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Sample records for grain eesti abistab

  1. Grain boundaries

    SciTech Connect

    Balluffi, R.W.; Bristowe, P.D.

    1991-01-01

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990--February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: Study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  2. Interstellar grains

    NASA Technical Reports Server (NTRS)

    Snow, T. P.

    1986-01-01

    There are few aspects of interstellar grains that can be unambiguously defined. Very little can be said that is independent of models or presuppositions; hence issues are raised and questions categorized, rather than providing definitive answers. The questions are issues fall into three general areas; the general physical and chemical nature of the grains; the processes by which they are formed and destroyed; and future observational approaches.

  3. Grain Spectroscopy

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.

    1992-01-01

    Our fundamental knowledge of interstellar grain composition has grown substantially during the past two decades thanks to significant advances in two areas: astronomical infrared spectroscopy and laboratory astrophysics. The opening of the mid-infrared, the spectral range from 4000-400 cm(sup -1) (2.5-25 microns), to spectroscopic study has been critical to this progress because spectroscopy in this region reveals more about a materials molecular composition and structure than any other physical property. Infrared spectra which are diagnostic of interstellar grain composition fall into two categories: absorption spectra of the dense and diffuse interstellar media, and emission spectra from UV-Vis rich dusty regions. The former will be presented in some detail, with the latter only very briefly mentioned. This paper summarized what we have learned from these spectra and presents 'doorway' references into the literature. Detailed reviews of many aspects of interstellar dust are given.

  4. Interstellar grains within interstellar grains

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.; Amari, Sachiko; Zinner, Ernst K.; Lewis, Roy S.

    1991-01-01

    Five interstellar graphite spherules extracted from the Murchison carbonaceous meteorite are studied. The isotopic and elemental compositions of individual particles are investigated with the help of an ion microprobe, and this analysis is augmented with structural studies of ultrathin sections of the grain interiors by transmission electron microscopy. As a result, the following procedure for the formation of the interstellar graphite spherule bearing TiC crystals is inferred: (1) high-temperature nucleation and rapid growth of the graphitic carbon spherule in the atmosphere of a carbon-rich star, (2) nucleation and growth of TiC crystals during continued growth of the graphitic spherule and the accretion of TiC onto the spherule, (3) quenching of the graphite growth process by depletion of C or by isolation of the spherule before other grain types could condense.

  5. Whole Grains and Fiber

    MedlinePlus

    ... fiber. Some examples of refined grains are wheat flour, enriched bread and white rice. Most refined grains are enriched , which means that ... grains. Some examples of enriched grains are wheat flour, enriched bread and white rice. Eating whole grains provides important health benefits: Many ...

  6. Grain Grading and Handling.

    ERIC Educational Resources Information Center

    Rendleman, Matt; Legacy, James

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

  7. Grain Handling and Storage.

    ERIC Educational Resources Information Center

    Harris, Troy G.; Minor, John

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

  8. Grain structure and composition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chapter 4 covers general information about structure and composition of cereal grains as well as the unique features of each cereal grain. Cereal grains are the fruits of cultivated grasses and members of Gramineae family. The fruit of a cereal is botanically known as caryopsis, featured by fusion...

  9. Marketing Farm Grain Crops.

    ERIC Educational Resources Information Center

    Ridenour, Harlan E.

    This vocational agriculture curriculum on grain marketing contains three parts: teacher guide, student manual, and student workbook. All three are coordinated and cross-referenced. The course is designed to give students of grain marketing a thorough background in the subject and provide practical help in developing grain marketing strategies for…

  10. 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

  11. Detection of insects in grain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Detecting insects hidden inside kernels of grain is important to grain buyers because internal infestations can result in insect fragments in products made from the grain, or, if the grain is stored before use, the insect population can increase and damage the grain further. In a study in the Unite...

  12. All About the Grains Group

    MedlinePlus

    ... the Grains Group? Any food made from wheat, rice, oats, cornmeal, barley or another cereal grain is ... bulgur (cracked wheat), oatmeal, whole cornmeal, and brown rice. Refined grains have been milled, a process that ...

  13. Circumstellar grain formation

    NASA Technical Reports Server (NTRS)

    Draine, B. T.

    1986-01-01

    Dust formation around cool giant and supergiant stars is examined in terms of grain formulation. Optical properties of small clusters, molecular physics of cluster nucleation and growth, circumstellar mass flows, and their application to alpha Ori are discussed.

  14. Presolar Grains in Indarch

    NASA Astrophysics Data System (ADS)

    Gao, X.; Nittler, L. R.; Swan, P. D.; Walker, R. M.

    1995-09-01

    We report results for the EH(4) Indarch. Earlier work [1] found 20 micrometers clumps of sub-micron SiC whose presolar nature was inferred from step-wise combustion, noble gas [2], and ion probe isotopic measurements. Our results indicate that the clumps were an artifact of sample preparation. Our sample was first cleaned using 6N HCl, and water and isopropanol rinses, then powdered and reacted with HCl-HF/HCl, KOH, and H3BO3-HCl/HCl giving a C-rich residue 1.14 wt.% of the original. X-ray mapping showed SiC grains and 5x as many Si3N4 grains, but no fine-grained clumps. Large (6 micrometers to 20 micrometers) C-rich spheroids were also present. The sample was further treated with KOH/HNO3 and NH3H2O; attempts to do density-separates were unsuccessful. An aliquot was treated with perchloric acid and separated into <1 micrometers and >1 micrometer fractions. SEM-EDS measurements of 73 (<1 micrometer) grains showed 44 SiC, 19 Si3N4, 4 C only, and 6 C with minor Si (both the C and Si in these particles are isotopically normal). A similar distribution of species was found for 37 (>1 micrometer) grains with the addition of 2 spinel and one Al2O3 grains. The whole rock concentration of SiC was 5.8 ppm, higher than previous determinations [1,3,9]. Confirming earlier suggestions [1,2], we find that SiC in Indarch is much finer-grained than in Murchison; about 2/3 of the mass is in grains <=0.3 micrometers compared to only about 4% for Murchison. This may represent size-sorting in the nebula or selective destruction of fine-grained material. Ion probe measurements of 22 (1-3 micrometers) grains gave isotopic results in the range previously measured for Murchison SiCs [4]. Several normal Si3N4 grains (>1 micron) were measured; probably exsolution products similar to those in Qingzhen [7]. Ion mapping was used to search for presolar oxide grains using previously developed techniques [5]. Seven candidate grains out of ~1000 were found. Multiple imaging confirmed an ^(16)O/^(18

  15. Desorption from interstellar grains

    NASA Technical Reports Server (NTRS)

    Leger, A.; Jura, M.; Omont, A.

    1985-01-01

    Different desorption mechanisms from interstellar grains are considered to resolve the conflict between the observed presence of gaseous species in molecular clouds and their expected depletion onto grains. The physics of desorption is discussed with particular reference to the process of grain heating and the specific heat of the dust material. Impulsive heating by X-rays and cosmic rays is addressed. Spot heating of the grains by cosmic rays and how this can lead to desorption of mantles from very large grains is considered. It is concluded that CO depletion on grains will be small in regions with A(V) less than five from the cloud surface and n(H) less than 10,000, in agreement with observations and in contrast to expectations from pure thermal equilibrium. Even in very dense and obscured regions and in the absence of internal ultraviolet sources, the classical evaporation of CO or N2 and O2-rich mantles by cosmic rays is important.

  16. Fingering phenomena during grain-grain displacement

    NASA Astrophysics Data System (ADS)

    Mello, Nathália M. P.; Paiva, Humberto A.; Combe, G.; Atman, A. P. F.

    2016-05-01

    Spontaneous formation of fingered patterns during the displacement of dense granular assemblies was experimentally reported few years ago, in a radial Hele-Shaw cell. Here, by means of discrete element simulations, we have recovered the experimental findings and extended the original study to explore the control parameters space. In particular, using assemblies of grains with different geometries (monodisperse, bidisperse, or polydisperse), we measured the macroscopic stress tensor in the samples in order to confirm some conjectures proposed in analogy with Saffman-Taylor viscous fingering phenomena for immiscible fluids. Considering an axial setup which allows to control the discharge of grains and to follow the trajectory and the pressure gradient along the displacing interface, we have applied the Darcy law for laminar flow in fluids in order to measure an "effective viscosity" for each assembly combination, in an attempt to mimic variation of the viscosity ratio between the injected/displaced fluids in the Saffman-Taylor experiment. The results corroborate the analogy with the viscous fluids displacement, with the bidisperse assembly corresponding to the less viscous geometry. But, differently to fluid case, granular fingers only develop for a specific combination of displaced/injected geometries, and we have demonstrated that it is always related with the formation of a force chain network along the finger direction.

  17. 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.

  18. Grain quality inspection system

    NASA Technical Reports Server (NTRS)

    Flood, C. A., Jr.; Singletow, D. P.; James, S. N.

    1979-01-01

    A review of grain quality indicators and measurement methods was conducted in order to assess the feasibility of using remote sensing technology to develop a continuous monitoring system for use during grain transfer operations. Most detection methods were found to be too slow or too expensive to be incorporated into the normal inspection procedure of a grain elevator on a continuous basis. Two indicators, moisture content and broken corn and foreign material, show potential for automation and are of an economic value. A microprocessor based system which utilizes commercially available electronic moisture meter was developed and tested. A method for automating BCFM measurement is described. A complete system description is presented along with performance test results.

  19. Grain optical properties

    NASA Technical Reports Server (NTRS)

    Hanner, Martha

    1988-01-01

    The optical properties of small grains provide the link between the infrared observations presented in Chapter 1 and the dust composition described in Chapter 3. In this session, the optical properties were discussed from the viewpoint of modeling the emission from the dust coma and the scattering in order to draw inference about the dust size distribution and composition. The optical properties are applied to the analysis of the infrared data in several ways, and these different uses should be kept in mind when judging the validity of the methods for applying optical constants to real grains.

  20. Charging of interplanetary grains

    NASA Technical Reports Server (NTRS)

    Baragiola, R. A.; Johnson, R. E.; Newcomb, John L.

    1995-01-01

    The objective of this program is to quantify, by laboratory experiments, the charging of ices and other insulators subject to irradiation with electrons, ions and ultraviolet photons and to model special conditions based on the data. The system and conditions to be studied are those relevant for charging of dust in magnetospheric plasmas. The measurements are supplemented by computer simulations of charging or grains under a variety of conditions. Our work for this period involved experiments on water ice, improved models of charging of ice grains for Saturn's E-ring, and the construction of apparatus for electron impact studies and measurements of electron energy distributions.

  1. Grain boundary curvature and grain growth kinetics with particle pinning

    NASA Astrophysics Data System (ADS)

    Shahandeh, Sina; Militzer, Matthias

    2013-08-01

    Second-phase particles are used extensively in design of polycrystalline materials to control the grain size. According to Zener's theory, a distribution of particles creates a pinning pressure on a moving grain boundary. As a result, a limiting grain size is observed, but the effect of pinning on the detail of grain growth kinetics is less known. The influence of the particles on the microstructure occurs in multiple length scales, established by particle radius and the grain size. In this article, we use a meso-scale phase-field model that simulates grain growth in the presence of a uniform pinning pressure. The curvature of the grain boundary network is measured to determine the driving pressure of grain growth in 2D and 3D systems. It was observed that the grain growth continues, even under conditions where the average driving pressure is smaller than the pinning pressure. The limiting grain size is reached when the maximum of driving pressure distribution in the structure is equal to the pinning pressure. This results in a limiting grain size, larger than the one predicted by conventional models, and further analysis shows consistency with experimental observations. A physical model is proposed for the kinetics of grain growth using parameters based on the curvature analysis of the grain boundaries. This model can describe the simulated grain growth kinetics.

  2. Edible grain legumes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Edible grain legumes including dry bean, dry pea, chickpeas, and lentils, have served as important sources of protein for human diets for thousands of years. In the US, these crops are predominately produced for export markets. The objective of this study was to examine yield gains in these crops ov...

  3. Interstellar Grain Surface Chemistry

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M.; Cuzzi, Jeffrey N. (Technical Monitor)

    1995-01-01

    Chemistry on grain surfaces plays an Important role in the formation of interstellar Ices, It can also influence the composition of the gas phase through outgassing near luminous, newly formed stars. This paper reviews the chemical processes taking place on Interstellar grain surfaces with the emphasis on those transforming CO into other hydrocarbons. At low, molecular cloud temperatures (approximately equal to 10K), physisorption processes dominate interstellar grain surface chemistry and GO is largely hydrogenated through reactions with atomic H and oxidized through reactions with atomic O. The former will lead to the formation of H2CO and CH3OH ices, while the latter results in CO2 ice. The observational evidence for these ices in molecular clouds will be discussed. Very close to protostars, the gas and grain temperatures are much higher (approximately equal to 500K) and chemisorption processes, including catalytic surface reactions, becomes important. This will be illustrated based upon our studies of the Fischer-Tropsch Synthesis of CH4 from CO on metallic surfaces. Likely, this process has played an important role in the early solar nebula. Observational consequences will be pointed out.

  4. Dust grain charging in a wake of other grains

    SciTech Connect

    Miloch, W. J.; Block, D.

    2012-12-15

    The charging of dust grain in the wake of another grains in sonic and supersonic collisionless plasma flows is studied by numerical simulations. We consider two grains aligned with the flow, as well as dust chains and multiple grain arrangements. It is found that the dust charge depends significantly on the flow speed, distance between the grains, and the grain arrangement. For two and three grains aligned, the charges on downstream grains depend linearly on the flow velocity and intergrain distance. The simulations are carried out with DiP3D, a three dimensional particle-in-cell code with both electrons and ions represented as numerical particles [W. J. Miloch et al., Phys. Plasmas 17, 103703 (2010)].

  5. Why Is It Important to Eat Grains, Especially Whole Grains?

    MedlinePlus

    ... B vitamins (thiamin, riboflavin, niacin, and folate), and minerals ( iron , magnesium , and selenium). Dietary fiber from whole grains or other foods, ... diets. Whole grains are sources of magnesium and selenium. Magnesium is a mineral used in building bones ...

  6. Grain rotation mediated by grain boundary dislocations in nanocrystalline platinum

    PubMed Central

    Wang, Lihua; Teng, Jiao; Liu, Pan; Hirata, Akihiko; Ma, En; Zhang, Ze; Chen, Mingwei; Han, Xiaodong

    2014-01-01

    Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials. In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm. Here, in tensile-loaded Pt thin films under a high-resolution transmission electron microscope, we show that the plasticity mechanism transitions from cross-grain dislocation glide in larger grains (d>6 nm) to a mode of coordinated rotation of multiple grains for grains with d<6 nm. The mechanism underlying the grain rotation is dislocation climb at the grain boundary, rather than grain boundary sliding or diffusional creep. Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank–Bilby dislocation content in the grain boundary. PMID:25030380

  7. COMMINGLING EFFECTS AND RESIDUAL GRAIN DURING GRAIN RECEIVING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Concern about the possible effects of genetically modified crops has increased the demand for segregating grains during handling and processing operations. Research on the amount of commingling of different grains in an elevator is limited. This study evaluated the level of commingling at a grain ...

  8. History of Presolar Grains

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.

    2005-01-01

    Papers on the History of Presolar Grains. This has been a very productive period in which much of the laboratory work conducted in the previous year and during this funding cycle were brought to completion. In the last year we have published or submitted for peer review 4 research papers, 4 review papers, and 11 abstracts in research areas supported under this grant. Brief synopses of the results of the research papers are presented, followed by short summaries of the topics discussed in the review papers. Several areas of research are of course being actively pursued, and the appended list of abstracts gives citations to this ongoing work. In a paper submitted to the Astrophysical Journal, 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, with and without previously formed internal crystals of titanium carbide (TIC) are reported.

  9. FINE GRAIN NUCLEAR EMULSION

    DOEpatents

    Oliver, A.J.

    1962-04-24

    A method of preparing nuclear track emulsions having mean grain sizes less than 0.1 microns is described. The method comprises adding silver nitrate to potassium bromide at a rate at which there is always a constant, critical excess of silver ions. For minimum size grains, the silver ion concentration is maintained at the critical level of about pAg 2.0 to 5.0 during prectpitation, pAg being defined as the negative logarithm of the silver ion concentration. It is preferred to eliminate the excess silver at the conclusion of the precipitation steps. The emulsion is processed by methods in all other respects generally similar to the methods of the prior art. (AEC)

  10. Oxalate in grain amaranth.

    PubMed

    Gélinas, Bruce; Seguin, Philippe

    2007-06-13

    Grain amaranth (Amaranthus spp.) is a widely adaptable C4 pseudo-cereal crop that has interesting nutritional characteristics including high protein and calcium concentrations and a lack of gluten. To date, no antinutrient has been found at problematic levels in grain amaranth; however, oxalate has not been thoroughly studied. Dietary oxalate is a potential risk factor for kidney stone development, and its presence in food lowers calcium and magnesium availability. Oxalate concentration and forms and calcium and magnesium concentrations were determined in 30 field-grown grain amaranth genotypes from the species A. cruentus, A. hybrid, and A. hypochondriacus. The effects of seeding date and fertilization with calcium ammonium nitrate were evaluated in field experiments conducted in multiple environments; the effects of cooking were also evaluated. Mean total oxalate concentration in the 30 genotypes analyzed was 229 mg/100 g, with values ranging between 178 and 278 mg/100 g, the greatest proportion being insoluble (average of 80%). Calcium concentration averaged 186 mg/100 g and ranged between 134 and 370 mg/100 g, whereas magnesium averaged 280 mg/100 g and ranged between 230 and 387 mg/100 g. Fertilization only marginally increased total oxalate concentration and had no effects on other variables. Seeding date had no effects on any of the variables studied. Boiling increased the proportion of soluble oxalate but did not affect total oxalate concentration. Grain amaranth can be considered a high oxalate source, however, as most is in insoluble form, and due to its high calcium and magnesium concentrations, oxalate absorbability could be low. This should be confirmed by bioavailability studies. PMID:17511467

  11. Isotropic Monte Carlo Grain Growth

    Energy Science and Technology Software Center (ESTSC)

    2013-04-25

    IMCGG performs Monte Carlo simulations of normal grain growth in metals on a hexagonal grid in two dimensions with periodic boundary conditions. This may be performed with either an isotropic or a misorientation - and incliantion-dependent grain boundary energy.

  12. Storing Peanuts in Grain Bags

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was executed to determine the potential of storing farmers stock peanuts and shelled peanuts for crushing in hermetically sealed grain bags. The objectives of the study were to evaluate equipment for loading and unloading the grain bags, the capacity of the grain bags, and the changes in qu...

  13. Grain-grain interaction in stationary dusty plasma

    SciTech Connect

    Lampe, Martin; Joyce, Glenn

    2015-02-15

    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 larger 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.

  14. Special Grain Boundaries in Ultrafine-Grained Tungsten

    NASA Astrophysics Data System (ADS)

    Dudka, O. V.; Ksenofontov, V. A.; Sadanov, E. V.; Starchenko, I. V.; Mazilova, T. I.; Mikhailovskij, I. M.

    2016-07-01

    Field ion microscopy and computer simulation were used for the study of an atomic structure high-angle grain boundary in hard-drawn ultrafine-grained tungsten wire. These boundaries with special misorientations are beyond the scope of the coincident site lattice model. It was demonstrated that the special non-coincident grain boundaries are the plane-matching boundaries, and rigid-body displacements of adjacent nanograins are normal to the <110> misorientation axis. The vectors of rigid-body translations of grains are described by broad asymmetric statistical distribution. Mathematical modeling showed that special incommensurate boundaries with one grain oriented along the {211} plane have comparatively high cohesive energies. The grain-boundary dislocations ½<110> were revealed and studied at the line of local mismatch of {110} atomic planes of adjacent grains.

  15. Special Grain Boundaries in Ultrafine-Grained Tungsten.

    PubMed

    Dudka, O V; Ksenofontov, V A; Sadanov, E V; Starchenko, I V; Mazilova, T I; Mikhailovskij, I M

    2016-12-01

    Field ion microscopy and computer simulation were used for the study of an atomic structure high-angle grain boundary in hard-drawn ultrafine-grained tungsten wire. These boundaries with special misorientations are beyond the scope of the coincident site lattice model. It was demonstrated that the special non-coincident grain boundaries are the plane-matching boundaries, and rigid-body displacements of adjacent nanograins are normal to the <110> misorientation axis. The vectors of rigid-body translations of grains are described by broad asymmetric statistical distribution. Mathematical modeling showed that special incommensurate boundaries with one grain oriented along the {211} plane have comparatively high cohesive energies. The grain-boundary dislocations ½<110> were revealed and studied at the line of local mismatch of {110} atomic planes of adjacent grains. PMID:27416905

  16. Destruction of nanograins by grain-grain collisions

    NASA Astrophysics Data System (ADS)

    Ohnishi, Naofumi; Bringa, Eduardo; Remington, Bruce; Gilmer, George; Minich, Roger; Yamaguchi, Yasutaka; Tielens, Alexander

    2008-04-01

    Atomistic simulations of grain-grain collisions have been carried out for spherical grains of 1.4 and 4 nm radii with relative velocities of 3.6--6.1 km/s and a number of random impact parameters. Since the initial grains are crystallites without any pre-existing defects, grain shattering due to nucleation of cracks was not observed in our simulations. We find grain fusion in some events, but generally melting occurs due to the small size of grain. The melting leads to nucleation, growth and linkage of voids in the melt, and finally small clusters are produced through a web-like structure. The size distribution does not obey a single power law and can be considered as four different regimes in the cluster size.

  17. Coarse graining in micromagnetics.

    PubMed

    Grinstein, G; Koch, R H

    2003-05-23

    Numerical solutions of the micromagnetic Landau-Lifshitz-Gilbert equations provide valuable information at low temperatures (T), but produce egregious errors at higher T. For example, Curie temperatures are often overestimated by an order of magnitude. We show that these errors result from the use of block or coarse-grained variables, without a concomitant renormalization of the system parameters to account for the block size. Renormalization solves the problem of the Curie-point anomaly and improves the accuracy of more complicated micromagnetic simulations, even at low T. PMID:12785922

  18. Evolution of Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Allamandola, Lou J.; DeVincenzi, Donald L. (Technical Monitor)

    1998-01-01

    During the past two decades observations combined with laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the raw materials from which planets, comets and stars form. Most interstellar material is concentrated in large molecular clouds where simple molecules are formed by dust-grain and gas-phase reactions. Gaseous species striking the cold (10K) dust stick, forming an icy grain mantle. This accretion, coupled with UV photolysis, produces a complex chemical mixture containing volatile, non-volatile, and isotopically fractionated species. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, H2, and perhaps some NH3 and H2CO, as well as more complex species. The evidence for these compounds, as well as carbon-rich materials, will be reviewed and the possible connections with comets and meteorites will be presented in the first part of the talk . The second part of the presentation will focus on interstellar/precometary ice photochemical evolution and the species likely to be found in comets. The chemical composition and photochemical evolution of realistic interstellar/pre-cometary ice analogs will be discussed. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and more complex molecules. When ices representative of interstellar grains and comets are exposed to UV radiation at low temperature a series of moderately complex organic molecules are formed in the ice including: CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), and R-C=N (nitriles). Several of these are already known to be in the interstellar medium, and their presence indicates the importance of grain processing. After warming to room temperature an organic residue remains. This is composed primarily of hexamethylenetetramine (HMT, C6H12N4), with lesser amounts of polyoxymethylene-related species (POMs), amides, and ketones. This is in sharp contrast to the organic residues produced by

  19. Lunar and Planetary Science XXXV: Presolar Grains

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Topics discussed include: Presolar Silicate Grains; Presolar Silicates from Primitivr Chondrites; Oxygen and Magnesium Isotopic Ratios of Presolar Spinel Grains; Study of Two New Presolar Grains from Bishunpur Ordinary Chondrite; Extinct Technetium in Presolar Grains; etc.

