Another two graphite spherules have extremely low {sup 12}C/{sup 13}C ratios with marginal solar Si-isotopes. The morphologies, Raman spectra, and C- and Si-isotopic distributions of the presolar graphite grains from the Qingzhen enstatite chondrite are similar to those of the low-density fractions from Murchison carbonaceous chondrites. This study suggests a homogeneous distribution of presolar graphite grains in the solar nebula.« less

Gas-Grain Models for Interstellar Anion Chemistry

NASA Technical Reports Server (NTRS)

Cordiner, M. A.; Charnely, S. B.

2012-01-01

Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment

Carpel size, grain filling, and morphology determine individual grain weight in wheat

PubMed Central

Xie, Quan; Mayes, Sean; Sparkes, Debbie L.

2015-01-01

Individual grain weight is a major yield component in wheat. To provide a comprehensive understanding of grain weight determination, the carpel size at anthesis, grain dry matter accumulation, grain water uptake and loss, grain morphological expansion, and final grain weight at different positions within spikelets were investigated in a recombinant inbred line mapping population of bread wheat (Triticum aestivum L.)×spelt (Triticum spelta L.). Carpel size, grain dry matter and water accumulation, and grain dimensions interacted strongly with each other. Furthermore, larger carpels, a faster grain filling rate, earlier and longer grain filling, more grain water, faster grain water absorption and loss rates, and larger grain dimensions were associated with higher grain weight. Frequent quantitative trait locus (QTL) coincidences between these traits were observed, particularly those on chromosomes 2A, 3B, 4A, 5A, 5DL, and 7B, each of which harboured 16−49 QTLs associated with >12 traits. Analysis of the allelic effects of coincident QTLs confirmed their physiological relationships, indicating that the complex but orderly grain filling processes result mainly from pleiotropy or the tight linkages of functionally related genes. After grain filling, distal grains within spikelets were smaller than basal grains, primarily due to later grain filling and a slower initial grain filling rate, followed by synchronous maturation among different grains. Distal grain weight was improved by increased assimilate availability from anthesis. These findings provide deeper insight into grain weight determination in wheat, and the high level of QTL coincidences allows simultaneous improvement of multiple grain filling traits in breeding. PMID:26246614

On Presolar Stardust Grains from CO Classical Novae

NASA Astrophysics Data System (ADS)

Iliadis, Christian; Downen, Lori N.; José, Jordi; Nittler, Larry R.; Starrfield, Sumner

2018-03-01

About 30%–40% of classical novae produce dust 20–100 days after the outburst, but no presolar stardust grains from classical novae have been unambiguously identified yet. Although several studies claimed a nova paternity for certain grains, the measured and simulated isotopic ratios could only be reconciled, assuming that the grains condensed after the nova ejecta mixed with a much larger amount of close-to-solar matter. However, the source and mechanism of this potential post-explosion dilution of the ejecta remains a mystery. A major problem with previous studies is the small number of simulations performed and the implied poor exploration of the large nova parameter space. We report the results of a different strategy, based on a Monte Carlo technique, that involves the random sampling over the most important nova model parameters: the white dwarf composition; the mixing of the outer white dwarf layers with the accreted material before the explosion; the peak temperature and density; the explosion timescales; and the possible dilution of the ejecta after the outburst. We discuss and take into account the systematic uncertainties for both the presolar grain measurements and the simulation results. Only those simulations that are consistent with all measured isotopic ratios of a given grain are accepted for further analysis. We also present the numerical results of the model parameters. We identify 18 presolar grains with measured isotopic signatures consistent with a CO nova origin, without assuming any dilution of the ejecta. Among these, the grains G270_2, M11-334-2, G278, M11-347-4, M11-151-4, and Ag26 have the highest probability of a CO nova paternity.

Theoretical study on interaction of cytochrome f and plastocyanin complex by a simple coarse-grained model with molecular crowding effect

NASA Astrophysics Data System (ADS)

Nakagawa, Satoshi; Kurniawan, Isman; Kodama, Koichi; Arwansyah, Muhammad Saleh; Kawaguchi, Kazutomo; Nagao, Hidemi

2018-03-01

We present a simple coarse-grained model with the molecular crowding effect in solvent to investigate the structure and dynamics of protein complexes including association and/or dissociation processes and investigate some physical properties such as the structure and the reaction rate from the viewpoint of the hydrophobic intermolecular interactions of protein complex. In the present coarse-grained model, a function depending upon the density of hydrophobic amino acid residues in a binding area of the complex is introduced, and the function involves the molecular crowding effect for the intermolecular interactions of hydrophobic amino acid residues between proteins. We propose a hydrophobic intermolecular potential energy between proteins by using the density-dependent function. The present coarse-grained model is applied to the complex of cytochrome f and plastocyanin by using the Langevin dynamics simulation to investigate some physical properties such as the complex structure, the electron transfer reaction rate constant from plastocyanin to cytochrome f and so on. We find that for proceeding the electron transfer reaction, the distance between metals in their active sites is necessary within about 18 Å. We discuss some typical complex structures formed in the present simulation in relation to the molecular crowding effect on hydrophobic interactions.

Solid-substrate fermentation of wheat grains by mycelia of indigenous species of the genus Ganoderma (higher Basidiomycetes) to enhance the antioxidant activities.

PubMed

Subramaniam, Sarasvathy; Sabaratnam, Vikineswary; Kuppusamy, Umah Rani; Tan, Yee Shin

2014-01-01

Species of the genus Ganoderma are a cosmopolitan wood decaying white rot fungi, which has been used by the Asians for therapeutic purposes for centuries. In the present study, solid-substrate fermentation (SSF) of wheat grains (Triticum aestivum L.) was carried out with indigenous Ganoderma australe (KUM60813) and G. neo-japonicum (KUM61076) selected based on ethnomycological knowledge. G. lucidum (VITA GL) (a commercial strain) was also included in the study. Antioxidant activities of the crude ethanol and aqueous extracts of the fermented and unfermented wheat grains were investigated by ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC), diphenyl-1-picryl-hydrazyl (DPPH) free radical scavenging ability, and lipid peroxidation assay. Among the six mycelia extracts tested, the ethanol extract from wheat fermented with KUM61076 mycelia showed the most potent antioxidant activities, whereas the ethanol extract of wheat grains fermented with KUM60813 mycelia has a good potential in protecting frying oils against oxidation. Total phenolic content (TPC) in the ethanol extracts were higher than that in the aqueous extract. The wheat grains fermented with G. australe (KUM60813) and G. neo-japonicum KUM61076 have greater antioxidant potential compared to the commercially available G. lucidum (VITA GL). The antioxidant activities of the mycelia extracts had a positive correlation with their phenolic contents. Thus phenolic compounds may play a vital role in the antioxidant activities of the selected Ganoderma spp.

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 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

A Cosserat crystal plasticity and phase field theory for grain boundary migration

NASA Astrophysics Data System (ADS)

Ask, Anna; Forest, Samuel; Appolaire, Benoit; Ammar, Kais; Salman, Oguz Umut

2018-06-01

The microstructure evolution due to thermomechanical treatment of metals can largely be described by viscoplastic deformation, nucleation and grain growth. These processes take place over different length and time scales which present significant challenges when formulating simulation models. In particular, no overall unified field framework exists to model concurrent viscoplastic deformation and recrystallization and grain growth in metal polycrystals. In this work a thermodynamically consistent diffuse interface framework incorporating crystal viscoplasticity and grain boundary migration is elaborated. The Kobayashi-Warren-Carter (KWC) phase field model is extended to incorporate the full mechanical coupling with material and lattice rotations and evolution of dislocation densities. The Cosserat crystal plasticity theory is shown to be the appropriate framework to formulate the coupling between phase field and mechanics with proper distinction between bulk and grain boundary behaviour.

Carpel size, grain filling, and morphology determine individual grain weight in wheat.

PubMed

Xie, Quan; Mayes, Sean; Sparkes, Debbie L

2015-11-01

Individual grain weight is a major yield component in wheat. To provide a comprehensive understanding of grain weight determination, the carpel size at anthesis, grain dry matter accumulation, grain water uptake and loss, grain morphological expansion, and final grain weight at different positions within spikelets were investigated in a recombinant inbred line mapping population of bread wheat (Triticum aestivum L.)×spelt (Triticum spelta L.). Carpel size, grain dry matter and water accumulation, and grain dimensions interacted strongly with each other. Furthermore, larger carpels, a faster grain filling rate, earlier and longer grain filling, more grain water, faster grain water absorption and loss rates, and larger grain dimensions were associated with higher grain weight. Frequent quantitative trait locus (QTL) coincidences between these traits were observed, particularly those on chromosomes 2A, 3B, 4A, 5A, 5DL, and 7B, each of which harboured 16-49 QTLs associated with >12 traits. Analysis of the allelic effects of coincident QTLs confirmed their physiological relationships, indicating that the complex but orderly grain filling processes result mainly from pleiotropy or the tight linkages of functionally related genes. After grain filling, distal grains within spikelets were smaller than basal grains, primarily due to later grain filling and a slower initial grain filling rate, followed by synchronous maturation among different grains. Distal grain weight was improved by increased assimilate availability from anthesis. These findings provide deeper insight into grain weight determination in wheat, and the high level of QTL coincidences allows simultaneous improvement of multiple grain filling traits in breeding. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Zone-specific cell biosynthetic activity in mature bovine articular cartilage: a new method using confocal microscopic stereology and quantitative autoradiography.

PubMed

Wong, M; Wuethrich, P; Eggli, P; Hunziker, E

1996-05-01

A new methodology was developed to measure spatial variations in chondrocyte/matrix structural parameters and chondrocyte biosynthetic activity in articular cartilage. This technique is based on the use of a laser scanning confocal microscope that can "optically" section chemically fixed, unembedded tissue. The confocal images are used for morphometric measurement of stereologic parameters such as cell density (cells/mm3), cell volume fraction (%), surface density (l/cm), mean cell volume (micron3), and mean cell surface area (micron2). Adjacent pieces of tissue are simultaneously processed for conventional liquid emulsion autoradiography, and a semiautomated grain counting program is used to measure the silver grain density at regions corresponding to the same sites used for structural measurements. An estimate of chondrocyte biosynthetic activity in terms of grains per cell is obtained by dividing the value for grain density by that for cell density. In this paper, the newly developed methodology was applied to characterize the zone-specific behavior of adult articular cartilage in the free-swelling state. Cylinders of young adult bovine articular cartilage were labelled with either [3H]proline or [35S]sulfate, and chondrocyte biosynthesis and structural parameters were measured from the articular surface to the tidemark. The results showed that chondrocytes of the radial zone occupied twice the volume and surface area of the chondrocytes of the superficial zone but were 10 times more synthetically active. This efficient and unbiased technique may prove useful in studying the correlation between mechanically induced changes in cell form and biosynthetic activity within inhomogeneous tissue as well as metabolic changes in cartilage due to ageing and disease.

Can grain size sensitive creep lubricate faults during earthquake propagation?

NASA Astrophysics Data System (ADS)

De Paola, N.; Holdsworth, R.; Viti, C.; Collettini, C.; Bullock, R. J.; Faoro, I.

2014-12-01

In the shallow portion of crustal fault zones, fracturing and cataclasis are thought to be the dominant processes during earthquake propagation. In the lower crust/upper mantle, viscous flow is inferred to facilitate aseismic creep along shear zones. Recent studies show that slip zones (SZs), in natural and experimental carbonate seismic faults, are made of nanograins with a polygonal texture, a microstructure consistent with deformation by grain boundary sliding (GBS) mechanisms. Friction experiments performed on calcite fine-grained gouges, at speed v = 1 ms-1, normal stress sn = 18 MPa, displacements d = 0.009-1.46 m, and room temperature and humidity, show a four stage-evolution of the fault strength: SI) attainment of initial value, f = 0.67; SII) increase up to peak value f = 0.82; SIII) sudden decrease to low steady-state value, f = 0.18; and SIV) sudden increase to final value, f = 0.44, during sample deceleration. Samples recovered at the end of each displacement-controlled experiments (Stages I-IV) show the following microstructures evolution of the SZ material, which is: SI) poorly consolidated, and made of fine-grained (1 < D < 5 microns), angular clasts formed by brittle fracturing and cataclasis; SII) cohesive, and made of larger clasts of calcite (D ≈ 1 microns), exhibiting a high density of free dislocations and hosting subgrains (D ≤ 200 nm), dispersed within calcite nanograins. SIII) made of nanograin aggregates exhibiting polygonal grain boundaries, and 120° triple junctions between equiaxial grains. The grains display no preferred elongation, no crystal preferred orientation and low free dislocation densities, possibly due to high temperature (> 900 C) GBS creep deformation. Our microstructural observations suggest that GBS mechanisms can operate in geological materials deformed at high strain rates along frictionally heated seismogenic slip surfaces. The observed microstructures in experimental slip zones are strikingly similar to those

Processing of crack-free high density polycrystalline LiTaO3 ceramics

DOE PAGES

Chen, Ching-Fong; Brennecka, Geoff L.; King, Graham; ...

2016-11-04

Our work achieved high density (99.9%) polycrystalline LiTaO 3. The keys to the high density without cracking were the use of LiF-assisted densification to maintain fine grain size as well as the presence of secondary lithium aluminate phases as grain growth inhibitors. The average grain size of the hot pressed polycrystalline LiTaO 3 is less than 5 μm, limiting residual stresses caused by the anisotropic thermal expansion. Dilatometry results clearly indicate liquid phase sintering via the added LiF sintering aid. Efficient liquid phase sintering allows densification during low temperature hot pressing. Electron microscopy confirmed the high-density microstructure. Furthermore, Rietveld analysismore » of neutron diffraction data revealed the presence of LiAlO 2 and LiAl 5O 8 minority phases and negligible substitutional defect incorporation in LiTaO 3.« less

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.

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

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

Softening due to disordered grain boundaries in nanocrystalline Co.

PubMed

Yuasa, Motohiro; Hakamada, Masataka; Nakano, Hiromi; Mabuchi, Mamoru; Chino, Yasumasa

2013-08-28

Nanocrystalline Co consisting of fcc and hcp phases was processed by electrodeposition, and its mechanical properties were investigated by hardness tests. In addition, high-resolution transmission electron microscopy observations and molecular dynamics (MD) simulations were performed to investigate the grain boundary structure and dislocation nucleation from the grain boundaries. A large amount of disorders existed at the grain boundaries and stacking faults were formed from the grain boundaries in the as-deposited Co specimen. The as-deposited specimen showed a lower hardness than did the annealed specimen, although the grain size of the former was smaller than that of the latter. The activation volume of the as-deposited specimen (=1.5b(3)) was lower than that of the annealed specimen (=50b(3)), thus indicating that nucleation of dislocations from grain boundaries is more active in the as-deposited specimen than in the annealed specimens. The MD simulations showed that dislocation nucleation was closely related to a change in the defect structures at the boundary. Therefore, it is suggested that a significant amount of defects enhance changes in the defect structures at the boundary, resulting in softening of the as-deposited specimen.

Softening due to disordered grain boundaries in nanocrystalline Co

NASA Astrophysics Data System (ADS)

Yuasa, Motohiro; Hakamada, Masataka; Nakano, Hiromi; Mabuchi, Mamoru; Chino, Yasumasa

2013-08-01

Nanocrystalline Co consisting of fcc and hcp phases was processed by electrodeposition, and its mechanical properties were investigated by hardness tests. In addition, high-resolution transmission electron microscopy observations and molecular dynamics (MD) simulations were performed to investigate the grain boundary structure and dislocation nucleation from the grain boundaries. A large amount of disorders existed at the grain boundaries and stacking faults were formed from the grain boundaries in the as-deposited Co specimen. The as-deposited specimen showed a lower hardness than did the annealed specimen, although the grain size of the former was smaller than that of the latter. The activation volume of the as-deposited specimen (=1.5b3) was lower than that of the annealed specimen (=50b3), thus indicating that nucleation of dislocations from grain boundaries is more active in the as-deposited specimen than in the annealed specimens. The MD simulations showed that dislocation nucleation was closely related to a change in the defect structures at the boundary. Therefore, it is suggested that a significant amount of defects enhance changes in the defect structures at the boundary, resulting in softening of the as-deposited specimen.

Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus).

PubMed

Vas, Judit; Andersen, Inger Lise

2015-01-01

Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus) in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e., distance travelled, nearest and furthest neighbour distance) and activity budgets (e.g., resting, feeding, social activities) were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period). The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation.

Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus)

PubMed Central

Vas, Judit; Andersen, Inger Lise

2015-01-01

Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus) in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e. distance travelled, nearest and furthest neighbour distance) and activity budgets (e.g. resting, feeding, social activities) were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period). The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation. PMID:26657240

Settling equivalence of detrital minerals and grain-size dependence of sediment composition

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Andò, Sergio; Vezzoli, Giovanni

2008-08-01

This study discusses the laws which govern sediment deposition, and consequently determine size-dependent compositional variability. A theoretical approach is substantiated by robust datasets on major Alpine, Himalayan, and African sedimentary systems. Integrated (bulk-petrography, heavy-mineral, X-ray powder diffraction) multiple-window analyses at 0.25ϕ to 0.50ϕ sieve interval of eighty-five fluvial, beach, and eolian-dune samples, ranging from very fine silt to coarse sand, document homologous intrasample compositional trends, revealed by systematic concentration of denser grains in finer-grained fractions (“size-density sorting”). These trends are explained by the settling-equivalence principle, stating that detrital minerals are deposited together if their settling velocity is the same. Settling of silt is chiefly resisted by fluid viscosity, and Stokes' law predicts that size differences between detrital minerals in ϕ units (“size shifts”) are half the difference between the logarithms of their submerged densities. Settling of pebbles is chiefly resisted by turbulence effects, and the Impact law predicts double size shifts than Stokes' law. Settling of sand is resisted by both viscosity and turbulence, the settling-equivalence formula is complex, and size shifts increase - with increasing settling velocity and grain size - from those predicted by Stokes' law to those predicted by the Impact law. In wind-laid sands, size shifts match those predicted by the Impact law; size-density sorting is thus greater than in water-laid fine sands. New analytical, graphical, and statistical techniques for rigorous settling-equivalence analysis of terrigenous sediments are illustrated. Deviations associated with non-spherical shape, density anomalies, inheritance from source rocks, or mixing of detrital species with contrasting provenance and different size distribution are also tentatively assessed. Such integrated theoretical and experimental approach allows us

Characterization of the Endoproteases Appearing during Wheat Grain Development.

PubMed Central

Dominguez, F.; Cejudo, F. J.

1996-01-01

The pattern of endoproteolytic activities occurring during wheat (Triticum aestivum, cultivar Chinese Spring) grain development was investigated. Total endoprotease activity, assayed in solution with azocasein as a substrate, increased during the early stages of grain development to reach a maximum at 15 d postanthesis that was maintained until the grain was mature. Endoprotease activity was also assayed in gradient polyacrylamide gels co-polymerized with gelatin. The increase in endoproteolytic activity was due to the appearance of up to 18 endoproteolytic bands that were arbitrarily classified into five groups (A, B, C, D, and E). The presence of serine, aspartic, metallo, and, to a lesser extent, thiol proteases in developing wheat grains was demonstrated by the use of class-specific protease inhibitors. The appearance of the different classes of endoproteases during seed development was subject to temporal control; serine proteases were more abundant at early stages and aspartic and metallo proteases were more abundant at later stages. At intermediate stages of development (15-20 d postanthesis), most of the endoproteases were localized in the aleurone, testa, and embryo. The content of acidic thiol proteases was low in the developing starchy endosperm. PMID:12226440

Disintegration of Dust Aggregates in Interstellar Shocks and the Lifetime of Dust Grains in the ISM

NASA Technical Reports Server (NTRS)

Dominik, C.; Jones, A. P.; Tielens, A. G. G. M.; Cuzzi, Jeff (Technical Monitor)

1994-01-01

Interstellar grains are destroyed by shock waves moving through the ISM. In fact, the destruction of grains may be so effective that it is difficult to explain the observed abundance of dust in the ISM as a steady state between input of grains from stellar sources and destruction of grains in shocks. This is especially a problem for the larger grains. Therefore, the dust grains must be protected in some way. Jones et al. have already considered coatings and the increased post-shock drag effects for low density grains. In molecular clouds and dense clouds, coagulation of grains is an important process, and the largest interstellar grains may indeed be aggregates of smaller grains rather than homogeneous particles. This may provide a means to protect the larger grains, in that, in moderate velocity grain-grain collisions in a shock the aggregates may disintegrate rather than be vaporized. The released small particles are more resilient to shock destruction (except in fast shocks) and may reform larger grains later, recovering the observed size distribution. We have developed a model for the binding forces in grain aggregates and apply this model to the collisions between an aggregate and fast small grains. We discuss the results in the light of statistical collision probabilities and grain life times.

A coarse-grained model to study calcium activation of the cardiac thin filament

NASA Astrophysics Data System (ADS)

Zhang, Jing; Schwartz, Steven

2015-03-01

Familial hypertrophic cardiomyopathy (FHC) is one of the most common heart disease caused by genetic mutations. Cardiac muscle contraction and relaxation involve regulation of crossbridge binding to the cardiac thin filament, which regulates actomyosin interactions through calcium-dependent alterations in the dynamics of cardiac troponin (cTn) and tropomyosin (Tm). An atomistic model of cTn complex interacting with Tm has been studied by our group. A more realistic model requires the inclusion of the dynamics of actin filament, which is almost 6 times larger than cTn and Tm in terms of atom numbers, and extensive sampling of the model becomes very resource-demanding. By using physics-based protein united-residue force field, we introduce a coarse-grained model to study the calcium activation of the thin filament resulting from cTn's allosteric regulation of Tm dynamics on actin. The time scale is much longer than that of all-atom molecular dynamics simulation because of the reduction of the degrees of freedom. The coarse-grained model is a good template for studying cardiac thin filament mutations that cause FHC, and reduces the cost of computational resources.

Thermally activated switching at long time scales in exchange-coupled magnetic grains

NASA Astrophysics Data System (ADS)

Almudallal, Ahmad M.; Mercer, J. I.; Whitehead, J. P.; Plumer, M. L.; van Ek, J.; Fal, T. J.

2015-10-01

Rate coefficients of the Arrhenius-Néel form are calculated for thermally activated magnetic moment reversal for dual layer exchange-coupled composite (ECC) media based on the Langer formalism and are applied to study the sweep rate dependence of M H hysteresis loops as a function of the exchange coupling I between the layers. The individual grains are modeled as two exchange-coupled Stoner-Wohlfarth particles from which the minimum energy paths connecting the minimum energy states are calculated using a variant of the string method and the energy barriers and attempt frequencies calculated as a function of the applied field. The resultant rate equations describing the evolution of an ensemble of noninteracting ECC grains are then integrated numerically in an applied field with constant sweep rate R =-d H /d t and the magnetization calculated as a function of the applied field H . M H hysteresis loops are presented for a range of values I for sweep rates 105Oe /s ≤R ≤1010Oe /s and a figure of merit that quantifies the advantages of ECC media is proposed. M H hysteresis loops are also calculated based on the stochastic Landau-Lifshitz-Gilbert equations for 108Oe /s ≤R ≤1010Oe /s and are shown to be in good agreement with those obtained from the direct integration of rate equations. The results are also used to examine the accuracy of certain approximate models that reduce the complexity associated with the Langer-based formalism and which provide some useful insight into the reversal process and its dependence on the coupling strength and sweep rate. Of particular interest is the clustering of minimum energy states that are separated by relatively low-energy barriers into "metastates." It is shown that while approximating the reversal process in terms of "metastates" results in little loss of accuracy, it can reduce the run time of a kinetic Monte Carlo (KMC) simulation of the magnetic decay of an ensemble of dual layer ECC media by 2 -3 orders of magnitude

Passive acoustic measurement of bedload grain size distribution using self-generated noise

NASA Astrophysics Data System (ADS)

Petrut, Teodor; Geay, Thomas; Gervaise, Cédric; Belleudy, Philippe; Zanker, Sebastien

2018-01-01

Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

Increasing abscisic acid levels by immunomodulation in barley grains induces precocious maturation without changing grain composition

PubMed Central

Staroske, Nicole; Conrad, Udo; Kumlehn, Jochen; Hensel, Götz; Radchuk, Ruslana; Erban, Alexander; Kopka, Joachim; Weschke, Winfriede; Weber, Hans

2016-01-01

Abscisic acid (ABA) accumulates in seeds during the transition to the seed filling phase. ABA triggers seed maturation, storage activity, and stress signalling and tolerance. Immunomodulation was used to alter the ABA status in barley grains, with the resulting transgenic caryopses responding to the anti-ABA antibody gene expression with increased accumulation of ABA. Calculation of free versus antibody-bound ABA reveals large excess of free ABA, increasing signficantly in caryopses from 10 days after fertilization. Metabolite and transcript profiling in anti-ABA grains expose triggered and enhanced ABA-functions such as transcriptional up-regulation of sucrose-to-starch metabolism, storage protein synthesis and ABA-related signal transduction. Thus, enhanced ABA during transition phases induces precocious maturation but negatively interferes with growth and development. Anti-ABA grains display broad constitutive gene induction related to biotic and abiotic stresses. Most of these genes are ABA- and/or stress-inducible, including alcohol and aldehyde dehydrogenases, peroxidases, chaperones, glutathione-S-transferase, drought- and salt-inducible proteins. Conclusively, ABA immunomodulation results in precocious ABA accumulation that generates an integrated response of stress and maturation. Repression of ABA signalling, occurring in anti-ABA grains, potentially antagonizes effects caused by overshooting production. Finally, mature grain weight and composition are unchanged in anti-ABA plants, although germination is somewhat delayed. This indicates that anti-ABA caryopses induce specific mechanisms to desensitize ABA signalling efficiently, which finally yields mature grains with nearly unchanged dry weight and composition. Such compensation implicates the enormous physiological and metabolic flexibilities of barley grains to adjust effects of unnaturally high ABA amounts in order to ensure and maintain proper grain development. PMID:26951372

Simulation study of spheroidal dust gains charging: Applicable to dust grain alignment

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

Zahed, H.; Sobhanian, S.; Mahmoodi, J.

2006-09-15

The charging process of nonspherical dust grains in an unmagnetized plasma as well as in the presence of a magnetic field is studied. It is shown that unlike the spherical dust grain, due to nonhomogeneity of charge distribution on the spheroidal dust surface, the resultant electric forces on electrons and ions are different. This process produces some surface charge density gradient on the nonspherical grain surface. Effects of a magnetic field and other plasma parameters on the properties of the dust particulate are studied. It has been shown that the alignment direction could be changed or even reversed with themore » magnetic field and plasma parameters. Finally, the charge distribution on the spheroidal grain surface is studied for different ambient parameters including plasma temperature, neutral collision frequency, and the magnitude of the magnetic field.« less

Transmission Electron Microscopy of Plagioclase-Rich Itokawa Grains: Space Weathering Effects and Solar Flare Track Exposure Ages

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.; Berger, Eve L.

2017-01-01

Limited samples are available for the study of space weathering effects on airless bodies. The grains returned by the Hayabusa mission to asteroid 25143 Itokawa provide the only samples currently available to study space weathering of ordinary chondrite regolith. We have previously studied olivine-rich Itokawa grains and documented their surface alteration and exposure ages based on the observed density of solar flare particle tracks. 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.

Active sensing: An innovative tool for evaluating grain yield and nitrogen use efficiency of multiple wheat genotypes

NASA Astrophysics Data System (ADS)

Naser, Mohammed Abdulridha

Precision agricultural practices have significantly contributed to the improvement of crop productivity and profitability. Remote sensing based indices, such as Normalized Difference Vegetative Index (NDVI) have been used to obtain crop information. It is used to monitor crop development and to provide rapid and nondestructive estimates of plant biomass, nitrogen (N) content and grain yield. Remote sensing tools are helping improve nitrogen use efficiency (NUE) through nitrogen management and could also be useful for high NUE genotype selection. The objectives of this study were: (i) to determine if active sensor based NDVI readings can differentiate wheat genotypes, (ii) to determine if NDVI readings can be used to classify wheat genotypes into grain yield productivity classes, (iii) to identify and quantify the main sources of variation in NUE across wheat genotypes, and (iv) to determine if normalized difference vegetation index (NDVI) could characterize variability in NUE across wheat genotypes. This study was conducted in north eastern Colorado for two years, 2010 and 2011. The NDVI readings were taken weekly during the winter wheat growing season from March to late June, in 2010 and 2011 and NUE were calculated as partial factor productivity and as partial nitrogen balance at the end of the season. For objectives i and ii, the correlation between NDVI and grain yield was determined using Pearson's product-moment correlation coefficient (r) and linear regression analysis was used to explain the relationship between NDVI and grain yield. The K-means clustering algorithm was used to classify mean NDVI and mean grain yield into three classes. For objectives iii and iv, the parameters related to NUE were also calculated to measure their relative importance in genotypic variation of NUE and power regression analysis between NDVI and NUE was used to characterize the relationship between NDVI and NUE. The results indicate more consistent association between grain

The Charging of Dust Grains in the Inner Heliosheath

NASA Astrophysics Data System (ADS)

Avinash, K.; Slavin, J.; Zank, G. P.; Frisch, P.

2008-12-01

Equilibrium electric charge and surface potential on a dust grain in the heliosheath are calculated. The grain is charged due to heliosheath plasma flux, photo electrons flux, secondary electron emission flux and transmission flux. Realistically, the heliosheath plasma consists of solar electrons, solar wind ions [SWI] and pick up ions [PUI]. These species interact differently with TS and thus have different characteristics down stream in the heliosheath. The PUI suffer multiple reflections at TS and are accelerated to high energies in the range of ~ 106 K. The solar electrons, on the other hand, are heated adiabatically through the TS and have temperature in the range ~ 5x105 K. The SWI may have a smaller temperature typically in the range 1-5x104 K The density of electrons could be in the range ~5 x 10-4 cm-3, while the ratio of PUI to SWI density could range from 0.1 to 0.5. Taking into account these parameters, grain charging due to different plasma species and other fluxes mentioned earlier, is calculated. Our results show that (a) surface potential is very sensitive to electron temp. It goes through a maxima and for realistic values close to or less than 5x105 K it can be as big as 26V which is twice the value calculated by Kimura and Mann1. This may have implications for electrostatic disruption and the size distribution of dust particles in the heliosheath. With PUI density the surface potential increases about 10 to 20 %. Though temperature of PUI is significantly larger than that of electrons, it is not large enough to make up for the mass ratio of electrons to protons. On account small temperature and electron/proton mass ratio, the effect of SWI on dust charge is very weak. (1) H. Kimura and I. Mann, Ap.J. 499, 454 (1998).

The role of boundary variability in polycrystalline grain-boundary diffusion

NASA Astrophysics Data System (ADS)

Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

2015-01-01

We investigate the impact of grain-boundary variability on mass transport in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion in prototypical microstructures in which there is either a discrete spectrum of grain-boundary activation energies or else a complex distribution of grain-boundary character, and hence a continuous spectrum of boundary activation energies. An effective diffusivity is calculated for these structures using simplified multi-state models and, for the case of a continuous spectrum, employing experimentally obtained grain-boundary energy data. We identify different diffusive regimes for these cases and quantify deviations from Arrhenius behavior using effective medium theory. Finally, we examine the diffusion kinetics of a simplified model of an interfacial layering (i.e., complexion) transition.

