Science.gov

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. 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…

  9. 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...

  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. 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 ...

  5. 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)].

  6. 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 ...

  7. 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

  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 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)

  14. 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.

  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 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

  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 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

  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. 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.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  14. 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.

  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. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  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. 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

  6. 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.

  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. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  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. 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).

  17. 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

  18. 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.

  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. 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.

  1. 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.

  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. 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.

  5. 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.

  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. 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.

  10. 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...

  11. 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

  12. 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 ...

  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. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  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. 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 ...

  5. 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...

  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. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  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 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.

  9. 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

  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

    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

  12. 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.

  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. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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)

  6. 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

  7. 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.

  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. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  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. 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.

  19. 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.

  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. 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

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  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. 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

  13. 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.

  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. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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.

  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 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. IRSL from fine-grained glacifluvial sediment

    NASA Astrophysics Data System (ADS)

    Gemmell, Alastair M. D.

    1999-02-01

    Samples of suspended sediment were obtained from the Dora di Ferret, a glacifluvial stream in the Italian Alps, over a period of 24 h. IRSL analysis of the sediment indicates that the residual ( INAT) signal is almost completely zeroed within 3 km of fluvial transport during daylight hours. In contrast, samples collected at night possess environmental doses ( DE) in excess of 100 Gy, probably the luminescence signal of the parent till from which the fine-grained suspended load has been derived. Quaternary deposits of glacifluvial sediment will contain a mixture of daylight and night transported mineral grains, the resulting complex behaviour accounting for difficulties in luminescence dating such materials. Adaptations of single-aliquot protocols and single-grain protocols appear to offer the best chance of dating glacifluvial deposits accurately.

  11. Ion implantation effects in 'cosmic' dust grains

    NASA Technical Reports Server (NTRS)

    Bibring, J. P.; Langevin, Y.; Maurette, M.; Meunier, R.; Jouffrey, B.; Jouret, C.

    1974-01-01

    Cosmic dust grains, whatever their origin may be, have probably suffered a complex sequence of events including exposure to high doses of low-energy nuclear particles and cycles of turbulent motions. High-voltage electron microscope observations of micron-sized grains either naturally exposed to space environmental parameters on the lunar surface or artificially subjected to space simulated conditions strongly suggest that such events could drastically modify the mineralogical composition of the grains and considerably ease their aggregation during collisions at low speeds. Furthermore, combined mass spectrometer and ionic analyzer studies show that small carbon compounds can be both synthesized during the implantation of a mixture of low-energy D, C, N ions in various solids and released in space by ion sputtering.

  12. 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.

  13. The mechanism of grain growth in ceramics

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    The theory of grain boundary migration as a thermally activated process is reviewed, the basic mechanisms in ceramics being the same as in metals. However, porosity and non-stochiometry in ceramic materials give an added dimension to the theory and make quantitative treatment of real systems rather complex. Grain growth is a result of several simultaneous (and sometimes interacting) processes; these are most easily discussed separately, but the overall rate depends on their interaction. Sufficient insight into the nature of rate controlling diffusion mechanisms is necessary before a qualitative understanding of boundary mobility can be developed.

  14. Enhanced diffusion of phosphorus at grain boundaries

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Enhanced diffusion of phosphorus at grain boundaries in cast polycrystalline photovoltaic materials (Wacker, HEM, and Semix) was studied. It was found that the enhancements for the three materials were the same, indicating that the properties of boundaries are similar, even though they were grown by different techniques. In addition, it was observed that grain boundaries capable of enhancing the diffusion always have strong recombination activities. Both phenomena could be related to dangling bonds existing at the boundaries. The present study gives the first evidence that incoherent second order twins of 111/115-plane type are diffusion-active.

  15. The effect of grain size, microcracking and grain boundary grooving on osteoblast attachment in hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Smith, Ian Orland

    This research examined the effect of particle size, microcracking and grain-boundary grooving in hydroxyapatite (HA) ceramics on osteoblast (OB) attachment, with the overall goal of understanding the role of physical characteristics in optimized scaffolds for bone tissue engineering. Bimodally porous HA scaffolds were fabricated by foaming and sintering either micron-scale or nano-scale HA powder, yielding two sets with average grain diameters of 8.6 +/- 1.9 mum and 588 +/- 55 nm, respectively. OBs were seeded onto these scaffolds and counted at 0.5, 1, 2 and 4 hours for attachment and 1, 3 and 5 days for proliferation using a hemacytometer. Results showed that OB attachment and proliferation was not significantly affected by the change in grain size and may depend more on the bimodal porosity of the implant. However, as our attempt to reduce the error in the hemacytometer counts was not fully successful, a more accurate method of counting the OBs, such as a quantifiable dye, must be used to verify this trend. While microcracks occur as a result of thermal processing of HA, these TEA-induced cracks are not easily controlled. For our studies we used Vickers-induced microcracks to quantify the effect of microcracking on OB attachment in HA. OB attachment was not significantly affected at one hour, but increased at four hours to 61% higher than on non-microcracked control specimens. This increase indicates that microcracking does have an effect on OB attachment and should be studied further, to assess its effect on OB proliferation and differentiation. It is not surprising that microcracks have a positive effect on OB attachment, as this mimics the natural process of bone remodeling. However, they are not likely to occur in nano-grained HA as a result of processing, as its small grain size falls below the known values of critical grain size for microcracking (GCR) in HA. Grain boundary grooving in dense HA is also investigated in this dissertation. OBs were seeded

  16. Whole grain intake: The Baltimore Longitudinal Study of Aging

    PubMed Central

    Maras, Janice E.; Newby, P.K.; Bakun, Peter J.; Ferrucci, Luigi; Tucker, Katherine L.

    2009-01-01

    Our objective was to identify major dietary sources of whole grains and to describe the construction of a database of whole grain content of foods. Dietary information was collected with 7-d food records from men and women in the Baltimore Longitudinal Study of Aging, mean age 62.1 ± 16.0 years, who participated in the dietary assessment portion of the study (n = 1516), and estimates of whole grain intake were obtained from a newly developed database. The Pyramid Servings database and 1994–1996 Continuing Survey of Food Intakes by Individuals (CSFII) recipe ingredients database were then used to calculate both servings and gram weights of whole grain intakes. Mean intakes of whole grains, refined grains, and total grains, as well as frequency of intake for major whole grain food groups and whole grain content for each group, were calculated. Top contributors of whole grains were ready-to-eat breakfast cereals (made with whole grain as well as bran), hot breakfast cereals (made with whole grain), multi-grain bread, and whole wheat bread. While more research is needed to better understand the benefits of whole grains, the development of research tools, including databases to accurately assess whole grain intake, is a critical step in completing such research. PMID:20126297

  17. Organic grain coatings in primitive interplanetary dust particles: Implications for grain sticking in the Solar Nebula

    NASA Astrophysics Data System (ADS)

    Flynn, George J.; Wirick, Sue; Keller, Lindsay P.

    2013-10-01

    The chondritic porous interplanetary dust particles (CP IDPs), fragments of asteroids and comets collected by NASA high-altitude research aircraft from the Earth's stratosphere, are recognized as the least altered samples of the original dust of the Solar Nebula available for laboratory examination. We performed high-resolution, ~25 nm/pixel, x-ray imaging and spectroscopy on ultramicrotome sections of CP IDPs, which are aggregates of >104 grains, and identified and characterized ~100 nm thick coatings of organic matter on the surfaces of the individual grains. We estimated the minimum tensile strength of this organic glue to be ~150 to 325 N/m2, comparable to the strength of the weakest cometary meteors, based on the observation that the individual grains of ~5 μm diameter aggregate CP IDPs are not ejected from the particle by electrostatic repulsion due to charging of these IDPs to 10 to 15 volts at 1 A.U. in space. Since organic coatings can increase the sticking coefficient over that of bare mineral grains, these organic grain coatings are likely to have been a significant aid in grain sticking in the Solar Nebula, allowing the first dust particles to aggregate over a much wider range of collision speeds than for bare mineral grains.

  18. The Strength-Grain Size Relationship in Ultrafine-Grained Metals

    NASA Astrophysics Data System (ADS)

    Balasubramanian, N.; Langdon, Terence G.

    2016-04-01

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

  19. Simulation of grain size effects in nanocrystalline shape memory alloys

    NASA Astrophysics Data System (ADS)

    Ahluwalia, Rajeev; Quek, Siu Sin; Wu, David T.

    2015-06-01

    Recently, it has been demonstrated that martensitic transformation in nanocrystalline shape memory alloys can be suppressed for small grain sizes. Motivated by these results, we study the grain size dependence of martensitic transformations and stress-strain response of nanocrystalline shape memory alloys within the framework of the Ginzburg-Landau (GL) theory. A GL model for a square to rectangle transformation in polycrystals is extended to account for grain boundary effects. We propose that an inhibition of the transformation in grain boundary regions can occur, if the grain boundary energy of the martensite is higher than that of the austenite phase. We show that this inhibition of transformation in grain boundary regions has a strong influence on domain patterns inside grains. Although the transformation is inhibited only at the grain boundaries, it leads to a suppression of the transformation even inside the grains as grain size is decreased. In fact, below a critical grain size, the transformation can be completely suppressed. We explain these results in terms of the extra strain gradient cost associated with grain boundaries, when the transformation is inhibited at grain boundaries. On the other hand, no significant size effects are observed when transformation is not inhibited at grain boundaries. We also study the grain size dependence of the stress strain curve. It is found that when the transformation is inhibited at grain boundaries, a significant reduction in the hysteresis associated with stress-strain curves during the loading-unloading cycles is observed. The hysteresis for this situation reduces even further as the grain size is reduced, which is consistent with recent experiments. The simulations also demonstrate that the mechanical behavior is influenced by inter-granular interactions and the local microstructural neighbourhood of a grain has a stronger influence than the orientation of the grain itself.

  20. Assessment of MARMOT Grain Growth Model

    SciTech Connect

    Fromm, B.; Zhang, Y.; Schwen, D.; Brown, D.; Pokharel, R.

    2015-12-01

    This report assesses the MARMOT grain growth model by comparing modeling predictions with experimental results from thermal annealing. The purpose here is threefold: (1) to demonstrate the validation approach of using thermal annealing experiments with non-destructive characterization, (2) to test the reconstruction capability and computation efficiency in MOOSE, and (3) to validate the grain growth model and the associated parameters that are implemented in MARMOT for UO2. To assure a rigorous comparison, the 2D and 3D initial experimental microstructures of UO2 samples were characterized using non-destructive Synchrotron x-ray. The same samples were then annealed at 2273K for grain growth, and their initial microstructures were used as initial conditions for simulated annealing at the same temperature using MARMOT. After annealing, the final experimental microstructures were characterized again to compare with the results from simulations. So far, comparison between modeling and experiments has been done for 2D microstructures, and 3D comparison is underway. The preliminary results demonstrated the usefulness of the non-destructive characterization method for MARMOT grain growth model validation. A detailed analysis of the 3D microstructures is in progress to fully validate the current model in MARMOT.

  1. Iron Isotopic Diagnostics of Presolar Supernova Grains

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.; Meyer, B. S; The, L.-S.

    2002-01-01

    We study the abundance and isotopic composition of iron in a massive-star supernova to identify those isotopic characteristics that can identify the location of the condensing matter that is contained in the presolar supernova grains from meteorites. Additional information is contained in the original extended abstract.

  2. Against the Grain: Teaching Historical Complexity

    ERIC Educational Resources Information Center

    Neumann, Dave

    2013-01-01

    Many teachers and scholars have written about the importance of inquiry in effective history instruction. At its core, inquiry involves student investigation of a significant historical problem. Experienced teachers, however, often reveal their skill in purposely teaching against the grain. Skilled teachers help students appreciate historical…

  3. [Amino acid composition of rice grain proteins].

    PubMed

    Peruanskiĭ, Iu V; Savich, I M

    1976-01-01

    The composition of the major reserve proteins of rice grain--globulins, prolamines and glutelins--was examined in four rice varieties (Dubovsky 129, Kuban 3, Alakul, Ushtobinsky). Globulins proved to be most heterogeneous whereas glutelins appeared to be least heterogeneous. In regards to the ratio of components globulins showed high variability and glutelins displayed high stability. PMID:1005365

  4. Grain Unloading Of Arsenic Species In Rice

    EPA Science Inventory

    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 dim...

  5. Mineral Analysis of Whole Grain Total Cereal

    ERIC Educational Resources Information Center

    Hooker, Paul

    2005-01-01

    The quantitative analysis of elemental iron in Whole Grain Total Cereal using visible spectroscopy is suitable for a general chemistry course for science or nonscience majors. The more extensive mineral analysis, specifically for the elements iron, calcium and zinc, is suitable for an instrumental or quantitative analysis chemistry course.

  6. Math on the Job. Grain Farmer.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. National Center for Research in Vocational Education.

    This booklet is intended to help mainstreamed mentally retarded, emotionally disturbed, or learning disabled high school students acquire a basic understanding of the responsibilities and working conditions of grain farming and to practice basic math skills necessary in the occupation. The first section provides a brief introduction to the…

  7. Grain legume genetic resources for allele mining

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sequencing capacities for higher throughput at significantly lower costs have enabled larger scale genotyping of plant genetic resources. One challenge to sequencing the USDA grain legume collections of pea, chickpea and lentil core accessions is the amount of heterogeneity in the landrace accessio...

  8. The initiation of grain movement by wind

    NASA Astrophysics Data System (ADS)

    Nickling, William G.

    1987-11-01

    When air blows across the surface of dry, loose sand, a critical shear velocity must be achieved to initiate motion. Since most natural sediments consist of a range of grain sizes, fluid threshold for any sediment cannot really be defined by a finite value but should be viewed as a threshold range which is a function of the mean size, sorting, and packing of the sediment. In order to investigate the initiation of particle movement by wind, a series of wind tunnel tests were carried out on a range of screened sands and commercially available glass beads of differing size, sorting, and shape characteristics. In addition, individual samples of the glass beads were mixed to produce rather poorly sorted bimodal distributions. Test results suggest the when velocity is slowly increased over the sediment surface the smaller or more exposed grains are first engrained by the fluid drag of the air either in surface creep or in saltation. As velocity continues to rise, the larger more protected grains may also be moved by fluid drag. The data also indicate that predicted values based on the modified Bagnold equation fall within the range of threshold values defined by the transition section of the grain movement/shear velocity plots. Moreover, the predicted values are very similar to the threshold values derived for the point maximum inflection on the curves.

  9. The initiation of grain movement by wind

    NASA Astrophysics Data System (ADS)

    Nickling, W. G.

    1986-05-01

    When air blows across the surface of dry, loose sand, a critical shear velocity must be achieved to inititate motion. Since most natural sediments consist of a range of grain sizes, fluid threshold for any sediment cannot really be defined by a finite value but should be viewed as a threshold range which is a function of the mean size, sorting, and packing of the sediment. In order to investigate the initiation of particle movement by wind, a series of wind tunnel tests were carried out on a range of screened sands and commercially available glass beads of differing sizes, sorting, and shape characteristics. In addition, individual samples of the glass beads were mixed to produce rather poorly sorted bimodal distributions. Test results suggest that when velocity is slowly increased over the sediment surface the smaller or more exposed grains are first entrained by the fluid drag of the air either in surface creep or in saltation. As velocity continues to rise, the larger more protected grains may also be moved by fluid drag. The data also indicate that predicted values based on the modified Bagnold equation fall within the range of threshold values defined by the transition section of the grain movement/shear velocity plots. Moreover, the predicted values are very similar to the threshold values derived for the point maximum inflection on the curves.

  10. Sorghum Midge Resistance in Grain Sorghum Hybrids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although grain sorghum is a good rotation crop, the plants are impacted by a variety of insects and pathogens from the seedling stage through maturity in the Coastal Plain region. Nine insect pests of sorghum in southern Georgia were detected in 2006. They were, in order of importance: sorghum mid...

  11. US Feed Grains Mycotoxin Conference Report

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mycotoxins are toxic compounds produce by fungi (molds). Mycotoxins are a major problem throughout the world. Grains and foods can become infected with these fungi which produce mycotoxins and when these commodities are fed to animals or consumed by humans pose a significant threat to both animal ...

  12. Dislocation creep of fine-grained olivine

    NASA Astrophysics Data System (ADS)

    Faul, U. H.; Fitz Gerald, J. D.; Farla, R. J. M.; Ahlefeldt, R.; Jackson, I.

    2011-01-01

    Deformation experiments conducted in a gas medium apparatus at temperatures from 1200 to 1350°C with a fine-grained, solution-gelation derived Fe-bearing olivine show a stress dependence of the strain rate at stresses above ˜150 MPa, which is much stronger than previously reported for polycrystalline samples. The data can be fit by a power law with ??σn with n ˜ 7-8, or equally well by a Peierls creep law with exponential stress dependence. Due to the observed strong stress dependence the samples deform at significantly higher strain rates at a given stress than single crystals or coarse-grained polycrystals with n ˜ 3.5. TEM observations indicate the presence of dislocations with at least two different Burgers vectors, with free dislocations predominantly of screw character. Subgrain walls are present but are only weakly developed and have small misorientation angles. Both the rheology and dislocation structures are consistent with creep rate-limited by dislocation glide or cross slip for aggregates with grain sizes smaller than or approaching the recrystallized grain size. Deformation mechanism maps extrapolated to lithospheric temperatures using the melt-free diffusion creep rheology of Faul and Jackson (2007), the dislocation creep rheology of Hirth and Kohlstedt (2003), and the results described here indicate that deformation conditions of ultramylonitic shear zones fall near the triple point of Peierls, dislocation, and diffusion creep.

  13. Dynamic Abnormal Grain Growth in Refractory Metals

    NASA Astrophysics Data System (ADS)

    Noell, Philip J.; Taleff, Eric M.

    2015-11-01

    High-temperature plastic deformation of the body-centered cubic (BCC) refractory metals Mo and Ta can initiate and propagate abnormal grains at significantly lower temperatures and faster rates than is possible by static annealing alone. This discovery reveals a new and potentially important aspect of abnormal grain growth (AGG) phenomena. The process of AGG during plastic deformation at elevated temperatures, termed dynamic abnormal grain growth (DAGG), was observed at homologous temperatures between 0.52 and 0.72 in both Mo and Ta sheet materials; these temperatures are much lower than those for previous observations of AGG in these materials during static annealing. DAGG was used to repeatedly grow single crystals several centimeters in length. Investigations to date have produced a basic understanding of the conditions that lead to DAGG and how DAGG is affected by microstructure in BCC refractory metals. The current state of understanding for DAGG is reviewed in this paper. Attention is given to the roles of temperature, plastic strain, boundary mobility and preexisting microstructure. DAGG is considered for its potential useful applications in solid-state crystal growth and its possibly detrimental role in creating undesired abnormal grains during thermomechanical processing.

  14. Distillers Grains: Production, Properties and Utilization (Book)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The book, Distillers Grains: Production, Properties and Utilization, brings together cutting edge information on many aspects of DDGS. It consists of six major sections, having 26 chapters in total. Section 1 has six chapters and covers introduction, perspectives, history, structure and compositio...

  15. Fruit, vegetable, and grain processing wastes

    SciTech Connect

    Andrews, R.M.; Soderquist, M.R.

    1980-06-01

    This is a literature review of fruit, vegetable and grain processing wastes. The factors affecting water usage and methods of conservation were examined. Various processes were investigated which included the pulp recovery from caustic peeled tomato skin, the dewatering of citrus, washing leafy vegetables with recycled process water and the potato processing industry.

  16. The Grain Group. The Food Guide Pyramid.

    ERIC Educational Resources Information Center

    Frost, Helen

    This booklet for young children is part of a series that supports national science standards related to physical health and nutrition, describing and illustrating the importance of using the Food Guide Pyramid and eating sufficient servings of grains. Colorful photographs support early readers in understanding the text. The repetition of words and…

  17. Large grain cavities from pure niobium ingot

    DOEpatents

    Myneni, Ganapati Rao; Kneisel, Peter; Cameiro, Tadeu

    2012-03-06

    Niobium cavities are fabricated by the drawing and ironing of as cast niobium ingot slices rather than from cold rolled niobium sheet. This method results in the production of niobium cavities having a minimum of grain boundaries at a significantly reduced cost as compared to the production of such structures from cold rolled sheet.

  18. Women in Grains Research Project--Extract.

    ERIC Educational Resources Information Center

    Berrisford, Nickie

    Research aimed at recognizing, encouraging, enhancing, and harnessing the skills and contributions of women in the Australian grains industry involved a number of women in Victoria in focus groups, telephone interviews, and questionnaire surveys. Results indicate that women perceived themselves as providing guidance, operational assistance,…

  19. IMPACT OF OZONE ON GRAIN SORGHUM YIELD

    EPA Science Inventory

    Grain sorghum(sorghum vulgare Pers.) is an important animal feed crop, and it is sometimes planted as a substitute for field corn. Although sorghum is grown in areas of the central and southern U.S. where potentially damaging concentrations of 03 exist, no data are available rega...

  20. New market opportunities for rice grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Breeding efforts for rice have been focusing on increasing yield and improving quality (milling yield and grain quality), while maintaining cooked rice sensory properties to meet consumer preferences. These breeding targets will no doubt continue as the main foci for the rice industry. However, the ...

  1. Whole Grains: Processing, fiber, color, and phytonutrients

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased consumption of whole grains, especially wheat, can reduce cancer and cardiovascular disease due to dietary fiber and phenolic antioxidants. Yet, remarkably little is known about the fate of fiber (arabinoxylans) and phenolics during wheat food processing. Our long-term goal is to facilitat...

  2. Structure and Composition of the Grain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a crop with a wide range of genetic diversity, sorghum grain composition and structure can vary widely. Such variability can be of great benefit in supplying a diversity of uses but can also be a negative when viewed from the standpoint of uniformity. Despite sharing similarities to other cereals...

  3. Whole Grain Intake Reduces Pancreatic Cancer Risk

    PubMed Central

    Lei, Qiucheng; Zheng, Huazhen; Bi, Jingcheng; Wang, Xinying; Jiang, Tingting; Gao, Xuejin; Tian, Feng; Xu, Min; Wu, Chao; Zhang, Li; Li, Ning; Li, Jieshou

    2016-01-01

    Abstract Mounting evidence from epidemiology studies suggests that whole grain intake may reduce pancreatic cancer risk, but convincing evidence is scarce. We conducted a meta-analysis to assess the association between whole grain intake and pancreatic cancer risk. Relevant observational studies were identified by searching PubMed, Embase, Scopus, and Cochrane library databases for the period from January 1980 to July 2015, with no restrictions. We calculated the summary odds ratios (ORs) for pancreatic cancer using random-effects model meta-analysis. Between-study heterogeneity was analyzed using the I2 statistic. A total of 8 studies regarding whole grain intake were included in the meta-analysis. The pooled OR of pancreatic cancer for those with high versus low whole grain intake was 0.76 (95% confidence interval [CI], 0.64–0.91; P = 0.002). There was no significant heterogeneity across these studies (I2 = 11.7%; Pheterogeneity = 0.339). In the subgroup analysis by geographic area, the summary ORs of developing pancreatic cancer were 0.64 (95% CI, 0.53–0.79; P < 0.001; I2 = 0%; Pheterogeneity = 0.482) in the United States (n = 4) and 0.95 (95% CI, 0.63–1.43; P = 0.803; I2 = 45.6%; Pheterogeneity = 0.175) in Europe (n = 2). In the subgroup analysis by type of whole grain, the summary ORs were 0.72 (95% CI, 0.60–0.87; P = .001; I2 = 0; Pheterogeneity = 0.876) for grains (n = 4) and 0.74 (95% CI, 0.27–2.02; P = 0.554; I2 = 86.3%; Pheterogeneity = 0.007) for wheat (n = 2). A high intake of whole grains was associated with a reduced risk of pancreatic cancer. Because of the absent of more cohort studies, further prospective studies need to be conducted to ensure conclusions that are more robust. PMID:26945361

  4. Analysis of Grain Boundary Character in a Fine-Grained Nickel-Based Superalloy 718

    NASA Astrophysics Data System (ADS)

    Araujo, L. S.; dos Santos, D. S.; Godet, S.; Dille, J.; Pinto, A. L.; de Almeida, L. H.

    2014-11-01

    In the current work, sheets of superalloy 718 were processed via thermomechanical route by hot and cold rolling, followed by annealing below the δ phase solvus temperature and precipitation hardening to optimum strength. Grain boundary character distribution throughout the processing was mapped via EBSD and its evolution discussed. The results show that it is possible to process the alloy to a fine grain size obtaining concomitantly a considerably high proportion of special boundaries Σ3, Σ9, and Σ27. The precipitation of δ phase presented a strong grain refining role, without significantly impairing the twinning mechanism and, consequently, the Σ3, Σ9, and Σ27 boundary formations.

  5. Grain boundary migration: Atomistic simulation studies

    NASA Astrophysics Data System (ADS)

    Upmanyu, Moneesh

    Control of microstructural evolution is the goal of much of materials processing. Properties of grain boundaries and associated higher order defects determine fundamental microstructural parameters such as grain size/shape and texture, which in turn control an amalgam of material properties and applications. Microstructural evolution theories are based on certain assumptions, and attempts to experimentally validate them have not been promising, predominantly due to the presence of impurities. In this thesis, classical molecular dynamics simulation techniques are used to investigate boundary kinetics. Validity of the assumptions inherent in the theory of grain boundary migration is first ascertained. The U-shaped half-loop geometry is employed in a two-dimensional (triangular lattice) Lennard-Jones system to observe steady-state, curvature driven boundary migration. The classical linear relation between the migration rate and the driving force is recovered at low driving forces. Three-dimensional, highly parallelized simulations of <111> tilt grain boundaries in aluminum (EAM potentials) also confirm this result. The boundary mobility is found to have an Arrhenius dependence on temperature. However, the extracted activation energies of migration are significantly lower than those extracted in experiments, confirming the presence of impurities in the latter. Structurally similar boundaries are found to exhibit the compensation effect. Both boundary mobility and energy vary non-monotonically with the boundary misorientation, exhibiting maxima and minima for high symmetry (low Sigma) special misorientations, respectively. Using these anisotropic boundary properties in a Potts model reveals that the evolution of two-dimensional random textures is mostly controlled by boundary energy anisotropy, not the mobility anisotropy. Atomistic migration mechanism studies suggest that while single hops across the boundary are frequent, migration occurs primarily due to correlated

  6. Grain boundary niobium carbides in Inconel 718

    SciTech Connect

    Gao, M.; Wei, R.P.