  20. Dehumidification Grain Dryer

    SciTech Connect

    Lula, J.W.; Bohnert, G.W.

    1998-05-13

    A new technique developed during this project dries grain with mildly heated, dehumidified air in a closed-loop process. This proposed technique uses about one-tenth the energy and dries grain at a lower temperature, producing less damage to the kernels.Approximately 250 million automotive and truck tires are discarded each year in the U.S. The very properties that ensure a safe ride and long service life make the disposal of these scrap tires difficult. In spite of this, scrap tire recycling/reuse has rapidly grown from 10% in 1985 to over 90% today. The majority of scrap tires that are recycled/reused are burned for fuel in power plants and cement kilns. Since tires have somewhat higher heating value than coal, this would at first seem to be an acceptable option. But burning scrap tires recovers only 25% of the energy originally used to manufacture the rubber. An alternative is to use the scrap tires in the form of crumb rubber, by which 98% of the original energy is recovered. This project sought to explore potential formulations of crumb rubber with various thermoplastic binders, with one goal being developing a material for a low-cost, high-performance roofing composition. What was the state-of-the-art of the product/process prior to initiation of the project? Why was the project needed (e.g., performance, quality, cost, time to market)? Describe the strengths and interests of each party and how they are complementary with respect to the project. What KCP expertise was needed and how did it complement the partner's capabilities?

  1. Grain Flow at High Stresses

    NASA Astrophysics Data System (ADS)

    McSaveney, M. J.

    2015-12-01

    The transport mechanism of rapid long-runout rock avalanches was a hotly debated topic when I came on the scene in 1967. So how come it is still debated today? My explanation is that it is the expected outcome of peer review, poor comprehension, and technological advances outpacing intellectual advances. Why think about the problem when we can model it! So let us think about the problem. Shreve thought that rock avalanches fell upon and trapped a layer of air. What physics was he thinking about? It is how feathers and tissue papers fall. When my rock avalanches fly, they fly like unlubricated bricks using the physics of projectiles and ballistics. But the main transport mechanism is not flight. The dominant impression from watching a rock avalanche in motion is of fluid flow, as Heim described it in 1882. A rock avalanche is a very large grain flow. Bagnold studied dispersive grain flows, but why should one assume that rock avalanches are dispersive grain flows as many do. The more common grain flow type is a dense grain flow and rock avalanches are dense grain flows in which the weight can and does generate very high stresses at grain contacts. Brittle rock deforms elastically up to its compressive strength, whereupon it breaks, releasing elastic strain as transient elastic strain (seismic energy to a seismologist, acoustic energy to a physicist). Melosh and others have shown that acoustic energy can fluidize a grain mass. There is no exotic physics behind grain flow at high stress. When grains break, the released elastic strain has to go somewhere, and it goes somewhere principally by transmission though grain contacts. Depending on the state of stress at the grain contact, the contact will pass the stress or will slip at conventional values of Coulomb friction. Enough thinking! A physical model of the entire process is too big for any laboratory. So whose numerical model will do it?

  2. Grain Size and Morphological Variability

    NASA Astrophysics Data System (ADS)

    Macmahan, J.; Gallagher, E.; Reniers, A.; Thornton, E.

    2008-12-01

    Grain size on natural beaches has traditionally been assumed to be uniform and modeling efforts assume a single mean grain size for an entire beach environment. Many recent studies contradict this assumption and suggest that sediment grain size on a beach is not homogeneous and that variations in sediment size and supply are important in sediment transport and morphodynamics at all scales. Unfortunately, measuring grain size is difficult, tedious and time consuming. Therefore, in spite of the evidence pointing to the importance of grain size in sediment transport and morphodynamics, many previous studies have been based on only a few field samples. Rubin (2004) introduced a technique for measuring surface grain size in situ in rivers and deeper coastal waters, using a digital camera and auto-correlation of digital images. Using this technique, information about the surface grain size distribution can be obtained quickly and inexpensively. Following Rubin (2004), we have developed a mobile digital imaging system (DIS) for surveying grain size on beaches. The DIS was used during two experiments: RCEX, a rip current experiment in Monterey, CA in April 2007 and Truc Vert '08, a multi-institutional, international experiment, on the Atlantic coast of France in March 2008. Preliminary results suggest that grain size varies spatially with the morphology of beach features and temporally with changes in tide level, wave energy, and morphodynamics. These data are being used to examine the relationship between morphological, sedimentological and hydrodynamic variability.

  3. Grain Size and Morphological Variability

    NASA Astrophysics Data System (ADS)

    Gallagher, E. L.; Reniers, A. J.; Macmahan, J. H.; Thornton, E. B.

    2009-12-01

    Grain size on natural beaches has traditionally been assumed to be uniform and modeling efforts assume a single mean grain size for an entire beach environment. Many recent studies contradict this assumption and suggest that sediment grain size on a beach is not homogeneous and that variations in sediment size and supply are important in sediment transport and morphodynamics at all scales. Unfortunately, measuring grain size is tedious and time consuming. Therefore, in spite of the evidence pointing to the importance of grain size in sediment transport and morphodynamics, many previous studies have been based on only a few field samples. Rubin (2004) introduced a technique for measuring surface grain size in situ in rivers and deeper coastal waters, using a digital camera and auto-correlation of digital images. Using this technique, information about the surface grain size distribution can be obtained quickly and inexpensively. Following Rubin (2004), we have developed a mobile digital imaging system (DIS) for surveying grain size on beaches. The DIS was used during three experiments: RCEX and REX, both rip current experiments in Monterey, CA (April 2007 and April 2009) and Truc Vert ’08, a multi-institutional, international experiment, on the Atlantic coast of France in March 2008. In 2007 and 2008 spatial surveys of surface grain size were completed every few days over large (~500x500m) intertidal areas. The 2009 experiment focused on twice-daily sampling of two cross shore lines to examine temporal grain size variability of the intertidal beach. Preliminary results suggest that grain size varies spatially with the morphology of beach features (eg, rip channels and shoals) and temporally with changes in tide level, wave energy, and morphodynamics. These data are being used to examine the relationship between morphological, sedimentological and hydrodynamic variability.

  4. Detrital Mineral Grains in Tektites.

    PubMed

    Bairnes, V E

    1963-12-27

    Abundant detrital crystalline mineral grains have been found in layered Muong Nong-type indochinite tektites from Nong Sapong, northeastern Thailand. These grains are an integral part of some tektite layers, and their presence furnishes strong presumptive evidence that indochinites, as well as other tektite groups in which layered specimens occur, formed from surficial earth materials. PMID:17834370

  5. Autonomous grain combine control system

    SciTech Connect

    Hoskinson, Reed L.; Kenney, Kevin L.; Lucas, James R.; Prickel, Marvin A.

    2013-06-25

    A system for controlling a grain combine having a rotor/cylinder, a sieve, a fan, a concave, a feeder, a header, an engine, and a control system. The feeder of the grain combine is engaged and the header is lowered. A separator loss target, engine load target, and a sieve loss target are selected. Grain is harvested with the lowered header passing the grain through the engaged feeder. Separator loss, sieve loss, engine load and ground speed of the grain combine are continuously monitored during the harvesting. If the monitored separator loss exceeds the selected separator loss target, the speed of the rotor/cylinder, the concave setting, the engine load target, or a combination thereof is adjusted. If the monitored sieve loss exceeds the selected sieve loss target, the speed of the fan, the size of the sieve openings, or the engine load target is adjusted.

  6. Whole grain gluten-free flat breads

    Technology Transfer Automated Retrieval System (TEKTRAN)

    USDA food guide recommends that at least ½ of all the grains eaten should be whole grains. FDA allows label health claims for food containing 11 g and 51% whole grains. This is the only report demonstrating innovative whole grain products. Whole grain gluten-free flat breads were prepared with cor...

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

    SciTech Connect

    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 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.

  8. Impact into Coarse Grained Spheres

    NASA Technical Reports Server (NTRS)

    Barnouin-Jha, O. S.; Cintala, M.; Crawford, D. A.

    2005-01-01

    Several experimental studies [1,2,3] indicate that differences in the grain size of the target relative to the projectile could influence the cratering process. Impacts into coarse sand grains of size comparable to the projectile show some discrepancies with existing relationships for crater growth [e.g. 4]. Similarly, targets of ne grained, uniform in diameter glass spheres show differences in crater depth, transient crater diameter, and volume of ejecta excavated as a function of grain size [2,3]. The purpose of this work is to continue investigating how the relative grain size may influence early time coupling between a projectile and target, with implications for subsequent ejecta excavation and crater growth. In previous efforts we used numerical techniques to focus on the propagation of shock waves in coarse, granular media emphasizing the influence of relative grain size on crater growth, ejecta production, cratering efficiency, target strength, and crater shape [5,6,7]. In this study, we use experimental techniques - in part as a reality check for the numerical studies - to report on how coarse grained targets might influence ejecta excavation and crater shape. This body of work possesses important implications for ejecta excavation and cratering efficiency on asteroids that may possess rubble pile-like structures, and on planets that may possess either pre-fractured surfaces or large-scale heterogeneities in shock impedance.

  9. Quantitative characterisation of sedimentary grains

    NASA Astrophysics Data System (ADS)

    Tunwal, Mohit; Mulchrone, Kieran F.; Meere, Patrick A.

    2016-04-01

    Analysis of sedimentary texture helps in determining the formation, transportation and deposition processes of sedimentary rocks. Grain size analysis is traditionally quantitative, whereas grain shape analysis is largely qualitative. A semi-automated approach to quantitatively analyse shape and size of sand sized sedimentary grains is presented. Grain boundaries are manually traced from thin section microphotographs in the case of lithified samples and are automatically identified in the case of loose sediments. Shape and size paramters can then be estimated using a software package written on the Mathematica platform. While automated methodology already exists for loose sediment analysis, the available techniques for the case of lithified samples are limited to cases of high definition thin section microphotographs showing clear contrast between framework grains and matrix. Along with the size of grain, shape parameters such as roundness, angularity, circularity, irregularity and fractal dimension are measured. A new grain shape parameter developed using Fourier descriptors has also been developed. To test this new approach theoretical examples were analysed and produce high quality results supporting the accuracy of the algorithm. Furthermore sandstone samples from known aeolian and fluvial environments from the Dingle Basin, County Kerry, Ireland were collected and analysed. Modern loose sediments from glacial till from County Cork, Ireland and aeolian sediments from Rajasthan, India have also been collected and analysed. A graphical summary of the data is presented and allows for quantitative distinction between samples extracted from different sedimentary environments.

  10. Fluctuation effects in grain growth

    NASA Astrophysics Data System (ADS)

    Kim, Seong Gyoon; Park, Yong Bum

    2016-08-01

    In this study, we attempted to clarify the roles of fluctuation effects in grain growth. To capture the persistent nature in both space and time of fluctuations due to variations in the local surroundings of individual grains, we developed a local mean-field model. The fluctuation strength in this model is arbitrarily controlled by employing an artificial number, n , of nearest neighbor grains. Large-scale numerical computations of the model for various n values and initial GSDs were carried out to follow transient behaviors and determine the steady states. This study reveals that, in the classical mean-field model with no fluctuation effects, the steady state is not unique but is strongly dependent upon the initial GSD. However, a small fluctuation drives the mean-field model to reach the Hillert solution, independent of the fluctuation strength and initial GSD, as long as the fluctuation strength is sufficiently small. On the other hand, when the fluctuation is sufficiently strong, the fluctuation pushes the steady state of the mean-field model out of the Hillert solution, and its strength determines a unique steady state independent of the initial GSD. The strong fluctuation makes the GSD more symmetric than the Hillert distribution. Computations designed to mimic actual 2 and 3D grain growth were carried out by taking the number of nearest neighbors of each grain as a function of the scaled grain size. The resultant GSDs in two and three dimensions were compared with the direct simulations of ideal grain growth.

  11. Why Is It Important to Eat Grains, Especially Whole Grains?

    MedlinePlus

    ... foods or supplements. This reduces the risk of neural tube defects, spina bifida, and anencephaly during fetal ... with folate before and during pregnancy helps prevent neural tube defects during fetal development. Grains All About ...

  12. Lunar soil grain size distribution

    NASA Technical Reports Server (NTRS)

    Carrier, W. D., III

    1973-01-01

    A comprehensive review has been made of the currently available data for lunar grain size distributions. It has been concluded that there is little or no statistical difference among the large majority of the soil samples from the Apollo 11, 12, 14, and 15 missions. The grain size distribution for these soils has reached a steady state in which the comminution processes are balanced by the aggregation processes. The median particle size for the steady-state soil is 40 to 130 microns. The predictions of lunar grain size distributions based on the Surveyor television photographs have been found to be quantitatively in error and qualitatively misleading.

  13. Presolar oxide grains in meteorites

    NASA Astrophysics Data System (ADS)

    Nittler, Larry R.

    1997-03-01

    Ninety-two refractory oxide grains (primarily Al2O3) with highly unusual O-isotopic ratios have been found in acid-resistant residues of five primitive meteorites. Thirty-five of these also have large excesses of 26Mg, attributable to the in situ decay of radioactive 26Al. The extreme ranges of isotopic compositions of the grains indicate that they are unprocessed stellar condensates. The grains have been divided into four groups. Group 1 grains have 17O excesses and moderate 18O depletions, relative to solar, and most likely formed around red giants and asymptotic giant branch (AGB) stars. However, many individual stars with different masses and initial compositions are required to explain the range of O-isotopic ratios and inferred 26Al/27Al ratios observed in the grains. Group 3 grains, which have 17O and 18O depletions, probably originated in O-rich red giants of very low mass (M<~1.4Msolar) and low metallicity. The Group 3 grains' compositions are probably strongly influenced by the chemical evolution of the Galaxy; they also provide a new method of determining the age of our Galaxy. Group 2 grains have large 18O depletions, 17O enrichments and high inferred 26Al/27Al ratios; they probably formed in low-mass AGB stars in which extra mixing (``cool bottom processing'') occurred. The four Group 4 grains have 18O enrichments. Possible explanations for these excesses include dredge-up of this isotope in early thermal pulses in AGB stars or an origin in low-mass red giants of unusually high metallicity. One grain, T54, is extremely enriched in 17O and depleted in 18O, and may have formed in an AGB star undergoing hot-bottom-burning. Presolar oxides are underabundant in meteorites, relative to presolar SiC, perhaps because Al condenses more readily into silicates than into refractory oxides or because presolar Al2O3 has a finer grain size distribution. No presolar oxide grains from supernovae have been identified, despite expectations that they should be present.

  14. Choosing Whole-Grain Foods: 10 Tips for Purchasing and Storing Whole-Grain Foods

    MedlinePlus

    ... Newsroom Dietary Guidelines Communicator’s Guide Choosing Whole-Grain Foods You are here Home Choosing Whole-Grain Foods ... 10 TIPS NUTRITION EDUCATION SERIES Choosing Whole-Grain Foods 10 tips for purchasing and storing whole-grain ...

  15. Theory of grain alignment in molecular clouds

    NASA Technical Reports Server (NTRS)

    Roberge, Wayne G.

    1993-01-01

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

  16. All About the Grains Group

    MedlinePlus

    ... Tips to Help You Eat Vegetables Beans and Peas Are Unique Foods Food Gallery Grains All About ... Tips to Help You Eat Vegetables Beans and Peas Are Unique Foods Food Gallery Protein Foods All ...

  17. MYCOTOXIN CONTROL DURING GRAIN PROCESSING.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Controlling mycotoxin formation by fungi growing in and on cereal grains involves a multifactorial approach for defining multiple variables. The scope includes varietial (maturity, date, GMO) selection, tillage (time, depth), planting (density, spacing), fertilizion (type, amount, timing), irrigati...

  18. Dense, finely, grained composite materials

    DOEpatents

    Dunmead, Stephen D.; Holt, Joseph B.; Kingman, Donald D.; Munir, Zuhair A.

    1990-01-01

    Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

  19. Spring Small Grains Area Estimation

    NASA Technical Reports Server (NTRS)

    Palmer, W. F.; Mohler, R. J.

    1986-01-01

    SSG3 automatically estimates acreage of spring small grains from Landsat data. Report describes development and testing of a computerized technique for using Landsat multispectral scanner (MSS) data to estimate acreage of spring small grains (wheat, barley, and oats). Application of technique to analysis of four years of data from United States and Canada yielded estimates of accuracy comparable to those obtained through procedures that rely on trained analysis.

  20. Stability of grain boundary texture during isothermal grain growth in UO2 considering anisotropic grain boundary properties

    NASA Astrophysics Data System (ADS)

    Hallberg, Håkan; Zhu, Yaochan

    2015-10-01

    In the present study, mesoscale simulations of grain growth in UO2 are performed using a 2D level set representation of the polycrystal grain boundary network, employed in a finite element setting. Anisotropic grain boundary properties are considered by evaluating how grain boundary energy and mobility varies with local grain boundary character. This is achieved by considering different formulations of the anisotropy of grain boundary properties, for example in terms of coincidence site lattice (CSL) correspondence. Such modeling approaches allow tracing of the stability of a number of characteristic low-Σ boundaries in the material during grain growth. The present simulations indicate that anisotropic grain boundary properties have negligible influence on the grain growth rate. However, considering the evolution of grain boundary character distribution and the grain size distribution, it is found that neglecting anisotropic boundary properties will strongly bias predictions obtained from numerical simulations.

  1. Complex Chemistry on Interstellar Grains

    NASA Astrophysics Data System (ADS)

    Widicus Weaver, Susanna L.; Kelley, Matthew J.; Blake, Geoffrey A.

    Early interstellar chemical models considered complex molecule formation on grains [Allen & Robinson (1977)], but current models assume that simple molecules form on grains and subsequent gas phase ion-molecule reactions produce the more complex species [Ruffle & Herbst (2001), Charnley (2001)]. It has been shown, however, that gas phase ion-molecule reactions are insufficient for the production of such complex organic species as ethanol (CH3CH2OH) and methyl formate (CH3OCHO) [Horn et al. (2004)]. Organics such as acetaldehyde (CH3CHO), ethanol, methyl formate, acetic acid (CH3COOH), and glycolaldehyde (CH2OHCHO) have also been detected in high abundance in regions of grain mantle disruption or evaporation, indicating that these species are formed on grain surfaces [see Chengalur & Kanekar (2003), Bottinelli et al. (2004), Hollis et al. (2001)]. The mechanisms for complex molecule production on grains are clearly much more important, and much more complex, than has been recognized. Recent observational studies of these types of species have offered insight into the mechanisms for their possible grain surface synthesis. The relative hot core abundances of the 2C structural isomers methyl formate, acetic acid, and glycolaldehyde (52:2:1, respectively [Hollis et al. (2001)]) indicate that if they form on grains it is not from kinetically-controlled single-atom addition reactions. Likewise, the 3C aldose sugar, glyceraldehyde (CH2OHCHOHCHO), was not detected in Sgr B2(N-LMH) [Hollis et al. (2004)] while the 3C ketose sugar, dihydroxyacetone (CO(CH2OH)2) was detected in this source [Widicus Weaver & Blake (2005)]. Chemical pathways favoring the more stable carbonates over acids and aldehydes are required to explain these results. Interestingly, all of these species can be formed from reactions involving the abundant grain mantle constituents CO, HCOOH, and CH3OH and their radical precursors. A model has been developed to investigate this type of chemical network, and

  2. The History of Presolar Grains

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.

    2004-01-01

    Below we summarize the results of our investigations into the history of presolar grains that were conducted in the last year. During this time we have expended much of our effort in the development of experimental techniques and sample preparation methods that are needed to laboratory in December, 2000. Specific information on this instrument is contained in the Full Proposal of PI Ernst Zinner and will not be repeated here. Our general strategy in the past year has been in large measure to explore novel sample handling methods for the very small (sub-micron), but more representative, presolar grains that can now be characterized isotopically in the NanoSIMS. We have developed experimental techniques that will permit NanoSIMS analyses of the very same ultramicrotome sections studied in the TEM, and we have developed grain dispersion, handling and mounting techniques that permit NanoSIMS isotopic analysis as well as field emission SEM, high energy TEM, and atomic force microscopy of pristine presolar grains. Although much of this has been slow and very difficult work that has no immediate payoff in terms of publishable results, we considered it absolutely necessary groundwork for future discoveries, especially in the realm of individual presolar grains that have been inaccessible to past studies due to size constraints. As discussed below, we have been largely successful in these endeavors, and expect to reap the benefits of this work in the next year. We also report on our continued morphologic studies of pristine presolar grains, on our investigations of presolar graphite grains from supernovae as well as on rarer types of presotar SIC, on the search for presolar silicates, and on our efforts to obtain direct size-distribution information on presolar SiC through X-ray mapping techniques.

  3. Simultaneous Grain Growth and Grain Refinement in Bulk Ultrafine-Grained Copper under Tensile Deformation at Room Temperature

    NASA Astrophysics Data System (ADS)

    Yu, Hailiang; Lu, Cheng; Tieu, Anh Kiet; Li, Huijun; Godbole, Ajit; Kong, Charlie; Zhao, Xing

    2016-08-01

    Grain growth and grain refinement behavior during deformation determine the strength and ductility of ultrafine-grained materials. We used asymmetric cryorolling to fabricate ultrafine-grained copper sheets with an average grain width of 230 nm and having a laminate structure. The sheets show a high-true failure strain of 1.5. Observation of the microstructure at the fracture surface reveals that ultrafine laminate-structured grains were simultaneously transformed into both equiaxed nanograins and coarse grains under tensile deformation at room temperature.

  4. Experiments on Dust Grain Charging

    NASA Technical Reports Server (NTRS)

    Abbas, M. N.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; West, E. A.

    2004-01-01

    Dust particles in various astrophysical environments are charged by a variety of mechanisms generally involving collisional processes with other charged particles and photoelectric emission with UV radiation from nearby sources. The sign and the magnitude of the particle charge are determined by the competition between the charging processes by UV radiation and collisions with charged particles. Knowledge of the particle charges and equilibrium potentials is important for understanding of a number of physical processes. The charge of a dust grain is thus a fundamental parameter that influences the physics of dusty plasmas, processes in the interplanetary medium and interstellar medium, interstellar dust clouds, planetary rings, cometary and outer atmospheres of planets etc. In this paper we present some results of experiments on charging of dust grains carried out on a laboratory facility capable levitating micron size dust grains in an electrodynamic balance in simulated space environments. The charging/discharging experiments were carried out by exposing the dust grains to energetic electron beams and UV radiation. Photoelectric efficiencies and yields of micron size dust grains of SiO2, and lunar simulates obtained from NASA-JSC will be presented.

  5. Sustainable production of grain crops for biofuels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grain crops of the Gramineae are grown for their edible, starchy seeds. Their grain is used directly for human food, livestock feed, and as raw material for many industries, including biofuels. Using grain crops for non-food uses affects the amount of food available to the world. Grain-based biofuel...

  6. Solid propellant grain design and internal ballistics

    NASA Technical Reports Server (NTRS)

    1972-01-01

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

  7. Fractal dust grains in plasma

    SciTech Connect

    Huang, F.; Peng, R. D.; Liu, Y. H.; Chen, Z. Y.; Ye, M. F.; Wang, L.