The magnetized sheath of a dusty plasma with grains size distribution

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

Ou, Jing, E-mail: ouj@ipp.ac.cn; Gan, Chunyun; Lin, Binbin

2015-05-15

The structure of a plasma sheath in the presence of dust grains size distribution (DGSD) is investigated in the multi-fluid framework. It is shown that effect of the dust grains with different sizes on the sheath structure is a collective behavior. The spatial distributions of electric potential, the electron and ion densities and velocities, and the dust grains surface potential are strongly affected by DGSD. The dynamics of dust grains with different sizes in the sheath depend on not only DGSD but also their radius. By comparison of the sheath structure, it is found that under the same expected valuemore » of DGSD condition, the sheath length is longer in the case of lognormal distribution than that in the case of uniform distribution. In two cases of normal and lognormal distributions, the sheath length is almost equal for the small variance of DGSD, and then the difference of sheath length increases gradually with increase in the variance.« less

Density of very small meteoroids

NASA Astrophysics Data System (ADS)

Kikwaya Eluo, Jean-Baptiste

2015-08-01

Knowing the density of meteoroids helps to determine the physical structure and gives insight into the composition of their parent bodies. The density of meteoroids can provide clues to their origins, whether cometary or asteroidal. Density helps also to characterize the risk meteoroids may pose to artificial satellites.Ceplecha (1968) calculated the density of small meteoroids based on a parameter KB (meteoroid beginning height) and classified them in four categories (A,B,C,D) with densities going from 2700 to 180 kgm-3.Babadzhanov(2002) applied a model based on quasi-continuous fragmentation (QCF) on 413 photographic Super-Schmidt meteors by solely fitting their light curves. Their densities range from 400 to 7800 kgm-3. Bellot Rubio et al. (2002) analyzed the same 413 photographic meteors assuming the single body theory based on meteoroid dynamical properties and found densities ranging from 400 to 4800 kgm-3. A thermal erosion model was used by Borovicka et al. (2007) to analyze, simultaneously, the observed decelerations and light curves of six Draconid meteors. The density was found to be 300 kgm-3, consistent with the fact that the Draconid meteors are porous aggregates of grains associated with the Jupiter-family-comet 21P/Giacobini-Zinner (Jacchia, L.G., 1950).We used the Campbell-Brown and Koschny (2004) model of meteoroid ablation to determine the density of faint meteoroids from the analysis of both observed decelerations and light curves of meteoroids (Kikwaya et al., 2009; Kikwaya et al., 2011). Our work was based on a collection of six and ninety-two sporadic meteors. The grain masses used in the modeling ranged from 10-12 Kg to 10-9 Kg. We computed the orbit of each meteoroid and determined its Tisserand parameter. We found that meteoroids with asteroidal orbits have bulk densities ranging from 3000-5000 kgm-3. Meteoroids consistent with HTC/NIC parents have bulk densities from 400 kgm-3 to 1600 kg m-3. JFC meteoroids were found to have surprisingly

Iminosugar inhibitors of carbohydrate-active enzymes that underpin cereal grain germination and endosperm metabolism

PubMed Central

Andriotis, Vasilios M. E.; Rejzek, Martin; Rugen, Michael D.; Svensson, Birte; Smith, Alison M.; Field, Robert A.

2016-01-01

Starch is a major energy store in plants. It provides most of the calories in the human diet and, as a bulk commodity, it is used across broad industry sectors. Starch synthesis and degradation are not fully understood, owing to challenging biochemistry at the liquid/solid interface and relatively limited knowledge about the nature and control of starch degradation in plants. Increased societal and commercial demand for enhanced yield and quality in starch crops requires a better understanding of starch metabolism as a whole. Here we review recent advances in understanding the roles of carbohydrate-active enzymes in starch degradation in cereal grains through complementary chemical and molecular genetics. These approaches have allowed us to start dissecting aspects of starch degradation and the interplay with cell-wall polysaccharide hydrolysis during germination. With a view to improving and diversifying the properties and uses of cereal grains, it is possible that starch degradation may be amenable to manipulation through genetic or chemical intervention at the level of cell wall metabolism, rather than simply in the starch degradation pathway per se. PMID:26862201

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

Formation of ions and radicals from icy grains in comets

NASA Technical Reports Server (NTRS)

Jackson, William M.; Gerth, Christopher; Hendricks, Charles

1991-01-01

Ion and radical formation in comets are thought to occur primarily by photodissociation of gas phase molecules. Experimental evidence and theoretical calculations are presented that show that some of the radical and ions can come directly from ice grains. The experimental evidence suggest that if the frozen molecules on the surface of grains undergo direct dissociation then they may be able to release radicals directly in the gas phase. If the molecules undergo predissociation it is unlikely that they will release radicals in the gas phase since they should be quenched. Calculations of this direct photodissociation mechanism further indicate that even if the parent molecule undergoes direct dissociation, the yield will not be high enough to explain the rays structure in comets unless the radicals are stored in the grains and then released when the grain evaporates. Calculations were also performed to determine the maximum number of ions that can be stored in an icy grain's radius. This number is compared with the ratio of the ion to neutral molecular density. The comparison suggests that some of the ions observed near the nucleus of the comet could have originally been present in the cometary nucleus. It is also pointed out that the presence of these ions in icy grains could lead to radical formation via electron recombination. Finally, an avalanche process was evaluated as another means of producing ions in comets.

Whole Grains in Amelioration of Metabolic Derangements

PubMed Central

Develaraja, Samir; Reddy, Anup; Yadav, Mukesh; Jain, Shalini; Yadav, Hariom

2017-01-01

Daily diet influences whole body metabolism, and intricately linked to the prevention or progression of metabolic diseases including obesity, diabetes and cardiovascular diseases. Several epidemiological and large scale studies have shown that diets enriched with whole grains improves metabolic function and protect from the development of metabolic diseases. Direct impact of whole grain diet can be mediated on several levels of metabolic functions i.e. reduced glycemic index, improved fat oxidation potential, increased cholesterol clearance or decreased cholesterol biosynthesis and modulation of gut microbiome. In this article we reviewed several studies indicating the beneficial effects of whole grain diets on metabolic functions, as well as discussed the potential active phytochemicals present in these whole grain foods to contribute in modulation of metabolic function in our body. PMID:28944285

Nucleation and Growth of Crystalline Grains in RF-Sputtered TiO 2 Films

DOE PAGES

Johnson, J. C.; Ahrenkiel, S. P.; Dutta, P.; ...

2009-01-01

Amore » morphous TiO 2 thin films were radio frequency sputtered onto siliconmonoxide and carbon support films on molybdenum transmission electron microscope (TEM) grids and observed during in situ annealing in a TEM heating stage at 250 ∘ C. The evolution of crystallization is consistent with a classical model of homogeneous nucleation and isotropic grain growth. The two-dimensional grain morphology of the TEM foil allowed straightforward recognition of amorphous and crystallized regions of the films, for measurement of crystalline volume fraction and grain number density. By assuming that the kinetic parameters remain constant beyond the onset of crystallization, the final average grain size was computed, using an analytical extrapolation to the fully crystallized state. Electron diffraction reveals a predominance of the anatase crystallographic phase.« less

Replacing with whole grains and legumes reduces Lp-PLA2 activities in plasma and PBMCs in patients with prediabetes or T2D1

PubMed Central

Kim, Minjoo; Jeung, Se Ri; Jeong, Tae-Sook; Lee, Sang-Hyun; Lee, Jong Ho

2014-01-01

To determine dietary effects on circulating lipoprotein-associated phospholipase A2 (Lp-PLA2) activity and enzyme activity in peripheral blood mononuclear cells (PBMCs), 99 patients with impaired fasting glucose, impaired glucose tolerance, or newly-diagnosed T2D were randomly assigned to either a control group (usual diet with refined rice) or the whole grain and legume group. Substitution of whole grains and legumes for refined rice was associated with the replacement of 7% of energy from carbohydrates with energy from protein (about 4%) and fat. After 12 weeks, the whole grain and legume group showed a significant decrease in fasting glucose, insulin, homeostasis model assessment-insulin resistance, hemoglobin A1c, malondialdehyde, plasma Lp-PLA2 activity, and oxidized LDL (ox-LDL), and an increase in LDL particle size. The changes (Δs) in these variables in the whole grain and legume group were significantly different from those in controls after adjustment for the baseline levels. When all subjects were considered, Δ plasma Lp-PLA2 positively correlated with Δ glucose, Δ PBMC Lp-PLA2, Δ ox-LDL, and Δ urinary 8-epi-prostaglandin F2α after being adjusted for confounding factors. The Δ PBMC Lp-PLA2 correlated positively with Δ glucose and Δ ox-LDL, and negatively with Δ LDL particle size and baseline PBMC Lp-PLA2. The substitution of whole grains and legumes for refined rice resulted in a reduction in Lp-PLA2 activities in plasma and PBMCs partly through improved glycemic control, increased consumption of protein relative to carbohydrate, and reduced lipid peroxides. PMID:24904022

Effect of Grain Misorientation Angle on Twinning Propagation in Ti-15Mo Alloy

NASA Astrophysics Data System (ADS)

Im, Y.-D.; Lee, Y.-K.; Song, K. H.

2018-07-01

This study was carried out to evaluate the effect of grain misorientation angle distribution on the deformation behavior and twinning of Ti-15Mo alloy. Cold rolling exhibited a significant texture with grains oriented along the {111}//normal direction, which correlate with a higher fraction of low-angle boundaries. This material showed a lower yield strength and higher elongation than those of the hot rolled material. The twinning propagation mainly occurred between neighboring grains with a low-angle relation. Consequently, the texture development was correlated with low-angle boundaries and affected by the increase in the twinning density, which increased the strain hardening rate.

Percolation Thresholds in Angular Grain media: Drude Directed Infiltration

NASA Astrophysics Data System (ADS)

Priour, Donald

Pores in many realistic systems are not well delineated channels, but are void spaces among grains impermeable to charge or fluid flow which comprise the medium. Sparse grain concentrations lead to permeable systems, while concentrations in excess of a critical density block bulk fluid flow. We calculate percolation thresholds in porous materials made up of randomly placed (and oriented) disks, tetrahedrons, and cubes. To determine if randomly generated finite system samples are permeable, we deploy virtual tracer particles which are scattered (e.g. specularly) by collisions with impenetrable angular grains. We hasten the rate of exploration (which would otherwise scale as ncoll1 / 2 where ncoll is the number of collisions with grains if the tracers followed linear trajectories) by considering the tracer particles to be charged in conjunction with a randomly directed uniform electric field. As in the Drude treatment, where a succession of many scattering events leads to a constant drift velocity, tracer displacements on average grow linearly in ncoll. By averaging over many disorder realizations for a variety of systems sizes, we calculate the percolation threshold and critical exponent which characterize the phase transition.

A Statistical Study of the Distribution and Dynamics of Icy Grains in the Enceladus Gas Plume by Cassini's Ion Neutral Mass Spectrometer

NASA Astrophysics Data System (ADS)

HSU, J.; Lai, I.; Ip, W.; Teolis, B. D.; Perryman, R.; Waite, J. H.

2013-12-01

A very interesting finding by the Ion Neutral Mass Spectrometer on Cassini is about the detection of tiny icy grains embedded in the Enceladus gas plume during close encounters of the Cassini spacecraft with this active icy satellite of Saturn. Entering of an icy grain into the antechamber of INMS would lead to the generation of a sharp spike superimposed on the countrate profile of the gas molecules in the mass channel under measurement. Employing Monte Carlo simulations and data analysis of the INMS instrument performance, Teolis et al. (2010) investigated the time histories of the 'dust spikes' and the associated icy grain density distributions along the paths of the E3 and E5 encounters, respectively. Following similar method, we have studied the corresponding dust measurements from the E7, E14, E17 and E18 flybys. The different encounter geometries allow us to have a better understanding of the relation between the source regions of the 'dust spikes' from INMS and the jet locations and directions identified by Spitale and Porco (2007). In addition, fitting of the gas plume density profiles provide constraints on the initial conditions of the gas outflow from which the trajectories of dust particles of different sizes could be computed and compared with the INMS measurements.

Reproductive sink of sweet corn in response to plant density and hybrid

USDA-ARS?s Scientific Manuscript database

Improvements in plant density tolerance have played an essential role in grain corn yield gains for ~80 years; however, plant density effects on sweet corn biomass allocation to the ear (the reproductive ‘sink’) is poorly quantified. Moreover, optimal plant densities for modern white-kernel shrunke...

Modeling of grain size strengthening in tantalum at high pressures and strain rates

DOE PAGES

Rudd, Robert E.; Park, H. -S.; Cavallo, R. M.; ...

2017-01-01

Laser-driven ramp wave compression experiments have been used to investigate the strength (flow stress) of tantalum and other metals at high pressures and high strain rates. Recently this kind of experiment has been used to assess the dependence of the strength on the average grain size of the material, finding no detectable variation with grain size. The insensitivity to grain size has been understood theoretically to result from the dominant effect of the high dislocation density generated at the extremely high strain rates of the experiment. Here we review the experiments and describe in detail the multiscale strength model usedmore » to simulate them. The multiscale strength model has been extended to include the effect of geometrically necessary dislocations generated at the grain boundaries during compatible plastic flow in the polycrystalline metal. Lastly, we use the extended model to make predictions of the threshold strain rates and grain sizes below which grain size strengthening would be observed in the laser-driven Rayleigh-Taylor experiments.« less

Increasing abscisic acid levels by immunomodulation in barley grains induces precocious maturation without changing grain composition.

PubMed

Staroske, Nicole; Conrad, Udo; Kumlehn, Jochen; Hensel, Götz; Radchuk, Ruslana; Erban, Alexander; Kopka, Joachim; Weschke, Winfriede; Weber, Hans

2016-04-01

Abscisic acid (ABA) accumulates in seeds during the transition to the seed filling phase. ABA triggers seed maturation, storage activity, and stress signalling and tolerance. Immunomodulation was used to alter the ABA status in barley grains, with the resulting transgenic caryopses responding to the anti-ABA antibody gene expression with increased accumulation of ABA. Calculation of free versus antibody-bound ABA reveals large excess of free ABA, increasing signficantly in caryopses from 10 days after fertilization. Metabolite and transcript profiling in anti-ABA grains expose triggered and enhanced ABA-functions such as transcriptional up-regulation of sucrose-to-starch metabolism, storage protein synthesis and ABA-related signal transduction. Thus, enhanced ABA during transition phases induces precocious maturation but negatively interferes with growth and development. Anti-ABA grains display broad constitutive gene induction related to biotic and abiotic stresses. Most of these genes are ABA- and/or stress-inducible, including alcohol and aldehyde dehydrogenases, peroxidases, chaperones, glutathione-S-transferase, drought- and salt-inducible proteins. Conclusively, ABA immunomodulation results in precocious ABA accumulation that generates an integrated response of stress and maturation. Repression of ABA signalling, occurring in anti-ABA grains, potentially antagonizes effects caused by overshooting production. Finally, mature grain weight and composition are unchanged in anti-ABA plants, although germination is somewhat delayed. This indicates that anti-ABA caryopses induce specific mechanisms to desensitize ABA signalling efficiently, which finally yields mature grains with nearly unchanged dry weight and composition. Such compensation implicates the enormous physiological and metabolic flexibilities of barley grains to adjust effects of unnaturally high ABA amounts in order to ensure and maintain proper grain development. © The Author 2016. Published by

Synchrotron characterization of nanograined UO 2 grain growth

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

Mo, Kun; Miao, Yinbin; Yun, Di

2015-09-30

This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructuremore » based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize our preliminary synchrotron radiation experiments at APS to determine the grain size of nanograin UO 2. The methodology and experimental setup developed in this experiment can directly apply to the proposed in-situ grain growth measurements. The investigation of the grain growth kinetics was conducted based on isothermal annealing and grain growth characterization as functions of duration and temperature. The kinetic parameters such as activation energy for grain growth for UO 2 with different stoichiometry are obtained and compared with molecular dynamics (MD) simulations.« less

Local activation time sampling density for atrial tachycardia contact mapping: how much is enough?