    1997-12-15

    A coordinated, multidisciplinary investigation was conducted to determine the mechanisms and rate controlling processes for environmentally assisted crack growth under sustained (static) loading in Inconel 718 at elevated temperatures. The results showed that oxygen had a significant influence on crack growth, increasing the crack growth rate, for example, by nearly four orders of magnitude at 973 K. Based on results from the companion surface chemical and metallurgical studies, it was suggested that the mechanism for crack growth enhancement by oxygen was the formation and fracture of a brittle niobium oxide (Nb{sub 2}O{sub 5}-type) film on the grain boundary surfaces. The Nb came principally from the oxidation and decomposition of NbC (or Nb-rich carbides) at the grain boundaries, and crack growth was controlled by the rate of oxidation and decomposition of these carbides. Because there was extensive oxidation of the primary NbC, these carbides were implicitly considered to be the primary source of Nb. Although these carbides were large and contained substantial amounts of Nb, they were too few and spaced too far apart to be of concern (averaging one NbC for two grain boundary facets and spaced about 25 {micro}m apart). To wit, whether the freed Nb could diffuse over such a large distance and be oxidized to support the postulated mechanism for crack growth? The presence of other Nb-rich carbides elsewhere on the grain boundaries, or other sources for Nb, therefore, needs to be re-examined and is the focus of this study. In this paper, the results of a study of grain boundary niobium carbides and their distribution in Inconel 718 are reported, and are discussed in terms of their contribution to crack growth.

  7. Geometry and crystallographic configuration of grain boundaries

    NASA Astrophysics Data System (ADS)

    Eichler, Jan; Weikusat, Ilka; Kipfstuhl, Sepp; Binder, Tobias

    2015-04-01

    Ice cores provide a unique opportunity to study fundamental mechanisms which control the internal flow of ice sheets. Different kinds of deformation processes acting on the micro-scale are responsible for the viscoplastic behavior on large scale. Careful interpretation of microstructural features such as grain size, shape, lattice orientation and the occurrence of subgrain boundaries can help us to follow these processes and to improve our understanding of ice rheology. Polarized light microscopy experienced a quick development in the last decade. A new generation of automatic fabric analyzers enables to measure c-axis orientations in µm-resolution. This high amount and quality of fabric data motivates to apply digital-image-processing routines (DIP) for the recognition and quantification of microstructural patterns. Here we present a study on grain boundaries based on the acquisition of more than 700 fabric images recorded along the NEEM ice core (Greenland). Geometrical characteristics of grain boundaries are studied as well as their cross-sectional orientations in relation to the c-axis orientations of the corresponding adjacent grains. We could follow the evolution from the initial N-type and P-type low-angle boundaries (Weikusat et al., 2011) to high angle boundaries during rotation recrystallization. In agreement with some previous studies we confirm that the established three-stage-recrystallization model may be an oversimplification. According to our results, rotation recrystallization as well as grain boundary migration are actually present in all depths with varying intensities at NEEM. I. Weikusat, A. Miyamoto, S. H. Faria, S. Kipfstuhl, N. Azuma, and T. Hondoh: Subgrain boundaries in Antarctic ice quantified by X-ray Laue diffraction. J. Glaciol., 57(201):85-94, 2011. doi: 10013/epic.36402.

  8. Worker hazards associated with the use of grain vacuum systems.

    PubMed

    Field, W E; Heber, D J; Riedel, S M; Wettschurack, S W; Roberts, M J; Grafft, L J

    2014-07-01

    Over the past two decades, there has been more widespread use of pneumatic handling of grain at commercial grain storage facilities and on farms as these operations have increased grain storage capacity and handle larger volumes of grain and feed In some cases, manufacturers have suggested that the use of these systems is a safer alternative to removing residual grain manually in conjunction with the use of sweep augers. The use of grain vacuum systems has also been increasingly documented as a strategy in responding to grain storage fires and human entrapment and engulfment in flowing grain. With greater utilization of these machines have come reports of entrapments and engulfments. This article summarizes 27 such documented incidents, including 21 fatalities, that resulted from the use of portable grain vacuum systems. It includes specific recommendations for engineering, educational, and regulatory strategies to reduce the risks associated with the use of these systems. PMID:25174148

  9. A continuum theory of grain size evolution and damage

    NASA Astrophysics Data System (ADS)

    Ricard, Y.; Bercovici, D.

    2009-01-01

    Lithospheric shear localization, as occurs in the formation of tectonic plate boundaries, is often associated with diminished grain size (e.g., mylonites). Grain size reduction is typically attributed to dynamic recrystallization; however, theoretical models of shear localization arising from this hypothesis are problematic because (1) they require the simultaneous action of two creep mechanisms (diffusion and dislocation creep) that occur in different deformation regimes (i.e., in grain size stress space) and (2) the grain growth ("healing") laws employed by these models are derived from normal grain growth or coarsening theory, which are valid in the absence of deformation, although the shear localization setting itself requires deformation. Here we present a new first principles grained-continuum theory, which accounts for both coarsening and damage-induced grain size reduction in a monomineralic assemblage undergoing irrecoverable deformation. Damage per se is the generic process for generation of microcracks, defects, dislocations (including recrystallization), subgrains, nuclei, and cataclastic breakdown of grains. The theory contains coupled macroscopic continuum mechanical and grain-scale statistical components. The continuum level of the theory considers standard mass, momentum, and energy conservation, as well as entropy production, on a statistically averaged grained continuum. The grain-scale element of the theory describes both the evolution of the grain size distribution and mechanisms for both continuous grain growth and discontinuous grain fracture and coalescence. The continuous and discontinuous processes of grain size variation are prescribed by nonequilibrium thermodynamics (in particular, the treatment of entropy production provides the phenomenological laws for grain growth and reduction); grain size evolution thus incorporates the free energy differences between grains, including both grain boundary surface energy (which controls coarsening

  10. On the interaction of solutes with grain boundaries

    DOE PAGESBeta

    Dingreville, Remi Philippe Michel; Berbenni, Stephane

    2015-11-01

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

  11. On the interaction of solutes with grain boundaries

    SciTech Connect

    Dingreville, Remi Philippe Michel; Berbenni, Stephane

    2015-11-01

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

  12. 4-D XRD for strain in many grains using triangulation

    SciTech Connect

    Bale, Hrishikesh A.; Hanan, Jay C.; Tamura, Nobumichi

    2006-12-31

    Determination of the strains in a polycrystalline materialusing 4-D XRD reveals sub-grain and grain-to-grain behavior as a functionof stress. Here 4-D XRD involves an experimental procedure usingpolychromatic micro-beam X-radiation (micro-Laue) to characterizepolycrystalline materials in spatial location as well as with increasingstress. The in-situ tensile loading experiment measured strain in a modelaluminum-sapphire metal matrix composite using the Advanced Light Source,Beam-line 7.3.3. Micro-Laue resolves individual grains in thepolycrystalline matrix. Results obtained from a list of grains sorted bycrystallographic orientation depict the strain states within and amongindividual grains. Locating the grain positions in the planeperpendicular to the incident beam is trivial. However, determining theexact location of grains within a 3-D space is challenging. Determiningthe depth of the grains within the matrix (along the beam direction)involved a triangulation method tracing individual rays that producespots on the CCD back to the point of origin. Triangulation wasexperimentally implemented by simulating a 3-D detector capturingmultiple diffraction images while increasing the camera to sampledistance. Hence by observing the intersection of rays from multiple spotsbelonging to the corresponding grain, depth is calculated. Depthresolution is a function of the number of images collected, grain to beamsize ratio, and the pixel resolution of the CCD. The 4DXRD methodprovides grain morphologies, strain behavior of each grain, andinteractions of the matrix grains with each other and the centrallylocated single crystal fiber.

  13. Five-parameter grain boundary analysis of a grain boundary-engineered austenitic stainless steel.

    PubMed

    Jones, R; Randle, V; Engelberg, D; Marrow, T J

    2009-03-01

    Two different grain boundary engineering processing routes for type 304 austenitic stainless steel have been compared. The processing routes involve the application of a small level of strain (5%) through either cold rolling or uni-axial tensile straining followed by high-temperature annealing. Electron backscatter diffraction and orientation mapping have been used to measure the proportions of Sigma3(n) boundary types (in coincidence site lattice notation) and degree of random boundary break-up, in order to gain a measure of the success of the two types of grain boundary engineering treatments. The distribution of grain boundary plane crystallography has also been measured and analyzed in detail using the five-parameter stereological method. There were significant differences between the grain boundary population profiles depending on the type of deformation applied. PMID:19250462

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

    MedlinePlus

    ... pastas. Look at the Nutrition Facts labels and ingredients lists to find choices lower in sodium, saturated (solid) ... the word “whole” at the beginning of the ingredients list Some whole-grain ingredients include whole oats, whole- ...

  15. The accumulation and trapping of grains at planet gaps: Effects of grain growth and fragmentation

    NASA Astrophysics Data System (ADS)

    Gonzalez, J.-F.; Laibe, G.; Maddison, S. T.; Pinte, C.; Ménard, F.

    2015-10-01

    We model the dust evolution in protoplanetary disks with full 3D, Smoothed Particle Hydrodynamics (SPH), two-phase (gas+dust) hydrodynamical simulations. The gas+dust dynamics, where aerodynamic drag leads to the vertical settling and radial migration of grains, is consistently treated. In a previous work, we characterized the spatial distribution of non-growing dust grains of different sizes in a disk containing a gap-opening planet and investigated the gap's detectability with the Atacama Large Millimeter/submillimeter Array (ALMA). Here we take into account the effects of grain growth and fragmentation and study their impact on the distribution of solids in the disk. We show that rapid grain growth in the two accumulation zones around planet gaps is strongly affected by fragmentation. We discuss the consequences for ALMA observations.

  16. (Investigations of ultrasonic wave interactions with grain boundaries and grain imperfections)

    SciTech Connect

    Not Available

    1990-01-01

    The main objective of our research is to obtain a better understanding of ultrasonic wave interaction with interfaces in polycrystalline materials. This report discusses two recently developed experimental techniques: scanning acoustic microscope and optical point sensors. As for general wave propagation problems in anisotropic media, four major topics are discussed in separate sections. First, single boundaries between large bicrystals are considered. The reflection and transmission coefficients of such interfaces are calculated for imperfect boundary conditions by using the finite interface stiffness approach. Ultrasonic transmission through multiple-grain structures are investigated by computer simulation based on the statistical evaluation of repeated acoustical wave interactions with individual grain boundaries. The number of grains interacting with the propagating acoustical wave is considered to be high enough to approximate the wave-material interaction as scattering on elastic inhomogeneities. The grain scattering induced attenuation of Rayleigh waves is investigated in polycrystalline materials. 41 refs., 43 figs.

  17. Two-dimensional grain growth in rapidly solidified succinonitrile films

    NASA Astrophysics Data System (ADS)

    Palmer, M.; Rajan, K.; Glicksman, M.; Fradkov, V.; Nordberg, J.

    1995-05-01

    The kinetics and topological mechanisms of normal grain growth have been examined through in situ dynamic studies on rapidly solidified succinonitrile (SCN). The in situ studies allowed for continuous monitoring of the evolution of individual grains during growth. We have assessed the Mullins—Von Neumann topological grain growth law and the Burke—Turnbull parabolic rate law and have determined rate constants that describe grain growth. This work demonstrates that both laws are both obeyed globally and consistently. These in situ studies permit one to follow the unit operations associated with grain growth kinetics. This article demonstrates the usefulness of succinonitrile as a model analog system for studying grain growth.

  18. On the theory of dynamics of dust grain in plasma

    SciTech Connect

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

    2013-03-15

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

  19. The effect of grain source and grain processing on performance of feedlot cattle: a review.

    PubMed

    Owens, F N; Secrist, D S; Hill, W J; Gill, D R

    1997-03-01

    Effects of grain species and grain processing method on DMI, rate and efficiency of gain, and feeding value for cattle fed high concentrate diets were appraised by statistically compiling results from 605 comparisons from feeding trials published in North American journals and experiment station bulletins since 1974. Metabolizable energy (ME) values for each grain and processing method were calculated by quadratic procedures from DMI and animal performance. Averaged across processing methods, ME values for corn, milo, and wheat grain (3.40, 3.22, and 3.46 Mcal/kg DM) fell within 9% of ME estimates from NRC (1996) for beef cattle. In contrast, ME values for barley and oats grain (3.55 and 3.46 Mcal/kg DM) were 24% and 17% greater than NRC (1996) estimates. Compared with the dry rolled forms, high moisture corn and milo resulted in lower ADG and DMI. Compared with dry rolling, either steam rolling or flaking of corn, milo, and wheat decreased DMI without decreasing ADG and improved feed efficiency by 10, 15, and 10%, respectively. Compared with dry rolled grain, steam flaking increased (P < .05) body weight-adjusted ME of corn and milo grain by 15 and 21%, respectively; body weight-adjusted ME for whole corn was 9% greater (P < .05) than for rolled corn grain. Steam flaking was surprisingly effective (13%) at increasing (P < .05) the body weight-adjusted ME of wheat, but steam flaking failed to increase the ME of barley and oats. Higher moisture content of high-moisture corn decreased dry matter intake without depressing ADG and improved efficiency and increased ME of the grain. Compared with steam flakes of moderate thinness, processing milo or barley to a very thin flake tended to reduce ADG and failed to improve feed efficiency. The ideal roughage source and roughage moisture content for maximum ME and ADG varied with grain processing method. Feeding corn silage rather than alfalfa and wet rather than dry roughage depressed (P < .01) ADG of cattle and reduced (P

  20. Grain boundary motion and grain rotation in aluminum bicrystals: recent experiments and simulations

    NASA Astrophysics Data System (ADS)

    Molodov, D. A.; Barrales-Mora, L. A.; Brandenburg, J.-E.

    2015-08-01

    The results of experimental and computational efforts over recent years to study the motion of geometrically different grain boundaries and grain rotation under various driving forces are briefly reviewed. Novel in-situ measuring techniques based on orientation contrast imaging and applied simulation techniques are described. The experimental results obtained on specially grown aluminum bicrystals are presented and discussed. Particularly, the faceting and migration behavior of low angle grain boundaries under the curvature force is addressed. In contrast to the pure tilt boundaries, which remained flat/faceted and immobile during annealing at elevated temperatures, mixed tilt-twist boundaries readily assumed a curved shape and steadily moved under the capillary force. Computational analysis revealed that this behavior is due to the inclinational anisotropy of grain boundary energy, which in turn depends on boundary geometry. The shape evolution and shrinkage kinetics of cylindrical grains with different tilt and mixed boundaries were studied by molecular dynamics simulations. The mobility of low angle <100> boundaries with misorientation angles higher than 10°, obtained by both the experiments and simulations, was found not to differ from that of the high angle boundaries, but decreases essentially with further decrease of misorientation. The shape evolution of the embedded grains in simulations was found to relate directly to results of the energy computations. Further simulation results revealed that the shrinkage of grains with pure tilt boundaries is accompanied by grain rotation. In contrast, grains with the tilt-twist boundaries composed of dislocations with the mixed edge-screw character do not rotate during their shrinkage. Stress driven boundary migration in aluminium bicrystals was observed to be coupled to a tangential translation of the grains. The activation enthalpy of high angle boundary migration was found to vary non-monotonically with

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

    PubMed

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

    2016-04-01

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

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

    PubMed Central

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

    2016-01-01

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

  3. Directional grain growth from anisotropic kinetic roughening of grain boundaries in sheared colloidal crystals

    PubMed Central

    Gokhale, Shreyas; Nagamanasa, K. Hima; Santhosh, V.; Sood, A. K.; Ganapathy, Rajesh

    2012-01-01

    The fabrication of functional materials via grain growth engineering implicitly relies on altering the mobilities of grain boundaries (GBs) by applying external fields. Although computer simulations have alluded to kinetic roughening as a potential mechanism for modifying GB mobilities, its implications for grain growth have remained largely unexplored owing to difficulties in bridging the widely separated length and time scales. Here, by imaging GB particle dynamics as well as grain network evolution under shear, we present direct evidence for kinetic roughening of GBs and unravel its connection to grain growth in driven colloidal polycrystals. The capillary fluctuation method allows us to quantitatively extract shear-dependent effective mobilities. Remarkably, our experiments reveal that for sufficiently large strains, GBs with normals parallel to shear undergo preferential kinetic roughening, resulting in anisotropic enhancement of effective mobilities and hence directional grain growth. Single-particle level analysis shows that the mobility anisotropy emerges from strain-induced directional enhancement of activated particle hops normal to the GB plane. We expect our results to influence materials fabrication strategies for atomic and block copolymeric polycrystals as well. PMID:23169661

  4. Crossover Fields in Grain-Boundary Flux Pinning in Magnesium Diboride Films with Columnar Grains

    NASA Astrophysics Data System (ADS)

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

    We studied temperature and magnetic-field dependence of grain boundary pinning effect in MgB2 films with columnar grains by measuring the angular dependence of the resistivity and the critical current density (Jc). MgB2 films grown by using a hybrid physical chemical vapor deposition method under appropriate conditions exhibit a peculiar columnar growth with their columns oriented along the c axis. The pinning effect by grain boundaries was manifested in the comparable or even higher Jc for magnetic fields (H) parallel to the c axis (H‖c) than that for fields parallel to the ab plane (H‖ab) below certain temperature-dependent crossover fields. The crossover field, Bcr, was around 1.6 T at 5 K and decreased to around 0.9 T at 30 K depending weakly on the sample characters, and Bcr lay well below the upper critical fields in the phase diagram. Above Bcr, Jc for H‖c decreased very rapidly. The vortex spacing at Bcr was closely correlated with the temperature dependence of the penetration depth, indicating that the degree of the vortex-vortex overlap is an important parameter to determine the number of vortices allowed per unit length of grain boundaries. Thus, Bcr was thought to demarcate the accommodation capability of flux lines by the grain boundaries, and a rapid decrease of Jc above Bcr was ascribed to flux motion of the less strongly pinned vortices located away from the grain boundaries.

  5. Genetic Dissection of Grain Size and Grain Number Trade-Offs in CIMMYT Wheat Germplasm

    PubMed Central

    Griffiths, Simon; Wingen, Luzie; Pietragalla, Julian; Garcia, Guillermo; Hasan, Ahmed; Miralles, Daniel; Calderini, Daniel F.; Ankleshwaria, Jignaben Bipinchandra; Waite, Michelle Leverington; Simmonds, James; Snape, John; Reynolds, Matthew

    2015-01-01

    Grain weight (GW) and number per unit area of land (GN) are the primary components of grain yield in wheat. In segregating populations both yield components often show a negative correlation among themselves. Here we use a recombinant doubled haploid population of 105 individuals developed from the CIMMYT varieties Weebill and Bacanora to understand the relative contribution of these components to grain yield and their interaction with each other. Weebill was chosen for its high GW and Bacanora for high GN. The population was phenotyped in Mexico, Argentina, Chile and the UK. Two loci influencing grain yield were indicated on 1B and 7B after QTL analysis. Weebill contributed the increasing alleles. The 1B effect, which is probably caused by to the 1BL.1RS rye introgression in Bacanora, was a result of increased GN, whereas, the 7B QTL controls GW. We concluded that increased in GW from Weebill 7B allele is not accompanied by a significant reduction in grain number. The extent of the GW and GN trade-off is reduced. This makes this locus an attractive target for marker assisted selection to develop high yielding bold grain varieties like Weebill. AMMI analysis was used to show that the 7B Weebill allele appears to contribute to yield stability. PMID:25775191

  6. The effects of grain size and grain boundary characteristics on the thermal conductivity of nanocrystalline diamond

    NASA Astrophysics Data System (ADS)

    Spiteri, David; Anaya, Julian; Kuball, Martin

    2016-02-01

    Molecular dynamics simulation was used to study the effects of each grain dimension and of grain boundary characteristics on the inter-grain thermal boundary resistance (TBR) and intragrain thermal conductivity of nanocrystalline diamond. The effect of the grain boundaries perpendicular to the heat flow was studied using a multiple slab configuration, which greatly reduced the artifacts associated with the heat source/sink. The TBR between the slabs was found to be more sensitive to the atomic arrangement at the boundary than to the tilt angle between the slabs. When the atomic arrangement at the interface was altered from the minimum energy configuration, the TBR increased by a factor of three, suggesting that a sub-optimal interface quality between the grains could play a large role in reducing the thermal conductivity of nanocrystalline diamond. The thermal conductivity between the boundaries was found to be similar to the bulk value, even when the boundaries were only 25 nm apart. The effect of grain boundaries parallel to the heat flow was found to have a large dependence on the microstructural details. Parallel boundaries which were 2 nm apart reduced the thermal conductivity of defect-free diamond by between one third and a factor of ten.

  7. Genetic dissection of grain size and grain number trade-offs in CIMMYT wheat germplasm.

    PubMed

    Griffiths, Simon; Wingen, Luzie; Pietragalla, Julian; Garcia, Guillermo; Hasan, Ahmed; Miralles, Daniel; Calderini, Daniel F; Ankleshwaria, Jignaben Bipinchandra; Waite, Michelle Leverington; Simmonds, James; Snape, John; Reynolds, Matthew

    2015-01-01

    Grain weight (GW) and number per unit area of land (GN) are the primary components of grain yield in wheat. In segregating populations both yield components often show a negative correlation among themselves. Here we use a recombinant doubled haploid population of 105 individuals developed from the CIMMYT varieties Weebill and Bacanora to understand the relative contribution of these components to grain yield and their interaction with each other. Weebill was chosen for its high GW and Bacanora for high GN. The population was phenotyped in Mexico, Argentina, Chile and the UK. Two loci influencing grain yield were indicated on 1B and 7B after QTL analysis. Weebill contributed the increasing alleles. The 1B effect, which is probably caused by to the 1BL.1RS rye introgression in Bacanora, was a result of increased GN, whereas, the 7B QTL controls GW. We concluded that increased in GW from Weebill 7B allele is not accompanied by a significant reduction in grain number. The extent of the GW and GN trade-off is reduced. This makes this locus an attractive target for marker assisted selection to develop high yielding bold grain varieties like Weebill. AMMI analysis was used to show that the 7B Weebill allele appears to contribute to yield stability. PMID:25775191

  8. GrainGenes 2.0. an improved resource for the small-grains community.

    PubMed

    Carollo, Victoria; Matthews, David E; Lazo, Gerard R; Blake, Thomas K; Hummel, David D; Lui, Nancy; Hane, David L; Anderson, Olin D

    2005-10-01

    GrainGenes (http://wheat.pw.usda.gov) is an international database for genetic and genomic information about Triticeae species (wheat [Triticum aestivum], barley [Hordeum vulgare], rye [Secale cereale], and their wild relatives) and oat (Avena sativa) and its wild relatives. A major strength of the GrainGenes project is the interaction of the curators with database users in the research community, placing GrainGenes as both a data repository and information hub. The primary intensively curated data classes are genetic and physical maps, probes used for mapping, classical genes, quantitative trait loci, and contact information for Triticeae and oat scientists. Curation of these classes involves important contributions from the GrainGenes community, both as primary data sources and reviewers of published data. Other partially automated data classes include literature references, sequences, and links to other databases. Beyond the GrainGenes database per se, the Web site incorporates other more specific databases, informational topics, and downloadable files. For example, unique BLAST datasets of sequences applicable to Triticeae research include mapped wheat expressed sequence tags, expressed sequence tag-derived simple sequence repeats, and repetitive sequences. In 2004, the GrainGenes project migrated from the AceDB database and separate Web site to an integrated relational database and Internet resource, a major step forward in database delivery. The process of this migration and its impacts on database curation and maintenance are described, and a perspective on how a genomic database can expedite research and crop improvement is provided. PMID:16219925

  9. Abnormal grain growth in AISI 304L stainless steel

    SciTech Connect

    Shirdel, M.; Mirzadeh, H.; Parsa, M.H.

    2014-11-15

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

  10. Coarse-graining Landau-Lifshitz damping

    NASA Astrophysics Data System (ADS)

    Feng, Xuebing; Visscher, P. B.

    2001-06-01

    High speed switching in magnetic materials is usually studied with the Landau-Lifshitz (LL) equation, which describes damping through a phenomenological coefficient. The results of micromagnetic calculations based on the LL equation have been observed to depend strongly on the cell size. We take a coarse-graining or renormalization-group approach to this cell size dependence: from a simulation using cell size L, we look at the dynamics of a cell of size 2L and determine an effective damping coefficient that describes the larger-scale dynamics. This can be thought of as a Green-Kubo calculation of the effective damping coefficient. In principle, this makes it possible to coarse grain from the atomic scale to determine the micromagnetic damping coefficient.

  11. Superfluidity of grain boundaries and supersolid behavior

    NASA Astrophysics Data System (ADS)

    Balibar, Sebastien

    2007-03-01

    We have found that, at the liquid-solid equilibrium pressure Pm, supersolid behavior is due to the superfluidity of grain boundaries in solid helium [1]. After describing this experiment and reviewing some of the related theoretical work [2], we discuss the possibility that , at larger pressure (P > Pm), grain boundaries could also explain the supersolid behavior which was observed with torsional oscillators [3-6]. [1] S. Sasaki, R. Ishiguro, F. Caupin, H.J. Maris, and S. Balibar, Science 313, 1098 (2006)[2] E. Burovski, E. Kozik, A. Kuklov, N. Prokof'ev, and B. Svistunov, Phys. Rev. Lett. 94, 165301 (2005)[3] E. Kim and M.H. Chan, Nature 427, 225 (2004)[4] E. Kim and M.H. Chan, Science 305, 1941 (2004)[5] A.S.C. Rittner and J.D. Reppy, Phys. Rev. Lett. 97, 165301 (2006)[6] K. Shirahama, Bull. Am. Phys. Soc. 51, 302 (2006)

  12. GROWTH OF GRAINS IN BROWN DWARF DISKS

    SciTech Connect

    Meru, Farzana; Galvagni, Marina; Olczak, Christoph

    2013-09-01

    We perform coagulation and fragmentation simulations using the new physically motivated model by Garaud et al. to determine growth locally in brown dwarf disks. We show that large grains can grow and that if brown dwarf disks are scaled-down versions of T Tauri disks (in terms of stellar mass, disk mass, and disk radius) growth at an equivalent location with respect to the disk truncation radius can occur to the same size in both disks. We show that similar growth occurs because the collisional timescales in the two disks are comparable. Our model may therefore potentially explain the recent observations of grain growth to millimeter sizes in brown dwarf disks, as seen in T Tauri disks.

  13. Sublimating grains model of cometary coma.

    NASA Astrophysics Data System (ADS)

    Faggi, S.; Tozzi, G. P.; Brucato, J. R.