    2012-09-15

    Fractal dust grains of different shapes are observed in a radially confined magnetized radio frequency plasma. The fractal dimensions of the dust structures in two-dimensional (2D) horizontal dust layers are calculated, and their evolution in the dust growth process is investigated. It is found that as the dust grains grow the fractal dimension of the dust structure decreases. In addition, the fractal dimension of the center region is larger than that of the entire region in the 2D dust layer. In the initial growth stage, the small dust particulates at a high number density in a 2D layer tend to fill space as a normal surface with fractal dimension D = 2. The mechanism of the formation of fractal dust grains is discussed.

  8. Workshop on geophysical grain flows

    NASA Astrophysics Data System (ADS)

    Hanes, Daniel M.

    “Geophysical Grain Flows: Fluid-Grain Interactions in Coastal Sand Transport” was the focus of a workshop held from March 10 to 14 on Amelia Island, Fla. The workshop was sponsored by the National Science Foundation and the University of Florida. Approximately thirty-five participants from ten different countries attended, representing universities, government laboratories, and private companies. During the workshop, one of the largest and strongest storms in the recorded history of North America impacted the eastern half of the United States. The local response of the beach at Amelia Island to this storm was striking and somewhat surprising. There was substantial accretion and widening of the beach. While the morphological changes in the beach profile were of medium to large scale, it is intriguing to realize that the changes resulted from the integrated motion of an uncountable number of sand grains, each moving more or less independently, yet cumulatively producing a wider beach.

  9. Organic Model of Interstellar Grains

    NASA Astrophysics Data System (ADS)

    Yabushita, S.; Inagaki, T.; Kawabe, T.; Wada, K.

    1987-04-01

    Extinction efficiency of grains is calculated from the Mie formula on the premise that the grains are of organic composition. The optical constants adopted for the calculations are those of E. coli, polystyrene and bovine albumin. The grain radius a is assumed to obey a distribution of the form N(a) ∝ a-α and the value of α is chosen so as to make the calculated extinction curve match the observed interstellar extinction curve. Although the calculated curve gives a reasonably good fit to the observed extinction curve for wavelengths less than 2100 Å, at longer wavelength regions, agreement is poor. It is concluded that another component is required for the organic model to be viable.

  10. Bakery product from distiller's grain

    SciTech Connect

    Reddy, J.A.; Stoker, R.

    1993-07-06

    A method is described for preparing a bran from a solid fermentation wet distiller's grain (WDG) or distiller's dried grain with solubles (DDGS), which consisting essentially of: adding sodium bicarbonate at about 0.05-5 weight percent, amino acid at about 0.05-5 weight percent and potato starch at about 10-50 weight percent in the form of additives to WDG or DDGS; blending the WDG/DDGS-additive mix; and drying the blended mix to form a bran suitable for use in products for human consumption.

  11. Choosing Whole-Grain Foods: 10 Tips for Purchasing and Storing Whole-Grain Foods

    MedlinePlus

    ... whole-grain ingredients include whole oats, whole-wheat flour, whole-grain corn, whole-grain brown rice, and whole rye. Foods that say “multi-grain,” “ ... the shelf life varies too. Most whole-grain flours keep well in the ... for 6 to 8 months. Cooked brown rice can be refrigerated 3 to 5 days and ...

  12. SPECTRAL IMAGING TECHNIQUES FOR GRAIN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three spectral imaging techniques were employed for the purpose of assessing the quality of cereal grains. Each of these techniques provided unique, yet complementary, information. Nuclear magnetic resonance (NMR), also called magnetic resonance imaging (MRI), was used to detect mobile components ...

  13. Grain production for alcohol fuels

    SciTech Connect

    Lockeretz, W.

    1980-05-01

    This report provides primarily an assessment of the resource base for producing alcohol fuel from grain. The effect of different levels of alcohol production are discussed with respect to farm income, land conservation practices, food prices, and exports. The economics of ethanol production from the standpoint of feedstock availability and price are comprehensively examined.

  14. GRAIN REFINEMENT OF URANIUM BILLETS

    DOEpatents

    Lewis, L.

    1964-02-25

    A method of refining the grain structure of massive uranium billets without resort to forging is described. The method consists in the steps of beta- quenching the billets, annealing the quenched billets in the upper alpha temperature range, and extrusion upset of the billets to an extent sufficient to increase the cross sectional area by at least 5 per cent. (AEC)

  15. 75 FR 81965 - Grain Inspection Advisory Committee Reestablishment

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-29

    ...; ] DEPARTMENT OF AGRICULTURE Grain Inspection, Packers and Stockyards Administration Grain Inspection Advisory Committee Reestablishment AGENCY: Grain Inspection, Packers and Stockyards Administration, USDA. ACTION... reestablished the Grain Inspection, Packers and Stockyards Administration (GIPSA) Grain Inspection...

  16. 77 FR 76452 - Grain Inspection Advisory Committee Reestablishment

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-28

    ... Grain Inspection, Packers and Stockyards Administration Grain Inspection Advisory Committee Reestablishment AGENCY: Grain Inspection, Packers and Stockyards Administration, USDA. ACTION: Notice to... Grain Inspection, Packers and Stockyards Administration (GIPSA) Grain Inspection Advisory...

  17. 7 CFR 868.310 - Grades and grade requirements for the classes Long Grain Milled Rice, Medium Grain Milled Rice...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled Rice. (See also Â... classes Long Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled Rice...) (percent) Chalky kernels 1,2 In long grain rice (percent) In medium or short grain rice (percent)...

  18. Impact fracture experiments simulating interstellar grain-grain collisions

    NASA Astrophysics Data System (ADS)

    Freund, Friedemann; Chang, Sherwood; Dickinson, J. Thomas

    1990-04-01

    Oxide and silicate grains condensing during the early phases of the formation of the solar system or in the outflow of stars are exposed to high partial pressures of the low-z elements H, C, N and O and their simple gaseous compounds. Though refractory minerals are nominally anhydrous and non-carbonate, if they crystallize in the presence of H2O, N2 and CO or CO2 gases, they dissolve traces of the gaseous components. The question arises: How does the presence of dissolved gases or gas components manifest itself when grain-grain collisions occur. What are the gases emitted when grains are shattered during a collision event. Researchers report on fracture experiments in ultrahigh vacuum (UHV, approximately less than 10 to the -8th power mbar) designed to measure (by means of a quadrupole mass spectrometer, QMS, with microns to ms time resolution) the emission of gases and vapors during and after impact (up to 1.5 sec). Two terrestrial materials were chosen which represent structural and compositional extremes: olivine (San Carlos, AZ), a densely packed Mg-Fe(2+) silicate from the upper mantle, available as 6 to 12 mm single crystals, and obsidian (Oregon), a structurally open, alkaline-SiO2-rich volcanic glass. In the olivine crystals OH- groups have been identified spectroscopically, as well as H2 molecules. Obsidian is a water-rich glass containing OH- besides H2O molecules. Olivine from the mantle often contains CO2, either as CO2-rich fluid in fluid inclusions or structurally dissolved or both. By analogy to synthetic glasses CO2 in the obsidian may be present in form of CO2 molecules in voids of molecular dimensions, or as carbonate anions, CO3(2-). No organic molecules have been detected spectroscopically in either material. Results indicate that refractory oxide/silicates which contain dissolved traces of the H2O and CO/CO2 components but no spectroscopically detectable traces of organics may release complex H-C-O (possibly H-C-N-O) molecules upon fracture

  19. Grain size and grain shape analysis of fault rocks

    NASA Astrophysics Data System (ADS)

    Heilbronner, Renée; Keulen, Nynke

    2006-12-01

    New methods for microstructural analysis of fault rocks (new shape descriptors for convexity/concavity and angularity) and visualization (D-mapping) were developed and tested on experimentally deformed granites. The samples were deformed at 300 °C, 500 MPa confining pressure, and 10 - 4 s - 1 strain rate. SEM micrographs of the resulting fault rocks were used for digital image analysis. Cracked fragments and mature gouges can be differentiated on the basis of the slope D on a log-log plot of the grain size distribution. Both types of fault rocks exhibit two slopes: for grain sizes < 2 μm, D ≈ 1.0 for both types; for grain sizes > 2 μm, cracked material shows D ≈ 1.6 while gouge has D ≥ 2.0. In the case of the gouge, the fractal nature of the grain size distribution is questioned. The D-mapping technique was introduced to visualize the spatial distribution and connectivity of gouge and cracked material in fault rocks. Grain shape analyses show clear differences between cracked minerals and fault gouges and between quartz and K-feldspar grains. The aspect ratio is measured as L/ S (longest/shortest diameter): L/ S of cracked quartz (range: 1.0-8.0, average 2.9) is higher than that of K-feldspar (range: 1.0-4.0, average 2.1). L/ S of gouge is always low (range: 1.0-3.0, average 1.5). From the difference between a shape and its convex envelope, two shape descriptors are derived: the paris factor and the area difference deltA. Both show decreasing values from cracked to gouge material, and the values of cracked K-feldspar (range: 0-100%, average: 15%) are higher than those for quartz (range: 0-100%, average: 5%). Gouge always shows low paris factors (range: 0-20%, average: 2.5%). From the histogram of vertex angles, the Ω-value (fraction of angles < 0°) is derived: Ω of cracked material is significantly higher (30-40%) than that of gouge (10-20%). Automatic digitization enhances the distinction between cracked and gouge material.

  20. Impact fracture experiments simulating interstellar grain-grain collisions

    NASA Technical Reports Server (NTRS)

    Freund, Friedemann; Chang, Sherwood; Dickinson, J. Thomas

    1990-01-01

    Oxide and silicate grains condensing during the early phases of the formation of the solar system or in the outflow of stars are exposed to high partial pressures of the low-z elements H, C, N and O and their simple gaseous compounds. Though refractory minerals are nominally anhydrous and non-carbonate, if they crystallize in the presence of H2O, N2 and CO or CO2 gases, they dissolve traces of the gaseous components. The question arises: How does the presence of dissolved gases or gas components manifest itself when grain-grain collisions occur. What are the gases emitted when grains are shattered during a collision event. Researchers report on fracture experiments in ultrahigh vacuum (UHV, approximately less than 10 to the -8th power mbar) designed to measure (by means of a quadrupole mass spectrometer, QMS, with microns to ms time resolution) the emission of gases and vapors during and after impact (up to 1.5 sec). Two terrestrial materials were chosen which represent structural and compositional extremes: olivine (San Carlos, AZ), a densely packed Mg-Fe(2+) silicate from the upper mantle, available as 6 to 12 mm single crystals, and obsidian (Oregon), a structurally open, alkaline-SiO2-rich volcanic glass. In the olivine crystals OH- groups have been identified spectroscopically, as well as H2 molecules. Obsidian is a water-rich glass containing OH- besides H2O molecules. Olivine from the mantle often contains CO2, either as CO2-rich fluid in fluid inclusions or structurally dissolved or both. By analogy to synthetic glasses CO2 in the obsidian may be present in form of CO2 molecules in voids of molecular dimensions, or as carbonate anions, CO3(2-). No organic molecules have been detected spectroscopically in either material. Results indicate that refractory oxide/silicates which contain dissolved traces of the H2O and CO/CO2 components but no spectroscopically detectable traces of organics may release complex H-C-O (possibly H-C-N-O) molecules upon fracture

  1. Grain Refinement of Deoxidized Copper

    NASA Astrophysics Data System (ADS)

    Balart, María José; Patel, Jayesh B.; Gao, Feng; Fan, Zhongyun

    2016-08-01

    This study reports the current status of grain refinement of copper accompanied in particular by a critical appraisal of grain refinement of phosphorus-deoxidized, high residual P (DHP) copper microalloyed with 150 ppm Ag. Some deviations exist in terms of the growth restriction factor (Q) framework, on the basis of empirical evidence reported in the literature for grain size measurements of copper with individual additions of 0.05, 0.1, and 0.5 wt pct of Mo, In, Sn, Bi, Sb, Pb, and Se, cast under a protective atmosphere of pure Ar and water quenching. The columnar-to-equiaxed transition (CET) has been observed in copper, with an individual addition of 0.4B and with combined additions of 0.4Zr-0.04P and 0.4Zr-0.04P-0.015Ag and, in a previous study, with combined additions of 0.1Ag-0.069P (in wt pct). CETs in these B- and Zr-treated casts have been ascribed to changes in the morphology and chemistry of particles, concurrently in association with free solute type and availability. No further grain-refining action was observed due to microalloying additions of B, Mg, Ca, Zr, Ti, Mn, In, Fe, and Zn (~0.1 wt pct) with respect to DHP-Cu microalloyed with Ag, and therefore are no longer relevant for the casting conditions studied. The critical microalloying element for grain size control in deoxidized copper and in particular DHP-Cu is Ag.

  2. AGB stars and presolar grains

    SciTech Connect

    Busso, M.; Trippella, O.; Maiorca, E.; Palmerini, S.

    2014-05-09

    Among presolar materials recovered in meteorites, abundant SiC and Al{sub 2}O{sub 3} grains of AGB origins were found. They showed records of C, N, O, {sup 26}Al and s-element isotopic ratios that proved invaluable in constraining the nucleosynthesis models for AGB stars [1, 2]. In particular, when these ratios are measured in SiC grains, they clearly reveal their prevalent origin in cool AGB circumstellar envelopes and provide information on both the local physics and the conditions at the nucleosynthesis site (the H- and He-burning layers deep inside the structure). Among the properties ascertained for the main part of the SiC data (the so-called mainstream ones), we mention a large range of {sup 14}N/{sup 15}N ratios, extending below the solar value [3], and {sup 12}C/{sup 13}C ratios ≳ 30. Other classes of grains, instead, display low carbon isotopic ratios (≳ 10) and a huge dispersion for N isotopes, with cases of large {sup 15}N excess. In the same grains, isotopes currently feeded by slow neutron captures reveal the characteristic pattern expected from this process at an efficiency slightly lower than necessary to explain the solar main s-process component. Complementary constraints can be found in oxide grains, especially Al{sub 2}O{sub 3} crystals. Here, the oxygen isotopes and the content in {sup 26}Al are of a special importance for clarifying the partial mixing processes that are known to affect evolved low-mass stars. Successes in modeling the data, as well as problems in explaining some of the mentioned isotopic ratios through current nucleosynthesis models are briefly outlined.

  3. Abundance, Grain Size and PDF Orientations of Shocked Quartz Grains Around the Chicxulub Crater

    NASA Astrophysics Data System (ADS)

    Goto, K.; Nakano, Y.; Matsui, T.; Tada, R.; Tajika, E.

    2011-03-01

    We measured abundance, grain size, and PDF orientations of shocked quartz grains around the Chicxulub crater in order to investigate the distribution and variation of shocked quartz grains produced by the Chicxulub impact.

  4. Evolutionary characteristics of a bimodal grain model. [interstellar grains

    NASA Technical Reports Server (NTRS)

    Greenberg, J. M.; Seung, S. H.

    1974-01-01

    A bimodal model of interstellar grains consisting of silicate cores of size approximately 0.06 micron with modified ice mantles of approximately 0.1 micron and very small particles of silicate and/or graphite of size approximately 0.005 micron is followed through various stages of evolution. Starting with a distribution of core-mantle cylinders producing average wavelength dependence of polarization and extinction, changes in physical and optical characteristics of the model are studied going first into regions of dense cloud condensation and coming out at the other end of star formation into young H2 regions. Physical justification is presented to show that not only in dense clouds must the core mantle grains be larger than normal, but also in young H2 regions.

  5. Grain Growth in Cerium Metal

    NASA Astrophysics Data System (ADS)

    Cooley, Jason; Katz, Martha; Mielke, Charles; Montalvo, Joel

    We report on grain growth in forged and rolled cerium plate for temperatures from 350 to 700 degrees C and times from 30 to 120 minutes. The cerium was made by arc-melting into a 25 mm deep by 80 mm diameter copper mold. The resulting disk was forged at room temperature to a 25% reduction of thickness four times with a 350 degree C strain relief heat treatment for 60 minutes between forging steps. The resulting 8 mm thick plate was clock rolled at room temperature to a 25% reduction of thickness three times with a 350 C strain relief heat treatment between steps resulting in a plate approximately 3 mm thick. 5 x 10 mm coupons were cut from the plate for the grain growth study.

  6. Coarse-graining in peridynamics.

    SciTech Connect

    Silling, Stewart Andrew

    2010-11-01

    The peridynamic theory is an extension of traditional solid mechanics that treats discontinuous media, including the evolution of discontinuities due to fracture, on the same mathematical basis as classically smooth media. A recent advance in the linearized peridynamic theory permits the reduction of the number of degrees of freedom modeled within a body. Under equilibrium conditions, this coarse graining method exactly reproduces the internal forces on the coarsened degrees of freedom, including the effect of the omitted material that is no longer explicitly modeled. The method applies to heterogeneous as well as homogeneous media and accounts for defects in the material. The coarse graining procedure can be repeated over and over, resulting in a hierarchically coarsened description that, at each stage, continues to reproduce the exact internal forces present in the original, detailed model. Each coarsening step results in reduced computational cost. This talk will describe the new peridynamic coarsening method and show computational examples.

  7. Photophoretic force on aggregate grains

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin S.; Kimery, Jesse B.; Wurm, Gerhard; de Beule, Caroline; Kuepper, Markus; Hyde, Truell W.

    2016-01-01

    The photophoretic force may impact planetary formation by selectively moving solid particles based on their composition and structure. This generates collision velocities between grains of different sizes and sorts the dust in protoplanetary discs by composition. This numerical simulation studied the photophoretic force acting on fractal dust aggregates of μm-scale radii. Results show that aggregates tend to have greater photophoretic drift velocities than spheres of similar mass or radii, though with a greater spread in the velocity. While the drift velocities of compact aggregates continue to increase as the aggregates grow larger in size, fluffy aggregates have drift velocities which are relatively constant with size. Aggregates formed from an initially polydisperse size distribution of dust grains behave differently from aggregates formed from a monodisperse population, having smaller drift velocities with directions which deviate substantially from the direction of illumination. Results agree with microgravity experiments which show the difference of photophoretic forces with aggregation state.

  8. Grain Alignment in Starless Cores

    NASA Astrophysics Data System (ADS)

    Jones, T. J.; Bagley, M.; Krejny, M.; Andersson, B.-G.; Bastien, P.

    2015-01-01

    We present near-IR polarimetry data of background stars shining through a selection of starless cores taken in the K band, probing visual extinctions up to {{A}V}˜ 48. We find that {{P}K}/{{τ }K} continues to decline with increasing AV with a power law slope of roughly -0.5. Examination of published submillimeter (submm) polarimetry of starless cores suggests that by {{A}V}≳ 20 the slope for P versus τ becomes ˜-1, indicating no grain alignment at greater optical depths. Combining these two data sets, we find good evidence that, in the absence of a central illuminating source, the dust grains in dense molecular cloud cores with no internal radiation source cease to become aligned with the local magnetic field at optical depths greater than {{A}V}˜ 20. A simple model relating the alignment efficiency to the optical depth into the cloud reproduces the observations well.

  9. Grain Dynamics in Flowing Sand

    NASA Astrophysics Data System (ADS)

    Durian, Douglas J.

    1998-03-01

    Granular materials can exhibit a rigid, solid-like character because thermal energies are not sufficient to move grains around one another. Granular materials can also exhibit a liquid-like character in which they flow and deform smoothly when acted on by large external forces. A central questions in understanding such flows, then, is the fate of the energy supplied by the driving forces. Rather than shake or tilt a sandpile, we have thus created two dynamical systems in which energy is supplied continuously and homogeneously throughout the entire medium at a known rate. The first consists of a rectangular hopper, or hourglass, with uniform cross section; the hydrodynamic flow in the interior is controlled by a sieve at the bottom(N. Menon and D.J. Durian, Science 275), 1920 (1997).. The second is a gas-fluidized bed in which motion is excited by an upward flow of gas(N. Menon and D.J. Durian, Phys. Rev. Lett. 79), 3407 (1997).. In both, we probe the resulting grain dynamics via diffusing-wave spectroscopy (DWS). We discover that grains fly ballistically between collisions with typical mean free times and paths that are far too short to be measured by conventional imaging techniques: 10-5 s and 10 nm, respectively, for 0.1 mm diameter grains. Though surprising, these scales are in rough accord with energy conservation, showing that random collisions (the so-called ``granular temperature''), rather than kinetic friction, can dominate dissipation even in slow dense flows. Our DWS data also invalidate common assumptions regarding the connection of the granular temperature to velocity gradients and to the self-diffusion constant.

  10. Isotopic anomalies in extraterrestrial grains.

    PubMed

    Ireland, T R

    1996-03-01

    Isotopic compositions are referred to as anomalous if the isotopic ratios measured cannot be related to the terrestrial (solar) composition of a given element. While small effects close to the resolution of mass spectrometric techniques can have ambiguous origins, the discovery of large isotopic anomalies in inclusions and grains from primitive meteorites suggests that material from distinct sites of stellar nucleosynthesis has been preserved. Refractory inclusions, which are predominantly composed of the refractory oxides of Al, Ca, Ti, and Mg, in chondritic meteorites commonly have excesses in the heaviest isotopes of Ca, Ti, and Cr which are inferred to have been produced in a supernova. Refractory inclusions also contain excess 26Mg from short lived 26Al decay. However, despite the isotopic anomalies indicating the preservation of distinct nucleosynthetic sites, refractory inclusions have been processed in the solar system and are not interstellar grains. Carbon (graphite and diamond) and silicon carbide grains from the same meteorites also have large isotopic anomalies but these phases are not stable in the oxidized solar nebula which suggests that they are presolar and formed in the circumstellar atmospheres of carbon-rich stars. Diamond has a characteristic signature enriched in the lightest and heaviest isotopes of Xe, and graphite shows a wide range in C isotopic compositions. SiC commonly has C and N isotopic signatures which are characteristic of H-burning in the C-N-O cycle in low-mass stars. Heavier elements such as Si, Ti, Xe, Ba, and Nd, carry an isotopic signature of the s-process. A minor population of SiC (known as Grains X, ca. 1%) are distinct in having decay products of short lived isotopes 26Al (now 26Mg), 44Ti (now 44Ca), and 49V (now 49Ti), as well as 28Si excesses which are characteristic of supernova nucleosynthesis. The preservation of these isotopic anomalies allows the examination of detailed nucleosynthetic pathways in stars. PMID

  11. Lunar soils grain size catalog

    NASA Technical Reports Server (NTRS)

    Graf, John C.

    1993-01-01

    This catalog compiles every available grain size distribution for Apollo surface soils, trench samples, cores, and Luna 24 soils. Original laboratory data are tabled, and cumulative weight distribution curves and histograms are plotted. Standard statistical parameters are calculated using the method of moments. Photos and location comments describe the sample environment and geological setting. This catalog can help researchers describe the geotechnical conditions and site variability of the lunar surface essential to the design of a lunar base.

  12. Solid Propellant Grain Structural Integrity Analysis

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The structural properties of solid propellant rocket grains were studied to determine the propellant resistance to stresses. Grain geometry, thermal properties, mechanical properties, and failure modes are discussed along with design criteria and recommended practices.

  13. Mechanical Behavior of Grain Boundary Engineered Copper

    SciTech Connect

    Carter, S B; Hodge, A M

    2006-08-08

    A grain boundary engineered copper sample previously characterized by Electron Backscatter Diffraction (EBSD) has been selected for nanoindentation tests. Given the fact that grain boundaries have thicknesses in the order of 1 micron or less, it is essential to use nanomechanics to test the properties of individual grain boundaries. The Hysitron nanoindenter was selected over the MTS nanoindenter due to its superior optical capabilities that aid the selection and identification of the areas to be tested. An area of 2mm by 2mm with an average grain size of 50 microns has been selected for the study. Given the EBSD mapping, grains and grain boundaries with similar orientations are tested and the hardness and modulus are compared. These results will give a relationship between the mechanical properties and the engineered grain boundaries. This will provide for the first time a correlation between grain boundary orientation and the mechanical behavior of the sample at the nanoscale.