PubMed

Williams, Steven E; Harrison, James L; Chubb, Henry; Whitaker, John; Kiedrowicz, Radek; Rinaldi, Christopher A; Cooklin, Michael; Wright, Matthew; Niederer, Steven; O'Neill, Mark D

2018-02-01

Local activation time (LAT) mapping forms the cornerstone of atrial tachycardia diagnosis. Although anatomic and positional accuracy of electroanatomic mapping (EAM) systems have been validated, the effect of electrode sampling density on LAT map reconstruction is not known. Here, we study the effect of chamber geometry and activation complexity on optimal LAT sampling density using a combined in silico and in vivo approach. In vivo 21 atrial tachycardia maps were studied in three groups: (1) focal activation, (2) macro-re-entry, and (3) localized re-entry. In silico activation was simulated on a 4×4cm atrial monolayer, sampled randomly at 0.25-10 points/cm2 and used to re-interpolate LAT maps. Activation patterns were studied in the geometrically simple porcine right atrium (RA) and complex human left atrium (LA). Activation complexity was introduced into the porcine RA by incomplete inter-caval linear ablation. In all cases, optimal sampling density was defined as the highest density resulting in minimal further error reduction in the re-interpolated maps. Optimal sampling densities for LA tachycardias were 0.67 ± 0.17 points/cm2 (focal activation), 1.05 ± 0.32 points/cm2 (macro-re-entry) and 1.23 ± 0.26 points/cm2 (localized re-entry), P = 0.0031. Increasing activation complexity was associated with increased optimal sampling density both in silico (focal activation 1.09 ± 0.14 points/cm2; re-entry 1.44 ± 0.49 points/cm2; spiral-wave 1.50 ± 0.34 points/cm2, P < 0.0001) and in vivo (porcine RA pre-ablation 0.45 ± 0.13 vs. post-ablation 0.78 ± 0.17 points/cm2, P = 0.0008). Increasing chamber geometry was also associated with increased optimal sampling density (0.61 ± 0.22 points/cm2 vs. 1.0 ± 0.34 points/cm2, P = 0.0015). Optimal sampling densities can be identified to maximize diagnostic yield of LAT maps. Greater sampling density is required to correctly reveal complex activation and

Comparison of Phase Field Crystal and Molecular Dynamics Simulations for a Shrinking Grain

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

Radhakrishnan, Balasubramaniam; Gorti, Sarma B; Nicholson, Don M

2012-01-01

The Phase-Field Crystal (PFC) model represents the atomic density as a continuous function, whose spatial distribution evolves at diffusional, rather than vibrational time scales. PFC provides a tool to study defect interactions at the atomistic level but over longer time scales than in molecular dynamics (MD). We examine the behavior of the PFC model with the goal of relating the PFC parameters to physical parameters of real systems, derived from MD simulations. For this purpose we model the phenomenon of the shrinking of a spherical grain situated in a matrix. By comparing the rate of shrinking of the central grainmore » using MD and PFC we obtain a relationship between PFC and MD time scales for processes driven by grain boundary diffusion. The morphological changes in the central grain including grain shape and grain rotation are also examined in order to assess the accuracy of the PFC in capturing the evolution path predicted by MD.« less

Grain boundary modification to suppress lithium penetration through garnet-type solid electrolyte

NASA Astrophysics Data System (ADS)

Hongahally Basappa, Rajendra; Ito, Tomoko; Morimura, Takao; Bekarevich, Raman; Mitsuishi, Kazutaka; Yamada, Hirotoshi

2017-09-01

Garnet-type solid electrolytes are one of key materials to enable practical usage of lithium metal anode for high-energy-density batteries. However, it suffers from lithium growth in pellets on charging, which causes short circuit. In this study, grain boundaries of Li6.5La3Zr1.5Ta0.5O12 (LLZT) pellets are modified with Li2CO3 and LiOH to investigate the influence of the microstructure of grain boundaries on lithium growth and to study the mechanism of the lithium growth. In spite of similar properties (relative density of ca. 96% and total ionic conductivity of 7 × 10-4 S cm-1 at 25 °C), the obtained pellets exhibit different tolerance on the short circuit. The LLZT pellets prepared from LiOH-modified LLZT powders exhibit rather high critical current density of 0.6 mA cm-2, at which short circuit occurs. On the other hand, the LLZT pellets without grain boundary modification short-circuited at 0.15 mA cm-2. Microstructural analyses by means of SEM, STEM and EIS suggest that lithium grows through interconnected open voids, and reveal that surface layers such as Li2CO3 and LiOH are not only plug voids but also facilitate the sintering of LLZT to suppress the lithium growth. The results indicate a strategy towards short-circuit-free lithium metal batteries.

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.

Optimization of processing conditions to improve antioxidant activities of apple juice and whey based novel beverage fermented by kefir grains.

PubMed

Sabokbar, Nayereh; Khodaiyan, Faramarz; Moosavi-Nasab, Marzieh

2015-06-01

A central composite design (CCD) was used to evaluate the effects of fermentation temperature (20-30 ºC) and kefir grains amount (2-8%w/v) on total phenolic content and antioxidant activities of apple juice and whey based novel beverage fermented by kefir grains. The response surface methodology (RSM) showed that the significant second-order polynomial regression equation with high R(2) (>0.86) was successfully fitted for all response as function of independent variable. The overall optimum region was found to be at the combined level of 7.56%w/v kefir grains and temperature of 24.82 ºC with the highest value for total phenolic content (TPC) and antioxidant activities. At this optimum point TPC, 1, 1-Diphenyl-2-picrylhydrazyl radical scavenging, metal chelating effect, reducing power, inhibition of linoleic acid autoxidation and inhibition of ascorbate autoxidation were 165.02 mgGA/l, 0.38 ml/1 ml, 0.757 (absorbance at 700 nm), 46.12 %, 65.33 % and 21 %, respectively. No significant difference (p < 0.05) was found between actual values and predicated values.

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

Straight from the source's mouth; a quantitative study of grain-size export for an entire active rift, the Corinth Rift, central Greece

NASA Astrophysics Data System (ADS)

Watkins, Stephen E.; Whittaker, Alexander C.; Bell, Rebecca E.; Brooke, Sam A. S.; McNeill, Lisa C.; Gawthorpe, Robert L.

2017-04-01

The volumes, grain sizes and characteristics of sediment supplied from source catchments fundamentally controls basin stratigraphy. However, to date, few studies have constrained sediment budgets, including grain size, released into an active rift basin at a regional scale. The Gulf of Corinth, central Greece, is one of the most rapidly extending rifts in the world, with geodetic measurements of 5 mm/yr in the East to 15 mm/yr in the West. It has well-constrained climatic and tectonic boundary conditions and bedrock lithologies are well-characterised. It is therefore an ideal natural laboratory to study the grain-size export for a rift. In the field, we visited the river mouths of 49 catchments draining into the Corinth Gulf, which in total drain 83% of the rift. At each site, hydraulic geometries, surface grain-size of channel bars and full-weighted grain-size distributions of river sediment were obtained. The surface grain-size was measured using the Wolman point count method and the full-weighted grain-size distribution of the bedload by in-situ sieving. In total, approximately 17,000 point counts and 3 tonnes of sediment were processed. The grain-size distributions show an overall increase from East to West on the southern coast of the gulf, with largest grain-sizes exported from the Western rift catchments. D84 ranges from 20 to 110 mm, however 50% of D84 grain-sizes are less than 40 mm. Subsequently, we derived the full Holocene sediment budget for the Corinth Gulf by combining our grain size data with catchment sediment fluxes, constrained using the BQART model and calibrated to known Holocene sediment volumes in the basin from seismic data (c.f. Watkins et al., in review). This is the first time such a budget has been derived for the Corinth Rift. Finally, our estimates of sediment budgets and grain sizes were compared to regional uplift constraints, fault distributions, slip rates and lithology to identify the relative importance of these controls on

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.

Background risk of breast cancer and the association between physical activity and mammographic density.

PubMed

Trinh, Thang; Eriksson, Mikael; Darabi, Hatef; Bonn, Stephanie E; Brand, Judith S; Cuzick, Jack; Czene, Kamila; Sjölander, Arvid; Bälter, Katarina; Hall, Per

2015-04-02

High physical activity has been shown to decrease the risk of breast cancer, potentially by a mechanism that also reduces mammographic density. We tested the hypothesis that the risk of developing breast cancer in the next 10 years according to the Tyrer-Cuzick prediction model influences the association between physical activity and mammographic density. We conducted a population-based cross-sectional study of 38,913 Swedish women aged 40-74 years. Physical activity was assessed using the validated web-questionnaire Active-Q and mammographic density was measured by the fully automated volumetric Volpara method. The 10-year risk of breast cancer was estimated using the Tyrer-Cuzick (TC) prediction model. Linear regression analyses were performed to assess the association between physical activity and volumetric mammographic density and the potential interaction with the TC breast cancer risk. Overall, high physical activity was associated with lower absolute dense volume. As compared to women with the lowest total activity level (<40 metabolic equivalent hours [MET-h] per day), women with the highest total activity level (≥50 MET-h/day) had an estimated 3.4 cm(3) (95% confidence interval, 2.3-4.7) lower absolute dense volume. The inverse association was seen for any type of physical activity among women with <3.0% TC 10-year risk, but only for total and vigorous activities among women with 3.0-4.9% TC risk, and only for vigorous activity among women with ≥5.0% TC risk. The association between total activity and absolute dense volume was modified by the TC breast cancer risk (P interaction = 0.05). As anticipated, high physical activity was also associated with lower non-dense volume. No consistent association was found between physical activity and percent dense volume. Our results suggest that physical activity may decrease breast cancer risk through reducing mammographic density, and that the physical activity needed to reduce mammographic density may depend

Modulus spectroscopy of grain-grain boundary binary system

NASA Astrophysics Data System (ADS)

Cheng, Peng-Fei; Song, Jiang; Li, Sheng-Tao; Wang, Hui

2015-02-01

Understanding various polarization mechanisms in complex dielectric systems and specifying their physical origins are key issues in dielectric physics. In this paper, four different methods for representing dielectric properties were analyzed and compared. Depending on the details of the system under study, i.e., uniform or non-uniform, it was suggested that different representing approaches should be used to obtain more valuable information. Especially, for the grain-grain boundary binary non-uniform system, its dielectric response was analyzed in detail in terms of modulus spectroscopy (MS). Furthermore, it was found that through MS, the dielectric responses between uniform and non-uniform systems, grain and grain boundary, Maxwell-Wagner polarization and intrinsic polarization can be distinguished. Finally, with the proposed model, the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics were studied. The colossal dielectric constant of CCTO at low frequency was attributed to the pseudo relaxation process of grain.

Multiscale simulation of xenon diffusion and grain boundary segregation in UO₂

DOE PAGES

Andersson, David A.; Tonks, Michael R.; Casillas, Luis; ...

2015-07-01

In light water reactor fuel, gaseous fission products segregate to grain boundaries, resulting in the nucleation and growth of large intergranular fission gas bubbles. The segregation rate is controlled by diffusion of fission gas atoms through the grains and interaction with the boundaries. Based on the mechanisms established from earlier density functional theory (DFT) and empirical potential calculations, diffusion models for xenon (Xe), uranium (U) vacancies and U interstitials in UO₂ have been derived for both intrinsic (no irradiation) and irradiation conditions. Segregation of Xe to grain boundaries is described by combining the bulk diffusion model with a model formore » the interaction between Xe atoms and three different grain boundaries in UO₂ (Σ5 tilt, Σ5 twist and a high angle random boundary), as derived from atomistic calculations. The present model does not attempt to capture nucleation or growth of fission gas bubbles at the grain boundaries. The point defect and Xe diffusion and segregation models are implemented in the MARMOT phase field code, which is used to calculate effective Xe and U diffusivities as well as to simulate Xe redistribution for a few simple microstructures.« 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

Experimental studies of Micro- and Nano-grained UO 2: Grain Growth Behavior, Sufrace Morphology, and Fracture Toughness

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

Miao, Yinbin; Mo, Kun; Jamison, Laura M.

This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructure-basedmore » materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize the experimental efforts in FY16 including the following important experiments: (1) in-situ grain growth measurement of nano-grained UO 2; (2) investigation of surface morphology in micrograined UO 2; (3) Nano-indentation experiments on nano- and micro-grained UO 2. The highlight of this year is: we have successfully demonstrated our capability to in-situ measure grain size development while maintaining the stoichiometry of nano-grained UO 2 materials; the experiment is, for the first time, using synchrotron X-ray diffraction to in-situ measure grain growth behavior of UO 2.« less

How grain boundaries affect the efficiency of poly-CdTe solar-cells: A fundamental atomic-scale study of grain boundary dislocation cores using CdTe bi-crystal thin films.

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

Klie, Robert

It is now widely accepted that grain boundaries in poly-crystalline CdTe thin film devices have a detrimental effect on the minority carrier lifetimes, the open circuit voltage and therefore the overall solar-cell performance. The goal of this project was to develop a fundamental understanding of the role of grain boundaries in CdTe on the carrier life-time, open-circuit voltage, Voc, and the diffusion of impurities. To achieve this goal, i) CdTe bi-crystals were fabricated with various misorientation angels, ii) the atomic- and electronic structures of the grain boundaries were characterized using scanning transmission electron microscopy (STEM), and iii) first-principles density functionalmore » theory modeling was performed on the structures determined by STEM to predict the grain boundary potential. The transport properties and minority carrier lifetimes of the bi-crystal grain boundaries were measured using a variety of approaches, including TRPL, and provided feedback to the characterization and modeling effort about the effectiveness of the proposed models.« less

All the catalytic active sites of MoS 2 for hydrogen evolution

DOE PAGES

Li, Guoqing; Zhang, Du; Qiao, Qiao; ...

2016-11-29

MoS 2 presents a promising low-cost catalyst for the hydrogen evolution reaction (HER), but the understanding about its active sites has remained limited. Here we present an unambiguous study of the catalytic activities of all possible reaction sites of MoS 2, including edge sites, sulfur vacancies, and grain boundaries. We demonstrate that, in addition to the well-known catalytically active edge sites, sulfur vacancies provide another major active site for the HER, while the catalytic activity of grain boundaries is much weaker. Here, the intrinsic turnover frequencies (Tafel slopes) of the edge sites, sulfur vacancies, and grain boundaries are estimated tomore » be 7.5 s –1 (65–75 mV/dec), 3.2 s –1 (65–85 mV/dec), and 0.1 s –1 (120–160 mV/dec), respectively. We also demonstrate that the catalytic activity of sulfur vacancies strongly depends on the density of the vacancies and the local crystalline structure in proximity to the vacancies. Unlike edge sites, whose catalytic activity linearly depends on the length, sulfur vacancies show optimal catalytic activities when the vacancy density is in the range of 7–10%, and the number of sulfur vacancies in high crystalline quality MoS 2 is higher than that in low crystalline quality MoS 2, which may be related with the proximity of different local crystalline structures to the vacancies.« less

Global exospheric temperatures and densities under active solar conditions. [measured by OGO-6

NASA Technical Reports Server (NTRS)

Wydra, B. J.

1975-01-01

Temperatures measured by the OGO-6 satellite using the 6300 A airglow spectrum are compared with temperatures derived from total densities and N2 densities. It is shown that while the variation of the total densities with latitude and magnetic activity agree well with values used for CIRA (1972), the temperature behavior is very different. While the temperatures derived from the N2 density were in much better agreement there were several important differences which radically affect the pressure gradients. The variation of temperature with magnetic activity indicated a seasonal and local time effect and also a latitude and delay time variation different from previous density derived temperatures. A new magnetic index is proposed that is better correlated with the observed temperatures. The temperature variations at high latitudes were examined for three levels of magnetic activity for both solstices and equinox conditions. A temperature maximum in the pre-midnight sector and a minimum in the noon sector were noted and seasonal and geomagnetic time and latitude effects discussed. Neutral temperature, density, pressure and boundary oxygen variations for the great storm of March 8, 1970 are presented.

The Strength-Grain Size Relationship in Ultrafine-Grained Metals

NASA Astrophysics Data System (ADS)

Balasubramanian, N.; Langdon, Terence G.

2016-12-01

Metals processed by severe plastic deformation (SPD) techniques, such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the Hall-Petch (H-P) relationship. Examples of this behavior are discussed using experimental data for Ti, Al, and Ni. These materials typically have grain sizes greater than 50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. However, both high strength and high ductility may be achieved simultaneously by imposing high strain to obtain ultrafine-grain sizes and high fractions of high-angle grain boundaries. This facilitates grain boundary sliding, and an example is presented for a cast Al-7 pct Si alloy processed by HPT. In some materials, SPD may result in a weakening even with a very fine grain size, and this is due to microstructural changes during processing. Examples are presented for an Al-7034 alloy processed by ECAP and a Zn-22 pct Al alloy processed by HPT. In some SPD-processed materials, it is possible that grain boundary segregation and other features are present leading to higher strengths than predicted by the H-P relationship.

Exploration of the mechanisms of temperature-dependent grain boundary mobility: Search for the common origin of ultrafast grain boundary motion

DOE PAGES

O’Brien, C. J.; Foiles, S. M.