    Billion years of space weathering produces a crust of organic matter (see e.g. Kanuchova et al. 2012) that will be released when a comet enter for the first time in the inner Solar System. New comets, coming form the Oort Colud at their first passage close to the Sun, are particularly important because they are not differentiated by the Solar radiation and they are supposed to have a large quantity of ice organic matter close to the surface. When a comet approach to the Sun, its activity is driven by the sublimation of these nucleus ices: if the heliocentric distances, R_H , is greater than 3 AU the sublimation of CO and CO_2 ices is the main source of comet activity, otherwise at shorter distances, the sublimation of water become the most important mechanism of activity. These gases, escaping from the nucleus, drag in the coma grains that can be refractory dust (silicates, carbon), water ice and/or organic ices. Oort comets at their first passage in the inner Solar System, should produce an halo of organic or water icy particles. Our group has been monitoring new, inbound, bright Oort comets (C/2011 F1, C/2012 S1, C/2012 K1, C/2013 V5, C/2012 F3, C/2013 US10, C/2013 X1) to search for these icy grains. The method consists in detecting the cloud of sublimating grains in the inner coma by using the Sigma Af function (Tozzi et al. 2007) directly from images. However this over-population of grains, beside the sublimation, can be also due to short time activity (outburst) or too big grains expanding at very slow velocity, as it has been found in comet 67P/C-G (Tozzi eta al, 2011, A&A, 531, 54). To disentangle between the phenomena it is necessary to monitor the comet both at short timescale, for the outbursts (by repeating the observations after few nights), and at long term (weeks-months). If the cloud does not expand with the decreasing of the heliocentric distance there is high probability that we are in presence of organic and/or water ice grains. We can disentangle

  14. The Energy of Olivine Grain Boundaries Deduced from Grain Boundary Frequency Analyses

    NASA Astrophysics Data System (ADS)

    Marquardt, K.; Rohrer, G. S.

    2015-12-01

    The properties of grain boundaries strongly differ from those of the crystal lattice, and there is growing evidence that the presence of grain boundaries influence detected geophysical signals such as electrical conductivity and seismic velocities especially in aggregates with a LPO that favours the alignment of specific grain boundaries. However, neither the anisotropic frequency or energy distribution of grain boundary networks are understood in olivine dominated aggregates, neither with nor without LPO. We used electron backscatter diffraction, EBSD to detect the orientations of over 1.4x104 grains corresponding to roughly 5000mm length of grain boundary separating them. Subsequently we used a stereological approach to determine the grain boundary character distribution, GBCD, defined as the relative areas of grain boundaries of different types, distinguished by their five degrees of freedom (Rohrer, 2007). The grain boundary planes showed a preference for low index planes, which is in agreement with recent findings on other materials (e.g. MgO, TiO2, SrTiO3, MgAl2O4). However, our inferred surface energies are controversial with respect to previously simulated surface energies (Watson et al., 1997; de Leeuw et al., 2000; Gurmani et al., 2011). We find that the principal crystallographic planes have the lowest energies and that at 60° misorientation specific grain boundaries with common [100] axis of misorientation are favored compared to 60° misorientations about random axis of rotation. This seems to support the results of (Faul and Fitz Gerald, 1999), even though our data imply that 90°/[001] (100)(010) should be even less favorable for the propagation of melt films. These differences and similarities will be discussed with respect to the different methods and their limitations. References: Faul U. H. and Fitz Gerald J. D. (1999) Phys. Chem. Miner. 26, 187-197. Gurmani S. F. et al. (2011). J. Geophys. Res. 116, B12209. De Leeuw N. H. et al. (2000) Phys

  15. Cytoplasm affects grain weight and filled-grain ratio in indica rice

    PubMed Central

    2011-01-01

    Background Cytoplasmic effects on agronomic traits -involving cytoplasmic and nuclear genomes of either different species or different cultivars - are well documented in wheat but have seldom been demonstrated in rice (Oryza sativa L.). To detect cytoplasmic effects, we introgressed the nuclear genomes of three indica cultivars - Guichao 2, Jiangchengkugu, and Dianrui 449 - into the cytoplasms of six indica cultivars - Dijiaowujian, Shenglixian, Zhuzhan, Nantehao, Aizizhan, and Peta. These 18 nuclear substitution lines were evaluated during the winter season of 2005 in Sanya, Hainan, China, and during the summer season of 2006 in Kunming, Yunnan, China. The effects of 6 cytoplasm sources, 3 nucleus sources, 2 locations and their interactions were estimated for plant height, panicle length, panicle number per plant, spikelet number per panicle, grain weight, filled-grain ratio, and yield per plot. Results For five of the seven traits, analysis of variance showed that there were no significant cytoplasmic effects or interactions involving cytoplasmic effects. The effect of cytoplasm on 1000-grain weight was highly significant. Mean 1000-grain weight over the two locations in four of the six cytoplasms clustered close to the overall mean, whereas plants with Nantehao cytoplasm had a high, and those with Peta cytoplasm a low mean grain weight. There was a highly significant three-way interaction affecting filled-grain ratio. At Sanya, cytoplasms varied in very narrow ranges within nuclear backgrounds. Strong cytoplasmic effects were observed only at Kunming and in only two of the three nuclear backgrounds; in the Jianchenkugu nuclear background, there was no evidence of strong cytoplasmic effects at either location. In the Dianrui 449 and Guichao 2 nuclear background evaluated at Kunming, filled-grain ratios of the six cytoplasms showed striking rank shifts Conclusions We detected cytoplasmic variation for two agronomically important traits in indica rice. The

  16. Grain-scale Dynamics in Explosives

    SciTech Connect

    Reaugh, J E

    2002-09-30

    High explosives can have reactions to external stimuli that range from mild pressure bursts to full detonation. The ability to predict these responses is important for understanding the performance as well as the safety and reliability of these important materials. At present, we have only relatively simple phenomenological computational models for the behavior of high explosives under these conditions. These models are limited by the assumption that the explosive can be treated as homogeneous. In reality the explosive is a highly heterogeneous composite of irregular crystallites and plastic binder. The heterogeneous nature of explosives is responsible for many of their unique mechanical and chemical properties. We use computational models to simulate the response of explosives to external mechanical stimuli at the grain-scale level. The ultimate goal of this work is to understand the detailed processes involved with the material response, so that we can develop realistic material models, which can be used in a hydrodynamics/multi-physics code to model real systems. The new material models will provide a more realistic description of the explosive system during the most critical period of ignition and initiation. The focus of this work is to use the results of grain-scale simulations to develop an advanced macroscopic reactive flow model that is consistent with our understanding of the grain-scale details, and that can incorporate such information quantitatively. The objective is to connect changes to observed properties of the explosive (grain size distribution, binder thickness distribution, void shape, size, and separation distribution, binder mechanical properties, etc.) with predictions of the resulting sensitivity and performance.

  17. Genetic engineering for high methionine grain legumes.

    PubMed

    Müntz, K; Christov, V; Saalbach, G; Saalbach, I; Waddell, D; Pickardt, T; Schieder, O; Wüstenhagen, T

    1998-08-01

    Methionine (Met) is the primary limiting essential amino acid in grain legumes. The imbalance in amino acid composition restricts their biological value (BV) to 55 to 75% of that of animal protein. So far improvement of the BV could not be achieved by conventional breeding. Therefore, genetic engineering was employed by several laboratories to resolve the problem. Three strategies have been followed. A) Engineering for increased free Met levels; B) engineering of endogenous storage proteins with increased numbers of Met residues; C) transfer of foreign genes encoding Met-rich proteins, e.g. the Brazil nut 2S albumin (BNA) and its homologue from sunflower, into grain legumes. The latter strategy turned out to be most promising. In all cases the gene was put under the control of a developmentally regulated seed specific promoter and transferred into grain legumes using the bacterial Agrobacterium tumefaciens-system. Integration into and copy numbers in the plant genome as well as Mendelian inheritance and gene dosage effects were verified. After correct precursor processing the mature 2S albumin was intracellularly deposited in protein bodies which are part of the vacuolar compartment. The foreign protein amounted to 5 to 10% of the total seed protein in the best transgenic lines of narbon bean (Vicia narbonensis L., used in the authors' laboratories), lupins (Lupinus angustifolius L., used in CSIRO, Australia), and soybean (Glycine max (L.) Merr., used by Pioneer Hi-Bred, Inc., USA). In the narbon bean the increase of Met was directly related to the amount of 2S albumin in the transgenic seeds, but in soybean it remained below the theoretically expected value. Nevertheless, trangenic soybean reached 100%, whereas narbon bean and lupins reached approximately 80% of the FAO-standard for nutritionally balanced food proteins. These results document that the Met problem of grain legumes can be resolved by genetic engineering. PMID:9739551

  18. A new model of composite interstellar grains

    NASA Astrophysics Data System (ADS)

    Voshchinnikov, N. V.; Il'in, V. B.; Henning, Th.; Dubkova, D. N.

    The approach to model composite interstellar dust grains using the exact solution to the light scattering problem for multi-layered spheras suggested by Voshchinnikov & Mathis (1999) is further developed. Heterogeneous scatterers are represented by particles with very large numof shells each including a homogeneous layer per material considered (here amorphous carbon, astronomical silicate and vacuum). It is demonstrated that the scattering characteristics (cross-sections, albedo, asymmetry factor, etc.) well converge with the increase of the number of shells (layers) and each of the characteristics has the same limit independent of the layer order in the shells. The limit obviously corresponds to composite particles consisting of several well mixed materials. However, our results indicate that layered particles with even a few shells (layers) have the characteristics close enough to these limits. The applicability of the effective medium theory (EMT) mostly utilized earlier to approximate inhomogeneous interstellar grains is examined on the base of the model. It is shown that the used EMT rules generally have the accuracy of several percents in the whole range of particle sizes provided the porosity does not exceed about 50%. For larger porosity, the rules give wrong results. Using the model we reanalyze basics of interpretation of various manifestations of cosmic dust --- interstellar extinction, scattered radiation, infrared radiation, radiation pressure, etc. It is found that an increase of porosity typically leads to the increase of cross-sections, albedo and the sweeping efficiency of small grains as well as to the decrease of dust temperature and the strength of infrared bands (the EMT fails to produce these effects). We also conclude that pure iron even in negligible amount (<˜1 % by the volume fractis unlikely to form a layer on or inside a grain because of peculiar absorption of radiation by such particles. As an example of the potential of the model, it

  19. Nature of dust grains in comets

    NASA Technical Reports Server (NTRS)

    Swamy, K. S. Krishna; Shah, G. A.

    1988-01-01

    The observed reddening in the wavelength range 0.26-2.25 microns for comae of several comets can be represented quite well with model grains having real and imaginary parts of refractive index, m = m-prime - im-double prime, given by m-prime of about 1.38 and m-double prime of about 0.039, respectively. It is also possible to explain the observations of linear polarization and geometric albedo of comet comae.

  20. Grain Boundaries In Thin Film Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Bougher, Cortney; Huston, Shawn; Lees, Eitan; Ward, Jeremy; Obaid, Abdul; Loth, Marsha; Anthony, John; Jurchescu, Oana; Conrad, Brad

    2012-02-01

    We utilize conductive atomic force microscopy (C-AFM) and tunneling atomic force microscopy (TUNA) to characterize dynamics of electronic transport across fluorinated triethylsilylethynyl anthradithiophene (diF-TES ADT) grain boundaries. The crystallization of diF-TES ADT grown on SiO2 will be discussed and related to comparable molecules. The resulting voltage drop between individual crystals as a function of dopants will be discussed in terms of charge transport models and compared to current device work.

  1. Ochratoxin A in several grains in Iran.

    PubMed

    Beheshti, Hamed Reza; Asadi, Mohammad

    2013-01-01

    Ochratoxin A content in 100 grain and derived products were determined by high-performance liquid chromatography with immunoaffinity column clean-up and fluorometric detection. Ochratoxin A was detected in 32% of green gram, 13.3% of chickpea, 10% of lentil and 17.5% of wheat flour. Ochratoxin contamination was below the regulatory limits of the European Union and of Iran. Recovery was 97% and the limit of detection was 0.12 ng g⁻¹. PMID:24779905

  2. Exposure to grain dust in Great Britain.

    PubMed

    Spankie, Sally; Cherrie, John W

    2012-01-01

    Airborne grain dust is a complex mixture of fragments of organic material from grain, plus mineral matter from soil, and possible insect, fungal, or bacterial contamination or their toxic products, such as endotoxin. In the 1990s, grain workers in Britain were frequently exposed to inhalable dust >10 mg.m(-3) (8 h), with particularly high exposures being found at terminals where grain was imported or exported and in drying operations (personal exposure typically approximately 20 mg.m(-3)). Since then, the industry has made substantial progress in improving the control of airborne dust through better-designed processes, increased automation, and an improved focus on product quality. We have used information from the published scientific literature and a small survey of industry representatives to estimate current exposure levels. These data suggest that current long-term exposure to inhalable dust for most workers is on average less than approximately 3 mg.m(-3), with perhaps 15-20% of individual personal exposures being >10 mg.m(-3). There are no published data from Britain on short-term exposure during cleaning and other tasks. We have estimated average levels for a range of tasks and judge that the highest levels, for example during some cleaning activities and certain process tasks such as loading and packing, are probably approximately10 mg.m(-3). Endotoxin levels were judged likely to be <10⁴ EU m(-3) throughout the industry provided inhalable dust levels are <10 mg.m(-3). There are no published exposure data on mycotoxin, respirable crystalline silica, and mite contamination but these are not considered to present widespread problems in the British industry. Further research should be carried out to confirm these findings. PMID:21976307

  3. Synthesis of fine-grained TATB

    DOEpatents

    Lee, Kien-Yin; Kennedy, James E.

    2003-04-15

    A method for producing fine-grained triamino-trinitrobenzene (TATB) powders having improved detonation-spreading performance and hence increased shock sensitivity when compared with that for ultrafine TATB is described. A single-step, sonochemical amination of trichloro-trinitrobenzene using ammonium hydroxide solution in a sealed vessel yields TATB having approximately 6 .mu.m median particle diameter and increased shock sensitivity.

  4. Measuring Crack Length in Coarse Grain Ceramics

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Ghosn, Louis J.

    2010-01-01

    Due to a coarse grain structure, crack lengths in precracked spinel specimens could not be measured optically, so the crack lengths and fracture toughness were estimated by strain gage measurements. An expression was developed via finite element analysis to correlate the measured strain with crack length in four-point flexure. The fracture toughness estimated by the strain gaged samples and another standardized method were in agreement.

  5. Grain-growth law during Stage 1 sintering of materials

    NASA Astrophysics Data System (ADS)

    He, Zeming; Ma, J.

    2002-09-01

    This work investigates the grain-growth behaviour of powder compact during Stage 1 sintering (<90{%} theoretical density). It is widely accepted that grain size is an important state variable in the constitutive modelling in material sintering. However, it is noted that all the existing grain-growth laws proposed in the literature do not incorporate the effect of externally applied stress independently. In this work, a grain-growth law with externally applied stress as a variable was proposed. Alumina powders were forge-sintered at different applied stresses to examine the proposed grain-growth relationship. The proposed grain-growth law was then applied to model the grain-growth process on the sinter forging of tool steel. It is shown that the present proposed grain-growth law provides a good description on the experimental results.

  6. Grain boundary and triple junction diffusion in nanocrystalline copper

    SciTech Connect

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

    2014-09-07

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

  7. Experimental observations of stress-driven grain boundary migration.

    PubMed

    Rupert, T J; Gianola, D S; Gan, Y; Hemker, K J

    2009-12-18

    In crystalline materials, plastic deformation occurs by the motion of dislocations, and the regions between individual crystallites, called grain boundaries, act as obstacles to dislocation motion. Grain boundaries are widely envisaged to be mechanically static structures, but this report outlines an experimental investigation of stress-driven grain boundary migration manifested as grain growth in nanocrystalline aluminum thin films. Specimens fabricated with specially designed stress and strain concentrators are used to uncover the relative importance of these parameters on grain growth. In contrast to traditional descriptions of grain boundaries as stationary obstacles to dislocation-based plasticity, the results of this study indicate that shear stresses drive grain boundaries to move in a manner consistent with recent molecular dynamics simulations and theoretical predictions of coupled grain boundary migration. PMID:20019286

  8. Advanced Biorefinery of Distriller's Grain and Corn Stover Blends

    SciTech Connect

    2006-04-01

    Fuel ethanol can be produced via the dry milling process, which converts corn grain to ethanol. The co-product, distiller’s grain (DG), is sold as a low-cost, high-protein feed source for livestock.

  9. "Eat Fresh Vegetables, Fruit, and Whole Grain Products"

    MedlinePlus

    ... turn Javascript on. Feature: Diverticulitis "Eat fresh vegetables, fruit, and whole grain products." Past Issues / Winter 2010 ... diverticulitis. I once again eat fresh vegetables and fruit and whole grain products. My two episodes of ...

  10. Grain Refinement of Permanent Mold Cast Copper Base Alloys

    SciTech Connect

    M.Sadayappan; J.P.Thomson; M.Elboujdaini; G.Ping Gu; M. Sahoo

    2005-04-01

    Grain refinement is a well established process for many cast and wrought alloys. The mechanical properties of various alloys could be enhanced by reducing the grain size. Refinement is also known to improve casting characteristics such as fluidity and hot tearing. Grain refinement of copper-base alloys is not widely used, especially in sand casting process. However, in permanent mold casting of copper alloys it is now common to use grain refinement to counteract the problem of severe hot tearing which also improves the pressure tightness of plumbing components. The mechanism of grain refinement in copper-base alloys is not well understood. The issues to be studied include the effect of minor alloy additions on the microstructure, their interaction with the grain refiner, effect of cooling rate, and loss of grain refinement (fading). In this investigation, efforts were made to explore and understand grain refinement of copper alloys, especially in permanent mold casting conditions.

  11. Formation of water on warm dust grains

    NASA Astrophysics Data System (ADS)

    Vidali, Gianfranco; He, Jiao; Shi, Jianming; Hopkins, Tyler; Kaufman, Michael

    2015-08-01

    The early stage of water formation on dust grains in the ISM depends on sticking and retention of atoms and molecules on surfaces of grains. We investigated the interaction of oxygen with amorphous silicates. We find that atomic oxygen is retained on an amorphous silicate surface with a much higher binding energy (1850K ± 90K) than previously estimated (800K). We then used such value in the simulation of the chemical evolution of an interstellar environment - a molecular cloud edge in star-forming regions in Orion exposed to FUV illumination, and found that OH and H2O formation on grains is considerably enhanced while O2 formation is suppressed because of the higher O binding energy. These effects are especially important in dense gas exposed to high FUV fields because of the wider temperature range in which oxygen can reside. Because of the higher binding energy, photodesorption controls the gas phase chemistry. Consequences of this discovery for observations will be discussed.This work is supported by the NSF Astronomy and Astrophysics Division (Grant No.1311958 to GV) and by NASA support for US research with the Herschel Space Observatory (RSA No. 1427170 to MJK).

  12. Therapeutic Effect of Cereal Grains: A Review.

    PubMed

    Singhal, Poonam; Kaushik, Geetanjali

    2016-04-01

    Over the last few decades, life style changes have resulted in drastic increase in the incidence of diabetes all over the world, especially in the developing countries. Oral hypoglycemic agents and insulin form the main stay in controlling diabetes but they have prominent side effects and fail to significantly alter the course of diabetic complications. Appropriate diet and exercise programs that form a part of lifestyle modifications have proven to be greatly effective in the management of this disease. Dietary therapy is showing a bright future in the prevention and treatment of diabetes. Cereal grains which form the staple diet for humans in most of the countries are increasingly being used to treat diabetes and other associated disorders in view of their anti-diabetic and anti-lipidemic potential. Given this background, this paper reviews the possible mechanisms of lowering blood sugar and cholesterol levels possessed by various commonly consumed cereal grains. It is concluded that cereal grains are not only the potential sources of energy but also possess the therapeutic role in preventing metabolic disorders and decreasing the risk factors for cardiovascular and renal diseases. PMID:25746052

  13. Coarse-grained distributions and superstatistics

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri

    2006-01-01

    We show an interesting connection between non-standard (non-Boltzmannian) distribution functions arising in the theory of violent relaxation for collisionless stellar systems [D. Lynden-Bell, Mon. Not. R. Astron. Soc. 136 (1967) 101.] and the notion of superstatistics recently introduced by [Beck and Cohen Physica A 322 (2003) 267]. The common link between these two theories is the emergence of coarse-grained distributions arising out of fine-grained distributions. The coarse-grained distribution functions are written as a superposition of Boltzmann factors weighted by a non-universal function. Even more general distributions can arise in case of incomplete violent relaxation (non-ergodicity). They are stable stationary solutions of the Vlasov equation. We also discuss analogies and differences between the statistical equilibrium state of a multi-components self-gravitating system and the metaequilibrium (or quasi-equilibrium) states of a collisionless stellar system. Finally, we stress the important distinction between entropies, generalized entropies, relative entropies and H-functions. We discuss applications of these ideas in two-dimensional turbulence and for other systems with long-range interactions.

  14. Process for producing large grain cadmium telluride

    DOEpatents

    Hasoon, F.S.; Nelson, A.J.

    1996-01-16

    A process is described for producing a cadmium telluride polycrystalline film having grain sizes greater than about 20 {micro}m. The process comprises providing a substrate upon which cadmium telluride can be deposited and placing that substrate within a vacuum chamber containing a cadmium telluride effusion cell. A polycrystalline film is then deposited on the substrate through the steps of evacuating the vacuum chamber to a pressure of at least 10{sup {minus}6} torr.; heating the effusion cell to a temperature whereat the cell releases stoichiometric amounts of cadmium telluride usable as a molecular beam source for growth of grains on the substrate; heating the substrate to a temperature whereat a stoichiometric film of cadmium telluride can be deposited; and releasing cadmium telluride from the effusion cell for deposition as a film on the substrate. The substrate then is placed in a furnace having an inert gas atmosphere and heated for a sufficient period of time at an annealing temperature whereat cadmium telluride grains on the substrate grow to sizes greater than about 20 {micro}m.

  15. Process for producing large grain cadmium telluride

    DOEpatents

    Hasoon, Falah S.; Nelson, Art J.

    1996-01-01

    A process for producing a cadmium telluride polycrystalline film having grain sizes greater than about 20 .mu.m. The process comprises providing a substrate upon which cadmium telluride can be deposited and placing that substrate within a vacuum chamber containing a cadmium telluride effusion cell. A polycrystalline film is then deposited on the substrate through the steps of evacuating the vacuum chamber to a pressure of at least 10.sup.-6 torr.; heating the effusion cell to a temperature whereat the cell releases stoichiometric amounts of cadmium telluride usable as a molecular beam source for growth of grains on the substrate; heating the substrate to a temperature whereat a stoichiometric film of cadmium telluride can be deposited; and releasing cadmium telluride from the effusion cell for deposition as a film on the substrate. The substrate then is placed in a furnace having an inert gas atmosphere and heated for a sufficient period of time at an annealing temperature whereat cadmium telluride grains on the substrate grow to sizes greater than about 20 .mu.m.

  16. ACCELERATION OF SMALL ASTROPHYSICAL GRAINS DUE TO CHARGE FLUCTUATIONS

    SciTech Connect

    Ivlev, A. V.; Morfill, G. E.; Lazarian, A.; Hoang, Thiem; Tsytovich, V. N.; De Angelis, U.

    2010-11-01

    We discuss a novel mechanism of dust acceleration which may dominate for particles smaller than {approx}0.1 {mu}m. The acceleration is caused by their direct electrostatic interactions arising from fluctuations of grain charges. The energy sources for the acceleration are the irreversible plasma processes occurring on the grain surfaces. We show that this mechanism of charge-fluctuation-induced acceleration likely affects the rate of grain coagulation and shattering of the population of small grains.

  17. Nanoscale abnormal grain growth in (001) epitaxial ceria

    SciTech Connect

    Solovyov, Vyacheslav F.; Develos-Bagarinao, Katherine; Nykypanchuk, Dmytro

    2009-09-01

    X-ray reciprocal-space mapping and atomic force microscopy (AFM) are used to study kinetics and mechanisms of lateral grain growth in epitaxial (001) ceria (CeO{sub 2}) deposited by pulsed laser deposition on (001) yttria-stabilized zirconia (YSZ) and (12 lowbar 10) (r-cut) sapphire. Rate and character of the grain growth during postannealing at 1050 deg. C are found to be strongly dependent on the type of the epitaxial substrate. Films deposited on YSZ exhibit signatures of normal grain growth, which stagnated after the lateral grain size reaches 40 nm, consistent with the grain-boundary pinning by the thermal grooving. In contrast, when r-cut sapphire substrate was used, abnormal (secondary) grain growth is observed. A small population of grains grow to well over 100 nm consuming smaller, <10 nm, grains, thus forming well-defined >100 nm large (001) terminations and rendering the sample single-crystalline quality. The grain growth is accompanied by reduction in lateral rms strain, resulting in a universal grain size--rms strain dependence. Analysis of the AFM and x-ray diffraction data leads to the conclusion that bimodal initial grain population consisting of grains with very different sizes is responsible for initiation of the abnormal growth in (001) CeO{sub 2} films on r-cut sapphire. Due to different surface chemistry, when a YSZ substrate is used, the initial grain distribution is monomodal, therefore only normal growth is active. We demonstrate that a 2.2 deg. miscut of the sapphire substrate eliminates the large-grain population, thus suppressing abnormal grain growth. It is concluded that utilization of abnormal grain growth is a promising way for synthesis of large (001) ceria terminations.

  18. Experimental studies of the structure of grain boundaries

    SciTech Connect

    Sass, S.L.

    1993-04-01

    Goals are to understand factors affecting structure of grain boundaries in intermetallic compounds, understand how solute segregation affects grain boundary structure and causes embrittlement in Fe-base alloys, and explore control of grain boundary properties. Fe and boron-doped Ni[sub 3]Al and NiAl were studied. 7 figs, 1 tab, 18 refs.

  19. Experimental studies of the structure of grain boundaries. Progress report

    SciTech Connect

    Sass, S.L.

    1993-04-01

    Goals are to understand factors affecting structure of grain boundaries in intermetallic compounds, understand how solute segregation affects grain boundary structure and causes embrittlement in Fe-base alloys, and explore control of grain boundary properties. Fe and boron-doped Ni{sub 3}Al and NiAl were studied. 7 figs, 1 tab, 18 refs.