  14. U. S. grain exports: Concerns about quality

    SciTech Connect

    Not Available

    1986-01-01

    Complaints are on the rise from wheat producers who see grain leaving their farms in good condition, but who then suspect that export elevators add dust and other material to the grain to boost the elevators' profits. Some believe that this is a reason why an increasing number of foreign purchasers of U.S. grain have been expressing dissatisfication with the quality of the grain they have received. Fear has also been expressed that these purchasers will turn to other countries to satisfy their grain needs, if they have not already done so. GAO made a number of recommendations in the past dealing with the quality of U.S. grain shipped overseas that if implemented would have resulted in inspection certificates that more accurately reflected the actual quality of the grain, provided end-users with better information on certain quality factors, and assured greater uniformity in grain quality within a shipment. The recommendations have not been implemented.

  15. Thermal properties of heterogeneous grains

    NASA Technical Reports Server (NTRS)

    Lien, David J.

    1988-01-01

    Cometary dust is not spherical nor homogeneous, yet these are the assumptions used to model its thermal, optical, and dynamical properties. To better understand the effects of heterogeneity on the thermal and optical properties of dust grains, the effective dielectric constant for an admixture of magnetite and a silicate were calculated using two different effective medium theories: the Maxwell-Garnett theory and the Bruggeman theory. In concept, the MG theory describes the effective dielectric constant of a matrix material into which is embedded a large number of very small inclusions of a second material. The Bruggeman theory describes the dielectric constant of a well mixed aggregate of two or more types of materials. Both theories assume that the individual particles are much smaller than the wavelength of the incident radiation. The refractivity for a heterogeneous grain using the MG theory is very similar to the refractivity of the matrix material, even for large volume fractions of the inclusion. The equilibrium grain temperature for spherical particles sized from .001 to 100 microns in radius at 1 astronomical unit from the sun was calculated. Further explanation is given.

  16. Model exchange-spring nanocomposite magnetic grains

    NASA Astrophysics Data System (ADS)

    Szlaferek, A.

    2004-05-01

    The magnetization reversal in nanocomposite two-phase grains embedded in a soft magnetic matrix is calculated using Brown's equation. The grains are spherical, consisting of a soft core surrounded by a hard shell. The calculation yields nonlinear algebraic expressions whose solutions describe the nucleation field as a function of the geometrical and magnetic parameters of the grains. The magnetization reversal depends not only on the total grain size but also on the shell thickness.

  17. 7 CFR 457.113 - Coarse grains crop insurance provisions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Grains Crop Provisions 1. Definitions Coarse grains. Corn, grain sorghum, and soybeans. Grain sorghum... cash grain price per bushel for the U.S. No. 2 yellow corn, U.S. No. 2 grain sorghum, or U.S. No. 1... yellow corn and grain sorghum, or U.S. No. 1 grade for soybeans. Factors not associated with...

  18. 7 CFR 457.113 - Coarse grains crop insurance provisions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Grains Crop Provisions 1. Definitions Coarse grains. Corn, grain sorghum, and soybeans. Grain sorghum... cash grain price per bushel for the U.S. No. 2 yellow corn, U.S. No. 2 grain sorghum, or U.S. No. 1... yellow corn and grain sorghum, or U.S. No. 1 grade for soybeans. Factors not associated with...

  19. 7 CFR 457.113 - Coarse grains crop insurance provisions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Grains Crop Provisions 1. Definitions Coarse grains. Corn, grain sorghum, and soybeans. Grain sorghum... cash grain price per bushel for the U.S. No. 2 yellow corn, U.S. No. 2 grain sorghum, or U.S. No. 1... yellow corn and grain sorghum, or U.S. No. 1 grade for soybeans. Factors not associated with...

  20. Alignment mechanisms of paramagnetic grains revisited

    NASA Technical Reports Server (NTRS)

    Seki, Munezo

    1989-01-01

    Taking into account the tight coupling of grain axis with angular momentum due to effective dissipation of rotation energy, the alignment of spheroidal grains was investigated by paramagnetic relaxation. Alignment degree will be significantly improved in diffuse clouds. The inclusions of superparamagnetic (SPM) substances may play a key role in grain alignment in dark clouds as well as in diffuse clouds.

  1. Single grain heating due to inelasltic cotunneling.

    SciTech Connect

    Glatz, A.; Beloborodov, I. S.; Materials Science Division; Cal State Univ. at Northridge

    2010-01-25

    We study heating effects of a single metallic quantum dot weakly coupled to two leads. The dominant mechanism for heating at low temperatures is due to inelastic electron cotunneling processes. We calculate the grain temperature profile as a function of grain parameters, bias voltage, and time and show that for nanoscale size grains the heating effects are pronounced and easily measurable in experiments.

  2. Ancient whole grain gluten-free flatbreads

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. Whole grain gluten-free flat breads

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The USDA food guide recommends that at least ½ of all the grains eaten should be whole grains. The FDA allows food health claim labels for food containing 51% whole gains and 11 g of dietary fiber. This is the only report demonstrating innovative whole grain gluten free (without yeast or chemicals) ...

  4. Grain and subgrain boundaries in ultrafine-grained materials

    SciTech Connect

    Saxl, Ivan; Kalousova, Anna; Ilucova, Lucia; Sklenicka, Vaclav

    2009-10-15

    The attractive metallographic electron backscatter diffraction (EBSD) method is used to describe the effect of the number N of passes on the subgrain and grain structures of pure aluminium and copper processed by equal channel angular pressing (ECAP). The remarkable feature of the aluminium structure is the lack of high angle boundaries after a low number (N = 2, 4) of passes and this remains preserved even after a relatively long annealing time. On the other hand, the boundary structure of copper is relatively stable and high angle boundaries always prevail.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  6. 75 FR 76254 - Official Performance and Procedural Requirements for Grain Weighing Equipment and Related Grain...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-08

    ... Grain Inspection, Packers and Stockyards Administration 7 CFR Part 802 RIN 0580-AB19 Official Performance and Procedural Requirements for Grain Weighing Equipment and Related Grain Handling Systems AGENCY: Grain Inspection, Packers and Stockyards Administration, USDA. ACTION: Direct final rule. SUMMARY:...

  7. Grain size control of rhenium strip

    NASA Technical Reports Server (NTRS)

    Schuster, Gary B.

    1991-01-01

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

  8. 3D modeling of metallic grain growth

    SciTech Connect

    George, D.; Carlson, N.; Gammel, J.T.; Kuprat, A.

    1999-06-01

    This paper will describe simulating metallic grain growth using the Gradient Weighted Moving Finite Elements code, GRAIN3D. The authors also describe the set of mesh topology change operations developed to respond to changes in the physical topology such as the collapse of grains and to maintain uniform calculational mesh quality. Validation of the method is demonstrated by comparison to analytic calculations. The authors present results of multigrain simulations where grain boundaries evolve by mean curvature motion and include results which incorporate grain boundary orientation dependence.

  9. Grain size control of rhenium strip

    NASA Astrophysics Data System (ADS)

    Schuster, Gary B. A.

    1991-01-01

    Pure Re is being used in the SP-100. To obtain the desired final grain size it is necessary to both control the grain size of the starting Re strip and to avoid excessive grain growth during subsequent fabrication. It was found that the as-received strip, supplied by commerical vendors, typicall showed a large amount of scatter in its grain size. It was also observed that considerable grain growth often occurred during fabrication. The latter was due to strain induced grain boundary migration. A program was undertaken to develop a procedure to produce Re strip with a small and uniform grain size. In addition pure Re tapered tensile specimens were fabricated and tested to qunatify the effects of the grain boundary migration. Results of the work with Re strip showed that its grain size could be made fine and uniform by following a rolling procedure that employs relatively large reductions between short intermediate anneals. The tapered tensile specimen tests showed that the amount of grain growth due to grain boundary migration increases greatly with higher annealing temperatures. Also the critical strain regime varies inversely with this temperature-- that is the critical strain regime decreases to a lower range of strain values at higher annealing temperatures.

  10. Spin-related magnetism of interstellar grains

    NASA Technical Reports Server (NTRS)

    Srnka, L. J.; De, B. R.

    1978-01-01

    The magnetic dipole moments and internal magnetic fields due to the spin of electrically charged elongated nonmagnetic interstellar grains in kinetic equilibrium with their surroundings are computed for the grain-size range from 0.01 to 1.0 micron. It is shown that the induced magnetic moments and internal magnetic fields of charged spinning nonmagnetic grains of arbitrary composition and prolate spheroidal shape can be appreciable, possibly even exceeding 0.01 emu/cu cm for 0.01-micron grains. The results indicate that virtually all grains smaller than 0.1 micron in mean diameter, and all elongated grains smaller than about 1 micron in length, are immersed in local magnetic fields due to spin that are much larger than the ambient galactic field. Some implications of this effect are discussed in relation to the polarization of starlight by aligned dust grains and the primordial remanent magnetization found in primitive carbonaceous chondrites.

  11. 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. PMID:23514771

  12. Grain alignment in starless cores

    SciTech Connect

    Jones, T. J.; Bagley, M.; Krejny, M.; Andersson, B.-G.; Bastien, P.

    2015-01-01

    We present near-IR polarimetry data of background stars shining through a selection of starless cores taken in the K band, probing visual extinctions up to A{sub V}∼48. We find that P{sub K}/τ{sub K} continues to decline with increasing A{sub V} with a power law slope of roughly −0.5. Examination of published submillimeter (submm) polarimetry of starless cores suggests that by A{sub V}≳20 the slope for P versus τ becomes ∼−1, indicating no grain alignment at greater optical depths. Combining these two data sets, we find good evidence that, in the absence of a central illuminating source, the dust grains in dense molecular cloud cores with no internal radiation source cease to become aligned with the local magnetic field at optical depths greater than A{sub V}∼20. A simple model relating the alignment efficiency to the optical depth into the cloud reproduces the observations well.

  13. Grain Growth in Collapsing Clouds

    NASA Astrophysics Data System (ADS)

    Rossi, S. C. F.; Benevides-Soares, P.; Barbuy, B.

    1990-11-01

    RESUMEN. Se ha considerado un proceso de coagulaci6n de granos en nubes colapsantes de diferentes metalicidades. Se aplicaron los calculos al intervalo de densidades n = lO to , forrespondiendo a la fase isotermica de contracci6n de nubes. A lo largo de esta fase en el colap- so, la temperatura es por lo tanto constante, en donde se alcanza T Q lOKpara nubes de metalicidad solar y T 100 K para nubes de baja metalicidad. El tamano final del grano es mayor para las mayores metali- cidades. ABSTRACT. A process of grain coagulation in collapsing clouds of different metallicities is considered. The calculations are applied to the density range n = 1O to , corresponding to the isothermal phase of cloud contraction. Along this phase in the collapse, the temperature is thus a constant, where T % 10 K for solar-metallicity clouds, and T % 100 K for low metallicity clouds is reached. The final grain size is larger for the higher metallicities. Keq : INTERSTELLAR-CLOUDS - INTERSTELLAR-CRAINS

  14. Survival of carbon grains in shocks

    NASA Technical Reports Server (NTRS)

    Seab, C. Gregory

    1990-01-01

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

  15. Consideration of Grain Size Distribution in the Diffusion of Fission Gas to Grain Boundaries

    SciTech Connect

    Paul C. Millett; Yongfeng Zhang; Michael R. Tonks; S. B. Biner

    2013-09-01

    We analyze the accumulation of fission gas on grain boundaries in a polycrystalline microstructure with a distribution of grain sizes. The diffusion equation is solved throughout the microstructure to evolve the gas concentration in space and time. Grain boundaries are treated as infinite sinks for the gas concentration, and we monitor the cumulative gas inventory on each grain boundary throughout time. We consider two important cases: first, a uniform initial distribution of gas concentration without gas production (correlating with post-irradiation annealing), and second, a constant gas production rate with no initial gas concentration (correlating with in-reactor conditions). The results show that a single-grain-size model, such as the Booth model, over predicts the gas accumulation on grain boundaries compared with a polycrystal with a grain size distribution. Also, a considerable degree of scatter, or variability, exists in the grain boundary gas accumulation when comparing all of the grain boundaries in the microstructure.

  16. 7 CFR 457.113 - Coarse grains crop insurance provisions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Grains Crop Provisions 1. Definitions Coarse grains— Corn, grain sorghum, and soybeans. Grain sorghum... cash grain price per bushel for the U.S. No. 2 yellow corn, U.S. No. 2 grain sorghum, or U.S. No. 1... yellow corn and grain sorghum, or U.S. No. 1 grade for soybeans. Factors not associated with...

  17. Interstellar Silicate Dust: Modeling and Grain Alignment

    NASA Astrophysics Data System (ADS)

    Das, Indrajit

    We examine some aspects of the alignment of silicate dust grains with respect to the interstellar magnetic field. First, we consider possible observational constraints on the magnetic properties of the grains. Second, we investigate the role of collisions with gas atoms and the production of H2 molecules on the grain surface in the alignment process when the grain is drifting in the gaseous medium. Paramagnetism associated with Fe content in the dust is thought to play a critical role in alignment. Min et al (2007) claimed that the Fe content of the silicate dust can be constrained by the shape of the 10 μm extinction feature. They found low Fe abundances, potentially posing problems for grain alignment theories. We revisit this analysis modeling the grains with irregularly shaped Gaussian Random Sphere (GRS). We give a comprehensive review of all the relevant constraints researchers apply and discuss their effects on the inferred mineralogy. Also, we extend this analysis to examine whether constraints can be placed on the presence of Fe-rich inclusions which could yield "super-paramagnetism". This possibility has long been speculated, but so far observational constraints are lacking. Every time a gas atom collides with a grain, the grain's angular momentum is slightly modified. Likewise when an H2 molecule forms on the surface and is ejected. Here also we model the grain with GRS shape and considered various scenarios about how the colliding gas particles depart the grain. We develop theoretical and computational tools to estimate the torques associated with these aforementioned events for a range of grain drift speeds---from low subsonic to high supersonic speeds. Code results were verified with spherical grain for which analytical results were available. Finally, the above torque results were used to study the grain rotational dynamics. Solving dynamical equations we examine how these torques influence the grain alignment process. Our analysis suggests that

  18. 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

  19. Detecting grain rotation at the nanoscale

    PubMed Central

    Chen, Bin; Lutker, Katie; Lei, Jialin; Yan, Jinyuan; Yang, Shizhong; Mao, Ho-kwang

    2014-01-01

    It is well-believed that below a certain particle size, grain boundary-mediated plastic deformation (e.g., grain rotation, grain boundary sliding and diffusion) substitutes for conventional dislocation nucleation and motion as the dominant deformation mechanism. However, in situ probing of grain boundary processes of ultrafine nanocrystals during plastic deformation has not been feasible, precluding the direct exploration of the nanomechanics. Here we present the in situ texturing observation of bulk-sized platinum in a nickel pressure medium of various particle sizes from 500 nm down to 3 nm. Surprisingly, the texture strength of the same-sized platinum drops rapidly with decreasing grain size of the nickel medium, indicating that more active grain rotation occurs in the smaller nickel nanocrystals. Insight into these processes provides a better understanding of the plastic deformation of nanomaterials in a few-nanometer length scale. PMID:24550455

  20. Whole grain for whom and why?

    PubMed Central

    Frølich, Wenche; Åman, Per

    2010-01-01

    A definition of whole grain is a critical first step in investigating health claims for whole grain and its products. Today, there is no internationally accepted definition of whole grain. Some existing definitions are broad and commodity-based, including grains with similar end uses, while others are more restricted. Scientific knowledge must be the basis for inclusion of certain grains. It is better to start with a restricted list of grains (a precautionary principle) and extend this as more knowledge becomes available. An exact definition of the raw materials (milled, cracked, crushed, rolled, or flaked) and knowledge of the components providing health effects would appear to be crucial issues for the European authorities when approving health claims. It is important that health claims are evidence-based, sustainable, and officially validated. PMID:20300475

  1. Grain processes in massive star formation

    NASA Technical Reports Server (NTRS)

    Wolfire, M. G.; Cassinelli, J. P.

    1986-01-01

    Observational evidence suggests that stars greater than 100 M(solar) exist in the Galaxy and Large Magellanic Cloud (LMC), however classical star formation theory predicts stellar mass limits of only approx. 60 M(solar). A protostellar accretion flow consists of inflowing gas and dust. Grains are destroyed as they are near the central protostar creating a dust shell or cocoon. Radiation pressure acting on the grain can halt the inflow of material thereby limiting the amount of mass accumulated by the protostar. We first consider rather general constraints on the initial grain to gas ratio and mass accretion rates that permit inflow. We further constrain these results by constructing a numerical model. Radiative deceleration of grains and grain destruction processes are explicitly accounted for in an iterative solution of the radiation-hydrodynamic equations. Findings seem to suggest that star formation by spherical accretion requires rather extreme preconditioning of the grain and gas environment.

  2. Grain boundary segregation and intergranular failure

    SciTech Connect

    White, C.L.

    1980-01-01

    Trace elements and impurities often segregate strongly to grain boundaries in metals and alloys. Concentrations of these elements at grain boundaries are often 10/sup 3/ to 10/sup 5/ times as great as their overall concentration in the alloy. Because of such segregation, certain trace elements can exert a disproportionate influence on material properties. One frequently observed consequence of trace element segregation to grain boundaries is the occurrence of grain boundary failure and low ductility. Less well known are incidences of improved ductility and inhibition of grain boundary fracture resulting from trace element segregation to grain boundaries in certain systems. An overview of trace element segregation and intergranular failure in a variety of alloy systems as well as preliminary results from studies on Al 3% Li will be presented.

  3. Abnormal grain growth in TD-nickel.

    NASA Technical Reports Server (NTRS)

    Petrovic, J. J.; Ebert, L. J.

    1972-01-01

    Characteristics of the coarse grain transformation occurring in TD-nickel 1 in. bar under certain conditions of deformation and annealing were examined. The transformation exhibits Avrami-type kinetics, with an activation energy of 250 kcal per mole. Characteristics of untransformed regions are like those of the as-received state. The transformed grain size increases with increasing deformation and decreasing annealing temperature. The coarse grain transformation is significantly different from primary recrystallization in pure nickel. Its characteristics cannot be rationalized in terms of primary recrystallization concepts, but may be explained in terms of an abnormal grain growth description. The coarse grain transformation in TD-nickel is abnormal grain growth rather than primary recrystallization. The analysis suggests an explanation for the effect of thermomechanical history on the deformation and annealing behavior of TD-nickel.

  4. Jamming of Cylindrical Grains in Vertical Channels

    NASA Astrophysics Data System (ADS)

    Baxter, G. William; Spier, Gregory; Barr, Nicholas; Steel, Fiona

    2012-02-01

    We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. These cylindrical grains resemble antacid tablets, poker chips, or coins since their height is less than their diameter. Grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Within this channel, grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by the grain dimensions and channel size. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories.

  5. Grain orientation studies in superconductors

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, Sudhakar; Schulze, Walter A.

    1990-01-01

    Grain oriented fabrication of ceramics utilizes the presence of some form of anisotropy in the particles of the starting material to obtain textured microstructures. The molten salt, or flux method, a popular technique for growing crystals and particles with anisotropic morphology, is utilized in this study. The formation of Ba2YCu3O(7-x) in the presence of molten salts of Na, K, Li belonging to chloride and sulfate systems does not appear feasible in the temperature range up to 900 C. Researchers also present the results of studies in using BaY2CuO5 as seed crystals in the formation of Ba2YCu3O(7-x) wherein BaY2CuO5 has been observed to have better stability in water and against most of the salts as compared to Ba2YCu3O(7-x). Additional results of molten salt processing of bismuth systems are also presented.

  6. Perennial Grain and Oilseed Crops.

    PubMed

    Kantar, Michael B; Tyl, Catrin E; Dorn, Kevin M; Zhang, Xiaofei; Jungers, Jacob M; Kaser, Joe M; Schendel, Rachel R; Eckberg, James O; Runck, Bryan C; Bunzel, Mirko; Jordan, Nick R; Stupar, Robert M; Marks, M David; Anderson, James A; Johnson, Gregg A; Sheaffer, Craig C; Schoenfuss, Tonya C; Ismail, Baraem; Heimpel, George E; Wyse, Donald L

    2016-04-29

    Historically, agroecosystems have been designed to produce food. Modern societies now demand more from food systems-not only food, fuel, and fiber, but also a variety of ecosystem services. And although today's farming practices are producing unprecedented yields, they are also contributing to ecosystem problems such as soil erosion, greenhouse gas emissions, and water pollution. This review highlights the potential benefits of perennial grains and oilseeds and discusses recent progress in their development. Because of perennials' extended growing season and deep root systems, they may require less fertilizer, help prevent runoff, and be more drought tolerant than annuals. Their production is expected to reduce tillage, which could positively affect biodiversity. End-use possibilities involve food, feed, fuel, and nonfood bioproducts. Fostering multidisciplinary collaborations will be essential for the successful integration of perennials into commercial cropping and food-processing systems. PMID:26789233

  7. Coarse-graining stiff bonds

    NASA Astrophysics Data System (ADS)

    Español, P.; de la Torre, J. A.; Ferrario, M.; Ciccotti, G.

    2011-11-01

    The method of constraints in molecular dynamics is useful because it avoids the resolution of high frequency motions with very small time steps. However, the price to pay is that both the dynamics and the statistics of a constrained system differ from those of the unconstrained one. Instead of using constraints, we propose to dispose of high frequency motions by a coarse-graining procedure in which fast variables are eliminated. These fast variables are thus modeled as friction and thermal fluctuations. We illustrate the methodology with a simple model case, a diatomic molecule in a monoatomic solvent, in which the bond between the atoms of a diatomic molecule is stiff. Although the example is very simple and does not display the interesting effects of "wrong" statistics of the constrained system (i.e. the well-known issue connected to the Fixman potential), it is well suited to give the proof of concept of the whole procedure.

  8. Superfluidity of grain boundaries and supersolid behavior.

    PubMed

    Sasaki, S; Ishiguro, R; Caupin, F; Maris, H J; Balibar, S

    2006-08-25

    When two communicating vessels are filled to a different height with liquid, the two levels equilibrate because the liquid can flow. We have looked for such equilibration with solid (4)He. For crystals with no grain boundaries, we see no flow of mass, whereas for crystals containing several grain boundaries, we detect a mass flow. Our results suggest that the transport of mass is due to the superfluidity of grain boundaries. PMID:16873608

  9. Ultrafine-grained titanium for medical implants

    DOEpatents

    Zhu, Yuntian T.; Lowe, Terry C.; Valiev, Ruslan Z.; Stolyarov, Vladimir V.; Latysh, Vladimir V.; Raab, Georgy J.

    2002-01-01

    We disclose ultrafine-grained titanium. A coarse-grained titanium billet is subjected to multiple extrusions through a preheated equal channel angular extrusion (ECAE) die, with billet rotation between subsequent extrusions. The resulting billet is cold processed by cold rolling and/or cold extrusion, with optional annealing. The resulting ultrafine-grained titanium has greatly improved mechanical properties and is used to make medical implants.

  10. Grain boundary wetness of partially molten dunite

    NASA Astrophysics Data System (ADS)

    Mu, Shangshang; Faul, Ulrich H.