2016-04-19

The temperature dependence of grain boundary mobility is complex, varied, and rarely fits ideal Arrhenius behavior. This work presents a series of case studies of planar grain boundaries in a model FCC system that were previously demonstrated to exhibit a variety of temperature-dependent mobility behaviors. It is demonstrated that characterization of the mobility versus temperature plots is not sufficient to predict the atomic motion mechanism of the grain boundaries. Herein, the temperature-dependent motion and atomistic motion mechanisms of planar grain boundaries are driven by a synthetic, orientation-dependent, driving force. The systems studied include CSL boundaries with Σ values of 5,more » 7, and 15, including both symmetric and asymmetric boundaries. These boundaries represent a range of temperature-dependent trends including thermally activated, antithermal, and roughening behaviors. Examining the atomic-level motion mechanisms of the thermally activated boundaries reveals that each involves a complex shuffle, and at least one atom that changes the plane it resides on. The motion mechanism of the antithermal boundary is qualitatively different and involves an in-plane coordinated shuffle that rotates atoms about a fixed atom lying on a point in the coincident site lattice. Furthermore, this provides a mechanistic reason for the observed high mobility, even at low temperatures, which is due to the low activation energy needed for such motion. However, it will be demonstrated that this mechanism is not universal, or even common, to other boundaries exhibiting non-thermally activated motion. This work concludes that no single atomic motion mechanism is sufficient to explain the existence of non-thermally activated boundary motion.« less

Changes of Dust Opacity with Density in the Orion A Molecular Cloud

NASA Astrophysics Data System (ADS)

Roy, Arabindo; Martin, Peter G.; Polychroni, Danae; Bontemps, Sylvain; Abergel, Alain; André, Philippe; Arzoumanian, Doris; Di Francesco, James; Hill, Tracey; Konyves, Vera; Nguyen-Luong, Quang; Pezzuto, Stefano; Schneider, Nicola; Testi, Leonardo; White, Glenn

2013-01-01

We have studied the opacity of dust grains at submillimeter wavelengths by estimating the optical depth from imaging at 160, 250, 350, and 500 μm from the Herschel Gould Belt Survey and comparing this to a column density obtained from the Two Micron All Sky Survey derived color excess E(J - K s). Our main goal was to investigate the spatial variations of the opacity due to "big" grains over a variety of environmental conditions and thereby quantify how emission properties of the dust change with column (and volume) density. The central and southern areas of the Orion A molecular cloud examined here, with N H ranging from 1.5 × 1021 cm-2 to 50 × 1021 cm-2, are well suited to this approach. We fit the multi-frequency Herschel spectral energy distributions (SEDs) of each pixel with a modified blackbody to obtain the temperature, T, and optical depth, τ1200, at a fiducial frequency of 1200 GHz (250 μm). Using a calibration of N H/E(J - Ks ) for the interstellar medium (ISM) we obtained the opacity (dust emission cross-section per H nucleon), σe(1200), for every pixel. From a value ~1 × 10-25 cm2 H-1 at the lowest column densities that is typical of the high-latitude diffuse ISM, σe(1200) increases as N 0.28 H over the range studied. This is suggestive of grain evolution. Integrating the SEDs over frequency, we also calculated the specific power P (emission power per H) for the big grains. In low column density regions where dust clouds are optically thin to the interstellar radiation field (ISRF), P is typically 3.7 × 10-31 W H-1, again close to that in the high-latitude diffuse ISM. However, we find evidence for a decrease of P in high column density regions, which would be a natural outcome of attenuation of the ISRF that heats the grains, and for localized increases for dust illuminated by nearby stars or embedded protostars.

Raman Optical Activity Spectra from Density Functional Perturbation Theory and Density-Functional-Theory-Based Molecular Dynamics.

PubMed

Luber, Sandra

2017-03-14

We describe the calculation of Raman optical activity (ROA) tensors from density functional perturbation theory, which has been implemented into the CP2K software package. Using the mixed Gaussian and plane waves method, ROA spectra are evaluated in the double-harmonic approximation. Moreover, an approach for the calculation of ROA spectra by means of density functional theory-based molecular dynamics is derived and used to obtain an ROA spectrum via time correlation functions, which paves the way for the calculation of ROA spectra taking into account anharmonicities and dynamic effects at ambient conditions.

Introduction to Agronomy, Grain Crops, Weeds and Controls. A Learning Activity Pac in Agricultural Education Courses in Wisconsin.

ERIC Educational Resources Information Center

Wisconsin State Dept. of Public Instruction, Madison. Div. of Instructional Services.

This learning activity pac contains information to help the teachers of high school vocational agriculture in the instructional area of agronomy. Each of the two main sections, grain crops and weeds and controls, includes teacher and student units for the section lessons. Teacher units include special instructions--equipment needed (film…

The temperature of large dust grains in molecular clouds

NASA Technical Reports Server (NTRS)

Clark, F. O.; Laureijs, R. J.; Prusti, T.

1991-01-01

The temperature of the large dust grains is calculated from three molecular clouds ranging in visual extinction from 2.5 to 8 mag, by comparing maps of either extinction derived from star counts or gas column density derived from molecular observations to I(100). Both techniques show the dust temperature declining into clouds. The two techniques do not agree in absolute scale.

Impact of grain size and rock composition on simulated rock weathering

NASA Astrophysics Data System (ADS)

Israeli, Yoni; Emmanuel, Simon

2018-05-01

Both chemical and mechanical processes act together to control the weathering rate of rocks. In rocks with micrometer size grains, enhanced dissolution at grain boundaries has been observed to cause the mechanical detachment of particles. However, it remains unclear how important this effect is in rocks with larger grains, and how the overall weathering rate is influenced by the proportion of high- and low-reactivity mineral phases. Here, we use a numerical model to assess the effect of grain size on chemical weathering and chemo-mechanical grain detachment. Our model shows that as grain size increases, the weathering rate initially decreases; however, beyond a critical size no significant decrease in the rate is observed. This transition occurs when the density of reactive boundaries is less than ˜ 20 % of the entire domain. In addition, we examined the weathering rates of rocks containing different proportions of high- and low-reactivity minerals. We found that as the proportion of low-reactivity minerals increases, the weathering rate decreases nonlinearly. These simulations indicate that for all compositions, grain detachment contributes more than 36 % to the overall weathering rate, with a maximum of ˜ 50 % when high- and low-reactivity minerals are equally abundant in the rock. This occurs because selective dissolution of the high-reactivity minerals creates large clusters of low-reactivity minerals, which then become detached. Our results demonstrate that the balance between chemical and mechanical processes can create complex and nonlinear relationships between the weathering rate and lithology.

Grain Boundary Sliding in Olivine + Clinopyroxene Aggregates: Weakening Mechanism and Microstructure

NASA Astrophysics Data System (ADS)

Zhao, N.; Hirth, G.; Cooper, R. F.; Kruckenberg, S. C.

2017-12-01

Constraining the viscosity of olivine-rich aggregates is critical for modeling geodynamic processes in the upper mantle. The presence of pyroxenes can complicate the rheology of mantle rocks owing to heterogeneous phase boundary properties and the potential impacts of incompatible elements on interface viscosity. Thus, in the grain boundary sliding (GBS) regime, it may be inappropriate to extrapolate flow laws of end-member aggregates to predict the behavior of multiphase aggregates. We deformed mixtures of fine-grained olivine (Ol) and clinopyroxene (Cpx) with various phase ratios in a general shear geometry at a confining pressure of 1.5 GPa, 1100-1200ºC and strain rate of 10­-3-10-5 s-1 to shear strains up to 8.5. We observed a peak stress followed by weakening in each experiment (except for those at 1200ºC), yet at steady state Ol-Cpx samples are substantially weaker than either pure Ol or pure Cpx end members scaled to the same grain size. Flow law parameters are quantified and indicate that the dominant deformation mechanism is reaction-limited diffusional creep. In addition, the results are consistent with a microphysical model that does not require the diffusion of Si (Sundberg & Cooper, 2008), providing an explanation for the observed weakening of olivine and pyroxene aggregates. Olivine exhibits an axial-[010] fabric or a B-type fabric. Analysis of low-angle (2º-10º) boundary axes indicate the activation of (010)[100] slip system, but no evidence for activation of the (010)[001] slip system that is hypothesized to generate a B-type fabric by dislocation creep. In the samples with strong fabric, we sorted the grains by their grain orientation spread (GOS, a measurement of how substructured the grain is or how active the dislocations were in the grain). The low-GOS grains have smaller grain sizes, smaller aspect ratios and weaker shape preferred orientation compared to high-GOS grains. Yet, low-GOS grains also have the strongest B-type fabric, while

Experimental investigation of grain boundaries misorientations and nano twinning induced strengthening on addition of silicon carbide in pulse electrodeposited nickel tungsten composite coating

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

Rahman, O.S. Asiq; Wasekar, Nitin P.; Sundararajan, G.

Nanoindentation was performed on silicon carbide (SiC) reinforced pulse electrodeposited nickel-tungsten (Ni-W) composite coating. Addition of 5 vol.% of SiC in Ni-W coating increased the hardness from 10.31 ± 0.65 GPa to 14.32 ± 0.63 GPa and elastic modulus from 119.74 ± 3.15 GPa to 139.26 ± 2.09 GPa. Increased hardness and elastic modulus directly translates to the improved strengthening in the coating. An experimental investigation of strengthening mechanism was carried out in Ni-W-5 vol.% SiC alloy. Two simultaneous phenomena viz. grain refinement and increased internal strain was observed, which increased the dislocation density from 5.51 × 10{sup 18} m{supmore » −2} to 1.346 × 10{sup 19} m{sup −2} on reinforcement of 5 vol.% of SiC in Ni-W coating. Increased dislocation density promoted the formation of grain boundary misorientations and nano twinning. Low angle grain boundary, high angle grain boundary and nano twinning were identified using high resolution transmission electron microscope (HR-TEM) image and their role in strengthening mechanism was discussed in details. - Highlights: • SiC reinforced pulse electrodeposition Ni-W coating was deposited on steel. • Nanoindentation showed the increased mechanical properties on addition of SiC. • Grain refinement and increased internal strain was observed in Ni-W-SiC coating. • Dislocation density increased on reinforcement of SiC in Ni-W coating. • Increased dislocation density triggered grain boundary misorientation and twinning.« less

Recombination activity of nickel, copper, and oxygen atoms segregating at grain boundaries in mono-like silicon crystals

NASA Astrophysics Data System (ADS)

Ohno, Yutaka; Kutsukake, Kentaro; Deura, Momoko; Yonenaga, Ichiro; Shimizu, Yasuo; Ebisawa, Naoki; Inoue, Koji; Nagai, Yasuyoshi; Yoshida, Hideto; Takeda, Seiji

2016-10-01

Three-dimensional distribution of impurity atoms was determined at functional Σ5{013} and small-angle grain boundaries (GBs) in as-grown mono-like silicon crystals by atom probe tomography combined with transmission electron microscopy, and it was correlated with the recombination activity of those GBs, CGB, revealed by photoluminescence imaging. Nickel (Ni), copper (Cu), and oxygen atoms preferentially segregated at the GBs on which arrays of dislocations existed, while those atoms scarcely segregated at Σ5{013} GBs free from dislocations. Silicides containing Ni and Cu about 5 nm in size and oxides about 1 nm in size were formed along the dislocation arrays on those GBs. The number of segregating impurity atoms per unit GB area for Ni and that for Cu, NNi and NCu, were in a trade-off correlation with that for oxygen, NO, as a function of CGB, while the sum of those numbers was almost constant irrespective of the GB character, CGB, and the dislocation density on GBs. CGB would be explained as a linear combination of those numbers: CGB (in %) ˜400(0.38NO + NNi + NCu) (in atoms/nm2). The GB segregation of oxygen atoms would be better for solar cells, rather than that of metal impurities, from a viewpoint of the conversion efficiency of solar cells.

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.

Direct imaging of thermally-activated grain-boundary diffusion in Cu/Co/IrMn/Pt exchange-bias structures using atom-probe tomography

NASA Astrophysics Data System (ADS)

Letellier, F.; Lechevallier, L.; Lardé, R.; Le Breton, J.-M.; Akmaldinov, K.; Auffret, S.; Dieny, B.; Baltz, V.

2014-11-01

Magnetic devices are often subject to thermal processing steps, such as field cooling to set exchange bias and annealing to crystallize amorphous magnetic electrodes. These processing steps may result in interdiffusion and the subsequent deterioration of magnetic properties. In this study, we investigated thermally-activated diffusion in Cu/Co/IrMn/Pt exchange biased polycrystalline thin-film structures using atom probe tomography. Images taken after annealing at 400 °C for 60 min revealed Mn diffusion into Co grains at the Co/IrMn interface and along Pt grain boundaries for the IrMn/Pt stack, i.e., a Harrison type C regime. Annealing at 500 °C showed further Mn diffusion into Co grains. At the IrMn/Pt interface, annealing at 500 °C led to a type B behavior since Mn diffusion was detected both along Pt grain boundaries and also into Pt grains. The deterioration of the films' exchange bias properties upon annealing was correlated to the observed diffusion. In particular, the topmost Pt capping layer thickness turned out to be crucial since a faster deterioration of the exchange bias properties for thicker caps was observed. This is consistent with the idea that Pt acts as a getter for Mn, drawing Mn out of the IrMn layer.

An experimental test of density-dependent selection on temperament traits of activity, boldness and sociability.

PubMed

Le Galliard, J-F; Paquet, M; Mugabo, M

2015-05-01

Temperament traits are seen in many animal species, and recent evolutionary models predict that they could be maintained by heterogeneous selection. We tested this prediction by examining density-dependent selection in juvenile common lizards Zootoca vivipara scored for activity, boldness and sociability at birth and at the age of 1 year. We measured three key life-history traits (juvenile survival, body growth rate and reproduction) and quantified selection in experimental populations at five density levels ranging from low to high values. We observed consistent individual differences for all behaviours on the short term, but only for activity and one boldness measure across the first year of life. At low density, growth selection favoured more sociable lizards, whereas viability selection favoured less active individuals. A significant negative correlational selection on activity and boldness existed for body growth rate irrespective of density. Thus, behavioural traits were characterized by limited ontogenic consistency, and natural selection was heterogeneous between density treatments and fitness traits. This confirms that density-dependent selection plays an important role in the maintenance of individual differences in exploration-activity and sociability. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Fine-grained sediment dispersal along the California coast

USGS Publications Warehouse

Warrick, Jonathan A.; Storlazzi, Curt D.

2013-01-01

Fine-grained sediment (silt and clay) enters coastal waters from rivers, eroding coastal bluffs, resuspension of seabed sediment, and human activities such as dredging and beach nourishment. The amount of sediment in coastal waters is an important factor in ocean ecosystem health, but little information exists on both the natural and human-driven magnitudes of fine-grained sediment delivery to the coastal zone, its residence time there, and its transport out of the system—information upon which to base environmental assessments. To help fill these information gaps, the U.S. Geological Survey has partnered with Federal, State, and local agencies to monitor fine-grained sediment dispersal patterns and fate in the coastal regions of California. Results of these studies suggest that the waves and currents of many of the nearshore coastal settings of California are adequately energetic to transport fine-grained sediment quickly through coastal systems. These findings will help with the management and regulation of fine-grained sediment along the U.S. west coast.

The effects of snowpack grain size on satellite passive microwave observations from the Upper Colorado River Basin

USGS Publications Warehouse

Josberger, E.G.; Gloersen, P.; Chang, A.; Rango, A.

1996-01-01

Understanding the passive microwave emissions of a snowpack, as observed by satellite sensors, requires knowledge of the snowpack properties: water equivalent, grain size, density, and stratigraphy. For the snowpack in the Upper Colorado River Basin, measurements of snow depth and water equivalent are routinely available from the U.S. Department of Agriculture, but extremely limited information is available for the other properties. To provide this information, a field program from 1984 to 1995 obtained profiles of snowpack grain size, density, and temperature near the time of maximum snow accumulation, at sites distributed across the basin. A synoptic basin-wide sampling program in 1985 showed that the snowpack exhibits consistent properties across large regions. Typically, the snowpack in the Wyoming region contains large amounts of depth hoar, with grain sizes up to 5 mm, while the snowpack in Colorado and Utah is dominated by rounded snow grains less than 2 mm in diameter. In the Wyoming region, large depth hoar crystals in shallow snowpacks yield the lowest emissivities or coldest brightness temperatures observed across the entire basin. Yearly differences in the average grain sizes result primarily from variations in the relative amount of depth hoar within the snowpack. The average grain size for the Colorado and Utah regions shows much less variation than do the grain sizes from the Wyoming region. Furthermore, the greatest amounts of depth hoar occur in the Wyoming region during 1987 and 1992, years with strong El Nin??o Southern Oscillation, but the Colorado and Utah regions do not show this behavior.

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.

Differential adsorption of CHON isomers at interstellar grain surfaces

NASA Astrophysics Data System (ADS)

Lattelais, M.; Pauzat, F.; Ellinger, Y.; Ceccarelli, C.