  20. Whole grain foods and health - a Scandinavian perspective.

    PubMed

    Frølich, Wenche; Aman, Per; Tetens, Inge

    2013-01-01

    The food-based dietary guidelines in the Scandinavian countries that recommend an intake of minimum 75 g whole grain per 10 MJ (2,388 kcal) per day are mainly derived from prospective cohort studies where quantitative but little qualitative details are available on whole grain products. The objective of the current paper is to clarify possible differences in nutritional and health effects of the types of whole grain grown and consumed in the Scandinavian countries. A further objective is to substantiate how processing may influence the nutritional value and potential health effects of different whole grains and whole grain foods. The most commonly consumed whole grain cereals in the Scandinavian countries are wheat, rye, and oats with a considerable inter-country variation in the consumption patterns and with barley constituting only a minor role. The chemical composition of these different whole grains and thus the whole grain products consumed vary considerably with regard to the content of macro- and micronutrients and bioactive components. A considerable amount of scientific substantiation shows that processing methods of the whole grains are important for the physiological and health effects of the final whole grain products. Future research should consider the specific properties of each cereal and its processing methods to further identify the uniqueness and health potentials of whole grain products. This would enable the authorities to provide more specific food-based dietary guidelines in relation to whole grain to the benefit of both the food industry and the consumer. PMID:23411562

  1. ESTIMATING DIETARY INTAKE OF ANTIOXIDANTS FROM OATS AND OTHER GRAINS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several large cohort studies have shown that subjects with high consumption of whole grain cereals have significantly lower coronary heart disease. High intakes of whole grain, fruits and vegetables have also been associated with lower risk of some cancers. Apart from dietary fiber, whole grains als...

  2. Automatic monitoring of insect pests in stored grain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Manual sampling of insects in stored grain is a laborious and time consuming process. Automation of grain sampling should help to increase the adoption of stored-grain integrated pest management. To make accurate insect management decisions, managers need to know both the insect species and numbers ...

  3. Ethanol production performance of ozone treated tannin grain sorghum flour

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grain sorghum lines containing tannins have been reported to exhibit increased resistance to drought, birds, mold, preharvest germination, and higher grain yield than non-tannin grain sorghum lines, but tannins have been considered an adverse factor in the utilization of sorghum as a feedstock for b...

  4. Microbial Characterization of Distillers Wet Grains: Results and Challenges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Distillers grains are co-produced with ethanol and carbon dioxide during the production of fuel ethanol from the dry milling and fermentation of corn grain, yet there is little basic microbiological information on these materials. We have characterized the microbiology of distillers wet grains (DWG...

  5. Does whole grain consumption alter gut microbiota and satiety?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This review summarizes recent studies examining whole grain consumption and its effect on gut microbiota and satiety in healthy humans. Both individual whole grain cereals and interventions with combined whole grain cereals were considered. Possible links between the fermentation of non-digestible c...

  6. Whole grain foods and health – a Scandinavian perspective

    PubMed Central

    Frølich, Wenche; Åman, Per; Tetens, Inge

    2013-01-01

    The food-based dietary guidelines in the Scandinavian countries that recommend an intake of minimum 75 g whole grain per 10 MJ (2,388 kcal) per day are mainly derived from prospective cohort studies where quantitative but little qualitative details are available on whole grain products. The objective of the current paper is to clarify possible differences in nutritional and health effects of the types of whole grain grown and consumed in the Scandinavian countries. A further objective is to substantiate how processing may influence the nutritional value and potential health effects of different whole grains and whole grain foods. The most commonly consumed whole grain cereals in the Scandinavian countries are wheat, rye, and oats with a considerable inter-country variation in the consumption patterns and with barley constituting only a minor role. The chemical composition of these different whole grains and thus the whole grain products consumed vary considerably with regard to the content of macro- and micronutrients and bioactive components. A considerable amount of scientific substantiation shows that processing methods of the whole grains are important for the physiological and health effects of the final whole grain products. Future research should consider the specific properties of each cereal and its processing methods to further identify the uniqueness and health potentials of whole grain products. This would enable the authorities to provide more specific food-based dietary guidelines in relation to whole grain to the benefit of both the food industry and the consumer. PMID:23411562

  7. 7 CFR 75.21 - Grain sample inspection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND CERTIFICATION OF QUALITY OF AGRICULTURAL AND VEGETABLE SEEDS Inspection § 75.21 Grain sample inspection. A sample inspection shall be performed by examining official grain samples received from FGIS to... 7 Agriculture 3 2012-01-01 2012-01-01 false Grain sample inspection. 75.21 Section...

  8. 7 CFR 75.21 - Grain sample inspection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND CERTIFICATION OF QUALITY OF AGRICULTURAL AND VEGETABLE SEEDS Inspection § 75.21 Grain sample inspection. A sample inspection shall be performed by examining official grain samples received from FGIS to... 7 Agriculture 3 2014-01-01 2014-01-01 false Grain sample inspection. 75.21 Section...

  9. 7 CFR 75.21 - Grain sample inspection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND CERTIFICATION OF QUALITY OF AGRICULTURAL AND VEGETABLE SEEDS Inspection § 75.21 Grain sample inspection. A sample inspection shall be performed by examining official grain samples received from FGIS to... 7 Agriculture 3 2013-01-01 2013-01-01 false Grain sample inspection. 75.21 Section...

  10. 7 CFR 800.98 - Weighing grain in combined lots.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Weighing grain in combined lots. 800.98 Section 800.98 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS...

  11. 7 CFR 800.16 - Certification requirements for export grain.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Certification requirements for export grain. 800.16 Section 800.16 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE...

  12. 7 CFR 75.21 - Grain sample inspection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Grain sample inspection. 75.21 Section 75.21... AND CERTIFICATION OF QUALITY OF AGRICULTURAL AND VEGETABLE SEEDS Inspection § 75.21 Grain sample inspection. A sample inspection shall be performed by examining official grain samples received from FGIS...

  13. 7 CFR 800.99 - Checkweighing sacked grain.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Checkweighing sacked grain. 800.99 Section 800.99 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS...

  14. 7 CFR 800.30 - Foreign commerce grain business.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Foreign commerce grain business. 800.30 Section 800.30 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS...

  15. 7 CFR 800.99 - Checkweighing sacked grain.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Checkweighing sacked grain. 800.99 Section 800.99 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS...

  16. 7 CFR 810.801 - Definition of mixed grain.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS...

  17. 7 CFR 800.16 - Certification requirements for export grain.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Certification requirements for export grain. 800.16 Section 800.16 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE...

  18. 7 CFR 810.801 - Definition of mixed grain.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Definition of mixed grain. 810.801 Section 810.801 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE OFFICIAL UNITED STATES STANDARDS...

  19. 7 CFR 75.21 - Grain sample inspection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Grain sample inspection. 75.21 Section 75.21... AND CERTIFICATION OF QUALITY OF AGRICULTURAL AND VEGETABLE SEEDS Inspection § 75.21 Grain sample inspection. A sample inspection shall be performed by examining official grain samples received from FGIS...

  20. 7 CFR 800.30 - Foreign commerce grain business.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Foreign commerce grain business. 800.30 Section 800.30 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE GENERAL REGULATIONS...

  1. Oat Grain Density and the Physical Basis of Test Weight

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Test weight or bulk density of oats (Avena sativa L.) has a major influence on the monetary value of oat grain. Test weight can be attributed to grain density and packing efficiency. We have measured oat grain volume and density by a sand displacement method and thus derived the packing factor for s...

  2. Ancient Whole Grain Gluten-free Egg-free Pasta

    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 per serving. This is the only report demonstrating innovative ancient whole grain, gluten-free, egg-fre...

  3. Critical time scale of coarse-graining entropy production

    NASA Astrophysics Data System (ADS)

    Sohn, Jang-il

    2016-04-01

    We study coarse-grained entropy production in an asymmetric random walk system on a periodic one-dimensional lattice. In coarse-grained systems, the original dynamics are unavoidably destroyed, but the coarse-grained entropy production is not hidden below the critical time-scale separation. The hidden entropy production is rapidly increasing near the critical time-scale separation.

  4. Infrared spectra of meteoritic SiC grains

    NASA Astrophysics Data System (ADS)

    Andersen, A. C.; Jäger, C.; Mutschke, H.; Braatz, A.; Clément, D.; Henning, Th.; Jørgensen, U. G.; Ott, U.

    1999-03-01

    We present here the first infrared spectra of meteoritic SiC grains. The mid-infrared transmission spectra of meteoritic SiC grains isolated from the Murchison meteorite were measured in the wavelength range 2.5-16.5 mu m, in order to make available the optical properties of presolar SiC grains. These grains are most likely stellar condensates with an origin predominately in carbon stars. Measurements were performed on two different extractions of presolar SiC from the Murchison meteorite. The two samples show very different spectral appearance due to different grain size distributions. The spectral feature of the smaller meteoritic SiC grains is a relatively broad absorption band found between the longitudinal and transverse lattice vibration modes around 11.3 mu m, supporting the current interpretation about the presence of SiC grains in carbon stars. In contrast to this, the spectral feature of the large (> 5 mu m) grains has an extinction minimum around 10 mu m. The obtained spectra are compared with commercially available SiC grains and the differences are discussed. This comparison shows that the crystal structure (e.g., beta -SiC versus alpha -SiC) of SiC grains plays a minor role on the optical signature of SiC grains compared to e.g. grain size.

  5. FRACTIONATION TECHNIQUES TO CONCENTRATE NUTRIENT STREAMS IN DISTILLERS GRAINS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Corn, the most widely produced feed grain in the United States, accounts for more than 90% of the total value and production of feed grains. It is also used for food, industrial materials, and fuel ethanol production. Distillers grains, the major coproduct from ethanol manufacturing, are used as li...

  6. 76 FR 53717 - Notice of National Grain Car Council Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-29

    ... Surface Transportation Board Notice of National Grain Car Council Meeting AGENCY: Surface Transportation Board. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car Council (NGCC), pursuant to section 10(a)(2) of the Federal...

  7. 77 FR 50763 - Notice of National Grain Car Council Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-22

    ... Surface Transportation Board Notice of National Grain Car Council Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car Council (NGCC), pursuant to section 10(a)(2) of the Federal...

  8. 75 FR 53736 - Notice of National Grain Car Council Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-01

    ... Surface Transportation Board Notice of National Grain Car Council Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car Council (NGCC), pursuant to section 10(a)(2) of the Federal...

  9. 78 FR 52606 - Notice of National Grain Car Council Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-23

    ... Surface Transportation Board Notice of National Grain Car Council Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of National Grain Car Council meeting. SUMMARY: Notice is hereby given of a meeting of the National Grain Car Council (NGCC), pursuant to the Federal Advisory Committee Act, 5...

  10. Grain-to-Grain Compositional Variations and Phase Segregation in Copper-Zinc-Tin-Sulfide Films.

    PubMed

    Alvarez Barragan, Alejandro; Malekpour, Hoda; Exarhos, Stephen; Balandin, Alexander A; Mangolini, Lorenzo

    2016-09-01

    We have performed a rigorous investigation of the structure and composition of individual grains in copper-zinc-tin-sulfide (CZTS) films realized by sulfurization of a sputtered metal stack. Although on average close to the ideal CZTS stoichiometry, elemental analysis shows significant grain-to-grain variations in composition. High-resolution Raman spectroscopy indicates that this is accompanied by grain-to-grain structural variations as well. The intensity from the 337 cm(-1) Raman peak, generally assigned to the kesterite phase of CZTS, remains constant over a large area of the sample. On the other hand, signals from secondary phases at 376 cm(-1) (copper-tin-sulfide) and 351 cm(-1) (zinc-sulfide) show significant variation over the same area. These results confirm the great complexity inherent to this material system. Moreover, structural and compositional variations are recognized in the literature as a factor limiting the efficiency of CZTS photovoltaic devices. This study demonstrates how a seemingly homogeneous CZTS thin film can actually have considerable structural and compositional variations at the microscale, and highlights the need for routine microscale characterization in this material system. PMID:27538122

  11. Supplying materials needed for grain growth characterizations of nano-grained UO2

    SciTech Connect

    Mo, Kun; Miao, Yinbin; Yun, Di; Jamison, Laura M.; Lian, Jie; Yao, Tiankei

    2015-09-30

    This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructure based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize our preliminary synchrotron radiation experiments at APS to determine the grain size of nanograin UO2. The methodology and experimental setup developed in this experiment can directly apply to the proposed in-situ grain growth measurements. The investigation of the grain growth kinetics was conducted based on isothermal annealing and grain growth characterization as functions of duration and temperature. The kinetic parameters such as activation energy for grain growth for UO2 with different stoichiometry are obtained and compared with molecular dynamics (MD) simulations.

  12. Ultrafast analysis of individual grain behavior during grain growth by parallel computing

    NASA Astrophysics Data System (ADS)

    Kühbach, M.; Barrales-Mora, L. A.; Mießen, C.; Gottstein, G.

    2015-08-01

    The possibility to characterize in an automatized way the spatial-temporal evolution of individual grains and their properties is essential to the understanding of annealing phenomena. The development of advanced experimental techniques, computational models and tools helps the acquisition of real time and real space-resolved datasets. Whereas the reconstruction of 3D grain representatives from serial-sectioning or tomography datasets becomes more common and microstructure simulations on parallel computers become ever larger and longer lasting, few efforts have materialized in the development of tools that allow the continuous tracking of properties at the grain scale. In fact, such analyses are often left neglected in practice due to the large size of the datasets that exceed the available physical memory of a computer or the shared-memory cluster. We identified the key tasks that have to be solved in order to define suitable and lean data structures and computational methods to evaluate spatio-temporal grain property datasets by working with parallel computer architectures. This is exemplified with data from grain growth simulations.

  13. H2 recombination on interstellar grains. [due to hydrogen atom chemisorption on graphite grains

    NASA Technical Reports Server (NTRS)

    Barlow, M. J.; Silk, J.

    1976-01-01

    From a consideration of relevant theoretical and experimental data it is concluded that H atoms (but not H2 molecules) will be chemisorbed on interstellar graphite grains, with H2 formation proceeding efficiently for graphite grain temperatures less than 70 K. It is argued that graphite grains will act as the principal sites for H2 formation, with a formation rate of about 4 to the minus 17th cu cm per sec. Heating by H2 molecules formed by surface recombination is analyzed in the context of the available experimental data, and a heating rate is derived and compared with other suggested cloud heating mechanisms. It is concluded that H2 recombination will provide the largest heat source in diffuse clouds if the albedo of interstellar dust in the 912-1200 A region is high (about 0.9), whereas if the albedo in this wavelength region is lower (about 0.5), photoelectron ejection from grains will tend to predominate, and can explain observed cloud temperatures with a carbon depletion factor of approximately 2, a factor attributable to a normal interstellar abundance of graphite grains.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. INTEGRATING THE STORED GRAIN ADVISOR PRO EXPERT SYSTEM WITH AN AUTOMATED ELECTRONIC 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 numbe...

  16. Grain size modeling and optimization of rotary forged Alloy 718

    SciTech Connect

    Domblesky, J.P.; Shivpuri, R.

    1997-04-01

    The study presented describes the simulation procedure and methodology used to develop two models for predicting recrystallized grain size in Alloy 718 billet. To simulate multiple pass forging of billet, controlled, high temperature compression testing was used to apply alternate deformation and dwell cycles to Alloy 718 specimens. Grain size obtained by simulation was found to be in excellent agreement with grain size from forged billet when cooling rate was included. The study also revealed that strain per pass and forging temperature were the predominant factors in controlling the recrystallized grain size. Both models were found to accurately predict the recrystallized grain size obtained by compression tests performed at super-solvus temperatures.

  17. Grain Boundary Traction Signatures: Quantitative Predictors of Dislocation Emission.

    PubMed

    Li, Ruizhi; Chew, Huck Beng

    2016-08-19

    We introduce the notion of continuum-equivalent traction fields as local quantitative descriptors of the grain boundary interface. These traction-based descriptors are capable of predicting the critical stresses to trigger dislocation emissions from ductile ⟨110⟩ symmetrical-tilt nickel grain boundaries. We show that Shockley partials are emitted when the grain boundary tractions, in combination with external tensile loading, generate a resolved shear stress to cause dislocation slip. The relationship between the local grain boundary tractions and the grain boundary energy is established. PMID:27588865

  18. Grain Boundary Traction Signatures: Quantitative Predictors of Dislocation Emission

    NASA Astrophysics Data System (ADS)

    Li, Ruizhi; Chew, Huck Beng

    2016-08-01

    We introduce the notion of continuum-equivalent traction fields as local quantitative descriptors of the grain boundary interface. These traction-based descriptors are capable of predicting the critical stresses to trigger dislocation emissions from ductile ⟨110 ⟩ symmetrical-tilt nickel grain boundaries. We show that Shockley partials are emitted when the grain boundary tractions, in combination with external tensile loading, generate a resolved shear stress to cause dislocation slip. The relationship between the local grain boundary tractions and the grain boundary energy is established.

  19. Molecular functions of genes related to grain shape in rice

    PubMed Central

    Zheng, Jia; Zhang, Yadong; Wang, Cailin

    2015-01-01

    Because grain shape is an important component of rice grain yield, the discovery of genes related to rice grain shape has attracted much attention of rice breeding programs. In recent years, some of these genes have been cloned and studied. They have been found not only regulate grain shape by changing the shape of the spikelet hull, but also regulate endosperm development through control of cell division using different molecular mechanisms. In this paper, we review the recent research on genes related to rice grain shape and their possible regulatory mechanisms. PMID:26069441

  20. The Grain Structure of Castings: Some Aspects of Modelling

    NASA Technical Reports Server (NTRS)

    Hellawell, A.

    1995-01-01

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

  1. Ion Implantation into Presolar Grains: A Theoretical Model

    NASA Astrophysics Data System (ADS)

    Verchovsky, A. B.; Wright, I. P.; Pillinger, C. T.

    A numerical model for ion implantation into spherical grains in free space has been developed. It can be applied to single grains or collections of grains with known grain-size distributions. Ion-scattering effects were taken into account using results of computer simulations. Possible isotope and element fractionation of the implanted species was investigated using this model. The astrophysical significance of the model lies in the possible identification of energetically different components (such as noble gases) implanted into presolar grains (such as diamond and SiC) and in establishing implantation energies of the components.

  2. Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis.

    PubMed

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

    2016-01-01

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

  3. Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis

    PubMed Central

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

    2016-01-01

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

  4. Radiation Pressure on Fluffy Submicron-sized Grains

    NASA Astrophysics Data System (ADS)

    Silsbee, Kedron; Draine, Bruce T.

    2016-02-01

    We investigate the claim that the ratio β of radiation pressure force to gravitational force on a dust grain in our solar system can substantially exceed unity for some grain sizes, provided that grain porosity is high enough. For model grains consisting of random aggregates of silicate spherules, we find that the maximum value of β is almost independent of grain porosity, but for small (\\lt 0.3 μ {{m}}) grains, β actually decreases with increasing porosity. We also investigate the effect of metallic iron and amorphous carbon inclusions in the dust grains and find that while these inclusions do increase the radiation pressure cross-section, β remains below unity for grains with 3 pg of silicate material. These results affect the interpretation of the grain trajectories estimated from the Stardust mission, which were modeled assuming β values exceeding one. We find that radiation pressure effects are not large enough for particles Orion and Hylabrook captured by Stardust to be of interstellar origin given their reported impact velocities. We also consider the effects of solar radiation on transverse velocities and grain spin, and show that radiation pressure introduces both transverse velocities and equatorial spin velocities of several hundred meters per second for incoming interstellar grains at 2 au. These transverse velocities are not important for modeling trajectories, but such spin rates may result in centrifugal disruption of aggregates.

  5. Grain size evolution and convection regimes of the terrestrial planets

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  6. Jamming of Cylindrical Grains in Featureless Vertical Channels

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  7. Imaging grain boundary scattering of graphene in real space

    NASA Astrophysics Data System (ADS)

    Ji, Shuai-Hua; Hannon, James B.; Tromp, Ruud M.; Subbiah, Chockalingam; Pasupathy, Abhay; Heinz, Tony F.; Ross, Frances M.

    2012-02-01

    Graphene grain boundaries are unavoidable defects in most growth methods, in particular chemical vapor deposition and thermal decomposition on the SiC(0001) surface. How electrons are scattered by those grain boundaries has not been experimentally demonstrated at the nanoscale. Here we report atomic-scale images of grain boundary scattering measured by scanning tunneling potentiometry (STP). Monolayer graphene sheets were synthesized on the SiC(0001) surface by thermal decomposition in a background of disilane, using low energy electron microscopy to monitor the graphene thickness during its formation. High resolution scanning tunneling microscopy (STM) reveals graphene grain boundaries and various grain orientations, and STP shows variations in voltage across grains and terraces as current flows across the graphene layer. We have identified two types of grain boundary. One shows a trench structure in STM images; potential mapping shows prominent potential drops. These boundaries between grains appear to be weak links and the dominant scattering locations. The other type of boundary shows a continuous lattice between the grains, with periodic dislocations accommodating the grain misorientation. Potential mapping indicates much weaker scattering despite the grain misorientation. We will discuss transport in polycrystalline graphene based on these measurements.

  8. Grain Growth and Silicates in Dense Clouds

    NASA Technical Reports Server (NTRS)

    Pendeleton, Yvonne J.; Chiar, J. E.; Ennico, K.; Boogert, A.; Greene, T.; Knez, C.; Lada, C.; Roellig, T.; Tielens, A.; Werner, M.; Whittet, D.

    2006-01-01

    Interstellar silicates are likely to be a part of all grains responsible for visual extinction (Av) in the diffuse interstellar medium (ISM) and dense clouds. A correlation between Av and the depth of the 9.7 micron silicate feature (measured as optical depth, tau(9.7)) is expected if the dust species are well 'mixed. In the di&se ISM, such a correlation is observed for lines of sight in the solar neighborhood. A previous study of the silicate absorption feature in the Taurus dark cloud showed a tendency for the correlation to break down at high Av (Whittet et al. 1988, MNRAS, 233,321), but the scatter was large. We have acquired Spitzer Infrared Spectrograph data of several lines of sight in the IC 5 146, Barnard 68, Chameleon I and Serpens dense clouds. Our data set spans an Av range between 2 and 35 magnitudes. All lines of sight show the 9.7 micron silicate feature. The Serpens data appear to follow the diffuse ISM correlation line whereas the data for the other clouds show a non-linear correlation between the depth of the silicate feature relative to Av, much like the trend observed in the Taurus data. In fact, it appears that for visual extinctions greater than about 10 mag, tau(9.7) begins to level off. This decrease in the growth of the depth of the 9.7 micron feature with increasing Av could indicate the effects of grain growth in dense clouds. In this poster, we explore the possibility that grain growth causes an increase in opacity (Av) without causing a corresponding increase in tau(9.7).

  9. A Nondestructive Method of Grain Microstructure Determination

    SciTech Connect

    Lai, J.

    2004-09-03

    Customarily, a material has been sectioned to study its internal grain microstructure and thus in the process is destroyed. Using x-rays, however, there are two nondestructive methods of determining the sources of diffraction spots and hence the internal grain microstructure of a sample. One technique consists of placing a wire in the path of a diffracted ray so that its image is prevented from appearing on the detector screen. Ray-tracing is then done to locate the source within the sample from whence the rays emanate. In this experiment, we investigate the other technique of determining source location by recording diffraction patterns at ten equally-spaced detector distances and then graphing the data with reasonable-fit lines using the least-squares fitting routine. We then perform a ray-tracing triangulation technique to pinpoint the location of the source from which the rays are coming. Cluster analyses are employed and plots of ray number versus pixel position of certain points at some particular detector distances are created. An error propagation analysis is then carried out as a check to the cluster analyses and graphs of error deviation along the detector path versus ray number are constructed. With statistical error analyses and construction of error boxes using chosen pixel error deviations and delta z error values, the best error measurement using the detector method was found to be plus/minus 100 microns. In this study, it was found that the detector method provided a much poorer resolution than the traditional wire technique of which there is a source size precision of within 1-5 microns. The detector method, though, is sufficient for large-grain material studies.

  10. Atomistic simulations of dislocation pileup: Grain boundaries interaction

    SciTech Connect

    Wang, Jian

    2015-05-27

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

  11. Relict grains in chondrules: Evidence for chondrule recycling

    NASA Technical Reports Server (NTRS)

    Jones, R. H.

    1994-01-01

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

  12. Atomistic simulations of dislocation pileup: Grain boundaries interaction

    DOE PAGESBeta

    Wang, Jian

    2015-05-27

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

  13. Comments on 'Extinct radioactivities: Trapped residuals of presolar grains'

    NASA Technical Reports Server (NTRS)

    Trivedi, B. M. P.

    1977-01-01

    It has recently been suggested that extinct I-129 and Pu-244 were trapped in primitive-solar-nebula ('presolar') grains and decayed into radiogenic Xe-129 and fission Xe before the grains were incorporated into meteorite bodies. This idea is reconsidered in light of the thermal and metamorphic history of meteorites. The criteria that parent and daughter species should never separate and that minerals or grains containing the anomalous xenon should not be subjected to temperatures exceeding 500 C are applied to iron meteorites, achondrites, and chondrites to determine whether presolar grains could be the carriers of rare-gas anomalies to meteorites. The results strongly indicate that the xenon anomaly could not have originated in presolar grains. Other difficulties with the presolar-grain model are discussed, including insufficiently small grain sizes, large variations in Xe-129/I-127 ratios in various meteorites, and apparently unrealistic meteorite formation times and locations.

  14. The adiabatic motion of charged dust grains in rotating magnetospheres

    NASA Astrophysics Data System (ADS)

    Northrop, T. G.; Hill, J. R.

    1983-01-01

    Adiabatic equations of motion are derived for the micrometer-sized dust grains detected in the Jovian and Saturn magnetospheres by the Pioneer 10 and 11 spacecraft. The adiabatic theory of charged particle motion is extended to the case of variable grain charge. Attention is focused on the innermost and outermost limits to the grain orbit evolution, with all orbits tending to become circular with time. The parameters such as the center equation of motion, the drift velocity, and the parallel equation of motion are obtained for grains in a rotating magnetosphere. Consideration is given to the effects of periodic grain charge-discharge, which are affected by the ambient plasma properties and the grain plasma velocity. The charge-discharge process at the gyrofrequency is determined to eliminate the invariance of the magnetic moment and cause the grain to exhibit radial movement. The magnetic moment increases or decreases as a function of the gyrophase of the charge variation.

  15. Metal precipitation at grain boundaries in silicon: Dependence on grain boundary character and dislocation decoration

    SciTech Connect

    Buonassisi, T.; Istratov, A. A.; Pickett, M. D.; Marcus, M. A.; Ciszek, T. F.; Weber, E. R.