    2016-05-01

    Samples of Fo90 olivine and basaltic melt were annealed at a range of temperatures and a pressure of 1 GPa in a piston cylinder apparatus from 1 to 336 h. Post-run samples have melt contents from 0.3 to 6.8 % and mean grain sizes from 4.3 to 84.5 μm. Grain boundary wetness, a measure of the intergranular melt distribution, was determined by analyzing scanning electron microscope images with sufficiently high resolution to detect thin layers wetting grain boundaries, as well as small triple junctions. The measurements show that grain boundary wetness increases with increasing melt content to values well above those predicted by the idealized isotropic equilibrium model for a finite dihedral angle. Additionally, the melt geometry changes with grain size, with grain boundary wetness increasing with increasing grain size at fixed melt content. Grain boundary wetness and dihedral angle of samples annealed at a range of temperatures, but constant melt content does not depend on temperature. These observations emphasize that the dihedral angle alone is not adequate to characterize the melt distribution in partially molten rocks, as the idealized isotropic model does not account for the influence of grain growth. Diffusion creep viscosities calculated from the measured wetness reflect the grain size and melt content dependence. Accordingly, experimentally measured viscosities at small grain sizes underestimate the effect of melt to weaken partially molten rocks for coarser grain sizes. The presence of melt in the mantle may therefore enhance diffusion creep relative to dislocation creep.

  11. Grain-boundary resistance in polycrystalline metals

    NASA Astrophysics Data System (ADS)

    Reiss, G.; Vancea, J.; Hoffmann, H.

    1986-05-01

    Grain boundaries are known to reduce significantly the electrical dc conductivity of polycrystalline metallic materials. In this paper, we give a quantum mechanical calculation of the grain-boundary resistance based on the transfer matrix approach. The results show an exponential decrease of the conductivity with respect to the number of grain boundaries per mean free path in accord with an empirical model proposed recently.

  12. Magnetic alignment of grains. [in interstellar space

    NASA Technical Reports Server (NTRS)

    Hildebrand, Roger H.

    1988-01-01

    This paper reviews mechanisms that have been proposed to account for alignment of dust grains in diffuse clouds and in dense clouds. The mechanisms that have proved inadequate are considered, including alignment by nonmagnetic and magnetic processes. The results thus far favor the Davis-Greenstein mechanism, in which paramagnetic relaxation of spinning grains removes components of rotation perpendicular to the magnetic field. Polarization measurements showing the alignment of grains in cool dense clouds are discussed.

  13. 7 CFR 868.310 - Grades and grade requirements for the classes Long Grain Milled Rice, Medium Grain Milled Rice...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled Rice. (See also Â... Milled Rice Principles Governing Application of Standards § 868.310 Grades and grade requirements for the classes Long Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled...

  14. 7 CFR 868.310 - Grades and grade requirements for the classes Long Grain Milled Rice, Medium Grain Milled Rice...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled Rice. (See also Â... Milled Rice Principles Governing Application of Standards § 868.310 Grades and grade requirements for the classes Long Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled...

  15. 7 CFR 868.310 - Grades and grade requirements for the classes Long Grain Milled Rice, Medium Grain Milled Rice...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled Rice. (See also Â... classes Long Grain Milled Rice, Medium Grain Milled Rice, Short Grain Milled Rice, and Mixed Milled Rice... (percent) Removed by a 5 plate 3 (percent) Removed by a 6 plate 3 (percent) Through a 6 sieve 3...

  16. GIS-based detection of grain boundaries

    NASA Astrophysics Data System (ADS)

    Li, Yingkui; Onasch, Charles M.; Guo, Yonggui

    2008-04-01

    The recognition of grain boundaries in deformed rocks from images of thin-sections or polished slabs is an essential step in describing and quantifying various fabric elements and strain. However, many of the methods in use today require labor-intensive manual digitization of grain boundary information. Here, we propose an automated, GIS-based method to detect grain boundaries and construct a grain boundary database in which the shape, orientation, and spatial distribution of grains can be quantified and analyzed in a reproducible manner. The proposed method includes a series of operations and functions to identify grain boundaries and construct the grain boundary database. These processes are integrated into a GIS model using ArcGIS ModelBuilder; thus, little or no operator intervention is required to perform the entire analysis. The method was evaluated using thin section images taken from three sandstone samples. The results indicate that the proposed method can correctly identify >70% of grains recognized manually without any intervention and is especially suitable for analyses where large numbers of grains are required.

  17. Segregation of Defects at Grain Boundaries.

    NASA Astrophysics Data System (ADS)

    Alsayed, Ahmed M.; Yodh, Arjun G.

    2007-03-01

    Interstitial impurity segregation at grain boundaries plays an important role in materials properties such as cohesion, grain growth kinetics, and transport. Unfortunately, direct measurement of grain boundary composition is difficult in bulk crystals and polycrystals. In this contribution we directly study impurity segregation at grain boundaries using a model colloidal crystal. The polycrystals are made of temperature-sensitive micron size NIPA microgel particles [1]. We add 100-200 nm fluorescent polystyrene particles to this system to model interstitial impurities. The impurities are then tracked using video microscopy close to and far from the grain boundaries. We find that impurities hop from one position to another and diffuse anisotropically when far from the grain boundaries, and they diffuse isotropically in the grain boundaries. Upon increasing the temperature, the packing volume fraction of NIPA particles decreases and grain boundaries start to melt. We also explored the effects of the segregated impurities on grain boundary melting. [1] A. M. Alsayed, M. F. Islam, J. Zhang, P. J. Collings, A. G. Yodh, Science 309, 1207 (2005). This work was supported by grants from NSF (DMR-0505048 and MRSEC DMR05-20020) and NASA (NAG8-2172).

  18. Health benefits of whole grain phytochemicals.

    PubMed

    Okarter, Neal; Liu, Rui Hai

    2010-03-01

    A whole grain consists of the intact, ground, cracked, or flaked caryopsis, whose principal anatomical components--the starchy endosperm, germ, and bran--are present in the same relative proportions as they exist in the intact caryopsis. Whole grain food products can be intact, consisting of the original composition of bran, germ, and endosperm, throughout the entire lifetime of the product, or reconstituted, in which one or more of the original components of a whole grain is recombined to the relative proportion naturally occurring in the grain kernel. Increased consumption of whole grains has been associated with reduced risk of major chronic diseases including cardiovascular disease, type II diabetes, and some cancers. Whole grain foods offer a wide range of phytochemicals with health benefits that are only recently becoming recognized. The unique phytochemicals in whole grains are proposed to be responsible for the health benefits of whole grain consumption. In this paper, whole grain phytochemicals and the health benefits associated with their consumption are reviewed. PMID:20301011

  19. The size distribution of interstellar grains

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.

    1987-01-01

    Three major areas involving interstellar grains were investigated. First, studies were performed of scattering in reflection nebulae with the goal of deriving scattering characteristics of dust grains such as the albedo and the phase function asymmetry throughout the visible and the ultraviolet. Secondly, studies were performed of the wavelength dependence of interstellar extinction designed to demonstrate the wide range of grain size distributions naturally occurring in individual clouds in different parts of the galaxy. And thirdly, studies were also performed of the ultraviolet powered emission of dust grains in the 0.5 to 1.0 micron wavelength range in reflection nebulae. Findings considered of major importance are highlighted.

  20. 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.

    2016-07-01

    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.

  1. Global Goss grain growth and grain boundary characteristics in magnetostrictive Galfenol sheets

    NASA Astrophysics Data System (ADS)

    Na, S. M.; Flatau, A. B.

    2013-12-01

    Single Goss grains were globally grown in magnetostrictive Galfenol thin sheets via an abnormal grain growth (AGG) process. The sample behaves like single crystal Galfenol, exhibiting large magnetostriction along the <100> axes. Small variations in surface energy conditions, which were governed by different flow rates of 0.5% H2S gas in argon during annealing, had a significant impact of the development of AGG. AGG with a fully developed Goss (011) grain over 95% of the sample surface is very reproducible and feasible for a broad range of annealing conditions. In addition, the <100> orientation of the single-crystal-like Galfenol sheet aligns exactly with the rolling direction, and produces magnetostriction values of ˜300 ppm. AGG often produces isolated grains inside Goss grains due to anisotropic properties of grain boundaries. To better understand island formation mechanisms, grain orientation and grain boundary characteristics of island grains in Goss-oriented Galfenol thin sheets were also investigated. We examined samples annealed either under an argon atmosphere or under a sulfur atmosphere, and characterized the observed island grain boundaries in terms of grain misorientation angles. Trends in measured and simulated data on misorientation angles indicate that the presence of (001) island grain boundaries with angles higher than 45° can be explained by the high energy grain boundary (HEGB) model, whereas (111) boundaries with intermediate angles (20°-45°) cannot. The role of low energy coincident site lattice (CSL) boundaries on AGG in both annealing cases was found to be negligible.

  2. A New Grain Harvesting System for Single Pass Grain Harvest, Biomass Collection, Crop Residue Sizing and Grain Segregation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A cereal grain harvesting system is introduced that combines existing technologies in a unique way to improve cereal grain harvest performance, profitability and efficiently collect biomass. The harvesting system is comprised of three machines – one to gather the crop and prepare the residue for no...

  3. A New Grain Harvesting System for Single-Pass Grain Harvest, Biomass Collection, Crop Residue Sizing, and Grain Segregation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A cereal grain harvesting system is introduced that combines existing technologies in a unique way to improve cereal grain harvest performance, profitability and efficiently collect biomass. The harvesting system is comprised of three machines – one to gather the crop and prepare the residue for no...

  4. Supercube grains leading to a strong cube texture and a broad grain size distribution after recrystallization

    NASA Astrophysics Data System (ADS)

    Lin, F. X.; Zhang, Y. B.; Pantleon, W.; Jensen, D. Juul

    2015-08-01

    This work revisits the classical subject of recrystallization of cold-rolled copper. Two characterization techniques are combined: three-dimensional X-ray diffraction using synchrotron X-rays, which is used to measure the growth kinetics of individual grains in situ, and electron backscatter diffraction, which is used for statistical analysis of the microstructural evolution. As the most striking result, the strong cube texture after recrystallization is found to be related to a few super large cube grains, which were named supercube grains. These few supercube grains become large due to higher growth rates. However, most other cube grains do not grow preferentially. Because of the few supercube grains, the grain size distribution after recrystallization is broad. Reasons for the higher growth rates of supercube grains are discussed, and are related to the local deformed microstructure.

  5. The Role of Grain Boundary Energy on Grain Boundary Complexion Transitions

    SciTech Connect

    Bojarski, Stephanie A.; Rohrer, Gregory S.

    2014-09-01

    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 in 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.

  6. Genetic and molecular basis of grain size and grain number and its relevance to grain productivity in higher plants.

    PubMed

    Gupta, Pushpendra K; Rustgi, Sachin; Kumar, Neeraj

    2006-06-01

    Grain size and grain number constitute 2 important components of grain yield. In particular, the grain size also influences the end-use quality (e.g., flour yield and protein content) and attracts consumer preference. These 2 traits are also the components of the domestication syndrome of crop plants. A number of important studies have recently been conducted to understand the genetic and molecular basis of these 2 important yield-contributing traits. Information generated from these studies was collected and synthesized for the benefit of plant biologists, particularly plant breeders. In the present article, this information is briefly reviewed and the prospects of using this information for improvement of grain productivity in crop plants are discussed. PMID:16936836

  7. Grain Unloading of Arsenic Species in Rice

    SciTech Connect

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

    2010-01-11

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

  8. 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.

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

    PubMed

    Dey, Sanchita; Mardinly, John; Wang, Yongqiang; Valdez, James A; Holesinger, Terry G; Uberuaga, Blas P; Ditto, Jeff J; Drazin, John W; Castro, Ricardo H R

    2016-06-22

    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 we tested this concept in nanocrystalline zirconia doped with lanthanum. Although the dopant is observed 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. PMID:27282392

  10. INTEGRATING THE STORED GRAIN ADVISOR PRO EXPERT SYSTEM WITH AN AUTOMATED ELECTRONIC GRAIN PROBE TRAPPING SYSTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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. To make accurate insect management decisions, managers need to know both the insect species and number...

  11. Grain-grain contact geometry and the propagation of elastic waves in granular media

    NASA Technical Reports Server (NTRS)

    Jones, B. W.

    1974-01-01

    It is shown that the compliance of an orthogonal grain-grain contact is so insensitive to the grain geometry in the contact region that this geometry is not at present an important parameter in theories of the speed of propagation of elastic waves in granular media, such as occur in the earth and in the moon.

  12. STORED GRAIN ADVISOR PRO: DECISION SUPPORT SYSTEM FOR INSECT MANAGEMENT IN COMMERCIAL GRAIN ELEVATORS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A decision support system, Stored Grain Advisor Pro (SGA Pro), was developed to provide insect pest management information for grain stored at commercial elevators. The program uses a model to predict future risk based on current insect density, grain temperature and moisture. A rule-based system wa...

  13. 77 FR 74781 - Safety Zones; Columbia Grain and United Grain Corporation Facilities; Columbia and Willamette Rivers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-18

    ... Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice of Proposed Rulemaking A... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zones; Columbia Grain and United Grain.... SUMMARY: The Coast Guard is establishing temporary safety zones around the Columbia Grain facility on...

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

    EPA Science Inventory

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

  15. Chemical composition of distillers grains, a review

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years, increasing demand for ethanol as a fuel additive and decreasing dependency on fossil fuels have resulted in a dramatic increase in the amount of grains used for ethanol production. Dry-grind is the major process, resulting in distillers dried grains with solubles (DDGS) as a major ...

  16. Microwave Dielectric Properties of Cereal Grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of five cereal grains (wheat, corn, barley, oats, and grain sorghum) were 19 measured at 23 oC over broad microwave frequency range (5 GHz to 15 GHz) with a free-space-transmission 20 technique. Results of dielectric properties measurement are tabulated for each material for mo...

  17. Potential bleaching techniques for corn distillers grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ethanol industry is booming, and extensive research is now being pursued to develop alternative uses for distillers dried grains (DDG) and distillers dried grains with solubles (DDGS), coproducts of the ethanol production process. Currently, DDG and DDGS are used exclusively as livestock feed. P...

  18. Analysis of grain quality at receival

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The major cereal grains - wheat, maize, and rice - undergo a series of stages between harvest and food or feed processing plant, involving storage, overland transport, terminal storage and overseas shipment. At each transfer point, a document accompanies a grain consignment that pertains to its qual...

  19. Interspecific Associations Among Stored-Grain Beetles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many laboratory studies have described interspecific relationships of stored grain insects, but little is known about such relationships under field conditions. Compared to most other habitats, natural or man-made, a loaded grain silo constitutes a uniquely uniform habitat in which food availability...

  20. Inheritance of grain proteins in wheat.

    PubMed

    Kraljević-Balalić, M; Stajner, D; Gašić, O

    1982-06-01

    Diallel crosses between five divergent vulgare wheat cultivars were made in order to evaluate the mode of inheritance and combining ability of grain proteins. Significant differences in grain protein content were found between cultivars and their hybrids. It was established that the inheritance of seed protein in the F1 generation included both additive and non-additive gene action. PMID:24270758

  1. AN ATMOSPHERIC STRUCTURE EQUATION FOR GRAIN GROWTH

    SciTech Connect

    Ormel, C.W.

    2014-07-01

    We present a method to include the evolution of the grain size and grain opacity κ{sub gr} in the equations describing the structure of protoplanetary atmospheres. The key assumption of this method is that a single grain size dominates the grain size distribution at any height r. In addition to following grain growth, the method accounts for mass deposition by planetesimals and grain porosity. We illustrate this method by computation of a simplified atmosphere structure model. In agreement with previous works, grain coagulation is seen to be very efficient. The opacity drops to values much below the often-used ''interstellar medium opacities'' (∼1 cm{sup 2} g{sup –1}) and the atmosphere structure profiles for temperature and density resemble that of the grain-free case. Deposition of planetesimals in the radiative part of the atmosphere hardly influences this outcome as the added surface is quickly coagulated away. We observe a modest dependence on the internal structure (porosity), but show that filling factors cannot become too large because of compression by gas drag.

  2. Grain transport mechanics in shallow flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A physical model based on continuum multiphase flow is described to represent saltating transport of grains in shallow overland flows. The two-phase continuum flow of water and sediment considers coupled St.Venant type equations. The interactive cumulative effect of grains is incorporated by a dispe...

  3. Grain transport mechanics in shallow overland flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A physical model based on continuum multiphase flow is described to represent saltating transport of grains in shallow overland flow. The two phase continuum flow of water and sediment considers coupled St.Venant type equations. The interactive cumulative effect of grains is incorporated by a disper...

  4. Analysis of grain quality at receival

    Technology Transfer Automated Retrieval System (TEKTRAN)

    With an emphasis on wheat and to a lesser extent, barley, we describe the series of post harvest transfer stages of grain between the first point of sale and the export terminal. At each transfer point, a document accompanies a grain consignment that pertains to its quality (class, purity, sanitatio...

  5. Insect Population Dynamics in Commercial Grain Elevators

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data were collected in 1998-2002 from wheat stored in commercial grain elevators in south-central Kansas. Storage bins at these elevators had concrete walls and were typically 6-9 m in diameter and 30-35 m tall. A vacuum-probe sampler was used to collect ten 3-kg grain samples in the top 12 m of the...

  6. Pollen grains for oral vaccination

    PubMed Central

    Atwe, Shashwati U.; Ma, Yunzhe; Gill, Harvinder Singh

    2015-01-01

    Oral vaccination can offer a painless and convenient method of vaccination. Furthermore, in addition to systemic immunity it has potential to stimulate mucosal immunity through antigen-processing by the gut-associated lymphoid tissues. In this study we propose the concept that pollen grains can be engineered for use as a simple modular system for oral vaccination. We demonstrate feasibility of this concept by using spores of Lycopodium clavatum (clubmoss) (LSs). We show that LSs can be chemically cleaned to remove native proteins to create intact clean hollow LS shells. Empty pollen shells were successfully filled with molecules of different sizes demonstrating their potential to be broadly applicable as a vaccination system. Using ovalbumin (OVA) as a model antigen, LSs formulated with OVA were orally fed to mice. LSs stimulated significantly higher anti-OVA serum IgG and fecal IgA antibodies compared to those induced by use of cholera toxin as a positive-control adjuvant. The antibody response was not affected by pre-neutralization of the stomach acid, and persisted for up to seven months. Confocal microscopy revealed that LSs can translocate in to mouse intestinal wall. Overall, this study lays the foundation of using LSs as a novel approach for oral vaccination. PMID:25151980

  7. Pollen grains for oral vaccination.

    PubMed

    Atwe, Shashwati U; Ma, Yunzhe; Gill, Harvinder Singh

    2014-11-28

    Oral vaccination can offer a painless and convenient method of vaccination. Furthermore, in addition to systemic immunity it has potential to stimulate mucosal immunity through antigen-processing by the gut-associated lymphoid tissues. In this study we propose the concept that pollen grains can be engineered for use as a simple modular system for oral vaccination. We demonstrate feasibility of this concept by using spores of Lycopodium clavatum (clubmoss) (LSs). We show that LSs can be chemically cleaned to remove native proteins to create intact clean hollow LS shells. Empty pollen shells were successfully filled with molecules of different sizes demonstrating their potential to be broadly applicable as a vaccination system. Using ovalbumin (OVA) as a model antigen, LSs formulated with OVA were orally fed to mice. LSs stimulated significantly higher anti-OVA serum IgG and fecal IgA antibodies compared to those induced by use of cholera toxin as a positive-control adjuvant. The antibody response was not affected by pre-neutralization of the stomach acid, and persisted for up to 7 months. Confocal microscopy revealed that LSs can translocate into mouse intestinal wall. Overall, this study lays the foundation of using LSs as a novel approach for oral vaccination. PMID:25151980

  8. Stabilizing Nanocrystalline Grains in Ceramic-Oxides

    SciTech Connect

    Aidhy, Dilpuneet S; Zhang, Yanwen; Weber, William J

    2013-01-01

    Nanocrystalline ceramic-oxides are prone to grain growth rendering their highly attractive properties practically unusable. Using atomistic simulations ofon ceria as a model material system, we elucidate a framework to design dopant-pinned grain boundaries that prevent this grain growth. While in metallic systems it has been shown that a large mismatch between host and dopant atomic size prevents grain growth, in ceramic-oxides we find that this concept is not applicable. Instead, we find that dopant-oxygen vacancy interaction, i.e., dopant migration energy in the presence of oxygen vacancy, and dopant-oxygen vacancy binding energy are the controlling factors in grain growth. Our prediction agrees with and explains previous experimental observations.

  9. Submicron-grained transparent yttria composites

    NASA Astrophysics Data System (ADS)

    Kear, Bernard H.; Sadangi, Rajendra; Shukla, Vijay; Stefanik, Todd; Gentilman, Richard

    2005-05-01

    New materials with improved mechanical properties and high optical transmission in the full 3-5 micron MWIR region wavelength are required. Commercially available polycrystalline transparent Yttria, with >100 micron average grain size, does not perform satisfactorily in demanding applications because of its modest strength. One way to improve strength is to develop an ultra-fine grained material with acceptable optical transmission properties. To realize fine grains it is necessary to use other phases to inhibit grain growth during fabrication. A promising processing method comprises: (a) synthesis of an extended metastable solid solution by plasma melting and quenching, and (b) consolidation of the metastable ceramic powder to form dense submicron-grained (<1 micron) composites. Two ceramic composites containing 20 and 50 vol% of second phase are evaluated in this study. Optical transmission, hardness, and indentation fracture toughness are measured and correlated with structure.

  10. Recent Progress in Presolar Grain Studies

    PubMed Central

    Amari, Sachiko

    2014-01-01

    Presolar grains are stardust that condensed in stellar outflows or stellar ejecta, and was incorporated in meteorites. They remain mostly intact throughout the journey from stars to the earth, keeping information of their birthplaces. Studies of presolar grains, which started in 1987, have produced a wealth of information about nucleosynthesis in stars, mixing in stellar ejecta, and temporal variations of isotopic and elemental abundances in the Galaxy. Recent instrumental advancements in secondary ion mass spectrometry (SIMS) brought about the identification of presolar silicate grains. Isotopic and mineralogical investigations of sub-μm grains have been performed using a combination of SIMS, transmission electron microscopy (TEM) and focused ion beam (FIB) techniques. Two instruments have been developed to study even smaller grains (∼50 nm) and measure isotopes and elements of lower abundances than those in previous studies. PMID:26819886

  11. The origin of presolar nova grains

    NASA Astrophysics Data System (ADS)

    José, Jordi; Hernanz, Margarita

    2007-08-01

    Infrared observations reveal that classical novae often form dust in their expanding shells ejected into the interstellar medium as a consequence of violent outbursts. Recent experimental efforts have led to the identification of presolar nova candidate grains from the Acfer 094 and Murchison meteorites. Recently, however, concerns have been raised about the stellar paternity of these grains by new measurements on another sample of SiC grains: these grains are characterized by 12C/13C and 14N/15N ratios similar to the ones reported for the nova grains, but a number of different imprints suggest that a possible supernova origin cannot be excluded. Here we review the predicted nucleosynthetic imprints accompanying nova explosions and discuss the chances to synthesize heavier species, such as titanium, in nova-like events.