2015-06-01

Context. The CHON generic chemical formula covers different isomers such as isocyanic acid (HNCO), cyanic acid (HOCN), fulminic acid (HCNO), and isofulminic acid (HONC); the first three have been identified in a large variety of environments in the interstellar medium (ISM). Several phenomena could be at the origin of the observed abundances, such as different pathways of formation and destruction involving gas phase reactions with different possible activation barriers and/or surface processes depending on the local temperature and the nature of the support. Aims: The scope of this article is to shed some light on the interaction of the CHON isomers with interstellar grains as a function of the nature of the surface and to determine the corresponding adsorption energies in order to find whether this phenomenon could play a role in the abundances observed in the ISM. Methods: The question was addressed by means of numerical simulations using first principle periodic density functional theory (DFT) to represent the grain support as a solid of infinite dimension. Results: Regardless of the nature of the model surface (water ice, graphene, silica), two different classes of isomers were identified: weakly bound (HNCO and HCNO) and strongly bound (HOCN and HONC), with the adsorption energies of the latter group being about twice those of the former. The range of the adsorption energies is (from highest to lowest) HOCN > HONC > HNCO > HCNO. They are totally disconnected from the relative stabilities, which range from HNCO > HOCN > HCNO > HONC. Conclusions: The possibility of hydrogen bonding is the discriminating factor in the trapping of CHON species on grain surfaces. Whatever the environment, differential adsorption is effective and its contribution to the molecular abundances should not be ignored. The theoretical adsorption energies provided here could be profitably used for a more realistic modeling of molecule-surfaces interactions.

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.

Ultrathin amorphous coatings on lunar dust grains.

PubMed

Bibring, J P; Duraud, J P; Durrieu, L; Jouret, C; Maurette, M; Meunier, R

1972-02-18

UItrathin amorphous coatings have been observed by high-voltage electron microscopy on micrometer-sized dust grains from the Apollo 11, Apollo 12, Apollo 14, and Luna 16 missions. Calibration experiments show that these coatings result from an "ancient" implantation of solar wind ions in the grains. This phenomenon has interdisciplinary applications concerning the past activity of the sun, the lunar albedo, the ancient lunar atmosphere and magnetic field, the carbon content of lunar soils, and lunar dynamic processes.

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.

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

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.

Influence of hydrothermal processing on functional properties and grain morphology of finger millet.

PubMed

Dharmaraj, Usha; Meera, M S; Reddy, S Yella; Malleshi, Nagappa G

2015-03-01

Finger millet was hydrothermally processed followed by decortication. Changes in color, diameter, density, sphericity, thermal and textural characteristics and also some of the functional properties of the millet along with the grain morphology of the kernels after hydrothermal processing and decortication were studied. It was observed that, the millet turned dark after hydrothermal processing and color improved over native millet after decortication. A slight decrease in grain diameter was observed but sphericity of the grains increased on decortication. The soft and fragile endosperm turned into a hard texture and grain hardness increased by about 6 fold. Hydrothermal processing increased solubility and swelling power of the millet at ambient temperature. Pasting profile indicated that, peak viscosity decreased significantly on hydrothermal processing and both hydrothermally processed and decorticated millet exhibited zero breakdown viscosity. Enthalpy was negative for hydrothermally processed millet and positive for decorticated grains. Microscopic studies revealed that the orderly structure of endosperm changed to a coherent mass after hydrothermal processing and the different layers of seed coat get fused with the endosperm.

Spatially resolved mapping of electrical conductivity across individual domain (grain) boundaries in graphene.

PubMed

Clark, Kendal W; Zhang, X-G; Vlassiouk, Ivan V; He, Guowei; Feenstra, Randall M; Li, An-Ping

2013-09-24

All large-scale graphene films contain extended topological defects dividing graphene into domains or grains. Here, we spatially map electronic transport near specific domain and grain boundaries in both epitaxial graphene grown on SiC and CVD graphene on Cu subsequently transferred to a SiO2 substrate, with one-to-one correspondence to boundary structures. Boundaries coinciding with the substrate step on SiC exhibit a significant potential barrier for electron transport of epitaxial graphene due to the reduced charge transfer from the substrate near the step edge. Moreover, monolayer-bilayer boundaries exhibit a high resistance that can change depending on the height of substrate step coinciding at the boundary. In CVD graphene, the resistance of a grain boundary changes with the width of the disordered transition region between adjacent grains. A quantitative modeling of boundary resistance reveals the increased electron Fermi wave vector within the boundary region, possibly due to boundary induced charge density variation. Understanding how resistance change with domain (grain) boundary structure in graphene is a crucial first step for controlled engineering of defects in large-scale graphene films.

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.

Bayesian calibration of coarse-grained forces: Efficiently addressing transferability

NASA Astrophysics Data System (ADS)

Patrone, Paul N.; Rosch, Thomas W.; Phelan, Frederick R.

2016-04-01

Generating and calibrating forces that are transferable across a range of state-points remains a challenging task in coarse-grained (CG) molecular dynamics. In this work, we present a coarse-graining workflow, inspired by ideas from uncertainty quantification and numerical analysis, to address this problem. The key idea behind our approach is to introduce a Bayesian correction algorithm that uses functional derivatives of CG simulations to rapidly and inexpensively recalibrate initial estimates f0 of forces anchored by standard methods such as force-matching. Taking density-temperature relationships as a running example, we demonstrate that this algorithm, in concert with various interpolation schemes, can be used to efficiently compute physically reasonable force curves on a fine grid of state-points. Importantly, we show that our workflow is robust to several choices available to the modeler, including the interpolation schemes and tools used to construct f0. In a related vein, we also demonstrate that our approach can speed up coarse-graining by reducing the number of atomistic simulations needed as inputs to standard methods for generating CG forces.

Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium

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

Zhu, Chaoyi; Livescu, Veronica; Harrington, Tyler

The influence of microstructural anisotropy on shear response of high-purity titanium was studied using the compact forced-simple-shear specimen (CFSS) loaded under quasi-static loading conditions. Post-mortem characterization reveals significant difference in shear response of different directions in the same material due to material crystallographic texture anisotropy. Shear bands are narrower in specimens in which the shear zone is aligned along the direction with a strong {0001} basal texture. Twinning was identified as an active mechanism to accommodate strains in the shear region in both orientations. This paper confirms the applicability of the CFSS design for the investigation of differences in themore » shear response of materials as a function of process-induced crystallographic texture. A detailed, systematic approach to quantifying shear band evolution by evaluating geometrically necessary dislocations (GND) associated with crystallographic anisotropy is presented. Finally, the results show that: i) line average GND density profiles, for Ti samples that possess a uniform equiaxed-grain structure, but with strong crystallographic anisotropy, exhibit significant differences in GND density close to the shear band center; ii) GND profiles decrease steadily away from the shear band as the plastic strain diminishes, in agreement with Ashby's theory of work hardening, where the higher GND density in the through-thickness (TT) orientation is a result of restricted < a > type slip in the shear band compared with in-plane (IP) samples; iii) the anisotropy in deformation response is derived from initial crystallographic texture of the materials, where GND density of < a > GNDs are higher adjacent to the shear band in the through-thickness sample oriented away from easy slip, but the density of < c+a > type GNDs are very similar in these two samples; and iv) the increase in grain average GND density was determined to have strong correlation to an increase in the

Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium

DOE PAGES

Zhu, Chaoyi; Livescu, Veronica; Harrington, Tyler; ...

2017-03-31

The influence of microstructural anisotropy on shear response of high-purity titanium was studied using the compact forced-simple-shear specimen (CFSS) loaded under quasi-static loading conditions. Post-mortem characterization reveals significant difference in shear response of different directions in the same material due to material crystallographic texture anisotropy. Shear bands are narrower in specimens in which the shear zone is aligned along the direction with a strong {0001} basal texture. Twinning was identified as an active mechanism to accommodate strains in the shear region in both orientations. This paper confirms the applicability of the CFSS design for the investigation of differences in themore » shear response of materials as a function of process-induced crystallographic texture. A detailed, systematic approach to quantifying shear band evolution by evaluating geometrically necessary dislocations (GND) associated with crystallographic anisotropy is presented. Finally, the results show that: i) line average GND density profiles, for Ti samples that possess a uniform equiaxed-grain structure, but with strong crystallographic anisotropy, exhibit significant differences in GND density close to the shear band center; ii) GND profiles decrease steadily away from the shear band as the plastic strain diminishes, in agreement with Ashby's theory of work hardening, where the higher GND density in the through-thickness (TT) orientation is a result of restricted < a > type slip in the shear band compared with in-plane (IP) samples; iii) the anisotropy in deformation response is derived from initial crystallographic texture of the materials, where GND density of < a > GNDs are higher adjacent to the shear band in the through-thickness sample oriented away from easy slip, but the density of < c+a > type GNDs are very similar in these two samples; and iv) the increase in grain average GND density was determined to have strong correlation to an increase in the

Measuring grain boundary character distributions in Ni-base alloy 725 using high-energy diffraction microscopy

DOE PAGES

Bagri, Akbar; Hanson, John P.; Lind, J. P.; ...

2016-10-25

We use high-energy X-ray diffraction microscopy (HEDM) to characterize the microstructure of Ni-base alloy 725. HEDM is a non-destructive technique capable of providing three-dimensional reconstructions of grain shapes and orientations in polycrystals. The present analysis yields the grain size distribution in alloy 725 as well as the grain boundary character distribution (GBCD) as a function of lattice misorientation and boundary plane normal orientation. We find that the GBCD of Ni-base alloy 725 is similar to that previously determined in pure Ni and other fcc-base metals. We find an elevated density of Σ9 and Σ3 grain boundaries. We also observe amore » preponderance of grain boundaries along low-index planes, with those along (1 1 1) planes being the most common, even after Σ3 twins have been excluded from the analysis.« less

Respiratory symptoms and ventilatory performance in workers exposed to grain and grain based food dusts.

PubMed

Deacon, S P; Paddle, G M

1998-05-01

A health surveillance study of male grain food manufacturing workers used a respiratory health questionnaire and spirometry to assess the prevalence of work-related respiratory symptoms and impaired ventilatory performance. The prevalence of cough, breathlessness, wheeze and chest tightness was between 8-13% but was 20% for rhinitis. Rhinitis was the most common symptom with 37% of those reporting rhinitis describing this as work-related. A case-control analysis of workers reporting rhinitis did not identify any specific occupational activities associated with increased risk of rhinitis. Smoking habit and all respiratory symptoms apart from rhinitis had a significant effect upon ventilatory performance. Occupational exposure to raw grains, flour, ingredients and finished food was categorized as high, medium or low in either continuous or intermediate patterns. Multiple regression analysis confirmed the effects of height, age and smoking upon ventilatory performance. However, occupational exposure to grain, flour, food ingredients and cooked food dusts had no effect upon ventilatory performance. It is concluded that smoking habit is the major determinant of respiratory symptoms and impaired ventilatory function. The excess complaints of rhinitis warrant further study but it would appear that the current occupational exposure limits for grain, flour, food ingredients and cooked food dusts are adequate to protect workers against impairment of ventilatory performance.

Bone mineral density in subjects using central nervous system-active medications.

PubMed

Kinjo, Mitsuyo; Setoguchi, Soko; Schneeweiss, Sebastian; Solomon, Daniel H

2005-12-01

Decreased bone mineral density defines osteoporosis according to the World Health Organization and is an important predictor of future fractures. The use of several types of central nervous system-active drugs, including benzodiazepines, anticonvulsants, antidepressants, and opioids, have all been associated with increased risk of fracture. However, it is unclear whether such an increase in risk is related to an effect of bone mineral density or to other factors, such as increased risk of falls. We sought to examine the relationship between bone mineral density and the use of benzodiazepines, anticonvulsants, antidepressants, and opioids in a representative US population-based sample. We analyzed data on adults aged 17 years and older from the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994). Total femoral bone mineral density of 7114 male and 7532 female participants was measured by dual-energy x-ray absorptiometry. Multivariable linear regression models were used to quantify the relation between central nervous system medication exposure and total femoral bone mineral density. Models controlled for relevant covariates, including age, sex, and body mass index. In linear regression models, significantly reduced bone mineral density was found in subjects taking anticonvulsants (0.92 g/cm2; 95% confidence interval [CI]: 0.89 to 0.94) and opioids (0.92 g/cm2; 95% CI: 0.88 to 0.95) compared with nonusers (0.95 g/cm2; 95% CI: 0.95 to 0.95) after adjusting for several potential confounders. The other central nervous system-active drugs--benzodiazepines or antidepressants--were not associated with significantly reduced bone mineral density. In cross-sectional analysis of NHANES III, anticonvulsants and opioids (but not benzodiazepines or antidepressants) were associated with significantly reduced bone mineral density. These findings have implications for fracture-prevention strategies.

Density of Plutonium Turnings Generated from Machining Activities

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

Gonzales, John Robert; Vigil, Duane M.; Jachimowski, Thomas A.

The purpose of this project was to determine the density of plutonium (Pu) turnings generated from the range of machining activities, using both surrogate material and machined Pu turnings. Verify that 500 grams (g) of plutonium will fit in a one quart container using a surrogate equivalent volume and that 100 grams of Pu will fit in a one quart Savy container.

Implementing an Inexpensive and Accurate Introductory Gas Density Activity with High School Students

ERIC Educational Resources Information Center

Cunningham, W. Patrick; Joseph, Christopher; Morey, Samantha; Santos Romo, Ana; Shope, Cullen; Strang, Jonathan; Yang, Kevin

2015-01-01

A simplified activity examined gas density while employing cost-efficient syringes in place of traditional glass bulbs. The exercise measured the density of methane, with very good accuracy and precision, in both first-year high school and AP chemistry settings. The participating students were tasked with finding the density of a gas. The…

Optimization of Melt Treatment for Austenitic Steel Grain Refinement

NASA Astrophysics Data System (ADS)

Lekakh, Simon N.; Ge, Jun; Richards, Von; O'Malley, Ron; TerBush, Jessica R.

2017-02-01

Refinement of the as-cast grain structure of austenitic steels requires the presence of active solid nuclei during solidification. These nuclei can be formed in situ in the liquid alloy by promoting reactions between transition metals (Ti, Zr, Nb, and Hf) and metalloid elements (C, S, O, and N) dissolved in the melt. Using thermodynamic simulations, experiments were designed to evaluate the effectiveness of a predicted sequence of reactions targeted to form precipitates that could act as active nuclei for grain refinement in austenitic steel castings. Melt additions performed to promote the sequential precipitation of titanium nitride (TiN) onto previously formed spinel (Al2MgO4) inclusions in the melt resulted in a significant refinement of the as-cast grain structure in heavy section Cr-Ni-Mo stainless steel castings. A refined as-cast structure consisting of an inner fine-equiaxed grain structure and outer columnar dendrite zone structure of limited length was achieved in experimental castings. The sequential of precipitation of TiN onto Al2MgO4 was confirmed using automated SEM/EDX and TEM analyses.

Isolating magnetic moments from individual grains within a magnetic assemblage

NASA Astrophysics Data System (ADS)

Béguin, A.; Fabian, K.; Jansen, C.; Lascu, I.; Harrison, R.; Barnhoorn, A.; de Groot, L. V.

2017-12-01

Methods to derive paleodirections or paleointensities from rocks currently rely on measurements of bulk samples (typically 10 cc). The process of recording and storing magnetizations as function of temperature, however, differs for grains of various sizes and chemical compositions. Most rocks, by their mere nature, consist of assemblages of grains varying in size, shape, and chemistry. Unraveling the behavior of individual grains is a holy grail in fundamental rock magnetism. Recently, we showed that it is possible to obtain plausible magnetic moments for individual grains in a synthetic sample by a micromagnetic tomography (MMT) technique. We use a least-squares inversion to obtain these magnetic moments based on the physical locations and dimensions of the grains obtained from a MicroCT scanner and a magnetic flux density map of the surface of the sample. The sample used for this proof of concept, however, was optimized for success: it had a low dispersion of the grains, and the grains were large enough so they were easily detected by the MicroCT scanner. Natural lavas are much more complex than the synthetic sample analyzed so far: the dispersion of the magnetic markers is one order of magnitude higher, the grains differ more in composition and size, and many small (submicron) magnetic markers may be present that go undetected by the MicroCT scanner. Here we present the first results derived from a natural volcanic sample from the 1907-flow at Hawaii. To analyze the magnetic flux at the surface of the sample at room temperature, we used the Magnetic Tunneling Junction (MTJ) technique. We were able to successfully obtain MicroCT and MTJ scans from the sample and isolate plausible magnetic moments for individual grains in the top 70 µm of the sample. We discuss the potential of the MMT technique applied to natural samples and compare the MTJ and SSM methods in terms of work flow and quality of the results.