    2006-07-24

    Synchrotron-based analytical microprobe techniques, electron backscatter diffraction, and defect etching are combined to determine the dependence of metal silicide precipitate formation on grain boundary character and microstructure in multicrystalline silicon (mc-Si). Metal silicide precipitate decoration is observed to increase with decreasing atomic coincidence within the grain boundary plane (increasing {sigma} values). A few low-{sigma} boundaries contain anomalously high metal precipitate concentrations, concomitant with heavy dislocation decoration. These results provide direct experimental evidence that the degree of interaction between metals and structural defects in mc-Si can vary as a function of microstructure, with implications for mc-Si device performance and processing.

  16. Development of quick cooking multi-grain dalia utilizing sprouted grains.

    PubMed

    Mridula, D; Sharma, Monika; Gupta, R K

    2015-09-01

    Multi-grain dalia (MGD) formulations were prepared utilizing sprouted wheat and mixer of other three grains (barley, sorghum and pearl millet) in the ratio of 100:0 (MGD-A), 75:25 (MGD-B), 50:50 (MGD-C), 25:75 (MGD-D) and 0:100 (MGD-E), respectively. The mixer of barley, sorghum and pearl millet was prepared using 50, 25, 25 parts of these grains, respectively. The recovery of grits/ dalia (particle size 1.41 to 2 mm) from sprouted wheat and barley was 74.56 and 69.77 %, respectively while sorghum and pearl millet yield 47.94 and 49.39 % (particle size 0.954 to 1.41 mm), respectively. Sprouting brought a reduction of cooking time by about 50 % as compared to un-sprouted studied grains. Cooking time for different MGD formulations ranged from 3.91 to 4.42 min, which was slightly increased with increasing proportion of mixer of barley, sorghum and pearl millet (p > 0.05). Rehydration ratio of MGD samples varied from 3.12 to 3.45 with minimum in MGD-E sample. Though protein content was decreased with increasing proportion of mixer of three grains in MGD samples but in vitro protein digestibility (58.68 to 62.75 %) was similar (p > 0.05). The mean overall sensory acceptability scores for MGD samples ranged from 7.50 to 8.49 with ≥8.0 in samples having up to 75 % grits of mixer of three grains. In view of very good overall sensory acceptability, rich in crude fibre, calcium and iron content and low cooking time, 25:75 parts of sprouted wheat and mixer of studied three grains, respectively may be considered for preparation of acceptable quality quick cooking multi-grain dalia. PMID:26344997

  17. Granular fingers on jammed systems: new fluidlike patterns arising in grain-grain invasion experiments.

    PubMed

    Pinto, S F; Couto, M S; Atman, A P F; Alves, S G; Bernardes, A T; de Resende, H F V; Souza, E C

    2007-08-10

    In this Letter we report spontaneous pattern formation in dense granular assemblies confined to a Hele-Shaw cell and quasistatic regime. Varied unexpected patterns, ranging from rounded to fingered, are observed due to the displacement of one granular material by another. Computer simulations reproduce the major features observed in these experiments. Two mechanisms are responsible for the pattern formation: crystallization of the injected grains and plastic deformation of the displaced grains. The experiment suggests analogies with viscous fingering and jamming transition experiments. PMID:17930866

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  19. Early season spring small grains proportion estimation

    NASA Technical Reports Server (NTRS)

    Phinney, D. E.; Trichel, M. C.

    1984-01-01

    An accurate, automated method for estimating early season spring small grains from Landsat MSS data is discussed. The method is summarized and the results of its application to 100 sample segment-years of data from the US Northern Great Plains in 1976, 1977, 1978, and 1979 are summarized. The results show that this estimator provides accurate estimates earlier in the growing season than previous methods. Ground truth is required only in the estimator development, and data storage, transmission, preprocessing, and processing requirements are minimal.

  20. Optical properties of irregular interstellar grains

    NASA Technical Reports Server (NTRS)

    Perrin, J. M.; Lamy, P. L.

    1989-01-01

    In order to study the interaction of light with interstellar grains, the authors represent an irregular particle by a network of interacting dipoles whose polarizability is determined in a first approach by the Clausius-Mossoti relationship. Typically, 10,000 dipoles are considered. In the case of spherical particles, the results from Mie theory are fully recovered. The main interest of this method is to study with good accuracy the implications of surface roughness and/or inhomogeneities on optical properties in the infrared spectral range, particularly of the silicate emission features.

  1. Electronic and molecular structure of carbon grains

    NASA Technical Reports Server (NTRS)

    Almloef, Jan; Luethi, Hans-Peter

    1990-01-01

    Clusters of carbon atoms have been studied with large-scale ab initio calculations. Planar, single-sheet graphite fragments with 6 to 54 atoms were investigated, as well as the spherical C(sub 60) Buckminsterfullerene molecule. Polycyclic aromatic hydrocarbons (PAHs) have also been considered. Thermodynamic differences between diamond- and graphite-like grains have been studied in particular. Saturation of the peripheral bonds with hydrogen is found to provide a smooth and uniform convergence of the properties with increasing cluster size. For the graphite-like clusters the convergence to bulk values is much slower than for the three-dimensional complexes.

  2. Coarse-grained modelling of supercoiled RNA

    NASA Astrophysics Data System (ADS)

    Matek, Christian; Šulc, Petr; Randisi, Ferdinando; Doye, Jonathan P. K.; Louis, Ard A.

    2015-12-01

    We study the behaviour of double-stranded RNA under twist and tension using oxRNA, a recently developed coarse-grained model of RNA. Introducing explicit salt-dependence into the model allows us to directly compare our results to data from recent single-molecule experiments. The model reproduces extension curves as a function of twist and stretching force, including the buckling transition and the behaviour of plectoneme structures. For negative supercoiling, we predict denaturation bubble formation in plectoneme end-loops, suggesting preferential plectoneme localisation in weak base sequences. OxRNA exhibits a positive twist-stretch coupling constant, in agreement with recent experimental observations.

  3. Coarse grained open system quantum dynamics

    SciTech Connect

    Thanopulos, Ioannis; Brumer, Paul; Shapiro, Moshe

    2008-11-21

    We show that the quantum dynamics of a system comprised of a subspace Q coupled to a larger subspace P can be recast as a reduced set of 'coarse grained' ordinary differential equations with constant coefficients. These equations can be solved by a single diagonalization of a general complex matrix. The method makes no assumptions about the strength of the couplings between the Q and the P subspaces, nor is there any limitation on the initial population in P. The utility of the method is demonstrated via computations in three following areas: molecular compounds, photonic materials, and condensed phases.

  4. Grain size segregation in debris discs

    NASA Astrophysics Data System (ADS)

    Thebault, P.; Kral, Q.; Augereau, J.-C.

    2014-01-01

    Context. In most debris discs, dust grain dynamics is strongly affected by stellar radiation pressure. Because this mechanism is size-dependent, we expect dust grains to be spatially segregated according to their sizes. However, because of the complex interplay between radiation pressure, grain processing by collisions, and dynamical perturbations, this spatial segregation of the particle size distribution (PSD) has proven difficult to investigate and quantify with numerical models. Aims: We propose to thoroughly investigate this problem by using a new-generation code that can handle some of the complex coupling between dynamical and collisional effects. We intend to explore how PSDs behave in both unperturbed discs at rest and in discs pertubed by planetary objects. Methods: We used the DyCoSS code to investigate the coupled effect of collisions, radiation pressure, and dynamical perturbations in systems that have reached a steady-state. We considered two setups: a narrow ring perturbed by an exterior planet, and an extended disc into which a planet is embedded. For both setups we considered an additional unperturbed case without a planet. We also investigated the effect of possible spatial size segregation on disc images at different wavelengths. Results: We find that PSDs are always spatially segregated. The only case for which the PSD follows a standard dn ∝ s-3.5ds law is for an unperturbed narrow ring, but only within the parent-body ring itself. For all other configurations, the size distributions can strongly depart from such power laws and have steep spatial gradients. As an example, the geometrical cross-section of the disc is very rarely dominated by the smallest grains on bound orbits, as it is expected to be in standard PSDs in sq with q ≤ -3. Although the exact profiles and spatial variations of PSDs are a complex function of the set-up that is considered, we are still able to derive some reliable results that will be useful for image or SED

  5. Coarse-grained modelling of surface nanobubbles

    NASA Astrophysics Data System (ADS)

    Grosfils, Patrick

    2013-05-01

    Surface nanobubbles are nanoscale gaseous objects that form on hydrophobic surfaces in contact with water. Understanding nanobubble formation and stability remains challenging due to the lack of appropriate theoretical framework and adequate modelling. Here we present a non-equilibrium coarse-grained model for nanobubbles at hydrophobic surfaces. The model is based on a lattice-gas model that has been proposed to understand the hydrophobic effect to which dynamical properties are added. The results presented demonstrate the ability of the model to reproduce the basic features of stable surface nanobubbles, which, thereby, supports the dynamical origin of these objects.

  6. Chondrule synthesis using fine-grained precursors

    NASA Astrophysics Data System (ADS)

    Fox, George Ernest

    2002-11-01

    High temperature petrologic experiments have been used in order to reproduce the textures of chondrules, which are rounded to irregularly shaped ferromagnesion silicate objects. Such experiments shed light on the conditions that existed and mechanisms that operated in the early solar nebula, as natural chondrules are believed to have formed there due to some type of heating event. The exact nature of this heating event and the conditions that existed at the time of the formation of the solar nebula are not completely understood. Chondrules, which are believed to be composed of some of the oldest remnants of the solar system, nebular condensates, are the basic components of chondrites. Chondrites comprise ˜82% of all meteorites. Despite years of petrographic examination and experimental petrology, the thermal history of chondrules still remains uncertain. Natural chondrules exhibit a variety of different textures ranging from glassy, barred, porphyritic, microporphyritc to protoporphyritc. Petrologic experiments in a muffle tube furnace under controlled fugacity conditions using type IAB bulk composition analogs have been successful in reproducing each of these textures in the laboratory. Charges are prepared, heated, water quenched, mounted, polished and photographed using back-scattered electron imagery. Subsequent analysis provides numerical data, which can then be used to calculate the nominal grain size of the olivine crystals in each charge. Porphyritic chondrules are the most abundant in nature by far and any model for chondrule formation must be capable of producing porphyritic textures. To reproduce this texture in the laboratory, however, seems to require a very narrow range of maximum temperature and soak time parameters even when using a variety of different types of fine-grained and agglomerated olivine precursor material. Experiments undertaken in this study bring into question some of the basic assumptions of various classical models of chondrule

  7. GRAIN BOUNDARY STRENGTHENING PROPERTIES OF TUNGSTEN ALLOYS

    SciTech Connect

    Setyawan, Wahyu; Kurtz, Richard J.

    2012-10-10

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

  8. Cereal grains and coronary heart disease.

    PubMed

    Truswell, A S

    2002-01-01

    Cereal grains and their products provide around 30% of total energy intake in British adults, (much more than any of the other major food groups). Coronary heart disease (CHD) is the largest single cause of death in Britain and many other Western countries. This review examines the question whether there is a relation between cereal consumption and CHD. Several of the nutrients in cereals have known potential for reducing risk factors for CHD: the linoleic acid, fibre, vitamin E, selenium and folate. Cereals also contain phytoestrogens of the lignan family and several phenolic acids with antioxidant properties. Processing generally reduces the content of these nutrients and bioprotective substances. Although cereals at the farm gate are very low in salt, processed cereal foods, eg bread and some breakfast cereals, are high-salt foods and thus could contribute to raising blood pressure. Human experiments have clearly shown that oat fibre tends to lower plasma total and LDL cholesterol but wheat fibre does not. Rice bran and barley may also lower cholesterol but most people do not eat enough barley to have an effect. Cereal foods with low glycaemic index such as pasta and oats are beneficial for people with diabetes and might lower plasma lipids. Between 1996 and 2001 an accumulation of five very large cohort studies in the USA, Finland and Norway have all reported that subjects consuming relatively large amounts of whole grain cereals have significantly lower rates of CHD. This confirms an earlier report from a small British cohort. The protective effect does not seem to be due to cholesterol-lowering. While cohort studies have shown this consistent protective effect of whole grain cereals, there has been (only one) randomised controlled secondary prevention trial of advice to eat more cereal fibre. In this there was no reduction of the rate of reinfarction. The trial had some weaknesses, eg there were eight different diets, compliance was not checked objectively

  9. Influence of anisotropic grain boundary properties on the evolution of grain boundary character distribution during grain growth—a 2D level set study

    NASA Astrophysics Data System (ADS)

    Hallberg, Håkan

    2014-12-01

    The present study elaborates on a 2D level set model of polycrystal microstructures that was recently established by adding the influence of anisotropic grain boundary energy and mobility on microstructure evolution. The new model is used to trace the evolution of grain boundary character distribution during grain growth. The employed level set formulation conveniently allows the grain boundary characteristics to be quantified in terms of coincidence site lattice (CSL) type per unit of grain boundary length, providing a measure of the distribution of such boundaries. In the model, both the mobility and energy of the grain boundaries are allowed to vary with misorientation. In addition, the influence of initial polycrystal texture is studied by comparing results obtained from a polycrystal with random initial texture against results from a polycrystal that initially has a cube texture. It is shown that the proposed level set formulation can readily incorporate anisotropic grain boundary properties and the simulation results further show that anisotropic grain boundary properties only have a minor influence on the evolution of CSL boundary distribution during grain growth. As anisotropic boundary properties are considered, the most prominent changes in the CSL distributions are an increase of general low-angle Σ1 boundaries as well as a more stable presence of Σ3 boundaries. The observations also hold for the case of an initially cube-textured polycrystal. The presence of this kind of texture has little influence over the evolution of the CSL distribution. Taking into consideration the anisotropy of grain boundary properties, grain growth alone does not seem to be sufficient to promote any significantly increased overall presence of CSL boundaries.

  10. Mechanical Spectroscopy of Grain Boundaries: Insights into Grain and Phase Boundary Sliding (Invited)

    NASA Astrophysics Data System (ADS)

    Sundberg, M.

    2010-12-01

    Grain boundary sliding has been identified as an important contributor to plastic deformation of polycrystalline rocks. Grain boundary sliding commonly acts in kinetic series with some other, usually rate-limiting, step such as grain boundary diffusion or dislocation propagation. Consequently, the mechanical properties of grain and phase boundaries are not typically measurable during steady-state creep tests. In contrast, measurements of the intrinsic shear attenuation (QG-1 ) of a polycrystalline rock as a function of frequency and temperature hold the potential to provide direct measurements of the grain boundary viscosity. Reciprocating torsion tests can be complemented by small-strain transient creep tests that monitor the short-time transient mechanical response of a polycrystalline solid to an instantaneous increase in stress. To develop and test a viscoelastic model that can describe both time- and frequency-domain mechanical behavior and thus allow extrapolation of experimental results to natural conditions, we have conducted an experimental study of low-frequency (10-2.25grained (d~5μm) aggregates of olivine and orthopyroxene ranging in composition from 6-75 vol % opx. The attenuation spectra reveal “high-temperature background” behavior at low to moderate frequencies. At higher frequencies (f>10-0.5 Hz) the attenuation spectra reveal the onset of an apparent Debye peak in the attenuation spectra, likely due to elastically-accommodated grain boundary sliding. A modified Andrade viscoelastic model that incorporates both the high-temperature background and the Debye

  11. Strength of Rocks Affected by Deformation Enhanced Grain Growth

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    One way of looking into the possibility of long-term strength changes in the lithosphere is to study transient effects resulting from modifications of the microstructure of rocks. It is generally accepted that mechanical weakening may occur due to progressive grain size refinement resulting from dynamic recrystallization. A decrease in grain size may induce a switch from creep controlled by grain size insensitive dislocation mechanisms to creep governed by grain size sensitive (GSS) mechanisms involving diffusion and grain boundary sliding processes. This switch forms a well-known scenario to explain localization in the lithosphere. However, fine-grained rocks in localized deformation zones are prone to grain coarsening due to surface energy driven grain boundary migration (SED-GBM). This might harden the rock, affecting its role in localizing strain in the long term. The question has arisen if grain growth by SED-GBM in a rock deforming in the GSS creep field can be significantly affected by strain. The broad aim of this study is to shed more light onto this. We have experimentally investigated the microstructural and strength evolution of fine-grained (~0.6 μm) synthetic forsterite and Fe-bearing olivine aggregates that coarsen in grain size while deforming by GSS creep at elevated pressure (600 MPa) and temperature (850-1000 °C). The materials were prepared by `sol-gel' method and contained 0.3-0.5 wt% water and 5-10 vol% enstatite. We performed i) static heat treatment tests of various time durations involving hot isostatic pressing (HIP), and ii) heat treatment tests starting with HIP and continuing with deformation up to 45% axial strain at strain rates in the range 4x10-7 - 1x10-4 s-1. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. In addition to the experiments, we studied microstructural evolution in simple two-dimensional numerical models, combining deformation and SED-GBM by means of the

  12. Segregation of solute elements at grain boundaries in an ultrafine grained Al-Zn-Mg-Cu alloy.

    PubMed

    Sha, Gang; Yao, Lan; Liao, Xiaozhou; Ringer, Simon P; Chao Duan, Zhi; Langdon, Terence G

    2011-05-01

    The solute segregation at grain boundaries (GBs) of an ultrafine grained (UFG) Al-Zn-Mg-Cu alloy processed by equal-channel angular pressing (ECAP) at 200 °C was characterised using three-dimensional atom probe. Mg and Cu segregate strongly to the grain boundaries. In contrast, Zn does not always show clear segregation and may even show depletion near the grain boundaries. Trace element Si selectively segregates at some GBs. An increase in the number of ECAP passes leads to a decrease in the grain size but an increase in solute segregation at the boundaries. The significant segregation of alloying elements at the boundaries of ultrafine-grained alloys implies that less solutes will be available in the matrix for precipitation with a decrease in the average grain size. PMID:21159437

  13. Laboratory Investigations of Catalysis on Grain Analogs

    NASA Astrophysics Data System (ADS)

    Smith, T. C.; Ferrante, R. F.; Moore, M. H.; Hallenbeck, S. L.

    1998-09-01

    We have begun a set of laboratory measurements to study the possible conversion of CO into CH_4 and other alkanes via Fischer-Tropsch catalysis in the presence of interstellar dust analogs containing iron. The dust analogs are sub-micron size iron silicate smokes made in a grain condensation chamber by reacting SiH_4 with O_2 in the presence of Fe (CO)_5 . The smokes are amorphous in phase and composition; based on our gas adsorption measurements they have a surface area of near 125 m(2) g(-1) . In the catalytic experiment, a mixture of H_2 + CO (2 : 1) is continuously circulated in a closed system through 0.1 g of iron silicate smoke. The smoke is heated to near 300 C while the gas reacts for a 3 hour period. The reacted gas is condensed onto a 10 K mirror attached to the tail of a cryostat. The infrared spectrum of the condensed gas is used to identify new species formed by catalysis. There is evidence for the conversion of CO into CH_4, C_2H_6 and C_2H_4. Similarly obtained background spectra not containing the catalyst do not show the same spectral signatures. Further experiments will quantitatively determine the efficiency of this conversion to determine if grain-catalyzed reactions such as these could play an important role in the chemistry of the solar nebula.NASA/Goddard

  14. Coarse-Grain Modeling of Energetic Materials

    NASA Astrophysics Data System (ADS)

    Brennan, John

    2015-06-01

    Mechanical and thermal loading of energetic materials can incite responses over a wide range of spatial and temporal scales due to inherent nano- and microscale features. Many energy transfer processes within these materials are atomistically governed, yet the material response is manifested at the micro- and mesoscale. The existing state-of-the-art computational methods include continuum level approaches that rely on idealized field-based formulations that are empirically based. Our goal is to bridge the spatial and temporal modeling regimes while ensuring multiscale consistency. However, significant technical challenges exist, including that the multiscale methods linking the atomistic and microscales for molecular crystals are immature or nonexistent. To begin addressing these challenges, we have implemented a bottom-up approach for deriving microscale coarse-grain models directly from quantum mechanics-derived atomistic models. In this talk, a suite of computational tools is described for particle-based microscale simulations of the nonequilibrium response of energetic solids. Our approach builds upon recent advances both in generating coarse-grain models under high strains and in developing a variant of dissipative particle dynamics that includes chemical reactions.

  15. Deuterium enrichment of the interstellar grain mantle

    NASA Astrophysics Data System (ADS)

    Das, Ankan; Sahu, Dipen; Majumdar, Liton; Chakrabarti, Sandip K.

    2016-01-01

    We carry out Monte Carlo simulation to study deuterium enrichments of interstellar grain mantles under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C, CH3, CH2D, OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ˜2 × 104 cm-3), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (˜106 cm-3), water and methanol productions are suppressed but surface coverages of CO, CO2, O2 and O3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high fractionation of methanol but surprisingly water fractionation is found to be low. This is in contradiction with our model results indicating alternative routes for de-fractionation of water. Effects of various types of energy barriers are also studied. Moreover, we allow grain mantles to interact with various charged particles (such as H+, Fe+, S+ and C+) to study the stopping power and projected range of these charged particles on various target ices.

  16. An adiabatic approximation for grain alignment theory

    NASA Astrophysics Data System (ADS)

    Roberge, W. G.

    1997-10-01

    The alignment of interstellar dust grains is described by the joint distribution function for certain `internal' and `external' variables, where the former describe the orientation of the axes of a grain with respect to its angular momentum, J, and the latter describe the orientation of J relative to the interstellar magnetic field. I show how the large disparity between the dynamical time-scales of the internal and external variables - which is typically 2-3 orders of magnitude - can be exploited to simplify calculations of the required distribution greatly. The method is based on an `adiabatic approximation' which closely resembles the Born-Oppenheimer approximation in quantum mechanics. The adiabatic approximation prescribes an analytic distribution function for the `fast' dynamical variables and a simplified Fokker-Planck equation for the `slow' variables which can be solved straightforwardly using various techniques. These solutions are accurate to O(epsilon), where epsilon is the ratio of the fast and slow dynamical time-scales. As a simple illustration of the method, I derive an analytic solution for the joint distribution established when Barnett relaxation acts in concert with gas damping. The statistics of the analytic solution agree with the results of laborious numerical calculations which do not exploit the adiabatic approximation.

  17. An Adiabatic Approximation for Grain Alignment Theory

    NASA Astrophysics Data System (ADS)

    Roberge, W. G.

    1997-12-01

    The alignment of interstellar dust grains is described by the joint distribution function for certain ``internal'' and ``external'' variables, where the former describe the orientation of a grain's axes with respect to its angular momentum, J, and the latter describe the orientation of J relative to the interstellar magnetic field. I show how the large disparity between the dynamical timescales of the internal and external variables--- which is typically 2--3 orders of magnitude--- can be exploited to greatly simplify calculations of the required distribution. The method is based on an ``adiabatic approximation'' which closely resembles the Born-Oppenheimer approximation in quantum mechanics. The adiabatic approximation prescribes an analytic distribution function for the ``fast'' dynamical variables and a simplified Fokker-Planck equation for the ``slow'' variables which can be solved straightforwardly using various techniques. These solutions are accurate to cal {O}(epsilon ), where epsilon is the ratio of the fast and slow dynamical timescales. As a simple illustration of the method, I derive an analytic solution for the joint distribution established when Barnett relaxation acts in concert with gas damping. The statistics of the analytic solution agree with the results of laborious numerical calculations which do not exploit the adiabatic approximation.

  18. Mesoscopic superconductivity in ultrasmall metallic grains

    SciTech Connect

    Alhassid, Y.; Nesterov, K. N.

    2014-10-15

    A nano-scale metallic grain (nanoparticle) with irregular boundaries in which the single-particle dynamics are chaotic is a zero-dimensional system described by the so-called universal Hamiltonian in the limit of a large number of electrons. The interaction part of this Hamiltonian includes a superconducting pairing term and a ferromagnetic exchange term. Spin-orbit scattering breaks spin symmetry and suppresses the exchange interaction term. Of particular interest is the fluctuation-dominated regime, typical of the smallest grains in the experiments, in which the bulk pairing gap is comparable to or smaller than the single-particle mean-level spacing, and the Bardeen-Cooper-Schrieffer (BCS) mean-field theory of superconductivity is no longer valid. Here we study the crossover between the BCS and fluctuation-dominated regimes in two limits. In the absence of spin-orbit scattering, the pairing and exchange interaction terms compete with each other. We describe the signatures of this competition in thermodynamic observables, the heat capacity and spin susceptibility. In the presence of strong spin-orbit scattering, the exchange interaction term can be ignored. We discuss how the magnetic-field response of discrete energy levels in such a nanoparticle is affected by pairing correlations. We identify signatures of pairing correlations in this response, which are detectable even in the fluctuation-dominated regime.

  19. 77 FR 65855 - Cancellation of Indianapolis Grain Inspection & Weighing Service, Inc. Designation; Selection of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-31

    ... Grain Inspection, Packers and Stockyards Administration Cancellation of Indianapolis Grain Inspection... Indianapolis, IN Area AGENCY: Grain Inspection, Packers and Stockyards Administration, USDA. ACTION: Notice. SUMMARY: Indianapolis Grain Inspection & Weighing Service, Inc. (Indianapolis) is designated to...

  20. 78 FR 51138 - Partial Cancellation of Fremont Grain Inspection Department Inc. Designation; Selection of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-20

    ... Grain Inspection, Packers and Stockyards Administration Partial Cancellation of Fremont Grain Inspection... Area AGENCY: Grain Inspection, Packers and Stockyards Administration, USDA. ACTION: Notice. SUMMARY: Fremont Grain Inspection Department, Inc. (Fremont) is designated to provide official inspection...

  1. Transmission Electron Microscopy of Itokawa Regolith Grains

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Berger, E. L.

    2013-01-01

    Introduction: In a remarkable engineering achievement, the JAXA space agency successfully recovered the Hayabusa space-craft in June 2010, following a non-optimal encounter and sur-face sampling mission to asteroid 25143 Itokawa. These are the first direct samples ever obtained and returned from the surface of an asteroid. The Hayabusa samples thus present a special op-portunity to directly investigate the evolution of asteroidal sur-faces, from the development of the regolith to the study of the effects of space weathering. Here we report on our preliminary TEM measurements on two Itokawa samples. Methods: We were allocated particles RA-QD02-0125 and RA-QD02-0211. Both particles were embedded in low viscosity epoxy and thin sections were prepared using ultramicrotomy. High resolution images and electron diffraction data were ob-tained using a JEOL 2500SE 200 kV field-emission scanning-transmission electron microscope. Quantitative maps and anal-yses were obtained using a Thermo thin-window energy-dispersive x-ray (EDX) spectrometer. Results: Both particles are olivine-rich (Fo70) with µm-sized inclusions of FeS and have microstructurally complex rims. Par-ticle RA-QD02-0125 is rounded and has numerous sub-µm grains attached to its surface including FeS, albite, olivine, and rare melt droplets. Solar flare tracks have not been observed, but the particle is surrounded by a continuous 50 nm thick, stuctur-ally disordered rim that is compositionally similar to the core of the grain. One of the surface adhering grains is pyrrhotite show-ing a S-depleted rim (8-10 nm thick) with nanophase Fe metal grains (<5 nm) decorating the outermost surface. The pyrrhotite displays a complex superstructure in its core that is absent in the S-depleted rim. Particle RA-QD02-0211 contains solar flare particle tracks (2x109 cm-2) and shows a structurally disordered rim 100 nm thick. The track density corresponds to a surface exposure of 103-104 years based on the track production rate

  2. Awns reduce grain number to increase grain size and harvestable yield in irrigated and rainfed spring wheat

    PubMed Central

    Rebetzke, G. J.; Bonnett, D. G.; Reynolds, M. P.