  12. Recent Progress in Presolar Grain Studies.

    PubMed

    Amari, Sachiko

    2014-01-01

    Presolar grains are stardust that condensed in stellar outflows or stellar ejecta, and was incorporated in meteorites. They remain mostly intact throughout the journey from stars to the earth, keeping information of their birthplaces. Studies of presolar grains, which started in 1987, have produced a wealth of information about nucleosynthesis in stars, mixing in stellar ejecta, and temporal variations of isotopic and elemental abundances in the Galaxy. Recent instrumental advancements in secondary ion mass spectrometry (SIMS) brought about the identification of presolar silicate grains. Isotopic and mineralogical investigations of sub-μm grains have been performed using a combination of SIMS, transmission electron microscopy (TEM) and focused ion beam (FIB) techniques. Two instruments have been developed to study even smaller grains (∼50 nm) and measure isotopes and elements of lower abundances than those in previous studies. PMID:26819886

  13. ISOCHRONS IN PRESOLAR GRAPHITE GRAINS FROM ORGUEIL

    SciTech Connect

    Zinner, Ernst; Jadhav, Manavi

    2013-05-10

    Primitive meteorites contain tiny dust grains that condensed in stellar outflows and explosions. These stardust grains can be extracted from their host meteorites and studied in detail in the laboratory. We investigated depth profiles of the Al-Mg, Ca-K, and Ti-Ca isotopic systems obtained during NanoSIMS isotopic analysis of presolar graphite grains from the CI carbonaceous meteorite Orgueil. Large {sup 26}Al/{sup 27}Al, {sup 41}Ca/{sup 40}Ca, and {sup 44}Ti/{sup 48}Ti ratios, inferred from {sup 26}Mg, {sup 41}K, and {sup 44}Ca excesses from the decay of the short-lived radioisotopes {sup 26}Al, {sup 41}Ca, and {sup 44}Ti, indicate a supernova (SN) origin. From the depth distribution of the radiogenic isotopes and the stable isotopes of their parent elements we constructed isochron-type correlation plots. The plots indicate quantitative retention of radiogenic {sup 26}Mg, {sup 41}K, and {sup 44}Ca in most grains. Deviations from straight lines in the Al-Mg and Ca-K plots can be explained by contamination with {sup 27}Al and isotopically normal Ca, respectively. For the Ti-Ca system in some grains, the lack of parent-daughter correlation indicates either redistribution of radiogenic {sup 44}Ca or heterogeneity in the initial {sup 44}Ti/{sup 48}Ti ratio. We also obtained Si isotopic depth profiles in three graphite grains with large {sup 29}Si and {sup 30}Si excesses, for which a SN origin has been proposed. In two grains no Si-rich subgrains are observed; in the third grain with an apparent Si-rich subgrain the anomalous Si isotopic ratios in the subgrain are the same as in the rest of the graphite host. Our studies show that by measuring depth profiles, information on presolar grains can be obtained that cannot be obtained by whole-grain analysis.

  14. Interaction of shear-coupled grain boundary motion with crack: Crack healing, grain boundary decohesion, and sub-grain formation

    NASA Astrophysics Data System (ADS)

    Aramfard, Mohammad; Deng, Chuang

    2016-02-01

    Stress-driven grain boundary motion is one of the main mechanisms responsible for microstructural evolution in polycrystalline metals during deformation. In this research, the interaction of shear-coupled grain boundary motion (SCGBM) in face-centered cubic metals with crack, which is a common type of structural defects in engineering materials, has been studied by using molecular dynamics simulations in simple bicrystal models. The influences of different parameters such as metal type, temperature, grain boundary structure, and crack geometry have been examined systematically. Three types of microstructural evolution have been identified under different circumstances, namely, crack healing, grain boundary decohesion, and sub-grain formation. The underlying atomistic mechanisms for each type of SCGBM-crack interaction, particularly grain boundary decohesion and crack healing, have also been examined. It is found that crack healing is generally favoured during the SCGBM-crack interaction at relatively high temperature in metals with relatively low stacking fault energy and grain boundary structure with relatively low misorientation angles. The results of this work may open up new opportunities for healing severely damaged materials.

  15. Plant Density Effect on Grain Number and Weight of Two Winter Wheat Cultivars at Different Spikelet and Grain Positions

    PubMed Central

    Ni, Yingli; Zheng, Mengjing; Yang, Dongqing; Jin, Min; Chen, Jin; Wang, Zhenlin; Yin, Yanping

    2016-01-01

    In winter wheat, grain development is asynchronous. The grain number and grain weight vary significantly at different spikelet and grain positions among wheat cultivars grown at different plant densities. In this study, two winter wheat (Triticum aestivum L.) cultivars, ‘Wennong6’ and ‘Jimai20’, were grown under four different plant densities for two seasons, in order to study the effect of plant density on the grain number and grain weight at different spikelet and grain positions. The results showed that the effects of spikelet and grain positions on grain weight varied with the grain number of spikelets. In both cultivars, the single-grain weight of the basal and middle two-grain spikelets was higher at the 2nd grain position than that at the 1st grain position, while the opposite occurred in the top two-grain spikelets. In the three-grain spikelets, the distribution of the single-grain weight was different between cultivars. In the four-grain spikelets of Wennong6, the single-grain weight was the highest at the 2nd grain position, followed by the 1st, 3rd, and 4th grain positions. Regardless of the spikelet and grain positions, the single-grain weight was the highest at the 1st and 2nd grain positions and the lowest at the 3rd and 4th grain positions. Overall, plant density affected the yield by controlling the seed-setting characteristics of the tiller spike. Therefore, wheat yield can be increased by decreasing the sterile basal and top spikelets and enhancing the grain weight at the 3rd and 4th grain positions, while maintaining it at the 1st and 2nd grain positions on the spikelet. PMID:27171343

  16. Abnormal grain growth in Ni-5at.%W

    NASA Astrophysics Data System (ADS)

    Witte, M.; Belde, M.; Barrales Mora, L.; de Boer, N.; Gilges, S.; Klöwer, J.; Gottstein, G.

    2012-12-01

    The growth of abnormally large grains in textured Ni-5at.%W substrates for high-temperature superconductors deteriorates the sharp texture of these materials and thus has to be avoided. Therefore the growth of abnormal grains is investigated and how it is influenced by the grain orientation and the annealing atmosphere. Texture measurements and grain growth simulations show that the grain orientation only matters so far that a high-angle grain boundary exists between an abnormally growing grain and the Cube-orientated matrix grains. The annealing atmosphere has a large influence on abnormal grain growth which is attributed to the differences in oxygen partial pressure.

  17. Phloem transport of arsenic species from flag leaf to grain during grain filling

    SciTech Connect

    Carey, Anne-Marie; Norton, Gareth J.; Deacon, Claire; Scheckel, Kirk G.; Lombi, Enzo; Punshon, Tracy; Guerinot, Mary Lou; Lanzirotti, Antonio; Newville, Matt; Choi, Yongseong; Price, Adam H.; Meharg, Andrew A.

    2011-09-20

    Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was investigated. Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analog) on grain As accumulation in arsenite-treated panicles was examined. Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently retranslocated from flag leaves to rice grain; arsenate was poorly retranslocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no retranslocation. Within grains, DMA rapidly dispersed while MMA and inorganic As remained close to the entry point. Germanic acid addition did not affect grain As in arsenite-treated panicles. Three-dimensional SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains. These results demonstrate that inorganic As is poorly remobilized, while organic species are readily remobilized, from leaves to grain. Stem translocation of inorganic As may not rely solely on silicic acid transporters.

  18. Phloem Transport of Arsenic Species from Flag Leaf to Grain During Grain Filling

    SciTech Connect

    A Carey; G Norton; C Deacon; K Scheckel; E Lombi; T Punshon; M Guerinot; A Lanzirotti; M Newville; et al.

    2011-12-31

    Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was investigated. Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analog) on grain As accumulation in arsenite-treated panicles was examined. Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently retranslocated from flag leaves to rice grain; arsenate was poorly retranslocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no retranslocation. Within grains, DMA rapidly dispersed while MMA and inorganic As remained close to the entry point. Germanic acid addition did not affect grain As in arsenite-treated panicles. Three-dimensional SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains. These results demonstrate that inorganic As is poorly remobilized, while organic species are readily remobilized, from leaves to grain. Stem translocation of inorganic As may not rely solely on silicic acid transporters.

  19. Phloem transport of arsenic species from flag leaf to grain during grain filling

    PubMed Central

    Carey, Anne-Marie; Norton, Gareth J.; Deacon, Claire; Scheckel, Kirk G.; Lombi, Enzo; Punshon, Tracy; Guerinot, Mary Lou; Lanzirotti, Antonio; Newville, Matt; Choi, Yongseong; Price, Adam H.; Meharg, Andrew A.

    2013-01-01

    Summary Strategies to reduce arsenic in rice grain, below levels that represent a serious human health concern, require that the mechanisms of arsenic accumulation within grain be established. Therefore, re-translocation of arsenic species from flag leaves into filling rice grain was investigated.Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analogue) on grain arsenic accumulation in arsenite treated panicles was examined.Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently re-translocated from flag leaves to rice grain; arsenate was poorly re-translocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no re-translocation. Within grains, DMA rapidly dispersed while MMA and inorganic arsenic remained close to the entry point. Germanic acid addition did not affect grain arsenic in arsenite treated panicles. 3D SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains.These results demonstrate that inorganic arsenic is poorly re-mobilized, while organic species are readily re-mobilized, from leaves to grain. Stem translocation of inorganic arsenic may not rely solely on silicic acid transporters. PMID:21658183

  20. Photoluminescence Imaging of Large-Grain CdTe for Grain Boundary Characterization

    SciTech Connect

    Johnston, Steve; Allende Motz, Alyssa; Reese, Matthew O.; Burst, James M.; Metzger, Wyatt K.

    2015-06-14

    In this work, we use photoluminescence (PL) imaging to characterize CdTe grain boundary recombination. We use a silicon megapixel camera and green (532 nm) laser diodes for excitation. A microscope objective lens system is used for high spatial resolution and a field of view down to 190 um x 190 um. PL images of large-grain (5 to 50 um) CdTe samples show grain boundary and grain interior features that vary with processing conditions. PL images of samples in the as-deposited state show distinct dark grain boundaries that suggest high excess carrier recombination. A CdCl2 treatment leads to PL images with very little distinction at the grain boundaries, which illustrates the grain boundary passivation properties. Other process conditions are also shown, along with comparisons of PL images to high spatial resolution time-resolved PL carrier lifetime maps.

  1. Detection of solute segregation at grain boundaries

    SciTech Connect

    Briceno-Valero, J.; Gronsky, R.

    1980-03-01

    Studies of grain boundary segregation in metallurgical systems are traditionally based upon the premise that grain boundaries are more likely sites for solute atoms than their surrounding grains. This idea is manifested in experimental studies which distinguish the solute concentration at boundaries from that of grain interiors using various spectroscopic techniques, including more recently, energy dispersive x-ray analysis in TEM/STEM instruments. A typical study consists of spot or line scans across a grain boundary plane in order to detect concentration gradients at the boundary region. It has also been pointed out that there are rather severe problems in quantitatively determining the absolute solute concentration within the grain boundary, and data correction schemes for this situation have been proposed. The present paper is concerned with an alternative study of grain boundary segregation where the distribution of solute atoms along the boundary plane (as opposed to that across the boundary plane) is sought. The interest here is to establish whether or not a relationship exists between the structural defect configuration of the boundary plane and site preference for solute segregation.

  2. Interstellar chemical differentiation across grain sizes

    NASA Astrophysics Data System (ADS)

    Ge, J. X.; He, J. H.; Li, Aigen

    2016-07-01

    In this work, we investigate the effects of ion accretion and size-dependent dust temperatures on the abundances of both gas-phase and grain-surface species. While past work has assumed a constant areal density for icy species, we show that this assumption is invalid and the chemical differentiation over grain sizes is significant. We use a gas-grain chemical code to demonstrate this numerically for two typical interstellar conditions: a dark cloud (DC) and a cold neutral medium (CNM). It is shown that, although the grain-size distribution variation (but with the total grain surface area unchanged) has little effect on the gas-phase abundances, it can alter the abundances of some surface species by up to ∼2-4 orders of magnitude. The areal densities of ice species are larger on smaller grains in the DC model as a consequence of ion accretion. However, the surface areal density evolution tracks are more complex in the CNM model due to the combined effects of ion accretion and dust temperature variation. The surface areal density differences between the smallest ( ∼ 0.01 μm) and the biggest ( ∼ 0.2 μm) grains can reach ∼1 and ∼5 orders of magnitude in the DC and CNM models, respectively.

  3. Pinning of Austenite Grain Boundaries by

    NASA Astrophysics Data System (ADS)

    Doğan, Ömer N.; Michal, G. M.; Kwon, H.-W.

    1992-08-01

    The growth behavior of austenite grains in the presence of A1N precipitates varies with the temperature and time of anneal. To study this behavior, two iron alloys, (in weight percent) a 0.1 carbon base chemistry with 0.03A1/0.01N and 0.09A1/0.04N, respectively, were annealed between 1000 °C and 1200 °C for times of up to 180 minutes. Using optical microscopy, as many as 1000 austenite grains per heat-treatment condition were measured. Conditions of sup- pressed, abnormal, and uniform grain growth were observed. Using an extraction replica tech- nique, the size, shape, and distribution of the A1N particles were determined using transmission electron microscopy (TEM). The largest grain boundary curvatures calculated, using the Hellman- Hillert pinning model, were in close agreement with independent calculations of curvatures using the grain size data. The largest grains in the lognormal size distribution of austenite grains were found to be the ones with the potential to grow to abnormally large sizes.

  4. Quasiclassical coarse graining and thermodynamic entropy

    SciTech Connect

    Gell-Mann, Murray; Hartle, James B.

    2007-08-15

    Our everyday descriptions of the universe are highly coarse grained, following only a tiny fraction of the variables necessary for a perfectly fine-grained description. Coarse graining in classical physics is made natural by our limited powers of observation and computation. But in the modern quantum mechanics of closed systems, some measure of coarse graining is inescapable because there are no nontrivial, probabilistic, fine-grained descriptions. This essay explores the consequences of that fact. Quantum theory allows for various coarse-grained descriptions, some of which are mutually incompatible. For most purposes, however, we are interested in the small subset of 'quasiclassical descriptions' defined by ranges of values of averages over small volumes of densities of conserved quantities such as energy and momentum and approximately conserved quantities such as baryon number. The near-conservation of these quasiclassical quantities results in approximate decoherence, predictability, and local equilibrium, leading to closed sets of equations of motion. In any description, information is sacrificed through the coarse graining that yields decoherence and gives rise to probabilities for histories. In quasiclassical descriptions, further information is sacrificed in exhibiting the emergent regularities summarized by classical equations of motion. An appropriate entropy measures the loss of information. For a 'quasiclassical realm' this is connected with the usual thermodynamic entropy as obtained from statistical mechanics. It was low for the initial state of our universe and has been increasing since.

  5. The Search for Interstellar Sulfide Grains

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Messenger, Scott

    2010-01-01

    The lifecycle of sulfur in the galaxy is poorly understood. Fe-sulfide grains are abundant in early solar system materials (e.g. meteorites and comets) and S is highly depleted from the gas phase in cold, dense molecular cloud environments. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium, indicating that little sulfur is incorporated into solid grains in this environment. It is widely believed that sulfur is not a component of interstellar dust grains. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. Fe sulfide grains are ubiquitous in cometary samples where they are the dominant host of sulfur. The Fe-sulfides (primarily pyrrhotite; Fe(1-x)S) are common, both as discrete 0.5-10 micron-sized grains and as fine (5-10 nm) nanophase inclusions within amorphous silicate grains. Cometary dust particles contain high abundances of well-preserved presolar silicates and organic matter and we have suggested that they should contain presolar sulfides as well. This hypothesis is supported by the observation of abundant Fe-sulfides grains in dust around pre- and post-main sequence stars inferred from astronomical spectra showing a broad 23 micron IR feature due to FeS. Fe-sulfide grains also occur as inclusions in bona fide circumstellar amorphous silicate grains and as inclusions within deuterium-rich organic matter in cometary dust samples. Our irradiation experiments show that FeS is far more resistant to radiation damage than silicates. Consequently, we expect that Fe sulfide stardust should be as abundant as silicate stardust in solar system materials.

  6. Static Recrystallized Grain Size of Coarse-Grained Austenite in an API-X70 Pipeline Steel

    NASA Astrophysics Data System (ADS)

    Sha, Qingyun; Li, Guiyan; Li, Dahang

    2013-12-01

    The effects of initial grain size and strain on the static recrystallized grain size of coarse-grained austenite in an API-X70 steel microalloyed with Nb, V, and Ti were investigated using a Gleeble-3800 thermomechanical simulator. The results indicate that the static recrystallized grain size of coarse-grained austenite decreases with decreasing initial grain size and increasing applied strain. The addition of microalloying elements can lead to a smaller initial grain size for hot deformation due to the grain growth inhibition during reheating, resulting in decreasing of static recrystallized grain size. Based on the experimental data, an equation for the static recrystallized grain size was derived using the least square method. The grain sizes calculated using this equation fit well with the measured ones compared with the equations for fine-grained austenite and for coarse-grained austenite of Nb-V microalloyed steel.

  7. Summary of prior grain entrapment rescue strategies.

    PubMed

    Roberts, M J; Deboy, G R; Field, W E; Maier, D E

    2011-10-01

    Entrapment in flowable agricultural material continues to be a relevant problem facing both farmers and employees of commercial grain storage and handling operations. While considerable work has been done previously on the causes of entrapment in grain and possible preventative measures, there is little research on the efficacy of current first response or extrication techniques. With the recent introduction of new grain rescue equipment and training programs, it was determined that the need exists to document and summarize prior grain rescue strategies with a view to develop evidence-based recommendations that would enhance the efficacy of the techniques used and reduce the risks to both victims and first responders. Utilizing the Purdue University Agricultural Entrapment Database, all data were queried for information related to extrication of victims from grain entrapments documented over the period 1964-2006. Also analyzed were data from other sources, including public records related to entrapments and information from onsite investigations. Significant findings of this study include the following: (1) between 1964 and 2006, the number of entrapments averaged 16 per year, with the frequency increasing over the last decade; (2) of all cases documented, about 45% resulted in fatality; (3) no less than 44% of entrapments occurred in shelled corn; (4) fatality was the result in 82% of cases where victims were submerged beneath the grain surface, while fatality occurred in 10% of cases where victims were only partially engulfed; (5) the majority of rescues were reported to have been conducted by untrained personnel who were at the scene at the time of entrapment; and (6) in those cases where the rescue strategies were known, 56% involved cutting or punching holes in the side walls of the storage structure, 19% involved utilizing onsite fabricated grain retaining walls to extricate partially entrapped victims, and the use of grain vacuum machines as a rescue

  8. Grain Boundary Chemistry in Mantle Rocks

    NASA Astrophysics Data System (ADS)

    Hiraga, T.; Anderson, I. M.; Kohlstedt, D. L.

    2002-12-01

    We show that the same elements segregate to olivine grain boundaries in both natural rocks and synthetic aggregates. We conclude that this chemical segregation is an energetically favorable phenomenon that will influence the physical and chemical properties of mantle rocks. Two natural samples with unaltered and tight grain boundaries were chosen. One is an ultramylonite from Balmuccia peridotite in the Ivrea Zone. The other is a basaltic rock with olivine phenocrysts from Kilauea, Hawaii. Two olivine phenocrysts often contact one another forming straight and long grain boundaries. Two synthetic aggregates, one composed of olivine + diopside and the other of olivine + anorthite, were synthesized. The diopside and anorthite powders were mechanically mixed with dried San Carlos olivine powder and subsequently isostatically hot-pressed inside an Fe jacket at 1373 K and 300 MPa in a gas-medium apparatus. Some of the hot-pressed samples were annealed at 1373 K and room pressure. Scanning-transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM/EDX) profiling was used to determine the chemical compositions of olivine grain boundaries. In this study, we used a Philips CM200 TEM/STEM equipped with a Schottky field emission gun (FEG) and operated at 200 kV to obtain a probe size (full width at half maximum) of 1.3-1.4 nm. The profiles across every grain boundary exhibited similar chemical features. The primary features are 1) significant Ca enrichment, 2) weak Si and Mg depletion, and 3) weak to significant Al and Ti enrichment. Both the enrichment and the depletion are restricted a zone <5 nm wide along the grain boundaries. The Ca concentration in the grain boundaries is positively correlated with that in the grains. Segregation can result from kinetic and thermodynamic effects. In nature, a decrease in the solubility of specific elements in the grains during cooling of a rock can cause segregation. However, the effect cannot explain the

  9. Grain refinement control in TIG arc welding

    NASA Technical Reports Server (NTRS)

    Iceland, W. F.; Whiffen, E. L. (Inventor)

    1975-01-01

    A method for controlling grain size and weld puddle agitation in a tungsten electrode inert gas welding system to produce fine, even grain size and distribution is disclosed. In the method the frequency of dc welding voltage pulses supplied to the welding electrode is varied over a preselected frequency range and the arc gas voltage is monitored. At some frequency in the preselected range the arc gas voltage will pass through a maximum. By maintaining the operating frequency of the system at this value, maximum weld puddle agitation and fine grain structure are produced.

  10. Parsing abnormal grain growth in specialty aluminas

    NASA Astrophysics Data System (ADS)

    Lawrence, Abigail Kremer

    Grain growth in alumina is strongly affected by the impurities present in the material. Certain impurity elements are known to have characteristic effects on abnormal grain growth in alumina. Specialty alumina powders contain multiple impurity species including MgO, CaO, SiO2, and Na 2O. In this work, sintered samples made from alumina powders containing various amounts of the impurities in question were characterized by their grain size and aspect ratio distributions. Multiple quantitative methods were used to characterize and classify samples with varying microstructures. The grain size distributions were used to partition the grain size population into subpopulations depending on the observed deviation from normal behavior. Using both grain size and aspect ratio a new visual representation for a microstructure was introduced called a morphology frequency map that gives a fingerprint for the material. The number of subpopulations within a sample and the shape of the distribution on the morphology map provided the basis for a classification scheme for different types of microstructures. Also using the two parameters a series of five metrics were calculated that describe the character of the abnormal grains in the sample, these were called abnormal character values. The abnormal character values describe the fraction of grains that are considered abnormal, the average magnitude of abnormality (including both grain size and aspect ratio), the average size, and variance in size. The final metric is the correlation between grain size and aspect ratio for the entire population of grains. The abnormal character values give a sense of how different from "normal" the sample is, given the assumption that a normal sample has a lognormal distribution of grain size and a Gaussian distribution of aspect ratios. In the second part of the work the quantified measures of abnormality were correlated with processing parameters such as composition and heat treatment conditions. A

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

    SciTech Connect

    Ott, R. T.; Geng, J.; Besser, M. F.; Kramer, M. J.; Wang, Y. M.; Park, E. S.; LeSar, R.; King, A. H.

    2015-06-27

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

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

    DOE PAGESBeta

    Ott, R. T.; Geng, J.; Besser, M. F.; Kramer, M. J.; Wang, Y. M.; Park, E. S.; LeSar, R.; King, A. H.

    2015-06-27

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

  13. THE EFFECTS OF GRAIN SIZE AND GRAIN GROWTH ON THE CHEMICAL EVOLUTION OF COLD DENSE CLOUDS

    SciTech Connect

    Acharyya, Kinsuk; Hassel, George E.; Herbst, Eric

    2011-05-10

    We investigate the formation of molecules during the chemical evolution of a cold dense interstellar cloud using a gas-grain numerical code in order to study the effects of grain-size distribution and grain growth on molecular abundances. Three initial size distributions have been used, based on earlier models. To incorporate different granular sizes, we divided the distribution of sizes utilized into five logarithmically equally spaced ranges, integrated over each range to find its total granular number density, and assigned that number density to an average size in that range. We utilized rate coefficients for surface reactions, accretion, and desorption as functions of grain size. We then followed the chemical evolution of the surface populations of the five average-sized grains along with the gas-phase chemistry. We find that the total effective granular surface area of a distribution is an important parameter in the determination of surface abundances, with and without grain growth. The effect on gas-phase abundances can also be sizable. Grain growth with time increases the rate of depletion of molecules, such as CO, produced in the gas phase. Use of a size distribution for grains in gas-grain models does not improve the agreement of calculated and observed abundances, in the gas or on grains, as compared with models containing 'classical' grains of a fixed radius of 0.1 {mu}m. This result helps to verify the quality of the classical grain approximation for cold cloud models. Further, it provides an important basis for future gas-grain models.