Effect of TiO2 Addition on Grain Growth, Anodic Bubble Evolution and Anodic Overvoltage of NiFe2O4-Based Composite Inert Anodes

NASA Astrophysics Data System (ADS)

Wang, Bin; Du, Jinjing; Liu, Yihan; Fang, Zhao; Hu, Ping

2017-11-01

A two-step powder compaction and sintering process was employed to fabricate TiO2-doped NiFe2O4 ceramic-based inert anodes. Grain growth during isothermal sintering was analyzed using Brook grain growth model. The bubble behavior of NiFe2O4 ceramic-based inert anodes was investigated in a two-compartment see-through quartz cell for aluminum electrolysis process. Anodic overvoltage and potential decay curves of the inert anodes were measured by using the steady state and current interruption technique. The results showed that the kinetic index of grain growth decreased with an increase in temperature. The average activation energy of grain growth for 1.0 wt.% TiO2-doped NiFe2O4 ceramic samples with a sintering temperature range from 1373 to 1673 K dropped from 675.30 to 183.47 kJ/mol. The diameter size of bubbles before releasing from the bottom surface of the anodes was reduced with increasing the current density, and the larger average releasing bubble size for carbon anode at the same current density could be obtained, which was compared to the NiFe2O4 inert anodes. Besides, the cell voltage of carbon anodes fluctuated much more violently under the same experimental conditions. After adding small amount of TiO2, a minor reduction in anodic overvoltage of NiFe2O4-based anodes can be observed.

Enhancing the Bioactivity of Yttria-Stabilized Tetragonal Zirconia Ceramics via Grain-Boundary Activation.

PubMed

Ke, Jinhuan; He, Fupo; Ye, Jiandong

2017-05-17

Yttria-stabilized tetragonal zirconia (Y-TZP) has been proposed as a potential dental implant because of its good biocompatibility, excellent mechanical properties, and distinctive aesthetic effect. However, Y-TZP cannot form chemical bonds with bone tissue because of its biological inertness, which affects the reliability and long-term efficacy of Y-TZP implants. In this study, to improve the bioactivity of Y-TZP ceramics while maintaining their good mechanical performance, Y-TZP was modified by grain-boundary activation via the infiltration of a bioactive glass (BG) sol into the surface layers of Y-TZP ceramics under different negative pressures (atmospheric pressure, -0.05 kPa, and -0.1 kPa), followed by gelling and sintering. The in vitro bioactivity, mechanical properties, and cell behavior of the Y-TZP with improved bioactivity were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), electron probe microanalysis (EPMA), and Raman spectroscopy. The results of the bioactivity test conducted by immersing Y-TZP in simulated body fluid (SBF) showed that a bonelike apatite layer was produced on the entire surface. The mechanical properties of the modified Y-TZP decreased as the negative pressure in the BG-infiltration process increased relative to those of the Y-TZP blank group. However, the samples infiltrated with the BG sol under -0.05 kPa and atmospheric pressure still retained good mechanical performance. The cell-culture results revealed that the bioactive surface modification of Y-TZP could promote cell adhesion and differentiation. The present work demonstrates that the bioactivity of Y-TZP can be enhanced by grain-boundary activation, and the bioactive Y-TZP is expected to be a potential candidate for use as a dental implant material.

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.

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- ...

Flume Experiments on the Influence of Salmon Spawning Density on Grain Stability and Bedload Transport in Gravel-bed Streams

NASA Astrophysics Data System (ADS)

Buxton, T. H.

2015-12-01

Salmon spawning in streams involves the female salmon digging a pit in the bed where she deposits eggs for fertilization before covering them with gravel excavated from the next pit upstream. Sequences of pit excavation and filling winnow fines, loosen sediment, and move bed material into a tailspill mound resembling the shape of a dune. Research suggests salmonid nests (redds) destabilize streambeds by reducing friction between loosened grains and converging flow that elevates shear stress on redd topography. However, bed stability may be enhanced by form drag from redds in clusters that lower shear stress on the granular bed, but this effect will vary with the proportion of the bed surface that is occupied by redds (P). I used simulated redds and water-worked ("unspawned") beds in a laboratory flume to evaluate these competing influences on grain stability and bedload transport rates with P=0.12, 0.34, and 0.41. Results indicate that competence (largest-grain) and reference transport rate estimates of critical conditions for particle entrainment inversely relate to P. Bedload transport increased as exponential functions of P and excess boundary shear stress. Therefore, redd form drag did not overcome the destabilizing effects of spawning. Instead, grain mobility and bedload transport increased with P because larger areas of the bed were composed of relatively loose, unstable grains and redd topography that experienced elevated shear stress. Consequently, the presence of redds in fish-bearing streams likely reduces the effects of sedimentation from landscape disturbance on stream habitats that salmon use for reproduction.

The impact of tax reforms designed to encourage healthier grain consumption.

PubMed

Nordström, Jonas; Thunström, Linda

2009-05-01

In this paper, we simulate the effects of tax reforms aimed at encouraging healthier grain consumption. We use a rich data set on household grain consumption in 2003 from the market research institute GfK Sweden, combined with information on the nutritional content of the consumption. We estimate behavioral parameters, which are used to simulate the impact on the average household of tax reforms entailing either a subsidy on commodities particularly rich in fiber or a subsidy of the fiber density in grain products. Our results suggest that to direct the fiber intake towards nutritional recommendations, reforms with a substantial impact on consumer prices are required. Regardless of the type of subsidy implemented, the increase in the intake of fiber is accompanied by unwanted increases in nutrients that are often overconsumed: fat, salt and sugar. Funding the subsidies by taxing these nutrients, or less healthy commodities, helps to counteract such developments.

Nuts and Grains: Microbiology and Preharvest Contamination Risks.

PubMed

Brar, Pardeepinder K; Danyluk, Michelle D

2018-04-01

Low-water-activity foods have been involved in recalls and foodborne disease outbreaks. Increased consumption; better detection methods and reporting systems; improved surveillance, trace-back, and ability to connect sporadic foodborne illnesses; and inadequate implementation of food safety programs are some of the likely reasons for the increase in frequency of recalls and outbreaks linked to dry foods. Nuts and grains can be contaminated with foodborne pathogens at any stage during production, processing, storage, and distribution. Focusing on preharvest contamination, the various potential sources of contamination include soil, animal intrusion, contaminated harvesting equipment, harvest and preharvest handling, storage conditions, and others. The low water activity of nuts and grains prevents the growth of most foodborne pathogens on their surfaces. The long-term survival of bacterial foodborne pathogens ( Salmonella , Escherichia coli O157:H7, and Listeria monocytogenes ) on dry foods has been documented in the literature for different nut types. Preventing contamination is the key to avoiding foodborne disease risks linked to dry foods. The implementation of good agricultural practices and other food safety systems provides a proactive approach to address concerns thoroughly. A plethora of research is available on preventing the growth of mycotoxin-producing fungi on the surface of nuts and grains. Milling is an effective mechanism to reduce the microbial load on grains. This review focuses on providing information about associated foodborne microorganisms, preharvest contamination sources, and good agricultural practice recommendations for nuts and grains.

GRAIN BOUNDARY STRENGTHENING PROPERTIES OF TUNGSTEN ALLOYS

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

Setyawan, Wahyu; Kurtz, Richard J.

2012-10-10

Density functional theory was employed to investigate grain boundary (GB) properties of W alloys. A range of substitutional solutes across the Periodic Table was investigated to understand the behavior of different electronic orbitals in changing the GB cleavage energy in the Σ27a[110]{525} GB. A number of transition metals were predicted to enhance the GB cohesion. This includes Ru, Re, Os, Ir, V, Cr, Mn, Fe, Co, Ti, Hf, Ta and Nb. While lanthanides, s and p elements were tended to cause GB embrittlement.

Rice grain yield and quality responses to free-air CO2 enrichment combined with soil and water warming.

PubMed

Usui, Yasuhiro; Sakai, Hidemitsu; Tokida, Takeshi; Nakamura, Hirofumi; Nakagawa, Hiroshi; Hasegawa, Toshihiro

2016-03-01

Rising air temperatures are projected to reduce rice yield and quality, whereas increasing atmospheric CO2 concentrations ([CO2 ]) can increase grain yield. For irrigated rice, ponded water is an important temperature environment, but few open-field evaluations are available on the combined effects of temperature and [CO2 ], which limits our ability to predict future rice production. We conducted free-air CO2 enrichment and soil and water warming experiments, for three growing seasons to determine the yield and quality response to elevated [CO2 ] (+200 μmol mol(-1) , E-[CO2 ]) and soil and water temperatures (+2 °C, E-T). E-[CO2 ] significantly increased biomass and grain yield by approximately 14% averaged over 3 years, mainly because of increased panicle and spikelet density. E-T significantly increased biomass but had no significant effect on the grain yield. E-T decreased days from transplanting to heading by approximately 1%, but days to the maximum tiller number (MTN) stage were reduced by approximately 8%, which limited the panicle density and therefore sink capacity. On the other hand, E-[CO2 ] increased days to the MTN stage by approximately 4%, leading to a greater number of tillers. Grain appearance quality was decreased by both treatments, but E-[CO2 ] showed a much larger effect than did E-T. The significant decrease in undamaged grains (UDG) by E-[CO2 ] was mainly the result of an increased percentage of white-base grains (WBSG), which were negatively correlated with grain protein content. A significant decrease in grain protein content by E-[CO2 ] accounted in part for the increased WBSG. The dependence of WBSG on grain protein content, however, was different among years; the slope and intercept of the relationship were positively correlated with a heat dose above 26 °C. Year-to-year variation in the response of grain appearance quality demonstrated that E-[CO2 ] and rising air temperatures synergistically reduce grain appearance quality of

Bottom-up coarse-grained models that accurately describe the structure, pressure, and compressibility of molecular liquids

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

Dunn, Nicholas J. H.; Noid, W. G., E-mail: wnoid@chem.psu.edu

2015-12-28

The present work investigates the capability of bottom-up coarse-graining (CG) methods for accurately modeling both structural and thermodynamic properties of all-atom (AA) models for molecular liquids. In particular, we consider 1, 2, and 3-site CG models for heptane, as well as 1 and 3-site CG models for toluene. For each model, we employ the multiscale coarse-graining method to determine interaction potentials that optimally approximate the configuration dependence of the many-body potential of mean force (PMF). We employ a previously developed “pressure-matching” variational principle to determine a volume-dependent contribution to the potential, U{sub V}(V), that approximates the volume-dependence of the PMF.more » We demonstrate that the resulting CG models describe AA density fluctuations with qualitative, but not quantitative, accuracy. Accordingly, we develop a self-consistent approach for further optimizing U{sub V}, such that the CG models accurately reproduce the equilibrium density, compressibility, and average pressure of the AA models, although the CG models still significantly underestimate the atomic pressure fluctuations. Additionally, by comparing this array of models that accurately describe the structure and thermodynamic pressure of heptane and toluene at a range of different resolutions, we investigate the impact of bottom-up coarse-graining upon thermodynamic properties. In particular, we demonstrate that U{sub V} accounts for the reduced cohesion in the CG models. Finally, we observe that bottom-up coarse-graining introduces subtle correlations between the resolution, the cohesive energy density, and the “simplicity” of the model.« less

Hardness as a modification index for malting red and white sorghum (kaffir) grains.

PubMed

Uvere, Peter O; Ngoddy, Patrick O; Nwankwo, Chibuzo S

2014-03-30

This study investigated changes in the resistance to fracture of malting red and white sorghum grains using a hardness tester as another method for monitoring grain modification. Grain hardness decreased progressively from 134.35 N and 137.29 N in malting red and white sorghums and levelled off after 120 h at 76.98 N and 69.14 N. In the red grain malts traditionally used for burukutu production, moisture content (r = -0.983), dhurrinase activity (r = -0.981), malting loss (r = -0.981), free amino nitrogen (r = -0.909) and cold water extract (r = -0.908) were better indicators of grain hardness than root length (r = -0.89). In the white sorghum malts, malting loss (r = -0.988), dhurrinase activity (r = -0.954) and diastatic activity (r = -0.936) were better indicators of grain modification than root length (r = -0.916). The soluble nitrogen ratio at the end of malting was lower in the red (0.049) compared with the white (0.0548). Grain hardness using a hand-held tester is a simple, fast and good index of modification of malting red and white sorghum grains. Oven-dried red and white sorghum malts could be considered to be well modified at hardness values/indices below 77 N/0.5730 and 72 N/0.5036, respectively. © 2013 Society of Chemical Industry.

The Effects of Sex-Ratio and Density on Locomotor Activity in the House Fly, Musca domestica

PubMed Central

Bahrndorff, Simon; Kjærsgaard, Anders; Pertoldi, Cino; Loeschcke, Volker; Schou, Toke M.; Skovgård, Henrik; Hald, Birthe

2012-01-01

Although locomotor activity is involved in almost all behavioral traits, there is a lack of knowledge on what factors affect it. This study examined the effects of sex—ratio and density on the circadian rhythm of locomotor activity of adult Musca domestica L. (Diptera: Muscidae) using an infra—red light system. Sex—ratio significantly affected locomotor activity, increasing with the percentage of males in the vials. In accordance with other studies, males were more active than females, but the circadian rhythm of the two sexes was not constant over time and changed during the light period. There was also an effect of density on locomotor activity, where males at intermediate densities showed higher activity. Further, the predictability of the locomotor activity, estimated as the degree of autocorrelation of the activity data, increased with the number of males present in the vials both with and without the presence of females. Overall, this study demonstrates that locomotor activity in M. domestica is affected by sex—ratio and density. Furthermore, the predictability of locomotor activity is affected by both sex—ratio, density, and circadian rhythm. These results add to our understanding of the behavioral interactions between houseflies and highlight the importance of these factors when designing behavioral experiments using M. domestica.

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

Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976-2013): Dominant roles of riverine discharge and sediment grain size

NASA Astrophysics Data System (ADS)

Wu, Xiao; Bi, Naishuang; Xu, Jingping; Nittrouer, Jeffrey A.; Yang, Zuosheng; Saito, Yoshiki; Wang, Houjie

2017-09-01

The presently active Yellow River (Huanghe) delta lobe has been formed since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaerial and the subaqueous components, and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution. The critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station Lijin, the last gauging station approximately 100 km upstream from the river mouth. The results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages. During the first stage (1976-1981) after the channel migration, the unchannelized river flow enhanced deposition within the channel and floodplain between Lijin station and the river mouth. Therefore, the critical sediment supply calculated by the river inputs obtained from station Lijin was the highest. However, the actual sediment load at this stage (0.84 Gt/yr) was more than twice of the critical sediment load ( 0.35 Gt/yr) for sustaining the active subaerial area, which favored a rapid seaward progradation of the Yellow River subaerial delta. During the second stage (1981-1996), the engineering-facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0.29 Gt/yr. The active delta lobe still gradually prograded seaward at an accretion rate of 11.9 km2/yr at this stage as the annual sediment load at Lijin station was 0.55 Gt/yr. From 1996 to 2002, the critical sediment load further decreased to 0.15 Gt/yr with the sediment grain size increased to 22.5 �

Coarse graining the distribution function of cold dark matter - II

NASA Astrophysics Data System (ADS)

Henriksen, R. N.