    2016-01-01

    Genotypic variation in ear morphology is linked to differences in photosynthetic potential to influence grain yield in winter cereals. Awns contribute to photosynthesis, particularly under water-limited conditions when canopy assimilation is restricted. We assessed performance of up to 45 backcross-derived, awned–awnletted NILs representing four diverse genetic backgrounds in 25 irrigated or rainfed, and droughted environments in Australia and Mexico. Mean environment grain yields were wide-ranging (1.38–7.93 t ha−1) with vegetative and maturity biomass, plant height, anthesis date, spike number, and harvest index all similar (P >0.05) for awned and awnletted NILs. Overall, grain yields of awned–awnletted sister-NILs were equivalent, irrespective of yield potential and genetic background. Awnletted wheats produced significantly more grains per unit area (+4%) and per spike (+5%) reflecting more fertile spikelets and grains in tertiary florets. Increases in grain number were compensated for by significant reductions in grain size (–5%) and increased frequency (+0.8%) of small, shrivelled grains (‘screenings’) to reduce seed-lot quality of awnletted NILs. Post-anthesis canopies of awnletted NILs were marginally warmer over all environments (+0.27 °C) but were not different and were sometimes cooler than awned NILs at cooler air temperatures. Awns develop early and represented up to 40% of total spikelet biomass prior to ear emergence. We hypothesize that the allocation of assimilate to large and rapidly developing awns decreases spikelet number and floret fertility to reduce grain number, particularly in distal florets. Individual grain size is increased to reduce screenings and to increase test weight and milling quality, particularly in droughted environments. Despite the average reduction in grain size, awnless lines could be identified that combined higher grain yield with larger grain size, increased grain protein concentration, and reduced

  3. Grain Development Mutants of Barley ([alpha]-Amylase Production during Grain Maturation and Its Relation to Endogenous Gibberellic Acid Content).

    PubMed Central

    Green, L. S.; Faergestad, E. M.; Poole, A.; Chandler, P. M.

    1997-01-01

    Barley (Hordeum vulgare L. Himalaya) mutants with altered grain morphology were isolated to investigate whether defects in grain development, possibly involving gibberellins (GAs) and abscisic acid, would lead to altered patterns of [alpha]-amylase gene expression. Following treatment with sodium azide, 75 mutants, typically showing grain shriveling, were identified. At grain maturity 15 of the 75 mutants had higher [alpha]-amylase activities in shriveled grains compared with either phenotypically normal grains that developed on the same heterozygous plant or with grains of cv Himalaya. Studies of four of these mutants demonstrated increased levels of both high- and low-isoelectric point [alpha]-amylase isozymes midway through grain development. This category of mutant has been designated pga, for premature grain [alpha]-amylase. One such mutant (M326) showed an endosperm-determined inheritance pattern. When crossed into a (GA-deficient) dwarfing background there was a 10- to 20-fold reduction in [alpha]-amylase activity, suggesting a requirement for GA biosynthesis. Endogenous GAs and abscisic acid were quantified by combined gas chromatography-specific ion monitoring in normal and mutant grains of heterozygous M326 plants during the period of [alpha]-amylase accumulation. Mutant grains had significantly higher (5.8-fold) levels of the bioactive GA1 compared with normal grains but much lower (approximately 10-fold) levels of the 2[beta]-hydroxylated ("inactive") GAs, typical of developing barley grains (e.g. GA8, GA34, GA48). We propose that a reduced extent of 2[beta]-hydroxylation in the mutant grains results in an increased level of GA1, which is responsible for premature [alpha]-amylase gene expression. PMID:12223700

  4. Awns reduce grain number to increase grain size and harvestable yield in irrigated and rainfed spring wheat.

    PubMed

    Rebetzke, G J; Bonnett, D G; Reynolds, M P

    2016-04-01

    Genotypic variation in ear morphology is linked to differences in photosynthetic potential to influence grain yield in winter cereals. Awns contribute to photosynthesis, particularly under water-limited conditions when canopy assimilation is restricted. We assessed performance of up to 45 backcross-derived, awned-awnletted NILs representing four diverse genetic backgrounds in 25 irrigated or rainfed, and droughted environments in Australia and Mexico. Mean environment grain yields were wide-ranging (1.38-7.93 t ha(-1)) with vegetative and maturity biomass, plant height, anthesis date, spike number, and harvest index all similar (P >0.05) for awned and awnletted NILs. Overall, grain yields of awned-awnletted sister-NILs were equivalent, irrespective of yield potential and genetic background. Awnletted wheats produced significantly more grains per unit area (+4%) and per spike (+5%) reflecting more fertile spikelets and grains in tertiary florets. Increases in grain number were compensated for by significant reductions in grain size (-5%) and increased frequency (+0.8%) of small, shrivelled grains ('screenings') to reduce seed-lot quality of awnletted NILs. Post-anthesis canopies of awnletted NILs were marginally warmer over all environments (+0.27 °C) but were not different and were sometimes cooler than awned NILs at cooler air temperatures. Awns develop early and represented up to 40% of total spikelet biomass prior to ear emergence. We hypothesize that the allocation of assimilate to large and rapidly developing awns decreases spikelet number and floret fertility to reduce grain number, particularly in distal florets. Individual grain size is increased to reduce screenings and to increase test weight and milling quality, particularly in droughted environments. Despite the average reduction in grain size, awnless lines could be identified that combined higher grain yield with larger grain size, increased grain protein concentration, and reduced screenings. PMID

  5. Nanoscale Deformation Behavior of Phase-Reversion Induced Austenitic Stainless Steels: The Interplay Between Grain Size from Nano-Grain Regime to Coarse-Grain Regime

    NASA Astrophysics Data System (ADS)

    Misra, R. D. K.; Venkatsurya, P. K. C.; Somani, M. C.; Karjalainen, L. P.

    2012-12-01

    We have used the recently adopted concept of phase reversion to obtain grain size from the nanograined/ultrafine-grained (NG/UFG) to fine grain (FG) regime by varying temperature-time annealing sequence of cold deformed metastable austenite. The phase-reversion induced NG/UFG structure was characterized by high strength-high ductility combination. The concept of phase reversion involves severe cold deformation of metastable austenite to generate strain-induced martensite. Upon annealing, martensite transforms back to austenite through a diffusional reversion mechanism with NG/UFG, sub-micron grains (SMG) or FG structure, depending on the annealing condition. Depth-sensing nanoindentation experiments were combined with electron microscopy to elucidate the dependence of grain size from nanograin/ultrafine-grain (NG/UFG) to coarse grain (CG) regime on the deformation mechanisms. There was distinct transition in the deformation mechanism from intense mechanical twinning and stacking faults in NG/UFG structure to strain-induced martensite formation at the intersection of shear bands in the CG structure. The transition in the deformation mechanism is discussed in terms of increase in austenite stability with decrease in grain size.

  6. Utilization of wet distillers grains in high-energy beef cattle diets based on processed grain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Distiller's grains (DG) are used extensively by beef cattle feeding operations in the United States, including the Southern Great Plains. Our regional research consortium has been conducting research focused on utilization of wet DG in feedlot diets based on steam-flaked corn (SFC). Effects of DG on...

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

    NASA Astrophysics Data System (ADS)

    Mariappan, C. R.

    2014-05-01

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

  8. Interaction of grain co-products with grain processing: Associative effects and management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The vast majority of research with corn milling byproducts such as distiller’s grains (DG) and corn gluten feed (CGF) has been conducted in the northern Great Plains and Corn Belt with finishing diets common to that area. In the past few years, these byproducts have become available for use in the ...

  9. Identifying whole grain foods: a comparison of different approaches for selecting more healthful whole grain products

    PubMed Central

    Mozaffarian, Rebecca S; Lee, Rebekka M; Kennedy, Mary A; Ludwig, David S; Mozaffarian, Dariush; Gortmaker, Steven L

    2015-01-01

    Objective Eating whole grains (WG) is recommended for health, but multiple conflicting definitions exist for identifying whole grain (WG) products, limiting the ability of consumers and organizations to select such products. We investigated how five recommended WG criteria relate to healthfulness and price of grain products. Design We categorized grain products by different WG criteria including: the industry-sponsored Whole Grain stamp (WG-Stamp); WG as the first ingredient (WG-first); WG as the first ingredient without added sugars (WG-first-no-added-sugars); the word ‘whole’ before any grain in the ingredients (‘whole’-anywhere); and a content of total carbohydrate to fibre of ≤10:1 (10:1-ratio). We investigated associations of each criterion with health-related characteristics including fibre, sugars, sodium, energy, trans-fats and price. Setting Two major grocery store chains. Subjects Five hundred and forty-five grain products. Results Each WG criterion identified products with higher fibre than products considered non-WG; the 10:1-ratio exhibited the largest differences (+3.15 g/serving, P<0.0001). Products achieving the 10:1-ratio also contained lower sugar (−1.28 g/serving, P=0.01), sodium (−15.4 mg/serving, P=0.04) and likelihood of trans-fats (OR=0.14, P<0.0001), without energy differences. WG-first-no-added-sugars performed similarly, but identified many fewer products as WG and also not a lower likelihood of containing trans-fats. The WG-Stamp, WG-first and ‘whole’-anywhere criteria identified products with a lower likelihood of trans-fats, but also significantly more sugars and energy (P<0.05 each). Products meeting the WG-Stamp or 10:1-ratio criterion were more expensive than products that did not (+$US 0.04/serving, P=0.009 and +$US 0.05/serving, P=0.003, respectively). Conclusions Among proposed WG criteria, the 10:1-ratio identified the most healthful WG products. Other criteria performed less well, including the industry

  10. Grain Accumulation of Selenium Species in Rice (Oryza sativa L.)

    SciTech Connect

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

    2012-09-05

    Efficient Se biofortification programs require a thorough understanding of the accumulation and distribution of Se species within the rice grain. Therefore, the translocation of Se species to the filling grain and their spatial unloading were investigated. Se species were supplied via cut flag leaves of intact plants and excised panicle stems subjected to a {+-} stem-girdling treatment during grain fill. Total Se concentrations in the flag leaves and grain were quantified by inductively coupled plasma mass spectrometry. Spatial accumulation was investigated using synchrotron X-ray fluorescence microtomography. Selenomethionine (SeMet) and selenomethylcysteine (SeMeSeCys) were transported to the grain more efficiently than selenite and selenate. SeMet and SeMeSeCys were translocated exclusively via the phloem, while inorganic Se was transported via both the phloem and xylem. For SeMet- and SeMeSeCys-fed grain, Se dispersed throughout the external grain layers and into the endosperm and, for SeMeSeCys, into the embryo. Selenite was retained at the point of grain entry. These results demonstrate that the organic Se species SeMet and SeMeSeCys are rapidly loaded into the phloem and transported to the grain far more efficiently than inorganic species. Organic Se species are distributed more readily, and extensively, throughout the grain than selenite.

  11. Marketing whole grain breads in Canada via food labels.

    PubMed

    Sumanac, Dunja; Mendelson, Rena; Tarasuk, Valerie

    2013-03-01

    A recommendation for increased whole grain consumption was released in Canada in 2007 to promote adequate intakes of fibre and magnesium. Since then, a proliferation of 'whole grain' claims on food packaging has been observed, but whole grain labelling is voluntary and unregulated in Canada. Through a detailed survey of bread sold in three supermarkets, this study examined how the presence of front-of-package reference to whole grain relates to (i) the presence and nature of whole grain ingredients, (ii) nutrient content, and (iii) price of the product. Twenty-one percent of breads bore a reference to whole grain on the front-of-package and the front-of-package reference to whole grain was a better predictor of fibre content than any information that could be gleaned from the ingredient list. On average, breads with a whole grain reference were higher in fibre and magnesium and lower in sodium. Mean price did not differ by presence of a whole grain reference, but breads with whole grain labelling were less likely to be low in price. Voluntary nutrition labelling may be targeting a discrete market of health-conscious consumers who are willing to pay premium prices for more healthful options. PMID:23178749

  12. Reducing arsenic accumulation in rice grain through iron oxide amendment.

    PubMed

    Farrow, Eric M; Wang, Jianmin; Burken, Joel G; Shi, Honglan; Yan, Wengui; Yang, John; Hua, Bin; Deng, Baolin

    2015-08-01

    Effects of soil-arsenic (As), phosphorus and iron oxide on As accumulation in rice grain were investigated. Cultivars that have significantly different sensitivity to As, straighthead-resistant Zhe 733 and straighthead-susceptible Cocodrie, were used to represent different cultivar varieties. The grain accumulation of other elements of concern, selenium (Se), molybdenum (Mo), and cadmium (Cd) was also monitored. Results demonstrated that high soil-As not only resulted in high grain-As, but could also result in high grain-Se, and Zhe 733 had significantly less grain-As than Cocodrie did. However, soil-As did not impact grain-Mo and Cd. Among all elements monitored, iron oxide amendment significantly reduced grain-As for both cultivars, while the phosphate application only reduced grain-Se for Zhe 733. Results also indicated that cultivar type significantly impacted grain accumulation of all monitored trace elements. Therefore, applying iron oxide to As-contaminated land, in addition to choosing appropriate rice cultivar, can effectively reduce the grain accumulation of As. PMID:25910688

  13. Trace element depth profiles in presolar silicon carbide grains

    NASA Astrophysics Data System (ADS)

    King, Ashley J.; Henkel, Torsten; Rost, Detlef; Lyon, Ian C.

    2012-10-01

    We have analyzed eleven presolar SiC grains from the Murchison meteorite using time-of-flight secondary ion mass spectrometry. The Si isotopic compositions of the grains indicate that they are probably of an AGB star origin. The average abundances of Mg, Fe, Ca, Al, Ti, and V are strongly influenced by their condensation behavior into SiC in circumstellar environments. Depth profiles of Li, B, Mg, Al, K, Ca, Ti, V, Cr, and Fe in the SiC grains show that trace elements are not always homogenously distributed. In approximately half of the SiC grains studied here, the trace element distributions can be explained by condensation processes around the grains' parent stars. These grains appear to have experienced only minimal processing before their arrival in the presolar molecular cloud, possibly due to short residence times in the interstellar medium. The remaining SiC grains contained elevated abundances of several elements within their outer 200 nm, which is attributed to the implantation of energetic ions accelerated by shockwaves in the interstellar medium. These grains may have spent a longer period of time in this region, hence increasing the probability of them passing through a shockfront. Distinct groups of presolar SiC grains whose residence times in the interstellar medium differ are consistent with previous findings based on noble gas studies, although some grains may also have been shielded from secondary alteration by protective outer mantles.

  14. Presolar spinel grains from the Murray and Murchison carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Zinner, Ernst; Amari, Sachiko; Guinness, Robert; Nguyen, Ann; Stadermann, Frank J.; Walker, Robert M.; Lewis, Roy S.

    2003-12-01

    With a new type of ion microprobe, the NanoSIMS, we determined the oxygen isotopic compositions of small (<1μm) oxide grains in chemical separates from two CM2 carbonaceous meteorites, Murray and Murchison. Among 628 grains from Murray separate CF (mean diameter 0.15 μm) we discovered 15 presolar spinel and 3 presolar corundum grains, among 753 grains from Murray separate CG (mean diameter 0.45 μm) 9 presolar spinel grains, and among 473 grains from Murchison separate KIE (mean diameter 0.5 μm) 2 presolar spinel and 4 presolar corundum grains. The abundance of presolar spinel is highest (2.4%) in the smallest size fraction. The total abundance in the whole meteorite is at least 1 ppm, which makes spinel the third-most abundant presolar grain species after nanodiamonds (if indeed a significant fraction of them are presolar) and silicon carbide. The O-isotopic distribution of the spinel grains is very similar to that of presolar corundum, the only statistically significant difference being that there is a larger fraction of corundum grains with large 17O excesses ( 17O/ 16O > 1.5 × 10 -3), which indicates parent stars with masses between 1.8 and 4.5 M ⊙.

  15. PRAM C:a new programming environment for fine-grain and coarse-grain parallelism.

    SciTech Connect

    Brown, Jonathan Leighton; Wen, Zhaofang.

    2004-11-01

    In the search for ''good'' parallel programming environments for Sandia's current and future parallel architectures, they revisit a long-standing open question. Can the PRAM parallel algorithms designed by theoretical computer scientists over the last two decades be implemented efficiently? This open question has co-existed with ongoing efforts in the HPC community to develop practical parallel programming models that can simultaneously provide ease of use, expressiveness, performance, and scalability. Unfortunately, no single model has met all these competing requirements. Here they propose a parallel programming environment, PRAM C, to bridge the gap between theory and practice. This is an attempt to provide an affirmative answer to the PRAM question, and to satisfy these competing practical requirements. This environment consists of a new thin runtime layer and an ANSI C extension. The C extension has two control constructs and one additional data type concept, ''shared''. This C extension should enable easy translation from PRAM algorithms to real parallel programs, much like the translation from sequential algorithms to C programs. The thin runtime layer bundles fine-grained communication requests into coarse-grained communication to be served by message-passing. Although the PRAM represents SIMD-style fine-grained parallelism, a stand-alone PRAM C environment can support both fine-grained and coarse-grained parallel programming in either a MIMD or SPMD style, interoperate with existing MPI libraries, and use existing hardware. The PRAM C model can also be integrated easily with existing models. Unlike related efforts proposing innovative hardware with the goal to realize the PRAM, ours can be a pure software solution with the purpose to provide a practical programming environment for existing parallel machines; it also has the potential to perform well on future parallel architectures.

  16. Chemically anomalous, pre-accretionally irradiated grains in interplanetary dust -- interstellar grains?. [Abstract only

    NASA Technical Reports Server (NTRS)

    Bradley, J. P.

    1994-01-01

    Ultrafine-grained matrix is a unique and fundamental building block of chondritic porous (CP) interplanetary dust particles. Most IDPs so far determined to be of cometary origin belong to the CP class. The matrix in CP IDPs is not homogeneous but rather a loose mixture of discrete single crystals (e.g., olivine, pyroxene, Fe sulfides) and polyphase grains. The petrographic diversity observed among the polyphase grains suggest that they were formed under variable physiochemical conditions. One particular class of polyphase grains are a dominant component in cometary IDPs. Although their occurrence is well documented, the terminology used to describe them is confused. They have been called many names. Here they are simply called GEMS (Glass with Embedded Metal and Sulfides). The bulk compositions of GEMS are within a factor of 3 chondritic (solar) for all major elements except C. Quantitative thin-film X-ray (EDS) analyses have shown that GEMS are systematically depleted in Mg and Si, enriched in S, Fe, and Ni, and stoichiometrically enriched in O. Electron energy-loss spectroscopy (EELS) suggests that the excess O is present as hydroxyl (-OH) groups. These same chemical 'anomalies' were observed in solar-wind-irradiated amorphous rims on the surfaces of IDPs, suggesting that the compositions of GEMS reflect prior exposure to ionizing radiation. In order to test this hypothesis, a sample of Allende (CV3) matrix was exposed to proton flux. Radiation-damaged amorphous rims on olivine and pyroxene crystals in the Allende sample were found to be depleted in Mg and Ca, enriched in S, Fe, and Ni, and stoichiometrically enriched in O. Thus, the compositions of GEMS are indeed consistent with exposure to ionizing radiation. This study suggests that chemical as well as isotopic anomalies may be used to identify presolar interstellar grains in primitive meteoritic materials.

  17. Grain formation around carbon stars. 1: Stationary outflow models

    NASA Technical Reports Server (NTRS)

    Egan, Michael P.; Leung, Chun Ming

    1995-01-01

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

  18. Grain size distribution of the matrix in the Allende chondrite

    NASA Astrophysics Data System (ADS)

    Toriumi, M.

    1989-03-01

    Results are presented from analytical TEM, high-resolution TEM, and SEM studies of the Allende chondrite, showing that the matrix consists of very fine-grained Fe-rich olivine, Ca-poor and Fe-rich clinopyroxene, Fe-rich spinel, and Ni-bearing troilite. Slightly sintered and non-sintered very fine-grained aggregates are observed. The results suggest that the coarse-grained olivine aggregates experienced a heating event, whereas the ultrafine-grained aggregates did not. The size and frequency distributions of matrix grains are measured. The frequency distribution displays a long-term tail with power law and a log-normal pattern with a peak at 5 nm in the range from 1 to 10 nm. This suggests that the fine-grained matrix was probably formed at conditions far from equilibrium in the protosolar cloud.

  19. Kinetic constants of abnormal grain growth in nanocrystalline nickel

    NASA Astrophysics Data System (ADS)

    Aleshin, A. N.

    2016-02-01

    The grain growth in nanocrystalline nickel with a purity of 99.5 at % during non-isothermal annealing was experimentally investigated using differential scanning calorimetry and transmission electron microscopy. Nanocrystalline nickel was prepared by electrodeposition and had an average grain size of approximately 20 nm. It was shown that, at a temperature corresponding to the calorimetric signal peak, abnormal grain growth occurs with the formation of a bimodal grain microstructure. Calorimeters signals were processed within the Johnson-Mehl-Avrami formalism. This made it possible to determine the exponent of the corresponding equation, the frequency factor, and the activation energy of the grain growth, which was found to be equal to the activation energy of the vacancy migration. The reasons for the abnormal grain growth in nanocrystalline nickel were discussed.

  20. Atomically ordered solute segregation behaviour in an oxide grain boundary

    NASA Astrophysics Data System (ADS)

    Feng, Bin; Yokoi, Tatsuya; Kumamoto, Akihito; Yoshiya, Masato; Ikuhara, Yuichi; Shibata, Naoya

    2016-03-01

    Grain boundary segregation is a critical issue in materials science because it determines the properties of individual grain boundaries and thus governs the macroscopic properties of materials. Recent progress in electron microscopy has greatly improved our understanding of grain boundary segregation phenomena down to atomistic dimensions, but solute segregation is still extremely challenging to experimentally identify at the atomic scale. Here, we report direct observations of atomic-scale yttrium solute segregation behaviours in an yttria-stabilized-zirconia grain boundary using atomic-resolution energy-dispersive X-ray spectroscopy analysis. We found that yttrium solute atoms preferentially segregate to specific atomic sites at the core of the grain boundary, forming a unique chemically-ordered structure across the grain boundary.

  1. Grain growth and structural relaxation of nanocrystalline Bi₂Te₃

    SciTech Connect

    Humphry-Baker, Samuel A.; Schuh, Christopher A.

    2014-10-21

    Recovery and grain growth behavior is investigated systematically for the nanocrystalline thermoelectric compound bismuth telluride, synthesized by mechanical alloying. During annealing treatments at elevated temperatures, structural evolution is tracked using x-ray diffraction, electron microscopy and calorimetry. Below a homologous temperature of about 0.6T{sub m}, grain growth occurs slowly with an activation energy of 89 kJ/mol. However above this temperature grain growth becomes more rampant with an activation energy of 242 kJ/mol. The transition is attributed to a shift from a relaxation or recovery process that includes some reordering of the grain boundary structure, to a more conventional diffusionally-limited grain growth process. By extrapolating the measured grain growth and microstrain evolution kinetics, a thermal budget map is constructed, permitting recommendations for improving the thermoelectric properties of nanocrystalline materials processed via a powder route.

  2. Small non-spherical grains in envelopes of M giants

    NASA Astrophysics Data System (ADS)

    Il'In, V. B.

    1994-01-01

    The drift of spheroidal and spherical grains in the envelopes of M giants is considered. It is found that for small metallic grains, the velocity relative to the gas should strongly depend on the grain shape. For example, the velocity of a dirty iron spheroid with a semiaxes ratio of 2-4 is about 1.5-3 times larger than the velocity of an equal volume sphere, the difference of the velocities being as large as a 1 km/s. Probably, a dependence of the velocity on grain shape also occurs for normal size silicate grains. Thus, in modeling the dynamics of the envelopes, one should bear in mind the possibility of a much more efficient interaction of radiation with dust than usually proposed due to a deviation of grains' shape from a spherical one. The same effect could occur in the envelopes of carbon-rich giants and protostars.

  3. Computer Simulation of Grain Growth Kinetics with Solute Drag

    SciTech Connect

    Chen, L.; Chen, S.P.; Fan, D.

    1998-12-23

    The effects of solute dragon grain growth kinetics were studied in two dimensional (2-D) computer simulations by using a diffuse-interface field model. It is shown that, in the low velocity / low driving force regime, the velocity of a grain boundary motion departs from a linear relation with driving force (curvature) with solute drag. The nonlinear relation of migration velocity and driving force comes from the dependence of grain boundary energy and width on the curvature. The growth exponent m of power growth law for a polycrystalline system is affected by the segregation of solutes to grain boundaries. With the solute drag, the growth exponent m can take any value between 2 and 3 depending on the ratio of lattice diffusion to grain boundary mobility. The grain size and topological distributions are unaffected by solute drag, which are the same as those in a pure system.

  4. Vortices of self-gravitating grains in dusty plasmas

    SciTech Connect

    Nebbat, E.; Annou, R.

    2012-09-15

    Vortices are an attractive expression of the non-linear dynamics of fluids along with plasmas. In complex plasmas, Nebbat and Annou [Phys. Plasmas 17, 093702 (2010)] proposed a time dependent non-linear model that considers vortices as a consequence of an instability. The model is augmented hereafter by incorporating the gravitational grain-grain attraction, particle drift due to self-gravity field, self-consistent inter-particle distance, the permeability of grains along with the grain charge excess due to the non-linear dependence of the grain capacitance on its size. Effects of the latter parameters as well as the effect of grain mass to charge ratio on the characteristics of the vortex such as density are investigated.