  14. 7 CFR 800.99 - Checkweighing sacked grain.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... being sacked, or while the grain is at rest in a warehouse or holding facility, in accordance with... while the grain is at rest in a warehouse or holding facility, or while the grain is being sacked,...

  15. 7 CFR 800.99 - Checkweighing sacked grain.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... being sacked, or while the grain is at rest in a warehouse or holding facility, in accordance with... while the grain is at rest in a warehouse or holding facility, or while the grain is being sacked,...

  16. 7 CFR 800.99 - Checkweighing sacked grain.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... being sacked, or while the grain is at rest in a warehouse or holding facility, in accordance with... while the grain is at rest in a warehouse or holding facility, or while the grain is being sacked,...

  17. Could Eating More Whole Grains Help You Live Longer?

    MedlinePlus

    ... grain foods include whole-wheat flour, oatmeal, brown rice and whole cornmeal. When grains are refined, they ... many of the B vitamins. White breads, white rice and white flour are all refined grains, according ...

  18. Large Grain Superconducting RF Cavities at DESY

    SciTech Connect

    Singer, W.; Brinkmann, A.; Ermakov, A.; Iversen, J.; Kreps, G.; Matheisen, A.; Proch, D.; Reschke, D.; Singer, X.; Spiwek, M.; Wen, H.; Brokmeier, H. G.

    2007-08-09

    The DESY R and D program on cavities fabricated from large grain niobium explores the potential of this material for the production of approx. 1000 nine-cell cavities for the European XFEL. The program investigates basic material properties, comparing large grain material to standard sheet niobium, as well as fabrication and preparation aspects. Several single-cell cavities of TESLA shape have been fabricated from large grain niobium. A gradient up to 41 MV/m at Q0 = 1.4{center_dot}1010 (TB = 2K) was measured after electropolishing. The first three large grain nine-cell cavities worldwide have been produced under contract of DESY with ACCEL Instruments Co. The first tests have shown that all three cavities reach an accelerating gradient up to 30 MV/m after BCP (Buffered Chemical Polishing) treatment, what exceeds the XFEL requirements for RF test in the vertical cryostat.

  19. Grain nucleation and growth during phase transformations.

    PubMed

    Offerman, S E; van Dijk, N H; Sietsma, J; Grigull, S; Lauridsen, E M; Margulies, L; Poulsen, H F; Rekveldt, M Th; van der Zwaag, S

    2002-11-01

    The mechanical properties of polycrystalline materials are largely determined by the kinetics of the phase transformations during the production process. Progress in x-ray diffraction instrumentation at synchrotron sources has created an opportunity to study the transformation kinetics at the level of individual grains. Our measurements show that the activation energy for grain nucleation is at least two orders of magnitude smaller than that predicted by thermodynamic models. The observed growth curves of the newly formed grains confirm the parabolic growth model but also show three fundamentally different types of growth. Insight into the grain nucleation and growth mechanisms during phase transformations contributes to the development of materials with optimal mechanical properties. PMID:12411699

  20. Fine-grained zirconium-base material

    DOEpatents

    Van Houten, G.R.

    1974-01-01

    A method is described for making zirconium with inhibited grain growth characteristics, by the process of vacuum melting the zirconium, adding 0.3 to 0.5% carbon, stirring, homogenizing, and cooling. (Official Gazette)

  1. Making Pure Fine-Grained Inorganic Powder

    NASA Technical Reports Server (NTRS)

    Wood, C.

    1985-01-01

    Sustained arc plasma chemical reactor fabricates very-fine-grained inorganic solids having low thermal conductivity. Powder fabrication method, based on plasma tube technique produces pure solids without contamination commonly produced by grinding.

  2. Characterization of grain boundaries in silicon

    NASA Technical Reports Server (NTRS)

    Cheng, L. J.; Shyu, C. M.; Stika, K. M.; Daud, T.; Crotty, G. T.

    1983-01-01

    Zero-bias conductance and capacitance measurements at various temperatures were used to study trapped charges and potential barrier height at the boundaries. Deep-level transient spectroscopy (DLTS) was applied to measure the density of states at the boundary. A study of photoconductivity of grain boundaries in p-type silicon demonstrated the applicability of the technique in the measurement of minority carrier recombination velocity at the grain boundary. Enhanced diffusion of phosphorus at grain boundaries in three cast polycrystalline photovoltaic materials was studied. Enhancements for the three were the same, indicating that the properties of boundaries are similar, although grown by different techniques. Grain boundaries capable of enhancing the diffusion were found always to have strong recombination activities; the phenomena could be related to dangling bonds at the boundaries. Evidence that incoherent second-order twins of (111)/(115) type are diffusion-active is presented.

  3. Optomechanics: Listening to quantum grains of sound

    NASA Astrophysics Data System (ADS)

    Favero, Ivan

    2015-04-01

    An optomechanical device has allowed quanta, or 'grains', of mechanical vibration to be counted by optical means. The system may open up new possibilities in acoustics and thermal engineering. See Letter p.522

  4. Do grain boundaries in nanophase metals slide?

    SciTech Connect

    Bringa, E M; Leveugle, E; Caro, A

    2006-10-27

    Nanophase metallic materials show a maximum in strength as grain size decreases to the nano scale, indicating a break down of the Hall-Petch relation. Grain boundary sliding, as a possible accommodation mechanisms, is often the picture that explain computer simulations results and real experiments. In a recent paper, Bringa et al. Science 309, 1838 (2005), we report on the observation of an ultra-hard behavior in nanophase Cu under shock loading, explained in terms of a reduction of grain boundary sliding under the influence of the shock pressure. In this work we perform a detailed study of the effects of hydrostatic pressure on nanophase Cu plasticity and find that it can be understood in terms of pressure dependent grain boundary sliding controlled by a Mohr-Coulomb law.

  5. Externalities from grain consumption: a survey.

    PubMed

    Metzgar, Matthew

    2012-06-01

    The US Department of Agriculture (USDA) publishes their MyPyramid plan as a recommended eating model for all Americans. As part of this model, grain consumption is emphasized. This grain consumption has the potential to generate positive externalities, such as reduced rates of obesity, diabetes and other chronic diseases. Such positive externalities can potentially produce tangible economic benefits in terms of public health. In contrast, newer nutritional research shows that grain consumption may have negative effects on health for certain population groups. Celiac disease is four times as common as it was 50 years ago and is often under-diagnosed. Other population groups exhibit gluten sensitivity which can impact the development of asthma, allergies and neurological difficulties. This survey intends to provide a comprehensive description of both the positive and negative externalities associated with grain consumption and the resulting impact on human health. PMID:22082016

  6. Barium Isotopes in Single Presolar Grains

    NASA Technical Reports Server (NTRS)

    Pellin, M. J.; Davis, A. M.; Savina, M. R.; Kashiv, Y.; Clayton, R. N.; Lewis, R. S.; Amari, S.

    2001-01-01

    Barium isotopic compositions of single presolar grains were measured by laser ablation laser resonant ionization mass spectrometry and the implications of the data for stellar processes are discussed. Additional information is contained in the original extended abstract.

  7. Interface texture development during grain growth

    NASA Astrophysics Data System (ADS)

    Gruber, Jason

    Simulations of 2D and 3D grain growth with misorientation dependent anisotropic interfacial energy and mobility were performed using standard numerical methods. Average grain size, grain size distribution, and area and number weighted misorientation distribution functions (MDFs) were computed at equal time intervals throughout each simulation. The initial microstructures for all simulations were produced through isostropic coarsening of a domain with all single pixel/voxel grains. Grain orientations were either assigned randomly or were chosen to produce a single component orientation texture. Various combinations of energy and mobility functions were used, in particular isotropic (constant value), Read-Shockley type, and step functions. The simulations were validated by MDF measurements in polycrystalline magnesia. Simulations of 3D grain growth with inclination dependent properties were performed using the moving finite element method with a microstructure discretized as a tetrahedral mesh. In these simulations, the grain boundary character distribution (GBCD) was measured. The initial microstructure was produced through isotropic coarsening with randomly assigned subdomains. Grain orientations were assigned randomly. Energy and mobility functions used took the form of a summation over the values of a given function for the interface plane in either grain reference system. The simulations were validated by comparison with the measured GBCD in magnesia. In simulations with misorientation dependent properties and random initial orientation texture, both the area and number weighted MDFs reached steady-state distributions after a moderate amount of grain growth. Similar qualitative results are found in all cases, regardless of the functional form of the boundary properties, crystal symmetry, or dimensionality. Grain boundaries with relatively low energy have larger average areas occur in greater number than those with higher relative energies. Mobility anisotropy

  8. Thermomagnetic Stability in Pseudo Single Domain Grains

    NASA Astrophysics Data System (ADS)

    Nagy, Lesleis; Williams, Wyn; Muxworthy, Adrian; Fabian, Karl; Conbhuí, Pádraig Ó.

    2016-04-01

    The reliability of paleomagnetic remanences are well understood for fine grains of magnetite that are single-domain (SD, uniformly magnetized). In particular Néel's theory [1] outlined the thermal energies required to block and unblock magnetic remanences. This lead to determination of thermal stability for magnetization in fine grains as outlined in Pullaiah et. al. [2] and a comprehensive understanding of SD paleomagnetic recordings. It has been known for some time that single domain magnetite is possible only in the grain size range 30 - 80nm, which may only account for a small fraction of the grain size distribution in any rock sample. Indeed rocks are often dominated by grains in the pseudo single domain (PSD) size range, at approximately 80 - 1000nm. Toward the top end of this range multi-domain features begin to dominate. In order to determine thermomagnetic stability in PSD grains we need to identify the energy barriers between all possible pairs of local energy minima (LEM) domain states as a function of both temperature and grain size. We have attempted to do this using the nudged elastic band (NEB) method [3] which searches for minimum energy paths between any given pair of LEM states. Using this technique we have determined, for the first time, complete thermomagnetic stability curves for PSD magnetite. The work presented is at a preliminary stage. However it can be shown that PSD grains of magnetite with simple geometries (e.g. cubes or cuboctahedra) have very few low energy transition paths and the stability is likely to be similar to that observed for SD grains (as expected form experimental observations). The results will provide a basis for a much more rigorous understanding of the fidelity of paleomagnetic signals in assemblages of PSD grains and their ability to retain ancient recordings of the geomagnetic field. References: [1] Néel, Louis. "Théorie du traînage magnétique des ferromagnétiques en grains fins avec applications aux terres

  9. Grain boundary engineering and superstrength of nanocrystals

    NASA Astrophysics Data System (ADS)

    Glezer, A. M.; Stolyarov, V. L.; Tomchuk, A. A.; Shurygina, N. A.

    2016-01-01

    A new paradigm of hardening of nanocrystals is proposed based on the competing influence of various mechanisms of plastic deformation, i.e., dislocation sliding and grain-boundary slip. It has been confirmed using the results of computer modeling and the experimental data that the use of grain boundary engineering on the basis of the proposed ideas makes it possible to enhance substantially the strength of titaniumbased materials up to ultimate (theoretical) values.

  10. Image analysis applications for grain science

    NASA Astrophysics Data System (ADS)

    Zayas, Inna Y.; Steele, James L.

    1991-02-01

    Morphometrical features of single grain kernels or particles were used to discriminate two visibly similar wheat varieties foreign material in wheat hardsoft and spring-winter wheat classes and whole from broken corn kernels. Milled fractions of hard and soft wheat were evaluated using textural image analysis. Color image analysis of sound and mold damaged corn kernels yielded high recognition rates. The studies collectively demonstrate the potential for automated classification and assessment of grain quality using image analysis.

  11. Coarse-graining methods for computational biology.

    PubMed

    Saunders, Marissa G; Voth, Gregory A

    2013-01-01

    Connecting the molecular world to biology requires understanding how molecular-scale dynamics propagate upward in scale to define the function of biological structures. To address this challenge, multiscale approaches, including coarse-graining methods, become necessary. We discuss here the theoretical underpinnings and history of coarse-graining and summarize the state of the field, organizing key methodologies based on an emerging paradigm for multiscale theory and modeling of biomolecular systems. This framework involves an integrated, iterative approach to couple information from different scales. The primary steps, which coincide with key areas of method development, include developing first-pass coarse-grained models guided by experimental results, performing numerous large-scale coarse-grained simulations, identifying important interactions that drive emergent behaviors, and finally reconnecting to the molecular scale by performing all-atom molecular dynamics simulations guided by the coarse-grained results. The coarse-grained modeling can then be extended and refined, with the entire loop repeated iteratively if necessary. PMID:23451897

  12. Thermodynamically Consistent Coarse-Graining of Polymers

    NASA Astrophysics Data System (ADS)

    Guenza, Marina

    2015-03-01

    Structural and dynamical properties of macromolecular liquids, melts and mixtures, bridge an extensive range of length- and time-scales. For these systems, the computational limitations of the atomistic description prevent the study of the properties of interest and coarse-grained models remain the only viable approach. In coarse-grained models, structural and thermodynamic consistency across multiple length scales is essential for the predictive role of multi-scale modeling and molecular dynamic simulations that use mesoscale descriptions. This talk presents a coarse-graining approach that conserves structural and thermodynamic quantities independent of the extent of coarse-graining, and describes a model for the reconstruction of the dynamics measured in mesoscale simulations of the coarse-grained system. Some of the general challenges of preserving structural and thermodynamic consistency in coarse-grained models are discussed together with the conditions by which the problem is lessened. This material is based upon work partially supported by the National Science Foundation under Grant No. CHE-1362500.

  13. Grain size dependence of wear in ceramics

    SciTech Connect

    Wu, C.CM.; Rice, R.W.; Johnson, D.; Platt, B.A.

    1985-08-01

    Pin-on-disk (POD) microwear tests of Al2O3, MgO, MgAl2O4, and ZrO2 crystalline structures were conducted as a function of grain size and the results compared with data from single crystals of the same materials. Extrapolation to infinite grain size in the Hall-Petch type relationship for the structures resulted in lower intercepts than the single-crystal values. In addition, the macrowear grain-size dependence appears to decrease with increased wear. It is suggested that thermal expansion anisotropy (of Al2O3) significantly affects the grain size dependence of POD wear, giving a negative intercept, while elastic anisotropy is a factor in the grain-size dependence of the cubic (MgO, MgAl2O4, and ZrO2 materials. The reduced grain-size dependence is attributed to overlapping wear tracks, reducing the effects of enhanced wear damage. 9 references.

  14. Dynamic Abnormal Grain Growth in Molybdenum

    NASA Astrophysics Data System (ADS)

    Worthington, Daniel L.; Pedrazas, Nicholas A.; Noell, Philip J.; Taleff, Eric M.

    2013-11-01

    A new abnormal grain growth phenomenon that occurs only during continuous plastic straining, termed dynamic abnormal grain growth (DAGG), was observed in molybdenum (Mo) at elevated temperature. DAGG was produced in two commercial-purity molybdenum sheets and in a commercial-purity molybdenum wire. Single crystals, centimeters in length, were created in these materials through the DAGG process. DAGG was observed only at temperatures of 1713 K (1440 °C) and above and occurred across the range of strain rates investigated, ~10-5 to 10-4 s-1. DAGG initiates only after a critical plastic strain, which decreases with increasing temperature but is insensitive to strain rate. Following initiation of an abnormal grain, the rate of boundary migration during DAGG is on the order of 10 mm/min. This rapid growth provides a convenient means of producing large single crystals in the solid state. When significant normal grain growth occurs prior to DAGG, island grains result. DAGG was observed in sheet materials with two very different primary recrystallization textures. DAGG grains in Mo favor boundary growth along the tensile axis in a <110> direction, preferentially producing single crystals with orientations from an approximately <110> fiber family of orientations. A mechanism of boundary unpinning is proposed to explain the dependence of boundary migration on plastic straining during DAGG.

  15. Grain growth and experimental deformation of fine-grained ice aggregates

    NASA Astrophysics Data System (ADS)

    Diebold, Sabrina; de Bresser, Hans; Spiers, Chris; Durham, William B.; Stern, Laura

    2010-05-01

    Ice is one of the most abundant materials in our solar system. It is the principal constituent of most of the moons of the outer solar system. Thus, the flow behavior of ice is of great interest when studying geodynamic processes on icy moons. Grain growth is an elementary process that is assumed to be important in the ice sheet layering of planetary moons, where temperatures 100-273 K exist. We concentrate on the questions to what extent grain growth may influence the evolution of strength of deforming ice and if the grain growth process is independent or dependent of deformation. The answers to these questions will help us to quantitatively test the hypothesis that the progressive evolution of the grain (crystal) size distribution of deforming and recrystallizing ice directly affects its rheological behaviour in terms of composite grain-size-sensitive (GSS) and grain-size-insensitive (GSI) creep, and that this might, after time, result in a steady state balance between mechanisms of GSS and GSI creep. We performed static grain growth experiments at different temperatures and a pressure (P) of 1 atm, and deformation experiments at P = 30-100 MPa starting in the GSS-creep field. The starting material ice Ih has a grain size < 2 μm and was generated by a special pressure-release technique described by Stern et al. (1997) resulting in dense ice aggregates. The ice grains of the polycrystalline starting samples were randomly oriented and the material has a porosity of < 0.5%. For the grain growth tests a Hart Scientific temperature bath was filled with d-Limonene as cooling medium. The ice specimens were put into sealed alumina cylinders. For the grain growth tests, temperatures (T) between 213 K and 268 K were chosen. The durations of these tests varied between one day and two weeks. For the deformation experiments, temperatures of > 170 K and strain rates between 10-8 s-1 and 10-4 s-1 were chosen. Grain sizes, grain size distributions and grain topologies were

  16. The Influence of Grain Boundary Type upon Damage Evolution at Grain Boundary Interfaces

    SciTech Connect

    Perez-Bergquist, Alejandro G; Brandl, Christian; Escobedo, Juan P; Trujillo, Carl P; Cerreta, Ellen K; Gray III, George T; Germann, Timothy C

    2012-07-09

    In a prior work, it was found that grain boundary structure strongly influences damage evolution at grain boundaries in copper samples subjected to either shock compression or incipient spall. Here, several grain boundaries with different grain boundary structures, including a {Sigma}3 (10-1) boundary, are interrogated via conventional transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) to investigate the effects of atomic-scale structural differences on grain boundary strength and mobility. Boundaries are studied both before and after shock compression at a peak shock stress of 10 GPa. Results of the TEM and HRTEM work are used in conjunction with MD modeling to propose a model for shock-induced damage evolution at grain boundary interfaces that is dependent upon coincidence.

  17. BHQ revisited (1) - Looking at grain size

    NASA Astrophysics Data System (ADS)

    Heilbronner, Renée; Kilian, Rüdiger; Tullis, Jan

    2016-04-01

    Black Hills Quartzite (BHQ) has been used extensively in experimental rock deformation for numerous studies. Coaxial and general shear experiments have been carried out, for example, to define the dislocation creep regimes of quartz (Hirth & Tullis, 1992), to determine the effect of annealing (Heilbronner & Tullis, 2002) or to study the development of texture and microstructure with strain (Heilbronner & Tullis, 2006). BHQ was also used to determine the widely used quartz piezometer by Stipp & Tullis (2003). Among the microstructure analyses that were performed in those original papers, grain size was usually determined using CIP misorientation images. However, the CIP method (= computer-integrated polarization microscopy, details in Heilbronner and Barrett, 2014) is only capable of detecting the c-axis orientation of optically uniaxial materials and hence is only capable of detecting grain boundaries between grains that differ in c-axis orientation. One of the puzzling results we found (Heilbronner & Tullis, 2006) was that the recrystallized grain size seemed to depend on the crystallographic preferred orientation of the domain. In other words the grain size did not only depend on the flow stress but also on the orientation of the c-axis w/r to the shear direction. At the time, no EBSD analysis (electron back scatter diffraction) was carried out and hence the full crystallographic orientation was not known. In principle it is therefore possible that we missed some grain boundaries (between grains with parallel c-axes) and miscalculated our grain sizes. In the context of recent shear experiments on quartz gouge at the brittle-viscous transition (see Richter et al., this conference), where EBSD is used to measure the recrystallized grain size, we wanted to re-measure the CIP grain sizes of our 2006 samples (deformed in regime 1, 2 and 3 of dislocation) in exactly the same way. In two companion posters we use EBSD orientation imaging to repeat, refine and expand the

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

    DOE PAGESBeta

    Fan, Haidong; Aubry, Sylvie; Arsenlis, A.; El-Awady, Jaafar

    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.

  19. Grain boundaries and grain size distributions in nanocrystalline diamond films derived from fullerene precursors

    SciTech Connect

    Csencsits, R.; Zuiker, C.D.; Gruen, D.M.; Krauss, A.R.

    1995-12-31

    Film growth from C{sub 60}/Ar mixtures results in very pure diamond. Diamond films grown using C{sub 60} as a carbon source have been shown to be nanocrystalline with average grain sizes of 15 nm and standard deviations of 13 nm. The measured grain size distribution for two separate films, each based on measurements of over 400 grains, were found to be very similar and well approximated by a gamma distribution. Unlike typical CVD grown diamond films, these nanocrystalline films do not exhibit columnar growth. From the measured grain size distributions, it is estimated that 2% of the carbon atoms are located in the grain boundaries. The structure of the carbon in the grain boundaries is not known, but the films survive extended wear tests and hold together when the substrate is removed, indicating that the grains are strongly bound. The grain boundary carbon may give rise to additional features in the Raman spectrum and result in absorption and scattering of light in the films. We also expect that the grain boundary carbon may affect film properties, such as electrical and thermal conductivity.