2004-12-01

We study analytically the coarse- and fine-grained distribution function (DF) established by the self-similar infall of collisionless matter. We find this function explicitly for isotropic and spherically symmetric systems in terms of cosmological initial conditions. The coarse-grained function is structureless and steady but the familiar phase-space sheet substructure is recovered in the fine-grained limit. By breaking the self-similarity of the halo infall we are able to argue for a central density flattening. In addition there will be an edge steepening. The best-fitting analytic density function is likely to be provided by a high-order polytrope fit smoothly to an outer power law of index -3 for isolated systems. There may be a transition to a -4 power law in the outer regions of tidally truncated systems. As we find that the central flattening is progressive in time, dynamically young systems such as galaxy clusters may well possess a Navarro, Frenk and White type density profile, while primordial dwarf galaxies, for example, are expected to have cores. This progressive flattening is expected to end either in the non-singular isothermal sphere, or in the non-singular metastable polytropic cores; as the DFs associated with each of these arise naturally in the bulk halo during the infall. We suggest, based on previous studies of the evolution of de-stabilized polytropes, that a collisionless system may pass through a family of polytropes of increasing order, finally approaching the limit of the non-singular isothermal sphere, if the `violent' collective relaxation is frequently re-excited by `merger' events. Thus central dominant (cD) galaxies, and indeed all bright galaxies that have grown in this fashion, should be in polytropic states. Our results suggest that no physics beyond that of wave-particle scattering is necessary to explain the nature of dark matter density profiles. However, this may be assisted by the scattering of particles from the centre of the

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

Local free energies for the coarse-graining of adsorption phenomena: The interacting pair approximation

NASA Astrophysics Data System (ADS)

Pazzona, Federico G.; Pireddu, Giovanni; Gabrieli, Andrea; Pintus, Alberto M.; Demontis, Pierfranco

2018-05-01

We investigate the coarse-graining of host-guest systems under the perspective of the local distribution of pore occupancies, along with the physical meaning and actual computability of the coarse-interaction terms. We show that the widely accepted approach, in which the contributions to the free energy given by the molecules located in two neighboring pores are estimated through Monte Carlo simulations where the two pores are kept separated from the rest of the system, leads to inaccurate results at high sorbate densities. In the coarse-graining strategy that we propose, which is based on the Bethe-Peierls approximation, density-independent interaction terms are instead computed according to local effective potentials that take into account the correlations between the pore pair and its surroundings by means of mean-field correction terms without the need for simulating the pore pair separately. Use of the interaction parameters obtained this way allows the coarse-grained system to reproduce more closely the equilibrium properties of the original one. Results are shown for lattice-gases where the local free energy can be computed exactly and for a system of Lennard-Jones particles under the effect of a static confining field.

DELIVERY OF DUST GRAINS FROM COMET C/2013 A1 (SIDING SPRING) TO MARS

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

Tricarico, Pasquale; Samarasinha, Nalin H.; Sykes, Mark V.

Comet C/2013 A1 (Siding Spring) will have a close encounter with Mars on 2014 October 19. We model the dynamical evolution of dust grains from the time of their ejection from the comet nucleus to the close encounter with Mars, and determine the flux at Mars. Constraints on the ejection velocity from Hubble Space Telescope observations indicate that the bulk of the grains will likely miss Mars, although it is possible that a few percent of the grains with higher velocities will reach Mars, peaking approximately 90-100 minutes after the close approach of the nucleus, and consisting mostly of millimeter-radiusmore » grains ejected from the comet nucleus at a heliocentric distance of approximately 9 AU or larger. At higher velocities, younger grains from submillimeter to several millimeters can also reach Mars, although an even smaller fraction of grains is expected have these velocities, with negligible effect on the peak timing. Using NEOWISE observations of the comet, we can estimate that the maximum fluence will be of the order of 10{sup –7} grains m{sup –2}. We include a detailed analysis of how the expected fluence depends on the grain density, ejection velocity, and size-frequency distribution, to account for current model uncertainties and in preparation of possible refined model values in the near future.« less

Active zone density is conserved during synaptic growth but impaired in aged mice

PubMed Central

Chen, Jie; Mizushige, Takafumi; Nishimune, Hiroshi

2013-01-01

Presynaptic active zones are essential structures for synaptic vesicle release, but the developmental regulation of their number and maintenance during aging at mammalian neuromuscular junctions (NMJs) remains unknown. Here, we analyzed the distribution of active zones in developing, mature, and aged mouse NMJs by immunohistochemical detection of the active zone-specific protein Bassoon. Bassoon is a cytosolic scaffolding protein essential for the active zone assembly in ribbon synapses and some brain synapses. Bassoon staining showed a punctate pattern in nerve terminals and axons at the nascent NMJ on embryonic days 16.5–18.5. Three-dimensional reconstruction of NMJs revealed that the majority of Bassoon puncta within an NMJ were attached to the presynaptic membrane from postnatal day 0 to adulthood, and colocalized with another active zone protein Piccolo. During postnatal development, the number of Bassoon puncta increased as the size of the synapses increased. Importantly, the density of Bassoon puncta remained relatively constant from postnatal day 0 to 54 at 2.3 puncta/μm2, while the synapse size increased 3.3-fold. However, Bassoon puncta density and signal intensity were significantly attenuated at the NMJs of 27-month-old aged mice. These results suggest that synapses maintain the density of synaptic vesicle release sites while the synapse size changes, but this density becomes impaired during aging. PMID:21935939

Improved yield and Zn accumulation for rice grain by Zn fertilization and optimized water management.

PubMed

Wang, Yu-yan; Wei, Yan-yan; Dong, Lan-xue; Lu, Ling-li; Feng, Ying; Zhang, Jie; Pan, Feng-shan; Yang, Xiao-e

2014-04-01

Zinc (Zn) deficiency and water scarcity are major challenges in rice (Oryza sativa L.) under an intensive rice production system. This study aims to investigate the impact of water-saving management and different Zn fertilization source (ZnSO4 and Zn-EDTA) regimes on grain yield and Zn accumulation in rice grain. Different water managements, continuous flooding (CF), and alternate wetting and drying (AWD) were applied during the rice growing season. Compared with CF, the AWD regime significantly increased grain yield and Zn concentrations in both brown rice and polished rice. Grain yield of genotypes (Nipponbare and Jiaxing27), on the average, was increased by 11.4%, and grain Zn concentration by 3.9% when compared with those under a CF regime. Zn fertilization significantly increased Zn density in polished rice, with a more pronounced effect of ZnSO4 being observed as compared with Zn-EDTA, especially under an AWD regime. Decreased phytic acid content and molar ratio of phytic acid to Zn were also noted in rice grains with Zn fertilization. The above results demonstrated that water management of AWD combined with ZnSO4 fertilization was an effective agricultural practice to elevate grain yield and increase Zn accumulation and bioavailability in rice grains.

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.

Sedimentary differentiation of aeolian grains at the White Sands National Monument, New Mexico, USA

NASA Astrophysics Data System (ADS)

Fenton, Lori K.; Bishop, Janice L.; King, Sara; Lafuente, Barbara; Horgan, Briony; Bustos, David; Sarrazin, Philippe

2017-06-01

Gypsum (CaSO4·2H2O) has been identified as a major component of part of Olympia Undae in the northern polar region of Mars, along with the mafic minerals more typical of Martian dune fields. The source and age of the gypsum is disputed, with the proposed explanations having vastly different implications for Mars' geological history. Furthermore, the transport of low density gypsum grains relative to and concurrently with denser grains has yet to be investigated in an aeolian setting. To address this knowledge gap, we performed a field study at White Sands National Monument (WSNM) in New Mexico, USA. Although gypsum dominates the bulk of the dune field, a dolomite-rich [CaMg(CO3)2] transport pathway along the northern border of WSNM provides a suitable analog site to study the transport of gypsum grains relative to the somewhat harder and denser carbonate grains. We collected samples along the stoss slope of a dune and on two coarse-grained ripples at the upwind margin of the dune field where minerals other than gypsum were most common. For comparison, additional samples were taken along the stoss slope of a dune outside the dolomite transport pathway, in the center of the dune field. Visible and near-infrared (VNIR), X-ray powder diffraction (XRD), and Raman analyses of different sample size fractions reveal that dolomite is only prevalent in grains larger than ∼1 mm. Other minerals, most notably calcite, are also present in smaller quantities among the coarse grains. The abundance of these coarse grains, relative to gypsum grains of the same size, drops off sharply at the upwind margin of the dune field. In contrast, gypsum dominated the finer fraction (<∼1 mm) at all sample sites, displaying no spatial variation. Estimates of sediment fluxes indicate that, although mineralogical differentiation of wind-transported grains occurs gradually in creep, the process is much more rapid when winds are strong enough to saltate the ⩾1 mm grains. The observed grain

Role of grain-size in phyllonitisation: Insights from mineralogy, microstructures, strain analyses and numerical modeling

NASA Astrophysics Data System (ADS)

Bose, Narayan; Dutta, Dripta; Mukherjee, Soumyajit

2018-07-01

Brittle Y- and P-planes exist in an exposure of greywacke in the Garhwal Lesser Himalaya, India. Although, Y-planes are well developed throughout, the P-planes are prominent only in some parts (domain-A), and not elsewhere (domain-B). To investigate why the P-planes developed selectively, the following studies were undertaken: 1. Clay-separated XRD analyses: clinochlore and illite are present in both the domains. 2. Strain analyses by Rf-φ method: it deduces strain magnitudes of ∼1.8 for the ductile deformed quartz grains from both the domains A and B. 3. Grain size analyses of quartz clasts: domain-A is mostly composed of finer grains (area up to 40,000 μm2), whereas domain-B consists of a population of coarser grains (area >45,000 μm2). A 2D finite element modeling of linear elastic material was performed using COMSOL software to investigate the control of grain-size variation on the generation brittle shear planes. The results of numerical modeling corroborate the known fact that an increase in grain-size reduces the elastic strain energy density. A broader grain-size distribution increases the effects of diffusion creep and resists the onset of dislocation creep. Thus, rocks with coarser grain population (domain B) tend to resist the generation of shear fractures, unlike their fine-grained counterpart (domain A).

Engineering α-amylase levels in wheat grain suggests a highly sophisticated level of carbohydrate regulation during development

PubMed Central

Whan, Alex; Dielen, Anne-Sophie; Mieog, Jos; Bowerman, Andrew F.; Robinson, Hannah M.; Byrne, Keren; Colgrave, Michelle; Larkin, Philip J.; Howitt, Crispin A.; Morell, Matthew K.; Ral, Jean-Philippe

2014-01-01

Wheat starch degradation requires the synergistic action of different amylolytic enzymes. Our spatio-temporal study of wheat α-amylases throughout grain development shows that AMY3 is the most abundant isoform compared with the other known α-amylases. Endosperm-specific over-expression of AMY3 resulted in an increase of total α-amylase activity in harvested grains. Unexpectedly, increased activity did not have a significant impact on starch content or composition but led to an increase of soluble carbohydrate (mainly sucrose) in dry grain. In AMY3 overexpression lines (A3OE), germination was slightly delayed and triacylglycerol (TAG) content was increased in the endosperm of mature grain. Despite increased AMY3 transcript and protein content throughout grain development, alterations of α-amylase activity and starch granule degradation were not detected until grain maturation, suggesting a post-translational inhibition of α-amylase activity in the endosperm during the starch filling period. These findings show unexpected effects of a high level of α-amylase on grain development and composition, notably in carbon partitioning and TAG accumulation, and suggest the presence of a hitherto unknown regulatory pathway during grain filling. PMID:25053646

Hydrocarbons in the ISM: Their Evolution and the Grain-to-Molecule Transition

NASA Astrophysics Data System (ADS)

Jones, Anthony P.

The evolution of hydrocarbon grains in the ISM is determined, principally, by the effects of photo-processing (annealing) which lead to a progressive loss of hydrogen from the structure and an associated 'graphitisation' of the material. Eventually this 'graphitisation' results in a low-density, highly aromatic material that can disaggregate into its aromatic-rich molecular components. These changes are followed through the use of an extended random covalent network (RCN) model for the hydrocarbon structure. This type of 'top down' process could be a significant source of the large molecular infrared band carriers in photon dominated regions. On the basis of this simple model there should thus be a relationship between the small grain and large molecule infrared emission bands across, and within, astrophysical boundaries such as photo-dissociation regions. 1. Introduction Carbon is the most abundant dust-forming element in the ISM and a large fraction of this carbon is in the form of grains comprised, principally, of hydrocarbon materials, including those where the hydrogen content is minimal. Interstellar hydrocarbon grains include: graphite, hydrogenated amorphous aliphatic and/or aromatic hydrocarbons (a-C, a-C:H) and (nano)diamond. These hydrocarbon dusts play a pivotal role in determining, amongst other things, the interstellar extinction, the dust thermal emission and the photo-electric heating of the gas in the ISM. 2. Hydrocarbon grains in the ISM Hydrocarbon grains are formed in the circumstellar shells around C-rich evolved stars, in supernova ejecta and also in the ISM itself via accretion and solid-state chemistry. The physical and chemical properties of hydrocarbon grains are indeed complex and vary in response to the ambient conditions (density, temperature, radiation field, ...). For example they can undergo both chemical and physical processing (growth and changes in chemical composition through accretion and reaction, erosion via inertial or chemi

Evaluation of a microwave resonator for predicting grain moisture independent of bulk density

USDA-ARS?s Scientific Manuscript database

This work evaluated the ability of a planar whispering mode resonator to predict moisture considering moisture and densities expected in an on-harvester application. A calibration model was developed to accurately predict moisture over the moisture, density and temperature ranges evaluated. This mod...

Significance of grain sliding mechanisms for ductile deformation of rocks

NASA Astrophysics Data System (ADS)

Dimanov, A.; Bourcier, M.; Gaye, A.; Héripré, E.; Bornert, M.; Raphanel, J.; Ludwig, W.

2013-12-01

Ductile shear zones at depth present polyphase and heterogeneous rocks and multi-scale strain localization patterns. Most strain concentrates in ultramylonitic layers, which exhibit microstructural signatures of several concomitant deformation mechanisms. The latter are either active in volume (dislocation creep), or in the vicinity and along interfaces (grain sliding and solution mass transfer). Because their chronology of appearance and interactions are unclear, inference of the overall rheology seems illusory. We have therefore characterized over a decade the rheology of synthetic lower crustal materials with different compositions and fluid contents, and for various microstructures. Non-Newtonian flow clearly related to dominant dislocation creep. Conversely, Newtonian behavior involved grain sliding mechanisms, but crystal plasticity could be identified as well. In order to clarify the respective roles of these mechanisms we underwent a multi-scale investigation of the ductile deformation of rock analog synthetic halite with controlled microstructures. The mechanical tests were combined with in-situ optical microscopy, scanning electron microscopy and X ray computed tomography, allowing for digital image correlation (DIC) techniques and retrieval of full strain field. Crystal plasticity dominated, as evidenced by physical slip lines and DIC computed slip bands. Crystal orientation mapping allowed to identify strongly active easy glide {110} <110> systems. But, all other slip systems were observed as well, and especially near interfaces, where their activity is necessary to accommodate for the plastic strain incompatibilities between neighboring grains. We also evidenced grain boundary sliding (GBS), which clearly occurred as a secondary, but necessary, accommodation mechanism. The DIC technique allowed the quantification of the relative contribution of each mechanism. The amount of GBS clearly increased with decreasing grain size. Finite element (FE) modeling

Effects of grain size, mineralogy, and acid-extractable grain coatings on the distribution of the fallout radionuclides 7Be, 10Be, 137Cs, and 210Pb in river sediment

NASA Astrophysics Data System (ADS)

Singleton, Adrian A.; Schmidt, Amanda H.; Bierman, Paul R.; Rood, Dylan H.; Neilson, Thomas B.; Greene, Emily Sophie; Bower, Jennifer A.; Perdrial, Nicolas

2017-01-01

Grain-size dependencies in fallout radionuclide activity have been attributed to either increase in specific surface area in finer grain sizes or differing mineralogical abundances in different grain sizes. Here, we consider a third possibility, that the concentration and composition of grain coatings, where fallout radionuclides reside, controls their activity in fluvial sediment. We evaluated these three possible explanations in two experiments: (1) we examined the effect of sediment grain size, mineralogy, and composition of the acid-extractable materials on the distribution of 7Be, 10Be, 137Cs, and unsupported 210Pb in detrital sediment samples collected from rivers in China and the United States, and (2) we periodically monitored 7Be, 137Cs, and 210Pb retention in samples of known composition exposed to natural fallout in Ohio, USA for 294 days. Acid-extractable materials (made up predominately of Fe, Mn, Al, and Ca from secondary minerals and grain coatings produced during pedogenesis) are positively related to the abundance of fallout radionuclides in our sediment samples. Grain-size dependency of fallout radionuclide concentrations was significant in detrital sediment samples, but not in samples exposed to fallout under controlled conditions. Mineralogy had a large effect on 7Be and 210Pb retention in samples exposed to fallout, suggesting that sieving sediments to a single grain size or using specific surface area-based correction terms may not completely control for preferential distribution of these nuclides. We conclude that time-dependent geochemical, pedogenic, and sedimentary processes together result in the observed differences in nuclide distribution between different grain sizes and substrate compositions. These findings likely explain variability of measured nuclide activities in river networks that exceeds the variability introduced by analytical techniques as well as spatial and temporal differences in erosion rates and processes. In short, we

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.