  5. Relationship of spectral data to grain yield variation

    NASA Technical Reports Server (NTRS)

    Tucker, C. J.; Holben, B. N.; Elgin, J. H., Jr.; Mcmurtrey, J. E., III

    1980-01-01

    Two-band hand-held radiometer data from a winter wheat field, collected on 21 dates during the spring growing season, were correlated with within-field final grain yield. Significant linear relationships were found between various combinations of the red and photographic infrared radiance data collected and the grain yield. The spectral data explained about 64 percent of the within-field grain yield variation. This variation in grain yield could not be explained using meteorological data as these were similar for all areas of the wheat field. Most importantly, data collected early in the spring were highly correlated with grain yield, a five-week time window existed from stem elongation through anthesis in which the spectral data were most highly correlated with grain yield, and manifestations of wheat canopy water stress were readily apparent in the spectral data.

  6. Whole grain cereals: functional components and health benefits.

    PubMed

    Borneo, Rafael; León, Alberto Edel

    2012-02-01

    Cereal-based food products have been the basis of the human diet since ancient times. Dietary guidelines all over the world are recommending the inclusion of whole grains because of the increasing evidence that whole grains and whole-grain-based products have the ability to enhance health beyond the simple provision of energy and nutrients. In this review we will examine the main chemical components present in whole grains that may have health enhancing properties (dietary fiber, inulin, beta-glucan, resistant starch, carotenoids, phenolics, tocotrienols, and tocopherols) and the role that whole grains may play in disease prevention (cardiovascular diseases and strokes, hypertension, metabolic syndrome, type 2 diabetes mellitus, obesity, as well as different forms of cancer). The knowledge derived from the functional properties of the different chemical components present in whole grains will aid in the formulation and development of new food products with health enhancing characteristics. PMID:22134555

  7. Circumstellar grains and the intrinsic polarization of starlight

    NASA Technical Reports Server (NTRS)

    Forrest, W. J.; Gillett, F. C.; Stein, W. A.

    1975-01-01

    Twenty-five long-period variable stars exhibiting intrinsic variable polarization have been monitored over the range 3.5-11 microns for several cycles. No conclusive evidence for gross changes in amount of circumstellar grains has been found. Thus circumstellar infrared emission is attributed to the total abundance of grains surrounding the star, which does not change by a large amount with time, while intrinsic polarization is attributed to more localized scattering and absorption effects. Spectrophotometry with resolution of about 0.015 over the 8-14 microns wavelength range of several stars with different chemical compositions indicates excess emission characteristic of 3 types of grains: (1) 'blackbody' grains, (2) silicate grains, and (3) silicon carbide grains.

  8. Design of modular control system for grain dryers

    NASA Astrophysics Data System (ADS)

    He, Gaoqing; Liu, Yanhua; Zu, Yuan

    In order to effectively control the temperature of grain drying bin, grain ,air outlet as well as the grain moisture, it designed the control system of 5HCY-35 which is based on MCU to adapt to all grains drying conditions, high drying efficiency, long life usage and less manually. The system includes: the control module of the constant temperature and the temperature difference control in drying bin, the constant temperature control of heating furnace, on-line testing of moisture, variety of grain-circulation speed control and human-computer interaction interface. Spatial curve simulation, which takes moisture as control objectives, controls the constant temperature and the temperature difference in drying bin according to preset parameter by the user or a list to reduce the grains explosive to ensure the seed germination percentage. The system can realize the intelligent control of high efficiency and various drying, the good scalability and the high quality.

  9. The bio refinery; producing feed and fuel from grain.

    PubMed

    Scholey, D V; Burton, E J; Williams, P E V

    2016-04-15

    It is both possible and practicable to produce feed and fuel from grain. Using the value of grain to produce renewable energy for transport, while using the remaining protein content of the grain as a valuable protein source for livestock and for fish, can be seen as a complimentary and optimal use of all the grain constituents. Consideration must be given to maximise the value of the yeast components, as substantial yeast is generated during the fermentation of the grain starch to produce ethanol. Yeast is a nutritionally rich feed ingredient, with potential for use both as feed protein and as a feed supplement with possible immunity and gut health enhancing properties. Bioprocessing, with the consequent economies of scale, is a process whereby the value of grain can be optimised in a way that is traditional, natural and sustainable for primarily producing protein and oil for feed with a co-product ethanol as a renewable fuel. PMID:26617037

  10. Atomically ordered solute segregation behaviour in an oxide grain boundary

    PubMed Central

    Feng, Bin; Yokoi, Tatsuya; Kumamoto, Akihito; Yoshiya, Masato; Ikuhara, Yuichi; Shibata, Naoya

    2016-01-01

    Grain boundary segregation is a critical issue in materials science because it determines the properties of individual grain boundaries and thus governs the macroscopic properties of materials. Recent progress in electron microscopy has greatly improved our understanding of grain boundary segregation phenomena down to atomistic dimensions, but solute segregation is still extremely challenging to experimentally identify at the atomic scale. Here, we report direct observations of atomic-scale yttrium solute segregation behaviours in an yttria-stabilized-zirconia grain boundary using atomic-resolution energy-dispersive X-ray spectroscopy analysis. We found that yttrium solute atoms preferentially segregate to specific atomic sites at the core of the grain boundary, forming a unique chemically-ordered structure across the grain boundary. PMID:27004614

  11. OBSERVATIONS OF ENHANCED RADIATIVE GRAIN ALIGNMENT NEAR HD 97300

    SciTech Connect

    Andersson, B-G; Potter, S. B. E-mail: sbp@saao.ac.z

    2010-09-10

    We have obtained optical multi-band polarimetry toward sightlines through the Chamaeleon I cloud, particularly in the vicinity of the young B9/A0 star HD 97300. We show, in agreement with earlier studies, that the radiation field impinging on the cloud in the projected vicinity of the star is dominated by the flux from the star, as evidenced by a local enhancement in the grain heating. By comparing the differential grain heating with the differential change in the location of the peak of the polarization curve, we show that the grain alignment is enhanced by the increase in the radiation field. We also find a weak, but measurable, variation in the grain alignment with the relative angle between the radiation field anisotropy and the magnetic field direction. Such an anisotropy in the grain alignment is consistent with a unique prediction of modern radiative alignment torque theory and provides direct support for radiatively driven grain alignment.

  12. A generic fine-grained parallel C

    NASA Technical Reports Server (NTRS)

    Hamet, L.; Dorband, John E.

    1988-01-01

    With the present availability of parallel processors of vastly different architectures, there is a need for a common language interface to multiple types of machines. The parallel C compiler, currently under development, is intended to be such a language. This language is based on the belief that an algorithm designed around fine-grained parallelism can be mapped relatively easily to different parallel architectures, since a large percentage of the parallelism has been identified. The compiler generates a FORTH-like machine-independent intermediate code. A machine-dependent translator will reside on each machine to generate the appropriate executable code, taking advantage of the particular architectures. The goal of this project is to allow a user to run the same program on such machines as the Massively Parallel Processor, the CRAY, the Connection Machine, and the CYBER 205 as well as serial machines such as VAXes, Macintoshes and Sun workstations.

  13. Liquid Nucleation at Superheated Grain Boundaries

    NASA Astrophysics Data System (ADS)

    Frolov, T.; Mishin, Y.

    2011-04-01

    Grain boundaries with relatively low energies can be superheated above the melting temperature and eventually melt by heterogeneous nucleation of liquid droplets. We propose a thermodynamic model of this process based on the sharp-interface approximation with a disjoining potential. The distinct feature of the model is its ability to predict the shape and size of the critical nucleus by using a variational approach. The model reduces to the classical nucleation theory in the limit of large nuclei but is more general and remains valid for small nuclei. Contrary to the classical nucleation theory, the model predicts the existence of a critical temperature of superheating and offers a simple formula for its calculation. The model is tested against molecular dynamic simulations in which liquid nuclei at a superheated boundary were obtained by an adiabatic trapping procedure. The simulation results demonstrate a reassuring consistency with the model.

  14. Dust grains from the heart of supernovae

    NASA Astrophysics Data System (ADS)

    Bocchio, M.; Marassi, S.; Schneider, R.; Bianchi, S.; Limongi, M.; Chieffi, A.

    2016-03-01

    Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. With this aim, we have developed a new code, GRASH_Rev, that allows following the dynamics of dust grains in the shocked SN ejecta and computing the time evolution of the mass, composition, and size distribution of the grains. We considered four well-studied SNe in the Milky Way and Large Magellanic Cloud: SN 1987A, CasA, the Crab nebula, and N49. These sources have been observed with both Spitzer and Herschel, and the multiwavelength data allow a better assessment the mass of warm and cold dust associated with the ejecta. For each SN, we first identified the best explosion model, using the mass and metallicity of the progenitor star, the mass of 56Ni, the explosion energy, and the circumstellar medium density inferred from the data. We then ran a recently developed dust formation model to compute the properties of freshly formed dust. Starting from these input models, GRASH_Rev self-consistently follows the dynamics of the grains, considering the effects of the forward and reverse shock, and allows predicting the time evolution of the dust mass, composition, and size distribution in the shocked and unshocked regions of the ejecta. All the simulated models aagree well with observations. Our study suggests that SN 1987A is too young for the reverse shock to have affected the dust mass. Hence the observed dust mass of 0.7-0.9 M⊙ in this source can be safely considered as indicative of the mass of freshly formed dust in SN ejecta. Conversely, in the other three SNe, the reverse shock has already destroyed between 10-40% of the

  15. HREM of general and twist grain boundaries.

    SciTech Connect

    Merkle, K. L.; Thompson, L. J.

    1999-03-10

    The observation of atomic-scale structures of grain boundaries (GBs) via axial illumination HREM has been largely restricted to tilt GBs, due to the requirement that the electron beam be parallel to a low-index zone axis on both sides of the interface. This condition can be fulfilled for all tilt GBs with disorientation about a low-index direction. The information obtained through HREM studies in many materials has brought important insights concerning the atomic-scale structure of such boundaries. However, it is well known that tilt GBs occupy only an infinitesimally small fraction of the 5-dimensional phase space which describes the macroscopic geometry of all GBs. Therefore, although tilt GBs are very important due to their low energy, it would be useful to also study twist GBs and general GBs that contain twist and tilt components.

  16. Dust grain resonant capture: A statistical study

    NASA Technical Reports Server (NTRS)

    Marzari, F.; Vanzani, V.; Weidenschilling, S. J.

    1993-01-01

    A statistical approach, based on a large number of simultaneous numerical integrations, is adopted to study the capture in external mean motion resonances with the Earth of micron size dust grains perturbed by solar radiation and wind forces. We explore the dependence of the resonant capture phenomenon on the initial eccentricity e(sub 0) and perihelion argument w(sub 0) of the dust particle orbit. The intensity of both the resonant and dissipative (Poynting-Robertson and wind drag) perturbations strongly depends on the eccentricity of the particle while the perihelion argument determines, for low inclination, the mutual geometrical configuration of the particle's orbit with respect to the Earth's orbit. We present results for three j:j+1 commensurabilities (2:3, 4:5 and 6:7) and also for particle sizes s = 15, 30 microns. This study extends our previous work on the long term orbital evolution of single dust particles trapped into resonances with the Earth.

  17. Detection of organic matter in interstellar grains.

    PubMed

    Pendleton, Y J

    1997-06-01

    Star formation and the subsequent evolution of planetary systems occurs in dense molecular clouds, which are comprised, in part, of interstellar dust grains gathered from the diffuse interstellar medium (DISM). Radio observations of the interstellar medium reveal the presence of organic molecules in the gas phase and infrared observational studies provide details concerning the solid-state features in dust grains. In particular, a series of absorption bands have been observed near 3.4 microns (approximately 2940 cm-1) towards bright infrared objects which are seen through large column densities of interstellar dust. Comparisons of organic residues, produced under a variety of laboratory conditions, to the diffuse interstellar medium observations have shown that aliphatic hydrocarbon grains are responsible for the spectral absorption features observed near 3.4 microns (approximately 2940 cm-1). These hydrocarbons appear to carry the -CH2- and -CH3 functional groups in the abundance ratio CH2/CH3 approximately 2.5, and the amount of carbon tied up in this component is greater than 4% of the cosmic carbon available. On a galactic scale, the strength of the 3.4 microns band does not scale linearly with visual extinction, but instead increases more rapidly for objects near the Galactic Center. A similar trend is noted in the strength of the Si-O absorption band near 9.7 microns. The similar behavior of the C-H and Si-O stretching bands suggests that these two components may be coupled, perhaps in the form of grains with silicate cores and refractory organic mantles. The ubiquity of the hydrocarbon features seen in the near infrared near 3.4 microns throughout out Galaxy and in other galaxies demonstrates the widespread availability of such material for incorporation into the many newly forming planetary systems. The similarity of the 3.4 microns features in any organic material with aliphatic hydrocarbons underscores the need for complete astronomical observational

  18. Randomized Grain Boundary Liquid Crystal Phase

    NASA Astrophysics Data System (ADS)

    Chen, D.; Wang, H.; Li, M.; Glaser, M.; Maclennan, J.; Clark, N.

    2012-02-01

    The formation of macroscopic, chiral domains, in the B4 and dark conglomerate phases, for example, is a feature of bent-core liquid crystals resulting from the interplay of chirality, molecular bend and molecular tilt. We report a new, chiral phase observed in a hockey stick-like liquid crystal molecule. This phase appears below a smectic A phase and cools to a crystal phase. TEM images of the free surface of the chiral phase show hundreds of randomly oriented smectic blocks several hundred nanometers in size, similar to those seen in the twist grain boundary (TGB) phase. However, in contrast to the TGB phase, these blocks are randomly oriented. The characteristic defects in this phase are revealed by freeze-fracture TEM images. We will show how these defects mediate the randomized orientation and discuss the intrinsic mechanism driving the formation of this phase. This work is supported by NSF MRSEC Grant DMR0820579 and NSF Grant DMR0606528.

  19. Method of making fine-grained triaminotrinitrobenzene

    DOEpatents

    Benziger, T.M.

    1983-07-26

    A method is given for forming a fine-grained species of the insensitive high explosive sym-triaminotrinitrobenzene (TATB) without grinding. In accordance with the method, 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) is aminated by reaction with gaseous ammonia in an emulsion of toluene in water. The ratio of water to toluene in the emulsion is selected so that toluene is the dispersed phase in the emulsion. The size of the dispersed TCTNB-containing toluene droplets determines the particle size of the resulting TATB. The emulsion is preferably formed with an emulsifier such as ammonium oleate, which may be generated in situ from oleic acid, and stabilized with a protective colloid such as polyvinyl alcohol.

  20. Method of making fine-grained triaminotrinitrobenzene

    DOEpatents

    Benziger, Theodore M.

    1984-01-01

    A method of forming a fine-grained species of the insensitive high explosive sym-triaminotrinitrobenzene (TATB) without grinding. In accordance with the method, 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) is aminated by reaction with gaseous ammonia in an emulsion of toluene in water. The ratio of water to toluene in the emulsion is selected so that toluene is the dispersed phase in the emulsion. The size of the dispersed TCTNB-containing toluene droplets determines the particle size of the resulting TATB. The emulsion is preferably formed with an emulsifier such as ammonium oleate, which may be generated in situ from oleic acid, and stabilized with a protective colloid such as polyvinyl alcohol.

  1. Pre-precipitation phenomena at grain boundaries

    SciTech Connect

    Briceno-Valero, J.; Gronsky, R.

    1982-03-01

    A high spatial resolution study of the behavior of Zn solute in Al bicrystals has been conducted using x-ray energy-dispersive spectroscopy (EDS) in a TEM/STEM instrument. Specimens subjected to short annealing cycles are found to exhibit a periodic distribution of Zn along the grain boundary plane prior to the appearance of any evidence suggesting precipitation has occurred. The periodicity of the segregation event bears no exact relationship with the transition lattice models of boundary structure but its behavior as a function of misorientation angle does agree with the expected intervals of atomic relaxation in the O-lattice. High resolution images and convergent beam microdiffraction are used to confirm the structural characteristics of these solute-rich regions.

  2. Coarse-grained modeling of DNA curvature

    NASA Astrophysics Data System (ADS)

    Freeman, Gordon S.; Hinckley, Daniel M.; Lequieu, Joshua P.; Whitmer, Jonathan K.; de Pablo, Juan J.

    2014-10-01

    The interaction of DNA with proteins occurs over a wide range of length scales, and depends critically on its local structure. In particular, recent experimental work suggests that the intrinsic curvature of DNA plays a significant role on its protein-binding properties. In this work, we present a coarse grained model of DNA that is capable of describing base-pairing, hybridization, major and minor groove widths, and local curvature. The model represents an extension of the recently proposed 3SPN.2 description of DNA [D. M. Hinckley, G. S. Freeman, J. K. Whitmer, and J. J. de Pablo, J. Chem. Phys. 139, 144903 (2013)], into which sequence-dependent shape and mechanical properties are incorporated. The proposed model is validated against experimental data including melting temperatures, local flexibilities, dsDNA persistence lengths, and minor groove width profiles.

  3. Gas-Grain Simulation Facility (GGSF)

    NASA Technical Reports Server (NTRS)

    Greenwald, Ken

    1992-01-01

    The goal of the Gas-Grain Simulation Facility project is to provide a microgravity laboratory to facilitate research relevant to exobiology (the study of the origin and evolution of life in the universe). Such a facility will also be useful in other areas of study important to NASA including planetary science, biology, atmospheric science, astrophysics, chemistry, and physics. To achieve this goal, the project will develop and support the GGSF, a modular facility-class payload planned for inclusion on Space Station Freedom. The GGSF will consist of the following: an experiment chamber(s) supported by subsystems that provide chamber environment regulation and monitoring capabilities; sample generation, injection, positioning, and retrieval capabilities; and computer control, data acquisition, and housekeeping capabilities. The facility will also provide analytical tools such as light-scattering measurement systems, aerosol size-spectrum measurement devices, and optical imaging systems.

  4. Ceres Revealed in a Grain of Salt

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E.; Bodnar, R. J.; Fries, M.; Chan, Q. H.-S.; Kebukawa, Y.; Mikouchi, T.; Hagiya, K.; Komatsu, M.; Ohsumi, K.; Steele, A.

    2016-01-01

    Introduction: Zag and Monahans (1998) are H chondrite regolith breccias containing 4.5 giga-year-old halite crystals which contain abundant inclusions of aqueous fluids, solids and organics. These all originated on a cryo-volcanically-active C class asteroid, probably 1 Ceres; the halite was transported to the regolith of the H chondrite parent asteroid, potentially 6 Hebe. Detailed analysis of these solids will thus potentially reveal the mineralogy of Ceres. Mineralogy of solids in the Monahans Halite Solid grains are present in the halites, which were entrained within the mother brines during eruption, including material from the interior and surface of the erupting body. The solids include abundant, widely variable organics that could not have been significantly heated (which would have resulted in the loss of fluids from the halite). Our analyses by Raman microprobe, SEM/EDX, synchrotron X-ray diffraction, UPLC-FD/QToF-MS, C-XANES and TEM reveal that these trapped grains include macromolecular carbon (MMC) similar in structure to CV3 chondrite matrix carbon, aliphatic carbon compounds, olivine (Fo99-59), high- and low-Ca pyroxene, feldspars, phyllosilicates, magnetite, sulfides, metal, lepidocrocite, carbonates, diamond, apatite and zeolites. Conclusions: The halite in Monahans and Zag derive from a water and carbon-rich object that was cryo-volcanically active in the early solar system, probably Ceres. The Dawn spacecraft found that Ceres includes C chondrite materials. Our samples include both protolith and aqueously-altered samples of the body, permitting understanding of alteration conditions. Whatever the halite parent body, it was rich in a wide variety of organics and warm, liquid water at the solar system's dawn.

  5. Soil Sampling Techniques For Alabama Grain Fields

    NASA Technical Reports Server (NTRS)

    Thompson, A. N.; Shaw, J. N.; Mask, P. L.; Touchton, J. T.; Rickman, D.

    2003-01-01

    Characterizing the spatial variability of nutrients facilitates precision soil sampling. Questions exist regarding the best technique for directed soil sampling based on a priori knowledge of soil and crop patterns. The objective of this study was to evaluate zone delineation techniques for Alabama grain fields to determine which method best minimized the soil test variability. Site one (25.8 ha) and site three (20.0 ha) were located in the Tennessee Valley region, and site two (24.2 ha) was located in the Coastal Plain region of Alabama. Tennessee Valley soils ranged from well drained Rhodic and Typic Paleudults to somewhat poorly drained Aquic Paleudults and Fluventic Dystrudepts. Coastal Plain s o i l s ranged from coarse-loamy Rhodic Kandiudults to loamy Arenic Kandiudults. Soils were sampled by grid soil sampling methods (grid sizes of 0.40 ha and 1 ha) consisting of: 1) twenty composited cores collected randomly throughout each grid (grid-cell sampling) and, 2) six composited cores collected randomly from a -3x3 m area at the center of each grid (grid-point sampling). Zones were established from 1) an Order 1 Soil Survey, 2) corn (Zea mays L.) yield maps, and 3) airborne remote sensing images. All soil properties were moderately to strongly spatially dependent as per semivariogram analyses. Differences in grid-point and grid-cell soil test values suggested grid-point sampling does not accurately represent grid values. Zones created by soil survey, yield data, and remote sensing images displayed lower coefficient of variations (8CV) for soil test values than overall field values, suggesting these techniques group soil test variability. However, few differences were observed between the three zone delineation techniques. Results suggest directed sampling using zone delineation techniques outlined in this paper would result in more efficient soil sampling for these Alabama grain fields.

  6. Peculiarities of the Field Electron Emission from Dust Grains

    SciTech Connect

    Richterova, I.; Beranek, M.; Pavlu, J.; Nemecek, Z.; Safrankova, J.

    2008-09-07

    The goal of the paper is investigation of the electron field emission that limits the attainable grain charge and can prevent electrostatic fragmentation of loosely bounded aggregates of dust grains. We have found that the effective work function of the spherical amorphous carbon grains does not depend on the relative beam energy. Preliminary results on an influence of the ion treatment/cleaning using the simultaneous electron and ion bombardments are discussed.

  7. The scaling state in two-dimensional grain growth

    SciTech Connect

    Mulheran, P.A. . Dept. of Physics)

    1994-11-01

    A new model of normal grain growth in two-dimensional systems is derived from considerations of Potts model simulations. This Randomly Connected Bubble model is based on Hillert's theory and combines the essential topological features of the grain boundary network with the action of capillarity. It successfully predicts what the scaling state of the network should be and explains why the system evolves into this state. The implications for grain growth in real materials are also discussed.

  8. Electronic Structure of a Disordered Grain Boundary in Graphene

    NASA Astrophysics Data System (ADS)

    Lambin, Ph.; Vancso, P.; Nemes-Incze, P.; Mark, G.; Biró, L. P.

    2013-05-01

    Grain boundaries are constitutional elements of graphene grown on a solid metallic surface by CVD. The electronic properties of computer models of grain boundaries in graphene have been investigated by tight-binding calculations and compared with available ab initio data and with recent experimental scanning tunneling spectroscopic measurements. It is shown that twofold coordinated atoms and non-hexagonal rings, both present in grain boundaries, give rise to specific features in the local density of states.

  9. Climate and the Soviet Grain Crisis of 1928

    NASA Astrophysics Data System (ADS)

    Welker, Jean Edward

    1995-01-01

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

  10. Stability of Small Grains in HII Regions and Reflection Nebulae

    NASA Technical Reports Server (NTRS)

    Werner, M. W.; Gauthier, T. N., III; Cawlfield, T.

    1993-01-01

    We have analyzed IRAS data to assess the relative amounts of small and large grains in HII regions and reflection nebulae. Our most important finding is that no evidence for small grain destruction is seen in reflection nebulae, even for [high] values of the radiation energy density at which significant grain destruction apparently occurs in HII regions. This suggests that it is not only the total radiant energy density but also the energy per photon which determines the stability of small grains in astrophysical environments.

  11. Tribocharging and charged interaction in same-material, microscopic grains

    NASA Astrophysics Data System (ADS)

    Waitukaitis, S.; Lee, V.; Jaeger, H.

    2015-10-01

    We experimentally address the causes and consequences of charging between same-material, microscopic grains. We confirm quantitatively that differences in grain size alone drive charging. By comparing our data to independent thermoluminescence measurements, we show that trapped electrons are not the charged species being transferred. We observe and quantify a zoology of interactions between grains, including attractive orbits and repulsive slingshot events, cluster growth and annihilation via collisions, and granular molecule formation. Our results highlight the important role played by grain polarizability in aggregation and have implications for the dynamics of dust particles in protoplanetary disks.

  12. Computer simulation of grain growth with mobile particles

    SciTech Connect

    Hassold, G.N.; Srolovitz, D.J.

    1995-05-15

    The authors have studied the influence of mobile particles on grain growth kinetics. Three time regimes are evident in the observed coarsening. Initially, most grains grow unhindered by particles, with a growth exponent close to 1/2. As with static impurities, once the mean grain size approaches the average inter-particle separation the microstructure becomes effectively pinned. With mobile impurities, however, the loaded grain boundaries eventually resume their motion. The depinning time is observed to be independent of particle concentration. The observed kinetic behavior, growth exponents, and depinning time are in agreement with a simple theoretical model with different mobilities for boundaries with and without attached particles.

  13. Grain metamorphism in polar nitrogen ice on Triton

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Mckay, Christopher P.; Pollack, James B.; Cruikshank, Dale P.

    1989-01-01

    The rate of nitrogen grain growth on putative N2-rich polar caps on Triton is calculated. For most plausible assumptions of independent variables, mean grain sizes in polar N2 are meter-scale. Triton's polar caps should constitute the definitive solar-system test bed for the process of ice grain metamorphism. Interpretation of data already in hand may require long path length through condensed N2, possibly due to grain growth. Upcoming Voyager data may clarify the situation, although possible complications in detecting a glaze of N2 ice exist.

  14. Magnetoresistance of polycrystalline gadolinium with varying grain size

    SciTech Connect

    Chakravorty, Manotosh Raychaudhuri, A. K.

    2015-01-21

    In this paper, we report a study of evolution of low field magnetoresistance (MR) of Gadolinium as the grain size in the sample is changed from few microns (∼4 μm) to the nanoscopic regime (∼35 nm). The low field MR has a clear effect on varying grain size. In large grain sample (few μm), the magnetic domains are controlled by local anisotropy field determined mainly by the magnetocrystalline anisotropy. The low field MR clearly reflects the temperature dependence of the magnetocrystalline anisotropy. For decreasing gain size, the contribution of spin disorder at the grain boundary increases and enhances the local anisotropy field.