  20. Organic Wheat Farming Improves Grain Zinc Concentration.

    PubMed

    Helfenstein, Julian; Müller, Isabel; Grüter, Roman; Bhullar, Gurbir; Mandloi, Lokendra; Papritz, Andreas; Siegrist, Michael; Schulin, Rainer; Frossard, Emmanuel

    2016-01-01

    Zinc (Zn) nutrition is of key relevance in India, as a large fraction of the population suffers from Zn malnutrition and many soils contain little plant available Zn. In this study we compared organic and conventional wheat cropping systems with respect to DTPA (diethylene triamine pentaacetic acid)-extractable Zn as a proxy for plant available Zn, yield, and grain Zn concentration. We analyzed soil and wheat grain samples from 30 organic and 30 conventional farms in Madhya Pradesh (central India), and conducted farmer interviews to elucidate sociological and management variables. Total and DTPA-extractable soil Zn concentrations and grain yield (3400 kg ha-1) did not differ between the two farming systems, but with 32 and 28 mg kg-1 respectively, grain Zn concentrations were higher on organic than conventional farms (t = -2.2, p = 0.03). Furthermore, multiple linear regression analyses revealed that (a) total soil zinc and sulfur concentrations were the best predictors of DTPA-extractable soil Zn, (b) Olsen phosphate taken as a proxy for available soil phosphorus, exchangeable soil potassium, harvest date, training of farmers in nutrient management, and soil silt content were the best predictors of yield, and (c) yield, Olsen phosphate, grain nitrogen, farmyard manure availability, and the type of cropping system were the best predictors of grain Zn concentration. Results suggested that organic wheat contained more Zn despite same yield level due to higher nutrient efficiency. Higher nutrient efficiency was also seen in organic wheat for P, N and S. The study thus suggests that appropriate farm management can lead to competitive yield and improved Zn concentration in wheat grains on organic farms. PMID:27537548

  1. The HEALTHGRAIN definition of 'whole grain'.

    PubMed

    van der Kamp, Jan Willem; Poutanen, Kaisa; Seal, Chris J; Richardson, David P

    2014-01-01

    Most cereal products, like white bread, pasta, and biscuits, are based on flour after removal of bran and germ, the two parts of grain kernels containing most of the dietary fibre and other bioactive components. In the past decade, consumers have been rediscovering whole grain-based products and the number of wholegrain products has increased rapidly. In most countries in Europe and worldwide, however, no legally endorsed definition of wholegrain flour and products exists. Current definitions are often incomplete, lacking descriptions of the included grains and the permitted flour manufacturing processes. The consortium of the HEALTHGRAIN EU project (FP6-514008, 2005-2010) identified the need for developing a definition of whole grain with the following scope: 1) more comprehensive than current definitions in most EU countries; 2) one definition for Europe - when possible equal to definitions outside Europe; 3) reflecting current industrial practices for production of flours and consumer products; 4) useful in the context of nutritional guidelines and for labelling purposes. The definition was developed in a range of discussion meetings and consultations and was launched in 2010 at the end of the HEALTHGRAIN project. The grains included are specified: a wide range of cereal grains from the Poaceae family, and the pseudo-cereals amaranth, buckwheat, quinoa, and wild rice. The definition also describes manufacturing processes allowed for producing wholegrain flours. This paper compares the HEALTHGRAIN definition with previous definitions, provides more comprehensive explanations than in the definition itself regarding the inclusion of specific grains, and sets out the permitted flour manufacturing processes. PMID:24505218

  2. Organic Wheat Farming Improves Grain Zinc Concentration

    PubMed Central

    Helfenstein, Julian; Müller, Isabel; Grüter, Roman; Bhullar, Gurbir; Mandloi, Lokendra; Papritz, Andreas; Siegrist, Michael; Schulin, Rainer; Frossard, Emmanuel

    2016-01-01

    Zinc (Zn) nutrition is of key relevance in India, as a large fraction of the population suffers from Zn malnutrition and many soils contain little plant available Zn. In this study we compared organic and conventional wheat cropping systems with respect to DTPA (diethylene triamine pentaacetic acid)-extractable Zn as a proxy for plant available Zn, yield, and grain Zn concentration. We analyzed soil and wheat grain samples from 30 organic and 30 conventional farms in Madhya Pradesh (central India), and conducted farmer interviews to elucidate sociological and management variables. Total and DTPA-extractable soil Zn concentrations and grain yield (3400 kg ha-1) did not differ between the two farming systems, but with 32 and 28 mg kg-1 respectively, grain Zn concentrations were higher on organic than conventional farms (t = -2.2, p = 0.03). Furthermore, multiple linear regression analyses revealed that (a) total soil zinc and sulfur concentrations were the best predictors of DTPA-extractable soil Zn, (b) Olsen phosphate taken as a proxy for available soil phosphorus, exchangeable soil potassium, harvest date, training of farmers in nutrient management, and soil silt content were the best predictors of yield, and (c) yield, Olsen phosphate, grain nitrogen, farmyard manure availability, and the type of cropping system were the best predictors of grain Zn concentration. Results suggested that organic wheat contained more Zn despite same yield level due to higher nutrient efficiency. Higher nutrient efficiency was also seen in organic wheat for P, N and S. The study thus suggests that appropriate farm management can lead to competitive yield and improved Zn concentration in wheat grains on organic farms. PMID:27537548

  3. Porphyrins in the interstellar medium (in grains)

    NASA Technical Reports Server (NTRS)

    Johnson, Fred M.

    1994-01-01

    Spectral sensitivity of the chromophores to their immediate chemical environment establishes some of the chemical constituents of the grains in which they reside. These are: (1) Paraffins, such as, octane, nonane, decane, and others...(needed for Shpolskii matrices and producing quasilines); and (2) Pyridine. The presence of pyridine is required not only to produce the spectral DIB matching, but also to produce the 36 cm(sup -1) crystal field splitting of the S(sub 1) electronic state. The presence of pyridine in the grains can be confirmed spectroscopically. Pyridine produces a transmission window at 2175 A, matching exactly the well known UV hump. On grain reflection, some of the incoming UV radiation is absorbed into the grain's outer layers. Spikes in the lab and in the astronomical data are due to vibronic transitions in pyridine. The lab spectroscopy reported here clearly establishes the presence of MgTBP, H2TPB, and pyridine in the interstellar grains. The high fluorescence efficiency of MgTBP (being optically pumped in the visible) apparently accounts for all the observed UIR emissions.

  4. 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

  5. Interstellar grain chemistry and organic molecules

    NASA Astrophysics Data System (ADS)

    Allamandola, L. J.; Sandford, S. A.

    1990-04-01

    The detection of prominant infrared absorption bands at 3250, 2170, 2138, 1670 and 1470 cm(-1) (3.08, 4.61, 4.677, 5.99 and 6.80 micron m) associated with molecular clouds show that mixed molecular (icy) grain mantles are an important component of the interstellar dust in the dense interstellar medium. These ices, which contain many organic molecules, may also be the production site of the more complex organic grain mantles detected in the diffuse interstellar medium. Theoretical calculations employing gas phase as well as grain surface reactions predict that the ices should be dominated only by the simple molecules H2O, H2CO, N2, CO, O2, NH3, CH4, possibly CH3OH, and their deuterated counterparts. However, spectroscopic observations in the 2500 to 1250 cm(-1)(4 to 8 micron m) range show substantial variation from source reactions alone. By comparing these astronomical spectra with the spectra of laboratory-produced analogs of interstellar ices, one can determine the composition and abundance of the materials frozen on the grains in dense clouds. Experiments are described in which the chemical evolution of an interstellar ice analog is determined during irradiation and subsequent warm-up. Particular attention is paid to the types of moderately complex organic materials produced during these experiments which are likely to be present in interstellar grains and cometary ices.

  6. Colloidal crystal grain boundary formation and motion

    PubMed Central

    Edwards, Tara D.; Yang, Yuguang; Beltran-Villegas, Daniel J.; Bevan, Michael A.

    2014-01-01

    The ability to assemble nano- and micro- sized colloidal components into highly ordered configurations is often cited as the basis for developing advanced materials. However, the dynamics of stochastic grain boundary formation and motion have not been quantified, which limits the ability to control and anneal polycrystallinity in colloidal based materials. Here we use optical microscopy, Brownian Dynamic simulations, and a new dynamic analysis to study grain boundary motion in quasi-2D colloidal bicrystals formed within inhomogeneous AC electric fields. We introduce “low-dimensional” models using reaction coordinates for condensation and global order that capture first passage times between critical configurations at each applied voltage. The resulting models reveal that equal sized domains at a maximum misorientation angle show relaxation dominated by friction limited grain boundary diffusion; and in contrast, asymmetrically sized domains with less misorientation display much faster grain boundary migration due to significant thermodynamic driving forces. By quantifying such dynamics vs. compression (voltage), kinetic bottlenecks associated with slow grain boundary relaxation are understood, which can be used to guide the temporal assembly of defect-free single domain colloidal crystals. PMID:25139760

  7. Interstellar grain chemistry and organic molecules

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Sandford, S. A.

    1990-01-01

    The detection of prominant infrared absorption bands at 3250, 2170, 2138, 1670 and 1470 cm(-1) (3.08, 4.61, 4.677, 5.99 and 6.80 micron m) associated with molecular clouds show that mixed molecular (icy) grain mantles are an important component of the interstellar dust in the dense interstellar medium. These ices, which contain many organic molecules, may also be the production site of the more complex organic grain mantles detected in the diffuse interstellar medium. Theoretical calculations employing gas phase as well as grain surface reactions predict that the ices should be dominated only by the simple molecules H2O, H2CO, N2, CO, O2, NH3, CH4, possibly CH3OH, and their deuterated counterparts. However, spectroscopic observations in the 2500 to 1250 cm(-1)(4 to 8 micron m) range show substantial variation from source reactions alone. By comparing these astronomical spectra with the spectra of laboratory-produced analogs of interstellar ices, one can determine the composition and abundance of the materials frozen on the grains in dense clouds. Experiments are described in which the chemical evolution of an interstellar ice analog is determined during irradiation and subsequent warm-up. Particular attention is paid to the types of moderately complex organic materials produced during these experiments which are likely to be present in interstellar grains and cometary ices.

  8. Photoemission from glass dust grains: First measurements

    NASA Astrophysics Data System (ADS)

    Nouzak, Libor; Pechal, Radim; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek

    2014-05-01

    Dust grains are present in the interstellar space and also on surfaces of space objects like the Moon. The grains are charged by photoemission caused by solar UV radiation and by charged particles from the ambient plasma (solar wind, planetary magnetospheres). A balance of different charging processes on both sunlit and night sides of the Moon causes interesting phenomena as dust horizon glow, dust fountains, and dust levitation. To contribute to a better understanding of these processes, we present laboratory investigations that use a single SiO2 grain of micron size (an archetype of the lunar dust) caught in the electrodynamic trap. We irradiate it by HeI (21.2 eV) photons and electrons and discuss a contribution of these two processes to the grain charge. The grain specific charge is evaluated by an analysis of its motion and position in the trap. We compare equilibrium charge-to-mass ratios given by the electron emissions induced by electrons and by the UV photons from the HeI lamp. First measurements indicate that the resulting charge is about twice larger for photoemission than that caused by an electron impact.

  9. Control and characterization of individual grains and grain boundaries in graphene grown by chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Yu, Qingkai; Jauregui, Luis A.; Wu, Wei; Colby, Robert; Tian, Jifa; Su, Zhihua; Cao, Helin; Liu, Zhihong; Pandey, Deepak; Wei, Dongguang; Chung, Ting Fung; Peng, Peng; Guisinger, Nathan P.; Stach, Eric A.; Bao, Jiming; Pei, Shin-Shem; Chen, Yong P.

    2011-06-01

    The strong interest in graphene has motivated the scalable production of high-quality graphene and graphene devices. As the large-scale graphene films synthesized so far are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient chemical vapour deposition on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene’s electronic properties. The graphene grains show no definite epitaxial relationship with the Cu substrate, and can cross Cu grain boundaries. The edges of these grains are found to be predominantly parallel to zigzag directions. We show that grain boundaries give a significant Raman ‘D’ peak, impede electrical transport, and induce prominent weak localization indicative of intervalley scattering in graphene. Finally, we demonstrate an approach using pre-patterned growth seeds to control graphene nucleation, opening a route towards scalable fabrication of single-crystal graphene devices without grain boundaries.

  10. Activation of Big Grain1 significantly improves grain size by regulating auxin transport in rice

    PubMed Central

    Liu, Linchuan; Tong, Hongning; Xiao, Yunhua; Che, Ronghui; Xu, Fan; Hu, Bin; Liang, Chengzhen; Chu, Jinfang; Li, Jiayang; Chu, Chengcai

    2015-01-01

    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. PMID:26283354

  11. Reaction of sorghum hybrids to anthracnose, grain mold and grain weathering in Burleson County, Texas, 2007

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thirty commercial hybrids were evaluated for resistance against anthracnose, caused by Colletotrichum sublineolum and grain mold or grain weathering caused by a number of fungal species at the Texas A&M University Agricultural Experiment Station in College Station (Burleson County). Six hybrids wer...

  12. Grain growth and fracture toughness of fine-grained silicon carbide ceramics

    SciTech Connect

    Kim, Y.W.; Mitomo, Mamoru; Hirotsuru, Hideki

    1995-11-01

    Fine-grained silicon carbide ceramics with an average grain size of 0.11 {micro}m were liquid-phase sintered from fine {beta}-SiC powder by hot pressing. The hot-pressed materials were subsequently annealed to enhance grain growth. The diameters and aspect ratios of grains in the hot-pressed and annealed materials were measured on polished and etched surfaces. The bimodal grain size distribution in annealed materials was obtained at 1,850 C without appreciable phase transformation. The average diameter and average aspect ratio increased with annealing time. The fracture toughness of a fine-grained silicon carbide ceramic determined by the Vickers indentation method was 1.9 MPa {center_dot} m{sup 1/2}. The fracture toughness increased to 6.1 MPa {center_dot} m{sup 1/2} after grain growth by annealing at 1,850 C for 12 h. Higher fracture toughness of annealed materials is due to bridging by elongated grains as evidenced by R-curve-like behavior.

  13. 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. PMID:26283354

  14. Evaluation of an in situ Grain Moisture Sensor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grain storage managers could improve the quality of stored grain if they could directly monitor grain moisture content in storage bins, which is a key indicator of stored grain quality and an early indicator of deterioration. However, the necessary sensors are not commercially available. A new capa...

  15. 7 CFR 800.30 - Foreign commerce grain business.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

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

  16. 7 CFR 800.30 - Foreign commerce grain business.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

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

  17. Isotopic Composition of Presolar Silicon Carbide Grains Analyzed with CHILI

    NASA Astrophysics Data System (ADS)

    Stephan, T.; Trappitsch, R.; Davis, A. M.; Pellin, M. J.; Rost, D.; Savina, M. R.; Jadhav, M.; Kelly, C. H.

    2015-07-01

    Twenty-two presolar SiC grains were analyzed for Sr, Zr, and Ba isotopes with the Chicago Instrument for Laser Ionization. Most grains showed isotope patterns consistent with formation in AGB star like observed previously. One grain is a supernova grain.

  18. 7 CFR 800.98 - Weighing grain in combined lots.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) Grain uniform in quality. An applicant may request that grain be weighed and certificated as a combined lot whether or not the grain is uniform in quality for the purpose of inspection under the Act. (c... 7 Agriculture 7 2014-01-01 2014-01-01 false Weighing grain in combined lots. 800.98 Section...

  19. 7 CFR 800.98 - Weighing grain in combined lots.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... weighing. (3) Grain uniform in quality. An applicant may request that grain be weighed and certificated as a combined lot whether or not the grain is uniform in quality for the purpose of inspection under... 7 Agriculture 7 2013-01-01 2013-01-01 false Weighing grain in combined lots. 800.98 Section...

  20. 7 CFR 800.98 - Weighing grain in combined lots.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... weighing. (3) Grain uniform in quality. An applicant may request that grain be weighed and certificated as a combined lot whether or not the grain is uniform in quality for the purpose of inspection under... 7 Agriculture 7 2012-01-01 2012-01-01 false Weighing grain in combined lots. 800.98 Section...

  1. 7 CFR 800.98 - Weighing grain in combined lots.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... weighing. (3) Grain uniform in quality. An applicant may request that grain be weighed and certificated as a combined lot whether or not the grain is uniform in quality for the purpose of inspection under... other than as described in this section or (ii) which shows a weight of grain different from the...

  2. Grain Boundary Character Distributions In Isostructural Materials

    NASA Astrophysics Data System (ADS)

    Ratanaphan, Sutatch

    Anisotropic grain boundary character distributions (GBCDs), which influence macroscopic materials properties, are thought to be controlled by the grain boundary energy anisotropy. Structurally, grain boundary could be viewed as two free surfaces joined together. Grain boundary energy could be simply defined by the total excess energy for creating two free surfaces minus the energy gained when new bonds are formed between these surfaces. This implies that different crystal structure should have different GBEDs and GBCDs. It was recently discovered that grain boundary energy distributions (GBED) in isostructural materials, a class of materials that share the same crystal structure, are directly related to one another. This suggests that GBCDs in isostructural materials might also be related in a similar way. To test this hypothesis, electron backscatter diffraction (EBSD) was used to map grain orientations in Ag, Au, Cu, Fe, and Mo. The GBCDs were determined from the stereological interpretation of EBSD maps containing on the order of 100,000 grains. It was found that the GBCDs of face-centered cubic (FCC) metals are statistically correlated, while the GBCDs of body-centered cubic (BCC) Fe and Mo are not correlated to the GBCD of FCC metals. The degree of the correlations among the FCC metals is weaker if there are significant differences in grain shape or texture. For example, Ag has the weakest correlation to the other FCC materials and also has quantitatively different grain shapes and texture. The relationship between the populations and energies of grain boundaries was also studied. By comparing the GBCDs of Al, Au, Cu, and Ni to the energies of 388 grain boundaries previously calculated by the Embedded Atom Method (EAM), we observed a moderately inverse correlation between the relative areas of grain boundaries and their energies. Interestingly, there are strong inverse correlations between the energies and populations of the most common grain boundaries (Sigma

  3. The separation of grain and grain boundary impedance in thin yttria stabilized zirconia (YSZ) layers

    PubMed Central

    Gerstl, M.; Navickas, E.; Friedbacher, G.; Kubel, F.; Ahrens, M.; Fleig, J.

    2011-01-01

    An improved electrode geometry is proposed to study thin ion conducting films by impedance spectroscopy. It is shown that long, thin, and closely spaced electrodes arranged interdigitally allow a separation of grain and grain boundary effects also in very thin films. This separation is shown to be successful for yttria stabilized zirconia (YSZ) layers thinner than 20 nm. In a series of experiments it is demonstrated that the extracted parameters correspond to the YSZ grain boundary and grain bulk resistances or to grain boundary and substrate capacitances. Results also show that our YSZ films produced by pulsed-laser deposition (PLD) on sapphire substrates exhibit a bulk conductivity which is very close to that of macroscopic YSZ samples.

  4. Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility.

    PubMed

    Wu, Xiaolei; Yang, Muxin; Yuan, Fuping; Wu, Guilin; Wei, Yujie; Huang, Xiaoxu; Zhu, Yuntian

    2015-11-24

    Grain refinement can make conventional metals several times stronger, but this comes at dramatic loss of ductility. Here we report a heterogeneous lamella structure in Ti produced by asymmetric rolling and partial recrystallization that can produce an unprecedented property combination: as strong as ultrafine-grained metal and at the same time as ductile as conventional coarse-grained metal. It also has higher strain hardening than coarse-grained Ti, which was hitherto believed impossible. The heterogeneous lamella structure is characterized with soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The unusual high strength is obtained with the assistance of high back stress developed from heterogeneous yielding, whereas the high ductility is attributed to back-stress hardening and dislocation hardening. The process discovered here is amenable to large-scale industrial production at low cost, and might be applicable to other metal systems. PMID:26554017

  5. Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility

    PubMed Central

    Wu, Xiaolei; Yang, Muxin; Yuan, Fuping; Wu, Guilin; Wei, Yujie; Huang, Xiaoxu; Zhu, Yuntian

    2015-01-01

    Grain refinement can make conventional metals several times stronger, but this comes at dramatic loss of ductility. Here we report a heterogeneous lamella structure in Ti produced by asymmetric rolling and partial recrystallization that can produce an unprecedented property combination: as strong as ultrafine-grained metal and at the same time as ductile as conventional coarse-grained metal. It also has higher strain hardening than coarse-grained Ti, which was hitherto believed impossible. The heterogeneous lamella structure is characterized with soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The unusual high strength is obtained with the assistance of high back stress developed from heterogeneous yielding, whereas the high ductility is attributed to back-stress hardening and dislocation hardening. The process discovered here is amenable to large-scale industrial production at low cost, and might be applicable to other metal systems. PMID:26554017

  6. Organics Synthesized Using Iron-Grain Silicates

    NASA Technical Reports Server (NTRS)

    Johnson, N. M.; Cody, G. D.; Nuth, J. A., III

    2003-01-01

    We use Fischer-Tropsch type (FTT) synthesis to produce hydrocarbons by hydrogenating carbon monoxide via catalytic reactions. The products of these reactions have been studied using 'natural' catalysts and calculations of the efficiency of FTT synthesis in the Solar Nebula suggest that these types of reactions could make significant contributions to the composition of material near three AU. We coat Fe-silicate grains with organic material using FTT synthesis to simulate the chemistry in the early Solar Nebula. In our experimental setup, we roughly model a nebular environment where grains are successively transported from hot to cold regions of the nebula. In other words, the starting gases and FTT products are continuously circulated through the grains at high temperature with intervals of cooling. Organics generated in this manner could represent the carbonaceous material incorporated in comets and meteorites. We analyze the resulting organics and present the results.

  7. Stability of Charged Grains in Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, D.; Hamilton, D. P.

    2012-12-01

    Hypervelocity impacts of interplanetary micrometeoroids with orbiting ring particles generate dusty debris of all sizes. These ejecta particles become electrically charged by interactions with orbiting plasma and solar photons. Accordingly, they experience both gravity and Lorentz forces, whose combined effects cause interesting and complex dynamics. For simplicity, we initially model the magnetic field of Saturn as a centered and aligned dipole and investigate the stability of motion for grains launched from circularly-orbiting parent bodies. In this approximation, the magnetic equator and the ring-plane coincide. We begin with numerical models, determining the stability of dust grain trajectories in both the radial and vertical directions as a function of launch distance from the planet, and over all charge-to-mass ratios from ions to rocks. We find that positively-charged sub-micron dust grains over a limited range in size are radially unstable, colliding with the planet if launched from within synchronous orbit and escaping entirely if launched from outside this distance. Escaping grains have been observed as high-velocity dust streams at Saturn and at Jupiter. In addition, positively and negatively-charged smaller grains are vertically unstable and spiral up magnetic field lines to sustain non-linear vertical oscillations or to collide with the planet at high latitude. We then undertake local and global stability analyses and derive stability criteria that match our numerical data extremely well. Our work builds upon studies led by Burns, Hamilton, Horanyi, Howard, Mendis, Mitchell, Northrop, Schaffer, and others. We confirm that for charged dust grains launched at the Kepler speed, planetary gravity cannot be ignored, even in the limit of electromagnetically-dominated grains. Some stability boundaries can be obtained analytically while others require more complicated semianalytic methods. Our solutions are general and can be applied wherever an aligned

  8. Abnormal Grain Growth Suppression in Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J. (Inventor); Claytor, Harold Dale (Inventor); Alexa, Joel A. (Inventor)

    2015-01-01

    The present invention provides a process for suppressing abnormal grain growth in friction stir welded aluminum alloys by inserting an intermediate annealing treatment ("IAT") after the welding step on the article. The IAT may be followed by a solution heat treatment (SHT) on the article under effectively high solution heat treatment conditions. In at least some embodiments, a deformation step is conducted on the article under effective spin-forming deformation conditions or under effective superplastic deformation conditions. The invention further provides a welded article having suppressed abnormal grain growth, prepared by the process above. Preferably the article is characterized with greater than about 90% reduction in area fraction abnormal grain growth in any friction-stir-welded nugget.

  9. On the electric charge of interplanetary grains

    NASA Astrophysics Data System (ADS)

    Lafon, J. P. J.

    The importance of surface effects on grain charging in the interplanetary plasma is considered. It is shown by numerical calculations that the photoemission and the thermoemission of electrons can govern the charge and reverse it at radial distances of a few solar radii. Properties relative to the calculations, such as solar wind in high speed streams, are illustrated, and the electric potential reached by the grains versus radial distance is plotted. It is found that electrical potential reaches saturation-like values at large distances from the sun, that electric photoemission weakens the negative potential at small radial distances and renders the potential positive at large distances, and that thermoemission prevents grain disruption. Further laboratory measurements and theoretical models of surface effects are necessary to continue studies.

  10. Dust Spectroscopy and the Nature of Grains

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.

    2006-01-01

    Ground-based, air-borne and space-based, infrared spectra of a wide variety of objects have revealed prominent absorption and emission features due to large molecules and small dust grains. Analysis of this data reveals a highly diverse interstellar and circumstellar grain inventory, including both amorphous materials and highly crystalline compounds (silicates and carbon). This diversity points towards a wide range of physical and chemical birthsites as well as a complex processing of these grains in the interstellar medium. In this talk, I will review the dust inventory contrasting and comparing both the interstellar and circumstellar reservoirs. The focus will be on the processes that play a role in the lifecycle of dust in the interstellar medium.