  15. New Process for Grain Refinement of Aluminum. Final Report

    SciTech Connect

    Dr. Joseph A. Megy

    2000-09-22

    A new method of grain refining aluminum involving in-situ formation of boride nuclei in molten aluminum just prior to casting has been developed in the subject DOE program over the last thirty months by a team consisting of JDC, Inc., Alcoa Technical Center, GRAS, Inc., Touchstone Labs, and GKS Engineering Services. The Manufacturing process to make boron trichloride for grain refining is much simpler than preparing conventional grain refiners, with attendant environmental, capital, and energy savings. The manufacture of boride grain refining nuclei using the fy-Gem process avoids clusters, salt and oxide inclusions that cause quality problems in aluminum today.

  16. Computation of grain boundary stiffness and mobility from boundary fluctuations.

    SciTech Connect

    Hoyt, Jeffrey John; Foiles, Stephen Martin

    2005-06-01

    Grain boundary stiffness and mobility determine the kinetics of curvature-driven grain growth. Here the stiffness and mobility are computed using an analysis of fluctuations in the grain boundary position during molecular dynamics simulations. This work represents the first determination of grain boundary stiffness for a realistic three-dimensional system. The results indicate that the boundary stiffness for a given boundary plane has a strong dependence on the direction of the boundary distortion. The mobility deduced is comparable with that determined in previous computer simulation studies. The advantages and limitations of the fluctuation approach are discussed.

  17. Grain boundary oxidation and fatigue crack growth at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Liu, H. W.; Oshida, Y.

    1986-01-01

    Fatigue crack growth rate at elevated temperatures can be accelerated by grain boundary oxidation. Grain boundary oxidation kinetics and the statistical distribution of grain boundary oxide penetration depth were studied. At a constant delta K-level and at a constant test temperature, fatigue crack growth rate, da/dN, is a function of cyclic frequency, nu. A fatigue crack growth model of intermittent micro-ruptures of grain boundary oxide is constructed. The model is consistent with the experimental observations that, in the low frequency region, da/dN is inversely proportional to nu, and fatigue crack growth is intergranular.

  18. Coalescence kinetics under the action of alternative grain growth mechanisms

    SciTech Connect

    Gubanov, P. Yu. Maksimov, I. L.

    2008-01-15

    The coalescence process is considered for the case where the prevailing grain growth mechanism is block-to-block diffusion, during which the motion of atoms in a solution occurs in the form of diffusion flux along the block boundaries. Numerical and analytical investigation of the coalescence kinetics in a homogeneous supersaturated solution is performed with allowance for the finite maximum grain size, and the time evolution of the size distribution function of new-phase grains is theoretically described. Possible transition regimes arising during coalescence at a change in the dominant grain growth mechanism are considered.

  19. Dissolution of populations of ultrafine grains with applications to feldspars

    NASA Astrophysics Data System (ADS)

    Talman, S. J.; Nesbitt, H. W.

    1988-06-01

    Mineral dissolution studies are difficult to interpret when the solid reactant displays a wide range in grain sizes, since the rate of dissolution of the finest grains may not be simply related to their surface area. The transient apparent rate of dissolution of a population of fine-grained reactants is modeled to predict changes to the solution composition, as well as changes in the size distribution of ultra-fine particles as functions of time. The model is applied to the experimental data on Amelia albite of HOLDREN and BERNER (1979) from which both solution composition and grain size distribution have been obtained. The observed size distribution cannot be duplicated if the dissolution rate is proportional to surface area ( i.e.dV/dt = Kr 2); other contributions to the rate, such as dependence on grain size and the specific contributions from edges and corners, must be invoked. The observed grain size distribution and pseudo-parabolic rate can be reproduced when the rate of dissolution of the fine grains is proportional to its radius ( i.e.dV/dt = kr ). The rate constant, k, is consistent with a rate limited by dissolution at the edges of the grains. The possibility of predicting both the contribution of ultra-fine particles to the observed dissolution rate and the time evolution of the grain size distribution makes the model a useful tool for interpreting mineral dissolution data.

  20. Effects of climate change on US grain transport

    NASA Astrophysics Data System (ADS)

    Attavanich, Witsanu; McCarl, Bruce A.; Ahmedov, Zafarbek; Fuller, Stephen W.; Vedenov, Dmitry V.

    2013-07-01

    The United States is a global grain supplier. Agriculture uses 22% of all US transported tonnage with grain being the largest component. Crop mix shifts are an often cited consequence of climate change and such shifts may change the demands grain places on the transport system. Studies also find that climate change could decrease Great Lakes water levels, shorten the duration of ice cover in the winter and alter grain supplies in grain-exporting countries. This study investigates the effects of such phenomena on US grain transportation movements both in volumes and modes. Specifically we examine the effects of possible shifts in: crop production patterns; Great Lakes water levels; winter navigation possibilities; and foreign grain production. We find that crop mix shifts reduce the importance of Lower Mississippi River ports, but increase the role of Pacific Northwest ports, Great Lakes ports and Atlantic ports. We also find a shift from barge to rail and truck transport. Conversely, a longer navigation season or a reduction in Great Lake water levels increases grain shipments to the ports in the Lower Mississippi River. Higher use of Great Lakes ports occurs under a reduction of grain production in European exporting countries that compete with Great Lakes ports.

  1. Jamming of Monodisperse Cylindrical Grains in Featureless Vertical Channels

    NASA Astrophysics Data System (ADS)

    Friedl, Nicholas; Baxter, G. William

    2014-03-01

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

  2. Production and Recoil Loss of Cosmogenic Nuclides in Presolar Grains

    NASA Astrophysics Data System (ADS)

    Trappitsch, Reto; Leya, Ingo

    2016-05-01

    Presolar grains are small particles that condensed in the vicinity of dying stars. Some of these grains survived the voyage through the interstellar medium (ISM) and were incorporated into meteorite parent bodies at the formation of the Solar System. An important question is when these stellar processes happened, i.e., how long presolar grains were drifting through the ISM. While conventional radiometric dating of such small grains is very difficult, presolar grains are irradiated with galactic cosmic rays (GCRs) in the ISM, which induce the production of cosmogenic nuclides. This opens the possibility to determine cosmic-ray exposure (CRE) ages, i.e., how long presolar grains were irradiated in the ISM. Here, we present a new model for the production and loss of cosmogenic 3He, 6,7Li, and 21,22Ne in presolar SiC grains. The cosmogenic production rates are calculated using a state-of-the-art nuclear cross-section database and a GCR spectrum in the ISM consistent with recent Voyager data. Our findings are that previously measured 3He and 21Ne CRE ages agree within the (sometimes large) 2σ uncertainties and that the CRE ages for most presolar grains are smaller than the predicted survival times. The obtained results are relatively robust since interferences from implanted low-energy GCRs into the presolar SiC grains and/or from cosmogenic production within the meteoroid can be neglected.

  3. Effect of processing sorghum grain on dairy calf performance.

    PubMed

    Abdelgadir, I E; Morrill, J L

    1995-09-01

    Two trials evaluated the effect of sorghum grain processing on dairy calf performance. In trial 1, Holstein calves (n = 76; .5 to 8 wk of age) were fed one of three calf starters that contained either raw, roasted (exit temperature of 135 degrees C), or conglomerated sorghum grain. The conglomeration process consisted of grinding the grain, adding water, pelleting the mixture, and then roasting it. Raw and roasted sorghum grains were ground through a 3.2-mm screen and then included in complete pelleted starters; conglomerated sorghum grain pellets were mixed with the other pelleted ingredients of the starter. Processing did not enhance calf performance or affect selected ruminal and blood metabolites. In trial 2, roasted and conglomerated sorghum grains were ground through a 3.2-mm screen, and each was included in a pelleted starter fed for ad libitum intake to Holstein calves (n = 48) from .5 to 8 wk of age. Calf performance was not affected by method of grain processing, and ruminal and blood metabolites were similar; however, 22% of calves on the conglomerated sorghum grain starter bloated during the postweaning period, which probably resulted in reduced feed intake from wk 6 to 8. Measures to prevent bloat may be necessary to realize a potential benefit of conglomerating sorghum grain for calves. PMID:8550913

  4. In situ studies of grain growth in thin metal films

    SciTech Connect

    Nichols, C.S.; Mansuri, C.M. . Dept. of Materials Science and Engineering); Townsend, S.J. . Dept. of Physics); Smith, D.A. . T.J. Watson Research Center)

    1993-06-01

    Grain growth in thin films of aluminum has been studied using in situ transmission electron microscopy and a heating stage. Videotapes taken during grain growth were analyzed with the intent of searching for the predominant local rearrangement processes responsible for growth. Evolution of a soap froth can be decomposed into only two elementary local topology rearranging events. The authors have found numerous exceptions to prevailing theories that compare grain growth in thin films to the evolution of such froths. These observations suggest that a more complete picture of grain growth is necessary and that such a theory must include more complex local rearrangement processes.

  5. Film grain noise modeling in advanced video coding

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

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

  6. Influence of point defects on grain boundary diffusion in oxides

    SciTech Connect

    Stubican, V.S.

    1991-03-15

    The influence of point defects on grain boundary diffusion of Co ions in NiO was studied using polycrystalline films and bicrystals. Grain boundary diffusion was studied at 750 C at oxygen partial pressure. Two diffusion regions were found. At low oxygen pressures, extrinsic diffusion was observed. Above oxygen pressure of 10{sup {minus}7}, influence of intrinsic point defects was detected. It was determined that grain boundary diffusion was > 3 orders of magnitude faster than volume diffusion. However, it seems that grain boundary diffusion is influenced by the point defects in a similar way as the volume diffusion. 4 figs.

  7. Abnormal Grain Growth in M-252 and S-816 Alloys

    NASA Technical Reports Server (NTRS)

    Decker, R F; Rush, A I; Dano, A G; Freeman, J W

    1957-01-01

    An experimental investigation was carried out on air- and vacuum-melted M-252 and S-816 alloys to find conditions of heating and hot-working which resulted in abnormal grain growth. The experiments were mainly limited to normal conditions of heating for hot-working and heat treatment and normal temperatures of solution treatment were used to allow grain growth after susceptibility to abnormal grain growth was developed by various experimental conditions. Results indicated that small reductions of essentially strain-free metal were the basic cause of such grain growth.

  8. Phase field modeling of grain growth in porous polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Ahmed, Karim E.

    The concurrent evolution of grain size and porosity in porous polycrystalline solids is a technically important problem. All the physical properties of such materials depend strongly on pore fraction and pore and grain sizes and distributions. Theoretical models for the pore-grain boundary interactions during grain growth usually employ restrictive, unrealistic assumptions on the pore and grain shapes and motions to render the problem tractable. However, these assumptions limit the models to be only of qualitative nature and hence cannot be used for predictions. This has motivated us to develop a novel phase field model to investigate the process of grain growth in porous polycrystalline solids. Based on a dynamical system of coupled Cahn-Hilliard and All en-Cahn equations, the model couples the curvature-driven grain boundary motion and the migration of pores via surface diffusion. As such, the model accounts for all possible interactions between the pore and grain boundary, which highly influence the grain growth kinetics. Through a formal asymptotic analysis, the current work demonstrates that the phase field model recovers the corresponding sharp-interface dynamics of the co-evolution of grain boundaries and pores; this analysis also fixes the model kinetic parameters in terms of real materials properties. The model was used to investigate the effect of porosity on the kinetics of grain growth in UO2 and CeO2 in 2D and 3D. It is shown that the model captures the phenomenon of pore breakaway often observed in experiments. Pores on three- and four- grain junctions were found to transform to edge pores (pores on two-grain junction) before complete separation. The simulations demonstrated that inhomogeneous distribution of pores and pore breakaway lead to abnormal grain growth. The simulations also showed that grain growth kinetics in these materials changes from boundary-controlled to pore-controlled as the amount of porosity increases. The kinetic growth

  9. Crystal structure instability of FeSe grains: Formation of non-superconducting phase at the grain surface

    NASA Astrophysics Data System (ADS)

    Izawa, Hiroki; Tanaka, Yuji; Mizuguchi, Yoshikazu; Miura, Osuke

    2016-05-01

    We investigated the magnetization and crystal structure of FeSe polycrystalline samples with various grain sizes. For the samples with large grains, a large magnetic critical current density J c was observed. For the samples with small grains, superconductivity signals were not observed; instead, magnetization hysteresis, which is not a result of superconductivity, was observed. In the X-ray diffraction pattern for the samples with small grains, broad additional peaks were observed, corresponding to the formation of the non-superconducting (monoclinic) Fe–Se phase at the FeSe grain surface. The crystal structure instability at the grain surface would be the reason for the low superconducting properties of the Fe-chalcogenide polycrystalline wires investigated thus far.

  10. Method of aeration disinfecting and drying grain in bulk and pretreating seeds and a transverse blow silo grain dryer therefor

    DOEpatents

    Danchenko, Vitaliy G.; Noyes, Ronald T.; Potapovych, Larysa P.

    2012-02-28

    Aeration drying and disinfecting grain crops in bulk and pretreating seeds includes passing through a bulk of grain crops and seeds disinfecting and drying agents including an ozone and air mixture and surrounding air, subdividing the disinfecting and drying agents into a plurality of streams spaced from one another in a vertical direction, and passing the streams at different heights through levels located at corresponding heights of the bulk of grain crops and seeds transversely in a substantially horizontal direction.

  11. Effects of grain size and grain boundary on critical current density of high T(sub c) superconducting oxides

    NASA Technical Reports Server (NTRS)

    Zhao, Y.; Zhang, Q. R.; Zhang, H.

    1990-01-01

    By means of adding impurity elements in high T sub c oxides, the effects were studied of grain size and grain boundary on the critical current density of the following systems: YBa2Cu3O(7-y) and Bi-Pr-Sr-Ca-Cu-O. In order to only change the microstructure instead of the superconductivity of the grains in the samples, the impurity elements were added into the systems in terms of the methods like this: (1) substituting Y with the lanthanide except Pr, Ce, and Tb in YBa2Cu3O(7-y) system to finning down grains in the samples, therefore, the effect can be investigated of the grain size on the critical current density of 1:2:3 compounds; (2) mixing the high T sub c oxides with the metal elements, such as Ag, according to the composition of (high T sub c oxide)1-xAgx to metallize the grain boundaries in the samples, studying the effect of the electric conductivity of the grain boundaries on the critical current density; (3) adding SiO2, PbO2, and SnO2 into the high T sub c oxide to form impurity phases in the grain boundaries, trying to find out the effects of the impurity phases or metalloid grain boundaries on the critical current density of the high T sub c superconductors. The experimental results indicate that in the case of of the presence of the metalloid grain boundaries finning down grains fails to enhance the j sub c, but restrains it strongly, the granular high T sub c superconductors with the small size grains coupled weakly is always the low j sub c system.

  12. High night temperatures during grain number determination reduce wheat and barley grain yield: a field study.

    PubMed

    García, Guillermo A; Dreccer, M Fernanda; Miralles, Daniel J; Serrago, Román A

    2015-11-01

    Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area (GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9 °C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 to 17.2 °C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C(-1) ), due to GN reductions (ca. 6% °C(-1) ) linked to a lower number of spikes per m(2) . An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change. PMID:26111197

  13. The effects of grain size composition on the efficiency of fine-grained coal separation

    SciTech Connect

    Blahova, O.; Rezek, K.; Novacek, J.

    1994-12-31

    One factor that favorably affects the economics of exploitation and preparation of coal is reducing the loss of coal matter in the tailings from washeries. Thus, it is necessary to modify existing technologies for the preparation of coking coal. This study of the effects of grain size composition for run-of-mine coal on the efficiency of coal separation, as well as on the quality of the products, was performed on the following equipment used for fine-grained coal separation: fine coal jigs (0.5 to 10/15 mm); jigs (0.5 to 40 mm); heavy medium cyclones (0.5 to 10 mm); slurry hydrocyclones (0.0 to 0.5 mm); HIRST hydrocyclones (0.0 to 0.5 mm); and spiral concentrators (0.0 to 3.0 mm). The results of the study lead to the following conclusions. (1) It is impossible to attain efficient separation in a wide range of fine grain sizes processed simultaneously in a single piece of equipment. (2) Among the equipment available for separation, one type can be found with the highest efficiency for a given grain size of fine coal. (3) The newly introduced spiral concentrators have attained such an efficiency of separation and are so economical that they could be included with advantage between the jigs and the lotion process. This would favorably affect the output and the efficiency of separation of all the equipment involved in the process. (4) All measures to be taken in the flow sheet of coal preparation plants and designed to increase the efficiency of separation should be documented with data that show the expected economic benefits of any change for both the mine and the preparation plant.

  14. Modeling the Role of Small Scale Physics in Sediment Transport From Grain Size to Grain Shape

    NASA Astrophysics Data System (ADS)

    Calantoni, J.; Holland, K. T.

    2007-12-01

    In recent years work has focused on the detailed physics of sediment transport at or near the grain scale. Although computational resources often restrict the domain size, deterministic models for sediment motions can prove useful in improving our understanding of sediment dynamics. Using a discrete particle model (DPM), we have performed computer simulations that describe the collective and individual motions of sediment grains immersed in fluid in an effort to emulate the physics of the sea floor, at the fluid-sediment interface, in shallow water under forcing from waves and currents. Examples of our DPM (briefly described) are shown for research applications at a range scales from millimeters to meters involving fluid flow models from simple one- dimensional eddy viscosity up to three-dimensional direct numerical simulation. Based on hundreds of different simulations over the past decade, our findings have shown: how a parameterization of pressure gradients or equivalently fluid accelerations on particle motions under waves influences sand bar migration in the surf zone; how grain shape changes bulk bedload transport rates; how efforts to model sediment particle motions in the swash zone can yield insight toward models for shoreline erosion and accretion; how recently simulated bedload transport using bimodal size distributions has uncovered a new power law; how upcoming work focuses on simulating the role of grain size distributions in small-scale sand ripple dynamics. Good agreement is found between comparisons of model output for both bulk transport rates and time dependent concentration profiles with laboratory data. Likewise, parameterizations obtained from simulation results have demonstrated skill in hindcast applications to both field and laboratory measurements. Conclusions will discuss the future role of reductionism in sediment transport modeling.

  15. Grain-size distribution of volcaniclastic rocks 2: Characterizing grain size and hydraulic sorting

    NASA Astrophysics Data System (ADS)

    Jutzeler, Martin; McPhie, Jocelyn; Allen, Sharon R.; Proussevitch, A. A.

    2015-08-01

    Quantification of the grain size distribution of sediments allows interpretation of processes of transport and deposition. Jutzeler et al. (2012) developed a technique to determine grain size distribution of consolidated clastic rocks using functional stereology, allowing direct comparison between unconsolidated sediments and rocks. Here, we develop this technique to characterize hydraulic sorting and infer transport and deposition processes. We compare computed grain size and sorting of volcaniclastic rocks with field-based characteristics of volcaniclastic facies for which transport and depositional mechanisms have been inferred. We studied pumice-rich, subaqueous facies of volcaniclastic rocks from the Oligocene Ohanapecosh Formation (Ancestral Cascades, Washington, USA), Pliocene Dogashima Formation (Izu Peninsula, Honshu, Japan), Miocene Manukau Subgroup (Northland, New Zealand) and the Quaternary Sierra La Primavera caldera (Jalisco State, Mexico). These sequences differ in bed thickness, grading and abundance of matrix. We propose to evaluate grain size and sorting of volcaniclastic deposits by values of their modes, matrix proportion (< 2 mm; F-1) and D16, instead of median diameter (D50) and standard deviation parameters. F-1 and D16 can be uniformly used to characterize and compare sieving and functional stereology data. Volcaniclastic deposits typically consist of mixtures of particles that vary greatly in density and porosity. Hydraulic sorting ratios can be used to test whether mixed clast populations of pumice and dense clasts are hydraulically sorted with each other, considering various types of transport underwater. Evaluation of this ratio for our samples shows that most studied volcaniclastic facies are deposited by settling from density currents, and that basal dense clast breccias are emplaced by shear rolling. These hydraulic sorting ratios can be applied to any type of clastic rocks, and indifferently on consolidated and unconsolidated samples.

  16. S–Te Interdiffusion within Grains and Grain Boundaries in CdTe Solar Cells

    DOE PAGESBeta

    Li, C.; Poplawsky, J.; Paudel, N.; Pennycook, T. J.; Haigh, S. J.; Al-Jassim, M. M.; Yan, Y.; Pennycook, S. J.

    2014-09-19

    At the CdTe/CdS interface, a significant Te-S interdiffusion has been found a few nanometers into the grain interiors with scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). S substitution at Te sites has been directly resolved in CdTe with STEM Z-contrast images. Moreover, when enough S substitutes for Te, a structural transformation from zinc-blende to wurtzite has been observed. Cl segregation has also been found at the interface. STEM electron-beam-induced current (EBIC) shows that the p-n junction occurs a few nm into the CdTe grains, which is consistent with the S diffusion range we observe. The shiftmore » of the p-n junction suggests a buried homo-junction which would help reduce non-radiative recombination at the junction. Meanwhile, long-range S diffusion in CdTe grain boundaries (GBs) has been detected, as well as Te and Cl diffusion in CdS GBs.« less

  17. S–Te Interdiffusion within Grains and Grain Boundaries in CdTe Solar Cells

    SciTech Connect

    Li, C.; Poplawsky, J.; Paudel, N.; Pennycook, T. J.; Haigh, S. J.; Al-Jassim, M. M.; Yan, Y.; Pennycook, S. J.

    2014-09-19

    At the CdTe/CdS interface, a significant Te-S interdiffusion has been found a few nanometers into the grain interiors with scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). S substitution at Te sites has been directly resolved in CdTe with STEM Z-contrast images. Moreover, when enough S substitutes for Te, a structural transformation from zinc-blende to wurtzite has been observed. Cl segregation has also been found at the interface. STEM electron-beam-induced current (EBIC) shows that the p-n junction occurs a few nm into the CdTe grains, which is consistent with the S diffusion range we observe. The shift of the p-n junction suggests a buried homo-junction which would help reduce non-radiative recombination at the junction. Meanwhile, long-range S diffusion in CdTe grain boundaries (GBs) has been detected, as well as Te and Cl diffusion in CdS GBs.

  18. 3D reconstruction of grains in polycrystalline materials using a tessellation model with curved grain boundaries

    NASA Astrophysics Data System (ADS)

    Šedivý, Ondřej; Brereton, Tim; Westhoff, Daniel; Polívka, Leoš; Beneš, Viktor; Schmidt, Volker; Jäger, Aleš

    2016-06-01

    A compact and tractable representation of the grain structure of a material is an extremely valuable tool when carrying out an empirical analysis of the material's microstructure. Tessellations have proven to be very good choices for such representations. Most widely used tessellation models have convex cells with planar boundaries. Recently, however, a new tessellation model - called the generalised balanced power diagram (GBPD) - has been developed that is very flexible and can incorporate features such as curved boundaries and non-convexity of cells. In order to use a GBPD to describe the grain structure observed in empirical image data, the parameters of the model must be chosen appropriately. This typically involves solving a difficult optimisation problem. In this paper, we describe a method for fitting GBPDs to tomographic image data. This method uses simulated annealing to solve a suitably chosen optimisation problem. We then apply this method to both artificial data and experimental 3D electron backscatter diffraction (3D EBSD) data obtained in order to study the properties of fine-grained materials with superplastic behaviour. The 3D EBSD data required new alignment and segmentation procedures, which we also briefly describe. Our numerical experiments demonstrate the effectiveness of the simulated annealing approach (compared to heuristic fitting methods) and show that GBPDs are able to describe the structures of polycrystalline materials very well.

  19. GrainGenes, the genome database for small-grain crops.

    PubMed

    Matthews, David E; Carollo, Victoria L; Lazo, Gerard R; Anderson, Olin D

    2003-01-01

    GrainGenes, http://www.graingenes.org, is the international database for the wheat, barley, rye and oat genomes. For these species it is the primary repository for information about genetic maps, mapping probes and primers, genes, alleles and QTLs. Documentation includes such data as primer sequences, polymorphism descriptions, genotype and trait scoring data, experimental protocols used, and photographs of marker polymorphisms, disease symptoms and mutant phenotypes. These data, curated with the help of many members of the research community, are integrated with sequence and bibliographic records selected from external databases and results of BLAST searches of the ESTs. Records are linked to corresponding records in other important databases, e.g. Gramene's EST homologies to rice BAC/PACs, TIGR's Gene Indices and GenBank. In addition to this information within the GrainGenes database itself, the GrainGenes homepage at http://wheat.pw.usda.gov provides many other community resources including publications (the annual newsletters for wheat, barley and oat, monographs and articles), individual datasets (mapping and QTL studies, polymorphism surveys, variety performance evaluations), specialized databases (Triticeae repeat sequences, EST unigene sets) and pages to facilitate coordination of cooperative research efforts in specific areas such as SNP development, EST-SSRs and taxonomy. The goal is to serve as a central point for obtaining and contributing information about the genetics and biology of these cereal crops. PMID:12519977

  20. Grain structure of thin electrodeposited and rolled copper foils

    SciTech Connect

    Merchant, H.D. . E-mail: HarishMerchant@aol.com; Liu, W.C.; Giannuzzi, L.A.; Morris, J.G.

    2004-12-15

    Planar and cross-section light optical and transmission electron microscopy (TEM) and X-ray diffraction analysis have been used to characterize the technologically relevant thin copper films and foils. The grain structure and grain orientation of (i) 1-15 {mu}m deposit on the polyimide (PI) substrate (ii) 5-35 {mu}m free-standing foil and (iii) 200 {mu}m sheet prepared by the industrial scale rolling or electrodeposit process have been examined. It is shown that the rolled foil structure is highly anisotropic due to grain stretching during rolling; the pancaked grains circumscribe a dislocation cell substructure. Thermal exposure in the 423-453 K range results in full anneal softening, while initiating the polygonization of cellular substructure, the formation of new large grains by discontinuous recrystallization and the transformation of the near <111> deformation textures into the near <100> anneal textures. The texture transformation is facilitated when the oxygen content of copper is reduced from the normal 100-400 ppm level or when a low level silver ({approx}200 ppm) addition is made to copper. Depending upon the electrodeposition conditions or the nature of additives introduced in the electrolyte, it is possible to develop an electrodeposit with (a) a truly equiaxed, fine, twin-free, randomly oriented grain structure or (b) a relatively coarse grain structure, accompanied by extensive twinning, z (growth)-direction grain extension, columnar grain morphology and strong <220> crystallographic texture. Between (a) and (b), it is possible to tailor the processing to obtain a mix of fine and coarse grains, a large fraction of random orientation component (weak near <220> textures), moderate twinning, and vestiges of columnar grain morphology and z-direction grain extension. The anneal softening is not accompanied by significant grain structure modification or by texture change; somewhat above the softening temperature, an in situ grain growth ensues. For both